KR20110059304A - Organic electro-luminescence device - Google Patents

Abstract

PURPOSE: An organic electroluminescent device is provided to improve color reproduction by including an optical compensation layer on the outside of a substrate or between a protection film and an organic electroluminescent diode. CONSTITUTION: A driving thin film transistor and an organic electroluminescent diode are formed on a substrate. A protection film(120) covers the driving thin film transistor and the organic electroluminescent diode. The light from the organic electroluminescent diode transmits a first optical compensation layer(200). The first optical compensation layer is formed between the protection film and the organic electroluminescent diode or between the organic electroluminescent diode and the substrate. A second optical compensation layer is formed between an inorganic protection layer and an organic protection layer(120b).

Description

Organic electroluminescent device

The present invention relates to an organic light emitting device, and more particularly, to an organic light emitting device having improved optical characteristics.

Until recently, cathode ray tubes (CRT) have been mainly used as display devices. However, in recent years, flat panel such as plasma display panel (PDP), liquid crystal display device (LCD), organic electro-luminescence device (OLED), which can replace CRT Display devices are widely researched and used.

Among the flat panel display devices as described above, the organic light emitting display device (hereinafter referred to as OLED) is a self-light emitting device, and since the backlight used in the liquid crystal display device which is a non-light emitting device is not necessary, a light weight can be achieved.

In addition, the viewing angle and contrast ratio are superior to the liquid crystal display device, and it is advantageous in terms of power consumption, it is possible to drive the DC low voltage, the response speed is fast, and the internal components are solid, so it is strong against external shock, and the operating temperature range is also high. It has a wide range of advantages.

In particular, since the manufacturing process is simple, there is an advantage that can reduce the production cost more than the conventional liquid crystal display device.

In addition, recently, flexible OLEDs manufactured to maintain display performance even when bent like paper using a flexible material such as plastic are rapidly emerging as next-generation flat panel displays.

1 is a view schematically illustrating a cross section of a general flexible OLED, and the OLED is a top emission type.

As shown, the flexible OLED 10 has a driving thin film transistor DTr and an organic light emitting diode formed on the substrate 1.

In more detail, the driving thin film transistor DTr is formed in each pixel region P on the substrate 1 formed of flexible glass, plastic, stainless steel, or the like having flexible characteristics. The organic light emitting layer 13 and the upper portion of the organic light emitting layer 13 that emit light of a specific color on the first electrode 11 and the first electrode 11 connected to each driving thin film transistor DTr. The second electrode 15 is formed.

The organic light emitting layer 13 expresses colors of red, green, and blue. In general, separate organic materials 13a, 13b, and 13c emitting red, green, and blue colors are used for each pixel.

The first and second electrodes 11 and 15 and the organic light emitting layer 13 formed therebetween form an organic light emitting diode. In this case, the OLED 10 having such a structure configures the first electrode 11 as an anode and the second electrode 15 as a cathode.

The driving thin film transistor DTr and the organic light emitting diode are provided with a protective film 20, so that the flexible OLED 10 is encapsulated through the protective film 20.

Through this, the OLED 10 has a flexible characteristic.

Meanwhile, the protective film 20 encapsulating the flexible OLED 10 alternates at least one inorganic insulating material and at least one organic insulating material in order to prevent moisture and oxygen from penetrating into the OLED 10. It consists of multiple layers laminated | stacked.

However, the flexible OLED 10 which encapsulates through the protective film 20 in which the inorganic insulating material and the organic insulating material are alternately stacked has the characteristic difference between the inorganic insulating material and the organic insulating material of the protective film 20. Compared to the OLED encapsulated through the existing glass substrate (not shown), the brightness and color reproduction rate are lowered.

The present invention is to solve the above problems, it is an object to improve the brightness and color reproduction of the flexible OLED.

In order to achieve the object as described above, the present invention includes a substrate formed with a driving thin film transistor and an organic light emitting diode; A protective film covering the driving thin film transistor and the organic light emitting diode; Light emitted from the organic light emitting diode provides an organic light emitting device that transmits at least one first compensation layer formed between the protective film and the organic light emitting diode or between the organic light emitting diode and the substrate. .

In this case, the protective film is an inorganic protective layer containing silicon nitride (SiNx), silicon oxide (Si0 ₂ ) or alumina (Al ₂ O ₃ ) and polyacrylate (polyacrylate), polyimide (polyimide), polyamide (polyamide) ) Or a plurality of organic protective layers containing benzocyclobutene (BCB) are alternately stacked, and further comprising a second optical compensation layer between the inorganic protective layer and the organic protective layer.

The refractive indices of the first and second optical compensation layers are greater than the refractive indices of the organic light emitting diodes and the protective film, and the refractive indices of the first and second optical compensation layers are the refractive indices of the organic light emitting diodes and the substrate. Greater than

Further, the first and second optical compensation layers have a satisfactory refractive index and thickness satisfying the cancellation interference condition 2n ₂ t = mλ, where (n ₂ = refractive index of the optical compensation layer, t = optical compensation layer Is the thickness, λ = wavelength of visible light, m = 1, 2, 3, 4 ...).

The first and second optical compensation layers may include an inorganic insulating material including silicon nitride (SiNx), silicon oxide (Si0 ₂ ) or alumina (Al ₂ O ₃ ), polyacrylate, and polyimide ( It is made of one selected from organic insulating materials including polyimide, polyamide or benzocyclobutene (BCB), or the inorganic insulating material and the organic insulating material are alternately stacked, and the substrate is flexible It is composed of one selected from glass substrate or plastic.

The driving thin film transistor may include a semiconductor layer, a gate electrode, a source and a drain electrode, and the organic light emitting diode may include a first electrode, an organic light emitting layer, and a second electrode connected to the driving thin film transistor.

As described above, by further comprising an optical compensation layer between the protective film and the organic light emitting diode for encapsulation or on the outside of the substrate according to the present invention, between the organic light emitting diode and the protective film or between the organic light emitting diode and By offsetting light between the substrates, there is an effect of preventing the extinction interference by reducing the refractive index and reflectance generated at the interface between the protective film and the organic light emitting diode.

Through this, there is an effect that the brightness and color reproduction rate can be prevented from being lowered compared to the OLED encapsulated with the existing glass material or the OLED using the glass substrate as a substrate.

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

FIG. 2 is a cross-sectional view schematically illustrating a flexible OLED of a top emission type according to an exemplary embodiment of the present invention, and FIG. 3 is an enlarged cross-sectional view of a portion of FIG. 2.

Meanwhile, the OLED 100 is divided into a top emission type and a bottom emission type according to the transmission direction of emitted light. Hereinafter, the top emission method will be described as an example.

As shown, a plurality of driving thin film transistors DTr and organic light emitting diodes E are formed in the pixel region P of the top emission type OLED 100 according to the present invention.

In more detail, the semiconductor layer 201 is formed on the substrate 101 of the pixel region P of the OLED 100, and the semiconductor layer 201 is made of silicon, and the center portion of the OLED region 100 is formed of an active region that forms a channel. 201a) and source and drain regions 201b and 201c doped with a high concentration of impurities on both sides of the active region 201a.

The gate insulating film 203 is formed on the semiconductor layer 201.

A gate electrode 205 and a gate wiring extending in one direction are formed on the gate insulating film 203 so as to correspond to the active region 201a of the semiconductor layer 201.

In addition, a first interlayer insulating film 207a is formed on the entire surface of the gate electrode 205 and the gate wiring (not shown), wherein the first interlayer insulating film 207a and the gate insulating film 203 below are formed in an active region. First and second semiconductor layer contact holes 209a and 209b exposing the source and drain regions 201b and 201c located on both sides thereof are provided.

Next, an upper portion of the first interlayer insulating layer 207a including the first and second semiconductor layer contact holes 209a and 209b is spaced apart from each other and exposed through the first and second semiconductor layer contact holes 209a and 209b. And source and drain electrodes 211 and 213 in contact with the drain regions 201b and 201c, respectively.

A second interlayer insulating film 207b having a source and drain electrodes 211 and 213 and a drain contact hole 215 exposing the drain electrode 213 is formed over the first interlayer insulating film 207a.

In this case, the semiconductor layer 201 including the source and drain electrodes 211 and 213, the source and drain regions 201b and 201c in contact with the electrodes 211 and 213, and the semiconductor layer 201 are formed on the semiconductor layer 201. The gate insulating film 203 and the gate electrode 205 form a driving thin film transistor DTr.

Although not shown in the drawing, data wirings (not shown) defining pixel areas are formed to cross the gate wirings (not shown). The switching thin film transistor (not shown) has the same structure as the driving thin film transistor DTr and is connected to the driving thin film transistor DTr.

In addition, the switching thin film transistor (not shown) and the driving thin film transistor DTr in the drawing show a top gate type in which the semiconductor layer 201 is made of a polysilicon semiconductor layer as an example. It may also be formed as a bottom gate type (bottom gate) type consisting of amorphous silicon of impurities.

In addition, the first electrode 111 constituting the organic light emitting diode E, the organic light emitting layer 113, and the second electrode 115 are sequentially disposed in an area that substantially displays an image on the second interlayer insulating film 207b. It is formed.

The first electrode 111 is connected to the drain electrode 213 of the driving thin film transistor DTr, and the first electrode 111 is formed for each pixel region, and between the first electrodes 111 formed for each pixel region. A bank 221 is located in the non-pixel area.

That is, the bank 221 is formed in a matrix type having a lattice structure as a whole of the substrate 101, and the bank 221 is formed as a boundary with respect to each pixel region P, so that the first electrode 111 is separated for each pixel region. It is formed into a structure.

In this case, the first electrode 111 is formed of indium tin oxide (ITO), which is a material having a relatively high work function value to serve as an anode electrode, and the second electrode 115 is formed of a cathode ( It is made of a metal material with a relatively low work function to act as a cathode.

In addition, the light emitted from the organic light emitting layer 113 is driven by the upper emission method emitted toward the second electrode 115.

In addition, the organic light emitting layer 113 may be formed of a single layer made of a light emitting material, and in order to increase the light emitting efficiency, a hole injection layer, a hole transporting layer, an emitting material layer, an electron It may be composed of multiple layers of an electron transporting layer and an electron injection layer.

When a predetermined voltage is applied to the first electrode 111 and the second electrode 115 according to the selected color signal, the OLED 100 may be formed from holes and second electrodes 115 injected from the first electrode 111. The applied electrons are transported to the organic light emitting layer 113 to form excitons, and when these excitons transition from the excited state to the ground state, light is generated and emitted in the form of visible light.

In this case, since the emitted light passes through the second electrode 115 to the outside, the OLED 100 implements an arbitrary image.

On the other hand, the substrate 101 may be formed of a transparent material such as glass, plastic material, and the protective film 120 in the form of a thin thin film on the driving thin film transistor DTr and the organic light emitting diode E. However, the OLED 100 of the present invention is encapsulated through the protective film 120.

Thus, the OLED 100 of the present invention can be formed by encapsulating through the protective film 120, the OLED 100 can be formed to a thin thickness than when encapsulated with glass, the overall of the OLED (100) The thickness can be reduced.

In addition, the OLED 100 has a flexible characteristic, thereby implementing a flexible OLED that can maintain the display performance as it is, even if bent like paper.

On the other hand, the protective film 120 is an inorganic protection including silicon nitride (SiNx), silicon oxide (Si0 ₂ ) or alumina (Al ₂ O ₃ ) in order to prevent the penetration of moisture and oxygen into the OLED (100). The layer 120a and the organic protective layer 120b including polyacrylate, polyimide, polyamide, or benzocyclobutene (BCB) are alternately stacked to form a plurality of layers.

At this time, the organic protective layer 120b is laminated in a structure surrounded by the inorganic protective layer 120a.

In particular, the protective film 120 of the present invention is characterized in that to further form the optical compensation layer (200).

The optical compensation layer 200 includes an inorganic insulating material including silicon nitride (SiNx), silicon oxide (Si0 ₂ ), or alumina (Al ₂ O ₃ ), polyacrylate, polyimide, and polyamide ( polyamide) or an organic insulating material including benzocyclobutene (BCB), or an inorganic insulating material and an organic insulating material may be formed as a plurality of layers alternately stacked.

The optical compensation layer 200 has a refractive index of 2.0 to 3.0. The optical compensation layer 200 includes a protective film 120 and an organic light emitting diode (E) between the protective film 120 and the organic light emitting diode (E). Due to the difference in refractive index of), it serves to prevent the light attenuation effect from occurring.

In more detail, the protective film 120 including the inorganic protective layer 120a and the organic protective layer 120b has a refractive index of about 1.5 depending on polarization of light, and the organic light emitting diode E is about 1.8. Has a refractive index of.

Thus, due to the difference in refractive index between the protective film 120 and the organic light emitting diode (E), the light disappears by interference and refraction generated at the interface between the protective film 120 and the organic light emitting diode (E). do.

In particular, since the protective film 120 is formed in a structure in which the inorganic protective layer 120a and the organic protective layer 120b are alternately stacked, the flexible OLED 100 encapsulated through the protective film 120. In this case, luminance and color reproduction are lowered compared to OLEDs encapsulated through a conventional glass substrate (not shown).

Thus, the present invention is to prevent such a problem by forming the optical compensation layer 200 having a refractive index of 2 to 3 between the protective film 120 and the organic light emitting diode (E).

Referring to this in more detail with reference to Figure 4, generally between the light having a different refractive index is absorbed or optically interfere with the reflection.

Thus, by including the optical compensation layer 200 in the protective film 120 of the flexible OLED 100 of the present invention, as shown in Figure 4 the organic light emitting diode (E) and the optical compensation layer 200 and The protective film 120 is incident to the optical compensation layer 200 at a predetermined angle, the light emitted from the organic light emitting diode (E), the incident light is the organic light emitting diode (E) and the optical compensation layer (200). The reflection and refraction are performed at the interface between h, i.e., a point defined in the drawing.

Here, the light reflected by the optical compensation layer 200 becomes the reflected light R1, and the light not reflected at point a passes through the optical compensation layer 200 to between the optical compensation layer 200 and the protective film 120. The interface of, i.e., the point b defined in the drawing is reached.

The light reaching the point b is also reflected and refracted, and the light reflected at the point b becomes the reflected light R2, which defines the interface between the optical compensation layer 200 and the organic light emitting diode E, that is, as defined in the drawing. After passing through the point, it comes out to the organic light emitting diode (E).

On the other hand, the light not reflected at the point b passes through the protective film 120, and reaches the point c defined in the interface, that is, the drawing of the protective film 120.

The light reaching the point c is reflected and refracted by the interface of the protective film 120 again. The light reflected at the point c becomes the reflected light R3, passing through the point d and the point f again to the organic light emitting diode ( E) will come out.

In addition, the light not reflected at point c is refracted to pass through the protective film 120, and the image is realized through the refracted light passing through the protective film 120.

Such reflected light causes reinforcement interference and destructive interference in the process of refraction and reflection at each interface. Reinforcement interference occurs when the phase of light reflected from the material coincides. It is a phenomenon that occurs when the phase of is reversed.

When constructive interference is made, the reflectance of light is improved, and when offset interference is made, the reflectance of light is lowered.

In particular, when the organic light emitting diode (E), the optical compensation layer 200 and the protective film 120 are made of a material having three different refractive indexes according to an embodiment of the present invention, interference of reflected light between each material The effect is

Formula (1)

2n ₂ t = mλ (m = 1, 2, 3, 4 ...)

Formula (2)

2n ₂ t = (m + 1/2) λ (m = 1, 2, 3, 4 ...)

It can be defined as.

Here, n ₂ represents the refractive index of the optical compensation layer 200 positioned between the organic light emitting diode E and the protective film 120, t represents the thickness of the optical compensation layer 200, λ is the visible light Indicates the wavelength.

In this case, the refractive index of the organic light emitting diode (E) is defined as n ₁ , the refractive index of the optical compensation layer 200 is defined as n ₂ and the refractive index of the protective film 120 as n ₃ , and each refractive index value is n _1. In the case of <n ₂ > n ₃ , equation (1) satisfies the cancellation interference condition, and equation (2) satisfies the constructive interference condition.

Accordingly, the cancellation interference condition can be summarized as follows.

Offset Interference Condition = 2n ₂ t = mλ _n2

Here, λ _n2 represents the wavelength of visible light of the optical compensation layer 200.

Thus, the optical compensation layer 200 of the present invention to have a refractive index and thickness that satisfies the above equation, thereby causing a destructive interference between the organic light emitting diode (E) and the protective film 120, the protective film ( It is to prevent the extinction interference by lowering the refractive index and reflectance generated at the interface between the 120 and the organic light emitting diode (E).

Here, the refractive index of the optical compensation layer 200 can be determined through the following equation (3).

Formula (3)

2n ₂ = λ / t

Through this, the refractive index value of the optical compensation layer 200 which may lower the refractive index and the reflectance between the organic light emitting diode E and the protective film 120 may be determined.

Subsequently, the thickness t of the optical compensation layer 200 may be determined by substituting the following equation (4) through the determined refractive index value of the optical compensation layer 200.

Formula (4)

t = λ / 2n ₂

Here, the difference in refractive index between the organic light emitting diode E, the optical compensation layer 200 and the protective film 120 is preferably 0.2 or more and 3 or less, and it is more preferable to increase the possible refractive index difference.

This is because when the difference in refractive index is less than 0.2, the light scattering effect at the interface is inferior and the reflectance of light irradiated from the organic light emitting diode E is increased.

Table 1 below is experimental data obtained by measuring color reproducibility and luminance according to the refractive index and thickness of the optical compensation layer 200 according to the embodiment of the present invention.

Optical compensation layer Blue (B) Green (G) Red (R) Color gamut
(%) Refractive index
(n) thickness
(A) efficiency
(cd / A) CIEx CIEy efficiency
(cd / A) CIEx CIEy efficiency
(cd / A) CIEx CIEy No optical compensation layer 16.35 0.1274 0.1355 62.52 0.2094 0.6494 23.04 0.6670 0.3125 83.10 1.6 500 16.15 0.1282 0.1331 64.10 0.2119 0.6522 22.21 0.6536 0.3239 81.15 1.8 500 16.29 0.1296 0.1293 65.69 0.2018 0.6592 25.23 0.6552 0.3253 83.55 2.0 500 16.31 0.1310 0.1246 67.21 0.1921 0.6681 28.32 0.6583 0.3251 86.71 2.2 500 16.20 0.1324 0.1195 68.35 0.1838 0.6776 31.05 0.6623 0.3233 90.16 2.4 500 15.97 0.1335 0.1147 68.86 0.1776 0.6866 33.04 0.6669 0.3205 93.54 2.6 500 15.64 0.1343 0.1108 68.83 0.1734 0.6944 34.09 0.6714 0.3172 96.52 2.8 500 15.31 0.1347 0.1082 68.33 0.1707 0.7005 34.20 0.6756 0.3138 98.92 3.0 500 15.03 0.1348 0.1066 67.23 0.1696 0.7041 33.57 0.6792 0.3106 100.56

Table (1)

Here, the efficiency is the luminous efficiency obtained by dividing the measured luminance when the reference current is applied to the organic light emitting diode E by the applied current, and the higher the value, the higher the efficiency.

The efficiency depends on the internal quantum efficiency indicating the amount of light generated inside the organic light emitting diode E and the external quantum efficiency indicating the amount of light generated outside the organic light emitting diode E. Is determined by.

As can be seen from Table 1, it can be seen that the color reproducibility is improved by including the optical compensation layer 200 as compared with the case without the optical compensation layer 200.

At this time, when the refractive index of the optical compensation layer 200 is 1.6, 1.8, since the thickness of the optical compensation layer 200 becomes too thick, it is preferable to set the refractive index of the optical compensation layer 200 to 2.0 to 3.0.

In particular, when the refractive index of the optical compensation layer 200 is 3.0 and the thickness of the optical compensation layer 200 is 500 Å, it can be seen that the color reproducibility is increased by about 18% compared with the case without the optical compensation layer 200. .

As described above, the flexible OLED 100 of the present invention further comprises an optical compensation layer 200 between the protective film 120 and the organic light emitting diode (E), thereby the organic light emitting diode (E) and the protective film. By canceling the light interference between the 120, by reducing the refractive index and reflectance generated at the interface between the protective film 120 and the organic light emitting diode (E) is to prevent the extinction interference.

Meanwhile, in the above description, the optical compensation layer 200 has been described in which both the optical compensation layer 200 is provided at the interface between the inorganic protective film 120a and the organic protective film 120b of the protective film 120. It is possible to form only one layer between the specific inorganic protective film 120a and the organic protective film 120b in the protective film 120.

Here, the optical compensation layer 200 may be configured using a spin coating, a slit coating, a roll printing method, an inkjet coating method, and FIGS. 5A to 5G. Let's take a closer look.

5A to 5G are cross-sectional views of manufacturing a flexible OLED of a top emission type according to an embodiment of the present invention.

As illustrated, the driving thin film transistor DTr is formed on the substrate 101, and the driving thin film transistor Dtr is formed of the semiconductor layer 201 and the gate insulating layer 203 and the gate electrode formed on the semiconductor layer 201. 205 and the first interlayer insulating film 207a and the source and drain electrodes 211 and 213 formed on the gate electrode 205.

A second interlayer insulating film 207b having a source and drain electrodes 211 and 213 and a drain contact hole 215 exposing the drain electrode 213 is formed over the first interlayer insulating film 207a.

Although not shown in the drawings, the method for forming the same is described in detail. After depositing amorphous silicon, coating of photoresist, exposure through a mask, development of exposed photoresist, and remaining amorphous photoresist exposed after development The semiconductor layer 201 is formed by performing a series of processes called patterning through a mask process such as etching the silicon layer and ashing or stripping the remaining photoresist.

In this case, the method may further include crystallizing polysilicon by heat treatment after dehydrogenation of the semiconductor layer 201.

Next, the second insulating material and the first metal layer are sequentially deposited on the substrate 101 on which the semiconductor layer 201 is formed, and then, as described above, the second insulating material is formed at the center of the semiconductor layer 201 through a mask process. Is formed of the gate insulating film 203.

The first metal layer is formed as the gate electrode 205 with the gate insulating film 203 as a lower layer.

Here, it is preferable that the second insulating material is any one of silicon nitride (SiNx) or silicon oxide (Si0 ₂ ), which is an inorganic insulating material.

The first metal layer may be formed by depositing one or two or more materials selected from metal materials such as aluminum (Al) or aluminum alloy (AlNd), molybdenum (Mo), nickel (Ni), tungsten (W), or the like. It is preferable to set it as a double layer.

Next, in the substrate 101 on which the semiconductor layer 201 is formed, the gate electrode 205 and the gate insulating film 203 exposed to the outside of the gate wiring (not shown) are etched and removed, and then, the substrate 101 is applied to the substrate 101. N + or p + doping is performed by ion implantation having a dose amount.

At this time, the portion of the semiconductor layer 201 where the ion implantation is blocked by the gate electrode 205 forms the active layer 201a, and the other ion implanted active regions are the source and drain regions 201b and 201c. Will form.

As a result, the semiconductor layer 201 including the active region 201a and the source and drain regions 201b and 201c is completed.

Next, an inorganic insulating material is deposited on the exposed source and drain regions 201b and 201c including the gate electrode 205 and patterned by performing a mask process, thereby forming source and drain regions 201b on both sides of the gate electrode 205. And a first interlayer insulating film 207a having first and second semiconductor layer contact holes 209a and 209b exposing a portion thereof, respectively.

Next, the first and second semiconductor layers are deposited by depositing a metal material on the entire surface of the substrate 101 having the first and second semiconductor layer contact holes 209a and 209b and forming a mask process. Source and drain electrodes 211 and 213 in contact with the source and drain regions 201b and 201c are formed through the contact holes 209a and 209b, respectively.

In this case, the source and drain electrodes 211 and 213 are spaced apart from each other with the gate electrode 205 therebetween.

Next, an organic insulating material such as photo acryl or benzocyclobutene (BCB) is coated on the entire surface of the substrate 101 on which the source and drain electrodes 211 and 213 are formed and patterned through a mask process. 101. A second interlayer insulating film 207b is formed over the entire surface.

In this case, the second interlayer insulating film 207b has a drain electrode contact hole 215 exposing the drain electrode 213.

Next, as shown in FIG. 5B, an organic light emitting diode E is formed on the second interlayer insulating film 207b, and the organic light emitting diode E is formed of the first and second electrodes 111 and 115. ) And an organic light emitting layer 113 formed therebetween.

Here, the organic light emitting diode (E) forms an anode as an constituent element of the organic light emitting diode (E) on the second interlayer insulating film (207b), and then forms a first electrode (111). The bank 221 is formed on the first electrode 111 by applying and patterning a photosensitive organic insulating material, for example, photo acryl or benzocyclobutene (BCB) on the first electrode 111. do.

The bank 221 is formed in a matrix type having a lattice structure as a whole to distinguish between pixel regions.

Next, an organic light emitting layer 113 is formed by applying or depositing an organic light emitting material on the bank 221.

Next, the organic electroluminescent diode E is formed by forming a second electrode 111 having a thick transparent conductive material deposited on the translucent metal film on which the metal material having a low work function is thinly deposited on the organic light emitting layer 113. You are done.

Next, as shown in FIG. 5C, an inorganic protective layer 120a made of an inorganic insulating material is formed on the organic light emitting diode E. Referring to FIG.

The inorganic protective layer 120a is formed of an inorganic insulating material such as silicon nitride (SiNx) or silicon oxide (Si0 ₂ ) or alumina (Al ₂ O ₃ ), where the inorganic protective layer 120a is formed by chemical vapor deposition. Vapor Deposition: Formed by CVD or sputtering equipment.

Next, as shown in FIG. 5D, the organic protective layer 120b is formed on the inorganic protective layer 120a. The organic protective layer 120b may be formed of polyacrylate, polyimide, It is formed of an organic insulating material such as polyamide or benzocyclobutene (BCB), where the organic protective layer 120b is an inkjet device, a nozzle coating, a bar coating, a slit ) By coating on the entire surface using a coating, spin coating device or a print device.

Next, as shown in FIG. 5E, the optical compensation layer 200 is formed on the organic protective layer 120b. The optical compensation layer 200 may be formed of silicon nitride (SiNx), silicon oxide (Si0 ₂ ), or alumina ( Inorganic insulating materials such as Al ₂ O ₃ ) or organic insulating materials such as polyacrylate, polyimide, polyamide or benzocyclobutene (BCB) may be selected to form a single layer or multiple layers. In this case, when the optical compensation layer 200 is formed of an inorganic insulating material, the optical compensation layer 200 is formed through chemical vapor deposition (CVD) or sputtering equipment.

Alternatively, when the optical compensation layer 200 is to be formed of an organic insulating material, the optical compensation layer 200 may include an inkjet device, a nozzle coating, a bar coating, a slit coating, and a spin ( It is formed by coating on the entire surface using a spin coating device or a print device.

Here, the refractive index n ₂ and the thickness t of the optical compensation layer 200 are formed to satisfy the condition of Equation (1) as described above.

In this case, when the refractive index of the organic light emitting diode E is about 1.8 and the refractive indices of the first and second protective layers 120a and 120b are about 1.5 depending on the polarization of light, the optical compensation layer 200 of the present invention. ) Preferably has a refractive index of 2-3.

In addition, the thickness t of the optical compensation layer 200 is preferably substituted with the above refractive index n ₂ in the above-described formula (5) to have a thickness t satisfying the formula (5). .

Next, as shown in FIG. 5F, the first protective layer 120a, the second protective layer 120b, and the optical compensation layer 200 are alternately formed on the optical compensation layer 200, and are formed as described above. Form through the same method.

As a result, the flexible OLED 100 according to the embodiment of the present invention is completed.

Meanwhile, in the above description, the flexible light emitting diode (OLED) of the upper emission type in which the substrate 101 is formed of glass, plastic, or the like and light emitted from the organic light emitting diode E is emitted toward the protective film 120 ( 100 has been described as an example, the present invention is also applicable to the flexible OLED 100 of the bottom emission method in which light emitted from the organic light emitting diode E is emitted toward the substrate 101.

That is, as shown in FIG. 6, the flexible light emitting diode 100 of the bottom emission method allows light emitted from the organic light emitting layer 113 of the organic light emitting diode E to pass through the first electrode 111 to the outside. Therefore, the OLED 100 realizes any image.

At this time, the substrate 101 is made of a plastic or polymer material, the substrate 101 has a refractive index of about 1.5 depending on the polarization of light, the organic electroluminescent diode (E) has a refractive index of about 1.8, The optical compensation layer 200 having a refractive index of 2 to 3 is formed between the organic light emitting diode E and the substrate 101, and is generated at an interface between the substrate 101 and the organic light emitting diode E. Lowers refraction and reflectivity to prevent extinction interference.

Therefore, it is possible to prevent a decrease in luminance and color reproducibility compared to an OLED using a conventional glass substrate (not shown) as a substrate.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

1 is a schematic cross-sectional view of a typical flexible OLED.

2 is a cross-sectional view schematically showing a flexible OLED of the top emission type according to an embodiment of the present invention.

3 is an enlarged cross-sectional view of a portion of FIG. 2;

4 schematically illustrates the absorption or reflection of light between materials having different refractive indices.

5A to 5G are cross-sectional views of manufacturing flexible OLEDs of the top emission type according to the embodiment of the present invention.

6 is a cross-sectional view schematically showing a flexible OLED of a bottom emission type according to an embodiment of the present invention.

Claims (10)

A substrate on which a driving thin film transistor and an organic light emitting diode are formed; A protective film covering the driving thin film transistor and the organic light emitting diode; The light emitted from the organic light emitting diode is transmitted through the first optical compensation layer formed between at least one of the protective film and the organic field diode or between the organic light emitting diode and the substrate. The method of claim 1, The protective film is an inorganic protective layer containing silicon nitride (SiNx), silicon oxide (Si0 ₂ ) or alumina (Al ₂ O ₃ ), polyacrylate, polyimide, polyamide or An organic electroluminescent device which is a plurality of layers in which an organic protective layer containing benzocyclobutene (BCB) is alternately laminated. The method of claim 2, An organic electroluminescent device further comprising a second optical compensation layer between the inorganic protective layer and the organic protective layer. The method of claim 3, wherein The refractive index of the first and second optical compensation layer is larger than the refractive index of the organic light emitting diode and the protective film. The method of claim 3, wherein The refractive index of the first and second optical compensation layer is greater than the refractive index of the organic light emitting diode and the substrate. The method of claim 3, wherein The first and second optical compensation layers have a cancellation interference condition of 2n ₂ t = mλ (n ₂ = refractive index of the optical compensation layer, t = thickness of the optical compensation layer, λ = wavelength of visible light, m = 1, 2, 3 And an organic electroluminescent device having a satisfactory refractive index and thickness satisfying 4 ···). The method of claim 3, wherein The first and second optical compensation layers include an inorganic insulating material including silicon nitride (SiNx), silicon oxide (Si0 ₂ ) or alumina (Al ₂ O ₃ ), polyacrylate, polyimide, An organic light emitting device comprising one selected from organic insulating materials including polyamide and benzocyclobutene (BCB), or alternately stacked between the inorganic insulating material and the organic insulating material. In the first, The substrate is an organic light emitting display device composed of a selected one of a flexible (flexible) glass substrate or plastic. The method of claim 1, The driving thin film transistor may include a semiconductor layer, a gate electrode, a source, and a drain electrode. The method of claim 9, The organic light emitting diode includes an organic light emitting diode including a first electrode, an organic light emitting layer, and a second electrode connected to the driving thin film transistor.

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