JP4486425B2 - Method for calculating optical parameters of twisted alignment liquid crystal film - Google Patents

Description

  The present invention relates to a method for calculating an optical parameter of a twisted alignment liquid crystal film used for quality control of a twisted alignment liquid crystal film in which an alignment axis is twisted along the thickness direction.

  As a monitor for a personal computer or the like, a liquid crystal display is often used from the viewpoint of space saving. In a liquid crystal display, a twisted alignment liquid crystal film in which an alignment axis is twisted along the thickness direction is often used particularly from the viewpoint of thinning and improving productivity.

  For such a twist-aligned liquid crystal film, quality control is important. In general, optical parameters such as the twist angle of the alignment axis and retardation Δnd (Δn is birefringence, d represents the thickness of the twisted alignment liquid crystal film) and the like are used as a standard for the quality of the twist alignment liquid crystal film. The quality control of the twisted alignment liquid crystal film is performed. Therefore, when quality control is performed on a large amount of twisted alignment liquid crystal film, it is important to calculate the optical parameters efficiently.

  As such an optical parameter calculation method, a method disclosed in Patent Document 1 below is known. In Patent Document 1, for a liquid crystal cell having a known twist angle, the liquid crystal cell is inserted between a polarizer and an analyzer, and the polarization angle of the polarizer is 45 ° from the alignment direction of the light incident surface of the liquid crystal cell. Tilt and measure the transmitted light intensity of the polarizer in a state where the polarization angle of the analyzer is further tilted by 45 ° from the alignment direction of the light exit surface of the liquid crystal cell, and calculate the retardation Δnd based on the measured light intensity Is disclosed.

Further, as an optical parameter calculation method for the twisted alignment liquid crystal film, an ellipsometry method is also known. In the ellipsometry, measurement is performed at a single wavelength, the polarization state of incident light and the polarization state of outgoing light after passing through the twisted alignment liquid crystal film are analyzed, and the optical characteristics of the twist alignment liquid crystal film are determined.
JP-A-4-3071212

  However, with the optical parameter calculation method described in Patent Document 1, the retardation of a liquid crystal cell with a known twist angle can be easily calculated. However, for a twist-aligned liquid crystal film with an unknown twist angle, the optical parameters such as retardation can be accurately measured. It cannot be calculated well.

  In addition, although the ellipsometry described above is measured at a single wavelength, the measurement speed is fast, but the polarization state of the emitted light affects the measurement sensitivity. Therefore, depending on the optical characteristics of the twisted alignment liquid crystal film, parameters such as retardation can be accurately measured. I can't find it well.

  The present invention has been made in view of the above circumstances, and the optical parameter of the twist-aligned liquid crystal film can accurately calculate the optical parameters of the twist-aligned liquid crystal film whose twist angle is unknown, regardless of the optical characteristics of the twist-aligned liquid crystal film. An object is to provide a parameter calculation method.

The present invention relates to a method for calculating an optical parameter of a twisted alignment liquid crystal film in which an alignment axis is twisted along a thickness direction, the first step of disposing the twisted alignment liquid crystal film between a polarizer and an analyzer, A second step of measuring a transmission spectrum by dispersing light emitted through the polarizer, the twisted alignment liquid crystal film, and the analyzer; and a minimum value of transmittance in the transmission spectrum measured in the second step is minimized. Adjusting the angle Δθ formed between the transmission axis of the polarizer and the transmission axis of the analyzer so that the wavelength λ _min indicating the minimum transmittance at that time is read, and the Δθ and λ _min And a fourth step of calculating optical parameters of the twisted alignment liquid crystal film based on the fourth step.

  According to this optical parameter calculation method, the optical parameters of the twist-aligned liquid crystal film whose twist angle is unknown can be accurately calculated regardless of the optical characteristics of the twist-aligned liquid crystal film.

In the fourth step, the twist angle φ _tw of the alignment axis as an optical parameter of the twist alignment liquid crystal film is, for example, the following formula (1):
φ _tw = Δθ−90 ° ± 180 ° × n (1)
(In the above formula (1), φ _tw represents the twist angle of the alignment axis in the twisted alignment liquid crystal film, and Δθ represents the angle formed by the transmission axis of the polarizer and the transmission axis of the analyzer).
N can be calculated by substituting the calculated n and Δθ obtained in the third step into the equation (1).

（上記式（２）中、λ_ｍｉｎは前記透過率の極小値が最小となる波長、Δｎｄ（λ_ｍｉｎ）はλ_ｍｉｎの波長におけるリタデーションを表す）
に基づいて、前記ねじれ配向液晶フィルムの光学パラメータとしてのねじれ角φ_ｔｗおよびリタデーションΔｎｄを算出する。 In the fourth step, the following formula (1) is obtained from Δθ and λ _min obtained in the third step:
φ _tw = Δθ−90 ° ± 180 ° × n (1)
(In the above formula (1), φ _tw represents the twist angle of the alignment axis in the twisted alignment liquid crystal film, Δθ represents the angle formed by the transmission axis of the polarizer and the transmission axis of the analyzer) and the following formula (2):

(In the above formula (2), λ _min represents a wavelength at which the minimum value of the transmittance is minimized, and Δnd (λ _min ) represents retardation at a wavelength of λ _min ).
Based on, calculate a twist angle phi _tw and the retardation Δnd as an optical parameter of the twisted aligned liquid crystal film.

In this case, the retardation is also calculated with high accuracy by calculating the twist angle with high accuracy. In the optical parameter calculation method according to the present invention, the relative angle between the transmission axes of the polarizer and the analyzer is calculated between the third step and the fourth step based on Δθ obtained in the third step. The polarizer and the analyzer are rotated while being maintained at (Δθ−90 °), and the light emitted through the polarizer, the twisted liquid crystal film, and the analyzer is dispersed to measure a transmission spectrum. And a sixth step of adjusting the transmission axis θ _{p of the} polarizer and the angle of the transmission axis of the analyzer so that the minimum value of the transmittance is minimized in the transmission spectrum measured in the fifth step. further comprising the door, in the fourth step, the theta _p, calculate the optical parameters of the twisted alignment liquid crystal film on the basis of the Δθ and the lambda _min.

  In this case, the optical parameters of the twisted alignment liquid crystal film can be calculated with higher accuracy than in the case where the fifth step and the sixth step are not included.

In the fourth step, the following formula (4):
φ = θ _p −45 ° (4)
(In the above formula, φ represents the orientation axis on the polarizer side of the twisted alignment liquid crystal film, and θ _p represents the angle of the transmission axis of the polarizer)
Thus, a polarizer-side alignment axis as an optical parameter of the twisted alignment liquid crystal film may be obtained.

In this case, since θ _p is calculated with high accuracy, the angle of the orientation axis on the polarizer side can be calculated with high accuracy.

（上記式（２）中、λ_ｍｉｎは前記透過率の極小値が最小となる波長、Δｎｄ（λ_ｍｉｎ）はλ_ｍｉｎの波長におけるリタデーションを表す）
に基づいて、前記ねじれ配向液晶フィルムの光学パラメータとしてのねじれ角およびリタデーションを、それぞれｎとｍを用いた関係式で表す第８工程と、
下記式（３）：

から算出される理論スペクトルと前記第７工程で得られた透過スペクトルとが一致するように前記式（１）および（２）のｎおよびｍを決定し、前記ねじれ配向液晶フィルムの光学パラメータとしてのねじれ角およびリタデーションを求める第９工程とを更に含む。
In the optical parameter calculation method, the fourth step includes arranging the transmission axis of the polarizer at θ _p and the transmission axis of the analyzer at θ _p + Δθ, and the polarizer, the twisted alignment liquid crystal film, and From the seventh step of measuring the transmission spectrum by splitting the light emitted through the analyzer and Δθ and λ _min obtained in the third step, the following formula (1):
φ _tw = Δθ−90 ° ± 180 ° × n (1)
(In the above formula (1), φ _tw represents the twist angle of the alignment axis in the twisted alignment liquid crystal film, Δθ represents the angle formed by the transmission axis of the polarizer and the transmission axis of the analyzer) and the following formula (2):

(In the above formula (2), λ _min represents a wavelength at which the minimum value of the transmittance is minimized, and Δnd (λ _min ) represents retardation at a wavelength of λ _min ).
The twist angle and retardation as optical parameters of the twist-alignment liquid crystal film based on the eighth step, respectively represented by a relational expression using n and m,
Following formula (3):

N and m in the formulas (1) and (2) are determined so that the theoretical spectrum calculated from the above and the transmission spectrum obtained in the seventh step coincide with each other as the optical parameters of the twisted alignment liquid crystal film. twist angle and further including a ninth step of obtaining the retardation.

  In this case, the twist angle and retardation, which are optical parameters of the twist-aligned liquid crystal film, can be calculated with higher accuracy.

  According to the optical parameter calculation method for the twist-aligned liquid crystal film of the present invention, the optical parameters of the twist-aligned liquid crystal film whose twist angle is unknown can be accurately calculated regardless of the optical characteristics of the twist-aligned liquid crystal film.

  Hereinafter, the embodiment of the optical parameter calculation method of the twist alignment liquid crystal film of the present invention is described in detail.

  First, prior to the description of the optical parameter calculation method, an optical parameter calculation apparatus that calculates optical parameters will be described.

  FIG. 1 is a schematic diagram illustrating an example of an optical parameter calculation apparatus. As shown in FIG. 1, the optical parameter calculation device 1 includes a light source 2, a polarizer 3, an analyzer 5, and a spectrometer 6. The light source 2, the polarizer 3, the analyzer 5 and the spectrometer 6 are sequentially arranged along the optical axis 7. As the light source 2, one that emits white light is used.

  The polarizer 3 has a transmission axis, and converts the light emitted from the light source 2 into linearly polarized light that vibrates along the transmission axis. The analyzer 5 has a transmission axis and is from the side of the polarizer 3. The incident light is converted into linearly polarized light that oscillates along the transmission axis. Both the polarizer 3 and the analyzer 5 can rotate the transmission axis around the optical axis 7, and the angle between the transmission axis of the polarizer 3 and the transmission axis of the analyzer 5 can be arbitrarily set. It is possible to adjust. In the present embodiment, the polarizer 3 and the analyzer 5 are connected to a computer via a driving device (not shown), and the polarizer 3 and the analyzer 5 can be automatically rotated by operating the computer. ing.

  The spectroscope 6 is for measuring the transmission spectrum by dispersing the light incident from the analyzer 5.

  Next, the optical parameter calculation method of the twist alignment liquid crystal film using the optical parameter calculation apparatus 1 mentioned above is demonstrated.

First, a twist-aligned liquid crystal film (hereinafter simply referred to as “liquid crystal film”) 4 is prepared. Here, the liquid crystal film 4 has a first surface and a second surface parallel to each other, and the alignment axis of the liquid crystal is parallel to the first surface or the second surface. As the liquid crystal film 4 of the present embodiment, one for a liquid crystal display, that is, one having a wavelength λ _{min at} which the minimum value of transmittance is minimum is in the visible wavelength range (for example, in the range of 400 to 800 nm) is used. It is done. Then, the liquid crystal film 4 is arranged between the polarizer 3 and the analyzer 5 so that the first surface or the second surface is orthogonal to the optical axis 7 (first step).

Next, the transmission spectrum is measured (second step). The measurement of the transmission spectrum can be performed by turning on the light source 2 and separating the light emitted from the light source 2 through the polarizer 3, the liquid crystal film 4, and the analyzer 5 with the spectroscope 6. At this time, as shown in FIG. 2, in the transmission spectrum, the transmittance becomes minimum at the wavelength λ _min in the visible light wavelength region. This means that for light of wavelength λ _min , linearly polarized light incident on the liquid crystal film 4 is emitted as linearly polarized light.

Then, while observing the measurement result of the transmission spectrum, the analyzer 5 is rotated around the optical axis 7 while the polarizer 3 is fixed, so that the minimum value of the transmittance in the transmission spectrum is minimized. The angle Δθ formed by the transmission axis of the optical element 3 and the transmission axis of the analyzer 5 is adjusted, and the wavelength λ _min indicating the minimum transmittance at that time is read (third step).

  Here, the reason for adjusting Δθ with reference to the minimum value of transmittance is that the transmittance of the spectroscope 6 may be saturated in the case where the maximum value of transmittance is used as a reference. This is because there is a possibility that the deviation from the actual optical parameter becomes very large.

  The angle formed between the transmission axis of the polarizer 3 and the transmission axis of the analyzer 5 is the polarizer when the transmission axis of the polarizer 3 and the transmission axis of the analyzer 5 are projected on a plane orthogonal to the optical axis 7. 3 is an angle formed by the transmission axis 3 and the transmission axis of the analyzer 5.

  Next, the polarizer 3 and the analyzer 5 are rotated while maintaining the relative angle (Δθ−90 °) between the polarizer 3 and the analyzer 5 based on Δθ obtained in the third step, and the polarizer 3 Then, the light emitted through the twisted alignment liquid crystal film 4 and the analyzer 5 is dispersed to measure the transmission spectrum (fifth step).

  Subsequently, in the transmission spectrum measured in the fourth step, the angles of the transmission axis θp of the polarizer 3 and the transmission axis of the analyzer 5 are adjusted so that the minimum value of the transmittance is minimized (sixth step). .

When θ _p , Δθ, and λ _min are obtained as described above, the optical parameters of the twisted alignment liquid crystal film 4 are calculated based on θ _p , Δθ, and λ _min (fourth step).

Here, a method for calculating the optical parameters of the twisted alignment liquid crystal film 4 based on θ _p , Δθ, and λ _min will be specifically described.

  First, the transmission axis of the polarizer 3 is set to θp, the transmission axis of the analyzer 5 is set to θp + Δθ, and the light emitted through the polarizer 3, the liquid crystal film 4 and the analyzer 5 is dispersed to measure the transmission spectrum ( (7th process).

（上記式（２）中、λ_ｍｉｎは透過率の極小値が最小となる波長、Δｎｄ（λｍｉｎ）はλ_ｍｉｎの波長におけるリタデーションを表す） Next, from Δθ and λ _min obtained in the third step, based on the following formulas (1) and (2), the twist angle and retardation which are optical parameters of the liquid crystal film 4 are used for n and m, respectively. (8th step).
φ _tw = Δθ−90 ° ± 180 ° × n (1)
(In the above formula (1), phi _tw twist angle of the orientation axis of the liquid crystal film 4, [Delta] [theta] represents the angle between the transmission axis of the transmission axis and the analyzer 5 of the polarizer 3)

(In the above formula (2), λ _min is the wavelength at which the minimum value of transmittance is minimized, and Δnd (λmin) represents retardation at the wavelength of λ _min ).

  Here, the derivation process of the formula (1) will be described.

  FIG. 3 is a front view showing the liquid crystal film 4 when the light source 2 is viewed from the analyzer 5 side. In FIG. 3, reference numeral 8 denotes a transmission axis of the analyzer 5, reference numeral 9 denotes a liquid crystal alignment axis on the analyzer 5 side of the liquid crystal film 4, reference numeral 10 denotes a transmission axis of the polarizer 3, and reference numeral 11 denotes a polarizer of the liquid crystal film 4. It shows the alignment axis of the liquid crystal on the 3rd side.

As shown in FIG. 3, when the minimum value of the transmittance in the transmission spectrum is minimized, the transmission axis 8 of the analyzer 5 is advanced from the transmission axis 10 of the polarizer 3 by the twist angle + 90 ° of the liquid crystal film. Will be placed. Since the transmission axes of the polarizer and the analyzer are indistinguishable from head to tail, they cannot be distinguished from 0 ° and ± 180 °. Therefore, if the angle of the transmission axis 10 of the polarizer 3 is θ _p , the angle of the transmission axis 8 of the analyzer 5 is θ _A, and θ _A −θ _p is Δθ, then the twist angle φ _tw is
θ _A = θ _p + φ _tw + 90 °
φ _tw = θ _A −θ _p −90 °
= Δθ-90 °
It is represented by However, since the polarizer and the analyzer cannot distinguish between 0 ° and 180 °, there is an answer at a cycle of 180 ° when actually obtaining the twist angle from Δθ. That is, φ _tw is actually expressed by the following formula:
φ _tw = θ _A −θ _p −90 ° ± 180 ° × n
It is represented by

  As described above, the reason why the relative angle between the transmission axis 10 of the polarizer 3 and the transmission axis 8 of the analyzer 5 corresponds to the twist angle of the liquid crystal film 4 when the minimum value of the transmittance in the transmission spectrum is minimized. Is as follows.

で表される。そして、透過スペクトルにおける透過率の極小値が最小となる場合においては、理論的にはＴ＝０となる。そこで、上記式において、Ｔ＝０の場合の解を算出すると、偏光子３の透過軸１０と検光子５の透過軸８の相対角度が、液晶フィルム４のねじれ角＋９０°もしくは−９０°に対応する角度となる。 That is, the transmittance T is generally expressed by the following formula:

It is represented by When the minimum value of the transmittance in the transmission spectrum is minimized, theoretically, T = 0. Therefore, in the above equation, when the solution for T = 0 is calculated, the relative angle between the transmission axis 10 of the polarizer 3 and the transmission axis 8 of the analyzer 5 becomes the twist angle + 90 ° or −90 ° of the liquid crystal film 4. The corresponding angle.

から算出される理論スペクトルと上記第７工程で得られた透過スペクトルとが一致するように式（１）および（２）のｎおよびｍを決定する。こうして決定したｎおよびΔθを上記式（１）に代入することにより、液晶フィルム４の光学パラメータの一つであるねじれ角φ_ｔｗが求められる。 If the twist angle and retardation which are the optical parameters of the liquid crystal film 4 are expressed by the relational expressions using n and m, respectively, the following formula (3):

N and m in the equations (1) and (2) are determined so that the theoretical spectrum calculated from the above matches the transmission spectrum obtained in the seventh step. By substituting n and Δθ determined in this way into the above equation (1), the twist angle φ _tw which is one of the optical parameters of the liquid crystal film 4 is obtained.

Further, by substituting m determined as described above, the twist angle φ _tw , and λ _min into the above equation (2), the retardation Δnd which is one of the optical parameters of the liquid crystal film 4 is obtained (first). 9 steps).

According to the optical parameter calculation method, even if the twist angle of the liquid crystal film 4 is unknown, the twist angle φ _tw and the retardation Δnd can be accurately calculated regardless of the optical characteristics of the liquid crystal film 4.

After calculating the twist angle φ _tw and the retardation Δnd as described above, the orientation axis on the polarizer 3 side of the liquid crystal film 4 may be calculated from the transmission axis of the obtained polarizer 3 (tenth Process).

  Here, the calculation method of the orientation axis by the side of the polarizer 3 of the liquid crystal film 4 is demonstrated concretely.

If Δθ−90 ° is substituted into the above equation (1), there is another condition that T = 0. That is, the angle between the transmission axis 10 of the polarizer 3 and the orientation axis 11 on the polarizer 3 side of the liquid crystal film 4 and the transmission axis 8 of the analyzer 5 and the orientation axis 9 on the analyzer 5 side of the liquid crystal film 4. This is a case where the formed angle is 45 °. At this time, an angle formed by the transmission axis 10 of the polarizer 3 (transmission axis 8 of the analyzer 5) and the alignment axis 11 of the liquid crystal film 4 on the polarizer 3 side (orientation axis 9 of the liquid crystal film 4 on the analyzer 5 side), Since the angle formed by the transmission axis 8 of the analyzer 5 and the alignment axis 9 on the analyzer 5 side of the liquid crystal film 4 is always 45 °, the polarizer is T = 0 under the condition of Δθ−90 °. Find 3 transmission axes 10. Thereby, the orientation axis 11 on the polarizer 3 side of the liquid crystal film 4 can be immediately obtained from the following formula (4).
φ = θ _p −45 ° (4)
(In the above formula (4), φ represents the orientation axis of the liquid crystal film 4 on the polarizer 3 side, and θ _p represents the angle of the transmission axis of the polarizer 3).

  Thus, when calculating | requiring the orientation axis | shaft 11 by the side of the polarizer 3 of the liquid crystal film 4, (theta) p can be calculated more accurately, Therefore The orientation axis | shaft 11 by the side of the polarizer 3 can also be calculated with a higher precision.

The optical parameter calculation method of the twist alignment liquid crystal film concerning this invention is not limited to the said embodiment. For example, in the above embodiment, after calculating the twist angle φ _tw and retardation Δnd, the alignment axis 11 on the polarizer 3 side of the liquid crystal film 4 (the alignment axis on the analyzer 5 side of the liquid crystal film 4) is calculated. In the optical parameter calculation method of the present invention, after calculating the alignment axis 11 of the liquid crystal film 4 on the polarizer 3 side (the alignment axis of the liquid crystal film 4 on the analyzer 5 side), the twist angle φ _tw and the retardation Δnd are calculated. These may be calculated simultaneously. If attention is paid to the calculation geometry, there is no problem with either the alignment axis on the polarizer side of the liquid crystal film or the alignment axis on the analyzer side of the liquid crystal film.

Furthermore, in the above embodiment, the twist angle and retardation are calculated simultaneously, but it is also possible to calculate the retardation Δnd after calculating the twist angle φ _tw . At this time, the twist angle is calculated as follows, for example. That twist angle phi _tw axis of orientation of the liquid crystal film 4, for example, the formula (1):
φ _tw = Δθ−90 ° ± 180 ° × n (1)
N can be calculated by substituting the calculated n and Δθ obtained in the third step into the above equation (1).

  Here, as a method of calculating n, for example, there is a method such as film cross-sectional observation with an electron microscope.

In the above embodiment, after calculating the twist angle φ _tw using the above formula (1), the retardation can be calculated based on the twist angle φ _tw thus calculated and the above formula (2).
However, in this case, in the above formula (2), m is the following condition:
mπ> φ _tw ,
m = 1-4
Shall be satisfied.

It is the schematic which shows an example of the measuring apparatus used for the optical parameter calculation method of this invention. It is a graph which shows the transmission spectrum of the twist alignment liquid crystal film measured in the state arrange | positioned between a polarizer and an analyzer. It is a front view which shows the twist orientation liquid crystal film when a light source is looked at from the analyzer side.

Explanation of symbols

_{DESCRIPTION OF} SYMBOLS 3 ... Polarizer, 4 ... Twist orientation liquid crystal film, 5 ... Analyzer, (phi) _tw ... Twist angle | corner, (DELTA) (theta) ... Angle between the transmission axis of a polarizer, and the transmission axis of an analyzer, (DELTA) nd ... Retardation, (DELTA) delta ... Phase difference, λ _min is the wavelength at which the minimum value of transmittance is minimized.

Claims (2)

In the optical parameter calculation method of the twist alignment liquid crystal film in which the alignment axis is twisted along the thickness direction,
A first step of disposing the twisted alignment liquid crystal film between a polarizer and an analyzer;
A second step of measuring a transmission spectrum by dispersing light emitted through the polarizer, the twisted alignment liquid crystal film, and the analyzer;
The angle Δθ formed between the transmission axis of the polarizer and the transmission axis of the analyzer is adjusted so that the minimum value of the transmittance in the transmission spectrum measured in the second step is minimized, and the minimum transmittance at that time is adjusted A third step of reading a wavelength λ _min indicating
A fourth step of calculating optical parameters of the twisted alignment liquid crystal film based on the Δθ and the λ _min ;
Only including,
Between the third step and the fourth step,
Based on Δθ obtained in the third step, the polarizer and the analyzer are rotated while maintaining the relative angle between the transmission axes of the polarizer and the analyzer at (Δθ−90 °), A fifth step of measuring a transmission spectrum by dispersing light emitted through the polarizer, the twisted alignment liquid crystal film and the analyzer;
In the transmission spectrum measured in the fifth step, a sixth step of adjusting the angle θ _p of the transmission axis of the polarizer and the angle of the transmission axis of the analyzer so that the minimum value of the transmittance is minimized. In addition,
The fourth step is
Wherein the transmission axis of the polarizer theta _p, wherein the transmission axis of the analyzer is arranged to theta _{p +} [Delta] [theta], the polarizer, the twisted alignment liquid crystal film and the spectrally the light emitted through the analyzer transmission spectrum A seventh step of measuring
From Δθ and λ _min obtained in the third step, the following formula (1):
φ _tw = Δθ−90 ° ± 180 ° × n (1)
(In the above formula (1), φ _tw represents the twist angle of the alignment axis in the twisted alignment liquid crystal film, Δθ represents the angle formed by the transmission axis of the polarizer and the transmission axis of the analyzer) and the following formula (2):

(In the above formula (2), λ _min represents a wavelength at which the minimum value of the transmittance is minimized, and Δnd (λ _min ) represents retardation at a wavelength of λ _min ).
The twist angle and retardation as optical parameters of the twist-alignment liquid crystal film based on the eighth step, respectively represented by a relational expression using n and m,
Following formula (3):

N and m in the formulas (1) and (2) are determined so that the theoretical spectrum calculated from the above and the transmission spectrum obtained in the seventh step coincide with each other as the optical parameters of the twisted alignment liquid crystal film. A ninth step for obtaining a twist angle and retardation;
An optical parameter calculation method for a twist-aligned liquid crystal film, comprising: In the fourth step,
Following formula:
φ = θ _p −45 ° (4)
(In the above formula, φ represents the orientation axis on the polarizer side of the twisted alignment liquid crystal film, and θ _p represents the angle of the transmission axis of the polarizer)
More optical parameter calculation method according to claim 1, wherein the determination of the polarizer side orientation axis of an optical parameter of the twisted aligned liquid crystal film.

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