Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2002-04-02
2003-06-17
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C345S076000
Reexamination Certificate
active
06580227
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel suitably used for a flat display panel, a manufacturing method thereof, and a plasma display. The present invention more specifically relates to a plasma display panel with improved contrast, a manufacturing method thereof, and a plasma display.
2. Description of the Related Art
There are two kinds of plasma display panels (PDPs), AC type and DC type PDPs. The AC type PDP has electrodes covered with dielectric because of the operating method and is indirectly operated in an AC discharge state. The DC type PDP has electrodes exposed in a discharge space and is operated in a DC discharge state. The AC type plasma displays are divided based on the driving method into a memory operation type using display cell memories, and a refresh operation type that does not use memories. Note that the luminance by the plasma display is in proportion with the number of discharge. The refresh type display whose luminance is reduced for an increased display capacity is mainly used for a plasma display with a small display capacity.
FIG. 1
is a perspective view of a single display cell in an AC type plasma display panel.
FIGS. 2A and 2B
are a plan view and a sectional view, respectively showing in detail the shapes of a scan electrode and a common electrode in a conventional plasma display panel.
A display cell is provided with two insulating glass substrates
101
and
102
. The insulating substrate
101
is to be a back panel substrate, while the insulating substrate
102
is to be a front panel substrate.
Transparent electrodes
103
and
104
are provided on the surface of the insulating substrate
102
facing the insulating substrate
101
. The transparent electrodes
103
and
104
extend in the horizontal direction of the panel (in the horizontal direction). Bus electrodes
105
and
106
are provided to overlap the transparent electrode
103
and the common electrode
104
, respectively. The bus electrodes
105
and
106
are each for example a thin film electrode of CrCu or Cr having a thickness from 1 &mgr;m to 4 &mgr;m. The bus electrodes are provided to reduce the electrode resistance values between the electrodes and externally provided drives. The transparent electrode
103
and the bus electrode
105
form a scan electrode
115
, while the transparent electrode
104
and the bus electrode
106
form a common electrode
116
. Within one display cell, the bus electrodes
105
and
106
are provided in the furthermost positions from the surface discharge gap between the transparent electrodes
103
and
104
. There are a dielectric layer
112
to cover the transparent electrodes
103
and
104
and a protection layer
114
of magnesium oxide or the like to protect the dielectric layer
112
against discharge.
There is a data electrode
107
perpendicular to the scan electrode
103
and the common electrode
104
on the surface of the insulating substrate
101
facing the insulating substrate
102
. The data electrode
107
therefore extends in the vertical direction of the panel (the vertical direction). There are barrier ribs
109
to divide display cells in the vertical direction. A dielectric layer
113
to cover the data electrode
107
is provided. A phosphor layer
111
to convert a ultraviolet beam generated by gas discharge into a visible light beam
110
is formed on the side of the barrier rib
109
and the surface of the dielectric layer
113
. A discharge gas space
108
is secured by the barrier ribs
109
in the space between the insulating substrates
101
and
102
. Then, a helium, neon, or xenon gas, or a mixture gas thereof as a discharge gas is filled in the discharge gas space
108
.
In the plasma display panel as described above, when the potential difference between the scan electrode
115
and the common electrode
116
is above a prescribed value, discharge is generated, and light emission
110
is caused accordingly.
Writing selective type driving operation in the conventional plasma display panel as described above will now be described.
FIG. 3
is a timing chart for use in illustration of the writing selective type driving operation in the conventional plasma display panel. Each sub field consists of four periods, a priming period, an address period, a sustaining period, and a charge erasure period. These four periods are sequentially set.
In the priming period, a saw-toothed priming pulse Ppr-s is applied to the scan electrode, and a rectangular waveform priming pulse Ppr-c is applied to the common electrode. The priming pulse Ppr-s is a pulse of the positive polarity, while the priming pulse Ppr-c is a pulse of the negative polarity. According to
The Technical Report of The Proceeding of The Institute of Electronics, Information and Communication Engineers
, vol. EID 98-95, p. 91, January 1991, the use of voltage in a ramp voltage waveform at 7.5 V/&mgr;sec or less can lower the black luminance. The smaller the gradient of the voltage, the lower is the black luminance, while at too small a gradient the time period for the voltage to reach the necessary level for priming discharge is prolonged, which prolongs the priming period. Then, the sustaining period must be shortened, and the peak luminance is lowered in the sustaining discharge, which lowers the contrast. Therefore, a voltage gradient of about 4 V/&mgr;sec is typically used.
In response to the applied priming pulses Ppr-s and Ppr-c, priming discharge is generated in a discharge space in the vicinity of the gap between the scan electrode and the common electrode. Active particles which make easier the following sustaining discharge in the cell are generated, while wall charge of the negative polarity is attached on the scan electrode and wall charge of the positive polarity is attached on the common electrode. Then, a charge control pulse Ppe-s is applied to the scan electrode. This causes weak discharge to take place, so that the wall charge of the negative polarity on the scan electrode and the wall charge of the positive polarity on the common electrode are reduced.
In the following address period, a display cell for light emission is selected, and writing discharge is generated only at a cell selected by a scan pulse Psc-s of the negative polarity applied to the scan electrode and a data pulse Pd of the positive polarity applied to a data electrode. Wall charge is attached to the electrode of the cell to emit light in the following sustaining period. When writing discharge is generated, wall charge is attached to the discharge cell. In contrast, discharge cells without writing discharge remain with little wall charge after the charge erasure.
In the following sustaining period, light emission is caused for display, a pulse starts to be applied from the common electrode side, and then sustaining pulses Psus-s and Psus-c of the negative polarity are alternately applied to the scan electrode and the common electrode, respectively. At the time, since there is extremely little wall charge at the discharge cells without writing during the address period, sustaining discharge is not generated when a sustaining pulse is applied to the discharge cells.
Meanwhile, in the discharge cell with writing discharge during the address period, the scan electrode is attached with positive charge, while the common electrode is attached with negative charge. Therefore, the sustaining pulse voltage of the negative polarity to the common electrode and the wall charge voltage are superposed on each other, the voltage across the region between the electrodes exceeds the threshold voltage for discharge, and intensified discharge is generated (hereinafter referred to as “strong discharge”).
Once discharge is generated, wall discharge is provided to cancel voltage being applied to each electrode. Therefore, the negative charge is attached to the common electrode, while the positive charge is attached to the scan electrode. For the following sustaining pulse, the scan electrode side has a positive voltage pulse,
NEC Corporation
Vu David
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