JP2003131229A - Light emitting device and display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device which improves color purity when using an auxiliary light source of red, green and blue. SOLUTION: This light emitting device is provided with three kinds of light sources 1a, 1b, 1c whose light emission colors are red, green and blue and filters 5 which mainly transmit red, green and blue respectively, and therein, it is a feature of this light emitting device that the maximum transmissivity of the filter which transmits the red color is lower than the maximum transmissivity of at least one side of the filter which transmits the green color and the filter which transmits the blue color.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has emission colors of red, green,
The present invention relates to an auxiliary light source device that includes three types of light sources that are blue and filters that mainly transmit red, green, and blue, respectively, and a display device that uses the auxiliary light source device.

[0002]

2. Description of the Related Art In a display device such as a liquid crystal display device,
Various conventional techniques have been proposed as a method for improving the color purity, and a typical example thereof is a method for improving the color purity of the color filter itself. For example, the color purity is improved by narrowing the wavelength range of the wavelengths that are transmitted through the color filter.

Even if the spectral characteristics of the color filter are not changed, it is possible to increase the color purity by using a light source having a sharp emission spectrum as the auxiliary light source used.

Although these two types of means are different, the emission spectrum of the display device is the same and the effect is the same.

Here, as an example of these, a spectrum of a red color filter is schematically considered as shown in FIG. 6, and a color of a broad light source such as a standard light D65 and a color of a steep spectrum such as an LED light source are considered. Indicates the difference in degree coordinates. In FIG. 7, the spectrum of the standard light D65 is shown by a broken line, and an example of the spectrum of the LED is shown by a solid line.

The chromaticity coordinates of FIG. 6 based on these spectra are LE, as shown in FIG.
With a D light source, it looks like d. In the chromaticity coordinates, the line of the outer frame (monochromatic light locus) has the highest color purity, indicating that the LED light source has a higher color purity than the standard light D65.

[0007]

FIG. 9 shows an example of a spectrum of a color filter which has been used conventionally. Here, since there is a trade-off relationship between the light utilization efficiency and the color purity, if the transmission wavelength range of the filter is widened in order to increase the light utilization efficiency, the color purity is lowered, and the color purity of the filter is increased. There is a problem in that the light utilization efficiency decreases when the transmission wavelength range is narrowed, and there is a limit to narrowing the wavelength range when considering the light utilization efficiency.

Further, since a broad white light source such as a cold cathode tube has been used conventionally, if the color purity of the color filter is designed to be high, the utilization efficiency of light becomes very poor. Therefore, a color filter having high color purity is used. And, even if it was used, sufficient performance could not be exhibited.

Therefore, there is a method of using red, green, and blue LEDs as a method of increasing color purity without deteriorating the utilization efficiency of light, but in this case, it is possible to obtain a certain effect by using a conventional color filter. However, the expected effect of improving the color purity cannot be obtained. This is because the conventional color filter has been designed mainly for a broad light source.

The present invention has been made in view of the above problems, and provides a display device capable of improving color purity when red, green, and blue auxiliary light sources are used.

[0011]

A first invention of the present application is a light emitting device provided with three types of light sources whose emission colors are red, green and blue, and a filter which mainly transmits red, green and blue respectively. In above, the maximum transmittance of the filter that transmits red is lower than the maximum transmittance of at least one of the filter that transmits the green and the filter that transmits the blue.

A second invention of the present application is characterized in that a light emitting diode is used as the three types of light sources.

A third invention of the present application is a display device using the light emitting device of the first or second invention.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings. Here, FIG. 1 is an explanatory diagram showing a schematic configuration of the display device of the present embodiment, FIG. 2 is an explanatory diagram showing an example of a spectrum of a coloring material used for a red filter in the present embodiment, and FIG. 3 is a color diagram of the present embodiment. It is explanatory drawing which shows the spectrum of a filter.

FIG. 4 is an explanatory view showing the chromaticity coordinates of the red filter used in this embodiment and the conventionally used red filter with respect to the D65 light source, and FIG. 5 is the red filter used in this embodiment and the conventionally used filter. It is an explanatory view showing the chromaticity coordinates with respect to the LED light source with the conventional red filter.

In FIG. 1, 1a, 1b and 1c are red, green and blue LEDs, respectively, which are used as auxiliary light sources. Light is transmitted from the light sources 1a, 1b, 1c to the light guide plate 2, passes through the polarizing plate 3, and is input to the liquid crystal device 4. The liquid crystal is driven according to the image signal input to the liquid crystal device 4, and gradation display can be performed. The input image signal is not shown here.

The light from the liquid crystal device 4 is separated into color components by the color filter 5 and passes through the optical film 6 and the polarizing plate 7 to be displayed as an image.

In the present embodiment, in order to improve the color purity of the red filter, the absorption spectrum of the coloring material used for the red filter is set so as to mainly absorb the blue wavelength region as shown in FIG. , The colorant is being designed.

As an example of such a color material, a color material such as NK-3390 and NK-2638 manufactured by Japan Photosensitive Dye Research Institute Co., Ltd. can be used. In addition, a plurality of kinds of these color materials may be used in combination to obtain a desired spectrum.

FIG. 3 shows a spectrum obtained as a result of using such a coloring material in the red filter which has been conventionally used.
The blue and green filters are exactly the same as conventional ones.

Since the color material shown in FIG. 2 is used for the red filter, it can be confirmed in FIG. 3 that the transmission of the red filter in the blue region is almost eliminated. But,
Although it mainly absorbs the blue wavelength range, it also absorbs other wavelength ranges, resulting in a decrease in the transmittance of the red filter in the red range.

That is, comparing FIG. 3 with FIG. 9, the maximum transmittance of the red filter is higher than the maximum transmittance of the green filter in FIG. 9, but in FIG. It can be seen that the rate is lower than the maximum transmission of the green filter. This is due to the effect of absorption of the coloring material shown in FIG.

When discussing these maximum transmittances,
It is natural to discuss in the wavelength range of 380 nm to 780 nm, which is the wavelength range of visible light, and in particular, to discuss the maximum transmittance in the wavelength range of 400 nm to 700 nm, which has a large influence on the calculation of chromaticity coordinates. desirable.

FIG. 4 shows the results of calculating the chromaticity coordinates of these red spectra with standard light D65. In FIG. 4, the coordinate indicated by e is the conventional red filter (spectrum is FIG. 9), and the coordinate indicated by f is the red filter used in the present embodiment (spectrum is FIG. 3). The green and blue filters are the same, and are not shown.

In the chromaticity coordinates, the outermost frame line (monochromatic light locus) has the highest color purity, which indicates that the color purity of the new red filter is improved. At this time, the luminous transmittance slightly decreased from 22.7% to 21.1%, but it was not a big problem and the effect of improving the color purity was observed.

Further, in FIG. 5, the chromaticity coordinates obtained by the LED light source are obtained for the conventional color filter by a.
The value obtained for the color filter used in the present embodiment is shown by b. In this embodiment, since the red color filter is designed in consideration of the blue light source, it can be seen that the color purity is further improved as compared with the D65 light source.

Further, the chromaticity coordinates using the LED light source are shifted to the long wavelength side while maintaining high color purity.
Since the red light source having a relatively long wavelength is used as the light source, the color gamut is widened as a result, which is a desirable result. Since this color gamut is generally compared by the area surrounded by chromaticity coordinates of red, green, and blue, if red has the longest wavelength, red moves to the lower right of the coordinates, and as a result, the area tends to increase.

Although the liquid crystal device is used in this embodiment, the invention is not limited to this. Further, in the present embodiment, the color filter and the liquid crystal device are configured separately, but the color filter may be incorporated in a part of the liquid crystal device. For example, a glass substrate that configures the liquid crystal device is a color filter. May be

Further, in the present embodiment, the auxiliary light source is provided on the back surface of the liquid crystal device, but the present invention is not limited to this, and for example, a reflection type liquid crystal may be used as a front light.

[0030]

As described above, according to the present invention,
By using a color material that absorbs the wavelength band of blue in the red filter, by setting the maximum transmittance of the red filter lower than the maximum transmittance of at least one of the green or blue filter, the purity It is possible to obtain a light-emitting device that emits high-red light.

Further, since the light emitting diodes are used as the three kinds of light sources, it is possible to more effectively obtain the light emitting device which emits red light having high color purity. Further, by using the light emitting device as a display device, a display device that displays red with high color purity can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a display device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of a spectrum of a coloring material used for a red filter in the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a spectrum of a color filter according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing chromaticity coordinates of a red filter used in one embodiment of the present invention and a conventionally used red filter with respect to a D65 light source.

FIG. 5 is an explanatory diagram showing chromaticity coordinates of a red filter used in an embodiment of the present invention and a conventionally used red filter with respect to an LED light source.

FIG. 6 is an explanatory diagram showing a spectrum of a red filter.

FIG. 7 is an explanatory diagram showing emission spectra of an LED light source and a D65 light source.

FIG. 8 is an explanatory diagram showing chromaticity coordinates for a D65 light source and an LED light source in a conventional red filter.

FIG. 9 is an explanatory diagram showing an example of a spectrum of a color filter used in a conventional display device.

[Explanation of symbols]

1a red LED 1b green LED 1c blue LED 2 Polarizer 3 Light guide plate 4 Liquid crystal device 5 color filters 6 Optical film 7 Polarizer

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Claims (3)

[Claims] 1. A light-emitting device comprising three types of light sources whose emission colors are red, green, and blue, and a filter mainly transmitting red, green, and blue, respectively, wherein the filter transmitting red is the maximum. A light emitting device having a transmittance lower than a maximum transmittance of at least one of the filter for transmitting green and the filter for transmitting blue. 2. The light emitting device according to claim 1, wherein light emitting diodes are used as the three types of light sources. 3. A display device comprising the light emitting device according to claim 1 or 2.