IE87388B1 - Hydrophilic particle manufacturing method and hydrophilic particle - Google Patents

Abstract

To provide a hydrophilic particle manufacturing method which enables easy obtaining of hydrophilic particles with both moderate flexibility and hydrophilic property and a hydrophilic particle. The hydrophilic particle manufacturing method comprises a baking step wherein polyorganosiloxane particles whose 10%K value is within the range between 2GPa to20GPa are baked in the atmosphere whose oxygen concentration is 7 vol% or more. With regard to the hydrophilic particle obtained from the polyorganosiloxane particle, water absorption is 2% or more and 10%K value is within the range between 2GPa to25GPa.

Description

HYDROPHILIC PARTICLE MANUFACTURING METHOD AND HYDROPHILIC PARTICLE TECHNICAL FIELD The present invention relates to a hydrophilic particle manufacturing method and a hydrophilic particle.

BACKGROUND A core-shell particle as a functional particle has been widely studied heretofore. It is known that a hydrophilic treatment, which is a physical or chemical treatment technique for surface reforming of a core particle, is applied for the improvement of adhesiveness between a core particle and a shell layer.

Examples of physical treatment techniques for hydrophilizing a surface of a core particle include argon laser irradiation, plasma treatment and ozone irradiation. For example, Patent Document 1 discloses a method for obtaining a fine particle with a metallic coating, wherein a high polymer fine particle (core particle) of which surface is hydrophilized by a low-temperature plasma treatment is used as the fine particle so that the adhesiveness between the fine particle and a metal layer is improved.

However, the low—temperature plasma treatment disclosed by Paten Document 1 needs to be conducted in a vacuum environment with a special large-scale equipment. In addition, it is difficult to apply plasma (etching process) to the entire surface of every fine particle evenly and uniformly.

Thereby, the low-temperature plasma treatment is not necessarily appropriate as a hydrophilic treatment of a fine particle.

On the other hand, examples of chemical treatment techniques for hydrophilizing a surface of a core particle include a treatment technique for bringing a surface of a core particle into direct contact with gas. For example, Patent Document 2 discloses a method for hydrophilizing a surface of a core particle, wherein a vinyl polymer fine particle is processed with mixed gas consisting of fluorine gas and compound gas including oxygen atom so that the hydrophilic property is ensured.

However, the gas used in the chemical treatment technique described above includes fluorine gas that is toxic and hazardous, which leads to safety concerns. The other problem with this chemical treatment technique is that an adequate heat resistance cannot be acquired if a core particle is a high polymer fine particle, which results in restrictions on the purposes for which the particle can be used.

PRIOR ART DOCUMENT Patent Document Patent Document 1: Japanese Unexamined Patent Application Publication No.2007- l 84278A Patent Document 2: Japanese Unexamined Patent Application Publication No.2010-072492A SUMMARY OF THE INVENTION Problem to be Solved by the Invention Compared with the vinyl polymer fine particle described above, a polyorganosiloxane particle can be suitably used as a core particle of a functional particle due to its characteristics such as precise particle size, moderate flexibility and heat-resistance. However, a polyorganosiloxane particle itself is hydrophobic, which leads to a problem that its moderate flexibility is lost if any treatment for hydrophilizing a polyorganosiloxane particle itself is applied.

It is an object of the present invention to provide the hydrophilic particle manufacturing method which enables easy obtaining of a hydrophilic particle with both moderate flexibility and hydrophilic property and a hydrophilic particle.

Means to Solve the Problem The hydrophilic particle manufacturing method according to the present invention to achieve the above object comprises a baking step wherein polymethylsiloxane particles whose 10%K value is within the range between 2GPa to 20GPa are baked in the atmosphere whose oxygen concentration is 7 vol% or more, wherein the difference between 10%K value of polymethylsiloxane particles before the baking step and 10%K value of hydrophilic particles obtained by the baking step is within 7 GPa, the hydrophilic particles have an water absorption of 2% or more, and the %K value is calculated by the formula: %K value [N/mm2] = (3/21") > where F represents the load [N] at 10% compressive deformation of the particle, S represents the displacement [mm] at 10% compressive deformation of the particle, and R represents the radius [mm] of the particle. id="p-11" id="p-11" id="p-11" id="p-11" id="p-11"

[0011] According to the manufacturing method described herein, the use of polyorganosiloxane particles with the said 10%K value prevents the polyorganosiloxane particles from hardening rapidly even if it is baked in the atmosphere whose oxygen concentration is 7 vol% or more. Also, baking polyorganosiloxane particles in the atmosphere with the said oxygen concentration appropriately improves their water absorption. id="p-12" id="p-12" id="p-12" id="p-12" id="p-12"

[0012] In the hydrophilic particle manufacturing method described above, it is preferable to obtain hydrophilic particles whose water absorption is 2% or more and whose 10%K value is within the range between 2GPa to 25GPa through the said baking step. id="p-13" id="p-13" id="p-13" id="p-13" id="p-13"

[0013] In the hydrophilic particle manufacturing method described above, the said polyorganosiloxane particles are preferably polymethylsiloxane particles, the said oxygen concentration is preferably within the range between 20 vol% to 40 vol%, and a baking temperature in the said baking step is preferably within the range between 300°C to 480°C. id="p-14" id="p-14" id="p-14" id="p-14" id="p-14"

[0014] In the hydrophilic particle manufacturing method described above, a baking duration in the said baking step is preferably within the range between 1 hour to 150 hours.

With regard to hydrophilic particles obtained from polymethylsiloxane particles, its water absorption is preferably 2% and its 10%K value is preferably within the range between 2GPa to 25GPa.

EFFECT OF THE INVENTION id="p-15" id="p-15" id="p-15" id="p-15" id="p-15"

[0015] According to the present invention, hydrophilic particles with both moderate flexibility and hydrophilic property are easily obtained.

BEST MODE FOR CARRYING OUT THE INVENTION [00 16] The following is a description of the hydrophilic particle manufacturing method and the hydrophilic particle according to the method described herein.

First, the hydrophilic particle is described as follows.

The hydrophilic particle is obtained from a polyorganosiloxane particle.

The polyorganosiloxane, of which main part is a siloxane framework, has organo groups. Examples of polyorganosiloxan include trialkoxysilane condensate. [00 17] Examples of trialkoxysilane include methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilan, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, y- glycidoxypropyltrimethoxysilane, y- acryloyloxypropyltrimethoxisilane, y- methacryloyloxypropyltrimethoxysilane. One or more kinds of trialkoxysilane can be used. [00 1 8] Trialkoxysilane can also be used in combination with at least one chosen from among tetraalkoxysilane, dialkoxysilane and monoalkoxysilane.

Arbitrary choice from among these silane compounds and organic substituents also enables designing of various physical properties of the particle, such as mechanical properties, as desired. Polyorganosiloxane is preferably polymethylsiloxane from the point of view of easy adjustment to any desired physical properties. [00 19] %K value of the hydrophilic particles is between 2GPa to 25GPa, preferably between 2GPa to 20GPa, more preferably within the range between 5GPa to lSGPa. id="p-20" id="p-20" id="p-20" id="p-20" id="p-20"

[0020] For example, if the hydrophilic particles or complex particles whose core particles are the hydrophilic particles are to be used as a spacer for electronic components, 10%K value of the hydrophilic particles is more preferably 5GPa or more so that their interlayer retentivity (spacer function) is ensured. Also, from the point of view of protecting peripheral components that the hydrophilic particles make contact with from physical damages as much as possible, 10%K value of the hydrophilic particles is more preferably 20GPa or less. Examples of peripheral components that the hydrophilic particles make contact with include oriented films and protective films formed on substrates, color filters, and electric elements such as ITO conductive films and circuits. id="p-21" id="p-21" id="p-21" id="p-21" id="p-21"

[0021] Water absorption of the hydrophilic particles is 2% or more, preferably % or more. The hydrophilic particles whose water absorption is 2% or more have better water dispersibility, thereby, for example, are able to form a more uniform coating film on it through an aqueous solution treatment. It is presumed that the higher the water absorption of the hydrophilic particle is, the more the entire particle including the inside part of the polyorganosiloxane particle is reformed (hydrophilized). In particular, if water absorption of the hydrophilic particle is 5% or more, the inside part of the particle is presumed to be fully hydrophilized as well, which allows formation of a more uniform coating film. id="p-22" id="p-22" id="p-22" id="p-22" id="p-22"

[0022] The amount of OH groups existing on the surface of the hydrophilic particles can be expressed by the ratio of OH groups to O atoms combined with Si atoms, namely the surface atomic concentration ratio (OH/O ratio). The surface atomic concentration ratio (OH/O ratio) can be measured by a quantitative analysis utilizing the Electron Spectroscopy for Chemical Analysis (ESCA) that is described later. The surface atomic concentration ratio of the hydrophilic particle (OH/O ratio) is preferably 0.003 or more from the point of view of improving water dispersibility of the hydrophilic particle. id="p-23" id="p-23" id="p-23" id="p-23" id="p-23"

[0023] A particle sizes of the hydrophilic particles, in terms of an average particle size obtained by the Coulter counter method, is preferably within the range between 0.5um to 200um. The hydrophilic particles with the particle size within this range and complex particles whose core particle is such a hydrophilic particle can be suitably used, for example, as a spacer for electronic components. An average particle size of hydrophilic particles can be adjusted according to intended uses. For example, an average particle size of hydrophilic particles to be used as a spacer for a liquid crystal panel is preferably within the range between lum to 15 um. For example, an average particle size of hydrophilic particles to be used as a spacer for an organic electro luminescence device is preferably within the range between 6pm to l6um. For example, an average particle size of hydrophilic particles to be used as a spacer for a PDLC (polymer dispersion type liquid crystal) device is preferably within the range between 7pm to 25 um. For example, an average particle size of hydrophilic particles to be used as a spacer for a 3D shutter is preferably within the range between 25pm to 50pm. For example, an average particle size of hydrophilic particles to be used as a spacer for LED lighting device is preferably within the range between 40um to 120um. id="p-24" id="p-24" id="p-24" id="p-24" id="p-24"

[0024] Particle size distribution of hydrophilic particles is expressed by CV (coefficient of variation) value. CV value of hydrophilic particles is preferably % or less, more preferably 2.5% or less. Hydrophilic particles whose CV value is 5% or less have a less variation in their particle sizes and can be suitably used as a spacer. In addition, hydrophilic particles are preferably spherical-shaped monodisperse particles. id="p-25" id="p-25" id="p-25" id="p-25" id="p-25"

[0025] The hydrophilic particle can also be used as a particle with excellent slurry dispersibility. Because the hydrophilic particle is able to form a good coating film with only a few defects on the particle surface, the hydrophilic particle is particularly suitable for a core particle of a complex particle. For example, the hydrophilic particle can be suitably used as a core particle of a conductive particle. In other words, it is possible to obtain a conductive particle by forming a conductive film on the surface of the hydrophilic particle.

Examples of conductive films include silver coating films, gold coating films and copper coating films. A conductive film can be formed by an aqueous solution treatment such as the electroless plating method. Apart from a conductive film, a complex particle with such specific functions as adhesiveness and stickiness can also be made by the formation of a resin film made of curing resin, thermoplastic resin, or the like on the particle surface. In addition, if the hydrophilic particle is used as a core particle of functional fillers such as a conductive filler, such characteristics as a stress relaxation characteristic led by the flexibility of the hydrophilic particle may also be produced. id="p-26" id="p-26" id="p-26" id="p-26" id="p-26"

[0026] Second, the hydrophilic particle manufacturing method is described as follows.

The hydrophilic particle manufacturing method comprises a baking step wherein a polyorganosiloxane particle whose 10%K value is within the range between 2GPa to 20GPa is baked in the atmosphere whose oxygen concentration is 7 vol% or more. The method is not particularly limited, provided that the hydrophilic particle whose water absorption is 2% or more and whose 10%K value is within the range between 2 GPa to 25GPa is obtained. However, according to the manufacturing method described herein, it is possible to obtain homogeneous hydrophilic particles with the said water absorption and the said 10%K value productively and conveniently. id="p-27" id="p-27" id="p-27" id="p-27" id="p-27"

[0027] Here, the flexibility of the polyorganosiloxan particle is produced by organo groups (organic constituent). In other words, the higher the 10%K value of the polyorganosiloxan particles is, the less organic constituent the polyorganosiloxan particle has. In the case of the said polyorganosiloxan particle whose 10%K value is 2GPa or more, since it has comparatively less organic constituent, it is easy to make the organic constituent baked slowly even if it is baked in the atmosphere whose oxygen concentration is 7 vol% or more. In this way, rapid baking of organic constituent in the polyorganosiloxan particle, in other words, excessive hardening of the particle, and variation in flexibility and hydrophilic property due to uneven baking can be easily avoided. id="p-28" id="p-28" id="p-28" id="p-28" id="p-28"

[0028] Polyorganosiloxan to be used for a polyorganosiloxan particle can be the one referred to in the above description of the hydrophilic particle.

In the hydrophilic particle manufacturing method, the hydrophilic particle is obtained as the result of the said baking step, wherein each organo group included in a polyorganosiloxan particle partially undergoes oxidative decomposition and thereby becomes a hydroxyl group. For example, if the baking step is conducted in the atmosphere whose oxygen concentration is less than 7 vol%, the hydrophilic particle cannot be efficiently obtained because the oxidative decomposition of organic constituent, in other words, hydrophilization of the polyorganosiloxan particle is not facilitated. Therefore, from the point of view of more efficient oxidative decomposition of organic constituent, oxygen concentration in the baking step is 7 vol% or more, preferably 15 vol% or more, more preferably 20 vol% or more. Such a baking step can also be conducted in the atmosphere whose oxygen concentration is 21 vol%. In addition, oxygen concentration in the baking step is preferably 40 vol% or less from the point of view of both safety and simplification of equipment. id="p-29" id="p-29" id="p-29" id="p-29" id="p-29"

[0029] A baking temperature and a baking duration in the baking step can be adjusted according to such elements as the kind, 10%K value, and oxygen concentration of the baking atmosphere of a polyorganosiloxan particle. For example, if a polymethylsiloxane particle used as a polyorganosiloxan particle is baked in the atmosphere whose oxygen concentration is within the range between 20 vol% to 40 vol%, the baking temperature is preferably within the range between 300°C to 480°C. The temperature setting in this specific range enables both maintenance of flexibility and improvement of hydrophilic property for the particle. In addition, setting the baking duration within the range between 1 hour to 150 hours within this specific temperature range will make it easy to improve productivity of manufacturing hydrophilic particles with both flexibility and hydrophilic property. id="p-30" id="p-30" id="p-30" id="p-30" id="p-30"

[0030] Baking equipment for the said baking step is not particularly limited.

Examples of such baking equipment includes electric furnaces and rotary kilns.

Rotary kilns can bake polyorganosiloxan particles while stirring them, thereby conduct oxidative decomposition of organic constituent in a polyorganosiloxan particle more uniformly. In this way, the hydropholic particles with stable quality are easily obtained. id="p-31" id="p-31" id="p-31" id="p-31" id="p-31"

[0031] In the hydrophilic particle manufacturing method, process conditions of the baking step can also be adjusted based on the measurement results on physical properties of the particles before and after the baking step. The difference between the average particle size of polyorganosiloxan particles before the baking step and the average particle size of hydrophilic particles after the baking step is preferably within lum. The difference between 10%K value of polyorganosiloxan particles before the baking step and 10%K value of hydrophilic particles after the baking step is preferably within 7 GPa. id="p-32" id="p-32" id="p-32" id="p-32" id="p-32"

[0032] Lastly, functions and effects of the method described herein is described as follows. (1) The hydrophilic particle manufacturing method comprises a baking step wherein polyorganosiloxane particles whose 10%K value is within the range between 2GPa to 20GPa are baked in the atmosphere whose oxygen concentration is 7 vol% or more. According to this manufacturing method, the use of polyorganosiloxane particles with the said 10%K value prevents polyorganosiloxane particles from hardening rapidly even if they are baked in the atmosphere whose oxygen concentration is 7 vol% or more. Also, baking polyorganosiloxane particles in the atmosphere with the said oxygen concentration appropriately improves their water absorption. In this way, the present method described herein makes it possible to obtain hydrophilic particles with both moderate flexibility and hydrophilic property easily. id="p-33" id="p-33" id="p-33" id="p-33" id="p-33"

[0033] (2) In the hydrophilic particle manufacturing method, it is preferable to obtain hydrophilic particles whose water absorption is 2% or more and whose %K value is within the range between 2GPa to 25GPa through the baking step. The present method described herein makes it possible to obtain hydrophilic particles with such a flexibility and hydrophilic property, for example. id="p-34" id="p-34" id="p-34" id="p-34" id="p-34"

[0034] (3) If a polymethylsiloxane particle is used as a polyorganosiloxane particle, an oxygen concentration in the baking step is preferably within the range between 20 vol% to 40 vol%, and a baking temperature in the baking step is preferably within the range between 300°C to 480°C. This is one of the examples of baking condition settings to enable easy obtaining of the hydrophilic particles with both flexibility and hydrophilic property from polymethylsiloxane particles used as a raw material. In addition, if the baking duration in the baking step is set within the range between 1 hour and 150 hours, productivity in making the hydrophilic particles with both flexibility and hydrophilic property can be improved easily. id="p-35" id="p-35" id="p-35" id="p-35" id="p-35"

[0035] (4) The hydrophilic particle is obtained from a polymethylsiloxane particle. With regard to this hydrophilic particle, water absorption is 2% or more and 10%K value is within the range between 2GPa to 25GPa. With this composition, for example, a functional coating film can be formed on the surface of the hydrophilic particle by an aqueous solution treatment. The hydrophilic particles have moderate flexibility, thereby can be suitably used, for example, as a spacer for electronic components.

EXAMPLES id="p-36" id="p-36" id="p-36" id="p-36" id="p-36"

[0036] Examples and comparative examples of the present invention are described as follows.

EXAMPLE 1 As shown in Table 1, 150g of polyorganosiloxane particles whose 10%K value was 14.23 GPa, average particle size was 7.01pm and CV value was 1.58% (polymethylsiloxane particles, trade name: HIPRESICA TS N5N manufactured by UBE EXSYMO CO., LTD.) were baked in a muffle furnace (KBF728N manufactured by Koyo Thermo Systems Co., Ltd.) in the air atmosphere at a temperature of 350°C for 1 hour, thereby the hydrophilic particles were obtained. id="p-37" id="p-37" id="p-37" id="p-37" id="p-37"

[0037] EXAMPLE 2, 3 As shown in Table 1, the same conditions with EXAMPLE 1 except for the baking duration were applied, thereby the hydrophilic particles of EXAMPLE 2 and 3 were obtained. id="p-38" id="p-38" id="p-38" id="p-38" id="p-38"

[0038] EXAMPLE 4 As shown in Table 1, 150g of polyorganosiloxane particles whose 10%K value was 8.18 GPa, average particle size was 3.11pm and CV value was 2.04% (polymethylsiloxane particles, trade name: HIPRESICA TS N5 aN manufactured by UBE EXSYMO CO., LTD.,) were baked in a muffle furnace (KBF728N produced by Koyo Thermo Systems Co., Ltd.) in the air atmosphere at a temperature of 350°C for 48 hour, thereby the hydrophilic particles were obtained. id="p-39" id="p-39" id="p-39" id="p-39" id="p-39"

[0039] EXAMPLE 5 As shown in Table 1, the same conditions with EXAMPLE 4 except for the baking duration were applied, thereby the hydrophilic particles were obtained. id="p-40" id="p-40" id="p-40" id="p-40" id="p-40"

[0040] EXAMPLE 6 As shown in Table 1, 150g of polyorganosiloxane particles whose 10%K value was 5.41 GPa, average particle size was 5.23pm and CV value was 1.63% (polymethylsiloxane particles, trade name: HIPRESICA TS N6N manufactured by UBE EXSYMO CO., LTD.) were baked in a muffle furnace (KBF728N manufactured by Koyo Thermo Systems Co., Ltd.) in the air atmosphere at a temperature of 330°C for 7 hours, thereby the hydrophilic particles was obtained. id="p-41" id="p-41" id="p-41" id="p-41" id="p-41"

[0041] EXAMPLE 7, 8 As shown in Table 1, the same conditions with EXAMPLE 1 except for the baking temperature and baking duration were applied, thereby the hydrophilic particles of EXAMPLE 7 and 8 were obtained. id="p-42" id="p-42" id="p-42" id="p-42" id="p-42"

[0042] COMPARATIVE EXAMPLE 1 In COMPARATIVE EXAMPLE 1, the polyorganosiloxane particles of EXAMPLE 1 (polymethylsiloxane particles, trade name: HIPRESICATS N5N manufactured by UBE EXSYMO CO., LTD.) were used. id="p-43" id="p-43" id="p-43" id="p-43" id="p-43"

[0043] COMPARATIVE EXAMPLE 2 As shown in Table 1, 150g of polyorganosiloxane particles whose 10%K value was 1.55 GPa, average particle size was 7.08pm and CV value was 1.57% (polymethylsiloxane particles, trade name: HIPRESICA TS N7N manufactured by UBE EXSYMO CO., LTD.) were baked in a muffle furnace (KBF728N manufactured by Koyo Thermo Systems Co., Ltd.) in the air atmosphere at a temperature of 35 0°C for 7 hours, thereby the hydrophilic particles were obtained. id="p-44" id="p-44" id="p-44" id="p-44" id="p-44"

[0044] MEASURING METHOD FOR 10%K VALUE, AVERAGE PARTICLE SIZE AND CV VALUE The 10%K value of sample particles could be measured with the following procedure: 10%K value was measured on 10 particles respectively and then the average value of these 10%K values was calculated. This measurement used a micro compression testing machine (MCTE-200 manufactured by SHIMADZU CORPORATION). The 10%K value was calculated by the formula (1) shown below. id="p-45" id="p-45" id="p-45" id="p-45" id="p-45"

[0045] %K value [N/mm2] = (3/21") XFXS'3/2XR'1/2...(1) In the above formula (1), F represents the load [N] at 10% compressive deformation of the particle, and S represents the displacement [mm] at 10% compressive deformation of the particle. Also, R represents the radius [mm] of the particle. id="p-46" id="p-46" id="p-46" id="p-46" id="p-46"

[0046] The average particle size and CV value of sample particles were obtained with a Coulter counter (Multisizer IVe manufactured by Beckman Coulter, Inc.). The coefficient of variation (CV value) in particle distribution could be calculated by the formula (2) shown below. id="p-47" id="p-47" id="p-47" id="p-47" id="p-47"

[0047] CVvalue (%) = {standard deviation of particle sizes [um] / average particle size [um] }><100...(2) Measurement results on the physical properties described above in each EXAMPLE are shown in Table 1 and Table 2.

EVALUATION ON WATER DISPERSIBILITY g of deionized water and 5g of dry powder as sample particles were poured into a 110mL screw tube bottle, and then was shaken and sonicated for minutes in a sonicator set at room temperature. id="p-48" id="p-48" id="p-48" id="p-48" id="p-48"

[0048] The liquid surface in the screw tube bottle after the sonication was observed, and was judged good (0) if all the particles were immersed and dispersed in the liquid, meanwhile, judged bad ( X) if there was any visible particle floating on the liquid. The results are shown in Table 2. id="p-49" id="p-49" id="p-49" id="p-49" id="p-49"

[0049] SURFACE ATOMIC CONCENTRATION RATIO (OH/O RATIO) OH groups existing on the surface of the particle was measured by Electron Spectroscopy for Chemical Analysis (ESCA). The measurement of OH groups existing on the surface of the particle used an analysis method described below, wherein Br atoms that functionalized OH groups with a ratio of one Br atom to one OH group were quantitated. This analysis method enabled a quantitative comparison of O atom, OH group and C atom (derived from organic groups) combined with Si atom at the surface (within a depth of a few nm below the surface layer) of a polyorganosiloxane particle whose main part was siloxane frameworks. id="p-50" id="p-50" id="p-50" id="p-50" id="p-50"

[0050] l. Functionalization of OH group Sample particles were immersed in functionalizing reagent (including brominated organic compounds) and left at room temperature overnight. Next, the sample particles were cleansed thoroughly with acetonitrile and filtered, and then sampled after being dried, thereby sample particles whose OH groups on the surface of the particles were replaced with Br groups were obtained. id="p-51" id="p-51" id="p-51" id="p-51" id="p-51"

[0051] . Equipment and measurement conditions Elemental contents on the surface of the sample particles were measured. First, powder as the sample particles was fixed on a piece of adhesive tape, which then was fixed on a stage and finally set in an X-ray photoelectron spectroscope. The X-ray photoelectron spectroscope measured the surface atomic concentration of the powder, from which carbon amount on the surface of a particle (mass %) was calculated. In this measurement, the surface atomic concentration was calculated based on the peak strength in a narrow spectrum of detected elements (C, O, Si, Br), utilizing a relative sensitivity factor provided by ULVAC-PHI, Inc. The name of equipment and measurement conditions used for this measurement are listed below. id="p-52" id="p-52" id="p-52" id="p-52" id="p-52"

[0052] Equipment name: l600S type X-ray photoelectron spectroscope manufactured by ULVAC-PHI, Inc.

Measurement conditions: X-ray source MgKa 100W, analyzed area 0.8><2.0mm MEASUREMENT OF WATER ABSORPTION First, sample particles were put in a glass dish and dried in an oven set at 150°C for at least 1 hour, then cooled down to room temperature in a desiccator. After this, approximately 15g of sample particles were weighed with electronic scale. The glass dish used for weighing the sample particles was dried at 150°C for 3 hours, then immediately cooled down in a desiccator with phosphorus pentaoxide in it. After it was cooled down to room temperature, the mass of sample particles was measured. This mass value was presumed to be the mass of sample particle before they absorb water. id="p-53" id="p-53" id="p-53" id="p-53" id="p-53"

[0053] Second, sample particles were left in a constant temperature and humidity chamber set at 30°C and 90%RH and allowed to absorb water. The mass of sample particles (the mass of sample particles after they absorb water) was measured every 24 hours and its water absorption was calculated by the formula (3) shown below. When the variation in the water absorption after a lapse of approximately 24 hours became 0.5% or less, the water absorption was judged to have reached a saturation point and the measurement was ended. id="p-54" id="p-54" id="p-54" id="p-54" id="p-54"

[0054] Water absorption [%] = (K2-K1) / K1><100...(3) In the above formula (3), K1 represents the mass of sample particles before they absorb water and K2 represents the mass of sample particles after they absorb water. The measurement was conducted three times for each sample particle, and their average value was decided to be the water absorption. id="p-55" id="p-55" id="p-55" id="p-55" id="p-55"

[0055] [Table 1] Polyorganosiloxane . particle Bakmg step Average 0 IOAK particle CV Oxygen. Temperature Duration value size value concentration GPa um % Vol% °C EXAMPLE 1 14.23 7.01 1.58 21 350 EXAMPLE 2 14.23 7.01 1.58 21 350 EXAMPLE 3 14.23 7.01 1.58 21 350 EXAMPLE 4 8.18 3.11 2.04 21 350 48 EXAMPLE 5 8.18 3.11 2.04 21 350 120 EXAMPLE 6 5.41 5.23 1.63 21 330 EXAMPLE 7 14.23 7.01 1.58 21 450 EXAMPLE 8 14.23 7.01 1.58 21 500 COMPARATIVE EXAMPLE 1 14.23 7.01 1.58 - - COMPARATIVE EXAMPLE 2 1.55 7.08 1.57 21 350 id="p-56" id="p-56" id="p-56" id="p-56" id="p-56"

[0056] [Table 2] Hydrophilic particle H dro hilic %K. y 0%/ Awm?g3 CV value _ Water _ 0 Water paftlde value d1spers1b111ty ratio absorption size GPa um % % OC % EXAMPLE 1 11.12 0 0.005 2.61 6.96 1.57 EXAMPLE 2 10.84 0 0.005 5.17 6.99 1.59 EXAMPLE 3 10.65 0 0.005 5.68 6.96 1.59 EXAMPLE 4 9.66 o 0.007 9.21 3.06 1.89 EXAMPLE 5 11.21 0 0.008 10.16 3.02 2.14 EXAMPLE 6 5.42 o 0.004 2.23 5.21 1.66 EXAMPLE 7 17.18 0 0.007 6.10 6.40 1.59 EXAMPLE 8 20.73 0 0.008 6.52 6.29 1.59 COMPARATIVE - >< 0.000 0.66 - - EXAMPLE 1 COMPARATIVE 37.60 0 0.015 7.10 7.00 1.60 EXAMPLE 2 The hydrophilic particles of EXAMPLE 1 to 8 shown in Table 1 and 2 were obtained by a baking step wherein polyorganosiloxane particles used as a raw material whose 10%K value was within the range between 2GPa to 20GPa were baked in the atmosphere whose oxygen concentration was 7 vol% or more. In the case of the hydrophilic particles of all EXAMPLEs, the 10%K value was 20.73GPa or less and water absorption was 2.23% or more. id="p-57" id="p-57" id="p-57" id="p-57" id="p-57"

[0057] On the other hand, the particles of COMPARATIVE EXAMPLE 1 did not undergo any baking step, so that they could not acquire the level of hydrophilic property that the hydrophilic particles of all EXAMPLEs acquired.

In COMPARATIVE EXAMPLE 2, polyorganosiloxane particles whose 10%K value was less than 2GPa were used as raw material. In the COMPARATIVE EXAMPLE 2, a baking was performed with the same conditions with EXAMPLE 2, as the result, the 10%K value was 37.60GPa. This implied that the polyorganosiloxane particles of COMPARATIVE EXAMPLE 2 were hardened rapidly through the baking, thereby it was difficult to obtain hydrophilic particles with flexibility that were obtained in all EXAMPLEs. id="p-58" id="p-58" id="p-58" id="p-58" id="p-58"

[0058] MAKING OF CONDUCTIVE PARTICLE 1. Forming step of metallic core Metallic cores were formed on the surface of samples of the hydrophilic particles of EXAMPLE 1. As the procedure for forming a metallic core, 10g of sample particles were immersed in 68mL of mixed solvent of isopropyl alcohol and methanol, and then 0.086g of chlorauric acid (HAuCI4 - 4H20) and 1.14mL of 3-aminopropyltrimethoxysilane were added to them. They then became reduced with 0.036g of sodium tetrahydroborate (NaBH4) and thereby a particle with a metallic core on its surface was obtained. id="p-59" id="p-59" id="p-59" id="p-59" id="p-59"

[0059] . Forming step of conductive film g of sample particles on which metallic cores were formed were dispersed in 523mL of water, and then 0.073mL of 3-mercaptotriethoxysilane was added to them and an ultrasonic wave was irradiated to them. They then were added to a mixed solvent of 450mL of methanol and 150mL of water.

After this, 6.043g of silver nitrate that had been mixed with 60mL of water in advance and 121mL of 25 mass % aqueous solution of ammonium were also added to the mixed solvent. In addition, lSlmL of 37% formaldehyde solution was added so that silver ion in the liquid was reduced. Thus, conductive particles, which were the hydrophilic particles of EXAMPLE 1 having a silver coating film serving as a conductive film on their surface, were obtained. id="p-60" id="p-60" id="p-60" id="p-60" id="p-60"

[0060] With the same procedure as the above, conductive particles were made from the hydrophilic particles of EXAMPLE 2 to 8 and COMPARATIVE EXAMPLE 2 as well through the formation of silver coating films. In the process of forming a metallic core and forming a conductive coating film, for example, the blending quantity of silver nitrate used as a raw material of a conductive coating film were appropriately adjusted according to an average particle size of hydrophilic particles, so that conductive coating films with nearly uniform thickness were formed on the hydrophilic particles. id="p-61" id="p-61" id="p-61" id="p-61" id="p-61"

[0061] On the particles of COMPARATIVE EXAMPLE 1, a progress of reaction for the formation of a metallic core and a silver film was not observed, and no coating film could be formed.

RESULT OF CONDUCTIVE PARTICLE FORMATION All of the particles prepared by the formation of metallic cores on the surface of samples of the hydrophilic particles of EXAMPLE 1 to 8 and COMPARATIVE EXAMPLE 2 exhibited a red color. id="p-62" id="p-62" id="p-62" id="p-62" id="p-62"

[0062] On conductive particles obtained from the hydrophilic particles of EXAMPLE 1 to 8 and COMPARATIVE EXAMPLE 2, the values of silver film thickness calculated from the difference between the average particle size of the hydrophilic particles and the average particle size of the conductive particles were all 0.05pm or more. id="p-63" id="p-63" id="p-63" id="p-63" id="p-63"

[0063] Appearance of coating films formed on the surface of conductive particles, namely the surface of the hydrophilic particles (core particles), was observed with a Scanning Electron Microscope (J SM-6700F manufactured by JEOL Ltd.) at 1,000 to 10,000-fold magnification which approximately allowed to 50 hydrophilic particles to be recognized on one screen and was evaluated according to the criteria listed below. The evaluation results are shown in Table 3. id="p-64" id="p-64" id="p-64" id="p-64" id="p-64"

[0064] O: The coating film is finely formed so that neither defect nor discontinuous part is recognized.

A: A defect is recognized at a part of the coating film.

X: The coating film is formed discontinuously, or no coating film is formed. id="p-65" id="p-65" id="p-65" id="p-65" id="p-65"

[0065] AVERAGE ELECTRIC RESISTANCE Electrical connectivity of the conductive particles was evaluated by an electric resistance measurement. Specifically, a micro compression testing machine (manufactured by SHIMADZU CORPORATION) was used to measure electric resistance on each of 20 conductive particles, and their average value was decided to be the average electric resistance. The results are shown in Table 3. id="p-66" id="p-66" id="p-66" id="p-66" id="p-66"

[0066] INCIDENCE The term "incidence" in this document refers to the percentage of the number of particles on which electric resistance is able to be measured. For example, if an electric resistance measurement is impossible due to poor formation, stripping or poor adhesion of a coating film, the measurement result is judged as O.R. (off the resister). Incidence can be obtained by the electric resistance measurement on each of 20 conductive particles with micro compression testing machine (manufactured by SHIMADZU CORPORATION) and a calculation with the formula (4) shown below. id="p-67" id="p-67" id="p-67" id="p-67" id="p-67"

[0067] Incidence (%) = the number of particles on which electric resistance was able to be measured / the total number of measured particles X 100... (4) The results of the incidence calculation are shown in Table 3. id="p-68" id="p-68" id="p-68" id="p-68" id="p-68"

[0068] [Table] Conductivity evaluation Appearance Average electric Incidence evaluation resistance (n=20) - Q % Example 1 o 3.3 80 Example 2 o 3.0 100 Example 3 o 3.1 100 Example 4 o 3.5 100 Example 5 o 3.3 100 Example 6 o 4.1 85 Example 7 o 3.0 100 Example 8 o 3.0 85 Comparative >< OR. 0 Example 1 (Off the register) Com arative ExaEnple 2 O 3'0 100