Device for regulating the entry of light

Abstract

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.

Claims

1. A device for regulating the entry of light into a room, comprising: a switchable layer S having a thickness d of greater than 12 m, 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 n of the liquid-crystalline medium of layer S:
d<1 m/n and where the molecules of the liquid-crystalline medium of layer S are in a twisted nematic state in the switching state of the device without an applied electrical voltage or in the switching state of the device with an applied electrical voltage; wherein the dielectric anisotropy AE of the liquid-crystalline medium is less than 3; wherein the liquid-crystalline medium comprises one or more chiral compounds; wherein said device has only one switchable layer S; and wherein the twist of the orientation axes of the molecules of the liquid-crystalline medium of layer S in the twisted nematic state, over the entire layer thickness, is between 100 and 260, or the twist of the orientation axes of the molecules of the liquid-crystalline medium of layer S in the twisted nematic state, over the entire layer thickness, is between 270 and 1800.

2. The device according to claim 1, wherein the following applies to the thickness d of layer S and the optical anisotropy n of the liquid-crystalline medium of layer S:
d<0.9 m/n
and
d>0.2 m/n.

3. The device according to claim 1, wherein precisely one orientation layer, called O1, is adjacent to one side of the switchable layer S, and precisely one other orientation layer, called O2, is adjacent to the opposite side of the switchable layer S.

4. The device according to claim 3, wherein orientation layers O1 and O2 are designed 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 O1 and O2 include an angle of 30 to 270.

6. The device according to claim 3, wherein orientation layers O1 and O2 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 O1 and O2 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 O1 or O2.

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 70 with the plane of orientation layer O1 or O2.

10. The device according to claim 1, wherein said device does not include a polarizer.

11. The device according to claim 1, wherein layer S has a thickness between 13 and 50 m.

12. The device according to claim 1, wherein layer S comprises at least two different dichroic compounds.

13. The device according to claim 1, wherein said device is colorless when looked through in all its switching states.

14. The device according to claim 1, wherein at least one of the dichroic compounds is selected from 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 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 are in an untwisted nematic state and in a homeotropic alignment in the switching state of the device with an applied voltage.

16. A device for regulating the entry of light into a room, comprising: a switchable layer S having a thickness d of greater than 12 m, 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 n of the liquid-crystalline medium of layer S:
d<1 m/n and where the molecules of the liquid-crystalline medium of layer S are in a twisted nematic state in the switching state of the device without an applied electrical voltage or in the switching state of the device with an applied electrical voltage; wherein the dielectric anisotropy AE of the liquid-crystalline medium is less than 3; wherein the liquid-crystalline medium comprises one or more chiral compounds; wherein said device has only one switchable layer S; and wherein the liquid-crystalline medium has a value of the optical anisotropy (n) of less than 0.075.

17. 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 320 and three complete rotations.

18. The device according to claim 1, wherein the optical anisotropy n of the liquid-crystalline medium is less than 0.075.

19. 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.

20. The device according to claim 1, wherein said device comprises a device for the conversion of light energy into electrical energy.

21. A window containing a device according to claim 1.

22. A method for homogeneous regulation of the passage of light into a room comprising transmitting light into the room via a device according to claim 1.

23. The device according to claim 16, wherein the twist of the orientation axes of the molecules of the liquid-crystalline medium of layer S in the twisted nematic state, over the entire layer thickness, is between 100 and 260.

24. The device according to claim 16, wherein the twist of the orientation axes of the molecules of the liquid-crystalline medium of layer S in the twisted nematic state, over the entire layer thickness, is between 270 and 1800.

25. The device according to claim 16, 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 135 and 270.

26. The device according to claim 16, wherein the liquid-crystalline medium has a value of the optical anisotropy (n) of less than 0.06.

27. The device according to claim 1, wherein the following applies to the thickness d of layer S and the optical anisotropy n of the liquid-crystalline medium of layer S:
d<0.75 m/n and d>0.5 m/n.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a preferred layer sequence of a device according to the invention. Substrate layer (1), electrically conductive layer (2), orientation layer O1 (3a), switchable layer S (4), orientation layer O2 (3b), a further electrically conductive layer (2) and a further substrate layer (1) are arranged one behind the other and directly adjacent to one another here.

(2) FIG. 2 shows a perpendicular view of orientation layers O1 (3a) and O2 (3b). O2 is behind O1, seen from the observer. Arrow (5) represents the rubbing direction of orientation layer O1. Arrow (6) represents the rubbing direction of orientation layer O2. Symbol (7) illustrates the twist of the liquid-crystalline compounds of the switchable layer between orientation layers O1 and O2. In the present case, the liquid-crystalline compounds describe a left-handed helix having an angle of rotation of 270 between orientation layers O1 and O2, since they are aligned parallel to the rubbing direction of O1 at the interface to O1, and are aligned parallel to the rubbing direction of O2 at the interface to O2.

DESCRIPTION OF THE REFERENCE NUMERALS

(3) 1 Substrate layer, preferably comprising glass or polymer 2 Electrically conductive layer 3a Orientation layer O1 4 Switchable layer S 3b Orientation layer O2 5 Rubbing direction in orientation layer O1 6 Rubbing direction in orientation layer O2 7 Twist angle of the liquid-crystalline compounds of the switchable layer (left-handed helix if O2 is behind O1)

WORKING EXAMPLES

(4) In the following text, structures of liquid-crystalline compounds are reproduced by abbreviations (acronyms). These abbreviations are explicitly presented and explained in WO 2012/052100 (pp. 63-89), so that reference is made to the said published application for an explanation of the abbreviations in the present application. In addition, the following acronyms are use:

(5) ##STR00097##

(6) All physical properties are determined in accordance with Merck Liquid Crystals, Physical Properties of Liquid Crystals, Status November 1997, Merck KGaA, Germany, and apply for a temperature of 20 C. The value of n is determined at 589 nm.

(7) A) Construction of the devices

(8) The devices used are produced and have the following layer sequence:

(9) a) Glass layer comprising polished 1.1 mm soda-lime glass from Corning

(10) b) ITO layer, 200 Angstrom

(11) c) Orientation layer O1 comprising polyimide JALS-2096-R1 from JSR, rubbed

(12) d) Switchable layer comprising liquid-crystalline medium (composition and thickness indicated below in the case of the corresponding examples)

(13) e) Orientation layer O2, built up like c); rubbed at the angle indicated below to the rubbing direction of layer c)

(14) f) as b)

(15) g) as a)

(16) The ITO layers are correspondingly provided with contacts in order to be electrically switchable.

(17) B) Liquid-crystalline mixtures used

(18) The following mixtures are prepared:

(19) TABLE-US-00003 Mixture M-1 n.sub.e (20 C., 589.3 nm) 1.5514 n.sub.o (20 C., 589.3 nm) 1.4737 n (20 C., 589.3 nm) 0.0777 _parallel (20 C., 1 kHz) 3.40 _perpendicular (20 C., 1 kHz) 7.1 (20 C., 1 kHz) 3.7 HTP (S-811, 20 C.) 10.06 m.sup.1 Composition Compound % CY-3-O2 12 CY-5-O2 12 CCY-3-O2 13 CCY-5-O2 13 CCY-3-1 8 CCZC-3-3 4 CCZC-3-5 3 CCZC-4-3 3 CC-3-4 6 CC-3-5 6 CC-3-O3 8 CC-5-O1 4 CC-5-O2 4 CP-3-O2 4

(20) TABLE-US-00004 Mixture M-2 n.sub.e (20 C., 589.3 nm) 1.5186 n.sub.o (20 C., 589.3 nm) 1.4750 n (20 C., 589.3 nm) 0.0436 _parallel (20 C., 1 kHz) 3.32 _perpendicular (20 C., 1 kHz) 8.11 (20 C., 1 kHz) 4.8 HTP (S-811, 20 C.) 8.22 m.sup.1 Composition Compound % CCN-47 20 CCN-55 21 CC-3-O1 11 CC-5-O1 5 CC-5-O2 5 CCZC-3-3 4 CCZC-3-5 4 CCZC-4-3 4 CCZC-4-5 4 BCN-55 22

(21) TABLE-US-00005 Mixture M-3 n.sub.e (20 C., 589.3 nm) 1.5222 n.sub.o (20 C., 589.3 nm) 1.4779 n (20 C., 589.3 nm) 0.0443 _parallel (20 C., 1 kHz) 3.39 _perpendicular (20 C., 1 kHz) 8.94 (20 C., 1 kHz) 5.5 HTP (S-811, 20 C.) Composition Compound % CCN-47 15 CCN-55 15 CCN-33 8 CCZC-3-3 3 CCZC-3-5 3 CC-3-O1 11 CC-5-O1 5 CCZCC-2-3 2 CCZCC-3-2 2 CCZCC-4-2 2 CCZCC-4-3 2 BCN-35 16 BCN-55 16

(22) C) Dyes used

(23) ##STR00098##

(24) D) Chiral dopant used

(25) ##STR00099##

(26) E) Method for Measurement of the Transmission

(27) The spectra with the individual STN cells are measured in a Perkin Elmer Lambda 1050 spectrometer against a reference, i.e. optical losses due to reflection at interfaces are illuminated.

(28) The measurements are carried out in an Autronic DMS-301 up to 80 C.

(29) In all cases, the devices are switched from the dark state to the bright state by application of a voltage between the electrodes. In both states, the light transmittance is in each case determined in accordance with the EN 410 standard, equation (1).

Comparative Example 1

(30) 0.5% of D1, 0.9% of D2 and 1.1% of D3 are added to 97.5% of mixture M-1. 0.78% of chiral dopant is added to 98.26% of this mixture. The pitch is 12.7 m.

(31) The mixture is introduced into the device described above having a layer thickness of 8.5 m. The tilt angle of the cell is 87.3 relative to the substrate plane. The twist (angle between the rubbing directions of O1 and O2) is 240.

(32) The transmission values of the device are determined as indicated under E):

(33) TABLE-US-00006 Temperature .sub.V bright state .sub.V [ C.] .sub.V dark state [%] [%] [%] 20 24.0 74.5 50.5

(34) The device from Comparative Example 1 exhibits clearly visible streaks from the glass waviness or visible particle defects.

Comparative Example 2

(35) 0.278% of D1, 0.500% of D2 and 0.611% of D3 are added to 98.611% of mixture M-1. 0.43% of chiral dopant is added to 99.57% of this mixture. The pitch is 23.1 m.

(36) The mixture is introduced into the device described above having a layer thickness of 15.5 m. The tilt angle of the cell is 87.3 relative to the substrate plane. The twist (angle between the rubbing directions of O1 and O2) is 240.

(37) The transmission values of the device are determined as indicated under E):

(38) TABLE-US-00007 Temperature .sub.V dark state .sub.V bright state .sub.V [ C.] [%] [%] [%] 20 29.4 74.4 45.0

(39) In a comparison of Comparative Example 2 with Comparative Example 1, it can be seen that the increase in the layer thickness from 8.5 m to 15.5 m results in a significant loss of transmission range (.sub.v) at 20 C. of 5.5%. However, the device from Comparative Example 1 exhibits clearly visible streaks from the glass waviness or visible particle defects compared with the device from Comparative Example 2.

Example 1

(40) 0.33% of D1, 0.50% of D2 and 0.60% of D3 are added to 98.57% of mixture M-2. 1.18% of chiral dopant are added to 98.82% of this mixture. The pitch is 10.32 m.

(41) The mixture is introduced into the device described above having a layer thickness of 15.4 m. The tilt angle of the cell is 88.5 relative to the substrate plane. The twist (angle between the rubbing directions of O1 and O2) is 240.

(42) The transmission values of the device are determined as indicated under E):

(43) TABLE-US-00008 Temperature .sub.V dark state .sub.V bright state .sub.V [ C.] [%] [%] [%] 20 24.4 71.8 47.4

(44) The device from Example 1 exhibits an improvement in the transmission range (.sub.v) of 2.4% compared with Comparative Example 2 at 15.4 m. The improvement in the transmission range in the case of greater layer thicknesses is clearly evident. In addition, the almost doubled layer thickness compared with Comparative Example 1 means that fewer visible streaks from the glass waviness or fewer visible particle defects are evident.

Example 2

(45) 2.0% of D4, 0.33% of D5, 0.26% of D6 and 0.70% of D7 are added to 96.71% of mixture M-2. 1.18% of chiral dopant are added to 98.82% of this mixture. The pitch is 10.32 m.

(46) The mixture is introduced into the device described above having a layer thickness of 15.4 m. The tilt angle of the cell is 88.5 relative to the substrate plane. The twist (angle between the rubbing directions O1 and O2) is 240.

(47) The transmission values of the device are determined as indicated under E):

(48) TABLE-US-00009 Temperature .sub.V dark state .sub.V bright state .sub.V [ C.] [%] [%] [%] 20 26.1 72.9 47.4

(49) The device from Example 2 exhibits an improvement in the transmission range (.sub.v) at 20 C. of 1.8% compared with Comparative Example 2 at a layer thickness of 15.4 m. In addition, the almost doubled layer thickness compared with Comparative Example 1 means that fewer visible streaks from the glass waviness or fewer visible particle defects are evident.

Example 3

(50) 0.33% of D1, 0.50% of D2 and 0.60% of D3 are added to 98.57% of mixture M-3. 0.524% of chiral dopant is added to 99.476% of this mixture. The pitch is 23.1 m.

(51) The mixture is introduced into the device described above having a layer thickness of 15.4 m. The tilt angle of the cell is 88.5 relative to the substrate plane. The twist (angle between the rubbing directions of O1 and O2) is 240.

(52) The transmission values of the device are determined as indicated under E):

(53) TABLE-US-00010 Temperature .sub.V dark state .sub.V bright state .sub.V [ C.] [%] [%] [%] 20 C. 22.9 72.7 49.8

(54) Example 3 exhibits a clear improvement in the transmission range (.sub.v) of 4.8% compared with Comparative Example 2 at 15.4 m. The reduction in the transmission range (.sub.v) due to the greater layer thickness between Comparative Examples 1 and 2 has been compensated for in Example 3.

(55) In addition, the almost doubled layer thickness compared with Comparative Example 1 means that fewer visible streaks from the glass waviness or fewer visible particle defects are evident.