JPH0374383B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a capsule toner used for converting a latent image formed in a recording method such as electrophotography into a visible image. The present invention relates to a method for producing an insulating capsule toner having the following properties.

Description of Known Art There are three known methods for fixing toner images in recording methods such as electrophotography: heat fixing, solvent fixing, and pressure fixing. Of these,
Since the pressure fixing method does not use heat or solvent, it does not suffer from the various problems associated with methods such as heat fixing or solvent fixing, and the access time is fast, making it possible to follow high-speed fixing methods. It has various inherent advantages. The present invention provides a method for producing a capsule toner suitable for the pressure fixing method in this category.

While the pressure fixing method has many advantages as mentioned above, it has poor fixing properties compared to fixing methods such as heat fixing, the fixed image is easily peeled off when rubbed, and it requires considerably high pressure for fixing. Therefore, fatigue of the support medium such as transfer paper is likely to occur due to breakage of the fibers of the support medium, the surface of the support medium tends to become excessively glossy, and the need to apply high pressure Since there is a limit to the miniaturization of the pressure roller, there is a problem in that there is a limit to the miniaturization of the entire copying apparatus.

In order to solve the above-mentioned problems associated with the pressure fixing method, capsule toner in which toner is contained in microcapsules has already been developed. Capsule toner is a microcapsule type obtained by forming an outer shell that can be destroyed by applying pressure around a core material containing a coloring material such as carbon black and a binder such as a polymer or a high-boiling solvent. It is a toner. Capsule toner is said to be a toner suitable for pressure fixing because it does not require high pressure for fixing and has excellent fixing properties. It cannot be said that the properties that are originally required are necessarily satisfactory.

In other words, the toner used as an electrophotographic developer has good powder properties and excellent development performance.
It is necessary that the toner does not stain the surface of the photoreceptor, which is the surface on which the latent image is formed, and that the toner used in the pressure fixing method has good pressure fixing properties.
It is also necessary that the pressure roller used for pressure fixing is less prone to offset phenomenon (a phenomenon in which toner adheres to the surface of the pressure roller and stains it). In other words, the toner used in the pressure fixing method has characteristics such as powder properties, fixability to support media such as paper (including shelf life of fixed images), non-offset properties, and chargeability depending on the developing method used. All properties such as electrical resistance (or conductivity) must be at a high level. However, hitherto known capsule toners have not always been satisfactory in terms of the above-mentioned properties.

OBJECTS OF THE INVENTION The present invention provides a method for producing an insulating capsule toner that has especially high electrical resistance among these various properties. In other words, typical methods for charging capsule toner include a method in which the capsule toner is mixed with a carrier such as iron powder to generate frictional charging, and a method in which the capsule toner is charged by rubbing it against a material such as fur. There are known methods to do this. The capsule toner used in such a method of charging using frictional charging must be an insulating capsule toner with high electrical resistance in order to achieve efficient charging and maintain the charge stably. . That is, when the above-mentioned frictional charging is performed using capsule toner with poor electrical resistance, sufficient charging is not achieved, and the charging tends to leak out in a short period of time, making it difficult to perform development properly. Problems such as becoming difficult to use are likely to occur.

The present inventors believe that the reason why it is difficult for the electrical resistance of the capsule toner to reach a sufficiently high level is that various impurities, especially ionic substances, that adhere to the surface of the capsule toner during the production process of the capsule toner reduce the electrical resistance of the toner. Furthermore, the removal of such impurities can be efficiently achieved by washing the capsule toner with water containing an ion exchange resin, and this washing operation results in the removal of such impurities. The present invention was achieved by discovering that an insulating capsule toner can be obtained.

SUMMARY OF THE INVENTION Accordingly, the present invention provides microcapsules by forming an outer shell around an oil droplet core material containing a coloring material and a binder dispersed in an aqueous liquid, and then separating and drying the microcapsules. Provided is a method for producing an insulating capsule toner, which comprises washing the microcapsules with water in the presence of an ion exchange resin before drying the microcapsules. It is.

A core material containing a colored material, such as carbon black, and a binder, such as a polymer, high-boiling solvent, is dispersed in the form of oil droplets in an aqueous liquid such as water, and then a pressure is applied around the oil droplet core material. As mentioned above, a method for producing a capsule toner is already known, which comprises forming microcapsules by forming an outer shell having the property of breaking down by applying a silica gel, and then separating the microcapsules from an aqueous liquid and drying them.

There are no particular limitations on the composition of the core material, the material of the outer shell, and the method for manufacturing microcapsules that can be used in carrying out the method for manufacturing the capsule toner of the present invention. For example, various known materials and methods for manufacturing microcapsules may be used. can do.

However, as the binder, it is desirable to use a binder composition containing a polymer and a high boiling point solvent that can dissolve or swell the polymer.

Examples of polymers include polyolefin, olefin copolymer, styrenic resin, and styrene.
Butadiene copolymer, epoxy resin, polyester, rubber, polyvinylpyrrolidone, polyamide, coumaron/indene copolymer, methyl vinyl ether/maleic anhydride copolymer, amino resin, polyurethane, polyurea, homopolymer or copolymer of acrylic ester, methacrylic Homopolymers or copolymers of acid esters, copolymer oligomers of acrylic acid and long-chain alkyl methacrylates, polyvinyl acetate, and polyvinyl chloride can be mentioned.

Particularly preferred among these polymers are:
Homopolymers or copolymers of acrylic esters, homopolymers or copolymers of methacrylic esters, or styrene-butadiene copolymers.

Examples of high-boiling solvents that can dissolve or swell the polymers mentioned above include phthalate esters such as dibutyl phthalate; aliphatic dicarboxylic acid esters such as diethyl malonate; and tricresyl phosphate. phosphoric acid esters such as o-acetyltriethyl citrate; benzoic acid esters such as butyl benzoate; fatty acid esters such as dioctyl adipate; alkylnaphthalenes such as methylnaphthalene; Alkyl diphenyl ethers such as o-methyl diphenyl ether;
Amide compounds of higher fatty acids or aromatic sulfonic acids such as N,N-dimethyllauramide, N-butylbenzenesulfonamide; trimellitic acid esters such as trioctyl trimellitate; and 1-isopropyl-phenyl-2 -Diarylalkanes such as phenylmethane may be mentioned.

Particularly preferred among the above high boiling point solvents are phthalic acid esters, aliphatic dicarboxylic acid esters,
alkylnaphthalenes and diarylalkanes.

As a coloring material for electrophotographic toner,
Black toners such as carbon black and grafted carbon black are commonly used.
Various chromatic colorants such as blue, red, and yellow have also been used. These known coloring materials can also be used in producing the capsule toner of the present invention.

The core material of the capsule toner may contain magnetic particles. As the magnetic particles, known magnetic particles (magnetizable particulate matter) for magnetic toner can be used. Examples of such magnetic particles include magnetic particles made of a single metal such as cobalt, iron, or nickel, an alloy, or a metal compound. Note that when colored magnetic particles such as black magnetite are used as the magnetic particles, the superchromic magnetic particles such as magnetite can also be used as a component that serves as both the magnetic particles and the colored material.

Note that the capsule toner may contain various additives, for example, a release agent such as a fluororesin, if desired.

A method for manufacturing microcapsules is already known in which an outer shell made of a polymeric material is formed around a core material dispersed in the form of oil droplets containing magnetic particles, a coloring material, and a binder in an aqueous liquid. , these known methods can also be used to produce the capsule toner of the present invention.

For example, an interfacial polymerization method can be mentioned as a method for producing microcapsules that can be used for producing the capsule toner of the present invention.

Other examples of methods for producing microcapsules that can be used in the present invention include an internal polymerization method, a phase separation method, an external polymerization method, a melt dispersion cooling method, and a coacervation method.

Note that the method for manufacturing microcapsules that can be used in the present invention is not limited to those exemplified above, and other methods for manufacturing microcapsules can also be used.

The polymer material forming the outer shell is not particularly limited, but examples include polyurethane resin, polyamide resin, polyester resin, polysulfonamide resin, polyurea resin, epoxy resin, polysulfanate resin, and polycarbonate resin. can. The outer shell made of these resins can be easily formed by a known interfacial polymerization method.

Among these polymeric substances, preferred are polyurea resin and polyurethane resin,
These include polyisocyanates such as diisocyanates, triisocyanates, tetraisocyanates, and polyisocyanate prepolymers, polyamines such as diamines, triamines, and tetraamines, prepolymers containing two amino groups, piperazine and its derivatives, By reacting polyol etc. with interfacial polymerization method in an aqueous solvent,
It can be easily formed as an outer shell of a microcapsule.

In addition to the polymer materials mentioned above, examples of the outer shell material include melamine resins, urea resins, polymers of styrene or substituted products thereof, and copolymers thereof (e.g., polystyrene, polyparachlorostyrene). , styrene/butadiene copolymer, styrene/acrylic acid copolymer, styrene/acrylic acid ester copolymer, styrene/methacrylic acid copolymer, styrene/methacrylic acid ester copolymer, styrene/maleic anhydride copolymer , styrene/vinyl acetate copolymer, etc.), polyvinyl toluene resin, acrylic acid ester homopolymer, methacrylic acid ester homopolymer, xylene resin, methyl vinyl ether/maleic anhydride resin, vinyl butyral resin, polyvinyl alcohol resin, and polyvinyl Pyrrolidone and the like can also be used.

Further, it is particularly preferable that the outer shell of the capsule toner is a composite wall formed from various polymeric materials. Particularly desirable composite walls for use in the present invention are composite walls made of polyurea resin and polyamide resin, and composite walls made of polyurethane resin and polyamide resin. Alternatively, it may be a composite wall made of polyurea resin, polyurethane resin, and polyamide resin.

A composite wall made of polyurethane resin and polyamide resin is prepared, for example, by an interfacial polymerization method using polyisocyanate, acid chloride, polyamine and polyol, adjusting the pH of the emulsifying medium serving as the reaction solution, and then heating it. be able to. Further, a composite wall made of a polyurea resin and a polyamide resin can be prepared by using polyisocyanate, acid chloride, and polyamine, adjusting the pH of the emulsifying medium serving as the reaction solution, and then heating it. Details of the manufacturing method of these composite walls made of polyurea resin and polyamide resin, and of composite walls made of polyurethane resin and polyamide resin are described in the specification of Japanese Patent Application No. 165262/1983. Such composite-walled shells are particularly suitable for forming magnetic capsule toners containing magnetic particles within the core material.

When forming a composite wall containing a polyamide resin as described above, a process of adjusting the pH using an alkali such as sodium carbonate is generally inserted, but the alkali metal ions etc. introduced into the microcapsule manufacturing reaction system in this way are When cations adhere to the surface of the capsule toner, the electrical resistance of the toner decreases significantly. Therefore, the method for producing a capsule toner of the present invention requires a composite wall containing magnetic particles in the core material and an outer shell containing a polyamide resin, such as a polyurea resin/polyamide resin composite wall,
It is particularly advantageous when used in the production of capsule toners having a polyurethane resin/polyamide resin composite wall, a polyurea resin/polyurethane resin/polyamide resin composite wall.

Microcapsules produced by forming an outer shell around a core material in an aqueous liquid are then separated from the liquid phase and dried. This separation and drying operation is usually carried out by spray drying a dispersion containing microcapsules.

The method for producing a capsule toner of the present invention is characterized in that, before drying the microcapsules formed in an aqueous liquid, the microcapsules are washed with water containing an ion exchange resin. The microcapsules according to the present invention are preferably washed, for example, by the following operation.

First, microcapsules formed in an aqueous liquid are separated from the aqueous liquid (reaction medium) as a slurry by a method such as centrifugation,
This slurry is then pre-washed by dispersing it in water (preferably ion-exchanged water or distilled water). Microcapsules are then separated from this wash water. It is desirable to repeat this pre-washing step for microcapsules.
For example, it is repeated 5 times or more, preferably 10 times or more.

Next, the microcapsule slurry is dispersed in water containing an ion exchange resin (preferably ion exchange water or distilled water) to wash the microcapsules. This cleaning step using water containing ion exchange resin may be performed only once.
Alternatively, it may be performed repeatedly.

The ion exchange resin used in the present invention is not particularly limited, and known cation exchange resins and anion exchange resins can be used. However, in the microcapsule cleaning process according to the present invention, it is desirable to remove both anions and cations attached to the microcapsules, so it is preferable to use both a cation exchange resin and an anion exchange resin. preferable. Further, since the attachment of cations such as alkali metal ions tends to lower the electrical resistance of the capsule toner, it is advantageous to use a cation exchange resin when only one type of ion exchange resin is used.

The microcapsules washed according to the invention are then dried by known methods.

The capsule toner produced as described above exhibits high electrical resistance due to less adhesion of impurities, especially ionic impurities, to the surface, and therefore exhibits excellent properties as a capsule toner for electrophotography that uses triboelectric charging. .

Note that it is desirable that the separated and dried microcapsules be further subjected to heat treatment. This heat treatment particularly improves the powder properties of the capsule toner.
The heat treatment is preferably carried out at a temperature in the range of 50 to 300°C, and particularly preferably at a temperature in the range of 80 to 150°C. The heating time varies depending on the heating temperature and the type of core material used, but is usually selected from a range of 10 minutes to 48 hours, and more generally from a range of 2 to 24 hours.

There are no particular restrictions on the equipment and appliances used for the heat treatment, and for example, any heating drying equipment or heating drying equipment such as an electric furnace, matsuru furnace, hot plate, electric dryer, fluidized bed dryer, infrared dryer, etc. can be used. Can be used.

The outer shell of the capsule toner may contain, if desired,
Metal-containing dyes, charge control agents such as nigrosine, flow agents such as hydrophobic silica, or other optional additives may be added. These additive substances can be incorporated into the outer shell of the capsule toner at any time, such as when the outer shell is formed or after the capsule toner is separated and dried.

Furthermore, when carrying out the method for manufacturing the capsule toner of the present invention, Japanese Patent Application Laid-Open Nos. 57-179860, 58-21259, 58-66948, 58
−66949, 58−66950, 58−68753, 58−70236, 58
−91464, 58−95353, 58−100855, 58−100856,
58−100857, 58−100858, 58−111050, 58−
Publications Nos. 144932 and 58-145233, and patent applications No. 57-64673, 57-175404, 57-189139,
58−41960, 58−48418, 58−58419, 58−57421,
It is also possible to use it in appropriate combination with the capsule toner and capsule toner manufacturing technology described in patent applications No. 58-57422 and No. 58-174895.

Next, Examples and Comparative Examples of the present invention will be shown.

[Example 1] 50% of polyisobutyl methacrylate (trade name: Acrybase, MM-2002-2: manufactured by Fujikura Kasei Co., Ltd.)
wt% containing 1-isopropyl-phenyl-2
-Phenylethane (Product name: CPE: Kureha Chemical Co., Ltd.)
A dispersion liquid (magnetic ink) was prepared by kneading and dispersing 40 g of a solution of the product manufactured by Toda Kogyo Co., Ltd. and 50 g of magnetite magnetic particles (trade name: EPT-1000, manufactured by Toda Kogyo Co., Ltd.) in an automatic mortar.

Separately, add terephthalic acid chloride to 20 g of ethyl acetate.
2.2g, 9.9g of addition compound of toluylene diisocyanate and trimethylolpropane (trade name: Burnock D-750: manufactured by Dainippon Ink & Chemicals Co., Ltd.)
A solution was prepared, and this solution was mixed with the above dispersion. Next, add this mixture to methylcellulose (product name: Metrose-60SH: manufactured by Shin-Etsu Chemical Co., Ltd.).
It was emulsified and dispersed in 200 g of a 5% aqueous solution. After adjusting the average size of oil droplet particles in the emulsion to about 13 μm, about 10 minutes later, 50 g of a 2.5% aqueous solution of diethylenetriamine and then a 5% aqueous solution of sodium carbonate were added to adjust the pH to 11.0. This emulsion was heated at 65℃.
The mixture was stirred in a constant temperature bath for about 3 hours to complete encapsulation.

The resulting microcapsule dispersion was centrifuged to precipitate the microcapsules, and the supernatant liquid was replaced with distilled water. The microcapsules were redispersed in this distilled water, and the microcapsules were similarly washed by centrifugation and replacement of the supernatant with distilled water. After performing this washing operation 20 times, cation exchange resin (product name: DOWEX)
50W: manufactured by Dow Chemical Company) and anion exchange resin (product name: Dowex 1: manufactured by Dow Chemical Company)
Distilled water containing (1/1/2 of the solid weight of the microcapsules containing cation exchange resin and anion exchange resin, respectively)
After dispersing the microcapsules in water (approximately 20 times the solid weight of the microcapsules) and washing with water, and removing the ion exchange resin by filtration, the microcapsule slurry was placed in an oven at 100°C for 5 hours. A powdered capsule toner was obtained by drying.

The electrical resistance of the obtained powder capsule toner is:
7× under the conditions of 28℃, 85%RH, 1×10 ⁴ V/cm
It was 10 ¹⁴ Ω・cm.

The capsule toner described above is a very smooth and highly fluid powder, and microscopic observation confirmed that most of the capsule particles existed independently.

An electrostatic latent image formed by ordinary electrophotography was developed with the above capsule toner to form a toner image, and then the toner image was transferred to transfer paper to obtain a visible image. This visible image is fixed using a pressure fixing roller.
When pressure fixing was carried out at a pressure of 350 kg/cm ² , a copy image with high sharpness was obtained.

[Comparative Example 1] Except that the cleaning process using distilled water containing ion exchange resin was replaced with a cleaning process using only distilled water.
The operation described in Example 1 was carried out to obtain a powdered capsule toner.

The electrical resistance of the obtained powdered capsule toner was 5×10 ¹³ Ω·cm under the same conditions as in Example 1.

[Example 2] Microcapsules separated from aqueous reaction medium
The procedure described in Example 1 was repeated, except that 20 washing steps were performed with well water and the washing step with distilled water containing ion exchange resin was replaced with a washing step with well water using the same amount of ion exchange resin. A powdered capsule toner was obtained.

The electrical resistance of the obtained powder capsule toner is:
5× under the conditions of 280℃, 85%RH, 1×10 ⁴ V/cm
It was 10 ¹⁴ Ω・cm.

The capsule toner described above is a very smooth and highly fluid powder, and microscopic observation confirmed that most of the capsule particles existed independently.

When an electrophotographic operation was carried out using the above capsule toner according to the method described in Example 1, a copied image with high sharpness was obtained.

[Comparative Example 2] Except that the cleaning process using well water containing ion exchange resin was replaced with a cleaning process using only well water.
The same operation as in Example 2 was carried out to obtain a powdered capsule toner.

The electrical resistance of the obtained powder capsule toner is:
Under the same conditions as in Example 2, the resistance was 1×10 ¹³ Ω·cm.

[Example 3] A cleaning process using distilled water containing both a cation exchange resin and an anion exchange resin was replaced with a cleaning process using distilled water containing only a cation exchange resin (the amount of cation exchange resin used was the same). A powdered capsule toner was obtained by carrying out the operation described in Example 1, except that the following procedure was performed.

The electrical resistance of the obtained powder capsule toner is:
3.5× under the conditions of 28℃, 85%RH, 1×10 ⁴ V/cm
It was 10 ¹⁴ Ω・cm.

The capsule toner described above is a very smooth and highly fluid powder, and microscopic observation confirmed that most of the capsule particles existed independently.

When an electrophotographic operation was carried out using the above capsule toner according to the method described in Example 1, a copied image with high sharpness was obtained.

Claims (1)

[Claims] 1. Forming an outer shell around an oil droplet-like core substance containing a coloring material and a binder dispersed in an aqueous liquid to form microcapsules, and then separating and drying the microcapsules. A method for producing an insulating capsule toner comprising washing the microcapsules with water in the presence of an ion exchange resin before drying the microcapsules. 2. The method for producing an insulating capsule toner according to claim 1, characterized in that a cation exchange resin and an anion exchange resin are used in combination as the ion exchange resins. 3. The method for producing an insulating capsule toner according to claim 1, characterized in that a cation exchange resin is used as the ion exchange resin. 4. The method for producing an insulating capsule toner according to claim 1, wherein the outer shell is made of a composite wall containing a polyurea resin and/or polyurethane resin and a polyamide resin. 5. The method for producing an insulating capsule toner according to claim 1, wherein the core substance contains magnetic particles.