BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure relates to an organic light emitting display device, and, more particularly, to an organic light emitting display device improving light emitting efficiency by reducing an amount of light that dissipates while the light generated from an emission layer is discharged to the outside environment.

Description of the Related Art

An organic light emitting display device is a self-emission display device which has an organic light emitting diode that emits light to display an image. Since the organic light emitting display device has characteristics such as low power consumption, high luminance, and a high response speed, the organic light emitting display device currently receives attention as a display device.

In general, in the organic light emitting display device, a portion of the device generating light is called a display unit, and the display unit includes a hole injection electrode, an emission layer, and an electron injection electrode. In the organic light emitting display device, holes supplied from the hole injection electrode and electrons supplied from the electron injection electrode are coupled with each other in the emission layer to generate light. Generally, the hole injection electrode is an anode, and the electron injection electrode is a cathode.

However, the display unit can be easily damaged by an external gas such as oxygen or moisture, and the display unit may deteriorate due to contact with oxygen or moisture. Accordingly, in order to prevent oxygen or moisture from penetrating from the outside, an encapsulation structure for sealing and protecting the display unit is required.

As an example of such an encapsulation structure, an encapsulation layer, specifically a thin film encapsulation layer, in which inorganic layers and organic layers are alternately laminated is adopted. That is, the encapsulation layer, in which inorganic layers and organic layers are alternately laminated, is formed on the display unit, which is formed on a substrate to seal the display unit and thus protect the display unit. Here, the organic layer mainly functions to give flexibility to a flat panel display, and the inorganic layer mainly serves to prevent oxygen or moisture from penetrating into the device.

However, when the light generated from the emission layer is discharged to the outside environment, a large amount of light dissipates while passing through a laminated structure such as the encapsulation layer disposed on the emission layer. The light efficiency of the organic light emitting display device is not good because the light dissipates. Accordingly, in order to increase the light efficiency in the organic light emitting display device, dissipation of the light needs to be minimized.

SUMMARY OF THE INVENTION

The present disclosure has been made in an effort to provide an organic light emitting display device having improved light extraction efficiency by properly controlling a refractive index difference between a display unit and an encapsulation layer to properly establish a resonance condition.

Further, the present disclosure has been made in an effort to provide an organic light emitting display device including a light efficiency reduction preventing layer between the display unit and the encapsulation layer.

An embodiment of the present disclosure provides an organic light emitting display device, including: a substrate; a display unit disposed on the substrate; a light extraction reduction preventing layer disposed on the display unit; and an encapsulation layer disposed on the light extraction reduction preventing layer.

The encapsulation layer may have a structure in which a plurality of inorganic layers and a plurality of organic layers are alternately laminated.

A thickness of the organic layers may be larger than a thickness of the inorganic layers.

A refractive index of the encapsulation layer may be in the range of from about 1.5 to about 2.0.

A capping layer may be disposed between the display unit and the light extraction reduction preventing layer.

A thickness of the capping layer may be in the range of from about 20 nm to about 200 nm.

The capping layer may comprise at least one selected from a group consisting of tris(8-hydroxyquinolinato) aluminum (Alq3), ZnSe, 2,5-bis(6′-(2′,2″-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole, 4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD), and 1,1-bis[di-(4-tolylamino)phenyl] cyclohexane (TAPC).

A refractive index of the capping layer may be in the range of from about 1.6 to about 3.0.

A refractive index of the light extraction reduction preventing layer may be in the range of from about 1.1 to less than about 1.5.

The light extraction reduction preventing layer may comprise at least one selected from CaF2, NaF, Na3AlF6, SiOx, AlF3, LiF, MgF2, and IF3.

A thickness of the light extraction reduction preventing layer may be in the range of from about 20 nm to about 200 nm.

The display unit may include a first electrode formed on the substrate; an emission layer formed on the first electrode; and a second electrode formed on the emission layer.

Another embodiment of the present disclosure provides a manufacturing method of an organic light emitting display device, including: forming a display unit on a substrate; forming a light extraction reduction preventing layer on the display unit; and forming an encapsulation layer on the light extraction reduction preventing layer.

The manufacturing method of an organic light emitting display device may further include forming a capping layer before the forming of the light extraction reduction preventing layer and after the forming of the display unit.

In the forming of the encapsulation layer, laminating inorganic layers and laminating organic layers may be alternately performed one or more times.

A refractive index of the capping layer may be in the range of from about 1.6 to about 3.0.

A refractive index of the light extraction reduction preventing layer may be in the range of from about 1.1 or more to less than about 1.5.

Yet another embodiment of the present disclosure provides an organic light emitting display device, including: a substrate; a first electrode disposed on the substrate; an emission layer disposed on the first electrode; a second electrode formed on the emission layer; a capping layer disposed on the second electrode; a light extraction reduction preventing layer disposed on the capping layer; and an encapsulation layer disposed on the light extraction reduction preventing layer, in which a refractive index of the light extraction reduction preventing layer is lower than a refractive index of the capping layer and lower than a refractive index of the encapsulation layer.

According to an embodiment of the present disclosure, a light extraction reduction preventing layer is disposed between a display unit and an encapsulation layer, and thus while light generated from an emission layer is discharged to the outside environment, resonance efficiently occurs reducing light dissipation, thereby improving light emission efficiency of the organic light emitting display device. Particularly, in the case where a capping layer having a high refractive index is disposed on the display unit, the light extraction reduction preventing layer is disposed between the capping layer and the encapsulation layer and thus a difference in a refractive index between the capping layer and the encapsulation layer occurs, and as a result, a resonance condition can be efficiently established during a light extraction process. As a result, it is possible to improve light emission efficiency by improving light extraction efficiency.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

