JPH042764A - Production of thin-film el element - Google Patents

Abstract

PURPOSE:To change the concn. at the light emitting center in a light emitting layer without changing the crystallinity of a base material and depositing rate by keeping the energy of an electron beam flowing into a raw pellet constant and changing the amplitude of an AC magnetic field generated by a deflecting coil. CONSTITUTION:The element is formed with a glass substrate 1, transparent electrode 2, SiO2 film 3, Si-N film 4, light emitting layer 5 consisting of ZnS:Mn, Si-N film 6, Al2O3 film 7 and back plate 8 of the Al film. When the light emitting layer 5 is formed, the raw pellet 11 is placed on a hearth 12 in a vacuum deposition device 20, the substrate 1 is set, the chamber 10 is evacuated, and the substrate 1 is kept at a certain temp. by a heater 16. A shutter 15 is then opened, the pellet surface 11a is irradiated with an electron beam of constant energy from an electron gun 14 while scanning the surface, and ZnS and Mn are vapor-deposited. At this time, the amplitude of the AC magnetic filed generated by the deflecting coil 17 is made smaller than before to reduce the scanning width, and irradiation is carried out. The Mn concn. increases as the width is reduced, and a desired Mn concn. is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of manufacturing a thin film EL element used as a display device of electronic equipment, and more specifically to a method of forming a light emitting layer of a thin film EL element.

<Prior Art> Generally, as this type of thin film EL element, one having a three-layer structure as shown in FIG. 9, for example, is known. This thin film EL element is made of ITO (
A band-shaped transparent electrode 22 made of (tin-doped indium oxide) is formed in a parallel pattern at intervals, and oxide A is formed on this.
A first dielectric film 24 is formed of ltOs, 5iOt, T i O* or nitride S t s N 4 . On top of this, a light-emitting layer 25 having a composition in which a trace amount of Mn is added as a light-emitting center to a base material made of ZnS or Zn5e, etc., and a second dielectric film 26 made of the above-mentioned oxide or nitride are formed in order. On top, a band-shaped back electrode 28 made of Al is arranged in a direction perpendicular to the transparent electrode 22.
A pattern is formed in parallel at intervals.

The thin film EL device manufactured in this way has a transparent electrode 2
By selectively applying a voltage to the picture electrodes 22 and 28, the light emitting layer 25 at the intersection of the picture electrodes 22 and 28 can be caused to emit light in any combination in the form of dots, thereby producing a desired dot matrix display.

When forming the light emitting layer 25 of the thin film EL device, first the Z
Additives such as Mn, which should form luminescent centers, are mixed into a base material such as nS at a constant ratio, and this mixture is molded and sintered to produce raw material pellets. These raw material pellets are deposited on the first dielectric film 24 on the surface of the transparent substrate 21 by electron beam evaporation.

At this time, as shown in Fig. 8, the electron beam is scanned in the X-axis and Y-axis directions by an alternating magnetic field generated by a deflection coil so that the surface 11a of the raw material pellet II can be uniformly heated and evaporated. while irradiating. That is, a square area A inscribed in the edge of the circular surface 11a of the raw material pellet If.

The electron beam is irradiated over the entire area. Note that the scan widths in the X-axis direction and the Y-axis direction at this time are each expressed as l for convenience. The scan frequency is, for example, 50 Hz in the X-axis direction and 500 Hz in the Y-axis direction.

By the way, the Mn concentration in the light emitting layer 25 is an important factor that determines the light emitting characteristics of the thin film EL element.

First, the brightness changes as shown in FIG. 6 according to the Mn concentration and shows a peak. Therefore, M indicating this peeling
High brightness can be obtained by adjusting the density to n. In addition, when the Mn concentration is high, the brightness-voltage curve (B
-V curve) becomes steep, making it easier to obtain high brightness, but when the Mn concentration is low, the change in brightness with respect to voltage becomes gradual, and the gradation level becomes variable. Furthermore, M
When the n concentration is increased, a memory function occurs and it becomes possible to use it as a memory panel. In this way, by controlling the Mn concentration in the light-emitting layer 25, thin film EL elements with various functions can be manufactured, such as a gradation panel, a high-brightness panel, and a memory panel, in order of decreasing Mn concentration. I can do it.

Conventionally, in order to change the Mn concentration in the light emitting layer 25 depending on the application, there has been a method of controlling the Mn additive content in the raw material pellet 11 by changing the ratio of the Mn additive in the raw material pellet 11, and a method of controlling the temperature of the substrate 21 when performing electron beam evaporation of the light emitting layer 25. A method of controlling the temperature by changing the substrate temperature is known. In the case of the method of controlling by changing the ratio of Mn additive in raw material pellet) 11, the sublimation temperature of ZnS and MnS is 1080 ° C. at a vapor pressure of 10-” torr, respectively.
Unlike at 1500°C, the Mn concentration in the steam is lower than the proportion of the Mn additive in the raw material pellets 11, so the proportion of the Mn additive in the raw material pellets 11 is set in advance to the target Mn
Electron beam evaporation is performed with the concentration higher than the concentration. On the other hand, in the case of the method of changing the substrate temperature, the relationship between the Mn concentration in the light emitting layer 25 and the substrate temperature is determined by using the fact that the Mn concentration increases as the substrate temperature rises, as shown in FIG.
Electron beam evaporation is performed with the substrate temperature set so that the target Mn concentration is achieved. Note that as the substrate temperature rises, M
The reason why the n concentration increases is that while the adhesion coefficient of ZnS to the substrate 21 decreases as the substrate temperature increases,
This is because the adhesion coefficient of MnS is hardly related to the substrate temperature.

<Problems to be Solved by the Invention> However, in the case of the method of changing the ratio of Mn additive in the raw material pellet ll, the luminescent layer 25 with a certain Mn concentration
There is no problem when just forming the Mn additive, but when it is desired to change the Mn concentration of the light emitting layer 25 in order to give the thin film EL device various functions, it is necessary to prepare several types of raw material pellets with different proportions of Mn additive. There is a problem that it must be done.

In addition, in the case of the method of changing the substrate temperature, the crystallinity of ZnS changes depending on the substrate temperature, and as mentioned above, ZnS
Since the deposition rate of Mn changes, it is not preferable as a method for controlling the Mn concentration.

Therefore, an object of the present invention is to develop a thin film EL device in which the concentration of luminescent centers in the luminescent layer can be changed using raw material pellets with the same proportion of additives without changing the crystallinity or deposition rate of the base material. The purpose is to provide a manufacturing method.

Means for Solving the Problems> In order to achieve the above object, the present invention mixes additives to form a luminescent center in a fixed ratio into a base material constituting a luminescent layer, and molds this mixture. Using an electron beam evaporation method, the surface of the raw material pellet is irradiated with an electron beam while scanning with an alternating magnetic field generated by a deflection coil, and the base material and additives are evaporated onto the substrate to form a light emitting layer. In the method for manufacturing a thin film EL device, the energy of the electron beam flowing into the raw material pellet per unit time is kept constant, and the amplitude of the alternating magnetic field generated by the deflection coil is changed in one direction or perpendicular to each other. The present invention is characterized in that the energy density of the electron beam per unit area of the region of the surface of the raw material pellet to which the electron beam is irradiated is set by changing the scanning width in two directions.

Further, it is preferable that the center value of the alternating magnetic field is changed at a period longer than the period of the alternating magnetic field, so that the entire surface of the raw material pellet is irradiated with the electron beam.

Further, it is desirable to rotate the raw material pellet at a period longer than the period of the alternating magnetic field so that the entire surface of the raw material pellet is irradiated with the electron beam.

Furthermore, it is desirable to change the scan width as the vapor deposition progresses to form a light-emitting layer having the concentration distribution of the additive in the film thickness direction.

Effect> By keeping the energy of the electron beam flowing into the raw material pellet per unit time constant, the evaporation rate of the base material becomes constant. Therefore, by keeping the substrate temperature constant, vapor deposition can be performed without changing the deposition rate of the base material. Moreover, by changing the amplitude of the alternating magnetic field in this state, the scanning width of the electron beam is changed, and the energy density per unit area of the electron beam is set on the surface of the raw material pellet. The temperature of the irradiated area can be varied. When the temperature of the area irradiated with the electron beam is changed,
The ratio of the evaporation rates of the base material and the additive changes depending on the temperature dependence of vapor pressure, and as a result, the concentration of luminescent centers in the luminescent layer changes. Therefore, by changing the scan width of the electron beam, the concentration of luminescent centers in the luminescent layer can be freely controlled.

Furthermore, if the central value of the alternating magnetic field is changed at a period longer than the period of the alternating magnetic field, and the entire surface of the raw material pellet is irradiated with the electron beam, even if the scanning width of the electron beam is narrowed. , the entire surface of the raw material pellet evaporates approximately evenly. Therefore, a portion of the raw material pellets does not remain without being evaporated, and the entire raw material pellets are effectively utilized.

Furthermore, when the raw material pellet is rotated at a cycle longer than the cycle of the alternating magnetic field and the entire surface of the raw material pellet is irradiated with the electron beam, the electron beam scans as in the case described above. Even if the width is narrowed down, the entire surface of the raw material pellet evaporates approximately evenly. Therefore, a portion of the raw material pellets does not remain without being evaporated, and the entire raw material pellets are effectively utilized.

Furthermore, when a light emitting layer having the above scan width is formed as vapor deposition progresses, thin film EL elements having various functions depending on the purpose can be manufactured.

<Example> Hereinafter, the method for manufacturing a thin film EL element of the present invention will be explained in detail with reference to Examples.

FIG. 5 shows an example of a cross section of a thin film EL device manufactured according to the present invention. 1 shows a glass substrate with a thickness of 1 to 3 III, and 2 shows an ITO (tin-doped indium oxide) film formed on this glass substrate L with a thickness of 1000 to 1800 by sputtering, and then etched to form a large number of ITO (tin-doped indium oxide) films. This figure shows a transparent electrode formed by parallel strip-shaped turns. Next, 3 is a Sio2 film deposited on this transparent electrode 2 to a thickness of 200 to 800 mm by sputtering method, and 4 is this 5
Ift film 3 is coated with a thickness of 1000 to 30 mm by sputtering method.
The figure shows a 5t-N film laminated to 0.00. The above Si
The O* film 3 and the 5t-N film 4 constitute a first dielectric layer A. Further, 5 is a Z layer formed on the 5t-N film 4 to a thickness of 6,000 to 8,000 by the electron beam evaporation method described later.
nS: indicates a light-emitting layer made of Mn. 6 is a 5i-N film laminated to a thickness of 1000 to 3000 nm on this light emitting layer 5 by sputtering, and 7 is an A Q deposited on this 5i-N film 6 to a thickness of 200 to 600 nm by sputtering.
*03 membrane is shown. The above 5t-N film 6 and AQ,
The O5 film 7 constitutes the second dielectric layer B. 8 is this A
On the QtO1 film 7, a thickness of 2000 to 6
The back electrode is formed by forming an AQ film of 0.0000000000000 and etching it to form a pattern into a large number of parallel strips in a direction perpendicular to the transparent electrode 2.

An AC rolling voltage 9 is applied between the transparent electrode 2 and the back electrode 8 to perform dot matrix display. Note that the surface of this thin film EL element is sealed with seal glass or the like to prevent moisture.

When forming the above-mentioned light-emitting layer 5, first, 0.40 to 0.0. ．． They are mixed at a ratio of 50 wt%, and this mixture is molded and sintered to produce raw material pellets 11. Then, as shown in FIG. 4, the raw material pellets 11 are placed on the hearth 12 in the vacuum evaporation apparatus 20. Further, a glass substrate l on which a light emitting layer 5 is to be formed is set directly under the heater 16 of this vacuum evaporation apparatus 20. Then, the inside of the chamber 10 is evacuated through the exhaust hole 10a to create a vacuum state, and the glass substrate 1 is heated to 200 to 280 cm by the heater 16.
Maintain a constant temperature in the range of 0°C. In this state, the shutter 15 is opened, and the surface 11a of the raw material pellet 11 is irradiated with an electron beam from the electron gun 14 with a constant energy in the output range of 500 to 800 W while scanning. and,
Raw material pellets) 11 are heated and evaporated to be deposited on the first dielectric layer A on the surface of the glass substrate l. At this time, next
Or, as described in (2), the amplitude of the alternating magnetic field generated by the deflection coil 17 is made smaller than that of the conventional method, and the scan width is narrowed down for irradiation.

■As shown in FIG. 1(a), in order to increase the energy density per unit area of the area of the surface 11a of the raw material pellet 11 that is irradiated with the electron beam, the scanning width in the X-axis direction ==l, Scan width in the x-axis direction = X (X = 0 ~
l). That is, the area Ax is scanned by changing the scan width in one direction compared to the conventional method. When deposited in this manner, the relationship between the Mn concentration in the light emitting layer 5 and the scan width X changes as shown in FIG. 2, depending on the temperature dependence of the vapor pressures of ZnS and MnS. That is, as the scan width X is narrowed down, the Mn concentration increases. therefore,
By adjusting the scan width X, a desired Mn concentration can be obtained.

However, if only the area Ax+ is scanned, a part (the right half) of the raw material pellet 11 will remain without being evaporated.

Therefore, by changing the center value of the alternating magnetic field generated by the deflection coil 17, the X-axis position (scan center) is slowly vibrated in the X-axis direction as shown in FIG. 1(b). The period of vibration is set to IHz or less, for example, 1760Hz. In this case, the entire raw material pellet 11 can be irradiated with an electron beam and evaporated uniformly, and the entire raw material pellet 11 can be effectively utilized. Note that both the X-axis position and the Y-axis position may be fixed, and the hearth 12 holding the raw material pellets 11 may be provided with an autorotation mechanism to cause the raw material pellets 11 to rotate. With this method as well, the entire raw material pellet 11 can be irradiated with the electron beam and evaporated uniformly, and the raw material pellet 11
The whole can be used effectively.

Furthermore, the Mn concentration distribution in the film thickness direction of the light-emitting layer 5 may be changed by changing the scan width X in the X-axis direction as the vapor deposition progresses. Thereby, thin film EL elements having various functions depending on the purpose can be manufactured.

■As shown in Figure 3 (a), the scan width in two directions is changed compared to the conventional one, Y-axis scan width = y, x-axis scan width = x (y = 0 to 1, x = 0). ~1).

Then, the value of area xy of area Axy is adjusted. In this case, as shown in FIG. 2, the area xy of the area Axy
As becomes smaller, the Mn concentration in the light emitting layer 5 becomes higher. Therefore, a desired Mn concentration can be obtained by adjusting the area xy of the region Axy. Moreover, the energy density of the electron beam per unit area can be set higher than in the case described in (2), and a higher Mn concentration can be obtained.

In this case, in order to effectively utilize the entire raw material pellet 11, as shown in FIG. All you have to do is vibrate it to make the scan center move in a circular or elliptical motion. In addition, as mentioned in ■, Haas 12
An autorotation mechanism may be provided to cause the raw material pellets 11 to rotate.

Furthermore, the scan width X in the X-axis direction and the Y-axis direction.

The Mn concentration distribution in the thickness direction of the light-emitting layer 5 may be changed by changing y as the vapor deposition progresses. Thereby, thin film EL elements having various functions depending on the purpose can be manufactured.

<Effects of the Invention> As is clear from the above, the method for manufacturing a thin film EL device of the present invention is such that the energy of the electron beam flowing into the raw material pellet per unit time is kept constant, and the energy of the electron beam generated by the deflection coil is kept constant. By changing the amplitude of the alternating magnetic field, the scan width in one direction or in two directions perpendicular to each other is changed to increase the energy density of the electron beam per unit area of the region of the surface of the raw material pellet to which the electron beam is irradiated. Since the concentration of the luminescent center in the luminescent layer can be freely controlled.

Furthermore, if the center value of the alternating magnetic field is changed at a period longer than the period of the alternating magnetic field, and the entire surface of the raw material pellet is irradiated with the electron beam, the entire raw material pellet can be effectively utilized. can.

Furthermore, if the raw material pellet is rotated at a cycle longer than the cycle of the alternating magnetic field and the entire surface of the raw material pellet is irradiated with the electron beam, the entire raw material pellet can be effectively utilized as well. .

Furthermore, when forming a light-emitting layer having a concentration distribution of the additive material in the film thickness direction by changing the scan width as vapor deposition progresses, it is possible to form a thin film EL with various functions depending on the application.
A device can be manufactured.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1(a) is a diagram showing a state in which the surface of a raw material pellet is irradiated with an electron beam according to a method for manufacturing a thin film EL device according to an embodiment of the present invention, and FIG. FIG. 2 is a diagram showing the relationship between the scan width of the electron beam and the Mn concentration in the light emitting layer. FIG. Figures illustrating the state in which the surface of a raw material pellet is irradiated with an electron beam according to the manufacturing method of a thin film EL element. Figures (b) and (c) show the temporal changes in the scanning center of the electron beam in the X-axis direction and Y-axis direction, respectively. 4 is a diagram showing a vacuum evaporation apparatus used for irradiating an electron beam, and FIG. 5 is a diagram showing a thin film E to be produced.
Figure 6 is a diagram showing the cross-sectional structure of the L element, Figure 6 is a diagram showing the relationship between the Mn concentration in the light emitting layer and brightness, and Figure 7 is a diagram showing the relationship between the substrate temperature during electron beam evaporation and the Mn concentration in the light emitting layer. Figure 8 is a diagram showing a state in which the surface of a raw material pellet is irradiated with an electron beam by a conventional thin film EL device manufacturing method;
The figure is a diagram showing a cross-sectional structure of the conventional thin film EL element. l...Glass substrate, 2...Transparent electrode, 3...St
ow film, 4.6...5i-N film, 5... light emitting layer, 7
... AQ*Os film, 8... Back electrode, 9... AC driving voltage, lO... Chamber, 11... Raw material pellet, lla... Surface, 12... Hearth, 14...・・・
Electron gun, 15...Shutter, 16...Heater, 20
...Vacuum deposition apparatus, A...First dielectric layer, A, +
, A X t , A XY...irradiation area, B.
-Second dielectric layer. Patent Applicant Sharp Co., Ltd. Agent Patent Attorney Aobai Ao and 1 other famous family 3 leaps

Claims (4)

[Claims] (1) Additives to form a luminescent center are mixed in a fixed ratio into a base material that is to form a luminescent layer, and an electron beam is deflected onto the surface of a raw material pellet made by molding this mixture using an electron beam evaporation method. In a method for manufacturing a thin film EL device in which a light-emitting layer is formed by depositing the base material and additives on a substrate by scanning and irradiating with an alternating magnetic field generated by a coil, the material flows into the raw material pellets per unit time. While keeping the energy of the electron beam constant, by changing the amplitude of the alternating magnetic field generated by the deflection coil, the scanning width in one direction or in two mutually perpendicular directions is changed, and the surface of the raw material pellet is A method for manufacturing a thin film EL device, characterized in that the energy density of the electron beam per unit area of the region to be irradiated with the electron beam is set. (2) The electron beam is irradiated onto the entire surface of the raw material pellet by changing the center value of the alternating magnetic field at a cycle longer than the cycle of the alternating magnetic field. A method for manufacturing a thin film EL element. (3) The thin film EL element according to claim 1, wherein the raw material pellet is rotated at a period longer than the period of the alternating magnetic field, and the entire surface of the raw material pellet is irradiated with an electron beam. manufacturing method. (4) The thin film according to claim 1, 2 or 3, wherein the scan width is changed as the vapor deposition progresses to form a light-emitting layer having a concentration distribution of the additive in the film thickness direction. A method for manufacturing an EL element.