KR20090081242A - A rare-earth phospho-vanadate red-emitting phosphor for the cold cathode fluorescent lamp - Google Patents

Abstract

A rare earth element phosphovanadate-based red phosphor, and a cold cathode fluorescent lamp using the phosphor are provided to improve luminous characteristic and color purity at the excitation wavelength of 254 nm. A rare earth element phosphovanadate-based red phosphor excites in the long wavelength UV range of 250 ~ 350 nm and is represented by (Y_(1-a-b-d) Gd_b Sc_d)(P_(1-c) V_c)O4:Eu_a, wherein 0.1 <= a <= 0.4; 0 <= b <= 0.6; 0.4 <= c <= 1; and 0 <= d <= 0.4.

Description

A rare-earth phospho-vanadate red-emitting phosphor for the cold cathode fluorescent lamp

The present invention can be usefully used as a red phosphor for cold cathode fluorescent lamps (CCFLs) as a rare earth phospho-vanadate phosphor having luminescence intensity and high color purity under 254 nm ultraviolet excitation.

Recently, research has been actively conducted on a backlight unit having high efficiency and high color purity characteristics used in liquid crystal display (LCD) televisions and monitors. LCD, which has emerged as the core display of digital multimedia devices, does not emit light by itself unlike plasma display panels (PDPs) and field emission displays (FEDs), so that the entire LCD screen is uniformly revealed. The state requires a separate light emitting unit. Most of the backlights commonly used with this unit use a cold cathode fluorescent lamp (CCFL) as the light source.

In the cold cathode fluorescent lamp, electrons present in the tube are attracted to the electrode (anode) by a high voltage induced at both ends of the glass tube in which the quantitative mercury gas is mixed. Is initiated. 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. Accordingly, the applied fluorescent material absorbs 254 nm ultraviolet rays and emits visible light having a relatively long wavelength.

As the demand for high-quality LCD is expanded, more than 95% of the color reproduction range is required compared to NTSC (National Television System Committee) to improve color purity characteristics, which are relatively weak compared to competing media such as PDP and CRT. Therefore, it is essential to develop a phosphor having high color reproducibility in order to widen the range of color reproduction.

On the other hand, Japanese Laid-Open Patent Publication No. 1999-73138 discloses that the (Y, Gd, Eu) (P, V) O ₄ phosphor having the same composition as in the present invention is already luminous efficiency, luminance and color purity under vacuum ultraviolet (147 nm) excitation. Discloses that is improved. This discloses only the effect at 147 nm, which is a vacuum ultraviolet region, and has limited use thereof.

In the present invention, the rare earth phospho-vanadate phosphor, which is known as a red phosphor excellent in the ultraviolet excitation conditions, has a high luminous intensity and improved color purity in the 254 nm ultraviolet region under mercury-sealing conditions, and thus can be applied to a light emitting device such as CCFL. The purpose is to know and provide them.

The present invention is characterized by a rare earth phospho-vanadate-based red phosphor represented by the following general formula (1) which is excited in a long wavelength ultraviolet region in the range of 250 to 350 nm.

(Y _1-abd Gd _b Sc _d ) (P _1-c V _c ) O ₄ : Eu _a

In Formula 1, 0.1 ≦ a ≦ 0.4, 0 ≦ b ≦ 0.6, 0.4 ≦ c ≦ 1.0, and O ≦ d ≦ 0.4.

In addition, the present invention has another feature of the cold cathode fluorescent lamp manufactured by applying the rare earth phospho-vanadate-based red phosphor.

The red phosphor according to the present invention has excellent luminescence brightness and color purity under 250-350 nm excitation, which is an ultraviolet region, and in particular, since the luminescence properties and color purity at 254 nm excitation wavelength are improved compared to conventional commercial phosphors, Application is possible.

The present invention relates to a rare earth phospho-vanadate red phosphor having high brightness under 254 nm excitation, which is a long wavelength ultraviolet region, and having excellent color purity, which can be usefully applied to CCFLs.

The phosphor composition similar to the present invention is a composition which is conventionally known as a red phosphor for ultraviolet excitation, in particular, for PDP (Japanese Patent Laid-Open No. 1999-73138). In general, the required physical properties vary greatly depending on the field in which the phosphor is applied. The red phosphor of Japanese Patent Application Laid-Open No. 1999-73138 uses a wavelength of 147 nm as an excitation source in a high vacuum of 10 ^-2 torr or less to provide a PDP field. In order to be easy to apply and to apply for CCFL like the present invention, ultraviolet rays having a wavelength of 254 nm at 50 to 70 torr having a low degree of vacuum are used as excitation sources.

Even in the case of the phosphor of the same composition, the light emitting properties are completely different depending on the field of use, and related literatures known in this regard are described in more detail as follows.

YBO ₃ : Eu, GdBO ₃ : Eu, and (Y, Gd) BO ₃ : Eu, which are red phosphors for PDP using 147 nm excitation source, which is vacuum ultraviolet light, have very low light efficiency with respect to other excitation sources. There is a deterioration problem and its use is not suggested.

In addition, YVO ₄ : In the case of Eu, the luminance characteristic varies significantly depending on the excitation wavelength and the operating temperature. At room temperature, the emission efficiency is better than that at 365 nm when using a wavelength of 254 nm as the excitation source, but 365 nm at a high temperature of 200 ° C. or higher. Luminous efficiency is better under excitation source. In the case of the representative Y ₂ SiO ₅ : Ce ³⁺ and Tb ³⁺ phosphors as the luminance change according to the concentration of the light emitting element, when the concentration of Ce ³⁺ is less than 1 atom, the excitation wavelength is 254 nm than that of 365 nm. Although it emits light efficiently, it is more efficient at 365 nm when the concentration of Ce ³⁺ is 3 atom or more.

Therefore, even though phosphors of the same component have different luminous efficiencies due to factors such as excitation source energy, temperature, and activator concentration, the optimum physical properties of the phosphors required for a specific application must be secured. [Reference: Shigeo Shiomoya, William M. Yen , Phosphor handbook, CRC press, 1998, Chapters 5-10].

Accordingly, the phosphor of the present invention exhibits excellent luminescent properties in the long wavelength ultraviolet region of 250 to 350 nm, which is completely different from the known excitation wavelength, and relates to a phosphor for a new use that is easy to apply for CCFL. As described above, since the conventional phosphor exhibits completely different light emission characteristics according to the change of the excitation wavelength, the phosphor having a specific use of the present invention is not a result obtained by simply applying different excitation wavelength ranges.

In addition, the phosphor of formula (1) according to the present invention is particularly preferably when a certain amount of scandium (Sc), a = 0.10, b = 0.40, c = 0.80 in the formula (1), and change to O ≤ d ≤ 0.4 In this case, the mixed scandium (Sc) emits high purity red light because it exhibits characteristics close to the color coordinate of CIE (x, y) = (0.77, 0.34), which is an NTSC-red standard coordinate system.

Looking at the method for producing a rare earth phospho-vanadate-based red phosphor according to the present invention in more detail.

First, a mixture is prepared by weighing a yttrium (Y) precursor, a gadolinium (Gd) precursor, a scandium (Sc) precursor, a phosphorus (P) precursor, a vanadium (V) precursor, and a europium (Eu) precursor in the range shown in Chemical Formula 1. .

The yttrium (Y) precursor, gadolinium (Gd) precursor, scandium (Sc) precursor, phosphorus (P) precursor vanadium (V) precursor and europium (Eu) precursor are generally used in the art, but are not particularly limited. One or a mixture of two or more selected from the respective nitrates, acetates, chlorides, oxides and carbonates can be used. Preferably, the yttrium (Y) precursor is yttrium oxide, the gadolinium (Gd) precursor is gadolinium oxide, the scandium (Sc) precursor is scandium oxide, the phosphorus (P) precursor is diammonium hydrogen phosphate, and the vanadium (V) precursor is vanadium oxide And europium (Eu) precursor may use europium oxide.

The mixture of precursors is sufficiently mixed to have a uniform composition using a solvent selected from acetone, alcohol and water for more effective mixing and using a mixer such as ball milling or agate mortar. The solvent is used in the range of 100 to 500% by weight with respect to the precursor mixture. If the amount is less than 100% by weight, it is difficult to form the precursor mixture in the slurry phase. It is preferable to maintain the above range because a problem occurs that the solvent removal process is not easily performed.

Next, the mixture is dried at 100 to 150 캜, preferably at 120 to 130 캜 for 1 to 24 hours. The drying is performed to remove the solvent used to form the slurry phase of the precursor, is carried out using a method commonly used in the art, in the present invention uses a drying oven. If the drying temperature is less than 100 ℃, it is difficult to completely remove the solvent used, and if it exceeds 150 ℃, the boiling point of the solvent in the temperature range above the boiling point of the solvent used may cause loss of sample due to the problem of loss of operation. It is preferable to maintain the above range because is generated.

Next, the dried mixture is heat treated at 900 to 1200 ° C, preferably at 1000 to 1100 ° C for 10 hours or less, preferably 3 to 10 hours. The heat treatment is not particularly limited to a method generally used in the art, but in the present invention, the heat treatment is performed by using an electric furnace in a high purity alumina boat. If the firing temperature is less than 900 ℃, the substitution of the europium activator, calcium, strontium element is not completely made, if it exceeds 1200 ℃ it is preferable to maintain the above range because aggregation occurs between the phosphor particles.

Next, the heat treated phosphor is subjected to a post-treatment process such as pulverization, and the pulverization is pulverized into various sizes according to the size of the target particle. The pulverization is performed by a method generally used in the art, and specifically, a mortar, a ball mill, or the like may be used.

And a red phosphor prepared as described above is a CIE chromaticity coordinate x of 0.658 ~ 0.675 CIE y is 0.324 ~ 0.330, the Y ₂ O ₃ in a commercially available prior art The relative luminance (%) relative to the Eu phosphor is in the range of 75 to 112, and in particular, the red phosphor containing scandium has more excellent color coordinate characteristics, and the CIE x of the color coordinates is 0.674 to 0.675 and the CIE y is 0.325 to 0.326.

Such a rare earth phospho-vanadate-based red phosphor is excited in a long wavelength ultraviolet ray region in the range of 250 to 350 nm and exhibits excellent light emission characteristics as described above, which is advantageous for application to a light emitting device such as a cold cathode fluorescent lamp (CCFL).

Hereinafter, the present invention has been described in more detail based on the following examples, but the present invention is not limited to the following examples.

Examples 1-4: (Y _0.80-x Gd _0.20 ) (P _0.60 V _0.40 ) O ₄ Eu _x Phosphor

Yttrium oxide, gadolinium oxide, diammonium hydrogen phosphate, vanadium oxide, and europium oxide were weighed according to the compositional formula shown in Table 1 below, and 200% by weight of acetone was added thereto, followed by mixing sufficiently evenly using agate mortar. Was prepared. The prepared mixed sample was dried at 120 ° C. for 1 hour using an oven, placed in a high purity alumina boat, and heat-treated at 1200 ° C. under an atmospheric condition for 8 hours using an electric furnace. The heated product was sufficiently ground to prepare (Y _0.80-x Gd _0.20 ) (P _0.60 V _0.40 ) O ₄ : Eu _x red phosphor.

Examples 2-4: (Y _0.80-x Gd _0.20 ) (P _0.60 V _0.40 ) O ₄ Eu _x Phosphor

But the same manner as in Example 1, by mixing while changing the molar ratio of the europium content ratio shown in the following Table 1 (Y _x Gd _{0 .80- 0 .20)} (P _{0 .60 0 .40} V) O ₄ : A red phosphor of Eu _x was prepared.

Examples 5-7: (Y _0.90-x Gd _x ) (P _0.60 V _0.40 ) O ₄ Eu _0.10 Phosphor

But the same manner as in Example 1, 0.1 mol of europium was fixed and varying the molar ratio of yttrium to gadolinium is composition _{(Y 0 .90- x Gd x)} (P 0 .60 V 0 .40) O 4 : To prepare a red phosphor Eu _{0 .10.}

Examples 8-10: (Y _0.50 Gd _0.40 ) (P _1.00-x V _x ) O ₄ Eu _0.10 Phosphor

Example 1, but the same manner and, by fixing the gadolinium 0.4 moles changing the molar ratio of phosphorus and vanadium the composition _{(Y 0 .50 Gd 0 .40)} (P 1 .00- x V x) O 4 : To prepare a red phosphor Eu _{0 .10.}

Examples 11-15: (Y _0.50-x Gd _0.40 Sc _x ) (P _0.20 V _0.80 ) O ₄ Eu _0.10 Phosphor

The synthesis was carried out as Example 1, but weighed by the addition of scandium oxide, vanadium fixed 0.8 mol and by changing the composition and the molar ratio of yttrium and scandium _{(Y 0 .50-x Gd 0.40} Sc x) (P 0.20 V _A red phosphor of _0.80 ) O ₄ : Eu _0.10 was prepared.

Comparative Example 1

Commercial Y ₂ O ₃ : Eu red phosphor.

Comparative Example 2

Commercially available (Y, Gd) BO ₃ : Eu red phosphor.

Experimental Example 1

The phosphors obtained in Examples 1 to 15 and Comparative Examples 1 and 2 were observed for absorption and emission spectra in a wavelength range of 200 to 500 nm using a monochromator and a photomultiplier tube (PSI). Color coordinate values were measured using the same system, and the results are shown in Table 1 below.

Table 1 shows the relative luminance and color coordinates of the example when the light emission luminance of the Y ₂ O ₃ : Eu phosphor is represented by 100 using light of 254 nm wavelength as the excitation energy source. For example 1, relative luminance of up to 112% is shown. In addition, the color coordinate at this time moved to (X, Y) = (0.668, 0.325), which was improved from the conventional color coordinates (X, Y) = (0.647, 0.343), thereby exhibiting excellent color purity characteristics. In particular, when scandium (Sc) was added, color purity improved further with color coordinates (X, Y) = (0.674, 0.326).

Accordingly, it was found that the red phosphor of the present invention is a red phosphor having the property of being excited from ultraviolet rays of 254 nm wavelength, which is superior to the conventional red phosphor and is suitable as a red phosphor for CCFL. From these results, the phosphor of the present invention is excellent not only in an excitation energy source such as vacuum ultraviolet ray (Japanese Patent Laid-Open Publication No. 1999-73138) but also in the ultraviolet region, so that the phosphor can be used for CCFL as well as PDP. It was possible to confirm.

1 is a representative red phosphor Y ₂ O ₃ : Eu phosphor according to the present invention _{(Y 0.45 Gd 0.40 Sc 0.05)} (P 0.20 V 0.80) O 4: Eu 0 .10 illustrates the light emission characteristics (Photoluminescence, PL) of the phosphor, according to the present invention (Y _0.45 Gd _0.40 Sc _0.05 ) (P _0.20 V _0.80 ) O ₄ : Eu _{0.10 The} phosphor has a slightly lower emission luminance at 94% of Y ₂ O ₃ : Eu at an excitation wavelength of 254 nm, but high color reproducibility is required because of excellent color purity. It was confirmed that it can be usefully used for the CCFL light emitting device.

2 shows (Y, Gd) (P, V) O ₄ : Excitation spectrum and emission spectrum of the red phosphor represented by Eu are compared with Y ₂ O ₃ : Eu red phosphor, and FIG. 3 shows (Y, Gd, Sc) (P, V) to which scandium (Sc) is added. The color coordinates of the O ₄ : Eu red phosphor are shown in comparison with the Y ₂ O ₃ : Eu red phosphor. It can be seen from FIG. 2 that the phosphor of the embodiment has an excellent absorption characteristic compared to the Y ₂ O ₃ : Eu phosphor at an excitation wavelength of 254 nm, thereby causing an increase in the luminance of light emitted. It was confirmed that the phosphor of, Gd, Sc) (P, V) O ₄ : Eu had better color purity than the Y ₂ O ₃ : Eu red phosphor.

1 illustrates (Y, Gd, Sc) (P, V) O ₄ according to the present invention. : The emission spectrum of the Eu red phosphor at ultraviolet wavelength 254 nm is shown.

2 shows (Y, Gd) (P, V) O ₄ according to the present invention. : Excitation spectrum showing PL relative intensity according to the wavelength range of 200 nm to 500 nm of Eu red phosphor and emission spectrum when UV irradiation at excitation wavelength 254 nm.

3 shows (Y, Gd) (P, V) O ₄ according to the present invention. : Color coordinate of Eu red phosphor is shown.

Claims (2)

Rare earth phospho-vanadate-based red phosphors represented by the following general formula (1) excited in the long wavelength ultraviolet region in the range of 250 to 350 nm: [Formula 1] (Y _1-abd Gd _b Sc _d ) (P _1-c V _c ) O ₄ : Eu _a In Formula 1, 0.1 ≦ a ≦ 0.4, 0 ≦ b ≦ 0.6, 0.4 ≦ c ≦ 1, and O ≦ d ≦ 0.4. Cold cathode fluorescent lamp prepared by applying a rare earth phospho-vanadate-based red phosphor represented by the following formula (1) excited in the long wavelength ultraviolet range of 250 ~ 350 nm: [Formula 1] (Y _1-abd Gd _b Sc _d ) (P _1-c V _c ) O ₄ : Eu _a In Formula 1, 0.1 ≦ a ≦ 0.4, 0 ≦ b ≦ 0.6, 0.4 ≦ c ≦ 1, and O ≦ d ≦ 0.4.

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