JPS60231784A - Phosphor consisting of alkaline earth sulfide - Google Patents

Abstract

PURPOSE:To prepare a high-luminance multicolor phosphor consisting of an alkaline earth sulfide and having a long afterglow, by adding Y, Sc, Al, Ga or I as co-activator to a phosphor activated with a divalent cation. CONSTITUTION:At least one of yttrium, aluminum, gallium and indium is added as co-activator to a phosphor activated with a divalent cation. When a divalent cation such as Mn<2+>, Cu<2+> or Eu<2+> is used as activator, it replaces CA<2+> ion and does not cause surplus or shortage of valency electrons in a matrix crystal. When a trivalent cation is added as co-activator, it also replaces Ca<2+> ion, but is forms a deep electron trap and produces long afterglow, for a part of an excited carrier is returned to a basic state via the electron trap.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to alkaline earth sulfide phosphors, and more particularly to long afterglow phosphors. Alkaline earth sulfide substrates, mainly CaS, have been known for a long time as phosphor matrix materials that emit light with high efficiency, but due to their properties, their applications are limited to infrared stimulable phosphors and short-afterglow electron beams. It was limited to excitation fluorophores. However, in recent years, terminals such as information processing equipment, automatic control equipment, electronic computers, educational electronic equipment, electronic games, etc.
Demand for cathode ray tubes for displays is rapidly expanding. This cathode ray tube requires a phosphor with an extremely long afterglow compared to the moving picture cathode ray tubes conventionally used for televisions and the like. This is to suppress flickering that occurs as a result of displaying the still image of nine characters at a low sweep frequency. However, since the crystal structure of the alkaline earth sulfide substrate is simpler than that of the phosphor matrix, which has an oxygen octahedral structure,
Generally, it is difficult to obtain a long afterglow phosphor because of insufficient shielding between activated ions and between ions and host lattices9.

There are only a few long afterglow monochromatic display phosphors for display tubes that have been put into practical use, and the green phosphor Zn2SiO4:
Cds (Po4)z ・CdC6z: Mn(XO
Afterglow time τ1/.

Σ30mmec) is the main one. As this elongated afterglow color display phosphor, hexagonal ZnS:'''A2 (blue)
and Zn5(PO4)2: Mn (red) * Mg
SiO3: Mn (red).

Zn2 Si04: Mn, As (green), etc., and for white display, mixed phosphor hexagonal Z
nS:Ag7' lath (Zn, Cd)S:Cu is often used. Compared to these existing practical phosphors, C
The afterglow time of alkaline earth sulfide phosphors, mainly aS, is short, and C, which is said to have the longest afterglow time.
a8: Mn also 'each. However, as mentioned above, alkaline earth sulfide phosphors are one of the few phosphors that emit light with high efficiency, and the type of activator and composition of the matrix are It has the excellent feature that it is possible to control the color tone in the entire visible range by adjusting it. Therefore, if it can be made to have a long afterglow by some means, it will be possible to apply it to a V-display tube.

The object of the present invention is to achieve the long afterglow property of the above-mentioned alkaline earth sulfide phosphor.

In order to achieve this objective, the present invention uses an alkali which is added to a phosphor activated with divalent cations and at least one member selected from the group consisting of yttrium, scandium, aluminum, gallium, and indium as a co-activator. Earth sulfide phosphors are disclosed. Divalent cations as activators, such as Mn'' and Cu''.

When Eu2+ etc. are used, these cations become Ca2+
Since ions are replaced, there is no excess or deficiency of valence electrons within the host crystal. However, when the co-activator of trivalent cations is added to this, these elements also replace Ca2+ ions,
At this time, it was found that deep electron drag occurs and some of the excited carriers return to the ground state via this electron trap, resulting in a long afterglow.

Hereinafter, the present invention will be described in detail based on examples.

(Example 1) 0.1 mol of manganese oxide was thoroughly mixed with calcium carbonate, and the mixture was heated to 1200 molar mass in a hydrogen sulfide atmosphere.
Mntt activated calcium sulfide C by keeping at °C
aS: Mn (0.1 mg%) was fired. This sample was divided into six parts and yttrium oxide was mixed therein. The concentration of yttrium mixed in each divided sample was 0.05 mol.

They are 0.1 mol %, 0.3 mol %, 0.5 mol %, and 1.0 mol %. These were refired under the above conditions together with divided samples containing no yttrium oxide, and the resulting phosphor was 17
Surface afterglow time τa. was measured under ultraviolet light (253.7 nm mercury line) irradiation. In addition, each phosphor forms a precipitated film, and 25
Excite with KV electron beam to obtain chromaticity coordinates and 3Cds (PO4)
g.CaCl2: Relative brightness 9 luminous efficiency with respect to Mn was investigated.

This is shown in Table 1.

Table 1 Fluorescent properties of CaS:Mn (0.1 mot%), Y From the results in Table 1, the higher the concentration of co-activator Y, the longer the afterglow of the phosphor becomes, and the chromaticity coordinates show a strong red dust. However, it can be seen that the luminous efficiency (luminance) decreases. CDP, a cadmium-based phosphor currently used as an orange phosphor for display devices, namely 3 Cds (PO4
)+1 ・CdC4z: In this example, an afterglow time comparable to that of Mn was obtained in a sample with a Y concentration of about 0.3 mot%, and the luminous efficiency (brightness) was also comparable to that of CDP. However, the color tone is more yellow than CDP.

Then, the afterglow time was measured using samples with different colors. C
There are several ways to change the color tone of an aS phosphor. The main methods include a method of varying the concentration of the activator, a method of using a mixed crystal matrix, and a method of using a co-activator. Here, an example in which the Mn concentration of the activator is varied is shown.

The sample was fired using the same process as above. Each of the obtained phosphors Ca8: Mn (amat%), Y (03
mot%) to form a precipitated film, and UV-excited PL as described above.
Table 2 shows the results of measuring τ''Ao, relative brightness and chromaticity coordinates using 25 KV electron beam excitation CL.

Table 2 CaS: Mn (amot%), Y (0
, 3mo1%) From this table, it can be seen that as the concentration of the activator Mn increases, the afterglow time becomes shorter, the color tone becomes more reddish, and the brightness decreases. The color tone and afterglow time comparable to the currently used cadmium-based phosphor CDP were obtained by test shooting B-3, and the brightness was also comparable to CDP. Therefore, the orange phosphor having the composition B-3 can be applied to display tubes in place of the current orange phosphor that contains the pollutant cadmium, and contributes to reducing the cost of cathode ray tubes because there is no cadmium treatment cost. I can do it. In addition, it was confirmed that the PL had a long afterglow, so
The phosphor of this example can also be applied to a phosphor for lamps.

(Example 2) Ca1-1Srz8 : Mn (0, 2mo
L%) was fired. After pulverizing this, different matrix composition ratios
Co-activator scandium was added in the form of 0.3 molar thioxide to each sample with
It was kept in a hydrogen sulfide atmosphere for an hour. As a result, Ca 1-
X5rXS: Mn (0.2mol%), Se(
A yellow-orange phosphor having a composition of 0.03 mot %) was obtained. As in the previous example, after forming a precipitated film, the afterglow time was measured using PL using 253.7 nm mercury beam excitation, and other fluorescent properties were measured using CL using 25 KV acceleration and consonant beam excitation. The cadmium-based orange phosphor CDP was used again as a standard sample, and the results obtained are listed in Table 3.

Table 3 Ca 1-1srzs: Mn(0,2mo
t%) + Fluorescent properties of 5C (0.3 mat%) As the Sr composition ratio X increases, the chromaticity point shifts from orange to yellow and at the same time the afterglow time increases. Although the relative brightness slightly improves as X increases due to visibility dependence, it tends to become saturated due to a decrease in luminous efficiency. If a Ca 1-1 S rxS mixed crystal is used as the matrix as in this example, it is possible to shift the color tone of the Mn-activated long afterglow phosphor to a more yellow side than in the previous example. Although not mentioned in Table 3, C
It was a DP-processed light with a long afterglow. For example, in the case of electron beam excitation at 25 KV acceleration, Mo is 108 m
5ec, which was significantly higher than CDP's 29m5ec.

(Example 3) Calcium carbonate, magnesium sulfate, #
Ca 1-y
MgyS: Cu (0.2 mol-%),
The Y blue phosphor was fired. Once pulverized, 1 mol of sodium carbonate was mixed and the mixture was heated at 110 yuan and calcined again in hydrogen sulfide. A precipitated film of the obtained blue phosphor was prepared, and its properties at room temperature were measured by PL and CL in the same manner as in the previous example. The results are shown in Table 4.

The standard sample is crystalline ZnS:Ag.

Table 4 Ca 1 y Mgy S: Cu (0,
2mo1%n.

According to Table 4 of the fluorescent properties of Na (2mol1%) + Y (Cmol-%), it can be seen that saturation of the co-activator Y causes the blue phosphor to have a significantly longer afterglow. However, the luminous efficiency is higher than that of the blue phosphor ZnS for color cathode ray tubes: Ag.
It remains at around 70-80% of the total. However, there are few examples of such long afterglow blue phosphors, and they are promising as blue phosphors for display tubes. Yttrium concentration 0.05-5
Within the range of molti, longer afterglow was observed than when no yttrium was added. Also, replace the co-activator with yttrium and use scandium.

Long afterglow was also observed when aluminum, gallium, and indium were used. For example, the coactivator concentration C is set to 0.
3 molti, the phosphor obtained under the same firing conditions as the yttrium coactivation shown in Table 4 (composition ratio y =
0), under the same measurement conditions as in Table 4, the fan was made of scandium 800 maee, aluminum 44 m5ec,
Gallium was 38 m5ec, indium was 39m5ec, and the afterglow was longer than when no co-activator was added.

(Example 4) Lucium carbonate, europium oxide.

Powders of cerium oxide, ll & scandium oxide were mixed well and sulfurized repeatedly at 1200°C to form Ca8:Eu(0,
1 mot %), Co (0, O 1 mat %).

A Be(Cmot%) red phosphor was fired. Coactivator S
The properties of the precipitated phosphor films of several samples obtained by varying the C concentration C were measured by PL and CL in the same manner as in the previous example. The results obtained are shown in Table 5.

In the case of this example, the standard samples were Cab:F without SC;
u (0,1 mot%), Ce (o, o 1 mg%
). The energy efficiency (absolute efficiency) of electron beam excited luminescence of this standard phosphor at room temperature was about 17 cm.

Table 5 CaS: Eu (0.1mol1%),
Co (0.01 mot%).

Fluorescence properties of Be (Cmol, %) As the concentration of the co-activator Sc increases, the luminous efficiency decreases, but τ! λ. It can be used as a long afterglow deep red phosphor.

In the above fifth embodiment, CaS, (Ca, Sr)S, (Ca
, Mg 2 )S has been described, but the present invention is not limited thereto, and is also effective for other alkaline earth sulfide phosphors. In addition, although only the method of heating in a hydrogen sulfide atmosphere has been described as the phosphor firing method, the presence of Y, Sc, At, Ga, or In as a coactivator is fundamental for long afterglow. It is obvious that the present invention is also effective with other calcination methods such as the reduction sulfidation method and the heating calcination method after wet sulfide synthesis.

According to the present invention, a long afterglow of a high-intensity multicolor alkaline earth sulfide phosphor has been achieved, and its use as a phosphor for display gray tubes and a phosphor for rungs has been greatly expanded.

Patent Applicant Rare Metallic Co., Ltd. Agent Patent Attorney Masami Akimoto

Claims (1)

[Claims] Yttrium, scandium, aluminum, f! An alkaline earth sulfide phosphor, characterized in that it contains at least one element selected from the group consisting of lithium and indium. 2. The divalent cations mentioned in the previous section are Mn and Cu. The alkaline earth sulfide phosphor according to claim 1, characterized in that the phosphor is one selected from the group consisting of and Eu''+.