KR20130098564A - Method of forming a light extraction layer, organic light emitting display device and method of manufacturing an organic light emitting display device - Google Patents

Abstract

PURPOSE: A method for forming a light extraction layer, an organic light emitting display device, and a manufacturing method thereof are provided to form the light extraction layer which improves luminous characteristics by only the deposition process without an etching process or an imprinting process. CONSTITUTION: A light extraction layer (120) with an uneven part or a corrugated part is formed on the rear side of a substrate (100). The light extraction layer is formed by using light extraction compositions mixed with silicate sol solutions and titanium oxide sol solutions. A first electrode (110) is formed on the front side of the substrate. An organic layer (130) includes a hole transport layer and a light emitting layer which are successively formed on the first electrode. A second electrode (140) is formed on the organic layer.

Description

TECHNICAL FIELD OF FORMING A LIGHT EXTRACTION LAYER, ORGANIC LIGHT EMITTING DISPLAY DEVICE AND METHOD OF MANUFACTURING AN ORGANIC LIGHT EMITTING DISPLAY DEVICE}

The present invention relates to a method of forming a light extraction layer, an organic light emitting display device, and a method of manufacturing an organic light emitting display device. More specifically, the present invention relates to a method of forming a light extraction layer, an organic light emitting display device including the light extraction layer, and a method of manufacturing an organic light emitting display device including the light extraction layer.

Organic light emitting display (OLED) devices use holes and holes provided from an anode and a cathode, respectively, and light generated by combining electrons in the organic light emitting layer positioned between the anode and the cathode. A display device capable of displaying information such as images, characters, and the like. The organic light emitting diode display has attracted attention as a promising next-generation display device because it has various advantages such as wide viewing angle, fast response speed, thin thickness, and low power consumption.

The organic light emitting diode display may include electrodes stacked on a transparent substrate, such as a glass substrate, and organic layers including a hole transport layer, an organic light emitting layer, an electron transport layer, and the like. Therefore, a difference in refractive index may occur at the interface between the transparent substrate, the electrodes, and the organic layers. Light generated in the organic layer may not be emitted to the outside due to a total reflection due to the difference in refractive index, and may be trapped inside the organic light emitting diode display.

Therefore, a method of reducing the above-mentioned light trapping phenomenon and improving the luminous efficiency and quantum efficiency of the organic light emitting diode display has been studied.

One object of the present invention is to provide a method for forming a light extraction layer excellent in excellent light extraction efficiency.

Another object of the present invention is to provide a method of manufacturing an organic light emitting display device including the light extraction layer.

Another object of the present invention is to provide an organic light emitting display device including the light extraction layer.

However, the problem to be solved by the present invention is not limited to the above-described problems, and may be variously expanded within a range without departing from the spirit and scope of the present invention.

According to the method of forming the light extraction layer according to the exemplary embodiments of the present invention for achieving the above object of the present invention, the light extraction by mixing a silicate (SiO ₂ ) sol solution and titanium oxide (TiOx) sol solution Prepare the composition. The light extraction composition is used to form a light extraction layer having a wrinkled or uneven structure on the transparent substrate through a spin-coating process.

According to exemplary embodiments, the SiO ₂ sol solution may be prepared by mixing TEOS (tetraethyl orthosilicate) with an alcohol solvent.

According to exemplary embodiments, the TiOx sol solution may be prepared by mixing a titanium alkoxide compound with an alcohol solvent.

According to exemplary embodiments, the volume ratio of the SiO ₂ sol solution and the TiOx sol solution to the total volume of the light extraction composition may range from 30:70 to 50:50.

According to exemplary embodiments, the spin-coating process may be performed at a rotation speed in the range of 3500 rpm to 5500 rpm.

According to exemplary embodiments, when the volume ratio of the TiOx sol solution to the total volume of the light extraction composition is 65% or more and the rotational speed is 5000rpm or more, the corrugated or uneven structure of the light extraction layer has a two-dimensional It may have a net shape.

According to exemplary embodiments, as the volume ratio of the TiOx sol solution to the total volume of the light extraction composition increases, the width of the wrinkled or uneven structure of the light extraction layer may decrease.

According to exemplary embodiments, as the rotational speed increases, the width of the wrinkled or uneven structure of the light extraction layer may decrease.

In the method of manufacturing the organic light emitting diode display according to the exemplary embodiments of the present invention for achieving the above object of the present invention, a transparent substrate having a first electrode formed on the front surface is prepared. On the back surface of the transparent substrate, a light extraction layer having a SiO ₂ sol solution and a TiOx sol solution is mixed to form a light extraction layer having a wrinkled or uneven structure through a spin-coating process. The organic layer and the second electrode are sequentially formed on the first electrode.

In example embodiments, the SiO ₂ sol solution may be prepared by mixing TEOS with an alcohol solvent, and the TiOx sol solution may be prepared by mixing a titanium alkoxide compound with an alcohol solvent.

According to exemplary embodiments, the volume ratio of the SiO ₂ sol solution and TiOx sol solution to the total volume of the light extraction composition is in the range of 30:70 to 50:50, the rotational speed of the spin-coating process is 3500rpm to 5500rpm It can be a range.

According to exemplary embodiments, the width of the corrugated or uneven structure of the light extraction layer may decrease as the volume ratio of the TiOx sol solution increases or the rotational speed increases with respect to the total volume of the light extraction composition. .

According to exemplary embodiments, when the volume ratio of the TiOx sol solution to the total volume of the light extraction composition is 65% or more and the rotational speed is 5000rpm or more, the corrugated or uneven structure of the light extraction layer has a two-dimensional It may have a net shape.

In example embodiments, the back surface of the transparent substrate may be subjected to an oxygen plasma treatment before the light extraction layer is formed.

In accordance with another aspect of the present invention, an organic light emitting display device includes a transparent substrate having a first electrode formed on a front surface thereof, a SiO ₂ sol solution, and TiOx formed on a rear surface of the transparent substrate. And a light extraction layer having a wrinkled or uneven structure formed by spin-coating a light extraction composition including a sol solution, an organic layer formed on the first electrode, and a second electrode formed on the organic layer.

According to the exemplary embodiments of the present invention as described above, according to the exemplary embodiments of the present invention, by using a mixture of SiO ₂ sol solution and TiOx sol solution through a spin-coating process of the uneven or corrugated structure An OLED device including a light extraction layer may be manufactured. Therefore, the light extraction layer may be formed to improve the light emitting characteristics of the OLED device by a simple deposition process without an etching or imprinting process. In addition, in the spin-coating process, the shape of the surface morphology of the light extraction layer may be changed by adjusting the rotation speed and the composition ratio of the mixture.

1 is a cross-sectional view illustrating an organic light emitting display device in accordance with example embodiments.
2A and 2B are cross-sectional views illustrating a light extraction mechanism of an organic light emitting diode display according to example embodiments.
3 to 6 are cross-sectional views illustrating a method of manufacturing an organic light emitting diode display according to example embodiments.
7A to 7C are optical microscope pictures showing a morphology change of the light extraction layer according to the change in the rotational speed of the spin-coating device.
8a to 8c are optical micrographs showing the morphology change of the light extraction layer according to the concentration change of the light extraction composition.
9A to 9C are graphs showing the surface profile of the light extraction layer according to the spin-coating speed and the light extraction composition concentration.
10A and 10B are graphs illustrating light emission characteristics of an organic light emitting diode display according to a change in spin-coating speed.
11A and 11B are graphs illustrating light emission characteristics of an organic light emitting diode display according to a change in content of a SiO ₂ sol solution.
12A and 12B are graphs illustrating spectrums of emission intensities of an organic light emitting diode display including a light extracting layer according to example embodiments.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. In the accompanying drawings, the dimensions of the structures are enlarged to illustrate the present invention in order to clarify the present invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, the terms "comprising ", or" having ", and the like, are intended to specify the presence of stated features, integers, steps, operations, elements, or combinations thereof, , Steps, operations, elements, or combinations thereof, as a matter of principle, without departing from the spirit and scope of the invention.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

1 is a cross-sectional view illustrating an organic light emitting display device in accordance with example embodiments. Hereinafter, the organic light emitting display device will be abbreviated as OLED device.

Referring to FIG. 1, the OLED device includes a first electrode 110, an organic layer 130, and a second electrode 140 sequentially stacked on the substrate 100. In example embodiments, a light extraction layer 120 having a concave-convex or corrugated shape may be provided on the rear surface of the substrate 100.

The substrate 100 may include a glass substrate or a transparent plastic substrate. For example, the transparent plastic substrate may be made of polyimide, acryl, polyethylene terephthalate, polycarbonate, polyacrylate, polyether, or the like. have. A lower structure (not shown) including a switching element, an insulating layer, and the like may be provided on the substrate 100. The switching device may include a thin film transistor (TFT) device or an oxide semiconductor device.

The light extraction layer 120 may be formed using a mixed light extraction composition of a silicate (SiO ₂ ) sol solution and a sol solution of titanium oxide (TiOx). According to exemplary embodiments, the light extraction layer 120 may have a corrugated shape or a wave shape including a plurality of irregularities.

According to exemplary embodiments, the morphology or surface profile of the light extraction layer 120 may be changed according to the content ratio of the silicate and the titanium oxide of the mixture. As the content of the silicate increases, the thickness and / or height of the wrinkles or irregularities of the light extraction layer 120 increases, and the shape may have a substantially one-dimensional line shape. On the other hand, as the content of titanium oxide increases, the thickness and / or height of wrinkles or irregularities of the light extraction layer 120 may decrease, and the gap may be reduced. In this case, the light extraction layer 120 may have a corrugated or uneven structure of a substantially two-dimensional network or net structure.

The first electrode 110 may be formed on the entire surface of the substrate 100. The first electrode 110 may include a metal oxide having a relatively high work function and having excellent transparency and conductivity. For example, the first electrode 110 may include indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnOx), gallium oxide (GaOx), tin oxide (SnOx), or the like. These may be used alone or in combination with each other. In addition, the first electrode 110 may have a single layer structure or a multilayer structure including the metal oxide. In example embodiments, the first electrode 110 may correspond to an anode that provides holes to the organic layer 130. In addition, the first electrode 110 may be electrically connected to the source electrode or the drain electrode of the switching element provided on the substrate 100.

The organic layer 130 may include a hole transport layer (HTL) and an emission layer (EML) that are sequentially stacked on the first electrode 110. The hole transport layer is a non-limiting example of 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPB), 4,4'-bis [N- (3-methylphenyl ) -N-phenylamino] biphenyl (TPD), N, N-di-1-naphthyl-N, N-diphenyl-1,1-biphenyl-4,4-diamine (NPD), N-phenyl Hole transport materials such as carbazole, polyvinylcarbazole, and the like. These may be used alone or in combination of two or more.

The light emitting layer may include light emitting materials for generating different color lights such as red (R) light, green (G) light, and blue (B) light. In addition, the light emitting layer 150 may have a multilayer structure in which a plurality of light emitting materials for realizing different color lights such as red light, green light, and blue light are stacked to emit white light. In example embodiments, the light emitting layer 150 may further include a fluorescent or phosphorescent host material having a band gap substantially larger than that of the above-described light emitting materials. According to exemplary embodiments, the light emitting layer may include a known light emitting material, and the present invention is not limited by the light emitting material.

In one embodiment, a hole injection layer (HIL) may be further provided below the hole transport layer. The hole injection layer may serve to facilitate hole injection from the first electrode 110 to the hole transport layer. For example, the hole injection layer may include a hole injection material such as copper phthalocyanine (CuPc), poly (3,4) -ethylenedioxythiophene (PEDOT), polyaniline (PANI), or the like.

In one embodiment, an electron transport layer (ETL) may be disposed on the light emitting layer. The electron transporting layer is, by way of non-limiting example, tris (8-quinolinolato) aluminum (Alq3), 2- (4-biphenylyl) -5-4-tert-butylphenyl-1,3,4-oxy Electron transport materials such as diazole (PBD), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (BAlq), vasocuproin (BCP), and the like. These may be used alone or in combination of two or more.

In one embodiment, an electron injection layer (EIL) may be further disposed on the electron transport layer. The electron injection layer may include an inorganic electron injection material such as alkali metal, alkaline earth metal, oxide and / or fluoride of the alkali metal or alkaline earth metal. Alternatively, the electron injection layer may include an organic electron injection material such as Alq3, PBD.

In one embodiment, a hole blocking layer may be further provided between the emission layer and the electron transport layer. The hole blocking layer may include a material having excellent electron transport ability while decreasing hole transport ability. Examples of the material for the hole blocking layer include Bathocuproine (BCP), 3- (4-biphenylyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4 -Triazole (TAZ) etc. are mentioned. In addition, an electron blocking layer may be further provided between the emission layer and the hole transport layer. The electron blocking layer may include a material having excellent hole transport ability while significantly decreasing electron transport ability, and may include, for example, Ir (ppz) ₃ or the like.

The second electrode 140 is disposed on the organic layer 130. The second electrode 140 may be transparent, such as indium tin oxide, indium oxide, indium zinc oxide, zinc oxide, tin oxide, gallium zinc oxide, gallium indium zinc oxide, or aluminum doped zinc oxide, depending on whether the electrode is a transparent electrode or a reflective electrode. It may include a conductive material or may include metals such as silver, aluminum, platinum, gold, chromium, tungsten, molybdenum, titanium, palladium, alloys thereof, and the like. In example embodiments, the second electrode 140 may serve as a cathode for providing electrons to the organic layer 130.

2A and 2B are cross-sectional views illustrating a light extraction mechanism of an organic light emitting diode display according to example embodiments.

2A is a view showing a path of light when the light extraction layer is not formed on the back surface of the substrate 100. Referring to FIG. 2A, the path of the light may be broken according to the difference in refractive index at the interface of the light emitting layer 130. For example, the first electrode 110 and the organic layer 130 including ITO may have refractive indices of about 1.7 to 2, respectively. When the substrate 100 is a glass substrate, the refractive index is about 1.5, and the refractive index of air is about 1.0. Referring to FIG. 2A, light generated in the light emitting layer 130 may be emitted to the outside of the rear surface of the substrate 100 according to its path or angle of incidence, and may be totally reflected and trapped inside the OLED device. For example, when the incident angle is formed smaller than the critical angle at the interface between the substrate 100 and the air, some light (denoted as Ray A) may be extracted outside the rear surface of the substrate 100. However, when the incident angle at the interface between the substrate 100 and the air is greater than the critical angle, some light (denoted by Ray B) may be totally reflected at the interface and trapped inside the OLED device.

2B is a view showing a path of light when the light extraction layer according to the exemplary embodiments is formed on the back surface of the substrate 100.

As shown in FIG. 2B, light entering the light extraction layer 120 from the substrate 100 (denoted by Ray C) is due to the morphology or surface profile of the light extraction layer 120 at the interface with air. The angle of incidence is reduced. Therefore, most of the light can be emitted to the outside without total reflection. Accordingly, light extraction efficiency and / or quantum efficiency of the OLED device may be increased, which may improve light emission characteristics such as luminance of the OLED device.

3 to 6 are cross-sectional views illustrating a method of manufacturing an organic light emitting diode display according to example embodiments. On the other hand, Figure 5 is a cross-sectional view schematically showing a mechanism in which the wrinkle structure of the light extraction layer is formed.

Referring to FIG. 3, a substrate 100 on which a first electrode 110 is formed is prepared. As the substrate 100, a glass substrate or a transparent plastic substrate can be used. The first electrode 110 may be formed using a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnOx), gallium oxide (GaOx), tin oxide (SnOx), or the like. . The first electrode 110 may be formed by performing a sputtering process, a chemical vapor deposition (CVD) process, a vacuum deposition process, a printing process, or the like.

Referring to FIG. 4, the light extraction layer 120 is formed on the rear surface of the substrate 100. According to exemplary embodiments, the light extraction layer 120 is a spin-coating process using a light extraction composition mixed with a silicate (SiO ₂ ) sol solution and a titanium oxide (TiOx) sol solution Can be formed. The light extraction layer 120 may be formed in a substantially corrugated or wave shape including a plurality of irregularities.

The SiO ₂ sol solution may be obtained by mixing the silicate precursor with a volatile solvent of alcohols such as methanol, 2-methoxy ethanol and the like. Tetraethyl orthosilicate (TEOS) is mentioned as an example of the said silicate precursor. The SiO ₂ sol solution may further include an organosilane-based material such as, for example, (3-glycidoxypropyl) trimethoxysilane (GPTMS).

The TiOx sol solution may be obtained by mixing a titanium oxide precursor with a volatile solvent such as alcohol. Examples of the titanium oxide precursor include titanium alkoxide compounds such as titanium tetra isopropoxide, titanium tetra butoxide and the like.

According to exemplary embodiments, the morphology or surface profile of the light extraction layer 120 may be changed by adjusting the composition ratio of the SiO ₂ sol solution and the TiOx sol solution included in the light extraction composition. As the content of the SiO ₂ sol solution included in the light extraction composition decreases or as the content of the TiOx sol solution increases, the uneven or wrinkled structure of the light extraction layer 120 may be miniaturized. According to one embodiment, The light extraction layer 120 may have a two-dimensional substantially net or reticulated structure. On the contrary, when the content of the SiO ₂ sol solution is increased, the width of the irregularities or wrinkles of the light extraction layer 120 is increased. In one embodiment, the light extraction layer 120 has a substantially one-dimensional line pattern shape. It may have an uneven or wrinkled structure.

According to exemplary embodiments, the SiO ₂ sol solution and the TiOx sol solution may be mixed in a ratio of about 30:70 to about 50:50 based on volume ratio. When the volume of the SiO ₂ sol solution relative to the total volume of the light extraction composition exceeds 50%, sufficient concave-convex or wrinkled structure may not be formed. When the volume of the SiO ₂ sol solution is less than 30% of the total volume of the light extraction composition, the adhesion of the light extraction layer 120 may be lowered, thereby causing a problem of peeling from the substrate 100.

The TiOx sol solution evaporates relatively faster than the SiO ₂ sol solution while being spin-coated onto the substrate 100. Therefore, gelation may occur on the substrate 100 before the sufficient leveling effect is exerted, thereby forming the above-mentioned concave-convex or wrinkled structure on the substrate 100. On the other hand, the pure SiO ₂ sol solution has superior flowability and adhesion compared to the TiOx sol solution. Therefore, by mixing the SiO ₂ sol solution and the TiOx sol solution, the light extraction layer 120 having the concave-convex or wrinkled structure can be formed while maintaining excellent adhesion to the substrate 100.

Hereinafter, the mechanism of forming the uneven or wrinkled structure of the light extraction layer 120 will be briefly described with reference to FIG. 5.

Referring to FIG. 5, droplets of the light extraction composition may contact each other on the substrate 100, and the preliminary light extraction layer 115 may be formed while being spread in the initial stage of the spin-coating process (S10). Subsequently, while the solvents included in the light extraction composition evaporate, a substantially wave-shaped light extraction layer 120 having the uneven or wrinkled structure may be formed (S20). The uneven or wrinkled structure is presumed to be due to a striation phenomenon. Specifically, when the solvent is evaporated, the temperature of the preliminary light extracting layer 115 may decrease and local deviation of surface tension may appear. Areas with locally high surface tension draw in surrounding material to form the ridges of the waves, whereby areas with locally low surface tension can form valleys of the waves. Therefore, when the evaporation of the solvent is completed, it is possible to obtain a wave-shaped light extraction layer 120 having the concave-convex or wrinkled structure.

In one embodiment, impurities may be removed by cleaning the back surface of the substrate 100 with oxygen plasma before forming the light extraction layer 120. If the impurities are not removed, disturbance may occur in the surface tension distribution, thereby lowering the regularity of the desired irregularities or wrinkles.

According to exemplary embodiments, the morphology or surface profile of the light extraction layer 120 may be changed by adjusting the rotation speed of the spin-coating process. As the rotational speed increases, the uneven or wrinkled structure of the light extraction layer 120 may be refined. As the rotational speed decreases, the width of the unevenness or wrinkles of the light extraction layer 120 increases. The number of irregularities or wrinkles may be reduced.

According to exemplary embodiments, the rotation speed may have a value in the range of about 3500 to 5500 rpm. When the rotational speed is less than 3500 rpm, sufficient uneven or wrinkled patterns may not be formed. On the other hand, when the rotation speed exceeds 5500rpm, the light extraction layer 120 may be flattened by the leveling effect.

Referring to FIG. 6, an organic light emitting display device according to example embodiments may be obtained by sequentially forming the organic layer 130 and the second electrode 140 on the first electrode 110. In an exemplary embodiment, the upper surface of the first electrode 110 may be cleaned by ultrasonication using acetone, alcohol, or the like before forming the organic layer 130. Accordingly, contaminants generated in the spin-coating process for forming the light extraction layer 120 may be removed.

According to example embodiments, the organic layer 130 may include a hole transport layer and a light emitting layer sequentially stacked on the first electrode 110. In addition, a hole injection layer may be further formed below the hole transport layer. The hole transport layer, the light emitting layer, and the hole injection layer may be formed using, for example, the above-described hole transport material, light emitting material, and hole injection material, for example, a vacuum deposition process, a thermal deposition process, a spin-coating process, a printing process, or a transfer process. It may be formed through a process or the like.

In an embodiment, an electron transport layer and / or an electron injection layer may be formed on the emission layer. The electron transport layer and the electron injection layer may be formed using, for example, a vacuum deposition process, a thermal deposition process, a spin-coating process, a printing process or a transfer process using the above-described electron transport material and electron injection material. .

In example embodiments, a hole blocking layer may be further formed between the emission layer and the electron transport layer by using the hole blocking material described above. In addition, an electron blocking layer may be further formed between the emission layer and the hole transport layer by using the above-described electron blocking material.

The second electrode 140 may be transparent, such as indium tin oxide, indium oxide, indium zinc oxide, zinc oxide, tin oxide, gallium zinc oxide, gallium indium zinc oxide, or aluminum doped zinc oxide, depending on whether the electrode is a transparent electrode or a reflective electrode. It may be formed using a conductive material or using metals such as silver, aluminum, platinum, gold, chromium, tungsten, molybdenum, titanium, palladium, and alloys thereof. For example, the second electrode 140 may be formed by performing a sputtering process, a CVD process, a vacuum deposition process, a printing process, or the like.

As described above, the above-described light extraction layer can be used to increase the luminous efficiency and quantum efficiency of the OLED device. However, the use of the light extraction layer is not limited to the OLED device. The light extracting layer according to exemplary embodiments may be attached to a rear surface of a transparent substrate used in various display devices such as a liquid crystal display device and a plasma display device, and may be utilized to improve luminous efficiency, brightness, and the like.

Experimental Example

Preparation of Light Extraction Layer Composition

1) Preparation of SiO ₂ Sol Solution

0.77 ml of TEOS (tetraethyl orthosilicate), 3.5 ml of (3-glycidoxypropyl) trimethoxysilane (GPTMS), 1.2 ml of methanol, 0.065 ml of acetic acid and 1 ml of deionized water at room temperature for 3 hours. Mix with stirring. To the obtained solution, 2.6 ml of methanol and 1.9 ml of 2-methoxy ethanol were added to prepare a SiO ₂ sol solution.

2) Preparation of TiOx Sol Solution

4.3 ml of titanium tetra isopropoxide (TTIP) was added dropwise to 5.1 ml of methanol, and 0.76 ml of cooled acetic acid was added at room temperature. A TiOx sol solution was prepared by adding 0.2 ml of deionized water to the solution obtained after 30 minutes and further proceeding the reaction for 24 hours.

3) Preparation of Light Extraction Layer Composition

The SiO ₂ sol solution and the TiOx sol solution were mixed for 1 hour in a vortex mixer to prepare a light extract composition. Compositions 1, 2 and 3 were prepared by mixing the SiO ₂ sol solution and the TiOx sol solution in 35:65, 40:60 and 45:55 mixing ratios (vol / vol), respectively.

Formation and Morphology Analysis of Light Extraction Layer

After the light extraction layer was formed on the glass substrate using the composition 1, composition 2 and composition 3, the morphology of the light extraction layer was analyzed.

A glass substrate (1 inch x 1 inch) substrate with an ITO layer coated on the front surface was prepared. The back surface of the glass substrate was cleaned by treatment with oxygen plasma for about 10 minutes. Using the light extracting layer compositions, a light extraction layer was formed on the rear surface of the glass substrate through a spin-coating process. The rotational speed of the spin-coating device was varied, and samples with the plurality of light extraction layers formed were prepared using different light extraction layer compositions. The prepared samples were stored for about 10 minutes in a convection oven at about 70 ° C. The morphology or surface profile of the formed light extraction layer was analyzed using an optical microscope (L150 from Nikon) and a Veeco Dektak-8 surface profiler (stylus weight: 15 mg, stylus tip radius: 2.5 μm).

7A to 7C are optical microscope pictures showing a morphology change of the light extraction layer according to the change in the rotational speed of the spin-coating device.

Specifically, FIGS. 7A to 7C are images taken after spin-coating for about 30 seconds by adjusting the rotational speeds 5000 rpm, 4500 rpm, and 4000 rpm using the above-described composition 2, respectively. 7A to 7C are all images of the same magnification taken at the same distance from the obtained light extraction layer.

7A to 7C, it can be seen that the light extraction layers are all formed to have a morphology of substantially wave-like, corrugated or uneven. In addition, it can be seen that the thickness of the wrinkles or irregularities increases from FIG. 7A to FIG. 7C. That is, it can be seen that as the spin-coating speed is increased, a light extraction layer having a fine uneven or wrinkled structure can be formed.

8a to 8c are optical micrographs showing the morphology change of the light extraction layer according to the concentration change of the light extraction composition.

Specifically, FIGS. 8A-8C are images of light extraction layers obtained using Composition 3, Composition 2 and Composition 1, respectively. 8A to 8C are spin-coating speeds fixed at 5000 rpm, and images of the same magnification taken at the same distance from the obtained light extraction layer.

8A to 8C, it can be seen that the light extraction layers are all formed to have a morphology of substantially wave-like, corrugated or uneven. In addition, it can be seen that the thickness of the wrinkles or unevenness decreases from FIG. 8A to FIG. 8C. That is, in the light extraction layer composition, it can be seen that as the concentration or volume ratio of the SiO ₂ sol solution decreases, a light extraction layer having a fine wrinkle or concave-convex structure can be formed. In particular, as shown in FIG. 8C, when the mixing ratio (vol / vol) of the SiO ₂ sol solution and the TiOx sol solution is 35:65 (composition 1), a wrinkle structure or irregularities having a substantially two-dimensional network or net shape The light extraction layer of the structure was formed.

9A to 9C are graphs showing the surface profile of light extraction according to the spin-coating speed and the light extraction composition concentration.

Specifically, FIGS. 9A and 9B show light formed at a spin-coating speed of 4000 rpm and 5000 rpm, respectively, using a light extraction composition (composition 2) having a mixing ratio (vol / vol) of a SiO ₂ sol solution and a TiOx sol solution of 40:60. It is a graph of the surface profile of the extraction layer. 9C is a surface profile graph of a light extraction layer formed at a spin-coating speed of 5000 rpm using a light extraction composition (composition 3) having a mixing ratio (vol / vol) of SiO ₂ sol solution and TiOx sol solution at 45:55. The x axis of the graphs represents the horizontal distance from the center of the glass substrate on which the light extraction layer is formed, and the y axis represents the height of the uneven or corrugated structure of the light extraction layer.

9A and 9B, more peaks of irregularities or wrinkles appear in the light extraction layer formed at the spin-coating speed of 5000 rpm (FIG. 9B), and the adjacent peaks may be formed more densely. . 9b and 9c, it can be seen that the number of peaks decreases and the width of the peaks increases as the content of the SiO ₂ sol solution increases at the same spin-coating speed.

The properties of the surface profile according to the mixing ratio and spin-coating speed of the light extraction composition are summarized in Table 1 below.

Table 1

In Table 1 the peak width represents the total length of light extraction divided by the number of formed peaks, and the peak height represents the average of the heights of the peaks.

Referring to Table 1, it can be seen that the width of the peaks decreases as the spin-coating rate increases and the content of the TiOx sol solution in the light extraction composition increases. In addition, it can be seen that the height of the peaks decreases as the spin-coating speed increases. This is presumably due to the phenomenon that the evaporation rate of the solvent included in the light extraction composition increases as the spin-coating rate increases and the content of the TiOx sol solution increases. Particularly, when the volume of the TiOx sol solution is 65% (composition 1) with respect to the total volume of the light extraction composition, and the spin-coating speed is 5000 rpm or more, the light extraction layer has a two-dimensional network-like irregularities or wrinkles. Indicated.

Evaluation of emission characteristics of OLED device including light extraction layer

A glass substrate (1 inch x 1 inch) substrate with an ITO layer coated on the front surface was prepared. The back surface of the glass substrate was cleaned by treatment with oxygen plasma for about 10 minutes. Samples were prepared by spin-coating a light extraction layer on the back side of the glass substrate using composition 2 (mixing ratio 40:60) at rotational speeds of 4000 rpm, 4500 rpm and 5000 rpm, respectively. In addition, a reference sample was prepared in which the light extraction layer was not formed. The four samples prepared were stored for about 10 minutes in a convection oven at about 70 ° C. Thereafter, the top surface of the ITO layer was cleaned using acetone and isopropyl alcohol in an ultrasonic cleaner to remove contaminants that may occur in the spin-coating process. In addition, the upper surface of the ITO layer was UV treated for 10 minutes in an ozone atmosphere. Four OLED device samples were prepared by forming a hole transport layer, a light emitting layer, an electron injection layer and an anode layer on the ITO layer of each of the samples.

The hole transport layer, the light emitting layer, the electron injection layer and the anode layer were obtained through a thermal deposition process using NPB, Alq ₃ , LiF and Al, respectively. The obtained thicknesses of the hole transport layer, the light emitting layer, the electron injection layer and the anode layer were measured at 40 nm, 50 nm, 0.5 nm and 100 nm, respectively.

The luminescence properties or luminescence efficiencies of the OLED device samples produced by the process described above were measured using a Keithley 2400 source measurement unit.

10A and 10B are graphs showing light emission characteristics of OLED devices according to changes in spin-coating speeds.

Referring to FIG. 10A, it can be seen that all three OLED device samples in which the light extraction layer is formed show higher luminance at the same current density than the reference sample. This means that more light generated in the light emitting layer by the light extraction layer has been extracted outside of the OLED device samples.

Additionally, as shown in the upper left graph of FIG. 10A, all four samples showed similar voltage-current density curves. That is, even if the light extraction layer is added it can be seen that does not change the basic current-voltage characteristics.

Referring to FIG. 10B, all three OLED device samples in which the light extraction layer is formed show higher luminous efficiency and external quantum efficiency at the same luminance as a reference sample. Able to know. The reference sample showed a light emission efficiency of about 3.55 cd / A at a luminance of 5000 cd / m ² , but the samples having the light extraction layer recorded a light emission efficiency of up to about 4.05 cd / A at a luminance of 5000 cd / m ² .

In addition, as shown in FIGS. 10A and 10B, it can be seen that an OLED device sample manufactured at 5000 rpm has the best overall luminance, luminous efficiency and / or external quantum efficiency. That is, by increasing the spin-coating speed, it can be seen that the uneven or wrinkled structure of the light extraction layer can be formed more finely, and thus the light extraction effect can be increased.

On the other hand, the spin-coating speed is fixed at 5000rpm, using the light extraction compositions of the content of SiO ₂ sol solution 35% (composition 1), 40% (composition 2) and 45% (composition 3), respectively, Three OLED device samples were prepared using processes and / or materials substantially the same as the process and / or materials, the reference sample as described above.

11A and 11B are graphs illustrating light emission characteristics of OLED devices according to changes in content of SiO ₂ sol solution.

Referring to FIG. 11A, it can be seen that all three OLED device samples in which the light extraction layer is formed show higher luminance at the same current density than the reference sample.

Referring to FIG. 11B, all three OLED device samples in which the light extraction layer is formed show higher luminous efficiency and external quantum efficiency at the same luminance as a reference sample. Able to know.

Additionally, as shown in FIGS. 11A and 11B, it can be seen that the OLED device samples using Composition 1 having the lowest content of SiO ₂ sol solution at 35% had the best overall brightness, luminous efficiency and / or external quantum efficiency. have. That is, as the content of the TiOx sol solution increases, it can be seen that the uneven or wrinkled structure of the light extraction layer can be formed more finely, and thus the light extraction effect can be increased.

12A and 12B are graphs showing emission intensity spectra of an OLED device including a light extraction layer according to exemplary embodiments.

Specifically, FIG. 12A shows graphs of normalized intensity varying with the rotation angle of the OLED device at 175 mA / cm ² current density. The curve connected by the black squares is a radiation pattern graph of a conventional OLED device in which no light extraction layer is formed. The curves connected by triangles are graphs of radiation patterns measured while rotating an OLED device comprising light extraction according to exemplary embodiments along an axis perpendicular to the light extraction layer. The curve connected by the circle is a graph of the radiation pattern measured while rotating an OLED device comprising light extraction according to exemplary embodiments along an axis parallel to the light extraction layer.

As shown in FIG. 12A, the radiation pattern measured while rotating along an axis perpendicular to the light extraction layer has a shape similar to that of a conventional OLED device, but measured by rotating along an axis parallel to the light extraction layer. It can be seen that the radiation pattern exhibits improved emission intensity than the radiation pattern of the conventional OLED device. That is, it can be seen that more light generated in the light emitting layer by the light extraction layer is extracted outside the OLED device according to the change of viewing angle.

12B is a graph illustrating a spectrum of relative EL intensity according to wavelength change. The emission intensity of the OLED device (shown with w / pattern) and the conventional OLED device (shown with w / o pattern) not including the light extracting layer according to the exemplary embodiments is 0, 30, Each was shown at 60 ° viewing angles.

As shown in FIG. 12B, as the light extracting layer is formed, the emission intensity increases at the same viewing angle and the same wavelength, but the shape of the spectrum is maintained in a similar shape. Therefore, it can be seen that by introducing the light extraction layer, the light extraction efficiency or the quantum efficiency can be increased while maintaining the basic light emission characteristics of the OLED device.

According to exemplary embodiments of the present invention, an OLED device including an uneven or corrugated light extraction layer may be manufactured using a mixture of SiO ₂ sol solution and TiOx sol solution through a spin-coating process. Therefore, the light extraction layer may be formed to improve the light emitting characteristics of the OLED device by a simple deposition process without an etching or imprinting process. The light extraction layer may be employed in various display devices such as an LCD device, a liquid crystal display device, a plasma display device, and the like.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It will be understood that the invention may be modified and varied without departing from the scope of the invention.

100: substrate 110: first electrode
115: preliminary light extraction layer 120: light extraction layer
130: organic layer 140: second electrode

Claims (15)

Preparing a light extraction composition by mixing a silicate (SiO ₂ ) sol solution and a titanium oxide (TiOx) sol solution; And
Forming a light extraction layer comprising the step of forming a light extraction layer having a wrinkled or uneven structure on the transparent substrate through a spin-coating process using the light extraction composition. The method of claim 1, wherein the SiO ₂ sol solution is prepared by mixing TEOS (tetraethyl orthosilicate) with an alcohol solvent. The method of claim 1, wherein the TiOx sol solution is prepared by mixing a titanium alkoxide compound in an alcohol solvent. The method of claim 1, wherein the volume ratio of the SiO ₂ sol solution and the TiOx sol solution to the total volume of the light extraction composition is in the range of 30:70 to 50:50. The method of claim 4, wherein the spin-coating process is performed at a rotation speed in the range of 3500 rpm to 5500 rpm. According to claim 5, When the volume ratio of the TiOx sol solution to the total volume of the light extraction composition is 65% or more and the rotational speed is 5000rpm or more, the corrugated or uneven structure of the light extraction layer has a two-dimensional mesh shape Method for forming a light extraction layer, characterized in that having a. The method of claim 5, wherein the width of the wrinkled or uneven structure of the light extraction layer decreases as the volume ratio of the TiOx sol solution increases with respect to the total volume of the light extraction composition. The method of claim 5, wherein the width of the wrinkled or uneven structure of the light extraction layer decreases as the rotation speed increases. Preparing a transparent substrate having a first electrode formed on a front surface thereof;
Forming a light extraction layer having a wrinkled or uneven structure through a spin-coating process by using a light extraction composition mixed with a SiO ₂ sol solution and a TiOx sol solution on a rear surface of the transparent substrate; And
And sequentially forming an organic layer and a second electrode on the first electrode. The method of claim 9, wherein the SiO ₂ sol solution is prepared by mixing TEOS with an alcohol solvent, and the TiOx sol solution is prepared by mixing a titanium alkoxide compound with an alcohol solvent. . The volume ratio of the SiO ₂ sol solution and TiOx sol solution to the total volume of the light extraction composition is in the range of 30:70 to 50:50, and the rotational speed of the spin-coating process is in the range of 3500 rpm to 5500 rpm. A method of manufacturing an organic light emitting display device, characterized in that. The method of claim 11, wherein the volume ratio of the TiOx sol solution with respect to the total volume of the light extraction composition, or as the rotational speed is increased, the width of the wrinkled or uneven structure of the light extraction layer is reduced A method of manufacturing an organic light emitting display device. 12. The method of claim 11, wherein when the volume ratio of the TiOx sol solution to the total volume of the light extraction composition is 65% or more and the rotational speed is 5000rpm or more, the corrugated or uneven structure of the light extraction layer has a two-dimensional mesh shape The manufacturing method of the organic light emitting display device characterized by having. The method of claim 9, further comprising oxygen plasma treating the back surface of the transparent substrate before forming the light extraction layer. A transparent substrate having a first electrode formed on a front surface thereof;
A light extraction layer having a wrinkled or uneven structure formed by spin-coating a light extraction composition comprising a SiO ₂ sol solution and a TiOx sol solution on a rear surface of the transparent substrate;
An organic layer formed on the first electrode; And
An organic light emitting display device comprising a second electrode formed on the organic layer.

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