KR20100127341A - Coating on the surface of silicate phosphor - Google Patents

Abstract

PURPOSE: A surface coating of a silicate phosphor containing an organic/inorganic nanocomposite is provided to improve the initial luminance of the phosphor, and to increase the lifetime of the phosphor at the high temperature and humidity. CONSTITUTION: A silicate phosphor is coated with an organic/inorganic nanocomposite on the surface. The organic/inorganic nanocomposite contains the following: a metal oxide selected from the group formed with SiO_2, TiO_2, and MgO; and a polymer selected from the group consisting of polystyrene and polymethylmethacrylate. 0.1~50wt% of organic/inorganic nanocomposite is coated on the phosphor. The average particle diameter of the metal oxide is 3~100 nanometers.

Description

Silicate Phosphor Surface Coatings {COATING ON THE SURFACE OF SILICATE PHOSPHOR}

The present invention relates to a silicate phosphor, and more particularly, to provide a silicate phosphor which improves light efficiency and reliability by coating an organic-inorganic nanocomposite composed of a metal oxide and a polymer on a phosphor surface.

The phenomenon of absorbing external energy of a material and emitting visible light is called luminescence, and the substance causing such a phenomenon is called phosphor. Such a phosphor is a material having a characteristic of emitting light with a long wavelength by short wavelength energy excitation of a light emitting diode (LED) of a light emitting diode, and is mainly used for a backlight light source for a mobile phone and a display device. Therefore, the efficiency of the phosphor is a major variable directly related to the efficiency of the light emitting diode to which the phosphor is applied.

In general, a phosphor for a light emitting diode is mixed with an encapsulant to surround the light emitting diode. At this time, the phosphor is attacked by moisture and impurities in the encapsulant, so that the active material is oxidized or the crystallinity of the phosphor is inferior. There is a problem that the efficiency of the decrease.

In order to solve the above problems, the Republic of Korea Patent Publication No. 10-0885510 is coated with a transparent sol-gel material on the surface of the phosphor, the phosphor is mixed with the encapsulant and then the coating layer acts as a protective wall when used in practice, the stable color of the light source To maintain the reliability of the phosphor. In addition, Korean Patent Publication No. 10-2006-0079746 discloses a method of coating a silicon oxide film on the surface of a sulfide phosphor using a silane-based modifier, and by coating the silicon oxide film to improve the chemical stability of the sulfide phosphor. However, the above methods have a problem in that the coating layer is thick and unevenly produced, thereby lowering the initial luminance of the phosphor.

Therefore, there is a need for researches on the development of phosphors for light emitting diodes, which can ensure stability of phosphors against external environments such as moisture and impurities, and at the same time achieve phosphor phosphor improvement.

The present invention is to provide a silicate phosphor with improved light efficiency and extended life.

The present invention is an organic-inorganic nanocomposite silicate phosphor comprising at least one metal oxide selected from the group consisting of SiO ₂ , TiO ₂ , and MgO, and at least one polymer selected from the group consisting of polystyrene and polymethyl methacrylate. It provides a silicate phosphor that is coated on the surface of.

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

The present invention coats organic and inorganic nanocomposites composed of metal oxides and polymers on the surface of phosphor particles to improve light efficiency through high absorption and low reflectance of light emitted from blue LED devices, and to block moisture and impurities in the encapsulant, thereby improving reliability. It is to provide a phosphor for a light emitting diode that is excellent and has little deterioration.

In order to achieve the above technical problem, the present invention provides a method for coating an organic-inorganic nanocomposite of SiO ₂ , TiO ₂ , MgO, polystyrene or polymethyl methacrylate on the surface of the phosphor.

The organic-inorganic nanocomposite coating method on the surface of the silicate phosphor particles is characterized by coating through a method of mixing the oxide and polymer in water or alcohol to remove the solvent after stirring.

In the organic-inorganic nanocomposite of the present invention, the average particle diameter of the metal oxide may be 3 nm to 100 nm, preferably 10 nm to 50 nm, more preferably 10 nm to 20 nm. The average particle diameter of the metal oxide is preferably 3 nm or more in terms of high temperature and high humidity stability, and 100 nm or less is preferable in view of improving the light efficiency.

In addition, the average particle diameter of the polymer may be 10 nm to 500 nm, preferably 50 nm to 300 nm, more preferably 100 nm to 150 nm. The average particle diameter of the polymer is preferably 10 nm or more in terms of high temperature and high humidity stability, and 500 nm or less is preferable in view of improving the light efficiency.

In addition, the organic-inorganic nanocomposite may vary slightly depending on the type of coating oxide and the coating process, but the organic-inorganic nanocomposite is 0.1 wt% to 50 wt% based on the weight of the silicate phosphor. Is preferably included at 0.5 wt% to 20 wt%. If the organic-inorganic nanocomposite is less than 0.1 wt%, it is difficult to expect a sufficient coating effect. If the organic / inorganic nanocomposite is more than 50 wt%, the thickness may be excessively thick and unevenly coated, resulting in deterioration of luminance characteristics associated with phosphor particles. . According to certain conditions, it is more preferable that the organic-inorganic nanocomposite is added in an amount of 3 wt% to 10 wt%.

Here, the metal oxide may be added to the mixed solution at 0.05 wt% to 49.05 wt%, preferably 1 to 20 wt%, more preferably 3 to 10 wt% based on the weight of the phosphor. The metal oxide content is preferably 0.05 wt% or more in terms of high temperature and high humidity stability, and 49.05 wt% or less in terms of improving light efficiency.

In addition, the polymer may be added to the mixed solution at 0.05 wt% to 49.05 wt%, preferably 1 to 20 wt%, more preferably 5 to 10 wt% based on the weight of the phosphor. The polymer content is preferably 0.05 wt% or more in terms of high temperature and high humidity stability, and 49.05 wt% or less in terms of improving light efficiency.

On the other hand, the present invention provides a surface coating method of the silicate phosphor as described above. The coating method includes a phosphor in a mixture of at least one metal oxide selected from the group consisting of SiO ₂ , TiO ₂ , and MgO, and at least one polymer selected from the group consisting of polystyrene and polymethylmethacrylate and an alcohol solvent. Coating the mixture on the surface of the phosphor by dipping, and removing the solvent from the phosphor coated with the mixture.

The coating process of the phosphor may be performed through, for example, a sol-gel reaction of the mixed solution.

On the other hand, after coating a mixture containing a metal oxide and a polymer on the surface of the phosphor, the step of removing the solvent from the phosphor coated with the mixture is performed. At this time, the solvent removal step may be performed by adjusting the optimum temperature range in consideration of the boiling point of the solvent under normal pressure or reduced pressure according to the type of solvent used. For example, it can be carried out using an evaporator at a temperature of 20 ° C to 100 ° C, preferably 30 to 80 ° C, more preferably 40 to 70 ° C. In addition, the coating phosphor from which the solvent is removed may optionally be further subjected to a drying step.

Here, the solvent removal step and the drying step is to set the lower limit temperature range in terms of solvent removal efficiency and uniform coating layer formation, for example, it is preferably carried out at a temperature of 20 ℃ or more when using an evaporator in the solvent removal process, It is more preferable to set the upper limit in terms of preventing degradation of the polymer nanoparticles included in the coating layer, for example, at a temperature of 100 ° C. or less when used during evaporation drying in a solvent removal process.

In addition, the present invention provides a light emitting diode comprising the silicate phosphor. Since the silicate phosphor is uniformly coated with the organic / inorganic nanocomposite, it is possible to secure the stability of the phosphor to the external environment such as moisture and impurities, and at the same time to achieve the improvement of the phosphor brightness. The improvement and the life extension effect can be obtained.

In the present invention, matters other than those described above can be added or subtracted as required, and therefore, the present invention is not particularly limited thereto.

The present invention can provide a silicate phosphor having an organic-inorganic nanocomposite composed of a predetermined metal oxide and a polymer coated on the surface of the phosphor, thereby improving light efficiency, life span, and reliability.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

Example  One. SiO ₂ - PS / Phosphor coating method

After adding 10 g of silicate [(Sr, Ba) SiO ₄ : Eu] phosphor to 100 mL of ethanol, SiO ₂ (3 wt%) and polystyrene (PS, 5 wt%) were added to the solution, followed by stirring at room temperature. The solvent was removed and the surface of the phosphor was coated with an organic / inorganic complex by the sol-gel method. The coated phosphor was dried at 60 ° C. for 12 hours after removing the solvent at 40 ° C. using an evaporator to prepare a phosphor coated with an organic / inorganic complex.

Example  2. TiO ₂ - PS / Phosphor coating method

10 g of the silicate phosphor was added to 100 mL of ethanol, and then TiO ₂ (5 wt%) and polystyrene (PS, 5 wt%) were added to the solution, followed by stirring at room temperature. An organic-inorganic composite coated phosphor was prepared by the method.

Example  3. MgO - PS / Phosphor coating method

10 g of the silicate phosphor was added to 100 mL of ethanol, and then MgO (5 wt%) and polystyrene (PS, 5 wt%) were added to the solution, followed by stirring at room temperature. To prepare a phosphor coated with an organic-inorganic complex.

Example  4. SiO ₂ - PMMA / Phosphor coating method

10 g of the silicate phosphor was added to 100 mL of ethanol, and then SiO ₂ (3 wt%) and PMMA (5 wt%) were added to the solution, followed by stirring in room temperature. An organic-inorganic composite coated phosphor was prepared.

Example  5. TiO ₂ - PMMA / Phosphor coating method

10 g of the silicate phosphor was added to 100 mL of ethanol, and then TiO ₂ (3 wt%) and PMMA (5 wt%) were added to the solution, followed by stirring in the same manner as in Example 1 An organic-inorganic composite coated phosphor was prepared.

Comparative example  One. SiO ₂ / Phosphor coating method

10 g of the silicate phosphor was added to 100 mL of ethanol, and then SiO ₂ (5 wt%) was added to the solution, followed by stirring at room temperature to remove the solvent, thereby forming an inorganic coating layer on the surface of the phosphor by a sol-gel method.

Comparative example  2. PS / Phosphor coating method

After adding 10 g of the silicate phosphor to 100 mL of ethanol, polystyrene (PS, 5 wt%) was added to the solution, and the solvent was removed after stirring at room temperature to form a polymer coating layer on the surface of the phosphor by a sol-gel method.

Comparative example  3

After adding 10 g of the silicate phosphor to 100 mL of ethanol, the solvent was removed after stirring at room temperature without generating a separate coating layer.

For the phosphors produced according to Examples 1 to 5 and Comparative Examples 1 to 3, the following method was evaluated in physical properties and shown in Table 1 below.

Light efficiency  Improvement

The luminance of the phosphor was measured using a fluorescence spectrometer, and the light efficiency improvement rate was shown compared to the measured value of the uncoated phosphor.

Relative efficiency

The relative efficiency of each phosphor was measured under a high temperature, high humidity oven at 85 ° C., 85 Rh%, and 500 h.

Average Particle Size of Coating Layer Components

SEM was used to determine the average particle size of each component.

division Metal oxide
(content) Polymer
(content) Polymer
Particle size
(nm) Metal oxide
Particle size
(nm) Light efficiency
Improvement
(%) Relative efficiency
(%) Example 1 SiO ₂
(3 wt%) PS
(5 wt%) 150 10 109 102 Example 2 TiO ₂
(5 wt%) PS
(5 wt%) 150 7 106 101 Example 3 MgO
(5 wt%) PS
(5 wt%) 150 20 108 99 Example 4 SiO ₂
(3 wt%) PMMA
(5 wt%) 100 15 108 98 Example 5 TiO ₂
(3 wt%) PMMA
(5 wt%) 100 10 104 97 Comparative Example 1 SiO ₂
(5 wt%) - - 15 103 92 Comparative Example 2 - PS
(5 wt%) 150 - 97 90 Comparative Example 3 - - - - 100 85

First, as shown in FIG. 1, PS (150 nm) particles and SiO ₂ (10 nm) particles are uniformly coated on a surface of a phosphor through SEM photographs of SiO ₂ -PS / phosphor prepared according to Example 1 I could confirm that

Referring to Table 1, it was confirmed that the light efficiency of the phosphor coated with the organic-inorganic composite of Examples 1 to 5 was improved to 104% ~ 109%. In particular, as shown in FIG. 2, it was confirmed that the emission luminance of the SiO ₂ -PS / phosphor prepared in Example 1 was improved to 109% compared to the phosphor before coating.

On the contrary, the SiO ₂ / phosphor according to Comparative Example 1 was only about 103% higher than the phosphor before coating, and the PS / phosphor according to Comparative Example 2 was reduced to 97% compared to the phosphor before coating. It can be seen that, according to Comparative Example 3, the proceeding phosphor that proceeded without a separate coating barely maintained the luminescence brightness at 100% compared to the phosphor before coating.

Accordingly, it can be seen that the phosphors of Examples 1 to 5 coated with the organic-inorganic composite according to the present invention exhibited superior luminance than those of SiO ₂ or polystyrene coated solely in Comparative Examples 1 and 2, respectively.

1 is a SEM photograph showing the surface of SiO ₂ -PS / phosphor according to Example 1 of the present invention.

2 is a light emission spectrum of a phosphor according to Example 1 of the present invention, which is a graph showing a change in the light spectrum of a phosphor before coating (NOno-coated phosphor) and a SiO ₂ -PS phosphor (SiO ₂ -PS coated phosphor).

Claims (4)

An organic-inorganic nanocomposite comprising at least one metal oxide selected from the group consisting of SiO ₂ , TiO ₂ , and MgO, and at least one polymer selected from the group consisting of polystyrene and polymethylmethacrylate is formed on the surface of the silicate phosphor. A silicate phosphor that is coated. The method of claim 1, The organic-inorganic nanocomposite is a silicate phosphor coated with 0.1 wt% to 50 wt% based on the weight of the phosphor. The method of claim 1, The silicate phosphor having an average particle diameter of the metal oxide is 3 nm to 100 nm. The method of claim 1, Silicate phosphor of the average particle diameter of the polymer is 10 nm to 500 nm.

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