JP3421869B2 - Polymer fine particles for electrophotographic developers - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to characteristics such as less fog over a long period of time, excellent cleaning properties, and little decrease in image density when continuous copying is performed. (Hereinafter referred to as "long-run characteristics"). [0002] Conventionally, a powder developer is known as a developer for developing an electrostatic latent image such as an electrophotographic method or an electrostatic printing method. In a powder developer, due to agglomeration between particles contained therein, the flow of individual particles becomes insufficient, and as a result, the resolution is reduced. To prevent this resolution loss,
Conventionally, a method of adding silica fine particles, fluororesin fine powder, or the like has been performed. However, there is a problem that the resolution is not sufficiently improved and the cleaning property is not sufficient, and the toner adheres to the surface of the photosensitive drum in a film form. In order to improve this disadvantage, for example, Japanese Patent Application Laid-Open No. 60-1868
For example, Japanese Patent Publication No. 51 (1993) discloses a method of adding thermoplastic polymer fine particles to a powder developer. In this method, although the initial image is good, when continuous copying is performed for a long time, the developer is stirred for a long time, so that the polymer fine particles adhere to the carrier surface due to local heat generation and impact. As a result, the reduction in image density and the reduction in fog increased, and the long-run characteristics were poor. SUMMARY OF THE INVENTION [0003] The present invention has been made in view of the above-mentioned conventional technical problems, and provides fine particles for an electronic developer that are excellent in long-run characteristics and can provide a high-resolution electronic developer. The purpose is to provide. SUMMARY OF THE INVENTION The present invention relates to a crosslinked polymer particle (A) obtained by polymerizing a polymerizable monomer having a crosslinkable monomer content of 10% by weight or more. Is partially or completely coated with a polymer (B) obtained by polymerizing a polymerizable monomer having a content of less than 10% by weight, and the weight ratio of (A) / (B) is 100 /
It is intended to provide 0.01 to 900 parts by weight of polymer fine particles for an electrophotographic developer. Less than,
The present invention will be described in detail. The polymer fine particles for an electrophotographic developer of the present invention contain a crosslinkable monomer having two or more groups containing a polymerizable double bond in the molecule (hereinafter simply referred to as “crosslinkable monomer”). Is polymerized by polymerizing a polymerizable monomer having a crosslinkable monomer content of less than 20% by weight on the surface of a crosslinked polymer particle (A) obtained by polymerizing a polymerizable monomer having 10% by weight or more. ) Is partially or entirely laminated, and the weight ratio of (A) / (B) is 100/0.
The particles are from 0.01 to 900 parts by weight. [0006] The content of the crosslinkable monomer in the polymerizable monomer used in the crosslinked polymer particles (A) is 10% by weight or more, preferably 15% by weight or more, more preferably 20% by weight or more. When the content of the crosslinking monomer is 10
When the amount is less than the weight%, particles adhere to the surface of the carrier, and the long-run characteristics are deteriorated. [0007] The content of the crosslinking monomer in the polymerizable monomer used in the polymer (B) is less than 10% by weight, preferably 8% by weight or less, more preferably 5% by weight or less. When the content of the crosslinkable monomer among the polymerizable monomers constituting the polymer (B) is 10% by weight or more, the powder dispersibility of the polymer fine particles after drying into powder becomes poor, and the resolution of electrophotography becomes low. . The amount of the polymer (B) partially or completely laminated on the surface of the crosslinked polymer particles (A) is 0.01 to 900 parts by weight based on 100 parts by weight of the crosslinked polymer particles (A).
Parts by weight, preferably 0.1 to 400 parts by weight, more preferably 0.5 to 200 parts by weight. When the amount of the polymer (B) is less than 0.01 part by weight, the resolution is reduced.
If it exceeds 900 parts by weight, the long-run characteristics are inferior. Also,
The polymer (B) is a polymer having a chemically reactive or ionic group in the molecule and having a functional group excluding a group containing a polymerizable double bond (hereinafter, simply referred to as “functional group”). And the powder charging characteristics can be further controlled. Here, the functional group is a carboxyl group,
It is at least one selected from reactive functional groups such as a hydroxyl group, an N-methylol group, a sulfone group, a maleic anhydride unit, an epoxy group, an amino group, an amide group, and a nitrile group. Preferred functional groups are carboxyl group,
They are a hydroxyl group, an amino group, and an amide group. The average particle size of the polymer fine particles for an electrophotographic developer of the present invention is 0.02 to 2 μm, preferably 0.05 to 2 μm.
To 1 μm, and more preferably 0.01 to 2 μm.
The average particle size here is measured by the following method. The average particle diameter of the polymer fine particles for an electrophotographic developer is measured by measuring the particle diameter of 100 particles directly from a transmission electron micrograph (when the particles are not spherical, the long diameter and the short diameter are measured). The average value was obtained.). The preferred glass transition temperature of the above polymer (B) is 50 ° C. or higher, especially 70 ° C. or higher. When the glass transition temperature of the polymer (B) is less than 50 ° C., the powder dispersibility becomes poor. Examples of the crosslinkable monomer used in the crosslinked polymer particles (A) and the polymerizable (B) include non-conjugated vinyl compounds represented by divinylbenzene and polyvalent acrylate compounds represented by trimethylenepropane trimethacrylate. The following compounds having two or more copolymerizable double bonds are exemplified,
These are used alone or in combination of two or more. Specific examples of the crosslinking monomer include polyethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-butylene glycol diacrylate, 1,6-hexanelene glycol diacrylate, and neopentyl glycol diacrylate. ,
Polypropylene diacrylate, 2,2'-bis (4-
Acryloxypropoxyphenyl) propane, 2,
Diacrylate compounds such as 2′-bis (4-acryloxydiethoxyphenyl) propane, triacrylate compounds such as trimethylolpropane triacrylate, trimethylolethane triacrylate, and tetramethylolmethane triacrylate; ditrimethylolpropane tetraacrylate; Tetraacrylate compounds such as tetramethylolmethane tetraacrylate and pentaerythritol tetraacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol methacrylate, polyethylene glycol methacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene Glycol dimethacrylate, 1,6-hexane glycol dimethacrylate, Methacrylate compounds such as pentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2-bis (4-methacryloxydiethoxyphenyl) propane, trimethylolpropane trimethacrylate, and trimethylolethane trimethacrylate. Trimethacrylate compounds, methylenebisacrylamide, divinylbenzene and the like can be mentioned. Of the above, it is preferable to use divinylbenzene, ethylene glycol dimethacrylate, or trimethylolpropane trimethacrylate, and particularly preferable is divinylbenzene. Among the polymerizable monomers other than the crosslinkable monomer, examples of the monomer having no functional group include the following compounds, which are used alone or in combination of two or more.
Aromatic monovinyl compounds such as styrene, ethylvinylbenzene, α-methylstyrene, fluorostyrene and vinylpyrine, butyl acrylate, 2-ethylhexyl acrylate, β-methacryloyloxyethyl hydrogendiene phthalate, N, N′-dimethylaminoethyl acrylate, etc. Acrylic acid ester monomer, 2
-Methacrylate monomers such as ethylhexyl methacrylate, methoxydiethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, N, N'-dimethylaminoethyl methacrylate, silicon-modified monomers, macromonomers and the like. Further examples include conjugated double bond compounds such as butadiene and isoprene, vinyl ester compounds such as vinyl acetate, 4-methyl-1-pentene, and other α-olefin compounds. Among the polymerizable monomers other than the crosslinkable monomer, the monomers having a functional group include mono- or dicarboxylic acid monomers such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid, and 2-acryloyloxyethyl-2-yl. Hydroxyethyl phthalic acid, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxyethyl methacrylate, N-methylolacrylamide, sodium styrenesulfonate, maleic anhydride,
Glycidyl acrylate, glycidyl methacrylate,
Examples thereof include amide compounds such as acrylamide, methacrylamide, and methylenebisamide; and vinyl cyanide compounds such as acrylonitrile and methacrylonitrile. In the present invention, the polymer fine particles for electrophotographic development wherein the monomer having a functional group is contained in the monomer constituting the polymer (B) in an amount of 0.05 to 20% by weight, particularly 0.1 to 15% by weight. It is preferable that the charging characteristics of the toner can be controlled within an appropriate range. Preferred polymerizable monomers are styrene, ethylvinylbenzene, acrylonitrile, tyl methacrylate, butyl acrylate, and monomers having a functional group. Preferred combinations of the polymerizable monomers constituting the crosslinkable polymer particles (A) include a crosslinkable monomer such as a non-conjugated vinyl compound and a polyvalent methacrylate compound, an aromatic monovinyl compound, an acrylate monomer, and a methacrylate ester. Examples thereof include a combination with a polymerizable monomer such as a monomer, and a combination of a non-conjugated vinyl compound and an aromatic monovinyl compound is particularly preferable. Preferred combinations of the polymerizable monomers constituting the polymer (B) include a non-conjugated vinyl compound, a crosslinkable monomer such as a polyvalent methacrylate compound and an aromatic monovinyl compound, an acrylate monomer, a methacrylate monomer, and the like. Examples of the combination include a polymerizable monomer and a monomer having a functional group, and a combination of a non-conjugated vinyl compound, an aromatic monovinyl compound, and a di- or monocarboxylic acid is particularly preferable. Next, a preferred method for producing the polymer fine particles for electrophotographic development of the present invention will be described. First, a polymerizable monomer having a crosslinkable monomer content of 10% by weight or more is polymerized preferably by an emulsion polymerization method to obtain crosslinked polymer particles (A). The average particle size of the crosslinked polymer particles (A) at this time is not particularly limited, and the crosslinkable polymer particles (A) may be crosslinked so that the desired average particle size of the finally obtained polymer fine particles for electrophotographic development is obtained. The average particle diameter of the polymer particles (A) is appropriately determined. The average particle size of the crosslinked polymer particles (A) can be controlled by the amount of the emulsifier, stirring, and other known methods. In the presence of 100 parts by weight of the crosslinked polymer particles (A), the content of the crosslinkable monomer is less than 10% by weight, and preferably the content of the monomer having a further functional group is 0.05 to 0.05%.
By polymerizing 0.01 to 900 parts by weight of a polymerizable monomer of 20% by weight, preferably by a polymerization method of an emulsion polymerization method,
The polymer (B) is appropriately laminated on the entire surface or a part of the surface of the crosslinked polymer particles (A). In the present invention, partially coating the surface of the crosslinked polymer particle with the polymer (B) means that the surface is less than 100% of the total surface area of the crosslinked polymer particle,
Preferably, 0.00001% or more and less than 100% are covered with the polymer (B). The method of adding the polymerizable monomer in the polymerization for obtaining the polymer (B) is preferably a method of adding a part or all of the monomer continuously or intermittently. As for the method of imparting a functional group to the polymer (B) by chemical treatment, for example, a polymer (B) having an epoxy group is obtained and then treated with ammonia, methylamine, or the like. An amino group can be provided, or a sulfone group can be provided by treating with sodium bisulfite or sulfuric acid. The polymerization initiator used in the above emulsion polymerization is not particularly limited as long as it is one used in ordinary emulsion polymerization and suspension polymerization. However, a polymerization initiator such as potassium persulfate, sodium persulfate and ammonium persulfate is used. Sulfate-based initiators, azo-based initiators, hydrogen peroxide, organic peroxides and the like may be used alone or in combination with various reducing agents such as ascorbic acid. In the above emulsion polymerization, a suspension protective agent or a surfactant is used to increase the stability of the polymerization reaction system. Usable surfactants can be used, for example, dodecyl benzene sulfonate, dodecyl sulfate, lauryl sulfate, dialkyl sulfosuccinate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethynyl alkenyl propenyl Examples thereof include anionic surfactants such as phenyl ether sulfate and formalin condensate of naphthalenesulfonic acid. Here, examples of the salt include sodium, ammonium and the like. Further, nonionic surfactants such as polyoxyethylene nonyl phenyl ether, polyethylene glycol monostearate, polyoxyethylene alkylpropenyl phenyl ether, and sorbitan monostearate can be used. A commonly known reactive emulsifier such as sodium naphthalenesulfonate can be used alone or in combination with the above-mentioned surfactant. As a preferable suspension protective agent, a water-soluble polymer such as polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, sodium polyacrylate, and hydroxypropylcellulose can be used. They are,
They may be used alone or in combination. Preferred combinations include a combination of an anionic surfactant, a nonionic surfactant and a water-soluble polymer. The production of the polymer fine particles for electrophotographic development of the present invention may be carried out in the same reaction system from the polymerization of the crosslinked polymer particles (A) to the polymerization of the polymer (B). The polymerization of A) and the polymerization of polymer (B) may be carried out in different reaction systems. When the polymerization of the crosslinked polymer particles (A) and the polymerization of the polymer (B) are performed in the same reaction system,
The monomer constituting the polymer (B) may be added when the polymerization addition rate of the crosslinked polymer particles (A) reaches 70% by weight, preferably 90% by weight or more. When polymerizing the crosslinked polymer particles (A), it is preferable to polymerize using polystyrene particles or the like as a seed. The polymer fine particles for electrophotographic development of the present invention can be mixed with a known toner to prepare an electrophotographic developer. Here, examples of the known toner include a one-component toner, a two-component toner, a negatively-charged toner, and a naturally-charged toner. The addition amount of the polymer fine particles for electrophotographic development of the present invention to the toner is usually 0.02 to 10% by weight, preferably 0.05 to 5% by weight, and particularly preferably 0.1 to 3% by weight. The present invention will now be described by way of examples, which should not be construed as limiting the invention thereto. In the following description, “parts” represents parts by weight, and “%” represents “% by weight”. Measurement method of particle diameter The average particle diameter of the polymer fine particles for electrophotographic development is measured by a particle diameter directly measured for 100 particles by a transmission electron micrograph (if the particles are not spherical, the long diameter may be determined). The minor axis was measured and the average value was determined.). Example 1 As the first step, divinylbenzene (commercial product, purity 55
%, The remaining 40% is ethyl vinyl benzene, the remaining 5%
Is diethylbenzene) 35 parts, styrene 55 parts, acrylic acid 10 parts, sodium dodecylbenzenesulfonate 1
0 parts, 900 parts of ion-exchanged water and 1 part of sodium persulfate
The mixture was charged into a reaction vessel and polymerized at 80 ° C. for 1 hour with stirring. Thereafter, as a second step, 8.7 parts of methyl methacrylate, 1 part of n-butyl acrylate, 2 parts of methacrylic acid and 1 part of ethylene glycol methacrylate
Part of the mixed monomer was continuously added for 3 hours to complete the polymerization, and further washed with a cross-flow filtration washing device (manufactured by NGK Insulators, Ltd.) using a ceramic membrane.
Polymer fine particles a for electrophotographic development were obtained. The average particle size of the obtained polymer fine particles a for electrophotographic development (hereinafter, referred to as particles a) was 0.08 μm. Next, 0.8 parts of the obtained particles a, which were powdered by spray drying, were mixed with a commercially available two-component toner (average particle diameter 12 μm).
m) 100 parts were mixed and stirred using a Henschel mixer to obtain a toner mixture. When the angle of repose of this mixture was measured using a powder property measuring device (Powder Tester, manufactured by Hosokawa Micron Corporation), it was 21 degrees. (The angle of repose of only a commercially available two-component toner is 36 degrees.) Ferrite carrier F-300H (manufactured by Nippon Iron Powder Co., Ltd.) as a carrier and a toner mixture having a toner concentration of 3%. , And an electrophotographic copying machine (P-570Z, manufactured by Minolta Camera Co., Ltd.) was used. 1 was subjected to a live-action test.
The resolution, the degree of cleaning, the fog, and the density reduction rate after the 50,000 sheets continuous actual shooting test were measured as follows. Table 1 shows the results. Resolution Electrophotographic Society Test Pattern No. 1m using 1
The limit resolution is checked to see how many lines can be distinguished per m. The cleaning base stain was visually judged, and x: when there was streak-like black stain, ○: when there was no stain at all. The fog base stain is visually determined. X: When there is a clear difference in whiteness from the original paper, ○: When there is almost no difference. Density reduction rate The optical density was measured by the Macbeth density diameter of the solid black, and from the comparison between the initial optical density value and the optical density after actual shooting of 50,000 sheets,
Determine the concentration reduction rate. Example 2 As a first step, polystyrene particles having a weight average molecular weight of 15,000 and an average particle diameter of 0.25 μm were added to 10
Parts, 5 parts of sodium dodecylbenzenesulfonate, 65 parts of divinylbenzene, 35 parts of styrene, 1 part of sodium persulfate, and 700 parts of ion-exchanged water were charged into a reaction vessel and polymerized at 80 ° C. for 1 hour with stirring while blowing nitrogen gas.
Thereafter, in the second step, 1 part of styrene, 1 part of methacrylic acid, 0.5 part of 2-hydroxyethyl methacrylate were added.
And 0.5 part of sodium persulfate were added, and the mixture was further polymerized at 80 ° C. for 3 hours to complete the polymerization, thereby producing polymer fine particles b for electrophotographic development. The obtained polymer fine particles b for electrophotographic development had an average particle diameter of 0.6 μm and were powdered in the same manner as in Example 1 to obtain a toner mixture. The resolution, the degree of cleaning, the fog, and the rate of density decrease were measured after the 50,000-sheet continuous actual photographing test was performed in the same manner as in Example 1. Table 1 shows the results. Example 3 In the second step of Example 2, 0.5 part of potassium persulfate was charged into a reaction vessel, and 100 parts of styrene, 50 parts of methyl methacrylate and 43 parts of n-butyl acrylate were used.
Parts, 7 parts of acrylic acid, 3 parts of ethylene glycol methacrylate, 40 parts of ion-exchanged water, and an emulsion formed by mixing 0.5 parts of dodecylbenzenesulfonic acid was added continuously for 3 hours to complete the polymerization, and the crosslinked polymer particles c Was manufactured. The average particle size of the obtained polymer fine particles for electrophotographic development c was 0.7 μm.
After the resulting composite polymer particles were dried, they were kneaded into a methyl methacrylate resin and the dispersibility of the particles was observed. As a result, the particles were dispersed with good affinity. The obtained polymer fine particles c for electrophotographic development had an average particle size of 0.7 μm.
Powdered in the same manner as described above to obtain a toner mixture. The resolution, the degree of cleaning, the fog, and the rate of density decrease were measured after the 50,000-sheet continuous actual photographing test was performed in the same manner as in Example 1. Table 1 shows the results. Example 4 In the second step of Example 2, 0.5 part of potassium persulfate was charged into a reaction vessel, and 95 parts of styrene and 5 parts of glycidyl methacrylate were continuously added over 2 hours to complete the polymerization. . Thereafter, the reaction temperature was cooled to 70 ° C., ammonia was added until the pH reached 11, and then 2
The reaction was carried out for 4 hours to obtain polymer fine particles d for electrophotographic development.
After purification of the resulting polymer fine particles d for electrophotographic development, the presence of amino groups was confirmed by taking an infrared absorption spectrum of the polymer fine particles d for electrophotographic development. The obtained polymer fine particles d for electrophotographic development had an average particle diameter of 0.6 μm.
Powdered in the same manner as described above to obtain a toner mixture. The resolution, the degree of cleaning, the fog, and the rate of density decrease were measured after the 50,000-sheet continuous actual photographing test was performed in the same manner as in Example 1. Table 1 shows the results. Example 5 As a first step, 10 parts of polystyrene particles having a weight average molecular weight of 5,000 and a mean particle size of 0.22 μm, 10 parts of sodium dodecylbenzenesulfonate, 20 parts of divinylbenzene, 80 parts of methyl methacrylate, While charging 0.3 parts of sodium persulfate and 700 parts of ion-exchanged water into a reaction vessel, polymerization was carried out at 80 ° C. for 3 hours with stirring. Then, after adding 0.5 parts of sodium persulfate in the second step, 80
156 parts of styrene and 44 parts of n-butyl acrylate were dropped and polymerized at 3 ° C. for 3 hours to produce polymer fine particles e for electrophotographic development. Observation of the obtained polymer fine particles e with a transmission electron microscope revealed that the particles were hollow particles having an outer diameter of 0.7 μm and an inner diameter of 0.2 μm.
When the glass transition point of the polymer was measured,
Met. The resolution, the degree of cleaning, the fog, and the rate of density decrease were measured after the 50,000-sheet continuous actual photographing test was performed in the same manner as in Example 1. Table 1 shows the results. COMPARATIVE EXAMPLE 1 A carrier and a toner were mixed in the same manner as in Example 1 except that the polymer fine particles were not added to the two-component toner. The resolution, the cleaning degree, the fog, and the density reduction rate after the continuous printing test for 10,000 sheets were measured. Table 1 shows the results. Comparative Example 2 Polymer particles having an average particle diameter of 0.07 μm obtained by performing only the first step in Example 1 were powdered in the same manner as in Example 1 to obtain a toner mixture. 5 in the same manner as in Example 1.
The resolution, the cleaning degree, the fog, and the density reduction rate after the continuous printing test for 10,000 sheets were measured. Table 1 shows the results. [Table 1] The polymer fine particles for electrophotographic development according to the present invention, when mixed with a toner to form an electrophotographic developer, have a long-term resolution, cleaning property, fog, and decrease in density when continuous copying is performed. It is excellent in such points as little.

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Claims (1)

(57) [Claim 1] The surface of crosslinked polymer particles (A) obtained by polymerizing a polymerizable monomer having a crosslinkable monomer content of 10% by weight or more has a crosslinkable monomer content. The polymer (B) obtained by polymerizing a polymerizable monomer having an amount of less than 10% by weight is partially or completely coated, and the weight ratio of (A) / (B) is 100 / 0.01 to 900.
Polymer fine particles for an electrophotographic developer, which are in parts by weight.