Device for regulating the entry of light
The application relates to a device for regulating the entry of light into a room, which comprises a switchable layer of specific design comprising a twisted nematic liquid-crystalline medium and a dichroic compound.
1. A window containing a device for regulating the transmission of light into a room, comprising a switchable layer S comprising a liquid-crystalline medium which comprises at least two different dichroic compounds,
where the following applies to the thickness d of layer S and the optical anisotropy Δn of the liquid-crystalline medium of layer S:
d< 2 μm/Δ n
wherein the molecules of the liquid-crystalline medium of switchable layer S are in a twisted nematic state in a switching state of the device and the switchable layer S is switchable between two different transmission levels, wherein the transmission level is determined by whether an electrical voltage is being applied or not being applied,
wherein the liquid crystalline medium has a clearing point in the temperature range from 70° C. to 170° C., and
wherein the device is colourless when looked through in all its switching states.
2. The device according to claim 1 , wherein the following applies to the thickness d of layer S and the optical anisotropy Δn of the liquid-crystalline medium of layer S:
d< 0.9 μm/Δ n
and
d> 0.2 μm/Δ n.
3. The device according to claim 1 , wherein precisely one orientation layer, called O 1 , is adjacent to one side of the switchable layer S, and precisely one other orientation layer, called O 2 , is adjacent to the opposite side of the switchable layer S.
4. The device according to claim 3 , wherein orientation layers O 1 and O 2 are in such a way that they each effect orientation axes of the molecules of the liquid-crystalline medium with different alignments in the adjacent region of layer S.
5. The device according to claim 3 , wherein the rubbing directions of orientation layers O 1 and O 2 include an angle of 30 to 270°.
6. The device according to claim 3 , wherein orientation layers O 1 and O 2 effect a homogeneous arrangement of the molecules of the liquid-crystalline medium of layer S adjacent to the orientation layer.
7. The device according to claim 3 , wherein orientation layers O 1 and O 2 have rubbed polyimide on their surface adjacent to layer S.
8. The device according to claim 3 , wherein the orientation axes of the molecules of the liquid-crystalline medium of layer S in the case of homogeneous alignment in the state without an applied voltage include an angle of 1° to 10° with the plane of orientation layer O 1 or O 2 .
9. The device according to claim 3 , wherein the orientation axes of the molecules of the liquid-crystalline medium of layer S in the case of homeotropic alignment in the state without an applied voltage include an angle of 89° to 80° with the plane of orientation layer O 1 or O 2 .
10. The device according to claim 1 , which does not include a polariser.
11. The device according to claim 1 , wherein layer S has a thickness between 2 and 12 μm.
12. The device according to claim 1 , wherein layer S has a light transmittance of the bright state τ v bright , calculated in accordance with European Standard EN410, equation (1), of at least 30%.
13. The device according to claim 1 , wherein layer S comprises at least two different dichroic compounds.
14. The device according to claim 1 , wherein at least one dichroic compound is selected from the group consisting of azo compounds, anthraquinones, methine compounds, azomethine compounds, merocyanine compounds, naphthoquinones, tetrazines, perylenes, terylenes, quaterylenes, higher rylenes, squaraines, benzothiadiazoles, diketopyrrolopyrroles and pyrromethenes.
15. The device according to claim 1 , wherein the twist of the orientation axes of the molecules of the liquid-crystalline medium of layer S in the twisted nematic state, regarded over the entire layer thickness, is between 100° and 260°.
16. The device according to claim 1 , the twist of the orientation axes of the molecules of the liquid-crystalline medium of layer S in the twisted nematic state, regarded over the entire layer thickness, is between 320° and three complete rotations.
17. The device according to claim 1 , wherein the dielectric anisotropy Δε of the liquid-crystalline medium is greater than 3 or less than −3.
18. The device according to claim 1 , wherein the liquid-crystalline medium comprises one or more chiral compounds in a total concentration of 0.01 to 3% by weight.
19. The device according to claim 1 , which comprises a device for the conversion of light energy into electrical energy.
20. The device according to claim 1 , which comprises one or more glass layers which have an antireflection characteristic.
21. The device according to claim 1 , which has an area extent of at least 0.05 m 2 .
22. The device according to claim 1 , which is suitable for the homogeneous regulation of the entry of light into a room through a surface.
23. A method for the homogeneous regulation of the passage of light through a light-transmitting surface into a room comprising passing the light through the device according to claim 1 .
24. A device for regulating the transmission of light into a room, comprising:
a switchable layer S comprising a liquid-crystalline medium which comprises at least one dichroic compound,
where the following applies to the thickness d of layer S and the optical anisotropy Δn of the liquid-crystalline medium of layer S:
d< 2 μm/Δ n
wherein the molecules of the liquid-crystalline medium of switchable layer S are in a twisted nematic state in a switching state of the device and the switchable layer S is switchable between two different transmission levels, wherein the transmission level is determined by whether an electrical voltage is being applied or not being applied,
wherein the liquid crystalline medium has a clearing point in the temperature range from 70° C. to 170° C.,
wherein the molecules of the liquid-crystalline medium are in a twisted nematic state and in a homogeneous alignment in the switching state of the device without an applied voltage and wherein the molecules of the liquid-crystalline medium are in an untwisted nematic state and in a homeotropic alignment in the switching state of the device with an applied voltage, and
wherein the device is colourless when looked through in all its switching states.