JPH11224782A - Electroluminescence - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the electroluminescence to obtain the prescribed quantity of light with small power consumption, and reduce the electromagnetic noise generated from an electroluminescence drive device, etc. SOLUTION: In an electroluminescence 1, an upper electrode 3, an electroluminescence layer 4, a dielectric layer 5, and a back side electrode 6 are formed in a layered manner, both external sides are covered with transparent plastic films 2a, 2b, and the electroluminescence layer 4 held between the upper electrode 3 and the back side electrode 6 emits the light by applying the AC voltage between the upper electrode 3 and the back side electrode 6. The upper electrode 3 is formed of a metallic material of high conductivity into mesh pattern of approximately same shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for forming a top electrode, a light-emitting layer, a dielectric layer, and a back electrode in a layered form and covering both outer surfaces with a transparent moisture-proof material. The present invention relates to electroluminescence (hereinafter, referred to as EL) that emits light from a light-emitting layer sandwiched between an upper electrode and a back electrode by applying an AC voltage therebetween.

[0002]

2. Description of the Related Art Many electronic devices including a liquid crystal panel such as a portable timepiece and a mobile phone use an EL as a backlight for the purpose of improving the visibility of the display surface of the liquid crystal panel. Conventionally, as this kind of EL, for example, an EL having a structure as shown in FIG. 8 is known. In this method, an upper electrode 3 (ITO electrode) is formed under a transparent plastic film 2a, and a luminescent layer 4 is formed thereunder.
After the dielectric layer 5 and the back electrode 6 are sequentially formed, they are covered again with the plastic film 2b. An upper electrode terminal 7 is provided at each end of the upper electrode 3 and the back electrode 6.
And a rear electrode terminal 8 are provided, respectively, and the driving device 10 is connected to the respective electrode terminals 7 and 8 via a cable 9.
It is connected to the.

In an EL having such a structure,
By applying an AC voltage to the upper electrode 3 and the back electrode 6,
The EL molecules of the light emitting layer 4 sandwiched between these electrodes 3 and 6 are excited, and a light emitting phenomenon appears. At this time, the upper electrode 3
Since is a transparent electrode made of ITO (Indium Tin Oxide), light emitted from the light emitting layer 4 is transmitted to the outside through the upper electrode 3 and the entire EL is illuminated brightly.

[0004]

By the way, the upper electrode 3 is made of a transparent plastic film 2a formed by doping a transparent ITO powder obtained by doping indium oxide with tin.
It is formed by vapor deposition on the top or by mixing the ITO powder with a transparent resin to form a coating and then by screen printing on the transparent plastic film 2a, which has the feature of high light transmittance. However, there is an advantage that high luminance can be secured. However, since the electric resistance is large and the conductivity is low, the plastic film 2
When formed on the entire surface of a, there is a problem that power consumption increases when trying to obtain a predetermined light amount. In particular, in the case of driving with a portable battery, the consumption of the battery is large and it is not suitable for long-time driving.

Accordingly, the present invention is to provide an EL which can obtain a predetermined amount of light with low power consumption.

[0006]

In order to solve the above problems, an EL according to claim 1 of the present invention comprises an upper electrode, a light emitting layer, a dielectric layer, and a back electrode which are formed in layers and have an outer electrode. Both sides are coated with a transparent moisture-proof material, and by applying an AC voltage between the upper electrode and the back electrode, the electroluminescence that emits light from the luminous body layer sandwiched between the upper electrode and the back electrode, The upper electrode is formed of a highly conductive metal material in a mesh pattern having substantially the same shape.

In the EL according to a second aspect of the present invention, the metal material is silver or graphite, the metal material powder is formed into a paint to form a metal paste, and the metal paste is screen-printed to form a mesh pattern. An upper electrode is formed.

The EL according to a third aspect of the present invention is the EL, wherein the total area of the upper electrode lines forming the mesh pattern is smaller than the total area of the meshes surrounded by the upper electrode lines, and The transfer dimension is not more than 1.5 mm.

The EL according to a fourth aspect of the present invention is characterized in that a luminous light emitting layer is formed on the upper surface of the upper electrode line forming the mesh pattern.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an EL according to the present invention will be described in detail with reference to the accompanying drawings. As shown in FIG. 1, the EL 1 according to the present invention comprises a back electrode 6, a dielectric layer 5, a luminous layer 4, and an upper electrode 3 sequentially laminated on a transparent plastic film 2b, and finally the transparent electrode again. This is a structure in which the upper surface of EL1 is covered with a plastic film 2a. Then, the end of the upper electrode 3 and the back electrode 6
Is connected to a driving device 10 via a cable 9 and an AC voltage is applied to the upper electrode 3 and the back electrode 6.

In the above structure, the upper electrode 3 is formed by a conventional I
Unlike the TO electrode, a metal paste such as silver or graphite having high conductivity is formed into a paint to form a metal paste, and this metal paste can be formed by screen printing on the upper surface of the light emitting layer 4. The mesh pattern is, for example, a turtle pattern as shown in FIG. 2 or a lattice pattern as shown in FIG. 3 formed by the upper electrode lines 11. Many meshes 12 surrounded by the upper electrode lines 11 have the same pattern and the same size. In addition, a lead wire 11 a connected to the driving device 10 via the cable 9 is provided at a terminal of the upper electrode 3 thus formed. Further, as another method of forming the upper electrode 3, it is also possible to form a predetermined mesh electrode pattern by depositing a metal powder on the entire upper surface of the light emitting layer 4 and then performing an etching process using a photomask.

The resistance value of the upper electrode 3 formed by the upper electrode wire 11 is slightly different depending on the type of the binder and the printing thickness. For example, a silver paste is printed with a thickness of 25 μm using a polyester resin as a binder. The resistance value at this time is about 0.05Ω. This resistance value is equal to the conventional I value.
It is extremely smaller than the resistance value of the TO electrode of 1 kΩ or more.

In the upper electrode 3, the total area of the upper electrode lines 11 forming a mesh pattern is smaller than the total area of the meshes 12 surrounded by the upper electrode lines 11. This is because the light emitted from the light emitting layer 4 passes through the mesh 12 to illuminate the upper surface of the EL 1 brightly, so that the total area of the upper electrode lines 11 constituting the upper electrode 3 is larger than the total area of the mesh 12. This is because, when it becomes large, the mesh pattern becomes conspicuous, and at the same time, the transmittance of light emitted from the light emitting layer 4 decreases, and the light emission luminance decreases as a whole.

Further, in the case of the turtle pattern shown in FIG. 4, the size of each mesh 12 of the upper electrode 3 is the distance L1 between the opposite sides of the upper electrode wire 11 constituting the hexagon of each mesh 12. Is desirably 1.5 mm or less, and the upper electrode line 11 which forms a square also in the case of the lattice pattern shown in FIG.
Is desirably 1.5 mm or less. As described above, the size of the mesh 12 is limited.
This is because if the total area of the mesh 12 is too large, light emission luminance unevenness occurs at a location near the upper electrode line 11 and at the center of the mesh 12. This is the upper electrode wire 11
In the vicinity of, the voltage value is high, so that the EL molecules in the light emitting layer 4 are activated and the luminous brightness is high, and conversely, the voltage value decreases toward the central part of the mesh 12 away from the respective upper electrode lines 11. This is because light emission luminance is reduced. From the above, the above range is desirable as a condition that does not cause luminance unevenness. For example, as shown in FIGS. 4 and 5, the line widths H1 and H2 of the upper electrode wire 11 are each 0.2 mm, and the distances L1 and L2 between the opposite sides of the regular polygon forming the mesh 12 are each 1.0 mm. When the thickness is 1.5 mm, it is possible to obtain a predetermined light emission luminance and light emission without luminance unevenness as a whole.

The mesh shape of the upper electrode 3 is not limited to the tortoise shape or the lattice shape, but is shown in FIG.
A polka dot pattern, a diamond pattern, or the like in which circles having the same shape as shown in FIG. If a specific character or pattern is to be emitted instead of emitting light from the entire surface of the light emitting layer 4, a thick upper electrode line 11 is applied to a portion where the outline of the character or pattern is formed. An electrode pattern formed of the turtle pattern, lattice pattern, polka dot pattern, diamond pattern, or the like may be formed inside the electrode wire 11.

The EL1 of the present invention can be a conventional one as it is for the portion other than the above-mentioned upper electrode 3. For example, in FIG. , Zinc sulfide (ZnS)
A small amount of an activator of a metal or a halogen element is added to the phosphor matrix to form a paint, which is formed on the dielectric layer 5 by screen printing. The dielectric layer 5 located on the lower surface side of the light emitting layer 4 is made of a material having a high withstand voltage such as barium titanate in order to protect the light emitting layer 4 from electrical breakdown. In particular, barium titanate has a high light reflectance and emits light emitted from the light emitting layer 4 to the upper electrode 3.
It also plays the role of a reflector that reflects light to the side. Further, the back electrode 6 is formed by pasting a metal powder such as silver or graphite having a high conductivity like the upper electrode 3 and performing screen printing on the plastic film 2b on the lower surface side. Finally, the upper surface of the upper electrode 3 is covered with a transparent plastic film 2a, and sealed with a plastic film 2b formed on the lower surface side by bonding or thermocompression bonding to complete EL1. Plastic films 2a, 2b covering the whole
Has both an insulating effect and a moisture-proof effect. still,
Although a plastic film is used in the present embodiment, any material may be used as long as it is transparent, has insulating properties, and has a high moisture-proof effect. For example, a glass plate or an acrylic plate may be used.

FIG. 7 shows an embodiment in which a luminous phosphor 13 is provided on the upper surface of the mesh-shaped upper electrode 3 described above. The luminous phosphor 13 is formed, for example, by applying a high-luminance, long-lasting luminous phosphor to a paint and screen-printing it on the upper electrode line 11 of the upper electrode 3. In this case, since the color tone of the phosphorescent phosphor 13 is substantially similar to the pale yellow-green color tone of the light emitting layer 4,
The black color of the upper electrode wire 11 can be hidden, and the appearance is good. Further, by providing the phosphorescent phosphor 13, when the EL1 is turned on, the light emitted from the light emitting layer 4 is amplified by the phosphorescent phosphor 13 to increase the light emission luminance, while the light is stored even when the EL1 is turned off. Phosphor 13
Has the effect of maintaining the function as a backlight by the afterglow action.

In the present invention, both the upper electrode 3 and the back electrode 6 are made of a paste of a highly conductive metal material such as silver or graphite, and the upper electrode 3 is meshed to form the back electrode 6.
Is formed in a plate shape. For this reason, each electrode serves as a terminal for connection to the outside as it is, and there is no need to provide a separately formed electrode terminal for cable connection as in the related art.

[0019]

As described above, according to the EL of the present invention, since the upper electrode is formed in a mesh shape with a metal having high conductivity, it is possible to obtain a predetermined luminous brightness without impairing the light transmittance. And the electrical resistance decreases, resulting in EL
The overall power consumption can be kept low.

Also, the total area of the upper electrode lines forming the mesh pattern is smaller than the total area of the meshes surrounded by the upper electrode lines, and the crossover dimension of each mesh is 1.5 mm or less. The pattern is not conspicuous, the emission luminance is not reduced, and the emission unevenness does not occur.

Further, since the luminous layer is formed on the upper surface of the upper electrode line forming the mesh pattern, the light emitted from the luminous layer is amplified by the luminous layer when the EL is turned on, so that the luminous brightness is increased. On the other hand, even when the EL is turned off, the function as a backlight is maintained by the afterglow action of the phosphorescent phosphor.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an EL according to the present invention.

FIG. 2 is a plan view of an upper electrode formed in a turtle-shape of EL according to the present invention.

FIG. 3 is a plan view of an upper electrode formed in an EL lattice shape according to the present invention.

FIG. 4 is an enlarged view of an upper electrode in FIG. 2;

FIG. 5 is an enlarged view of an upper electrode in FIG. 3;

FIG. 6 is a plan view showing another mesh pattern of the upper electrode according to the present invention.

FIG. 7 is a sectional view showing another embodiment of the EL according to the present invention.

FIG. 8 is a cross-sectional view of a conventional EL.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 EL 2a, 2b Plastic film 3 Upper electrode 4 Light emitting layer 5 Dielectric layer 6 Back electrode 11 Upper electrode line 12 Network

Claims (4)

[Claims] 1. An upper electrode, a luminescent layer, a dielectric layer, and a back electrode are formed in layers, and both outer surfaces are covered with a transparent moisture-proof material, and an alternating voltage is applied between the upper electrode and the back electrode. By doing so, in the electroluminescence that emits light from the luminous body layer sandwiched between the upper electrode and the back electrode, the upper electrode is formed of a highly conductive metal material in a mesh pattern having substantially the same shape. Electroluminescence. 2. The method according to claim 1, wherein the metal material is silver or graphite, and the metal material powder is formed into a paint to form a metal paste, and the metal paste is printed to form a mesh-shaped upper electrode. 2. The electroluminescence according to 1. 3. The total area of the upper electrode lines forming the mesh pattern is smaller than the total area of the meshes surrounded by the upper electrode lines, and the cross dimension of each mesh is 1.5 mm or less. The electroluminescence according to claim 1, wherein: 4. A luminous light-emitting layer is formed on an upper surface of an upper electrode line forming the mesh pattern.
Electroluminescence as described.