KR100268715B1 - A blue mixed phosphor - Google Patents

Abstract

PURPOSE: A mixed-blue fluorescent substance is provided for illuminating blue color of the display element driven under high current density and high pressure by preparing the substance with specific mixture of zinc sulfide and lanthanum oxide. CONSTITUTION: The mixed-blue fluorescent substance having luminescent blue color useful in the production of the display element comprises zinc surfide(ZnS:Ag,Al) having Ag restoring, Al co-restoring abilities and lanthanum oxide chloride(LaOCl:Tb) having Tb restoring ability in a ratio of less than 15 wt.% of LaOCl:Tb component based on the weight of ZnS:Ag,Al component. The blue fluorescent material has excellent brightness and gamma value designed by (the brightness at 120 micro-ampere to the brightness at 60 micro-ampere) x 1/6 under 25 kV.

Description

Mixed Blue Luminescent Phosphors

1 is a graph showing emission spectra of red light emitting phosphors (Y ₂ O ₃ : Eu) and green light emitting phosphors [LaOCl: Tb and Y ₃ (Al, Ga) ₅ O ₁₂ : Tb], where a is Y ₂ O ₃ For the: Eu phosphor, b for the LaOCl: Tb phosphor, c for the Y ₃ (Al, Ga) ₅ O ₁₂ : Tb phosphor.

2 is a graph showing the emission spectrum of the conventional phosphor and the mixed blue light emitting phosphor of the present invention, where a is for the conventional ZnS: Ag, Al phosphor, and b and c are for the mixed phosphor of the present invention.

The present invention relates to a mixed blue light emitting phosphor, and more particularly, to a projection mixed blue light emitting phosphor having high luminance saturation characteristics and high emission luminance.

Recently, color CRTs, display tubes, and projection tubes have become larger and higher in size. Since the cathode ray tube operates under a higher excitation than a conventional cathode ray tube, the temperature of the fluorescent surface increases significantly during operation, and thus, the used phosphor causes temperature quenching, saturation of current luminance, and deterioration. have.

Therefore, in order to solve such a problem, a method of controlling the temperature rise of the cathode ray tube fluorescent surface by air cooling or water cooling, or employing a phosphor having excellent current luminance saturation characteristics is employed.

In particular, in order to increase the luminance, the excitation voltage and the current density are increased, and thus, the use of a phosphor having excellent luminance characteristics (hereinafter referred to as γ characteristics) is required, which is high enough even when the current density increases during operation of the display device. To get it. Particularly, a phosphor having excellent γ properties is required for a blue phosphor. The green and red phosphors used for high current, density, and high voltage driving tubes or display tubes are composed of rare earth materials and have excellent γ properties. This is because the phosphor uses a conventional zinc sulfide-based phosphor having a low γ characteristic.

Accordingly, in the case of blue light emitting phosphors, ZnS: Ag, Al phosphors, which are different from ZnS: Ag, Cl, which are used in general commercial cathode ray tubes, have been developed and used to improve γ and deterioration characteristics. There is a lot of room for improvement of the luminance characteristic, and the research is continued.

Japanese Patent Laid-Open No. 52-30158 and Japanese Patent Laid-Open No. 55-1003 disclose that ZnS: Ag, Cl and ZnS: Ag, Al phosphors exhibit excellent luminescence properties when they have a cubic crystal structure. So-60-21676 discloses a technique of improving the luminance by shifting color coordinates toward longer wavelengths by adding Cu to a ZnS: Ag, Al phosphor. In European Patent Publication EP0408113 A1, Cd and ZnS: Ag, Al phosphors are disclosed. The technique which improved brightness by adding Se and adjusting a color coordinate is disclosed. However, both of them are insufficient to solve the fundamental problem of zinc sulfide-based phosphors.

SUMMARY OF THE INVENTION An object of the present invention is to provide a mixed blue light-emitting phosphor in which the γ characteristic and the luminance characteristic are greatly improved in response to the above studies.

The present invention for achieving the above object is characterized by being composed of a mixed blue light emitting phosphor of silver activating, aluminum sintered zinc sulfide phosphor (ZnS: Ag, Al) and terbium-activated lanthanum phosphate phosphor (LaOCl: Tb) have.

In particular, the mixing amount of the phosphor is preferably such that the amount of LaOCl: Tb phosphor is 15% by weight or less based on the ZnS: Ag, Al phosphor. When the mixing amount of LaOCl: Tb phosphor exceeds 15% by weight, the brightness enhancement effect is further increased, but color purity becomes disadvantageous. Therefore, the optimum mixing ratio considering the effects of brightness and color purity is 15% by weight or less, Since the effect of this invention is acquired, it is good to be larger than 9 weight%. More preferably, the amount of LaOCl: Tb phosphor is mixed so as to be in the range of 2 to 10% by weight of the ZnS: Ag, Al phosphor.

LaOCl: Tb phosphor is commonly used as a projection green light emitting phosphor, which is a rare earth-based phosphor having excellent γ characteristics (γ-0.75 of ZnS: Ag, Al phosphor and γ = 0.82 of LaOCl: Tb phosphor). Compared with this, the luminance due to the luminous efficiency is high. In the present invention, a small amount of LaOCl: Tb green light-emitting phosphor having such characteristics is mixed with a ZnS: Ag, Al blue light-emitting phosphor to obtain a significant increase in luminance and improvement of gamma characteristics due to a slight color coordinate change.

Hereinafter, the method of manufacturing the mixed phosphor of the present invention will be described in detail through specific examples.

First, a ZnS: Ag, Al phosphor is prepared as follows.

Each compound is uniformly mixed and then calcined at 990 ° C. for 2 hours in a reducing atmosphere using carbon or nitrogen gas. Post-treatment processes such as ball milling, washing and surface treatment are performed to obtain a ZnS: Ag, Al blue light emitting phosphor.

Next, LaOCl: Tb phosphor was prepared as follows.

First, in order to uniformly mix the two compounds, they are dissolved in an appropriate amount of nitric acid to prepare an oxalic acid co-precipitate of La and Tb using 70 g of oxalic acid. After drying, the mixture was dry mixed with 50 g of NH ₄ Cl and calcined at 1100 ° C. for 2 hours and 30 minutes in a reducing atmosphere using a tube furnace. Wash and dry to give LaOCl: Tb phosphor.

The obtained two phosphors were mixed to prepare a mixed blue light-emitting phosphor of the present invention, but the mixed amounts of LaOCl: Tb phosphors were 5% by weight (Sample # 2) and 10% by weight (Sample # 2) with respect to ZnS: Ag and Al phosphors. 3) and 15% by weight (sample # 4).

Phosphor characteristics for each obtained sample are shown in Table 1 below.

ZnS: Ag, Al single phosphor was designated as sample # 1.

TABLE 1

The color coordinates and relative luminance were measured by Cathodoluminescence System, and the γ characteristic was measured by changing the current value to 50 to 120μA at 20KV driving voltage using the PTE measurement system, and then measuring the brightness by changing the current value to 50 to 120μA. After the calculation was performed according to the following equation. At this time, the raster season was 30 cm x 3 cm.

Using the sample # 2 of Table 1 (when mixing 5 wt% of LaOCl: Tb phosphor) as an example, the characteristics of the mixed phosphor of the present invention are compared with a conventional ZnS: Ag, Al single phosphor (Sample # 1). It can be seen that the X coordinate is increased by 0.0043 and the Y coordinate is increased by about 0.01, which means that the green light emitting area is slightly changed. While there is no significant loss in terms of color purity, the luminance is improved by 16.3% and the γ characteristic is also greatly increased from 0.725 to 0.760.

When the LaOCl: Tb blue light-emitting phosphor is mixed with the ZnS: Ag, Al blue light-emitting phosphor as in the present invention, the color purity of blue may be degraded. By the way, it is known that the red phosphor and the green phosphor, which are usually used for high current density or high voltage driving CRTs, do not exhibit pure red color or pure green color, and have light emission peaks in areas other than the red and green areas.

The emission spectra of Y ₂ O ₃ : Eu (a), which are representative red light emitting phosphors, and LaOCl: Tb (b) and Y ₃ (Al, Ga) ₅ O ₁₂ : Tb (c) which are typical red light emitting phosphors in FIG. Indicated. The red light-emitting phosphor has the highest emission intensity near 615 nm, slightly larger peaks in the region of 700 nm or more, and smaller peaks in the region near 570 nm. The peak appearing in the wavelength range of 615 nm or more is red, so it does not matter, but the peak appearing in the area of 600 nm or less is an undesirably green peak. In the case of LaOCl: Tb and Y ₃ (Al, Ga) ₅ O ₁₂ : Tb phosphors, which are green light emitting phosphors, in addition to the peaks of the green light area (near 550 nm) which is the main light emission peak, the blue light emitting area is below 500 nm and the red light emitting area is 600 nm. It turns out that it has a peak in the above wavelength range. That is, the problem of the color purity change of the mixed blue light emitting phosphor of the present invention does not deviate significantly from the range of the color purity error of the conventional single phosphor.

FIG. 2 shows the emission spectra of the conventional single ZnS: Ag, Al blue light emitting phosphor (a) and the mixed blue light emitting phosphors (b, c) of the present invention, where a shows a conventional ZnS: Ag, Al phosphor. The curve shows the highest emission intensity in the blue region, and b (a phosphor mixed with 5% by weight of LaOCl: Tb phosphor) and c (a phosphor mixed with 15% by weight of LaOCl: Tb phosphor) representing the mixed phosphor of the present invention are green. It can be seen that the peak appears near the 550 nm, which is a light emitting region, unlike the conventional phosphor. In particular, it can be seen that as the mixing amount of LaOCl: Tb phosphor increases, the green peak in the region near 550 nm increases.

However, as described above with reference to FIG. 1, the emission spectra of the red and green light emitting phosphors, it can be seen that these incidental peaks are not a serious problem.

As described above, the mixed blue light-emitting phosphor of the present invention has an improved powder luminance of about 25% (when mixed by 10% by weight), and when used in a cathode ray tube, not only provides an effect of extending the life of the electron gun, but also provides a lower current to produce a constant luminance. Since it is possible to use, the electron beam diameter is reduced, and accordingly, the screen has a high definition effect, and the effect of extending the life of the fluorescent film is also expected.

Claims (2)

Silver-activated, aluminum ligated zinc sulfide phosphor (ZnS: Ag, Al) and terbium-activated lanthanum chloride phosphor (LaOCl: Tb) mixed blue light-emitting phosphor. The mixed blue light emitting phosphor according to claim 1, wherein the amount of the phosphor mixed with the LaOCl: Tb phosphor is 15 wt% or less based on the ZnS: Ag, Al phosphor.