Stephen I. Klink

Single-substrate liquid-crystal displays by photo-enforced stratification

Data visualization plays a crucial role in our society, as illustrated by the many displays that surround us. In the future, displays may become even more pervasive, ranging from individually addressable image-rendering wall hangings to data displays integrated in clothes. Liquid-crystal displays (LCDs) provide most of the flat-panel displays currently used. To keep pace with the ever-increasing possibilities afforded by developments in information technology, we need to develop manufacturing processes that will make LCDs cheaper and larger, with more freedom in design. Existing batch processes for making and filling LCD cells are relatively expensive, with size and shape limitations. Here we report a cost-effective, single-substrate technique in which a coated film is transformed into a polymer-covered liquid-crystal layer. This approach is based on photo-enforced stratification: a two-step photopolymerization-induced phase separation of a liquid-crystal blend and a polymer precursor. The process leads to the formation of micrometre-sized containers filled with a switchable liquid-crystal phase. In this way, displays can be produced on a variety of substrates using current coating technology. The developed process may be an important step towards new technologies such as ‘display-on-anything’ and ‘paintable displays’.

16.1: Robust Flexible LCDs with Paintable Technology

In this article the second-generation liquid crystal displays (LCDs) made by the Paintable LCD technology is presented. With this technology LCDs are manufactured by a sequence of simple coating and UV curing processes. Since the process can be carried out on plastic substrates and the stack of optical layers is only tens of micrometers thick, the resulting LCDs are ultra-thin and flexible.

Robust flexible LCDs with paintable technology

In this article, second-generation liquid-crystal displays (LCDs) made by Paintable LCD technology is presented. With this technology, LCDs are manufactured by a sequence of simple coating and UV curing processes. Since the process can be carried out on plastic substrates and the stack of optical layers is only tens of micrometers thick, the resulting LCDs are ultra-thin and flexible.

L‐5: Late‐News Paper: Single‐substrate LCDs Produced by Photo‐enforced Stratification

A new technique to produce polymer covered liquid crystal layers on a single substrate, called photo-enforced stratification, allows cost-effective production of ultra-thin LCDs. The two-step photopolymerisation-induced phase separation of a liquid crystal and a polymer precursor can be performed on a variety of substrates and provides freedom in display design.

Confocal Raman microscopy of liquid-crystal-filled polymer capsules made by photo-enforced stratification.

The applicability of confocal Raman microscopy for characterizing thin liquid-crystal (LC) filled polymer capsules obtained by photoenforced stratification is demonstrated. The investigated structure consists of an array of polymer capsules (typical size 500 × 500 × 20 μm) filled with LC material and is made by photopolymerization of a mixture of monomers and LC. Such an array can be used as the electro-optical component in liquid crystal displays. Confocal Raman microscopy does not require complex sample preparation, is non-invasive, and is shown to have adequate spatial and depth resolution. Although Raman spectroscopy is inherently insensitive, the use of data preprocessing and computational modeling makes it possible to quantify both the conversion of monomer to polymer and the compositions of both the polymer-rich and the LC-rich phase.

Photochromic laminates for improvement of the daylight contrast of cathode ray tubes and plasma displays

The contrast and color saturation of cathode ray tube (CRT) and plasma display images is negatively affected by the reflection of ambient light at the white phosphor dots. A variable photochromic transmission filter reversibly darkens upon exposure to sunlight, and could offer the optimal compromise between contrast and brightness of the image under a range of illumination conditions. The photochromic transmission filter that we present here consists of a soft polymer layer doped with a photochromic dye that has been sandwiched between the CRT screen and a front glass panel. The fabrication process of such a photochromic laminate involves the in-situ polymerization of a resin in the presence of the dye. For this purpose we have studied the radical polymerization of several (meth)acrylates in the presence of a photochromic dye, and evaluated the optical properties of the dye in the resulting polymer films. In this way a photochromic laminate has been developed that upon irradiation turns from a transparent state to an almost neutrally colored state and exhibits sufficiently fast coloration and decoloration kinetics. The photochromic laminate significantly improves the daylight contrast of the CRT under high illumination conditions (e.g. direct sunlight), while at the same time the brightness of the CRT is retained under low illumination conditions.