JP2008045959A - Device and method for inspecting liquid crystal display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reliably detect the contamination of the polarizing plate interposed between a liquid crystal display panel and the polarizing plate without lighting the liquid crystal display panel itself. <P>SOLUTION: The device for inspecting the liquid crystal display panel has a stage 15 having the polarizing plate pasted thereon as a panel to be inspected and holding the liquid crystal display panel 10, the transmission light source 21 provided under the stage 15 to supply light to the panel to be inspected, a reflected light source 23 provided above the stage 15 to obliquely supply light to the panel to be inspected and the imaging part 26 provided above the stage 15 to capture the image due to the light supplied from the transmission light source 21 to be transmitted through the panel to be inspected and the image due to the light supplied from the reflected light source 23 to be reflected from the surface of the panel to be inspected. A polarizing filter 25 having a polarizing axis crossing the polarizing axis of the polarizing plate of the panel to be inspected and inserted in and drawn out with respect a light path of reflected light is interposed between the stage 15 and the imaging part 26. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inspection apparatus and an inspection method for a liquid crystal display panel, and particularly to an inspection technique for a liquid crystal display panel to which a polarizing plate is attached.

  Since the liquid crystal display panel needs to use light that vibrates only in a certain direction, a polarizing plate that transmits light that vibrates only in a certain direction is attached to the surface of the liquid crystal display panel.

  A general polarizing plate, for example, adsorbs and stretches iodine on a polyvinyl alcohol film and vibrates only in a certain direction, that is, a polarizer for creating polarized light, and sandwiches the polarizer and faces each other. A pair of supports provided to be disposed and an adhesive layer provided on the surface of one of the supports and attached to the surface of the liquid crystal display panel are provided.

For example, Patent Document 1 includes a light source and a polarizing filter that converts light from the light source into linearly polarized light in a predetermined direction, and light between the polarizing filter and a polarizing plate with a protective film that is an inspection object. An inspection apparatus for a polarizing plate with a protective film, in which a retardation plate for compensating for the birefringence of light by the protective film of the polarizing plate is arranged on the road, is disclosed. According to this, since the phase change of the protective film of the polarizing plate is canceled and the birefringence of light by the protective film is compensated, it is possible to accurately detect defects such as foreign matter, scratches, and dents existing on the polarizing plate. It is stated that it can be done.
JP 2005-9919 A

  By the way, when sticking a polarizing plate to a liquid crystal display panel, a foreign substance (hereinafter referred to as a liquid crystal display panel), that is, between a glass substrate constituting the liquid crystal display panel and a polarizing plate, ie, an adhesive layer constituting the polarizing plate. , Referred to as “polarizing plate foreign matter”). If this polarizing plate foreign material is a foreign material that transmits light such as resin, it is detected as a bright spot by observing the surface of the liquid crystal display panel with the polarizing plate attached in a black display. In addition, a foreign object that does not transmit light is detected as a black spot in a state of being lit in white.

  Here, in order to light the liquid crystal display panel in order to detect the polarizing plate foreign matter, it is necessary to mount a mounting component such as a driver chip on the liquid crystal display panel. For this reason, attaching a mounting component to a liquid crystal display panel that becomes a defective product due to having a polarizing plate foreign matter of a predetermined level or more causes an increase in production cost.

  The present invention has been made in view of such a point, and the object of the present invention is to reliably prevent the polarizing plate foreign matter interposed between the liquid crystal display panel and the polarizing plate without lighting the liquid crystal display panel itself. It is to detect.

  In order to achieve the above object, the present invention relates to an image (observation) by transmitted light, an image (observation) by reflected light through the polarization axis of the attached polarizing plate, and the polarization axis of the attached polarizing plate. A foreign object is detected by an image (observation) using reflected light via orthogonal polarization axes.

  Specifically, an inspection apparatus for a liquid crystal display panel according to the present invention includes a pair of substrates disposed opposite to each other, and a liquid crystal layer provided between the pair of substrates, and polarized light is applied to the surface of each substrate. An apparatus for inspecting a liquid crystal display panel that detects foreign matter between each of the substrates and the polarizing plate with respect to the liquid crystal display panel to which the plates are attached, and a panel holding unit that holds the liquid crystal display panel that is the panel to be inspected. A transmission light source that is provided below the panel holding unit and supplies light from the one substrate side to the panel to be inspected, and is provided above the panel holding unit and is the other side with respect to the panel to be inspected. A reflection light source that supplies light obliquely from the substrate side, an image of the transmission light that is provided above the panel holding unit and that is supplied from the transmission light source and passes through the panel to be inspected, and the reflection light source And an imaging unit for taking an image of reflected light reflected from the surface of the panel to be inspected, and is attached to the other substrate side between the panel holding unit and the imaging unit. A polarizing filter having a polarization axis perpendicular to the polarization axis of the polarizing plate and capable of being inserted into and removed from the optical path of the reflected light is provided.

  According to the above configuration, the liquid crystal display panel to which the polarizing plate is attached, that is, the panel to be inspected, first, light is incident from one substrate side by the transmission light source, and an image by the transmitted light of the light is displayed. By photographing with the imaging unit, surface foreign matter and surface scratches on the panel to be inspected, and polarizing plate foreign matter between the substrate constituting the panel to be inspected and the polarizing plate are detected as a dark image by blocking transmitted light. Subsequently, light is incident on the panel to be inspected from a diagonally upper side on the other substrate side by a reflected light source, and an image of the reflected light of the light is polarized on the other substrate side by the imaging unit. Transparent through the surface foreign matter and surface scratches of the panel to be inspected and the polarizing plate foreign matter through the polarization axis parallel to the axis, that is, by taking a picture in a parallel Nicol state by removing the polarizing filter from the optical path of the reflected light A foreign object reflects light and is detected as a bright image. At this time, an opaque black foreign substance among the polarizing plate foreign substances is not detected because it does not reflect light. Further, light is incident on the panel to be inspected from a diagonally upper side on the other substrate side by a reflection light source, and the polarization axis of the polarizing plate attached to the other substrate side by the imaging unit is reflected by the reflected light of the light. Through the polarization axis orthogonal to the light path, that is, by inserting a polarizing filter in the optical path of the reflected light and photographing in the crossed Nicols state, the surface foreign matter and surface scratches of the panel to be inspected are reflected as light and detected as a bright image The At this time, the transparent foreign substance among the foreign substances of the polarizing plate is not detected because the reflected light is blocked by the polarizing filter in the crossed Nicol arrangement after the reflected light is polarized by the polarizing plate. Therefore, among the dark images detected by the transmitted light image, those that are not detected by the parallel Nicol state image by the reflected light are the polarizing plate black foreign matter, detected by the parallel Nicol state image by the reflected light, and Those that were not detected from the image of the crossed Nicols state by the reflected light are the transparent polarizers. Therefore, by comparing the image by the transmitted light, the image of the parallel Nicol state by the reflected light, and the image of the crossed Nicol state by the reflected light, the polarizing plate foreign matter including the polarizing plate black foreign matter and the polarizing plate transparent foreign matter and the panel to be inspected. Since the surface foreign matter and the surface scratch are distinguished, the polarizing plate foreign matter interposed between the liquid crystal display panel and the polarizing plate is reliably detected without lighting the liquid crystal display panel itself.

  A transparent protective film is provided on the surface of each polarizing plate of the panel to be inspected, and a phase difference adjusting unit for canceling the phase difference in the protective film is provided between the panel holding unit and the polarizing filter. It may be.

  According to the above configuration, since the phase difference adjusting unit is provided between the panel holding unit and the polarizing filter, even if the reflected light of the polarizing plate foreign matter becomes elliptically polarized light by the protective film on the surface of the polarizing plate, The reflected light returned to the linearly polarized light reaches the polarizing filter.

  The phase difference adjusting unit may include a variable phase difference layer whose phase difference amount can be electrically controlled.

  According to the above configuration, for example, by using a liquid crystal layer as the variable retardation layer and adjusting the applied voltage of the liquid crystal layer, the retardation amount can be controlled according to the protective film on the surface of the polarizing plate. become.

  An optical filter may be provided between the transmissive light source and the panel holding unit to equalize the luminance of each pixel in the panel to be inspected.

  According to said structure, since the brightness | luminance of each pixel of RGB of a to-be-inspected panel is equal in the image image | photographed with an imaging part, the effect of this invention is show | played effectively.

  The reflected light source may be configured to supply light from at least two directions to the panel to be inspected.

  According to the above configuration, since the reflected light source supplies light obliquely from at least two directions to the panel to be inspected, it is possible to detect even surface scratches formed in any direction.

  The reflective light source may be configured to supply light of a single wavelength.

  Here, since the state of elliptically polarized light by the protective film on the surface of the polarizing plate depends on the wavelength of the light, if the reflection light source supplies light of a single wavelength as in the above configuration, the surface of the polarizing plate The elliptically polarized light by the protective film is more reliably returned to linearly polarized light by the phase difference adjusting unit.

  In addition, a liquid crystal display panel inspection method according to the present invention includes a pair of substrates disposed opposite to each other, and a liquid crystal layer provided between the pair of substrates, and a polarizing plate is provided on the surface of each substrate. Is a liquid crystal display panel inspection method for detecting foreign matter between each of the substrates and the polarizing plate with respect to each of the liquid crystal display panels to which light is attached. A transmitted light observing step of observing the transmitted light from the other substrate side, and polarized light that is incident on the other substrate side obliquely from above and the reflected light of the light is attached to the other substrate side Reflected light parallel Nicol observation step for observing from the other substrate side through the polarization axis of the plate, and making light incident from obliquely above the other substrate side, and reflecting the reflected light to the other substrate side Of the attached polarizing plate Through polarization axes perpendicular to the optical axis; and a reflected light cross Nicol observation step of observing from the other substrate side.

  According to the above method, the liquid crystal display panel to which the polarizing plate is attached, that is, the panel to be inspected, first, in the transmitted light observation step, light is incident from one substrate side and the transmitted light of the light is transmitted. By observing the above, the surface foreign matter and surface scratches of the panel to be inspected, and the polarizing plate foreign matter between the substrate constituting the panel to be inspected and the polarizing plate are detected as a dark image by blocking the transmitted light. Subsequently, in the reflected light parallel Nicol observation step, light is incident on the panel to be inspected from obliquely above the other substrate side, and the reflected light of the light is polarized on the other substrate side. By observing in a parallel Nicol state via a polarization axis parallel to the axis, a transparent transparent foreign substance is detected as a bright image by reflecting light from the surface foreign matter and surface scratches of the panel to be inspected and the polarizing plate foreign matter. . At this time, an opaque black foreign substance among the polarizing plate foreign substances is not detected because it does not reflect light. Further, in the reflected light crossed Nicols observation step, light is incident on the panel to be inspected obliquely from the upper side of the other substrate side, and the polarization axis of the polarizing plate attached to the other substrate side is reflected. By observing in a crossed Nicols state through a polarization axis perpendicular to the surface, foreign matter and surface scratches on the panel to be inspected are reflected as light and detected as a bright image. At this time, the transparent foreign matter among the polarizing plate foreign matters is not detected because the reflected light is blocked by the polarization axis of the crossed Nicol arrangement after the reflected light is polarized by the polarizing plate. Therefore, among the dark images detected by observing transmitted light, those that were not detected by observing the reflected light in the parallel Nicol state are polarizing plate black foreign objects, and are detected by observing the reflected light in the parallel Nicol state. And what is not detected by observation of the reflected light in the crossed Nicols state is a polarizing plate transparent foreign matter. Therefore, by comparing the transmitted light and each reflected light from the inspected panel observed in each step of the transmitted light observation step, the reflected light parallel Nicol observation step, and the reflected light crossed Nicol observation step, Since the polarizing plate foreign matter including the transparent plate foreign matter is distinguished from the surface foreign matter and surface scratch of the panel to be inspected, the polarizing plate foreign matter interposed between the liquid crystal display panel and the polarizing plate without turning on the liquid crystal display panel itself. Is reliably detected.

  According to the present invention, the image (observation) by transmitted light, the image (observation) by reflected light through the polarization axis of the attached polarizing plate, and the polarization axis orthogonal to the polarization axis of the attached polarizing plate are used. Since the foreign matter is detected by the image (observation) by the reflected light, the polarizing plate foreign matter interposed between the liquid crystal display panel and the polarizing plate can be reliably detected without turning on the liquid crystal display panel itself.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment.

  FIG. 1 is a perspective view showing an inspection device 30 of a liquid crystal display panel 10 according to an embodiment of the present invention.

  First, the liquid crystal display panel 10 of the panel to be inspected will be described using the cross-sectional view of FIG.

  As shown in FIG. 2, the liquid crystal display panel 10 is provided between a pair of substrates (for example, the active matrix substrate 1 and the counter substrate 2) disposed opposite to each other and the active matrix substrate 1 and the counter substrate 2. The polarizing plate 4 is affixed on the surface of each substrate 1 and 2 opposite to the liquid crystal layer 3.

  An active matrix substrate (one substrate) 1 includes a glass substrate, a plurality of gate lines provided on the glass substrate so as to extend in parallel to each other, and a plurality of source lines provided so as to be orthogonal to the gate lines. A thin film transistor (TFT) provided as a switching element at each intersection of a gate line and a source line, a pixel electrode provided in each region surrounded by a pair of adjacent gate lines and source lines, and each pixel electrode And an alignment film provided so as to cover the surface. Each pixel electrode constitutes a pixel which is the minimum unit of an image and is arranged in a matrix to constitute a display area.

  The counter substrate (the other substrate) 2 is provided to cover the glass substrate, the color filter layer provided on the glass substrate, the overcoat layer provided to cover the color filter layer, and the overcoat layer. A common electrode, and an alignment film provided so as to cover the common electrode.

  The liquid crystal layer 3 includes nematic liquid crystal molecules having electro-optical characteristics.

  The polarizing plate 4 is disposed opposite to each other, and is formed of a pair of supports formed of a triacetyl cellulose film or the like, and a polyvinyl alcohol film dyed with iodine provided between the supports. A polarizer layer 4a including a polarizer having a directional polarization axis, a transparent protective film 4b provided on the surface of one support, and an active matrix substrate 1 or counter substrate provided on the surface of the other support 2 is provided with an adhesive layer for attaching to the surface of 2.

  Further, in the liquid crystal display panel 10, in each pixel, when the TFT is turned on by a gate signal from the gate line, a source signal is sent from the source line and a predetermined charge is written to the pixel electrode through the TFT. Thus, a potential difference is generated between the pixel electrode and the common electrode, and a predetermined voltage is applied to the liquid crystal layer 3. In the liquid crystal display panel 10, an image is displayed by adjusting the transmittance of light incident from the outside using the fact that the alignment state of the liquid crystal molecules changes according to the magnitude of the applied voltage.

  Furthermore, the liquid crystal display panel 10 injects and seals the liquid crystal material constituting the liquid crystal layer 3 between the produced active matrix substrate 1 and the counter substrate 2, respectively, and then each of the active matrix substrate 1 and the counter substrate 2. It is manufactured by sticking the polarizing plate 4 to the surface via an adhesive layer. In the liquid crystal display panel 10, as shown in FIG. 2, when the polarizing plate 4 is attached, a polarizing plate foreign material 13 is sandwiched between the active matrix substrate 1 and the counter substrate 2 and the polarizing plate 4, There is a possibility that the surface foreign matter 11 adheres to the plate 4 or the surface scratch 12 is formed.

  Below, the inspection apparatus 30 of this embodiment which inspects the liquid crystal display panel 10 of the said structure is demonstrated.

  As shown in FIG. 1, the inspection device 30 includes a transmission illumination 21, an optical filter 22, a stage 15, a reflection light source 23, a variable phase difference plate 24, a polarization filter 25, and an imaging unit 26 in order from the bottom.

  The stage 15 is a panel holding unit for holding the liquid crystal display panel 10 from the lower side, and is an opening that is opened in accordance with the display area of the liquid crystal display panel 10 that is held so that light from the transmission illumination 21 can be transmitted. (Not shown).

  The transmitted illumination 21 is a light source that is provided below the stage 15 and supplies light from the lower surface side to the liquid crystal display panel 10 on the stage 15.

  The optical filter 22 is an optical element that is provided between the stage 15 and the transmissive light source 21 and that equalizes the luminance of each of the RGB pixels in the liquid crystal display panel 10.

  The reflected light source 23 is provided above the stage 15 and is a light source for supplying light obliquely from at least two directions to the liquid crystal display panel 10 on the stage 15 from the upper surface side. According to this, even the surface flaw 12 formed in every direction on the liquid crystal display panel 10 can be reliably detected. The reflection light source 23 is configured to supply light having a single wavelength (for example, about 630 nm). Here, since the state of elliptically polarized light by the protective film 4b on the surface of the polarizing plate 4 depends on the wavelength of light, that is, wavelength dispersion is performed, the reflected light source 23 supplies light of a single wavelength. The elliptically polarized light by the protective film 4b on the surface of the polarizing plate 4 can be more reliably returned to linearly polarized light by the variable retardation plate 24. In the present embodiment, the reflection light source 23 is arranged in a U shape, and light is supplied to the liquid crystal display panel 10 from three directions.

  The variable phase difference plate 24 is provided above the stage 15, and a phase difference adjustment unit for canceling the phase difference in the protective film 4 b constituting the polarizing plate 4 on the upper surface side of the liquid crystal display panel 10 held on the stage 15. It is. Further, as shown in the cross-sectional view of FIG. 3, the variable retardation plate 24 is formed as a variable retardation layer between a pair of glass substrates 24a and 24b arranged to face each other and the glass substrates 24a and 24b. A liquid crystal layer 24c is provided, and a frame 24d is provided so as to hold the peripheral edge of the laminated body of the glass substrates 24a and 24b. Furthermore, in the variable retardation plate 24, a transparent electrode 24e is provided on the liquid crystal layer 24c side of each of the glass substrates 24a and 24b, and a predetermined voltage is applied to the liquid crystal layer 24c via each transparent electrode 24e. The orientation state of 24c changes and the necessary phase difference is created. According to this, even if the reflected light R of the polarizing plate foreign material 13 becomes elliptically polarized light by the protective film 4 b on the surface of the polarizing plate 4, the reflected light R returned to the linearly polarized light reliably reaches the polarizing filter 15. be able to.

  The polarization filter 25 is provided between the variable retardation plate 24 and the imaging unit 26 and has a polarization axis orthogonal to the polarization axis of the polarizing plate 4 attached to the upper surface side of the liquid crystal display panel 10 on the stage 15. The optical element can be inserted into and removed from the optical path of the reflected light R supplied from the reflection light source 23 and reflected by the surface of the liquid crystal display panel 10 on the stage 15.

  The imaging unit 26 is provided above the stage 15 and includes a lens unit 26a and a camera unit 26b. The imaging unit 26 is supplied from the transmissive light source 21 and is transmitted through the liquid crystal display panel 10 on the stage 15, and the reflected light source. 23 is used to take an image of the reflected light R supplied from 23 and reflected by the surface of the liquid crystal display panel 10 on the stage 15.

  Next, operation | movement of the test | inspection apparatus 30 of the said structure is demonstrated for every usage form using FIG.4, FIG.5, FIG.6 and FIG. Here, FIG. 4 is an explanatory view showing the operation of the inspection apparatus 30 when the transmissive light source 21 is used, and FIG. 5 is an explanatory view showing the operation of the inspection apparatus 30 when the reflected light source 23 is used. FIG. 6 is an explanatory view showing the polarization state of the reflected light R by the surface foreign matter 11, and FIG. 7 is an explanatory view showing the polarization state of the reflected light R by the polarizing plate transparent foreign matter 13b.

  When the transmissive light source 21 is used, as shown in FIG. 4, the light L1 is incident from the lower surface side of the liquid crystal display panel 10 by the transmissive light source 21, and an image of the transmitted light T of the light L1 is taken by the imaging unit 26. Thus, the surface foreign matter 11, the surface scratch 12, and the polarizing plate foreign matter 13 included in the liquid crystal display panel 10 block the transmitted light T and are detected as dark images.

  When the reflection light source 23 is used, as shown in FIG. 5 (when the polarization filter 25 is a solid line), the reflection light source 23 causes the light L2 to enter from an obliquely upper side on the upper surface side of the liquid crystal display panel 10, and the reflection of the light L2 A parallel Nicol state in which an image of the light R is extracted by the imaging unit 26 through the polarization axis of the polarizing plate 4 attached to the substrate on the upper surface side of the liquid crystal display panel 10, that is, the polarizing filter 25 is removed from the optical path of the reflected light R. The transparent transparent foreign matter (13b) among the surface foreign matter 11, the surface scratch 12, and the polarizing plate foreign matter 13 included in the liquid crystal display panel 10 reflects light and is detected as a bright image.

  Further, in FIG. 5, as in the case where the polarizing filter 25 is a two-dot chain line, the polarization axis of the polarizing plate 4 in which the image by the reflected light R is pasted on the substrate on the upper surface side of the liquid crystal display panel 10 by the imaging unit 26. The surface foreign matter 11 (and the surface flaw 12) included in the liquid crystal display panel 10 is obtained through the polarization axis perpendicular to the optical axis, that is, by inserting the polarizing filter 25 in the optical path of the reflected light R and photographing in the crossed Nicols state. As shown in FIG. 6, the reflected light R reflected from the light L2 is detected as a bright image through the non-polarized light NP by the variable phase plate 24 and the linearly polarized light LP by the polarizing filter 25. At this time, the transparent foreign matter 13b of the polarizing plate foreign matter 13 is reflected by the linearly polarized light LP1 by the polarizer layer 4a, the elliptically polarized light EP by the protective film 4b, and the variable retardation plate 24, as shown in FIG. The light passes through the linearly polarized light LP2 and is not detected because it is blocked by the polarizing filter 25 in a crossed Nicols arrangement with respect to the polarization axis of the polarizing plate 4a. 6 and 7, LA indicates the fast axis in the protective film 4b and the variable phase difference plate, and DA indicates the slow axis.

  Next, a method for inspecting the liquid crystal display panel 10 using the inspection apparatus 30 having the above configuration will be described. Note that the inspection method of this embodiment includes a transmitted light observation step, a reflected light parallel Nicol observation step, and a reflected light crossed Nicol observation step.

<Transmitted light observation process>
First, the liquid crystal display panel 10 is held on the stage 15 so that, for example, the active matrix substrate 1 side faces down.

  Subsequently, the transmission light source 21 causes the light L1 to enter from the active matrix substrate 1 side, and the polarization filter 25 is inserted to adjust the phase difference of the variable retardation plate 24 so that the transmitted light T of the light L1 becomes the darkest. (Optimize).

  Thereafter, with the polarizing filter 25 pulled out, an image of the transmitted light T of the light L1 is taken by the imaging unit 26, whereby the surface foreign matter 11, the surface scratch 12 and the polarizing plate foreign matter on the counter substrate 2 side of the liquid crystal display panel 10 are captured. 13 (polarizing plate black foreign matter 13a and polarizing plate transparent foreign matter 13b) blocks transmitted light T and is detected as a dark image as shown in FIG.

<Reflected light parallel Nicol observation process>
As shown in FIG. 5, the light L2 is incident on the liquid crystal display panel 10 on the stage 15 from the diagonally upper side on the counter substrate 2 side, and an image of the reflected light R of the light L2 is captured by the imaging unit 26. A liquid crystal display is obtained by taking a picture in a parallel Nicol state through a polarization axis parallel to the polarization axis of the polarizing plate 4 attached to the counter substrate 2 side, that is, by extracting the polarizing filter 25 from the optical path of the reflected light R. The surface foreign matter 11, the surface scratch 12, and the polarizing plate transparent foreign matter 13b on the counter substrate 2 side of the panel 10 reflect the light L2 and are detected as a bright image as shown in FIG. At this time, the polarizing plate black foreign matter 13a is not detected because it does not reflect light.

<Reflected light crossed Nicols observation process>
As shown in FIG. 5, the light L2 is incident on the liquid crystal display panel 10 on the stage 15 from the diagonally upper side on the counter substrate 2 side, and an image of the reflected light R of the light L2 is captured by the imaging unit 26. A variable phase difference plate 24 optimized in the transmitted light observation step is disposed through a polarization axis orthogonal to the polarization axis of the polarizing plate 4 attached to the counter substrate 2 side, that is, in the optical path of the reflected light R. By inserting the polarizing filter 5 and photographing in the crossed Nicols state, the surface foreign matter 11 and the surface scratch 12 on the counter substrate 2 side of the liquid crystal display panel 10 reflect the light L2 and detect it as a bright image as shown in FIG. (See FIG. 6). At this time, as shown in FIG. 7, the polarizing transparent foreign matter 13 b is reflected by the polarizing film 4 and then elliptically polarized by the protective film 4 b and further optimized by the variable retardation plate 24. The light is returned to the linearly polarized light again and is not detected because it is blocked by the polarizing filter 25 in the crossed Nicols arrangement.

  As described above, the surface foreign matter 11, the surface scratch 12, the polarizing plate black foreign matter 13a, and the polarizing plate transparent foreign matter 13b on the counter substrate 2 side of the liquid crystal display panel 10 can be detected. Thereafter, the liquid crystal display panel 10 on the stage 15 is turned upside down, and the above-described transmitted light observation process, reflected light parallel Nicol observation process, and reflected light crossed Nicol observation process are performed. Surface foreign matter 11, surface scratches 12, polarizing plate black foreign matter 13a and polarizing plate transparent foreign matter 13b on the active matrix substrate 1 side can be detected.

  When the liquid crystal display panel 10 is specifically inspected, the display area of the liquid crystal display panel 10 is divided into, for example, four parts, and the front (counter substrate 2) side and the back (active matrix) are divided into the divided areas. The image by the transmitted light on the substrate 1) side and the image by the reflected light (parallel Nicol and crossed Nicol) are respectively taken.

  Thereafter, the captured images of the front side and back side transmitted light are subjected to data processing to extract defect candidates including surface foreign matter 11, surface scratch 12, polarizing plate black foreign matter 13a, and polarizing plate transparent foreign matter 13b, and their positions, Information such as area, size and gray value is stored.

  Next, the image data by the transmitted light on the front side and the image data by the transmitted light on the back side are compared, and the defect candidates that are not detected at the same position in both data are moved when the surface is reversed. The foreign object 11 is determined.

  Furthermore, while processing the image by the reflected light in crossed Nicols and referring to the data of the area corresponding to each defect candidate, if the average gray value of the area is brighter than a predetermined threshold, the defect Candidates are determined as surface foreign matter 11 and surface flaws 12 (on the front side image or on the back side if it appears in the front side image). Of the remaining defect candidates, the average gray value of the corresponding region in the image by the reflected light in the parallel Nicols on the front side and the back side appears brighter than a predetermined threshold (in the image on the front side). In other words, if it appears in the image on the front side or on the back side, it is determined as the polarizing plate transparent foreign matter 13b, and the remaining defect candidate is determined as the polarizing plate black foreign matter 13a. Here, the relationship between the defect candidates detected in each image and specific defects (surface foreign matter, surface scratch, polarizing plate black foreign matter, and polarizing plate transparent foreign matter) is as shown in Table 1 below. In Table 1, a circle indicates that it is detected in each corresponding image, and a cross indicates that it is not detected in each corresponding image.

  As described above, according to the inspection apparatus 30 and the inspection method for the liquid crystal display panel 10 of the present embodiment, the transmission light source 21 is first applied to the liquid crystal display panel (panel to be inspected) 10 to which the polarizing plate 4 is attached. By making the light incident from the active matrix substrate 1 side and taking an image of the transmitted light T of the light L1 with the imaging unit 26, the surface foreign matter 11 and the surface scratch 12 of the panel to be inspected 10, and the panel to be inspected 10 Polarizing plate foreign matter 13 (polarizing plate black foreign matter 13a and polarizing plate transparent foreign matter 13b) between the counter substrate 2 and the polarizing plate 4 that constitutes the polarizing plate 4 is detected as a dark image by blocking the transmitted light (transmitted light observation step) .

  Subsequently, the reflected light source 23 causes the light L2 to enter the panel 10 to be inspected obliquely from the counter substrate 2 side, and an image of the reflected light R of the light L2 is attached to the counter substrate 2 side by the imaging unit 26. The surface foreign matter 11 and the surface of the panel to be inspected 10 are photographed through a polarization axis parallel to the polarization axis of the polarizing plate 4, that is, by taking out the polarizing filter 25 from the optical path of the reflected light R and taking a picture in a parallel Nicol state. Of the scratches 12 and the polarizing plate foreign matter 13, the transparent polarizing plate transparent foreign matter 13b reflects light and is detected as a bright image. At this time, the opaque polarizing plate black foreign matter 13a among the polarizing plate foreign matters 13 is not detected because it does not reflect light (reflected light parallel Nicol observation step).

  Further, light L2 is incident on the panel 10 to be inspected obliquely from the counter substrate 2 side by the reflection light source 23, and an image of the reflected light R of the light L2 is pasted on the counter substrate 2 side by the imaging unit 26. When the polarizing filter 25 is inserted into the optical path of the reflected light R through the polarizing axis perpendicular to the polarizing axis of the polarizing plate 4 and photographed in a crossed Nicols state, the surface foreign matter 11 and surface scratches of the panel 10 to be inspected are obtained. 12 reflects light and is detected as a bright image. At this time, the polarizing plate transparent foreign matter 13b out of the polarizing plate foreign matter 13 is not detected because the reflected light R is blocked by the polarizing filter 25 in the crossed Nicols arrangement after being polarized by the polarizing plate 4 (reflected light crossed Nicol observation step). ).

  Therefore, the dark image detected by the transmitted light image that is not detected by the parallel Nicol state image by the reflected light is the polarizing plate black foreign substance 13a, and is detected by the parallel Nicol state image by the reflected light, And what is not detected by the image of the crossed Nicol state by reflected light is the polarizing plate transparent foreign material 13b. Therefore, by comparing the image by the transmitted light T, the image in the parallel Nicol state by the reflected light R, and the image in the crossed Nicol state by the reflected light R, the polarizing plate foreign matter including the polarizing plate black foreign matter 13a and the polarizing plate transparent foreign matter 13b. 13 and the surface foreign matter 11 and the surface scratch 12 of the panel 10 to be inspected are distinguished from each other between the liquid crystal display panel 10 and the polarizing plate 4 without lighting the liquid crystal display panel 10 itself using a driver chip or the like. The intervening polarizing plate foreign material 13 can be reliably detected.

  In the above embodiment, the liquid crystal display panel 10 to which the polarizing plate 4 before the mounting component such as the driver chip is attached is illustrated as an inspection. However, the present invention is applied after the mounting component such as the driver chip is attached. This can also be applied to the inspection of the liquid crystal display panel 10 to which the polarizing plate 4 is attached and the polarizing plate 4 alone.

  Furthermore, in the said embodiment, although illustrated about the test | inspection with respect to the liquid crystal display panel 10 with which the polarizing plate 4 which has the protective film 4b was affixed on the surface, this invention is a liquid crystal with which the polarizing plate without the protective film 4b was affixed. The present invention can also be applied to inspection for display panels.

  In the above embodiment, one liquid crystal display panel 10 is held on the stage 15, but the present invention holds each liquid crystal display panel 10 by holding a plurality of liquid crystal display panels 10 on the stage 15. You may inspect at the same time.

  As described above, the present invention cancels the influence of surface foreign matter and surface scratches and the protective film of the polarizing plate by image processing, and can reliably detect the foreign matter of the polarizing plate. It is useful for automatic inspection equipment that inspects automatically.

It is a perspective view of inspection device 30 concerning one embodiment of the present invention. It is sectional drawing of the to-be-inspected panel 10 test | inspected with the test | inspection apparatus 30. FIG. 4 is a cross-sectional view of a variable phase difference plate 24 that constitutes an inspection apparatus 30. FIG. It is explanatory drawing which shows operation | movement of the test | inspection apparatus 30 when using the transmissive light source 21. FIG. It is explanatory drawing which shows operation | movement of the test | inspection apparatus 30 when using the reflective light source 23. FIG. It is explanatory drawing which shows the polarization state of the reflected light R by the surface foreign material 11. FIG. It is explanatory drawing which shows the polarization state of the reflected light R by the polarizing plate transparent foreign material 13b. 3 is a captured image obtained by transmitted light photographed using the inspection apparatus 30. FIG. It is a picked-up image by reflected light (parallel Nicol) image | photographed using the test | inspection apparatus 30. FIG. It is a captured image by reflected light (crossed Nicols) photographed using the inspection apparatus 30.

Explanation of symbols

R Reflected light T Transmitted light 1 Active matrix substrate (one substrate)
2 Counter substrate (the other substrate)
3 Liquid crystal layer 4 Polarizing plate 4a Polarizer layer 4b Protective film 10 Liquid crystal display panel (panel to be inspected)
15 stage (panel holder)
21 Transmitted light source 22 Optical filter 23 Reflected light source 24 Variable phase difference plate (phase difference adjustment unit)
24c Liquid crystal layer (variable retardation layer)
25 Polarizing filter 26 Imaging unit 30 Inspection device

Claims (7)

A liquid crystal display panel comprising a pair of substrates disposed opposite to each other and a liquid crystal layer provided between the pair of substrates, and a polarizing plate attached to the surface of each of the substrates. An inspection apparatus for a liquid crystal display panel that detects foreign matter between a substrate and a polarizing plate,
A panel holding unit for holding the liquid crystal display panel as a panel to be inspected;
A transmission light source that is provided below the panel holding portion and supplies light from the one substrate side to the panel to be inspected;
A reflective light source that is provided above the panel holding portion and supplies light obliquely from the other substrate side to the panel to be inspected;
An image of transmitted light that is provided from the transmission light source and transmitted through the panel to be inspected, and an image of reflected light that is supplied from the reflection light source and reflected from the surface of the panel to be inspected is provided above the panel holding unit. And an imaging unit for
Between the panel holding unit and the imaging unit, there is a polarization filter that has a polarization axis perpendicular to the polarization axis of the polarizing plate attached to the other substrate side and can be inserted into and removed from the optical path of the reflected light. An inspection apparatus for a liquid crystal display panel, which is provided. The liquid crystal display panel inspection apparatus according to claim 1,
On the surface of each polarizing plate of the panel to be inspected, a transparent protective film is provided,
An inspection apparatus for a liquid crystal display panel, wherein a phase difference adjusting unit for canceling a phase difference in the protective film is provided between the panel holding unit and the polarizing filter. The inspection apparatus for a liquid crystal display panel according to claim 2,
The liquid crystal display panel inspection apparatus, wherein the phase difference adjusting unit includes a variable phase difference layer whose phase difference amount can be electrically controlled. The liquid crystal display panel inspection apparatus according to claim 1,
An inspection apparatus for a liquid crystal display panel, characterized in that an optical filter is provided between the transmissive light source and the panel holding portion to equalize the luminance of each pixel in the panel to be inspected. The liquid crystal display panel inspection apparatus according to claim 1,
The inspection apparatus for a liquid crystal display panel, wherein the reflected light source is configured to supply light from at least two directions to the panel to be inspected. The inspection apparatus for a liquid crystal display panel according to claim 2,
An inspection apparatus for a liquid crystal display panel, wherein the reflected light source is configured to supply light having a single wavelength. A liquid crystal display panel comprising a pair of substrates disposed opposite to each other and a liquid crystal layer provided between the pair of substrates, and a polarizing plate attached to the surface of each of the substrates. An inspection method for a liquid crystal display panel for detecting foreign matter between a substrate and a polarizing plate,
A transmitted light observation step of making light incident from the one substrate side and observing transmitted light of the light from the other substrate side;
Reflected light parallel in which light is incident from an oblique upper side on the other substrate side and the reflected light of the light is observed from the other substrate side via the polarization axis of a polarizing plate attached to the other substrate side Nicole observation process,
The light is incident from obliquely above the other substrate side, and the reflected light of the light is incident on the other substrate side through a polarization axis perpendicular to the polarization axis of the polarizing plate attached to the other substrate side. A method for inspecting a liquid crystal display panel, comprising: a reflected light crossed Nicols observation step for observing from a liquid crystal display.

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