JP4377215B2 - Silica fine particles - Google Patents

Description

  The present invention relates to a novel silica fine particle. Specifically, it has a special particle shape that is simpler than fumed silica and more complicated than spherical fused silica, and is particularly excellent in various applications such as fillers for semiconductor sealing resins and toner external additives for electrophotography. The present invention relates to a silica fine particle capable of exhibiting excellent characteristics.

  Silica fine particles having an average particle size of 1 μm or less are widely used in applications such as a semiconductor sealing resin filler and an electrophotographic toner external additive. The reason for this is that, in the filler for semiconductor encapsulating resin, the silica fine particles having such a particle size are settled in a liquid state resin (hereinafter also referred to as a liquid resin) in a molten state or a solution state before molding. Therefore, it is advantageous in maintaining a uniform composition, and in the application of an external toner additive for electrophotography, the silica fine particles having such a particle size have high adhesion to the surface of the toner resin. This is because it is advantageous in imparting the fluidity of the toner resin.

  Conventionally, there have been many reports on the use of fumed silica (so-called dry silica) produced by flame hydrolysis of chlorosilane as a filler for semiconductor sealing resin (see, for example, Patent Document 1). .

  By the way, due to increasing awareness of environmental issues in recent years, solder that does not use lead has begun to be used for mounting on various wiring boards used in semiconductor packages and the like. It tends to rise. Therefore, it has become necessary to increase the amount of filler added to the semiconductor sealing resin of the semiconductor package in order to improve heat resistance.

  However, the fumed silica has a property of imparting high viscosity only by adding a small amount to the liquid resin, and when the addition amount is increased, there is a problem that it becomes difficult to mold the resin for semiconductor encapsulation.

  In order to suppress the high viscosity-imparting property of the fumed silica and enable high filling, the use of spherical fused silica having an average particle size controlled to 1 μm or less has been proposed (for example, (See Patent Document 2).

  By using the spherical fused silica, the increase in the viscosity of the resin to be filled is surely suppressed, and the filling rate of the filler can be increased. However, in the case of a filler made of spherical fused silica, the strength of the resin in which this is highly filled is insufficient and there is room for improvement.

  On the other hand, use of the fumed silica has also been reported for use as an electrophotographic toner external additive (see, for example, Patent Document 3). However, fumed silica is insufficient in the effect of imparting toner fluidity due to its complicated particle structure. It has also been reported that spherical fused silica is used as an external additive for toner (for example, see Patent Document 4). However, in this case as well, the adhesion to the surface of the toner resin particles is poor due to the spherical shape, and the surface of the toner particles from which the silica fine particles have dropped contacts the photoconductor surface of the copying machine, so that the toner is transferred to a predetermined paper. However, there is a problem that it tends to remain on the surface of the photoreceptor.

Japanese Patent Laid-Open No. 1-161065 JP-A-8-245214 JP 2002-116575 A JP 2002-154820 A

  Accordingly, the object of the present invention is to solve the problems caused by the use of fumed silica and spherical fused silica as silica fine particles of 1 μm or less in various uses such as fillers for semiconductor encapsulating resins and toner external additives for electrophotography. There is to solve.

  In order to solve the above technical problems, the present inventors have prepared the production conditions of silica fine particles, the thickening action of the silica fine particles obtained, the resin strength reinforcing property, the fluidity imparting effect, and the anti-dropping effect from the toner resin particle surface. The relationship between the two has been studied earnestly. As a result, fumed silica is prepared by adjusting the conditions for producing silica fine particles to a specific range by a reaction in a flame such as a flame hydrolysis method or a flame pyrolysis method (hereinafter also referred to as a flame reaction method). We have succeeded in developing silica particles with special particle shapes that are simpler and more complicated than spherical fused silica.

That is, according to the present invention, in the flame reaction method of a silicon compound, it is obtained by partial welding while adjusting the aggregation of silica particles in the flame, the specific surface area is 35 m ² / g or more, and the average particle In the small angle X-ray scattering measurement, the fractal shape parameter α _{1 in the} analysis target range 50 nm to 150 nm and the fractal shape parameter α _{2 in} the analysis target range 150 nm to 353 nm are expressed by the following formulas (1) and ( 2):
−0.0068S + 2.548 ≦ α ₁ ≦ −0.0068S + 3.748 (1)
−0.0011S + 1.158 ≦ α ₂ ≦ −0.0011S + 2.058 (2)
(In the above formula, S represents the BET specific surface area (m ² / g) of the silica fine particles.)
A silica fine particle characterized by satisfying the conditions indicated by is provided.

  In addition, according to the present invention, there are provided a filler for semiconductor encapsulating resin, and an electrophotographic toner external additive comprising the above-mentioned silica fine particles.

  Generally, it is generally known that a fractal shape parameter (α value) determined from a scattering pattern obtained when small-angle X-ray scattering measurement is performed on a powder serves as an index representing the degree of complexity of the shape of independent particles. . That is, the closer the α value is to 4, the closer the particle shape is to a true spherical particle (the α value of the true spherical particle is 4), and the smaller the value, the more complicated the particle shape.

The present inventors compared the α value of the silica fine particles of the present invention having the specific particle structure and the existing silica fine particles. As a result, the silica fine particles of the present invention have an analysis target range of 50 nm to 50 nm to the existing silica fine particles. It was confirmed that the α value (α ₁ ) obtained from the scattering pattern of 150 nm and the α value (α ₂ ) obtained from the scattering pattern in the analysis target range of 150 nm to 353 nm each showed a unique value.

  In addition, according to the small-angle X-ray scattering measurement, it is possible to obtain information on a periodic structure of nanometers or more that cannot be obtained by ordinary X-ray diffraction (information on the period and frequency of the structure). The value can be determined. For example, when fumed silica is measured by small-angle X-ray scattering, fumed silica is derived from its production method, and a plurality of primary particles are consolidated together to form extremely strong aggregated particles having various shapes and particle sizes. The small-angle X-ray scattering curve obtained because it is an aggregate of (or fused particles) is a superposition of scattering curves with periods of various sizes.

  Therefore, by analyzing the obtained small-angle X-ray scattering curve, the “fractal shape parameter (α value) serving as an index of the shape of agglomerated (fused) particles” corresponding to the frequency of periodic structures of various sizes can be obtained. Can be determined. That is, since there is a relationship of the following formula among the scattering intensity (I), the scattering vector (k), and the fractal shape parameter (α) in small-angle X-ray scattering, the horizontal axis is plotted as k and the vertical axis is plotted as I. The α value can be determined from the small angle X-ray scattering curve.

I∝k ^-α
(However, k = 4πλ ⁻¹ sin θ)
The unit of k is nm ⁻¹ , π is the pi, λ is the wavelength of incident X-rays (unit is nm), θ is the X-ray scattering angle (θ is the detector scanning angle of 0.5). It is a doubled value).

  In order to obtain a small-angle X-ray scattering curve, first, monochromatic X-rays are narrowed down using slits and blocks, irradiated onto the sample, and the X-rays scattered by the sample are changed while changing the scanning angle of the detector. And the horizontal axis is k and the vertical axis is I.

If the logarithmic scale is plotted at this time, the slope of the tangent at k of the scattering curve becomes equal to -α, so that the α value can be obtained. Further, when the analysis target range is D, the Bragg equation between D, the X-ray scattering angle θ, and the incident X-ray wavelength λ:
2Dsin θ = λ
Therefore, the relationship of the following equation is established between k and D.

D = 2πk ⁻¹
Therefore, as shown in FIG. 1, the horizontal axis of the logarithmic plot of k and I is
Logk = −1.377 to −0.902 (D = 50 to 150 nm)
and,
Logk = −1.750 to −1.377 (D = 150 to 353 nm)
And by approximating the curve of each divided range with a straight line and obtaining the slope of the approximate straight line, the fractal shape parameters α ₁ and α ₂ for each analysis target range can be determined.

  The silica fine particles of the present invention have the characteristics of spherical particles and particles having a complicated structure. For example, the viscosity is difficult to increase even when added in a large amount to a liquid resin before curing or at the time of melting. Have In addition, in the preparation of a silica dispersion as an abrasive or an inkjet paper coating liquid, the amount of filler added can be increased without increasing the viscosity of the liquid, and the amount added can be increased.

  The silica fine particles of the present invention, when used as an external toner additive for electrophotography, can impart good fluidity to the toner due to its special particle structure, and also can be easily removed from the toner resin particles. Demonstrate the prevention.

The silica fine particles of the present invention have an average particle diameter of 0.05 to 1 μm, preferably 0.1 to 1 μm. That is, when the average particle diameter is smaller than 0.05 μm, the fractal shape parameters α ₁ and α ₂ described later are smaller than the ranges represented by the expressions (1) and (2), and the average particle diameter When 1 exceeds 1 μm, α ₁ and α ₂ are larger than the ranges shown by the equations (1) and (2).

Incidentally, the average particle diameter means the average value based on volume measured by a laser diffraction scattering method (D _50).

The greatest feature of the silica fine particles of the present invention is that the fractal shape parameter α ₁ in the analysis target range 50 nm to 150 nm satisfies the following expression (1), and the fractal shape parameter α _{2 in} the analysis target range 150 nm to 353 nm is the following (2 ) Is satisfied.

−0.0068S + 2.548 ≦ α ₁ ≦ −0.0068S + 3.748 (1)
−0.0011S + 1.158 ≦ α ₂ ≦ −0.0011S + 2.058 (2)
(In the formula, S represents the BET specific surface area of the silica fine particles.)
Of fractal shape parameter of the silica fine particles, fractal shape parameter alpha ₁ of the analysis target range 50nm~150nm, among the aggregated particles having a variety of shapes and particle sizes in which a plurality of primary particles are mutually fused, relatively small aggregates It indicates the complexity of the shape in the particle size range, and the fractal shape parameter α _{2 in} the analysis target range of 150 nm to 353 nm indicates the complexity of the shape in the relatively large aggregate particle size range. . In general, α ₁ and α ₂ have a relationship of α ₁ > α ₂ .

The silica fine particles having the complexity of the particle shape are proposed for the first time by the present invention. That is, the known fumed silica described above has a complicated shape greatly separated from a sphere, and the value of α ₁ and / or α ₂ is less than the lower limit of the above range, as shown in a comparative example described later. In addition, the spherical fused silica has a value of α ₁ and / or α ₂ exceeding the upper limit of the above range, and has a shape close to a spherical shape. On the other hand, the silica fine particles of the present invention in which the values of α ₁ and α ₂ are in the range of the above formulas (1) and (2), the complexity of the particle shape is the above fumed silica and spherical fused silica. It is in the middle.

Further, the BET specific surface area of the silica fine particles of the present invention showing the average particle diameter and the fractal shape parameter is generally 5 to 5 at an average particle diameter of 0.05 to 1 μm.
May range from 5~150m ² / g in 300m ² /g,0.1~1μm.

  The BET specific surface area is a value measured by a nitrogen adsorption method.

  Since the silica fine particles of the present invention have the special particle structure, it is possible to reduce the above-mentioned problematic properties while enjoying the superior properties of fumed silica and fused spherical silica in its use. .

  For example, in the application of a filler for semiconductor encapsulating resin, the resin can be uniformly and highly filled, and in the application of an external toner additive for electrophotography, it has high fluidity with respect to toner resin particles. Application and high anti-drop-off property can be exhibited.

  As long as the silica fine particles of the present invention satisfy the above-mentioned conditions, other properties are not particularly limited, but the concentration of alkali elements such as halogen elements and sodium contained is 50 ppm or less, preferably 30 ppm or less. For example, when filled in a resin, etc., corrosion of metal wiring caused by silica fine particles can be reduced, and in applications as an external toner for electrophotography, the magnitude of the charge amount and the rising speed of the charge amount It is suitable for suppressing the variation of.

(Method for producing silica fine particles)
The method for producing silica fine particles of the present invention can be obtained by a reaction in a flame such as a flame hydrolysis method or a flame pyrolysis method, particularly by partially welding while adjusting the aggregation of particles in the flame. can get.

  Specifically, hydrogen and / or hydrocarbons (hereinafter these gases are collectively referred to as flammable gases) and oxygen are respectively supplied to the outer periphery of the supply port for supplying the raw material silicon compound in the form of gas to form an outer flame. By converting the silicon compound into silica fine particles and fusing appropriately in a flame, the fused silica fine particles are then cooled and collected in a dispersed state (for example, passing through a pipe). After being caulked, the silica fine particles of the present invention can be produced by collecting with a bag filter.

  In the above production method, one of the conditions that particularly affects the value of the fractal shape parameter is the flow velocity at the outlet of the burner, and the flow velocity is preferably adjusted between 0.5 and 10 m / second.

Another condition that particularly affects the value of the fractal shape parameter is the concentration of the raw silicon compound, that is, the silica concentration in the flame, and this concentration is 0.05 to 5 mol in terms of SiO _2. / M ³ , particularly 0.1 to 3 mol / m ³ is preferred.

  Further, in the above production method, the adjustment of the average particle size and specific surface area is performed by adjusting the concentration of the raw material silicon compound, the burner outlet flow velocity, the length of the peripheral flame, and the like, and the value of the fractal shape parameter together with the above conditions. This can be done by adjusting the temperature.

  Generally, when the concentration of the raw material silicon compound is increased, the average particle size is increased, the specific surface area is decreased, and the value of the fractal shape parameter is increased. Further, when the burner outlet flow velocity is increased, the average particle size is decreased, the specific surface area is increased, and the value of the fractal shape parameter is decreased. Further, when the length of the peripheral flame is increased, the average particle diameter is increased, the specific surface area is decreased, and the value of the fractal shape parameter is increased. Furthermore, when the temperature of the peripheral flame is increased, the average particle diameter increases, the specific surface area decreases, and the value of the fractal shape parameter increases.

  In the production method, the silicon compound is in a gaseous or liquid state at normal temperature without particular limitation. For example, siloxanes such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldisiloxane, octamethyltrisiloxane, tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, Alkoxysilanes such as methyltriethoxysilane, organic silane compounds such as tetramethylsilane, diethylsilane and hexamethyldisilazane, silicon halides such as monochlorosilane, dichlorosilane, trichlorosilane and tetrachlorosilane, inorganic silanes such as monosilane and disilane A compound can be used as a raw material silicon compound.

  In particular, by using siloxanes and / or silazanes or alkoxysilanes as the silicon compound, it is possible to obtain a higher purity silicon oxide (silica fine particles) in which impurities such as chlorine are significantly reduced. , Handling is also improved.

  The silica fine particles of the present invention may be surface-treated with at least one treatment agent selected from the group consisting of silylating agents, silicone oils, siloxanes, metal alkoxides, fatty acids, and metal salts thereof, depending on the application. Good.

  Specific silylating agents include tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, n-butyltri Methoxysilane, i-butyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyl Diethoxysilane, i-butyltriethoxysilane, decyltriethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycine Sidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ Alkoxysilanes such as-(2-aminoethyl) aminopropyltrimethoxysilane and γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane, hexabutyl Silazanes such as disilazane, hexapentyldisilazane, hexahexyldisilazane, hexacyclohexyldisilazane, hexaphenyldisilazane, divinyltetramethyldisilazane, dimethyltetravinyldisilazane, etc. It is below.

  Silicone oils include dimethyl silicone oil, methyl hydrogen silicone oil, methylphenyl silicone oil, alkyl modified silicone oil, fatty acid modified silicone oil, polyether modified silicone oil, alkoxy modified silicone oil, carbinol modified silicone oil, amino Modified silicone oil, terminal reactive silicone oil, etc. are mentioned.

  Examples of siloxanes include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldisiloxane, and octamethyltrisiloxane.

  Examples of the metal alkoxide include trimethoxyaluminum, triethoxyaluminum, tri-i-propoxyaluminum, tri-n-butoxyaluminum, tri-s-butoxyaluminum, tri-t-butoxyaluminum, mono-s-butoxydi-i. -Propyl aluminum, tetramethoxy titanium, tetraethoxy titanium, tetra-i-propoxy titanium, tetra-n-propoxy titanium, tetra-n-butoxy titanium, tetra-s-butoxy titanium, tetra-t-butoxy titanium, tetraethoxy zirconium , Tetra-i-propoxyzirconium, tetra-n-butoxyzirconium, dimethoxytin, diethoxytin, di-n-butoxytin, tetraethoxytin, tetra-i-propoxytin, tetra-n-butoxytin, di Butoxy zinc, magnesium methoxide, magnesium ethoxide, magnesium isopropoxide, and the like.

  Further specific examples of fatty acids and metal salts thereof include undecyl acid, lauric acid, tridecyl acid, dodecyl acid, myristic acid, palmitic 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.

  Among the above surface treatment agents, hexamethyldisilazane, dimethylsilicone oil, γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) are used for the fine silica particles used for the electrophotographic toner external additive. More preferably, the surface treatment is performed with at least one treatment agent selected from the group consisting of aminopropylmethyldimethoxysilane.

  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.

  The surface-treated silica fine particles have a halogen element and / or alkali element concentration of 50 ppm or less, and preferably 30 ppm or less, thereby reducing the corrosion of metals and the like caused by the filled silica fine particles and the electrophotographic toner. In the use as an additive, it is suitable for suppressing variation in the charge amount and the rising speed of the charge amount. For that purpose, the treating agent used is one purified to the above degree. It is preferable.

  When the silica fine particles of the present invention are used as a filler for a semiconductor encapsulating resin, the compounding amount can be 5 to 300 parts by weight with respect to 100 parts by weight of the liquid resin. As the liquid resin, an uncured thermosetting resin used for semiconductor encapsulation such as epoxy resin, phenol resin, polyimide resin, maleimide resin, etc. is used. A hardening agent, hardening accelerator, a coloring agent, a mold release agent, etc. are mix | blended with a material. For example, the above-mentioned silica fine particles of the present invention having a small average particle diameter are mixed with other filler particles having a large average particle diameter (for example, fused spherical silica particles), etc. It should be used for filling.

  In addition, when the silica fine particles of the present invention are used as an electrophotographic toner external additive, the external addition amount is generally 0.2 to 3 parts by weight with respect to 100 parts by weight of the toner resin particles. .

  In order to describe the present invention more specifically, examples and comparative examples will be described below, 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. Small-angle X-ray scattering measurement Silica fine particles of a sample are filled into through-holes (length 40 mm, width 5 mm, height 1 mm) provided in a substrate, and both sides of the filled sample are swollen with a polypropylene film having a thickness of 6 μm. The held one was used for measurement. Measurement was performed under the following conditions using a biaxial small-angle X-ray scattering device (M18XHF ²² ) manufactured by MacScience equipped with Kratzky-U-slit.

Incident X-ray: Cu-Kα ray Tube voltage: 40 kV
Tube current: 300mA
Slit width: 10 μm
Detector scanning angle: 0.025 ° to 0.900 ° Average Particle Diameter Measurement A 50% cumulative average particle diameter (D ₅₀ ) on a volume basis was measured using a laser diffraction / scattering particle size distribution analyzer (LA-920) manufactured by Horiba. For measurement, 0.5 g of silica fine particles was added to 150 ml of pure water, and then a silica slurry dispersed with an ultrasonic homogenizer with an output of 200 W for 1 minute was used as a measurement sample.

3. Specific surface area measurement It measured by the nitrogen adsorption BET 1-point method using the specific surface area measuring apparatus (SA-1000) made by Shibata Rika.

4). Viscosity measurement 4 parts by weight of silica fine particles were added to an epoxy resin (Epicoat 815) manufactured by Japan Epoxy Resin Co., Ltd. and dispersed at 3000 rpm for 2 minutes at room temperature using a homomixer manufactured by Tokushu Kika Kogyo Co., Ltd. For 2 hours, and the viscosity at 60 rpm was measured using a BL type rotational viscometer.

5. Strength of cured resin at high filling The various components were blended in the proportions shown below, kneaded with a heating roll, cooled, and pulverized to obtain an epoxy resin composition. This epoxy resin composition was thermally cured in a mold heated to 175 ° C. to obtain a cured epoxy resin of 10 mm × 20 mm × 5 mm. Ten cured epoxy resins were allowed to stand in a thermo-hygrostat set at 25 ° C and 80% relative humidity for 24 hours, then immersed in an oil bath at 250 ° C for 10 seconds. The strength of was evaluated.

[Epoxy resin composition]
Epoxy resin (biphenyl type epoxy resin): 100 parts by weight curing agent (phenol novolac resin): 52.3 parts by weight Curing accelerator (triphenylphosphine): 3.0 parts by weight Release agent (ester wax): 14.9 Part by weight Colorant (carbon black): 3.0 parts by weight Silane coupling agent (epoxysilane): 6.0 parts by weight Fused spherical silica (average particle size: 17 μm): 1238.8 parts by weight Sample silica fine particles: 74.6 Weight part 6. Characteristic evaluation as an external additive for electrophotographic toner For the characteristic evaluation (fluidity, image characteristic, cleaning property) as an external toner for electrophotography, 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 in 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.

6-1. Fluidity To a spherical polystyrene resin (SX-500H manufactured by Soken Chemical Co., Ltd., average particle size 5 μm), a silica sample was added 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)
In the above formula (3), the loose apparent specific gravity and the hard apparent specific gravity are as follows.

1) Loose apparent specific gravity: specific gravity measured in a 100 ml cup without sample tapping 2) Solid apparent specific gravity: apparent specific gravity after placing sample powder in a 100 ml cup and tapping 180 times The smaller the value, 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.

6-2. Image properties 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 using a commercially available copying machine, and then 10 full-color images were output in B4 size. It was determined that the image characteristic was better as the whiteout occurrence in the image was smaller.

  ○: Almost no white spots are seen.

  Δ: Some white spots are observed.

  X: Many white spots are seen.

6-3. Regarding the cleaning performance evaluation, after the evaluation of the actual machine, the scratches on the surface of the latent image carrier and the 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.

7). Impurity analysis The elements of iron, aluminum, chromium, nickel, sodium and chlorine were quantified by ICP emission spectrophotometry, atomic absorption spectrophotometry and ion chromatography.

Examples 1-4
Silica fine particles shown in Table 2 were produced by burning and oxidizing octamethylcyclotetrasiloxane in an oxyhydrogen flame under the combustion conditions described in Table 1 in an outer flame formed by an oxygen-hydrogen flame. .

Table 1 shows the average particle diameter, BET specific surface area, fractal shape parameter α ₁ value, α ₂ value, viscosity, and resin cured product strength calculated by small-angle X-ray scattering measurement of the obtained silica fine particles. In any case, no significant increase in viscosity is observed compared to the comparative example. Table 3 shows the impurity measurement results.

Comparative Examples 1-5
Table 2 shows the average particle diameter, BET specific surface area, fractal shape parameter α ₁ value, α ₂ value, viscosity, and resin cured product strength of commercially available fumed silica particles and fused silica particles.

  However, in Comparative Examples 1 to 3, since the viscosity was too high when the epoxy resin composition was prepared, kneading with a heating roll became impossible, and the strength of the cured resin product could not be measured. Table 3 shows the impurity measurement results.

実施例５〜８
オクタメチルシクロテトラシロキサンを酸水素火炎中で燃焼酸化させることによって、表４に記載した各燃焼条件でシリカ微粒子を製造した。得られたシリカ微粒子の平均粒子径、ＢＥＴ比表面積、フラクタル形状パラメータα_１値、α_２値、および電子写真用トナー外添剤としての特性評価（流動性、画像特性、クリーニング性）を表５に示す。また、不純物測定結果を表６に示す。

Examples 5-8
Silica fine particles were produced under the respective combustion conditions listed in Table 4 by burning and oxidizing octamethylcyclotetrasiloxane in an oxyhydrogen flame. Table 5 shows the average particle diameter, BET specific surface area, fractal shape parameter α ₁ value, α ₂ value, and characteristics evaluation (fluidity, image characteristics, cleaning properties) as an electrophotographic toner external additive of the obtained silica fine particles. Shown in In addition, Table 6 shows the impurity measurement results.

Comparative Examples 6-10
About commercially available fumed silica particles and fused silica particles, average particle diameter, BET specific surface area, fractal shape parameter α ₁ value, α ₂ value, and characteristics evaluation as an external additive for toner for electrophotography (fluidity, image characteristics) Table 5 shows the cleaning properties. In addition, Table 6 shows the impurity measurement results.

The figure for demonstrating the method of calculating | requiring (alpha) ₁ and (alpha) ₂ from the graph which plotted the logarithm of the scattering intensity (I) when small-angle X-ray scattering measurement was carried out with respect to the logarithm of the scattering vector (k).

Claims (7)

In a flame reaction method of a silicon compound, the specific surface area is 35 m ² / g or more, and the average particle diameter is 0.05 to 1 μm , obtained by partial welding while adjusting the aggregation of silica particles in the flame. Yes, in the small-angle X-ray scattering measurement, the fractal shape parameter α _{1 in the} analysis target range 50 nm to 150 nm and the fractal shape parameter α _{2 in} the analysis target range 150 nm to 353 nm are expressed by the following formulas (1) and (2):
−0.0068S + 2.548 ≦ α ₁ ≦ −0.0068S + 3.748 (1)
−0.0011S + 1.158 ≦ α ₂ ≦ −0.0011S + 2.058 (2)
(In the above formula, S represents the BET specific surface area (m ² / g) of the silica fine particles.)
Silica fine particles characterized by satisfying the conditions shown in FIG. 2. The silica fine particles according to claim 1, wherein the halogen element concentration is 50 ppm or less. The silica fine particles according to claim 1, wherein the concentration of sodium element is 50 ppm or less. 2. The silica fine particles according to claim 1, which are surface-treated with at least one treatment agent selected from the group consisting of silylating agents, silicone oils, siloxanes, metal alkoxides, fatty acids and metal salts thereof. The filler for semiconductor sealing resin which consists of a silica particle of Claim 1. An electrophotographic toner external additive comprising the silica fine particles according to claim 1. The silica fine particles are surface-treated with at least one treatment agent selected from the group consisting of hexamethyldisilazane, dimethyl silicone oil, γ-aminopropyltriethoxysilane, and γ- (2-aminoethyl) aminopropylmethyldimethoxysilane. The toner external additive for electrophotography according to claim 6.

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