JP2778935B2 - Method for measuring azimuthal anchoring energy of nematic liquid crystal device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring azimuthal anchoring energy of a nematic liquid crystal element for measuring, for example, azimuthal anchoring energy of a twisted nematic liquid crystal cell.

[0002]

2. Description of the Related Art Liquid crystal display devices have many advantages such as light weight, thinness, and low power consumption, and are therefore widely used as display devices for small electronic devices. Most of the liquid crystal display elements currently in practical use are TN (Twisted Nemati).
c) method and STN (Super Twisted Nematic) method.

In order to improve the electro-optical characteristics of a liquid crystal display device, it is important to control the interface alignment. The rubbing method is widely used industrially because the method of aligning liquid crystal molecules at the interface is relatively simple. It is important to evaluate the effect of the rubbing strength on the backside alignment for improving the characteristics of the liquid crystal display device. Measurement of the anchoring strength in the azimuthal direction at the interface is one of the important parameters for evaluating the interface orientation.

As one of simple evaluation methods for measuring the anchoring strength in the azimuth direction, there is a twist angle measurement method as shown in FIG. In FIG. 10, the rubbing directions at the interface between the upper and lower alignment films are parallel. When a liquid crystal to which a chiral material is attached is injected into a wedge-shaped cell, the liquid crystal is oriented as shown in FIG. That is, the liquid crystal molecules are fixed so as to be aligned in parallel by the interface anchoring force. Here, from the _{A φ / K 2 = (π} -2φ s) / dsinψ, anchoring strength A _phi is determined. Where K
₂ is the twist elastic constant, ψ is the twist angle, and d is the cell thickness. Using a polarizing microscope, ψ (and φ _s ) is obtained by rotating the deflection plate, and the anchoring strength A _φ can be evaluated from the above equation.

[0005]

The method shown in FIG. 10 is excellent as a simple measuring method. However, it is necessary to produce a parallel alignment cell as a measurement sample, which is not suitable for applications such as testing the anchoring strength of a TN cell product manufactured in a factory. Further, when the anchoring strength is high, φ _s detected by the above method is very small and cannot be measured by a polarizing microscope.

[0006] The present invention has been made in view of the above points, and its object is to determine the twist angle of a TN liquid crystal cell,
It is an object of the present invention to provide a method for measuring the azimuthal anchoring energy of a liquid crystal element in which the azimuthal anchoring energy is obtained by calculation from the twist angle.

[0007]

According to a first aspect of the present invention, there is provided a method for measuring azimuthal anchoring energy of a liquid crystal cell.
After the laser light emitted from the laser light source is polarized through a polarizer, the laser light is incident on a liquid crystal cell, and the laser light emitted from the liquid crystal cell is subjected to light transmittance T through an analyzer. In the method for measuring the anchoring energy in the azimuthal direction of the liquid crystal cell by measuring with a photodetector, the liquid crystal cell is rotated once around the optical axis of the laser light and detected by the photodetector. that a first step of obtaining the rotation angle [psi ₀₀ of the liquid crystal cell light transmittance T is minimized, the liquid crystal cell and the analyzer said Le - the rotational speed in the same direction around the optical axis of the laser light The rotation angle ψ _{p of the} analyzer that makes one rotation at a ratio of 1: 2 and minimizes the light transmittance T detected by the photodetector.
(2) a second step for obtaining (1), inserting a retardation plate between the liquid crystal cell and the analyzer so as to be at 45 degrees with the polarizer, rotating the liquid crystal cell little by little, Each time the laser is rotated, the analyzer is rotated once around the optical axis of the laser beam, and the rotation angle ψ _p (2) of the analyzer that minimizes the light transmittance T detected by the photodetector. ) And the rotation angle ψ ₀ (2) of the liquid crystal cell at that time, the rotation angle ψ _{00 of} the liquid crystal cell obtained in the first step, and the rotation angle ψ _{00 of} the liquid crystal cell obtained in the second step. Photon rotation angle ψ _p (1),
The rotation angle of the analyzer ψ _p obtained in the third step ψ _p (2)
A fourth step of obtaining a twist angle Φt of the liquid crystal cell based on the rotation angle ψ ₀ (2) of the liquid crystal cell at that time; and a step of obtaining the twist angle Φt of the liquid crystal cell based on the twist angle Φt obtained in the fourth step. And a fifth step of obtaining the anchoring energy in the azimuthal direction by a predetermined calculation formula.

According to a second aspect of the present invention, there is provided a method for measuring anchoring energy in an azimuthal direction of a liquid crystal cell, wherein a fourth step of the first aspect comprises a general formula T (Φt, u,
条件₀ , ψ _p ,) are partially differentiated by ψ ₀ , ψ _p , respectively, and the relationship between u and t is calculated for a value where the twist angle is smaller than 90 degrees. retardation plate inserted it put on condition obtaining the light transmittance T formula _{T (Φt, u, ψ 0} , ψ p,) and [psi _0, [psi
By substituting the relationship between the twist angle Φt and u into an equation that makes the equations partially differentiated by _p zero, the rotation angle of the liquid crystal cell ψ ₀ and the rotation angle of the analyzer ψ _p are calculated. It is characterized in that it is obtained.

The present invention provides a laser radiated from a laser light source.
After the light is polarized through a polarizer, the light is incident on the liquid crystal cell, and the laser light emitted from the liquid crystal cell is measured through an analyzer to determine the light transmittance T with a photodetector. In the method of measuring the anchoring energy in the azimuthal direction, the liquid crystal cell is rotated once around the optical axis of the laser light so that the light transmittance T detected by the photodetector is minimized. The angle ψ ₀₀ is determined, and the liquid crystal cell and the analyzer are rotated in the same direction about the optical axis of the laser beam in the same direction at a rotation speed of 1: 2 and 1
The rotation angle ψ _p (1) of the analyzer, which is rotated and the light transmittance T detected by the photodetector is minimized, is obtained, and the phase difference plate is set to 45 degrees with the polarizer by using the liquid crystal cell and the analyzer. Inserted between
The liquid crystal cell is rotated little by little, and every time the liquid crystal cell is rotated little by little, the analyzer is rotated once around the optical axis of the laser beam, and the light transmittance T detected by the photodetector is minimized. The rotation angle ψ _p (2) and the rotation angle ψ ₀ (2) of the liquid crystal cell at that time were obtained, and the obtained rotation angle ψ ₀₀ of the liquid crystal cell and the obtained rotation angle ψ _p (1) of the analyzer were obtained. Analyzer rotation angle ψ
The twist angle Φt of the liquid crystal cell is obtained based on _p (2) and the rotation angle ψ ₀ (2) of the liquid crystal cell at that time, and the anchoring energy in the azimuthal direction of the liquid crystal cell is calculated based on the twist angle Φt. It is determined from a predetermined formula.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

Liquid crystal molecules are substances having anisotropy in shape, dielectric constant, refractive index and conductivity. When an external field such as an electric field is applied to the liquid crystal, an alignment phenomenon of molecular axes and an unstable phenomenon accompanied by a flow of liquid crystal molecules occur. These change the optical material of the liquid crystal to which the electric field is applied. This is generally called an electro-optic effect of the liquid crystal. Specifically, ITO (IndiumTi
TN liquid crystal cell 10 is sandwiched between two glass substrates coated with a transparent electrode such as n Oxide) with a thickness of several μm to several tens μm, and has a light transmittance and a light polarization for liquid crystal in a thin film state. An optical change is described by a surface change or the like.

Referring to FIG. 8, TN (Twisted Nematic)
The effect will be described. This TN effect is a mode that can be said to be a basic type of liquid crystal display. In the TN mode, the liquid crystal molecular axis is arranged parallel to the glass electrode surface, and FIG.
As shown in (2), the upper and lower alignment treatment directions are perpendicular to each other so that the molecular axis is twisted by 90 ° from one substrate surface to the other substrate surface.

Then, the polarizing plate 1 is set so that the polarizing axes are orthogonal to each other.
When the voltage is not applied to the TN liquid crystal cell 10 when no voltage is applied as shown in FIG. However, when a voltage equal to or higher than the threshold is applied, the liquid crystal molecules are arranged in the direction of the electric field and the optical rotation is lost as shown in FIG. Blocked by plate 11b.

By performing a physical or chemical treatment on the surface of the substrate of the liquid crystal cell, it is possible to create a direction in which the liquid crystal molecules are easily arranged in a fixed direction parallel to the substrate. This direction is called an easy-orientation axis. For example, when the substrate surface is rubbed, the liquid crystal molecules are likely to be oriented in the rubbing direction. This is because, when the liquid crystal molecules are arranged in this direction in the surface layer, the elastic energy due to torsion or the like is minimized. On the substrate surface,
Such a force that restricts the liquid crystal molecule alignment is called anchoring energy.

[0015] The anchoring energy - is as shown in FIG. 9, the polar angle direction of the anchoring energy -A _theta and azimuthal anchoring energy -A from that binding direction
_φ is divided into

[0016] The present invention is to measure the anchoring energy -A _phi azimuthal direction of the liquid crystal cell as described above. To measure the anchoring energy -A _phi azimuthal direction may be measured twist angle Φt of the liquid crystal molecules in the cell.

Next, an apparatus for measuring the anchoring energy of the liquid crystal cell in the azimuthal direction will be described with reference to FIG. In FIG. 1, reference numeral 21 denotes a laser oscillator for outputting a He-Ne laser. The laser light output from the laser oscillator 21 enters a TN liquid crystal cell 24 via a chopper 22 and a polarizer 23.

The laser light emitted from the TN liquid crystal cell 24 is incident on a photodetector 26 for detecting a light transmittance T via an analyzer 25.

Reference numeral 27 shown by a broken line is a λ / 4 retardation plate.

The TN liquid crystal cell 24 is configured to be rotatable about the optical axis 21a of the laser light output from the laser oscillator 21. The TN liquid crystal cell 24 is driven by a stepping motor m1 at a predetermined angle. The driving of the stepping motor m1 is controlled by the computer 31.

Further, the analyzer 25 is provided with the TN liquid crystal cell 2 described above.
4, the laser output from the laser oscillator 21 is used.
It is configured to be rotatable around the optical axis 21a of the light. This analyzer 25 is a stepping motor for each set angle.
Driven by m2. The driving of the stepping motor m2 is controlled by the computer 31.

The chopper 22 is a lock-in amplifier 3
2 is controlled.

The laser light detected by the photodetector 26 is amplified by a lock-in amplifier 32, and then amplified by a computer 31.
Is input to

A control signal from the temperature controller 33 is input to the TN liquid crystal cell 24 to control the temperature of the TN liquid crystal cell 24.

The coordinate system will be described with reference to FIG. In FIG. 7, ni is n director on the entrance side of the TN liquid crystal cell 24, and no is n director on the exit side of the TN liquid crystal cell 24.
Director, P is the polarizer 23, A is the analyzer 25, ψ ₁ is the angle between the x-axis and the polarizer P, ψ ₀ is the TN liquid crystal cell 24
The angle between the ni director on the entrance side and the polarizer P, ψ
_p indicates the angle between the polarizer P and the analyzer A, and Φt indicates the angle between the n director ni on the incident side and the n director no on the output side of the TN liquid crystal cell 24, that is, the twist angle.

A measurement method for measuring the azimuthal anchoring energy of the liquid crystal cell using the measuring apparatus having the above-described configuration will be described.

First, from the theoretical formula of the transmittance T, the retardation plate 2
If not inserted 7, the transmittance T [psi _0, when it is inserted and the retarder 27 holds when partial differentiation with [psi _p, the transmittance T [psi _0, when partial differentiation with [psi _p The following is a description of the equation that holds.

First, the transmittance in the case of the coordinate system as shown in FIG. 7 and the arrangement of the TN liquid crystal cell 24 as shown in FIG. 1 is obtained by a known method as follows.

T = Equation 1

[0030]

(Equation 1)

When the transmittance T is minimized with respect to ψ ₀ and ψ _p when the phase difference plate 27 is not inserted,
The partial differential value of the transmittance T at ψ ₀ and the partial differential value of the transmittance T at ψ _p are zero.

That is, the relationship shown in Expressions 2 and 3 is obtained.

[0033]

(Equation 2)

[0034]

(Equation 3)

[0035] Then, when not inserted retardation plate 27, since a δ = 0, (1) When zero value obtained by partially differentiating in [psi ₀ the equation, the number 4 in relation holds.

[0036]

(Equation 4)

Here, in order to satisfy the expression (4), sin
2 may satisfy the _{(Φt + 2ψ 0 -ψ p)} = 0.

Therefore, Equation 5

(Equation 5)

The following relationship holds.

When the phase difference plate 27 is not inserted, δ = 0, and if the value obtained by partially differentiating the equation (1) with ψ _p is set to zero, the relation of Equation 6 is established.

[0041]

(Equation 6)

That is, when the transmittance T is minimized by ψ _p , the relationship of equation (6) holds.

Next, when the phase difference plate 27 is inserted,
_{If 1} = −π / 4 and a λ / 4 plate is used as the phase difference plate 27, the transmittance T becomes as shown in Expression 7 because δ = π / 2.

[0044]

(Equation 7)

Therefore, 2T becomes as shown in Expression 8.

[0046]

(Equation 8)

When the phase difference plate 27 is inserted,
When the TN liquid crystal cell 24 is rotated to detect ψ ₀ that minimizes the transmittance T in Expression (8), the _{value obtained} by partially differentiating Expression (8) with ψ ₀ becomes zero.

That is, the relationship of Expression 9 is established.

[0049]

(Equation 9)

When the phase difference plate 27 is inserted, T
When the N liquid crystal cell 24 is fixed and the analyzer 25 is rotated to detect ψ _p that minimizes the transmittance T in equation (8), the equation (8) is partially differentiated by ψ _p Becomes zero.

That is, the relationship of Expression 10 is established.

[0052]

(Equation 10)

Next, the operation will be specifically described using the measuring apparatus of FIG. First, an angle ψ _p formed between the polarizer 23 and the analyzer 25 is appropriately set.

The stepping motor is controlled by the computer 31.
The rotation of the liquid crystal cell 24 is controlled until the liquid crystal cell 24 rotates once by a predetermined angle by driving the head m1. Thus, the liquid crystal cell 24
During one rotation, the light passing through the TN liquid crystal cell 24 and the analyzer 25 is detected by the photodetector 26. That is, by rotating the TN liquid crystal cell 24, the TN liquid crystal cell 24 is rotated.
The angle ψ ₀ formed between the director on the incident side of the sample and the analyzer 25 is changed.

In this manner, T-ψ as shown in FIG.
₀ characteristics are obtained.

[0056] As shown in FIG. 2, ψ ₀ = ψ ₀₀ at transmittance T
Has a local minimum. And thus, obtains the rotation angle [psi ₀₀ that the transmittance T and the minimum (the first step).

[0057] That is, ψ ₀ = ψ value obtained by partially differentiating the ₀₀ at transmittance T in [psi ₀ is described above becomes zero (4) the relationship equation holds.

[0058] Therefore, as the transmittance T is above the ψ ₀ = ψ ₀₀ has a minimum value for ψ _0, (5) formula relationship is established.

Next, the TN liquid crystal cell 24 and the analyzer 25 are rotated once in the same direction about the optical axis of the laser light at a rotation speed of 1: 2, and the light detected by the photodetector 26 is rotated. Transmittance T
The analyzer rotation angles ψ _p (1) and ψ ₀ (1) that are minimized are obtained (second step).

Next, while the condition of the equation (5) is satisfied, the value obtained by partially differentiating the transmittance T with ψ _p is shifted to zero. Assuming that the transmittance T is measured by rotating the polarizer 23 and the analyzer 25 in the opposite direction by the same angle (ψ ₀ is fixed), ψ ₀ and ψ _p are respectively ψ ′ ₀ = ψ ₀ + θ. (11) ψ ′ _p = ψ _p + 2θ (12)

Here, the expressions (11) and (12) are converted to the expression (5).
Since the relationship of the formula is satisfied, it is sufficient to continuously change θ to obtain ψ _p at which the transmittance T is minimized.

Incidentally, since the laser oscillator 21 is linearly polarized light, when the polarizer 23 is rotated, the transmitted light intensity after passing through the polarizer 23 changes. Therefore, in the present invention, the polarizer 23 is fixed by rotating the ψ _p by 2θ when the 子₀ is rotated by θ.
And (the ₀ [psi fixed) rotated by the same angle in the opposite direction and the analyzer 25 can produce the same state as measuring the transmittance T by.

That is, the liquid crystal cell 24 and the analyzer 25 are rotated in the same direction about the optical axis of the laser beam at a rotation speed of 1: 2.

As described above, the liquid crystal cell 24 and the analyzer 25
And the rotational speed in the same direction about the optical axis of the laser beam is 1:
Rotating at a ratio of 2 means that equation (11) and (1)
It is expressed by equation (2). Equations (11) and (12) satisfy the condition of equation (5). Therefore, the liquid crystal cell 24
Even when the analyzer 25 and the analyzer 25 are rotated in the same direction about the optical axis of the laser light at a rotation speed of 1: 2, the partial differential value of the light transmittance T at ψ ₀ is zero. Can be kept.

Even when the liquid crystal cell 24 and the analyzer 25 are rotated in the same direction about the optical axis of the laser beam at the rotation speed of 1: 2, the liquid crystal cell 24 is set at $ _00. Can be kept.

In this state, ψ _p and ψ ₀ at which the transmittance T becomes minimum are ψ _p (1) and ψ ₀ (1), respectively.

Next, a retardation plate (λ / 4 plate) 27 is inserted, ψ ₀ is changed little by little, and ψ _p is scanned each time, and the transmittance T is measured. At this time, as shown in FIG. 4, ψ _p and ψ ₀ at which the light transmittance T becomes minimum are respectively set to ψ _p
(2), ψ ₀ (2) (third step).

By the way, the theoretical equation in which the partial differential value at ψ _p of the light transmittance T when the phase difference plate (λ / 4 plate) 27 is not inserted is zero is equation (6).

In equation (6), there are three variables (Φt, ψ
_p , u).

Therefore, by substituting ψ _p (1) obtained in the second step, a relational expression between the twist angle Φt and ψ ₀ is obtained.

Here, since the twist angle φt is approximately 90 °, the twist angle φt ′ is set to 90.0 °, 88.8 °, 88.7 °,
, And u ′ when each is substituted into the equation (6).
This calculation is performed by numerical calculation in the computer 31.

Thus, the table shown in FIG. 5 is completed.

Next, a theoretical equation derived from the condition that the partial differential value of the transmittance T at ψ ₀ when the phase difference plate 27 is inserted is zero and the partial differential value of the transmittance T at ψ _p is zero is obtained. Are the expressions (9) and (10) as described above.

Each of these two equations has four variables (Φt, u, ψ ₀ , ψ _p ).

Here, the relationship between the twist angle φt and u has the relationship described in the table shown in FIG.

[0076] Thus, (9) and (10) Te shown in FIG. 5 in formula - Bull Phi] t ', u' by substituting, obtained by numerical calculation the relationship between [psi ₀ and [psi _p. The result obtained in this way is the table shown in FIG. In FIG. 6, ψ ₀ and ψ _p obtained by calculation are ψ ₀ (c) and ψ _p (c).

From the table of FIG. 6, of ψ _p (c),
The twist angle Φt corresponding to ψ _p closest to ψ _p (2) obtained in the third step is the actual twist angle (fourth step).

For example, when the value of ψ _p (2) is closest to A in the table of FIG. 6, the twist angle Φt is 89.8 °.

Next, the anchoring energy -A _φ in the azimuthal direction of the TN liquid crystal cell is determined from the twist angle Φt by the theoretical equation (11).

[0080]

[Equation 11]

In equation (11), K ₂ is the twist elastic constant, d is the cell gap, ΔΦ = (Φr−Φt) / 2
(Φr is 90 °).

As described above, the anchoring energy of the TN liquid crystal cell 24 in the azimuthal direction can be measured.

As described above, according to the present invention, the first step of rotating the TN liquid crystal cell 24, the second step of rotating the analyzer 25 in the same direction at twice the speed of the TN liquid crystal cell 24, insert the plate 27, each for rotating the TN liquid crystal cell 24 gradually, was [psi ₀₀ obtained by scanning the analyzer _{25, ψ p (1),} ψ 0 (1), ψ p (2)
, Ψ ₀ (2), the twist angle Φt is obtained from the theoretical formula, and the azimuthal anchoring energy -A _φ of the TN liquid crystal cell 24 is obtained from the twist angle Φt. TFT (Thin Film Transi
even when implementing the stor), it is possible to obtain the anchoring energy -A _phi of azimuthal TN liquid crystal cell 24.

Further, ψ ₀₀ , ψ _p (1), ψ ₀ (1), ψ _p (2), and ψ ₀ (2) which are the minimum values of the transmittance T in FIGS. 2 to 4 are obtained. Since there is no need for a fitting process for checking whether the waveforms in FIGS. 2 to 4 match other waveforms, the processing can be simplified.

The present invention is not limited to the TN liquid crystal cell,
It is also applicable to STN (Super Twisted Nematic) liquid crystal elements.

In FIG. 1, the TN liquid crystal cell 24,
The analyzer 25 is rotated by the separate stepping motors m1 and m2, but only one motor m1 is used.
The rotation speed of the N liquid crystal cell 24 may be reduced by a reduction mechanism.

[0087]

As described in detail above, according to the present invention, the twist angle of the liquid crystal cell is obtained, and the anchoring energy in the azimuthal direction of the liquid crystal cell is calculated from the twist angle. An energy measurement method can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an apparatus used for a method for measuring azimuthal anchoring energy of a liquid crystal cell according to an embodiment of the present invention.

FIG. 2 shows a T-[psi ₀ characteristic in the embodiment.

FIG. 3 shows a T-[psi _p characteristics in the embodiment.

FIG. 4 shows a T-[psi _p characteristics in the embodiment.

FIG. 5 is a diagram showing Φt'-u 'characteristics.

FIG. 6 is a diagram showing Φt ′, u ′, ψ ₀ (c), and ψ _p (c) characteristics.

FIG. 7 is a diagram showing a coordinate system of a liquid crystal cell.

FIG. 8 is a diagram showing the operation principle of the TN mode.

FIG. 9 is a diagram for explaining anchoring energy.

FIG. 10 is a view for explaining a conventional torsion angle measuring method.

[Explanation of symbols]

21 laser oscillator, 22 chopper, 23 polarizer,
24: TN liquid crystal cell; 25: analyzer; 26: photodetector.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 21/00-21/01 G01N 21/17-21/61

Claims (2)

(57) [Claims] 1. A laser light emitted from a laser light source is polarized through a polarizer and then incident on a liquid crystal cell, and the laser light emitted from the liquid crystal cell is transmitted through an analyzer. In the method for measuring the azimuthal anchoring energy of the liquid crystal cell by measuring the light transmittance T with a photodetector, the liquid crystal cell is rotated about the optical axis of the laser light to detect the light. the first step and the liquid crystal cell and the analyzer the LES light transmittance T detected by the vessel seeks the rotation angle [psi ₀₀ of the liquid crystal cell to minimize - the same direction around the optical axis of the laser light A second step of determining the rotation angle ψ _p (1) of the analyzer so as to minimize the light transmittance T detected by the photodetector by rotating the rotation speed at a ratio of 1: 2; A phase difference plate is inserted between the liquid crystal cell and the analyzer so as to be at an angle of 45 degrees with the analyzer. The crystal cell is rotated little by little, and each time the crystal cell is rotated little by little, the analyzer is rotated once around the optical axis of the laser beam to minimize the light transmittance T detected by the photodetector. The rotation angle of the analyzer ψ _p (2) and the rotation angle of the liquid crystal cell at that time ψ ₀ (2)
And a rotation angle _{00 of} the liquid crystal cell obtained in the first step.
The rotation angle of the analyzer ψ _p (1) obtained in the second step
, The rotation angle of the analyzer obtained in the third step ψ
_a fourth step of obtaining a twist angle Φt of the liquid crystal cell based on _p (2) and a rotation angle ψ ₀ (2) of the liquid crystal cell at that time; and a twist angle Φt obtained in the fourth step. A fifth step of determining the azimuthal anchoring energy of the liquid crystal cell from a predetermined calculation formula. Wherein said fourth step, the formula T to obtain the light transmittance _{T (Φt, u, ψ 0} , ψ p,) and [psi _0, conditions for expression and zero obtained by partially differentiating respectively [psi _p The twist angle Φ
The relationship between t and u is calculated for a value where the twist angle is smaller than 90 degrees, and the general formula T (Φt, u,
ψ _0, ψ _p,) and [psi _0, the equation of equations zero obtained by partially differentiating respectively [psi _p, the rotation angle [psi ₀ and above the liquid crystal cell by substituting the relationship between the twist angle Φt and u rotation angle [psi _p and azimuthal anchoring energy of the nematic liquid crystal device according to claim 1, characterized in that the seek operation to the analyzer - measuring method.