JP4013709B2 - Gap thickness measuring device, gap thickness measuring method, and liquid crystal device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gap thickness measuring device, a gap thickness measuring method, and a liquid crystal device manufacturing method capable of appropriately measuring a gap of an electro-optical panel having a very small retardation.
[0002]
[Prior art]
As a cause of unevenness of the liquid crystal display panel, a non-uniform cell gap can be cited, and an apparatus capable of easily measuring the gap of a liquid crystal display panel has been demanded. As such a gap thickness measuring apparatus, the following techniques are known (for example, refer to Patent Document 1 and Patent Document 2). FIG. 5 is a block diagram showing an example of a conventional gap thickness measuring apparatus for a liquid crystal display panel. This gap thickness measuring apparatus 500 is a linear arrangement of the light source 1, the first polarizing plate 2, the second polarizing plate 5 disposed with the liquid crystal display panel 501 to be measured interposed therebetween, and the photodetector 7 of the spectrometer 6. A measuring instrument 8 is connected to the photodetector 7. The measurement result of the measuring device 8 is sent to the personal computer 9.
[0003]
The first polarizing plate 2 has a polarization angle of 45 degrees, and the polarization angle of the second polarizing plate 5 is orthogonal to the polarization angle of the first polarizing plate 2 by 90 degrees. The linearly polarized light that has passed through the first polarizing plate 2 further passes through the liquid crystal display panel 501, becomes elliptically polarized light, and enters the second polarizing plate 5. The second polarizing plate 5 transmits only the polarization angle component of the elliptically polarized light. Here, as shown in FIG. 6, the transmission of light through the liquid crystal display panel 501 is in the xy direction with respect to the time axis T (the polarization angles are perpendicular to each other between the first deflection plate 2 and the second deflection plate 5). ) Is delayed by θ, which converts linear deflection into elliptical deflection.
[0004]
Here, assuming that the wavelength of the light beam of the light source is λ, the thickness of the liquid crystal display panel is d, the normal refractive index is no, and the extraordinary refractive index is ne, these relationships are expressed by the following equation: θ = 2π · Δn · d / λ ... (1)
It is represented by Δn = no−ne. Δn · d is a birefringence phase difference (retardation R) between an ordinary ray and an extraordinary ray.
[0005]
The wavelength λ is in a certain range by the light source 1, and Δn is known by the liquid crystal display panel 501. The gap d of the liquid crystal display panel 501 is a value to be obtained. In the above formula (1), the wavelength λp at which the transmittance reaches a peak, that is, θ is delayed by 2π by the light source that irradiates light with a wavelength in a predetermined range. This is a case where the wavelength λp at which the light passing through the panel 501 becomes polarized light orthogonal to the polarization direction of the second polarizing plate 5 is λ = Δn · d.
[0006]
For this reason, when the polarized light that has passed through the second polarizing plate 5 is measured by the spectrometer 6, the wavelength λp at which the transmittance exhibits the lowest peak may be regarded as Δn · d. Here, λp can be specified by the lowest peak value of the spectrometer 6 and Δn is known, so that the gap d of the liquid crystal display panel 501 can be derived. For example, the measurement result by the spectrometer 6 is as shown in FIG. 7, and when the wavelength λp = 550 nm, Δn · d = 550, and therefore the gap d of the liquid crystal display panel 501 is 550 / Δn. Become.
[0007]
FIG. 8 is a table showing an example of the relationship between the wavelength λ and the retardation Δn · d according to the above equation (1). For example, consider a case where the wavelength λ is 0.3, 0.6, 0.9 and the retardation Δn · d is 0.3, 0.6, 0.9. First, when the wavelength λ is 0.3 and the retardation Δn · d is 0.3, λ = Δn · d as in the above case, so that θ = 2π and a peak appears. Further, when the wavelength λ is 0.6, even if the retardation Δn · d is 0.3, it is delayed by 4π, so that a peak is obtained. Similarly, even if the wavelength λ is 0.9.
[0008]
Next, when the wavelength λ is 0.6, when the retardation Δn · d is 0.3, only π is delayed, so no peak appears. Similarly, when the reduction Δn · d is 0.9, there is no peak because it is delayed by 3π. However, when the reduction Δn · d is 0.6, since λ = Δn · d, a peak appears with a delay of 2π. Further, when the wavelength λ is 0.9, the retardation Δn · d is 0.3, and when it is 0.3, it is delayed by 2 / 3π, and when it is 0.6, no peak appears. However, when the reduction Δn · d is 0.9, λ = Δn · d, so that a peak appears with a delay of 2π. From the above, depending on the retardation Δn · d, a plurality of peaks λp may appear. In such a case, the wavelength λ close to the design value is adopted to determine the retardation Δn · d.
[0009]
[Patent Document 1]
JP-A-4-3071212 [Patent Document 2]
JP-A-4-80641
[Problems to be solved by the invention]
However, the conventional gap thickness measuring apparatus 500 is suitable for these measurements because a transmissive LCD (= TN mode) including a TFD (thin film diode) has a large retardation. Since the transmissive LCD (= internal reflection mode) is designed to have a small retardation, there is a problem that it is not suitable for the gap measurement of these liquid crystal display panels. That is, as shown in FIG. 4, the practical range of the wavelength λ that can be measured by the ordinary spectrometer 6 is 380 nm to 780 nm, and the peak in the case of the liquid crystal display panel 501 having a large retardation appears in this range. On the other hand, it is known that the peak of the liquid crystal display panel having a small retardation appears in the range of 190 nm to 320 nm outside the range. For this reason, the gap of the liquid crystal display panel having a small retardation cannot be measured by the ordinary spectrometer 6. On the other hand, a measuring instrument in such a range is very expensive.
[0011]
Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a gap thickness measuring apparatus and a gap thickness measuring method capable of appropriately measuring a gap of an electro-optical panel having a very small retardation. .
[0012]
[Means for Solving the Problems]
In order to achieve the above-described object, a gap thickness measuring apparatus according to the present invention includes a retardation between a light source, a first polarizer that transmits a linearly polarized component of light emitted from the light source, and the first polarizer. An optical anisotropic body in which an object to be measured of Δn ₁ · d ₁ (d ₁ is a desired gap thickness) is located, and its retardation Δn ₂ · d ₂ is known, and a straight line in a direction orthogonal to the first polarizer A second polarizer that transmits the polarization component and a measuring instrument that measures the intensity of the transmitted light that has passed through the second polarizer are arranged on the optical path, and the retardation Δn · d is calculated based on the measured light intensity. Calculation means for obtaining the gap thickness d ₁ of the measurement object from the retardation Δn · d of the optical anisotropic body Δn ₂ · d ₂ and the known birefringence phase difference Δn ₁ of the measurement object. It is characterized by having.
[0013]
The gap thickness measuring apparatus according to the next invention is characterized in that, in the above configuration, the optical anisotropic body is composed of a plurality of optical anisotropic bodies with known retardations.
[0014]
A gap thickness measurement method according to the next invention includes a light source, a first polarizer that transmits a linearly polarized component of light emitted from the light source, an optical anisotropic body having a known retardation Δn ₂ · d ₂ , A second polarizer that transmits a linearly polarized component in a direction orthogonal to the first polarizer and a measuring instrument that measures the intensity of transmitted light that has passed through the second polarizer are arranged on the optical path, and the first polarizer An object to be measured with retardation Δn ₁ · d ₁ (d ₁ is a gap thickness to be obtained) is inserted between the second polarizer and the light transmitted through the second polarizer. The retardation Δn · d is obtained based on the measured light intensity, the retardation Δn · d, the retardation Δn ₂ · d _{2 of} the optical anisotropic body, and the known birefringence phase difference Δn of the measurement object. ₁ to obtain the gap thickness d ₁ of the object to be measured It is a sign.
[0015]
In the gap thickness measuring method according to the next invention, in the above configuration, the optical anisotropic body is formed of a plurality of optical anisotropic bodies whose retardation is known, and any or all of the optical anisotropic bodies are placed on the optical path. Thus, the retardation of all of the measurement object and the optical anisotropic body is adjusted.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by a so-called person skilled in the art or those that are substantially the same.
[0017]
1 is a configuration diagram of a gap measuring apparatus according to Embodiment 1 of the present invention. The gap thickness measuring apparatus 100 includes a light source 1, a first polarizing plate 2, an optical anisotropic plate 4 disposed with a TFD liquid crystal display panel 3 having a small retardation to be measured, a second polarizing plate 5, and the like. The photodetector 7 of the spectrometer 6 is arranged on a straight line, and the measuring device 8 is connected to the photodetector 7. The measurement result of the measuring device 8 is sent to the personal computer 9. The first polarizing plate 2 has a polarization angle of 45 degrees, and the polarization angle of the second polarizing plate 5 is orthogonal to the polarization angle of the first polarizing plate 2 by 90 degrees.
[0018]
The optically anisotropic plate 4 may have the same retardation Δn · d as that of a very small retardation such as a TFD liquid crystal display panel to be measured. An anisotropic plate 4 may be used. By adding the retardation Δn ₁ · d ₁ of the TFD liquid crystal display panel 3 to be measured and the retardation Δn ₂ · d _{2 of} the optical anisotropic plate 4, the first polarizing plate 2 and the second polarizing plate 5 can be considered as one optical anisotropic body existing between the two.
[0019]
That is, the retardation Δn · d between the first polarizing plate 2 and the second polarizing plate 5 is
Δn · d = Δn ₁ · d ₁ + Δn ₂ · d ₂ (2)
It is represented by The following is a description when the TFD liquid crystal display panel 3 is twisted by 0 degrees.
[0020]
As described above, the wavelength of the light beam from the light source 1 is λ, the thickness of the liquid crystal display panel 3 is d, the normal refractive index is no, and the extraordinary refractive index is ne. These relationships are expressed by the above equation θ = 2π · Δn · d / λ (1)
It is represented by Therefore, from the equations (1) and (2), θ = 2π · (Δn ₁ · d ₁ + Δn ₂ · d ₂ ) / λ (3)
It can be expressed.
[0021]
The wavelength λ is in a certain range by the light source 1, and Δn ₁ is known by the liquid crystal display panel 3. Further, Δn ₂ · d _{2 of} the optical anisotropic plate 4 is also known. The gap d ₁ of the liquid crystal display panel 3 is a required value. In the above equation (3), the light source 1 that emits light of a wavelength in a predetermined range causes the wavelength λp at which the transmittance reaches a peak, that is, the light that has passed through the liquid crystal display panel 3 due to the delay of θ by 2π to be the second polarizing plate 5. In this case, the wavelength λp of the polarized light orthogonal to the polarization direction is λ = Δn ₁ · d ₁ + Δn ₂ · d ₂ .
[0022]
For this reason, when the polarized light that has passed through the second polarizing plate 5 is measured by the spectrometer 6, the wavelength λp at which the transmittance exhibits the lowest peak may be regarded as Δn ₁ · d ₁ + Δn ₂ · d ₂ . Here, λp can be specified by the lowest peak value of the spectrometer 6 and Δn ₁ and Δn ₂ · d ₂ are known, so that the gap d ₁ of the liquid crystal display panel 3 can be derived. The function of the optical anisotropic plate 4 will be described using an example shown in the graph of FIG. Retardation peak by Δn ₁ · d ₁ wavelength λp of the TFD liquid crystal display panel 100 _{ou t} (320nm) lies outside the practical range of the spectrometer 6, because it can not measure the gap, the TFD liquid crystal display panel 3 litter By adding the retardation Δn ₂ · d ₂ of the optical anisotropic plate 4 to the retardation Δn ₁ · d ₁ , the overall retardation Δn · d becomes Δn ₁ · d ₁ + Δn ₂ · d ₂ and the peak wavelength λp _in (640 nm) is put in the practical range of the spectrometer 6.
[0023]
In this way, the cell gap of the TFD liquid crystal display panel 3 can be measured within the practical range of the spectrometer 6. For example, Δn ₁ · d ₁ + Δn ₂ · d ₂ = λp _in (640 nm), and the required gap d ₁ is
d ₁ = (λp _in −Δn ₂ · d ₂ ) / Δn ₁ (4)
It becomes. The overall retardation of the combined TFD liquid crystal display panel and optically anisotropic plate is _{Δn · d = Δn 1 · d} 1 + Δn 2 · d 2 = λp in. The actual gap of the TFD liquid crystal display panel 3 can be obtained by putting the measured value and known value into this equation (4).
[0024]
As described above, in the gap thickness measuring apparatus 100, an optical anisotropic body having a known retardation even in an electro-optical panel having a very small retardation (for example, a reflective LCD or a transflective LCD of TFD or TFT). By inserting the plate 4, the peak wavelength can be shifted to the practical range of the spectrometer 6, so that even the electro-optical panel 3 can appropriately measure the cell gap.
[0025]
In the above example, the peak wavelength is shifted to the practical range of the spectrometer 6 by inserting one optical anisotropic plate 4, but this optical anisotropic plate 4 needs to be one. There is no. That is, a plurality of known optical anisotropic plates can be overlapped to correspond to one optical anisotropic plate 4. For example, when two optical anisotropic plates 4 and 4 are overlapped, the retardation between the first polarizing plate 2 and the second polarizing plate 5 is:
Δn · d = Δn ₁ · d ₁ + Δn ₂ · d ₂ + Δn ₃ · d ₃ (5)
It can be processed with simple addition. The same applies when three or more optical anisotropic plates 4, 4, 4,. In this case, any one of a plurality of optical anisotropic bodies 4, 4... Is selectively placed on the optical path, the overall retardation Δn · d (= λp _in ) is adjusted, and the wavelength of the spectrometer 6 It can also be put in a practical range. That is, when only one optical anisotropic body 4 cannot express the peak wavelength λpin _{in the} practical wavelength range of the spectrometer 6 depending on the TFD liquid crystal display panel, the optical anisotropic body 4 is further added to the peak wavelength λp. Adjust so that _in falls within the practical wavelength range of the spectrometer 6. Thereby, even if it is a TFD liquid crystal display panel having a relatively different retardation, it is not necessary to prepare a dedicated optical anisotropic body 4 and the apparatus can be simplified.
[0026]
Next, the TFD liquid crystal display panel 3 has a twist angle in the range of 0 degrees to 90 degrees. In this case, the retardation between the first polarizing plate 2 and the second polarizing plate 5 is the liquid crystal display panel. 3 and each optical anisotropic plate 4 cannot be obtained by simple addition. The relationship between each element at that time is
θ = 2π · (Δn ₁ · d ₁ , Δn ₂ · d ₂ ) / λ (6)
It becomes. In particular, Δn ₁ cannot be simply added because light passes through many liquid crystal molecules, and the total of Δn ₁ · d ₁ and Δn ₂ · d ₂ must be considered. In this case, the gap d ₁ is obtained after Δn ₁ is determined by simulation.
[0027]
Suitable examples of the measurement by the gap thickness measuring apparatus 100 include an STN liquid crystal display panel having a large retardation and a retardation film in addition to the TFD liquid crystal display panel 3.
[0028]
【Example】
FIG. 3 is a graph showing the results of measuring the cell gap of a 0 ° twist liquid crystal display panel. It was confirmed that the cell gap thickness of the 0 ° twist liquid crystal display panel can be measured by the gap measuring device.
[0029]
[Measurement condition]
Liquid crystal display panel Δn ₁ : 0.100
Cell thickness (d): 5.0
Δn ₁ · d ₁ : 0.500
Twist angle: 0 °
Optical anisotropic plate R (Δn ₂ · d ₂ ): 0.100
First polarizing plate θ = 135 °
Second polarizing plate θ = 45 °
[0030]
As a result of measuring the light intensity, a peak appeared at around 510 nm without the optical anisotropic plate, but a peak λp appeared at 600 nm when the optical anisotropic plate was inserted.
Substituting the above measurement conditions into equation (4),
d ₁ = (λp _in −Δn ₂ · d ₂ ) / Δn ₁ (4)
5.0 = (0.600-0.100) /0.100
Thus, it was found that the relational expression (4) was satisfied. Note that the peak value in the absence of the optical anisotropic plate is not 500 nm, and that even if an optical anisotropic plate is added, it does not change 100 nm simply because of the wavelength dispersion of the refractive index of each optical anisotropic plate. Because of the characteristics.
[0031]
FIG. 4 is a graph showing the results of measuring the cell gap of a 40 ° twisted liquid crystal display panel. It was confirmed that the cell gap thickness of a 40 ° twisted liquid crystal display panel can be measured by the gap measuring device.
[0032]
[Measurement condition]
Liquid crystal display panel Δn ₁ : 0.065
Cell thickness (d): 5.0
Δn ₁ · d ₁ : 0.325
Twist angle: -40 °
Optical anisotropic plate R (Δn ₂ · d ₂ ): 0.615
θ = 0 °
First polarizing plate θ = 35 °
Second polarizing plate θ = 75 °
[0033]
From the results of this experiment, the optical intensity changed from a flat characteristic to a characteristic having a peak at 550 nm by inserting an optical anisotropic plate. For this reason, the cell thickness can be similarly obtained by substituting the above condition into the equation (6).
[0034]
【The invention's effect】
As described above, in the gap thickness measuring device and the gap thickness measuring method of the present invention, even if the retardation is a very small measurement object, by inserting an optical anisotropic plate with known retardation, Since the peak wavelength can be shifted to the practical range of the optical measuring instrument, the cell gap can be measured appropriately.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a gap measuring apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a graph for explaining wavelength shift.
FIG. 3 is a graph showing a result of measuring a cell gap of a 0 ° twist liquid crystal display panel.
FIG. 4 is a graph showing a result of measuring a cell gap of a 40 ° twist liquid crystal display panel.
FIG. 5 is a configuration diagram showing an example of a conventional gap thickness measuring device for a liquid crystal display panel.
FIG. 6 is an explanatory diagram showing a delay of θ.
FIG. 7 is a graph showing the relationship between transmittance and wavelength.
FIG. 8 is a chart showing an example of the relationship between wavelength λ and retardation Δn · d.
[Explanation of symbols]
100 Gap thickness measuring device 1 Light source 2 First polarizing plate 3 Liquid crystal display panel 4 Optical anisotropic plate 5 Second polarizing plate 6 Spectrometer Δn · d retardation

Claims (5)

A light source;
A first polarizer that transmits a linearly polarized component of light emitted from a light source;
An optical anisotropic body in which a measurement object of retardation Δn ₁ · d ₁ (d ₁ is a required gap thickness) is positioned between the first polarizer and the retardation Δn ₂ · d ₂ is known;
A second polarizer that transmits a linearly polarized component in a direction orthogonal to the first polarizer;
A measuring instrument for measuring the intensity of transmitted light transmitted through the second polarizer;
On the light path,
The retardation Δn · d is obtained based on the measured light intensity, the retardation Δn · d, the retardation Δn ₂ · d _{2 of} the optical anisotropic body, and the known birefringence phase difference of the measurement object. An apparatus for measuring a gap thickness, comprising a calculating means for obtaining a gap thickness d ₁ of an object to be measured from Δn ₁ . 2. The gap thickness measuring apparatus according to claim 1, wherein the optical anisotropic body is composed of a plurality of optical anisotropic bodies with known retardations. A light source, a first polarizer that transmits a linearly polarized component of light emitted from the light source, an optical anisotropic body with known retardation Δn ₂ · d ₂ , and a straight line in a direction perpendicular to the first polarizer A second polarizer that transmits the polarization component and a measuring instrument that measures the intensity of transmitted light that has passed through the second polarizer are arranged on the optical path,
Between the first polarizer and the second polarizer, put a measurement object of retardation Δn ₁ · d ₁ (d ₁ is a desired gap thickness),
The light transmitted through the second polarizer is measured with a measuring instrument, and the retardation Δn · d is obtained based on the measured light intensity. The retardation Δn · d and the retardation Δn ₂ of the optical anisotropic body are obtained. A gap thickness measurement method characterized in that a gap thickness d ₁ of a measurement object is obtained from d ₂ and a known birefringence phase difference Δn ₁ of the measurement object.   The optical anisotropic body is composed of a plurality of optical anisotropic bodies with known retardations, and any or all of the optical anisotropic bodies are placed on the optical path, whereby the measurement object and all of the optical anisotropic bodies are retarded. The gap thickness measuring method according to claim 3, wherein the foundation is adjusted. A liquid crystal device having a liquid crystal layer between a pair of substrates, comprising a step of measuring the thickness of the liquid crystal layer using the gap thickness measuring method according to claim 3 or 4.

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