JPH04144094A - Electroluminescent element for back light - Google Patents

Abstract

PURPOSE:To enhance the brightness and prolong the lifetime by forming an EL light emitting layer in multi-layer structure, and performing the drive for each light emitting layer. CONSTITUTION:Electrode leads 8A, 8B are connected with the two sides of a common electrode 7 obtained by forming clear electrodes 7b, 7c on both sides of a clear film 7a, and EL light emitting layers 1A. 1B are provided. Electrodes 2A, 2B are furnished on the outsides of these light emitting layers 1A, 1B, and there electrode leads 4A, 4B are connected, and an upper and a lower base board 6A, 6B are provided through water refilling layers 5A, 5B. The light emitting layers 1A, 1B light up simultaneously when a voltage is impressed between the leads 4A and 8A and between 8B and 4B. Thereby the brightness can be heightened, and the time for degradation till a certain level of absolute brightness be elongated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an EL for a backlight, and particularly to an EL suitable for a bank light of a liquid crystal display device.

[Conventional technology]

A conventional EL has a structure as shown in FIG.

A PET film (polyester film) 2a is placed on the top surface of the EL light emitting layer 1 to which ZnSKMn, Cu, etc. are added.
K I T O (indium tin oxide)zb
Two transparent upper plate electrodes are provided by vapor deposition, and a lower plate electrode 2B made of an aluminum reflective plate is provided on the lower surface of the EL light emitting layer l with an insulating layer 3 made of baricum titanate interposed therebetween. Electrode leads 4A and 4B plated with phosphor bronze KAu are connected to the upper and lower plate electrodes 2A and 2B, respectively, and an upper substrate 6A made of ethylene trifluoride chloride resin is connected via water replenishment layers 5A and 5B made of nylon film. , a lower substrate 6B is provided.

Incidentally, examples related to this type of EL include, for example, Japanese Unexamined Utility Model Publication No. 1-135483.

[Problem to be solved by the invention]

In conventional EL, for example, the driving condition is 100V/400Hz.
When the initial brightness is 50cd/4', the half-life (50% brightness)
1800 hours at normal temperature and humidity, approximately 250 hours at 50℃ and 90%
It's time. When the initial brightness is increased, the half-life (lifetime) decreases inversely.

An object of the present invention is to provide an EL for a backlight that has high brightness and a long service life.

[Means to solve the problem]

In order to achieve the above object, the EL light emitting layer is formed in multiple layers and each EL light emitting layer is driven individually.

[Effect]

By forming the EL light emitting layer into multiple layers and driving each EL light emitting layer, the brightness increases and the deterioration time to a predetermined absolute brightness is extended. In other words, high brightness and long life EL can be obtained.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to FIG. Note that the same members as in FIG. 3 will be described with the same numbers. P
Electrode leads 8A and 8B are connected to both sides of the common electrode 70, which has ITO films 7b and 7c formed on the inner surface of the ET film 7a, and an upper EL light emitting layer IA and a lower EL light emitting layer IB.
is provided. On the outside of the upper and lower EL light-emitting layers IA and 1B, an upper plate electrode 2A is provided on the upper surface of the upper EL light-emitting layer IA, and a lower plate electrode 2A is provided on the lower surface of the lower EL light-emitting layer IB with an insulating layer 3 in between, as in the conventional case. A plate electrode 2B is provided.

Further, the upper and lower plate electrodes 2A and 2B are provided with electrode leads 4A.

4B are connected, and an upper substrate 6A and a lower substrate 6B are provided via water replenishment layers 5A and 5B.

Therefore, a voltage (for example, 100
By applying V/400Hz), the upper EL light emitting layer IA lights up. Similarly, electrode leads 8B and 4B
By applying a voltage (for example, 100 V/400 Hz) between them, the lower EL light emitting layer IB lights up. That is, both E
When the L light-emitting layers IA and IB are turned on at the same time, the brightness increases and the deterioration time (life) until a predetermined absolute brightness is reached is extended.

In addition, by changing the color tone of the upper and lower EL light-emitting layers IA and IB and adjusting the brightness of the upper and lower EL light-emitting layers IA and IB, the EL
You can control the overall color tone.

FIG. 2 shows a liquid crystal display device in which the multilayer EL 10 configured as described above is arranged on the back side of the liquid crystal display element 11. The structure of the liquid crystal display element 11 is that the opposing surfaces of an upper electrode substrate 12 and a lower electrode substrate 13 are subjected to alignment treatment, a liquid crystal material is sealed inside, and an upper polarizing plate 14 and a lower polarizing plate 1 are formed.
It has a well-known structure that is sandwiched at 5.

Therefore, a multilayer EL device placed on the back side of the liquid crystal display element 11
By turning on I(1), the liquid crystal display element 11 is illuminated, and a liquid crystal display device with high contrast and good visibility can be obtained.

〔Effect of the invention〕

According to the present invention, since the EL light emitting layer is multilayered and each EL light emitting layer is driven individually, the brightness can be increased and the deterioration time until a predetermined absolute brightness is reached is extended. Furthermore, by changing the color tone of each EL light emitting layer and controlling the brightness of each layer, any desired color tone and brightness can be obtained as a whole.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing one embodiment of the present invention, and Fig. 2 is a cross-sectional view showing one embodiment of the present invention.
A side view of a liquid crystal display device using multilayer EL gold shown in the figure.
FIG. 3 is a sectional view of a conventional example. IA...Top EL light emitting layer, IB...Bottom EL light emitting layer, 2 A゛=upper plate electrode, 2B °°°lower plate electrode, 〆], Agent: Patent attorney Masaru Ogawa Diagram 6B

Claims (1)

[Claims] 1. An EL for backlight comprising at least an EL light-emitting layer and a pair of electrodes for driving the FL light-emitting layer, characterized in that the EL light-emitting layer is multilayered and each EL light-emitting layer is driven individually. EL for back light
.