JPH11273872A - Electroluminescent device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce electromagnetic noise due to an effect of a driving device for electroluminescent device as well as electromagnetic noise generated in the electroluminescent device itself. SOLUTION: In an electroluminescent device comprising a transparent electrode 3a, an light emitting layer 4, a dielectric layer 5 and a back electrode 6a layered on a transparent substrate 2a, and emitting light from the light emitting layer 4 by an alternating-current voltage applied from the side of a drive device 10 to a transparent-electrode terminal 3b disposed on the transparent electrode 3a and to a back-electrode terminal 6b disposed on the back electrode 6a, a conductive film 8a is newly provided on the back electrode 6a with an insulator layer 7 sandwiched therebetween, and the conductive film 8a is caused to be conducted to the transparent electrode 3a and grounded to a ground line on the driving device 10 side, via a signal wire led out from the transparent-electrode terminal 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of electroluminescence (hereinafter, referred to as EL) which has been subjected to a treatment for preventing electromagnetic noise.

[0002]

2. Description of the Related Art Many electronic devices such as a portable timepiece and a cellular phone use a backlight by EL for the purpose of improving the visibility of a display unit. Conventionally, as this type of EL, for example, an EL having a structure as shown in FIG. 6 is known. In this method, a transparent electrode 3a (ITO electrode) is formed on a transparent substrate 2a made of a plastic film, and a light emitting layer 4, a dielectric layer 5, and a back electrode 6a are formed thereon.
Are sequentially laminated, and the whole is covered with a transparent moisture-proof sheet 2b. A transparent electrode terminal 3b and a back electrode terminal 6b are provided at each end of the transparent electrode 3a and the back electrode 6a, respectively.
b is connected to a driving device 10 via a cable 9.

In an EL having such a structure,
When an AC voltage is applied between the transparent electrode 3a and the back electrode 6a, the EL molecules in the light emitting layer 4 are excited, and a light emission phenomenon appears. By the way, the applied AC voltage is approximately 35 to
Since the inverter is used in a voltage range of about 150 V and an inverter for converting into an AC voltage is provided in the driving device 10, the inverter easily becomes a source of electromagnetic noise, and the electromagnetic noise is generated through the driving circuit board and the connection cable. And the image of the liquid crystal display unit arranged and used to overlap the EL may be disturbed. Conventionally, as a method of minimizing electromagnetic noise generated by an inverter as a source, for example, a clamp core using a ferrite material and a common mode choke coil are provided on the output side and the power supply side of a circuit board disposed in the drive device 10. Thus, there has been a method of attenuating electromagnetic noise generated on the EL side.

[0004]

However, the above-described electromagnetic noise attenuating method is effective for a driving device serving as a noise generating source and has an effect of reducing electromagnetic noise to some extent. A small amount of electromagnetic noise is generated, and this is
L was affected through a cable. Also, EL
And was also affected by electromagnetic noise generated in the EL itself when a voltage was applied.

Therefore, the present invention provides a new conductive film having an electromagnetic shielding effect on an EL structure, and furthermore, short-circuits this conductive film and either a transparent electrode or a back electrode and grounds the EL structure. An object of the present invention is to reduce electromagnetic noise generated in a computer.

[0006]

According to an aspect of the present invention, there is provided an EL according to the first aspect of the present invention, wherein a transparent electrode, a luminescent layer, a dielectric layer, and a back electrode are laminated on a transparent substrate. By applying an AC voltage from the driving device side to the transparent electrode terminal disposed on the transparent electrode and the rear electrode terminal disposed on the back electrode, the EL layer emits light, and the EL layer emits light. A conductive film is newly provided with an insulator layer interposed therebetween, the conductive film is electrically connected to the transparent electrode, and the conductive film is grounded to a ground line on the driving device side via a signal line led out from a terminal for the transparent electrode. And

The EL according to a second aspect of the present invention has a structure in which a transparent electrode, a light emitting layer, a dielectric layer, and a back electrode are laminated on a transparent substrate, and an alternating voltage is applied between the transparent electrode and the back electrode. In the EL in which the luminous body layer emits light by applying, a transparent conductive film is newly provided on the transparent substrate opposite to the transparent electrode, and the transparent conductive film is electrically connected to the back electrode and connected to the ground line. It is grounded.

[0008]

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. FIG. 1 shows a first embodiment of an EL according to the present invention. This E
L1 has a transparent electrode 3a, a light emitting layer 4, a dielectric layer 5, and a back electrode 6 on a transparent substrate 2a made of a plastic film.
a, an insulator layer 7, and a conductive film 8a are sequentially laminated, and finally the entire structure is covered with a transparent moisture-proof sheet 2b.
The transparent electrode 3a is provided with a transparent electrode terminal 3b.
The back electrode 6a is provided with a back electrode terminal 6b,
From each of the electrode terminals 3b, 6b, a cable 9a,
9b, it is connected to the driving device 10 and an AC voltage is applied between the transparent electrode 3a and the back electrode 6a. Further, the conductive film 8a has a conductive film terminal 8b provided at an end thereof.
Is connected to the transparent electrode 3a via the conductive line 11 and is in an electrically short-circuit state. Furthermore, the transparent electrode terminal 3
The cable 9a drawn out of b is connected to a control signal line for driving the transparent electrode 3a and also to a ground line of the driving device 10.

Next, a method of forming the EL 1 having the above structure will be described. First, indium oxide is doped on the transparent substrate 2a with tin, and the obtained ITO (Indium Tin O 2
xide) Powder is deposited to form a transparent metal film. next,
This metal film is formed into a transparent electrode pattern having a desired shape by etching to form a transparent electrode 3a (ITO electrode). Note that, in addition to the above-described etching, it is also possible to form a paint by mixing ITO powder with a transparent resin, and to form it by a printing method.

The luminous body layer 4 is formed into a paint by adding a trace amount of an activator of a metal or a halogen element to a phosphor of zinc sulfide (ZnS), and the paint is formed by screen printing.
It is formed on top.

The dielectric layer 5 is made of a material having a high withstand voltage in order to protect the light emitting layer 4 from electrical breakdown. As such a material, there is barium titanate, which is formed on the luminous layer 4 by screen printing with a coating material in which barium titanate is dispersed. In particular, when barium titanate is used, since the reflectance of light is high, it also serves as a reflector for reflecting light emitted from the light emitting layer 4 toward the transparent electrode 3a serving as a display surface. The back electrode 6a is formed on the dielectric layer 5 by vapor deposition using a metal powder such as silver or another metal having high conductivity. Further, the metal powder and graphite may be formed into a paint and formed by screen printing, or may be formed by bonding a metal foil.

The insulator layer 7 is formed by screen printing a fluorine resin paint having excellent moisture proof properties.
In particular, the resin is not limited to a fluororesin, and may be another resin having an insulating property.

The conductive film 8a is preferably a metal thin film having good conductivity. For example, a thin film of aluminum is used, but the present invention is not limited to this. Further, as a forming method, a metal thin film may be formed by vapor deposition other than the method of attaching a metal thin plate. Finally,
The whole structure is completed by covering the whole with the transparent moisture-proof sheet 2b and sealing it by bonding or thermocompression bonding. This moistureproof sheet 2
b is provided for the purpose of insulating effect and moisture-proof effect.

FIG. 2 shows a second embodiment of the EL according to the present invention. This EL12 is similar to the above-described embodiment.
A transparent electrode 3a, a light emitting layer 4, a dielectric layer 5, and a back electrode 6a are sequentially laminated on a transparent substrate 2a made of a plastic film, and the whole is covered with a transparent moisture-proof sheet 2b. Is different from the transparent electrode 3a
The transparent conductive film 13 is newly provided on the transparent substrate 2a on the side opposite to the above. In this embodiment, the transparent conductive film 1
Since 3 is provided on the transparent substrate 2a side, it is necessary to have light transmissivity so as not to hinder emission of light from the light emitting layer 4. The transparent conductive film 13 is a transparent electrode 3
It is formed in the same manner as a.

The transparent electrode 3a has a transparent electrode terminal 3b.
The back electrode 6a is provided with a back electrode terminal 6b. Then, they are connected to the driving device 10 by cables 9a, 9b extending from the electrode terminals 3b, 6b, and an AC voltage is applied between the transparent electrode 3a and the back electrode 6a. Further, the transparent conductive film 13 is connected to a conductive wire 15 from a terminal 14 for a transparent conductive film provided at an end thereof.
And is electrically connected to the back electrode 6a via the. Further, the cable 9a drawn from the back electrode terminal 6b is connected to a control signal line for driving the back electrode 6a and also to the ground line of the driving device 10.

The conductive film 8a in the first embodiment and the transparent conductive film 13 in the second embodiment are not limited to those formed by solid electrodes over the entire surface, but may be stripes, lattices, or turtles. Such a shape is applicable.

[0017]

FIG. 3 to FIG. 5 show an EL according to the first embodiment.
Is compared with the EL of the conventional structure. In each graph, the vertical axis indicates the electric field strength (dBuV /
m), the frequency (MHz) is plotted on the horizontal axis, and the electromagnetic noise (H) generated in the horizontal direction and the electromagnetic noise (V) generated in the vertical direction with respect to EL are shown on a graph.
In addition, an international standard value (VCCI Class1 (3 m)) regarding radio interference such as an information processing device is indicated by a solid line (Lim
It), and the dotted line (Margin) indicates the standard value of the measurement object itself excluding the margins of the apparatus and the measuring instrument. The measuring device for electromagnetic noise is ADVANTEST.
Ambient temperature (22 ° C)
All measurement conditions such as humidity (37%) were set the same.

(Embodiment 1) In an anechoic chamber, an EL1 of the present invention is set on a table together with a driving device 10, and a power supply voltage (3.0V DC) is applied to the driving device 10 while rotating the table to emit light from the EL. In this state, the electromagnetic noise generated by the EL 1 and the driving device 10 was measured. FIG. 3 is a graph showing the electromagnetic noise (H) generated in the horizontal direction and the electromagnetic noise (V) generated in the vertical direction.

(Embodiment 2) E mounted on the table
The power supply voltage (DC 3.0 V) is applied to the driving device 1 with respect to L1.
Electromagnetic noise generated by the peripheral devices such as the apparatus and the measuring instrument was measured in a state where the EL did not emit light without being applied to 0. FIG. 4 shows the electromagnetic noise (H) generated in the horizontal direction and the electromagnetic noise (V) generated in the vertical direction at that time.

(Comparative Example) In order to measure the electromagnetic noise generated by the EL having the conventional structure, an experiment was performed by the same means as in the first embodiment, and the power supply voltage (3.0 V DC) was applied to the driving device 1.
Electromagnetic noise when EL was emitted by applying 0 was measured. FIG. 5 shows the electromagnetic noise (H) generated in the horizontal direction and the electromagnetic noise (V) generated in the vertical direction at that time.

Next, a description will be given based on the experimental data shown in FIGS. The electric field strength in FIG. 4 is a state in which the EL is not lit, and is not an electromagnetic noise generated by the EL itself, but an electromagnetic noise due to an electric field strength of the surrounding environment or an error of the measuring instrument. Also, comparing FIG. 3 with FIG. 4, a slight difference in the electric field strength in the vertical direction occurs in the vicinity of 40 to 50 MHz. The same numbers are shown. From this, when the EL is turned on by applying a predetermined voltage, electromagnetic noise is generated from the driving device 10 in the vicinity of 40 to 50 MHz, but it can be confirmed that the amount is very small. (Margi
n) is clear enough.

On the other hand, in the conventional example shown in FIG. 5, the curves of the electric field strength in the horizontal direction and the electric field strength in the vertical direction at 240 MHz or less are largely different from the curves of the present invention in FIG. Moreover, the numerical values of all the curves are much larger than the numerical values of the curve of FIG. From this, it can be confirmed that the electromagnetic noise is greatly amplified in the horizontal and vertical directions. In addition, the frequency exceeds the VCCI standard value (Margin) in several frequency regions.

Although the above-described embodiment was performed for EL1, the same results as for EL1 were obtained for EL12.

[0024]

As described above, the EL according to the present invention is provided.
According to the method described above, a conductive film or a transparent conductive film made of a metal film or the like is newly provided on the conventional EL structure, and the conductive film or the transparent conductive film is short-circuited to one of the transparent electrode and the back electrode. Noise is reduced by grounding the ground line in the drive unit via the cable drawn out from the electrode terminal or the back electrode terminal, so that electromagnetic noise generated externally from the drive unit or electromagnetic generated in the EL itself is eliminated. There is an effect that noise can be effectively blocked by the conductive film or the transparent conductive film, and electromagnetic noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment of an EL according to the present invention.

FIG. 2 is a cross-sectional view of a second embodiment of the EL according to the present invention.

FIG. 3 is a measurement diagram of electromagnetic noise when the EL according to the first embodiment is turned on.

FIG. 4 is a measurement diagram of electromagnetic noise when the EL according to the first embodiment is turned off.

FIG. 5 is a measurement diagram of electromagnetic noise when an EL having a conventional structure is turned on.

FIG. 6 is a cross-sectional view of a conventional EL.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 EL 2a Transparent substrate 3a Transparent electrode 3b Terminal for transparent electrode 4 Light emitting layer 5 Dielectric layer 6a Back electrode 6b Terminal for back electrode 7 Insulator layer 8a Conductive film 8b Terminal for conductive film 10 Driver 12 EL 13 Transparent conductive film

Claims (2)

[Claims] 1. A transparent electrode, a light-emitting layer, a dielectric layer, and a back electrode are laminated on a transparent substrate, and a transparent electrode terminal provided on the transparent electrode and a back electrode terminal provided on the back electrode. In the electroluminescence in which the light emitting layer emits light by applying an AC voltage from the driving device side, a new conductive film is provided on the back electrode with an insulating layer interposed therebetween, and the conductive film is formed on the transparent electrode. The electroluminescence is characterized in that it is made conductive and is grounded to a ground line on the driving device side via a signal line drawn from a transparent electrode terminal. 2. A transparent electrode, a luminescent layer, a dielectric layer, and a back electrode are laminated on a transparent substrate, and the luminescent layer emits light by applying an AC voltage between the transparent electrode and the back electrode. In the electroluminescence described above, a transparent conductive film is newly provided on a transparent substrate opposite to the transparent electrode, and the transparent conductive film is electrically connected to the back electrode and grounded to a ground line.