JPH0458022B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a capsule toner for developing electrostatic latent images formed in electrophotography. Conventionally, the method for producing toner used in electrophotography involves mixing and containing colorants such as carbon black and dyes in various natural or synthetic resins using a blending method, and then pulverizing them into fine powder; A method of dispersing the material in a solvent and pulverizing it by spray drying; A method of obtaining a fine polymer powder by polymerizing an aqueous suspension of a polymerizable monomer while stirring; A method of obtaining a fine powder by dispersing the dispersion in a solvent and then suspending the dispersion in a solvent that is incompatible or difficult to miscible with the above-mentioned solvent; suspending the dispersion in the same manner as described above; A method of obtaining a fine powder by spray drying; or a method of dispersing the material in a solvent and stirring and mixing it with a solvent that is compatible with the solvent and does not dissolve the resin to form a fine powder is known. . The above method is suitable for pulverizing non-adhesive resin and obtaining heat fixable toner, but
This method is inappropriate as a method for obtaining a pressure-fixable toner by pulverizing a sticky resin. That is, it is difficult to form into a toner due to the tackiness of the resin, and even if it could be formed into a toner, the toners would aggregate and the fluidity would be greatly reduced. In addition, in the case of a two-component toner consisting of toner and a carrier, the toner adheres to the carrier and causes contamination of the carrier, and in the case of a one-component toner consisting only of toner, it adheres to the sleeve via a magnet during development.
This may cause sleeve fusion. Against this background, many methods using microencapsulation methods have been proposed in recent years as a method for turning sticky resin into toner. For example, in the method described in JP-A No. 48-90977, a single-phase solution consisting of two or more polymeric substances with different solubility is prepared, and by spray drying this, the one with higher solubility is used as the core material. In this method, the surrounding area is covered with a wall film made of a polymer substance with low solubility, but there is a risk of fire because a flammable solvent is used, and the equipment must be installed to prevent fires. It is complicated and difficult to operate. Further, in JP-A No. 48-80478, a mixture of wall materials is formed in a solvent, a core material is dispersed or dissolved in the mixture to form a dispersion in which the mixture is a dispersed phase, and the solvent for the mixture is A method is disclosed for sequentially phase-separating the aforementioned core and wall materials, respectively, by varying the solubility properties of the core and wall materials, thus forming capsules consisting of a core material coated with a wall material. However, when this method mixes colorants or magnetic substances into the core material, the viscosity of the core material becomes extremely high, making it difficult to emulsify and form fine particles by stirring (which easily destroys the dispersed phase), and When agitated, the colorant or magnetic material in the core material jumps out into the dispersed phase, so the particle size and composition of the toner is not constant and it is difficult to produce a spherical toner. Therefore, even if such toner is used for development, a good quality image cannot be obtained. Furthermore, US Pat. No. 3,745,118 discloses that a water-soluble polymeric substance such as gelatin or maleic anhydride resin is formed into coacervate droplets by a complex coacervation method, which is mixed with a colorant and a resin emulsion, and then spray-dried. It describes how to do this. However, since this method uses a water-soluble polymer substance, it has a negative effect on the moisture resistance of the toner, and it is not possible to obtain a toner with good charging characteristics. Furthermore, there are still many problems as described below. For example, 1. The adhesion between the core particle and the shell material is poor, resulting in poor durability. 2. In the encapsulation step, a microcapsule toner having a coarse particle size is obtained because encapsulation is performed while the core particles are agglomerated or coalesced, or because the encapsulated particles are coalesced with each other. 3. During the encapsulation process, free particles formed only from the core material or only from the shell material are by-produced. The free particles produced as a by-product result in sleeve contamination and a decrease in image density. 4. In the encapsulation process, it is difficult to completely coat the core particle surface with the shell material, often resulting in defective films. As a result, for example, the pot life is poor, the toners tend to coalesce and block, and even the phenomenon of filming on the drum surface tends to occur. The present invention provides a microcapsule toner which solves these drawbacks and is characterized by retaining bulky and hard anions as counterions and using a thermoplastic cationic polymer as a shell material. Still another object of the present invention is to provide a microcapsule toner in which the surface of core particles is coated with a shell material having good film-forming properties. Another object of the present invention is to provide a microcapsule toner having stable triboelectric charging characteristics under various environments, particularly under high temperature and high humidity conditions. Still another object of the present invention is to provide a microcapsule toner that can be developed and fixed at a sufficiently high speed with small pressure. Specifically, the present invention uses ClO ₄ , BF ₄ , IO ₄ ,
An electrostatic latent material characterized in that a thermoplastic cationic polymer holding an anion selected from the group consisting of SbF ₄ and PF ₆ as a counter ion is used as a shell material, and a core particle is covered with the shell material. The present invention relates to a microcapsule toner for image development. The bulky and hard anions that are a feature of the present invention are described by Pearson in J.Chem.Educ., 45 , 643 (1968),
It is defined based on the HSAB rule described in . In other words, it means an anion with a large anion radius and a small polarizability. The present invention uses a thermoplastic cationic polymer containing bulky and hard anions, such as perchlorate ions, periodate ions, and boron tetrafluoride ions as counterions, as a shell material to coat core particles. This was achieved by providing a microcapsule toner with the following characteristics. The thermoplastic cationic polymer used in the present invention tends to take the form of an elongated thread structure due to charge repulsion in a solvent, which is convenient for encapsulation. At this time, by changing the counter ion to a bulky and hard anion with a so-called low polarizability, the moisture resistance properties can be further improved. This is thought to be due to the fact that as the ion diameter of the counter ion increases, the interaction between positive and negative ions can be reduced, and on the contrary, the repulsion between like ions is strengthened. In addition, since the hygroscopicity is significantly improved, a stable amount of triboelectric charge can be maintained even in high temperature and high humidity conditions. In the present invention, when used as a pressure fixing toner, waxes such as polyethylene wax, oxidized polyethylene, paraffin, fatty acids, fatty acid esters, fatty acid amides, fatty acid metal salts, and higher alcohols; ethylene-acetic acid Vinyl resin, cyclized rubber, etc. can be used. As the coloring agent contained in the core material of the capsule toner of the present invention, known dyes and pigments can be used. For example, various carbon blacks, aniline blacks, naphthol yellows, molybdenum oranges,
Examples include rhodamine lake, alizarin lake, methyl violet lake, phthalocyanine blue, nigrosine methylene blue, rose bengal, and quinoline yellow. When the capsule toner of the present invention is used as a magnetic toner, magnetic powder can be contained in the core material. Magnetic powders include iron, cobalt,
These include ferromagnetic elements such as nickel or manganese, and alloys and compounds containing these such as magnetite and ferrite. This magnetic powder may also be used as a coloring agent. Furthermore, this magnetic powder may be treated with various hydrophobizing agents such as silane coupling agents, titanium coupling agents, surfactants, and the like. The content of this magnetic powder is the total amount of resin in the core material.
It is preferably 15 to 70 parts by weight per 100 parts by weight. Carbon black, various dyes and pigments, hydrophobic colloidal silica, and the like can be added or mixed to the capsule toner of the present invention for the purpose of charge control, imparting fluidity, coloring, and the like. As the shell material used in the present invention, various thermoplastic cationic polymers are used. Thermoplastic cationic polymers can be obtained as single or copolymers using cationic monomers, or can be cationized by further treating the obtained polymer with a cationizing agent. . Furthermore, the cationic polymer used in the present invention can be obtained by exchanging the counter ion of the obtained cationic polymer with the desired bulky and hard anion.
Cationic polymers include dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, N-vinylcarbazole, vinylpyridine,
A monomer containing a nitrogen atom in its molecule, such as 2-vinylimidazole, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, N-n-butoxyacrylamide, and a monomer obtained by quaternizing this with a cationizing agent, alone or as follows. Various monomers mentioned in , such as styrene, P-chlorostyrene, P-dimethylamino-styrene, and its substituted products; methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate , methacrylic acid N,N-
Acrylic acid or methacrylic acid esters such as dimethylaminoethyl ester; maleic anhydride or half esters, half amides or diesterimides of maleic anhydride; nitrogen-containing vinyls such as vinylpyridine and N-vinylimidazole; vinyl formal, vinyl butyral, etc. vinyl acetal; vinyl monomers such as vinyl chloride, acrylonitrile, and vinyl acetate; vinylidene monomers such as vinylidene chloride and vinylidene fluoride; and olefin monomers such as ethylene and propylene. The obtained cationic polymer can also be used in combination with various known resins. For example, it is a resin made of the following monomers.
Styrene and substituted products thereof such as styrene, P-chlorostyrene, and P-dimethylamino-styrene;
Methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, N,N methacrylate
- esters of acrylic or methacrylic acid such as dimethylaminoethyl ester; maleic anhydride or half esters of maleic anhydride;
Nitrogen-containing vinyls such as half-amide or diesterimide, vinylpyridine, and N-vinylimidazole; Vinyl acetals such as vinyl formal and vinyl butyral; Vinyl monomers such as vinyl chloride, acrylonitrile, and vinyl acetate; Vinylidene such as vinylidene chloride and vinylidene fluoride Monomer: Olefin monomers such as ethylene and propylene. In addition, polyester, polycarbonate, polysulfonate, polyamide, polyurethane, polyurea, epoxy resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, melamine resin, polyphenylene Homopolymers or copolymers such as polyether resins such as nylene oxide or thioether resins,
Alternatively, a mixture can be used. As the cationizing agent, halides represented by aliphatic halides and aromatic halides are effective in the present invention from the viewpoint of material availability, cost, and reactivity. Specifically, alkyl halides represented by chlorinated methyl, chlorinated ethyl, brominated methyl, brominated ethyl, brominated propyl, iodized methyl, iodized ethyl, iodized propyl, etc.; chlorinated benzoyl, bromine Halogenated benzoyls represented by benzoyl chloride and benzoyl iodide; benzyl halides represented by benzyl chloride, benzyl bromination, and benzyl iodine are particularly effective. Furthermore, as a method of anion exchange for bulky and hard anions according to the present invention, anion exchange is easily carried out by adding an acid and a salt containing bulky and hard anions to the aqueous phase and the organic solvent phase.
Bulky and hard anions used in the present invention include ClO ₄ , BF ₄ , IO ₄ , SbF ₄ , PF ₆ and the like. Particularly preferably CCl ₄ , BF ₄ , IO ₄
is valid. The average particle size of the capsule toner is preferably 3 to 20 microns (preferably 5 to 10 microns). The toner has a core containing 1 to 30 wt% (preferably 5 to 15 wt%) of a coloring dye and pigment, and a hard material of 0.01 to 2 μm (preferably 0.1 to 2 μm) surrounding the core.
It is coated to a thickness of 0.3μ). Various known encapsulation techniques can be used to produce the capsule toner. For example, spray drying method, interfacial polymerization method, coacervation method, phase separation method, in-situ polymerization method, described in U.S. Patent No. 3338991, U.S. Patent No. 3326848, U.S. Pat. You can use the methods described. A particularly preferred method is to apply a strong shearing force to a core material that has been heated and melted in advance in an aqueous medium together with an emulsifier or/and a suspending agent to obtain a core material having a desired particle size and uniform particle size distribution. A coacelvation method is effective, in which the core particles are dispersed in a good solvent and then a poor solvent is gradually added to fix the shell film onto the surface of the core particles. At this time, if necessary, it is also possible to use the product after removing the emulsifier and/or suspending agent used before the encapsulation step. Example 1 "Microcrystalline wax M-160" (manufactured by Sanoko) 30 parts by weight "Hoechst KSL wax" (manufactured by Hoechst)
30 parts by weight of "triiron tetroxide" 40 parts by weight of "styrene-diethylaminoethyl methacrylate" 2 parts by weight The above substances were kneaded for 1 hour while heating to 120° C. in an attritor. Meanwhile, 2 parts by weight of colloidal silica "Aerosil #300" and 2 parts of ion-exchanged water were added to a 3-separable flask equipped with a Homomixer manufactured by Tokushu Kika Kogyo Co., Ltd.
While stirring at 12,000 rpm, the mixture was heated until the internal temperature reached 90°C. Add 100g of the above kneaded material into this,
Atomization was continued using a Coulter counter until the volume average particle size reached 13 μm. After completion of the dispersion, the dispersion was cooled and caustic soda was added so that the pH of the solution was 12. After stirring for 4 hours, filtering and washing operations were repeated using a rotary centrifuge until the dispersion was neutralized. After drying, encapsulation was continued. Particles" 100 parts by weight "Polymer obtained by quaternizing styrene-dimethylaminoethyl methacrylate-methyl methacrylate terpolymer with benzyl chloride
10 parts by weight "acetone" 100 parts by weight The above dispersion was discharged and atomized from a spray drying device equipped with a disc atomizer to obtain a desired microcapsule toner. Further, this capsule toner was transferred into a flask equipped with a dropping funnel, ion-exchanged water was added, and the mixture was sufficiently stirred. Next, a 30% aqueous tetrafluoroboric acid solution was gradually added dropwise from the dropping funnel, and the mixture was allowed to react at room temperature for 1 hour. After the reaction, an over-drying operation was performed to obtain a microcapsule toner in which the counter ions were replaced with tetrafluoroborate ions. Whether or not anions were exchanged was confirmed by IR spectrum and elemental analysis. Example 2 "Microcrystalline wax M-160" (manufactured by Sanoko) 30 parts by weight "Hoechst KSL wax" (manufactured by Hoechst)
30 parts by weight of "triiron tetroxide" 40 parts by weight of "styrene-diethylaminoethyl methacrylate" 2 parts by weight The above substances were kneaded for 1 hour while heating to 120° C. in an attritor. Meanwhile, 2 parts by weight of colloidal silica "Aerosil 300" and 2 parts of ion-exchanged water were added to a 3-separable flask equipped with a homomixer manufactured by Tokushu Kika Kogyo Co., Ltd., and the rotation speed was 12,000 rpm.
While stirring, the mixture was heated until the internal temperature reached 90°C.
100 g of the above-mentioned kneaded material was put into this, and atomization was continued until the particle size of the dispersed particles reached 13 μm (volume average particle size using a Coulter counter). After the dispersion was completed, the dispersion was cooled and caustic soda was added so that the pH of the solution became 12. After stirring for 4 hours, filtering and washing were repeated using a rotary centrifuge until neutralized. After drying, encapsulation was continued. ``Core particles'' 100 parts by weight ``Styrene-dimethylaminoethyl methacrylate copolymer quaternized with benzyl chloride 10 parts by weight ``Acetone'' 100 parts by weight or more of substances were placed in a separable flask equipped with a homomixer. Add and while stirring thoroughly,
A microcapsule toner was obtained by gradually dropping methanol. After this capsule toner was sufficiently dispersed in water again, a 30% aqueous perchloric acid solution was added and stirring was continued for 1 hour. After drying, a microcapsule toner in which counter ions were exchanged with perchlorate ions was obtained. Examples 3 to 6 Encapsulation and anion exchange operations shown in the table were carried out in accordance with Example 1. Images were produced using the toners obtained in the above manner under various environments. The image was printed using an improved PC-10 machine (manufactured by Canon Inc.), and the image was fixed using a metal roller set at a linear pressure of 10 kg/cm. Furthermore, the degree of film formation was observed using a scanning microscope (SEM). The results are shown in the table below.

【table】

【table】

Claims (1)

[Claims] 1 ClO ₄ , BF ₄ , IO ₄ , SbF ₄ and PF ₆
A microcapsule toner for developing electrostatic latent images, characterized in that a thermoplastic cationic polymer holding an anion selected from the group consisting of as a counterion is used as a shell material, and core particles are covered with the shell material. .