JP3769124B2 - Thin film EL device and method for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin film electroluminescent (EL) element used in a thin display device and a method for manufacturing the same.
[0002]
[Prior art]
Thin film EL elements that exhibit electroluminescence (EL) when applied with voltage are attracting attention as thin display devices because they have many excellent features such as high-luminance light emission, high-speed response, wide viewing angle, thin and light weight, and high resolution. Yes.
[0003]
The thin film EL element is a self-luminous type, and the color of light emitted is determined by the combination of the material of the light emitting layer of each element, that is, the combination of the semiconductor matrix constituting the light emitting layer and the light emission center added thereto. Conventionally, ZnS, CaS, SrS or the like is selected as a base material as a material of a light emitting layer, and a light emitting center material is selected from, for example, a group of transition metal elements. By these combinations, a yellow-orange light emitting element using ZnS: Mn or the like, a red light emitting element using CaS: Eu or ZnS: Sm, a green light emitting element using ZnS: Tb, CaS / Ce, or the like, and SrS: Blue light emitting elements using Ce, ZnS: Tm, and the like are known.
[0004]
However, what is currently put into practical use is only a yellow-orange monochromatic display using ZnS: Mn doped with manganese sulfide (Mn) in zinc sulfide (ZnS).
[0005]
For this reason, multicolor and full color are strongly desired, and in particular, an EL element using an alkaline earth metal sulfide light emitting layer has attracted attention.
[0006]
For example, as the most promising white light emitting element, J.A. J. et al. Appl. Phys. Vol. 25, no. 3, March, 1986, pp. As disclosed in L225-L227, there is a laminate of ZnS: Mn that emits yellow light and SrS: Ce that emits blue light, which is a complementary color thereof. If a white light emitting device is put into practical use, a monochrome display or a color display combined with a color filter can be realized. As a proposal for reducing the hysteresis characteristic of a white EL element for practical use of a white light emitting element, Japanese Patent Application Laid-Open No. 8-273833 discloses a transparent electrode 2 and a lower insulating layer on one surface of a translucent substrate 1. 3. The EL light emitting layer 4 ′, the upper insulating layer 6, and the upper electrode 7 are laminated in this order, and the EL light emitting layer 4 ′ has a laminated structure of ZnS: Mn and SrS: CeN, and the upper and lower layers sandwiching the SrS: CeN layer 4b. A layer in which ZnS: Mn layers 4a and 4c are formed is described (FIG. 7).
[0007]
[Problems to be solved by the invention]
In order to improve luminance and life characteristics, EL light-emitting layers such as alkaline earth metal sulfides generally have inert gas and / or post-treatment for stabilization of the light-emitting layer after film formation of the light-emitting layer. , Hydrogen sulfide (H ₂ Heat treatment is performed with a mixed gas containing S) and sulfur (S). Incidentally, in the thin film EL element described in the above-mentioned Japanese Patent Application Laid-Open No. 8-273833, after the upper insulating layer 8 is formed, a heat treatment is performed at 630 ° C. for 1 hour, and then the upper electrode 9 is formed. A white EL element is obtained.
[0008]
However, since equipment costs such as a heat treatment device and its exhaust gas treatment device are required, it has been difficult to obtain a stable alkaline earth metal sulfide EL light emitting layer at low cost.
[0009]
In addition, when a small amount of water vapor or carbon dioxide adsorbs oxygen on the surface of the light emitting layer, oxygen atoms on the surface of the light emitting layer move due to voltage application, resulting in a change in the crystal field around the light emission center such as Ce (cerium) This causes problems such as changes in element characteristics (display color and the like), fluctuations in threshold voltage, and deterioration in life characteristics. Although measures have been taken by increasing the number of light emitting layers, further improvements are desired.
[0010]
The present invention has been made paying attention to the above-mentioned problems, prevents adsorption of carbon dioxide gas, water vapor, etc. to the substrate surface, and is excellent in light emission luminance and life characteristics without performing heat treatment as a post-treatment after forming the light emitting layer. An object of the present invention is to provide a manufacturing method for obtaining a thin film EL device having an alkali metal sulfide EL light emitting layer at low cost and a thin film EL device having such excellent characteristics.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problems, a thin film electroluminescent (EL) device according to claim 1 is formed on a insulating substrate in order by a first electrode, a first insulating layer, a light emitting layer, and a second insulating layer. , And a thin film electroluminescent (EL) device comprising a second electrode, an electroluminescent (EL) light emitting layer comprising an alkaline earth metal sulfide, and a laminate on the electroluminescent light emitting layer An IIb-VIb group compound or an immediately upper layer obtained by adding a luminescent center selected from transition metals to the IIb-VIb group compound, and formed between the electroluminescent light emitting layer and the immediately upper layer; A transition metal-doped intermediate layer having a transition metal concentration higher than that of the immediately above layer. The transition metal doped intermediate layer has a higher transition metal concentration than the immediately above layer to a concentration that does not affect light emission. Features.
[0012]
The thin film electroluminescent (EL) device according to claim 2 is the thin film electroluminescent (EL) device according to claim 1, wherein a side surface of the light emitting layer and a side surface of the immediately upper layer are the second insulating layer. It is covered with.
[0013]
The thin film electroluminescent (EL) device according to claim 3 is the thin film electroluminescent (EL) device according to claim 1 or 2, wherein the transition metal-doped intermediate layer has a thickness of 50 nm or less. It is characterized by.
[0014]
5. The thin film electroluminescent (EL) device according to claim 4, wherein the thin film electroluminescent (EL) device according to any one of claims 1 to 3 is sulfided as the IIb-VIb group compound in the immediately upper layer. Zinc (ZnS) is used.
[0015]
The thin film electroluminescent (EL) element according to claim 5 is the thin film electroluminescent (EL) element according to any one of claims 1 to 4, wherein manganese (Mn) is used as the transition metal in the immediately upper layer. It is characterized by using.
[0017]
Claim 6 Thin film electroluminescent (EL) devices Claim 1-5 In the thin film electroluminescent (EL) element, zinc sulfide (ZnS) is used as the IIb-VIb group compound of the transition metal doped intermediate layer.
[0018]
Claim 7 Thin film electroluminescent (EL) devices Claim in any one of Claims 1-6 In the thin film electroluminescent (EL) element, manganese (Mn) is used as the transition metal of the transition metal-doped intermediate layer.
[0019]
Claim 8 Thin film electroluminescent (EL) devices Claim 7 In the thin film electroluminescent (EL) element, the transition metal concentration in the transition metal doped intermediate layer is 2 to 5 wt%.
[0020]
Claim 9 Thin film electroluminescent (EL) devices The method according to claim 1. In the thin film electroluminescent (EL) element, the film thickness of the immediately upper layer is 200 nm or more and 500 nm or less.
[0021]
Claim 10 A thin film electroluminescent (EL) element is a thin film EL element comprising a first electrode, a first insulating layer, a light emitting layer, a second insulating layer, and a second electrode in order on an insulating substrate. An electroluminescent (EL) light emitting layer containing an alkaline earth metal sulfide is provided as the light emitting layer, and a light emitting center selected from IIb-VIb group compounds or transition metals is added on the EL light emitting layer. A layer immediately above the IIb-VIb group compound is laminated with a thickness of 200 to 500 nm, and after the formation of the light emitting layer, it undergoes a heat treatment as a post-treatment for stabilizing the light emitting layer. The transition metal-doped intermediate layer has a higher transition metal concentration than the immediately above layer so as not to affect light emission. Features.
[0022]
Claim 11 Thin film electroluminescent (EL) devices Claim 10 In the thin film electroluminescent (EL) element, zinc sulfide (ZnS) is used as the IIb-VIb group compound in the immediately upper layer.
[0023]
Claim 12 Thin film electroluminescent (EL) devices The claim 10 or 11 In the thin film electroluminescent (EL) element, manganese (Mn) is used as the transition metal in the immediately upper layer.
[0024]
Claim 13 Thin film electroluminescent (EL) devices Claim in any one of Claims 10-12 A thin film electroluminescent (EL) device is characterized in that a transition metal-doped intermediate layer having a transition metal concentration higher than that of the immediately above layer is provided between the light emitting layer and the immediately above layer. Ru .
[0025]
Claim 14 A method for manufacturing a thin film electroluminescent (EL) element is a thin film in which a first electrode, a first insulating layer, a light emitting layer, a second insulating layer, and a second electrode are sequentially formed on an insulating substrate. In the method for manufacturing an electroluminescent (EL) element, a thin film EL light emitting layer containing an alkaline earth metal sulfide is formed as the light emitting layer on the first insulating layer, and the alkaline earth metal is formed. A transition metal-doped intermediate layer made of a IIb-VIb group compound doped with a transition metal is formed on the sulfide thin-film EL light-emitting layer, and a IIb-VIb group compound or a transition metal is formed on the transition metal-doped intermediate layer. The luminescent center selected from is laminated so that the concentration of the transition metal in the transition metal-doped intermediate layer is higher than the concentration of the transition metal in the immediately above layer to form a layer immediately above, After the formation of the light emitting layer Heat treatment is performed as a post-treatment for the stabilization of the light emitting layer to First, after forming the light emitting layer, before forming the immediately upper layer, a transition metal doped intermediate layer in which the concentration of the transition metal, which is the emission center, is higher than the immediately upper layer to a concentration that does not affect light emission. Deposit It is characterized by that.
[0026]
Claim 15 A method for manufacturing a thin film electroluminescent (EL) element is a thin film in which a first electrode, a first insulating layer, a light emitting layer, a second insulating layer, and a second electrode are sequentially formed on an insulating substrate. In the method for manufacturing an electroluminescent (EL) element, an alkaline earth metal sulfide EL light-emitting layer comprising an alkaline earth metal sulfide is formed on the first insulating layer, and the alkaline earth metal is formed. On the sulfide EL light emitting layer, an IIb-VIb group compound or an IIb-VIb group compound added with an emission center selected from transition metals is formed with a film thickness of 200 to 500 nm, and the light emitting layer is formed. After the film, a heat treatment is performed as a post-treatment for stabilizing the light emitting layer. First, after forming the light emitting layer, before forming the immediately upper layer, a transition metal doped intermediate layer in which the concentration of the transition metal, which is the emission center, is higher than the immediately upper layer to a concentration that does not affect light emission. Deposit It is characterized by that.
[0028]
Claim 16 The manufacturing method of the thin film electroluminescent (EL) element is: Claim 15 In the method of manufacturing a thin film electroluminescent (EL) element, the film thickness of the transition metal doped intermediate layer is 50 nm or less.
[0029]
Claim 17 The manufacturing method of the thin film electroluminescent (EL) element is: Claim 15 or 16 In the method for manufacturing a thin film electroluminescent (EL) element, manganese (Mn) is used as the transition metal.
[0030]
Claim 18 The manufacturing method of the thin film electroluminescent (EL) element is: Claim 17 In the method for manufacturing a thin film electroluminescent (EL) element, the concentration of the emission center in the transition metal-doped intermediate layer is 2 to 5 wt%.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail with reference to the accompanying drawings.
[0032]
In the present invention, as shown in FIG. 1, a lower electrode 2 as a first electrode and a lower insulating layer 3 as a first insulating layer are sequentially formed on a substrate 1, and a light emitting layer is formed on the lower insulating layer 3. The EL light emitting layer 4 comprising an alkaline earth metal sulfide is provided. Further, an IIb-VIb group compound, for example, zinc sulfide (ZnS), or an upper layer 5 formed by adding a luminescent center to the IIb-VIb group compound is provided immediately above the light emitting layer 4. Further, an upper insulating layer 6 as a second insulating layer is provided on the upper layer 5. The side surface 4 a of the light emitting layer 4 and the side surface 5 a immediately above it are covered with the upper insulating layer 6. Further, an upper electrode 7 as a second electrode is provided, and the upper electrode 8 and the lower electrode 2 are connected to a power source 8 to operate as a thin film electroluminescent (EL) element.
[0033]
As the substrate 1, a light transmitting substrate, for example, a glass substrate can be used.
[0034]
As the first electrode 2 and the second electrode 7, at least one of them can be a translucent electrode, for example, an ITO electrode.
[0035]
As the light-emitting layer 4, a material containing an alkaline earth metal sulfide as a base and a transition metal as a light emission center can be used. Examples of the alkaline earth metal sulfide include SrS, CaS, BaS, MgS, a mixed film thereof, and a film in which these are laminated. Examples of transition metals include manganese (Mn), cerium (Ce), terbium (Tb), thulium (Tm), and the like.
[0036]
However, highly reactive light-emitting layers for EL, including alkaline earth metal sulfides, are carbon dioxide (CO, CO ₂ ) And water vapor (water) react very well to cause a change in composition, so that stable device characteristics cannot be obtained as it is.
[0037]
In order to solve this problem, in the present invention, when the upper insulating layer 6 is formed, the upper surface of the upper layer 5 is covered with an insulating film, and the upper layer 5 and the light emitting layer 4 are formed from reactive substances such as carbon dioxide and water vapor. In addition, the side surface 4a of the light emitting layer 4 and the side surface 5a of the upper layer 5 are also covered with an insulating material, so that the entire light emitting layer 4 and the upper layer 5 are completely covered by the lower insulating layer 3 and the upper insulating layer 6. To be embedded in. By adopting such a structure, the light emitting layer 4 is effectively shielded from reactive substances such as carbon dioxide gas, water vapor, etc., so that the light emission performed after the formation of the light emitting layer as conventionally performed is performed. Stable device characteristics can be obtained without performing heat treatment as a post-treatment for stabilizing the layer.
[0038]
As the upper layer 5, a IIb-VIb group compound or a film obtained by adding a luminescent center selected from transition metals to this is formed. As the IIb-VIb group compound used for the immediately upper layer 5, zinc sulfide (ZnS) is particularly preferable. Examples of the transition metal as the luminescent center added to the IIb-VIb group compound include rare earth such as Ce, Eu, Pr, and a mixture of metals such as Mn. The film thickness of the immediately upper layer 5 is suitably 200 to 500 nm. When the film thickness of the immediately upper layer is 200 nm or less, the surface unevenness of the alkaline earth metal sulfide light-emitting layer cannot be sufficiently uniformed, so that the effect of laminating the immediately upper layer may not appear. Further, as the thickness of the immediately upper layer increases, carbon dioxide gas (CO, C0 to the alkaline earth metal sulfide light-emitting layer 4 is increased. ₂ ) And water vapor (water). However, if the thickness of the upper layer 5 is 500 nm or more, as shown in FIG. 2, the threshold voltage of the EL element is increased, which may easily cause dielectric breakdown and increase the cost of the driver circuit. It becomes a problem. Therefore, a layer in which zinc sulfide or zinc sulfide (ZnS) is added with an emission center such as manganese (Mn) is preferably laminated on the surface of the element substrate, preferably 200 to 500 nm, immediately above the alkali metal sulfide light emitting layer 4. It is preferable to reduce the influence of the adsorbed gas and improve the device characteristics.
[0039]
In addition, as a material of the insulating layer, for both the lower insulating layer 3 and the upper insulating layer 6, for example, SiO ₂ , SiON, Y ₂ 0 _Three , Ti0 ₂ , A1 ₂ O _Three , Hf0 ₂ , Ta ₂ O _Five , BaTa ₂ 0 _Five , SrTiO _Three , PbTiO _Three , ZrO ₂ Or a mixed film or a laminated film thereof.
[0040]
As an electrode material, a metal used for a normal thin film EL element, for example, Al, Cu or the like can be used.
[0041]
The thin film electroluminescent (EL) element of the present invention as described above can be manufactured as follows. That is, a first electrode (lower electrode) is provided on an insulating substrate by EB vapor deposition or high-frequency sputtering, and a first insulating layer is formed thereon by sputtering or the like. On this first insulating layer, a thin-film EL light-emitting layer containing alkaline earth metal sulfide is formed as a light-emitting layer by an electron beam evaporation method. On the alkaline earth metal sulfide thin film EL light-emitting layer, a layer immediately above the IIb-VIb group compound or a IIb-VIb group compound to which a light emission center selected from transition metals is added is deposited by an electron beam evaporation method to a film thickness of 200- A film is formed with a thickness of 500 nm, a second insulating layer is formed on the immediately upper layer by sputtering or the like, and a second electrode is formed by electron beam evaporation or the like. In this case, after the formation of the light emitting layer, heating is involved in forming the immediately upper layer, the second insulating layer, and the second electrode, but no heat treatment is performed otherwise. That is, a heat treatment as a post-treatment for stabilizing the light emitting layer (for example, a heat treatment at 630 ° C. for 1 hour after the formation of the upper insulating layer 8 described in the above-mentioned Japanese Patent Application Laid-Open No. 8-273833) ) Is not performed. In this way, as will be described later with reference to FIG. 5, a stable thin-film electroluminescent (EL) element with a surprisingly little decrease in luminance with time can be obtained by a simple method.
[0042]
Furthermore, an intermediate layer shown in FIG. 3 described later can be provided. In this way, the light emission luminance and life characteristics can be further improved.
[0043]
FIG. 3 is a schematic cross-sectional view of a thin film EL element according to another embodiment of the present invention. The same members as those of the thin film EL element shown in FIG. In the thin film EL device according to the present embodiment, the upper layer comprising the alkaline earth metal sulfide light emitting layer 4 and the IIb-VIb group compound or a transition metal such as manganese (Mn) added with an emission center. An intermediate layer is inserted between 5. This intermediate layer is a transition metal-doped intermediate layer 9 made of a transition metal, for example, a IIb-VIb group compound doped with manganese at a higher concentration than the directly upper layer 5, for example, zinc sulfide (ZnS).
[0044]
By providing the transition metal-doped intermediate layer 9, oxygen atoms diffusing into the alkaline earth metal sulfide light-emitting layer and the transition metal, for example, Mn are combined to trap oxygen atoms, and the alkaline earth metal sulfide. It is possible to reduce oxygen uptake into the light emitting layer, prevent a change in the crystal field around the light emitting center (Ce, etc.) in the light emitting layer, and further reduce the influence of the active gas adsorbed on the element substrate surface. it can.
[0045]
Further, the transition metal used for the transition metal-doped intermediate layer 9 may be the same element as or different from the transition metal contained in the upper layer 5. When the same transition metal element is used, there is an advantage that the emission color does not change. On the other hand, the emission color can be adjusted by using different transition metal elements. Even when different transition metal elements are used, in order not to affect light emission, it is preferable to contain a high concentration of light emission centers.
[0046]
When the emission color is not changed, the film thickness of the highly concentrated transition metal-doped intermediate layer 9 is usually 50 nm or less. If the film thickness exceeds 50 nm, the light emission from the transition metal-doped intermediate layer is affected, and the emission color changes, and the threshold voltage may be increased. Moreover, when the film thickness is less than 10 nm, these effects may not be sufficient.
[0047]
Further, the IIb-VIb group compound of the transition metal-doped intermediate layer, for example, zinc sulfide, is doped with a transition metal at a concentration that does not change the emission color. For example, in the case of Mn, O.D. The highest luminance and luminous efficiency can be obtained at a concentration of about 5 Wt%, but there is almost no EL emission at a Mn concentration of 2 Wt% or more. Therefore, the Mn concentration is set to 2 Wt% or more in order to easily react with the diffusing oxygen atoms without causing a change in emission color. However, if the Mn concentration exceeds 5 wt%, the energy loss in the transition metal doped intermediate layer increases, and the luminous efficiency of the entire device decreases. Therefore, the alkaline earth metal sulfide is reduced by reducing the thickness of the zinc sulfide (ZnS) layer having a Mn concentration of 2 to 5 wt% to 10 to 50 nm or less so as not to affect the luminance, emission color, and threshold voltage. Oxidation of manganese atoms (Mn) to oxygen atoms diffusing into the material light emitting layer reduces oxygen uptake into the alkaline earth metal sulfide light emitting layer, and crystals around the emission center such as Ce (cerium) The change in the field can be prevented, the influence of the adsorbed gas on the surface of the element substrate can be reduced, and the element characteristics can be improved.
[0048]
FIG. 4 is a schematic cross-sectional view of a thin film electroluminescent device according to still another embodiment of the present invention. In the present embodiment, as in the embodiment shown in FIG. 3, the transition metal-doped intermediate layer 9 is provided between the light emitting layer 4 and the layer 5 immediately above, and in the same manner as the thin film electroluminescent device shown in FIG. The side surface 4 a of the light emitting layer 4 and the side surface 5 a immediately above are covered with the upper insulating layer 6. Therefore, the stability effect of the device is further improved.
[0049]
The device described with reference to FIGS. 3 and 4 can be manufactured in the same manner as the device described with reference to FIG. However, the transition metal doped intermediate layer can be formed by an electron beam evaporation method or the like.
[0050]
【Example】
[Example 1]
A thin film electroluminescent (EL) device having the structure shown in FIG. 1 was prepared using strontium sulfide (SrS) pellets in which 0.2 mol% of cerium (Ce) was doped as a luminescent center in a strontium sulfide (SrS) matrix.
[0051]
First, an ITO electrode having a film thickness of about 200 nm is provided on a glass substrate, and a 30 nm-thick SiO2 film is formed by sputtering. ₂ And Si with a film thickness of 180 nm _Three N _Four Were sequentially formed as an insulating layer.
[0052]
A light-emitting layer having a thickness of 1000 nm was formed at a substrate temperature of 500 ° C. by electron beam evaporation.
[0053]
Next, the film thickness was changed to 150, 250, and 350 nm at a substrate temperature of 250 ° C. by an electron beam evaporation method, and a ZnS: Mn (Mn was 0.5 wt%) layer was laminated.
[0054]
Furthermore, Si film having a film thickness of 180 nm is formed by sputtering. _Three N _Four And 30 nm thick SiO ₂ Were sequentially formed to form an insulating layer, and an Al metal electrode was formed by an electron beam evaporation method.
[0055]
Further, heat treatment (630 ° C., 1 hour) was performed on some device samples after forming the ZnS: Mn layer.
[0056]
The result of evaluating the life characteristics of the EL device of Example 1 is shown in FIG.
[0057]
As is apparent from the results shown in FIG. 5, when ZnS: Mn is provided to a thickness of 200 nm or more, it is understood that the relative luminance is substantially maintained or slightly improved without stabilization by heat treatment. . Further, the improvement in luminance is saturated at 400 nm or more. On the other hand, when the heat treatment was performed as in the conventional case, the relative luminance decreased with the passage of time. Therefore, according to the present invention, a stabilized element can be obtained unexpectedly without requiring a costly process such as heat treatment.
[0058]
[Example 2]
First, an ITO electrode having a film thickness of about 200 nm is provided on a glass substrate, and a 30 nm-thick SiO2 film is formed by sputtering. ₂ And Si with a film thickness of 180 nm _Three N _Four Were sequentially formed as an insulating layer.
[0059]
A strontium cerium sulfide (SrS: Ce) light-emitting layer having a thickness of 1000 nm and a substrate temperature of 500 ° C. was formed by electron beam evaporation. The same strontium sulfide pellets used in Example 1 were used.
[0060]
Next, a ZnS + 2.5 wt% Mn layer having a thickness of 30 nm was formed by electron beam evaporation at a substrate temperature of 250 ° C., and a ZnS + 0.5 wt% Mn layer having a thickness of 250 nm was formed thereon.
[0061]
Furthermore, Si film having a film thickness of 180 nm is formed by sputtering. _Three N _Four And 30 nm thick SiO ₂ Were sequentially formed to form an insulating layer, and an Al metal electrode was formed by an electron beam evaporation method to produce an EL device having the structure shown in FIG.
[0062]
The result of evaluating the life characteristics of the EL element of Example 2 is shown in FIG.
[0063]
As is clear from the results shown in FIG. 6, when the device sample provided with the transition metal doped intermediate layer (also referred to as a highly doped layer) is compared with the device sample without such a heavily doped layer, the highly doped layer The device sample with the initial relative luminance is almost the same as the device sample without the high-concentration doped layer, but the deterioration with time is negligible and the lifetime characteristics are superior to the device sample without the high-concentration doped layer. I understand that.
[0064]
【The invention's effect】
A IIb-VIb group compound (for example, zinc sulfide (ZnS)) or a material in which a luminescent center selected from transition metals (for example, Mn) is added to the Alkali metal sulfide light-emitting layer is laminated, and has high reactivity. By reducing the influence of the adsorbed gas on the device, oxygen uptake into the alkali metal sulfide light-emitting layer is reduced, and changes in the crystal field around the luminescence center such as Ce (cerium) are prevented. Lifetime characteristics such as stabilization of voltage and suppression of decrease in luminance are improved, and stable EL element characteristics can be obtained at low cost without performing heat treatment as post-treatment for stabilization of the light emitting layer after the light emitting layer is formed. be able to.
[0065]
Also, between the alkaline earth metal sulfide light-emitting layer and the IIb-VIb group compound such as zinc sulfide (ZnS) or an immediately upper layer formed by adding a light emission center selected from transition metals such as manganese (Mn) to this. By inserting a IIb-VIb group compound (for example, zinc sulfide (ZnS)) layer doped with a transition metal (for example, manganese (Mn)) at a high concentration into the intermediate layer, that is, an alkaline earth metal Oxygen atoms diffusing into the sulfide light-emitting layer are trapped by oxidizing manganese (Mn), reducing oxygen uptake into the alkaline earth metal sulfide light-emitting layer, and reducing the emission center such as Ce (cerium) Prevents changes in the surrounding crystal field, improves the life characteristics such as stabilization of threshold voltage and suppression of luminance reduction, and obtains stable EL element characteristics without heat treatment after the light-emitting layer is formed. It is possible.
[0066]
Therefore, a stable alkaline earth metal sulfide EL light emitting device can be obtained at low cost without incurring equipment costs such as a heat treatment apparatus or an exhaust gas treatment apparatus thereof.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view illustrating the structure of a thin film electroluminescent (EL) element of the present invention.
FIG. 2 is a graph showing the relationship between the film thickness of the ZnS layer and the threshold voltage in the thin film electroluminescent (EL) device of the present invention.
FIG. 3 is a schematic cross-sectional view illustrating the structure of a thin film electroluminescent (EL) device of the present invention having a transition metal doped intermediate layer.
FIG. 4 is a schematic cross-sectional view illustrating the structure of a thin film electroluminescent (EL) device of the present invention having a transition metal doped intermediate layer.
5 is a graph showing the life characteristics of the thin film electroluminescent (EL) device of Example 1. FIG.
6 is a graph showing the life characteristics of the thin film electroluminescent (EL) device of Example 2. FIG.
FIG. 7 is a schematic cross-sectional view illustrating the structure of a conventional white EL element.
[Explanation of symbols]
1 (Glass) substrate
2 Lower electrode (first electrode)
3 Lower insulation layer (first insulation layer)
4,4 'light emitting layer
4a Lower ZnS: Mn layer
4b SrS: CeN layer
4c Upper ZnS: Mn layer
5 Upper layer
6 Upper insulating layer (second insulating layer)
7 Upper electrode (second electrode)
8 Power supply
9 Transition metal doped interlayer

Claims (18)

An alkaline earth metal sulfide in a thin film electroluminescent (EL) device comprising a first electrode, a first insulating layer, a light emitting layer, a second insulating layer, and a second electrode sequentially on an insulating substrate An electroluminescent (EL) light-emitting layer comprising an object, and a layer directly above the electroluminescent light-emitting layer, the light emitting center selected from IIb-VIb group compounds or transition metals added thereto And an intermediate layer formed between the electroluminescent light-emitting layer and the immediately above layer and made of a IIb-VIb group compound and a transition metal, wherein the transition metal concentration is higher than that of the immediately above layer. possess a doped intermediate layer, wherein the transition metal-doped intermediate layer is a thin film electroluminescent, characterized in that it has increased to a concentration that does not affect the emission concentration of the transition metal than the straight upper EL) element.   2. The thin film electroluminescent (EL) device according to claim 1, wherein a side surface of the light emitting layer and a side surface of the immediately upper layer are covered with the second insulating layer.   3. The thin film electroluminescent (EL) device according to claim 1, wherein a film thickness of the transition metal-doped intermediate layer is 50 nm or less.   The thin film electroluminescent (EL) device according to claim 1, wherein zinc sulfide (ZnS) is used as the IIb-VIb group compound in the immediately upper layer.   5. The thin film electroluminescent (EL) device according to claim 1, wherein manganese (Mn) is used as the transition metal in the upper layer. The thin film electroluminescent (EL) device according to claim 1 , wherein zinc sulfide (ZnS) is used as the IIb-VIb group compound of the transition metal-doped intermediate layer. The thin film electroluminescent (EL) device according to claim 1 , wherein manganese (Mn) is used as the transition metal of the transition metal-doped intermediate layer. The thin film electroluminescent (EL) device according to claim 7, wherein the transition metal concentration in the transition metal doped intermediate layer is 2 to 5 wt%. The thin film electroluminescent (EL) device according to any one of claims 1 to 8, wherein a film thickness of the immediately upper layer is 200 nm or more and 500 nm or less. In a thin film EL device comprising a first electrode, a first insulating layer, a light emitting layer, a second insulating layer, and a second electrode on an insulating substrate in sequence, alkaline earth metal sulfide is used as the light emitting layer. An electroluminescent (EL) light-emitting layer is provided, and an upper layer composed of a IIb-VIb group compound in which an emission center selected from a IIb-VIb group compound or a transition metal is added on the EL light-emitting layer is 200. It is laminated with a film thickness of ˜500 nm, and after the formation of the light emitting layer, it has not undergone a heat treatment as a post-treatment for stabilizing the light emitting layer, and the transition metal doped intermediate layer is more than the layer immediately above A thin film electroluminescent (EL) device characterized in that the transition metal concentration is increased to a concentration that does not affect light emission . 11. The thin film electroluminescent (EL) device according to claim 10 , wherein zinc sulfide (ZnS) is used as the IIb-VIb group compound in the immediately upper layer. The thin film electroluminescent (EL) device according to claim 10 or 11 , wherein manganese (Mn) is used as the transition metal in the immediately upper layer. 13. The thin film electro of claim 10 , wherein a transition metal-doped intermediate layer having a transition metal concentration higher than that of the immediately above layer is provided between the light emitting layer and the immediately above layer. Luminescent (EL) element. In the method for manufacturing a thin film electroluminescent (EL) element, which sequentially forms a first electrode, a first insulating layer, a light emitting layer, a second insulating layer, and a second electrode on an insulating substrate, A thin-film EL light-emitting layer containing an alkaline earth metal sulfide is formed as the light-emitting layer on the first insulating layer, and a transition metal is doped on the alkaline-earth metal sulfide thin film EL light-emitting layer. A transition metal-doped intermediate layer made of a IIb-VIb group compound is formed, and an emission center selected from a IIb-VIb group compound or a transition metal is formed on the transition metal-doped intermediate layer in the transition metal-doped intermediate layer. The added metal is laminated so that the concentration of the transition metal is higher than the concentration of the transition metal in the immediately above layer, and the immediately above layer is formed. After the formation of the light emitting layer, the stability of the light emitting layer is stabilized. Heat treatment as post-processing Little as, after forming the light emitting layer, wherein before forming the straight upper, the straight upper transition metal-doped intermediate layer was increased to a concentration that does not affect the emission concentration of the transition metal, which is the emission center than A method of manufacturing a thin film electroluminescent (EL) element, wherein In the method for manufacturing a thin film electroluminescent (EL) element, which sequentially forms a first electrode, a first insulating layer, a light emitting layer, a second insulating layer, and a second electrode on an insulating substrate, Forming an alkaline earth metal sulfide EL light emitting layer comprising an alkaline earth metal sulfide on the first insulating layer, and forming a IIb-VIb group compound on the alkaline earth metal sulfide EL light emitting layer; Alternatively, an immediately upper layer made of a IIb-VIb group compound to which a luminescent center selected from transition metals is added is formed with a film thickness of 200 to 500 nm, and after the formation of the luminescent layer, the light emitting layer is stabilized for later. After forming the light emitting layer without performing heat treatment as a treatment, before forming the immediately upper layer, the concentration of the transition metal that is the emission center is set higher than the immediately upper layer to a concentration that does not affect light emission. Deposit transition metal doped intermediate layer Method of manufacturing a thin film electroluminescent (EL) element characterized. 16. The method of manufacturing a thin film electroluminescent (EL) device according to claim 15, wherein the thickness of the transition metal doped intermediate layer is 50 nm or less. The method for producing a thin film electroluminescent (EL) device according to claim 15 or 16, wherein manganese (Mn) is used as the transition metal. The method of manufacturing a thin film electroluminescent (EL) device according to claim 17, wherein the concentration of the emission center in the transition metal doped intermediate layer is 2 to 5 wt%.

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