U.S. Philips Corporation

Rifat A Hikmet

Dirk J Broer

Dirk Jan Broer

Johan Lub

Ingrid E Heynderickx

Aemilianus G Staring

Robert G Gossink

Reinhold Wimberger Friedl

Thomas A Welker

Hermannus F Schoo

David B Braun

Henri M Boots

Ralf Raue

Light source having a luminescent layer (,) whose light is guided through an optical filter (,) comprising at least one cholesteric crystal layer (cholesteric filter).

Light source having a luminescent layer

Electro-optical device wherein orientation layers have grating structure

An optical system includes comprising a polarizing element in the form of a layer which comprises an isotropic material having a refractive index n.sub.i and an anisotropic material having refractive indices n.sub.a,e and n.sub.a,o. The refractive index n.sub.i is substantially equal to n.sub.a,e or n.sub.a,o. The optical system includes a retroflector for back-reflecting the polarization component diffused in the polarizing element.

Optical system which utilizes polarized light

Polarizing element having a first layer and a second layer. When an unpolarized light beam is incident on the element, the direction of at least one of the polarization components of the unpolarized beam will be influenced by the first layer. These polarization components have different directions of polarization. The second layer influences the direction of a polarized beam incident thereon. A polarization-rotating layer is present between the first layer and the second layer. An unpolarized beam can be substantially completely converted into a polarized beam having mainly the same direction of polarization.

Polarizing element including layer having alternating areas of

The invention provides a simple method of manufacturing a broadband, switchable cholesteric filter. To this end, a mixture of polymerizable, liquid-crystalline molecules is provided between two, substantially parallel substrates, which are each provided with an electrode. This mixture is subsequently polymerized with UV light to form an optically active layer of cholesteric order comprising a three-dimensional polymeric network. If the mixture also contains a quantity of a photo-stabilizing compound, a broadband, cholesteric filter is obtained. The mixture preferably comprises, in addition to maximally 5 wt. % of the photo-stabilizing compound, maximally 2 wt. % of monomers having at least two polymerizable groups, maximally 90 wt. % of liquid-crystalline monomers having one polymerizable group, as well as a mixture of chiral and/or achiral liquid-crystalline molecules without a polymerizable group. Switchable cholesteric filters having a bandwidth of 200 nm and more can be obtained in this manner.

Method of manufacturing a switchable cholesteric filter as well as a

The invention relates to a switchable cholesteric filter. Said filter comprises an optically active layer which is situated between two substrates which are both provided with an electrode for applying an electric field. The optically active layer comprises a liquid-crystalline material which is in the cholesteric phase. In accordance with the invention, the optically active layer comprises a three-dimensional polymer network which consists of the polymerization product of maximally 2 wt. % of monomers with at least two polymerizable groups and maximally 30 wt. % of liquid-crystalline monomers with one polymerizable group, and the rest of the optically active layer consists predominantly of a mixture of chiral and achiral liquid-crystalline molecules. An optically active layer of this composition can be switched in a simple and reproducible manner by means of an electric field. The invention also relates to a luminaire comprising such a switchable cholesteric filter.

Switchable cholesteric filter and luminaire having such a filter

A description is given of an electroluminescent device (1) having an LED structure, which is composed of an active layer (7) of oriented liquid-crystalline and electroluminescent compounds and a transparent positive electrode layer (5) which is preferably made from an electroconductive polymer. By previously rubbing the electrode layer (5) in one direction with a velvet cloth, an orientation is induced in the molecules in the active layer (7), the orientation being frozen by cooling or polymerization. The electroluminescent device (1) emits polarized light whose direction of polarization is parallel to the direction of rubbing.

Electroluminescent device having electroluminescent compound and liquid

An optical modulation device is described, which comprises two substrates, which are provided with at least one electrode, and an optically active layer situated between said two substrates, the optically active layer comprising a liquid crystalline material having ferroelectric, antiferroelectric or electroclinic properties. In accordance with the invention, the device is characterized in that the optically active layer comprises a permanently oriented anisotropic network of polymerized material containing free molecules of a chiral liquid crystalline material. Said network is preferably composed of a polymer formed from reactive monomers comprising at least two reactive groups on the basis of acrylates, methacrylates, epoxy compounds and/or thiolene systems. By means of such an optical modulation device grey levels which can be passively maintained for a relatively long period of time can be obtained in a relatively simple manner. In addition, the device in accordance with the invention is little sensitive to shocks. Besides, the device in accordance with the invention can be constructed so as to comprise a relatively thick optically active layer, without the occurrence of a disturbing loss of contrast caused by 'chevrons'.

Optical modulation device having a polymer network containing free

The invention relates to a piezoelectric element comprising a piezoelectric material 1, in the form of a polymer network, between at least two electrodes 2, 3. The piezoelectric material is formed from a starting material comprising a liquid crystalline monomeric material and a chiral compound. The starting material is brought to a temperature at which a smectic phase is formed, and an electric field is applied to obtain a dipolar orientation in the starting material, after which the polymer network is formed by means of photopolymerisation. The piezoelectric element thus manufactured can suitably be used for various electromechanical applications, as a sensor material, for pyroelectric applications and, in particular, also for optical applications.

Piezoelectric material comprising a polymer network

A display device comprising a display cell consisting of a substrate which is formed by two oppositely located plates whose facing sides are provided with electrode layers to which an orientation layer is applied and a sealing material which is provided between the end portions of the plates, a liquid crystalline material being filled into the space between the plates and the sealing material. In said display device, the liquid crystalline material is locally formed into a polymer network in accordance with a desired pattern. By virtue thereof, the desired pattern of picture elements can be designed with a substantial degree of freedom because it is possible to locally raise the switching threshold of the liquid crystalline material if image formation is not desired at locations where electrodes or conductor patterns cross each other.

Display device comprising liquid crystalline material locally formed

An orientation layer for a liquid crystal display device is formed from a mixture of at least one reactive liquid-crystal material and at least one non-reactive liquid-crystal material. The mixture is brought into contact with a surface of a mold having an orienting effect, as a result of which the molecules in the mixture are oriented. Subsequently, the reactive liquid-crystal material is made to cure, thereby forming an oriented polymer network in which the non-reactive liquid-crystal material is dispersed. The orientation layer thus manufactured is very suitable for use in an active display device. The liquid crystal device formed has a liquid crystal layer and orientation layers of an oriented polymer network in which liquid crystal material is dispersed.

Liquid crystal device orientation layer of an oriented polymer network

In a device for doubling the frequency of a light wave, a fundamental light wave 2 originating from a laser light source 1 is guided through a nonlinear optical medium 5 while forming a second harmonic wave 6. The nonlinear optical medium is formed from a polymer network and elements having a great hyperpolarizability. In the device, phase matching is realised by the application of a polymer network having a helical structure. The pitch of the helical structure is adapted to the phase-matching conditions by the selection of the polymerization conditions during the formation of the network.

Device for doubling the frequency of a light wave using a three

A liquid-crystal display device having a twisted nematic liquid-crystalline material is provided with a layer of an optically anisotropic material to obtain a colourless display device which is rich in contrast. The optically anisotropic material is a synthetic resin composition comprising a polymer network having a helicoidal order manufactured from a curable liquid-crystalline composition having a chiral dopant.

Liquid-crystal display device

A light-scattering element comprising a liquid-crystal material which is dispersed in a matrix of a transparent polymer material is manufactured by mixing at least one polymerizable liquid-crystal material and at least one non-reactive liquid-crystal material. The mixture is provided between two substrates 1 and 2 in the form of a thin layer 5, rubbed polymer layers 3 and 4 being present on the side of the substrates where the mixture is to be provided, as a result of which the molecules in the mixture are oriented. The reactive material is made to cure by means of actinic radiation thereby forming a polymer network in which the non-polymerizable material is present as a continuous phase. The difference between one of the refractive indices of the cured material and the corresponding refractive index of the non-polymerizable liquid-crystal material is less than 0.10, as a result of which the light-scattering element forms a simple polarizer.

Light-scattering element

A liquid crystalline material in the form of an anisotropic gel comprising a polymerized liquid crystalline material and a low-molecular weight liquid crystalline material, can be used in a display cell, said polymerized material forming a permanently oriented network in the low-molecular weight liquid crystalline material.

Growing community of inventors

Eindhoven, Netherlands

Rifat A Hikmet