JP5144425B2 - Method for producing composite film - Google Patents

Description

  The present invention relates to a composite film of a thermally conductive filler and a matrix resin excellent in thermal conductivity in the thickness direction, and a method for producing the same.

  In recent years, due to high integration of semiconductor elements, thinning of light emitters such as organic EL, and higher output of motors due to hybridization of automobiles, the heat generated in electronic equipment, electrical equipment, etc. has increased, and more efficiently It is necessary to dissipate heat. In electronic equipment, electrical equipment, etc., heat dissipation measures such as attaching a heat dissipation film with high thermal conductivity to the heat generating component, surrounding the heat generating component with a casing with high thermal conductivity, etc. In order to further improve the above, various studies on composite materials of thermally conductive filler and matrix resin have been conducted.

For example, in Patent Document 1, the filler is highly filled by improving the degree of dispersion of the filler in the polyarylene sulfide resin. In Patent Document 2, a carbon short having a high thermal conductivity in the fiber axis direction is used. A composite molded body in which a fiber filler is blended in a matrix has been studied. Moreover, in patent document 3, it is performed to shape | mold the resin composition containing the vapor grown carbon fiber excellent in the dispersibility, and a heat resistant resin, and in patent document 4, a filler is disperse | distributed in matrix resin, The filler is continuously welded to each other with a low melting point metal.
JP 2007-146129 A JP 2007-291576 A JP 2006-137938 A Japanese Patent Laid-Open No. 6-196684

  In order to improve the heat dissipation efficiency, it is preferable that the thermal conductivity of the composite film of the thermally conductive filler and the matrix resin is high in the thickness direction. However, in the composite material as described above, the direction of heat dissipation has not been studied. In addition, when the filler is highly filled, although the thermal conductivity is improved in the entire composite material including the thickness direction, the composite material becomes brittle and there is a problem in practicality.

  Accordingly, an object of the present invention is to provide a composite material of a thermally conductive filler and a matrix resin, which can have high thermal conductivity in the thickness direction without being highly filled with the thermally conductive filler. And

The present invention that has solved the above problems includes a step of applying a dispersion containing a photocurable resin and a dielectric filler dispersed in the resin to a support that is moved by being discharged from a nozzle, and the photocurable resin. A method for producing a composite film including a step of curing
When discharging the dispersion liquid from the nozzle, an electric field is applied by two electrodes provided on the upstream side and the downstream side in the moving direction of the support so as to sandwich the dispersion liquid in the nozzle. It is a manufacturing method. In the present invention, the applied electric field is preferably a sine wave having a frequency of 0.01 to 100 kHz, and the electric field strength is preferably 1 to 30 kV / mm. The dielectric filler is preferably non-spherical. In this invention, you may further perform the process of peeling a support body from a composite film.

  The present invention is also a composite film produced by the production method.

  The present invention further relates to a composite film including a dielectric filler and a cured product of a photocurable resin, wherein the thermal conductivity in the thickness direction is 1.2 times or more the thermal conductivity in the plane direction. It is. Here, in the composite film, a plurality of the dielectric fillers are arranged in a row in the thickness direction. The dielectric filler is a non-spherical filler, and is preferably oriented so that the major axis direction of the non-spherical filler is parallel to the thickness direction of the film. It is preferable that the content rate of a dielectric filler is 1-50 mass%. The composite film can be suitably used for a heat dissipation film.

  ADVANTAGE OF THE INVENTION According to this invention, the composite film which has favorable toughness is provided, having high thermal conductivity in the thickness direction. The composite film is suitable for a heat dissipation film that is used by being attached to a component that generates heat in an electronic device or an electric device.

The present invention includes a step (application step) of applying a dispersion liquid containing a photocurable resin and a dielectric filler dispersed in the resin to a support that is moved by being discharged from a nozzle, and the photocurable resin. A method for producing a composite film including a step of curing (curing step),
When discharging the dispersion liquid from the nozzle, an electric field is applied by two electrodes provided on the upstream side and the downstream side in the moving direction of the support so as to sandwich the dispersion liquid in the nozzle. It is a manufacturing method.

  The dielectric filler used in the present invention only needs to have a dielectric constant of 4 or more, for example, a paraelectric such as aluminum oxide, aluminum nitride, boron nitride, or silicon carbide, or a ferroelectric such as barium titanate. A filler can be used individually or in combination of 2 or more types. If the dielectric constant is less than 4, it is difficult to polarize when an electric field is applied, and there is a possibility that the dielectric fillers are hardly arranged, and the dielectric constant is preferably 10 or more.

  The shape of the dielectric filler is not particularly limited, but is preferably non-spherical. When a non-spherical dielectric filler is used, the effect of improving the thermal conductivity in the thickness direction can also be obtained by orienting the filler so that the major axis direction and the direction in which the electric field is applied are parallel. Therefore, the larger the aspect ratio (major axis / minor axis) of the filler used is, the higher the effect is obtained in the present invention.

  As the size of the dielectric filler, the average particle size is preferably 0.05 μm or more, and more preferably 0.1 μm or more. When the average particle size is smaller than 0.05 μm, the energy for arranging the dielectric fillers becomes smaller than the thermal energy.

  As a compounding quantity of a dielectric filler, it is preferable that it is 1-50 mass% with respect to the composite film after photocuring, and it is preferable that it will be 5-40 mass%. If the blending amount is less than 1%, sufficient thermal conductivity and mechanical strength may not be obtained, and if it exceeds 50%, the resulting film may be brittle.

  The photocurable resin is not particularly limited as long as it can be crosslinked and cured by ultraviolet rays, electron beams, etc., and has sufficient strength as a composite film after curing. For example, epoxy acrylate, urethane acrylate, polyester acrylate, Ether acrylate, reactive polyacrylate, carboxyl-modified reactive polyacrylate, polybutadiene acrylate, silicone acrylate, aminoplast resin acrylate, and the like can be used alone or in combination of two or more. In order to maintain the arrangement state of the filler, an addition reaction type resin having a small curing shrinkage is preferable. Further, the photocurable resin usually contains a photopolymerization initiator.

  About the method of disperse | distributing a dielectric filler to photocurable resin, what is necessary is just to disperse | distribute using a well-known disperser. For example, when the viscosity is 20 Pa · s or less, dispersion by ultrasonic irradiation, bead mill, ball mill, or the like is effective, and when the viscosity exceeds 20 Pa · s, by wing stirring, centrifugal stirring by rotation / revolution, three rolls, etc. Dispersion is effective.

  The viscosity of the dispersion is preferably 10 to 100 Pa · s. If it is less than 10 Pa · s, convection is likely to occur when an electric field is applied, and in the case of a filler having a large specific gravity, sedimentation may occur and the arrangement state may not be maintained. On the other hand, if it is greater than 100 Pa · s, the polarization filler generated by the electric field is difficult to move due to the resistance of viscosity, and may not be arranged when passing through the nozzle.

  Even if a resin component other than a photocurable resin, a filler component other than a dielectric filler, an additive such as a surfactant, a solvent, or the like is added to the dispersion within a range that does not impair the object of the present invention. Good.

  The support is not particularly limited as long as the dispersion can be applied and cured. For example, polyester film (eg, polyethylene terephthalate film), polyimide film, aluminum foil, polytetrafluoroethylene film, etc. Can be used. In addition, when a support is unnecessary depending on the use of the composite film, it is preferable to select a material that can be easily peeled off, such as a release-treated one.

  In the present invention, when the dispersion liquid is discharged from the nozzle in the coating step, an electric field is applied by two electrodes provided on the upstream side and the downstream side in the moving direction of the support so as to sandwich the dispersion liquid in the nozzle. To do. Thereby, the dielectric filler is arranged in the dispersion along the direction corresponding to the thickness direction of the film. This arrangement of dielectric fillers is preferably performed over as long a distance as possible in the thickness direction of the film. However, even if several fillers are arranged in a row, the effect of improving the thermal conductivity in the thickness direction can be obtained. On the other hand, when using a non-spherical filler, before the alignment takes place, first, the orientation of the filler occurs so that the major axis direction of the filler and the direction in which the electric field is applied are parallel, and this orientation causes the heat conduction in the thickness direction. A rate improvement effect is obtained. Therefore, in this case, the electric field may be applied to such an extent that the dielectric fillers are slightly arranged.

  The two electrodes are preferably arranged at the same height. The electrode may be coated with dielectric glass. By coating the dielectric glass, the conduction current can be suppressed and an electric field can be stably applied.

  For the electric field to be applied, application conditions that cause the arrangement of the dielectric fillers may be appropriately selected. In the case of a direct current electric field, the filler may be electrophoresed, and therefore an alternating electric field is preferable to a direct current electric field. Moreover, it is preferable that it is a sine wave.

  The frequency of the electric field is preferably 0.01 kHz to 100 kHz. If it is less than 0.01 kHz, there is a risk that dielectric breakdown may occur due to mechanical instability of the electric fluid, and if it exceeds 100 kHz, dielectric breakdown tends to occur due to high-frequency heat generation.

  The electric field strength is preferably 1 to 30 kV / mm. If it is less than 1 kV / mm, the dielectric filler may not be arranged, and if it is more than 30 kV / mm, dielectric breakdown may occur due to dielectrophoresis.

  In the coating step, the support is moved at such a speed that the arrangement of the dielectric fillers along the direction corresponding to the thickness direction of the film is maintained. Moreover, according to the use of a composite film, it is good to adjust suitably the moving speed of a support body, and the application quantity of a dispersion liquid so that the composite film of desired thickness may be obtained.

  The curing step can be carried out by irradiating with ultraviolet rays, electron beams or the like according to a known method. In order to maintain the arrangement of the dielectric fillers, it is preferable to cure immediately after applying the dispersion.

  In the present invention, when a support is not required in consideration of the application, the step of peeling the support from the composite film may be further performed according to a known method.

  An example of an embodiment of the present invention is shown in FIG.

  In FIG. 1, a part of the nozzle 1 (upstream portion and downstream portion of the nozzle 1 with respect to the moving direction of the support 6) has a function as an electrode, whereby a pair of electrodes 2 are connected to the nozzle. 1 is provided on the upstream side and the downstream side in the moving direction of the support 6 so as to sandwich the dispersion liquid 5 in it. These electrodes 2 are insulated and separated. The dispersion 5 includes a non-spherical dielectric filler 3 and a photocurable resin 4. In FIG. 1, a part of the nozzle 1 is an electrode 2, but the electrode may be attached inside the nozzle. The discharge port of the nozzle 1 has a rectangular cross-sectional shape, and the long side direction of the rectangle corresponds to the width direction of the film, and the short side direction of the rectangle corresponds to the thickness direction of the film.

  An electric field is applied between the pair of electrodes 2. In FIG. 1, since an electric field is applied parallel to the moving direction of the support 6 (the direction of the arrow below the support 6), the nozzle 1 is aspherical in the direction corresponding to the film thickness direction. The dielectric 3 is first oriented and further aligned.

  Dispersion liquid 5 in which dielectric fillers 3 are arranged at the tip of nozzle 1 sandwiched between electrodes 2 is applied onto support 6, and dielectric 3 is aligned so that the major axis direction is parallel to the thickness direction of the film. The plurality of dielectrics 3 are aligned and arranged in the thickness direction of the film.

  The applied dispersion 5 is irradiated with ultraviolet rays from a UV lamp 7 to cure the photocurable resin 4, whereby a composite film can be obtained.

  In the composite film obtained by the manufacturing method of the present invention, since the dielectric fillers are arranged in the thickness direction, the thermal conductivity in the thickness direction is higher than that in the plane direction. In particular, the thermal conductivity in the thickness direction is 1.2 times or more the thermal conductivity in the plane direction.

  Therefore, the present invention is also a composite film including a dielectric filler and a cured product of a photocurable resin, wherein the thermal conductivity in the thickness direction is 1.2 times or more the thermal conductivity in the plane direction. It is a composite film (the upper limit of magnification is determined by the type of matrix such as a dielectric filler and a photocurable resin).

  In the composite film, a plurality of dielectric fillers are arranged in a row in the thickness direction. For this reason, the composite filler is not highly filled, that is, the composite film is not brittle, High thermal conductivity is obtained. Here, the dielectric filler is a non-spherical filler, and the non-spherical filler is preferably oriented so that the major axis direction of the non-spherical filler is parallel to the thickness direction of the film. Directional thermal conductivity is higher. The content rate of a dielectric filler is 1-50 mass%, for example.

  The size (length, width and thickness) of the composite film may be appropriately determined according to the application.

  Since the composite film of the present invention has high thermal conductivity in the thickness direction and good toughness, it is preferably used for a heat dissipation film that is used by being attached to a component that generates heat in an electronic device or an electric device. be able to.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these Examples.

Example 1
A polyurethane acrylate dispersion containing 8.5% by mass of boron nitride having a viscosity of 33 Pa · s with the formulation shown in Table 1 was prepared. Next, the dispersion liquid in the tank was discharged from the tip of the nozzle while applying an electric field in the moving direction of the support from the two electrodes arranged across the nozzle with the pressure of air. At this time, the electric field applied to the tip of the nozzle was a sine wave having a frequency of 10 kHz and an intensity of 10 kV / mm, and the discharge amount was set to 5 g / min by adjusting the gap width of the discharge port of the nozzle. Moreover, although the dispersion liquid discharged from the nozzle is applied to the support, the coating thickness is determined by the moving speed. In this example, the moving speed of the support was 80 mm / min, and the coating thickness was 200 μm. The dispersion applied to the support was immediately cured by UV irradiation. The UV irradiation was performed for 7.6 seconds at a distance of 10 mm using LA-410UV-1 manufactured by Hayashi Watch Industry as a device and a 200 W ozoneless mercury xenon lamp (UV intensity: 4500 mW / cm ² ) as a UV lamp.

  Finally, the cured product of the dispersion was peeled from the support to obtain a boron nitride-polyurethane acrylate composite film. When the thermal conductivity in the thickness direction and the plane direction of this film was measured by the method described later, they were 0.41 W / mK and 0.30 W / mK, respectively. In addition, when the cross section of the film was observed with a scanning electron microscope (SEM), the orientation of the filler occurred in such a state that the major axis direction of the boron nitride filler was along the thickness direction of the film. It was observed that the sequence was caused in succession (see FIG. 2).

Example 2
A composite film was produced in the same manner as in Example 1 except that the frequency of the applied electric field was changed to 0.1 kHz. When the thermal conductivity in the thickness direction and the plane direction of this film was measured, they were 0.37 W / mK and 0.31 W / mK, respectively.

Comparative Example 1
A composite film was produced in the same manner as in Example 1 except that no electric field was applied. When the thermal conductivity in the thickness direction and the plane direction of this film was measured, they were 0.33 W / mK and 0.34 W / mK, respectively.

〔Thermal conductivity〕
The thermal diffusivity of the composite film was determined by the Xe flash method using an apparatus manufactured by Bruker AXS. Moreover, specific heat was calculated | required with the temperature increase rate of 10 degree-C / min using the DSC apparatus made from SII nanotechnology. Moreover, specific gravity was calculated | required by the butanol immersion method. And thermal conductivity was computed from thermal conductivity = thermal diffusivity x specific heat x specific gravity.

  The results are summarized in Table 2. As is clear from Table 2, it can be seen that the thermal conductivity in the thickness direction is increased by the production method of the present invention in which an electric field is applied to the dispersion.

It is the schematic which shows an example of the embodiment of the manufacturing method of this invention. 2 is a scanning electron microscope (SEM) photograph of a cross section of the composite film obtained in Example 1. FIG. The vertical direction of the photograph corresponds to the thickness direction of the composite film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nozzle 2 Electrode 3 Dielectric filler 4 Photocurable resin 5 Dispersion liquid 6 Support body 7 UV lamp

Claims (4)

A composite film comprising a step of applying a dispersion liquid containing a photocurable resin and a dielectric filler dispersed in the resin to a support that is moved by being discharged from a nozzle, and a step of curing the photocurable resin. A manufacturing method comprising:
When discharging the dispersion liquid from the nozzle, an electric field is applied by two electrodes provided on the upstream side and the downstream side in the moving direction of the support so as to sandwich the dispersion liquid in the nozzle. Manufacturing method.   The manufacturing method according to claim 1, wherein the applied electric field is a sine wave having a frequency of 0.01 to 100 kHz, and the electric field strength is 1 to 30 kV / mm.   The manufacturing method according to claim 1, wherein the dielectric filler is non-spherical. The manufacturing method in any one of Claims 1-3 which further includes the process of peeling a support body from a composite film .