JPH0814719B2 - Electrostatic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an electrostatic toner used in a method of converting an electrostatic latent image into a visible image, such as electrophotography and ion flow recording. .

(Prior art) As a powder toner for converting an electrostatic latent image into a visible image, a dye, a pigment, a magnetic powder, and the like are dispersed in a resin for toner by melt-kneading, cooled, and then mechanically pulverized. Generally, a method of classifying the particles is used.

However, it has been pointed out that the toner obtained by this method has an irregular shape, it is difficult to obtain a uniform charge, and the fluidity is poor.

Further, in manufacturing, the consumption of electric energy required for melt-kneading and pulverization is enormous, and it has been studied to obtain powder toner by a method other than the so-called pulverization method.

Spray drying method, suspension polymerization method, interfacial polymerization method and the like are known as methods for producing powder toner other than the so-called pulverization method, which is produced by the above-mentioned melt-kneading and pulverization.

Among them, the method of manufacturing by the spray drying method produces a spherical toner, so that a uniform charge is obtained and the fluidity is good, but it is necessary to cope with the explosion proof of the spray dryer and to collect the solvent. However, there are drawbacks such as that the thermal energy consumption required for drying is enormous, the solvent remains in the toner after drying, and it is difficult to remove it. In addition, sufficient physical properties of the toner are imparted. At times, there are restrictions on the materials, and it is difficult to obtain toner with sufficient characteristics by this method alone.

In addition to the above, Japanese Patent Laid-Open No. 36-10231, 47-51830, 51-14
895, 55-50962, 59-28164, 59-152450 and the like have been proposed to produce toner by the interfacial polymerization method. These have the advantages that the energy consumption required for particle generation (crushing) is smaller than that of the conventional crushing method, and that uniform spherical particles can be obtained. However,
Dispersants and stabilizers used during the production of toner particles in water remain on the surface of the toner particles and are difficult to remove.
It has been pointed out that even after it is dried and made into powder toner, it absorbs moisture in the air to lower the electrical resistance of the toner, making it difficult to copy on plain paper, and making the charge on the toner surface uneven. .

As a method for treating the surface of such a toner, Japanese Patent Laid-Open No.
No. 54-76233 discloses a method of treating residual polyvinyl alcohol with a melamine condensate to insolubilize it, and a method of depositing a ketone-aldehyde resin on the toner surface by a coacervation method.

However, there is a problem that sufficient electric resistance of the toner cannot be obtained even if the residual polyvinyl alcohol is insolubilized. In addition, the coacervation method requires the use of an organic solvent, and other easy processing methods are required. Was needed.

(Problems to be Solved by the Invention) An object of the present invention is to improve non-uniform charging of the toner surface generated in water, hydrophilicity of the toner surface, and poor triboelectric charging property due to resistance reduction.

[Structure of Invention]

(Means for Solving the Problem) In the present invention, the toner particles formed in water have resin particles having an average particle diameter of 0.01 to 1 μm and a glass transition temperature of the resin.
The resin particles are adhered to the outer surface of the toner particles by mixing with an aqueous resin dispersion liquid having a temperature of 40 ° C. or higher and 100 ° C. or lower, and then the toner is dried by drying at a temperature higher than the glass transition temperature of the adhered resin. The present invention relates to an electrostatic toner having a surface coated with the above resin.

The method of producing toner particles in water according to the present invention includes, for example, the following methods, but is not limited to this method.

Toner particles produced by the suspension polymerization method are prepared by dissolving or dispersing a magnetic powder, a colorant, a wax, a thermoplastic resin, etc. in a polymerizable monomer into fine droplets in an aqueous solution containing a dispersion stabilizer. It can be obtained by carrying out polymerization. At this time, magnetic powder, colorant, etc. can be directly dispersed in the monomer as a powder without applying mechanical shearing force, but the effect can be obtained, but the binder is soluble or swollen in the monomer in advance. A better effect can be obtained by applying mechanical shearing force to disperse the mixture, mixing the dispersion in the monomer, and then initiating the polymerization.

Further, in the case of the microcapsule toner by the interfacial polymerization method, for example, there is the following manufacturing method. In addition to the binder and colorant, magnetic powder, solvent, wax, etc. added as needed are dispersed by applying mechanical shearing force to obtain an oily soft ink. The ink-like material is dispersed as fine particles in an aqueous solution containing a dispersion stabilizer by an emulsifying machine or the like, and a hard shell is formed on the particles by a known interfacial polymerization method to obtain microcapsules. The solvent is preferably one that dissolves or swells the binder, but even a solvent that does not dissolve the binder can be used as a part of the solvent. Besides this,
For example, there is a method disclosed in JP-A-60-57350.

The particle size of the toner particles obtained by the above method is in the range of 5 to 20 μm.

In all of these methods for producing toner particles in water, a dispersion stabilizer agent is used in order to stably disperse the toner particles in water.

As dispersion stabilizers, polyvinyl alcohol, polyvinylpyrrolidone, hydroxyethyl cellulose, carboxymethyl cellulose, cellulose gum, silica powder,
Examples include water-soluble polymer compounds such as sodium lauryl sulfate and sodium oleate, metal oxides, and surfactants.
These dispersion stabilizers act to make the toner particles finer and to make the particle diameter uniform, but they remain on the toner surface even after washing, and it is difficult to completely remove them. This remnant is
This may cause uneven charging on the toner surface and poor charging due to a decrease in resistance on the toner surface.

In the present invention, the toner particles obtained by the above method are mixed with an aqueous dispersion liquid of a resin having a particle diameter smaller than that of the toner particles to adhere the resin particles to the surface of the toner particles. Such an aqueous resin dispersion does not contain an activator,
The dispersion liquid produced by so-called soap-free emulsion polymerization can be used as it is or after being concentrated.

A dispersion obtained by such a soap-free emulsion polymerization is a dispersion obtained by a technique disclosed in Japanese Patent Application Laid-Open No. 58-127702, 59-1503, 59-199703, etc. The particles are spherical, about 0.01 to 1μ,
Those having a uniform particle size are preferable because a uniform film can be obtained.

Further, the resin in the resin dispersion liquid is a styrene-methylmethacrylate copolymer or isobutylmethacrylate for the purpose of covering the outer surface of the toner and improving the moisture resistance of the toner or contributing to the improvement of the fixing property of the toner. -Acrylic resins such as methyl methacrylate copolymer are preferred.

It is also effective to use two or more kinds of aqueous resin dispersion liquids for the purpose of changing the properties of the outer surface of the toner in a multifaceted manner with resin fine particles having different properties.

Furthermore, in order to improve the covering density of the toner surface, it is effective to use two or more kinds of resin fine particles having different particle diameters.

The following vinyl-based monomers can be used for polymerization.

That is, as the vinyl monomer, styrene, vinyltoluene, 2-methylstyrene, styrene monomer such as t-butylstyrene, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, Acrylic acid or methacrylic acid alkyl esters such as methylmethacrylate, ethylmethacrylate, propylmethacrylate, n-butylmethacrylate, isobutylmethacrylate, 2-ethylhexylmethacrylate, monobasic acids such as acrylic acid, methacrylic acid, crotonic acid, fumaric acid, itacone Acids, dibasic acids such as maleic acid or their anhydrides, ethylenically unsaturated carboxylic acid monomers, N-methylol acrylamide, N-methylol methacrylamide, N-butoxymethyl N-substituted (meth) acrylic monomers such as crylamide, N-butoxymethylmethacrylamide, hydroxyl-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl acrylate, glycidyl methacrylate, etc. The epoxy group-containing monomer and the like.

The above resin particles have a glass transition temperature of 40 ℃ or higher, 100 ℃
It is necessary to be below, especially above 45 ℃ and below 70 ℃. This is because the particles produced by soap-free polymerization actually have hydrophilic groups on the surface, which causes the same problem as the residual dispersion stabilizer. In order to suppress the influence of this hydrophilic group, when drying the toner,
It is necessary to heat above the glass transition temperature of the adhered resin particles. At this time, the surface of the fine resin particles is made hydrophobic.
Also, by heating above the glass transition temperature of the resin fine particles, the resin fine particles are softened and the coverage and airtightness increase,
Better surface treatment is performed. At this time, when the glass transition temperature of the resin fine particles is 100 ° C or higher, the surface is not sufficiently modified by heating when drying the toner, and at 40 ° C or lower, the surface modification is good, but the storage stability of the toner is high. Causes a problem.

As for the effect of resin dispersion, 0.3 to 10 parts by weight in terms of solid content relative to 100 parts by weight of toner particles is also used. If it is less than 0.3 parts by weight, the toner surface cannot be sufficiently covered, and if it is more than 10 parts by weight, the effect just added cannot be obtained. In addition, the toner particles may aggregate.

As a method of coating the surface of the toner by adhering the resin of the resin dispersion to the surface of the toner, for example, an aqueous dispersion of the toner is mixed with an aqueous resin dispersion, stirred, and dried by a spray dryer. It is obtained by

During spray drying, even if the resin fine particles in the resin dispersion do not adhere to the outer surface of the toner and are partially mixed in the toner, the resin fine particles still have the effect as a charging aid. A favorable effect can be obtained.

The powder toner of the present invention can also be obtained by removing water by filtration or the like, drying by vacuum drying, hot-air drying or the like without using a spray dryer, and then crushing the dried product.

In addition, after mixing the toner dispersion and the aqueous resin dispersion, the aqueous resin dispersion around the toner is added by means such as addition of a solvent, pH adjustment, heating or cooling agglomeration, and particle charging. You may use the operation which attaches the resin inside.

In the present invention, it is also effective to add other particles to the resin particle dispersion liquid and to adhere the resin particles together with the resin particles for the purpose of charge control and other purposes.

As such charge control agents, oil-soluble dyes, metal-containing dyes, acid dyes, metal salts of naphthenic acid, fatty acid metal soaps and the like are used.

In addition, hydrophobic silica for the purpose of fluidity modification, carbon random, alumina, cerium oxide, etc. as abrasives,
Further, as the lubricant, fine powder of metallic soap, fine particles of polyvinylidene fluoride, polytetrafluoroethylene, etc. can be used.

Examples of the present invention will be described below. In the examples, parts indicate parts by weight.

Example 1 A separable flask equipped with a stirrer, a thermometer, a condenser, a dropping funnel, and a gas introduction tube was preheated to 80 ° C.
Add 1500 g of 2.0% polyvinyl alcohol (Nippon Gosei Kagaku Co., Ltd. trade name GH-20) aqueous solution and a liquid material premixed according to the following prescription, and use a volume of 3 l Ultra Homo Mixer (Nippon Seiki Co., Ltd.) to 1000 rpm And stirred for 10 minutes.

Styrene 240 g Methyl methacrylate 60 g Tetraferric oxide powder 300 g Benzoyl peroxide 60% xylene solution 12 g After stirring was stopped, the above emulsion was replaced with nitrogen,
Stir at low temperature for 7 hours at ℃, continue polymerization reaction, average particle size 12μ
To obtain spherical toner particles. The operation of stirring, washing and decanting with warm water of 50 ° C. was repeated 4 times.

Next, after removing the supernatant liquid of the toner particles so that the solid content is 30%, an aqueous resin dispersion liquid (ME, manufactured by Soken Chemical Co., Ltd.)
−4651; Butyl acrylate resin (glass transition temperature 60
C.) 20% dispersion having a resin particle size of about 0.2μ) was mixed with the spherical resin fine particles so as to be 3%.

The above mixture was spray-dried with a spray dryer (Palvis GA-31 Yamato Chemical Co., Ltd.) at an inlet temperature of 120 ° C.
Then, 0.5% of colloidal silica (R-972, manufactured by Nippon Aerosil Co., Ltd.) was added to the powder obtained by spray drying, and then vacuum dried on a plate heated to 70 ° C. for 6 hours,
Toner particles were used.

A printing test was conducted on the above toner particles with a commercially available copying machine (UBix1200, manufactured by Konishi Rokusha Kogyo Co., Ltd.), and good images were obtained even under high temperature and high humidity (30 ° C., 70% RH). It was

Comparative Example 1 In Example 1, spray drying was performed without adding the aqueous resin dispersion. Add colloidal silica (R-972) to the obtained powder.
0.3% of Nippon Aerosil Co., Ltd. was added and the same test as in Example 1 was conducted, but almost no image was obtained.

Comparative Example 2 In Example 1, as an aqueous resin dispersion, SIXEN A (self-emulsifying polyolefin particle diameter of several micron of Iron Manufacturing Chemical Co., Ltd.) was used. However, since the resin particles are coarse, the toner particles are not coated. It was insufficient.

Example 2 Synthetic wax (Sun Wax 131-P manufactured by Sanyo Kasei Co., Ltd.) 5 parts Ethylene-vinyl acetate copolymer (containing 30% vinyl acetate) 5 parts Petroleum-based resin (Corporex # 2100 Toho Petroleum Resin)
5 parts Dioctyl phthalate 10 parts High boiling point solvent (Hisol 100 manufactured by Nippon Petrochemical Co., Ltd.) 20 parts Magnetic powder (EPT-500 manufactured by Toda Kogyo Co., Ltd.) 40 parts The mixture of the above formulation is dispersed with a three-roll mill to give a soft ink. Obtained.

To 300 parts of this ink material, 70 parts of isocyanate (Millionate MR-200 Nippon Polyurethane Co., Ltd.) was added and mixed, and then 0.75% polyvinyl alcohol aqueous solution 1200
In addition to the parts, emulsification was performed for 5 minutes at 10,000 rpm with a colloid mill (a tabletop colloid mill manufactured by Nippon Seiki Co., Ltd.).

After emulsification, the emulsified liquid was transferred to another container, and 180 parts of a 10% aqueous solution of diethylenetriamine was added thereto while stirring at a low speed, followed by stirring for 3 hours to produce microcapsules by an interfacial polymerization reaction.

After standing overnight, the supernatant was removed, and the operation of stirring and washing with warm water at 50 ° C. and decanting was repeated four times to adjust the pH of the emulsion to about 6.

An aqueous dispersion of the above-mentioned toner particles has a solid content of toner particles of 30%.
After removing the supernatant so that it becomes, an aqueous resin dispersion (ME-4A51 manufactured by Soken Chemical Industry Co., Ltd .; butylmethacrylate resin (glass transition temperature 45 ° C) 20% dispersion with a resin particle size of about 0.2μ) , So that the solid content of the toner particles was 3%.

The above mixture was spray-dried with a spray dryer (Palvis GA-31 Yamato Scientific Co., Ltd.) at an inlet temperature of 120 ° C.

The powder obtained by spray drying was subjected to the same post-treatment as in Example 1, and a commercially available copying machine (U, manufactured by Konishi Roku Photo Co., Ltd., U) was used.
When a printing test was performed with Bix1200), good images were obtained.

Comparative Example 3 In Example 2, spray drying was performed without adding the aqueous resin dispersion liquid. Add colloidal silica (R-972) to the obtained powder.
Example 2 by adding 0.3% of Nippon Aerosil Co., Ltd.
A similar test was conducted, but almost no image was obtained.

Comparative Example 4 In Example 2, N, N-dimethylolurea was added instead of the aqueous resin dispersion to insolubilize the residual polyvinyl alcohol, but the resistance of the toner was lower than that of the powder of Comparative Example 1. It was observed and almost no image was obtained.

Comparative Example 6 After washing the microcapsules obtained by interfacial polymerization in Example 2, water was removed and then washed with methanol.

This was made into a dispersion having a solid content of 25% in methanol, and then a methanol solution of a ketone-aldehyde resin was added so as to have a solid content ratio of 3% by weight based on the solid content of the microcapsules. .

Next, water is added to the methanol dispersion to obtain a ketone-
The aldehyde resin was deposited on the toner particles. This dispersion was spray dried. However, when the microcapsules were washed with methanol, the core component in the capsules was dissolved through the shell in methanol, so that only sticky powder was obtained by spray drying.

It was also confirmed that the resistance was lower than in Comparative Example 3.

Comparative Example 7 Instead of ME-4A51 as the aqueous resin dispersion in Example 2, VE-2029 (styrene-methylmethacrylate copolymer, particle size about 0.2 μ, glass transition temperature 120 ° C., spherical resin fine particles 20 % Dispersion, manufactured by Soken Chemical Industry Co., Ltd., the same test as in Example 2 was performed, and the image density was slightly lowered. Also, when these toners were put in an oven at 160 ° C for 5 minutes, the one using VE-2029 was ignited because the ink inside the capsule was vaporized because the coating layer was not completely airtight. Those using −4A51 did not ignite.

Example 3 Petroleum-based resin (DRA-100P manufactured by Toho Petroleum Resin Co., Ltd.) 2
Part Paraffin wax (SP-0145 Nippon Seiro Co., Ltd. 7 parts Carnauba wax (Powder 1 Nippon Seiro Co., Ltd.)
55 parts Toluene 30 parts Magnetic powder (MAT305 Toda Kogyo Co., Ltd.) 40 parts Diisopropylnaphthalene 10 parts The mixture of the above formulation was melt-dispersed with a homodisper.

To 200 parts of the above melt dispersion, 45 parts of heated isocyanate (same as in Example 2) was added, mixed and dissolved, and then 80
The mixture was added to 1500 parts of a 2% aqueous solution of polyvinyl alcohol heated to ℃, and emulsified at 10,000 rpm for 3 minutes using a homomixer (UH-10 manufactured by Nippon Seiki Co., Ltd.).

After emulsification, 150 parts of 10% aqueous solution of diethylenetriamine was added, and stirring was continued for 3 hours to produce microcapsules by interfacial polymerization reaction.

Hereinafter, the aqueous resin dispersion was coated by the same operation as in Example 2. When a printing test similar to that in Example 2 was performed, a good image without fog could be obtained.

〔The invention's effect〕

According to the present invention, since the toner particles are emulsified (crushed) in water in a liquid state, the energy required for the crushing can be greatly reduced as compared with the conventional method. In addition, the toner particles generated in water can be treated in the state of the aqueous dispersion, and the coating treatment can be performed without a drying step.

Further, since the aqueous resin dispersion can be used as it is obtained by emulsion polymerization, it is inexpensive because it does not go through the steps of drying and collecting for powdering fine particles.

In addition, the step of agglomerating fine particles generated during powdering to obtain resin fine particles from the aqueous resin dispersion liquid and the step of crushing the fine particles can be omitted, and therefore, it is easy to uniformly attach the fine particles to the surface of the toner.

Further, since the above aqueous resin dispersion forms a high resistance coating having good moisture resistance on the surface of the toner after drying, the dispersion stabilizer used during the emulsification of the core substance remains on the surface of the toner. However, the toner can have good moisture resistance.

Claims (4)

[Claims] 1. A toner particle produced in water, wherein the resin particle has an average particle diameter of 0.01 to 1 .mu.
The resin particles are adhered to the outer surface of the toner particles by mixing with an aqueous resin dispersion liquid having a temperature of 40 ° C. or higher and 100 ° C. or lower, and then the toner is dried by drying at a temperature higher than the glass transition temperature of the adhered resin. An electrostatic toner having a surface coated with the above resin. 2. The electrostatic toner according to claim 1, wherein the toner particles are spherical toners produced by suspension polymerization. 3. The electrostatic toner according to claim 1, wherein the toner particles are obtained by encapsulating a core material having a pressure fixing property with a shell formed by interfacial polymerization. 4. The electrostatic toner according to claim 1, wherein two or more aqueous resin dispersions are used.