JPH08152399A - Method and apparatus for measuring retardation of composite layer - Google Patents

Abstract

PURPOSE: To accurately measure the optical main axis direction and the retardation value even when the degree of polarization of a polarizing filter layer is not sufficient by providing a compensating polarizing plate at the filter layer side of a composite layer sample, and compensating the polarizing characteristics of the layer. CONSTITUTION: A polarizer X-stage 5 and a polarizer θ-stage 6 for forwarding or retracting and rotating a polarizer 8 are provided at the lower side of a filter 4 on an optical axis A. Further, a compensating polarizing plate θ-stage 10 for mounting and rotating a compensating polarizing plate 9, a sample base 11 and an analyzer X-stage 12 ad an analyzer θ-stage 13 for forwarding or retreating and rotating an analyzer 15 with respect to an X-axis are sequentially provided at the lower side of the state 5. The transmitted light transmitted through the composite layer sample of the plate 9 and the base 11 is passed through the analyzer 15, which is rotated relatively to the polarizing direction of the sample, the relationship between the intensity of the transmitted light and the polarizing bearing of the analyzer is measured. From the result, the optical main axis direction and the retardation value of the sample are obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method and an apparatus for measuring retardation of a composite layer sample, for example, a composite layer sample such as a composite sheet in which a polarizing film and a retardation film used in a liquid crystal display panel are laminated. Is.

[0002]

2. Description of the Related Art As liquid crystal display elements have been widely used, there has been an increasing demand for a liquid crystal display panel having a large area and a wide range in the visible direction. Therefore, it is desired to develop a technique capable of easily measuring the characteristics of a film-shaped polarizing filter (polarizing film) or a retardation film in the production process of those films.

Usually, the display board of a liquid crystal display device is
As an optical element, a polarization filter is provided on one surface of a liquid crystal cell in which a liquid crystal substance is sealed, and a retardation film, a polarization filter and a protective film are sequentially laminated on the other surface (observation side). There is. The retardation film is for compensating the polarization characteristics of the liquid crystal cell and is made of a birefringent material. Of these, the state of a composite sheet (also called “elliptic polarizing plate”) in which a polarizing filter and a retardation film are laminated and bonded, for example, the polarization transmission axis direction of the polarizing filter, the optical principal axis direction of the retardation film And the inspection of retardation value etc. is required.

Further, in the display panel of the liquid crystal display device, the characteristics when viewed from a direction other than the direction perpendicular to the surface,
That is, the viewing angle characteristic is also an important characteristic. In order to evaluate the viewing angle characteristics, it is necessary to measure the retardation value when the incident angle of the measurement light is changed in the state of the composite sheet. However, at present, white light is made incident on the composite sheet, and evaluation is performed by the spectrum of the transmitted light.

[0005]

The present inventors have proposed a method for measuring the retardation of a composite sheet in which a polarizing filter and a retardation film are laminated (JP-A-6-317).
519 publication). When various composite sheet samples were measured by the method, some samples could be measured accurately and others were not. As a result of further study, when the polarization degree of the polarizing filter used for the composite sheet is about 99% or more, the above measured value can be obtained with high accuracy. It has been found that when the degree is less than 99%, the calculation results of the retardation value and the optical principal axis direction are largely different, resulting in a decrease in measurement accuracy and sometimes an unmeasurable situation.
In the method of evaluating the viewing angle characteristics of the composite sheet by the spectroscopy, it is not easy to quantify and express the evaluation result, and it is difficult to set an objective evaluation standard.

The first object of the present invention is to provide a composite layer sample including a polarization filter layer and a birefringent layer, and in the case of a composite layer sample in which the polarization degree of the polarization filter layer is not sufficient, An object of the present invention is to provide a method and an apparatus capable of accurately measuring a retardation value. The second object of the present invention is to
Even in the case of such a composite layer sample, the evaluation of the viewing angle characteristics should be quantified.

[0007]

In the present invention, a compensating polarizing plate is arranged on the polarizing filter layer side of a composite layer sample in which a polarizing filter layer and a birefringent layer are laminated, and a polarizing filter layer and a compensating polarizing plate are arranged. The polarization transmission axes of are kept parallel to each other to compensate the polarization characteristics of the polarization filter layer. Then, in the measurement of the retardation value and the like, the measuring light is irradiated from the compensating polarizing plate side, the transmitted light that has passed through the compensating polarizing plate and the composite layer sample is passed through the analyzer, and the polarization directions of the analyzer are combined. By rotating the sample relative to the polarization direction of the layer sample, the relationship between the intensity of the light transmitted through the analyzer and the polarization direction of the analyzer is obtained. This significantly improves the measurement accuracy.

In measuring the retardation value and the like, the measurement light beam is applied to the compensation polarizing plate without passing through the polarizer, that is, in the unpolarized state, and when the light incident side of the compensation polarizing plate is parallel to the analyzer. This includes both cases in which a polarizer that maintains a predetermined polarization azimuth relationship such as the Nicol state is arranged, and the measurement light flux is irradiated to the compensation polarization plate through the polarizer.

In order to make it possible to quantify the evaluation of the viewing angle characteristics, first, with the plane of the composite layer sample arranged in a state perpendicular to the optical path of the measurement light, the polarization direction of the analyzer is set to the composite layer sample. The relative retardation value and the optical principal axis direction of the composite layer sample are obtained by rotating the sample relative to the polarization direction. The optical principal axis direction is the principal refractive index direction, and there are two directions of the maximum refractive index and the minimum refractive index, and these two directions are orthogonal to each other. Either of these two optical principal axis directions may be used, but the polarization direction of the analyzer is again set relative to the polarization direction of the composite layer sample in a state where the surface of the composite layer sample is tilted with one of them as the tilt axis. Rotation is performed to detect the relationship between the intensity of the light transmitted through the analyzer and the polarization direction of the analyzer, and the retardation value of the composite layer sample in the tilted state is obtained.

The retardation measuring device of the present invention comprises a light source section for irradiating a measurement light beam on a measurement optical path, a sample stage for holding a composite layer sample in which a polarization filter layer and a birefringent layer are laminated on the measurement optical path, and a sample stage. The rotatably supported analyzer placed on the measurement light flux exit side of the composite layer sample held by and the measurement light flux entrance side of the composite layer sample held on the sample stand, and rotate independently of the analyzer. A compensating polarizing plate that is supported as much as possible and that compensates the polarization characteristics of the polarizing filter layer of the composite layer sample, and a light receiving unit that detects the transmitted light intensity of the light that has passed through the analyzer from the compensating polarizing plate through the composite layer sample. An arithmetic and control unit for calculating the retardation and the optical principal axis direction of the composite layer sample from the rotation angle of the analyzer and the transmitted light intensity detected by the light receiving section.

A polarizer may be further arranged on the side of the compensating polarizing plate where the measurement light beam enters, and in that case, the polarizer and the analyzer can be rotated while maintaining a predetermined polarization azimuth relationship with each other, for example, a parallel Nicol state. To support. The compensating polarizing plate and the analyzer may be arranged so that they can be inserted into and removed from the measurement optical path, and if a polarizer is provided, the polarizer can also be arranged so that they can be inserted into and removed from the measurement optical path.

In order to make it possible to quantify the evaluation of the viewing angle characteristics with the retardation measuring apparatus of the present invention, a mechanism for rotating the held composite layer sample in its plane as a sample stage, and the composite layer sample And a tilting mechanism for tilting the composite layer sample about a straight line along the surface of the.

In the present invention, the "composite layer" is a layer in which films, sheets, plates or the like having or not having independence are directly stacked in contact with each other or indirectly stacked with inclusions or spaces. The terms include film comrades, sheet comrades, plate comrades, and overlapping of these different types.
In addition, "lamination" is fixed or semi-fixed by using or fusing an adhesive material, an adhesive material, a glue material, or the like,
Not limited to those that are pasted or joined together, but those that are fixed or temporarily superposed in a predetermined positional relationship by using members such as Velcro, or by utilizing electric / magnetic force, mechanical force, or other force. Shall also be included.

[0014]

The light from the light source used for the measurement in the present invention is white light and is non-polarized light having no polarization characteristic.
A composite layer sample in which a polarizing filter layer and a birefringent layer are laminated, for example, a composite sheet obtained by laminating a polarizing film and a retardation film, when irradiated with light from the polarizing film side, linear retardation in a certain direction is generated in the retardation film. The incident light and the transmitted light of the composite sheet become elliptically polarized light.

When the polarization degree of the polarizing film is not sufficient, the polarizing film does not act as an ideal polarizing filter. However, by disposing a compensating polarizing plate having a sufficiently high degree of polarization on the light incident side of the polarizing film and keeping the polarization transmission axes of the polarizing film and the compensating polarizing plate parallel to each other, the characteristics of the polarizing film having a low degree of polarization are It is compensated by the compensating polarizing plate. The higher the degree of polarization of the compensating polarizing plate is, the more preferable it is. However, considering the accuracy level of other measuring systems, it is 99%.
The above is enough. At this time, performance of a measurement error of retardation of several nm or less and a measurement error of 1 degree or less in the optical principal axis direction can be satisfied. Therefore, the transmitted light of the compensating polarizing plate and the composite layer sample is passed through the analyzer, and the analyzer is rotated relative to the composite layer sample to measure the relationship between the polarization direction of the analyzer and the transmitted light intensity. Thereby, the optical axis direction and the retardation value of the composite layer sample can be accurately measured.

The major axis direction and ellipticity of the elliptically polarized light of the transmitted light of the composite layer sample can be measured by rotating the analyzer relative to the composite layer sample. (And the polarization absorption axis orthogonal to it)
And the retardation value and the optical principal axis direction of the retardation film can be calculated. These values can be calculated also when a polarizer is arranged on the light incident side of the compensating polarizing plate and the polarizer and the analyzer are kept in a predetermined polarization azimuth relationship and synchronously rotated. Details of these calculations are given in the examples.

[0017]

EXAMPLE FIG. 1 schematically shows the configuration of an example of a retardation measuring apparatus for a composite layer sample of the present invention. In FIG. 1, 1 is a white light source, 2 is an optical transmission line, and an optical fiber bundle is used as the optical transmission line 2. Reference numeral 3 is an optical system such as a condenser lens for obtaining a parallel light flux from the output of the optical transmission line 2. Reference numeral 4 denotes a filter portion for transmitting light of a specific wavelength. A plurality of narrow band interference filters having different transmission wavelengths are attached on a disc 4a rotatable about an axis B, and the disc 4a rotates. Is configured so that an arbitrary filter is selectively arranged on the optical path. By switching the filters, light of a specific wavelength is selected from the emitted light of the white light source 1, and the light is guided to the optical path centered on the optical axis A. Get burned.

On the optical axis A, below the filter portion 4, there is provided a polarizer X stage 5 for advancing and retracting the polarizer 8 with respect to the optical axis A in a horizontal plane. A polarizer θ stage 6 for rotating the polarizer 8, a motor 20 for driving the rotation of the stage 6, and a rotation angle positioning encoder 7 for the polarizer 8 are mounted on the X stage 5 for the polarizer. The polarizer 8 is mounted on the polarizer θ stage 6.

On the optical axis A, the compensating polarizing plate θ stage 10 for mounting and rotating the compensating polarizing plate 9 below the X stage 5 for the polarizer, the sample stage 11, and the horizontal plane. An X stage 12 for an analyzer that sequentially advances and retracts the analyzer 15 with respect to the optical axis A is provided therein. A motor 19 for driving the rotation of the compensating polarizing plate θ stage 10 is provided, and an encoder for detecting the rotation angle of the compensating polarizing plate 9 may be further provided. On the analyzer X stage 12, the analyzer θ stage 1 for rotating the analyzer 15 around the optical axis A is provided.
3, a motor 21 for driving the rotation of the stage 13, and a rotation angle positioning encoder 14 for the analyzer 15 are provided, and the analyzer 15 is attached to the θ stage 13 for the analyzer.

On the optical axis A, a light receiving element 16 is further arranged on the lower side of the analyzer 15, that is, on the light emitting side. The θ stage 6 for polarizer and the θ stage 13 for analyzer are respectively encoders. Through the angular position signals of 7 and 14, the arithmetic and control unit 17 performs angular position correction, and controls so as to maintain the parallel Nicols state and rotate synchronously. As the motor 20 for rotating the polarizer and the motor 21 for rotating the analyzer, it is preferable to use a stepping motor. In that case, each time the motors 20 and 21 rotate by a predetermined angle by the control pulse from the arithmetic and control unit 17, the rotation may be temporarily stopped and the output of the light receiving element 16 may be sampled. Since it is extremely short, it is possible to sample the output of the light receiving element 16 while continuously rotating the motors 20 and 21.

The apparatus of the present invention can also be used for the retardation measurement of a normal sample which is not a composite layer sample. In the measurement of a normal sample, the compensating polarizing plate 9 is separated from the optical path, the X stages 5 and 12 are moved leftward to the state shown in the figure, and the polarizer 8 and the analyzer 15 mounted on the stage are irradiated with light. The polarizer 8 is placed on the road.
The analyzer 15 is rotated around the optical axis A while maintaining the polarization directions in a parallel Nicol relationship with each other to measure the retardation. In order to separate the compensation polarizing plate 9 from the optical path, an X stage for advancing / retreating to the optical path similar to the X stages 5 and 12 may be provided for the θ stage 10, and the compensating polarizing plate 9 may be used. The θ stage 10 may be configured to be attachable to and detachable from the θ stage 10.

In any case, according to the present invention, the retardation of a normal sample or the retardation of a composite layer sample in which a polarizing film and a retardation film are laminated is measured by changing or switching a part of the apparatus configuration. Can also be used.

The retardation measurement of the composite layer sample can be performed with or without the polarizer 8. In the composite layer sample measurement, the sample S is set on the sample table 11 with the polarizing film facing the light source side (upper side in the figure). Then, when the polarizer 8 is not mounted in the optical path, only the analyzer θ stage 13 is rotated, and when the polarizer 8 is mounted in the optical path, the polarizer θ stage 6 and the analyzer θ stage 13 are rotated. While rotating the stage 13 synchronously, the change in transmitted light intensity is measured. Specifically, the arithmetic and control unit 17, which controls the entire device and processes the measurement data, controls the rotation of the motor 19 for rotating the compensating polarizing plate 9, and the polarizer 8 is not attached to the optical path. In this case, feedback control is performed by the signal from the encoder 14 to rotate the analyzer 15, and when the polarizer 8 is mounted in the optical path, the polarizer rotating motor 20 and the analyzer rotating motor 21 are rotated in synchronization. Feedback control is performed by the signals of the encoders 7 and 14, and the polarizer 8 and the analyzer 1
Rotate 5. Then, the arithmetic and control unit 17 uses the analyzer 1
5, the light receiving element 1 at a constant angular interval of rotation, for example, at 1 ° intervals.
The output of No. 6 is taken in, data processing is performed, the retardation value of the sample is calculated, and the result is output to the display / recording device 18 for display and printing.

When the polarization degree of the polarizing film used in the composite sheet of the composite layer sample, which is the main object of the measurement according to the present invention, is less than 99%, the retardation value of the retardation film and the measurement accuracy of the optical principal axis are measured. Therefore, the compensating polarizing plate 9 is used for the measurement. The measurement method is X
The polarizers 8 and the analyzer 15 are retracted by retracting the stages 5 and 12.
Out of the optical path. By setting the sample S on the sample table 11 with the polarizing film facing up and measuring the transmitted light intensity while rotating the compensating polarizing plate (polarization degree 99% or more) once, the polarization of the polarizing film of the composite sheet Either the orthogonal position or the parallel position between the transmission axis and the polarization transmission axis of the compensation polarizing plate is obtained. The orthogonal position of both polarization transmission axes is the position where the amount of transmitted light is minimum, the parallel position is the position where the amount of transmitted light is maximum,
The orthogonal position is easier to obtain accurately. Then, when the orthogonal position of both polarization transmission axes is obtained, the compensation polarizing plate is rotated by 90 °. In any case, the polarization transmission axis of the polarizing film and the polarization transmission axis of the compensating polarizing plate are superposed in the same direction, that is, both polarization transmission axes are in a parallel state.

Next, the X stage 12 is moved forward to move the analyzer 1
After arranging 5 on the optical path, the change of the transmitted light intensity is measured by the light receiving element 16 while rotating the analyzer 15, and the transmission / transmission axis direction of the polarizing film of the composite sheet, the retardation value of the retardation film, and the optical property are measured. Calculate the main axis direction.

The retardation of the composite sheet is calculated as follows. First, the case where the polarizer 8 is not used will be described. The wavelength for obtaining the retardation value of the sample is λ, the retardation value is R, the polarization transmission axis of the polarizing film of the sample and the optical principal axis 1 of the retardation film (one of two optical principal axes 1 and 2 orthogonal to each other). the contact angle of phi ₂ and (in one direction in a plane perpendicular to the optical axis a, x direction shown in FIG. 2) polarization transmission axis device coordinate axes of the polarizing film to the angle between the phi ₁ . φ ₁ can be measured separately, and the sample can be set on the sample table 11 so that it becomes 0, but here φ ₁ is also unknown because the measurement operation is generally handled.

The intensity of light transmitted through the composite sheet sample and the analyzer is I (θ). θ is the rotation angle of the analyzer from the reference direction. Description will be given with reference to FIG. Since the linearly polarized light transmitted through the polarizing film is incident on the retardation film of the sample, the light intensity of the linearly polarized light is I ₀ and the amplitude is A ₀ . Optical main axis 1 of light incident on the retardation film
The amplitude of the polarization component in the direction is A ₀ cosφ ₂ , the other optical principal axis 2
The amplitude of the polarization component in the direction is A ₀ sin φ ₂ . The analyzer-direction components A ₁ and A ₂ of these two components are respectively A ₁ = A ₀ cos φ ₂ · cos (φ ₁ + φ ₂ −θ) A ₂ = A ₀ sin φ ₂ · sin (φ ₁ + φ ₂ − θ). The transmitted light of the analyzer is the light of the above two components overlapped with the phase difference δ, and the retardation angle δ and the retardation R of the retardation film have a relationship of 2πR / λ = δ, and the light transmitted through the sample and the analyzer. When the amplitude of the light and a, the a is the cosine ^{theorem, a 2 = I (θ)} = a 1 2 + a 2 2 -2A 1 a 2 cosδ = a 0 2 {cos 2 φ 2 · cos 2 (φ 1 ^{_{+ φ 2 -θ) + sin 2}} φ 2 · sin 2 (φ 1 + φ 2 -θ) -2cosφ 2 · sinφ 2 · cos (φ 1 + φ 2 -θ) sin (φ 1 + φ 2 -θ) cosδ} ··· (1)

A ^{2 in the} above equation is the output of the light receiving element 16.
Here want sought is a cos [delta], the obtained direct is theta and I (theta), because although phi ₁ and phi ₂ are unknown _{constants, cosφ 2 = K, sinφ 2} = L, φ ₁ + φ ₂ −
By rewriting the above equation with θ = Ψ, I (θ) = (K ² cos ² Ψ + L ² sin ² Ψ-2KLcos Ψsin Ψcos δ) A ₀ ² . If this is further rewritten, there is a relation of L ² = 1-K ² , K ² = 1-L ² , and K ² + L ² = 1. Therefore, the above equation is I (θ) = (K ² cos ² Ψ + ^{(1-K 2) sin 2} Ψ-KLsin2Ψcosδ) a 0 2 and becomes I (θ) = {(1 -L 2) cos 2 Ψ + L 2 sin 2 Ψ-KLsin2Ψccosδ} a 0 2. Adding these two formulas and dividing by two gives I (θ) = (K ² cos ² Ψ-sin ² Ψ) + sin ² Ψ-L ² (cos ² Ψ-sin ² Ψ) + cos ² Ψ-2KLsin2 Ψcosδ}. the ^{_{a 0 2/2 = {(}} K 2 -L 2) cos2Ψ-2KLsin2Ψcosδ + 1} a 0 2/2. From this equation, I (θ) changes by one cycle during half rotation of the analyzer. The maximum transmitted light intensity is s
When in2Ψ = 0, the minimum is when cos2Ψ = 0. Therefore, Imax = A ₀ ² · K ² Imin = A ₀ ² (K ² −2KL cos δ) / 2. Further, since it is _{K = cosφ 2, L = sinφ} 2,
By deleting L from the above equation, Imin = A ₀ ² {1-2K (1-K ² ) 1 / 2-cosδ} / 2. Therefore, substituting Imax1 / 2 / A ₀ to K of this _{Imin, cosδ = {(A 0} 2 -2Imin) -2Imax1 / 2 (A 0 2 -Imax) 1/2} / A 0 2 . Therefore, the cos [delta] Since it can be obtained, the retardation R can be determined from cos δ.

In the above equation, A ₀ ² is the intensity of light transmitted through the polarizing film of the sample, and in the apparatus of FIG. 1, the sample is set with its polarizing film side facing the analyzer side and the analyzer is rotated. It can be obtained in advance as the maximum value of the output of the light-receiving element when it is caused. In addition, the angle φ formed by the polarization transmission axis of the sample polarizing film and the optical axis 1 of the retardation film
_2, when obtaining the K ² from the above ^{_{Imax = A 0 2 · K 2}} , K
Can be obtained from K = cos φ ₂ .

The above is one example of the data processing method for obtaining the retardation in the present invention, and the method for actually obtaining the retardation is not limited to the above. For example, the retardation and φ ₂ are calculated in advance for various combinations of Imin / A ₀ ² and Imax / A ₀ ² values according to the above formula (1) to prepare a table, and the measured I
The retardation of the sample and φ ₂ may be assigned from min and Imax by interpolation.

The calculation in the above-described embodiment is carried out by the θ for the polarizer mounted on the X stage 5 for the polarizer in the apparatus of FIG.
This is performed by retreating the stage 6 to the right in the figure and removing the polarizer 8 from the optical path, and mathematical treatment is simple. However, although the mathematical treatment becomes somewhat complicated, the retardation of the above-mentioned composite sheet can be measured even when the polarizer 8 is left in the optical path. Such an embodiment is described here. In this case, the X stages 5 and 12 are moved forward to arrange the polarizer 8 and the analyzer 15 on the optical path, and then the light receiving element 1 is rotated while synchronizing the polarizer 8 and the analyzer 15.
The change in transmitted light intensity is measured according to 6, and the transmission / transmission axis direction of the polarizing film of the composite sheet, the retardation value of the retardation film, and the optical principal axis direction are calculated.

The polarizer 8 and the analyzer 15 are parallel Nicols to each other.
State. If the same reference numerals are used as in the previous embodiment,
The intensity I (θ) of the light incident on the optical element 16 can be expressed by the following equation.
It I (θ) = A₀ ²(cos²φ₂・ Cos²(φ₁+ φ₂-θ) + sin²φ₂・ Sin²(φ₁+ φ₂-θ) -2 cosφ₂・ Sinφ₂・ Cos (φ₁+ φ₂-θ) sin (φ₁+ φ₂-θ) cosδ} ・ cos ² (φ₁-θ) ・ ・ ・ (2) This equation is cos in the equation (1).²(φ₁Is an extra term for −θ)
It has become a thing.

Therefore, the polar coordinate graph of I (θ) may be not only a simple cocoon shape, an ellipse or an S shape, but also a four-lobed shape as shown in FIG. Therefore, I (θ)
It is generally not possible to easily find cos δ from the maximum and minimum values of. It is a general method to actually measure I (θ) for some values of θ and substitute it in the above equation to solve as a simultaneous equation for cosδ and cosφ ₂ . In this case, the direction of the polarization transmission axis of the polarizing film portion of the sample is detected and this is aligned with the reference direction x of the device. That is φ ₁ =
Setting it to 0 makes the expression somewhat easier to handle.

In order to detect the direction of the polarization transmission axis of the polarizing film portion, the polarizer 8 is removed from the measurement optical path and the sample is set with the polarizing film side facing the analyzer side, and the transmitted light intensity becomes maximum. It suffices to detect the direction of the analyzer or the direction obtained by adding 90 ° to the direction in which the transmitted light intensity becomes the minimum. Instead of performing the operation to solve the simultaneous equations, about the combination of various values of retardation and φ ₂ in advance,
By the equation (2), previously created by calculating the polar coordinate graph of I (theta), the graph with the registration of the outline of the retardation and phi ₂ from I (theta) of the actual measurement, a retardation and phi ₂ Assuming that a polar coordinate graph is assumed, the calculation may be repeated so that the actual measurement shape is obtained. This method can also be applied to the above-mentioned embodiment. In any case, the specific method of data processing for realizing the principle of the method of the present invention is arbitrary.

In each of the above-mentioned embodiments, the transmittance of the retardation film portion of the sample in the biaxial directions is equal, but the two transmittances may be different from each other. If this transmittance ratio is a (a <1 or a> 1 depending on which of the two axis directions is the denominator, a <1),
The equations (1) and (2) become the following equations (1 ') and (2'), respectively. ^{_{I (θ) = A 0 2}} {a 2 cos 2 φ 2 · cos 2 (φ 1 + φ 2 -θ) + sin 2 φ 2 · sin 2 (φ 1 + φ 2 -θ) -2acosφ 2 · sinφ 2 · cos (φ ₁ + φ ₂ -θ) sin (φ ₁ + φ ₂ -θ) cos δ} …… (1 ') I (θ) = A ₀ ² {a ² cos ² φ ₂・ cos ² (φ ₁ + ^{_{φ 2 -θ) + sin 2 φ}} 2 · sin 2 (φ 1 + φ 2 -θ) -2acosφ 2 · sinφ 2 · cos (φ 1 + φ 2 -θ) sin (φ 1 + φ 2 -θ) cosδ}・ Cos ² (φ ₁ -θ) …… (2 ')

In the above description, regarding the polarization transmission axis direction φ ₁ of the polarizing film of the composite sheet and the angle φ ₂ formed between this polarization transmission axis direction and the optical principal axis 1 direction of the retardation film, the retardation R of the composite layer sample At the time of determination, φ ₁ is slightly changed in several steps before and after the initially obtained value, and φ ₁
If φ ₂ and R are calculated for each value of φ and the values of φ ₁ , φ ₂ and R are determined so that the residual convergence value is minimized, the measurement accuracy is further improved.

In the above embodiments, the sample table 11 is described as holding the composite layer sample S so that its surface is perpendicular to the optical axis A. However, in order to evaluate the viewing angle characteristics of the composite layer sample S, the sample stage 11 can rotate the composite layer sample S in its plane and tilt the sample about a straight line along the surface of the composite layer sample S. Need to be able to. FIG. 4 shows an example of such a sample table 11a, and the details of the sample table 11a are shown in FIG. The sample holder 70 has a hole 72 in the center, the back surface is hollowed out in a ring shape to form a recess, and the upper surface is provided with two holding plates 74 for holding and holding the sample. A turntable 78 having a ring-shaped convex portion 76 that fits into the concave portion on the back surface of the sample holding unit 70 is attached to the substrate 80,
The sample holder 70 is held rotatably around an axis perpendicular to the sample surface. A belt 86 is mounted between the side surface of the sample holder 70 fitted on the rotary table 78 and the pulley 84 attached to the rotating shaft of the stepping motor 82, and the motor 82 rotates the sample holder 70. Motor 8
2 is also attached to the substrate 80, and the motor 82 is arranged so that the pulley 84 and the sample holder 70 are arranged in one plane.
And a mounting surface of the turntable 78 is configured. Board 80
The shafts 88 and 90 are attached to the pair of side surfaces of the
The central axes of 8 and 90 are arranged so as to come to the surface of the sample holder 70. These shafts 80 and 90 are supported by the measuring device body. A pulley 62 is attached to one of the shafts 88, a belt 64 is hung between the pulley 66 of a stepping motor 68 provided on the measuring apparatus main body side and the pulley 62, and the substrate 80 is tilted by the motor 68. The arithmetic and control unit 17 also controls the operations of the motors 68 and 82.

When the viewing angle characteristics of the composite layer sample are measured using the sample table 11a shown in FIGS. First, the composite layer sample S is attached to the sample holder 70, the sample surface is arranged so as to be perpendicular to the optical axis A, and the analyzer 15 is rotated once to rotate the retardation R of the composite layer sample S.
And the optical principal axis direction is calculated.

Next, the motor 82 is driven so that one of the two optical principal axis directions is the central axis (tilt axis) of the axes 88 and 90.
The composite layer sample S is rotated in the plane so as to be in the direction of.
Then, the motor 68 is driven, the sample holding unit 70 is tilted at a constant angle, for example, 10 degrees around the tilt axis, and the analyzer 15 is rotated once again to calculate the retardation R of the composite layer sample S. In this way, the retardation is obtained while changing the inclination of the composite layer sample S. The arithmetic and control unit 17 reads the inclination angle of the sample holder 70 by the drive pulse of the motor 68.

[Experimental Example 1] a) In the device having the configuration shown in FIG. 1, a polarizing plate (polarizing plate B) having a polarization degree of 95.0% forms an angle of 90 between the polarization transmission axis and the coordinate axis x of the device. The polarizing plate is fixed on the sample table 11 so that the optical axis of the polarizing plate is 30 ° (φ).
₂ ) Laminate to form a composite sheet sample. The polarizer 8 and the analyzer 15 are placed on the optical path and kept in a parallel Nicol relationship for synchronous rotation, and the transmitted light intensity is measured, for example, every 10 degrees of rotation. From this measurement result, the angle φ formed between the polarization transmission axis of the polarizing plate of the composite sheet and the coordinate axis x of the device
_{1. The} angle φ ₂ (deg.) Formed by the polarization transmission axis of the polarizing plate and the optical principal axis of the retardation film and the retardation value R of the retardation film were calculated. The measurement of the same content was performed for each of the 9 types of retardation films by exchanging only the retardation film and commonly using the same polarizing plate for each measurement of one sample. Table 1 shows the results. R ₀ is the retardation value of 9 types of retardation films alone.

B) In the device having the configuration shown in FIG.
For the same composite sheet sample as above, a compensating polarizing plate (polarization degree 99.9%) 9 (polarizing plate A) is placed on the light incident side of the sample as shown in the figure, and the polarizer 8 and the analyzer 15 are exposed to light. The polarization plate for compensation 9 is rotated on the optical path in a state where it is separated from the path to detect a change in transmitted light intensity, and the polarization transmission axis of the polarization plate for compensation 9 becomes parallel to the polarization transmission axis of the polarization plate of the sample. Was set. The angle φ ₁ (deg.) Formed by the azimuth of the polarization transmission axis of the polarizing plate of the composite sheet and the coordinate axis x of the device was obtained from the rotation angle position of the compensation polarizing plate 9 at this time.

With the polarization transmission axis of the compensating polarizing plate 9 and the polarization transmission axis of the sample polarizing plate set parallel to each other,
The polarizer 8 and the analyzer 15 are returned to the optical path, both are rotated synchronously while maintaining the relationship of parallel Nicols, and the transmitted light intensity is measured for each rotation of 10 degrees, and from this measurement result, the polarizing plate of the composite sheet The angle φ ₂ (deg.) Formed by the optical principal axis of the retardation film with respect to the polarization transmission axis and the retardation value R of the retardation film were calculated. The measurement of the same content was performed for each of the 9 types of retardation films by exchanging only the retardation film and commonly using the same polarizing plate for each measurement of one sample. The results are shown in Table 1 in correspondence with the above a).

[0043]

[Table 1] a) without compensation polarizing plate b) with compensation polarizing plate ─────────── ────────── Sample R ₀ R φ ₁ (°) φ ₂ (°) R φ ₁ (°) φ ₂ (°) 1 152.5 124.0 84 -44 153.0 90 -31 2 218.7 196.0 86 -32 220.4 90 -28 3 241.2 223.5 87 -31 243.3 90 -30 4 271.9 261.7 89 -30 266.2 90 -30 5 362.3 350.7 -88 -27 367.0 90 -30 6 382.9 365.0 -87 -25 386.8 90 -30 7 413.4 393.0 -86 -24 417.7 90 -30 8 395.0 378.1 -87 -25 400.9 90 -30 9 416.8 393.1 -86 -23 423.1 90 -30

C) Comparing the results of a) and b),
When the compensating polarizing plate is not used, the retardation value R has a large error of about 5% on average and about 20% at the maximum, and a considerably large error of about 5 ° on average and 14 ° at the maximum in the optical axis direction φ _2. occured. On the other hand, when the compensating polarizing plate was used, the retardation value R had an error of ± 2% or less and an average of 1.4%, and there was almost no error in the optical principal axis direction φ ₂ . Therefore, according to the present invention, it has been found that even a composite sheet using a polarizing film having a poor degree of polarization can ensure sufficient accuracy and reliability. The same measurement as the above a) and b) was performed using a polarizing plate having a polarization degree of 99.9% instead of the polarizing plate B. As a result, a),
b) In both measurements, the retardation value and the optical principal axis direction could be measured accurately.

[Experimental Example 2] The same composite sheet as in Experimental Example 1 was tested with the configuration of FIG. 1 with the polarizer 8 removed from the measurement optical path and the compensation polarizing plate 9 removed from the optical path. The same measurement as in a) of Example 1 was performed, and the same measurement as in b) was performed with the polarizing plate 9 for compensation placed in the optical path. The results are shown in Table 2.

[0046]

[Table 2] a) Without compensation polarizing plate b) With compensation polarizing plate ─────────── ────────── Sample R ₀ R φ ₁ (°) φ ₂ (°) R φ ₁ (°) φ ₂ (°) 1 152.5 153.0 89 30 152.0 89 31 2 218.7 219.7 89 29 218.7 90 29 3 241.2 238.7 90 29 246.0 89 31 4 271.9 260.6 90 30 273.1 89 31 5 362.3 364.7 89 31 363.8 90 30 6 382.9 385.1 89 30 385.9 90 30 7 413.4 415.1 90 29 417.1 90 30 8 395.0 397.6 90 29 397.1 90 30 9 416.8 419.5 90 29 420.8 89 31

From the measurement results in Table 2, when the compensating polarizing plate was not used, there was a considerable error in the retardation value up to about 4%, and an error of about 1 degree occurred on average in the optical principal axis direction. When the compensating polarizing plate was used, the error in retardation value was within ± 1%, and there was almost no error in the direction of the optical principal axis, which was 0.3% on average. Therefore, in the case where the polarizer was not used, the difference due to the use or non-use of the compensating plate was not as remarkable as in Experimental Example 1 using the polarizer, but the difference was remarkable depending on the measurement wavelength. The polarization degree is 99.
The same measurement as the above a) and b) was performed using a 9% polarizing plate. As a result, the retardation value and the direction of the optical principal axis could be measured with high accuracy in both measurements a) and b).

[Experimental Example 3] FIGS. 6A and 6B show a compensating polarizing plate (polarization degree 99.9%) (polarizing plate A) used in Experimental Examples 1 and 2 and a composite layer polarizing plate (polarizing plate). FIG. 6 shows the respective spectral transmission characteristics with respect to 95.0% (polarizing plate B).
6A shows the spectral transmittance when the polarizer is arranged in the crossed Nicols with respect to the polarizing plate A, and FIG. 6B shows the spectral transmittance when the polarizer is arranged in the crossed Nicols with respect to the polarizing plate B.

In the polarizing plate A, transmitted light is not detected in the wavelength range of 700 nm or less, whereas in the polarizing plate B, 700 n
There is transmitted light even at m or less. The transmittance in the range of 570 to 640 is as small as around 1%, but the transmittance of several percent occurs in the range of 400 to 550 nm. Polarization degree 95%
Means, for example, that the average transmittance in the orthogonal Nicol arrangement in the wavelength region of 400 to 800 nm is 5%.

Since the measured light wavelength in Experimental Examples 1 and 2 is 590 nm, the transmittance in the crossed Nicols is small, and the difference between the case where the compensating polarizing plate is used and the case where it is not used is relatively small. But other wavelengths, eg 500 nm
It is estimated that the difference between the two is considerably large when the measurement light of 1 is used. Therefore, it can be said that the present invention using the compensating polarizing plate has an effect that accurate measurement can be performed over a wide wavelength range.

An example of measuring the viewing angle characteristics of the composite layer sample will be described. Retardation value of 393.8 each
of two types of retardation films A and B of 1 nm and 584.1 nm
The retardation value was measured by tilting the optical axis having the larger refractive index of the two optical axes described above as the tilt axis to make the incident angle of the measurement light beam different.

A polarizing film having a transmittance of about 44% by itself is superposed on the two types of retardation films, and the angle formed by the optical principal axis of the retardation film and the polarization absorption axis of the polarizing film is about 35 °. The composite sheet was also used as a sample. For the composite sheet sample, the same as in the case of the retardation film alone after using the compensating polarizing plate and compensating the polarization characteristics of the polarizing filter layer by keeping the polarization transmission axes of the polarizing film and the compensating polarizing plate parallel to each other. The retardation value was measured by tilting the optical axis of the retardation film having the larger refractive index as the tilt axis and changing the incident angle of the measurement light beam. Table 3 shows the results.

[0053]

[Table 3] Retardation film A Retardation film B Incident angle Single layer Single layer Single layer Overlap ─── ─────────────────── 0 ° 393.8nm 394.1nm 584.1nm 587.9nm 10 ° 399.2 399.2 587.7 591.2 20 ° 413.1 414.1 599.1 603.5 30 ° 435.1 438.0 612.2 617.5 40 ° 464.4 467.6 639.8 618.3

From the results shown in Table 3, the retardation value of the composite sheet is almost the same as that of the retardation film alone, and it can be seen that the viewing angle characteristics of the laminated optical film can be evaluated. As a result, the present invention can be used for shipping inspections by optical film laminating makers and acceptance inspections by panel makers, and can contribute to stabilizing the quality of laminated products.

[0055]

【The invention's effect】

1) According to the present invention, a compensating polarizing plate having polarization characteristics superior to those of a polarizing filter layer is arranged on the polarizing filter layer side of a composite layer sample in which a polarizing filter layer and a birefringent layer are laminated, and the polarizing filter layer and the compensating polarizing plate are compensated. Since the polarization transmission axes of the polarizing plates for use are kept parallel to each other to compensate for the polarization characteristics of the polarizing filter layer, even when a material with a low degree of polarization is used for the polarizing filter layer, it covers a relatively wide wavelength range. The retardation value of the birefringent layer and the optical principal axis direction can be measured with sufficient accuracy. Therefore, it is also useful for expanding the application range of the birefringence measuring device and reducing the manufacturing cost of the liquid crystal display panel.

2) Birefringence can be obtained by a simple device construction and by using a compensating polarizing plate and rotating the analyzer or rotating the polarizer and the analyzer to measure the transmitted light intensity. It is possible to measure the retardation value of the functional layer and the optical axis direction. Therefore, it is also useful for both process control by online measurement at the manufacturing site and quality control of finished products. 3) It is possible to select between ordinary retardation measurement of a birefringent sample and retardation measurement of a composite layer sample by partially changing or switching the device configuration. 4) In addition, even for a composite layer sample using a material having a low degree of polarization as the polarization filter layer, the viewing angle characteristics can be evaluated as a retardation value, and the quality of the bonded product can be stabilized. You can

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the principle of the present invention.

FIG. 3 is an example of a graph of transmitted light intensity in polar coordinate display according to the present invention.

FIG. 4 is a schematic perspective view showing a sample table in another embodiment.

FIG. 5 is an exploded perspective view showing the sample table in detail.

FIG. 6 is a spectrum diagram showing a spectral transmission characteristic of a polarization filter, where (A) is a polarization filter with a high degree of polarization,
(B) is an example of a polarizing filter having a low degree of polarization.

[Explanation of symbols]

 1 White Light Source 2 Optical Fiber 3 Condenser Lens 4 Narrow Band Interference Filter 5 Polarizer Forward / Reverse X Stage 6 Polarizer Rotation θ Stage 7 Polarizer Rotation Positioning Encoder 8 Polarizer 9 Compensating Polarizing Plate 10 Compensating Polarizing Plate Plate rotation θ stage 11, 11a Sample stage 12 Analyzer forward / backward X stage 13 Analyzer rotation θ stage 14 Analyzer rotation positioning encoder 15 Analyzer 16 Light receiving element 17 Control device 18 Display device 19 Compensation polarizing plate Rotation θ-stage motor 20 Polarizer rotation θ-stage motor 21 Analyzer rotation θ-stage motor

Claims (7)

[Claims] 1. A compensating polarizing plate is disposed on the polarizing filter layer side of a composite layer sample in which a polarizing filter layer and a birefringent layer are laminated, and the polarizing transmission axes of the polarizing filter layer and the compensating polarizing plate are parallel to each other. The step of maintaining the polarization characteristics of the polarizing filter layer and compensating, irradiating the measuring light from the side of the polarizing plate for compensation, passing the transmitted light passing through the polarizing plate for compensation and the composite layer sample to the analyzer, The polarization transmission axis is rotated relative to the polarization transmission axis of the compensating polarizing plate and the composite layer sample, and the relationship between the intensity of the analyzer transmitted light and the polarization direction of the analyzer is detected to detect the letter of the composite layer sample. And the step of obtaining the optical axis direction of the optical axis,
A method for measuring retardation of a composite layer, comprising: 2. The retardation measuring method for a composite layer according to claim 1, wherein the measuring light is applied to the compensation polarizing plate in a non-polarized state. 3. The retardation measurement of the composite layer according to claim 1, wherein a polarizer is arranged on the light incident side of the compensation polarizing plate, and the polarizer and the analyzer are kept in a predetermined polarization azimuth relationship with each other. Method. 4. The transmitted light intensity is measured while rotating the compensating polarizing plate once relative to the polarizing filter layer in a state where neither a polarizer nor an analyzer is arranged in the optical path, The method for measuring retardation of a composite layer according to claim 1, wherein the polarization transmission axis and the polarization transmission axis of the compensating polarizing plate are parallel to each other. 5. The retardation and the optical principal axis direction of the composite layer sample are determined by arranging the surface of the composite layer sample in a state perpendicular to the optical path of the measuring light, and then, of the two determined optical principal axis directions. While tilting the surface of the composite layer sample with one of them as the tilt axis, the polarization transmission axis of the analyzer is again rotated relative to the polarization transmission axis of the composite layer sample, and the intensity of the analyzer transmitted light is The method for measuring the retardation of a composite layer according to claim 4, further comprising the step of determining the retardation of the composite layer sample by detecting the relationship with the polarization direction of the analyzer. 6. A light source section for irradiating a measurement light beam on a measurement optical path, a sample stage for holding a composite layer sample in which a polarization filter layer and a birefringent layer are laminated on the measurement optical path, and a composite layer sample held on the sample stage. The rotatably supported analyzer placed on the measurement light flux exit side of the sample, and the composite layer held on the sample stage, provided on the measurement light flux entrance side of the sample and rotatably supported independently of the analyzer. The compensating polarizing plate that compensates the polarization characteristics of the polarizing filter layer of the sample, the light receiving part that detects the transmitted light intensity of the light that has passed through the analyzer from the compensating polarizing plate through the composite layer sample, and the rotation angle of the analyzer. A retardation measuring device for a composite layer, comprising: an arithmetic and control unit for calculating the retardation of the composite layer sample and the optical principal axis direction from the transmitted light intensity detected by the light receiving section. 7. The sample stage comprises a mechanism for rotating the held composite layer sample in its plane and an inclining mechanism for inclining the composite layer sample about a straight line along the surface of the composite layer sample. 7. The retardation measuring device for a composite layer according to claim 6.