JPH11258110A - Method for evaluating optical anisotropy, manufacture for liquid crystal display apparatus and optical inspecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve correct inspection and measurement by inserting an anisotropy correction optical part offsetting an optical anisotropy of at least one layer of a multilayer structure into an optical path of a polarized light and evaluating the remaining optical anisotropy of the multilayer structure. SOLUTION: A light emitted from a light source 3 is formed into a highly directive parallel light by a collimator lens, etc., reflected at a mirror 34 and brought perpendicularly to a substrate 10. Before reaching the substrate 10, the parallel light enters perpendicularly a polarizer 32 of a high extinction ratio. The polarizer 32 is equipped with a rotating mechanism. The light passing the polarizer 32 becomes a linearly polarized light of a high polarization degree and enters an optical anisotropy compensator 5. The light passing the optical anisotropy compensator 5 enters the substrate 10. The light passing the substrate 10 enters an analyzer 33 which is rotatable about an optical axis of an image formation optical system of a high extinction ratio. The polarizer 32 and analyzer 33 are controlled so that respective polarization directions are at right angles. The light passing the analyzer 33 forms an image of a surface of the substrate 10 at an image pickup face of a superhigh-sensitivity pickup device 2 which picks up two-dimensional images.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating optical anisotropy, a method for manufacturing a liquid crystal display device, a method for optically inspecting components, and an inspection device therefor, and more particularly, to an optical device for forming a multilayer structure. The present invention relates to an optical evaluation method for a transparent body having optical anisotropy such as an alignment film of a liquid crystal display device, a method for manufacturing a display device using the same, a method for inspecting display device components, and an inspection device therefor.

[0002]

2. Description of the Related Art Production of liquid crystal displays (LCDs) typified by TFTs (thin film transistors) has been increasing and costs have been reduced with the spread of information equipment. One of the most important production processes of the liquid crystal display device is an alignment film forming process. The liquid crystal display device forms a transparent electrode on the substrate glass,
An alignment film such as polyimide is formed thereon, and the alignment characteristics are imparted by giving anisotropy to the alignment of molecules on the film surface by means such as rubbing. When the liquid crystal touches the alignment film, the directional liquid crystal molecules follow the alignment direction on the alignment film surface and are aligned in a certain direction. It is important to align the directions of the liquid crystal molecules in this way in order to maintain good display quality of the liquid crystal display device. For this reason, it is very important to know the state of anisotropy accompanying the orientation of the molecules on the surface of the alignment film in order to ensure the quality of LCD display.

[0003] The orientation film has a thickness of about 5 nm. However, when a rubbing method used for a usual orientation property imparting means is adopted, the molecular anisotropy is caused by the thickness of the orientation layer. It is said that it is only about 1 nm. Therefore, it is difficult to detect such a thin anisotropic layer.
Conventionally, as a method of optically detecting this anisotropy, 1 mm
A laser beam having a diameter is irradiated perpendicularly to the alignment film, optical heterodyne is detected using polarized light, and anisotropic retardation (parallel to the two axes of anisotropy of the anisotropic medium and in phase with each other) In some cases, after two linearly polarized light components have passed through the anisotropic medium, the phase difference between the polarized light components is measured with an accuracy of about 0.02 degrees. However, in this method, it takes a time in seconds to measure one point, and only average anisotropy data with a diameter of 1 mm is obtained, and it is impossible to know detailed characteristics.

[0004] In the light transmission type detection described above, the optical anisotropy of the glass substrate is always affected. In particular, when the anisotropy of the glass substrate is large compared to the optical anisotropy of the alignment film, the difference of the alignment film is large. It is very difficult to accurately detect anisotropy.

As a prior art, Japanese Patent Application Laid-Open No. 6-5923
No. 0 discloses a rubbing inspection device that irradiates a substrate with linearly polarized light, and among the reflected light, a polarizing plate that transmits polarized light orthogonal to the irradiated linearly polarized light and detects the light passing therethrough with a TV camera. I have.

However, no consideration has been given to detecting or measuring an object having an optical anisotropy intensity (retardation) Ψ of about 0.1 °, such as an alignment film of a liquid crystal display device. Was. Also, no consideration has been given to the fact that the polarization state of the light reflected from the underlayer changes and has an adverse effect.

Due to such a situation, conventionally, the liquid crystal is suspended and sandwiched between two substrates subjected to the alignment treatment, and the optical anisotropy of the liquid crystal molecules aligned according to the alignment direction of the molecules on the alignment film surface. Was used to check the condition of the alignment film.

[0008]

Among the above-mentioned prior arts, those which can evaluate the anisotropy of the alignment film without using a liquid crystal are lasers.
Is used. However, in the above-described method, a great deal of time is required to view a part or all of the alignment process of the substrate as a two-dimensional screen. Even if a diameter of 1 mm can be detected in one second, it takes 14 hours or more to inspect the entire screen area having a diagonal diameter of 13 inches. Moreover, since the resolution is 1 mm, fine defects cannot be detected any more.

Further, accurate quantitative evaluation is almost impossible due to the optical anisotropy of the glass substrate as described above.
On the other hand, the method of checking the pinch between two substrates by dropping liquid crystal takes a long time to set up, delays the timing of feeding back to the production process of the alignment film, and results in defective products.

Further, the present invention evaluates the optical anisotropy of only a specific layer in an optical component forming a multi-layer structure, for example, an optical component of only an alignment film formed on a glass substrate of a liquid crystal display device. When evaluating the optical anisotropy, it is necessary to remove the influence of the optical anisotropy of the glass substrate, but it can be put into the manufacturing site of liquid crystal display devices, etc., the operation is simple and the measurement accuracy is sufficient There was no way to get it.

[0011]

According to an embodiment in which the present invention is applied to the evaluation of an alignment film of a liquid crystal display device in order to solve the above-mentioned problems, the alignment film surface has high directivity and is almost perfect. Irradiates linearly polarized light, makes the transmitted light incident on the analyzer,
The light transmitted through the analyzer is received by the two-dimensional image pickup device.
At this time, the alignment film and the photoelectric conversion surface (sensor surface) of the imaging device are connected in a conjugate relationship with each other, and optical anisotropy is present in the optical path of linearly polarized light irradiating the alignment film surface or the optical path between the alignment film and the analyzer. A controllable optical anisotropy compensator can be inserted. Thus, the optical anisotropy of the substrate is compensated, and the optical characteristics of the alignment film are evaluated. This makes it possible to easily inspect the alignment film.

Further, the optical anisotropy compensator is provided with a transparent plate having little anisotropy, and by applying a force uniformly to the transparent plate in at least one direction, the optical anisotropy of the transparent plate is reduced. To be controlled. The transparent plate rotates relative to the substrate about an axis parallel to the optical axis of the light to be irradiated, so that the direction of optical anisotropy generated by the optical anisotropy compensator in a desired direction. Allows you to control. At this time, the compensation of the optical anisotropy of the substrate by the optical anisotropy compensator is such that the synthesis of the optical anisotropy generated by the optical anisotropy compensator and the optical anisotropy of the substrate is substantially isotropic. To

By doing so, the optical anisotropy of the substrate can be compensated, and the optical anisotropy of the alignment film alone can be accurately obtained.

By feeding back the inspection result of the alignment film thus obtained to the means for imparting the above-mentioned alignment characteristics, an optical component for a liquid crystal display device or the like can be manufactured without producing a large number of defective products. Can be manufactured.

At this time, the oscillation plane of the linearly polarized light is maintained at an angle of 90 ° between the vibration plane of the linearly polarized light and the direction of the polarized light passing through the analyzer (the transmission axis direction). The plane and the transmission axis of the analyzer are rotated relative to the liquid crystal substrate about the optical axis of the imaging optical system. By collecting a plurality of images obtained at different rotation angles in this way, and by further improving the measurement accuracy of the anisotropic direction and the anisotropic intensity by interpolation using a polynomial approximation based on this data, Quantitative inspection of alignment film anisotropy with high accuracy can be performed.

In the plurality of images obtained at different rotation angles in this way, the intensity of a pixel corresponding to a desired position on the substrate, that is, the brightness of the pixel corresponding to the change in the relative rotation angle is determined. Of the plurality of images is calculated. The optical characteristics of the alignment film on the substrate are detected by determining the optical anisotropy at a location corresponding to the pixel from the change in the rotation angle and the pixel intensity at this time.

At this time, a rotation angle at which the average intensity of the plurality of images obtained at the different rotation angles is minimum or maximum is determined, the relative rotation angle is determined based on the angle, and the change of the rotation angle is determined. , A change in intensity between a plurality of images of pixels is obtained. By doing so, a more accurate quantitative inspection of the orientation film anisotropy can be performed.

[0018]

FIG. 1 shows an embodiment of the present invention. TFT, a pair of substrates constituting a liquid crystal display device
The substrate and the color filter substrate are subjected to predetermined processes such as cutting and washing to reach an alignment film forming apparatus 112. In the alignment film forming apparatus 112, a material obtained by dissolving an alignment film material in a solvent is printed on the surface of the substrate, and dried and fired. The alignment film thus formed on the surface of the substrate is given anisotropy to the surface of the alignment film by the 130 alignment property imparting device. As a means for imparting such anisotropy, for example, there are rubbing with a cloth with hairy fur wound on a rotating drum, irradiation with linearly polarized ultraviolet light, and the like. When anisotropy is formed on the surface of the alignment film by such means, optical anisotropy also occurs. Therefore, the substrate is transported along a path 110 to one optical inspection apparatus described later in detail, and the anisotropy is generated. The anisotropic situation is checked. That is, with this inspection device 1, the anisotropy intensity of the alignment film surface is uniform regardless of the location, the anisotropy intensity is an appropriate amount, or the anisotropy direction is constant regardless of the location. And so on. At this time, if the optical anisotropy of the glass substrate on which the alignment film is formed is large, the optical anisotropy of the alignment film to be detected cannot be accurately obtained. Therefore, an optical anisotropy compensator that compensates for the optical anisotropy of the glass substrate is inserted by a method described later in detail, thereby compensating the optical anisotropy of the glass substrate and accurately detecting the optical characteristics of the alignment film. . If the anisotropy of the alignment film is determined for the above items in this way, it is possible to grasp in advance the abnormality of the alignment characteristic imparting device 130 and the alignment film forming device 112 or the signs of the abnormality. .

Of course, in order for such a determination to be made accurately, it is necessary to use a seal, which is a post-process of the orientation characteristic imparting means 130.
After the process of forming the metal material (device 150) and enclosing the liquid crystal (device 160), the accumulation of data relating to the correspondence between the result obtained by the lighting inspection of 190, which is the final process, and the result obtained by the optical inspection device 1. is necessary. That is, the inspection results by the optical inspection device 1 corresponding to the locations corresponding to the display defects detected by the lighting results obtained by the 190 lighting inspection devices are quantitatively compared, and the corresponding data is compared with the optical inspection device 1. In the internal memory (not shown). If such data is collected over a long period of time, a highly accurate correspondence can be obtained.

In the optical inspection apparatus 1, the substrate for checking the state of imparting the alignment characteristics to the alignment film is not necessarily an actual substrate, but is easily inspected by this inspection apparatus and has no display electrode pattern. -It may be a substrate. When an actual substrate in the manufacturing process is used, a substrate that passes this inspection is conveyed to the next step, a seal forming apparatus 150, along the path 111. If this test finds a failed board,
The cause of rejection is specified based on the previously stored data.

If the cause is in the alignment film forming apparatus 112, the signal is fed back to the film coating conditions, drying conditions or firing conditions of the alignment film forming apparatus 112 through the signal path 102. When the rejection is caused by the orientation property imparting device 130, the orientation property imparting device 130
Is fed back to the various parameters. The feedback to the alignment film forming device 112 or the alignment characteristic imparting device 130 is not always automatically performed on the signal path described above, but the condition setting and the parameter setting are performed by human intervention. Sometimes.

When the optical anisotropy of the substrate glass is large, the anisotropy of the alignment film on the substrate glass cannot be determined accurately. A compensator is inserted to compensate for the optical anisotropy of the glass substrate and accurately detect the optical characteristics of the alignment film. Although details will be described later in this compensation calculation, if the optical anisotropy of the substrate glass is accurately obtained, the optical characteristics of the alignment film can be detected more accurately. For this reason, the substrate after firing from the alignment film forming apparatus 112 is carried into the optical inspection apparatus 1 along the path 121 before being carried into the orientation property providing apparatus 130, and the optical difference of the glass substrate before the orientation property is provided. Measure the anisotropy. After doing so, it is conveyed to the orientation property giving device 130 along the path 122 to give the orientation property to the orientation film on the glass substrate. After the orientation characteristics are imparted, the substrate is transported again to the optical inspection apparatus 1 through the path 110, and the substrate after the orientation characteristics are imparted is inspected by a method described later, and a more accurate inspection of the optical anisotropy of the alignment film is performed. Will be

FIG. 2 is a diagram showing details of an embodiment of the optical anisotropy inspection apparatus 1 described in the embodiment of the present invention in FIG. Reference numeral 3 denotes a light source capable of forming light having high luminance and high directivity, such as a metal halide lamp or a xenon lamp. The light emitted from this light source is formed into parallel light having high directivity by a collimator lens or the like, is reflected by the mirror 34, and travels substantially perpendicularly to the substrate 10, which is the inspection object.

The substrate 10 is mounted on an XY stage (not shown) having an opening for allowing detection light to pass therethrough, and can inspect a desired place. The parallel light has an extremely high extinction ratio before reaching the substrate 10 (for example, an extinction ratio of 10 ⁶ or more. Specifically, a birefringent polarizer such as Glan-Thomson or Glan-Taylor, or a very high extinction) (A polarizing plate capable of obtaining a ratio is preferable). The polarizer 32 is provided with a rotation mechanism (not shown), and the polarizer 32 rotates around the optical axis of the imaging optical system. The light transmitted through the polarizer 32 is linearly polarized light having a very high degree of polarization, and is incident on an optical anisotropy compensator 5 described later with reference to FIG.

The light transmitted through the optical anisotropy compensator 5 is incident on a substrate 10 which is an object to be inspected. The light transmitted through the substrate 10 is converted into a second polarizer having an extremely high extinction ratio (for example, an extinction ratio of 10 ⁶ or more. Specifically, a birefringent polarizer such as Glan-Thomson or Glan-Taylor, or an extremely high extinction ratio). (A polarizing plate capable of obtaining an extinction ratio is preferable.) The analyzer 33 is also rotatable about the optical axis of the imaging optical system. The polarizer 32 and the analyzer 33 are controlled by the control circuit 6 so that the polarization directions of the transmitted light (the transmission azimuth of the polarizer) are always perpendicular to each other. The accuracy of the right angle is about 1 minute in order to detect a very slight optical anisotropy. The light transmitted through the analyzer can be imaged by the imaging lens 4 into an ultra-high-sensitivity imaging device 2 that captures a two-dimensional image (for example, a weak light image of about 0.1 lux can be captured at a sufficient S / N ratio). Specifically, the CCD imaging device is cooled by a Peltier device or the like, and an image of the surface of the inspection object is formed on the imaging surface in a low-speed scanning operation).

The details of the optical anisotropy compensator 5 will be described with reference to FIGS. The optical anisotropy compensator 5 includes a rotation mechanism 57, a tension mechanism 56, and the isotropically uniform glass 51. The rotation mechanism 57 includes a tension mechanism 56.
And rotates about the optical axis O. The rotation mechanism 57 has an opening 58 through which light passes, and the isotropic uniform glass 51 is disposed in the opening 58.
The right end of the isotropic uniform glass 51 is clamped and fixed to the right end of a frame 561 having an opening.
The left end of the isotropic uniform glass 51 is fixed by a glass end holding mechanism 541, and the glass end holding mechanism 541 is tensioned to the left by a tension generator 52 via a pulley 53 and a pull rod 55 by a flexible wire 54. Pulled by. The thickness of the isotropic uniform glass 51 is 1 m
If it is about m, applying a pulling force in the range of 0 to several hundred grams causes anisotropy in the pulling direction, and the retardation changes linearly in a range of several degrees or less. The rotation of the rotation mechanism 57 is controlled by a signal from the control device 6, and the amount of tension of the tension mechanism 56 is controlled in accordance with the degree of anisotropy of the glass substrate 10. The anisotropy of the glass substrate 10 can be corrected (compensated) according to the direction of the anisotropy and the strength of the anisotropy.

Next, a method of correcting (compensating) an arbitrary anisotropic direction and intensity existing on the glass substrate 10 will be described more specifically. There are roughly two methods for compensating the optical anisotropy of the glass substrate 10 using the optical anisotropy compensator 5.

The first method is to measure the optical anisotropy of the glass substrate 10 in advance when the film to be measured has not been given optical anisotropy yet or when the film has not been formed yet. The data is used to compensate for the optical anisotropy of the glass substrate 10.

The second method is a case where there is no data on the glass substrate 10 before the optical anisotropy is given.

First, the first method will be described. FIG.
Of the substrate 10 before the orientation characteristics are imparted by the orientation characteristics imparting device 130 or the substrate 10 before the anisotropic film or layer to be detected is formed.
Is mounted on a substrate stage (not shown). The tension of the optical anisotropy compensator 5 is set to 0 or the optical anisotropy compensator 5 is
Remove from the optical path of the imaging optical system. The XY stage (not shown) is adjusted so that a two-dimensional image of a place to be inspected on the substrate 10 is obtained. Next, the polarizer and the analyzer are rotated while maintaining their transmission linear polarization planes at 90 degrees to each other, and the polarizer at the time when the average value of the detection image of the ultra-high-sensitivity imaging device 2 becomes minimum is obtained. Find the direction of the transmission axis. The transmission axis direction of the polarizer when the average value becomes the minimum is obtained by visually checking or inspecting a two-dimensional detection image from the ultra-high sensitivity imaging device 2 corresponding to the region to be inspected on the CRT monitor. The determination may be made based on the magnitude of the electric signal from the ultra-high-sensitivity imaging device 2 corresponding to the area where the image is present. The transmission axis azimuth θ _min of the polarizer when this average value is minimized is represented by x shown in FIG.
Angle measured counterclockwise from the axis (hereinafter referred to as substrate 10
In the plane parallel to the plane (2), the angle measured from the x-axis in FIG. This angle θ _min substantially indicates the direction of the anisotropy of the substrate glass 10. However, this direction is orthogonal to the principal axis of the refractive index (the principal axis of the refractive index ellipsoid)
Therefore, it is not known at this time whether the refractive index is large or small.

Next, from this angle θ _min , +45 degrees−α, +
Rotate the transmission axis of the polarizer 32 by 45 degrees and +45 degrees + α (the transmission axis of the analyzer 33 is
Maintain a 90 degree relationship. The same applies hereinafter), and three two-dimensional image data are collected for the same region on the substrate 10.
Note that α is set to about 15 degrees or less.

Hereinafter, in this specification, a position in a two-dimensional area is represented by an image (i, j) for convenience.

For each pixel (i, j) in the two-dimensional image, intensity data I _ij (θ
_min + 45−α), I _ij (θ _min +45) and I _ij (θ
_min + 45 + α) is applied to a quadratic expression, and the angle θ _max (i, j) at which the intensity becomes maximum and the maximum intensity I _max (i, j) are obtained by interpolation.

Next, the optical anisotropy compensator 5 is rotated so that the tension application direction by the tension generator 52 of the optical anisotropy compensator 5 coincides with the θ _min direction of the substrate 10. Next, the inspection area is again imaged by the high-sensitivity imaging device 2 with the tension adjusted to the desired value T applied and the transmission axis of the polarizer adjusted to the angle θ _min +45 degrees.

In the present specification, with respect to the retardation normally treated as a positive value, the value is defined as follows, considering the positive and negative values. That is, for the retardation Ψ ′ (the retardation Ψ ′ is positive) corresponding to the intensity data I ′ _ij (θ _min +45), | Ψ | =
符号 ', a signed retardation Ψ is newly defined as follows, and thereafter, this signed retardation Ψ
Is referred to as a retardation in this specification.

[0036] _{I 'ij (θ min +45)} ≦ I ij (θ min +45) when [psi ≦ 0 the refractive index of the optic axis direction in this case theta _min of, theta _min +90
It is larger than the refractive index of the principal axis in the degree direction.

[0037] _{I 'ij (θ min +45)} > When [psi> 0 refractive index of the optic axis direction in this case theta _min of I _ij (θ _min +45) is, theta _min +90
Refractive index in the degree direction is smaller than the refractive index of the main axis.

Thus, the direction θ _g (i, j) of the optical anisotropy of the substrate 10 and the retardation Ψ _g (i, j)
Thus, this data is stored in the control circuit 6. The retardation Ψ _g (i, j) and the intensity data I
_max (i, j) is βI _max (i, j) ≡ | Ψ _g (i, j)
| ² . Here, β is a proportional coefficient between the detection intensity and the square of the anisotropy intensity. The _{reason why} I _max (i, j) is proportional to Ψ _g ² (i, j) is that the absolute value of the retardation Ψ _g (I, j) is sufficiently smaller than 2π and sin (Ψ
_This is because the relationship of _g (i, j))) _g (i, j) is established by the liquid crystal alignment film and the glass substrate.

Next, in order to give the alignment film characteristics to the substrate 10 and measure the alignment characteristics of the alignment film provided with the alignment characteristics, the substrate 10 is installed in the optical inspection apparatus 1 again.
At this stage, since the optical anisotropy of the glass substrate 10 is already known, this anisotropy is compensated as described below. That is, as described above, the anisotropic direction of the substrate glass 10 is θ _g (i, j), and the anisotropic strength is β
_{I max (i, j) (} = | Ψ g (i, j) |. ² to become) become.

Here, the average value in this area obtained from Ψ _g (i, j) and θ _g (i, j) obtained for the two-dimensional area on the substrate 10 is <Ψ _g >, respectively. And <θ _g >.

The glass substrate 10 is controlled by the optical anisotropy compensator 5.
To compensate for the anisotropy sets the rotation angle theta _c of the optical anisotropy compensator 5 as follows.

When the average value <Ψ _g > of Ψ _g (i, j) is negative, the rotation angle θ _c of the optical anisotropy compensator 5 is set to θ _g (i, j)
Mean value of equal to _{<θ g>, Ψ g (} i, j) the average value of <[psi
_{When g} > is positive, the rotation angle θ _c of the optical anisotropy compensator 5 is set to <
θ _c is set equal to θ _g > +90 degrees. Next, the anisotropy intensity Ψ _c provided by the optical anisotropy compensator 5 becomes Ψ _g (i,
The tension given by the optical anisotropy compensator 5 is set so as to be equal to the average value <Ψ _g > of j).

In general, the refractive index in the direction in which the tension is applied is smaller than the refractive index in the direction perpendicular to the tension.

By setting the optical anisotropy compensator 5 as described above, the anisotropy of only the glass substrate 10 is compensated on average with respect to the substrate 10 to which the orientation characteristics are given.

As described above, with the anisotropy of the glass substrate 10 compensated for by the optical anisotropy compensator 5, the transmission axis of the analyzer 33 is polarized with respect to the glass substrate 10 having the orientation characteristics. The polarizer 32 and the analyzer 33 are rotated while being perpendicular to the transmission axis of the polarizer 32, so that the average intensity (brightness) of the two-dimensional image captured by the ultra-high sensitivity imaging device 2 is maximized. 32 rotation angles are obtained. When this angle is θ _dmax , the respective intensities I _ij (θ _dmax ), I _ij (I _ij (θ _dmax ) and I _ij (I _ij (θ _dmax )) of the imaging signal when the transmission axis of the polarizer 32 is _set to θ _dmax , θ _dmax + α and θ _dmax −α. θ _dmax + α) and I _ij (θ
_dmax- α). Θ _d that gives the maximum value of the intensity at each point (i, j) by quadratic approximation from these three data
When (i, j) and its maximum value I _dmax (i, j) are obtained, the anisotropic direction θ _d (i, j) and the anisotropy intensity of the alignment film are determined by βI _dmax (i, j) ( ≡Ψ _d ² (i, j), Rita
The square of the ition is calculated.

Next, a description will be given of the second method, that is, a method in the case where there is no data on the glass substrate 10 before imparting optical anisotropy. Glass substrate 10 provided with orientation characteristics
The average anisotropy direction <θ _d > and the anisotropy strength <Ψ _d > are known from the conditions at the time of imparting the alignment characteristics (local anisotropy). The direction of sex and the strength of anisotropy are unknown). Therefore, the optical anisotropy of the glass substrate 10 is determined as described below using the known predicted value.

First, the tension of the optical anisotropy compensator 5 is set to 0, and the total (glass + alignment film) optical anisotropy is determined in consideration of the anisotropy of the glass substrate 10 and the anisotropy of the alignment film. .
For the two-dimensionally expanded pixel group, the rotation angle θ _mmax (i, j) of the transmission axis of the polarizer that maximizes the imaging signal of each pixel (i, j) is obtained in the same manner as described in the first method. The maximum intensity _Immax (i, j) at that time is obtained. Hereinafter, the symbols (i, j) are omitted, the direction of the anisotropy of the glass substrate + the alignment film is θ _m , and the strength of the anisotropy of the glass substrate + the alignment film is { ² _m }
Put as βI _mmax . In order to compensate by the optical anisotropy compensator 5, the following equations are established when the direction of the anisotropy and the strength of the anisotropy of the unknown glass substrate 10 to be obtained are θ _g and Ψ _g , respectively.

[0048] ^{_{b = T ~ 1 D Φ D}} T D T g ~ 1 Φ g T g a = T ~ 1 m Φ m
T _m a ...... (Equation 1) where a vibration vector of the light incident on the substrate, b is the vibration vector of light transmitted through the glass substrate 10 and the alignment film. T _D is a matrix of coordinate transformation relating to the direction of anisotropy of the alignment film, and T ~ ¹ _D is an inverse matrix of T _D. Φ _D is a matrix related to the anisotropic strength (retardation) of the alignment film, T
_g is a matrix for coordinate transformation related to the anisotropic direction of the glass substrate 10, and Φ _g is a matrix related to the anisotropic strength (retardation) of the glass. T _m is a matrix for coordinate transformation relating to the direction of anisotropy of the glass substrate 10 + alignment film, and Φ _m is a matrix relating to the anisotropy strength (retardation) of the glass substrate 10 + alignment film. Each can be represented as follows using the above symbols. Component of the matrix T _D regarding the alignment layer, respectively, and t _d11, t _d12, t _d21 and t _d22. Similarly the components of Φ _D φ _d11, φ _d12, and phi _d21 and phi _d22. The components of the matrix T _g relating to the glass substrate are represented by t _g11 ,
_Let t _g12 , t _g21 and t _g22 . Similarly, _let the component of Φ _{g be} φ
_g11 , _φg12 , _φg21, and _φg22 . Further glass substrate + orientation films each component of the matrix T _m about t
_m11, and t _m12, t _m21 and t _m22. Similarly the components of Φ _m φ _m11, φ _m12, and phi _m21 and phi _m22. The components of each matrix are as follows.

T _d11 = t _d22 = cos θ _d , t _d12 = −t _d21 = sin θ _d t _g11 = t _g22 = cos θ _g , t _g12 = −t _g21 = sin θ _g t _m11 = t _m22 = cos θ _m , t _{m12 = -t m21 = sinθ m φ d11} = 1, φ d12 = φ d21 = 0, φ d22 = exp (-iΨ d) φ g11 = 1, φ g12 = φ g21 = 0, φ g22 = exp (-iΨ g on the glass substrate 10 fixed on di (not _{shown) -) φ m11 = 1,} φ m12 = φ m21 = 0, φ m22 = exp (-iΨ m) Note θ is stearyl 4 The angle of the main refractive index axis measured counterclockwise from the x-axis of the coordinates, and the main axis that is within ± 45 degrees from the x-axis of the two main refractive index axes orthogonal to each other is used in the above equation. Therefore, the above θ has an absolute value of 4
5 degrees or less. Also, assuming that the refractive index of the main axis of refraction n ₁ is n ₂ with respect to the refractive index of the main axis of refraction n ₂ , the phase difference between the two directions of polarization caused by passing through the optical path of thickness d is Ψ and the wavelength is λ, which is given by the following equation.

Ψ = 2πd (n ₂ −n ₁ ) / λ (2) a is a vector representing the xy component of linearly polarized light transmitted through the polarizer, and the rotation angle of the transmission axis of the polarizer is represented by θ. Then, each component is represented by the following equation.

A _x = cos θ and a _y = sin θ.

B is a vector representing the xy component of the complex amplitude of the light transmitted through the glass substrate 10 + the alignment film. For xy components b _x, b _y the the transmission axis of the analyzer are perpendicular at all times to the transmission axis of the polarizer, the complex amplitude A after passing through the analyzer, and the intensity I is rotation angle of the transmission axis of the polarizer It is given by the following equation using θ.

[0053] _{A = -b x sin (θ)} + b y cos (θ) ...... ( number ^{3) I = | A | 2} ...... ( Equation 4) Therefore the complex amplitude of the pixel of interest is above the A Then, the intensity of I at the pixel of interest is detected by the ultra-high sensitivity imaging device.

From the relationship of the middle side = left side of the above equation (Equation 1), the direction θ _g of the optical anisotropy of the substrate and the strength of the anisotropy (the
Calculate _g ) as follows. As described above, the average anisotropy <Ψ _d > and the direction <
It is assumed that the value of θ _d > is known from the conditions of the alignment film applying means (local value is unknown). That is, the matrix T _D of equation (Equation 1)
And Φ _D are known. The capital of the glass substrate + alignment layer - optical anisotropy of barrel is measured, the direction theta _m and strength [psi _m is detected for each pixel of the image captured by the imaging device. When the average value of θ _m and Ψ _m detected for each pixel over the entire screen is adopted, the matrix T _m of Expression (1) is obtained.
And Φ _m are known values. Unknown component theta _g and [psi _g of the unknown matrix T _g and [Phi _g it is possible to determine by calculation of these known matrix used if determinant (number 1). The theta _m and [psi _m in order to increase the accuracy of the calculation may be used the results of measurement by a plurality of theta with different transmission axis of the polarizer. When the direction θ _g and the intensity Ψ _g of the anisotropy of the glass substrate are obtained by the above method, the anisotropy is compensated for by the optical anisotropy compensator 5. That is, as shown in FIG. 4, optic axes n _g1 of the glass substrate without the x-axis and the angle theta _g, refractive index of principal axis orthogonal to the refractive index n _g1 of the shaft is small n _g2 [psi
_{When g} becomes negative, the direction of the optical anisotropy compensator 5 (direction in which tension is applied) θ _c is made equal to θ _g, and Ψ _c = −
を Apply tension to make _g . The optical anisotropy compensator 5 in the direction (direction apply tension) theta _c when the refractive index n _g2 of the spindle orthogonal to the refractive index n _g1 conversely large [psi _g becomes positive theta _g +90 degrees Equal and Ψ _c =
Apply tension so that −Ψ _g . In this way, the anisotropy of the glass substrate 10 is canceled by the optical anisotropy compensator 5.

The optical anisotropy of the substrate was compensated by the above method, and the optical anisotropy compensator 5 + the anisotropy of the glass substrate could be made substantially zero. It is possible to accurately determine the anisotropy.

The transmission axis of the polarizer 32 and the analyzer 3 shown in FIG.
3 are rotated (the rotation angle of the polarizer becomes θ, and the rotation angle of the analyzer becomes θ + 90 degrees) while maintaining the directions of the transmission axes 90 ° to each other, and the two-dimensional region detected by the ultra-high-sensitivity imaging device 2 The average of the image intensities (the average of the intensities of all the pixels) <I> is set to be the maximum or the minimum.

If the angle θ _min at which <I> is minimized is found first, this direction becomes the average anisotropic direction of the alignment film, that is, the alignment direction <θ _d >. If <θ _d > is known, polarizer 3
By rotating the analyzer 2 and the analyzer 33 further 45 degrees, the angle θ _max (= θ _min +45 degrees) giving the maximum of <I> is obtained, so that the following three angles θ _max -α, θ _max and θ _max + α are obtained. The transmission axis of the polarizer 32 is set, and three images are detected by the ultra-high sensitivity imaging device 2. For each pixel of the obtained image signal, an angle θ that gives the true maximum intensity is obtained in the same manner as in the fitting method using the above-described quadratic equation, and this angle is the direction of the anisotropy of the alignment film at this pixel. the θ _d. At the same time the strength of the angle theta, the maximum intensity I _max is the intensity of the optical anisotropy, i.e., Rita - Deishon [psi ² _d of the square (= beta I
_max ). In this way, using the three image signals, the anisotropic direction θ _d (i,
j) and the degree of anisotropy of the alignment film (retardation)
Ψ Find _d (i, j).

In some cases, it is necessary to confirm whether or not the compensation for the anisotropy of the substrate glass has been performed correctly. In such a case, when the transmission axis direction θ of the polarizer 32 is equal to the alignment direction θ _{d of the} alignment film, the intensity of light transmitted through the analyzer 33 should be minimum. This can be confirmed, and the transmission image of the polarizer 32 is set to three azimuths of θ _d , θ _d + α and θ _d −α, and the image is picked up by the ultra-high-sensitivity imaging device 2. The average value of the intensity of the image at each azimuth angle is obtained, and the angle θ _min that truly gives the minimum value is determined by a fitting method using a quadratic equation.
The determination is performed using the following threshold value Δθ with respect to the angle θ _min .

| Θ _min −θ _d | ≦ Δθ (Equation 5) If θ _min satisfies this condition, the optical anisotropy compensator works properly and the optical anisotropy of the glass substrate is compensated. Will be. Here, Δθ is, for example, 0.5 degrees. If this condition is not satisfied, the direction and intensity of the anisotropy provided by the optical anisotropy compensator are changed so as to reduce the deviation, and the above confirmation is performed again. By doing so, the optical anisotropy of the glass substrate 10 is almost completely canceled, and the accurate optical anisotropy of the alignment film is obtained.

As described above, when the optical anisotropy has not yet been imparted to the film to be measured, the optical anisotropy of the glass substrate is measured, and the measured value is used for correction by the anisotropy compensator. In this case, the optical anisotropy of the alignment film can be obtained accurately even when there is no data on the glass substrate before the optical anisotropy is imparted.

The range in which the above-mentioned optical anisotropy is compensated is within the image frame picked up by the ultra-high-sensitivity image pickup device, and within this range, the direction and strength of the optical anisotropy of the glass substrate are limited. It is assumed that it is almost constant. In the case of a liquid crystal display device having a display screen having a diagonal diameter of several tens of cm, such a condition is almost satisfied in a range of several cm. This problem is solved by the method shown in FIG.

The first method narrows the detection field of view and makes the optical anisotropy of the glass substrate substantially constant within the field of view. In the second method, a large detection field is divided into regions each having the same anisotropy characteristic, and different corrections are performed in each divided region. In the third method, a wide field of view is corrected at once by using a two-dimensional optical anisotropic distribution providing device capable of providing a desired two-dimensional distribution of optical anisotropy.

An embodiment of such a two-dimensional optical anisotropic distribution providing device 5 will be described with reference to FIG. 5 is an optical anisotropy compensator having a two-dimensional optical anisotropy distribution providing function. The light-transmitting opening 50 includes a plurality of independently controllable optical anisotropy imparting means 500. As shown in FIG. 6, there is a thin partition wall 501 between the optical anisotropy imparting means 500. A stress-generating stacker 502 whose structure is shown in FIG. Stress generator 5
02 is a portion 5 where a tensile stress is generated as shown in FIG.
021 and a portion 5022 that generates shear stress. The stress generating stacker 502 is adhered to all side surfaces (surfaces perpendicular to the paper surface) of the mesh-like partition walls. All the stress-generating laminates 502 are provided with drive electric signal lines (not shown) for controlling the tensile stress and the shear stress.

The portion 5021 of the stress generating stacker 502 that generates tensile stress and the portion 502 that generates shear stress
2, a piezo element is used, for example. In the light transmitting portion surrounded by the partition 501 and connected to the stress generating stacker 502, there is a uniform synthetic quartz glass 503 having extremely small optical anisotropy. The synthetic quartz glass 503 and the four stress-generating laminates 502 on the four sides of the synthetic quartz glass 503 are bonded to each other, but if no voltage is applied to the piezoelectric element of the stress-generating laminate 502, the synthetic quartz 503 is Adhesion that does not generate distortion is applied so that almost no optical anisotropy occurs.

A desired optical anisotropy can be imparted by driving a piezo element that generates tensile and shear stress on opposing sides of the rectangular synthetic quartz 503 in each opening 50. Therefore, the glass substrate 1 with the alignment film
Even if the optical anisotropy of 0 is finely changed locally, the fine change can be corrected by the optical anisotropy compensator 5 having the function of providing a two-dimensional optical anisotropy distribution. This makes it possible to accurately determine the optical anisotropy of the alignment film.

As is clear from the detailed description of the embodiments, the optical anisotropy accompanying the molecular orientation of the alignment film of the liquid crystal display device is microscopically determined according to the imaging magnification of the imaging optical system 4. It is possible to view it in a magnified manner, or to see a wide field of view as a whole. In addition, the microscope optical system and the wide field of view are provided by both having the optical system of the microscope and the optical system of viewing the wide field of view as a whole, or by switching and viewing the stage on which the substrate is mounted, or the xy stage. The optical system for viewing the whole image is separated by a fixed distance, and two optical axes are provided. By moving the stage, the observation point is moved to a desired optical axis, and inspection can be performed at a desired magnification.

The inspection of the alignment film according to the present invention makes it possible to evaluate the alignment film alone and quantitatively, so that the display performance of the liquid crystal display device, in particular, various brightness unevenness or color unevenness of display. The main cause of the problem can be managed upstream of the manufacturing process, and it is possible to greatly improve the quality of display unevenness, which was difficult in the past, and to manufacture a liquid crystal display device having display intensity unevenness of 1% or less. Is now possible. The optical anisotropy compensator of the present invention is not limited to the method for measuring the optical anisotropy of the above-mentioned alignment film using an ultra-sensitive imaging device. That is, the present invention is also applied to a method of measuring various optical anisotropies such as an optical heterodyne method using a laser, and a great effect is obtained.

In the optical anisotropy compensator, the substance that generates optical anisotropy when stress is applied is not limited to the glass in the above-described embodiment, but may be one that exhibits a photoelastic effect. If so, you can use it.

In the above description, the present invention is an example of evaluating the optical anisotropy of only a specific layer in an optical component forming a multilayer structure, which is formed on a glass substrate of a liquid crystal display device. Although an example in which only an alignment film is evaluated was used, the present invention is not limited to this, and optical characteristics such as anisotropy of a specific layer of an optical component in which a multilayer interference film is formed on a glass substrate by vapor deposition. Of course, it can be applied to the evaluation of

[0070]

According to the present invention, for example, the alignment characteristics of an alignment film can be inspected without using a liquid crystal. Further, even when the optical anisotropy of the substrate on which the alignment film to be inspected is formed is large, the inspection can be performed. As a result, inspections can be performed upstream of the liquid crystal display device manufacturing process, and feedback can be immediately provided to the manufacturing process, thereby significantly improving the display quality of the product and the manufacturing yield of the product. Became.

[Brief description of the drawings]

FIG. 1 is a flowchart of a method for manufacturing a liquid crystal display device according to one embodiment of the present invention.

FIG. 2 is a perspective view illustrating an optical inspection method according to another embodiment of the present invention.

FIG. 3 is a top view showing one embodiment of the optical anisotropy compensator according to the present invention.

FIG. 4 is a diagram illustrating a polarization function of an optical component such as an optical anisotropy compensator according to the present invention.

FIG. 5 is a top view of another embodiment of the optical anisotropy compensator having a function of providing a two-dimensional optical anisotropic distribution according to the present invention.

FIG. 6 is a partially enlarged detailed plan view of an optical anisotropy compensator having a function of providing a two-dimensional optical anisotropic distribution according to the present invention.

FIG. 7 is a partially enlarged cross-sectional detailed view of an optical anisotropy compensator having a function of providing a two-dimensional optical anisotropic distribution according to the present invention.

[Explanation of symbols]

1 is an optical inspection device, 130 is an orientation property imparting device, 10
Is a substrate having an alignment film, 2 is an ultra-sensitive imaging device, 3 is a light source, 32 is a polarizer, 33 is an analyzer, 4 is an imaging lens, 5
Is an optical anisotropy compensator, and 6 is a control circuit.

Claims (22)

[Claims] In an optical anisotropy evaluation method for evaluating the optical anisotropy of a component forming a multilayer structure by transmitting polarized light, at least one optical anisotropy of the multilayer structure is offset. An optical anisotropy evaluation method for inserting an anisotropy correcting optical component having anisotropy in a direction to be polarized into the optical path of the polarized light, and evaluating the remaining optical anisotropy in the multilayer structure. 2. The anisotropy correcting optical component is made of a material exhibiting a photoelastic effect, and the anisotropy in a direction that cancels out the optical anisotropy of at least one of the layers has an external force applied to the material exhibiting the photoelastic effect. The optical anisotropy evaluation method according to claim 1, wherein the optical anisotropy evaluation method is generated by adding 3. A method of detecting light emitted from a component forming a multilayer structure by an analyzer having a transmission axis orthogonal to a vibration plane of the polarized light incident on the component forming the multilayer structure. The method for evaluating optical anisotropy according to claim 1 or 2, wherein: 4. An optical anisotropy evaluation method according to claim 1, wherein said at least one layer includes a glass substrate of a component forming said multilayer structure. 5. The method for evaluating optical anisotropy according to claim 2, wherein the substance exhibiting the photoelastic effect is glass. 6. The method according to claim 2, wherein the external force applied to the substance exhibiting the photoelastic effect is a tension (tensile force). 7. The method according to claim 7, wherein after the step of imparting alignment characteristics to the surface of the alignment film for aligning liquid crystal molecules formed on the substrate, the surface of the alignment film on the substrate is irradiated with substantially perfect linearly polarized light and transmitted therethrough. Through the analyzer, when entering the two-dimensional image pickup device having a photoelectric conversion surface optically conjugate with the alignment film surface, the linearly polarized light path irradiating the alignment film surface or In the optical path between the alignment film surface and the analyzer, an optical anisotropy compensator whose optical anisotropy can be controlled is inserted to reduce or cancel out the influence of the optical anisotropy of the substrate, and the alignment film is formed. A method for manufacturing a liquid crystal display device, comprising a step of imaging a surface and evaluating an optical characteristic of the alignment film to inspect the alignment film. 8. The optical anisotropy compensator controls the magnitude of optical anisotropy by uniformly applying a force to a transparent plate having low anisotropy in at least one direction. Item 7
The manufacturing method of the liquid crystal display device according to the above. 9. The optical anisotropy compensator is generated by rotating the transparent plate relative to the substrate about an axis parallel to an optical axis of light incident on the transparent plate. 9. The method according to claim 8, wherein the direction of the optical anisotropy to be tightened is controlled to a desired direction. 10. Compensation of the optical anisotropy of the substrate by the optical anisotropy compensator generally includes combining optical anisotropy by the optical anisotropy compensator with optical anisotropy of the substrate. The method for manufacturing a liquid crystal display device according to any one of claims 7, 8 and 9, wherein the method is performed in a manner to be one-sided. 11. A method for manufacturing a liquid crystal display device according to claim 7, wherein a result obtained by inspecting said alignment film is fed back to a step of giving said alignment characteristics. 12. The liquid crystal substrate with the linearly polarized light oscillating surface and the analyzer centered on the optical axis of the imaging optical system while maintaining the linearly polarized light oscillating surface and the analyzer transmission axis at 90 ° with each other. 8. The method according to claim 7, wherein the optical characteristics of the alignment film are evaluated based on a plurality of pieces of image data according to a change in the rotation angle of the liquid crystal display device. 13. The method of manufacturing a liquid crystal display device according to claim 12, wherein a change in intensity between a plurality of images due to a change in the rotation angle is detected in the same visual field on the substrate. 14. In the same field of view on the substrate, first,
Setting the vibration plane of the linearly polarized light to the rotation angle at which the average intensity of the captured image is the minimum or maximum, and rotating the vibration plane of the linearly polarized light to both sides of the rotation angle at which the minimum or the maximum is obtained. 14. The liquid crystal according to claim 13, wherein the minimum or maximum rotation angle and the measurement accuracy of the intensity of the captured image at the rotation angle are improved by interpolation by polynomial approximation based on intensity change data between images. A method for manufacturing a display device. 15. A component in which a thin film having optical anisotropy is formed on a transparent substrate is irradiated with almost perfect linearly polarized light, and the transmitted light is optically combined with the thin film via an analyzer. When the light enters a two-dimensional image pickup device having a photoelectric conversion surface having a conjugate relationship with each other, an optical anisotropy is applied to an optical path of linearly polarized light irradiating the thin film surface or an optical path between the thin film surface and the analyzer. Inserting a controllable optical anisotropy compensator, evaluating the optical characteristics of the thin film by compensating for the optical anisotropy of the transparent substrate, to inspect the thin film, Optical inspection method for parts 16. The optical anisotropy compensator includes a transparent plate having little anisotropy, and applies a force uniformly in at least one direction of the transparent plate to thereby provide an optical anisotropy of the transparent plate. The method for optically inspecting a component according to claim 15, wherein the size of the component is controlled. 17. By rotating the transparent plate provided in the optical anisotropy compensator relative to the transparent substrate about an axis parallel to the optical axis of irradiation of the linearly polarized light. 17. The method according to claim 15, wherein the direction of the optical anisotropy compensated by the optical anisotropy compensator is controlled. 18. The optical anisotropy of the transparent substrate is compensated for by the optical anisotropy compensator, wherein the optical anisotropy of the optical anisotropy compensator and the optical anisotropy of the transparent substrate are adjusted. 2. The method according to claim 1, wherein the composition is made to be substantially isotropic.
The method for optically inspecting a component according to any one of 5, 16, and 17. 19. The linearly polarized light oscillating surface and the analyzer are transmitted through the transparent optical axis around the optical axis of the imaging optical system while maintaining the transmission axis of the analyzer at 90 ° with respect to the linearly polarized light oscillating surface. 17. The method for optically inspecting a component according to claim 16, wherein the optical characteristics of the thin film are evaluated based on a plurality of pieces of image data according to a change in a rotation angle rotated relative to the substrate. 20. In the same field of view on the transparent substrate,
20. The method for optically inspecting a component according to claim 15, wherein a change in intensity between the plurality of images due to the change in the rotation angle is detected. 21. In the same field of view on the substrate, first,
Setting the vibration plane of the linearly polarized light to the rotation angle at which the average intensity of the captured image is the minimum or maximum, and rotating the vibration plane of the linearly polarized light to both sides of the rotation angle at which the minimum or the maximum is obtained. 21. The optical component according to claim 20, wherein the minimum or maximum rotation angle and the intensity of the captured image at the rotation angle are obtained again by interpolation using polynomial approximation based on intensity change data between images. Inspection method. 22. A light source, a polarizing means for converting light emitted from the light source into substantially perfect linearly polarized light, an analyzing means for receiving light passing through the object to be measured through the polarizing means, and said polarizing means. An optical anisotropy compensator inserted between the light detecting means, an image forming optical system for forming an image of light passing through the light detecting means, and a two-dimensional image picking up an image by the image forming optical system An optical inspection device comprising: a device; and a control circuit for driving and controlling the polarizing means, the light detecting means, and the optical anisotropy compensator.