JP2009085887A - Measuring device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring device and method for rapidly and accurately measuring a birefringence state, for example, the orientation state, of a birefringence film, such as orientation film. <P>SOLUTION: This measuring device measures the orientation state of the orientation film 100. The device comprises a photoelastic modulator 30 that transmits measuring light coming via a polarizer 20, is driven at a predetermined elastic frequency, and varies the birefringence phase modulation amount, in association with the elastic frequency; and a light-receiving means 50 for transmitting the photoelastic modulator, receiving the measuring light reflected by the orientation film 100 via an analyzer 40, and converting it into light intensity information indicating the light intensity. A reference component extracting means 60 performs processing of extracting the amplitude component, of at least the elastic frequency and a frequency twice as much as it as a reference component from the light intensity information. An orientation state arithmetic means 70 determines a physical quantity, showing the orientation state of the orientation film based on the extracted reference component. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a measuring apparatus and method for measuring the birefringence state of a birefringent film.

  In the manufacturing process of a liquid crystal display, rubbing is the most important process for aligning liquid crystals.

  In recent years, photo-alignment has been attracting attention as a clean method capable of high-speed, arbitrary alignment directions.

  Birefringence measurement has attracted attention for the evaluation of this photo-alignment amount.

  Conventionally, in order to perform such a measurement, there is a technique using an ellipsometer as described in Non-Patent Document 1. In this method, a phase plate or a polarizing plate is rotated to apply polarization modulation, and an ellipticity and an ellipticity azimuth are obtained from a change in light intensity obtained at that time.

  As another technique, a liquid crystal alignment film inspection apparatus is known as described in Non-Patent Document 2. This apparatus is formed as a rotary analyzer type, and an orientation sample is placed on a rotary table to perform polarization analysis.

As another technique, a birefringence meter using a photoelastic modulator is also known.
Azzam, Bashara: Ellipometry and Polarized (Elsevier, 1986). Moritex, Monthly Display (2006,12) pp.55-59.

  However, the conventional measurement method has the following problems.

  First, the birefringence phase difference generated with respect to the orientation strength by the photo-alignment becomes a very small value as compared with the conventional mechanical rubbing method. For this reason, it has been difficult to accurately measure the alignment state of the alignment film by the conventional method.

  The liquid crystal display has a stacked structure in which a color filter, a transparent electrode, an alignment film, and the like are sequentially stacked on a glass substrate having a transparent electrode and an alignment film stacked on the surface. Therefore, in the conventional method of reflecting the measurement light on the alignment film and analyzing the reflected light, the measurement light incident on the alignment film is separated into transmitted light and reflected light on the alignment film surface, and the transmitted light has a laminated structure. There is a problem in that the light is sequentially reflected at the boundary surface and is superimposed on the light reflected from the alignment film surface as back surface reflected light, and this back surface reflected light causes measurement errors in the alignment state of the alignment film.

  Further, in the method of transmitting the measurement light through the alignment film that is a sample, there is a problem that all the laminated information other than the alignment film is included in the transmitted light.

  An object of the present invention is to provide a measuring apparatus and method for measuring a birefringence state of a birefringent film such as an alignment film, for example, an alignment state at high speed and accurately.

(1) The present invention
In an apparatus for measuring the birefringence state of a birefringent film,
Photoelastic modulation means that transmits measurement light incident through a polarizer, is driven at a given elastic frequency, and a birefringence phase modulation amount changes in association with the elastic frequency;
A light receiving means for transmitting the measurement light reflected through the photoelastic modulation means and reflected by the birefringent film through an analyzer, and converting the light into light intensity information representing the light intensity;
A reference component extraction means for performing a process of extracting at least the elastic frequency and an amplitude component of twice the frequency as a reference component from the light intensity information;
Birefringence state calculation means for obtaining a physical quantity representing the birefringence state of the birefringent film based on the extracted reference component;
including.

  Here, the photoelastic modulator includes a piezo element region and a light transmission region. The photoelastic modulator expands and contracts when an electrical signal for generating a given elastic frequency and a given amplitude is applied to the piezo element region from the outside, and birefringence is generated in the light transmission region by the photoelastic effect. To do.

  Then, the measurement light transmitted through the photoelastic modulation means and reflected by the birefringent film surface is received by the light receiving means via the analyzer, and is changed to light intensity information representing the light intensity.

  The light intensity information representing the light intensity includes a frequency for driving the photoelastic modulation means, that is, an amplitude component of the elastic frequency and an amplitude component of twice the frequency.

  In the present invention, the reference component extraction circuit extracts from the light intensity information the amplitude component of the elastic frequency and twice the frequency as a reference component of the light intensity information, and the orientation state calculation means is the extracted piezo component Based on the above, a physical quantity representing the birefringence state of the birefringent film is obtained.

  Since such a series of arithmetic processing can be executed in almost real time, the birefringence state of the birefringent film can be measured in almost real time as a physical quantity representing the birefringence state (for example, orientation state). . Therefore, for example, in a production line such as a liquid crystal display, real-time and continuous measurement of the birefringence state of the birefringent film can be performed.

  In addition, according to the present invention, the elastic wave frequency extracted from the light intensity information and the amplitude component of twice the frequency include information for obtaining a physical quantity representing the birefringence state of the birefringent film. For example, the change in the alignment state generated in the birefringent film with respect to the alignment strength by photo-alignment can be accurately obtained as a physical quantity.

(2) In the present invention,
The reference component extraction means includes
Further processing to extract the direct current component as one of the reference components from the light intensity information,
The birefringence state calculating means includes:
Based on the extracted reference component, at least one of the phase difference of the birefringent film and the complex reflection amplitude ratio is obtained as the physical quantity.

  The direct current component included in the light intensity information of the present invention includes a physical quantity representing the birefringent state of the birefringent film, particularly information for obtaining a phase difference.

  Therefore, according to the present invention, as a physical quantity representing the birefringence state of the birefringent film, at least one of the phase difference and the complex reflection amplitude ratio of the birefringent film (for example, the alignment film) can be accurately obtained in real time. Therefore, it is possible to realize a measuring apparatus capable of quickly determining the quality of the birefringent film region.

(3) In the present invention,
The principal axis directions of the polarizer and the analyzer were set to have a given relationship with respect to the principal axis direction of the photoelastic modulation means.

  Here, the main axis direction of the polarizer is preferably set to 45 ° with respect to the main axis direction of the light intensity modulating means, or an angle obtained by adding an angle multiplied by 90 ° thereto.

  Further, the main axis direction of the analyzer is preferably set to the same angle as the main axis direction of the polarizer or an angle obtained by adding a multiplication angle of 90 ° thereto.

  Thereby, the measurement light used for the measurement can be efficiently used and received by the light receiving means, and the birefringence state of the birefringent film can be measured with higher accuracy.

(4) In the present invention,
Laser light in the UV band is used as the measurement light.

  Even when a birefringent film is formed on the surface of the multilayer structure by using laser light in the UV band as measurement light, the laser beam from the back side that is superimposed on the reflected light from the surface of the birefringent film is used. The reflected light, particularly the reflected light from the substrate surface can be attenuated, thereby reducing the influence of the back surface reflection and realizing more accurate measurement.

(5) In the present invention,
An opening through which the reflected light from the front surface side of the birefringent film is passed and the reflected light from the back surface side is removed on the reflected light path until the measurement light reflected by the birefringent film reaches the light receiving means. Was provided.

  According to the present invention, it is possible to remove the influence of the reflected light from the back surface side superimposed on the reflected light from the surface of the birefringent film at the opening, and reduce the influence.

(6) In the present invention,
The incident direction of the measurement light to the birefringent film is set to a representative reference measurement direction in which the reflected light intensity of the birefringent film appears remarkably.

  When measuring the birefringence state of the birefringent film formed on the substrate, the magnitude of the light intensity obtained depends on the direction from which the measurement light is incident with respect to the direction of the liquid crystal molecules. It will be.

  In the present invention, when the measurement light is incident on the surface of the birefringent film, the measurement light is incident from a representative measurement direction in which the characteristic of the birefringent film appears most, so that a more accurate birefringence state ( For example, the orientation state) can be measured.

(7) The present invention also provides:
At the same measurement point of the birefringent film,
Measurement light is incident from at least two different directions, each reflected measurement light is individually received, and the physical quantities are individually calculated.

  In this way, the measurement light is incident from two directions, each reflected measurement light is individually received, and the calculation of the physical quantity is performed, thereby reducing the influence of the measurement light incident direction and reducing the birefringent film. The refraction state can be measured more accurately.

(8) The present invention also provides:
A hemispherical lens made of a transparent elastic resin is brought into close contact with the surface of the birefringent film, and measurement light is introduced into the birefringent film through the lens. Thereby, scattering due to unevenness on the surface of the birefringent film can be prevented, and noise in measurement can be reduced.

(9) The present invention also provides:
The measurement light transmitted from the photoelastic modulation means is branched into a plurality of incident optical paths by a plurality of incident light side beam splitters, and incident on a plurality of measurement spots on the surface of the birefringent film,
The measurement light reflected from the plurality of measurement spots is combined into measurement light of one optical path by a plurality of reflected light side beam splitters and incident on the light receiving means,
Each of the plurality of incident light paths is provided with shutter means for selectively blocking measurement light, and selectively receives measurement light from the plurality of measurement spots on the light receiving means.

  According to the present invention, a plurality of measurement spots on the birefringent film surface can be measured sequentially and almost simultaneously.

(10) The present invention also provides:
A plurality of the photoelastic modulation means are provided, each photoelastic modulation means is driven at a different elastic frequency, and the measurement light transmitted through each photoelastic modulation means is incident on a plurality of measurement spots on the surface of the birefringent film,
The measurement light reflected from the plurality of measurement spots is combined with the measurement light of one optical path by the reflected light side beam splitter and is incident on the light receiving means.

  According to the present invention, it is possible to simultaneously measure a plurality of measurement spots on the surface of the birefringent film.

(11) The present invention also provides:
Photoelastic modulation means that transmits measurement light incident through a polarizer, is driven at a given elastic frequency, and a birefringence phase modulation amount changes in association with the elastic frequency;
A light receiving means for transmitting the measurement light reflected through the photoelastic modulation means and reflected by the birefringent film through an analyzer, and converting the light into light intensity information representing the light intensity;
In the method of measuring the birefringence state of the birefringent film using
A reference component extraction procedure for performing a process of extracting, from the light intensity information, an amplitude component of at least the elastic frequency and twice the frequency as a reference component;
Birefringence state calculation means for obtaining a physical quantity representing the birefringence state of the birefringent film based on the extracted reference component;
including.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment described below is an example of the present invention, and the present invention is not limited to this. Moreover, this invention shall also include what combined the following content freely.

(1) Device Configuration FIG. 1 shows a schematic configuration of the measurement device of the present embodiment.

  The measuring device includes an optical system 2, a reference component extracting unit 60, and a computer 70 functioning as an orientation state calculating unit, and measures the birefringence state of the birefringent film as a measurement target. In the present embodiment, for example, a physical quantity representing the alignment state of the alignment film 100 on the substrate or the substrate film is measured.

  Specifically, the refractive index anisotropy representing the orientation azimuth angle, orientation tilt angle, and orientation degree of the alignment film 100 for measuring the photo-alignment characteristics is detected as a complex reflection amplitude ratio Ψ and a phase difference Δ of the reflected light. .

  In this embodiment, as an example of the birefringent film, a case where a physical quantity representing the alignment state of the alignment film is measured will be described as an example. The present invention can also be applied to measurement of a physical quantity representing the birefringence of a film.

1-1: Optical system 2
The optical system 2 includes a light source 10, a polarizer 20, a photoelastic modulator 30 (also referred to as “PEM”), an analyzer 40, and a detector 50.

  The light source 10, the polarizer P, and the photoelastic modulator 30 are provided on the incident optical path side where the measurement light L is incident on the alignment film 100 as a measurement target.

  The analyzer 40 and the detector 50 are provided on the reflected light path side of the measurement light reflected from the surface of the alignment film 100 as a measurement target.

  The light source 10 supplies the measurement light L, and is configured to emit UV band light as the measurement light L in the present embodiment.

  By using laser light in the UV band as measurement light, the influence of back surface reflection of the alignment film 100 can be reduced, and the alignment state of the alignment film 100 can be measured more accurately. That is, by using measurement light in the UV band, it is possible to reduce the emitted light emitted from the back surface side of the alignment film, particularly significantly reduce back surface reflection from the substrate on which the alignment film 100 is provided, Measurement accuracy can be increased. Here, a He—Cd laser is used as the light source 100, and a laser beam of 325 nm is used as the measurement light L.

  The polarizer 20 is an incident-side polarizer that is paired with the analyzer 40 and uses the measurement light emitted from the light source 10 as linearly polarized light.

  The analyzer 40 is an output-side polarizer that is paired with the polarizer 20 and uses the measurement light reflected by the surface of the alignment film 100 as linearly polarized light.

  The polarizer 20 and the analyzer 40 are arranged such that their principal axis directions are 45 ° with respect to the main axis direction of the photoelastic modulator 30. The angles of the principal axis directions of the polarizer 20 and the analyzer 40 may be appropriately changed as necessary, and the angle of the principal axis direction of the analyzer with respect to the polarizer 20 is also set to have a phase difference of 90 °, for example. May be.

1-2: Photoelastic modulator 30
The photoelastic modulator 30 is a modulator that transmits measurement light incident through the polarizer 20 and is driven at a given elastic frequency, and the amount of birefringence phase modulation changes in association with the elastic frequency.

  FIG. 2 shows a specific configuration of the photoelastic modulator 30.

This photoelastic modulator 30 forms a piezoelectric element region 30A by attaching quartz piezoelectric vibrators 32a and 32b so as to face one region of an isotropic transparent substance (quartz, CaF _2, etc.). In the other region, a transmission region 30B that transmits the measurement light is formed.

In the present embodiment, the PEM controller 36 uses the modulation amount with an angular frequency ω (ω = 2πf, f is a frequency) as an elastic frequency and an amplitude δ ₀ as an electric signal in the piezoelectric element region 30A of the photoelastic modulator 30. When applied, birefringence is generated by the photoelastic effect in the isotropic transparent material constituting the piezoelectric element region 30A and the transmission region 30B.

  That is, when a drive voltage having a given elastic frequency and amplitude is applied to the piezoelectric vibrators 32a and 32b in the piezoresistive region 30A, the piezoelectric vibration corresponding to the elastic frequency is as shown in FIGS. And uniaxial anisotropy that vibrates at the elastic frequency also occurs in the transmission region 30B. As a result, the birefringence phase modulation amount δ of the transmission region 30B changes.

  FIG. 4 shows an example of the relationship between the position and amplitude in the transmission region 30B.

  Therefore, as shown in FIG. 5, the measurement light L transmitted through the transmission region 30B is modulated and output in association with the birefringence phase modulation amount δ.

  Then, the measurement light L modulated as described above by the photoelastic modulator 30 is incident on a predetermined measurement spot on the surface of the alignment film 100 as a measurement target.

1-3: Alignment State of Alignment Film 100 FIG. 6 shows a measurement light incident on the surface of the alignment film 100 and reflected, and a schematic diagram of the alignment state of the alignment film 100.

  As shown in FIG. 6A, a polymer 110 is oriented in a predetermined direction in the orientation film 100. Here, it is assumed that the plane including the incident and reflected light of the measurement light L is a vertical plane, the vertical direction of this vertical plane is y, the horizontal direction is z, and the direction orthogonal to the vertical plane is x.

  FIG. 6B shows an example of the orientation state of the polymer 110 in the x, y, and z coordinate axes. In the figure, n1, n2, and n3 represent main refractive indexes in the respective axial directions.

  FIG. 7 schematically shows the orientation direction of the polymer 110 in the y and x planes orthogonal to the y and z planes that are the incident and reflection surfaces of the measurement light L shown in FIG.

  Here, Ψ represents the complex reflection amplitude ratio of the reflected measurement light.

  And a and b represent the major axis and minor axis of the ellipse, and the ratio b / a represents the ellipticity. χ represents the ellipticity angle.

  In the present embodiment, the phase difference is detected as Δ.

  Then, the measurement light L reflected by the surface of the alignment film 100 passes through the analyzer 40 and enters the detector 50 that functions as a light receiving means.

The light intensity of the measurement light L detected by the detector 50 is proportional to a ² + b ² .

  The detector 50 detects the light intensity of the incident measurement light, converts it into an electrical signal as light intensity information indicating the light intensity, and outputs the electrical signal.

1-4: Reference component extraction means 60 and computer 70
The reference component extraction unit 60 performs a process of extracting, from the light intensity information output from the detector 50, at least the elastic frequency and an amplitude component having a frequency twice that of the elastic frequency as a reference component.

  In the present embodiment, the reference component extraction unit 60 includes a low-pass filter 62 and first and second lock-in amplifiers 64 and 66.

  The low-pass filter 62 performs a process of extracting the direct current component as one of the reference components from the light intensity information I output from the detector 50, and outputs the output to the AD converter 68.

  The first lock-in amplifier 64 extracts the amplitude component of the reference elastic frequency as one of the reference components from the light intensity information I output from the detector 50, and outputs it to the AD converter 68.

  The second lock-in amplifier 66 extracts, from the light intensity information I output from the detector 50, an amplitude component having a frequency twice the elastic frequency as a reference component, and outputs the reference component to the AD converter 68.

  The AD converter 68 converts each reference component including the direct current component of the light intensity information input in this way, the amplitude component of the elastic frequency, and the amplitude component of the frequency twice the elastic frequency into a digital signal, and sends it to the computer 70. Output.

  Based on the extracted reference component, the computer 70 executes birefringence state calculation processing for obtaining a physical quantity representing the birefringence state (“alignment state” in the present embodiment) of the alignment film 100. Details thereof will be described later.

(2) Measurement Principle of Alignment Film Next, the measurement principle of the measurement apparatus of the present embodiment will be described.

2-1: Polarization Matrix of Optical System 2 In the optical system 2 of the present embodiment, the Mueller matrices of the polarizer 20, the photoelastic modulator 30, the alignment film 100, and the analyzer 40 are P, PEM, X, and A, respectively. If the polarization state s _in of the measurement light before the polarizer 20 is incident and the polarization state of the measurement light incident on the detector 50 from the analyzer 40 is s _out , the polarization of the measurement light L incident on the analyzer 50 The state s _out (Stokes parameter) is given by equation (10a). The expression (10a) is expressed as the expression (10b).

Then, by calculating the expression (10b), the expression (10b) becomes the expression (10c).
Since the detected light intensity I (t) is the S ₀ component of the Stokes parameter, the value is given by equation (1a).

2-2: Relationship between Modulation by Photoelastic Modulator 30 and Light Intensity I (t) As described above, the piezo element region 30A of the photoelastic modulator 30 has an angular frequency ω (ω = 2πf, f is a frequency) ), A modulation amount having an amplitude δ ₀ is applied as an electric signal.

As a result, the photoelastic modulator 30 expands and contracts as shown in FIG. 3, and birefringence is generated in the light transmission region 30B such as quartz by the photoelastic effect.
The birefringence phase modulation amount δ at this time is
It can be expressed as
And (1a) is
It becomes.

  The first term of equation (4) is a bias, and the third and fourth terms are the amplitudes of the light intensity modulated at frequencies 1f and 2f, respectively.

Here, if d ₀ = 2.405 rad, J ₀ (d ₀ ) = 0, and the second term in Eq. (4) disappears.

In this embodiment, the amplitude δ ₀ is set by the voltage applied from the PEM controller 36 to the photoelastic modulator 30 so that the second term of the equation (4) disappears.

J ₁ (d ₀ ) = 0.519, J ₂ (d ₀ ) = 0.432, so rewriting equation (4),
It becomes.

  In actual measurement, the measurement light L modulated by the photoelastic modulator 30 is photoelectrically converted by the detector 50 and detected as a voltage signal, and is sent to the low-pass filter 62 and the first and second lock-in amplifiers 62 and 66. Entered.

The low pass filter 62 detects the bias I _{dc of the} light intensity. Since the DC component of equation (4b) can be detected,
It becomes.

Next, the two lock-in amplifiers 64 and 66 measure the amplitudes I _1f and I _2f of the frequencies 1f and 2f, respectively.

The lock-in amplifier I _1f 64 detects the amplitude and phase of the component of the frequency f in the measurement electric signal of the equation (4b) using f as the modulation frequency of the photoelastic modulator 30 as a reference signal (here, amplitude) only).

The detected I _1f is
It becomes.

Similarly, the lock-in amplifier I _2f 66 is synchronized with a frequency 2f that is twice the frequency f of the PEM (the lock-in amplifier has such a function), and the lock-in amplifier I _2f 66 includes The amplitude and phase of the component of frequency 2f are detected (only amplitude here).

The detected I _2f is
It becomes.

  In this way, the signals detected and output by the low-pass filter 62 and the lock-in amplifiers 64 and 66 are converted into digital signals by the AD converter 68 and input to the computer 70.

  The computer 70 functions as birefringence state calculation means, and from the basic component of the light intensity I (t) detected and output as the above formulas (5) to (7), the complex reflection amplitude ratio Ψ, phase difference of the alignment film 100 is calculated. Δ is obtained based on the following equation.

Thus, in this embodiment, the phase difference Δ and the complex reflection amplitude ratio Ψ can be obtained in real time as physical quantities indicating the alignment state of the alignment film 100.

  In the present embodiment, the case where both the phase difference and the complex reflection amplitude ratio are obtained as physical quantities has been described as an example. However, when only the phase difference Δ is obtained, the low-pass filter 62 can be omitted.

(3) Countermeasures for Back Surface Reflection and Surface Rough Reflection FIG. 8 is a schematic diagram of measurement light incident on the alignment film 100 and reflected measurement light.

  As shown in FIG. 8A, when the measurement light L is incident on the alignment film 100, the measurement light L is not only reflected by the surface 100a of the alignment film 100, but a part of the measurement light L is in the alignment film 100. And reflected on the back surface 100b side, and as a result, as shown in FIG. 8C, the front surface reflected light I1 and the back surface reflected light I2 enter the detector 50 in a superimposed state. .

  In the present embodiment, in order to reduce the influence of such back surface reflection, a first light blocking device provided with a first pin pole 80a (opening) for narrowing incident light into a thin light beam on the incident light path side of measurement light. A second pinhole 82a (which is provided with a plate 80, further transmits only the reflected measurement light I1 from the surface of the alignment film 100 in front of the detector 50 on the reflection light path side of the measurement light, and shields the back surface reflected light I2). A second shading plate 82 provided with an opening) is installed.

  Thereby, the influence of the back surface reflection of the alignment film 100 can be reduced, and the physical quantity of the alignment film 100 can be measured with higher accuracy.

  Further, as shown in FIG. 8B, by attaching a material 104 having a refractive index close to that of the alignment film 100 to the back surface side of the alignment film 100, back surface reflection on the back surface 100b side of the alignment film 100 is further reduced. Further, the measurement accuracy of the physical quantity of the alignment film 100 can be further improved.

  In the present embodiment, as a countermeasure against surface irregular reflection, a configuration is adopted in which a hemispherical lens made of a transparent elastic resin is brought into close contact with the surface of the birefringent film, and the measurement light is introduced into the birefringent film through the lens. May be. Thereby, scattering due to unevenness on the surface of the birefringent film can be prevented, and noise in measurement can be reduced.

  Specifically, as shown in FIG. 14, by installing a hemispherical lens 150 made of a transparent elastic resin on the surface of the photo-alignment film 100 laminated on the substrate 102, the reflection component of the photo-alignment film 100 is further increased. It can be detected efficiently.

  For example, if the refractive index of the hemispherical lens 150 is different from that of the photo-alignment film 100, reflection at the interface with the lens 150 is efficiently generated. Conversely, if the refractive index is the same, reflection at the surface portion can be reduced. Thereby, reflection information at the interface between the substrate layer 102 and the photo-alignment film 100 can be captured, and polarization information of the photo-alignment film 100 can be captured.

(4) Incident direction of measurement light on the surface of the alignment film 100 When the incident direction of the measurement light L on the surface 100a of the alignment film 100 changes, the physical quantity representing the detected alignment state of the alignment film 100 also changes.

  The experimental results are shown in FIGS.

  In this experiment, as shown in FIG. 9, the optical system 2 is fixed, and the alignment film 100 is rotated in the horizontal direction in the range of 0 to 360 ° on the xz plane. It verified whether it changed to.

  FIG. 10 shows data when the phase difference Δ of the glass substrate is obtained as a measurement sample instead of the alignment film 100. It was confirmed that the phase difference Δ obtained when the glass substrate was rotated 360 ° was almost zero.

  FIG. 11 shows phase difference Δ data obtained when a photo-alignment film is used as the alignment film 100 and rotated in the range of 0 to 360 °. It was confirmed that the phase difference Δ can be accurately measured even when the photo-alignment film is rotated in the range of 0 to 360 °.

  FIG. 12 shows a measurement result when a mechanical rubbing film is used as the measurement object as the alignment film 100. It was confirmed that even when the optical rubbing film was rotated by 0 to 360 °, the phase difference Δ indicating the alignment state of the optical elliptical film could be measured with high accuracy.

  As described above, it was confirmed that the measurement apparatus of the present embodiment accurately measures the physical quantity indicating the alignment state of the alignment film 100, particularly the phase difference Δ.

  As is clear from FIGS. 11 and 12, when the alignment film 100 is rotated by 0 to 360 °, it can be seen that there is a typical reference measurement orientation in which the polarization state of the alignment film 100 appears remarkably. For example, as shown in FIG. 12, when a mechanical rubbing film is used as the alignment film 100 as a measurement object, the mechanical rubbing film has a large phase difference Δ indicating the alignment state of the photoelliptic film at around 0 ° and 120 °. Takes a value.

  As described above, when measuring the alignment state of the alignment film formed on the substrate, the physical quantity indicating the alignment state obtained depends on which direction the measurement light is incident on the direction in which the liquid crystal molecules are directed. The size will be different.

  For this reason, when the measurement light is incident on the alignment film surface, if the typical measurement direction in which the characteristic of the alignment film appears most is known in advance, the measurement light is incident from the representative measurement direction. Thus, it becomes possible to measure the alignment state with higher accuracy.

  In addition, measurement light may be incident on the same measurement point of the alignment film 100 from at least two different directions, and each reflected measurement light may be individually received, and the physical quantities may be individually calculated.

  In this way, the measurement light is incident from two directions, each reflected measurement light is individually received, and the calculation of the physical quantity is performed, thereby reducing the influence of the incident direction of the measurement light and changing the alignment state of the alignment film. It can be measured more accurately.

(5) Multipoint Measurement FIG. 13 shows an example of the case where the measuring apparatus according to the present embodiment is formed for multipoint measurement of the photo-alignment film 100.

  On the light incident optical path side, three incident optical paths are formed by two beam splitters 90-1 and 90-2 and a mirror 92 from the measurement light that has passed through the elastic modulator 30. Each incident light is made incident on the measurement spot. Then, the measurement light reflected by the three measurement spots is synthesized into one reflected light path by two beam splitters 94-1 and 94-2 and a mirror 96 provided on the reflected light path. It is comprised so that it may inject into the detector 50 via.

  On the detector 50 side, shutters 91-1, 91-2, and 91-3 are provided on the three incident light paths so that it can be selected from which measurement spot the light is incident. Only one of 91-1 to 91-3 is controlled to be in an on state that transmits light, and the other two are controlled to be in an off state that does not transmit light.

  Here, the shutters are controlled cyclically so that the shutters are sequentially turned on in the order of the shutters 91-1, 91-2, and 91-3. As a result, the measurement light detected by the detector 50 can be determined from which measurement spot of the alignment film 100, and the alignment states at the plurality of measurement spots of the alignment film 100 are individually detected substantially in real time. be able to.

  In the embodiment shown in FIG. 13, when the sheet-like alignment film 100 wound around the first roll 120 is wound up by the second roll 130, three measurement spots provided in the width direction of the alignment film 100. Thus, the alignment state of the alignment film 100 is measured in real time and the quality is determined.

  The apparatus according to the present embodiment can inspect the alignment state of the alignment film 100 in real time in the moving direction while moving the alignment film 100 in the roll direction indicated by the arrow in the drawing, and can be used in the manufacturing field of liquid crystal displays. In particular, it is extremely effective as a quality inspection apparatus in a photoalignment film production line that is expected to be put to practical use in the future.

  As another example of measuring the alignment film 100 at multiple points, for example, the photoelastic modulators 30 are individually provided on a plurality of incident optical paths with respect to a plurality of measurement spots of the alignment film 100, and each photoelastic modulator 30 is provided. A configuration may be adopted in which each is driven at a different elastic frequency.

  In this case, even when the measurement light reflected from each measurement spot is combined with the measurement light of one optical path from the reflected light side beam splitter and received by the light receiving means, the measurement light from each measurement spot has a different elastic frequency. Have an amplitude component of.

  That is, the light intensity signal output from the detector 50 includes the elastic frequency component of the photoelastic modulator 30 corresponding to each measurement spot.

  Therefore, by extracting the amplitude component of the elastic frequency and the amplitude component of twice the frequency in each measurement light, the physical quantity indicating the orientation state of each measurement spot, in particular, the phase difference Δ can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic explanatory drawing of the measuring apparatus to which this invention was applied. Explanatory drawing of the photoelastic modulator used for the measuring apparatus of this Embodiment. Explanatory drawing of operation | movement of a photoelastic modulator. Explanatory drawing of the piezoelectric operation of a photoelastic modulator. Explanatory drawing of the measurement light which permeate | transmits a photoelastic modulator. Explanatory drawing which shows the orientation state of an alignment film. Explanatory drawing of the alignment state of alignment film. Explanatory drawing of the structure for removing the back surface reflection of alignment film. Explanatory drawing in the case of changing the incident direction of an alignment film 0-360 degrees in an optical system. The figure which shows the measurement result which used the glass substrate as the measuring object. The figure which shows the measurement result of a photo-alignment film. The figure which shows the measurement result of an optical rubbing film | membrane. Explanatory drawing in the case of performing multipoint measurement using the system of this Embodiment. Explanatory drawing of the optical system which provided the hemispherical lens on the surface of the birefringent film as a countermeasure against surface irregular reflection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Light source 20 ... Polarizer 30 ... Photoelastic modulator 40 ... Analyzer 50 ... Detector 60 ... Reference | standard component extraction means 62 ... Low pass filter 64, 66 ... 1st and 2nd lock-in amplifier 68 ... AD converter 70 ... Computer 100 that functions as alignment state calculation means 100 ... alignment film

Claims (11)

In an apparatus for measuring the birefringence state of a birefringent film,
Photoelastic modulation means that transmits measurement light incident through a polarizer, is driven at a given elastic frequency, and a birefringence phase modulation amount changes in association with the elastic frequency;
A light receiving means for transmitting the measurement light reflected through the photoelastic modulation means and reflected by the birefringent film through an analyzer, and converting the light into light intensity information representing the light intensity;
A reference component extraction means for performing a process of extracting at least the elastic frequency and an amplitude component of twice the frequency as a reference component from the light intensity information;
Birefringence state calculation means for obtaining a physical quantity representing the birefringence state of the birefringent film based on the extracted reference component;
Including measuring device. In claim 1,
The reference component extraction means includes
Further processing to extract the direct current component as one of the reference components from the light intensity information,
The birefringence state calculating means includes:
A measuring apparatus for obtaining at least one of a phase difference and a complex reflection amplitude ratio of a birefringent film as the physical quantity based on an extracted reference component. In any one of Claims 1, 2.
A measuring apparatus in which the principal axis directions of the polarizer and the analyzer are set to have a given relationship with respect to the principal axis direction of the photoelastic modulation means. In any one of Claims 1-3,
A measuring apparatus using laser light in the UV band as the measuring light. In any one of Claims 1-4,
An opening through which the reflected light from the front surface side of the birefringent film is passed and the reflected light from the back surface side is removed on the reflected light path until the measurement light reflected by the birefringent film reaches the light receiving means. Measuring device. In any one of Claims 1-5,
A measuring apparatus that sets the incident direction of the measurement light to the birefringent film to a representative reference measurement direction in which the reflected light intensity of the birefringent film is notable. In any one of Claims 1-6,
At the same measurement point of the birefringent film,
A measuring apparatus that receives measurement light from at least two different directions, individually receives each reflected measurement light, and individually calculates the physical quantity. In any one of Claims 1-7,
A measuring apparatus in which a hemispherical lens made of a transparent elastic resin is brought into close contact with the surface of a birefringent film, and measurement light is introduced into the birefringent film through the lens. In any one of Claims 1-8,
The measurement light transmitted from the photoelastic modulation means is branched into a plurality of incident optical paths by a plurality of incident light side beam splitters, and incident on a plurality of measurement spots on the surface of the birefringent film,
The measurement light reflected from the plurality of measurement spots is combined into measurement light of one optical path by a plurality of reflected light side beam splitters and incident on the light receiving means,
A measuring device that includes shutter means for selectively blocking measurement light in each of the plurality of incident light paths, and selectively enters measurement light from the plurality of measurement spots into the light receiving means. In any one of Claims 1-8,
A plurality of the photoelastic modulation means are provided, each photoelastic modulation means is driven at a different elastic frequency, and the measurement light transmitted through each photoelastic modulation means is incident on a plurality of measurement spots on the surface of the birefringent film,
A measuring apparatus that combines measurement light reflected from the plurality of measurement spots into measurement light on one optical path by a reflected light side beam splitter and enters the measurement light. Photoelastic modulation means that transmits measurement light incident through a polarizer, is driven at a given elastic frequency, and a birefringence phase modulation amount changes in association with the elastic frequency;
A light receiving means for transmitting the measurement light reflected through the photoelastic modulation means and reflected by the birefringent film through an analyzer, and converting the light into light intensity information representing the light intensity;
In the method of measuring the birefringence state of the birefringent film using
A reference component extraction procedure for performing a process of extracting, from the light intensity information, an amplitude component of at least the elastic frequency and twice the frequency as a reference component;
Birefringence state calculation means for obtaining a physical quantity representing the birefringence state of the birefringent film based on the extracted reference component;
Measuring method including