JP7495582B1 - Glass-coated aluminum nitride powder, its manufacturing method, and polymer molded product - Google Patents
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Abstract
【課題】粒子表面をほぼ完全にガラスで被覆した耐水性の高いガラス被覆窒化アルミニウム粉末と、該粉末をフィラーとして含む耐水性の高い高分子成形体を提供する。
【解決手段】窒化アルミニウム粒子の粒子表面がガラスで被覆されたガラス被覆窒化アルミニウム粒子からなるガラス被覆窒化アルミニウム粉末であって、窒化アルミニウム粒子のＤ５０が０．５～１００μｍであり、ガラス厚さが２～１００ｎｍであり、粒子表面のガラス被覆率が９５％以上である。窒化アルミニウム粒子とガラス前駆体とを含む混合液を霧状に又は面上に広げた状態で乾燥させることにより、ガラス前駆体被覆窒化アルミニウム粒子を作製し、加熱してガラス前駆体をガラス化することにより、ガラス被覆窒化アルミニウム粒子を作製する。
【選択図】図５
The present invention provides a highly water-resistant glass-coated aluminum nitride powder in which the particle surfaces are almost completely coated with glass, and a highly water-resistant polymer molded article containing the powder as a filler.
[Solution] A glass-coated aluminum nitride powder consisting of glass-coated aluminum nitride particles in which the particle surfaces of aluminum nitride particles are coated with glass, the aluminum nitride particles have a D50 of 0.5 to 100 μm, a glass thickness of 2 to 100 nm, and a glass coverage of the particle surfaces of 95% or more. The glass precursor-coated aluminum nitride particles are produced by drying a mixed liquid containing aluminum nitride particles and a glass precursor in a mist form or while spread on a surface, and the glass precursor is vitrified by heating to produce the glass-coated aluminum nitride particles.
[Selected figure] Figure 5
Description
本発明は、ガラス被覆窒化アルミニウム粉末とそれを含む高分子成形体に関するものである。 The present invention relates to glass-coated aluminum nitride powder and a polymer molded body containing the same.
窒化アルミニウム粉末は、その優れた熱伝導性を活かし、樹脂、グリース、接着剤、塗料などの材料に混合するフィラーとして利用されている。しかし、窒化アルミニウムは、当該混合前のみならず、当該混合後であっても条件次第では、大気中の水分によって熱伝導性の低い水酸化アルミニウムに変化するとともに、腐食性のアンモニアを発生させる。そこで、窒化アルミニウム粉末をガラス等で被覆することにより、耐水性の向上を図ることが検討されている。 Taking advantage of its excellent thermal conductivity, aluminum nitride powder is used as a filler to be mixed into materials such as resins, greases, adhesives, and paints. However, depending on the conditions, not only before but also after mixing, aluminum nitride can change into aluminum hydroxide, which has low thermal conductivity, due to moisture in the air and generate corrosive ammonia. Therefore, it is being considered to improve the water resistance of aluminum nitride powder by covering it with glass or the like.
特許文献１には、窒化アルミニウム粒子と、ｄ５０が０．３～５０μｍであるガラスフリットとを混合し、その混合物を坩堝（るつぼ）に入れるか又はペレットに賦形してガラスフリットのガラス転移温度以上かつ２０００℃以下の温度で熱処理し、窒化アルミニウム粒子に対してガラスフリットを被覆して被覆粒子を得、その被覆粒子を解砕して、ｄ５０が１０～２００μｍのガラス被覆窒化アルミニウム粒子を製造する方法が開示されている。実施例のガラス被覆厚は１０～６６０ｎｍである。
特許文献２には、ｄ５０が１０～２００μｍである窒化アルミニウム粒子と、ガラス成分を含むｄ５０が０．３～５０μｍの組成物粉との混合物をメカノケミカル法により剪断力を付与しながら混合し、その混合物を坩堝（るつぼ）に入れてガラス成分のガラス転移温度以上かつ２０００℃以下の温度で熱処理し、その熱処理物を解砕して、ガラス被覆窒化アルミニウム粒子を製造する方法が開示されている。 Patent Document 2 discloses a method for producing glass-coated aluminum nitride particles by mixing a mixture of aluminum nitride particles having a d50 of 10 to 200 μm with a composition powder containing a glass component and having a d50 of 0.3 to 50 μm while applying shear force by a mechanochemical method, placing the mixture in a crucible and heat-treating it at a temperature equal to or higher than the glass transition temperature of the glass component and equal to or lower than 2000°C, and crushing the heat-treated product.
特許文献３には、窒化アルミニウム粒子を攪拌しながら有機シリコーン化合物を噴霧などで添加して乾式混合することにより、窒化アルミニウム粒子の表面を有機シリコーン化合物により覆い、その覆われた窒化アルミニウム粒子を３００℃以上１０００℃未満の温度で加熱して、珪素含有酸化物（シリカ又は珪素アルミ複合酸化物）被覆窒化アルミニウム粒子を製造する方法が開示されている。
珪素含有酸化物被覆窒化アルミニウム粒子は、炭素原子の含有量が１０００質量ｐｐｍ未満であり、珪素含有酸化物被膜のＬＥＩＳ分析による被覆率が１５％以上１００％以下であり、比表面積に対する珪素原子の含有量が特定の関係式を満たすとされている。
Patent Document 3 discloses a method for producing aluminum nitride particles coated with a silicon-containing oxide (silica or silicon-aluminum composite oxide), in which an organosilicon compound is added by spraying or the like while stirring the aluminum nitride particles, followed by dry mixing to cover the surfaces of the aluminum nitride particles with the organosilicon compound, and the covered aluminum nitride particles are heated at a temperature of 300° C. or higher and lower than 1000° C.
The aluminum nitride particles coated with silicon-containing oxide have a carbon atom content of less than 1,000 ppm by mass, a coverage rate of the silicon-containing oxide coating according to LEIS analysis of 15% or more and 100% or less, and the content of silicon atoms relative to the specific surface area satisfies a specific relationship.
しかし、特許文献１，２の製造方法は、混合物を坩堝（るつぼ）に入れるか又はペレットに賦形して熱処理する、すなわち粒子どうしが接触している状態で熱処理するものであるから、ガラス融液が窒化アルミニウム粒子間に大きい毛管力で浸透し、粒子が凝集する。その凝集度合いは、窒化アルミニウム粒子が小径（例えばＤ５０が０．５～５μｍ程度）であるほど、大きくなる。そのため、その後の解砕に相当量のエネルギーを投入しなければならず、その結果、被覆されたガラス層の剥離や破壊が起こり、ガラス被覆率が低下して、耐水性が低下するという問題がある。
However, in the manufacturing methods of
また、特許文献３の低エネルギーイオン散乱（ＬＥＩＳ）分析は、表層０．１ｎｍ程度の浅い領域の情報となるため、極僅かでもシリカ又は珪素アルミ複合酸化物が付着していると検出されるところ、被覆率は実施例６の８８％が最大である。また、被覆率について「より好ましくは９５％以下であり…（中略）…９５％超えであると、熱伝導率が低下する場合があることが分った」との記載はあるが、９５％超えの具体例は示されていない。よって、ほぼ完全（９５％以上）な被覆は達成できていないと推認される。 Furthermore, the low energy ion scattering (LEIS) analysis in Patent Document 3 provides information on a shallow region of about 0.1 nm from the surface, and therefore detects even the slightest adhesion of silica or silicon-aluminum composite oxide, with the maximum coverage being 88% in Example 6. In addition, although there is a description regarding the coverage that "it is more preferably 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 is presumed that nearly complete coverage (95% or more) has not been achieved.
そこで、本発明の目的は、粒子表面をほぼ完全にガラスで被覆した耐水性の高いガラス被覆窒化アルミニウム粉末と、該粉末をフィラーとして含む耐水性の高い高分子成形体を提供することにある。 The object of the present invention is to provide a highly water-resistant glass-coated aluminum nitride powder in which the particle surfaces are almost completely coated with glass, and a highly water-resistant polymer molded article that contains the powder as a filler.
［１］窒化アルミニウム粒子の粒子表面がガラスで被覆されたガラス被覆窒化アルミニウム粒子からなるガラス被覆窒化アルミニウム粉末であって、窒化アルミニウム粒子のＤ５０が０．５～１００μｍであり、ガラス厚さが２～１００ｎｍであり、粒子表面のガラス被覆率が９５％以上であるガラス被覆窒化アルミニウム粉末。 [1] A glass-coated aluminum nitride powder consisting of glass-coated aluminum nitride particles in which the particle surfaces of the aluminum nitride particles are coated with glass, in which the D50 of the aluminum nitride particles is 0.5 to 100 μm, the glass thickness is 2 to 100 nm, and the glass coverage of the particle surfaces is 95% or more.
［２］前記窒化アルミニウム粒子のＤ５０が１０μｍ未満である［１］記載のガラス被覆窒化アルミニウム粉末。 [2] The glass-coated aluminum nitride powder according to [1], in which the aluminum nitride particles have a D50 of less than 10 μm.
［３］前記ガラス厚さが１０ｎｍ未満である［１］又は［２］記載のガラス被覆窒化アルミニウム粉末。 [3] The glass-coated aluminum nitride powder according to [1] or [2], wherein the glass thickness is less than 10 nm.
［４］前記ガラス被覆率が１００％である［１］～［３］のいずれか一項に記載のガラス被覆窒化アルミニウム粉末。
ガラス被覆率の測定は、ＴＥＭ分析によるものとし、ガラス厚さが２ｎｍ未満の領域は耐水性の観点からは被覆不十分であることから実質的に被覆無しとみなすものとする。
[4] The glass-coated aluminum nitride powder according to any one of [1] to [3], wherein the glass coverage is 100%.
The glass coverage is measured by TEM analysis, and regions where the glass thickness is less than 2 nm are considered to be substantially uncovered since they are insufficiently covered from the viewpoint of water resistance.
［５］前記［１］～［４］のいずれか一項に記載のガラス被覆窒化アルミニウム粉末をフィラーとして含む高分子材料で成形された高分子成形体。 [5] A polymer molded body made of a polymer material containing the glass-coated aluminum nitride powder described in any one of [1] to [4] above as a filler.
［６］前記［１］～［４］のいずれか一項に記載のガラス被覆窒化アルミニウム粉末のＤ５０が相異なる少なくとも２種をフィラーとして含む高分子材料で成形された高分子成形体。 [6] A polymer molded body made of a polymer material containing at least two types of glass-coated aluminum nitride powder having different D50 values as a filler, the glass-coated aluminum nitride powder being described in any one of [1] to [4] above.
［７］前記高分子成形体が放熱部材である［５］記載の高分子成形体。 [7] The polymer molded product according to [5], which is a heat dissipation member.
［８］前記高分子成形体が放熱部材である［６］記載の高分子成形体。 [8] The polymer molded product according to [6], which is a heat dissipation member.
［９］窒化アルミニウム粒子とガラス前駆体とを含む混合液を霧状に又は面上に広げた状態で乾燥させることにより、ガラス前駆体で粒子表面が被覆されたガラス前駆体被覆窒化アルミニウム粒子からなるガラス前駆体被覆窒化アルミニウム粉末を作製するガラス前駆体被覆工程と、
前記ガラス前駆体被覆窒化アルミニウム粒子をガラス前駆体が溶融する温度以上に加熱してガラス前駆体をガラス化することにより、ガラスで粒子表面が被覆されたガラス被覆窒化アルミニウム粒子からなるガラス被覆窒化アルミニウム粉末を作製する熱処理工程と
を含むガラス被覆窒化アルミニウム粉末の製造方法。
[9] A glass precursor coating step of producing a glass precursor-coated aluminum nitride powder consisting of glass precursor-coated aluminum nitride particles whose particle surfaces are coated with a glass precursor by drying a mixed liquid containing aluminum nitride particles and a glass precursor in a mist form or in a state where the mixed liquid is spread on a surface;
and a heat treatment step of heating the glass precursor-coated aluminum nitride particles to a temperature equal to or higher than the temperature at which the glass precursor melts to vitrify the glass precursor, thereby producing glass-coated aluminum nitride powder consisting of glass-coated aluminum nitride particles whose particle surfaces are coated with glass.
［１０］前記ガラス前駆体被覆工程が、前記混合液を空中に噴霧するスプレードライによるものである［９］記載のガラス被覆窒化アルミニウム粉末の製造方法。 [10] The method for producing glass-coated aluminum nitride powder according to [9], wherein the glass precursor coating process is carried out by spray drying, in which the mixed liquid is sprayed into the air.
［１１］前記ガラス前駆体被覆工程が、前記混合液を受け部材の面上に膜状又は分散状に広げて行うものである［９］記載のガラス被覆窒化アルミニウム粉末の製造方法。 [11] The method for producing glass-coated aluminum nitride powder described in [9], in which the glass precursor coating process is carried out by spreading the mixed liquid in a film or dispersed form on the surface of the receiving member.
［１２］前記ガラス前駆体被覆工程と熱処理工程との間で、凝集したガラス前駆体被覆窒化アルミニウム粒子を解砕する解砕工程を行う［９］～［１１］のいずれか一項に記載のガラス被覆窒化アルミニウム粉末の製造方法。 [12] A method for producing a glass-coated aluminum nitride powder according to any one of [9] to [11], comprising a crushing step for crushing aggregated glass precursor-coated aluminum nitride particles between the glass precursor coating step and the heat treatment step.
［１３］前記熱処理工程が、ガラス前駆体被覆窒化アルミニウム粒子をキャリアガスに分散させた状態で管状炉に連続的に投入して行うものである［９］～［１２］のいずれか一項に記載のガラス被覆窒化アルミニウム粉末の製造方法。 [13] The method for producing glass-coated aluminum nitride powder according to any one of [9] to [12], in which the heat treatment step is carried out by continuously feeding glass precursor-coated aluminum nitride particles dispersed in a carrier gas into a tubular furnace.
［１４］前記熱処理工程が、ガラス前駆体被覆窒化アルミニウム粒子をロータリーキルンに連続的に供給して行うものである［９］～［１２］のいずれか一項に記載のガラス被覆窒化アルミニウム粉末の製造方法。 [14] A method for producing a glass-coated aluminum nitride powder according to any one of [9] to [12], in which the heat treatment step is carried out by continuously supplying glass precursor-coated aluminum nitride particles to a rotary kiln.
［１５］前記熱処理工程が、ガラス前駆体被覆窒化アルミニウム粒子をさやに入れてローラーハースキルンに通して行うものである［９］～［１２］のいずれか一項に記載のガラス被覆窒化アルミニウム粉末の製造方法。 [15] The method for producing glass-coated aluminum nitride powder according to any one of [9] to [12], in which the heat treatment step is carried out by placing the glass precursor-coated aluminum nitride particles in a sheath and passing the sheath through a roller hearth kiln.
［１６］窒化アルミニウム粒子とガラス前駆体とを含む混合液を霧状に又は面上に広げた状態で乾燥させるとともにガラス前駆体が溶融する温度以上に加熱することにより、ガラス前駆体がガラス化したガラスで粒子表面が被覆されたガラス被覆窒化アルミニウム粒子からなるガラス被覆窒化アルミニウム粉末を作製するガラス被覆窒化アルミニウム粉末の製造方法。 [16] A method for producing glass-coated aluminum nitride powder, which comprises drying a mixed liquid containing aluminum nitride particles and a glass precursor in a mist form or while spreading it on a surface, and heating it to a temperature equal to or higher than the temperature at which the glass precursor melts, to produce glass-coated aluminum nitride powder made of glass-coated aluminum nitride particles whose particle surfaces are coated with glass produced by vitrifying the glass precursor.
本発明によれば、粒子表面をほぼ完全にガラスで被覆した耐水性の高いガラス被覆窒化アルミニウム粉末と、該粉末をフィラーとして含む耐水性の高い高分子成形体を提供することができる。 The present invention provides highly water-resistant glass-coated aluminum nitride powder, the particle surfaces of which are almost completely coated with glass, and highly water-resistant polymer molded articles that contain the powder as a filler.
＜１＞原料の窒化アルミニウム粒子
原料の窒化アルミニウム粉子は、窒化アルミニウム以外の物質、例えば、製造方法由来の希土類化合物、カルシウム化合物等を含有していてもよいが、その量はできるだけ少ないほうがよい。含有量が多いと、ガラスに取り込まれた際のガラスの組成変化が大きくなり、それによりガラスの融点が上昇して溶融されにくくなったり、ガラス化範囲からはずれてガラス状にならなくなったりする。ガラス被覆率９５％以上とするために、窒化アルミニウム以外の物質を０．５重量％以下に減らすことが好ましい。さらに好ましくは０．２重量％以下である。含有量を減らす方法としては、無機酸や有機酸を用いた溶出処理が知られている。
原料の窒化アルミニウム粉末の平均粒径（メジアン径）Ｄ５０が、０．５μｍ以上であると凝集しにくいため使用しやすく、１００μｍ以下であると高分子成形体を薄くしやすい。Ｄ５０が１０μｍ未満であると、ガラス前駆体被覆工程を前記スプレードライにより行いやすく、また、熱処理工程を前記キャリアガスに分散させた状態で行いやすい点で、好ましい。
<1> Aluminum nitride particles as raw material The aluminum nitride powder as raw material may contain substances other than aluminum nitride, such as rare earth compounds and calcium compounds derived from the manufacturing method, but the amount should be as small as possible. If the content is large, the composition of the glass will change significantly when it is incorporated into glass, which will increase the melting point of the glass and make it difficult to melt, or it will fall outside the vitrification range and not become vitrified. In order to achieve a glass coverage 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 is 0.2% by weight or less. As a method for reducing the content, leaching treatment using inorganic acids or organic acids is known.
When the average particle size (median diameter) D50 of the raw material aluminum nitride powder is 0.5 μm or more, it is difficult to aggregate and easy to use, and when it is 100 μm or less, it is easy to make the polymer molded body thin. When D50 is less than 10 μm, it is preferable in that the glass precursor coating step is easily performed by the spray drying and the heat treatment step is easily performed in a state where the aluminum nitride powder is dispersed in the carrier gas.
＜２＞ガラス
ガラスとしては、特に限定されないが、ケイ酸塩ガラス、ホウケイ酸ガラス、ビスマス系ガラス、錫－リン酸系ガラス、バナジウム系ガラス、鉛系ガラス等を例示できる。
ガラスは、ＳｉＯ２、Ａｌ２Ｏ３及びＢ２Ｏ３から選ばれる２成分以上を含有することが好ましい。
ガラスは、熱膨張係数を低減させるために、ＺｎＯ成分を含有することができる。
ガラスは、Ｎａ２Ｏ、Ｋ２Ｏなどのアルカリ金属の酸化物を含有することができるが、耐湿性の観点からは、その含有量は少ない方が好ましい。
ガラスは、ＣａＯ、ＳｒＯ、ＭｇＯ、ＢａＯ、ＳｎＯなどの任意成分を含んでいてもよい。
<2> Glass The glass is not particularly limited, but examples thereof include silicate glass, borosilicate glass, bismuth-based glass, tin-phosphate-based glass, vanadium-based glass, and lead-based glass.
The glass preferably contains two or more components selected from SiO 2 , Al 2 O 3 and B 2 O 3 .
The glass may contain a ZnO component to reduce the thermal expansion coefficient.
The glass can contain oxides of alkali metals such as Na 2 O and K 2 O, but from the viewpoint of moisture resistance, the content is preferably small.
The glass may contain optional components such as CaO, SrO, MgO, BaO, and SnO.
ガラス厚さが、２ｎｍ以上であると耐水性の観点からはガラスの被覆が十分となり、１００ｎｍ以下であるとガラスの介在による熱伝導率の低下を抑制できる。ガラス厚さが１０ｎｍ未満であると、ガラスの介在による熱伝導率の低下をさらに抑制できる点で好ましい。 If the glass thickness is 2 nm or more, the glass coating is sufficient from the viewpoint of water resistance, and if it is 100 nm or less, the decrease in thermal conductivity due to the presence of glass can be suppressed. If the glass thickness is less than 10 nm, it is preferable in that the decrease in thermal conductivity due to the presence of glass can be further suppressed.
ガラス被覆率が９５％以上であると、耐水性が向上する。ガラス被覆率が１００％であると、耐水性がさらに向上する。 If the glass coverage is 95% or more, water resistance is improved. If the glass coverage is 100%, water resistance is further improved.
＜３＞ガラス前駆体被覆工程
本発明におけるガラス前駆体被覆工程は、窒化アルミニウム粒子とガラス前駆体とを含む混合液を霧状に又は面上に広げた状態で乾燥させるため、乾燥が急速に行われる。ガラス前駆体の被覆は、乾燥処理に伴って起こるガラス成分の各元素の塩の析出を急速に進行させることが肝要である。ガラス成分の各元素の塩の飽和溶解度はそれぞれ異なり、乾燥処理時には飽和溶解度の小さい順に析出していくこととなるが、乾燥処理に長時間をかけると析出後のガラス成分の各元素の分布状態の不均質性が高まる。従って、それを熱処理して均質な組成の溶融ガラスを得ようとすると、より高温でより長時間加熱保持する必要が出てくる。本発明によれば前記のとおり乾燥が急速に行われることで、析出後のガラス成分の各元素の分布状態の不均質性を小さくでき、低温・短時間の熱処理でも均質な組成の溶融ガラスが得られることから、エネルギーコストおよび生産効率の面で有利となる。
<3> Glass precursor coating process In the glass precursor coating process of the present invention, the mixed liquid containing aluminum nitride particles and the glass precursor is dried in a mist or in a state of being spread on a surface, so that drying is performed rapidly. It is essential for the coating of the glass precursor to rapidly advance the precipitation of the salts of the elements of the glass components that occurs with the drying process. The saturation solubility of the salts of the elements of the glass components is different, and they are precipitated in order of decreasing saturation solubility during the drying process, but if the drying process is performed for a long time, the heterogeneity of the distribution state of each element of the glass components after precipitation increases. Therefore, if it is intended to heat treat it to obtain molten glass of a homogeneous composition, it becomes necessary to heat and hold it at a higher temperature for a longer period of time. According to the present invention, the drying is performed rapidly as described above, so that the heterogeneity of the distribution state of each element of the glass components after precipitation can be reduced, and molten glass of a homogeneous composition can be obtained even with low-temperature and short-time heat treatment, which is advantageous in terms of energy cost and production efficiency.
ガラス前駆体被覆工程としては、特に限定されないが、次のものを例示できる。
（ア）前記混合液を空中に噴霧するスプレードライによるもの。同方法は、原料の窒化アルミニウム粉末が、沈降しにくいＤ５０が１０μｍ未満である場合に適する。
（イ）前記混合液を受け部材の面上に膜状又は分散状に広げて行うもの。同方法は、原料の窒化アルミニウム粉末が、沈降しやすいＤ５０が１０μｍ以上である場合に適する。受け部材としては、特に限定されないが、ＰＥＴフィルム、ガラス板、セラミック板等を例示できる。
The glass precursor coating step is not particularly limited, but the following can be exemplified.
(A) By spray drying, the mixture is sprayed into the air. This method is suitable when the raw aluminum nitride powder has a D50 of less than 10 μm, which is difficult to settle.
(a) The mixture is spread on the surface of a receiving member in a film or dispersion state. This method is suitable when the raw aluminum nitride powder has a D50 of 10 μm or more, which is prone to settling. The receiving member is not particularly limited, but examples thereof include a PET film, a glass plate, and a ceramic plate.
＜４＞解砕工程（必要時）
本発明におけるガラス前駆体被覆工程は、窒化アルミニウム粒子が１個１個分散しやすい。そして、例えばスプレードライ時に噴霧された液滴１個につき、窒化アルミニウム粒子１個が含まれているのが理想である。しかし、図３（ａ）に示すように、原料スラリーの固形分濃度や噴霧の条件によっては、１個の液滴に複数個の窒化アルミニウム粒子が含まれることがあり、乾燥後は複数個が集まった凝集粒子となる。その場合は、必要に応じて熱処理工程の前に解砕処理を行うことが好ましい。
図３（ｂ）に示すように、粒子同士の結合部に存在していた、ガラス成分元素の混合塩は、解砕処理によってどちらかの粒子に多く持っていかれることが予想され、場合によっては窒化アルミニウム粒子の表面が露出してしまうことも考えられる。
図３（ｃ）に示すように、ガラス前駆体コート粉においてコート層に凹凸ができていたとしても、熱処理によりコート層を溶融させることによって、窒化アルミニウム粒子表面に濡れ拡がり、再び均質なコート層となる。粒子毎でコート厚さに若干の差が生じるが、平均すればほぼ設計どおりの厚さとなる。
<4> Crushing process (if necessary)
In the glass precursor coating process of the present invention, aluminum nitride particles are easily dispersed one by one. Ideally, one droplet sprayed during spray drying contains one aluminum nitride particle. However, as shown in FIG. 3(a), depending on the solid content concentration of the raw material slurry and the spraying conditions, one droplet may contain multiple aluminum nitride particles, and after drying, the particles become aggregated particles consisting of multiple particles. In that case, it is preferable to perform a crushing process before the heat treatment process as necessary.
As shown in FIG. 3( b ), it is expected that the mixed salt of glass component elements that was present at the bond between the particles will be carried away by one of the particles in a larger amount by the crushing treatment, and in some cases, it is thought that the surface of the aluminum nitride particles may become exposed.
As shown in Fig. 3(c), even if the coating layer of the glass precursor coating powder has unevenness, the coating layer is melted by heat treatment, so that it spreads over the aluminum nitride particle surface and becomes a homogeneous coating layer again. Although there are slight differences in the coating thickness for each particle, on average it is almost the designed thickness.
＜５＞熱処理工程
熱処理工程としては、特に限定されないが、次のものを例示できる。
（ア）ガラス前駆体被覆窒化アルミニウム粒子をキャリアガスに分散させた状態で管状炉に連続的に投入して行うもの。粒子どうしが接触しないため好ましい。同方法は、原料の窒化アルミニウム粉末が、キャリアガスで流動しやすいＤ５０が１０μｍ未満である場合に適する。
（イ）ガラス前駆体被覆窒化アルミニウム粒子をロータリーキルンに連続的に供給して行うもの。同方法は、原料の窒化アルミニウム粉末が、キャリアガスで流動しにくいＤ５０が１０μｍ以上である場合に適する。
（ウ）ガラス前駆体被覆窒化アルミニウム粒子をさやに入れてローラーハースキルンに通して行うもの。同方法は、原料の窒化アルミニウム粉末が、キャリアガスで流動しにくいＤ５０が１０μｍ以上である場合に適する。
これらの方法により、急速加熱＆冷却を実現できる。なお、（イ）及び（ウ）は、（ア）と異なり、粒子どうしが接触することとなるが、粒径が大きく、ガラス厚さも小さいので、ガラス溶融に伴う凝集はほぼ起こらない。
<5> Heat Treatment Step The heat treatment step is not particularly limited, but the following can be exemplified.
(A) The glass precursor-coated aluminum nitride particles are continuously fed into a tubular furnace in a state where they are dispersed in a carrier gas. This is preferred because the particles do not come into contact with each other. This method is suitable when the raw aluminum nitride powder has a D50 of less than 10 μm, which makes it easy for the raw material aluminum nitride powder to flow in the carrier gas.
(a) Continuously supplying the glass precursor-coated aluminum nitride particles to a rotary kiln. This method is suitable for aluminum nitride powder raw material with a D50 of 10 μm or more, which is difficult to flow with a carrier gas.
(c) Glass precursor-coated aluminum nitride particles are placed in a sheath and passed through a roller hearth kiln. This method is suitable when the raw aluminum nitride powder has a D50 of 10 μm or more and is difficult to flow with a carrier gas.
These methods can realize rapid heating and cooling. Note that (B) and (C) are different from (A) in that the particles come into contact with each other, but because the particle size is large and the glass thickness is small, aggregation that accompanies glass melting hardly occurs.
＜６＞ガラス被覆窒化アルミニウム粉末の用途
ガラス被覆窒化アルミニウム粉末の用途としては、特に限定されないが、高分子材料、グリース、接着剤、塗料などの材料に混合するフィラーを例示できる。
<6> Uses of Glass-Coated Aluminum Nitride Powder Uses of the glass-coated aluminum nitride powder are not particularly limited, but examples include fillers to be mixed into materials such as polymer materials, greases, adhesives, and paints.
＜７＞高分子成形体
本発明の窒化アルミニウム粉末はフィラーとして高分子材料に充填することにより、熱伝導率が高い高分子成形体を作製し使用することができる。
また、ガラス被覆窒化アルミニウム粉末のＤ５０が相異なる少なくとも２種を高分子材料に充填することにより、ガラス被覆窒化アルミニウム粉末の充填率が高くなるため、熱伝導率がさらに高い高分子成形体を作製することができる。
高分子材料としては、樹脂、ゴム、エラストマー等を例示できる。高分子成形体の用途としては、特に限定されないが、半導体等の発熱体の放熱部材等を例示できる。
<7> Polymer Molded Articles By filling a polymer material with the aluminum nitride powder of the present invention as a filler, a polymer molded article having high thermal conductivity can be produced and used.
Furthermore, by filling a polymer material with at least two types of glass-coated aluminum nitride powder having different D50, the filling rate of the glass-coated aluminum nitride powder increases, making it possible to produce a polymer molding with even higher thermal conductivity.
Examples of the polymeric material include resin, rubber, elastomer, etc. Applications of the polymeric molded article are not particularly limited, but examples include heat dissipation members for heat generating bodies such as semiconductors.
次に、本発明を具体化した実施例について、比較例と比較しつつ、図面を参照して説明する。なお、実施例の各部の材料、数量及び条件は例示であり、発明の要旨から逸脱しない範囲で適宜変更できる。
表１に示す比較例１～４の窒化アルミニウム粉末を用意し、比較例５，６及び実施例１～９のガラス被覆窒化アルミニウム粉末を作製した。
Next, examples embodying the present invention will be described with reference to the drawings, while comparing them with comparative examples. Note that the materials, quantities and conditions of each part in the examples are merely examples, and can be appropriately changed without departing from the gist of the invention.
Aluminum nitride powders of Comparative Examples 1 to 4 shown in Table 1 were prepared, and glass-coated aluminum nitride powders of Comparative Examples 5 and 6 and Examples 1 to 9 were produced.
（比較例１）
比較例１は、被覆無しの窒化アルミニウム粉末であり、ＭＡＲＵＷＡ社（本願出願人）製の「Ａ－０１－Ｆ」（Ｄ５０＝１．１５μｍ、比表面積３．０６ｍ２／ｇ）である。
(Comparative Example 1)
Comparative Example 1 is an uncoated aluminum nitride powder, "A-01-F" (D50=1.15 μm, specific surface area 3.06 m 2 /g) manufactured by Maruwa Co., Ltd. (the applicant of the present application).
（比較例２）
比較例２は、被覆無しの窒化アルミニウム粉末であり、同社製の「Ａ－０４－Ｆ」（Ｄ５０＝３．９８μｍ、比表面積０．６７ｍ２／ｇ）である。
(Comparative Example 2)
Comparative Example 2 was an uncoated aluminum nitride powder, "A-04-F" (D50=3.98 μm, specific surface area 0.67 m 2 /g) manufactured by the same company.
（比較例３）
比較例３は、被覆無しの窒化アルミニウム粉末であり、同社製の「Ｓ－３０」（Ｄ５０＝３７．６μｍ、比表面積０．０６ｍ２／ｇ）である。
(Comparative Example 3)
Comparative Example 3 is an uncoated aluminum nitride powder, "S-30" (D50=37.6 μm, specific surface area 0.06 m 2 /g) manufactured by the same company.
（比較例４）
比較例４は、被覆無しの窒化アルミニウム粉末であり、同社製の「Ｓ－８０」（Ｄ５０＝８２．８μｍ、比表面積０．０３ｍ２／ｇ）である。
(Comparative Example 4)
Comparative Example 4 is an uncoated aluminum nitride powder, "S-80" (D50=82.8 μm, specific surface area 0.03 m 2 /g) manufactured by the same company.
（比較例５）
比較例５は、出発原料としての前記「Ａ－０１－Ｆ」に、次のように前記特許文献１の方法に準じてガラス被覆した窒化アルミニウム粉末である。
（１）Ｓｉ源としてＳｉＯ２、Ｂ源としてＢ２Ｏ３、Ａｌ源としてＡｌ２Ｏ３、Ｌｉ源として炭酸リチウム、Ｋ源として炭酸カリウム、を用い、酸化物（ＳｉＯ２、Ｂ２Ｏ３、Ａｌ２Ｏ３、Ｌｉ２Ｏ、Ｋ２Ｏ）換算でそれぞれ７１．７ｍｏｌ％、２４．８ｍｏｌ％、０．７ｍｏｌ％、２．５ｍｏｌ％、０．３ｍｏｌ％となるように配合して、ガラス溶融炉において溶融し、冷却後に乾式粉砕することにより、１次粒子径０．１μｍのガラスフリットを作製した。
（２）前記「Ａ－０１－Ｆ」に（１）のガラスフリットを添加した。添加量は、ＡｌＮ粉末の比表面積と狙いのガラス厚さに応じて調整した。本例の狙いのガラス厚さは９ｎｍとした。
（３）（２）をポリプロピレン製の密閉容器に入れ、流動パラフィンと直径１０ｍｍのアルミナボールを加えて、乾式ボールミルで混合した。
（４）（３）を直径３０ｍｍの金型に充填し、１０ＭＰａの圧力で成形した。
（５）（４）の成形体をボックス炉（株式会社モトヤマ、スーパーバーンＮＬＴ－２０２５Ｄ）にて窒素中１３５０℃で３０分間加熱した。
（６）（５）の成形体をジェットミルで解砕処理して、ガラス被覆窒化アルミニウム粒子からなる窒化アルミニウム粉末を得た。
(Comparative Example 5)
Comparative Example 5 is an aluminum nitride powder obtained by coating the starting material "A-01-F" with glass in accordance with the method of
(1) SiO 2 as a Si source, B 2 O 3 as a B source, Al 2 O 3 as an Al source, lithium carbonate as a Li source, and potassium carbonate as a K source were used and mixed to be 71.7 mol %, 24.8 mol %, 0.7 mol %, 2.5 mol %, and 0.3 mol %, respectively, calculated as oxides ( SiO 2 , B 2 O 3 , Al 2 O 3 , Li 2 O, and K 2 O). The mixture was melted in a glass melting furnace, cooled, and then dry-pulverized to produce a glass frit having a primary particle size of 0.1 μm.
(2) The glass frit of (1) was added to the above "A-01-F". The amount added was adjusted according to the specific surface area of the AlN powder and the target glass thickness. The target glass thickness in this example was 9 nm.
(3) (2) was placed in a polypropylene airtight container, and liquid paraffin and alumina balls having a diameter of 10 mm were added thereto, followed by mixing in a dry ball mill.
(4) (3) was filled into a mold having a diameter of 30 mm and molded under a pressure of 10 MPa.
(5) The compact of (4) was heated in nitrogen at 1350° C. for 30 minutes in a box furnace (Motoyama Corporation, Superburn NLT-2025D).
(6) The molded body of (5) was crushed in a jet mill to obtain aluminum nitride powder consisting of glass-coated aluminum nitride particles.
（比較例６）
比較例６は、前記「Ａ－０４－Ｆ」に酸を用いて窒化アルミニウム以外の不純物の溶出処理を行ったもの、を出発原料粉末にして、次のように特許文献１の方法に準じてガラス被覆した窒化アルミニウム粉末である。
（１）Ｓｉ源としてＳｉＯ２、Ｂ源としてＢ２Ｏ３、Ａｌ源としてＡｌ２Ｏ３、を用い、それぞれ７３．４ｍｏｌ％、２５．４ｍｏｌ％、１．２ｍｏｌ％となるように配合して、ガラス溶融炉において溶融し、冷却後に乾式粉砕することにより、１次粒子径０．１μｍのガラスフリットを作製した。
（２）前記出発原料粉末に（１）のガラスフリットを添加した。添加量は、ＡｌＮ粉末の比表面積と狙いのガラス厚さに応じて調整した。本例の狙いのガラス厚さは９ｎｍとした。
その後は、比較例５の（３）～（６）と同じようにして、ガラス被覆窒化アルミニウム粒子からなる窒化アルミニウム粉末を得た。
(Comparative Example 6)
Comparative Example 6 is an aluminum nitride powder obtained by using the above-mentioned "A-04-F" as a starting raw material powder, which was subjected to a treatment of dissolving impurities other than aluminum nitride using an acid, and coating the resulting powder with glass in accordance with the method described in
(1) SiO 2 as a Si source, B 2 O 3 as a B source, and Al 2 O 3 as an Al source were used, and were mixed to be 73.4 mol %, 25.4 mol %, and 1.2 mol %, respectively. The mixture was melted in a glass melting furnace, cooled, and then dry-pulverized to produce a glass frit having a primary particle size of 0.1 μm.
(2) The glass frit of (1) was added to the starting raw material powder. The amount added was adjusted according to the specific surface area of the AlN powder and the target glass thickness. The target glass thickness in this example was 9 nm.
Thereafter, the same procedures as in (3) to (6) of Comparative Example 5 were carried out to obtain an aluminum nitride powder consisting of glass-coated aluminum nitride particles.
（実施例１）
実施例１は、出発原料としての前記「Ａ－０１－Ｆ」に、次のようにガラス被覆した窒化アルミニウム粉末である。
（１）Ｓｉ源としてテトラアルコキシシランを変性して水溶性にしたもの、Ｂ源としてホウ酸、Ａｌ源として硝酸アルミニウム九水和物、Ｌｉ源として硝酸リチウム、Ｋ源として硝酸カリウム、を用い、酸化物（ＳｉＯ２、Ｂ２Ｏ３、Ａｌ２Ｏ３、Ｌｉ２Ｏ、Ｋ２Ｏ）換算でそれぞれ７１．７ｍｏｌ％、２４．８ｍｏｌ％、０．７ｍｏｌ％、２．５ｍｏｌ％、０．３ｍｏｌ％となるように配合して（比較例５と同一組成）、アルコールに溶解させた。
（２）（１）で使用したアルコールと同じものを分散媒として用い、「Ａ－０１－Ｆ」のスラリーを調製した。固形分濃度は１０ｖｏｌ％とした。分散媒へ「Ａ－０１－Ｆ」を投入後に超音波による分散処理を行った。
（３）（２）に（１）を加えて撹拌した。添加量は、ＡｌＮ粉末の比表面積と狙いのガラス厚さに応じて調整した。本実施例での狙い厚さは９ｎｍとした。
（４）（３）を、図１に示すように、スプレードライヤー（ビュッヒ製、Ｂ－２９０）で霧状に噴霧し加熱乾燥して粉体化し、ガラス前駆体被覆窒化アルミニウム粒子を得た。乾燥温度は２２０℃とし、乾燥ガスには窒素を使用した。
（５）（４）のガラス前駆体被覆窒化アルミニウム粒子を、図３（ｂ）に示すように、乾式ジェットミル（日本ニューマチック工業製、ＰＪＭ－８０）で解砕処理した。粉砕圧は０．１ＭＰａとした。
（６）（５）のガラス前駆体被覆窒化アルミニウム粒子を、図２に示すように、窒素をキャリアガスとして管状炉の中へ連続的に供給することでガラス被覆窒化アルミニウム粒子を得た。キャリアガス流量と炉心管内径から計算される炉内滞留時間が３０秒～２分程度になるよう、キャリアガス量を調整した。炉内へ供給されたガラス前駆体被覆窒化アルミニウム粒子が、ガラスを形成する複合酸化物の融点以上に加熱されるよう、炉内の最高温度を１３５０℃にした。炉内でガラス前駆体が融液となっている時間は５～２０秒程度であり、炉外に粒子が出てくると、融液は急冷されてガラス化し、ガラス被覆窒化アルミニウム粒子となる。
Example 1
In Example 1, the starting material "A-01-F" was coated with glass as follows to produce aluminum nitride powder.
(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 mixed to give oxide equivalents ( SiO2 , B2O3 , Al2O3 , Li2O , K2O ) of 71.7 mol%, 24.8 mol%, 0.7 mol%, 2.5 mol%, and 0.3 mol%, respectively (same composition as in Comparative Example 5), and dissolved in alcohol.
(2) Using the same alcohol as used in (1) as a dispersion medium, a slurry of "A-01-F" was prepared. The solid content was 10 vol%. After "A-01-F" was added to the dispersion medium, a dispersion treatment was performed using ultrasonic waves.
(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 form using a spray dryer (B-290, manufactured by Buchi Co., Ltd.) and dried by heating to obtain glass precursor-coated aluminum nitride particles, as shown in Fig. 1. The drying temperature was 220°C, and nitrogen was used as the drying gas.
(5) The glass precursor-coated aluminum nitride particles of (4) were crushed in a dry jet mill (PJM-80, manufactured by Nippon Pneumatic Mfg. Co., Ltd.) as shown in Fig. 3(b) at a crushing pressure of 0.1 MPa.
(6) The glass precursor-coated aluminum nitride particles of (5) were continuously supplied into a tubular furnace using nitrogen as a carrier gas, as shown in FIG. 2, to obtain glass-coated aluminum nitride particles. 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 about 30 seconds to 2 minutes. The maximum temperature in the furnace was set to 1350° C. so that the glass precursor-coated aluminum nitride particles supplied into the furnace were heated to a temperature equal to or higher than the melting point of the composite oxide that forms the glass. The time that the glass precursor remained in the furnace as a molten liquid was about 5 to 20 seconds, and when the particles came out of the furnace, the molten liquid was quenched and vitrified to become glass-coated aluminum nitride particles.
（実施例２）
実施例２は、前記「Ａ－０４－Ｆ」に酸を用いて窒化アルミニウム以外の不純物の溶出処理を行ったもの、を出発原料粉末にして、次のようにガラス被覆した窒化アルミニウム粉末である。
（１）Ｓｉ源としてテトラアルコキシシランを変性して水溶性にしたもの、Ｂ源としてホウ酸、Ａｌ源として硝酸アルミニウム九水和物、を用い、酸化物（ＳｉＯ２、Ｂ２Ｏ３、Ａｌ２Ｏ３）換算でそれぞれ７３．４ｍｏｌ％、２５．４ｍｏｌ％、１．２ｍｏｌ％となるように配合して（比較例６と同一組成）、アルコールに溶解させた。
（２）（１）で使用したアルコールと同じものを分散媒として用い、前記出発原料粉末のスラリーを調製した。固形分濃度は１０ｖｏｌ％とした。分散媒へ前記出発原料粉末を投入後に超音波による分散処理を行った。
（３）（２）に（１）を加えて撹拌した。狙い厚さは３ｎｍとした。
（４）（３）を、図１に示すように、スプレードライヤーで粉体化し、ガラス前駆体被覆窒化アルミニウム粒子を得た。乾燥温度は１５０℃とし、乾燥ガスには窒素を使用した。
（５）（４）のガラス前駆体被覆窒化アルミニウム粒子を、実施例１と同様に加熱してガラス被覆窒化アルミニウム粒子を得た。炉内の最高温度は１５００℃とした。
Example 2
In Example 2, the starting raw material powder was the above-mentioned "A-04-F" which had been subjected to a treatment using acid to dissolve impurities other than aluminum nitride, and the resulting aluminum nitride powder was then glass-coated as follows.
(1) Tetraalkoxysilane modified to be water-soluble was used as the Si source, boric acid was used as the B source, and aluminum nitrate nonahydrate was used as the Al source. These were mixed so that the oxide amounts ( SiO2 , B2O3 , Al2O3 ) were 73.4 mol%, 25.4 mol%, and 1.2 mol%, respectively (the same composition as in Comparative Example 6), and dissolved in alcohol.
(2) The same alcohol as used in (1) was used as a dispersion medium to prepare a slurry of the starting raw material powder. The solid content was 10 vol %. After the starting raw material powder was put into the dispersion medium, it was subjected to a dispersion treatment by ultrasonic waves.
(3) (1) was added to (2) and stirred. The target thickness was 3 nm.
(4) (3) was powdered in a spray dryer as shown in Fig. 1 to obtain glass precursor-coated aluminum nitride particles. The drying temperature was 150°C, and nitrogen was used as the drying gas.
(5) The glass precursor-coated aluminum nitride particles of (4) were heated in the same manner as in Example 1 to obtain glass-coated aluminum nitride particles. The maximum temperature in the furnace was set to 1500°C.
（実施例３）
実施例３は、狙い厚さを６ｎｍに変えた以外は、実施例２と同じようにガラス被覆した窒化アルミニウム粉末である。
Example 3
Example 3 is an aluminum nitride powder glass-coated in the same manner as Example 2, except that the target thickness was changed to 6 nm.
（実施例４）
実施例４は、狙い厚さを９ｎｍに変えた以外は、実施例２と同じようにガラス被覆した窒化アルミニウム粉末である。
Example 4
Example 4 is an aluminum nitride powder glass-coated in the same manner as Example 2, except that the target thickness was changed to 9 nm.
（実施例５）
実施例５は、狙い厚さを１５ｎｍに変えた以外は、実施例２と同じようにガラス被覆した窒化アルミニウム粉末である。
Example 5
Example 5 is an aluminum nitride powder glass-coated in the same manner as Example 2, except that the target thickness was changed to 15 nm.
（実施例６）
実施例６は、狙い厚さを３０ｎｍに変えたこと、およびスラリーの固形分濃度を５ｖｏｌ％にした以外は、実施例２と同じようにガラス被覆した窒化アルミニウム粉末である。
Example 6
Example 6 is an aluminum nitride powder coated with glass in the same manner as in Example 2, except that the target thickness was changed to 30 nm and the solids concentration of the slurry was changed to 5 vol %.
（実施例７）
実施例７は、前記「Ｓ－３０」に分級を施して、Ｄ５０が２０．５μｍで、比表面積が０．１１ｍ２／ｇの粉末とし、さらに酸を用いて窒化アルミニウム以外の不純物の溶出処理を行ったもの、を出発原料粉末にして、次のようにガラス被覆した窒化アルミニウム粉末である。
（１）Ｓｉ源としてテトラアルコキシシランを変性して水溶性にしたもの、Ｂ源としてホウ酸、Ａｌ源として硝酸アルミニウム九水和物、Ｎａ源として硝酸ナトリウム、Ｋ源として硝酸カリウム、を用い、酸化物（ＳｉＯ２、Ｂ２Ｏ３、Ａｌ２Ｏ３、Ｎａ２Ｏ、Ｋ２Ｏ）換算でそれぞれ８３．１ｍｏｌ％、１１．５ｍｏｌ％、１．３ｍｏｌ％、３．８ｍｏｌ％、０．３ｍｏｌ％となるように配合して、アルコールに溶解させた。
（２）前記出発原料粉末に（１）を添加し、自転公転ミキサーでペースト状に調製した。（１）の添加量は、窒化アルミニウム粉末の比表面積と狙いのガラス厚さに応じて調整した。本実施例での狙い厚さは９ｎｍとした。
（３）厚さ０．０５ｍｍのポリエチレンテレフタレート（ＰＥＴ）製のフィルム上に、フィルムアプリケータを用いて、厚さが０．５ｍｍになるように塗布した。
（４）（３）を２２０℃に加熱した乾燥機に入れて溶媒を除去して粉体化し、ガラス前駆体被覆窒化アルミニウム粒子を得た。
（５）（４）のガラス被覆窒化アルミニウム粒子をさやに充填し、窒素気流中でトップ温度１３５０℃に加熱したローラーハースキルンに通すことで、ガラス被覆窒化アルミニウム粒子を得た。炉内滞留時間は３０分とし、うちガラスを形成する複合酸化物の融点以上に加熱される時間が１０分以下になるよう、炉内の温度プロファイルを調整した。
(Example 7)
In Example 7, the "S-30" was classified to obtain a powder with a D50 of 20.5 μm and a specific surface area of 0.11 m2 /g, and impurities other than aluminum nitride were further dissolved using acid. This was used as the starting raw material powder, and the aluminum nitride powder was glass-coated 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 mixed to give oxide equivalents ( SiO2 , B2O3 , Al2O3 , Na2O , K2O ) 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 raw material powder, and the mixture was made into a paste using a planetary centrifugal mixer. The amount of (1) added was adjusted according to the specific surface area of the aluminum nitride powder and the target glass thickness. The target thickness in this example was 9 nm.
(3) The mixture was applied to a polyethylene terephthalate (PET) film having a thickness of 0.05 mm using 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 powderize the mixture, thereby obtaining glass precursor-coated aluminum nitride particles.
(5) The glass-coated aluminum nitride particles of (4) were packed into a sheath and passed through a roller hearth kiln heated to a top temperature of 1350° C. in a nitrogen gas flow 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 particles were heated to the melting point of the composite oxide that forms the glass was 10 minutes or less.
（実施例８）
実施例８は、出発原料粉末として前記「Ｓ－３０」に酸を用いて窒化アルミニウム以外の不純物の溶出処理を行ったもの、を用いた以外は、実施例７と同じようにガラス被覆した窒化アルミニウム粉末である。
(Example 8)
Example 8 is an aluminum nitride powder coated with glass in the same manner as Example 7, except that the starting raw material powder used was the "S-30" described above, which was treated with an acid to dissolve impurities other than aluminum nitride.
（実施例９）
実施例９は、出発原料粉末として前記「Ｓ－８０」に酸を用いて窒化アルミニウム以外の不純物の溶出処理を行ったもの、を用いた以外は、実施例７と同じようにガラス被覆した窒化アルミニウム粉末である。
Example 9
Example 9 is an aluminum nitride powder coated with glass in the same manner as Example 7, except that the starting raw material powder used was the "S-80" described above, which had been treated with acid to dissolve impurities other than aluminum nitride.
［ガラス被覆窒化アルミニウム粉末の特性］
１．平均粒径（メジアン径）Ｄ５０
０．１質量％のピロリン酸ナトリウム水溶液５０ｍｌに、各例のガラス被覆窒化アルミニウム粉末（比較例１～４は被覆無し）０．５ｇを投入し、株式会社日本精機製作所製の型式ＵＳ－３００Ｅを使用して出力８０％で３分間分散させたものを、株式会社島津製作所製のレーザー回折式粒度分布測定装置、型式ＳＡＬＤ－２２００を使用して、体積基準の粒度分布を測定した。そのＤ５０［μｍ］を表１に示す。
[Characteristics of glass-coated aluminum nitride powder]
1. Average particle size (median size) D50
0.5 g of the glass-coated aluminum nitride powder of each example (comparative examples 1 to 4 were uncoated) was added to 50 ml of 0.1% by mass aqueous solution of sodium pyrophosphate, and dispersed for 3 minutes at 80% output using a US-300E model manufactured by Nippon Seiki Seisakusho Co., Ltd. The particle size distribution based on volume was measured using a laser diffraction particle size distribution analyzer, model SALD-2200, manufactured by Shimadzu Corporation. The D50 [μm] is shown in Table 1.
２．ガラス厚さ
Ｄ５０［μｍ］±４０％の粒子３０個のＴＥＭ観察を行った。１つの粒子につき、倍率５００，０００～２，０００，０００の写真を４５°ずつ回転させて８か所撮影し、各写真の中央部のガラス厚さを測定し、全ての測定値の平均を求めた。このガラス厚さ［μｍ］を表１に示す。
なお、観察用サンプルは、必要に応じて樹脂に包埋し集束イオンビーム（ＦＩＢ）加工などで薄片化処理を行った。実際の観察は、日本電子株式会社の電界放出型透過電子顕微鏡ＪＥＭ－２１００Ｆで行った。加速電圧は２００ｋＶである。
また、ガラス層とＡｌＮ粒子との境界は、結晶格子像の有無（ガラス層はアモルファスのため結晶格子像が見えない）、もしくは元素分析にてガラス成分（本願の場合は、主にＳｉ）の検出の有無、により判別した。図４は比較例６、図５は実施例１、図６は実施例２、図７は実施例５の各ＴＥＭ写真であり、加入した白色破線は窒化アルミニウム粒子表面とガラスとの境界を示している。
2. Glass thickness Thirty particles with D50 [μm] ±40% were observed by TEM. For each particle, eight photographs were taken at magnifications of 500,000 to 2,000,000, rotating the particle by 45° each time, and the glass thickness at the center of each photograph was measured, and the average of all the measured values was calculated. The glass thickness [μm] is shown in Table 1.
The samples for observation were embedded in resin and thinned by focused ion beam (FIB) processing, etc., as necessary. Actual observations were performed using a field emission transmission electron microscope JEM-2100F manufactured by JEOL Ltd. The accelerating voltage was 200 kV.
The boundary between the glass layer and the AlN particles was determined by the presence or absence of a crystal lattice image (the glass layer is amorphous, so the crystal lattice image is not visible) or the presence or absence of detection of glass components (mainly Si in this case) by elemental analysis. Figure 4 shows the TEM photographs of Comparative Example 6, Figure 5 shows the TEM photographs of Example 1, Figure 6 shows the TEM photographs of Example 2, and Figure 7 shows the TEM photographs of Example 5, in which the white dashed lines indicate the boundaries between the surfaces of the aluminum nitride particles and the glass.
３．ガラス被覆率
上述のＴＥＭ写真を用いて、ガラス厚さが２ｎｍ未満の領域は耐水性の観点からは被覆不十分であることから実質的に被覆無しとみなして、ガラス被覆率を算出した。このガラス被覆率を表１に示す。
比較例５，６は、熱処理後の解砕によってガラス被覆の剥離や破壊が起こったため、ガラス被覆率が６５％以下と低かった。
これに対し、実施例１～９は、ガラス被覆率が９５％以上であった。
3. Glass Coverage Using the above TEM photograph, the glass coverage was calculated assuming that the area with a glass thickness of less than 2 nm was substantially uncovered since the coverage was insufficient from the viewpoint of water resistance. The glass coverage is shown in Table 1.
In Comparative Examples 5 and 6, the glass coating was peeled off or broken due to crushing after the heat treatment, and therefore the glass coating rate was low at 65% or less.
In contrast, in Examples 1 to 9, the glass coverage was 95% or more.
４．８５℃耐水時間
（１）ポリプロピレン製の密閉容器に蒸留水（林純薬工業株式会社、ＧＲグレード、ｐＨ５．５～６．０）を１０ｇ秤量した。
（２）（１）に粉末１ｇを添加して超音波バスに入れ、３分間の分散処理を行った。
（３）８５℃の恒温槽（エスペック株式会社、ＰＨＰ－２Ｊ）に入れ、容器内の水のｐＨが９以上になるまでの時間を計測した。最長５００ｈまで実施した。この８５℃耐水時間［ｈ］を表１に示す。
比較例１～４は、８５℃耐水時間が１時間未満と短く、比較例５，６でも、８５℃耐水時間がさほど改善されていない。
これに対し、実施例１～９は、耐水性が著しく改善された。特に実施例１，３～９は、ガラス被覆率が１００％であったため、耐水性が更に改善された。
4. Water resistance time at 85° C. (1) 10 g of distilled water (Hayashi Pure Chemical Industries, Ltd., GR grade, pH 5.5 to 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 dispersion treatment for 3 minutes.
(3) The container was placed in a thermostatic chamber (PHP-2J, Espec Corporation) at 85° C., and the time until the pH of the water in the container reached 9 or more was measured. This was carried out for up to 500 hours. The 85° C. water resistance time [h] is shown in Table 1.
In Comparative Examples 1 to 4, the 85° C. water resistance time is short, being less than 1 hour, and even in Comparative Examples 5 and 6, the 85° C. water resistance time is not significantly improved.
In contrast, the water resistance was significantly improved in Examples 1 to 9. In particular, in Examples 1 and 3 to 9, the glass coverage was 100%, and therefore the water resistance was further improved.
［樹脂成形体の作製（応用例１～８）］
表２に示す応用例１～８の樹脂成形体を、次のように作製した。
[Preparation of resin molded body (Application Examples 1 to 8)]
The resin molded bodies of Application Examples 1 to 8 shown in Table 2 were produced as follows.
（１）ビスフェノールＦ型エポキシ樹脂（株式会社ＡＤＥＫＡ、ＥＰ－４９０１Ｈ）、イミダゾール型硬化剤（株式会ＡＤＥＫＡ、ＥＨ－２０２１）、分散剤、及び希釈溶剤ＰＧＭＥＡ（プロピレングリコールモノメチルエーテルアセテート）からなる樹脂組成物を、自転公転ミキサー（株式会社シンキー、ＡＲＶ－２００）で２分間混練した。自転速度は１０００ｒｐｍで公転速度は２０００ｒｐｍとした。
（２）（１）の樹脂組成物に、各例のガラス被覆窒化アルミニウム粉末（比較例１～４は被覆無し）のＤ５０が相異なる少なくとも２種を表２に示す所定の割合で配合したものを、硬化後に７５ｖｏｌ％もしくは８０ｖｏｌ％になるようにフィラーとして添加して、２分間混錬した。その後に５０Ｔｏｒｒの減圧条件で２分間混錬しながら脱泡処理した。
（３）（２）の粉末配合樹脂組成物を、厚さ０．０５ｍｍのＰＥＴ製のフィルム２枚の上に、フィルムアプリケータを用いて、厚さが０．８ｍｍになるように塗布した。
（４）（３）を９０℃で３０分間乾燥して希釈溶剤を除去した。
（５）（４）の粉末配合樹脂組成物からなる２枚のシートを、ＰＥＴ基材と接していない面同士が向かい合うように重ね合わせ、１２０℃×１０ＭＰａ×３０分の条件で熱プレスして縦５ｃｍ×横５ｃｍ×厚さ０．７ｍｍの樹脂成形体シートを得た。
(1) A resin composition consisting of a bisphenol F type epoxy resin (ADEKA Corporation, EP-4901H), an imidazole type curing agent (ADEKA Corporation, EH-2021), a dispersant, and a dilution solvent PGMEA (propylene glycol monomethyl ether acetate) was kneaded for 2 minutes in a planetary centrifugal mixer (Thinky Corporation, ARV-200). The rotation speed was 1000 rpm and the revolution speed was 2000 rpm.
(2) At least two kinds of glass-coated aluminum nitride powders (Comparative Examples 1 to 4 are uncoated) having different D50 were mixed in the prescribed ratios shown in Table 2 to the resin composition of (1), and the mixture was added as a filler so that the content after curing was 75 vol % or 80 vol %, and kneaded for 2 minutes. Then, the mixture was degassed while kneading for 2 minutes under reduced pressure of 50 Torr.
(3) The powder-blended resin composition (2) was applied onto two 0.05 mm-thick PET films using a film applicator to a thickness of 0.8 mm.
(4) (3) was dried at 90° C. for 30 minutes to remove the dilution solvent.
(5) Two sheets made of the powder-blended resin composition of (4) were stacked together with the surfaces not in contact with the PET substrate facing each other, and heat-pressed at 120°C x 10 MPa x 30 minutes to obtain a resin molded sheet measuring 5 cm long x 5 cm wide x 0.7 mm thick.
［樹脂複合体の特性］
１．熱伝導率
上記の方法で得られた樹脂成形体シートから縦１ｃｍ×横１ｃｍのサンプルを３枚切り出し、熱拡散率をフラッシュ法（ＮＥＴＺＳＣＨ製ＬＦＡ－４６７を使用）で測定した。測定値にシートの比熱と密度を掛け合わせて、熱伝導率を算出し、３枚の平均値を採用した。この熱伝導率［Ｗ／（ｍＫ）］を表２に示す。
応用例６はガラス被覆が無いため熱伝導率が高いのに対して、応用例１～３はガラス被覆が有ってもガラス厚さが小さいため熱伝導率は同等に高く、応用例４，５はガラス厚さがやや大きいことで熱伝導率が若干低下しているが用途により実用になる。
同様に、応用例８はガラス被覆が無いため熱伝導率が高いのに対して、応用例７はガラス被覆が有ってもガラス厚さが小さいため熱伝導率は同等に高い。
[Characteristics of resin composite]
1. Thermal Conductivity Three samples measuring 1 cm long x 1 cm wide were cut out from the resin molded sheet obtained by the above method, and the thermal diffusivity was measured by the flash method (using LFA-467 manufactured by NETZSCH). The measured value was multiplied by the specific heat and density of the sheet to calculate the thermal conductivity, and the average value of the three sheets was used. The thermal conductivity [W/(mK)] is shown in Table 2.
Application example 6 has a high thermal conductivity because there is no glass coating, whereas application examples 1 to 3 have equally high thermal conductivity because there is a glass coating but the glass thickness is small. Application examples 4 and 5 have a slightly larger glass thickness, resulting in a slightly lower thermal conductivity, but may be practical depending on the application.
Similarly, Application Example 8 has a high thermal conductivity because there is no glass coating, whereas Application Example 7 has a glass coating but a small glass thickness, so the thermal conductivity is equally high.
２．耐水試験（９５℃耐水時間）及び耐水試験後の熱伝導率変化
（１）容量１００ｍＬのポリプロピレン製の密閉容器に蒸留水（林純薬工業株式会社、ＧＲグレード、ｐＨ５．５～６．０）を９０ｇ秤量した。
（２）（１）に、樹脂成形体シートから切り出した縦１ｃｍ×横１ｃｍのサンプルを３枚投入した。
（３）（２）を９５℃の恒温槽（エスペック株式会社、ＰＨＰ－２Ｊ）に入れ、容器内の水のｐＨが８以上になるまでの時間を計測した。最長１０００ｈまで実施した。この９５℃耐水時間［ｈ］を表２に示す。
（４）ｐＨが８以上もしくは１０００ｈ経過後のサンプルの熱伝導率を測定し、耐水性試験前の測定値からの変化率を算出した。この熱伝導率変化率［％］を表２に示す。
応用例６，８はガラス被覆が無いため、９５℃耐水時間が短く、熱伝導率変化率（低下）が大きい。
これに対し、応用例１～５，７はガラス被覆が有るため、９５℃耐水時間、熱伝導率変化率ともに著しく改善された。
2. Water resistance test (95°C water resistance time) and change in thermal conductivity after water resistance test (1) 90 g of distilled water (Hayashi Pure Chemical Industries, Ltd., GR grade, pH 5.5 to 6.0) was weighed into a 100 mL polypropylene airtight container.
(2) Three samples, each measuring 1 cm in length and 1 cm in width, cut out from the resin molded sheet were placed in (1).
(3) (2) was placed in a thermostatic chamber (PHP-2J, ESPEC Corporation) at 95°C, and the time until the pH of the water in the container reached 8 or more was measured. This was carried out for up to 1000 hours. The 95°C water resistance time [h] is shown in Table 2.
(4) The thermal conductivity of the samples with a pH of 8 or more or after 1000 hours had elapsed was measured, and the rate of change from the measured value before the water resistance test was calculated. The rate of change in thermal conductivity [%] is shown in Table 2.
Application Examples 6 and 8 have no glass coating, so the 95°C water resistance time is short and the rate of change (decrease) in thermal conductivity is large.
In contrast, since Application Examples 1 to 5 and 7 have a glass coating, both the 95° C. water resistance time and the rate of change in thermal conductivity were significantly improved.
なお、本発明は前記実施例に限定されるものではなく、発明の要旨から逸脱しない範囲で適宜変更して具体化することができる。 The present invention is not limited to the above-mentioned examples, and can be modified as appropriate without departing from the spirit of the invention.
Claims (16)
前記ガラス前駆体被覆窒化アルミニウム粒子をガラス前駆体が溶融する温度以上に加熱してガラス前駆体をガラス化することにより、ガラスで粒子表面が被覆されたガラス被覆窒化アルミニウム粒子からなるガラス被覆窒化アルミニウム粉末を作製する熱処理工程と
を含むガラス被覆窒化アルミニウム粉末の製造方法。 a glass precursor coating step of producing a glass precursor-coated aluminum nitride powder consisting of glass precursor-coated aluminum nitride particles whose particle surfaces are coated with a glass precursor by drying a mixed liquid containing aluminum nitride particles and a glass precursor in a mist form or in a state where the mixed liquid is spread on a surface;
and a heat treatment step of heating the glass precursor-coated aluminum nitride particles to a temperature equal to or higher than the temperature at which the glass precursor melts to vitrify the glass precursor, thereby producing glass-coated aluminum nitride powder consisting of glass-coated aluminum nitride particles whose particle surfaces are coated with glass.
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| JP2001270788A (en) | 2000-03-28 | 2001-10-02 | Ngk Insulators Ltd | Sintered compact of aluminum nitride |
| JP6340443B2 (en) | 2006-09-26 | 2018-06-06 | オプティス ワイヤレス テクノロジー エルエルシー | User equipment and transmission method |
| WO2019124147A1 (en) | 2017-12-21 | 2019-06-27 | 昭和電工株式会社 | Glass-coated aluminum nitride particles, method for producing same, and heat dissipating resin composition containing same |
| WO2019235234A1 (en) | 2018-06-06 | 2019-12-12 | 昭和電工株式会社 | Method for producing glass-coated aluminum nitride particles, and method for producing heat-dissipating resin composition containing said glass-coated aluminum nitride particles |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001270788A (en) | 2000-03-28 | 2001-10-02 | Ngk Insulators Ltd | Sintered compact of aluminum nitride |
| JP6340443B2 (en) | 2006-09-26 | 2018-06-06 | オプティス ワイヤレス テクノロジー エルエルシー | User equipment and transmission method |
| WO2019124147A1 (en) | 2017-12-21 | 2019-06-27 | 昭和電工株式会社 | Glass-coated aluminum nitride particles, method for producing same, and heat dissipating resin composition containing same |
| WO2019235234A1 (en) | 2018-06-06 | 2019-12-12 | 昭和電工株式会社 | Method for producing glass-coated aluminum nitride particles, and method for producing heat-dissipating resin composition containing said glass-coated aluminum nitride particles |
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