JPH0787046B2 - Polymer composite dielectric - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a polymer composite dielectric.

<Prior Art> Most of the plastics used as a dielectric material have a dielectric ε <5, and a composite material of these plastics and a ferroelectric ceramic such as PZT (lead zirconium titanate) is formed. By doing so, it is considered that the dielectric constant is improved.

FIG. 4 (b) is a schematic view of a metal titanium composite material. By hydrothermally synthesizing metal titanium in a barium hydroxide solution,
A coating of barium titanate 21, which is a ferroelectric substance, is formed on the surface of metallic titanium 20. The metal titanium 20 has a particle size of about 30 μm, and the barium titanate 21 has a film thickness of about 2 μm. The applicants have already submitted (unpublished) a method for producing the metal titanium composite material.

<Problems to be Solved by the Invention> When a dielectric thin film material, for example, a polymer composite dielectric using a metal titanium composite as a filler is formed, the following method can be considered as a method for further increasing the dielectric constant.

(1) Increase the filling rate of the dielectric filler (filler).

(2) Use a dielectric filler and matrix resin having a large relative dielectric constant.

However, regarding (1), if the amount of the filler is unnecessarily increased, the properties of the plastic are impaired, and particularly the mechanical strength is significantly deteriorated, so that good composite characteristics cannot be obtained. On the other hand, with respect to (2), when a dielectric filler and a matrix having a high dielectric constant are used, the dielectric loss tan δ becomes large, so that there is a limit in using it for dielectric applications such as electric signal transmission. From this situation,
Although a composite dielectric having a high function having both a high dielectric constant and a reinforcing property of the base material is desired, a composite dielectric effective for practical use has not been formed yet.

It is an object of the present invention to provide a novel composite dielectric material that satisfies the above demands by applying the technique previously submitted by the present applicants.

<Means for Solving the Problems> The polymer composite dielectric of the present invention is a matrix in which a dielectric material in which a titanate-based dielectric coating is formed on the surface of titanium metal having anisotropy is a polymer resin. It is characterized by being dispersed as a filler in a directional state.

<Operation> As shown in FIG. 1, Ti particles having metallic titanium 1a on the inside and BaTiO ₃ 1b which is a ferroelectric substance coated on the surface are used as filler 1 in the medium of matrix resin 3 made of polymer resin. FIG. 2 shows a schematic diagram in the case where electrodes 4 are attached to both ends of a composite body formed by dispersing the same in a state where a voltage is applied by an AC power source 5, and a simplified equivalent circuit thereof is shown in FIG.

R _Ti is a resistance component per one metallic titanium particle that serves as a core, C
_BT is the capacitance of the BaTiO ₃ coating layer on the surface of titanium metal particles (the loss is omitted as it is sufficiently small), R _mat and C _mat are constants when the complex impedance of the matrix material is expressed by a parallel equivalent circuit, and R _mat Is the capacity component of the matrix resin, and C _mat is the loss component of the matrix resin.

Now, the filler particles are BaTiO ₃ as shown in FIG. 4 (a).
If a spherical particle composed of only the capacitance C _BT1 per one _{particle, C BT1 = 4πε 0 ε r} a: is a (a particle radius) ... (1) in FIG. 4 (b) On the metal titanium surface as shown
In the case of coating BaTiO ₃ , (A: particle size of metallic titanium, b: particle outer diameter). From equations (1) and (2), If the film thickness ba of BaTiO ₃ is extremely small, Therefore, the apparent capacitance can be increased as compared with the case where the particles made of only BaTiO ₃ are used as the filler, and as a result, the effective dielectric constant is increased.

FIG. 5 is a graph showing the relationship between the resistance R _Ti of the metallic titanium particle portion shown in FIG. 3 and its dielectric loss tan δ.
As shown in FIG. 5, the dielectric loss tan δ largely depends on the resistance R _Ti . That is, tan δ also decreases as the resistance R _Ti decreases. In the case of the present invention, R _Ti is very small (resistivity ρ = 0.478 × 10 ⁻⁴ Ω · cm) because it is a particle whose core is metal titanium, that is, conductor, and therefore tan δ
Is also very small.

Metallic titanium, which is the core, can form thin films in various shapes such as plate, fiber, rod, and so on.For example, by forming a ferroelectric thin film such as BaTiO _{3 on} the core of metal titanium whiskers, it is anisotropic. A composite dielectric material in which a dielectric material is formed, and in which a filler is dispersed in a matrix made of a polymer resin in a directional state is a high dielectric constant, low dielectric loss and mechanical properties as a whole. Highly functional material with high dynamic strength. In addition, in the composite dielectric in which the filler is dispersed in a directional state as described above, the difference in relative permittivity and dielectric loss can be increased depending on the directional property.

<Example> Example 1) A metal titanium powder and barium hydroxide were mixed at a molar ratio of 1: 1 and water was added to make the barium concentration 1 mol%, and the mixture was filled in an autoclave and kept at 250 ° C for 24 hours. By performing the hydrothermal reaction of BaTiO ₃ as shown in FIG. 4 (b).
Titanium particles are synthesized with the film coated to a thickness of about 10 μm. Table 1, the electrical characteristics of the coated particles of titanium, BaTiO ₃ as shown in FIG. 4 (a)
The case of particles consisting of only is taken as a comparative example, and the case under the conditions of 25 ° C. and 1 MHz is shown. As shown in Table 1, BaTiO ₃ coated Ti particles as compared to particles consisting only of BaTiO _3, the dielectric constant is high, the dielectric loss tanδ has a first very small about 30 minutes.

Further, the coated titanium particles are mixed as a filler with a matrix resin such as epoxy in the present embodiment at a ratio of 50 wt% to form a composite dielectric. Second
The table shows the electrical characteristics after the composite under the conditions of 25 ° C and 1MHz, using the Ti particles coated with the BaTiO ₃ film as the filler and the particles made of only BaTiO ₃ as the filler. It is a thing.

As shown in Table 2, when BaTiO ₃ coated Ti particles are used as a filler, the relative dielectric constant is about three times as high as when the particles made of BaTiO ₃ alone are used as a filler, and the dielectric loss is about 10 minutes. It is 1.

Example 2) A film of barium titanate was formed on the surface of fibrous metallic titanium in the same manner as in Example 1 using fiber-shaped metallic titanium having a diameter of 1 μm and a length of 150 μm. This was used as a filler and nylon 6 was used as a matrix resin to form a composite dielectric. The filler content is 50 wt%, and the kneading and molding of the filler and matrix is performed by roll pressing,
The orientation of the filler was applied. Third as an example of mechanical properties
The table shows tensile strength, flexural modulus and flexural stress. Tensile strength is defined as the yield point at which the material breaks or the larger load at breakage is divided by the cross-sectional area of the test piece after the stress-strain curve when the material is pulled at a constant speed is bounded by the yield point of the curve. It is the value. Further flexural modulus
S _Y (kg / mm) can be expressed by the following equation (4).

L: Distance between fulcrums (mm) b: Specimen width (mm) d: Specimen thickness (mm) P: Load (kg) Y: Deformation (mm) In addition, bending strength _SF (kg / mm ² ) is the maximum stress until the test piece breaks under bending load, and can be expressed by the following equation (5).

Table 3 shows the mechanical strength characteristics of the composite resin of the filler and the matrix resin after the composite, as compared with the case of the matrix resin before the composite alone. Nylon 6 was used as the matrix resin, and the filling rate of the filler was 50 when composited.
This is the case when wt% is set.

As shown in Table 3, the tensile strength, bending elastic modulus, and bending stress after compounding are higher than those before compounding. This is because the filler has a fibrous shape, so that it is possible to obtain the effect of strengthening the base material by pulling and bending by compounding.

Next, Table 4 shows the electrical characteristics of the filler and the matrix resin after the composite, in comparison with the case where only the matrix resin before the composite was used. Nylon 6 is used as the matrix resin, and the filling rate of the filler is
This is the case when 50 wt% is set.

As shown in Table 4, since the filler has shape anisotropy, the electrical characteristics when viewed from the direction perpendicular to or parallel to the long axis of the fiber are different, and the fiber has anisotropy. .

<Effects of the Invention> As described above, according to the polymer composite dielectric of the present invention, a dielectric material in which a titanic acid-based dielectric film is formed on the surface of titanium metal having anisotropy is used as a polymer. As the filler is dispersed in the resin matrix in a directional state, it is possible to increase the relative permittivity as a whole and to reduce the dielectric loss. Since it can be improved and the fiber can be reinforced, the mechanical strength can be improved and a high-performance material can be obtained. Further, in the relative permittivity and the dielectric loss, the difference between them can be increased depending on the directionality. Therefore, for example, when this polymer composite dielectric is used as a capacitor, the unity area can be selected by selecting the directionality. Effective usage can be realized, for example, the capacity per hit can be dramatically increased.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is a schematic circuit connection diagram used in an experiment of the embodiment of the present invention, FIG. 3 is an equivalent circuit diagram thereof, and FIG. 4 is an explanation of filler particles. 5 and FIG. 5 are graphs showing the relationship between the resistance of titanium metal particles and dielectric loss, and FIG. 6 is a diagram showing the direction during electrical measurement of the examples. 1 …… Filler 1a …… Metal titanium 1b …… Titanate dielectric 3 …… Matrix resin

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Claims (1)

[Claims] 1. A dielectric material in which a titanic acid-based dielectric film is formed on the surface of titanium metal having anisotropy is dispersed as a filler in a matrix made of a polymer resin in a directional state. Polymer composite dielectrics.