Organic light emitting diode display device
阅读说明：本技术 有机发光二极管显示装置 (Organic light emitting diode display device ) 是由 沈东敏 张志向 金津泰 于 2019-06-21 设计创作，主要内容包括：一种有机发光二极管显示装置包括：基板；在所述基板上的涂覆层,所述涂覆层包括多个凸部和多个凹部；在所述涂覆层上的第一电极；在所述第一电极上的发光层,所述发光层包括第一发光材料层；和在所述发光层上的第二电极,其中所述多个凸部中的第一发光材料层与所述第二电极分开第一距离,并且其中所述多个凹部中的第一发光材料层与所述第二电极分开与所述第一距离不同的第二距离。(An organic light emitting diode display device includes: a substrate; a coating layer on the substrate, the coating layer including a plurality of protrusions and a plurality of recesses; a first electrode on the coating layer; a light emitting layer on the first electrode, the light emitting layer including a first light emitting material layer; and a second electrode on the light emitting layer, wherein the first light emitting material layer in the plurality of convex portions is separated from the second electrode by a first distance, and wherein the first light emitting material layer in the plurality of concave portions is separated from the second electrode by a second distance different from the first distance.)
1. An organic light emitting diode display device comprising:
a substrate;
a coating layer on the substrate, the coating layer including a plurality of protrusions and a plurality of recesses;
a first electrode on the coating layer;
a light emitting layer on the first electrode, the light emitting layer including a first light emitting material layer; and
a second electrode on the light-emitting layer,
wherein a first light emitting material layer in the plurality of protrusions is separated from the second electrode by a first distance, and
wherein a first layer of light emitting material in the plurality of recesses is separated from the second electrode by a second distance different from the first distance.
2. The organic light emitting diode display device of claim 1, wherein at least one of the plurality of protrusions comprises a bottom surface portion, a top surface portion, and a side surface portion between the bottom surface portion and the top surface portion,
wherein a slope of the side surface portion increases from the bottom surface portion to the top surface portion, and
wherein the side surface portion has a maximum slope at the effective light emitting area.
3. The organic light emitting diode display device according to claim 2, wherein a distance from the second electrode to the first luminescent material layer in the plurality of protrusions is determined by the following equation:
L1-D1 cos θ, where θ is 20-60 °,
wherein L1 is a distance from the second electrode to the first light-emitting material layer in the plurality of convex portions, D1 is a distance from the second electrode to the first light-emitting material layer in the plurality of concave portions, and θ is an angle of a tangent line of the side surface portion with respect to the bottom surface portion.
4. An organic light emitting diode display device according to claim 3, further comprising a second light emitting material layer between the first light emitting material layer and the first electrode,
wherein a distance from the second electrode to the second light emitting material layer in the plurality of protrusions is determined by the following equation:
L2-D2 cos θ, where θ is 20-60 °,
wherein L2 is a distance from the second electrode to the second light emitting material layer in the plurality of convex portions, D2 is a distance from the second electrode to the second light emitting material layer in the plurality of concave portions, and θ is an angle of a tangent of the side surface portion with respect to the bottom surface portion.
5. An organic light emitting diode display device according to claim 4, further comprising a third light emitting material layer between the second light emitting material layer and the first electrode,
wherein a distance from the second electrode to the third light emitting material layer in the plurality of protrusions is determined by the following equation:
l3 ═ ((D2+ D3)/2) × cos θ, where θ is 20 ° to 60 °,
wherein L3 is a distance from the second electrode to the third light emitting material layer in the plurality of convex portions, D3 is a distance from the second electrode to the third light emitting material layer in the plurality of concave portions, and θ is an angle of a tangent of the side surface portion with respect to the bottom surface portion.
6. An organic light emitting diode display device according to claim 5, wherein a distance from the second electrode to the first light emitting material layer in the plurality of recesses is about
wherein a distance from the second electrode to the second light emitting material layer in the plurality of recesses is about
wherein a distance from the second electrode to the third light emitting material layer in the plurality of recesses is about
7. The organic light emitting diode display device according to claim 2, wherein a distance from the second electrode to the first luminescent material layer in the plurality of recesses is determined by the following equation:
Y1＝L1*(1/cosθ)，
l1. ltoreq.Y 1, and
θ＝20°～60°，
wherein Y1 is a distance from the second electrode to the first light-emitting material layer in the plurality of concave portions, L1 is a distance from the second electrode to the first light-emitting material layer in the plurality of convex portions, and θ is an angle of a tangent line of the side surface portion with respect to the bottom surface portion.
8. An organic light emitting diode display device according to claim 7, further comprising a second light emitting material layer between the first light emitting material layer and the first electrode,
wherein a distance from the second electrode to the second light emitting material layer in the plurality of recesses is determined by the following equation:
Y2＝L2*(1/cosθ)，
y2-cos 60 DEG-L2-Y2-cos 20 DEG, and
θ＝20°～60°，
wherein Y2 is a distance from the second electrode to the second light emitting material layer in the plurality of concave portions, L2 is a distance from the second electrode to the second light emitting material layer in the plurality of convex portions, and θ is an angle of a tangent of the side surface portion with respect to the bottom surface portion.
9. An organic light emitting diode display device according to claim 8, further comprising a third light emitting material layer between the second light emitting material layer and the first electrode,
wherein a distance from the second electrode to the third light emitting material layer in the plurality of recesses is determined by the following equation:
Y3＝L3*(1/cosθ)，
y3-cos 60 DEG-L3-Y3-cos 20 DEG, and
θ＝20°～60°，
wherein Y3 is a distance from the second electrode to the third light emitting material layer in the plurality of concave portions, L3 is a distance from the second electrode to the third light emitting material layer in the plurality of convex portions, and θ is an angle of a tangent of the side surface portion with respect to the bottom surface portion.
10. An organic light emitting diode display device according to claim 9, wherein the light emitting layer has a thickness of about
11. The organic light-emitting diode display device according to claim 1, wherein a thickness of the light-emitting layer corresponding to the plurality of convex portions is smaller than a thickness of the light-emitting layer corresponding to the plurality of concave portions.
12. An organic light emitting diode display device according to claim 9, wherein the first light emitting material layer and the third light emitting material layer emit light of a first color, and the second light emitting material layer emits light of a second color different from the first color.
13. An organic light emitting diode display device according to claim 12, wherein the first colour corresponds to a wavelength in the range of about 440 to 480nm and the second colour corresponds to a wavelength in the range of about 510 to 590 nm.
14. An organic light emitting diode display device according to claim 9, wherein the first light emitting material layer, the second light emitting material layer and the third light emitting material layer include a first blue light emitting layer, a yellow-green light emitting layer and a second blue light emitting layer, respectively.
Technical Field
The present invention relates to an organic light emitting diode display device, and more particularly, to an organic light emitting diode display device that improves light extraction efficiency.
Background
Recently, as information-oriented society develops, the display field is rapidly developing due to an increase in interest in information displays for processing and displaying a large amount of information and a demand for portable information media. Accordingly, various thin and light flat panel display devices have been developed and are receiving attention.
Among various flat panel display devices, an Organic Light Emitting Diode (OLED) display device is a light emitting type device, and does not require a backlight unit used in a non-light emitting type device such as a Liquid Crystal Display (LCD) device. As a result, the OLED display device has a light weight and a thin profile.
In addition, the OLED display device has advantages of viewing angle, contrast, power consumption, and the like, compared to the LCD device. In addition, the OLED display device may be driven with a low Direct Current (DC) voltage and have a fast response speed. In addition, since the internal elements of the OLED display device have a solid phase, the OLED display device has high durability against external impacts and has a wide usable temperature range.
In the OLED display device, a large amount of light is lost when light emitted from the light emitting layer is emitted to the outside through various components. As a result, light emitted to the outside of the OLED display device is only about 20% of light emitted from the light emitting layer.
Here, since the amount of light emitted from the light emitting layer increases with the amount of current applied to the OLED display device, the luminance of the OLED display device may be further increased by applying more current to the light emitting layer. However, in this case, power consumption increases, and the life of the OLED display device also decreases.
Therefore, in order to improve the light extraction efficiency of the OLED display device, an OLED display device has been proposed in which a microlens array (MLA) is attached to an outer surface of a substrate or microlenses are formed in an overcoat layer (overcoat).
However, when a microlens array is attached to the outer surface of the substrate or microlenses are formed in the overcoat layer, the visibility of black is deteriorated due to a relatively high reflectance.
Disclosure of Invention
Accordingly, the present invention is directed to an organic light emitting diode display device that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an organic light emitting diode display device that improves light extraction efficiency and improves black visibility by reducing reflectance.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. These objects and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, an organic light emitting diode display device includes: a substrate; a coating layer on the substrate, the coating layer including a plurality of protrusions and a plurality of recesses; a first electrode on the coating layer; a light emitting layer on the first electrode, the light emitting layer including a first light emitting material layer; and a second electrode on the light emitting layer, wherein the first light emitting material layer in the plurality of convex portions is separated from the second electrode by a first distance, and wherein the first light emitting material layer in the plurality of concave portions is separated from the second electrode by a second distance different from the first distance.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:
fig. 1 is a cross-sectional view illustrating an organic light emitting diode display device according to an embodiment of the present invention;
fig. 2 is an enlarged view of a portion a of fig. 1;
fig. 3 is a cross-sectional view illustrating a light emitting diode of an organic light emitting diode display device according to an embodiment of the present invention;
fig. 4A, 4B and 4C are graphs showing light intensities at positions of a first emitting material layer, a second emitting material layer and a third emitting material layer, respectively, of an organic light emitting diode display device according to an embodiment of the present invention;
fig. 5A and 5B are graphs showing light intensity according to wavelength of light extracted from an organic light emitting diode display device having a microlens and an organic light emitting diode display device according to an embodiment of the present invention, respectively;
fig. 6 is a graph showing an aspect ratio of a microlens and a reflectance of the microlens for an organic light emitting diode display device according to an embodiment of the present invention;
fig. 7A, 7B and 7C are graphs showing voltages and luminous efficiencies of a red sub-pixel, a green sub-pixel and a blue sub-pixel of an organic light emitting diode display device according to an embodiment of the present invention, respectively.
Detailed Description
Reference will now be made in detail to the present invention, examples of which are illustrated in the accompanying drawings.
Fig. 1 is a cross-sectional view illustrating an organic light emitting diode display device according to an embodiment of the present invention. All the components of the organic light emitting diode display device according to all the embodiments of the present invention may be operatively combined and configured.
In fig. 1, an Organic Light Emitting Diode (OLED) display device 100 may have a top emission type or a bottom emission type according to an emission direction of light. A bottom emission type OLED display device will be exemplarily described hereinafter.
The OLED display device 100 includes a substrate 101 having a driving Thin Film Transistor (TFT) DTr and a light emitting diode E thereon, and a protective film 102 encapsulating the substrate 101.
The substrate 101 includes a plurality of pixel regions P each including a light emitting region EA in which a light emitting diode E is disposed and an image is substantially displayed and a non-light emitting region NEA along an edge of the light emitting region EA. The non-light emitting region NEA includes a switching region TrA provided with a driving TFT DTr.
The semiconductor layer 103 is disposed in the switching region TrA of the non-light emitting region NEA of the pixel region P on the substrate 101. The semiconductor layer 103 may include silicon and may have an active region 103a in a central portion and source and drain regions 103b and 103c in both sides of the active region 103 a. The active region 103a may serve as a channel of the driving TFT DTr, and the source and drain regions 103b and 103c may be doped with relatively high concentration impurities.
A gate insulating layer 105 is disposed on the semiconductor layer 103.
A gate electrode 107 and a gate line are disposed on the gate insulating layer 105. The gate electrode 107 corresponds to the active region 103a of the semiconductor layer 103, and the gate line is connected to the gate electrode 107 and extends in one direction.
The first interlayer insulating layer 109a is disposed on the gate electrode 107 and the gate line. The first interlayer insulating layer 109a and the gate insulating layer 105 have first and second semiconductor contact holes 116 exposing the source region 103b and the drain region 103c located in both side portions of the active region 103 a.
A source electrode 110a and a drain electrode 110b spaced apart from each other are disposed on the first interlayer insulating layer 109a having the first and second semiconductor contact holes 116. The source electrode 110a is connected to the source region 103b through the first semiconductor contact hole 116, and the drain electrode 110b is connected to the drain region 103c through the second semiconductor contact hole 116.
A second interlayer insulating layer 109b is disposed on the source and drain electrodes 110a and 110b and the first interlayer insulating layer 109a exposed between the source and drain electrodes 110a and 110 b.
The source electrode 110a and the drain electrode 110b, the semiconductor layer 103 including the source region 103b and the drain region 103c in contact with the source electrode 110a and the drain electrode 110b, respectively, the gate insulating layer 105, and the gate electrode 107 constitute a driving tft dttr.
The data line may be disposed on the second interlayer insulating layer 109 b. The data line may cross the gate line to define each pixel region P. A switching TFT having the same structure as the driving TFT DTr may be connected to the driving TFT DTr.
The switching TFT and the driving TFT DTr may exemplarily have a top gate type in which the semiconductor layer 103 includes polysilicon or an oxide semiconductor material. In another embodiment, the switching TFT and the driving TFT DTr may have a bottom gate type in which the semiconductor layer 103 includes intrinsic amorphous silicon and impurity-doped amorphous silicon.
The substrate 101 may comprise glass or a flexible transparent plastic such as polyimide. For example, polyimide, which can endure a deposition step of a relatively high temperature due to excellent heat resistance, may be used for the substrate 101. The entire front surface of the substrate of polyimide may be covered with at least one buffer layer.
The threshold voltage of the driving TFT DTr in the switching region TrA may be shifted due to light. In order to prevent the threshold voltage shift, the OLED display device 100 may further include a light-shielding layer under the semiconductor layer 103.
The light-shielding layer may be disposed between the substrate 101 and the semiconductor layer 103 to block light incident to the semiconductor layer 103 through the substrate 101. As a result, threshold voltage shift due to external light is minimized or prevented. The light-shielding layer may be covered with at least one buffer layer.
The wavelength conversion layer 106 is provided on the second interlayer insulating layer 109b corresponding to the light emitting region EA of each pixel region P.
The wavelength conversion layer 106 may include a color filter that transmits only light having a wavelength of a predetermined color corresponding to each pixel region P among white light emitted from the light emitting diode E to the substrate 101.
The wavelength conversion layer 106 may transmit only light having a wavelength corresponding to red, green, or blue. For example, in the OLED display device 100, a single unit pixel region may include red, green and blue pixel regions P, and the wavelength conversion layer 106 in the red, green and blue pixel regions P may include a red color filter, a green color filter and a blue color filter, respectively.
In the OLED display device 100, the single unit pixel region may further include a white pixel region where the wavelength conversion layer 106 is not disposed.
In another embodiment, the wavelength conversion layer 106 may include quantum dots having a size capable of emitting light of a predetermined color corresponding to each pixel region P according to white light emitted from the light emitting diode E to the substrate 101. Here, the quantum dot may include at least one selected from the group consisting of: CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdHgSeS, CdHgSeTe, HgZnSeS, HgZnSeTe, HgZnSTe, GaN, GaP, GaAs, AlN, AlP, AlAs, InN, InP, InAs, GaInAs, AlNP, AlPAS, InNP, GaInNP, GaInNPs, GaInNAs, AlNAs, AlNAN, AlNAs, AlnNAs, AlnAs, AlnNAP, AlnAs, AlnNAs, and AlnAs. However, the material of the quantum dot is not limited thereto.
For example, wavelength conversion layer 106 in the red pixel region may include quantum dots of CdSe or InP, wavelength conversion layer 106 in the green pixel region may include quantum dots of CdZnSeS, and wavelength conversion layer 106 in the blue pixel region may include quantum dots of ZnSe. The OLED display device 100 in which the wavelength conversion layer 106 includes quantum dots may have relatively high color reproducibility.
In another embodiment, wavelength-converting layer 106 may include a color filter containing quantum dots.
An overcoat layer 108 is disposed on the wavelength conversion layer 106, and the overcoat layer 108 and the second interlayer insulating layer 109b have a first drain contact hole 108a exposing the drain electrode 110 b. The coating layer 108 has a plurality of recesses 118 and a plurality of protrusions 117 on a top surface thereof. The plurality of concave portions 118 and the plurality of convex portions 117 are alternately arranged with each other to constitute the microlens ML.
The coating layer 108 may include an insulating material having a refractive index of about 1.5. For example, the coating layer 108 may include one of acrylic resin, epoxy resin, phenolic resin, polyamide resin, polyimide resin, unsaturated polyester resin, polyphenyl resin, polyphenylene sulfide resin, benzocyclobutene, and photoresist.
The plurality of protrusions 117 may have a structure defining or surrounding the plurality of recesses 118, respectively, and may have a bottom surface portion 117a, a top surface portion 117b, and a side surface portion 117 c. The side surface portion 117c may be the entire inclined surface constituting the top surface portion 117 b. The slope of the side surface portion 117c may increase from the bottom surface portion 117a to the top surface portion 117b, so that the side surface portion 117c may have a maximum slope Smax at a portion adjacent to the top surface portion 117 b.
Since the path of light emitted from the light emitting layer 113 becomes toward the substrate 101 through the plurality of protrusions 117, the light extraction efficiency of the OLED display device 100 increases.
A first electrode 111 connected to the drain electrode 110b of the driving TFT DTr is disposed on the overcoat layer 108 constituting the microlens ML. For example, the first electrode 111 may be an anode of the light emitting diode E and may include a material having a relatively high work function.
The first electrode 111 is disposed in each pixel region P, and the bank 119 is disposed between the first electrodes 111 in the adjacent pixel regions P. The first electrode 111 is divided in each pixel region P with the bank 119 as a boundary between adjacent pixel regions P.
The bank 119 includes an opening exposing the first electrode 111, and the opening of the bank 119 is disposed to correspond to the light emitting area EA. A plurality of convex portions 117 and a plurality of concave portions 118 constituting the microlenses ML are provided in the entire opening of the bank 119. For example, the plurality of protrusions 117 and the plurality of recesses 118 may contact edge portions of the bank 119.
Further, the opening of the bank 119 is provided so as to correspond to the wavelength conversion layer 106. For example, edge portions of the banks 119 may overlap with edge portions of the wavelength conversion layer 106. Since the wavelength conversion layer 106 overlaps the bank 119, leakage of light that does not pass through the wavelength conversion layer 106 is prevented.
The light emitting layer 113 is disposed on the first electrode 111. The light emitting layer 113 may have a single layer of light emitting material. Alternatively, the light emitting layer 113 may have multiple layers including a hole injection layer, a hole transport layer, a light emitting material layer, an electron transport layer, and an electron injection layer to increase light emitting efficiency.
The first electrode 111 and the light emitting layer 113, which are sequentially located on the overcoat layer 108, may have a shape according to the surface morphology of the plurality of protrusions 117 and the plurality of recesses 118 of the top surface of the overcoat layer 108 to constitute the microlens ML.
The light emitting layer 113 may have different thicknesses in the convex 117 and concave 118 of the microlens ML.
The thickness of the light-emitting layer 113 in the region corresponding to the side surface portion 117c of the convex portion 117 of the microlens ML may be smaller than the thickness of the light-emitting layer 113 in the region corresponding to the concave portion 118 of the microlens ML. The thickness of the light emitting layer 113 may be defined as a length perpendicular to tangents C1 and C2 (fig. 2) of the top and bottom surfaces of the light emitting layer 113.
In the OLED display device 100, since the light emitting layer 113 has different thicknesses in the convex 117 and the concave 118 constituting the microlens ML, the distance from the second electrode 115 to the light emitting material layers 203a, 203b, and 203c (fig. 3) of the light emitting layer 113 in the concave 118 of the microlens ML is different from the distance from the second electrode 115 to the light emitting material layers 203a, 203b, and 203c of the light emitting layer 113 in the side surface portion 117c of the convex 117 of the microlens ML.
Accordingly, in the OLED display device 100, the light emitting material layers 203a, 203b, and 203c are disposed in the light emitting layer 113 constituting the microlens ML.
Since the light emitting material layers 203a, 203b, and 203c are disposed at specific positions in the light emitting layer 113 constituting the microlens ML, the light extraction efficiency of light emitted from the light emitting diode E is increased and the visibility of black is improved.
The second electrode 115 is provided over the entire light-emitting layer 113. For example, the second electrode 115 may be a cathode.
The second electrode 115 may have a shape following the surface morphology of the plurality of protrusions 117 and the plurality of recesses 118 of the top surface of the overcoat layer 108 to constitute the microlens ML.
When a voltage is applied to the first electrode 111 and the second electrode 115 according to a signal, holes injected from the first electrode 111 and electrons injected from the second electrode 115 are transported to the light emitting layer 113 to constitute excitons. When the excitons transit from the excited state to the ground state, light may be emitted from the light emitting layer 113 as visible rays.
Light of the light emitting layer 113 may pass through the transparent first electrode 111 to be emitted to the outside, thereby displaying an image.
Since the overcoat layer 108 constitutes the microlens ML, light confined inside the light emitting layer 113 due to total reflection may propagate through the microlens ML of the overcoat layer 108 at an angle smaller than a critical angle of total reflection, thereby being extracted to the outside through multiple reflections. As a result, the light extraction efficiency of the OLED display device 100 is improved.
Further, since the microlenses ML of the overcoat layer 108, the first electrode 111, the light-emitting layer 113, and the second electrode 115 are disposed in the entire opening of the bank 119 corresponding to the light-emitting area EA, the entire light-emitting area EA is used for the microlenses ML, and the light extraction efficiency is maximized.
A thin film type protective film 102 is provided on the driving TFT DTr and the light emitting diode E, and a surface sealing portion 104 is provided between the light emitting diode E and the protective film 102. The face seal 104 may include an organic material or an inorganic material that is transparent and has adhesiveness. The protective film 102 and the substrate 101 may be attached to each other to encapsulate the OLED display device 100.
In order to prevent external oxygen and moisture from penetrating into the inside of the OLED display device 100, the protective film 102 may include at least two inorganic protective films. An organic protective film for complementing impact resistance of the at least two inorganic protective films may be interposed between the at least two inorganic protective films.
In the structure in which the organic protective film and the inorganic protective film are alternately laminated with each other, the inorganic protective film may completely wrap the organic protective film such that moisture and oxygen are prevented from penetrating through the side surface of the organic protective film.
As a result, moisture and oxygen can be prevented from penetrating from the outside to the inside of the OLED display device 100.
In the OLED display device 100, a polarizing plate for preventing contrast from being lowered due to external light may be disposed on an outer surface of the transparent substrate 101. Since the polarizing plate is disposed on the surface of the OLED display device 100, the contrast ratio increases in a driving mode in which light is emitted from the light emitting layer 113.
In the OLED display device 100, since the light emitting material layers 203a, 203b, and 203c are disposed at specific positions in the light emitting layer 113 constituting the microlens ML due to the overcoat layer 108, the light extraction efficiency of light emitted from the light emitting diode E is increased and the visibility of black is improved.
Fig. 2 is an enlarged view of a portion a of fig. 1.
In fig. 2, a first electrode 111, a light emitting layer 113, and a second electrode 115 are sequentially disposed on an overcoat layer 108 having a microlens ML having a plurality of recesses 118 and a plurality of projections 117 alternating with each other. The first electrode 111, the light emitting layer 113, and the second electrode 115 constitute a light emitting diode E.
The first electrode 111, the light emitting layer 113, and the second electrode 115 have shapes according to the surface morphology of the top surface of the overcoat layer 108 to constitute the microlens ML.
Each protrusion 117 may have a bottom surface portion 117a, a top surface portion 117b, and a side surface portion 117 c. The side surface portion 117c may be the entire inclined surface constituting the top surface portion 117 b.
The side surface portion 117c may be divided into a lower area LA, an intermediate area MA, and an upper area UA according to a total height H between the bottom surface portion 117a and the top surface portion 117 b. The lower area LA may be defined as an area from the bottom surface portion 117a to half (H/2) of the total height H.
The intermediate area MA between the lower area LA and the upper area UA may be defined as an area from half (H/2) of the total height H to four fifths (4H/5) of the total height H. The upper region UA may be defined as a region from four fifths (4H/5) of the total height H to the top surface portion 117 b.
In order to further increase the light extraction efficiency of the light-emitting layer 113, the convex portion 117 of the coating layer 108 may have a structure in which the top surface portion 117b has a sharp shape (sharp shape). For example, the convex portion 117 may have a triangular cross section including a vertex corresponding to the top surface portion 117b, a base corresponding to the bottom surface portion 117a, and a hypotenuse corresponding to the side surface portion 117 c.
The angles θ 1 and θ 2 of the side surface portion 117c of the convex portion 117 of the coating layer 108 may gradually increase from the bottom surface portion 117a to the top surface portion 117 b. The angles θ 1 and θ 2 are defined as angles between tangents C1 and C2 of the side surface portion 117C and the horizontal plane (i.e., the bottom surface portion 117 a). When the angles θ 1 and θ 2 become maximum values, the side surface portion 117c may have a maximum slope Smax in the effective light emitting area B. The slope may be defined as the tangent (tan θ) of the angle.
Since the angles θ 1 and θ 2 of the side surface portion 117c may gradually increase from the bottom surface portion 117a to the top surface portion 117b, the side surface portion 117c of the convex portion 117 of the coating layer 108 has the maximum slope Smax in the upper region UA adjacent to the top surface portion 117 b.
The first electrode 111, the light emitting layer 113, and the second electrode 115 on the overcoat layer 108 having the microlenses ML including the concave portions 118 and the convex portions 117 have the microlenses ML on the top surfaces thereof. The convex portion 117 may include a bottom surface portion 117a, a top surface portion 117b, and a side surface portion 117c, and the side surface portion 117c may include an upper area UA, a middle area MA, and a lower area LA.
In the OLED display device 100, since the light emitting layer 113 is disposed on the overcoat layer 108 constituting the microlens ML, the light emitting layer 113 may have different thicknesses d1, d2, d3, and d4 in different regions. The light emitting layer 113 may be formed to have different thicknesses d1, d2, d3, and d4 corresponding to the concave portions 118 and the convex portions 117 of the microlens ML.
The thickness of the light emitting layer 113 may be defined as a length perpendicular to the tangents C1 and C2 of the light emitting layer 113. For example, the third thickness d3 and the fourth thickness d4 of the light emitting layer 113 at the side surface portions 117c of the convex portions 117 of the microlens ML may be smaller than the first thickness d1 and the second thickness d2 of the light emitting layer 113 at the top surface portions 117b of the concave portions 118 and the convex portions 117.
The thicknesses d3 and d4 of the light-emitting layer 113 of the side surface portions 117c of the convex portion 117 may gradually decrease from the lower area LA to the upper area UA.
Since the light emitting layer 113 is formed on the overcoat layer 108 having the microlenses ML, the side surface portions 117c of the convex portions 117 of the overcoat layer 108 may have angles θ 1 and θ 2 that gradually increase from the bottom surface portion 117a to the top surface portion 117 b. As a result, the third thickness d3 and the fourth thickness d4 of the light emitting layer 113 at the side surface part 117c are smaller than the first thickness d1 and the second thickness d2 of the light emitting layer 113 at the recess 118 and the top surface part 117 b.
Since the angles θ 1 and θ 2 of the side surface part 117c gradually increase from the lower area LA to the upper area UA, the light emitting layer 113 of the side surface part 117c may have the fourth thickness d4 as a minimum value in the upper area UA in which the angle θ 2 has a relatively large value, and the third thickness d3 as a maximum value in the middle area MA in which the angle θ 1 has a relatively small value.
For example, the first thickness d1 may be equal to or greater than the second thickness d2, the second thickness d2 may be greater than the third thickness d3, and the third thickness d3 may be greater than the fourth thickness d4, e.g., d1 ≧ d2> d3> d 4.
In the light emitting diode E, light emission is generated in a region having a relatively high current density. Since the light-emitting layer 113 has the relatively small fourth thickness d4 in the upper region UA of the convex portion 117, the light-emitting layer 113 can have a relatively high current density and relatively strong light emission in the upper region UA of the convex portion 117. Further, since the light-emitting layer 113 has a relatively large thickness d1 in the lower region LA of the convex section 117, the light-emitting layer 113 can have a relatively low current density and relatively weak light emission in the lower region LA of the convex section 117. As a result, the upper region UA of each of the plurality of convex sections 117, which produces stronger light emission, can be defined as an effective light emitting region B. When the light emitting diode E is driven, an electric field is locally concentrated on the effective light emitting area B. As a result, a main current path is constituted in the effective light emitting area B and main light emission is generated.
The light-emitting layer 113 has main light emission in the effective light-emitting region B having a relatively small thickness d4, as compared with the top surface portion 117B of the projection 117 and the recess 118. Since the light-emitting material layers 203a, 203B, and 203c are provided at specific positions of the light-emitting layer 113 based on the thickness of the light-emitting layer 113 in the effective light-emitting region B, the light extraction efficiency of light emitted from the light-emitting diode E increases and the visibility of black is improved.
The light emitting layer 113 constituting the microlens ML is formed to satisfy the following equation based on the effective light emitting region B, so that the light extraction efficiency can be increased and the visibility of black can be improved.
[ equation 1]
T2＝T1*cosθ
Here, T1 is the first thickness d1 of the light-emitting layer 113 in the concave portion 118, and T2 is the fourth thickness d4 of the light-emitting layer 113 in the effective light-emitting region B of the side surface portion 117c of the convex portion 117. Further, θ is a second angle θ 2 of a second tangent line C2 of the side surface portion 117C of the convex portion 117 in the effective light-emitting area B with respect to the horizontal plane (i.e., the bottom surface portion 117 a).
When the side surface portion 117c has the maximum slope Smax, the side surface portion 117c has the maximum angle θ max and the thickness T2 of the light emitting layer 113 can be obtained from the equation T2-T1-cos θ max. As a result, T2 may be determined as the fourth thickness d4 of the light emitting layer 113.
For example, the maximum angle θ max of the tangent line C2 of the side surface portion 117C in the effective light emitting area B with respect to the horizontal plane (i.e., the bottom surface portion 117a) may be about 20 degrees to about 60 degrees. When the maximum angle θ max is less than about 20 degrees, the propagation angle of light in the light emitting layer 113 having the microlenses ML does not change much compared to the propagation angle of light in a flat light emitting layer. As a result, the light extraction efficiency is not sufficiently improved.
When the maximum angle θ max is greater than about 60 degrees, the propagation angle of light in the light emitting layer 113 becomes greater than the critical angle of total reflection at the interface of the substrate 101 (fig. 1) and the external air layer. As a result, the amount of light confined in the OLED display device 100 increases, and the light extraction efficiency of the light emitting layer 113 having the microlenses ML decreases compared to that of a flat light emitting layer.
Therefore, in the effective light emitting area B of the convex portion 117 of the overcoat layer 108, the maximum angle θ max of the side surface portion 117c may be determined to be in the range of about 20 degrees to about 60 degrees.
Based on equation 1, the distance from the second electrode 115 to the light emitting material layers 203a, 203b, and 203c of the light emitting layer 113 may be defined according to equation 2 below.
[ equation 2]
L＝D*cosθ
Here, D is a distance from the second electrode 115 to the light emitting material layers 203a, 203b, and 203c of the light emitting layer 113 in the concave portion 118. L is a distance from the second electrode 115 to the light emitting material layers 203a, 203b, and 203c of the light emitting layer 113 in the side surface portion 117c of the convex portion 117 where main light emission is generated. Further, cos θ is a parameter that compensates for a decrease in the thickness of the light emitting layer 113 in the effective light emitting region B due to the second angle θ constituting the slope.
Based on equations 1 and 2, since the light emitting layer 113 having the microlens ML has different thicknesses d1, d2, d3, and d4 in the convex 117 and the concave 118, the distance from the second electrode 115 to the light emitting material layers 203a, 203b, and 203c of the light emitting layer 113 in the concave 118 is different from the distance from the second electrode 115 to the light emitting material layers 203a, 203b, and 203c of the light emitting layer 113 in the side surface portion 117c of the convex 117.
In the OLED display device 100, the side surface portion 117c of the convex portion 117 constituting the microlens ML is defined as an effective light emitting region B of the light emitting layer 113. The light emitting material layers 203a, 203b, and 203c are disposed at specific positions in the light emitting layer 113 based on the shape of the convex portion 117 according to equations 1 and 2. Since the light emitting material layers 203a, 203B, and 203c are disposed at specific positions in the light emitting layer 113 based on the effective light emitting region B of the side surface portion 117c of the convex portion 117, the light extraction efficiency can be further increased.
Further, in the OLED display device 100, since the light emitting material layers 203a, 203B, and 203c are disposed at specific positions in the light emitting layer 113 based on the effective light emitting area B according to the following equation 3, the visibility of black is improved.
[ equation 3]
Y＝L*(1/cosθ)；L≤Y
In the above equation, Y is a target thickness for evaporation of the light emitting material layers 203a, 203b, and 203c of the light emitting layer 113. Y may be a distance from the second electrode 115 to the light emitting material layers 203a, 203b, and 203c of the light emitting layer 113 in the recess 118. L is defined by D cos θ according to equation 2.
As a result, the distance from the second electrode 115 to the light-emitting material layers 203a, 203B, and 203c of the light-emitting layer 113 in the side surface portion 117c of the convex portion 117 corresponding to the effective light-emitting area B is equal to or smaller than the distance from the second electrode 115 to the light-emitting material layers 203a, 203B, and 203c of the light-emitting layer 113 in the concave portion 118.
Based on the thicknesses d1, d2, d3, and d4 of the light-emitting layer 113 in the concave portions 118 and the convex portions 117 of the microlens ML satisfying equation 3, the thickness of the light-emitting layer 113 in the effective light-emitting area B on the overcoat layer 108 can be determined to be about
The thickness of the light emitting layer 113 obtained by using equations 2 and 3 may be determined such that the OLED display device 100 has a microcavity effect.
The microcavity effect is a phenomenon in which light of one wavelength is enhanced by constructive interference and light of other wavelengths is weakened by destructive interference when the light is reflected between mirror surfaces. As a result, the intensity of light of a predetermined wavelength can be increased by the microcavity effect. In the OLED display device 100, the thicknesses of the light emitting material layers 203a, 203B, and 203c of the light emitting layer 113 of the microlenses ML in the effective light emitting area B may be determined such that the light emitting layer 113 has a microcavity effect.
For example, the distance L from the second electrode 115 to the light emitting material layers 203a, 203B, and 203c of the light emitting layer 113 in the side surface portion 117c of the convex portion 117 corresponding to the effective light emitting region B may be determined such that the light emitting material layers 203a, 203B, and 203c of the light emitting layer 113 have the microcavity effect, and the distance Y from the second electrode 115 to the light emitting material layers 203a, 203B, and 203c of the light emitting layer 113 in the concave portion 118 may be determined according to equation 3.
As a result, the light extraction efficiency of light emitted from the light emitting diode E may be increased, and the visibility of black due to a relatively high reflectance may be prevented from being deteriorated.
Fig. 3 is a cross-sectional view illustrating a light emitting diode of an organic light emitting diode display device according to an embodiment of the present invention.
In fig. 3, the light emitting diode E includes a first electrode 111 and a second electrode 115 and a light emitting layer 113 between the first electrode 111 and the second electrode 115, and the light emitting layer 113 includes a first light Emitting Material Layer (EML)203a, a second light Emitting Material Layer (EML)203b, and a third light Emitting Material Layer (EML)203 c.
The first electrode 111 may be an anode that provides holes and has a relatively large work function. For example, the first electrode 111 may include one of the following materials: metal oxides such as Indium Tin Oxide (ITO) and Indium Zinc Oxide (IZO); metalAnd mixtures of oxides, such as zinc oxide and aluminum (ZnO: Al) and tin oxide and antimony (SnO)2: sb); and conductive polymers such as poly (3-methylthiophene), poly [3,4- (ethylene-1, 2-dioxy) thiophene](PEDT), polypyrrole and polyaniline. In addition, the first electrode 111 may include one of a Carbon Nanotube (CNT), graphene, and a silver nanowire.
The second electrode 115 may be a cathode that supplies electrons and has a relatively small work function. For example, the second electrode 115 may have: a single layer of an alloy of a first metal (e.g., Ag) and a second metal (e.g., Mg), a double layer of a first metal and a second metal, or a multilayer of an alloy of a first metal and a second metal, which have a relatively small work function.
The second electrode 115 may be a reflective electrode and the first electrode 111 may be a transflective electrode. Alternatively, the first electrode 111 may be a reflective electrode, and the second electrode 115 may be a transparent electrode. For example, at least one of the first electrode 111 and the second electrode 115 may be a reflective electrode.
The second electrode 115 may include a material having a reflectivity equal to or greater than about 90% in the visible ray band, and the first electrode 111 may include a material having a transmissivity equal to or greater than about 80% in the visible ray band. For example, the visible ray band may be a wavelength band of about 380nm to about 800 nm.
When the second electrode 115 has a reflectance equal to or greater than about 90%, most of light from the light emitting layer 113 to the second electrode 115 may be reflected by the second electrode 115 to propagate toward the first electrode 111. In addition, when the first electrode 111 has a transmittance equal to or greater than about 80%, a large amount of light may pass through the first electrode 111.
In order to increase the reflectivity in the visible ray band, the second electrode 115 may have a thickness of about 90nm to about 120 nm. However, the thickness of the second electrode 115 is not limited thereto, and may vary according to the material of the second electrode 115. In order to increase the transmittance in the visible ray band, the first electrode 111 may have a thickness of about 115nm to about 135 nm. However, the thickness of the first electrode 111 is not limited thereto, and may vary according to the material of the first electrode 111.
A first Electron Transport Layer (ETL)205 is disposed between the second electrode and the first emitting material layer 203a, and a first auxiliary layer 208 is disposed between the first emitting material layer 203a and the second emitting material layer 203 b. The second auxiliary layer 209 is disposed between the second and third light emitting material layers 203b and 203c, and the first Hole Transport Layer (HTL)207 is disposed between the third light emitting material layer 203c and the first electrode 111.
An Electron Injection Layer (EIL) may be disposed between the second electrode 115 and the first electron transport layer 205. The electron injection layer may assist injection of electrons from the second electrode 115 to the first electron transport layer 205.
The first electron transport layer 205 may have at least two layers or may include at least two materials. A Hole Blocking Layer (HBL) may be disposed between the first electron transport layer 205 and the first luminescent material layer 203 a. Since the hole blocking layer prevents the holes injected into the first light emitting material layer 203a from being transferred to the first electron transport layer 205, the combination of the holes and the electrons is improved in the first light emitting material layer 203a, and the light emitting efficiency of the first light emitting material layer 203a is improved.
The first electron transport layer 205 and the hole blocking layer may be formed as a single layer. The electron injection layer, the first electron transport layer 205, and the hole blocking layer may be referred to as an electron transport layer.
Electrons are supplied from the second electrode 115 to the first light emitting material layer 203a through the first electron transport layer 205, and holes are supplied from the first auxiliary layer 208 to the first light emitting material layer 203 a. The electrons supplied through the first electron transport layer 205 and the holes supplied from the first auxiliary layer 208 are recombined in the first luminescent material layer 203a to generate light.
The first luminescent material layer 203a may emit light of a first color. The first light emitting material layer 203a may include one of a blue light emitting layer, a deep blue light emitting layer, and a sky blue light emitting layer. The light emitted from the first luminescent material layer 203a may have a wavelength of about 440nm to about 480 nm.
The first luminescent material layer 203a may include at least one host and at least one dopant, or include a mixed host in which at least two hosts are mixed and at least one dopant. When the mixed host includes a host having a hole transporting property and a host having an electron transporting property, the charge balance of the first luminescent material layer 203a may be adjusted and the efficiency of the first luminescent material layer 203a may be improved. The dopant may include a fluorescent dopant or a phosphorescent dopant.
The first auxiliary layer 208 may include a second hole transport layer adjacent to the first emitting material layer 203a and a second electron transport layer adjacent to the second emitting material layer 203 b.
A hole injection layer may be disposed between the second hole transport layer and the second light emitting material layer 203b, and an electron injection layer may be disposed between the second electron transport layer and the first light emitting material layer 203 a.
An Electron Blocking Layer (EBL) may be disposed between the first light emitting material layer 203a and the second hole transporting layer. Since the electron blocking layer prevents electrons injected into the first light emitting material layer 203a from being transferred to the second hole transporting layer, the combination of holes and electrons is improved in the first light emitting material layer 203a, and the light emitting efficiency of the first light emitting material layer 203a is improved.
In addition, a Hole Blocking Layer (HBL) may be disposed between the second electron transport layer and the second light emitting material layer 203 b. Since the hole blocking layer prevents the holes injected into the second light emitting material layer 203b from being transferred to the second electron transfer layer, the combination of the holes and the electrons is improved in the second light emitting material layer 203b, and the light emitting efficiency of the second light emitting material layer 203b is improved.
The electron blocking layer and the second hole transporting layer may be formed as a single layer, and the second electron transporting layer and the hole blocking layer may be formed as a single layer. The hole injection layer, the second hole transport layer, and the electron blocking layer may be referred to as a hole transport layer, and the electron injection layer, the second electron transport layer, and the hole blocking layer may be referred to as an electron transport layer.
A first Charge Generation Layer (CGL) may be disposed between the second hole transport layer and the second electron transport layer of the first auxiliary layer 208. The first charge generation layer may adjust charge balance between the first and second light emitting material layers 203a and 203 b. For example, a hole injection layer may be disposed between the second hole transport layer and the first charge generation layer, and an electron injection layer may be disposed between the first charge generation layer and the second electron transport layer.
The first charge generation layer may include a positive charge generation layer (P-CGL) and a negative charge generation layer (N-CGL). The positive type charge generation layer may supply holes to the first light emitting material layer 203a, and the negative type charge generation layer may supply electrons to the second light emitting material layer 203 b.
Electrons are supplied from the first auxiliary layer 208 to the second light emitting material layer 203b, and holes are supplied from the second auxiliary layer 209 to the second light emitting material layer 203 b. The electrons supplied from the first auxiliary layer 208 and the holes supplied from the second auxiliary layer 209 are recombined in the second light emitting material layer 203b to generate light.
The second luminescent material layer 203b may emit light of a second color. The second luminescent material layer 203b may include one of the following layers: a yellow-green light emitting layer, a yellow-green light emitting layer + a red light emitting layer, a yellow light emitting layer + a red light emitting layer, and a green light emitting layer + a red light emitting layer.
When the second light emitting material layer 203b includes a yellow-green light emitting layer, light emitted from the second light emitting material layer 203b may have a wavelength of about 510nm to about 580 nm. When the second light emitting material layer 203b includes a yellow-green light emitting layer + a red light emitting layer, light emitted from the second light emitting material layer 203b may have a wavelength of about 510nm to about 650 nm.
When the second light emitting material layer 203b includes a yellow light emitting layer + a red light emitting layer, light emitted from the second light emitting material layer 203b may have a wavelength of about 540nm to about 650 nm. When the second light emitting material layer 203b includes a green light emitting layer + a red light emitting layer, light emitted from the second light emitting material layer 203b may have a wavelength of about 510nm to about 650 nm.
The second luminescent material layer 203b may include at least one host and at least one dopant, or include a mixed host mixed with at least two hosts and at least one dopant. When the mixed host includes a host having a hole transporting property and a host having an electron transporting property, the charge balance of the second light emitting material layer 203b may be adjusted and the efficiency of the second light emitting material layer 203b may be improved. The dopant may include a fluorescent dopant or a phosphorescent dopant.
The second auxiliary layer 209 may include a third hole transport layer adjacent to the second light emitting material layer 203b and a third electron transport layer adjacent to the third light emitting material layer 203 c.
A hole injection layer may be disposed between the third hole transport layer and the third light emitting material layer 203c, and an electron injection layer may be disposed between the third electron transport layer and the second light emitting material layer 203 b.
An Electron Blocking Layer (EBL) may be disposed between the second light emitting material layer 203b and the third hole transport layer. Since the electron blocking layer prevents electrons injected into the second light emitting material layer 203b from being transferred to the third hole transport layer, the combination of holes and electrons is improved in the second light emitting material layer 203b, and the light emitting efficiency of the second light emitting material layer 203b is improved.
In addition, a Hole Blocking Layer (HBL) may be disposed between the third electron transport layer and the third light emitting material layer 203 c. Since the hole blocking layer prevents the holes injected into the third light emitting material layer 203c from being transferred to the third electron transport layer, the combination of the holes and the electrons is improved in the third light emitting material layer 203c, and the light emitting efficiency of the third light emitting material layer 203c is improved.
The electron blocking layer and the third hole transporting layer may be formed as a single layer, and the third electron transporting layer and the hole blocking layer may be formed as a single layer. The hole injection layer, the third hole transport layer, and the electron blocking layer may be referred to as a hole transport layer, and the electron injection layer, the third electron transport layer, and the hole blocking layer may be referred to as an electron transport layer.
A second Charge Generation Layer (CGL) may be disposed between the third hole transport layer and the third electron transport layer of the second auxiliary layer 209. The second charge generation layer may adjust charge balance between the second and third light emitting material layers 203b and 203 c. For example, a hole injection layer may be disposed between the third hole transport layer and the second charge generation layer, and an electron injection layer may be disposed between the second charge generation layer and the third electron transport layer.
The second charge generation layer may include a positive charge generation layer (P-CGL) and a negative charge generation layer (N-CGL). The positive type charge generation layer may supply holes to the second emission material layer 203b, and the negative type charge generation layer may supply electrons to the third emission material layer 203 c.
Electrons are supplied from the second auxiliary layer 209 to the third light emitting material layer 203c, and holes are supplied from the first electrode 111 to the third light emitting material layer 203c through the first hole transporting layer 207. The electrons supplied from the second auxiliary layer 209 and the holes supplied through the first hole transport layer 207 are recombined in the third light emitting material layer 203c to generate light.
The third light emitting material layer 203c may emit light of a third color identical to the first color of the light of the first light emitting material layer 203 a. The third light emitting material layer 203c may include one of a blue light emitting layer, a deep blue light emitting layer, and a sky blue light emitting layer. The light emitted from the third luminescent material layer 203c may have a wavelength of about 440nm to about 480 nm.
The third luminescent material layer 203c may include at least one host and at least one dopant, or include a mixed host mixed with at least two hosts and at least one dopant. When the mixed host includes a host having a hole transporting property and a host having an electron transporting property, the charge balance of the third light emitting material layer 203c may be adjusted and the efficiency of the third light emitting material layer 203c may be improved. The dopant may include a fluorescent dopant or a phosphorescent dopant.
In the OLED display device 100, the light emitting diode E includes three light emitting material layers 203a, 203b, and 203c between the first electrode 111 and the second electrode 115. In another embodiment, the light emitting diode may include two layers of light emitting material.
Since the distances from the second electrode 115 to the first, second, and third light emitting material layers 203a, 203b, and 203c are determined according to equation 2, the first, second, and third light emitting material layers 203a, 203b, and 203c are disposed to correspond to the microlenses ML of the light emitting layer 113, so that the light emitting diode E has a microcavity effect. As a result, the light extraction efficiency of the OLED display device 100 is improved.
The positions of the first, second, and third light emitting material layers 203a, 203b, and 203c in the light emitting layer 113 may be determined according to equations 4, 5, and 6 below.
[ equation 4]
L1 ═ D1 ═ cos θ, where θ is 20 ° to 60 °
[ equation 5]
L2 ═ D2 ═ cos θ, where θ is 20 ° to 60 °
[ equation 6]
L3 ═ ((D2+ D3)/2) × cos θ, where θ is 20 ° to 60 °
In the above equation, D1, D2, and D3 are the first distance, the second distance, and the third distance from the second electrode 115 to the first light emitting material layer 203a, the second light emitting material layer 203b, and the third light emitting material layer 203c of the light emitting layer 113, respectively, in the recess 118. L1, L2, and L3 are a first distance, a second distance, and a third distance from the second electrode 115 to the first light-emitting material layer 203a, the second light-emitting material layer 203b, and the third light-emitting material layer 203c of the light-emitting layer 113, respectively, in the side surface portion 117c of the projection 117 where main light emission is generated.
The first distance D1, the second distance D2, and the third distance D3 of the light-emitting layer 113 in the concave portion 118 are different from the first distance L1, the second distance L2, and the third distance L3 of the light-emitting layer 113 in the convex portion 117 of the effective light-emitting region B. The first distance L1, the second distance L2, and the third distance L3 of the light emitting layer 113 in the convex portion 117 of the effective light emitting region B can be obtained from the light emitting diode E having the microcavity effect, and the first distance D1, the second distance D2, and the third distance D3 of the light emitting layer 113 in the concave portion 118 can be obtained from equation 4, equation 5, and equation 6. The first, second, and third distances D1, D2, and D3 may be used as target thicknesses for depositing the first, second, and third emitting material layers 203a, 203b, and 203 c. As a result, the light extraction efficiency of the OLED display device 100 is improved.
For example, the thickness from the upper surface of the first electrode 111 of the anode to the lower surface of the second electrode 115 of the cathode may be about
In the OLED display device 100, when the first electrode 111 is a transparent electrode transmitting light and the second electrode 115 is a transflective electrode transmitting a portion of the light and reflecting the other portion of the light, light efficiency may be improved due to a microcavity effect between the first electrode 111 and the second electrode 115.
The microcavity effect is a phenomenon in which constructive interference of light occurs and light efficiency is improved due to repeated reflection and re-reflection between the first electrode 111 and the second electrode 115. For constructive interference, the first, second, and third light emitting material layers 203a, 203b, and 203c emitting light may be disposed at a resonance position between the first and second electrodes 111 and 115 according to wavelength. The resonance position may correspond to a resonance distance from the second electrode 115, and the resonance distance may be obtained from an integral multiple of a half wavelength of the emitted light.
When the first, second, and third luminescent material layers 203a, 203b, and 203c are disposed at the resonance position, light of the respective wavelengths is enhanced by constructive interference and extracted to the outside with increased intensity. In addition, light of other wavelengths is weakened by destructive interference and extracted to the outside with the strength weakened.
Since light efficiency of only light having a wavelength corresponding to a resonance distance is improved due to the microcavity effect, light emitted from the first, second, and third light emitting material layers 203a, 203b, and 203c has different light emission spectra according to the length of the light path when the light is extracted through the first electrode 111. As a result, in order to improve light efficiency using the microcavity effect, the first, second, and third emitting material layers 203a, 203b, and 203c are disposed at resonance positions corresponding to resonance distances.
Specifically, in the OLED display device 100, since the light emitting layer 113 constitutes the microlens ML in which the light emitting layer 113 has different thicknesses d1, d2, d3, and d4 in the convex portion 117 and the concave portion 118, the first light emitting material layer 203a, the second light emitting material layer 203B, and the third light emitting material layer 203c of the effective light emitting region B of the light emitting layer 113 are disposed at the resonance position. As a result, the light efficiency of the OLED display device 100 is improved due to the microcavity effect.
Fig. 4A, 4B and 4C are graphs showing light intensities at positions of a first emitting material layer, a second emitting material layer and a third emitting material layer, respectively, of an organic light emitting diode display device according to an embodiment of the present invention.
In FIG. 4A, the first luminescent material layer 203a when emitting light of a wavelength of about 440nm to about 480nmAbout a distance from the second electrode 115
In fig. 4B, when the second light emitting material layer 203B emitting light of a wavelength of about 510nm to about 590nm is about from the second electrode 115
In fig. 4C, when the third light emitting material layer 203C emitting light of a wavelength of about 440nm to about 480nm is about from the second electrode 115
Thus, the first luminescent material layer 203a is disposed at a first position having a thickness of about
In the OLED display device 100 in which the light emitting layer 113 constitutes the microlens ML (in which the light emitting layer 113 has different thicknesses d1, d2, d3, and d4 in the convex 117 and concave 118), since the first light emitting material layer 203a, the second light emitting material layer 203B, and the third light emitting material layer 203c of the effective light emitting region B of the light emitting layer 113 are disposed at the resonance position based on the microlens ML, the light efficiency of the OLED display device 100 is improved due to the microcavity effect.
Fig. 5A and 5B are graphs showing light intensity according to wavelength of light extracted from an organic light emitting diode display device having a microlens and an organic light emitting diode display device according to an embodiment of the present invention, respectively.
In fig. 5A and 5B, sample 1 corresponds to an organic light emitting diode display device according to the related art, sample 2 corresponds to an organic light emitting diode display device having a microlens without a microcavity effect, and sample 3 corresponds to an organic light emitting diode display device 100 having a microlens with a microcavity effect according to an embodiment of the present invention.
The x-axis represents the wavelength of light and the y-axis represents the intensity of light. The intensity is a relative value with respect to the maximum value of the light emission spectrum. For example, a value of 0.34(a.u.) of the blue emission spectrum is a maximum value, and a relative value of the yellow-green emission spectrum with respect to the maximum value is shown.
In fig. 5A, sample 2 has a higher luminescence spectrum compared to sample 1.
The OLED display device (sample 2) having the micro lenses ML (fig. 2) of the coating layer 108 (fig. 2) without the microcavity effect has a larger amount of light in the visible ray band than the OLED display device (sample 1) without the micro lenses.
In fig. 5B, sample 3 has a higher luminescence spectrum compared to sample 2 as well as sample 1.
The OLED display device 100 (sample 3) having the micro lens ML of the coating layer 108 and the microcavity effect has a larger amount of light in the visible ray band than the OLED display device (sample 2) having the micro lens ML without the microcavity effect. The OLED display device 100 (sample 3) has higher light extraction efficiency than the OLED display device (sample 2) and the OLED display device (sample 1).
In the light emitting diode E of the OLED display device 100, the distances L1, L2, and L3 from the second electrode 115 to the light emitting material layers 203a, 203B, and 203c in the convex 117 of the effective light emitting region B may be determined such that the microlens ML has the microcavity effect, and the target thicknesses Y1, Y2, and Y3 may be determined according to equation 3, the target thicknesses Y1, Y2, and Y3 being the distances from the second electrode 115 to the light emitting material layers 203a, 203B, and 203c in the concave 118. As a result, the visibility of black is improved.
For example, the thicknesses of the first, second, and third light emitting material layers 203a, 203b, and 203c may be determined according to the following equations 7, 8, and 9.
[ equation 7]
Y1＝L1*(1/cosθ)；L1≤Y1；θ＝20°～60°
[ equation 8]
Y2＝L2*(1/cosθ)；Y2*cos60°≤L2≤Y2*cos20°；θ＝20°～60°
[ equation 9]
Y3＝L3*(1/cosθ)；Y3*cos60°≤L3≤Y3*cos20°；θ＝20°～60°
In the above equation, Y1, Y2, and Y3 are the first distance, the second distance, and the third distance from the second electrode 115 to the first light emitting material layer 203a, the second light emitting material layer 203b, and the third light emitting material layer 203c of the light emitting layer 113 in the recess 118. For example, each of Y1, Y2, and Y3 is at about
Further, L1, L2, and L3 are a first distance, a second distance, and a third distance from the second electrode 115 to the first light-emitting material layer 203a, the second light-emitting material layer 203B, and the third light-emitting material layer 203c of the light-emitting layer 113 in the convex portion 117 of the effective light-emitting region B.
The OLED display device 100 having improved visibility of black is realized by determining the first, second, and third distances Y1, Y2, and Y3 according to equations 7, 8, and 9.
In equations 8 and 9, cos60 ° (-0.5) is used for the minimum thickness of the light emitting material layers 203b and 203c corresponding to the maximum slope of the maximum angle θ of the convex portion 117 of the microlens ML, and cos20 ° (-0.94) is used for the maximum thickness of the light emitting material layers 203b and 203c corresponding to the minimum slope of the minimum angle θ of the convex portion 117 of the microlens ML. Since the first light emitting material layer 203a is disposed adjacent to the second electrode 115, light emitted from the first light emitting material layer 203a is absorbed by the second electrode 115 due to a surface plasmon phenomenon (surface plasmon phenomenon). When the thickness of the first luminescent material layer 203a is reduced, the light extraction effect of the first luminescent material layer 203a may be reduced. As a result, the minimum value of the distance L1 from the second electrode 115 to the first light-emitting material layer 203a is omitted in equation 7.
The first distance L1 may be determined to be about according to equation 7, equation 8, and equation 9
Fig. 6 is a graph showing an aspect ratio of a microlens and a reflectance of the microlens of the organic light emitting diode display device according to the embodiment of the present invention.
In fig. 6, as the aspect ratio of the microlens ML increases, the reflectivity of the microlens ML increases. Further, in the similar aspect ratio of the microlens ML, the reflectance of the microlens ML varies according to the thickness of the light emitting layer 113.
For example, a thickness of less than about
The aspect ratio a/R of the microlens ML may be defined as a value of the height H of the top surface portion 117b of the coating layer 108 with respect to half of the diameter D of the bottom surface portion 117 a. For example, the aspect ratio of the microlens ML may have an aspect ratio of about 0.4 to about 0.5.
When the thickness of the light emitting layer 113 is less than aboutIn this case, the reflectance with respect to the wavelength is clearly reduced.
Fig. 7A, 7B and 7C are graphs respectively showing voltages and luminous efficiencies of a red sub-pixel, a green sub-pixel and a blue sub-pixel of an organic light emitting diode display device according to an embodiment of the present invention, and table 1 shows distances from a second electrode to a light emitting material layer of the organic light emitting diode display device according to the present invention.
[ Table 1]
In fig. 7A, fig. 7B, and fig. 7C and table 1, sample 5, sample 6, and sample 7 correspond to the case where the light emitting layer 113 has a thickness equal to or greater than that of the light emitting layer
In fig. 7A, the luminous efficiencies of the red sub-pixels of sample 5, sample 6, and sample 7 are similar to the luminous efficiencies of the red sub-pixels of sample 8, sample 9, and sample 10.
In fig. 7B, the luminous efficiencies of the green sub-pixels of sample 5, sample 6, and sample 7 are similar to the luminous efficiencies of the green sub-pixels of sample 8, sample 9, and sample 10.
In fig. 7C, the luminous efficiencies of the blue sub-pixels of sample 5, sample 6, and sample 7 are similar to the luminous efficiencies of the blue sub-pixels of sample 8, sample 9, and sample 10.
Since the first distance L1, the second distance L2, and the third distance L3 are determined according to equations 7, 8, and 9, even when the light emitting layer 113 has a height greater than about
Since the reflectance is reduced, the reflectance visibility of black in the black state of the OLED display device 100 may be improved, and a user may recognize clear black.
For example, since the OLED display device according to the related art has a relatively high reflectivity in a black state, a user cannot recognize a clear black color. However, since the OLED display device 100 has a relatively low reflectance due to the positions of the light emitting material layers 203a, 203b, and 203c, reflectance visibility may be improved and a user may recognize clear black.
In the OLED display device 100, the distances Y1, Y2, and Y3 from the second electrode 115 to the light emitting material layers 203a, 203B, and 203c in the concave portion 118 are determined based on the distances L1, L2, and L3 from the second electrode 115 to the light emitting material layers 203a, 203B, and 203c in the convex portion 117 of the effective light emitting region B according to equation 3.
Further, distances L1, L2, and L3 from the second electrode 115 to the light-emitting material layers 203a, 203B, and 203c in the convex portion 117 of the effective light-emitting region B are determined based on the microcavity effect.
As a result, the distances Y1, Y2, and Y3 from the second electrode 115 to the light emitting material layers 203a, 203B, and 203c in the concave portion 118 are determined to be different from the distances L1, L2, and L3 from the second electrode 115 to the light emitting material layers 203a, 203B, and 203c in the convex portion 117 of the effective light emitting region B.
Thus, according to the embodiment of the invention, in the OLED display device 100, light extraction efficiency is improved and the reduction of visibility of black due to relatively high reflectance is prevented.
The present invention also relates to (but is not limited to) the following aspects.
In the present invention, an organic light emitting diode display device includes: a substrate; a coating layer on the substrate, the coating layer including a plurality of protrusions and a plurality of recesses; a first electrode on the coating layer; a light emitting layer on the first electrode, the light emitting layer including a first light emitting material layer; and a second electrode on the light emitting layer, wherein the first light emitting material layer in the plurality of convex portions is separated from the second electrode by a first distance, and wherein the first light emitting material layer in the plurality of concave portions is separated from the second electrode by a second distance different from the first distance.
In the present invention, at least one of the plurality of convex portions includes a bottom surface portion, a top surface portion, and a side surface portion located between the bottom surface portion and the top surface portion, wherein a slope of the side surface portion increases from the bottom surface portion to the top surface portion, and wherein the side surface portion has a maximum slope at an effective light emitting area.
In the present invention, the distance from the second electrode to the first light-emitting material layer in the plurality of protrusions is determined by the following equation: l1 ═ D1 ═ cos θ, where θ is 20 ° to 60 °, where L1 is the distance from the second electrode to the first light-emitting material layer in the plurality of convex portions, D1 is the distance from the second electrode to the first light-emitting material layer in the plurality of concave portions, and θ is the angle of the tangent to the side surface portion with respect to the bottom surface portion.
In the present invention, the organic light emitting diode display device further includes a second light emitting material layer between the first light emitting material layer and the first electrode, wherein a distance from the second electrode to the second light emitting material layer in the plurality of protrusions is determined by the following equation: l2 ═ D2 ═ cos θ, where θ is 20 ° to 60 °, where L2 is the distance from the second electrode to the second light-emitting material layer in the plurality of convex portions, D2 is the distance from the second electrode to the second light-emitting material layer in the plurality of concave portions, and θ is the angle of the tangent to the side surface portion with respect to the bottom surface portion.
In the present invention, the organic light emitting diode display device further includes a third light emitting material layer between the second light emitting material layer and the first electrode, wherein a distance from the second electrode to the third light emitting material layer in the plurality of protrusions is determined by the following equation: l3 ═ ((D2+ D3)/2) × cos θ, where θ is 20 ° to 60 °, where L3 is a distance from the second electrode to the third light emitting material layer in the plurality of convex portions, D3 is a distance from the second electrode to the third light emitting material layer in the plurality of concave portions, and θ is an angle of a tangent line of the side surface portion with respect to the bottom surface portion.
In the present invention, the distance from the second electrode to the first light-emitting material layer in the plurality of concave portions is aboutTo
In the present invention, the distance from the second electrode to the first light-emitting material layer in the plurality of recesses is determined by the following equation: y1 ═ L1 ═ L1 ≦ Y1, and θ ═ 20 ° to 60 °, where Y1 is a distance from the second electrode to the first light-emitting material layer in the plurality of concave portions, L1 is a distance from the second electrode to the first light-emitting material layer in the plurality of convex portions, and θ is an angle of a tangent line of the side surface portion with respect to the bottom surface portion.
In the present invention, the organic light emitting diode display device further includes a second light emitting material layer between the first light emitting material layer and the first electrode, wherein a distance from the second electrode to the second light emitting material layer in the plurality of recesses is determined by the following equation: y2 ═ L2 ═ L2 ≦ cos60 ≦ L2 ≦ Y2 ≦ cos20 °, and θ ═ 20 ° to 60 °, wherein Y2 is a distance from the second electrode to the second light emitting material layer in the plurality of concave portions, L2 is a distance from the second electrode to the second light emitting material layer in the plurality of convex portions, and θ is an angle of a tangent line of the side surface portion with respect to the bottom surface portion.
In the present invention, the organic light emitting diode display device further includes a third light emitting material layer between the second light emitting material layer and the first electrode, wherein a distance from the second electrode to the third light emitting material layer in the plurality of recesses is determined by the following equation: y3 ═ L3 ═ L3 ≦ cos60 ≦ L3 ≦ Y3 ≦ cos20 °, and θ ═ 20 ° to 60 °, wherein Y3 is a distance from the second electrode to the third light emitting material layer in the plurality of concave portions, L3 is a distance from the second electrode to the third light emitting material layer in the plurality of convex portions, and θ is an angle of a tangent line of the side surface portion with respect to the bottom surface portion.
In the present invention, the light emitting layer has a thickness of about
In the present invention, the thickness of the light-emitting layer corresponding to the plurality of convex portions is smaller than the thickness of the light-emitting layer corresponding to the plurality of concave portions.
In the present invention, the first luminescent material layer and the third luminescent material layer emit light of a first color, and the second luminescent material layer emits light of a second color different from the first color.
In the present invention, the first color corresponds to a wavelength in the range of 440nm to 480nm, and the second color corresponds to a wavelength in the range of 510nm to 590 nm.
In the present invention, the first, second, and third light emitting material layers include a first blue light emitting layer, a yellow-green light emitting layer, and a second blue light emitting layer, respectively.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
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