JPS5981693A - Field light emitting display - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electroluminescent display device in which a luminescent electroluminescent display element is used as an ambient light sensing element.

In general, electroluminescent display elements are used as nighttime illumination members or light-emitting display members for light-receiving elements such as instrument dials and LCDs. In order to do this automatically, conventionally it was necessary to provide an additional ambient light sensing element.

In consideration of the above-mentioned black hair, the present invention uses an electroluminescent display element as a light emitting element and also as an ambient light detection element, and detects the state of the ambient light with the electroluminescent display element itself.
An object of the present invention is to provide an electroluminescent display device in which a voltage applied to an electroluminescent display element is variably controlled to turn on and off the light.

Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 1 shows a cross-sectional view of an electroluminescent display element of the present invention, in which a transparent electrode 2 is formed on a transparent insulating substrate 1 made of glass or plastic.

On this transparent electrode 2, a ZnS:Mn phosphor is formed as a light-emitting layer 3, and on this light-emitting layer 3, aluminum [
AQ] is formed as a reflective conductive film 4.

Electroluminescent display element 5 configured as described above, hair current detection section 6
is connected in series to an AC power supply l, and when the current detection unit 6 detects the current flowing through the electroluminescent display element 5, the electroluminescent display element 5 emits light, compared to a case such as at night when there is no ambient light (
(See Figure 2 (A)), in the case of pregnancy, etc. where ambient light is input to the electroluminescent display element 5 (See Figure 2 (B)), the circuit as shown in Figure 3 (C) and B. The peak value of the current flowing through the sensor changes greatly from 11 to 12, but this change is approximately proportional to the intensity of ambient light. This phenomenon occurs in the light emitting layer.
It is thought that electrons in the impurity level formed in the forbidden cloth are excited by the incident light, rise to the conduction band, become conduction electrons, and increase the current.

Further, this current is not affected by the light emission of the electroluminescent display element 75, and this increase/decrease change does not affect the light emission of the electroluminescent display element 5.

FIG. 4 shows a block diagram of an electroluminescent display device according to an embodiment of the present invention, in which 5 is an electroluminescent display element, 8 is a current detection section, 9 is a power supply section, 10 is a voltage control section, 11 is a switch, the current detection section 8 detects the current of the circuit, and determines the relationship between the three detection levels IA, In, and IC, and the voltage control section 10.

For example, it is composed of a microcomputer and outputs a switching signal to output two voltage levels V1 and 2 to the power supply section 9 according to the relationship between the seven circuit current i and each detection level IA, Ill, and IC. Further, iI is the current when the voltage v1 is applied, 12 is the current when the voltage V2 is applied, VLh is the light emission starting voltage, ■ 1] is the current when the light emission starting voltage ■th is applied, and V 2 < V th < V 1(7) relationship.

Next, the operation of this embodiment will be explained using FIG. 5, which shows the relationship between the current +3 of the electroluminescent display element 5, which increases and decreases depending on the ambient brightness L, and FIG. 6, which shows the switching range of the voltage. explain. First, when the switch 11 is turned on, the power supply section 9
outputs voltage v1, and the brightness around the electroluminescent display element 5 is 1. At this time, a current of i 1++3 flows through the circuit (see curve C in FIG. 6), and at this time, the electroluminescent display element 5 emits light. Next, when the ambient light increases and becomes brighter, the current i3 increases, and the current 13up for a certain brightness Lup
, and the circuit current becomes i1+1Bup (see curve C in Figure 6). At that time, the voltage control section 10 instructs the power supply section 9 to change the voltage to v2, and the electroluminescent display element 5 turns off. Thereby, the circuit current is i2+13up(
(see curve C in Figure 6). When the ambient light decreases and becomes dark, the current i3 decreases to a current +31oυ corresponding to a certain brightness Ll, oν, and the circuit current becomes i 2 + i
3], ow (see curve C in Figure 6). At that time,
The voltage control unit 1o instructs the current to change to Vl,
The electroluminescent display element 5 emits light. Therefore, times? 8 current becomes il to i3 ], ow (see curve C in Figure 6).

The same operation is then repeated.

Note that the current curve Δ-,5 in FIG. 6 is as shown in the table below.

[Table 1 Δ: i2+13m1n B: i2+i31ow=Ic (light emission switching level) C: j2+13up D: i2+i3maxE: i
l+i3mjn=IB ('9J light lower limit level) F e
il+i3]ow G: il+i3 H: i 1+13up =IA (light-off switching level) J: t 1 +i3max Furthermore, the voltage switching range is as shown in Table 2 below.

[Table 2] Range [11i≧■^ (Curve 1 (, J) ■+→■2 range [
■K II3≦i<JA (curve E, C, G) V+ range [1111IC<i<l13 (curve C, D) V2 range [IV] IC≧i (curve A, l3) V2
-)V.

As explained above, according to the present invention, an electroluminescent display element can be automatically turned on and off depending on the surrounding brightness, and in this case, an ambient light detection sensor is required. First, by arbitrarily setting the detection level, there is an advantage that the light emission/extinguish point can be arbitrarily set with respect to the amount of light.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an electroluminescent display element of the present invention and a circuit diagram for detecting a current flowing through the electroluminescent display element, and FIG. 2 is an explanatory diagram illustrating the characteristics of the electroluminescent display element of FIG. 1.
FIG. 3 is a diagram showing a current waveform flowing through the electroluminescent display element of FIG. 1, FIG. 4 is a circuit diagram of an electroluminescent display device according to an embodiment of the present invention, and FIG. FIG. 6, which is a diagram showing the relationship between the current flowing through the element and the surrounding brightness, is a diagram showing the voltage switching range 4 of the power supply section in FIG. 4. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Transparent electrode, 3... Light emitting layer, 4... Reflective conductive film, 5... Electroluminescent display element, 6... Current detection part, 7 ... AC power supply, 8... Current detection section, 9... Power supply section, [0... Voltage control section, 1
1...Switch. Patent Applicant Nippon Seiki Co., Ltd. Procedural Correction Band (Method) March 22, 1980 Director General of the Patent Office Mr. Kazuo Wakasugi■, Incident Indication 1981 Patent Application No. 191235 2, Name of Invention Electroluminescent Display Device 3. Relationship with the case of the person making the amendment Patent Applicant Address: 2-2-34 Higashizao, Nagaoka City, Niigata Prefecture Name: Nippon Seiki Co., Ltd. Representative: Atsuo Nagai 4, Agent Address: City, Chiba Prefecture Kokubu 4-chome 13-10 (Delivery date: February 22, 1982) 6. Column 8 for a brief explanation of the drawings in the specification subject to the amendment. Contents of the amendment, page 7, line 2, “Figure 6 is , to an electroluminescent display element" is corrected to "FIG. 5 is an electroluminescent display element."that's all

Claims (1)

[Claims] An electroluminescent display element that emits light in response to the application of voltage, and the current flowing through it changes depending on the state of ambient light, and two types of voltages, one higher and one lower than the light emission starting voltage of the electroluminescent display element. 5. a power supply section that selectively outputs the voltage to the electroluminescent display element, a current detection section that detects a current flowing through a connection circuit between the electroluminescence display element and the power supply section, and a state of the current detected by the current detection section. and a voltage control section that outputs a signal for selecting an output voltage of the power supply section according to the voltage control section.