TW201903009A - Method for producing sheet containing anisotropic filler - Google Patents

Abstract

A method for producing a sheet containing an anisotropic filler, the method including a step of forming a film of an ink containing the anisotropic filler and a resin on a support, and a step of applying an oscillation having a frequency of at least 5 kHz to the film while the film is still in a fluid state.

Description

Manufacturing method of sheet containing anisotropic filler

The present invention relates to a method for manufacturing a sheet containing an anisotropic filler, that is, a sheet containing an anisotropic filler having an anisotropic particle shape (different diameters depending on directions) and a resin.

Anisotropic fillers with anisotropic particle shapes often have anisotropy in their physical properties. Using this property, sheets containing anisotropic fillers and resins are used in various applications. As a representative example, it is known to use, for example, flaky hexagonal boron nitride, in one direction (specifically, the major axis direction (plane direction)) compared to other directions (specifically, It is a thermally conductive sheet of an anisotropic filler having a high thermal conductivity in the short diameter direction (thickness direction). In such a thermally conductive sheet, the major axis direction of the anisotropic filler should preferably be aligned parallel to the direction requiring thermal conductivity (that is, the thickness direction of the sheet) (hereinafter also referred to as "longitudinal alignment"). However, if a composition containing an anisotropic filler and a resin serving as a binder is simply coated into a sheet shape with a doctor blade or the like, the major axis direction of each particle will be aligned parallel to the surface direction of the sheet (hereinafter also referred to as ("Horizontal alignment"), so a sheet with high thermal conductivity cannot be obtained.

In this regard, Patent Document 1 discloses that agglomerated boron nitride particles are made into particles (agglomerated particles) that are quasi-isotropic in thermal conductivity, and the particles are used to produce a thermally conductive sheet. However, this method requires the preparation of agglomerated particles. In addition, it is unavoidable that voids are mixed into the agglomerated particles. If there are voids in the sheet, the thermal conductivity will decrease. Therefore, a thermally conductive sheet having a sufficiently high thermal conductivity cannot be obtained even if the lateral arrangement of the anisotropic filler is prevented.

Furthermore, Non-Patent Document 1 discloses the use of a spouting nozzle to drip a liquid to form a potting of a paste containing hexagonal boron nitride particles and a resin, and forming a large number of sealants by repeatedly forming them. The aggregate is made into a sheet in which hexagonal boron nitride particles are aligned vertically. In addition, Patent Document 2 discloses a method in which a primary sheet obtained by aligning the major axis direction and the surface direction of hexagonal boron nitride particles in parallel with each other to obtain a laminated body is obtained by using a method derived from the primary sheet surface. The laminated body is sliced at an angle of 0 to 30 degrees, thereby forming a sheet in which hexagonal boron nitride particles are vertically aligned. However, among these methods, a method for manufacturing a sheet is complicated, and there is a problem in mass productivity. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-6980 [Patent Document 2] Japanese Patent Laid-Open No. 2012-38763

[Non-Patent Document 1] "2. Development of heat sink material that controls the orientation of ceramic particles", Saga Kiln Technology Center Heisei 25 Annual Report, pages 9 to 13

[Problems to be Solved by the Invention]

In view of the above-mentioned problems, the present invention has a problem in that an anisotropic filler is produced with a simple method and good efficiency, and the sheet containing the anisotropic filler may be aligned in the longitudinal direction as much as possible. [Means for solving problems]

The inventors of the present case found that during a period when the film (layer) containing an anisotropic filler and a resin is fluid (that is, a period during which it can flow), an anisotropic filler (primary particle) is applied to the film at a high frequency It will be rearranged randomly, and as a result, the proportion of vertical alignment is increased, and the present invention is completed using this knowledge.

That is, the present invention is as follows: [1] A method for manufacturing a sheet containing an anisotropic filler, comprising the following steps: forming a film of an ink containing anisotropic filler and a resin on a support; and While the film is flowing, a vibration with a frequency of 5 kHz or more is applied to the film. [2] The method for producing a sheet containing an anisotropic filler according to [1], wherein the frequency of the vibration is 10 to 1000 kHz. [3] The method for producing a sheet containing an anisotropic filler according to [1] or [2], wherein the average longest diameter of the anisotropic filler is 0.5 μm to 200 μm. [4] The method for producing an anisotropic filler-containing sheet according to any one of [1] to [3], wherein the anisotropic filler has an aspect ratio of 2 or more. [5] The method for producing a sheet containing an anisotropic filler according to any one of [1] to [4], wherein the anisotropic filler contains scaly boron nitride particles. [6] The method for producing a sheet containing an anisotropic filler according to any one of [1] to [5], wherein the anisotropic filler contains hexagonal boron nitride particles. [7] The method for producing an anisotropic filler-containing sheet according to any one of [1] to [6], wherein a volume ratio of the anisotropic filler in the film is 10 to 90% by volume. [8] The method for producing a sheet containing an anisotropic filler according to any one of [1] to [7], wherein the resin contains a thermosetting resin. [9] The method for producing a sheet containing an anisotropic filler according to any one of [1] to [8], further including a step of pressing the film. [Effect of the invention]

According to the present invention, only by forming a coating film of an ink containing an anisotropic filler and a resin and applying a high-frequency vibration to it, the horizontal alignment of the anisotropic filler can be prevented, and anisotropic fillers can be produced in a simple and efficient manner The directional filler is a random or longitudinally oriented sheet. Therefore, according to the present invention, a thermally conductive sheet having a high thermal conductivity can be manufactured with good efficiency and with a simple method.

Hereinafter, the embodiment for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail, but the present invention is not limited to this, and various modifications may be made without departing from the gist.

The method of this embodiment includes a step of forming a coating film of an ink containing an anisotropic filler and a resin on a support. In this embodiment, the anisotropic filler is particles having an anisotropic shape (the diameter of which varies depending on the direction), for example, it is composed of inorganic compounds such as carbon, inorganic oxides, inorganic nitrides, and inorganic carbon compounds, resins, etc. Specifically, for example, metal oxides such as boron nitride, aluminum nitride, aluminum oxide, zinc oxide, silicon carbide, and aluminum hydroxide, metal nitrides, metal carbon compounds, and metal hydroxides; metals, alloys; graphite, graphite Carbon materials, such as diamonds, diamonds; fibrous, needle-like, scale-like, whisker-like particles composed of highly thermally conductive resins. Among them, in view of thermal conductivity, hexagonal boron nitride particles are preferred, and the shape includes flat, scaly, plate, linear, flat, granular, fibrous, and whisker shapes. Among them, Scale-like, plate-like or linear, and more preferably scale-like or plate-like, especially scale-like. In this embodiment, only one kind of anisotropic filler may be used, and two or more kinds of anisotropic fillers may be included within a range that does not impair the effect of the present invention. For example, boron nitride particles can be used with other anisotropic fillers.

When the anisotropic filler is scaly or flat, the aspect ratio (ratio of the longest diameter to the thickness) is not limited, but is preferably 2 or more, more preferably 5 or more, and more preferably 10 or more. There is no upper limit to the aspect ratio, but it is usually below 1000.

In addition, when a sheet containing an anisotropic filler is used as a thermally conductive sheet, particularly when it is assembled to a heat-generating electronic component, it may be used at a high temperature of 180 ° C or higher. In order to ensure that the life of peripheral components can be extended and reliability such as high thermal conductivity and withstand voltage characteristics can be maintained even at such a high temperature of 180 ° C or higher, the average longest diameter of the anisotropic filler should be 1/2 of the sheet thickness Below, it is better to 1/3. If the average longest diameter exceeds 1/2 of the sheet thickness, the anisotropic filler may protrude from the sheet surface, the shape of the sheet surface may deteriorate, and the adhesion with other members of the laminate may decrease, and the withstand voltage Degradation. On the other hand, if the average longest diameter of the anisotropic filler is too small, the probability that the heat conduction paths are connected from top to bottom in the thickness direction of the thermal conductive sheet becomes small, and the thermal conductivity in the thickness direction of the thermal conductive sheet may be insufficient. From the above viewpoints, although the particle diameter of the anisotropic filler is not limited, the average longest diameter is preferably 0.1 to 500 μm, more preferably 0.5 to 200 μm, and even more preferably 1 to 100 μm. Moreover, even in the case of having the above average longest diameter, there may be very large particles in the raw material that do not affect the average longest diameter. Therefore, in this embodiment, the anisotropic filler should preferably be sieved or removed from the raw material with a particle size larger than a predetermined size before use.

The anisotropic filler may be in a state of agglomerated particles (secondary particles) formed by agglomeration of the primary particles in the ink. In the case of agglomerated particles, depending on the vibration application conditions (frequency, application time, etc.) in the high frequency vibration application step, the rearrangement of the filler may not be sufficiently achieved, and voids may remain in the finally obtained sheet. Therefore, in the case of an anisotropic filler, it is preferable to use the one which exists as a primary particle.

The shape, particle diameter, and aspect ratio of the anisotropic filler can be determined by observing the particles with an electron microscope. Specifically, from an image taken by a scanning electron microscope (SEM) (for example, FE-SEM-EDX (SU8220): manufactured by Hitachi Advanced Technology Co., Ltd.), 200 or more particles are randomly selected, and the shape is determined. The longest diameter is defined as the length of the long side of the rectangle that circumscribes the particle and has the smallest area. In the case of a scale-like or plate-shaped anisotropic filler, 200 or more particles were randomly picked out in the plane direction, and the longest diameter was determined. In addition, the aspect ratio can be determined by randomly selecting more than 200 particles photographed in the plane direction and particles photographed in the thickness in the image, calculating the average value of the longest diameter and the thickness, and determining the ratio.

In this embodiment, the volume ratio of the anisotropic filler in the film (printing ink) (the content of the anisotropic filler in the solid content) can be appropriately set according to the application, and can be, for example, 10 to 90% by volume or more. If the anisotropic filler is less than 10% by volume, the anisotropic filler may be too small, and the desired characteristics (for example, thermal conductivity) may not be obtained. Conversely, if the content of the anisotropic filler exceeds 90% by volume, the anisotropic filler may be excessive, and the sheet may become brittle or the electrical insulation of the sheet may decrease. In addition, the viscosity of the ink may increase, and it may be difficult to obtain a thin and flat sheet. Here, the volume of the anisotropic filler is defined as a value obtained from the specific gravity of the material (compound) constituting the anisotropic filler and the mass of the anisotropic filler contained in the printing ink.

In this embodiment, the resin contained in the printing ink is not limited, for example, thermoplastic resin (such as polyolefin, polyvinyl chloride resin, methyl methacrylate, nylon, fluororesin, etc.), hardening resin (such as epoxy Resin, phenolic resin, urea resin, melamine resin, unsaturated polyester resin, silicone resin, etc.), synthetic rubber, etc. Among them, a curable resin is preferable, and a thermosetting resin is more preferable. In addition, the curable resin in this embodiment can be added to the uneven film in the form of a resin composition mixed with a curing agent and a curing catalyst, and can also be used as a corresponding raw material (monomer, dimer, oligomer, etc.). Precursor).

Examples of the thermosetting resin include a polyimide resin, a polyaminobismaleimide (polybismaleimide) resin, a bismaleimide-triazabenzene resin, and a polyimide resin. Polyimide resins such as fluorene amine imine resin, polyether amine imine resin; benzo Azole resins; polyether resins; benzocyclobutene resins; polysiloxane resins; epoxy resins such as phenol-based epoxy resins and alcohol-based epoxy resins. Among them, because of its high thermal conductivity and good solubility in organic solvents, epoxy resins or polyether resins, benzocyclobutene resins, polysiloxane resins, and epoxy resins are particularly preferred. These resins may be used individually by 1 type, and may use 2 or more types of resins in arbitrary combinations and a mixing ratio.

In this embodiment, the ink may contain a solvent or a dispersion medium as needed. In particular, when a thermosetting resin is used as the resin, it is preferable to contain a solvent or a dispersion medium. The type of the solvent (dispersion medium) is not particularly limited, for example, ketones such as acetone, methyl ethyl ketone, methylcellulose, and cyclopentanone; aromatic hydrocarbons such as toluene and xylene; and rings such as cyclohexane and cyclopentane. Alkanes; Alcohols such as methanol, ethanol, n-butanol; Esters such as ethyl acetate, propyl acetate, butyl acetate; Amines such as dimethylformamide; Propylene glycol monomethyl ether and its acetates, etc. Organic solvents. The solvents may be used singly or in combination of two or more kinds. Considering the viewpoints of adjusting the viscosity of the printing ink to be fixed during film formation and imparting high-frequency vibration and rapidly drying the ink after imparting high-frequency vibration, the solvent used should preferably be an evaporation rate of 4.5 times or less of butyl acetate. If the evaporation rate is too fast, a large amount of solvent is volatilized during film formation and during the process of imparting high frequency vibration, which will change the viscosity of the printing ink. On the other hand, if the evaporation rate is too slow, it is difficult to dry the solvent and high-temperature and long-term drying is required. In the case of using a thermosetting resin for the resin, such drying causes the resin to harden. From this viewpoint, it is more preferable to use a solvent having an evaporation rate of 0.05 to 4.5 times that of butyl acetate. The content of the solvent (dispersion medium) is not limited. For example, the viscosity of the printing ink can be appropriately determined in consideration of the viscosity, and usually, it is about 10 to 50% by mass of the printing ink. If the amount of the solvent is insufficient, it is difficult to form a film having a uniform thickness, and the film surface may be uneven. Conversely, if the amount of the solvent is excessive, the alignment retention of the anisotropic filler in the film after high frequency vibration is sometimes deteriorated.

In this embodiment, in addition to an anisotropic filler, a resin, and a solvent / dispersion medium, the printing ink may contain various additives conventionally used in accordance with the application. Such additives include, for example, a coupling agent for improving the adhesion between an anisotropic filler and a resin, the above-mentioned hardener and hardening catalyst, a resin hardening accelerator, a viscosity modifier, and a dispersion stabilizer. , Surfactant, emulsifier, low elasticizer, diluent, defoamer, ion trapping agent, etc. These additives may be used singly or in combination of two or more in any combination and mixing ratio.

The coupling agent may be appropriately used in general for the surface treatment of an anisotropic filler, and its type is not particularly limited. Specifically, for example, amine-based silanes such as γ-aminopropyltriethoxysilane and N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane; γ- (2,3- Glycidoxy) propyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and other epoxy silane systems; γ-methacrylic acid oxypropyltrimethoxysilane , Vinyltri (β-methoxyethoxy) silane and other vinyl silane series; N- (β- (N-vinylbenzylamino) ethyl) -γ-aminopropyltrimethoxysilane hydrochloride Cationic silanes such as salts; silane coupling agents such as phenylsilanes. These silane coupling agents can be used individually by 1 type or in combination of 2 or more types. Although the coupling agent is determined according to the surface area of the anisotropic filler, it is preferable to add 0.01 to 10% by mass relative to the anisotropic filler, and more preferably to add 1 to 2% by mass. The coupling agent can be added to the anisotropic filler in advance, and the method is not limited. For example, a dry method of uniformly dispersing the coupling agent stock solution in the anisotropic filler in high-speed stirring through a stirrer, and immersing the anisotropic filler in Wet method in which the coupling agent is diluted in the solution and stirred.

The viscosity of the printing ink is not limited, and may be set to, for example, 0.1 to 100 Pa ･ s, or 5 to 20 Pa ･ s. The method for preparing the ink is not particularly limited, and the components may be mixed. In this case, in order to uniformly mix the components, well-known processes such as stirring, mixing, and kneading processes may be performed.

In this embodiment, a film is formed on a support. The support is preferably one that can hold the film, has the strength to withstand high-frequency vibration, and has good release properties when subsequently peeled. Specifically, for example, metal foil or metal plate such as copper or aluminum, plastic film or plastic plate, and the like. The support can be peeled after the sheet is formed. Especially when the support has characteristics that are not suitable for the use of the sheet (for example, when the sheet is a thermally conductive sheet for an insulating layer of an electronic circuit, a conductive material such as a metal foil is used as the support), The support should be peeled from the sheet. On the other hand, in the absence of the above case, the support does not necessarily need to be peeled off, and finally the laminated body with the support remaining can be used as a sheet. When the support is peeled from the sheet, although the timing of the peeling step is not limited, it is preferable that the film is cured to a certain degree and can be self-supported.

In this embodiment, the method for forming the above-mentioned ink film on such a support is not limited, and examples thereof include a gravure coating method, a roll coating method, a stick coating method, a die casting mold coating method, and a dipping method , Blade coating method and other coating methods using rollers; spraying method; doctor blade coating method; spin coating method; screen printing and other printing and other applications using various applicators for coating. When the resin is a thermoplastic resin, melt coating such as a hot melt coating method may be performed. In the manufacturing method of this embodiment, in the subsequent step of applying high-frequency vibration, the anisotropic fillers in the film are rearranged, so it is not necessary to consider the orientation state of the anisotropic fillers determined at the time of film formation, and it can be freely Select the coating film formation method. The thickness of the coating film can be appropriately determined according to the use, purpose, and the like, and can be set to, for example, 10 to 5000 μm.

In the manufacturing method of this embodiment, the film formation step is continued, and there is a step of applying vibration to the film at a frequency of 5 kHz or more. According to the research of the inventors of this case, it is found that if high frequency vibration is applied to the film, the anisotropic filler will be rearranged. If the original system is in the horizontal alignment, it will gradually approach the random alignment and further approach the vertical alignment. Such a rearrangement phenomenon is presumed to be caused by a shock wave effect when a bubble is broken due to a cavitation effect phenomenon caused by high-frequency vibration, but the mechanism is not limited thereto. At this time, in order to allow the rearrangement of the anisotropic filler as the film to be imparted with a vibration object, it must be flowable, that is, liquid (liquid (including sol and gel)). When the printing ink does not contain a solvent or a dispersing medium and the resin is a thermoplastic resin (when the printing ink is a hot-melt printing ink), the film formation method is a hot-melt coating method, but in this case, there is As the film cools, it hardens (cures). Therefore, in this case, the film is continuously heated to maintain a flowable state, or the cured hardened film is heated to return it to a liquid state, and the like, so that the film is in a flowable state in the step of imparting high-frequency vibration.

The method for imparting high-frequency vibration to the coating film is not limited. For example, an ultrasonic generator can be used to impart vibration to the coating film via a support holding the coating film. The frequency of vibration is 5 kHz or more, and there is no upper limit. For example, it can be set to 10 to 1000 kHz or 15 to 1000 kHz. In addition, the types of frequencies to be used are not limited, and vibrations having a single frequency can be imparted, or vibrations whose frequencies change with time can be used. Furthermore, it is also effective to use a combination of a plurality of vibrations (swipe vibrations) having different frequencies. The appropriate frequency varies depending on the shape and size of the anisotropic filler. In general, the larger the particle size of the filler, the more suitable it is for lower frequencies, and the smaller the particle size, the more suitable it is for higher frequencies. That is, as the frequency of the impact force of the high-frequency vibration (ultrasonic wave) decreases, the larger the frequency becomes, the higher the frequency, the larger the particle size of the anisotropic filler tends to be random alignment. On the other hand, as the frequency of the standing wave interval system becomes higher, the frequency becomes narrower. If the frequency is adjusted lower, it is effective for making the anisotropic filler with a small particle size to have random orientation. The time for applying high-frequency vibration is not limited, and it can be appropriately determined in accordance with the vibration frequency and the film thickness. For example, it can be set to 1 second to 300 seconds.

In this embodiment mode, the method may further include a step of pressing the film after the anisotropic fillers are rearranged in the above manner, thereby removing voids contained in the film. If there are voids in the film, the thermal conductivity may decrease. Therefore, when the sheet is used as a thermally conductive sheet, such pressing is particularly effective. The pressing conditions (pressure, temperature, time, ambient atmosphere, etc.) at this time are not limited, as long as the type of anisotropic filler or resin, the content of filler in the film, etc. are considered, and the anisotropic filler in the film is appropriately determined. The conditions for alignment and removal of voids are sufficient. The pressing pressure may be set to 0.01 to 20 MPa, for example, or 10 MPa or less, and usually 5 MPa or less is sufficient. In addition, in the case where the viscosity of the printing ink constituting the film is low and it is difficult to directly press, etc., a part or all of the solvent may be removed from the film before the pressing step, and the film may be semi-hardened. The method of removing the solvent at this time is not limited, and methods such as vacuum drying and heat drying can be suitably used.

The film formed as described above can be appropriately dried and / or hardened as required. When it is hardened, the hardening method is not limited, and it can be hardened by heating or light according to the kind of resin.

In this embodiment, the thickness of the sheet containing the anisotropic filler may be appropriately determined depending on the application, and may be, for example, 10 to 1,000 μm. When the sheet containing an anisotropic filler is a thermally conductive sheet, the thermal conductivity in the thickness direction of the sheet is preferably 0 W / m ･ K or more, more preferably 7.0 W / m ･ K or more, and 10.0 W / m. ･ K is better. There is no upper limit for thermal conductivity, the larger the better. According to the manufacturing method of this embodiment, such a high thermal conductivity thermally conductive sheet can also be manufactured. [Example]

Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples at all. The method for measuring the characteristics of the anisotropic filler-containing sheet produced in the examples and comparative examples will be described below. <Evaluation method of each characteristic> (1) Thermal conductivity A test piece (10 mm × 10 mm × thickness 1 mm) was cut out of a sheet (C sheet described later) obtained in Examples and Comparative Examples, and xenon made by NETZSCH was used for the test piece. The flash LFA447 thermal conductivity analyzer uses a laser flash method to determine the thermal diffusivity of the test piece. The thermal diffusivity obtained in the above manner; the density of the sheet measured using a density meter (MS-DNY-43 manufactured by Mettler Toledo Co., Ltd.); and the specific heat of each of the boron nitride and the resin (hardened material) ( The specific heat of boron nitride: 0.81J / g ･ K, resin: 0.80J / g ･ K) and their mass ratio in the sheet (corresponding to the average mass of the mass ratio proportionally distributed) was calculated. Multiply to calculate the thermal conductivity (W / m ･ K). (2) The alignment intensity is higher than that of the primary particles of boron nitride in the sheet. The intensity of I (002) diffraction rays (2θ = 26.5 °) and I (100) diffraction rays (2θ) in the X-ray diffraction method are used. = 41.5 °) to evaluate the intensity ratio (I (002) / I (100)). However, the X-ray diffraction method is used to evaluate the orientation of particles existing in the vicinity of the sheet surface. The boron nitride primary particles having a hexagonal structure have a thickness direction consistent with the crystallographic I (002) ray around the c-axis direction, and its in-plane direction is consistent with I (100) ray around the a-axis direction. In the case where the boron nitride primary particles constituting the boron nitride particle aggregate are completely random (non-aligned), (I (002) / I (100)) ≒ 6.7 ("JCPDS [Powder X-ray Diffraction Database] No. 34-0421 [BN] 's crystal density 値 [Dx]). The smaller (I (002) / I (100)), the more the a-axis direction of the hexagonal boron nitride particles is aligned toward the thickness direction. Specifically, a test piece (5 mm × 5 mm × thickness 0.2 mm) was cut out from the sheets obtained in the examples and comparative examples, and the “automatic horizontal multi-purpose X-ray diffraction device SmartLab” (manufactured by Rigaku, X-ray source) was used. : CuKα line, tube voltage: 45 kV, tube current: 360 mA), X-rays were irradiated to the thickness direction of the test piece, and the intensity of the I (002) ray and the I (100) ray were measured.

(Example 1) Using the method of the present invention, a sheet containing scaly boron nitride particles and a resin was produced. 100 parts by mass of a triphenylmethane type epoxy resin ("EPPN-501H" manufactured by Nippon Kayaku Co., Ltd.) and 63 parts by mass of a hardener (phenol novolac resin-based hardener, Meiwa Kasei "DL-92"), And 0.01 parts by mass of a hardening catalyst (2-phenylimidazole, manufactured by Shikoku Chemical Co., Ltd.) were mixed and prepared into a resin composition. The blending ratio of the epoxy resin and the hardener was defined as the functional group of the epoxy resin / hardener, and was 1.0 in terms of equivalent ratio. Next, to 100 parts by mass of an anisotropic filler, boron nitride primary particles having an average particle diameter of 45 μm (“PT110” manufactured by Momentive Performance), 1.5 parts by mass of 3-glycoside propyltrimethylester as a coupling agent was added dropwise. Oxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was stirred with a rotation revolution mixer (THINKY AR-100). Then, 50 parts by mass of a total of 50 parts by mass of 39 vol% of the resin composition and 61 vol% of the boron nitride primary particles to which the coupling agent was added were mixed in 50 parts by mass of a solvent (methyl ethyl ketone) to prepare a printing ink. This ink was applied on a support (copper foil) with an applicator (manufactured by Imoto Co., Ltd.) (with a gap of about 1.5 mm) to form a flat coating film. Then, it was placed on an aluminum plate, and the vibration element of the ultrasonic generator (ultrasonic homogenizer-US-600T manufactured by Nippon Seiki Seisakusho Co., Ltd.) was brought into contact with the above-mentioned aluminum plate, and the coating film was applied for 3 minutes via the aluminum plate and copper foil. The ultrasound vibrates and then stands still. Then, the coating film was dried at 120 ° C for 10 minutes, and the solvent was removed to prepare a semi-hardened sheet (B sheet) (about 1.5 mm thick). This was vacuum-pressed under a condition of 180 ° C. under vacuum for 2 hours and 10 MPa to harden it. Finally, the copper foil was peeled to produce a sheet (C sheet) containing an anisotropic filler.

(Example 2) Except that the pressing pressure during vacuum pressing of the semi-hardened sheet was set to 5 MPa, it was the same as in Example 1 to obtain a sheet containing an anisotropic filler. (Example 3) In 50 parts by mass of a solvent (methyl ethyl ketone), a total of 50 parts by mass of a total of 30 parts by volume of the resin composition and 70 parts by volume of a boron nitride primary particle to which a coupling agent was added was prepared to prepare a printing ink. (The proportion of the anisotropic filler in the solid content of the printing ink was changed.) Other than that, the sheet containing the anisotropic filler was produced in the same manner as in Example 1. (Example 4) A boron nitride primary particle having an average particle diameter of 12 µm ("πBN-S03" manufactured by Tokuyama) was used as an anisotropic filler, except that the same procedure as in Example 1 was used to prepare a sheet containing an anisotropic filler. material. (Example 5) Except that the compression pressure when the semi-hardened sheet was vacuum-pressed was set to 5 MPa, it was the same as Example 4, and a sheet containing an anisotropic filler was obtained. (Example 6) Into 50 parts by mass of a solvent (methyl ethyl ketone), a total of 50 parts by mass of a total of 30 parts by volume of the resin composition and 70 parts by volume of a boron nitride primary particle to which a coupling agent was added was prepared to prepare a printing ink. (The proportion of the anisotropic filler in the solid content of the printing ink was changed.) Other than that, the sheet was made into an anisotropic filler in the same manner as in Example 4.

(Comparative example 1) Except that ultrasonic vibration was not given, it was the same as Example 1, and the sheet | seat containing an anisotropic filler was obtained. (Comparative example 2) Except that ultrasonic vibration was not given, it carried out similarly to Example 3, and obtained the sheet containing an anisotropic filler. (Comparative example 3) Except that ultrasonic vibration was not given, it was the same as Example 4, and the sheet | seat containing an anisotropic filler was obtained. (Comparative example 4) Except that ultrasonic vibration was not applied, it was the same as Example 6, and the sheet | seat containing an anisotropic filler was obtained. (Comparative Example 5) A sheet containing an anisotropic filler was produced in the same manner as in Example 1 except that agglomerated boron nitride particles ("SGPS" by Denka) were used as the anisotropic filler and no ultrasonic vibration was imparted. material. (Comparative Example 6) A sheet containing an anisotropic filler was produced in the same manner as in Example 3 except that agglomerated boron nitride particles ("SGPS" by Denka) were used as an anisotropic filler and no ultrasonic vibration was imparted. material.

Table 1 discloses the thermal conductivity of the anisotropic filler-containing sheets produced in Examples 1 to 6 and Comparative Examples 1 to 6 and the alignment strength ratio of the primary particles of boron nitride (I (002) / I (100)). . The sheets of Examples 1 and 2 had a smaller orientation intensity ratio (I (002) / I (100)) (compared to random) compared to Comparative Example 1, which was made without using high-frequency vibrations, using the same printing ink. The theoretical value of alignment is 6.7), and the thermal conductivity is about 2 to 3 times higher. Also, in any of Examples 1 and 2, Comparative Example 1, the orientation intensity ratio of particles near the surface of the sheet evaluated by the X-ray diffraction method was higher after pressing (C sheet) than before (B sheet). ) Is large, which can be considered to be because a part of the particles in the longitudinal alignment existing near the surface of the sheet is horizontally aligned by being pressed by the pressing plate, and it can be considered that the random alignment is still maintained in the interior of the sheet. In fact, from the cross-sectional SEM images of the sheet (C sheet) obtained in Example 2 and Comparative Example 1, it was confirmed that the particles inside the sheet obtained without high-frequency vibration were horizontally aligned (Comparative Example 1, FIG. 2) ), In contrast, particles inside the sheet obtained by imparting high-frequency vibration are randomly oriented (Example 2, FIG. 1). Similarly, the thermal conductivity of any of the sheets of Examples 3 to 6 was about twice as high as that of a control (Comparative Examples 2 to 4) made without applying high frequency vibration using the same printing ink. In addition, the sheet of Example 4 has a larger alignment strength than the sheet of Comparative Example 5 which was produced in the same manner as the sheet of Comparative Example 5 except that the agglomerated boron nitride particles were used as an anisotropic filler and no high-frequency vibration was imparted. , But the porosity is low, resulting in high thermal conductivity. Similarly, the sheet of Example 6 is compared with the sheet of Comparative Example 6 made by using the same agglomerated boron nitride particles as an anisotropic filler without imparting high-frequency vibration, and the alignment strength is compared. Large, but low porosity, resulting in high thermal conductivity.

[Table 1] [Industrial availability]

The sheet containing an anisotropic filler produced by the production method of the present invention can be used in various applications. The sheet containing an anisotropic filler manufactured by the manufacturing method of the present invention can be used as a thermally conductive sheet when the anisotropic filler uses a thermally conductive substance. In particular, it has both high thermal conductivity and insulation. Therefore, it can be suitably used in various applications that need to have thermal conductivity and insulation (for example, materials for heat-dissipating insulating layers and adhesive layers in heat-generating electronic components such as circuit boards for power equipment and semiconductor power devices).

This patent application is based on a Japanese patent application (Japanese Patent Application No. 2017-114377) filed with the Japan Patent Office on June 9, 2017, the contents of which are incorporated herein by reference.

1 is an FE-SEM image of a cross section of a sheet (C sheet) containing an anisotropic filler obtained in Example 2. FIG. FIG. 2 is an FE-SEM image of a cross section of an anisotropic filler-containing sheet (C sheet) obtained in Comparative Example 1. FIG.

Claims (9)

A method for manufacturing a sheet containing an anisotropic filler includes the following steps; forming a film of an ink containing anisotropic filler and a resin on a support; and applying a frequency of 5 kHz to the film while the film is flowable The above vibration. For example, the method for manufacturing a sheet containing an anisotropic filler in the scope of the first patent application, wherein the frequency of the vibration is 10 to 1000 kHz. For example, the method for manufacturing a sheet containing an anisotropic filler in item 1 of the scope of patent application, wherein the average longest diameter of the anisotropic filler is 0.5 μm to 200 μm. For example, the method for manufacturing an anisotropic filler-containing sheet according to the first patent application range, wherein the aspect ratio of the anisotropic filler is 2 or more. For example, the method for manufacturing a sheet containing an anisotropic filler according to item 1 of the patent application scope, wherein the anisotropic filler contains scaly boron nitride particles. For example, the method for manufacturing a sheet containing an anisotropic filler according to item 1 of the patent application scope, wherein the anisotropic filler contains hexagonal boron nitride particles. For example, the method for manufacturing a sheet containing an anisotropic filler in the scope of application for a patent, wherein the volume ratio of the anisotropic filler in the film is 10 to 90% by volume. For example, the method for producing a sheet containing an anisotropic filler according to item 1 of the patent application scope, wherein the resin contains a thermosetting resin. For example, the method for manufacturing a sheet containing an anisotropic filler in the scope of patent application No. 1 further includes a step of pressing the film.