Birefringent optical element, lcd device with a birefringent optical element, and manufacturing process for a birefringent optical element

\u3cp\u3eA birefringent optical element comprises a polymerized and/or cross-linked mixture (301) of a liquid crystalline compound and a photo-isomerizable compound. The birefringence of the element can be determined with high precision by manipulating the order parameter and polarization anisotropy of said mixture. For this purpose, the photo-isomerizable compound is converted from a trans-form to a cis-form during manufacturing by means of irradiation. Preferably the photo-isomerizable compound is a cinnamate compound. The irradiated mixture is polymerized and/or cross-linked after irradiation. The irradiation preferably takes place through a greyscale mask (305) so that within the mixture (301) portions (302R, 302G, 302B) are defined that obtain different birefringence values. The process is for example suitable for manufacturing a retarder layer or compensation foil inside the liquid crystalline cell of a Liquid Crystal Display (LCD) device, and in particular for manufacturing a patterned retarder layer having portions with different retardation, associated with the primary colors of a color LCD device.\u3c/p\u3

Synthesis, properties, and photopolymerization of liquid-crystalline oxetanes:Application in transflective liquid-crystal displays

\u3cp\u3eMixtures of liquid-crystalline di-oxetanes and mono-oxetanes are made for the purpose of making birefringent films by photopolymerization. The composition of a di-oxetane mixture that forms spin-coated films of planarly aligned nematic monomers is reported. These films are photopolymerized in air. The molecular order of the monomers can be changed on the microscale to form thin films with alternating birefringent and isotropic parts by using a combination of photopolymerization and heating. The interface observed between the birefringent and isotropic 10 μm × 10 μm domains is very sharp and the films show hardly any surface corrugation. In addition, the polymerized films are thermally stable, making them very suitable for use as patterned thin-film retarders in high-performance transflective liquid-crystal displays (LCDs) which satisfy customer demand for displays that are brighter and thinner and that deliver better optical performance than conventional LCDs with an external non-patterned retarder.\u3c/p\u3

Patterned retarders prepared by photoisomerization and photopolymerization of liquid crystalline films

\u3cp\u3eIsomerizable diacrylates derived from cinnamic acid are designed, synthesized and mixed with liquid crystalline diacrylates with the aim of making films with alternating birefringent and isotropic domains by applying the E - Z isomerization process at room temperature. The effects of the structure of the isomerizable-mesogenic group on the isotropization efficacy, the efficiency of the E - Z isomerization reaction, and film formation are discussed. Compounds derived from cyclohexyl cinnamate are proved to be good candidates that meet a whole set of parameters related to processing and application. These compounds exhibit a low nematic-to-isotropic transition temperature. In addition, they show no yellowing upon irradiation, unlike similar compounds derived from phenyl cinnamate. To elucidate the origin of isotropization of the film by irradiation, the pure Z -isomer is prepared by photolysis of the E -isomer and subsequent chromatographic separation of both isomers. Analysis of reference samples containing the pure isomers reveals that the decrease in transition temperature can be attributed exclusively to the E - Z photoisomerization process. Finally, thin films with alternating birefringent and isotropic parts of 100×100 μm 2 are obtained by using a combination of photoisomerization in air and photopolymerization in a nitrogen atmosphere, which is referred to as photo-patterning.\u3c/p\u3

Formation of optical films by photo-polymerisation of liquid crystalline acrylates and application of these films in liquid crystal display technology

\u3cp\u3ePhoto-polymerisation of liquid crystalline di-acrylates is a very versatile method to produce homogeneously aligned polymer films. The orientation of the liquid crystals and hence the anisotropic optical properties of the films are frozen in by the photo-polymerisation process. Homogeneously aligned nematic liquid crystals form birefringent films that find application as retarders, while splayed nematic liquid crystalline mixtures form, angle dependent birefringent films that find application as wide viewing angle foils. In addition, cholesteric liquid crystals form reflecting films that can be used as colour filters or polarisers and smectic liquid crystals form highly ordered films that find application as polarisers. Moreover, modulating the light during the manufacturing process either in lateral or in-depth direction of the film can create complex structures not attainable with liquid crystalline polymers. All these films are mechanically, thermally and chemically stable and therefore very suitable to be processed in liquid crystal display manufacturing as additional films or as in-cell optical components.\u3c/p\u3

A collimator for use in a backlight liquid crystal display system

\u3cp\u3eThe present invention relates to a system for lighting a display. The system comprises a light source (102), a collimator (120), and a liquid crystal display configured to receive a collimated light beam (126) and adapted to modulate the collimated light beam (126). The system further comprises a reflective sheet (110) having one or more pin holes (112) therein and having a reflective surface (116) facing the light source (102) and the other surface facing the collimator (120). The reflective sheet (110) is configured to transmit a part (114) of a light beam (108) to the collimator (120) and configured to reflect to a reflector (106) other parts (118) of the light beam (108).\u3c/p\u3

Transflective liquid crystal displays with patterned optical layer

\u3cp\u3eA transflective liquid crystal display comprising a plurality of pixels, each pixel comprising a liquid crystal layer (3) sandwiched between a front substrate (1) and a back substrate (2), and an optical layer (7) comprising a birefringent material, said pixels being divided into at least one transmissive (5) and at least one reflective subpixel (4), and said optical layer (7) being at least partly sandwiched between the liquid crystal layer (3) and one of said front substrate (1) or back substrate (2), and being patterned into domains (8, 9), each domain covering at least part of a reflective subpixel (4) or at least part of a transmissive subpixel (5).\u3c/p\u3

Technologies towards patterned optical foils applied to transflective LCDs

\u3cp\u3eFor better front-of-screen performance for transflective LCDs, a technology with extra free optimization parameters for the optical stack is needed. Thin wet coatable retarders which enable adjustment of the optical activity on the (sub)pixel level have been developed. Isotropic domains have been created in nematic retardation films by thermal patterning or photopatterning. Employing such a patterned retarder in a transflective LCD leads to an LCD that is lighter and thinner with good reflectivity, high transmission, and low chromaticity at all gray levels and wide viewing angles. The patterned thin-film technology has been proven to be versatile and applicable in various LCD designs.\u3c/p\u3