JPH0563789B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a toner for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like.

Prior Art Conventionally, toners for electrostatic charge development are produced by melt-kneading a soft polymer and a colorant, dispersing the colorant in the polymer, and finely pulverizing the colorant-dispersed polymer. The fine powder obtained by this manufacturing method has a very wide particle size distribution, and in order to obtain a toner that can be put to practical use, it must be further classified, which ultimately complicates the manufacturing process and increases costs. That was a drawback. In addition, since the particle shape of the product is amorphous, it has a drawback of poor fluidity.

On the other hand, a production method using a polymerization method has been proposed as a method for directly producing colored polymer fine particles without a pulverization process (for example, Japanese Patent Publication No. 36-10231,
No. 47-51830, No. 51-14895, Japanese Patent Application Publication No. 1983-17735
No. 53-17736 and No. 53-17737).

These are based on the so-called suspension polymerization method, in which a polymerizable composition containing a polymerizable monomer, a polymerization initiator, and a colorant is suspended in an aqueous dispersion medium and polymerized to directly produce toner. It is something to do.

This method has the advantage that the toner particles produced are spherical and have excellent fluidity, the manufacturing process is simple, and the cost is low, but it is difficult to make the particle size distribution uniform, and , it is impossible to create a functional toner with a coating layer.

Purpose This invention specifically aims to provide an electric field-dependent toner.

Structure The structure of the present invention includes a core particle made of a substantially spherical polymer, and an electric resistance of 10 ² to 10 ⁹ Ω ^-1 formed from a mixture of at least a coloring agent and fine polymer particles on the surface of the core particle. cm, and a second coating layer made of at least polymer particles and having an electrical resistance of 10 ⁹ Ω ^-1 cm or more and a second coating layer formed on the first coating layer. This is a toner for charge development.

The structure of the above toner will be explained in detail with reference to FIG. 1. First, a conductive first coating layer 2 made of a mixture of at least a colorant and fine polymer particles is formed on the surface of a spherical core particle 1. The toner is provided with at least an insulating second coating layer 3 or a third coating layer 4 made of polymer particles thereon.

The method for manufacturing these core particles or coating layer and toner is as follows: A) Spherical polymer core particles The material is transparent thermoplastic particles such as acrylic acid ester resin or styrene resin. These core particles can be purchased commercially, but when they are manufactured, they are manufactured using a granulation method such as the usual spray drying method, suspension polymerization method, organic solvent dispersion polymerization method, or seed emulsion polymerization method. can.

Although there is a permissible particle size range of about 1 to 20μ for toner cores, toners with a uniform particle size distribution (having a variation within ±25% of the average particle size value) in this invention are produced. In order to achieve this, it is necessary to make the particle size distribution of the core particles uniform. Therefore, when considering the above manufacturing methods for that purpose, spray drying method and suspension polymerization method are
Although classification is required, classification is not necessary in the case of organic solvent dispersion polymerization method and seed emulsion polymerization method.

B) Coating layer consisting of a mixture of conductive agent and polymer The spherical core particles and the conductive agent are added to the fine polymer particle dispersion system under conditions that do not cause aggregation or coalescence of the fine polymer particles, and uniformly dispersed. After being dispersed, the first coating layer 2 made of a mixture of a polymer and a conductive agent is formed on the surface of the spherical core particles by spray drying at a temperature higher than the glass transition temperature (Tg) of the fine polymer particles.

The important point in forming this coating layer is to maintain the stability of the minute polymer particles (latex particles) against pH changes and mechanical shearing action. To explain these specifically, 1. The emulsifier is a condensate of alkyl (benzene) sulfate, alkyl sulfate ester salt, sodium sulfate, etc., and the amount thereof is 0.5 to 10 parts by weight per 100 parts by weight of resin. , preferably 1 to 5 parts by weight.

2 PH control is suitably PH8 or higher, preferably PH9 or higher.

3. In order to suppress the increase in viscosity, it is necessary to adjust the stirring power from time to time.

As the polymerizable monomer for producing the latex particles of this invention, any polymerizable monomer may be used, and self-polymerizable vinyl monomers may be used, and for example, polymerizable monomers may be used. Although monomers such as dibasic acids and glycols that can produce ester resins may be used, vinyl monomers are preferred.

Specific examples of the polymerizable monomers used in this invention are listed below.

For example, styrene, o-methylstyrene, m-
Methylstyrene, p-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-chlorostyrene , 3,4-dichlorostyrene, and styrene derivatives, with styrene monomers being most preferred.

Examples of other vinyl monomers include ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl chloride;
Vinyl halides such as vinylidene chloride, vinyl bromide, and vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate; Isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, α-
Methyl chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate,
α-methylene aliphatic monocarboxylic acid esters such as dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate; acronitrile; Acrylic acid or methacrylic acid derivatives such as methacrylonitrile and acrylamide; Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether; Vinyl methyl ketone,
Vinyl ketones such as vinylhexyl ketone and methyl isopropenyl ketone; N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone; and vinylnaphthalenes.

These vinyl monomers may be used alone or may be used in combination to form a copolymer.

In the above-mentioned polymerization method, the polymer composition is dispersed and suspended in a dispersion medium such as water as dispersed particles of a required particle size by mechanical stirring, and polymerization is carried out. However, as the polymerization progresses, the dispersed particles become sticky. In order to increase the particle size, it is necessary to prevent particles from coalescing into large particles, and a dispersion stabilizer is used for this purpose.

The materials used as such dispersion stabilizers are generally divided into water-soluble polymeric substances and fine powders of poorly soluble inorganic compounds. Water-soluble polymeric substances include gelatin, starch, polyvinyl alcohol, and others. , poorly soluble inorganic compounds include barium sulfate, calcium sulfate, barium carbonate, calcium carbonate,
These include poorly soluble salts such as calcium phosphate, inorganic polymer substances such as talc, clay, silicic acid, diatomaceous earth, metal oxides, and other powders.

In this invention, a polymer is obtained by polymerizing a polymerizable monomer, and a polymerization initiator may be used during the polymerization. Examples of the polymerization initiator include lauroyl peroxide, benzoyl peroxide, 2,2'-
Examples include azobisisobutyronitrile, 2,2'-azobis-(2,4-dimethylvaleronitrile), orthochlorobenzoyl peroxide, and orthomethoxybenzoyl peroxide.

Examples of the conductive agent used in the present invention include, in addition to carbon black, inorganic materials such as copper iodide, ruthenium oxide, and various metal powders, and conductive polymer substances such as polyacetylene, polypyrrole, and polythienylene. A coloring agent, magnetic powder, etc. may be added as appropriate to the first coating layer. Examples of the coloring agent include the following pigments and dyes.

Black pigments: carbon black, acetylene black, lamp black, aniline black.

Yellow pigments Yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast iodine, nickel titanium yellow, Naples yellow, naphthol yellow S, Hanser yellow G, Hanser yellow 10G, benzidine yellow G, benzidine yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake.

Orange pigment Red yellow lead, Molybdenum orange, Permanent orange GTR, Pyrazolone orange, Vulcan orange, Indanthrene brilliant orange
RK, Benzidine Orange G, Indanthrene Brilliant Orange GK.

Red pigment red pigment, cadmium red, red lead, cadmium sulfide hydroxide, permanent red 4R, resol red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin Rake, brilliant carmine
3B.

Purple pigments Manganese purple, Fast Violet B, Methyl Violet Lake.

Blue pigments: navy blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, first sky blue, indanthrene blue BC.

Green pigments Chrome green, chromium oxide, Pigment Green B, Malachite Green Lake, Huanal Yellow Green.

White pigments: zinc white, titanium oxide, antimony white, zinc sulfide.

Extender pigments barite powder, barium carbonate, clay, silica,
White carbon, talc, alumina white.

Various dyes (basic, acidic dispersion, direct dyes, etc.) Nigrosine, methylene blue, rose bengal, quinoline yellow, ultraman blue, etc.

Examples of magnetic powder include fine powders of conventionally known magnetic materials such as triiron tetroxide (Fe ₃ O ₄ ), iron sesquioxide, (γ-
Fe ₂ O ₃ ), zinc iron oxide (ZnFe ₂ O ₄ ), yttrium iron oxide (Y ₃ Fe ₅ O ₁₂ ), cadmium iron oxide (CdFe ₂ O ₄ ), gadolinium iron oxide (Gd ₃ Fe ₅ O ₁₂ ), Copper iron oxide (CuFe ₂ O ₄ ), lead iron oxide (PbFe ₁₂ O ₁₉ ), nickel iron oxide (NiFe ₂ O ₄ ), neodymium iron oxide (NdFeO ₃ ), barium iron oxide (BaFe ₁₂ O ₁₉ ), iron oxide One or more of magnesium (MgFe ₂ O ₄ ), iron manganese oxide (MnFe ₂ O ₄ ), lanthanum iron oxide (LaFeO ₃ ), iron powder (Fe), cobalt powder (Co), nickel powder (Ni), etc. combinations are used. Particularly suitable magnetic material pigments are triiron tetroxide and γ-type iron sesquioxide.

C) Coating layer made of polymer or mixture of polymer and colorant The second coating layer 3 shown in the drawing is also a coating layer formed from a polymer on the first coating layer 2 by a similar method. A colorant and a charge control agent are appropriately added to the second coating layer. As the coloring agent, those mentioned above are used.

Furthermore, in the developer of the present invention, it has been confirmed that the transfer efficiency is better when the magnetic toner is triboelectrically charged to a polarity opposite to the polarity applied to the transfer paper during the electrostatic transfer process. Nigrosine, monoazo dyes, zinc hexadecyl succinate, alkyl esters or alkylamides of naphthoic acid,
Adding highly polar substances called charge control agents in this field, such as nitrofumic acid, N,N'-tetramethyldiaminebenzophenone, N,N'-tetramethylbenzidine, triazine, and salicylic acid metal complexes. is preferred.

D) If necessary, a third coating layer 4, which is the same as the second coating layer 3, is formed by the same method as the second coating layer 3.

A fluidizing agent or the like can be added as appropriate to modify the toner.

As properties improving agents such as fluidity of the toner, it is also possible to add and mix, for example, silica, hard resin fine powder, zinc oxide, higher fatty acids, higher fatty acid metal salts, silicone oil, fluorine oil, and the like.

It is possible that various functionalities can be developed from toner having such a multilayer structure. For example, a toner with the following functions can be produced.

For example, in the toner shown in FIG.
The coating layer 2 is made of a material with low electrical resistance (10 ² to 10 ⁹ Ω
^- cm), a material with high electrical resistance (10 ⁹ Ω ^- cm or more) is used as the second coating layer 3, and there is no coating layer on the outside of the toner, the following characteristics must be provided. I can do it.

For example, the conductivity of the developing toner can be measured by the measuring method described in column 3 of U.S. Patent No. 3,639,245, but the conductivity of the toner (Ω ^-1 cm
^-1 ) and the applied voltage (Vcm ^-1 ) as shown in Figure 2.

In both conventional conductive toner and insulating toner, the conductivity of the toner changes only slowly in response to changes in the electric field, as shown by lines 5 and 6 in FIG. 2, respectively. In toner, a certain breakdown electric field as shown in line 7
It exists in the range of 10 ² to ^{10 4} V/cm, and the conductivity increases rapidly.

Therefore, by using this toner, development is performed with an electric field in area B that is larger than the breakdown point (Eb) shown in Figure 2, and transfer is performed with an electric field in area A that is smaller than the breakdown point. This can solve the drawbacks of conventional one-component processes.

In other words, in the conventional one-component development process, there was a contradiction that the toner had to be conductive during development and insulative during transfer, but when the toner of this invention has a layered structure, it becomes electric field dependent and can be applied easily. By making the electric field values different during development and transfer, the same toner can exhibit both conductive and insulating functions.

Hereinafter, the production of the toner of the present invention and the effects of the toner will be specifically explained with reference to Examples.

Example 1) Method for producing core particles, 100 parts of styrene, 2 parts of 2-2' azobisisobutyronitrile (polymerization initiator), 0.75% methylcellulose aqueous solution, 400 parts of lauryl sulfate, as a dispersion medium in a homogeneous dispersion having the above composition. A composition containing 0.05 part of sodium was added, and homomixing was performed at 4000 rpm for 10 minutes at room temperature.

This mixture was degassed and replaced with nitrogen, then heated to 70°C and polymerized for 6 hours with regular stirring.

The product had particles with an average particle size of 9 μm (particle size distribution varied by more than ±50%). This was classified to obtain core particles with an average particle size of 8 μm (dispersion within ±25% of particle size distribution).

2) Production of aqueous dispersion of fine polymer particles, Styrene 80 parts 2 Ethylhexyl acrylate 15 parts n-butyl methacrylate 1.5 parts t-butyl mercaptan 15 parts 1.5% sodium lauryl sulfate aqueous solution 200 parts Ammonium persulfate (initiator) 0.2 parts of the above composition The mixture was degassed and purged with nitrogen at 60 °C.
Emulsion polymerization was carried out for 18 hours to produce an aqueous dispersion of fine polymer particles.

3) Manufacture of toner, a) Aqueous dispersion of fine polymer particles (solid content: 30
%), an aqueous dispersion of conductive carbon black (15 parts of conductive carbon black/300 parts of water uniformly dispersed by high-shear stirring) and an aqueous sodium hydroxide solution were added to the PH >8 to obtain a stable and uniform aqueous dispersion.

While continuing to stir this, 200 parts of nuclear particle slurry (solid content 20%) was added, maintaining pH > 8,
A uniform aqueous dispersion was created that suppressed the increase in viscosity due to agglomeration and coalescence of minute polymer particles.

While stirring this uniform aqueous dispersion, the inlet temperature was 140°C.
Spray dried at ~160°C, outlet temperature 50-70°C.

In this way, core particles having a first coating layer containing a colorant and having a relatively low electrical resistance were produced.

This particle has an average particle size of 10μ (variation within ±30%)
The volume resistivity was 8.2×10 ⁶ Ω−cm.

b) The above micro polymer particle aqueous dispersion (solid content 30
%) and a dispersion of 2 parts of carbon black/300 parts of water (uniform dispersion obtained by high shear stirring) and an aqueous sodium hydroxide solution while stirring to form a stable homogeneous water with a pH>8. I made a dispersion.

Add 200 parts of the particle slurry (solid content 20%) with the first coating layer made in step a) above to this, and maintain the pH > 8 while stirring to prevent viscosity increase due to agglomeration and coalescence of minute polymer particles. Spray drying at an inlet temperature of 140-160℃ and an outlet temperature of 50-70℃ while suppressing
A magnetic toner having a functional multilayer structure with a first coating layer (resistance) was produced.

The average particle size of this toner was 11 μm, and the variation in particle size was within ±30%.

4) Image formation, using this toner as a developer,
When images were formed using a prototype device based on a recording method called the LIST method described in No. 84955, clear images were obtained.

Note that 2), which is the second step in the above example,
Among the raw materials for producing the aqueous dispersion of fine polymer particles, sodium lauryl sulfate, which is an emulsifier, is mixed with other substances, such as sodium dodecylbenzenesulfonate, sodium alkylnaphthylenesulfonate, and β-naphthalenesulfonic acid formalin condensate sodium salt. Even if the toner was replaced and the toner was manufactured in the same process as in the example with other conditions, a toner with the same effects as the example could be manufactured.

However, when potassium oleinate, sodium oleate, sodium tallowate, etc. are used as emulsifiers, the results are not good.

This aqueous dispersion of fine polymer particles usually needs to be alkaline or neutral, and if acidic substances are introduced and the liquid becomes acidic, particularly at a pH of 5 or lower, it becomes unstable and tends to aggregate.

The amount of emulsifier was set at 0.5, as in the above example, if the concentration of the emulsifier aqueous solution was less than 0.5%, it would have no effect.
% is suitable.

Effects As explained above, the toner of the present invention can provide the following effects.

1) Since the particles are spherical, the fluidity of the toner is good, and therefore the toner can be replenished smoothly.

2) Since the toner particle size distribution is uniform, Q/M
It has a sharp distribution and stable charge characteristics.

3) Since the toner has a multilayer structure, it is possible to create a functional toner, which is effective in improving image quality.

[Brief explanation of drawings]

FIG. 1 is an enlarged cross-sectional view of toner particles showing an outline of the structure of the toner of the present invention, and FIG. 2 is a correlation diagram of the applied electric field and toner conductivity, showing the characteristics of the toner of one application example of the toner of the present invention. . DESCRIPTION OF SYMBOLS 1... Nucleus particle, 2... First coating layer, 3... Second coating layer, 4... Third coating layer, 5... Line indicating electrical conductivity of conductive toner, 6... Line indicating electrical conductivity of insulating toner ,
7...Line showing the electrical conductivity of the toner of this invention.

Claims (1)

[Claims] 1 Core particles consisting of a substantially spherical polymer;
A first coating layer with an electrical resistance of 10 ² to 10 ⁹ Ω ^-1 cm formed from a mixture of at least a conductive agent and fine polymer particles is provided on the surface of the core particle; 1. A toner for electrostatic charge development, comprising one or more second coating layers formed from polymer particles and having an electrical resistance of 10 ⁹ Ω ^-1 cm or more.