JPH01144061A - Electrostatic toner - Google Patents

Abstract

PURPOSE:To improve nonuniform electrifiability and hydrophilicity and poor triboelectrifiability due to low resistivity on the surface of a toner by mixing toner particles produced in water with an aqueous resin dispersion, attaching the resin on the surface of the toner particles, drying them at a temperature of the glass transition point of the resin or higher to coat the surfaces with the resin. CONSTITUTION:The surfaces of the toner particles are coated with the resin by mixing the toner particles produced in water with the aqueous resin dispersion having an average particle diameter of 0.01-1mum and a glass transition point of 40-100 deg.C to attach the resin to the surfaces of the toner particles, and drying them at a temperature of the glass transition point or higher, thus permitting the obtained toner particles to be improved in nonuniformity of triboelectrifiability and poor triboelectrifiability due to low resistivity.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an electrostatic toner used in a method of converting an electrostatic latent image into a visible image in electrophotography, ion flow recording, etc. .

(Prior art) As a powder toner for converting an electrostatic latent image into a visible image,
A common method is to disperse dyes, pigments, magnetic powders, etc. in toner resin by melt-kneading, mechanically crush the resultant after cooling, and then classify.

However, it has been pointed out that the toner obtained by this method has disadvantages such as being amorphous, making it difficult to obtain a uniform charge, and having poor fluidity.

Furthermore, in production, the consumption of electrical energy required for melting, kneading, and pulverization is enormous, and methods other than so-called pulverization are being considered to obtain powder toner.

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

Among these methods, the spray drying method produces toner in the form of two spheres, which provides a uniform charge and good fluidity, but requires explosion-proofing of the spray dryer and recovery of the solvent. The disadvantages include that the thermal energy required for drying is enormous, and that the solvent remains in the toner even after drying and is difficult to remove.

Furthermore, when imparting sufficient physical properties to toner, there are restrictions on the materials, and it is difficult to obtain toner with sufficient properties using this method alone.

In addition, in addition to the above, JP-A-36-10231.47-51
830.51-14895.55-50962゜59-
28164.59-152450 and the like have been proposed to produce toner using an interfacial polymerization method. These methods require less energy to generate (pulverize) particles than conventional pulverization methods.

It has the advantage that uniform spherical particles can be obtained. However, dispersants, stabilizers, etc. used during the production of toner particles in water remain on the surface of the toner particles and are difficult to remove, and even after washing and drying to form a powder toner, they absorb moisture in the air. It has been pointed out that this method lowers the electrical resistance of the toner, making it difficult to copy on plain paper, and also makes the charge on the toner surface non-uniform.

As a method for treating the surface of such toner, Japanese Patent Application Laid-open No. 5
No. 4-76233 discloses a method of treating residual polyvinyl alcohol with a melamine condensate to insolubilize it.

Further, a method of precipitating a ketone-aldehyde resin on the surface of a toner by a coacervation method is disclosed.

However, even if residual polyvinyl alcohol is insolubilized, there are problems such as not being able to obtain sufficient electrical resistance of the toner, and the coacervation method requires the use of an organic solvent, and other easy processing methods cannot be used. was needed.

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

[Structure of the invention]

(Another Means to Solve the Problem) The present invention provides toner particles produced in water in which the average particle size of the resin particles is 0.01 to 1μ and the glass transition temperature of the resin is 40°C or higher and 100°C or lower. The resin particles are attached to the outer surface of the toner particles by mixing with a certain aqueous resin dispersion, and then the toner surface is coated with the resin by drying at a temperature higher than the glass transition temperature of the attached resin. This invention relates to an electrostatic toner characterized by:

Examples of the method for producing toner particles in water in the present invention include the following method, but the method is not necessarily limited to this method.

The toner particles produced by the suspension polymerization method include magnetic powder 1 colorant.

It is obtained by polymerizing a liquid obtained by dissolving or dispersing wax, thermoplastic resin, etc. in a polymerizable monomer while dispersing it into fine droplets in an aqueous solution containing a dispersion stabilizer.

At this time, the effect can be obtained even if the magnetic powder 2 coloring agent is directly dispersed in the monomer as a powder without applying any mechanical shearing force, but it is possible to obtain the effect by dispersing the coloring agent directly in the monomer as a powder without applying any mechanical shearing force. Disperse by applying mechanical shear force.

Even better effects can be obtained by starting the polymerization after mixing this dispersion into the monomer.

In the case of microcapsule toner produced by interfacial polymerization, there are two manufacturing methods, for example, as follows. Binder 1 Magnetic powder, solvent, wax, etc. added as necessary in addition to the colorant are dispersed by applying mechanical shearing force to form an oil-based soft ink-like material. This ink-like material is dispersed as fine particles in an aqueous solution containing a dispersion stabilizer using an emulsifier or the like, and a hard shell is formed on the particles by a known interfacial polymerization method to form microcapsules. The solvent is preferably one that dissolves or swells the binder, but a solvent that does not dissolve the binder can also be used as part of the solvent. In addition to this, there is also a method disclosed, for example, in Japanese Patent Application Laid-Open No. 60-57350.

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

All of these methods of producing toner particles in water use a dispersion stabilizer to stably disperse the toner particles in water.

Examples of the dispersion stabilizer include water-soluble polymer compounds such as polyvinyl alcohol, polyvinylpyrrolidone, hydroxyethyl cellulose, carboxymethyl cellulose, cellulose gum, silica powder, sodium lauryl sulfate, and sodium oleate, metal oxides, and surfactants. These dispersion stabilizers have the effect of making toner particles finer and having a more uniform particle size, but they remain on the toner surface even after washing and are difficult to completely remove.

This residue causes non-uniform charging of the toner surface and poor charging performance 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 of a resin having a particle size smaller than that of the toner particles, and the resin particles are attached to the surface of the toner particles.

As such an aqueous resin dispersion, a dispersion produced by so-called soap-free emulsion polymerization that does not contain an activator or the like can be used as it is or after being concentrated.

Dispersions obtained by such soap-free emulsion polymerization are disclosed in JP-A-58-127702.59-1503.
．． Although it is obtained by the technique disclosed in Publication No. 59-199703, etc., the number of dispersed particles is 0.01.
It is preferable that the particles be spherical and have a uniform particle size of about 1 μm to obtain a uniform film.

In addition, the resin in the resin dispersion liquid is made of styrene-methyl methacrylate copolymer, isobutyl Acrylic resins such as methacrylate-methyl methacrylate copolymer are preferred.

Furthermore, it is also effective to use two or more types of aqueous resin dispersions for the purpose of multifacetedly changing the properties of the outer surface of the toner using fine resin particles having different properties.

Furthermore, in order to improve the coating density on the toner surface,
It is also effective to use two or more types of resin fine particles having different particle sizes.

In addition, those obtained by polymerizing the following vinyl monomers can be used.

That is, examples of vinyl monomers include styrene monomers such as styrene, vinyltoluene, 2-methylstyrene, and t-butylstyrene, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, and 2-ethylhexyl. Acrylate, methyl methacrylate, ethyl methacrylate propyl methacrylate, n-butyl methacrylate.

Acrylic acid or methacrylic acid alkyl esters such as isobutyl methacrylate and 2-ethylhexyl methacrylate, monobasic acids such as acrylic acid, methacrylic acid, and crotonic acid, dibasic acids such as fumaric acid, itaconic acid, and maleic acid, or their anhydrides. Ethylenically unsaturated carboxylic acid monomers such as N-methylol acrylamide, N-methylol methacrylamide.

N-substituted (meth)acrylic monomers such as N-butoxymethylacrylamide and N-butoxymethylmethacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate,
Examples include hydroxyl group-containing monomers such as hydroxypropyl methacrylate, and epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate.

The resin fine particles have a glass transition temperature of 40°C or higher.

It is necessary that the temperature is 100°C or lower, and particularly preferably 45°C or higher and 70°C or lower. This is because particles produced by soap-free polymerization actually have hydrophilic groups on their surfaces, 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 the toner to a temperature higher than the glass transition temperature of the attached resin particles. At this time, the surface of the resin fine particles is made hydrophobic. Further, by heating the resin particles to a temperature higher than the glass transition temperature, the resin particles are softened, coating properties and airtightness are increased, and better surface treatment is performed.

At this time, if the glass transition temperature of the resin particles is 100°C or higher, the surface will not be sufficiently modified even by heating during toner drying.
Further, at temperatures below 40° C., although surface modification is good, a problem arises in the storage stability of the toner.

For the influence of the resin dispersion, a solid content ratio of 0.3 to 10 parts by weight is used with respect to 100 parts by weight of toner particles. If it is less than 0.3 parts by weight, the toner surface cannot be sufficiently coated, and if it is more than 10 parts by weight, the effect of adding it cannot be obtained.

Furthermore, there is a possibility that toner particles may aggregate with each other.

A method for coating the surface of the toner by attaching the resin of the resin dispersion to the surface of the toner is 9, for example, mixing an aqueous resin dispersion with an aqueous toner dispersion, stirring, and drying with a spray dryer. It can be obtained by

Furthermore, during spray drying, even if the resin particles in the resin dispersion do not adhere to the outer surface of the toner and are partially mixed into the toner, the resin particles will still function as a charging aid. A desirable effect can be obtained.

In addition, without using a spray dryer, remove moisture by filtration etc., dry by vacuum drying, hot air drying etc., and then,
The powder toner of the present invention can also be obtained by crushing the dried material.

After mixing the toner dispersion and the aqueous resin dispersion, the aqueous resin dispersion can be mixed around the toner by means such as adding a solvent, adjusting the pH, heating, or adding cooling agglomeration and charging one particle. An operation for adhering the resin inside may also be used.

In the present invention, it is also effective to add other particles to the resin fine particle dispersion and deposit them on the outer surface of the toner together with the resin fine particles for charge control and other purposes.

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

In addition, hydrophobic silica is used for the purpose of improving fluidity, and carborundum, alumina, cerium oxide, etc. are used as abrasives.

Further, as a lubricant, metal soap powder, fine particles of polyvinylidene fluoride, polytetrafluoroethylene, etc. can also be used.

Two embodiments of the present invention will be described below. In the examples, 2 parts indicate parts by weight.

Example 1 In a separable flask equipped with a stirrer, thermometer, condenser, dropping funnel, and gas introduction tube, 1500 g of a 2.0% polyvinyl alcohol (Nippon Gosei Kagaku brand name GH-20) aqueous solution previously heated to 80°C and the following were added. Add the pre-mixed liquid according to the recipe, and mix at 11,000 rpm for 10 minutes using a 31-volume Ultra Homo mixer (Nippon Seiki side model).
Stir for a minute.

Styrene 240g Methyl methacrylate 60g Triiron tetroxide powder
300g benzoyl peroxide 60% xylene solution 12g After stopping stirring, the emulsion was replaced with nitrogen.

One polymerization reaction was continued by stirring at a low speed at 90° C. for 7 hours to obtain spherical toner particles with an average particle size of 12 μm. The operations of stirring, washing, and decantation with 50° C. warm water were repeated four times.

Next, after removing the supernatant liquid so that the solid content of the toner particles is 30%, an aqueous resin dispersion (ME-
4651? Butyl acrylate resin (glass transition temperature 6
0°C) 20% dispersion with a resin particle size of approximately 0.2μ).

It was mixed in an amount of 3% with respect to the spherical resin fine particles.

The above mixture was spray-dried at an inlet temperature of 120° C. using a spray dryer (Palvis GA-31 manufactured by Yamato Kagaku ■). Then, 0.5% of colloidal silica (R-972 manufactured by Nippon Aerosil ■) was added to the powder obtained by spray drying.
Thereafter, it was vacuum dried on a plate heated to 70° C. for 6 hours to obtain toner particles.

The above toner particles were applied to a commercially available copying machine (manufactured by Konishiroku Photo Industry ■,
A printing test was conducted using UB i x 1200).

Good images could be obtained even under high temperature and high humidity conditions (30° C., 70% RH).

Comparative Example 1 Spray drying was carried out in Example 1 without adding the aqueous resin dispersion. 0.3% of colloidal silica (R-972 manufactured by Nippon Aerosil ■) was added to the obtained powder, and the same test as in Example 1 was conducted, but almost no image was obtained.

Comparative Example 2 In Example 1, Zaixen A was used as the aqueous resin dispersion.
(Steel Manufacturing Chemical's self-emulsifying polyolefin particle size of several microns) was used, but the resin particles were coarse and the toner particles were insufficiently coated.

Example 2 Synthetic wax (Sunwax 131-P manufactured by Sanyo Chemical Industries) 5 parts ethylene-vinyl acetate copolymer (containing 30% vinyl acetate)
Part 5 petroleum resin (Coholex #2100 Toho Oil Resin)
5 parts dioctyl phthalate 10 parts High boiling point solvent (Hisol 100 manufactured by Nippon Petrochemicals) 20 parts Magnetic powder (EPT-500 manufactured by Toda Kogyo) 40 parts The mixture of the above formulation was dispersed in a three-roll mill to obtain a singing ink-like material. Ta.

After adding and mixing 70 parts of isocyanate (Millionate MR-200 manufactured by Nippon Polyurethane ■) to 300 parts of this ink-like material, the mixture was added to 1200 parts of a 0.75% polyvinyl alcohol aqueous solution, and the mixture was mixed with a colloid mill (Tabletop colloid mill manufactured by Nippon Seiki ■). ) for 5 minutes at 110,000 rpm.

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

After standing overnight, the supernatant liquid was removed, and the operations of stirring and washing with 50°C warm water and decantation were repeated four times.

The pH of the emulsion was set to about 6.

The aqueous dispersion of the above toner particles has a toner particle solid content of 30%.
After removing the supernatant liquid, aqueous resin dispersion (ME-4A51 manufactured by Soken Kagaku ■; butyl methacrylate resin (glass transition temperature 45°C) resin particle size of approximately 0.2μ 20
% dispersion liquid) was mixed in an amount of 3% based on the solid content of the toner particles.

The above mixture was spray-dried at an inlet temperature of 120° C. using a spray dryer (Palvis GA-31 manufactured by Yamato Kagaku ■).

The powder obtained by spray drying was subjected to the same post-treatment as in Example 1, and a commercially available copying machine (manufactured by Konishiroku Photo Industry ■) was used.

When a printing test was conducted using UBix1200), a good image could be obtained.

Comparative Example 3 In Example 2, spray drying was carried out without adding the aqueous resin dispersion. Colloidal silica (R-972
A test similar to that of Example 2 was carried out by adding 0.3% of Nippon Aerosil ■, but almost no images were obtained.

Comparative example 4 In Example 2, N was used instead of the aqueous resin dispersion.

Although N-dimethylol urea was added to insolubilize the residual polyvinyl alcohol, the resistance of the toner was observed to be lower than that of the powder of Comparative Example 1, and almost no second image was obtained.

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

This was made into a dispersion with a solid content of 25% in methanol, and then a methanol solution of ketone-aldehyde resin was prepared.

The solid content was added at a solid content ratio of 3% by weight based on the solid content of the microcapsules.

Next, water was added to the methanol dispersion to precipitate the ketone-aldehyde resin onto the toner particles. This dispersion was spray dried. However, the micro cuff.

When the cell was washed with methanol, the core component inside the capsule was dissolved through the shell in the methanol, so that only a sticky powder could be obtained even by spray drying.

Furthermore, it was confirmed that the resistance was lower than that of Comparative Example 3.

Comparative Example 7 In place of ME-4A51 as the aqueous resin dispersion in Example 2, VE-2029 (styrene-methyl methacrylate copolymer 1 particle size approximately 0.2μ, glass transition temperature 1
20% dispersion of 1 spherical resin particles at 20℃, manufactured by Soken Chemical Co., Ltd.)
When a test similar to that of Example 2 was conducted using the following, the density of one image was slightly lowered. Also, use these toners at 160
I put it in the oven at ℃ for 5 minutes.

In the case using VE-2029, the ink inside the capsule vaporized and ignited because the coating layer was not completely airtight, but the case using ME-4A51 did not ignite.

Example 3 Petroleum resin (DRA-100P manufactured by Toho Oil Resin ■)
2 parts Paraffin wax (SP-0145 Nippon Watanou ■) 7 parts Carnauba wax (Powder 1 Nippon Watanou ■) 55 parts Toluene 30 parts Magnetic powder (MA7305 Toda Kogyo side) 40 parts Diisopropylnaphthalene 10 parts Mixture of the above formulation was melted and dispersed using a homodisper.

To 200 parts of the above melted dispersion, heated isocyanate (
After adding 45 parts (same as Example 2) and mixing and dissolving, 8 parts
2% polyvinyl alcohol aqueous solution heated to 0°C 15
In addition to 00 copies, Homomixer (U) I-10th Japan side■
Emulsification was carried out for 1,010,000 rpm using

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

Thereafter, the same operation as in Example 2 was performed to coat the aqueous resin dispersion. When the same printing test as in Example 2 was carried out, a good image without capri could be obtained.

〔Effect of the invention〕

According to the present invention, since toner particles are emulsified (pulverized) in a liquid state in water, the energy required for pulverization can be significantly reduced compared to conventional methods. Further, toner particles generated in water can be treated in the state of an aqueous dispersion, and can be coated without going through a drying process.

In addition, since the aqueous resin dispersion can be used as it is in the state obtained by emulsion polymerization, it is possible to dry it to form fine particles.
It is inexpensive because it does not go through the process of replenishment.

In addition, it is possible to omit the steps of agglomeration and crushing of the fine particles that occur during powdering to obtain fine resin particles from an aqueous resin dispersion, and therefore it is easy to uniformly adhere to the surface of the toner.

Furthermore, in order to form a high-resistance coating with good moisture resistance on the surface of the toner after drying, the aqueous resin dispersion does not contain residual dispersion stabilizers used in the emulsification of the core substance on the surface of the toner. However, it can be a toner with good moisture resistance.

Claims (1)

[Claims] 1. The toner particles produced in water are prepared by using resin particles having an average particle diameter of 0.01 to 1 μm and a glass transition temperature of the resin of 40 μm.
The resin particles are attached to the outer surface of the toner particles by mixing with an aqueous resin dispersion having a temperature of at least 100 degrees Celsius, and then dried at a temperature equal to or higher than the glass transition temperature of the attached resin to form a toner surface. An electrostatic toner characterized by being coated with the above resin. 2. The electrostatic toner according to claim 1, wherein the toner particles are spherical toner produced by suspension polymerization. 3. The electrostatic toner according to claim 1, wherein the toner particles have a core material having pressure fixability encapsulated in a shell formed by interfacial polymerization. 4. The electrostatic toner according to claim 1, which uses two or more kinds of aqueous resin dispersions.