Display device, organic light emitting display device, and head-mounted display device

A display device includes a substrate, a first display element which is disposed on the substrate, and a plurality of diffraction patterns which are disposed on a path of light emitted from the first display element and arranged along a direction with a first period. when a width of a cross section of one of the plurality of diffraction patterns is defined as a first length, the first period and the first length satisfy Inequality (1): 0.4≤d1/DP1≤1,  (1)

This application claims priority to Korean Patent Application No. 10-2017-0055626, filed on Apr. 28, 2017, 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

Exemplary embodiments of the invention relate to a display device, an organic light emitting display device, and a head-mounted display device.

2. Description of the Related Art

With a development of multimedia, an importance of display devices is increasing. Accordingly, various types of display devices such as liquid crystal displays and organic light emitting displays are being used.

Of these display devices, an organic light emitting display displays an image using an organic light emitting element which generates light through recombination of electrons and holes. Organic light emitting displays have advantages such as fast response speed, high luminance, wide viewing angle, and low power consumption.

A head-mounted display device may be mounted on a user's head and may be in a form of a pair of glasses or a helmet. The head-mounted display device allows the user to recognize an image by displaying the image in front of user's eyes.

SUMMARY

Exemplary embodiments of the invention provide a display device, an organic light emitting display device, and a head-mounted display device which may increase an effective emission area ratio.

Exemplary embodiments of the invention also provide a display device, an organic light emitting display device, and a head-mounted display device which may minimize the degree of blurring perceived.

Exemplary embodiments of the invention also provide a head-mounted display device which may improve a screen door effect (“SDE”).

However, exemplary embodiments of the invention are not restricted to the one set forth herein. The above and other exemplary embodiments of the invention will become more apparent to one of ordinary skill in the art to which the invention pertains by referencing the detailed description of the invention given below.

An exemplary embodiment of the invention discloses a display device including a substrate, a first display element which is disposed on the substrate, and a plurality of diffraction patterns which are disposed on a path of light emitted from the first display element and arranged along a direction with a first period. when a width of a cross section of one of the plurality of diffraction patterns may be defined as a first length, the first period and the first length may satisfy Inequality (1):
0.4≤d1/DP1≤1,  (1)where DP1may be the first period, and d1is the first length.

An exemplary embodiment of the invention also discloses an organic light emitting display device including a substrate, a first organic light emitting element which is disposed on the substrate, an encapsulation layer which is disposed on the first organic light emitting element, and a plurality of diffraction patterns which are disposed on the encapsulation layer and generate a reference emission pattern and a first duplicate emission pattern by diffracting light emitted from the first organic light emitting element. The plurality of diffraction patterns may be arranged along a direction with a first period, and when a distance between the reference emission pattern and the first duplicate emission pattern may be defined as a diffraction distance and a distance between the first organic light emitting element and the plurality of diffraction patterns may be defined as a separation distance, the diffraction distance satisfies Equation (1):

β=z·tan⁡[sin-1⁡(λDP⁢⁢1·1nEN)],(1)where β may be the diffraction distance, z may be the separation distance, DP1may be the first period, λ may be a wavelength of light emitted from the first organic light emitting element, and nEN may be a refractive index of the encapsulation layer.

An exemplary embodiment of the invention also discloses a head-mounted display device including a display unit which includes a first display element and a plurality of diffraction patterns disposed on a path of light emitted from the first display element, and a lens unit which is disposed on the path of the light emitted from the display unit. The plurality of diffraction patterns may be arranged along a direction with a first period, and when a width of a cross section of one of the plurality of diffraction patterns may be defined as a first length, the first period and the first length may satisfy Inequality (1):
0.4≤d1/DP1≤1,  (1)where DP1may be the first period, and d1may be the first length.

An exemplary embodiment of the invention discloses a head-mounted display device including a first display element, a second display element which displays the same color as that of the first display element, a plurality of diffraction patterns which are disposed on a path of light emitted from the first and second display elements and generate a reference emission pattern and a first duplicate emission pattern by diffracting light emitted from the first display element, and an intermediate layer which is disposed on the plurality of diffraction patterns and has a first refractive index. The plurality of diffraction patterns may be arranged along a direction with a first period and each have a second refractive index. when a width of a cross section of one of the plurality of diffraction patterns may be defined as a first length, the first period and the first length may satisfy Inequality (1) below, when a distance between the reference emission pattern and the first duplicate emission pattern may be defined as a diffraction distance and a distance between the first display element and the plurality of diffraction patterns may be defined as a separation distance, the diffraction distance may satisfy Equation (2) below, when a distance between the first display element and the second display element may be defined as an inter-display element distance, the inter-display element distance and the diffraction distance may satisfy Inequality (3) below, and the first refractive index, the second refractive index, and a thickness of one of the plurality of diffraction patterns may satisfy Inequality (4) below:
0.4≤d1/DP1≤1,  (1)where DP1may be the first period, and d1may be the first length,

β=z·tan⁡[sin-1⁡(λDP⁢⁢1·1nEN)],(2)where β may be the diffraction distance, z may be the separation distance, DP1may be the first period, λ may be a wavelength of light emitted from the first display element, and nEN may be a refractive index of an encapsulation layer,
0.1≤β/PP1≤1.9,  (3)where PPI may be the inter-display element distance, and β may be the diffraction distance,
(m*λ)−60 (nm)≤A(nm)≤(m*λ)+60 (nm)
A≠Δn·t1 (nm),  (4)where Δn=n1−n2|, n1may be the first refractive index, n2may be the second refractive index, t1may be the thickness of one of the plurality of diffraction patterns, λ may be the wavelength of the light emitted from the first display element, and m may be an integer of 0 or more.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the invention will be described with reference to the attached drawings.

FIG. 1is a cross-sectional view of an organic light emitting display device according to an exemplary embodiment.FIG. 2illustrates both a plane and a cross section of a first pixel unit PX1shown inFIG. 1.

Referring toFIGS. 1 and 2, the organic light emitting display device according to the current embodiment includes a first substrate110, a plurality of pixel electrodes120including a first pixel electrode121, a pixel defining layer130, a plurality of organic light emitting elements140including a first organic light emitting element141, a common electrode150, a buffer layer151, an encapsulation layer160, and a diffraction pattern layer170. A pixel unit including the first pixel electrode121and the first organic light emitting element141will hereinafter be referred to as the first pixel unit PX1.

The first substrate110may be an insulating substrate. In an exemplary embodiment, the first substrate110may include a material such as glass, quartz, or polymer resin. In an exemplary embodiment, the polymer material may be polyethersulphone (“PES”), polyacrylate (“PA”), polyarylate (“PAR”), polyetherimide (“PEI”), polyethylene naphthalate (“PEN”), polyethylene terephthalate (“PET”), polyphenylenesulfide (“PPS”), polyallylate, polyimide (“PI”), polycarbonate (“PC”), cellulosetriacetate (“CAT”), cellulose acetate propionate (“CAP”), or a combination of these materials. In an exemplary embodiment, the first substrate110may be a flexible substrate including PI.

The pixel electrodes120may be disposed on the first substrate110. Although not illustrated in the drawings, a plurality of components may be further disposed between the first substrate110and the pixel electrodes120. In an exemplary embodiment, the components may include a buffer layer, a plurality of conductive wiring layers, an insulating layer, and a plurality of thin film transistors (“TFTs”). In an exemplary embodiment, each of the TFTs may use amorphous silicon, polysilicon, low temperature polysilicon (“LIPS”), an oxide semiconductor, an organic semiconductor, or the like as a channel layer. The types of the respective channel layers of the TFTs may be different from each other. In an exemplary embodiment, a TFT including an oxide semiconductor and a TFT including low-temperature polysilicon may all be included in one pixel unit in consideration of the role or process order of a TFT.

The pixel electrodes120will be described based on the first pixel electrode121. The first pixel electrode121may be an anode in an exemplary embodiment. When the first pixel electrode121is an anode, the first pixel electrode121may include a reflective material. In an exemplary embodiment, the reflective material may include one or more reflective films selected from silver (Ag), magnesium (Mg), chromium (Cr), gold (Au), platinum (Pt), nickel (Ni), copper (Cu), tungsten (W) and aluminum (Al) and a transparent or translucent electrode disposed on the reflective films, for example.

In an exemplary embodiment, the transparent or translucent electrode may include one or more of indium tin oxide (“ITO”), indium zinc oxide (“IZO”), sane oxide (ZnO), indium oxide (In2O3), indium gallium oxide (“IGO”) and aluminum zinc oxide (“AZO”), for example.

The pixel defining layer130may be disposed on the first pixel electrode121. An opening OP1which exposes at least part of the first pixel electrode121is defined in the pixel defining layer130. The pixel defining layer130may include an organic material or an inorganic material. In an exemplary embodiment, the pixel defining layer130may include a material such as photoresist, polyimide resin, acrylic resin, a silicon compound, or polyacrylic resin.

The first pixel electrode121may be rhombic in an exemplary embodiment. In an exemplary embodiment, the opening OP1of the pixel defining layer130may be rhombic in an exemplary embodiment. However, the shape of the first pixel electrode121and the shape of the opening OP1of the pixel defining layer130are not limited to those illustrated inFIG. 2. That is, the shape of the first pixel electrode121and the shape of the opening OP1of the pixel defining layer130may vary depending on the arrangement of a plurality of pixel units.

The organic light emitting elements140may be disposed on the pixel electrodes120and the pixel defining layer130. The organic light emitting elements140will be described based on the first organic light emitting element141. The first organic light emitting element141may be disposed on a region of the first pixel electrode121which is exposed through the opening OP1of the pixel defining layer130. That is, the first organic light emitting element141may overlap the opening OP1of the pixel defining layer130. In an exemplary embodiment, the first organic light emitting element141may cover at least part of the opening OP1of the pixel defining layer130.

The first organic light emitting element141may emit one of red light, green light, and blue light in an exemplary embodiment. In an exemplary embodiment, the red light may have a wavelength of about 620 nanometers (nm) to about 750 nm, and the green light may have a wavelength of about 495 inn to about 570 nm, for example. In an exemplary embodiment, the blue light may have a wavelength of about 450 nm to about 495 nm, for example.

In an exemplary embodiment, the first organic light emitting element141may emit white light. When the first organic light emitting element141emits white light, it may have, in an exemplary embodiment, a structure in which a red light emitting layer, a green light emitting layer, and a blue light emitting layer are stacked. In addition, a color filter for displaying red, green, and blue colors may further be included. However, the invention is not limited thereto, and the first organic light emitting element141may emit various other color lights.

Although not illustrated in the drawings, the first organic light emitting element141may have a multilayer structure including a hole injection layer (“HIL”), a hole transport layer (“HTL”), an electron transport layer (“ETL”), and an electron injection layer (“EIL”).

The common electrode150may be disposed on the first organic light emitting element141and the pixel defining layer130. In an exemplary embodiment, the common electrode150may be disposed over the entire surface of the first organic light emitting element141and the pixel defining layer130. The common electrode150may be a cathode in an exemplary embodiment. In an exemplary embodiment, the common electrode150may include any one or more of Li, Ca, Lif/Ca, LiF/Al, Al, Au, and Mg, for example. In addition, the common electrode150may include a metal thin film having a low work function. In an exemplary embodiment, the common electrode150may be a transparent or translucent electrode including any one or more of ITO, IZO, zinc oxide (ZnO), indium oxide (In2O3), IGO and AZO, for example.

The buffer layer151may be disposed on the common electrode150. The material of the buffer layer151is not particularly limited. In an exemplary embodiment, the buffer layer151may include an inorganic material or an organic material. In an alternative exemplary embodiment, the buffer layer151may have a structure in which at least one of an organic layer and an inorganic layer is stacked in a single-layer structure or a stacked layer structure. In an exemplary embodiment, the buffer layer151may be an air layer. Here, when the buffer layer151is an air layer, it means that no particular components are disposed between the common electrode150and the encapsulation layer160.

Although not illustrated in the drawings, a capping layer may be disposed on the common electrode150. The capping layer may prevent light incident on the common electrode150from being lost by total reflection. The capping layer may include an organic film or an inorganic film in an exemplary embodiment.

The encapsulation layer160may be disposed on the first substrate110to cover the organic light emitting elements140. That is, the organic light emitting elements140may be disposed between the first substrate110and the encapsulation layer160. The encapsulation layer160may block the organic light emitting elements140from external oxygen and moisture.

The encapsulation layer160may be a transparent insulating substrate in an exemplary embodiment. The encapsulation layer160may be a glass substrate, a quartz substrate, a transparent resin substrate, or the like. A sealing member may be provided between the encapsulation layer160and the first substrate110to bond the encapsulation layer160and the first substrate110together. A case where the encapsulation layer160is a transparent insulating substrate will hereinafter be described as an example.

The diffraction pattern layer170may be disposed on the encapsulation layer160. More specifically, the diffraction pattern layer170may be disposed on the path of light emitted from the organic light emitting elements140. The position of the diffraction pattern layer170is not limited as long as the diffraction pattern layer170is disposed on the path of light emitted from the organic light emitting elements140. In an exemplary embodiment, the diffraction pattern layer170may be disposed on or under the encapsulation layer160based onFIG. 1, for example. In the specification, a case where the diffraction pattern layer170is disposed on the encapsulation layer160will be described as an example.

A plurality of diffraction patterns171may increase an emission area by diffracting light emitted from the organic light emitting elements140. This will be described later with reference toFIGS. 7A to 7C.

The diffraction patterns171may have periodicity. All of the diffraction patterns171may have the same shape in an exemplary embodiment. The periodicity and shape of the diffraction patterns171will be described in more detail with reference toFIGS. 3 through 5.

FIG. 3is a perspective view of the encapsulation layer160and the diffraction pattern layer170illustrated inFIG. 1.FIG. 4is a plan view of the encapsulation layer160and the diffraction pattern layer170illustrated inFIG. 3.FIG. 5is a cross-sectional view taken along line I2-I2′ ofFIG. 4.

Referring toFIGS. 3 through 5, the diffraction pattern layer170may include a plurality of diffraction patterns171disposed on the encapsulation layer160.

The diffraction pattern layer170may include the diffraction patterns171. In an exemplary embodiment, the diffraction patterns171may protrude upward from the encapsulation layer160based onFIG. 5. Here, the upward direction is the direction of the path of light emitted from the organic light emitting elements140(refer toFIG. 1).

The diffraction patterns171may be cylindrical in an exemplary embodiment. That is, upper and lower surfaces of the diffraction patterns171may be circular. Here, the circular shape is a concept including a shape substantially close to a circle in a plan view. In an exemplary embodiment, the circle shape may include an ellipse or a polygon substantially close to a circle, for example.

The diffraction patterns171may have a first thickness t1. The first thickness t1refers to a distance from the lower surfaces to the upper surfaces of the diffraction patterns171based onFIG. 5.

The diffraction patterns171may be arranged with a first period DP1. In addition, the diffraction patterns171may have a first length d1. The definition of the first period. DP1and the first length d1will be described based on a first diffraction pattern171aand a second diffraction pattern171bby referring toFIGS. 5 and 6.

FIG. 6is a cross-sectional view taken along a first virtual line cl1ofFIG. 5. More specifically,FIG. 6illustrates a cross-sectional area cs1taken along the first virtual line cl1ofFIG. 5. Here, the first virtual line cl1refers to a line passing through a halfway point of the first thickness t1of each of the diffraction patterns171. Reference numeral171a1indicates a cross section of the first diffraction pattern171ataken along the first virtual line cl1. Reference numeral171b1indicates a cross section of the second diffraction pattern171btaken along the first virtual line cl1.

Referring toFIG. 6, the first period DP1is defined as a distance from a side of the cross section171a1of the first diffraction pattern71aadjacent to a side of the cross section171b1of the second diffraction pattern171bto the other side of the cross section171b1of the second diffraction pattern171bopposite the above side of the cross section171b1of the second diffraction pattern171b. In addition, the first length d1of, e.g., the second diffraction pattern171bdenotes a width of the cross section171b1of the second diffraction pattern171b.

That is, the first period DP1and the first length d1of the diffraction patterns171are defined based on the cross sections of the diffraction patterns171taken along the first virtual line cl1.

Referring again toFIGS. 3 and 4, a period between diffraction patterns arranged along a first direction X among the diffraction patterns171and a period between diffraction patterns arranged along a second direction Y among the diffraction patterns171may all be the first period DP1in an exemplary embodiment. In addition, the number of diffraction patterns arranged along the first direction X and the number of diffraction patterns arranged along the second direction Y may be equal to each other in an exemplary embodiment. Here, the first direction X is defined as a row direction based onFIGS. 3 and 4. The second direction Y is defined as a column direction perpendicular to the first direction X based onFIGS. 3 and 4.

When at least one of the first period. DP1, the first length d1and the first thickness t1of the diffraction patterns171is changed, a first diffraction angle θ1(refer toFIG. 7A) of light emitted from the organic light emitting elements140, a second diffraction angle θ2(refer toFIG. 7A) of the light passing through the diffraction pattern layer170, a diffraction distance β (refer toFIG. 7B), and luminance may be changed. This will be described later.

FIGS. 7A to 7Care views for explaining the enlargement of the emission area of the organic light emitting display device illustrated inFIG. 1.

With reference toFIGS. 1 and 7A to 7C, a case where the emission area is enlarged by the diffraction of light L1emitted from the first organic light emitting element141will be described based on the first pixel unit PX1. For ease of description, some components illustrated inFIG. 1are omitted fromFIGS. 7A to 7C.

An emission pattern generated in a first region TA1by the light L1emitted from the first organic light emitting element141is defined as a first emission pattern EP1. In addition, emission patterns generated in a second region TA2by lights L2a, L2band L2cpassing through the diffraction pattern layer170are defined as second emission patterns EP2. Here, the lights L2a, L2band L2cpassing through the diffraction pattern layer170will be referred to as diffracted lights.

The light L1emitted from the first organic light emitting element141may be provided to the diffraction pattern layer170via the encapsulation layer160. The path of the light L1emitted from the first organic light emitting element141may be changed at a predetermined angle by refractive indices of the encapsulation layer160and the buffer layer151. The change in the path of the light L1by the refractive indices of the encapsulation layer160and the buffer layer151will be described later in relation to the diffraction distance β.

The diffraction pattern layer170may diffract the light L1emitted from the first organic light emitting element141, thereby generating the first through third diffracted lights L2athrough L2c. Each of the first through third diffracted lights L2athrough L2cmay include zeroth- and first-order diffracted lights. Here, the zeroth-order diffracted light refers to light having the same path before and after being diffracted by the diffraction pattern layer170, in addition, the first-order diffracted light refers to light having its path changed by the diffraction pattern layer170and having the second diffraction angle θ2with respect to the zeroth-order diffracted light.

InFIG. 7A, for example, reference numerals L2b1, L2a1and L2c1indicate zeroth-order diffracted lights. In addition, reference numerals L2b2, L2b3, L2a2, L2a3, L2c2and L2c3indicate first-order diffracted lights. In an exemplary embodiment, each of the first through third diffracted lights L2athrough L2cmay further include a second or higher-order diffracted light. In the specification, a case where each of the first through third diffracted lights L2athrough L2cincludes the zeroth-order diffracted light and the first-order diffracted light will be described as an example.

The first, second and third diffracted lights L2a, L2band L2cmay include first, second and third effective lights L2a1, L2b3, and L2c2having paths perpendicular to the first substrate110, respectively. Here, the perpendicular direction may include not only a direction perfectly perpendicular to the first substrate110but also a direction substantially perpendicular to the first substrate110. The order of diffracted light is not limited as long as effective light has a path perpendicular to the first substrate110. That is, the effective light may include both the zeroth-order diffracted light and the first-order diffracted light as long as its path is perpendicular to the first substrate110.

The diffraction pattern layer170may generate the first, second and third effective lights L2a1, L2b3and L2c2by diffracting the light L1emitted from the first organic light emitting element141. Accordingly, the second emission patterns EP2may include a reference emission pattern Pref and a plurality of duplicate emission patterns P1through P8duplicated from the reference emission pattern Pref. However, the luminance of the reference emission pattern Pref may be different from that of the first duplicate emission pattern P1. The duplicate emission patterns P1through P8will hereinafter be described based on the first duplicate emission pattern P1.

The first region TA1and the second region TA2have the same area. The number of emission patterns included in the second region TA2is larger than the number of emission patterns included in the first region TA1. This indicates that the area of an emission region is larger in the second region TA2than in the first region TA1. That is, it may also be expressed that the area of a non-emission region is smaller in the second region TA2than in the first region TA1.

A wide emission area may be expressed as a high effective emission area ratio. The effective emission area ratio is defined as a ratio of the area of emission patterns existing in a region to the area of the region. Here, the emission patterns used to calculate the effective emission area ratio may include both a reference emission pattern and duplicate emission patterns. In an exemplary embodiment, the second region TA2has nine emission patterns including the reference emission pattern Pref and the duplicate emission patterns P1through P8, while the first region TA1has one emission pattern, for example. Accordingly, the effective emission area ratio of the second region TA2is greater than that of the first region TA1.

Here, the duplicate emission patterns used to calculate the effective emission area ratio may be defined as duplicate emission patterns having a luminance of about 3 percent (%) or more of the luminance of the reference emission pattern, for example. In an exemplary embodiment, when the duplicate emission patterns P1through P8have a luminance of about 3% or more of the luminance of the reference emission pattern Pref, the duplicate emission patterns P1through P8may be used to calculate the effective emission area ratio, for example. When the duplicate emission patterns have a luminance of about 3% or more of the luminance of the reference emission pattern, the luminance of the duplicate emission patterns may be higher than that of the reference emission pattern.

FIG. 8is a view for explaining an increase in the effective emission area ratio of the organic light emitting display device illustrated inFIG. 1.FIG. 8(a)shows a region where emission patterns before light passes through the diffraction pattern layer170(refer toFIG. 7A) are arranged, andFIG. 8(b)shows a region where emission patterns after the light passes through the diffraction pattern layer170are arranged. Reference numeral TA1′ indicates an example of the first region TA1(refer toFIG. 7C). In addition, reference numeral TA2′ illustrated inFIG. 8(b)indicates an example of the second region TA2(refer toFIG. 7B). Hereinafter, the first region TA1′ and the second region TA2′ having the same area will be described as an example.

Referring toFIG. 8, it may be seen that the emission region has increased in the second region TA2′ as compared to the first region TA1′ having the same area as the second region TA2′. This indicates that the effective emission area ratio has increased. That is, the organic light emitting display device according to the exemplary embodiment may increase the effective emission area ratio by diffracting the light L1(refer toFIG. 7A) emitted from the organic light emitting elements140(refer toFIG. 1). In addition, as the effective emission area ratio increases, the organic light emitting display device according to the exemplary embodiment may improve the luminous efficiency of the light L1emitted from the organic light emitting elements140.

Factors required for the luminance of at least one of the duplicate emission patterns P1through P8to satisfy at least about 3% of the luminance of the reference emission pattern Pref will now be described with reference toFIGS. 9 through 11.

FIG. 9is a more detailed cross-sectional view taken along line I2-I2′ ofFIG. 4.FIG. 10shows graphs illustrating the luminance of each of the reference emission pattern Pref, the first duplicate emission pattern P1and the fifth duplicate emission pattern. P5ofFIG. 7by display color in order to explain a luminance for satisfying the emission region.FIG. 11shows graphs obtained by normalizing the luminance of each of the first duplicate emission pattern P1and the fifth duplicate emission pattern P5based on the luminance of the reference emission pattern Pref illustrated inFIG. 7B. InFIG. 9, a case where an air layer AL is disposed on the diffraction pattern layer170will be described as an example.

The luminance of each of the reference emission pattern Pref and the duplicate emission patterns P1through P8may be affected by the first period DP1, the first length d1, the first thickness t1, a refractive index n1of each of the diffraction patterns171, and a refractive index n2of the air layer AL.

Here, when the relationship between the first period DP1and the first length d1satisfies Inequality (1) below and when the relationship between the first thickness t1, the refractive index n1of each of the diffraction patterns171and the refractive index n2of the air layer AL satisfies Inequality (2) below, the luminance of at least one of the duplicate emission patterns P1through P8may be about 3% or more of the luminance of the reference emission pattern Pref.

Of the duplicate emission patterns P1through P8, the first through fourth duplicate emission patterns P1through P4arranged in the same row or column as the reference emission pattern Pref may have the same luminance in an exemplary embodiment. In addition, of the duplicate emission patterns P1through P8, the fifth through eighth duplicate emission patterns P5through P8arranged diagonally to the reference emission pattern Pref may have the same luminance in an exemplary embodiment. However, the first through fourth duplicate emission patterns P1through P4may have different luminance from the fifth through eighth duplicate emission patterns P5through P8in an exemplary embodiment. The following description will be made based on the reference emission pattern Pref, the first duplicate emission pattern P1, and the fifth duplicate emission pattern P5.

First, the relationship between the first period DP1and the first length d1will be described. The first period DP1and the first length d1described above with reference toFIGS. 5 and 6should satisfy Inequality (1) below:
0.4≤d1/DP1≤1.  (1)

Inequality (1) will be described in more detail with reference toFIGS. 7A to 7C, 10 and 11.FIG. 10(a)is a graph illustrating luminance with respect to a d1/DP1value when an organic light emitting element emits blue light.FIG. 10(b)is a graph illustrating luminance with respect to the d1/DP1value when the organic light emitting element emits green light.FIG. 10(c)is a graph illustrating luminance with respect to the d1/DP1value when the organic light emitting element emits red light.FIGS. 11(a) through 11(c)are graphs obtained by normalizing the luminances of the first duplicate emission pattern P1and the fifth duplicate emission pattern P5illustrated inFIGS. 10(a) through 10(c)based on the luminance of the reference emission pattern Pref InFIGS. 10 and 11, intensity indicates the intensity of luminance.

Referring toFIGS. 10(a) through 10(c), when the d1/DP1value increases, the luminance of the reference emission pattern Pref generally decreases, while the luminance of the first emission pattern P1and the luminance of the fifth emission pattern P5generally increase.

Referring toFIGS. 11(a) through 11(c)obtained by normalizing luminance based on the luminance of the reference emission pattern Pref, when the d1/DP1value is about 0.4 or more, the luminance of the first duplicate emission pattern P1is about 3% or more of the luminance of the reference emission pattern Pref. When the d1/DP1value is about 0.7 to 0.9, the luminance of the first duplicate emission pattern P1may be higher than the luminance of the reference emission pattern Pref.

When the d1/DP1value is 1, it indicates that the first period DP1and the first length d1are equal to each other. However, since the diffraction patterns171of the organic light emitting display device according to the exemplary embodiment have circular cross sections, even when the first period DP1and the first length d1are equal to each other, the cross section of each of the diffraction patterns171has a region not in contact with the cross section of an adjacent diffraction pattern171. Therefore, the d1/DP1value may include 1.

Next, the first thickness t1of each of the diffraction patterns171, the refractive index n1of each of the diffraction patterns171, and the refractive index n2of the air layer AL should satisfy Inequality (2) below InFIG. 7, a case where the air layer AL is disposed on the diffraction patterns171is illustrated as an example. However, an intermediate layer, e.g., a protective layer191(refer toFIG. 49), may also be disposed on the diffraction patterns171, instead of the air layer AL. When another component (the intermediate layer) instead of the air layer AL is disposed on the diffraction patterns171, n2may be replaced with a refractive index of the component.
(m*λ)−60 (nm)≤A≤(m*λ)+60 (nm)
A≠Δn·t1,  (2)
where units of Δn·t1and A are nm, Δn=|n1−n2|, λ is a wavelength of light emitted from the first organic light emitting element141, and m is an integer of 0 or more.

Inequality (2) will now be described in more detail with reference toFIGS. 7, 9, 12 and 13.

FIG. 12(a)is a graph illustrating luminance with respect to a Δn·t1value when an organic light emitting element emits blue light.FIG. 12(b)is a graph illustrating luminance with respect to the Δn·t1value when the organic light emitting element emits green light.FIG. 12(c)is a graph illustrating luminance with respect to the Δn·t1value when the organic light emitting element emits red light.FIGS. 13(a) through 13(c)are graphs obtained by normalizing the luminances of the first duplicate emission pattern P1and the fifth duplicate emission pattern P5illustrated inFIGS. 12(a) through 12(c)based on the luminance of the reference emission pattern Pref.

Referring toFIGS. 12(a) through 12(c), the luminance of the reference emission pattern Pref is repeatedly increased or decreased as the Δn·t1value increases. The luminance of the reference emission pattern Pref according to the Δn·t1value may generally have a sinusoidal shape on the graph.

Referring toFIGS. 13(a) through 13(c)obtained by normalizing luminance based on the luminance of the reference emission pattern Pref, as the Δn·t1value increases, the luminance of each of the first duplicate emission pattern P1and the fifth duplicate emission pattern P5is repeatedly increased or decreased. That is, the luminance of each of the first duplicate emission pattern P1and the fifth duplicate emission pattern P5according to the Δn·t1value may have a substantially sinusoidal shape on the graph.

The following description will be given based onFIG. 13(c). Referring toFIG. 13(c), sections m1through m3are regions in which both the luminance of the first duplicate emission pattern P1and the luminance of the fifth duplicate emission pattern P5are less than about 3% of the luminance of the reference emission pattern Pref. That is, the sections m1through m3are included in the range of A in Inequality (2) above. Therefore, the range of the Δn·t1value corresponds to the range excluding the range of A in Inequality (2).

In an exemplary embodiment, the section m2inFIG. 13(c)is a section indicating the range of the A value when m=1, for example. Since λ is 620 nm inFIG. 13(c), the above values may be reflected in Inequality (2) as follows:
(1*620 nm)−60 (nm)≤A≤(1*620 nm)+60 (nm)
=>560 nm≤A≤680 nm.

Referring toFIG. 13(c), it may be seen that both the luminance of the first duplicate emission pattern P1and the luminance of the fifth duplicate emission pattern P5are less than about 3% of the luminance of the reference emission pattern Pref within the range of A (560 nm≤A≤680 nm).

Accordingly, when the Δn·t1value is within the range excluding the range of A of Inequality (2), at least one of the luminance of the first duplicate emission pattern P1and the luminance of the fifth duplicate emission pattern P5may be about 3% or more of the luminance of the reference emission pattern Pref.

That is, in the organic light emitting display device according to the exemplary embodiment, the relationship between the first period DP1and the first length d1may satisfy Inequality (1), and the relationship between the first thickness t1, the refractive index n1of each of the diffraction patterns171and the refractive index n2of the air layer AL may satisfy Inequality (2).

Accordingly, the luminance of at least one of the duplicate emission patterns P1through P8may be about 3% or more of the luminance of the reference emission pattern Pref.

The range of the first period DP1and the range of the first length d1are not particularly limited as long as the relationship between the first period DP1and the first length d1satisfies Inequality (1). In an exemplary embodiment, the first period DP1may be in the range of about 3.5 micrometers (μm) to about 20 μm, for example. In this case, the first length d1may be in the range of about 1.4 μm to about 20 μm, for example.

In addition, values of Δn and t1are not particularly limited as long as the relationship between the first thickness t1, the refractive index n1of each of the diffraction patterns171and the refractive index n2of the air layer AL satisfies Inequality (2). In an exemplary embodiment, Δn may be about 0.47, for example. In addition, the first thickness t1may be about 500 nm to about 650 nm, for example.

Referring toFIG. 11, when the d1/DP1value is 0.45 to 1, both the luminance of the first duplicate emission pattern P1and the luminance of the fifth duplicate emission pattern P5may be about 3% or more of the luminance of the reference emission pattern Pref.

That is, when the d1/DP1value is within the range of 0.45 to 1 and the value of Δn·t1is outside the range of A of Inequality (2), both the luminance of the first duplicate emission pattern P1and the luminance of the fifth duplicate emission pattern P5may be about 3% or more of the luminance of the reference emission pattern Pref. This indicates that the luminances of all of the duplicate emission patterns P1through P8may be about 3% or more of the luminance of the reference emission pattern Pref.

Next, the relationship between the effective emission area ratio and the diffraction distance β will be described.

Referring to Table 1 below, it may be seen that the effective emission area ratio increases substantially as the diffraction distance β increases. Here, the diffraction distance β is defined as a shortest distance between the reference emission pattern Pref and one of the duplicate emission patterns P1through P8(refer toFIG. 7B). In an exemplary embodiment, the diffraction distance β may be defined as a distance from the reference emission pattern Pref to the first duplicate emission pattern P1, for example.

That is, the effective emission area ratio may be affected by the diffraction distance β. Hereinafter, factors that affect the diffraction distance β will be described.

Factors that determine the diffraction distance β will be described with reference toFIG. 14.FIG. 14is a view for explaining factors that determine the diffraction distance β.

Referring toFIG. 14, in an exemplary embodiment, the diffraction distance β may be determined by an emission color of the first organic light emitting element141, a distance Z between the diffraction pattern layer170and the organic light emitting elements140, refractive indices of components disposed between the diffraction pattern layer170and the organic light emitting elements140(that is, a refractive index nEN of the encapsulation layer160, a refractive index n151of the buffer layer151), the first period DP1of the diffraction patterns171, the first diffraction angle θ1, the second diffraction angle θ2, and the like. When the buffer layer151is an air layer as described above, the refractive index n151of the buffer layer151may be expressed as a refractive index (about 1) of the air layer.

More specifically, the diffraction distance β may be given by Equation (3) below:
β=z1·tan θ1+z2·tan θ2.  (3)

Here, the distance Z between the first organic light emitting element141and the diffraction pattern layer170is defined as the sum of z1and z2. Here, z1indicates a shortest distance between the first organic light emitting element141and the encapsulation layer160, and z2indicates a shortest distance between the encapsulation layer160and the diffraction pattern layer170. That is, z2may also be defined as a thickness of the encapsulation layer160. As described above, θ1and θ2indicate the first diffraction angle and the second diffraction angle, respectively.

The first diffraction angle θ1may be given by Equation (4) below:

θ1=sin-1⁡(λDP⁢⁢1·1n⁢⁢151),(4)
where λ indicates the wavelength of the emission color of the first organic light emitting element141.

In addition, the second diffraction angle θ2may be given by Equation (5) below:

That is, the first diffraction angle θ1may be determined by the first period DP1and the refractive index n151of the buffer layer151. In addition, the second diffraction angle θ2may be determined by the first period DP1and the refractive index nEN of the encapsulation layer160.

If Equations (4) and (5) are substituted into Equation (3), the diffraction distance β may be given by Equation (6) below:

In an exemplary embodiment, when another component instead of the buffer layer151is disposed between the encapsulation layer160and the first organic light emitting element141, n151of Equation (6) may be replaced with a refractive index of the component. In an exemplary embodiment, when the buffer layer151is omitted and an air layer is disposed between the encapsulation layer160and the first organic light emitting element141, n151of Equation 6 may be replaced with a refractive index (about 1) of the air layer.

In an exemplary embodiment, when the thickness of the buffer layer151is negligibly small, the shortest distance Z between the first organic light emitting element141and the diffraction pattern layer170may be defined as the thickness of the encapsulation layer160. In this case, a diffraction distance β′ may be given by Equation (7) below:

The organic light emitting display device according to the exemplary embodiment may control the diffraction distance β by adjusting the emission color of the first organic light emitting element141, the distance Z between the diffraction pattern layer170and the organic light emitting elements140, the refractive index nEN of the encapsulation layer160, the first period DP1of the diffraction patterns171, the first diffraction angle θ1and the second diffraction angle θ2.

As described above, the effective emission area ratio may generally increase when the diffraction distance β increases. However, the increased diffraction distance β can cause blurring. Blurring refers to an image blurring phenomenon caused by overlapping display colors of adjacent pixels. Therefore, it is required to calculate an appropriate diffraction distance β in order to balance an increase in effective emission area ratio and blurring.

Each of the effective emission area ratio and blurring may also be affected by the distance between pixels.

In an exemplary embodiment, even when the diffraction distance β is the same in two organic light emitting display devices having different pixel arrangements, the distance between adjacent pixels may be different due to the different pixel arrangements, for example. Accordingly, the two organic light emitting display devices may have different effective emission area ratios and different degrees of blurring.

That is, in order to strike a balance between the effective emission area ratio and the blurring, it is necessary to consider not only the diffraction distance1but also the distance between adjacent pixels.

The distance between pixels will first be defined with reference toFIG. 15.

FIG. 15is a plan view illustrating the pixel arrangement of an organic light emitting display device according to an exemplary embodiment. Although a first pixel unit PX1is illustrated inFIG. 15to explain the pixel arrangement structure, the first pixel unit PX1illustrated inFIG. 1and the first pixel unit PX1illustrated inFIG. 15do not have the same configuration.

Referring toFIG. 15, as for the arrangement relationship of first through fourth pixel units PX1through PX4, the first pixel unit PX1may neighbor the third pixel unit PX3along the first direction X. The second pixel unit PX2may neighbor the fourth pixel unit PX4along the first direction X. The first pixel unit PX1may neighbor the second pixel unit PX2in a direction diagonal to the first direction X and the second direction Y. The third pixel unit PX3may neighbor the fourth pixel unit PX4along the second direction Y. That is, the first through fourth pixel units PX1through PX4may be arranged in a parallelogram shape in an exemplary embodiment. In the specification, when it is expressed that “a first component and a second component neighbor each other”, it means that the same component as the first component and the second component is not disposed between the first component and the second component.

Although the first through fourth pixel units PX1through PX4are all illustrated as being rhombic as an exemplary embodiment, the shape and size of each of the first through fourth pixel units PX1through PX4are not limited to those illustrated inFIG. 15.

The first pixel unit PX1may display a red color in an exemplary embodiment. That is, the first pixel unit PX1may include a red organic light emitting layer that emits red light. The second and fourth pixel units PX2and PX4may display a green color in an exemplary embodiment. That is, the second and fourth pixel units PX2and PX4may include a green organic light emitting layer that emits green light. The third pixel unit PX3may display a blue color in an exemplary embodiment. That is, the third pixel unit PX3may include a blue organic light emitting layer that emits blue light.

The first through fourth pixel units PX1through PX4may form one pixel unit. That is, the first through fourth pixel units PX1through PX4may be arranged in a pixel area DA1in an RGBG pentile manner. However, the arrangement relationship of a plurality of pixel units in the pixel area DA1is not limited to that illustrated inFIG. 15. In an exemplary embodiment, the arrangement relationship of a plurality of pixel units may vary according to the display colors of the pixel units, the applied resolution and aperture ratio of an organic light emitting display device, and the like, for example.

Here, a distance PP1between pixels is defined as a distance between pixel units that display the same color. More specifically, the inter-pixel distance PP1is defined as a distance between center points of pixel electrodes included in pixel units displaying the same color. Hereinafter, the second pixel unit PX2and the fourth pixel unit PX4which emit green light will be described as an example.

The inter-pixel distance PP1may be defined as a shortest distance between a first center point cp1located in the second pixel unit PX2and a second center point cp2located in the fourth pixel unit PX4. In an exemplary embodiment, the first center point cp1and the second center point cp2may be center points of pixel electrodes included in the second pixel unit PX2and the fourth pixel unit PX4, respectively.

Next, the relationship between the diffraction distance β, the inter-pixel distance PP1, and the effective emission area ratio will be described. Table 2 below shows the effective emission area ratio according to the value of the diffraction distance β/the inter-pixel distance PP1.

Referring to Table 2, the effective emission area ratio may generally increase as the value of the diffraction distance β/the inter-pixel distance PP1increases.

Next, the relationship between the diffraction distance β, the inter-pixel distance PP1, and blurring will be described with reference to Table 3. Table 3 below shows a blurring perception score according to the value of the diffraction distance β/the inter-pixel distance PP1. Here, the blurring perception score is the result of experimenting on the degrees of blurring perception of users while changing the value of the diffraction distance β/the inter-pixel distance PP1. The blurring perception score is represented by an average value of the degrees of blurring reception of the users. Here, when the blurring perception score is 5 or more, blurring is perceived to such an extent that the users may feel discomfort when viewing the screen.

Referring to Table 3, when the value of the diffraction distance β/the inter-pixel distance PP1is about 1.89 or more, the blurring perception score of the users is 5 or more. This indicates that, when the value of the diffraction distance β/the inter-pixel distance PP1is greater than about 1.9, most users perceive blurring and feel discomfort.

Therefore, in view of Tables 2 and 3, the value of the diffraction distance β/the inter-pixel distance PP1may satisfy Inequality (8) below:
0.1≤β/PP1≤1.9.  (8)

That is, the value of the diffraction distance β/the inter-pixel distance PP1may be set to 0.1 to 1.9 in order to balance the effective emission area ratio and the degree of blurring perception. Accordingly, the organic light emitting display device according to the exemplary embodiment may improve luminous efficiency by increasing the effective emission area ratio without causing discomfort due to the perception of blurring.

If the value of the diffraction distance β/the inter-pixel distance PP1is in the range of 0.1 to 1.9, the value of each of the diffraction distance β and the inter-pixel distance PP1is not particularly limited. In an exemplary embodiment, the shortest distance z2between the encapsulation layer160and the diffraction pattern layer170, i.e., the thickness z2of the encapsulation layer160and the first period DP1may have values specified in Table 4 below:

Next, an exemplary embodiment of the diffraction pattern layer170will be described.

FIG. 16is a perspective view of an exemplary embodiment of the diffraction pattern layer170illustrated inFIG. 1.FIG. 17is a plan view of a diffraction pattern layer170aillustrated inFIG. 16.FIG. 18is a cross-sectional view taken along line I3-I3′ ofFIG. 17.FIG. 19is a cross-sectional view taken along a second virtual line cl2ofFIG. 18. For simplicity, a redundant description of components identical to those described above with reference toFIGS. 1 through 15will be omitted.

Referring toFIGS. 16 through 19, the diffraction pattern layer170amay be disposed on the encapsulation layer160. A plurality of diffraction patterns172may penetrate the diffraction pattern layer170a. The diffraction patterns172may be shaped like engraved cylinders in an exemplary embodiment. That is, while the diffraction patterns171illustrated inFIGS. 3 through 5protrude from the encapsulation layer160in a light emission direction, the diffraction patterns172illustrated inFIGS. 16 through 18may be in the form of holes penetrating from the diffraction pattern layer170atoward the encapsulation layer160.

The diffraction patterns172may have a second thickness t2. The second thickness t2refers to a distance from lower surfaces of the diffraction patterns172(i.e., an upper surface of the encapsulation layer160) to upper surfaces (i.e., upper surfaces of the diffraction patterns172) based onFIG. 18.

The diffraction patterns172may be arranged with a second period DP2. In addition, the diffraction patterns172may have a second length d2. Here, the second period DP2and the second length d2are defined based on a cross-sectional area cs2taken along the second virtual line cl2. The second virtual line cl2refers to a line passing through a halfway point of the second thickness t2of each of the diffraction patterns172. Reference numeral172a1indicates a cross section of a first diffraction pattern172ataken along the second virtual line cl2. Reference numeral172b1indicates a cross section of a second diffraction pattern172btaken along the second virtual line cl2.

Referring toFIG. 19, the second period DP2is defined as a distance from a side of the cross section172a1of the first diffraction pattern172aadjacent to a side of the cross section172bof the second diffraction pattern172bto the other side of the cross section172b1of the second diffraction pattern172bopposite the above side of the cross section172b1of the second diffraction pattern172b. In addition, the second length d2of the second diffraction pattern172bdenotes, for example, a width of the cross section172b1of the second diffraction pattern172b.

Referring again toFIGS. 16 through 18, a period between diffraction patterns arranged along the first direction X and a period between diffraction patterns arranged along the second direction Y among the diffraction patterns172may all be the second period DP2in an exemplary embodiment. In addition, the number of diffraction patterns arranged along the first direction X and the number of diffraction patterns arranged along the second direction Y may be equal to each other in an exemplary embodiment.

FIG. 20is a perspective view of an exemplary embodiment of the diffraction pattern layer170illustrated inFIG. 1.FIG. 21is a plan view of a diffraction pattern layer170billustrated inFIG. 20.FIG. 22is a cross-sectional view taken along line I4-I4′ ofFIG. 21.FIG. 23is a cross-sectional view taken along a third virtual line cl3ofFIG. 22. For simplicity, a redundant description of components identical to those described above with reference toFIGS. 1 through 19will be omitted.

The diffraction pattern layer170bmay include a plurality of diffraction patterns173. In an exemplary embodiment, the diffraction patterns173may protrude upward from the encapsulation layer160based onFIG. 20.

The diffraction patterns173may be quadrilateral in a plan view. In an exemplary embodiment, the diffraction patterns173may be square in a plan view. That is, the diffraction patterns173may be cubic in an exemplary embodiment.

The diffraction patterns173may have a third thickness t3. The third thickness t3refers to a distance from lower surfaces of the diffraction patterns173(i.e., the upper surface of the encapsulation layer160) to upper surfaces (i.e., upper surfaces of the diffraction patterns173) based onFIG. 22.

The diffraction patterns173may be arranged with a third period DP3. In addition, the diffraction patterns173may have a third length d3. Here, the third period DP3and the third length d3are defined based on a cross-sectional area cs3taken along the third virtual line cl3. The third virtual line cl3refers to a line passing through a halfway point of the third thickness t3of each of the diffraction patterns173. Reference numeral173a1indicates a cross section of a first diffraction pattern173ataken along the third virtual line cl3. Reference numeral173bindicates a cross section of a second diffraction pattern173btaken along the third virtual line cl3.

Referring toFIG. 23, the third period DP3is defined as a distance from a side of the cross section173a1of the first diffraction pattern173aadjacent to a side of the cross section173bof the second diffraction pattern173bto the other side of the cross section173b1of the second diffraction pattern173bopposite the above side of the cross section173b1of the second diffraction pattern173b. In addition, the third length d3of the second diffraction pattern173bdenotes, for example, a width of the cross section173b1of the second diffraction pattern173b.

Referring again toFIGS. 20 through 22, a period between diffraction patterns arranged along the first direction X and a period between diffraction patterns arranged along the second direction Y among the diffraction patterns173may all be the third period DP3in an exemplary embodiment. In addition, the number of diffraction patterns arranged along the first direction X and the number of diffraction patterns arranged along the second direction Y may be equal to each other in an exemplary embodiment.

As illustrated inFIGS. 20 through 23, when the cross sections of the diffraction patterns173are square, Inequality (1) may be changed to 0.4≤d1/DP1<1.

Since the diffraction patterns173have quadrilateral cross sections, the organic light emitting display device according to the exemplary embodiment does not include a minimum space required for diffraction when the first period DP1and the first length d1are equal to each other. Thus, a case where the d1/DP1value is 1 is excluded.

FIG. 24is a perspective view of an exemplary embodiment of the diffraction pattern layer170illustrated inFIG. 1.FIG. 25is a plan view of a diffraction pattern layer170cillustrated inFIG. 24.FIG. 26is a cross-sectional view taken along line I5-I5′ ofFIG. 25.FIG. 27is a cross-sectional view taken along a fourth virtual line cl4ofFIG. 26. For simplicity a description of components identical to those described above with reference toFIGS. 1 through 23will be omitted.

Referring toFIGS. 24 through 27, the diffraction pattern layer170cmay be disposed on the encapsulation layer160. A plurality of diffraction patterns174may penetrate the diffraction pattern layer170c. The diffraction patterns174may be shaped like engraved quadrilateral pillars in an exemplary embodiment. That is, upper and lower surfaces of the diffraction patterns174illustrated inFIGS. 24 through 27may have quadrilateral cross sections, and the diffraction patterns174may be in the form of holes penetrating from the diffraction pattern layer170ctoward the encapsulation layer160.

The diffraction patterns174may have a fourth thickness t4. The fourth thickness t4refers to a distance from the lower surfaces of the diffraction patterns174(i.e., the upper surface of the encapsulation layer160) to upper surfaces (i.e., the upper surfaces of the diffraction patterns174) based onFIG. 26.

The diffraction patterns174may be arranged with a fourth period DP4. In addition, the diffraction patterns174may have a fourth length d4. Here, the fourth period DP4and the fourth length d4are defined based on a cross-sectional area cs4taken along the fourth virtual line cl4. The fourth virtual line cl4refers to a line passing through a halfway point of the fourth thickness t4of each of diffraction patterns174. Reference numeral174a1indicates a cross section of a first diffraction pattern174ataken along the fourth virtual line cl4. Reference numeral174b1indicates a cross section of a second diffraction pattern174btaken along the fourth virtual line cl4.

Referring toFIG. 27, the fourth period DP4is defined as a distance from a side of the cross section174a1of the first diffraction pattern174aadjacent to a side of the cross section174b1of the second diffraction pattern174bto the other side of the cross section174b1of the second diffraction pattern174bopposite the above side of the cross section174b1of the second diffraction pattern174b. In addition, the fourth length d4of the second diffraction pattern174bdenotes, for example, a width of the cross section174b1of the second diffraction pattern174b.

Referring again toFIGS. 24 through 26, a period between diffraction patterns arranged along the first direction X and a period between diffraction patterns arranged along the second direction Y among the diffraction patterns174may all be the fourth period DP4in an exemplary embodiment. In addition, the number of diffraction patterns arranged along the first direction X and the number of diffraction patterns arranged along the second direction Y may be equal to each other in an exemplary embodiment.

The upper and lower surfaces of the diffraction patterns171through174described above with reference toFIGS. 3 through 6 and 16 through 27may have the same area in an exemplary embodiment. Hereinafter, a case where the areas of the upper and lower surfaces of a plurality of diffraction patterns are different from each other will be described with reference toFIGS. 28 through 30.

FIGS. 28(a) through 30(b)illustrate embodiments of a case where the areas of upper and lower surfaces of a plurality of diffraction patterns of a diffraction pattern layer are different.

FIG. 28(a)is a cross-sectional view of a diffraction pattern layer170daccording to an exemplary embodiment.FIG. 28(b)is a cross-sectional view taken along a fifth virtual line cl5ofFIG. 28(a).

Referring toFIGS. 28(a) and 28(b), the diffraction pattern layer170dmay include a plurality of diffraction patterns175disposed on the encapsulation layer160and having a hemispherical shape. That is, the diffraction patterns175may protrude from the encapsulation layer160in a hemispheric shape in the light emission direction.

The diffraction patterns175may have a fifth thickness t5. The fifth thickness t5refers to a distance from lower surfaces of the diffraction patterns175(i.e., the upper surface of the encapsulation layer160) to upper surfaces (i.e., upper surfaces of the diffraction patterns175) based onFIG. 28(a).

The diffraction patterns175may be arranged with a fifth period DP5. In addition, the diffraction patterns175may have a fifth length d5. Here, the fifth period DP5and the fifth length d5are defined based on a cross-sectional area cs5taken along the fifth virtual line cl5. The fifth virtual line cl5refers to a line passing through a halfway point of the fifth thickness t5of each of the diffraction patterns175. Reference numeral175a1indicates a cross section of a first diffraction pattern175ataken along the fifth virtual line cl5. Reference numeral175b1indicates a cross section of a second diffraction pattern175btaken along the fifth virtual line cl5.

Referring toFIG. 28(b), the fifth period DP5is defined as a distance from a side of the cross section175a1of the first diffraction pattern175aadjacent to a side of the cross section175b1of the second diffraction pattern175bto the other side of the cross section175b1of the second diffraction pattern175bopposite the above side of the cross section175b1of the second diffraction pattern175b. In addition, the fifth length d5of the second diffraction pattern175bdenotes, for example, a width of the cross section175b1of the second diffraction pattern175b.

FIG. 29(a)is a cross-sectional view of a diffraction pattern layer170eaccording to an exemplary embodiment.FIG. 29(b)is a cross-sectional view taken along a sixth virtual line cl6ofFIG. 29(a).

Referring toFIGS. 29(a) and 29(b), the diffraction pattern layer170emay include a plurality of diffraction patterns176disposed on the encapsulation layer160and having a trapezoidal shape. That is, the diffraction patterns176may protrude from the encapsulation layer160in a trapezoidal shape in the light emission direction.

The diffraction patterns176may have a sixth thickness t6. The sixth thickness t6refers to a distance from lower surfaces of the diffraction patterns176(i.e., the upper surface of the encapsulation layer160) to upper surfaces (i.e., upper surfaces of the diffraction patterns176) based onFIG. 29(a).

The diffraction patterns176may be arranged with a sixth period DP6. In addition, the diffraction patterns176may have a sixth length d6. Here, the sixth period DP6and the sixth length d6are defined based on a cross-sectional area cs6taken along the sixth virtual line cl6. The sixth virtual line cl6refers to a line passing through a halfway point of the sixth thickness t6of each of the diffraction patterns176. Reference numeral176a1indicates a cross section of a first diffraction pattern176ataken along the sixth virtual line cl6. Reference numeral176b1indicates a cross section of a second diffraction pattern176btaken along the sixth virtual line cl6.

Referring toFIG. 29(b), the sixth period DP6is defined as a distance from a side of the cross section176a1of the first diffraction pattern176aadjacent to a side of the cross section176b1of the second diffraction pattern176bto the other side of the cross section176b1of the second diffraction pattern176bopposite the above side of the cross section176b1of the second diffraction pattern176b. In addition, the sixth length d6of the second diffraction pattern176bdenotes, for example, a width of the cross section176b1of the second diffraction pattern176b.

FIG. 30(a)is a cross-sectional view of a diffraction pattern layer170faccording to an exemplary embodiment.FIG. 30(b)is a cross-sectional view taken along a seventh virtual line cl7ofFIG. 30(a).

Referring toFIGS. 30(a) and 30(b), the diffraction pattern layer170fmay include a plurality of diffraction patterns177disposed on the encapsulation layer160and engraved in a trapezoidal shape. That is, while the diffraction patterns176illustrated inFIG. 29protrude from the encapsulation layer160in the light emission direction, the diffraction patterns177illustrated inFIG. 30may be in the form of holes penetrating from the diffraction pattern layer170ftoward the encapsulation layer160.

Even when the diffraction patterns177are engraved, the seventh length d7and the seventh period DP7of the diffraction patterns177are defined based on a cross-sectional area cs7taken along the seventh virtual line cl7.

That is, even when the areas of lower and upper surfaces of diffraction patterns of a diffraction pattern layer are different from each other, the period and length of the diffraction patterns are defined based on a cross section taken along a virtual line passing through the middle of the thickness of the diffraction pattern layer.

A method of forming the diffraction pattern layers170,170a,170b,170c,170d,170eand170fis not particularly limited. In an exemplary embodiment, the diffraction pattern layers170,170a,170b,170c,170d,170eand170fmay be provided by forming an inorganic layer on the encapsulation layer160and then performing an etching process. Here, the inorganic layer may include any one or more of silicon oxide (SiOx), silicon nitride (SiNx), and silicon oxynitride (SiONx). In addition, although the etching process is not particularly limited, dry etching may be used as an exemplary embodiment.

InFIGS. 1 through 30, a case where the diffraction pattern layers170,170a,170b,170c,170d,170eand170fare provided separately from the encapsulation layer160has been described. However, the invention is not limited to this case. Hereinafter, a case where an encapsulation layer and a diffraction pattern layer are unitary with each other will be described with reference toFIGS. 31 through 36. In the specification, when it is expressed that “a first component and a second component are unitary,” it means that the first and second components include the same material. However, when “the first component and the second component are unitary,” it does not necessarily mean that they are provided at the same time by the same process.

FIG. 31is a perspective view of an exemplary embodiment of the encapsulation layer160and the diffraction patterns171illustrated inFIG. 1.FIG. 32is a plan view of an encapsulation layer161unitary with a plurality of diffraction patterns178illustrated inFIG. 31.FIG. 33is a cross-sectional view taken along line I6-I6′ ofFIG. 32.FIG. 34is a cross-sectional view taken along an eighth virtual line cl8ofFIG. 33. For simplicity, a redundant description of components identical to those described above with reference toFIGS. 1 through 30will be omitted.

Referring toFIGS. 31 through 34, the diffraction patterns178may be unitary with the encapsulation layer161. That is, the diffraction patterns178may be engraved on the encapsulation layer161.

In an exemplary embodiment, the diffraction patterns178may be quadrilateral in a plan view. In addition, the diffraction patterns178may be cubic in an exemplary embodiment. However, the shape of the diffraction patterns178may also be circular in a plan view. In addition, the diffraction patterns178may be cylindrical in an exemplary embodiment.

The diffraction patterns178may have an eighth thickness t8. The eighth thickness t8refers to a distance from lower surfaces to upper surfaces of the diffraction patterns178based onFIG. 33.

The diffraction patterns178may be arranged with an eighth period DP8. In addition, the diffraction patterns178may have an eighth length d8. Here, the eighth period DP8and the eighth length d8are defined based on a cross-sectional area cs8taken along the eighth virtual line cl8. The eighth virtual line cl8refers to a line passing through a halfway point of the eighth thickness t8of each of the diffraction patterns178. Reference numeral178a1indicates a cross section of a first diffraction pattern178ataken along the eighth virtual line cl8. Reference numeral178b1indicates a cross section of a second diffraction pattern178btaken along the eighth virtual line cl8.

Referring toFIG. 34, the eighth period DP8is defined as a distance from a side of the cross section178a1of the first diffraction pattern178aadjacent to a side of the cross section178b1of the second diffraction pattern178bto the other side of the cross section178b1of the second diffraction pattern178bopposite the above side of the cross section178b1of the second diffraction pattern178b. In addition, the eighth length d8of the second diffraction pattern178bdenotes, for example, a width of the cross section178b1of the second diffraction pattern178b.

Referring again toFIGS. 31 through 33, a period between diffraction patterns arranged along the first direction X and a period between diffraction patterns arranged along the second direction Y among the diffraction patterns178may all be the eighth period DP8in an exemplary embodiment. In addition, the number of diffraction patterns arranged along the first direction X and the number of diffraction patterns arranged along the second direction Y may be equal to each other in an exemplary embodiment.

That is, even when the encapsulation layer161and the diffraction patterns178are unitary in an organic light emitting display device according to an exemplary embodiment, the period and length of the diffraction patterns178may be defined based on a cross section taken along the eighth virtual line cl8.

FIGS. 35 and 36illustrate embodiments of a diffraction pattern layer unitary with the encapsulation layer161illustrated inFIG. 31.

Referring toFIG. 35, a plurality of diffraction patterns179amay be unitary with an encapsulation layer162and may have a hemispherical shape as an exemplary embodiment. In addition, referring toFIG. 36, a plurality of diffraction patterns179bmay be unitary with an encapsulation layer163and may be engraved in a hemispherical shape as an exemplary embodiment. A plurality of diffraction patterns may also have a polygonal shape including a triangular shape, a pentagonal shape, and a hexagonal shape in a plan view. In an exemplary embodiment the diffraction patterns may have a sinusoidal shape, for example.

FIGS. 37 and 38are cross-sectional views of embodiments of the diffraction pattern layer170illustrated inFIG. 1.

Referring toFIG. 37, a plurality of diffraction patterns179cmay include a base member179c1and a plurality of protruding patterns179c2protruding upward from the base member179c1based onFIG. 37. The base member179c1may be disposed on an encapsulation layer160and may be unitary with the protruding patterns179c2. In an exemplary embodiment, the protruding patterns179c2may have quadrilateral cross sections, for example.

Referring toFIG. 38, a plurality of diffraction patterns179dmay include a base member179d1and a plurality of protruding patterns179d2protruding upward from the base member179d1based onFIG. 38. The base member179d1may be disposed on an encapsulation layer160and may be unitary with the protruding patterns179d2. In an exemplary embodiment, the protruding patterns179d2may have hemispherical cross sections, for example.

That is, since the diffraction patterns179cand179dinclude the base members179c1and179d1as illustrated inFIGS. 37 and 38, an upper surface of the encapsulation layer160located between the protruding patterns179c2and179d2may be covered with the base member179c1and179d1.

The size and shape of the diffraction patterns179cand179dare not limited to those illustrated inFIGS. 37 and 38.

A method of forming the diffraction patterns178and179is not particularly limited. In an exemplary embodiment, when the encapsulation layer160is a glass insulating substrate, the diffraction pattern layers178and179may be provided by etching an upper portion of the glass insulating substrate through an etching process. The etching process is not particularly limited, but wet etching may be used as an exemplary embodiment.

FIGS. 39(a)through46illustrate the shape, period, and arrangement of a plurality of diffraction patterns of a diffraction pattern layer in organic light emitting display devices according to embodiments and the shape and diffraction distance of second emission patterns corresponding to the above exemplary embodiments. For simplicity, a redundant description of components identical to those described above with reference toFIGS. 1 through 38will be omitted.

An organic light emitting display device having a plurality of diffraction patterns210aextending in the second direction Y will be described first with reference toFIGS. 39 and 40.

FIG. 39(a)is a plan view of a diffraction pattern layer200aaccording to an exemplary embodiment.FIG. 39(b)is a cross-sectional view taken along line I11-I11′ ofFIG. 39(a).FIG. 39(c)is a cross-sectional view taken along a ninth virtual line cl9ofFIG. 39(b).

Referring toFIGS. 39(a) through 39(c), the diffraction pattern layer200amay include the diffraction patterns210adisposed on an encapsulation layer160. The diffraction patterns210amay extend along the second direction Y. In addition, the diffraction patterns210amay neighbor each other along the first direction X. The diffraction patterns210amay be shaped like rectangular parallelepipeds in an exemplary embodiment.

The diffraction patterns210amay have a ninth thickness t9. In addition, the diffraction patterns210amay have a ninth period DP9. Here, the ninth period DP9is defined based on a cross-sectional area cs9taken along the ninth virtual line cl9as described above. That is, the ninth period DP9is defined based on a cross section211a1of a first diffraction pattern211aand a cross section212a1of a second diffraction pattern212a.

Referring toFIGS. 14 and 40, a first duplicate emission pattern P1aand a second duplicate emission pattern P2a, which are arranged in the same row as a reference emission pattern Pref, may be generated in a second region TA2. The following description will be given based on the first duplicate emission pattern P1a. A diffraction distance β1abetween the reference emission pattern Pref and the first duplicate emission pattern P1amay be given by Equation (9) below:

An organic light emitting display device including a plurality of diffraction patterns210bhaving a predetermined period and arranged in an arbitrary form will be described with reference toFIGS. 14, 41, and 42. For simplicity, a redundant description of components identical to those described above with reference toFIGS. 39 and 40will be omitted.

FIG. 41(a)is a plan view of a diffraction pattern layer200baccording to an exemplary embodiment.FIG. 41(b)is a cross-sectional view taken along line I12-I12′ ofFIG. 41(a).FIG. 41(c)is a cross-sectional view taken along a tenth virtual line cl10ofFIG. 41(b).

Referring toFIGS. 41(a) through 41(c), the diffraction pattern layer200bmay include the diffraction patterns210bdisposed on an encapsulation layer160. The diffraction patterns210bmay include first through third diffraction patterns211bthrough213b.

The arrangement of the first through third diffraction patterns211bthrough213bwill be described based onFIG. 41.

The first diffraction pattern211bmay neighbor the third diffraction pattern213balong the first direction X. The first diffraction patterns211bmay neighbor the second diffraction pattern212balong the diagonal direction. An angle defined between a virtual line vl1aconnecting a center of the first diffraction pattern211band a center of the second diffraction pattern212band a virtual line vl2aconnecting the center of the first diffraction pattern211band a center of the third diffraction pattern213bmay be represented by θ1. That is, the second diffraction pattern212band the third diffraction pattern213bmay be arranged to have an included angle of θ1with respect to the first diffraction pattern211b.

The diffraction patterns210bmay have a tenth thickness tl0. Referring to FIGS.41(b) and41(c), a period between the first diffraction pattern211band the second diffraction pattern212bmay be a10athperiod DP10a. In addition, a period between the first diffraction pattern211band the third diffraction pattern213bmay be a10bthperiod DP10b. Here, the10athperiod DP10aand the10bthperiod DP10bare defined based on a cross-sectional area cs10taken along the tenth virtual line cl10as described above.

Accordingly, a first diffraction angle θ1aand a second diffraction angle θ2amay be given by Equations (10) and (11), respectively:

As the first diffraction angle θ1aand the second diffraction angle θ2avary, the form and the number of duplicate emission patterns disposed in a second region TA2also vary. Referring toFIG. 42, a first duplicate emission pattern P1bmay be separated from a reference emission pattern Pref by a first diffraction distance β2a. In addition, a fifth duplicate emission pattern P5bmay be separated from the reference emission pattern Pref by a second diffraction distance β2b. An angle of a1inFIG. 42may be (180−φ1) degrees in an exemplary embodiment.

The first diffraction distance β2aand the second diffraction distance β2bmay be given by Equations (12) and (13), respectively:

An organic light emitting display device including a plurality of diffraction patterns210cthat are rectangular in a plan view will be described with reference toFIGS. 14, 43and44.

FIG. 43(a)is a plan view of a diffraction pattern layer200caccording to an exemplary embodiment.FIG. 43(b)is a cross-sectional view taken along line II3-II3′ ofFIG. 43(a).FIG. 43(c)is a cross-sectional view taken along an eleventh virtual line cl11ofFIG. 43(b).

Referring toFIGS. 43(a) through 43(c), the diffraction pattern layer200cmay include the diffraction patterns210cdisposed on an encapsulation layer160. The diffraction patterns210cmay include first through third diffraction patterns211cthrough213c.

Based onFIG. 43, the number of diffraction patterns arranged along the first direction X and the number of diffraction patterns arranged along the second direction Y may be equal to each other in an exemplary embodiment. The first diffraction pattern211cmay neighbor the third diffraction pattern213calong the first direction X. The first diffraction pattern211cmay neighbor the second diffraction pattern212calong the second direction Y. An angle defined between a virtual line vl1bconnecting a center of the first diffraction pattern211cand a center of the second diffraction pattern212cand a virtual line vl2bconnecting the center of the first diffraction pattern211cand a center of the third diffraction pattern213cmay be about 90 degrees.

The diffraction patterns210cmay have an eleventh thickness t11. Referring toFIGS. 43(b) and 43(c), a period between the first diffraction pattern211cand the second diffraction pattern212cmay be an11athperiod DP11a. In addition, a period between the first diffraction pattern211cand the third diffraction pattern213cmay be an11bthperiod DP11b. Here, the11athperiod DP11aand the11bthperiod DP11bare defined based on a cross-sectional area cs11taken along the eleventh virtual line cl11as described above. In an exemplary embodiment, the11athperiod DP11aand the11bthperiod DP11bmay be different from each other.

Referring toFIG. 44, a first duplicate emission pattern P1cseparated from a reference emission pattern Pref by a first diffraction distance β3aand a fourth duplicate emission pattern P4cseparated from the reference emission pattern Pref by a second diffraction distance β3bmay be generated in a second region TA2.

The first diffraction distance β3abetween the reference emission pattern Pref and the first duplicate emission pattern P1cmay be given by Equation (14) below:

In addition, the second diffraction distance β3bbetween the reference emission pattern Pref and the fourth duplicate emission pattern P4cmay be given by Equation (15) below:

An organic light emitting display device including a plurality of diffraction patterns210darranged in a hexagonal shape will be described with reference toFIGS. 14, 45 and 46.

FIG. 45(a)is a plan view of a diffraction pattern layer200daccording to an exemplary embodiment.FIG. 45(b)is a cross-sectional view taken along line I14-I14′ ofFIG. 45(a).FIG. 45(c)is a cross-sectional view taken along a twelfth virtual line cl12ofFIG. 45(b).

Referring toFIGS. 45(a) through 45(c), the diffraction pattern layer200dmay include the diffraction patterns210ddisposed on an encapsulation layer160. The diffraction patterns210dmay include first through third diffraction patterns211dthrough213d. The arrangement of the diffraction patterns210dwill be described based on the first through third diffraction patterns211dthrough213d.

The diffraction patterns210dmay be arranged in a hexagonal structure, for example. More specifically, the first diffraction pattern211dmay neighbor the third diffraction pattern213dalong the first direction X. The first diffraction pattern211dmay neighbor the second diffraction pattern212dalong the diagonal direction. An angle defined between a virtual line vl1cconnecting a center of the first diffraction pattern211dand a center of the second diffraction pattern212dand a virtual line vl2cconnecting the center of the first diffraction pattern211dand a center of the third diffraction pattern213dmay be represented by φ2. In an exemplary embodiment, φ2may be about 60 degrees, for example. That is, the second diffraction pattern212dand the third diffraction pattern213dmay be arranged to have an included angle of φ2(about 60 degrees) with respect to the first diffraction pattern211d.

The diffraction patterns210dmay have a twelfth thickness t12. Referring toFIGS. 45(b) and 45(c), a period between the first diffraction pattern211dand the second diffraction pattern212dmay be a12athperiod DP12a. In addition, a period between the first diffraction pattern211dand the third diffraction pattern213dmay be a12bthperiod DP12b. Here, the12athperiod DP12aand the12bthperiod DP12bare defined based on a cross-sectional area cs12taken along the twelfth virtual line cl12as described above.

Accordingly, a first diffraction angle θ1band a second diffraction angle θ2bmay be given by Equations (16) and (17), respectively:

As the first diffraction angle θ1band the second diffraction angle θ2bvary, the form and the number of duplicate emission patterns disposed in a second region TA2vary. Referring toFIG. 46, a first duplicate emission pattern P1dmay be separated from a reference emission pattern Pref by a first diffraction distance β4a. In addition, a fifth duplicate emission pattern P5dmay be separated from the reference emission pattern Pref by a second diffraction distance β4b. Here, the12athperiod DP12amay be the same as the12bthperiod DP12b. Accordingly, the first diffraction distance β4amay be the same as the second diffraction distance β4b.

Therefore, the first diffraction distance β4a(or the second diffraction distance β4b) may be given by Equation (18) below:

That is, the first diffraction angle θ1(refer toFIG. 7A) of light emitted from the organic light emitting elements140(refer toFIGS. 1 and 7A), the second diffraction angle θ2(refer toFIG. 7A) of the light passing through the diffraction pattern layer170, the diffraction distance β (refer toFIG. 7B), and luminance may be controlled by changing the period, shape and arrangement structure of a plurality of diffraction patterns.

As described above, when the distance between pixels is changed, at least one of the effective emission area ratio and blurring may be changed. Hereinafter, embodiments of pixel arrangement for defining the distance between pixels will be described with reference toFIGS. 47 and 48.

FIGS. 47 and 48are plan views of pixel arrangements of organic light emitting display devices according to embodiments.

Referring toFIG. 47, first through fourth pixel units PX1athrough PX4amay be arranged to neighbor each other in the same row. The first through fourth pixel units PX1athrough PX4amay be rectangular in an exemplary embodiment. However, the shape and size of each of the first through fourth pixel units PX1athrough PX4aare not limited to those illustrated inFIG. 47.

The first pixel unit PX1amay display a red color in an exemplary embodiment. That is, the first pixel unit PX1amay include a red organic light emitting layer that emits red light. The second and fourth pixel units PX2aand PX4amay display a green color in an exemplary embodiment. That is, the second and fourth pixel units PX2aand PX4amay include a green organic light emitting layer that emits green light. The third pixel unit PX3amay display a blue color in an exemplary embodiment. That is, the third pixel unit PX3amay include a blue organic light emitting layer that emits blue light.

The first through fourth pixel units PX1athrough PX4amay form one pixel unit. That is, the first through fourth pixel units PX1through PX4may be arranged in an RGBG pentile manner.

A distance PP2between pixels is defined as a distance between pixel units that display the same color. Hereinafter the second pixel unit PX2aand the fourth pixel unit PX4athat emit green light will be described as an example.

The inter-pixel distance PP2may be defined as a shortest distance between a first virtual center point cp1blocated in the second pixel unit PX2aand a second virtual center point cp2blocated in the fourth pixel unit PX4a.

Referring toFIG. 48, first through sixth pixel units PX1bthrough PX6bmay be arranged to neighbor each other in the same row. The first through sixth pixel units PX1bthrough PX6bmay be rectangular in an exemplary embodiment. The first through third pixel units PX1bthrough PX3bmay display red, green, and blue colors, respectively, in an exemplary embodiment. In addition, the fourth through sixth pixel units PX4bthrough PX6bmay display red, green, and blue colors, respectively, in an exemplary embodiment.

The first through third pixel units PX1bthrough PX3bmay form one pixel unit. In addition, the fourth through sixth pixel units PX4bthrough PX6bmay form one pixel unit.

A distance PP3between pixels is defined as a distance between pixel units that display the same color. Accordingly, the inter-pixel distance PP3may be defined as a shortest distance between a first virtual center point cp1clocated in the second unit PX2band a second virtual center point cp2clocated in the fifth pixel unit PX5b.

That is, the shortest distance between pixels is defined as the shortest distance between pixel units that display the same color, and the value of the shortest distance between pixels may vary according to the form of pixel arrangement.

FIG. 49is a cross-sectional view of an organic light emitting display device according to an exemplary embodiment. For simplicity, a redundant description of components identical to those described above with reference toFIGS. 1 through 48will be omitted. In addition, an exemplary embodiment applicable to the exemplary embodiments described above with reference toFIGS. 16 through 48is also applicable to the organic light emitting display device illustrated inFIG. 49. That is, the organic light emitting display device according to the exemplary embodiment ofFIG. 49also includes a diffraction pattern layer170to increase the effective emission area ratio. In addition, a first diffraction angle θ1(refer toFIG. 7A) of light emitted from a plurality of organic light emitting elements140(refer toFIGS. 1 and 7A), a second diffraction angle θ2(refer toFIG. 7A) of the light passing through the diffraction pattern layer170, a diffraction distance β (refer toFIG. 7B), and luminance may be controlled by changing the period, shape, length, thickness, distance from the organic light emitting elements and arrangement structure of a plurality of diffraction patterns.

Referring toFIG. 49, the organic light emitting display device according to the current embodiment may include an encapsulation layer180, a buffer layer190, and a protective layer191.

The encapsulation layer180may be provided by stacking at least one of an organic layer and an inorganic layer in a single-layer structure or in a multilayer structure. More specifically, the encapsulation layer180may include a first inorganic layer181, an organic layer182, and a second inorganic layer183.

The first inorganic layer181may be disposed on a common electrode150. In an exemplary embodiment, the first inorganic layer181may include any one or more of silicon oxide (SiOx), silicon nitride (SiNx), and silicon oxynitride (SiONx), for example.

The organic layer182may be disposed on the first inorganic layer181. In an exemplary embodiment, the organic layer182may include any one of epoxy, acrylate, and urethane acrylate, for example. The organic layer182may planarize a step provided by a pixel defining layer130.

The second inorganic layer183may be disposed on the organic layer182. In an exemplary embodiment, the second inorganic layer183may include at least one of silicon oxide (SiOx), silicon nitride (SiNx), and silicon oxynitride (SiONx), for example.

InFIG. 49, each of the first inorganic layer181, the organic layer182and the second inorganic layer183is illustrated as a single layer. However, each of the first inorganic layer181, the organic layer182and the second inorganic layer183may also be provided in a multilayer structure

The buffer layer190may be disposed on the second inorganic layer183. The material of the buffer layer190is not particularly limited. That is, the buffer layer190may include an inorganic material or an organic material. In an alternative exemplary embodiment, the buffer layer190may be provided by stacking at least one of an organic layer and an inorganic layer in a single-layer structure or in a multilayer structure. The buffer layer190may have a predetermined thickness to maintain a predetermined distance between a plurality of organic light emitting elements140and the diffraction pattern layer170. The buffer layer190may have a thickness of about 200 μm or less in an exemplary embodiment. In another exemplary embodiment, the buffer layer190may also be omitted.

The protective layer191may be disposed on the diffraction pattern layer170. The protective layer191may cover a plurality of diffraction patterns171in an exemplary embodiment. The material of the protective layer191is not particularly limited. In an exemplary embodiment, the protective layer191may include at least one of LiF, MgF2, and CaF2, for example.

In the specification, the diffraction pattern layer170is disposed on the encapsulation layer180. However, the invention is not limited to this case. That is, the diffraction pattern layer170may include the same material as that of the encapsulation layer180and may be disposed on an upper surface of an organic or inorganic layer included in the encapsulation layer180. In an exemplary embodiment, the diffraction pattern layer170may be provided by etching an upper surface of the second inorganic layer183.

FIG. 50is a view for explaining factors that determine a diffraction distance in the organic light emitting display device ofFIG. 49. For simplicity, a redundant description of components identical to those described above with reference toFIG. 14will be omitted. In addition, for ease of description, the refraction of light emitted from a first organic light emitting element141by the encapsulation layer180is not illustrated inFIG. 50.

A distance Z′ between the first organic light emitting element141and the diffraction pattern layer170may be defined as the sum of reference numerals z3, z4, z5and z6inFIG. 50.

Z3is defined as a shortest distance from the first organic light emitting element141to a lowermost surface of the organic layer182. Here, the lowermost surface of the organic layer182is a surface located at the shortest distance from the first organic light emitting element141among surfaces in direct contact with the first inorganic layer181. Z4is defined as a shortest distance from the lowermost surface of the organic layer182to an upper surface of the organic layer182in the first organic light emitting element141. The upper surface of the organic layer182is a surface in direct contact with the second inorganic layer183. Z5is defined as a shortest distance from the upper surface of the organic layer182to the buffer layer190. Z5may also be defined as a thickness of the second inorganic layer183. Z6is defined as a shortest distance from an upper surface of the second inorganic layer183to the diffraction pattern layer170. Z6may also be defined as a thickness of the buffer layer190.

In addition, respective refractive indices of the first inorganic layer181, the organic layer182, the second inorganic layer183and the buffer layer190will be indicated by n181, n182, n183and n190, respectively.

Accordingly, a diffraction distance β may be given by Equation (19) below:

In an exemplary embodiment, when another component exists between the diffraction pattern layer170and the first organic light emitting element141, the diffraction distance β may be changed in consideration of the refractive index and thickness of the component. In an exemplary embodiment, when the encapsulation layer180and the buffer layer190have the same refractive index (the refractive index of the encapsulation layer180is indicated by n180), a diffraction distance β″ between the first organic light emitting element141and the diffraction pattern layer170may be given by Equation (20) below:

The organic light emitting display device according to the exemplary embodiment may control the diffraction distance β by adjusting an emission color of the first organic light emitting element141, the distance Z′ between the diffraction pattern layer170and the organic light emitting elements140, the refractive indices n181, n182, n183and n190of the components disposed between the diffraction pattern layer170and the organic light emitting elements140, a first period DP1, the first diffraction angle θ1, and the second diffraction angle θ2.

Although not illustrated in the drawings, display elements that provide light to the diffraction pattern layer170are not limited to the organic light emitting elements140. That is, the display elements may include liquid crystal display (“LCD”) elements, light emitting diodes (“LEDs”), electroluminescent (“EL”) elements, semiconductor light emitting elements, field emission display (“FED”) elements, and quantum dot laser elements.

In addition, in the specification, a case where the encapsulation layer160(refer toFIG. 1) is a glass substrate and a case where the encapsulation layer180(refer toFIG. 49) is a stack of an organic layer and an inorganic layer have been described as an example. However, the invention is not limited to this example. That is, the encapsulation layer may be omitted or replaced with a general substrate or an insulating layer depending on the type of the display elements and the type of a display device.

FIGS. 51A and 51Bare a perspective view and a cross-sectional view of a head-mounted display device including the organic light emitting display device illustrated inFIG. 1. For simplicity, a redundant description of components identical to those described above with reference toFIGS. 1 through 50will be omitted.

Referring toFIGS. 1, 51A and 51B, the head-mounted display device10according to the current embodiment may include a first display unit11and a lens unit12. Although not illustrated in the drawings, the head-mounted display device10according to the current embodiment may further include a camera, an infrared sensor, a signal processing unit, and a frame that may be mounted on a user's head.

The lens unit12may receive light from the first display unit11. The lens unit12may be disposed between an object and a user in an exemplary embodiment. The lens unit12may be configured as an opaque lens to realize virtual reality in an exemplary embodiment. The lens unit12may be configured as a transparent lens or a translucent lens to realize augmented reality in an exemplary embodiment. The lens unit12may be a convex lens in an exemplary embodiment.

The first display unit11may include a diffraction pattern layer170disposed on an encapsulation layer160. Here, the encapsulation layer160may be a glass insulating substrate as an exemplary embodiment. The emission area of the first display unit11may be increased by a light interference phenomenon that may occur when light emitted from organic light emitting elements140passes through the diffraction pattern layer170. This indicates that the effective emission area ratio may be increased.

A user may magnify an image of the first display unit11using the lens unit12and view the magnified image. However, the magnified environment may cause a screen door effect (“SDE”). That is, the magnified environment enables the user to visually recognize gaps between portions of a pixel defining layer in the first display unit11. However, the region visually recognized by the user due to the magnified environment is a non-emission region.

As described above, the effective emission area ratio refers to the proportion of an emission region in a region. Increasing the effective emission area ratio denotes increasing the area of the emission region. This may be expressed as a decrease in the area of the non-emission region.

That is, the head-mounted display device10according to the current embodiment may reduce the area of the non-emission region and reduce the area of the non-emission region visible to a user due to the magnified environment. As a result, the SDE may be improved.

FIGS. 52A and 52Bare a perspective view and a cross-sectional view of a head-mounted display device including the organic light emitting display device illustrated inFIG. 49. For simplicity, a redundant description of components identical to those described above with reference toFIG. 51will be omitted.

Referring toFIGS. 52B, a second display unit13may include an encapsulation layer180and a buffer layer190disposed on the encapsulation layer180. The encapsulation layer180may be provided by stacking organic and inorganic layers in an exemplary embodiment.

The emission area of the second display unit13may be increased by a light interference phenomenon that may occur when light emitted from organic light emitting elements140passes through a diffraction pattern layer170. This indicates that the effective emission area ratio may be increased.

Therefore, the head-mounted display device10according to the current embodiment may improve the SDE by increasing the effective emission area ratio.

FIG. 53illustrates the SDE in a conventional head-mounted display device.FIG. 54illustrates an improvement in the SDE in a head-mounted display device according to an exemplary embodiment.

Referring toFIG. 53, gaps between portions of a pixel defining layer are visually recognized as a web. That is, the SDE is recognized. Referring toFIG. 54, gaps between portions of a pixel defining layer are less visible as compared withFIG. 53. This indicates that the SDE has been improved.

According to embodiments, an effective emission area ratio may be increased.

In addition, the degree of blurring perceived may be minimized.

Furthermore, the SDE of a head-mounted display device may be improved.