JP2003041250A - Phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphor that emits red light emission with higher brightness. SOLUTION: Europium oxide (Eu2 O3 ), Gadolinium chloride (GdCl3 ), lithium carbonate (Li2 CO3 ), and ammonium chloride (NH4 Cl) are mixed with a calcium sulfide (CaS) crystal powder. The mixture is put in an alumina crucible and baked at 1,000 deg.C in a nitrogen atmosphere for two hours.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a phosphor that emits fluorescence upon being excited by an electron beam.

[0002]

2. Description of the Related Art In an electron beam excitation light emitting device having a low acceleration voltage such as a fluorescent display tube, a phosphor that emits light even when an anode voltage is 10 V or less (a phosphor for low speed electron beam excitation) is used. For example, a ZnO: Zn phosphor that emits green light is well known as a phosphor of this type. Further, in recent years, in order to enable multicolor display, phosphors that can obtain various emission colors have been developed. For example, ZnCdS: Ag, Cl phosphor is mainly used as a red light emitting phosphor at present.

However, due to various regulations, the use of Cd is restricted, and it is becoming difficult to sell phosphors containing cadmium and devices using the same. On the other hand, there is CaS: Eu as a red light emitting phosphor that does not contain a regulated substance. In this, CaS is added (doped) as an activator as an emission center. Furthermore, with CaS: Eu, Li, Cl doped with Li and Cl as a co-activator, almost practical brightness is obtained. Here, in the phosphor, a mechanism has been proposed in which the activator serves as a donor and the co-activator serves as an acceptor to form a related luminescence center.

[0004]

However, while the red light emitting phosphor having higher brightness is required, the above-mentioned Ca
Even with S: Eu, Li, and Cl, the brightness has not been obtained to the required extent. The present invention has been made to solve the above problems, and an object of the present invention is to obtain red light emission with higher brightness.

[0005]

The phosphor according to one embodiment of the present invention comprises a matrix made of calcium sulfide, an activator made of europium, and a coactivator made of a rare earth element other than europium. It is a thing. In this phosphor, the luminescence from the co-activator due to electron impact is absorbed by the matrix and consumed by the red luminescence energy from the europium activator.

In the above phosphor, for example, lithium and chlorine may be added to the matrix. In the above phosphor, the coactivator may be, for example, cerium, gadolinium, or praseodymium.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. <Embodiment 1> First, a configuration example of the phosphor according to the first embodiment of the present invention will be described. The phosphor of the present embodiment is composed of a matrix made of calcium sulfide (CaS), an activator made of europium (Eu), and a co-activator made of cerium (Ce) which is a rare earth element other than europium. And lithium and chlorine are added.

A brief description will be made on a method for manufacturing this phosphor. Crystalline powder of calcium sulfide (CaS), europium oxide (Eu ₂ O ₃ ) and cerium chloride (CeCl) are used.
₃ ), lithium carbonate (Li ₂ CO ₃ ) and ammonium chloride (NH ₄ ) are mixed, these mixtures are put in an alumina crucible, and baked at 1000 ° C. for 2 hours in a nitrogen atmosphere. Each material had Eu ₂ O ₃ 0.
005 mol, CeCl ₃ 0.03 mol, Li ₂ CO ₃
Mix 0.1 mol and NH ₄ 0.1 mol.
As a result, a CaS: Eu, Ce, Li, Cl phosphor was obtained.

<Second Embodiment> Next, a structural example of a phosphor according to another embodiment of the present invention will be described. The phosphor of the present embodiment is composed of a matrix of CaS, an activator of Eu, and a coactivator of gadolinium (Gd) which is a rare earth element other than europium, and lithium and chlorine. Is added.

A brief description of the method for producing this phosphor
Then, it is oxidized into crystalline powder of calcium sulfide (CaS).
Europium (Eu₂O₃) And gadolinium chloride (Gd
Cl ₃) And lithium carbonate (Li₂CO₃) And ammonium chloride
Monium (NH_FourCl) are mixed and these mixtures are mixed with each other.
Put in a mina crucible, 1000 ℃, 2 hours in a nitrogen atmosphere
Is fired. Each material is Eu for 1 mol of CaS.
₂O₃0.005 mol, GdCl₃0.05 mol, L
i₂CO₃0.1 mol, NH_FourRatio of 0.1 mol of Cl
Mix with. As a result, CaS: Eu, Gd, Li, C
l phosphor was obtained.

CaS: Eu, Ce, L as described above
The characteristics of each of the i, Cl phosphor, the CaS: Eu, Gd, Li, Cl phosphor, and the conventional CaS: Eu, Li, Cl phosphor were investigated. In the investigation, first, a fluorescent display tube using each phosphor was prepared. In the manufactured fluorescent display tube, In ₂ O ₃ was added to each phosphor in the phosphor layer.
25 wt% was used. CaS: Eu, L
For fluorescent display tubes using i, Cl phosphors, CaS: E
In a fluorescent display tube using u, Ce, Li, and Cl phosphors,
The brightness is improved by 30%. In addition, CaS: Eu, Li, C
For a fluorescent display tube using a l phosphor, CaS: Eu, G
In the fluorescent display tube using the d, Li, and Cl phosphors, the brightness was improved by 50%.

Here, the CaS: Eu, Li, Cl phosphor will be considered. The excitation spectrum of the CaS: Eu, Li, Cl phosphor extends from the ultraviolet region to the visible region. When Ce is added as a co-activator to this phosphor, blue light emission is also seen from Ce ions, but while the concentration of Ce ions is low, all the blue light emission from Ce ions is absorbed by the matrix CaS, It is consumed as the energy of red emission from Eu ions. Thus, Ce
When the ions are added, the energy given to the Ce ions to emit light by electron impact is also reduced as a result.
It is considered that the red emission intensity is increased because the energy of red emission from the ions is obtained.

Similarly, when Gd is added as a co-activator, the ultraviolet rays generated from Gd ions are the main component of Ca.
It is considered that it is absorbed by S and is consumed as energy of red light emission from Eu ions, and as a result, the red light emission intensity is increased. The same thing as these occurs even when other rare earth element other than europium such as praseodymium (Pr) is added as a co-activator, and the red emission intensity can be increased.

[0014]

As described above, according to the present invention,
Since a coactivator made of a rare earth element other than Eu is added to the CaS: Eu phosphor, an excellent effect that red light emission can be obtained with higher brightness can be obtained.

Claims (3)

[Claims] 1. A phosphor comprising a matrix of calcium sulfide, an activator of europium, and a coactivator of a rare earth element other than europium. 2. The phosphor according to claim 1, wherein the base is one to which lithium and chlorine are added. 3. The phosphor according to claim 1, wherein the coactivator is any one of cerium, gadolinium and praseodymium.