JPH0153460B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a toner for developing latent images in electrophotography, electrostatic recording, electrostatic printing, and the like. Methods for developing electrostatic latent images are roughly divided into liquid development method, cascade method, bristle brush method, magnetic brush method, impression method, powder cloud method, electrostatic induction method, jumping method, and other methods using natural or synthetic resins. There is a dry development method that uses a powder developer called toner containing a coloring agent such as carbon black dispersed therein, and the present invention relates to a toner used in the latter dry development method. More specifically, the present invention relates to a powder toner that is quickly and firmly fixed to a medium even in an apparatus using a heat (pressure) roller fixing method. Powder toners conventionally used for developing electrostatic latent images use dielectric resins with different thermal properties depending on the fixing method. Recently, it has become common for copying machines and the like to use a contact heated roller fixing method which has good thermal efficiency. In this fixing method, the powder toner becomes sticky due to heating, so that a portion of the powder toner adheres to the surface of the heated roller, resulting in so-called "offset development." Conventionally, various fixing methods and fixing devices have been devised to prevent this offset. For example, the roller surface is made of a material that has excellent releasability for toner, such as fluorine-based resin, and an offset prevention liquid such as silicone oil is further supplied to the surface to coat the roller surface with a thin film of liquid. things are being done. Although this method is extremely effective in preventing toner offset, it generates an odor due to heating of the offset prevention liquid and requires a separate device for supplying the offset prevention liquid. However, since the mechanism of the copying machine becomes complex and high precision is required to obtain stable results, the copying machine becomes expensive. However, if the offset prevention liquid is not supplied, toner will adhere to the surface of the fixing roller and an offset phenomenon will occur, so despite these drawbacks, it is currently necessary to supply the offset prevention liquid. It is. On the other hand, attempts have been made to improve toner properties in order to solve the above-mentioned offset phenomenon. For example, low-volume polyolefins, waxes, higher fatty acids or their metal salts, chlorinated paraffins, etc. have been added as lubricants. A method has also been proposed. The basic concept of these offset prevention methods is that when the toner comes onto the heat roller, a lubricant comes out onto the toner surface and the heat roller surface, and the lubricant's releasability is used to prevent offset. It is. However, with this type of toner, it takes time for the lubricant to come out to the interface between the toner surface and the heated roller.
It cannot be used for high-speed copying. Furthermore, when a large amount of lubricant is added, other properties of the toner such as toner agglomeration, poor flowability, poor stability, triboelectric chargeability, and charge controllability are adversely affected. Furthermore, it is known that vinyl resins and epoxy resins can be used alone or as a blend of the two as binders for powder toners. Toners using these alone or in blends as binders are generally used in open fixing methods, and when used in hot roller fixing methods,
An offset phenomenon occurs in which toner adheres to the roller. In addition, a method is known in which a vinyl monomer having two or more polymerizable double bonds is used as a crosslinking agent, but in this case, since the crosslinking agent is relatively short chain, the resulting The polymer tends to become hard and infusible, resulting in poor colorant dispersion and deterioration in fixing properties. Additionally, this polymer has the disadvantage that the quality of the product is not stable. SUMMARY OF THE INVENTION An object of the present invention is to provide a powder toner that can be efficiently and properly fixed with a heat roller without causing toner offset even when a fixing roller that does not supply an anti-offset liquid to the surface of the heat roller is used. It's about doing. Furthermore, it is an object of the present invention to provide a powder toner with excellent storage stability, good fluidity, and long life. Still another object is to provide a powder toner in which the resulting polymer is stable and the colorant has good dispersibility. As a result of intensive research to achieve the above object, the present inventors have discovered a modified epoxy resin containing a vinyl monomer and an average of 1.1 or more unsaturated bonds copolymerizable with the vinyl monomer in the molecule. The present inventors have discovered that a powder toner made of a polymer that is polymerized in the presence of a polymerization initiator can achieve the above object, and have completed the present invention. That is, the polymer obtained in the present invention is a crosslinked product of a vinyl polymer and a modified epoxy resin, so in addition to the advantages of a vinyl polymer alone, an epoxy resin alone, or a blend, it also has the disadvantage of offset. It solves the phenomenon. Furthermore, because it is cross-linked with modified epoxy resin,
Provides a powder toner that has a relatively low crosslinking density, does not increase the hardness of the resin even though the molecular weight has increased, has improved impact resistance, and is less likely to be pulverized by carrier collisions even after repeated copying for a single period of time. As the molecular weight of the polymer increases and the molecular weight distribution widens, the offset phenomenon to the heated roller does not occur even without the use of an offset preventive agent such as silicone oil, and the fixing properties are good. , which made it possible to create higher-speed electrophotographs. Vinyl monomers used in the present invention include styrene, vinyltoluene, 2-methylstyrene,
Styrenic monomers such as t-butylstyrene, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate,
Acrylic acid or methacrylic acid alkyl esters such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, monobasic acids such as acrylic acid, methacrylic acid, crotonic acid, etc. , ethylenically unsaturated carboxylic acid monomers such as dibasic acids such as fumaric acid, itaconic acid, maleic acid or their anhydrides, N-methylolacrylamide, N-methylolmethacrylamide, N-butoxymethylacrylamide, N- N-substituted (meth)acrylic monomers such as butoxymethylmethacrylamide,
Examples include hydroxyl group-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate, and epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate. The modified epoxy resin used in the present invention, which has an average of 1.1 or more unsaturated groups in the molecule that can be copolymerized with the vinyl monomer, has a molecular weight of about 350 to 5000, and includes, for example, oil-modified epoxy resin, acrylic There are acid-modified epoxy resins, etc., and these resins are selected alone or as a mixture, and have a
0.005-50% by weight, preferably 0.1-30% by weight is used. If the molecular weight of the modified epoxy resin is less than 350, the advantages of the modified epoxy resin as a powder toner cannot be imparted to the obtained polymer. Furthermore, if the molecular weight of the modified epoxy resin exceeds 5,000, it will interfere with the polymerization operation when obtaining a polymer. Further, when the modified epoxy resin is less than 0.005% by weight based on the total vinyl monomer,
The effect of the modified epoxy resin as a crosslinking component is small, and if it exceeds 50% by weight, the obtained polymer becomes difficult to melt, so that the object of the present invention cannot be achieved. In the reaction related to the present invention, a polymerization initiator, chain transfer, etc. are used as necessary. Polymerization initiators are primarily free radical generating compounds;
It is selected depending on the polymerization method, half-life of free radicals, etc.
For example, in the case of emulsion polymerization, a hydrophilic initiator such as ammonium persulfate, potassium persulfate, or hydrogen peroxide is used alone, or a redox-based initiator is used.
In the case of suspension polymerization method or solution polymerization method, oil-soluble peroxides such as benzoyl peroxide and dicumyl peroxide, azo compounds such as azobisisobutyronitrile, etc. are used, and the amount used is based on the amount of vinyl monomer. Based on 100 parts by weight of body and modified epoxy resin
0.01-10 parts by weight are used. If the amount is less than 0.01 part by weight, the polymerization reaction will be incomplete, and if it exceeds 10 parts by weight, the amount of decomposed products of the polymerization initiator will increase, which will have an adverse effect on the polymerization product. When using the above polymerization initiators, chain transfer agents such as methyl alcohol, ethyl alcohol, carbon tetrachloride, etc. are used as necessary. Various conventional methods can be used to produce powder toner. For example, the binder according to the present invention and a coloring agent such as carbon black or phthalocyanine blue are melt-kneaded, and then pulverized to give a powder of about 0.5 to 50% The particle size is reduced to approximately micrometer (μ). Alternatively, when the vinyl monomer and the modified epoxy resin are reacted, a coloring agent or the like can be mixed in advance and the reaction can be carried out. Also,
A vinyl polymer, a coloring agent, and the like may be dissolved or dispersed in a solvent, and this may be made into a toner by a spray drying method or the like. Incidentally, instead of or in addition to the colorant, magnetic powder, usually 0.1 to 5 μm, may be mixed, and furthermore, a charge control agent, a fixing aid, a lubricant, etc. may be used in combination. It is also possible to add other resins as binder components or for other purposes within a range that does not impede the effects of the present invention. In some cases, a low molecular weight crosslinking agent such as divinylbenzene may also be used in combination. The powder toner of the present invention is used in dry development methods in electrophotography, electrostatic recording, electrostatic printing, and the like.
It can be applied to various developing methods. The present invention will be explained below using Examples. In the examples, "parts" indicate parts by weight. Example 1 A flask equipped with a stirrer, thermometer, condenser, dropping funnel, and gas introduction tube was charged with 74 parts of epoxy resin (Epicote 828, manufactured by Ciel Chemical Co., Ltd.).
Add triethylamine to 28 parts of acrylic acid in a dropping funnel.
Epoxy acrylate (modified epoxy resin, molecular weight Approximately 500). Next, in a flask equipped with a stirrer, a thermometer, a condenser, and a gas inlet tube, 15 parts of the obtained epoxy acrylate and 2 parts of benzoyl peroxide were mixed with 60 parts of styrene (ST) and methyl methacrylate (MMA).
30 parts of butyl methacrylate (BMA), 350 parts of a 0.2% aqueous solution of polyvinyl alcohol (GH-20, manufactured by Nippon Gosei Kagaku Co., Ltd.) was added, stirred to disperse, and nitrogen gas was blown. The mixture was reacted at 85°C for about 8 hours while stirring to obtain a pearl-like polymer (softening temperature 74°C, TMA method). 90 parts of the polymer, 5 parts of metal-containing dye, and 5 parts of carbon black were kneaded for 2 hours using two heated rolls, and then pulverized to prepare a toner having an average particle size of about 12 μm, which was used as a sample. Meanwhile, instead of the above polymer, 2.4 parts of Epicote 828 was added to the polymer 150 of st/MMA/2EHA=113/15/22.
A toner having an average size of 12 μm was prepared as a comparison sample by the same procedure except that a blend of the above-mentioned toners was used. 5 parts of each of the above sample and comparative sample were prepared using carrier iron powder of approximately 150μ in average size.
Two kinds of developers were prepared by mixing the same with the fluorocarbons, and using these developers, the fixing roller was coated with FEP (a copolymer of fluoroethylene and hexafluoropropylene, manufactured by DuPont) (at 190°C). As a result of repeated tests using a test copying machine using pressure contact, the comparison sample showed that offset phenomenon occurred from the beginning even when the roller surface was coated with silicone oil, which is an anti-offset liquid. On the other hand, the example samples obtained good results in both fixing (cellophane tape peeling test) and offset phenomenon (visual evaluation of the surface of the heat roller) even without silicone oil. Moreover, the obtained image was good with no background stains. Example 2 A flask equipped with a stirrer, a thermometer, and a condenser was charged with 300 parts of epoxy resin (Epicote 1004, manufactured by Schiel Chemical Co., Ltd.), 20 parts of maleic anhydride, and 213 parts of butyl cellosolve, and the mixture was heated at 130°C for 4 hours to give an acid value of 14. The adduct was produced by reacting until . The resulting reaction solution was stripped to remove most of the butyl cellosolve, yielding the same modified epoxy resin (molecular weight approximately 1700). A pearl-shaped polymer (softening temperature: 78°C) was obtained by suspension polymerization in the same manner as in Example 1, except that 1.5 parts of this resin was used. The above polymer 50 parts Magnetic powder 45 parts Nigrosine dye 5 parts After kneading the above composition in a pressure kneader for 2 hours,
The toner was cooled and pulverized to obtain a toner having an average particle size of about 15 μm. 0.3% finely powdered silica was dry-mixed as a flow improver to this toner to obtain a final toner. For comparison, instead of the modified epoxy resin,
A toner having the same composition except that a polymer crosslinked with 1.5 parts of divinylbenzene was used and having an average diameter of about 15 microns was obtained. This toner was used as a comparative sample to evaluate colorant dispersion, fixing properties, and offset. The results are shown in Table 1.

[Table] As shown in Table 1, the crosslinking agent divinylbenzene does not disperse the colorant sufficiently because the distance between crosslinks is narrow. On the other hand, in the present invention (Example), the heat meltability of the polymer is also higher than in the comparative example, so it seems that the colorant is sufficiently dispersed. For the above-mentioned reasons, as shown in Table 1, the results of Examples were good in fixability, high charge amount, and good image quality. Example 3 Instead of the modified epoxy resin used in Example 1,
Epoxy acrylate SP-4010 manufactured by Showa Kobunshi Co., Ltd.
A polymer having a softening temperature of 66° C. was obtained by reacting in the same manner except for using 1.5 parts of (acid value: 3 or less). The above polymer: 95 parts Carbon black: 5 parts After kneading the above composition in a heating kneader for 5 hours, approx.
A powder toner with an average particle size of 10μ was produced. 90 parts of carrier iron powder of 100μ was mixed with 10 parts of this toner to prepare a developer. When this developer was used to investigate the suitable temperature range for fixing offset using a fixing roller similar to that used in Example 1, it was found that both fixing and offset were good at a roller surface temperature of 130 DEG C. to 200 DEG C. Example 4 Styrene was added to a stainless steel reactor equipped with a stirrer.
250 parts of butyl acrylate, 0.01 part of the modified epoxy resin obtained in Example 1, 3 parts of lauryl mercaptan, and 10 parts of azobisisobutyronitrile were charged and polymerized at 85°C for 3 hours and then at 130°C for 7 hours. After that, the polymer was taken out in a molten state, and after cooling, the bulk polymer was pulverized. (Softening temperature: 62°C) 95 parts of the above polymer 5 parts of carbon black A powder toner was prepared using the above composition in the same manner as in Example 3 and tested. As a result, the powder toner had good fixing properties and offset. It was hot.

Claims (1)

[Claims] 1. Use as a binder of a vinyl polymer obtained by reacting a vinyl monomer and a modified epoxy resin having an average of 1.1 or more unsaturated groups per molecule that can be copolymerized with the monomer. Powder toner featuring: 2. The powder toner according to claim 1, wherein the modified epoxy resin has a molecular weight of 350 to 5,000. 3 Modified epoxy resin for vinyl monomer
The powder toner according to claim 1 or 2, wherein the powder toner is used in an amount of 0.005 to 50% by weight.