JPH04318559A - Manufacture of negatively chargeable toner - Google Patents

Abstract

PURPOSE:To enhance resolution, sharpness, halftone reproduction performance, cleaning performance, and the like, to reduce variation of chargeable amount due to environment, and to stabilize chargeability against the lapse of time by oxidizing the surface of colored resin particles. CONSTITUTION:Synthetic resin particles fine in particle diameter and narrow in particle diameter distribution are dyed and the surfaces of the dyed resin particles are oxidized by dry method, and further oxidized by low temperature plasma reaction to control the ratio between carbon of surface and oxygen to be combined to 1-50 atomic % in the surfaces. The resin particles to be used is preferably, prepared by adding a polymer dispersant soluble in a hydrophilic organic solvent, a vinyl monomer soluble in this solvent but almost insolubilized only swellable in it when polymerized.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to electrophotography, electrostatic recording,
The present invention relates to a method for producing a negatively chargeable toner for developing an electrostatically charged image in electrostatic printing or the like.

0002

[Prior Art] As means for developing an electrostatic latent image formed on an electrophotographic photoreceptor or an electrostatic recording medium, there are two methods: a method using a liquid developer (wet development method), and a method using a liquid developer (wet development method). dye,
A method using a toner in which colorants such as pigments and a charge control agent are dispersed as necessary, or a one-component or two-component dry developer in which this toner is mixed with a solid carrier (dry development method). is generally adopted. and,
Although each of these methods has its own advantages and disadvantages, the dry developing method is currently in most use.

Incidentally, in order to provide high image quality and high durability, toner particles are required to have small particle size, sharp particle size distribution, sufficient coloring power, and uniform charging control. That is, reducing the particle size improves qualities such as resolution, sharpness, halftone reproducibility, and photographic reproducibility. Further, a sharp particle size distribution improves particularly halftone reproducibility and photographic reproducibility. Furthermore, the particle size distribution of the toner in the developer does not change even when used for a long time, resulting in stable image quality and a longer lifespan of the developer.

[0004] Toner manufactured by the conventional general manufacturing method of toner, that is, a method in which resin, dye/pigment, and charge control agent are melt-kneaded, and then crushed and classified using a mechanical or air collision type crusher. In particular, when attempting to obtain particles of small size, there are the following drawbacks. That is, (1) production capacity and yield decrease, resulting in higher costs. (2) As the particle size becomes smaller, toner charging characteristics become poorer due to non-uniform dispersion of the charge control agent, and background smearing and toner scattering are more likely to occur. (3) Furthermore, the surface of the small particle diameter toner obtained by pulverization has many protrusions, which tends to cause filming on the carrier, triboelectric charging member, or photoreceptor. (4) When the particle size is reduced, the coloring power of each toner becomes weaker. (5) It is difficult to clean small particle size toner remaining on the photoreceptor. (6) If an attempt is made to obtain a toner with a particularly narrow distribution, the production capacity and yield will be significantly reduced, the cost will increase, and even if classification is repeated, there is a limit to the particle size distribution that can be obtained.

[0005] Therefore, many proposals have been made regarding toners that provide high image quality and high durability and methods for producing the toners. For example, core particles containing colored pigments and charge control agents may be formed by a suspension polymerization method (Japanese Patent Publication No.
14895, Japanese Patent Publication No. 47-51830), this method uses a dispersion stabilizer that adheres to the surface,
It is difficult to remove surfactants, etc., easily causes electrostatic deterioration, and is also susceptible to environmental fluctuations. Furthermore, with this method, it is difficult to stably produce particles with a small particle size and a narrow particle size distribution.

On the other hand, as a method for easily obtaining toner with a small particle size and a narrow particle size distribution, Japanese Patent Application Laid-Open No. 58-106554
No. 61-18965 and No. 61-275766, attempts are made to produce toners with a so-called core-shell structure by attaching and coating colorants and toner characteristic imparting substances onto particles with a narrow particle size distribution. However, toners having such a structure have the disadvantage of poor electrical properties and durability due to the presence of coloring substances and other substances on the surface.

[0007] Furthermore, as another toner manufacturing method, a method has been proposed in which resin particles are immersed in a dye solution and dyed (Japanese Patent Application Laid-Open Nos. 50-46333 and 1999-10363).
No. 1, JP-A-56-154738, JP-A No. 61-2284
No. 58, No. 63-106667, No. 64-90454
Publications, etc.). Although these methods are preferable because they require fewer manufacturing steps, none of them have been sufficiently tested, and it is unclear whether the dye is uniformly colored within the particles, and furthermore, the above-mentioned literature does not Knowledge of the content alone was not enough to put it into practical use. In addition, JP-A-61-22
Publication No. 8458 describes an attempt to color particles by adding a dye to particles produced by dispersion polymerization, but according to this method, the polarity of the toner can be controlled by a dispersion stabilizer permanently attached to the particle surface. Therefore, the triboelectric charging property is unstable due to environmental changes, and the stability over time is also poor. Furthermore, in the proposed toner,
In either case, the problem of poor cleaning due to the reduction in particle size has not been sufficiently solved.

[0008]

[Problems to be Solved by the Invention] In other words, a toner with a small particle size and narrow particle size distribution that has sufficiently stable triboelectric charging characteristics and good cleaning properties has not yet been found. This is the current situation.

Therefore, an object of the present invention is to provide a manufacturing method capable of obtaining a small-sized toner having a narrow particle size distribution that solves the above-mentioned problems. A toner that is highly colored, has excellent properties and photographic reproducibility, has little change in charge due to the environment, has stable chargeability over time, and has good cleaning properties. The purpose is to provide a method.

0010

[Means for Solving the Problems] As a result of intensive studies, the present inventors found that a manufacturing method including a step of oxidizing the surface of colored resin particles is suitable for the above purpose, and completed the present invention. reached.

That is, according to the present invention, after coloring small synthetic resin particles with a narrow particle size distribution by a dyeing method, the surface of the obtained colored resin particles is oxidized by a dry method. A method for producing a negatively chargeable toner is provided.

According to the method of the present invention, small particle size synthetic resin particles having a narrow particle size distribution are colored by a dyeing method, and the surface of the obtained colored resin particles is dry oxidized to obtain small particle size and narrow particle size distribution. A highly reliable toner with a particle size distribution, high coloring power, excellent resolution, sharpness, halftone reproducibility, and photographic reproducibility, and a stable charge amount against changes in the environment and over time. .

(Synthetic Resin Particles) In the present invention, small-sized synthetic resin particles with a narrow particle size distribution are used as raw materials. In this case, the synthetic resin particles are prepared by adding a polymer dispersant that dissolves in the organic liquid to a hydrophilic organic liquid, and then adding a polymer dispersant that dissolves in the organic liquid. resin particles (hereinafter referred to as resin particles
) is preferably used. The resin particles A usually have a ratio of volume average particle diameter (Dv) to number average particle diameter (Dp) of 1.
It is in the range of 00≦(Dv/Dp)≦1.20, and Dv is 1 to 10 μm.

[0014] The method for producing the resin particles A also includes a reaction in which a polymer having a narrow particle size distribution, which is smaller than the target particle size, is used and grown in the above-mentioned system. The monomer utilized in the growth reaction may be the same monomer that produced the seed particles or a different monomer, but the polymer must not be soluble in the hydrophilic organic liquid.

Examples of the hydrophilic organic liquid used as a monomer diluent during the formation of the seed particles and the growth reaction of the seed particles include methyl alcohol, ethyl alcohol, denatured ethyl alcohol, isopropyl alcohol,
n-butyl alcohol, isobutyl alcohol, ter
t-butyl alcohol, sec-butyl alcohol, t
Alcohols such as ert-amyl alcohol, 3-pentanol, octyl alcohol, benzyl alcohol, cyclohexanol, furfuryl alcohol, tetrahydrofurfuryl alcohol, ethylene glycol, glycerin, diethylene glycol; methyl cellosolve, cellosolve, isopropyl cellosolve, butyl cellosolve, ethylene Examples include ether alcohols such as glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, and diethylene glycol monoethyl ether. These organic liquids can be used alone or in a mixture of two or more.

[0016] Organic liquids other than alcohols and ether alcohols can be used in combination with the above-mentioned alcohols and ether alcohols under various conditions that do not provide solubility to the polymer particles produced in the organic liquid. By changing the SP value and changing the polymerization conditions, it is possible to suppress the size of the particles produced, the coalescence of seed particles, and the generation of new particles. In this case, organic liquids used in combination include hydrocarbons such as hexane, octane, petroleum ether, cyclohexane, benzene, toluene, and xylene; halogenated hydrocarbons such as carbon tetrachloride, trichlorethylene, and tetrabromoethane; ethyl ether; , dimethyl glycol, trioxane, tetrahydrofuran, and other ethers; methylal, diethyl acetal, and other acetals;
Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexane; Esters such as butyl formate, butyl acetate, ethyl propionate, and cellosolve acetate; Acids such as formic acid, acetic acid, and propionic acid; Nitropropene, nitrobenzene, and dimethylamine , sulfur- and nitrogen-containing organic compounds such as monoethanolamine, pyridine, dimethyl sulfoxide, and dimethyl formamide;
Also includes water.

[0017] In the above-mentioned solvent mainly composed of a hydrophilic organic liquid, SO4 ions (-2 valence), NO2 ions (-1 valence), P
O4 ion (-3 valence), Cl ion (-1 valence), Na ion (+1 valence), K ion (+1 valence), Mg ion (+
Polymerization may be carried out in the presence of Ca ions (+2 valence), Ca ions (+2 valence), and other inorganic ions. Furthermore, by changing the type and composition of the mixed solvent at the start of polymerization, during polymerization, and at the end of polymerization, it is possible to adjust the average particle size, particle size distribution, drying conditions, etc. of the resulting polymer particles.

[0018] Suitable examples of the polymeric dispersant used during the production of the seed particles or the production of the grown particles include:
For example, acids such as acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride; acrylic monomers containing hydroxyl groups, such as acrylic β-hydroxyethyl acid, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, γ-hydroxypropyl acrylate, γ-hydroxypropyl methacrylate, 3-chloro-2-hydroxy acrylate Propyl, 3-chloro-2-hydroxypropyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerin monoacrylate, glycerin monomethacrylate, N-methylol acrylamide, N-methylol methacrylamide, etc.; vinyl Ethers of alcohol or vinyl alcohol, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, etc.; Esters of vinyl alcohol and compounds containing a carboxyl group, such as vinyl acetate, vinyl propionate, vinyl butyrate, etc.; acrylamide, Methacrylamide, diacetone acrylamide or their methylol compounds; acid chlorides such as acrylic acid chloride and methacrylic acid chloride; homogeneous substances having nitrogen atoms or their heterocycles such as vinylpyridine, vinylpyrrolidone, vinylimidazole, and ethyleneimine; Polymer or copolymer system; polyoxyethylene, polyoxypropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl phenyl Examples include polyoxyethylene-based ethers, polyoxyethylene stearyl phenyl ether, polyoxyethylene nonylphenyl ether, and celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose.

[0019] Furthermore, the above hydrophilic monomer and styrene, α
- Those having a benzene nucleus such as methylstyrene and vinyltoluene, derivatives thereof, or copolymers such as acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; Furthermore, crosslinking monomers such as ethylene glycol dimethacrylate, Copolymers with diethylene glycol dimethacrylate, allyl methacrylate, divinylbenzene, etc. can also be used.

These polymeric dispersants are appropriately selected depending on the hydrophilic organic liquid used, the desired species of polymer particles, and the production of seed particles or grown particles. In order to mainly sterically prevent this, a material is selected that has high affinity and adsorption to the polymer particle surface, and high affinity and solubility to hydrophilic organic liquids. In addition, in order to enhance the repulsion between particles sterically, those with molecular chains of a certain length, preferably those with a molecular weight of 10,000 or more, are selected. However, if the molecular weight is too high, the viscosity of the liquid will increase significantly, resulting in poor operability and stirring performance, and the probability of precipitation of the produced polymer on the particle surface will vary, so care must be taken. In addition, some of the monomers of the polymer dispersant mentioned above,
It is also effective for stabilization to coexist with the monomers constituting the target polymer particles.

Furthermore, together with these polymeric dispersants, metals such as cobalt, iron, nickel, aluminum, copper, tin, lead, and magnesium, or alloys thereof (particularly preferred are those with a particle size of 1 μm or less); iron oxide, copper oxide, Inorganic compound fine powder of oxides such as nickel oxide, zinc oxide, titanium oxide, and silicon oxide; Anionic surfactants such as higher alcohol sulfate ester salts, alkylbenzene sulfonates, α-olefin sulfonates, and phosphate esters; Alkyl Amine salts, aminoalcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt types such as imidazoline, alkyltrimethylammonium salts, dialkyldimethylammonium salts,
Quaternary ammonium salt type cationic surfactants such as alkyldimethylbenzylammonium salts, pyridium salts, alkylisoquinolinium salts, and benzethonium chloride; Nonionic surfactants such as fatty acid amide derivatives and polyhydric alcohol derivatives; For example, Even when used in combination with amino acid type amphoteric surfactants such as alanine type [e.g. dodecyl di(aminoethyl)glycine, di(octylaminoethyl) glycine] or betaine type amphoteric surfactants, the stability and particle size distribution of the resulting polymer particles can be improved. can be further increased.

In general, the amount of polymer dispersant used during the production of seed particles varies depending on the type of polymerizable monomer for forming the desired polymer particles, but it is usually 0.
．． It is 1 to 10% by weight, preferably 1 to 5% by weight. When the concentration of the polymer dispersant is low, the resulting polymer particles have a relatively large particle size, and when the concentration is high, the polymer particles have a small particle size. Even if it is used in excess, there is little effect on reducing the particle size.

[0023] The above-mentioned polymeric dispersants and inorganic fine powders, pigments, and surfactants added as necessary are not only necessary during the production of seed particles, but also during the growth reaction. In order to prevent particles from coalescing, they may be present in the vinyl monomer solution or seed particle dispersion to be added for polymerization.

The initially formed particles are stabilized by a polymeric dispersant distributed in a balanced manner in the hydrophilic organic liquid and on the surface of the polymer particles, but the unreacted vinyl monomer is stabilized by the hydrophilic organic liquid. If it is present in a large amount in the liquid, it will have a somewhat swollen viscosity and will overcome the steric repulsion of the polymeric dispersant and coagulate. Furthermore, if the amount of monomer is extremely large relative to the hydrophilic organic liquid, the resulting polymer will be completely dissolved and will not precipitate until the polymerization has progressed to a certain extent. In this case, the state of precipitation is such that highly sticky lumps are formed. Therefore, the amount of monomer to hydrophilic organic liquid when producing particles is naturally limited, and although it varies somewhat depending on the type of hydrophilic organic liquid, the monomer/hydrophilic organic liquid ratio is approximately 1 or less,
Preferably, 1/2 or less is appropriate.

[0025] The above-mentioned vinyl monomer is one that can be dissolved in a hydrophilic organic liquid, such as styrene, o-
Methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,
4-dimethylstyrene, p-n-butylstyrene, p-
tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-
Styrenes such as chlorostyrene and 3,4-dichlorostyrene; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate , 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate,
Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, α-methyl fatty acid monocarboxylic acid esters such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; vinyl chloride, vinylidene chloride, vinyl bromide, fluoride It means a mixture of halogenated vinyl such as vinyl alone or a mixture thereof, and a monomer containing 50% by weight or more of these and copolymerizable with them.

Further, the polymer used in the present invention may be polymerized in the presence of a so-called crosslinking agent having two or more polymerizable double bonds in order to improve offset resistance. Preferably used crosslinking agents include divinylbenzene, divinylnaphthalene, and aromatic divinyl compounds that are derivatives thereof, as well as ethylene glycol dimethacrylate, diethylene glycol methacrylate,
triethylene glycol methacrylate, trimethylolpropane triacrylate, allyl methacrylate,
Diethylene carboxylic acid esters such as tert-butylaminoethyl methacrylate, tetraethylene glycol methacrylate, and 1,3-butanediol dimethacrylate; all divinyl compounds such as N,N-divinylaniline, divinyl ether, divinyl sulfide, and divinyl sulfone; Compounds having two or more vinyl groups can be mentioned, and these can be used alone or as a mixture.

[0027] When a growth polymerization reaction is successively carried out using the seed particles crosslinked in this manner, the interior of the growing polymer particles becomes crosslinked. On the other hand, when the vinyl monomer solution used in the growth reaction contains the above-mentioned crosslinking agent, a polymer having a hardened particle surface can be obtained.

Furthermore, in the production of raw resin particles, polymerization may be carried out in the presence of a compound having a large chain transfer constant for the purpose of adjusting the average molecular weight. Examples include low molecular weight compounds having a mercapto group, carbon tetrachloride, carbon tetrabromide, and the like.

[0029] Furthermore, as a polymerization initiator for the monomer,
For example, 2,2'-azobisisobutyronitrile, 2,2
Azo polymerization initiators such as '-azobis(2,4-dimethylvaleronitrile), peroxide polymerization initiators such as lauryl peroxide, benzoyl peroxide, tert-butyl peroctoate, potassium persulfate, etc. A persulfide-based initiator or a system in which it is combined with sodium thiosulfate, an amine, etc. is used. The concentration of the polymerization initiator is 0.1 to 1 with respect to 100 parts by weight of vinyl monomer.
0 parts by weight is preferred.

Polymerization conditions for obtaining resin particles A include the concentration and blending of the polymer dispersant and vinyl monomer in the hydrophilic organic liquid in accordance with the target average particle size and target particle size distribution of the polymer particles. The ratio is determined. Generally, if the average particle size of the particles is to be made small, the concentration of the polymeric dispersant is set high, and if the average particle size is to be made large, the concentration of the polymeric dispersant is set to be low. On the other hand, if you want to make the particle size distribution very sharp, you need to lower the vinyl monomer concentration and
If a relatively wide distribution is acceptable, the vinyl monomer concentration is set high.

The resin particles A are manufactured by completely dissolving the polymer dispersant in a hydrophilic organic liquid, and then adding one or more vinyl monomers, a polymerization initiator, and other inorganic fine powders as necessary. Adding surfactants, dyes, pigments, etc., 30 to 300
With normal stirring at rpm, preferably at the lowest possible speed,
Moreover, by using turbine-type stirring blades rather than paddle-type stirring blades at a speed that makes the flow uniform in the tank, and heating at a temperature corresponding to the decomposition rate of the initiator used, polymerization is carried out. It is done. Note that since the temperature at the initial stage of polymerization has a large effect on the particle size produced, it is desirable to raise the temperature to the polymerization temperature after adding the monomers and to dissolve the initiator in a small amount of solvent before adding it. During polymerization, it is necessary to sufficiently expel oxygen in the air in the reaction vessel using an inert gas such as nitrogen gas or argon gas. If the oxygen purge is insufficient, fine particles are likely to be generated.

[0032] In order to carry out polymerization in a high polymerization rate range, 5 to 40
Although several hours of polymerization time is required, the polymerization rate can be accelerated by stopping the polymerization when the desired particle size and particle size distribution are achieved, by sequentially adding a polymerization initiator, or by conducting the reaction under high pressure. be able to. After polymerization, the polymer slurry can be used as it is for the dyeing process, or it can be used as a polymer slurry after removing unnecessary fine particles, residual monomers, polymer dispersants, etc. through operations such as sedimentation, centrifugation, and decantation. It may be collected as a dye and dyed. However, if the polymer dispersant is not removed, the dyeing system will be more stable and unnecessary aggregation will be suppressed.

(Dyeing Step) In the present invention, small synthetic resin particles with a narrow particle size distribution, preferably resin particles A obtained as described above, are first colored by a dyeing method. Any method can be used as the dyeing method, but the following method is particularly preferred. That is, the resin particles are dispersed in an organic solvent that does not dissolve the raw resin particles, and before and after dissolving the dye in the solvent, the dye is infiltrated into the resin particles to color them, and then the solvent is dispersed. In the method of obtaining a dyed toner by removing dye, the relationship between the solubility of the dye in the organic solvent [D1] and the solubility of the dye in the resin of the resin particles [D2] is [D1].
]/[D2]≦0.5, (particularly preferably [D1]/[
D2]≦0.2), and according to this method, it is possible to efficiently produce a toner in which the dye penetrates (diffuses) deep into the resin particles.

[0034] In the above dyeing method, the solubility is 2
Defined as measured at a temperature of 5°C. The solubility of the dye in the resin has exactly the same definition as the solubility of the dye in the solvent, and means the maximum amount of the dye that can be contained in the resin in a compatible state. The state of dissolution or the state of precipitation of the dye can be easily observed using a microscope. Note that in order to know the solubility of the dye in the resin, an indirect observation method may be used instead of the above-mentioned direct observation method. This method is
A liquid having a solubility coefficient similar to that of the resin, that is, a solvent that dissolves the resin well, is used, and the solubility of the dye in this solvent is determined as the solubility in the resin.

In addition, as dyes, water-soluble dyes such as cationic dyes and anionic dyes may be subject to large environmental fluctuations, and the resistance of the toner may become low, resulting in deterioration of the transfer rate, so vat dyes, Disperse dyes and oil-soluble dyes are preferably used, and oil-soluble dyes are particularly preferred. Note that several types of dyes can be used in combination depending on the desired color tone. The ratio (weight) of the dye to be dyed and the raw resin particles is arbitrarily selected depending on the degree of coloring, but usually the ratio (weight) of the dye to be dyed and the raw resin particles is 100
Preferably, 1 to 50 parts by weight of the dye is used.

For example, when an alcohol such as methanol or ethanol with a high SP value is used as the dyeing solvent and a styrene/acrylic resin with an SP value of about 9 is used as the resin particles, the dyes that can be preferably used include: Examples include the following dyes. C. I. SOLVENT YELLOW(6,9,1
7, 31, 35, 100, 102, 103, 105)C
．． I. SOLVENT Orange (2, 7, 13
, 14, 66) C. I. SOLVENT RED (5
,16,17,18,19,22,23,143,14
5,146,149,150,151,157,158
)C. I. SOLVENT VIOLET(31,3
2,33,37)C. I. SOLVENT BLUE
(22, 63, 78, 83-86, 91, 94, 95,
104)C. I. SOLDENT GREEN (24
, 25) C. I. SOLDENT Brown (3,
9) etc.

Commercially available dyes include, for example, vertical dye SOT dye Yellow-1, 3, 4 and Orange from Hodogaya Chemical Industry Co., Ltd.
e-1, 2, 3, Scarlet-1, Red-1, 2
,3,Brown-2,Blue-1,2,Viole
t-1, Green-1, 2, 3, Black-1, 4
, 6, 8 and BASF's sudan dye, Yellow
-140,150, Orange-220, Red-2
90, 380, 460, Blue-670, Mitsubishi Kasei Diaresin, Yellow-3G, F, H2G, H
G, HC, HL, Orange-HS, G, Red-G
G, S, HS, A, K, H5B, Violet-D, B
lue-J, G, N, K, P, H3G, 4G, Green
n-C, Brown-A, orient chemical oil color, Yellow-3G, GG-S, #105, Or
ange-PS, PR, #201, Scarlet-#
308, Red-5B, Brown-GR, #416,
Green-BG, #502, Blue-BOS, II
N, Black-HBB, #803, EE, EX, Sumitomo Chemical Co., Ltd. Sumiplast, Blue GP, OR, Red FB, 3B, Yellow FL7G, GC, Nippon Kayaku Co., Ltd. Kayalon, Polyester Black EX-SH300, Kayaset Red -B Blue A-2R, etc. can be used. Of course, the dye is not limited to the above example, since it is appropriately selected depending on the combination of the resin particles A and the solvent used during dyeing.

[0038] The organic solvent used to dye the resin particles with the dye is one that does not dissolve the resin particles used, or one that causes some swelling, specifically, the solubility parameter [SP value] of the organic solvent. It is preferable that the difference between the [SP value] and the [SP value] of the resin particles used is 1.0 or more, preferably 2.0 or more. For example, for styrene/acrylic resins, alcohols such as methanol, ethanol, and n-propanol, which have a high [SP value], or [
It is preferable to use n-hexane, n-heptane, etc., which have a low SP value. Of course, if the difference in [SP value] is too large, wetting to the resin particles will be poor and good dispersion of the resin particles will not be obtained.
5 is preferred.

In carrying out the dyeing, it is preferable to disperse the resin particles in an organic solvent in which the dye has been dissolved, and then maintain the liquid temperature below the glass transition temperature of the resin particles and stir the mixture. This prevents agglomeration of resin particles and makes it possible to dye them. Stirring may be carried out using a commercially available stirrer, such as a homomixer or a magnetic stirrer.

Alternatively, the dye may be directly added to the slurry obtained at the end of dispersion polymerization, that is, a solution in which polymerized resin particles are dispersed in an organic solvent, and then heated and stirred under the above conditions. good. If the heating temperature exceeds the glass transition temperature, resin particles will fuse together.

The method of drying the slurry after dyeing is not particularly limited, but it may be air-dried after filtration, drying under reduced pressure after filtration, or direct drying under reduced pressure without filtration. In the present invention, the colored particles obtained by air drying or vacuum drying after filtration have almost no agglomeration, and reproduce the particle size distribution of the introduced resin particles with almost no damage.

(Surface oxidation step) In the present invention, the colored resin particles are subsequently subjected to a surface oxidation treatment to impart negative charge control ability.

[0043] In general, methods for surface modification of plastics are divided into wet and dry methods, and examples of wet surface modification methods include treatment with an acidic or alkaline aqueous solution, polymer coating, and the like. On the other hand, examples of dry surface modification methods include methods using electron beams or gamma rays used in radiation chemistry, methods using corona discharge, and methods using plasma reactions. In the case of a wet system, the sample is immersed in a strongly acidic or alkaline solution, so although surface modification is carried out, the properties of the sample itself may be adversely affected. In the case of a dry system, there is no acid or alkali atmosphere, so the above phenomenon does not occur.

Therefore, the surface oxidation treatment of colored resin particles in the present invention is carried out by a dry system (dry method). As this surface oxidation treatment method, any method can be adopted, such as the method using electron beams or gamma rays, the method using corona discharge, or the method using plasma reaction, but in particular, the method using plasma reaction. is preferred. This is because the energy of plasma reactions is approximately 1/10,000 times lower (approximately 10 eV) than that of electron beams or gamma rays, so the ability to penetrate materials is low, and the reaction is limited to the vicinity of the surface of the material. This is because it best matches the purpose.

However, in plasma reactions, although the energy is low, the concentration of active species is high, so chemical changes occur at high density. Furthermore, since the chemical changes occur randomly on the surface of the material, it is expected that reactions that are undesirable for surface modification may also occur. Examples of undesirable reactions include a phenomenon in which a bond dissociation reaction that is not the intended reaction occurs, which adversely affects mechanical properties. For example, a main chain molecule is cut in the surface structure to generate radicals, and the radical portion causes a hydrogen abstraction reaction. If the hydrogen abstraction reaction occurs disorderly, the desired reaction product will not be obtained. Therefore, it is necessary to control chemical changes on the material surface caused by plasma reactions.

Therefore, when carrying out surface oxidation treatment, oxygen is used as the introduced gas, and in order to suppress unintended reactions, plasma reaction conditions are set such that reactions caused by ions among the active species generated by plasma are suppressed as much as possible. It is preferable to adopt the method and install the material in a place where the surface of the material is not exposed to ions. The reaction caused by ions mentioned here includes a sputtering phenomenon. By sputtering, the surface of the material is bombarded with ions and bonds are broken in a disordered manner, resulting in a decrease in mechanical strength. In other words, in sputtering that uses physical force, the target bond formation due to oxygen does not occur.

As mentioned above, the desired reaction does not occur in the reaction by sputtering, so we investigated reaction conditions in which the reaction by radicals would occur as selectively as possible, and found that the material to be surface treated was placed at a location away from between the electrodes. It has been found that the desired reaction can be easily achieved by installing a plasma generator and lowering the accelerating voltage during the plasma reaction to a considerably low condition that is possible for plasma generation.

Note that this surface oxidation treatment reduces the ratio of oxygen bonded to carbon on the toner surface to 1 to 50 atomic %, particularly 5 to 50 atomic %.
It is preferable to set the amount to about 40 atom %.

(Others) In the method of the present invention,
The toner contains fine particles with relatively high Tg that have been atomized by means such as recrystallization, crushing, and emulsification, such as PMMA (polymethyl methacrylate), PTFE (polytetrafluoroethylene), and PVDF (polyvinylidene fluoride). It is also possible to implant micron particles. , also polyolefins, fatty acid esters, fatty acid metal salts,
A release agent such as higher alcohols or paraffin wax can also be applied to the surface of the toner.

Furthermore, in the present invention, the toner particles can contain additives. As the additive in this case, known fine particles such as titanium oxide particles, hydrophobic silica particles, zinc stearate, and magnesium stearate are used. As a mixing method, a general mixing device such as a V blender or a ball mill may be used.

[0051]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto. Note that all parts and percentages shown below are based on weight.

Example 1 First, base particles were produced by the dispersion polymerization method as described below. That is, 320 parts of methanol was placed in a three-necked flask equipped with a stirring blade and a condenser, and 6.4 parts of polyvinylpyrrolidone (average molecular weight: 40,000) was added little by little with stirring to completely dissolve it. Furthermore, the following composition was added and completely dissolved. styrene
25.6 copies
n-butyl methacrylate
6.4 parts 2,2'-azobisisobutyronitrile 0.2 parts

[
While stirring these, the inside of the flask was purged with nitrogen gas and left for 1 hour. Polymerization was started in a constant temperature water bath at 60° C.±0.1° C. while stirring at a stirring speed of 200 rpm. 15 minutes after heating, the liquid begins to become cloudy and 2
Even after 0 hours of polymerization, the dispersion remained cloudy and stable. A portion of the sample was measured using gas chromatography using an internal standard method, and as a result, the polymerization rate was confirmed to be 92%.

When the obtained dispersion was cooled and centrifuged at 2000 rpm using a centrifuge, the polymer particles were completely settled and the upper liquid was transparent. The supernatant liquid was removed, 200 parts of methanol was newly added, and the mixture was stirred and washed for 1 hour. The procedure of centrifuging and washing with methanol was repeated, followed by filtration. The filtered product was dried under reduced pressure at 50° C. for 24 hours to obtain white powder styrene/n-butyl methacrylate copolymer particles with a yield of 95%. The obtained particles had a volume average particle diameter Dv=7.40 μm and a Dv/Dp=1.07 (number average particle diameter 6.92 μm). Also, Tg is 65
It was ℃.

Next, 1.0 part of Oil Black 803 (Orient Chemical Co., Ltd.) was heated and dissolved in 200 parts of methanol, cooled, and filtered through a 1 μm filter to prepare a dye solution. Subsequently, 24 parts of the above-mentioned copolymer particles were added to the filtrate to disperse it, and the mixture was heated and stirred at 50° C. for 1 hour. Thereafter, the dispersion was cooled to room temperature and filtered, and then heated to 50°C for 24 hours.
It was dried under reduced pressure for hours to obtain colored resin particles.

[0056] Next, an RIE apparatus [manufactured by Nichiden Anelva: reactive ion etching (RIE) apparatus (DEM)
-451 type)] was used to conduct a low-temperature plasma reaction of colored resin. The sample was placed next to the exhaust port, away from the electrodes, to avoid ion bombardment as much as possible. The inside of the chamber was brought to a high vacuum of 0.2 Pa, the oxygen gas flow rate was set to 50 SCCM while introducing oxygen gas, and the gas pressure was set to 20 Pa by adjusting the exhaust system. Once the gas pressure became constant, high-frequency waves were oscillated to generate plasma. The traveling wave and reflected wave at this time were each 200W and Ca. It was set to 5W. Further, the acceleration voltage at the above time was 400V. The substrate temperature was room temperature. The reaction of radicals in the plasma was completed in 50 seconds, and after the reaction was completed, the degree of vacuum was maintained at 5 Pa with the gas flowing. Thereafter, gas introduction was stopped, and the sample was left in a high vacuum of 0.2 Pa for 20 seconds.

[0057] Take out the sample and check the surface condition using ESCA.
As a result of measurement, new peaks due to carbonyl groups and carboxyl groups appeared (the surface composition ratio was 12%). Furthermore, no decrease or increase in mechanical strength was observed in dynamic viscoelasticity measurements. In other words, it can be said from the above data that no dissociation of main chain bonds on the polymer surface or recrystallization of main chains occurs due to physical sputtering by ions, and that almost only reactions due to radicals occur. It will be done.

The toner of the present invention was obtained in the manner described above. The amount of charge of the obtained toner was measured using a blow-off device and was found to be -22.6 (μC/g). Using this toner, the Ricoh digital copier Imagio 420
When an image was formed using this method, a clear image with good fine line reproducibility and vivid halftones was obtained.

Example 2 First, base particles were produced by the dispersion polymerization method as described below. That is, 320 parts of methanol was placed in a three-necked flask equipped with a stirring blade and a condenser, and 6.4 parts of polyvinylpyrrolidone (average molecular weight: 40,000) was added little by little with stirring to completely dissolve it. Furthermore, the following composition was added and completely dissolved. styrene
25.6 copies
methyl acrylate
6.4 parts 2,2'-azobisisobutyronitrile 0.2 parts

While stirring these, the inside of the flask was purged with nitrogen gas and left for 1 hour. Polymerization was started in a constant temperature water bath at 60° C.±0.1° C. while stirring at a stirring speed of 200 rpm. 15 minutes after heating, the liquid begins to become cloudy.
Even after 20 hours of polymerization, the dispersion remained cloudy and stable. A portion of the sample was measured using gas chromatography using an internal standard method, and as a result, it was confirmed that the polymerization rate was 90%.

When the obtained dispersion was cooled and centrifuged at 2000 rpm using a centrifuge, the polymer particles were completely settled and the upper liquid was transparent. The supernatant liquid was removed, 200 parts of methanol was newly added, and the mixture was stirred and washed for 1 hour. The procedure of centrifuging and washing with methanol was repeated, followed by filtration. The filtered product was dried under reduced pressure at 50° C. for 24 hours to obtain white powder styrene/methyl acrylate copolymer particles with a yield of 94%. The obtained particles had a volume average particle diameter Dv=7.20 μm and a Dv/Dp=1.15 (number average particle diameter 6.26 μm). Moreover, Tg was 69°C.

Next, 1.0 part of Oil Black 803 (Orient Chemical Co., Ltd.) was heated and dissolved in 200 parts of methanol, cooled, and filtered through a 1 μm filter to prepare a dye solution. Subsequently, 24 parts of the above-mentioned copolymer particles were added to the filtrate to disperse it, and the mixture was heated and stirred at 50° C. for 1 hour. Thereafter, the dispersion was cooled to room temperature and filtered, and then heated to 50°C for 24 hours.
It was dried under reduced pressure for hours to obtain colored resin particles.

Next, an RIE device [manufactured by Nichiden Anelva: reactive ion etching (RIE) device (DEM)
-451 type)] was used to conduct a low-temperature plasma reaction of colored resin. The sample was placed next to the exhaust port, away from the electrodes, to avoid ion bombardment as much as possible. The inside of the chamber was brought to a high vacuum of 0.2 Pa, the oxygen gas flow rate was set to 50 SCCM while introducing oxygen gas, and the gas pressure was set to 20 Pa by adjusting the exhaust system. Once the gas pressure became constant, high-frequency waves were oscillated to generate plasma. The traveling wave and reflected wave at this time were each 200W and Ca. It was set to 5W. Further, the acceleration voltage at the above time was 400V. The substrate temperature was room temperature. The radical reaction in the plasma was completed in 20 seconds, and after the reaction was completed, the degree of vacuum was maintained at 5 Pa with the gas flowing. Thereafter, gas introduction was stopped, and the sample was left in a high vacuum of 0.2 Pa for 20 seconds.

[0064] Take out the sample and check the surface condition using ESCA.
As a result of measurement, new peaks due to carbonyl groups and carboxyl groups appeared (the surface composition ratio was 8%). Furthermore, no decrease or increase in mechanical strength was observed in dynamic viscoelasticity measurements. In other words, it can be said from the above data that no dissociation of main chain bonds on the polymer surface or recrystallization of main chains occurs due to physical sputtering by ions, and that almost only reactions due to radicals occur. It will be done.

The toner of the present invention was obtained in the manner described above. The amount of charge of the obtained toner was measured using a blow-off device and was found to be -20.1 (μC/g). Using this toner, the Ricoh digital copier Imagio 420
When an image was formed using this method, a clear image with good fine line reproducibility and vivid halftones was obtained.

Comparative Example The colored resin particles obtained in Example 2 (prior to surface treatment by low-temperature plasma reaction) were used as toner.

The amount of charge of this toner was measured using a blow-off device and found to be +78.4 (μC/g). When an image was formed using Imageo 420 using this toner, no clear image was obtained at all.

[0068]

[Effects of the Invention] In the method for producing a negatively charged toner of the present invention, small synthetic resin particles with a narrow particle size distribution are colored by a dyeing method, and the surfaces of the obtained colored resin particles are further oxidized. This configuration provides the following outstanding effects. (a) A highly colored toner with excellent resolution, sharpness, halftone reproducibility, and photographic reproducibility can be obtained. (b) There is little change in the amount of charge due to the environment, and the particle size distribution and charge amount of the toner in the developer do not change even after long periods of use.
Highly reliable toner can be obtained. (c) A toner with very good cleaning properties can be obtained. (d) Compared to conventional toner manufacturing methods, toner can be obtained efficiently with simple equipment and at low cost.

Claims (2)

[Claims] 1. A negatively charged toner characterized in that small synthetic resin particles with a narrow particle size distribution are colored by a dyeing method, and then the surfaces of the obtained colored resin particles are oxidized by a dry method. Production method. 2. The surface of the colored resin particles is oxidized by a low-temperature plasma reaction, and the ratio of oxygen bonded to carbon on the surface is 1 to 50 atomic %.
A method for producing the negatively chargeable toner described above.