WO2009091166A2 - Blue light-emitting silicate-based phosphor - Google Patents

Abstract

The invention relates to: a light-emitting device which uses a blue light-emitting silicate-based phosphor of the following formula 1 and also uses wavelength capable of directly exciting Eu2+ ion with excitation wavelength; and to a display device employing the light-emitting device. In addition, this invention provides a silicate-based phosphor represented by the following formula 2 and a light-emitting device or a display device employing the silicate-based phosphor. When excited at 254nm, a phosphor of (SrxBay)MgSi2O8:Euz (x/y <1) exhibits higher luminance than that of a phosphor of (SrxBay)MgSi2O8:Euz (x/y >1). Moreover, the phosphor of (SrxBay)MgSi2O8:Euz (x/y <1) exhibits high luminance even in much higher Eu concentration since the trend in the concentration of conventional (SrxBay)MgSi2O8:Euz and Eu is different.

Description

Blue light emitting silicate-based phosphor

The present invention relates to a blue light emitting phosphor having excellent light emission characteristics and color purity, a light emitting device and a display device including the same.

The display device is divided into a self-luminous display in which the pixels themselves emit light and a non-luminous display in which an image is combined with a separate lamp to implement an image. Examples of the self-luminous display include a plasma display panel (PDP), a cathode ray tube (CRT), an organic or inorganic light emitting display device (OLED), and an example of a non-luminous display is a liquid crystal display device (LCD). . In general, these display devices use phosphors that emit visible light of a particular wavelength for color realization.

For example, in the case of the liquid crystal display device of the display device, particularly in the transmissive liquid crystal display device, the phosphor is used for a backlight that provides light to the liquid crystal layer serving as an optical switch. As the backlight, a fluorescent lamp type backlight such as a fluorescent bulb or a cold cathode fluorescent lamp (CCFL), or a white light emitting diode type backlight formed of a combination of red, green, or blue light emitting diodes is used. .

In the case of the liquid crystal display device, the image quality such as luminance and color reproducibility is determined by the characteristics of the red, green or blue light emitting phosphor applied to the above-described fluorescent lamp for backlight. Blue luminescent phosphors commercially available as fluorescent lamps in liquid crystal display devices are mainly aluminate-based phosphors, for example, so-called BAM phosphors such as BaMgAl ₁₀ O ₁₇ : Eu ²⁺ .

In general, a fluorescent lamp using a BAM phosphor has not been developed in consideration of the color reproducibility of a liquid crystal display, but has been proposed for illumination, and has been studied in terms of color temperature, brightness, lifetime and efficiency. For this reason, the fluorescent lamp to which the BAM phosphor is applied has excellent color purity and luminance characteristics when applied to a color TV or color monitor, but has a problem in that the color reproduction ability is not sufficient. Due to these problems, new blue light emitting phosphors and various display apparatuses using the same are required for backlights of liquid crystal display devices.

An object of the present invention is to provide a blue light emitting phosphor that can improve the color reproduction ability of the display by improving the color purity in order to replace the conventional BAM phosphor.

Another object of the present invention is to provide a light emitting device capable of providing excellent color reproduction capability using the above-described phosphor and various display apparatuses using the phosphor.

The present invention provides a light emitting device and a display device having the light emitting device, characterized in that the blue light emitting phosphor of Formula 1 is used, and a wavelength capable of directly exciting Eu ²⁺ ions is used.

[Formula 1]

(Sr _x Ba _y ) Mg _a Si _b O ₈ : Eu _z

(Wherein

0.5 ≦ x ≦ 1.5, 1.5 ≦ y ≦ 2.5,

2.9 ≦ x + y ≦ 3.4, x <y,

z is 0.01 <z <0.23,

a is 0.99 ≦ a ≦ 1.1,

b is 1.9 ≦ b ≦ 2.1.)

In addition, the present invention provides a silicate-based phosphor represented by the following formula (2) and a light emitting device or a display device provided with the silicate-based phosphor.

[Formula 2]

(Sr _x Ba _y ) Mg _a Si _b O ₈ : Eu _z

(Wherein

0.5 ≦ x ≦ 1.5, 1.5 ≦ y ≦ 2.5,

2.9 ≦ x + y ≦ 3.4, x <y,

z is 0.12 ≦ z <0.23,

a is 0.99 ≦ a ≦ 1.1,

b is 1.9 ≦ b ≦ 2.1.)

The light emitting device using the phosphor of Chemical Formula 1 preferably has an excitation wavelength of 240 to 300 nm, more preferably 250 to 300 nm.

On the other hand, the phosphor of Formula 1 or Formula 2 is the center of the emission wavelength is in the range of 420 nm to 450 nm.

In particular, it is preferable that the phosphor of the formula (2) has a shorter wavelength (central wavelength) at the emission spectrum maximum luminance at the 254 nm excitation wavelength than that of the BAM. In addition, it is preferable that the light emission luminance at the 254 nm excitation wavelength is higher than that of the BAM.

In addition, the phosphor of Formula 2 preferably has an excitation wavelength absorbed by the host lattice mainly in a range of 100 to 200 nm, and an excitation wavelength absorbed by direct Eu ²⁺ ions is mainly in a range of 240 to 300 nm.

When excited at _{254nm, (Sr x Ba y)} MgSi 2 O 8: _{of: <(1 Eu z (x} / y Eu z x / y) 1) phosphor _{(Sr x Ba y) MgSi 2} O 8 in> Higher brightness than the phosphor. In addition, the phosphor of (Sr _x Ba _y ) MgSi ₂ O ₈ : Eu _z (x / y <1) has a much higher Eu than the conventional (Sr _x Ba _y ) MgSi ₂ O ₈ : Eu _z and Eu concentrations. High brightness even at concentration.

1 is a cross-sectional view of a cold cathode fluorescent lamp using the silicate phosphor of the present invention.

FIG. 2 shows a 254 nm photoluminescent emission (PL) spectrum of Sr _0.8 Ba _2.1 Mg ₁ Si ₂ O ₈ : Eu _{0.1 which} is a silicate-based phosphor prepared in Example 1. FIG.

3 shows a light spectrum upon 147 nm excitation of the silicate-based phosphors prepared in Example 2. FIG.

4 shows luminance at 147 nm excitation of the silicate-based phosphors prepared in Example 2. FIG.

FIG. 5 shows the central wavelength at 147 nm excitation of the silicate-based phosphors prepared in Example 2. FIG.

6 shows a light spectrum upon 254 nm excitation of the silicate-based phosphors prepared in Example 2. FIG.

FIG. 7 shows luminance at 254 nm excitation of the silicate-based phosphors prepared in Example 2. FIG.

FIG. 8 shows the center wavelength at 254 nm excitation of the silicate-based phosphors prepared in Example 2. FIG.

9 shows a light spectrum at 147 nm excitation of the silicate-based phosphors prepared in Example 3. FIG.

FIG. 10 shows luminance at 147 nm excitation of the silicate-based phosphors prepared in Example 3. FIG.

FIG. 11 shows the central wavelength at 147 nm excitation of the silicate-based phosphors prepared in Example 3. FIG.

FIG. 12 shows the light spectrum at 254 nm excitation of the silicate-based phosphors prepared in Example 3. FIG.

FIG. 13 shows luminance at 254 nm excitation of the silicate-based phosphors prepared in Example 3. FIG.

FIG. 14 shows the center wavelength at 254 nm excitation of the silicate-based phosphors prepared in Example 3. FIG.

FIG. 15 shows light spectra of Phosphor 1 (y = 1.0) to Phosphor 4 (x = 1.95) prepared in Example 4. FIG.

FIG. 16 shows light spectra of Phosphor 5 (y = 2.1) and Phosphor 6 (y = 2.4) prepared in Example 4. FIG.

FIG. 17 shows light spectra of Phosphor 7 (z = 0.05) to Phosphor 11 (z = 0.25) prepared in Example 5. FIG.

18 is selected from phosphor 1 (y = 1.0), phosphor 3 (y = 1.5), phosphor 4 (y = 1.8), phosphor 5 (y = 2.1) and phosphor 6 (y = 2.4) prepared in Example 4 To X-ray diffraction (XRD) characteristics.

In the present specification, the term "blue light emission" refers to the blue wavelength due to the phosphor of the present invention, which is emitted not only when light belonging to the blue wavelength band is emitted, but also when used with a phosphor of another color or a light source of another color. It also refers to the case where the band is included. For example, in a display device that emits white light by using a phosphor according to the present invention together with a phosphor having a different color of light emitting property, it should be understood that such a display device also has blue light emitting property.

On the other hand, since the wavelength of visible light ranges from 720 nm to 380 nm, light having a wavelength shorter than 380 nm is ultraviolet light. In addition, since light having a wavelength shorter than 200 nm is strongly absorbed by air, it can be handled only in a vacuum, so it is called vacuum ultraviolet ray.

In general, when the phosphors have different compositions, optical properties such as brightness, center wavelength, and crystallinity are different.

In the past, phosphors based on SrO-BaO-MgO-SiO ₂ have been mainly focused on PDP display applications using an excitation wavelength of 147 nm. In the case of using vacuum ultraviolet ray 147nm as the excitation wavelength, the emission principle is that the bandgap absorption of the phosphor occurs preferentially, and then some of the absorbed energy is transferred to an activator to emit light. When 147 nm is used as the excitation wavelength, it exhibits different optical properties according to various physical properties such as the composition, crystallinity, and surface state of the phosphor, and the emission principle is different from directly exciting Eu ²⁺ .

The present invention seeks to develop an excellent blue phosphor by directly exciting Eu ²⁺ as the main emission principle, for example by using 254 nm as the excitation wavelength, and comparing it with the 147 nm excitation wavelength.

The inventors have conducted experiments that phosphors of (Sr _x Ba _y ) MgSi ₂ O ₈ : Eu _z have a lower luminance than BAM when excited at 147 nm (FIGS. 4 and 10), but at a specific composition when excited at 254 nm It was found to have higher luminance than BAM (FIGS. 7 and 13).

In addition, the present inventors experimented, when (Sr _x Ba _y ) MgSi ₂ O ₈ : Eu _z is [Sr] / [Ba] <1 when [Sr] / [Ba]> 1 when excited at 254nm Was found to exhibit higher luminance (Fig. 13).

In addition, when (Sr _x Ba _y ) MgSi ₂ O ₈ : Eu _z to [Sr] / [Ba] <1 as in the present invention, conventionally (Sr _x Ba _y ) MgSi ₂ O ₈ : Eu _z and Eu concentrations Different trends were found for high luminance at much higher Eu concentrations. That is, even if the concentration of Eu is 0.1 or more, at least 0.22 shows high luminance.

The present invention is based on the above findings, and the above results can be interpreted as follows.

In the case where the excitation wavelength is 254 nm, the band gap energy transition does not occur in Eu ²⁺ after the host lattice itself absorbs, but the principle that Eu ²⁺ absorbs and emits the energy corresponding to the excitation wavelength is mainly applied. The higher the concentration of Eu, the stronger the emission intensity. However, in general, concentration quenching occurs when the concentration of Eu ²⁺ is higher than or equal to a predetermined value, and thus the concentration of Eu ²⁺ cannot be arbitrarily increased. However, as Ba ²⁺ having a larger atomic radius is substituted for Sr ²⁺ ion sites, the lattice expansion of the crystal lattice occurs. This increases the distance between the Eu ²⁺ ions present in the expanded lattice. As the distance between Eu ²⁺ ions increases, the concentration at which concentration quenching starts may increase. Therefore, the present invention is controlled to [Sr] / [Ba] <1 in the phosphor of (Sr _x Ba _y ) MgSi ₂ O ₈ : Eu _z , so that even at 254 nm excitation, the concentration of Eu is higher than that of the conventional phosphor, for example, Eu concentration. Even up to 0.22, the light emission intensity can be increased. That is, in the case of the same fluorescent substance as before, a high emission intensity can be obtained even at a high Eu ²⁺ ion concentration which is not reached. In addition, due to the increased concentration of Eu, it is possible to exhibit higher luminance than BAM at 254 nm excitation (FIG. 7).

On the other hand, when the excitation wavelength is 147 nm, the principle is that the host lattice itself absorbs energy of the excitation wavelength preferentially, and the energy absorbed by the host lattice is transferred to Eu ²⁺ and excited. If the ratio of Ba having a large ion radius is substituted for a relatively small Sr, the host lattice is changed and the crystal field is distorted accordingly, which impedes the transfer of energy absorbed from the host to Eu ²⁺ ions. It is relatively high in the [Sr] / [Ba]> 1 region.

On the other hand, the phosphor according to the present invention can be prepared by a general method for producing a metal oxide by firing except using the composition shown in formula (1) or (2).

For example, the manufacturing method may include preparing raw materials; First grinding and mixing process; Calcination process; Second grinding and mixing process; Firing process.

To prepare blue light emitting phosphors having the formula (Sr _x Ba _y ) Mg _a Si _b O ₈ : Eu _z with various composition ratios according to the invention, for example, strontium as a source of strontium, barium, magnesium and silicon Carbonate (SrCO ₃ ), barium carbonate (BaCO ₃ ), magnesium oxide (MgO) and silicon oxide (SiO ₂ ) may be used. However, this is merely illustrative, and as a source of these elements, materials degradable at high temperatures such as hydroxide, carbonate, nitrate, halide, oxalate, etc. of each element may be used. An oxide such as Eu ₂ O ₃ may be used as a source of Eu, which is an activator of the phosphor. However, as the Eu source, fluoride or the like may be used in addition to the oxide.

The first grinding and mixing process of the metal compounds may be performed for about 40 minutes to 1 hour .

The metal compounds may be ground and / or mixed using, for example, a device used in a typical industry such as a ball mill, a V-type mixer, an agitator, and a jet-mill, and may be a dry mixing method or a wet mixing method. Either way is good.

In addition, a solvent such as acetone, alcohol or distilled water may be used to facilitate the first grinding and mixing process. If a solvent is used, loss of powder can be prevented by carrying out a drying process to remove the solvent in the mortar.

Flux may be added to the raw metal compounds prior to the first grinding and mixing process described above, or may be used in a step before the firing process described later to assist in mixing and phase-forming each of the raw metal compounds in the firing process described below. Can be added.

As the flux, for example, LiF, NaF, KF, LiCl, NaCl, KCl, Li₂CO₃, Na₂CO₃, K₂CO₃, NaHCO₃, NH₄FHF, NH₄Cl, NH₄I, MgF₂, CaF₂, SrF₂, BaF₂, MgCl₂, CaCl₂, SrCl₂, BaCl₂, MgI₂, CaI₂, SrI₂ And BaI₂ At least one substance selected from, typically NH₄Cl to 0.05 wt% to 20wt% of the total raw material, Preferably at about 1 wt% concentration.

Through the first mixing and grinding process, a calcination process is performed on the dried mixed powder. The calcination process can be carried out by heating up to 800 ° C. to 1000 ° C. at a rate of 5 ° C./min to 10 ° C./min, heating at that temperature for 2 to 4 hours in an oxygen or air atmosphere and then furnace cooling.

Thereafter, for the calcined mixed powder, a second grinding and mixing process is performed. The second grinding and mixing process is preferably carried out dry without using a separate solvent. After the second mixing and grinding process is performed for about 10 to 20 minutes, the firing process is performed.

The firing process may be carried out at least 900 ℃ to 1600 ℃, preferably at 1000 ℃ to 1300 ℃ for crystallization. When the firing temperature is higher than 1600 ° C., the constituent elements of the phosphor powder may volatilize, excessively shift from the stoichiometric ratio, or cause a decrease in crystallinity, thereby causing a sharp decrease in luminance. The firing process may be performed for 1 to 8 hours. In addition, the firing process may be performed at least once.

The firing process may be carried out under a nitrogen atmosphere or a weak reducing atmosphere. In order to provide a weak reducing atmosphere, a mixed gas of nitrogen / hydrogen in which a small amount of hydrogen is added to satisfy, for example, N ₂ : H ₂ = 95: 5 (volume ratio) may be used.

The phosphor obtained by the above-described method may be pulverized using a ball mill, a jet mill, or the like, and pulverization and firing may be repeated two or more times. Moreover, the fluorescent substance obtained can be wash | cleaned or classified as needed.

On the other hand, the following illustrates a method of manufacturing a phosphor paste for providing a light emitting device or display with a phosphor according to the present invention.

The phosphor paste is prepared by dispersing and mixing the blue light emitting phosphor powder according to the present invention in an organic material such as a solvent and a binder. At this time, optional red and green luminescent phosphor powders well known in the art may be added to the phosphor paste.

Non-limiting examples of the solvent include alcohols having a high boiling point among monohydric alcohols, polyhydric alcohols such as diol or triol such as ethylene glycol or glycerin, Etherified and / or esterified alcohols such as ethylene glycol mono-alkyl ethers, ethylene glycol dialkyl ethers, Ethylene Glycol Alkyl Ether Acetate, Diethylene Glycol Monoalkyl Ether Acetate, Diethylene Glycol Dialkyl Ether, Propylene Glycol Monoalkyl Ether Acetate Propylene glycol dialkyl ether, propylene glycol alkyl acetate, etc. Can be.

Non-limiting examples of the binder, cellulose-based resins (ethyl cellulose, methyl cellulose, nitrocellulose, acetylcellulose, cellulose propionate) , Hydroxy propyl cellulose, butyl cellulose, benzyl cellulose, modified cellulose, etc., acrylic resins (acrylic acid, methacrylic acid, methyl acrylate) (methyl acrylate), methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl Acrylate (isopropyl acrylate), isopropyl methacrylate, n-butyl acrylate, n- Butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, 2-hydroxy ethyl acrylate, 2-hydroxy propyl methacrylate, benzyl acrylate acrylate, benzyl methacryate, phenoxy acrylate, phenoxy methacrylate, isobornyl acrylate, isobornyl methacrylate, At least one of monomers such as glycidyl methacrylate, styrene, α-methyl styrene acrylamide, metha acrylamide, acrylonitrile and meta acrylonitrile Polymers, ethylene-vinyl acetate copolymer resins, polyvinyl butyral, polyvinyl alcohol, propylene glycol, poly There may be mentioned ethylene oxide (polyethylene oxide), polyurethane (urethane) resin, melamine (melamine) resin, phenol (phenol) resins.

Meanwhile, an example of a light emitting device using the blue light emitting phosphor of Formula 1 or Formula 2 according to the present invention is a lighting device.

In one example, the lighting device includes a phosphor inside the seal and a discharge gas enclosed in the seal. The lighting apparatus may be a fluorescent lamp in which the discharge gas is discharged by a cold cathode or a filament. In addition, the discharge gas may include mercury or a mixed gas of mercury and argon.

1 is a cross-sectional view of a cold cathode fluorescent lamp 100 using a silicate phosphor according to an embodiment of the present invention. The above-described phosphor paste is applied to an inner wall of an enclosure 101 such as a glass tube, and a drying process is performed, followed by heat treatment at a temperature range of about 300 ° C. to 600 ° C. to form the phosphor layer 102. Thereafter, the electrodes 103 and 104 are disposed at both ends of the sealing body 101, and a rare gas such as argon (Ar) or mercury (Hg) or a mixed mixed gas 105 of the predetermined pressure is enclosed in the sealing body. To produce a cold cathode fluorescent lamp (100). If a filament (not shown) is disposed instead of the electrodes 103 and 104, a conventional fluorescent bulb can be provided.

The cold cathode fluorescent lamp 100 discharges the enclosed gas 105 by the electron emission caused by the strong electric field between the electrodes 103 and 104. The phosphor layer 102 may be excited by 254 nm UV emitted from the discharged gas.

The blue light-emitting phosphor of Formula 1 or Formula 2 according to the present invention may be used alone as described above to provide a blue light-emitting device, and may be used in combination with phosphors of different colors, for example, red and green light-emitting phosphors. It is also possible to provide an apparatus for emitting light of different colors. In addition, other types of blue light emitting phosphors may be used in addition to the blue light emitting phosphors according to the embodiment of the present invention.

Non-limiting examples of blue light emitting phosphors that can be used in the light emitting device of the present invention include BaMgAl ₁₀ O ₁₇ : Eu and (Sr, Ba, Ca) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu, and the like. Non-limiting examples include CaAlSiN ₃ : Eu, Sr ₂ Si ₅ N ₈ : Eu, (Ba, Mg) SiO ₄ : Eu, Y ₂ O ₃ : Eu, YVO ₄ : Eu, and the like. Further non-limiting examples of green phosphors include Ba ₂ MgSi ₂ O ₇ : Eu, BaAl ₂ O ₄ : Eu, BaMg ₂ Al 1 ₆ O ₂₇ : Eu, LaPO ₄ : Ce, Tb and BaMgAl ₁₀ O ₁₇ : Eu, Mn Etc.

The display device according to the present invention may be an LCD in which a light emitting device such as a fluorescent lamp is combined with a liquid crystal layer. The LCD and the like are structures known in the art to which the present invention pertains, and methods of using fluorescent lamps are already known, and thus detailed descriptions of these displays will be omitted.

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

<Example 1>

The raw material powders of SrCO ₃ , BaCO ₃ , MgO, SiO ₂ and Eu ₂ O ₃ were 0.498 g /1.749 g /0.170 so that Sr, Ba, Mg, Si and Eu are 0.8, 2.1, 1, 2 and 0.1 molar ratios, respectively. g /0.507g /0.074g were weighed, 0.024g NH ₄ Cl was added to these raw materials to have a concentration of about 1 wt%, and the first milling and mixing process was carried out using a ball mill for about 1 hour .

Thereafter, the calcination process was performed by heating up to 900 ° C. at a rate of 5 ° C./min, heating in an air atmosphere for 3 hours, and then furnace cooling. Thereafter, the calcined mixed powder was subjected to a second milling and mixing process using a ball mill for about 20 minutes without using a separate solvent. Thereafter, the mixture was heated at a rate of 3 ° C./min to a temperature of about 1200 ° C. while providing a nitrogen / hydrogen mixed gas mixed at a volume ratio of N ₂ : H ₂ = 95: 5 at a flow rate of about 0.25 l / min, and 1200 ° C. The firing process was carried out by heating at 3 hours and then by quenching at a rate of 5 ° C./min.

We prepared a reproducibility test sample 2 having the same compositional formula as sample 1 having a composition formula of Sr _0.8 Ba _2.1 Mg ₁ Si ₂ O ₈ : Eu _0.1 .

Professional Scientific Instrument Co. Using the DARSA PRO 5100 PL System of Korea Co., Ltd., the optical (PL) spectrum and the center wavelength, luminance, and CIE color coordinates of the prepared phosphor powder were measured, and the excitation wavelength was 254 nm.

FIG. 2 shows photoluminescent emission (PL) spectra of samples 1 and 2 having the compositional formula Sr _0.8 Ba _2.1 Mg ₁ Si ₂ O ₈ : Eu _0.1 according to the present embodiment and a light spectrum of a commercially available BAM phosphor (Nichia). Shown together.

Referring to FIG. 2, as shown by the curve (R), the conventional commercially available BAM-based phosphor exhibits a center wavelength (wavelength representing the maximum peak) at 450 nm. However, the blue light-emitting phosphors of Sr _0.8 Ba _2.1 Mg ₁ Si ₂ O ₈ : Eu _0.1 of Samples 1 and 2 according to Example 1 have a center wavelength at 437 nm, as shown by curves (a) and (b), respectively. Have That is, the center wavelength of the blue light-emitting phosphor having a compositional formula of Sr _0.8 Ba _2.1 Mg ₁ Si ₂ O ₈ : Eu _0.1 according to Example 1 is shifted toward the shorter wavelength by Δ13 nm from the center wavelength of the commercially available BAM phosphor, thereby improving blue purity. It has a high brightness at the center wavelength.

Example 2 Luminance Change According to Eu Content

According to the same preparation method described in Example 1, (Sr _0.8 , Ba _2.1 ) MgSi ₂ O ₈ : Eu _z (z = 0.005, 0.01, 0.06, 0.1, 0.15, 0.17, 0.2, 0.22, 0.23, 0.25, 0.4) And 147 nm and 254 nm, respectively, were used as excitation wavelengths. Using the DARSA PRO 5100 PL System of Korea Co., Ltd., the optical (PL) spectrum, the center wavelength, and the luminance of the prepared phosphor powder were measured. The spectrum, luminance and center wavelength at the excitation wavelength 147 nm are shown in Figs. 3 to 5, respectively. The spectrum, luminance and center wavelength at the excitation wavelength 254 nm are shown in Figs.

(Sr _0.8 , Ba _2.1 ) MgSi ₂ O ₈ : Eu _z prepared in Example 2 was [Sr] / [Ba] <1, and exhibited high luminance at 0.1 <Eu <0.23 when excited at 147 nm. Central wavelength = 440 nm (FIGS. 4 and 5).

Moreover, when it was excited at 254 nm, it showed high luminance at 0.01 <Eu <0.23, and center wavelength = 439 nm (FIGS. 7 and 8).

Conventionally, in the (Sr _x Ba _y ) MgSi ₂ O ₈ : Eu _z phosphor, when it is excited at 147 nm, when the concentration of Eu becomes 0.1 or more, the luminance is rapidly decreased.

However, as in the present invention _{(Sr x Ba y) MgSi 2} O 8: If the [Sr] / [Ba] < 1 in the Eu _z is the conventional _{(Sr x Ba y) MgSi 2} O 8: Eu concentration of Eu _z phosphor Different trends were shown for high luminance even at much higher Eu concentrations. That is, even if the concentration of Eu was 0.1 or more, the luminance was high up to at least 0.22.

According to the invention for (Sr _x Ba _y ) MgSi ₂ O ₈ : Eu _z for [Sr] / [Ba] <1 a high Eu ²⁺ ion concentration, such as 254 nm excitation, which has not been reached in the case of conventional phosphors Therefore, the reason why the optimum concentration of Eu is 0.22 is high. It can be inferred as follows.

When the excitation wavelength is 254 nm, Eu ²⁺ excitation is performed directly without performing band gap energy transition of the host lattice. Therefore, when the concentration of Eu is high, the emission intensity increases, but the concentration of Eu ²⁺ cannot be arbitrarily increased. If a large amount of Eu is added, concentration quenching occurs. Lattice expansion occurs as Ba ²⁺ with a larger atomic radius is substituted for Sr ²⁺ ion sites, increasing the distance between Eu ²⁺ ions in the expanded lattice. As the distance between Eu ²⁺ ions increases, the concentration at which concentration quenching starts is increased, thereby increasing the emission intensity.

Example 3 Luminance Variation According to Ba / Sr Ratio

According to the same preparation method described in Example 1, (Sr _x Ba _y ) MgSi ₂ O ₈ : Eu _z (z = 0.01, 0.17) (x = 0.6 y = 2.3, x = 0.8 y = 2.1, x = 1.6 y = 1.3, x = 1.9, y = 1.0), using 147 nm and 254 nm as excitation wavelengths, respectively. Using the DARSA PRO 5100 PL System of Korea Co., Ltd., the optical (PL) spectrum, the center wavelength, and the luminance of the prepared phosphor powder were measured. The spectrum, luminance and center wavelength at the excitation wavelength 147 nm are shown in Figs. 9 to 11, respectively. The spectrum, luminance and center wavelength at the excitation wavelength 254 nm are shown in Figs. 12 to 14, respectively.

(Sr _0x , Ba _y ) MgSi ₂ O ₈ : Eu _z prepared in Example 3 exhibited high luminance when [Sr] / [Ba] <1 when excited at 254 nm, but when excited at 147 nm [ The case of Sr] / [Ba] <1 showed low luminance.

On the other hand, the reason for showing the optimum Eu concentration at a relatively high [Sr] / [Ba] at 147 nm excitation is as follows.

In 147nm excitation, a host interband transition occurs mainly, and at 254nm excitation, a direct excitation transition occurs in which Eu ²⁺ ions are directly excited. Therefore, the mechanism of light absorption differs depending on the excitation wavelength. At 147nm excitation, the energy absorbed by the host lattice is transferred to Eu ²⁺ , and when the ratio of Ba having a large ion radius is substituted for relatively small Sr, the energy absorbed at the host is transferred to Eu ²⁺ ion. This is because it becomes an obstacle.

<Example 4>

In order to evaluate the change of optical properties according to the relative composition change of Sr and Ba, the composition ratio of Sr and Ba according to the composition formula of (Sr _x Ba _y ) Mg _a Si _b O ₈ : Eu _z is controlled as shown in Table 1. Phosphor powder was prepared. That is, a blue light emitting phosphor having a composition in which the molar ratio x of Sr is reduced to 1.9, 1.7, 1.4, 1.1, 0.8, and 0.5, and the molar ratio y of Ba is increased to 1.0, 1.2, 1.5, 1.8, 2.1, and 2.4, was prepared, respectively. . Provided that z is 0.1, a is 1, and b is 2.

Table 1

Example	Furtherance	Corrected luminance compared to BAM (%)	Center wavelength (nm)	CIE color coordinates
Phosphor 1	(Sr 1.9 Ba 1.0 ) MgSi 2 O 8 : Eu 0.1	68%	438	(0.1541, 0.0291)
Phosphor 2	(Sr 1.7 Ba 1.2 ) MgSi 2 O 8 : Eu 0.1	65%	432	(0.1582, 0.0209)
Phosphor 3	(Sr 1.4 Ba 1.5 ) MgSi 2 O 8 : Eu 0.1	67%	431	(0.1590, 0.0193)
Phosphor 4	(Sr 1.1 Ba 1.8 ) MgSi 2 O 8 : Eu 0.1	73%	436	(0.1586, 0.0197)
Phosphor 5	(Sr 0.8 Ba 2.1 ) MgSi 2 O 8 : Eu 0.1	73%	438	(0.1573, 0.0215)
Phosphor 6	(Sr 0.5 Ba 2.4 ) MgSi 2 O 8 : Eu 0.1	75%	436	(0.1579, 0.0203)
Comparative Example 1	BaMgAl 10 O 17 : Eu (commercial BAM)	100%	451	(0.1461, 0.0525)

In Fig. 15, the light spectra of phosphors 1 (y = 1.0) to phosphors 4 (y = 1.8) are shown by curves (a) to (d), respectively, when excited at 254 nm in the same manner as in Example 1 (Fig. (E) is BAM at 15), and in FIG. 16, the optical spectra of phosphors 5 (y = 2.1) and phosphors 6 (y = 2.4) are excited by 254 nm in the same manner as in Example 1, respectively. It is shown as (b) (in Figure 16 (c) is BAM). The luminance, the central wavelength, and the CIE color coordinates of the phosphors according to the phosphors 1 to 6 are summarized in Table 1 below. Here, luminance (% corrected luminance relative to BAM) means [(phosphor luminance / phosphor CIE y value) / (BAM luminance / BAM CIE y value)] × 100.

15 and Table 1, the central wavelengths of the phosphors 1 to 3 are 438 nm, 432 nm and 431 nm, respectively. According to this, as the molar ratio y of Ba increases from 1.0 to 1.5, it can be seen that the movement of the central wavelength toward the shorter wavelength.

Referring to FIG. 16 and Table 1, the central wavelengths of the phosphors 4 to 6 are 436 nm, 438 nm, and 436 nm, respectively. As the molar ratio y of Ba increases to 1.5 or more, the central wavelength moves toward the longer wavelength.

Referring to FIG. 16 along with FIG. 15, (Sr_xBa_yMg_aSi_bO₈: Eu_z                  In the phosphor having the compositional formula, when the molar ratio y of Ba increases, the center wavelength shifts toward shorter wavelengths until y = 1.5, and the center wavelength shifts toward longer wavelengths after y = 1.8. Also, in the case of phosphors 4, 5, and 6 in which the center wavelength is shifted to the longer wavelength than the phosphor 3, the center wavelength is less than 450 nm, so that excellent color purity can be obtained. In particular, in the case of a blue light-emitting phosphor having a molar ratio y of Ba of 1.0 ≦ y <2.5, the center wavelength is in the range of 430 nm to 440 nm, and thus has excellent color reproduction.

FIG. 18 shows Phosphor 1 (y = 1.0), Phosphor 3 (y = 1.5), Phosphor 4 (y = 1.8), Phosphor 5 (y = 2.1) and Phosphor 6 (y = among the various phosphors prepared in the above embodiment Is a graph showing the results of performing X-ray diffraction (XRD) characteristic evaluation by selecting 2.4). In Fig. 18, curves (a) to (e) show X-ray diffraction characteristics of phosphors 6, 5, 4, 3 and 1, respectively. Referring to FIG. 18, it can be seen that the blue light emitting phosphors have a low background intensity even at a low angle of 20 ^° and have excellent crystallinity as each diffraction peak is sharp.

Example 5

In order to evaluate the change of optical properties according to the relative change of Ba and Eu, the composition z of Eu according to the composition formula of (Sr _x Ba _y ) Mg _a Si _b O ₈ : Eu _z is controlled as shown in Table 2. Phosphor powder was prepared. That is, z was increased to 0.05, 0.1, 0.15, 0.2 and 0.25. However, x is 0.8, y is 2.1, a is 1, and b is 2.

TABLE 2

Example	Furtherance	Center wavelength (nm)	CIE color coordinates
Phosphor 7	(Sr 0.8 Ba 2.1 ) MgSi 2 O 8 : Eu 0.05	437	(0.1574, 0.0215)
Phosphor 8	(Sr 0.8 Ba 2.1 ) MgSi 2 O 8 : Eu 0.1	438	(0.1579, 0.0209)
Phosphor 9	(Sr 0.8 Ba 2.1 ) MgSi 2 O 8 : Eu 0.15	440	(0.1569, 0.0225)
Phosphor 10	(Sr 0.8 Ba 2.1 ) MgSi 2 O 8 : Eu 0.2	440	(0.1567, 0.0231)
Phosphor 11	(Sr 0.8 Ba 2.1 ) MgSi 2 O 8 : Eu 0.25	440	(0.1574, 0.0725)

In FIG. 17, light spectra of phosphors 7 (z = 0.05) to phosphors 11 (z = 0.25) when 254 nm excited in the same manner as in Example 1 are shown as curves (a) to (e), respectively. Summarizes the central wavelength and CIE color coordinates of phosphors 7-11.

17 and Table 2, the center wavelengths of the phosphors 7 to 11 are 437 nm, 438 nm, 440 nm, 440 nm and 440 nm, respectively. According to this, in the range of 0.03 to 0.25 including 0.05, 0.1, 0.15, 0.2 and 0.25 (= molar ratio z of Eu), the central wavelength of the blue light-emitting phosphor is 440 nm or less and the y-coordinate of CIE is 0.03 or less. Color purity can be secured. It can be confirmed that a difference in luminance occurs as the molar ratio z of Eu changes. That is, the molar ratio z of Eu is preferably in the range of 0.1 to 0.2, the blue light emitting phosphor has excellent luminance, and it can be seen that the luminance decreases when the molar ratio z of Eu exceeds 0.25.

<Example 6>

In order to evaluate the change of optical properties according to the composition of Mg, the composition a of Mg according to the composition formula of (Sr _x Ba _y ) Mg _a Si _b O ₈ : Eu _z is controlled as shown in Table 3. Prepared. That is, a was increased to 0.99, 1.00 and 1.1. However, x is 0.8, y is 2.1, z is 0.1, and b is 2.

TABLE 3

	Furtherance	Center wavelength (nm)	CIE color coordinates
Phosphor 12	(Sr 0.8 Ba 2.1 ) Mg 0.99 Si 2 O 8 : Eu 0.1	440	(0.1577, 0.0853)
Phosphor 13	(Sr 0.8 Ba 2.1 ) Mg 1.0 Si 2 O 8 : Eu 0.1	437	(0.1579, 0.0198)
Phosphor 14	(Sr 0.8 Ba 2.1 ) Mg 1.1 Si 2 O 8 : Eu 0.1	437	(0.1580, 0.0195)

In Table 3, when 254 nm is excited by the same method as in Example 1, the composition wavelengths of Mg are 0.99, 1.00, and 1.1, and the center wavelengths are 440 nm, 437 nm, and 437 nm, respectively, and the y-coordinate values of CIE are 0.0853, 0.0198, and 0.0195. Therefore, phosphors satisfying 0.99 ≦ a ≦ 1.1 can secure excellent color purity. However, in terms of luminance, since the phosphor 13 and the phosphor 14 have better luminance characteristics than the phosphor 12, the Mg composition a may be preferably in the range of 1.0 to 1.1.

<Example 7>

In order to evaluate the change of optical properties according to the composition of Si, the composition b of Si according to the composition formula of (Sr _x Ba _y ) Mg _a Si _b O ₈ : Eu _z was controlled as shown in Table 4. Prepared. That is, b was increased to 1.9, 2.0 and 2.1. However, x is 0.8, y is 2.1, z is 0.1, and a is 1.

Table 4

Example	Furtherance	Center wavelength (nm)	CIE color coordinates
Phosphor 15	(Sr 0.8 Ba 2.1 ) Mg 0.99 Si 1.9 O 8 : Eu 0.1	441	(0.1756, 0.3189)
Phosphor 16	(Sr 0.8 Ba 2.1 ) Mg 0.99 Si 2 O 8 : Eu 0.1	437	(0.1579, 0.0198)
Phosphor 17	(Sr 0.8 Ba 2.1 ) Mg 0.99 Si 2.1 O 8 : Eu 0.1	442	(0.1687, 0.2692)

Referring to Table 4, when excited at 254 nm in the same manner as in Example 1, phosphors 15 to 17 have a central wavelength of 442 nm or less and a y coordinate value of CIE of 0.3189 or less. Phosphors satisfying 1.9 ≦ b ≦ 2.1 can secure excellent color purity and luminance characteristics.

Claims (15)

1. A light emitting device using a blue light emitting phosphor of Formula 1 and using a wavelength region capable of directly exciting Eu ²⁺ ions as an excitation wavelength:

   [Formula 1]

   (Sr _x Ba _y ) Mg _a Si _b O ₈ : Eu _z

   (Wherein

   0.5 ≦ x ≦ 1.5, 1.5 ≦ y ≦ 2.5,

   2.9 ≦ x + y ≦ 3.4, x <y,

   z is 0.01 <z <0.23,

   a is 0.99 ≦ a ≦ 1.1,

   b is 1.9 ≦ b ≦ 2.1.)
2. The light emitting device of claim 1, wherein the excitation wavelength is 240 to 300 nm.
3. The light emitting device according to claim 2, wherein the excitation wavelength is 254 nm.
4. The light emitting device according to claim 1, wherein the center of the emission wavelength of the phosphor is in the range of 420 nm to 450 nm.
5. The light emitting device of claim 1, further comprising: a blue light emitting phosphor of Chemical Formula 1 applied inside the sealing body; And a lighting device including a discharge gas enclosed in the sealing body.
6. 6. The light emitting device according to claim 5, wherein the discharge gas is discharged by a cold cathode or a filament.
7. The light emitting device of claim 5, wherein the discharge gas comprises mercury or a mixed gas of mercury and argon.
8. The light emitting device of claim 1, further comprising at least one phosphor selected from among red light emitting phosphors, green light emitting phosphors, and other types of blue light emitting phosphors.
9.  A display device comprising the light emitting device according to any one of claims 1 to 8.
10. Silicate phosphors represented by the following general formula (2):

    [Formula 2]

    (Sr _x Ba _y ) Mg _a Si _b O ₈ : Eu _z

    (Wherein

    0.5 ≦ x ≦ 1.5, 1.5 ≦ y ≦ 2.5,

    2.9 ≦ x + y ≦ 3.4, x <y,

    z is 0.12 ≦ z <0.23,

    a is 0.99 ≦ a ≦ 1.1,

    b is 1.9 ≦ b ≦ 2.1.)
11. The silicate-based phosphor according to claim 10, wherein the excitation wavelength absorbed by the host lattice is mainly 100 to 200 nm, and the excitation wavelength absorbed by direct Eu ²⁺ ions is mainly 240 to 300 nm.
12. The silicate-based phosphor according to claim 10, wherein the central wavelength at the 254 nm excitation wavelength is shorter than the central wavelength of the BAM.
13. The silicate-based phosphor according to claim 10, wherein the luminance at the 254 nm excitation wavelength is larger than that of the BAM.
14. The silicate-based phosphor according to claim 10, wherein the center of the emission wavelength is in the range of 420 nm to 450 nm.
15. The display apparatus provided with the silicate type fluorescent substance of Claim 10-14.

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