JP3601290B2 - EL display device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an EL (electroluminescence) display device.
[0002]
[Prior art]
A simple matrix drive EL display device is expected to be a next-generation flat panel display because it has the advantages of being thin, lightweight, low cost, self-luminous and high luminance. As shown in FIG. 5, in a conventional EL display device, a plurality of light-transmitting first electrodes and a plurality of second electrodes sandwich a light-emitting medium at least on a light-transmitting insulating substrate, and a first electrode line and a second electrode are connected to each other. It consists of a pixel group formed by electrode lines intersecting each other. When a voltage is applied between the first electrode line and the second electrode line, a current flows between the first electrode and the second electrode in a region corresponding to the pixel at the intersection, and light is emitted from the sandwiched light emitting medium.
[0003]
The portion of the light emitted from the light emitting medium that faces the first light-transmitting electrode is transmitted through the first light-transmitting electrode and the light-transmitting insulating substrate, and is emitted from the display surface. The portion facing the second electrode is reflected once by the second electrode, then passes through the light emitting medium, the first translucent electrode, and the translucent insulating substrate, and is emitted from the display surface. As described above, two components of the light emission, which are oriented substantially perpendicular to the substrate, are used for display.
[0004]
[Problems to be solved by the invention]
However, the external light incident on the display surface passes through the light-transmitting insulating substrate, the light-transmitting first electrode, and the light-emitting medium, is reflected by the second electrode, and is reflected by the light-emitting medium, the light-transmitting first electrode, and the light-transmitting light. The light passes through the insulating substrate and is emitted from the display surface. This reflection of external light becomes a background at the time of non-lighting, and causes a decrease in contrast.
[0005]
Further, the transparent conductor used for the light-transmitting first electrode has a resistivity several orders of magnitude lower than that of metal. In a high-definition, large-screen EL display device, it is necessary to flow a large current. However, a large voltage drop occurs at that time, and there is a problem of deterioration in uniformity and efficiency.
[0006]
The present invention has been made to solve these problems, and provides an EL display device which suppresses external light reflection and has good contrast. In addition, the present invention provides an EL display device in which uniformity and efficiency are improved by lowering electric resistance of an electrode.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, as a first aspect, a plurality of first electrodes and a plurality of second electrodes sandwich a light emitting medium at least on a light-transmitting insulating substrate, and the first electrode row and the second electrode row. In an EL display device including a pixel group formed by intersecting with each other, at least a first electrode in a region corresponding to the pixel includes at least a light absorption layer on a light-transmitting insulating substrate side and a light reflection layer of a light-emitting medium, Further, the EL display device has a slit-shaped or dot-shaped light transmitting hole.
[0008]
According to a second aspect, in the first electrode having the slit-shaped or dot-shaped light transmitting holes, the maximum width of the non-transmission pattern in the pixel portion is 1/1000 to 1/2 of the minimum width of the pixel, 2. The EL display device according to claim 1, wherein the aperture ratio in the portion is 5% to 60%.
[0009]
According to a third aspect, a color filter layer of an absorption type, an interference type, or a fluorescence wavelength conversion type is provided in the light transmitting portion of the first electrode or between the first electrode and the light transmitting insulating substrate. An EL display device according to any one of claims 1 to 2.
[0010]
According to a fourth aspect, the light absorption layer of the first electrode is made of a black resin layer or an incomplete metal oxide or incomplete metal nitride, and the light reflection layer is made of a metal. 3. The EL display device according to any one of (1) to (3).
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
[0012]
According to the first aspect of the present invention, the first electrode includes at least a light absorbing layer and a light reflecting layer, and has a slit-shaped or dot-shaped light transmitting hole.
[0013]
Of the light emitted from the light emitting medium and directed toward the first electrode, the light corresponding to the light transmitting region is directly emitted from the display surface. The portion corresponding to the non-transmissive region among the portions facing the first electrode, and the portion facing the second electrode, after repeating reflection between the light reflecting layer of the first electrode and the second electrode, The light is emitted from the display surface through the light transmitting portion of the electrode. As described above, the two components of the light emission that are oriented in a direction substantially perpendicular to the substrate are used for display, as in the related art.
[0014]
On the other hand, of the external light incident on the display surface, the portion corresponding to the light transmitting region of the first electrode is transmitted through the light transmitting insulating substrate and the light emitting medium, is reflected by the second electrode, and is reflected by the light emitting medium. The light passes through the insulating substrate and is emitted from the display surface. Further, of the external light, the portion corresponding to the non-transmissive region of the first electrode is absorbed by the light absorbing layer of the first electrode. Therefore, reflection of external light is reduced, and a high-contrast display is obtained.
[0015]
Assuming that the conventional light emission intensity is I and the external light reflection is R, the conventional contrast is I / R. If the transmissive aperture ratio (area ratio of the light transmissive region) is α (<1), ignoring the loss in transmission and reflection, the emission intensity in the present invention is I, the external light reflection is αR, and the contrast is It is improved to I / αR. That is, since the reflection of external light can be reduced while maintaining the emission intensity substantially, the contrast is improved.
[0016]
The slit-shaped or dot-shaped light transmission hole of the first electrode is formed at least in a region corresponding to the pixel.
[0017]
According to a second aspect, in the first electrode having the slit-shaped or dot-shaped light transmitting holes, the maximum width of the non-transmission pattern in the pixel portion is 1/1000 to 1/2 of the minimum width of the pixel, 2. The EL display device according to claim 1, wherein the aperture ratio in the portion is 5% to 60%.
[0018]
If the width of the non-transmissive pattern of the first electrode is large, the pattern will be visible when observed near. However, since the size of the pixel of the display device is determined in consideration of the distance from the observer, when the size of the pixel is large, it does not matter whether the width of the non-transmissive pattern is large. That is, the optimum width of the non-transmission pattern of the first electrode has a relative relationship depending on the width of the pixel. Since a pattern that is too fine makes the process difficult, the maximum width of the non-transmissive pattern is preferably 1/1000 to 1/2 of the minimum width of the pixel, and more preferably 1/100 to 1/10.
[0019]
Also, if the width of the non-transmissive pattern is large, the number of reflections until display increases, and the luminance is reduced due to loss. For this reason, the width of the non-transmissive pattern is desirably 0.5 μm to 50 μm.
[0020]
Since the reciprocal of the aperture ratio improves the contrast, the improvement effect is reduced when the aperture ratio is large. Also, when the aperture ratio is small, the number of reflections until display increases, the loss increases, and the luminance decreases. From these, the opening ratio is preferably 5% to 60%, and more preferably 10% to 40%.
[0021]
According to a third aspect, a color filter layer of an absorption type, an interference type, or a fluorescence wavelength conversion type is provided in the light transmitting portion of the first electrode or between the first electrode and the light transmitting insulating substrate. An EL display device according to any one of claims 1 to 2.
[0022]
By combining with a color filter, the contrast can be further improved, and a full-color or multi-color EL display device can be easily provided even if one kind of light-emitting medium is used.
[0023]
According to a fourth aspect, the light absorption layer of the first electrode is made of a black resin layer or an incomplete metal oxide or incomplete metal nitride, and the light reflection layer is made of a metal. 3. The EL display device according to any one of (1) to (3).
[0024]
As the light absorbing layer, a black resin used for a color filter or the like, an imperfect metal oxide such as a CrO _X / Cr layer, an imperfect metal nitride such as GaN _X , or the like can be used. As the light reflecting layer, a metal such as Ag, Al, Co, Cr, Mo, Nb, Pd, Pt, Rh, Sn, Ta, Ti, or an alloy containing one or more of these metal elements can be used. In particular, Ag and Al have high reflectivity in the visible region and are suitable materials.
[0025]
In particular, it is preferable to use a slit-shaped hole parallel to the stripe because the wiring resistance can be further reduced even with the same opening ratio.
[0026]
Note that a glass substrate, a plastic substrate, or the like can be used as the light-transmitting insulating substrate in the EL display device of the present invention.
[0027]
Examples of the luminescent medium in the present invention include 9,10-diarylanthracene derivatives, salicylates, pyrene, coronene, perylene, rubrene, tetraphenylbutadiene, 9,10-bis (phenylethynyl) anthracene, lithium 8-quinolinolate, and tris (8-quinolinolate) aluminum complex, tris (5,7-dichloro, 8-quinolinolate) aluminum complex, tris (5-chloro-8-quinolinolate) aluminum complex, bis (8-quinolinolate) zinc complex, tris (5-fluoro -8-quinolinolate) aluminum complex, tris (4-methyl-5-trifluoromethyl-8-quinolinolate) aluminum complex, tris (4-methyl-5-cyano-8-quinolinolate) aluminum complex, bis (2-methyl- 5-to Fluoromethyl-8-quinolinolate) [4- (4-cyanophenyl) phenolate] aluminum complex, bis (2-methyl-5-cyano-8-quinolinolate) [4- (4-cyanophenyl) phenolate] aluminum complex, tris (8-quinolinolate) scandium complex, bis [8- (paratosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4-tetraphenylcyclopentadiene, pentaphenylcyclopentadiene, poly-2,5-diheptyl Examples thereof include oxy-para-phenylenevinylene, fluorescent substances described in JP-A-4-31488, U.S. Pat. Nos. 5,141,671 and 4,769,292, and N, N'-diaryl-substituted pyrrolopyrrole compounds.
[0028]
【Example】
First, one embodiment of the EL display device of the present invention is shown in FIGS.
[0029]
A slit-shaped hole 4 a is formed in the pixel portion of the first electrode 4. A color filter 2 is provided between the first electrode 4 and the translucent insulating substrate 1.
[0030]
The manufacturing process of this EL display device is shown in FIGS.
[0031]
First, a color filter 2 is formed on a glass substrate 1 by a known method, and is covered with an overcoat layer 3 (see FIG. 3A). Next, the laminated films 5 and 6 of CrO _x / Cr having a thickness of 0.2 μm are formed (see FIG. 3B). Then, a stripe having a width of 1 mm, a width of 20 μm, and a slit-shaped light transmitting hole 4a having an aperture ratio of 40% is processed by a conventional photo-etching technique, that is, formation of a photoresist pattern and wet etching (see FIG. 3C). .
[0032]
Next, the conductivity and the light reflectivity are improved by performing Ag plating 7 of 0.3 μm (see FIG. 3D).
[0033]
Then, a light emitting medium 8 is formed on the entire surface (see FIG. 4E). As the luminescent medium 8, the hole transport layer 9 was laminated to 0.07 μm, and the electron transporting luminescent layer 10 was laminated to 0.07 μm. Then, as the second electrode 11, AlLi is formed to a thickness of 0.3 μm in a stripe shape crossing the first electrode pattern by mask evaporation (see FIG. 4 (f)). Finally, a sealing layer 12 is formed on the entire surface (see FIG. 4G).
[0034]
In the sample manufactured in this way, although the luminance was slightly reduced as compared with the conventional device, the contrast was improved about 1.5 times.
[0035]
[Effect of non-transparent pattern width]
The non-transmitting pattern width was changed to 1 μm, 10 μm, 100 μm, and 500 μm under the conditions of the first electrode width of 1 mm and the aperture ratio of 50%. These are 1/1000 to 1/2 of the first electrode width corresponding to the pixel width. In each case, a contrast improving effect was observed. However, in the case of 1 μm, a high-precision patterning technique is required, and there is no point in making it finer. In the case of 500 μm, the non-transmissive pattern becomes visible, and if it is rougher, the image quality is reduced.
[0036]
[Effect of aperture ratio]
The aperture ratio was changed to 1%, 5%, 10%, 20%, 40%, 60%, and 80% under the conditions of the first electrode width of 1 mm and the non-transmission pattern width of 100 μm. At 5% to 60%, a contrast improving effect was observed. At an aperture ratio of 1%, the luminance was significantly reduced, and at an aperture ratio of 80%, the effect of reducing the reflection of external light was weak, and the contrast did not improve in any case.
[0037]
【The invention's effect】
According to the present invention, by using the first electrode having a hole instead of the transparent conductive film, it is possible to provide an EL display device which suppresses external light reflection and has good contrast. Further, it is possible to provide an EL display device in which electric resistance can be reduced and uniformity and efficiency are improved.
[0038]
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an example of an EL display device of the present invention.
FIG. 2 is a plan view of the EL display device of FIG.
FIG. 3 is an explanatory diagram illustrating a manufacturing process of the EL display device in FIG. 1;
FIG. 4 is an explanatory diagram illustrating a manufacturing process of the EL display device in FIG. 1;
FIG. 5 is a cross-sectional view illustrating an example of a conventional EL display device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transparent insulating substrate 2 Color filter 3 Overcoat insulating layer 4 First electrode 4a Light transmitting hole 4X Translucent first electrode 5 Light absorbing layer 6 Intermediate layer 7 Light reflecting layer 8 Light emitting medium 9 Hole transport layer 10 Electrons Transportable light emitting layer 11 Second electrode 12 Sealing layer

Claims (4)

An EL display including a pixel group in which a plurality of first electrodes and a plurality of second electrodes sandwich a light-emitting medium at least on a light-transmitting insulating substrate, and where the first electrode row and the second electrode row cross each other. In the device, at least a first electrode in a region corresponding to a pixel includes at least a light-absorbing layer on a light-transmitting insulating substrate side and a light-reflecting layer on a light-emitting medium side, and has a slit-shaped or dot-shaped light transmitting hole. An EL display device, characterized in that: In the first electrode having the slit-shaped or dot-shaped light transmitting holes, the maximum width of the non-transmission pattern in the pixel portion is 1/1000 to 1/2 of the minimum width of the pixel, and the aperture ratio in the pixel portion is The EL display device according to claim 1, wherein the content is 5% to 60%. An absorption type, an interference type, or a fluorescence wavelength conversion type color filter layer is provided in the light transmitting portion of the first electrode or between the first electrode and the light transmitting insulating substrate. 3. The EL display device according to any one of 2. The light-absorbing layer of the first electrode is made of a black resin layer or an incomplete metal oxide or an incomplete metal nitride, and the light reflection layer is made of a metal. EL display device.

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