KR100777740B1 - Organic light emitting display apparatus - Google Patents

Abstract

An organic light emitting display device is provided to enhance brightness with low power consumption by increasing the brightness of light generated from an intermediate layer having at least a light emitting layer. An organic light emitting display device includes a substrate(110), a first electrode(131), a second electrode(134), an intermediate layer(133), and a buffer layer(140). The first electrode is formed on the substrate. The second electrode is formed at the upper part of the first electrode to face the first electrode. The intermediate layer is formed between the first electrode and the second electrode, and has a light emitting layer. The buffer layer generates light resonance. The intermediate layer emits light to the outside through the first electrode and the substrate. The buffer layer is formed between the substrate and the first electrode.

Description

Organic light emitting display apparatus

1 is a cross-sectional view schematically illustrating an organic light emitting display device according to an exemplary embodiment of the present invention.

2 is a cross-sectional view schematically illustrating an organic light emitting display device according to another exemplary embodiment of the present invention.

3 is a cross-sectional view schematically illustrating an organic light emitting display device according to another exemplary embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

110 substrate 120 thin film transistor

128: passivation film 129: pixel defining film

131: first electrode 133: intermediate layer

134: second electrode 140: buffer layer

The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device which is easy to manufacture while improving light extraction efficiency and brightness.

The organic light emitting display device has various layer structures, and thus passes through many layers until light generated in the light emitting layer is extracted to the outside. In this process, only about 30% of the light generated in the light emitting layer is extracted to the outside due to its own light loss inside the layer, and various attempts have been made to increase the light extraction rate.

Among such attempts, the method of raising the supply voltage makes it possible to achieve the intended brightness enhancement, but it is contrary to the weight reduction accompanied with the increase in the capacity of the battery, and also reduces the lifespan of the pixels provided in the battery and the display device. For this reason, the following prior arts have been proposed to improve the luminance while lowering the supply voltage.

Japanese Patent Application Laid-open No. Hei 4-192290 discloses an inorganic EL device in which a plurality of microlenses for condensing having a size equal to or larger than that of the inorganic EL element are provided on the outer surface of the translucent substrate on which the inorganic EL element is formed. have. The light incident at an angle greater than or equal to the critical angle at the interface between the translucent substrate and the air has an angle of incidence less than or equal to the critical angle in the microlens to reduce total reflection and direct the light emission direction in a predetermined direction, thereby increasing luminance in that direction. will be. However, in the above invention, since the EL element is a surface light source, when a microlens having a size equal to or larger than that of the EL element is used, EL light is not condensed, but rather diffused light is inevitably generated. There is a problem that the sharpness of the image is lowered due to duplication.

Japanese Patent Application Laid-open No. Hei 7-037688 discloses an EL element formed on a substrate having a high refractive index portion formed of a material having a refractive index larger than the surroundings in a columnar shape in the thickness direction. It is to increase the light extraction efficiency by allowing the light of the EL element to pass through the high refractive index portion. However, the present invention has a problem that the luminance of the EL light passing through the high refractive index portion is diffused as shown in FIG.

In Japanese Patent Application Laid-open No. Hei 10-172756, one or more condensing lenses are formed between the lower electrode constituting the organic EL element and the outer surface of the translucent substrate, and the organic EL element and the condensing lens are formed. An organic EL light emitting device is provided so as to correspond thereto. The light of the EL element passing through the condenser lens is incident on the interface between the substrate and the air at a critical angle or less to increase the light extraction efficiency. However, the present invention has a problem in that the sharpness of the image is lowered due to overlapping with the image by adjacent EL elements.

The present invention has been made to solve various problems including the above problems, and an object thereof is to provide an organic light emitting display device which is easy to manufacture while improving light extraction efficiency and luminance.

In order to achieve the above object and various other objects, the present invention provides a substrate, a first electrode disposed on the substrate, a second electrode disposed to face the first electrode, and the first electrode. An intermediate layer including at least a light emitting layer interposed between an electrode and the second electrode, disposed between at least one of the substrate and the first electrode and an upper portion of the second electrode, so that the luminance of light emitted from the intermediate layer is the highest. An organic light emitting display device comprising a buffer layer whose thickness is determined according to a wavelength of light emitted from the intermediate layer.

According to another feature of the present invention, the refractive index of the buffer layer may be 1.5 to 2.3.

According to another feature of the invention, the buffer layer may be formed of silicon nitride (SiN _x ), tantalum oxide (Ta ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ) or titanium oxide (TiO ₂ ). have.

According to another feature of the invention, the light emitted from the intermediate layer is emitted to the outside through the second electrode, the buffer layer may be disposed above the second electrode.

In order to achieve the above object, the present invention also provides a substrate, a first electrode disposed on the substrate, a second electrode disposed to face the first electrode, the first electrode, and the second electrode. And an intermediate layer including at least a light emitting layer interposed therebetween, and a buffer layer disposed between at least one of the substrate and the first electrode and an upper portion of the second electrode, the buffer layer including a high refractive index layer and a low refractive layer. The present invention provides an organic light emitting display device.

According to another aspect of the present invention, the buffer layer may be a buffer layer in which a plurality of high and low refractive layers are alternately arranged.

According to another feature of the invention, the refractive index of the high refractive index layer of the buffer layer may be 1.6 to 2.5.

According to another feature of the invention, the high refractive layer is to be formed of silicon nitride (SiN _x ), tantalum oxide (Ta ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ) or titanium oxide (TiO ₂ ). Can be.

According to still another feature of the present invention, the refractive index of the low refractive layer of the buffer layer may be 1.0 to 1.6.

According to another feature of the present invention, the low refractive layer may be formed of silicon oxide (SiO ₂ ), lithium fluoride (LiF) or magnesium fluoride (Mg ₂ F ₂ ).

According to another feature of the present invention, the layers of the buffer layer may have a thickness determined according to the wavelength of light emitted from the intermediate layer so that the luminance of the light emitted from the intermediate layer is the highest.

According to another feature of the invention, the light emitted from the intermediate layer is emitted to the outside through the second electrode, the buffer layer may be disposed above the second electrode.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view schematically illustrating an organic light emitting display device according to a first exemplary embodiment of the present invention.

The present invention can be applied to various types of organic light emitting display devices, and FIG. 1 is a so-called active driving type (AM) including at least one thin film transistor 120 for controlling light emission of each subpixel. active matrix) relates to an organic light emitting display device. Of course, the present invention can be applied to a passive matrix organic light emitting display device.

Each subpixel has at least one thin film transistor 120 as shown in FIG. 1. Referring to FIG. 1, a buffer layer (not shown) may be formed of SiO ₂ on the substrate 110 as necessary, and the thin film transistor 120 may be provided on the substrate 110. The thin film transistor 120 includes electrodes such as the gate electrode 121, the source electrode 123, and the drain electrode 124, the semiconductor layer 125, the gate insulating layer 126, and the like, and the thin film transistor 120 The interlayer insulating film 127 may be further provided depending on the structure of the interlayer insulating film 127. Of course, a so-called coplanar silicon thin film transistor is shown in FIG. 1, but other types of thin film transistors such as various types of thin film transistors and organic thin film transistors may be provided. It is not limited to what is shown.

A passivation film 128 made of SiO ₂ or the like is formed on the thin film transistor, and a pixel definition film 129 made of acryl, polyimide, or the like is formed on the passivation film 128. The passivation film 128 may serve as a protective film for protecting the organic thin film transistor and may serve as a planarization film for planarizing an upper surface thereof.

Although not shown in the drawings, at least one capacitor may be connected to the thin film transistor. The circuit including the thin film transistor is not necessarily limited to the example illustrated in FIG. 1, and may be variously modified.

Meanwhile, the organic light emitting diode is connected to the drain electrode 124. The organic light emitting device includes a first electrode 131 and a second electrode 134 opposed to each other, and an intermediate layer 133 including at least a light emitting layer interposed between the electrodes. The second electrode 134 may be variously modified, such as may be formed in common among the plurality of pixels.

Meanwhile, in FIG. 1, the intermediate layer 133 is shown to be patterned so as to correspond only to the subpixels, but this is illustrated for convenience of description of the configuration of the subpixels, and the intermediate layer 133 is integral with the intermediate layer of the adjacent subpixels. Of course, it may be formed as. In addition, some layers of the intermediate layer 133 may be formed for each subpixel, and other layers may be integrally formed with an intermediate layer of an adjacent subpixel.

The first electrode 131 functions as an anode electrode, and the second electrode 134 functions as a cathode electrode. Of course, the polarity of the first electrode 131 and the second electrode 134 may be reversed.

The first electrode 131 may be provided as a transparent electrode or a reflective electrode. When used as a transparent electrode may be provided with ITO, IZO, ZnO or In ₂ O ₃ , when used as a reflective electrode Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr and compounds thereof After the reflection film is formed, or the like, ITO, IZO, ZnO, or In ₂ O ₃ can be formed thereon. However, the organic light emitting diode according to the present exemplary embodiment illustrated in FIG. 1 corresponds to the case where the first electrode 131 is a reflective electrode. This will be described later.

The second electrode 134 may also be provided as a transparent electrode or a reflective electrode, and when used as a transparent electrode, Li, Ca, LiF / Ca, LiF / Al, Al, Mg, and a compound thereof are directed toward the intermediate layer 133. After the deposition, the auxiliary electrode or the bus electrode line may be formed on the transparent electrode forming material such as ITO, IZO, ZnO or In ₂ O ₃ . When used as a reflective electrode, Li, Ca, LiF / Ca, LiF / Al, Al, Mg, and compounds thereof are formed by full deposition. The organic light emitting diode according to the present exemplary embodiment illustrated in FIG. 1 corresponds to a case in which the second electrode 134 is a transparent electrode. This will also be described later.

The intermediate layer 133 provided between the first electrode 131 and the second electrode 134 may be formed of low molecular weight or high molecular organic material. In case of using low molecular weight organic material, hole injection layer (HIL), hole transport layer (HTL), organic emission layer (EML), electron transport layer (ETL), electron injection layer (EIL) The electron injection layer may be formed by stacking a single or complex structure, and the usable organic materials may be copper phthalocyanine (CuPc), N, N-di (naphthalen-1-yl) -N, N '-Diphenyl-benzidine (N, N'-Di (naphthalene-1-yl) -N, N'-diphenyl-benzidine: NPB), tris-8-hydroxyquinoline aluminum ( Alq3) can be used in various ways. These low molecular weight organic materials may be formed in a predetermined pattern by a method such as vapor deposition.

In the case of the polymer organic material, the structure may include a hole transporting layer (HTL) and a light emitting layer (EML). In this case, PEDOT is used as the hole transporting layer, and PPV (Poly-Phenylenevinylene) and polyfluorene are used as the light emitting layer. Polymer organic materials such as (Polyfluorene) are used.

The buffer layer 140 is disposed on the second electrode 134. The buffer layer 140 is different in thickness depending on the wavelength of light emitted from the intermediate layer 133.

As described above, the organic light emitting diode according to the present exemplary embodiment is a so-called top emission type organic light emitting display device in which light emitted from the intermediate layer 133 is extracted to the outside through the second electrode 134. In this case, the intermediate layer 133 The light generated in the) may generate a resonance between the first electrode 131 and the second electrode 133 to increase luminance. In this case, by placing the buffer layer 140 on the second electrode 134 in the direction in which light is extracted, the light is again generated between the first electrode 131 and the buffer layer 140 or in the buffer layer 140. By causing resonance to occur, the luminance of light emitted to the outside can be further increased. In this case, since the optical resonance occurs more efficiently when the refractive index of the buffer layer 140 is higher than the refractive index of the upper and lower layers, the refractive index of the buffer layer 140 is preferably 1.5 to 2.3.

At this time, the wavelength of the light generated in the intermediate layer 133 is different for each sub-pixel, and the conditions under which optical resonance occurs, that is, the thickness of the buffer layer 140 is different according to the wavelength, so that the thickness of the buffer layer 140 is the intermediate layer ( It is desirable to vary depending on the light emitted from 133). That is, the thickness of the buffer layer 140 is preferably determined according to the wavelength of the light emitted from the intermediate layer 133 so that the brightness of the light emitted from the intermediate layer 133 is the highest.

Red blue green Buffer layer thickness (nm) Luminance ratio x y Luminance ratio x y Luminance ratio x y 20 74% 0.679 0.320 63% 0.136 0.136 70% 0.326 0.642 40 51% 0.683 0.316 53% 0.137 0.141 51% 0.349 0.626 60 100% 0.678 0.321 100% 0.136 0.105 100% 0.315 0.650 80 114% 0.685 0.314 110% 0.131 0.169 104% 0.342 0.630 100 140% 0.688 0.311 95% 0.139 0.215 109% 0.365 0.614 120 240% 0.688 0.312 101% 0.140 0.195 152% 0.356 0.622 140 76% 0.592 0.308 47% 0.140 0.174 51% 0.386 0.593 160 119% 0.686 0.313 64% 0.138 0.117 73% 0.350 0.622 180 43% 0.687 0.312  59% 0.136 0.112 45% 0.343 0.629 200 48% 0.685 0.314 78% 0.131 0.143 59% 0.320 0.647

Table 1 shows the results of calculating the luminance of the light emitted from each subpixel and the color coordinate of the light by increasing the thickness of the buffer layer from 20 nm to 200 nm in 20 nm units. In this case, the luminance ratio represents a relative ratio based on a thickness of 60 nm, and the buffer layer is formed by plasma chemical vapor deposition (PECVD) using silicon nitride.

As shown in Table 1, in the case of red, the luminance of the red light was maximum when the thickness of the buffer layer was 120 nm, in the case of blue, the luminance of the blue light was maximum when the thickness of the buffer layer was 80 nm, and in the case of green, the thickness of the buffer layer. Was 120 nm, the luminance of the green light was maximum. As described above, the thickness of the buffer layer having the maximum luminance varies depending on the wavelength of light generated in each subpixel in all the subpixels. Therefore, rather than forming buffer layers having the same thickness irrespective of the wavelength of light generated in each subpixel, the subpixels are generated in each subpixel such that the luminance of light generated in each subpixel is maximized, as in the organic light emitting display device according to the present embodiment. It is preferable that the thickness of the buffer layer is determined according to the wavelength of the light.

As the buffer layer 140, in addition to silicon nitride as described above, a relatively high refractive index tantalum oxide (Ta ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ), titanium oxide (TiO ₂ ), or the like may be used. In addition, the organic material layer having a high refractive index can also be used. In addition, a buffer layer having a different thickness for each subpixel may be easily formed through deposition using a halftone mask.

On the other hand, the organic light emitting device according to the embodiment shown in FIG. 1 is for the top emission type, the present invention can also be applied to the bottom emission type light is extracted to the outside through the substrate 110. However, since the thickness of the buffer layer is different for each subpixel, it is not easy to form the thin film transistor 120 on the buffer layer after forming the buffer layer, and thus the manufacturing cost may increase and the yield may decrease. Therefore, when the present invention is applied to the top emission type, a greater effect can be obtained.

2 is a cross-sectional view schematically illustrating an organic light emitting display device according to a second exemplary embodiment of the present invention.

The organic light emitting display device according to the present embodiment differs from the organic light emitting display device according to the above-described embodiment in that the structure of the buffer layer 140 is different. That is, although the buffer layer included in the organic light emitting display device according to the above-described embodiment was a single layer, the buffer layer 140 according to the present embodiment includes a high refractive layer 141 and a low refractive layer 142. Table 2 shows a case where the buffer layer 140 having the high refractive layer 141 formed of silicon nitride and the low refractive layer 142 formed of silicon oxide is provided, and the thickness of the high refractive layer 141 is fixed to 120 nm and is low. It is the luminance ratio and the color coordinate of each subpixel measured while increasing the thickness of the refractive layer 142 from 20 nm to 260 nm in 20 nm units.

Red blue green Low refractive layer thickness (nm) Luminance ratio x y Luminance ratio x y Luminance ratio x y 20 96% 0.684 0.315 98% 0.133 0.137 90% 0.340 0.632 40 114% 0.686 0.314 105% 0.132 0.167 103% 0.345 0.628 60 190% 0.681 0.318 134% 0.132 0.159 159% 0.325 0.644 80 106% 0.690 0.310 82% 0.139 0.181 88% 0.362 0.616 100 161% 0.687 0.312 98% 0.138 0.244 122% 0.338 0.635 120 69% 0.689 0.310 63% 0.138 0.149 61% 0.362 0.615 140 62% 0.588 0.311 64% 0.136 0.131 56% 0.352 0.621 160 59% 0.688 0.311 72% 0.135 0.122 60% 0.332 0.636 180 59% 0.688 0.312 86% 0.132 0.133 71% 0.314 0.652 200 97% 0.682 0.317 124% 0.131 0.131 122% 0.282 0.675 220 107% 0.680 0.319 132% 0.131 0.159 150% 0.283 0.680 240 88% 0.684 0.316 95% 0.139 0.210 107% 0.331 0.646 260 100% 0.686 0.314 84% 0.143 0.197 96% 0.353 0.627

As described above, it can be seen that the luminance can be remarkably improved by changing the thickness of the low refractive layer 142 in the buffer layer 140 having the high refractive layer 141 and the low refractive layer 142. That is, when the thickness of the low refractive layer 142 is 60nm, it can be seen that the brightness of the red, blue, and green light all increased significantly.

 In particular, even in this case, the thickness of the buffer layer 140 may be determined according to the wavelength of the light emitted from the intermediate layer 133 so that the luminance of the light emitted from the intermediate layer 133 is the highest.

As the material of such a high refractive layer, in addition to silicon nitride, relatively high refractive index tantalum oxide (Ta ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ), or titanium oxide (TiO ₂ ) may be used. Preferably, a material having a refractive index of 1.6 to 2.5 can be used. As the material of the low refractive index layer, lithium fluoride (LiF), magnesium fluoride (Mg ₂ F ₂ ), or the like may be used in addition to silicon oxide. In addition, a material having a refractive index of 1.0 to 1.6 may be used.

2 illustrates a structure in which the high refractive layer 141 is formed on the second electrode 134 and the low refractive layer 142 is disposed on the high refractive layer 141, whereas the low refractive layer is the second electrode. It may be formed on the high refractive layer and disposed on top of the low refractive layer. Table 3 shows the result of increasing the thickness of the low refractive layer in 20 nm units from 20 nm to 260 nm in such a structure.

Red blue green Low refractive layer thickness (nm) Luminance ratio x y Luminance ratio x y Luminance ratio x y 20 122% 0.684 0.315 117% 0.131 0.171 114% 0.342 0.632 40 139% 0.687 0.312 103% 0.139 0.239 111% 0.377 0.604 60 225% 0.686 0.314 110% 0.140 0.214 150% 0.366 0.612 80 70% 0.692 0.308 39% 0.143 0.215 43% 0.404 0.576 100 98% 0.688 0.311 49% 0.139 0.154 60% 0.363 0.610 120 30% 0.695 0.304 32% 0.138 0.159 30% 0.353 0.625 140 25% 0.589 0.310 39% 0.138 0.122 31% 0.335 0.638 160 27% 0.683 0.315 59% 0.135 0.107 40% 0.315 0.651 180 34% 0.680 0.319 87% 0.126 0.152 64% 0.292 0.669 200 69% 0.671 0.328 138% 0.122 0.186 146% 0.259 0.696 220 107% 0.668 0.330 137% 0.135 0.261 191% 0.292 0.679 240 113% 0.682 0.317 65% 0.159 0.304 87% 0.395 0.590 260 103% 0.691 0.308 44% 0.154 0.221 57% 0.423 0.563

As described above, even when the low refractive layer is formed on the second electrode and the high refractive layer is disposed on the low refractive layer, the brightness of the light generated in the light emitting layer can be increased by appropriately adjusting the thickness of the low refractive layer or the high refractive layer.

3 is a cross-sectional view schematically illustrating an organic light emitting display device according to a third exemplary embodiment of the present invention.

The difference between the organic light emitting display device according to the second embodiment and the organic light emitting display device according to the present embodiment is that the buffer layer 140 is not a structure having one high refractive index layer and one low refractive index layer. The layers 141 and the low refractive layers 142 are alternately arranged. By introducing the buffer layer 140 having a structure in which the plurality of high refractive layers 141 and the low refractive layers 142 are alternately arranged, the luminance of the extracted light may be further improved.

In the above embodiments, the organic light emitting display apparatuses having the top light emitting structure have been described, but the present invention is not limited thereto. Of course, the present invention can be applied to the light emitting structure.

According to the organic light emitting display device of the present invention made as described above, it is possible to further improve the brightness of the light generated in the intermediate layer including at least the light emitting layer, it is possible to implement a display device with low power consumption and high brightness.

Although the present invention has been described with reference to the embodiments shown in the drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (12)

Board; A first electrode disposed on the substrate; A second electrode disposed on the first electrode so as to face the first electrode; An intermediate layer including a light emitting layer interposed between the first electrode and the second electrode; And And a buffer layer to allow optical resonance to occur. The light emitted from the intermediate layer is emitted to the outside through the first electrode and the substrate, and the buffer layer is disposed between the substrate and the first electrode. The method of claim 1, The refractive index of the buffer layer is an organic light emitting display device, characterized in that 1.5 to 2.3. The method of claim 1, The buffer layer is formed of silicon nitride (SiN _x ), tantalum oxide (Ta ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ) or titanium oxide (TiO ₂ ). Board; A first electrode disposed on the substrate; A second electrode disposed on the first electrode so as to face the first electrode; An intermediate layer including a light emitting layer interposed between the first electrode and the second electrode; And And a buffer layer to allow optical resonance to occur. The light emitted from the intermediate layer is emitted to the outside through the second electrode, the buffer layer is an organic light emitting display device, characterized in that disposed on top of the second electrode. Board; A first electrode disposed on the substrate; A second electrode disposed to face the first electrode; An intermediate layer including a light emitting layer interposed between the first electrode and the second electrode; And And a buffer layer including a high refractive index layer and a low refractive index layer. The light emitted from the intermediate layer is emitted to the outside through the first electrode and the substrate, the buffer layer is disposed between the substrate and the first electrode. The method of claim 5, And the buffer layer is a buffer layer in which a plurality of high refractive layers and low refractive layers are alternately arranged. The method of claim 5, An organic light emitting display device, characterized in that the refractive index of the high refractive index layer of the buffer layer is 1.6 to 2.5. The method of claim 5, The high refractive index layer is formed of silicon nitride (SiN _x ), tantalum oxide (Ta ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ) or titanium oxide (TiO ₂ ). The method of claim 5, The refractive index of the low refractive layer of the buffer layer is an organic light emitting display device, characterized in that 1.0 to 1.6. The method of claim 5, The low refractive index layer is an organic light emitting display device, characterized in that formed of silicon oxide (SiO ₂ ), lithium fluoride (LiF) or magnesium fluoride (Mg ₂ F ₂ ). The method of claim 5, And the layers of the buffer layer have a thickness determined according to the wavelength of the light emitted from the intermediate layer so that the luminance of the light emitted from the intermediate layer is the highest. Board; A first electrode disposed on the substrate; A second electrode disposed on the first electrode so as to face the first electrode; An intermediate layer including a light emitting layer interposed between the first electrode and the second electrode; And And a buffer layer including a high refractive index layer and a low refractive index layer. The light emitted from the intermediate layer is emitted to the outside through the second electrode, the buffer layer is an organic light emitting display device, characterized in that disposed on top of the second electrode.

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