JP2018030752A - Boron nitride particle agglomerate, method for producing the same, composition and resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel boron nitride particle agglomerate that can improve thermal conductivity of a resin sheet in the thickness direction.SOLUTION: A boron nitride particle agglomerate contains hexagonal boron nitride primary particles, with the hexagonal boron nitride primary particles having (0001) faces overlapping each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a boron nitride particle aggregate, a method for producing the same, a composition, and a resin sheet.

  2. Description of the Related Art In recent years, the heat generation density inside an electronic device has been increasing year by year with the increase in the speed and integration of circuits of electric devices or electronic devices and the increase in the mounting density of heat-generating electronic components on printed wiring boards. Therefore, a member having high thermal conductivity and electrical insulation that efficiently dissipates heat generated in an electronic component or the like is required.

  Boron nitride particles having a hexagonal crystal structure are characterized by being relatively easy to synthesize and excellent in thermal conductivity, solid lubricity, chemical stability, and heat resistance. For applications such as thermal conductive rubber, heat-dissipating grease, heat-dissipating sealant, semiconductor encapsulating resin, or many other applications such as molten metal and molten glass mold release agents, solid lubricants, and cosmetic raw materials It's being used.

  In recent years, in high-performance electronic devices, with higher integration, higher speed, smaller size, and lighter weight, the amount of heat generated in various electronic components has increased, and even higher heat than before. There is a need for a thermally conductive sheet having conductivity. Therefore, various heat conductive sheets have been proposed in which boron nitride, which is excellent in heat conductivity and electrical insulation, is dispersed and blended in an organic matrix material as a heat conductive filler.

  Boron nitride particles are generally scaly derived from the hexagonal crystal form, and are known to have directional anisotropy in their thermal conductivity. Normal scaly boron nitride particles have higher thermal conductivity in the surface direction (a-axis direction) than in the thickness direction (c-axis direction). In the heat conductive sheet in which such scaly boron nitride particles are blended, the c-axis direction of the boron nitride particles is easily oriented in the thickness direction of the insulating heat radiating sheet, and therefore, compared to the surface direction of the heat conductive sheet. There is a problem that the thermal conductivity in the thickness direction is inferior.

  For example, Patent Document 1 proposes an aggregate of boron nitride particles in which primary boron nitride particles are aggregated randomly in order to improve the thermal anisotropy of such boron nitride particles.

  Further, Patent Document 2 proposes a boron nitride particle aggregate in which primary boron nitride particles are aggregated radially.

  Further, Patent Document 3 proposes a boron nitride particle aggregate in which boron nitride primary particles to which a silane coupling agent having a vinyl group is added are aggregated so as to be randomly oriented.

JP-A-9-202663 Japanese Patent Laid-Open No. 2015-6980 JP 2012-56818 A

  The boron nitride agglomerated particles described in Patent Documents 1 to 3 are aggregates (secondary particles) in which boron nitride primary particles are randomly aggregated, and therefore in the process of producing a resin sheet, such as when kneading with a resin. The secondary particles may collapse, and there is still room for improvement in the thermal conductivity in the thickness direction of the resin sheet.

  This invention is made | formed in view of the said problem, and it aims at providing the novel boron nitride particle aggregate which can improve the thermal conductivity of the thickness direction of a resin sheet.

  The present inventors diligently studied to solve the above problems. As a result, it has been found that the above problems can be achieved by a novel boron nitride particle aggregate in which the (0001) faces of the boron nitride primary particles overlap and aggregate, and the present invention has been completed.

That is, the present invention is as follows.
<1>
A boron nitride particle aggregate containing hexagonal boron nitride primary particles,
A boron nitride particle aggregate in which the (0001) faces of the hexagonal boron nitride primary particles overlap each other.
<2>
The boron nitride particle aggregate according to <1>, which has a columnar shape.
<3>
The relationship between the longest diameter R in the stacking direction of the boron nitride particle aggregate and the longest diameter r in the width direction of the boron nitride particle aggregate is represented by the following formula (1), <1> or <2> Boron nitride particle aggregate described in 1.
0.3r <R (1)
<4>
<1>-<3> The manufacturing method of the boron nitride particle aggregate according to any one of
Adding a coupling agent to the hexagonal boron nitride primary particles (A);
A step (B) of dispersing the hexagonal boron nitride primary particles added with the coupling agent obtained in the step (A) in a solvent;
The manufacturing method of the boron nitride particle aggregate containing this.
<5>
The method for producing a boron nitride particle aggregate according to <4>, wherein the coupling agent has one or more selected from the group consisting of an aryl group, an amino group, an epoxy group, a cyanate group, a mercapto group, and a halogen.
<6>
The method for producing an aggregate of boron nitride particles according to <4> or <4>, wherein the coupling agent includes a silane coupling agent having a crosslinked structure or a silane coupling agent having an aryl group.
<7>
<1>-<3> The composition containing the filler containing the boron nitride particle aggregate of any one of <1>, and resin.
<8>
The composition according to <7>, wherein the resin is a thermosetting resin.
<9>
<7> or <8> The resin sheet containing the composition as described in <8>, and a support body.
<10>
<002> The resin sheet according to <9>, wherein an intensity ratio (I <002> / I <100>) between the intensity of X-ray diffraction and <100> X-ray diffraction is 30 or less.

  ADVANTAGE OF THE INVENTION According to this invention, when it is set as a resin sheet, the novel boron nitride particle aggregate which improves the thermal conductivity of the thickness direction can be provided.

FIG. 1 is an explanatory diagram for explaining R and r in the present embodiment. FIG. 2A is an SEM image of the boron nitride particle aggregate according to Example 1 at a magnification of 120,000 times. FIG. 2B is an SEM image of the boron nitride particle aggregate according to Example 1 at a magnification of 50000 times. FIG. 3A is an SEM image of the hexagonal boron nitride primary particles not aggregated, that is, a magnification of 25,000 times that of the conventional hexagonal boron nitride primary particles. FIG. 3B shows a portion where the end face side is observed in the SEM image of the hexagonal boron nitride primary particles in which the hexagonal boron nitride primary particles are not aggregated. FIG. 4 is an SEM image at a magnification of 1000 times of a conventional boron nitride particle aggregate randomly aggregated. FIG. 5 is a view for showing the scale of the boron nitride particle aggregates observed in FIG. FIG. 6 is a diagram showing the scale of the three boron nitride particle aggregates observed in FIG.

  Hereinafter, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described. In addition, this embodiment is an illustration for demonstrating this invention, and this invention is not limited only to this embodiment.

(Boron nitride particle aggregate)
The boron nitride particle aggregate of this embodiment is a boron nitride particle aggregate containing hexagonal boron nitride primary particles, and the (0001) planes of the hexagonal boron nitride primary particles overlap each other. Since it is comprised in this way, when the boron nitride particle aggregate of this embodiment is used as a resin sheet, the thermal conductivity in the thickness direction of the resin sheet can be improved. Details of the resin sheet will be described later.

  The particle shape of the hexagonal boron nitride primary particles in the present embodiment is not particularly limited, and examples thereof include a scale shape, a flat shape, a granule shape, a spherical shape, a fiber shape, and a whisker shape, and among these, a scale shape is preferable.

The average particle diameter of the hexagonal boron nitride primary particles is not particularly limited, but the median diameter is preferably 0.1 to 50 μm, more preferably 0.1 to 5 μm, and particularly preferably 0.1 to 1 μm. When the average particle diameter is in the above range, the (0001) faces of the hexagonal boron nitride primary particles are easily overlapped and aggregated, and as a result, the thermal conductivity in the thickness direction of the resin sheet tends to be improved.
Here, the average particle diameter of the hexagonal boron nitride primary particles can be measured by, for example, a wet laser diffraction / scattering method.

  The aggregation form of the boron nitride particle aggregate in which the (0001) faces of the hexagonal boron nitride primary particles are aggregated and aggregated is not particularly limited, but includes natural aggregation, aggregation by an aggregating agent, physical aggregation, and the like. Can be mentioned. Examples of natural aggregation include, but are not limited to, aggregation caused by van der Waals force, electrostatic force, adsorbed moisture, and the like. Aggregation by the aggregating agent is not limited to the following, and examples include aggregating by an aggregating agent such as a coupling agent, an inorganic salt, and a polymer substance. For example, when a coupling agent is used as the flocculant, it is preferable that the hexagonal boron nitride primary particles are agglomerated by changing the surface state to a state where the surface energy is high, that is, a state where the primary particles tend to aggregate. Examples of physical agglomeration include methods of agglomeration by operations such as mixed granulation, extrusion granulation, and spray drying. Among these, from the viewpoint of cohesive strength, aggregation with a coupling agent is preferable.

  In this specification, the “boron nitride particle aggregate” is an aggregate unit of secondary particles formed by aggregation of inorganic fillers including hexagonal boron nitride primary particles, and can take various shapes. That is, the shape of the boron nitride particle aggregate is not particularly limited as long as the (0001) faces of the hexagonal boron nitride primary particles overlap each other, for example, columnar, flat, granular, massive, Any of spherical shape, fibrous shape, and the like may be used.

  In this embodiment, when the boron nitride particle aggregate has a columnar shape, when the resin sheet is used, the a-axis direction of the hexagonal boron nitride primary particles may coincide with the thickness direction of the resin sheet (hereinafter, simply This is also preferable because it tends to increase. In this specification, “columnar” means a shape derived from the aggregation mode of hexagonal boron nitride primary particles, and means a shape including a prismatic shape, a cylindrical shape, a rod shape, and the like, which is different from a spherical shape. . Further, the columnar shape includes those that extend straight in the vertical direction, those that extend in an inclined shape, those that extend while curving, and those that branch and extend in a branch shape. It can be easily confirmed that the boron nitride particle aggregate has a columnar shape by observation with a scanning electron microscope (SEM).

A typical example of the method for confirming that the boron nitride particle aggregate of the present embodiment has a columnar shape is not limited to the following, but includes the longest diameter R in the stacking direction of the boron nitride particle aggregate and the boron nitride particle aggregate. And the longest diameter r in the width direction is identified by SEM observation, and a method of confirming the magnitude relationship between them is exemplified. In the present embodiment, it is preferable that the boron nitride particle aggregate satisfies R> 0.3r from the viewpoint of increasing the orientation. In the present embodiment, it is more preferable that R> r is satisfied from the viewpoint of further improving the orientation. The “stacking direction” here is a direction substantially parallel to the c-axis direction of the hexagonal boron nitride primary particles. The “width direction” is a direction substantially perpendicular to the stacking direction. In other words, the width direction is a direction substantially parallel to the surface direction (a-axis direction) of the (0001) plane in at least one hexagonal boron nitride primary particle. In the present embodiment, the longest diameter in the width direction is, for example, the longest diameter in the surface direction of the (0001) plane of the hexagonal boron nitride primary particles when the boron nitride particle aggregate has a columnar shape extending straight in the vertical direction. However, the longest diameter in the width direction may be larger than the longest diameter in the surface direction of the (0001) plane of the hexagonal boron nitride primary particles. Here, “substantially parallel” means a state within ± 10 ° from the parallel direction, and “substantially perpendicular” means a state within ± 10 ° from the vertical direction.
R and r will be specifically described with reference to FIG. The hexagonal boron nitride primary particles illustrated in FIG. 1A are two-dimensionally shown as a typical example, and the long side (r) corresponds to the (0001) plane. The short side (R) corresponds to the end face. The boron nitride particle aggregate illustrated in FIG. 1B is obtained by agglomerating rectangular hexagonal boron nitride primary particles so that their long sides, that is, (0001) planes overlap each other. The short side of the aggregate corresponds to r (that is, the longest diameter in the width direction of the boron nitride particle aggregate), and the long side corresponds to R (that is, the longest diameter in the stacking direction of the boron nitride particle aggregate). doing.

  The boron nitride particle aggregate of the present embodiment has a structure in which hexagonal boron nitride primary particles are laminated as described above, and the laminated structure is not particularly limited, but the hexagonal boron nitride primary per layer is not particularly limited. The number of particles is preferably 2 or less, more preferably 1. Since it has the tendency for orientation to improve when it has such a laminated structure, it is preferable.

  As described above, the longest diameter in the stacking direction of the boron nitride particle aggregate is not particularly limited, and the longest diameter in the width direction of the boron nitride particle aggregate is not particularly limited. In this embodiment, when the average particle diameter of the hexagonal boron nitride primary particles is A (μm), R = 0.3 × A to 10 × A (μm) and r = 0.3 × A to 3 × A. (Μm) is preferably satisfied. Specifically, taking the case where the average particle diameter of the hexagonal boron nitride primary particles is 0.5 μm as an example, it is typical that R = 0.15 to 5 μm, and r = 0.15. Typically, it takes a value of about ~ 1.5 μm. Specific examples of the method for measuring the longest diameter are not limited to the following, but in a captured SEM image, if the boron nitride particle aggregate is columnar, the shape approximates a rectangle, and the long side of the rectangle and For example, the length of the short side is measured.

  In this embodiment, as long as the hexagonal boron nitride primary particles are stacked so as to form a columnar shape as the boron nitride particle aggregate, “the (0001) faces of the hexagonal boron nitride primary particles overlap” The state of being overlapped is not limited to a completely overlapping aspect, and includes an aspect in which they overlap in the width direction.

  In addition, the longest diameter r in the width direction of the boron nitride particle aggregate tends to depend on the particle size and the degree of aggregation of the hexagonal boron nitride primary particles, and is not particularly limited. The thickness of the molded product is preferably less than T (r <T), more preferably r <0.9 × T, and even more preferably r <0.5 × T. When satisfying the above range, r tends to be able to prevent a decrease in smoothness due to unevenness on the surface of the molded product, and r is sufficiently smaller than T from the viewpoint that it can be used as a raw material for a thinner resin sheet. Is preferred.

  The boron nitride particle aggregate of the present embodiment may contain an inorganic filler other than the hexagonal boron nitride primary particles. Examples of such an inorganic filler include, but are not limited to, aluminum nitride, aluminum oxide, Metal oxides such as zinc oxide, silicon carbide, aluminum hydroxide, metals and alloys such as metal nitrides, metal carbides, metal hydroxides, spheres, powders, fibers, needles made of carbon, graphite, diamond, Examples include scale-like and whisker-like fillers. These may be contained independently and may contain multiple types.

  The boron nitride particle aggregate of this embodiment may contain a binder from the viewpoint of increasing the robustness of the boron nitride particle aggregate. Here, “robustness” is a property indicating the strength of bonding when the hexagonal boron primary particles are bonded together in the present embodiment. The binder originally acts to firmly bind the primary particles to each other and stabilize the shape of the aggregate.

  As such a binder, a metal oxide is preferable, and specifically, aluminum oxide, magnesium oxide, yttrium oxide, calcium oxide, silicon oxide, boron oxide, cerium oxide, zirconium oxide, titanium oxide, and the like are preferably used. Among these, aluminum oxide and yttrium oxide are preferable from the viewpoints of thermal conductivity and heat resistance as an oxide, and bonding strength for bonding hexagonal boron nitride primary particles. The binder may be a liquid binder such as alumina sol, or an organic metal compound that is converted into a metal oxide by firing. These binders may be used individually by 1 type, and may mix 2 or more types.

(Method for producing boron nitride particle aggregate)
The boron nitride particle aggregate of this embodiment is not particularly limited as long as the above-described configuration is obtained, but is preferably manufactured by the following method. That is, a preferable method for producing an aggregate of boron nitride particles in the present embodiment includes the step (A) of adding a coupling agent to hexagonal boron nitride primary particles and the coupling agent obtained by the step (A). A step (B) of dispersing boron nitride primary particles in a solvent. More preferably, the method further includes a step (C) of separating the boron nitride particle aggregates from the dispersion obtained from the step (B).
When the step (A) and the step (B) are included, the hexagonal boron nitride primary particles to which the coupling agent is added are aggregated between the (0001) faces due to surface charges in the dispersion, and the binder phase is coupled between the coupling agents. This is preferable because a boron nitride particle aggregate having the desired configuration of the present embodiment is easily obtained.

In the step (A), the method of adding the coupling agent to the hexagonal boron nitride primary particles is not particularly limited, but the coupling agent stock solution is uniformly dispersed in the hexagonal boron nitride primary particles that are being stirred at high speed by a stirrer. A dry method for treatment, a wet method in which hexagonal boron nitride primary particles are immersed in a dilute solution of a coupling agent and stirred are suitable.
In the stage of the step (A), there is a case where the hexagonal boron nitride primary particles to which a coupling agent is added are bonded to form a boron nitride particle aggregate. The stirring temperature is not particularly limited, but special temperature control such as heating and cooling is not necessary. Usually, the temperature rises by stirring, but is preferably 200 ° C. or lower. Although the stirring speed is not particularly limited, it is usually preferable to stir at 10 to 10,000 rpm, and more preferably 100 to 3000 rpm. The stirring time is preferably 5 minutes to 180 minutes, and more preferably 10 minutes to 60 minutes in view of effective stirring time and productivity.

  The above coupling agent preferably has at least one selected from the group consisting of an aryl group, an amino group, an epoxy group, a cyanate group, a mercapto group, and a halogen from the viewpoints of cohesive strength and robustness. Examples of such a coupling agent include, but are not limited to, coupling agents such as silane, titanate, zirconate, zirconium aluminate, and aluminate. Among these, silane coupling agents (hereinafter also referred to as “silane coupling agents”) are preferable from the viewpoint of cohesive strength.

  The silane coupling agent preferably has at least one selected from the group consisting of an aryl group, an amino group, an epoxy group, a cyanate group, a mercapto group, and a halogen. Among them, it is more preferable to have an aryl group because it has a π-π bond and a bond between silane coupling agents becomes stronger. Examples of such a coupling agent include, but are not limited to, phenyltrimethoxysilane, phenyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, p-styryltrimethoxysilane, and naphthyltrimethoxysilane. Naphthyltriethoxysilane, (trimethoxysilyl) anthracene, (triethoxysilyl) anthracene, and the like.

  Moreover, it is also preferable to use the silane coupling agent which has a crosslinked structure as said coupling agent. Specific examples of such silane coupling agents include, but are not limited to, 1,6-bis (trimethoxysilyl) hexane, tris- (trimethoxysilylpropyl) isocyanurate, bis (triethoxysilylpropyl) tetra Examples thereof include sulfide and hexamethyldisilazane.

  Moreover, the silane coupling agent which has the above-mentioned crosslinked structure is obtained also by making it react between organic functional groups, and bridge | crosslinking. The combination of the organic functional groups in this case is not limited to the following. For example, amino group-epoxy group, epoxy group-cyanate group, amino group-cyanate group, amino group-sulfonic acid group, amino group-halogen, mercapto Examples include a combination of organic functional groups of a coupling agent such as a group-cyanate group.

  The various coupling agents mentioned above may be used alone or in combination of two or more.

  The amount of the coupling agent added in the step (A) is 0.01 to 10 with respect to the hexagonal boron nitride primary particles, although it depends on the surface area of the inorganic filler, that is, the surface area of the hexagonal boron nitride primary particles. It is preferable to add mass%, and it is more preferable to add 1-2 mass%.

  In the production method of the present embodiment, the stirring method that can be used when adding the coupling agent is not particularly limited, and examples thereof include a vibration mill, a bead mill, a ball mill, a Henschel mixer, a drum mixer, a vibration stirrer, and a V-shaped mixer. Stirring can be performed using a general stirrer such as a machine.

  In the step (B), the hexagonal boron nitride primary particles added with the coupling agent obtained in the step (A) are dispersed in a solvent. The method for dispersing the hexagonal boron nitride primary particles added with the coupling agent in a solvent is not particularly limited. Since the hexagonal boron nitride primary particles to which a coupling agent having an aromatic skeleton is added tend to aggregate (0001) faces, it is preferably ultrasonically dispersed in a solvent.

It does not specifically limit about the solvent used at a process (B), Water and / or various organic solvents can be used. In the case of using hexagonal boron nitride primary particles having an aromatic ring skeleton, that is, an aryl group-containing coupling agent, a highly polar solvent is preferable.
The amount of the solvent used is 0.5 to 20 times the mass of the hexagonal boron nitride primary particles from the viewpoint of reducing the load during separation in the step (C) and from the viewpoint of uniformly dispersing in the step (B). It is preferable to do.

  In the step (B), various surfactants may be added from the viewpoint of adjusting the degree of aggregation of the boron nitride particle aggregate. The surfactant is not particularly limited, and for example, an anionic surfactant, a cationic surfactant, a nonionic surfactant and the like can be used, and these may be used alone. Two or more kinds may be mixed and used. The surfactant concentration in the dispersion obtained from the step (B) is not particularly limited, but can be usually 0.1% by mass to 10% by mass, and 0.5% by mass to 5% by mass. It is preferable to do.

  In the step (C), the boron nitride particle aggregate is separated from the dispersion obtained in the step (B). The method for separating the boron nitride particle aggregates from the dispersion obtained from the step (B) is not particularly limited, and for example, stationary separation, filtration, centrifuge, heat treatment and the like can be used.

You may perform another process with respect to the boron nitride particle aggregate obtained from these. For example, surface oxidation that is temperature-treated under oxygen, water vapor treatment, surface modification with an organometallic compound or polymer using a carrier or a reaction gas at room temperature or under heating, and a sol-gel method using boehmite or SiO ₂ can be used. It is. These treatments may be used alone or in combination of two or more.

  Furthermore, typical post-processes such as inspection, grinding, classification, purification, washing, and drying may be performed on the boron nitride particle aggregate of the present embodiment produced as described above, as necessary. If fines are included, they may be removed first. As an alternative to sieving, the pulverization of the boron nitride particle agglomerates may be performed using a sieving net, a classification mill, a structured roller crusher or a cutting wheel. For example, dry milling in a ball mill is also possible.

Although the use of the boron nitride particle aggregate of this embodiment is not particularly limited, it is preferably used as a composition containing a filler containing the boron nitride particle aggregate and a resin. That is, the composition of this embodiment contains the filler containing the boron nitride particle aggregate of this embodiment and a resin. As described above, the composition obtained by filling the boron nitride particle aggregate of the present embodiment has low anisotropy in thermal conductivity, high thermal conductivity, low entrainment of bubbles, and high. Insulation resistance. Furthermore, even if the resin is highly filled, an increase in viscosity at the time of kneading is suppressed, and excellent moldability can be exhibited. The filler in the present embodiment may contain an inorganic filler in addition to the boron nitride particle aggregate. Examples of such an inorganic filler include, but are not limited to, aluminum nitride, aluminum oxide, zinc oxide, Metal oxides such as silicon carbide and aluminum hydroxide, metals and alloys such as metal nitrides, metal carbides and metal hydroxides, spherical, powdery, fibrous, acicular, scaly, carbon, graphite, diamond, Examples include whisker-like fillers. These may be contained independently and may contain multiple types.
Examples of the above-mentioned resins include, but are not limited to, thermoplastic resins (polyolefin, vinyl chloride resin, methyl methacrylate resin, nylon, fluorine resin), thermosetting resins (epoxy resin, phenol resin, urea resin, melamine). Resin, unsaturated polyester resin, silicon resin), synthetic rubber, and liquid gel. Among the above, a thermosetting resin is preferable.
Although it does not specifically limit as a manufacturing method of the composition of this embodiment, For example, the method of mix | blending each component with a solvent one by one and fully stirring is mentioned. At this time, in order to uniformly dissolve or disperse each component, known processes such as stirring, mixing, and kneading can be performed. Specifically, the dispersibility of fillers such as boron nitride particle aggregates in the composition can be improved by performing the stirring and dispersing treatment using a stirring tank provided with a stirrer having an appropriate stirring ability. The above stirring, mixing, and kneading treatment can be appropriately performed using, for example, a known device such as a ball mill or a bead mill for mixing, or a revolving or rotating mixing device.
In preparing the composition of the present embodiment, an organic solvent can be used as necessary. The type of organic solvent is not particularly limited as long as it can dissolve a part or all of the resin component in the composition. For example, ketones such as acetone, methyl ethyl ketone, methyl cellosolve, cyclohexanone; toluene, xylene Aromatic hydrocarbons such as: Amides such as dimethylformamide; Propylene glycol monomethyl ether and its acetate. A solvent may be used individually by 1 type, or may use 2 or more types together.

Furthermore, it is preferable to use as a resin sheet containing the above-mentioned composition and a support. That is, the resin sheet of this embodiment includes the composition of this embodiment and a support. In addition, the resin sheet of this embodiment is used as one means of thinning, and can be manufactured by, for example, directly applying and drying the composition on a support such as a metal foil or a film.
Although it does not specifically limit as a support body in this embodiment, The well-known thing used for various printed wiring board materials can be used. Specific examples of the support include polyimide film, polyamide film, polyester film, polyethylene terephthalate (PET) film, polybutylene terephthalate (PBT) film, polypropylene (PP) film, polyethylene (PE) film, aluminum foil, copper foil, Examples include gold leaf. Among these, electrolytic copper foil and PET film are preferable.
Examples of the coating method include a method in which a solution obtained by dissolving the composition of the present embodiment in a solvent is coated on a support with a bar coater, a die coater, a doctor blade, a baker applicator, or the like.
The resin sheet is preferably one obtained by applying the composition of the present embodiment to a support and then semi-curing (B-stage). Specifically, for example, after the composition is applied to a support such as a copper foil, it is semi-cured by a method of heating in a dryer at 100 to 200 ° C. for 1 to 60 minutes to produce a resin sheet. The method etc. are mentioned. The adhesion amount of the resin composition to the support is preferably in the range of 1 to 1000 μm as the resin thickness of the resin sheet.

  The resin sheet preferably has a strength ratio of <002> X-ray diffraction to <100> X-ray diffraction (I <002> / I <100>) of 30 or less. Here, the intensity ratio between <002> X-ray diffraction and <100> X-ray diffraction (I <002> / I <100>) is the X-ray in the thickness direction of the resin composition sheet. That is, the ratio of <002> diffraction line intensity and <100> diffraction line peak intensity (I <002> / I <) obtained by irradiation at an angle of 90 ° with respect to the sheet length direction. 100>). In the present embodiment, the strength ratio of 30 or less suggests that the orientation is sufficiently high, and the thermal conductivity in the sheet thickness direction tends to be higher.

The boron nitride particle aggregate of this embodiment may also be used for other uses, for example, for producing a sintered body.
Specifically, it can be used for various applications known as applications of boron nitride particles. If a particularly suitable use is illustrated, the use as a filler for resin aiming at an electrical insulation improvement, thermal conductivity provision, etc. by filling resin is mentioned.

  Other applications include raw materials for processed hexagonal boron nitride products such as cubic boron nitride and hexagonal boron nitride molded products, engineering plastic nucleating agents, phase change materials, solid or liquid thermal interface materials, melting Examples include mold release agents for metals and molten glass molds, cosmetics, and composite ceramic raw materials.

  Next, the present embodiment will be described in more detail by way of examples, but the present embodiment is not limited to these examples.

<Evaluation method of each characteristic>
(1) Thermal conductivity A test piece (10 mm × 10 mm × 1 mm thickness) was cut out from a press-molded sheet described later. With respect to this test piece, the thermal conductivity in the sheet thickness direction was measured with a laser flash using a xenon flash analyzer LFA447 type thermal conductivity meter manufactured by NETZSCH.
(2) Orientation Strength Ratio The orientation of the hexagonal boron nitride primary particles in the composite sheet is determined by the intensity of I (002) diffraction line (2θ = 26.5 °) and I (100) diffraction by the X-ray diffraction method. Evaluation was based on the ratio (I (002) / I (100)) to the intensity of the line (2θ = 41.5 °).
In addition, the thickness direction of the boron nitride primary particles which are hexagonal crystals coincides with the crystallographic I (002) diffraction line, that is, the c-axis direction, and the in-plane direction coincides with the I (100) diffraction line, that is, the a-axis direction. Yes. When the hexagonal boron nitride primary particles constituting the boron nitride particle aggregate have a completely random orientation (non-orientation), (I (002) / I (100)) ≈6.7 (“JCPDS [ Powder X-ray diffraction database] ”No. 34-0421 [BN] crystal density value [Dx]). When (I (002) / I (100)) is small, the a-axis direction of the hexagonal boron nitride particles is oriented in the thickness direction of the composite sheet, that is, the orientation is increased, resulting in heat in the thickness direction. Conductivity increases.
In the above-described measurement, a composite sheet having a size of 5 mm × 5 mm × thickness 0.2 mm was cut out from a press-molded sheet described later to obtain a measurement sample. Further, using a “fully automatic horizontal multi-purpose X-ray diffractometer SmartLab” (manufactured by Rigaku Corporation), X-rays were irradiated in the thickness direction of the composite sheet on a 5 mm × 5 mm plane of the composite sheet. At the time of measurement, CuKα ray was used as the X-ray source, the tube voltage was 45 kV, and the tube current was 360 mA.

Example 1
1.5% by mass of phenyltrimethoxylane (manufactured by Tokyo Chemical Industry Co., Ltd.) as a coupling agent was dropped into primary hexagonal boron nitride particles (“UHP-S2” manufactured by Showa Denko) having an average particle size of 0.5 μm, and a mixer To obtain primary hexagonal boron nitride particles to which a coupling agent was added. Subsequently, hexagonal boron nitride primary particles obtained by adding the above coupling agent to methyl ethyl ketone were added and sufficiently dispersed with an ultrasonic disperser to obtain a dispersion. This dispersion was allowed to stand for 6 hours, the upper fine was removed, and boron nitride particle aggregates were obtained. This boron nitride particle aggregate was further ultrasonically dispersed in ethanol, spread on an aluminum foil, and after the solvent was evaporated, it was pressed against a carbon tape, and an SEM image of the boron nitride particle aggregate was observed. The results are shown in FIGS. 2 (a) and 2 (b).

  In the SEM images shown in FIGS. 2A and 2B, the end faces of the hexagonal boron nitride primary particles are observed more than the (0001) face of the hexagonal boron nitride primary particles, and most of the boron nitrides are observed. The primary particles were found to be agglomerated with the (0001) faces overlapping. That is, many boron nitride particles (boron nitride particle aggregates) aggregated by overlapping (0001) faces of boron nitride primary particles were observed. In the boron nitride particle aggregate shown in FIG. 2 (a), the number of hexagonal boron nitride primary particles per layer is 1, the longest diameter R in the stacking direction of the boron nitride particle aggregate, and the boron nitride particles When the longest diameter r in the width direction of the aggregate was measured, R = 0.66 μm, r = 0.49 μm, and R / r = 1.35. R was specified as shown in FIG. Further, from FIG. 2B, three boron nitride particle aggregates (boron nitride particle aggregates 1 to 3) having a particularly typical columnar shape are selected, and the particle size is measured by a method described later. did. In all of the boron nitride particle aggregates 1 to 3, the number of hexagonal boron nitride primary particles per layer was one. This boron nitride particle aggregate was charged, and the SEM image was distorted. Table 1 shows the results of obtaining r and R in the boron nitride particle aggregates 1 to 3. These Rs were specified as shown in FIG.

(Measurement of particle size)
The form of the boron nitride particle aggregate was analyzed by electron microscope (FE-SEM-EDX (SU8220): manufactured by Hitachi High-Technology Corporation) with a plurality of SEM observation images of 2.5 μm × 1.8 μm square. R and r of boron nitride particles (boron nitride particle aggregates) present in the observation range and aggregated by overlapping (0001) faces of boron nitride primary particles were measured. At that time, the boron nitride particles observed in the SEM image were approximated to a rectangle as shown in FIG. 1B, and the length of the side corresponding to R and the length of the side corresponding to r were measured.

(Comparative Example 1)
The boron nitride particles of Comparative Example 1 were obtained in the same manner as in Example 1 except that the surface treatment with the coupling agent was not performed on the hexagonal boron nitride primary particles. An SEM observation image of the obtained boron nitride particles is shown in FIG.

  As can be seen from FIG. 3 (a), it was observed that the (0001) plane of many hexagonal boron nitride primary particles faced the upper surface of the sample. That is, a structure in which (0001) of hexagonal boron nitride primary particles overlapped was not observed. In addition, as shown in FIG. 3B, it was observed that the surface direction of the end face of the hexagonal boron nitride primary particles partially coincided with the thickness direction of the sample. Boron nitride particles observed in these SEM images were approximated to a rectangle as shown in FIG. 1A, and the length of the side corresponding to R and the length of the side corresponding to r were measured. The longest diameter r ′ in the width direction of the hexagonal boron nitride primary particles is 0.3 to 1.0 μm, and the longest diameter R ′ in the direction perpendicular to the width direction of the hexagonal boron nitride primary particles is 0.01. It was -0.05 micrometer. That is, all of the observed hexagonal boron nitride primary particles had R ′ <0.3r ′.

(Comparative Example 2)
A boron nitride particle aggregate of Comparative Example 2 was obtained in the same manner as in Example 1 except that a commercially available boron nitride particle random aggregate (“SGPS” manufactured by Denki Kagaku Kogyo) was used. The SEM observation image of the obtained boron nitride particle aggregate is shown in FIG. As can be seen from FIG. 4, a structure in which the hexagonal boron nitride primary particles were randomly aggregated was observed. That is, a structure in which (0001) of hexagonal boron nitride primary particles overlapped was not observed. In the obtained random aggregate, the number of hexagonal boron nitride primary particles per layer was 3 or more, and the shape of the random aggregate was spherical.

  As shown in FIG. 2, it was confirmed that by using the manufacturing method of the present embodiment, a boron nitride particle aggregate in which the (0001) planes of the boron nitride particles overlap and aggregate can be realized.

Next, the boron nitride particle aggregate ((0001) area layer type) of Example 1, the hexagonal boron nitride primary particles of Comparative Example 1, and the boron nitride particle aggregate (Random Aggregate) of Comparative Example 2 were used as fillers. Using each, composite sheets with resin were prepared.
As resin (base resin), 100 parts by mass of epoxy resin (“EPPN-501H” manufactured by Nippon Kayaku Co., Ltd.) and 63 parts by mass of curing agent (“Phenonovolak-based curing agent,“ DL-92 ”manufactured by Meiwa Kasei Co., Ltd.), curing catalyst A mixture with 0.1 part by mass (2-phenylimidazole, manufactured by Shikoku Chemicals) was used.
Next, after mixing 40% by volume of each base resin and 60% by volume of the filler of Example 1, Comparative Example 1 or Comparative Example 2 using methyl ethyl ketone as a solvent, this mixed solution was applied to a copper foil, A semi-cured sheet was produced by drying at 130 ° C. This was cured using a vacuum press at 180 ° C. and 10 MPa to prepare a composite sheet.

  Table 2 shows the results of measuring the thermal conductivity of the composite sheets of Example 1, Comparative Example 1 and Comparative Example 2 and the orientation strength ratio of the hexagonal boron nitride primary particles in the composite sheet.

Claims (10)

A boron nitride particle aggregate containing hexagonal boron nitride primary particles,
A boron nitride particle aggregate in which the (0001) faces of the hexagonal boron nitride primary particles overlap each other.   The boron nitride particle aggregate according to claim 1, which has a columnar shape. The relationship between the longest diameter R in the stacking direction of the boron nitride particle aggregate and the longest diameter r in the width direction of the boron nitride particle aggregate is represented by the following formula (1). Boron nitride particle aggregate.
0.3r <R (1) It is a manufacturing method of the boron nitride particle aggregate according to any one of claims 1 to 3,
Adding a coupling agent to the hexagonal boron nitride primary particles (A);
A step (B) of dispersing the hexagonal boron nitride primary particles added with the coupling agent obtained in the step (A) in a solvent;
The manufacturing method of the boron nitride particle aggregate containing this.   The method for producing a boron nitride particle aggregate according to claim 4, wherein the coupling agent has one or more selected from the group consisting of an aryl group, an amino group, an epoxy group, a cyanate group, a mercapto group, and a halogen.   The method for producing a boron nitride particle aggregate according to claim 4 or 5, wherein the coupling agent includes a silane coupling agent having a crosslinked structure or a silane coupling agent having an aryl group.   The composition containing the filler containing the boron nitride particle aggregate of any one of Claims 1-3, and resin.   The composition according to claim 7, wherein the resin is a thermosetting resin.   A resin sheet comprising the composition according to claim 7 or 8 and a support.   The resin sheet according to claim 9, wherein an intensity ratio (I <002> / I <100>) of <002> X-ray diffraction and <100> X-ray diffraction is 30 or less.