JPH03207786A - Fluorescent substance composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a novel phosphor composition (Zn, Mg) S:Pr''+ whose main emission is in the blue-green to deep red region,
The present invention relates to the composition of a phosphor that exhibits excellent characteristics when applied to white EL displays and illumination light sources.

[Conventional technology]

The following documents are examples of conventional examples in which luminescent ions are introduced into a (Zn, Mg)S bus bar and the host body.

1) Journal of Electrochemical Society Vol. 99, No. 4, pp. 155-158 [J. E
1 electrochemical Soc. 9 9 (
4) 155-158 (1952)] In this document, MgS is 25 mol% or less, and the rest is Zn.
From S to a certain (Zn, Mg) S matrix (:u, Age p
b, As, Sb, Bi and Cu-Mn,
Luminescence characteristics by ultraviolet excitation and electron beam excitation are shown for phosphors labeled with Pb-Mn and C'u-Pb, respectively.

2) Journal of Materials Science Volume 21,
2100 pages 2lo8 pages rJ. ofMaterial
Science2 top 2yuoo~21o8 (1 9
8 5) In this document, Znx-xMgxs: Cu, B
It has been reported that the emission peak wavelength of dispersive EL using r shifts from 525 nm to 436 nm as X increases6 3) Lasian Journal of Inorganic
Chemistry Volume 9, Report 4, Pages 512 to 516 [R
ussian j. of InorganicChem
istry 9 (4) 5 1 2~5 1 6 (1
9 6 4) 1 This document states that MgS dissolves up to 22 mol % in ZnS as a solid solution, and that both the hexagonal lattice constants ao and QO increase as the amount of solid solution increases.

Next, there is the following literature regarding a phosphor in which a ZnS matrix which does not contain MgS as a solid solution is activated with Pr''.

4) S.I.D. 80 Digest page 106-1
Page 07 [SID 80 Digest, p.
106-107, (1980)] This document describes that the light-emitting layer ZnS:PrFa is made of Si. The voltage-luminance characteristics of a thin film EL device sandwiched between an aNa insulating layer and a YzOa insulating layer are shown.

5) Fujika Status Solidiy A69 Volume 11
Page-66 [Physica Status Soli
dia 6911-66 (1982), page 36, this document shows the EL emission spectrum of ZnS:PrFs in comparison with other rare earth fluoride activated cases. On the other hand, regarding the structure of the EL element, for example, 6) Unexamined Japanese Patent Publication No. 6
1-49397, a red, green, or blue light emitting EL element is formed on one transparent substrate, and the remaining two color light emitting EL elements are formed on a separate transparent substrate, A full color thin film EL device is disclosed in which both substrates are disposed facing each other.

[Problem to be solved by the invention]

Of the above conventional examples, 1) and 2) are related to phosphors into which luminescent ions different from Pr3+ are introduced, and both
It lacks red light emitting components in the wavelength range longer than nm. Furthermore, thin film EL devices produced using these phosphors as starting materials either do not emit light at all, or even if they do emit light, the brightness is extremely low. Next, conventional example 3) involves only the matrix into which no luminescent ions are introduced, and sufficient luminescence (
(self-attached active light) is difficult to obtain. In addition, conventional examples 4) and 5) are Z
Although this is a phosphor in which the same Prs+ as in the present invention is introduced into the nS matrix, the drawback is that the light emission in the 520 to 620 nm region is weak in order to obtain a white display.

Furthermore, Conventional Example 6) has the disadvantage that the element structure becomes complicated in order to obtain a white display.

It is an object of the present invention to provide a new phosphor composition that overcomes many of the problems mentioned above.

[Means to solve the problem]

The above purpose is to create a P in which the E1 transition is distributed from blue-green to deep red.
This is achieved by selecting r3+ as a light-emitting ion and expanding the ZnS host lattice so as to facilitate the introduction of Pr2l''.

As is well known, the ionic radius r = 1.09A of Prs+
In contrast, that of Zn''+ is as small as r=o.74, so it is desirable to expand the host lattice in order to introduce the required amount of Pr3+.As a means of expanding the host lattice, MgS
into a solid solution. for example. When 22 mol% of MgS is dissolved in ZnS, it becomes a hexagonal crystal system, and the lattice constant ao is 1.9%.
, the lattice constant CO increases by 1.1%. In addition, when introducing trivalent luminescent ions such as Pr8+ into divalent cation lattice points such as Zn'' and Mg'', high-purity Mg raw materials are used instead of intermediate raw materials starting from MgO. We used an intermediate raw material starting from Mg metal, and adopted a sintering method that minimizes the intervention of sulfate radicals and oxygen ions. [Operation] The first advantage of the present invention is that Pr for brightness optimization is
This makes it easier to adjust the 8+ concentration, and also discloses a versatile means that overcomes the common sense that it is difficult to introduce a sufficient concentration when introducing not only Pr8+ but other trivalent rare earth ions into ZnS. ing. For example, in a thin film EL device, the upper limit of the Pr3+ concentration in the light emitting layer can be increased by more than an order of magnitude compared to the case of a ZnS matrix. The second advantage is that the light emission in the 520-620 nm region, which is weak in the conventional phosphor ZnS:Pr8+, is increased by solid solution of MgS, and the emission intensity can be adjusted depending on the amount of solid solution of MgS. Furthermore, in the thin film ELi,
The emission intensity can also be adjusted by changing the driving frequency. As a result, by taking advantage of the second advantage mentioned above, the correlated color temperature is 2300.
A wide range of white display or white illumination can be obtained depending on the field of application, from K to 5000 K, ie from warm white to neutral white.

〔Example〕

Hereinafter, the present invention will be explained according to examples.

Example 1 General formula Znz-aMgaS: In Pr, a >
0 is a feature of the present invention. In order to clarify that the effect of a > O is not due to impurities in the Mg raw material, especially oxygen impurities that are easily mixed with Mg, two types of
Using the M material, a target for phosphor aggregation and vapor deposition was prepared according to the flowchart in FIG. 1, and a thin film EL device was further prepared from the target.

Two types of Mgj! Both X materials are represented by MgSOa99
．． It has a purity of 9% or more, but its starting materials are different.
The one starting from MgO will be abbreviated as (A), and the one starting from high-purity Mg metal will be abbreviated as (B). First, (A)
, CB) and a=0.1, that is, Zno. eMgo. t
As a result of preparing and analyzing a target with a composition of S:0.03Pr according to Fig. 1, the (B) method showed a difference in comparison with the (A) method. Ca from 700ppm to 20ppm, Cr,
It was confirmed that Mn, Fe, and Cu were reduced from 220 ppm to 10 ppm or less. It is presumed that the oxygen impurity concentration is also reduced in proportion to these impurity concentrations.

Next, using the targets (A) and (B) above as the evaporation source, a normal three-layer structure thin film E was formed by EB (electron beam) evaporation method.
An L element was created. The well-known YZOJI was used for the insulating film sandwiching the light emitting layer. Table 1 shows comparative examples of the characteristics of the obtained elements. As is clear from the table, for devices with luminescent layers of the same layer thickness, starting from the raw material of the method (B), the emission starting voltage, relative brightness, and frequency characteristics are all better than those of the method (A). I found out that it will happen.

As shown in Table 1 and above, in the Mg-containing phosphor, which is a feature of the present invention, first of all, the effect of Mg raw material purity on various properties is remarkable;
In other words, this example has revealed that this effect can only be achieved by using a purified Mg raw material.

Example 2 In the general formula Znx-aM gaS: Pr8+, M
The a value representing the gS solid solution amount is a=O (comparative example), 0.01
．． Evaporation source targets having compositions varied in five stages of 0.05, 0.10, and 0.15 were prepared using the same method as in Example 1. Here, as the Mg raw material, method (B), which was confirmed to have good properties in Example 1, was used.

A conventional three-layer thin film EL device was fabricated from the target using the EB evaporation method. The thickness of the light-emitting layer was kept constant at 0.66 μm as in Table 1.

Relative brightness, chromaticity coordinates, and correlated color temperature calculated from the chromaticity coordinates under sine wave driving at a frequency of 5 KHz are summarized in Table 2. The relative brightness of the table is. a=O or Mg
Known phosphor ZnS that does not contain S as a solid solution: 0.03Pr
It is a relative value of the value actually measured at +30V for the element with a > O, based on the luminance at the emission start voltage V th of +30V.

As is clear from the table, higher luminance was obtained when a>O than the element with a=O, and a maximum value of 173% was obtained when a=0.05. Although attempts were made to synthesize phosphors and create devices for a>0.15, the variation in brightness characteristics became large and the average brightness remained at around 100%. a inferred from l) and 3) of the publicly known examples cited earlier
=0.22~0.25. That is, this phenomenon is considered to be due to the fact that the solid solubility limit of MgS in ZnS is close to 22 to 25 mol%.

Table 2 Next, if we focus on the chromaticity coordinates in Table 2, we can see that the y value of the chromaticity coordinate is not necessarily monotonous as the a value increases, but rather it tends to decrease, and the a value mentioned above This shows that the brightness improvement associated with an increase in y is not due to an apparent increase in y value. It has been found that the chromaticity coordinates also change depending on the driving frequency. For example, 5KHz and IKH
The chromaticity difference 1Δx1, 1Δy1 in z is a maximum of 0.0 0 1 for ZnS:Pr8+ with a = 0, but is larger by more than one order of magnitude, with a maximum of 0.0 2 1 for a = 0.05. I understand.

Figure 2 shows that a = 0.05, that is, Zno, where the maximum brightness was obtained.
．． e6Mgo. This is the emission spectrum of a device consisting of osS: 0.03Pr under 5KHz and sine wave driving.

ZnS:Pr3 described in the publicly known example 5) cited above
Compared to the emission spectrum of +, 520-620n+
The emission intensity in the n region has increased, and it is thought that the introduction of just 5 mol % of MgS causes mixing of the Prs+ J state and increases the emission transition probability. When a > O, in addition to an increase in the emission intensity in the above wavelength range, deep red emission tends to appear stronger than blue-green emission regardless of the frequency, and as a result, the a-dependent emission as shown in Table 2 Significant changes in correlated color temperature were obtained.

FIG. 3 shows a typical three-layer structure thin film E. In accordance with the L element fabrication process, a 02+
This is the result of investigating the distribution of Mg/Zn, Pr/Zn, and Y/Zn in the film thickness direction in a 0.8 m" region of the two-layer structure film by ion irradiation. From the figure, it can be seen that the luminescent ion Pr' hand in the film thickness direction It can be seen that the distribution corresponds well to the distribution of Mg in the parent body.

This confirms that Pr''+ is effectively introduced in the presence of Mg.

Example 3 For the purpose of comparing the brightness with and without MgS due to excitation other than an electric field, the following compositions were first evaluated. In the sample used for comparison, the Prs concentration was one order of magnitude lower than in Example 1.2, and the matrix composition was Zr+O. which corresponds to a=0.05 in the general formula. ssMgo. or+S and a=O
It was set as ZnS corresponding to . After weighing and dry mixing the above composition according to the flowchart in Fig. 1 (reference numeral 2 in the figure), 100 g of the mixture was filled into a transparent quartz boat by its own weight.
By omitting the step number 3 in the figure, the Ar flow rate is 200 m.
A/win, incinerated at 1000°C for 2 hours. Ar gas was discharged all day and night before and after firing.

Next, the obtained powder phosphor was applied by water precipitation, and the powder brightness under electron beam excitation was compared. The excitation conditions were an accelerating voltage of 27 KV and a current density of 0.16 μA/Ci. ”
Based on the luminance of the known phosphor ZnS:0.003Pr8+ corresponding to O, a=0.05 according to the present invention. ssM go. os S: 0.0 0
With 3P rδ+, 3.6 times the brightness was obtained.

〔Effect of the invention〕

As explained above, in the present invention, the known phosphor ZnS:P
By dissolving MgS in the matrix of rs+, the matrix lattice is expanded and the introduction of luminescent ions Pr" is facilitated,
ZnS applied to the light-emitting layer of a thin-film EL device using the same film-forming method:
1.7 times the brightness can be obtained compared to the Pr8+-containing EL element. Furthermore, by adjusting the amount of MgS solid solution, it is possible to significantly adjust the correlated color temperature from 5000K to 2300K. M
The effect of gS solid solution is not limited to the above-mentioned thin III EL element. 6The effect of solid solution of gS is not limited to the above-mentioned thin III EL element.
If it is a field where ZnS has been applied in the past or present. The effect is achieved by optimizing the Pr'' concentration and MgS solid solution amount, and the brightness of electron beam excitation is more than three times that of conventional phosphors. It is effective when applied to white display elements and white illumination light sources where visibility is important, and the effect is particularly remarkable in fields where warm white color is required. Although the present invention is effective by introducing PrB+ into the Mg-containing matrix,
Even if a small amount of luminescent ions other than Pr8+ are introduced, Pr
8+ The effect of light emission is not impaired.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a method for synthesizing a phosphor composition described in Examples of the present invention and a method for producing an evaporation source target using the same, and FIG. saM go. oI
! FIG. 3 is an emission spectrum diagram of a thin film EL device having a light emitting layer of s: 0.0 3 P r . FIG. 3 is a diagram showing the constituent ion distribution in the film thickness direction within the light emitting layer of FIG. 2. No. 1 Mouth No. 2 Figure 5L Cloth (ttv) Taku 3 Tuchi Seki (Shun

Claims (4)

[Claims] 1. General formula Zn_1_-_aMg_aS: Pr^3^+, 0<a≦
0.20, the matrix composition consists of a solid solution system of zinc sulfide and magnesium sulfide, and the main luminescence is caused by Pr^3^+. 2. The phosphor composition according to claim 1, characterized in that 0.05≦a≦0.10. 3. An EL device, wherein at least one component of a light-emitting layer constituting the EL device is composed of the phosphor composition according to claim 1. 4. An evaporation source target, which can be formed into a film to obtain the phosphor composition according to claim 1.