JP2002280185A - Thin film el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide technology capable of enhancing luminescent efficiency of a thin film EL element. SOLUTION: In this thin EL element provided with a pair of a first electrode layer and a second electrode layer interposing a luminescent layer on an insulating base, a thin layer having a quantum size is provided between the luminescent layer and the first electrode layer and between the luminescent layer and the second electrode layer are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film light emitting device, and more particularly, to a thin film electroluminescence device (hereinafter, referred to as a thin film light emitting device).
(Referred to as a thin-film EL element) and a technology effective when applied to the structure of the light emitting layer interface.

[0002]

2. Description of the Related Art In a conventional display device using a thin-film EL element as a light-emitting element, light-emitting layer materials for various thin-film EL elements that emit red, green, and blue light have been developed in order to realize full color. I have. However, among these light-emitting layer materials, in particular, for blue, a material having sufficient luminous efficiency to withstand practical use has not been obtained so far. Also for red and green, it is strongly desired to realize higher luminous efficiency.

In order to improve the luminous efficiency of these light emitting layer materials, new light emitting layer materials have been actively developed. Regarding the luminous efficiency of conventional main light emitting layer materials, see, for example, Yoshimasa A. Ono "Electro
luminescent displays "(Wor
ld Scientific, published in 1995) 84
It is disclosed in Table 13 of the page. According to this document, the material having the highest luminous efficiency among all the luminescent layer materials has ZnS: Mn (zinc sulfide: manganese) obtained by activating manganese (Mn) on zinc sulfide (ZnS) as a luminescent layer. It is a thin film EL element that emits yellow-orange light. Note that 19
Several new light emitting layer materials have been developed since 1995, but no light emitting layer material having a luminous efficiency exceeding ZnS: Mn has been developed yet.

FIG. 5 is a cross-sectional view for explaining the basic structure of a conventional double-insulated thin film EL device using ZnS: Mn as a light emitting layer. FIG. 6 is a sectional view showing the applied voltage of the thin film EL device shown in FIG. V (V) -luminous efficiency η (lm / W), applied voltage V
It is a figure which shows the example of the light emission characteristic of (V)-brightness | luminance L (cd / m < ² >).

As is clear from FIG. 5, a conventional thin film EL
In the device, ITO (Indi) is formed on the upper surface of the glass substrate 506.
um Tin Oxide) transparent electrode layer 505 is formed.
Then, silicon nitride (S
i_ThreeN_Four) Has a structure in which the insulating layer 504 is formed.
You. On the upper surface of the insulating layer 504, a light emitting layer of ZnS: Mn
503 is formed and surrounds the light emitting layer 503.
Silicon nitride (Si _ThreeN_Four) Is formed.
The upper surface of the insulating layer 502 is made of aluminum (Al).
A metal electrode layer 501 is formed, and a thin film EL element is formed.
ing.

In driving or light emission of the thin film EL element, an AC voltage or a bipolar pulse voltage from a drive circuit 507 is applied between the metal electrode layer 501 and the transparent electrode layer 505.

The luminous efficiency η in this case is the measured value 6 in FIG.
02, it is about 2 to 4 (lm / W) at the maximum. Further, as is apparent from the measured value 601, the luminance L is a maximum of 2000 when driven by an AC voltage of 1 kHz.
It is about 4000 (cd / m ² ).

[0008]

SUMMARY OF THE INVENTION The present inventor has found the following problems as a result of studying the prior art.

The light emitting mechanism of a thin film EL device using ZnS: Mn for the light emitting layer 503 has been analyzed in detail. For example, Shionoya and
W. M. Hen Phosphor handbook
(CRC Press, 1999). According to this document, the excitation ratio P (also referred to as excitation probability) of the emission center, which indicates the luminous efficiency of the thin-film EL element, is given by the following equation (1).

[0010]

(Equation 1) Where σ (E) is the excitation cross section of Mn ²⁺ ion, f
(E) is the energy distribution function of the electrons, and E0 is the threshold energy.

FIG. 7 shows the f obtained for ZnS: Mn.
It is a figure showing distribution of (E) and σ (E). FIG. 7 also shows the energy levels of Mn ²⁺ ions for reference.

FIG. 7 shows that the intensity of the electric field applied to ZnS: Mn ranges from 1 × 10 ⁶ (V / cm) to 2 × 10
Despite having doubled to ⁶ (V / cm), f
The peak value of the distribution (E) is from 1.8 eV to 2.1 eV.
, And as a result, the luminous efficiency P shown by the equation (1) does not greatly improve. In addition, Zn
S: The electric field intensity applied to Mn is 1 × 10 ⁶ (V / c
m) to 2 × 10 ⁶ (V / cm), the withstand voltage of the thin-film EL element must be significantly improved. As a result, it has been very difficult to improve the luminous efficiency of the thin-film EL element even with ZnS: Mn, which has the highest luminous efficiency among the conventional EL materials, without changing the element structure of the conventional thin-film EL element.

An object of the present invention is to provide a technique capable of improving the luminous efficiency of a thin film EL device.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0015]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

(1) A thin-film EL comprising a pair of a first electrode layer and a second electrode layer with a light-emitting layer interposed on an insulating substrate
In the device, a quantum-sized thin film layer is provided between the light emitting layer, the first electrode layer, and the second electrode layer.

(2) A thin film EL comprising a pair of a first electrode layer and a second electrode layer with a light emitting layer interposed on an insulating substrate
In the device, a porous thin film layer having a quantum particle size is provided between the light emitting layer and the first electrode layer or the second electrode layer.

According to the above-described means, in a thin-film EL device comprising a pair of first and second electrode layers having a light-emitting layer interposed on an insulating substrate, the light-emitting layer and the first
Between the first electrode layer and the second electrode layer, a thin film layer having a quantum size, that is, a thin film layer having a size in which a quantum size effect appears, is provided. Since the peak energy value of (E) can be largely shifted to the high energy side, the excitation probability P of the emission center shown in the equation (1) can be greatly improved, and as a result, the light emission of the thin film EL element can be improved. Efficiency can be improved.

In a thin film light emitting device comprising a pair of a first electrode layer and a second electrode layer having a light emitting layer interposed on an insulating substrate, the light emitting layer and the first electrode layer or the first By providing a porous thin film layer having a particle size of quantum size, that is, a particle size at which a quantum size effect appears, between the two electrode layers, the peak energy of the electron energy distribution f (E) of the electrons can be obtained. Since the value can be greatly shifted to the high energy side, the excitation probability P of the luminescence center shown in the equation (1) is greatly improved, and the luminous efficiency of the thin film EL device can be improved.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings together with embodiments (examples) of the present invention.

In all the drawings for describing the embodiments of the present invention, components having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

(Embodiment 1) FIG. 1 is a diagram for explaining a schematic configuration of a thin-film electroluminescence element (hereinafter, referred to as a thin-film EL element) according to Embodiment 1 of the present invention. In particular, FIG. 1A is a cross-sectional view for explaining the basic structure of the thin-film light emitting device of Embodiment 1, and FIG. 1B is a diagram for explaining the basic structure of the laminated thin-film layer. is there. However, in the following description, a case will be described in which ZnS: Mn capable of emitting yellow-orange light is used as the material of the light-emitting layer 103. A large number of materials are used for the light-emitting layer 103, and terbium is added to zinc sulfide. In addition to ZnS: Tb, which provides active green light emission, ZnS: C
u, SrS: Cu, ZnS: Sm, CaS: Eu, Sr
S: Ce, SrGa ₂ S ₄ : Ce, CaGa ₂ S ₄ : Ce,
It goes without saying that other light emitting color materials such as CaS: Pb and BaAl ₂ S ₄ : Eu may be used.

In FIG. 1, reference numeral 101 denotes a metal electrode layer (first
, 102 is a first insulating layer, 103 is a light emitting layer,
104 is a second insulating layer, 105 is a transparent electrode layer (second electrode layer), 106 is a glass substrate, 107 is a drive circuit, 10
8a and 108b are interface layers, 109 is a first thin film layer, 11
0 indicates a second thin film layer.

As is apparent from FIG.
The thin-film EL element according to mode 1 is a glass substrate 1 serving as an insulating substrate.
06 on the glass substrate
Second electrode layer 10 formed by depositing ITO on 106
5 is formed on the second electrode layer 105._ThreeN_FourTo
A second insulating layer 104 formed by deposition is formed.
You. On the upper part of the second insulating layer 104, a quantum size wire
4 nm, which is the size (film thickness) where the quantum size effect appears
The following Si_ThreeN_FourIt is made by alternately depositing thin films and ZnS thin films.
The manufactured interface layer 108b is formed. Interface layer 108
a light emitting layer formed by depositing ZnS: Mn
103 is formed. On the light emitting layer 103, a quantum
4 nm, which is the film thickness at which the quantum size effect appears.
The following Si _ThreeN_FourIt is made by alternately depositing thin films and ZnS thin films.
The manufactured interface layer 108a is formed.

On top of this interface layer 108a, Si ₃ N ₄
Is formed. In particular, in the first embodiment, the first insulating layer 102 covers the side surfaces of the interface layers 108a and 108b and the light emitting layer 103, and the second insulating layer 102 is formed. It is formed so as to reach 104. That is, in the thin-film EL element of Embodiment 1, the first insulating layer 102 and the second insulating layer 104 form the interface layer 10
8a, 108b and the light emitting layer 103 are wrapped.

As described above, in the thin-film EL device of the first embodiment, the interface layer 108b formed on the surface of the light emitting layer 103 on the glass substrate 106 side faces the surface of the light emitting layer 103 on the glass substrate 106 side. Interface layer 10 formed on the side surface
8a, the light emitting layer 103 is sandwiched therebetween.

In the first embodiment, the interface layer 108
The case of a laminated film of Si ₃ N ₄ and ZnS will be described as “a” and “108b”. However, the present invention is not limited to this, and there are many specific laminated materials.
a ₂ O ₅ , SiO ₂ , Al ₂ O ₃ , SrTiO ₃ , AlTiO
_{3, Si, SrS, CaS,} SrGa 2 S 4, CaGa 2 S
_4. Needless to say, a combination of various insulating layer materials such as BaAl ₂ S ₄ , a semiconductor material, and a base material of EL may be used.

Next, the film forming conditions of the above-described thin film EL device are shown in Tables 1 and 2, and the outline of the method of manufacturing the thin film EL device which is the thin film light emitting device of the first embodiment will be described below.

[0029]

[Table 1]

[0030]

[Table 2] First, a second substrate is placed on a glass substrate 106 which is an insulating substrate.
The ITO thin film which is the electrode layer 105 is formed. This IT
The O thin film is formed by a vacuum evaporation or sputtering method. In the first embodiment, the O thin film is formed by a sputtering method.
For example, it is formed to have a thickness of about 200 nm.

Next, a second insulating layer 104 is formed on the second electrode layer 105. This second insulating layer 104
Is a thin film having a thickness of, for example, 200 nm formed by a high-frequency magnetron sputtering method as shown in the section of the insulating layer in Table 1. The conditions for forming the second insulating layer 104 are, for example, S
The target of i ₃ N ₄ is sputtering with a gas plasma of 100% argon (Ar). Under this film forming condition, a single layer film of Si ₃ N ₄ is formed and the second insulating layer 10 is formed.
It is set to 4. Other sputtering conditions for forming the second insulating layer 104 are as shown in Table 1.

Next, an interface layer 108b is formed on the second insulating layer 104. The interface layer 108b formed between the second insulating layer 104 and the light emitting layer 103 is formed by a high-frequency magnetron sputtering method, as shown in the section of the light emitting layer interface in Table 1.

The interface layers 108a and 108b can be made of, for example, a laminated thin film having a total thickness of 100 nm in which a 1 nm-thick Si ₃ N ₄ thin film and a 4 nm-thick ZnS thin film are alternately deposited 20 times. . In this case, the layer that comes into contact with the light emitting layer 103 is either the Si ₃ N ₄ thin film or the ZnS thin film,
Even when it comes into contact with, there is no difference in the effect of improving the electron acceleration.

The cause of the improvement in the acceleration of electrons is that when a large number of electrons pass through the interface layers 108a and 108b made of a laminated film, only the electrons whose acceleration has been insufficient are selectively applied to the interface layer 108a. , 108b, it is considered that the energy of the entire electron distribution is greatly improved.

Further, even when the interface layers 108a and 108b are composed of a single thin film of quantum size, the interface layer 10
Although the effect of improving the electron acceleration can be seen as compared with the case where 8a and 108b are not inserted, the effect of improving the electron acceleration can be sufficiently improved by inserting the interface layers 108a and 108b composed of a multilayer film having 10 or more layers. And the electron peak energy value can be largely shifted to a higher energy side.

The conditions for forming the interface layer 108b include, for example, setting a target of ZnS and Si ₃ N ₄ to argon (Ar).
Was sputtered with a gas plasma of 95% and 5% hydrogen sulfide (H2S), especially ZnS and S
By controlling the shutter so that the target of i ₃ N ₄ is alternately sputtered, the ZnS thin film having a quantum size of 4 nm or less and Si ₃ N ₄ shown in FIG.
Interface layer 108 which is a multilayer thin film in which thin films are alternately stacked
b is formed. In this way, by performing shutter control and sequentially switching the target to be sputtered,
It facilitates the formation of a multilayer thin film. Also, the interface layer 108
Other sputtering conditions when forming b are as shown in Table 1.

Next, the light emitting layer 103 is formed on the same plane above the interface layer 108b. This light emitting layer 103
As shown in Table 2, it is a thin film having a thickness of, for example, 500 nm formed by a multi-source evaporation method. The film forming conditions of the light emitting layer 103 are as follows.
The ZnS: Mn thin film is formed by heating S at 920 ° C., Mn at 680 ° C., and the substrate temperature at 120 ° C. by resistance heating of a heater or electron beam irradiation, and vapor-depositing them on the same plane above the interface layer 108b. Is formed.

Next, an interface layer 108a is formed in the same plane above the light emitting layer 103. The interface layer 108a formed between the light emitting layer 103 and the first insulating layer 102 is formed by a high-frequency magnetron sputtering method as shown in the section of the light emitting layer interface in Table 1, similarly to the above-described interface layer 108b. Filmed.

Next, the first insulating layer 102 is formed on the interface layer 108a. This first insulating layer 102
Similarly to the above-mentioned second insulating layer, as shown in the section of the insulating layer in Table 1, the film is formed by a high-frequency magnetron sputtering method.
However, in Embodiment 1, the first insulating layer 102 is formed such that the first insulating layer 102 covers the side surfaces of the interface layers 108a and 108b and the light emitting layer 103 and reaches the second insulating layer 104. Film.

Next, a metal electrode layer 101 is formed on the first insulating layer 102. This metal electrode layer 101
For example, a film is formed by depositing or depositing aluminum (Al) by an evaporation method or a sputtering method. In the thin-film EL element according to the first embodiment, the side of the glass substrate 106 is a side from which light is emitted, so that the metal electrode layer 101 becomes a back electrode.

In the thin-film EL device thus formed,
As before, the metal electrode layer 101 and the transparent electrode layer 105 are connected to a desired drive circuit 107 for generating an AC voltage or a bipolar pulse voltage, and the metal electrode layer 101 and the transparent electrode layer 10 are connected.
When a predetermined voltage is applied between the light emitting layer 5 and the light emitting layer 5, the light emitting layer 103 emits light, and the emitted light is emitted from the glass substrate 106 side. At this time, each thin film layer formed on the glass substrate 106 can be protected by enclosing the thin film EL element in, for example, a plastic container or a glass container.

However, as a method of protecting each thin film layer formed on the glass substrate 106, for example, after a thin film EL element is formed, a connection terminal portion is provided on a lower edge portion on the glass substrate 106, and a metal electrode is formed. The connection terminal portion and the metal electrode layer 1 are formed by an electrode layer extending from the layer 101 and the transparent electrode layer 105.
01 and the transparent electrode layer 105 are connected. Note that this connection terminal portion can be formed by forming a conductive metal layer such as nickel or gold by an evaporation method, a sputtering method, or the like, and then dividing the conductive metal layer by a photoetching method or the like.

Next, for example, the same second glass plate as the glass substrate 106 is fixed on the back side of the glass substrate 106 on which the thin film EL element is formed, that is, on the side on which the thin film EL element is formed. Since each of the formed thin film layers is inside the space formed by the glass substrate 106 and the second glass plate, it is protected. Note that the second glass substrate can be fixed, for example, by applying an adhesive or the like around the inside on the back side of the glass substrate 106 and bonding the glass substrate 106 and the second glass plate.

Therefore, for example, a plurality of vertical transparent electrode layers 105 are formed on the upper surface of the glass substrate 106 on which the thin film EL element of the first embodiment shown in FIG. Of the light emitting layer 103 and the interface layers 108a and 108b in a region where the metal electrode layer 101 and the transparent electrode layer 105 intersect with each other.
An L display device can be manufactured.

Further, a so-called TFT, which is a switching element for controlling the power applied to the thin-film EL element of the first embodiment shown in FIG. An active matrix thin film EL display device may be manufactured.

FIG. 2 is a diagram showing the energy distribution of electrons in the thin film EL device of the first embodiment.

FIG. 2 shows, similarly to FIG.
1 × 10 ⁶ (V / cm);
FIG. 3 is a diagram showing a distribution of electron energy when the electron energy is changed to 3 × 10 ⁶ (V / cm) and 1.6 × 10 ⁶ (V / cm). However, 201 has an average electric field intensity of 1 × 10 ⁶ (V /
cm), 202 is the electron energy distribution when the average electric field strength is 1.3 × 10 ⁶ (V / cm), 203 is the average electric field strength is 1.6 × 10 ⁶
4 shows the energy distribution of electrons at (V / cm).

As is apparent from FIG. 2, in the thin-film EL device of the first embodiment, the light-emitting layer 103, ie, the interface layers 108a and 108b formed by laminating a plurality of thin layers having a quantum size (usually 4 nm or less) in multiple layers. The average electric field strength is
1 × 10 ⁶ (V / cm) to 1.6 × 10 ⁶ (V / cm)
It can be seen that the peak value of the energy distribution f (E) of the electrons has increased 2.1 times from 2.5 eV to 5.3 eV, although it has increased only 1.6 times.

On the other hand, in the conventional ZnS: Mn thin-film EL element shown in FIG. 7A, the peak energy value of the electron energy distribution f (E) is 1
Despite the double increase from × 10 ⁶ (V / cm) to 2 × 10 ⁶ (V / cm), from 1.8 eV to 2.1 eV,
It has increased only about 1.2 times. As described above, in the thin-film EL device of the first embodiment, a quantum-sized multilayer thin film, that is, the interface layer 108a,
By forming 108b, the peak energy value of the electron energy distribution f (E) can be largely shifted to the higher energy side. As a result, the excitation probability P of the luminescence center represented by the equation (1) can be greatly improved,
The luminous efficiency of the thin film EL device can be improved.

FIG. 3 shows the relationship between the applied voltage V (V) -luminous efficiency η (lm / W) and the applied voltage V of the thin film EL device of the first embodiment.
It is a figure which shows the measurement result of the light emission characteristic of (V) -luminance L (cd / m < ² >). Here, 301 indicates a measured value of the applied voltage V-luminance L characteristic, and 302 indicates a measured value of the applied voltage V-luminous efficiency η characteristic.

As is apparent from FIG. 3, the light emitting layer 103 of the above-mentioned structure, that is, ZnS: Mn
The luminance L of the thin-film EL element according to the first embodiment formed so as to sandwich a and 108b is 2,000 to 5,000 (c max.) from the measured value 301 when driven by an AC voltage of 1 kHz.
d / m ² ), and no decrease in luminance is observed even when compared with the conventional thin film EL device shown in FIG.

On the other hand, the luminous efficiency η of the thin film EL device of the first embodiment is 4 to 10 (l
m / W). That is, the conventional thin film EL shown in FIG.
It can be seen that the luminous efficiency has been improved by a factor of 2 or more compared to 2 to 4 (lm / W) of the device.

Therefore, as described above, when a thin-film EL display device is manufactured using the thin-film EL device of Embodiment 1, it is possible to obtain a sufficient light emission amount with low power consumption. Since a sufficient light emission amount can be obtained with low power consumption, it is not necessary to greatly improve the withstand voltage, so that the thin film EL element can be miniaturized.
More thin film EL elements can be formed in a limited area. As a result, when a display device using the thin-film EL element according to the first embodiment is created, it is possible to display a finer image in a limited display area.

When a thin-film EL display device is manufactured using the thin-film EL element of the first embodiment, it is possible to obtain a sufficient amount of light emission with less power consumption per unit display area of the display device than before. Accordingly, power consumption in the case where a large-area display device is manufactured can be significantly reduced as compared with the related art.

In the first embodiment, the case where the glass substrate 106 is used as the insulating substrate has been described, but it goes without saying that a ceramics substrate or the like may be used as the insulating substrate. For example, instead of the glass substrate 106 of FIG. 1, a metal electrode is provided above (on the front side of) a ceramic substrate, and an insulating layer, an interface layer, a light emitting layer, an interface layer, and an insulating layer are formed thereon under the manufacturing conditions shown in Tables 1 and 2. The above-described effects can be obtained by forming a thin-film EL element having a structure in which the transparent electrodes ITO are deposited by vacuum evaporation or sputtering after sequentially depositing the thin films to be layers.

In the first embodiment, the insulating layer 102,
Although the case where Si ₃ N ₄ is used as the insulating material of 104 has been described, the present invention is not limited to this, and there are many specific insulating materials. For example, Ta ₂ O ₅ , SiO ₂
Needless to say, an insulating layer thin film made of ₂ , Al ₂ O ₃ , SrTiO ₃ , AlTiO ₃ , Si ₃ N ₄ or the like, or a deposited film made of a combination of these insulating materials may be used.

(Embodiment 2) FIG. 4 is a view for explaining a schematic configuration of a thin-film EL element according to Embodiment 2 of the present invention. However, in the following description, the first embodiment is described.
Similarly to the case described above, the case where ZnS: Mn that can emit yellow-orange light is used as the material of the light emitting layer 402 will be described.
As a material of the light emitting layer 402, there are many materials, and ZnS which can provide green light emission by activating terbium to zinc sulfide:
Tb, ZnS: Cu, SrS: Cu, Z
nS: Sm, CaS: Eu, SrS: Ce, SrGa ₂
S ₄ : Ce, CaGa ₂ S ₄ : Ce, CaS: Pb, Ba
It goes without saying that a material of another emission color such as Al ₂ S ₄ : Eu may be used.

In FIG. 4, reference numeral 401 denotes a transparent electrode layer;
2 denotes a light emitting layer, 403 denotes a porous thin film layer, 404 denotes a ceramic substrate, and 405 denotes a metal electrode layer.

As is clear from FIG. 4, the thin-film EL device of the second embodiment is a thin-film EL device using a ceramic substrate 404, and is irradiated from the back side (back side) of the ceramic substrate 404, that is, from the light emitting layer 402. The structure is such that a metal electrode layer 405 is formed on a surface side opposite to a side irradiated with light.

On the other hand, on the surface side of the ceramic substrate 404, a porous thin film layer 403 made of a porous ceramic thin film having a quantum size, that is, a particle size of 4 nm or less, at which the quantum size effect appears, is formed. . On top of the porous thin film layer 403, ZnS:
A light emitting layer 402 formed by depositing Mn is formed, and a transparent electrode layer 401 formed by depositing ITO is formed on the light emitting layer 402.

Next, an outline of a method for manufacturing a thin-film EL device which is a thin-film light-emitting device according to the second embodiment will be described.

First, as a ceramic substrate 404, an Al electrode is formed on the back surface of a barium titanate substrate having a thickness of 0.1 mm by a vapor deposition method, and a metal electrode layer 405 is formed.
Next, the ceramic substrate is immersed in a solution obtained by mixing hydrogen fluoride HF (60 wt%) and ethyl alcohol at a mixing ratio of 1: 1. Is 0 to 100 mA
/ Cm ² . At this time, a region in which the current density is reduced to about ² mA / cm ² several times is formed on the way, and a porous thin film layer 403 whose grain size is modulated in the depth direction is formed. Thus, a porous thin film layer 403 having a nano structure is formed on the surface of the ceramic substrate 404. Next, the porous thin film layer 40
3 is formed on the ceramic substrate 404 on which the ZnS: Mn light emitting layer 402 shown in Table 2 of Embodiment 1 is formed, and then a transparent electrode (ITO) layer is further formed on the light emitting layer 402. 401 is formed by a sputtering method or the like, and the thin-film EL element of Embodiment 2 is completed.

A thin film EL using this ceramic substrate
Also in the device, the ceramic substrate 404 and the light emitting layer 40
By forming the porous thin film layer 403 having a particle size of 4 nm or less, which is the quantum size, at the interface with the light emitting layer 2, electrons in the light emitting layer 402 and the porous thin film layer 403 are formed in the same manner as described in the first embodiment. Electron energy distribution f
Since the peak energy value of (E) can be largely shifted to the high energy side, the excitation probability P of the luminescence center shown in the above-mentioned equation (1) is greatly improved, and the luminous efficiency of the thin film EL device is improved. can do.

In the thin film EL device thus formed,
As in the conventional case, the transparent electrode layer 401 and the metal electrode layer 405 are connected to a desired drive circuit 107 for generating an AC voltage or a bipolar pulse voltage, and the transparent electrode layer 401 and the metal electrode layer 40 are connected.
When a predetermined voltage is applied between the light emitting layer 5 and the light emitting layer 5, the light emitting layer 402 emits light, and the emitted light is emitted from the transparent electrode layer 401 side. At this time, similarly to the first embodiment, for example, each thin film layer formed on the ceramic substrate 404 can be protected by enclosing the thin film EL element in a plastic container, a glass container, or the like.

Therefore, similarly to the first embodiment, even when a thin-film EL display device is manufactured using the thin-film EL element of the second embodiment, a sufficient amount of light can be obtained with low power consumption. . Since a sufficient amount of light emission can be obtained with low power consumption, it is not necessary to greatly improve the breakdown voltage of the thin film EL element. Therefore, the thin film EL element can be miniaturized, and more thin films can be formed in a limited area. E
An L element can be formed. As a result, even when a display device using the thin-film EL element according to the second embodiment is created, it is possible to display a finer image in a limited display area.

Also, when a thin-film EL display device is manufactured using the thin-film EL device of the second embodiment, it is possible to obtain a sufficient amount of light emission with less power consumption per unit display area of the display device than before. Therefore, the power consumption in the case where a large-area display device is manufactured can be significantly reduced as compared with the related art.

In the first and second embodiments, the film thicknesses of the first and second electrode layers 101 and 105, the first and second insulating layers 102 and 104, and the light emitting layer 103 constituting the thin film light emitting device are changed. Although the thickness is 200 nm, it is not limited to this, and it goes without saying that another film thickness may be used.

In the second embodiment, the case where the porous thin film layer 403 is provided on the ceramic substrate 404 has been described, but instead of the porous thin film layer 403,
The present invention also includes the thin film EL element in the case where the interface layers 108a and 108b described in Embodiment 1 are provided.

As described above, the invention made by the present inventor is:
Although the present invention has been specifically described based on the embodiments, the present invention is not limited to the embodiments of the present invention, and it is needless to say that various modifications can be made without departing from the scope of the invention. .

[0070]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows. (1) By forming an interface layer which is a multilayer thin film having a quantum size at the interface of the light emitting layer, the peak energy value of the electron energy distribution f (E) can be largely shifted to the high energy side. The center excitation probability P can be greatly improved, and the luminous efficiency of the thin-film EL element can be improved. (2) At the interface between the substrate and the light emitting layer, a quantum size of 4n
By forming a porous thin film layer having a particle diameter of not more than m, the peak energy value of the energy distribution f (E) of electrons in the light emitting layer can be largely shifted to the high energy side, so that the excitation probability P of the emission center can be increased. Can be greatly improved, and the luminous efficiency of the thin-film EL element can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a schematic configuration of a thin-film electroluminescence device which is a thin-film light-emitting device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a distribution of electron energy in the thin-film EL element according to the first embodiment.

FIG. 3 shows an applied voltage V of the thin-film EL element according to the first embodiment.
(V)-luminous efficiency η (lm / W), applied voltage V (V)-
It is a figure showing the measurement result of the luminescence characteristic of luminance L (cd / m ² ).

FIG. 4 is a thin film E which is a light emitting device according to Embodiment 2 of the present invention.
FIG. 3 is a diagram for explaining a schematic configuration of an L element.

FIG. 5 is a cross-sectional view illustrating a basic structure of a conventional thin film EL element having a double insulating structure using ZnS: Mn as a light emitting layer.

FIG. 6 shows applied voltage V (V) -luminous efficiency η (lm / W), applied voltage V (V) -luminance L (cd) of a conventional thin film EL element.
/ M ² ) is a diagram showing an example of light emission characteristics.

FIG. 7 is a diagram showing distributions of f (E) and σ (E) obtained for ZnS: Mn in a conventional thin film EL device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 ... Metal electrode layer 102 ... 1st insulating layer 103 ... Light emitting layer 104 ... 2nd insulating layer 105 ... Transparent electrode layer 106 ... Glass substrate 107 ... Drive circuit 108a, 10
8b: Interface layer 109: First thin film layer 110: Second thin film layer 201: Energy distribution of electrons when the average electric field intensity is 1 × 10 ⁶ (V / cm) 202: Average electric field intensity is 1.3 × Energy distribution of electrons at 10 ⁶ (V / cm) 203: Energy distribution of electrons at an average electric field intensity of 1.6 × 10 ⁶ (V / cm) 301—Measured value of applied voltage V-luminance L characteristic Reference numeral 302: applied voltage V-measured value of luminous efficiency η characteristic 401: transparent electrode layer 402: light emitting layer 403: porous thin film layer 404: ceramic substrate 405: metal electrode layer 501: metal electrode layer 502, 504: insulating layer 503 Light emitting layer 505 Transparent electrode layer 506 Glass substrate 507 Drive circuit 601 Measured value of applied voltage V-luminance L characteristic 602 Measured value of applied voltage V-luminance efficiency η characteristic

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Isao Tanaka 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Research Institute (72) Inventor Yoji Inoue 1-10-11 Kinuta, Setagaya-ku, Tokyo No. Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Yoshitaka Izumi 1-10-11 Kinuta, Setagaya-ku, Tokyo F-term in Japan Broadcasting Corporation Broadcasting Research Institute 3K007 AB03 CA01 CA02 CB01 DA05 DB02 DC02 EA03 EA04

Claims (6)

[Claims] 1. A thin film EL device comprising a pair of a first electrode layer and a second electrode layer having a light emitting layer interposed on an insulating substrate, wherein the light emitting layer, the first electrode layer and the first 2
A thin film layer having a quantum size between the first and second electrode layers. 2. The thin-film EL device according to claim 1, wherein two or more quantum-sized thin-film layers are stacked. 3. A thin film EL device comprising a pair of a first electrode layer and a second electrode layer having a light emitting layer interposed on an insulating substrate, wherein the light emitting layer and the first electrode layer or the first 2
Characterized in that a porous thin film layer having a quantum particle size is provided between the thin film EL element and the electrode layer. 4. The thin-film EL device according to claim 1, wherein the quantum-size thin-film layer or the quantum-size thin film has a particle size of 4 nm or less. EL element. 5. The thin-film EL device according to claim 1, wherein the thin film layer having the quantum size or the porous thin film layer, the first electrode layer and the second thin film layer are formed. A thin-film EL element, wherein an insulating layer is formed between each of the electrode layers. 6. The thin-film EL device according to claim 1, wherein the insulating substrate is a ceramic substrate.