JP2007272030A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method for obtaining an image with high definition and high picture quality without disturbance and achieving a small consumption of toner and no melt sticking of the toner on a developing member. <P>SOLUTION: An image is developed by using a developing roll and a developer and by forming a layer of the developer on the developing roll; in which the developing roll comprises at least a core metal and a rubber part having ionic conductivity and covering the core metal and has an average surface roughness (Ra) of 0.5 to 2 μm, and the developer uses a toner having an apparent density of 0.36 to 0.46 g/ml and a circularity of 0.88 to 0.94. The rubber part of the developing roll preferably contains at least nitrile rubber and/or epihalohydrin rubber. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming method using an electrophotographic method, an electrostatic recording method, or the like, and more particularly to an image forming method characterized by a developing method related to a developing roll and a toner.

  In general, an image forming apparatus such as an electrophotographic copying machine or printer forms a latent image on a photoconductive photoconductor, and the latent image forms a carrier or a charging member constituting a part of a developing device. Insulating toner that has obtained triboelectric charge by friction is electrostatically attached and developed, and then the formed toner image is transferred to a transfer medium such as plain paper or film, and then heated, pressurized, solvent vapor, etc. The basic principle is to form a copy image or a print image by fixing the sheet on the sheet.

  In recent years, with the progress of electrophotographic technology and electrophotographic toner technology, colorization has rapidly progressed. Under such circumstances, copiers and printers are required to have superior image quality and low toner consumption from the viewpoint of reducing printing costs. In order to improve image quality and reduce toner consumption, the toner should be uniformly formed in a thin layer on the developing roll, the fluidity of the toner on the developing roll should be properly controlled, and the toner transportability should be improved. It must be an excellent developing roll. It is also necessary to prevent the toner from contaminating the developing member such as the developing roll and the charging blade or fusing to the developing member. For this reason, many studies have been made from the developing roll surface and from the toner surface.

  In order to form a uniform and thin layer of toner on the developing roll, the toner transportability and electrical characteristics of the developing roll are important. From the viewpoint of toner transportability, it has been proposed to adjust and specify the surface roughness of the developing roll. In addition, the toner transportability is related not only to the properties of the developing roll but also to the fluidity of the toner. This fluidity is related to the particle diameter and circularity of the toner, the amount of additive added, and the like. Yes. As a method for evaluating the fluidity of the toner, the apparent density (bulk density) of the toner can usually be used because of easy measurement and excellent reproducibility of the results. If the fluidity of the toner is not appropriate, the toner may agglomerate or cause fusing.

  In addition, the developing roll has a function of charging the toner and moving the toner toward the photoreceptor, and the electrical characteristics of the developing roll are extremely important in order to exhibit both of these functions satisfactorily. It is required that the electrical resistance value be controlled to a certain level, be uniform, and not change depending on the environment. When the electric resistance value of the developing roll is high, image disturbance can be prevented well, but the toner becomes difficult to fly and the image density is lowered. On the other hand, when the electrical resistance value on the surface of the developing roll is low, the toner is likely to fly and the image density becomes high, but the electrostatic latent image formed on the surface of the photoreceptor is disturbed, and the sharpness of the image is lowered. Will cause problems.

  As a method for controlling the electric resistance value of the developing roll to a certain level, usually, a so-called rubber part constituting the developing roll is mixed with a conductive filler such as conductive carbon black, metal powder, or carbon fiber. Examples include a control method by electronic conduction, a so-called ion conduction control method in which a rubber component having ionic conductivity is used in advance, or an ionic conductive agent such as a lithium salt or a quaternary ammonium salt is mixed with the rubber component. . In the case of a control method using electronic conduction, it is not easily affected by temperature, humidity, and the like, but is likely to cause fluctuations in the electrical resistance value in the developing roll and local non-uniformity due to uneven distribution and aggregation of the conductive filler. Therefore, as a result of the poor uniformity of the electrical resistance value, there is a problem that the toner layer is not uniformly formed on the developing roll and a high-definition image is not formed, or image disturbance is likely to occur. On the other hand, in the case of the control method using ion conduction, since the electrical resistance value in the developing roll is excellent in uniformity, a toner layer is uniformly formed on the developing roll, and a high-definition image can be obtained. There are few. However, it has not solved the problems of reducing the toner consumption and fusing to the developing member at the same time.

  The combination of the developing roll and the toner is extremely important in order to obtain a high-definition and high-quality image without disturbance and to reduce toner consumption and prevent fusing. Cited Document 1 has an average surface roughness of the developing roll, Cited Document 2 has an apparent toner density (bulk density), and Cited Document 3 has a developing roll using an electronic conductive agent and an ionic conductive agent in the rubber part. Reference 4 proposes a conductive rubber composition, but at present, sufficient measures have not been taken for the above requirement.

JP-A-6-308817 JP 2005-99824 A Japanese Patent Laid-Open No. 7-13415 Republished patent WO97 / 03122

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method that obtains a high-definition and high-quality image without disturbance and that consumes less toner. It is another object of the present invention to provide an image forming method that does not cause toner fusion to a developing member.

  As a result of intensive studies on the developing roll, the toner, and a combination thereof in order to achieve the above-mentioned problems, the present inventor can form a good image, consume less toner, and cause no fusing. The method has been found and the present invention has been completed.

  That is, the image forming method of the present invention comprises a charging means for charging the surface of the photoreceptor, an exposure means for irradiating the charged surface of the photoreceptor with light to form an electrostatic latent image, and the electrostatic latent image. Developing means for supplying a developer using a developing roll, transfer means for transferring the developer on the photoreceptor developed by the developing roll to a transfer material, and fixing means for fixing an image on the transfer material The developing means comprises at least a cored bar and an ionic conductive rubber part covering the cored bar, and the average surface roughness (Ra) is 0. An image forming method using a developing roll having a size of 5 to 2 μm and a developer using toner having an apparent density of 0.36 to 0.46 g / ml and a circularity of 0.88 to 0.94 (Claim 1), and there is little rubber part of the developing roll. Also contains nitrile rubber and / or epihalohydrin rubber (Claim 2), the Shore hardness of the rubber part of the developing roll is 40 to 55Hs (Claim 3), and the developing means is a non-magnetic one-component developing system. (Claim 4). The present invention is also applied to full color image formation.

  According to the image forming method of the present invention, a high-definition and high-quality image without disturbance can be obtained, and the toner consumption can be reduced. Further, the toner does not adhere to the developing member.

The image forming method of the present invention is characterized by developing means using a specific developing roll and developer. First, the developing roll will be described.
<Development roll>
The developing roll according to the present invention comprises at least a cored bar and a rubber part covering the cored bar. An example of the configuration will be described with reference to FIG. Reference numeral 1 denotes a stainless steel core bar. A rubber part is coated on the cored bar 1. In this example, the cored bar 1 has a columnar shape (bar shape), but may have a cylindrical shape (tubular shape). Both ends of the core metal 1 are cut to a required diameter. The core metal 1 is preferably non-magnetic.
The core metal has conductivity, and it is preferable to use a metal. It is preferable to use an aluminum alloy or stainless steel as the metal. The core metal may be a non-conductive material such as ceramic, synthetic stone, or plastic coated with a conductive material. One or more intermediate layers may be provided between the rubber part and the cored bar as necessary.

  The average surface roughness (Ra) of the rubber part of the developing roll is 0.5 to 2 μm, preferably 0.7 to 1.6 μm, and more preferably 0.8 to 1.2 μm. When the average surface roughness (Ra) is less than 0.5 μm, the transportability of the developer is lowered, the image quality becomes uneven, the image density is lowered, and the toner is easily fused to a developing member such as a charging blade. Cause problems. If it exceeds 2 μm, a uniform toner thin layer is not formed, and the image becomes non-uniform. Toner consumption also increases. In addition, when the surface of the rubber part is worn over time, the toner conveyance amount changes greatly, which may adversely affect the image.

  The average surface roughness (Ra) is based on JIS B 0601: 2001, and was measured in the circumferential direction of the developing roll. The measuring machine used the Keyence Corporation ultra-deep color 3D shape measurement microscope brand name: VK-9500 Generation II. The cut-off value was automatically obtained from the curvature of the roll with the software attached with the optimum value.

The Shore hardness of the rubber part of the developing roll is preferably 40 to 55 Hs, more preferably 42 to 53 Hs, and even more preferably 45 to 50 Hs. If the shore hardness of the rubber part is less than 40 Hs, it is easy to be damaged by the charging blade, and if it exceeds 55 Hs, the toner is easily fused to the developing member such as the charging blade, and it is difficult to form a uniform layer and the image quality is deteriorated. .
The measuring method of Shore hardness is according to JIS Z 2246: 2000.

  The rubber part of the developing roll used in the image forming method of the present invention needs to have ionic conductivity. In order for the rubber part to have ionic conductivity, there is a method of selecting a material having ionic conductivity for the rubber component itself or adding an ionic conductive agent to the rubber component. Further, the rubber part contains a vulcanizing agent, a vulcanization aid, a vulcanization accelerator, a reinforcing agent, a filler, an acid acceptor, a colorant and the like as necessary.

[Rubber component]
The rubber component of the present invention is not particularly limited as long as it is usually used in a developing roll. For example, rubber having an unsaturated double bond; hydrogenated acrylonitrile-butadiene rubber (hydrogenated nitrile rubber: H-NBR), acrylonitrile-butadiene rubber (nitrile rubber: NBR), chloroprene rubber (CR), natural rubber (NR), butadiene rubber (BR), butyl rubber (IIR), ethylene-propylene-diene rubber (EPDM), silicone rubber , Styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene rubber, isoprene rubber (IR), etc., polyurethane elastomer, urethane rubber, epihalohydrin rubber, epoxy-containing rubber, acrylic rubber, ethylene-acrylate rubber, chloro Sulfonated polyethylene Ngomu, fluorine rubber, and the like. Of these, nitrile rubber (NBR), epihalohydrin rubber, chloroprene rubber, and urethane rubber are preferable.

  In order to impart ionic conductivity to the rubber part, some nitrile rubbers (NBR) or the like are imparted with ionic conductivity, but usually epihalohydrin rubber can be used. The ratio of the epihalohydrin rubber in the rubber component is preferably 20 to 100% by weight, more preferably 30 to 90% by weight, and still more preferably 40 to 70% by weight. If it is less than 20% by weight, the effect of imparting ionic conductivity is small. Note that the use of a large amount of epihalohydrin rubber requires caution because it excessively lowers the electrical resistance of the rubber part and is difficult to process due to large shrinkage during molding.

  Epihalohydrin rubber has a halogen atom in the molecular chain, and examples thereof include epichlorohydrin rubber (CO, CHR), epichlorohydrin-ethylene oxide rubber (ECO, CHC), epichlorohydrin-propylene oxide rubber, and allyl glycidyl ether modified products thereof. In the present invention, epichlorohydrin rubber and epichlorohydrin-ethylene oxide rubber are preferable, and epichlorohydrin-ethylene oxide rubber (ECO) is more preferable. The allyl glycidyl ether-modified product is preferable because it has an excellent oil / cold resistance balance, particularly excellent heat softening resistance and weather resistance.

[Ion conductive agent]
In order to impart ionic conductivity to the rubber portion of the developing roll, an ionic conductive agent can also be used. Conventionally, in order to adjust the electric resistance of the developing roll, a conductive filler such as carbon black, metal powder, carbon fiber or the like has been included. Such a conductive filler is also known as an electronic conductive agent. being called. It is known that the conductivity when using an electronic conductive agent is due to the contact and tunnel effect of conductive filler particles dispersed in the rubber component, and the distance between the conductive filler particles varies. Then, electric resistance fluctuates. Therefore, the distance between the conductive filler particles becomes non-uniform due to the flow of the material when forming the rubber part, resulting in fluctuations in electrical resistance and local non-uniformity, making it difficult to obtain a high-definition and undisturbed image. In order to avoid such harmful effects, it is preferable to use an ionic conductive agent.

The ion conductive _{agent, LiI, LiCl, LiClO 4,} LiSCN, LiBF 4, LiAsF 4, LiCF 2 SO 2, LiC 6 F 12 SO 3, LiCF 3 CO 2, LiHgI 2, NaI, NaSCN, NaBr, KI, CsSCN , AgNO ₃ , CuC ₁₂ Mg (ClO ₄ ) _{2 and} other inorganic ion salts containing at least one of Li, Na, K, Cs, Ag, Cu or Mg; lithium stearylsulfonate, sodium octylsulfonate, dodecylbenzenesulfone Organic ion salts such as lithium acid, sodium naphthalenesulfonate, lithium dibutylnaphthalenesulfonate, potassium octylnaphthalenesulfonate, potassium dodecylnaphthalenesulfonate; trimethyloctadecylammonium chloride, benzylto Quaternary ammonium compounds such as methylammonium chloride, trioctylpropyleneammonium chloride, trioctylpropylammonium bromide, trimethyloctadecylammonium perchlorate, tetrabutylammonium hydrogen sulfate, tetrabutylammonium hydroxide, and perchlorates of these quaternary ammonium compounds Benzoate, nitrite, sulfate, hydrate and the like. These may be used alone or in combination of two or more. Of these, tetrabutylammonium hydrogen sulfate and tetrabutylammonium hydroxide are preferably used.

  The content of the ionic conductive agent in the rubber part is preferably 1 to 20 parts by weight, more preferably 1 to 10 parts by weight, and still more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the rubber component. If the ionic conductive agent is less than 1 part by weight, the electrical resistance of the rubber part is too high, and the toner does not easily migrate, resulting in a low image density. If it exceeds 20 parts by weight, the electric resistance value of the rubber part becomes too low, the electrostatic latent image formed on the surface of the photoreceptor is disturbed, and the sharpness of the image is lowered. In addition, problems such as being easily affected by temperature and humidity and bleeding (moving) to the surface also occur.

[Rubber part compounding chemicals]
In order for the rubber part to maintain strength and form, it is necessary to crosslink the rubber component, and a crosslinking agent is used. As a method for crosslinking the rubber component, sulfur is most commonly used, but organic peroxides, azo compounds, oxime compounds, metal oxides, and the like can be used without particular limitation.

  The blending ratio of these vulcanizing agents varies depending on the type of rubber component and the type of vulcanizing agent, but is usually 0.1 to 10 parts by weight, preferably 0.5 to 100 parts by weight of the rubber component. ~ 5 parts by weight. Vulcanizing agents can be used alone or in combination of two or more.

  In the rubber part constituting the present invention, vulcanization accelerators such as dithiocarbamates, thiurams, guanidines and thiazoles, vulcanization aids such as stearic acid and metal oxides (such as zinc oxide) are optionally provided. , Anti-aging agent, white carbon (silica), calcium carbonate, hard clay, magnesium carbonate, carbon black and other reinforcing agents, calcium carbonate, clay and other fillers, coupling agents, plasticizers, acid acceptors, dispersants, etc. Various compounding agents for rubber can be blended. As the compounding chemicals, those which do not contaminate the toner and the photoreceptor can be used.

[Development roll production method]
The production method of the developing roll used in the image forming method of the present invention is as follows.
A rubber component such as a rubber component, an ionic conductive agent, a vulcanizing agent, and a reinforcing agent is kneaded with a Banbury mixer or the like to form, for example, a ribbon-shaped rubber portion composition using an open roll or the like. Extrusion molding is performed on the outer peripheral surface of the conductive cored bar. Next, the rubber part composition molded into a predetermined shape is vulcanized, and then subjected to secondary processing such as polishing to adjust the surface roughness to obtain a final product.

  In order to adjust the surface roughness of the rubber part of the developing roll to a value within a predetermined range, a polishing machine having a grindstone is usually used, and polishing conditions such as the rotation speed of the grindstone and the feed speed of the object to be polished are selected. Is possible. Moreover, you may implement a blast process. More specifically, as a blasting condition, the type of blasting material, the compressed air pressure, the blasting time, the distance between the blasting nozzle and the developing roll, and the like are appropriately adjusted to obtain a desired surface roughness. Examples of the blast material include sand, glass beads, and steel balls.

<Toner>
Next, the toner used in the image forming method of the present invention will be described.
The toner of the present invention may be a non-magnetic toner or a magnetic toner. It contains a binder resin and a colorant, and contains a release agent, a fixing aid, a charge control agent, magnetic powder and the like as necessary. In addition, a fluidizing agent or the like is externally added as necessary to adhere to the surface.

The apparent density (bulk density) of the toner constituting the present invention is 0.36 to 0.46 g / ml in the case of a non-magnetic toner, preferably 0.38 to 0.44 g / ml, and 0.39 to 0. More preferred is .42 g / ml. When the apparent density is less than 0.36 g / ml, the fluidity of the toner is lowered and the triboelectric charge amount of the toner is lowered, the toner layer is not uniformly formed, the image is non-uniform, and the fog is increased. To do. If it exceeds 0.46 g / ml, the fluidity of the toner becomes excessive, the toner layer on the developing roll becomes thin, and fusing tends to occur. In particular, when a large amount of an external additive is added, fusion is more likely to occur.
The apparent density is measured according to JIS K 5101-12-1.

The circularity of the toner constituting the present invention is preferably 0.88 to 0.94, more preferably 0.89 to 0.93, and further preferably 0.90 to 0.92. . If the circularity is less than 0.88, the toner layer becomes non-uniform and the image quality deteriorates, the toner conveyance amount increases and the toner consumption also increases. If it exceeds 0.94, it is difficult to form a toner layer, the image quality becomes non-uniform, and the anti-fusing property deteriorates. The circularity is defined by the following formula (1).
Circularity = π · (diameter of circle equal to particle image area) / perimeter of particle image (1)
The circularity was measured by a flow type particle image analyzer (manufactured by Sysmex Corporation, trade name: FPIA-2100).

The volume average particle diameter of the toner constituting the present invention is preferably 6 to 11 μm, more preferably 6 to 10 μm, and further preferably 6 to 9 μm. If the volume average particle diameter is less than 6 μm, the amount of ultrafine powder of 3 μm or less increases, which adversely affects image quality and fusion. In addition, the pulverization efficiency is poor and there is a problem with the economy. If it exceeds 11 μm, there are problems that it becomes difficult to obtain a high-definition image and that the amount of toner consumption increases.
The volume average particle diameter is a 50% volume diameter measured with a Coulter Multisizer II manufactured by Coulter Beckman.

Next, raw materials used for the toner constituting the image forming method of the present invention will be described.
The binder resin of the toner of the present invention may be any resin that is usually used in toners. Styrene-acrylic acid copolymer resins, styrene-acrylic acid ester copolymer resins, styrene resins, acrylic resins Acid resins, acrylate resins, olefin resins (eg, α-olefin resins such as polyethylene and polypropylene), vinyl resins (eg, polyvinyl chloride, polyvinylidene chloride, etc.), polyester resins, polyamides Resin, polyether resin, urethane resin, epoxy resin, polyphenylene oxide resin, terpene phenol resin, polylactic acid resin, hydrogenated rosin, cyclized rubber, cycloolefin copolymer resin, thermoplastic elastomer (polyester heat Plastic elastomer, polyamide thermoplastic elastomer Include polyolefin and thermoplastic elastomers) or the like. These can be used alone or in combination of two or more.
In the present invention, styrene acrylate copolymer resins and polyester resins are preferably used.

Examples of the colorant blended in the toner constituting the present invention include black pigments for black toners, magenta pigments, cyan pigments, yellow pigments and the like for color toners.
Examples of the black pigment include black magnetic powder such as carbon black, iron oxide, and ferrite.
The number average particle diameter, oil absorption, PH, etc. of the carbon black are not particularly limited. Examples of commercially available products include those manufactured by Cabot Corporation of the United States, trade names: REGAL 400, 660, 330, 300, SRF-S, STERLING SO, V, NS, R; manufactured by Columbia Carbon Japan, Product name: Raven H20, MT-P, 410, 420, 430, 450, 500, 760, 780, 1000, 1035, 1060, 1080; manufactured by Mitsubishi Chemical Corporation, product names: # 5B, # 10B, # 40, # 2400B, MA-100 and the like. These carbon blacks can be used alone or in combination of two or more.

  The content of carbon black in the toner is preferably 0.1 to 20% by weight, more preferably 1 to 10% by weight, still more preferably 3 to 10% by weight, and particularly preferably 4 to 10% by weight. If the carbon black content is too small, the image density is lowered, and if it is too much, the image quality is liable to be lowered, and the toner moldability is also lowered.

  Examples of the magenta pigment include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 163, 202, 206, 207, 209; I. Pigment violet 19; C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35, etc. are mentioned. These magenta pigments can be used alone or in combination of two or more.

Examples of the cyan pigment include C.I. I. Pigment blue 2, 3, 15, 16, 17; I. Bat Blue 6; C.I. I. Acid Blue 45 etc. are mentioned. These cyan pigments can be used alone or in combination of two or more.
Examples of yellow pigments include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 74, 83, 93, 94, 97, 155, 180 etc. are mentioned. These yellow pigments can be used alone or in combination of two or more.

From the viewpoint of color mixing and color reproducibility, the color pigment of the full color toner is C.I. I. Pigment Red 57 and 122 are C.I. I. Pigment Blue 15 is C.I. I. Pigment Yellow 17, 74, 93, 155, and 180 can be preferably used.
The content of the color pigment constituting the toner of the present invention is 1 to 20% by weight in the toner, preferably 3 to 10% by weight, more preferably 3 to 8% by weight, and particularly preferably 3 to 6% by weight. %. When the content of the color pigment is too smaller than the above range, the image density is lowered, and when it is too much, the charging stability is deteriorated and the image quality is liable to be lowered. It is also disadvantageous in terms of cost. As the color pigment, a so-called master batch in which a color pigment is dispersed at a high concentration in a resin that can be a binder resin in advance may be used.

  The toner constituting the present invention preferably contains a release agent in order to further improve the fixing characteristics. The release agent is not particularly limited as long as the dispersibility with the binder resin is good. For example, polyolefin wax such as polyethylene wax, polypropylene wax, modified polyethylene wax; Fischer-Tropsch wax, polyester synthetic wax, etc. Synthetic wax; Petroleum wax such as paraffin wax and microcrystalline wax; Animal wax such as beeswax and whale wax; Plant wax such as carnauba wax, candelilla wax and rice wax; Cured oil such as hardened castor oil; Montan wax , Mineral waxes such as ozokerite and ceresin. These release agents can be used alone or in combination of two or more. In the present invention, since an amorphous polyester resin is used for the binder resin, it is preferable to use a polyester synthetic wax from the viewpoint of compatibility.

  The content of the release agent in the toner is usually about 0.5 to 20% by weight, but in the present invention, it is preferably 1 to 10% by weight, more preferably 1 to 5% by weight, still more preferably. 2 to 5% by weight (particularly preferably 2 to 4% by weight). If the content of the release agent exceeds 20% by weight, the toner's anti-fusing property, heat storage property and moldability may be deteriorated. On the other hand, when the content of the release agent is less than 0.5% by weight, a winding phenomenon is likely to occur, and the fixing characteristics may be deteriorated.

  At least one of the release agents in the present invention preferably has a melting point measured by a differential scanning calorimeter of 50 to 120 ° C, more preferably 50 to 100 ° C, and still more preferably 50 to 85 ° C. . If the melting point of the release agent is less than 50 ° C., the anti-fusing property and heat storage stability of the toner may be reduced, and if it exceeds 120 ° C., the low-temperature fixing characteristics and fixing strength of the toner may be deteriorated.

The melting point of the release agent is measured as follows according to ASTM D3418-82. About 10 mg of a sample is weighed and placed in an aluminum cell and placed on a differential scanning calorimeter (DSC) (trade name: SCC-6200, manufactured by Seiko Instruments Inc.), and 50 ml of N ₂ gas is supplied per minute. Infuse. Then, the temperature is raised between 20 ° C. and 200 ° C. at a rate of 10 ° C. per minute, held at 200 ° C. for 10 minutes, and then lowered from 200 ° C. to 20 ° C. at a rate of 10 ° C. per minute. In the DSC temperature rise curve observed at that time, the temperature at the top of the endothermic peak due to the melting of the release agent is The melting point.

The toner constituting the present invention may contain a charge control agent, if necessary.
Examples of positively chargeable charge control agents include modified products of nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate Diorganotin oxides such as dibutyltin oxide, dioctyltin oxide and dicyclohexyltin oxide; diorganotin borates such as dibutyltin borate, dioctyltin borate and dicyclohexyltin borate; pyrididium salts, azines, triphenylmethane compounds, cationic functional groups And low molecular weight polymers having These positively chargeable charge control agents may be used alone or in combination of two or more. Among these positively chargeable charge control agents, nigrosine compounds and quaternary ammonium salts are preferably used.

Examples of negative charge control agents include, for example, acetylacetone metal complexes, monoazo metal complexes, naphthoic acid or salicylic acid metal complexes or salts, organometallic compounds, chelate compounds, and low molecular weight compounds having an anionic functional group Examples thereof include polymers. These negatively chargeable charge control agents can be used alone or in combination of two or more. Among these negatively chargeable charge control agents, salicylic acid metal complexes and monoazo metal complexes are preferably used.
The content of the charge control agent is usually in the range of 0.1 to 5 parts by weight, preferably 0.5 to 4 parts by weight, more preferably 1 to 4 parts by weight with respect to 100 parts by weight of the binder resin. It is. The charge control agent is preferably colorless or light color for color toners.

  The toner constituting the present invention may further contain magnetic powder, if necessary. Examples of magnetic powder include metals such as cobalt, iron, and nickel; alloys of aluminum, copper, iron, nickel, magnesium, tin, zinc, gold, silver, selenium, titanium, tungsten, zirconium, and other metals; aluminum oxide And metal oxides such as iron oxide and nickel oxide; ferrite, magnetite and the like. The content of the magnetic powder is usually 1 to 70% by weight, preferably 5 to 50% by weight in the toner. As magnetic powder, that whose average particle diameter is 0.01-3 micrometers can be used conveniently.

  The toner constituting the present invention may further contain various additives as necessary, for example, stabilizers (for example, ultraviolet absorbers, antioxidants, heat stabilizers, etc.), flame retardants, antifogging agents, dispersants, plasticizers. Contains agents (phthalate esters, fatty acid plasticizers, phosphate plasticizers, etc.), polymer antistatic agents, low molecular antistatic agents, compatibilizers, conductive agents, fillers, fluidity improvers, etc. Also good.

[Toner Preparation Method]
The method for producing the toner used in the image forming method of the present invention is not particularly limited, and examples thereof include known methods such as a melt-kneading and pulverizing method, a suspension polymerization method, an emulsion polymerization method, and a spray drying method.
As an example, the melt-kneading pulverization method is as follows. It comprises a step of obtaining a resin composition by hot melt kneading, and a step of pulverizing and classifying the resin composition. In the case of hot melt kneading, if necessary, a colorant, a charge control agent, a release agent. Etc. are also used.

  Examples of the hot melt kneading method applied in the present invention include a method using a twin screw extruder, a method using a Banbury mixer, a method using a pressure roller, a pressure kneader, and a method using an open roll type continuous extruder. From the viewpoint of productivity, moldability, and versatility, a method using a twin-screw extruder or an open roll type continuous extruder is preferable. In the case of a biaxial extruder, the resin composition is obtained by hot-melt kneading the mixture with a biaxial extruder and extruding from a die (die) at the tip of the biaxial extruder. The kneading temperature T of the twin screw extruder is 70 to 200 ° C, preferably 80 to 180 ° C, more preferably 80 to 160 ° C. Examples of the pulverization method include a pulverization method using an apparatus such as a hammer mill, a cutter mill, or a jet mill. Moreover, as a classification method, the method by an airflow classifier like a dry-type centrifugal classifier is mentioned normally.

In the toner constituting the present invention, after the classification, externally added fine particles such as inorganic fine particles and resin fine powder are preferably adhered to the surface for improving fluidity and charging stability. Examples of the inorganic fine particles include silica, alumina, talc, clay, calcium carbonate, magnesium carbonate, titanium oxide, carbon black powder, and magnetic powder. These inorganic fine particles may be used alone or in combination of two or more. Of these inorganic fine particles, silica can be particularly preferably used. Silica is not particularly limited, such as an average particle diameter, a BET specific surface area, and a surface treatment, and can be appropriately selected depending on the application. Among them, those having a BET specific surface area in the range of 50 to 400 m ² / g are preferable, and surface-treated hydrophobic silica is more preferable. In the toner constituting the present invention, in addition to the inorganic powder particles, resin fine powders such as polytetrafluoroethylene resin powder, polyvinylidene fluoride resin, and acrylic resin powder may be adhered to the surface.

The ratio of adding the inorganic fine particles or resin fine powder can be appropriately selected from the range of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, and more preferably 0.1 to 100 parts by weight of the toner. -4 parts by weight, particularly preferably 0.3-3 parts by weight. If the ratio to be added is less than 0.01 parts by weight, there is little effect on the fluidity and charging stability of the toner, and it is difficult to form a uniform image, and if it exceeds 10 parts by weight, inorganic fine particles are easily released, It adheres to the photoconductor and the developing machine member and degrades the image quality.
The externally added fine particles are adhered to the toner surface by stirring using a stirrer such as a turbine stirrer, a Henschel mixer, or a super mixer.

  The image forming method of the present invention is not particularly limited in use of the developing method, and can be applied to a two-component developing method, a magnetic one-component developing method, and a non-magnetic one-component developing method. Preferably applied. Further, it is preferably applied to a non-contact type development system.

  As the carrier in the two-component development system, for example, nickel, cobalt, iron oxide, ferrite, iron, glass beads and the like can be used. These carriers may be used alone or in combination of two or more. The carrier preferably has an average particle size of 20 to 150 μm. In addition, the surface of the carrier may be coated with a coating agent such as a fluorine resin, an acrylic resin, or a silicone resin. Further, a magnetic material dispersed in a binder resin may be used.

  The image forming method of the present invention can be applied to mono-color image formation and full-color image formation, but is suitable for full-color image formation in that a high-definition image can be formed.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In addition, a compounding ratio is a weight part.
First, details of developing rolls and toners used in Examples and Comparative Examples, and evaluation results are shown below.

<Preparation of developing roll>
[Preparation of Developing Rolls A to E]
The following raw materials were kneaded with a Banbury mixer and then formed into a ribbon using an open roll. This rubber composition was put into an extruder, and a developing roll in which an unvulcanized rubber was coated to about 15 mmφ × 235 mm around a 9 mmφ stainless steel core using a crosshead was obtained.
Next, the unvulcanized developing roll was heated in a vulcanizing can at 160 ° C. for 60 minutes to obtain a developing roll molded article having ionic conductivity.
The surface of the obtained molded product was adjusted with a polishing machine to obtain 15 mmφ × 235 mm developing rolls A to E having different average surface roughness.
Rubber component: 50 parts of acrylonitrile butadiene rubber (NBR) (manufactured by Nippon Zeon Co., Ltd., trade name: Nipol 1042)
Rubber component: 50 parts of epichlorohydrin-ethylene oxide rubber (ECO) (manufactured by Nippon Zeon Co., Ltd., trade name: Gechron T3100, allyl glycidyl ether modified product)
-Reinforcing agent: 20 parts of silica (manufactured by Nippon Silica Industry, trade name: Nipsil VN3)
Acid acceptor: MgO 4 parts (Kyowa Chemical Co., Ltd., trade name: Kyowa Mug # 150)
・ Vulcanization aid: 5 parts of zinc oxide (Mitsui Metal Mining Co., Ltd., trade name: Zinc Hana)
・ Vulcanization aid: 1 part of stearic acid (manufactured by Kao Corporation) ・ 15 parts of plasticizer (manufactured by Idemitsu Kosan Co., Ltd., trade name: Process Oil PW-380)
・ Vulcanizing agent: Sulfur (manufactured by Hosoi Chemical Co., Ltd.) 1 part ・ Vulcanizing accelerator 0.5 part (manufactured by Kawaguchi Chemical Industry Co., Ltd., trade name: Accelerator 22)
・ Vulcanization accelerator 0.5 part (Ouchi Shinsei Chemical Co., Ltd., trade name: Noxeller TS)
・ Vulcanization accelerator 1.5 parts (manufactured by Kawaguchi Chemical Industry Co., Ltd., trade name: Accel CZ)

The average surface roughness and shore hardness of the developing rolls A to E are as follows.
Developing roll A: Average surface roughness (Ra) 1.00 μm, Shore hardness 46 Hs, Developing roll B: Average surface roughness (Ra) 0.80 μm, Shore hardness 47 Hs, Developing roll C: Average surface roughness (Ra ) 1.60 μm, Shore hardness 46 Hs, Development roll D: Average surface roughness (Ra) 0.45 μm, Shore hardness 46 Hs, Development roll E: Average surface roughness (Ra) 2.27 μm, Shore hardness 47 Hs.

[Preparation of Development Roll F]
・ 100 parts of acrylonitrile butadiene rubber (manufactured by Nippon Zeon Co., Ltd., trade name: Nipol 1042)
・ Carbon: 20 parts of conductive carbon black (trade name: Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.)
The average surface is the same as that of the developing roll A except that the rubber component is 100 parts of the above NBR, 20 parts of carbon black is used as the conductive agent, and no reinforcing agent (silica), acid acceptor, or coupling agent is used. A developing roll F having an electronic conductivity with a roughness of 1.00 μm and a Shore hardness of 50 Hs was produced.

<Production of toner>
[Material components]
-Amorphous polyester resin 89 parts (Mitsubishi Rayon Co., Ltd., trade name: FC1142, Tg: 66 ° C.)
Polyester synthetic wax 4 parts (manufactured by NOF Corporation, trade name WEP-5, melting point: 84 ° C.)
Cyan pigment for toner C.I. I. Pigment Blue 15: 3 6 parts (manufactured by Clariant Japan Co., Ltd., trade name: Hostaperm Blue B2G)
Boron-based charge control agent 1 part (made by Nippon Carlit Co., Ltd., trade name: LR147)
Using a biaxial kneading extruder (PCM-30, manufactured by Ikegai Co., Ltd.), the respective materials were appropriately set within a range of 90 to 150 ° C. and melt-kneaded, and a thickness of 2 to 3 mm. A plate-like extrudate was obtained. Next, the extruded product was pulverized with an airflow pulverizer (trade name: Jet Mill IDS, manufactured by Nippon Pneumatic Kogyo Co., Ltd.), and then classified with a dry airflow classifier, so that the volume average particle size was about 8 μm. Toner particles were obtained. Hydrophobic silica A (TS-530, manufactured by Cabot Corporation) and hydrophobic silica B (NA-50H, manufactured by Nippon Aerosil Co., Ltd.) are added to 100 parts of the obtained toner particles, and the mixture is added to a Henschel mixer. Thus, externally added toners A to D and F in which hydrophobic silica was adhered to the toner particle surfaces were obtained by stirring and mixing at a peripheral speed of 40 m / sec for 10 minutes.
The amount of hydrophobic silica A added was 1 part toner A, 2 parts toner B, 0.3 parts toner C, 3 parts toner D, and 2 parts toner F. The amount of hydrophobic silica B added was 0.6 parts.
Toner E is the same as Toner B except that the degree of circularity is adjusted by pulverizing with a dry airflow pulverizer and then pulverizing with an impact pulverizer (trade name: Kryptron Eddy KTM-EX type). Produced.

The apparent density, circularity, and volume average particle diameter of the toners A to F are as follows.
Toner A: Apparent density 0.409 g / ml, circularity 0.908, volume average particle diameter 8.0 μm. Toner B: Apparent density 0.425 g / ml, circularity 0.910, volume average particle diameter 8.1 μm. Toner C: Apparent density 0.354 g / ml, circularity 0.909, volume average particle diameter 8.0 μm. Toner D: Apparent density 0.467 g / ml, circularity 0.910, volume average particle diameter 8.0 μm. Toner E: Apparent density 0.428 g / ml, circularity 0.942, volume average particle diameter 7.9 μm. Toner F: Apparent density 0.410 g / ml, circularity 0.873, volume average particle diameter 8.1 μm.

[Evaluation]
Examples 1 to 4 and Comparative Examples 1 to 7 with combinations of developing rolls and toners shown in Tables 1 and 2 were used. Evaluation environment: 22 ° C., 65% RH, non-magnetic one-component full color printer (printing speed: A4 Evaluation was performed using 4 sheets per minute, non-contact development system).

<Evaluation items>
1. Image quality (solid image uniformity)
After printing 10 A4 originals with an image ratio of 5%, a solid image with an image density of about 1.2 was printed. Thereafter, 5000 A4 originals with an image ratio of 5% were printed, and a solid image was printed every 1000 sheets during printing. We confirmed solid image uniformity, omission, and image quality defects.
◯: Excellent solid image uniformity, no density unevenness, no image quality defect △: Excellent solid image uniformity at the beginning of printing, no image quality defect, but solid image uniformity is lost as printing progresses , Image quality defects occur.
X: Solid image has no uniformity, density unevenness and blurring occur.
2. Toner consumption amount 5000 A4 originals with an image ratio of 5% were printed. The total toner consumption was determined from the difference in weight of the toner cartridges before and after printing, and the toner consumption per 1000 prints (g / 1000 sheets) was determined. The target of toner consumption is 30 g / 1000 sheets or less, but 20 g / 1000 sheets or less is preferable.
3. Fusing resistance 5000 A4 originals with an image ratio of 5% were printed. After printing 5000 sheets, it was visually confirmed whether toner fusion was observed on the charging member (charging blade) of the developing machine.
○: No toner fusion.
X: Toner fused.
4). Comprehensive evaluation From the viewpoint of practicality of toner, a comprehensive evaluation was performed in consideration of the balance between image quality and consumption and anti-fusing property.
○: Excellent in image quality, consumption and anti-fusing property.
X: Any one of image quality, consumption, and anti-fusing property is not sufficient.

  As is apparent from Tables 1 and 2, the developed image forming methods of Examples 1 to 4 according to the present invention were excellent in solid uniformity, toner consumption and anti-fusing property, and had no practical problems.

On the other hand, the image forming method of Comparative Example 1 was inferior in solid uniformity and anti-fusing property because the average surface roughness of the developing roll was small.
In the image forming method of Comparative Example 2, since the average surface roughness of the developing roll was large, the solid uniformity was inferior and the amount of toner consumption was large.
The image forming method of Comparative Example 3 was poor in solid uniformity because it contained carbon in the rubber component of the developing roll and was electronically conductive.
In the image forming method of Comparative Example 4, since the apparent density of the toner is small, the fluidity of the toner is lowered, the solid uniformity is inferior, and the toner consumption is large.
In the image forming method of Comparative Example 5, since the apparent density of the toner is large, the fluidity of the toner becomes excessive, the toner layer on the developing roll becomes thin, and the anti-fusing property is inferior.
The image forming method of Comparative Example 6 was inferior in solid uniformity and anti-fusing property due to the large circularity of the toner.
The image forming method of Comparative Example 7 was inferior in solid uniformity because the circularity of the toner was small. In addition, the toner consumption was large.

  According to the image forming method of the present invention, a high-definition and high-quality image without disturbance can be obtained, and the amount of toner consumed is small. In addition, it is difficult to cause fusion on the developing member, and it can be applied to all developing methods. In particular, it is suitable as an image forming method of a non-magnetic one-component development system and is suitable for full color image formation.

The perspective view which shows an example of the image development roll concerning this invention

Explanation of symbols

1. Core metal 2. Rubber part

Claims (5)

A charging means for charging the surface of the photosensitive member, an exposure means for forming an electrostatic latent image by irradiating light on the charged surface of the photosensitive member, and supplying a developer to the electrostatic latent image using a developing roll An image forming method comprising: a developing unit; a transfer unit that transfers a developer on the photosensitive member developed by the developing roll to a transfer material; and a fixing unit that fixes an image on the transfer material;
The developing means is composed of at least a cored bar and a rubber part having ionic conductivity covering the cored bar, and an average surface roughness (Ra) of 0.5 to 2 μm;
An image forming method comprising using a developer using toner having an apparent density of 0.36 to 0.46 g / ml and a circularity of 0.88 to 0.94.   The image forming method according to claim 1, wherein the rubber portion of the developing roll contains at least a nitrile rubber and / or an epihalohydrin rubber.   The image forming method according to claim 1, wherein the rubber hardness of the developing roll has a Shore hardness of 40 to 55 Hs.   4. The image forming method according to claim 1, wherein the developing unit is a non-magnetic one-component developing system.   5. The image forming method according to claim 1, wherein the image forming method is applied to full color image formation.

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