JPH05114482A - Manufacture of transmission type electroluminescent element - Google Patents

Abstract

PURPOSE:To easily manufacture a transmission type electroluminescent element capable of fully displaying the high luminous efficacy of zinc sulfide, when this material expected to display high luminous efficacy as the base material of a luminous layer is used. CONSTITUTION:The first transparent electrode layer 2 of ZnO:Al, the first insulation layer 3 of ZnO, a luminous layer 4 of ZnS:Mn, the second insulation layer 5 of Y2O3 and the second transparent electrode layer 6 of ZnO:Al are formed in order on a transparent glass substrate 1. ZnO in the first transparent electrode 2 is intensively oriented to the direction of (001) and more intensively than ZnO in the layer 3 to the same direction. The luminous layer 4 with ZnS having the same crystal structure as ZnO as a base material is influenced by the crystal of ZnO, and formed under improved crystal quality. As a result, a low quality layer hardly exists near the interface of the first insulation layer 3 and the luminous layer 4, and the crystal grain of the layer 4 also grows to or above a hundred and several tens of mum, thereby ensuring high luminous efficacy due to zinc sulfide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a transmissive electroluminescence (EL) element used as a light emitting element for a dial illumination, a display and the like.

[0002]

2. Description of the Related Art A thin film EL device has a first electrode layer, a first insulating layer, a light emitting layer, a second insulating layer and a second electrode layer, which are sequentially laminated on a substrate. The light emitting layer emits light by applying a voltage equal to or higher than a predetermined threshold value between and. If desired, a substrate may be further laminated on the second electrode layer. In this thin film EL element, the substrate, the first electrode layer, and the first and second insulating layers are normally formed transparently. However, in the transmissive EL element in which the second electrode layer is also transparently formed, the light of the light emitting layer Is transmitted through the first insulating layer and the first electrode layer and radiated from the front substrate, and is transmitted through the second insulating layer and the second electrode layer and radiated from the back substrate. To be done.

In a general transmissive EL element, a transparent glass substrate is used as a substrate and I and I are used as the first and second electrode layers.
_{n 2 O 3 -SnO 2 (ITO} ) or ZnO: Al (Zn
O with a few% Al added. The same applies below. ) Is adopted, Y ₂ O ₃ , Ta ₂ O ₅ or Si ₃ N ₄ is adopted as the first and second insulating layers, and ZnS: Mn or ZnS: TbF ₃ is adopted as the light emitting layer. This transmissive EL
In the device, a ZnS: Mn or ZnS: TbF ₃ light emitting layer is used to exhibit good light emission efficiency, and a transparent glass substrate is used by using the first and second electrode layers and the first and second insulating layers. And the first electrode layer, between the first electrode layer and the first insulating layer, and between the second insulating layer and the second electrode layer, good durability is exhibited.

Further, in the non-transmissive EL element in which the second electrode layer is formed with metallic luster and the light of the light emitting layer is reflected by this second electrode layer, ZnO: Al is adopted as the first electrode layer. , AlN—Si ₃ N ₄ system is adopted as the first and second insulating layers, alkaline earth chalcogenide such as SrS is adopted as the base material of the light emitting layer, and Al is adopted as the second electrode layer. Known (JP-A-2-82493)
Publication). In this non-transmissive EL device, the first transparent electrode layer made of ZnO: Al and the first and second insulating layers made of AlN—Si ₃ N ₄ are used while using the alkaline earth chalcogenide as a base material of the light emitting layer. By adopting this, the durability is improved by the good adhesion between the first electrode layer and the first insulating layer.

[0005]

However, in the above-mentioned general transmissive EL element, when ZnS, which can be expected to have excellent luminous efficiency, is adopted as the base material of the light emitting layer, it is adopted as the first and second insulating layers. Y ₂ O ₃ , Ta ₂ O ₅ or Si ₃ N
_{Since 4} is amorphous, the light emitting layer is formed on the first insulating layer (11
1) Although it can be formed with an oriented zinc blende structure, a poor quality layer exists in a large thickness in the vicinity of the interface between the first insulating layer and the light emitting layer, and the crystal grain of the light emitting layer is several μm or less.
It became clear that it was only about several tens of μm. Therefore, the light emission efficiency of the transmissive EL element is about 2 (lm / W) even when a ZnS: Mn light emitting layer (yellow-orange light emission), which is expected to have the highest light emission efficiency, is employed, which is relatively large. When a light emitting layer of ZnS: TbF ₃ (green light emission), which is expected to have light emitting efficiency, is adopted, it is about 1 (lm / W) or less.

In the non-transmissive EL device described in the above publication, if a transparent glass substrate is used as the substrate and the second electrode layer is made of, for example, ZnO: Al instead of Al, a transmissive EL device can be obtained. also in transmission type EL element obtained, the first and second insulating layers AlN-Si ₃ N
_{Since the 4} type is also amorphous, when ZnS is adopted as the base material of the light emitting layer, sufficient luminous efficiency cannot be exhibited as in the above case.

The present invention has been made in view of the above-mentioned conventional problems, and when ZnS, which can be expected to have excellent luminous efficiency, is adopted as the base material of the light emitting layer, the excellent luminous efficiency can be sufficiently exhibited. The purpose is to easily manufacture a transmissive EL device.

[0008]

A method of manufacturing a transmissive EL device according to the present invention comprises a first step of forming a first transparent electrode layer made of ZnO and Al on a transparent substrate, and the first transparent electrode layer. A second step of forming a first insulating layer of ZnO thereon,
A third step of forming a light emitting layer having ZnS as a base material on the first insulating layer by sputtering at 400 to 500 ° C., and a second insulating layer and a second transparent electrode layer on the light emitting layer in this order. And a fourth step of forming.

In the first step, ZnO and Al are formed on the transparent substrate.
And a first transparent electrode layer made of (ZnO: Al) is formed. As the substrate, a transparent substrate that can withstand the heat in the third step described later can be used, and for example, a transparent glass substrate can be used. The first transparent electrode layer is ZnO: A
It consists of l. In order to form this first transparent electrode layer, a known film forming method such as a sputtering method, a vacuum vapor deposition method, a CVD (chemical vapor deposition) method can be adopted, but the temperature of the transparent substrate is 200 to 400 ° C. It is preferably formed by a sputtering method. If the first transparent electrode layer is formed by the sputtering method, the evaporation source can be made common by performing the other steps by the sputtering method, and each layer can be formed by changing the atmosphere gas. This is because the property is improved. Further, if the first transparent electrode layer is formed on the transparent substrate at a temperature of 200 to 400 ° C. by the sputtering method, ZnO: Al is likely to be strongly oriented in the (001) direction.

In the second step, ZnO is formed on the first transparent electrode layer.
Forming a first insulating layer. For forming the first insulating layer, a known film forming method such as a sputtering method, a vacuum evaporation method, or a CVD method can be adopted, but the temperature of the transparent substrate is 200 to 200 for the same reason as in the first step. It is preferably formed by a sputtering method at 400 ° C. Third
In the step, a light emitting layer containing ZnS as a base material is formed on the first insulating layer by sputtering at 400 to 500 ° C. For the light emitting layer, Zn using Mn as an activator
S: Mn, ZnS: Tb using TbF ₃ as an activator
F ₃ can be adopted. If the light emitting layer is formed at a temperature of less than 400 ° C. by the sputtering method, the crystal will be (111).
In addition to having a zincblende structure oriented in a vertical direction, the size of the crystal grains is about several tens of μm, and the crystals exhibit a relatively weak orientation strength, the transmissive EL element obtained cannot exhibit sufficient luminous efficiency. .. The light emitting layer is formed by the sputtering method.
If the temperature is higher than 00 ° C., the transparent substrate is likely to be distorted and the product yield is reduced. Further, even if the light emitting layer is formed by MOCVD (metal organic chemical vapor deposition) method or ALE (atomic layer epitaxy) method instead of the sputtering method by the sputtering device, the crystal grains of the light emitting layer can be grown large. The method causes complication of the device. In the fourth step, the second insulating layer and the second transparent electrode layer are sequentially formed on the light emitting layer. Examples of the second insulating layer include ZnO similar to that of the first insulating layer, Y ₂ O ₃ , Ta ₂ O ₅ , and Si.
A high dielectric material such as ₃ N ₄ , Sm ₂ O ₃ , or Al ₂ O ₃ can be used. In order to form this second insulating layer, a known film forming method such as a sputtering method, a vacuum evaporation method, a CVD method can be adopted. For the same reason as in the first step, ZnO is preferably used as the second insulating layer, and the transparent substrate is preferably formed by a sputtering method in which the temperature is 200 to 400 ° C. As the second transparent electrode layer, in addition to the same ZnO: Al as the first transparent electrode layer, ITO, SnO ₂ ,
In ₂ O ₃ or the like can be used. To form this second transparent electrode layer, a sputtering method, a vacuum deposition method,
A known film forming method such as a CVD method can be used. For the same reason as in the first step, ZnO: Al was used as the second transparent electrode layer.
It is preferable that the transparent substrate is formed by a sputtering method in which the temperature is 200 to 400 ° C.

[0011]

As a result of earnest research, the present inventor has found that the above object can be achieved by employing the first electrode layer, the first insulating layer and the light emitting layer, and has completed the present invention. That is, in the manufacturing method of the present invention, Zn is first formed on the transparent substrate.
A first transparent electrode layer of O: Al is formed. In this first transparent electrode layer, ZnO is strongly oriented with a wurtzite structure in the (001) direction on the transparent substrate even if the transparent substrate is an amorphous one such as a transparent glass substrate, and Al is contained inside. Addition of a few% shows conductivity of 10 ⁻³ Ω · cm or less.

Next, ZnO is formed on the first transparent electrode layer.
Forming a first insulating layer. In this first insulating layer, ZnO composed of the same element is further formed on the first transparent electrode layer in which ZnO is already strongly oriented in the (001) direction, so that ZnO has a stronger wurtzite structure in the (001) direction. Be oriented. Then, a light emitting layer containing ZnS as a base material is formed on the first insulating layer. This light emitting layer uses ZnS having the same crystal structure as ZnO in the first transparent electrode layer and the first insulating layer as a base material, and therefore is affected by ZnO crystals and is formed with improved crystallinity. it is conceivable that. For this reason, it is difficult for a poor quality layer to exist near the interface between the first insulating layer and the light emitting layer, and the crystal grains of the light emitting layer have a grain size of a few hundreds of μm.
To grow above.

After that, a second insulating layer and a second transparent electrode layer are sequentially formed on the light emitting layer to obtain a transmissive EL device. In the transmissive EL device thus obtained, as described above, since it is difficult for the light emitting layer to have a poor quality layer at the interface with the first insulating layer and crystal grains are sufficiently grown, the base material of the light emitting layer is formed. The excellent luminous efficiency of the barrel ZnS is sufficiently exhibited.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. (Example 1) {First step} 1.1 m thick as a transparent substrate
m non-alkali transparent glass substrate 1 is prepared, the transparent glass substrate 1 is washed, dried and set in a magnetron type sputtering apparatus. Then, the inside of the film forming chamber of the sputtering apparatus was evacuated to 2 × 10 ⁻⁶ Torr or less, the transparent glass substrate 1 was heated to 200 to 400 ° C., and then ZnO and A were added.
1 and 2 are used as targets and are sputtered in an (Ar + O ₂ ) sputter gas. At this time, the sputtering power applied to each target is adjusted so that the Al concentration in ZnO is about 2 wt%. In this way, the first transparent electrode layer 2 of ZnO: Al is formed to a thickness of 200 nm on the transparent glass substrate 1.

{Second Step} Subsequently, while the transparent glass substrate 1 is heated to 200 to 400 ° C., sputtering is carried out in (Ar + O ₂ ) sputtering gas with ZnO as a target. Thus, the first insulating layer 3 made of ZnO is formed on the first transparent electrode layer 2 with a thickness of 200 to 400 nm.

{Third step} The transparent glass substrate 1 is heated to 400 ° C.
In the state of being heated to, the targets are ZnS and Mn, and sputtering is performed in an Ar sputtering gas. At this time, Z
The sputtering power to be applied to each target is adjusted so that nS is 99.5 wt% and Mn is 0.5 wt%. Thus, the ZnS: Mn light emitting layer 4 is formed on the first insulating layer 3 to have a thickness of 400 to 600 nm.

{Fourth step} 100 to 100% transparent glass substrate 1
Sputtering is performed in a (Ar + O ₂ ) sputter gas using Y ₂ O ₃ as a target while heating at 300 ° C. Thus, the second insulating layer 5 made of Y ₂ O _{3 is} formed on the light emitting layer 4 to have a thickness of 400 nm. Further, while the transparent glass substrate 1 is heated to 200 to 400 ° C., sputtering is performed in (Ar + O ₂ ) sputtering gas with ZnO and Al as targets. At this time, the Al concentration in ZnO is 2 wt%
The sputtering power to be applied to each target is adjusted so as to be about the same level. Thus, ZnO: Al is formed on the second insulating layer 5.
The second transparent electrode layer 6 is formed to a thickness of 200 nm to obtain a transmissive EL element.

As shown in FIG. 1, this transmissive EL device comprises a transparent glass substrate 1, a first transparent electrode layer 2 of ZnO: Al, a first insulating layer 3 of ZnO, and ZnS: M.
n light emitting layer 4, a second insulating layer 5 made of Y ₂ O ₃ , and Z
A second transparent electrode layer 6 of nO: Al is sequentially laminated. (Example 2) In the above {third step}, the heating temperature of the transparent glass substrate 1 was set to 450 ° C, the other steps and conditions were the same as in Example 1 to obtain a transmissive EL device. (Example 3) In the above {third step}, the heating temperature of the transparent glass substrate 1 was set to 500 ° C, and the other steps and conditions were the same as in Example 1 to obtain a transmissive EL device. (Comparative Example 1) In the above {second step}, by using Y ₂ O ₃ as a target, a first insulating layer made of Y ₂ O ₃ having a thickness of 400 nm was formed on the first transparent electrode layer, and other steps and The conditions are the same as in Example 1 to obtain a transmissive EL device.

As shown in FIG. 2, this transmission type EL device comprises a transparent glass substrate 11, a first transparent electrode layer 12 of ZnO: Al, a first insulating layer 13 made of Y ₂ O _3, and a Z layer.
A light emitting layer 14 of nS: Mn, a second insulating layer 15 of Y ₂ O _3, and a second transparent electrode layer 16 of ZnO: Al are sequentially laminated. (Comparative Example 2) In the above {third step}, the heating temperature of the transparent glass substrate 1 was set to 350 ° C, the other steps and conditions were the same as in Example 1, and a transmissive EL element was obtained. (Evaluation) An alternating electric field was applied to the transmissive EL elements of Examples 1 to 3 and Comparative Examples 1 and 2 to measure the luminous efficiency. The luminous efficiency of the transmissive EL element of Example 1 was 4.3 ( l
m / W), and the luminous efficiency of the transmissive EL device of Example 2 is 4.
The luminous efficiency of the transmissive EL device of Example 3 was 9 (lm / W) and 4.7 (lm / W). On the other hand, the luminous efficiency of the transmissive EL device of Comparative Example 1 is 2.0 (lm / W), and Comparative Example 2
The light emission efficiency of the transmissive EL element of was 1.6 (lm / W).

When the crystal structures of the light emitting layers of the transmissive EL elements of Examples 1 to 3 and Comparative Examples 1 and 2 were examined, the transmissive EL elements of Examples 1 to 3 were oriented in (001). The wurtzite structure and the size of the crystal grains were about 150 to 200 μm, indicating strong orientation strength. On the other hand, in the transmission type EL elements of Comparative Examples 1 and 2, the (111) -oriented zincblende structure and the size of the crystal grains are about 30 to 50 μm, which is weaker than those of Examples 1 to 3. Showed strength. In particular, in the transmissive EL device of Comparative Example 1, a poor quality layer was present with a large thickness in the vicinity of the interface between the first insulating layer 13 and the light emitting layer 14.

Therefore, in Comparative Examples 1 and 2, even if ZnS, which can be expected to have excellent light emitting efficiency, is used as the base material of the light emitting layer, the transmissive EL cannot exhibit sufficient light emitting efficiency.
It turns out that the element is manufactured. On the other hand, Examples 1 to
It can be seen that in No. 3, it is possible to easily manufacture the transmissive EL element that can sufficiently exhibit the excellent luminous efficiency by ZnS: Mn.

[0022]

As described above in detail, in the manufacturing method of the present invention, the first transparent electrode layer of ZnO: Al is formed on the transparent substrate, and the first insulating layer made of ZnO is formed on the first transparent electrode layer. Since a layer is formed and a light emitting layer containing ZnS as a base material is formed on the first insulating layer at 400 to 500 ° C. by a sputtering method, a transmissive EL device capable of sufficiently exhibiting excellent light emitting efficiency by ZnS. The device can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a transmissive EL element of Example 1.

FIG. 2 is a cross-sectional view of a transmissive EL element of Comparative Example 1.

[Explanation of symbols]

1 ... Transparent glass substrate 2 ... First transparent electrode layer 3
... first insulating layer 4 ... light emitting layer 5 ... second insulating layer 6
... Second transparent electrode layer

Claims (1)

[Claims] 1. A first substrate comprising ZnO and Al on a transparent substrate.
A first step of forming a transparent electrode layer, a second step of forming a first insulating layer made of ZnO on the first transparent electrode layer, and a light emitting layer containing ZnS as a base material on the first insulating layer. Transmission type including a third step of forming at 400 to 500 ° C. by a sputtering method and a fourth step of sequentially forming a second insulating layer and a second transparent electrode layer on the light emitting layer. Manufacturing method of electroluminescent element.