Variation of Driving Margin

In this work, full sized forty-six inch panels were made. The MgO films were deposited on the PDP’s front panel by electron beam evaporation. Also, the conventional phosphorous layers for PDP application were printed on the rear panels.

In order to figure out the relationship between phosphor and MgO thin films, some experimental panels are made with mono color, which means only one phosphor is printed on the panel. As Tab. 5.1 shows, the panel No.1 and No. 2 are printed with red phosphor. Panel No.3 and No.4 are printed with green phosphor. Panel No. 5 and No.

6 are printed with blue phosphor. Panel No. 7 and No. 8, as conventional PDP panels, are printed with red, green and blue phosphor. The main component of red, green and blue phosphorous layers are (Y, Gd, Eu) BO₄, (Zn, Mn)₂SiO₄ and (Ba, Eu) MgAl₁₀O₁₇, respectively. Each color is provided by two companies. KX504A, P1G1S are manufactured by KASEI OPTONIX. NP360-53, NP200-205 and NP107-743 are manufactured by NICHIA co. One of the blue phosphor is made by LG Chem.

Table 5.1 Experimental PDP Setup Panel No. Phosphor

Name Main Component Abbreviated

Name Manufacturer 1 KX-504A (Y,Gd,Eu)BO₃ YGB KASEI

OPTONIX 2 NP360-53 (Y,Gd,Eu)BO₃ YGB NICHIA co

3 P1-G1S (Zn,Mn)2Sio4 ZSM KASEI

To speed up the degradation of MgO thin films and phosphorous layer, the experimental panels were sent into the aging process. The process what we called aging plays a very important role for PDP panels. For typical ac-PDP manufacture process, the panels are sent into aging for several hours after fabrication. During aging, high-frequency sustained pulse is applied to the panels. For mass production line, the purpose of this process is to activate the MgO thin films and make the panel performance stable. Aging process is time consuming but essential for high-quality panels. For typical ac-PDP, aging lasts for only 18 hours. In this work, the experimental panels are sent into aging for 1000 hours to achieve faster degradation.

Luminance, color performance and driving margin are recorded at the selected time to observe the variation of panel properties.

Before we continue, one of the measurement techniques called dynamic driving margin should be introduced first. The margin area defines the range of applied

voltage. The Vs indicated the sustain voltage while Vxg represents the address voltage.

For PDP driving, both the applied Vs and Vxg must be in the margin area otherwise the ow or iw occurs in some areas on the PDP panels. Ow, which means over write, usually occurs when too high voltage is applied to the panels. Luminance in the ow cells appear to be higher than the normal cells. Sometimes cross talk with other sub cells appears simultaneously and makes luminance and color non-uniform for the whole panel. Iw, which means insufficient write, usually occurs when too low voltage is applied on the panel. Luminance in the iw cells is lower than other cells. The cells can not be ignited completely so the flicker occurs. Lower minimum address and sustain voltage can decrease power consumption and cost of driving circuit. The variation of margin data as a function of time could be observed. Fig. 5.1 (a) and (b) show the driving margin area of the No.1 panel after accelerated test time 18 hour and 1000 hour, respectively.

After long time operation, the minimum address voltage increased, while minimum sustain voltage decreased. The maximum address and sustain voltage decreased and made the driving margin area decrease. This is due to the degradation of MgO thin film by the ion bombardment in plasma. Fig. 5.2 to Fig. 5.8 shows the variation of driving margin of panel No.2 to No.8. From the result, the panels with red phosphor have an obvious degradation. However, the Panels with green phosphor only varied slightly. The panels with blue phosphor almost remain the same. The panels with three kinds of phosphor (red, green and blue phosphor) also have obvious degradation. The driving margin is directly related to properties of MgO thin films. In this experiment, MgO thin films of all panels are deposited with the same parameters by one machine.

The only difference is their phosphor. Therefore, we demonstrated that the degraded margin area of the panel No. 1 and No.2 is caused by contaminations in the Mgo thin films by red phosphor. We think red phosphor also cause the degradation of panel No.7 and No.8.

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Fig 5.1 The driving margin of the panel with red phosphor KX504A after (a) 18 hour and (b) 1000 hour accelerated test time (aging).

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Fig 5.2 The driving margin of the panel with red phosphor NP360-53 after (a) 18 hour and (b) 1000 hour accelerated test time (aging).

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Fig 5.3 The driving margin of the panel with green phosphor P1G1S after (a) 18 hour and (b) 1000 hour accelerated test time (aging).

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Fig 5.4 The driving margin of the panel with green phosphor NP200-205 after (a) 18 hour and (b) 1000 hour accelerated test time (aging).

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Fig 5.5 The driving margin of the panel with blue phosphor NP107-343 after (a) 18 hour and (b) 1000 hour accelerated test time (aging).

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Fig 5.6 The driving margin of the panel with blue phosphor LG Chem after (a) 18 hour and (b) 1000 hour accelerated test time (aging).

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Fig 5.7 The driving margin of the panel with RGB phosphor after (a) 18 hour and (b) 1000 hour accelerated test time (aging).

(a) (b)

Fig 5.8 The driving margin of the panel with RGB phosphor after (a) 18 hour and (b) 1000 hour accelerated test time (aging).