JP3126233B2 - Inspection equipment for liquid crystal display panel substrates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting a liquid crystal display panel substrate for inspecting a defect which may occur in a liquid crystal display panel substrate used for, for example, television image display.

[0002]

2. Description of the Related Art In recent years, various color televisions employing a liquid crystal color panel for image display have been put to practical use. This liquid crystal color panel uses a polycrystalline silicon thin film transistor (T
(FT) A quartz glass substrate on which an array is formed, and a liquid crystal display panel substrate in which liquid crystal is sealed between the quartz glass substrate and a transparent glass substrate on which a color filter is formed, and an image is displayed in a twisted nematic mode. It has become. Such a liquid crystal color panel generally employs an active matrix system which is advantageous for achieving a large area and a high density, and is currently being put to practical use from a relatively small one. A liquid crystal color panel using this active matrix system is manufactured as follows. First, after manufacturing a liquid crystal display panel substrate, the transparent glass substrate is arranged on the panel substrate via a spacer, and then, liquid crystal is sealed in a gap between the liquid crystal display panel substrate and the transparent glass substrate. . Many of the liquid crystal color panels manufactured in this way have a number of pixels ranging from 250,000 to 500,000. At present, a liquid crystal color panel having a number of pixels of 1,000,000 or more is also manufactured.

[0003]

By the way, in order to form a wiring to a pixel electrode provided for each of a large number of pixels on a substrate, various film forming processes are required in a clean room in which dust and the like are extremely reduced. Done. However, when the width of the pixel or the wiring is extremely narrowed, the presence of a slight amount of micro dust contained in the manufacturing atmosphere gives a disconnection defect or a short-circuit defect to the wiring of the pixel electrode. For example, about 10 defective pixels per liquid crystal display panel substrate are allowed, and if there are more defective pixels, it is presently regarded as a product defect. In other words, it is extremely difficult to reduce the number of defective pixels below the allowable limit in the current manufacturing technology. Therefore, a liquid crystal panel having a large number of pixels necessarily has a high defect rate. It also contributes to the high price.

Conventionally, as a method for inspecting a liquid crystal display panel substrate, a method using a prober after manufacturing the substrate has been known. However, this method involves too many pixels to be inspected, which greatly reduces the number of inspection steps. Since it takes a long time, there is a problem in cost and it is not practical. For this reason, the inspection of the liquid crystal display panel substrate is not performed in the manufacturing process, and when the substrate manufacturing is completed, power is supplied to each panel substrate, and the operating state at this time is visually inspected to judge pass / fail. Therefore, even if a defect is revealed in this visual inspection, it cannot be returned to the manufacturing process, and the defective product is discarded, which is a poor yield of the liquid crystal display panel. In addition, there is a disadvantage that a quantitative defect rate cannot be obtained by visual inspection. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has as its object to provide a liquid crystal display panel substrate inspection apparatus capable of quickly and quantitatively grasping a defect in the substrate before assembling the liquid crystal panel.

[0005]

According to the present invention, there is provided an electro-optical element whose light transmittance changes according to the intensity of an applied electric field;
A test voltage is applied between the electro-optical element and a liquid crystal display panel substrate disposed opposite to the lower part of the electro-optical element, and light is radiated onto the electro-optical element. In an inspection apparatus for inspecting a display panel substrate, voltage control means for controlling an applied polarity and a voltage level of the inspection voltage according to an imaging timing of an imaging means for imaging the electro-optical element, and frame data generated for each of the imaging timings And image input means for removing drift components and noise components of the frame data, converting the output of the image input means into voltage values, smoothing the converted image data, Image processing means for binarizing, and extracting and displaying defective pixels of the liquid crystal display panel substrate from the binarized image data It is characterized by comprising an extraction process means for

[0006]

According to the above arrangement, the voltage control means controls the polarity and the voltage level of the inspection voltage applied between the electro-optical element and the liquid crystal display panel substrate at each imaging timing, and the image input means controls the imaging timing. A plurality of frames of frame data generated each time are accumulated, and image data from which a drift component and a noise component have been removed is generated. Then, the image data representing the brightness is converted into a voltage value by the image processing means, which is smoothed and binarized. As a result, the quality of the pixels on the liquid crystal display panel substrate is identified, and the extraction processing means extracts defective pixels based on the binarized image data, and displays the defective pixels on the display. As a result, defective pixels on the liquid crystal display panel substrate can be quickly and quantitatively grasped.

[0007]

【Example】

A. Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram schematically showing an inspection apparatus according to one embodiment of the present invention. In this figure, 1 is a light source such as a halogen lamp, and 2 is an electro-optical element whose optical characteristics change according to an applied electric field. The electro-optical element 2 has a liquid crystal sheet 8 in which polymer dispersed liquid crystal is sealed.
And a light reflector 9 of a gold vapor-deposited film or a dielectric layer film formed on the bottom surface of the sheet 8, and a transparent thin-film electrode 2a adhered to the upper surface of the sheet 8. Reference numeral 3 denotes a CCD camera for capturing an image on the surface of the electro-optical element 2 having the above configuration. Reference numeral 4 denotes an image processing device which performs image processing based on a video signal supplied from the CCD camera 3 and displays the number and position of defective pixels on the liquid crystal display panel substrate 5 based on information obtained as a result. The details of the image processing device 4 will be described later.

The liquid crystal display panel substrate 5 installed on the table 26 has a well-known structure as shown in FIG. 2, and has a source and a gate terminal commonly connected to the thin film transistor 14 provided for each pixel. Wiring 10,
, 10 and gate wirings 11, ..., 11 are formed in a matrix, and a pixel electrode 13 is connected to each drain terminal of the transistor 14. In the figure, reference numerals 15,
Reference numeral 16 denotes a shorting bar that is connected to the source wiring 10 and the gate wiring 11 and prevents electrostatic breakdown of the thin film transistor 14. These shorting bars 1
Reference numerals 5 and 16 are formed in the manufacturing stage of the liquid crystal display panel substrate 5, and are cut and deleted in a later process after the manufacturing stage. Reference numeral 7 denotes a voltage application device for applying a predetermined bias voltage between the thin-film transparent electrode 2a and each pixel electrode 13 of the liquid crystal display panel substrate 5. In applying the bias voltage, the above-described shorting bars 15 and 16 are used.

Next, an outline of the inspection performed in the above configuration will be described. First, a predetermined level of bias voltage is supplied between the transparent thin-film electrode 2a and each pixel electrode 13 by the voltage application device 7. Here, the above-described source wiring 1
In the case where there is no disconnection or short circuit in 0 and the gate wiring 11 and the thin film transistor 14 operates normally, that is, when there is no defective pixel in the liquid crystal display panel substrate 5,
An electric field according to the bias voltage level is applied to the entire electro-optical element 2. In the electro-optical element 2 to which the electric field is applied, the enclosed liquid crystal molecules are aligned in the same direction, so that the liquid crystal sheet 8 transmits light. When light is emitted from the light source 1 in such a state, the light transmitted through the liquid crystal sheet 8 is reflected by the light reflector 9, and reflected light of uniform intensity is reflected by the CCD camera 3.
Caught in

On the other hand, when a defective pixel exists, the applied electric field at a portion corresponding to the pixel changes, and the light transmittance of the electro-optical element 2 changes accordingly. As a result, the CCD camera 3 captures a bright image in a pixel portion to which an electric field is normally applied and a dark image in a defective pixel portion. Then, the image processing device 4 performs image processing based on the above-described relationship based on the video signal supplied from the CCD camera 3, thereby extracting / displaying information such as the number and position of defective pixels. I have.

B. Next, the configuration of the above-described image processing apparatus 4 will be described with reference to FIG. In this figure, parts corresponding to the respective parts shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the figure, reference numeral 20 denotes an image processor. The image processor 20 performs A / D conversion of the video signal supplied from the CCD camera 3 to generate frame data, stores data for a plurality of frames in a frame buffer, and pre-processes the data read from the buffer. And outputs it as image data. The pre-processing is, for example, a process in which four frames of frame data are regarded as one scene, and noise reduction or binarization is performed on the one scene frame data. Reference numeral 21 denotes a host computer that controls each unit and performs image processing described below on image data supplied from the image processor 20. Reference numeral 22 denotes a peripheral device including a keyboard, a display device, an external storage device, and the like. The display device displays an image processing result supplied from the host computer 21, that is, a defect state of the liquid crystal display panel substrate 5.

Reference numeral 23 denotes a timing generator. The timing generator 23 generates and outputs a timing signal that defines an imaging timing for each frame based on a video synchronization signal supplied from the host computer 21. Reference numeral 24 denotes a pattern generator that generates a predetermined pattern signal according to the timing signal. This pattern signal is a signal for controlling the polarity of the bias voltage applied to each pixel electrode 13 for each frame, and for example,
When four consecutive frames are sequentially imaged to form one scene, the polarity of the bias voltage is set to “+”, “−”, “−”,
Change in the order of “+”. Then, the above-described voltage applying device 7 applies a bias voltage of a level specified by a level control signal supplied from the host computer 21 to
It is generated with a polarity corresponding to the pattern signal described above, and is applied to the transparent thin-film electrode 2a and each pixel electrode 13. Reference numeral 25 denotes a power control circuit that controls power supplied to the light source 1.

C. Operation of Image Processing Apparatus 4 Next, the operation of the image processing apparatus 4 having the above configuration will be described with reference to FIG. First, in a state where the inspection setup as shown in FIG. 1 is performed, when the power is turned on to the device 4, a control program is started, and various registers and memories are initialized, and then a standby state is set. In this state, when the operator performs a key input of a predetermined control command, the host computer 21 shifts to a setting mode in which various signals are supplied to each unit of the apparatus. In this setting mode, initial settings of the light source 1, the CCD camera 3, and the voltage applying device 7 are performed. Next, when a start switch (not shown) is operated by the operator, processing according to the flowchart shown in FIG. 4 is performed.

First, at step S1, the image processor 20 takes in a video signal, performs A / D conversion on the video signal, generates frame data for one screen, and stores this in a frame buffer. Then, the next step S2
Then, it is determined whether or not frame data for four frames has been captured. In this case, since data for four frames has not been fetched, the result of this determination is "NO", the process returns to step S1, and the next frame data is fetched. Thus, in steps S1 and S2,
This is repeated until data for four frames is obtained. By the way, these four frame data are respectively divided into frames A,
When frame B, frame C, and frame D are obtained, a bias voltage having a polarity corresponding to the above-described pattern signal is applied between the transparent thin-film electrode 2a and each pixel electrode 13 at the time of acquiring the frame data. For example, “+5 V” is supplied when capturing the frame A, “−5 V” is supplied when capturing the frame B, “−5 V” is supplied when capturing the frame C, and “+5 V” is supplied when capturing the frame D.

Next, in step S3, the four frame data thus captured is treated as one scene, and after averaging processing is performed after removing noise components from the data for one scene. This averaging process is a process for removing a drift component from data for one scene. The drift component has a property of linearly increasing with time when acquiring data for one scene. To remove such a drift component, the drift superimposed on each frame data is canceled based on the following equation. That is, X = {(A + s) − (B + 2s) − (C + 3s) + (D + 4s)]} / 2 = {A−B−C + D} / 2 where X represents the luminance of the drift-removed image, and s represents the drift. Represents a component. A to D represent the luminance in each frame pattern described above. As is clear from this equation, the drift component is canceled by calculating the above-described difference between the frames A and B and the sum of the frames C and D, and further calculating the average of these differences.

In step S4, the absolute value of the data from which the drift component has been removed is obtained, and the absolute value of the data is subjected to scale conversion. In this scale conversion, data representing a luminance level is converted into data representing a voltage. In this conversion, a first-order approximation is performed based on gain data (described later) of the liquid crystal display panel substrate 5 obtained prior to the inspection, and the data becomes voltage representing the voltage. Here, the gain data is data representing a luminance level when a reference bias voltage is applied to the panel substrate 5 and corresponds to a slope in a linear approximation. Next, in step S5, the images are smoothed by the spatial averaging process. The smoothing means that, for example, 3 × 3 pixels are taken from the pixels forming an image of one scene, and the pixel data (central value) of the upper, lower, left, right, and diagonal are taken with respect to the central pixel data (central value). ) Is reflected, for example, eight neighboring values and a central value are averaged with the same weight. When such smoothing is performed, noise components are removed from the image. Next, in step S6, a binarization process is performed on each pixel data. That is, each pixel data representing the voltage level is binarized by a predetermined threshold voltage, whereby the level of the voltage applied to each pixel is separated, and pixels having the threshold voltage or more are set to “1”, and other pixels are set to “1”. The pixel is set to “0”.

In step S7, an AND (logical product) process of the above-described binarization result and the pixel map is performed. This pixel map is a lattice pattern corresponding to the pixel cell size of the liquid crystal display panel substrate 5. Then, the lattice pattern and the binarized result processed in step S6 are superimposed by an AND process as an inter-image operation. This is because the binarization result is obtained by the CCD camera 3
Since the image data is based on the imaging pixels of the liquid crystal display panel substrate 5, the pixels are associated with the pixel cells of the liquid crystal display panel substrate 5. For example, 3 × 3 pixels (imaging pixels) are associated with the pixel cells of the liquid crystal display panel substrate 5. Next, in step S8,
Defective pixel cells of the liquid crystal display panel substrate 5 associated in this manner are extracted. Here, a defective pixel cell is one in which the binarization result of the center pixel of 3 × 3 pixels (imaging pixels) constituting the pixel cell is “0”, that is, does not reach a predetermined threshold voltage. Then, as a result of the extraction, the position and the number of defective pixels are displayed on the display device, and the process proceeds to the next step S9. In step S9,
A prompt as to whether or not to perform the next image sampling is displayed on the display device, and the operator performs a key input according to the prompt. Here, when the input to perform the next sampling is performed, the process returns to the above-described step S1 and the same operation is repeated. On the other hand, when a key input for terminating the inspection is performed, the inspection operation is completed. As described above, since the defective pixels of the liquid crystal front panel substrate 5 are automatically extracted by the image processing,
An extremely high-speed inspection can be performed, and moreover, in this inspection, defective pixels can be quantitatively grasped. Further, since such inspection is performed in-process, the yield is greatly improved.

In the above embodiment, a bias voltage having a predetermined pattern is applied. Alternatively, a modulation signal modulated at a predetermined frequency may be applied. In this case, a change in brightness of each pixel, for example, a decay time constant of a change in brightness is detected by image processing to determine the quality of the panel substrate.

[0019]

As described above, according to the present invention, the voltage control means controls the polarity and voltage level of the inspection voltage applied between the electro-optical element and the liquid crystal display panel substrate at each imaging timing. The image input means accumulates a plurality of frames of frame data generated at each imaging timing and generates image data from which a drift component and a noise component have been removed. Then, the image data representing the brightness is converted into a voltage value by the image processing means, which is smoothed and binarized. As a result, the quality of the pixel on the liquid crystal display panel substrate is identified, and the extraction processing means extracts the defective pixel based on the binarized image data and displays the defective pixel on the display. Can be quickly and quantitatively grasped. In addition, since this inspection is performed in-process, the effect of significantly improving the yield can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an outline of inspection according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a liquid crystal display panel substrate 5 in the embodiment.

FIG. 3 is a block diagram showing a configuration of an image processing apparatus 4 according to the embodiment.

FIG. 4 is a flowchart for explaining the operation of the embodiment;

[Description of Signs] 1 light source 2 electro-optical element 2a transparent thin film electrode 3 CCD camera 4 image processing device 5 liquid crystal display panel substrate 7 voltage application device 20 image processor 21 host computer 23 timing generator 24 pattern generator

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI G09F 9/00 352 G06F 15/62 405A (56) References JP-A-3-142498 (JP, A) JP-A 64-18073 (JP, A) JP-A-3-167490 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/84-21/958 G01M 11/00 G01R 31/00 G02F 1 /13

Claims (1)

(57) [Claims] 1. An inspection voltage is applied between an electro-optical element whose light transmittance changes according to an applied electric field intensity and a liquid crystal display panel substrate disposed under the electro-optical element. In an inspection apparatus that irradiates light onto the electro-optical element and inspects the liquid crystal display panel substrate according to the intensity of reflected light of the electro-optical element, the inspection is performed according to an imaging timing of an imaging unit that images the electro-optical element. Voltage control means for controlling the applied polarity and voltage level of a voltage, image input means for accumulating a plurality of frames of frame data generated at each of the imaging timings, and removing a drift component and a noise component of the frame data, Image processing means for converting the output of the image input means to a voltage value, smoothing the converted image data, and binarizing the image data; An inspection apparatus for a liquid crystal display panel substrate, comprising extraction processing means for extracting and displaying defective pixels of the liquid crystal display panel substrate from the binarized image data.