JP2004334069A - Titanium oxide for toner and toner for use in electrostatic development using same, as well as image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a titanium oxide that can uniformly be dispersed on the surface of toner particles and can stably maintain the electrostatic charging property of toner even if in a high humidity environment. <P>SOLUTION: A conductive layer is formed on the surface of the titanium oxide particles obtained by a vapor-phase oxidation method, and further the surface is treated by using a hydrophobizing agent. Here, from a viewpoint of preventing cohesion of toner furthermore, preferably the percentage of the conductive layer is made to fall within a range of 5-30 wt % to the titanium oxide particles. Also, from a viewpoint of further stabilizing toner charge in a high temperature and high humidity environment, preferably the percentage of hydrophobizing agent is made not less than 2wt % to the titanium oxide particles. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００６７】
本発明の要件を満足する実施例１〜３のトナーでは、３０万枚耐刷試験後も帯電量１２μＣ／ｇ以上と安定しており、画像濃度（ＩＤ）及びカブリ濃度（ＦＤ）は良好な値であった。また、画像白点やドラムフィルミング、ドラム放電破壊は発生しなかった。これに対し、導電層を有しない酸化チタンを用いた比較例１のトナーでは、トナー帯電量が１６．７μＣ／ｇと大きくなりＩＤが１．２８と低かった。また画像白点およびドラム放電破壊が発生した。他方、疎水化処理していない酸化チタンを用いた比較例２のトナー、及び液相法で作製された酸化チタンを用いた比較例３のトナーでは、トナー帯電量が低くなりＦＤが許容範囲を超えて大きくなった。また比較例３のトナーではドラムフィルミングも発生した。
【００６８】
【発明の効果】
本発明の酸化チタンでは、気相酸化法によって得られた酸化チタン粒子の表面に導電層を形成し、さらに疎水化剤によって表面処理した構成としたので、トナー粒子表面に均一に分散し、また高湿環境下であってもトナーの帯電性を安定して維持することができる。
【００６９】
また本発明のトナーでは、前記酸化チタンをトナー粒子表面に混合添加してなるので、均一な帯電が得られ、また高温高湿環境下であっても帯電量の低下が生じず優れた画像品質が得られる。
【００７０】
さらに本発明の画像形成装置では、感光体として非晶質シリコン感光体を用い、トナーとして前記トナーを用いるので、複写画像に感光体の絶縁破壊に起因する黒点が表れるこがなく、また高温高湿環境下であっても画像カブリが発生することがない。
【図面の簡単な説明】
【図１】本発明に係る画像形成装置の一例を示す構成図である。
【図２】図１の画像形成装置における現像装置の拡大構成図である。
【符号の説明】
１ 感光体（像担持体）
２ 帯電手段
３ 露光手段
４ 現像装置
５ 転写手段
６ クリーニング手段
７ 被転写部材
４１ 現像ローラ
４２ マグネット
４３ ブレード
４４ パドルローラ
４５ 現像剤
４５ａ 磁気ブラシ
４６ セパレータ
４７ トナー補給部
４８ 補給ローラ
６１ クリーニングブラシ
６２ クリーニングブレード[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a titanium oxide used for a toner for electrostatic development (hereinafter, may be simply referred to as “toner”), a toner using the same, and an image forming apparatus.
[0002]
[Prior art]
Titanium oxide that has been externally added to a toner for the purpose of improving fluidity or the like has generally been produced by a liquid phase oxidation method. The liquid phase oxidation method includes two methods, a sulfuric acid method and a hydrochloric acid method. In the sulfuric acid method, insoluble titanium oxide hydroxide is produced from the following reaction formula, and this is calcined to obtain titanium oxide.
FeTiO ₃ + 2H ₂ SO ₄ → FeSO ₄ + TiOSO ₄ + H ₂ O
TiOSO ₄ + 2H ₂ O → TiO (OH) ₂ + H ₂ SO ₄
[0003]
On the other hand, in the hydrochloric acid method, a strong base such as sodium hydroxide is added to an aqueous hydrochloric acid solution obtained by dissolving titanium tetrachloride in water to precipitate titanium hydroxide, and the titanium hydroxide is calcined in the same manner as described above. Titanium oxide.
[0004]
Since the water-soluble component in the production process is inevitably remaining in the titanium oxide produced by such a liquid phase oxidation method, when it is used as an external additive of the toner, it may be subjected to a high humidity environment. There is a problem that toner charging is reduced.
[0005]
Therefore, titanium oxide produced by a gas-phase oxidation method, which has a higher degree of hydrophobicity than that of a liquid-phase oxidation method, has recently been used as an external additive for toner (for example, Patent Document 1).
[0006]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-172006 (Claims)
[0007]
[Problems to be solved by the invention]
However, titanium oxide formed by the vapor phase oxidation method has a higher degree of hydrophobicity than that obtained by the liquid phase oxidation method, and thus easily aggregates. Therefore, the toner cannot be uniformly dispersed on the surface of the toner particles, and the charging of the toner is not stable. In addition, dielectric breakdown may occur in the photoconductor due to the aggregated titanium oxide, and a black spot may appear on a copied image. Such a problem is conspicuous in a high-temperature and high-humidity environment, particularly as a decrease in toner charge and image fog.
[0008]
The present invention has been made in view of such a conventional problem, and aims at uniformly dispersing the toner particles on the surface of the toner particles and stabilizing the chargeability of the toner even under a high humidity environment. It is to provide a titanium oxide which can be maintained.
[0009]
Another object of the present invention is to provide a toner that can obtain uniform charge and does not cause a decrease in charge amount even under a high temperature and high humidity environment.
[0010]
It is a further object of the present invention to provide an image forming apparatus in which black spots due to dielectric breakdown of a photoreceptor do not appear in a copied image and image fog does not occur even in a high temperature and high humidity environment. It is in.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the titanium oxide of the present invention has a configuration in which a conductive layer is formed on the surface of titanium oxide particles obtained by a gas phase oxidation method, and the surface is further treated with a hydrophobizing agent.
[0012]
Here, from the viewpoint of further suppressing the aggregation of the toner, the ratio of the conductive layer is preferably in the range of 5 to 30 wt% with respect to the titanium oxide particles. Further, from the viewpoint of further stabilizing the charge amount of the toner under a high-temperature and high-humidity environment, the ratio of the hydrophobizing agent is preferably 2 wt% or more based on the titanium oxide particles.
[0013]
Further, the toner of the present invention has a configuration in which the above-mentioned titanium oxide is mixed and added as an external additive to toner particles.
[0014]
Further, in the image forming apparatus of the present invention, the electrostatic latent image carrier, a charging unit for charging the surface of the electrostatic latent image carrier, and irradiating the charged surface of the electrostatic latent image carrier with light. Exposure means for forming an electrostatic latent image by means of a developing means, a developing means for supplying toner to the electrostatic latent image for development, and transferring the toner on the electrostatic latent image carrier developed by the developing means to a member to be transferred And a fixing unit for melting and fixing the toner on the member to be transferred, using an amorphous silicon photoconductor as the electrostatic latent image carrier, and using the electrostatic developing toner as the toner. The configuration was used.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The present inventor intends to further improve the charging stability by using titanium oxide by a gas phase oxidation method and further performing a surface treatment with a hydrophobizing agent in order to prevent a decrease in toner charge in a high humidity environment. As a result of intensive studies to suppress the increase in the cohesiveness of titanium oxide accompanying this, it was found that the cohesiveness of titanium oxide can be suppressed by forming a conductive layer on the surface of the titanium oxide particles. I've reached the point.
[0016]
That is, the present invention is characterized in that a conductive layer is formed on the surface of titanium oxide particles obtained by a gas phase oxidation method, and that the surface is treated with a hydrophobizing agent. Hereinafter, the configuration of the present invention will be sequentially described.
[0017]
First, the titanium oxide particles used in the present invention need to be produced by a gas phase oxidation method. A conventionally known method can be adopted as the gas phase oxidation method. For example, it may be manufactured as follows. First, liquid titanium tetrachloride is heated in advance, vaporized, and introduced into a reaction furnace. Next, an oxygen gas is introduced into the reaction furnace together with titanium tetrachloride to perform an oxidation reaction. The oxidation reaction temperature is preferably from 500 to 1200C, more preferably from 600 to 1100C. During the oxidation reaction, hydrogen gas or steam may be supplied into the reaction furnace together with titanium tetrachloride and oxygen gas to control the rutile ratio of titanium oxide. When the titanium oxide particles are generated by the oxidation reaction, the titanium oxide particles are cooled. For cooling the titanium oxide, a cooling tank having a cooling jacket or the like can be used, and the generated titanium oxide particles are cooled while being brought into contact with an inert gas such as a nitrogen gas. Thereafter, the cooled titanium oxide particles are collected, and chlorine gas remaining in the titanium oxide particles is removed by a heat treatment to obtain titanium oxide particles. Examples of the heat treatment include vacuum heat treatment, heating in an air or nitrogen gas atmosphere, and steam treatment. If necessary, the generated titanium oxide may be subjected to a classification treatment. The titanium oxide thus obtained may be pulverized or crushed. As a crushing or crushing method, a vibration mill, a ball mill, a disk mill, a turbo mill, a tower mill, a paint shaker, a lightning crusher, a vibration crusher, or the like is used.
[0018]
The particle properties such as the particle size and specific surface area of the titanium oxide particles used in the present invention are not particularly limited, but the average particle size is preferably in the range of 0.03 to 1 μm, and the specific surface area is in the range of 10 to 100 m ² / g. Is preferred. Note that the titanium oxide particles produced by the vapor phase oxidation method have a rutile type crystal form.
[0019]
Next, in the titanium oxide of the present invention, it is also important to form a conductive layer on the surface of the produced titanium oxide particles. Examples of such a conductive layer include a metal oxide layer. As a method for forming the metal oxide layer, a conventionally known method can be used. For example, in the case where a metal oxide layer which is a conductive layer is formed on the surface of titanium oxide particles using tin oxide to which antimony oxide is added, the following may be performed. A water-soluble tin compound and a water-soluble antimony compound are added to an aqueous suspension of titanium oxide fine particles, neutralized, and the surface of the titanium oxide fine particles is coated with a hydrated oxide of tin and a hydrated oxide of antimony. To wear. The concentration of the titanium oxide fine particles in the suspension is preferably in the range of 20 to 300 g / l. When using an aqueous hydrochloric acid solution of tin chloride and antimony chloride as a tin compound and an antimony compound, neutralization is performed by adding an aqueous solution of hydrochloric acid after the addition of the aqueous solution of hydrochloric acid, and a hydrate of tin oxide and antimony oxide is used as fine particles of titanium oxide. Apply to the surface. In this case, it is recommended to add an aqueous alkaline solution simultaneously with the aqueous hydrochloric acid solution so that the pH of the suspension is maintained at 2 to 7. Examples of the aqueous alkaline solution include aqueous solutions of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and the like.
[0020]
When an alcohol solution or an acetone solution of tin chloride and antimony chloride is used, the suspension is heated in advance to 70 to 90 ° C., and an alcohol solution or an acetone solution is added thereto, and the tin oxide is hydrolyzed. And a hydrate of antimony oxide are deposited on the inorganic fine particles.
[0021]
Then, the suspension is filtered and washed, and the obtained cake is dried as necessary. Then, the resultant cake is baked at 300 to 800 ° C., and then pulverized to form a conductive layer made of tin oxide to which antimony oxide is added. To obtain titanium oxide fine particles.
[0022]
The ratio of the conductive layer to the titanium oxide particles is preferably in the range of 5 to 30 wt%. If the proportion of the conductive layer is less than 5 wt%, the aggregation of the toner may not be sufficiently suppressed, while if it exceeds 30 wt%, the charge retention of the toner may be reduced and the toner may be unstable. Because. A more preferred ratio of the conductive layer is in the range of 10 to 20 wt%.
[0023]
Other metal oxides that can form the conductive layer include tin oxide to which phosphorus, indium, and fluorine are added; indium oxide to which antimony, phosphorus, fluorine, tin, and zinc are added; antimony, phosphorus, indium, and fluorine; Zinc oxide to which aluminum is added is given.
[0024]
In the titanium oxide of the present invention, it is also important to perform a surface treatment with a hydrophobizing agent. This is because the surface treatment with the hydrophobizing agent improves the environmental stability of the toner. The degree of hydrophobicity of titanium oxide may be appropriately determined based on the amount of toner used, the type of toner, and the like, but is generally preferably 50% or more by the methanol wettability method.
[0025]
The ratio of the hydrophobizing agent is not particularly limited, but is preferably 2% by weight or more based on the titanium oxide particles. If the ratio of the hydrophobizing agent is less than 2% by weight, the hydrophobization may be insufficient and the chargeability of the toner may be unstable. A more preferred ratio of the hydrophobizing agent is 2.5% by weight or more. On the other hand, the preferable upper limit of the ratio of the hydrophobizing agent is 10% by weight.
[0026]
As the hydrophobizing agent that can be used in the present invention, a conventionally known one can be used, and examples thereof include a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a silicone oil, and a silicone varnish.
[0027]
As a surface treatment method using a hydrophobizing agent, a conventionally known method can be used. For example, a dry method in which a liquid obtained by diluting a hydrophobizing agent with a solvent is added to titanium oxide and mixed, and then heated and dried to disintegrate, or a hydrophobizing agent is added to a suspension in which titanium oxide is dispersed in an aqueous medium. And a wet method of heating and drying to disintegrate the mixture.
[0028]
Next, the toner of the present invention will be described. The toner of the present invention is greatly characterized in that the titanium oxide is added to the toner particles. As a result, uniform charging can be obtained, and the charge amount does not decrease even in a high temperature and high humidity environment.
[0029]
As a method for mixing and adding the titanium oxide to the toner particles, a conventionally known treatment can be used. For example, a method in which the titanium oxide and the toner particles are charged into a high-speed fluid type stirrer or a V-type mixer and stirred and mixed is exemplified. The longer the mixing time and the higher the stirring speed, the more uniformly the titanium oxide is dispersed on the surface of the toner particles.
[0030]
The addition amount of titanium oxide is preferably in the range of 0.5 to 2% by weight based on the toner particles. If the added amount of titanium oxide is less than 0.5 wt%, the effect of the present invention may not be sufficiently obtained. On the other hand, if the added amount exceeds 2 wt%, the fluidity of the toner deteriorates and the image density is reduced from the beginning. This is because there is a risk of shortage.
[0031]
The toner particles used in the present invention are not particularly limited, and conventionally known toner particles can be used. For example, toner particles obtained by dispersing and mixing a colorant in a binder resin and adding a charge control agent, wax, magnetic powder, and the like as necessary.
[0032]
Examples of the binder resin used here include a thermoplastic resin and a thermosetting resin that is not effective or is an initial condensate. Specific examples include a vinyl aromatic resin such as polystyrene, a styrene-acryl copolymer, an acrylic resin, a polyvinyl acetal resin, a polyester resin, an epoxy resin, and a phenol resin.
[0033]
Examples of the coloring agent contained in the binder resin include black pigments such as acetylene black, lamp black and aniline black; and yellow pigments such as graphite, zinc yellow, cadmium yellow, yellow iron oxide, and mineral fast. Yellow, nickel titanium yellow, navels yellow, naphthol yellow S, Hanza yellow G, Hanza yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, tartrazine lake; , Molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, induslen brilliant orange RK, benzidine orange G, induslen brilliant orange GK; red face , Bengala, Cadmium Red, Lead Red, Cadmium Mercury Sulfide, Permanent Red 4R, Lysole Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B; violet pigment, manganese purple, fast violet B, methyl violet lake; blue pigment, navy blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated product, first sky Blue, Indaslen Blue BC; green pigments such as chrome green, chromium oxide, pigment green B, malachite green lake, Le Yellow Green G; as a white pigment include zinc white, titanium oxide, antimony white, zinc sulfide, barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white can be used. Such a colorant is preferably used in an amount of 2 to 20 parts by weight, particularly 5 to 15 parts by weight, per 100 parts by weight of the binder resin.
[0034]
The charge control agent is not particularly limited, and a conventionally known charge control agent can be used.Examples of the positive charge control agent include a nigrosine dye, a fatty acid-modified nigrosine dye, a carboxyl group-containing fatty acid-modified nigrosine dye, and a quaternary ammonium. Salts, amine compounds, organometallic compounds, and the like can be used. As the negative charge control agent, metal complexes of oxycarboxylic acids, metal complexes of azo compounds, metal complex dyes, salicylic acid derivatives, and the like can be used. The addition amount of the charge control agent is preferably in the range of 0.1 to 10 parts by weight based on 100 parts by weight of the binder resin.
[0035]
As the wax contained in the binder resin, conventionally known waxes can be used. For example, polyhydric alcohol esters of fatty acids, higher alcohol esters of fatty acids, alkylenebisfatty acid amide compounds, natural waxes, and a number average molecular weight of 1,000 Examples include polypropylene, polyethylene, and propylene-ethylene copolymers in the range of from 10,000 to 10,000, particularly from 2,000 to 6,000. The amount of the wax is preferably in the range of 0.1 to 10 parts by weight based on 100 parts by weight of the binder resin.
[0036]
The toner of the present invention can be produced by a method known per se such as a pulverization classification method, a melt granulation method, a spray granulation method, a suspension / emulsion polymerization method, and the like. The method can be suitably used. In such a pulverizing and classifying method, a toner composition such as a binder resin and a first magnetic powder, and if necessary, a charge control agent and a release agent are premixed with a Henschel mixer or a V-type mixer, and then mixed with a twin-screw extruder. Melt kneading is performed using a melt kneading apparatus. After cooling the melt-kneaded product, it is roughly pulverized and finely pulverized, and if necessary, classified to obtain toner particles having a predetermined particle size distribution. As described above, inorganic fine particles are externally added to the surface of the toner particles to obtain a toner. The toner of the present invention may be used as it is as a one-component developer, or may be mixed with a carrier and used as a two-component developer.
[0037]
When the toner of the present invention is used as a two-component developer, the carrier to be used is not limited. For example, magnetic metals such as iron, nickel and cobalt and alloys thereof, or alloys containing rare earth elements, hematite, magnetite Sintering of magnetic material such as manganese-zinc ferrite, nickel-zinc ferrite, manganese-magnesium ferrite, soft ferrite such as lithium ferrite, iron oxide such as copper-zinc ferrite and mixtures thereof And magnetic particles produced by performing atomization and the like, and those obtained by coating the surfaces of the magnetic particles with a resin. Further, a magnetic material-dispersed resin can be used as the carrier. In this case, the above magnetic material can be used as the magnetic material to be used, and as the binder resin, for example, a vinyl resin, polyester resin, epoxy resin, phenol resin, urea resin, polyurethane resin, polyimide resin, cellulose resin, polyether Resins or mixtures thereof can be mentioned.
[0038]
The particle size of the carrier is generally from 20 to 200 μm, particularly preferably from 30 to 150 μm, expressed in terms of particle size by electron microscopy. In addition, the apparent density of the carrier, when mainly composed of a magnetic material, varies depending on the composition and surface structure of the magnetic substance, but is generally preferably in the range of 2.4 to 3.0 g / cm ³ .
[0039]
The toner concentration in the two-component developer composed of the toner and the carrier is 1 to 20% by weight, preferably 3 to 15% by weight. If the toner concentration is less than 1% by weight, the image density becomes too light, while if the toner concentration exceeds 20% by weight, the toner scatters in the developing device, and the toner adheres to the inside of the apparatus and the background portion such as transfer paper. This is because there is a possibility that a malfunction may occur.
[0040]
Next, the image forming apparatus of the present invention will be described. FIG. 1 is a schematic diagram showing an embodiment of the image forming apparatus of the present invention. The apparatus shown in FIG. 1 is a magnetic brush development using a two-component developer composed of a toner and a carrier as a developer.
[0041]
The photoconductor 1 is rotated at a constant speed in the direction of the arrow. Around the photoreceptor 1, a charging unit 2, an exposure unit 3, a developing device 4, a transfer unit 5, and a cleaning unit 6 are arranged along the rotation direction. The surface of the photoconductor 1 is uniformly charged to a predetermined potential by the discharge of the charging unit 2. The photoconductor 1 rotates in the direction of the arrow, and then an electrostatic latent image corresponding to the image is formed on the surface of the photoconductor 1 by the exposure unit 3. Since this image forming apparatus employs the reversal development method, the surface potential of the latent image portion is attenuated, and the surface potential of the non-exposed portion is maintained at the initial charging potential. Next, the developing device 4 develops the electrostatic latent image with toner.
[0042]
FIG. 2 is a schematic diagram of a developing device 4 of a two-component magnetic brush developing system. The developing roller 41 is arranged so that the closest distance to the photoconductor 1 is at least about 500 μm at least during development, and the magnetic brush 45 a of the developer carried on the outer surface of the developing roller 41 contacts the surface of the photoconductor 1. It is set as follows. The contact area between the magnetic brush 45a and the photoconductor 1 is a developing area.
[0043]
The basic configuration of the developing device 4 includes a developing roller 41 that conveys a developer 45 to a developing area, and a blade 43 for forming a uniform thickness of the developer layer on the developing roller 41. Forward development is performed in the same direction as the photoconductor surface. The plurality of fixed magnets 42 function to capture the developer 45 from the paddle roller 44 onto the developing roller 41, to form a uniform developer layer thickness by the blade 43, and to form a soft magnetic brush in the developing area. It has a function and a function of peeling off the developer in which the amount of toner is reduced after the development, and exerts these functions by the magnetic field created by selecting the magnetic polarity and magnetic force of the magnets adjacent to each other. The developer 45 supplied from the paddle roller 44 to the developing roller 41 is carried to the blade 43 by the action of the magnet 42 fixed in the developing roller 41 as the developing roller 41 rotates. Here, the amount of the developer carried to the developing area is adjusted by the gap between the blade 43 and the developing roller 41, and the surplus developer rises along the vertical surface of the blade 43, and flows on the separator 46 to the paddle roller 44. Circulate. The developer conveyed to the developing area becomes a magnetic brush 45 a by the action of the magnet 42, and when the developer contacts the photosensitive drum 1, the toner in the developer becomes an electrostatic latent image (exposure) formed on the photosensitive body 1. And visualizes the latent image.
[0044]
When the toner concentration in the developer is detected by the toner concentration detecting means (not shown) to be lower than the predetermined range, the supply roller 48 is driven to rotate, and the toner in the toner supply unit 47 is supplied into the developer 45. The toner concentration in the developer 45 is controlled to be within a predetermined range.
[0045]
In FIG. 1, when the photoconductor 1 is located at a position facing the transfer unit 5, the toner image on the photoconductor 1 is transferred to the transfer member 7. Thereafter, heat and pressure are applied to the toner image on the transfer receiving member 7 by a fixing unit (not shown), and the toner image is fused and fixed on the transfer receiving member 7. On the other hand, the untransferred toner remaining on the photoreceptor 1 is cleaned in advance by the cleaning brush 61 in the cleaning means 6 and then completely cleaned by the cleaning blade 62.
[0046]
The material of the photoconductor (image carrier) that can be used in the present invention is not limited, and conventionally known materials can be used. For example, a photoconductor such as an amorphous silicon photoconductor, an organic photoconductor, a Se photoconductor, a ZnO photoconductor, and a CdS photoconductor may be used. Among them, the toner of the present invention can be particularly effectively used for a photosensitive member such as an amorphous silicon photosensitive member in which dielectric breakdown is relatively likely to occur. An amorphous silicon photoreceptor is also preferable from the viewpoint of durability. In addition, from the viewpoint of increasing the sensitivity of the photoconductor, it is recommended that the thickness of the photosensitive layer of the amorphous silicon photoconductor be 20 μm or less. The shape of the photoreceptor is not limited, and a conventionally known shape can be used. For example, a shape such as a drum shape, a sheet shape, a belt shape, and a web shape may be used. Among them, a drum shape is preferable.
[0047]
【Example】
Hereinafter, the titanium oxide, the toner, and the image forming apparatus of the present invention will be described in more detail based on examples. Note that the present invention is not limited to these examples.
[0048]
(Production of titanium oxide A)
A mixture of titanium tetrachloride and chlorine gas obtained by a gas phase method was introduced into a gas phase oxidation reactor, and reacted at a temperature of 1000 ° C. in a gas phase to obtain a bulk of titanium oxide. The obtained titanium oxide bulk was pulverized by a hammer mill, washed, and then dried at a temperature of 110 ° C. And it was crushed by a jet mill to obtain titanium oxide particles.
The obtained titanium oxide particles are dispersed in water to form a suspension (100 g / l), which is heated to 70 ° C. To this suspension, a solution prepared by dissolving 24 g of tin chloride (SnCl ₂ / 5H ₂ O) and 8 g of antimony chloride (SbCl ₂ ) in a 2N hydrochloric acid aqueous solution and a 10% aqueous sodium hydroxide solution were added. No. 3 was added over 1 hour to maintain a conductive layer composed of a hydrate of tin oxide and antimony oxide on the surface of the titanium oxide particles. After the suspension was filtered and washed, it was baked at a temperature of 600 ° C. and crushed by a jet mill to obtain titanium oxide on which a conductive layer was formed. Next, this titanium oxide and 3.0 wt% of isopropyl triisostearoyl titanate with respect to the titanium oxide are charged into a Henschel mixer, mixed at a temperature of 130 ° C., subjected to a coupling reaction, and dried and crushed. Titanium oxide A was used.
[0049]
(Production of titanium oxide B)
The aqueous solution of titanium sulfate obtained by the sulfuric acid method was diluted with water to crystallize a heated titanium titanyl salt. Then, the titanyl sulfate was dissolved in water and hydrolyzed by heating to precipitate titanium hydroxide. This was fired at a temperature of 1000 ° C. to obtain a bulk of titanium oxide. The bulk of the obtained titanium oxide was pulverized by a hammer mill, washed, dried at 110 ° C., and pulverized by a jet mill to obtain titanium oxide particles. Thereafter, titanium oxide B was obtained in the same manner as titanium oxide A.
[0050]
(Production of titanium oxide C)
Except that the amount of tin chloride (SnCl ₂ / 5H ₂ O) added was 9 g, the amount of antimony chloride (SbCl ₂ ) added was 3 g, and the amount of isopropyl triisostearoyl titanate was 3.0 wt%, the titanium oxide A and Similarly, titanium oxide C was obtained.
[0051]
(Production of titanium oxide D)
Except that the addition amount of tin chloride (SnCl ₂ / 5H ₂ O) was 48 g, the addition amount of antimony chloride (SbCl ₂ ) was 16 g, and the addition amount of isopropyl triisostearoyl titanate was 3.0 wt%, the titanium oxide A and Similarly, titanium oxide D was obtained.
[0052]
(Preparation of titanium oxide E)
Except that the addition amount of tin chloride (SnCl ₂ / 5H ₂ O) was 0 g, the addition amount of antimony chloride (SbCl ₂ ) was 0 g, and the addition amount of isopropyl triisostearoyl titanate was 3.0 wt%, Similarly, titanium oxide E was obtained.
[0053]
(Production of titanium oxide F)
Same as titanium oxide A except that the amount of tin chloride (SnCl ₂ / 5H ₂ O) added was 24 g, the amount of antimony chloride (SbCl ₂ )) was 8 g, and the amount of isopropyl triisostearoyl titanate was 0 wt%. Thus, titanium oxide F was obtained.
[0054]
The ratio of the conductive layer and the ratio of the hydrophobizing agent of each of the prepared titanium oxides were measured by the following methods. Table 1 shows the measurement results.
[0055]
(Ratio of conductive layer (SnO ₂ ))
The measurement of the SnO ₂ content is performed as follows. 0.5 g of titanium oxide and 15 g of ammonium sulfate are added to a small amount of water to form a slurry. To this, 30 ml of sulfuric acid is added, and the mixture is heated and dissolved until white sulfuric acid smoke has run out. This was cooled and diluted to 250 ml with water. Four 25 ml sample solutions were prepared, and tin standard solutions (1.0 mg Sn / ml) were added thereto in 0 ml, 1.0 ml, 3.0 ml, and 5.0 ml, respectively. The light emission intensity of tin was measured using an ICPS-8000 high frequency inductively coupled plasma emission spectrometer manufactured by Shimadzu Corporation, and tin oxide was quantified by a standard addition method.
[0056]
(Ratio of conductive layer (Sb ₂ O ₃ ))
The measurement of the Sb ₂ O ₃ content is performed as follows. 0.5 g of titanium oxide and 15 g of ammonium sulfate are added to a small amount of water to form a slurry. To this, 30 ml of sulfuric acid is added, and the mixture is heated and dissolved until white sulfuric acid smoke has run out. This was cooled and diluted with water to 250 ml, and four 25 ml sample solutions were prepared, and the antimony standard solution (1.0 mg Sb / ml) was added thereto at 0 ml, 0.5 ml, 1.0 ml, and 1.5 ml, respectively. The added product is measured for the emission intensity of antimony with an ICPS-8000 high-frequency inductively coupled plasma emission spectrometer manufactured by Shimadzu Corporation, and antimony trioxide is quantified by a standard addition method.
[0057]
(Ratio of hydrophobizing agent)
The ratio of the hydrophobizing agent was measured as the carbon C content. Specifically, 0.5 g of a titanium oxide sample, 0.3 g of granular tin, and about 1.0 g of iron powder were weighed on a porcelain crucible using a Horiba Seisakusho's "EMIA-520 carbon analyzer". Measure by burning.
[0058]
(Production of toner)
Polyester resin ("Tuffton NE-6900" manufactured by Kao Corporation) 100 parts by weight Carbon black ("# 44" manufactured by Mitsubishi Chemical Corporation) 5 parts by weight Magnetic powder ("MTS-106" manufactured by Toda Kogyo) 2.5 parts by weight Electric charge Control agent (“BONTRONP-51” manufactured by Fujikura Kasei Co., Ltd.) 5 parts by weight Charge control resin (“FS201PS” manufactured by Fujikura Kasei Co., Ltd.) 7 parts by weight Wax (“UMEX 110TS” manufactured by Orient Chemical Co., Ltd.) 5 parts by weight After mixing with a mixer, the resin composition for toner obtained by melt-kneading with a twin-screw extruder is finely pulverized with an air-flow pulverizer (“IDS-2” manufactured by Nippon Pneumatic) and classified with an air classifier. After the treatment, toner particles having an average particle diameter of 9 μm were obtained. With respect to 100 parts by weight of the toner particles, 0.6 parts by weight of hydrophobic silica (“REA200” manufactured by Nippon Aerosil Co., Ltd., number average particle diameter 13 nm), and hydrophobic silica (“NA50H” manufactured by Nippon Aerosil Co., Ltd., number average particle size) 0.8 parts by weight (diameter: 20 nm) and 1.5 parts by weight of the prepared titanium oxides A to F are mixed by a Henschel mixer (“20B” manufactured by Mitsui Mining Co., Ltd., blade speed: 30 m / s) for 3 minutes. The toners of Examples 1 to 3 and Comparative Examples 1 to 3 were produced.
[0059]
(Manufacture of developer)
A carrier ("KBB60" manufactured by Powder Tech Co., Ltd.) and each of the toners were mixed with a Nauter mixer so that the toner concentration was 4%, to prepare developers of Examples 1 to 3 and Comparative Examples 1 to 5.
[0060]
(Characteristic evaluation)
A 300,000-sheet printing durability test was performed using "FS-C8008N" (using an amorphous silicon photoconductor as a photoconductor) having the configuration shown in FIG. Then, the toner charge amount, image density (ID) and fog density (FD) after printing were measured, and the presence or absence of image white spot, drum filming, and drum discharge destruction were observed. Table 1 shows the results. The specific evaluation method is as follows.
[0061]
(Charging stability)
The toner charge amount was measured under an environment of 35 ° C./85%. The evaluation criteria are 12 μC / g or more in absolute value.
[0062]
(Measurement of image density and fog density)
Using a reflection densitometer (Model TC-6DS manufactured by Tokyo Denshoku Co., Ltd.), the density of the black solid portion and the background portion of the copied image were measured. Evaluation criteria are that the image density is 1.4 or more and the fog density is 0.004 or less.
[0063]
(Image white point)
The copied image was visually observed, and was evaluated as “点” when there was no white point, and as “X” when there was a white point.
[0064]
(Drum filming)
The surface of the photoreceptor drum was visually observed, and “○” indicates that no filming was observed on the surface of the photoreceptor drum, and “×” indicates that filming was observed.
[0065]
(Drum discharge breakdown)
The surface of the photoreceptor drum and the copy image are visually observed, and there is no discharge breakdown on the photoreceptor drum surface even in a low-temperature and low-humidity environment (10 ° C./20% RH). In the case, "◎" indicates that the photoconductor drum surface has a slight discharge breakdown but the copied image has no black spots due to the discharge breakdown, and "○" indicates that the photoconductor drum surface has a discharge breakdown. A case where black spots due to discharge breakdown were observed in the image was rated "x".
[0066]
[Table 1]

[0067]
The toners of Examples 1 to 3 satisfying the requirements of the present invention are stable at a charge amount of 12 μC / g or more even after a 300,000-sheet printing test, and have good image density (ID) and fog density (FD). Value. No white spots, drum filming or drum discharge breakdown occurred. In contrast, in the toner of Comparative Example 1 using titanium oxide having no conductive layer, the toner charge amount was as large as 16.7 μC / g and the ID was as low as 1.28. Further, image white spots and drum discharge breakdown occurred. On the other hand, in the toner of Comparative Example 2 using the titanium oxide not subjected to the hydrophobic treatment and the toner of Comparative Example 3 using the titanium oxide produced by the liquid phase method, the toner charge amount is low, and the FD is within the allowable range. Beyond it. Drum filming also occurred with the toner of Comparative Example 3.
[0068]
【The invention's effect】
In the titanium oxide of the present invention, a conductive layer is formed on the surface of the titanium oxide particles obtained by the gas phase oxidation method, and the surface is further treated with a hydrophobizing agent. Even in a high humidity environment, the chargeability of the toner can be stably maintained.
[0069]
Further, in the toner of the present invention, since the titanium oxide is mixed and added to the surface of the toner particles, uniform charging can be obtained, and even in a high-temperature and high-humidity environment, the charge amount does not decrease and excellent image quality is obtained. Is obtained.
[0070]
Further, in the image forming apparatus of the present invention, since the amorphous silicon photoreceptor is used as the photoreceptor and the toner is used as the toner, black spots due to dielectric breakdown of the photoreceptor do not appear on the copied image, Image fog does not occur even in a humid environment.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating an example of an image forming apparatus according to the present invention.
FIG. 2 is an enlarged configuration diagram of a developing device in the image forming apparatus of FIG.
[Explanation of symbols]
1 Photoconductor (image carrier)
2 Charging means 3 Exposure means 4 Developing device 5 Transfer means 6 Cleaning means 7 Transferred member 41 Developing roller 42 Magnet 43 Blade 44 Paddle roller 45 Developer 45a Magnetic brush 46 Separator 47 Toner replenishing unit 48 Supply roller 61 Cleaning brush 62 Cleaning blade

Claims (5)

A titanium oxide used for an electrostatic developing toner, wherein a conductive layer is formed on the surface of titanium oxide particles obtained by a vapor phase oxidation method, and the surface is further treated with a hydrophobizing agent. The titanium oxide according to claim 1, wherein a ratio of the conductive layer is in a range of 5 to 30 wt% with respect to the titanium oxide particles. The titanium oxide according to claim 1, wherein a ratio of the hydrophobizing agent is 2 wt% or more based on the titanium oxide particles. In an electrostatic developing toner obtained by mixing and adding an external additive to toner particles,
A toner for electrostatic development, wherein the titanium oxide according to claim 1 is used as the external additive. An electrostatic latent image carrier, charging means for charging the surface of the electrostatic latent image carrier, and exposure for irradiating the charged surface of the electrostatic latent image carrier with light to form an electrostatic latent image Means, a developing means for supplying toner to the electrostatic latent image to develop the toner, a transferring means for transferring the toner of the electrostatic latent image carrier developed by the developing means to a member to be transferred, and Fixing means for melting and fixing the toner to the image forming apparatus,
Using an amorphous silicon photoconductor as the electrostatic latent image carrier,
An image forming apparatus, wherein the toner for electrostatic development according to claim 4 is used as the toner.

Images