Thermal radiation film, method for producing the thermal radiation film, and electronic device

Abstract

To provide a heat radiation film that has excellent versatility and is suitable as a heat radiation material and a method for producing the same, and an electronic apparatus including the heat radiation film.SOLUTION: A heat radiation film has a first resin layer, a second resin layer, a metal particle arrangement layer and a third resin layer in this order.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a thermal radiation film, a method for manufacturing the thermal radiation film, and an electronic device. [Background technology]

[0002] In recent years, the amount of heat generated per unit area has tended to increase with the miniaturization and multi-functionalization of electronic devices. As a result, heat spots occur in electronic devices where heat is concentrated locally, causing problems such as failure of the electronic devices, shortened life span, reduced operational stability, and reduced reliability. For this reason, it is becoming increasingly important to dissipate heat generated by heating elements to the outside and mitigate the occurrence of heat spots.

[0003] As a heat dissipation measure for electronic devices, a heat sink such as a metal plate is attached near the heat generating element of the electronic device, and the heat generated by the heat generating element is conducted to the heat sink and dissipated to the outside. However, as electronic devices become smaller, it is sometimes difficult to attach a heat sink to the electronic device. Therefore, a method of applying a heat dissipating paint to the surface of an electronic device has been considered as a heat dissipation means that can be adapted to the miniaturization of electronic devices.

[0004] For example, Patent Document 1 describes a heat-dissipating powder coating composition containing an infrared-absorbing binder resin and infrared-absorbing inorganic particles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-169372 A Summary of the Invention [Problem to be solved by the invention]

[0006] When a coating film is formed on the surface of a heating element using a paint having heat dissipation properties, the desired heat dissipation properties may not be obtained if there is a bias in the distribution of particles contained in the coating film, if the coating film has an uneven thickness, etc. This problem is particularly noticeable when the coating film is formed by a method other than industrial methods, and there are limitations to the range of application as a product. In view of the above circumstances, the present disclosure has an object to provide a heat emitting film useful as a heat dissipation material with excellent versatility, and a method for producing the same. Another object of the present disclosure is to provide an electronic device using the heat emitting film. [Means for solving the problem]

[0007] Means for solving the above problems include the following embodiments. <1> A thermal radiation film comprising a first resin layer, a second resin layer, a metal particle arranged layer, and a third resin layer in this order. <2> The first resin layer is peelable from the second resin layer. <1> 2. The thermal radiation film according to claim 1 . <3> The second resin layer has adhesiveness. <1> or <2> 2. The thermal radiation film according to claim 1 . <4> The third resin layer contains a crosslinked product of a photocrosslinkable acrylic resin, <1> ~ <3> 13. The thermal radiation film according to any one of claims 1 to 12. <5> The thickness of the third resin layer is 50 μm or more. <1> ~ <4> 13. The thermal radiation film according to any one of claims 1 to 12. <6> the metal particles contained in the metal particle arranged layer include at least one type selected from the group consisting of copper and aluminum; <1> ~ <5> 13. The thermal radiation film according to any one of claims 1 to 12. <7> The volume average particle size of the metal particles contained in the metal particle arranged layer is 1.0 μm to 6.0 μm. <1> ~ <6> 13. The thermal radiation film according to any one of claims 1 to 12. <8> the average aspect ratio of the metal particles contained in the metal particle arranged layer is 1 to 1.2; <1> ~ <7> 13. The thermal radiation film according to any one of claims 1 to 12. <9> the peak of the wavelength spectrum of the electromagnetic wave radiated from the metal particle arranged layer is in the range of 1 μm to 6 μm; <1> ~ <8> 13. The thermal radiation film according to any one of claims 1 to 12. <10> <1> ~ <9> A method for producing the thermal radiation film according to any one of claims 1 to 4, disposing metal particles on the second resin layer; and placing a third resin layer on the metal particles, in that order. <11> Without the first resin layer <1> ~ <9> 2. An electronic device comprising the thermal radiation film according to claim 1. Effect of the Invention

[0008] According to the present disclosure, there is provided a heat emitting film useful as a heat dissipation material with excellent versatility, a method for producing the same, and an electronic device using the heat emitting film. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic cross-sectional view showing an example of the structure of a thermal radiation film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments for carrying out the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to the numerical values ​​and their ranges, and do not limit the present disclosure.

[0011] In the present disclosure, the term "step" includes not only a step that is independent of other steps, but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved. In the present disclosure, a numerical range indicated using "~" includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in the present disclosure in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple types of the corresponding substance. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, the particles corresponding to each component may include multiple types. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified. In this disclosure, the term "layer" includes cases where the layer is formed over the entire area when the area in which the layer exists is observed, as well as cases where the layer is formed over only a portion of the area. When an embodiment of the present disclosure is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. In addition, the size of the members in each drawing is conceptual, and the relative relationship between the sizes of the members is not limited to this.

[0012] <Heat radiation film> The thermal radiation film of the present disclosure is a thermal radiation film having a first resin layer, a second resin layer, a metal particle arranged layer, and a third resin layer in this order.

[0013] The thermal radiation film of the present disclosure can efficiently dissipate heat generated by a heat generating element. Since the thermal radiation film of the present disclosure is used by being attached to the heating element or housing of an electronic device, there is no risk of bias in particle distribution, uneven thickness, etc., as occurs in methods in which a coating film is formed on the surface of a heating element using thermal radiation paint, and therefore the film is highly adaptable to a variety of usage patterns, including heat dissipation measures for electronic devices used by general consumers.

[0014] The reason why the thermal radiation film of the present disclosure exhibits a heat dissipation effect is not necessarily clear, but is thought to be as follows.

[0015] The metal particle arranged layer included in the thermal radiation film has a fine and periodic uneven structure caused by metal particles. Therefore, when heat from a heating element is transmitted to the metal particle arranged layer, surface plasmon resonance occurs, which is thought to change the wavelength range of the radiated electromagnetic waves. As a result, for example, the emissivity of electromagnetic waves in a wavelength range that is difficult for resin to absorb increases relatively, suppressing heat storage by the resin and improving heat dissipation. The "resin" referred to here can include both the resin contained in the heat emitting film and the resin placed around the heat generating element (such as a resin case).

[0016] An example of the structure of a thermal radiation film is shown in FIG. The heat emitting film 10 shown in FIG. 1 includes a first resin layer 1, a second resin layer 2, a metal particle arranged layer 4, and a resin layer 3. In the thermal radiation film 10 shown in FIG. 1, the second resin layer 2 is made up of a pressure-sensitive adhesive layer 2a, a base layer 2b, and a pressure-sensitive adhesive layer 2c, but the present disclosure is not limited to this configuration. In the heat radiation film 10 shown in FIG. 1, part of the third resin layer 3 is embedded between the metal particles contained in the metal particle arranged layer 4, but the present disclosure is not limited to this configuration.

[0017] The type of resin contained in the first resin layer, the second resin layer, and the third resin layer constituting the thermal radiation film is not particularly limited, and can be selected from known thermoplastic resins, photocrosslinkable resins, thermosetting resins, etc. Specific examples include acrylic resins, polyester resins, polyimide resins, polyamide resins, polyolefin resins, phenolic resins, alkyd resins, aminoalkyd resins, urea resins, silicone resins, melamine resins, epoxy resins, polyurethane resins, unsaturated polyester resins, vinyl acetate resins, chlorinated rubber resins, vinyl chloride resins, fluororesins, thermoplastic elastomers, etc. If necessary, a pressure-sensitive adhesive may be used as the resin. The thermal radiation film may contain only one type of resin, or two or more types of resin.

[0018] (1st resin layer) The first resin layer is removed when the thermal radiation film is attached to an electronic device. From the viewpoint of ease of removal of the first resin layer, it is preferable that the first resin layer is peelable from the second resin layer. In order to facilitate peeling of the first resin layer from the second resin layer, a release agent may be applied to the surface of the first resin layer that contacts the second resin layer.

[0019] The thickness of the first resin layer is not particularly limited and may be selected from the range of 0.1 μm to 5 μm, for example.

[0020] (2nd resin layer) The second resin layer preferably has adhesiveness. The second resin layer may have adhesiveness on the surface facing the metal particle array layer, on the surface facing the first resin layer, or on both surfaces. If the surface of the second resin layer facing the metal particle arranged layer has adhesiveness, it becomes easier to uniformly attach the metal particles to the surface of the second resin layer in the process of producing the heat radiation film. If the surface of the second resin layer facing the first resin layer has adhesiveness, the adhesiveness of the second resin layer can be used to attach the heat radiation film to an electronic device after the first resin layer has been removed.

[0021] A method of imparting adhesion to the second resin layer includes a method of incorporating an adhesive into the second resin layer. The type of adhesive is not particularly limited, and can be selected in consideration of adhesion, releasability, heat resistance, etc. Specific examples include acrylic adhesives, silicone adhesives, and urethane adhesives. From the viewpoint of adhesion, acrylic adhesives are preferred.

[0022] The second resin layer may consist of only one layer or two or more layers. When the second resin layer is made up of two or more layers, the layer may have a structure including a base layer and a pressure-sensitive adhesive layer located on one or both sides of the base layer. The second resin layer has a base material layer, which can impart sufficient strength to the thermal radiation film. From the viewpoint of availability and balance of properties, the resin contained in the base material layer is preferably a polyester resin such as polyethylene terephthalate (PET).

[0023] The thickness of the second resin layer is not particularly limited and may be selected from the range of 1 μm to 10 μm, for example.

[0024] (3rd resin layer) The third resin layer is preferably a crosslinked product of a photocrosslinkable acrylic resin. When the third resin layer is a crosslinked product of a photocrosslinkable acrylic resin, in the manufacturing process of the heat emitting film, the surface of the third resin layer before crosslinking can be adhered to the metal particle arranged layer, and then the third resin layer can be crosslinked by irradiating it with light such as ultraviolet light. This makes it possible to obtain a third resin layer that has excellent adhesion to the metal particle arranged layer and sufficient heat resistance. From the viewpoint of making the film thickness of the third resin layer uniform, the third resin layer is preferably a crosslinked product of a photocrosslinkable acrylic resin film.

[0025] In one embodiment, the third resin layer is located on the side of the heat emitting film opposite the side facing the electronic device.

[0026] The thickness of the third resin layer is not particularly limited and may be selected from the range of 20 μm to 500 μm, for example. As shown in the examples described later, the inventors have found that the thicker the third resin layer is, the greater the heat dissipation effect of the heat radiation film is. Therefore, the thickness of the third resin layer is preferably 50 μm or more, more preferably 75 μm or more, and even more preferably 100 μm or more. From the viewpoint of ensuring the flexibility of the heat radiation film, the thickness of the third resin layer is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 200 μm or less. From the viewpoint of obtaining a sufficient heat dissipation effect while ensuring the flexibility of the heat radiation film, it is preferable to make the third resin layer relatively thick and the second resin layer relatively thin. For example, the thickness of the third resin layer is preferably 5 times or more, more preferably 10 times or more, and even more preferably 20 times or more, the thickness of the second resin layer. When a part of the third resin layer penetrates between the metal particles contained in the metal particle arranged layer, the thickness of the third resin layer includes the thickness of the metal particle arranged layer.

[0027] (Metal particle arrangement layer) As described above, the metal particle arranged layer included in the heat emitting film has the function of changing the wavelength spectrum of the electromagnetic waves radiated by the heat emitting film from the wavelength spectrum of the electromagnetic waves incident on the heat emitting film. Resins generally tend to be poor at absorbing (easy to transmit) electromagnetic waves in the infrared range with relatively short wavelengths (e.g., 2 μm to 10 μm). Therefore, in one embodiment, the metal particle arranged layer included in the heat emitting film has the function of changing the wavelength range of the electromagnetic waves radiated by the heat emitting film so as to increase the emissivity of electromagnetic waves in the infrared range. The peak of the wavelength spectrum of the electromagnetic wave radiated from the metal particle layer is preferably in the range of 1 μm to 6 μm.

[0028] Whether or not the metal particle arranged layer contained in the thermal emitting film has the function of changing the wavelength spectrum of electromagnetic waves can be determined by whether or not the absorption wavelength spectrum measured with a Fourier transform infrared spectrophotometer changes. Specifically, this can be confirmed by comparing the absorption wavelength spectrum of the thermal emitting film of the present disclosure with the absorption wavelength spectrum of a sample prepared under the same conditions as the thermal emitting film of the present disclosure except that it does not contain a metal particle arranged layer.

[0029] The state of the metal particle array layer is not particularly limited as long as it is in a state where surface plasmon resonance can be generated. For example, a clear boundary may or may not be formed between the metal particle array layer and the adjacent resin layer. For example, the metal particle array layer may be in a state where a part of the adjacent resin layer is inserted between the metal particles. The metal particles in the metal particle arranged layer may or may not be in contact with adjacent metal particles, and may or may not overlap with each other in the thickness direction of the thermal radiation film.

[0030] The thickness of the metal particle arranged layer (if the thickness is not constant, the thickness of the portion with the maximum thickness) is not particularly limited. For example, it may be within the range of 1 μm to 10 μm. The thickness of the metal particle arranged layer can be adjusted by, for example, the amount of metal particles contained in the metal particle arranged layer, the size of the metal particles, etc.

[0031] The density of the metal particles in the metal particle arranged layer is not particularly limited as long as it is in a state where surface plasmon resonance can be generated. For example, when the metal particle arranged layer is observed from the front, the proportion of the metal particles occupying the observed surface is preferably 50% or more, more preferably 75% or more, and even more preferably 90% on an area basis. In this disclosure, "observation surface when observed from the front of the metal particle arranged layer" means a surface observed from a direction perpendicular to the arrangement direction of the metal particles (the surface direction of the heat emitting film) (the thickness direction of the heat emitting film). The above ratio can be calculated, for example, from an electron microscope image using image processing software.

[0032] In the present disclosure, the term "metal particles" refers to particles having at least a part of a surface made of metal, and the inside of the particles may or may not be made of metal. From the viewpoint of improving heat dissipation by thermal conduction, the inside of the particles is preferably made of metal. When at least a portion of the surface of a metal particle is made of metal, substances other than metals, such as resins and metal oxides, may be present around the metal particle, so long as external electromagnetic waves can reach the surface of the metal particle.

[0033] Specific examples of metals contained in the metal particles include copper, aluminum, nickel, iron, silver, gold, tin, titanium, chromium, and palladium. The metal particles may contain only one type of metal or two or more types of metals. The metal particles may contain a single metal or an alloy. From the viewpoint of thermal conductivity, the metal particles preferably contain at least one of copper and aluminum.

[0034] The volume average particle diameter of the metal particles is preferably within the range of 1.0 μm to 6.0 μm. When the volume average particle diameter of the metal particles is 6.0 μm or less, electromagnetic waves (especially infrared light with a relatively short wavelength) that contribute to improving heat dissipation tend to be sufficiently emitted. When the volume average particle diameter of the metal particles is 1.0 μm or more, the cohesive force of the metal particles is suppressed, making it easier to arrange the metal particles evenly.

[0035] The volume average particle diameter of the metal particles may be set in consideration of the type of material other than the metal particles used in the thermal radiation film. For example, the smaller the volume average particle diameter of the metal particles, the smaller the period of the uneven structure formed on the surface of the metal particle array layer, and the shorter the wavelength at which the surface plasmon resonance generated in the metal particle array layer is maximized. The absorption rate of electromagnetic waves by the metal particle array layer is maximized at the wavelength at which the surface plasmon resonance is maximized. Therefore, when the wavelength at which the surface plasmon resonance generated in the metal particle array layer is maximized becomes shorter, the wavelength at which the absorption rate of electromagnetic waves by the metal particle array layer is maximized becomes shorter, and according to Kirchhoff's law, the emissivity of electromagnetic waves at that wavelength tends to increase. Therefore, by appropriately selecting the volume average particle diameter of the metal particles, the radiation wavelength of the metal particle array layer can be converted to a wavelength range that is difficult to absorb by the resin contained in the thermal radiation film, and the heat dissipation tends to be further improved.

[0036] In the present disclosure, the volume average particle size of metal particles is the particle size (D50) at which the cumulative total from the small diameter side reaches 50% in a volume-based particle size distribution curve obtained by a laser diffraction / scattering method.

[0037] From the viewpoint of effectively controlling the absorption or emission wavelength of electromagnetic waves by the metal particle arranged layer, it is preferable that the variation in particle size of the metal particles contained in the metal particle arranged layer is small. By suppressing the variation in particle size of the metal particles, it becomes easier to form a periodic uneven structure on the surface of the metal particle arranged layer, and surface plasmon resonance tends to occur more easily.

[0038] The particle size variation of the metal particles is, for example, such that, when the particle size (D10) when the accumulation from the small diameter side in a volume-based particle size distribution curve is 10% is A (μm) and the particle size (D90) when the accumulation from the small diameter side is 90% is B (μm), the value of A / B is preferably about 0.3 or more, more preferably about 0.4 or more, and even more preferably about 0.6 or more.

[0039] Specific examples of the shape of the metal particles include spheres, flakes, needles, rectangular parallelepipeds, cubes, tetrahedrons, hexahedrons, polyhedrons, cylinders, hollow bodies, and three-dimensional needle-like structures extending from a core in four different axial directions. Among these, spheres or shapes close to spheres are preferred.

[0040] The metal particles preferably have an average aspect ratio of 1 to 1.2. When the average aspect ratio of the metal particles is 1.2 or less, the uniformity of the arrangement of the metal particles improves, and the desired surface plasmon resonance tends to occur more easily. The average aspect ratio of metal particles is the arithmetic mean value of the aspect ratios measured for 30 metal particles. The aspect ratio of metal particles is the value obtained by dividing the length of the long axis of a metal particle by the length of the short axis (long axis / short axis), and is a number equal to or greater than 1.

[0041] The thermal radiation film may include materials other than metal particles and resin, for example, ceramic particles, additives, and the like.

[0042] When the thermal radiation film contains ceramic particles, for example, the heat dissipation effect of the thermal radiation film can be further improved. Specific examples of ceramic particles include particles of boron nitride, aluminum nitride, aluminum oxide, magnesium oxide, titanium oxide, zirconia, iron oxide, copper oxide, nickel oxide, cobalt oxide, lithium oxide, and silicon dioxide. The ceramic particles contained in the thermal radiation film may be of one type or two or more types. In addition, the surface may be covered with a film composed of a resin, an oxide, or the like.

[0043] The size and shape of the ceramic particles are not particularly limited, and may be the same as those described above as preferred embodiments of the size and shape of the metal particles.

[0044] The thermal emitting film can be endowed with desired functions by including an additive in the thermal emitting film. Specific examples of the additive include a dispersant, a film-forming assistant, a plasticizer, a pigment, a silane coupling agent, and a viscosity modifier.

[0045] The shape of the thermal radiation film is not particularly limited and can be selected according to the application, etc. For example, the thermal radiation film may be cut to fit the shape of the area of ​​the electronic device to which the thermal radiation film is to be attached, or may not be cut. Alternatively, the thermal radiation film may be in the shape of a tape cut into a strip.

[0046] The total thickness of the heat emitting film is not particularly limited. For example, it may be 20 μm to 500 μm, 50 μm to 300 μm, or 100 μm to 200 μm. When the total thickness of the heat emitting film is 500 μm or less, the flexibility of the heat emitting film is sufficiently ensured. When the total thickness of the heat emitting film is 20 μm or more, the heat dissipation function of the heat emitting film is sufficiently obtained.

[0047] Although there are no particular limitations on the wavelength range of electromagnetic waves absorbed or radiated by the thermal radiation film, from the viewpoint of thermal radiation properties, the closer to 1.0 the absorptance or emissivity for each wavelength in the range of 3 μm to 30 μm at room temperature (25° C.) is, the more preferable. Specifically, the absorptance or emissivity is preferably 0.8 or more, and more preferably 0.9 or more.

[0048] The electromagnetic wave absorptance or emissivity can be measured by an emissivity measuring device (e.g., D and S AERD, manufactured by Kyoto Electronics Manufacturing Co., Ltd.), a Fourier transform infrared spectrophotometer, etc. According to Kirchhoff's law, the electromagnetic wave absorptance and emissivity can be considered to be equal. The wavelength range of electromagnetic waves absorbed or radiated by the thermal emitting film can be measured by a Fourier transform infrared spectrophotometer. Specifically, the transmittance and reflectance of the wavelength of electromagnetic waves absorbed or radiated by the thermal emitting film are measured, and the wavelength range can be calculated by the following formula. Absorptance (emissivity) = 1 - transmittance - reflectance

[0049] The use of the heat radiation film is not particularly limited. For example, it may be attached to a portion of an electronic device that corresponds to a heat generating body or a housing, and used to dissipate heat generated by the heat generating body. It may also be used to transfer heat generated by the heat generating body to a heat sink such as a metal plate or a heat sink.

[0050] <Method of manufacturing heat radiation film> The method for producing a thermal radiation film of the present disclosure is a method for producing a thermal radiation film as described above, which includes, in this order, a step of arranging metal particles on the second resin layer and a step of arranging a third resin layer on the metal particles.

[0051] In the above method, the method of performing the step of disposing metal particles on the second resin layer (metal particle disposing step) is not particularly limited. For example, the method of disposing metal particles or a composition containing metal particles using a brush, a sieve, a sprayer, an electrospray, a coater, an inkjet device, a screen printing device, etc. can be mentioned. When the metal particles form aggregates, it is preferable to perform a process of breaking down the aggregates before disposing.

[0052] In the above method, the orientation of the second resin layer when the metal particles are disposed thereon and the third resin layer when disposed on the metal particles are not particularly limited, and they may be disposed horizontally, obliquely, or vertically. In the above method, the orientation of the surface of the second resin layer on which the metal particles are disposed is not particularly limited, and may be upward when viewed in the direction of gravity, or in another direction (for example, downward).

[0053] From the viewpoint of suppressing uneven distribution of the metal particles arranged on one side of the second resin layer, it is preferable that the surface of the second resin layer on which the metal particles are arranged has adhesiveness. When the surface of the second resin layer on which the metal particles are arranged has adhesiveness, the movement of the metal particles when arranged on the second resin layer is appropriately controlled, and uneven distribution of the metal particles tends to be suppressed.

[0054] The method of disposing the third resin layer on the metal particles disposed on one side of the second resin layer is not particularly limited, and examples thereof include a method of disposing a sheet-like third resin layer on the metal particles, and a method of applying a liquid resin composition onto the metal particles. In order to enhance the adhesion between the third resin layer and the metal particles, the third resin layer may be disposed while applying pressure.

[0055] The above method may include a step of irradiating light such as ultraviolet light after the step of disposing a third resin layer on the metal particles. For example, a third resin layer containing a resin before crosslinking may be disposed on the metal particles, and then the resin contained in the third resin layer may be crosslinked by irradiating light.

[0056] <Electronic equipment> The electronic device of the present disclosure is an electronic device including the above-mentioned heat radiation film with the first resin layer removed. The heat radiation film is attached to the surface of, for example, a heat generating element included in the electronic device or a housing of the electronic device.

[0057] Examples of heat generating elements contained in electronic devices include electronic components such as integrated circuits and semiconductor elements, and heat pipes.

[0058] There are no particular limitations on the manner in which the heat radiation film is attached to the electronic device. For example, the heat radiation film may be attached directly or with an adhesive or the like.

[0059] If necessary, the electronic device may include a heat sink. In this case, it is preferable that a heat radiation film is interposed between the heat generating body and the heat sink of the electronic device. By interposing the heat radiation film between the heat generating body and the heat sink, excellent heat dissipation properties are achieved. Examples of the heat sink include a plate made of a metal such as aluminum, iron, or copper, and a heat sink.

[0060] The portion of the electronic device to which the thermal radiation film is attached may be flat or non-flat. If the portion of the electronic device to which the thermal radiation film is attached is not flat, it is preferable to use a thermal radiation film that is flexible enough to be deformed to fit the shape of the portion. EXAMPLES

[0061] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the contents described in the following examples.

[0062] <Example 1> (Making of heat radiation film) A double-sided tape (100 mm x 100 mm, thickness: 5 μm) having a structure in which a release separator, an adhesive layer containing an acrylic adhesive, a PET substrate, an adhesive layer containing an acrylic adhesive, and a release separator are laminated in this order was peeled off from one of the release separators, and copper particles (volume average particle diameter: 1.6 μm, average aspect ratio: 1.15) were attached to the adhesive layer exposed by peeling off the release separator from one side, to form a metal particle arrayed layer. Next, a photocrosslinkable acrylic resin film (thickness: 100 μm) formed on a PET substrate was laminated on the metal particle arrayed layer while heating to 90°C. The PET substrate was then peeled off, and the photocrosslinkable acrylic resin film was crosslinked by irradiating it with ultraviolet light. Through the above steps, a heat radiation film was obtained in which a release separator as a first resin layer, an adhesive layer 1 as a second resin layer, a laminate consisting of a PET substrate and an adhesive layer 2, a metal particle arrayed layer, and a crosslinked product of a photocrosslinkable acrylic resin film as a third resin layer were arranged in this order.

[0063] (Evaluation of heat dissipation) The heat radiation properties of the produced thermal radiation films were evaluated by the following method. A commercially available sheet heating element (polyimide heater) is sandwiched between a pair of aluminum plates (20 mm x 20 mm, 2 mm thick). A K-type thermocouple is attached to the surface of the aluminum plate with solder for aluminum. The release separator of the heat radiation film is then peeled off, and a heat radiation film is attached to the surface of one of the aluminum plates to create a sample. The sample is placed in the center of a thermostatic chamber set to 25°C, and the temperature change on the surface of the aluminum plate is measured. At this time, the heater output is set to 1.2 W. Since the heater generates a constant amount of heat, the higher the heat dissipation effect of the sample, the lower the temperature of the aluminum plate surface. In other words, the lower the surface temperature of the sample, the higher the heat dissipation effect. The measured surface temperatures (maximum temperatures) of the samples are shown in Table 1.

[0064] <Example 2> A heat radiation film was produced in the same manner as in Example 1, except that the thickness of the photocrosslinkable acrylic resin film was changed to 75 μm, and the heat dissipation property was evaluated. The results are shown in Table 1.

[0065] <Example 3> A heat radiation film was produced in the same manner as in Example 1, except that the thickness of the photocrosslinkable acrylic resin film was changed to 50 μm, and the heat dissipation property was evaluated. The results are shown in Table 1.

[0066] <Example 4> A heat radiation film was produced in the same manner as in Example 1, except that the thickness of the photocrosslinkable acrylic resin film was changed to 25 μm, and the heat dissipation property was evaluated. The results are shown in Table 1.

[0067] <Example 5> A heat radiation film was produced in the same manner as in Example 1, except that the copper particles were replaced with aluminum particles having a volume average particle size of 2.0 μm and an average aspect ratio of 1.05, and the heat dissipation properties were evaluated. The results are shown in Table 1.

[0068] <Example 6> A heat radiation film was produced in the same manner as in Example 4, except that the copper particles were replaced with aluminum particles having a volume average particle size of 2.0 μm and an average aspect ratio of 1.05, and the heat dissipation properties were evaluated. The results are shown in Table 1.

[0069] <Comparative Example 1> Without attaching a heat radiation film to the aluminum plate, the heat dissipation property was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0070] <Comparative Example 2> A thermal radiation film was produced in the same manner as in Example 1, except that no metal particle arranged layer was formed on adhesive layer 2, and the heat dissipation properties were evaluated. The results are shown in Table 1.

[0071] <Comparative Example 3> A heat radiation film was produced in the same manner as in Example 1, except that the photocrosslinkable acrylic resin film was not laminated on the metal particle arranged layer, and the heat dissipation property was evaluated. The results are shown in Table 1.

[0072] <Comparative Example 4> A heat radiation film was produced in the same manner as in Example 5, except that the photocrosslinkable acrylic resin film was not laminated on the metal particle arranged layer, and the heat dissipation property was evaluated. The results are shown in Table 1.

[0073] [Table 1]

[0074] As shown in Table 1, the samples prepared using the thermal radiation films of Examples 1 to 6, which have a third resin layer on top of a metal particle array layer, have superior heat dissipation properties compared to the sample of Comparative Example 1, which does not have a thermal radiation film attached, the sample of Comparative Example 2, in which the thermal radiation film does not have a metal particle array layer, and the samples of Comparative Examples 3 and 4, in which the thermal radiation film does not have a third resin layer.

Claims

1. a first resin layer, a second resin layer, a metal particle arranged layer, and a third resin layer in this order; The second resin layer has a base layer and a pressure-sensitive adhesive layer disposed on one or both sides of the base layer, A thermal radiation film, wherein the third resin layer has a thickness of 50 μm or more.

2. The thermal radiative film of claim 1 , wherein the first resin layer is peelable from the second resin layer.

3. The thermal radiation film according to claim 1 or 2, wherein the second resin layer has a base layer and pressure-sensitive adhesive layers disposed on both sides of the base layer.

4. The thermal radiation film according to any one of claims 1 to 3, wherein the third resin layer comprises a crosslinked product of a photocrosslinkable acrylic resin.

5. 5. The thermal radiation film according to claim 1, wherein the metal particles contained in the metal particle arranged layer include at least one type of metal particles selected from the group consisting of copper and aluminum.

6. 6. The thermal radiation film according to claim 1, wherein the volume average particle size of the metal particles contained in the metal particle arranged layer is 1.0 μm to 6.0 μm.

7. 7. The thermal radiation film according to claim 1, wherein the metal particles contained in the metal particle arranged layer have an average aspect ratio of 1 to 1.

2.

8. 8. The thermal radiation film according to claim 1, wherein the wavelength spectrum of the electromagnetic wave radiated from the metal particle arranged layer has a peak in the range of 1 μm to 6 μm.

9. A method for producing the thermal radiation film according to any one of claims 1 to 8, comprising the steps of: disposing metal particles on the second resin layer; and disposing a third resin layer on the metal particles, in that order.

10. 9. An electronic device comprising the thermal radiation film according to claim 1, in a state in which the first resin layer has been removed.

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