JP3065458B2 - EL element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-luminous EL (electroluminescent) element used as, for example, a flat and thin display means.

[0002]

2. Description of the Related Art FIG. 7 is a side view showing a conventional EL element 41. The EL element 41 includes a translucent substrate 42, first and second strip electrodes 43 and 47, first and second insulating layers 44 and 46, an EL light emitting layer 45, and a spectral filter 48. For example, an EL structure having a double insulating layer structure is formed on one surface 42a of a light-transmitting substrate 42 made of, for example, glass. That is, on the surface 42a, a plurality of parallel first strip electrodes 43, first insulating layers 44, EL
The light emitting layer 45, the second insulating layer 46, a plurality of second parallel
The strip electrodes 47 are formed by laminating in this order. The first band-shaped electrode 43 is a transparent electrode realized by, for example, ITO (Indium Tin Oxide), and the second band-shaped electrode 47 is a metal electrode realized by, for example, Al. Further, the first and second strip electrodes 43 and 47 are formed in directions orthogonal to each other, and the intersection of the electrodes 43 and 47 is formed by the pixels 49a and 49b.
It is. On the other hand, on the other surface 42b of the translucent substrate 42,
A plurality of filters 48 corresponding to the pixels 49a and 49b
The spectral filter 48 including the components a and b is formed.

[0003]

SUMMARY OF THE INVENTION The aforementioned EL element 41
In the above, display is performed by applying a voltage equal to or higher than a predetermined threshold voltage to the EL light emitting layer 45 disposed between the first and second strip electrodes 43 and 47 to cause the EL light emitting layer 45 to emit light. . Light generated by causing the EL light emitting layer 45 to emit light passes through the first insulating layer 44, the first band-shaped electrode 43, the light transmitting substrate 42, and the spectral filter 48 in this order, and is emitted. At this time, for example, the light 50a emitted from the pixel 49a in a direction substantially perpendicular to the display screen is:
Light 50 that passes through the filter 48a corresponding to the pixel 49a but is emitted from a direction inclined with respect to the display screen.
b does not pass through the filter 48a but exits, for example, through the adjacent filter 48b. This is caused by the fact that the substrate 42 has a thickness.
The thickness of the EL layer 45 and the filter 48 increases as the thickness of the filter increases.
The deviation from “a” becomes large, and light leakage as described above becomes remarkable.

[0004] As described above, since the EL element 41 has a viewing angle dependency, a disadvantage such as a decrease in the color purity of the emitted light occurs, and the EL element 41 is not practical as a display means for performing color display. Absent. Further, as described above, when the spectral filter 48 is used, the light is dispersed and the luminance is reduced. Therefore, when the spectral filter 48 is used as a light source of a non-light emitting type display unit such as a liquid crystal display device, the Have difficulty.

An object of the present invention is to provide an EL element which has a small viewing angle dependence and can obtain a display with high definition and high brightness.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a substrate having a high refractive index portion formed by embedding a plastic material having a higher refractive index than the surroundings in the thickness direction of the substrate and forming a columnar shape. An EL structure is formed on a substrate made of a black plastic material having a small refractive index. The EL structure has an EL light emitting layer disposed between at least first and second strip electrodes. Between
An insulating layer is arranged between both or any one of them, and a pixel which is an intersection of the first and second strip electrodes is formed corresponding to the high refractive index portion. EL element.

[0007]

Further, the present invention is characterized in that a spectral filter including a plurality of filters corresponding to the pixels is formed on a surface of the substrate opposite to a surface on which the EL structure is formed. .

[0009]

According to the present invention, the EL element is formed by embedding a plastic material having a higher refractive index than its surroundings in the thickness direction of the substrate and embedding at least the first and second strip electrodes on the substrate having a high refractive index portion formed in a columnar shape. An EL structure in which an EL layer is disposed between the electrodes and the EL layer, and an insulating layer is disposed between and / or between the electrodes and the EL layer. The pixel which is the intersection of the two strip electrodes is formed corresponding to the high refractive index portion. When a voltage higher than a predetermined threshold voltage is applied to the EL light emitting layer disposed between the first and second strip electrodes, the EL light emitting layer emits light to generate light. The light generated by this emission
The light exits through the high refractive index portion of the substrate. That is, the light passes through the high-refractive-index portion while being reflected at the interface between the high-refractive-index portion and the surrounding made of a material having a low refractive index. Therefore, almost all of the light generated in each pixel exits through the high refractive index portion corresponding to each pixel, so that light leakage is reduced and luminance is improved.

[0010] The substrate is made of a black plastic material having a smaller refractive index than the high refractive index portion. Therefore, a light absorbing portion made of a light absorbing material is formed around the high refractive index portion. The light generated by the emission of the EL light-emitting layer passes through the high refractive index portion of the substrate while being reflected at the interface between the high refractive index portion and the surrounding made of a material having a low refractive index. The light does not reflect, for example, light incident on the interface at a high angle does not reflect but enters around the high refractive index portion. If the light incident on the periphery is emitted without passing through the high-refractive-index portion corresponding to each pixel, light leakage occurs and the contrast is reduced, but the light-absorbing portion formed around the high-refractive-index portion As a result, light is absorbed, so that light leakage does not occur and the contrast is improved.

According to the invention, a spectral filter including a plurality of filters corresponding to the pixels is formed on a surface of the substrate opposite to a surface on which the EL structure is formed. Light generated when the EL light emitting layer emits light is:
The light passes through the high-refractive-index portion and further passes through the spectral filter and is emitted. At this time, the light emitted from the direction inclined with respect to the display screen passes through the same filter as the light emitted from the vertical direction, regardless of the displacement between the EL light emitting layer and the spectral filter due to the thickness of the substrate. For this reason,
As the luminance of the EL element is improved, the viewing angle dependency is reduced, and a high-definition color display can be obtained.

[0012]

FIG. 1 is a side view showing an EL device 1 according to a first embodiment of the present invention. The EL element 1 includes a light-transmitting substrate 2
, First and second strip electrodes 3 and 7, first and second strip electrodes
Including insulating layers 4 and 6, EL light emitting layer 5, and spectral filter 8. For example, an EL structure having a double insulating layer structure is formed on one surface 2a of the light-transmitting substrate 2 made of, for example, glass. That is, on the surface 2a, a plurality of first strip electrodes 3 parallel to each other, a first insulating layer 4, an EL light emitting layer 5,
A second insulating layer 6 and a plurality of second band-shaped electrodes 7 parallel to each other are formed by laminating in this order. The first strip electrode 3 is a transparent electrode realized by, for example, ITO or ZnO: Al.
The second strip electrode 7 is a metal electrode realized by, for example, Al. The first and second strip electrodes 3 and 7 are formed in directions orthogonal to each other, and the intersection of the electrodes 3 and 7 is
a, 11b (when collectively referred to as “pixel 11”)
It is.

The first and second insulating layers 4 and 6 are realized by, for example, SiO ₂ or Al ₂ O ₃ . The first and second strip electrodes 3, 7 and the first and second insulating layers 4, 6 are formed by a thin film forming method such as a sputtering method or an electron beam evaporation method. The EL light emitting layer 5
Is realized by, for example, SrS: Ce, Eu, and the EL light emitting layer 5 emits white light. In addition, other than these, a rare earth element such as Sm, Tm and Pr, a transition metal element such as Mn, and other Al, Ag, Cl and the like are used for a II-VI group semiconductor base material such as ZnS, SrS and CaS. It is also possible to use a material to which an element is added. The EL light emitting layer 5 is formed by a thin film forming method such as an electron beam evaporation method.

On the other hand, on the other surface 2b of the transparent substrate 2,
For example, a spectral filter 8 of three primary colors including a red filter 8a, a green filter 8b, and a blue filter (not shown).
Is formed. After the EL structure is formed, the spectral filter 8 is formed using, for example, a spin coating method or a photolithography method, and the filters 8a and 8b are formed corresponding to the pixels 11a and 11b, respectively.

FIG. 2 is a plan view showing the translucent substrate 2. The light-transmitting substrate 2 on which the EL structure and the spectral filter 8 are formed has a plurality (four in this embodiment) of high refractive index portions 9, and the high refractive index portions 9 are arranged from the periphery thereof. It is made of a material having a large refractive index. The high refractive index portion 9 is formed, for example, in a columnar shape in the thickness direction of the substrate 2 by, for example, an ion exchange method. The pixels 11 are formed corresponding to the high refractive index portions 9. The ion exchange method for forming the high-refractive-index portion 9 is a method used for forming a high-refractive-index portion and a low-refractive-index portion on a uniform-refractive-index substrate, for example, in the manufacture of a microlens array.

In the EL element 1, a voltage equal to or higher than a predetermined threshold voltage is applied to the EL light emitting layer 5 disposed between the first and second strip electrodes 3 and 7 to cause the EL light emitting layer 5 to emit light. Is displayed. When the EL light emitting layer 5 emits light, light is generated. The generated light is supplied to the first insulating layer 4, the first strip-shaped electrode 3, the light-transmitting substrate 2, and the spectral filter 8.
Pass through in this order and exit. For example, the light beams 12a and 12b emitted from the pixel 11a pass through the inside of the high refractive index portion 9a corresponding to the pixel 11a of the substrate 2 while being reflected at the interface between the high refractive index portion 9a and its surroundings.
The light exits through a. As described above, almost all of the light generated in each pixel 11 is emitted from the filter corresponding to each pixel 11, so that the light that has conventionally been diffused in the translucent substrate is condensed, and the luminance is reduced. Is improved.

The light 12b emitted from the direction inclined with respect to the display screen, as well as the light 12a emitted from the direction perpendicular to the display screen without passing through an adjacent filter, for example, the filter 8b, as well as the pixel 12b. The light passes through the filter 8a corresponding to 11a and is emitted. As the thickness of the substrate 2 increases, the shift between the EL light-emitting layer 5 and the spectral filter 8 increases, but the light generated at each pixel 11 corresponds to each pixel 11 without being affected by such increase in the shift. The light exits through the filtered filter. Therefore, the color shift due to the viewing angle is reduced, and the decrease in color purity is reduced. Therefore, a clear and high-definition color display can be obtained.

FIG. 3 shows an EL device according to a second embodiment of the present invention.
FIG. 4 is a side view showing an element 21. The EL element 21 is provided by the E
The light-transmitting substrate 22 is composed of a plurality of glass fibers 25, though it is configured almost similarly to the L element 1. In the EL element 21, members having the same configuration as the EL element 1 are denoted by the same reference numerals.

FIG. 4 is a plan view showing the translucent substrate 22. The translucent substrate 22 is composed of a plurality (16 in this embodiment) of glass fibers 25 having a core 23 made of a high refractive material and a clad 24 made of a low refractive index material. The plurality of glass fibers 25 are grouped by an appropriate number and have a suitable thickness as the light-transmitting substrate 22.
Cut in the cross-sectional direction. The pixels 11 are formed so as to correspond to the core portions 23 of the plurality of glass fibers 25, respectively.

Transparent substrate 2 made of glass fiber 25
2 has a first surface 22a similar to the EL element 1.
An EL structure in which the strip electrode 3, the first insulating layer 4, the EL light emitting layer 5, the second insulating layer 6, and the second strip electrode 7 are laminated in this order is formed. The spectral filter 8 is similarly formed on the other surface 22b. In this example, ZnS: Mn was used for the EL light emitting layer 5. The EL light emitting layer 5 includes
It emits yellow light. As the spectral filter 8, a two-color spectral filter including a red filter 8a and a green filter 8b was used.

The EL element 21 performs display in the same manner as the EL element 1. For example, the pixel 11a
And the light 26a, 26b generated by the emission of the EL light emitting layer 5 causes the inside of the core 23a made of the high refractive index material of the glass fiber 25 to pass through the core 23a and the cladding made of the low refractive index material. The light passes through the translucent substrate 22 while being reflected at the interface with 24a. As described above, almost all of the light generated in each pixel 11 is emitted from the filter corresponding to each pixel 11, so that the luminance is improved as in the first embodiment. The light 26b emitted from the direction inclined with respect to the display screen passes through the filter 8a similarly to the light 26a emitted from the direction perpendicular to the display screen. For this reason, similarly to the first embodiment, the color shift due to the viewing angle is reduced, and the decrease in the color purity is reduced. Therefore, a clear and high-definition multi-color display can be obtained.

In this embodiment, an example in which one glass fiber is formed corresponding to one pixel has been described. However, an example in which a plurality of glass fibers are formed corresponding to one pixel is also provided by the present invention. It belongs to the range, and the same effects as in the present embodiment can be obtained.

FIG. 5 shows an EL device according to a third embodiment of the present invention.
FIG. 4 is a side view showing an element 31. The EL element 31 is
The light absorbing portion 34 is formed on the substrate 32, though it is configured almost similarly to the L element 1. In the EL element 31, the same components as those of the EL element 1 are denoted by the same reference numerals.

FIG. 6 is a plan view showing the substrate 32. A number of fine holes (4 in this embodiment) penetrating in the thickness direction are provided on the substrate 32 made of a low-refractive-index black heat-resistant plastic material serving as the light-absorbing portion 34. The high refractive index portion 33 is formed by embedding a plastic material having an excellent translucency. The pixels 11 are formed corresponding to the high refractive index portions 33, respectively.

On one surface 32a of such a substrate 32, like the EL element 1, the first strip electrode 3, the first insulating layer 4, the EL light emitting layer 5, the second insulating layer 6, and the second strip electrode 7 are formed. Are formed in this order, and the spectral filter 8 is similarly formed on the other surface 32b.

In the above-described EL elements 1 and 21, the light generated by the emission of the EL light-emitting layer 5 causes the light in the high refractive index portion of the substrate to move between the high refractive index portion and the periphery made of a material having a small refractive index. Although light passes through while being reflected at the interface, not all light is reflected, and light incident at a high angle with respect to the interface enters the periphery without being reflected.
Light that has entered the surroundings does not pass through the corresponding filter but passes through another filter and exits, so that pixels that do not emit light appear to dim. This is EL
This causes a reduction in the contrast of the device.

However, in the EL element 31 of the present embodiment, for example, the light 35 incident on the periphery of the high refractive index portion 33a
Since c is absorbed by the light absorbing unit 34, it does not pass through another filter and exit. For this reason, the weak light emission of the pixel that does not emit light due to the leak light as described above is eliminated, and a high-contrast, high-brightness color display can be obtained. Further, similarly to the first and second embodiments,
Since a color shift due to a viewing angle is reduced and a decrease in color purity is reduced, a clear and high-definition color display can be obtained.

In the first to third embodiments, an example in which an EL structure having a double insulating layer structure is formed on a substrate has been described.
An example of forming a structure also belongs to the scope of the present invention. Further, although the example of the cylindrical high refractive index portion has been described, the high refractive index portion may be a columnar shape, and is not limited to a columnar shape.

[0029]

As described above, according to the present invention, the substrate on which the EL structure is formed is filled with a plastic material having a higher refractive index than its surroundings in the thickness direction so as to correspond to the pixels. A refractive index portion is formed. For this reason, almost all of the light generated in each pixel passes through the high refractive index portion of the substrate corresponding to each pixel, and is emitted, so that light leakage is reduced and luminance is improved.

Further, the substrate is made of a black plastic material having a smaller refractive index than the high refractive index portion. Therefore, a light absorbing portion made of a light absorbing material is formed around the high refractive index portion. Light that has entered the periphery of the high refractive index portion without being reflected by the high refractive index portion is absorbed by the light absorbing portion, so that no light leaks and the contrast is improved.

According to the present invention, a spectral filter including a plurality of filters corresponding to each pixel is formed on the surface of the substrate opposite to the surface on which the EL structure is formed.
The light generated at each pixel passes through the high refractive index portion of the substrate corresponding to each pixel, and further exits through the filter corresponding to each pixel. As described above, regardless of the displacement between the EL light emitting layer and the filter, the light generated in each pixel is emitted through the filter corresponding to the pixel. For this reason, the luminance is improved and the viewing angle dependency is reduced, so that a high-definition color display can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view showing an EL element 1 according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a light-transmitting substrate 2 of the EL element 1;

FIG. 3 is a side view showing an EL element 21 according to a second embodiment of the present invention.

FIG. 4 is a plan view showing a light-transmitting substrate 22 of the EL element 21.

FIG. 5 is a side view showing an EL element 31 according to a third embodiment of the present invention.

FIG. 6 is a plan view showing a substrate 32 of the EL element 31.

FIG. 7 is a side view showing a conventional EL element 41.

[Explanation of symbols]

 1,21,31 EL element 2,22 Translucent substrate 3 First band electrode 4 First insulating layer 5 EL light emitting layer 6 Second insulating layer 7 Second band electrode 8 Spectral filter 8a, 8b Filter 9,9a, 33 , 33a High refractive index portion 11, 11a, 11b Pixel 23, 23a Core portion 24, 24a Cladding portion 25 Glass fiber 32 Substrate 34 Light absorbing portion

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-122614 (JP, A) JP-A-63-94293 (JP, A) JP-A-63-314795 (JP, A) JP-A 5- 19246 (JP, A) Japanese Utility Model 63-54184 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 33/00-33/28

Claims (2)

(57) [Claims] 1. A substrate having a high refractive index portion formed by embedding a plastic material having a higher refractive index than its surroundings in the thickness direction of the substrate in a columnar shape, wherein the black plastic material has a lower refractive index than the high refractive index portion. An EL structure is formed on a substrate comprising: an EL structure including at least a first and a second strip-shaped electrode having an EL light-emitting layer disposed between the electrode and the EL light-emitting layer; Alternatively, an insulating layer is disposed between any one of the first and second strip-shaped electrodes, and a pixel which is an intersection of the first and second strip-shaped electrodes is formed corresponding to the high refractive index portion.
L element. 2. A spectral filter comprising a plurality of filters corresponding to the pixels is formed on a surface of the substrate opposite to a surface on which an EL structure is formed. The EL element as described in the above.