JP2023098163A - Method for producing silicon-containing oxide-coated aluminum nitride particles and method for producing resin composition - Google Patents

Abstract

To provide a method for producing silicon-containing oxide-coated aluminum nitride particles that maintain high thermal conductivity of aluminum nitride particles and have excellent moisture resistance with at least one coating, and a method for producing a resin composition containing the silicon-containing oxide-coated aluminum nitride particles produced by the production method. A method is provided for producing silicon-containing oxide-coated aluminum nitride particles comprising aluminum nitride particles and a silicon-containing oxide coating film covering the surface of the aluminum nitride particles. The method includes a first step of controlling an amount of water per unit volume of a reaction field to be 1.5 g/m3 or more, a second step of covering the surface of the aluminum nitride particles with an organosilicone compound containing a structure shown by the formula (1) in the reaction field given after the amount of water is controlled, and a third step of heating the aluminum nitride particles covered with the organosilicone compound at a predetermined temperature.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a method for producing silicon-containing oxide-coated aluminum nitride particles and a method for producing a resin composition, and more particularly to a method for producing silicon-containing oxide-coated aluminum nitride particles and a silicon-containing oxide produced by the production method. The present invention relates to a method for producing a resin composition containing material-coated aluminum nitride particles.

Aluminum nitride has high thermal conductivity and excellent electrical insulation. Therefore, aluminum nitride is promising as a filler for resin compositions used in products such as heat dissipation sheets and sealing materials for electronic parts. However, aluminum nitride reacts with moisture to cause hydrolysis and transform into aluminum hydroxide with low thermal conductivity. Aluminum nitride also generates corrosive ammonia during hydrolysis.

Hydrolysis of aluminum nitride also proceeds with atmospheric moisture. As a result, products containing aluminum nitride not only suffer from deterioration in moisture resistance and thermal conductivity under high temperature and high humidity conditions, but also suffer from corrosion due to ammonia generated by hydrolysis of aluminum nitride. There is concern about deterioration.

Techniques for improving the moisture resistance of aluminum nitride include a method of forming a layer composed of Si—Al—O—N on the surface of aluminum nitride powder (see, for example, Patent Document 1), and a method of applying a silicate treatment agent to the surface of aluminum nitride powder. and a coupling agent (see, for example, Patent Document 2), a method of treating with a silicate treatment agent to leave organic groups on the surface of the aluminum nitride powder (see, for example, Patent Document 3), and aluminum nitride particles. A method of surface modification using a specific acidic phosphate (see, for example, Patent Document 4) has been proposed.

The moisture-proof aluminum nitride powder of Patent Document 1 is coated with a silicate ester layer on the surface of the aluminum nitride powder, and then fired at a high temperature of 350 to 1000 ° C. to form a layer composed of Si-Al-O-N on the surface. forming. The aluminum nitride-based powder of Patent Document 2 forms a coating layer on the surface by performing a high-temperature heat treatment after surface treatment with a silicate treatment agent and a coupling agent. The aluminum nitride powder of Patent Document 3 is subjected to heat treatment at a temperature not exceeding 90° C. after surface treatment with a silicate treatment agent to leave organic groups, thereby improving compatibility with resin. The surface-modified particles of Patent Document 4 have improved moisture resistance due to aluminum nitride particles surface-modified with a specific acid phosphate.

Japanese Patent Publication No. 07-507760 JP 2004-083334 A JP 2006-290667 A JP 2015-71730 A WO2020/040309

However, the prior art has the following problems.
The aluminum nitride powder described above has a reaction layer of Si--Al--O--N, a coating layer formed of a silicate treatment agent and a coupling agent, a surface modification layer, etc., in order to improve moisture resistance. As a result, improvement in moisture resistance is recognized, but it is not yet at a sufficient level, and conversely, the coating used as a means for improving moisture resistance often reduces the original thermal conductivity of aluminum nitride. Furthermore, there is a problem that it is difficult to mix the filler in various materials at a high filling rate.
In order to solve the above-described problems, in the production method of Patent Document 5, aluminum nitride particles are coated with a specific organosilicon compound by a specific method. As a result, improvement in moisture resistance is recognized, but further improvement in moisture resistance is required.

The present invention has been made to solve the above-described problems, and provides silicon-containing oxide-coated aluminum nitride particles that maintain high thermal conductivity of aluminum nitride particles and have excellent moisture resistance after being coated at least once. Provided are a production method that can be produced, and a production method of a resin composition containing silicon-containing oxide-coated aluminum nitride particles produced by the production method.

As a result of intensive studies, the present inventors have found that the above problems can be solved by coating aluminum nitride particles with a specific organosilicon compound by a specific method, and have completed the present invention. That is, the present invention has the following configurations.

（式（１）中、Ｒは炭素数が１以上４以下のアルキル基である。）
［２］前記第３工程の加熱温度は３００℃以上９００℃以下であり、前記珪素含有酸化物被膜がシリカ被膜であり、前記珪素含有酸化物被覆窒化アルミニウム粒子がシリカ被覆窒化アルミニウム粒子である、上記［１］に記載の珪素含有酸化物被覆窒化アルミニウム粒子の製造方法。
［３］前記第１工程において、前記反応場の単位容積当たりの水分量を４．２ｇ／ｍ^３以上に制御する、上記［１］又は［２］に記載の珪素含有酸化物被覆窒化アルミニウム粒子の製造方法。
［４］前記第１工程において、前記反応場の単位容積当たりの水分量を４０．０ｇ／ｍ^３以下に制御する、上記［１］～［３］のいずれかに記載の珪素含有酸化物被覆窒化アルミニウム粒子の製造方法。
［５］前記第２工程が、気相吸着法によって行われる、上記［１］～［４］のいずれかに記載の珪素含有酸化物被覆６窒化アルミニウム粒子の製造方法。
［６］前記第１工程において、前記反応場における気相中の酸素ガス濃度を８体積％以下に制御する、上記［１］～［５］のいずれかに記載の珪素含有酸化物被覆窒化アルミニウム粒子の製造方法。
［７］前記式（１）で示される構造を含む有機シリコーン化合物が、下記式（２）で示される化合物および下記式（３）で示される化合物の少なくとも一方を含む、上記［１］～［６］のいずれかに記載の珪素含有酸化物被覆窒化アルミニウム粒子の製造方法。

（式（２）中、Ｒ１およびＲ２は、それぞれ独立に、水素原子またはメチル基であり、Ｒ１およびＲ２の少なくとも一方は水素原子であり、ｍは０～１０の整数である。）

（式（３）中、ｎは３～６の整数である。）
［８］前記第２工程は、１０℃以上２００℃以下の温度条件下で行われる、上記［１］～［７］のいずれかに記載の珪素含有酸化物被覆窒化アルミニウム粒子の製造方法。
［９］前記窒化アルミニウム粒子は、ＢＥＴ比表面積が０．１５ｍ^２／ｇ以下である、上記［１］～［８］のいずれかに記載の珪素含有酸化物被覆窒化アルミニウム粒子の製造方法。
［１０］前記窒化アルミニウム粒子は、体積累積粒径Ｄ５０が２０μｍ以上である、上記［１］～［９］のいずれかに記載の珪素含有酸化物被覆窒化アルミニウム粒子の製造方法。
［１１］前記窒化アルミニウム粒子のＢＥＴ比表面積（ＢＥＴ）に対する前記珪素含有酸化物被覆窒化アルミニウム粒子に被覆された珪素含有酸化物の珪素原子の含有量（ΔＳｉ）の比（ΔＳｉ／ＢＥＴ）が５２０質量ｐｐｍ・ｇ／ｍ^２以上である、上記［１］～［１０］のいずれかに記載の珪素含有酸化物被覆窒化アルミニウム粒子の製造方法。
［１２］上記［１］～［１１］のいずれかに記載の珪素含有酸化物被覆窒化アルミニウム粒子の製造方法により珪素含有酸化物被覆窒化アルミニウム粒子を製造する製造工程と、前記珪素含有酸化物被覆窒化アルミニウム粒子と樹脂とを混合する混合工程を含む、樹脂組成物の製造方法。 That is, the present invention provides the following [1] to [11].
[1] A method for producing silicon-containing oxide-coated aluminum nitride particles comprising aluminum nitride particles and a silicon-containing oxide film covering the surfaces of the aluminum nitride particles, wherein the water content per unit volume of the reaction field is 1 In the first step of controlling to 5 g/m ³ or more, and in the reaction field after the water content is controlled, the surface of the aluminum nitride particles is coated with an organic silicone compound having a structure represented by the following formula (1) and a third step of heating the aluminum nitride particles coated with the organosilicon compound at a temperature of 300° C. or more and 1000° C. or less. .

(In Formula (1), R is an alkyl group having 1 to 4 carbon atoms.)
[2] The heating temperature in the third step is 300° C. or higher and 900° C. or lower, the silicon-containing oxide coating is a silica coating, and the silicon-containing oxide-coated aluminum nitride particles are silica-coated aluminum nitride particles. The method for producing silicon-containing oxide-coated aluminum nitride particles according to [1] above.
[3] The silicon-containing oxide-coated aluminum nitride particles according to [1] or [2] above, wherein in the first step, the water content per unit volume of the reaction field is controlled to 4.2 g/m ^{3 or} more. manufacturing method.
[4] The silicon-containing oxide coating according to any one of [1] to [3] above, wherein in the first step, the water content per unit volume of the reaction field is controlled to 40.0 g/m ³ or less. A method for producing aluminum nitride particles.
[5] The method for producing silicon-containing oxide-coated 6-aluminum nitride particles according to any one of [1] to [4] above, wherein the second step is performed by a vapor phase adsorption method.
[6] The silicon-containing oxide-coated aluminum nitride according to any one of [1] to [5] above, wherein in the first step, the oxygen gas concentration in the gas phase in the reaction field is controlled to 8% by volume or less. Particle production method.
[7] The above [1]-[ 6] The method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of 6].

(In formula (2), R1 and R2 are each independently a hydrogen atom or a methyl group, at least one of R1 and R2 is a hydrogen atom, and m is an integer of 0 to 10.)

(In formula (3), n is an integer of 3 to 6.)
[8] The method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of [1] to [7] above, wherein the second step is performed at a temperature of 10°C or higher and 200°C or lower.
[9] The method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of [1] to [8] above, wherein the aluminum nitride particles have a BET specific surface area of 0.15 m ² /g or less.
[10] The method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of [1] to [9] above, wherein the aluminum nitride particles have a volume cumulative particle diameter D50 of 20 μm or more.
[11] The ratio (ΔSi/BET) of the silicon atom content (ΔSi) of the silicon-containing oxide coated with the silicon-containing oxide-coated aluminum nitride particles to the BET specific surface area (BET) of the aluminum nitride particles is 520 The method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of [1] to [10] above, wherein the mass is ppm·g/m ² or more.
[12] A production step of producing silicon-containing oxide-coated aluminum nitride particles by the method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of [1] to [11] above, and the silicon-containing oxide coating. A method for producing a resin composition, comprising a mixing step of mixing aluminum nitride particles and a resin.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a production method capable of producing silicon-containing oxide-coated aluminum nitride particles having excellent moisture resistance by at least one coating while maintaining high thermal conductivity of the aluminum nitride particles, and the production. A method for producing a resin composition containing silicon-containing oxide-coated aluminum nitride particles produced by the method can be provided.

1 is a flow chart showing a method for producing silica-coated aluminum nitride particles of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The present invention also includes aspects in which the items described in this specification are arbitrarily selected or arbitrarily combined.
In the present specification, the definition of being preferred can be arbitrarily selected, and it can be said that a combination of the definitions of being preferred is more preferred.
In this specification, the description "XX to YY" means "XX or more and YY or less".
In this specification, for preferred numerical ranges (for example, ranges of content etc.), the lower and upper limits described stepwise can be independently combined. For example, from the statement "preferably 10 to 90, more preferably 30 to 60", combining "preferred lower limit (10)" and "more preferred upper limit (60)" to "10 to 60" can also

In the present invention, the "BET specific surface area" is a value measured by the BET flow method (single-point method) using N ₂ gas as an adsorbate according to JIS R 1626:1996. The BET specific surface area is an index showing the fineness of the AlN particles, and it can be said that the larger the value of the BET specific surface area, the finer the AlN particles.
As an evaluation device, Macsorb HM model-1210 manufactured by Mounttech can be used.

In the present specification, "cumulative volume particle size D50" indicates a particle size at which the integrated value of cumulative volume is 50% with respect to a certain particle size distribution. The volume cumulative particle size D50 is obtained from the particle size distribution by a laser diffraction scattering method. (manufactured by the company) can be used for measurement.

As used herein, the term "reaction field" means "a space in which the aluminum nitride particles and the organosilicon compound containing the structure represented by formula (1) react". For example, in the examples described later, the "reaction field" is the "space within the reaction tank".

As used herein, the term “moisture content per unit volume” refers to “the mass of water contained in 1 m ³ of the space where the aluminum nitride particles and the organosilicon compound containing the structure represented by formula (1) react at 25° C. For example, in the examples, it means "mass of water contained in 1 m ³ of space in the reaction vessel". The "moisture content per unit volume of the reaction field" can be calculated from the inflow of gas whose moisture content has been adjusted in advance, and a digital thermo-hygrometer (SK-110TRH2 TYPE- 5) can be used for measurement.
As used herein, "the content of the organic silicone compound containing the structure represented by the above formula (1) per unit volume in the reaction field (organic silicone compound concentration)" means "aluminum nitride particles and the formula (1) The mass of the organosilicon compound containing the structure represented by formula (1) contained in 1 m ³ of space where the organosilicon compound containing the structure shown reacts. The mass of the organosilicon compound containing the structure represented by formula (1) contained in 1 m ³ ", and is substituted by the vapor saturation amount of the organosilicon compound.

（式（１）中、Ｒは炭素数が１以上４以下のアルキル基である。） [Method for producing silicon-containing oxide-coated aluminum nitride particles]
The method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention produces silicon-containing oxide-coated aluminum nitride particles comprising aluminum nitride particles and a silicon-containing oxide film covering the surfaces of the aluminum nitride particles. be. Examples of the "silicon-containing oxide" of the silicon-containing oxide film and silicon-containing oxide-coated aluminum nitride particles include silica and composite oxides of silicon and aluminum, which will be described later in detail. The oxides include oxides, oxynitrides, oxycarbonitrides, and the like.
The method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention comprises a first step of controlling the water content per unit volume of the reaction field to a predetermined amount; a second step of covering the surfaces of the aluminum nitride particles with a predetermined organosilicon compound containing a structure represented by the following formula (1); and a third step of heating the aluminum nitride particles covered with the organosilicon compound at a predetermined temperature. and a step.

(In Formula (1), R is an alkyl group having 1 to 4 carbon atoms.)

The method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention will be described in detail with reference to FIG. FIG. 1 is a flow chart showing a method for producing silica-coated aluminum nitride particles of the present invention as an example of the method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention.

<Aluminum Nitride Particles>
In the method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention, known aluminum nitride particles such as commercially available products can be used as raw materials. The method for producing aluminum nitride particles is not particularly limited. For example, a direct nitridation method in which metal aluminum powder and nitrogen or ammonia are directly reacted, and a nitridation reaction is performed simultaneously by heating alumina in a nitrogen or ammonia atmosphere while reducing it with carbon. There is a reduction nitriding method and the like.

As the aluminum nitride particles, particles obtained by sintering aggregates of fine aluminum nitride particles into granules can be used. For example, sintered granules made from high-purity fine aluminum nitride particles can be preferably used.

Here, the high-purity aluminum nitride fine particles are particles having a low oxygen content and a small amount of metal impurities. Specifically, for example, high-purity aluminum nitride having an oxygen content of 1% by mass or less and a total content of metal impurities (that is, metal atoms other than aluminum) of 1000 mass ppm or less is a silicon-containing oxide It is suitable for obtaining higher thermal conductivity of the aluminum nitride particles contained in the coated aluminum nitride particles.
Aluminum nitride particles can be used alone or in combination.

The oxygen content described above can be measured by an inorganic analyzer or the like equipped with an infrared detector for detecting oxygen. Specifically, the oxygen content can be measured by using an oxygen/nitrogen/hydrogen analyzer (ONH836: manufactured by LECO Japan LLC).

Also, the total content of metal atoms other than aluminum can be measured with an ICP (Inductively Coupled Plasma) mass spectrometer or the like. Specifically, the total content of metal atoms other than aluminum can be measured by using an ICP mass spectrometer (ICPMS-2030: manufactured by Shimadzu Corporation).

The shape of the aluminum nitride particles used in the present invention is not particularly limited, and examples thereof include amorphous (crushed), spherical, elliptical, plate-like (scale-like) and the like. Further, when the silicon-containing oxide-coated aluminum nitride particles are dispersed and contained in the resin composition as a filler, the aluminum nitride particles are the same type of aluminum nitride particles having the same shape and structure (single substance ) alone may be used, but it is also possible to use a mixture of aluminum nitride particles in which two or more kinds of aluminum nitride particles having different shapes and structures are mixed in various proportions.

When the silicon-containing oxide-coated aluminum nitride particles are dispersed and contained in the resin composition, the volume ratio (filling amount) of the aluminum nitride particles constituting the silicon-containing oxide-coated aluminum nitride particles to the resin composition is The larger the value, the higher the thermal conductivity of the resin composition. Therefore, it is preferable that the shape of the aluminum nitride particles is close to a spherical shape which causes little increase in the viscosity of the resin composition due to the addition of the silicon-containing oxide-coated aluminum nitride particles.

The volume cumulative particle diameter D50 of the aluminum nitride particles used in the present invention is not particularly limited, but is preferably 20 μm or more, more preferably 20 μm or more and 200 μm or less, still more preferably 25 μm or more and 100 μm or less, particularly preferably 30 μm or more and 80 μm or less. is.

When the volume cumulative particle diameter D50 of the aluminum nitride particles is within the above-described range, even when a resin composition containing silicon-containing oxide-coated aluminum nitride particles is used as a heat dissipation material for mounting electric power electronic components, It is possible to supply a thin heat-dissipating material with a minimum thickness, and the moisture resistance of the aluminum nitride particles is further improved, probably because the coating tends to uniformly cover the surfaces of the aluminum nitride particles.

The BET specific surface area of the aluminum nitride particles used in the present invention is not particularly limited, but is preferably 0.15 m ² /g or less, more preferably 0.03 m ² /g or more and 0.12 m ² /g or less. more preferably 0.06 m ² /g or more and 0.11 m ² /g or less.
When the BET specific surface area of the aluminum nitride particles is equal to or less than the above upper limit, it is possible to suppress the adhesion amount of the organic silicone compound from becoming excessive, thereby suppressing the occurrence of aggregation and the like.

<Organic silicone compound used for coating>
In the method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention, the organosilicone compound used as a raw material for the silicon-containing oxide coating constituting the silicon-containing oxide-coated aluminum nitride particles is represented by the above formula (1). As long as it is an organic silicone compound containing a structure, it can be used without any particular limitation regardless of whether it is linear, cyclic or branched. The structure represented by formula (1) is a hydrogensiloxane unit in which hydrogen is directly bonded to a silicon atom.

In the above formula (1), R, which is an alkyl group having 1 to 4 carbon atoms, is a methyl group, an ethyl group, a propyl group, a t- A butyl group is preferred, and a methyl group is particularly preferred. In the method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention, the organic silicone compound used as a raw material is, for example, an oligomer or polymer containing a structure represented by formula (1).

（式（２）中、Ｒ１およびＲ２は、それぞれ独立に、水素原子またはメチル基であり、Ｒ１およびＲ２の少なくとも一方は水素原子であり、ｍは０～１０の整数である。）
なお、ｍが前記下限値以上前記上限値以下であると、第二工程における有機シリコーン化合物の蒸気濃度を確保することができる。

（式（３）中、ｎは３～６の整数である。）
なお、ｎが前記下限値以上前記上限値以下であると、第二工程における有機シリコーン化合物の蒸気濃度を確保することができる。 As the organic silicone compound, for example, at least one of the compound represented by the following formula (2) and the compound represented by the following formula (3) is suitable.

(In formula (2), R1 and R2 are each independently a hydrogen atom or a methyl group, at least one of R1 and R2 is a hydrogen atom, and m is an integer of 0 to 10.)
In addition, when m is not less than the lower limit and not more than the upper limit, the vapor concentration of the organosilicon compound in the second step can be ensured.

(In formula (3), n is an integer of 3 to 6.)
In addition, the vapor|steam concentration of the organosilicon compound in a 2nd process can be ensured as n is above the said lower limit and below the said upper limit.

In particular, a cyclic hydrogensiloxane oligomer in which n is 4 in the above formula (3) is excellent in that it can form a uniform coating on the aluminum nitride particle surface. The weight average molecular weight of the organic silicone compound containing the structure represented by formula (1) is preferably 100 or more and 2000 or less, more preferably 150 or more and 1000 or less, and still more preferably 180 or more and 500 or less. It is presumed that the use of an organic silicone compound having a weight-average molecular weight within this range and having the structure represented by formula (1) facilitates the formation of a thin and uniform coating on the surface of the aluminum nitride particles. In addition, in Formula (2), it is preferable that m is 1.
When the weight-average molecular weight of the organic silicone compound containing the structure represented by formula (1) is at least the lower limit, safety during the reaction can be ensured. It is possible to ensure the vapor concentration of the organosilicon compound in the two steps.

In the present specification, the weight average molecular weight is the polystyrene equivalent weight average molecular weight using gel permeation chromatography (GPC). ) and a differential refractive index detector (Shodex (registered trademark) RI-71S: manufactured by Showa Denko KK).

<First step>
In the first step, the water content per unit volume of the reaction field is controlled.
In the first step, the method is not particularly limited as long as the water content per unit volume of the reaction field can be controlled to 1.5 g/m ³ or more.
The amount of water per unit volume in the reaction field is not particularly limited as long as it is 1.5 g/m ³ or more, preferably 2.3 g/m ³ or more and 40.0 g/m ³ or less, more preferably 4 2 g/m ³ or more and 30.0 g/m ³ or less, more preferably 4.5 g/m ³ or more and 23.0 g/m ³ or less. When the water content per unit volume in the reaction field is equal to or higher than the lower limit of the preferable range, the silicon-containing oxide layer laminated on the surface of the obtained silicon-containing oxide-coated aluminum nitride particles is thickened, and the silicon-containing oxide layer is thickened at least once. Moisture resistance can be improved with a coating of Further, if the amount of water per unit volume in the reaction field is equal to or less than the upper limit of the preferred range, water and It is possible to suppress deterioration reaction from occurring on the aluminum nitride surface.
The content of aluminum nitride particles per unit volume in the reaction field is not particularly limited, but is preferably 3.0 kg/m ³ or less, more preferably 2.0 kg/m ³ or less, still more preferably 1.5 kg/m 3 or less. m ³ or less. If the content of aluminum nitride particles per unit volume in the reaction field is equal to or less than the upper limit of the preferred range, the diffusion of the volatile gas of the organosilicon resin in the reaction field can be maintained.
The temperature of the reaction field in the first step is not particularly limited, but is preferably 10 to 50°C, more preferably 15 to 40°C, still more preferably 20 to 35°C.

As a water content control method (moisture introduction method) in the first step, for example, (i) the reaction field is evacuated to reduce the pressure, dry nitrogen gas and humidified nitrogen gas are introduced, and the reaction field is reduced to normal pressure (0. 1 MPa) to adjust the water content per unit volume of the reaction field, (ii) stepwise introduction of water vapor at normal pressure (0.1 MPa), (iii) the required amount under reduced pressure. and a method of introducing water in the form of a liquid.
Note that “dry nitrogen gas” means nitrogen gas having a dew point of −60° C. or lower, and “humidified nitrogen gas” means that the moisture content per unit volume is 18.5 g/at room temperature (25° C.). m ³ or more means nitrogen gas. Humidified nitrogen gas can be prepared by bubbling dry nitrogen gas into room temperature water at room temperature to absorb moisture.
In the reaction field after the water content per unit volume is controlled to a predetermined amount by the above-described water content control method (moisture introduction method), in the second step described later, the surface of the aluminum nitride particles is treated by the above formula (1) Vapor of the organic silicone compound containing the structure represented by the above formula (1) alone or mixed gas with an inert gas such as nitrogen gas is introduced so as to cover with the organic silicone compound containing the structure represented by. Here, when the second step is a step in a closed system, the water content in the reaction field controlled by the water content control in the first step is maintained from the beginning of the reaction to the end of the reaction in the second step.

The oxygen gas concentration in the gas phase in the reaction field controlled in the first step is not particularly limited, but from the viewpoint of ensuring safety in production, it is preferably 8% by volume or less, more preferably 4% by volume or less. and more preferably 2% by volume or less.

<Second step>
In the second step, the surfaces of the aluminum nitride particles are covered with an organic silicone compound having a structure represented by formula (1).
In the second step, in the reaction field after the water content is controlled in the first step, as long as the surface of the aluminum nitride particles can be covered with the organic silicone compound containing the structure represented by the above formula (1), especially The method is not limited.
The content of the organic silicone compound containing the structure represented by formula (1) per unit volume in the reaction field (concentration of the organic silicone compound) is not particularly limited, but is preferably 7 from the viewpoint of coating efficiency. .5 g/m ³ or more, more preferably 10 g/m ³ or more, and still more preferably 12.5 g/m ³ or more. Also, the upper limit of the concentration of the organic silicone compound is the saturated concentration, and in the examples described later, the concentration of the organic silicone compound is the saturated concentration.

As a coating method in the second step, in the examples described later, a petri dish containing an organosilicon compound having a structure represented by the above formula (1) is placed in a reaction vessel and then heated to a predetermined temperature. , a vapor phase adsorption method is used in which the vapor alone obtained by evaporating the organosilicon compound in the petri dish is adhered or vapor-deposited on the surface of the still aluminum nitride particles, but it is not limited to this, It is also possible to use a vapor phase adsorption method in which a mixed gas of a vapor of an organosilicon compound having a structure represented by formula (1) and an inert gas such as nitrogen gas is adhered or vapor-deposited on the surface of the aluminum nitride particles left still. . The temperature condition of the reaction field in this case is not particularly limited because it depends on the boiling point and vapor pressure of the silicone compound containing the structure represented by formula (1), but the preferred temperature is 10° C. or higher and 200° C. or lower. , more preferably 20° C. or higher and 150° C. or lower, and still more preferably 40° C. or higher and 100° C. or lower. Further, if necessary, the inside of the system can be pressurized or decompressed. As an apparatus that can be used in this case, a closed system and an apparatus that can easily replace the gas in the system are preferable. When the aluminum nitride particles are coated with the organosilicon compound without stirring, the treatment time should be longer. However, by intermittently placing the processing container on the vibrator, it is possible to efficiently move the position of the powder even in places where the powder is in contact with each other and is in the shade, or for powder far from the upper air layer. can handle well.
Further, in the examples described later, in the first step, the petri dish containing the organosilicon compound containing the structure represented by the above formula (1) is placed in the reaction vessel. As long as there is no effect on the water content, the timing of introduction of the organosilicon compound containing the structure represented by the above formula (1) may be either the first step or the second step. However, when the organic silicone compound containing the structure represented by the above formula (1) is introduced in the first step, it must be introduced before heating (elevating the temperature). When introducing an organic silicone compound having a structure represented by formula (1), it is necessary to control the water content per unit volume of the reaction field and the oxygen gas concentration in the gas phase in the reaction field.

<Third step>
In the third step, the aluminum nitride particles coated with the organosilicon compound obtained in the second step are heated to 300° C. or higher and 1000° C. or lower, preferably 300° C. or higher and 950° C. or lower, more preferably 300° C. or higher and 900° C. or lower, More preferably, it is heated at a temperature of 500°C or higher and 880°C or lower. Thereby, a silicon-containing oxide film can be formed on the surface of the aluminum nitride particles.
When the heating in the third step is at a low temperature, a silica film is formed on the surface of the aluminum nitride particles, and silica-coated aluminum nitride particles can be produced. Further, when the heating in the third step is at a high temperature, a coating of a composite oxide of silicon element and aluminum element is formed on the surface of the aluminum nitride particles, and a composite oxide coating of silicon element and aluminum element is formed on the aluminum nitride particle surface. Particles can be produced. When the temperature in the third step increases, the aluminum constituting the aluminum nitride particles emerges from the surface of the aluminum nitride particles, forming a composite oxide together with silicon derived from the organosilicon compound to form a composite oxide with elemental silicon and elemental aluminum. It is presumed that a film of complex oxide is formed.
In the third step, the aluminum nitride particles coated with the organosilicon compound obtained in the second step are heated to 300° C. or higher and 1000° C. or lower, preferably 300° C. or higher and 950° C. or lower, more preferably 300° C. or higher and 900° C. or lower, More preferably, if it can be heated at a temperature of 500°C or higher and 880°C or lower, that is, the aluminum nitride particles coated with the organosilicon compound obtained in the second step are heated to 300°C or higher and 1000°C or lower, preferably 300°C. A general heating furnace can be used as long as it can maintain the temperature in the range of 950° C. or higher, more preferably 300° C. or higher and 900° C. or lower, still more preferably 500° C. or higher and 880° C. or lower.

In addition, silica coating means that it is coated with a thin film containing silica as a main component. However, since there may be multiple inorganic compounds at the interface between the coated silica and aluminum nitride particles, ToF-SIMS (Time of Flight Secondary Ion Mass Spectrometry, When analyzed by ION-TOF, TOF.SIMS 5), recombination of secondary ions and decomposition during ionization overlap, and segments such as AlSiO ₄ ions and SiNO ions are simultaneously detected as subcomponents. In some cases. A composite segment analyzed by this ToF-SIMS analysis can also be defined as a partial detection product when aluminum nitride is silicified. As a guideline, if the amount of secondary electrons in silica is larger than that in other fractions, silica can be considered to be the main component.

As an experiment to further improve the accuracy and confirm the purity of silica, the surface of a sample on which a silica film was formed on an aluminum nitride polycrystalline substrate by the same method was measured by a photoelectron spectrometer (XPS: X-ray Photoelectron Spectroscopy, ULVAC, Inc.). Since the kinetic energy of Si-derived photoelectrons measured and detected by Quantera II) by Phi Corporation approximately matches the standard peak of 103.7 eV for silica, it is assumed that most of the photoelectrons have a SiO ₂ structure. Depending on the heating temperature, there may be cases where organic components remain. An organic siloxane component may be mixed within a range that does not impair the effects of the present invention.

The carbon atom content can be measured by a carbon/sulfur analyzer or the like using a non-dispersive infrared absorption method by a tubular electric furnace method. Specifically, it can be measured by using a carbon/sulfur analyzer (Carbon Anlyzer EMIA-821: manufactured by Horiba, Ltd.).

The heating temperature (heat treatment temperature) in the third step is 300°C or higher and 1000°C or lower, preferably 300°C or higher and 950°C or lower, more preferably 300°C or higher and 900°C or lower, still more preferably 500°C or higher and 880°C or lower. By carrying out within this temperature range, a silicon-containing oxide film having good moisture resistance and thermal conductivity is formed. Specifically, when heated at 300° C. or higher, the moisture resistance is improved, probably because the silicon-containing oxide coating is densified and moisture is less permeable. Also, when heated at 1000° C. or lower, preferably 950° C. or lower, more preferably 900° C. or lower, and even more preferably 880° C. or lower, the thermal conductivity is improved. On the other hand, when the temperature exceeds 1000°C, the moisture resistance and thermal conductivity are deteriorated. In addition, if the heating temperature is 300° C. or higher and 1000° C. or lower, preferably 300° C. or higher and 950° C. or lower, more preferably 300° C. or higher and 900° C. or lower, and still more preferably 500° C. or higher and 880° C. or lower, the surfaces of the aluminum nitride particles A uniform silicon-containing oxide film is formed. Also, if the heating temperature is 300° C. or higher, the silicon-containing oxide film has excellent insulating properties, and is 1000° C. or lower, preferably 950° C. or lower, more preferably 900° C. or lower, further preferably 880° C. or lower. If so, it is also effective in terms of energy cost. The heating temperature is preferably 500° C. or higher.

The heating time is preferably 30 minutes or more and 12 hours or less, more preferably 2 hours or more and 10 hours or less, and still more preferably 4 hours or more and 8 hours or less. If the heat treatment time is 30 minutes or longer, there is no residue of decomposition products of the organic group (alkyl group having 4 or less carbon atoms) of the organosilicon compound, and silicon-containing oxidation with very low carbon atom content on the surface of the aluminum nitride particles. It is preferable in that a solid film can be obtained. Further, it is preferable to set the heating time to 6 hours or less in that the silicon-containing oxide-coated aluminum nitride particles can be produced with high production efficiency.

The atmosphere of the heat treatment in the third step is not particularly limited, and may be, for example, an inert gas atmosphere such as N ₂ , Ar, or He, or an atmosphere containing a reducing gas such as H ₂ , CO, or CH ₄ , or oxygen gas. may be carried out in an atmosphere containing, for example, the atmosphere (in the air).

After the heat treatment in the third step, the silicon-containing oxide-coated aluminum nitride particles may partially fuse together. In that case, by pulverizing it, silicon-containing oxide-coated aluminum nitride particles free from sticking and agglomeration can be obtained. The apparatus used for pulverization is not particularly limited, but general pulverizers such as roller mills, hammer mills, jet mills and ball mills can be used.

In addition, by controlling the moisture content in the first step, sufficient moisture resistance can be obtained through the second and third steps. The first to third steps may be performed in order. That is, the steps of sequentially performing the first to third steps may be repeated.

In the second step, the coating method in which the surface of the aluminum nitride particles is covered with an organosilicon compound by the vapor phase adsorption method can form a uniform and thin silicon-containing oxide film, compared to the coating method in which liquid treatment is performed. be. Therefore, even if the steps of sequentially performing the first to third steps are repeated a plurality of times, for example, about 2 to 5 times, the aluminum nitride particles can exhibit good thermal conductivity.

On the other hand, with respect to humidity resistance, a positive correlation is observed between the number of steps in which the first to third steps are performed in order and humidity resistance. Therefore, the number of times the first to third steps are performed in order can be freely selected according to the level of moisture resistance required for actual use.

The silicon-containing oxide-coated aluminum nitride particles obtained by the method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention maintain the high thermal conductivity inherent to aluminum nitride particles, and are also excellent in moisture resistance. Therefore, it can be widely applied as a filler for heat dissipation materials used in the electrical and electronic fields.

<Silicon-Containing Oxide-Coated Aluminum Nitride Particles>
The silicon-containing oxide-coated aluminum nitride particles of the present invention, that is, the aluminum nitride particles and the silicon-containing oxide film covering the surface of the aluminum nitride particles are provided by the method for producing the silicon-containing oxide-coated aluminum nitride particles of the present invention. Silicon-containing oxide-coated aluminum nitride particles can be obtained. Examples of the "silicon-containing oxide" of the silicon-containing oxide film and the silicon-containing oxide-coated aluminum nitride particles include the above-mentioned silica and composite oxides of silicon element and aluminum element. The oxides include oxides, oxynitrides, oxycarbonitrides, and the like.

Such silicon-containing oxide-coated aluminum nitride particles of the present invention maintain the high thermal conductivity of the aluminum nitride particles, and are excellent in moisture resistance after being coated at least once, as shown in Examples described later. Become.
For example, the silicon-containing oxide-coated aluminum nitride particles of the present invention are put into a hydrochloric acid aqueous solution adjusted to pH 4 and treated at 100° C. or 120° C. for 2 hours (that is, the silicon-containing oxide-coated aluminum nitride particles are adjusted to pH 4. When immersed in a prepared hydrochloric acid aqueous solution at 100° C. or 120° C. for 2 hours), the concentration of ammonia extracted in the hydrochloric acid aqueous solution can be 20 mg/L or less, and the humidity resistance is extremely excellent. In addition, since the hydrolysis reaction is accelerated in an acidic solution than in the air, an accelerated moisture resistance test can be performed by exposing the particles to an aqueous solution of hydrochloric acid adjusted to pH 4. Therefore, the humidity resistance of the silicon-containing oxide-coated aluminum nitride particles can be evaluated by using an aqueous hydrochloric acid solution having a pH of 4, and it can be said that the humidity resistance is good when the ammonia concentration is 20 mg/L or less. In addition, chemical resistance can be compared by using an aqueous solution of hydrochloric acid having a pH of 4.
The concentration of the extracted ammonia is preferably 10 mg/L or less, more preferably 6 mg/L or less, still more preferably 7 mg/L or less, even more preferably 6 mg/L or less, particularly preferably 5 mg/L or less, and most preferably Preferably it is 3 mg/L or less.
From the viewpoint of moisture resistance, the lower the carbon atom content, the better. Here, in the method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention, since the organic silicone compound having the structure represented by formula (1) is used as a raw material, the silicon-containing oxide-coated aluminum nitride particles are made of carbon It often contains atoms, for example, 50 mass ppm or more, and sometimes 60 mass ppm or more.

Further, in the silicon-containing oxide-coated aluminum nitride particles of the present invention, the BET specific surface area of the silicon-containing oxide-coated aluminum nitride particles is x (m ² /g), and silicon is coated on the silicon-containing oxide-coated aluminum nitride particles. When the silicon atom content (ΔSi amount) of the contained oxide is y (mass ppm), it is preferable that the following formulas (4) and (5) are satisfied, and the following formula (6) is more preferably satisfied.
y≦1000x+2000 (4)
y≧10 (5)
0.03≦x≦10 (6)
In the above formula (4), the intercept is 2000, but it is preferably 1900, more preferably 1700, and even more preferably 1500 from the viewpoint of preventing a decrease in thermal conductivity due to excessive adhesion.
Regarding the above formula (5), the lower limit is 10, but from the viewpoint of ensuring the improvement of moisture resistance by keeping the amount of ΔSi due to the humidification effect to a certain level or more, it is preferably 100, more preferably 115, and even more preferably 130. is.
Although the upper limit of formula (6) is 10, it is preferably 9, more preferably 7, and even more preferably 5 from the viewpoint of powder handling.

The silicon atom content (ΔSi content) of the silicon-containing oxide coated on the silicon-containing oxide-coated aluminum nitride particles can be measured by the ICP method. Also, the BET specific surface area x of the silicon-containing oxide-coated aluminum nitride particles can be measured in the same manner as the BET specific surface area of the aluminum nitride particles described above.

In addition, the silicon atom content (ΔSi amount) of the silicon-containing oxide coated on the silicon-containing oxide-coated aluminum nitride particles is not particularly limited, but is preferably 10000 mass ppm or less, more preferably 8000 mass ppm or less, It is more preferably 7800 mass ppm or less, particularly preferably 7500 mass ppm or less. The silicon atom content (ΔSi content) of the silicon-containing oxide coated on the silicon-containing oxide-coated aluminum nitride particles is, for example, 50 ppm by mass or more.
The silicon atom content (ΔSi content) of the silicon-containing oxide coated on the silicon-containing oxide-coated aluminum nitride particles can be calculated by the method described in Examples below.

In addition, the ratio (ΔSi/BET) of the silicon atom content (ΔSi) of the silicon-containing oxide coated with the silicon-containing oxide-coated aluminum nitride particles to the BET specific surface area (BET) of the aluminum nitride particles is not particularly limited. is preferably 520 mass ppm·g/m2 or ^more , more preferably 550 mass ppm·g/ ^m2 or more, still more preferably 600 mass ppm·g/ ^m2 or more, still more preferably 1000 mass ppm·g /m ² or more.
The ratio (ΔSi/BET) of the silicon atom content (ΔSi) of the silicon-containing oxide coated with the silicon-containing oxide-coated aluminum nitride particles to the BET specific surface area (BET) of the aluminum nitride particles can be It can be calculated by the method described in the example.

[Method for producing resin composition]
A resin composition can be produced using the silicon-containing oxide-coated aluminum nitride particles of the present invention. That is, the method for producing the resin composition of the present invention comprises a production step for producing silicon-containing oxide-coated aluminum nitride particles by the above-described method for producing silicon-containing oxide-coated aluminum nitride particles, and a step of producing silicon-containing oxide-coated aluminum nitride particles. and a mixing step of mixing with a resin. Examples of the "silicon-containing oxide" of the silicon-containing oxide film and the silicon-containing oxide-coated aluminum nitride particles include the above-mentioned silica and composite oxides of silicon element and aluminum element. The oxides include oxides, oxynitrides, oxycarbonitrides, and the like.
The silicon-containing oxide-coated aluminum nitride particles produced by the method for producing silicon-containing oxide-coated aluminum nitride particles maintain the high thermal conductivity of the aluminum nitride particles, and the moisture resistance is improved by coating at least once. , the resin composition obtained by the method for producing a resin composition of the present invention is excellent in moisture resistance and thermal conductivity.

In the mixing step, the silicon-containing oxide-coated aluminum nitride particles produced by the method for producing silicon-containing oxide-coated aluminum nitride particles are mixed with a resin.

The resin to be mixed in the mixing step is not particularly limited, but it is preferably a thermosetting resin, a thermoplastic resin, or a mixture of a thermosetting resin and a thermoplastic resin because the resulting resin composition has excellent heat resistance. . Examples of thermosetting resins include silicone resins such as polydimethylsiloxane, epoxy resins, phenol resins, bismaleimide resins, cyanate resins, urethane resins, (meth)acrylic resins, vinyl ester resins, unsaturated polyester resins, poly Examples include vinyl alcohol acetal resins, which can be used alone or in combination of two or more. Furthermore, a mixture obtained by adding a curing agent or a curing accelerator to a thermosetting resin may be used. In particular, epoxy resins are preferred in terms of heat resistance, adhesiveness and electrical properties after curing, and silicone resins are preferred in applications where flexibility adhesion is emphasized.

Silicone resins include addition reaction-curable silicone resins, condensation reaction-curable silicone resins, organic peroxide-curable silicone resins, and the like, and may be used alone or in combination of two or more types having different viscosities. . In particular, when the resulting resin composition is used in applications where flexibility and adhesion are emphasized, the silicone resin is, for example, an addition reaction-curable liquid silicone resin that does not generate by-products that can cause air bubbles. The silicone resin cured product is obtained by reacting an organopolysiloxane having an alkenyl group as a base polymer and an organopolysiloxane having a Si—H group as a crosslinking agent in the presence of a curing agent at room temperature or by heating. can be obtained. Specific examples of the organopolysiloxane that is the base polymer include those having, for example, vinyl, allyl, propenyl, and hexenyl groups as alkenyl groups. In particular, vinyl groups are preferred as the organopolysiloxane. As the curing catalyst, for example, a platinum metal-based curing catalyst can be used, and in order to achieve the desired hardness of the resin cured product, the amount added can be adjusted.

Epoxy resins include bifunctional glycidyl ether type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, biphenyl type epoxy resin; hexahydrophthalic acid; Glycidyl ester type epoxy resins such as glycidyl ester and dimer acid glycidyl ester; Linear aliphatic epoxy resins such as epoxidized polybutadiene and epoxidized soybean oil; Heterocyclic epoxy resins such as triglycidyl isocyanurate; ',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-1,3-benzenedi(methanamine), 4-(glycidyloxy)-N,N-diglycidyl Glycidylamine type epoxy resins such as aniline, 3-(glycidyloxy)-N,N-diglycidylaniline; phenol novolak type epoxy resin, cresol novolak type epoxy resin, biphenylaralkyl type epoxy resin, naphthalene aralkyl type epoxy resin, tetrafunctional polyfunctional glycidyl ether type epoxy resins such as naphthalene type epoxy resins and triphenylmethane type epoxy resins; The above epoxy resins can be used alone or in combination of two or more.

When the epoxy resin described above is used, a curing agent and a curing accelerator may be blended. Examples of curing agents include alicyclic acid anhydrides such as methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and himic anhydride; aliphatic acid anhydrides such as dodecenyl succinic anhydride; aromatic acid anhydrides such as mellitic acid; bisphenols such as bisphenol A, bisphenol F and bisphenol S; phenols such as phenol-formaldehyde resin, phenol-aralkyl resin, naphthol-aralkyl resin, phenol-dicyclopentadiene copolymer resin Resins; organic dihydrazides such as dicyandiamide and adipic acid dihydrazide; , and derivatives thereof; imidazoles such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and derivatives thereof; These can be used singly or in combination of two or more.

In the mixing step, a commonly used filler such as boron nitride, alumina, silica, or zinc oxide may be used together with the silicon-containing oxide-coated aluminum nitride particles.

In the mixing step, the silicon-containing oxide-coated aluminum nitride particles and the filler other than the silicon-containing oxide-coated aluminum nitride particles may be mixed in an amount that provides a desired resin composition.
The total content of fillers other than the silicon-containing oxide-coated aluminum nitride particles and the silicon-containing oxide-coated aluminum nitride particles in the resulting resin composition is preferably 50% by mass or more and 99% by mass or less, more preferably 60% by mass. % or more and 97 mass % or less, more preferably 70 mass % or more and 95 mass % or less. If the total content is 50% by mass or more, good heat dissipation can be exhibited, and if the total content is 99% by mass or less, good workability can be obtained when the resin composition is used.

The content of the silicon-containing oxide-coated aluminum nitride particles in the resulting resin composition is 30 masses of the total content of the silicon-containing oxide-coated aluminum nitride particles and the filler other than the silicon-containing oxide-coated aluminum nitride particles. % or more and 100 mass % or less, more preferably 40 mass % or more and 100 mass % or less, and still more preferably 50 mass % or more and 100 mass % or less. When the total content is 30% by mass or more, good heat dissipation can be exhibited.

In the mixing step, if necessary, flexibility imparting agents such as silicone, urethane acrylate, butyral resin, acrylic rubber, diene rubber and copolymers thereof, silane coupling agents, titanium coupling agents, inorganic Ion scavengers, pigments, dyes, diluents, solvents and the like can be added as appropriate.

The mixing method in the mixing step is not particularly limited. For example, silicon-containing oxide-coated aluminum nitride particles, resins, other additives, etc. , a method of mixing, dissolving, and kneading by heating, if necessary, by using a dispersing/dissolving device such as a roll mill or the like, or in combination thereof.

Moreover, the obtained resin composition can be molded into a sheet shape and reacted as necessary to form a heat-dissipating sheet. The resin composition and the heat-dissipating sheet described above can be suitably used for bonding applications such as semiconductor power devices and power modules.

As a method for producing a heat-dissipating sheet, a method in which a resin composition is sandwiched between both sides of a substrate film and molded by a compression press or the like, a resin composition is applied onto a substrate film by a bar coater, screen printing, blade coater, die coater, or the like. Examples include a method of coating using a device such as a comma coater. Further, the heat-dissipating sheet after molding and application may be subjected to additional processing steps such as a step of removing the solvent, conversion to B-stage by heating, and complete curing. As described above, it is possible to obtain various forms of heat-dissipating sheets depending on the process, and it is possible to respond to a wide range of target application fields and usage methods.

When applying or forming the resin composition on the substrate film, a solvent can be used to improve workability. Examples of the solvent include, but are not limited to, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone and cyclohexanone; ether solvents such as 1,4-dioxane, tetrahydrofuran and diglyme; glycol ether solvents such as methyl Cellosolve, ethyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, diethylene glycol methyl ethyl ether; other benzyl alcohol; N-methylpyrrolidone; γ- Butyrolactone; ethyl acetate; N,N-dimethylformamide; and the like can be used singly or in combination of two or more.

In order to form the resin composition into a sheet, it is necessary to have sheet formability to maintain the sheet shape. A high molecular weight component can be added to the resin composition in order to obtain sheet formability. For example, phenoxy resin, polyimide resin, polyamide resin, polycarbodiimide resin, cyanate ester resin, (meth) acrylic resin, polyester resin, polyethylene resin, polyethersulfone resin, polyetherimide resin, polyvinyl acetal resin, urethane resin, acrylic rubber Among them, phenoxy resins, polyimide resins, (meth)acrylic resins, acrylic rubbers, cyanate ester resins, polycarbodiimide resins, etc. are preferable from the viewpoint of excellent heat resistance and film formability, and phenoxy resins, polyimide resins , (meth)acrylic resin, and acrylic rubber are more preferred. They can be used alone or as a mixture or copolymer of two or more.

The weight average molecular weight of the high molecular weight component is preferably 10,000 or more and 100,000 or less, more preferably 20,000 or more and 50,000 or less.

A good sheet shape with good handleability can be maintained by adding a weight-average molecular weight component within the above range.

The amount of the high molecular weight component added is not particularly limited, but in order to maintain the sheet properties, it is preferably 0.1% by mass or more and 20% by mass or less, more preferably 1% by mass, based on the resin composition. 15 mass % or less, more preferably 2 mass % or more and 10 mass % or less. It should be noted that an addition amount of 0.1% by mass or more and 20% by mass or less facilitates easy handling and formation of a good sheet or film.

The base film used in the production of the heat-dissipating sheet is not particularly limited as long as it withstands process conditions such as heating and drying during production. Examples include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). A film made of polyester having an aromatic ring such as a polypropylene film, a polyimide film, a polyetherimide film, and the like. The film described above may be a multilayer film in which two or more types are combined, or the surface thereof may be treated with a release agent such as a silicone-based release agent. In addition, the thickness of the base film is preferably 10 μm or more and 100 μm or less.

The thickness of the heat dissipation sheet formed on the base film is preferably 20 μm or more and 500 μm or less, more preferably 50 μm or more and 200 μm or less. When the thickness of the heat-dissipating sheet is 20 μm or more, a heat-dissipating sheet having a uniform composition can be obtained, and when the thickness is 500 μm or less, good heat dissipation can be obtained.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

<Method for calculating physical properties>
(Method for calculating silicon atom content (Si content) of silicon-containing oxide-coated aluminum nitride particles)
The silicon atom content (Si content) of the silicon-containing oxide-coated aluminum nitride particles was calculated by the following procedure.
(1) 10 mL of a solution obtained by mixing 97% by mass sulfuric acid (super special grade, manufactured by Wako Pure Chemical Industries, Ltd.) and ion-exchanged water at a 1:2 (volume ratio) in a 20 mL Teflon (registered trademark) container; A 0.5 g sample of silicon-containing oxide-coated aluminum nitride particles was added.
(2) The entire Teflon (registered trademark) container was placed in a stainless steel pressure container and maintained at 230° C. for 15 hours to dissolve the charged silicon-containing oxide-coated aluminum nitride particle sample.
(3) Take out the solution mixed in (1), measure the concentration of silicon atoms using ICP (manufactured by Shimadzu Corporation, ICPS-7510), and from the measured concentration of silicon atoms, the silicon-containing oxide coating The silicon atom content (Si content) (unit: mass ppm) of the aluminum nitride particles was calculated.

(Method for calculating the silicon atom content (ΔSi amount) of the silicon-containing oxide coated on the silicon-containing oxide-coated aluminum nitride particles)
By subtracting the silicon content of only the aluminum nitride raw material calculated by the same method from the silicon atom content (Si content) of the silicon-containing oxide-coated aluminum nitride particles calculated by the above calculation method, the silicon-containing oxide The silicon atom content (ΔSi amount) (unit: mass ppm) of the silicon-containing oxide coated on the coated aluminum nitride particles was calculated.

(Method for calculating the ratio of the silicon atom content of the silicon-containing oxide coated with the silicon-containing oxide-coated aluminum nitride particles to the BET specific surface area (BET) of the aluminum nitride particles (ΔSi amount/BET))
By dividing the silicon atom content (ΔSi amount) of the silicon-containing oxide coated with the silicon-containing oxide-coated aluminum nitride particles calculated by the above calculation method by the BET specific surface area (BET) of the aluminum nitride particles, The ratio (ΔSi/BET) of the silicon atom content (ΔSi) of the silicon-containing oxide coated with the silicon-containing oxide-coated aluminum nitride particles to the BET specific surface area (BET) of the aluminum nitride particles (unit: mass ppm g /m ² ) was calculated.

(Measurement of thermal conductivity of resin molding)
Thermal conductivity (unit : W/m·K) was measured.
-Production of resin moldings-
Polydimethylsiloxane gel (trade name: DOWSIL (registered trademark) EG-3100, manufactured by Toray Industries, Inc.) A solution and B solution were each weighed into a container at 50% by mass with respect to a total of 100 parts by mass, and shown in Table 1. Weigh the various fillers so that the composition (parts by mass) of is obtained, and use a rotation / revolution mixing mixer (manufactured by Thinky Co., Ltd., product name: ARV-310P) for 30 seconds at a rotation speed of 1000 rpm while stirring and mixing while reducing the pressure. bottom. Once cooled to room temperature (25° C.). Compositions 1 to 5 were respectively placed on a PET substrate, sandwiched between the PET substrates, stretched to a thickness of 2 mm with rolling rolls, and cured by heat treatment at 100° C. for 15 minutes to obtain resin molded test pieces 1 to 5. rice field.
However, the details of each component in Table 1 are shown below.
AA-3: Advanced alumina (trade name: Sumicorundum (registered trademark), manufactured by Sumitomo Chemical Co., Ltd., volume cumulative particle size D50 = 3 μm)
AKP-30: high-purity alumina (trade name: AKP-30, manufactured by Sumitomo Chemical Co., Ltd., volume cumulative particle size D50 = 0.3 μm)
EG-3100 (A): A solution of polydimethylsiloxane gel (trade name: DOWSIL (registered trademark) EG-3100, manufactured by Toray Industries, Inc.) (viscosity 420 mPa s, mixture of vinyl oil and platinum catalyst)
EG-3100 (B): Polydimethylsiloxane gel (trade name: DOWSIL (registered trademark) EG-3100, manufactured by Toray Industries, Inc.) B liquid (viscosity 320 mPa s, mixture of vinyl oil and cross-linking agent)

(Evaluation of moisture resistance of particles)
(1) A 50 mL Teflon (registered trademark) container was charged with 17 g of a hydrochloric acid aqueous solution adjusted to pH 4 and 3 g of silicon-containing oxide-coated aluminum nitride particles.
(2) Place the entire Teflon (registered trademark) container in a stainless steel pressure container, maintain at a predetermined temperature (120 ° C. for aluminum nitride particles A, 100 ° C. for aluminum nitride particles B to E) for 2 hours, and then take out 1 after taking out. After slowly cooling at room temperature for a period of time, the ammonia concentration (unit: mg/L) in the supernatant was measured at a temperature of 25° C. using an ammonia electrode (ammonia electrode 5002A: manufactured by Horiba, Ltd.).
The "content of aluminum nitride particles per unit volume in the reaction field" was 1.25 kg/m ³ (sample: 50 g x 5, reactor: 250 L).

(Example 1)
Surface coating of aluminum nitride particles was carried out using a reactor made using a large oven having a reactor volume of 250 L. In the reaction tank of the reactor, aluminum nitride particles A (JM: manufactured by Toyo Aluminum Co., Ltd.) having a volume cumulative particle size D50 of 3 μm and a BET specific surface area of 2.4 m ² /g, a volume cumulative particle size D50 of 16 μm, BET Aluminum nitride particles B (TFZ-N15P: manufactured by Toyo Aluminum Co., Ltd.) having a specific surface area of 0.35 ^{m 2 /} g, and aluminum nitride particles C (FAN -f30-A1: manufactured by Furukawa Denshi Co., Ltd.), aluminum nitride particles D having a volume cumulative particle size D50 of 48 μm and a BET specific surface area of 0.09 m ² /g (FAN-f50-A1: manufactured by Furukawa Denshi Co., Ltd.), volume 50 g each of aluminum nitride particles E (FAN-f80-A1: manufactured by Furukawa Denshi Co., Ltd.) having a cumulative particle diameter D50 of 77 μm and a BET specific surface area of 0.06 m ² /g are placed in separate aluminum square trays of 240 mm × 180 mm × 30 mm. It was spread evenly and allowed to stand. Next, 400 g of organosilicon compound A (“D4H” in Table 2: cyclic methylhydrogensiloxane tetramer: manufactured by Tokyo Chemical Industry Co., Ltd.) having n = 4 in formula (3) is placed in the reactor of the reactor. 100 g of each was divided into four glass petri dishes (inner diameter 150 mm×height 20 mm) and placed at rest. Here, in order to maintain saturated conditions from the beginning to the end even if some volatilization occurs during evacuation, the organosilicon compound A was added in excess of the assumed necessary amount. After that, the reaction vessel of the reactor was closed. Since hydrogen gas is generated by the reaction, the inside of the reaction vessel was evacuated in advance, and then dry nitrogen gas and humidified nitrogen gas were flowed into the reaction vessel to return the internal pressure to normal pressure (0.1 MPa). Adjustments were made so that the oxygen gas concentration in the internal gas phase was 2% by volume or less and the water content per unit volume was 2.3 g/m ³ (first step). Here, the moisture content was calculated from the humidity measured using a digital thermohygrometer (SK-110TRH2 TYPE-5 manufactured by Sato Keiryoki Seisakusho Co., Ltd.). The temperature of the reaction field in the first step was 25°C. After that, the reactor was heated to 80° C., and the reaction was carried out for 7.5 hours after the temperature was stabilized (second step). After completing the second step, the samples A to E taken out from the reaction vessel were put into crucibles made of alumina, and the samples A and B were heated at 700°C for 3 hours, and the samples C to E were heated at 800°C for 3 hours in the atmosphere. Silica-coated aluminum nitride particles were obtained by performing the heat treatment of the third step under the condition of 6 hours. The obtained silica-coated aluminum nitride particles were subjected to "calculation of Si content", "calculation of ΔSi content", "measurement of thermal conductivity of resin molding", and "evaluation of moisture resistance of particles" by the methods described above. did Table 2 shows the results.
The "assumed necessary amount" means "the amount required to fill the reaction field with the saturated vapor pressure of the organic silicone compound A", and the volume of the reaction field and the saturated vapor pressure of the organic silicone compound A can be calculated based on

(Example 2)
In Example 1, instead of adjusting the water content per unit volume to 2.3 g/m ³ , dry nitrogen and humidified nitrogen were added so that the water content per unit volume was 4.6 g/m ³ . Silica-coated aluminum nitride particles were obtained in the same manner as in Example 1, except that the volume ratio was adjusted. ”, “Measurement of thermal conductivity of resin molding”, and “Evaluation of moisture resistance of particles”. Table 2 shows the results.

(Example 3)
In Example 1, instead of adjusting the water content per unit volume to 2.3 g/m ³ , dry nitrogen and humidified nitrogen were added so that the water content per unit volume was 11.5 g/m ³ . Silica-coated aluminum nitride particles were obtained in the same manner as in Example 1, except that the volume ratio was adjusted. ”, “Measurement of thermal conductivity of resin molding”, and “Evaluation of moisture resistance of particles”. Table 2 shows the results.

(Example 4)
In Example 1, instead of adjusting the water content per unit volume to 2.3 g/m ³ , dry nitrogen and humidified nitrogen were added so that the water content per unit volume was 16.1 g/m ³ . Silica-coated aluminum nitride particles were obtained in the same manner as in Example 1, except that the volume ratio was adjusted. ”, “Measurement of thermal conductivity of resin molding”, and “Evaluation of moisture resistance of particles”. Table 2 shows the results.

(Example 5)
In Example 1, instead of adjusting the water content per unit volume to 2.3 g/m ³ , dry nitrogen and humidified nitrogen were added so that the water content per unit volume was 23.0 g/m ³ . Silica-coated aluminum nitride particles were obtained in the same manner as in Example 1, except that the volume ratio was adjusted. ”, “Measurement of thermal conductivity of resin molding”, and “Evaluation of moisture resistance of particles”. Table 2 shows the results.

(Comparative example 1)
In Example 1, instead of adjusting the water content per unit volume to 2.3 g/m ³ , dry nitrogen and humidified nitrogen were added so that the water content per unit volume was 0.0 g/m ³ . Silica-coated aluminum nitride particles were obtained in the same manner as in Example 1, except that the volume ratio was adjusted. ”, “Measurement of thermal conductivity of resin molding”, and “Evaluation of moisture resistance of particles”. Table 2 shows the results.

(Comparative example 2)
In Example 1, instead of adjusting the water content per unit volume to 2.3 g/m ³ , dry nitrogen and humidified nitrogen were added so that the water content per unit volume was 1.2 g/m ³ . Silica-coated aluminum nitride particles were obtained in the same manner as in Example 1, except that the volume ratio was adjusted. ”, “Measurement of thermal conductivity of resin molding”, and “Evaluation of moisture resistance of particles”. Table 2 shows the results.

・・・構造式（Ｘ） (Comparative Example 3)
In Comparative Example 1, instead of using organosilicon compound A (“D4H” in Table 2: cyclic methylhydrogensiloxane tetramer: manufactured by Tokyo Chemical Industry Co., Ltd.) where n = 4 in formula (3), the following structure Silica-coated aluminum nitride particles were prepared in the same manner as in Comparative Example 1, except that the organic silicone compound B of formula (X) (“D3” in Table 2: hexamethylcyclotrisiloxane: manufactured by Tokyo Chemical Industry Co., Ltd.) was used. Furthermore, for the obtained silica-coated aluminum nitride particles, "calculation of Si amount", "calculation of ΔSi amount", "measurement of thermal conductivity of resin molded body", and "evaluation of moisture resistance of particles ” was performed. Table 2 shows the results.

... structural formula (X)

(Comparative Example 4)
In Example 3, instead of using the organosilicon compound A (“D4H” in Table 2: cyclic methylhydrogensiloxane tetramer: manufactured by Tokyo Chemical Industry Co., Ltd.) where n = 4 in formula (3), the above structure Silica-coated aluminum nitride particles were prepared in the same manner as in Example 3, except that the organic silicone compound B of formula (X) (“D3” in Table 2: hexamethylcyclotrisiloxane: manufactured by Tokyo Chemical Industry Co., Ltd.) was used. Furthermore, for the obtained silica-coated aluminum nitride particles, "calculation of Si amount", "calculation of ΔSi amount", "measurement of thermal conductivity of resin molded body", and "evaluation of moisture resistance of particles ” was performed. Table 2 shows the results.

In the conventional method (for example, the method described in Patent Document 5), as in Comparative Examples 1 and 2, the water content per unit volume of the reaction field is controlled to less than 1.5 g / m ³ , and then the reaction By coating with silica in situ, silica-coated aluminum nitride particles having higher moisture resistance than the silica-coated aluminum nitride particles obtained in Comparative Examples 3 and 4 were obtained. In the method of the present invention, as in Examples 1 to 5, the water content per unit volume of the reaction field is controlled to 1.5 g/m ³ or more, and then the reaction field is coated with silica, so nitriding The high thermal conductivity of the aluminum particles is maintained and silica-coated aluminum nitride particles with better moisture resistance can be obtained with at least one coating.
In Comparative Examples 3 and 4, the organic silicone compound B having the structural formula (X) was used instead of the organic silicone compound A containing the structure represented by the formula (1). You can only get particles.

Claims (12)

A method for producing silicon-containing oxide-coated aluminum nitride particles comprising aluminum nitride particles and a silicon-containing oxide film covering the surfaces of the aluminum nitride particles,
a first step of controlling the water content per unit volume of the reaction field to be 1.5 g/m ³ or more;
a second step of covering the surface of the aluminum nitride particles with an organosilicon compound containing a structure represented by the following formula (1) in the reaction field after the water content is controlled;
and a third step of heating the aluminum nitride particles coated with the organosilicon compound at a temperature of 300° C. or higher and 1000° C. or lower.

(In Formula (1), R is an alkyl group having 1 to 4 carbon atoms.) The heating temperature in the third step is 300° C. or higher and 900° C. or lower,
2. The method for producing silicon-containing oxide-coated aluminum nitride particles according to claim 1, wherein said silicon-containing oxide coating is a silica coating, and said silicon-containing oxide-coated aluminum nitride particles are silica-coated aluminum nitride particles. 3. The method for producing silicon-containing oxide-coated aluminum nitride particles according to claim 1, wherein in said first step, the water content per unit volume of said reaction field is controlled to 4.2 g/m ^<3> or more. The method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of claims 1 to 3, wherein in the first step, the water content per unit volume of the reaction field is controlled to 40.0 g/m ³ or less. . The method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of claims 1 to 4, wherein the second step is performed by a gas phase adsorption method. The method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of claims 1 to 5, wherein in the first step, the oxygen gas concentration in the gas phase in the reaction field is controlled to 8% by volume or less. . Any one of claims 1 to 6, wherein the organic silicone compound containing the structure represented by the formula (1) includes at least one of a compound represented by the following formula (2) and a compound represented by the following formula (3). 3. A method for producing silicon-containing oxide-coated aluminum nitride particles according to claim 1.

(In formula (2), R1 and R2 are each independently a hydrogen atom or a methyl group, at least one of R1 and R2 is a hydrogen atom, and m is an integer of 0 to 10.)

(In formula (3), n is an integer of 3 to 6.) The method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of claims 1 to 7, wherein said second step is carried out at a temperature of 10°C or higher and 200°C or lower. The method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of claims 1 to 8, wherein the aluminum nitride particles have a BET specific surface area of 0.15 m ² /g or less. The method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of claims 1 to 9, wherein the aluminum nitride particles have a volume cumulative particle size D50 of 20 µm or more. The ratio (ΔSi/BET) of the silicon atom content (ΔSi) of the silicon-containing oxide coated with the silicon-containing oxide-coated aluminum nitride particles to the BET specific surface area (BET) of the aluminum nitride particles is 520 ppm by mass. g/m ² or more, the method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of claims 1 to 10. a production step of producing silicon-containing oxide-coated aluminum nitride particles by the method for producing silicon-containing oxide-coated aluminum nitride particles according to any one of claims 1 to 11; and the silicon-containing oxide-coated aluminum nitride particles. A method for producing a resin composition, comprising a mixing step of mixing with a resin.

Images