JP4705417B2 - Display panel inspection method and apparatus - Google Patents

Description

The present invention relates to a testing method and apparatus for de I spray panel, in particular, accuracy in the flat display panel represented by a plasma display panel, a liquid phosphor layer formed on a substrate pattern (in particular, the radius of curvature or height) The present invention relates to an inspection method and apparatus that can be inspected well.

  Usually, phosphors for R (red), G (green), and B (blue) are repeatedly applied in a stripe pattern on the back plate of the plasma display panel, but each phosphor is applied uniformly. If it is not worn, there will be problems such as color unevenness in which the luminance and color tone of the display are not uniform, or a dark spot that cannot be put into a light emitting state due to omission of coating.

  In order to prevent the back plate having a defect in the phosphor coating state from being bonded to the front plate, and if a defect occurs in the coating state, the defective part of the manufacturing process is immediately corrected to be defective. In order not to make the product, it is necessary to inspect immediately after applying the phosphor.

To inspect the application state of the liquid phosphor applied to the back plate of the plasma display panel, for example, the technique described in Patent Document 1 can be applied. In this technique, light is incident on a measurement surface, the reflected light is captured, and the amount of reflected light obtained is measured to inspect the coating amount.
JP 2003-75294 A

  However, the technique described in Patent Document 1 still has a problem that there are many false detections. That is, in the method of inspecting unevenness of the coating amount by injecting light into the measurement surface, capturing the reflected light, and measuring the intensity change of the obtained reflected light amount, the reflected light amount is exponential with respect to the coating amount. To change. In the inspection of coating unevenness, a high-pass filter is generally applied to a signal obtained to detect a change exceeding a threshold value as unevenness. For this reason, if the sensitivity of the reflected light intensity obtained with respect to the coating amount is not uniform, it may cause erroneous detection. In particular, in the case of a substrate having gentle coating unevenness over the entire substrate, the sensitivity is increased at a portion where the coating amount is large, leading to occurrence of erroneous detection. When erroneous detection occurs frequently, it is necessary to stop the line each time and check whether it is an actual defect or not, so that the operating rate of the manufacturing facility is lowered.

  Accordingly, an object of the present invention is to solve the above-described problems in the prior art, and to provide an inspection method and apparatus capable of accurately and accurately inspecting even a substrate having gentle coating unevenness over the entire substrate. The purpose is to increase the operating rate of the equipment and lower the manufacturing cost.

In order to solve the above problems, Oite the present invention, as the inspection method of the curved surface, and the illumination means and reflected at substantially the same angle as the incident light incident angle among emitted from the illuminating means to the measured curved light reflected A basic technical idea comprising a method for obtaining a curvature radius of a curved surface to be measured from an amount of reflected light and a curvature radius coefficient obtained by the imaging means, having an imaging means for mainly imaging light and a signal processing means. It is said.

  In particular, the technical idea according to the present invention is optimal for inspecting the pattern (particularly, the curvature radius and height) of the liquid phosphor layer formed on the substrate in the flat display panel as described above. That is, the display panel inspection method according to the present invention includes an illuminating unit and an imaging unit that mainly images light reflected from the illuminating unit and reflected from the illuminating unit at a substantially same angle as the incident light incident angle. And a signal processing means, the curvature radius of the liquid phosphor layer is obtained from the amount of reflected light and the curvature radius coefficient obtained by the imaging means, and the curvature radius and the upper interval between the partition walls on both sides of the liquid phosphor layer, The height of the liquid phosphor layer is calculated from the height of the partition wall.

  In this display panel inspection method, it is possible to measure the amount of reflected light for each liquid phosphor layer while relatively moving the substrate, the illumination means, and the imaging means in a direction intersecting the liquid phosphor layer.

Oite the present invention, as the inspection apparatus of the curved surface, and the illumination means, the imaging means mainly for imaging the light reflected at substantially the same angle as the incident light incident angle among emitted from the illuminating means to the measured curved light reflected a signal processing unit, and a condition input means for inputting at least the curvature radius coefficient, the apparatus characterized by determining the radius of curvature of the measured curved surface from the obtained reflected light and the curvature radius coefficient imaging means basic Technical idea.

  The display panel inspection apparatus according to the present invention includes an illuminating unit and an imaging unit that mainly captures light reflected from the illuminating unit and reflected from the illuminating unit on the liquid phosphor layer at substantially the same angle as the incident light incident angle. And a signal processing means, and a condition input means for inputting at least the curvature radius coefficient and the upper interval between the partition walls on both sides of the liquid phosphor layer, the amount of reflected light obtained by the imaging means and the input curvature radius coefficient, The apparatus is characterized in that at least one of the radius of curvature of the liquid phosphor layer and the height of the liquid phosphor layer is calculated from the partition upper space and the partition height.

  The display panel inspection apparatus may further include a scanning unit that relatively moves the substrate, the illuminating unit, and the imaging unit in a direction intersecting the liquid phosphor layer.

According to the inspection method and apparatus for engaging Lud I spray panel in the present invention, even for a substrate having a gentle uneven coating of the liquid phosphor layer across the substrate, less false detection with a sensitivity close to the visual accuracy High inspection can be performed. As a result, there is no need for confirmation of erroneous detection, and it becomes possible to increase the operating rate of the manufacturing facility and reduce the manufacturing cost.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a display panel inspection apparatus, particularly a plasma display panel inspection apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a back plate (substrate) of a plasma display panel (hereinafter also abbreviated as PDP) used for inspection. The PDP back plate 1 is shown in FIG. In this manner, phosphors 305, 306, and 307 for R (red), G (green), and B (blue) are repeatedly applied in order in a stripe shape.

  In the plasma display panel 300, as shown in FIG. 3, RGB phosphors 305, 306, and 307 are striped between barrier ribs 304 on a dielectric layer 303 on which address electrodes 302 are arranged on a back glass substrate 301. A front glass substrate 308 having a dielectric layer 310 on which display electrodes 309 are disposed and a protective film 311 is provided above the PDP back plate 1 that is repeatedly applied to the phosphor layer and the front plate. The space is filled with a discharge gas.

  The discharge gas is turned into plasma by the voltage applied between the display electrode 309 and the address electrode 302, and ultraviolet rays are generated. As a result, the phosphor layer at the selected position is colored, and depending on the combination of the coloring of each phosphor. Desired color display is performed.

  The plasma 312 is generated in the space between the phosphor layer and the front plate. Depending on the shape of the space, the amount of generated ultraviolet light changes, that is, the amount of display light changes. That is, if the phosphor shape is not uniform, color unevenness is caused. Therefore, it is necessary to make the shape of the phosphor layer uniform and keep the shape of the space uniform.

  Examples of methods for applying the RGB phosphors 305, 306, and 307 to the PDP back plate 1 include screen printing and nozzle application. In screen printing, as shown in the side view of FIG. 4, first, a mask screen 402 in which openings 403 having a predetermined width are provided at a pitch three times the pitch P is aligned with the PDP back plate 1. And arranged so as to face the partition wall 404. Next, a phosphor paste 405 (liquid phosphor) in which a phosphor of a predetermined emission color and a binder are mixed is discharged from the opening as shown in FIG. At this time, as the phosphor paste 405, one having a solid content concentration of 10 to 50% is used in order to provide a space for generating plasma as described above. In order to discharge this phosphor paste from the opening to the glass substrate side, the squeegee 401 is moved in the direction of the arrow. The amount of the phosphor paste discharged into the gap between the partition walls can be adjusted by the moving speed, angle, and pushing amount of the squeegee 401.

  In the nozzle coating method, as shown in the side view shown in FIG. 5, the discharge holes 503 provided in the base 501 at a pitch three times the pitch P are aligned with the PDP back plate 1 and face the partition wall 504. Arrange to do. Next, pressure is applied from the pressure application holes 502, the phosphor paste 505 is ejected from the ejection holes 503 and dropped into the partition walls 504, and the base 501 is moved in parallel to the partition walls 504 (in the depth direction of the drawing in FIG. 5). Then, the phosphor paste 505 is applied to the entire surface of the substrate. The phosphor paste used is the same as that used in the above screen printing. The amount of the phosphor paste discharged into the gap between the barrier ribs can be adjusted by the applied pressure.

  Next, the phosphor paste is dried and baked to remove the binder component and form a phosphor layer having a predetermined shape. FIG. 6A shows a cross-sectional view of the PDP back plate immediately after applying the phosphor paste (when the amount of the applied phosphor paste is large (601a) and small (601b), respectively), and FIG. 6 (b). Fig. 5 shows a cross-sectional view of the PDP back plate after drying and baking (in the case where the amount of the phosphor paste to be applied is large (602a) and small (602b), respectively). As can be seen from this figure, when the amount of the phosphor paste applied changes, the shape of the phosphor layer after firing and drying changes, and defects such as color unevenness and missing coating occur. Reasons for the amount of phosphor paste to be applied change include screen clogging in screen printing, scratches on the squeegee and poor adjustment of the phosphor coating device, nozzle nozzle clogging, and changes in applied pressure in nozzle coating. Can be considered. Once these defects are generated, they become continuous defects that occur continuously over all the substrates and cause a significant reduction in yield. It will be necessary to conduct an inspection while in liquid form.

  In addition, the rib space | interval of PDP is about 200-500 micrometers. If it is this space | interval, the surface of the apply | coated liquid fluorescent substance layer will become a circular arc as shown in FIG. 6a because of surface tension. In addition, when applying the liquid phosphor layer under conditions that are convex upward, the liquid phosphor may adhere to the top of the partition wall, resulting in a defect.

  FIG. 7A is a graph in which the substrate coated by the nozzle coating method is scanned across a partition groove with a confocal laser displacement meter, and the height of the liquid phosphor layer in each groove is plotted. . The height of the liquid phosphor layer is the distance between the lowest point of the liquid phosphor layer recess and the dielectric.

  Of the stripes 701a, 702a, and 703a having a small coating amount, the darkest appearance after commercialization is not 701a having the lowest liquid phosphor layer height but 702a having a large difference from the periphery (that is, moving average line). 702a) having the largest difference with respect to 704. This is due to a visual characteristic called “Mach effect”, which is low in sensitivity to gentle changes, but high in sensitivity to abrupt differences from the surroundings.

  As shown in FIG. 7B, by setting a threshold value for a graph obtained by normalizing the graph of FIG. 7A with a moving average, the visual sensitivity and the inspection sensitivity can be matched. This process is generally used when removing changes in formation and has the same effect as a high-pass filter.

  Actually, the confocal laser displacement meter has a problem that the scanning speed is slow and it is easy to be affected by vibration. Therefore, as in the present invention, light is incident on the substrate, the reflected light is captured, and the amount of reflected light obtained is obtained. Inspection by the method of measuring is desirable.

  Such defects in the application of the RGB phosphors 305, 306, and 307 to the PDP back plate 1 are inspected by the inspection apparatus shown in FIG. As will be described with reference to FIG. 1 again, the PDP back plate 1 is conveyed by the conveying means 2 provided with conveying rollers and the like, and the conveying means 2 is controlled by the drive control means 3. Above the transport means 2, an illumination means 4 and an imaging means 6 controlled by the lighting control device 5 are arranged. The drive control unit 3 is for scanning the imaging range of the imaging unit 6 over the entire surface of the PDP back plate 1 and transports the PDP back plate 1 at a constant speed. The illumination unit 4 irradiates the liquid phosphor layer coated on the PDP back plate 1 with light, and the regular reflection light reaches the imaging unit 6. As the illumination means 4, LED illumination, optical fiber illumination using a halogen lamp, or the like can be used, but LED illumination is desirable because a cooling fan is unnecessary and dust generation is not required. The imaging means 6 divides a certain range on the PDP back plate 1 into pixels, measures the regular reflection light intensity for each pixel, converts it into a video signal, and transmits it to the image processing device 7. In these imaging means, the light receiving elements are arranged one-dimensionally and are built in, and can output a one-dimensional image along the direction of the phosphor layer. The image processing device 7 is for detecting defects generated in the liquid phosphor layer. The image processing device 7 inputs a video signal picked up by the image pickup means 6 and performs image analysis using an image processing technique to detect defects. The image processed by the image processing device 7 can be displayed on the display device 8.

  FIG. 8 shows a comparison between a video signal (hereinafter referred to as a luminance signal) output from the imaging means 6 and a substrate. From the grooves e and k including the liquid phosphors 801 and 803 which are not normally applied, a large luminance signal is applied from the grooves b and h including the liquid phosphors 800 and 802 which are normally applied and have a flat surface shape. A luminance signal having a small value is obtained, and the same brightness as that of the grooves e and k can be obtained from the grooves a, c, d, f, g, i, j, and l not coated with the liquid phosphor. ing. Here, in the luminance signal waveform 820, the vertices of the luminance corresponding to the position of the groove to which the liquid phosphor is applied or the groove to be applied are designated as 810, 811, 812 and 813, respectively, and are hereinafter referred to as the luminance peak.

  In the PDP, since the liquid phosphor is applied at a predetermined interval, the luminance peaks 810, 811, 812, 813 of the obtained luminance signal waveform have a period corresponding to the application interval of the liquid phosphor. Appear at regular intervals. Therefore, a luminance peak at a point separated from a certain Nth luminance peak by a period from the luminance waveform 820 is extracted as the (N + 1) th luminance peak, and this is repeated for all luminance peaks to be applied to each groove on the substrate. The value of the luminance peak from the obtained liquid phosphor is obtained. The luminance peak value 840 having the luminance peaks 830, 831, 832, and 833 corresponding to the vertices 810, 811, 812, and 813 is obtained by using these luminance peak values as the representative luminance for each groove and connecting them in order. .

  Next, the relationship between the state of the liquid phosphor layer and the luminance peak is shown in FIG. 9 (FIG. 9A shows the application state of the liquid phosphor layer, and FIG. 9B shows the application amount and luminance in the corresponding application state. Shows the relationship with the peak). As shown in FIG. 9, when the gap between the barrier ribs is filled with the phosphor paste as in 904a, that is, when the upper surface of the liquid phosphor layer is flat, the luminance peak is maximized. When the discharge amount of the phosphor paste is smaller than this state, the upper surface of the liquid phosphor layer becomes a concave arc like 903a due to surface tension. Further, as the discharge amount of the phosphor paste decreases, the radius of the arc decreases (for example, the state of 902a), the video signal also decreases, and when there is no phosphor paste (for example, the state of 901a). The video signal has a minimum value such as 901b.

  Next, the result of measuring the luminance peak waveform for the substrate used in FIG. 7 is shown in FIG. FIG. 10B shows a graph obtained by normalizing the luminance peak waveform with a moving average value in order to match the visual and sensitivity in the same manner as described above. The signal variation on the right side of the graph is large because it is influenced by the sensitivity curve in FIG. 9B, and the sensitivity is extremely high in the portion where the coating amount is large. In FIG. 10B, the magnitudes of the signals 102b and 103b are switched, and if a threshold value is set to detect 102b, 103b that should not be detected is erroneously detected.

  As a result of intensive investigations to eliminate this false detection, the present inventors have derived from experiments that the luminance peak is proportional to the curvature radius of the concave portion of the liquid phosphor layer, and the liquid phosphor layer height and the liquid phosphor layer are derived from the curvature radius. The inventors reached the present invention by conceiving that the filling rate can be measured.

Since the luminance peak Kd is proportional to the radius of curvature R of the concave portion of the liquid phosphor layer, the following formula (1) is established. The curvature radius constant C is a constant determined from the substrate conditions, the optical system conditions, the light source intensity, and the paste reflectance, and is constant for the same measurement system.
Kd = C · R (1)
From this equation, by measuring with a confocal laser displacement meter in advance and measuring the luminance peak of the groove where the curvature radius R of the concave portion of the liquid phosphor layer is known, and obtaining the curvature radius constant C from the Kd at that time, The radius of curvature R can be obtained from the luminance peak Kd.

  Next, the liquid phosphor layer height hp can be obtained from the radius of curvature R and the substrate condition by the formula (2) (Equation 1).

  Furthermore, the filling rate V can be obtained from the equation (3) (Equation 2). This filling rate is proportional to the discharge amount of the phosphor paste. For this reason, for example, in the case of a nozzle coating method in which the discharge amount is controlled by compressed air, the filling rate can be easily adjusted to a predetermined filling rate by measuring the filling rate.

In addition, the board | substrate conditions (FIG. 11) in said Formula (2), (3) are as follows.
R: radius of curvature of paste surface w: upper partition wall spacing w ': lower partition wall spacing k: partition height

  As described above, according to the present invention, it is possible to perform a highly accurate inspection with a sensitivity close to visual observation with few false detections even on a substrate having gentle coating unevenness over the entire substrate.

  FIG. 12 shows an example of a plasma display panel back plate to be inspected by the inspection apparatus according to the present invention. In this example, a horizontal partition 313 extending in the horizontal direction is provided together with the partition 304 extending in the vertical direction.

It is a schematic block diagram of the inspection apparatus of the plasma display panel which concerns on one embodiment of this invention. It is a schematic plan view of a plasma display panel back plate. It is a partial longitudinal cross-sectional view of a plasma display panel. It is a longitudinal cross-sectional view which shows the example of fluorescent substance paste application to the plasma display panel backplate by screen printing. It is a longitudinal cross-sectional view which shows the example of fluorescent substance paste application to the plasma display panel backplate by nozzle application. (A) is a partial longitudinal cross-sectional view immediately after the phosphor paste application | coating process of a plasma display panel backplate, (b) is a partial longitudinal cross-sectional view after drying and baking of a plasma display panel backplate. (A) is the graph which plotted the height of the liquid fluorescent substance layer with the confocal laser displacement meter, (b) is the graph which normalized the graph of (a) by the moving average. It is a figure which shows contrast with the video signal output from an imaging means, and a board | substrate. It is a figure which shows the relationship between the state of a liquid fluorescent substance layer, and a luminance peak. (A) is the graph which plotted the luminance peak for every liquid phosphor layer, (b) is the graph which normalized the graph of (a) by the moving average. It is a figure which shows board | substrate conditions etc. It is a fragmentary perspective view which shows an example of the plasma display panel backplate used as the test object in the test | inspection apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plasma display panel 2 Conveying means 4 Drive control apparatus 5 Lighting control apparatus 6 Imaging means 7 Image processing means 8 Display apparatus 9 Control apparatus 301 Rear glass substrate 302 Address electrode 303 Dielectric layer 304 Partition 305 Phosphor (R color)
306 Phosphor (G color)
307 Phosphor (B color)
308 Front glass substrate 309 Display electrode 310 Dielectric layer 311 Protective film 312 Plasma 313 Horizontal partition 401 Squeegee 402 Printing screen 403 Printing screen opening 404 Inter-partition 405 Phosphor paste 501 Base 502 Pressure application hole 503 Discharge hole 504 Inter-partition 505 Phosphor pastes 601a and 602a, liquid phosphor layers 601b and 602b, phosphor layers after drying and firing

Claims (4)

  An illumination unit; an imaging unit that mainly captures light reflected from the illumination unit on the liquid phosphor layer and reflected at an angle substantially equal to an incident light incident angle; and a signal processing unit. The curvature radius of the liquid phosphor layer is determined from the obtained amount of reflected light and the radius of curvature coefficient, and the height of the liquid phosphor layer is calculated from the curvature radius and the upper interval between the partition walls on both sides of the liquid phosphor layer and the height of the partition walls. A method for inspecting a display panel, characterized by calculating the thickness. A direction intersecting the liquid phosphor layer, measuring the reflection light quantity of the liquid phosphor layers each while relatively moving the substrate and the illumination means and the imaging means, the inspection method of a display panel according to claim 1.   Illumination means, imaging means for mainly imaging light reflected from the illumination means on the liquid phosphor layer and reflected at substantially the same angle as the incident light incident angle, signal processing means, at least a radius of curvature coefficient and liquid Condition input means for inputting the upper interval of the partition walls on both sides of the phosphor layer, and at least a liquid phosphor based on the amount of reflected light obtained by the imaging means, the input curvature radius coefficient, the upper partition interval, and the partition height An inspection apparatus for a display panel, wherein one of a curvature radius of the layer and a height of the liquid phosphor layer is calculated. 4. The display panel inspection apparatus according to claim 3 , further comprising scanning means for relatively moving the substrate, the illuminating means, and the imaging means in a direction crossing the liquid phosphor layer.

Images