JP3980111B2 - Image forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic charge developing toner used for image formation by electrophotography, a toner resin, and an image forming method using the toner.
[0002]
[Prior art]
In electrophotographic copying machines and printers, toner is temporarily attached to an image carrier such as a photosensitive member on which an electrostatic charge image is formed in the development process, and then transferred to transfer paper in the transfer process and then fixed. The image is fixed by the process. Examples of the toner adhesion (development) to the image carrier include so-called regular development in which the charge of the electrostatic image is opposite to the charging polarity of the toner, and reversal development in which both are the same polarity.
The toner used in the development includes a two-component toner used together with a carrier and a one-component toner using only the toner as a developer. The one-component toner includes a one-component toner containing a magnetic material and a non-magnetic one-component toner containing no magnetic material There is. An electrostatic transfer method is widely used in the transfer process, and a corona transfer method, a roller transfer method, a belt transfer method, and the like are known. In electrophotographic image formation, a combination of methods selected from these various development methods or transfer methods is used.
[0003]
As a method for producing a toner, a method of blending a binder resin with necessary components such as a colorant and a charge control agent, and kneading and classifying after melt kneading is widely performed.
The required performance of the toner is that when an image is formed, the image density is sufficient and there is no image defect, or there is no toner scattering or filming on the photoreceptor, good cleaning properties, and stable use over a long period of time. There are a wide variety of problems, from production processes to problems with formed images and equipment used, such as no blocking during toner production processes, storage, and transportation. In order to satisfy these requirements, many proposals have been made regarding the properties of the materials to be melt-kneaded, the blending prescription, the kneading conditions, and the like. For example, JP-A-54-48245 and JP-A-59-197048 report that an offset phenomenon is prevented by adding silicone oil when melt-kneading a resin, a colorant, magnetic powder and the like. Has been. Various external additives typified by silica have also been proposed.
[0004]
[Problems to be solved by the invention]
However, these conventional methods do not always satisfy the performance required for the toner. Further, depending on the development, transfer, and other methods employed in the image forming apparatus, sufficient effects cannot be obtained. In particular, in the roller transfer method in which a toner layer is transferred by an electric field generated by applying a direct current to a recording paper via a conductive rubber roller or a dielectric roller provided with a dielectric layer on a conductive rubber, characters are transferred in the process of transferring the toner. Omission defects often occur. This is related to the cohesive force or fluidity between the toners, and the cohesive force between the toners is low, and those with good toner fluidity are known to have no missing characters, but the cause is complicated, At present, there is not necessarily an effective proposal for means for solving this. On the other hand, when the particle size of the binder resin is reduced in order to improve the dispersibility of each component in the toner, the fluidity of the resin particles is deteriorated, and bridging and adhesion to the apparatus wall are serious in each process during toner production. This lowers the toner productivity. Furthermore, if the glass transition point of the resin is lowered for the purpose of fixing at a low temperature due to the recent demand for energy saving, a new problem has arisen that it becomes easy to cause blocking during transportation and storage.
The present invention has been made in view of such circumstances, and the object thereof is to obtain a clear and clean image with no voids in characters, and to prevent obstacles during production, storage or transportation. It is to provide an improved toner.
[0005]
[Means for Solving the Problems]
As a result of diligent studies to solve the above-mentioned object, the present inventors have found that the above problem can be solved by using a binder resin containing oil in advance, thereby achieving the present invention.
That is, the present invention relates to a development process for attaching toner to an image carrier on which an electrostatic charge image is formed, a transfer process for transferring the attached toner to transfer paper by a roller transfer method, and fixing the transferred toner to the transfer paper. An image forming method for sequentially performing each step of the fixing step, wherein a mixture of resin particles having an average particle size of 1 mm or less obtained by polymerizing a monomer in the presence of straight silicone oil and a colorant is melted. The present invention resides in an image forming method characterized by being obtained by pulverization and classification after kneading.
[0006]
Hereinafter, the present invention will be described in detail.
In the toner resin of the present invention, it is important to previously contain an oil component in the resin, and as a result, compared to the method of the above-mentioned publication in which oil is added when kneading the toner resin and other components, The fluidity of the resin can be remarkably improved.
The toner resin containing the oil component according to the present invention can be obtained, for example, by adding the oil component during resin production, that is, during polymerization of the monomer.
[0007]
The toner resin of the present invention is not particularly limited, and various conventionally known resins can be used. For example, vinyl resin, polyester resin, or a mixed resin thereof can be used. Examples of monomers used for vinyl resin production include styrene, α-methylstyrene, and o-methyl group, m-methyl group, p-methyl group, p-ethyl group, and 2,4-dimethyl group as a nuclear substituent. , Styrene derivatives having a p-butyl group, a p-hexyl group, a p-octyl group, a p-nonyl group, a p-decyl group, a p-methoxy group, a p-phenyl group, etc., general formula: CH ₂ ═CR— Acrylic acid esters or methacrylic acid esters represented by COOR (where R represents hydrogen or a methyl group. R ′ represents a methyl group, an ethyl group, an n-butyl group, an isobutyl group, an s-butyl group, or a t-butyl group. Group, n-pentyl group, n-hexyl group, n-octyl group, 2-ethylhexyl group, n-nonyl group, isononyl group, decyl group, dodecyl group, tridecyl group, stearyl group, docosyl group Alkyl groups such as cyclohexyl groups; cycloalkyl groups such as cyclohexyl groups; aralkyl groups or aryl groups such as benzyl groups and phenyl groups; alkoxyalkyl or aryloxyalkyl groups such as methoxyethyl groups, ethoxyethyl groups, butoxyethyl groups, and phenoxyethyl groups And vinyl esters such as vinyl acetate and vinyl propionate, acrylonitrile, methacrylonitrile, and the like, and can be used as one or a mixture of two or more according to the purpose.
[0008]
The styrene polymer or styrene copolymer may be cross-linked or a mixed resin. The polyester resin is obtained by condensation polymerization of a divalent or higher carboxylic acid and a divalent or higher alcohol component. The divalent carboxylic acid is maleic anhydride, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid. , Isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid, isododecenyl succinic acid, n-octyl succinic acid , N-octenyl succinic acid, and the like, and anhydrides thereof can also be used. Examples of the trivalent carboxylic acid include 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8- Examples include octanetetracarboxylic acid, pyromellitic acid, and empole trimer acid. These acid anhydrides can also be used.
[0009]
Examples of the divalent alcohol include polyoxypropylene (2,2) -2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene (3,3) -2,2-bis (4-hydroxyphenyl) propane. , Polyoxyethylene (2,0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2,0) -polyoxyethylene (2,0) -2,2-bis (4-hydroxy) Phenyl) propane, polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane and other etherified bisphenols, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene Glycol, 1,4-butanediol, 1,4-butenediol, neopentyl Coal, 1,5-pentane glycol, 1,6-hexane glycol, 1,5-pentane glycol, 1,6-hexane glycol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetra Methylene glycol, bisphenol A, bisphenol Z, hydrogenated bisphenol A, and the like can be used. Examples of the trivalent alcohol include sorbitol, 1,2,3,6-hexanetetol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2 , 5-pentatriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene and the like.
[0010]
The toner resin of the present invention is preferably a resin containing a vinyl monomer, more preferably a toner resin containing a styrene monomer, more preferably styrene and one or more acrylic acids. It is a binder resin containing a copolymer of ester or methacrylate.
[0011]
The oil in the present invention refers to oil that is liquid at room temperature, does not dissolve in water, and has viscosity. That is, oil is a hydrophobic oily substance, such as mineral oil, liquid paraffin, α-olefin oligomer, liquid polypropylene, liquid isobutylene, liquid polybutene, Isopar L, Isopar M, liquid chloroprene, silicone oil, spindle oil, vegetable oil, linseed oil Etc. The index indicating the viscosity is viscosity, and the viscosity (kinematic viscosity) of the oil used in the present invention is preferably 1 to 10,000 centistokes (cs). Particularly preferred is 10 to 1,000 centistokes. In the present invention, the oil is particularly preferably silicone oil. Silicone oils should have excellent releasability and releasability, but in addition to straight silicone oils such as dimethyl silicone oil, methylphenyl silicone oil, and methylhydrogen silicone oil, polyether-modified silicone oil and epoxy-modified silicone Examples include various modified silicone oils such as oil, methacryl-modified silicone oil, long-chain alkyl-modified silicone oil, and fluorine-modified silicone oil. In the case of a vinyl resin, silicone oil having a reactive vinyl group capable of reacting with a polymerizable monomer is also used.
In the present invention, straight silicone oil is particularly preferred, and dimethyl silicone oil is particularly preferred.
And as for the oil content in resin, it is desirable that it is 0.01-10 weight part with respect to 100 weight part of resin (except oil).
[0012]
Examples of the polymerization method for obtaining the binder resin include solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization. In the present invention, suspension polymerization is particularly preferable. Then, during the polymerization reaction, the oil is allowed to exist in the system for polymerization to obtain a resin containing the oil. Specifically, there are a method of polymerizing by mixing oil with a monomer from the beginning of the reaction, and a method of adding oil in the middle of the polymerization reaction, but a method of adding oil from the initial stage for ease of operation, especially containing oil in the monomer. A method of polymerizing after the polymerization is preferred.
[0013]
In order to produce a resin for toner containing the oil of the present invention by polymerizing vinyl monomer by suspension polymerization using silicone oil as oil, for example, monomer, silicone oil, polymerization initiator (for example, benzoyl peroxide, azo Compound), an oil phase to which a chain transfer agent is added if necessary, a suspension stabilizer such as water and polyvinyl alcohol, and an aqueous phase to which a dispersion aid is further added if necessary. Make a dispersion (suspension). The ratio of the oil phase to the water phase is a weight ratio, and the water phase is set to 10 or less, preferably 2 to 5 with respect to the oil phase 1. The droplet dispersion is heated to a predetermined polymerization temperature for polymerization. Next, the reaction mixture is dehydrated to separate the polymer, washed with water as necessary, and dried to obtain the desired resin.
[0014]
In order to improve the dispersibility of each component in the toner, the average particle size of the resin containing oil is preferably 1 mm or less. Further, since the glass transition point (Tg) of the resin is also related to the Tg of the toner, it is preferably 60 ° C. or lower from the recent trend of low-temperature fixing.
If necessary, toner constituents other than oil such as a colorant, a charge control agent, an additive such as wax, and a magnetic material may be added to the resin during polymerization.
In producing the toner of the present invention, the resin containing the oil component is kneaded together with the colorant and, if necessary, other components. The other component is appropriately selected from known ones such as a charge control agent, magnetic powder, and wax, but at this time, a binder resin and silicone oil may be further used in combination at the time of kneading. Kneading is performed using a kneader such as a heating roll, a kneader, or an extruder. The kneaded composition is cooled and solidified, pulverized and classified to a desired particle size, and then an external additive such as silica is further added as necessary to obtain a toner.
[0015]
The toner of the present invention can be applied to any formulation of magnetic one-component toner containing magnetic powder, non-magnetic one-component toner containing no magnetic powder, or two-component toner used by mixing with a carrier.
Examples of the colorant used in the present invention include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa Yellow G, rhodamine dyes, chrome yellow, quinacridone, benzidine yellow, Any conventionally known dyes and pigments such as rose bengal, triallylmethane dyes, monoazo dyes and disazo dyes can be used alone or in combination.
[0016]
In the toner of the present invention, the colorant may have magnetism. In the case of a magnetic toner, generally, black or brown magnetic particles are used as a colorant. The magnetic particle used in the present invention is a ferromagnetic material that exhibits ferrimagnetism or ferromagnetism at a use environment temperature (around 0 ° C. to 60 ° C.) of a copying machine or the like, for example, magnetite (Fe ₃ O ₄ ). , Maghemite (γ-Fe ₂ O ₃ ), an intermediate between magnetite and maghemite, ferrite (MxFe ₃ -xO ₄ ; where M is Mn, Fe, Co, Ni, Cu, Mg, Zn, Cd, or a mixture thereof Spinel ferrite such as BaO · 6Fe ₂ O ₃ , hexagonal ferrite such as SrO · 6Fe ₂ O ₃ , garnet type oxide such as Y ₃ Fe ₅ O ₁₂ and Sm ₃ Fe ₅ O ₁₂ , CrO ₂ Among the rutile oxides such as Fe, Mn, Ni, Co, and Cr, and other ferromagnetic alloys, those exhibiting ferromagnetism or ferrimagnetism at around 0 ° C to 60 ° C are mentioned. Fine particles having an average particle diameter of 3 μm or less, more preferably about 0.05 to 1 μm, such as netite, maghemite, and an intermediate between magnetite and maghemite, are preferable in terms of performance and price. The magnetic particles are not limited to being used alone, but two or more kinds can be used in combination.
In addition, the toner of the present invention is particularly effective when an image forming method having a roller transfer method is used, and a good image that is unavoidable with the prior art and has no missing characters can be obtained.
[0017]
【Example】
EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples. “Parts” represents “parts by weight” unless otherwise specified.
Example 1
45 parts of styrene, 15 parts of n-butyl acrylate, 0.3 parts of dimethyl silicone oil (trade name KF96-100cs, manufactured by Shin-Etsu Chemical Co., Ltd., viscosity 100 cs) are rotated at about 8,000 rpm by a multidisperser (manufactured by Mitamura Riken). Then, 3 parts of 2,2′-azobisisobutyronitrile was dissolved to obtain an oil phase mixture.
On the other hand, 180 parts of 1% aqueous solution of polyvinyl alcohol (trade name GM-14, manufactured by Nippon Synthetic Chemical Co., Ltd.) was used as the aqueous phase.
The oil phase was dispersed in the water phase using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) and stirred for 15 minutes at a rotational speed of about 6,000 rpm. Thereafter, the dispersion was transferred to a stainless steel polymerization can equipped with a stirrer, a thermometer and a nitrogen introduction tube, and heated at 80 ° C. for 8 hours under a nitrogen stream while stirring at a rotation speed of about 500 rpm to complete the polymerization reaction.
[0018]
The polymer particles are separated from the resulting reaction solution by a centrifugal separator as solids, washed with water, repeatedly filtered, and then vacuum dried to obtain a silicon oil-containing toner having an average particle size of 100 μm and Tg of 55 ° C. A binder resin was obtained.
Next, after mixing 100 parts of this resin and 5 parts of carbon black as a colorant, the mixture was once stored in a tank, and then a certain amount of the mixture was supplied to a kneader and kneaded. Bridging due to the resin was not observed in each of the mixing, storage, and kneading steps, and stable production was possible.
Further, this resin was stored at 45 ° C. for 1 week, but there was no blocking.
[0019]
Comparative Example 1
In Example 1, a resin was produced in the same manner except that no silicone oil was used, and a binder resin for toner having an average particle size of 100 μm and a Tg of 55 ° C. was obtained.
Thereafter, the toner was manufactured through exactly the same process as in Example 1. As a result, bridging occurred in the storage tank, resulting in poor feed amount during kneading.
Further, when this resin was stored at a temperature condition of 45 ° C. for one week, resin agglomerates were slightly generated.
[0020]
Reference example 1
A non-magnetic one-component developer was obtained with the following blending ratio.
Binder resin of Example 1 100 parts by weight Carbon black MA100 (manufactured by Mitsubishi Chemical) 6 parts by weight Bontron S34 (manufactured by Orient Chemical) 2 parts by weight Polypropylene wax 550P (manufactured by Sanyo Kasei) 4 parts by weight After mixing these with a Henschel mixer A toner lump was obtained by melt-kneading with a twin-screw extruder. This was coarsely pulverized with a feather mill and then finely pulverized with a jet mill. Thereafter, toner particles having a 50% volume average particle diameter of 9 μm were obtained using an airflow classifier. Further, the toner 100 parts by weight, spherical silica fine particles (manufactured by Nippon Aerosil Co. R972) 0.8 parts were mixed with a super mixer to obtain a non-magnetic one-component electrophotographic developer. When this toner was subjected to print evaluation by modifying a commercially available printer using a non-magnetic one-component developing system, a clear image with no missing characters was obtained.
[0021]
Reference example 2
A nonmagnetic one-component electrophotographic developer was obtained in exactly the same manner as in Reference Example 1 , except that the resin obtained in Comparative Example 1 was used instead of the resin obtained in Example 1. When this was evaluated in the same manner by the printer, a missing character was generated.
[0022]
Example 2
A magnetic one-component developer was obtained with the following blending ratio.
Binder resin of Example 1 100 parts by weight Magnetic powder EPT500 (manufactured by Toda Kogyo) 70 parts by weight Charge control agent T77 (manufactured by Hodogaya Chemical) 1 part by weight Polypropylene wax NP505 (manufactured by Mitsui Petrochemicals) 4 parts by weight After mixing, the mixture was melt kneaded with a twin screw extruder to obtain a toner lump. This was coarsely pulverized with a feather mill and then finely pulverized with a jet mill. Thereafter, toner particles having a 50% volume average particle diameter of 8 μm were obtained using an airflow classifier. Further, 0.5 part of spherical silica fine particles (R972, manufactured by Nippon Aerosil Co., Ltd.) were mixed with 100 parts by weight of the toner by a super mixer to obtain a magnetic one-component electrophotographic developer. For the toner print evaluation, a commercially available printer using a magnetic one-component development system was modified. This printer has an organic photoreceptor (OPC) as a photoreceptor, and is equipped with a roller charging system and a roller transfer system.
As a result of the printing evaluation, a clear image with no missing characters was obtained.
[0023]
Comparative Example 2
A magnetic one-component electrophotographic developer was obtained in the same manner as in Example 2, except that the resin obtained in Comparative Example 1 was used instead of the resin obtained in Example 1. When this was evaluated in the same manner by the printer, a missing character was generated.
[0024]
Example 3
A magnetic one-component electrophotographic developer was obtained in exactly the same manner as in Example 2 except that the formulation was as follows.
Binder resin of Example 1 100 parts by weight Magnetic powder EPT500 (manufactured by Toda Kogyo) 70 parts by weight Charge control agent T77 (manufactured by Hodogaya Chemical) 1 part by weight Polypropylene wax NP505 (manufactured by Mitsui Petrochemicals) 4 parts by weight Silicone oil (trade name KF96) -100 cs, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.3 parts by weight When the same printing evaluation was performed with the printer used in Example 2 , a clear image with no missing characters was obtained as in Example 2 . .
[0025]
Comparative Example 3
A magnetic one-component electrophotographic developer was obtained in the same manner as in Example 3 except that the resin obtained in Comparative Example 1 was used instead of the resin obtained in Example 1. When this was evaluated in the same manner with the printer, character omission occurred, which was better than the result of Comparative Example 2 , but at a level that was practically satisfactory compared to Example 2 and Example 3. There wasn't.
[0026]
【The invention's effect】
As is clear from the above description, the binder resin containing the oil component of the present invention, particularly the binder resin containing silicone oil during polymerization, causes bridging during toner production even when the resin particles have a small particle size. Without increasing the stable productivity. Even when the Tg of the resin is low, the storage stability is excellent. Further, the electrostatic charge developing toner obtained through at least a step of kneading the oil-containing binder resin and the colorant has an effect of obtaining a clear and high-quality image with no missing characters.

Claims (10)

Development process for attaching toner to an image carrier on which an electrostatic charge image is formed, transfer process for transferring the attached toner to transfer paper by a roller transfer method, and fixing process for fixing the transferred toner to transfer paper Image forming method in which the toner is polymerized in the presence of a straight silicone oil and a mixture containing resin particles having an average particle diameter of 1 mm or less and a colorant is melt-kneaded and then pulverized An image forming method characterized by being obtained by classification. The image forming method according to claim 1 , wherein the monomer is a vinyl monomer. Monomers, image forming method according to claim 1 or 2, characterized in that a mixture of styrene or styrene and other monomers. 3. The image forming method according to claim 1, wherein the monomer is a mixture containing styrene and an acrylate ester and / or a methacrylate ester. The image forming method according to any one of claims 1 to 4 viscosity of the oil is characterized in that it is of 1～10,000Cs. The image forming method according to any one of claims 1 to 4 viscosity of the oil is characterized in that it is of 1～1,000Cs. The polymerization of the monomers, the resulting resin is 100 parts by weight of the resin relative to, oil according to any one of claims 1 to 6, characterized in that as a proportion of 0.01 to 10 parts by weight Image forming method. The image forming method according to any one of claims 1 to 7, characterized in that the polymerization is suspension polymerization. The image forming method according to any one of claims 1 to 8, characterized in that the colorant is a colorant of the non-magnetic. The image forming method according to any one of claims 1 to 9 colorant characterized in that it is a colorant having magnetic.