JP2006206414A - Silica particulate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide silica particulates, maintaining satisfactory fluidity by suppressing the burying thereof into toner particles, also preventing a filming phenomenon by the defect in the scraping of a cleaning blade, and also suppressing the variation in toner electrification quantity, when used as a toner external addition agent for electrophotography. <P>SOLUTION: In the silica particulates obtained by the combustion of a silicon compound, the average particle diameter lies in the range of 0.05 to <0.1 μm, also, the value of the gradient n in a particle size distribution expressed by a Rosin-Rammler diagram is ≥2, and also, molten particles of ≥1 μm are not contained according to measurement by a laser diffraction scattering method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel silica fine particle. Specifically, the present invention provides a silica fine particle comprising fine fused silica having an average particle size in the range of 0.05 μm or more and less than 0.1 μm, a sharp particle size distribution, and substantially free of coarse fused particles. Is.

  For toners used as developers in electrophotographic technology such as copying machines and laser printers, silica and alumina having an average particle size of 0.006 to 0.04 μm for the purpose of imparting fluidity and controlling the amount of charge In addition, a powder such as titania and an external additive obtained by surface-treating the above inorganic powder are used.

  In recent years, with the increase in electrophotographic image quality and image quality, toner particles have become smaller in diameter and toner particles have a lower melting point, and the adhesion between the toner particles tends to increase and fluidity tends to deteriorate. In external additives that coat the surface of particles, an anti-blocking effect and a fluidity-imparting effect have been required more than ever.

  However, since the particle size of the external additive is small, stress such as stirring is continuously applied, so that the toner is buried in the toner resin and does not serve as an anti-blocking, and the fluidity is lowered. Scraping becomes difficult and image quality degradation due to filming phenomenon becomes a problem.

  Therefore, although an external additive having a large particle size is desired, if the particle size is too large, the fluidity imparting effect cannot be obtained. In particular, when a large amount of coarse particles having a primary particle diameter exceeding 1 μm is contained, the photoreceptor drum is denatured or scraped.

  The external additive is also required to control the charge of the toner particles. However, if the particle size distribution of the particles used is broad, there will be a problem in charge control because the dispersibility and adhesion to the toner will be uneven. It is easy to do, and the fall of image quality tends to be a problem.

  Conventionally, silica fine particles that do not contain particles having a melt particle diameter of 1 μm or more and have a sharp particle size distribution include those by the sol-gel method (see Patent Document 1), but generally a wet method represented by the sol-gel method. In the process, coarse particles are formed by the growth and sintering of particles at the firing stage in which moisture is removed from the gelled silica. Therefore, the coarse particles must be removed by classification or sieving (see Patent Document 2). However, with the current technology, there is no precision classification technology capable of separating particles of about 1 μm, and when an external toner additive containing such particles of 1 μm or more is used, the photosensitive drum is damaged. There is.

  Further, in the dry method represented by the flame combustion method, those having a primary particle size not including 1 μm or more are produced by combustion of alkoxysilane (see Patent Documents 3 and 4), but those having a sharp particle size distribution are produced. Therefore, when such particles are used as an external toner additive, there is a problem in that the toner charge amount varies and the image quality deteriorates.

JP-A-3-267945 Japanese Patent Laid-Open No. 2002-3213 JP 2000-258947 A JP 2001-194819 A

  Therefore, the object of the present invention is to maintain good fluidity by suppressing the embedding in the toner particles when used as an external toner additive for electrophotography, and the filming phenomenon due to the scraping defect of the cleaning blade. In addition, it has a particle size suitable for preventing toner particles, and does not substantially contain molten particles of 1 μm or more that cause modification or scraping of the photosensitive drum. Furthermore, the particle size distribution is sharp and the toner charge amount varies. It is to provide suppressed silica fine particles.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have adopted a condition in which the silica concentration in the flame is set to be significantly lower than that in the conventional manufacturing technique in the combustion of the silicon compound. The present inventors have succeeded in obtaining silica fine particles that have achieved the above object, and have completed the present invention.

  That is, according to the present invention, the average particle diameter is in the range of 0.05 μm or more and less than 0.1 μm, the gradient n of the particle size distribution shown in the rosin-Rammler diagram is 2 or more, and the laser diffraction / scattering method is used. Silica fine particles that do not contain molten particles of 1 μm or more as measured by particle size distribution.

  In addition, in this invention, an average particle diameter represents the number average diameter of the particle diameter measured by the image analysis method. Further, in the present invention, the image analysis method is a method of measuring the particle diameter by enlarging an image using a scanning electron microscope or a transmission electron microscope, and a known technique can be used.

  In the present invention, the rosin-ramler diagram is a particle size diagram representing a particle size distribution according to the following rosin-ramler equation (1), and is obtained from the particle diameter measured by the image analysis method.

R (Dp) = 100exp (-b · Dp n) (1)
(Where R (Dp) is the cumulative volume% from the maximum particle size to the particle size Dp, Dp is the particle size, and b and n are constants.)
Here, the gradient n of the particle size distribution displayed in the rosin-ramler diagram is such that the cumulative volume% from the maximum particle diameter to the particle diameter Dp in the rosin-ramler diagram is in the range of at least 15% by volume and 85% by volume. This means a gradient represented by a straight line connecting points, and a large value of n indicates that the particle size distribution is sharp.

  In the present invention, a laser diffraction / scattering particle size distribution measuring apparatus manufactured by HORIBA, Ltd. was used for the particle size distribution measurement by the laser diffraction / scattering method.

  In the measurement, in order to disperse the silica fine particles, the wet method using an aqueous dispersion medium is used, and the silica fine particles are dispersed using ultrasonic waves before the measurement.

  Further, in the present invention, the molten particles are particles obtained by burning (consolidating) primary particles obtained by a combustion method and particles having various shapes.

  Furthermore, in the present invention, it is confirmed that the molten particles of 1 μm or more are not included. As a result of sampling 20 arbitrary points with respect to the generated silica fine particles and measuring by the laser diffraction / scattering method, the particle size distribution is 1 μm or more in all cases. It means not showing a peak.

  According to the present invention, the average particle diameter is in the range of 0.05 μm or more and less than 0.1 μm, the gradient n of the particle size distribution shown in the rosin-Rammler diagram is 2 or more, and laser diffraction / scattering A novel silica fine particle free from molten particles of 1 μm or more is provided by particle size distribution measurement by the method.

  In addition, when this silica fine particle is used as an external toner additive, good fluidity is maintained by suppressing the embedding in the toner particles, and the filming phenomenon due to the scraping defect of the cleaning blade is prevented, and the photoconductor The drum is not denatured or scraped, and the variation in the toner charge amount is suppressed. In practice, a very good effect not seen with conventional silica fine particles is exhibited.

  The silica fine particles of the present invention have an average particle size in the range of 0.05 μm or more and less than 0.1 μm. That is, when the average particle diameter is smaller than 0.05 μm, when used as a toner external additive, the silica fine particles are buried in the toner resin by continuous use, and the function of the external additive cannot be exhibited. Transferability deteriorates. On the other hand, when the average particle diameter exceeds 0.1 μm, the fluidity of the toner is lowered.

  The silica fine particles of the present invention have a particle size distribution gradient n represented by a rosin-Rammler diagram of 2 or more. When the value of the gradient n is lower than 2, the width of the particle size distribution becomes wide and the dispersion and adhesion to the toner becomes non-uniform, and image deterioration such as streaks, fogging and blurring is likely to occur due to continuous use.

  Further, the silica fine particles of the present invention do not contain molten particles of 1 μm or more in the particle size distribution measurement by the laser diffraction / scattering method. When a particle size distribution peak is observed at 1 μm or more as measured by the laser diffraction / scattering method, since the molten particles of 1 μm or more are contained, the image quality deteriorates due to the modification or shaving of the photosensitive drum.

  In the silica fine particles of the present invention, the configuration other than the above features is not particularly limited, but preferred configurations include iron less than 20 ppm, aluminum less than 5 ppm, nickel less than 5 ppm, chromium less than 5 ppm, sodium less than 3 ppm, and chlorine. Is preferably less than 3 ppm. When the metal is contained as an impurity, charging control becomes difficult, and therefore, it tends to be unsuitable for use as an external toner additive.

  The method for producing silica fine particles of the present invention described above is not particularly limited as long as it is based on combustion of a silicon compound. That is, by using such a dry process, it is possible to prevent coarse particles from growing due to adhesion between particles and sintering in a firing stage in which moisture is removed.

  As the silicon compound used in the present invention, an inorganic silicon compound or an organic silicon compound can be used without any particular limitation. For example, inorganic silicon compounds such as silicon tetrachloride, silicon trichloride, silicon dichloride, siloxanes such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldisiloxane, octamethyltrisiloxane, etc. And alkoxysilicon such as tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, and methyltriethoxysilane, and organosilicon compounds such as tetramethylsilane, diethylsilane, and hexamethyldisilazane.

  In particular, by selecting an organosilicon compound containing no halogen, preferably siloxane, as the silicon compound, it is possible to obtain finer fused silica particles with higher purity in which impurities such as chlorine are significantly reduced, and Handling is also improved, which is preferable.

  In the present invention, the silicon compound is supplied into a peripheral flame formed by oxygen, an inert gas, and a combustible gas. Hydrogen and hydrocarbons are used as the combustible gas. As the hydrocarbon, those conventionally used as fuels can be advantageously used industrially. For example, acetylene, methane, ethylene, propane, butane and the like can be used alone or in combination.

  The method of supplying the silicon compound is preferably a method of supplying it by gasification by atomization or vaporization. At that time, the silicon compound may be supplied together with the carrier gas, and as the carrier gas, nitrogen, helium, argon or the like is suitable. Further, when the silicon compound is an organosilicon compound such as siloxane, oxygen can be used for a part or all of the carrier gas, which is a preferred embodiment for preventing coloring of the resulting silica fine particles. . The amount of oxygen may be appropriately determined depending on the amount of carbon contained in the organosilicon compound.

In the present invention, it is preferable to adjust the silica concentration in the flame to less than 0.2 kg / Nm ³ . That is, when the silica concentration in the flame is 0.2 kg / Nm ³ or more, the growth of the silica fine particles becomes non-uniform, and the particle size distribution of the generated silica fine particles tends to be broad. Further, since the silica concentration in the flame is too and productivity becomes poor low, it is preferable to adjust the silica concentration to less than 0.05 kg / Nm ³ or more 0.2 kg / Nm ^3.

  Further, the silica fine particles of the present invention are at least one treatment selected from the group consisting of a silylating agent substantially free of halogen, silicone oil, siloxanes, metal alkoxides, fatty acids and metal salts, depending on the application. The surface of the silica fine particles may be treated with an agent. Specific silylating agents include tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, n- Butyltrimethoxysilane, i-butyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane , Diphenyldiethoxysilane, i-butyltriethoxysilane, decyltriethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ -Glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane , Γ- (2-aminoethyl) aminopropyltrimethoxysilane, alkoxysilanes such as γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane, hexa Examples thereof include silazanes such as butyldisilazane, hexapentyldisilazane, hexahexyldisilazane, hexaphenyldisilazane, divinyltetramethyldisilazane, and dimethyltetravinyldisilazane.

  Silicone oils include dimethyl silicone oil, methyl hydrogen silicone oil, methylphenyl silicone oil, alkyl modified silicone oil, carboxylic acid modified silicone oil, fatty acid modified silicone oil, polyether modified silicone oil, alkoxy modified silicone oil, Examples include diol-modified silicone oil, amino-modified silicone oil, and terminal-reactive silicone oil.

  Furthermore, examples of siloxanes include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldisiloxane, octamethyltrisiloxane and the like.

  Furthermore, as the metal alkoxide, trimethoxy aluminum, triethoxy aluminum, tri-i-propoxy aluminum, tri-n-butoxy aluminum, tri-s-butoxy aluminum, tri-t-butoxy aluminum, mono-s-butoxy di- i-propylaluminum, tetramethoxytitanium, tetraethoxytitanium, tetra-i-propoxytitanium, tetra-n-propoxytitanium, tetra-n-butoxytitanium, tetra-s-butoxytitanium, tetra-t-butoxytitanium, tetraethoxy Zirconium, tetra-i-propoxyzirconium, tetra-n-butoxyzirconium, dimethoxytin, diethoxytin, di-n-butoxytin, tetraethoxytin, tetra-i-propoxytin, tetra-n-butoxytin Diethoxy zinc, magnesium methoxide, magnesium ethoxide, magnesium isopropoxide, and the like.

  Further specific examples of fatty acids and their metal salts include undecyl acid, lauric acid, tridecyl acid, dodecyl acid, myristic acid, valmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, olein. Examples include long-chain fatty acids such as acid, linoleic acid, and arachidonic acid, and metal salts thereof include salts with metals such as zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.

  As the surface treatment method using the surface treatment agent, a known method can be used without any limitation. For example, a method in which silica fine particles are sprayed with a surface treatment agent with stirring or contacted with steam is common.

  Needless to say, the silica fine particles of the present invention are not limited to the use as an electrophotographic toner external additive, and can be used in various applications alone or in combination with other particles.

  For example, quartz glass members such as quartz crucibles, optical fibers, abrasives, precision resin molding fillers, dental fillers, electronic circuit laminates, liquid crystal sealing agents, LED sealing agents, IC tape automated It can be suitably used for applications such as a bonding carrier tape film, an IC lead frame fixing tape, an inkjet paper coating layer, and a semiconductor sealing material.

  Examples and comparative examples are shown to specifically describe the present invention, but the present invention is not limited to these examples.

  In addition, various physical property measurements in the following examples and comparative examples are based on the following methods.

(1) Average particle diameter The particle diameter of 10000 arbitrary particles (magnification 100000 times) was measured with a scanning electron microscope apparatus (JSM-840F) manufactured by JEOL, and the average particle diameter was determined by number average.

(2) Gradient n according to Rosin-Rammler diagram
Based on the particle size distribution obtained by (1) above, the particle size is plotted on the horizontal axis and the cumulative volume distribution is plotted on the vertical axis on the Rosin-Rammler diagram. A straight line was determined by the method of least squares when the cumulative volume distribution was in the range of 15 volume% to 85 volume%, and the n value was determined from the slope of the straight line.

(3) Confirmation of particles having a melt particle diameter of 1 μm or more by laser diffraction / scattering method Silica fine particles obtained by Examples and Comparative Examples were placed in a container containing water and ultrasonically dispersed. Thereafter, measurement with an aqueous dispersion medium was performed at 20 points from an arbitrary place using a laser diffraction scattering type particle size distribution measuring apparatus (LA-920) manufactured by Horiba.

4). Characteristic evaluation as external toner additive for electrophotography For evaluation of characteristics as external toner additive for electrophotography (fluidity, image characteristics, cleaning properties), silica fine particles whose surface is hydrophobized with hexamethyldisilazane Was used. The method of hydrophobizing with hexamethyldisilazane is as follows. First, silica fine particles were put into a mixer and stirred, and the mixture was replaced with a nitrogen atmosphere, and simultaneously heated to 250 ° C. Thereafter, the mixer was sealed, 60 parts by weight of hexamethyldisilazane was sprayed, and the mixture was stirred as it was for 30 minutes to carry out a hydrophobic treatment.

(Evaluation as an external additive for toner)
1. A silica sample was added to a flowable spherical polystyrene resin (SX-500H manufactured by Soken Chemical Co., Ltd., average particle size 5 μm) so as to be 2% by weight, and mixed for 5 minutes with a mixer. This was conditioned at 35 ° C. and 85% relative humidity. The fluidity of the mixed powder sample was evaluated by measuring the degree of compression with a powder tester (manufactured by Hosokawa Micron Corporation, PT-R type). The degree of compression is expressed by the following equation (3).
Compressibility = (solid apparent specific gravity-slack apparent specific gravity) / hard apparent specific gravity × 100
(3)
Here, the loose apparent specific gravity and the hard apparent specific gravity in the formula are as follows.

Loose Apparent Specific Gravity: Apparent specific gravity measured in a state where the sample powder was put into a 100 ml cup without tapping. Apparent specific gravity: Apparent specific gravity after the sample powder was put into a 100 ml cup and tapped 180 times.

  The smaller the value of the compression degree, the better the fluidity. Further, the degree of compression when the mixing time in the mixer was changed from 5 minutes to 60 minutes was also measured, and the durability against the decrease in fluidity when the number of developed images was increased under actual use was evaluated.

2. Image characteristics 1% of the above silica sample was added to a toner having an average particle diameter of 7 μm and mixed by stirring to prepare a toner composition. Using this toner composition, 30,000 copies were made with a commercially available copying machine, and the image density, the presence or absence of fogging, and the like were visually observed and evaluated.

○: Stable and good image Δ: Image density is slightly low, or slight fogging is observed ×: Image density is low, fogging occurs, and unevenness occurs in the image Cleaning performance With regard to the cleaning performance evaluation, after completion of the actual machine evaluation, scratches on the surface of the latent image carrier and occurrence of sticking of residual toner and the influence on the output image were visually evaluated.

  A: Not generated.

  ○: Slight scratches are observed, but there is no effect on the image.

  Δ: Residual toner and scratches are observed, but the effect on the image is small.

  ×: Residual toner is considerably large, and vertical stripe-like image defects occur.

  XX: Residual toner adheres and many image defects occur.

Examples 1-3, Comparative Example 1
Silica fine particles were produced by burning and oxidizing in an oxyhydrogen flame under the production conditions shown in Table 1 using octamethylcyclotetrasiloxane as the silicon compound. The average particle diameter of the silica fine particles obtained, the gradient n in the rosin-Rammler diagram, the presence or absence of particles having a melt particle diameter of 1 μm or more by laser diffraction / scattering method, and evaluation of characteristics as an external additive for toner for electrophotography Table 1 also shows image characteristics and cleaning properties. The impurity results are shown in Table 2.

Comparative Examples 2-3
Regarding commercially available fumed silica and fused silica particles, the average particle size, the gradient n in the Rosin-Rammler diagram, the presence or absence of particles with a melt particle size of 1 μm or more by laser diffraction / scattering method, and as an external additive for toner for electrophotography The characteristic evaluation (fluidity, image characteristics, cleaning properties) is also shown in Table 1. The impurity results are shown in Table 2.

Comparative Example 4
About the mixed silica fine particles obtained by mixing 1% by weight of the commercially available fused silica particles used in Comparative Example 3 with the silica fine particles of Example 1, the average particle diameter, the gradient n in the Rosin-Rammler diagram, and the melting by the laser diffraction / scattering method The presence / absence of particles having a particle diameter of 1 μm or more and the characteristics evaluation (fluidity, image characteristics, cleaning properties) as an electrophotographic toner external additive are also shown in Table 1. The impurity results are shown in Table 2.

Claims (6)

  Silica fine particles obtained by combustion of a silicon compound, having an average particle size in the range of 0.05 μm or more and less than 0.1 μm, and a gradient n of the particle size distribution displayed in the rosin-Rammler diagram is 2 or more Also, silica fine particles characterized by not containing molten particles of 1 μm or more as measured by a laser diffraction / scattering method.   2. The silica fine particles of claim 1, wherein iron is less than 20 ppm, aluminum is less than 5 ppm, nickel is less than 5 ppm, chromium is less than 5 ppm, sodium is less than 3 ppm, and chlorine is less than 3 ppm.   3. The silica fine particles according to claim 1, wherein the silicon compound is a silicon compound containing no halogen.   The silica fine particles according to any one of claims 1 to 3, wherein the silicon compound is siloxane having a boiling point of 100 to 250 ° C.   The silica according to any one of claims 1 to 4, which is surface-treated with a treatment agent selected from the group consisting of a silylating agent substantially free of halogen, silicone oil, siloxanes, metal alkoxides, fatty acids and metal salts thereof. Fine particles. An external toner additive using the silica fine particles according to any one of claims 1 to 5.