JP4760442B2 - Test method for optically anisotropic film - Google Patents

Description

  The present invention provides optical anisotropy capable of obtaining refractive index anisotropy (difference in refractive index) and an accurate refractive index value with 3 digits or more after the decimal point by an easy calculation without complicated data processing. The present invention relates to a method for testing a conductive film.

Optically anisotropic films capable of changing the polarization state of light are used in various optical devices such as liquid crystal display devices as retardation plates and viewing angle compensation plates.
As a method for evaluating this optically anisotropic film, for example, Patent Document 1 proposes a method of measuring the incident angle dependence of the intensity of reflected light generated when light having a plurality of wavelengths is incident. Patent Document 2 proposes a method of measuring from the dependence of the reflected light intensity on the incident angle and the incident azimuth.
In Patent Document 3, incident light that is linearly polarized is condensed using a lens, and the incident angle and incident azimuth dependence of the reflected light intensity due to incident light having only the S-polarized component and only the P-polarized component is efficiently managed. A method of measuring automatically has been proposed. However, these methods require data processing such as the least square method to determine the parameters, and it takes time to calculate. In addition, the refractive index anisotropy of 3 digits or more after the decimal point and the accurate refractive index value are set. It is not required.

  In Patent Document 4, the incident azimuth dependence of the polarization state of reflected light generated when light in a certain polarization state is incident on an anisotropic thin film at a certain angle, and the polarization of the measured reflected light is measured. Calculating a Fourier coefficient related to the incident direction of the phase difference component and the amplitude ratio component of the state, calculating a difference between the maximum value and the minimum value of the phase difference component, and calculating a difference between the maximum value and the minimum value of the amplitude ratio component, A method for evaluating an anisotropic thin film based on a Fourier coefficient and each difference has been proposed. However, this method also requires data processing called Fourier transform, and it is impossible to obtain a refractive index anisotropy and an accurate refractive index value of 3 digits or more after the decimal point.

JP-A-5-5699 Japanese Patent Laid-Open No. 3-65637 JP-A-8-152307 JP 2000-155092 A

  It is an object of the present invention to test an optically anisotropic film that can obtain a refractive index anisotropy and an accurate refractive index value of 3 digits or more after the decimal point by an easy calculation without complicated data processing. It is to provide a method.

The present inventor has investigated in order to achieve the above object, the optically anisotropic film, and measuring the transmission phase difference delta _O when the light of wavelength λ at an incident angle theta _O, the wavelength λ the transmission phase difference delta _T when the light at an incident angle theta _T measured, further, the wavelength reflection amplitude ratio angle when light at an incident angle theta _R of lambda [psi _R or transmission amplitude ratio angle [psi _T measured either, and the measured transmission phase difference delta _O, and transmission phase difference delta _T, by based on either one bets reflection amplitude ratio angle [psi _R or transmission amplitude ratio angle [psi _T, simple algebraic calculations, it was found that the refractive index of the optically anisotropic film n _x, n _y, and n _z can be easily determined. The present invention has been completed based on this finding.

Thus, according to the present invention,
(1) the optically anisotropic film, a step of measuring the transmission phase difference delta _O1 when the light of wavelength λ at an incident angle theta _O1,
The optically anisotropic film, a step of measuring the transmission phase difference delta _T1 when the light of the wavelength λ at an incident angle theta _T1,
Measuring a reflection amplitude ratio angle Ψ _R1 when light having the wavelength λ is incident on the optical anisotropic film at an incident angle θ _R1 ;
The measured transmission phase difference delta _O1, transmission phase difference delta _T1, and on the basis of the reflection amplitude ratio angle [psi _R1, a step of determining the refractive index of the optically anisotropic film,
A method for testing an optically anisotropic film comprising:

(2) the optically anisotropic film, a step of measuring the transmission phase difference delta _O2 when the light of wavelength λ at an incident angle theta _O2,
The optically anisotropic film, comprising the steps of: transmitting a phase difference delta _T2 measurement when the incident light of the wavelength λ at an incident angle theta _T2,
Measuring a transmission amplitude ratio angle Ψ _T2 when light having the wavelength λ is incident on the optical anisotropic film at an incident angle θ _R2 ;
Obtaining a refractive index of the optically anisotropic film based on the measured transmission phase difference Δ _O2 , transmission phase difference Δ _T2 , and transmission amplitude ratio angle Ψ _T2 ;
A method for testing an optically anisotropic film comprising:
(3) A method for producing an optically anisotropic film, comprising using the test method according to (1) or (2).
Is provided.

  According to the test method for an optically anisotropic film of the present invention, it is possible to obtain a refractive index anisotropy and an accurate refractive index value of three decimal places or more by an easy calculation without complicated data processing. it can,

The optically anisotropic film to which the test method of the present invention can be applied is not particularly limited as long as it has a property of transmitting light. The optically anisotropic film usually has a thickness of 20 to 250 μm, preferably 40 to 180 μm. Since the optically anisotropic film is usually thin, the x axis and y axis perpendicular to each other are taken in a direction parallel to the film surface, the z axis is taken in a direction perpendicular to the film (thickness), and _nx is optically different. plane slow axis direction of the refractive index of the isotropic film, the refractive index in the direction orthogonal to n _y in a plane in the in-plane slow axis of the optically anisotropic film, the thickness direction of the n _z optically anisotropic film Is defined as the refractive index. Moreover, it is preferable that the light used for the test method of this invention is a thin parallel light beam like a laser beam. The range of light irradiated to the optical anisotropic film can be narrowed, and a more accurate test can be performed.
Specific examples of the optically anisotropic film include a retardation plate (retardation film) obtained by stretching a transparent resin film, a film coated with an optically anisotropic substance such as liquid crystal, and a compound having a polar group. And a rubbing-treated film (such as an alignment film).

Test Method of the first optically anisotropic film of the present invention, the optically anisotropic film, a step of measuring the transmission phase difference delta _O1 when the light of wavelength λ at an incident angle theta _O1,
The optically anisotropic film, a step of measuring the transmission phase difference delta _T1 when the light of the wavelength λ at an incident angle theta _T1,
Measuring a reflection amplitude ratio angle Ψ _R1 when light having the wavelength λ is incident on the optical anisotropic film at an incident angle θ _R1 ;
And calculating the refractive index of the optically anisotropic film based on the measured transmission phase difference Δ _O1 , transmission phase difference Δ _T1 , and reflection amplitude ratio angle Ψ _R1 .

Transmission phase difference delta _O1 and delta _T1 is ellipsometer such as an ellipsometer, by birefringence analyzer can be measured.
The optically anisotropic film, transmission phase difference delta _O1 when the light of wavelength λ at an incident angle theta _O1, when the incident plane is xz plane can be expressed by Equation (1).
_{Δ O1 = (n x (1} -ξ O1 2 / n z 2) 0.5
^{_{-N y (1-ξ O1 2}} / n y 2) 0.5) × d (1)
However, ξ _O1 = sin θ _O1 .
Further, d thickness, n _x plane slow axis direction of the refractive index of the optically anisotropic film, n _y is a refractive index in the direction perpendicular in the plane in the in-plane slow axis of the optically anisotropic film , _Nz is the refractive index in the thickness direction of the optically anisotropic film.
In particular, when the incident angle theta _O1 is 0 °, delta _{O1 becomes (n x -n y) × d} .

Similarly, the optically anisotropic film, the transmission phase difference delta _T when the light of wavelength λ is incident at an incident angle theta _T, when the incident plane is xz plane can be expressed by Equation (2) .
_{Δ T1 = (n x (1} -ξ T1 2 / n z 2) 0.5
^{_{-N y (1-ξ T1 2}} / n y 2) 0.5) × d (2)
However, ξ _T1 = sin θ _T1 .

There are no particular limitations on the incident angles θ _O1 and θ _T1 when the transmission phase difference Δ _O1 and the transmission phase difference Δ _T1 are determined. In order to increase the measurement accuracy, the incident angle θ _O1 is preferably 25 degrees or less, more preferably 10 degrees or less, and particularly preferably 0 degrees. Further, the incident angle θ _T1 is preferably 30 degrees or more, and more preferably 40 degrees or more. Even when the incident plane is the yz plane, it is possible to obtain the same expression for the transmission phase difference delta _O1 and transmission phase difference delta _T1, depending on the incident surface, the transmission phase difference delta _O1 and transmission phase difference to select the equation of Δ _T1.

The reflection amplitude ratio angle Ψ _R1 can be measured by an ellipsometer. In the measurement of the reflection amplitude ratio angle, we want to measure only the reflected light on the surface of the optical anisotropic film, so in order to suppress reflection on the back surface of the optical anisotropic film, a light absorbing material or light diffusing material is installed on the back side It is preferable to provide it.
The reflection amplitude ratio angle Ψ _R1 when the light of wavelength λ is incident on the optically anisotropic film at an incident angle θ _R1 is a value defined by tan ⁻¹ | R _p / R _s |. R _p is the complex amplitude reflectivity of p-polarized light, and R _s is the complex amplitude reflectivity of s-polarized light.
Since the optically anisotropic film feels isotropic for s-polarized light, the Fresnel reflection coefficient equation can be applied to s-polarized light as it is.
On the other hand, since the optically anisotropic film is felt as an anisotropic crystal for p-polarized light, Maxwell's electromagnetic wave theory formula is applied to the reflection of p-polarized light.

First, the propagation vector of each partial wave propagating through the anisotropic film is obtained from the Maxwell equation, and the polarization vector of the partial wave is obtained. Next, the complex amplitude reflectance R _p is obtained by applying boundary conditions to the air-anisotropic film interface. As a result, tan Ψ _R1 can be expressed by Expression (3) when the incident surface is the xz plane.
tan Ψ _R1 = | ((ξ _p + αξ _R ) cos θ _R1 −1) × (cos θ _R1 + ξ _s ))
/ ((Ξ _p + αξ _R ) cos θ _R1 +1) × (cos θ _R1 + ξ _s )) | Equation (3)
_{However, ξ R = sinθ R1, ξ} s = n y (1-ξ R 2 / n y 2) 0.5,
_{ξ p = n x (1-} ξ R 2 / n z 2) 0.5,
^{_{α = (n x 2 -ξ p}} 2 -ξ R ξ p) / (ξ R 2 + ξ R ξ p -n z 2)
It is. The measurement is usually so performed in air, the refractive index n _i of the surrounding of the optically anisotropic film is 1.

The incident angle θ _R1 for obtaining the reflection amplitude ratio angle Ψ _R1 is not particularly limited, but the incident angle θ _R1 is preferably set to 30 degrees or more, and is preferably set to 40 degrees or more in order to improve measurement accuracy. More preferred. Further, when θ _R1 is the Brewster angle of the optically anisotropic film of the present invention, the measurement accuracy becomes the highest. Note that when the incident plane is the yz plane also, it is possible to obtain the same expression for the reflection amplitude ratio angle [psi _R1, depending on the incident surface, to select an expression of reflection amplitude ratio angle [psi _R1.

The film thickness d can be measured with a micrometer or the like. Then, n _x , n _y , and _nz can be calculated by algebraic calculation by solving the simultaneous equations of the above formulas (1), (2), and (3).

By measuring the transmission phase difference Δ _O1 , the transmission phase difference Δ _T1 , and the reflection amplitude ratio angle Ψ _R1 by switching the wavelength λ of the incident light with a spectroscopic device or the like, the respective wavelength dependency can be understood. For example, the wavelength dependence of the transmission phase difference Δ _O1 , the transmission phase difference Δ _T1 , and the reflection amplitude ratio angle Ψ _R1 as shown in FIGS.
Then, by solving the simultaneous equations for each wavelength of incident light, the refractive indexes _nx , _ny , and _nz for each wavelength can be obtained. Thereby, the wavelength dependency of the refractive index as shown in FIG. 4 is required.

Test Method for second optically anisotropic film of the present invention, the optically anisotropic film, a step of measuring the transmission phase difference delta _O2 when the light of wavelength λ at an incident angle theta _O2,
The optically anisotropic film, comprising the steps of: transmitting a phase difference delta _T2 measurement when the incident light of the wavelength λ at an incident angle theta _T2,
Measuring a transmission amplitude ratio angle Ψ _T2 when light having the wavelength λ is incident on the optical anisotropic film at an incident angle θ _R2 ;
And calculating the refractive index of the optically anisotropic film based on the measured transmission phase difference Δ _O2 , transmission phase difference Δ _T2 , and transmission amplitude ratio angle Ψ _T2 .

Transmission phase difference delta _O2 and delta _T2 is ellipsometer such as an ellipsometer, by birefringence analyzer can be measured.
The optically anisotropic film, transmission phase difference delta _O2 when the light of wavelength λ at an incident angle theta _O2, when the incident plane is xz plane can be expressed by Equation (4).
_{Δ O2 = (n x (1} -ξ O2 2 / n z 2) 0.5
^{_{-N y (1-ξ O2 2}} / n y 2) 0.5) × d Equation (4)
However, ξ _O2 = sin θ _O2 .
Further, d thickness, n _x plane slow axis direction of the refractive index of the optically anisotropic film, n _y is a refractive index in the direction perpendicular in the plane in the in-plane slow axis of the optically anisotropic film , _Nz is the refractive index in the thickness direction of the optically anisotropic film.
In particular, when the incident angle theta _O2 is 0 °, delta _{O2 becomes (n x -n y) × d} .

Similarly, the optically anisotropic film, transmission phase difference delta _T2 when the light at an incident angle theta _T2 of wavelength λ, when the incident plane is xz plane can be represented by the formula (5) .
_{Δ T2 = (n x (1} -ξ T2 2 / n z 2) 0.5
^{_{-N y (1-ξ T2 2}} / n y 2) 0.5) × d Formula (5)
However, ξ _T2 = sin θ _T2 .

There are no particular limitations on the incident angles θ _O2 and θ _T2 when the transmission phase difference Δ _O2 and the transmission phase difference Δ _T2 are determined. In order to increase the measurement accuracy, the incident angle θ _O2 is preferably 25 degrees or less, more preferably 10 degrees or less, and particularly preferably 0 degrees. In addition, the incident angle θ _T2 is preferably 30 degrees or more, and more preferably 40 degrees or more. Even when the incident plane is the yz plane, it is possible to obtain the same expression for the transmission phase difference delta _O2 and transmission phase difference delta _T2, in response to the incident surface, the transmission phase difference delta _O2 and transmission phase difference to select the equation of Δ _T2.

The transmission amplitude ratio angle Ψ _T2 can be measured by an ellipsometer.
The transmission amplitude ratio angle Ψ _T2 when light of wavelength λ is incident at an incident angle θ _R2 is a value defined by tan ⁻¹ | T _P1 · T _P2 / T _S1 · T _S2 |. That is, tan Ψ _T2 is expressed by Expression (6).
tan Ψ _T2 = | T _P1 · T _P2 / T _S1 · T _S2 | Equation (6)
Note that when the incident surface is the xz plane, the optically anisotropic film is felt isotropic with respect to the s-polarized light. Therefore, T _S1 and T _S2 are expressed by the following equations according to the Fresnel equation.
T _S1 = 2n _i cos θ _{R2
/ (N i cosθ R2 + n} y (1- (n i sinθ R2 / n y) 2) 0.5)
_{T S2 = 2n y (1- (} n i sinθ R2 / n y) 2) 0.5
_{/ (N y (1- (n} i sinθ R2 / n y) 2) 0.5 + n i cosθ R2)

On the other hand, when the incident surface is the xz plane, the optically anisotropic film feels anisotropic with respect to the p-polarized light, so the crystal optics theory and Maxwell's electromagnetic wave theory are applied. Next, boundary conditions at the air-anisotropic film interface are considered. As a result, T _P1 and T _P2 are expressed by the following equations.
T _P1 = [(ξ _z1 ^(r) −ξ _z1 ⁽ⁱ⁾ ) −ξ _x (tan α _r1 + tan α _i1 )]
/ [([Xi] _z1 ^(r)- [xi] _z1 ^(t) )-[ _xi ] _x (tan [alpha] _r1 + tan [alpha] _t1 )]
× [(1 + tan ² α _t1 ) / (1 + tan ² α _i1 )] ^0.5
Where ξ _x = n _i sin θ _R2 , ξ _z1 ⁽ⁱ⁾ = n _i cos θ _R2 ,
ξ _z1 ^(r) = −n _i cos θ _R2 ,
^{_{ξ z1 (t) = n x}} (1-ξ x 2 / n z 2) 0.5,
tanα _i1 = tanθ _R2 , tanα _r1 = tanθ _R2 ,
^{_{tanα t1 = -ξ x ξ z1 (}} t) / (ξ x 2 -n z 2), it is.

^{_{T P2 = [(ξ z2 (}} r) -ξ z2 (i)) -ξ x (tanα r2 + tanα i2)]
/ [([Xi] _z2 ^(r)- [xi] _z2 ^(t) )-[ _xi ] _x (tan [alpha] _r2 + tan [alpha] _t2 )]
× [(1 + tan ² α _t2 ) / (1 + tan ² α _i2 )] ^0.5 ,
_{^{However, ξ z2 (i) = n}} x (1-ξ x 2 / n z 2) 0.5, ξ z2 (r) = -ξ z2 (i),
ξ _z2 ^(t) = n _i cos θ _R2 ,
^{_{tanα i2 = -ξ x ξ z2 (}} i) / (ξ x 2 -n z 2),
^{_{tanα r2 = ξ x ξ z2 (}} r) / (ξ x 2 -n z 2),
tan α _t2 = tan θ _R2 . The measurement is usually so performed in air, the refractive index n _i of the surrounding of the optically anisotropic film is 1.

The incident angle θ _R2 for obtaining the transmission amplitude ratio angle Ψ _T2 is not particularly limited. However, in order to improve measurement accuracy, the incident angle θ _R2 is preferably set to 30 degrees or more, and preferably set to 40 degrees or more. More preferably, it is particularly preferably 60 degrees or more. Even when the incident plane is the yz plane, a similar expression can be obtained for the reflection amplitude ratio angle Ψ _T2 , so the transmission amplitude ratio angle Ψ _T2 is selected according to the incident plane.

The film thickness d can be measured with a micrometer or the like. Then, n _x , n _y , and _nz can be calculated by algebraic calculation by solving the simultaneous equations of the above equations (4), (5), and (6).

By measuring the transmission phase difference Δ _O2 , the transmission phase difference Δ _T2 , and the transmission amplitude ratio angle Ψ _T2 by switching the wavelength λ of the incident light with a spectroscopic device or the like, the respective wavelength dependence can be understood. Then, by solving the simultaneous equations for each wavelength of incident light, the refractive indexes _nx , _ny , and _nz for each wavelength can be obtained.

  As described above, according to the test method of the present invention, the transmitted light phase difference at at least two incident angles is measured, the transmitted amplitude ratio angle or the reflected amplitude ratio angle at at least one incident angle is measured, and the value is obtained. Based on this, the refractive index anisotropy of the optically anisotropic film and the refractive index in the three directions can be accurately obtained only by performing algebraic geometric calculation without performing complicated data processing such as the method of least squares. Can do.

The manufacturing method of the optically anisotropic film of the present invention is a manufacturing method including using the test method.
In a method for producing an optically anisotropic film, such as a method of forming a transparent resin by an extrusion molding method or a solution cast molding method; a method of further stretching; a method of applying an optically anisotropic substance such as liquid crystal; In order to obtain an optically anisotropic film having a desired refractive index anisotropy and refractive index, various conditions of the manufacturing process, for example, conditions such as temperature, pressure, film thickness, film forming speed, viscosity, etc. are changed and refraction is performed. Feedback control is performed automatically or manually so that the rate or the like approaches a desired value. Then, the test method of the present invention is used to obtain the refractive index anisotropy and the accurate value of the refractive index necessary for this feedback control.

Refractive index at a wavelength of 550nm is optically isotropic plastic material 1.533 and transverse stretching, to obtain a film having an average thickness of 43 .mu.m, of the present invention the refractive indices _n x of the _film, n y, _{n z} The test was conducted using the test method. A spectroscopic ellipsometer (M-2000, manufactured by JA Woollam Co., Ltd.) was used to measure the transmission phase difference and the reflection amplitude ratio angle.
First, the film was set so that the optical principal axis of the film coincided with the coordinate system xyz (experimental coordinate system) of the measuring apparatus.
Under the condition of normal incidence (incidence angle 0 °) was measured transmission phase difference delta _O with respect to the wavelength λ in the visible light region. The results are shown in FIG.

Film was placed to rotate by the incident angle of 60 degrees conditions (incident surface was xz plane), and measuring the transmission phase difference delta _T for the wavelength λ in the visible light region. The results are shown in FIG.

In order to remove the influence of back reflection, black vinyl tape was attached to the back of the film. The film was placed under conditions of an incident angle of 70 degrees (the incident surface was the xz plane), and the reflection amplitude ratio angle Ψ _R with respect to the wavelength λ in the visible light region was measured. The results are shown in FIG.

The film thickness from which Δ _O , Δ _T , and Ψ _R were measured was measured with a micrometer. The film thickness was 43.0 μm.

Finally, FIGS. 1, 2, and measurements delta _O shown in FIG. 3, delta _T, the [psi _R, equation (1), formula (2) are substituted into equation _(3), n x, _{n y} , _Nz were calculated. The results are shown in FIG.

In Example 1, at the same time as measuring the transmission phase difference delta _T of the incident angle of 60 degrees was measured transmission amplitude ratio angle [psi _T. The results are shown in FIG.
The thickness of the film from which Δ _O , Δ _T , and Ψ _T were measured was measured with a micrometer. The film thickness was 43.0 μm.

Finally, FIGS. 1, 2, and measurements delta _O shown in FIG. 5, delta _T, the [psi _T, equation (4), equation (5) are substituted into equation _(6), n x, _{n y} , _Nz were calculated. The results are shown in FIG.

From the above results, delta at each wavelength _O, delta _T, [psi _R measured, the value equation (1), equation (2), only into equation (3), _n x at each wavelength, n: _It can be seen that _y and _nz can be calculated by simple algebraic calculation. Similarly, delta _O at each wavelength, delta _T, measured [psi _T, the value equation (4), Equation (5), only into equation (6), _n x at each _{wavelength, n} y, It can be seen that _nz can be calculated by simple algebraic calculation.

It is the figure which showed the wavelength dependence of transmission phase difference (DELTA) _{O in case of} an incident angle of 0 degree | times. It is the figure which showed the wavelength dependence of transmission phase difference (DELTA) _{T in case of} an incident angle of 60 degree | times. It is the figure which showed the wavelength dependence of reflection amplitude ratio angle | corner (PSI) _{R in case} of 70 degrees of incident angles. Delta _O, a diagram showing the wavelength dependence of delta _T, and Ψ computed _n x based on the _{R, n y,} and _{n z.} It is the figure which showed the wavelength dependence of transmission amplitude ratio angle | corner (PSI) _{T in case} of the incident angle of 60 degree | times. Delta _O, a diagram showing the wavelength dependence of delta _T, and the calculated _n x based on Ψ _{T, n y,} and _{n z.}

Explanation of symbols

Δ _O : Transmission phase difference at an incident angle of 0 degree Δ _T : Transmission phase difference at an incident angle of 60 degrees Ψ _R : Reflection amplitude ratio angle at an incident angle of 70 degrees Ψ _T : When the incident angle is 60 degrees transmission amplitude ratio angle n _x: refractive index in the in-plane slow axis direction of the optically anisotropic film n _y: refractive index in a direction perpendicular in a plane in the in-plane slow axis of the optically anisotropic film n _z: optical Refractive index in the thickness direction of anisotropic film

Claims (2)

X-axis and y-axis is taken in a direction parallel to the optically anisotropic film surface, the z-axis is taken in a direction perpendicular to the membrane, and the in-plane slow axis (x-axis of the optically anisotropic film a n _x orthogonal to each other ) Direction refractive index, _ny is the in-plane orthogonal refractive index of the optical anisotropic film (y axis), and _nz is the optical anisotropic film thickness (z axis) direction. When the refractive index is
The optically anisotropic film, a step of measuring the transmission phase difference delta _O1 when the light of wavelength λ at an incident angle theta _O1,
The optically anisotropic film, a step of measuring the transmission phase difference delta _T1 when the light of the wavelength λ at an incident angle theta _T1,
Measuring a reflection amplitude ratio angle Ψ _R1 when light having the wavelength λ is incident on the optical anisotropic film at an incident angle θ _R1 ;
(However, the incident surfaces of light in the measurement of Δ _O1 , Δ _T1 and Ψ _R1 are the same and are either the xz plane or the yz plane of the optical anisotropic film, and the incident angles θ _O1 , θ _T1 and θ _R1 are Represents the angle that the light makes with the z-axis in the plane of incidence, and θ _O1 and θ _T1 are not equal.)
Using the measured transmission phase difference Δ _O1 , transmission phase difference Δ _T1, and reflection amplitude ratio angle Ψ _R1 , when the incident surface is an xz plane, the incident surface is yz based on the equations (1) to (3). If a surface based on equation (1 ') to (3') comprises a refractive index of the optically anisotropic film n _x, and obtaining a n _y and n _z, the optically anisotropic film Test method.

_{Δ O1 = (n x (1} -ξ O1 2 / n z 2) 0.5
^{_{-N y (1-ξ O1 2}} / n y 2) 0.5) × d (1)
[However, ξ _O1 = sin θ _O1 . ]

_{Δ T1 = (n x (1} -ξ T1 2 / n z 2) 0.5
^{_{-N y (1-ξ T1 2}} / n y 2) 0.5) × d (2)
[However, ξ _T1 = sin θ _T1 . ]

tan Ψ _R1 = | ((ξ _p + αξ _R ) cos θ _R1 −1) × (cos θ _R1 + ξ _s ))
/ ((Ξ _p + αξ _R ) cos θ _R1 +1) × (cos θ _R1 + ξ _s )) | Equation (3)
[However,
ξ _R = sinθ _R1
ξ _s = _ny (1-ξ _R ² / _ny ² ) ^0.5
_{ξ p = n x (1-} ξ R 2 / n z 2) 0.5
alpha = a ^{_{(n x 2 -ξ p 2 -ξ}} R ξ p) / (ξ R 2 + ξ R ξ p -n z 2). ]

Δ _O1 = ( _ny (1-ξ _O1 ² / _nz ² ) ^{0.5
_{-N x (1-ξ O1 2}} / n x 2) 0.5) × d Formula (1 ')
[However, ξ _O1 = sin θ _O1 . ]

Δ _T1 = ( _ny (1-ξ _T1 ² / _nz ² ) ^{0.5
_{-N x (1-ξ T1 2}} / n x 2) 0.5) × d (2 ')
[However, ξ _T1 = sin θ _T1 . ]

tan Ψ _R1 = | ((ξ _p + αξ _R ) cos θ _R1 −1) × (cos θ _R1 + ξ _s ))
/ ((Ξ _p + αξ _R ) cos θ _R1 +1) × (cos θ _R1 + ξ _s )) | formula (3 ′)
[However,
ξ _R = sinθ _R1
ξ _s = n _x (1-ξ _R ² / n _x ² ) ^0.5
ξ _p = _ny (1-ξ _R ² / _nz ² ) ^0.5
alpha = a ^{_{(n y 2 -ξ p 2 -ξ}} R ξ p) / (ξ R 2 + ξ R ξ p -n z 2). ]
X-axis and y-axis is taken in a direction parallel to the optically anisotropic film surface, the z-axis is taken in a direction perpendicular to the membrane, and the in-plane slow axis (x-axis of the optically anisotropic film a n _x orthogonal to each other ) Direction refractive index, _ny is the in-plane orthogonal refractive index of the optical anisotropic film (y axis), and _nz is the optical anisotropic film thickness (z axis) direction. When the refractive index is
The optically anisotropic film, a step of measuring the transmission phase difference delta _O2 when the light of wavelength λ at an incident angle theta _O2,
The optically anisotropic film, comprising the steps of: transmitting a phase difference delta _T2 measurement when the incident light of the wavelength λ at an incident angle theta _T2,
A step of measuring a transmission amplitude ratio angle Ψ _T2 when light having the wavelength λ is incident on the optical anisotropic film at an incident angle θ _R2 ;
(However, the incident surfaces of light in the measurement of Δ _O2 , Δ _T2 and Ψ _T2 are the same and are either the xz plane or the yz plane of the optical anisotropic film, and the incident angles θ _O2 , θ _T2 and θ _R2 are Represents the angle that the light makes with the z-axis in the plane of incidence, and θ _O2 and θ _T2 are not equal.)
Using the measured transmission phase difference Δ _O2 , transmission phase difference Δ _T2, and transmission amplitude ratio angle Ψ _T2 , when the incident surface is the xz plane, the incident surface is yz based on the equations (4) to (6). If the surface is a surface, the refractive index n _x , _ny and _nz of the optical anisotropic film is obtained based on the formulas (4 ′) to (6 ′) , and an optical anisotropic film comprising: Test method.

_{Δ O2 = (n x (1} -ξ O2 2 / n z 2) 0.5
^{_{-N y (1-ξ O2 2}} / n y 2) 0.5) × d Equation (4)
[However, ξ _O2 = sin θ _O2 . ]

Δ _T2 = (n _x (1-ξ _T2 ² / _nz ² ) ^{0.5
_{-N y (1-ξ T2 2}} / n y 2) 0.5) × d Formula (5)
[However, ξ _T2 = sin θ _T2 . ]

tan Ψ _T2 = | T _P1 · T _P2 / T _S1 · T _S2 | Equation (6)
[However,
T _S1 = 2n _i cos θ _{R2
/ (N i cosθ R2 + n} y (1- (n i sinθ R2 / n y) 2) 0.5)
_{T S2 = 2n y (1- (} n i sinθ R2 / n y) 2) 0.5
_{/ (N y (1- (n} i sinθ R2 / n y) 2) 0.5 + n i cosθ R2)
T _P1 = [(ξ _z1 ^(r) −ξ _z1 ⁽ⁱ⁾ ) − ξ _x (tan α _r1 + tan α _i1 )]
/ [(Ξ _z1 ^(r) −ξ _z1 ^(t) ) − ξ _x (tan α _r1 + tan α _t1 )]
× [(1 + tan ² α _t1 ) / (1 + tan ² α _i1 )] ^0.5
{However,
ξ _x = n _i sin θ _R2
ξ _z1 ⁽ⁱ⁾ = n _i cosθ _R2
ξ _z1 ^(r) = −n _i cos θ _R2
ξ _z1 ^(t) = n _x (1−ξ _x ² / n _z ² ) ^0.5
tanα _i1 = tanθ _R2
tan α _r1 = tan θ _R2
tan α _t1 = −ξ _x ξ _z1 ^(t) / (ξ _x ² −n _z ² ). }
T _P2 = [(ξ _z2 ^(r) −ξ _z2 ⁽ⁱ⁾ ) − ξ _x (tan α _r2 + tan α _i2 )]
/ [(Ξ _z2 ^(r) −ξ _z2 ^(t) ) − ξ _x (tan α _r2 + tan α _t2 )]
× [(1 + tan ² α _t2 ) / (1 + tan ² α _i2 )] ^0.5
{However,
^{_{ξ z2 (i) = n x}} (1-ξ x 2 / n z 2) 0.5
ξ _z2 ^(r) = −ξ _z2 ⁽ⁱ⁾
ξ _z2 ^(t) = n _i cosθ _R2
tan α _i2 = −ξ _x ξ _z2 ⁽ⁱ⁾ / (ξ _x ² −n _z ² )
tan α _r2 = ξ _x ξ _z2 ^(r) / (ξ _x ² −n _z ² )
It is a tanα _t2 = tanθ _R2. }. ]

Δ _O2 = ( _ny (1-ξ _O2 ² / _nz ² ) ^{0.5
_{-N x (1-ξ O2 2}} / n x 2) 0.5) × d Formula (4 ')
[However, ξ _O2 = sin θ _O2 . ]

Δ _T2 = ( _ny (1-ξ _T2 ² / _nz ² ) ^{0.5
_{-N x (1-ξ T2 2}} / n x 2) 0.5) × d Formula (5 ')
[However, ξ _T2 = sin θ _T2 . ]

tan Ψ _T2 = | T _P1 · T _P2 / T _S1 · T _S2 | Formula (6 ′)
[However,
T _S1 = 2n _i cos θ _R2
/ (N _i cos θ _R2 + n _x (1− (n _i sin θ _R2 / n _x ) ² ) ^0.5 )
T _S2 = 2n _x (1− (n _i sin θ _R2 / n _x ) ² ) ^0.5
/ (N _x (1− (n _i sin θ _R2 / n _x ) ² ) ^0.5 + n _i cos θ _R2 )
T _P1 = [(ξ _z1 ^(r) −ξ _z1 ⁽ⁱ⁾ ) − ξ _y (tan α _r1 + tan α _i1 )]
/ [(Ξ _z1 ^(r) −ξ _z1 ^(t) ) − ξ _y (tan α _r1 + tan α _t1 )]
× [(1 + tan ² α _t1 ) / (1 + tan ² α _i1 )] ^0.5
{However,
ξ _y = n _i sin θ _R2
ξ _z1 ⁽ⁱ⁾ = n _i cosθ _R2
ξ _z1 ^(r) = −n _i cos θ _{R2
^{ξ z1 (t) = n y}} (1-ξ y 2 / n z 2) 0.5
tanα _i1 = tanθ _R2
tan α _r1 = tan θ _R2
tan α _t1 = −ξ _y ξ _z1 ^(t) / (ξ _y ² −n _z ² ). }
T _P2 = [(ξ _z2 ^(r) −ξ _z2 ⁽ⁱ⁾ ) − ξ _y (tan α _r2 + tan α _i2 )]
/ [((Ξ _z2 ^(r) −ξ _z2 ^(t) ) − ξ _y (tan α _r2 + tan α _t2 )]
× [(1 + tan ² α _t2 ) / (1 + tan ² α _i2 )] ^0.5
{However,
^{_{ξ z2 (i) = n y}} (1-ξ y 2 / n z 2) 0.5
ξ _z2 ^(r) = −ξ _z2 ⁽ⁱ⁾
ξ _z2 ^(t) = n _i cosθ _R2
tan α _i2 = −ξ _y ξ _z2 ⁽ⁱ⁾ / (ξ _y ² −n _z ² )
tan α _r2 = ξ _y ξ _z2 ^(r) / (ξ _y ² −n _z ² )
It is a tanα _t2 = tanθ _R2. }. ]

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