JP6786778B2 - Heat-dissipating resin sheet and devices containing the heat-dissipating resin sheet - Google Patents

Description

The present invention relates to a heat-dissipating resin sheet containing a boron nitride filler, and also relates to a device containing the heat-dissipating resin sheet.

Boron nitride (hereinafter referred to as "BN") is an insulating ceramic, and has various types such as c-BN having a diamond structure, h-BN having a graphite structure, α-BN having a multi-layer structure, and β-BN. Crystal type is known.
Among these, h-BN has the same layered structure as graphite, is relatively easy to synthesize, and has the characteristics of being excellent in thermal conductivity, solid lubricity, chemical stability, and heat resistance. Therefore, it is widely used in the fields of electrical and electronic materials.

In recent years, especially in the electric and electronic fields, heat generation due to high density of integrated circuits has become a big problem, and how to dissipate heat has become an urgent issue. Taking advantage of the feature that h-BN has high thermal conductivity in spite of its insulating property, h-BN has attracted attention as such a thermally conductive filler for heat-dissipating members, and by being composited in a resin, h-BN is formed. It is also being considered for use as a sheet.

On the other hand, boron nitride is a soft filler, and it is said that the adhesive strength of the resin layer may decrease in the resin layer containing boron nitride. Therefore, in Patent Document 1, a resin layer is provided by forming a multilayer resin sheet including a resin layer containing an epoxy resin monomer, a curing agent, and a filler, and an adhesive layer arranged on at least one surface of the resin layer. A technique has been proposed in which the filler inside is transferred to the adhesive layer in the thickness direction of the multilayer resin sheet to achieve both thermal conductivity and adhesive strength.

Further, in Patent Document 2, an adhesive layer is arranged on at least one surface of a resin composition layer containing a thermosetting resin and a filler and the resin composition layer, and the adhesive layer faces the resin composition layer of the adhesive layer. A technique has been proposed in which both thermal conductivity and adhesive strength are achieved by setting the surface that does not have a specific arithmetic average surface roughness.

Japanese Unexamined Patent Publication No. 2013-048257 Patent No. 5141853

As described in paragraph [0022] of Patent Document 1, thermal conductivity and adhesive strength are contradictory properties, and in order to improve thermal conductivity, increasing the content of the filler lowers the adhesive strength. In particular, it has been considered very difficult to achieve both thermal conductivity and adhesive strength in a single-layer sheet.
An object of the present invention is to provide a technique for achieving both thermal conductivity and adhesive strength in a single-layer heat radiating sheet, which has been considered difficult in the past.

As a result of diligent studies to solve the above problems, the present inventors have made a heat-dissipating sheet even if the filler content is increased by using a resin having specific properties when forming the heat-dissipating sheet. It has become possible to provide sufficient adhesive strength without becoming brittle. As a result, a heat radiating sheet having good thermal conductivity was completed by containing a large amount of filler.
The present inventors consider the mechanism by which the present invention exerts such an effect as follows.
Due to the flexibility of the resin, the adhesive strength is increased by adsorbing to the filler interface or the substrate. Further, since the resin has flexibility, the toughness of the heat radiating sheet can be imparted, and the stress of deformation due to changes such as linear expansion of the heat radiating sheet due to thermal changes can be relaxed.

That is, the present invention is as follows.
[1] A heat-dissipating resin sheet containing a resin and a boron nitride filler.
A heat-dissipating resin sheet in which the content of the boron nitride filler is 30 vоl% or more and 60 vоl% or less, and the Tg of the resin is 60 ° C. or less.
[2] The heat-dissipating resin sheet according to [1], wherein the resin contains an epoxy resin.
[3] The heat-dissipating resin sheet according to [1] or [2], wherein the resin contains two or more types of epoxy resins, and at least one of them is a phenoxy resin.
[4] The epoxy resin is one or more selected from a phenoxy resin having a fluorene skeleton and / or a biphenyl skeleton, a bisphenol A type phenoxy resin, and a bisphenol F type phenoxy resin, according to [2] or [3]. Epoxy resin sheet.
[5] The heat-dissipating resin sheet according to any one of [1] to [4], wherein the boron nitride filler is agglomerated particles.
[6] The heat-dissipating resin sheet according to any one of [1] to [5], wherein the boron nitride filler is spherical aggregated particles.
[7] The heat-dissipating resin sheet according to any one of [1] to [6], wherein the boron nitride filler is agglomerated particles having a card house structure.
[8] The heat-dissipating resin sheet according to any one of [1] to [7], wherein the 90 ° peel test strength is 1.5 N / cm or more.
[9] A device including the heat-dissipating resin sheet according to any one of [1] to [8].
[10] A resin composition for a heat radiating sheet containing a resin and a boron nitride filler.
A resin composition in which the content of the boron nitride filler is 30 vоl% or more and 60 vоl% or less, and the Tg of the resin is 60 ° C. or less.

The heat-dissipating resin sheet of the present invention has good thermal conductivity due to its high filler content, has sufficient strength despite its high filler content, and further has sufficient adhesive strength. .. Therefore, it can be suitably applied to the heat dissipation sheet of the device.

6 is an SEM image showing the boron nitride agglomerated particles used.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof.

The heat radiating sheet according to the embodiment of the present invention contains a resin and a boron nitride filler. It is preferably a single-layer sheet.
A single-layer sheet means a sheet made of a single material and physical properties. For example, a heat radiating sheet having an adhesive layer on one or both surfaces of the heat radiating sheet is not a single layer sheet. In addition, a sheet that has been surface-treated with a surface treatment agent so that one or both surfaces of the heat-dissipating sheet has characteristics, or a sheet that has been subjected to plasma irradiation or the like to have characteristics on one or both surfaces of the heat-dissipating sheet. , A single layer sheet.

<Boron Nitride Filler>
In the embodiment of the present invention, the content of the boron nitride filler is 30 vоl% or more and 60 vоl% or less. In a heat radiating sheet containing a resin and a filler, when the content of the filler is large, the thermal conductivity is high, but the sheet tends to be brittle. In the present embodiment, the heat-dissipating sheet has a large content of the boron nitride filler, high thermal conductivity, and sufficient strength.

The content of the boron nitride filler is preferably 35 vоl% or more, more preferably 40 vоl% or more. Moreover, 55vоl% or less is preferable, and 50vоl% or less is more preferable.

The boron nitride filler may be primary particles or secondary particles in which the primary particles are aggregated. From the viewpoint of thermal conductivity, it is preferable that the primary particles are aggregated secondary particles. In the case of secondary particles, the average particle size (D ₅₀ ) will be described in the section “Boron Nitride Aggregated Particles”.

When the boron nitride filler is a primary particle, the average particle diameter is usually 5 μm or more, preferably 10 μm or more, and more preferably 20 μm or more. Further, it is usually 300 μm or less, preferably 200 μm or less, and more preferably 100 μm or less.

The boron nitride filler may be surface-treated with a surface treatment agent. As the surface treatment agent, a known surface treatment agent can be used.

When the boron nitride filler is agglomerated particles in which primary particles are agglomerated, it has high thermal conductivity and breaking strength, which is preferable in the present invention.

<Boron Nitride Aggregated Particles>
In the case of agglomerated particles, the average particle diameter (D ₅₀ ) is usually 5 μm or more, preferably 10 μm or more, more preferably 25 μm or more, still more preferably 26 μm or more, particularly preferably 30 μm or more, and most preferably 40 μm. As described above, 45 μm or more is preferable, and 50 μm or more is preferable.
Further, it is usually 200 μm or less, preferably 150 μm or less, and more preferably 100 μm or less. If it is too large, the smoothness of the surface will deteriorate when it is formed into a molded body, and the gaps between the agglomerated particles will increase, so the thermal conductivity will not improve. There is a tendency that the contact resistance between the particles increases and the thermal conductivity of the agglomerated particles themselves decreases.

Note that D ₅₀ means the particle size when the cumulative volume is exactly 50% when the cumulative volume is drawn with the volume of the powder used for measurement as 100%, and the measurement method is a wet measurement method. Can be measured using a laser diffraction / scattering particle size distribution measuring device or the like on a sample in which aggregated particles are dispersed in a pure water medium containing sodium hexametaphosphate as a dispersion stabilizer. Can be measured using "Morphorugi" manufactured by Malvern.

In the case of agglomerated particles, the breaking strength is usually 2.5 MPa or more, preferably 3.0 MPa or more, more preferably 3.5 MPa or more, further preferably 4.0 MPa or more, usually 20 MPa or less, preferably 15 MPa or less. More preferably, it is 10 MPa or less. If it is too large, the strength of the particles is too strong, so that the surface smoothness tends to deteriorate and the thermal conductivity tends to decrease when the molded product is formed. If the size is too small, the particles are generated by the pressure when the molded product is manufactured. It tends to be easily deformed and the thermal conductivity does not improve.

The fracture strength can be calculated by a compression test of one particle according to JIS R 1639-5 and the following formula. Usually, particles are measured at 5 points or more, and the average value is adopted.
Formula: Cs = 2.48P / πd ²
Cs: Breaking strength (MPa)
P: Destruction test force (N)
d: Particle diameter (mm)

In the case of agglomerated particles, the total pore volume is usually 2.2 cm ³ / g or less. When the total pore volume is small, the inside of the agglomerated particles is dense, so that it is possible to reduce the boundary surface that inhibits heat conduction, and the agglomerated particles have higher thermal conductivity. If the total pore volume of the agglomerated particles is too large, when used as a filler in the composition, the resin may be incorporated into the pores and the apparent viscosity may increase, and the composition may be molded or the coating liquid may be used. Coating can be difficult.

The lower limit of the total pore volume is not particularly limited, but is usually 0.01 cm ³ / g or more. It is preferably 0.02 cm ³ / g or more, preferably 2 cm ³ / g or less, and more preferably 1.5 cm ³ / g or less.
The total pore volume can be measured by the nitrogen adsorption method and the mercury intrusion method.

In the case of agglomerated particles, the specific surface area is usually 1 m ² / g or more, preferably 3 m ² / g or more and 50 m ² / g or less, and more preferably 5 m ² / g or more and 40 m ² / g or less. Further, it is preferably 8 m ² / g or less, and preferably 7.25 m ² / g or less. When the specific surface area of the agglomerated particles is in this range, the contact resistance between the agglomerated particles tends to be reduced when the agglomerated particles are combined with the resin, and the viscosity increase of the agglomerated particle-containing resin composition can be suppressed, which is preferable. The specific surface area can be measured by the BET 1-point method (adsorbed gas: nitrogen).

In the case of agglomerated particles, the bulk density of the agglomerated particles should be large in order to minimize the uptake of the resin, and is usually preferably 0.3 g / cm ³ or more, more preferably 0.35 g / cm ^3. Above, more preferably 0.4 g / cm ³ or more. If the bulk density of the agglomerated particles is too small, the apparent volume will be large, the volume of the agglomerated particles to be added will be large with respect to the resin in the agglomerated particle-containing resin composition, and the uptake of the resin will be large. The handleability of agglomerated particles tends to be significantly deteriorated. The upper limit of the bulk density of the agglomerated particles is not particularly limited, but is usually 0.95 g / cm ³ or less, preferably 0.9 g / cm ³ or less, and more preferably 0.85 g / cm ³ or less. If the bulk density of the agglomerated particles is too large, the dispersion of the agglomerated particles in the resin composition is biased and tends to settle easily.
The bulk density of the agglomerated particles can be determined by using a usual device or method for measuring the bulk density of the powder.

In the case of agglomerated particles, the major axis of the primary particles constituting the agglomerated particles is usually 0.5 μm or more, preferably 0.6 μm or more, more preferably 0.8 μm or more, still more preferably 1.0 μm or more, and particularly preferably 1.0 μm or more. It is 1.1 μm or more. Further, it is usually 10 μm or less, preferably 5 μm or less, and more preferably 3 μm or less.
The semimajor axis is a value obtained by enlarging one agglomerated particle obtained by SEM measurement and averaging the maximum lengths of the primary particles observable on the image for the primary particles constituting the one agglomerated particle. is there.

The crystal structure of the primary particles in the case of agglomerated particles is not particularly limited, but those containing hexagonal boron nitride (h-BN) as a main component are preferable in terms of ease of synthesis and thermal conductivity. When the binder contains inorganic components other than boron nitride, they crystallize in the process of heat treatment, but it is sufficient that boron nitride is contained as the main component. The crystal structure of the boron nitride primary particles can be confirmed by powder X-ray diffraction measurement.

In the case of agglomerated particles, the average crystallite diameter of the primary particles obtained from the (002) plane peak of the primary particles obtained by powder X-ray diffraction measurement of the agglomerated particles is not particularly limited, but the average crystallite diameter is Larger is preferable from the viewpoint of thermal conductivity. For example, it is usually 300 Å or more, preferably 320 Å or more, more preferably 375 Å or more, still more preferably 380 Å or more, still more preferably 390 Å or more, particularly preferably 400 Å or more, usually 5000 Å or less, preferably 2000 Å or less, and further. It is preferably 1000 Å or less. If the average crystallite diameter is too large, the primary particles grow too much, so that the gaps in the aggregated particles increase, the moldability when forming a molded product deteriorates, and the thermal conductivity increases due to the large gaps. It tends not to improve. If the average crystallite diameter is too small, the grain boundaries in the primary particles increase, so that phonon scattering occurs at the crystal grain boundaries, which tends to result in low thermal conductivity.

The powder X-ray diffraction measurement is performed by filling a glass sample plate having a depth of 0.2 mm with aggregated particles so that the surface becomes smooth.
Here, the "average crystallite diameter" is the crystallite diameter obtained from the (002) plane peak of the primary particles obtained by powder X-ray diffraction measurement by the Scherrer equation as described in Examples described later. Is.

In the case of agglomerated particles, it is obtained by filling a glass sample plate having a depth of 0.2 mm with agglomerated particles of powder before molding into a molded body such as a sheet so that the surface is smooth, and measuring powder X-ray diffraction. The peak intensity ratio ((100) / (004)) of the (100) plane and the (004) plane of the primary particles is preferably 3 or more.
The peak intensity ratio of the (100) plane and the (004) plane of the primary particles is more preferably 3.2 or more, further preferably 3.4 or more, particularly preferably 3.5 or more, and usually 10 or less, preferably 8 Below, it is more preferably 7 or less. If it is larger than the above upper limit, the particles tend to collapse easily when the molded product is formed, and if it is less than the above lower limit, the thermal conductivity in the thickness direction tends not to be improved.
The peak intensity ratio can be calculated from the intensity ratio of the corresponding peak intensity measured by powder X-ray diffraction measurement.

In the case of agglomerated particles, the agglomerated particles are placed at 0.85 ton / cm with a powder tablet molding machine of 10 mmφ.
The peak area intensity ratio ((100) / (004) planes of the (100) plane and (004) plane of the primary particles obtained by powder X-ray diffraction measurement of the pellet-shaped sample obtained by molding at the molding pressure of ^2. )) Is preferably 0.25 or more. This peak area intensity ratio ((100) / (004)) may be 0.3 or more, 0.5 or more, more preferably 0.7 or more, still more preferably 0.81. As mentioned above, it is particularly preferably 0.85 or more, and particularly preferably 0.91 or more. The upper limit is not particularly limited, but is usually 10.0 or less, preferably 5.0 or less, more preferably 4.0 or less, still more preferably 2.0 or less, and particularly preferably 1.6 or less. Is.

Further, the primary particles constituting the agglomerated particles in the pellet-shaped sample obtained by molding the agglomerated particles with a powder tablet molding machine of 10 mmφ at a molding pressure of 0.85 ton / cm ² or more and 2.54 ton / cm ² or less. The peak area intensity ratio ((100) / (004)) of the (100) plane and the (004) plane is usually 0.25 or more, preferably 0.30 or more, more preferably 0.35 or more, and further preferably 0. It is .40 or more, usually 2.0 or less, preferably 1.5 or less, and more preferably 1.2 or less. If it is too large, the contact resistance between the agglomerated particles tends to increase when the molded product is formed, and if it is too small, the agglomerated particles tend to collapse and the thermal conductivity in the thickness direction tends not to improve.

Usually, the optimum press pressure condition for a heat radiating sheet or the like differs depending on the type of the heat radiating sheet. The agglomerated particles dispersed in the resin matrix are exposed to pressure conditions depending on the application, but the particles usually tend to have the ab plane oriented in a direction orthogonal to the pressure direction. Even when agglomerated particles are used, particle deformation occurs with respect to the forming pressure, and as a result, the ab surface tends to be oriented in a direction orthogonal to the pressure direction.
For example, a high heat dissipation substrate made of resin is compared with 0.85 ton / cm ² or more and 2.54 ton / cm ² or less in order to reduce voids inside the resin substrate and to completely contact dispersed agglomerated particles. It is considered to be molded with a high pressure. Therefore, agglomerated particles with little change in the orientation of the primary particles even in the above pressure range are required for improving the thermal conductivity.

In the case of agglomerated particles, it is preferable that the primary particles constituting the agglomerated particles have a card house structure, that is, a mutual reinforcing structure in which the primary particles come into contact with each other at the plane portion and the end face portion of the primary particles, and in a wide molding pressure range. It is possible to suppress the deformation of agglomerated particles. The optimum pressure range differs depending on the application, but in order to achieve high thermal conductivity in the thickness direction of the molded product, at least a certain level of primary particle orientation is required in the range of 0.85 ton / cm ² or more and 2.54 ton / cm ^2. It is preferable to achieve a state in which

The primary particle orientation above a certain level is expressed by, for example, the peak area intensity ratio ((100) / (004)) of the (100) plane and the (004) plane of the primary particles, which is the (004) plane, that is, , It expresses how small the ratio of the ab planes oriented in the direction orthogonal to the pressure direction is. Therefore, the larger the above-mentioned peak area intensity ratio, the less the deformation of the agglomerated particles due to the molding pressure. In order to achieve high thermal conductivity, it is necessary that the peak area intensity ratio is at least 0.25 or more. The lower and upper limits of the peak area intensity ratio are as described above.
The peak area intensity ratio in the range of 0.85 ton / cm ² or more and 2.54 ton / cm ² does not have any problem as long as even one point in the above pressure range satisfies a predetermined value, and it is necessary to achieve it in the entire pressure range of the present invention. Absent. Also, preferably 0.85 ton / cm ² , 1.
A predetermined numerical value is satisfied at three points of 69 ton / cm ² and 2.54 ton / cm ² .

The peak area strength ratio is as follows: A tablet molding machine (10 mmφ) is filled with about 0.2 g of powder, and a manual hydraulic pump (P-1B-041 manufactured by RIKEN Seiki Co., Ltd.) is used at various press pressures. The tableted sample is subjected to measurement (eg, 0.85 ton / cm ² , 1.69 ton / cm ² , 2.54 ton / cm ^2, etc.). The measurement is X'Pe manufactured by PANalytical in the Netherlands.
The intensity ratio of the corresponding peak area can be calculated by using the rtPro MPD powder X-ray diffractometer.

<Manufacturing method of boron nitride agglomerated particles>
In the case of agglomerated particles, the production method thereof is not particularly limited, and the agglomerated particles can be produced according to a conventional method. As a preferable production method, particles are granulated using a slurry containing a raw material boron nitride powder having a viscosity of 200 to 5000 mPa · s (hereinafter, may be referred to as “BN slurry”), and the granulated particles are heat-treated. By doing so, the crystallites of the primary particles constituting the aggregated particles can be grown and produced while maintaining the size of the granulated particles. The viscosity of the BN slurry is preferably 300 mPa · s or more, more preferably 500 mPa · s or more, further preferably 700 mPa · s or more, particularly preferably 1000 mPa · s or more, preferably 4000 mPa · s or less, more preferably 3000 mPa. -S or less.

The viscosity of the BN slurry, the average particle diameter D ₅₀ based on volume of the resulting aggregated particles and,
Greatly affects the average crystallite size of the primary particles constituting the aggregated particles, by making the the viscosity 200 mPa · s or more, the average particle diameter D ₅₀ of the volume-based average crystallite diameter and BN agglomerated particles of primary particles It can be made larger.
On the other hand, by setting the viscosity of the BN slurry to 5000 mPa · s or less, granulation can be facilitated. The method for preparing the viscosity of the BN slurry will be described later.

The viscosity of the BN slurry is the viscosity measured at a blade rotation speed of 100 rpm using a rotational viscometer "VISCO BASIC Plus R" manufactured by FUNGILAB.

In the preparation of the slurry, the raw material powder is synthesized from commercially available h-BN, commercially available α and β-BN, boron nitride prepared by a reduction nitride method of a boron compound and ammonia, and a nitrogen-containing compound such as a boron compound and melamine. Any of the above-mentioned boron nitride and the like can be used without limitation, but h-BN is particularly preferably used because it exerts the effect of the present invention more.

As the form of the raw material powder used for preparing the slurry, powdery particles having a wide half-value width of the peak obtained by powder X-ray diffraction measurement and low crystallinity are preferable. As a measure of crystallinity, the peak width at half maximum of the (002) plane obtained from powder X-ray diffraction measurement is usually 0.4 ° or more, preferably 0.45 ° or more, more preferably 0.5 at an angle of 2θ. It is above °. Further, it is usually 2.0 ° or less, preferably 1.5 ° or less, and more preferably 1 ° or less. If it is larger than the above upper limit, the crystallites do not become sufficiently large, and it takes a long time to make them large, so that the productivity tends to deteriorate. If it is less than the above lower limit, the crystallinity is too high, sufficient crystal growth cannot be expected, and the dispersion stability at the time of producing the slurry tends to deteriorate. The powder X-ray diffraction measurement method will be described in the section of Examples described later.

It is preferable that oxygen atoms are present to some extent in the raw material powder used for preparing the slurry, and the total oxygen concentration in the raw material powder is usually 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more. More preferably, it is 4% by mass or more. Further, it is usually 10% by mass or less, more preferably 9% by mass or less. If it is larger than the above upper limit, oxygen tends to remain even after the heat treatment, so that the effect of improving the thermal conductivity tends to be small. If it is less than the above lower limit, the crystallinity is too high, crystal growth cannot be expected, and the peak intensity ratio that can be confirmed from the powder X-ray diffraction measurement tends to deviate from the desired range.

As a method for adjusting the total oxygen concentration of the raw material powder within the above range, for example, a method of synthesizing boron nitride at a low temperature of 1500 ° C. or lower, or a raw material powder in a low temperature oxidizing atmosphere of 500 ° C. to 900 ° C. There is a method of heat-treating the powder.
The total oxygen concentration of the raw material powder can be measured by an inert gas melting-infrared absorption method using an oxygen / nitrogen analyzer manufactured by Horiba Seisakusho Co., Ltd.

The total pore volume of the raw material powder used for preparing the slurry is usually 1.0 cm ³ / g or less, but preferably 0.3 cm ³ / g or more and 1.0 cm ³ / g or less, more preferably 0.5 cm ³ / G or more and 1.0 cm ³ / g or less. When the total pore volume is 1.0 cm ³ / g or less, the raw material powder is dense, so that granulation with a high degree of sphericity is possible.

The specific surface area of the raw material powder is usually 50 m ² / g or more, but 60 m ² / g or more is preferable, and 70 m ² / g or more is more preferable. Usually, it is 1000 m ² / g or less, but 500 m ² / g or less is preferable, and 300 m ² / g or less is more preferable. It is preferable that the specific surface area of the raw material powder is 50 m ² / g or more because the dispersed particle size in the slurry used for spheroidization by granulation can be reduced. Further, it is preferable to set the content to 1000 m ² / g or less because an increase in slurry viscosity can be suppressed.
The total pore volume of the raw material powder can be measured by the nitrogen adsorption method and the mercury intrusion method.
The specific surface area can be measured by the BET 1-point method (adsorbed gas: nitrogen). Specific measurement methods for the total pore volume and specific surface area of the raw material powder will be described in the section of Examples described later.

The medium used for preparing the slurry is not particularly limited, and water and / or various organic solvents can be used, but water is preferably used from the viewpoint of ease of spray drying and simplification of the apparatus. Pure water is more preferable.

As for the amount of the medium used for preparing the slurry, it is preferable to add an amount having a viscosity of the slurry of 200 to 5000 mPa · s.
Specifically, the amount of the medium used for preparing the slurry is usually 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, and usually 70% by mass or less, preferably 65% by mass. Hereinafter, it is more preferably 60% by mass or less. If the amount of the medium used is larger than the above upper limit, the viscosity of the slurry becomes too low, so that the uniformity of the slurry due to sedimentation or the like is impaired, and the crystallite diameter of the primary particles constituting the obtained aggregated particles tends to deviate from the desired range. There is. If it is less than the lower limit, the slurry viscosity is too high, and granulation tends to be difficult. That is, if the amount of the medium used is out of the above range, it becomes difficult to simultaneously satisfy the size of the agglomerated particles, the crystallinity of the primary particles constituting the agglomerated particles, and the reduction of the crystal grain boundaries in the primary particles.

When preparing the slurry, it is preferable to add various surfactants from the viewpoint of adjusting the viscosity of the slurry and the dispersion stability (agglutination suppression) of the raw material powder in the slurry.
As the surfactant, an anionic surfactant, a cationic surfactant, a nonionic surfactant and the like can be used, and one of these may be used alone or two or more thereof may be mixed. May be used.

In general, surfactants can change the viscosity of the slurry. Therefore, when a surfactant is added to the slurry, the amount thereof is adjusted so that the viscosity of the slurry is 200 to 5000 mPa · s. For example, as the raw material BN, boron nitride having a half-value width 2θ of the (002) plane peak obtained by powder X-ray diffraction measurement of 0.67 ° and an oxygen concentration of 7.5% by mass is used to have a solid content of 50% by mass. When preparing the slurry, the active ingredient of the anionic surfactant is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, based on the total amount of the slurry. It is usually added in an amount of 10% by mass or less, preferably 7% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less. If it is larger than the above upper limit, the viscosity of the slurry tends to decrease too much, and the carbon component derived from the surfactant tends to remain in the generated aggregated particles. If it is less than the above lower limit, the slurry viscosity tends to be too high and the granulation itself tends to be difficult.

When preparing the slurry, a binder may be included in order to effectively granulate the raw material powder into particles. The binder acts to tightly bind the primary particles and stabilize the granulated particles.
The binder used for the slurry may be any binder that can enhance the adhesiveness between the boron nitride particles, but since the granulated particles are heat-treated after being granulated, the heat resistance to high temperature conditions in this heat treatment step is improved. It is preferable to have.

As such a binder, metal oxides such as aluminum oxide, magnesium oxide, yttrium oxide, calcium oxide, silicon oxide, boron oxide, cerium oxide, zirconium oxide, and titanium oxide are preferably used. Among these, aluminum oxide and yttrium oxide are preferable from the viewpoints of thermal conductivity and heat resistance as oxides and a bonding force for bonding boron nitride particles to each other. As the binder, a liquid binder such as alumina sol may be used, or a binder that reacts during the heat treatment and is converted into other inorganic components may be used. One of these binders may be used alone, or two or more of these binders may be mixed and used.

The amount of the binder used (in the case of a liquid binder, the amount used as a solid content) is usually 0% by mass or more and 30% by mass or less, preferably 0% by mass or more and 20% by mass, based on the raw material powder in the BN slurry. % Or less, more preferably 0% by mass or more and 15% by mass or less. When the above upper limit is exceeded, the content of the raw material powder in the granulated particles is reduced, which not only affects the crystal growth but also reduces the effect of improving the thermal conductivity when used as a thermally conductive filler.

The slurry preparation method is not particularly limited as long as the raw material powder and medium, and if necessary, the binder and the surfactant are uniformly dispersed and prepared in a desired viscosity range, but the raw material powder and medium, and further, if necessary, a binder. , When a surfactant is used, it is preferably prepared as follows.

A predetermined amount of the raw material powder is weighed in a resin bottle, and then a predetermined amount of binder is added. Further, after adding a predetermined amount of the surfactant, a zirconia-based ceramic ball is added, and the mixture is stirred on a pot mill turntable for about 0.5 to 5 hours until the desired viscosity is reached.
The order of addition is not particularly limited, but when a large amount of raw material powder is slurried, agglomerates such as lumps are likely to be formed. Therefore, after preparing an aqueous solution in which a surfactant and a binder are added to water, a predetermined amount is added. Raw material powder may be added little by little, zirconia-based ceramic balls may be added thereto, and the powder may be dispersed and slurryed on a pot mill turntable.

In addition to the pot mill, a dispersion device such as a bead mill or a planetary mixer may be used for dispersion. At the time of slurrying, the temperature of the slurry is 10 ° C. or higher and 60 ° C. or lower. If it is lower than the lower limit, the viscosity of the slurry increases and tends to deviate from the desired viscosity range, and if it is higher than the upper limit, the raw material powder is easily decomposed into ammonia in the aqueous solution. Usually, it is 10 ° C. or higher and 60 ° C. or lower, preferably 15 ° C. or higher and 50 ° C. or lower, more preferably 15 ° C. or higher and 40 ° C. or lower, and further preferably 15 ° C. or higher and 35 ° C. or lower.

In order to obtain granulated particles from the prepared BN slurry, general granulation methods such as a spray dry method, a rolling method, a fluidized bed method, and a stirring method can be used, and among these, the spray dry method is preferable.
In the spray-drying method, granulated particles of a desired size are produced by the concentration of the slurry as a raw material, the amount of liquid to be introduced into the apparatus per unit time, and the compressed air pressure and the amount of compressed air when spraying the transferred slurry. It is also possible to obtain spherical granulated particles. There are no restrictions on the spray-drying device used, but a rotary disc is optimal for larger spherical granulated particles. Examples of such a device include a spray dryer F series manufactured by Okawara Kakoki Co., Ltd., a spray dryer "MDL-050M" manufactured by Fujisaki Electric Co., Ltd., and the like.

The average particle size of the granulated particles obtained by the granulation, if preferably the average range of particle diameter on a volume basis of the agglomerated particles to 5μm or 200μm or less, usually 3μm in an average particle diameter D ₅₀ of the volume-based The above is preferably 5 μm or more, more preferably 10 μm or more, further preferably 15 μm or more, still more preferably 20 μm or more, particularly preferably 25 μm or more, still more preferably 25 μm or more, even 26 μm or more, preferably 30 μm or more. It is preferable that it is present, and it is preferable that it is 35 μm or more. Further, it is preferably 150 μm or less, and more preferably 100 μm or less. Here, the average particle diameter D _{50 based on} the volume of the granulated particles can be measured by, for example, "LA920" manufactured by HORIBA, Ltd. for the wet type and "Morphorogi" manufactured by Malvern for the dry type.

The above-mentioned granulated particles can be further heat-treated in a non-oxidizing gas atmosphere to produce aggregated particles.
Here, the non-oxidizing gas atmosphere is an atmosphere of nitrogen gas, helium gas, argon gas, ammonia gas, hydrogen gas, methane gas, propane gas, carbon monoxide gas and the like. The crystallization rate of agglomerated particles differs depending on the type of atmospheric gas used here, and in order to carry out crystallization in a short time, nitrogen gas or a mixed gas in which nitrogen gas and another gas are used in combination is particularly preferably used. ..
The heat treatment temperature is usually 1800 ° C. or higher and 2300 ° C. or lower, preferably 1900 ° C. or higher, and preferably 2200 ° C. or lower. If the heat treatment temperature is too low, the growth of the average crystallite of boron nitride may be insufficient, and the thermal conductivity of the aggregated particles and the molded product may be reduced. If the heat treatment temperature is too high, boron nitride may be decomposed.

By setting the heat treatment temperature to 1800 ° C. or higher and 2300 ° C. or lower, the peak intensity ratio ((100) / (004)) of the (100) plane and the (004) plane of the primary particles can be set to a desired value. ..
The heat treatment time is usually 3 hours or more, preferably 4 hours or more, more preferably 5 hours or more, and usually 20 hours or less, preferably 15 hours or less. If the heat treatment time is less than the above lower limit, crystal growth becomes insufficient, and if the heat treatment time exceeds the above upper limit, BN may be partially decomposed.

Since the heat treatment is carried out in a non-oxidizing gas atmosphere, it is preferable that the inside of the firing furnace is usually exhausted using a vacuum pump and then heated to a desired temperature while introducing the non-oxidizing gas. Although it is heated, if the inside of the firing furnace can be sufficiently replaced with a non-oxidizing gas, the temperature may be raised by heating while introducing the non-oxidizing gas under normal pressure. Examples of the firing furnace include batch type furnaces such as muffle furnaces, tubular furnaces, and atmospheric furnaces, and continuous furnaces such as rotary kilns, screw conveyor furnaces, tunnel furnaces, belt furnaces, pusher furnaces, and vertical continuous furnaces, depending on the purpose. It can be used properly.

Generally, the granulated particles to be heat-treated are placed in a circular graphite-covered crucible and fired in order to reduce the non-uniformity of the composition during firing. At this time, in addition to reducing the non-uniformity of the composition, a graphite partition may be provided for the purpose of suppressing sintering of the agglomerated particles by firing. The number of divisions by the partition is not particularly limited as long as sintering can be suppressed, but is usually 2 or more and 16 or less. If the number of divisions is larger than the above upper limit, sintering can be suppressed, but the crystals of the primary particles tend not to grow sufficiently, and if the number of divisions is smaller than the above lower limit, sintering may proceed.

The agglomerated particles after the heat treatment are preferably classified in order to reduce the particle size distribution and suppress an increase in viscosity when blended in the resin composition. This classification is usually performed after the heat treatment of the granulated particles, but it may be performed on the granulated particles before the heat treatment and then subjected to the heat treatment.

The classification may be either wet or dry, but the dry classification is preferable from the viewpoint of suppressing the decomposition of boron nitride. In particular, when the binder has water solubility, dry classification is particularly preferably used.
Dry classification includes classification by sieving and wind classification by the difference between centrifugal force and fluid drag, but swirling flow type classification machine, forced vortex centrifugal type classification machine, semi-free vortex centrifugal type classification machine, etc. It can also be performed using a classifier of. Among these, particles to be classified, such as a swirling air flow classifier for classifying small particles in the submicron to single micron range, and a semi-free vortex centrifugal classifier for classifying larger particles. It may be used properly according to the particle size of.

<Resin>
The resin used in this embodiment has a Tg of 60 ° C. or lower. By using a resin having a low Tg of 60 ° C. or lower, it has sufficient strength even if the content of the boron nitride filler is increased, and the adhesiveness of the heat radiating sheet can be further improved.
Thermal conductivity and adhesive strength are contradictory properties, and it has been considered very difficult to achieve both thermal conductivity and adhesive strength, especially in a single-layer sheet. However, as a result of the study by the present inventor, it is said that by using a resin having a low Tg of 60 ° C. or lower, the content of the boron nitride filler is increased to improve the thermal conductivity and the adhesiveness of the heat radiating sheet is improved. We have come up with the idea of achieving conflicting properties in single-layer fillers.

The Tg of the resin is preferably 55 ° C. or lower, more preferably 50 ° C. or lower, from the viewpoint of further improving the adhesiveness of the heat radiating sheet. The lower limit is not particularly limited, but is usually 5 ° C. or higher, preferably 10 ° C. or higher.

The type of resin is not particularly limited as long as the above Tg is satisfied, but a curable resin and / or a thermoplastic resin is preferable. For example, examples of the curable resin include thermosetting, photocurable, and electron beam curable, and thermosetting resins and / or thermoplastic resins are used in terms of heat resistance, water absorption, dimensional stability, and the like. Of these, epoxy resin is more preferable. Two or more of these resins may be used in combination.

The epoxy resin may be only an epoxy resin having one kind of structural unit, but a plurality of epoxy resins having different structural units may be combined. Further, the epoxy resin is used together with a curing agent for epoxy resin and a curing accelerator, if necessary.

Here, in order to reduce voids in the cured product and obtain a cured product having high thermal conductivity in addition to coating property, film forming property, and adhesiveness, at least a phenoxy resin described later as an epoxy resin (hereinafter, "epoxy resin") It may be referred to as "(A)"). The mass ratio of the epoxy resin (A) to the total amount of the epoxy resin is not particularly limited, but is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and particularly preferably 16.0% by mass. % Or more, particularly preferably 18.0% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 80% by mass or less.

The phenoxy resin usually refers to a resin obtained by reacting epihalohydrin with a divalent phenol compound, or a resin obtained by reacting a divalent epoxy compound with a divalent phenol compound, but in the present invention. Of these, the phenoxy resin having a high molecular weight having a weight average molecular weight of 10,000 or more is designated as the epoxy resin (A).
Here, the weight average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography.

The epoxy resin (A) is a phenoxy resin or bisphenol having at least one skeleton selected from the group consisting of a naphthalene skeleton, a fluorene skeleton, a biphenyl skeleton, an anthracene skeleton, a pyrene skeleton, a xanthene skeleton, an adamantan skeleton and a dicyclopentadiene skeleton. A type phenoxy resin, bisphenol F type phenoxy resin, naphthalene type phenoxy resin, phenol novolac type phenoxy resin, cresol novolac type phenoxy resin, phenol aralkyl type phenoxy resin, biphenyl type phenoxy resin, triphenylmethane type phenoxy resin, dicyclopentadiene type Phenoxy resin, glycidyl ester type phenoxy resin, and glycidylamine type phenoxy resin are preferable. Among them, a phenoxy resin having a fluorene skeleton and / or a biphenyl skeleton, a bisphenol A type phenoxy resin, and a bisphenol F type phenoxy resin are particularly preferable because heat resistance and adhesion are further enhanced.
One of these may be used alone, or two or more thereof may be mixed and used.

In addition to the epoxy resin (A), the epoxy resin preferably contains an epoxy resin having two or more epoxy groups in the molecule (hereinafter, may be referred to as "epoxy resin (B)"). Examples of the epoxy resin (B) include bisphenol A type epoxy resin, bisphenol F type epoxy resin, naphthalene type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, phenol aralkyl type epoxy resin, and biphenyl type epoxy resin. , Triphenylmethane type epoxy resin, dicyclopentadiene type epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, polyfunctional phenol type epoxy resin and the like. Of these, bisphenol A type epoxy resin, bisphenol F type epoxy resin, glycidylamine type epoxy resin, and polyfunctional phenol type epoxy resin are preferable in terms of improving heat resistance and adhesion.
One of these may be used alone, or two or more thereof may be mixed and used.

From the viewpoint of controlling the melt viscosity, the epoxy resin (B) has a weight average molecular weight of preferably 100 to 5000, more preferably 200 to 2000. If the weight average molecular weight is lower than 100, the heat resistance tends to be inferior, and if it is higher than 5000, the melting point of the epoxy resin tends to be high and the workability tends to be lowered.

Further, the epoxy resin may contain an epoxy resin (hereinafter, may be referred to as "another epoxy resin") other than the epoxy resin (A) and the epoxy resin (B) as long as the purpose is not impaired. Good. The content of the other epoxy resin is usually 50% by mass or less, preferably 30% by mass or less, based on the total of the epoxy resin (A) and the epoxy resin (B).

The curing agent for epoxy resin is appropriately selected according to the type of resin used. For example, an acid anhydride-based curing agent and an amine-based curing agent can be mentioned. Examples of the acid anhydride-based curing agent include tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and benzophenone tetracarboxylic acid anhydride. Examples of the amine-based curing agent include aliphatic polyamines such as ethylenediamine, diethylenetriamine and triethylenetetramine, aromatic polyamines such as diaminodiphenylsulfone, diaminodiphenylmethane, diaminodiphenylether and m-phenylenediamine, and dicyandiamide. One of these may be used alone, or two or more thereof may be mixed and used. These curing agents for epoxy resins are usually blended in an equivalent ratio of 0.3 or more and 1.5 or less with respect to the epoxy resin.

The curing accelerator is appropriately selected according to the type of resin and curing agent used. For example, examples of the curing accelerator for the acid anhydrous curing agent include boron trifluoride monoethylamine, 2-ethyl-4-methylimidazole, 1-isobutyl-2-methylimidazole, and 2-phenyl-4-methylimidazole. Can be mentioned. One of these may be used alone, or two or more thereof may be mixed and used. These curing accelerators are usually used in a range of 0.1 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the epoxy resin.

Further, the resin contained in the heat radiating sheet may be a thermoplastic resin. Examples of the thermoplastic resin include polyolefin resins such as polyethylene resin, polypropylene resin and ethylene-vinyl acetate copolymer resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyester resin such as liquid crystal polyester resin, polyvinyl chloride resin and phenoxy. Examples thereof include resins, acrylic resins, polycarbonate resins, polyphenylene sulfide resins, polyphenylene ether resins, polyamide resins, polyamideimide resins, polyimide resins, polyetheramideimide resins, polyetheramide resins and polyetherimide resins. In addition, copolymers such as those block copolymers and graft copolymers are also included. These may be used alone or in admixture of two or more.

The resin contained in the heat radiating sheet may contain a rubber component, and examples of the rubber component include natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, and ethylene-propylene copolymer. Examples thereof include rubber, ethylene-propylene-diene copolymer rubber, butadiene-acrylonitrile copolymer rubber, isobutylene-isoprene copolymer rubber, chloroprene rubber, silicon rubber, fluorine rubber, chloro-sulfonated polyethylene and polyurethane rubber. One of these may be used alone, or two or more thereof may be mixed and used.

The content of the resin in the heat radiating sheet is usually 20 vоl% or more, preferably 30 vоl% or more. Further, it is usually 70 vоl% or less, and preferably 50 vоl% or less.

<Other ingredients>
The heat-dissipating resin sheet in the present embodiment may contain other components as long as the effects of the present invention are not impaired. Specifically, inorganic fillers such as aluminum nitride, silicon nitride, fibrous, plate-like, and particulate aggregated BN nitride particles, alumina, fibrous alumina, zinc oxide, magnesium oxide, beryllium oxide, titanium oxide, and the like. Insulating metal oxides, inorganic fillers such as diamond, fullerene, aluminum hydroxide, magnesium hydroxide, surface treatment agents such as silane coupling agents that improve the interfacial adhesion strength between inorganic fillers and matrix resins, and insulating properties such as reducing agents. Examples thereof include a carbon component, a resin curing agent, a resin curing accelerator, a viscosity modifier, and a dispersant.

<Manufacturing method of heat dissipation sheet>
In the present embodiment, the heat radiating sheet can be manufactured by a commonly used method. For example, it can be obtained by preparing a resin composition containing a filler and a resin and molding the resin composition into a sheet. The resin composition before being molded into a sheet is also another embodiment of the present invention. That is, another embodiment of the present invention is a resin composition for a heat radiating sheet containing a resin and a boron nitride filler, wherein the content of the boron nitride filler is 30 vоl% or more and 60 vоl% or less, and the above-mentioned A resin composition in which the Tg of the resin is 60 ° C. or lower.

The resin composition can be obtained by uniformly mixing the filler, the resin, and in some cases the inorganic particles, and other components added as needed by stirring or kneading. For the mixing, for example, a general kneading device such as a mixer, a kneader, a single shaft or a twin shaft kneader can be used, and in the mixing, heating may be performed if necessary.

The mixing order of each compounding component is also arbitrary as long as there are no particular problems such as reaction or precipitation, but for example, a resin is mixed and dissolved in an organic solvent (for example, methyl ethyl ketone) to prepare a resin solution. A sufficiently mixed mixture of filler and other components is added to the obtained resin solution and mixed, and then an organic solvent is further added and mixed for viscosity adjustment, and then a resin curing agent, a curing accelerator, or a curing accelerator or , A method of adding an additive such as a dispersant and mixing.

The prepared resin composition becomes a heat radiating sheet by being formed into a sheet. As a method for molding the molded product, a generally used method can be used.
For example, when the resin composition has plasticity and fluidity, it can be molded by curing the resin composition in a desired shape, for example, in a state of being housed in a mold.

In the production of such a molded product, injection molding, injection compression molding, extrusion molding, compression molding and vacuum compression molding can be utilized.
When the above slurry contains a solvent, the solvent can be removed by a known heating method such as a hot plate, a hot air furnace, an IR heating furnace, a vacuum dryer, and a high frequency heater.
When the resin composition is a thermosetting resin composition such as an epoxy resin or a silicone resin, molding, that is, curing of the molded product can be performed under the respective curing temperature conditions.

When the resin composition is a thermoplastic resin composition, the molded product can be molded under the conditions of a temperature equal to or higher than the melting temperature of the thermoplastic resin and a predetermined molding speed and pressure.
The heat radiating sheet can also be obtained by carving a cured product of the resin composition into a desired shape.

The thickness of the heat radiating sheet is appropriately set depending on the intended use, but is usually 50 μm or more, preferably 100 μm or more, and usually 500 μm or less, preferably 300 μm or less.

<Heat dissipation sheet>
In the heat radiating sheet according to the embodiment of the present invention, the difference between the elastic modulus E'25 at 25 ° C. and the elastic modulus E'175 at 175 ° C. is preferably 1 GPa or more. By satisfying such physical properties, it becomes possible to give the heat radiating sheet toughness, which is preferable.
The difference in elastic modulus E'is preferably 1 GPa or more, more preferably 2 GPa or more, and the upper limit is not limited, but is usually 100 GPa or less, more preferably 10 GPa or less.
The difference in elastic modulus E'can be set within the preferable range by adjusting the resin / filler ratio or appropriately selecting the resin type.

Further, the heat radiating sheet according to the embodiment of the present invention preferably has a 90 ° peel test strength of 1.5 N / cm or more, more preferably 1.7 N / cm or more, and usually 100 N / cm or less. Yes, preferably 80 N / cm or less.
The 90 ° peel test strength is measured by performing the test of JIS K6854-1: 1999 at a test speed of 50 mm / min using a desktop material tester STA-1225 manufactured by Orientec Co., Ltd.
The 90 ° peel test strength in the above-mentioned preferable range can be achieved by adjusting the resin / filler ratio, appropriately selecting the resin type, and the like.

Further, the heat radiating sheet according to the embodiment of the present invention preferably has sufficient thermal conductivity, and is usually 2 WmK or more, preferably 5 W / mK or more, more preferably 10 W / mK or more, still more preferably 15 W / mK or more. Especially preferably, it is 17 W / mK or more.

Further, the heat radiating sheet according to the embodiment of the present invention preferably has sufficient withstand voltage performance, and is usually 10 kV / mm or more, preferably 15 kV / mm or more, and particularly preferably 20 kV / mm or more.

<Device>
The heat radiating sheet in this embodiment is preferable as a heat radiating sheet for devices, particularly power devices.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded. The values of various conditions and evaluation results in the following examples indicate the preferable range of the present invention as well as the preferable range in the embodiment of the present invention, and the preferable range of the present invention is the above-described embodiment. It can be determined in consideration of the preferable range and the range indicated by the combination of the values of the following examples or the values of the examples.

Production example of BN agglomerated particles (BN-A) (raw material)
Raw material h-BN powder (half-value width of (002) plane peak obtained by powder X-ray diffraction measurement (X-ray: CuKα ₁ ) is 2θ = 0.67 °, oxygen concentration is 7.5% by mass): 10000 g binder ( Taki Chemical Co., Ltd. "Taxerum M160L", solid content concentration 21% by mass): 11496 g Surfactant (Kao Co., Ltd. surfactant "Ammmon Lauryl Sulfate": solid content concentration 14% by mass): 250 g
(Preparation of slurry)
A predetermined amount of the raw material h-BN powder was weighed in a resin bottle, and then a predetermined amount of binder was added. Further, after adding a predetermined amount of the surfactant, zirconia-based ceramic balls were added, and the mixture was stirred on a pot mill turntable for 1 hour.
The viscosity of the slurry was 810 mPa · s.

(Granulation)
Granulation from the BN slurry was carried out using FOC-20 manufactured by Okawara Kakoki Co., Ltd. at a disk rotation speed of 20000 to 23000 rpm and a drying temperature of 80 ° C. to obtain spherical BN granulated particles.

(Preparation of BN-A aggregated particles)
After vacuuming the above BN granulated particles at room temperature, nitrogen gas is introduced to repressurize the particles, and the temperature is raised to 2000 ° C. at 83 ° C./hour while introducing nitrogen gas as it is. It was held for 5 hours while introducing gas. Then, it cooled to room temperature, and spherical BN-A aggregated particles having a card house structure were obtained.

(Classification)
Further, the BN-A agglomerated particles after the heat treatment were lightly pulverized using a mortar and a pestle, and then classified using a sieve having an opening of 90 μm. After classification, the average crystallite diameter of the BN primary particles constituting the BN-A agglomerated particles, the peak intensity ratio of the (100) plane to the (004) plane of the BN primary particles ((100) / (004)), BN- D _{50 of} A agglomerated particles was measured. The measurement results are as follows.
Average crystallite diameter of BN primary particles: 415 Å
Intensity ratio ((100) / (004)): 3.6
D ₅₀ : 50 μm

Production example of BN agglomerated particles (BN-D) Spherical BN- having a card house structure is the same as BN-A except that the mixing ratio of the raw materials is changed as follows and the slurry is prepared as follows. D agglomerated particles were obtained.
(material)
Raw material h-BN powder: 2400 g
Pure water: 2199 g
Binder: 1380g
Surfactant: 60g
(Slurry preparation)
A predetermined amount of the raw material h-BN powder was weighed in a resin bottle, and then a predetermined amount of pure water and a binder were added in this order. Further, after adding a predetermined amount of the surfactant, zirconia-based ceramic balls were added, and the mixture was stirred on a pot mill turntable for 1 hour. The viscosity of the slurry was 155 mPa.
Average crystallite diameter of BN primary particles: 250 Å
Intensity ratio ((100) / (004)): 6.0
D ₅₀ : 5 μm

Example 1
BN agglomerated particles BN-A having a card house structure 4.7 parts by mass, boron nitride PTX25 having a non-card house structure (manufactured by Momentive Co., Ltd., D50: 19.8 μm, (100) / (004) of BN primary particles Surface peak intensity ratio: 1.4, average crystallite diameter of BN primary particles: 537 Å) 1.6 parts by mass, and an epoxy resin containing 20% by mass of phenoxy resin containing bisphenol F type phenoxy resin with respect to the total amount of epoxy resin ( Tg: 50 ° C.) 2.1 parts by mass, solvent (cyclohexanone / methyl ethyl ketone) 5.9 parts by mass, dispersant (trade name: BYK-2155, manufactured by Big Chemie Japan Co., Ltd.) 0.44 parts by mass, 1-cyanoethyl -2-Undecyl imidazole (trade name: C11Z-CN, manufactured by Shikoku Kasei Kogyo Co., Ltd.) 0.12 parts by mass was mixed to prepare a slurry for a heat dissipation sheet. The volume ratios of the BN filler and the resin component at this time are 54.3 vol% and 45.7 vol%, respectively.
The prepared heat-dissipating sheet slurry was applied to a base material by a doctor blade method, and after heat-drying, a heat-dissipating sheet having a sheet thickness of 245 μm was obtained. The sheet was made into a size of 25 mm in width and 60 mm in length, and a 90 ° peel test (JIS K6554-1:) was performed by stacking 25 mm wide and 90 mm long base materials with one end aligned and pressing so that a 30 mm base material was left over. A test piece for 1999) was obtained.
The obtained test piece was subjected to a 90 ° peel test (JIS K6854-1: 1999) using a desktop material testing machine STA-1225 manufactured by Orientec Co., Ltd. at a test speed of 50 mm / min. The peel test strength was 4.37 N / cm.
The thermal conductivity was measured to be 18 W / mK, and the elastic modulus E'25 at 25 ° C. and the elastic modulus E'175 at 175 ° C. were measured to be 3.7 × 10 ⁹ Pa and 3.1, respectively. It was × 10 ⁸ Pa.

Example 2
BN agglomerated particles BN-A having a card house structure 4.7 parts by mass, boron nitride PTX25 having a non-card house structure (manufactured by Momentive Co., Ltd., D50: 19.8 μm, (100) / (004) of BN primary particles Surface peak intensity ratio: 1.4, average crystallite diameter of BN primary particles: 537 Å) 1.6 parts by mass, and epoxy resin (Tg: 20 ° C) containing 33.3% by mass of phenoxy resin with respect to the total amount of epoxy resin 2 .1 part by mass, solvent (cyclohexanone / methylethylketone) 5.9 part by mass, dispersant (trade name: BYK-2155, manufactured by Big Chemie Japan Co., Ltd.) 0.41 part by mass, 1-cyanoethyl-2-undecylimidazole (Product name: C11Z-CN, manufactured by Shikoku Kasei Kogyo Co., Ltd.) 0.14 parts by mass were mixed to prepare a slurry for a heat dissipation sheet. The volume ratios of the BN filler and the resin component at this time are 54.3 vol% and 45.7 vol%, respectively.
The prepared heat-dissipating sheet slurry was applied to a base material by a doctor blade method, and after heat-drying, a heat-dissipating sheet having a sheet thickness of 222 μm was obtained. The sheet was made into a size of 25 mm in width and 60 mm in length, and a 90 ° peel test (JIS K6554-1:) was performed by stacking 25 mm wide and 90 mm long base materials with one end aligned and pressing so that a 30 mm base material was left over. A test piece for 1999) was obtained.
A 90 ° peel test (JIS K6854-1: 1999) was performed on the obtained test piece using a desktop material tester STA-1225 manufactured by Orientec Co., Ltd. at a test speed of 50 mm / min. The peel test strength was 1.87 N / cm.
Moreover, when the thermal conductivity was measured, it was 18 W / mK.

Example 3
BN agglomerated particles BN-A having a card house structure, 3.5 parts by mass, boron nitride PTX25 having a non-card house structure (manufactured by Momentive Co., Ltd., D50: 19.8 μm, BN primary particles (100) / (004)) Surface peak intensity ratio: 1.4, average crystallite diameter of BN primary particles: 537 Å) 1.2 parts by mass, and an epoxy resin containing 20% by mass of phenoxy resin containing bisphenol F type phenoxy resin with respect to the total amount of epoxy resin ( Tg: 50 ° C.) 4.0 parts by mass, solvent (cyclohexanone / methyl ethyl ketone) 5.5 parts by mass, dispersant (trade name: BYK-2155, manufactured by Big Chemie Japan Co., Ltd.) 0.42 parts by mass, 1-cyanoethyl -2-Undecyl imidazole (trade name: C11Z-CN, manufactured by Shikoku Kasei Kogyo Co., Ltd.) 0.24 parts by mass was mixed to prepare a slurry for a heat dissipation sheet. The volume ratios of the BN filler and the resin component at this time are 34.2 vol% and 65.8 vol%, respectively.
The prepared heat-dissipating sheet slurry was applied to a base material by a doctor blade method, and after heat-drying, a heat-dissipating sheet having a sheet thickness of 200 μm was obtained. The sheet was made into a size of 25 mm in width and 60 mm in length, and a 90 ° peel test (JIS K6554-1:) was performed by stacking 25 mm wide and 90 mm long base materials with one end aligned and pressing so that a 30 mm base material was left over. A test piece for 1999) was obtained.
The obtained test piece was subjected to a 90 ° peel test (JIS K6854-1: 1999) using a desktop material tester STA-1225 manufactured by Orientec Co., Ltd. at a test speed of 50 mm / min. The peel test strength was greater than the measurement limit of 15 N / cm of the testing machine.

Example 4
BN agglomerated particles having a card house structure BN-A 3.5 parts by mass, boron nitride PTX25 having a non-card house structure (manufactured by Momentive Co., Ltd., D50: 19.8 μm, (100) / (004) plane of BN primary particles Peak intensity ratio: 1.4, average crystallite diameter of BN primary particles: 537 Å) 1.1 parts by mass, and epoxy resin (Tg: 20 ° C.) containing 33.3% by mass of phenoxy resin with respect to the total amount of epoxy resin. 0 parts by mass, solvent (cyclohexanone / methyl ethyl ketone) 5.6 parts by mass, dispersant (trade name: BYK-2155, manufactured by Big Chemie Japan Co., Ltd.) 0.48 parts by mass, 1-cyanoethyl-2-undecylimidazole (1-cyanoethyl-2-undecylimidazole) Product name: C11Z-CN, manufactured by Shikoku Kasei Kogyo Co., Ltd. 0.25 parts by mass were mixed to prepare a slurry for a heat dissipation sheet. The volume ratios of the BN filler and the resin component at this time are 33.6 vol% and 66.4 vol%, respectively.
The prepared heat-dissipating sheet slurry was applied to a base material by a doctor blade method, and after heat-drying, a heat-dissipating sheet having a sheet thickness of 192 μm was obtained. The sheet was made into a size of 25 mm in width and 60 mm in length, and a 90 ° peel test (JIS K6554-1:) was performed by stacking 25 mm wide and 90 mm long base materials with one end aligned and pressing so that a 30 mm base material was left over. A test piece for 1999) was obtained.
The obtained test piece was subjected to a 90 ° peel test (JIS K6854-1: 1999) using a desktop material tester STA-1225 manufactured by Orientec Co., Ltd. at a test speed of 50 mm / min. The peel test strength was greater than the measurement limit of 15 N / cm of the testing machine.

Example 5
BN agglomerated particles BN-A having a card house structure, 3.9 parts by mass, boron nitride PTX25 having a non-card house structure (manufactured by Momentive Co., Ltd., D50: 19.8 μm, (100) / (004) of BN primary particles Surface peak intensity ratio: 1.4, average crystallite diameter of BN primary particles: 537 Å) 1.3 parts by mass, alumina particles (AX25-45 manufactured by Micron Technology Co., Ltd.) 5.2 parts by mass, bisphenol F type with respect to the total amount of epoxy resin Epoxy resin (Tg: 50 ° C.) containing 20% by mass of phenoxy resin containing phenoxy resin 2.9 parts by mass, solvent (cyclohexanone / methyl ethyl ketone) 6.0 parts by mass, dispersant (trade name: B)
YK-2155, manufactured by Big Chemie Japan Co., Ltd. 0.57 parts by mass, 1-cyanoethyl-2-undecylimidazole (trade name: C11Z-CN, manufactured by Shikoku Chemicals Corporation) 0.18 parts by mass mixed Then, a slurry for a heat dissipation sheet was prepared. At this time, the volume ratios of the BN filler, the alumina filler and the resin component are 34.4 vol%, 19.6 vol% and 46.0 vol%, respectively.
The prepared heat-dissipating sheet slurry was applied to a base material by a doctor blade method, and after heat-drying, a heat-dissipating sheet having a sheet thickness of 205 μm was obtained. The sheet was made into a size of 25 mm in width and 60 mm in length, and a 90 ° peel test (JIS K6554-1:) was performed by stacking 25 mm wide and 90 mm long base materials with one end aligned and pressing so that a 30 mm base material was left over. A test piece for 1999) was obtained.
The obtained test piece was subjected to a 90 ° peel test (JIS K6854-1: 1999) using a desktop material tester STA-1225 manufactured by Orientec Co., Ltd. at a test speed of 50 mm / min. The peel test strength was 8.44 N / cm.

Comparative Example 1
BN agglomerated particles BN-A 6.3 parts by mass having a card house structure, boron nitride PTX25 having a non-card house structure (manufactured by Momentive Co., Ltd., D50: 19.8 μm, (100) / (004) of BN primary particles Surface peak intensity ratio: 1.4, average crystallite diameter of BN primary particles: 537 Å) 2.1 parts by mass, and epoxy containing 16.7% by mass of phenoxy resin containing bisphenol F type phenoxy resin with respect to the total amount of epoxy resin Resin (Tg: 190 ° C.) 2.9 parts by mass, solvent (cyclohexanone / methyl ethyl ketone) 8.0 parts by mass, dispersant (trade name: BYK-2155, manufactured by Big Chemie Japan Co., Ltd.) 0.56 parts by mass, 1 -Cyanoethyl-2-undecylimidazole (trade name: C11Z-CN, manufactured by Shikoku Kasei Kogyo Co., Ltd.) 0.17 parts by mass was mixed to prepare a slurry for a heat dissipation sheet. The volume ratios of the BN filler and the resin component at this time are 54.7 vol% and 45.3 vol%, respectively.
The prepared heat-dissipating sheet slurry was applied to a base material by a doctor blade method, and after heat-drying, a heat-dissipating sheet having a sheet thickness of 189 μm was obtained. The sheet was made into a size of 25 mm in width and 60 mm in length, and a base material having a width of 25 mm and a length of 90 mm was overlapped with one end and pressed so that a base material of 30 mm was left over. A test piece for 1999) was obtained.
The obtained test piece was subjected to a 90 ° peel test (JIS K6854-1: 1999) using a desktop material tester STA-1225 manufactured by Orientec Co., Ltd. at a test speed of 50 mm / min. The peel test strength was 1.16 N / cm.

Comparative Example 2
BN agglomerated particles BN-A having a card house structure, 5.3 parts by mass, boron nitride PTX25 having a non-card house structure (manufactured by Momentive Co., Ltd., D50: 19.8 μm, BN primary particles (100) / (004)) Surface peak intensity ratio: 1.4, average crystallite diameter of BN primary particles: 537 Å) 1.8 parts by mass, alumina particles (AX25-45 manufactured by Micron Technology) 2.4 parts by mass and bisphenol F type with respect to the total amount of epoxy resin Epoxy resin (Tg: 190 ° C.) containing 16.7% by mass of phenoxy resin containing phenoxy resin 2.9 parts by mass, solvent (cyclohexanone / methyl ethyl ketone) 7.0 parts by mass, dispersant (trade name: BYK-2155) , Big Chemie Japan Co., Ltd.) 0.55 parts by mass, 1-cyanoethyl-2-undecylimidazole (trade name: C11Z-CN, manufactured by Shikoku Kasei Kogyo Co., Ltd.) 0.17 parts by mass are mixed and dissipated. A sheet slurry was prepared. At this time, the volume ratios of the BN filler, the alumina filler and the resin component are 46.0 vol%, 8.7 vol% and 45.3 vol%, respectively.
The prepared heat-dissipating sheet slurry was applied to a base material by a doctor blade method, and after heat-drying, a heat-dissipating sheet having a sheet thickness of 186 μm was obtained. The sheet is 25 mm wide and 60 mm long.
A test piece for a 90 ° peel test (JIS K6554-1: 1999) was obtained by stacking 25 mm wide and 90 mm long base materials on top of each other and pressing so that the 30 mm base material was left over. It was.
The obtained test piece was subjected to a 90 ° peel test (JIS K6854-1: 1999) using a desktop material testing machine STA-1225 manufactured by Orientec Co., Ltd. at a test speed of 50 mm / min. The peel test strength was 1.35 N / cm.

Comparative Example 3
There are 16 phenoxy resins containing 4.3 parts by mass of BN agglomerated particles BN-A having a card house structure, 1.4 parts by mass of BN agglomerated particles BN-D having a card house structure, and bisphenol F type phenoxy resin with respect to the total amount of epoxy resin. .7% by mass epoxy resin (Tg: 190 ° C.) 2.4 parts by mass, solvent (cyclohexanone / methyl ethyl ketone) 6.1 parts by mass, dispersant (trade name: BYK-2155, manufactured by Big Chemie Japan Co., Ltd.) 0.40 parts by mass and 0.15 parts by mass of 1-cyanoethyl-2-undecylimidazole (trade name: C11Z-CN, manufactured by Shikoku Kasei Kogyo Co., Ltd.) were mixed to prepare a slurry for a heat dissipation sheet. The volume ratios of the BN filler and the resin component at this time are 50.2 vol% and 49.8 vol%, respectively.
The prepared heat-dissipating sheet slurry was applied to a base material by a doctor blade method, and after heat-drying, a heat-dissipating sheet having a sheet thickness of about 200 μm was obtained. The sheet was made into a size of 25 mm in width and 60 mm in length, and a 90 ° peel test (JIS K6554-1:) was performed by stacking 25 mm wide and 90 mm long base materials with one end aligned and pressing so that a 30 mm base material was left over. 1999)
I got a test piece for.
The obtained test piece was subjected to a 90 ° peel test (JIS K6854-1: 1999) using a desktop material tester STA-1225 manufactured by Orientec Co., Ltd. at a test speed of 50 mm / min. The peel test strength was 1.38 N / cm.
Moreover, when the thermal conductivity was measured, it was 5 W / mK.

Claims (6)

A heat-dissipating resin sheet containing a resin and a boron nitride filler.
The boron nitride filler is agglomerated particles,
The content of the boron nitride filler is 40 vоl% or more and 60 vоl% or less .
The Tg of the resin is 60 ° C. or lower,
The resin contains two or more kinds of epoxy resins, at least one of them is a phenoxy resin, and the phenoxy resin is 18.0% by mass or more and 95% by mass or less based on the total amount of the epoxy resin.
A heat-dissipating resin sheet having a 90 ° peel test strength of 1.5 N / cm or more and a thermal conductivity of 10 W / mK or more . The heat-dissipating resin sheet according to claim 1 , wherein the epoxy resin is one or more selected from a phenoxy resin having a fluorene skeleton and / or a biphenyl skeleton, a bisphenol A type phenoxy resin, and a bisphenol F type phenoxy resin. The heat-dissipating resin sheet according to claim 1 or 2 , wherein the boron nitride filler is spherical aggregated particles. The heat-dissipating resin sheet according to any one of claims 1 to 3 , wherein the boron nitride filler is agglomerated particles having a card house structure. A device including the heat-dissipating resin sheet according to any one of claims 1 to 4 . A resin composition for a heat radiating sheet containing a resin and a boron nitride filler.
The boron nitride filler is agglomerated particles,
The content of the boron nitride filler is 40 vоl% or more and 60 vоl% or less .
The Tg of the resin is 60 ° C. or lower,
The resin contains two or more kinds of epoxy resins, at least one of them is a phenoxy resin, and the phenoxy resin is 18.0% by mass or more and 95% by mass or less based on the total amount of the epoxy resin.
A resin composition having a 90 ° peel test strength of a heat radiating sheet formed by molding the resin composition of 1.5 N / cm or more and a thermal conductivity of the heat radiating sheet of 10 W / mK or more .