JP2009197185A - Transparent thermal conductive adhesive film and its application - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent thermal conductive adhesion film which has high transparency and high thermal conductivity, can increase the thermal conductivity easily at low cost, and has stable quality and durability. <P>SOLUTION: The transparent thermal conductive adhesive film is an adhesive film comprising a resin and transparent/white fine particles. One or more crests (peaks) of a frequency particle diameter distribution of the fine particles are observed in each of a range of 3-100 μm and a range of 0.004-0.5 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transparent heat conductive adhesive film which has high heat conductivity and is transparent and can be used for semiconductors, lighting applications and the like.

In recent years, research on applying light-emitting elements instead of fluorescent lamps and incandescent lamps such as white LEDs, organic ELs, and inorganic ELs to lighting has become active. Many of these light-emitting elements have a high refractive index, and light is reflected from the surface of the element, resulting in a problem of low luminous efficiency. Further, since the heat is not diffused and becomes high temperature, the voltage / current is limited, and it is difficult to increase the amount of light (see Non-Patent Document 1). Therefore, various attempts have been made to increase the thermal conductivity in addition to increasing the light extraction efficiency. For example, in JP-A-2005-202361, the thermal conductivity is improved by setting the thermal conductivity of the filler to 3 W / m · K or more. On the other hand, in the pamphlet of International Publication No. 05/044875, high thermal conductivity is achieved by adding a photopolymerization initiator and a thermal polymerization initiator to a thermally conductive inorganic filler. Furthermore, there are materials that satisfy transparency and thermal conductivity using carbon fiber as disclosed in Japanese Patent Application Laid-Open Nos. 2002-266170 and 2007-91884.
However, these methods do not always have sufficient transparency and thermal conductivity because the orientation of particles and fibers and the particle size distribution are not optimal.

JP-A-2005-202361 International Publication No. 05/044875 Pamphlet JP 2002-266170 A JP 2007-91884 A Mehmet Arik and Stanton Weaver: “Effects of chip end bonding defect on the junction tempratures of high brightness and high efficiency diodes” brightness light-emitting diodes) ", Optical Engineering, 44 (11), 2005, p. 111305 Shunchao Gu, Shouji Inukai, Mikio Konno: “Soap-Free Synthesis of Monodispens Micronized Polystyrene Particles in Aquamedia” -Sized polystyrenic particles in Aqueous Media), Journal of Chemical Engineering of Japan, 2003, Vol. 36, No. 10, p. 1231-1235 Yoshio Kobayashi, Shunchao Gu, Tomohiro Kondo, Eichi Mine, Daisuke Nagao, Daisuke Nagao Fabrication of Sub-micronized Titania Hollow Spheres ", Journal of Chemical Engineering of Japan, Vol.7, Journal of Chemical Engineering, Japan, Vol.7, Journal of Chemical Engineering of Japan, Vol.7, Journal of Chemical Engineering of Japan, Vol. . 912-914 Eichi Mine, Mitsuki Hirose, Daisuke Nagao, Yoshio Kobayashi, Mikio Conno (Mikio Konno) Rical Particles with a sol-gel method and there application to the colloidal photonic crystals (Synthesis of submicrometer-sized titania mineral particles with the thiol method and the thiol method. onic crystals), Journal of colloid and interface science (Journal of Colloid and Interface Science), 2005 years, 291 Vol., No. 1, p. 162-168

In view of the above, the surface of the adhesive film has high adhesiveness so that it can be easily sealed by suppressing reflection on the surface of the organic and inorganic high-refractive-index light-emitting elements, and further has thermal conductivity and high transmittance. It is desired to increase the light extraction efficiency and increase the amount of light by using an adhesive film with little reflection at the surface.
An object of the present invention is to provide a transparent heat conductive adhesive film that can easily increase the thermal conductivity at low cost, and has a stable quality and durability.

The inventor of the present invention provides a method for producing a transparent adhesive film having a high thermal conductivity, a method for selecting a material for an optical film having a refractive index distribution structure that increases the light extraction efficiency with a lower refractive index than that of the adhesive film, and a method for sealing the light emitting element. A stopping method was found and the present invention was completed.
The present invention relates to the following.
(1) An adhesive film containing a resin and transparent or white fine particles, and a peak of the frequency particle size distribution of the fine particles is 1 to 3 μm to 100 μm and 0.004 μm to 0.5 μm. A transparent heat conductive adhesive film characterized by having two or more.
(2) In an adhesive film containing a resin and thermally conductive fine particles or thermally conductive fibers dispersed in the resin, the thermally conductive fine particles or thermally conductive fibers are oriented in a direction substantially perpendicular or parallel to the surface of the adhesive film. Is a plate-like, rod-like or fibrous anisotropic white or transparent fine particle or fiber having high thermal conductivity in the orientation direction, and the adhesive film is a kneading of the resin and the fine particle or fiber. A transparent heat conductive adhesive film formed by laminating a plurality of sheets formed from a product, and then slicing the obtained laminate in a direction perpendicular or parallel to the lamination surface.
(3) Using transparent fibers or anisotropic transparent fine particles, a layer that is highly filled with transparent fibers or transparent fine particles, and a layer that is not filled or low-filled with transparent fibers or transparent fine particles are alternately laminated, The transparent heat conductive adhesive film as described above, wherein the transparent heat conductive adhesive film is sliced perpendicularly to the laminated direction.
(4) Transparent fibers or transparent fine particles are used, and transparent fibers or transparent fine particles are alternately laminated by laminating a layer that is highly filled with transparent fibers or transparent fine particles, and a layer that is not filled or low filled with transparent fibers or transparent fine particles. The transparent heat conductive adhesive film as described above, wherein the layer filled with a material is exposed and bonded to the light emitting surface side.
(5) The transparent heat conductive adhesive film as described above, wherein the heat conductive fiber is a fiber coated with a material having high heat conductivity.
(6) The transparent heat conductive adhesive film as described above, wherein transparent or white fine particles or fibers are adhered or buried on the resin surface.
(7) The transparent heat conductive adhesive film described above, wherein the transparent or white fine particles or fibers have a refractive index in the visible light region of 1.8 or more.
(8) In the layer of the adhesive film, 2/3 or more of the fine particles or fibers are biased to one of the center lines in the layer.
(9) An optical semiconductor device having an optical semiconductor element sealed with the transparent heat conductive adhesive film.
(10) A solar cell panel sealed with the transparent heat conductive adhesive film.
(11) A display in which a color filter is sealed with the transparent heat conductive adhesive film.

  According to the present invention, it is possible to efficiently produce a heat conductive adhesive film having high heat conductivity, locally having a high refractive index, and being transparent. As a result, it is possible to increase the light quantity of the light emitting element and improve the light extraction efficiency.

  The first essential point of the present invention is to use particles having two or more peaks in the particle size distribution. Furthermore, it is preferable to use the following methods 1) to 3) together. 1) The refractive index of particles having a particle size of not more than a wavelength is made larger than the refractive index of particles having a particle size of not less than a wavelength. 2) Limit particles having a diameter equal to or greater than the wavelength to the vicinity of the light emitting surface. 3) The particle size distribution should not overlap with the region where the particle size is 0.5 μm or more and 3 μm or less. By using any one or a plurality of methods 1) to 3), the thermal conductivity and the light extraction efficiency can be effectively increased.

  When the light scatterer can be approximated as a sphere, the Mie scattering formula holds, and when the particle size is equal to or smaller than the wavelength, the scattering intensity increases in proportion to the size of the particle. It is known that the scattering intensity does not increase so much when the wavelength length exceeds the particle size. On the other hand, it is known that the filling rate of the particles into the resin can be increased by combining large particles and small particles. By increasing the filling rate, the thermal conductivity of the resin containing particles can be increased. Therefore, by selecting a particle size distribution that is highly filled while keeping the particle size below the wavelength, both transparency and high heat conduction can be achieved.

  The second essential point of the present invention is to achieve both improvement in thermal conductivity and improvement in light extraction efficiency by orienting particles or fibers having anisotropy and high thermal conductivity. Compared with the case where there is no orientation, the thermal conductivity can be remarkably improved.

  When the particles or fibers are dispersed in the resin, the same filling amount can increase the thermal conductivity in the direction in which the particles or fibers are oriented. If the oriented direction is parallel to the adhesive film, heat can be quickly diffused in the horizontal direction. If the oriented direction is perpendicular to the adhesive film as shown in FIG. 1, heat can be quickly transferred to the heat reservoir in the vertical direction. Also, the orientation does not deteriorate the transmittance.

In order to achieve the above object, the transparent heat conductive adhesive film of the present invention is configured as follows, for example.
Resin (thermosetting resin) and transparent or white fine particles, and the peak of the frequency particle size distribution of the fine particles is one or more in each of 3 μm to 100 μm and 0.004 μm to 0.5 μm is there. Further, in a part of the fine particles, the thermal conductivity is 2.5 W / m · K or more, the glass transition temperature of the thermosetting resin containing the fine particles is 60 ° C. or less, and further, the thermosetting resin can be cured at 60 ° C. or more. Is preferred.
Alternatively, in an adhesive film including a resin and thermally conductive fine particles or thermally conductive fibers dispersed in the resin, the thermally conductive fine particles or thermally conductive fibers are oriented in a direction substantially perpendicular or parallel to the surface of the adhesive film. An anisotropic white or transparent particle or fiber such as a plate, rod or fiber having high thermal conductivity in the orientation direction, and the adhesive film is a kneading of the resin and the particle or fiber After laminating a plurality of sheets formed from a product, the obtained laminate is formed by slicing in a direction perpendicular or parallel to the lamination surface.

[First Embodiment]
The transparent heat conductive adhesive film of the present invention is composed of an adhesive film containing fine particles as shown in FIG. 2, and includes (1) transparent or white fine particles, and (2) a peak (peak) of the frequency particle size distribution of the fine particles. There is one or more in each of 3 μm to 100 μm and 0.004 μm to 0.5 μm. An adhesive film is a film having adhesiveness or tackiness. It is desirable that the glass transition temperature of the adhesive film is 60 ° C. or lower and that thermocompression bonding is possible at 60 ° C. or higher. The refractive index of the resin of the adhesive film is preferably 1.42 or more.

  Examples of the transparent or white fine particles include silica, titanium oxide, zinc oxide, zirconia, ceria, aluminum nitride, aluminum oxide, silicon nitride, silicon carbide, and diamond. Among these, the thermal conductivity of the particles is preferably 2.5 W / m · K or more, more preferably 4 W / m · K or more. Examples of the particles having a thermal conductivity of 2.5 W / m · K or more include zinc oxide, ceria, titania, zirconia, aluminum nitride, silicon carbide, and diamond. Aluminum nitride and titania are preferably coated with aluminum oxide or silica. The particles may be amorphous and indeterminate, or smaller particles may be collected and optically regarded as one particle.

The white color range of the fine particles is as follows ^: when a white halogen lamp with chromaticity (u0 ′, v0 ′) is used in the u′v ′ chromaticity diagram of the CIE1976L ^* u ^* v ^* uniform color space, The distance between the chromaticity of the reflected light and the chromaticity of the halogen lamp is preferably 0.1 or less, and more preferably 0.05 or less. As the transparent range of the fine particles, it is sufficient that the fine particles are mixed and the adhesive film satisfies the total light transmittance described later. As a method for measuring chromaticity, there is a method of using a luminance meter made by TOPCON. The light emitted from the halogen lamp is guided by a flexible light guide, guided to the adhesive film surface by two lenses, and the transmitted light emitted from the adhesive film is measured with a luminance meter on an extension line in the traveling direction of incident light.

  Regarding the thermal conductivity of the transparent thermal conductive adhesive film, the thermal diffusivity in the direction perpendicular to the adhesive film surface is measured by a laser flash method (TC-7000, manufactured by Vacuum Riko), and this thermal diffusivity and differential scanning calorimetry are measured. The thermal conductivity was calculated from the product of the specific heat capacity obtained by the apparatus (Pyris 1 manufactured by Perkin Elmer) and the specific gravity obtained by the Archimedes method. The thermal conductivity is preferably 1 W / m · K or more, more preferably 3 W / m · K or more. The higher the thermal conductivity, the faster the temperature of the sealed element can be lowered.

  The total light transmittance is preferably 60% or more when the thickness of the adhesive film is 20 μm in order to increase the light utilization efficiency. More preferably, it is 80% or more. The total light transmittance is calculated by a numerical value including Fresnel loss. When the surface is smooth and the film itself does not absorb, if the refractive index of the film is 1.5, the total light transmittance is 92%. If the film has absorption or backscattering, it will be less than 92%. The incident angle of the total light transmittance measurement is θi in FIG.

  The adhesive film may be integrated with the prism sheet. In that case, a laser is used as a method for measuring the total light transmittance of the film. Using a He-Ne laser 632.8 nm light, measurement is performed with a power meter. In order to cancel the polarization dependence, measurement is performed under two conditions where the polarization of incident light is different by 90 °, and the average is used as a measurement value. Further, if necessary, the measurement is similarly performed with 442 nm light from a He—Cd laser or 514.5 nm light from an Ar laser. In the case where the prism sheet and the adhesive film are an integral sealing film, light is incident perpendicularly to the surface from the surface of the adhesive film opposite to the optical film. When the emitted light is diffused light without a clear diffraction pattern, an integrating sphere may be used for measuring the light amount.

  The adhesive film can be attached to a light emitting element as shown in FIG. In the case of a white LED, the pasting surface is on a layer containing a phosphor that converts light into white or on a blue light emitting surface. In the case of organic EL, for example, it is on sealing glass. As a method of kneading the fine particles in the adhesive film, a twin screw extruder or a calender roll can be used. When a die is used to press the adhesive film on the light emitting surface, it is preferable to use a perforated material in order to release air and residual solvent.

  If the glass transition temperature of the adhesive film is not 60 ° C. or lower, the flexibility of the film may be lowered, and wrinkles are likely to occur because there is no step following property to the surface of the light emitting element during thermosetting. The glass transition temperature is more preferably 40 ° C. or lower. The glass transition temperature is more preferably 20 ° C. or lower. The lower the glass transition temperature, the wider the range of the thermosetting temperature can be taken, and the damage to the light emitting element due to heat can be reduced.

  A frequency particle size distribution of 0.5 μm or more and 100 μm or less is observed at room temperature (25 ° C.) by SEM (scanning electron microscope) method. A large particle diameter can be a fibrous particle. In that case, a long diameter in a bent state is used. A distribution having a frequency particle size distribution of 0.004 μm or more and less than 0.5 μm is measured by SEM or TEM. The major axis in the SEM photograph is used as the particle size of the SEM. As the SEM, Philips XL30 manufactured by Philips can be used. When observing with SEM, after casting with an epoxy resin, it is cut out with a diamond cutter, polished with sandpaper having a roughness of 800, and buffed with 0.3 μm and 0.05 μm alumina particles in the order of pure water. Observe after ultrasonic cleaning in air and drying in air. The particle size distribution is obtained when the number of sample particles is 200 or more. Polishing is performed by holding the sample with a hand and rotating a polisher with a polishing cloth.

  Particles on the sheet surface on the light emitting surface side of the adhesive film may be polished by sandpaper or abrasive grains and a buffing pad before sealing. The particles may be surface-treated with a silane coupling agent before or after sealing, regardless of the presence or absence of polishing. When the surface is observed with SEM, it is preferable that 50% or more of the area is covered with particles, more preferably 70% or more, and still more preferably 80% or more. When the particles are present on the surface, the thermal conductivity and the light extraction efficiency are increased.

  The filling rate of all particles is preferably 40% or more and 80% or less, more preferably 50% or more and 80% or less, and still more preferably 70% or more and 80% or less. The larger the particle filling rate, the better the thermal conductivity, but it is difficult to achieve a high filling exceeding 80%.

  The volume ratio of the particle size distribution of the fine particles of 3 μm to 100 μm and 0.004 μm to 0.5 μm is preferably in the range of 6: 4 to 9: 1. The filling rate can be increased by optimizing the ratio. There is an optimal volume ratio to make the particles highly packed. The particle size distribution of the finer particles is more preferably 0.004 μm or more and 0.2 μm or less. More preferably, they are 0.004 micrometer or more and 0.02 micrometer or less. The more detailed, the more transparent. On the other hand, the particle size distribution of the coarser particles is more preferably 8 μm or more and 100 μm or less. By increasing the size of large particles, the number of interfaces that scatter light can be reduced. Further, the volume ratio of fine particles of 0.5 μm or more and 3 μm or less to the whole fine particles is preferably 30% or less, more preferably 10% or less, and further preferably 5% or less. If the volume ratio is smaller, the number of scattering particles can be reduced if the filling rate is the same, so that the total light transmittance can be increased. As a particle size distribution satisfying the above conditions, for example, there is a distribution as shown in FIG.

  For the measurement of the refractive index, a prism coupler can be used by making the adhesive film before thermocompression bonding into a thin film. For example, Metricon Model 2010 prism coupler can be used. An interference microscope can be used for the adhesive film after thermocompression bonding. For example, a transmission type two-beam interference microscope manufactured by Mizojiri Optical Co., Ltd. can be used. A sample for measurement is cut out with a microtome or the like as necessary. By setting the refractive index of the resin of the adhesive film to 1.42 or more, the refractive index difference between the light emitting element having a high refractive index and the adhesive film can be reduced, and reflection can be suppressed. Moreover, by making it transparent, light absorption can be suppressed and light extraction efficiency can be increased. The refractive index of the adhesive film is more preferably 1.6 or more, and still more preferably 1.7 or more.

  For the refractive index of the adhesive film, the refractive index of the highest layer is used when the distribution is multilayered or inclined, and the average refractive index within the layer is used when the phases are separated in the layer.

  Adhesive film adherends include optical film acrylic, lead frame copper, transparent electrode ITO, near-UV white light conversion element SiC, GaN sapphire, organic EL sealing glass silica, etc. There are various possibilities. In any case, the strength is preferably 1 N / chip or more in the peel test after curing at 100 ° C. for 1 hour. More preferably, it is 2N / chip or more. However, the tip is 5 mm square. The adhesive film preferably has a solder heat resistance of 265 ° C.

The adhesive properties and solder heat resistance of this adhesive film were evaluated as follows.
(1) Peel strength against adherend: (Adhesive properties) On a hot plate at 100 ° C, an adhesive film was laminated on the chip (5 mm square) of the adherend and cured at 100 ° C for 1 hour. The peel strength of this sample was measured at 100 ° C.
(2) Solder heat resistance: The light emitting device sealed with the produced adhesive film was treated at 85 ° C. and humidity of 85% for 48 hours, and then floated on a soldering iron at 265 ° C. for 1 minute to examine whether there was blistering or peeling. .

  The adhesive film of the present invention has a weight average molecular weight containing a crosslinkable functional group of 100,000 or more and a high molecular weight component having a Tg of −50 to 50 ° C. of 15 to 40% by weight, a thermosetting component mainly composed of an epoxy resin. It is preferably an adhesive film containing 60 to 85% by weight, and there are no particular restrictions on its constituent components, but since it has an appropriate tack strength and good handleability in the form of a film, it has a high molecular weight component, heat In addition to the curable component and the filler, a curing accelerator, a catalyst, an additive, a coupling agent, and the like may be included. Examples of the filler include particles and fibers.

  High molecular weight components include polyimide resins having crosslinkable functional groups such as epoxy groups, alcoholic or phenolic hydroxyl groups, carboxyl groups, (meth) acrylic resins, silicone resins, urethane resins, polyphenylene ether resins, polyetherimide resins, phenoxy Examples thereof include, but are not limited to, resins and modified polyphenylene ether resins.

  In the above adhesive film, when the high molecular weight component is contained in an amount of 15 to 40% by weight of the resin, the filling step of the surface of the light emitting element becomes good, and the content of the high molecular weight component is more preferably 20 to 37% by weight. Particularly preferred is 25 to 35% by weight.

  The high molecular weight component is preferably a high molecular weight component having a Tg (glass transition temperature) of −50 ° C. to 50 ° C. and a weight average molecular weight having a crosslinkable functional group of 100,000 or more.

  As the high molecular weight component, for example, an epoxy group-containing (meth) acrylic copolymer having a weight average molecular weight of 100,000 or more obtained by polymerizing a monomer containing a functional monomer such as glycidyl acrylate or glycidyl methacrylate is preferable. . As the epoxy group-containing (meth) acrylic copolymer, for example, (meth) acrylic acid ester copolymer, acrylic rubber and the like can be used, and acrylic rubber is more preferable.

  Acrylic rubber is a rubber mainly composed of an acrylate ester and mainly composed of a copolymer such as butyl acrylate and acrylonitrile, a copolymer such as ethyl acrylate and acrylonitrile, or the like. Further, the acrylate may contain sulfur in order to obtain a high refractive index. For example, 4,4′-bis (β-methacryloyloxyethylthio) diphenylsulfone, 4,4′-bis (β-hydroxyethylthio) diphenylsulfone-monoacrylate, sulfur cyclic structure, cyclic thiocarbonate structure, cyclic dithio Carbonate structure and cyclic trithiocarbonate structure. For example, JP 2004-115713 A describes a method for producing an acrylic adhesive containing sulfur.

  When the Tg of the high molecular weight component exceeds 50 ° C., the flexibility of the film may be lowered. When the Tg is less than −50 ° C., the flexibility of the film is too high, so that the film is difficult to cut during wafer dicing. In some cases, burrs are likely to occur.

  The weight average molecular weight of the high molecular weight component is preferably 100,000 or more and 1,000,000 or less. If the molecular weight is less than 100,000, the heat resistance of the film may be lowered. If the molecular weight exceeds 1,000,000, The flow may decrease. In addition, a weight average molecular weight is a polystyrene conversion value using the calibration curve by a standard polystyrene by the gel permeation chromatography method (GPC). The measuring method of the weight average molecular weight by normal temperature GPC in the present invention is as follows. Measuring instrument: LC-6C manufactured by Shimadzu Corporation Column: shodex KF-802.5 + KF-804 + KF-806 Solvent: THF (tetrahydrofuran) Temperature: Room temperature (25 ° C.) Standard substance: Polystyrene flow rate: 1.0 ml / min (sample concentration about 0) .2%) Injection volume: 200 μl.

  A high molecular weight component having a Tg of −20 ° C. to 40 ° C. and a weight average molecular weight of 100,000 to 900,000 is preferable in that the adhesive film is easily cut during wafer dicing, and resin waste is not easily generated. High molecular weight components having a Tg of −10 ° C. to 40 ° C. and a weight average molecular weight of 200,000 to 850,000 are more preferred.

  The thermosetting component used in the present invention is preferably an epoxy resin having heat resistance and moisture resistance required for sealing a semiconductor light emitting device. In the present invention, the “thermosetting component mainly composed of epoxy resin” includes an epoxy resin curing agent. The epoxy resin is not particularly limited as long as it is cured and has an adhesive action. Bifunctional epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin, novolac type epoxy resins such as phenol novolac type epoxy resin and cresol novolak type epoxy resin, and the like can be used. Moreover, what is generally known, such as a polyfunctional epoxy resin, a glycidyl amine type epoxy resin, a heterocyclic ring-containing epoxy resin, or an alicyclic epoxy resin, can be applied.

  In particular, the molecular weight of the epoxy resin is preferably 1000 or less, and more preferably 500 or less, in view of the high flexibility of the film in the semi-cured B-stage state. Further, a bisphenol A type or bisphenol F type epoxy resin having a molecular weight of 500 or less excellent in flexibility and 50 to 90% by weight of a polyfunctional epoxy resin having a molecular weight of 800 to 3000 excellent in heat resistance of the cured product, and It is preferable to use together.

  As the epoxy resin curing agent, known curing agents that are usually used can be used. For example, amines, polyamides, acid anhydrides, polysulfides, boron trifluoride, bisphenol A, bisphenol F, and bisphenol S can be used. Examples thereof include bisphenols having two or more such phenolic hydroxyl groups in one molecule, phenol resins such as phenol novolac resins, bisphenol A novolac resins, and cresol novolac resins.

The adhesive film is preferably colorless and transparent after curing in order to eliminate coloring. CIE1976L ^* u ^* v ^{* In} the u'v 'chromaticity diagram of uniform color space, when using a white halogen lamp with chromaticity (u0', v0 '), the chromaticity of the transmitted light of the adhesive film and the halogen lamp The distance from the chromaticity is preferably 0.1 or less, more preferably 0.05 or less. Moreover, in order to prevent wrinkles when attaching to the light emitting element, the elastic modulus should be low to some extent, and the storage elastic modulus at 100 ° C. is preferably 200 to 3000 MPa.

  Further, an adhesive film may be sandwiched between the cover film and the base film. The cover film and the base film preferably have a glass transition temperature of 100 ° C. or higher. More preferably, it is 150 degreeC or more.

  There is no restriction | limiting in particular as a material of the said cover film or a base film, For example, there exist a polyester film, a polypropylene film, a polyethylene terephthalate film, a polyimide film, a polyetherimide film, a polyether naphthalate film, a methylpentene film etc.

  Moreover, the adhesive film of the present invention includes an adhesive film A having a film thickness of 0.1 μm to 14 μm and a refractive index of 1.6 or more, and an adhesive film A adjacent to the adhesive film B. And B may have a difference in refractive index of 0.1 or more, and the entire film thickness of the adhesive film may be 100 μm or more.

  By separating the adhesive films A and B, the B layer can have a high refractive index, and the A layer can have different characteristics required for other adhesive films. Can be raised. When the adhesive film B has a film thickness of 0.1 μm or more and 14 μm or less and a refractive index of 1.6 or more, the light extraction efficiency can be increased when the adhesive film B is adhered to the light emitting surface of the light emitting element. In general, the B layer having a high refractive index of the resin has a low transmittance, and if the film thickness is too large, the transmittance is lowered. Therefore, it is out of the design of the optimum light extraction efficiency. On the other hand, even if the thickness of the B layer is too thin, the difference in refractive index between the A layer and the light emitting surface cannot be relaxed, so that the design is not optimal for the light extraction efficiency.

  By making the refractive index of the adhesive film A 0.1 or more larger than that of the adhesive film B, the magnitude relationship of the refractive index can be changed to light emitting element> adhesive film B> adhesive film A, and the change in refractive index at each interface. Is relaxed, the reflectance can be reduced. The unevenness | corrugation on the surface of a light emitting element can be embedded because the film thickness of an adhesive film is 100 micrometers or more.

  The A layer can be formed by spin coating or roll coating. Formation of the B layer can be performed by roll-coating the previously prepared A layer or by batch multi-layer lamination of the A layer and B layer by a roll. Conversely, the B layer may be coated first, and the A layer may be formed thereon.

  In the design of taking out light from the opposite side of the electrode as disclosed in JP-A-2005-354020, sealing is performed from the back side of the electrode. In the adhesive film for such use, the light extraction ability is more important than the embedding property. At this time, the light extraction efficiency increases as the thickness of the adhesive film is smaller and the refractive index is higher.

  The adhesive film of the present invention includes an adhesive film A and an adhesive film B adjacent to the adhesive film A, the adhesive film B includes a total of 10% or more of amide, imide resin, or silicone resin, and has an average particle size. The adhesive film A contains 1% or more of an inorganic filler of 10 μm or less, does not contain a resin having an amide or imide, or contains 10% or less, and contains 20% or more of an epoxy resin. The% used here is% by weight.

The refractive index Nb of the adhesive film B is preferably in the range of (Na · Ne) ^1/2 ± 0.2, where Na is the refractive index of the adhesive film A and Ne is the refractive index of the light emitting surface. Furthermore, it is preferable that Nb · db is in the vicinity of the wavelength λ · (1/4 + m / 2) where db is the thickness of the adhesive film B. Here, m is an integer of 0 or more, and wavelength λ is a wavelength in vacuum. However, since the refractive index of the resin is as small as about 1.5, it is difficult to satisfy this condition. If the inorganic filler is dispersed, the refractive index can be increased while being transparent. However, 1) it is difficult to disperse the fine particles. 2) The transmittance is small. 3) There was a problem that the haze value (turbidity) was large. These problems are as follows: 1) Except for the vicinity of the interface between the light emitting surface and the adhesive layer, ultrafine particles having a particle size small enough not to scatter light are used. 2) Prevent ultrafine particles from agglomerating in the resin. 3) This can be solved by satisfying the condition that the ultrafine particles themselves do not absorb light. For this purpose, it is necessary to select appropriate ultrafine particles, resin, and dispersant. As described above, the key to the production of a transparent adhesive having high thermal conductivity is to uniformly disperse the inorganic filler.

  One way to improve dispersion is to apply an appropriate coupling agent or dispersant to a material in which fine particles and a resin are kneaded. By using a coupling agent or a dispersant, an adhesive film having high transparency without aggregation of fine particles can be obtained. It is preferable to use a coupling agent such as isocyanate silane, epoxy silane, anilino silane, methyl silane, phenyl silane, amino silane, ureido silane, vinyl silane, alkyl silane, mercapto silane, organic titanate, aluminum alcoholate from the viewpoint of improving dispersibility. . There is no restriction | limiting in particular about the usage method of these coupling agents, You may use it, after processing to an inorganic filler beforehand. Moreover, you may use by the integral blend method at the time of the mixing | blending of another raw material. Examples of the dispersing agent include Disperbyk-110, Disperbyk-111, Disperbyk-116 and the like of Big Chemie Japan. In order to prepare a resin containing fine particles, there are two types: a case where a solid powder is mixed into a solution and a case where the solid powder is dispersed in a solution at the time when the particles are synthesized. When the fine particles are solid powder, the resin and the fine particles can be dispersed by kneading by a ball milling method using a planetary bead mill, a method of applying pressure and high temperature, a method of shearing, or the like. When the fine particles are dispersed in the solution, they can be dispersed by stirring with a stirrer or ultrasonic waves. The dispersibility can also be increased by using a resin, and the dispersibility can be increased by using an amide or imide resin or a silicone resin which is a highly polar functional group.

  When the adhesive film B contains amide or imide resin or silicone resin in a total of 10% or more, heat resistance can be imparted and the dispersibility of the inorganic filler can be increased. By including 1 wt% or more of an inorganic filler having an average particle size of 10 μm or less, high heat resistance and a high refractive index can be realized. The adhesive film A does not include a resin having an amide or imide, or includes 5% by weight or less, and includes 20% by weight or more of an epoxy resin, thereby improving the embedding property.

The film thickness of the adhesive film is preferably 14 μm or less, more preferably 10 μm or less, and still more preferably 5 μm or less.
Furthermore, the adhesive film after thermocompression bonding preferably contains 1% by weight or more and 80% by weight or less of filler in terms of improving dicing properties.
By blending a filler, the refractive index can be increased and the light extraction efficiency can be increased. On the other hand, if the filler content is too large, problems such as an excessive increase in storage elastic modulus of the adhesive film, a decrease in adhesiveness, and a decrease in electrical characteristics due to residual voids are likely to occur. Is preferred. When the blending amount of the filler is small, resin burrs during dicing tend to occur.

  Details of the preparation method for the adhesive containing an imide resin are described in JP-A No. 2002-185687. In addition, the details of the preparation method for the adhesive containing an amideimide resin are described in JP-A No. 2002-146321. Further, details of a method for producing an adhesive containing a silicone resin are described in JP-A-6-322349.

  Furthermore, the adhesive film of the present invention is also intended to improve the dicing property of the adhesive film in the B-stage state, improve the handleability of the adhesive film, improve the thermal conductivity, adjust the melt viscosity, and impart thixotropic properties. And a filler, preferably an inorganic filler.

  The average particle size of the inorganic filler in the B layer of the adhesive film is preferably 0.1 μm or more and 10 μm or less for titania, zirconia, alumina, and zinc oxide. Moreover, it is more preferable that it is 1 micrometer or less. More preferably, it is 0.8 micrometer or less, Most preferably, it is 0.1-0.3 micrometer. By optimizing the particle size, light can be scattered and light extraction efficiency can be increased. Moreover, it is preferable that the refractive index difference of the refractive index of particle | grains with the light emission surface is 0.5 or less.

  In the adhesive film of the present invention, it is preferable that 2/3 or more of the particles or fibers are biased to one of the center lines in the layer as shown in FIG. In the adhesive film layer, the center of gravity of 2/3 or more of particles or fibers enters one of the center lines in the layer, so that the light extraction efficiency from the light emitting element, thermal conductivity, and adhesive strength are compatible. It becomes easy. Since the adhesive force of the surface with many particles decreases, it is advantageous from the viewpoint of improving the adhesive force to collect the particles only on the light emitting surface side when the thermal conductivity in the direction perpendicular to the surface is not necessary. In addition, since the refractive index can be changed smoothly, the light extraction efficiency is also improved. In the region on the side of the larger volume of the particles separated by the center line, NL is the number of large particles having a particle size of 5 μm or more, and NS is the number of small particles having a particle size of 0.004 μm or more and 0.5 μm or less. In this case, NL0 is the number of large particles having a particle size of 5 μm or more in the entire region, NS0 is the number of small particles having a particle size of 0.004 μm or more and 0.5 μm or less. It is desirable that 1.2 × NS / NS0 <NL / NL0 is satisfied in the region on the side having a larger amount. More preferably, 2 × NS / NS0 <NL / NL0. The viscosity at the time of making the primary sheet is 0.002 Pa · s or more and 1.0 Pa · s or less, the film thickness is 2 times or more of the average particle diameter, and after coating for 2 minutes or more and 0.002 Pa · s or more and 1.0 Pa・ Bias can be made by keeping it below s.

  Moreover, as an application of an adhesive film, there exist optical semiconductor sealing like FIG. 4, sealing of a solar cell panel, sealing of a color filter, etc. Since sealing of the solar cell panel can release heat from the panel surface by the sealing, an improvement in weather resistance can be expected. In sealing the color filter, excellent discoloration resistance can be realized by diffusing heat.

  The adhesive film of the present invention includes an adhesive film A and an adhesive film B adjacent to the adhesive film A, and the adhesive films A and B have (1) an epoxy resin and (2) a weight average molecular weight including a functional group of 100,000 or more. (3) an adhesive composition containing an imidazole compound, the adhesive composition being compatible with the high molecular weight component before curing of the epoxy resin, After curing, phase separation from the high molecular weight component to form a sea-island structure, the average of the width of the sea and islands in the center of the adhesive film A when viewed in a cross section perpendicular to the film is 0.3 μm or less, The average width of the sea and the island in the center of the adhesive film B is 0.3 μm or more.

  The combination of (1) epoxy resin used in the present invention and (2) a high molecular weight component having a functional group-containing weight average molecular weight of 100,000 or more is preferably a low molecular weight glycidyl epoxy resin as an epoxy resin. An epoxy resin having an aromatic glycidyl ether group and an epoxy resin having an aromatic glycidyl ether group are preferred. The high molecular weight component having a functional group-containing weight average molecular weight of 100,000 or more is preferably a high molecular weight component such as a thermoplastic, a cross-linked reaction rubber, or a thermoplastic elastomer having a functional group having a polarity close to that of an epoxy resin.

  This is because compatibilization depends on the difference in the molecular weight of the resin to be mixed and the polarity of each mixture, and phase separation is formed by the increase in the molecular weight of the epoxy resin due to curing. This is because such a phase separation structure tends to be formed by increasing the compatibility between the epoxy resin and the high molecular weight component and slowing the thermodynamic phase separation rate. More specific resins selected in this way include epoxy resins having a molecular weight of less than 400 and epoxy group-containing acrylic polymers, epoxy resins having a molecular weight of 400 or less and epoxy group-containing polyethylene, and epoxy resins having a molecular weight of 400 or less and containing epoxy groups. Examples thereof include a thermoplastic plastic mixture, and among them, a low molecular weight bisphenol A type epoxy resin and an epoxy group-containing acrylic copolymer are preferable in terms of molecular weight, polarity and curing. Details of the resin synthesis method used are described in JP-A-2006-183020.

  Further, when viewed in a cross section perpendicular to the film, the average width of the sea and the island at the center of the adhesive film A is each 0.3 μm or less, and the average width of the sea and the island at the central portion of the adhesive film B is 0 respectively. An adhesive film including an adhesive film that is 3 μm or more is preferable. When the average width of the sea and the island is 0.5 μm or less, an adhesive film with high transmittance and high light extraction efficiency can be realized. More preferably, it is 0.2 μm or less. On the other hand, in the vicinity of the surface of the light emitting element, by providing a sea or island portion having a high refractive index, total reflection on the surface of the light emitting element can be prevented and light extraction efficiency can be increased. At this time, the difference in refractive index between the sea and the island is preferably 1/3 or more, more preferably 1/2 or more, of the difference in refractive index between the light emitting element surface and the adhesive film B. Moreover, it is more preferable that the average width of the sea and the island is 1 μm or more.

  The adhesive film of the present invention includes an adhesive film A and an adhesive film B adjacent to the adhesive film A, the adhesive film A has a weight average molecular weight of 100,000 or more and a glass transition temperature Tg of −50 to 50. It contains 100 parts by weight of a resin containing 15 to 40% by weight of a high molecular weight component and 60 to 85% by weight of a thermosetting component mainly composed of an epoxy resin, and 20 to 200 parts by weight of an inorganic filler. The adhesive film B preferably has a transparent adhesive film having a refractive index higher than that of the adhesive film A by 0.1 or more.

  By separating the adhesive films A and B, the B layer can have a high refractive index and thermal conductivity, and the A layer can have a embeddability. If a resin contains a large amount of fine particles in order to obtain a high refractive index and thermal conductivity, the transparency is lowered and the embedding property is also deteriorated. Thus, these problems can be avoided.

  Since the adhesive film B has a refractive index higher than that of the adhesive film A by 0.1 or more, the light emitting element> the adhesive film B> the adhesive film A can be obtained, and the change in the refractive index at each interface is alleviated. The rate can be reduced. It is more preferable that the adhesive film B has a refractive index higher than the adhesive film A by 0.2 or more.

  When the Tg of the high molecular weight component exceeds 50 ° C., the flexibility of the film may be lowered. When the Tg is less than −50 ° C., the flexibility of the film is too high, so that the film is difficult to cut during wafer dicing. In some cases, burrs are likely to occur.

  The weight average molecular weight of the high molecular weight component is preferably 100,000 or more and 1,000,000 or less. If the molecular weight is less than 100,000, the heat resistance of the film may be lowered. If the molecular weight exceeds 1,000,000, The flow may decrease. Here, the weight average molecular weight is a value measured by normal temperature GPC.

  A high molecular weight component having a Tg of −20 ° C. to 40 ° C. and a weight average molecular weight of 100,000 to 900,000 is preferable in that the adhesive film is easily cut during wafer dicing, and resin waste is not easily generated. High molecular weight components having a Tg of −10 ° C. to 40 ° C. and a weight average molecular weight of 200,000 to 850,000 are more preferred.

  The particles contained in the adhesive film have an average particle size in the range of 0.04 to 0.6 times the film thickness of the adhesive film, and the average particle size is 0.4 μm or more and 100 μm or less, It is preferable that the average particle diameter of the particles entering 10% by volume from the large diameter particles is smaller than 1.5 times the average particle diameter of the whole particles. The average particle size is a volume average particle size. The particle size can be measured by SEM or TEM (transmission electron microscope).

It is preferable that the absolute value of the difference between the refractive index of the particle surface and the refractive index of the adherend surface is 0.5 or less and the Mohs hardness of the particle is 5 or less.
By curing the adhesive film as shown in FIG. 8 by applying pressure, the surface of the particles can be brought into contact with the light emitting surface to prevent total reflection of light incident on the light emitting surface, and the extraction efficiency can be increased. Moreover, the light extraction efficiency can be further increased by setting the absolute value of the difference between the refractive index of the particle surface and the refractive index of the adherend surface to 0.5 or less. By using soft particles having a Mohs hardness of 5 or less, it becomes difficult to damage the light emitting surface when pressure is applied, and the contact area between the light emitting surface and the particles can be increased, so that the light extraction efficiency can be increased.

  It is preferable that the particles contained in the adhesive film have a higher refractive index on the particle surface than on the particle surface, and the storage modulus of the material inside the particle is 1 to 3000 MPa.

  In addition to the optical design in which the adhesive film B has an average high refractive index, an optical design in which high refractive index particles are attached to the high refractive index light-emitting surface is also possible. In this case, the average particle size is preferably 0.4 μm or more and 3 μm or less. Further, it is preferable that 30% by weight or more of the adhesive film B is particles having a high refractive index. Further, the difference between the refractive index of the particles and the refractive index of the light emitting surface is preferably 0.5 or less.

  The particles in the adhesive film may have a high refractive index on the outside. Here, the height of the refractive index is determined by the real part of the complex refractive index. For example, silver has a refractive index of 0.17 to 3.4i, but this real part is 0.17. By making the outside of the particles have a high refractive index, it is possible to use a flexible low refractive index material on the inside, and when thermocompression bonding, the contact interface between the light emitting surface and the high refractive index or high heat conductive material is formed. Can be increased. The light extraction efficiency can be increased by increasing the contact area between the high refractive index material and the light emitting surface. As the low refractive index material, acrylic, epoxy, or silicone resin can be used. As the high refractive index material, titania, ITO, zirconia, or the like can be used. In this case, the average particle size in the adhesive film B is preferably 0.4 μm or more and 10 μm or less. If it is too small, it will not diffract, and if it is too large, it will hinder adhesion.

  When the refractive index in the vicinity of the surface of the particle is high, light emitted from the light-emitting surface to be bonded can be scattered to prevent total reflection, so that the light extraction efficiency is increased. Moreover, since the storage elastic modulus of the material inside the particles is 1 to 3000 MPa, the contact area after thermocompression bonding can be increased as shown in FIG. 10, and the total reflection of light incident on the light emitting surface can be prevented and light extraction can be performed. Efficiency can be increased. Here, the inside of the particle is preferably a resin such as polystyrene, epoxy, acrylic, polyimide, polycarbonate, and the particle surface is preferably an inorganic material such as titania or zirconia. Organic fine particles having a uniform particle diameter can be prepared by an emulsion polymerization method (see Non-Patent Documents 2 and 3 or JP-A-7-141912). Commercially available organic fine particles may be obtained. The surface coating with an inorganic material can add a reactive titanium compound to emulsion-polymerized polystyrene (see Non-Patent Documents 3 and 4). For the surface treatment of the resin particles, for example, sulfonation with concentrated sulfuric acid can be used.

  The adhesive film preferably includes particles having a difference from the refractive index of the light emitting surface of 0.5 or less, and a cross section of the particles is exposed on the surface. As one method, there is a method in which the adhesive surface of an adhesive film is polished using abrasive grains in which alumina, ceria, or silica is dispersed in water. These are commercially available as abrasives. The light extraction efficiency can be improved by including particles having a difference from the refractive index of the light emitting surface of 0.5 or less. In addition, by exposing the cross section of the particles to the surface, the contact area with the light emitting surface can be increased when adhered to the light emitting surface. As a result, the light extraction efficiency can be improved. A CMP slurry “HS-T” manufactured by Hitachi Chemical Co., Ltd. can be used as the abrasive. Polishing is done with sandpaper and buffing, and a load is applied to the adhesive film.

  The adhesive film contains particles having an absolute value of a difference from the refractive index of the light emitting surface of 0.5 or less, and the major axis of the particles is 1.5 times longer than the minor axis, so that the major axis of the particles after thermocompression bonding Can be in contact with the light emitting surface, and the contact area between the particles and the light emitting surface can be increased. Titanium oxide rutile tends to form needle crystals and can be used. For example, there is TTO-S manufactured by Ishihara Sangyo.

  In addition, the adhesive film of the present invention may be used by being laminated with an uneven optical film before thermocompression bonding, the optical film has a glass transition temperature of 60 ° C. or higher, and the adhesive film has a glass transition temperature of 60 ° C. or higher. And the surface of the optical film opposite to the adhesive film has a refractive index distribution having irregularities with an average groove depth of 0.1 μm or more, or a refractive index change with a refractive index difference of 0.2 or more, or inside the optical film. There is a refractive index distribution structure having a refractive index change with a refractive index difference of 0.015 or more, or there are irregularities with an average groove depth of 0.1 μm or more at the interface between the optical film and the adhesive film, and the refractive index of the adhesive film is 1. A transparent adhesive film of .42 or more is preferable.

  Unless the optical film has a glass transition temperature higher than the thermocompression bonding temperature required for sealing the adhesive film, the optical film is deformed during the thermocompression bonding of the adhesive film, and the light extraction efficiency decreases. Since the thermocompression bonding temperature is 60 ° C. or higher, the glass transition temperature is preferably 60 ° C. or higher. More preferably, it is 100 degreeC or more, More preferably, it is 150 degreeC or more, More preferably, it is 200 degreeC or more. This is because the heating temperature for thermocompression bonding of the adhesive film is preferably 60 to 240 ° C, and more preferably 100 to 180 ° C.

  If the adhesive film does not have heat resistance after sealing, the adhesive film peels off or discolors due to heat emitted from the light emitting element. The glass transition temperature is more preferably 100 ° C. or higher, still more preferably 150 ° C. or higher, and even more preferably 200 ° C. or higher. This is because the heat emitted from the light emitting element can be lowered to 80 ° C. if a radiator made of graphite or aluminum is attached, but it becomes 200 ° C. or more without a radiator.

  By setting the refractive index of the adhesive film to 1.42 or more, the refractive index difference between the light-emitting element having a high refractive index and the adhesive film can be reduced, and reflection can be suppressed. Moreover, by making it transparent, light absorption can be suppressed and light extraction efficiency can be increased. The refractive index of the adhesive film is more preferably 1.55 or more, and further preferably 1.65 or more. There may be irregularities with an average groove depth of 0.1 μm or more at the interface between the optical film and the adhesive film. Thereby, reflection at the interface between the optical film and the adhesive film may be suppressed. Even if reflection at the interface between the air and the film cannot be suppressed, the light extraction efficiency can be increased by bending the light in the direction perpendicular to the emission surface. When the unevenness for suppressing reflection on the exit surface of the optical film is periodic and the average groove width is 0.4 μm or more and 5 μm or less, the unevenness of the optical film surface on the side opposite to the adhesive film should be not periodic. preferable. By not being periodic, the generation of rainbows due to spectroscopy can be suppressed. The term “not periodic” means that the standard deviation of the groove width is a sample parameter of 20 and is 0.2 μm or more. The average groove depth is preferably 0.4 μm or more, more preferably 0.8 μm or more.

[Second Embodiment]
In an adhesive film including a resin and thermally conductive fine particles or thermally conductive fibers dispersed in the resin, the thermally conductive fine particles or thermally conductive fibers are oriented in a direction substantially perpendicular or parallel to the surface of the adhesive film. An anisotropic white or transparent particle or fiber such as a plate, rod or fiber having high thermal conductivity in the direction, and the adhesive film is a kneaded product of resin and particle or fiber A transparent heat conductive adhesive film formed by laminating a plurality of sheets formed from the above, and then slicing the obtained laminate in a direction perpendicular or parallel to the lamination surface.

The anisotropy of the fine particles refers to a shape different from a highly symmetric shape such as a sphere or a regular polyhedron such as a rectangular parallelepiped, a needle shape, or a flat plate shape. The ratio of the major axis to the minor axis is 1.5 or more. In the process of laminating these, since the major axis spontaneously faces the plane direction, anisotropy appears in the thermal conductivity. Since the major axis direction of the particles is often aligned in a direction parallel to the laminated film, the thermal conductivity is improved in the direction in which the particles are aligned. In addition, when applied to a light emitting element, the diffusion angle range can be controlled. When the filler is a fiber or needle-like particle and is oriented in parallel to the adhesive film surface, the diffusion angle range of the emitted light is wide in a plane perpendicular to the fiber or the needle. In this way, the direction in which the heat conduction is high and the direction in which the diffusion angle is wide can be made perpendicular.
The color of the particles is preferably white or transparent in order to suppress light absorption. As a laminating method, there is a method of extruding into a multilayer by a roll. Alternatively, there is a method of spin coating a plurality of times. Each of the stacked sheets is called a primary sheet.

  The degree of orientation can be known by wide-angle X-ray diffraction. The adhesive film in which the primary sheet is simply laminated and the adhesive film sliced in the direction perpendicular to the laminated surface are used as samples with the same thickness and area. If there is periodicity between cuboids of fine particles, between needles, or between plates, it can be observed as X-ray diffraction. It is considered that the X-ray diffraction is oriented when the intensity of the X-ray diffraction is greatly different in a direction perpendicular to the laminated surface.

  The degree of orientation is compared with the peak having the strongest intensity among the X-ray diffraction peaks assigned to the layers between the plates and between the needles arranged in parallel. The X-ray diffraction peak is, for example, as shown in FIG. X-rays are incident in a direction parallel to the direction perpendicular to the laminated surface, and the diffraction intensity is measured. CuKα is used as the X-ray source, and high-purity silicone is used as the standard substance. The apparatus is an X-ray diffractometer Geigerflex made by Rigaku Denki Kogyo. At this time, the peak area ratio is preferably 2: 1 or more, more preferably 5: 1 or more, and further preferably 10: 1 or more. The larger the area ratio, the higher the degree of orientation and the higher the thermal conductivity.

  The slice thickness is preferably 0.1 to 2 mm. More preferably, it is 0.2-1 mm. By making it moderately thin, it is possible to maintain adhesion and to achieve both thermal conductivity and transparency.

  For example, cellulose or liquid crystal polymer can be used as the fiber. For example, an aramid fiber (a staple fiber (cotton) of Teijin Techno Products' Technora) which is a kind of liquid crystal polymer.

  The heat conductive fiber may be coated with a high heat conductive material. As a type of coating, there is a technique of coating an alumina ceramic film using an aerosol deposition method.

[Third Embodiment]
In the adhesive film of the present invention, transparent fibers or anisotropic transparent fine particles are used, and a layer that is highly filled with fine particles and a layer that is not filled or low filled are alternately laminated and sliced perpendicular to the direction of lamination. A transparent heat conductive adhesive film characterized by that.

  The low filling adhesive film preferably has a particle or fiber filling ratio of 50% by weight or less as compared with a high filling adhesive film. More preferably, it is 20% by weight or less. Cutting it out improves the heat conduction in the direction perpendicular to the surface. The number of stacked layers is 2 or more, and the ratio of the thickness of the layer filled with fine particles to the layer not filled or low filled is preferably 2: 1 to 1: 2. The thickness of the layer highly filled with fine particles is preferably 5 μm to 50 μm.

  Further, by alternately laminating, it is possible to compensate for a decrease in adhesive force accompanying the increase in particle filling. As a laminating method, there is a method of extruding with a roll to multiplex. As a method of slicing, there is a method of cutting with a blade like a planer. At this time, the temperature of the adhesive film is preferably set to −70 ° C. or higher and 0 ° C. or lower. More preferably, it is -70 degreeC or more and -20 degreeC or less. When the temperature is low, the resin has rigidity, so that the adhesive film can be easily cut out. Although productivity falls, you may cut out with a microtome. As the slicer, a large slicer for resin manufactured by Marunaka Co., Ltd. can be used. The design / evaluation of particle size, thermal conductivity or transparency is the same as in the first and second embodiments. Another method of slicing is to cut with a rotary blade such as a diamond cutter.

[Fourth Embodiment]
In the adhesive film of the present invention, zinc oxide, ceria, titania, zirconia, aluminum nitride, aramid fiber, carbon nanotube, cellulose, etc. are used for the fine particles or fibers, and the layer filled with fine particles and not filled or low filled It is a transparent heat conductive adhesive film characterized by alternately laminating the above layers and adhering the finely filled surface toward the light emitting surface. The heat conduction improves in the direction parallel to the surface. At the same time, the efficiency of extracting light from the light emitting surface can be improved by exposing particles having a high refractive index to the surface of the film.

  It is preferable to modify the titania and the surface with silica from the viewpoint of dispersibility of the particles in the resin and prevention of deterioration of the resin. The surface of aluminum nitride is preferably modified with aluminum oxide from the viewpoint of stability of the particles themselves or prevention of deterioration of the resin. The particle filling rate, the ratio of the thickness of the highly filled layer to the unfilled or lowly filled layer, the laminating method, the slicing method, etc. are the same as in the first to third embodiments.

[Fifth Embodiment]
It may be a transparent heat conductive adhesive film in which transparent fine particles or fibers are attached or buried on the resin surface. For particles having a particle center of gravity at a distance equal to or smaller than the average particle diameter from the surface of the adhesive film, the average distance between the particle surface and the substrate is preferably 0.05 μm or less, more preferably 0.02 μm or less. Moreover, about the adhesive film per unit area, the average distance to the fiber from an adhesive film surface becomes like this. Preferably it is 0.05 micrometer or less, More preferably, it is 0.02 micrometer or less. The distance is calculated by observing a cross section as shown in FIG. 11 with an SEM. Specifically as a method for producing these protrusions, (1) a method of dispersing and adhering particles and fibers, (2) a method of adding particles and fibers when forming an adhesive film, and (3) particles and fibers It is possible to apply a method of spraying and adhering to a heated and softened adhesive film.

  As the method (1), there is a method in which a dispersion liquid in which particles and fibers are dispersed in acetone or cyclohexanone is directly applied to an adhesive film and then dried. As the method (2), there is a method in which a dispersion liquid in which particles and fibers are dispersed in acetone or cyclohexanone is applied and dried on an aluminum foil and then applied to an adhesive film and then dried. As the method (3), there is a method in which a dispersion liquid in which particles and fibers are dispersed in acetone or cyclohexanone is directly applied to an adhesive film heated and softened on a hot plate.

Hereinafter, although the example demonstrates the adhesive film of this invention concretely, this invention is not limited to this.
Example 1
2,2-bis [4- (4-aminophenoxy) phenyl] propane in a 0.5 liter four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and cooling tube with an oil / water separator under a nitrogen stream 45.92 g (112 mmol) was added and dissolved by adding 50 g of N-methyl-2-pyrrolidone. Next, 23.576 g (112 mmol) of trimellitic anhydride chloride was added while cooling so as not to exceed 20 ° C. After stirring at room temperature (25 ° C.) for 1 hour, 13.5744 g (134.4 mmol) of triethylamine was added while cooling so as not to exceed 20 ° C., and the mixture was allowed to react at room temperature (25 ° C.) for 3 hours. Manufactured. The obtained polyamic acid varnish was further subjected to a dehydration reaction at 190 ° C. for 6 hours to produce a polyamideimide resin varnish. A precipitate obtained by pouring the polyamideimide resin varnish into water was separated, ground and dried to obtain a polyamideimide resin powder (PAI-1) soluble in a polar solvent at room temperature (25 ° C.).

As a polyamide-imide resin powder, 50 parts by weight of PAI-1 and as an epoxy resin, 30 parts by weight of a bisphenol F type epoxy resin (epoxy equivalent 160, trade name YD-8170C manufactured by Tohto Kasei Co., Ltd.), a cresol novolac type epoxy resin ( Epoxy equivalent 210, Toto Kasei Co., Ltd. trade name YDCN-703 used) 10 parts by weight; Epoxy resin curing agent Phenol novolac resin (Dainippon Ink Chemical Co., Ltd. trade name Priofen LF2882) 27 parts by weight ; Epoxy group-containing acrylic rubber as epoxy group-containing acrylic copolymer (weight average molecular weight of 800,000 by gel permeation chromatography, 3% by weight of glycidyl methacrylate, Tg of -7 ° C, trade name of Nagase ChemteX Corporation, trade name HTR- 86 28 parts by weight; using P-3DR; 0.1 parts by weight of an imidazole-based curing accelerator (using Suzukoku Kasei Kogyo Co., Ltd., Curazole 2PZ-CN); Silica filler (manufactured by Admafine, S0-) C2 (specific gravity: 2.2 g / cm ³ , Mohs hardness 7, average particle size 0.5 μm, specific surface area 6.0 m ² / g)) 95 parts by weight; as silane coupling agent (manufactured by Nihon Unicar Co., Ltd.) Cyclohexanone was added to the composition consisting of 0.25 parts by weight (using trade name A-189) and 0.5 parts by weight (using trade name A-1160 manufactured by Nihon Unicar Co., Ltd.), and mixed by stirring. Care was taken to obtain an adhesive varnish. This adhesive varnish is used as a binder resin.

  An epoxy resin containing the above amideimide resin is used as the binder resin. Zirconium oxide nanoparticles having a diameter of 40 nm made by Sumitomo Osaka Cement were kneaded in 100 parts by weight of the binder resin in a mortar so as to be 50 parts by weight with respect to the binder resin. Further, similarly, 100 parts by weight of zirconia particles (Niimi NZ beads (average particle size: 30 μm) manufactured by Niimi Sangyo) was mixed, and the easy-release surface of the PET film was sandwiched vertically to form an adhesive film. The refractive index of the adhesive film is 1.9. The film thickness of the adhesive film is 150 μm. The total light transmittance of this adhesive film was measured. The total light transmittance was 55% at a wavelength of 632.8 nm. The film was cloudy. Moreover, it was 0.9 W / m * K when the heat conductivity was measured.

  As a sample for sealing, Toyoda Gosei's E1S40-1W0C6-01 was used as the white LED. In Examples 1 and 2 and Comparative Examples 1 and 2, this LED was polished with a sandpaper to leave a fluorescent layer, and the surface layer portion was removed, which was used as a white LED. Ten of these were arranged on a lead frame as an interposer, sealed together, and then separated with a dicer. In the batch sealing, the sealing film was thermocompression bonded at 80 ° C. and a molding pressure of 1 kg · f / cm for 120 seconds and then heated at 150 ° C. for 1 hour. The light extraction efficiency indicates how many times the amount of light emission has increased compared to the case where the LED is not attached to the light emitting surface. In Example 1, it was 1.3 times.

Example 2
100 parts by weight of binder resin prepared in the same manner as Example 1 and 100 parts by weight of alumina particles (Showa Denko flaky alumina, A-42-2 (average particle diameter: 3.2 μm)) could be mixed. The easy-release surface of the PET film was sandwiched between top and bottom to form the primary sheet of the adhesive film. The refractive index of the adhesive film is 1.6. The film thickness of the adhesive film is 15 μm. The thickness of the 10 layers was 150 μm. This cross section was cut out perpendicular to the film surface with a large slicer for resin manufactured by Marunaka Steel Works. The film thickness is 0.3 mm. The total light transmittance was 70% at a wavelength of 632.8 nm. Moreover, it was 4.1 W / m * K when the heat conductivity of the perpendicular direction was measured. The light extraction efficiency was 1.1 times. Moreover, as a result of measuring the diffusion angle of light perpendicularly incident on the adhesive film surface with a He—Ne laser, the half-value width of the diffusion angle distribution is 1 when compared with the case where it is parallel to the case where it is parallel to the thin flake surface of alumina. .2 times increase.

Comparative Example 1
100 parts by weight of binder resin prepared in the same manner as in Example 1 and 100 parts by weight of zirconia particles (EP Zirconium Oxide (average particle size: 2 μm) manufactured by Daiichi Elemental Chemical Co., Ltd.) could be mixed. The total light transmittance was 50% at a wavelength of 632.8 nm. The film was cloudy. Moreover, it was 0.8 W / m * K when heat conductivity was measured. The light extraction efficiency was 1.2 times.

Comparative Example 2
100 parts by weight of binder resin prepared in the same manner as in Example 1 and 100 parts by weight of alumina particles (spherical alumina manufactured by Tatsumori (average particle diameter: 3.3 μm)) could be mixed. The easy-release surface of the PET film was sandwiched between top and bottom to form the primary sheet of the adhesive film. The refractive index of the adhesive film is 1.52. The film thickness of the adhesive film is 15 μm. Ten sheets of these were stacked to have a film thickness of 150 μm. This cross section was cut out perpendicular to the film surface with a large slicer for resin manufactured by Marunaka Steel Works. The film thickness is 0.3 mm. The total light transmittance was 60% at a wavelength of 632.8 nm. Further, when the thermal conductivity in the vertical direction was measured, it was 2.3 W / m · K. The light extraction efficiency was 1.2 times.

  Table 1 shows the results of applying the same production evaluation conditions to the adhesive film while changing only the particle type, particle size distribution, and orientation in addition to the results of the above Examples and Comparative Examples. “Vertical” orientation means that the orientation of the filler is perpendicular to the finally obtained adhesive film surface. The thermal conductivity in the direction perpendicular to the adhesive film surface is described. The total light transmittance was evaluated with a film thickness of 0.3 mm. The intermediate region of the particle size distribution represents a particle size of 0.5 to 3 μm, and the intermediate region was small when the volume ratio of the particle size was 0 to 10%. The middle region has a volume ratio of 20% or more. ZIRCAR Zirconia Bulk fibers were used for the zirconia anisotropic particles.

It is a figure which shows the particle | grains orientated perpendicularly to the incident light and the adhesive film surface. It is sectional drawing which shows one embodiment of the particle size distribution in a sample cross section. It is a figure which shows the particle | grains orientated horizontally with the oblique incident light of the incident angle (theta) i with respect to the normal line of a sample surface, and an adhesive film surface. It is sectional drawing which shows one embodiment of sealing of the LED semiconductor by the adhesive film of this invention. It is a figure which shows the example of the particle size distribution which has two or more peaks of the particle | grains used for this invention. It is a figure of the X-ray diffraction angle distribution of resin containing the oriented particle | grains when an horizontal axis is incident angle (theta) with respect to a sample surface, and a vertical axis | shaft is relative diffraction intensity. It is the schematic which shows the distance of particle | grains and a base-material surface. It is the schematic which shows the example of the heat | fever and pressure which apply to an adhesive film. It is a figure which shows the bias | inclination of the particle | grains in an adhesive film layer. It is a figure which shows the grounding state of the particle | grain surface after thermocompression bonding. It is a figure which shows the positional relationship of particle | grains and a light emission surface.

Explanation of symbols

12 Adhesive film 14. Resin 16. 17. High thermal conductivity particles with high refractive index Mold 20. Adhesive film 22. Wire for wire bonding 24. Light emitting element 26. Conductive paste 28. Interposer 30. Positive distance between the particle surface and the substrate 32. Negative distance between particle surface and substrate 34. 35. Adhesive layer containing particles having a high refractive index on the outside after thermocompression bonding A light emitting element having electrodes opposite to the light emitting surface 38. Distance between particle and substrate 40. Particle center of gravity 42. High refractive index, high thermal conductivity, small particle size 44. Large particle size high refractive index, high thermal conductivity 46. Dotted line indicating the center of the adhesive film layer

Claims (11)

  An adhesive film containing a resin and transparent or white fine particles, and the frequency particle size distribution peak (peak) of the fine particles is one or more in each of 3 μm to 100 μm and 0.004 μm to 0.5 μm A transparent heat conductive adhesive film characterized by that.   In an adhesive film including a resin and thermally conductive fine particles or thermally conductive fibers dispersed in the resin, the thermally conductive fine particles or thermally conductive fibers are oriented in a direction substantially perpendicular or parallel to the surface of the adhesive film. Plate-like, rod-like, or fiber-like anisotropic white or transparent fine particles or fibers that have high thermal conductivity in the direction, and an adhesive film is formed from a resin and a mixture of fine particles or fibers A transparent heat conductive adhesive film formed by laminating a plurality of sheets, and then slicing the obtained laminate in a direction perpendicular or parallel to the lamination surface.   Using transparent fibers or anisotropic transparent fine particles, the layers in which the transparent fibers or transparent fine particles are highly filled and the layers that are not filled or transparently filled with the transparent fibers or transparent fine particles are alternately laminated, and the lamination direction The transparent heat conductive adhesive film according to claim 1, wherein the transparent heat conductive adhesive film is sliced vertically.   Using transparent fibers or transparent fine particles, layers with high filling of transparent fibers or transparent fine particles and layers with no or low filling of transparent fibers or transparent fine particles are stacked alternately to make high filling of transparent fibers or transparent fine particles The transparent heat conductive adhesive film according to claim 1 or 2, wherein the layer is exposed and adhered to the light emitting surface side.   5. The transparent heat conductive adhesive film according to claim 2, wherein the heat conductive fiber is a fiber coated with a material having a high heat conductivity.   6. The transparent heat conductive adhesive film according to claim 1, wherein transparent or white fine particles or fibers are adhered or buried on the resin surface.   The transparent heat conductive adhesive film according to any one of claims 1 to 6, wherein a transparent or white fine particle or fiber has a refractive index in a visible light region of 1.8 or more.   The transparent heat conductive adhesive film according to any one of claims 1 to 7, wherein in the adhesive film layer, 2/3 or more of the fine particles or fibers are biased to one of the center lines in the layer. .   An optical semiconductor device having an optical semiconductor element sealed with the transparent heat conductive adhesive film according to claim 1.   A solar cell panel sealed with the transparent heat conductive adhesive film according to claim 1.   A display having a color filter sealed with the transparent heat conductive adhesive film according to claim 1.

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