JP2000331781A - Organic electroluminescence display device - Google Patents

Abstract

(57) [Problem] To provide a compact organic electroluminescence display device capable of displaying a plurality of types by reducing the number of drive circuits and reducing the capacity. SOLUTION: An organic electroluminescence element 2 includes a pair of transparent electrodes 5 and a back electrode 7 which are arranged at least one of which is transparent and are opposed to each other, and has a multilayer structure of an organic multilayer structure including a light emitting layer between the electrodes 5 and 7. A film unit 6 is provided. The multilayer film forming section 6 has two types, a forward voltage light emitting film forming section 6a that emits light when a forward voltage is applied and a reverse voltage light emitting film forming section 6b that emits light when a reverse voltage is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent display device used for a light source or a display.

[0002]

2. Description of the Related Art In a conventional organic electroluminescent display device, as a method for realizing two-color light emission, a method in which organic electroluminescent elements having different emission colors are arranged adjacent to each other in parallel or a stacked structure has been proposed. I have.

Further, in order to emit light of three primary colors by a dot matrix method, it is possible to form a film by alternately forming respective element structures and to combine the lights to form a full color, thereby realizing multicolor.

The means for changing the display mode is realized by changing the light emitting dots in accordance with the display contents by the dot matrix method.

[0005]

However, according to the above-mentioned structure in which the organic electroluminescent elements having different emission colors are arranged adjacent to each other in parallel or in a laminated structure, the former case requires two drive power supplies. In the latter case, there is a problem that a driving power supply of two circuits and a further advanced film forming technique are required.

On the other hand, a full-color display device is used for applications that do not require full-color, such as two-color display when an organic electroluminescence element is used as a backlight or multi-color display where one part is displayed in two colors. This is an issue in terms of cost, and multi-color display using the current segment method cannot display two colors on the same element. Therefore, a segment for each emission color is required, and a drive circuit is also required separately. ,Moreover,
There is also a problem that the display cannot be made at the same place.

Further, in a segment type display device, in order to change the light emission mode, segments are divided so that predetermined display contents can be displayed, and the display contents are changed by a combination thereof. Are divided in accordance with the display contents, so that the electrode wiring becomes complicated and the number of lead-out terminals increases, and further, a large-capacity drive circuit and an increase in panel size have been problems.

In view of the above problems, an object of the present invention is to provide a compact organic electroluminescent display device capable of displaying a plurality of types by reducing the number of drive circuits and reducing the capacity.

[0009]

The technical means for solving the above-mentioned problems includes a pair of electrodes disposed at least one of which is transparent and disposed opposite to each other, and a light emitting layer disposed between the electrodes. In an organic electroluminescence display device having a multilayer film-forming portion having an organic multilayer structure, the multilayer film-forming portion emits light by applying a forward voltage, and emits light by applying a reverse voltage. And a reverse voltage light emitting film forming section.

The forward voltage light emitting film forming section and the reverse voltage light emitting film forming section may have different emission colors.

Further, the forward voltage light emitting film forming section and the reverse voltage light emitting film forming section may have different display forms.

[0012] Further, a structure comprising a constant current power supply unit for applying a voltage between the two electrodes and flowing a current, and a power supply switching control unit for controlling a voltage application direction to be switched between a forward direction and a reverse direction. Is also good.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional view of an organic electroluminescent element 2 in an organic electroluminescent display device 1, and a glass plate and a resin plate. Etc., and an IT deposited on the transparent substrate 4
A transparent electrode 5 made of an anode material such as O, Au, ZnO,
A multi-layered film forming section 6 having an organic multi-layer structure formed on the transparent electrode 5; and Al, MgAg, AlLi, etc., formed by covering the multi-layered film forming section 6 so as to be sandwiched between the transparent electrodes 5. And a back electrode 7 made of a cathode material.

A forward voltage applying unit 9 for applying a forward voltage between the transparent electrode 5 and the back electrode 7;
A reverse voltage application unit 10 for applying a reverse voltage;

The multilayer film forming section 6 includes two types of a forward voltage light emitting film forming section 6a that emits light when a forward voltage is applied and a reverse voltage light emitting film forming section 6b that emits light when a reverse voltage is applied. Each forward voltage light emitting film forming section 6a and each reverse voltage light emitting film forming section 6b
Are separated from each other by an insulating film 6c, so that mutual interference is prevented.

Each of the forward voltage light emitting film forming sections 6a includes a hole injection layer 16a, a hole transport layer 16b, an electron transport layer 16c as a light emitting layer, a back electrode 7 and an electron injection layer 16d for alleviating an energy barrier at an interface between the electron transport layer 16 and the electron transport layer 16c.

The material of each layer is, for example, ITO as the transparent electrode 5, CuPc as the hole injection layer 16a,
NPD as hole transport layer 16b, Alq as electron transport layer 16c, LiF as electron injection layer 16d, back electrode 7
May be used as Al. In addition, the hole injection layer 16a and the electron injection layer 16d are not particularly required, and the materials of the respective layers are not limited to the above-described types, and the general transparent electrode 5, the hole injection layer 16a, and the hole transport layer Materials suitable for the electron transport layer 16b, the electron transport layer 16c, the electron injection layer 16d, and the back electrode 7 may be used.

Each of the reverse voltage light emitting film forming sections 6b has an electron injection layer 26a, an electron transport layer 26b, and a light emitting layer on the transparent electrode 5 in the opposite order of the film forming order of the forward voltage light emitting film forming section 6a. The layers are formed in the order of the hole transport layer 26c and the hole injection layer 26d. However, since the transparent electrode 5 made of an anode material is not suitable as an electron injection electrode from the viewpoint of an energy barrier, the transparent electrode 5 Al, AlLi between electron injection layers 26a
A cathode material layer 26e made of a cathode material such as an alloy is formed so thin that the transmittance does not significantly decrease.

Further, the back electrode 7 made of the cathode material is also not suitable as a hole injection electrode from the surface of the energy impingement wall.
Between d, an anode material layer 26f made of an anode material such as ITO is formed.

The material of each layer is, for example, ITO as the transparent electrode 5, Al as the cathode material layer 26e, LiF as the electron injection layer 26a, and A as the electron transport layer 26b.
lq, NPD as the hole transport layer 26c, the hole injection layer 26
CuPc may be used for d, ITO may be used for the anode material layer 26f, and Al may be used for the back electrode 7. In this case, the materials of the respective layers are not limited to the above-mentioned types, and are generally used for the electron injection layer 26a, the electron transport layer 26b, the hole transport layer 26c, the hole injection layer 26d, the cathode material layer 26e, and the anode. A material suitable for each of the material layers 26f may be used.

FIG. 2 shows a driving means of the organic electroluminescence element 2, and includes a single constant current power supply section 12 for applying a voltage between both electrodes 5 and 7 to flow a current, a transistor, an FET, A power supply switching control unit 13 that controls switching of the switch circuits S1 and S2 configured by relays and the like is provided.

Then, the power supply switching control unit 13
A forward voltage application state in which the switch circuit S2 side is connected to the constant current power supply unit 12 to apply a forward voltage, and a reverse voltage in which the switch circuit S1 side is connected to the constant current power supply unit 12 and a reverse voltage is applied. It is configured to be switchable between the application state and the application state.

The present embodiment is configured as described above. In a forward voltage application state in which a forward voltage is applied between the transparent electrode 5 and the back electrode 7, Each forward voltage light emitting film forming section 6a emits light, and each reverse voltage light emitting film forming section 6b does not emit light. In a reverse voltage application state in which a reverse voltage is applied between both electrodes 5 and 7, each reverse voltage light emitting film forming unit 6b emits light and each forward voltage light emitting film forming unit 6a does not emit light. .

Therefore, as shown in FIG. 3, the forward voltage light emitting area 6A of the forward voltage light emitting film forming section 6a and the reverse voltage light emitting area 6B of the reverse voltage light emitting film forming section 6b are arranged at equal intervals and at a narrow pitch. If they are arranged alternately and emit light of different colors, only the forward voltage light emitting areas 6A emit light when a forward voltage is applied, and only the reverse voltage light emitting areas 6B emit light when a reverse voltage is applied. A luminescent color stripe pattern can be displayed.

At this time, by setting the mutual light emission brightness of the forward voltage light emitting area 6A and the reverse voltage light emitting area 6B high enough that the non-light emitting areas 6A and 6B that do not emit light cannot be recognized, square different light emitting colors can be obtained. Can be displayed. In addition, the control of the switching timing by the power supply switching control unit 13 causes the human to be indistinguishable.
For example, if the voltage application direction is switched between forward and reverse at a cycle of about 60 Hz or higher,
Emission color of forward voltage light emitting film forming section 6a and reverse voltage light emitting film forming section 6b
It is possible to display by the mixed color of the light emission color and the light emission color of the forward voltage emission film forming unit 6a by variably adjusting the voltage application time ratio in the forward direction and the reverse direction. It is also possible to arbitrarily approximate the color or the light emission color of the reverse voltage light emitting film forming section 6b, and there is an advantage that the display color mode can be increased.

As shown in FIG. 4, the forward voltage light emitting area 6A of the forward voltage light emitting film forming section 6a and the reverse voltage light emitting film forming section 6a
The reverse voltage light-emitting areas 6B of FIG. b are arranged alternately at equal intervals and at a narrow pitch, and each forward voltage light-emitting film forming section 6a is formed such that its length is gradually shortened downward so as to form a downward triangle,
If each reverse voltage light emitting film forming section 6b is formed to have a gradually increasing length in a downward direction so as to form an upward triangle, only a forward voltage light emitting area 6A emits light by application of a forward voltage, and a downward triangle is formed. Only the reverse voltage light emitting area 6B emits light by application of the reverse voltage, so that an upward triangle can be displayed and a different display mode can be displayed. In this case, the emission colors of the forward voltage light emitting film forming section 6a and the reverse voltage light emitting film forming section 6b may be the same, or different light emitting colors may be adopted.

Further, as shown in FIG. 5, the outer periphery of the square is defined as a forward voltage light emitting area 6A of the forward voltage light emitting film forming section 6a, and the inside thereof is defined as a reverse voltage light emitting area 6B of the reverse voltage light emitting film forming section 6b. For example, by applying the forward direction voltage, the display becomes a hollow positive direction display, and by applying the reverse direction voltage, the display becomes a solid square display.

Further, as shown in FIG. 6, for example, the display characters 6C (ODO) are formed on the transparent electrode 5 by the forward voltage light emitting film forming section 6a, and the reverse voltage light emitting film forming section 6b is formed. Therefore, there is an advantage that two types of character display can be performed by switching the application direction of the voltage.

As described above, according to the present embodiment, between the pair of electrodes 5 and 7, the forward voltage light emitting film forming section 6a that emits light when a forward voltage is applied, and emits light when a reverse voltage is applied. A reverse voltage light emitting film forming section 6b and two kinds thereof are formed and disposed,
By switching the voltage application direction between the forward direction and the reverse direction, a single organic electroluminescence element 2 enables two colors or two types of display modes, and a plurality of driving modes corresponding to a plurality of elements as in the related art. Compared to the case of displaying with a power supply, the number of drive circuits can be reduced and the capacity can be reduced.
It is possible to provide a compact organic electroluminescent display device 1 capable of displaying a plurality of types.

Further, the forward voltage light emitting film forming section 6a and the reverse voltage light emitting film forming section 6b need only be changed in film forming order, and can be constituted by ordinary materials and ordinary film forming methods. No film technology is required, and a decrease in luminous efficiency can be effectively prevented, and each display mode can be set arbitrarily.

For example, a display segment or the like that does not require simultaneous light emission, for example, in the case of static driving by the segment method, can be shared as one segment. If the number of driving circuits is suppressed and the direction of voltage application is switched, two types of display segments can be used. Can be displayed, the capacity of the drive circuit can be reduced, and various types of display can be realized with a small area.

In the above embodiment, the structure is shown in which the insulating film 6c is arranged between the forward voltage light emitting film forming section 6a and the reverse voltage light emitting film forming section 6b. May have a structure without the insulating film 6c.

[0033]

As described above, according to the organic electroluminescence display device of the present invention, the multilayer film-forming portion of the organic multilayer structure including the light-emitting layer disposed between both electrodes is formed by applying a forward voltage. It has two types, a forward voltage light emitting film forming unit that emits light, and a reverse voltage light emitting film forming unit that emits light by applying a reverse voltage, and switches the voltage application direction between the forward direction and the reverse direction. Thus, a single organic electroluminescence display device can provide two colors or two types of display modes, and compared to a conventional display device that displays with a plurality of elements and a plurality of drive power supplies corresponding to the drive circuit, It is advantageous in that a compact organic electroluminescence display device capable of displaying a plurality of types can be provided.

There is also an advantage that different desired display modes can be obtained by using different emission colors and different display modes for the forward voltage light emitting film forming section and the reverse voltage light emitting film forming section.

Further, according to the structure comprising a constant current power supply section for applying a voltage between the two electrodes to flow a current, and a power supply switching control section for controlling the voltage application direction to switch between the forward direction and the reverse direction. By controlling the switching timing, it is possible to display not only the color difference between the light emission color of the forward voltage light emission film formation unit and the light emission color of the reverse voltage light emission film formation unit, but also display in a mixed color, and also has the advantage of increasing the display color mode is there.

[Brief description of the drawings]

FIG. 1 is a sectional view of an organic electroluminescence device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a driving unit according to the embodiment.

FIG. 3 is an explanatory diagram showing a display mode example.

FIG. 4 is an explanatory diagram showing a display mode example.

FIG. 5 is an explanatory diagram showing a display mode example.

FIG. 6 is an explanatory diagram showing a display mode example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Organic electroluminescent display device 2 Organic electroluminescent element 4 Transparent substrate 5 Transparent electrode 6 Multilayer film formation part 6a Forward voltage light emission film formation part 6A Forward voltage light emission area 6b Reverse voltage light emission film formation part 6B Reverse voltage light emission area 7 Back electrode 12 Constant current power supply unit 13 Power supply switching control unit

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Nobuyuki Minami 1-7-10 Kikuzumi, Minami-ku, Nagoya-shi, Aichi F-term in Harness Research Institute, Inc. (Reference) 3K007 AB00 BA06 CA01 CA05 CB01 DA00 DB03 GA00 5C080 AA06 BB08 CC03 DD22 EE25 FF09 GG02 JJ01 JJ02 JJ06 5C094 AA15 AA45 BA27 CA19 CA24 EA05 EB02 GA10

Claims (4)

[Claims] 1. An organic electroluminescent display comprising a pair of electrodes disposed at least one of which is transparent and opposed to each other, and a multilayer film-forming portion having an organic multilayer structure including a light-emitting layer disposed between both electrodes. In the apparatus, the multilayer film forming section has two types of a forward voltage light emitting film forming section that emits light when a forward voltage is applied and a reverse voltage light emitting film section that emits light when a reverse voltage is applied. An organic electroluminescence display device characterized by the above-mentioned. 2. The organic electroluminescent display device according to claim 1, wherein the forward voltage light emitting film forming section and the reverse voltage light emitting film forming section have different emission colors. 3. The organic electroluminescence display device according to claim 1, wherein the forward voltage light emitting film forming section and the reverse voltage light emitting film forming section have different display forms. 4. A constant current power supply unit for applying a voltage between the two electrodes to flow a current, and a power supply switching control unit for controlling a voltage application direction to be switched between a forward direction and a reverse direction. The organic electroluminescence display device according to claim 1, 2, or 3.