JP2007248097A - Method and apparatus for measuring anisotropy of dielectric constant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure an anisotropy of a dielectric constant using one resonator without rotating a sample. <P>SOLUTION: A cylindrical cavity resonator composed of a pair of bottomed cylindrical members opposed to each other so as to leave a gap is excited in a TE<SB>11n</SB>(n is a natural number) mode and the sample is arranged to the gap. Two resonance frequencies of TE<SB>11n</SB>mode degenerated to one before the arrangement of the sample and separated into two by the relief of degeneracy due to the arrangement of the sample are measured and the maximum and minimum specific inductivities in an in-plane direction of the sample are calculated from two resonance frequencies or the anisotropic degrees of the specific inductivities in the in-plane direction of the sample are calculated on the basis of the difference between two resonance frequencies to measure the dielectric constant anisotropy of the sheetlike or sheetlike sample having an anisotropy in dielectric constant in the in-plane direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a measuring method and apparatus for measuring the dielectric anisotropy of a thin plate-like substrate such as plastic, rubber, and ceramic, and a sheet-like material such as paper, nonwoven fabric, and polymer film by microwaves.

  As a method for measuring the anisotropy of a polymer material such as a polymer film, a method based on birefringence is known. This method measures the birefringence or retardation (birefringence index × thickness) in the sheet surface, and can be measured while moving the sample (see Patent Document 1). However, this method based on birefringence has a problem that it is not possible to measure an opaque substance because it is necessary to measure by transmitting visible light (polarized light).

  In order to solve this problem, an orientation measuring device has been proposed that uses a microwave dielectric resonator to measure the orientation of a sheet-like sample by bringing a detection unit into direct contact with or close to one side of the sheet-like substance. (See Patent Document 2).

  This orientation measuring apparatus is based on the basic principle that the orientation of the sheet-like substance can be evaluated as the orientation of the dielectric constant. In this orientation measuring apparatus, a prismatic or cylindrical dielectric resonator having an opening inserted into a shield container is used, and a sheet-like substance as a sample is installed so as to cover the opening of the dielectric resonator. . Among the various resonance modes of the dielectric resonator, a resonance mode in which the electric field vector is parallel on the upper surface of the dielectric resonator and the electric field strength in the sample is as strong as possible is used for orientation measurement. Is done.

  The resonance frequency of the dielectric resonator decreases toward a lower frequency as the dielectric constant of the sample increases. When there is anisotropy of the dielectric constant in the surface of the sample, the amount of decrease in the resonance frequency is greatest when the direction of the large dielectric constant matches the direction of the electric field vector on the upper surface of the dielectric resonator. When the direction in which the dielectric constant is large and the direction of the electric field vector on the upper surface of the dielectric resonator are orthogonal, the amount of decrease in the resonance frequency is the smallest.

Therefore, if the sample is rotated once and the fluctuation of the resonance frequency is measured directly or indirectly, the degree of anisotropy of the dielectric constant in the surface of the sample can be evaluated. In addition, in the case of so-called on-line evaluation in which measurement is performed while moving the sheet-like material in the manufacturing process, instead of rotating the sample (sheet-like material), a plurality of directions are used so that the directions of the upper surface electric field vectors are different from each other. The dielectric resonators may be arranged close to each other.
Japanese Patent Laid-Open No. 4-89553 JP 2001-91476 A

  However, the above-described orientation measuring apparatus cannot perform measurement with high resolution unless a large number of dielectric resonators are arranged. Further, if the number of dielectric resonators increases, the cost increases, leading to an increase in the size of the device and the complexity of data processing.

  The present invention has been made in view of the above circumstances, and even for an opaque thin plate or sheet sample, the anisotropy of dielectric constant is measured using a single resonator without rotating the sample. It is an object of the present invention to provide a measuring method and apparatus that can be used.

The dielectric anisotropy measuring method of the present invention is a method for measuring the dielectric anisotropy of a thin plate-like or sheet-like sample having anisotropy in the in-plane direction. The following steps (A) to (D) are included.
(A) exciting a TE _11n (n is a natural number) mode of a cylindrical cavity resonator composed of a pair of bottomed cylindrical members facing each other with a gap;
(B) disposing the sample in the gap;
(C) Measure the resonance frequency f _L on the low frequency side and the resonance frequency f _H on the high frequency side of the TE _11n mode after sample placement, and (D) the resonance frequency f _L on the low frequency side and the resonance frequency on the high frequency side. Obtain the maximum relative permittivity ε _MAX and the minimum relative permittivity ε _MIN in the in-plane direction of the sample from f _H.
In the step (D), the maximum relative dielectric constant ε _MAX in the in-plane direction of the sample is approximately obtained from the resonance frequency f _L on the low frequency side, and the minimum ratio in the in-plane direction of the sample from the resonance frequency f _H on the high frequency side. The dielectric constant ε _MIN can also be obtained.

The second aspect of the dielectric anisotropy measuring method of the present invention is the difference between the two measured resonance frequencies f _L and f _H as a step (D) instead of the step (D) of the first aspect. Based on the above, the degree of anisotropy of the relative dielectric constant in the in-plane direction of the sample is obtained.
Here, the resonance frequencies f _L and f _H are the frequencies on the low frequency side and the high frequency side of the two resonance frequencies of the TE _11n mode which are separated from each other by the arrangement of the sample.

A dielectric anisotropy measuring apparatus according to the present invention includes a cylindrical cavity resonator formed of a pair of bottomed cylindrical members facing each other with a gap, and an excitation device that is provided on one end side of the resonator and introduces a microwave into the resonator. And a cylindrical cavity resonance device provided on the other end side of the resonator and provided with a detection device for detecting the microwave in the resonator, a microwave generation device for generating a microwave in the resonator by the excitation device, A microwave signal detection / analysis device that inputs and analyzes a microwave signal detected by the detection device, and a control device that controls the microwave generation device and the microwave signal analysis device. The control device detects the resonance frequency f _L on the low frequency side and the resonance frequency f _H on the high frequency side of the TE _11n mode after sample placement, and the detected two resonance frequencies f _L and f _H. And dielectric anisotropy calculating means for calculating the dielectric anisotropy of the sample based on the above.

The first form of the dielectric anisotropy calculating means is that the maximum relative dielectric constant ε _MAX and the minimum relative dielectric constant in the in-plane direction of the sample from the detected resonance frequency f _L on the low frequency side and resonance frequency f _H on the high frequency side. ε _MIN is calculated.
In this embodiment, the dielectric anisotropy calculating means approximately calculates the maximum relative dielectric constant ε _MAX in the in-plane direction of the sample from the resonance frequency f _L on the low frequency side, and from the resonance frequency f _H on the high frequency side. The minimum relative dielectric constant ε _MIN in the in-plane direction of the sample can be calculated.

In the second form of the dielectric anisotropy calculating means, an index representing the degree of anisotropy of the relative dielectric constant in the in-plane direction of the sample is based on the difference between the detected two resonance frequencies f _L and f _H. Is to be calculated.
Examples of such indicators are (f _H −f _L ) or (f _H −f _L ) / (f _H + f _L ).

The cylindrical cavity resonator is preferably such that an electromagnetic wave excitation loop antenna and an electromagnetic wave detection loop antenna are vertically attached to the bottom surface of each bottomed cylindrical member.
The cylindrical cavity resonator is preferably such that the electromagnetic wave excitation loop antenna and the electromagnetic wave detection loop antenna are provided at a position rotated 90 degrees as viewed from the center of the cross section of the cylindrical cavity resonator cylinder.
It is preferable that the cylindrical cavity resonator is further arranged so that the loop surface of the electromagnetic wave excitation loop antenna and the loop surface of the electromagnetic wave detection loop antenna are orthogonal to each other.

  The dielectric anisotropy measuring device of the present invention can be further provided with a sample moving mechanism for moving the sample so as to pass through the gap of the cylindrical cavity resonator, thereby making it an on-line measuring device.

The dielectric anisotropy measuring method of the present invention excites the TE _11n mode of the cylindrical cavity resonator, and the two resonance frequencies f _L and f of the TE _11n mode separated into two by decoupling the arrangement of the sample and releasing them. The maximum relative dielectric constant ε _MAX and the minimum relative dielectric constant ε _MIN in the in-plane direction of the sample are measured by measuring _H , or the in-plane direction of the sample based on the difference between the two resonance frequencies f _H and f _L The degree of anisotropy of the relative dielectric constant was determined.

Further, in the dielectric anisotropy measuring apparatus of the present invention, in the microwave signal detection / analysis apparatus for inputting and analyzing the microwave signal detected by the detection apparatus for detecting the microwave in the cylindrical cavity resonator, the detection means includes The TE _11n mode low-frequency resonance frequency f _L and high-frequency resonance frequency f _H of the TE _11n mode after sample placement are detected, and the dielectric anisotropy calculation means calculates the sample based on the two resonance frequencies f _L and f _H. The dielectric anisotropy of was calculated.

According to the dielectric anisotropy measuring method and apparatus of the present invention as described above, the dielectric constant is measured using a single cylindrical cavity resonator without rotating the sample with respect to an opaque thin plate-like or sheet-like sample. Can be measured.
At that time, a cylindrical cavity resonator in which an electromagnetic wave excitation loop antenna and an electromagnetic wave detection loop antenna are vertically attached to the bottom surface of each bottomed cylindrical member is used, or further, an electromagnetic wave excitation loop antenna and an electromagnetic wave are used. If the detection loop antenna is provided at a position rotated 90 degrees from the center of the cylindrical cross section of the cylindrical cavity resonator, separation of the resonance peak of the TE _11n mode due to the influence of the loop antenna is prevented. The error of dielectric anisotropy measurement can be reduced.

If the loop surface of the electromagnetic wave excitation loop antenna and the loop surface of the electromagnetic wave detection loop antenna are arranged so as to be orthogonal to each other, the sample is separated by inserting an anisotropic sample. It becomes easy to simultaneously detect and detect both the resonance peaks of the TE _11n mode.

  Further, in the measurement step (B), if online measurement is performed by moving the gap between the pair of bottomed cylindrical members of the cylindrical cavity resonator so that the sample passes, a thin plate or sheet that moves in the manufacturing process The sample can be evaluated online.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the structure of a cylindrical cavity resonator 10 used in the dielectric anisotropy measuring method of the present invention. (A) is a top view which shows the positional relationship of the hole which fixes an antenna in each bottom face, (B) is sectional drawing in the XY line position of (A).
The cylindrical cavity resonator 10 includes an upper bottomed tubular member 11 and a lower bottomed tubular member 12 which are a pair of bottomed tubular members.

The upper bottomed cylindrical member 11 and the lower bottomed cylindrical member 12 are formed of a metal material such as copper or aluminum, and these openings are aligned with a gap, and the sample 2 is arranged in the gap. ing. Flange portions 111 and 121 are provided around the respective openings so that the sample 2 can be easily placed in the gap.
Sample 2 may be a thin plate or a sheet made of organic or inorganic materials. These thicknesses are about 50-500 micrometers.

  And the hole 5 is formed in the bottom face of the upper bottomed cylindrical member 11, the hole 4 is formed in the bottom face of the lower bottomed cylindrical member 12, and it forms in the front-end | tip of a coaxial cable from these holes 5 and 4. The loop antennas 6 and 7 are inserted and fixed. One of the pair of loop antennas 6 and 7 is an electromagnetic wave excitation loop antenna, and the other is an electromagnetic wave detection loop antenna. Now, the loop antenna 6 is used for electromagnetic wave excitation, and the loop antenna 7 is used for electromagnetic wave detection. In the measurement, the cylindrical cavity resonator is excited by the electromagnetic wave excitation loop antenna 6, detected by the electromagnetic wave detection loop antenna, and the resonance frequency is measured by a measuring instrument such as a network analyzer connected thereto. .

Both loop antennas 6 and 7 are arranged on the bottom surfaces of the respective cylindrical members and are fixed so as to be perpendicular to the bottom surfaces, and crossing the cylinders at positions away from the center of the bottom surfaces of the respective cylindrical members. It is provided at a position rotated 90 degrees from the center of the surface.
Assuming that the diameter of the inner cylinder of the cylindrical cavity resonator 10 is D, the position where both the loop antennas 6 and 7 are provided is preferably a position within a distance of (3/8) D from the center of the cylinder. To D / 4.

In FIG. 1, the loop surface of the electromagnetic wave excitation loop antenna 6 and the loop surface of the electromagnetic wave detection loop antenna 7 are arranged so as to be orthogonal to each other. Such an arrangement of the loop antennas 6 and 7 facilitates simultaneous excitation detection of two resonance peaks of the TE _11n (n is a natural number) mode separated by insertion of an anisotropic thin plate or sheet sample. It comes to have an effect.

  Here, the principle of the dielectric anisotropy measurement method of the present invention will be described. Although different from the actually used cylindrical cavity resonator, FIG. 11 shows an undivided cylindrical cavity resonator 3 as a calculation model. (A) is a vertical sectional view along the axis of a cylinder, and (B) is a plan view showing an electric field vector in a plane perpendicular to the axis. Illustration of a loop antenna and the like for resonating is omitted.

The TE _11n (n is a natural number) mode of the cylindrical cavity resonator 3 shown in FIG. 11 has an electric field vector substantially linearly in a plane perpendicular to the axis of the cylinder in the absence of a sample, and is double degenerate. is doing. Here, the double degeneracy is a phenomenon that is observed like a single resonance electromagnetic field because the resonance frequencies of two independent resonance electromagnetic fields are the same. FIG. 11 shows one distribution of the electric field vector E in the double degenerate TE _11n mode.

As shown in FIG. 1, this double-degenerate TE _11n mode allows a thin plate or sheet sample 2 having dielectric anisotropy to be perpendicular to the cylinder axis at a position where the electric field distribution of the cylindrical cavity is strong. It was found by the process of the present invention that the degeneracy is solved by inserting so that the resonance frequency is separated and the resonance frequency is separated.

Furthermore, when n is an odd number, the TE _11n mode electric field is maximized at the central portion of the cylindrical cavity in the cylindrical axis direction, so that the present invention becomes easier to implement. In the TE _11n mode, TE ₁₁₁ , TE ₁₁₂ , TE ₁₁₃ ,... Are excited together with other resonance modes. Since the resonance frequency becomes higher as the higher-order mode increases, and it becomes easier to interfere with other modes, the TE ₁₁₁ mode is most suitable for measurement. Also measurements made of TE ₁₁₂ mode, to around TE ₁₁₃ mode for practical use.

In the two resonance modes that are degenerated and separated from the resonance frequency, the direction of the main electric field vector is the direction in which the dielectric constant in the sample plane inserted perpendicularly to the axis of the cylinder is the maximum. It has been found by the process of the present invention that it is oriented in the minimum direction. This was confirmed by the verification results described later. That is, the TE _11n mode having an electric field vector along the direction in which the dielectric constant in the sample surface is maximum becomes the low resonance frequency mode, and the TE _11n mode having an electric field vector along the direction in which the dielectric constant is minimum is high resonance. It becomes frequency mode. In addition, the sample plane means a direction in a plane perpendicular to the thickness direction of a thin plate or sheet sample.

The maximum relative dielectric constant and the minimum relative dielectric constant can be approximately obtained from the resonance frequencies of these resonance modes. That is, the maximum relative dielectric constant ε _MAX in the sample surface can be obtained from the resonance frequency f _L in the low resonance frequency mode, and the minimum relative dielectric constant ε _MIN in the sample surface can be obtained from the resonance frequency f _{H in} the high resonance frequency mode. be able to. An approximate calculation method in this case will be described.

In order to simplify the calculation of the relative dielectric constant, first, consider a case where the sample has an isotropic dielectric constant ε in the plane (FIG. 2A). As a calculation model, consider a case where the sample 2 having an isotropic dielectric constant ε is completely inserted into the cylindrical cavity resonator 3 (FIG. 2B).
In the case of FIG. 2B, ε can be calculated by the following equation from the resonance frequency f ₀ of the TE _11n mode.

ただし、ｃは光速であり、Ｘ、Yは次式で与えられる。

However, c is the speed of light, and X and Y are given by the following equations.

ここで、ｔは試料の厚み、ｎはＴＥ_11n共振モードの次数ｎ、ｋ₀＝２πｆ₀／ｃ，ｋ_r＝１．８４１２／Ｒである。ｋ₀−ｋ_r＜０の場合、YはｊY’（ｊは虚数単位）で置き換えられる。

Here, t is the thickness of the sample, n is the order n of the TE _11n resonance mode, k ₀ = 2πf ₀ / c, and k _r = 1.8412 / R. When k ₀ −k _r <0, Y is replaced with jY ′ (j is an imaginary unit).

ε obtained by putting f _H in equation (1) instead of f ₀ is an approximate value of ε _MIN , and ε obtained by putting f _L in equation (1) instead of f ₀ is an approximate value of ε _MAX It becomes. In this way, approximate values of ε _MIN and ε _MAX can be calculated.

Further, ε _MAX and ε _MIN can be determined more strictly from f _H and f _L by using numerical analysis such as FEM. Here, FEM (finite element method) is a kind of simulation technique for numerically analyzing an electromagnetic field or the like, and in the present invention, a technique capable of calculating a resonance frequency is required. It is also possible to use commercially available software such as HFSS.

Furthermore, an index representing the degree of anisotropy can be obtained from f _L and f _H. As such an index, for example, an index (f _H −f _L ) for evaluating the difference (ε _MAX −ε _MIN ) between the maximum relative dielectric constant ε _MAX and the minimum relative dielectric constant ε _MIN , or the degree of anisotropy It is possible to obtain (f _H −f _L ) / (f _H + f _L ) for evaluating (ε _MAX −ε _MIN ) / (ε _MAX + ε _MIN ).

In the present invention, in order to prevent the separation of the resonance peak of the TE _11n (n is a natural number) mode due to the influence of the loop antenna when the sample is not arranged, and to reduce the error of dielectric anisotropy measurement, FIG. As shown in FIG. 2, it is preferable to insert the electromagnetic wave excitation loop antenna perpendicularly to one bottom surface of the cylindrical cavity resonator and insert the electromagnetic wave detection loop antenna perpendicularly to the other bottom surface of the cylindrical cavity resonator.

  For the same reason, these loop antennas may be provided at the center of the bottom surface of each of the cylindrical cavity resonators. However, as shown in FIG. Preferably it is provided.

In FIG. 1, the loop surface of the electromagnetic wave excitation loop antenna and the loop surface of the electromagnetic wave detection loop antenna are arranged so as to be orthogonal to each other. The TE _11n (n is a natural number) mode resonance peak separated by the insertion of the sample can be easily excited and detected at the same time.

  In the measurement methods described so far, a thin plate-like or sheet-like sample is measured by being sandwiched between a pair of bottomed cylindrical members, but the sample is moved between a pair of bottomed cylindrical members. Thus, it can be measured. That is, by arranging this cylindrical cavity resonator in the production line of a thin plate or sheet product, the anisotropy in the in-plane direction of the product is evaluated in the production process of the thin plate or sheet product. be able to.

At this time, two TE _11n mode resonance peaks are generated by the moving sample by exciting the TE _11n mode in the cylindrical cavity resonator in the same manner as the above measurement method in which the thin plate or sheet sample is fixed. However, when measuring, if the frequency is swept at a speed sufficiently faster than the speed at which the sample moves in the manufacturing process, these two resonance modes appear almost simultaneously, so a thin plate or sheet that moves in the manufacturing process. Even when an on-line evaluation of a sample is performed, it is only necessary to install one cavity resonator.

  Here, when the present invention is used in a manufacturing process of a sheet-like material (sample), as shown in FIG. 3, a predetermined gap g is provided, and a pair of upper and lower bottomed cylindrical members are opposed to each other. It is desirable that the sheet-like material is arranged so as to move between them. In FIG. 3, reference numeral 13 denotes a sample supply mechanism for moving the continuous sheet-like material 2a schematically shown. For example, rollers arranged on both sides of the continuous sheet-like material 2a and This is a mechanism composed of a motor to be driven.

At this time, the gap g is g <λ _0L / (2ε _MAX ^0.5 ) and g <λ _0H / (2ε _MIN ^0.5 ) so that the electromagnetic field does not radiate from the gap g.
It is necessary to satisfy the relationship. However, λ _0L is the wavelength at the resonance frequency f _L , and λ _0H is the wavelength at the resonance frequency f _H.

In this case, since it is different from the cylindrical cavity resonator that is the basis of the equation (1), the use of the equation (1) makes it possible to obtain only a rough approximate value of the dielectric constant. It is necessary to obtain ε _MAX and ε _MIN from the measured values of f _L and f _H by numerical analysis such as FEM.
Also in this case, since f _L and f _H themselves can be obtained, the difference between f _L and f _H can also be used as a parameter representing the magnitude of anisotropy of the sheet-like material.

The result of verifying the validity of the measurement method described so far is shown.
A cylindrical cavity resonator 10 having a diameter (D) of 35 mm and a height (H) of 25 mm and having the shape shown in FIG. 1 was produced. That is, the loop antennas 6 and 7 are arranged at positions that are separated from each other by a distance of D / 4 from the center on the bottom surface of each cylindrical member and rotated 90 degrees from each other when viewed from the center in the cross section of the cylinder. In the vertical direction, the loop surfaces are fixed in directions perpendicular to each other.

FIG. 4A shows a result of measuring the resonance peak using the cylindrical cavity resonator 10 in a state where no sample is arranged. Resonance peaks of several modes are obtained. Among them, the resonance peak of the TE ₁₁₁ mode is shown in FIG. Although there are two resonance peaks in the TE ₁₁₁ mode, it can be confirmed that the peaks are not separated because they are degenerated when no sample is arranged.

Here, when the arrangement position and direction of the loop antennas 6 and 7 are changed without changing the shape and size of the cylindrical cavity resonator, how the resonance peak of the TE ₁₁₁ mode changes when the sample is not arranged. Find out what to do.

First, the loop antennas 6 and 7 are arranged on the side surfaces of the respective cylindrical members, and the positions thereof are positions H / 4 (H is the height of the cylindrical cavity resonator) from the central cross section where the sample is to be arranged. And arranged at positions that are 180 degrees to each other in the cross section of the cylinder, and fixed in a direction perpendicular to the side surfaces. That is, the loop surfaces are parallel to each other. FIG. 5A shows the result of measuring the resonance peak with the cylindrical cavity resonator in this state in a state where no sample is arranged. Among the resonance peaks of several modes, the resonance peak of the TE ₁₁₁ mode is shown in FIG. 5B by enlarging the horizontal axis. The two resonance peaks of the TE ₁₁₁ mode are slightly separated by 0.002 GHz. Can be confirmed.

Next, the loop antennas 6 and 7 are separated from the center by a distance of D / 4 at the bottom surface of each cylindrical member and are arranged at the same position in the cross section of the cylinder, and the loop surfaces are perpendicular to each bottom surface. Fixed in a parallel direction. FIG. 6 (A) shows the result of measuring the resonance peak with the cylindrical cavity resonator in this state without placing the sample. Among the resonance peaks of several modes, the resonance peak of the TE ₁₁₁ mode is shown in FIG. 6B with the horizontal axis enlarged, and this peak is the peak top position of the two resonance peaks of the TE ₁₁₁ mode is 0. It can be estimated that two TE ₁₁₁ peaks having different intensities (peak heights) are overlapped with each other with a deviation of about 0.001 GHz.

Thus, when the loop antenna was not placed at the optimum position, it was confirmed that the TE ₁₁₁ mode showed a slight separation of 0.001 to 0.002 GHz before inserting the sample. Assuming that this peak separation frequency of 0.002 GHz gives uncertainties of f _L and f _{H in} the measurement of relative dielectric anisotropy, it will be examined how much error occurs.

In Table 1 showing the measurement results of Examples described later, ε _MAX = 11.236 is obtained from f _L = 6.1673 GHz for an A-plane sapphire having a thickness of 0.610 mm, but an error of 0.002 GHz at f _L =. If there is, Δε _f = 0.008 occurs as an error of ε _MAX . This is negligible since it is usually less than the effect of 1 μm thickness error Δε _t = 0.02, which is unavoidable.

On the other hand, in Table 1, in the PET film having a thickness of 0.127 mm, ε _MAX = 2.945 is obtained from f _L = 7.66871 GHz. If there is an error of 0.002 GHz in f _L , the error of ε _MAX As a result, Δε _f = 0.026. This is almost _{equal to} Δε _t = 0.02, which is an effect of a thickness error of 1 μm, which is usually unavoidable, and cannot be ignored. Further, in the PET film, Δε _f = 0.026 is 10% or more with respect to ε _MAX −ε _MIN = 0.2, which cannot be ignored from this viewpoint.

Based on the above considerations, for samples with a small thickness and a low relative dielectric constant, if the loop antenna is not placed at the optimum position, the TE ₁₁₁ mode shows a slight separation before sample insertion. It cannot be ignored.

  Therefore, based on such results, as a best mode of the present invention, a pair of bottomed cylindrical shapes are used by using a cylindrical cavity resonator 10 in which the positions and directions of the loop antennas 6 and 7 are fixed as shown in FIG. The sheet-like sample 2 was sandwiched between the members 11 and 12, and the resonance frequency of the cylindrical cavity resonator 10 was measured.

  Measurement of an A-plane sapphire substrate with a C axis in the plane as a sample having significant anisotropy in relative permittivity, and measurement of a PET (polyethylene terephthalate) film as a sample having a small anisotropy in relative permittivity Was done.

FIG. 7 shows the measurement result of the TE ₁₁₁ mode resonance peak of the A-plane sapphire substrate, and FIG. 8 shows the measurement result of the TE ₁₁₁ mode resonance peak of the PET film. 7 and 8, the horizontal axis represents frequency, and the vertical axis IL (insertion loss) represents the amount of attenuation of the power transmitted through the cylindrical cavity resonator 10 with respect to the input power in dB (decibel).

In FIG. 7, peak separation corresponding to the dielectric constant ε _MAX = 11.5 (document value) parallel to the C axis of the A-plane sapphire substrate and the perpendicular dielectric constant ε _MIN = 9.4 (document value) occurs. Is recognized. In FIG. 8, it is recognized that peak separation due to slight anisotropy of dielectric constant is also generated in the PET film.

(Δε)² =(Δε_t)² + (Δε_f)² Table 1 shows approximate values of the maximum relative permittivity ε _MAX and the minimum relative permittivity ε _MIN obtained from the resonance frequency f _L and the resonance frequency f _{H at} each resonance peak by the equation (1).

(Δε) ² = (Δε _t ) ² + (Δε _f ) ²

Here, the numerical value “±” shown in the table is an error, and the error Δε of ε is the ε error Δε _t resulting from the uncertainty of the sample thickness _t and the repeated measurement of the resonance frequency f. It is obtained as the mean square error of the error Δε _f of ε resulting from the error.
From the results shown in Table 1, ε _MAX and ε _MIN of the A-plane sapphire substrate are values close to the literature values 11.5 and 9.4, indicating that the validity of this measurement method was verified. Yes.

  7 and 8, in order to confirm that a constant peak separation corresponding to the anisotropy of the dielectric constant occurs even when the sample is inserted at an arbitrary angle, a pair of bottomed cylindrical members is used. The sample 2 is placed between 11 and 12, and the resonance waveform is measured (FIG. 7 (A), FIG. 8 (A)). Next, the sample is measured by rotating 45 degrees (FIG. 7 (B), FIG. 8). (B)) The sample was further rotated by 90 degrees and measured (FIGS. 7C and 8C). From the results of the measurement waveforms with different rotation angles, a constant peak separation corresponding to the anisotropy of the dielectric constant can be obtained without depending on the relative angle between the sample and the bottomed cylindrical members 11 and 12. It can be confirmed that it is observed.

FIG. 9 schematically shows an embodiment of a dielectric anisotropy measuring apparatus. (A) is a block diagram showing the overall configuration, and (B) is a block diagram showing functions of the microwave signal detection and analysis apparatus.
The cylindrical cavity resonator device is shown in FIG. 1 as an example. A cylindrical cavity resonator 20 formed of a pair of bottomed cylindrical members facing each other with a gap, and the resonator 20 provided on one end side of the resonator 20. An excitation device 22 for introducing microwaves therein and a detection device 24 for detecting the microwaves in the resonator 20 provided on the other end side of the resonator 20 are provided. An example of the cylindrical cavity resonance device is shown in FIG. 1, and the excitation device 22 and the detection device 24 are each a loop antenna.

  In order to generate microwaves in the resonator 20 by the excitation device 22, a microwave generation device 26 called a sweeper is connected to the excitation device 22. A microwave signal detection / analysis device 28 such as a network analyzer is connected to the detection device 24 in order to input and analyze the microwave signal detected by the detection device 24. A control device 30 is provided to control the measurement operation by this cylindrical cavity resonator. Specifically, the control device 30 controls the microwave generation device 26 and the microwave signal detection analysis device 28. The control device 30 is realized by a personal computer, for example.

Furthermore, in the present invention, as shown in FIG. 9B, the control device 30 detects the resonance frequency f _L on the low frequency side and the resonance frequency f _H on the high frequency side of the TE _11n mode after the sample is placed. Means 30a and dielectric anisotropy calculating means 30b for calculating the dielectric anisotropy of the sample based on the two detected resonance frequencies f _L and f _H are provided. The detection unit 30 a and the dielectric anisotropy calculation unit 30 b are functions realized by a dielectric anisotropy calculation program incorporated in the control device 30.

An example of the dielectric anisotropy measurement operation by this cylindrical cavity resonator device will be described with reference to the flowchart of FIG.
In response to a command from the control device 30, the microwave generation device 26 sweeps (sweeps) the microwave signal in a frequency region including the resonance frequency of the TE ₁₁₁ mode, and the excitation device 22 excites the resonator 20. The microwave signal detection / analysis device 28 inputs the microwave signal detected by the detection device 24 when the sample is placed in the resonator 20, and the low frequency side resonance frequency f _L and the high frequency side of the TE ₁₁₁ mode. detecting the resonance frequency f _H. Then, the maximum relative dielectric constant ε _MAX and the minimum relative dielectric constant ε _MIN in the in-plane direction of the sample are calculated by the control device 30 by the equation (1) or by a numerical analysis method such as FEM.

More specifically, the commercially available network analyzer as the microwave signal detection and analysis device 28 has a frequency at a point where IL is the largest in the frequency region in which IL (insertion loss) is measured. Since there is a function (Max function) for automatically measuring the resonance frequency, it is possible to measure the top frequency of the resonance peak, that is, the resonance frequency. When a network analyzer is used as the microwave signal detection / analysis device 28 and f _L measurement is automatically performed using this function, the measurement is performed as follows.

1) The control device (specifically, a personal computer) 30 issues an instruction to the microwave generator 26 to sweep the frequency around the predetermined initial value of f _L , and then the control device 30 A Max function instruction is issued to the network analyzer 28 to obtain an approximate value of f _L.

2) Next, the control device 30 issues an instruction to the microwave generator 26 so as to sweep the frequency within a narrow range with the approximate value of f _L as the center, and again issues a Max function instruction to the network analyzer 28 to indicate f _L. Find precise value.

The same applies when _fH measurement is performed.
The program in the control device 30 includes a part for instructing such a measurement operation and a part for calculating ε _MAX and ε _MIN from f _L and f _H.

The control device 30 may calculate an index representing the degree of anisotropy of the relative dielectric constant in the in-plane direction of the sample based on the difference between the two detected resonance frequencies f _L and f _H.

It is a figure showing the cylindrical cavity resonator which inserted the sample, (A) is a top view which shows the positional relationship of the hole which fixes an antenna in each bottom face, (B) is the XY line position of (A). It is sectional drawing. (A) is a cylindrical cavity resonator model in which a sample is inserted, which is simplified for use in approximate calculation, and (B) is a further simplified computational model. 1 is a cross-sectional view of a hollow cylindrical resonator for measuring sheet material online. FIG. (A) is a waveform diagram showing a resonance peak in a state where a sample is not arranged when the cylindrical cavity resonator of FIG. 1 is used, and (B) is a waveform diagram showing a resonance peak of TE ₁₁₁ mode by enlarging the horizontal axis. It is. (A) is a waveform diagram showing a resonance peak in a state where the sample is not arranged when the arrangement position and direction of the loop antenna are different from those of the cylindrical cavity resonator of FIG. 1, and (B) is a resonance peak of the TE ₁₁₁ mode. It is a wave form diagram which expands and shows a horizontal axis. (A) is a waveform diagram showing a resonance peak in a state where the sample is not arranged when the arrangement position and direction of the loop antenna are different from those of the cylindrical cavity resonator of FIG. 1, and (B) is a resonance peak of the TE ₁₁₁ mode. It is a wave form diagram which expands and shows a horizontal axis. It is a figure which shows the two resonance peaks of _TE11n mode of the cavity cylindrical resonator which inserted the sapphire substrate when the cylindrical cavity resonator of FIG. 1 is used. It is a figure which shows two resonance peaks of _TE11n mode of the hollow cylindrical resonator which inserted PET film when using the cylindrical hollow resonator of FIG. (A) is a block diagram schematically showing an embodiment of a dielectric anisotropy measuring device, and (B) is a block diagram showing a function of a control device for obtaining a dielectric anisotropy. It is a flowchart which shows operation | movement of the Example of a dielectric anisotropy measuring apparatus. (A) is sectional drawing along the rotating shaft of a cylindrical cavity resonator, (B) is a figure which shows electric field distribution in the plane perpendicular _| vertical to the rotating shaft of _TE11n mode.

Explanation of symbols

2 Sample 3,20 Cylindrical cavity resonator 4,5 hole 6,7 Loop antenna 11,12 Bottomed cylindrical member 22 Exciting device 24 Detector 26 Microwave generator 28 Microwave signal detection analyzer 30 Controller 28a Resonant frequency Detection means 28b Dielectric anisotropy calculation means

Claims (8)

The dielectric anisotropy of a thin plate-like or sheet-like sample having an anisotropy in the in-plane direction is measured including the following steps (A) to (D): Anotropic measurement method.
(A) exciting a TE _11n (n is a natural number) mode of a cylindrical cavity resonator composed of a pair of bottomed cylindrical members facing each other with a gap;
(B) disposing a sample in the gap;
(C) Measure the resonance frequency f _L on the low frequency side and the resonance frequency f _H on the high frequency side of the TE _11n mode after sample placement, and (D) the resonance frequency f _L on the low frequency side and the resonance frequency on the high frequency side Obtain the maximum relative permittivity ε _MAX and the minimum relative permittivity ε _MIN in the in-plane direction of the sample from f _H.
Here, the resonance frequencies f _L and f _H are the frequencies on the low frequency side and the high frequency side of the two resonance frequencies of the TE _11n mode which are separated from each other by the arrangement of the sample. In the step (D), the maximum relative dielectric constant ε _MAX in the in-plane direction of the sample is approximately obtained from the resonance frequency f _L on the low frequency side, and the minimum in the in-plane direction of the sample from the resonance frequency f _H on the high frequency side. The dielectric anisotropy measuring method according to claim 1, wherein a relative dielectric constant ε _MIN is obtained. The dielectric anisotropy of a thin plate-like or sheet-like sample having an anisotropy in the in-plane direction is measured including the following steps (A) to (D): Anotropic measurement method.
(A) exciting a TE _11n mode of a cylindrical cavity resonator composed of a pair of bottomed cylindrical members facing each other with a gap;
(B) disposing a sample in the gap;
(C) Measure the resonance frequency f _L on the low frequency side and the resonance frequency f _H on the high frequency side of the TE _11n mode after sample placement, and (D) the difference between the two resonance frequencies f _L and f _H. Obtain the degree of anisotropy of relative permittivity in the in-plane direction of the sample. A cylindrical cavity resonator composed of a pair of bottomed cylindrical members facing each other with a gap, an excitation device for introducing a microwave into the resonator provided at one end of the resonator, and a resonance provided at the other end of the resonator A cylindrical cavity resonance device having a detection device for detecting microwaves in the resonator, a microwave generation device for generating microwaves in the resonator by the excitation device, and a microwave signal detected by the detection device are input. A microwave signal detection and analysis device that performs analysis, and a control device that controls the microwave generation device and the microwave signal analysis device,
The control device is charged with detection means for detecting the resonance frequency f _L on the low frequency side and the resonance frequency f _H on the high frequency side of the TE _11n mode after sample placement, and the two detected resonance frequencies f _L and f _H. And a dielectric anisotropy calculating means for calculating the dielectric anisotropy of the sample based on the step (D) in the dielectric anisotropy measuring method according to any one of Items 1 to 3. A dielectric anisotropy measuring device.   5. The dielectric anisotropy measurement according to claim 4, wherein the cylindrical cavity resonator has an electromagnetic wave excitation loop antenna and an electromagnetic wave detection loop antenna attached to the bottom surface of each bottomed cylindrical member in a vertical direction. apparatus.   6. The dielectric anisotropy measurement according to claim 5, wherein the electromagnetic wave excitation loop antenna and the electromagnetic wave detection loop antenna are provided at a position rotated by 90 degrees when viewed from the center of a cross section of a cylinder of the cylindrical cavity resonator. apparatus.   The dielectric anisotropy measuring device according to claim 5 or 6, wherein a loop surface of the electromagnetic wave excitation loop antenna and a loop surface of the electromagnetic wave detection loop antenna are arranged to be orthogonal to each other. The dielectric anisotropy measuring device according to claim 4, further comprising a sample moving mechanism for moving the sample so as to pass through the gap, and being an on-line measuring device.

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