JPH04133284A - Manufacturing method of thin film phosphor - Google Patents

Abstract

PURPOSE:To improve properties of crystals and high luminance brightness light emission by making a thin film phosphor of main component of alkaline earth metal phosphate on a substrate through vacuum deposition, followed by heating in an inert gas. CONSTITUTION:A transparent electrode such as ITO is formed on a glass substrate. Over it is formed an insulation layer of a high dielectric thin film such as Ta2O5. Over it is formed a thin film phosphor as a light emitting layer of SrS or Ce with main components of MgS, CaS, SrS, and BaS by electron beam deposition. With the substrate temperature of less than 400 deg.C, patterning is made with a deposition mask. This thin film element is then heat treated at a temperature higher than 600 deg.C in inert gas with a heating device. and finally an aluminum electrode is deposited on the light emitting layer to make an alternate current thin film electric field light emitting element. This improves properties of crystals and high brightness light emission and makes the patterning very fine.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to, for example, various display devices and light emitting units [Summary of the Invention] The present invention relates to electroluminescent elements used in display devices and light emitting application devices. In particular, it relates to the production of thin film phosphors used in AC thin film electroluminescent devices.

Specifically, alkaline earth metal sulfides (MgS, CaS
, SrS, Ba5) as main components is produced at a low temperature (less than about 400°C) without raising the substrate temperature to a high temperature (about 400°C or higher), and then heated using a heating device such as an electric furnace or a lamp. These thin film phosphors are heat treated in an inert gas. According to the present invention, it is possible to manufacture a thin film phosphor for an electroluminescent device that has the same or better characteristics than those manufactured at a high substrate temperature. Further, since the vacuum device can be manufactured without raising the substrate temperature to a high temperature, a simple mechanism is sufficient since the vacuum device does not require heat resistance measures. Furthermore, a vapor deposition mask can be used for the patterning required to separate thin-film phosphors that emit light in different colors for color display.

If the plate temperature is increased, the vapor deposition mask will be deformed due to thermal expansion, making it difficult to perform high-definition patterning on the thin film electroluminescent phosphor.

An object of the present invention is to provide a method for manufacturing a thin film electroluminescent phosphor with good crystallinity and high brightness even when the substrate temperature during vacuum deposition is lowered.

[Conventional technology 1] In the conventional thin film phosphor manufacturing method, the substrate temperature is
Alkaline earth metal sulfides (MgS, CaS, SrS, Ba5) are produced using a vacuum evaporation method at a high temperature of 00°C or higher.
We have obtained a thin film electroluminescent phosphor with good crystallinity and high brightness luminescence, which consists of .

[Means for Solving the Problems] The present invention provides a thin film phosphor containing an alkaline earth metal sulfide as a main component on a substrate by a vacuum evaporation method in which the temperature of the substrate is below 400°C. It is characterized by heat-treating the thin film phosphor in an inert gas.

[Problem to be Solved by the Invention 1] However, the vapor deposition equipment used in the production of thin-film phosphors must be able to withstand high-temperature environments and corrosion caused by sulfides in this high-temperature environment, so they are expensive. It became. In addition, in the present invention, even if the substrate temperature during vacuum deposition is lowered, by applying heat treatment in an inert gas, thin film electroluminescent fluorescence with good crystallinity and high brightness luminescence can be obtained. You can manufacture your body. Since the substrate temperature can be lowered during vacuum deposition, the structure of the deposition apparatus can be simplified and the patterning of the thin film phosphor can be patterned with higher precision.

[Example 1 The present invention will be explained below by way of examples.

A case will be described in which the present invention is applied to, for example, manufacturing an AC thin film electroluminescent device.

First, ITO (indium tin oxide) is placed on the substrate glass.
A transparent electrode such as, for example, a high dielectric thin film such as tantalum pentoxide (Ta*Os) as an insulating layer is formed thereon by a conventional method. here.

A dielectric thin film such as zinc sulfide (ZnS) may be formed as a buffer layer on the high dielectric thin film.

Next, alkaline earth metal sulfides (MgS, C
For example, Sr containing aS, SrS, Ba5) as the main component
S: Form a thin film phosphor such as Ce. At this time, the thin film is formed by resistance heating or electron beam vapor deposition, the substrate temperature is kept below 400° C., and patterning is performed using a vapor deposition mask. A dielectric thin film such as zinc sulfide (ZnS) may be formed as a buffer layer on this thin film phosphor.

Next, the thin film element thus formed is heated in an inert gas by a heating device such as an electric furnace or a lamp, for example, at 600°C.
Heat treatment is performed at a temperature of ℃ or higher. Note that in a type of device called a double insulation type, a second insulating layer is sometimes formed on the light emitting layer, and heat treatment may be performed after forming the second insulating layer.

However, there is also a type in which the second insulating layer is omitted.

Finally, an aluminum electrode is deposited on the heat-treated light emitting layer or the second insulating layer to obtain an AC thin film electroluminescent device.

[Experimental Example I An insulating layer of tantalum pentoxide (TB, Os) was formed in advance by high-frequency sputtering on a glass substrate equipped with a transparent electrode such as ITO, and zinc sulfide (ZnS) was further vapor-deposited as a buffer layer. Thereafter, a light emitting layer of strontium sulfide (SrS:Ce) with cerium (Ce) inactivated was formed by electron beam evaporation at a substrate temperature of 200 to 300°C. At this time, the length is 50 mm and the width is 0 using the vapor deposition mask.
．． A 3 mm strip pattern was formed. Next, zinc sulfide (ZnS) was further formed as a buffer layer on the light emitting layer by vapor deposition. The thus formed thin film element was heated in an electric furnace in argon gas at about 600 to 700°C, and after cooling, an insulating layer made of Ta205 and an aluminum electrode were formed.

FIG. 1 shows the brightness-voltage characteristics (Example) when a 1 kHz sinusoidal AC voltage was applied to the AC thin film electroluminescent device manufactured in this way. Compared to the brightness-applied voltage characteristics (comparative example) of an electroluminescent device using a light-emitting layer manufactured by a conventional method at a substrate temperature of 600°C, the AC thin film electroluminescent device according to the present invention (example) has higher luminance. It can be seen that it shows gender.

[Effect of the invention 1 As explained above, according to the method of the present invention, even if the substrate temperature during vacuum deposition is lowered, good crystallinity and high quality can be achieved by performing heat treatment in an inert gas. A thin film phosphor that emits luminance can be manufactured.

Furthermore, as the substrate temperature decreases, it is possible to simplify the structure of the vapor deposition apparatus and to increase the precision of the thin film phosphor film. Furthermore, depending on the type of thin film phosphor, the purity of the emission spectrum can be improved, which is convenient when used as part of the three primary colors.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the brightness-applied voltage characteristics of an AC thin film electroluminescent device using a thin film phosphor obtained according to the present invention and a conventional thin film phosphor.

Claims (1)

[Claims] 1) After producing a thin film phosphor containing an alkaline earth metal sulfide as a main component on a substrate by a vacuum evaporation method at a temperature of the substrate below 400°C, the thin film phosphor is heat-treated in an inert gas. A method for producing a thin film phosphor, characterized by: