Optical film for reducing color shift and organic light-emitting display device employing the same

An optical film includes: a high refractive index pattern layer including a material having a refractive index greater than about 1, where a plurality of grooves, each having a curved groove surface and a depth greater than a width thereof, is defined on a first surface of the high refractive index pattern layer, the plurality of grooves defines a pattern, the plurality of grooves are two-dimensionally arranged in a first direction and a second direction, and a first distance between adjacent grooves in the first direction and a second distance between adjacent grooves in the second direction are different from each other; and a low refractive index pattern layer including a material having a refractive index less than the refractive index of the high refractive index pattern layer and further including a plurality of fillers which fills the plurality of grooves, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Korean Patent Application No. 10-2013-0122816, filed on Oct. 15, 2013, and all the benefits accruing therefrom under 35 U.S.C. § 119, the content of which in its entirety is herein incorporated by reference.

BACKGROUND

The disclosure relates to an optical film for reducing a color shift, and an organic light-emitting display device including the optical film.

2. Description of the Related Art

An organic light-emitting device (“OLED”) typically includes an anode, an organic light-emitting layer and a cathode. In such an OLED, when a voltage is applied between the anode and the cathode, holes are injected from the anode into the organic light-emitting layer and electrons are injected from the cathode into the organic light-emitting layer. When the holes and the electrons that are injected into the organic light-emitting layer recombine in the organic light-emitting layer, excitons are generated in the organic light-emitting layer, and light is thereby emitted when the states of the excitons change from an excited state to a ground state.

The OLED, where a light-emitting material is an organic material, may degrade and thus has a short lifespan. Accordingly, various technologies have been developed to improve the lifespan of the OLED.

One of the technologies is a technology using a microcavity structure which involves resonating light of a specific wavelength to increase intensity and emitting the light with the increased intensity. The microcavity structure typically includes a structure in which distances between an anode and a cathode are designed to match representative wavelengths of red (R), green (G) and blue (B) light, and thus only a corresponding light is resonated and emitted to the outside and the intensity of lights of other wavelengths is relatively weakened. As a result, the intensity of the light beam emitted to the outside is increased and sharpened, thereby increasing luminance and color purity. The increase in the luminance leads to low current consumption and a long lifespan.

SUMMARY

In an organic light-emitting diode (“OLED”) having a micro cavity structure that resonates light of a specific wavelength to increase intensity, wavelengths to be amplified are determined based on the thickness of an organic deposition material layer. Here, length of a light path changes at a lateral side, thereby causing an effect similar to change of thickness of an organic deposition material layer. Therefore, wavelengths to be amplified are changed.

According, in such an OLED, as the viewing angle is tilted from a front to a side, the maximum resolution wavelength becomes shorter, and thus color shift occurs as the maximum resolution wavelength decreases. For example, even if white color is embodied at the front, the white color may become bluish at a lateral side due to blue shift phenomenon.

Provided are embodiments of an optical film for reducing a color shift and an organic light-emitting display device including the optical film.

According to an embodiment of the invention, an optical film includes: a high refractive index pattern layer including a material having a refractive index greater than about 1, where a plurality of grooves, each having a curved surface and a depth greater than a width thereof, is defined on a first surface of the high refractive index pattern layer, the plurality of grooves defines a pattern of the high refractive index pattern layer, the plurality of grooves are two-dimensionally arranged in a first direction and a second direction, and a first distance between adjacent grooves in the first direction and a second distance between adjacent grooves in the second direction are different from each other; and a low refractive index pattern layer including a material having a refractive index less than the refractive index of the high refractive index pattern layer and further including a plurality of fillers which fills the plurality of grooves, respectively.

In an embodiment, a cross-sectional shape of each of the plurality of grooves in the first surface may be an isotropic shape.

In an embodiment, the plurality of grooves may be arranged in a quadrangular form.

In an embodiment, the plurality of grooves may be arranged in a rectangular form.

In an embodiment, the plurality of grooves may be arranged along a plurality of straight lines, which extends in the first direction and may be spaced apart from one another in the second direction, and the grooves on adjacent straight lines of the plurality of straight lines are alternately disposed.

In an embodiment, the plurality of grooves may be irregularly arranged, where an average of first distances between adjacent grooves in the first direction and an average of second distances between adjacent grooves in the second direction are different from each other.

In an embodiment, an area ratio of an area of the pattern to an area of a boundary surface between the high refractive index pattern layer and the low refractive index pattern layer may be equal to or greater than about 25% and equal to or less than about 50%.

In an embodiment, a ratio of the depth to the width of each of the plurality of grooves may be in a range from about 2 to about 2.8.

In an embodiment, the low refractive index pattern layer may further include a flat portion which connects the plurality of fillers.

In an embodiment, the optical film may further include: an anti-reflection film disposed on a second surface of the high refractive index pattern layer, which is opposite to the first surface; and an adhesive layer disposed on the low refractive index pattern layer.

In an embodiment, the optical film may further include a circular polarization film disposed between the high refractive index pattern layer and the anti-reflection film, and including a phase shift layer and a linear polarization layer.

In an embodiment, the optical film may further include a transmittance-adjusting layer disposed between the high refractive index pattern layer and the anti-reflection film.

According to another embodiment of the invention, an organic light-emitting display device includes: an organic light-emitting panel including a plurality of pixels including organic light-emitting layers, where the organic light-emitting layers emit light of different wavelengths from each other and each of the plurality of pixels has a microcavity structure which resonates light corresponding to one of the different wavelengths; and an embodiment of the optical film described above, which is disposed on the organic light-emitting panel.

In an embodiment, the first direction and the second direction, in which the plurality of grooves are two-dimensionally arranged, may respectively correspond to a horizontal direction and a vertical direction of the organic light-emitting panel.

In an embodiment, the second distance may be less than the first distance.

In an embodiment, the plurality of grooves may be irregularly arranged in the optical film, and an average of second distances between adjacent grooves in the second direction may be less than an average of first distances between adjacent grooves in the first direction.

DETAILED DESCRIPTION

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

FIG. 1is an exploded perspective view illustrating an embodiment of an optical film1according to the invention.

In an embodiment, the optical film1includes a high refractive index pattern layer110including a pattern defined by a plurality of grooves GR, each having a curved groove surface and a depth greater than a width thereof, and a low refractive index pattern layer120disposed on the high refractive index pattern layer110. In such an embodiment, the low refractive index pattern layer120includes a plurality of fillers122corresponding to the plurality of grooves GR. In one embodiment, for example, the grooves GR of the high refractive index pattern layer110may be engraved on a surface thereof, and the fillers122of the low refractive index pattern layer120may fill the grooves GR.

The plurality of grooves GR are two-dimensionally arranged in a first direction DR1and a second direction DR2. In one embodiment, for example, the first and second directions may be perpendicular to each other. A first distance S1between adjacent grooves GR in the first direction and a second distance S2between adjacent grooves GR in the second direction DR2may be set to be different from each other. A cross-sectional shape of each of the grooves GR may be, but is not limited to, an isotropic shape. The plurality of grooves GR may be arranged in a quadrangular form, and may be arranged in a rectangular shape in the first direction DR1and the second direction DR2, as shown inFIG. 1. However, embodiments of the invention are not limited thereto. In an alternative embodiment, the plurality of grooves GR may be arranged in predetermined pattern in the first direction DR1and the second direction DR2.

The first distance S1between adjacent grooves GR in the first direction DR1and the second distance S2between adjacent grooves GR in the second direction DR2may determine the amount of improvement in a color shift in the first direction DR1and the second direction DR2, which will be described later in detail with computer simulation results.

In an embodiment, an aspect ratio of each of the grooves GR, which is a ratio of a depth d to a width W of each of the grooves GR, may be in a range from about2to about2.8.

An area ratio of the area occupied by the groove patterns to an area of a boundary surface between the high refractive index pattern layer110and the low refractive index pattern layer120may be equal to or greater than about 25% and equal to or less than about 45%. Hereinafter, the area ratio will be referred to as a ‘pattern occupying ratio’. The pattern occupying ratio is a design factor that is considered to obtain a predetermined front transmittance or more when a shape or an arrangement type of the pattern is determined in consideration of the amount of improvement in a color shift, which will be described later in detail with computer simulation results.

The high refractive index pattern layer110may include be formed of a material having a refractive index that is equal to or greater than about 1, for example, a transparent plastic material. The high refractive index pattern layer110may include or be formed of a transparent plastic material and a light diffuser or a light absorber. In an embodiment, the light diffuser may include diffusing beads, and the light absorber may include a black dye such as carbon black, for example. In such an embodiment, the light diffuser functions to planarize a peak that may occur in a color shift (Δu′v′) and luminance profile with respect to viewing angle and thus to improve visual characteristics. In such an embodiment, the light absorber may include a dye that selectively absorbs a specific wavelength or carbon black that may absorb nearly all wavelengths of visible light to increase a contrast ratio or a color purity.

A surface of each of the grooves GR is a curved surface, for example, the groove GR may have any of various aspheric surfaces such as an elliptical surface, a parabolic surface, or a hyperbolic surface, for example.

The low refractive index pattern layer120may include or be formed of a resin material having a refractive index that is less than a refractive index of the high refractive index pattern layer110. In an embodiment, the low refractive index pattern layer120may include or be formed of a transparent plastic material and a light diffuser or a light absorber. In such an embodiment, the light diffuser may include diffusing beads, and the light absorber may be a black dye such as carbon black, for example.

The low refractive index pattern layer120may include the fillers122having shapes corresponding to the grooves GR defined in the high refractive index pattern layer110, and may further include a flat portion121that connects the plurality of fillers122. In an embodiment, shapes of the fillers122are the same as those of the grooves GR, and shapes of the fillers122and the grooves GR may have the same meaning herein when used to describe a shape of the pattern.

The optical film1that refracts and emits light, which is incident in one direction, in various directions according to incident positions functions to mix light, which will be described hereinafter with reference toFIGS. 2 and 3.

FIG. 2is a cross-sectional view illustrating an optical path through which light vertically incident on the optical film1ofFIG. 1is emitted.FIG. 3is a cross-sectional view illustrating an optical path through which light obliquely incident on the optical film1ofFIG. 1is emitted.

Referring toFIGS. 2 and 3, in an embodiment, a boundary surface between the high refractive index pattern layer110and the low refractive index pattern layer120includes a curved surface110athat defines a groove GR and a flat surface110b, and the curved surface110afunctions as a lens surface.

Referring toFIG. 2, light vertically incident on the optical film1is refracted and emitted from the optical film1in directions according to positions at which the light meets the curved surface110a. That is, light beams incident to the optical film1(e.g., toward curved surface110athereof) with the same incident angle are refracted in various directions according to positions at which the light meets the curved surface110a, thereby the optical film1diffuses light.

Referring toFIG. 3, light obliquely incident on the optical film1is refracted in various directions according to positions at which the light is incident. In such an embodiment, as shown inFIG. 3, light L1that passes through the flat surface110band meets the curved surface110ain the high refractive index pattern layer110is totally reflected by the curved surface110aand emitted from the optical film1. In such a path, an angle at which the light L1is emitted from a top surface of the high refractive index pattern layer110is less than an angle at which the light L1is incident on the optical film1. In such an embodiment, light L2that passes through the flat surface110bwithout passing through the curved surface110ais refracted at a boundary between the high refractive index pattern layer110and the outside, with a refraction angle that is greater than an incident angle. That is, the light L2is emitted from the optical film1at an angle that is greater than the incident angle at which the light L2is incident on the optical film1. In such an embodiment, light L3that meets the curved surface110ain the low refractive index pattern layer120is refracted by the curved surface110aand then is refracted again by the top surface of the high refractive index pattern layer110, such that the light L3is emitted from the optical film1at a refraction angle that is greater than that of the light L2that is emitted after passing through the flat surface110bwithout meeting the curved surface110a. As such, the lights L1, L2, and L3that are obliquely incident on the optical film1at the same angle are emitted from the optical film1at different refraction angles according to positions on the optical film1at which the lights L1, L2and L3are incident.

In an embodiment, as described above, during light beams are passing through the optical film1, light beams incident on the optical film1at various angles are mixed together.

InFIGS. 2 and 3, a specific optical path through which incident light is diffused is exemplary, and is also exaggerated for convenience of illustration. For example, refraction of light that may occur at a flat surface110bis not shown. Also, an optical path may be slightly changed based on a refractive index difference between the high refractive index pattern layer110and the low refractive index pattern layer120, an aspect ratio of each of the grooves GR in the high refractive index pattern layer110, cycles in which the grooves GR are repeatedly arranged, the width W of each of the grooves GR, and a shape of a curved surface of the groove GR, and thus an extent to which light is mixed and a luminance of emitted light are also changed based on the changes in the optical path.

In an embodiment, when light beams incident on the optical film1have different optical characteristics according to their incident angles, the light beams are emitted after the optical characteristics are uniformly combined by the light mixing effect describe above. In one embodiment, for example, when light is emitted from an organic light-emitting device (“OLED”), a color shift that is a phenomenon where color characteristics slightly vary according to an angle at which the light is emitted occurs. However, since light of different color shift are mixed after the light passes through the optical film1having the above-described structure, the degree of color shift according to viewing angles is reduced.

In the description above, the cross-sectional views ofFIGS. 2 and 3may correspond to any cross-sectional view perpendicular to a surface defined by the first direction DR1and the second direction DR2inFIG. 1. In an embodiment, the optical film1may mix light beams, which are incident at various angles on the optical film1, at any azimuth angle.

FIG. 4is an exploded perspective view illustrating a structure of a comparative embodiment of an optical film1′.

The comparative embodiment of the optical film1′ shown inFIG. 4includes a high refractive index pattern layer110′ and a low refractive index pattern layer120′, and each of the grooves GR is defined or formed in a stripe shape that extends in one direction. Hereinafter, a display device including such a comparative embodiment of the optical film will be referred to as a “comparative example”.

FIG. 5is a graph illustrating a color shift distribution of light passing through a display panel including a comparative embodiment of an optical film and a display panel including no optical film (also referred to as, a “bare case”).

The graphs show computer simulation results obtained after measuring an organic light-emitting display panel including an OLED having a microcavity structure. A color shift seen at each azimuth angle was calculated under conditions where a viewing angle is about 60° and front white (x, y)=(0.28, 0.29).

Referring to the graph ofFIG. 5, a color shift in the comparative example including the optical film is less than a color shift in the bare case including no optical film. In the comparative example, a color shift in a horizontal direction is reduced, but a reduction in a color shift in a vertical direction is reduced, thereby resulting in little improvement in a color shift in the vertical direction. In the comparative example, where a stripe-shaped pattern is used, a color shift in a direction perpendicular to the stripe-shaped pattern is mainly reduced.

In an embodiment of the invention, the optical film1is configured to include patterns that are two-dimensionally arranged to reduce a color shift in an overall azimuth angle range. As described above with reference toFIGS. 2 and 3, since color mixing occurs at various azimuth angles, a color shift in an overall azimuth angle range may be substantially improved. Also, a viewing angle at a specific azimuth angle may be increased by appropriately setting an arrangement type.

FIGS. 6 and 7are plan views illustrating arrangements of fillers in embodiments of the optical film1, according to the invention.

Referring toFIG. 6, in an embodiment, the plurality of fillers122are arranged in a rectangular form in the first direction DR1and the second direction DR2. InFIG. 6, a distance between adjacent fillers122in the first direction DR1is denoted by S1and a distance between adjacent fillers122in the second direction DR2is denoted by S2. A color shift may be reduced in an overall azimuth angle range by allowing the distances S1and S2between the adjacent fillers122in the first and second directions DR1and DR2to be substantially equal to each other, or a color shift in a corresponding direction may be further reduced by allowing any one of the distances S1and S2to be greater than the other.

Referring toFIG. 7, in an alternative embodiment, the plurality of fillers122are arranged on a plurality of straight lines that are parallel to one another in the first direction DR1and are spaced apart from one another in the second direction DR2, and the fillers122on adjacent straight lines alternate with each other, e.g., alternately disposed in a staggered shape or a zigzag manner. InFIG. 7, a distance between adjacent fillers122in the first direction DR1is denoted by S3, and a distance between adjacent fillers122in the second direction DR2is denoted by S4. In such an embodiment, a reduction in a color shift at a specific azimuth angle may be further enhanced by appropriately determining a ratio of the distance S3to the distance S4in the arrangement.

In an embodiment, as shown inFIGS. 6 and 7, the plurality of fillers122may be regularly arranged, but the embodiments of the invention are not limited thereto. In an alternative embodiment, the plurality of fillers122may be irregularly arranged. In such an embodiment, an average of first distances S1between adjacent fillers122in the first direction DR1and an average of second distances S2between adjacent grooves GR in the second direction DR2may be set as design factors that determines the color shift. In such an embodiment, the average of the first distances S1and the average of the second distances S2may be equal to each other to reduce the color shift by substantially the same amount in an overall azimuth angle range. Alternatively, to increase the amount of improvement in a color shift at a specific azimuth angle, a ratio of the average of the first distances S1to the average of the second distances S2may be appropriately set.

FIG. 8is a graph illustrating a color shift when a ratio S2/S1is changed in the arrangement of fillers inFIG. 6.

In cases1_1,1_2,1_3,1_4and1_5shown inFIG. 8, where a pattern occupying ratio is about 45% and the ratio S2/S1is 0.69, 0.83, 1, 1.21 and 1.45, respectively, as the ratio S2/S1increases, a color shift in a horizontal direction increases and a color shift in a vertical direction decreases. Also, a color shift in a diagonal direction in a rectangular arrangement is the smallest in an overall azimuth angle range in any of the cases1_1,1_2,1_3,1_4and1_5.

FIG. 9is a graph illustrating a color shift when a ratio S4/S3is changed in the arrangement of fillers inFIG. 7.

In cases2_1,2_2,2_3,2_4and2_5shown inFIG. 9, where a pattern ratio is about 45% and the ratio S4/S3is 0.4, 0.5, 0.6, 0.7 and 0.9, respectively, as the ratio S4/S3increases, a color shift in a horizontal direction increases and a color shift in a vertical direction decreases. Also, an azimuth angle at which a color shift is the smallest is repeatedly shown in cycles of 60° in an overall azimuth angle range in each of the cases2_1,2_2,2_3,2_4and2_5.

As shown in the graphs ofFIGS. 8 and 9, a color shift at a specific azimuth angle may be adjusted by appropriately determining a pattern arrangement type. In one embodiment, for example, a color shift requirement in a horizontal direction may be generally less than a color shift requirement in a vertical direction in a display panel. Accordingly, in such an embodiment, the ratio S2/S1may be set to be less than about 1, that is, the second distance S2may be set to be less than the first distance51, in the arrangement ofFIG. 6, to allow a color shift in a horizontal direction to be less than a color shift in a vertical direction.

FIG. 10is a graph illustrating an average improvement rate in an overall azimuth angle range when a pattern occupying ratio and an aspect ratio are changed in the case2_3and the case1_3ofFIGS. 8 and 9.

Referring to the graph ofFIG. 10, in the case2_3and the case1_3, an aspect ratio and an average improvement rate are in a range of about 2 to about 2.8, and an average improvement rate increases as a pattern occupying ratio increases.

FIG. 11is a graph illustrating a front transmittance when a pattern occupying ratio and an aspect ratio are changed in the case2_3and the case1_3ofFIGS. 8 and 9.

Referring to the graph ofFIG. 11, as a pattern occupying ratio increases, a front transmittance generally decreases. When a pattern occupying ratio is predetermined, e.g., remains the same, a front transmittance increases as an aspect ratio increases.

InFIGS. 10 and 11, a pattern occupying ratio may be set to be equal to or greater than about 25% and equal to or less than about 50% based on a shape of an increase in an average improvement rate or a front transmittance of about 85%.

FIG. 12is a perspective view illustrating an alternative embodiment of an optical film2according to the invention.

In an embodiment, the optical film2includes a high refractive index pattern layer210having a pattern defined by the plurality of grooves GR, each having a curved groove surface, and a low refractive index pattern layer220including a plurality of fillers222corresponding to the plurality of grooves GR. In such an embodiment, the plurality of fillers222may fill the plurality of grooves GR, respectively. In such an embodiment, the low refractive index pattern layer220may not include a flat portion that connects the fillers222, which is shown inFIG. 1. An arrangement and a shape of the fillers222are not limited to those shown inFIG. 12and may be variously modified, e.g., to those shown inFIGS. 6 and 7.

An embodiment of the optical film1or2shown inFIGS. 1 and 12may further include an adhesive layer, a circular polarization film, or a transmittance-adjusting layer that are typically included to be applied to an organic light-emitting display device, which will now be described in detail.

FIG. 13is a cross-sectional view illustrating an alternative embodiment of an optical film3according to the invention.

In an embodiment, as shown inFIG. 13, the optical film3may further include an anti-reflection film190disposed on the high refractive index pattern layer110, and a first adhesive layer131disposed under the low refractive index pattern layer120. In such an embodiment, a first base film141may be further disposed between the high refractive index pattern layer110and the anti-reflection film190.

The first adhesive layer131that is provided to be adhered to an organic light-emitting panel may include a pressure sensitive adhesive (“PSA”) layer including a light absorber or a light diffuser. In an embodiment, the high refractive index pattern layer110and/or the low refractive index pattern layer120may include or be formed of a transparent material including a light absorber. When a material including a light absorber is applied to various layers constituting an optical film, a reflectance of external light may be reduced, thereby improving visibility.

The first base film141, which may function as a substrate for forming the high refractive index pattern layer110during a manufacturing process, and the low refractive index pattern layer120may include or be formed of an optically isotropic material, for example, triacetyl cellulose (“TAC”).

FIGS. 14 and 15are cross-sectional views illustrating embodiments of an optical film4and5including a circular polarization film, according to the invention.

The circular polarization film may include a phase shift layer150and a linear polarization layer160. The phase shift layer150may be, for example, a λ/4 phase difference film. The linear polarization film160may include a polyvinyl alcohol (“PVA”) film or may have a TAO film-stacked structure or any of various other structures. The PVA film that polarizes light may be formed by adsorbing a dichroic pigment onto PVA that is a polymer.

Referring toFIGS. 14 and 15, an embodiment of the optical film4or5includes the adhesive layer131, the low refractive index pattern layer120, the high refractive index pattern layer110, the phase shift layer150, the linear polarization layer160, the first base film141and the anti-reflection film190, which are sequentially disposed one on another.

The circular polarization film, including the phase shift layer150and the linear polarization layer160, functions to reduce a reflectance of external light and improve visibility. When external non-polarized light is incident, the external non-polarized light is changed to linearly polarized light by passing through the linear polarization layer160, and the linearly polarized light is changed to circularly polarized light by passing through the phase shift layer150. The circularly polarized light passes through an interfacial surface between the phase shift layer150and the high refractive index pattern layer110, the high refractive index pattern layer110, the low refractive index pattern layer120and the first adhesive layer131, and is reflected by an interfacial surface between an organic light-emitting panel (not shown) and the first adhesive layer131, and thereby the circularly polarization direction thereof is inversed or changed oppositely. Then, the circularly polarized light having inversed direction is changed to linearly polarized light that is perpendicular to a transmission axis of the linear polarization layer160by passing through the phase shift layer150, such that the light is effectively prevented from being emitted to the outside.

As shown inFIG. 14, in such an embodiment, where the circular polarization film is disposed on the high refractive index pattern layer110, if the high refractive index pattern layer110includes or is formed of an anisotropic material whose optical axis is different from the circular polarization film, polarization may not be maintained, incident external light may be emitted to the outside again, a reflectance may be drastically increased, and thus visibility may be reduced. Accordingly, in an embodiment, the high refractive index pattern layer110may include or be formed of an isotropic material whose optical axis is the same as that of the circular polarization film, such as TAO or solvent-cast polycarbonate (“PC”), for example.

In an embodiment of the optical film5, as shown inFIG. 15, a second base film142and a second adhesive layer132are further provided between the high refractive index pattern layer110and the phase shift layer150to be sequentially disposed from the high refractive index pattern layer110toward the phase shift layer150.

FIG. 16is a cross-sectional view illustrating an embodiment of an optical film6including a transmittance-adjusting layer170, according the invention.

In such an embodiment, the transmittance-adjusting layer170may be a film that is formed by dispersing a black material for absorbing light such as a black dye, a pigment, carbon black or cross-linked particles, on which a black dye, a pigment or carbon black may be coated, in a polymer resin. In one embodiment, for example, the polymer resin may include, but are not limited to, a binder such as polymethyl methacrylate (“PMMA”) and an ultraviolet (“UV”)-curable resin such as an acryl-based resin. In an embodiment, a proportion of the black material contained in the polymer resin or a thickness of the transmittance-adjusting layer170may be determined or set based on optical properties of the black material. A transmittance of the transmittance-adjusting layer170may be equal to or greater than about 40%, which is slightly higher than a transmittance of the circular polarization film. Although the circular polarization film may completely block external light, a low transmittance is caused. The transmittance-adjusting layer170may be used to compensate for the disadvantage of low transmittance of the circular polarization film.

In an embodiment, the optical film6includes the first adhesive layer131, the low refractive index pattern layer120, the high refractive index pattern layer110, a first carrier film181, the transmittance-adjusting layer170and the anti-reflection film190, which are sequentially disposed one on another.

The first carrier film181may function as a base substrate for forming the high refractive index pattern layer110and the low refractive index pattern layer120, or as a base substrate for the anti-reflection film190or the transmittance-adjusting layer170, during a manufacturing process of the optical film6. In such an embodiment, where the optical film6ofFIG. 16does not include a linear polarization layer and does not need to maintain polarization, the optical film6may include or be formed of any of various materials including TAO, polyethylene terephthalate (“PET”) and PC, for example.

Although the high refractive index pattern layer110and the low refractive index pattern layer120in embodiments of the optical film3through6shown inFIGS. 13 through 16have a shape shown inFIG. 1, the shape is merely exemplary, and embodiments of the invention are not limited thereto. In such an embodiment, the shape of the high refractive index pattern layer110and the low refractive index pattern layer120may be modified to the shapes shown inFIGS. 6, 7 and 12or a combination thereof. Also, an arrangement in embodiments of the optical film3through6shown inFIGS. 13 through 16may be variously modified. In one embodiment, for example, positions of the phase shift layer150and the linear polarization layer160constituting the circular polarization film may be changed, or another layer may be disposed between the phase shift layer150and the linear polarization layer160. In an embodiment, a second base film and a second carrier film may be added.

An embodiment of the above optical film described above refracts and emits light that is vertically incident and light that is obliquely incident in various directions including a front direction and a side direction. Also, an embodiment of the optical film described above may mix incident light at various angles in an overall azimuth angle range as well as in a horizontal direction by two-dimensionally arranging a dot pattern.

An embodiment of the optical film described above may be applied to an organic light-emitting display device. The organic light-emitting display device may include an organic light-emitting layer that has a microcavity structure configured to increase color purity. In such an organic light-emitting display device including an embodiment of the optical film, a color shift according to a viewing angle may be reduced at any azimuth angle, thereby displaying a high-quality image.

FIG. 17is a cross-sectional view illustrating an embodiment of an organic light-emitting display device500according to the invention.

An embodiment of the organic light-emitting display device500includes an organic light-emitting panel510that includes a plurality of pixels including organic light-emitting layers and each having a microcavity structure configured to resonate light of a corresponding wavelength to thereby emit light of different wavelengths, and an optical film520that is disposed on the organic light-emitting panel510.

In an embodiment of the organic light-emitting display device500, the optical film520may be substantially the same as one of the embodiments of the optical film5shown inFIGS. 15 to 17, but not being limited thereto. In an alternative embodiment, the optical film520of the organic light-emitting display device500may have a structure of an embodiment of the optical film1,1′,2,3,4or6described above.

The organic light-emitting panel510may have a microcavity structure to increase a luminance and a color purity. In an embodiment, the organic light-emitting panel500includes a plurality of OLEDs that emit any of red (R), green (G), blue (B) and white light, and each OLED includes an anode13, an organic light-emitting layer14and a cathode15. As shown inFIG. 17, in an embodiment where the organic light-emitting panel510includes OLEDs whose unit pixels are configured to emit red, green and blue light, a microcavity structure may have a structure in which a distance between the anode14and the cathode16of the OLED that emits light of a longest wavelength (e.g., red light) is the longest, and a distance between the anode14and the cathode16of the OLED that emits light of a shortest wavelength (e.g., blue light) is the shortest. In such an embodiment, a distance between the anode13and the cathode15in the organic light-emitting panel510is set to correspond to a representative wavelength of each of red, green and blue light, to resonate and emit only light of corresponding wavelength to the outside and weaken light of other wavelengths.

A structure of an embodiment of the organic light-emitting panel510will now be described in detail.

In an embodiment, each sub-pixel of the organic light-emitting panel510may include an OLED that is disposed between a first substrate11and a second substrate19that face each other and includes the anode13, the organic light-emitting layer14and the cathode15, and a driving circuit unit12that is disposed on the first substrate11and is electrically connected to the anode13and the cathode15.

In an embodiment, the anode13may include or be formed of an opaque metal such as aluminum (Al), and the cathode15may be a transparent electrode including or formed of, for example, indium tin oxide (“ITO”), or a semi-transparent electrode including or formed of, for example, nickel (Ni), such that light emitted from the organic light-emitting layer14may be effectively transmitted through the cathode15

The driving circuit unit12may include at least two thin-film transistors (“TFT”s) (not shown) and capacitors (not shown), and controls a brightness of the OLED by controlling the amount of current supplied to the OLED based on a data signal.

In an embodiment, the driving circuit unit12, which is a circuit for driving a unit pixel of the organic light-emitting panel510, may include a gate line, a data line that may perpendicularly cross the gate line, a switching TFT that is connected to the gate line and the data line, a driving TFT that is connected to the OLED between the switching OLED and a power line, and a storage capacitor that is connected between a gate electrode of the driving TFT and the power line.

In such an embodiment, the switching TFT applies a data signal of the data line to a gate electrode of the driving TFT and the storage capacitor in response to a scan signal of the gate line. The driving TFT controls a brightness of the OLED by adjusting current supplied to the OLED from the power line in response to a data signal from the switching TFT. In such an embodiment, the storage capacitor stores a data signal from the switching TFT and applies a stored voltage to the driving TFT, and thus the driving TFT enables substantially constant current to be supplied even when the switching TFT is turned off.

The organic light-emitting layer14includes a hole injection layer (“HIL”), a hole transport layer (“HTL”), a light-emitting layer, an electron transport layer (“ETL”), and an electron injection layer (“EIL”) that are sequentially stacked on the anode13. In an embodiment, when a forward voltage is applied between the anode13and the cathode15, electrons move from the cathode15through the EIL and the ETL into the light-emitting layer, and holes move from the anode13through the HIL and the HTL into the light-emitting layer. The electrons and the holes injected into the light-emitting layer recombine in the light-emitting layer, to generate excitons, and light is emitted when the state of the excitons change from an excited state to a ground state. In such an embodiment, a brightness of the emitted light is substantially proportional to the amount of current that flows between the anode13and the cathode15.

In an embodiment, the organic light-emitting panel510includes a color filter17to improve color efficiency. In such an embodiment, the color filter17may be disposed on the second substrate19. In one embodiment, for example, a red color filter is disposed in a red sub-pixel region, a green color filter is disposed in a green sub-pixel region, and a blue color filter is disposed in a blue sub-pixel region. In an embodiment, where the unit pixel includes 4 colors (e.g., red, green, blue and white), the color filter17may be omitted in a white sub-pixel region.

In an embodiment, although not shown inFIG. 17, a black matrix for effectively preventing light leakage and color mixture may be further disposed at a boundary of each sub-pixel of the second substrate19.

In an embodiment of the organic light-emitting display device500having a microcavity structure, a color shift occurs toward a short wavelength because as a viewing angle tilts from a front to a lateral side, maximum resonant wavelength moves to short wavelength. In such an embodiment, although white light is observed at the front, a blue shift may occur at the lateral side, and thus light may become bluish.

In an embodiment, the organic light-emitting display device500includes the optical film520that is disposed on the organic light-emitting display panel510to reduce such a color shift.

In such an embodiment, the grooves GR of the optical film520may be two-dimensionally arranged in a first direction and a second direction as described with reference toFIG. 1, and the optical film520may be disposed on the organic light-emitting panel510such that the first direction and the second direction may correspond to a horizontal direction Y and a vertical direction Z of the organic light-emitting panel510.

In such an embodiment, as described with reference toFIGS. 2 and 3, the high refractive index pattern layer110and the low refractive index pattern layer120of the optical film520function as a color shift-reducing layer by allowing light that is incident at a constant angle to be emitted at various angles. The light emitted from the organic light-emitting display panel510may have a predetermined angle distribution at which light is emitted and has a color shift that varies according to the angle. After passing through the color shift-reducing layer including the high refractive index pattern layer110and the low refractive index pattern layer120, light that is incident on the color shift-reducing layer at an angle that causes a large color shift and light that is incident on the color shift-reducing layer at an angle that causes a small color shift are substantially uniformly mixed and emitted, thereby reducing a color shift according to a viewer's viewing angle. In such an embodiment, where the optical film520includes a pattern that is two-dimensionally arranged, a color shift according to a viewing angle may be reduced in an overall any azimuth angle range as well as in a horizontal direction.

In such an embodiment, where the optical film520is disposed to reduce a color shift according to a viewing angle, image distortion may occur due to the optical film520. Accordingly, in such an embodiment, a distance between the organic light-emitting layer14and the optical film520may be equal to or less than about 1.5 millimeters (mm) to minimize such image distortion.

While one or more embodiments of the invention have been described with reference to the figures, 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 following claims. Accordingly, the true technical scope of the invention is defined by the technical spirit of the appended claims.