KR20090106946A - Thin-film fluorescent material having complex structure and method of manufacture thereof - Google Patents

Abstract

PURPOSE: A thin-film fluorescent material with a complex structure is provided to ensure high luminous efficiency and excellent optical efficiency, and to reduce costs by not using slurry while using a fluorescent substance. CONSTITUTION: A thin-film fluorescent material with a complex structure comprises a substrate and a two dimensional photonic crystal structure(9). A fluorescent substance is coated on the substrate. The two dimensional photonic crystal structure is formed on the substrate. The surface of the substrate is a non-planar surface with roughness.

Description

Thin-film fluorescent material having complex structure and method of manufacture

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film phosphor having a composite structure, and more particularly, to a thin film phosphor having excellent luminous efficiency compared to a conventional fluorescent film and using less phosphor while using a slurry.

Phosphors are fluorescing materials such as petroleum, lead glass, platinum cyanide, etc. Typical examples of practical use include zinc sulfide (ZnS) or a mixture of zinc sulfide and cadmium sulfide, followed by firing at about 1,000 ° C. And ZnS: Cu. These zinc sulfides are mainly used for CRT, X-ray, electron microscope, etc., and fluorescent lamps include phosphates (Ca ₂ (PO4) ₂ , CaF ₂ : Sb, etc.), silicates, or pure tungstates (CaWO ₄ or MgWO _4). ) And the like.

On the other hand, the phosphor is an essential element for implementing a white LED, and so far YAG: Ce powder phosphor excited to a blue LED as a phosphor for white LED has been widely used. 1 is a cross-sectional view of a conventional white LED using a YAG: Ce powder phosphor. As shown in FIG. 1, a white LED is manufactured by applying a powdery YAG: Ce yellow phosphor onto an LED device. As such, when the powder-type phosphor is used, both the transmitted blue light and the yellow light generated by being excited by the LED may cause an optical problem in which the probability of scattering or disappearing increases.

Thus, in order to improve the color rendering index of white LEDs, white LEDs using ultraviolet / violet LEDs and three color phosphors of blue, green, and red instead of a combination of blue LEDs and yellow phosphors have been developed. 2 is a cross-sectional view of a white LED coated with blue, green, and red tricolor powder type phosphors on a purple LED or an ultraviolet LED. As shown in FIG. 2, since the trichromatic powder-type phosphor is excited by a purple or ultraviolet light emitting LED of 420 nm or less to realize white color, color rendering index is not only greatly improved, but the ratio of the phosphor is controlled, so that the color temperature can be easily adjusted. However, when using the three-color powder-type phosphor, there is also an optical problem that the probability of both the blue, green, and red tricolor light generated by being excited by the purple light and the LED is scattered or lost.

Thin film phosphors are designed to overcome the disadvantages of such powdery phosphors. Thin film phosphors have the advantages of being thermally stable, physically and chemically uniform, having strong adhesion to a substrate, minimizing gas generation, and having a low specific surface area. However, in spite of these various advantages, since the efficiency is lower than that of the powder-type phosphor, it has not been well utilized in actual LED devices until recently. The principle of low efficiency of the thin film phosphor can be explained through Equation 1 below. In the light emission path of the thin film phosphor, a considerable amount of light is totally reflected from the interface between the fluorescent surface and the air to be trapped in the thin film phosphor or disappear from the defect region. To explain this quantitatively, the principle of classical optics can be applied to calculate the amount of light emitted from a thin film phosphor to the front of the LED. The emission efficiency of light is calculated using classical optical calculations that are proportional to the refractive index. Equation 1 is well known by classical optical law, and it is an equation established when a light emitted from a thin film phosphor is assumed to be Lambertian type light. In Equation 1, it is assumed that light emitted toward the substrate is not reflected.

Where η _{external light} is external light efficiency and n _phosphor is the refractive index of the phosphor.

According to Equation 1, the external light efficiency depends on the refractive index of the thin film phosphor, and as the refractive index value increases, the light emission efficiency greatly decreases. Most thin film phosphors have a value of 1.5 or more, which is a refractive index value of glass. Among the representative sulfide-based phosphors, ZnS, the refractive index value is 2.4, the nitride GaN-based is 2.1 and the oxide-based Y ₂ O ₃ is 1.8. Therefore, in the case of the thin film phosphor, the amount of light emitted to the front surface is about 4 to 11.1% depending on the refractive index of the material, and the rest is trapped in the thin film or disappears in the thin film. Due to the classical optical reasons, the light emission efficiency of the thin film phosphor is greatly reduced, and thus, despite the excellent physical and chemical properties of the thin film phosphor, there is a difficulty in applying it to a device such as an LED device.

In order to overcome this problem, a thin film phosphor coated with a two-dimensional structure having a structure similar to a two-dimensional photonic crystal as a method of optically extracting light trapped in the thin film without affecting the film quality of the thin film phosphor is produced. The white LED structure with high efficiency was devised by attaching it to the device such as LED device in the front direction, and two-dimensional structure was applied to the thin film phosphor in two forms. 3 illustrates a case in which a two-dimensional photonic crystal structure is inserted into a thin film phosphor, and FIG. 4 illustrates a case in which a two-dimensional photonic crystal structure is attached to a thin film phosphor on a surface of the thin film phosphor. Both methods are known to effectively extract the emitted light trapped inside the thin film phosphor. However, in the case of the structure of FIG. 3, since the two-dimensional nanostructures having different refractive indices are inserted into the thin film phosphor, the materials of the two-dimensional nanostructure are mixed when the thin film phosphor is manufactured. In order to solve this problem, as shown in FIG. 4, a thin film phosphor may be manufactured and then two-dimensional nanostructures may be installed, but in this case, the two-dimensional nanostructure does not degrade the optical properties of the thin film phosphor, There is a limit that cannot be extracted. Therefore, in order to improve the light extraction efficiency of the two-dimensional nanostructure of Figure 4 it is necessary to introduce a new additional and complementary light extraction mode. The development of such phosphors requires enormous capital and time, and it is a task that requires both physical knowledge based on quantum mechanics and material engineering based on ceramic processing.

The present invention has been made to solve the problems of the prior art, the first problem to be solved by the present invention is to provide a thin film phosphor having high luminous efficiency and excellent optical uniformity.

In addition, a second problem to be solved by the present invention is to provide a method for manufacturing a thin film phosphor having high luminous efficiency and excellent optical uniformity.

The present invention to achieve the first object,

A thin film phosphor comprising a substrate coated with a phosphor and a two-dimensional photonic crystal structure formed on the substrate, wherein the surface of the substrate is a non-planar surface having a nano size roughness.

According to an exemplary embodiment of the present invention, light generated inside the phosphor coated on the substrate may be extracted to the outside of the substrate by scattering on a non-flat surface having a roughness of nano size.

According to another preferred embodiment of the present invention, light other than the light extracted to the outside of the substrate may be returned to the inside of the substrate by diffuse reflection on the non-flat surface having a nano-size roughness.

According to another preferred embodiment of the present invention, light generated inside the phosphor coated on the substrate may be scattered when passing through the two-dimensional photonic crystal structure.

According to another preferred embodiment of the present invention, the roughness of the phosphor is achieved by nanoparticles stacked on the substrate, the size of the nanoparticles may be 20 to 300nm.

According to another preferred embodiment of the present invention, the height of the two-dimensional photonic crystal structure is preferably 10nm to 5000nm.

According to another preferred embodiment of the present invention, the extinction coefficient of the thin film phosphor may be 10 ⁻² or less.

According to another preferred embodiment of the present invention, the phosphor may be prepared using any one selected from the group consisting of inorganic light emitting materials emitting light in the visible region, such as oxides, sulfides or nitrides that can be produced as a thin film phosphor.

In addition, the present invention to achieve the second object,

Provided is a method for manufacturing a thin film phosphor, comprising the step of forming a phosphor on a non-flat surface having a roughness of nano size on a substrate and forming a two-dimensional photonic crystal structure.

According to a preferred embodiment of the present invention, the step of forming the phosphor on the non-flat surface having a nano-size roughness on the substrate, preparing a sol-type phosphor by the sol-gel method; And spin-coating the sol-type phosphor on a substrate.

According to another preferred embodiment of the present invention, the sol-gel method may form a sol-type phosphor by dissolving a precursor to be produced as a phosphor in a solvent and then adding citric acid.

According to another preferred embodiment of the present invention, the precursor to be made of the phosphor may be any one of the group consisting of oxides, sulfides and nitrides.

According to another preferred embodiment of the present invention, the roughness of the thin film phosphor may be adjusted by adding a flux to the solvent.

According to another preferred embodiment of the present invention, the flux may be Li ₂ CO ₃ .

According to another preferred embodiment of the present invention, the roughness of the phosphor is achieved by the nanoparticles stacked on the substrate, the size of the nanoparticles can be increased to 20 to 300nm.

According to another preferred embodiment of the present invention, the process of forming the two-dimensional photonic crystal nanostructure comprises the steps of depositing a photonic crystal thin film on a substrate; Depositing chromium to be used as a mask on the photonic crystal thin film; Coating a photoresist on the chromium thin film; Exposing and developing the photoresist; Etching the chromium thin film through primary etching to pattern a chromium mask having a two-dimensional nanostructure, and forming a two-dimensional photonic crystal structure by secondly etching the exposed photonic crystal thin film.

According to another preferred embodiment of the present invention, the substrate may use a quartz or sapphire substrate coated with a thin film phosphor.

According to another preferred embodiment of the present invention, the step of depositing chromium is a thermal deposition method, the deposition thickness is preferably 20 to 100nm.

According to the present invention by providing a thin film phosphor having a complex structure solves the problem of light uniformity degradation and efficiency degradation inherent in the conventional powder-type phosphor due to light scattering. When a thin film phosphor including a non-planar surface having a nano-sized roughness of the present invention and a two-dimensional photonic crystal structure is used in a light source and a display device such as an LED lamp, the efficiency improvement is more than twice that of the conventional two-dimensional nanostructure thin film phosphor. It can be predicted. The efficiency of the composite structured nano thin film phosphor designed by the present invention has an advantage that it can be further improved by controlling the parameters of the two-dimensional nano structure and the size of the nano particles of the thin film phosphor, and the composite nano structured thin film phosphor is more uniform than the powder type phosphor. Because of the excellent luminous uniformity of the device such as a white LED lamp using a composite nano-structured thin film phosphor is also improved. In addition, when the thin film phosphor of the present invention is employed, since it uses less phosphor than when using a conventional powder-type phosphor, it does not use a slurry, so it can have advantages of cost reduction and simplification of the process, thereby facilitating mass production.

Hereinafter, the present invention will be described in more detail.

The present invention provides a thin film phosphor comprising a substrate coated with a phosphor and a two-dimensional photonic crystal structure formed on the substrate, wherein the surface of the substrate is a non-planar surface having a nano size roughness. The roughness refers to fine bending appearing at small intervals on the surface of the processed thin film. Figure 5 is a simplified illustration of the structure of the present invention and the path of the emitted light. According to the present invention, as shown in FIG. 5, the thin film is formed by the combination of scattering caused by nano-sized roughness and the Bragg scattering by the two-dimensional photonic crystal structure and synergistic effects thereof. It is based on a new mechanism that can extract most of the emitted light trapped inside the phosphor.

According to an exemplary embodiment of the present invention, light generated inside the phosphor coated on the substrate may be extracted to the outside of the substrate by scattering on a non-flat surface having a roughness of nano size. That is, a part of the light trapped at the surface having the roughness of nano size is extracted by the scattering mode, that is, the diffusion transmission mode.

On the other hand, in spite of the above process, the light remaining without being extracted to the outside of the substrate may be returned to the inside of the substrate by diffuse reflection on a non-flat surface having a nano-sized roughness. As a result, the remaining light in the substrate is extracted, thereby improving the efficiency of the thin film phosphor. That is, a part of the light trapped on the surface having the nano-sized roughness is extracted by the scattering mode (diffusion transmission mode) and the remaining light is diffusely reflected on the non-flat surface having the nano-sized roughness. Diffuse reflection takes place on a non-smooth surface, which can be thought of as a collection of small planes that are oriented in multiple directions, so that light incident from one direction uses the small side as a secondary new light source, This causes reflections and scattering. The light is extracted from the phosphor and the path is changed in the process of being reflected inside by the diffuse reflection on the non-flat surface having a nano-sized roughness. On the other hand, in the prior art in which the thin film phosphor has a smooth surface, the incident light is reflected evenly in the opposite direction, so most of the guiding light which is not extracted by the specular reflection is reflected inside and remains in the substrate. Therefore, as shown in FIG. 4, the two-dimensional photonic crystal structure only affects a part of the light that can be totally reflected. In the present invention, when the two-dimensional photonic crystal structure is coated on the nano-sized roughness phosphor, most of the guiding light whose path is changed by the diffusion reflection is extracted into the light of the Leaky mode by the photonic crystal structure and extracted outside the substrate. In the case of using a thin film phosphor having a smooth surface, only a part of the light trapped inside the thin film phosphor is extracted outside, and even if a two-dimensional structure is attached, the two-dimensional structure affects the light trapped inside the thin film phosphor. It solves the disadvantage of limited scope.

According to an embodiment of the present invention, light generated inside the phosphor coated on the substrate may be scattered when passing through the two-dimensional photonic crystal structure. Light generated inside the thin film phosphor is extracted in the front direction by the periodic structure of the two-dimensional nanostructure formed between the thin film phosphor and the air plane. That is, it is extracted in the front direction by the strong Bragg scattering phenomenon generated by the periodic structure of the refractive index. In addition, light is also extracted from the non-periodic nanostructure, and the light is extracted by the strong scattering phenomenon when the three-dimensional structure of the visible wavelength is formed on the surface of the phosphor is the same principle as the case of the periodic nanostructure. According to this principle, when the two-dimensional nanostructure is coated on the thin film phosphor to replace the powder phosphor, there is an effect of more than three times the efficiency improvement compared to the conventional thin film phosphor. FIG. 7 is a graph showing the improvement of the efficiency of the thin film phosphor by the two-dimensional photonic crystal, the efficiency of the thin film phosphor by the surface of the thin film having nano size roughness, and the composite efficiency improvement effect by the two effects. As shown in FIG. 7, the luminous efficiency of the phosphor is increased up to 6 times or more by the surface of the nano-film having a roughness compared to the conventional thin film phosphor, and up to 4 times or more by the two-dimensional photonic crystal. There is an improvement. In addition, in the case of a thin film phosphor having a structure in which a nano-sized roughness and a two-dimensional photonic crystal structure are combined, an increase in luminous efficiency exceeds 10 times the sum of the respective synergistic effects, thereby obtaining an improvement effect. It is a key point of the present invention to provide a thin film phosphor having an optimal luminous efficiency by synergistic effects of the two structures.

Roughness of the phosphor is achieved by nanoparticles stacked on the substrate, the size of the nanoparticles is preferably 20 to 300nm. If the thickness is less than 20 nm, the composite structure is not formed, and thus there is no difference in effect from the case of the thin film phosphor having a smooth surface. If the thickness is greater than 300 nm, the effect of the two-dimensional photonic crystal is greater than that of the nanoparticles. As a result, the luminous efficiency by the composite structure is reduced, which is undesirable. More preferably, the size of the phosphor particles is 41 to 45 nm, which is a condition for optimizing the luminous efficiency of the thin film phosphor of the present invention. As shown in FIG. 7, the size of the phosphor particles is closely related to the increase in luminous efficiency, which affects the thin film and the two-dimensional photonic crystal having a roughness of nano size, respectively. That is, as the size of the phosphor particles increases, the relative luminous efficiency of the thin film having nano size roughness is constantly reduced, and the relative luminous efficiency by the two-dimensional photonic crystal is constantly increased. Therefore, the present invention proposes an optimal size of phosphor particles to maximize luminous efficiency in consideration of these opposite tendencies, and thin film phosphors having phosphor particles of about 41 to 45 nm are due to the synergistic effect of the composite structure. The luminous efficiency exceeds 10 times, which is an optimal condition for improving the efficiency of the phosphor. However, this is only a preferred embodiment and the present invention is not limited thereto.

The height of the two-dimensional photonic crystal structure is preferably 10nm to 5000nm. When the height is less than 10nm, the effect of the photonic crystal is lowered, and when it exceeds 5000nm, since the light must experience several times the photonic crystal effect in the vertical direction, there is a problem that the characteristic is sharply lowered.

Meanwhile, the shape of the two-dimensional photonic crystal structure is preferably a three-dimensional solid structure engraved or embossed into a spherical shape, a cylindrical shape, a cuboid shape, or a triangular column shape. However, the present invention is not limited thereto. Light scattering occurs.

In addition, the extinction coefficient of the thin film phosphor may be 10 ⁻² or less. Extinction coefficient exceeds 10 ^-2 When light traverses in the thin film, the light is absorbed and extinguished before the two-dimensional photonic crystal is reached, so the effect of the photonic crystal cannot be obtained.

The phosphor may be prepared using an inorganic light emitting material that emits light in the visible region, such as an oxide, a sulfide, or a nitride, which may be manufactured as a thin film phosphor. The present invention relates to a complex structure related to light extraction so that light generated in the thin film phosphor can escape from the thin film fluorescence. The nanocomposite structure of the present invention can be applied to all kinds of thin film phosphors such as oxides, sulfides and nitrides. have.

On the other hand, the present invention provides a method for producing a thin film phosphor, comprising the step of forming a phosphor on a non-flat surface having a roughness of nano-size on the substrate and the step of forming a two-dimensional photonic crystal structure. In the present invention, a thin film phosphor is manufactured through the above two processes, and one of the two processes is not necessarily performed first.

Forming a phosphor on the substrate to a non-flat surface having a roughness of nano-size, comprising: preparing a sol-type phosphor by the sol-gel method; And spin-coating the sol-type phosphor on a substrate. At least one precursor to be prepared as a phosphor is dissolved in a solvent and then citric acid is added to form a sol-like mixture. Spin coating the sol-like mixture on a thin film, the thin film It may be a quartz or sapphire substrate. Since the thin film phosphor manufacturing process of the present invention includes a high temperature process of about 1000 ℃, it is preferable to use a quartz substrate having a relatively high melting point. In addition, sapphire is excellent in light transmission and rarely in the ceramic material has a thermal conductivity similar to that of metal, very stable without phase transformation from cryogenic to ultra-high temperature, has excellent mechanical properties and excellent chemical stability in the practice of the present invention Suitable. However, this is not only an example but may be a substrate used in the art for manufacturing phosphors. In the thin film manufacturing process, the thickness of the thin film phosphor may be adjusted according to the number of spin coating, and finally, the thin film phosphor is manufactured by firing at 900 to 1100 ° C. In one embodiment of the present invention by using Y (NO ₃ ) ₃ and Eu (NO ₃ ) ₃ as a precursor to be prepared as a phosphor to dissolve in 2-methoxyethanol as a solvent and then making a sol spin coating on a sapphire substrate A process of manufacturing a substrate coated with Y ₂ O ₃ : Eu phosphor is shown in FIG. 9.

The precursor to be made of the phosphor may be any one of a group consisting of oxides, sulfides, and nitrides, which is combined with two-dimensional photonic crystal nanostructures so that the surface of the thin film phosphor of the present invention has a non-planar surface having nano size roughness. The high efficiency of thin film phosphors is due to the complex structure of light extraction so that the light generated in the thin film phosphors can escape from the thin film fluorescence. Thus, the nanocomposite structure, which is the basic concept of the present invention, has all kinds of thin film phosphors such as oxides, sulfides and nitrides. Applicable to

Meanwhile, a flux may be added to the solvent to adjust the roughness of the thin film phosphor. A flux means a material mixed to promote dissolution, and when Li ₂ CO ₃ is added to control the surface roughness of the thin film phosphor, the flux acts as a flux to control the roughness of the surface of the thin film phosphor. That is, the nano-size roughness is due to the nanoparticles stacked on the substrate, and as the size of such nanoparticles increases, the surface of the thin film becomes larger, and when the size of the nanoparticles becomes smaller, the roughness becomes smaller. In addition, the size of the nanoparticles can be adjusted within the range of 20 to 300nm depending on the amount of the flux added. According to one preferred embodiment, when the amount of Li ₂ CO ₃ is added in 10, 20, 30% of the molar ratio, respectively, the particle size of the thin film phosphor can be increased from 23nm to 43, 53, 56nm respectively. Therefore, in order to manufacture a thin film phosphor having a maximum luminous efficiency, as described above, the particle size of the phosphor is preferably 41 to 45 nm, in which case the Li ₂ CO ₃ is 9 to 11 moles relative to the total phosphor coated on the substrate. It is preferable to add%. If less than 9 mol% of Li ₂ CO ₃ is added as a flux to the total phosphor coated on the substrate, the diameter of the nanoparticles is less than 41 nm, and if more than 11 mol% is added, the diameter of the nanoparticles is larger than 45 nm. Therefore, nanoparticles of a desired size cannot be obtained. It is an advantage of the present invention that the surface roughness of the thin film phosphor can be adjusted because the manufacturing conditions such as flux or the thin film phosphor firing temperature are changed.

A manufacturing process sequence of the two-dimensional photonic crystal nanostructure is shown in FIG. 8. The process of forming the two-dimensional photonic crystal nanostructure includes depositing a photonic crystal thin film on a substrate; Depositing chromium to be used as a mask on the photonic crystal thin film; Coating a photoresist on the chromium thin film; Exposing and developing the photoresist; Etching the chromium thin film through first etching to pattern a chromium mask having a two-dimensional nanostructure; And secondly etching the exposed photonic crystal thin film to form a two-dimensional photonic crystal structure.

The substrate may be a quartz or sapphire substrate coated with a thin film phosphor. Since the thin film phosphor manufacturing process of the present invention includes a high temperature process of about 1000 ℃, it is preferable to use a quartz substrate having a relatively high melting point. In addition, sapphire has excellent light transmittance, and has a thermal conductivity similar to that of metal, which is rare in ceramic materials. In addition, cryogenic to ultra-high temperature is very stable without phase transformation, has excellent mechanical properties, and excellent chemical stability is preferred. However, this is not only an example but may be a substrate used in the art for manufacturing phosphors.

The step of depositing chromium is a thermal deposition method, the deposition thickness is preferably set to 20 to 100nm. If the deposition thickness is less than 20nm, it is difficult to function as a mask layer and there is a risk of forming a non-uniform thin film layer, and if it exceeds 100nm is uneconomical and excessive process time during etching is not preferable.

Meanwhile, a positive or negative photoresist may be coated by spin coating on the chromium thin film. According to an embodiment of the present invention, when the positive photoresist is coated, the photoresist is exposed twice while rotating by 90 degrees with a laser interference exposure method to create a two-dimensional nanostructured pattern, and when the pattern is developed with a solvent, the photoresist is developed. Unnecessary parts of are removed. In the fourth dry etching step of FIG. 8, a chromium mask is manufactured as a two-dimensional nanostructure. Instead of photoresist, chromium can be used as a mask to fabricate two-dimensional nanostructures on thin phosphor substrates. The photo of the two-dimensional nanostructure produced by the above process is shown in FIG. 6. The two-dimensional nanostructures fabricated by the method described above have a very uniform and periodically embossed cylindrical structure as shown in FIG. 6. When the type of photoresist is changed to negative type, a two-dimensional intaglio nanohole structure is created. Both embossed or engraved structures can be used for light extraction if they form two-dimensional nanospheres. Furthermore, the shape of the two-dimensional photonic crystal structure of the present invention is preferably a three-dimensional solid structure engraved or embossed in a spherical shape, a cylindrical shape, a cuboid shape, or a triangular column shape, but the present invention is not limited thereto. Light scattering occurs regardless of the shape, and a method of manufacturing a structure such as a spherical shape, a cuboid shape, or a triangular column shape is apparent to those skilled in the art.

Regardless of the intaglio or embossment, if the period of the nano cylinders is 200 nm or more, the period of the nanostructured fluorescent film to be grown thereon is also 200 nm or more, thereby improving the efficiency of the thin film phosphor. As described above, a two-dimensional photonic crystal nanostructure having a period of 200 nm or more can be fabricated on the thin film phosphor by a laser interference exposure method, which is obvious to those skilled in the art.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are not intended to limit the scope of the present invention, which will be construed as to help the understanding of the present invention.

Comparative example  One.

Comparative example  1-1. Selection of phosphor

In order to test the efficiency of the phosphor according to the present invention, a two-dimensional nanostructured thin film phosphor was prepared by selecting a Y ₂ O ₃ : Eu (refractive index 1.85) phosphor, which is a representative phosphor among low refractive index phosphors, and measured its UV-excited emission efficiency. . The higher the refractive index value, the greater the amount of light trapped in the thin film phosphor, and thus, the Y ₂ O ₃ phosphor, which is one of the phosphors having the smallest refractive index value, was used as a model. Although this phosphor is not a white LED phosphor emitting blue excitation, it can be used as a white LED for ultraviolet excitation as a red phosphor for ultraviolet excitation and a standard phosphor because of its small refractive index value. Particularly, most of the oxide, sulfide and nitride phosphors used as yellow YAG: Ce or Silicate phosphors or red, green and blue tricolor phosphors widely used as phosphors for white LEDs have a refractive index higher than that of the Y ₂ O ₃ : Eu phosphors. The value is larger. Since the refractive index of most phosphors is in the range of 1.5 to 3.0, the refractive index of the two-dimensional photonic crystal material must also be 1.5 or more and transparent. Therefore, in the present invention, the basis for confirming the extraction effect by the two-dimensional photonic crystal structure using SiN _x (refractive index 1.95) Used as a material.

Comparative example  1-2. Preparation of Nanoscale Roughness-Free Phosphors

A Y ₂ O ₃ : Eu thin film was prepared on a sapphire substrate by a sol-gel method and a spin coating method. 95% Y (NO ₃ ) ₃ and 5% Eu (NO ₃ ) ₃ were dissolved in 2-methoxyethanol, citric acid was added, and then a sol was formed and coated on the sapphire substrate by spin coating. After coating was dried at 100 ℃ for 5 minutes and pyrolyzed at 600 ℃ for 5 minutes to remove unnecessary carbon compounds and UV / ozone irradiation to modify the surface of the thin film phosphor to hydrophilic coating the second sol. Since the coating process was repeated, the thickness of the thin film phosphor was controlled, and in the present comparative example and the example, five layers of the thin film phosphor were coated. Finally, the coated thin film was calcined for 1000 ° C., and thus crystallized Y ₂ O ₃ : Eu thin film phosphor.

Comparative example  1-3. 2D in nano-sized thin film Photonic crystal structure  Produce

A two-dimensional SiNx photonic crystal structure was prepared on the Y ₂ O ₃ : Eu thin film phosphor prepared in Comparative Example 1-2 by the sol-gel method and the spin coating method. A SiN _x thin film to be used as a two-dimensional photonic crystal on a Y ₂ O ₃ : Eu thin film phosphor coated sapphire substrate was deposited at about 200 nm by a plasma enhanced chemical vapor deposition (PECVD) method. On it, chromium to be used as a mask was thermally deposited to a thickness of 50 nm. Next, (SPR508-A, Shipley) was spin-coated as a positive photoresist on the chromium thin film to form a photoresist film having a thickness of 90 nm, and then the photoresist film was subjected to an interference exposure method using a (Cd-He) laser. A two-dimensional nanostructured pattern having a period of 200 nm was prepared by two exposures while rotating at 90 ° C. Then, the pattern was developed using (AZ 301, Shipley) to remove unnecessary portions of the photoresist film, followed by dry etching. By etching the chromium thin film through (O ₂ / Cl ₂ gas), a two-dimensional nanostructured chromium mask having a period of 580 nm was formed Next, through etching again, the SiN _x thin film was etched with CF ₄ gas and By removing the chrome mask (ashing with Cl ₂ gas), a two-dimensional photonic crystal structure having a period of 580 nm and a height of about 200 nm was formed on the thin film phosphor substrate.

Example  One.

Example  1-1. Preparation of Thin Films with Nanoscale Roughness (43 nm Particle size)

The present invention provides a method for forming a thin film having a roughness by forming a nano-sized particles by adding a flux to a solvent in the method for manufacturing a thin film phosphor, wherein the roughness can be adjusted according to the concentration of the flux. In Comparative Example 1-2, a flux was added to the solvent as Li ₂ CO ₃ , but the size of the nanoparticles was 43 nm using a sol-gel solution containing 10 mol% of Li ₂ CO ₃ compared to Y ₂ O ₃ : Eu. A Y ₂ O ₃ : Eu thin film phosphor was prepared.

Example  1-2. 2D Photonic crystal structure  Produce

The two-dimensional SiN _x photonic crystal structure was used on the Y ₂ O ₃ : Eu thin film phosphor having a size of 43 nm by the sol-gel method and the spin coating method, using the method of Comparative Example 1-3. It was prepared in the same structure as in Comparative Example 1-3.

Example  2.

Example  2-1. Preparation of Thin Films with Nano-size Roughness (53 nm Particle size)

In the same manner as in Example 1-1, a thin film having nanoscale roughness was prepared. However, Y ₂ O _3: Eu is added to a 20% molar compared to Li ₂ CO ₃ by the size of the nanoparticles 53nm Y ₂ O _3: Eu was prepared in a thin film phosphor.

Example  2-2. 2D Photonic crystal structure  Produce

The two-dimensional SiN _x photonic crystal structure on the Y ₂ O ₃ : Eu thin film phosphor having the size of the nanoparticles prepared in Example 2-1 was 53 nm was the same as that of Comparative Example 1-3 by the method of Comparative Example 1-3. Prepared.

Example  3.

Example  3-1. Preparation of Thin Films with Nano-size Roughness (56 nm Particle size)

In the same manner as in Example 1-1, a thin film having nanoscale roughness was prepared. However, Y ₂ O _3: Eu is added to a 20% molar compared to Li ₂ CO ₃ by the size of the nanoparticles 56nm Y ₂ O _3: Eu was prepared in a thin film phosphor.

Example  3-2. 2D Photonic crystal structure  Produce

The two-dimensional SiN _x photonic crystal structure on the Y ₂ O ₃ : Eu thin film phosphor having a size of 56 nm of the nanoparticles prepared in Example 3-1 was prepared in the same manner as in Comparative Example 1-3. Prepared.

The thin film phosphors having the composite structures prepared in Comparative Examples 1-3, Example 1-2, Example 2-2, and Example 3-2 are shown in FIG. 6 by an electron microscope. As shown in FIG. 6, the structure in which the two-dimensional photonic crystal structure is coated on the thin film phosphor having nano size roughness is almost in agreement with that predicted in FIG. 5.

Experimental Example  One

The light emission spectrum of the thin film phosphors prepared in Examples 1 to 3 and Comparative Example 1 was measured using ultraviolet (254 nm) as an excitation light source. The light emission efficiency was tested by measuring the area of the light emission spectrum relative to Comparative Example 1-2, and the results of the relative measurement based on the light emission amount of Comparative Example 1-2 as reference are shown in FIG. It was.

Evaluation of the result

In the case of the composite nanostructured thin film phosphor obtained through Examples 1-2, Example 2-2 and Example 2-3, the structure obtained by coating a two-dimensional nanostructure on a conventional flat thin film phosphor was obtained through Comparative Example 1-3. It was confirmed that the luminous efficiency was improved by about 2.4 times or more as compared with the phosphor. In order to examine the effect of the nano-size roughness effect of the thin film phosphor on the two-dimensional nanostructure phosphor, the improvement of the light efficiency was evaluated when the two-dimensional photonic crystal of uniform size was coated on the thin film phosphor having different roughness. As shown in FIG. 6, since the two-dimensional photonic crystal structure of the same size is uniformly coated on the surface having different roughness, and the two-dimensional photonic crystal is coated in each of the roughness, the increased luminance is shown in FIG. 7. If the size of the nanoparticles indicating the degree of roughness is less than 20 nm, the composite structure is not formed, so only the effect of the existing two-dimensional nanostructures is shown, resulting in about 4.2 times the brightness increase, but the size of the nanoparticles is greater than 20 nm. In this case, the effect of the composite structure is shown, thereby increasing the total efficiency. As shown in FIG. 7, the effect of the two-dimensional photonic crystal is reduced while the roughness of the thin film phosphor is increased, but the scattering effect of the nanoparticles is increased, so that the efficiency of the phosphor manufactured by Example 1-2 is almost improved. It will have a value of 10 times or more. This shows a concept of high efficiency of the thin film phosphor because the thin film phosphor having the roughness, which is the core idea of the present invention, is combined with the two-dimensional structure.

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

2 is a cross-sectional view of a conventional white LED coated with blue, green and red tricolor powder type phosphors on a purple LED or an ultraviolet LED.

3 is a schematic diagram showing a structure in which a thin film phosphor is coated on a conventional two-dimensional photonic crystal structure and an emission path of emitted light generated in the phosphor.

4 is a schematic diagram showing a structure in which a two-dimensional photonic crystal nanostructure is coated on a conventional thin film phosphor and an emission path of emitted light generated in the phosphor.

Fig. 5 is a schematic view showing a plan view of a thin film phosphor having a composite structure of the present invention and an emission path of light emitted from the structure.

FIG. 6 (a) is an electron microscope (SEM) plan view of a two-dimensional photonic crystal thin film phosphor coated with a two-dimensional photonic crystal structure having a 580 nm period on a conventional Y ₂ O ₃ : Eu thin film phosphor.

6 (b) to 6 (d) are electron microscopes of the composite structured nano thin film phosphors coated with a 580 nm period two-dimensional photonic crystal structure on Y ₂ O ₃ : Eu thin film phosphors having 43, 53, and 56 nm nanoparticles, respectively. (SEM) is a flat photo.

Figure 7 ₂ O conventional Y _3: comparison of efficiency of light emission of the light emission spectrum of the Eu coated with a two-dimensional photonic crystal structure on the thin film phosphor nanocomposite structure thin film phosphor relative: Eu thin film phosphor and nano-size Y ₂ O ₃ having a roughness of It is a graph.

8 is a flowchart illustrating a process of manufacturing a two-dimensional photonic crystal structure on a thin film phosphor using a laser interference exposure technique.

9 is a flowchart for preparing a Y ₂ O ₃ : Eu thin film phosphor by a sol-gel method.

<Description of the symbols for the main parts of the drawings>

1. Yellow phosphor

2. Reflector

3. epoxy adhesive

4. Blue LED Device

5. R, G, B, tricolor phosphor

6. Purple or UV LED Element

7. Thin film phosphor

8. low refractive two-dimensional photonic crystal structure,

9. High refractive two-dimensional photonic crystal structure

10.SiN _x thin film

11. Chrome thin film

12. Photoresist Thin Film

13. Exposure surface by ray interference exposure

14. Sapphire Substrate

15. Photoresist thin film of 2D nano structure

16. Two-dimensional nanostructured chromium thin film

17. SiN _x 2D Photonic Crystal Structure

Claims (18)

A thin film phosphor comprising a substrate coated with a phosphor and a two-dimensional photonic crystal structure formed on the substrate, wherein the surface of the substrate is a non-planar surface having a nano size roughness. The thin film phosphor of claim 1, wherein light generated inside the phosphor coated on the substrate is extracted to the outside of the substrate by scattering on a non-planar surface having nano size roughness.   3. The thin film phosphor according to claim 2, wherein light other than the light extracted outside of the substrate is returned to the inside of the substrate by diffusion reflection on a non-planar surface having a nano-sized roughness. The thin film phosphor of claim 1, wherein light generated in the phosphor coated on the substrate is scattered when passing through the two-dimensional photonic crystal structure. The thin film phosphor of claim 1, wherein roughness of the nano size is achieved by nano particles stacked on the substrate, and the size of the nano particles is 20 to 300 nm. The thin film phosphor according to claim 1, wherein the two-dimensional photonic crystal structure has a height of 10 nm to 5000 nm. The thin film phosphor according to claim 1, wherein an extinction coefficient of the thin film phosphor is 10 ⁻² or less. The thin film phosphor of claim 1, wherein the phosphor is manufactured by using any one selected from the group consisting of inorganic light emitting materials emitting light in a visible region, such as oxides, sulfides, or nitrides, which may be prepared as thin film phosphors. And forming a two-dimensional photonic crystal structure on the substrate and forming a phosphor on a non-flat surface having a roughness of nano size. The method of claim 9, wherein the forming of the phosphor on the substrate as a non-planar surface having nano size roughness comprises: preparing a sol-type phosphor by a sol-gel method; And spin-coating the sol-type phosphor on a substrate. The method of claim 10, wherein in the sol-gel method, a precursor to be prepared as a phosphor is dissolved in a solvent, and then a citric acid is added to form a sol-type phosphor. 12. The method of claim 11, wherein the precursor to be made of the phosphor is any one of a group consisting of an oxide, a sulfide and a nitride. 12. The method of claim 11, wherein a roughness of the thin film phosphor is controlled by adding a flux to the solvent. The method of claim 13, wherein the flux is Li ₂ CO ₃ . The method of claim 13, wherein roughness of the phosphor is achieved by nanoparticles stacked on the substrate, and the size of the nanoparticles is increased to 20 to 300 nm. The method of claim 9, wherein the forming of the two-dimensional photonic crystal nanostructure comprises: depositing a photonic crystal thin film on a substrate; Depositing chromium to be used as a mask on the photonic crystal thin film; Coating a photoresist on the chromium thin film; Exposing and developing the photoresist; Etching the chromium thin film through first etching to pattern a chromium mask having a two-dimensional nanostructure; And Forming a two-dimensional photonic crystal structure by second etching the exposed photonic crystal thin film. 17. The method of claim 16, wherein the substrate is a quartz or sapphire substrate coated with a thin film phosphor. The method of claim 16, wherein the depositing of chromium is performed by a thermal deposition method, and the deposition thickness is 20 to 100 nm.

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