KR20100052936A

KR20100052936A - White led device

Info

Publication number: KR20100052936A
Application number: KR1020080111833A
Authority: KR
Inventors: 도영락; 성연국
Original assignee: 국민대학교산학협력단; 피에스아이 주식회사
Priority date: 2008-11-11
Filing date: 2008-11-11
Publication date: 2010-05-20
Also published as: KR101003472B1

Abstract

A white LED device is provided.

The white LED device according to the present invention is an LED device that emits light in a first wavelength region, and is positioned above the LED element, and receives and excites light in a first wavelength region from the LED element, and then a second wavelength. A white LED light emitting device including a phosphor emitting light of a region, wherein a multilayer film layer including two or more thin films having different refractive indices is provided between the LED device and the phosphor, and the multilayer film layer emits light from the LED device. While the light of the first wavelength region is transmitted, the light of the second wavelength region irradiated from the phosphor is reflected, and the light emitted from the rear of the phosphor reflects the lost light back to the front, so the efficiency of the white LED This can increase the efficiency of the existing white LED utilizing phosphors by more than 20%, and the manufacturing process is simple, so the process is economical. All.

Description

White LED device {White LED device}

The present invention relates to white LED devices, and more particularly to more economical white LED devices with increased efficiency.

In the mid-1990s, the luminous efficiency of green and blue LEDs using nitride semiconductor InGaN exceeded that of incandescent bulbs, which led to the application of LEDs to a wide range of fields, including full-color displays. In particular, the emergence of so-called semiconductor lighting began in 1996 with the advent of high-brightness white LEDs made by applying fluorescent materials to InGaN blue LEDs.

Conventional methods for implementing white LEDs using phosphors are largely divided into two types. First, a blue LED is used as a light source, and a white color is realized by exciting yellow phosphors or green and red phosphors. This method has excellent luminous efficiency but has a color rendering index (CRI). It is low and CRI changes according to the current density, so much research is required to obtain white light close to sunlight. Secondly, there is a method of making white by excitation of three primary phosphors by using an ultraviolet light-emitting LED as a light source, which can be used under high current and is actively researched due to its excellent color.

In order to implement a white LED, a phosphor excited to a blue or ultraviolet / violet LED is required. Until now, a YAG: Ce powder phosphor excited to a blue LED has been widely used as a phosphor for a white LED.

1 is a cross-sectional view of a conventional white LED using a YAG: Ce powder phosphor.

Referring to FIG. 1, a white LED is manufactured by stacking a powdery YAG: Ce yellow phosphor 130 on a blue LED element 140. However, in this case, 40% of the yellow light generated by the blue light from the LED element penetrates the phosphor, and the remaining 60% is emitted to the back, and a large part of the light emitted to the back is emitted by the LED. It is known that the probability of being absorbed or scattered and lost is increased, which can cause various problems including light efficiency.

Therefore, in order to improve the color rendering index of the current white LED, a blue LED and a green / red two-color phosphor instead of a combination of the blue LED and the yellow phosphor are used, or ultraviolet / purple LEDs and three color phosphors of blue, green and red are used. The development of the white LED to be used is in progress.

Figure 2 shows the structure of a white LED device using the three-color powder-type phosphor described above.

Referring to FIG. 2, a white LED device is disclosed, which realizes white color by exciting a tricolor powder-type phosphor 230 with a violet or ultraviolet light emitting LED 240 of 420 nm or less, and the white LED device has a significant improvement in color rendering index. In addition, since the ratio of the phosphor is controlled, there is an advantage that the color temperature can be easily adjusted. However, in the white LED device disclosed in FIG. 2, a considerable proportion of the three colors of blue, green and red, or green and red light generated by being excited by a violet / ultraviolet light or a blue LED for the same reason as described above in FIG. As it is emitted and absorbed by the LED or scattered and lost, there is still a problem with the prior art.

As far as is known, attempts have been made to recycle light emitted to the back of the fluorescent film recently by the Rensseler polytechnic Institute (Phys. Stat. Sol. (A) 202, R60 (2005), Appl. Phys. Lett. 86). , 243505 (2005)).

Figure 3 shows the structure of the white LED device shown in the prior art 3.

Referring to Figure 3, the white LED device of the prior art 3 is a structure in which the fluorescent film is separated from the LED device and inserted into the cup-shaped structure optically coated with a reflector on the back, and according to the experimental results, the yellow phosphor emitted to the back Results in a 15.4% improvement (ie, a decrease) in light.

More recent technologies disclose more efficient white LED structures (hereinafter referred to as prior art 4) at the University of Cincinnati (Applied Physics Letters, 92, 143309 (2008)).

4 is a cross-sectional view of the white LED device of the prior art 4.

Referring to FIG. 4, the prior art 4 coats a fluorescent film on a hemispherical substrate, separates it from an LED device, and then returns a large amount of light from the lost light through a structure in which an optically planar reflector is coated on the back side thereof. It proposes a structure to extract by reflecting to the front. However, unlike the conventional method, the conventional technology 4 is a technology in which the reflective cups and the fluorescent film around the LED chip are separated from the LED device to combine the coated structure, and the manufacturing cost increases and the process cost increases. It is also expected that the LED size will be excessively large.

Therefore, all of the above-described prior arts have technical limitations in consideration of all aspects of improving light efficiency, improving economic efficiency, minimizing device size, and the like. The white LED element which laminated | stacked was developed. However, the white LED device according to the inventors of the present invention has a disadvantage in that it is difficult to stack a photonic crystal layer on the LED in spite of the effect of greatly improving the light efficiency and improving the color rendering effect.

Accordingly, the present invention has been made to solve the above problems and to provide a white LED device having improved light efficiency by effectively recycling the light emitted to the rear surface, and relatively low manufacturing and processing costs.

In order to solve the above problems, the present invention is an LED device that emits light in the first wavelength region, and is positioned on the LED device, and after receiving the light in the first wavelength region from the LED device and is excited, In a white LED light emitting device comprising a phosphor emitting light of two wavelengths, a multilayer film layer including two or more thin films having different refractive indices is provided between the LED device and the phosphor, and the multilayer film layer is formed from the LED device. Provided is a white LED device characterized in that while transmitting light in the first wavelength region to emit light, and reflects light in the second wavelength region irradiated from the phosphor. The multilayer film layer may have a structure in which a first thin film having a first refractive index and a second thin film having a refractive index higher than the first refractive index are repeatedly stacked, and as the number of layers of the multilayer film layer is increased, the first wavelength. The transmission characteristics for the light in the region and the reflection characteristics for the light in the second wavelength region are improved.

In one embodiment of the present invention, the LED device is a blue LED light emitting device, and the phosphor is a yellow phosphor, wherein at least one center of reflection spectrum (λ _max ) of the multilayer film layer is present in the emission spectrum of the phosphor.

In another embodiment of the present invention, the LED device is a blue LED light emitting device, and the phosphor is two kinds of phosphors consisting of green and red phosphors, wherein the center of the reflection spectrum (λ _max ) of the multilayer film layer is One or more in the emission spectrum wavelength band.

In another embodiment of the present invention, the LED device is a UV / violet light emitting device, and the phosphor is three kinds of phosphors consisting of blue, green, and red phosphors, wherein the center of the reflection spectrum (λ _max ) of the multilayer layer is 3 At least one is present in the emission spectral wavelength band of the species phosphor.

Furthermore, the multilayer film layer and the phosphor are sequentially stacked on the LED element,

The multilayer film layer has a structure laminated on a transparent substrate, wherein the white LED device has a structure in which the transparent substrate, the multilayer film layer on the transparent substrate and the phosphor on the multilayer film layer are sequentially stacked between the LED devices, or the multilayer film. The layer may be stacked on a transparent substrate, wherein the transparent substrate, the multilayer film layer on the transparent substrate, and the phosphor on the multilayer film layer may be formed to be spaced apart from the LED device.

The white LED device according to the present invention may provide a new concept of white LED which can increase the efficiency of the white LED because the white LED device reflects the light lost by being emitted to the back of the phosphor back to the front. That is, the white LED according to the present invention selectively reflects the light lost by being emitted to the rear side of the phosphor from the front, thereby improving the efficiency of the existing white LED using the phosphor, and thus improving the efficiency of the white LED by 20% or more. More efficient white LED structure can be realized. In addition, the white LED device according to the present invention has the advantage that the selective reflection / transmission characteristics can be achieved by a simple process, and the optical properties can be easily adjusted according to the process conditions. Furthermore, not only when the center (λ _max ) of the wavelength of the multilayer film layer coincides with the center (λ _max ) of the wavelength of the emission spectrum emitted from the fluorescent film, but also slightly different from the center (λ _max ) of the wavelength, the wavelength of the emission spectrum When the wavelength center of the multilayer film layer is adjusted within the range, the color rendering index and color temperature of the white LED can be adjusted as well as the efficiency of the white LED is improved.

The present invention focuses on improving the light efficiency of a white LED device by transmitting light emitted from the LED element (light source) while reflecting light from the phosphor that is emitted from the phosphor and is incident on the rear surface. That is, in the present invention, the multilayer film layer performs the function of reflecting the light emitted from the phosphor while transmitting light from the LED element as a light source, and the present invention provides two or more thin films having different refractive indices in order to achieve such an effect. The multilayer film layer including the was formed between the LED element and the phosphor, and the multilayer film layer had a reflection spectrum corresponding to the light emitted from the phosphor by freely adjusting the number of layers and the constituent conditions of the multilayer film layer.

Hereinafter, a method of selecting wavelengths of the reflection zone and the transmission zone in the present invention will be described in more detail. In the present invention, the Transfer Matrix Method (TMM) method was calculated using the following method in order to determine the wavelength of the reflection zone, the transmission zone and the absorption 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.

In Equation 1, + and-mean the advancing 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 as in Equation (2).

here

ego

Is the wavelength of light.

In the case of a multilayer film layer, the matrix may be multiplied sequentially. Also here optical admittance of the multilayer film layer

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 multilayer film layer in the above-described manner. If the desired reflection area and absorption area are determined, the conditions of the desired multilayer film layer are also set based on the above-described method. Can be.

The wavelength center (λ _max ) of the reflection spectrum of the multilayer film layer of the white LED element of the present invention is within the wavelength range of the emission spectrum emitted from the fluorescent film, and as a result, the light emitted from the fluorescent film to the back surface is Will be reflected. In this case, when the wavelength center of the emission spectrum of the fluorescent film coincides with the center of the reflective wavelength region of the multilayer film layer, the reflection effect is maximized. Even when the wavelength center does not match, the reflection wavelength center (λ _max ) of the multilayer film layer is increased in the fluorescent film. As long as the reflection effect is present within the wavelength range of the light emitting emission spectrum, it has an excellent effect of simultaneously controlling the color temperature or the color rendering index. Accordingly, the desired effect can be maximized by variously selecting the multilayer film layer conditions (number of layers, refractive index, thickness, etc.) according to the conditions under which the white LED element is applied (LED emitting first wavelength, phosphor emitting second wavelength, etc.). This will be described in more detail below.

In the case of the conventional white LED using the YAG: Ce yellow phosphor, the center of the wavelength of the emission spectrum of the phosphor is 550 nm, and thus, the prior art has a limitation in implementing a color temperature of the warm white side due to the weak emission of the red portion. However, in the present invention, when the center (λ _max ) of the wavelength of the multilayer film layer is shifted to about 580 nm (this can be easily achieved through the selection of the multilayer film material or the change of the multilayer film layer configuration), the light is emitted to the YAG: Ce yellow phosphor. It is surprising that the color temperature of the white LED which finally emits light by reflecting more light near 580nm can be adjusted to warm white.

In addition, in the present invention, in addition to the case of using the blue LED and the yellow phosphor described above, in the case of the blue LED and the white LED using the green and red phosphors, the thin film and the red phosphor emission spectra having the reflection spectrum within the wavelength range of the green phosphor emission spectrum may be used. It is possible to improve the luminous efficiency of white LEDs by stacking all thin films with reflection spectrum within the wavelength range. In the case of UV / purple LEDs and white LEDs using blue, green, and red phosphors, a thin film having a reflection spectrum in the wavelength range of the blue phosphor emission spectrum, a thin film having a reflection spectrum in the wavelength range of the green phosphor emission spectrum, and a red color By stacking thin films having reflection spectra within the wavelength range of the phosphor emission spectrum, the back emission loss of three kinds of phosphors is reduced, respectively, thereby improving the luminous efficiency of white LEDs.

If the cause of the efficiency of the fluorescent film in the present invention and the principle of the present invention for overcoming the same in detail as follows.

5 and 6 are schematic diagrams and spectral graphs for showing a decrease in efficiency according to the prior art.

Referring to FIGS. 5 and 6, light emitted from the phosphor (film) is emitted from the LED element as an excitation source and is scattered not only in the front surface but also in the rear direction on the fluorescent surface as described above. As a result, a significant amount of light emitted from the phosphor is directed toward the side of the LED element or chip and absorbed and lost by the LED element or other structure (FIG. 5). In addition, when the yellow YAG: Ce phosphor emits light by the 460nm excitation source, it compares the spectrum of the light emitted to the front side with the light emitted to the back side. Positive light is pointing to the back of the LED (FIG. 6).

Accordingly, the present invention is to solve the problem shown in Figures 5 and 6, Figure 7 shows an LED structure according to the present invention.

7 is a schematic diagram showing the basic principle of the present invention for solving the problems of the prior art shown in FIGS.

Referring to FIG. 7, the present invention uses a multilayer film layer composed of two or more kinds of thin films having different refractive indices. Although only two types are illustrated in the illustrated figure, the scope of the present invention is not limited thereto. That is, the multilayer film layer of the present invention is composed of a low refractive index first thin film 100 and a high refractive index second thin film 110 configured according to the calculated conditions. An LED device 120 is provided below the multilayer film layer, and light of a first wavelength region is irradiated from the LED device. Since the multilayer film layer has a high transmittance configured according to the equation with respect to the light in the first wavelength region, the light in the first wavelength region passes through the multilayer film layer and enters a phosphor (not shown). The excitation causes the light 140 in the second wavelength region to emit light. However, as described above, some of the light 140 in the second wavelength region is reincident toward the LED device.

Since the multilayer film layer has high reflectance with respect to the light 140 in the second wavelength region according to the above equation, the light 140 in the second wavelength region re-incident in the direction of the LED element is reflected by the multilayer film layer, It is irradiated to the front again. In addition, the present invention can improve light efficiency by selectively transmitting / reflecting light in an arbitrary wavelength region according to the multilayer film layer configuration, and color temperature control or color rendering control can be easily achieved, as described above. In terms of manufacturing, the present invention can achieve high light efficiency in a simple manner by sequentially stacking thin films or inserting a multilayer film-coated transparent substrate between the LED and the phosphor, and thus the manufacturing process is simpler than in the prior art.

8 is a schematic diagram of a white LED device according to an embodiment of the present invention to which the basic principle shown in FIG. 7 is applied.

Referring to FIG. 8, a white LED device according to an embodiment of the present invention uses a blue LED device (light source) as a light emitting source, and a multilayer film layer is provided between a phosphor and the blue LED device, wherein the multilayer film layer is separately provided. It is provided and supported on a glass substrate which is a transparent substrate of the glass substrate is directly laminated on the LED light source. However, in contrast, the transparent substrate and the LED light source may be spaced apart by a predetermined distance, and in this case, the space efficiency may be partially degraded. However, light emission conditions may be changed by inserting another multilayer film layer later. Alternatively, the multilayer film layer may be directly stacked on the LED instead of the glass substrate, in which case it is possible to partially prevent the light efficiency degradation due to the transparent substrate. However, even if any structure, the technical spirit of the present invention shown in FIG. 7 is the same, and any technique is employed within the scope of the present invention as long as it is adopted.

As described above, the present invention is very advantageous in terms of space efficiency. Compared with the prior art for forming a dome structure, the present invention can considerably save space of a white LED element. Furthermore, the present invention can improve the optical property effect, in particular the reflection effect, in particular by increasing the number of layers of the multilayer film layer in such a space, which will be described in more detail in the following experimental example.

The multilayer film layer of the present invention has a structure including a low refractive index first thin film and a high refractive index second thin film configured according to calculated conditions, and is not subject to a material having a specific composition, and an inorganic thin film, an organic thin film, and an organic-inorganic composite. All kinds of materials that can cause a difference in refractive index such as a thin film can be used.

Hereinafter, although an Example regarding a preferable multilayer film layer and the white LED using the said multilayer film layer is given and this invention is demonstrated in more detail, this invention is not restrict | limited by this.

Example 1

Example 1-1

A transparent dielectric multilayer film layer having a 7-layer structure of LHLHLHL was designed using a SiO ₂ thin film (L) as a low refractive index layer and a TiO ₂ thin film (H) as a high refractive index layer on the transparent glass.

Example 1-2

A transparent dielectric multilayer film layer having a 9-layer structure of LHLHLHLHL was designed using a SiO ₂ thin film (L) as a low refractive index layer and a TiO ₂ thin film (H) as a high refractive index layer on transparent glass.

Example 1-3

A transparent dielectric multilayer film layer having an 11-layer structure of LHLHLHLHLHL was designed using a SiO ₂ thin film (L) as the low refractive index layer and a TiO ₂ thin film (H) as the high refractive index layer on the transparent glass.

Example 2-1

A multilayer film layer having an 11-layer structure of LHLHLHLHLHLHL was prepared using a SiO ₂ thin film (L) as a low refractive index layer and a TiO ₂ thin film (H) as a high refractive index layer on a transparent glass. The SiO ₂ thin film (L) and TiO ₂ thin film (H) multilayer thin films are deposited in a vacuum evaporator using an electron beam (e-beam) to alternately deposit a certain thickness of SiO ₂ thin film (L) and TiO ₂ thin film (H) in the same evaporator. A transparent dielectric multilayer film layer was prepared.

Example 2-2

The low-refractive index layer SiO ₂ thin film (L), the high refractive index layer of the TiO ₂ thin film was changed in the same manner as in Example 1-1 to prepare a multi-layered multilayer film layer of 11 layers of LHLHLHLHLHLHL.

Example 3

White LED Device Manufacturing

To compare the YAG: Ce phosphor slurry with the conventional white LED device coated on the 460nm blue LED device, the phosphor slurry containing the YAG: Ce phosphor was applied on the multilayer film layer of Example 2-1, and then attached on the 460nm blue LED device. To prepare a white LED device. In order to analyze the effect on the multilayer film layer of Example 2-1 according to the change of the amount of the phosphor slurry containing the YAG: Ce phosphor and the change of the luminescence properties according to the change in the amount of phosphor applied, 2.2, 2.7, 3.1, 3.6, 4.0, A white LED device including a multilayer film layer based on a 460 nm blue LED device according to a change in the amount of YAG: Ce phosphor of 4.4 mg / cm ² was prepared.

Comparative Example 1

In order to compare the characteristics with the present invention, a white LED device without a multilayer film layer was manufactured in the same manner as in Example 3 except that the phosphor was applied on the transparent substrate instead of the multilayer film layer.

Experimental Example 1

Reflection Spectrum Calculation

In order to determine the wavelength of the reflection region of the multilayer film layers of Examples 1-1 to 1-3, it was calculated using the Transfer Matrix Method (TMM) method mentioned in the context of the present invention. The refractive index ( n ) and the extinction coefficient ( k ) of the low refractive index layer SiO ₂ thin film (L) and the high refractive index layer TiO ₂ thin film were measured and calculated by the TMM method.

Referring to FIG. 9, it can be seen that the multilayer film layer has a very high reflectance in a wavelength region (550 nm) of light in which YAG: Ce phosphors are excited and emit light. In particular, it can be seen that the multilayer film layer of Example 1-3 having a high number of layers has a very high reflectivity, which means that the higher the number of layers, the more the reflection effect is improved. Compared with the conventional LED device which requires an excessive size as a conventional dome structure, the present invention can maximize the reflection effect by filling the multilayer structure instead of leaving this space itself, which in turn provides a space contrast. In terms of efficiency, it means that the present invention has a very advantageous effect.

Experimental Example 2

Transmission Spectrum Calculation

The transmission spectra for the multilayered membrane layers of Examples 1-1 to 1-3 were calculated by using a Transfer Matrix Method (TMM) method and are shown in FIG. 10.

Referring to FIG. 10, it can be seen that high transmittance of almost 90% is exceeded in the vicinity of 450 nm, which is a wavelength region of the blue LED device.

The above results indicate that the multilayer thin film according to the present invention has a very high transmittance for the light emission of the LED element and a high reflectance for the light reincident from the phosphor.

Experimental Example 3

Scanning electron microscope (SEM) analysis

10A and 11B show photographic images obtained by measuring the multilayer membrane layers of Examples 2-1 and 2-2 with a scanning microscope.

Referring to FIGS. 11A and 11B, the multilayer thin film designed by the simulation is deposited by alternating SiO ₂ thin film (L) and TiO ₂ thin film (H) by an electron beam deposition method to easily prepare an 11-layer multilayer film layer made of LHLHLHLHLHLHL. It is well shown that the thickness of several nm can be easily adjusted, and the multilayer film layer according to the present invention can effectively produce a white LED device in a simpler manner as compared with the conventional technique of stacking phosphors in a dome structure in a circular manner. Indicates.

Experimental Example 3

Reflectance Spectrum Analysis

The reflectance spectrum obtained after irradiating a white Xe lamp to the multilayer film layers of Examples 2-1 and 2-2 was measured and shown in FIG.

Referring to FIG. 12, the film is well matched with the reflection spectrum of the multilayer film layer of FIG. 9 obtained by the above formula, and thus, the multilayer film layer manufactured by the multilayer film layer design has a wavelength range (550 nm) of light in which YAG: Ce phosphors are excited and emit light. It can be seen that the multilayer film layer has a reflectivity of 90% or more.

Experimental Example 4

Transmission Spectrum Analysis

In the same manner as in Experiment 3, the transmission spectra of the multilayer films of Examples 2-1 and 2-2 were measured and shown in FIG. 13.

Referring to FIG. 13, it can be seen that similarly to the calculation result of FIG. 10, high transmittance of more than 90% is exhibited in the vicinity of 460 nm, which is a wavelength region of the blue LED device.

The above results indicate that the multilayer film layer according to the present invention has a very high transmittance in the first wavelength region of the emitted light of the LED element and a high reflectivity in the second wavelength region of the light reincident from the phosphor. .

Experimental Example 5

LED efficiency measurement

FIG. 14 shows the emission intensity of a white LED device manufactured by applying a phosphor slurry of 3.6 mg / cm ^{2 to} a multilayer film layer according to Example 3 and a white LED device of the prior art (Comparative Example 1) Spectral graph.

Referring to FIG. 14, it can be seen that the emission intensity of the YAG: Ce fluorescent film of the white LED device according to the present invention is improved by 40% or more compared with the conventional white LED device. In addition, referring to FIG. 14, it can be seen that the blue light emission intensity emitted from the LED device has obtained a similar intensity as compared with the conventional white LED device. While transmitting without loss, yellow light, which is light of the second wavelength region, reflects with higher efficiency.

In addition, the color temperature of the white LED device of the prior art coated with a phosphor slurry of 3.6 mg / cm ² is 5990K and the color temperature of the white LED device according to the present invention coated with the same amount of phosphor is 4720K, so that the color temperature is warm. It shows how easy it is to move towards white.

FIG. 15 shows light emission of a white LED device prepared by applying a slurry according to a YAG: Ce phosphor amount change of 2.2, 2.7, 3.1, 3.6, 4.0, and 4.4 mg / cm ² according to Example 3 and a white LED device of the prior art. It is a graph measuring brightness.

Referring to FIG. 15, it can be seen that the emission intensity of the YAG: Ce fluorescent film of the white LED device according to the present invention is improved in luminance from 25% to 60% according to the increase in the amount of phosphor compared to the conventional white LED device. . That is, as the amount of phosphor increases, the amount of light re-incident from the phosphor and reflected by the multilayer film layer also increases. From this result, the white LED device including the multilayer film layer according to the present invention has a second wavelength which is a phosphor emission region. It is confirmed once again that it has high reflectivity with respect to the light of the area | region and has high transmittance in the 1st wavelength area | region which is LED light emission.

2 is a cross-sectional view showing the structure of a white LED device using a tricolor powder type phosphor.

3 is a cross-sectional view of the structure of the white LED device shown in the prior art 3.

4 is a cross-sectional view of the structure of the white LED device shown in the prior art 4.

7 is a schematic diagram of a multilayer film layer of a white LED device according to the present invention.

8 is a schematic diagram of a white LED device according to an embodiment of the present invention.

8 is a reflection spectral graph of the designed multilayer film layers of Examples 1-1 to 1-3.

9 is a transmission spectrum graph of the designed multilayer membrane layers of Examples 1-1 to 1-3.

11A and 11B are scanning micrographs of the multilayer films prepared in Examples 2-1 and 2-2.

12 is a reflection spectrum graph of the prepared multilayer film layers of Examples 2-1 and 2-2.

13 is a transmission spectrum graph of the multilayer film layers prepared in Examples 2-1 and 2-2.

14 is a light emission spectrum graph of the white LED device of the present invention and the white LED device of the prior art.

15 is a graph measuring the luminance of emission of the white LED device and the conventional white LED device of the present invention.

Claims

An LED element emitting light in a first wavelength region, and a phosphor positioned above the LED element, and receiving a light in the first wavelength region from the LED element, being excited, and then emitting a light in a second wavelength region. In a white LED light emitting device comprising:

A multilayer film layer including two or more thin films having different refractive indices is provided between the LED element and the phosphor, and the multilayer film layer is a second irradiated from the phosphor while transmitting light in a first wavelength region emitted from the LED element. White LED device, characterized in that for reflecting light in the wavelength range.

The method of claim 1,

The multi-layered film layer has a structure in which a first thin film having a first refractive index and a second thin film having a refractive index higher than the first refractive index are stacked repeatedly.

The method of claim 1,

The white LED device, characterized in that as the number of layers of the multilayer film layer increases, the transmission characteristics for the light in the first wavelength region and the reflection characteristics for the light in the second wavelength region are improved.

The method of claim 1,

The LED device is a blue LED light emitting device, the phosphor is a yellow phosphor, wherein the white LED device, characterized in that at least one of the center of the reflection spectrum (λ _max ) of the multilayer film layer in the emission spectrum wavelength region of the phosphor.

The method of claim 1,

The LED element is a blue LED light emitting element, the phosphor is a two-type phosphor consisting of green, red phosphor, wherein the center of the reflection spectrum (λ _max ) of the multilayer film layer is present in at least one emission spectrum wavelength range of the two phosphors A white LED device characterized by the above-mentioned.

The method of claim 1,

The LED element is a UV / violet light emitting element, and the phosphor is a three kinds of phosphors consisting of blue, green, and red phosphors, wherein the center of the reflection spectrum (λ _max ) of the multilayer film layer is in the emission spectrum wavelength range of the three kinds of phosphors. White LED element, characterized in that present.

The method of claim 1,

The multilayer LED layer and the phosphor is a white LED device, characterized in that sequentially stacked on the LED device.

The method of claim 1,

The multilayer film layer has a structure laminated on a transparent substrate, wherein the transparent substrate, the multilayer film layer on the transparent substrate and the phosphor on the multilayer film layer is a white LED device, characterized in that sequentially stacked between the LED device.

The method of claim 1,

The multilayer film layer has a structure laminated on a transparent substrate, wherein the transparent substrate, the multilayer film layer on the transparent substrate, and the phosphor on the multilayer film layer is a white LED device, characterized in that formed spaced apart from the LED device.