JPH07263141A - Electroluminescence display - Google Patents

Abstract

PURPOSE:To form an EL display out of an EL element multilayered structure so as to fully exhibit its function as a speed meter, etc. CONSTITUTION:A rearmost thin EL element 12 is so formed that, at least, an electrode on the light extracting side is composed of a transparent electrode. The forefront thin-film EL element 14, of which pair of both electrodes are composed of transparent electrodes, emits the same luminescent color and approximately the same luminance as the rearmost thin-film EL element 12. A breakage detection circuit 3 electrically detects breakage of respective thin- film EL elements 12, 14 and outputs a breakage detection signal to an element switching circuit 4. At first, the element switching circuit 4 electrically makes continuity between the rearmost thin-film EL element 12 and a drive circuit 2, and shuts off continuity between the forefront thin-film EL element 14 and the drive circuit 2. After that, when the circuit 4 receives a breakage detection signal from the breakage detection circuit 3, it electrically shuts off a section between the broken rearmost thin-film EL element 12 and the drive circuit 2 and electrically makes continuity between the forefront thin-film EL element 14 and the drive circuit 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescence display device, and more particularly, to a plurality of electroluminescence elements which emit light of the same emission color, and detects the destruction of the electroluminescence elements to automatically detect other electroluminescence elements. The present invention relates to an electroluminescence display device that is switched and driven.

[0002]

2. Description of the Related Art Conventionally, as an electroluminescence (hereinafter also simply referred to as EL) display, there is an EL element multi-layer structure type for the purpose of multicolor display (for example, JP-A-1-315987). ), EL
There are many types of devices with one layer structure.

[0003]

However, when the EL display of the EL element single layer structure type is used for a speedometer of an automobile which requires high reliability in display, the EL element for displaying a segment or a dot is one. If any of them is destroyed, it becomes impossible to display or the display quality is deteriorated, so that there is a problem that a sufficient function as a speedometer cannot be exhibited.

Therefore, in the electroluminescence display device according to the first aspect, the EL display has an EL element multi-layer structure, and even if one EL element is destroyed, another EL element is used instead of the EL element to display the speed. It is an object of the present invention to provide an EL display device that can exhibit a sufficient function as a meter or the like.

According to a second aspect of the electroluminescent display device, in the electroluminescent display device according to the first aspect, a plurality of EL elements are formed in the same shape to homogenize the display before and after the destruction. With the goal.

Further, the electroluminescence display device according to claim 3 is the electroluminescence display device according to claim 1 or 2, wherein the destruction detection is performed by electrically detecting a change in operation of the EL element to detect the breakdown. It is an object of the present invention to easily detect breakage of an EL element with a simple structure by configuring a circuit.

The electroluminescence display device according to a fourth aspect is the electroluminescence display device according to any one of the first, second and third aspects, wherein the emission brightness of each EL element is viewed from the light extraction side. By making them substantially the same, the purpose is to further homogenize the display before and after the destruction.

An electroluminescent display device according to a fifth aspect of the present invention is the electroluminescent display device according to any one of the first, second, third and fourth aspects, wherein the EL element having a multilayer structure is first formed. Is driven from the EL element at the end, and after that, each time it is destroyed
An object of the present invention is to improve the display quality by driving the element to eliminate the problem that the destruction pattern of the destroyed EL element is displayed by the light emission of the EL element in the rear.

An electroluminescence display device according to a sixth aspect of the present invention is the electroluminescence display device according to any one of the first, second, third, fourth and fifth aspects, wherein a breakdown detection circuit is provided. The purpose is to simplify the circuit configuration and accurately detect damage.

[0010]

For the above-mentioned purpose, the method according to claim 1
The electroluminescent display device according to, the rearmost electroluminescent element at least the electrode on the light extraction side is formed of a transparent electrode, and a pair of electrodes are both transparent electrodes, the same emission color as the last electroluminescent element. , At least one front electroluminescent element that emits light in a front-back direction, and an electroluminescent display that is configured by stacking a plurality of layers in the front-back direction; a drive circuit that drives the electroluminescent element; And a destruction detection circuit for detecting the destruction detection signal from the destruction detection circuit, electrically cut off between the destroyed electroluminescence element and the drive circuit,
An element switching circuit electrically connecting between one of the other electroluminescent elements and the drive circuit.

An electroluminescent display device according to a second aspect of the present invention is the electroluminescent display device according to the first aspect, wherein the plurality of electroluminescent elements are formed in the same shape.

An electroluminescence display device according to a third aspect of the present invention is the electroluminescence display device according to the first or second aspect, wherein the breakdown detection circuit is an electrostatic device that changes in accordance with the operation of the electroluminescence element. It is characterized in that the destruction of the electroluminescent element is detected based on the capacity or the current.

Further, an electroluminescence display device according to a fourth aspect is the electroluminescence display device according to any one of the first, second and third aspects, wherein the emission brightness of each of the plurality of electroluminescence elements is different. It is characterized in that they are configured to be substantially the same when viewed from the light extraction side.

The electroluminescence display device according to a fifth aspect is the electroluminescence display device according to any one of the first, second, third and fourth aspects, wherein the element switching circuit is first provided. When the destruction detection signal indicating that the rearmost electroluminescence element is destroyed is electrically connected from the destruction detection circuit by electrically connecting the rearmost electroluminescence element and the drive circuit, The electroluminescence element immediately before the electroluminescence element and the drive circuit are electrically connected to each other, and thereafter, each time the destruction detection signal is received, the electroluminescence element immediately before the destroyed electroluminescence element and the drive. Conduct electrical continuity with the circuit, and finally, the electro Characterized in that it is adapted for electrically connecting between the Minessensu element and the driving circuit.

An electroluminescence display device according to a sixth aspect is the electroluminescence display device according to any one of the first, second, third, fourth and fifth aspects, wherein the breakdown detection circuit is provided. Is a Sawyer-Tower in which a capacitor is inserted between an output terminal electrically connected to at least one of the upper electrode and the lower electrode of the electroluminescent element and the ground.
It is characterized in that it has a circuit and is configured to detect the destruction of the electroluminescence element by detecting a change in the charge of the capacitor by a comparator.

[0016]

According to the electroluminescence display device of the first aspect, the EL display has an EL element multi-layer structure, and even if one EL element is destroyed, another EL element is used for display instead. Therefore, it becomes possible to exert a sufficient function as a speedometer or the like.

Further, according to the electroluminescent display device of the second aspect, in the electroluminescent display device of the first aspect, since the plurality of EL elements are formed in the same shape, the display of each EL element becomes uniform, The display before and after destruction can be homogenized.

Further, according to the electroluminescence display device of the third aspect, in the electroluminescence display device of the first or second aspect, the operation change of the EL element is electrically detected and the destruction is detected. Since the detection circuit is configured, destruction of the EL element can be easily detected with a simple configuration.

According to the electroluminescence display device of the fourth aspect, in the electroluminescence display device of any one of the first, second and third aspects, the emission brightness of each EL element is changed from the light extraction side. Since they are made to be substantially the same as seen, the uniformity of light emission luminance is added to the uniformity of the display due to the same shape of the EL element,
It is possible to further homogenize the display before and after the destruction.

According to the electroluminescence display device of the fifth aspect, in the electroluminescence display device of any one of the first, second, third and fourth aspects, the EL element having a multilayer structure is formed. First, the EL element at the end is driven, and thereafter, the EL elements at the front are sequentially driven at each destruction, thereby eliminating the problem that the destruction pattern of the destroyed EL element is visually recognized by the light emission of the EL element at the rear. However, display quality can be improved.

Further, according to the electroluminescence display device of the sixth aspect, the circuit configuration of the breakdown detection circuit is simple, and the breakdown detection can be accurately performed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of an electroluminescent display device according to an embodiment.

The electroluminescent display device of this embodiment comprises an EL display 1 having a multi-layer structure (two-layer structure in the case shown), a known drive circuit 2, a breakdown detection circuit 3 and an element switching circuit 4. .

The EL display 1 includes an insulating substrate (eg glass substrate) 11, a rearmost thin film EL element 12 formed on the upper surface (front surface) of the insulating substrate 11, and a transparent insulating substrate 13 (eg glass). Substrate) and the transparent insulating substrate 13
Formed on the upper surface (rear surface) of the front surface of the insulating substrate 11 and a rear thin film EL element 12 and a front thin film EL element 14 facing the rearmost thin film EL element 12 (in the illustrated case, the front thin film EL element). Frame 15 made of resin, which is disposed in close contact with the outer peripheral portion of the rear surface of the transparent insulating substrate 13, and spacers (eg, glass beads) 16 premixed in the sealing frame 15. And a transparent insulating oil (for example, silicon oil) 17 enclosed by the sealing frame 15 in a room formed by the sealing frame 15.

In the rearmost thin film EL element 12, at least the electrode on the light extraction side is made of a transparent electrode. On the other hand, in the forefront thin film EL element 14, both the pair of electrodes are transparent electrodes. The rearmost thin film EL element 12 and the front thin film EL element 14 are selectively driven by the element switching circuit 4 as will be described later, and do not emit light at the same time. And
The rear thin film EL element 12 and the front thin film EL element 14 are
It is formed by using the same light emitting layer material, and is configured to have the same emission color. In addition, the last thin film EL element 12
The front thin film EL element 14 is formed in the same shape. Further, in the thin film EL elements 12 and 14, for example, the film thickness of each light emitting layer is adjusted so that the light emission brightness when viewed from the light extraction side is substantially the same, or the film thickness of each light emitting layer is the same. In the case, each thin film EL element 12 by the drive circuit 2,
It is configured to adjust the applied voltage to 14.

The breakdown detection circuit 3 is connected to, for example, an output terminal electrically connected to the upper electrode of each of the thin film EL elements 12 and 14 in the drive circuit 2 or an output terminal electrically connected to the lower electrode and the ground. A Sawyer-Tower circuit having a sense capacitor inserted between the two has a comparator (comparator) to detect a sudden change in charge of the sense capacitor.
The thin film EL elements 12 and 14 are detected by
Configured to detect the destruction of the.

That is, the breakdown detection circuit 3 is constructed as shown in FIG. In FIG. 2, 41 is a capacitor as a sense capacitor, 42 is an amplifier, 43 is a comparator, 44 is an EL power supply, and 45 is a signal output unit to the element switching circuit.

As another example of the destruction detection circuit 3,
A capacitor for detecting a terminal voltage between an output terminal electrically connected to the upper electrode of each EL element 12 and 14 and an output terminal electrically connected to the lower electrode is provided. Each EL element 12, 1 by detecting the change of electric charge
The destruction of No. 4 may be detected. Further, as another example of the destruction detection circuit 3, each thin film EL element 12, 1
The destruction may be detected by detecting a change in the current flowing through the switch 4. It should be noted that as the destruction detection circuit 3, FIG.
The one has a simple circuit configuration and is accurate in detecting damage.

The element switching circuit 4 includes a drive circuit 2 and each thin film E.
It electrically connects or disconnects from the L elements 12 and 14, and is composed of an analog switch or the like that performs a switch operation in response to a destruction detection signal from the destruction detection circuit 3. That is, the element switching circuit 4 is, as shown in FIG.
It is composed of a transistor 46 and a relay 47.
Specifically, the element switching circuit 4 firstly arranges the last thin film E.
When the destruction detection circuit 3 receives a destruction detection signal indicating that the rearmost thin film EL element 12 has been destroyed by electrically connecting the L element 12 and the drive circuit 2, the frontmost thin film EL element 14 and the drive circuit 2 are received. Electrically connects between and. The thin film E
In the case of an EL display having three or more L elements, the element switching circuit 4 first includes the last thin film EL element 12 and the drive circuit 2.
When a destruction detection signal indicating that the rearmost thin film EL element 12 is destroyed is received from the destruction detection circuit 3, the front thin film EL element immediately before the rearmost thin film EL element 12 is next received. The element and the drive circuit 2 are electrically conducted, and thereafter, each time the destruction detection signal is received, the thin film EL element immediately before the destroyed thin film EL element and the drive circuit 2 are electrically conducted. Finally, the foremost thin film EL element 14 and the drive circuit 2 are electrically connected.

Next, the operation of the EL display device having the above structure will be described.

First, the element switching circuit 4 electrically connects the drive circuit 2 and the rearmost thin film EL element 12 to each other, while electrically connecting the drive circuit 2 and the frontmost thin film EL element 14 to each other. It is shut off. Therefore, the EL display 1 performs a predetermined display by driving the rearmost thin film EL element 12 by the drive circuit 2. At this time, the frontmost thin film EL
The element 14 transmits the display by the rearmost thin film EL element 12.

When the rearmost thin film EL element 12 is driven and the rearmost thin film EL element 12 is destroyed, the destruction detection circuit 3 detects this destruction and outputs a destruction detection signal to the element switching circuit 4. To do. The element switching circuit 4 receiving this destruction detection signal electrically cuts off between the drive circuit 2 and the rearmost thin film EL element 12, and electrically disconnects between the drive circuit 2 and the frontmost thin film EL element 14. Make it conductive. Therefore, the EL display 1 will now perform a predetermined display by driving the forefront thin film EL element 14 by the drive circuit 2. At this time, the forefront thin film EL element 14 displays with the same emission color as the rearmost thin film EL element 12 and with substantially the same emission brightness. Further, the destruction pattern caused by the destruction of the rearmost thin film EL element 12 is
Is located behind the forefront thin film EL element 14 and is therefore not visible.

As described above, the EL according to the present embodiment
According to the display device, the EL display 1 has a thin-film EL element multilayer structure, and even if one thin-film EL element 12 is destroyed, another thin-film EL element 14 is used instead of the thin-film EL element 14 for display, which is sufficient as a speedometer or the like. It will be able to exert various functions.

Further, according to the EL display device of the present embodiment, since the plurality of thin film EL elements 12 and 14 are formed in the same shape, the display of each thin film EL element 12 and 14 becomes uniform, and the display before and after the destruction is displayed. It becomes possible to achieve homogenization.

Further, according to the EL display device of the present embodiment, since the destruction detection circuit 3 is configured to detect the destruction by electrically detecting the change in operation of the thin film EL element 12, the destruction of the thin film EL element 12 is easy. With such a configuration, it becomes possible to detect easily.

Further, according to the EL display device of the present embodiment, the emission luminances of the thin film EL elements 12 and 14 are made to be substantially the same when viewed from the light extraction side. , 14 has the same shape, and the uniformity of the light emission luminance is added to the homogenization of the display, so that the display before and after the destruction can be further homogenized.

Further, according to the EL display device of the present embodiment, since the last thin film EL element 12 is driven first,
The destruction pattern caused by the destruction of the rearmost thin film EL element 12 is not visually recognized by the light emission of the frontmost thin film EL element 14, and the display quality can be improved.

Further, in the EL display device according to the present embodiment, when a plurality of EL elements for displaying segments or dots are formed on the same insulating substrate, a drive circuit and a breakdown detection circuit are provided for each EL element. Alternatively, an element switching circuit may be installed. In that case, only the EL element immediately before the broken segment or dot may be electrically connected to the drive circuit.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an EL display device according to an embodiment.

FIG. 2 is an electrical connection diagram showing an example of a destruction detection circuit.

FIG. 3 is an electrical connection diagram showing an example of an element switching circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 EL display 12 Last thin film EL element (last EL element) 14 Foremost thin film EL element (front EL element) 2 Drive circuit 3 Breakage detection circuit 4 Element switching circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobue Ito 1-1, Showamachi, Kariya city, Aichi Nihon Denso Co., Ltd.

Claims (6)

[Claims] 1. A rearmost electroluminescent element in which at least an electrode on the light extraction side is a transparent electrode,
An electro device in which a pair of electrodes are both transparent electrodes, and a plurality of layers of at least one front electroluminescent device that emits the same emission color as the rearmost electroluminescent device are stacked in the front-rear direction. A luminescence display, a drive circuit for driving the electroluminescence element, a destruction detection circuit for detecting destruction of the electroluminescence element, and a destruction detection signal from the destruction detection circuit, and the destroyed electroluminescence element. An element switching circuit that electrically cuts off from the drive circuit and electrically connects between one of the other electroluminescence elements and the drive circuit, and an electroluminescence display characterized by the following: apparatus. 2. The electroluminescent display device according to claim 1, wherein the plurality of electroluminescent elements are formed in the same shape. 3. The breakdown detection circuit is configured to detect breakdown of the electroluminescent element based on a capacitance or a current that changes according to the operation of the electroluminescent element. Alternatively, the electroluminescence display device according to claim 2. 4. The light emitting luminance of each of the plurality of electroluminescent elements is configured to be substantially the same when viewed from the light extraction side. The electroluminescence display device according to any one of claims. 5. The element switching circuit first electrically connects the rearmost electroluminescence element and the drive circuit, and the destruction detection circuit indicates that the last electroluminescence element is destroyed. When receiving the destruction detection signal, then, electrically connecting between the drive circuit and the electroluminescent element immediately before the last electroluminescent element,
Thereafter, each time the destruction detection signal is received, the electroluminescence element immediately before the destroyed electroluminescence element and the drive circuit are electrically conducted, and finally, the electroluminescence element and the electroluminescence element at the forefront. The electroluminescence display device according to claim 1, wherein the electroluminescence display device is configured to be electrically connected to a drive circuit. 6. The Sawyer-Tow in which the destruction detection circuit has a capacitor inserted between an output terminal electrically connected to at least one of an upper electrode and a lower electrode of the electroluminescence element and a ground.
3. An er circuit is provided, which is configured to detect destruction of the electroluminescent element by detecting a change in the charge of the capacitor by a comparator. 6. The electroluminescent display device according to claim 4 or claim 5.