High dielectric constant film

Abstract

To provide a high dielectric constant film with a high relative permittivity and a low dielectric loss tangent. [Solution] A high dielectric constant film containing a thermoplastic resin and an inorganic filler, wherein the relative permittivity of the high dielectric constant film at 10 GHz is 10 or more, and the dielectric loss tangent of the high dielectric constant film at 10 GHz is 0.01 or less.

Description

Technical Field

[0001] The present invention relates to a high dielectric constant film.

Background Art

[0002] With the increase in the capacity and variety of communication information, the communication speed is accelerating. To cope with the increase in communication speed, it is necessary to increase the frequency of signals. Among transmission losses, dielectric losses caused by dielectrics such as resins and ceramics tend to decrease as the dielectric tangent decreases. Although ceramics have a high relative dielectric constant and a low dielectric tangent, it is difficult to increase the area. As a film material used for capacitors and the like, a high dielectric constant film containing a thermoplastic resin and an inorganic filler is known (see Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a high dielectric constant film having a high relative dielectric constant and a low dielectric tangent.

Means for Solving the Problems

[0005] To solve the above problems, the present invention adopts the following configuration. [1] A high dielectric constant film containing a thermoplastic resin and an inorganic filler, wherein the relative dielectric constant of the high dielectric constant film at 10 GHz is 10 or more, and the dielectric tangent of the high dielectric constant film at 10 GHz is 0.01 or less. [2] The high dielectric constant film according to [1], wherein the inorganic filler comprises one or more selected from the group consisting of calcium titanate, barium titanate, and titanium oxide. [3] The high dielectric constant film according to [1] or [2], wherein the inorganic filler content is 10 to 70% by mass. [4] The high dielectric constant film according to any one of [1] to [3], wherein the inorganic filler is either spherical particles or needle-shaped particles. [5] The high dielectric constant film according to any one of [1] to [4], wherein the dielectric loss tangent of the thermoplastic resin at 10 GHz is 0.01 or less. [6] The high dielectric constant film according to any one of [1] to [5], wherein the melt flow rate (MFR) of the thermoplastic resin is 50 g / 10 min or less. [7] The high dielectric constant film according to any one of [1] to [6], wherein the thermoplastic resin comprises an olefin resin. [8] The high dielectric constant film according to any one of [1] to [7], wherein the thermoplastic resin comprises a polyethylene resin. [9] The high dielectric constant film according to any one of [1] to [8], wherein when dynamic viscoelasticity (DMA) is measured for the high dielectric constant film under the conditions of a heating rate of 5°C / min and a frequency of 1 Hz, the storage modulus at 40°C is 500 MPa or less.

[10] A high dielectric constant film according to any one of [1] to [9], for use in antennas or high-frequency substrates. [Effects of the Invention]

[0006] According to the present invention, a high dielectric constant film is provided, which has a high relative permittivity and a low dielectric loss tangent. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic cross-sectional view showing an example of a high dielectric constant film according to one embodiment of the present invention. [Modes for carrying out the invention]

[0008] The present invention will be described below based on preferred embodiments.

[0009] A high dielectric constant film according to one embodiment of the present invention contains a thermoplastic resin and an inorganic filler. The relative permittivity of the high dielectric constant film at 10 GHz is 10 or more, and the dielectric loss tangent of the high dielectric constant film at 10 GHz is 0.01 or less.

[0010] Because the dielectric loss tangent of the high dielectric constant film at 10 GHz is 0.01 or less, it can reduce radio wave loss in applications where high-frequency radio waves are used, such as high-frequency communication applications. Because the relative permittivity of the high dielectric constant film at 10 GHz is 10 or more, it also possesses radio wave absorbing properties, which can contribute to the miniaturization of antenna substrates and the like.

[0011] Generally, the dielectric properties of a resin are easily governed by the dipole polarization caused by the polar groups in the resin. Therefore, resins with low dielectric loss tangent, which result in low losses, generally also have low relative permittivity. Conversely, resins with high relative permittivity tend to have high dielectric loss tangent. For this reason, to obtain a material with high relative permittivity and low dielectric loss tangent, it is preferable to use a composition containing an inorganic filler with high relative permittivity and low dielectric loss tangent, and a resin with low relative permittivity and low dielectric loss tangent.

[0012] The relative permittivity and dielectric loss tangent of the high dielectric constant film can be measured, for example, using a dielectric constant measuring device based on the cavity resonator method in accordance with JIS C 2565 (Test method for ferrite magnetic cores for microwaves).

[0013] <Inorganic filler> The high dielectric constant film of this embodiment contains an inorganic filler. The inorganic filler is preferably one with a high relative dielectric constant, and more preferably one with a low dielectric loss tangent.

[0014] Examples of the inorganic filler include calcium titanate, strontium titanate, barium titanate, magnesium titanate, zinc titanate, bismuth titanate, titanium oxide, lanthanum oxide, etc. It is preferable that the inorganic filler contains one or more selected from the group consisting of calcium titanate, barium titanate, and titanium oxide.

[0015] The content of the inorganic filler in the high dielectric constant film is preferably 10 to 70% by mass. When the content of the inorganic filler is at least the lower limit value, it is easy to obtain a high dielectric constant film with a high relative dielectric constant and a low dielectric tangent. When the content of the inorganic filler is at most the upper limit value, the film forming property of the high dielectric constant film is likely to be improved. The content may be 30% by mass, 40% by mass, etc.

[0016] Among the inorganic fillers, the total content of one or more selected from the group consisting of materials for the purpose of imparting high dielectric constant, such as calcium titanate, barium titanate, and titanium oxide, is preferably 10 to 70% by mass. The high dielectric constant film may contain other inorganic fillers, such as flame retardants, fillers, pigments, etc., for purposes different from the purpose of imparting high dielectric constant.

[0017] The particle shape of the inorganic filler is not particularly limited, but it is preferably either spherical particles or needle-like particles. The particle shape may be a shape that is regarded as spherical or needle-like when observed with an electron microscope. When the inorganic filler has the particle shape, even if the content of the inorganic filler is high, the film forming property of the high dielectric constant film is improved, and it is easy to achieve both a high filling rate and dielectric properties. Other particle shapes include plate-like particles, confetti-like particles, amorphous particles, etc.

[0018] The particle size of the inorganic filler is not particularly limited, but it is preferably smaller than the thickness of the high dielectric constant film, and preferably 50% or less, 30% or less, or 10% or less of the thickness of the high dielectric constant film. When the average particle size of the inorganic filler is appropriately small, the handleability, moldability, etc. of the resin composition containing the thermoplastic resin and the inorganic filler can be improved.

[0019] <Thermoplastic resin> The high dielectric constant film of this embodiment contains a thermoplastic resin. The thermoplastic resin is not particularly limited, and examples thereof include polyolefin resins such as polyethylene-based resins and polypropylene-based resins, acrylic resins, polynorbornene-based resins, polystyrene-based resins, polyester-based resins, polycarbonate-based resins, etc. The high dielectric constant film may use one of these resins alone or in combination of two or more.

[0020] The polyethylene-based resin is a homopolymer of ethylene or a copolymer obtained by copolymerizing ethylene mainly with other comonomers. Examples of the comonomer of the polyethylene-based resin include α-olefins such as propylene, 1-butene, 1-hexene, 1-octene, and methylpentene.

[0021] Specific examples of the polyethylene-based resin include polyethylenes such as high-density polyethylene resin (HDPE), medium-density polyethylene resin (MDPE), linear low-density polyethylene resin (LLDPE), very-low-density polyethylene resin (VLDPE), and low-density polyethylene resin (LDPE). In addition, the comonomer copolymerized with ethylene in the polyethylene-based resin may contain a polar vinyl-based monomer or a cycloolefin-based monomer.

[0022] Examples of the polar vinyl monomers include vinyl acetate, vinyl alcohol, acrylic acid esters, methacrylic acid esters, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride. Vinyl alcohol units can be produced by copolymerizing vinyl ester monomers such as vinyl acetate and then saponifying them.

[0023] Examples of the cycloolefin include cyclopentene, cyclohexene, norbornene, norbornadiene, and dicyclopentadiene. The ethylene copolymer may further contain α-olefins such as propylene, 1-butene, 1-hexene, 1-octene, and methylpentene as comonomers.

[0024] Specific examples of polyethylene resins containing polar vinyl monomers or cycloolefin monomers include ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl alcohol copolymer (EVOH), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylate copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene-cycloolefin copolymer (COC), and ionomer resin (ION).

[0025] The aforementioned polypropylene resin is a homopolymer of propylene, or a copolymer obtained by copolymerizing propylene with other comonomers. Specific examples of polypropylene resins include homopolypropylene, block polypropylene, and random polypropylene.

[0026] The dielectric loss tangent of the thermoplastic resin at 10 GHz is preferably 0.01 or less. By having a dielectric loss tangent of the thermoplastic resin that is below the upper limit, radio wave loss can be reduced in applications where high-frequency radio waves are used, such as high-frequency communication applications.

[0027] Generally, electromagnetic waves with frequencies lower than light rays (e.g., 3 THz or less) are called radio waves. For high-frequency applications, relatively high-frequency radio waves (e.g., 10 kHz or more) are used. Specific examples include long waves (LF), medium waves (MF), short waves (HF), very high frequency waves (VHF), ultra-high frequency waves (UHF), centimeter waves (SHF), millimeter waves (EHF), and submillimeter waves.

[0028] The dielectric loss tangent of the thermoplastic resin can be measured, for example, using a dielectric constant measuring device based on the cavity resonator method in accordance with JIS C 2565 (Test Method for Microwave Ferrite Magnetic Cores). The measurement sample of the thermoplastic resin may be, for example, a film molded without the inorganic filler.

[0029] The melt flow rate (MFR) of the thermoplastic resin is preferably 50 g / 10 min or less. By keeping the MFR of the thermoplastic resin below the upper limit, the processability of the high dielectric constant film can be improved.

[0030] The MFR of the thermoplastic resin can be measured in accordance with JIS K 7210 (Plastics - Method for determining melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastic plastics). If the thermoplastic resin is a polypropylene-based resin, JIS K 6921 should also be referred to, and if the thermoplastic resin is a polyethylene-based resin, JIS K 6922 should also be referred to.

[0031] When dynamic viscoelasticity (DMA) measurements are performed on the high dielectric constant film under the conditions of a heating rate of 5°C / min and a frequency of 1 Hz, it is preferable that the storage modulus at 40°C is 500 MPa or less. By having the storage modulus below the upper limit, the elasticity of the high dielectric constant film is suppressed.

[0032] <An embodiment of a high dielectric constant film> Figure 1 is a schematic cross-sectional view showing an example of a high dielectric constant film of this embodiment. The high dielectric constant film 10 is formed from a resin composition 11 containing the thermoplastic resin and the inorganic filler. The high dielectric constant film 10 has surfaces 12 and 13 on both sides in the thickness direction, respectively.

[0033] The high dielectric constant film can be manufactured by molding a resin composition containing the thermoplastic resin and the inorganic filler into a film. The resin composition may contain additives such as colorants, release agents, ion scavengers, flame retardants, antioxidants, slip agents, and antiblocking agents. Known film-forming methods include melt-kneading the blended materials in an extruder and then forming a film with a die. Examples of blending methods for the resin composition include dry blending and melt blending.

[0034] From the viewpoint of dispersing the inorganic filler in the thermoplastic resin at a high concentration and with good quality, it is preferable to use a twin-screw kneader. A twin-screw kneader is an extruder equipped with two screw shafts that rotate inside a barrel. In this case, the rotation directions of the two screw shafts may be the same or different (opposite rotation). A kneader, roll, single-screw kneader, etc., may be used to blend the resin composition.

[0035] The thickness of the high dielectric constant film is not particularly limited, but depending on the application, it is preferably 0.01 to 5 mm, and more preferably 0.02 to 2 mm. Since the high dielectric constant film is flexible, it can also be wound into a roll. It is preferable that both sides of the high dielectric constant film in the thickness direction are flat planes.

[0036] Applications for the high dielectric constant film include antennas and high-frequency substrates. Conductors such as antennas, high-frequency circuits, and wiring may be arranged on at least one of the two surfaces of the high dielectric constant film in the thickness direction. The high dielectric constant film has excellent film-forming properties and handling properties, making it easy to produce in large areas. The conductor is not particularly limited, but examples include metals such as copper, gold, silver, and aluminum.

[0037] In the aforementioned applications, a wireless system using radio waves such as microwaves can be employed. The transmitting antenna converts power supplied from a high-frequency circuit into radio waves and radiates them into the air. The receiving antenna receives radio waves propagating through the air, converts them into power, and supplies it to the high-frequency circuit. The antenna may be a transceiver antenna capable of both transmitting and receiving. The power may be an electrical signal for communication or electrical energy for energy transmission.

[0038] The aforementioned high dielectric constant film can be used as a diffusion film. As the frequency of radio waves increases, their directivity and directionality increase, thus limiting the direction in which the radio waves can be received. By irradiating a diffusion film with radio waves propagating through the air, the radio waves can be diffusely reflected. Examples of diffraction structures used in diffusion films include diffraction gratings, holograms, or surface irregularities (interfaces with the atmosphere).

[0039] The aforementioned high-dielectric-constant film can be used in metasurface reflectors. In a flat reflector without irregularities, specular reflection occurs where the angle of incidence and the angle of reflection are approximately equal and the reflections are on the same plane. By arranging a metasurface structure made of metal or the like with a structure sufficiently smaller than the wavelength of the radio wave on the high-dielectric-constant film, it becomes possible to reflect radio waves in a direction different from specular reflection. At high frequencies, the dimensions of the metasurface also increase with wavelength, so it is advantageous to use a high-dielectric-constant film that can be easily made into a large-area structure.

[0040] The aforementioned high dielectric constant film can be used as a lens film for Fresnel lenses and the like. By arranging a structure that focuses radio waves, such as a concentric conductive pattern, on the high dielectric constant film, a radio wave lens function can be realized. Examples of radio wave lens functions include converging radio waves that are incident in a diffused state and emitting them in a focused state.

[0041] The aforementioned high dielectric constant film can be used as an electromagnetic wave absorbing film. The energy of the electromagnetic waves absorbed by the electromagnetic wave absorbing film may be converted into heat and released into the air, or released into the ground through grounding. For heat dissipation, heat sinks, heat pipes, graphite sheets, heat dissipation fins, etc., may be used. When transmitting electrical energy, the power output becomes high, and the amount of heat generated due to losses also increases, so it is advantageous to use a high dielectric constant film that can be easily made into a large area.

[0042] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can also be adopted. [Examples]

[0043] The present invention will be described in more detail below with reference to specific examples. However, the present invention is not limited in any way to the examples shown below.

[0044] <Manufacturing of high dielectric constant films> The high dielectric constant films of Examples 1 to 5 were manufactured as shown below.

[0045] (Example 1) A high dielectric constant film with a thickness of 0.5 mm was manufactured by melt extrusion using a mixture of 44% by mass of ethylene-vinyl acetate copolymer (EVA, EV150 manufactured by Mitsui Dow Polychemicals) and 56% by mass of spherical particles of calcium titanate (CTP230706 manufactured by Denka).

[0046] (Example 2) The high dielectric constant film of Example 2 was manufactured in the same manner as in Example 1, except that 80% by mass of ethylene-vinyl acetate copolymer (EVA, EV150 manufactured by Mitsui Dow Polychemicals) and 20% by mass of needle-shaped titanium dioxide particles (FTL-300 manufactured by Ishihara Sangyo Co., Ltd.) were blended.

[0047] (Example 3) A high dielectric constant film of Example 3 was manufactured in the same manner as in Example 1, except that 50% by mass of ethylene-vinyl acetate copolymer (EVA, EV150 manufactured by Mitsui Dow Polychemicals) and 50% by mass of spherical particles of barium titanate (TITONEX manufactured by Sakai Chemical Industry Co., Ltd.) were blended.

[0048] (Example 4) A high dielectric constant film of Example 4 was manufactured in the same manner as in Example 1, except that it was blended with 44% by mass of LLDPE (manufactured by Ube Maruzen Polyethylene, 015AN) and 56% by mass of spherical particles of calcium titanate (manufactured by Denka, CTP230706).

[0049] (Example 5) A high dielectric constant film of Example 5 was manufactured in the same manner as in Example 1, except that it was formulated with 70% by mass of ethylene-vinyl acetate copolymer (EVA, EV150 manufactured by Mitsui Dow Polychemicals), 20% by mass of spherical particles of calcium titanate (Denka, CTP230706), and 10% by mass of spherical particles of titanium dioxide.

[0050] <Evaluation of relative permittivity and dielectric loss tangent> The relative permittivity and dielectric loss tangent of the high-dielectric-constant film at 10 GHz were measured using a dielectric constant measurement device based on the cavity resonator method.

[0051] <Evaluation of dynamic viscoelasticity> The storage modulus (E') of the high dielectric constant film was measured at 40°C by dynamic viscoelasticity (DMA) measurement under the conditions of a heating rate of 5°C / min and a frequency of 1 Hz.

[0052] [Table 1]

[0053] (Summary) As shown in Table 1, all of the high-dielectric-constant films of this embodiment have high relative permittivity and low dielectric loss tangent, making them excellent as high-dielectric-constant films for high-frequency applications. [Industrial applicability]

[0054] The present invention can provide a high dielectric constant film with a high relative permittivity and a low dielectric loss tangent. [Explanation of symbols]

[0055] 10... High dielectric constant film, 11... Resin composition, 12,13... Surface

Claims

1. A high dielectric constant film containing a thermoplastic resin and an inorganic filler, The relative permittivity of the aforementioned high dielectric constant film at 10 GHz is 10 or more. A high dielectric constant film wherein the dielectric loss tangent of the high dielectric constant film at 10 GHz is 0.01 or less.

2. The high dielectric constant film according to claim 1, wherein the inorganic filler comprises one or more selected from the group consisting of calcium titanate, barium titanate, and titanium oxide.

3. The high dielectric constant film according to claim 1, wherein the inorganic filler content is 10 to 70% by mass.

4. The high dielectric constant film according to claim 1, wherein the inorganic filler is either spherical particles or needle-shaped particles.

5. The high dielectric constant film according to claim 1, wherein the dielectric loss tangent of the thermoplastic resin at 10 GHz is 0.01 or less.

6. The high dielectric constant film according to claim 1, wherein the melt flow rate (MFR) of the thermoplastic resin is 50 g / 10 min or less.

7. The high dielectric constant film according to claim 1, wherein the thermoplastic resin includes an olefin-based resin.

8. The high dielectric constant film according to claim 1, wherein the thermoplastic resin includes a polyethylene resin.

9. The high dielectric constant film according to claim 1, wherein when dynamic viscoelasticity (DMA) is measured for the high dielectric constant film under the conditions of a heating rate of 5°C / min and a frequency of 1 Hz, the storage modulus at 40°C is 500 MPa or less.

10. The high dielectric constant film according to claim 1, which is for use in antennas or high-frequency substrates.

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