JPH04189892A - Production of electroluminescent layer - Google Patents

Abstract

PURPOSE:To obtain a uniform thin-film electroluminescent layer having large area at a low cost with relatively simple means by mixing a solution of a polyacid with a compound soluble in the solution to precipitate a compound having electroluminescent property and depositing the precipitate on a substrate. CONSTITUTION:A solution of a polyacid is added with a solution of barium chloride, calcium chloride, etc., soluble in the polyacid solution to precipitate a polyacid compound having electroluminescent property and expressed preferably by formula I to formula III (MA is 1-3 valent metal; L is Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm or Yb; MB is W, Mo, V, Nd or Ta; XA and XB are 3-5 valent element; x and y are positive integers determined to get the total valence number of zero). The precipitate is deposited on a substrate to obtain the objective electroluminescent layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing an electroluminescent layer, and more particularly to a method for manufacturing an electroluminescent layer made of a polyacid compound having electroluminescent properties.

[Conventional technology]

An electroluminescent display, which is commonly used as a flat display device, is constructed using an electroluminescent element having an electroluminescent layer.

The following methods are conventionally known as methods for manufacturing such electroluminescent layers.

■ Electron beam evaporation method, resistance heating evaporation method, sputtering method, atomic layer epitaxy method, organometallic chemical vapor deposition method,
A method of manufacturing a thin film electroluminescent layer using a vapor deposition method such as molecular beam epitaxy.

(2) A method for producing a dispersed electroluminescent layer, such as by dispersing an electroluminescent phosphor in a dielectric material made of an organic material or mixing it in a low melting glass.

[Invention or problem to be solved]

However, the method of manufacturing a thin film type electroluminescent layer using a vapor deposition method as described in (2) above has the disadvantage of increasing manufacturing costs because the manufacturing equipment is expensive. There is also the problem that it is difficult to form a thin film.

Furthermore, among the vapor deposition methods, electron beam evaporation in particular has the problem of easily forming clusters in the film, and sputtering has the problem that the film is easily damaged by sputtering gas ions, resulting in poor film uniformity. It is easy to cause deterioration or deterioration.

On the other hand, in the method of manufacturing a dispersed electroluminescent layer as in (2) above, it is difficult to make a thin film, and therefore the applied voltage required to make the electroluminescent layer emit light with sufficient brightness becomes high, resulting in a drive There is a problem with the voltage load on the power supply increasing.

Therefore, an object of the present invention is to provide a relatively simple method,
It is an object of the present invention to provide a method by which a uniform thin electroluminescent layer having a large area can be manufactured at low cost.

[Means to solve the problem]

In order to achieve the above object, the present inventors conducted extensive research and found that by adding a compound that dissolves in a solution of polyacid compound A, a polyacid compound B having electroluminescent properties can be produced. It has been discovered that a thin electroluminescent layer with a uniform thickness can be produced over a large area using a low-cost production apparatus by a method of precipitating and depositing the electroluminescent layer on a support, This has led to the completion of the present invention.

Therefore, the method for producing an electroluminescent layer of the present invention is a method for producing an electroluminescent layer that develops electroluminescent properties, and is a method for producing an electroluminescent layer that develops electroluminescent properties. It is characterized in that a polyacid compound B having properties is precipitated and deposited on a support.

Furthermore, the electroluminescent layer is characterized in that the polyacid compound B constituting the electroluminescent layer is represented by any one of the following general formulas (1) to (3).

General formula (1); (MA), (L ((MB)50
,,)2]y general formula (2); (MA)yo(L((X
A) (MB)zCh,)2]y general formula f3); (M
A), CL((Xs)2(Me)17061)2)
.

[In general formulas (1) to (3), MA represents a monovalent, divalent or trivalent metal, and L represents Ce, Pr, or Nd.

Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
m, Yb, MB represents W, Mo
, V, Nd, Ta, XA
and XB represent an element that can have a valence of 3, 4 or 5, and X and y are such that the overall valence is 0 in each of general formulas (1) to (3). represents a positive integer determined by . ] Furthermore, the general formula (11
~(3), where MA is Li, Na, K, Rb, C
s, Be, Mg, Ca.

Represents any metal of Sr, Ba, Cu, Bi, and L is Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm, Yb, Me represents W or MO, XA represents Si, Ge,
represents either P or As, and XB is P or A
s, and is characterized in that X and y represent positive integers determined to have a valence of 0 as a whole in each of the general formulas +1j to (3).

The present invention will be specifically explained below.

In the present invention, first, a solution of the polyacid compound A is prepared by dissolving the polyacid compound in a solvent.

Next, by adding a compound dissolved in this solution (hereinafter referred to as "deposition compound J") to the solution of polyacid compound A, polyacid compound B having electroluminescent properties is precipitated onto the support. to produce an electroluminescent layer.

Specifically, a solution of a polyacid compound as a raw material is placed in a container, and a support is placed at the bottom of the container so that its upper surface becomes the surface on which the electroluminescent layer is formed. In this state, a solution of the precipitation compound is added to this solution with gentle stirring, and then left to stand for a while. During this standing period, some of the constituent atoms of the polyacid compound A change to the constituent atoms of the precipitation compound. As a result, a polyacid compound B having electroluminescent properties different from that of the polyacid compound is precipitated, and this precipitated polyacid compound B is replaced by a support disposed at the bottom of the container. Deposited on the surface, a thin electroluminescent layer is formed over a large area and of uniform thickness.

The polyacid compound B constituting the electroluminescent layer is preferably one represented by the following general formulas (1) to (3).

General formula (1); (MA), [:L((MB), O,
5)2]y general formula (2: (MA), (L((XAX
MB) 1,02. )2]y general formula (3); (MA
)-(L((Xi)2(Ma)+tOs+)2]y The MA represents a monovalent, divalent, or trivalent metal, and among these, Li, Na, and K are particularly preferred.

Rb, Cs, Be, Mg, Ca, Sr, Ba, Cu, B
Any one of i is preferable, and moreover, Mg.

Any one of Ca, Sr, and Ba is preferable.

The above are Ce, Pr, Nd, Prn, Sm
, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y
b represents any metal, particularly Eu, Sm.

Any one of Tb, Dy, and Pr is preferable.

M8 represents any one of the metals W, Mo, V, Nd, and Ta, and among these, W or Mo is particularly preferable, and W is more preferable.

The XA and X8 represent elements that can be trivalent, quadrivalent or pentavalent, and among these, XA is preferably any one of Si, Ge, P, and As; is preferably Si, and XB is preferably P or As, and more preferably P.

The X and y represent positive integers determined to have an overall valence of O in each of the general formulas (1) to (3).

Among the general formulas (1) to (3), especially the general formula (1)
) is preferred.

In particular, MA is Mg, Ca, Sr, Ba, M8 is W, XA or Si, X8 or P
and L, Eu, Sm, Tb.

When the polyacid compound is either Dy or Pr, an electroluminescent layer having even better luminescent properties can be obtained.

In the general formulas (1) to (3), the constituent elements are:
It is a so-called rare earth element and is often used as a luminescent center in luminescent materials, but since this L is not easily influenced by other atoms that make up the polyacid compound, it is important to select the type of rare earth element concerned. Accordingly, various luminescent properties characteristic of the rare earth element can be obtained.

Specific examples of the polyacid compounds represented by the general formulas (1) to (3) are listed below. Note that the present invention is not limited to these exemplified compounds.

Exemplary compound I Bas [Eu(WsO+s)z:l
2 Exemplary Compound 2 Srs (Eu(WsO+5)
2) 2 Exemplary Compound 3 Cas (Eu(WsO+
5)z) 2 Exemplary Compound 4 Mgo (Eu(Ws
On)z)2 Exemplary Compound 5 L is (Eu(W
sO+m)2:1 Exemplary Compound 6 Nag(Eu(
WsO+5)z) Exemplary compound 7 Ko (Eu(W
sO+5)z) Exemplary compound 8 Cue (Eu(W
sO+s)J z Exemplary Compound 9 B it (Eu
(WsO+1)2) 2 Exemplary Compound 10 Bag
(Sm(WsO+5)z)2 Exemplary Compound 11 Ba
, (Tb(WsO++)2)2 Exemplary Compound 12 B
a, (Dy(wso+5)t)2 Exemplary Compound 13 8
a s (P r (WsO+s)) 2 Exemplary Compound 14 Bas (Ho(Wsolg)2) 2 Exemplary Compound 15 B a # CE r (WiO+5
)2)! Exemplary compound 16 Ba, (Tm(WsO
+5) 2) 2 Exemplary Compound 17 Bag (Yb(W
a(Ls)i) Ratio of 2 exemplified compounds Bag (Ce(
WsO+5)2)2 Exemplary Compound 19 Bag (N
d(WsO+*)z)2 Exemplary Compound 20 Bag
(Eu(MOsO+s)J 2 Exemplary Compound 2) S r
s (E u(MosO+5)2) 2 Exemplary Compound 22
Cas (Eu(MOsOw)z)2 Exemplary compound 23 Ban (Sm(MOsO+1)z)2 Exemplary compound 24 Ban (Tb(Mos○+1)2)
2 Exemplary Compound 25 Baa [Dy(MOsO+
5) x) 2 Exemplary Compound 26 Ba+i (Eu(S
iW, osi) 2) 2 Exemplary Compound 27 Sr+
2(Eu(SiW+10*5)2L Exemplary Compound 28
Catj[Eu(SiW++019)2) 2 Exemplary Compound 29 Mg+i (Eu(SiW++o3*
)2]2 Exemplary Compound 30 C1J+z (Eu(S
iW+102J2) 2 Exemplary Compound 31 Ba+
z(Sm(SiW++031)2:l 2 Exemplary Compound 3
2 Ba+z [Tb(S iW+(039)2)
2 Exemplary Compound 33 Ba+z (Dy(S 1w
1lo29:+2]2 Exemplary Compound 34 Ba+z
(Eu(SiMO++oz*)2)2 Exemplary compound 35
Sr+zl:Eu(SjMO++0zi)2)2 Exemplary Compound 36 Ca+z(Eu(SiMCz+Oz
*) 2) 2 Exemplary Compound 37 Mg+zl:Eu(S
iMO++Os*)z)2 Exemplary Compound 38 Cut
ff(Eu(SiMo++0ss)2:12 Exemplary Compound 39 Ba+*(Sm(SiMo1+o3o)
2) 2 Exemplary Compound 40 Ba+z (Tb(S
iMO++ohs)2]2 Exemplary Compound 41 Ban
[Dy(S jMo++0pn)2)y Exemplary Compound 4
2, Ba+3(Ell(GeW++0zs)2)
2 Exemplary Compound 43 Sr's (Eu(GeW++
O*5)2)2 Exemplary compound 44 Cabs (Eu
(GeW++02e)2]2 Exemplary Compound 45 Ba
+z (Sm(GeW++0ss)2)2 Exemplary compound 4
6 BaB (Tb(GeW+103*)2)2 Exemplary Compound 47 Ba+zCD)'(GeW++0z
s)2)2 Exemplary Compound 48 Batj(Eu(Ge
Mo++Oz*)i) 2 Exemplary Compound 49 Balt
(Eu(PW++O*5)z) 2 Exemplary Compound 50
Sr++ (Eu(PW, Oz*)x) 2 Exemplary Compound 51 Can (Eu(PW, 02s)z) 2
Exemplified compound 52 Ba++ (Sm(PW++Os
*)z)2 Exemplary Compound 53 8an (Tb(PW+
+02*)z)2 Exemplary Compound 54 Ba++ (D
y(PW++02s)2) 2 Exemplary Compound 55 Ba
H(Eu(AsW++0si)2)2 Exemplary Compound 56
Ba1t (Eu(PMo++0zs)2) 2 Exemplary Compound 57 Ba1t (Eu(AsMolIO
ss) J 2 Exemplary Compound 58 Balt CEu (
P*W+70**)) 2 Exemplary Compound 59 Sr+1
(Eu(PsW+i0g+)J2 Exemplary Compound 60
Ca+7(Eu(PzW+i0s+)2)2 Exemplary compound 61 Mg+7(Eu(P2W+tOa+)z) Exemplary compound 62 Cu+7(Eu(PtW+vOs)
+)2]2 Exemplary Compound 63 B a 17 (Sr
n(P2WuOg1)2) 2 Exemplary Compound 64 B
a17(Tb(P2W1tOs+)2)2 Exemplary Compound 6
5 8ait I:Dy(P2W+i0++)2)2
Exemplary compound 66 Ban (ELI(P2MO+7
011)2) 2 Exemplary Compound 67 S r IT
[Eu(P2MO+tOg+)2) 2 Exemplary Compound 68
Ca+7(Eu(P2MO+i0a+)2]2 Exemplary Compound 69 Mgr□(Eu(P2Mo+70+
+) 2) 2 Exemplary Compound 70 Cu+t (Eu(P
2MOztCL+)2]2 Exemplary Compound 71 Ba1
t (Sm(P2Mo+i0**)2)2 Exemplary Compound 7
2 Ban(Tb(PzMO+vOs+)2:lx
Exemplified compound 73 Ba+v(D)'(P2MO+t
O++) 2) 2 Exemplary Compound 74 B a 171:
E u (AS 2W+tog+)2) 2 Exemplary Compound 75 Sr+t(Eu(AS2W+70g+)2
]2 Exemplary Compound 76 Ca+t(Eu(AStWn
Og+)2) 2 Exemplary Compound 77 8aB (Sm(A
szWnOa+)2]2 Exemplary Compound 78 Balt
(Tb(As2W+70g+)2)2 Exemplary Compound 79
Ba+1(Dy(AstW+70g+)2)2 Exemplary compound 80 Ba1□(Eu(AS2MO+□O
s+)2)2 The solvent constituting the solution to the polyacid compound may be any solvent that dissolves the polyacid compound A.
Specifically, water or the like can be used.

In addition, as polyacid compound A, the general formulas (1) to (
It is preferable to select from those represented by any of 3), but in this case, it is preferable to use an aqueous solution of the polyacid compound A.

The polyacid compounds mentioned above are, for example, R, D, Peacoc
K and T. J. R. Weakley (J. Chem.
, Soc, A, 197I P1836~). for example,
Sodium tungstate dihydrate (Na 2WO
Dissolve 50 g of 4-2H2O) in 100-m water and adjust the pH to 7.2 with glacial acetic acid. the aqueous solution at 90°
C and stir, to which praseodymium nitrate (P r
(NO3)-) solution is added dropwise. After filtering, 5°C
Collect the precipitated sodium salt crystals. By dissolving this in warmed water again and recrystallizing it while cooling, Nag (Pr (Wi O+*) 2 ), which is an example of the polyacid compound described above, is obtained.

The compound for precipitation may be any compound as long as it dissolves in the solution of the polyacid compound A, and specifically, it is selected depending on the type of solution of the polyacid compound A.

For example, if a solution of polyacid compound A is prepared by the general formula ill~(
In the case of an aqueous solution of a polyacid compound represented by any of 3), it can be used in the form of an aqueous solution of barium chloride (BaC1z), calcium chloride (CaC12), or the like.

The deposition rate of polyacid compound B and the film thickness of the electroluminescent layer can be determined by adjusting the concentration and pH of the solution of polyacid compound A, or by adjusting the amount and concentration of the precipitation compound added and the standing time after addition. can be easily controlled by preparing

As explained above, the manufacturing method of the present invention is a simpler method compared to the conventional vapor phase deposition method, and can easily form a large-area electroluminescent layer using a manufacturing apparatus with a low cost and simple configuration. be able to.

In addition, the manufacturing method of the present invention has a sufficiently thin film thickness of 50 μm or less, preferably 10 μm or less, and a uniform thickness electroluminescent layer, compared to the conventional method of manufacturing a dispersed electroluminescent layer. layers can be easily formed, resulting in
The driving voltage required to make the electroluminescent layer emit light with sufficient brightness is low (which can reduce the voltage burden on the driving power source), and the luminance can be reached with a driving voltage within a practical range. The display characteristics are improved.

〔Example〕

Examples of the present invention will be described below along with comparative examples, but the present invention is not limited to these embodiments.

[Example 1] As the polyacid compound A, a polyacid compound represented by N a = (E u (WsO, -)2) was used, and its aqueous solution 200 - (concentration 10 g
#) in a container, and place a size 20 mm at the bottom of this container.
A support consisting of a conductive layer made of Nesa film provided on one surface of a glass substrate measuring mm x 20 mm x I was submerged so that the conductive layer was on the upper side. Note that portions of the conductive layer where the electroluminescent layer should not be formed were partially masked.

Using barium chloride (BaCfz) as a precipitation compound, 20rnl of its aqueous solution (concentration 100g/l) was gently added to the aqueous solution of the polyacid compound with stirring, and the mixture was heated for 10 minutes.
It was left standing for a minute.

After standing still, the support was taken out from the container and dried.

When we examined one side of the dried support on which the conductive layer was provided, we found a structure in which Na atoms, which are constituent atoms of polyacid compound A, were replaced by Ba atoms, which are constituent atoms of the precipitation compound. It was confirmed that an electroluminescent layer having a thickness of approximately 5 μm was formed, consisting of a deposited layer of polyacid compound B expressed as B a *(E u (WsO+5)z) 2 .

Using the support provided with the electroluminescent layer produced as described above, as shown in FIG. An electroluminescent device was produced by stacking the other surfaces of Mylar 4 provided with the aluminum vapor deposited film 3 on which the vapor deposited film 3 was not formed. In FIG. 1, 5 is a glass substrate, and 6 is a conductive layer made of a Nesa film.

Between the vapor deposited film 3 and the conductive layer 6 of this electroluminescent element, 30
When a test was conducted in which an alternating current voltage AC of 0 V and 1 kHz was applied, it was confirmed that the red light emission due to Eu''' occurred uniformly from the entire surface of the electroluminescent layer 2.
This is thought to be because the electroluminescent layer 2 is thin and has a sufficiently uniform thickness.

Furthermore, when the magnitude of the alternating current voltage AC was varied and the brightness-voltage characteristics were measured, the results shown in FIG. 2 were obtained.

As is clear from FIG. 2, the electroluminescent device equipped with the electroluminescent layer manufactured by the method of the present invention has a steep rise in luminance-voltage characteristics and exhibits excellent display characteristics. It is something to do.

[Example 2] In Example 1, an aqueous solution 2 (W (concentration 100 g/I) of barium chloride (BaCllz) was used as the precipitation compound.
Instead, use 20ml of an aqueous solution of calcium chloride (CaCf2) (concentration 100g/A) and let it stand for 2 hours.
An electroluminescent layer was formed in the same manner except that the time was changed to 0 minutes.

When we examined this electroluminescent layer, we found that it had a structure in which the Na atom, which is a constituent atom of polyacid compound A, was replaced by a Ca atom, which is a constituent atom of the precipitation compound, that is, Ca * (E u (WsO1)2). It was confirmed that an electroluminescent layer consisting of a deposited layer of polyacid compound B represented by 2 and having a thickness of about 5 μm was formed.

Using the support provided with the electroluminescent layer produced as described above, an electroluminescent device was produced in the same manner as in Example 1, and a test in which an alternating current voltage AC was applied was conducted in the same manner. It was confirmed that red light emission due to u 3+ occurred uniformly from the entire surface of the electroluminescent layer 2.

Furthermore, when the brightness-voltage characteristics were measured by changing the voltage magnitude of the alternating current voltage AC, good results similar to those of Example 1 were obtained.

[Example 3] In Example I, the aqueous solution of the polyacid compound was Na
An electroluminescent layer was formed in the same manner except that the aqueous solution 200- (concentration 10 g/l) of a polyacid compound represented by #(T b (WsO11)2) was used.

When we examined this electroluminescent layer, we found that it had a structure in which Na atoms, which are constituent atoms of the polyacid compound, were replaced with Ba atoms, which are constituent atoms of the precipitation compound, that is, B a s [T b (WsO11)2 ) It was confirmed that an electroluminescent layer having a thickness of about 5 μm consisting of a deposited layer of polyacid compound B represented by 2 was formed.

Using the support provided with the electroluminescent layer produced as described above, an electroluminescent device was produced in the same manner as in Example 1, and a test in which an alternating current voltage AC was applied was conducted in the same manner. It has been confirmed that the green light emission caused by " is occurring uniformly from the entire surface of the electroluminescent layer 2.

Furthermore, when the brightness-voltage characteristics were measured by changing the voltage magnitude of the alternating current voltage AC, good results similar to those of Example 1 were obtained.

[Comparative Example 1] B a s as a polyacid compound having electroluminescent properties
Using (E u (WsO1m)2) 2, a coating solution was prepared by dispersing its fine particles in a solution of cyanethyl cellulose (active binder) dissolved in methylformamide (solvent), and this coating solution was A conductive layer made of Nesa film is coated on the conductive layer of a support provided on one side of a glass substrate to form a coating film having a thickness of about 20 μm, and then dried to form a coating film made of the polyacid compound. An electroluminescent layer having a structure in which the electroluminescent layer was dispersed in a binder was formed.

Using the support provided with the electroluminescent layer produced as described above, an electroluminescent device was produced in the same manner as in Example 1, and a test was conducted in which alternating current voltage AC was applied in the same manner. Although red luminescence was obtained, the uniformity of the luminance was inferior to that obtained using the electroluminescent layer obtained in Example 1. This is due to the thickness of this electroluminescent layer and the This is thought to be because it is difficult to make the particle size and dispersion state of the acid compound particles uniform.

Furthermore, when the magnitude of the alternating current voltage AC was varied and the brightness-voltage characteristics were measured, the results shown in FIG. 2 were obtained.

As is clear from FIG. 2, an electroluminescent element having a structure in which a polyacid compound is dispersed in a binder, that is, a dispersed electroluminescent layer, is equipped with the electroluminescent layer obtained in Example 1. Compared to the electroluminescent device, the brightness-voltage characteristics rose slowly and the display characteristics were inferior.

〔Effect of the invention〕

As explained in detail above, the method for producing an electroluminescent layer of the present invention involves dissolving a precipitation compound in a solution of polyacid compound A, and then extracting polyacid compound B having electroluminescent properties from this solution. Because it is a precipitation method, the electroluminescent layer can be easily formed using low-cost manufacturing equipment, and it is also possible to form a thin layer of electroluminescent layer with uniform thickness over a large area. .

In addition, according to the electroluminescent device equipped with the electroluminescent layer manufactured by the manufacturing method of the present invention, the luminance of the electroluminescent layer that can be achieved with a driving voltage within a practical range is increased, and the display characteristics are improved. In addition, the driving voltage required to emit light with sufficient brightness may be low, and the voltage burden on the driving power source can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a configuration example of an electroluminescent device having an electroluminescent layer manufactured by the manufacturing method of the present invention, and FIG. 2 shows the brightness-voltage characteristics of the electroluminescent device obtained in Example 1. This is a graph showing. 1...Support 2...Electroluminescent layer 3...
Aluminum vapor deposited film 4...Mylar 5...Glass substrate 6...
・Conductive layer Fig. 11 Fig. 12 εP applied voltage (V)

Claims (3)

[Claims] (1) A method for producing an electroluminescent layer having electroluminescent properties, which comprises adding to a solution of polyacid compound A a compound soluble in this solution to precipitate polyacid compound B having electroluminescent properties. A method for producing an electroluminescent layer, characterized in that it is deposited on a support. (2) The method according to claim 1, wherein the polyacid compound B constituting the electroluminescent layer is represented by any one of the following general formulas (1) to (3). Method for manufacturing a light-emitting layer. General formula (1); (M_A)_x [L((M_B)_5O
_18)_2]_y General formula (2); (M_A)_x[L
((X_A)(M_B)_1_1O_3_9)_2]_
y general formula (3); (M_A)_x[L((X_B)_2
(M_B)_1_7O_6_1)_2]_y[General formula (
In 1) to (3), M_A represents a monovalent, divalent or trivalent metal, and L is
Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
y, Ho, Er, Tm, Yb; M_B represents any metal of W, Mo, V, Nd, Ta; X_A and X_B are trivalent, tetravalent, or pentavalent. x and y represent positive integers determined such that the overall valence is 0 in each of the general formulas (1) to (3). ] (3) In the method according to claim 2, M_A is Li, Na, K, Rb, Cs, Be, Mg,
Represents any metal of Ca, Sr, Ba, Cu, Bi, and L is Ce, Pr, Nd, Pm, Sm, Eu, Gd, T
b, Dy, Ho, Er, Tm, Yb, M_B represents W or Mo, X_A represents any element of Si, Ge, P, A_s, X_B represents P or A_s, and x and y represent positive integers determined such that the overall valence is 0 in each of general formulas (1) to (3). Method.