JPH06273342A - Defect detector for liquid crystal display - Google Patents

Abstract

PURPOSE:To provide an uneven color detector for liquid crystal display with which an inconspicuous unevenness of fading of color can be detected. CONSTITUTION:The defect detector for liquid crystal display 5 comprises a light source 1, means 3 for subjecting the light from the light source 1 to linear polarization such that the light of any wavelength directs in the same direction, and an optical rotation means 7 for directing the light from the means 3 toward an object to be inspected, i.e., the liquid crystal display 5, and imparting phase difference to the light transmitted through or reflected on the display 5 for every wavelength thereof thus making the angle of the plane of polarization different from each other. Output from the means 7 is detected and decided on whether it is shifted from normal state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color nonuniformity defect detection device for a liquid crystal display device, and more particularly to a color fading of a liquid crystal display panel,
The present invention relates to a defect detection device such as a scratch, a dent, and a pinhole.

[0002]

2. Description of the Related Art Liquid crystal display devices (LCDs) have been widely used for notebook type personal computers, liquid crystal televisions and the like because they can be easily made thin and multi-colored. The liquid crystal display device is formed by enclosing a liquid crystal between two glass plates having electrodes (not shown) formed on the surface. By applying a voltage between the electrodes, the orientation of the liquid crystal molecules is changed, the transmission of light from a backlight (not shown) is turned on / off, and display is performed. In such a liquid crystal display device, alignment of liquid crystal molecules is caused by unevenness in the intervals between glass plates, variations in the thickness of electrodes, and variations in the thickness of resin coating such as a diffusion plate (not shown) covering the outside of the glass plates. Can not be maintained in a certain direction, and uneven color or fading may occur. Furthermore, display unevenness will occur due to scratches on the glass plate, pinholes in the electrodes, and the like.

Defects such as fading, scratches, dents, and pinholes in liquid crystal display devices have been conventionally detected by visual inspection, and it is difficult for a considerable amount of skill to detect such defects, and automation is desired. Although an inspection device configured to detect the presence or absence of a defect has been proposed, it is far from practical use because it is impossible to distinguish between color unevenness and fading.

For example, as a liquid crystal panel inspection device, LC
R (red) G (green) B (blue) wavelengths are detected by detecting the transmitted light of D through an RGB filter with a color camera, and defect detection is performed by comparing the light intensity depending on the position. (Japanese Patent Laid-Open No. 2-156290). However, this device has a problem that the filter has a wide transmission wavelength band, and weak color unevenness and fading defects of the LCD cannot be detected.

By the way, the liquid crystal and the crystal have anisotropy of refractive index and cause birefringence. This is because the refractive index differs in the light traveling direction and the direction perpendicular to it, and when the incident light is linearly polarized light, it changes to a state close to circularly polarized light when passing through the liquid crystal or crystal, and the rotation of this light vector is Therefore, when exiting a liquid crystal or a crystal, the angle of the plane of polarization at the exit differs depending on each wavelength and becomes a dispersed state.

Therefore, by utilizing this phenomenon, there is also a method of distinguishing the color of an object to be inspected by multi-color decomposing the reflected light from the object to be inspected by using a liquid crystal cell in which birefringence control type liquid crystal elements are arranged in an array. It has been proposed (JP-A-2-21227, JP-A-63-249029). However, this method has the general characteristics described above: birefringence anisotropy that refracts in the direction perpendicular to the traveling direction of light, and optical rotation in which the incident light is linearly polarized light and becomes elliptically polarized while passing through the liquid crystal. Taking advantage of the nature
There is a problem in that it is impossible to detect defects such as color unevenness and fading, since only normality is detected.

Further, this system is an ECB constructed so that the twist angle of light in the liquid crystal part changes depending on the applied voltage.
Applicable only to liquid crystal, for example, STN with no voltage applied
Type liquid crystal (where the twist angle of light in the liquid crystal part is larger than that of a normal TN type liquid crystal) is not applicable because the polarizing plate and the liquid crystal molecules are orthogonal to each other and light is not emitted. Furthermore, this method
In the spectroscopy of light from one point of the object to be inspected, only the number of light guides made of a photoconductor such as glass fiber can be selected, and if the wavelength resolution is increased, the device of the liquid crystal element and the light guide becomes large. There is also. On the other hand, since it is necessary to tune the liquid crystal alignment voltage resolution, it is difficult to control and manufacture, and there is a problem that two-dimensional scanning takes time.

[0008]

As described above, in the conventional method, the detection of the color unevenness defect of the LCD is insufficient, and the high resolution cannot be obtained. There is a problem that fading cannot be detected.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a color unevenness inspection apparatus for a liquid crystal display device capable of detecting slight color unevenness and fading.

[0010]

Therefore, in the first aspect of the present invention, a light source, and a first linear polarization means for linearly polarizing the light from the light source so that light of all wavelengths are directed in the same direction, The output light of the first linear polarization means is applied to a liquid crystal display device as an object to be inspected, and a phase difference is given to each of the transmitted light and the reflected light of the liquid crystal display device for each wavelength, and the angle of the polarization plane is set for each wavelength. And a defect detection device of a liquid crystal display device for detecting whether or not there is a deviation from a normal state by detecting an output of the optical rotation device.

In the second aspect of the present invention, the light source, the first linear polarization means for linearly polarizing the light from the light source so that the light of all wavelengths are directed in the same direction, and the first linear polarization means. Apply the output light of the above to the liquid crystal display device to be inspected,
Optical rotation means for giving a phase difference for each wavelength to transmitted light or reflected light of the liquid crystal display device so that the angle of the polarization plane is different for each wavelength, and the output of the optical rotation means is linearly polarized only for a specific wavelength. It is equipped with a quarter-wave plate that allows the light to pass therethrough, and a second polarizing means that allows only light having an oscillating surface in the same direction to pass therethrough. Whether or not it deviates from the normal state by detecting the intensity of this output. A defect detecting device of a liquid crystal display device for detecting

In a third aspect of the present invention, a light source and a liquid crystal display device as an inspection target are provided with light from the light source, and a phase difference is given to each of transmitted light and reflected light of the liquid crystal display device for each wavelength. A plurality of sets of optical rotation means for making the angle of the polarization plane different for each wavelength and second polarization means for transmitting only the light having an oscillation plane in the same direction are alternately arranged. A defect detection device of a liquid crystal display device is configured that sequentially detects and detects whether or not there is a deviation from a normal state.

According to a fourth aspect of the present invention, a light source and a liquid crystal display device as an object to be inspected by the light from the light source are provided with a phase difference for each wavelength with respect to transmitted light or reflected light of the liquid crystal display device. , An optical rotation means for making the angle of the polarization plane different for each wavelength, a quarter wavelength plate for linearly polarizing the output of the optical rotation means and transmitting it, and an output of the quarter wavelength plate. A second polarizing means that is connected and transmits only light having an oscillating surface in the same direction as one pair is sequentially arranged, and a plurality of sets are sequentially arranged. A defect detection device for a liquid crystal display device is configured to detect whether or not the liquid crystal display device is present.

In a fifth aspect of the present invention, a light source, a first linear polarization means for linearly polarizing the light from the light source so that lights of all wavelengths are directed in the same direction, and the first linear polarization means. Apply the output light of the above to the liquid crystal display device to be inspected,
Optical rotation means for giving a phase difference for each wavelength to transmitted light or reflected light of the liquid crystal display device so that the angle of the polarization plane is different for each wavelength, and the output of the optical rotation means is linearly polarized only for a specific wavelength. 1/4 wavelength plate that allows the light to pass through
The second polarization means is arranged so that the normal direction is located at the Brewster angle of the output light of the / 4 wavelength plate, and only the light having the vibrating surface in the same direction is transmitted, and the intensity of this output is A defect detection device of a liquid crystal display device is configured to detect whether or not it is deviated from a normal state by detecting.

[0015]

According to the first aspect of the present invention, the liquid crystal display device is provided with
By irradiating white linearly polarized light, rotating the transmitted light or the reflected light, and then polarizing the light, any peak wavelength can be detected with high resolution.

Further, by detecting the light intensity, various defects such as faint color unevenness, fading, and scratches on the entire surface of the liquid crystal display device can be detected. Further, by elliptically polarized light or linearly polarized light by the optical rotation means, and further by selecting a specific wavelength by the polarizing plate, it is possible to measure the light intensity distribution at the specific wavelength and detect unevenness of color, fading, scratches, etc. .

The optical axis of the polarizing plate (the direction in which light passes) is aligned with the major axis of the ellipse of normal light, and the angle between the normal vector of the second polarizing plate and the incident light is maintained while maintaining this state. Is set to be Brewster's angle, the light reflected by the second polarizing plate becomes S-polarized light having a weak light intensity at the normal light wavelength. Therefore, it is possible to detect the increase / decrease in uneven color light of the LCD transmitted light by collecting the reflected light of the second polarizing plate and measuring the increase / decrease in the light intensity.

According to the second aspect of the present invention, the liquid crystal display device is irradiated with white linearly polarized light, the transmitted light or the reflected light is rotated, and then linearly polarized, whereby the measurement wavelength can be detected with high resolution. it can. If necessary, after the rotation, phase amplification may be performed and then linearly polarized light may be performed. Further, the wavelength to be measured can be detected with high resolution by passing it through an optical filter having a required transmission wavelength range.

It should be noted that wavelengths having the optical axis of the λ / 4 plate (direction in which light passes) in the major axis or minor axis direction of the ellipse of normal light are linearly polarized. Therefore, by setting the LCD normal light in this state, the uneven color light becomes elliptically polarized light and the normal light becomes linearly polarized light. The second polarizing plate is placed so that the plane of polarization of this normal light becomes p-polarized light, and tilted by the Brewster angle. With this configuration, when the light emitted from the optical rotatory material is close to linearly polarized light, normal light can be separated from abnormal light. Further, here, without using the second polarizing plate, the back surface antireflection coating glass may be used to separate the normal light and the light causing LCD color unevenness.

Further, since the entire separated color unevenness does not include normal light, when the light intensity of the entire color unevenness becomes large, the LCD
The transmitted light indicates that light other than the normal light is easily transmitted. Color unevenness can be detected by measuring the light intensity sum of all wavelengths over the entire LCD.

The optical axis of the second polarizing plate is aligned with the major axis of the ellipse of the elliptically polarized state of normal light, and the angle between the normal vector of the second polarizing plate and the incident light is maintained while maintaining this state. With the angle, the light reflected by the second polarizing plate becomes S-polarized light having a weak light intensity at the normal light wavelength. Therefore,
By collecting the reflected light of the second polarizing plate and measuring the increase / decrease in the light intensity thereof, the increase / decrease in the uneven color light of the LCD transmitted light can be detected.

According to a third aspect of the present invention, the first polarizing plate is eliminated in the first configuration, and a plurality of pairs of the optical rotatory means and the second polarizing plate are sequentially arranged to form the optical rotatory means and the second polarizing plate. The normal light and the light due to the defect can be separated and detected by and, and the detection is easy.

According to a fourth aspect of the present invention, the first polarizing plate is eliminated in the second configuration, and a plurality of combinations of the optical rotation means, the quarter-wave plate and the second polarizing plate are provided, whereby the sequential arrangement is performed. The normal light and the light due to the defect can be separately detected, and the detection is easy.

According to the fifth aspect of the present invention, the elliptically polarized light emitted from the optical rotation means is aligned with the optical axis of the second polarizing plate, that is, the light transmitting direction, in the major axis direction of the ellipse of normal light. Since the angle between the normal vector of the second polarizing plate and the light incident on it is kept at the Brewster angle while maintaining it, normal light can be removed and only abnormal light can be extracted.

[0025]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic explanatory view of a liquid crystal inspecting apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory view of a state of an optical element in each part, an optical element transmitted light vector, and an intensity distribution of each wavelength.

This device comprises a filter 2 for selectively transmitting light of a xenon lamp 1 which is a parallel light flux type high brightness light source and light of 310 to 700 nm, and a first polarizing plate 3.
The transmission type liquid crystal display device 5, which is an object to be inspected, is irradiated through the slits 4 having an interval of 10 mm, and the transmitted light has an interval of 3 mm.
The light is incident on the rotary λ / 2 plate 6 through the slit S and the optical rotatory material 7 made of quartz is rotated so that the molecular direction and the linear polarization direction from the transmissive liquid crystal display device 5 to be inspected become equal. In addition, the polarization plane of each wavelength is dispersed, that is, the angle of the polarization plane is made different for each wavelength, and this is guided to the second polarizing plate 9 through the achromat lens 8 and taken out in a linearly polarized state. It is partially taken out by the mirror 10 and detected by the photodiode 13 via the lenses 11 and 12. The remaining light rays are further guided to the visual screen 15 via the achromat lens 14.

The filter 2 is constructed so as to remove ultraviolet rays and infrared rays and allow only visible light to pass therethrough so as not to apply heat to the liquid crystal display device to be inspected. Further, as shown in FIG. 2, the first polarizing plate irradiates the liquid crystal display device to be inspected with linearly polarized light having an angle θ of the transmitted polarization plane.
The slit 4 determines the spatial resolution of the surface to be inspected, and the smaller the distance from the liquid crystal display device to be inspected, the smaller the influence of diffraction and the clearer the edge. The λ / 2 plate is rotated so that the transmitted light of the liquid crystal display device to be inspected is incident in the molecular direction of the optical rotatory material in a linearly polarized state. At this time, this angle is set and fixed and used for a normal liquid crystal display device to be inspected.

In this color unevenness detecting method, the optical element transmitted light vector at each portion shown in FIG. 2 will be described.

The plane wave vector E 0 (E _0x , E _0y , 0) of the wavelength λ of the light emitted from the light source 1 is as shown in the following equations (1) and (2), and φ _x and φ _y are random unpolarized light. Is.

The scalar wave of the vector E0 in the x and y directions is However, the vector E1 after passing through the first polarizing plate 3 is linearly polarized light, and φx−φy = 2πm, m = 0, ± 1, ± 2 .. .., and the phase difference from the origin is η, the first polarizing plate. Let θ1 be the angle of And passes through the first polarizing plate 3. Where ω is the angular frequency and λ
Is the wavelength, c is the luminous flux, and k is the wave number.

When the light of the vector E1 passes through the backlight side polarizing plate (inclination δ1) of the liquid crystal display device (LCD) to be inspected (see FIGS. 2 (a1) (b3)). Becomes When light passes through the liquid crystal, it rotates in an elliptically polarized state for each wavelength, but if the ellipticity is weak, assuming that it is almost linearly polarized, it will be in front of the display-side polarizing plate (Fig. 2 (a2) (b
4)) Here, α _λ is an optical rotation angle of the liquid crystal display device unit which varies depending on the wavelength, and is a size measured from the x axis. ST as an example
In the case of N liquid crystal, blue is 0 °, purple is −30 °, and green is 60 °.

Further, when passing through the display side polarizing plate of the liquid crystal display device, the inclination of the polarizing plate is set to δ _2. The light of vector E2 is incident on the optical rotator 7 having the optical axis in the same direction as E2, and the light emitted from this is Becomes ξ _λ is the optical rotation angle of the optical rotatory material that differs depending on the wavelength, and is the size measured from the x-axis as is the case with α _λ .

This light travels without change until immediately before the polarizing plate 9, but when it passes through the polarizing plate 9 with an inclination angle δ ₃ , the light is Then, this light is projected on the screen.

Since the light projected on the screen is blue, green and purple, the normal light blue and the auxiliary abnormal light green should be removed in order to detect the abnormal light purple.

To this end, the cos of the terms contained in S
(Θ1 −δ1) cos α _λ and cos (θ1 −δ1) si
Adjust θ 1 so that the green wavelength is attenuated by the term of nα _λ .
Here, δ1 is fixed.

[0037] When δ1 to 0, the above two equations take the minimum value θ1 and α
The combination of _λ is θ 1 = 90 °, α _G = arbitrary (α _G is the angle of rotation of green of α _λ ), and at this angle θ 1, the green vector E _4G is attenuated.

On the other hand, in order to remove the blue color, the vector E
Pay attention to δ ₃ and ξ _λ included in 4. Vector E
It is only necessary to minimize cos (ξ _λ −δ ₃ ) out of 4, so that if the polarizing plate 8 is rotated so that δ ₃ = ξ _B + π / 2, the blue vector E is obtained.
_4B = 0.

Therefore, it becomes possible to attenuate the vector E _4G and remove the vector E _4B without attenuating the extraordinary light vector E _4P .

If the normal portion light wavelength is Iλ and the abnormal portion light wavelength is Iλ−Δ, Iλ + Δ, the abnormal portion light wavelength Iλ + Δ can be weakened by the second polarizing plate to remove the normal portion light wavelength λ. Therefore, the light transmitted through the second polarizing plate becomes a wavelength group near the abnormal portion light wavelength Iλ−Δ. Abnormal light,
The method of selecting the normal light is arbitrary and can be changed depending on the inspection target. In addition, when there is a scratch on the liquid crystal display device to be inspected,
The polarization state changes at that portion, and a sharp change in light intensity appears.

These light intensity distributions are measured for the transmission wavelength of the second polarizing plate. This measurement is performed over the entire surface of the liquid crystal display device to be inspected to detect the position of the defective portion, specify the defect type, and select the defective product.

In this system, ECB type liquid crystal, STN type liquid crystal,
(For any type of liquid crystal display device such as an ordinary TN type liquid crystal, it is possible to detect color unevenness, fading, and the like, and it is also possible to automatically detect a scratch on the liquid crystal display device to be inspected.

Next, a second embodiment of the present invention will be described.

In the same manner as in the first embodiment, the light of the vector E2 that has passed through the display side polarizing plate of the liquid crystal display device to be inspected is incident on the optical rotatory member 27 having the optical axis in the same direction as the vector E2. its polarization state when the light emitted is in elliptical polarization states, the optical rotation angle by optical rotation member 27 and xi] _lambda from Becomes The phase difference may differ depending on the wavelength of the optical rotation, but in this case, only ζ _{3 in the} above equation changes, and if there is no loss, the other coefficients do not change.

At the time of designing the optical rotatory material, ζ ₃ is given so that the polarization state of the wavelength to be transmitted becomes a thick ellipse (the ratio of the major axis and the minor axis is a value close to 1). ζ ₃ is a phase difference generated by the optical rotatory material 27.

Next, this elliptically polarized light is incident on the λ / 4 plate, and the λ / 4 plate is rotated to align the major axis or the minor axis of the ellipse with the optical axis direction of the λ / 4 plate or the direction perpendicular thereto. And this ellipse becomes linearly polarized light, Becomes

There are two wavelengths in this state, as shown in FIG. 4 (a).

However, as shown in 43 (b), the elliptically polarized light in which the major axis or the minor axis of the ellipse does not coincide with the above-mentioned axis of the λ / 4 plate is still elliptically polarized light at the time of emission and is not linearized. As the change of elliptically polarized light, a phase change may occur during transmission through a λ / 4 plate, and this effect appears in the thickness of the ellipse, and will be described later if the state is not thin, that is, the phase difference is not close to 0. The full width at half maximum at the time of measurement can be reduced.

By the way, the light thus linearly polarized by the λ / 4 plate and the elliptically polarized light pass through the second polarizing plate 9, but when the second polarizing plate is aligned in the direction _directly E _4. , E _{4 straight}
Does not decay. That is, the extracted wavelength λ _p is E
_{It has four direct} vectors.

On the other hand, the wavelength of the elliptically polarized light is E _{4 ellipse 1 where} the vector of the ellipse along the long axis is E ₄ and the angle between this vector and the second polarizing plate is δ ′, the maximum amplitude of transmission is quite large.
Among the wavelengths that have passed through the second polarizing plate, the amplitude of E ₄ , which is a linearly polarized state, that is, the amount of light becomes maximum.

This effect is greatest when δ'is π / 2 and 3π / 2, and is best when _{│a E3X} │ = _{│a E3Y} │, that is, when the major axis and the minor axis are equal.

On the other hand, the second linearly polarized light is orthogonal to the optical direction of the second polarizing plate and therefore does not pass through.

[0053] can be taken out only the wavelength components of λp from among many wavelengths gun if the wavelength λp to be extracted in this way into a linear polarization state E _{4 straight.}

From the above consideration, first, the wavelength λ desired to be extracted
In order to linearize p, the λ / 4 plate is adjusted to the optical rotation angle of the wavelength λp, the second polarizing plate is adjusted to the optical rotation angle ξ _λ , and the first polarizing plate is controlled to change the angle θp of the polarization plane. , | Scos δ2 cos ξ _λ | = | S sin δ2 sin ξ
Try to get as close as possible to _λ | (δ 2 = constant, ξ _λ = constant).

Further, when it is desired to remove only the specific wavelength λp, the second polarizing plate is further set to the state of the optical rotation angle ± π / 2.

Furthermore, there are three methods for reducing the full width at half maximum as shown in FIG.

(1) δ ′ is increased so that the ellipse is as close to a circle as possible. To this end, the phase difference δ'with respect to the transmission wavelength of the optical rotator is The optimum value π / 2 or 3π / 2 is given.

(2) The first polarizing plate is controlled so as to approach | a _E3X | = | a _E3Y |.

(3) Use an optical filter. The center wavelength of the filter is adjusted to the desired wavelength λp.

In this way, it is possible to extract only the wavelength λp to be extracted, and by detecting this with the photodiode 13, it is possible to detect the presence or absence of color unevenness by detecting whether or not is normal. .

In this example, as shown in FIGS.
Instead of the λ / 2 plate 6 and the optical rotatory material 7 in the first embodiment,
It is characterized in that it is composed of a rotary optical rotator 27 and a λ / 4 plate 26. The output of the second polarizing plate 9 is partially taken out by the half mirror 10 and detected by the CCD 23 via the achromat lens 11 and the auxiliary optical filter 22.

That is, in this device, the white irradiation light is first emitted.
When the liquid crystal display device 5 to be inspected is irradiated with the linearly polarized light by the polarizing plate 3 of the above, the transmitted light or the reflected light is taken out as the linearly polarized light in which the normal part light Iλ, the abnormal part light Iλ−Δ, and Iλ + Δ are mixed. Then, the light intensity of each wavelength is slightly different.

This linearly polarized light is rotated by rotating the optical rotatory material 27 so that the molecular direction of the optical rotatory material and the linearly polarized light from the liquid crystal display device 5 to be inspected become equal. Here, similarly to the first embodiment, a ½ wavelength plate may be added in front of the optical rotatory material 27 so that linearly polarized light is incident in the molecular direction of the optical rotatory material.

The light thus incident on the optical rotatory material is internally phase-amplified by the optical rotatory material and the λ / 4 plate, and each wavelength after emission becomes an elliptically polarized state. The major axis of the elliptically polarized light has an angle formed with the X axis depending on the wavelength, and in order to enhance the wavelength detection resolution by the optical sensor such as the CCD 23, the rotatory material is considered so that the incident wavelengths are well distributed over 360 degrees. .

Then, this output is made incident on the λ / 4 plate 26, but light having a wavelength such that the major axis or the minor axis of the ellipse lies in the optical axis direction becomes linearly polarized light. Here, there is no phase difference between the vectors in the XY directions, but the amplitudes are different. The wavelength incident on the λ / 4 plate with the optical axis deviated is still in the elliptically polarized state even after the λ / 4 plate exits. Therefore, the wavelength at which elliptically polarized light becomes linearly polarized light is 2
Exist. Therefore, the long or short axis of the elliptically polarized light of the wavelength to be detected is linearly polarized by aligning it with the optical axis of the λ / 4 plate, and is incident on the rotatable second polarizing plate 9.
By adjusting the rotation angle of the polarizing plate to the direction of the linearly polarized light of the detection wavelength λ, wavelengths other than λ can be attenuated without attenuating the wavelength λ.

On the other hand, when each wavelength of the wavelength distribution f (λ) is linearly polarized, two of the wavelengths after passing through the λ / 4 plate are circularly polarized, but the other wavelengths are It becomes elliptically polarized light and enters the second polarizing plate. Of the wavelengths that pass through the second polarizing plate, those that are not attenuated are the two wavelengths that were circularly polarized at the time of incidence, but the other wavelengths are attenuated. The light emitted from the second polarizing plate is in a linearly polarized state at all wavelengths, but there is a wavelength band spread having a maximum peak of wavelength λ. Therefore, the selection and design of the polarizing material and the material of the λ / 4 plate,
Select by considering the thickness, incident wavelength, etc.

Also in this apparatus, the method of selecting the abnormal light and the normal light is arbitrary and can be changed depending on the inspection object. When the liquid crystal display device to be inspected has a flaw, the polarization state changes at that portion, and a sharp change in the light intensity appears.

This measurement is performed over the entire surface of the liquid crystal display device to be inspected, and the position of the defective portion is detected, the defect type is specified, and the defective product is selected.

Similar to the first embodiment, this method can detect color unevenness, fading, etc. in any type of liquid crystal display device such as ECB type liquid crystal, STN type liquid crystal (ordinary TN type liquid crystal), and can be inspected. A flaw in the liquid crystal display device can also be automatically detected.

[0070] FIG. 7 is a configuration explanatory diagram of a liquid crystal inspection device according to a third embodiment of the present invention.

This apparatus has the first polarizing plate 3 in the first embodiment, and the combination of the optical rotatory material 27 and the polarizing plate 29 is n.
They are arranged side by side and the output of each polarizing plate is detected by a sensor. This makes it possible to obtain n wavelength peaks.

In this method, the number of polarizing plates increases and the amount of light decreases as the number of n-th set increases. However, since n peaks can be obtained, after setting the optical system, the liquid crystal display device If the entire surface is scanned, a change in light intensity will appear at each wavelength and the wavelength of color unevenness can be specified.

FIG. 8 is a structural explanatory view of a liquid crystal inspection device according to the fourth embodiment of the present invention.

This apparatus uses the first polarizing plate 3 of the third embodiment, and has an optical rotatory material 27, a λ / 4 plate 26 and a polarizing plate 29.
In this case, n sets of combinations of and are arranged and the output of each polarizing plate is detected by a sensor. This makes it possible to obtain n wavelength peaks.

Even in this method, the number of polarizing plates increases and the amount of light decreases as the number of n-th set increases. However, since n peaks can be obtained, after setting the optical system, the liquid crystal display device If the entire surface is scanned, a change in light intensity will appear at each wavelength and the wavelength of color unevenness can be specified.

Next explained is the fifth embodiment of the invention.

In this example, as shown in FIG. 9, in Example 1, the optical axis of the second polarizing plate 9 is aligned with the wavelength to be extracted, for example, the major axis direction of elliptically polarized light of normal light, and while maintaining this state, The angle between the normal vector of the second polarizer and the incident light should be the Brewster's angle, the reflected light from this second polarizer is condensed, and the increase or decrease in the light intensity is measured to determine the color of the LCD transmitted light. The variation of uneven light is detected.

On the other hand, the reflected light from the second polarizing plate is shown in FIG.
As shown in FIG. 11, normal light has a peak wavelength as shown in FIG.

By measuring the reflected light from the second polarizing plate in this way, it is possible to detect the increase or decrease in color unevenness with high accuracy and easily.

Next, a sixth embodiment of the present invention will be described.

In this example, as shown in FIG.
In, the optical axis of the second polarizing plate 9 is aligned with the plane of polarization of the wavelength linearly polarized by the λ / 4 plate, and while maintaining this state, the angle between the normal vector of the second polarizing plate and the incident light is the Brewster angle. Then, the reflected light from the second polarizing plate is condensed, the increase / decrease in the light intensity thereof is measured, and the increase / decrease in the uneven color light of the LCD transmitted light is detected.

Here, the elliptically polarized light having a wavelength incident on the λ / 4 plate and having the major axis or the minor axis of the ellipse in the optical axis direction of the λ / 4 plate or in the direction perpendicular thereto becomes linearly polarized light. Therefore, if the normal light is changed to the P polarization state, the normal light is linearly polarized (P
Polarized light) and uneven color light become elliptically polarized light, and when the polarization plane of the second polarizing plate is aligned with the direction in which only S-polarized light is reflected, the reflected light does not include normal light, and as shown in FIG. The strength becomes 0. On the other hand, the transmitted light of this second polarizing plate is shown in FIG.
As shown in, normal light has a peak wavelength.

By measuring the reflected light of the second polarizing plate as described above, the normal light and the abnormal light can be separated and the color unevenness can be detected with high accuracy and easily.

Further, by measuring the sum of the light intensities for each wavelength over the entire liquid crystal display device, the light intensity is remarkably reduced in the normal light wavelength portion as shown in FIG. Where the color unevenness is weak, it becomes slightly smooth as shown in FIG. 15 (b), and in the area where the color unevenness is strong, the light intensity becomes high in areas other than the normal light wavelength portion as shown in FIG. 15 (c). By utilizing this, the degree of color unevenness can also be detected. Instead of the second polarizing plate 9,
By using a glass plate 49 coated as shown in FIG. 16, it is possible to obtain the same effect as that of the above embodiment. Here again, the λ / 4 plate is operated so that the normal light wavelength becomes linearly polarized, and the glass plate is installed so that the plane of polarization becomes P-polarized with respect to the glass plate. Further, the glass plate 49 is tilted so that the normal vector of the glass plate surface becomes the Brewster angle with the direction of the incident light. At this time, the light reflected by the glass plate does not include P-polarized light but only S-polarized light component.
Since the normal light includes only the P-polarized light component and does not include the S-polarized light component, the light intensity of the normal light wavelength in the reflected light becomes 0 as shown in FIG. On the other hand, the transmitted light of the glass plate 49 is shown in FIG.
As shown in, normal light has a peak wavelength.

Further, by comparing the integrated value of the light intensity of the reflected light or the transmitted light with the normal value, it is possible to detect the color unevenness with higher accuracy. This relationship is shown in FIG. In this figure, (a) and (A) are for the normal state, (b) and (B) are for the case where the transmission of the normal light is strong, and the integral value ξ2 of the reflected light at this time is the reflection for the normal state. It is smaller than the integrated value of light ξ1, while the integrated value of transmitted light at this time δ
2 is larger than the integral value δ1 of transmitted light in the normal state. When the normal light becomes weaker and the extraordinary light becomes stronger, the integrated value ξ3 of the reflected light at this time is larger than the integrated value ξ1 of the reflected light in the normal state, as shown in (c) and (C). The integral value Δ3 of the transmitted light at this time is smaller than the integral value Δ1 of the transmitted light in the normal state. In addition, if there is no change in light intensity for normal light and there is a change in light intensity between other wavelengths (d) and
As shown in (D), the integral value ξ4 of the reflected light at this time is not equal to the integral value ξ1 of the reflected light in the normal state, while the integral value δ4 of the transmitted light at this time is also the integral value of the transmitted light in the normal state. Not equal to the value δ 1.

Therefore, a predetermined threshold value of the error may be determined in advance, and when the error becomes larger than this value, it may be determined that there is an abnormality.

Further, as a seventh embodiment of the present invention, FIG.
As shown in 0, in Example 6, the optical axis of the second polarizing plate 9 is aligned with the direction perpendicular to the linearly polarized normal light, and while maintaining this state, the normal vector of the second polarizing plate is incident. Make the angle of light the Brewster's angle
By making the polarization plane of the polarizing plate of S to be S-polarized and completely shielding P-polarized light, transmitted light becomes only S-polarized component, normal light which is P-polarized becomes completely 0, and abnormal light is taken out as transmitted component. be able to. In this device, S of abnormal light
It is possible to take out only the polarized component, detect both transmitted light and reflected light, and take the sum to obtain the result of Fig. 21 (a) and
The presence of color unevenness can be detected as shown in (b).

[0088]

As described above, according to the present invention, various defects such as faint color unevenness, fading, and scratches on the entire surface of the liquid crystal display device can be easily detected with high accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing an inspection device for a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of the same.

FIG. 3 is a diagram showing an inspection device for a liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of the same.

FIG. 5 is an explanatory diagram of the same.

FIG. 6 is an explanatory diagram of the same.

FIG. 7 is a diagram showing an inspection device for a liquid crystal display device according to a third embodiment of the present invention.

FIG. 8 is a diagram showing an inspection device for a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 9 is a diagram showing an inspection device for a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 10 is a diagram showing an output of the device.

FIG. 11 is a diagram showing an output of the device.

FIG. 12 is a diagram showing an inspection device for a liquid crystal display device according to a sixth embodiment of the present invention.

FIG. 13 is a diagram showing an output of the device.

FIG. 14 is a diagram showing an output of the device.

FIG. 15 is a diagram showing an output of the device.

FIG. 16 is a diagram showing a modification of the embodiment of the present invention.

FIG. 17 is a diagram showing an output of the device.

FIG. 18 is a diagram showing an output of the device.

FIG. 19 is a diagram showing another determination method.

FIG. 20 is a diagram showing an inspection device for a liquid crystal display device according to a seventh embodiment of the present invention.

FIG. 21 is a diagram showing an output of the device.

[Explanation of symbols]

 1 Light Source 2 Filter 3 Polarizing Plate 4 Slit 5 Liquid Crystal Display Device 6 λ / 2 Plate 7 Optical Rotating Material 8 Achromatic Lens 9 Second Polarizing Plate 10 Half Mirror 11 Lens 12 Lens 13 Photodiode 14 Achromat Lens 15 Screen 22 Auxiliary Optical Filter 23 CCD 26 λ / 4 Plate 27 Optical Rotating Material 29 Polarizing Plate 47 Optical Rotating Material 49 Glass Plate

Claims (5)

[Claims] 1. A first linear polarization means for linearly polarizing the light from the light source so that the light of all wavelengths and the light of all wavelengths are directed in the same direction, and the output light of the first linear polarization means is inspected. In the liquid crystal display device as a target, optical rotation means for imparting a phase difference for each wavelength to transmitted light or reflected light of the liquid crystal display device and for dispersing so that the angle of the polarization plane is different for each wavelength, and the optical rotation means. A defect detection device for a liquid crystal display device, comprising: a polarizing plate for extracting a specific wavelength from the output of 1. 2. A light source and a first linearly polarizing means for linearly polarizing light from the light source so that all wavelengths of light are directed in the same direction, and output light from the first linearly polarizing means is an object to be inspected. In the liquid crystal display device as described above, optical transmission means for giving a phase difference for each wavelength to transmitted light or reflected light of the liquid crystal display device so that the angle of the polarization plane is different for each wavelength, and the output of the optical rotation means. Is equipped with a quarter-wave plate that linearly polarizes and transmits only a specific wavelength, and a second polarizing means that transmits only light having a vibrating surface in the same direction, and detects the intensity of the output of the specific wavelength. A defect detection device for a liquid crystal display device, which detects whether or not it is deviated from a normal state by performing. 3. A light source and a liquid crystal display device as an object to be inspected, the light from the light source being provided with a phase difference for each wavelength with respect to transmitted light or reflected light of the liquid crystal display device, and a polarization plane for each wavelength. A plurality of sets of optical rotation means for changing the angle of the optical axis and a second polarization means for transmitting only the light having an oscillating surface in the same direction as the output of the optical rotation means are alternately arranged. A defect detection device for a liquid crystal display device, which sequentially detects the defects and detects whether or not the condition is deviated from a normal state. 4. A light source and a liquid crystal display device as an object to be inspected, the light from the light source being provided with a phase difference for each wavelength with respect to transmitted light or reflected light of the liquid crystal display device, and a polarization plane for each wavelength. Are connected to the output of the optical rotation means, the quarter wavelength plate that linearly polarizes and transmits only the specific wavelength from the output of the optical rotation means, and the output of the quarter wavelength plate. A plurality of sets are sequentially arranged with one set of a third polarizing means that transmits only light having a vibrating surface in the same direction, and by detecting the intensity of this output, it is detected whether or not there is a deviation from the normal state. Defect detection device for liquid crystal display device. 5. A light source and first linear polarization means for linearly polarizing light from the light source so that light of all wavelengths are directed in the same direction, and output light of the first linear polarization means is an object to be inspected. In the liquid crystal display device as described above, optical transmission means for giving a phase difference for each wavelength to transmitted light or reflected light of the liquid crystal display device so that the angle of the polarization plane is different for each wavelength, and the output of the optical rotation means. Is arranged so that the normal direction comes to the Brewster angle of the output light of the 1/4 wavelength plate and the 1/4 wavelength plate that linearly polarizes and transmits only the specific wavelength, and the vibrating surface is arranged in the same direction as this. A defect detecting device for a liquid crystal display device, comprising: a second polarizing means for transmitting only the light that the device has, and detecting whether or not there is a deviation from a normal state by detecting the intensity of the output.