Patent Application
20110250817
The technology disclosed in this document relates to a method and an apparatus for producing a plasma display panel used in, for example, a display device.
A conventional apparatus for producing a plasma display panel (hereinafter, called PDP) has a head for piping coupled with a work which is a PDP currently in production, piping connected to the head, a gas cylinder from which a discharge gas is injected into the piping, and a discharge gas recovery circuit which recovers the discharge gas remaining in the piping, wherein the discharge gas recovery circuit is detachably connected to the piping by way of a coupler (for example, refer to Patent Document 1).
In the event that an impurity gas existent in the atmosphere enters the piping, the impurity gas further penetrates into the PDP. The impurity gas thus penetrating into the PDP causes a poor electric discharge in the PDP, undermining an image display quality of the PDP.
A method for producing a PDP includes the steps of: evacuating air from a discharge space formed between substrates facing each other through piping; introducing a discharge gas into the discharge space through gas piping that branches from the piping; and recovering the discharge gas remaining in the piping and the gas piping through the piping.
An apparatus for producing a PDP includes: air evacuation means for evacuating air from a discharge space formed between substrates facing each other through piping; discharge gas introduction means for introducing a discharge gas into the discharge space through gas piping that branches from the piping; and discharge gas recovery means for recovering the discharge gas remaining in the piping and the gas piping. The discharge gas recovery means is connected to the piping.
PDP 1 according to exemplary embodiments of the present invention is an alternating current surface discharge PDP. As illustrated in
Front plate 2 has display electrodes 8 each having scan electrode pair 6 and sustain electrode pair 7 formed on front glass substrate 5. Front plate 2 further has dielectric layer 9 provided to coat display electrodes 8, and protective layer 10 provided to coat dielectric layer 9. Scan electrode 6 and sustain electrode 7 may be structured such that bus electrodes 6b and 7b are respectively stacked on transparent electrodes 6a and 7a.
Rear plate 3 has multiple data electrodes 12 formed on a main surface of rear glass substrate 11. Rear plate 3 further has dielectric layer 13 provided to coat data electrodes 12, and barrier ribs 4 formed at positions corresponding with intervals between data electrodes 12 on dielectric layer 13. Rear plate 3 further has phosphor layers 14R, 14G, and 14B respectively formed between barrier ribs 4 adjacent to each other.
Discharge spaces 15 are formed when front plate 2 and rear plate 3 are joined with each other. An arrow of
As illustrated in
2-1. Prior to S31
As a preparatory step for sealing, sealing member 17 is formed in a peripheral portion of front plate 2 or rear plate 3 so as to encompass image display region 18 as illustrated in
To evacuate air from PDP 1, air supply/evacuation hole 19 is formed beforehand in PDP 1. Air supply/evacuation hole 19 is formed in a corner portion of PDP 1 mostly because of the two reasons described below. It is difficult to form air supply/evacuation hole 19 at positions where barrier ribs 4 are formed in image display region 18. It is difficult to form air supply/evacuation hole 19 in any of longitudinal and lateral sides of PDP 1 because flexible circuit substrates for feeding power to PDP 1 are provided there.
In PDP 1, it is desirable to make any area thereof other than image display region 18 (outer peripheral portion) as small as possible. Therefore, air supply/evacuation hole 19 is formed at a position near sealing member 17.
As illustrated in
2-2. Details of S31
2-2-1. Prior Art
As illustrated in
Vacuum exhaust device system 34 includes valve 36a, manifold 37a, vacuum exhaust device 38, main valve 39, and piping 50. Gas introduction device system 35 includes discharge gas introduction device 40a having a gas cylinder, valve 36b, manifold 37a, main valve 39, gas piping 52, and piping 50. Vacuum exhaust device system 34 and gas introduction device system 35 share a part of manifold 37a, main valve 39, and piping 50.
Referring to
In S35, heating mechanism 32 heats furnace unit 33 again to increase its internal temperature to a predetermined degree. Then, vacuum exhaust device system 34 evacuates air from PDP 1. The air in PDP 1 is evacuated through air evacuation head 23 and piping 50. During the evacuation of air, valve 36a of vacuum exhaust device system 34 is open, whereas valve 36b of gas introduction device system 35 is closed.
In S36, heating mechanism 32 reduces the internal temperature of furnace unit 33 to, for example, nearly room temperature.
In S37, the discharge gas is introduced into PDP 1. While the discharge gas is introduced into PDP 1, valve 36a is closed, but valve 36b is open. The discharge gas is, for example, a mixed gas having the composition of neon (Ne) by 80%-xenon (Xe) by 20%. After the discharge gas is introduced into PDP 1, PDP 1 has an internal pressure of approximately 53 kPa-80 kPa.
In S38, a predetermined section of air evacuation piping 21 is locally heated, and thereby melted and then blocked. The blocked section of air evacuation piping 21 is cut away to seal off air evacuation piping 21, so that PDP 1 is air-tightly sealed (chipoff).
In S39, PDP 1 is removed from PDP production apparatus 30a.
In S40, the discharge gas is further introduced until internal pressures of piping 50 and gas piping 52 reach the atmospheric pressure (approximately 101.3 kPa at sea level).
In S41, unnecessary portion 21a of the air evacuation piping (see
In S42, PDP 1 with air evacuation piping 21 and tablet 22 provided therein is placed in furnace unit 33.
In S43, the discharge gas is blown into air evacuation piping 21 for cleaning purpose.
A sequence of steps included in S31 is then completed.
S40 and S43 are particularly important steps. To omit these steps would possibly invite the contamination of PDP 1 with the impurity gas. The impurity gas possibly causes such problems as luminance degradation and color irregularity when an image is displayed on PDP 1.
2-3. Details of S38
As illustrated in
The internal pressure of air evacuation piping 21 at this time is equal to the internal pressure of PDP 1 (approximately 53 kPa-80 kPa). Thus, the internal pressure of air evacuation piping 21 is lower than the outside air pressure (atmospheric pressure). Therefore, the side surfaces of air evacuation piping 21 are gradually pulled inward of air evacuation piping 21 as illustrated in
As air evacuation piping 21 is further heated by gas burner 60, the melting walls thereof start to fuse into each other, generating a blocked section there. Then, the blocked section of air evacuation piping 21 is cut away as illustrated in
Conventionally, a single piping system constitutes gas piping 52 provided to introduce the discharge gas, leaving no choice but to use the discharge gas in S40 and S43.
An example of the discharge gas is a Ne—Xe mixed gas. Xe is a very rare gas which is included in the atmosphere in such a trace amount as 0.087 ppm. Further, Xe is now a material very difficult to obtain due to a limited volume of production and an ongoing upturn in demand. It is a possible solution to reduce a piping diameter so that piping volumetric capacity (Xe gas residue) is reduced, in which case, however, conductance during the evacuation of air drops, deteriorating an efficiency in the evacuation of air. Though another possible solution is to reduce piping length to compensate for the conductance drop, it is difficult to shorten the piping due to constraints of the production apparatus. Thus, reduction of the piping volumetric capacity is a very difficult task to accomplish, making it a deciding factor to control a usage volume of Xe.
Referring to
As illustrated in
PDP production apparatus 31 further has air evacuation port 43 equipped with valve 36d to be connected to recovery device 48. PDP production apparatus 31 further has inactive gas introduction device 40b and valve 36c.
According to the present exemplary embodiment, after PDP 1 is removed in S39, connector 41 is connected to air evacuation port 43 in S401 as illustrated in
Then, valve 36d is opened. It is checked by air evacuation device 42 that there is no leak from connector 41. Then, main valve 39 and valve 36e are opened. The discharge gas remaining in the piping system is stored in tank 44. After that, valve 36d is closed, and connector 41 and air evacuation port 43 are then disconnected from each other. The recovered discharge gas is pressurized by pressure intensifier unit 45 and then stored in recovery container 47.
In S402 and S43, valve 36c is opened so that the inactive gas is introduced from inactive gas introduction device 40b.
According to the present exemplary embodiment, PDP 1, vacuum exhaust device system 34, and gas introduction device 35 are configured to move concurrently with one another, whereas recovery device 48 is immovable. When post-chipoff PDP 1, vacuum exhaust device system 34, and gas introduction device 35 arrive in front of recovery device 48, connector 41 is connected to air evacuation port 43.
According to the present exemplary embodiment, the discharge gas remaining in the piping system is stored in recovery container 47 of recovery device 48. The recovered discharge gas is repurified to have a higher purity, and the higher purity gas thus obtained is reused.
According to the present exemplary embodiment, after connector 41 is connected to air evacuation port 43, valve 36g is opened with valve 36d being kept closed. Air evacuation device 42 evacuates air from a portion exposed to the atmosphere. The pressure of connector 41 is preferably reduced to at most 50 kPa in 20 seconds after the evacuation of air started.
The pressure is checked on a pressure gauge (not illustrated in the drawing) provided in connector 41. The target value, at most 50 kPa in 20 seconds, is decided by a relationship between the evacuation efficiency of air evacuation device 42 and an amount of allowable leak. The numeral value is preferably adjusted to be at most an impurity predetermined level during the repurification described later.
Next, main valve 39 and valve 36e, or valve 36e and valve 36f are opened so that vacuum exhaust device system 34 and gas introduction device system 35 are coupled with each other. Then, valve 36d is opened so that the discharge gas remaining in the piping system is discharged into tank 44 connected to a rear section of air evacuation device 42. When the evacuation of air is over, valve 36d is closed to disconnect connector 41. Pressure intensifier unit 45 intensifies the pressure of the discharge gas stored in tank 44. The pressure-intensified discharge gas is transferred to recovery container 47.
After that, unnecessary portion 21a of the air evacuation piping should be removed. However, the atmosphere flows into the piping system now having a negative internal pressure if unnecessary portion 21a of the air evacuation piping is immediately removed, contaminating the piping system with the impurity gas included therein.
It is unavoidable that the discharge gas is more or less left in the piping system. However, gas introduction device system 35 according to the present exemplary embodiment introduces the inactive gas into the piping system by using inactive gas introduction device 40b and valve 36c provided therein to successfully reduce the Xe remaining in the piping system.
Conventionally, the discharge gas is further introduced in S40 until the internal pressure of the piping system equals to the atmospheric pressure as described earlier.
In contrast, the present exemplary embodiment is different in that, in S402, valve 36c is opened to introduce the inactive gas into the piping system from inactive gas introduction device 40b. The inactive gas increases the internal pressure of the piping system to be as high as the atmospheric pressure.
A volume of reduction of the discharge gas is; about 4 L discharged into the atmosphere plus about 0.5 L used to clean air evacuation piping 21, resulting in about 4.5 L in total. The reduction volume can be attained as far as the recovered discharge gas can be repurified by 100%. The reduction volume is dependent on the volumetric capacity of the piping system.
Examples of the inactive gas which is a substitute gas for the discharge gas are; nitrogen (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). However, it is desirable to use any inactive gases but Xe in view of desirable reduction of the usage volume of Xe.
The present exemplary embodiment uses Ne as the inactive gas. Ne is an inexpensive gas and one of components of the discharge gas according to the present exemplary embodiment. Therefore, Ne, if penetrating into PDP 1, less affects light emission characteristics.
To prevent such an event that the inactive gas penetrates into PDP 1 due to, for example, malfunction of valve 36c, the production apparatus according to the present exemplary embodiment takes the following technical measures.
Manifold 37a is equipped with vacuum pressure gauge 46 to ensure that a degree of vacuum in the piping meets a predetermined reference level. Specifically, when valve 36a alone is opened with valves 36b and 36c and main valve 39 being kept closed, vacuum exhaust device 38 evacuates air from the piping system. During the evacuation of air, it is checked whether the pressure indicated by vacuum pressure gauge 46 is at most 1.0×10−5 Pa. Thus, as far as the degree of vacuum is at most the predetermined numeral value, PDP 1 can sustain a good image display quality independent of possible leak of the inactive gas into PDP 1 through valve 36c.
The pressure of inactive gas introduction device 40b is set lower than the pressure of discharge gas introduction device 40a. If there is any leak through valve 36c when the discharge gas is introduced into PDP 1, the discharge gas of discharge gas introduction device 40a is still preferentially introduced into PDP 1.
The two different manifolds are separately provided; manifold 37b for introducing the discharge gas, and manifold 37a for evacuating air. Manifold 37a and connector 41 are connected to each other by way of air evacuation port 43 because of the reason described below.
To evacuate (recover) gas from closed piping, an ultimate pressure conventionally relies on the performance of a pump. An amount of time for reaching the ultimate pressure relies on the volumetric capacity of the piping. The amount of time for reaching the ultimate pressure increases as the volumetric capacity of the piping is larger, whereas the amount of time decreases as the volumetric capacity is smaller.
As illustrated in
As described earlier, when recovery device 48 is connected to air evacuation port 43b to recover the discharge gas, the piping system evacuated to recover the discharge gas has a smaller volumetric capacity than connecting recovery device 48 to air evacuation port 43a to recover the discharge gas. In brief, it takes less amount of time to reach the pressure at which the discharge gas recovery ends, meaning a better efficiency in recovering the discharge gas.
In the case where air evacuation port 43b is provided, however, the impurity gas existent in the atmosphere possibly flows into gas piping 52 through air evacuation port 43b when recovery device 48 is removed from air evacuation port 43b in S37. The impurity gas that flows into gas piping 52 further penetrates into PDP 1 through air evacuation piping 21. The penetration of the impurity gas into PDP 1 results in a poor electric discharge in PDP 1. This inevitably undermines the image display quality of PDP 1, which is a serious problem that cannot be overlooked in the PDP 1 production apparatus.
According to the present exemplary embodiment, therefore, recovery device 48 is provided in vacuum exhaust device system 34 as illustrated in
An exemplary embodiment 2 of the present invention decides an amount of time for recovering the discharge gas. As illustrated in
Normally, the discharge gas can be recovered in an adequate amount when the recovery time is set long enough. However, the discharge gas remaining in the piping system is more recovered as the recovery time advances, while the total pressure of the recovered gas gradually falls as illustrated in
The recovered gas, however, contains therein a certain quantity of atmosphere as illustrated in
The atmosphere includes argon (Ar) by approximately 1 vol. %. It is comparatively difficult to remove Ar present in the recovered gas when the recovered gas is repurified. Therefore, PDP 1 is contaminated with Ar when the repurified discharge gas is used. Through the studies and discussions, the inventors of the present invention found out that Ar present in the discharge gas unfavorably increases a drive voltage required for image display as the power-on time of PDP 1 advances. This is a serious problem that leads to the product failure of PDP 1.
To ensure the recovery of the discharge gas in a sufficient amount and make the inflow of the impurity gas of the atmosphere less likely, in the present exemplary embodiment, the total pressure of the recovered gas is measured by vacuum pressure gauge 46. Based on variation of the total pressure values, the recovery of the discharge gas is suspended at a time point when the value indicated by the gauge equals to a predetermined value (or when a length of time based on the time point passed).
The time point when the recovery ends was decided as described below. First, variation of the drive voltage of PDP 1 relative to the concentration of Ar in the discharge gas was measured. It was then decided that the Ar concentration in the discharge gas should be at most 1 ppm in terms of volume to be able to sustain a good image display quality in PDP 1. Then, an allowable Ar concentration in the recovered gas was estimated. The allowable Ar concentration was calculated from the purifying performance of cryogenic separation which is a conventional gas purifying technique.
Then, the recovery operation was suspended when the total pressure of the recovered gas equaled to the pressure at which the allowable Ar concentration was reached (or when a length of time necessary for reaching the allowable Ar concentration passed).
Thus, the impurity gas included in the atmosphere can be prevented from flowing into PDP 1. As a result, the good production yield of PDP 1 can be prevented from deteriorating.
According to the exemplary embodiments 1 and 2, PDP production apparatus 31 is provided with inactive gas introduction device 40b which is inactive gas introduction means. However, inactive gas introduction device 40b is not an indispensable structural element of PDP production apparatus 31. As far as PDP production apparatus 31 is equipped with discharge gas introduction device 40a, air evacuation port 43 provided in vacuum exhaust device system 34, and recovery device 48 connected to air evacuation port 43, the discharge gas can be recovered, and the impurity gas present in the atmosphere can be prevented from entering the PDP.
The method for producing a PDP disclosed in the exemplary embodiments includes the steps of evacuating air from the discharge space formed between front plate 2 and rear plate 3 which are substrates facing each other through piping 50 (S35); introducing the discharge gas into the discharge space through gas piping 52 which branches from piping 50 (S37); and recovering the discharge gas remaining in the piping system through piping 50 (S401).
According to the method thus technically characterized, the discharge gas that failed to arrive at PDP 1 and stayed in the piping system can be recovered. Another advantage of the method is to prevent the impurity gas from flowing into PDP 1, thereby preventing the production yield of PDP 1 from deteriorating.
The step of recovering the discharge gas (S401) may further include a step of recovering the discharge gas through connector 41 which is recovery piping connected to air evacuation port 43 provided in piping 50. The method further including the step enables recovery device 48 to be readily connected and disconnected, thereby more efficiently recovering the discharge gas.
The step of recovering the discharge gas (S401) may further include a step of measuring a characteristic value of the recovered discharge gas, and a step of deciding an ending time of the step of recovering the discharge gas based on the measured characteristic value.
The method further including the steps can prevent such an unfavorable event that the recovered discharge gas is contaminated with the impurity gas of the atmosphere.
The characteristic value may be the pressure of the recovered discharge gas so that the characteristic value can be easily measured by, for example, a vacuum pressure gauge.
The characteristic value may be the concentration of at least one of oxygen, nitrogen, argon, and carbon dioxide included in the recovered discharge gas.
The method using such a characteristic value can directly measure the concentration of the impurity gas which may affect the electric discharge characteristics of PDP 1, thereby more accurately setting the recovery suspension time.
The method may further include a step of introducing the inactive gas through gas piping 52 (S402) after the step of recovering the discharge gas (S401).
The method further including the step can lessen the residual discharge gas in the piping system, thereby reducing the cost for repurifying the recovered discharge gas.
PDP production apparatus 31 disclosed in the exemplary embodiments includes: air evacuation device 38 configured to evacuate air from the discharge space formed between front plate 2 and rear plate 3 which are substrates facing each other through piping 50; discharge gas introduction device 40a which is discharge gas introduction means for introducing the discharge gas into the discharge space through gas piping 52 which branches from piping 50; and recovery device 48 which is discharge gas recovery means for recovering the discharge gas remaining in the piping system, wherein recovery device 48 is connected to piping 50.
According to the apparatus thus structurally characterized, the discharge gas that failed to arrive at PDP 1 and stayed in the piping system can be recovered. Another advantage of the apparatus is to prevent the impurity gas from flowing into PDP 1, thereby preventing the production yield of PDP 1 from deteriorating.
The recovery device may further include measurement means for measuring the characteristic value of the recovered discharge gas.
The apparatus further including the measurement means can prevent such an unfavorable event that the recovered discharge gas is contaminated with the impurity gas of the atmosphere.
The measurement means may be a pressure gauge or a gas concentration meter so that the characteristic value can be easily measured particularly when the pressure gauge is used. When the gas concentration gauge is used, the concentration of the impurity gas which may affect the electric discharge characteristics of PDP 1 can be directly measured. Therefore, the recovery suspension time can be more accurately preset.
Inactive gas introduction device 40b, which is inactive gas supply means, may further be connected to gas piping 52.
The apparatus thus structurally characterized can lessen the residual discharge gas in the piping system. As a result, the cost for repurifying the recovered discharge gas can be reduced.
PDP 1 according to the exemplary embodiments, wherein the suitable discharge gas is routinely introduced, did not undergo such problems as light emission irregularity and degraded luminance, and succeeded in a large reduction of the discharge gas to be used as compared to the prior art.
As described thus far, the present invention improves the use efficiency of the discharge gas during the PDP production process. The present invention thus providing an advantageous technology is universally applicable to PDP production.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-264507 | Nov 2009 | JP | national |
| 2009-290077 | Dec 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/006709 | 11/16/2010 | WO | 00 | 6/14/2011 |
