KR20010111834A - A blue emitting phosphor for low-voltage applications and a method of preparing the same - Google Patents

Abstract

The blue phosphor of the present invention is prepared by adding a flux to a SrTiO ₃ phosphor matrix, followed by primary firing, and then secondary firing in a reducing atmosphere. A flux is added to the mixture of strontium salt and titanium oxide (TiO ₂ ), followed by mixing, followed by primary firing at 1100 to 1400 ° C. for 1 to 6 hours in an air atmosphere. The primary fired material is secondary fired at 1000 to 1300 ° C. for 0.5 to 2 hours in a reducing atmosphere to impart conductivity to the phosphor. The low-voltage SrTiO ₃ blue phosphor of the present invention may be used by adding a conductive material such as In ₂ O ₃ , V ₂ O ₅ , WO _3, or the like.

Description

Low voltage blue phosphor and its manufacturing method {A BLUE EMITTING PHOSPHOR FOR LOW-VOLTAGE APPLICATIONS AND A METHOD OF PREPARING THE SAME}

[Industrial use]

The present invention relates to a low voltage blue phosphor and a method of manufacturing the same, and more particularly, to a low voltage driveable blue phosphor that can be applied to a low voltage display device such as VFD or FED and a method of manufacturing the same.

[Prior art]

Low voltage displays of less than 1 kV include vacuum fluorescent display (VFD) and field emission display (FED). VFD is mainly used for various display devices such as home appliances, AV, automobiles, etc., and FED is being actively researched as a next-generation small flat panel display device. These low voltage display devices have a structure in which electrons emitted from an electron emitter such as a hot wire emit light to emit a phosphor, thereby reproducing a desired image.

Phosphors for low voltage drive devices such as FED and VFD should have low resistance, low emission start voltage, high luminous efficiency at low speed voltage, no luminance saturation, less defects on the surface of phosphor particles, and low electron excitation emission state. It should be stable and not degrade.

Currently, sulfide phosphors are widely used as phosphors for low voltage driving devices. The sulfide-based phosphor used as the low voltage blue phosphor is ZnS: Zn. This phosphor is excellent in luminous efficiency but has a disadvantage in that the sulfide is decomposed under high current and low voltage conditions, so that the phosphor itself is not stable and the life is short.

Since sulfide-based phosphors have high resistance of a host material and emit low-speed electron beam excitation light emission, a conductive material is added and used as a method for lowering resistance. However, the development of non-sulfide-based phosphors has been actively progressed due to the problem of sulfide-based gas emission and phosphor material decomposing and scattering the electron beams during the electron beam excitation, thereby degrading the cathode filament and reducing phosphor efficiency.

An object of the present invention is to provide a low-voltage blue phosphor for chemical stability, long life and excellent conductivity, and a method of manufacturing the same.

It is another object of the present invention to provide an oxide-based blue phosphor that does not contaminate the cathode pilates.

In order to achieve the above object, in the present invention, the flux is added to the SrTiO ₃ phosphor matrix, and then calcined first, and then calcined in a reducing atmosphere to prepare a low voltage blue phosphor.

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

As a first step in the process of manufacturing the blue phosphor of the present invention, a flux is added to the mixture of strontium salt and titanium oxide (TiO ₂ ) and mixed. As the salt containing strontium, SrCO ₃ or Sr (NO ₃ ) ₂ may be used, and the molar ratio of strontium salt and titanium oxide is preferably 0.6 to 1: 1, more preferably 0.8 to 1: 1. And most preferably 0.8: 1. If the molar ratio of strontium salt and titanium oxide is out of the above range, it is not preferable because the luminance of the produced phosphor is lowered. Li ₃ PO ₄ , Li ₂ CO ₃ , Na ₃ PO ₄ , K ₂ HPO ₄ or KF may be used as the compound used as the flux. These compounds grow or control particle size. The amount of the flux is preferably 10 to 50 mol%, and if it exceeds this range, there is a problem that the luminance of the phosphor to be produced is lowered.

In a second step, the mixture is first calcined under an atmospheric atmosphere at a temperature of 1100-1400 ° C. for 1-6 hours. The SrTiO ₃ matrix is formed through a primary firing process, in which the flux is removed by volatilization.

The primary fired material is subjected to secondary firing at a temperature of 1000 to 1300 ° C. for 0.5 to 2 hours under a reducing atmosphere. Through this secondary firing process, the crystallinity of the phosphor may be increased to improve luminance. When the first calcined material is secondarily calcined in a oxygen-deficient reducing atmosphere, the phosphor becomes conductive. The reducing atmosphere is a mixed atmosphere of H ₂ 5 vol% and N ₂ 95 vol%.

The secondary calcined material is classified using a sieve to produce a low voltage blue phosphor. The low-voltage SrTiO ₃ blue phosphor of the present invention may be used by adding a conductive material such as In ₂ O ₃ , V ₂ O ₅ , WO _3, or the like. The conductive material is preferably added in an amount of 10 to 20% by weight based on the phosphor.

The following presents a preferred embodiment to aid the understanding of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to the following examples.

Example 1-3

SrCO ₃ , TiO ₂ and Li ₃ PO ₄ were mixed in the amounts shown in Table 1 below. The mixture was first calcined in an atmosphere and then calcined in a reducing atmosphere to prepare SrTiO ₃ , which is a blue phosphor. Temperature and time at the time of primary baking and secondary baking are as Table 1 below.

Example 4

A phosphor was prepared in the same manner as in Example 1, except that 15 wt% of In ₂ O ₃ was added to SrTiO ₃ , which is a blue phosphor.

Comparative Example 1

A blue phosphor was prepared in the same manner as in Example 1 except that SrCO ₃ and TiO ₂ were mixed in the amounts shown in Table 1 and Li ₃ PO ₄ was not added during the first firing.

Comparative Example 2

A blue phosphor was prepared in the same manner as in Comparative Example 1 except that the material was calcined in an air atmosphere for the second time.

SrCO ₃ [g] TiO ₂ [g] SrCO ₃ : TiO ₂ molar ratio Li ₃ PO ₄ [% by weight] Primary firing condition Second firing condition Temperature [℃] Time [h] Temperature [℃] Time [h] Example One 147.63 79.8986 1: 1 1.5 1300 6 1100 One 2 147.63 63.91904 1: 0.8 1.5 1300 6 1100 One 3 147.63 47.73928 1: 0.6 1.5 1300 6 1100 One 4 147.63 79.8988 1: 1 1.5 1300 6 1100 One Comparative example One 147.63 79.8988 1: 1 0 1300 6 1100 One 2 147.63 63.91904 1: 0.8 0 1300 6 1100 One

The CIE color coordinates and relative luminance of the phosphors of Examples 1-4 and Comparative Examples 1-2 were measured at a driving voltage of 27 V, and the results are shown in Table 2 below.

Color coordinates Relative luminance (%) x y Example One 0.18 0.19 100 2 0.19 0.20 120 3 0.18 0.19 70 4 0.19 0.21 200 Comparative example One 0.18 0.19 70 2 0.19 0.20 80

As shown in Table 2, it can be seen that the relative luminance of the phosphors of Examples 1 to 4 is superior to Comparative Examples 1 to 2.

The blue phosphor for low voltage according to the present invention is first baked after adding a flux to the SrTiO ₃ phosphor matrix, and then calcined in a reducing atmosphere to increase conductivity and to be chemically stable and thus have a long service life. In addition, the low driving voltage can be applied to low voltage display devices such as VFD or FED.

Claims (6)

Adding a flux to a mixture of strontium salt and titanium oxide (TiO ₂ ) and mixing the mixture; Firstly baking the mixture at 1100 to 1400 ° C. for 1 to 6 hours in an air atmosphere; And Second firing the first calcined material at 1000 to 1300 ° C. for 0.5 to 2 hours in a reducing atmosphere; A low voltage blue phosphor manufacturing method comprising a. The method of producing a blue phosphor for low voltage according to claim 1, wherein a mixing molar ratio of the strontium salt to titanium oxide is 0.6 to 1: 1. The method of claim 1, wherein the flux is selected from the group consisting of Li ₃ PO ₄ , Li ₂ CO ₃ , Na ₃ PO ₄ , K ₂ HPO _4, and KF. The method for producing a low voltage blue phosphor according to claim 3, wherein the addition amount of the flux is 10 to 50 mol%. A low voltage SrTiO ₃ blue phosphor prepared according to any one of claims 1 to 4. The low-voltage SrTiO ₃ blue phosphor according to claim ₅ , further prepared by adding a conductive material selected from the group consisting of In ₂ O ₃ , V ₂ O _5, and WO ₃ to the phosphor.