KR101608332B1 - Substrate for top emission type oled, method for fabricating thereof and top emission type oled having the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for a top emission type organic light emitting device, a method of manufacturing the same, and a top emission type organic light emitting device including the same, and more particularly, to a method for reducing color shift A method for manufacturing the same, and a top emission type organic light emitting device including the same.
In order to achieve the above object, according to the present invention, there is provided a substrate disposed on one surface of a top emission type organic light emitting device on which light emitted from the organic light emitting device is emitted to the outside, And a light refraction part for refracting the light emitted from the organic light emitting device, and a top emission type organic light emitting device including the same.

Description

Technical Field [0001] The present invention relates to a substrate for a top emission type organic light emitting device, a method of manufacturing the same, a top emission type organic light emitting device including the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for a top emission type organic light emitting device, a method of manufacturing the same, and a top emission type organic light emitting device including the same, and more particularly, to a method for reducing color shift A method for manufacturing the same, and a top emission type organic light emitting device including the same.

The top emission type organic light emitting device emits light to a cathode formed by stacking a metal having a low work function and a transparent electrode unlike a bottom emission type organic light emitting device. In this case, since the thin film transistor for driving the organic light emitting device is formed below the organic light emitting device, the top emission type organic light emitting device can have a relatively higher aperture ratio than the back light emitting type organic light emitting device.

However, as with the back emission type organic light emitting device, the front emission type organic emission device also emits only 20% of the emission amount to the outside, and about 80% of the light is emitted from the sealing glass formed on the cathode of the top emission type organic emission device, And a wave guiding effect due to a difference in refractive index between the organic light emitting layer including the hole injection layer, the electron transport layer, the light emitting layer, the electron transport layer, and the electron injection layer. It is lost due to the total reflection effect due to the difference in refractive index between the sealing glass and the air. That is, the refractive index of the inner organic light emitting layer is 1.7 to 1.8, and the refractive index of the material used as the cathode is about 1.9. At this time, the thicknesses of the two layers are extremely thin to about 200 to 400 nm, and the refractive index of the sealing glass is 1.5, so that a planar waveguide is naturally formed in the organic light emitting device. According to the calculation, the ratio of light lost in the internal waveguide mode due to the above causes is about 45%. The refractive index of the sealing glass is about 1.5 and the refractive index of the outside air is 1.0. Therefore, when the light exits from the sealing glass to the outside, the light incident at a critical angle or more is totally isolated and isolated inside the sealing glass. Is about 35%, so only about 20% of the light emission amount is emitted to the outside.

Conventionally, a micro-cavity structure is applied to a top emission type organic light emitting device in order to increase the luminous efficiency. The microcavity structure is a structure in which an anode is composed of a metal or transparent electrode / metal layer having a high work function, and a microcavity is formed between the anode and the cathode. In such a microcavity structure, light emitted from the organic light emitting element is reflected at the anode and partly reflected at the cathode, and is emitted through the constructive interference and resonance phenomenon in the microcavity. Thus, the front emission efficiency of the top emission type organic light emitting device employing the microcavity structure is increased.

However, there is a problem that the microcavity structure causes a color shift phenomenon in which the color changes as the viewing angle increases.

Korean Registered Patent No. 10-1074797 (October 12, 2011)

SUMMARY OF THE INVENTION It is an object of the present invention to provide a front emission type organic light emitting display capable of reducing a color shift phenomenon in which a color changes as a viewing angle increases, A method for manufacturing the same, and a top emission type organic light emitting device including the same.

In order to achieve the above object, according to the present invention, there is provided a substrate disposed on one surface of a top emission type organic light emitting device on which light emitted from the organic light emitting device is emitted to the outside, And a light refraction part for refracting light emitted from the organic light emitting device is formed on the substrate.

Here, the light refracting portion may be a groove formed inward from one side of the substrate.

At this time, the light refracting portion may be filled with air or a material having the same refractive index as the cathode of the organic light emitting element.

Further, when the refractive index of the substrate is n ₁ , the width w, the depth d, and the pitch p between adjacent optical refracting portions of the optical refracting portion may satisfy the following relational expression.

[Relational expression]

d: w: p≤2: 1: p c

^1/2 + 2 / (n ₁ ² -1) ^1/2 = p _c

In this case, when the refractive index of the substrate is 1.5, the pitch p of the optical refracting portion may be 1.15 times or less of the depth d of the optical refracting portion.

According to another aspect of the present invention, there is provided a method of manufacturing a substrate on one surface of a top emission type organic light emitting device, wherein light emitted from the organic light emitting device is emitted to the outside, And a light refraction part for refracting the light emitted from the organic light emitting device is formed in at least one part of the one surface facing the organic light emitting device.

In addition, the present invention provides a top emission type organic light emitting device, wherein the substrate for the top emission type organic light emitting device is provided as a sealing glass.

Here, the organic light emitting diode may be bonded to the substrate via a filler adhesive.

According to the present invention, a plurality of light refracting parts for changing the direction of light emitted from the organic light emitting device are formed inward from one surface facing the organic light emitting device to induce color mixing, It is possible to reduce the phenomenon of color shift that changes.

Further, according to the present invention, it is possible to prevent the occurrence of image blur by controlling the width w, the depth d and the pitch p between the light refractions, Can be removed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view of a top emission type organic light emitting device including a top emission type organic light emitting device substrate according to an exemplary embodiment of the present invention. FIG.
2 is an image showing the degree of occurrence of image blur according to the pitch (p) / depth (d) of the optical refracting portion according to the embodiment of the present invention.
FIGS. 3 to 6 are schematic views illustrating a method of manufacturing a top emission type organic light emitting device substrate according to an exemplary embodiment of the present invention.

Hereinafter, a top emission type organic light emitting device substrate, a method of manufacturing the same, and an organic light emitting device including the same will be described in detail with reference to the accompanying drawings.

In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1, a top emission type organic light emitting diode (OLED) substrate 100 according to an exemplary embodiment of the present invention includes a top emission type organic light emitting device 10 emitting light in the direction of the cathode 14 A substrate 14 facing the cathode 14 and serving as a path for protecting the top emission type organic light emitting diode 10 from the external environment and discharging light emitted toward the cathode 14 to the outside, That is, it is a substrate used as an encapsulation glass of the top emission type organic light emitting diode 10.

The organic light emitting device 10 includes an anode 12, an organic light emitting layer 13, and a cathode disposed between the substrate 100 and the substrate glass 11 opposed to the substrate 100 according to the embodiment of the present invention, (14). In this case, the top emission type organic light emitting diode 10 may have a micro-cavity structure for increasing the luminous efficiency. Accordingly, the anode 12 must be formed of a material that reflects light emitted from the organic light emitting layer 13 toward the front surface, that is, toward the cathode 14, and has a work function (for example, work function must be formed of large material. For example, the anode 12 may be formed of a metal material such as Au, In, or Sn, and may have a multi-layered structure of a metal layer and an oxide transparent electrode thin film such as indium tin oxide (ITO) Can also be formed.

Further, the cathode 14 is formed of a material having a small work function so that electron injection into the organic light emitting layer 13 can be performed well. In particular, since the organic light emitting device 10 according to the embodiment of the present invention has a front light emitting structure, the cathode 14 may be formed of Al, Al: Li or Mg: Ag A semitransparent electrode of a metal thin film of ITO and an oxide transparent electrode thin film such as ITO.

The organic light emitting layer 13 is formed to include a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer which are sequentially stacked on the anode 12. When a forward voltage is applied between the anode 12 and the cathode 14 according to the structure of the organic light emitting layer 13, electrons are moved from the cathode 14 to the light emitting layer through the electron injection layer and the electron transport layer, The hole is moved from the light emitting layer 12 to the light emitting layer through the hole injecting layer and the hole transporting layer. The electrons and holes injected into the light emitting layer are recombined in the light emitting layer to generate excitons. The excitons emit light while transitioning from an excited state to a ground state. At this time, the brightness of the emitted light is proportional to the amount of current flowing between the anode 12 and the cathode 14.

Meanwhile, the substrate 100 according to the embodiment of the present invention, which is applied to the top emission type organic light emitting device 10 and the sealing glass, may be bonded to each other via the filler 15. The filling adhesive 15 is preferably made of a material having the same refractive index as that of the cathode 14 in contact with the cathode 14 of the top emission type organic light emitting diode 10. For example, the filler adhesive 15 may be made of a UV resin.

As described above, the substrate 100 according to the embodiment of the present invention, which is applied to the sealing glass of the top emission type organic light emitting device 10, is formed on one surface facing the organic light emitting device 10, And a light refraction unit 110 formed on at least one side of the cathode 14 facing the cathode 14 to refract and scatter light emitted from the organic light emitting device 10. [ Here, the substrate 100 according to the embodiment of the present invention may be made of soda lime glass, alumino-silicate glass, or the like.

On the other hand, the light refraction part 110 is provided with a groove formed inward from one surface of the substrate 100 facing the cathode 14. For example, the photoreflecting portion 110 may be formed as a semi-oval or rhomboidal groove. Further, in the embodiment of the present invention, such a photoreflecting portion 110 is formed at a plurality of spaced apart from each other along one surface of the substrate 100.

In this case, when the substrate 100 and the organic light emitting diode 10 are bonded to each other, due to the structure of the light refracting portion 110 having a groove shape, the inside of the groove forming the light refracting portion 110 is filled with air . As the substrate 100 and the organic light emitting diode 10 are bonded to each other through the filler 15, the substrate 100 and the organic light emitting diode 10 are formed in the grooves forming the light refraction unit 110, The filling adhesive 15 made of a material having the same refractive index as the cathode 14 may flow and be filled in the bonding process.

The light refraction unit 110 changes the direction of the light emitted in the normal direction of the organic light emitting diode 10 to a direction deviating from the normal direction and changes the direction of the light emitted in the direction deviating from the normal direction to the normal direction Change it. That is, the photoreflecting portion 110 serves to induce color mixing by changing the direction of light emitted according to the viewing angle. Accordingly, in order to increase the luminous efficiency, the sealing glass of the top emission type organic light emitting diode 10 to which the micro-cavity structure is applied is provided with the light refraction portion 110 according to the embodiment of the present invention, (100), it is possible to reduce a color change, that is, a color shift phenomenon according to a change in viewing angle generated in the top emission type organic light emitting diode (10).

A part of the light emitted from the organic light emitting element 10 does not meet the light refraction part 110 but is incident on the interface between the substrate 100 and the air and the interface between the substrate 100 and the cathode 14 or the filling adhesive 15 And is reflected and scattered by the optical refracting portion 110. The image is blurred due to such light and the image quality of the display panel using the organic light emitting device 10 is lowered.

In order to solve such an image blurring problem, in order to control the light emitted above the angle? _C at which the total reflection occurs at the interface between the air and the substrate 100 to be scattered in the light refracting portion 110, It is preferable to control the width w, the depth d and the pitch p between adjacent photorefractive portions of the photoreflecting portion 110 so as to satisfy the following relational expression when the refractive index of the photoreceptor 100 is n ₁ .

[Relational expression]

d: w: p ≤ 2: 1: p c

^1/2 + 2 / (n ₁ ² -1) ^1/2 = p _c

That is, according to the relational expression, the depth d of the photoreflecting portion 110 is formed to be twice or less than the width w, so that a double image can be removed. The pitch p of the photoreflecting portion 110 is 1.15 times or less the depth d of the photoreflecting portion 110 in accordance with the above relational expression when the refractive index n ₁ of the substrate 100 is 1.5 The formation of image blur can be prevented.

Here, the above relation is derived as follows.

The angle? Determined by the width w, the depth d and the pitch p of the photoreflecting portion 110,

tan? = (p-w / 2) d

At this time, in order to prevent image blur generation,? Should be smaller than the critical angle? _C of total reflection.

θ <θ _c

Based on Snell's law, critical angle conditions and the above equations, the following results are obtained.

tan? = n ₂ / (n ₁ ² - n ₂ ² ) ^1/2 > tan? = (pw / 2) d

n ₂ / (n ₁ ² - n ₂ ² ) ^1/2 > (pw / 2) d

_{w / 2 + n 2 d (} n 1 2 - n 2 2) 1/2> p, w / 2 + n 2 d (n 1 2 - n 2 2) 1/2 = p c

As is known, if a dual image is not visible,

d: w? 2: 1

And since the refractive index of air is 1,

n ₂ = 1

^1/2 + 2 / (n ₁ ² -1) ^1/2 = p _c , d: w: p 2: 1: p _c

For example, when the refractive index n ₁ of the substrate 100 is 1.5,

p? ^1/2 + 2 / (1.5 ² -1) ^1/2 = 2.29

d: w: p? 2: 1: 2.29

That is, the depth d of the photoreflecting portion 110 should be not more than twice the width w and the pitch p should be not more than 1.15 times the depth d in order to prevent the occurrence of the image blur and the double image.

2 is an image showing the degree of image blur according to the pitch (p) / depth (d) of the optical refracting portion according to the embodiment of the present invention.

(a), a plurality of photorefractive portions formed along one surface of the substrate with a depth of 20.7 μm, a width of 11.1 μm and a pitch of 23.5 μm. At this time, the depth d of the photoreflecting portion is 1.86 times the width w and the pitch p is 1.14 times the depth d, all of the above relational expressions are satisfied. In this case, when a substrate having a light refracting portion having a size satisfying the above-described [relational expression] is used as an encapsulating glass for an organic light emitting diode as shown in the lower image of FIG. It can be visually confirmed that various shapes to be implemented are clearly displayed.

On the other hand, in the case of (b), a plurality of photorefractive portions formed along one side of the substrate with a depth of 9.5 μm, a width of 7.31 μm, and a pitch of 29.44 μm are shown. At this time, the depth d of the photoreflecting portion is 1.3 times the width w and satisfies the above relation, but the pitch p is 3.1 times the depth d and does not satisfy the above relational expression . In this case, it is visually confirmed that an image blur (indicated by a red circle) is severely generated as shown in the lower image of (b).

As described above, according to the embodiment of the present invention, by controlling the width w, the depth d and the pitch p between the light refracting portions 110 of the light refracting portion 110 according to the above relational expression, blur can be prevented from occurring and a double image can be removed.

Hereinafter, a method for manufacturing a top emission type organic light emitting device substrate according to an embodiment of the present invention will be described with reference to FIGS. 3 to 6. FIG.

A method of manufacturing a substrate for a top emission type organic light emitting diode according to an exemplary embodiment of the present invention includes the steps of forming at least one portion of one surface of a substrate 100 facing the organic light emitting device (10 in FIG. 1) through a photolithography process, (110 in FIG. 1) for refracting the light emitted from the organic light emitting element (10 in FIG. 1) is formed in the inward direction.

First, as shown in Fig. 3, a photoresist (PR) 20 is applied to the surface of the substrate 100. Then, as shown in Fig. 4, a photoresist 20 (not shown) is formed by using a photomask (not shown) so as to expose a plurality of regions of the surface of the substrate 100 on which the photoreflecting portion 110 ). 5, etching is performed on the surface of the exposed substrate 100 with, for example, dilute hydrofluoric acid (HF) as an etchant to form a semi-oval or rhombic light refraction part (110) is formed inward from one side of the substrate (100). At this time, the specific shape of the photoreflecting portion 110 can be controlled by adjusting the etchant concentration and the etching rate. 6, when the photoresist 20 remaining on the surface of the substrate 100 is removed through a strip process, a plurality of photorefractive portions 110 are formed on one surface The fabrication of the substrate 100 for the top emission type organic light emitting diode is completed.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. This is possible.

Therefore, the scope of the present invention should not be limited by the described embodiments, but should be determined by the scope of the appended claims as well as the appended claims.

100: substrate for organic light emitting diode for front emission, 110:
10: organic light emitting element for front emission 11: substrate glass
12: anode 13: organic light emitting layer
14: cathode 15: filled adhesive
20: Photoresist

Claims (8)

A substrate disposed on one surface of a top emission type organic light emitting device, wherein light emitted from the organic light emitting device is emitted to the outside,
A light refraction part for refracting the light emitted from the organic light emitting device is formed on at least one part of one surface facing the organic light emitting device,
Wherein a width (w), a depth (d) and a pitch (p) between neighboring optical refraction portions of the light refraction portion satisfy the following relational expression when the refractive index of the substrate is n _1: / RTI &gt;
[Relational expression]
d: w: p≤2: 1: p c
^1/2 + 2 / (n ₁ ² -1) ^1/2 = p _c
The method according to claim 1,
Wherein the light refracting portion is a groove formed in a direction inward from one surface of the substrate.
3. The method of claim 2,
Wherein the light refraction part is filled with air or a material having the same refractive index as the cathode of the organic light emitting device.
delete The method according to claim 1,
And the pitch p of the light refraction portion is 1.15 times or less the depth d of the light refraction portion when the refractive index of the substrate is 1.5.
A method for fabricating a substrate on one surface of a top emission type organic light emitting device, wherein light emitted from the organic light emitting device is emitted to the outside,
Forming a light refracting portion in the inward direction for refracting light emitted from the organic light emitting element in at least one portion of one surface facing the organic light emitting element through a photolithography process,
Wherein the light refracting portion is formed such that a width w, a depth d, and a pitch p between neighboring light refracting portions satisfy the following relational expression when the refractive index of the substrate is n ₁ : A method of manufacturing a substrate for a top emission type organic light emitting device.
[Relational expression]
d: w: p≤2: 1: p c
^1/2 + 2 / (n ₁ ² -1) ^1/2 = p _c
A top emission type organic light emitting device, comprising: the top emission type organic light emitting device substrate according to claim 1 as an encapsulating glass.
8. The method of claim 7,
And is bonded to the substrate via a filler adhesive.

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