Patent Application
20080259002
This Nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 10-2007-0038488 filed in Korea on Apr. 19, 2008, and Patent Application No. 10-2007-0140181 filed in Korea on Dec. 28, 2008, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a plasma display apparatus and, more particularly, to an electrode structure of a panel provided to a plasma display apparatus.
2. Discussion of Related Art
In general, a plasma display panel includes an upper substrate, a lower substrate and a barrier rib defining one unit cell between the upper and lower substrates. Each cell is filled with an inert gas containing a major discharge gas and a small amount of xenon, such as neon (Ne), helium (He) or a mixed gas of neon and helium (Ne+He). When discharge is generated by a high-frequency voltage, the inert gas generates vacuum ultraviolet rays, and a phosphor material formed between barrier ribs is excited with the vacuum ultraviolet rays, thereby displaying images. Since such a plasma display panel is thin and light, it has come into the spotlight as a next-generation display apparatus.
In the case of a general plasma display panel, scan and sustain electrodes are formed on an upper substrate, and each of the scan and sustain electrodes has a stack structure of transparent and bus electrodes formed from indium-tin-oxide (ITO) in order to secure the aperture ratio of the panel.
Recently, it has been required to manufacture a plasma display panel capable of saving manufacturing cost and improving visible and driving characteristics suitable for user's watching.
An object of the present invention is to provide a plasma display apparatus provided with a plasma display panel capable of saving manufacturing cost of the panel and improving the luminance of a display image by removing a transparent electrode formed from ITO.
A plasma display apparatus according to the present invention includes an upper substrate; first and second electrodes formed on the upper substrate; a lower substrate disposed opposite to the upper substrate; and a third electrode formed on the lower substrate. At least one of the first and second electrodes is formed as one layer, and comprises first and second electrode lines formed in a direction intersecting the third electrode and a connecting electrode that connects the first and second electrode lines. The distance between the first and second electrode lines has a value of 2 or more in one discharge cell.
A plasma display apparatus according to the present invention will now be described in detail in connection with specific embodiments with reference to the accompanying drawings.
Referring to
The upper panel 10 includes a sustain electrode pair 12 and 13 formed on an upper substrate 11 while making a pair. The sustain electrode pair 12 and 13 are divided into a scan electrode 12 and a sustain electrode 13 depending on their functions. The sustain electrode pair 12 and 13 are covered by an upper dielectric layer restricting a discharge current and insulating the electrode pair from each other, and a protection layer 15 is formed on the upper dielectric layer 14 to protect the upper dielectric layer 14 from sputtering of charged particles generated at the time of gas discharge and also increase emission efficiency of secondary electrons.
Discharge spaces between the upper substrate 11, a lower substrate 21 and barrier ribs 22 are injected with a discharge gas. Preferably, the discharge gas includes xenon (Xe) of 10% or more. In the event that the discharge gas includes the xenon (Xe) with the mixture ratio described above, discharge/luminous efficiency of the plasma display panel can be enhanced.
The lower panel 20 includes a plurality of discharge spaces, i.e., barrier ribs 22 partitioning discharge cells, formed on the lower substrate 21. Address electrodes 23 are disposed in a direction intersecting with the sustain electrode pair 12 and 13, and a phosphor layer 24 generating visible rays emitted by ultraviolet rays generated at the time of gas discharge is coated on surfaces of a lower dielectric layer 25 and the barrier ribs 22.
At this time, each of the barrier ribs 22 has a longitudinal barrier rib 22a formed in a direction parallel with the address electrodes 23 and a traverse barrier rib 22b formed in a direction traversing the address electrodes 23. The barrier rib 22 functions to partition discharge cells physically and prevent ultraviolet rays, which are generated by discharge, and a visible ray from leaking to neighboring discharge cells.
In the plasma display panel according to the present invention, the sustain electrode pair 12 and 13 include only opaque metal electrodes. That is, the sustain electrode pair 12 and 13 are not formed using ITO, which is a conventional transparent electrode material, but formed using silver (Ag), copper (Cu) or chrome (Cr), which is a conventional bus electrode material. In other words, each of the sustain electrode pair 12 and 13 of the plasma display panel according to the present invention does not include a conventional ITO electrode but includes a bus electrode as one layer.
For example, it is preferred that each of the sustain electrode pair 12 and 13 according to the embodiment of the present invention be formed of silver (Ag). Preferably, the silver (Ag) has a photosensitive property. In addition, each of the sustain electrode pair 12 and 13 according to the embodiment of the present invention may have a darker color and lower transmittance of light than the upper or lower dielectric layer 14 or 25.
The discharge cell may have a symmetric structure in which the pitches of the phosphor layers 24 of red (R), green (G) and blue (B) are the same as one another, or a non-symmetric structure in which the pitches of the phosphor layers 24 of red (R), green (G) and blue (B) are different from one another. The discharge cell may have a non-symmetric structure in which the phosphor layers 24 of red (R), green (G) and blue (B) have the order of the pitch of a red (R) cell<the pitch of a green (G) cell<the pitch of a blue (B) cell.
As shown in
Preferably, the first and second sustain electrodes 12 and 13 are respectively a scan electrode and a sustain electrode, in consideration of the aperture ratio and discharge diffusion efficiency caused by use of the opaque sustain electrode pair 12 and 13. That is, an electrode line having a narrow width is used in consideration of the aperture ratio, and a plurality of electrode lines are used in consideration of the discharge diffusion efficiency. At this time, the number of electrode lines may be determined in consideration of both the aperture ratio and discharge diffusion efficiency.
The structure shown in
In addition, the structure of the barrier ribs shown in
The electrode arrangements shown in
In accordance with an embodiment of the present invention, the reset period may be omitted in at least one of the plurality of subfields. For example, the reset period may exist only in the first subfield, or exist only in a subfield approximately between the first subfield and the entire subfields.
In each of the address periods A1, . . . , A8, a display data signal is applied to the address electrode X, and scan signals corresponding to the scan electrodes Y are sequentially applied to the address electrode X.
In each of the sustain periods S1, . . . , S8, a sustain pulse is alternately applied to the scan electrodes Y and the sustain electrodes Z. Accordingly, sustain discharge is generated in discharge cells on which wall charges are formed in the address periods A1, . . . , A8.
The luminance of the plasma display panel is proportional to the number of sustain discharge pulses within the sustain periods S1, . . . , S8, which is occupied in a unit frame. In the event that one frame to form 1 image is represented by eight subfields and 256 gray levels, different numbers of sustain pulses may be sequentially allocated to the respective subfields at a ratio of 1, 2, 4, 8, 16, 32, 64, and 128. For example, in order to obtain the luminance of 133 gray levels, sustain discharge can be generated by addressing the cells during the subfield1 period, the subfield3 period, and the subfield8 period.
The number of sustain discharges allocated to each subfield may be varied depending on the weight of a subfield according to an Automatic Power Control (APC) step. In other words, although an example in which one frame is divided into eight subfields has been described with reference to
Further, the number of sustain discharges allocated to each subfield may be changed in various ways in consideration of gamma characteristics or panel characteristics. For example, the degree of gray levels allocated to the subfield4 may be lowered from 8 to 6, and the degree of gray levels allocated to the subfield6 may be raised from 32 to 34.
Each subfield includes a pre-reset period where positive wall charges are formed on the scan electrodes Y and negative wall charges are formed on the sustain electrodes Z, a reset period where discharge cells of the entire screen are reset using wall charge distributions formed in the pre-reset period, an address period where discharge cells are selected, and a sustain period where the discharge of selected discharge cells is sustained.
The reset period includes a set-up period and a set-down period. In the set-up period, a ramp-up waveform is applied to the entire scan electrodes at the same time, so that a minute discharge occurs in the entire discharge cells and wall charges are generated accordingly. In the set-down period, a ramp-down waveform, which falls from a positive voltage lower than a peak voltage of the ramp-up waveform, is applied to the entire scan electrodes Y at the same time, so erase discharge is generated in the entire discharge cells. Accordingly, unnecessary charges are erased from the wall charges generated by the set-up discharge and spatial charges.
In the address period, a scan signal having a scan voltage Vsc of a negative polarity is sequentially applied to the scan electrodes Y and at the same time, a data signal of a positive polarity is applied to the address electrodes X. Address discharge is generated by a voltage difference between the scan signal and the data signal and a wall voltage generated during the reset period, so the cells are selected. Meanwhile, in order to enhance the efficiency of the address discharge, a sustain bias voltage Vzb is applied to the sustain electrode during the address period.
During the address period, the plurality of scan electrodes Y may be divided into two or more groups and sequentially supplied with the scan signal on a group basis. Each of the divided groups may be divided into two or more subgroups and sequentially supplied with the scan signal on a subgroup basis. For example, the plurality of scan electrodes Y may be divided into a first group and a second group. For example, the scan signal may be sequentially supplied to scan electrodes belong to the first group, and then sequentially supplied to scan electrodes belong to the second group.
In an embodiment of the present invention, the plurality of scan electrodes Y may be divided into a first group placed at the even number and a second group placed at the odd number depending upon a position formed on the panel. In another embodiment, the plurality of scan electrodes Y may be divided into a first group disposed on an upper side and a second group disposed on a lower side on the basis of the center of the panel.
The scan electrodes belonging to the first group divided according to the above method may be divided into a first subgroup placed at the even number and a second subgroup placed at the odd number, or a first subgroup disposed on an upper side and a second subgroup disposed on a lower side on the basis of the center of the first group.
In the sustain period, a sustain pulse having a sustain voltage Vs is alternately applied to the scan electrode and the sustain electrode, so sustain discharge is generated between the scan electrode and the sustain electrode in a surface discharge form.
A width of a first sustain signal or the last sustain signal of a plurality of sustain signals, which are alternately applied to the scan electrode and the sustain electrode during the sustain period, may be greater than that of the remaining sustain pulses.
After the sustain discharge is generated, an erase period in which wall charges remaining in the scan electrodes or the sustain electrodes of an on-cell selected in the address period are erased by generating weak discharge may be further included posterior to the sustain period.
The erase period may be included in all the plurality of subfields or some of the plurality of subfields. In this erase period, an erase signal for the weak discharge may be applied to electrodes to which the last sustain pulse was not applied in the sustain period.
The erase signal may include a ramp type signal that gradually rises, a low-voltage wide, a high-voltage narrow pulse, an exponential signal, a half-sinusoidal pulse or the like.
In addition, in order to generate the weak discharge, a plurality of pulses may be sequentially applied to the scan electrodes or the sustain electrodes.
The driving waveforms shown in
Referring to
Each of the sustain electrodes may further include a connecting electrode 62 or 72 connecting the two electrode lines 60 and 61 or 70 and 71.
The electrode lines 60, 61, 70 and 71 transverse the discharge cell and may extend in a direction parallel with a transverse barrier rib 50 of barrier ribs defining the discharge cell.
The connecting electrodes 62 and 72 allow discharge started at a central portion of the discharge cell to be easily diffused up to the electrode lines 61 and 71 disposed distant from the center of the discharge cell, respectively.
As described above, discharge efficiency is enhanced using the plurality of electrode lines 60, 61, 70 and 71 and the connecting electrodes 62 and 72, so that luminous efficiency of the plasma display panel can be entirely enhanced. Accordingly, an ITO transparent electrode can be removed without reducing luminance of the plasma display panel.
In the event that each of the sustain electrodes includes two electrode lines 60 and 61 or 70 and 71 as shown in
Thus, in the case of the plasma display apparatus according to the present invention, the distance between the two electrode lines 60 and 61 or 70 and 71 constituting the sustain electrode is variably adjusted, so that the luminance of a display images is not reduced, and a discharge firing voltage is decreased.
Referring to
That is, the distance between the first and second electrode lines 110 and 111 constituting a scan electrode may have a value of 2 or more, and the distance between the first and second electrode lines 120 and 121 constituting a sustain electrode may have a value of 2 or more.
Hereinafter, the embodiment of the electrode structure formed on the upper substrate of the plasma display panel according to the present invention will be described with respect to the first and second electrode lines 110 and 111 constituting the scan electrode.
Referring to
As shown in
That is, the distance between the first and second electrode lines 110 and 111 may have a maximum value d1 at a central portion overlapping with the center line between adjacent two longitudinal barrier ribs 105 and 106, and may have a minimum value d2 at an edge portion overlapping with the longitudinal barrier rib 105 or 106.
As shown in
Referring to
Through the protruding electrodes 130 and 140, discharge is diffused up to upper/lower edge regions of the discharge cell to be uniformly generated at the entire region of the discharge cell. Accordingly, the quality of a display image can be improved.
The following Table 1 lists the measurement results of a discharge firing voltage and luminance of a display image depending on the change in the distance d1 between the first and second electrode lines 110 and 111 at the central portion of the discharge cell and the distance d2 between the first and second electrode lines 110 and 111 at the edge portion of the discharge cell.
Referring to Table 1 and
For example, in the event that d1/d2 increases up to 1.11 or more, the discharge firing voltage may be rapidly lowered down to 180V or less as compared with when d1/d2 is below 1.11.
On the other hand, as shown in Table 1, as d1/d2 increases, the aperture ratio of the panel decreases at the central portion of the discharge cell, and therefore the luminance of a display image may be reduced. For example, in the event that d1/d2 exceeds 1.38, the luminance of a display image may be rapidly reduced down to 450 cd/m2 or less.
Preferably, the ratio d1/d2 of maximum to minimum values of the distance between the first and second electrode lines 110 and 111 is 1.11 to 1.38 so that the discharge firing voltage is maintained to be 180V or less, and the luminance of a display image is stably maintained to be 450 cd/m2 or more.
Considering the longitudinal width of the discharge cell, when the ratio d1/d2 of the maximum to minimum values of the distance between the first and second electrode lines 110 and 111 is 1.11 to 1.38, the distance g1 between the scan and sustain electrodes at the central portion of the discharge cell may be 1.05 to 1.4 of the distance g2 between the scan and sustain electrodes at the edge portion of the discharge cell.
That is, when the ratio g1/g2 of maximum to minimum values of the distance between the scan and sustain electrodes is 1.05 to 1.4, the discharge firing voltage can be lowered, and a reduction of the luminance of a display image can also be prevented.
In order to secure the aperture ratio of the panel and reduce the discharge firing voltage as described above, it is preferred that the distance g1 between the scan and sustain electrodes is 1.9 to 3 of the line width of the electrode line.
Although the section of each of the first electrode line 110 and 120 has a square shape in
Referring to
For example, the distance between the first and second electrode lines 210 and 211 may have a maximum value d1 at a central portion overlapping with the center line between adjacent two longitudinal barrier ribs 205 and 206, and may have a minimum value d2 at an edge portion overlapping with the longitudinal barrier rib 205 or 206.
As shown in
Referring to
Through the protruding electrodes 230, 231, 240 and 241, a discharge firing voltage is decreased, and discharge efficiency is enhanced, thereby improving a driving voltage margin. Further, the length of a current path is increased, thereby preventing a flickering delay generated due to the configuration of the first and second lines 210 and 211 or 220 and 221 constituting the sustain electrode.
As shown in
In the event that the two protruding electrodes 230 and 231 are disposed at a central portion of the discharge cell, the luminance of a display image may be lowered. Therefore, in order to enhance discharge efficiency without reducing the luminance of a display image, it is preferred that the distance a1 between adjacent two longitudinal barrier ribs 205 and 206 is 1.7 to 3 of the distance a2 between the protruding electrodes 230 and 231.
Referring to
Through the protruding electrodes 230 and 240, discharge is diffused up to upper/lower edge regions of the discharge cell to be uniformly generated at the entire region of the discharge cell. Accordingly, the quality of a display image can be improved.
The following Table 2 lists the measurement results of a discharge firing voltage and luminance of a display image depending on the change in the distance d1 between the first and second electrode lines 210 and 211 at the central portion of the discharge cell and the distance d2 between the first and second electrode lines 210 and 211 at the edge portion of the discharge cell.
Referring to Table 2 and
For example, in the event that d1/d2 decreases down to below 0.75, the discharge firing voltage may be rapidly increased up to 187V or more as compared with when d1/d2 is 0.75 or more.
As shown in Table 2, as d1/d2 increases, the aperture ratio of the panel decreases at the central portion of the discharge cell, and therefore the luminance of a display image may be reduced. For example, in the event that d1/d2 exceeds 0.94, the luminance of a display image may be rapidly reduced down to 450 cd/m2 or less.
Preferably, the ratio d1/d2 of maximum to minimum values of the distance between the first and second electrode lines 210 and 211 is 0.75 to 0.94 so that the luminance of a display image is enhanced, and the discharge firing voltage is not rapidly increased.
In order to secure the aperture ratio of the panel and reduce the discharge firing voltage as described above, it is preferred that the distance g1 between the scan and sustain electrodes be 1.9 to 3 of the line width of the electrode line.
Although in FIGS. 9 to 11,. In this case,. Although the section of each of the first electrode line 210 and 220 has a square shape in
Referring to
In the event that the amounts of wall charges formed in the two electrode lines 310 and 311 are different, the amount of light generated at the time of sustain discharge may be changed depending on the positions of the two electrode lines 310 and 311, and therefore a spot pattern may be produced in a display image.
For example, since wall charges are formed by diffused discharge in the electrode line 311 disposed at an edge portion of the discharge cell, the electrode line 311 may have the amount of wall charges formed by address discharge less than the electrode line 310 adjacent to the center of the discharge cell. Thus, the width b1 of the electrode line 311 disposed at the edge portion of the discharge cell is greater than the width b2 of the electrode line 310 adjacent to the center of the discharge cell, so that the amount of wall charges formed in the two electrode lines 310 and 311 can be uniform.
As described above, the amount of wall charges formed in the two electrode lines 310 and 311 is uniform, so that discharge is uniformly generated at the entire region of the discharge cell, thereby preventing quality reduction generated in a display image.
The following Table 3 lists whether a spot pattern occurred and the measurement results of luminance depending on changes in widths b1 and b2 of the adjacent two electrode lines 311 and 310.
Referring to Table 3, when the width b1 of the electrode line 311 disposed at the edge portion of the discharge cell is 44 μm or more, no spot pattern is produced in a display image. However, when the width b1 of the electrode line 311 disposed at the edge portion of the discharge cell is over 80 μm, the luminance of a display image is rapidly decreased down to 460 cd/m2 or less.
Thus, when the width b1 of the electrode line 311 disposed at the edge portion of the discharge cell is 1.1 to 2 of the width b2 of the electrode line 310 adjacent to the center of the discharge cell, a reduction of quality of a display image can be prevented, and the luminance of a display image can also be improved.
Alternatively, the width b1 of the electrode line 311 disposed at the edge portion of the discharge cell may be 1.15 to 1.5 of the width b2 of the electrode line 310 adjacent to the center of the discharge cell so that the amount of wall charges is uniform by increasing the amount of wall charges formed in the electrode line 311 without largely reducing discharge diffusion efficiency.
Referring to
As shown in
Referring to
As described above, the scan electrode 11 and the sustain electrode 12 may have a structure in which a transparent electrode and a bus electrode are stacked or may include only the bus electrode without the transparent electrode. Black matrices, which have a light-shielding function of absorbing external light generated externally and decreasing reflection of the light and a function of enhancing the purity and contrast of the upper substrate 10, may be arranged on the scan electrode 11 and the sustain electrode 12.
A protection layer 14 formed between the dielectric layer 13 and a discharge space may be formed from a material (for example, magnesium oxide (MgO)), which has a large number of secondary emission electrons when ions emitted from the discharge space collide against a surface and has less surface damage due to ion collision.
The discharge efficiency can be enhanced by the secondary emission electrons emitted from the protection layer 14 and therefore a discharge firing voltage can be lowered.
In the case of the plasma display panel according to the present invention, a crystal layer 16 including a material (for example, magnesium oxide (MgO) crystal), which has a large number of secondary emission electrons when ions emitted from the discharge space collide against a surface and has less surface damage due to ion collision, may be formed on the protection layer 14.
When comparing the peak of light emitted when ions emitted from the discharge space collide against a surface, the crystal layer 16 can perform light emission having a peak at a wavelength region lower than that of the protection layer 14.
In other words, the crystal layer 16 emits light having a peak at a wavelength region lower than that of the protection layer 14 when ions emitted from the discharge space collide against a surface, so the discharge efficiency enhanced by the protection layer 14 can be further enhanced.
For example, the crystal layer 16 may include a plurality of magnesium oxide (MgO) crystals having an average diameter of 500 angstrom or more, and the protection layer 14 may consist of MgO particles having a size, which is much smaller than that of the magnesium oxide (MgO) crystals.
A peak of light emitted from the crystal layer 16 when ions emitted from the discharge space collide against a surface may have a wavelength region lower than that of a peak of light emitted from the protection layer 14 according to the size of MgO.
The size of the magnesium oxide (MgO) crystals included in the crystal layer 16 may be decided so that light, which has a peak not overlapped with the peak of light emitted from the protection layer 14 and has a wavelength region lower than that of the light emitted from the protection layer 14, can be emitted from the crystal layer 16.
For example, the peak of light emitted from the crystal layer 16 when ions emitted from the discharge space collide against a surface may have a wavelength region of about 200 nm to 300 nm, and the peak of light emitted from the protection layer 14 may have a wavelength region of about 300 nm to 400 nm, which is a little higher than 200 nm to 300 nm.
As described above, since the protection layer 14 and the crystal layer 16 having different emission peak regions are formed over the upper substrate of the panel, the discharge efficiency can be further enhanced, and a discharge firing voltage can be lowered. Further, delay jitter of address discharge can be reduced by secondary electrons emitted from the two layers 14 and 16.
If the upper substrate of the present invention is constructed as shown in
As described above, in the event that the scan and sustain electrodes includes only the bus electrodes without the transparent electrodes, a gap between the scan and sustain electrodes can be increased to secure the aperture ratio of the panel, and the increase of a discharge firing voltage generated accordingly are compensated by the construction of the upper substrate of the panel shown in
Referring to
For example, the crystal layers 16a, 16b, and 16c may be formed at places where they are overlapped with the scan electrode 11 or the sustain electrode 12 in order to further improve the aperture ratio of the panel.
Referring to
Discharge is generated in the gap between the scan electrode 11 and the sustain electrode 12. Thus, if the crystal layer 17 is formed on the basis of the gap between the scan electrode 11 and the sustain electrode 12 as shown in
Referring to
In accordance with the plasma display apparatus constructed as described above according to the present invention, manufacturing cost of a plasma display panel can be saved by removing a transparent electrode made from ITO. Further, a discharge firing voltage can be reduced and the luminance of a display image can also be improved by variably adjusting the distance between two electrode lines constituting a scan or sustain electrode.
While the invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2007-0038488 | Apr 2007 | KR | national |
| 10-2007-0140181 | Dec 2007 | KR | national |
