KR100982312B1 - Organic light emitting diode display - Google Patents

Abstract

The present invention relates to an organic light emitting display device, wherein the organic light emitting display device includes an organic light emitting device including a first electrode, an organic light emitting layer formed on the first electrode, and a second electrode formed on the organic light emitting layer; Dual brightness enhancement film (DBEF) formed on the second electrode of the organic light emitting device, a first polarizing plate formed on the reflective polarizing film, cholesteric liquid crystal formed on the first polarizing plate , A CLC) film, a phase retardation plate which is a quarter wave plate formed on the cholesteric liquid crystal film, and a second polarizing plate formed on the phase retardation plate.

Cholesteric liquid crystal film, reflective polarizing film, polarizing plate, phase retardation plate, organic light emitting display device

Description

Organic Light Emitting Display {ORGANIC LIGHT EMITTING DIODE DISPLAY}

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

The organic light emitting diode display includes a plurality of organic light emitting diodes having a hole injection electrode, an organic emission layer, and an electron injection electrode. In the organic light emitting layer, light is emitted by energy generated when an exciton generated by combining electrons and holes falls from an excited state to a ground state, and the organic light emitting diode display forms an image by using the energy.

Therefore, the organic light emitting diode display has a self-luminous property and, unlike the liquid crystal display, does not require a separate light source, thereby reducing thickness and weight. In addition, the organic light emitting diode display has attracted attention as a next-generation display device for portable electronic devices because it exhibits high quality characteristics such as low power consumption, high luminance, and high response speed.

In general, at least one of the hole injection electrode and the electron injection electrode of the organic light emitting display may reflect light, and reflects not only the light generated from the organic light emitting layer but also the light flowing from the outside. Therefore, when the organic light emitting diode display is used in a bright place, there is a problem in that black expression and contrast are poor due to external light reflection.

In order to solve this problem, there is a configuration in which a polarizing plate and a phase retardation plate are disposed to suppress reflection of external light. However, when the polarizing plate and the phase retardation plate are disposed to suppress external light reflection, a large portion of light generated in the organic light emitting layer is also lost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problem, and an object of the present invention is to provide an organic light emitting display device which minimizes light loss generated in an organic light emitting layer while suppressing external light reflection.

The organic light emitting diode display according to the present invention includes an organic light emitting device including a first electrode, an organic light emitting layer formed on the first electrode, and a second electrode formed on the organic light emitting layer, and a reflection on which a second electrode of the organic light emitting device is formed. Dual brightness enhancement film (DBEF), a first polarizing plate formed on the reflective polarizing film, a cholesteric liquid crystal (CLC) film formed on the first polarizing plate, the cholesteric liquid crystal film And a phase delay plate that is a quarter wave plate formed on the second polarizing plate.

The polarization axis of the first polarizing plate and the polarization axis of the second polarizing plate may cross each other.

The polarization axis of the first polarizing plate and the polarization axis of the reflective polarizing film may be identical to each other.

The cholesteric liquid crystal film may pass one circularly polarized light and the other circularly polarized light among right circularly polarized light and left circularly polarized light.

Light linearly polarized through the second polarizer may be changed into circular polarized light while passing through the phase retardation plate.

The circularly polarized light passing through the phase retardation plate may pass through the cholesteric liquid crystal film.

Linearly polarized light having a polarization axis in the same direction as the optical axis of the cholesteric liquid crystal film may be changed into circularly polarized light when passing through the cholesteric liquid crystal film.

The polarization axis of the first polarizing plate and the optical axis of the cholesteric liquid crystal film may be identical to each other.

The linearly polarized light passing through the first polarizing plate is changed into circularly polarized light while passing through the cholesteric liquid crystal film, and the circularly polarized light passing through the cholesteric liquid crystal film is passed through the phase retardation plate while the polarization axis of the second polarizing plate is Can be changed to linearly polarized light having the same axial direction as.

The organic light emitting diode display may further include an additional phase retardation plate disposed between the organic light emitting diode and the reflective polarizing film.

The additional phase retardation plate is a quarter wave plate and can convert linearly polarized light into circularly polarized light through the reflective polarizing film.

According to the present invention, the organic light emitting diode display can minimize the loss of light generated in the organic light emitting layer while suppressing reflection of external light.

In addition, the organic light emitting diode display may improve black expression and contrast. That is, display characteristics of the organic light emitting diode display may be improved.

In addition, the OLED display can reduce power consumption and improve lifespan.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In addition, since the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of description, the present invention is not necessarily limited to the illustrated.

In order to clearly describe the present invention, parts irrelevant to the description are omitted, and like reference numerals designate like elements throughout the specification.

In addition, in order to clearly represent the various layers and areas in the drawings it is shown by enlarging the thickness. Like parts are designated by like reference numerals throughout the specification. Whenever a portion such as a layer, film, region, plate, or the like is referred to as being "on" or "on" another portion, it includes not only the case where it is "directly on" another portion but also the case where there is another portion in between. On the contrary, when a part is "just above" another part, there is no other part in the middle.

As shown in FIG. 1, the organic light emitting diode display 100 according to an exemplary embodiment of the present invention may include a driving circuit DC, an organic light emitting diode L1, a first phase retardation plate 586, and a reflective polarizing film. (dual brightness enhancement film, DBEF) 585, first polarizer 584, cholesteric liquid crystal (CLC) film 583, second phase retardation plate 582, and second polarizer 581. ).

The first phase retardation plate 586, the reflective polarizing film 585, the first polarization plate 584, the cholesteric liquid crystal film 583, the second phase retardation plate 582, and the second polarization plate 581 are It is disposed sequentially on the organic light emitting element (L1).

The driving circuit unit DC and the organic light emitting element L1 are generally formed on the first substrate 51. That is, the first substrate 51 includes a substrate member 511, a driving circuit portion DC formed on the substrate member 511, and an organic light emitting element L1 formed on the driving circuit portion DC.

The driving circuit part DC generally has an arrangement structure as shown in FIG. 2. That is, as shown in FIG. 2, the driving circuit unit DC includes at least two thin film transistors T1 and T2 and at least one storage capacitor C1. The thin film transistor basically includes a switching transistor T1 and a driving transistor T2.

The switching transistor T1 is connected to the scan line SL1 and the data line DL1, and converts the data voltage input from the data line DL1 into the driving transistor T2 according to the switching voltage input to the scan line SL1. send. The storage capacitor C1 is connected to the switching transistor T1 and the power supply line VDD and stores a voltage corresponding to a difference between the voltage received from the switching transistor T1 and the voltage supplied to the power supply line VDD.

The driving transistor T2 is connected to the power line VDD and the storage capacitor C1 to output an output current I _OELD proportional to the square of the difference between the voltage stored in the storage capacitor C1 and the threshold voltage. ) And the organic light emitting element L1 emits light by the output current I _OLED .

Referring again to FIG. 1, the driving transistor T2 includes a source electrode 533, a drain electrode 532, and a gate electrode 531.

The organic light emitting element L1 includes a first electrode 544, an organic emission layer 545 formed on the first electrode 544, and a second electrode 546 formed on the organic emission layer 545. In general, the first electrode 544 becomes an anode electrode, and the second electrode 546 becomes a cathode electrode.

The first electrode 544 of the organic light emitting element L1 is connected to the drain electrode 532 of the driving transistor T2.

The configuration of the driving circuit unit DC and the organic light emitting element L1 is not limited to the above-described example, and may be variously modified to a known configuration that can be easily implemented by those skilled in the art.

The first phase delay plate 586 and the second phase delay plate 582 change the phase of light passing through. Specifically, in the embodiment according to the present invention, a quarter wave plate is used for the first phase retardation plate 586 and the second phase retardation plate 582, and converts linearly polarized light into circularly polarized light.

The first polarizer 584 and the second polarizer 581 linearly polarize light. Specifically, the first polarizing plate 584 and the second polarizing plate 581 pass light corresponding to each polarization axis, and absorb light that does not coincide with the polarization axis. That is, when light passes through the first polarizing plate 584 and the second polarizing plate 581, the light is linearly polarized in the first polarization axis direction of the first polarizing plate 584 and the second polarization axis direction of the second polarizing plate 581, respectively. The luminance is reduced by the light lost by the first and second polarizing plates 584 and 581.

In one embodiment according to the present invention, the first polarizer 584 has a first polarization axis, and the second polarizer 581 has a second polarization axis that intersects the first polarization axis.

The first polarizing plate 584 and the first phase retardation plate 586 are circularly polarized to the left when the direction linearly polarized light formed while passing through the first polarizing plate 584 passes through the first phase retardation plate 586 again (hereinafter, left circularly polarized light). Are arranged together).

On the contrary, when the left circularly polarized light passes through the first phase retardation plate 586, the linearly polarized light is linearly polarized in the same direction as the first polarization axis of the first polarizing plate 584. That is, the left circularly polarized light is linearly polarized through the first phase retardation plate 586, and the linearly polarized light may pass through the first polarizing plate 584 as it is.

However, circularly polarized light (hereinafter referred to as right circularly polarized light) to the right passes through the first phase retardation plate 586 and linearly polarizes in the direction crossing the first polarization axis of the first polarizing plate 584. This linearly polarized light does not pass through the first polarizing plate 584.

Also, the second polarizing plate 581 and the second phase retardation plate 582 are arranged to be right circularly polarized when the linearly polarized light formed while passing through the second polarizing plate 581 passes through the second phase retardation plate 582 again.

On the contrary, when the right circularly polarized light passes through the second phase retardation plate 582, the linearly polarized light is linearly polarized in the same direction as the second polarization axis of the second polarizing plate 581. This linearly polarized light can pass through the second polarizing plate 581 as it is.

However, when the left circularly polarized light passes through the second phase retardation plate 582, the linearly polarized light is linearly polarized in the direction crossing the second polarization axis of the second polarization plate 581. That is, the left circularly polarized light passes linearly through the second phase retardation plate 582, and the linearly polarized light does not pass through the second polarizing plate 581.

Reflective polarizing film (DBEF) 585 also passes light that coincides with the polarization axis and reflects light that does not coincide with the polarization axis. The first polarizing plate 584 and the second polarizing plate 581 are different from the reflective polarizing film 585 in that they absorb light that does not coincide with the polarization axis.

In addition, the reflective polarizing film 585 is disposed between the first polarizing plate 584 and the first phase retardation plate 586 and has the same polarization axis as that of the first polarizing plate 584.

Accordingly, the linearly polarized light formed through the reflective polarizing film 585 may pass through the first polarizing plate 584 as it is, and the linearly polarized light formed through the first polarizing plate 584 may pass through the reflective polarizing film 585 as it is.

The cholesteric liquid crystal (CLC) film 583 is disposed between the second phase retardation plate 582 and the first polarizing plate 584. In addition, the cholesteric liquid crystal film 583 is disposed so that the optical axis in the direction opposite to the first polarizing plate 584 coincides with the first polarizing axis of the first polarizing plate 584.

The cholesteric liquid crystal forms a layered structure like the smectic liquid crystal, but the molecules of the long axis have an equilibrium arrangement similar to that of the nematic liquid crystal in plane. Specifically, in one plane, thin and long molecules are arranged neatly in the direction of the major axis, and the structure in which the molecular axes are slightly deviated as the molecules progress in the direction perpendicular to the plane, that is, the molecules The arrangement is like a spiraling helical shape. Therefore, the whole liquid crystal has a spiral structure. Accordingly, the cholesteric liquid crystal has characteristics such as optical sensitivities, selective light scattering, and circular polarization dichroism.

Therefore, the cholesteric liquid crystal film 583 can selectively transmit or reflect circularly polarized light. Specifically, the cholesteric liquid crystal film 583 according to the embodiment of the present invention passes right circularly polarized light and reflects left circularly polarized light. However, the present invention is not limited thereto. Therefore, the cholesteric liquid crystal film may pass left circularly polarized light and reflect right circularly polarized light, and may selectively transmit or reflect light differently from both sides of the cholesteric liquid crystal film.

In addition, the cholesteric liquid crystal film 583 passes circularly polarized light in the same direction as circularly polarized light formed by sequentially passing through the second polarizing plate 581 and the second phase retardation plate 582, and circularly polarized light in the other direction is Reflect. Here, circularly polarized light formed by sequentially passing through the second polarizing plate 581 and the second phase delay plate 582 is right circularly polarized light.

In addition, as described above, since the optical axis of the cholesteric liquid crystal film 583 and the first polarization axis of the first polarizing plate 584 coincide, the linearly polarized light formed through the first polarizing plate 584 is mostly cholesteric liquid crystal film ( Passes through 583) and changes into a right polarized light. The circularly polarized light is linearly polarized in a direction coinciding with the polarization axis of the second polarizing plate 581 while passing through the second phase retardation plate 582, so that the right polarized light can pass through the second polarizing plate 581 as it is.

As a result, the light passing through the first polarizing plate 584 passes through the cholesteric liquid crystal film 583 and the second phase retardation plate 582, thereby minimizing the loss to pass through the second polarizing plate 581. .

The second substrate 52 covers the first substrate 51 on which the organic light emitting element L1 and the driving circuit unit DC are formed. In addition, the second substrate 52 includes a first phase retardation plate 586, a reflective polarizing film 585, a first polarizing plate 584, and a cholesteric liquid crystal film 583, which are sequentially formed on the organic light emitting element L1. ), The second phase retardation plate 582, and the second polarizing plate 581 are also covered. However, the present invention is not necessarily limited thereto. Accordingly, the first phase retardation plate 586, the reflective polarizing film 585, the first polarization plate 584, the cholesteric liquid crystal film 583, the second phase retardation plate 582, and the second polarization plate 581. ) May be formed on the second substrate 52.

In addition, although not illustrated, the organic light emitting diode display 100 may further include an adhesive layer disposed between the second electrode 546 and the first phase retardation plate 586 of the organic light emitting diode L1.

By such a configuration, the organic light emitting diode display 100 may minimize the loss in the process of emitting light generated in the organic light emitting layer 545 (shown in FIG. 1) to the outside while effectively suppressing external light reflection.

In addition, the organic light emitting diode display 100 may improve black expression and contrast. That is, display characteristics of the organic light emitting diode display 100 may be improved.

In addition, the organic light emitting diode display 100 may reduce power consumption and improve lifespan.

Hereinafter, referring to FIG. 3, a principle in which reflection of external light is suppressed in the OLED display 100 will be described.

First, external light is linearly polarized in the second polarization axis direction (hereinafter, referred to as a second direction) of the second polarizing plate 581 while passing through the second polarizing plate 581. The linearly polarized light becomes right circularly polarized light while passing through the second phase retardation plate 582 and passes through the cholesteric liquid crystal film 583 as it is.

The right circularly polarized light that has passed through the cholesteric liquid crystal film 583 is linearly polarized in the first polarization axis direction (hereinafter, referred to as a first direction) of the first polarizing plate 584 while passing through the first polarizing plate 584. In this process, much of the light is lost. This is because only the light in the direction coinciding with the first polarization axis of the first polarizing plate 584 of the right circularly polarized light incident on the first polarizing plate 584 is absorbed by the first polarizing plate.

Therefore, the organic light emitting diode display 100 may reduce the reflection of external light by dissipating a substantial portion of light introduced from the outside in the first polarizing plate 584.

The linearly polarized light passing through the first polarizing plate 584 passes through the reflective polarizing film 585 without substantial loss and passes through the first phase retardation plate 586 to become left circularly polarized light. The left circularly polarized light is reflected by the second electrode 546 or the first electrode 544 (shown in FIG. 1) of the organic light emitting element L1 (shown in FIG. 1), shifted 180 degrees out of phase, and then changed into right circularly polarized light. It faces the first phase retardation plate 586.

In addition, the right polarized light is out of phase while passing through the first phase retardation plate 586. That is, the light passing through the first phase retardation plate 586 has various mixed direction components. Some of this light is linearly polarized while passing through the reflective polarizing film 585, and the rest is reflected and directed back to the first phase retardation plate 586.

As described above, the light is circulated between the reflective polarizing film 585 and the second electrode 546 or the first electrode 544 of the organic light emitting element L1, and a part of the reflective polarizing film 585 is formed. The process repeats the process of linear polarization as it passes through and the rest of it is reflected back. In addition, the first phase retardation plate 586 changes the phase of the circulating light so that the reflective polarizing film 585 can continuously linearly polarize a part of the light. Therefore, the light initially reflected by the reflective polarizing film 585 also becomes linearly polarized light while passing through the reflective polarizing film 585.

The linearly polarized light that has passed through the reflective polarizing film 585 passes through the first polarizing plate 584 and passes through the cholesteric liquid crystal film 583 to become right circularly polarized light. This is because the optical axis of the cholesteric liquid crystal film 583 coincides with the polarization axis of the first polarizing plate 584, and the cholesteric liquid crystal film 583 passes only right circularly polarized light. The right circularly polarized light formed while passing through the cholesteric liquid crystal film 583 is linearly polarized in the second direction while passing through the second phase retardation plate 582, and passes through the second polarizing plate 581 to the outside.

As described above, the organic light emitting diode display 100 extinguishes a substantial portion of the light introduced from the outside through the first polarizing plate and the second polarizing plate, which are disposed to cross each other, and only a part of the organic light emitting display 100 is reflected and comes out again.

Therefore, the organic light emitting diode display 100 may effectively suppress reflection of external light.

On the other hand, the principle that the light emitted from the organic light emitting element (L1) is emitted to the outside is the light introduced from the outside is reflected by the second electrode 546 or the first electrode 544 of the organic light emitting element (L1) It's the same with the principle of going out again.

Therefore, the loss in the process of emitting the light generated by the organic light emitting layer 545 to the outside can be minimized.

In addition, the first polarizing plate 584 and the reflective polarizing film 585 disposed side by side change the light passing through the same polarization axis into linearly polarized light, but there is a difference in its role. That is, the first polarizing plate 584 serves to dissipate light introduced from the outside, and the reflective polarizing film 585 passes through the first polarizing plate 584 without losing light generated by the organic light emitting element L1. To help them go outside.

In addition, one embodiment according to the present invention includes, but is not limited to, a first phase delay plate 586. Accordingly, the first phase delay plate 586 may be omitted in some cases. The first phase retardation plate 586 changes the phase when the light cycles between the reflective polarizing film 585 and the electrodes 544 and 546 of the organic light emitting element L1. Help them pass through (585) more effectively. However, even without the first phase delay plate 585, the light may circulate between the reflective polarizing film 585 and the electrodes 544 and 546 of the organic light emitting element L1.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the following claims. Those who are engaged in the technology field will understand easily.

1 is a partial cross-sectional view of an organic light emitting diode display according to an exemplary embodiment.

FIG. 2 is a layout view illustrating a circuit arrangement of a driving circuit unit and an organic light emitting diode of the organic light emitting diode display of FIG. 1.

FIG. 3 is a cross-sectional view illustrating a path of light introduced into the organic light emitting diode display of FIG. 1 and a path of light emitted from the light emitting device to the outside.

Claims (11)

An organic light emitting device including a first electrode, an organic light emitting layer formed on the first electrode, and a second electrode formed on the organic light emitting layer; A reflective polarization film (DBEF) on which a second electrode of the organic light emitting diode is formed; A first polarizing plate formed on the reflective polarizing film; A cholesteric liquid crystal (CLC) film formed on the first polarizing plate; A phase delay plate which is a quarter wave plate formed on the cholesteric liquid crystal film; And A second polarizer formed on the phase delay plate An organic light emitting display device comprising a. In claim 1, The organic light emitting diode display of claim 1, wherein the polarization axis of the first polarizing plate and the polarization axis of the second polarizing plate cross each other. In claim 2, The organic light emitting diode display of claim 1, wherein the polarization axis of the first polarizing plate and the polarization axis of the reflective polarizing film are the same. 4. The method of claim 3, The cholesteric liquid crystal film passes one circularly polarized light among the right circularly polarized light and the left circularly polarized light, and reflects the other circularly polarized light. In claim 4, The linearly polarized light passing through the second polarizing plate changes to circularly polarized light while passing through the phase retardation plate. In claim 5, The circularly polarized light passing through the phase retardation plate passes through the cholesteric liquid crystal layer. In claim 4, The linearly polarized light having a polarization axis in the same direction as the optical axis of the cholesteric liquid crystal film is changed into circularly polarized light when passing through the cholesteric liquid crystal film. In claim 7, The organic light emitting diode display of claim 1, wherein the polarization axis of the first polarizing plate and the optical axis of the cholesteric liquid crystal film are the same. In claim 8, The linearly polarized light passing through the first polarizing plate changes to circularly polarized light while passing through the cholesteric liquid crystal film. The circularly polarized light passing through the cholesteric liquid crystal film is changed to linearly polarized light having the same axial direction as the polarization axis of the second polarizing plate while passing through the phase retardation plate. The method according to any one of claims 1 to 9, And an additional phase retardation plate disposed between the organic light emitting element and the reflective polarizing film. In claim 10, And the additional phase retardation plate is a quarter wave plate and converts linearly polarized light into circularly polarized light through the reflective polarizing film.

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