KR100786753B1 - Device for detecting pixel state of flat-panel display - Google Patents

Abstract

An apparatus for detecting a state of a pixel in a flat display device and a method for manufacturing the apparatus are provided to check an electric state of the pixel using an electro-optical property of a TNLC(Twisted-Nematic Liquid Crystal) to detect whether the pixel is good or defective efficiently. A detecting apparatus is composed of a transparent electrode(12) and an upper alignment layer(16) formed on a rear surface of an upper glass substrate(10), a lower alignment layer(18) formed on a surface of a lower glass substrate(14), a TNLC formed between the upper alignment layer and the lower alignment layer, a reflection layer(26) formed on a rear surface of the lower glass substrate, and a glass block(30) and a polarization plate(32) formed on a surface of the upper glass substrate. A DC voltage is applied between the transparent electrode of the detecting apparatus and a common terminal of a flat display device, thereby respectively detecting field differences between the detecting apparatus and plural pixels of the flat display device.

Description

DEVICE FOR DETECTING PIXEL STATE OF FLAT-PANEL DISPLAY}

1 is a graph showing the transmittance of a pixel state detection apparatus using a conventional PDLC,

2 is a cross-sectional view showing an embodiment of a pixel state detection device of a flat panel display device according to the present invention;

3 is a view illustrating an operating principle of a pixel state detection device of the flat panel display shown in FIG. 2;

4 is a diagram illustrating an example in which the pixel state detection device of the flat panel display device shown in FIG. 2 is applied to the pixel state detection system of the flat panel display device;

5 is a graph illustrating transmittance of a pixel state detection device of the flat panel display shown in FIG. 2;

6 is a view showing an embodiment of a transparent electrode in a pixel state detection device of a flat panel display device according to the present invention;

<Explanation of symbols for the main parts of the drawings>

10: upper glass 12: transparent electrode

14 lower glass 16 upper alignment film

18 lower alignment film 20 liquid crystal

22, 24: sealant 26: reflecting film

28: adhesive layer 30: glass block

32: polarizing plate 122: ITO

124: insulator 300: flat display device

302, 306: normal pixel 304: bad pixel

308: electric field 310: detection device

312: DC power source 314: light source

316: optical separator 318: telecentric lens

320: CCD camera 322: image processor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a pixel state of a flat-panel display and a method of manufacturing the apparatus, in particular, in the production process of an active matrix liquid crystal display (AMLCD). An apparatus for detecting a state of a corresponding pixel by detecting the presence or absence of an electrical abnormality of each element on a thin film transistor (TFT) substrate, and a method of manufacturing the apparatus.

The operation principle of a device for inspecting a flat panel display device using PDLC (Polymer Dispersed Liquid Crystal) in US Pat.

The apparatus for inspecting a flat panel display in US Pat. No. 5,532,13 has a structure in which a reflective film, a lower indium-tin oxide (ITO), a PDLC layer, and an upper ITO are sequentially stacked. The reflective film, lower ITO, PDLC layer, and upper ITO are not shown in the figure.

In such a structure, when no voltage is applied to the lower and upper ITO, the PDLC is unevenly aligned. Thus, incident light provided from the upper ITO side is scattered at the upper ITO.

On the other hand, when the voltage is applied to the lower and upper ITO, the PDLC is uniformly aligned. Therefore, incident light provided from the upper ITO side passes through the upper ITO, the PDLC layer, and the lower ITO in turn and is reflected by the reflecting film.

By using such an operating principle, it is possible to detect whether or not each circuit corresponding to each pixel of the flat panel display is defective.

That is, the inspection apparatus is positioned on a surface of a flat panel display device (not shown in the drawing) in which a plurality of pixels are arranged in a matrix so as to maintain a predetermined distance from the surface of the flat panel display device. A high voltage is applied between the flat panel display device and the inspection device.

Accordingly, in the defective pixel region of the flat panel display device, since the electrical characteristics of the TFT corresponding to the defective pixel are not good, no electric field is formed in the PDLC layer of the defective pixel region. Therefore, since the PDLCs of the bad pixel regions are not uniformly aligned, the reflectance of the inspection apparatus is reduced in the bad pixel region.

On the other hand, in the normal pixel region of the flat panel display device, since the electrical characteristics of the TFT corresponding to the normal pixel are good, the electric field is well formed in the PDLC layer of the normal pixel region. Therefore, since the PDLCs of the normal pixel region are uniformly aligned, the reflectance of the inspection apparatus is increased in the normal pixel region.

Thereafter, a pre-installed charge-coupled device camera generates an electrical signal corresponding to the intensity of light reflected from the inspection apparatus.

The pre-installed image processor processes an electrical signal corresponding to the light intensity provided from the CCD camera, and displays an image according to the brightness of each pixel corresponding to each TFT array element formed in the flat panel display on a screen. do.

However, since the PDLC included in such an inspection apparatus requires an air gap of several micrometers in order to respond to an electric field, it must be maintained between several micrometers between the inspection apparatus and the flat display apparatus to be inspected. Therefore, there is a drawback that the inspection device is damaged by fine particles on the flat panel display.

In addition, due to PDLC characteristics, sensitivity is inferior to that of LC. Therefore, a high voltage must be applied between the flat panel display device and the inspection device. Even if a high voltage is applied between the flat display device and the inspection device, the electric field formed is small, so the distance between the inspection device and the flat display device should be small. As a result, as described above, since the distance between the inspection device and the flat display device is small, the inspection device is damaged by the fine particles on the flat display device.

FIG. 1 is a graph showing the transmittance of a conventional pixel state detection device using PDLC. PDLC shows an air gap of 12 μm between the flat display device under test and the detection device, and 10 au / around a bias voltage of 200 V. It can be seen that it has a V sensitivity and is significantly inferior to a twisted-nematic liquid crystal (TNLC) according to the present invention to be described below.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. In the production process of an active matrix type liquid crystal display device, the presence or absence of an abnormal pixel of a pixel is detected by detecting the presence or absence of an electrical abnormality of each element on a TFT substrate using the electro-optical characteristics of TNLC. SUMMARY OF THE INVENTION An object of the present invention is to provide a pixel state detection device for a flat panel display device and a manufacturing method thereof.

In order to achieve this purpose,

According to one embodiment of the present invention, a reflective film, a lower glass, a lower alignment film, a TNLC, an upper alignment film, a transparent electrode, and an upper glass are sequentially stacked; A glass block and a polarizing plate are sequentially stacked on the upper glass surface.

Preferably, the transparent electrode may have a shape consisting of a plurality of rectangular pixels having a matrix in which edges are connected to each other between adjacent pixels.

According to another aspect of the present invention, a reflective film, a lower glass, a lower alignment film, a TNLC, an upper alignment film, a transparent electrode, and an upper glass are laminated in this order; It is provided that the polarizing plate and the glass block are sequentially laminated on the upper glass surface.

Preferably, the transparent electrode may have a shape consisting of a plurality of rectangular pixels having a matrix in which edges are connected to each other between adjacent pixels.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view illustrating an embodiment of a pixel state detection device of a flat panel display device according to the present invention.

Such a detection device includes a reflective film 26, a lower glass (thickness 80 µm) 14, a lower alignment film (PI (Polyimide, polyimide)) 18, a liquid crystal (TNLC) 20, and an upper alignment film (PI) ( 16), a transparent electrode (ITO having a thickness of 400 GPa) 12, and an upper glass 10 are sequentially stacked. At this time, both sides of the lower alignment layer 18, the liquid crystal 20, and the upper alignment layer 16 are sealed.

The glass block 30 is adhered to the surface of the upper glass 10 by the adhesive layer 28, and the polarizing plate 32 is attached to the glass block 30. In this case, the polarizer 32 may be attached to the upper glass 10 instead of being attached to the glass block 30. The rest of the structure is as described above.

The transparent electrode 12 has a shape consisting of a plurality of rectangular pixels having a matrix in which edges are connected to each other between adjacent pixels.

The manufacturing method of the pixel state detection device of the flat panel display for each step is as follows.

First, a transparent electrode (ITO) 12 is deposited on the lower surface of the upper glass (Corning E2K 0.5t (thickness 0.5mm)) 10 to a thickness of 400 kV using a sputtering method.

Thereafter, as shown in FIG. 6, the transparent electrode 12 is patterned and an unnecessary portion is etched, so that the transparent electrode 12 is formed of a plurality of rectangular pixels having a matrix in which corners are connected to adjacent pixels. As such, the resolution of the pixel state detection according to the present invention is improved by forming the transparent electrode 12 in a shape consisting of a plurality of rectangular pixels having a matrix in which edges are connected between adjacent pixels. The size of each square pixel is appropriately 10 × 10 μm and the spacing of the square pixels is 5 μm. Here, reference numeral 122 denotes ITO and reference numeral 124 denotes an insulator.

On the surface of the transparent electrode 12 and on the upper surface of the lower glass (thickness of 100 μm or less) 14 and a region except for some regions on both sides, PIs which form an alignment force on the liquid crystal 20 in the post-process are respectively coated ( coating) to form upper and lower alignment layers 16 and 18, respectively. The partial region on both sides is an region to seal the liquid crystal 20 later.

In order to maximize the light efficiency, the surfaces of the upper and lower alignment layers 16 and 18 are rubbed at, for example, 55 degrees.

The upper and lower glasses 10 and 14 are bonded to each other with a cell gap of 3.9 μm so that the upper and lower alignment layers 16 and 18 face each other. Further, Δε of the liquid crystal 20 is 8.8 and Δn is 0.101.

The liquid crystal 20 is injected between the upper and lower alignment layers 16 and 18. The liquid crystal 20 uses TNLC for driving at low voltage.

Sealants 22 and 24 are sealed on the upper and lower alignment layers 16 and 18 and on both sides of the liquid crystal 20.

The lower glass 14 is slimmed to have a thickness of 100 μm or less. Slimming methods include etching and polishing, and one of them is used. Although slimming of the lower glass 14 is important to be as thin as possible, it is preferable to slim the lower glass 14 so that the thickness of the lower glass 14 is 80 µm in view of the breakage and processing variation of the lower glass 14.

The reflective film 26 reflecting a specific wavelength, for example, a red wavelength band (660 nm) is coated on the surface of the lower glass 14.

The glass block 30 is adhered to the surface of the upper glass 10 using the adhesive layer 28.

A 25 degree polarizing plate 32 is attached to the surface of the glass block 30. In this case, the polarizing plate 32 of 25 degrees may be attached to the surface of the upper glass 10 instead of attaching to the surface of the glass block 30. The rest of the process is as described above.

The operation of the pixel state detection device of the flat panel display device according to the present invention is as follows.

3 is a view illustrating an operating principle of a pixel state detection device of the flat panel display shown in FIG. 2.

First, FIG. 3 illustrates a liquid crystal behavior and an optical path when a direct current voltage is not applied between the transparent electrode and the test flat panel display. Since the liquid crystal maintains an initial twist state, the light incident from above is reflected through the reflective film. It is not reflected. That is, light incident through the polarizing plate passes through the liquid crystal layer and is reflected by the reflective film, and maintains 90 degrees while passing through the liquid crystal layer again. Therefore, when the incident light is reflected by the reflective film and passes through the liquid crystal, it cannot be transmitted through the polarizing plate because of the angle formed with the polarizing plate.

Next, FIG. 3 shows a liquid crystal behavior and an optical path when a direct current voltage is applied between the transparent electrode and the test flat panel display. As the liquid crystal behaves, there is no change in the optical path. It is reflected by the light as it passes through the polarizing plate. The light passed in this way is sensed by the CCD camera via the optical device and then processed by the image processor. Since an image corresponding to the image processed signal is displayed on the screen, the user can visually check whether the pixels and the TFTs formed in the test flat display device are defective.

4 is a diagram illustrating an example in which the pixel state detection device of the flat panel display device illustrated in FIG. 2 is applied to the pixel state detection system of the flat panel display device. In this case, the detection device 310 refers to a pixel state detection device of the flat panel display device illustrated in FIG. 2.

First, a DC power supply (bias voltage) 312 is applied between the transparent electrode 12 of the detection device 310 and the common terminal of the TFT array substrate formed on the planar display device 300 to be inspected. A plurality of TFTs respectively corresponding to the plurality of pixels 302, 304, and 306 formed in the display device 300 are driven. In this case, the detection device 310 is in a state of being close to the surface of the flat panel display device 300.

Accordingly, each electric field 308 is formed between the plurality of pixels 302, 304, and 306 formed in the flat panel display device 300 and the detection device 310. In this case, the difference between the electric fields between the normal pixels 302 and 306 and the defective pixel 304 having an electrical defect is formed differently.

In response to the difference in the electric field being formed differently, the reflectance of the light provided through the light splitter 316 from the light source 314 is different. As a result, each light reflected according to its different reflectance passes through the optical separator 316 and is provided to the CCD camera 320 through a telecentric lens 318.

The CCD camera 320 reduces and condenses the light provided through the telecentric lens 318 according to its CCD size.

In the CCD camera 320, each CCD element receives different amounts of light and converts each light into an electrical analog signal, and amplifies each analog signal through each amplifier, and each A / D converter. The analog / amplified analog signal is converted into a digital signal through an analog / digital converter and provided to the image processor 322.

The image processor 322 performs voltage image processing on the digital signal provided from the CCD camera 320 and detects a value out of a predetermined limit value on the program as a defective pixel having an electrical defect, for example, as shown in the screen 324. Display.

FIG. 5 is a graph illustrating transmittance of the pixel state detection device of the flat panel display device illustrated in FIG. 2. The TNLC shows a sensitivity of 37.5 au / V at an air gap of 20 μm and a bias voltage of 100 V between the flat display device and the detection device. Have That is, it can be seen that the TNLC according to the present invention exhibits sensitivity of about 3 to 4 times that of the conventional PDLC.

Therefore, the TNLC detection apparatus of the present invention can secure a much better defect detection rate while maintaining a larger air gap than the conventional PDLC detection apparatus.

The technical spirit of the present invention has been described above with reference to the accompanying drawings, but this is by way of example only and not intended to limit the present invention. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

As described above, the use of TNLC in the pixel state detection device of the flat panel display device according to the present invention improves the sensitivity of the liquid crystal in response to an electric field formed between the flat panel display device and the detection device. Therefore, since the air gap between the flat display device and the detection device can be increased, it is possible to prevent the detection device from being damaged by the particles present on the flat display device. In addition, it is possible to detect the minute characteristic difference between the TFT elements formed in the flat panel display device with improved sensitivity, and to detect spots caused by the pixel defect and the characteristic difference between adjacent pixels.

In addition, by preventing the detection device from being damaged by the particles, productivity is increased by reducing the replacement cost and equipment down time caused by the detection device damage in the TFT liquid crystal display manufacturing line.

Claims (6)

A transparent electrode and an upper alignment layer are formed on an upper surface of the upper glass, a lower alignment layer is formed on a lower glass surface, a TNLC is formed between the upper alignment layer and a lower alignment layer, and a reflective film is formed on the lower surface of the lower glass. Glass blocks and polarizers are formed in this order to form a detection device, The common terminal of the transparent electrode of the detection device and the flat panel display as the pixel state detection object are applied with a DC power source, And detecting respective electric field differences between the detection device and the plurality of pixels of the flat panel display device. A transparent electrode and an upper alignment layer are formed on an upper surface of the upper glass, a lower alignment layer is formed on a lower glass surface, a TNLC is formed between the upper alignment layer and a lower alignment layer, and a reflective film is formed on the lower surface of the lower glass. Polarizing plates and glass blocks are formed in this order to form a detection device, The common terminal of the transparent electrode of the detection device and the flat panel display as the pixel state detection object are applied with a DC power source, And detecting respective electric field differences between the detection device and the plurality of pixels of the flat panel display device. The method according to claim 1 or 2, The transparent electrode is a pixel state detection device of a flat panel display device, characterized in that the shape consisting of a plurality of rectangular pixels in the form of a matrix, the corners of the adjacent pixels connected to each other. (a) forming a transparent electrode on the lower surface of the upper glass; (b) forming upper and lower alignment layers on the surface of the transparent electrode, the upper surface of the lower glass, and regions except for some regions on both sides; (c) rubbing the surfaces of the upper and lower alignment layers; (d) bonding the upper and lower glasses so that the upper and lower alignment layers face each other; (e) injecting TNLC between the upper and lower alignment layers; (f) sealing the sealant on both sides of the upper and lower alignment layers and the TNLC; (g) slimming the bottom glass; (h) forming a reflective film on the surface of the lower glass; (i) forming a glass block on the surface of the upper glass; (j) forming a polarizing plate on the surface of the glass block. (a) forming a transparent electrode on the lower surface of the upper glass; (b) forming upper and lower alignment layers on the surface of the transparent electrode, the upper surface of the lower glass, and regions except for some regions on both sides; (c) rubbing the surfaces of the upper and lower alignment layers; (d) bonding the upper and lower glasses so that the upper and lower alignment layers face each other; (e) injecting TNLC between the upper and lower alignment layers; (f) sealing the sealant on both sides of the upper and lower alignment layers and the TNLC; (g) slimming the bottom glass; (h) forming a reflective film on the surface of the lower glass; (i) forming a polarizing plate on the surface of the upper glass; (j) forming a glass block on the surface of the polarizing plate. The method according to claim 4 or 5, In the step (a), the transparent electrode is a pixel state detection device manufacturing method of the flat display device, characterized in that formed in the shape consisting of a plurality of rectangular pixels of the matrix form the edges are connected to each other.

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