Abstract: A liquid crystal shutter construction, suitable for glass shields and automatically darkening welding glass filters, which shutter construction is switchable between a first state with high transmission of light and a second state with low transmission of light, and vice versa, in response to an electric control signal, the shutter construction having a nematic type liquid crystal cell disposed between transparent plates having electrodes for providing an electric field in response to the control signal, said plates having mutually facing surfaces, each of which is provided with alignment means for defining a respective molecule alignment direction for molecules in the proximity of said alignment means in the absence of said electric field, said liquid crystal cell being mounted between polarisers, wherein a retardation film is disposed between the polarisers in order to reduce remaining retardation in the liquid crystal cell when in an electrically activated state, said retardation film being arranged such t

Abstract: A liquid crystal welding glass structure whose density increases when welding is commenced includes two liquid crystal cells which are mounted between polarization filters which have an extinguishing effect on one another. When mounting the filters, the filters are turned so that their respective angular dependencies on the optical density counteract one another. With the intention of improving this compensating effect, the brushing/rubbing of the mutually opposing limiting walls which determine the direction of the molecules is limited to at least one of the component cells whose relative angular displacement differs from 90.degree. and is smaller than or coincident with 85.degree.. The angle is preferably between 20.degree. and 85.degree..

Abstract: A multiple layer protective glass, particularly a protective glass for a welding shield, for damping the light transmission, the layers of which are in turn comprised at least of a first polarizer, a first electrooptical cell, a second polarizer, a second electrooptical cell and a third polarizer, the electrooptical cells consisting of liquid crystals enclosed between transparent parallel plates coated with electrically conducting layers, said crystals being arranged in their non-excited condition to form a helically twisted structure for rotating the plane of polarization of the passing polarized light. The planes of polarization of the first and the second polarizer (2,4) are at right angles to each other. The planes of polarization of the second and the third polarizer (4,6) enclose an angle which is between 0.degree. and 60.degree.. The angle of rotation of the helical structure formed by the liquid crystals in the second electrooptical cell (5) is between 90.degree. and 30.degree.