The present invention relates to devices for the regulation of light transmission and in particular to switchable windows. The present invention in particular relates to window elements which comprise electrically switchable optical cells with a switchable layer containing a liquid-crystalline medium having a clearing point which is within the working temperature of the window element. The present invention also relates to liquid-crystalline media for use in the window elements.

The present invention relates to an assembly of switching layers for dimming and scattering of light and to window elements comprising the arrangement of switching layers.

The invention relates to a liquid-crystalline medium having negative dielectric anisotropy comprising one or more compounds of formula I

##STR00001##

and
one or more compounds selected from the group of the compounds of the formulae IIA, IIB and IIC,

##STR00002##

wherein the groups and parameters have the meanings indicated in claim 1, to a guest-host liquid crystal medium derived therefrom comprising one or more dichroic dyes and the use of said medium in devices such as light shutters, switchable windows, switchable mirrors and guest-host displays. The invention further relates to devices containing the liquid crystalline medium according to the invention.

An optical device that is disposed to manage light transmittance therethrough includes a multi-layer photochromic sheet that is composed of a first layer, a second layer, and a photochromic layer interposed therebetween. The photochromic layer is composed of a mixture of dichroic dye and photo-isomerizable material that are disposed in a liquid crystal host, and the first and second layers are each fabricated from a clear polymer.

Provided is a liquid crystal composite that is suitable for dimming and includes a liquid crystal composition satisfying at least one of characteristics such as a high maximum temperature, a low minimum temperature, a small viscosity, a large optical anisotropy and a large negative dielectric anisotropy or being suitably balanced between at least two of these characteristics, and a liquid crystal dimming device including the liquid crystal composite, where the liquid crystal composite includes a polymer and a liquid crystal composition including a specific compound having a large negative dielectric anisotropy, and the liquid crystal composite may further include a specific compound having a high maximum temperature or a low minimum temperature.

A liquid crystal composition for dimming that satisfies at least one of characteristics such as a high maximum temperature, a low minimum temperature, a small viscosity, a large optical anisotropy and a large positive dielectric anisotropy, or that is suitably balanced between at least two of these characteristics, and a liquid crystal dimming device including this composition. A liquid crystal composition for dimming that includes a specific compound having a large positive dielectric anisotropy as a first component and that may include a specific compound having a high maximum temperature or a low minimum temperature as a second component and a specific compound having a large dielectric anisotropy in the minor axis direction as a third component.

A pressure-sensitive adhesive and a liquid crystal cell including the same are disclosed herein. In some embodiments, a pressure-sensitive adhesive having a storage elastic modulus of 700 kPa or more at a temperature of 25? C. and a frequency of 6 rad/sec, and a gel fraction of 35% or more, wherein the gel fraction is defined by Equation 1:
B/A?100[Equation 1]
wherein, A is an initial mass (g) of the pressure-sensitive adhesive, B is a mass (g) of an insoluble content after the pressure-sensitive adhesive is immersed in a solvent at 60? C. for 24 hours and then dried at 150? C. for 30 minutes. The press-sensitive adhesive is advantageous for implementation into a flexible element between upper and lower substrates of a liquid crystal cell, and providing excellent electro-optical properties and appearance uniformity by minimizing defects.

A liquid crystal composition for dimming that satisfies at least one of characteristics such as a high maximum temperature, a low minimum temperature, a small viscosity, a large optical anisotropy and a large negative dielectric anisotropy, or that is suitably balanced between at least two of these characteristics, and a liquid crystal dimming device including this composition. A liquid crystal composition for dimming that includes a specific compound having a large negative dielectric anisotropy as a first component and that may include a specific compound having a high maximum temperature or a low minimum temperature as a second component.

A device for regulating the passage of energy from an outside space into an inside space includes a switching layer, where the switching layer comprises one or more compounds of the formula: ##STR00001##
wherein R.sup.1, Z.sup.1, Z.sup.2, Ar.sup.1 and X are defined herein.

Described herein are liquid crystal compositions and derivative mixtures thereof that can allow for the adjustment of their refractive indices by the application of an electric field. In addition, selectively dimmable reverse-mode polymer dispersed liquid crystal (PDLC) elements and devices using the aforementioned compositions are also described, which are transparent when no voltage is applied and opaque when a voltage is applied.