29.1: A New Achromatic Quarter‐Wave Film Using Liquid‐Crystal Materials for Anti‐Reflection of OLEDs

Abstract

We successfully developed a new achromatic quarter wave film for anti-reflection of OLEDs, consisting of multiple layers of liquid crystal materials. Applying an original optical design, a new liquid crystal compound, and multi-layer coating technology, we realized OLEDs with very low reflection in all viewing angles. This new film can be produced in a rolled single-sheet state, which enables the manufacture of a circular polarizer with high productivity by a conventional roll-to-roll process. Author Keywordsliquid crystals; quarter wave film; wide viewing angle; OLED; optical compensation film; discotic material. Objectives and BackgroundThe rapid spread of mobile devices, led by smartphones and tablet PCs, is progressing. OLEDs are growing in popularity as the display technology for these applications. OLEDs are well suited for mobile devices due to the high color saturation in their light emission, large field of view, and thin profile. However, a circular polarizing film is indispensable for OLEDs to obtain good black mode performance.Conventionally, achromatic quarter wave films (QWFs) have been used for the circular polarizing film. A superposition of a /4 and a /2 film or a polycarbonate-derivative QWF has been used because of their achromatic optical performance. However, these films' drawbacks include a narrow anti-reflection viewing angle and a complicated production process.To solve these problems, we developed a new achromatic QWF consisting of multiple layers of liquid crystal (LC) materials. We extended the alignment technologies of discotic and calamitic (rod-shaped) LC materials which we have been developing for many years [1,2], and succeeded in controlling the multi-layer alignment. Further, we applied a new optical design that allows adjustment of the total out-of-plane retardation of the multiple layers so that a wide anti-reflection viewing angle is obtained. This achromatic QWF can be produced by a roll-to-roll process because the alignment direction of each of the two LC layers is independently controllable. Results and DiscussionOptical Design: A circular polarizer in combination with a reflector prevents reflection by suppressing the exit of incident light. The black mode of OLEDs, which is derived from the light shielding characteristics of the circular polarizer, has a great influence on display performance properties such as contrast and color. The QWF is characterized by the wavelength dispersion of its birefringence. It is not easy to provide the same characteristics over the entire range of visible light.There are two ways to control the wavelength dispersion. One is to use reverse wavelength dispersion materials [3], and the other is to stack retardation films with an axial design (a superposition of a /4 and a /2 film) [4]. It is reported that some materials exhibit this reverse wavelength dispersion. However, the dispersion obtained by a single sheet of retardation film is not enough to achieve achromaticity. Therefore, we attempted the second approach, stacking retardati...

53‐3: Invited Paper: Negative Dispersion Compensation Film using Self‐organization of Smectic Host and Guest Reactive Mesogen Molecules

“…Although the single-layer ND retarder is cost-effective, the dispersion property of it is inferior to that of the multi-layer ND retarder. In addition, the FOV property of the single-layer ND retarder is narrower than the multi-layer one [6][7][8].…”

Brilliant cosmetic film for ambient displays, with cholesteric liquid crystal

“…. A decorative film comprising with a PCM film and a quarter wave retardation film (QWF) lamination is placed on the outermost surface of the display. In the OFF‐state, because external light is reflected by the decorative film, the pattern of the decorative film can be seen.…”

Design of an achromatic wide-view circular polarizer using normal dispersion films

“…The polarization state of light that has passed through the QWP depends on the wavelength because the phase retardation is inversely proportional to the wavelength of the incident light. Several approaches have been proposed to address this problem [5][6][7][8][9][10][11][12][13][14][15], and the so-called 'wide-band CP (WB-CP)' is widely used these days [6,7,[11][12][13]. In a WB-CP, the optical axis of a half-wave plate (HWP) and a QWP are ±15 and ±75°, respectively.…”