JPH04198941A - Electrostatically chargeable resin particles and toner for electrophotography using same - Google Patents

Abstract

PURPOSE:To improve durability and electrostatic chargeability by preparing core particles having positive or negative charges in an aq. medium, heating and melt-sticking fine particles having electric charges contrary to those of the core particles to the surfaces of the core particles. CONSTITUTION:Core particles of low mol. wt. resin having positive or negative charges in an aq. medium are prepd. and fine particles of high mol.wt. resin having electric charges contrary to those of the core particles in the aq. medium are heated and melt-stuck to the surfaces of the core particles. Since the core particles and the fine particles have electric charges of opposite polarities in the aq. medium, when they are mixed and dispersed in the medium, the fine particles stick electrically to the surfaces of the core particles and tight sticking is attained by carrying out melt sticking in the electrically sticking state. Since the core particles electrically repel each other, aggregation is not caused. Durability and electrostatic chargeability are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to chargeable resin particles and an electrophotographic toner using the same.

<Prior art> A developing method used in electrophotography, electrostatic printing, electrostatic recording, etc. is to develop an electrostatic latent image formed on a photoreceptor by charging and exposure with toner. The toner image is transferred onto a support such as transfer paper, and the toner image is fixed onto the support using a heating roller or a pressure roller to visualize the electrostatic latent image. In order to remove the toner remaining on the photoreceptor, the toner remaining on the photoreceptor is scraped off with a cleaning member such as a cleaning blade.

The toner is used for developing an electrostatic latent image as a two-component developer mixed with a carrier to form a developer, or as a one-component developer consisting only of toner.

In order to faithfully reproduce the original image using toner, it is necessary to make the amount of charge of each toner particle uniform, and prevent the toner from migrating to areas other than the electrostatic latent image due to uncharged particles, and from developing devices due to excessively charged particles. It is necessary to prevent the image density from decreasing due to the accumulation of toner within the electrostatic latent image and the decrease in the amount of toner adhering to the electrostatic latent image.

Conventional toners are generally manufactured by melting and kneading a fixing resin together with additives such as a charge control agent by heating, cooling, and then crushing and classifying the resin.

However, such toner may cause problems such as occurrence of so-called offset such as dirt on the back side and dirt on the fixing roller, and poor fixing especially when the fixing temperature is low. This offset mainly occurs when the molecular weight of the fixing resin of the toner is low, and fixing failure mainly occurs when the molecular weight of the fixing resin is high.

Therefore, Japanese Patent Application Publication No. 16144/1982 and Japanese Patent Application Laid-open No. 60-1989
As described in Japanese Patent Application No. 3644, a toner with a double peak molecular weight distribution, which uses a low molecular weight resin and a high molecular weight resin in combination, has been proposed as a fixing resin.

<Problem to be solved by the invention> However, the toner proposed above does not contain a low molecular weight resin,
It is manufactured by mixing high molecular weight resin, colorant, and charge control agent, melting, mixing, cooling, pulverizing, and classifying, so if mixing is not done sufficiently during the manufacturing process, the molecular weight distribution will not achieve the desired double peak, resulting in decreased fixation and offset.
It takes time to mix and cross-wire, and manufacturing is difficult.

The main object of the present invention is to provide chargeable resin particles whose molecular weight distribution can easily be made into a double peak.

Another object of the present invention is to provide an electrophotographic toner that has good charging properties, excellent fixing properties, and excellent durability.

Means and Effects for Solving the Problems The chargeable resin particles of the present invention are made of a core particle made of a low molecular weight resin and have a positive or negative charge in an aqueous medium, and a high molecular weight resin, and are made of a high molecular weight resin and have a positive or negative charge in an aqueous medium. It is characterized in that it consists of fine particles having an opposite charge to the core particles, and the fine particles are thermally fused to the surface of the core particles.

The electrophotographic toner of the present invention uses such chargeable resin particles.

The core particles and microparticles of the present invention have opposite charges to each other in an aqueous medium, so when they are mixed and dispersed in an aqueous medium, the microparticles are electrically attached to the surface of the core particles. Therefore, if the core particles and the fine particles are thermally fused in this state, their adhesion becomes strong, and the molecular weight distribution can easily be made into a double peak. Furthermore, since the core particles electrically repel each other, there is no fear of agglomeration.

When the chargeable resin particles of the present invention are used as a toner, the fine particles of resin attached to the surface of the core particles are positively or negatively charged, resulting in excellent chargeability.

In addition, the low molecular weight resin constituting the core particles improves fixing properties.1. A good image can be obtained. On the other hand, the high molecular weight resin that makes up the microparticles improves durability and provides a long service life.

Moreover, the toner surface is coated with a high molecular weight resin component.
The effect of improving durability is very high.

The present invention will be explained in detail below.

Core particles The resin particles constituting the core particles are made of a heptad homopolymer that has a positive or negative charge in an aqueous medium, or a copolymer with another monomer that has no charge.

Examples of positively charged monomers include those having a nitrogen atom in the molecule. In addition, examples of negatively charged monomers include, for example, sulfonic acid groups in the molecule.
503H (Tatashi, the hydrogen atom in the formula is a sodium atom,
Examples include those having a potassium atom or a calcium atom (which may be substituted with a potassium atom to form a salt).

Examples of monomers having a nitrogen atom in the molecule include dimethylaminoacrylate, diethylaminoethyl acrylate, dimethylaminoethyl acrylate, diethylaminopropyl acrylate, N-aminoethylaminopropylacrylate, dimethylaminomethacrylate, dimethylaminoethylmethacrylate, diethylaminoethylmethacrylate. , diethylaminopropyl methacrylate, N-aminoethylaminopropyl methacrylate, vinylpyrrolidine, 2-vinylimidazole, 2
Examples include nitrogen-containing monomers such as -hydroxy-3-acryloxypropylmethylammonium chloride and acrylonitrile.

Examples of monomers having sulfonic acid groups include styrene/l/phonic acid, vinyl sulfonic acid, acrylamide methylpropanesulfonic acid, methacryl sulfonic acid, acryl sulfonic acid, acrylic-2-ethyl sulfonic acid, and methacrylic-2-ethyl sulfonic acid. Examples include acids and their salts such as sodium, potassium, and calcium.

Other monomers copolymerized with such monomers include various radically polymerizable monomers, such as vinyl aromatic monomers, acrylic monomers, vinyl ester monomers, vinyl ether monomers, diolefin monomers, and monoolefins. Examples include monomers.

The vinyl aromatic monomer is represented by the following general formula (1) (wherein R1 is a hydrogen atom, a lower alkyl group, or a halogen atom, and R2 is a hydrogen atom, a lower alkyl group, a % halogen atom, an alkoxy group, a nitro group, or a vinyl atom). Examples include styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, Q-, m-, p-chlorostyrene, p-
Ethylstyrene, divinylbenzene, etc. may be used alone or in combination of two or more.

The acrylic monomer has the following general formula (2) (where R'' is a hydrogen atom or a lower alkyl group, and R4 is a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, a hydroxyalkyl group, or a vinyl ester group). ) Examples include methyl acrylate, ethyl acrylate, butyl acrylate, hexyl methacrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2 -ethylhexyl methacrylate, ethyl-β-hydroxyacrylate, propyl-γ-
Examples include hydroxyacrylate, butyl-σ-hydroxyacrylate, ethyl-β-hydroxymethacrylate, ethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate. .

Examples of vinyl ester monomers include vinyl esters represented by the following general formula (3) (wherein R5 represents a hydrogen atom or a lower alkyl group), such as vinyl formate, vinyl acetate, vinyl propionate, etc. can give.

Examples of vinyl ether monomers include vinyl ethers represented by the following general formula (4) CH2=CH(4) Pi〇-R6 (in the formula, R6 represents a monovalent hydrocarbon group having 1 to 12 carbon atoms). For example, vinyl
Examples include 〇-butyl ether, vinyl phenyl ether, and vinyl cyclohexyl ether.

As the diolefin monomer, the following general formula (in the formula,
・R7, R8 and R9 each represent a hydrogen atom, a lower alkyl group or a 10-gen atom), such as butadiene, isoprene, chloroprene and the like.

Examples of monoolefin monomers include monoolefins represented by the following general formula (6) (wherein R10 and R'' each represent a hydrogen atom or a lower alkyl group), such as ethylene, propylene, isobutylene, butene, etc. -1, Penten-
Examples include 1,4-methylpentene-1.

Among these monomers, styrene monomers and acrylic monomers are preferably used in view of control of molecular weight distribution and copolymerizability.

Polymerization of the monomer is carried out by a suspension polymerization method, a dispersion polymerization method, etc., and it is particularly preferable to employ a suspension polymerization method. Water or alcohols are used as the dispersion medium in the suspension polymerization method. The dispersion medium is generally used in an amount of 50 to 1000 parts by weight based on 100 parts by weight of the total amount of monomers.

As a polymerization initiator for monomers, 2,2'-azobis(
azo compounds such as 2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), azobisisobutyronitrile (AIBN), cumene hydroperoxide, t-butyl hydroperoxide, dicumyl Examples include oil-soluble polymerization initiators such as peroxides such as peroxide, di-t-butyl peroxide, potassium persulfate, benzoyl peroxide, and lauroyl peroxide. In addition, it may be used in combination with ionizing radiation such as gamma rays and accelerated electron beams, and various sensitizers.

The polymerization initiator is generally used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the total amount of monomers.

The molecular weight of the core particles is as low as about 5,000 to 5,000,000, and particularly when the particles of the present invention are used as a toner, it is preferably about 5,000 to 2,000,000.
150,000 to 1,500,000. If the molecular weight of the core particles is lower than this range, the fixing properties will decrease, and conversely, if the molecular weight of the core particles is lower than this range, the softening point will be too low and the core particles will tend to aggregate with each other. It is also not preferable.

Further, other additives to the core particles include colorants. Examples of the colorant used when the chargeable resin particles of the present invention are used as an electrophotographic toner include the following pigments and oil-soluble dyes.

Furnace black, channel black, thermal,
Gas black, oil black, acetylene black,
Carbon black, lamp black, aniline black yellow yellow lead, zinc white, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navels yellow, naphthol yellow 81 Hansa Yellow 01 Hansa Yellow-1061 Henge Jin Yellow G1 Henge Shin Yellow GR, Tartrazine Lake, Quinoline Yellow Lake, Permanent Yellow NCG.

C114 Tsurughent Yellow 2, C,! , Solvent Yellow 14, C, 1, Solvent Yellow-60 Orange Molybdenum Orange, Benzidine Orange G1 Permanent Orange GTR, Red Yellow Lead, Pyrazolone Orange,
Palkan Orange, Indanslen Brilliant Orange RK.

Indance Brilliant Orange GK.

C, 1, Solvent Bluff red Hengara, cadmium let, red lead, Mercury cadmium sulfide, Permanentret 4R.

lysolet, pyrazolonet, Wozochinkret calcium salt, Lakelet D1 Brilliant Carmine 6B.

Eosin Lake, Rhodamine Lake B1 Alizarin Lake, Brilliant Carmine 3B.

C,1, Turchen Red 3, C,1, Solvent Red 24, C,1, Solvent Red 27 Purple Manganese Purple, First Violet B1 Methyl Violet Lake, C,1, Solvent Violet 13 Blue Navy Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Partially Chlorinated Phthalocyanine Blue, Metal Free Phthalocyanine Blue, Fast Sky Blue, Indan Stremburu-BC.

C,1, Solvent Blue, C,1, Solvent Blue 35 Green Chrome Green, Chromium Oxide, Pigment Green B, Malachite Clean Lake, Final Yellow Green, C,1, Solvent Green 15 Brown C,1, Solvent Brown 5 White Various metal powders such as zinc white, titanium oxide, antimony white, zinc sulfide extender pigments, pallite powder, barium carbonate, clay, silica, white carbon, talc, alumina white conductive pigments conductive carbon black, aluminum powder, etc.43 magnetic pigments Iron oxide (magnetite - iron black), iron sesquioxide (γ-Fe20i), zinc iron oxide (Z n Fe 204), iron yttrium oxide (Y3 Fe 5012), iron cadmium oxide (CdFe204), iron gadolinium oxide ( CD, Fe
504), iron copper oxide (CuF C204)-.

Iron oxide complex (P b Fe 12019), iron nickel oxide (N i F C204), iron neodymium oxide (N
dFeOs), barium iron oxide (B a Fe 12019), magnesium oxide (MgFe204), manganese iron oxide (Mn Fe 204 ), lanthanum iron oxide (LaF
eO9) Iron powder, cobalt powder, nickel powder Photoconductive pigments Zinc oxide, selenium, cadmium sulfide, cadmium selenide These colorants are used singly or in combination of two or more to ensure a sufficient toner image. The amount obtained, for example 0.5 to 30 parts by weight, especially 1 to 2 parts by weight, per 100 parts by weight of the resin component.
It is preferred that it be used in a proportion of 0 parts by weight.

Further, as the charge control agent, a positive charge control agent or a negative charge control agent, which are known per se, is used. As the positive charge control agent, organic compounds having a basic nitrogen atom, such as basic dyes, aminopyrine, pyrimidine compounds, polynuclear polyamino compounds, aminoranes, or fillers surface-treated with these are used. Further, as the negative charge control agent, a carboxyl group-containing compound such as an alkyl salicylic acid metal chelate is used. Among these, metal-containing dyes that exhibit no charge in an aqueous medium can be particularly preferably used.

The amount of the charge control agent to be blended is 5 parts by weight or less, preferably 0.2 to 1 part by weight, per 100 parts by weight of the core particles, and when the amount of the charge control agent to be blended is greater than 5 parts by weight, , contamination of the carrier by the charge control agent and dyeing of the photoreceptor occur, which is undesirable.

Further, if desired, toner compounding agents known per se may be added. Examples of toner compounding agents include aliphatic resins, aliphatic metal salts, higher fatty acids, fatty acid esters,
Examples include mold release agents (offset inhibitors) made of aliphatic compounds such as partially saponified products thereof. As a mold release agent, especially low molecular weight ik (weight average molecular weight 1000~
100OOJ aliphatic resin is preferably used. Specifically, one or a combination of two or more of low molecular weight polypropylene, low molecular weight polyethylene, paraffin wax, low molecular weight olefin polymer consisting of a single olefin having 4 or more carbon atoms, and various waxes such as silicone oil are used. I can do it. The average molecular weight of the wax is preferably in the range of 2,000 to 15,000, particularly 300 to 1,000. It is generally preferable to use these waxes in an amount of 1 to 5 parts by weight, particularly 1.5 to 3 parts by weight, based on 100 parts by weight of the resin component.

During suspension polymerization of monomers, conventional suspension stabilizers can be used. Such suspension stabilizers include cationic surfactants, anionic surfactants, water-soluble polymers, and poorly water-soluble powdered inorganic compounds.

Examples of the cationic surfactant include alkylamine, alkylethylenecyamine, alkyltrimethylammonium, alkylpyridinium, and alkyldimethylbenzylammonium.

Examples of the anionic surfactant include sodium alkyl sulfate, sodium polyoxyethylene alkylaryl sulfonate, sodium alkyldiphenyl ether disulfonate, and sodium alkylbenzene sulfonate.

□ Examples of water-soluble polymers include polyacrylic acid, sodium polyacrylate, gelatin, gum tragacanth, starch, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyallyl chloride, and N-
Examples include those made by reacting dodecylpiperidine, dimethyldodecylamine, N-cetylpiperidine, and the like.

Examples of poorly water-soluble powdered inorganic compounds include barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, magnesium carbonate, calcium phosphate, talc, bentonite, diatomaceous earth, and clay.

The amount of the suspension stabilizer to be used is generally within the range of 3 to 20 parts by weight per 100 parts by weight of the suspended particles.

Granulation in the above suspension polymerization method is performed using a high-speed shearing stirrer such as a homomixer or homogenizer, and the core particles are adjusted to a particle size suitable for the purpose.

When using core particles as toner, the central particle size is 1
It is preferable to adjust the thickness to about 15 μm.

In addition, polymerization is usually carried out at a temperature of 50 to 100°C for 2 to 1
It will last about 2 hours.

In addition, instead of the suspension polymerization method, the core particles are thermoplastic resin particles produced by conventionally known resin particle manufacturing methods such as dispersion polymerization, or thermoplastic resin particles produced by pulverizing, classifying, or spray-trying thermoplastic resin particles. Plastic resin particles may also be used.

Also. Charges may be imparted to the core particles by attaching a charge imparting agent to the surface of the thermoplastic resin particles during suspension polymerization or dispersion polymerization, or by attaching a charge imparting agent to the surface of the thermoplastic resin particles obtained after polymerization, The charge imparting agent may be mixed with the charge imparting agent in an aqueous medium to adhere the charge imparting agent to the surface of the thermoplastic resin particles.

In this case, as the charge imparting agent, the aforementioned cationic surfactants, anionic surfactants, water-soluble polymers having ionic functional groups, etc. can be used.

The microparticles of the microparticle resin are composed of an emulsion copolymer of a monomer having an opposite charge to that of the core particle and, if necessary, other monomers.

As such a monomer and other monomers to be emulsion copolymerized with it if necessary, any of the monomers exemplified for the core particles can be used.

Suspension polymerization, dispersion polymerization, and emulsion copolymerization can be used to polymerize the monomer, but emulsion copolymerization is preferred because it can easily obtain microparticles with a smaller particle size than the core particle. Suitably adopted.

Emulsion copolymerization is carried out using a water-soluble initiator in an aqueous medium.
If the monomer polymerization is carried out in the presence of an emulsifier, or if the emulsifier remains on the surface of the polymer particles, the emulsifier will absorb water, and its hygroscopicity will adversely affect the charging properties of the polymer. Therefore, it is necessary to remove as much emulsifier as possible.

Therefore, in emulsion polymerization, it is preferable to perform so-called emulsifier-free emulsion polymerization without using an emulsifier. This polymerization method involves (1) using a reactive emulsifier, (2) non-emulsification polymerization of relatively hydrophilic monomers using a persulfate-based initiator, and (2) water-soluble polymers and oligomers (e.g. polyvinyl alcohol, etc.). ) in place of the emulsifier, or (2) a decomposable emulsifier is used to carry out the polymerization. Among these, it is particularly preferable to employ an emulsifier-free emulsion polymerization method using a persulfate-based polymerization initiator.

The molecular weight of this microparticle is 10,000 to 100oooo
The molecular weight is about 0. Further, when this fine particle is used as a toner, the particle size is about 50,000 to 4,000,000, preferably 800,000 to 2,000,000.

If the molecular weight of the microparticles is smaller than this range, the softening point will be too low, resulting in poor durability.On the other hand, if the molecular weight of the microparticles is larger than this range, it will not be able to be thermally melted and its fixing properties will deteriorate. , both cases are unfavorable.

The center particle diameter of the fine particles is preferably adjusted to about 0.01 to 2 μm. Further, if necessary, the above-mentioned coloring agent and other compounding agents may be included.

Polymerization is usually carried out at a temperature of 50 to 100°C for about 3 to 24 hours.

In addition, in the operation of imparting electric charge to the resin microparticles, instead of imparting an electric charge to the polymer using a monomer having an electric charge in an aqueous medium, microparticles are The charge imparting agent may be attached to the surface of the particles, or the charge imparting agent may be mixed with the charge imparting agent after polymerization and the charge imparting agent may be attached to the surface of the microparticles.

Further, if a monomer having no electric charge is polymerized using a persulfate as a polymerization initiator, a negative charge can be imparted to the monomer in an aqueous medium, so microparticles may be obtained by such a method.

11. The chargeable resin particles are formed by thermally fusing the core particles and the fine particles. Ru. That is, a suspension of core particles and an emulsion of microparticles are mixed and heat-treated at a temperature higher than the glass transition temperature of the core particles to attach the microparticles to the surface of the core particles, thereby increasing the chargeability. Obtain resin particles.

The blending ratio of the core particle suspension and the fine particle emulsion depends on the ratio of the particle sizes of both, but it is within the range of 100:0.1 to 100:20 in terms of solid content. is appropriate. When the proportion of the fine particles is smaller than this range, the core particles are insufficiently covered with the fine particles, so that interparticle crosslinking of the core particles by the fine particles occurs, resulting in the generation of aggregates. If the size is larger than this range, there will be surplus microparticles, which will not only make removal of the microparticles complicated, but if two or more layers of microparticles adhere to the surface of the core particle, electrostatic attraction will cause problems. If the adhesive strength is sufficient, the adhesion force becomes so weak that it peels off from the toner after it is formed into a toner, which is not preferable in either case.

Heat treatment of the core particles and microparticles is carried out at a temperature near or above the glass transition temperature of the core particles in order to fuse them together, but this also prevents aggregation of the microscopic resins attached to the core particles. Therefore, it is preferable to carry out the treatment at a temperature equal to or lower than the glass transition temperature of the microparticles.

When the chargeable resin particles thus obtained are used as an electrophotographic toner, the particle size is 3 to 25 μm.
It is preferable to use composite spherical particles with a particle size of 8 to 20 μm, and they have excellent fluidity, charging properties, fixing properties, and cleaning properties.

Furthermore, an abrasive for cleaning the photoreceptor may be added to the toner according to the present invention. Examples of abrasives include talc, kaolin, barium sulfate, aluminum silicate, surface-treated aluminum silicate, titanium dioxide, calcium carbonate, antimony trioxide, barium titanate, calcium titanate, strontium titanate,
Magnesium oxide, zinc oxide, etc. are preferred, and colloidal silica and surface-treated hydrophobic silica are particularly preferred.

Addition of an abrasive, particularly hydrophobic silica, improves the fluidity of the toner (developer).

The average particle size of the abrasive is 1 to 1100n, especially 10 to 3Qn
It is preferable if it is within the range of m. Further, the amount of the abrasive added is preferably 0.01 to 1 part by weight per 100 parts by weight of the toner. If the amount of the abrasive added is less than 0.01 part by weight, the fluidity of the toner will be poor, and if it is more than 1 part by weight, the photoreceptor will be easily damaged, both of which are undesirable.

Furthermore, for the purpose of adjusting the electrical resistance of the toner, the toner may be coated with an electrical resistance adjusting agent such as carbon black or aluminum oxide. The amount of these electrical resistance adjusting agents is suitably 0.01 to 1 part by weight per 100 parts by weight of the toner.

In addition to being used as a toner for electrostatic development, the chargeable resin particles of the present invention can be used, for example, as a photosensitive toner, or as a paint for electrostatic painting by containing a colorant. .

<Example> The electrophotographic toner of the present invention will be described below with reference to Examples and Comparative Examples.

2-Ethylhexyl 15 parts by weight Dimethylaminoethyl methacrylate 10 parts by weight Divinylbenzene 0.7 parts by weight 2-ethylene glycol 1.5 parts by weight Dimethacrylate metal-containing dye (charge control agent) 3 parts by weight (Bontron manufactured by Orient Chemical Co., Ltd.) S-34) Carbon black 5 parts by weight (HA'-100 manufactured by Mitsubishi Chemical Corporation) Polymerization initiator 3 parts by weight 2.2'-
Azobis(2,4-dimethylhaleronitrile) Polymerization initiator 1 part by weight 2.2'-
Azobis (2-methylbutyronitrile) Mix the substances in the above formulation and mix the mixture with 800 parts by weight of water and tricalcium phosphate (TCP-10 manufactured by Taihei Kagaku Sangyo Co., Ltd.).
, solid content concentration 10%) and 0.012 parts by weight of sodium lauryl sulfate.
A time polymerization reaction was performed. Next, the obtained polymer was washed with water, passed through the mouth, and redispersed three times to obtain a suspension of positively charged core particles 1.

Further, when the molecular weight distribution of the positively charged core particles 1 was measured using the GPC method, the weight average molecular weight was 460,000 and the number average molecular weight was 6,200.

Positively Charged Core Particles 2 A suspension of positively charged core particles 2 was obtained in the same manner as in the synthesis of positively charged core particles 1, except that 10 parts by weight of diethylaminopropyl methacrylate was used instead of dimethylaminoethyl methacrylate.

Further, the molecular weight distribution of the positively charged core particles 2 was a weight average molecular weight of 520,000 and a number average molecular weight of 5,700.

Negatively charged fine particles 1 Styrene 72 parts by weight 2-ethylhexyl methacrylate 25 parts by weight Sodium styrene sulfonate 3 parts by weight Water
900 parts by weight polymerization initiator (potassium persulfate)
1 part by weight of each substance in the above formulation was mixed, and the mixture was subjected to a polymerization reaction at 80° C. for 6 hours with gentle stirring to obtain an emulsion of negatively charged microparticles 1.

Further, the molecular weight distribution of the negatively charged fine particles 1 was a weight average molecular weight of 1,130,000 and a number average molecular weight of 910,000.

Negatively charged resin microparticles 2 An emulsion of negatively charged microparticles 2 was prepared in the same manner as the synthesis of negatively charged microparticles 1 above, except that 3 parts by weight of ethyl sulfonate methacrylate was used instead of sodium styrene sulfonate. Obtained.

In addition, the molecular weight distribution of the negatively charged microparticles 2 has a weight average molecular weight of 1240 CIOC1 and a number average molecular weight of 670000.
Met.

Example 1 100 parts by weight of a suspension of positively charged core particles 1 and 3 parts by weight of an emulsion of negatively charged microparticles 1 were mixed, 20 parts by weight of 12N hydrochloric acid was added to this mixture, and the mixture was stirred under gentle stirring. 70℃
The microparticles were fixed to the surface of the core particles by heat treatment for 1 hour. An electrophotographic toner was obtained by washing, rinsing, drying, and crushing this.

The particle size distribution of this toner was measured using a Coulter counter, and the median diameter on a volume basis was as follows. is 11.4
It had a sharp particle size distribution in μm.

Furthermore, 100 parts by weight of the obtained toner was mixed with 0.1 parts by weight of hydrophobic silica fine powder and mixed with a ferrite carrier engineered with silicone resin, resulting in a toner concentration of 3.8%. A developer was prepared. This developer was applied to an electrophotographic copying machine (DC-258 manufactured by Sanda Kogyo Co., Ltd.).
5), 10,000 original copies were made, and the fixing properties of the developer, anti-offset properties, dirtiness of the fixing roller, and durability were examined. The results are shown in Table 1.

Example 2 A toner and a developer were obtained in the same manner as in Example 1, except that 3 parts by weight of an emulsion of negatively charged fine particles 2 was used in place of the emulsion of negatively charged fine particles 1.

The particle size distribution of the obtained toner is the median diameter.

It had a sharp particle size distribution with a diameter of 10.8 μm.

In addition, the performance of this toner was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3 A toner and a developer were obtained in the same manner as in Example 1, except that 100 parts by weight of a suspension of positively charged core particles 2 was used instead of the suspension of positively charged core particles 1. .

The particle size distribution of the obtained toner has a median diameter I)s.

was 11.4 μm, and had a sharp particle size distribution.

In addition, the performance of this toner was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4 A toner and a developer were obtained in the same manner as in Example 3, except that 3 parts by weight of an emulsion of negatively charged fine particles 2 was used instead of the emulsion of negatively charged fine particles 1.

The particle size distribution of the obtained toner had a median diameter of D5° to 11°.
．． It was 3 μm and had a sharp particle size distribution.

In addition, the performance of this toner was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Negatively chargeable charge control copolymer styrene 6 o parts by weight α-phenylvinylphosponic acid 40!11 parts 2.2'-azobis (2,410 parts by weight - dimethylvaleronitrile) Methyl alcohol 400 parts by weight Each substance in the above formulation The mixture was heated under nitrogen atmosphere with gentle stirring for 80 minutes.
The polymerization reaction was carried out at ℃ for 12 hours. Next, the obtained polymer was powdered by evaporation to obtain a negatively chargeable charge control copolymer.

Comparative Example 1 Styrene 65 parts 2-ethylhexyl 15 parts methacrylate Negative charge control copolymer 10 parts divinylbenzene 0.7 parts 2-ethylene glycol 1.5 parts methacrylate metal-containing dye (charge control agent) 2 parts by weight (Bontron S-34 manufactured by Orient Chemical Co., Ltd.) Carbon black 5 parts by weight (MA-100 manufactured by Mitsubishi Chemical Corporation) Polymerization initiator 3 parts by weight 2.2'-
Azobis(2,4-dimethylvaleronitrile) Polymerization initiator 1 part by weight 2.2'-
Azobis (2-methylbutyronitrile) Mix the substances in the above formulation, mix the mixture with 800 parts by weight of water and tricalcium phosphate (TCP-10 manufactured by Taihei Kagaku Sangyo Co., Ltd.).
, solid content concentration 10%) and 0.012 parts by weight of sodium lauryl sulfate.
A time polymerization reaction was performed. Next, the resulting polymer was washed with a dilute acid, washed with water, passed through the mouth, and dried to obtain a toner.

The particle size distribution of the obtained toner is the median diameter.

It had a sharp particle size distribution with a diameter of 11.2 μm. Moreover, the weight average molecular weight was 470,000, and the number average molecular weight was 5,300.

Furthermore, a developer was prepared from the obtained toner in the same manner as in Example 1, and evaluated in the same manner as in Example 1. As shown in Table 1, the fixing properties, anti-offset properties, Although there was no problem with the staining of the fixing roller, a decrease in image density and background fogging due to carrier stains were observed after 7,000 copies were made.

Comparative Example 2 1.5 parts by weight of 2.2'-azobis(2゜4-dimethylvaleronitrile) as a polymerization initiator, 0 parts of 2.2'-azobis(2-methylbutyronitrile) as a polymerization initiator An attempt was made to obtain a polymer in the same manner as in Comparative Example 1 except that 0.5 parts by weight was used, but the polymerization reaction was not completed and no toner was obtained.

The fixing properties of the developer, anti-offset properties, degree of contamination of the fixing roller, and durability were investigated using the following methods.

Comparative Example 3 A toner and a developer were obtained in the same manner as in Comparative Example 1, except that 1.2 parts by weight of divinylbenzene was used.

The particle size distribution of the obtained toner has a median diameter I).

It had a sharp particle size distribution with a diameter of 11.5 μm. Moreover, the weight average molecular weight was 1,250,000, and the number average molecular weight was 23,000.

Furthermore, when the performance of this toner was evaluated in the same manner as in Example 1, as shown in Table 1, the fixability was poor from the initial image and peeling occurred. Also, after about 6,000 copies were made, stains appeared on the fixing heat roller.

Fixability evaluation method: Adhesive tape is pasted on the leftover image portion of the copied image obtained through 10,000 copies, then the tape is peeled off, and the density of the image before and after the tape is peeled off is measured. It was measured using a reflection densitometer (TC-6D manufactured by Tokyo Juishokusha), and the fixing rate (%) was calculated according to the following formula: O, fixing rate 95% △: fixing rate 90% or more but less than 95% ×: The fixation rate was evaluated as less than 90%.

Evaluation method for offset resistance: While 10,000 sheets of originals were being copied, it was observed whether or not an offset phenomenon occurred, and evaluation was made as ○: no offset occurred, ×: offset occurred.

Method for evaluating stains on the fixing roller Visually inspect the stains on the fixing heat roller and fixing pressure roller after copying 10,000 sheets, and observe stains on the back of the copied paper. 0: No stains on the roller ×: As if the rollers were dirty evaluated.

Durability evaluation method: After copying 10,000 originals, it was observed whether or not there was any deterioration in the images, and evaluation was made as ○: no image deterioration, ×: image deterioration.

Image Quality Evaluation Method The initial image quality, the image quality after 2000 copies, and the final image quality were visually evaluated according to the following evaluation criteria.

O: Good image quality without fogging △: Slight fogging, M: A lot of fogging: ×: Toner scatters from the developing sleeve (hereinafter referred to as margin) As is clear from Table 1, Examples 1 to 4 had good image quality. Both toners have excellent positive and negative chargeability. In addition, the obtained images were good, with no fogging not only in the initial image but also after 10,000 copies were made. Furthermore, the fixing properties and anti-offset properties were excellent, and the fixing roller did not become stained. On the other hand, Comparative Example 1 has no problems with fixing properties, anti-offset properties, and staining of the fixing roller, but is inferior in durability due to its low molecular weight. Further, in Comparative Example 2, no toner could be obtained. Furthermore, Comparative Example 3 had poor fixability due to its high molecular weight.

<Effects of the Invention> As described above, the chargeable resin particles of the present invention have a positive or negative charge, and the surface of the core particle made of a low molecular weight resin has a charge opposite to that of the core particle, Since the fine resin particles made of high molecular weight resin are firmly attached, the product has excellent durability with a double peak molecular weight distribution. In addition, due to the electrical charge of the microparticles attached to the surface of the core particle,
It has excellent charging characteristics.

Therefore, when the chargeable resin particles of the present invention are used as an electrophotographic toner, fogging and toner scattering are prevented, and high-quality images can be obtained. The occurrence of offset due to dirt on the fixing roller is prevented, fixing performance is improved, and durability is improved.

Patent applicant: Mita Kogyo Co., Ltd. Attorney: Hiroshi Kamei (two idiots)

Claims (1)

[Scope of Claims] 1. A core particle made of a low molecular weight resin and having a positive or negative charge in an aqueous medium, and a microparticle made of a high molecular weight resin and having an opposite charge to the core particle in an aqueous medium. A chargeable resin particle comprising: fine particles thermally fused to the surface of the core particle. 2. Consists of a core particle made of a low molecular weight resin and having a positive or negative charge in an aqueous medium, and a microparticle made of a high molecular weight resin and having an opposite charge to the core particle in an aqueous medium, and the microparticle is An electrophotographic toner using chargeable resin particles thermally fused to the surface of the core particles.