KR101815619B1 - White light emitting diode, backlight unit, and liquid crystal display including the same - Google Patents

Abstract

A liquid crystal display device including a white light emitting diode is provided. The white light emitting diode includes an LED light source that emits blue light and a light conversion layer that converts light incident from the LED light source into white light, and the light conversion layer includes green light emitting semiconductor nanocrystals and red light emitting semiconductor nanocrystals . The emission peak wavelength of the green light emitting semiconductor nanocrystals is about 530 nm or more, the emission peak wavelength of the red semiconductor nanocrystals is about 615 nm or more, and the half width of the emission peak of the green and red light emitting semiconductor nanocrystals , FWHM) is about 45 nm or less. The ratio of the emission spectrum of the green light emitting semiconductor nanocrystals to the green color filter is 95% or more of the maximum transmittance of the green color filter and the ratio of the red color filter is less than about 10% of the maximum transmittance of the red color filter , The ratio of the emission spectrum of the red light emitting semiconductor nanocrystals to the red color filter is at least about 95% of the maximum transmittance of the red color filter, and the ratio of the green color filter to the green color filter is about 10% .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white light emitting diode (LED), a backlight unit, and a liquid crystal display (LCD)

The present disclosure relates to a liquid crystal display device including a white light emitting diode.

White light emitting diodes (LEDs) using semiconductors have a long life span, can be miniaturized, have low power consumption, and are environmentally friendly, which does not include mercury, As one of the devices. Such a white light emitting diode is also used in a backlight of a liquid crystal display (LCD) or an instrument panel of an automobile.

(Red, green, and blue) light emitting diodes excellent in efficiency and color purity have been proposed for use as a backlight of a liquid crystal display. However, since the manufacturing cost is high and the driving circuit is complicated, There is a drawback that price competitiveness is greatly reduced. Therefore, it is required to develop a single chip solution which can reduce the manufacturing cost and simplify the device structure while maintaining the efficiency and color purity performance as in the conventional method.

As one of the single chip solutions, a white LED combining a YAG: Ce phosphor with an InGaN blue light emitting diode having a wavelength of 450 nm was developed. In such a light emitting diode, a part of the blue light generated in the blue light emitting diode excites the YAG: Ce phosphor to generate a yellow green color, and the blue and yellow green colors are synthesized to operate as a principle of emitting white light.

However, since white light of a combination of a blue light emitting diode and a YAG: Ce phosphor has only a spectrum in the visible light region, when the color rendering index is low and passes through the red, green, and blue color filters, The efficiency is lost because there are many parts that can not pass through the filter. Also, there is a problem that the color purity is low, which is not suitable for a display device requiring high picture quality such as TV.

Recently, a method of manufacturing a white light emitting diode by using an ultraviolet light emitting diode, which is expected to have high energy efficiency, as an excitation source and using a blue, green, and red light emitting material, as compared with the case where a blue light emitting diode is used as an excitation source . However, at present, development of a red phosphor having higher efficiency than blue and green is required.

As another method, a method of applying green and red inorganic phosphors on a blue light emitting diode has been attempted. However, a suitable material capable of exciting a relatively high energy excited inorganic phosphor to a blue wavelength in a visible light region has not been developed, The green phosphor developed until now can not solve the problem of low stability, poor color purity, and low efficiency of the red phosphor, so that there is a limit that the color purity and the light efficiency required for the light emitting diode for the backlight unit can not be secured.

One aspect of the present invention is to provide a liquid crystal display device including a white light emitting diode capable of maintaining white light stably while maintaining a high color reproduction ratio and high luminous efficiency.

According to an aspect of the present invention, there is provided a liquid crystal display device including a color filter that implements an image using a white light emitting diode and white light. Wherein the white light emitting diode comprises an LED light source emitting blue light and a light switching layer converting light incident from the LED light source into white light, wherein the light conversion layer comprises green light emitting semiconductor nanocrystals and red light emitting semiconductor nanocrystals A white light emitting diode is provided. Wherein the emission peak wavelength of the green light emitting semiconductor nanocrystals is about 530 nm or more, the emission peak wavelength of the red semiconductor nanocrystals is about 615 nm or more, and the full width at half maximum of the emission peak of the green and red light emitting semiconductor nanocrystals , FWHM) is about 45 nm or less. The ratio of the emission spectrum of the green light emitting semiconductor nanocrystals to the green color filter is 95% or more of the maximum transmittance of the green color filter and the ratio of the red color filter is less than about 10% of the maximum transmittance of the red color filter , The ratio of the emission spectrum of the red light emitting semiconductor nanocrystals to the red color filter is at least about 95% of the maximum transmittance of the red color filter, and the ratio of the green color filter to the green color filter is about 10% to be.

According to another aspect of the present invention, the emission peak wavelength of the green light emitting semiconductor nanocrystals is 530 nm or more, the emission peak wavelength of the red semiconductor nanocrystals is 615 nm or more, and the half width Is 45 nm or less, and has a color reproduction ratio of 90% or more, more preferably 100% or more, as compared with the NTSC color coordinates of the CIE 1931 coordinate.

(S / (A _G or A _R ) of the area S of the overlapping region of the total area (A _G ) of the emission spectrum of the green light emitting semiconductor nanocrystals with the total area (A _R ) of the emission spectrum of the red light emitting semiconductor nanocrystals )) May be about 10% or less, preferably about 7% or less.

The half-width of the emission peak of the green and red light-emitting semiconductor nanocrystals may be about 40 nm or less.

Wherein the emission peak wavelength of the LED light source emitting blue light is about 440 to about 460 nm, the emission peak wavelength of the green light emitting semiconductor nanocrystals is about 530 to about 550 nm, and the emission peak wavelength of the red light emitting semiconductor nanocrystals is about 620 Lt; / RTI >

The ratio of the emission intensity of the LED light source emitting the blue light is about 0.43 ± 0.05, the ratio of the emission intensity of the green light emitting semiconductor nanocrystals is about 0.27 ± 0.05, and the ratio of the emission intensity of the red light emitting semiconductor nanocrystals is about 0.28 Lt; / RTI >

The x coordinate of the color coordinate of the white light emitting diode is about 0.24 +/- 0.05, the y coordinate is about 0.21 +/- 0.05, and the color temperature is about 9500K to about 100000K.

Wherein the ratio of the emission spectrum of the green light emitting semiconductor nanocrystals to the green color filter is about 98% or more of the maximum transmittance of the green color filter and the ratio of the red color filter is less than about 5% of the maximum transmittance of the red color filter Wherein the ratio of the emission spectrum of the red light emitting semiconductor nanocrystals to the red color filter is about 98% or more of the maximum transmittance of the red color filter, and the ratio of the green color filter to the green color filter is about 5 % ≪ / RTI >

According to another aspect of the present invention, there is provided a liquid crystal display device including a liquid crystal panel including a color filter that implements an image using the white light emitting diode and the white light.

The ratio of the luminescence intensities of the blue, green and red luminescence spectra after passing through the color filter of the liquid crystal display device is in the range of about 1: 0.9 0.1: 0.8 0.1.

The white light emitting diode can maintain white light stably while maintaining a high color reproduction ratio and high luminous efficiency.

1 to 4 are sectional views of a white light emitting diode including a light conversion layer having various structures.
5 is a schematic view of a liquid crystal display device according to an embodiment of the present invention.
6 is a diagram showing an emission spectrum of a white light emitting diode according to Example 1. FIG.
7 is a diagram showing the emission spectrum of a white light emitting diode according to Example 1 after passing through a color filter.
8 is a diagram showing the emission spectra before and after the color filter of the white light emitting diode according to Example 1 and the relative transmittance ratios of blue, green and red of the color filter.
9 is a diagram showing an emission spectrum of an LED using a phosphor according to Comparative Example 3. Fig.
10 is a diagram showing the emission spectra before and after the color filter of the white light emitting diode according to Comparative Example 3 and the relative transmittance ratios of blue, green and red of the color filter.
11 is a graph showing the emission spectrum of the white light emitting diode of Example 1 with the white coordinate (x, y) of the backlight unit adjusted to 0.28 0.05 and 0.29 0.05.
12 is a diagram showing the emission spectra of the white light emitting diodes according to Example 1 and Comparative Example 3 after transmission through a color filter.
FIG. 13 is a graph showing the luminance spectra reflected by the photopic sensitivity of the white light emitting diode according to Example 1 and Comparative Example 3. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. Like parts are designated with like reference numerals throughout the specification. Whenever a portion of a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the case where it is "directly on" another portion, but also the case where there is another portion in between. Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

Hereinafter, a white light emitting diode according to an embodiment of the present invention will be described.

And a light conversion layer for converting the light incident from the LED light source into white light, wherein the light conversion layer comprises a white light emitting diode including green light emitting semiconductor nanocrystals and red light emitting semiconductor nanocrystals do.

In the white light emitting diode, green light emitting semiconductor nanocrystals and red light emitting semiconductor nanocrystals are excited by light emitted from a blue LED light source to emit green light and red light, and blue light emitted from the green light and red light, And white is realized.

The emission peak wavelength of the blue LED light source is in the range of 440 to 460 nm and the emission peak wavelength of the green light emitting semiconductor nanocrystals is in the range of about 530 nm or more, preferably 530 to 550 nm, and the emission peak of the red semiconductor nanocrystals The wavelength is at least about 615 nm, and preferably in the range of 620 to 640 nm. The half-width of the emission peak of the green and red light-emitting semiconductor nanocrystals is about 45 nm or less, preferably 40 nm or less. When the wavelength and the half width are within the above range, it is possible to provide a light emitting device having improved color reproduction rate and brightness .

* Since the color filters of the liquid crystal display device are widely distributed with overlapping portions of the respective colors, light is emitted in a part of the green region through the blue color filter or transmitted through the green color filter to emit light in the blue and red regions May occur at the same time, or may be simultaneously transmitted through the red color filter to emit light in the green region. Accordingly, when the color is driven in the liquid crystal display device, the color coordinates expressing the respective colors are changed to control the color reproduction rate.

Emitting diode of a white light emitting diode which can be used as a backlight unit, by using semiconductor nanocrystals, the emission spectrum of the green and red semiconductor nanocrystals of the white light emitting diode is controlled by the ratio of the green color filter and the red color filter, Efficiency, brightness and improved color reproduction can be obtained.

In one embodiment of the present invention, the ratio of the emission spectrum of the green light emitting semiconductor nanocrystals to the green color filter is about 95% or more, preferably about 98% or more of the maximum transmittance of the green color filter. Is less than about 10% of the maximum transmittance of the red color filter, preferably less than about 5%, and the ratio of the emission spectrum of the red light emitting semiconductor nanocrystals to the red color filter is about the maximum transmittance of the red color filter 95% or greater, preferably about 98% or greater, and the rate of transmission through the green color filter may be less than about 10%, and preferably less than about 5% of the maximum transmittance of the green color filter. By adjusting the transmittance in the above range, an improved color reproduction ratio and luminance can be obtained. The maximum transmittance of the color filter means a transmittance obtained by multiplying the emission intensity of the light source by the transmittance of the color filter, assuming that the transmittance at a wavelength representing the maximum transmittance of the color filter transmittance spectrum is 100%.

Another embodiment of the present invention provides a white light emitting diode having a color reproduction ratio of 90% or more, more preferably 100% or more, as compared with the NTSC color coordinates of the CIE 1931 coordinate.

(S / (A _G or A _R ) of the area S of the overlapping region of the total area (A _G ) of the emission spectrum of the green light emitting semiconductor nanocrystals with the total area (A _R ) of the emission spectrum of the red light emitting semiconductor nanocrystals )) May be about 10% or less, preferably about 7% or less. When the ratio of S / (A _G or A _R ) is in the above range, it is possible to provide a light emitting device having improved color reproduction rate and brightness. In order to adjust the color coordinates of the white light, the emission intensity ratio of the LED light source emitting the blue light is 0.43 ± 0.05, the emission intensity ratio of the green light emitting semiconductor nanocrystals is 0.27 ± 0.05, May be 0.28 +/- 0.05. When the light emission intensity is in the above range, white light having a color reproduction range of a wider area can be realized.

The x coordinate of the color coordinate of the white light emitting diode may be 0.24 ± 0.05, the y coordinate may be 0.21 ± 0.05, and the color temperature may be about 9500K to about 100000K. When the color coordinates and the color temperature are in the above range, white light having a wider color reproduction range can be realized, and various colors can be expressed when used as a light source of a display.

Examples of the semiconductor nanocrystals include a group II-VI compound, a group III-V compound, a group IV-VI compound, and a group IV compound. The semiconductor nanocrystalline particles may have a core / shell structure. The interface between the core and the shell in the core / shell may have a concentration gradient structure in which the concentration of the element existing in the shell decreases toward the center.

The II-VI compound may be selected from the group consisting of CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO MgSe, MgS, and mixtures thereof; Trivalent compounds selected from the group consisting of CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, CdZnS, CdZnSe, CdZnTe, MgZnSe, MgZnS and mixtures thereof; And a silane compound selected from the group consisting of CdZnSeS, CdZnSeTe, CdZnSTe, and mixtures thereof. The III-V compound is selected from the group consisting of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, and mixtures thereof. A trivalent compound selected from the group consisting of GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP and mixtures thereof; And a silicate compound selected from the group consisting of GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, . The semiconductor The emission peak wavelength and half bandwidth can be controlled through the particle size, composition, or concentration gradient of the nanocrystals.

The light conversion layer may be designed in various structures on an LED light source that emits blue light. For example, as shown in FIG. 1, the light conversion layer 12 may include a mixed layer of a green light emitting semiconductor nanocrystal 14 and a red light emitting semiconductor nanocrystal 16 on an LED light source 10 emitting blue light Lt; / RTI > 2, the green light-emitting semiconductor nanocrystals 24 are coated on the LED light source 10 emitting blue light, and then the red light-emitting semiconductor nanocrystals 26 are applied thereon to form the light-converting layer 22 . 3, a red light emitting semiconductor nanocrystal layer 34 is formed on an LED light source 10 emitting blue light, and a green light emitting semiconductor nanocrystal layer 36 is formed on the red light emitting semiconductor nanocrystal layer 34, . The red light emitting semiconductor nanocrystal layer 34 may be formed, and the green light emitting semiconductor nanocrystal layer 36 may be disposed on the red light emitting semiconductor nanocrystal layer 34. That is, the light conversion layer 32 in which the green light emitting semiconductor nanocrystal layer 34 and the red light emitting semiconductor nanocrystal layer 36 located thereon are present on the LED light source 10 may be provided. Although the drawing shows a light conversion layer in which only two layers are stacked, it is needless to say that a light conversion layer having a plurality of layers may also be provided. A light conversion layer 42 composed of composite particles of green semiconductor nanocrystals 44 and red semiconductor nanocrystals 46 may be provided as shown in FIG.

The white light emitting diode may be used as a backlight unit of a liquid crystal display device. A liquid crystal display device according to an embodiment of the present invention includes a liquid crystal panel including a white light emitting diode having the above-described structure and a color filter for implementing an image using the white light.

5 is a schematic view illustrating a liquid crystal display device according to an embodiment of the present invention.

Referring to FIG. 5, a liquid crystal display device includes a backlight unit 100 and a liquid crystal panel 500 that forms an image of a predetermined color using white light emitted from the backlight unit 100. The backlight unit 100 may be the white light emitting diode.

Here, the liquid crystal panel 200 may have a structure in which a first polarizer 201, a liquid crystal layer 202, a second polarizer 203, and a color filter 204 are sequentially disposed. The white light emitted from the backlight unit 100 is transmitted through the first polarizer 201, the liquid crystal layer 202 and the second polarizer 203. The transmitted white light is incident on the color filter 204, As shown in Fig. A diffuser plate may be positioned between the backlight unit 100 and the liquid crystal panel 200. [

Hereinafter, the present invention will be described in more detail with reference to examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

Manufacturing example  1: Synthesis of Green Light Emitting Multilayer Semiconductor Nanocrystals

16 g of trioctylamine ("TOA"), 0.128 g of octadecylphosphonic acid and 0.1 mmol of cadmium oxide are simultaneously charged into a 125 ml flask equipped with a reflux condenser, and the reaction temperature is adjusted to 300 ° C. with stirring. Separately, the Se powder is dissolved in trioctylphosphine ("TOP") to form a Se-TOP complex solution with a Se concentration of about 2M. 2 mL of a 2M Se-TOP complex solution is rapidly injected into the stirred reaction mixture and reacted for about 2 minutes. When the reaction is completed, the temperature of the reaction mixture is dropped to room temperature as soon as possible, and centrifugation is carried out by adding ethanol as a non-solvent. The supernatant of the solution except for the centrifuged precipitate is discarded, and the precipitate is dispersed in toluene to synthesize a CdSe nanocrystal solution.

8 g of TOA, 0.1 g of oleic acid and 0.1 mmol of zinc acetate are simultaneously put into a 125 ml flask equipped with a reflux condenser, and the reaction temperature is adjusted to 300 ° C with stirring. After adding the CdSe nanocrystals synthesized above to the reactants, 0.5 mL of 0.8 M S-TOP complex solution was added slowly and reacted for about 1 hour to grow ZnS nanocrystals on the surface of the CdSe nanocrystals. To form an alloy layer. When the reaction is completed, centrifugation is carried out in the same manner as in the separation of CdSe nanocrystals, followed by dispersion in toluene to synthesize nanocrystalline CdSe / ZnS having a multi-layer structure.

CdZnS is again formed on the surface of the CdSe / ZnS nanocrystals. 0.05 mmol of cadmium acetate, 0.1 mmol of zinc acetate, 0.43 g of oleic acid, and 8 g of TOA were placed in a 125 ml flask equipped with a reflux condenser, and the reaction temperature was adjusted to 300 ° C. with stirring, followed by injecting the nanocrystalline CdSe / ZnS synthesized above. Immediately thereafter, 0.8 mmol of octyl cyanide mixed with 2 mL of TOA was slowly injected and synthesized for 1 hour to form nanocrystals having a multi-layered structure of CdSe / ZnS / CdZnS. After the reaction is completed, the synthesized material is separated by centrifugation and dispersed in toluene.

Manufacturing example  2: Synthesis of red light emitting multi-layered semiconductor nanocrystals

32 g of TOA, 1.8 g of oleic acid and 1.6 mmol of cadmium oxide are simultaneously introduced into a 125 ml flask equipped with a reflux condenser, and the reaction temperature is adjusted to 300 ° C with stirring. 0.2 mL of the 2M Se-TOP complex solution synthesized in Example 1 is rapidly injected into the reaction, and 1 minute and 30 seconds later, 0.8 mmol of octyl cyan mixed with 6 mL of TOA is slowly injected. After 40 minutes of reaction, slowly inject 16 mL of separately synthesized zinc oleate complex solution.

The zinc oleate complex solution is prepared by adding 4 mmol of zinc acetate, 2.8 g of oleic acid and 16 g of TOA to a 125 mL flask equipped with a reflux condenser and adjusting the reaction temperature to 200 ° C. with stirring. The temperature is lowered to 100 캜 or lower and then injected. Upon completion of the injection of the zinc oleate complex solution, 6.4 mmol of the octyl complex complex solution mixed with 6 mL of TOA was added slowly and reacted for about 2 hours. Which in turn produced CdSe nanocrystals, then grown CdS nanocrystals on the surface, and grown ZnS one more time.

After the reaction is completed, the temperature of the reaction mixture is dropped to room temperature as soon as possible, and centrifugation is performed by adding ethanol as a non-solvent. The supernatant of the solution excluding the centrifuged precipitate is discarded, and the precipitate is dispersed in toluene to synthesize nanocrystalline CdSe / CdS / ZnS having a multilayer structure of 8 nm in size.

Example  1: Fabrication of white light emitting diode

A solution obtained by mixing the green light emitting semiconductor nanocrystals prepared in Preparation Example 1 and the red light emitting semiconductor nanocrystals prepared in Production Example 2 in hexane and ethanol in a volume ratio of 6: 4 was added and centrifuged at 6000 rpm for 10 minutes to obtain a precipitate. A chloroform solvent is added to the obtained precipitate to prepare a solution of about 1% by weight. The epoxy resin is prepared by mixing SJ4500 A and SJ4500 B resins, which are manufactured and sold by Dow Corning Corporation, in a 1: 1 volume ratio in advance to remove air bubbles. 1 wt% of a green light emitting semiconductor nanocrystal, 1 wt% of a red light emitting semiconductor nanocrystal, 0.1 mL of a chloroform solution, and 0.1 mL of an epoxy resin were mixed and stirred uniformly and maintained in a vacuum for about 1 hour to remove the chloroform solution . About 20 mL of the thus prepared green light emitting semiconductor nanocrystal, a mixture of red light emitting semiconductor nanocrystals and epoxy resin was applied to a cup-shaped lamp-type blue light emitting diode and cured at 100 ° C for 3 hours to prepare a light conversion layer do.

After the blue light emitting diode and the light conversion layer were first formed by the above method, a blue light emitting diode including a light conversion layer, which was first cured by putting only epoxy resin into a mold, Lt; / RTI > to form a lamp-shaped light emitting diode.

Comparative Example  1: Fabrication of white light emitting diode

A solution of hexane and ethanol in a volume ratio of 6: 4 was added to the red light emitting semiconductor nanocrystals prepared in Preparation Example 2, and the mixture was centrifuged at 6000 rpm for 10 minutes to obtain a precipitate. The obtained precipitate is added with a chloroform solvent to prepare a solution of about 1% by weight. The epoxy resin is prepared by mixing SJ4500 A and SJ4500 B resins, which are manufactured and sold by Dow Corning Corporation, in a 1: 1 volume ratio in advance to remove air bubbles. 1 wt% of red light emitting semiconductor nanocrystals, 0.1 mL of a chloroform solution and 0.1 mL of an epoxy resin are mixed and stirred to uniformly maintain a vacuum state for about 1 hour to remove the chloroform solution. After adding 0.05 g of the TG-3540 green inorganic phosphor prepared by Sarnoff, about 20 mL of the obtained mixture was applied onto a cup-shaped lamp-type blue light emitting diode and cured at 100 DEG C for 3 hours, .

After the blue light emitting diode and the light conversion layer were first formed by the above method, a blue light emitting diode including a light conversion layer, which was first cured by putting only epoxy resin into a mold, Lt; / RTI > to form a lamp-shaped light emitting diode.

Comparative Example  2: Fabrication of white light emitting diode

A solution obtained by mixing hexane and ethanol in a volume ratio of 6: 4 was added to the green semiconductor nanocrystals prepared in Production Example 1, and the mixture was centrifuged at 6000 rpm for 10 minutes to obtain a precipitate. The obtained precipitate is added with a chloroform solvent to prepare a solution of about 1% by weight. The epoxy resin is prepared by mixing SJ4500 A and SJ4500 B resins, which are manufactured and sold by Dow Corning Corporation, in a 1: 1 volume ratio in advance to remove air bubbles. 1 wt% of the green light emitting semiconductor nanocrystals, 0.1 mL of the chloroform solution and 0.1 mL of the epoxy resin are mixed and stirred uniformly and maintained in a vacuum for about 1 hour to remove the chloroform solution. After adding 0.1 g of Sr-Mg-P ₄ O ₁₆ red inorganic phosphor prepared by Sarnoff, about 20 mL of the resulting mixture was applied to a cup-shaped lamp-type blue light emitting diode, Lt; / RTI > to form a light conversion layer.

After the blue light emitting diode and the light conversion layer were first formed by the above method, a blue light emitting diode including a light conversion layer, which was first cured by putting only epoxy resin into a mold, Lt; / RTI > to form a lamp-shaped light emitting diode.

Comparative Example  3

0.05 g of the TG-3540 green inorganic phosphor manufactured by Sarnoff and 0.1 g of the red inorganic phosphor of the Sr-Mg-P ₄ O ₁₆ series are mixed with 0.1 mL of the epoxy resin and uniformly mixed. About 20 mL of the thus prepared mixture of the inorganic phosphor and the epoxy resin was applied on a lamp-type blue light emitting diode in the form of a cup, and the mixture was cured at 100 DEG C for 3 hours to prepare a light conversion layer.

 After the blue light emitting diode and the light conversion layer were first cured by the above method, a blue light emitting diode including a light emitting layer primarily cured with epoxy resin in a mold for molding into a lamp shape was heated at 100 ° C. for 3 hours And then the LED is cured again to manufacture a lamp-shaped light emitting diode.

In order to measure the spectra of the light emitting diodes of Example 1 and Comparative Examples 1 to 3 under the same conditions, the luminescence characteristics collected in the integrating sphere were evaluated using the ISP75 system, and the emission spectrum was analyzed.

Fig. 6 shows the emission spectrum of the LED using the white light-emitting semiconductor nanocrystal according to Example 1. Fig. The emission spectrum after passing through the color filter is shown in Fig. (28 nm) and 620 nm (36 nm), respectively, after the emission peak wavelengths (half widths) of the green and red luminescence spectra are 528 nm (28 nm) and 626 nm ), And it can be seen that there is almost no difference in emission peak wavelength and half width after transmission of the color filter. It is also seen from Fig. 7 that the area of the luminescence spectrum after passing through each color filter of the white light emitting diode has a ratio of about 1: 0.94: 0.84.

The relative transmittance ratios of the blue, green and red colors of the color filter and the emission spectrum before and after the color filter are also shown in FIG. 8 in order to examine the rate at which the white light emitting diode transmits the color filter. Referring to FIG. 8, the spectrum of each of the white light emitting diodes according to Example 1 has almost no difference in half width before and after the color filter, and the emission spectrum of the green light emitting semiconductor nanocrystals has almost no portion transmitting the red color filter. The emission spectrum of the nanocrystals appears to transmit a small amount of the green color filter.

Fig. 9 shows the emission spectrum of the LED using the phosphor according to Comparative Example 3. Fig. Referring to FIG. 9, it can be seen that the half width of the emission spectrum of green and red is considerably wide. The relative transmittance ratios of blue, green and red of the color filter are also shown in FIG. 10 in order to examine the ratio of the white light emitting diode according to Comparative Example 3 transmitting through the color filter. Referring to FIG. 10, the spectrum of each of the white light emitting diodes according to Comparative Example 3 has many portions overlapping with each other. The emission spectrum of the green phosphor is the portion through which the red color filter passes and the emission spectrum of the red phosphor transmits through the green color filter There are quite a lot of things to do.

11 is a graph showing the emission spectrum of the white light emitting diode of Example 1 with the white coordinate (x, y) of the backlight unit adjusted to 0.28 0.05 and 0.29 0.05.

Using the spectrum of the green semiconductor nanocrystals prepared in Preparation Example 1, the red semiconductor nanocrystals prepared in Preparation Example 2, and the green and red inorganic phosphors used in Comparative Example 3, the emission intensity was adjusted to match the white coordinates After adjusting, the color coordinates corresponding to red, green, and blue were calculated, and the relative color recall ratio and the relative brightness were obtained. The results are shown in Table 1. In Table 1, luminescent intensities for matching white coordinates at the bottom of each color coordinate are described together.

Red green blue Color coordinates opponent
Color recall (%) Relative luminance (%) Red green blue Example 1 Semiconductor nanocrystals Semiconductor nanocrystals LED (0.673, 0.308) (0.190, 0.707) (0.150, 0.057) 122 117 0.28 0.29 0.43 Comparative Example
One Semiconductor nanocrystals Phosphor LED (0.658, 0.318) (0.277, 0.655) (0.151, 0.046) 101 125 0.17 0.37 0.46 Comparative Example 2 Phosphor Semiconductor nanocrystals LED (0.675, 0.305) (0.205, 0.697) (0.151, 0.056) 120 92 0.46 0.21 0.33 Comparative Example 3 Phosphor Phosphor LED (0.659, 0.316) (0.282, 0.652) (0.151, 0.046) 100 100 0.31 0.30 0.39

As shown in Table 1, the light emitting diode according to Example 1 manufactured using green and red semiconductor nanocrystals had both a color reproducibility and a relative luminance in comparison with Comparative Examples 1 to 3 using green and / or red inorganic phosphors It can be seen that it is excellent.

FIG. 12 is a diagram showing the emission spectrum of a white light emitting diode according to Example 1 and Comparative Example 3 after transmission through a color filter. FIG. 13 is a graph showing the emission spectra of white light emitting diodes according to Example 1 and Comparative Example 3, Fig. 12, the white light emitting diodes according to Example 1 do not overlap the emission wavelengths of red, green, and blue, whereas the white light emitting diodes of Comparative Example 3 have emission wavelengths of red, green, . Also, as shown in the luminance spectrum of FIG. 13, which reflects the visibility, in the case of semiconductor nanocrystals having a relatively narrow emission spectrum, the region of the red spectrum can be maintained at a high visibility, which is advantageous in that the luminance can be increased. In order to maintain these characteristics more optimally, when the emission peak wavelength of the semiconductor nanocrystals is varied in various ways, it is most effective when the emission peak wavelengths of red and green are maintained at 630 nm and 530 nm in color reproduction ratio and luminance see.

The color reproduction ratio and the relative luminance according to the emission peak wavelength of the semiconductor nanocrystals are evaluated and are shown in Table 2 below.

Red green blue Red
Color coordinates green
Color coordinates blue
Color coordinates Color recall (%) Relative luminance (%) Semiconductor nanocrystals Semiconductor nanocrystals LED (0.673, 0.308) (0.190, 0.707) (0.150, 0.057) 122 118 630 nm 530 nm 0.28 0.29 0.43 Semiconductor nanocrystals Semiconductor nanocrystals LED (0.686, 0.296) (0.178, 0.717) (0.150, 0.058) 137 108 640 nm 530 nm 0.33 0.27 0.4 Semiconductor nanocrystals Semiconductor nanocrystals LED (0.671, 0.307) (0.239, 0.691) (0.152, 0.045) 115 120 630 nm 540 nm 0.25 0.29 0.46 Semiconductor nanocrystals Semiconductor nanocrystals LED (0.683, 0.295) (0.231, 0.699) (0.152, 0.045) 120 113 640 nm 540 nm 0.29 0.28 0.43 Semiconductor nanocrystals Semiconductor nanocrystals LED (0.658, 0.323) (0.212, 0.690) (0.150, 0.056) 112 118 620 nm 530 nm 0.25 0.29 0.46

As shown in Table 2, when the emission peak wavelengths of the green and red semiconductor nanocrystals are in the range of 530-540 nm and 620-640 nm, respectively, the color recall ratio and the relative luminance are both excellent.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

Claims (28)

A light emitting diode (LED) light source emitting blue light;
A light conversion layer for converting light incident from the LED light source into white light; And
A liquid crystal display device comprising a color filter for realizing an image using the white light,
Wherein the light conversion layer comprises a light emitting material,
The light emitting material includes only semiconductor nanocrystals, and the semiconductor nanocrystals include green light emitting semiconductor nanocrystals and red light emitting semiconductor nanocrystals
Wherein the emission peak wavelength of the green light emitting semiconductor nanocrystals is 530 nm or more, the emission peak wavelength of the red light emitting semiconductor nanocrystals is 615 nm or more,
Wherein the ratio of the emission spectrum of the green light emitting semiconductor nanocrystals to the green color filter is 95% or more, the ratio of the green color semiconductor nanocrystals to the red color filter is less than 10%
Wherein the ratio of the emission spectrum of the red light emitting semiconductor nanocrystals to the red color filter is 95% or more, and the ratio of the green color filter to the green color filter is less than 10%.
The method according to claim 1,
(S / (A _G or A _R ) of the area S of the overlapping region of the total area (A _G ) of the emission spectrum of the green light emitting semiconductor nanocrystals with the total area (A _R ) of the emission spectrum of the red light emitting semiconductor nanocrystals ) Is 10% or less.
The method according to claim 1,
(S / (A _G or A _R ) of the area S of the overlapping region of the total area (A _G ) of the emission spectrum of the green light emitting semiconductor nanocrystals with the total area (A _R ) of the emission spectrum of the red light emitting semiconductor nanocrystals ) Is 7% or less.
The method according to claim 1,
(S / (A _G or A _R ) of the area S of the overlapping region of the total area (A _G ) of the emission spectrum of the green light emitting semiconductor nanocrystals with the total area (A _R ) of the emission spectrum of the red light emitting semiconductor nanocrystals ) Is not more than 5%.
The method according to claim 1,
Wherein a half width of the emission peak of the green and red light emitting semiconductor nanocrystals is 40 nm or less.
The method according to claim 1,
Wherein the emission peak wavelength of the LED light source emitting blue light is 440 to 460 nm, the emission peak wavelength of the green light emitting semiconductor nanocrystals is 530 to 550 nm, and the emission peak wavelength of the red light emitting semiconductor nanocrystals is 620 to 640 nm Liquid crystal display device.
The method according to claim 1,
The emission intensity of the LED light source emitting blue light is 0.43 ± 0.05, the emission intensity of the green light emitting semiconductor nanocrystals is 0.27 ± 0.05, and the emission intensity of the red light emitting semiconductor nanocrystals is 0.28 ± 0.05.
The method according to claim 1,
The color coordinates of the white light are such that the x-coordinate is 0.24 ± 0.05 and the y-coordinate is 0.21 ± 0.05.
The method according to claim 1,
And the color temperature of the white light is from 9500K to 100000K.
The method according to claim 1,
Wherein the ratio of the emission spectrum of the green light emitting semiconductor nanocrystals to the green color filter is 98% or more of the maximum transmittance of the green color filter, the ratio of the red color filter transmitting is less than 5%
Wherein the ratio of the transmittance of the emission spectrum of the red light emitting semiconductor nanocrystals to the red color filter is 98% or more of the maximum transmittance of the red color filter, and the ratio of transmittance of the green color filter is less than 5% Device.
11. The method according to any one of claims 1 to 10,
Wherein the ratio of the luminescence intensities of the blue, green and red luminescence spectra after transmission of the color filter of the liquid crystal display device is in the range of 1: 0.9 0.1: 0.8 0.1.
An LED light source emitting blue light; And
A backlight unit including a light conversion layer for converting light incident from the LED light source into white light,
Wherein the light conversion layer comprises a light emitting material,
Wherein the light emitting material comprises only semiconductor nanocrystals, the semiconductor nanocrystals include green light emitting semiconductor nanocrystals and red light emitting semiconductor nanocrystals,
Wherein the emission peak wavelength of the green light emitting semiconductor nanocrystals is 530 nm or more, the emission peak wavelength of the red light emitting semiconductor nanocrystals is 615 nm or more, and the color reproduction ratio is 90% or more of the NTSC color coordinates of the CIE1931 coordinate.
13. The method of claim 12,
Wherein a half width of the emission peak of the green and red light emitting semiconductor nanocrystals is 40 nm or less.
13. The method of claim 12,
Wherein the emission peak wavelength of the LED light source emitting blue light is 440 to 460 nm, the emission peak wavelength of the green light emitting semiconductor nanocrystals is 530 to 550 nm, and the emission peak wavelength of the red light emitting semiconductor nanocrystals is 620 to 640 nm Backlight unit.
13. The method of claim 12,
Wherein the emission intensity of the LED light source emitting the blue light is 0.43 ± 0.05, the emission intensity of the green light emitting semiconductor nanocrystals is 0.27 ± 0.05, and the emission intensity of the red light emitting semiconductor nanocrystals is 0.28 ± 0.05.
13. The method of claim 12,
Wherein the color coordinates of the white light have an x coordinate of 0.24 +/- 0.05 and a y coordinate of 0.21 +/- 0.05.
13. The method of claim 12,
And the color temperature of the white light is 9500 K to 100000 K.
A backlight unit according to any one of claims 12 to 17; And
And a color filter that implements an image using white light emitted from the backlight unit.
19. The method of claim 18,
Wherein the ratio of the luminescence intensities of the blue, green and red luminescence spectra after transmission of the color filter of the liquid crystal display device is in the range of 1: 0.9 0.1: 0.8 0.1.
The method according to claim 1,
Wherein the luminescent material does not include a green luminescent inorganic phosphor and a red luminescent inorganic phosphor. The method according to claim 1,
Wherein the light conversion layer comprises a resin.
The method according to claim 1,
Wherein a half width of the emission peak of the green and red light emitting semiconductor nanocrystals is 45 nm or less.
delete 11. The method according to any one of claims 1 to 10,
And has a color reproduction ratio of 90% or more with respect to an NTSC color coordinate of a CIE1931 coordinate.
An LED light source emitting blue light; And
And a light conversion layer for converting light incident from the LED light source into white light,
Wherein the light conversion layer comprises a light emitting material,
Wherein the light emitting material comprises only semiconductor nanocrystals,
The semiconductor nanocrystals include green light emitting semiconductor nanocrystals and red light emitting semiconductor nanocrystals
Wherein the emission peak wavelength of the green light emitting semiconductor nanocrystals is 530 nm or more and the emission peak wavelength of the red light emitting semiconductor nanocrystals is 615 nm or more.
26. The method of claim 25,
And the color temperature of the white light is 9500K to 100000K.
26. The method of claim 25,
Wherein a half width of an emission peak of the green and red light emitting semiconductor nanocrystals is 45 nm or less.
26. The method of claim 25,
Wherein a half width of the emission peak of the green and red light emitting semiconductor nanocrystals is 40 nm or less.

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