JPH01315987A - Multicolor display type film electroluminescence element - Google Patents

Abstract

PURPOSE:To improve the luminous efficiency of 2 elementary colors of red and green and a color between them by providing a red emission element section and a green emission section and cutting off light with a wavelength of less than 570nm through a filter at a red color takeoff side. CONSTITUTION:A green emission element section B is positioned at a display side, and an electrode 9 is arranged such that the electrode 9 at a light takeoff side of a red emission element section A is opposed to an electrode 15 at one side of the element section B. A light emission layer 7 and insulation layers 6 and 8 made up of ZnS:Mn are installed between an element 5 and the electrode 9 made up of transparent conductive material at the element section A, at least at its light takeoff side. At the element section B, a light emission layer 13 made up of ZnS:Mn and F and insulation layers 12 and 14 is arranged between a pair of an electrode 11 and the electrode 15. A filter 10 installed at the light takeoff side of the element section A cuts off a light with a wavelength of less than 570nm to obtain a red light. Thereby, it is possible to emit 2 elementary colors of red and green and a color between them at high luminance and high efficiency.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an electroluminescent (hereinafter referred to as EL) element used in display devices, etc., and in particular, to an electroluminescent (hereinafter referred to as EL) element that emits light of two primary colors, red and green, and all intermediate colors between them. The present invention relates to a thin film EL device capable of displaying multiple colors.

[Conventional technology]

Conventionally, multicolor display type thin film El, which can emit light in the two primary colors of red and green and their intermediate colors, has been used as an element such as ZnS:Tb, F.
A three-terminal structure is obtained by stacking a green light-emitting EL element having a light-emitting layer and a red light-emitting EL element having a ZnS:Sm,F light-emitting layer (JAPAN DISPLAY '83
DIGEST), ZnS:Tb,F and Zns:srn,F by photolithographic patterning
Both of the light body parts have a light emitting layer arranged in a plane (Place of '87 SID
Int, Symp, ), a structure in which a red light-emitting EL device made of CaS:Eu and a blue-green light emitting EL device made of SrS:Ce are stacked with their transparent electrodes facing each other has been proposed (see the above-mentioned document).

However, the device with the first J3 terminal structure has a large number of laminated thin films in the device as a whole, which tends to result in unstable characteristics and is troublesome to form. . In addition, in an element in which the light-emitting layer of "Number 1" is patterned,
The problem is that extremely advanced microfabrication technology is required for forming the light emitting layer and its pattern, as well as for forming the electrodes, making it particularly difficult to produce a large-area, high-definition display. Second, the red light emitting material used in the above pixel element, ZnS:Sm,F, has a maximum luminance of 1.00
Since it is as low as about 0 cd/m, the brightness is insufficient for use as a display device such as an E I- or panel, making it impractical.

On the other hand, the third element also has insufficient brightness and has not yet reached a practical stage, and CaS and SrS, which are the base materials of the light emitters in both all-optical layers, are subject to significant deterioration due to moisture absorption. The disadvantage was that the durability of the material deteriorated.

Therefore, the present invention solves the conventional problems mentioned above,
The object of the present invention is to provide a multicolor display type thin film EL element that has excellent brightness and luminous efficiency and is easy to manufacture.

[Means to solve the problem]

In order to achieve the above object, the inventors have conducted extensive testing and have discovered a red light emitting element section that allows light emitted by a specific light emitting layer to be extracted as red light through a filter, and If the green light-emitting element portion is an EL element arranged facing each other in a specific configuration, light emission of the two primary colors red and green and all intermediate colors ranging from red to green can be obtained with high brightness and high luminous efficiency. However, the present inventors have discovered that it is possible to simply configure the drive circuit without requiring particularly advanced microfabrication technology in device fabrication, and have thus come up with this invention.

That is, the present invention provides a filter in which a light emitting layer and an insulating layer made of ZnS:Mn are disposed between a pair of electrodes made of a transparent conductive material at least on the light extraction side, and which cuts light with a wavelength of 570 nm or less on the light extraction side. A red light-emitting element portion comprising a LJ and a green light-emitting element portion comprising a ZnS:Tb,F light-emitting layer and an insulating layer disposed between a pair of electrodes both made of a transparent conductive material are placed on the display side. A multicolor display type (W film E L) in which a green light emitting element part is located, and the electrode on the light extraction side of the red light emitting element part is arranged opposite to the electrode on one side of the green light emitting element part. It is related to the element.

Further, in the present invention, a preferred embodiment of the above-mentioned EL element is such that a light-transmitting insulating material is interposed in the opposing gap between the red light-emitting element portion and the green light-emitting element portion.

[Structure and operation of the invention]

FIG. 1 shows an example of a multicolor display type El-element to which the present invention is applied.

In this E L element, a red light emitting element part provided on the back side made of glass and a green light emitting part B provided on a similar display side substrate 1b'2 are placed opposite to each other with a small gap.
The side substrates 1a, lb and an annular spacer 2 inserted between their peripheral parts are fixedly sealed with an adhesive 3 such as epoxy resin, and a translucent insulating material 4 made of silicone oil or the like is inside. The surface of the display-side substrate 1b serves as a display surface.

The red light emitting element part A is made of an Aβ thin film or an indium-tin composite oxide (hereinafter referred to as
A fourth electrode 5 is made of a thin film of a transparent conductive material such as ITO or tin oxide containing fluorine, and a first insulating layer 6, a light emitting layer 7 made of ZnS+Mn, and a second insulating layer are sequentially formed. A layer 8, a second electrode 9 made of a thin film of the above-mentioned transparent conductive material patterned into a predetermined shape are laminated,
Further, a red light transmitting filter 10 is provided covering the second electrode 9.
will be established.

Further, the green light emitting element section B includes a first electrode 11 made of a thin film of the same transparent conductive material formed on the entire surface of one side of the substrate 1b, a first insulating layer 12, a ZnS+Tb
, a light emitting layer 13 made of F, a second insulating layer 14, and a second electrode 15 made of a thin film of the same transparent conductive material as described above.

Note that the second electrode 15 is patterned in the same shape as the second electrode 9 to the red light emitting element section.

The red light-emitting element section A and the green light-emitting element section B are arranged facing each other with their second electrodes 9 and 15 overlapping vertically, and the pixel element sections A and B are each individually operated as an EL element. It is set up so that it can be driven.

In the multicolor display type thin film E L element with the above configuration, each element part A
Alternatively, an AC voltage higher than the light emission starting voltage of the light emitting layer 7 or 13 is applied between the picture electrodes 5 and 9 or 11 and 15 in B, so that the light emitting layer 7 or 13 emits light. This light emission is yellow-orange light emission due to ZnS:Mn in the light emitting layer 7,
The light-emitting layer 13 emits green light due to ZnS:Tb, F, but the yellow-orange light emitted by the light-emitting layer 7 is caused by light having a shorter wavelength than red when passing through the red light transmitting filter 10 provided on the light extraction side. It is cut and emitted as red light.

Therefore, on the surface of the display side substrate 1b, driving only the red light emitting element section A produces a red light emitting display, and driving only the green light emitting element section B produces a green light emitting display.
When B is simultaneously driven, an intermediate color light emission display in which red light emission and green light emission are mixed is performed. By changing the voltage, pulse width, number of pulses, frequency, etc. applied to the pixel elements A and B, and changing the intensity of both light emissions, the intermediate color light emission can be achieved.
It is possible to arbitrarily select all intermediate color emissions from a color mixture close to red to a color mixture close to green, and continuous color tone changes are also possible.

Here, ZnS constituting the light emitting layer 7 to the red light emitting element portion
:The original emission color of Mn is yellow-orange, but the wavelength is 500
It has a wide emission spectrum ranging from ~700nm and contains a considerable red component in the wavelength range of 600 to 700nm.Moreover, it has extremely high luminance of over 6,000cd/m and high luminous efficiency of over 311m/W when driven at 5KHz. It shows. Therefore, the red light emitted by the element part A is attenuated to some extent due to absorption and reflection when it passes through the red light transmitting filter 10 and the green light emitting element part B. ZnS:Sm, F has much higher luminance and is closer to the primary color of red than the light emitted by ZnS:Sm and F.
It can be made to be almost the same as the red color of De Ray Tube).

The red light transmission filter 10 may be any filter that cuts light with a wavelength of 570 nm or less, but color CRT
In order to obtain primary color emission close to red, it is preferable to use a material that cuts light with a wavelength of 580 nm or less and transmits 90% or more of light with a wavelength of 600 nm or more. In addition, if the upper limit of the wavelength of the light to be cut is 570 nmO, Z'n S : S
Red light emission almost matching m and F is obtained. However, if the upper limit of the wavelength of the light to be cut is longer than 580 nm, the color purity will improve, but the brightness will decrease significantly, which is not preferable.

In order to form this filter 10, a paint containing a pigment and a binder having the required selective light absorption ability is usually prepared, and this is dried on the second electrode 9 by a printing application method such as a screen printing method. Coat so that the thickness is about 0.5 to 20 μm.

Although drying may be sufficient, it is also possible to employ a thin film forming method in vacuum similar to that for each layer 5 to 9 and 11 to 15, which will be described later.

As the constituent material of the insulating layers 6, 8, 12.14, any existing insulating material can be used, for example, Ta20S, A
7!203, Y203.5iOz, Si, Ns,,T
iO□, Nbz o3, BaTi0+, 5rTiO+
, PbTi0+, etc., and different materials may be used for each insulating layer. Note that these insulating layers 6, 8, 12 .
14, each layer may be a laminate of two or more layers made of different constituent materials.

The thickness of each layer is 3,000 to 3,000 s, o for the light emitting layers 7 and 13.
oo people, 3.000 for insulation layers 6, 8, 12.14
~7,000 people, 50 for electrodes 5, 9, 11°15
Approximately 0 to 3,000 people. In addition, as means for forming these layers, various existing vacuum thin film forming methods such as vacuum evaporation methods such as electron beam evaporation and resistance heating evaporation, sputtering methods such as high frequency sputtering, and ion blating methods may be used depending on the material type used. It can be adopted as appropriate.

The translucent insulating material 4 has the function of reducing the difference in refractive index in the gap between the pixel elements A and B, thereby reducing the attenuation of light emission, and protecting the pixel elements A and B. Generally, an insulating fluid such as silicone oil is used, but it is also possible to use a cured layer of resin such as adhesive or molding resin. However, due to the above-mentioned considerations, it is difficult to select a material whose refractive index is close to that of the second electrode 9.15 and the filter 10 due to the quality of the moon. Note that the light-transmitting insulating material 4 may be omitted depending on the case.

On the other hand, in the E L element illustrated in the two sets, the pixel element part A2B
Are the second electrodes 9, 15 of the same pattern or all the electrodes 5, 9, 1.1. , ], 5 overlap vertically, intermediate color light emission can be obtained in this region. Therefore, the combination of electrodes with the same pattern between pixel parts A and B is electrode 5, ]1.5, and 15. The same is true for both .9 and 11. It is also possible to perform a multi-color light emitting display by shifting the light emitting regions of the pixel elements A and B so that intermediate color light is emitted in the overlapping region and red or green primary color light is emitted in the non-overlapping region.

Furthermore, one of the picture electrodes going to each element part or B is divided into a plurality of electrode parts, and the other electrode is used as a common electrode for these electrode parts, and the applied voltage and pulse width are applied to each electrode part or each group. By adopting a configuration that changes the number of pulses, frequency, etc., it is possible to display multiple colors and change the number of colors.

Also, 1 of this invention? , L elements are pixel element parts A and B
In addition to double insulation type E L elements as shown in the example, each element part A and B is composed of a table insulation type E L element with a single insulating layer.
An L element configuration is also possible.

(Effects of the invention) 1! II Q This multicolor display type EL element is made of Zn
Because it is a combination of a red light emitting element section with a light emitting layer made of S/Mn and a red light transmitting filter and a green light emitting element section with a light emitting layer made of ZnS:Tb,F in a specific arrangement, It can emit light in the two primary colors of red and green and all intermediate colors between them with high luminance and luminous efficiency sufficient for practical use as a display device such as an IEL panel.
Furthermore, since the pixel element itself has a structure similar to that of a normal monochromatic light-emitting EL element, the structure of the entire element is very simple and can be easily manufactured without requiring any special microfabrication technology.

Furthermore, by interposing a light-transmitting insulating material in the opposing gap between the pixel element portions of the EL element described in (g), the difference in refractive index in the gap is reduced and the attenuation of red light emission is suppressed, and
This has the advantage that the pixel element area is protected and durability is improved.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 A glass substrate with a thickness of 1.50 mm was deposited on one side of the entire surface of the back side substrate with a length of 34 mm, a width of 34 meters, and a thickness of 1.1 mm using a resistance heating vapor deposition method.
A first insulating layer made of TaO, a first insulating layer made of Ta2O, and a first insulating layer made of ZnS are sequentially formed on this electrode.
: A light-emitting layer made of Mn and a second insulating layer made of RA205 were each laminated to a thickness of 5,000 layers, and the second insulating layer was further made of ITO to a thickness of 2,000 layers. A second electrode was formed in a predetermined pattern. Note that both insulating layers were formed by high frequency sputtering, and the light emitting layer and second electrode were formed by electron beam evaporation.

Next, a red light transmitting filter having a thickness of 5 μrn was provided on the surface of the second electrode by screen printing to produce a red light emitting element portion. In addition, this filter is
Cutting light with a wavelength of 580 nm or less to a wavelength of 600 nm
It transmitted 95% of the following light.

On the other hand, a first electrode made of ITO with a thickness of 2□000 was formed on the entire surface of one side of the display side substrate made of glass similar to the back side substrate by electron beam evaporation, and on this electrode, TazOs was sequentially formed. A first insulating layer consisting of ZnS:Tb,
A light-emitting layer made of F' and a second insulating layer made of Ta205 were each laminated to a thickness of 5,000 yen by high-frequency snowmetering, and then a second insulating layer was formed to a thickness of 2,000 yen. A second electrode made of human doped FO was formed in the same pattern as the red light emitting element part by electron beam evaporation to produce a green light emitting element part.

Next, the pixel section is placed in a 100.degree. The two substrates are placed facing each other with a gap of +1 m, and a glass annular spacer is interposed between the peripheral parts of the substrates, and the spacer and both substrates are sealed with epoxy adhesive, and silicone oil is applied inside. A multicolor display type thin film EL device having the structure shown in FIG.

Note that this BL element was set so that the red light emitting element section and the green light emitting element section could be driven separately, and the applied voltage, pulse width, number of pulses, frequency, etc., could be adjusted respectively.

For the E L element produced in this way, ±200
When each element was driven using a sine wave voltage of V, 60 Hz, red light emission was 18 cd/n (green light emission was 60 cd/n).
cd/r&, and a brightness almost comparable to that of a color CRT was obtained. In addition, the chromaticity coordinate value of red light emission is X=0.62
, Y=0.33, which almost matched the red color of a color CRT.

In addition, when we simultaneously drove the pixel elements and changed the applied voltage to the pixel elements to change the relative brightness of red and green light, we found that the red A continuous change in luminescent color from green to green was obtained. In addition, in Fig. 2, the approximately semi-elliptical encircling line surrounding the straight line is CJ
This is based on the display of the E chromaticity diagram, which shows the visible color range.

Example 2 A multicolor display type thin film EL element was prepared in the same manner as in Example 1, except that a red light transmitting filter was used that filters out light with a wavelength of 510 nm or less and transmits 95% of light with a wavelength of 590 nm or more. was created.

When this EL element was driven in the same manner as the EL element of Example 1, red light emission had chromaticity coordinate values of X-0,64 and Y.
= 0.38, and the color tone was almost the same as the red emission by ZnS:Sm,F, but the luminance was 22cd'/
It showed a high value of −. Note that the green light emission was the same as that of Example 1.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of essential parts showing a structural example of a multicolor display type thin film electroluminescent device according to the present invention, and FIG. 2 is a chromaticity diagram showing changes in emitted light color in the device according to Example 1 of the present invention. be. A... Red light emitting element part, B... Green light emitting element part, 4
...transparent insulating material, 5,9. II, 15...Electrode, 6,8.12.14...Insulating layer, 7.13...Light emitting layer, 10...Filter patent applicant Hitachi Maxell, Ltd.

Claims (2)

[Claims] (1) A light emitting layer and an insulating layer made of ZnS:Mn are disposed between a pair of electrodes made of a transparent conductive material at least on the light extraction side, and a filter for cutting light with a wavelength of 570 nm or less is provided on the light extraction side. A red light-emitting element section consisting of a red light-emitting element section, and a green light-emitting element section consisting of a ZnS:Tb, F light-emitting layer and an insulating layer disposed between a pair of electrodes both made of a transparent conductive material, are arranged on the display side. A multi-color display type thin film electroluminescent element in which the electrodes on the light extraction side of the red light emitting element part are arranged opposite to each other so that the electrodes on the light extraction side of the red light emitting element part face the electrodes on one side of the green light emitting element part. (2) The multicolor display type thin film electroluminescent device according to claim (1), wherein a translucent insulating material is interposed in the opposing gap between the red light emitting element portion and the green light emitting element portion.