JPH04188156A - Manufacture of polymerized toner - Google Patents

Abstract

PURPOSE:To provide a toner with an excellent coloring property by lowering the temperature of suspended solution to a temperature or less where a separation agent is deposited, and performing polymerization at the temperature. CONSTITUTION:Polymerizing monomer is suspended in an aqueous solvent at a temperature a which it is dissolved or melted, and thereafter the temperature of suspended solution is lowered so that a separation agent can be deposited, and polymerization is carried out at the temperature. When the temperature of suspended solution decreases to the temperature or less at which the separation agent dissolved or melted in the particles after being suspended starts its deposition, the viscousity of particles becomes high by the influence of the deposited separation agent, and a coloring agent once dispersed is hard to coagulate again. With this constitution, the initial dispersion condition of coloring agent can be maintained during polymerization reaction so that a toner with high coloring power can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic image developer, and more particularly to a polymerized toner for developing an electrostatic image formed in electrophotography.

[Prior Art] Many electrophotographic methods are known, as described in U.S. Patent No. 2,297,691, etc.
Generally, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, the latent image is developed using toner, and the toner image is transferred to a transfer member such as paper as necessary. After the image is transferred, it is fixed using heat, pressure, solvent vapor, etc. to obtain a copy. Furthermore, various methods have been proposed as methods for developing with toner or methods for fixing toner images, and methods suitable for each image forming process are adopted.

Generally, toner is produced by melt-mixing colorants such as dyes and pigments and additives such as charge control agents in a thermoplastic resin, uniformly dispersing the mixture, and then using a pulverizer or a classifier to form the desired particles. Methods of manufacturing toner having a diameter are known.

Toner produced by these pulverization methods requires brittleness in the binder resin in order to provide sufficient pulverization properties, and in addition, since pulverization method toners have sharp protrusions, they are further pulverized in the developing device. or susceptible to powdering. As a result, increased fogging and scattering inside the machine occur, which is undesirable.

Addition of a crosslinking agent is generally used as a method of imparting brittleness, but this method is not suitable for low-temperature fixing of toners. Furthermore, since the toner produced by the pulverization method generally has an amorphous shape, there is a limit to faithfully reproducing a latent image, which is disadvantageous for achieving high image quality. In order to achieve high image quality in the pulverization method, it is necessary to pulverize into smaller particles. However, it is difficult to balance the brittleness of the binder resin, which affects the crushing efficiency, and the thermal properties, which affect fixation and storage stability.
It has been impossible to fully satisfy these performances.

As opposed to these irregularly shaped toners, spherical toners have been proposed. For example, in Japanese Patent Publication No. 56-13945, a spherical toner is obtained by a melt spray method, and in Japanese Patent Publication No. 57-51676, a small amount of an organic solvent is added to an amorphous toner, and the mixture is stirred under cooling. A method for obtaining spherical toner by this method is further disclosed in Japanese Patent Publication No. 36-10231, Japanese Patent Application Laid-open No. 59-53856, and Japanese Patent Application Laid-Open No. 59-538.
No. 9-61842 and the like disclose a method of obtaining a spherical toner using a polymerization method.

Since these spherical toners have a uniform shape, a latent image, especially an edge portion, can be faithfully developed, so that they are suitable for achieving high image quality. Furthermore, when a spherical toner is obtained by a polymerization method, it is easy to reduce the particle size of the particles, making it suitable for achieving high image quality.

As described above, although the polymerized toner solves some of the drawbacks of the pulverized toner, it has been found that it causes new drawbacks. Polymerized toner is produced by uniformly dissolving or dispersing other additives such as a polymerizable monomer, a colorant, a polymerization initiator, and if necessary, a crosslinking agent, a charge control agent, etc. to form a monomer composition. , by dispersing this monomer composition in a continuous phase containing a dispersion stabilizer, such as an aqueous phase, using a suitable stirrer, and simultaneously carrying out a polymerization reaction. Therefore, in the initial stage of the polymerization reaction, the viscosity of the polymerizable monomer composition is very low, so that the colorant that has been dispersed in the particles may re-agglomerate. This is undesirable as it causes deterioration of the colorant in the toner.

[Problems to be Solved by the Invention] An object of the present invention is to solve the problems as described above. That is, the present invention provides a method for producing a toner with high tinting power by preventing the colorant in the particles from re-agglomerating during polymerization of the suspended particles.

[Means and effects for solving the problems] An object of the present invention is to produce a polymerized toner obtained by suspension polymerizing a polymerizable monomer system containing at least a release agent and a colorant in an aqueous medium. In the method, a polymerizable monomer system is suspended in an aqueous medium at a temperature at which the mold release agent dissolves or melts in the polymerizable monomer system, and then suspended to a temperature below which the mold release agent precipitates. This is achieved by lowering the temperature of the suspension and conducting polymerization at that temperature.

The present invention will be explained in detail below.

As a result of extensive studies, the present inventors have developed a method for producing a polymerized toner obtained by suspension polymerizing a polymerizable monomer system containing a small amount of a release agent and a colorant in an aqueous medium. The mold release agent is dissolved in the polymerizable monomer system,
Or, by suspending the polymerizable monomer system in an aqueous medium at a temperature at which it melts, then lowering the temperature of the suspension to below the temperature at which the release agent precipitates, and conducting polymerization at this temperature, It has been discovered that a polymerized toner with excellent coloring power can be obtained by preventing the colorant in the particles from re-agglomerating.

In other words, polymerized toners are produced by adding various additives such as colorants to polymerizable monomers and dispersing them in an aqueous medium to form suspended particles and carry out a polymerization reaction. Therefore, at the initial stage of the polymerization reaction, the viscosity of the suspended particles is very low, and therefore the colorant dispersed in the particles is likely to reagglomerate. Therefore, the temperature of the suspension is lowered to a temperature at which the release agent dissolved or melted in the suspended particles precipitates or lower. As a result, the viscosity of the particles becomes high due to the influence of the precipitated mold release agent, and the highly dispersed colorant becomes difficult to re-agglomerate. The dispersed state is maintained and a toner with high coloring power is obtained.

The polymerized toner used in the present invention can be obtained by the following method. That is, additives such as a mold release agent, coloring agent, and charge control agent are added to the polymerizable monomer, heated until the mold release agent is dissolved or melted, and then uniformly dissolved using a homogenizer, ultrasonic disperser, etc. Alternatively, the dispersed monomer system is dispersed in an aqueous phase having the same temperature as the monomer system containing a dispersion stabilizer using a conventional stirrer, homomixer, homogenizer, or the like. Preferably, the stirring speed and time are adjusted so that the monomer droplets have a predetermined toner particle size, generally 30 μm or less, and after that, the particle state is maintained by the action of a dispersion stabilizer, and the particle size is maintained. It is sufficient to perform stirring to an extent that sedimentation is prevented. The polymerization temperature is set to a temperature below the precipitation temperature of the mold release agent, a polymerization initiator is added, and polymerization is carried out. After the reaction is completed, the generated toner particles are collected by washing and filtration, and then dried. In the suspension polymerization method, it is usually preferable to use 300 to 3000 parts by weight of water as a dispersion medium per 100 parts by weight of the monomer system.

Examples of polymerizable monomers that can be used in the polymerized toner include styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, and p-methylstyrene.
- Styrenic monomers such as methylstyrene, p-methoxystyrene, p-ethylstyrene, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate , acrylic acid esters such as dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and n-butyl methacrylate. , isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and other methacrylic acid esters; other acrylonitrile, methacrylate; Examples include monomers such as nitrile and acrylamide.

These monomers may be used alone or in combination. Among the above-mentioned monomers, it is preferable to use styrene or styrene derivatives alone or in combination with other monomers from the viewpoint of toner development characteristics and durability.

The dispersion medium used in the present invention may include any suitable stabilizer, such as polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose, sodium salt of carboxymethyl cellulose, polyacrylic acid and its salts, starch, starch, phosphoric acid, etc. Tricalcium, aluminum hydroxide, magnesium hydroxide, calcium metasilicate, barium sulfate,
Bentonite etc. can be used by dispersing it in the water phase.

The amount of this stabilizer is 0.00 parts per 100 parts of the polymerizable monomer.
Preferably, 2 to 20 parts by weight are used.

In addition, due to the fine dispersion of these stabilizers, the
O.1 part by weight of surfactant may be used. This is to promote the intended action of the above-mentioned dispersion stabilizers, and specific examples include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, and lauric acid. sodium, potassium stearate,
Examples include calcium oleate.

It is more preferable to add and polymerize a polymer/copolymer having a polar group as an additive to the monomer system. Furthermore,
In the present invention, a monomer system containing a polar group-containing polymer/copolymer or cyclized rubber is suspended in an aqueous phase in which a dispersant having an opposite charge to the polar polymer is dispersed, and polymerization is carried out. It is preferable to do so. That is, the cationic or anionic polymer/copolymer or cyclized rubber contained in the monomer system is polymerized with the oppositely charged anionic or cationic dispersant dispersed in the aqueous phase. The particles are electrostatically attracted to each other on the surface of the particles that become the toner, and the dispersant covers the particle surface to prevent the particles from coalescing and stabilize them, and the polar polymer added during polymerization gathers on the surface of the particles that become the toner. Therefore, it takes on a kind of shell-like shape, and the resulting particles become pseudo-capsules. A relatively high molecular weight polar polymer/copolymer or cyclized rubber is used to give toner particles excellent blocking properties and developer abrasion resistance, while a relatively low molecular weight internal material improves fixing properties. By carrying out polymerization in such a way that it contributes to the fixing properties, it is possible to obtain a toner that satisfies the contradictory requirements of fixing properties and blocking properties. Examples of polar polymers/copolymers and counterloading dispersants that can be used in the present invention are shown below.

(1) Examples of the cationic polymer include polymers of nitrogen-containing monomers such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate, or copolymers with styrene, unsaturated carboxylic acid esters, and the like.

(2) Examples of anionic polymers include nitrile monomers such as acrylonitrile, halogen-containing monomers such as vinyl chloride, unsaturated carboxylic acids such as acrylic acid and methacrylic acid,
Other examples include polymers of saturated dibasic acids, unsaturated dibasic acid anhydrides, nitro monomers, and copolymers with styrene monomers. Furthermore, cyclized rubber may be used instead of these polar polymers.

(3) As the anionic dispersant, silica fine powder is preferably used, especially with a BET specific surface area of 200 m2/g
The above colloidal silicas are suitable.

(4) As the cationic dispersant, aminoalkyl-modified colloidal silica (preferably has a BET specific surface area of 20
0 m2/g or more), hydrophilic positively chargeable silica fine powder, aluminum hydroxide, and the like.

It is preferable to use such a dispersant in an amount of 0.2 to 20 M parts based on 100 parts by weight of the polymerizable monomer. More preferably, it is 0.3 to 15 parts by weight.

In the present invention, it is desirable to add a charge control agent to the toner material for the purpose of controlling the chargeability of the toner. As these charge control agents, among known ones, those having almost no polymerization inhibiting property or water phase migration property are used. For example, as positive charge control agents, nigrosine dyes, triphenylmethane dyes, quaternary ammonium salts, Examples of negative charge control agents include amine and polyamine compounds.
Examples include metal-containing salicylic acid compounds, metal-containing monoazo dye compounds, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, and the like.

As the colorant used in the present invention, known colorants can be used, such as carbon black, iron black, C, 1,
Direct Red 1, C, 1, Direct Red 4, C
,1, acid red 1, c, r, basic red 1
, C,1, Modern Tread 30, C,1, Direct Blue 1, C,1, Direct Blue 2, C,1, Acid Blue 9, C,1, Acid Blue 15, C9■,
Basic Blue 3, C, 1, Basic Blue 5, C
, 1, Mordandbruer, C,I.

Direct Green 6, C, 1, Basic Green 4
, C,1, basic green 6 dyes, yellow lead, cadmium yellow, mineral fast yellow, navel yellow, naphthol yellow S, Hansa yellow G,
Permanent Yellow NCG, Tartrazine Lake, Molybdenum Orange, Permanent Orange GTR, Benzidine Orange G, Cadmium Red, Permanent Red 4R, Watching Red Calcium Salt, Brilliant Carmine 3B, Fast Violet B, Methyl Violet Lake, Navy Blue, Cobalt Blue, Alkali Blue Lake, Victoria Blue Lake, Quinacridone,
Pigments include Rhodamine B, Phthalocyanine Blue, Fast Sky Blue, Pigment Green B, Malachite Green Lake, and Final Yellow Green G. In the present invention, since the toner is obtained using a polymerization method, it is necessary to pay attention to the polymerization inhibiting property and aqueous phase migration property of the colorant. Preferably, surface modification, such as hydrophobicity using a substance that does not inhibit polymerization, is necessary. It is better to apply chemical treatment.

As the mold release agent used in the present invention, paraffin/polyolefin waxes and modified products thereof, such as
In addition to oxides and grafted products, examples include higher fatty acids, metal salts thereof, and amide waxes. It is desirable that these waxes have a softening point of 40 to 130°C, preferably 50 to 120°C, as determined by the ring and ball method (J I SK 2531). If the softening point is 40°C or lower, the blocking resistance and shape retention of the toner will deteriorate. If the temperature is 130°C or higher, the mold release effect will be insufficient.

Such a mold release agent is preferably used in an amount of 5 to 30 parts by weight per 100 parts by weight of the polymerizable monomer.

As the polymerization initiator, any suitable polymerization initiator such as 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1
, 1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-
Azo or diazo polymerization initiators such as dimethylvaleronitrile and azobisisobutyronitrile, peroxides such as benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxy carbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, etc. Examples include polymerization initiators. In addition, the above-mentioned peroxides as redox initiators, dimethylaniline, mercaptans, tertiary amines,
It may be used in combination with a reducing agent such as an iron (II) salt or sodium bisulfite. These polymerization initiators are suitably used to obtain a desired molecular weight, but generally an amount of 0.1 to 10% by weight of the polymerizable monomer is sufficient.

The mold release agent, polymerization initiator, and polymerization temperature in the present invention will be described in more detail.

When paraffin wax or the like, which generally has a low melting point or softening point, is used as a mold release agent, the temperature at which the mold release agent precipitates from the polymerizable monomer system is low, so the polymerization temperature is also low.

In such cases, it is preferable to use a redox initiator or 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, which has a short half-life.

Conversely, when a polyolefin wax or the like having a high melting point or softening point is used, it is preferable to use an autoclave or the like to dissolve or melt the release agent in the polymerizable monomer system. In this case, the precipitation temperature of the mold release agent is relatively high compared to the case of paraffin wax, so 2,2'-
It is preferable to use a polymerization initiator such as azobis(2,4-dimethylvaleronitrile) or dimethyl 2,2'-azobisisobutyrate.

Further, additives may be added to the toner of the present invention for the purpose of imparting various characteristics. In addition, from the viewpoint of durability when added to the toner, the additive should be added to the toner at a rate of 1% of the volume average diameter of the toner particles.
It is preferable that the particle size is /10 or less. The particle size of the additive means the average particle size determined by observing the surface of toner particles using an electron microscope. As additives for the purpose of imparting these characteristics, for example, the following are used.

1) Fluidity imparting agent: metal oxides (silicon oxide, aluminum oxide, titanium oxide, etc.), carbon black, carbon fluoride, etc. Each of them is more preferably subjected to hydrophobization treatment.

2) Abrasives: Metal oxides (strontium titanate, cerium oxide, aluminum oxide, magnesium oxide, chromium oxide, etc.), nitrides (silicon nitride, etc.), carbides (
silicon carbide, etc.), metal salts (calcium sulfate, barium sulfate, calcium carbonate, etc.), etc.

3) Lubricants: Fluorine resin powders (vinylidene fluoride, polytetrafluoroethylene, etc.), fatty acid metal salts (zinc stearate, calcium stearate, etc.), etc.

4) Charge controllable particles: metal oxides (tin oxide, titanium oxide, zinc oxide, silicon oxide, aluminum oxide, etc.), carbon black, etc.

These additives are added in an amount of 0.00 parts by weight per 100 parts by weight of toner particles.
1 to 10 parts by weight are used, preferably 0.1 to 5 parts by weight. Even if these additives are used alone,
Also, a plurality of them may be used together.

Particle size distribution measurement in the present invention will be described.

A Coulter counter TA-H model (manufactured by Coulter Co., Ltd.) was used as the measuring device, and the number average distribution was used.

Interface that outputs volume average distribution (manufactured by Nikkaki)
and CX-1 personal computer (manufactured by Canon)
The electrolyte is 1% Na using primary sodium chloride.
Prepare a CA aqueous solution.

As a measuring method, 0.1 to 5 mJ2 of a surfactant, preferably an alkylbenzenesulfonate salt, is added as a dispersant to 100 to 150 mβ of the electrolytic aqueous solution, and 0.5 to 50 mg of the measurement sample is added.

The electrolytic solution in which the sample was suspended was dispersed for about 1 to 3 minutes using an ultrasonic disperser, and the particle size distribution of particles of 2 to 40 Ltm was measured using the Coulter Counter TA-II model using a 100 μm aperture. to find the volume average distribution and number average distribution.

The volume average particle diameter is obtained from the volume average distribution and number average distribution thus determined.

[Example] Hereinafter, the present invention will be explained in detail based on the present invention. Note that all parts are parts by weight.

Example 1 The above formulation was heated to 70° C. in a container to dissolve the paraffin wax, and was sufficiently dissolved and dispersed using a homomixer to obtain a monomer composition.

Separately, add 10 parts of aminoalkyl-modified colloidal silica to 1200 parts of ion-exchanged water, add the above monomer system to a dispersion medium system adjusted to pH 6 with hydrochloric acid, and heat at 70°C with TK Homomixer (manufactured by Tokushu Kika Kogyo). The monomer system was granulated using Thereafter, the suspension was lowered to 20°C, and 10 parts of benzoyl peroxide (manufactured by Wako Tsumugi Pharmaceutical Co., Ltd.) was added as a polymerization initiator, and further 5 parts of ammonium thiocyanate (manufactured by Wako Tsumugi Pharmaceutical Co., Ltd.)
part was added. Thereafter, the temperature of the suspension was raised to 40°C, and polymerization was carried out under a nitrogen atmosphere. After the polymerization was completed, sodium hydroxide was added, the dispersant was removed, and the mixture was washed with water, filtered, and dried to obtain polymerized particles.

When the obtained particles were measured with a Coulter counter (aperture diameter 100 μm), the volume average diameter was 8.0 LLm.
It had a sharp particle size distribution. After dispersing these particles in an epoxy resin and curing, they were sliced into 2 μm thick slices using a microtome and evaluated for colorant dispersibility using an optical microscope. No colorant aggregates were observed. It was found that the particles were well dispersed.Also, 0.00 parts of hydrophobized fine silica powder was added to 100 parts of these particles.
5 parts were mixed to form a toner. 94 parts of acrylic coated ferrite carrier was mixed with 6 parts of the toner to prepare a developer.

Using the developer thus obtained, Canon's CL
When image quality was evaluated using C-500, the copies were very clear.

Example 2 The above formulation was heated to 150°C in an autoclave,
Polyethylene wax was melted and thoroughly dissolved and dispersed using a homomixer to obtain a monomer composition.

Separately, in an autoclave, add 10 parts of amino-modified coloiglucylsilic acid to 1200 parts of ion-exchanged water, and adjust the pH to 6 with hydrochloric acid.
The above monomer system was added to the dispersion medium system prepared in
The monomer system was granulated using a TK homomixer (manufactured by Tokushu Kika Kogyo) at ℃. The suspension was then lowered to 80°C and
To this was added 10 parts of dimethyl 2,2'-azobis-isobutyrate as a polymerization initiator, and polymerization was carried out under a nitrogen atmosphere. After polymerization, add sodium hydroxide,
The dispersant was removed, and the mixture was washed with water, filtered, and dried to obtain polymerized particles.

When the obtained particles were measured with a Coulter counter (aperture diameter: 100 μm), they had a volume average diameter of 8.2 μm and a sharp particle size distribution. When this particulate epoxy resin was dispersed and cured, it was sliced into 2 μm thick slices using a microtome, and the dispersibility of the colorant was evaluated using an optical microscope, and no colorant aggregates were observed. It was found that the agent was well dispersed.Also, 0.00 parts of hydrophobized fine silica powder was added to 100 parts of the particles.
5 parts were mixed to form a toner. 94 parts of acrylic coated ferrite carrier was mixed with 6 parts of the toner to prepare a developer.

Using the developer thus obtained, Canon's CL
When image quality was evaluated using C-500, the copies were very clear.

Example 3 Polymer particles were obtained in the same manner as in Example 1, except that the monomer composition was used as a dispersion medium system.

When the obtained particles were measured with a Coulter counter (aperture diameter 100 μm), the volume average diameter was 8.8 μm.
It had a sharp particle size distribution. These particles were dispersed in epoxy resin, and after curing, 2 μm was measured using a microtome.
The sample was sliced to a thickness of 100 mL, and the dispersibility of the colorant was evaluated using an optical microscope. No aggregates of the colorant were observed, and it was found that the colorant was well dispersed. Further, 0.5 part of amino-modified fine silica powder was mixed with 100 parts of the particles to prepare a toner. 94 parts of acrylic coated ferrite carrier was mixed with 6 parts of the toner to prepare a developer.

Using the developer thus obtained, Canon's NP
When image quality was evaluated at -3525, the copies were very clear.

Comparative Example 1 Using the same monomer composition and dispersion medium as in Example 1, granulation was carried out at 70°C, and 10 parts of dimethyl 2,2'-azobis-isobutyrate was added as a polymerization initiator. was added and polymerization was carried out at the same temperature. After the polymerization was completed, sodium hydroxide was added, the dispersant was removed, and the mixture was washed with water, filtered, and dried to obtain polymerized particles. When the obtained particles were measured with a Coulter counter (aperture diameter: 100 μm), they had a volume average diameter of 8.5 μm and a sharp particle size distribution. The particles were dispersed in epoxy resin, and after curing, sliced into 2 μm thick pieces using a microtome.
When the dispersibility of the colorant was evaluated using an optical microscope, some aggregates of the colorant were observed.

Comparative Example 2 Polymer particles were obtained by carrying out the same operation as in Example 1 without using paraffin wax. When the obtained particles were measured with a Coulter counter (aperture diameter: 100 μm), they had a volume average diameter of 7.8 parts m and a sharp particle size distribution.

These particles were dispersed in epoxy resin, and after curing, they were sliced into 2 μm thick slices using a microtome, and when the dispersibility of the colorant was evaluated using an optical microscope, some colorant aggregates were observed. .

[Effects of the Invention] As described above, according to the present invention, a toner with excellent dispersibility of colorant in toner particles and high coloring power can be obtained.

Claims (1)

[Claims] (1) In a method for producing a polymerized toner obtained by suspension polymerizing a polymerizable monomer system containing at least a release agent and a colorant in an aqueous medium, the release agent is included in the polymerizable monomer system. The polymerizable monomer system is suspended in an aqueous medium at a temperature at which it dissolves or melts, and then the temperature of the suspension is lowered to below the temperature at which the release agent precipitates, and polymerization is carried out at this temperature. A method for producing a polymerized toner, characterized by: