Method for producing functional layer

Abstract

To provide a method for producing a functional layer that is able to control the orientation of a filler in a functional layer containing the filler having a relatively large aspect ratio.SOLUTION: A method for producing a functional layer containing a filler having an aspect ratio of 2 or more and a resin, comprises: forming a coating layer containing the filler, the resin, a low-boiling-point solvent having a boiling point of less than 90°C, and a high-boiling-point solvent having a boiling point of 90°C or more; and heating and drying the coating layer to form the functional layer. The resin is preferably an adhesive resin, and the filler is preferably graphene having a two-dimensional structure.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a functional layer having a predetermined function, such as a function of thermal conductivity or adhesiveness.

Background Art

[0002] Conventionally, in electronic devices such as semiconductor devices such as thermoelectric conversion devices, photoelectric conversion devices, and large-scale integrated circuits, a heat dissipation material having thermal conductivity has been used to release the generated heat. For example, as a method for efficiently dissipating the heat generated from an electronic device to the outside, a heat dissipation sheet having excellent thermal conductivity is provided between the electronic device and the heat sink.

[0003] As an example of the heat dissipation sheet as described above, it is disclosed in Patent Document 1. The heat dissipation sheet of Patent Document 1 is manufactured by applying a coating liquid of a heat dissipation material containing an adhesive resin, an inorganic filler, a curing agent, and a solvent to a release sheet or a substrate and heating and drying it. As the inorganic filler, plate-like boron nitride particles having an aspect ratio of 10 to 200 and spherical alumina particles are used, and as the solvent, ethyl acetate is used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in some cases, the conventional heat dissipation sheets may not necessarily achieve the desired thermal conductivity. For example, when a composition containing plate-like inorganic particles with a large aspect ratio as described above is applied using the above-mentioned solvent and then heated and dried, in the formed layer, the contact frequency between the plate-like inorganic particles tends to be low, and as a result, the thermal conductivity may be low.

[0006] In view of such a situation, the present invention has been made, and an object of the present invention is to provide a method for manufacturing a functional layer capable of controlling the orientation of a filler having a relatively large aspect ratio in a functional layer containing the filler.

Means for Solving the Problems

[0007] In order to achieve the above object, first, the present invention provides a method for manufacturing a functional layer containing a filler having an aspect ratio of 2 or more and a resin, comprising forming a coating layer containing the filler, the resin, a low-boiling solvent having a boiling point of less than 90°C, and a high-boiling solvent having a boiling point of 90°C or more, and heating and drying the coating layer to form a functional layer (Invention 1).

[0008] In the above invention (Invention 1), due to the temperature difference between the surface and the inside of the coating layer caused by volatilization (heat of vaporization) during heating and drying, convection occurs, making it easier for the flow of high-aspect-ratio fillers to occur. As a result, the high-aspect-ratio fillers oriented in the plane direction of the coating layer by the shearing force during coating can flow and be oriented in the thickness direction of the coating layer. As a result, the contact frequency between the high-aspect-ratio fillers (especially in the thickness direction) is likely to increase, and for example, effects such as improvement in thermal conductivity and conductivity can be obtained. In this way, the orientation of the high-aspect-ratio fillers in the functional layer can be controlled.

[0009] In the above invention (Invention 1), it is preferable that the viscosity of the solution obtained by diluting the resin with methyl ethyl ketone to a concentration of 40% by mass is 0.5 Pa·s or more and 80 Pa·s or less (Invention 2).

[0010] In the above inventions (Inventions 1 and 2), it is preferable that the glass transition temperature (Tg) of the resin is -70°C or higher and 50°C or lower (Invention 3).

[0011] In the above inventions (Inventions 1 to 3), it is preferable that the resin is a pressure-sensitive adhesive resin (Invention 4).

[0012] In the above inventions (Inventions 1 to 4), it is preferable that the filler is a heat-conductive material (Invention 5).

[0013] In the above inventions (Inventions 1 to 5), it is preferable that the filler is graphene having a two-dimensional structure (Invention 6).

[0014] In the above inventions (Inventions 1 to 6), it is preferable that the ratio of the low-boiling solvent to the total amount of the low-boiling solvent and the high-boiling solvent is 10% by mass or more and 95% by mass or less (Invention 7).

[0015] In the above inventions (Inventions 1 to 7), it is preferable that the amount of the filler with respect to 100 parts by mass of the resin is 5 parts by mass or more and 100 parts by mass or less (Invention 8).

[0016] In the above inventions (Inventions 1 to 8), it is preferable that the total amount of the low-boiling solvent and the high-boiling solvent with respect to 100 parts by mass of the total amount of the filler and the resin in the coating layer is 100 parts by mass or more and 900 parts by mass or less (Invention 9).

[0017] In the above inventions (Inventions 1 to 9), it is preferable that the temperature of the heat drying is 75°C or higher and 150°C or lower (Invention 10).

[0018] In the above inventions (Inventions 1 to 10), it is preferable that the time of the heat drying is 5 seconds or more and 30 minutes or less (Invention 11).

[0019] In the above inventions (Inventions 1 to 11), there is provided a step of preparing a coating solution containing the filler, the resin, the low-boiling solvent, and the high-boiling solvent. The step of preparing the coating solution includes a first step of subjecting a mixture containing a part of the total amount of the resin to be blended, the filler, and at least one of the low-boiling solvent and the high-boiling solvent to a dispersion treatment to obtain a preliminary mixture, and a second step of adding at least the remainder of the resin to the preliminary mixture and subjecting it to a dispersion treatment, which is preferable (Invention 12).

[0020] In the above invention (Invention 12), in the first step, it is preferable to blend the low-boiling solvent and the high-boiling solvent with the mixture, and in the second step, to add the low-boiling solvent and the high-boiling solvent to the preliminary mixture (Invention 13).

[0021] In the above inventions (Inventions 12 and 13), the mixing amount of the resin in the first step is preferably 0.5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the filler (Invention 14).

Advantages of the Invention

[0022] According to the method for manufacturing a functional layer of the present invention, in a functional layer containing a filler having a relatively large aspect ratio, the orientation of the filler can be controlled.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present invention will be described. 〔Method for Manufacturing Functional Layer〕 One embodiment of the present invention is a method for manufacturing a functional layer containing a filler with an aspect ratio of 2 or more (hereinafter sometimes referred to as a "high aspect ratio filler") and a resin. The functional layer is not particularly limited, but for example, functions such as thermal conductivity and conductivity based on the action of the high aspect ratio filler, functions such as adhesiveness and hard coat property based on the action of the resin, desired mechanical properties (e.g., strength, elasticity, toughness, etc.) based on the interaction between the filler and the resin, and layers having two or more of these functions can be mentioned.

[0025] In this embodiment, a coating layer containing a high aspect ratio filler, a resin, a low boiling point solvent with a boiling point of less than 80°C, and a high boiling point solvent with a boiling point of 80°C or more is formed, and the coating layer is heated and dried to form a functional layer. Thus, when using a low boiling point solvent and a high boiling point solvent, a temperature difference is generated between the surface and the inside of the coating layer due to volatilization (heat of vaporization) during heating and drying, and convection occurs, so the flow of the high aspect ratio filler is likely to occur. As a result, the high aspect ratio filler oriented in the plane direction of the coating layer by the shearing force during coating can flow and be oriented in the thickness direction of the coating layer. As a result, the contact frequency between the high aspect ratio fillers (especially in the thickness direction) is likely to increase, and for example, effects such as improvement in thermal conductivity and conductivity can be obtained. Thus, according to the method for manufacturing a functional layer according to this embodiment, in a functional layer containing a high aspect ratio filler, the orientation of the high aspect ratio filler can be controlled.

[0026] 1. Each component (1) High aspect ratio filler The high aspect ratio filler used in this embodiment has an aspect ratio of 2 or more. Conventionally, it has been difficult to orient such a high aspect ratio filler with a relatively large aspect ratio in a desired direction due to factors such as the shearing force during coating, but according to the method according to this embodiment, the orientation can be controlled.

[0027] From the perspective of the purpose of orientation control, the aspect ratio of the high aspect ratio filler used in this embodiment is preferably 5 or more, particularly preferably 10 or more, and more preferably 30 or more. On the other hand, from the perspective of more effectively controlling the orientation, the aspect ratio is preferably 100,000 or less, more preferably 50,000 or less, particularly preferably 40,000 or less, and more preferably 30,000 or less. In this specification, the aspect ratio of a plate-like (including scaly) filler refers to the ratio of the average particle size to the thickness (average particle size / thickness). The aspect ratio of the filler in this specification can be calculated by image analysis using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0028] Examples of the high aspect ratio filler used in this embodiment include graphene having a two-dimensional structure, mica, talc, clay such as montmorillonite, carbon fiber (carbon nanotube, carbon nanofiber), cellulose nanofiber, glass fiber, metal fiber, boron nitride, and the like. These can be used alone or in combination of two or more.

[0029] When forming a functional layer having thermal conductivity, among the above, graphene having a two-dimensional structure is particularly preferable from the viewpoints of excellent thermal conductivity and control of orientation. Since graphene having a two-dimensional structure has a planar structure that spreads two-dimensionally, contact between graphenes is likely to occur, and a heat conduction path for transmitting heat in the coating layer is easily formed. In addition, graphene having a two-dimensional structure has a very high in-plane thermal conductivity of about 3000 W / m·K. Furthermore, graphene has a low specific gravity of about 2.25 and is difficult to sediment as compared with conventional inorganic fillers such as metals, metal oxides, and nitride compounds. Therefore, even if the content of the graphene having the above two-dimensional structure is small (for example, about 10% by volume), the resulting functional layer has excellent thermal conductivity. Specifically, it can exhibit very excellent thermal conductivity of 3.0 W / m·K or more.

[0030] Here, graphene is a two-dimensional compound composed of a single atomic layer, having a two-dimensional structure in which carbon atoms are regularly arranged in a hexagonal shape. The "graphene having a two-dimensional structure" in this specification may be a multi-layer one, and preferably has a thickness of 1 / 10 or less of the shortest length in the planar view shape. Note that the graphene in this specification includes those generated by thinly peeling (cleaving) graphite.

[0031] As described above, the graphene having a two-dimensional structure may be a single layer or a multi-layer one. In the case of a multi-layer, it is usually about 2 to 1,000 layers. The planar view shape of the graphene having a two-dimensional structure is not particularly limited.

[0032] The graphene having a two-dimensional structure used in this embodiment is preferably graphene having a two-dimensional crystal structure because of its excellent thermal conductivity. Here, the "graphene having a two-dimensional crystal structure" means having a structural periodicity in the two-dimensional direction, having a layer with a single atomic thickness, and consisting of only the layer or the layer laminated from 2 to about several hundred layers by van der Waals force. In such "graphene having a two-dimensional crystal structure", experimentally, in wide-angle X-ray diffraction measurement (WAXD), distinct crystal peaks can be obtained from its periodic structure. Also, in the case of a plurality of laminated ones, crystal peaks attributable to the periodic structure in the laminated thickness direction can also be obtained.

[0033] When a functional layer containing graphene having a two-dimensional crystal structure is measured by X-ray diffraction method using a CuKα ray source (wavelength 0.15418 nm), it is preferable that peaks are detected at positions where 2θ is 26.6° and 42.4°. The diffraction peaks at the positions where 2θ is 26.6° and 42.4° are the crystal peaks between the layers and in the plane of the graphene. By detecting peaks at such positions, it can be said that the graphene has a crystal structure.

[0034] The method for producing graphene having a two-dimensional structure is not particularly limited. For example, there are a method of physically cleaving graphite, a method of cleaving once-oxidized graphite to form a single layer (oxidized graphene), and then reducing it to produce (reduced graphene oxide (RGO)). Among them, graphene obtained by physically cleaving graphite is preferred because it has a good two-dimensional crystal structure and thus is excellent in thermal conductivity.

[0035] The average particle size of graphene having a two-dimensional structure is preferably 0.5 μm or more, more preferably 1.0 μm or more, particularly preferably 3.0 μm or more, and even more preferably 5.0 μm or more. This makes it easier for each graphene to come into contact with each other and easier to form a heat conduction path, so that the characteristics of the two-dimensional structure function and the functional layer becomes excellent in thermal conductivity. Also, the average particle size of graphene having a two-dimensional structure is preferably 30 μm or less, particularly preferably 20 μm or less, and even more preferably 15 μm or less. This makes it easier for graphene to flow due to convection by a low-boiling-point solvent and a high-boiling-point solvent, and easier to orient in the thickness direction of the coating layer, so that the functional layer becomes excellent in thermal conductivity.

[0036] Note that the average particle size of the filler in this specification can be calculated by a particle size distribution meter and image analysis by SEM or TEM.

[0037] The thickness of graphene having a two-dimensional structure is preferably 500 nm or less, more preferably 300 nm or less, particularly preferably 200 nm or less, and even more preferably 100 nm or less. When flexibility is required for the functional layer, the flexibility of the functional layer is maintained well as described above. On the other hand, the lower limit of the thickness of graphene having a two-dimensional structure is not particularly limited, but is usually 0.7 nm or more, and from the viewpoint of thermal conductivity, it is preferably 5.0 nm or more, particularly preferably 10 nm or more, and even more preferably 15 nm or more.

[0038] (2) Resin The resin used in this embodiment can be appropriately selected according to the purpose of the functional layer. For example, when the functional layer is an adhesive layer, a pressure-sensitive adhesive resin can be selected as the resin. When the functional layer is a cured layer, a hard coat layer, etc., a curable resin can be selected as the resin.

[0039] The viscosity of the solution obtained by diluting the resin used in this embodiment with methyl ethyl ketone to a concentration of 40% by mass is preferably 0.5 Pa·s or more and 80 Pa·s or less. When the viscosity is 0.5 Pa·s or more, a solvent is required for coating, and the effects of low-boiling solvents and high-boiling solvents can be exerted. Further, when the viscosity is within the above range, convection due to low-boiling solvents and high-boiling solvents occurs favorably, and the orientation of high aspect ratio fillers can be controlled more effectively. The viscosity measurement method in this specification is measured as the value at a temperature condition of 23°C and a shear rate of 10S using a rotational rheometer MCR302 manufactured by Anton-Paar and a cone plate CP50-0.5. -1 It is defined by the viscosity of the diluted solution because it is technically difficult to measure the viscosity of the resin itself used in this embodiment.

[0040] From the above viewpoints, the viscosity of the above diluted solution is more preferably 0.7 to 50 Pa·s, and particularly preferably 1.0 to 30 Pa·s.

[0041] The glass transition temperature (Tg) of the resin used in this embodiment is preferably -70°C or more and 50°C or less. When the glass transition temperature (Tg) of the resin is within the above range, convection due to low-boiling solvents and high-boiling solvents occurs favorably, and the orientation of high aspect ratio fillers can be controlled more effectively. The glass transition temperature (Tg) of the pressure-sensitive adhesive resin in this specification is a value calculated based on FOX's equation.

[0042] From the above viewpoints, the glass transition temperature (Tg) of the resin used in this embodiment is more preferably -70 to 25°C, particularly preferably -65 to 20°C.

[0043] Here, the case where the resin used in this embodiment is a pressure-sensitive adhesive resin will be described. The type of the pressure-sensitive adhesive resin is not particularly limited, and for example, it may be any of acrylic, polyester, polyurethane, rubber, silicone, etc. Further, the pressure-sensitive adhesive may be either an emulsion type or a solvent type, and may be either a crosslinked type or a non-crosslinked type. Furthermore, it may be non-curable by active energy rays or curable by active energy rays.

[0044] As the acrylic pressure-sensitive adhesive resin, a (meth)acrylic acid ester polymer obtained by polymerizing a (meth)acrylic acid ester monomer or the like is preferably mentioned. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Also, the concept of "copolymer" is included in the "polymer".

[0045] The (meth)acrylic acid ester polymer as the pressure-sensitive adhesive resin preferably contains a (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer. Thereby, the obtained functional layer can exhibit good adhesiveness. The alkyl group may be linear, branched or cyclic.

[0046] From the viewpoint of adhesiveness, (meth)acrylic acid alkyl esters having 1 to 20 carbon atoms in the alkyl group are preferred as the (meth)acrylic acid alkyl ester. Examples of the (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, and the like.

[0047] Among the above, from the viewpoints of imparting good adhesiveness and dispersibility of high aspect ratio fillers, (meth)acrylic acid alkyl esters having 1 to 9 carbon atoms in the alkyl group are more preferred, (meth)acrylic acid alkyl esters having 1 to 6 carbon atoms in the alkyl group are particularly preferred, and (meth)acrylic acid alkyl esters having 1 to 4 carbon atoms in the alkyl group are even more preferred. Specifically, methyl (meth)acrylate is preferred, and particularly methyl acrylate is preferably mentioned. These may be used alone or in combination of two or more.

[0048] From the viewpoints of imparting good adhesiveness and dispersibility of high aspect ratio fillers, the (meth)acrylic acid ester polymer preferably contains 20% by mass or more of (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer, more preferably 30% by mass or more, particularly preferably 35% by mass or more, and even more preferably 40% by mass or more. Further, from the viewpoint of ensuring the content of other monomers (for example, reactive functional group-containing monomers described later), it is preferably contained 99.9% by mass or less of (meth)acrylic acid alkyl ester, more preferably 95% by mass or less, particularly preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0049] As a pressure-sensitive adhesive resin, the (meth)acrylate polymer preferably contains a reactive functional group-containing monomer having a reactive functional group in the molecule as a monomer constituting the polymer. By containing the reactive functional group-containing monomer, the dispersibility of the high aspect ratio filler can be further improved due to its polarity and the like. Further, when the coating liquid for forming the functional layer contains a crosslinking agent, the reactive functional group derived from the reactive functional group-containing monomer can serve as a crosslinking point to form a crosslinked structure.

[0050] Examples of the reactive functional group-containing monomer include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxy group in the molecule (carboxy group-containing monomer), a monomer having an amino group in the molecule (amino group-containing monomer), and the like. Among these, from the viewpoint of the dispersibility of the high aspect ratio filler, a hydroxyl group-containing monomer is preferable. These reactive functional group-containing monomers may be used alone or in combination of two or more.

[0051] Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Among these, from the viewpoint of the dispersibility of the high aspect ratio filler, 2-hydroxyethyl (meth)acrylate is preferable, and 2-hydroxyethyl acrylate is particularly preferable. These may be used alone or in combination of two or more.

[0052] Examples of the carboxy group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used alone or in combination of two or more.

[0053] Examples of the amino group-containing monomer include aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0054] The (meth)acrylate polymer preferably contains a monomer having a reactive functional group as a monomer constituting the polymer in an amount of 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 1% by mass or more, and still more preferably 5% by mass or more as a lower limit. Further, the (meth)acrylate polymer (A) preferably contains a monomer having a reactive functional group as a monomer unit constituting the polymer in an amount of 40% by mass or less, more preferably 30% by mass or less, particularly preferably 25% by mass or less as an upper limit. When the (meth)acrylate polymer contains a monomer having a reactive functional group within the above range as a monomer unit constituting the polymer, the dispersibility of the high aspect ratio filler becomes better.

[0055] The (meth)acrylate polymer as the pressure-sensitive adhesive resin may further contain other monomers as monomers constituting the polymer. Examples of the other monomers include (meth)acrylic acid alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; non-crosslinkable acrylamides such as acrylamide and methacrylamide; (meth)acrylic acid esters having a non-crosslinkable tertiary amino group such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate; vinyl acetate; styrene and the like. These may be used alone or in combination of two or more.

[0056] The polymerization mode of the (meth)acrylate polymer may be a random polymer or a block polymer.

[0057] The weight-average molecular weight of the (meth)acrylate polymer is preferably 10,000 or more, more preferably 20,000 or more, particularly preferably 50,000 or more, and even more preferably 100,000 or more. Further, the above weight-average molecular weight is preferably 2,000,000 or less, more preferably 1,500,000 or less, particularly preferably 1,200,000 or less, and even more preferably 1,000,000 or less. When the weight-average molecular weight is within the above range, the dispersibility of the high aspect ratio filler in the thermally conductive adhesive composition becomes better, and the flexibility and adhesiveness also become better. The weight-average molecular weight in this specification is a value in terms of standard polystyrene measured by gel permeation chromatography (GPC) method.

[0058] In addition, the pressure-sensitive adhesive resin used in this embodiment may contain one kind of the above-described (meth)acrylate polymer, or may contain two or more kinds. Further, the pressure-sensitive adhesive resin used in this embodiment may contain another (meth)acrylate polymer together with the above-described (meth)acrylate polymer.

[0059] Here, when the acrylic pressure-sensitive adhesive resin is an active energy ray-curable one, for example, a (meth)acrylate polymer in which an active energy ray-curable group is introduced into the side chain can be used. For the introduction of the active energy ray-curable group, an unsaturated group-containing compound having a substituent can be used. Examples of the unsaturated group-containing compound having a substituent include 2-methacryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate; an acryloyl monoisocyanate compound obtained by reacting a diisocyanate compound or a polyisocyanate compound with hydroxyethyl (meth)acrylate; an acryloyl monoisocyanate compound obtained by reacting a diisocyanate compound or a polyisocyanate compound with a polyol compound and hydroxyethyl (meth)acrylate; glycidyl (meth)acrylate; (meth)acrylic acid, 2-(1-aziridinyl)ethyl (meth)acrylate, 2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline, and the like.

[0060] As the pressure-sensitive adhesive resin used in this embodiment, a rubber-based pressure-sensitive adhesive resin can also be used. Examples of the rubber-based pressure-sensitive adhesive resin preferably include polyisobutylene-based resins, polybutene-based resins, isoprene-isobutylene copolymers, styrene-isoprene-styrene block copolymers, styrene-butadiene-styrene block copolymers, styrene-butadiene rubber copolymers, natural rubber, modified natural rubber, and the like.

[0061] In this embodiment, the curable resin used when the functional layer is a cured layer, a hard coat layer, or the like may be an active energy ray-curable resin or a thermosetting resin.

[0062] As the active energy ray curable resin, active energy ray curable monomers and oligomers are preferably used. In this specification, for the sake of convenience, the active energy ray curable monomers are also regarded as active energy ray curable resins.

[0063] Examples of the active energy ray curable monomers and oligomers include monofunctional acrylate esters such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate, and polyfunctional acrylate esters such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and dimethyloltricyclodecane di(meth)acrylate, as well as polyester oligo(meth)acrylate, polyurethane oligo(meth)acrylate, and the like.

[0064] Examples of the thermosetting resin include epoxy resin, phenol resin, melamine resin, urea resin, polyester resin, urethane resin, acrylic resin, polyimide resin, benzoxazine resin, phenoxy resin, acid anhydride compound, amine-based compound, naphthol-based resin, active ester-based resin, benzoxazine-based resin, cyanate ester-based resin, and the like.

[0065] (3) Solvent (3-1) Low-boiling solvent The boiling point of the low-boiling solvent used in this embodiment is less than 90°C, preferably 85°C or lower, more preferably 80°C or lower, particularly preferably 75°C or lower, and even more preferably 70°C or lower. When the boiling point of the low-boiling solvent is as described above, convection occurs effectively during heat drying in the coating layer, and it becomes easier to control the orientation of the high aspect ratio filler.

[0066] The lower limit of the boiling point of the above-mentioned low-boiling solvent is not particularly limited, but from the viewpoints of ease of handling and the like, it is preferably 40 °C or higher, more preferably 45 °C or higher, particularly preferably 50 °C or higher, and even more preferably 55 °C or higher.

[0067] Examples of the low-boiling solvent having a boiling point of less than 90 °C include methyl ethyl ketone (79.6 °C), acetone (56.5 °C), ethyl acetate (77.1 °C), hexane (68.7 °C), methylene chloride (40 °C), methanol (64.7 °C), 2-propanol (82.3 °C), cyclohexane (80.7 °C), and the like. These may be used alone or in combination of two or more.

[0068] (3-2) High-boiling solvent The boiling point of the high-boiling solvent used in this embodiment is 90 °C or higher, preferably 95 °C or higher, more preferably 100 °C or higher, particularly preferably 110 °C or higher, and even more preferably 120 °C or higher. When the boiling point of the high-boiling solvent is as described above, a rapid increase in viscosity due to solvent volatilization during heat drying in the coating layer is suppressed, whereby convection is effectively generated, and the orientation of the high aspect ratio filler becomes easier to control.

[0069] The upper limit of the boiling point of the above-mentioned high-boiling solvent is preferably 220 °C or lower, more preferably 200 °C or lower, particularly preferably 180 °C or lower, and even more preferably 150 °C or lower, from the viewpoints of setting the heat drying temperature to an appropriate temperature and removing the residual solvent in the functional layer.

[0070] Examples of high-boiling solvents with a boiling point of 80 °C or higher include cyclohexanone (boiling point: 155.7 °C), propyl acetate (boiling point: 101.6 °C), toluene (boiling point: 110.6 °C), heptane (98.4 °C), xylene (137 - 144 °C), ethanol (95 °C), propanol (97.2 °C), 1-butanol (117 - 118 °C), 2-butanol (99.5 °C), 2-pentanone (101 °C), cyclohexanone (155.6 °C), butyl acetate (125 - 126 °C), ethyl cellosolve (135 °C), N,N-dimethylformamide (153 °C), N-methylpyrrolidone (202 °C), etc. These may be used alone or in combination of two or more.

[0071] The difference between the boiling point of the low-boiling solvent to be used and the boiling point of the high-boiling solvent is preferably 10 - 150 °C, more preferably 15 - 120 °C, particularly preferably 20 - 100 °C, and even more preferably 25 - 80 °C. Thereby, convection occurs effectively during heat drying in the coating layer, and it becomes easier to control the orientation of the high aspect ratio filler.

[0072] (4) Various additives In this embodiment, crosslinking agents, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, fillers, refractive index adjusters, rust preventives, flame retardants, etc. can be added to the coating liquid for forming the coating layer, if desired. Also, fillers other than the high aspect ratio filler may be added.

[0073] 2. Specific manufacturing method of the functional layer 2-1. Formation of the coating layer In this embodiment, a coating layer containing a high aspect ratio filler, a resin, a low-boiling solvent, and a high-boiling solvent is formed. The coating layer can be formed by applying a coating solution. The application of the coating solution may be carried out once or a plurality of times. In the case of multiple times, the type of the coating solution may be changed. For example, the first coating solution may be a coating solution containing a high aspect ratio filler, a resin, and a low-boiling solvent, and the second coating solution may be a coating solution containing a high aspect ratio filler, a resin, and a high-boiling solvent. However, in this embodiment, it is preferable that the coating solution is applied once. Hereinafter, the case will be described.

[0074] (1) Preparation of coating solution In this embodiment, a coating solution containing a high aspect ratio filler, a resin, a low-boiling solvent, and a high-boiling solvent is prepared.

[0075] The content of the high aspect ratio filler in the coating solution (coating layer) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, particularly preferably 15 parts by mass or more, and still more preferably 30 parts by mass or more with respect to 100 parts by mass of the resin. Thereby, the contact frequency of the high aspect ratio filler can be increased. As a result, for example, when the high aspect ratio filler has thermal conductivity, a heat conduction path is easily formed, and the thermal conductivity becomes more excellent.

[0076] Also, the content of the high aspect ratio filler in the coating solution (coating layer) is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, particularly preferably 60 parts by mass or less, and still more preferably 50 parts by mass or less with respect to 100 parts by mass of the resin. Thereby, the fluidity of the high aspect ratio filler in the coating layer can be ensured, and the orientation can be more easily controlled. Further, it is possible to suppress the generation of voids in the obtained functional layer. Furthermore, by relatively increasing the content of the resin, the effects of the resin (for example, flexibility, adhesiveness, hardness, etc.) are sufficiently exhibited.

[0077] The content of the resin in the coating liquid (coating layer) is preferably 10% by mass or more, more preferably 15% by mass or more, particularly preferably 20% by mass or more, and even more preferably 25% by mass or more, based on the total amount of solids (i.e., when the total solids excluding the solvent is 100% by mass). Also, the above content is preferably 95% by mass or less, more preferably 90% by mass or less, particularly preferably 80% by mass or less. When the content of the resin is within the above range, the control of the dispersibility and orientation of the high aspect ratio filler becomes better, and the effects of the resin (such as flexibility, adhesiveness, hardness, etc.) are fully exerted.

[0078] The total amount of the low-boiling solvent and the high-boiling solvent with respect to 100 parts by mass of the total amount of the high aspect ratio filler and the resin in the coating liquid (coating layer) is preferably 100 parts by mass or more, more preferably 120 parts by mass or more, particularly preferably 150 parts by mass or more. Also, the above total amount is preferably 900 parts by mass or less, more preferably 600 parts by mass or less, particularly preferably 400 parts by mass or less, and even more preferably 300 parts by mass or less. When the total amount of the low-boiling solvent and the high-boiling solvent is within the above range, the control of the dispersibility and orientation of the high aspect ratio filler becomes better, and the coating liquid can be coated well.

[0079] The ratio of the low-boiling solvent to the total amount of the low-boiling solvent and the high-boiling solvent in the coating liquid (coating layer) is preferably 10% by mass or more, more preferably 20% by mass or more, particularly preferably 25% by mass or more, and still more preferably 30% by mass or more. As a result, the heat of vaporization due to volatilization increases, a temperature difference is generated between the surface and the inside of the coating layer, and convection occurs, so that the flow of the high aspect ratio filler is likely to occur. Further, the ratio of the low-boiling solvent is preferably 95% by mass or less, more preferably 90% by mass or less, particularly preferably 85% by mass or less, and still more preferably 80% by mass or less. Thereby, it is possible to suppress the rapid drying during heat drying and the hindrance of the fluidity of the high aspect ratio filler. That is, when the ratio of the low-boiling solvent is within the above range, convection during heat drying and the flow of the high aspect ratio filler are more likely to occur, and the orientation of the high aspect ratio filler can be controlled more effectively.

[0080] Here, each component of the coating liquid may be mixed at once, but it is preferably mixed separately in a first step of obtaining a preliminary mixture and a second step of obtaining the target coating liquid. Specifically, a first step of subjecting a mixture containing a part of the total amount of the resin to be blended, a high aspect ratio filler, and a solvent (low-boiling solvent and / or high-boiling solvent) to a dispersion treatment to obtain a preliminary mixture, and adding the remaining portion of the resin and a solvent (low-boiling solvent and / or high-boiling solvent) to the preliminary mixture and performing a dispersion treatment in a second step are preferably performed. Thereby, a coating liquid in which the high aspect ratio filler is uniformly dispersed can be obtained.

[0081] In both the first step and the second step, it is preferable to use both a low-boiling solvent and a high-boiling solvent as the solvent. Thereby, a coating liquid in which the high aspect ratio filler is more uniformly dispersed can be obtained, and the orientation of the high aspect ratio filler can be more easily controlled by the convection generated during heat drying. Hereinafter, the first step and the second step will be described in detail.

[0082] (1-1) First step In the first step of this embodiment, a dispersion treatment is performed on a mixture containing a part of the total amount of the resin to be blended, a high aspect ratio filler, and a solvent (preferably a low boiling point solvent and a high boiling point solvent). As a result, the dispersion treatment is performed in a state where the viscosity is relatively high, and it is possible to suppress the aggregation of the high aspect ratio filler. As a result, the high aspect ratio filler can be uniformly dispersed in the mixture.

[0083] The upper limit of the mixing amount of the resin in the first step is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less with respect to 100 parts by mass of the high aspect ratio filler. As a result, the dispersion treatment can be performed in a state where the viscosity is relatively high, and it becomes easier to disperse the high aspect ratio filler more uniformly. Also, the lower limit of the mixing amount of the resin in the first step is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, particularly preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more with respect to 100 parts by mass of the high aspect ratio filler.

[0084] For the dispersion treatment of the above mixture, a conventionally known method may be used. For example, known kneaders and dispersers such as a homogenizer, bead mill, ball mill, jet mill, disper, mixer, kneader, ultrasonic disperser, etc. can be used. The dispersion treatment can be used alone or in combination of two or more devices.

[0085] Among these, from the viewpoint that it is possible to suppress a significant reduction in the function of the high aspect ratio filler due to excessive pulverization of the high aspect ratio filler, suppress aggregation of the high aspect ratio filler, and uniformly disperse the high aspect ratio filler in the mixture, it is preferable to perform a dispersion treatment using a disper, mixer, jet mill, or ultrasonic disperser. When performing the dispersion treatment of the above mixture using a disper, it is preferably performed by stirring at a rotational speed of 500 to 5000 rpm for 10 minutes or more, and more preferably performed by stirring at a rotational speed of 1000 to 4000 rpm for 20 minutes or more.

[0086] The upper limit value of the mixing amount (total amount) of the solvent in the first step is preferably 10,000 parts by mass or less, particularly preferably 5000 parts by mass or less, and more preferably 2000 parts by mass or less with respect to 100 parts by mass of the high aspect ratio filler. Thereby, the dispersion treatment can be performed in a state where the viscosity is relatively high, and it becomes easier to disperse the high aspect ratio filler more uniformly. Also, the lower limit value of the mixing amount (total amount) of the solvent in the first step is preferably 200 parts by mass or more, and more preferably 500 parts by mass or more with respect to 100 parts by mass of the high aspect ratio filler. Thereby, the dispersion treatment can be performed well.

[0087] The ratio of the low-boiling solvent to the total amount of the low-boiling solvent and the high-boiling solvent in the first step is preferably the same as the ratio in the above-described coating solution (coating layer). Thereby, a coating solution in which the high aspect ratio filler is more uniformly dispersed can be obtained, and the orientation of the high aspect ratio filler can be more easily controlled by the convection generated during heat drying.

[0088] (1-2) Second step In the second step of the present embodiment, at least the remainder of the above resin is added to the preliminary mixture obtained in the first step, and a dispersion treatment is performed. In this second step, it is also preferable to add a solvent (preferably a low-boiling solvent and a high-boiling solvent).

[0089] The amount of the solvent added in the second step may be such that the viscosity of the resulting coating solution is within a coatable range, and is not particularly limited, and can be appropriately selected according to the situation. Usually, it is preferably an amount such that the solid content concentration of the coating solution is 2 to 50% by mass, particularly preferably an amount such that it is 5 to 40% by mass, and more preferably an amount such that it is 10 to 35% by mass.

[0090] The ratio of the low-boiling solvent to the total amount of the low-boiling solvent and the high-boiling solvent in the second step is also preferably the same as the ratio in the above-described coating solution (coating layer). Thereby, a coating solution in which the high aspect ratio fillers are more uniformly dispersed can be obtained, and the orientation of the high aspect ratio fillers can be more easily controlled by the convection generated during heat drying.

[0091] Through the above steps, a coating solution in which high aspect ratio fillers are uniformly dispersed can be obtained.

[0092] (2) Formation of the coating layer The coating solution prepared as described above is applied to a desired object to form a coating layer. The object to be coated can be appropriately selected according to the purpose of the functional layer, and examples thereof include a desired film, a release sheet, a desired substrate, a desired member, and the like.

[0093] As a method for applying the coating solution, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.

[0094] The thickness of the coating layer may be set so that the target functional layer has a desired thickness. From the viewpoint of facilitating the generation of convection during heat drying, it is preferably 10 to 1000 μm, more preferably 15 to 500 μm, particularly preferably 25 to 300 μm, and even more preferably 25 to 250 μm.

[0095] 2-2. Formation of the functional layer The coating layer formed above is heated and dried to form a functional layer. During this heating and drying process, a temperature difference exists between the surface and the interior of the coating layer, causing convection, which makes it easier for the high aspect ratio fillers to flow. As a result, the orientation of the high aspect ratio fillers can be controlled.

[0096] The temperature for heating and drying is preferably 75 to 150 °C, more preferably 80 to 130 °C, particularly preferably 85 to 120 °C, and even more preferably 90 to 110 °C. By doing so, the above-mentioned convection is more likely to occur, and the flow of the high aspect ratio fillers is more likely to occur, and the orientation of the high aspect ratio fillers can be controlled more effectively.

[0097] The time for heating and drying is preferably 5 seconds to 30 minutes, more preferably 30 seconds to 20 minutes, particularly preferably 45 seconds to 15 minutes, and even more preferably 1 to 10 minutes. By doing so, the above-mentioned convection is more likely to occur, and the flow of the high aspect ratio fillers is more likely to occur, and the orientation of the high aspect ratio fillers can be controlled more effectively. Also, the high-boiling solvent can be sufficiently volatilized, and the residual solvent in the functional layer can be prevented. Thereby, the function of the functional layer can be surely exerted. For example, it is possible to prevent the thermal conductivity from decreasing due to the residual solvent.

[0098] In this embodiment, when the time (minutes) for the above-mentioned heating and drying is T, and the ratio (mass%) of the high-boiling solvent to the total amount of the low-boiling solvent and the high-boiling solvent in the coating solution (coating layer) is A, the following formula: X = A (mass%) / T (minutes) The X value calculated by is preferably 1 or more and 30 or less. When the X value is 30 or less, the residual amount of the solvent in the functional layer is reduced, and a desired function, such as high thermal conductivity, can be maintained. Also, when the X value is 1 or more, the balance between the convection during heating and drying and the fluidity of the high aspect ratio fillers becomes good, and the orientation of the high aspect ratio fillers can be controlled more effectively.

[0099] From the above viewpoints, the X value is more preferably from 1 to 25, and particularly preferably from 3 to 10.

[0100] In addition, if a curing period is required after heat drying, a curing period is provided to form the functional layer. For example, a curing period of about 1 to 2 weeks at room temperature (for example, 23°C, 50% RH) may be provided.

[0101] The thickness of the functional layer varies depending on its purpose, but is usually preferably from 2 to 500 μm, more preferably from 5 to 300 μm, particularly preferably from 10 to 100 μm, and still more preferably from 15 to 50 μm.

[0102] 〔Adhesive Sheet〕 Here, when the functional layer is an adhesive layer having thermal conductivity, an adhesive sheet can be manufactured by the method according to the present embodiment. The adhesive sheet of the present embodiment includes at least an adhesive layer having thermal conductivity. In this case, it is preferable to use graphene having a two-dimensional structure as the high aspect ratio filler.

[0103] A specific configuration as an example of the adhesive sheet according to the present embodiment is shown in FIG. 1. As shown in FIG. 1, an adhesive sheet 1 according to an embodiment includes two release sheets 12a and 12b, and an adhesive layer 11 sandwiched between the two release sheets 12a and 12b so as to be in contact with the release surfaces of the two release sheets 12a and 12b. Note that the release surface of the release sheet in this specification refers to the surface having releasability in the release sheet, and includes both the surface subjected to the release treatment and the surface showing releasability without performing the release treatment.

[0104] 1. Each Member 1-1. Adhesive Layer The pressure-sensitive adhesive layer 11 in the present embodiment is the functional layer manufactured in the above-described embodiment, which uses a pressure-sensitive adhesive resin as the resin and a thermally conductive filler, preferably graphene having a two-dimensional structure, as the high aspect ratio filler.

[0105] 1-2. Release Sheet The release sheets 12a and 12b protect the pressure-sensitive adhesive layer 11 until the pressure-sensitive adhesive sheet 1 is used, and are peeled off when the pressure-sensitive adhesive sheet 1 (pressure-sensitive adhesive layer 11) is used. In the pressure-sensitive adhesive sheet 1 according to the present embodiment, one or both of the release sheets 12a and 12b are not necessarily required.

[0106] Examples of the release sheets 12a and 12b include a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene vinyl acetate film, an ionomer resin film, an ethylene·(meth)acrylic acid copolymer film, an ethylene·(meth)acrylate copolymer film, a polystyrene film, a polycarbonate film, a polyimide film, a fluororesin film, etc. Further, crosslinked films of these are also used. Furthermore, laminated films of these may also be used.

[0107] It is preferable that a release treatment is performed on the release surface (particularly the surface in contact with the pressure-sensitive adhesive layer 11) of the release sheets 12a and 12b. Examples of the release agent used for the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Note that, among the release sheets 12a and 12b, one release sheet may be a heavy release type release sheet with a large release force, and the other release sheet may be a light release type release sheet with a small release force.

[0108] The thickness of the release sheets 12a and 12b is not particularly limited, but is usually about 20 to 150 μm.

[0109] 2. Manufacture of the pressure-sensitive adhesive sheet As one manufacturing example of the pressure-sensitive adhesive sheet 1, the above-described coating liquid is applied to the release surface of one of the release sheets 12a (or 12b) to form a coating layer. Next, the coating layer is dried by heating, and the release surface of the other release sheet 12b (or 12a) is superposed on the coating layer. If a curing period is required, a curing period is provided, and if no curing period is required, the coating layer directly becomes the pressure-sensitive adhesive layer 11 as it is. Thereby, the above pressure-sensitive adhesive sheet 1 is obtained.

[0110] 3. Physical properties, etc. (1) Thickness of the pressure-sensitive adhesive layer The thickness of the pressure-sensitive adhesive layer 11 (value measured according to JIS K7130) is preferably 2 μm or more, more preferably 5 μm or more, particularly preferably 10 μm or more, and even more preferably 20 μm or more from the viewpoint of adhesiveness.

[0111] Also, the thickness of the pressure-sensitive adhesive layer 11 is preferably 500 μm or less, more preferably 300 μm or less, particularly preferably 100 μm or less, and even more preferably 50 μm or less from the viewpoint of thermal conductivity.

[0112] (2) Thermal conductivity The thermal conductivity of the pressure-sensitive adhesive layer 11 is preferably 3.0 W / m·K or more, more preferably 3.5 W / m·K or more, and particularly preferably 4.0 W / m·K or more. Thereby, it can be said that the pressure-sensitive adhesive sheet 1 is excellent in thermal conductivity. According to the present embodiment, the pressure-sensitive adhesive sheet 1 excellent in thermal conductivity can be easily manufactured by controlling the orientation of the high aspect ratio filler. The method for measuring the thermal conductivity in this specification is as shown in the test example described later.

[0113] 〔Heat dissipation device〕 As shown in FIG. 2, a heat dissipation device 3 according to an embodiment of the present invention includes a heat generating member 31, a heat transfer member 32, and an adhesive layer 11 provided between the heat generating member 31 and the heat transfer member 32.

[0114] The adhesive layer 11 in the present embodiment is preferably the adhesive layer 11 of the adhesive sheet 1 according to the above-described embodiment, but it may be directly applied and formed on the heat generating member 31 or the heat transfer member 32.

[0115] The heat generating member 31 and the heat transfer member 32 are bonded via the adhesive layer 11. Since this adhesive layer 11 is excellent in thermal conductivity, the heat generated by the heat generating member 31 is favorably thermally conducted to the heat transfer member 32 through the adhesive layer 11, and is efficiently dissipated to the outside from the heat transfer member 32.

[0116] The heat generating member 31 in the present embodiment is a member that generates heat as it exhibits a predetermined function, but is a member that requires suppression of temperature rise, or a member that requires controlling the flow of heat generated by the member in a specific direction. Examples of such a heat generating member 31 include semiconductor devices such as thermoelectric conversion devices, photoelectric conversion devices, and large-scale integrated circuits, electronic devices such as LED light emitting elements, optical pickups, and power transistors, various electronic devices such as mobile terminals and wearable terminals, batteries, cells, motors, and engines.

[0117] The heat transfer member 32 in the present embodiment is a member that dissipates the received heat, or a member that transfers the received heat to another member. Such a heat transfer member 32 is preferably made of a material having high thermal conductivity, for example, a metal such as aluminum, stainless steel, or copper, or graphite, carbon nanofiber, or the like. The form of the heat transfer member 32 may be any of a substrate, a housing, a heat sink, a heat spreader, etc., and is not particularly limited.

[0118] To manufacture the heat dissipation device 3, for example, one release sheet 12a (or 12b) is peeled off from the adhesive sheet 1, and one surface of the exposed adhesive layer 11 is attached to the heating member 31. Next, the other release sheet 12b (or 12a) is peeled off from the adhesive layer 11 provided on the heating member 31, and the other surface of the exposed adhesive layer 11 is attached to the heat transfer member 32. Alternatively, after attaching one surface of the adhesive layer 11 to the heat transfer member 32, the heating member 31 may be bonded to the other surface of the adhesive layer 11.

[0119] The embodiments described above are provided to facilitate the understanding of the present invention and are not provided to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

[0120] For example, the release sheet 12a or the release sheet 12b laminated on the adhesive sheet 1 in FIG. 1 may be omitted.

[0121] Further, the adhesive sheet may be formed by laminating a desired base material, an adhesive layer 11, and a release sheet 12a (or 12b) in that order. The material constituting the base material is not particularly limited, and examples thereof include resin films, non-woven fabrics, paper, graphite sheets, graphene sheets, metal base materials, etc., and resin films are generally used. Examples of the resin material constituting the resin film include polyesters, polyolefins, polyamides such as nylon 6, nylon 66, and partially aromatic polyamides, polyimides, polyamide-imides, polyether-ether-ketones, polyether sulfones, polyphenylene sulfides, polycarbonates, polyurethanes, ethylene-vinyl acetate copolymers, fluororesins such as polytetrafluoroethylene, acrylic resins, polyacrylates, polystyrenes, polyvinyl chlorides, polyvinylidene chlorides, and other resins. The above resin film may be formed using a resin material containing a single kind of such resin, or may be formed using a resin material in which two or more kinds are blended. The above resin film may be unstretched or may be stretched (for example, uniaxially stretched or biaxially stretched).

[0122] Furthermore, the shapes of the heat generating member 31 and the heat transfer member 32 in the heat dissipation device 3 are not limited to those shown in FIG. 2, and may be various shapes.

Example

[0123] Hereinafter, the present invention will be described more specifically by way of examples and the like, but the scope of the present invention is not limited to these examples and the like.

[0124] 〔Example 1〕 5 parts by mass of an acrylate polymer as an adhesive resin (5 parts by mass in 100 parts by mass in total; solid content concentration), 43 parts by mass of graphene having a two-dimensional structure (manufactured by ADEKA Corporation, product name "CNS-1A1") (solid content concentration), 240 parts by mass of methyl ethyl ketone as a low-boiling solvent (boiling point: 79.6 °C), and 60 parts by mass of cyclohexanone as a high-boiling solvent (boiling point: 155.7 °C) were mixed, and dispersion treatment was performed by stirring at 3000 rpm for 30 minutes using a disper (manufactured by Primix Corporation, product name "Robomix") to prepare a preliminary mixture (first step). The details of the acrylate polymer and graphene having a two-dimensional structure are as follows. · Acrylate polymer: A copolymer obtained by copolymerizing 80 parts by mass of 2-ethylhexyl acrylate (2EHA) and 20 parts by mass of 2-hydroxyethyl acrylate (HEA), weight average molecular weight: 350,000, glass transition temperature (Tg): -61 °C, viscosity of a solution diluted to a concentration of 40% by mass with methyl ethyl ketone: 5.5 Pa·s (measurement method: Measured as the value at 23 °C and a shear rate of 10 S using a rotational rheometer MCR302 manufactured by Anton-Paar and a cone plate CP50-0.5). -1 (The measurement was carried out under these conditions.) · Graphene having a two-dimensional structure: Manufactured by ADEKA Corporation, product name "CNS-1A1", two-dimensional crystal structure, average particle size 12 μm, thickness 50 nm or less, aspect ratio 240 or more, Raman peak intensity ratio D / G = 0.1, when measured by X-ray diffraction using a CuKα radiation source (wavelength 0.15418 nm), peaks were detected at positions of 2θ = 26.6° and 42.4°.

[0125] To the above preliminary mixture, 95 parts by mass of the same acrylate polymer as above (95 parts by mass in 100 parts by mass in total; solid content concentration), 103 parts by mass of ethyl methyl ketone as a low-boiling solvent, and 26 parts by mass of cyclohexanone as a high-boiling solvent were added, and dispersion treatment was performed by stirring at 3000 rpm for 30 minutes using a disper (manufactured by Primix Corporation, product name "Robomix") (second step) to obtain a coating liquid of a thermally conductive adhesive composition. The solid content concentration of this coating liquid of the thermally conductive adhesive composition was 25% by mass.

[0126] The coating liquid of the obtained thermally conductive adhesive composition was applied with an applicator to the release-treated surface of a release film (manufactured by Lintec Corporation, product name "SP-PET381031") obtained by subjecting one side of a polyethylene terephthalate film to a release treatment with a silicone-based release agent to form a coating layer. After that, it was heat-treated at 100 °C for 3 minutes to dry and form an adhesive layer. Then, the release-treated surface of a release film (manufactured by Lintec Corporation, product name "SP-PET381130") obtained by subjecting one side of a polyethylene terephthalate film to a release treatment with a silicone-based release agent was bonded to the adhesive layer to produce an adhesive sheet (release film / adhesive layer / release film) with an adhesive layer thickness of 30 μm.

[0127] [Examples 2 to 9, Comparative Examples 1 to 3] An adhesive sheet was produced in the same manner as in Example 1, except that the type of acrylate polymer, the mixing amount of the filler, the type and mixing amount of the solvent, and the heat drying temperature were changed as shown in Tables 1 and 2.

[0128] Here, the acrylate polymer used in Example 9 is as follows. · Acrylate polymer: A copolymer obtained by copolymerizing 85 parts by mass of methyl acrylate (MA) and 15 parts by mass of 2-hydroxyethyl acrylate (HEA), weight average molecular weight: 350,000, glass transition temperature (Tg): -61 °C, viscosity of a solution diluted to a concentration of 40% by mass with methyl ethyl ketone: 9.5 Pa·s (measurement method: Measured as the value at 23 °C and a shear rate of 10 S -1 using a rotational rheometer MCR302 manufactured by Anton-Paar and a cone plate CP50-0.5).)

[0129] In the table, low-boiling solvent A and low-boiling solvent B, high-boiling solvent A and high-boiling solvent B mean the classification when a plurality of types of solvents are used. Also, since the types of the pressure-sensitive adhesive resin, low-boiling solvent A, low-boiling solvent B, high-boiling solvent A, and high-boiling solvent B used in the second step are the same as those used in the first step, the notations in the table are omitted.

[0130] The boiling points of the solvents used in each example are as follows. 〔Low-boiling solvent〕 · Methyl ethyl ketone (MEK) (boiling point: 79.6 °C) · Acetone (boiling point: 56.5 °C) · Ethyl acetate (boiling point: 77.1 °C) 〔High-boiling solvent〕 · Cyclohexanone (boiling point: 155.7 °C) · Propyl acetate (boiling point: 101.6 °C) · Toluene (boiling point: 110.6 °C)

[0131] The weight-average molecular weight (Mw) described above is the weight-average molecular weight in terms of polystyrene measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC). <Measurement conditions> · GPC measurement device: HLC-8020 manufactured by Tosoh Corporation · GPC column (passing in the following order): manufactured by Tosoh Corporation TSK guard column HXL-H TSK gel GMHXL (×2) TSK gel G2000HXL · Measurement solvent: Tetrahydrofuran · Measurement temperature: 40 °C

[0132] 〔Test Example 1〕 <Measurement of thermal conductivity> Samples in the form of 5 mm-sided squares were obtained from the adhesive layers of the pressure-sensitive adhesive sheets prepared in the examples and comparative examples. Using a thermal diffusivity / thermal conductivity measurement device (manufactured by AI Phase, product name "ai-phase mobile"), the thermal conductivity (W / m·K) of the above samples (adhesive layer) was measured in an environment of 23 °C and 50% RH in accordance with ISO 22007-3. The results are shown in Table 2.

[0133] Also, based on the following formula, the X value was calculated. The results are shown in Table 2. X = A (mass %) / T (min) A: Ratio (mass %) of the high-boiling solvent to the total amount of the low-boiling solvent and the high-boiling solvent in the coating liquid (coating layer) T: Heating and drying time (minutes)

[0134]

Table 1

[0135]

Table 2

[0136] As can be seen from Table 2, the pressure-sensitive adhesive sheet produced in the examples had excellent thermal conductivity. This indicates that the orientation of the filler in the pressure-sensitive adhesive layer could be controlled by the method of the examples.

Industrial Applicability

[0137] According to the manufacturing method of the present invention, for example, a pressure-sensitive adhesive layer and a pressure-sensitive adhesive sheet having excellent thermal conductivity can be manufactured.

Explanation of Reference Numerals

[0138] 1... Pressure-sensitive adhesive sheet 11... Pressure-sensitive adhesive layer 12a, 12b... Release sheet 3... Heat dissipation device 11... Pressure-sensitive adhesive layer 31... Heat generating member 32... Heat transfer member

Claims

1. A method for manufacturing a functional layer containing a filler with an aspect ratio of 2 or more and a resin, comprising: forming a coating layer containing the filler, the resin, a low-boiling solvent having a boiling point of less than 90°C, and a high-boiling solvent having a boiling point of 90°C or more; heating and drying the coating layer to form a functional layer The method for manufacturing a functional layer is characterized by the above.

2. The method for manufacturing a functional layer according to claim 1, wherein the viscosity of a solution obtained by diluting the resin with methyl ethyl ketone to a concentration of 40% by mass is 0.5 Pa·s or more and 80 Pa·s or less.

3. The method for manufacturing a functional layer according to claim 1, wherein the glass transition temperature (Tg) of the resin is -70°C or more and 50°C or less.

4. The method for manufacturing a functional layer according to claim 1, wherein the resin is a pressure-sensitive adhesive resin.

5. The method for manufacturing a functional layer according to any one of claims 1 to 4, wherein the filler is a heat-conductive material.

6. The method for manufacturing a functional layer according to claim 1, wherein the filler is graphene having a two-dimensional structure.

7. The method for manufacturing a functional layer according to claim 1, wherein the ratio of the low-boiling solvent to the total amount of the low-boiling solvent and the high-boiling solvent is 10% by mass or more and 95% by mass or less.

8. The method for manufacturing a functional layer according to claim 1, wherein the amount of the filler relative to 100 parts by mass of the resin is 5 parts by mass or more and 100 parts by mass or less.

9. The method for manufacturing a functional layer according to claim 1, wherein the total amount of the low-boiling solvent and the high-boiling solvent relative to 100 parts by mass of the total amount of the filler and the resin in the coating layer is 100 parts by mass or more and 900 parts by mass or less.

10. The method for manufacturing a functional layer according to claim 1, wherein the temperature of the heat drying is 75°C or more and 150°C or less.

11. The method for manufacturing a functional layer according to claim 1, wherein the time of the heat drying is 5 seconds or more and 30 minutes or less.

12. A step of preparing a coating liquid containing the filler, the resin, the low-boiling solvent, and the high-boiling solvent is provided, and the step of preparing the coating liquid is A first step of subjecting a mixture containing a part of the total amount of the resin to be combined, the filler, and at least one of the low-boiling solvent and the high-boiling solvent to a dispersion treatment to obtain a preliminary mixture; A second step of adding at least the remaining portion of the resin to the preliminary mixture and subjecting it to a dispersion treatment The method for producing a functional layer according to claim 1, characterized by including the above.

13. In the first step, the low-boiling solvent and the high-boiling solvent are combined with the mixture, In the second step, the low-boiling solvent and the high-boiling solvent are added to the preliminary mixture The method for producing a functional layer according to claim 12, characterized by the above.

14. The method for producing a functional layer according to claim 12, characterized in that the mixing amount of the resin in the first step is 0.5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the filler.

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