News Column

Patent Application Titled "Light-Extraction Element and Light-Emitting Device" Published Online

June 5, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventors CHIEN, Pei-Chi (Zhudong Township, TW); CHEN, Ping-Chen (Taipei City, TW), filed on June 21, 2013, was made available online on May 22, 2014.

No assignee for this patent application has been made.

Reporters obtained the following quote from the background information supplied by the inventors: "The technical field relates to a light-extraction element and light-emitting device.

"The light-emitting element of the organic light-emitting diode (OLED) is generally composed of glass substrates, conductive electrodes made of indium tin oxide (ITO), and an organic light-emitting layer. No matter whether the type of OLED is 'top-emitting' or 'bottom-emitting', the large difference between the refractive indices of the materials used in the components results in reflection on the interface. This reflection in OLEDs may cause a low efficiency of light extraction. According to the studies, in general OLEDs, almost a 70-80% loss of light, which cannot be guided outside the elements, is the resulted of the reflection on the interface. Since the difference of the refractive indices of the materials used in OLEDs is too large, the total light-extraction efficiency may be improved by selecting the materials of the internal components of OLEDs or changing the structure thereof. However, by altering materials and structures, the accompanying change in the manufacturing process brings a greater challenge to the development of OLEDs.

"So far, the external light extraction diffusion layer of OLEDs is generally composed of solid organic particles or inorganic particles with a high refractive index, and accomplishes the diffusion effects by light scattering. However, the effect of light extraction is unsatisfactory.

"Previous studies have demonstrated that a diffusion layer comprising microlens or solid inorganic particles as a light-extraction film, or forming a scattering layer using particles, ultrafine particles, and resin. Since the particles are surrounded by a high concentration of ultrafine particles with a large difference of refractive indexes, a good light-extraction efficiency can be obtained. However, the effect of reducing the color shift is limited. In addition, it has also been reported that color shift can be reduced by first coating a scattering layer (a particle with a high refractive index, the particle size being about 0.2-1 .mu.m) and then a light condenser layer (the refractive index of the particle being about 1.4-1.5, and the particle size being about 3-10 .mu.m) on the transparent resin substrate. Although the combination of two coatings as a light-extraction layer can reduce the color shift, the process is more complicated. It is known that forming the scattering layer using hollow particles can significantly reduce the color shift; however, although the light-extraction efficiency of the center viewing angle is good, the total light-extraction efficiency is worse since the light-extraction efficiency decreases with an increase in the viewing angle.

"Therefore, a method for improving the light-extraction efficiency of the light-emitting element of OLEDs is required."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "A detailed description is given in the following embodiments with reference to the accompanying drawings.

"According to an embodiment, the disclosure provides a light-extraction element, including a light-diffusion layer, which comprises a resin; a first particle with a single refractive index; and a second particle with two different refractive indices, wherein the second particle is a hollow particle or a core-shell particle, having different refractive indices between core and shell.

"In accordance with another embodiment, the disclosure also provides a light-emitting device, including a pair of electrodes composed of an anode and a cathode; an organic light-emitting unit disposed between the pair of electrodes, wherein the organic light-emitting unit includes a light-emitting layer; and a light-extraction element disposed on a light-extraction surface of the light-emitting device.

BRIEF DESCRIPTION OF DRAWINGS

"The disclosure can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

"FIG. 1 is a schematic view of a light-extraction element according to an embodiment.

"FIG. 2 is a cross-sectional view of a light-emitting device comprising a light-extraction element according to an embodiment.

"FIG. 3A is a cross-sectional view of a self-made hollow acrylic particle P50 according to an embodiment.

"FIG. 3B shows a particle size distribution of the self-made hollow acrylic particle P50 according to some embodiments of the disclosure.

"FIG. 4 shows the brightness change of the light-extraction element including different particle compositions where the materials of the light-diffusion layer are composed of the solid particle SBX6 and the hollow particle P50; and

"FIG. 5 shows the brightness change of the light-extraction element including different particle compositions where the materials of the light-diffusion layer are composed of the solid particle SBX17 and the hollow particle P50."

For more information, see this patent application: CHIEN, Pei-Chi; CHEN, Ping-Chen. Light-Extraction Element and Light-Emitting Device. Filed June 21, 2013 and posted May 22, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5629&p=113&f=G&l=50&d=PG01&S1=20140515.PD.&OS=PD/20140515&RS=PD/20140515

Keywords for this news article include: Patents.

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Source: Politics & Government Week


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