JPS63307691A - Ceramic insulating thin film el element - Google Patents

Abstract

PURPOSE:To reduce the vibration sound and use EL elements at the location requiring tranquility by providing damping electrodes corresponding individual electrodes. CONSTITUTION:Damping electrodes 7, 9 corresponding to an internal electrode 2 and a transparent electrode 5 respectively are formed either inside a ceramic substrate 1 or on the surface on the opposite side of a ceramic insulating layer 3 via a damping layer 8. The voltage or current synchronous with the voltage or current applied to EL elements for luminescence is applied to the damping electrodes 7, 9, the damping layer 8 pinched between the damping electrodes 7, 9 and generating electrostriction generates the vibration with the opposite phase to the electrostriction vibration generated when part of the voltage applied for luminescence is applied to the ceramic insulating layer 3 in the ceramic substrate 1. The vibration of whole ceramic insulating thin film EL elements is thereby reduced, and the noise is lowered.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a ceramic insulating thin film EL device used as a light emitting display device or a surface light source, and in particular to an AC drive type EL device using a high dielectric constant ceramic layer as an insulating layer. Ceramic insulation thin wA
Regarding EL elements.

[Conventional technology]

Conventionally, so-called ceramic insulated thin film EL devices have been known as EL devices that can be driven with low voltage AC and have a structure that is extremely stable against dielectric breakdown.
Research Conference Proceedings, page 173 (Confe
RenceRecord of the Intern
ational Display Re5earchC
(1985).

FIG. 2 is a sectional view of such a conventional ceramic insulating thin film EL element, showing a state in which a driving source is added.

As shown in FIG. 2, this EL element has a ceramic base 1
On top is an internal electrode 2 made of platinum, silver/palladium alloy, etc., PZT type, BaTiO3 type.

Alternatively, a ceramic substrate 12 formed by laminating a ceramic insulating layer 3 with a high dielectric constant made of a P bT i 03 type perovskite compound, etc., and a vacuum evaporation method or sputter evaporation method are applied on the ceramic insulating layer 3 of this ceramic substrate 12. Mn deposited by the method.

Z containing luminescent centers such as TbF3.5nF3 and PrFl
It is composed of a thin light emitting layer 4 made of nS and a transparent electrode 5 made of ITO or the like formed on the light emitting layer 4. In order to emit light from this EL element, it is driven by a low voltage AC power source 6 connected to the internal electrode 2 and the transparent electrode 5.

The example shown in Figure 2 is of the so-called single insulation type, but
A double insulation structure may be used in which a thin film insulation layer of Y2O, Ta205, or the like is inserted between the light emitting device 714 and the transparent electrode 5.

Next, the principle of light emission of the ceramic insulating thin film EL element having the above-described structure will be explained.

The light emitting layer 4 shown in FIG. 2 is considered to be a simple capacitor before the start of light emission. Therefore, when an AC voltage is applied from the AC power source 6 between the internal electrode 2 and the transparent electrode 5, a voltage is applied to the luminescent layer 4 and the ceramic insulating layer 3 according to their respective capacitances. When the applied electric field becomes sufficiently large (approximately 106 V/C11 or more), electrons are excited in the conduction band of the light emitting layer 4. These electrons are accelerated by the electric field and collide with the luminescent center with sufficient energy. When the electrons in the luminescent center, which have been raised to an appropriate excited state by the energy of this collision, return to the ground state, light with an energy value unique to the luminescent center is emitted. In reality, the emission spectrum has a certain degree of expansion due to interaction with the crystal lattice, and Mn and Tb are the emission centers.
When F3°5nF3 or PrF3 is used, yellow-orange, green, red, and white light emission is observed, respectively.

The light emitting principle of such a ceramic insulated thin film EL element is based on the conventional AC-driven thin film EL element in which a thin insulating layer and a light emitting layer are laminated on a glass substrate [Nis.I.D.74 Digest 1st Technical.・Papers 84 pages,
(SID 74 Digest pf Technic
However, such a ceramic insulating thin film EL element can significantly reduce the operating voltage and prevent dielectric breakdown due to the effect of the ceramic insulating layer 3, which is several tens of micrometers thick and has a very high dielectric constant. Both have achieved extremely high stability against voltage, and are expected to be used as low-cost surface light sources and light-emitting display devices.

[Problem that the invention seeks to solve]

As mentioned above, ceramic insulating thin film EL devices are capable of low voltage operation and have high stability against dielectric breakdown voltage, but the high dielectric constant ceramic used as the insulating layer exhibits electrostriction when a voltage is applied. arise. That is, when an AC voltage necessary for light emission is applied to the ceramic insulating thin film EL element, a part of this voltage is divided into the ceramic insulating layer, causing distortion in the ceramic insulating layer.

FIG. 3 is a sectional view of the ceramic insulating thin film E element in such an electrostrictive state.

As shown in Fig. 3, the ceramic insulating layer 3 expands in the direction of the arrow when voltage is applied (depending on the material, it may also contract in the opposite direction), so that the entire ceramic insulating thin film EL element changes in response to changes in the AC voltage. transform. Conventional ceramic insulating thin film EL elements have the drawback of causing vibration and noise due to this deformation.

An object of the present invention is to provide a ceramic insulating thin film EL element that solves the vibrations caused by electrostriction and the noise caused by the vibrations.

[Means for solving problems]

The present invention provides a ceramic insulating thin film EL element in which a light emitting layer and a transparent electrode are provided on a ceramic substrate having an internal electrode and a high dielectric constant ceramic insulating layer, the inside of the ceramic substrate and the side opposite to the ceramic insulating layer. Vibration damping electrodes corresponding to the internal electrodes and the transparent electrodes are formed on any one of the surfaces of the vibration damping layer via a damping layer.

[Effect]

The ceramic insulated thin film EL element of the present invention has a ceramic insulating layer which has been solved from the drawbacks of the prior art by arranging damping electrodes corresponding to the internal electrodes and the transparent electrodes respectively inside the ceramic substrate or on the ceramic surface opposite to the ceramic insulating layer. This reduces the noise generated by thin film EL elements. That is, by applying a voltage or current synchronized with the voltage or current applied to the EL element to emit light to the above-mentioned damping electrodes, the damping layer sandwiched between the damping electrodes and producing electrostriction causes light emission. The aim is to generate vibrations in the ceramic substrate that are opposite in phase to the electrostrictive vibrations that repel insects by applying a portion of the voltage to the ceramic insulating layer. This reduces the vibration of the entire ceramic insulating thin film EL element, thereby reducing noise.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of a ceramic insulating thin film EL element to which a driving source is added for explaining one embodiment of the present invention.

As shown in FIG. 1, such an EL element has internal electrodes 2. A ceramic insulating layer 31, a light-emitting layer 4, and a transparent electrode 5 are formed, while a first damping electrode 7°, a damping layer 8, and a second damping electrode 9 are formed on the lower surface of the ceramic base 1; The vibration damping electrode 9 is covered and protected by a protective insulating layer 10. In order to drive such an EL element to emit light, an AC power source 6 is connected to the internal electrode 2 and the transparent electrode 5, while the AC power source 6 is connected to a first vibration damper via a transformer 11 to prevent vibration of the EL element. The electrode 7 and the second vibration damping electrode 9 are transformer coupled.

The shape of the ceramic base 1 described above is a square with a thickness of approximately 1 dragon and a side length of 20 dragons, and the ceramic material thereof is a common mixture of alumina and borosilicate glass. The internal electrode 2 has a thickness of about 3 μm, and is made of an inexpensive silver-palladium alloy. The high dielectric constant ceramic insulating layer 3 only needs to have a thickness of about 5 to 1000 μm, but in this example it is 35 μm, and its material is a material that can obtain a high dielectric constant such as PZT, BaTiO3, or PbTiO3. In this example, a composite perovskite compound containing PB that can be fired at a low temperature is used.

The dielectric constant of this material is very large, over 15,000 at room temperature.The thin film light emitting layer 4 is made of ZnS containing about 1 mol% of Mn.
is deposited to a thickness of 0.4 μm.

Incidentally, the material for this light emitting layer 4 is not only ZnS (Zn
It is also possible to use sulfides and fluorides such as SeJIpCaS, SrS or other phosphor materials. In addition, the material that forms the luminescent center is not limited to Mn, but also TbFl, 5
Rare earth fluorides such as nF3 and PrF3, rare earth elements themselves, etc. can also be used. The transparent electrode 5 is formed on the light emitting layer 4, and is made of ITO by magnetron sputtering to form a square film having a thickness of 0.3 μm and 10+u sides.

A low voltage AC power source 6 for driving the EL element is connected to the transparent electrode 5 and a first vibration damping electrode 7, which will be described later. The first vibration damping electrode 7 has the same thickness and material as the internal electrode 2, and its planar shape is a 20-square square like the internal electrode 2 and the ceramic base 1. The damping layer 8 is made to match the thickness, material, and planar dimensions of the ceramic insulating layer 3 in order to effectively suppress the vibrations of the ceramic insulating layer 3. The second vibration damping electrode 9 has the same thickness and material as the internal electrode 2, and has a planar shape of a 10-square square like the transparent electrode 5. The protective insulating layer 10 is formed to cover the entire second damping electrode 9 electrically and mechanically from the outside, and is made of epoxy resin or the like.

In actual manufacturing, so-called green sheets are used for the ceramic base 1, the ceramic insulating layer 3, and the damping layer 8, and the unidirectional electrode 2, the first damping electrode 7, and the second damping electrode 9 are used. The pattern is screen printed on green sheets, and the required number of green sheets are stacked and pressed together.
It is bonded and fired to form a single piece. That is, a ceramic base 1, an internal electrode 2. Ceramic insulation layer 3. first rule i
t-pole7. Damping layer 8. ．． The second vibration damping electrode 9 is integrally sintered.

An AC power source 6 is connected to the transparent electrode 5 and the internal electrode 2 of the ceramic insulated thin film EL device thus prepared, and the first vibration damping electrode 7 and the second vibration damping electrode 9 are connected to each other via the transformer 11. A voltage from an AC power source 6 is applied to cause light emission.

At this time, when the microphone was placed at a distance of about 10C11 from the light emitting surface of the element and the sound pressure was measured, the damping electrodes 7 and 9
and 20 decibels (
dB) reduction in front and rear sound pressure can be achieved. This will lead to the realization of a ceramic insulated thin FyAEL element that is very audibly quiet.

This example describes an example in which a damping electrode and a damping layer are provided on a ceramic insulated thin film EL element having the most basic structure, but the thin film portion of the ceramic insulated thin film EL element is limited to the example described here. First, metal ions are transferred from the ceramic insulating layer 3 to the light emitting layer 4 between the ceramic insulating layer 3 and the light emitting layer 4.
Ceramic insulating thin film EL devices equipped with a thin insulating layer to prevent light from diffusing into the light, and ceramic insulating thin film EL devices in which a thin insulating layer is inserted between the light emitting layer 4 and the transparent electrode 5 to improve brightness rise characteristics. The present invention can also be applied to.

Regarding the planar shape of the damping electrodes in this example, the planar shape of the portion narrowed by the pair of damping electrodes should be similar to the planar shape of the portion narrowed by the transparent electrode and the internal electrode. They don't necessarily have to be similar,
Further, the vibration damping electrode does not necessarily have to continue without any interruption in a plane, and may have a partial cutout.

Furthermore, even if the material and thickness of the damping layer are different from those of the ceramic insulating layer, the same function can be achieved by appropriately adjusting the voltage or current applied to the damping layer.

Regarding the numerical values and materials of the examples described here,
This is merely an example, and does not limit the scope of the present invention.

〔Effect of the invention〕

As explained above, the ceramic insulating thin film EL element of the present invention has vibration damping electrodes corresponding to each electrode, so that
The vibration of the EL element can be significantly reduced, which has the effect of greatly reducing vibration noise. Therefore, the present invention has very high practical value, as it enables the use of EL elements in places where silence is required, such as indoors.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a ceramic insulating thin film EL element with a driving source added to explain an embodiment of the present invention, and FIG. 2 is a cross-sectional view of an EL element with a driving source added to explain a conventional example. 3 are cross-sectional views of a conventional ceramic insulating thin film EL element in an electrostrictive state.

Claims (1)

[Claims] In a ceramic insulating thin film EL element in which a light emitting layer and a transparent electrode are provided on a ceramic substrate having an internal electrode and a high dielectric constant ceramic insulating layer, either the inside of the ceramic substrate or the surface opposite to the ceramic insulating layer A ceramic insulating thin film EL device characterized in that vibration damping electrodes corresponding to the internal electrodes and the transparent electrodes are formed via a damping layer.