JPH11327498A - Color picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a high-quality display device by lowering emission ratios of other colors while noticing a color whose luminance is required to be raised most in order to achieve emission ratios to avoid the lack of the number of gradations in adjusting a white balance. SOLUTION: Coating film thicknesses of phosphors 104, 105 of R, G of a plasma display panel are made to be thinner as compared with the coating film thickness of the phosphor 106 of B of the panel. An emission luminance becomes smaller by making the film thickness of a phosphor to be coated thinner and, conversely, an emission luminance becomes larger by making the film thickness of a phosphor to be coated thicker. Consequently, emission efficiency of R, G are lowered by making film thicknesses of phosphors 104, 105 of R, G thinner as compared with the film thickness of the phosphor 106 of B to realize a desired white balance. The restriction of signal amplitudes for performing the white balance is made to be smaller by making white balance characteristics in the single body of a panel roughly even in this manner. Thus, the using of the number of gradations capable of being expressed by subfields is maximized and a picture degradation due to the lack of the number of gradations can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a color image display device for displaying a color video signal such as a television signal or a high-vision signal. The present invention is particularly suitable for application to a plasma display or the like in which the number of display gradations is limited, and the emission luminance with respect to the signal levels of red (R), green (G), and blue (B) cannot be independently controlled. Thus, high-quality display can be realized.

[0002]

2. Description of the Related Art In recent years, a conventional cathode ray tube (CRT)
In place of the display device, a flat panel type display device which is thin and light, has little screen distortion, and is hardly affected by geomagnetism and which seals a liquid crystal or a plasma is becoming widespread. Among them, in particular, a plasma display device which has a wide viewing angle due to a self-luminous type and which is relatively easy to produce a large panel has attracted attention as a next-generation color image display device. In such a flat panel display device, as shown in the plan view of the display panel in FIG. 1, the display panel 1 has pixels 100, which are the minimum units of display, two-dimensionally corresponding to horizontal and vertical resolutions. Are located. Further, one pixel 100 has three light-emitting cells: a light-emitting cell 101 of red (hereinafter, referred to as R), a light-emitting cell 102 of green (hereinafter, referred to as G), and a light-emitting cell 103 of blue (hereinafter, referred to as B). The color display is performed by controlling the amount of light emitted from each of the light emitting cells 101 to 103.

In a display device, such as a plasma display device, in which it is difficult to display an intermediate gradation between light emission and non-light emission, the light emission amount of each of the R, G, and B light emitting cells 101 to 103 is controlled to control the intermediate gradation. Is displayed. As a method for displaying the intermediate gradation, a so-called subfield method is employed. In the subfield method, one field is divided into a plurality of subfields, for example, subfields SF0 and S
F1... SF5 are divided into sub-fields, each sub-field is assigned a unique light-emission weight, and the presence or absence of light emission in each sub-field is controlled to express a gradation of luminance.

In the example shown in FIG. 2, one field is divided into six subfields SF0 to SF5, and light emission weights are assigned in the ratios of 1, 2, 4, 8, 16, and 32, respectively. To SF5, from which the light emission does not emit any light, to the gradation “63” (= 1 + 2 + 4 + 8 + 1) where all the six subfields emit light.
64 gradations up to 6 + 32) can be expressed.

One subfield includes address control periods 90a to 90f for controlling whether or not each pixel 100 is lit,
Sustain pulse periods 91a to 91f for determining light emission amount
It is composed of Various control pulses are used corresponding to these periods. These control pulses cannot be shorter than a predetermined time width in order to realize stable light emission control. For this reason, the number of subfields that can be configured in one field period is limited by the physical characteristics such as light emission response of the display panel, the resolution, and the like, and the gray scale expressed by the combination of the light emission of the subfields SF0 to SF5. The number is also limited.

The subfields SF0 to SF0 shown in FIG.
In the configuration of SF5, although the address control period and the sustain pulse period are clearly separated, the address / sustain multiplex drive for narrowing the occupation time of the address control period by time-shifting the sustain pulse period for each display line. There is also a method. Even in this address / sustain multiplex drive system, the number of subfields is similarly limited,
Display is performed with finite discrete gradations. In a color display based on R, G, B emission, R, G, B
If the emission luminance ratio of R, G, B
Even if a signal having 100% amplitude is input as the input signal, correct white color cannot be displayed. For example, CIExy
In the chromaticity diagram, R (0.67, 0.33), G (0.2
1, 0.71) and B (0.14, 0.08) R, G, and B light-emitting cells that emit light at chromaticity coordinates provide a color temperature of 65.
In order to display 00K white W (0.31, 0.329), the luminance ratio of R: G: B needs to be approximately 3: 6: 1. If a deviation occurs in the luminance ratio, correct color reproduction cannot be performed, which may cause deterioration in image quality.

In a display device using a conventional CRT, R,
There is a difference in light emission luminance with respect to a signal level due to a difference in phosphor materials of G and B, and when a signal of the same level is input to R, G and B, a light emission luminance ratio of R: G: B is 3: 6: 1
If not, the current amount of the electron beam is set to R, G, B
The white balance can be adjusted independently by controlling. In practice, an extreme difference in luminous efficiency is not preferable because the spot diameter of the electron beam is uniform, but the luminous brightness of R, G, and B can be adjusted in an analog and independent manner by changing the amount of current. For this reason, in a display device using a CRT, a phosphor material having a high luminous efficiency is selected from the viewpoint of power consumption and the like, and it is not necessary to consider a strict balance of R, G, and B luminous brightness.

[0008]

FIG. 3 is a plan view showing the outline of the electrode structure of each light emitting cell of the plasma display. In the figure, the R, G, and B light emitting cells 101, 10 are shown.
2 and 103, a common sustain electrode 110, an independent sustain electrode 111, and address electrodes 107, 108,
9 are provided. During the address control period, a discharge 111 between the address electrodes 107 to 109 and the independent sustain electrodes is performed.
As a result, an environment in which discharge is likely to occur in the cell is formed. By applying a sustain pulse between the common sustain electrode 110 and the independent sustain electrode 111 during the sustain pulse period, the address is designated by the address discharge during the address control period. The cell is discharged. The R, G, and B phosphors 104, 105, and 106 applied in the cell emit light due to the ultraviolet light generated by the discharge, and the R, G, and B light is emitted. The light emission intensity is substantially proportional to the number of sustain pulses, and is the number of pulses determined by the light emission weight in each subfield. In such a plasma display, the sustain electrodes 110 and 111 for applying a sustain pulse include R,
Since G and B are common, the configuration of each subfield and the number of sustain pulses in the subfield are R,
G and B are configured to be equal. Therefore, the light emission luminance of R, G, and B is set to CRT with respect to the signal level.
Cannot be adjusted independently as in

In such a display device, when performing white balance adjustment, the white balance adjustment is performed by changing the signal levels of R, G, and B. For example, R phosphor 10
In order to adjust the luminance of R to 50% because the light emission ratio of No. 4 is high, the signal level is reduced to half and the input signal level is adjusted to 50%.
25% emission luminance at 0%, input signal level 100%
At this time, the level conversion was performed so that the light emission luminance became 50%. However, since the plasma display is expressed by digital finite gradations depending on whether or not the sub-fields SF0 to SF5 are lit, there is a problem that the number of display gradations is reduced when such light emission luminance adjustment is performed based on the signal level. there were. For example, six subfields SF0
When the luminance of R is limited to 50% for white balance adjustment in a plasma display capable of displaying 64 gradations at SF5, 32 gradations from 0 to 31 out of 64 gradations are input from 0 to 100 of the input signal. %, The number of expressible gradations is reduced by half, and it is difficult to perform smooth gradation expression. Further, since the gain adjustment of R, G, and B is performed digitally, even when signals of the same level are input to R, G, and B, the stepwise change point of the gradation is R, G, and B. , B independently of each other, there is a problem that coloring not present in the input signal occurs particularly near the black level.

[0010] These problems can be solved by increasing the luminous efficiencies of the other two colors in accordance with the color having the highest luminous efficiency so that the luminous luminance ratio of R, G, and B becomes a desired ratio. However, it is necessary to develop a phosphor material with higher luminous efficiency, which requires a long time and a large development cost.

It is an object of the present invention to provide a color image display device in which, among phosphors having different luminous efficiencies, phosphors of colors having high luminous efficiency have reduced luminous brightness.

[0012]

In order to solve these problems, according to the present invention, for a desired emission ratio of red, green, and blue, a color which needs to have the highest luminance to achieve this emission ratio is required. , And is configured to reduce the luminous efficiency of the other one or two colors. Further, in the present invention, for a desired emission ratio of red, green, and blue, attention is paid to a color having the highest emission efficiency, and this emission efficiency is reduced. Therefore, in the present invention, in a panel having red, green, and blue phosphors having different emission luminances or luminous efficiencies with respect to an image signal, light is emitted from a phosphor having a high luminous luminance or luminous efficiency, and the luminous luminance obtained from the panel is obtained. Alternatively, means for reducing luminous efficiency is provided.

Further, as means for lowering the emission luminance of the phosphor material, the thickness of the coating of at least one phosphor is reduced. As another means for reducing the luminous efficiency, a non-luminous material is mixed into a phosphor having a high luminous efficiency so that the density of the phosphor material is reduced. As still another means for lowering the luminous efficiency, the light emitted is attenuated by a filter. As another means for reducing the luminous efficiency, a filter having a different transmittance depending on the wavelength is configured to attenuate the luminescence of the focused color.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below using some examples. FIG. 4 is a sectional view of a panel showing a first embodiment of the color image display device according to the present invention. In FIG. 4, a color plasma display as an example of a color image display device has a front glass plate 11.
3, a rear substrate 112, an address electrode 107 of R, an address electrode 108 of G, an address electrode 109 of B, sustain electrodes 110 and 111, a phosphor 104 of R, a phosphor 105 of G, and a phosphor 106 of B. ing.

The chromaticity coordinates of each of the phosphors 104 to 106 are R (0.67, 0.3) in the CIExy chromaticity diagram.
3), G (0.21, 0.71), B (0.14, 0.
08). The light emission luminance ratio when the cells 101 to 103 have the same structure by the phosphors 104 to 106 is 3: 4: 0.5 (R: G: B). When the color temperature of white display is set to 6500K, the luminance ratio of R: G: B needs to be 3: 6: 1.

Therefore, each of the R, G, B cells 101 to 1
In order to obtain a white balance by making the same 03, the luminous efficiency of blue is increased to 2 (= 1 / 0.5) times and the luminous efficiency of G is increased to 1.5 (= 6/4) times. Need to be done.
However, development of a phosphor material having higher luminous efficiency requires a long time and a large development cost, and cannot be easily realized. Further, in order to properly obtain a white balance using a panel having such light emission characteristics, the R amplitude of the display signal may be set to １ ／, and the G amplitude may be set to ／.

However, if the amplitude is greatly reduced by such signal amplitude adjustment, even if the display panel can display R in 64 gradations from 0 to 63, for example, the amplitude is reduced to 1/2. As a result, only the gradations from 0 to 31 can be used, and smooth gradation expression becomes difficult, which causes a large deterioration in image quality. As described above, the high luminous efficiency of the R phosphor does not contribute to improving the performance of the display at all. As the luminous efficiency increases, it becomes necessary to limit the amplitude for white balance adjustment. The tone is reduced and the image quality is degraded. In particular, in the panel having the above-described structure, the luminous efficiency of the phosphor 106 of B is low,
If it is attempted to set the set color temperature to 9300 K in a panel using a material having a high luminous efficiency of the R phosphor 104, it is necessary to further reduce the luminance of R, resulting in a significant deterioration in image quality due to a reduction in the number of gradations. Therefore, in the color image display device according to the present invention, the R and G phosphors 104 and 105 are used.
To achieve a desired white balance by lowering the luminous efficiency.

In the first embodiment shown in FIG. 4, the coating thickness of the R and G phosphors 104 and 105 of the plasma display panel is made thinner than that of the B phosphor 106. By reducing the thickness of the phosphor to be applied, the emission luminance is reduced. Conversely, when the thickness of the applied phosphor is increased (that is, the volume of the phosphor is increased), the emission luminance is increased. Therefore, by making the film thicknesses of the R and G phosphors 104 and 105 smaller than the film thickness of the B phosphor 106, the luminous efficiency of R and G can be reduced and a desired white balance can be realized. it can. As described above, by roughly adjusting the white balance characteristics of the panel alone, it is possible to reduce the signal amplitude limitation for performing the white balance adjustment. As a result, the maximum number of gradations that can be expressed by the subfield can be used, and image quality deterioration due to an insufficient number of gradations can be reduced. Further, since the luminous efficiency is lowered by changing the thickness of the phosphor using an existing phosphor material, it is not necessary to develop a new high-performance phosphor material, and the development cost can be reduced. Even if the luminous efficiencies of the R and G phosphors 104 and 105 are reduced according to the present invention, the luminance of the entire display panel is equivalent to that of the conventional case where the signal amplitude is reduced and white balance is adjusted. The number of display gradations can be increased to the display capability of the panel while maintaining the luminance. The panel shown in FIG. 4 focuses on the color (B) that requires the highest luminance, and is configured to reduce the luminous efficiency of the other two colors (R, G). A case where the luminous efficiency is reduced by focusing on the high color (R) will be described with reference to FIG.

FIG. 5 is a sectional view of a panel showing a second embodiment of the color image display device according to the present invention. In the panel of FIG. 5, the thickness of the G phosphor 105 is kept substantially the same as the thickness of the B phosphor 106 as compared with the panel of FIG. That is, the difference is that the thickness of the R phosphor 104 is smaller than the thickness of the G and B phosphors 105 and 106. Other points are the same as those in FIG.

As in the case of FIG. 4, the chromaticity coordinates of each phosphor material are R (0.67, 0.33), G (0.21,
0.71) and B (0.14, 0.08), and when setting the color temperature of white display to 6500K, it is necessary to set the emission luminances of R, G, and B to 3: 6: 1. is there. Further, it is assumed that the light emission luminance ratio when the structures of the light emitting cells 101 to 103 are equal is 3: 4: 0.5 (= 6: 8: 1). When the structures of the light emitting cells 101 to 103 are equalized, for white (6500K) display, R is 2 (= 6/3) times the light emission luminance and G is 1 with respect to B having low light emission efficiency. It has a light emission luminance of .33 times (= 8/6). In the present invention, as shown in FIG. 5, the emission luminance at the same number of sustain pulses is reduced to about 1/2 by making the coating thickness of the phosphor 104 of R having the highest luminous efficiency smaller than that of G and B. It is configured to be. As a result, the ratio of R to B, which has the lowest luminous efficiency, becomes a desired white balance ratio, so that it is not necessary to reduce the signal amplitude of R, thereby maximizing the number of gradations that can be expressed by the subfield. Can be. The emission luminance of G is R, B
Therefore, the white balance is adjusted by lowering the signal amplitude to ／ (= 6/8) since the signal amplitude remains high (1.33 times). As a result, although the number of gradations of G is reduced to approximately ／, it is possible to prevent the shortage of gradation of R, which was the most severely reduced in the number of gradations. Further, since only one kind of the R phosphor 104 is required to change the thickness of the phosphor coating, the manufacturing process can be simplified and the cost can be reduced. In the embodiments shown in FIGS. 4 and 5, the light emitting efficiency is reduced by reducing the thickness of the applied phosphor material. However, according to the present invention, the light emission of the phosphor of a specific color is performed by some means. By reducing the luminance with the same number of sustain pulses, it is possible to prevent the number of gradations from decreasing. Accordingly, another method of reducing the luminous efficiency will be described below.

FIG. 6 is a sectional view of a panel showing a third embodiment of the color image display device according to the present invention. In the figure, a non-light emitting material 114 is mixed in the R phosphor 104. As the non-light emitting material 114, for example, the back substrate 1
For example, the same material as used in Example 12 may be used in the form of particles, a pigment that absorbs red light, a pigment that absorbs unnecessary light other than red, or the like. The phosphor 104 is mixed with the non-light emitting material 114.
Becomes equivalently low, and the luminous efficiency can be reduced. The degree of decrease in luminous efficiency can be adjusted by the mixing ratio of the non-luminous material 114. With such a configuration, the coating thickness of the phosphor can be made common to R, G, and B, and there is an effect that the electric characteristics of discharge can be made uniform. In addition, since only one type of coating film thickness control is required, the manufacturing process can be simplified. Non-light emitting material 11
By using a pigment or the like that absorbs light as 4,
Light incident from the outside of the panel can be absorbed and attenuated, which also has the effect of improving the contrast of the panel. Also, by selecting a material that absorbs an unnecessary emission spectrum of the phosphor material 104, there is also an effect of increasing color purity.

FIG. 7 is a sectional view of a panel showing a fourth embodiment of the color image display device according to the present invention. In the figure, a filter 115 is arranged on a front glass plate 113 where the R phosphor 104 is located, and the light emitted by the R phosphor 104 is attenuated using the filter 115. The degree of decrease in luminous efficiency can be adjusted by the transmittance of the filter 115. As a characteristic of the filter 115, R
By setting the characteristics to reduce unnecessary light-emitting components generated in the phosphor 104, color purity can be increased and high-quality display can be performed. Further, the filter 115 can attenuate light incident from the outside of the panel, and has an effect of improving the contrast of the panel.

FIG. 8 is a sectional view of a panel showing a fifth embodiment of the color image display device according to the present invention. In the figure, a filter 118 having a different transmittance depending on the wavelength is provided on the entire surface of the front glass plate 113. The filter 118 can attenuate the emission of the color of interest. Compared to the configuration shown in FIG. 7, the filter 118 may be disposed on the entire surface regardless of the pixel arrangement, and thus the assembly during manufacturing becomes easier. Also, there is an effect of improving the contrast by attenuating light incident from the outside. Also, by selecting a material that absorbs unnecessary emission spectra of the phosphors 104, 105, and 106, there is also an effect of increasing color purity.

The embodiments of the present invention have been described above.
Irrespective of the chromaticity coordinates of R, G, and B, the set color temperature, the light emission luminance ratio in each cell having the same structure, etc., if the light emission luminance at the same number of sustain pulses is reduced, the white balance is adjusted. The object of the present invention can be achieved.

[0025]

According to the present invention, it is possible to avoid a shortage in the number of gradations at the time of white balance adjustment, and to realize a display device with high image quality.

[Brief description of the drawings]

FIG. 1 is a plan view of a display panel.

FIG. 2 is a schematic diagram showing a configuration of a subfield.

FIG. 3 is a plan view showing an outline of an electrode structure of each light emitting cell of the plasma display panel.

FIG. 4 is a sectional view of a panel showing a first embodiment of the display device according to the present invention.

FIG. 5 is a sectional view of a panel showing a second embodiment of the display device according to the present invention.

FIG. 6 is a sectional view of a panel showing a third embodiment of the display device according to the present invention.

FIG. 7 is a sectional view of a panel showing a fourth embodiment of the display device according to the present invention.

FIG. 8 is a sectional view of a panel showing a fifth embodiment of the display device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Display panel, 100 ... Pixel, 101 ... R light emitting cell,
102 ... G light emitting cell, 103 ... B light emitting cell, 104 ... R
Phosphor, 105 ... G phosphor, 106 ... B phosphor, 107
... R address electrode, 108 ... G address electrode, 109 ...
B address electrode, 110, 111 ... sustain electrode, 1
12: rear substrate, 113: front glass slope, 114: non-luminous material, 115, 116: filter.

Claims (25)

[Claims] A red light having a different light emission luminance with respect to an image signal;
In a panel having green and blue phosphors, a means is provided for reducing the emission luminance of light output from the panel, which is emitted from a phosphor having a high emission luminance with respect to a predetermined white balance. Color image display device. 2. The color image display device according to claim 1, wherein said image signal is divided into a plurality of sub-fields, one of which is assigned a light-emission weight, and said sub-field controls light emission of each phosphor. Address period,
The color image display device is divided into a sustain period in which the phosphor whose light emission is determined in the address period is emitted according to the assigned emission weight. 3. The color image display device according to claim 1, wherein said means makes the thickness of a phosphor having a high emission luminance smaller than the thickness of another phosphor with respect to a predetermined white balance. Characteristic color image display device. 4. The color image display device according to claim 1, wherein said means sets the film thickness of said red phosphor to a film thickness of another phosphor having a low light emission luminance with respect to a predetermined white balance. A color image display device characterized by being thin. 5. A color image display apparatus according to claim 1, wherein said means makes the red and green phosphors thinner than the blue phosphor. apparatus. 6. A color image display device according to claim 1, wherein said means mixes a non-light emitting material into a phosphor having a high light emission luminance with respect to a predetermined white balance. Display device. 7. The color image display device according to claim 6, wherein said non-light emitting material has a property of absorbing light. 8. A color image display device according to claim 6, wherein said non-luminous material has a characteristic of absorbing light generated from a phosphor mixed therein. 9. The color image display device according to claim 6, wherein said non-light emitting material is glass. 10. The color image display device according to claim 6, wherein said non-light emitting material is a pigment. 11. A color image display apparatus according to claim 1, wherein said means includes a filter above a phosphor having a high emission luminance with respect to a predetermined white balance. 12. A color image display device according to claim 11, wherein said filter reduces the transmittance of light emitted from said phosphor. 13. The color image display device according to claim 1, wherein said means includes a filter above said each of said phosphors, said filter having a transmittance different depending on a wavelength of light emitted from each of said phosphors. Color image display device. 14. A color image display device according to claim 13, wherein said filter attenuates light from a phosphor having a high emission luminance as compared with light from another phosphor in order to obtain a predetermined white balance. A color image display device. 15. A color image signal comprising red, green, and blue is
In a color image display device that supplies red, green, and blue light emitting cells, respectively, and displays them with a finite number of gradations,
A color image display device comprising: means for lowering the emission luminance of a red, green, and blue light emitting cell with respect to a drive signal of one color light emitting cell as compared to other colors. 16. A color image signal comprising red, green, and blue is
In a color image display device that supplies red, green, and blue light emitting cells, respectively, and displays them with a finite number of gradations,
Among the red, green, and blue light-emitting cells, a cell using a light-emitting material having a higher luminance than a predetermined white balance has means for reducing the light-emitting luminance with respect to a drive signal as compared with other colors. Color image display device. 17. A color image signal consisting of red, green, and blue is
In a color image display device that divides a plurality of subfields each assigned a light emission weight on a field-by-field basis and controls the presence or absence of light emission in each subfield to perform gradation expression, red, green, and blue light emitting cells are used. A color image display device, comprising: means for lowering the light emission luminance with respect to a drive signal of one color light emitting cell as compared to other colors. 18. A color image signal consisting of red, green, and blue is
In a color image display device that divides a plurality of subfields each assigned a light emission weight on a field-by-field basis and controls the presence or absence of light emission in each subfield to perform gradation expression, red, green, and blue light emitting cells are used. A color image display device comprising: means for lowering emission luminance with respect to a drive signal of a cell using a light-emitting material having a higher luminance than a predetermined white balance as compared with other colors. 19. The color image display device according to claim 17, wherein said color image display device is a plasma display. 20. A color image display device according to claim 15, wherein said means reduces the thickness of the luminescent material in the cell as compared with other colors. 21. A color image display device according to claim 15, wherein said means mixes a non-light-emitting material into a light-emitting material in the cell. 22. A color image display device according to claim 21, wherein said non-light emitting material has a property of absorbing light. 23. A color image display device according to claim 15, wherein said means attenuates emission of a predetermined color by a filter. 24. A color image display device according to claim 23, wherein said filters have different transmittances at wavelengths corresponding to red, green and blue. 25. A color image display device for supplying a color image signal consisting of red, green and blue to each of red, green and blue light emitting cells and displaying each with a finite number of gradations.
A color image display device characterized in that one of the thicknesses of the light-emitting materials in the green and blue light-emitting cells is different from the thickness of the other color.