Polymer Molded Body

Abstract

To provide glass-coated aluminum nitride powder having high water resistance, in which the surface of the particles is substantially completely coated with glass, and a polymer molding containing the powder as a filler.SOLUTION: Glass-coated aluminum nitride powder is composed of glass-coated aluminum nitride particles in which the surface of aluminum nitride particles is coated with glass, wherein D50 of the aluminum nitride particles is 0.5 to 100 μm, glass thickness is 2 to 100 nm, and a glass coating rate of the particle surface is 95% or more. Glass precursor-coated aluminum nitride particles are prepared by drying a mixed liquid containing aluminum nitride particles and a glass precursor in a misty state or a state of being spread on the surface, and glass-coated aluminum nitride particles are prepared by forming the glass precursor into a glass by heating.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to glass-coated aluminum nitride powder and a polymer molded body containing the same.

Background Art

[0002] Aluminum nitride powder is utilized as a filler to be mixed with materials such as resins, greases, adhesives, and paints, taking advantage of its excellent thermal conductivity. However, aluminum nitride changes into aluminum hydroxide with low thermal conductivity due to moisture in the air and generates corrosive ammonia, depending on the conditions not only before the mixing but also after the mixing. Therefore, improving the water resistance by coating aluminum nitride powder with glass or the like has been studied.

[0003] Patent Document 1 discloses a method for producing glass-coated aluminum nitride particles with a d50 of 10 to 200 μm, in which aluminum nitride particles and glass frit with a d50 of 0.3 to 50 μm are mixed, the mixture is placed in a crucible or shaped into pellets, and heat-treated at a temperature not lower than the glass transition temperature of the glass frit and not higher than 2000 °C to coat the aluminum nitride particles with the glass frit to obtain coated particles, and then the coated particles are crushed. The glass coating thickness in the examples is 10 to 660 nm.

[0004] Patent Document 2 discloses a method for producing glass-coated aluminum nitride particles, in which a mixture of aluminum nitride particles with a d50 of 10 to 200 μm and composition powder containing a glass component with a d50 of 0.3 to 50 μm is mixed while applying shear force by a mechanochemical method, the mixture is placed in a crucible and heat-treated at a temperature not lower than the glass transition temperature of the glass component and not higher than 2000 °C, and the heat-treated product is crushed.

[0005] Patent Document 3 discloses a method for producing silicon-containing oxide (silica or silicon-aluminum composite oxide) coated aluminum nitride particles by dry mixing aluminum nitride particles with an organosilicone compound by spraying while stirring, thereby coating the surface of the aluminum nitride particles with the organosilicone compound, and then heating the coated aluminum nitride particles at a temperature of 300°C or higher but less than 1000°C. Silicon-containing oxide coated aluminum nitride particles are defined as having a carbon atom content of less than 1000 ppm by mass, a coverage rate of 15% to 100% as determined by LEIS analysis of the silicon-containing oxide coating, and a specific relationship between the silicon atom content and the specific surface area. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6739669 [Patent Document 2] Patent No. 6606628 [Patent Document 3] Patent No. 7419938 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the manufacturing methods described in Patent Documents 1 and 2 involve placing the mixture in a crucible or shaping it into pellets and then heat-treating it, meaning the particles are in contact with each other during heat treatment. As a result, the molten glass penetrates between the aluminum nitride particles with strong capillary forces, causing the particles to aggregate. The degree of aggregation increases as the diameter of the aluminum nitride particles decreases (for example, D50 is around 0.5 to 5 μm). Consequently, a considerable amount of energy must be invested in the subsequent crushing, which leads to peeling or breakage of the coated glass layer, a decrease in the glass coating rate, and a reduction in water resistance.

[0008] Furthermore, the low-energy ion scattering (LEIS) analysis described in Patent Document 3 provides information from a shallow region of about 0.1 nm on the surface, and can detect even a very small amount of silica or silicon-aluminum composite oxide, with the maximum coverage being 88% in Example 6. In addition, while it is stated that "more preferably the coverage is 95% or less... (omitted)... it has been found that if it exceeds 95%, the thermal conductivity may decrease," no specific examples of coverage exceeding 95% are given. Therefore, it can be inferred that nearly complete coverage (95% or more) has not been achieved.

[0009] Therefore, the object of the present invention is to provide a highly water-resistant glass-coated aluminum nitride powder in which the particle surface is almost completely coated with glass, and a highly water-resistant polymer molded article containing the powder as a filler. [Means for solving the problem]

[0010] [1] Glass-coated aluminum nitride powder comprising glass-coated aluminum nitride particles in which the surface of aluminum nitride particles is coated with glass, wherein the D50 of the aluminum nitride particles is 0.5 to 100 μm, the glass thickness is 2 to 100 nm, and the glass coating rate of the particle surface is 95% or more.

[0011] [2] The glass-coated aluminum nitride powder according to [1], wherein the D50 of the aluminum nitride particles is less than 10 μm.

[0012] [3] The glass-coated aluminum nitride powder according to [1] or [2], wherein the glass thickness is less than 10 nm.

[0013] [4] The glass-coated aluminum nitride powder according to any one of [1] to [3], wherein the glass coating rate is 100%. The glass coating density shall be measured by TEM analysis, and areas with a glass thickness of less than 2 nm shall be considered to have virtually no coating from the standpoint of water resistance due to insufficient coating.

[0014] [5] A polymer molded body formed from a polymer material containing the glass-coated aluminum nitride powder according to any one of [1] to [4] above as a filler.

[0015] [6] A polymer molded body formed from a polymer material containing at least two kinds of glass-coated aluminum nitride powders having different D50s according to any one of [1] to [4] above as fillers.

[0016] [7] The polymer molded body according to [5], wherein the polymer molded body is a heat dissipation member.

[0017] [8] The polymer molded body according to [6], wherein the polymer molded body is a heat dissipation member.

[0018] [9] A glass precursor coating step of producing a glass precursor-coated aluminum nitride powder composed of glass precursor-coated aluminum nitride particles in which the particle surfaces are coated with a glass precursor by drying a mixed liquid containing aluminum nitride particles and a glass precursor in a mist state or in a state of being spread on a surface, and A heat treatment step of producing a glass-coated aluminum nitride powder composed of glass-coated aluminum nitride particles in which the particle surfaces are coated with glass by heating the glass precursor-coated aluminum nitride particles to a temperature equal to or higher than the melting temperature of the glass precursor to vitrify the glass precursor A method for producing a glass-coated aluminum nitride powder including the above steps.

[0019]

[10] The method for producing a glass-coated aluminum nitride powder according to [9], wherein the glass precursor coating step is by spray drying in which the mixed liquid is sprayed into the air.

[0020]

[11] The method for producing a glass-coated aluminum nitride powder according to [9], wherein the glass precursor coating step is performed by spreading the mixed liquid in a film shape or in a dispersed state on the surface of a receiving member.

[0021]

[12] The manufacturing method of glass-coated aluminum nitride powder according to any one of [9] to

[11] , wherein a crushing step of crushing the aggregated glass-precursor-coated aluminum nitride particles is performed between the glass-precursor coating step and the heat treatment step.

[0022]

[13] The manufacturing method of glass-coated aluminum nitride powder according to any one of [9] to

[12] , wherein the heat treatment step is performed by continuously charging glass-precursor-coated aluminum nitride particles into a tubular furnace in a state of being dispersed in a carrier gas.

[0023]

[14] The manufacturing method of glass-coated aluminum nitride powder according to any one of [9] to

[12] , wherein the heat treatment step is performed by continuously supplying glass-precursor-coated aluminum nitride particles to a rotary kiln.

[0024]

[15] The manufacturing method of glass-coated aluminum nitride powder according to any one of [9] to

[12] , wherein the heat treatment step is performed by putting glass-precursor-coated aluminum nitride particles in a sheath and passing them through a roller hearth kiln.

[0025]

[16] A manufacturing method of glass-coated aluminum nitride powder, wherein a glass-coated aluminum nitride powder composed of glass-coated aluminum nitride particles in which the surface of the particles is coated with glass in which the glass precursor is vitrified is produced by drying a mixed liquid containing aluminum nitride particles and a glass precursor in a mist state or in a state of being spread on a surface and heating to a temperature not lower than the temperature at which the glass precursor melts. [1] A polymer molded body formed from a polymer material containing, as fillers, first glass-coated aluminum nitride particles having a first average particle size D50, in which the particle surface of the aluminum nitride particles is coated with glass, and second glass-coated aluminum nitride particles having a second average particle size D50, which is larger than the first average particle size D50. [[ID=​​​​​​​​​​​​According to the present invention, it is possible to provide a highly water-resistant glass-coated aluminum nitride powder in which the particle surface is almost completely coated with glass, and a highly water-resistant polymer molded article containing the powder as a filler. [Brief explanation of the drawing]

[0027] [Figure 1] Figure 1 is a schematic diagram illustrating the spray drying process in Example 1. [Figure 2] Figure 2 is a schematic diagram illustrating the heat treatment in Example 1. [Figure 3] Figure 3 is a schematic diagram illustrating the crushing process (before heat treatment) in Example 1. [Figure 4] Figure 4 is a TEM image of the glass-coated aluminum nitride particles of Comparative Example 6 at a magnification of 500,000x. [Figure 5] Figure 5 is a TEM image of the glass-coated aluminum nitride particles of Example 1 at a magnification of 1,350,000x. [Figure 6] Figure 6 is a TEM image of the glass-coated aluminum nitride particles of Example 2 at a magnification of 1,350,000x. [Figure 7] Figure 7 is a TEM image of the glass-coated aluminum nitride particles of Example 5 at a magnification of 500,000x. [Modes for carrying out the invention]

[0028] <1> Raw material: aluminum nitride particles The raw material, aluminum nitride powder, may contain substances other than aluminum nitride, such as rare earth compounds and calcium compounds derived from the manufacturing process, but the amount should be as small as possible. If the content is high, the composition of the glass changes significantly when these substances are incorporated into the glass, which can raise the melting point of the glass, making it difficult to melt, or cause it to fall outside the vitrification range and not become glassy. To achieve a glass coating rate of 95% or more, it is preferable to reduce the amount of substances other than aluminum nitride to 0.5% by weight or less. More preferably, it should be 0.2% by weight or less. Methods for reducing the content include elution treatment using inorganic or organic acids. If the average particle size (median diameter) D50 of the raw material aluminum nitride powder is 0.5 μm or more, it is less likely to aggregate and is therefore easier to use, and if it is 100 μm or less, it is easier to make thin polymer molded articles. If D50 is less than 10 μm, it is preferable because the glass precursor coating process can be easily carried out by spray drying, and the heat treatment process can be easily carried out while dispersed in the carrier gas.

[0029] <2> glass Examples of glass include silicate glass, borosilicate glass, bismuth glass, tin-phosphate glass, vanadium glass, and lead glass, although these are not particularly limited. The glass preferably contains two or more components selected from SiO2, Al2O3, and B2O3. Glass can contain ZnO components to reduce its coefficient of thermal expansion. Glass can contain alkali metal oxides such as Na2O and K2O, but from the viewpoint of moisture resistance, it is preferable to have a low content of these oxides. Glass may contain any components such as CaO, SrO, MgO, BaO, and SnO.

[0030] A glass thickness of 2 nm or more provides sufficient glass coating from the viewpoint of water resistance, while a thickness of 100 nm or less suppresses the reduction in thermal conductivity due to the presence of glass. A glass thickness of less than 10 nm is preferable because it further suppresses the reduction in thermal conductivity due to the presence of glass.

[0031] Water resistance improves when the glass coating rate is 95% or higher. Water resistance improves even further when the glass coating rate is 100%.

[0032] <3> Glass precursor coating process In the glass precursor coating process of the present invention, a mixture containing aluminum nitride particles and a glass precursor is dried in a mist or spread on a surface, thus enabling rapid drying. The key to glass precursor coating is to rapidly promote the precipitation of salts of each element of the glass components that occurs during the drying process. Each element of the glass components has a different saturation solubility, and during the drying process, they precipitate in order of increasing saturation solubility. However, prolonged drying increases the heterogeneity of the distribution of each element of the glass components after precipitation. Therefore, to obtain molten glass with a homogeneous composition through heat treatment, it becomes necessary to heat and hold at higher temperatures for longer periods. According to the present invention, as described above, rapid drying reduces the heterogeneity of the distribution of each element of the glass components after precipitation, and molten glass with a homogeneous composition can be obtained even with low-temperature, short-duration heat treatment, thus offering advantages in terms of energy cost and production efficiency.

[0033] The glass precursor coating process is not particularly limited, but the following are examples. (a) By spray drying, in which the mixture is sprayed into the air. This method is suitable when the aluminum nitride powder used as the raw material has a D50 of less than 10 μm, which makes it less likely to settle. (i) The mixture is spread in a film-like or dispersed manner on the surface of the receiving member. This method is suitable when the raw material, aluminum nitride powder, has a D50 of 10 μm or more, which makes it prone to settling. The receiving member is not particularly limited, but examples include PET film, glass plate, ceramic plate, etc.

[0034] <4> Crushing process (if necessary) In the glass precursor coating process of the present invention, aluminum nitride particles are easily dispersed individually. Ideally, for example, each droplet sprayed during spray drying should contain one aluminum nitride particle. However, as shown in Figure 3(a), depending on the solid content concentration of the raw material slurry and the spraying conditions, a single droplet may contain multiple aluminum nitride particles, and after drying, these particles may aggregate into aggregated particles. In such cases, it is preferable to perform a crushing treatment before the heat treatment process as needed. As shown in Figure 3(b), the mixed salt of glass component elements present at the bonding sites between particles is expected to be largely carried away by the crushing process, and in some cases, the surface of the aluminum nitride particles may be exposed. As shown in Figure 3(c), even if the coating layer in the glass precursor coating powder has irregularities, the coating layer is melted by heat treatment, wetting and spreading across the surface of the aluminum nitride particles, resulting in a homogeneous coating layer once again. Although there are slight differences in coating thickness between individual particles, the average thickness is almost as designed.

[0035] <5> Heat treatment process The heat treatment process is not particularly limited, but the following are examples: (a) This method involves continuously feeding glass precursor-coated aluminum nitride particles, dispersed in a carrier gas, into a tubular furnace. This method is preferable because the particles do not come into contact with each other. This method is suitable when the raw material aluminum nitride powder has a D50 of less than 10 μm, which makes it easy to flow in the carrier gas. (i) This method involves continuously supplying glass precursor-coated aluminum nitride particles to a rotary kiln. This method is suitable when the raw material aluminum nitride powder has a D50 of 10 μm or more, which makes it difficult to flow with a carrier gas. (c) This method involves placing glass precursor-coated aluminum nitride particles in a sheath and passing them through a roller hearth kiln. This method is suitable when the raw material aluminum nitride powder has a D50 of 10 μm or more, which makes it difficult to flow with a carrier gas. These methods enable rapid heating and cooling. Note that, unlike (a), (b) and (c) involve particle-to-particle contact, but because the particle size is large and the glass thickness is small, aggregation associated with glass melting hardly occurs.

[0036] <6> Applications of glass-coated aluminum nitride powder The applications of glass-coated aluminum nitride powder are not particularly limited, but examples include use as a filler mixed into materials such as polymer materials, greases, adhesives, and paints.

[0037] <7> Polymer molded body The aluminum nitride powder of the present invention can be used to create and use polymer molded articles with high thermal conductivity by filling polymer materials with it as a filler. Furthermore, by filling the polymer material with at least two types of glass-coated aluminum nitride powder with different D50 phases, the filling rate of the glass-coated aluminum nitride powder is increased, making it possible to produce polymer molded articles with even higher thermal conductivity. Examples of polymer materials include resins, rubbers, and elastomers. While there are no particular limitations on the applications of polymer molded articles, examples include heat dissipation components for heat-generating elements such as semiconductors. [Examples]

[0038] Next, embodiments of the present invention will be described with reference to the drawings, in comparison with comparative examples. Note that the materials, quantities, and conditions of each part of the embodiments are illustrative and can be modified as appropriate without departing from the spirit of the invention. Aluminum nitride powders of Comparative Examples 1 to 4, as shown in Table 1, were prepared, and glass-coated aluminum nitride powders of Comparative Examples 5 and 6 and Examples 1 to 9 were manufactured.

[0039] [Table 1]

[0040] (Comparative Example 1) Comparative Example 1 is an uncoated aluminum nitride powder, specifically "A-01-F" (D50 = 1.15 μm, specific surface area 3.06 m²) manufactured by MARUWA Corporation (applicant in this application). 2 It is / g).

[0041] (Comparative Example 2) Comparative Example 2 is an uncoated aluminum nitride powder, specifically "A-04-F" (D50 = 3.98 μm, specific surface area 0.67 m²) manufactured by the same company. 2 It is / g).

[0042] (Comparative Example 3) Comparative Example 3 is an uncoated aluminum nitride powder, specifically "S-30" (D50 = 37.6 μm, specific surface area 0.06 m²) manufactured by the same company. 2 It is / g).

[0043] (Comparative Example 4) Comparative Example 4 is an uncoated aluminum nitride powder, specifically "S-80" (D50 = 82.8 μm, specific surface area 0.03 m²) manufactured by the same company. 2 It is / g).

[0044] (Comparative Example 5) Comparative Example 5 is aluminum nitride powder obtained by coating the aforementioned "A-01-F" as a starting material with glass in accordance with the method of Patent Document 1, as follows. (1) Using SiO2 as the Si source, B2O3 as the B source, Al2O3 as the Al source, lithium carbonate as the Li source, and potassium carbonate as the K source, the materials were blended to obtain oxide concentrations of 71.7 mol%, 24.8 mol%, 0.7 mol%, 2.5 mol%, and 0.3 mol%, respectively, in terms of SiO2, B2O3, Al2O3, Li2O, and K2O. The mixture was melted in a glass melting furnace, cooled, and then dry-ground to produce glass frit with a primary particle size of 0.1 μm. (2) The glass frit from (1) was added to "A-01-F". The amount added was adjusted according to the specific surface area of ​​the AlN powder and the target glass thickness. In this example, the target glass thickness was 9 nm. (3)(2) was placed in a sealed polypropylene container, liquid paraffin and 10 mm diameter alumina balls were added, and the mixture was mixed in a dry ball mill. (4)(3) was filled into a mold with a diameter of 30 mm and molded at a pressure of 10 MPa. (5) The molded bodies from (4) were heated in a box furnace (Motoyama Corporation, Superburn NLT-2025D) at 1350°C in nitrogen for 30 minutes. (6) The molded bodies from (5) were crushed using a jet mill to obtain aluminum nitride powder consisting of glass-coated aluminum nitride particles.

[0045] (Comparative Example 6) Comparative Example 6 is an aluminum nitride powder obtained by using "A-04-F" as a starting material powder and then coating it with glass according to the method of Patent Document 1, as follows. (1) Using SiO2 as the Si source, B2O3 as the B source, and Al2O3 as the Al source, the materials were blended in amounts of 73.4 mol%, 25.4 mol%, and 1.2 mol%, respectively, and melted in a glass melting furnace. After cooling, glass frit with a primary particle size of 0.1 μm was produced by dry grinding. (2) The glass frit from (1) was added to the starting material powder. The amount added was adjusted according to the specific surface area of ​​the AlN powder and the target glass thickness. In this example, the target glass thickness was 9 nm. Subsequently, aluminum nitride powder consisting of glass-coated aluminum nitride particles was obtained in the same manner as in (3) to (6) of Comparative Example 5.

[0046] (Example 1) Example 1 is aluminum nitride powder coated with glass as follows, using "A-01-F" as the starting material. (1) Tetraalkoxysilane modified to be water-soluble was used as the Si source, boric acid as the B source, aluminum nitrate nonahydrate as the Al source, lithium nitrate as the Li source, and potassium nitrate as the K source. These were blended to obtain oxide concentrations of 71.7 mol%, 24.8 mol%, 0.7 mol%, 2.5 mol%, and 0.3 mol%, respectively (same composition as Comparative Example 5), and dissolved in alcohol. (2) Using the same alcohol as in (1) as the dispersion medium, a slurry of "A-01-F" was prepared. The solid content concentration was 10 vol%. After adding "A-01-F" to the dispersion medium, ultrasonic dispersion treatment was performed. (3) (1) was added to (2) and stirred. The amount added was adjusted according to the specific surface area of ​​the AlN powder and the target glass thickness. In this example, the target thickness was 9 nm. (4)(3) was sprayed in a mist using a spray dryer (Büch, B-290) as shown in Figure 1, heated and dried to obtain glass precursor coated aluminum nitride particles. The drying temperature was 220°C, and nitrogen was used as the drying gas. The glass precursor-coated aluminum nitride particles described in (5)(4) were crushed using a dry jet mill (PJM-80, manufactured by Nippon Pneumatic Mfg. Co., Ltd.) as shown in Figure 3(b). The crushing pressure was 0.1 MPa. As shown in Figure 2, glass-coated aluminum nitride particles were obtained by continuously supplying the glass precursor-coated aluminum nitride particles of (6)(5) into a tubular furnace using nitrogen as a carrier gas. The amount of carrier gas was adjusted so that the residence time in the furnace, calculated from the carrier gas flow rate and the inner diameter of the furnace tube, was approximately 30 seconds to 2 minutes. The maximum temperature inside the furnace was set to 1350°C so that the glass precursor-coated aluminum nitride particles supplied into the furnace were heated above the melting point of the composite oxide that forms the glass. The time the glass precursor was in a molten state inside the furnace was approximately 5 to 20 seconds, and when the particles came out of the furnace, the molten state was rapidly cooled and vitrified to become glass-coated aluminum nitride particles.

[0047] (Example 2) Example 2 is an aluminum nitride powder obtained by using "A-04-F" as a starting material powder and then coating it with glass as follows. (1) Tetraalkoxysilane was modified to be water-soluble as the Si source, boric acid as the B source, and aluminum nitrate nonahydrate as the Al source. These were blended to obtain oxide concentrations of 73.4 mol%, 25.4 mol%, and 1.2 mol%, respectively (same composition as Comparative Example 6), and dissolved in alcohol. (2) The same alcohol used in (1) was used as the dispersion medium to prepare a slurry of the starting material powder. The solid content concentration was 10 vol%. After adding the starting material powder to the dispersion medium, ultrasonic dispersion treatment was performed. (3) Add (1) to (2) and stir. The target thickness was 3 nm. (4)(3) was powdered using a spray dryer as shown in Figure 1 to obtain glass precursor-coated aluminum nitride particles. The drying temperature was 150°C, and nitrogen was used as the drying gas. (5)(4) The glass precursor coated aluminum nitride particles were heated in the same manner as in Example 1 to obtain glass coated aluminum nitride particles. The maximum temperature in the furnace was 1500°C.

[0048] (Example 3) Example 3 is a glass-coated aluminum nitride powder, similar to Example 2, except that the target thickness was changed to 6 nm.

[0049] (Example 4) Example 4 is a glass-coated aluminum nitride powder, similar to Example 2, except that the target thickness was changed to 9 nm.

[0050] (Example 5) Example 5 is a glass-coated aluminum nitride powder, similar to Example 2, except that the target thickness was changed to 15 nm.

[0051] (Example 6) Example 6 is a glass-coated aluminum nitride powder, similar to Example 2, except that the target thickness was changed to 30 nm and the solid content concentration of the slurry was set to 5 vol%.

[0052] (Example 7) Example 7 involves classifying "S-30" as described above, resulting in a D50 of 20.5 μm and a specific surface area of ​​0.11 m². 2 The aluminum nitride powder is obtained by first processing a powder in the form of / g, and then treating it with an acid to dissolve impurities other than aluminum nitride, and then coating it with glass as follows. (1) Tetraalkoxysilane modified to be water-soluble was used as the Si source, boric acid as the B source, aluminum nitrate nonahydrate as the Al source, sodium nitrate as the Na source, and potassium nitrate as the K source. These were blended to obtain oxide concentrations of 83.1 mol%, 11.5 mol%, 1.3 mol%, 3.8 mol%, and 0.3 mol%, respectively, and dissolved in alcohol. (2) (1) was added to the starting material powder and prepared into a paste using a rotary-orbit mixer. The amount of (1) added was adjusted according to the specific surface area of ​​the aluminum nitride powder and the target glass thickness. In this example, the target thickness was 9 nm. (3) A film made of polyethylene terephthalate (PET) with a thickness of 0.05 mm was coated with a film applicator to a thickness of 0.5 mm. (4)(3) was placed in a dryer heated to 220°C to remove the solvent and pulverize it, obtaining glass precursor coated aluminum nitride particles. (5)(4) The glass-coated aluminum nitride particles were packed into a sheath and passed through a roller hearth kiln heated to a top temperature of 1350°C in a nitrogen stream to obtain glass-coated aluminum nitride particles. The residence time in the furnace was set to 30 minutes, and the temperature profile in the furnace was adjusted so that the time during which the material was heated above the melting point of the composite oxide forming the glass was 10 minutes or less.

[0053] (Example 8) Example 8 is a glass-coated aluminum nitride powder, similar to Example 7, except that the starting material powder used is "S-30" which has been treated with acid to dissolve impurities other than aluminum nitride.

[0054] (Example 9) Example 9 is a glass-coated aluminum nitride powder, similar to Example 7, except that the starting material powder used is "S-80" which has been treated with acid to dissolve impurities other than aluminum nitride.

[0055] [Properties of glass-coated aluminum nitride powder] 1. Average particle size (median diameter) D50 0.5 g of glass-coated aluminum nitride powder (uncoated for Comparative Examples 1-4) was added to 50 ml of a 0.1% by mass aqueous solution of sodium pyrophosphate. The mixture was dispersed for 3 minutes at 80% power using a US-300E laser analyzer manufactured by Nippon Seiki Seisakusho Co., Ltd. The volume-based particle size distribution was measured using a SALD-2200 laser diffraction particle size analyzer manufactured by Shimadzu Corporation. The D50 [μm] values ​​are shown in Table 1.

[0056] 2. Glass thickness TEM observations were performed on 30 particles with a diameter of D50 [μm] ± 40%. For each particle, eight images were taken at magnifications ranging from 500,000 to 2,000,000, rotated by 45° each time. The glass thickness at the center of each image was measured, and the average of all measurements was calculated. The resulting glass thickness [μm] is shown in Table 1. The observation samples were embedded in resin as needed and thinned using focused ion beam (FIB) processing or other methods. Actual observations were performed using a JEOL JEM-2100F field emission transmission electron microscope. The acceleration voltage was 200kV. Furthermore, the boundary between the glass layer and the AlN particles was determined by the presence or absence of a crystal lattice image (since the glass layer is amorphous, a crystal lattice image is not visible), or by the presence or absence of detection of glass components (mainly Si in this application) by elemental analysis. Figure 4 is the TEM image of Comparative Example 6, Figure 5 is the TEM image of Example 1, Figure 6 is the TEM image of Example 2, and Figure 7 is the TEM image of Example 5. The added white dashed lines indicate the boundary between the aluminum nitride particle surface and the glass.

[0057] 3. Glass coverage Using the TEM images described above, regions with a glass thickness of less than 2 nm were considered to have insufficient coating from a water resistance standpoint and were therefore treated as essentially uncoated. The glass coating rate was then calculated. This glass coating rate is shown in Table 1. In comparative examples 5 and 6, the glass coating rate was low (65% or less) because the glass coating peeled off or broke due to crushing after heat treatment. In contrast, Examples 1-9 had a glass coating rate of 95% or more.

[0058] 4.85℃ water resistance time (1) 10 g of distilled water (Hayashi Pure Chemical Industries, Ltd., GR grade, pH 5.5-6.0) was weighed into a sealed polypropylene container. (2) 1 g of powder was added to (1) and placed in an ultrasonic bath for 3 minutes of dispersion treatment. (3) The container was placed in an 85°C constant temperature bath (ESPEC Corporation, PHP-2J), and the time it took for the pH of the water inside the container to rise to 9 or higher was measured. This procedure was carried out for a maximum of 500 hours. The 85°C water resistance time [h] is shown in Table 1. Comparative Examples 1-4 had a short 85°C water resistance time of less than 1 hour, and Comparative Examples 5 and 6 did not show much improvement in 85°C water resistance time. In contrast, Examples 1-9 showed significantly improved water resistance. In particular, Examples 1, 3-9 had a glass coating rate of 100%, which further improved their water resistance.

[0059] [Fabrication of resin molded products (Application examples 1-8)] The resin molded articles for application examples 1 to 8 shown in Table 2 were manufactured as follows.

[0060] [Table 2]

[0061] (1) A resin composition consisting of bisphenol F type epoxy resin (ADEKA Corporation, EP-4901H), imidazole type curing agent (ADEKA Corporation, EH-2021), dispersant, and diluent PGMEA (propylene glycol monomethyl ether acetate) was kneaded for 2 minutes in a rotary-orbit mixer (Sinky Corporation, ARV-200). The rotation speed was 1000 rpm and the orbital speed was 2000 rpm. (2) The resin composition of (1) was mixed with at least two types of glass-coated aluminum nitride powder (uncoated for Comparative Examples 1-4) with different D50 values, in the predetermined proportions shown in Table 2, so that it would make up 75 vol% or 80 vol% after curing, and kneaded for 2 minutes. Then, degassing treatment was performed while kneading under reduced pressure of 50 Torr for 2 minutes. (3) The powder-based resin composition from (2) was applied to two PET films with a thickness of 0.05 mm using a film applicator to a thickness of 0.8 mm. (4)(3) was dried at 90°C for 30 minutes to remove the diluting solvent. Two sheets made from the powder-based resin compositions of (5) and (4) were stacked so that the sides not in contact with the PET substrate faced each other, and were heat-pressed at 120°C × 10 MPa × 30 minutes to obtain a resin molded sheet measuring 5 cm in length, 5 cm in width, and 0.7 mm in thickness.

[0062] [Properties of resin composites] 1. Thermal conductivity Three 1cm x 1cm samples were cut from the resin molded sheet obtained by the method described above, and their thermal diffusivity was measured using the flash method (NETZSCH LFA-467). The thermal conductivity was calculated by multiplying the measured value by the specific heat and density of the sheet, and the average value of the three samples was used. The thermal conductivity [W / (mK)] is shown in Table 2. Application example 6 has high thermal conductivity because it lacks a glass coating, while applications 1-3 have equally high thermal conductivity despite having a glass coating because the glass thickness is small. Applications 4 and 5 have slightly lower thermal conductivity due to the slightly larger glass thickness, but are still practical depending on the application. Similarly, application example 8 has high thermal conductivity because it lacks a glass coating, while application example 7 has equally high thermal conductivity despite having a glass coating because the glass thickness is small.

[0063] 2. Water resistance test (water resistance time at 95°C) and change in thermal conductivity after the water resistance test. (1) 90g of distilled water (Hayashi Pure Chemical Industries, Ltd., GR grade, pH 5.5-6.0) was weighed into a 100mL airtight polypropylene container. (2) Three samples measuring 1 cm x 1 cm, cut from a resin molded sheet, were placed in (1). (3)(2) was placed in a 95°C constant temperature bath (ESPEC Corporation, PHP-2J), and the time it took for the pH of the water in the container to reach 8 or higher was measured. This was carried out for a maximum of 1000 hours. The 95°C water resistance time [h] is shown in Table 2. (4) The thermal conductivity of samples was measured after the pH reached 8 or higher or after 1000 hours, and the percentage change from the measurement value before the water resistance test was calculated. This percentage change in thermal conductivity [%] is shown in Table 2. Application examples 6 and 8 lack a glass coating, resulting in a shorter 95°C water resistance time and a larger rate of change (decrease) in thermal conductivity. In contrast, applications 1-5 and 7, due to the presence of a glass coating, showed significant improvements in both 95°C water resistance time and thermal conductivity change rate.

[0064] It should be noted that the present invention is not limited to the embodiments described above, and can be appropriately modified and implemented without departing from the spirit of the invention.

Claims

1. The polymer material is molded using a filler containing first glass-coated aluminum nitride particles having a first average particle size D50, in which the particle surface of the aluminum nitride particles is coated with glass, and second glass-coated aluminum nitride particles having a second average particle size D50, which is larger than the first average particle size D50. The first glass-coated aluminum nitride particles and the second glass-coated aluminum nitride particles are polymer molded articles having a glass coating rate of 95% or more on the particle surface and a glass thickness of 2 nm or more.

2. The polymer molded article according to claim 1, wherein the second glass-coated aluminum nitride particles are blended in a larger amount than the first glass-coated aluminum nitride particles.

3. The polymer molded article according to claim 1, wherein the glass thickness of the first glass-coated aluminum nitride particles and the second glass-coated aluminum nitride particles is less than 10 nm.

4. The polymer molded body according to any one of claims 1 to 3, wherein the polymer molded body is a heat dissipation member.

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