JPH0652431B2 - Toner for electrophotography - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an electrophotographic toner, and more specifically, it contains a colorant and particles in a fixing resin polymerization step. The present invention relates to a method for manufacturing electrophotographic toner having a diameter within a range suitable for the toner at once. The present invention relates to a method for producing an electrophotographic toner which is excellent not only in fluidity but also in electrophotographic characteristics.

(Prior Art and Technical Problem of the Invention) In the field of electrophotography, a toner is used for the purpose of visualizing an electrostatic image. The toner particles are composed of a composition in which a colorant and, if necessary, another compounding agent such as a charge control agent are mixed in a resin medium in a certain particle size range, for example, a particle size range of 1 to 30 μm. As the resin medium, a resin having a desired electroscopic property and binding property, for example, a styrene resin or the like is used, and as the colorant, carbon black or another organic or inorganic color pigment is used. To be done.

The most typical method for producing an electrophotographic toner comprises a step of melt-kneading the above-mentioned resin medium and a colorant, cooling and pulverizing the kneaded composition, and classifying the pulverized material to make it uniform within a certain particle size range. However, the yield of the toner obtained by this pulverization / classification is extremely low, and a large amount of equipment is required for these operations, which makes the manufacturing cost of the toner extremely high. In addition, since the shape of the obtained particles is irregular, the fluidity of the toner is generally low,
The disadvantage that blocking is likely to occur is also recognized.

Heretofore, many proposals have been made for directly manufacturing a toner in a step of polymerizing a resin for the toner. A typical example thereof is a water-insoluble monomer in which a soluble polymerization initiator is dissolved, and an additive such as a colorant is further added, and the composition is mixed with a suitable dispersant such as a water-soluble polymer. The colored polymer particles are produced by suspending the mixture in an aqueous solution containing an inorganic powder, a surfactant and the like by high-speed shearing stirring and polymerizing the suspension. However, in this suspension polymerization method, the particle size of the final toner is determined by the state of suspension of the monomer composition in water, and the particle size distribution is determined by adding the monomer composition to water or stirring. Depending on the situation, it is very broad and it is difficult to obtain a single particle size. Further, in general, in this suspension polymerization method,
Only coarse particles of about several tens of μm to several mm are produced, and it is difficult to obtain a toner having a particle size of 1 to 30 μm, which is useful as a toner of a developer. Of course, it is possible to increase the blending amount of the dispersant to make the particle size of the produced toner finer, but in this case, the dispersant is contained in the toner,
Deterioration of electrophotographic characteristics such as sensitivity to humidity tends to occur. In order to prevent this, a special post-treatment operation is required, and the number of steps is large and impractical.

Further, a so-called emulsion polymerization method is known as a method for producing polymer particles having a relatively uniform particle size. The particles obtained by this polymerization method are fine particles having a particle size of 1 μm or less, or After the polymerization, it is difficult to directly obtain the colored resin for the toner during the polymerization process because a step of removing the emulsifier and the like is required.

(Object of the Invention) Therefore, an object of the present invention is to provide a method in which the above-mentioned various drawbacks of the conventional production of the electrophotographic toner are eliminated.

Another object of the present invention is to produce a colored resin, which has a particle size constitution suitable for use as a toner and which does not substantially contain an inhibitor for the electrophotographic properties of the toner, directly in the resin polymerization step. A method of manufacturing a photographic toner is provided.

Still another object of the present invention is to produce a toner in which the particle size of the colored resin is stably controlled in the range of 1 to 30 μm suitable for the toner during the polymerization process and the particle size distribution is uniformly maintained. To provide the law.

Still another object of the present invention is to provide a method for obtaining toner particles having the above characteristics by a relatively simple means.

(Structure of the Invention) According to the present invention, in a method for producing an electrophotographic toner comprising a composition of a fixing resin and a colorant dispersed in the resin, a radical polymerizable monomer and a colorant are used as a reaction medium. The radical-polymerizable monomer and the reaction medium are selected such that the monomer is dissolved in the reaction medium but the polymer produced is not dissolved in the reaction medium. Polymerization is initiated in the presence of a radical initiator in a part of the body, and the remaining monomer is dividedly added multiple times during the polymerization step,
Alternatively, it is continuously added during the polymerization process, whereby the composition of the produced polymer and the colorant is obtained, and the average particle size is 1
A method for producing an electrophotographic toner is provided, which comprises obtaining substantially spherical particles having a size of from 1 to 30 μm.

The present invention is described in detail below.

(Preferred Embodiment of the Invention) Principle and Effect In the present invention, the radically polymerizable monomer and the colorant are dissolved or dispersed in the reaction medium (solvent) and the polymerization is carried out in the presence of the radical initiator. It is an important feature that the radical-polymerizable monomer and the reaction medium have a combination such that the monomer dissolves in the reaction medium, but the produced polymer does not dissolve in the reaction medium. Under this combination condition, the particle size is larger than the resin particles obtained by the usual emulsion polymerization, the particle size is finer than the resin particles obtained by the usual suspension polymerization, and the particle size range is just suitable for the toner particles. It is based on the finding that a colored resin inside can be obtained. Generally, the polymerization that proceeds in a solution is called solution polymerization, whereas the polymer produced in this solution polymerization is dissolved in a solvent, whereas in the method of the present invention, the produced polymer is
They are distinguished by their insolubility in the solvent, ie the reaction medium.

In the present invention, the reason why the above-mentioned polymerization method produces colored particles having a particle size range within the above-mentioned specific range and having a relatively sharp particle size distribution is not restricted to this, but is as follows. It is considered to be a thing. That is, in the polymerization system of the present invention, the polymerization is initiated in the reaction medium at the initial stage of the polymerization, and the growing polymer chains are united with the colorant particles having a large specific surface area dispersed in the polymerization system. In the middle stage of polymerization, that is, after the polymer particles are produced, the interface between the polymer particles or the monomer is easily incorporated into the produced polymer particles, and the polymerization is initiated or the chain growth occurs inside the polymer particles. Thus, it is believed that the polymerization form has both emulsion polymerization and suspension polymerization. Therefore, it is considered that the colored polymer particles produced have a particle size in the toner suitable range between the resin particles obtained by the emulsion polymerization method and the resin particles obtained by the suspension polymerization method. When the diameter of the polymer particles in the polymerization system is r, the growth rate of the polymer particles is considered to be inversely proportional to the surface area of 4πr ² . On the other hand, the volume (4/3) πr ³ of the polymer particles increases in proportion to the polymerization time. Therefore, the rate of increase in particle size is large for fine polymer particles, and the rate is small for large polymer particles,
As a result, a particle having a relatively sharp particle size distribution and a uniform particle size can be obtained. Further, the colored polymer particles, which grow as the polymerization proceeds, have the advantage that they are maintained in a substantially perfect spherical shape due to the interfacial tension between the colored polymer particles and the reaction medium.

Thus, the colored particles obtained by the present invention do not require a classification operation or the like, have little loss of raw materials, are extremely excellent in productivity, and are excellent in fluidity and blocking resistance as a powder, and further are a dispersant. By controlling the amount of the active agent and the activator used, there is a remarkable advantage that there is substantially no factor that hinders the electrophotographic characteristics of the toner.

Another important feature of the present invention is that a part of the required monomer is polymerized in the presence of a radical initiator, and the remaining monomer is added in multiple portions during the polymerization step, or the polymerization is carried out. It lies in the point of continuous addition during the process. That is, it is considered that the concentration of the growing polymer radical is constant when the polymerization process is in a steady state, but when the concentration of the monomer in the reaction system decreases, an additional amount of the monomer is sequentially or continuously added. To maintain the steady state,
The colored polymer particles can be further grown. Of course,
At this time, due to the above-mentioned effects, the particle size distribution of the colored polymer particles produced becomes sharper, and the particle sizes are made uniform.

With some types of colorants, such as carbon black, the growing polymer radicals are trapped on the surface of the colorant particles, the growth of polymer chains is stopped, and extremely fine particles are mixed in the final product. Can occur. In order to prevent this, the radical initiator is also added in a divided manner over a plurality of times during the polymerization process, or it is continuously added during the polymerization process so that the growth of the polymer chain is stopped. Polymerization may be restarted at the particle surface. This preferred embodiment of the present invention has the advantage that substantially all of the colorant particles can be combined with the resulting polymer, eliminating the need for post-treatments such as sorting or classification.

In this latter embodiment, it is advisable to add an additional amount of radical initiator to an additional amount of monomer and to add the mixture either sequentially or continuously.

Raw Material In the present invention, the monomer used is a radically polymerizable monomer, and the resulting polymer has the fixability and the electric detection property required for the toner, and the monomer has ethylenic unsaturation. One kind or a combination of two or more kinds is used under the above-mentioned restrictions. Suitable examples of such monomers are:
Monovinyl aromatic monomers, acrylic monomers, vinyl ester monomers, vinyl ether monomers, diolefin monomers, monoolefin monomers and the like.

The monovinyl aromatic monomer has the formula In the formula, R ₁ is a hydrogen atom, a lower alkyl group or a halogen atom, and R ₂ is a hydrogen atom, a lower alkyl group, a halogen atom, an alkoxy group, an amino group, a nitro group, a vinyl group or a carboxyl group. Aromatic hydrocarbons such as styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene,
o-, m-, p-chlorostyrene, p-ethylstyrene,
Sodium styrenesulfonate and divinylbenzene may be used alone or in combination of two or more, and as the above-mentioned other monomers, the following may be mentioned, respectively.

formula In the formula, R ₃ is a hydrogen atom or a lower alkyl group, R ₄ is a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms, a hydroxyalkyl group, a vinyl ester group or an aminoalkyl group. Acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, β- Ethyl hydroxy acrylate, γ-hydroxy acrylate, δ-hydroxy butyl acrylate, β-hydroxy methacrylate, γ-amino acrylate, γ-NN-diethyl amino propyl acrylate, ethylene glycol dimethacrylate , Tetraethyl Glycol methacrylate and the like.

formula In the formula, R ₅ is a hydrogen atom or a lower alkyl group, and vinyl esters such as vinyl formate, vinyl acetate and vinyl propionate.

formula, In the formula, R ₆ is a monovalent hydrocarbon group having up to 12 carbon atoms, such as vinyl ether, for example, vinyl methyl ether, vinyl ethyl ether, vinyl-n-butyl ether, vinyl phenyl ether, vinyl cyclohexyl ether and the like.

formula, In the formula, each of R ₇ , R ₈ and R ₉ is a hydrogen atom, a lower alkyl group or a halogen atom, and diolefins, especially butadiene, isoprene, chloroprene and the like.

formula, In the formula, each of R ₁₀ and R ₁₁ is a hydrogen atom or a lower alkyl group, and monoolefins, especially ethylene, propylene, isobutylene, butene-1, pentene-1, 4-methylpentene-1 and the like.

In the present invention, it is particularly desirable that the radical-polymerizable monomer is such that the produced polymer is well dissolved in the monomer itself in order to make the particle size of the colorant resin particles uniform. Examples of such a monomer include monovinyl aromatic monomers, particularly styrenes, acrylic monomers, and combinations thereof.

As the colorant, various pigments and dyes (hereinafter simply referred to as color pigments) for coloring the toner are used.

Suitable examples of color pigments are:

Black pigment carbon black, acetylene black, lamp black, aniline black.

Yellow pigment Yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, hanzer yellow G,
Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Rake, Permanent Yellow NCG, Tartrazine Lake.

Orange pigment Red lead yellow molybdenum, Molypden orange, Permanent orange GTR, Pyrazolo orange, Vulcan orange, Indanthrene primillian orange RK, Benzidine orange G, Indanthrene brilliant orange GK.

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

Purple pigment Manganese purple, fast violet B, methyl violet lake.

Blue pigment Navy blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, fast sky blue, indanthrene blue B
C.

Green pigment chrome green, chrome oxide, pigment green B,
Malachite Green Rake, Fanal Yellow Green G.

White pigment Zinc white, titanium oxide, antimony white, zinc sulfide.

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

Conventional magnetic material pigments include, for example, ferric tetroxide (Fe
₃ O ₄ ), ferric sesquioxide (γ-Fe ₂ O ₃ ), zinc iron oxide (ZnFe
₂ O ₄ ), iron yttrium oxide (Y ₃ Fe ₅ O ₁₂ ), iron cadmium oxide (CdFe ₂ O ₄ ), gadolinium oxide (Gd ₃ Fe ₅ O ₁₂ ), iron copper oxide
(CuFe ₂ O ₃ ), iron oxide lead (PbFe ₁₂ O ₁₉ ), iron oxide nickel (NiF
e ₂ O), iron neodymium oxide (NdFeO ₃ ), iron oxide barium (BaF
e ₁₂ O ₁₉ ), magnesium iron oxide (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) ) And the like are known, and any of fine powders of these known magnetic materials can be used in the present invention.

In the present invention, an additive component that desirably contains a toner in addition to the above-described colorant may be added to the polymerization system prior to the polymerization.

For example, for use as a two-component pigment, a charge control agent known per se, for example, nigrosine base (CI504
5) Oil-soluble dyes such as oil black (CI26150) and spirone black, metal salts of naphthenic acid, soaps of fatty metal, resin acid soaps and the like can be blended, and in order to add an offset preventing effect to the toner. A release agent such as low molecular weight polyethylene, low molecular weight polypropylene, various waxes, and silicone oil may be included.

Polymerization Method According to the present invention, an organic solvent is used as a reaction medium which dissolves the above-mentioned monomer but does not dissolve the produced polymer. Further, it is desirable that this organic solvent is a readily volatile one in order to prevent the adverse effect of the residual solvent in the toner. The specific solvent name should be determined by the type of monomer and its polymer, but generally speaking, suitable organic solvents include alcohols, cellosolves, ketones and hydrocarbons. It is also possible to use the same or other organic solvents which are compatible with each other, or a mixed solvent with water or the like, but the present invention is not limited thereto. As alcohols, lower alcohols such as methanol, ethanol, propanol, etc., as cellosolves, methyl cellosolve, ethyl cellosolve, etc., as ketones, acetone, methyl ethyl ketone, methyl butyl ketone, etc. are used, and as hydrocarbons, n-hexane is used. , N-heptane, cyclohexane and the like.

Examples of the polymerization initiator include azo compounds such as azobisisobutyronitrile, cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide and di-t-
Butyl peroxide, benzoyl peroxide, lauroyl peroxide, and other peroxides that are soluble in the mixture of the monomer and the medium are used.

In addition to these, combinations of ionizing radiation such as γ-rays and accelerated electron beams and ultraviolet rays with various photosensitizers are also used.

The amount of the monomer charged is preferably such that the amount of the monomer in the reaction medium is 1 to 50% by weight, particularly 5 to 30% by weight, based on the reaction medium. The colorant may be added in an amount contained in the toner resin, and generally, the range of 1 to 30% by weight, particularly 3 to 20% by weight based on the charged amount of the monomer is suitable. Also,
When a magnetic substance is used as a pigment, it is generally suitable that the amount is 5 to 300 parts by weight, particularly 10 to 250 parts by weight, per the charged amount of the monomer.

The amount of the initiator such as an azo compound or peroxide may be a so-called catalyst proper amount, and generally 0.1 to 10% by weight based on the charged monomers.
It is good to use in the amount of. The polymerization temperature and time may be those known in the art, and in general, polymerization at a temperature of 40 to 100 ° C. for 1 to 50 hours is sufficient. The reaction system may be stirred gently so that a homogeneous reaction occurs as a whole, and in order to prevent inhibition of polymerization by oxygen, the reaction system is replaced with an inert gas such as nitrogen to carry out polymerization. May be.

The monomer may be charged into the medium either continuously or intermittently. In the case of intermittent feeding, the additional amount of the monomer should be 0.5 times or more, especially 1 time or more of the amount of the initially charged monomer, at least 2.
It is desirable to divide and add more than once. In this case, the type of the added monomer may be the same as that of the initially charged monomer or may be different.
It should be understood that in the latter case the formation of block copolymers is also possible. It is desirable that the average addition rate of the monomers be a rate substantially corresponding to the polymerization rate of the monomers.

Further, the additional amount of the polymerization initiator is preferably 0.1 to 10 times by weight, particularly 0.5 to 5 times by weight the initial amount of the polymerization initiator added, and the additional amount of the polymerization initiator is the additional amount of the monomer. It can also be dissolved in the polymer and added to the polymerization system.

Since the polymerization product after the reaction is obtained in the form of the above-mentioned particle size range, the produced particles are filtered, washed with the solvent if necessary, and dried to obtain colored particles for toner.

If necessary, the colored particles for toner are sprinkled with carbon black, hydrophobic silica or the like to obtain the final toner.

Further, in the production of toner, a dispersion stabilizer can be used if necessary. Examples of such dispersion stabilizers include polymers soluble in a medium such as polyvinyl alcohol, methyl cellulose, ethyl cellulose, polyacrylic acid, polyacrylamide, polyethylene oxide, poly (hydroxystearic acid-g-methyl methacrylate-CO. -Methacrylic acid) copolymer, nonionic or ionic surfactant, etc. are appropriately used.

The invention is illustrated by the following example.

Example 1 8 g of polyacrylic acid was dissolved in 800 ml of methanol, and 20 g of styrene, 5 g of n-butyl methacrylate, 5 g of carbon black (Printex L: manufactured by Degussa) and 1 g of azobisisobutyronitrile were added thereto. 80 ° C with stirring in a separable flask under a nitrogen stream at 150 rpm.
After 2 hours, 4 hours and 6 hours, 20 g of styrene and 5 g of -n-butyl methacrylate were additionally added and reacted for 15 hours to complete the polymerization. When the polymer was observed with an optical microscope, it was spherical black particles of about 10 μm. The polymer was separated by sedimentation, washed with methanol three times and then dried to obtain 105 g of a toner. The yield was 100%.
The particle size distribution of this toner was sharp as shown in Table 1 as the result of measurement by a Coulter counter. When this toner was placed in a mita DC-211 copying machine and copied, a clear image was obtained.

Comparative Example 1 Polymerization was completed in the same manner as in Example 1 except that 80 g of styrene, 20 g of methacrylic acid and 20 g of n-butyl were initially charged and no additional addition was made in the polymerization step. When the polymer was observed with an optical microscope, in addition to spherical particles of about 10 μm, transparent particles of a small amount of polymer of about 2 μm were observed.
The polymer was precipitated and separated, and washed with methanol three times to completely remove particles consisting of the polymer and then dried to obtain 95 g of a toner. The yield was 90%. The particle size distribution of this toner was bloat compared to that obtained in Example 1, as shown in Table 1 as the result of measurement by a Coulter counter. This toner is M
A clear image was obtained when copying was performed in itaDC-211, but the resolution was slightly lower than that of the example.

Claims (5)

[Claims] 1. A method for producing an electrophotographic toner comprising a composition of a fixing resin and a colorant dispersed in the resin, wherein a radically polymerizable monomer and a colorant are dissolved or dispersed in a reaction medium. Here, the radically polymerizable monomer and the reaction medium are selected such that the monomer is dissolved in the reaction medium but the produced polymer is not dissolved in the reaction medium, and a part of the required monomer is selected. Polymerization is initiated in the presence of a radical initiator, and the remaining monomer is dividedly added multiple times during the polymerization step or continuously added during the polymerization step, whereby the resulting polymer and colorant are added. Consisting of composition and having an average particle size of 1
A method for producing an electrophotographic toner, characterized in that substantially spherical particles of 30 to 30 μm are obtained. 2. The method according to claim 1, wherein the radical initiator is also dividedly added a plurality of times during the polymerization step or continuously added during the polymerization step. 3. The method according to claim 1, wherein the radical-polymerizable monomer is one in which the polymer produced is well soluble in the monomer itself. 4. The method according to claim 1, wherein the radical-polymerizable monomer is a monomer mainly containing styrene, and the reaction medium is a medium mainly containing alcohols, cellosolves or ketones. the method of. 5. The method according to claim 1, wherein the radically polymerizable monomer is a monomer mainly containing styrene, and the reaction medium is hydrocarbon.