KR101057349B1 - White light source with enhanced brightness - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white light source, comprising a blue cavity, a microcavity formed under the blue light source and reducing the spectral bandwidth of blue light emitted from the blue light source, and formed under the microcavity. And a yellow light reflecting filter and a yellow light reflecting filter, and a phosphor formed under the light recycling filter and absorbing blue light emitted from a blue light source to emit yellow light. The microcavity used in the white light source of the present invention reduces the spectral bandwidth of the blue light and re-reflects the blue light reflected from the phosphor, and the light recycling filter transmits the blue light and reflects the yellow light emitted from the phosphor. The brightness is improved.

Description

High-luminance white light source

The present invention relates to a white light source, and more particularly to a high-efficiency high-brightness white light source using a blue light source and a yellow phosphor.

White light sources are widely used for illumination, backlight sources of display elements, and the like. Conventional white light sources include a filament bulb in which filaments are heated to emit light by electrical resistance, and a fluorescent lamp to excite a white phosphor with ultraviolet rays generated from a discharged gas. However, the filament bulb has a problem that the light generation efficiency is very low and the life is short, and the fluorescent lamp also has a problem that the space efficiency is low and large volume.

Recently, attention has been focused on the implementation of a white light source using an organic light emitting diode. Organic light emitting diodes have the advantages of long life, high efficiency, and small volume, which can be applied to various lighting devices or display devices. In addition, when the organic light emitting diode is applied to a display device, the organic light emitting diode is a self-luminous display device, thereby ensuring a wide viewing angle, having a fast response speed, and low power consumption. In addition, when a substrate having elasticity such as a polymer resin is used, a flexible display can be realized, and since the panel is light, it is also attracting attention as a next-generation display device to replace a conventional flat panel display device such as a liquid crystal display device or a plasma display panel. have.

The organic light emitting diode generally includes a substrate, an anode, an organic layer, and a cathode, and the organic layer is formed by sequentially stacking a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer. In the organic light emitting diode, electrons injected from the cathode move to the light emitting layer through the electron injection layer and the electron transport layer, and holes injected from the anode move to the light emitting layer through the hole injection layer and the hole transport layer, respectively. Electrons and holes recombine into excitons, emitting light of a particular wavelength.

There are various conventional techniques for implementing a white light source using such an organic light emitting diode.

1 is a view for explaining conventional white light sources using an organic light emitting diode. FIG. 1A illustrates a structure of a horizontal RGB stack organic light emitting diode, and R, G, and B organic light emitting diodes are continuously disposed on the substrate 101, and white light is realized by color mixing. It was made. In the R, G, and B organic light emitting diodes, a red light emitting layer 103a, a green light emitting layer 103b, and a blue light emitting layer 103c are disposed between the transparent electrode 102 and the metal electrode 104, respectively. However, since the horizontal RGB stacked organic light emitting diodes must separately control the voltages applied to the organic light emitting diodes of R, G, and B, each cell cannot be driven by one voltage.

FIG. 1B illustrates a structure of a vertical RGB stack organic light emitting diode, wherein R, G, and G between the transparent electrode 102 and the metal electrode 104 formed on the substrate 101 are illustrated. The B light emitting layers 103a, 103b, and 103c are stacked so that white light is emitted to the entire surface by mixing. However, the vertical RGB stacked organic light emitting diode does not have high color purity of white due to a resonance effect between two electrodes, and has a problem in that color characteristics deviate from white depending on thickness conditions.

FIG. 1C illustrates a structure of a white light source in which a blue organic light emitting diode and a yellow phosphor are combined, and the transparent electrode 102, the blue light emitting layer 103c, and the metal electrode 104 formed on the substrate 101. The yellow phosphor 105 is excited by the blue light emitted from the blue organic light emitting diode consisting of), and yellow light is emitted, and white light is realized by the mixture of blue and yellow. However, the white light source has a problem of low luminous efficiency of the yellow phosphor due to blue light and a problem of not using the light emitted in the opposite direction from the yellow phosphor efficiently.

Accordingly, the problem to be solved by the present invention is to improve the absorption efficiency of the yellow phosphor to the blue light by reducing the spectral bandwidth of the blue light supplied to the yellow phosphor and to increase the light intensity at the peak, the light emitted from the yellow phosphor to the back Reflecting the light back to the front to provide a white light source to improve the overall luminous efficiency.

In order to achieve the above object, the present invention provides a blue light source, a microcavity formed under the blue light source and reducing the spectral bandwidth of the blue light emitted from the blue light source, and formed under the microcavity. It provides a white light source including a light recycling filter for transmitting and reflecting yellow light, and a phosphor formed under the light recycling filter and absorbs blue light emitted from a blue light source to emit yellow light.

According to an embodiment of the present invention, the microcavity may be formed by alternately stacking two material layers having different refractive indices.

According to another embodiment of the present invention, the two material layers having different refractive indices stacked alternately may be made of silicon oxide and titanium oxide, respectively.

According to another embodiment of the present invention, the microcavity may be formed by stacking two to four layers of two material layers having different refractive indices.

According to another embodiment of the present invention, the light recirculation filter may be formed by alternately repeating a first thin film having a predetermined refractive index and a second thin film having a refractive index higher than that of the first thin film.

According to another embodiment of the present invention, the first thin film may be made of silicon oxide, and the second thin film may be made of titanium oxide.

According to another embodiment of the present invention, the uppermost layer and the lowermost layer of the slag recycling filter may be formed of a first thin film.

According to another embodiment of the present invention, the uppermost layer and the lowermost layer have a thickness of 1/8 of the band center wavelength of the edge wavelength, and the layer between the uppermost layer and the lowermost layer is 1/1 of the band center wavelength of the edge wavelength. It is preferred to have a thickness of four.

According to another embodiment of the present invention, the light recirculation filter may change the center of the spectrum while reflecting the yellow light emitted from the phosphor.

The light recirculation filter used in the white light source of the present invention reflects the light emitted from the yellow phosphor back to the front surface, and the microcavity reduces the spectral bandwidth of the blue light to excite the yellow phosphor to improve the luminous efficiency of the yellow phosphor. At the same time, the blue light reflected from the yellow phosphor is reflected again and supplied to the yellow phosphor, thereby improving the overall luminous efficiency of the white light source.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The white light source of the present invention is a blue cavity, a microcavity formed under the blue light source and reducing the spectral bandwidth of the blue light emitted from the blue light source, and formed under the microcavity, the blue light transmits and yellow light. It is characterized in that it comprises a light recirculation filter for reflecting silver, and a phosphor formed under the light recirculation filter, and absorbs blue light emitted from a blue light source to emit yellow light.

2 illustrates a process in which white light is emitted from a white light source in which a blue organic light emitting diode and a yellow phosphor are combined. Referring to FIG. 2, when a predetermined voltage is applied to the transparent electrode 102 and the metal electrode 104 formed on the upper and lower surfaces of the blue light emitting layer 103c, blue light (filled arrow) is emitted from the blue light emitting layer 103c. . The emitted blue light passes through the substrate and is supplied to the yellow phosphor 105 formed on the lower surface of the substrate 101. The yellow phosphor 105 absorbs blue light to emit yellow light (unfilled arrow). White light is realized by the mixed color of yellow. At this time, the yellow light is emitted to both the bottom and the top of the substrate, the yellow light emitted upward is not the light emitted to the outside of the white light source, which causes a reduction in luminous efficiency. Another cause of reducing the luminous efficiency of a white light source is the reflection of blue light occurring in the phosphor. The blue light emitted from the blue organic light emitting diode is absorbed by the phosphor to excite the phosphor, but some of it is reflected or scattered and lost in the opposite direction. Therefore, the present invention reflects the light emitted toward the substrate out of the yellow light generated from the yellow phosphor by using the ash recirculation filter, and increases the blue light absorption efficiency of the yellow phosphor by using the microcavity and at the same time in the light recirculation filter It is an object to increase the luminance of a white light source by reducing the amount of reflected blue light.

3 is a view for explaining the function of the microcavity (microcavity) applied to the white light source of the present invention. Referring to FIG. 3A, a blue organic light emitting diode with a blue light emitting layer 303 is formed on the substrate 301 between the transparent electrode 302 and the metal electrode 304, and the organic light emitting diode and the substrate The microcavity 307 is formed therebetween, and a yellow phosphor layer 305 is formed under the substrate. The blue light emitted from the blue organic light emitting diode (filled arrow) passes through the substrate 301 and is supplied to the yellow phosphor 305, and the yellow phosphor 305 absorbs blue light to emit yellow light (unfilled arrow). White light is emitted to the outside due to the mixture of blue and yellow. Referring to FIG. 3B, the micro cavity 307 is formed by alternately stacking two materials 307a and 307b having different refractive indices. The two material layers having different refractive indices may be made of silicon oxide and titanium oxide, respectively, and the microcavity preferably has two material layers having different refractive indices stacked in a range of 2 to 4 layers. This is because when the number of layers of the microcavity exceeds four layers, the transmittance of blue light is lowered and the intensity of blue light supplied to the yellow phosphor is too weak. The microcavity of the present invention reduces the spectral band width of blue light and increases the blue light absorption efficiency of the yellow phosphor. The microcavity also serves to reflect the blue light reflected from the yellow phosphor back to the yellow phosphor. The yellow phosphor used in the present invention refers to a phosphor that absorbs blue light and emits yellow light, and this is also the case when one phosphor particle emits light in a yellow wavelength band, and a phosphor particle that emits light in a green wavelength band. The case where the phosphor which emits light of a red wavelength band is mixed and the light which emits light of a yellow wavelength band as a whole is used also belongs to the scope of the present invention.

Figure 4 shows the absorption spectrum of the blue organic light emitting diode and the yellow phosphor that can be used in the white light source of the present invention and the emission spectrum and modulation of light by the microcavity. The blue light emitting material used in the blue organic light emitting diode is DPVBi (4,4-Bis (2,2-diphenylvinyl) -1,1-biphenyl), and the yellow phosphor is YAG: Ce ((Y3Al5O12: Ce). Referring to (a), the emission spectrum of DPVBi and the absorption spectrum of YAG: Ce have similar bandwidths in the range of 400 nm to 500 nm, and in general, the luminous efficiency of the phosphor that absorbs and emits excitation light is determined by the excitation light. The higher the spectral center and the center of the absorption spectrum of the phosphor, the higher, and the narrower the band width of the excitation light is, the narrower the band width of the absorption spectrum becomes. This is because the loss of blue light used for excitation of the phosphor is reduced, as shown in Fig. 4B, where the blue light passing through the microcavity has a narrow bandwidth and a center wave. This tendency is increased by increasing the number of layers of materials with different refractive indices constituting the microcavity, which is caused by the microcavity effect, when light passes through multilayer films having different refractive indices. Multiple reflections in the light create destructive and constructive interference, so that only light of a certain wavelength is maintained and the light of the remaining wavelength is weakened, however, if the number of layers in the microcavity increases above a certain level, the total amount of blue light passing through the microcavity In this sense, the microcavity used in the present invention is an intermediate micro layer in which two material layers having different refractive indices are stacked in two to four layers. It can be called a cavity (moderate microcavity).

5 is a view for explaining the function of the light-recycling filter (light-recycling filter) applied to the white light source of the present invention. Referring to FIG. 5A, a blue organic light emitting diode including a blue light emitting layer 303 is formed on the upper surface of the substrate 301 between the transparent electrode 302 and the metal electrode 304. The slag recycling filter 306 and the yellow phosphor layer 305 are formed on the lower surface of the 301. The blue light emitted from the blue organic light emitting diode (filled arrow) passes through the substrate 301 and the slag recycle filter 306 and is supplied to the yellow phosphor 305, and the yellow phosphor 305 absorbs the blue light to emit yellow light ( Unfilled arrows), and white light is emitted outside of the white light source by a mixture of blue and yellow colors. At this time, the yellow light emitted upward of the substrate 301 is reflected by the slag recycling filter 306 and is emitted downward below the substrate 301, thereby reducing the loss of yellow light, thereby improving the overall luminous efficiency of the white light source.

The slag recycling filter is designed to transmit blue light having a short wavelength and to reflect yellow light having a long wavelength. Referring to FIG. 5B, the reclaim filter 306 is formed by alternately repeating a first thin film 306a having a relatively low refractive index and a second thin film 306b having a high refractive index. The uppermost layer and the lowermost layer of the slag recycling filter 306 consist of the first thin film 306a, and the thickness thereof is 1/8 of the edge wavelength, and the layer between the uppermost layer and the lowermost layer is 1 of the edge wavelength. It is preferred to have a thickness of / 4. The edge wavelength means the maximum wavelength of light that can pass through the slag recycling filter (see FIG. 9). This is designed by the Transfer Matrix Method below for the purpose of the light recycling filter to pass blue light and reflect yellow light. In the present invention, the first thin film may be made of silicon oxide (SiO ₂ ) having a relatively low refractive index, and the second thin film may be made of titanium oxide (TiO ₂ ) having a relatively high refractive index.

 By controlling the refractive index, the number of layers and the like of each layer constituting the light recirculation filter by the transfer matrix method, it is possible to select the wavelength range of the reflection zone and the transmission zone. The tangent components of the electric field (E) and the magnetic field (H) at the interface b of the thin films having different refractive indices are shown in Equation 1 below.

로 정의되는 물질의 optical admittance로 정의되는 양이다. 여기서

로 자유공간의 optical admittance이다. 본 발명에서는 투명 유전체의 박막을 고려하고 있으므로 굴절율의 성분이 실수성분인 n과 허수성분인 k로 나누어 진다. 즉 어떤 흡수물질의 굴절율은 다음과 같이 정의된다In Equation 1, +,-mean the direction of the electric and magnetic fields,

The amount defined by the optical admittance of a material defined by. here

The optical admittance of free space. In the present invention, since the thin film of the transparent dielectric material is considered, the component of the refractive index is divided into n which is a real component and k which is an imaginary component. The refractive index of an absorbent material is defined as

.

.

Here, when considering the boundary condition that the tangent components of the electric and magnetic fields are continuous at the interface, a matrix can be obtained.

이고

는 빛의 파장이다.here

ego

Is the wavelength of light.

를 도입하면 최종적인 matrix는 아래 수학식 2와 같다.In the case of a multilayer thin film, the matrix may be multiplied sequentially. Also here multilayer optical admittance

The final matrix is given by Equation 2 below.

The reflection R, transmission T, and absorption A are as shown in Equation 3 below.

The present invention finally calculated the desired reflection area and absorption area of the slag recycle filter in the above-described manner. If the desired reflection area and absorption area are determined, the conditions of the desired slag recycle filter are also based on the above-described method. Can be set.

The reflection spectral wavelength center λ _max of the light recycling filter used in the present invention exists within the wavelength range of the emission spectrum of the yellow phosphor, and as a result, the light emitted from the phosphor layer to the rear surface may be reflected to the front surface. In this case, the light recirculation filter may change the center of the spectrum λ _max while reflecting the light emitted from the yellow phosphor. The reflection effect is maximized when the wavelength center of the emission spectrum of the yellow phosphor coincides with the center of the reflection wavelength region of the light recirculation filter. It is possible to adjust the color purity of the white light by changing the wavelength center of the light.

6 illustrates a structure of a white light source and a process of emitting white light according to the present invention. Referring to FIG. 6, a blue organic light emitting diode including a microcavity 307, a transparent electrode 302, a blue light emitting layer 303, and a metal electrode 304 is sequentially formed on the substrate 301. The microcavity 307 is formed between the upper surface of the 301 and the transparent electrode 304. A slag recycling filter 306 and a yellow phosphor layer 305 are formed on the lower surface of the substrate 301. The blue light emitted by the blue organic light emitting diode (filled arrow) passes through the microcavity 307, the substrate 301, and the light recycling filter 306 to excite the yellow phosphor 305. At this time, the microcavity 307 allows the blue light to be supplied to the yellow phosphor layer 305 while reducing the spectral bandwidth of the blue light generated from the blue light emitting diode, and reflects the blue light reflected from the yellow phosphor layer 305 again. It serves to be supplied again in the direction of the yellow phosphor layer 305. The slag recycling filter 306 reflects the light emitted toward the substrate during the yellow phosphor layer 305 and emits the light to the outside again.

As described above, the white light source of the present invention excites a yellow phosphor with light generated from a blue light source, and has a principle that white light is realized by a mixture of blue light and yellow light. At this time, the light modulation effect of the microcavity (reducing the spectral bandwidth of the blue light), the rereflection effect of the blue light, and the reflection effect of the yellow light by the light recycling filter generate synergistic effects. The brightness can be increased significantly.

Hereinafter, the present invention will be described in more detail with reference to preferred examples. However, these examples are intended to illustrate the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited thereby.

Example 1 (Preparation of white light source comprising 1 pair of microcavity and 510 nm edge wavelength recirculation filter)

A white light source having a cross-sectional structure as shown in FIG. 6 was prepared. A microcavity layer was formed on the substrate, a blue light emitting diode was formed thereon, and a slag recycling filter and a yellow fluorescent layer were formed on the substrate. The substrate is a glass substrate, and the blue light emitting diode is TAT (9,10-bis (3 ', 5') which is a blue light emitting material of Formula 1 between a metal electrode made of aluminum and a transparent electrode made of indium tin oxide having a thickness of 150 nm. -diphenylphenyl) -10- (3 '", 5'"-diphenylbiphenyl-4 "-yl) anthracene) was formed and YAG: Ce was used as a yellow phosphor.

Formula 1

The microcavity was formed by depositing one layer of silicon oxide (SiO ₂ ) having a thickness of 80 nm and titanium oxide (TiO ₂ ) having a thickness of 50 nm by using electron beam deposition (e-beam deposition) to form a total of two layers. The slag recycling filter was repeatedly deposited by alternately depositing silicon oxide and titanium oxide using an electron beam deposition method. The uppermost layer and the lowermost layer of the slag recycling filter were formed of silicon oxide and titanium oxide so that 19 layers were included. At this time, the uppermost layer and the lowermost layer of the slag recycling filter were formed to have a thickness of 1/8 of the band center wavelength to form an edge wavelength set to 510 nm, and the layer therebetween had a thickness of 1/4 of the edge band center wavelength. Formed.

Example 2 (Preparation of white light source comprising a pair of microcavities and a light recirculation filter of 550 nm edge wavelength)

A white light source was manufactured in the same manner as in Example 1, except that the edge wavelength of the light recycling filter was set to 550 nm.

Example 3 (Preparation of White Light Source Including a Pair of Microcavities and a Light Recirculation Filter of 580 nm Edge Wavelength)

A white light source was manufactured in the same manner as in Example 1, except that the edge wavelength of the light recycling filter was set to 600 nm.

Comparative Example 1 (Preparation of white light source not including microcavity and slag recycle filter)

A white light source was manufactured in the same manner as in Example 1, except that the microcavity and the ash recycling filter were not formed.

Comparative Example 2 (Preparation of White Light Source Containing 1 Pair of Microcavity)

A white light source was manufactured in the same manner as in Example 1, except that the slag recycling filter was not formed on the lower surface of the substrate.

Comparative Example 3 (Preparation of White Light Source Containing 2 Pair Microcavity)

A white light source was manufactured in the same manner as in Comparative Example 2, except that 80 nm thick silicon oxide (SiO ₂ ) and 50 nm thick titanium oxide (TiO ₂ ) were alternately deposited to form microcavities.

Comparative Example 4 (Preparation of White Light Source Containing 4 Pair Microcavity)

A white light source was manufactured in the same manner as in Comparative Example 2, except that four layers of silicon oxide (SiO ₂ ) having a thickness of 80 nm and titanium oxide (TiO ₂ ) having a thickness of 50 nm were deposited alternately.

Comparative Example 5 (Production of White Light Source Including a Light Recycling Filter of 510nm Edge Wavelength)

A white light source was manufactured in the same manner as in Example 1, except that no microcavity was formed on the upper surface of the substrate.

Comparative Example 6 (Preparation of White Light Source Containing Light Recycling Filter with 550nm Edge Wavelength)

A white light source was manufactured in the same manner as in Comparative Example 5 except that the edge wavelength of the light recycling filter was set to 550 nm.

Comparative Example 7 (Preparation of White Light Source Including a Light Recycling Filter of 580 nm Edge Wavelength)

A white light source was manufactured in the same manner as in Comparative Example 5 except that the edge wavelength of the light recycling filter was set to 580 nm.

Experimental Example 1

For the blue light of Comparative Examples 1 to 4, the emission spectrum of the organic light emitting layer (TAT), the emission spectrum passing through the microcavity, and the absorption spectrum of YAG: Ce, which are yellow phosphors, were measured, and electrical and external quantum efficiency of blue light were measured. Measured.

7 shows spectral results of blue light with respect to blue light of Comparative Examples 1 to 4 and the efficiency of blue light. Referring to FIG. 7A, the blue light passing through the microcavity decreases in spectral bandwidth, and this tendency increases as the number of layers of the microcavity increases. In addition, the center of the wavelength was changed by the micro-cavity effect. It can be seen that due to the microcavity effect, the portion overlapping with the absorption spectrum of YAG: Ce, which is a yellow phosphor, of the blue light emission spectrum is increased. Referring to FIG. 7B, the blue light of Comparative Example 2 was measured to have higher electrical efficiency and external quantum efficiency than the blue light of Comparative Example 1. However, in Comparative Example 3, the external quantum efficiency was higher than that of Comparative Example 1, but the electrical efficiency was low. In Comparative Example 4, the external quantum efficiency and the electrical efficiency were the lowest. The electrical efficiency is the luminance in consideration of the luminous effect, and the external quantum efficiency is a value in which the luminous effect is not considered.

Experimental Example 2

The spectrum of white light generated in the white light sources of Comparative Examples 1 to 4, the efficiency of the white light source and the color coordinate / color temperature were measured. 8 shows the spectral results of the white light of Comparative Examples 1 to 4 and the efficiency of the white light source. Referring to (a) of FIG. 8, the white light source of Comparative Example 2 to which a microcavity of 1 pair is applied has an increased peak intensity and area of the white light spectrum compared to Comparative Example 1 to which the microcavity is not applied. Referring to FIG. 8B, the white light of Comparative Example 2 was measured to have higher electrical efficiency and external quantum efficiency than the white light of Comparative Example 1 (electrical efficiency is about 1.27 times and external quantum efficiency about 1.32 times). The white light of Comparative Example 3 showed similar or slightly improved electrical efficiency and external quantum efficiency, and Comparative Example 4 showed lower electrical efficiency and external quantum efficiency than Comparative Example 1. Referring to FIG. 8C, all of the white lights of Comparative Examples 1 to 4 exhibited similar color coordinates and color temperature.

Experimental Example 3

The reflectance according to the wavelength of the slag recycle filter applied to the white light source of Comparative Examples 5 to 7 was measured. 9 is a reflectance measurement result for the light recirculation filter of Comparative Examples 5 to 7. Referring to FIG. 9, the light recirculation filter transmits light of low wavelength and reflects light of high wavelength, and adjusts the thickness of the material layer constituting the light recirculation filter to adjust the edge wavelength of the light recirculation filter. It can be seen that the transmittance of the blue light (black graph) and the reflectance of the yellow light (blue graph) can be adjusted as a result.

Experimental Example 4

For the white light sources of Comparative Example 1 and Comparative Examples 5 to 7, the spectrum and efficiency of the white light were measured. 10 shows the spectral results of the white light and the efficiency of the white light source for the white light source of Comparative Example 1 and Comparative Examples 5 to 7. Referring to FIG. 10A, the white light source of Comparative Example 6 shifted the spectrum of white light and increased the area slightly compared with the white light source of Comparative Example 1. FIG. Referring to FIG. 10B, the electrical efficiency and the external quantum efficiency were also slightly increased in Comparative Example 6 and Comparative Example 7, and Comparative Example 5 was slightly decreased in Comparative Example 1. It is considered that the efficiency of Comparative Example 5 was reduced because the reflection efficiency of yellow light was increased by the application of the light recirculation filter, but the transmittance of blue light was decreased.

Experimental Example 5

The spectrum of white light was measured with respect to the white light source of Comparative Example 1, Comparative Example 2, Comparative Example 6, and Example 2. FIG. 11 shows the spectrum of white light with respect to the white light sources of Comparative Example 1, Comparative Example 2, Comparative Example 6 and Example 2. FIG. Referring to FIG. 11, the spectra of Comparative Example 1 and Comparative Example 6 did not show a large difference, but Comparative Example 2 had a significantly higher peak height in a shorter wavelength band than Comparative Example 1, and in Example 2, compared with Comparative Example 1 It can be seen that both the peak of the short wavelength band and the peak height of the long wavelength band are significantly larger.

Experimental Example 6

For the white light sources of Comparative Example 1, Comparative Example 2, Comparative Example 6 and Example 2, luminance and current efficiency according to current density were measured. 12 is a graph illustrating luminance and current efficiency measurement results according to current densities of white light sources of Comparative Example 1, Comparative Example 2, Comparative Example 6, and Example 2. FIG. Referring to FIG. 12A, the brightness increases exponentially with the increase of the current density, and the second embodiment has a significantly larger increase in brightness than the comparisons. Referring to (b) of FIG. 12, as the current density increases, the current efficiency rapidly increases to a certain level and then maintains or decreases slightly. In the case of Example 2, the current efficiency is significantly higher than that of the comparative examples.

Experimental Example 7

Electrical efficiency and external quantum efficiency of the white light sources of Comparative Example 1, Comparative Example 2, Comparative Example 5, and Examples 1 to 3 were measured. FIG. 13 illustrates electrical efficiency and external quantum efficiency measurement results for white light sources of Comparative Example 1, Comparative Example 2, Comparative Example 5, and Examples 1 to 3. FIG. Referring to FIG. 13, Comparative Example 2 showed higher electrical efficiency and external quantum efficiency than Comparative Example 1, and Comparative Example 5 showed higher electrical efficiency and lower external quantum efficiency than Comparative Example 1. The examples showed that the electrical efficiency and the external quantum efficiency were significantly higher than those of the comparative examples (the electrical efficiency is up to 1.92 times and the external quantum efficiency is up to 1.58 times than that of Comparative Example 1).

Experimental Example 8

The color coordinates and color temperature of the white light sources of Comparative Example 1, Comparative Example 2, Comparative Example 5, and Examples 1 to 3 were measured. FIG. 14 shows color coordinates and color temperature measurement results for white light sources of Comparative Example 1, Comparative Example 2, Comparative Example 5, and Examples 1 to 3. FIG. Referring to FIG. 14, all of the white light sources of Comparative Example 5 and Examples 1 to 3 exhibited similar color coordinates and color temperatures, which tended to increase in X and Y coordinates and decrease in color temperature as compared with Comparative Example 1. Accordingly, the color coordinates and color temperature of the white light sources of the examples are warm white as compared with Comparative Example 1.

Experimental Example 9

The change in luminance with respect to the viewing angle of the white light sources of Comparative Examples 1, 2, 5 and 2 was measured. FIG. 15 illustrates luminance measurement results according to viewing angles of white light sources of Comparative Examples 1, 2, 5, and 2; Referring to FIGS. 15A to 15D, Comparative Examples and Example 2 showed similar changes in luminance according to viewing angles, which are shown in FIG. 15E. Therefore, the viewing angle problem caused by the application of the microcavity and the slag recycle filter did not occur.

Experimental Example 10

For the white light sources of Comparative Example 1, Comparative Example 2, Comparative Example 5 and Example 2, the change in color coordinates according to the viewing angle was measured. FIG. 16 illustrates results of color coordinate changes according to viewing angles of white light sources of Comparative Examples 1, 2, 5, and 2; Referring to FIG. 16, both the X color coordinate and the Y color coordinate increased with increasing viewing angles in both the Comparative Examples and the Examples.

1 is a view for explaining conventional white light sources using an organic light emitting diode.

2 illustrates a process in which white light is emitted from a white light source in which a blue organic light emitting diode and a yellow phosphor are combined.

3 is a view for explaining the function of the microcavity applied to the white light source of the present invention.

Figure 4 shows the absorption spectrum of the blue organic light emitting diode and the yellow phosphor that can be used in the white light source of the present invention and the emission spectrum and modulation of light by the microcavity.

5 is a view for explaining the function of the ash recycling filter applied to the white light source of the present invention.

6 illustrates a structure of a white light source and a light emission process of white light according to the present invention.

7 shows spectral results of blue light with respect to blue light of Comparative Examples 1 to 4 and the efficiency of blue light.

8 shows the spectral results of the white light of Comparative Examples 1 to 4 and the efficiency of the white light source.

9 is a reflectance measurement result for the light recirculation filter of Comparative Examples 5 to 7.

10 shows the spectral results of the white light and the efficiency of the white light source for the white light source of Comparative Example 1 and Comparative Examples 5 to 7.

FIG. 11 shows the spectrum of white light with respect to the white light sources of Comparative Example 1, Comparative Example 2, Comparative Example 6 and Example 2. FIG.

12 is a graph illustrating luminance and current efficiency measurement results according to current densities of white light sources of Comparative Example 1, Comparative Example 2, Comparative Example 6, and Example 2. FIG.

FIG. 13 illustrates electrical efficiency and external quantum efficiency measurement results for white light sources of Comparative Example 1, Comparative Example 2, Comparative Example 5, and Examples 1 to 3. FIG.

FIG. 14 shows color coordinates and color temperature measurement results for white light sources of Comparative Example 1, Comparative Example 2, Comparative Example 5, and Examples 1 to 3. FIG.

FIG. 15 illustrates luminance measurement results according to viewing angles of white light sources of Comparative Examples 1, 2, 5, and 2;

FIG. 16 illustrates results of color coordinate changes according to viewing angles of white light sources of Comparative Examples 1, 2, 5, and 2;

Claims (9)

Blue light source; A microcavity formed under the blue light source, and having two material layers alternately stacked to reduce spectral bandwidths of blue light emitted from the blue light source, and having different refractive indices; A light recycling filter formed under the microcavity and transmitting blue light and reflecting yellow light; And And a phosphor formed under the light recycling filter and absorbing the blue light emitted from the blue light source to emit yellow light. delete The method of claim 1, The two layers of materials having different refractive indices, which are alternately stacked, are made of silicon oxide and titanium oxide, respectively. The method of claim 1, The microcavity is a white light source, characterized in that the two layers of the material layer having different refractive index is laminated in two to four layers. The method of claim 1, The slag recycling filter is a white light source, characterized in that the first thin film having a predetermined refractive index and the second thin film having a refractive index higher than the refractive index of the first thin film are alternately stacked. The method of claim 5, The first thin film is made of silicon oxide, the second thin film is a white light source, characterized in that made of titanium oxide. The method of claim 5, White light source, characterized in that the uppermost layer and the lowermost layer of the slag recycling filter consists of a first thin film. The method of claim 7, wherein The top layer and the bottom layer have a thickness of 1/8 of the band center wavelength of the edge wavelength, and the layer between the top layer and the bottom layer has a thickness of 1/4 of the band center wavelength of the edge wavelength. won. The method of claim 1, The light recirculation filter is a white light source, characterized in that for changing the center of the spectrum while reflecting the yellow light emitted from the phosphor.

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