JPH0242421A - Production of thin el film and pellet for vapor deposition - Google Patents

Abstract

PURPOSE:To uniformize the activator concn. in a luminescent film formed by vapor deposition in the thickness direction as well and to rapidly and surely produce the luminescent film having stable characteristics by pelletizing raw material powder only by pressing the powder with a pressurizing press at the time of producing a vapor deposition pellet in an electron beam vapor deposition method. CONSTITUTION:The bound body formed by applying a pressure to the powder for which the sulfide of metal is used as the base body and a transition metal is used as an activator is made into the vapor deposition pellet. This pellet is used in the electrode beam vapor deposition method. Splashing of a vapor deposition source by the instantaneous evaporation at the moment when an electron beam comes into contact with the pellet and local splashing of the gas is prevented in this way and the activator concn. distribution in the vapor deposited film is uniformized. Since the vapor deposition pellet is produced by the press, the pellet is easily produced in a short period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing an EL thin film and a pellet for vapor deposition that improve luminance and luminous efficiency.

[Prior Art] Recently, EL elements (electroluminescent dice) have been attracting attention as display members for computer displays, televisions, and other devices. The main reason for this is that they are thinner and more portable than display devices such as ORTs. In addition, because it is a type of element that emits light by itself, it is easy to see even in dark places, has a wide viewing angle, and has no polarization characteristics, so it is said to have higher display quality than liquid crystal elements, which are thin display elements similar to EL elements. This is also one of the big advantages.
It's happening.

Among them, the so-called thin 111EL element, which is composed of a thin film, has high luminance and can reduce the size of each dot when performing dot matrix driving, making it possible to create high-resolution displays and televisions. .

The light emitting film of this thin film EL element usually uses an activated rare earth or transition metal element as an activator to form a luminescent center in a metal sulfide or selenide as a matrix. The above-mentioned light-emitting film is usually made into a thin film using an electron beam method, but the above-mentioned material powder consisting of the above-mentioned base material and activator is press-molded as a vapor deposition source, heated at high temperature, and sintered. The use of prepared pellets has already been considered as described in Japanese Patent Publication No. 10358/1983.

There are two reasons why pressure sintered pellets are used as a deposition source in this way. The first reason is that when the electron beam hits the deposition source, it is necessary to form the deposition source powder into a relatively large lump in order to prevent the deposition source powder from scattering due to instantaneous evaporation or local gas scattering. The second problem is that the concentration of the activator in the created film differs from the concentration in the vapor deposition source due to the difference in vapor pressure between the elements constituting the base material and the activator, and the concentration of the activator in the created film differs. This is to solve the problem that the active agent concentration has a distribution in the thickness direction of the film, making it impossible to form a film with uniform characteristics. For pressure sintered pellets, when the electron beam is sufficiently narrowed and irradiated, only a very shallow depth and a small range from the surface of the pellet are rapidly heated, and only that portion of the pellet is instantaneously evaporated.

Therefore, all the elements evaporate at the same time, so that the concentration of the activator in the deposited film is almost the same as the concentration in the pellet. In addition, because the electron beam is rapidly scanned so that the beam always hits different parts, the distribution of the liquid phase-plane relationship of the activator does not occur, and as a result, the concentration of the activator changes over time. In other words, the concentration distribution of the activator does not occur in the thickness direction of the deposited film.

[Problems to be Solved by the Invention] As described above, when creating Thin Film B by the electron beam evaporation method, there are the following three problems as a method using pressure sintered pellets as the evaporation source. There is.

The first problem is that it takes a lot of effort to make pellets. That is, in order to create pressure sintered pellets, first, the raw material powder is molded under a pressure of 75), then degassed in a vacuum at around 500"C, and then heated at approximately 1000"C in that state. Since it requires heating at a temperature above and baking it to harden it, it takes a lot of time and requires the use of large-scale equipment such as a vacuum heating device.

A second problem is that the concentration of the activator in the extracted pellets may vary due to the temperature increase during sintering. Generally, the concentration on the pellet surface is lower than the concentration in the center, so if the pellet is evaporated sequentially from the surface, the concentration of the activator will gradually increase, and the concentration of the activator in the KL pattern will be uneven. There are some problems. Therefore, it is difficult to make pellets with an appropriate activator concentration, and the activator concentration is distributed in the thickness direction of the produced ELL optical film, resulting in a decrease in luminous efficiency and a shortened lifetime. It was causing deterioration.

Further, when the raw material powder of the pellets is prepared by method 1 of thermally diffusing an activator into the base powder, the activator has already entered the base powder and forms a luminescent center. This can be confirmed by the fact that fluorescence is emitted when the raw material powder is irradiated with ultraviolet light.

However, when such a powder is made into pellets by the above-described pressure sintering process and is irradiated with ultraviolet rays, the intensity of the fluorescent light emitted is substantially reduced compared to the case of powder. In general, the matrix used for EL emission has a large absorption coefficient for ultraviolet rays, and the ultraviolet rays irradiated onto the pellets are absorbed by the surface of the pellet.

The fact that the amount of fluorescent light excited and emitted by ultraviolet light has decreased is consistent with the idea that the pressure sintering process pulls out the activator near the surface of the pellet, reducing the number of luminescent centers. Korean matches.

A third problem is that pressure sintered pellets are easily charged by electron beams, resulting in a reduction in the deposition rate, an unstable state, and sometimes even failure in deposition. To counter this, delicate corrections such as increasing the acceleration voltage of the electron beam or making the beam current abnormally large have to be made, which poses problems in terms of equipment and cost. That is, in the electron beam evaporation method, an electron beam irradiated onto a pellet flows through the pellet as an electric current, and then flows into a conductive container supporting the pellet. At this time, most of the current flows through the surfaces and grain boundaries of the parent microcrystalline grains constituting the pellet. However, many of the base microcrystalline grains in the pressure sintered pellet are fused to each other, and the surface area of the microcrystalline grains is reduced as a whole, so there is no current channel for discharging the irradiated electron beam. The decrease in the chargeability of the pellets is one of the causes of the increase in the chargeability of the pellets. In addition, the activator added to the matrix contributes to improving electrical conductivity by creating an energy level within the forbidden energy level of electrons in the matrix, but the concentration of the activator near the pellet surface decreases. As a result, electrical conductivity decreases, making it easier for electron beams to be charged.

This invention provides a method for manufacturing an EL thin film that solves the problem with pressure sintered pellets by pelletizing the raw material powder simply by pressurizing it when producing pellets for deposition in the electrobeam evaporation method, and a deposition method for the deposition method. The purpose is to provide pellets.

[Means and effects for solving the problem] This method includes a powder consisting of a metal sulfide or selenide as a matrix and a transition metal or rare earth element as an activator, or a powder consisting of a matrix (Aa, Cd ,
, ) 3 (A selects at least one side from Zu, Br, and Oa, and α is the ratio between the music entry and Od, ranging from 0 to 1.
0) Au is used as an activator, and Q is used as a co-activator.
(Q is at least one selected from among At, Ga, In, F, O/, Br, and I) By using pellets formed by pressurizing and fixing powders in an electron beam evaporation method, It is possible to prevent the vapor deposition source from scattering due to instantaneous evaporation and local gas scattering when the electron beam hits the pellet, and to make the activator concentration distribution in the vapor deposited film uniform.

[Example 1] As the metal sulfide used as the base, for example, zinc sulfide (
As a transition metal as an activator in the Zn8) powder,
For example, a mixed powder mixed with manganese compound (Mn) powder is heated in a neutral atmosphere to diffuse and activate manganese into zinc sulfide microcrystals to form a raw material powder for pellets. The particle size of the zinc sulfide used as the base material of the pellets is 15 μm or less, and the ratio of manganese mixed into this zinc sulfide is 0.5 z amount to the zinc sulfide.

1.2 g of the raw material powder for pellets thus formed is fixed in a press by applying a pressure of 700 kg-Ji/- for 860 seconds. The pressed and fixed solid body has a cylindrical shape with a diameter of 1 cm, a thickness of approximately Q, and 5 cm, and is used as a pellet for vapor deposition.

When an EL light-emitting thin film was produced by an electron beam evaporation method using the above pellets for vapor deposition, an extremely good EL light-emitting film could be formed.

In other words, an evaporation pellet is irradiated with an electron beam to produce a evaporation film, but the pressed pellet does not break or fly away at all due to the beam, and the manganese in the produced zinc sulfide film The concentration of is the same as the concentration in the raw material powder for pellets (L 5 layers,
There was almost no loss of activator during pellet preparation.

Furthermore, since the pellets do not decrease their electrical conductivity, there is no charge, and there is no decrease in deposition rate as with pressure sintered pellets, allowing stable deposition at an electron beam acceleration voltage of 6 kV and a current of 10 to 20 mA. I was able to do it. Therefore, when using sintered pellets, the trouble of delicately adjusting the current between 10 mA and 100 mA depending on the charging state is eliminated, and sufficient current is passed through the pellet to stably supply heat. The deposition rate is fast and stable.

Using the manganese-activated zinc sulfide thin film produced by the above method, thin v! , produced an EL light emitting device.

That is, indium nine oquinide (
Yttrium oxide (Y) is deposited on top of it.
, 08) - Manganese-activated zinc sulfide (ZnS:Mn) - yttrium oxide (YtOs) - Each thin film of aluminum (A1) was formed in seven regions as a back electrode to form a double insulation structure thin film BL light emitting device. . When forming the thin film, the yttrium oxide thin film was made to have a thickness of 5,000 A by electron beam evaporation, and the manganese-activated zinc sulfide model was made to have a thickness of 10,000 A using the manufacturing method of the present invention.

The thin film EL light-emitting device fabricated by the method described above had sufficient luminance, for example, 200 cd/m when a 50 μsec pulse was applied (50) (z), and exhibited a high luminous efficiency. BL light emission that operates stably and has an extremely long device life is a mystery.

[Example 2] This GU describes an example of mixing europium (GU) compound powder as an activator with calcium sulfide (OaS) powder as a metal sulfide used as a base material.
At least one selected from among F, Cl, Br, and I is diffused as a co-activator. The particle size, mixing ratio, etc. of the mixture of Ca8 powder and Eu compound powder are the same as in the first embodiment (Eu is not activated by diffusion in OaS). This mixed powder is used as the raw material powder for pellets, and when applying pressure to this powder with a press machine, the pressure is reduced in a pressurized container with a Rokuri pump and then fixed under pressure to produce pellets for deposition. This is similar to the example.

When electron beam evaporation is performed using the evaporation pellets prepared in this example, the results are the same as in the first example (here,
There is no scattering of pellets, there is no decrease in the concentration of the activator in the deposited film, there is no variation in the concentration distribution in the thickness direction of the film, and there is no charging phenomenon of the pellets, so stable vapor deposition can be performed quickly.

The thin film deposited using the above procedure was evaporated in a N atmosphere for 6 hrs.
Heat treatment was performed at a temperature of 00° C. for about 30 minutes to complete the Eu doping.

When a thin film BL light emitting device similar to that of the first example was produced using the Eu-activated OaS thin film thus formed as a KL light emitting layer, it exhibited sufficient luminance and luminous efficiency. Further, the light emitting element is a light emitting film that operates stably over a long period of time.

In the above example, the pressure for compressing the powder was set at 500 to 8
00kg weight/c11, but 5001cg weight/
- If it is less than 800 kg/-, it will not be fixed sufficiently and
If this is the case, the powder crystal grains will be crushed and fixed, resulting in a decrease in the overall surface area of the microcrystal grains, a physical formation of luminescent centers, and a decrease in luminance.

[Example 3] (Zn0.9.OdO,1)S as a matrix A powder doped with 1700 ppm of Au as an activator and 600 ppm of At as a co-activator was used as the raw material powder for pellets. The conditions were the same as in Example 1, in which the pellets were depressurized using a rotary pump in a pressurized container, and then ζ pressure was applied to solidify the pellets to form pellets for trichome beam evaporation.

When electron beam evaporation is performed using the evaporation pellets prepared by J straining in this way, there is no scattering of the pellets as in the first embodiment, and the concentration of the activator and co-activator in the deposited film decreases, and the thickness of the film decreases. Variations in the concentration distribution in the direction were eliminated, and the charging phenomenon of the pellets was also eliminated, making it possible to perform stable vapor deposition quickly.

(ZnO-9, Odo, 1) S prepared by the above method
:Au.

An EL device was fabricated using an At thin film as an EL light emitting layer.

The insulating layer is made of Si and N produced by sputtering.

A double insulation type with a film thickness of about 230 mm was used.

The other configurations are the same as in the first embodiment.

Also (ZnO, 9, Odo, 1) S:Au, l'-
The light emitting layer is evaporated at a substrate temperature of 300°C9 a vacuum degree of lXl0
Electron beam evaporation was carried out under conditions of Torr to give a film thickness of 500 mn. Also, after forming the back insulating layer, the device is
Thermal annealing was performed for 30 minutes at 600'Q in an N atmosphere and air flow to activate Au, which is an activator.

50μsec@50μsec@FiL element fabricated as above.
When a 0 Hz symmetrical rectangular pulse was applied and the luminescence characteristics were measured, luminescence started at an applied voltage of 60 V, indicating that ZnS:M
It has become possible to drive at an extremely low voltage compared to n-type light-emitting layers. This is because the addition of Od to the matrix lowers the energy level of the interface level, which is the source of electrons for excitation of the luminescent center. Also, the luminescence o OIB chromaticity is x = 0.405, y = 0.567, and Zn8
; KL emission of Mn thin film (x=0549, y=OA 4
Compared to 6), it has been shifted to the yellow side, which is visually more sensitive, and is suitable for application to display devices, etc.

[Example 4] In this example, (8r0.9,0dO-1) was used as the parent body.
A powder obtained by adding 2000 ppm of Au as an activator and 1500 ppm of F as a co-activator to Example 8 was used as a raw material powder for pellets, and pellets for electron deposition were prepared in the same manner as in the third example.

When electron beam evaporation is performed using these pellets, the activator and coactivator concentrations in the deposited film are reduced, and the concentration distribution in the thickness direction of the film is reduced without scattering of the pellets, as in the first embodiment. In addition, the electrification phenomenon of the pellets was also eliminated, and precise vapor deposition could be carried out quickly.

The emission starting voltage of the thin film EL element having the luminescent layer composed in this manner is approximately 80 V, which is slightly higher than that of the element prepared in the third example, but the luminescence chromaticity is x = 0.250, y.
=Q-550, which showed a yellow-green to green color. The reason for this is thought to be that 8r, which has a large band gap, is included in the matrix.

Note that this invention is not limited to the above embodiments, and metal sulfides or selenium compounds include ZrS and O.
In addition to aS, OdS, 8r8. BaS, Zn5e.

0dSe, 5rSe and (Aa, act, a
)S (A is at least one selected from Zn and 5rOa, α is the ratio of A and Od above and takes a value of O to 1.0) may be used, and as an activator. In addition to Mn and Bu, transition metals or rare earth elements include Tb, (3e
, Pr, DyHo, Sm, Nd, Er, Tm, Yb, Au, etc. may be used, and At
, Ga, In, F', OzBr, and H, or a combination of these may be used as appropriate.

Furthermore, when activating the activator by diffusing it into the base powder material, it is preferable to select an oxidizing, neutral or reducing atmosphere depending on the material, and to heat the material in that atmosphere.

[Effects of the Invention] According to the present invention, since the evaporation pellets for electron beam evaporation are produced by pressing, they can be made extremely easily and in a short time.Moreover, large-scale equipment is not required, and the pellets are inexpensive. Because the activator concentration is uniform, the activator concentration in the deposited luminescent film is uniform in the thickness direction of the film, making it possible to quickly and reliably produce a luminescent film with stable characteristics. A method for producing an EL thin film and a pellet for deposition can be provided.

Claims (7)

[Claims] (1) A metal sulfide or selenide as a matrix,
Transition metal or rare earth element or A as activator
u, and Al, Ga, In as co-activators for this Au.
, F, Cl, Br, and I using an electron beam evaporation method in which a fixed body formed by applying pressure to a evaporated pellet is used. A method for producing an EL thin film. (2) Metal sulfide or selenide is Cds, Zns
, SrS, CaS, BaS, ZnSe, CdSe, Sr
Se and (A_α, Cd_1_−_α)S (A is Zr
, Br, and Ca, and α is A and C.
d), and the transition metals or rare earth elements are Mn, Tb, Ce, Pr, Dy,
2. The method for producing an EL thin film according to claim 1, wherein the materials are Ho, Sm, Nd, Ev, Tm, and Yb. (3) Transition metals, rare earth elements, or Au as an activator in the sulfide or selenide of the parent metal
was used as a coactivator for this Au, and Al, Ga, In,
2. The method for producing an EL thin film according to claim 1, wherein at least one selected from among F, Cl, Br, and I is diffused. (4) a metal sulfide or selenide as a matrix;
Transition metal or rare earth element or A as activator
u, and Al, Ga, In as co-activators for this Au.
, F, Cl, Br, and I. A vapor deposition pellet for use in an electron beam vapor deposition method, which is prepared by applying pressure and fixing powder made of at least one selected from among , F, Cl, Br, and I. (5) Metal sulfide or selenide is CdS, ZnS
, SrS, CaS, BaS, ZnSe, CdSe, Sr
Se and (A_α, Cd_1_−_α)S (A is Zn
, Sr, Ca, and α is A and C.
d), and the transition metals or rare earth elements are Mn, Tb, Eu, Ce, Pr,
The pellet for vapor deposition according to claim 4, characterized in that it contains Dy, Ho, Sm, Nd, Er, Tm, and Yb. (6) Claim 4, characterized in that the powder is fixed by applying a pressure of 500 to 800 kg weight/cm^3.
Pellet for deposition as described. (7) As a co-activator for rare earth elements, F, Cl, Br,
5. The deposition pellet according to claim 4, wherein at least one selected from I is diffused.