KR20100026474A - Synthetic method of red emitting gallate phosphors with high color purity - Google Patents

Abstract

PURPOSE: A synthetic method of red emitting gallate phosphors is provided to prepare red-emitting gallate phosphor powder with improved luminous efficiency and color purity in ultraviolet excitation conditions. CONSTITUTION: A synthetic method of red emitting gallate phosphors represented by chemical formula 1: Ln_(3-x)GaO_6:Eu_x comprises the steps of: preparing a precursor solution of 0.02-2 M concentration by adding a base material and a dopant doping the base material in a phosphor composition represented by chemical formula 1; and preparing phosphor powder by spraying the precursor solution inside a tubular reactor of a pyrolysis atomizer in which a temperature is maintained at 200-1500 °C.

Description

Synthetic method of red emitting gallate phosphors with high color purity

The present invention relates to a method for producing a gallium oxide-based phosphor powder having high color purity red light emission characteristics, and more specifically, using a gallium (Ga) oxide and an oxide of gadolinium (Gd) or yttrium (Y) as a matrix, The present invention relates to a method for producing a gallium oxide-based phosphor powder having a uniform particle size produced by spray pyrolysis without using europium (Eu) and further adding flux.

The gallium oxide-based phosphors represented by red phosphors can emit deep red light than the yttrium oxide-based phosphors, but the luminance efficiency is relatively low, so that actual commercialization is not achieved. [P. Guo, G. Li, F. Zhao, F. Liao, S. Tian and X. Jing, Journal of The Electrochemical Society , 150 (9) (2003) H201-H204].

Recently, as consumers prefer wider color reproducibility and slimmer electronic products, the development of high quality displays is urgently required, and thus, light emitting materials are newly attracting attention.

Cold Cathode fluorescent lamp (CCFL) is a high voltage induced at both ends of the glass tube in which the quantitative mercury gas is mixed, the electrons present in the tube are attracted to the electrode (anode) to move at high speed and collide with the electrode, Secondary electrons are emitted to initiate discharge. Electrons flowing by the discharge collide with mercury atoms in the tube to generate ultraviolet rays (254 nm), and the ultraviolet rays excite the fluorescent material applied to the inner wall of the glass tube to emit visible light. In a liquid crystal display device using a CCFL using a conventional phosphor as a light source, there is a problem of low color reproducibility and color balance. Although blue phosphors are known to have relatively good color purity, green and red phosphors tend to have low color purity. For example, Y ₂ O ₃ : Eu, which is a red phosphor, has a problem in color purity because the maximum emission wavelength is 611 nm. In order to improve the color rendering index of the red component, it is known that the emission wavelength of the red phosphor is most effective at 620 to 630 nm. Gd ₂ O ₃ : Eu is known as a phosphor that emits maximum light at a wavelength range of 620 to 630 nm. However, Gd ₂ O _3: Eu phosphors tend to the light-emitting characteristics change depending on the crystal structure of cubic system Gd ₂ O _3: Eu phosphor and a 611 ㎚ emission center wavelength, monoclinic Gd ₂ O _3: Eu phosphor Luminescence center wavelength is 623 nm. That is, the monoclinic Gd ₂ O ₃ : Eu phosphor has a luminescence spectrum distribution effective for improving the color rendering index of the red component, but the monocrystalline Gd ₂ O ₃ : Eu phosphor has a luminous efficiency of 20% of the Y ₂ O ₃ : Eu phosphor. It is only about. Therefore, there is a demand for the development of red phosphors which can be expected to increase color rendering and luminous efficiency.

On the other hand, the gadolium oxide-based phosphor in which europium (Eu) is added as an activator has been used as a synthesis method of a general phosphor, and a solid phase synthesis method has been used in which a certain proportion of solid phase materials are mixed and subjected to a long heat treatment at a high temperature. In the solid phase synthesis method, since the final calcination process is applied at a high temperature of 1450 ° C. or more for a long time of 24 hours or more, the aggregation of the phosphor particles is caused, and thus, the pulverization process is essentially performed as a post-treatment process. However, in the milling process performed as a post-treatment process, the surface of the phosphor is damaged or impurities are mixed, resulting in a loss of luminescence intensity. In addition, in the solid phase synthesis method, in order to obtain a pure single phase phosphor in which an unreacted phase or an additional secondary phase does not exist, alkali chlorides and alkali fluorides that promote the reactivity of high active elements must be used as fluxes. Must be added. Therefore, there is room for improvement in the solid phase synthesis method as a method for producing a gallium oxide-based phosphor using europium (Eu) as an activator.

It is an object of the present invention to provide a gallium oxide-based red phosphor powder with improved luminous efficiency and color purity under ultraviolet excitation conditions.

It is an object of the present invention to provide a method for producing a high-efficiency phosphor without the addition of a flux in a relatively low temperature conditions compared to the conventional solid phase synthesis method.

It is an object of the present invention to provide a method for producing a red light-emitting phosphor having a uniform particle size distribution and a uniform particle shape of several μm size.

The present invention comprises the steps of preparing a precursor solution of 0.02 M to 2 M concentration by adding the mother and the active agent doping the mother in the phosphor composition ratio represented by the following formula (1); And spraying the precursor solution into a tubular reactor of a spray pyrolysis apparatus maintained at a temperature of 200 ° C. to 1500 ° C. to produce a phosphor powder. The method of preparing a gallium oxide-based phosphor powder represented by the following Chemical Formula 1 includes By providing it, the said subject is solved.

Ln _{3 - x} GaO ₆ : Eu _x

In Formula 1, Ln is Y or Gd, and 0 <x ≦ 1.

Unlike the conventional solid phase synthesis method, the phosphor manufacturing method by spray pyrolysis according to the present invention performs heat treatment at a relatively low temperature condition, and has the effect of synthesizing a highly efficient phosphor without adding an additional flux.

The phosphor production method by spray pyrolysis according to the present invention has the effect that the production of phosphor powder having a uniform particle shape and particle size distribution is possible.

The present invention has the effect of synthesizing a red phosphor having excellent luminous efficiency and color coordinates under ultraviolet excitation conditions, compared to a phosphor of the same composition prepared using a conventional solid phase synthesis method.

The phosphor produced by the spray pyrolysis method according to the present invention has an effect that application to a red light-emitting phosphor such as a cold cathode fluorescent lamp (CCFL) is expected.

The method for preparing a gallium oxide-based phosphor represented by Chemical Formula 1 by spray pyrolysis according to the present invention will be described in more detail by the process.

In the first process, a precursor solution including a gadolinium (Gd) or yttrium (Y) precursor, a gallium (Ga) precursor, and an europium (Eu) precursor as an activator for doping the parent is prepared.

Since the precursor is water-soluble and excellent in solubility in alcohol, a precursor solution may be prepared using distilled water or an alcohol having 1 to 6 carbon atoms as a solvent. The content of each precursor included in the precursor solution is derived from the optimum composition ratio through various combinations within the range to satisfy the phosphor composition ratio of the formula (1). In particular, since the luminance of light emission may vary depending on the content (x) of europium (Eu) included as an active agent, the content (x) of europium (Eu) is maintained at 0 <x ≤ 1, preferably 0.01 ≤ x ≤ 0.4. Do it.

In addition, since the size of the phosphor particles to be produced is determined according to the concentration of the precursor solution, the concentration of the precursor solution must be appropriate to produce particles of a desired size. In the present invention, it is proposed to adjust the concentration of the precursor solution in the range of 0.02 M to 2 M, preferably in the range of 0.1 M to 2 M. As mentioned above, when the concentration of the precursor solution is lower than 0.02 M, there is a problem that the productivity of the powder is lowered, and when maintaining a high concentration of more than 2 M, the solubility of the precursor is lowered to obtain a satisfactory spray solution.

In the second process, the precursor solution is sprayed into a tubular reactor of a spray pyrolysis apparatus maintained at a temperature of 200 ° C. to 1500 ° C. to prepare a phosphor powder.

As a spray apparatus for spraying the precursor droplets, an ultrasonic spray apparatus, an air nozzle spray apparatus, or the like may be used. It is preferable that the diameter of the sprayed droplets is 0.1 μm to 100 μm, but when the diameter of the droplets does not reach 0.1 μm, there is a problem that the size of the resulting powder particles is too small, and the diameter of the droplets exceeds 100 μm. In contrast, a problem arises in that the size of particles produced is too large. In particular, in order to control the shape of the powder obtained, a device for generating fine droplets of several microns in size is required. In the present invention, the ultrasonic spraying apparatus was used as a spraying apparatus, and a large amount of the phosphors was generated by spray pyrolysis to generate a large amount of droplets per hour by using 12 vibrators, which generate droplets, to generate several tens of droplets per hour. This made it possible.

The droplets are sprayed into a tubular reactor maintained at a temperature of 200 ° C. to 1500 ° C., preferably 800 ° C. to 1200 ° C. to form a phosphor powder by heat treatment. Since Gd ₂ O ₃ : Eu phosphor powders are crystals obtained by reacting at a high temperature of 1,450 ° C. or more for 24 hours or more in a general solid phase synthesis method, a desired crystal phase may not be obtained in a spray pyrolysis process having a residence time of several seconds. Therefore, in the present invention, the process of heat treatment for 8 to 12 hours at 700 ℃ to 1300 ℃, preferably 900 ℃ to 1200 ℃ temperature in order to grow the crystal may be performed.

In the conventional solid phase synthesis method, a flux (Flux) is necessarily added to obtain a single crystal phase, and the crystal growth process is performed at a high temperature of 1450 ° C or higher. However, in the present invention, by adopting the spray pyrolysis method, a single phase can be obtained without adding flux, and the crystal growth process is also performed for a relatively short period of 5 to 12 hours at a relatively low temperature of 700 ° C to 1300 ° C. Even if it is possible to obtain the phosphor powder as the desired single crystal phase.

Gallium oxide-based phosphor powders prepared by the above manufacturing method were analyzed for the emission characteristics in the UV region (254 nm) in order to determine the application characteristics to the lamp for CCFL. As a result of the accompanying drawings, as shown in FIGS. 3 and 4, the gallium oxide-based phosphor prepared by the manufacturing method of the present invention is excellent in luminescence properties under ultraviolet excitation conditions, and thus is suitable for application to a red display device for high color purity.

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited by the examples.

EXAMPLE

Example 1. Gd _{2 .6} by spray pyrolysis GaO _6: Eu _{0 .4} produce a phosphor powder

Phosphor powder of Gd _2.6 GaO ₆ : Eu _0.4 was prepared as follows to prepare the spray pyrolysis method proposed by the present invention.

In order to form a parent, a precursor in which gadolinium (Gd), gallium (Ga) and europium (Eu) were dissolved was used in an equivalent ratio. The total concentration of the precursor solution was 0.5 M. The prepared precursor solutions were generated as droplets having a size of several μm using an ultrasonic atomizer which generates a large amount of droplets, and dried and pyrolyzed in a reactor to obtain a powder. At this time, the temperature of the reactor was maintained at 900 ℃. The ultrasonic atomizer used twelve vibrators with a frequency of 1.7 MHz as a device capable of generating a large amount of droplets. The droplets generated by the ultrasonic droplet generator are transported by a carrier gas to a high temperature tubular reactor, using compressed air as the carrier gas. The flow rate of the carrier gas was adjusted to 40 L / min to smoothly transport a large amount of droplets generated by the 12 ultrasonic vibrators. As the reactor, a quartz tube having an internal length of 1200 mm and an outer diameter of 55 mm was used. The temperature of the reaction part was maintained at 900 ° C. so that a large amount of droplets generated by the ultrasonic atomizer smoothly dried, precipitated, pyrolyzed and densified. Particles obtained through the reaction part were collected by a porous Teflon filter. Thus, the powders obtained by spray pyrolysis had a crystallinity of Gd ₃ GaO ₆ , and a heat treatment was performed at 1100 ° C. for 10 hours to sufficiently crystallize.

Preparation of Eu phosphor powder _{0 .4:} Comparative Example 1. Gd _{2 .6} GaO ₆ by solid phase synthesis

Gd _2.6 GaO ₆ : Eu _0.4 phosphor powder was prepared by the conventional solid-phase synthesis method, heat treatment was carried out at 1100 ℃ 24 hours.

According to the X-ray diffraction analysis results shown in FIG. 1, it was found that the phosphor (Example 1) prepared by spray pyrolysis according to the present invention forms a single crystal phase at a heat treatment temperature of 1100 ° C. On the contrary, the phosphor prepared by the solid-phase synthesis method (Comparative Example 1) was unable to form a single phase at 1100 ℃, it was confirmed that the pure (Gd ₃ GaO ₆ ) phase and impurity (Gd ₂ O ₃ ) phase present together, 1450 It was further confirmed that a single crystal phase was formed as a ratio when the heat treatment was performed at a high temperature of ℃ or more.

According to the emission spectrum shown in Fig. 3, it was confirmed that the phosphor prepared by spray pyrolysis (Example 1) exhibited better luminescence properties than the phosphor prepared by solid phase synthesis (Comparative Example 1) when excited with ultraviolet rays of 254 nm. Could.

5, the particle size distribution of the phosphor prepared by the spray pyrolysis method (Example 1) was uniform compared to the phosphor prepared by the solid phase synthesis method (Comparative Example 1), and the particle size was 3 μm to 5 Μm was maintained.

Example 2. Y ₃ GaO ₆ by Spray Pyrolysis: Preparation of Eu phosphor powder _{0 .4}

Y ₃ GaO ₆ : Eu _0.4 phosphor powder was prepared by the spray pyrolysis method of Example 1, and heat treatment for crystal growth was performed at 1200 ° C. for 9 hours.

Preparation of Eu phosphor powder _{0 .4:} Comparative Example 2. Y ₃ GaO ₆ by Spray Pyrolysis

Y ₃ GaO ₆ : Eu _0.4 phosphor powder was prepared by the conventional solid-phase synthesis method, heat treatment was carried out at 1,200 ℃ 24 hours.

According to the X-ray diffraction analysis results shown in FIG. 2, it was found that the phosphor (Example 2) prepared by spray pyrolysis according to the present invention forms a single crystal phase at a heat treatment temperature of 1200 ° C. On the contrary, the phosphor prepared by the solid-phase synthesis method (Comparative Example 2) was unable to form a single phase at 1200 ℃, it was confirmed that a pure (Y ₃ GaO ₆ ) phase and an impurity (Y ₂ O ₃ ) phase together, 1450 It was further confirmed that a single crystal phase was formed as a ratio when the heat treatment was performed at a high temperature of ℃ or more.

According to the emission spectrum shown in Fig. 4, it was confirmed that the phosphor prepared by spray pyrolysis (Example 2) exhibited better luminescence properties than the phosphor prepared by solid phase synthesis (Comparative Example 2) when excited with ultraviolet rays of 254 nm. Could.

6, the particle size distribution of the phosphor prepared by the spray pyrolysis method (Example 2) was uniform compared to the phosphor prepared by the solid phase synthesis method (Comparative Example 2), and the particle size was 3 μm to 5 Μm was maintained.

The relative luminance and color coordinate values of the phosphor powders prepared in Examples 1 and 2 and Comparative Examples 1 and 2 are collectively shown in Table 1 below.

division Relative luminance (%) (254 nm excitation) Color coordinates (x, y) Synthesis condition Example 1 80 (0.657, 0.334) Spray Pyrolysis (1100 ℃, 24h) Example 2 65 (0.658, 0.333) Spray Pyrolysis (1200 ℃, 24h) Comparative Example 1 48 (0.643, 0.341) Solid Phase Synthesis (1100 ℃, 24h) Comparative Example 2 54 (0.647, 0.338) Solid Phase Synthesis (1200 ℃, 24h) Commodity 100 (0.647, 0.344) -

Spray pyrolysis according to the present invention can be synthesized by a relatively low temperature heat treatment without additional flux additives compared to the conventional solid phase synthesis method, and exhibits a uniform particle size distribution characteristics. It was also confirmed that under 254 nm excitation conditions, which are mercury discharge conditions, the luminous efficiency and color coordinate characteristics were superior to the phosphors of the same composition prepared by the solid phase synthesis method. In addition, the phosphor prepared by the spray pyrolysis method according to the present invention is expected to be applied to a red light-emitting phosphor such as a cold cathode fluorescent lamp (CCFL).

1 is an X-ray diffraction analysis of the gallium oxide-based phosphor powder prepared by spray pyrolysis (Example 1) and solid phase synthesis (Comparative Example 1), respectively.

2 is an X-ray diffraction analysis of the gallium oxide-based phosphor powder prepared by spray pyrolysis (Example 2) and solid phase synthesis (Comparative Example 2), respectively.

3 is a light emission spectrum (excitation wavelength 254 nm) analysis results of the gallium oxide-based phosphor powder prepared by spray pyrolysis (Example 1) and solid phase synthesis (Comparative Example 1), respectively.

4 is a light emission spectrum (excitation wavelength 254 nm) of the gallium oxide-based phosphor powder prepared by spray pyrolysis (Example 2) and solid phase synthesis (Comparative Example 2), respectively.

5 is a scanning electron microscope (Scanning Electron Microscope, SEM) photograph of the gallium oxide-based phosphor powder prepared by the spray pyrolysis method (Example 1) and the solid-phase synthesis method (Comparative Example 1), respectively.

6 is a scanning electron microscope (Scanning Electron Microscope, SEM) photograph of the gallium oxide-based phosphor powder prepared by spray pyrolysis (Example 2) and solid-phase synthesis (Comparative Example 2), respectively.

Claims (5)

Preparing a precursor solution having a concentration of 0.02 M to 2 M by adding an active agent to dope the mother and the mother at a phosphor composition ratio represented by Formula 1 below; And Preparing a phosphor powder by spraying the precursor solution into a tubular reactor of a spray pyrolysis apparatus maintained at a temperature of 200 ° C. to 1500 ° C .; Method for producing a gallium oxide-based phosphor powder represented by the formula (1) characterized in that it comprises a. [Formula 1] Ln _{3 - x} GaO ₆ : Eu _x In Formula 1, Ln is Y or Gd, and 0 <x ≦ 1. The method of claim 1, wherein the parent and active agent are dissolved in distilled water or an alcohol having 1 to 6 carbon atoms to prepare a precursor solution. The method of claim 1, wherein the droplets generated by spraying have a diameter of 0.1 µm to 100 µm.  The method of claim 1, wherein the content (x) of europium (Eu) constituting the phosphor of Chemical Formula 1 is 0.1≤x≤0.4.  5. The method of claim 1, further comprising growing a crystal produced by spray pyrolysis at a temperature of 700 ° C. to 1300 ° C. 6.

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