Patent Application
20080145517
1. Field of the Invention
The present invention relates to a method for manufacturing a plasma display panel, and an apparatus for inspecting a plasma display panel. In particular, the present invention relates to a painted amount/painted position control in a phosphor painting process at the time of manufacturing a back plate of a plasma display panel, and to an effective technology for judging the result of the application with in high accuracy.
2. Description of the Related Art
When a plasma display panel (hereinafter referred to as “PDP”) is manufactured, a front plate on which transparent electrodes are located, and a back plate to which phosphors are painted, is separately made. Then, the front and back plates are joined together to form one panel. Usually, phosphors used for R (red), G (green), B (blue) are repeatedly and successively painted on the striped ribs of a back plate of a PDP. However, if each phosphor is not uniformly painted in ribs, for example, the following malfunctions occur: the brightness and hue of displaying become nonuniform, which is unevenness of color; a phosphor of a certain color extends over an adjacent phosphor region, which causes color mixture; and lack of paint creates a dark spot that cannot emit light.
In order to prevent a back plate, which may have the above-described malfunctions in a state in which phosphors are painted, from being joined together with a front plate, it is necessary to separately inspect the back plate without fail. In addition, if a malfunction occurs in the painted state, the malfunction in a manufacturing process should be immediately corrected to prevent a defective product from being manufactured. In order to achieve this, it is also necessary to separately inspect the back plate without fail. This inspection is usually performed by irradiating, with ultraviolet rays, a back plate of a plasma display panel to which each phosphor is painted so that the ultraviolet rays cause a phosphor layer to be excited and to emit light beams, and then by receiving the light beams.
For example, simple and easy methods for inspecting whether or not a phosphor layer is correctly painted and formed in ribs are disclosed in, for example, JP-A-Hei-11-16498 (Patent Document 1) and JP-A-2001-15030 (Patent Document 2). These inspection methods will be simply described with reference to
An ultraviolet source 142 irradiates, with ultraviolet light 143, a back plate 141 on which the formation of phosphors is completed. The phosphors are excited by the ultraviolet light. As a result, the phosphors emit light beams. The emitted light beams 144 are detected by a camera 145. A processing system 146 acquires a detected signal to inspect a defective state.
This is an inspection method for inspecting the whole surface of the back plate by consecutively scanning the back plate 141 or the ultraviolet source 142 and the camera 145. In Patent Document 2, other than the detection in a direction perpendicular to the substrate 141 by the detection camera 145, a method for detecting a defect at an angle of 45° or less is also disclosed.
In addition, in Patent Document 1, a method which includes a mechanism for exhausting ozone caused by ultraviolet light is also disclosed in the above document.
In Patent Documents 1 and 2, a phosphor layer formed in ribs is excited by ultraviolet light. This causes the phosphor layer to excite/emit light beams. Then, the emitted light beams are detected above a substrate or from an oblique direction at an angle of 45° or less. In these methods, an image signal detected by a camera is compared with a reference value to make a judgment as to whether or not a defect (for example, color mixture of phosphors, unpainted phosphor, a fluorescent light failure caused by foreign particles, or uneven brightness) exists. Therefore, a change in shape of the phosphor layer in the ribs is not correctly detected, which occurs in a painting process.
For the above reason, it is not possible to detect a change in state of phosphor paint, which is caused by fluctuations in process that are not judged to be a defect. Accordingly, the control of feedback to the manufacturing process including the painting process cannot be carried out. This is a problem to be solved.
The present invention has been made to solve the above problem. According to one aspect of the present invention, there is provided a plasma-display manufacturing method including a phosphor painting process for painting phosphors in ribs formed on a back plate, said plasma-display manufacturing method comprising:
a step of irradiating the phosphor layer with ultraviolet light to cause the phosphor layer to emit a light beam, the phosphors being painted in the ribs;
a step of preparing an imaging system so that the imaging system images the emitted light beams to acquire an image;
a step of separating the acquired image into RGB planes;
a step of inspecting a defect of the phosphors painted in the ribs based on each of the RGB planes;
a phosphor inspection step of obtaining information on a defect of the phosphor layer; and
a step of feeding back the information obtained in the phosphor inspection step to the phosphor painting process so that manufacturing equipment is controlled in the phosphor paint process.
According to another aspect of the present invention, there is provided a plasma-display manufacturing method including a phosphor painting process for painting phosphors in ribs formed on a back plate, the plasma-display manufacturing method comprising:
a step of irradiating the phosphor layer with ultraviolet light to cause the phosphor layer to emit a light beam, the phosphors being painted in the ribs;
a step of preparing an imaging system so that the imaging system images the emitted light beams in a certain direction to acquire an image;
a step of separating the acquired image into RGB planes;
a step of obtaining a differential area between the RGB planes;
a step of inspecting a defect of the phosphors painted in the ribs based on the obtained differential area;
a phosphor inspection step of obtaining information on a defect of the phosphor layer, the information including the position, shape, and size of the defect; and
a step of feeding back the information obtained in the phosphor inspection step to the phosphor painting process so that manufacturing equipment is controlled in the phosphor painting process.
According to another aspect of the present invention, there is provided a plasma-display manufacturing method including a phosphor painting process for painting phosphors in ribs formed on a back plate, the plasma-display manufacturing method comprising:
a step of irradiating the phosphor layer with ultraviolet light to cause the phosphor layer to emit a light beam, the phosphors being painted in the ribs;
a step of preparing an imaging system so that the imaging system images the emitted light beams in a plurality of directions to acquire a plurality of images;
a step of separating each of the acquired images into RGB planes;
a step of comparing the RGB planes with each other and inspecting a defect mode of the phosphors painted in the ribs;
a phosphor inspection step of obtaining information on a defect of the phosphor layer, the information including the defect mode; and
a step of feeding back the information obtained in the phosphor inspection step to the phosphor painting process so that manufacturing equipment is controlled in the phosphor painting process.
According to another aspect of the present invention, there is provided a plasma-display manufacturing method including a phosphor painting process for painting phosphors in ribs formed on a back plate, the plasma-display manufacturing method comprising:
a step of irradiating the phosphor layer with ultraviolet light to cause the phosphor layer to emit a light beam, the phosphors being painted in the ribs;
a step of preparing an imaging system so that the imaging system images the emitted light beams to acquire information on brightness;
a step of comparing the brightness information with correlation between a shape model of the phosphor layer and brightness signal information that have been obtained in advance;
a phosphor inspection step of obtaining a painted state of the phosphor layer painted in the ribs; and
a step of feeding back the information obtained in the phosphor inspection step to the phosphor painting process so that manufacturing equipment is controlled in the phosphor painting process.
According to another aspect of the present invention, there is provided a plasma-display inspection apparatus for inspecting a phosphor layer that is formed on a back plate of a plasma display, the plasma-display inspection apparatus comprising: ultraviolet-light irradiation optical system for exciting and irradiating the phosphor layer with ultraviolet light; an imaging unit for imaging light beams emitted from the phosphor layer that has been excited and irradiated by the ultraviolet-light irradiation optical system; an image processing unit for separating the image generated by the imaging unit into RGB planes to extract the feature (for example, brightness profile) of an emission state; and shape/in-plane distribution recognition unit for calculating a painted state (including shape and profile) of the phosphor layer from the extracted feature, and from data of the correlation between a phosphor-layer shape model and the feature of the emission state.
In addition, the image processing unit separates, into RGB planes, an image that is generated from at least one direction, and then determines each difference area between the RGB planes so that a position, a shape, and the area (size), of a defect are extracted.
Moreover, said shape/in-plane distribution recognition unit separates, into RGB planes, each of images that are acquired by imaging from at least two directions, and then compares each of the RGB planes of the image acquired by imaging from one direction with each of the RGB planes of the image acquired by imaging from the other direction to judge a defect mode.
A system for manufacturing a plasma display comprises:
a state judgment unit for, from phosphor-layer shape distribution data calculated by the shape/in-plane distribution recognition unit, judging fluctuations in a phosphor painting process; and
a control unit for controlling parameters of manufacturing equipment in the phosphor painting process on the basis of the result of the judgment.
If the manufacturing method according to the present invention is used, it is possible to correctly recognize (keep track of) a state in which phosphors are painted, and a shape of a phosphor layer, in a phosphor formation process included in a PDP manufacturing process, and to quickly feed back them to the manufacturing process. This produces extremely large effects of improving yields, improving the processes, and preventing a failure from occurring.
Moreover, if the inspection apparatus according to the present invention is used, it is possible to detect a minute defect, in particular, a slight change in phosphor shape, which is not judged to be a defect in the past, so that process fluctuations can be minutely recognized (kept track of).
Best modes for carrying out the present invention will be described as below.
A method for manufacturing a PDP and an apparatus for inspecting a PDP according to a first embodiment of the present invention will be described with reference to drawings as below. First of all, a simple configuration of a target PDP according to a first embodiment will be described with reference to
Next, a manufacturing process of PDP according to the first embodiment will be described with reference to
A back plate process also starts with glass substrate cleaning in like manner (S200). After the address electrode is formed by photolithography, or the like (S201 to S206), dielectric film is formed (S207). After that, in contrast to the front plate process, a rib material is printed and dried to form a rib layer (S208). Then, mask for sandblast is formed (S209). The ribs are formed by sandblasting (S210), and are then calcinated to complete the formation of the rib walls (S211). The rib walls are filled with phosphor paste by printing, or the like. The rib walls are then calcinated to cause the phosphors to adhere to the rib walls (S212).
Lastly, on the completion of the formation of the front and back plates, both of them are assembled and joined together (S300). Then, vacuuming is performed, and discharge gas is introduced therebetween before they are sealed (S301). Then, a driving circuit is mounted to the panel (S302), which is assembled as a TV set (S303).
Here, a phosphor printing (painting)/calcination process S212, which in particular relates to this embodiment, will be described in detail with reference to
As shown in
Next, as shown in
As shown in
Lastly, in a calcination process, the back plate 113 to which all of the phosphors have been printed is calcinated. As a result, the formation of a back plate 115 provided with the phosphors is completed.
The principles of a printer used for such a phosphor printing/calcination process S212 will be described with reference to
In addition, the principles of a painting apparatus using a dispenser method, which is another applying method, will be described with reference to
A configuration of an inspection apparatus for inspecting a state of a phosphor layer, which is formed in ribs in this manner, will be described with reference to
The emitted fluorescent light beams 9a, 9b, 9c are condensed by detection lenses 5a, 5b, 5c, each of which is located at a different position (left-inclined position, substantially vertical position, right-inclined position) at which the angle between the lens in question and the back plate 2 differs from the angle between each of the other lenses and the back plate 2. The detection lens 5a and a photodetector 6a can detect the fluorescent light beam 9a from the left rib wall. The detection lens 5c and a photodetector 6c can detect the fluorescent light beam 9c from the right rib wall. The condensed fluorescent light beams 9a, 9b, 9c are then detected by photodetectors 6a, 6b, 6c respectively. Image generation units 7a, 7b, 7c generate two-dimensional images from the detected signals, and then transmit the two-dimensional images to image processing units 8a, 8b, 8c respectively. The image processing units 8a, 8b, 8c calculate the position, shape, area (size) and the like of a defect, which are the features of the phosphor layer, from the two-dimensional images in imaging processing described below. The result of the calculation is then transmitted to a shape/in-plane distribution recognition unit 11. By the method described below, the shape/in-plane distribution recognition unit 11 calculates the shape of the phosphor layer of the detected substrate and data on the panel in-plane distribution of each shape parameter by use of design information/substrate information 10 on the height of the ribs, the shape of the phosphor layer and the like, the panel in-plane distribution of each shape parameter, the type of the substrate (back plate), and the like and by use of database 12 on correlation between a shape of the phosphor layer and light emission brightness model (database 12 on correlation between shape model and brightness profile). A state judgment unit 15 judges a state including a defect position, a defect mode, and process fluctuations on the basis of the calculated data. Then, the state judgment unit 15 judges the state such as defect position, defect mode, and process fluctuation and uploads the state information to a higher-level server 16. Incidentally, the higher-level server 16 manages the manufacturing process in an integrated manner, and gives an instruction to manufacturing equipment 17 (phosphor painting apparatus comprises phosphor printing/calcination apparatus, etc.) if necessary.
Next, each configuration will be described in detail.
In the case of a 50-inch PDP panel, on the assumption that a horizontal to vertical ratio of 16:9, which is used by high-definition television screens, is adopted, a rib interval of the back plate, the number of lateral pixels of which is 1920 (full high-definition television), is about 190 μm (Lp=190 μm as shown in
By the way, the limit of the height Hs of the rib wall that the photodetector 6 can image is decided by the aspect ratio of the rib height H and the rib pitch Lp. In general, it was assumed that Hs is also 190 μm at the maximum because rib pitch Lp and height H of the rib are same levels (the aspect ratio being 1.0) according to the restriction in the rib manufacturing and the thickness etc. of the phosphor layer. That is, when the inclination angle θ becomes 450 or more, since the height Hs of the rib wall that the photodetector 6 can image, becomes same 190 μm as rib pitch Lp, the photodetector 6 can image an entire area of the phosphor layer in the rib wall as the result. When the inclination angle θ becomes 450 for example, the height Hs of the rib wall that the photodetector 6 can image will be limited to about 69 μm.
Moreover, if the focus depth of the detection lens 5 is assumed as “1” when the inclination angle θ is 90°, the effective focus depth of the detection lens 5 at the time of inclination detection decreases in the proportion of sin θ in comparison with vertical detection. As a result, the focus depth becomes shallow becoming small of the inclination angle θ as shown in
As explained above, in the design of actual detection systems 5a˜5c, 6a˜6c, it may be performed under the condition of showing in
In case of the condition the inclination angle θ at low angle or more, since scanning direction detection resolution R may be large, the substrate can be scanned at high speed. However, the detection system provided the detection lens with beforehand very long focus depth or a mechanism that keeps constantly a distance between the substrate and the detection lens is needed. Oppositely, in case of the inclination angle θ at high angle, there is a necessity for reducing the scanning direction detection resolution R, and if the detection rate of the photodetector is invariable, there is a necessity for slowing down the detection speed (the scanning speed).
Next, an example of processing in the image processing units 8a, 8b, 8c will be described in detail with reference to
Processing of continuous defect detection according to the first embodiment will be described as below. First of all, a target image 42 to be subjected to the processing is taken out from an obtained detected image 701 by the image processing units 8a, 8b, 8c. For the sake of description, an example in which continuous position misalignment defects and a plurality of isolated defects exist is shown. An example in which continuous position misalignment defects have occurred at the time of applying B phosphors is shown (in comparison with a normal product image 40, all of the B phosphors deviate in an R phosphor direction).
The target image 42 which has been taken out from the detected image is separated into RGB planes of a color image by each of the imaging processing units (S31). A direction in which the RGB planes are arrayed, and the panel pixel pitch P, are acquired from substrate design information (substrate parameters) 702 by each of the image processing units. Then, according to the RGB arrayed direction, a B-plane image 42b is shifted by +⅓ P in a Y direction, and a G-plane image 42g is shifted by −⅓ P in the Y direction (S32). Next, “Gain adjustment” is performed on the image by each of the image processing units so that the brightness values in the planes coincide with one another. Then, images 42b′, 42r′, 42g′ after the brightness adjustment are acquired (S33). Next, the difference between the images is calculated by each of the image processing units to output a difference image 44a corresponding to (B plane)−(R plane), a difference image 44b corresponding to (R plane)−(G plane), and a difference image 44c corresponding to (G plane)−(B plane) (S34). As a result, each of the image processing units detects that a position misalignment defect occurs in a linear defect 46 included in the difference image 44a, and in a linear defect 47 included in the difference image 44c (S35). Because both of the difference images includes the B plane, it is judged that a position misalignment defect has occurs in the B phosphor. Moreover, judging from the difference area 48 included in the difference image 44b, it is also understood that an isolated defect has occurred.
Thus, by separating at least an image obtained from one direction (a specified direction) into the RGB planes to determine each difference area between the RGB planes, each of the image processing units can detect a change in phosphor shape, which conventionally has not been judged to be a defect, and identify a position, a shape, and the area (size), of the defect.
Next, an example of defect mode judgment performed in the shape/in-plane distribution recognition unit 11 will be described in detail with reference to
To be more specific, in the case of a defective area 51a (r), which has been detected in the R plane included in an image from the image processing unit 8a, the shape/in-plane distribution recognition unit 11 compares an area 51a (r) that has been detected in the plane R in an image of the left rib wall from the image processing unit 8a with areas 51a (g), 51a (b) in the other planes G, B from the image processing unit 8a and areas 51b (r), 51b (g), 51b (b) in the planes R, G, B in an image from the top of the ribs from the image processing unit 8b and areas 51c (r), 51c (g), 51c (b) in the planes R, G, B in an image of the right rib wall from the image processing unit 8c, all of which correspond to the same position on the substrate. Based on the comparison, it is judged that the areas 51c (r), 51c (g), 51c (b) in the images from the image processing unit 8c do not include a defect, and that the areas 51a (b), 51b (b) in the images from the B plane also do not include a defect. In addition, the size of the defect in the area 51a (r) is larger than that of the defect in the area 51b (r). Similarly, the size of the defect in the area 51a (g) is larger than the size of the defect in the area 51b (g). Therefore, the defect in the area 51a (r) is judged to have a shape as shown in the defect 51 in
Similarly, in the case of the defect in the area 52c (g) detected based on the image from the image processing unit 8c, because there is no defect in the other areas, the shape/in-plane distribution recognition unit 11 judges the defect in the area 52c (g) to be a phosphor missing defect on the G rib wall 63. This phosphor missing defect has a shape of the defect 52 shown in
Next, in the case of the defect in the area 53a (r), because both of the areas 53b (r), 53c (r) include a defect having nearly the same size, and because the other G, B planes do not include a defect, the shape/in-plane distribution recognition unit 11 judges the defect in the area 53a (r) to be a defect that has a shape of the defect 53 shown in
Moreover, in the case of the defect in the area 54a (r), because all of the areas 54b (r), 54a (b), 54b (b) include a defect having nearly the same size, and because the G plane and an image from the image processing unit 8c do not include a defect, the shape/in-plane distribution recognition unit 11 judges the defect in the area 54a (r) to be a color mixture defect that has a shape of the defect 54 shown in
Thus, the judgment of a defect mode makes it possible to correctly recognize a process state in the painting process of the phosphor layer.
Next, an example of phosphor-layer shape judgment performed by the shape/in-plane distribution recognition unit 11 will be described in detail with reference to
This makes it possible for the shape/in-plane distribution recognition unit 11 to detect a slight change in phosphor shape, which is not judged to be a defect, and to minutely recognize process fluctuations in the phosphor painting process.
Next, processing performed by the shape/in-plane distribution recognition unit 11, and processing performed by the state judgment unit 15, will be described with reference to
By generating such a defect distribution map, the shape/in-plane distribution recognition unit 11 can quickly recognize the tendency of process fluctuations in the phosphor painting process.
Next,
By generating such a deviation amount map, it is possible for the shape/in-plane distribution recognition unit 11 to quickly recognize the tendency of the amount of deviation in the phosphor painting process.
Next, an example of how to control a manufacturing process based on a manufacturing method according to the first embodiment will be described with reference to
Thus, according to the manufacturing method according to the first embodiment, from a phosphor application state and a shape of the phosphor layer in the phosphor formation process included in the PDP manufacturing process, it is possible to minutely and correctly recognize a process state in the phosphor painting process. Further, by quickly feeding back the process state to the phosphor painting process, it is possible to control the manufacturing equipment in the phosphor painting process. This produces extremely large effects of improving yields, improving the processes, and preventing a failure from occurring. In addition, as a result of the above-described phosphor inspection S220, the defect mode is known. Therefore, a judgment as to whether or not a defect can be corrected is also facilitated.
The above-described configuration makes it possible to carry out inspection at high speed even in the case of a large substrate, and to perform inspection in manufacturing tact. As a result, it is possible to realize an inline inspection apparatus.
Incidentally, the ultraviolet light can be produced by a low-pressure mercury lamp (having wavelengths of 184 nm, 254 nm). In addition, the ultraviolet light can also be produced, for example, by linearly scanning an ultraviolet laser beam having a wavelength of 400 nm or less. A KrF laser (248 nm), a KrCl laser (222 nm), an ArF laser (193 nm), and the like, can be used as a laser light source.
According to the second embodiment, the lens 5 and the photodetector 6 can be configured with one camera. This makes it possible to simplify the configuration of the inspection apparatus, and to reduce costs thereof. Moreover, if not only the image acquired in this embodiment, but also information about defects and adjustment, which has been acquired in a manner similar to that of the first embodiment, are fed back to the phosphor painting process S212, it is possible to decrease fluctuations in process state in the phosphor manufacturing process, and to manufacture the phosphor in a stable state.
Next,
Because a detected image detected from two directions is used, quicker processing becomes possible in comparison with the detection from three directions. Moreover, as is the case with the first embodiment, if information about defects and adjustment, which has been acquired in this embodiment, is fed back to the phosphor painting process S212, it is possible to decrease fluctuations in process state in the phosphor manufacturing process, and to manufacture the phosphor in a stable state.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-341665 | Dec 2006 | JP | national |
| 2007-185787 | Jul 2007 | JP | national |
