JPH02248959A - Method for manufacturing color toner particles - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a color developer used in electrophotography, electrostatic printing, etc. [Prior Art] Many electrophotographic methods have been known in the past, but generally a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means. Next, this latent image is developed using toner, and if necessary, the toner image is transferred to a transfer material such as paper, and then fixed by heating, pressure, etc., to obtain a copied image. Conventionally, toners used in these development methods are fine powders in which dyes and pigments are dispersed in synthetic resins. Particles obtained by dispersing a colorant and pulverizing particles to about 5 to 20 microns are used as toner. As the magnetic toner, one containing magnetic particles such as magnetite is used. In addition, in the case of a system using a so-called two-component developer, the toner is usually mixed with carrier particles such as iron powder, ferrite powder, those further coated with resin, or a mixture of resin and magnetic fine powder and granulated. and used. [Problem B to be solved by the invention] Toner for electrophotography is adaptable to any environment in which it is used and can be used continuously, so it has triboelectric properties,
Thermal properties, grindability, moisture resistance, powder fluidity, proprietary physical and
Color electrophotographic toners, which have been attracting attention in recent years, are required to have chemical properties, and of course they meet these properties, but in addition, toners must have certain chemical properties in order to faithfully reproduce the original. Good hue, saturation, transparency, and tinting power are required as essential conditions. On the other hand, various dyes and pigments have traditionally been used as colorants, which are the materials that determine the color of color toners. Among them, organic pigments are often used because of their vivid hue and excellent light fastness. ing. However, it is not easy to uniformly disperse organic pigments in binder resins for toners. For example, it is difficult to obtain the desired dispersion coloring for highly agglomerated pigments using the normal hot melt cross-fertilization method. The process also tends to involve multiple steps, which increases the work cost. In particular, for full-color toners whose main characteristic is color mixing by melting, there is a tendency to select binder resins with relatively low viscosity during heat-melting and fixing. is not desirable. Furthermore, in the suspension polymerization method, which is currently being developed as a method for producing toner, various studies have been conducted on the dispersion of pigments, particularly dispersion of pigments into low-viscosity liquids such as monomers.
It is still insufficient and further improvement is desired. As described above, for color toners, there is a strong demand for improvements in the pigment manufacturing process from the viewpoint of improving the dispersibility of the pigments used. For example, in the case of copper phthalocyanine pigments, ordinary crude copper phthalocyanine takes the form of coarse particles ranging from several microns to several 10 H, so as it is, the color is unclear and the coloring power is poor, so it is difficult to make pigments by mechanical or chemical means. to obtain the appropriate particle state. Chemical pigmentation, such as acid paste method or acid slurry method, is generally used for copper phthalocyanine.
Both methods involve dissolving crude copper phthalocyanine in an acid such as sulfuric acid and dispersing it in water to obtain fine particles.・It is recovered through a washing and drying process, but during this process, it becomes coarse aggregated particles with a size of several tens of microns due to drying and agglomeration. Therefore, when this pigment is used in a toner, coarse particles remain in the toner using ordinary mechanical dispersion means, and as a result, the coloring power of the phthalocyanine pigment is not fully exhibited. In addition, when this pigment is used in toner production by suspension polymerization, it is similarly difficult to uniformly disperse it in the monomer, and the presence of coarse particle pigments results in insufficient coloring power, resulting in the waste of using a large amount of pigment. In addition, non-uniform dispersion in toner particles or variation among toner particles leads to non-uniform properties of the toner. In general, many pigments themselves have some degree of triboelectrification, and uneven dispersion of pigments in the toner destabilizes the toner's triboelectrification, causing a wide distribution of triboelectrification and It also has a large effect on photographic developability, leading to defects such as development fog and scattering. As in this example, in the case of many organic pigments that are produced by a washing, filtering and drying process via an aqueous medium system, aggregation during the production process is an important problem. An object of the present invention is to provide a color toner for use in electrophotography that solves the above-mentioned problems. In other words, the dispersion of the colorant in the toner is uniform, the triboelectric charging properties of the toner particles are uniform and stable, and the coloring power and
To provide a color toner with high transparency and saturation. Another object of the present invention is to provide a method for achieving pigment dispersion in suspension polymerization much more efficiently and better than previously. [Means and effects for solving the problems] The present invention involves mixing an aqueous dispersion of a pigment or a water-containing cake with a polymerizable monomer in the process of producing a polymerized color developer containing an organic pigment, A color toner for electrophotography and a method for producing the same are characterized in that the color toner is produced through a step of transferring and dispersing a pigment in a polymerizable monomer. In the present invention, an aqueous dispersion or a water-containing cake of a finely divided organic pigment pigmented in an aqueous medium is not dried as usual, but is mixed directly into a polymerizable monomer to form a finely divided organic pigment. By transferring and dispersing pigments into the monomer phase without agglomerating them, it is possible to achieve a much better dispersion state than by mechanically dispersing dry, aggregated pigments into monomers. This is based on the knowledge that the polymerized color toner obtained by this method has excellent coloring properties and triboelectric charging properties. The aqueous dispersion of the pigmented organic pigment in the form of fine particles is dehydrated by, for example, a filter press, and has a water content of 60 to 80%.
．． It becomes a concentrated liquid of ii amount%. This water-containing cake is mixed with monomer to obtain a pigment water/monomer dispersion. The mixing ratio of JIL polymer and pigment dispersion acid in the water-containing cake depends on the amount of pigment required in the final toner, but is 5 to 200 parts by weight per 100 parts of monomer. It is blended within the range of. At this stage, due to its lipophilic nature, the pigment transfers as fine particles from the aqueous phase to the monomer phase and is uniformly dispersed in the monomer phase. If the amount of pigment added to the monomer falls within this range, the amount of pigment in the toner becomes excessive, impeding the sharpness of coloring and adversely affecting the triboelectric charging properties of the toner. Further, if the amount is below this range, the pigment will be insufficient and the coloring power will be insufficient. The amount of pigment ultimately required in the toner is - 1 to 20 parts per toner for boat fishing! The amount is more preferably 2 to 15% by weight. The monomer phase in which the pigment is dispersed is separated from the aqueous phase, and into this monomer phase are added an anti-offset agent, a charge control agent, an additional colorant, etc. necessary for forming the toner, and then the polymerized toner is added. Additives necessary for the polymerization reaction to obtain the polymer, such as a polymerization initiator and a crosslinking agent molecular weight regulator in the case of vinyl polymerization, are added. Thereafter, polymerization is carried out according to a known polymerization method to obtain colorant-containing toner particles. Colored particles obtained by the polymerization method can be obtained, for example, by the method shown below, but are not limited to these, monomers, colorants, polymerization initiators, and if necessary, crosslinking agents, charge control agents, polar polymers. A monomer system in which other additives are uniformly dissolved or dispersed is introduced into an aqueous phase (ie, continuous phase) containing a suspension stabilizer, and granulated and polymerized with stirring. Thereafter, the suspension stabilizer is removed, and the product is obtained by heating and drying. It is particularly preferable to obtain colored particles by such a suspension polymerization method because the particle size distribution is sharp. Polymerizable monomers that can be applied to form polymerized colored particles are monomers having a C1h-C< group as a reactive group, such as styrene, 0-methylstyrene, ■-methylstyrene, p-methylstyrene, p- Methoxystyrene, p-
Styrene such as ethylstyrene and its derivatives Niacrylic acid, methacrylic acid, maleic acid, maleic acid esters:
Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethyl methacrylate Methacrylic esters such as aminoethyl, diethylaminoethyl methacrylate, methyl niarylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate , acrylic esters such as stearyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate; reactive double bonds such as vinyl groups in acrylic acid or methacrylic acid moiety conductors such as acrylonitrile, methacrylonitrile, and acrylamide. There are monomers with These may be used alone or in combination. If necessary, a crosslinking agent may be used. Examples of the crosslinking agent include divinylbenzene, divinylnaphthalene, diethylene glycol dimethacrylate, and ethylene glycol dimethacrylate. obtain. The amount of the crosslinking agent added is usually 0.1 to 511 parts by weight per 100 parts by weight of the polymerizable monomer. In addition, a small amount of a polymer of these polymerizable monomers may be added to the monomer composition. Among the above-mentioned monomers, styrene, styrene having a substituent such as an alkyl group, or styrene Polymerized colored particles produced from a mixture of monomers and other monomers are preferred in consideration of developability and durability. Further, a preferable polymerized toner can be obtained by adding a polar polymer, a polar copolymer, or a cyclized rubber having a polar group as an additive during polymerization of the monomer to polymerize the polymerizable monomer. very. The polar polymer, polar copolymer, or cyclized rubber is preferably added in an amount of 0.5 to sag, preferably 1 to 40 parts by weight, per 100 parts by weight of the polymerizable monomer. If the amount is less than 5% by weight, it is difficult to obtain a sufficient pseudocapsule structure, and if the amount exceeds a certain part of SOW, the amount of polymerizable monomer becomes insufficient and the properties as a polymerized toner tend to deteriorate. A polymerizable monomer composition containing a polar polymer, a polar copolymer, or a cyclized rubber is suspended in an aqueous phase of an aqueous medium in which a dispersant having an opposite charge to the polar polymer is dispersed, and polymerization is carried out. That is, the cationic or anionic polymer, cationic or anionic copolymer or cyclized rubber contained in the polymerizable monomer composition preferably has an opposite charge dispersed in the aqueous medium. The polar anionic or cationic dispersant and the toner particle surface are electrostatically attracted to each other, and the dispersant covers the particle surface to prevent the particles from coalescing and stabilize them. Since the copolymer or cyclized rubber gathers on the surface layer of the toner particles, they form a kind of shell-like form, and the resulting particles become pseudo-capsules. Since the relatively high molecular weight polar polymer, polar copolymer, or cyclized rubber gathered on the surface layer of the particles encapsulates a large amount of low softening point compounds inside the toner particles, the polymer particles of the present invention have blocking properties. Examples of polar polymers (including polar copolymers and cyclized rubbers) and reverse charging dispersants that can be used in the present invention, which impart excellent developability and abrasion resistance, are shown below. Incidentally, polar polymers having a weight average molecular weight of 5,000 to 500,000 as measured by GPC are preferably used because they dissolve well in the polymerizable monomer and have durability. (i) Examples of the cationic polymer include polymers of nitrogen-containing monomers such as dimethylaminoethyl methacrylate and diethylaminoethyl acrylate, copolymers of styrene and the nitrogen-containing monomers, styrene, unsaturated carboxylic acid esters, etc. There is also a copolymer of the nitrogen-containing monomer and the nitrogen-containing monomer. (ii) Anionic polymers include polymers of nitrile monomers such as acrylonitrile, polymers of halogen-containing monomers such as vinyl chloride, polymers of unsaturated carboxylic acids such as acrylic acid and methacrylic acid, polymers of unsaturated dibasic acids,
There are polymers of anhydrides of unsaturated dibasic acids or copolymers of styrene and the monomer. The dispersant is preferably an inorganic fine powder that has the ability to stabilize the dispersion of monomer composition particles in an aqueous medium and is H-soluble in water.The amount of the dispersant added to the aqueous medium is based on water. It is preferable to add 0.11 to 50% by weight (preferably 1 to 20% by weight). (iii) As the anionic dispersant, Aerosil H
There are colloidal silicas such as OG and #3αO (manufactured by Nippon Aerosil Co., Ltd.). (iv) Aluminum oxide as a cationic dispersant;
Examples include magnesium hydroxide and hydrophilic positively charged silica fine powder such as aminoalkyl-modified colloidal silica treated with a coupling agent. An anionic cyclized rubber may be used instead of the above-mentioned polar polymer or copolymer. In the suspension polymerization method, a monomer composition in which a colorant or additives added as necessary are uniformly dissolved and dispersed is
An aqueous medium containing ~50% by weight of a suspension stabilizer (e.g., a poorly soluble inorganic dispersant) (e.g., heated to a temperature of 5° C. or higher, preferably 10° C. to 30° C. or higher than the polymerization temperature). The particles of the monomer composition, preferably melted or softened, are dispersed by a conventional stirrer or a homogenizer, etc. into the desired toner particle size,
301m or less in the shell (e.g. volume average particle size 0.1-20μ)
Adjust the stirring speed, time, and temperature of the aqueous medium to have the desired amount. Thereafter, the temperature of the aqueous medium is lowered to the polymerization temperature while stirring is performed to such an extent that sedimentation of the particles is prevented, so that this state is substantially maintained by the action of the dispersion stabilizer. ! It temperature is 50℃ or more, preferably 55~
set at a temperature of 80°C, particularly preferably 60-75°C,
Polymerization is carried out by adding a substantially water-insoluble polymerization initiator while stirring. After completion of the reaction, the generated toner particles are washed, removing the dispersion stabilizer, filtration, decanting, centrifugation, etc. by an appropriate method. By collecting and drying the particles, polymerized colored particles that can be used in the present invention are obtained. In the suspension polymerization method, 200 to 3000 parts by weight of water is usually used as an aqueous dispersion medium per 100 parts by weight of the polymerizable monomer and low softening point compound. In the present invention, waxes containing hydrocarbon compound rings and generally used as anti-offset agents may be added to the monomer system for the purpose of improving anti-offset properties during hot roll fixing of toner. Hydrocarbon compounds that can be used in the present invention have a melting point of 5
Paraffinic hydrocarbons in the range of 5 to 70°C are preferably used. For example, as paraffin wax, there are products manufactured by Nippon Oil and Nippon Seiro, and as branched paraffin wax, microcrystalline wax (Japan Seiro) is available. (Made from refined wax), Microwax (Made by Nippon Oil), etc. The amount of wax added is preferably 1 to 301 parts by weight per 100 parts by weight of the polymer. In addition, as the polymerization initiator, any suitable polymerization initiator,
For example, 2.2'-azobis-(2,4-dimethylvaleronitrile), 2.2'-azobisisobutyronitrile, 1.1'-azobis(cyclohexane-1-carbonitrile), 2.2' - Azo or diazo polymerization initiators such as azobis-4-methoxy-2,4-dimethylvaleronitrile and other azobisisobutyronitrile (^IBM); benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxy carbonate , Kyemen Hydroveroxide, 2.4
- Peroxide-based polymerization initiators such as dichloryl benzoyl peroxide and lauroyl peroxide can be mentioned. Generally, about 0.5 to 10% of the polymerization initiator based on the weight of the polymerizable monomer is sufficient. As the organic pigment used in the present invention, a lipophilic pigment is preferable among those that are finally produced in an aqueous medium system and made into a product through a filtration and drying process. In principle, the method of the present invention utilizes the transition of pigments from hydration to an oil phase, so the pigments must have lipophilic properties, but even those that are naturally highly hydrophilic can be treated during the manufacturing process. It can be used by making it lipophilic through surface treatment etc. For example, lipophilic pigments such as benzidine yellow and the above-mentioned copper phthalocyanine undergo oil phase migration very easily. Preferred types of pigments can be selected from a wide range of azo lake pigments, insoluble azo pigments, condensed azo pigments, phthalocyanine pigments, quinacridone pigments, and the like. The form of the pigment used may be either a suspension with a low dehydration rate or a water-containing cake (press cake) with a high dehydration rate, and the aqueous phase after pigment transfer is separated and removed. Water washing of the press cake and the like does not require strictness; in other words, the hydrophilic substances used in the pigment manufacturing process are removed together with the water, so contamination of hydrophilic substances that have a large effect on the moisture resistance of the toner can be avoided. In addition to the organic pigment used in the method of the present invention, colorants commonly used in toners can also be used in combination, and can be used in the form of being mixed into the monomer phase. In this case, in view of the purpose of the present invention, it is a prerequisite that the material has good dispersion in the monomer phase, and is selected from those that have no fear of migration into the aqueous phase. On the other hand, as the charge control substance to be added as necessary, a generally known one is selected that is anhydrous or light-colored and does not affect the hue and saturation of the color toner. For example, salicylic acid, metal complexes of dialkyl salicylic acid,
Alternatively, metal complexes of various derivatives having salicylic acid as a parent structure are preferred. Further, fine particles may be added and mixed (externally added) to the obtained toner particles for the purpose of improving fluidity. Examples of fluidity modifiers include colloidal silica, Teflon particles, and alumina particles. These are preferably blended in an amount of 0.2 to 15% by weight based on the toner particles.

【Example】

The present invention will be specifically explained below using examples. Note that the parts in the following formulations are parts by weight. Example 1 Copper phthalocyanine blue water-containing cake (water content 70%)
35 parts of styrene, 170 parts of styrene, and 30 parts of 2-ethylhexyl acrylate are mixed and stirred to transfer copper phthalocyanine to the monomer phase. Thereafter, the mixture is left to stand and separated, and then the aqueous phase and monomer phase are separated and separated to obtain a seven-mer pigment dispersion. Paraffin wax τ-5 was added to 200 parts of the obtained dispersion.
50 (manufactured by Taisei Kosan, melting point 155″F) 30 parts, G-ta
Two parts of a chromium complex of rt-butylsalicylic acid and 10 parts of a polymerization initiator (V-601) were mixed, heated to 60°C, and dissolved and dispersed to prepare a monomer system. Separately prepare an aqueous dispersion medium system. That is, ion exchange water 1
200 parts and 0.gamma-aminopropyltrimethoxysilane.
Add 25 parts of colloidal silica 1200 (Nippon Aerosil H), and heat to 60°C.
110 using a type homo mixer M type (manufactured by Tokushu Kika Kogyo)
Dispersion was carried out for 15 minutes at a rotation speed of 0 Gorp. Further l/l
A dispersion medium system was prepared by adding 0N-H (: 8.S.O.
The monomer system was suspended in the medium by stirring at Orpm for 60 minutes. The droplet size of this suspension system is approximately 8~
The suspension was transferred to a reaction vessel equipped with a paddle stirring blade, and the polymerization was completed at 70° C. for 20 hours with stirring. After the polymerization was completed, the reaction product was cooled, 20% NaOH aqueous solution was added to dissolve the dispersant, and filtration and water washing were repeated.
By drying, cyan polymerized toner particles were obtained. The particle size of the obtained cyan toner particles was measured with a Coulter Counter T^-■ type, and the volume average diameter was 11.3 microns. To 100 parts of this toner, 0.6 parts of colloidal silica (T-500, manufactured by Talco) as a fluidity imparting agent was added, and 8 parts of the silica-added toner and the surface of ferrite particles with an average particle size of 50 μm were coated with styrene. A developer was prepared by mixing with 92 parts of carrier coated with acrylic resin. Iron powder (EFV200/30) of this silica-added toner particles
The amount of triboelectrification by the blow-off method was 125 μc/g for 0° Nippon Iron Powder). Using this developer, I performed a copying test on Canon's CLC-1 and found that the initial image density was (1.45).
There were no problems with image density fluctuations, fogging, scattering, etc. during durability, and the color saturation and transparency were excellent. In addition, for the purpose of understanding the dependence on environmental humidity, copying tests were conducted under high temperature and high temperature environments, and low temperature and low humidity environments, and the performance was sufficient in both cases. Example 2 180 parts of styrene, 2-ethylhexyl acrylate 2
0 parts, quinacridone magenta water-containing cake (water content 80
%) were mixed and stirred to transfer to the monomer phase of quinacridone magenta, and then allowed to stand and separate, and the aqueous phase was removed from powder to obtain a pigment dispersion. 200 parts of the obtained dispersion, styrene-methacrylic acid copolymer (monomer ratio 90/10)
, weight average molecular weight 56,000) 10 parts, G-jerk-
2 parts of chromium complex of butylsalicylic acid, paraffin wax T-550 (manufactured by Taisei Kosan, melting point 155”F) 20
1 part, polymerization initiator (V-801) 10 parts, aO
A monomer system was prepared by heating to ℃, dissolving and dispersing. Separately, 1200 parts of ion-exchanged water, 0.5 part of γ-aminopropyltrimethoxysilane, 1200 parts of colloidal silica
(manufactured by Nippon Aerosil) was added and heated to 80°C.
1 using TK homomixer M type (manufactured by Tokushu Kika Kogyo)
Dispersion was performed at 10,000 rpm for 15 minutes. Further l/10H
Cj was added to adjust the system to pH 6 to prepare a dispersion medium system. The monomer system was added to the obtained dispersion medium system, and suspension polymerization was carried out in the same manner as in Example 1 under a nitrogen atmosphere. After the polymerization was completed, the reaction product was treated with a 20% NaOH aqueous solution to dissolve and remove silica as a dispersant, and after repeated filtration and water washing, magenta polymerized toner particles were obtained by drying. The obtained magenta toner particles had a volume average particle size of 10.8 μm as measured by a Coulter counter. 0.5 parts of colloidal silica (T-500) was added to 100 parts of the toner particles, and the silica-added toner 1
0 parts and 90 parts of carrier were mixed to prepare a two-component developer. Iron powder of the silica-added toner (EFV 200/300)
The blow-off charge amount was -23 μc/g. When this developer was used to produce images on a Canon CLC-1 color copier, sufficient image density (
1,42) was obtained, and no fogging or scattering was observed. Comparative Example 1 10 parts of copper phthalocyanine blue pigment powder that had undergone a normal dehydration and drying process, 170 parts of styrene, and 30 parts of 2-ethylhexyl acrylate were mixed and stirred to prepare a dispersion. 200 parts of the obtained pigment-dispersed monomer liquid, 30 parts of paraffin wax T-55, 2 parts of chromium di-tert-butylsalicylate complex, and 10 parts of initiator (V-601) were mixed, heated to 60°C, dissolved, and A monomer system was obtained by dispersion. Thereafter, polymerization was carried out in the same manner as in Example 1 to obtain a cyan polymerized toner and a two-component developer. When an image was produced using this developer in the same manner as in Example 1, a low image density (1, 12) was observed, which was determined to be due to insufficient coloring power of the toner. Example 3 An additional 10 parts of styrene-methacrylic acid copolymer (monomer ratio 90/10) was added to 200 parts of the monomer pigment dispersion.
Cyan polymerized toner particles were obtained in the same manner as in Example 1, except that 100% of the total weight average molecular weight was added. Furthermore, a two-component developer was prepared in the same manner as in Example 1, and CLC-
When an image was produced using No. 1, a stable and sufficient image density (1,46) was obtained, and there were no problems with fogging or scattering. Example 4 A water-containing cake of CI Pigment Yellow 12 (water content 70%) was used instead of the water-containing cake of pigment in Example 1, and 20 parts of cyclized rubber (Alpex GK- Yellow polymerized toner particles were obtained in the same manner as in Example 1 except that 514.514 (manufactured by Hoechst) was added. Furthermore, a sufficient image density (1,43) was obtained in the same image test as in Example 1, and there were no problems in image quality. [Effects of the Invention] As described above, in the toner of the present invention, the pigment in the toner is well and uniformly dispersed, so that the coloring power of the toner, that is, the coloring power and sharpness when the toner is heat-set on a support, is improved. The toner has excellent chroma and uniform triboelectric charging properties, making it possible to form images of excellent quality.

Claims (2)

[Claims] (1) After mixing a water-containing cake or an aqueous dispersion of an organic pigment with a monomer, the organic pigment is transferred and dispersed from the aqueous phase into the monomer phase by flashing treatment, and then the monomer is polymerized. A color toner containing the obtained polymer. (2) A method for producing a color developer containing a polymer obtained by polymerizing a monomer in the presence of an organic pigment, the method comprising: a monomer and a water-containing cake or an aqueous dispersion of the organic pigment; A method for producing a color toner, comprising a step of transferring and dispersing the organic pigment from an aqueous phase into a monomer phase by a flashing treatment after mixing, and then polymerizing the monomer.