1. Field of the Invention
The present invention relates to a plasma display device and a plasma display panel, especially suitable for an image display with a high color temperature.
2. Description of the Background Art
FIG. 29 is a block diagram of a plasma display device disclosed for example in U.S. Pat. No. 5,661,500. In FIG. 29, the reference numeral 100 designates a plasma display device; 1 is a plasma display panel (hereinafter referred to as xe2x80x9cPDPxe2x80x9d) including display electrodes EX and EY (hereinafter referred to as xe2x80x9cX electrode EXxe2x80x9d and xe2x80x9cY electrode EYxe2x80x9d) that induce display discharge in a space therebetween, and address electrodes (hereinafter referred to as xe2x80x9cA electrodexe2x80x9d); 110 is a scan control unit; 120 is an A/D converter (hereinafter referred to as xe2x80x9cA/Dxe2x80x9d) converting input signals from analog to digital; 130 is a frame memory storing the output of the A/D 120; 141 is an X-electrode driving circuit for supplying a driving signal to the X electrodes EX of the PDP 1; 142 is a Y-electrode driving circuit for supplying a driving signal to the Y electrodes EY of the PDP 1; 143 is an A-electrode driving circuit for supplying a driving signal to the A electrodes of the PDP 1; 2 is a driving control system comprising the X-electrode driving circuit 141, the Y-electrode driving circuit 142, and the A-electrode driving circuit 143.
We will now describe a method for driving the plasma display device 100.
FIGS. 30A through 30E are timing charts showing an example of waveforms of applied voltages during one subfield according to a subfield gradation technique, disclosed for example in Japanese Patent Laid-open No. 7-160218A.
In FIGS. 30A through 30E, n1 is a scan pulse; n2 is an address pulse; n3 is a sustain pulse; and n4 is a priming pulse (full writing pulse).
One subfield is divided into: (1) a reset period to erase wall charges; (2) an address period to store wall charges in cells that emit lights for display; and (3) a sustain discharge period to induce sustain discharge in the cells where the wall charges are stored during the address period, to produce light emissions for display.
In the reset period, the full writing pulse n4 is applied to the sustain electrode EX to induce discharge in all cells. The full writing pulse n4 may also be referred to as xe2x80x9cpriming pulsexe2x80x9d. At the falling edge of the full writing pulse n4, self-erase discharge is induced in all the cells to erase wall charges.
In the address period, the scan pulse n1 is sequentially applied to the Y electrodes EY1 to EYn, and the address pulse n2 is applied to the A electrodes 22j. This induces address discharge in cells to be lightened for display during the display period, and wall charges are stored in the surface of a protective layer 18 of those cells.
In the sustain discharge period, the sustain pulse n3 is alternately applied to the Y electrodes EYi (i=1 to n) and the X electrode EX to induce sustain discharge only in the cells where the address discharge occurs.
FIG. 31 a perspective view showing the structure of a conventional PDP 1 disclosed for example in U.S. Pat. No. 5,661,500. In FIG. 31, the reference number 11 designates a front or first substrate; 17 is a dielectric layer covering the X electrode EX and the Y electrode EY which will be described later; 18 is a protective layer formed for example of MgO and covering the surface of the dielectric layer 17; 22 is the A electrode; 21 is a rear or second surface; 28 is an uninterrupted phosphor stripe formed along the A electrode 22; 29 is a barrier rib provided on the side of the second substrate 21; 30 is a discharge space; 41 is a strip transparent conductive film (hereinafter referred to as xe2x80x9ctransparent electrodexe2x80x9d) which is formed of a tin oxide layer, etc. and disposed in parallel with each other at given intervals (discharge gap) to form the X electrode EX and the Y electrode EY; and 42 is a strip metal film (hereinafter referred to as xe2x80x9cmetal electrodexe2x80x9d) formed of a multilayer film such as Crxe2x80x94Cuxe2x80x94Cr or Crxe2x80x94Alxe2x80x94Cr to supplement conductivity of the transparent electrode 41. Each of the X electrode EX and the Y electrode EY is composed of the transparent electrode 41 and the additional metal electrode 42. The reference character EG designates a pixel, which is, in the case of color display devices, composed of unit luminescent areas EU emitting lights of a plurality of colors. The reference character S designates a display surface.
Next, we will describe operation of the conventional plasma display device. The plasma display device 100 comprises the PDP 1 and the driving control system 2 for driving the PDP 1, electrically connected to the PDP 1 via a flexible printed wiring board. In the driving control system 2, an analog input signal is converted into a digital form by the A/D 120; the digital output from the A/D 120 is stored in the frame memory 130 as a digital image signal; and according to the digital image signal, the output of the scan control unit 110 is supplied to the X-electrode driving circuit 141, the Y-electrode driving circuit 142, and the A-electrode driving circuit 143 to drive the PDP 1.
The PDP 1 is a surface discharge type PDP with a three electrode structure having a pair of display electrodes, namely X electrode EX and Y electrode EY, and the A electrode which correspond to the unit luminescent area EU. Both the X electrode EX and the Y electrode EY are composed of the transparent electrode 41 and the metal electrode 42 and disposed on a surface of the first substrate 11 on the side of the display surface S. On the second substrate 21, the barrier ribs 29 are provided, defining the height of the discharge space 30. The discharge space 30 is sectioned by the unit luminescent areas EU along an extending direction of the X and Y electrodes EX and EY (hereinafter referred to as xe2x80x9cfirst directionxe2x80x9d).
Between the parallel barrier ribs 29, an A electrode of a given width is disposed by printing and firing a pattern of a silver paste; and a phosphor stripe 28 is provided to cover side walls of the barrier ribs 29 and the second substrate 21 including the surface of the A electrode 22. The pixel EG is almost in the shape of a square, composed of three unit luminescent areas EU(28R), EU(28G), EU(28B) (generically referred to as xe2x80x9cunit luminescent area EUxe2x80x9d) which are approximately similar rectangles in shape and correspond to the emitted colors: red (R), green (G), and blue (B), respectively. That is, the unit luminescent area EU of each emitted color in the pixel EG is about the same in width in the first direction D1, constituting one third the width of the pixel in the first direction D1.
To prevent deterioration in contrast of the screen due to incident extraneous lights from the first substrate 11 of the PDP 1, a black low melting point glass (black stripe) may be provided between the pair of the X electrode EX and the Y electrode EY on the first substrate 11.
FIG. 32 is a schematic diagram showing an arrangement of phosphors viewed from the display surface S. As shown in FIG. 32, a pixel EG is basically composed of the unit luminescent areas EU with a red phosphor 28R, a green phosphor 28G, and a blue phosphor 28B (each alphabet designates the emitted color and the aforementioned phosphor 28 is a generic name for these three phosphors) corresponding to three primary colors: red (R), green (G), and blue (B), respectively. Color reproduction is thus made by additive mixing of color lights emitted from the unit luminescent areas EU corresponding to the three primary colors. For instance, the red phosphor 28R is formed of (Y, Gd) BO3:EU3+; the green phosphor 28G of Zn2SiO4:Mn; and the blue phosphor 28B of BaMgAl14O23:Eu2+.
The composition of materials of the phosphors is selected so that a mixture of the three colors becomes white (somewhat reddish white) when light emissions (excitation) from all the unit luminescent areas occurs simultaneously under the same conditions. Under normal circumstances, the white color temperature of approximately 6000 K is accomplished.
The aforementioned conventional plasma display panel has the following problems.
In order to obtain a so-called white color display with a high color temperature about 9300 K, i.e., a bluish white image with a high color temperature, the intensity of blue light emission has to be increased (to as much as the luminescence intensity of red). In the conventional device, however, the luminescent area of blue is about the same in size as the other luminescent areas of red and green as shown in FIG. 32, so that the luminescence intensity of blue is relatively low according to the properties of phosphors. Accordingly, the white display has a low color temperature.
For the purpose of relatively increasing the luminescence intensity of blue, it may be considered to increase the levels of blue gradations larger than those of red and green gradations or to reduce the levels of red and green gradations smaller than those of the blue gradations. However, reducing the levels of the red and green gradations (e.g., reducing 256-level red and green gradation to 128-level while maintaining a 256-level blue gradation) narrows down the representation of the red and green gradations, which interferes good color-image display. Further, if the amount of ultraviolet rays irradiating the blue phosphor is increased as compared with that irradiating the red and green phosphors in order to increase the amount of blue light emission, the blue phosphor will be deteriorated more than the red and green phosphors.
A first preferred embodiment of the present invention is directed to a surface discharge type plasma display panel comprising: a first substrate; a plurality of display electrode pairs formed on an inner surface of the first substrate in a first direction; a second substrate with a plurality of address electrodes formed in a second direction intersecting with the first direction, the second substrate and the first substrate sandwiching a discharge space therebetween; a plurality of phosphors provided for each of the plurality of address electrodes to emit a plurality of emitted colors; and a plurality of barrier ribs extending in the second direction on the second substrate and spaced in the first direction so that a substantial space corresponding to at least any one emitted color out of the plurality of emitted colors is different from a space corresponding to the other emitted colors, each of the plurality of barrier ribs having side walls on which each of the plurality of phosphors are deposited.
According to a second aspect of the present invention, in the surface discharge type plasma display panel of the first aspect, the second substrate comprises: a second substrate body; the plurality of address electrodes formed on the second substrate body; and a dielectric formed on the second substrate and on the plurality of address electrodes to cover the plurality of address electrodes, and the plurality of barrier ribs are formed on a surface of the dielectric.
According to a third aspect of the present invention, in the surface discharge type plasma display panel of the second aspect, the plurality of emitted colors include red, green, and blue.
According to fourth aspect of the present invention, in the surface discharge type plasma display panel of the third aspect, the any one emitted color is blue.
According to a fifth aspect of the present invention, the surface discharge type plasma display panel of the first aspect is composed of a plurality of pixels each including unit luminescent areas each corresponding to each of the plurality of emitted colors, wherein a substantial space between barrier ribs corresponding to the any one emitted color is larger than one third the width of any one pixel out of the plurality of pixels in the first direction.
According to a sixth aspect of the present invention, the surface discharge type plasma display panel of the first aspect is composed of a plurality of pixels each including unit luminescent areas each corresponding to each of the plurality of emitted colors, wherein a substantial space between barrier ribs corresponding to the any one emitted color is about a half of a space between barrier ribs corresponding to a given emitted color other than the any one emitted color.
According to a seventh aspect of the present invention, in the surface discharge type plasma display panel of the first aspect, the plurality of emitted colors include red, green, and blue; a phosphor of the red, a phosphor of the green, and a phosphor of the blue are defined as xe2x80x9cRxe2x80x9d, xe2x80x9cGxe2x80x9d, and xe2x80x9cBxe2x80x9d, respectively; a single pixel is composed of four unit luminescent areas; and phosphors in the single pixel are arranged in order of R, B, G, B in the first direction.
According to an eighth aspect of the present invention, in the surface discharge type plasma display panel of the first aspect, the plurality of emitted colors include red, green, and blue; a phosphor of the red, a phosphor of the green, and a phosphor of the blue are defined as xe2x80x9cRxe2x80x9d, xe2x80x9cGxe2x80x9d, and xe2x80x9cBxe2x80x9d, respectively; a single pixel is composed of four unit luminescent areas; and phosphors in the single pixel are arranged in order of B, G, B, R in the first direction.
According to a ninth aspect of the present invention, in the surface discharge type plasma display panel of the first aspect, a color temperature obtained by mixing the plurality of emitted colors is approximately 9300 K or more.
A tenth aspect of the present invention is directed to a surface discharge type plasma display device comprising: the surface discharge type plasma display panel of the first aspect; and a driving control system. The driving control system comprises: display-electrode driving circuits connected to a first electrode and a second electrode, respectively, the first and second electrodes forming each of the plurality of display electrode pairs of the surface discharge type plasma display panel, the display-electrode driving circuits driving the surface discharge type plasma display panel; an address-electrode driving circuit connected to the plurality of address electrodes of the surface discharge type plasma display panel; and a control unit configured to control the display-electrode driving circuits and the address-electrode driving circuit.
According to an eleventh aspect of the present invention, the surface discharge type plasma display device of the tenth aspect, further comprises: a filter provided forward of a substrate on a display surface side of the surface discharge type plasma display panel out of the first and second substrates and having a spectrum that transmittance of each wavelength is almost uniform in a visible luminescence wavelength region.
According to a twelfth aspect of the present invention, in the surface discharge type plasma display panel of the first aspect, a substrate on a display surface side of the surface discharge type plasma display panel out of the first and second substrates is colored and has a spectrum that transmittance of each wavelength is almost uniform in a visible luminescence wavelength region.
According to a thirteenth aspect of the present invention, the surface discharge type plasma display panel of the fourth aspect, further comprises: a dielectric layer formed on the inner surface of the first substrate to cover the plurality of display electrodes; and a filter provided in a portion of the dielectric layer corresponding to a cell of the blue emitted color and having a spectrum that transmittance of a blue light wavelength is higher than transmittance of a red light wavelength.
According to a fourteenth aspect of the present invention, in the surface discharge type plasma display panel of the first aspect, a first unit luminescent area corresponding to the any one emitted color and a second unit luminescent area corresponding to one of the other emitted colors are adjacent to each other in the first direction; a space between barrier ribs defining the first unit luminescent area is larger than a space between barrier ribs defining the second unit luminescent area; one of the barrier ribs defining the first unit luminescent area corresponds to one of the barrier ribs defining the second unit luminescent area, having a first side wall on the side of the first unit luminescent area and a second side wall on the side of the second unit luminescent area; and a thickness of a first phosphor covering a portion of the first side wall in the vicinity of the inner surface of the first substrate is smaller than a thickness of a second phosphor covering a portion of the second side wall in the vicinity of the inner surface of the first substrate.
According to a fifteenth aspect of the present invention, in the surface discharge type plasma display panel of the first aspect, of the plurality of address electrodes, a width of an address electrode of an unit luminescent area corresponding to the any one emitted color in the first direction is different from widths of address electrodes of unit luminescent areas corresponding to the other emitted colors in the first direction.
According to a sixteenth aspect of the present invention, in the surface discharge type plasma display panel of the fifteenth aspect, with an increase in the substantial space between barrier ribs defining the unit luminescent area of the any one emitted color, the width of the address electrode corresponding to the any one emitted color becomes narrower than the width of the address electrodes corresponding to the other emitted colors.
According to a seventeenth aspect of the present invention, in the surface discharge type plasma display panel of the fifteenth aspect, with an increase in the substantial space between barrier ribs defining the unit luminescent area of the any one emitted color, the width of the address electrode corresponding to the any one emitted color becomes wider than the width of the address electrodes corresponding to the other emitted colors.
An eighteenth aspect of the present invention is directed to a surface discharge type plasma display panel comprising: a first substrate; a group of display electrodes formed on an inner surface of the first substrate in a first direction; a second substrate with a group of address electrodes formed in a second direction intersecting with the first direction, the second substrate and the first substrate sandwiching a plurality of discharge spaces therebetween; and a plurality of phosphors provided for each of address electrodes in the group of address electrodes, on a portion of an inner surface of the second substrate facing a discharge space corresponding to each of the address electrodes, each of the plurality of phosphors emitting lights of various colors corresponding to each of the address electrodes, wherein a substantial luminescent area corresponding to at least any one emitted color out of a plurality of emitted colors is different in size from substantial luminescent areas corresponding to the other emitted colors.
According to a nineteenth aspect of the present invention, in the surface discharge type plasma display panel of the eighteenth aspect, the emitted colors is composed of red, green, and blue; and a substantial luminescent area of the blue is larger than substantial luminescent areas of the red and the green.
A twentieth aspect of the present invention is directed to a substrate for a surface discharge type plasma display panel, comprising: a plurality of barrier ribs spaced in a first direction on a surface of the substrate and extending in parallel with each other in a second direction intersecting with the first direction; and a plurality of phosphors formed on facing side walls of adjacent barrier ribs out of the plurality of barrier ribs and on a portion of the surface of the substrate sandwiched between the adjacent barrier ribs, each phosphor emitting a light of either of a plurality of emitted colors, wherein a substantial area of a portion covered with a phosphor corresponding to at least any one emitted color out of the plurality of emitted colors is different in size from substantial areas of portions covered with phosphors corresponding to the other emitted colors.
According to a twenty-first aspect of the present invention, in the surface discharge type plasma display panel of the first aspect, of the plurality of address electrodes, the width of an address electrode of an unit luminescent area corresponding to any one emitted color out of the plurality of emitted colors in the first direction is about the same as the width of address electrodes of unit luminescent areas corresponding to the other emitted colors in the first direction.
According to a twenty-second aspect of the present invention, in the surface discharge type plasma display panel of the fifteenth aspect, each of said plurality of address electrodes except its terminal portions connected to the outside is located about at the center between adjacent barrier ribs corresponding to that address electrode out of the plurality of barrier ribs; and respective terminal portions of the plurality of address electrodes are sequentially formed at regular intervals on the end portion of the second substrate.
According to a twenty-third aspect of the present invention, in the surface discharge type plasma display device of the tenth aspect, the plurality of emitted colors is composed of at least three colors; the surface discharge type plasma display panel is composed of a plurality of pixels; each of the plurality of pixels is composed of at least four unit luminescent areas; two of the four unit luminescent areas correspond to any one emitted color out of the plurality of emitted colors; and the address-electrode driving circuit comprises an address-electrode driving circuit board equipped with an address driver. For each pixel, of output terminals of the address driver, an output terminal of any one emitted color out of the plurality of emitted colors is electrically connected to a first end portion of a first signal line which will be branched into two branch signal lines on its way, on the address-electrode driving circuit board; and respective output terminals of the other emitted colors are electrically connected to corresponding first end portions of second signal lines which extend without intersecting with each other, on the address-electrode driving circuit board. One of the two branch signal lines forms a grade-separated intersection with at least one of the adjacent second signal lines; and respective second end portions of the first and second signal lines are electrically connected to corresponding terminal portions of the plurality of address electrodes.
According to a twenty-fourth aspect of the present invention, in the surface discharge type plasma display panel of the first aspect, a single pixel is composed of at least four unit luminescent areas; and of the plurality of address electrodes in the single pixel, a terminal portion of an address electrode of an unit luminescent area corresponding to any one emitted color out of the plurality of emitted colors is provided on one end portion of the second substrate and terminal portions of address electrodes of unit luminescent areas corresponding to the other emitted colors are provided on the other end portion of the second substrate, the one end portion and the other end portions of the second substrate being in an inverse relationship with respect to the second direction.
According to a twenty-fifth aspect of the present invention, in the surface discharge type plasma display panel of the fourth aspect, any two of the four unit luminescent areas which are sequentially arranged in the first direction correspond to the blue emitted color.
According to a twenty-sixth aspect of the present invention, in the surface discharge type plasma display panel of the twenty-fifth aspect, the four unit luminescent areas are composed of a first group including two unit luminescent areas of the blue emitted color and of the red emitted color; and a second group including two unit luminescent areas of the blue emitted color and of the green emitted color. The first and second groups form a display area for a single pixel, respectively.
The present invention with the aforementioned structure have the following effect:
The first through eighteenth and twentieth aspects of the present invention allow a plasma display device which is capable of displaying images without varying the sustain period and degrading the levels of other color gradations and further excellent in long-term color reproduction without deterioration of phosphors.
The third aspect of the present invention allows a full color image display.
The fourth aspect of the present invention allows a white color display with a high color temperature.
The fifth aspect of the present invention increases luminance of an emitted color with low spectral sensitivity.
The sixth aspect of the present invention increases luminance of any one emitted color even with the same driving conditions for each emitted color.
The seventh and eighth aspects of the present invention prevent occurrence of unnatural color lines.
The ninth aspect of the present invention allows a white color display with a high color temperature.
The eleventh and twelfth aspects of the present invention allow an excellent image display with a high color temperature with no damage to ornament and no influence on displays of the other emitted colors.
The thirteenth aspect of the present invention allows a display device capable of providing a white color display with a high color temperature while emitting lights excepting a light emitted by a discharge gas component (especially Ne) from the blue unit luminescent area, and improving color purity of blue.
The fourteenth aspect of the present invention makes it possible to desirably balance respective luminescence intensity of the emitted colors when the display surface is viewed directly from the front and improves display characteristics by suppressing the loss of viewing angles when the display surface is viewed from a tilt angle.
The fifteenth aspect of the present invention improves either of insufficient writing or self erasing during address discharge, or unnecessary discharge during address discharge, depending on various conditions of each panel.
The sixteenth aspect of the present invention avoids insufficient writing due to a decrease in address pulse voltage and self erasing due to an increase in address pulse voltage, thereby bringing about an advantage of achieving a stable display image with no flicker.
The seventeenth aspect of the present invention prevents occurrence of unnecessary discharge during address discharge through the achievement of a guard function against an electric field due to a wide address electrode.
The twenty-first aspect of the present invention facilitates the fabrication of address electrodes and prevents a break in the address electrodes and variations in the width of the address electrodes.
The twenty-second aspect of the present invention prevents electrodes on the substrate outside the panel, which are to be connected to the terminal portions of the corresponding address electrodes, from being arranged at irregular pitches.
The twenty-third and twenty-fourth aspects of the present invention avoid the necessity of forming a grade-separated intersection of the terminal portions of the address electrodes on the side of the second substrate.
The twenty-fifth aspect of the present invention readily achieves a white color display with a desired color temperature with two blue unit luminescent areas provided within the four unit luminescent areas.
The twenty-sixth aspect of the present invention has the effect of achieving a high-resolution image display with an increase in effective resolution while achieving a white color display with a desired color temperature.
Thus, an objective of the present invention is to provide a plasma display panel and a plasma display device that can provide a white color display with a high color temperature, e.g., 9300 K, without increasing deterioration of phosphors and sacrificing red and green gradations.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.