OPTICAL SWITCHING LAYER FOR USE IN AN OPTICAL SWITCHING ELEMENT

Abstract

The present invention presents a switching layer S for use in a switching element which has forwards-scattering properties in at least one switching state. Furthermore, a switching element which comprises the switching layer S and a window element which includes the switching element are presented.

Claims

1. Switching layer S for use in a switching element, where the switching layer S has switching states and comprises an upper switching layer plane USLP and a lower switching layer plane LSLP, and, arranged between USLP and LSLP, a liquid-crystalline medium, where, in one of the switching states, parallel light rays which hit the upper switching layer plane USLP in the directions of incidence D(=) are deflected out of D(=) on passing through the switching layer S, so that, after leaving the lower switching layer plane LSLP, the originally parallel light rays are scattered in the forwards-scattering directions D(<) away from the lower switching layer plane LSLP and are thus scattered forwards, resulting in forwards scattering, which is measured as diffusive transmission T.sub.d, where T.sub.d is >20%, and where T.sub.d is defined in accordance with formula (1)
T.sub.d=(I.sub.2.5/I.sub.tot).Math.100[%](1) in which I.sub.2.5 denotes the intensity of the large-angle scattering with scattering angles2.5 and I.sub.tot denotes the intensity of the total transmission.

2. Switching layer S according to claim 1, characterised in that the diffusive transmission T.sub.d in another switching state is <5%.

3. Switching layer S according to claim 1, characterised in that the liquid-crystalline medium comprises nematically arranged molecules and a polymer component.

4. Switching layer S according to claim 3, characterised in that the polymer component comprises a polymeric network which is obtained by polymerisation of reactive mesogens.

5. Switching layer S according to claim 4, characterised in that the nematically arranged molecules and the polymeric network are homogeneously distributed in one another.

6. Switching layer S according to claim 5, characterised in that the nematically arranged molecules have a proportion by weight w.sub.LC and the polymeric network has a proportion by weight w.sub.PN, and w.sub.PN, based on a weight w.sub.LC+w.sub.PN, is in the region<60% by weight.

7. Switching layer S according to claim 1, characterised in that the switching layer S comprises a liquid-crystalline medium which comprises a chiral dopant.

8. Switching layer S according to claim 7, characterised in that the molecules of the liquid-crystalline medium in the switching state where T.sub.d>20% are in a chirally nematic phase.

9. Switching layer S according to claim 8, characterised in that the chirally nematic phase is a phase aligned in polydomains.

10. Switching layer S according to claim 7, characterised in that the switching layer S has an average refractive index n, and the molecules of the liquid-crystalline medium have a pitch p, where the product n.Math.p is >0.8 m.

11. Switching layer S according to claim 7, characterised in that the chiral dopant has a proportion by weight w.sub.D in the liquid-crystalline medium of 0.1% by weight to 30.0% by weight.

12. Switching layer S according to claim 7, characterised in that the chiral dopant has a helical twisting power =(p.Math.c).sup.1 m.sup.1, where p is the pitch of the molecules of the liquid-crystalline medium in m and c is the concentration of the chiral dopant in % by weight, based on the entire liquid-crystalline medium, and is greater than 5 m.sup.1.

13. Switching layer S according to claim 1, characterised in that the liquid-crystalline medium has a clearing point of >90 C.

14. Switching layer S according to claim 1, characterised in that it comprises at least one dichroic dye in a dye concentration in the range from 0.01% by weight to 25% by weight, based on the weight of the liquid-crystalline medium.

15. Switching layer S according to claim 1, characterised in that the switching layer S has a thickness of 3 m to 200 m, and, in one switching state, the total transmission T.sub.total is between 60% and 100% and the diffusive transmission T.sub.d is between 25% and 100% at a wavelength of the light rays of 550 nm.

16. Switching layer S according to claim 1, characterised in that, in all its switching states, the switching layer S scatters less than 45% of the parallel light rays in the backwards-scattering directions D(>) away from the upper switching layer plane USLP.

17. Switching element comprising a switching layer S according to claim 1, where the switching layer S is arranged in a first layer sequence, and where the first layer sequence comprises, from the outside inwards, an outer substrate layer, an outer electrically conductive layer, the switching layer S, an inner electrically conductive layer and an inner substrate layer.

18. Switching element according to claim 17, characterised in that it comprises one or more layers which block UV light.

19. Switching element according to claim 17, characterised in that the switching element has a second layer sequence on the outer substrate layer of the first layer sequence and/or on the inner substrate layer of the first layer sequence, where the second layer sequence comprises, from the outside inwards, a substrate layer, an electrically conductive layer, a switching layer comprising a liquid-crystalline medium, an electrically conductive layer and a substrate layer.

20. Switching element according to claim 17, characterised in that the switching element has a third layer sequence on the outer substrate layer of the first layer sequence and/or on the inner substrate layer of the first layer sequence, where the third layer sequence comprises, from the outside inwards, a substrate layer, an electrically conductive layer, a switching layer comprising a liquid-crystalline medium, an electrically conductive layer, a substrate layer, an electrically conductive layer, a switching layer comprising a liquid-crystalline medium, an electrically conductive layer and a substrate layer.

21. Switching element according to claim 19, characterised in that the liquid-crystalline medium of the switching layer of the second layer sequence or the liquid-crystalline medium of one or both switching layers of the third layer sequence comprises at least one dichroic dye in a dye concentration in the range from 0.01% by weight to 25% by weight, based on the weight of the respective liquid-crystalline medium.

22. Window element which includes a switching element according to claim 17.

Description

WORKING EXAMPLES

[0154] The present invention is explained in greater detail in the following (comparative) examples.

[0155] In the switching layers of the (comparative) examples, base mixtures #1, #2, #3 and #4 having the proportions by weight of their components, i.e. the liquid-crystalline molecules, listed below are employed.

[0156] Base mixture #1 has a dielectric anisotropy =5.7 and consists of [0157] 13% by weight of CCN-33, [0158] 10% by weight of CZY-3-02, [0159] 10% by weight of CZY-4-02, [0160] 10% by weight of CZY-5-02, [0161] 4% by weight of CCZY-3-02, [0162] 14% by weight of PTY-3-02, [0163] 14% by weight of PTY-5-02, [0164] 5% by weight of CPTY-3-O1, [0165] 5% by weight of CPTY-3-02, [0166] 5% by weight of CPTY-3-03, [0167] 8% by weight of CP-3-01 and [0168] 2% by weight of CGPC-3-3.

[0169] Base mixture #2 has a dielectric anisotropy =+41.8, a refractive index anisotropy n=0.2574 and a clearing point of 92 C. and consists of [0170] 9% by weight of PZG-2-N, [0171] 10% by weight of PZG-3-N, [0172] 14% by weight of PZG-4-N, [0173] 2% by weight of PZG-5-N, [0174] 2% by weight of CP-3-N, [0175] 20% by weight of PPTUI-3-2, [0176] 28% by weight of PPTUI-3-4 and [0177] 3% by weight of CGPC-3-3.

[0178] Base mixture #3 has a dielectric anisotropy =+11.3, a refractive index anisotropy n=0.1349 and a clearing point of 114.5 C. and consists of [0179] 16% by weight of CP-3-N, [0180] 16% by weight of CP-5-N, [0181] 5% by weight of CPG-3-F, [0182] 5% by weight of CPG-5-F, [0183] 15% by weight of CPU-3-F, [0184] 15% by weight of CPU-5-F, [0185] 7% by weight of CCGU-3-F, [0186] 4% by weight of CGPC-3-3, [0187] 4% by weight of CGPC-5-3, [0188] 4% by weight of CGPC-5-5, [0189] 3% by weight of CCZPC-3-3, [0190] 3% by weight of CCZPC-3-4 and [0191] 3% by weight of CCZPC-3-5.

[0192] Base mixture #4 has a dielectric anisotropy =5.0, a refractive index anisotropy n=0.1531 and a clearing point of 81 C. and consists of [0193] 25% by weight of CY-3-04, [0194] 9% by weight of CY-5-02, [0195] 7% by weight of CCY-3-02, [0196] 4.5% by weight of CCY-3-03, [0197] 10% by weight of CPY-2-02, [0198] 10% by weight of CPY-3-02, [0199] 15% by weight of PYP-2-3, [0200] 10% by weight of PYP-2-4, [0201] 3% by weight of CCP-V-1, [0202] 2% by weight of CPP-3-2, [0203] 3.5% by weight of PP-1-2V1, [0204] 2% by weight of PGP-2-3, [0205] 3.5% by weight of PP-1-2V1 and [0206] 2% by weight of PGP-2-3.

[0207] The chemical structures of the components of base mixtures #2 and #3 have already been indicated explicitly. The chemical structures of the components of base mixtures #1 and #4 are indicated in the form of abbreviations, the meaning of which is described in WO 2012/052100 from page 3, line 24, to page 67, line 12.

Comparative Example 1

[0208] A comparative switching element 1 having the layer sequence shown is produced.

TABLE-US-00002 Glass substrate layer 1 Electrically conductive ITO layer 2 Polyimide orientation layer 3 Switching layer 4 consisting of 99.609% by weight of base mixture #3 and 0.391% by weight of dichroic dyes D1, D2 and D3, i.e. 0.077% by weight of D1, 0.146% by weight of D2 and 0.168% by weight of D3 Polyimide orientation layer 5a Electrically conductive ITO layer 5b Glass substrate layer 5c Optional glass substrate layer 5d Electrically conductive ITO layer 5e Rubbed polyimide orientation layer 6 Switching layer 7 with identical composition to switching layer 4 Rubbed polyimide orientation layer 8 Electrically conductive ITO layer 9 Glass substrate layer 10

[0209] Orientation layers 3 and 6 and orientation layers 5a and 8 align the liquid-crystalline molecules in the same direction, where orientation layer 5a is rotated by 90 relative to orientation layer 3, and orientation layer 8 is rotated by 90 relative to orientation layer 6.

[0210] Switching layers 4 and 7 each have a thickness of 24.5 m. The orientation axes of the liquid-crystalline molecules present in switching layers 4 and 7 lie [0211] in the switched-off state (U=0 V), planar with a small pre-tilt angle, for example with a pre-tilt angle of 1, pointing out of the respective switching layer plane and parallel to the respective rubbing directions of the respective adjacent orientation layers, and [0212] in the switched-on state (U=20 V), perpendicular to the respective orientation layer.

[0213] Comparative switching element 1 has a transmission intensity in the light switching state of 73% at a voltage of 20 V at the electrodes of switching layers 4 and 7. The liquid-crystalline molecules in switching layers 4 and 7 are in a homeotropic orientation here.

[0214] Comparative switching element 1 has a transmission intensity I.sub.observer in the dark switching state of 15% at a voltage of 0 V at the electrodes of switching layers 4 and 7. The liquid-crystalline molecules in switching layers 4 and 7 are in a planar orientation here.

[0215] Comparative switching element 1 is free from scattering (<1%) in both light and dark switching states and the intermediate states.

Comparative Example 2

[0216] A comparative switching element 2 having the layer sequence depicted diagrammatically below is produced.

TABLE-US-00003 Glass substrate layer 11 Electrically conductive ITO layer 12 Polyimide orientation layer 13 Switching layer 14 consisting of 99.218% by weight of base mixture #3 and 0.782% by weight of dichroic dyes D1, D2 and D3, i.e. 0.154% by weight of D1, 0.292% by weight of D2 and 0.336% by weight of D3 Polyimide orientation layer 15 Electrically conductive ITO layer 16 Glass substrate layer 17

[0217] Orientation layer 13 is rotated by 90 relative to orientation layer 15. Switching layer 14 has a thickness of 24.5 m. The orientation axes of the molecules present in switching layer 14 lie [0218] in the switched-off state (U=0 V), planar with a small pre-tilt angle, for example with a pre-tilt angle of 1, pointing out of switching layer plane 14 and parallel to the rubbing directions of orientation layers 13 and 15, [0219] in the switched-on state (U=20 V), perpendicular to orientation layers 13 and 15.

[0220] Comparative switching element 2 has a transmission intensity in the light switching state of 73% at a voltage of 20 V at the electrodes of switching layer 14. The liquid-crystalline molecules in switching layer 14 are in a homeotropic orientation here.

[0221] Comparative switching element 2 has a measured transmission intensity I.sub.observer in the dark switching state of 42% at a voltage of 0 V at the electrodes of switching layer 14. The molecules in switching layer 14 are in a planar orientation here.

[0222] Comparative switching element 2 is free from scattering (<1%) in both light and dark switching states and the intermediate states.

Comparative Example 3

[0223] A comparative switching element 3 having the layer sequence depicted diagrammatically below is produced.

TABLE-US-00004 Glass substrate layer 11 Electrically conductive ITO layer 12 Rubbed planar-orienting polyimide orientation layer 13 having a pre-tilt angle of 5 Switching layer 14 consisting of 95.23% by weight of base mixture #3, 3.91% by weight of dichroic dyes D1, D2 and D3, i.e. 0.77% by weight of D1, 1.46% by weight of D2 and 1.68% by weight of D3, 0.86% by weight of chiral dopant S-811 Rubbed planar-orienting polyimide orientation layer 15 having a pre-tilt angle of 5, where the rubbing direction runs at an angle of 240 to the rubbing direction of orientation layer 13 Electrically conductive ITO layer 16 Glass substrate layer 17

[0224] Switching layer 14 has a thickness of 5 m. The orientation axes of the liquid-crystalline molecules present in switching layer 14 lie [0225] in the switched-off state (U=0 V), planar with a pre-tilt angle of 5 pointing out of switching-layer plane 14 and parallel to the rubbing directions of orientation layers 13 and 15, [0226] in the switched-on state (U=12 V), perpendicular to orientation layers 13 and 14.

[0227] Comparative switching element 3 has a transmission intensity in the light switching state of 74%. The liquid-crystalline molecules in switching layer 14 are in a homeotropic orientation here.

[0228] Comparative switching element 3 has a transmission intensity I.sub.observer in the dark switching state of 22%. The liquid-crystalline molecules in switching layer 14 are in a planar orientation here.

[0229] Comparative switching element 3 is free from scattering (<1%) in both light and dark switching states and the intermediate states.

Example 1

[0230] A switching element 1 according to the invention has the layer sequence depicted diagrammatically below and comprises a switching layer S.sub.1 according to the invention in embodiment a), b) or c) shown in Table 1, where [0231] BM#2 and BM#3 denote base mixture #2 and base mixture #3 respectively, [0232] S-5011 denotes chiral dopant S-5011, [0233] Lambda denotes the estimated reflection wavelength and [0234] rubbed antiparallel, planar denotes a planar orientation with small tilt angles, where the orientations in orientation layers 20 and 21 adjacent to switching layer S.sub.1 are meant, and where the tilt angles on orientation layers 20 and 21 are rotated by 180 to one another, [0235] voltage denotes the switching voltage of switching layer S.sub.1 in the clear or opaque state, where clear means the light switching state and opaque means the dark switching state, and where, in the opaque switching state, the liquid-crystalline molecules of switching layer S, are in a state aligned in polydomains, which has a homogeneous visual appearance, but may have different structuring under the microscope.

[0236] Table 1-1 shows switching states and switching voltages in switching element 1 in embodiments a), b) and c), where switching layers S4 and S7 are in the light or dark state and switching layer S, is in the clear or opaque state.

TABLE-US-00005 TABLE 1 Embodiments of switching layer S.sub.1 Layer Forwards-scattering Orientation Voltage thickness liquid-crystalline Pitch Lambda of the clear opaque [m] medium [m] [nm] polyimide [V] [V] a) 7 99.28% by weight of BM#2 1.5 2070 homeotropic 10 6 0.72% by weight of S-5011 b) 23 99.46% by weight of BM#2 2.0 3290 rubbed 25 3 0.54% by weight of S-5011 antiparallel, planar c) 23 99.73% by weight of BM#3 4.0 6250 rubbed 25 5 0.27% by weight of S-5011 antiparallel, planar

TABLE-US-00006 TABLE 1-1 Switching states and switching voltages in switching element 1 Switching state Voltage Switching state Voltage in S4 and S7 in S4 and S7 in S.sub.1 in S.sub.1 a) 1 light 12 V clear 10 V 2 light 12 V opaque 6 V 3 dark 0 V clear 10 V 4 dark 0 V opaque 6 V b) 1 light 12 V clear 25 V 2 light 12 V opaque 3 V 3 dark 0 V clear 25 V 4 dark 0 V opaque 3 V c) 1 light 12 V clear 25 V 2 light 12 V opaque 5 V 3 dark 0 V clear 25 V 4 dark 0 V opaque 5 V

Layer Sequence of Switching Element 1

[0237]

TABLE-US-00007 Glass substrate layer 1 Electrically conductive ITO layer 2 Polyimide orientation layer 3 Switching layer 4 consisting of 99.609% by weight of base mixture #3 and 0.391% by weight of dichroic dyes D1, D2 and D3, i.e. 0.077% by weight of D1, 0.146% by weight of D2 and 0.168% by weight of D3 Polyimide orientation layer 5a Electrically conductive ITO layer 5b Glass substrate layer 5c Optional glass substrate layer 5d Electrically conductive ITO layer 5e Rubbed polyimide orientation layer 6 Switching layer 7 with identical composition to switching layer 4 Rubbed polyimide orientation layer 8 Electrically conductive ITO layer 9 Glass substrate layer 10 Glass substrate layer 18 Electrically conductive ITO layer 19 Polyimide orientation layer 20 Switching layer S.sub.1 comprising forwards-scattering liquid-crystalline medium in one of embodiments a), b) or c) shown in Table 1 Polyimide orientation layer 21 Electrically conductive ITO layer 22 Glass substrate layer 23

[0238] Switching element 1 in embodiment c) has [0239] a transmission intensity in switching state 1 of 78%, [0240] a transmission intensity I.sub.observer in switching state 4 of 9% and [0241] a transmission intensity I.sub.tot in switching state 4 of 14%.

[0242] Switching element 1 is irradiated here with parallel light rays on substrate layer 1.

[0243] Thus, in switching element 1 in the switched state of the scattering switching layer, {1(9/14)}.Math.100=36% of the light rays are deflected out of their originally parallel direction by scattering of more than 2.5. In the opaque switching state, the molecules of switching layer S.sub.1 are in a state aligned in polydomains.

[0244] The corresponding investigations were also carried out for versions a) and b) of the switching layer. With small deviations, the same values for the diffusive transmission in the scattering state were measured as for version c) explicitly described above.

Example 2a

[0245] A switching element 2a) according to the invention comprises a switching layer S.sub.2a) according to the invention having a thickness of 24.5 m in the layer sequence shown:

TABLE-US-00008 Glass substrate layer 1 Electrically conductive ITO layer 2 Polyimide orientation layer 3 Switching layer S.sub.2a) consisting of 99.34% by weight of base mixture #3 0.27% by weight of chiral dopant S-5011 and 0.39% by weight of dichroic dyes D1, D2 and D3, i.e. 0.077% by weight of D1, 0.146% by weight of D2 and 0.168% by weight of D3 Polyimide orientation layer 5a Electrically conductive ITO layer 5b Glass substrate layer 5c Optional glass substrate layer 5d Electrically conductive ITO layer 5e Polyimide orientation layer 6 Switching layer S7 with identical composition to switching layer S4 Polyimide orientation layer 8 Electrically conductive ITO layer 9 Glass substrate layer 10

[0246] Table 1-2 shows switching states and switching voltages in switching element 2a, where switching layer S7 is in the light or dark state and switching layer S.sub.2a is in the light-clear or dark-opaque state.

TABLE-US-00009 TABLE 1-2 Switching states and switching voltages in switching element 2a Switching state Voltage Switching state Voltage in S7 in S7 in S.sub.2a in S.sub.2a 1 light 12 V light-clear 25 V 2 dark 0 V light-clear 25 V 3 light 12 V dark-opaque 5 V 4 dark 0 V dark-opaque 5 V

[0247] Switching element 2a) is irradiated with parallel light rays on substrate layer 1 and has [0248] a transmission intensity in switching state 1 of 75%, [0249] a transmission intensity I.sub.observer in switching state 4 of 16%, and [0250] a transmission intensity I.sub.tot in switching state 4 of 28%, measured on the Ulbricht sphere, i.e. with scattered light.

[0251] Thus, in switching element 2a in the switched state of the scattering switching layer, {1(16/28)}.Math.100=43% of the light rays are deflected out of their originally parallel direction by scattering of more than 2.5. In the dark-opaque switching state, the molecules of switching layer S.sub.2a) are in a state aligned in polydomains.

Example 2b

[0252] A switching element 2b) according to the invention comprises a switching layer S.sub.2b according to the invention having a thickness of 25 m in the layer sequence depicted diagrammatically below.

[0253] Table 1-3 shows switching states and switching voltages in switching element 2b, where switching layer S4 is in the light or dark state and switching layer S.sub.2b is in the light-clear or dark-opaque state.

TABLE-US-00010 TABLE 1-3 Switching states and switching voltages in switching element 2b Switching Voltage Switching Voltage state in S4 in S4 state in S.sub.2b in S.sub.2b 1 light 12 V light-clear 25 V 2 dark 0 V light-clear 25 V 3 light 12 V dark-opaque 5 V 4 dark 0 V dark-opaque 5 V

TABLE-US-00011 Glass substrate layer 1 Electrically conductive ITO layer 2 Polyimide orientation layer 3 Switching layer 4 consisting of 99.609% by weight of base mixture #3 and 0.391% by weight of dichroic dyes D1 , D2 and D3, i.e. 0.077% by weight of D1, 0.146% by weight of D2 and 0.168% by weight of D3 Polyimide orientation layer 5a Electrically conductive ITO layer 5b Glass substrate layer 5c Optional glass substrate layer 5d Electrically conductive ITO layer 5e PI orientation layer 6 Switching layer S.sub.2b) consisting of 99.34% by weight of base mixture #3 0.27% by weight of chiral dopant S-5011 and 0.39% by weight of dichroic dyes D1, D2 and D3, i.e. 0.077% by weight of D1, 0.146% by weight of D2 and 0.168% by weight of D3 PI orientation layer 8 Electrically conductive ITO layer 9 Glass substrate layer 10

[0254] Switching element 2b) is irradiated with parallel light rays on substrate layer 1 and has [0255] a transmission intensity in switching state 1 of 75%, [0256] a transmission intensity I.sub.observer in switching state 4 of 16%, and [0257] a transmission intensity I.sub.tot in switching state 4 of 28%.

[0258] Thus, in switching element 2b in the switched state of the scattering switching layer, {1(16/28)}.Math.100=43% of the light rays are deflected out of their originally parallel direction by scattering of more than 2.5.

[0259] In the dark-opaque switching state, the molecules of switching layer S.sub.2b) are in a state aligned in polydomains.

Example 2c

[0260] A switching element 2c) according to the invention comprises two switching layers S.sub.2c1 and S.sub.2c2 according to the invention, each having a thickness of 25 m, in the layer sequence depicted diagrammatically below.

TABLE-US-00012 Glass substrate layer 1 Electrically conductive ITO layer 2 Polyimide orientation layer 3 Switching layer S.sub.2c1 consisting of 99.34% by weight of base mixture #3 0.27% by weight of chiral dopant S-5011 and 0.39% by weight of dichroic dyes D1, D2 and D3, i.e. 0.077% by weight of D1, 0.146% by weight of D2 and 0.168% by weight of D3 Polyimide orientation layer 5 Electrically conductive ITO layer Glass substrate layer Optional further glass substrate layer Electrically conductive ITO layer Rubbed polyimide orientation layer 6 Switching layer S.sub.2c2 consisting of 99.34% by weight of base mixture #3 0.27% by weight of chiral dopant S-5011 and 0.39% by weight of dichroic dyes D1, D2 and D3, i.e. 0.077% by weight of D1, 0.146% by weight of D2 and 0.168% by weight of D3 Rubbed polyimide orientation layer 8 Electrically conductive ITO layer 9 Glass substrate layer 10

[0261] Switching element 2c) is irradiated with parallel light rays which are incident perpendicularly on substrate layer 1.

[0262] The following switching states are switched:

[0263] Switching state 1: a voltage of 25 V is present at each of the two switching layers S.sub.2c1 and S.sub.2c2. The transmission intensity in this switching state is 76%. Both switching layers are in the light-clear state.

[0264] Switching state 2: a voltage of 25 V is present at one of switching layers S.sub.2c1 or S.sub.2c2 and a voltage of 5 V is present at the remaining switching layer S.sub.2c1 or S.sub.2c2. The transmission intensity in this switching state is 27% without scattered light. In this state, one of the two switching layers is in the light-clear state and the other is in the dark-opaque state.

[0265] Switching state 3: a voltage of 5 V is present at each of the two switching layers S.sub.2c1 and S.sub.2c2. The transmission intensity I.sub.observer in this switching state is 11%. Both switching layers are in the dark-opaque state.

[0266] For switching state 3, an I.sub.tot of 16% is measured.

[0267] Thus, in switching element 2c in the switched state of the scattering switching layer, {1(11/16)}.Math.100=31% of the light rays are deflected out of their originally parallel direction by scattering of more than 2.5.

[0268] In the dark-opaque switching state, the molecules of switching layers S.sub.2c1 and S.sub.2c2 are in a state aligned in polydomains.

Example 2d

[0269] A switching element 2d) according to the invention comprises two switching layers S.sub.2d1 and S.sub.2d2 according to the invention, each having a thickness of 25 m, in the layer sequence depicted diagrammatically below.

TABLE-US-00013 Glass substrate layer 1 Electrically conductive ITO layer 2 Polyimide orientation layer 3 Switching layer S.sub.2d1 consisting of 99.73% by weight of base mixture #3 0.27% by weight of chiral dopant S-5011 Polyimide orientation layer 5 Electrically conductive ITO layer Glass substrate layer Optional further glass substrate layer Electrically conductive ITO layer Rubbed polyimide orientation layer 6 Switching layer S.sub.2d2 consisting of 99.73% by weight of base mixture #3 0.27% by weight of chiral dopant S-5011 Rubbed polyimide orientation layer 8 Electrically conductive ITO layer 9 Glass substrate layer 10

[0270] Switching element 2d) is irradiated with parallel light rays which are incident perpendicularly on substrate layer 1.

[0271] Switching state 1: a voltage of 25 V is present at each of the two switching layers S.sub.2d1 and S.sub.2d2. The transmission intensity in this switching state is 79%. Both switching layers are in the clear state.

[0272] Switching state 2: a voltage of 5 V is present at each of the two switching layers S.sub.2d1 and S.sub.2d2. The transmission intensity I.sub.observer in this switching state is 59%. Both switching layers are in the opaque state.

[0273] For switching state 3, an I.sub.tot of 79% is measured.

[0274] Thus, in switching element 2d in the switched state of the scattering switching layer, {1(59/79)}.Math.100=25% of the light rays are deflected out of their originally parallel direction by scattering of more than 2.5. In the opaque switching state, the molecules of switching layers S.sub.2d1 and S.sub.2d2 are in a state aligned in polydomains.

Example 3

[0275] A switching element 3 according to the invention has the layer sequence depicted diagrammatically below and comprises a switching layer S.sub.3 according to the invention in embodiments a), b) and c) shown in Table 2, where [0276] BM#2 and BM#3 denote base mixture #2 and base mixture #3 respectively, [0277] S-5011 denotes chiral dopant S-5011, [0278] Lambda denotes the estimated reflection wavelength and [0279] rubbed antiparallel, planar denotes a planar orientation with small tilt angles, where the orientations in orientation layers 20 and 21 adjacent to switching layer S.sub.3 are meant, and where the tilt angles on orientation layers 20 and 21 are rotated by 180 to one another, [0280] voltage denotes the switching voltage of switching layer S.sub.3 in the clear or opaque state, where, in the opaque switching state, the molecules of switching layer S.sub.3 are in a state aligned in polydomains.

[0281] Table 1-4 shows switching states and switching voltages in switching element 3 in embodiments a), b) and c), where switching layer 14 is in the light or dark state and switching layer S.sub.3 is in the clear or opaque state.

TABLE-US-00014 TABLE 2 Layer Forwards-scattering Orientation Voltage thickness liquid-crystalline Pitch Lambda of the clear opaque [m] medium [m] [nm] polyimide [V] [V] a) 7 99.28% by weight of BM#2 1.5 2070 homeotropic 10 6 0.72% by weight of S-5011 b) 23 99.46% by weight of BM#2 2.0 3290 rubbed 23 8 0.54% by weight of S-5011 antiparallel, planar c) 23 99.73% by weight of BM#3 4.0 6250 rubbed 25 5 0.27% by weight of S-5011 antiparallel, planar

TABLE-US-00015 TABLE 1-4 Switching states and switching voltages in switching element 3 Switching Voltage Switching Voltage state in S14 in S14 state in S.sub.3 in S.sub.3 a) 1 light 12 V clear 10 V 2 light 12 V opaque 6 V 3 dark 0 V clear 10 V 4 dark 0 V opaque 6 V b) 1 light 12 V clear 23 V 2 light 12 V opaque 8 V 3 dark 0 V clear 23 V 4 dark 0 V opaque 8 V c) 1 light 12 V clear 25 V 2 light 12 V opaque 5 V 3 dark 0 V clear 25 V 4 dark 0 V opaque 5 V

Layer Sequence of Switching Element 3

[0282]

TABLE-US-00016 Glass substrate layer 11 Electrically conductive ITO layer 12 Polyimide orientation layer 13 Switching layer 14 consisting of 99.218% by weight of base mixture #3 and 0.782% by weight of dichroic dyes D1, D2 and D3, i.e. 0.154% by weight of D1, 0.292% by weight of D2 and 0.336% by weight of D3 Polyimide orientation layer 15 Electrically conductive ITO layer 16 Glass substrate layer 17 Optional glass substrate layer 18 Electrically conductive ITO layer 19 Polyimide orientation layer 20 Switching layer S.sub.3 comprising liquid-crystalline medium in one of embodiments a), b) or c) shown in Table 2 Polyimide orientation layer 21 Electrically conductive ITO layer 22 Glass substrate layer 23

[0283] Switching element 3 in embodiment c) has [0284] a transmission intensity in switching state 1 of 74%, [0285] a transmission intensity I.sub.observer in switching state 4 of 23% and [0286] a transmission intensity I.sub.tot in switching state 4 of 41%.

[0287] Switching element 3 is irradiated here with parallel light rays on substrate layer 11.

[0288] Thus, in switching element 3 in the switched state of the scattering switching layer, {1(23/41)}.Math.100=44% of the light rays are deflected out of their originally parallel direction by scattering of more than 2.5.

[0289] In the opaque switching state, the molecules of switching layer S.sub.3 are in a state aligned in polydomains.

[0290] The corresponding investigations were also carried out for versions a) and b) of the switching layer. With small deviations, the same values for the diffusive transmission in the scattering state were measured as for version c) explicitly described above.

Example 3a

[0291] A switching element 3a according to the invention comprises switching layers 14 and S3 according to the invention in the layer sequence depicted diagrammatically below.

TABLE-US-00017 Glass substrate layer 11 Electrically conductive ITO layer 12 Polyimide orientation layer 13 Switching layer 14 consisting of 99.34% by weight of base mixture #3 0.27% by weight of chiral dopant S-5011 and 0.39% by weight of dichroic dyes D1, D2 and D3, i.e. 0.077% by weight of D1, 0.146% by weight of D2 and 0.168% by weight of D3 Polyimide orientation layer 15 Electrically conductive ITO layer 16 Glass substrate layer 17 Optional glass substrate layer 18 Electrically conductive ITO layer 19 Polyimide orientation layer 20 Switching layer S.sub.3 comprising liquid-crystalline medium in one of embodiments a), b) or c) shown in Table 2 of Example 3 Polyimide orientation layer 21 Electrically conductive ITO layer 22 Glass substrate layer 23

[0292] The following switching states are switched:

TABLE-US-00018 Switching Voltage Switching Voltage state in S14 in S14 state in S.sub.3 in S.sub.3 1 light-clear 25 V light-clear 25 V 2 dark-opaque 5 V light-clear 25 V 3 light-clear 25 V dark-opaque 5 V 4 dark-opaque 5 V dark-opaque 5 V

[0293] Switching element 3a in embodiment c) has [0294] a transmission intensity in switching state 1 of 88%, [0295] a transmission intensity I.sub.observer in switching state 4 of 18% and [0296] a transmission intensity I.sub.tot in switching state 4 of 53%.

[0297] Switching element 3a is irradiated here with parallel light rays on substrate layer 11.

[0298] Thus, in switching element 3a in the switched state of the scattering switching layer, {1(18/53)}.Math.100=66% of the light rays are deflected out of their originally parallel direction by scattering of more than 2.5.

[0299] In the dark-opaque switching state, the molecules of switching layers 14 and S.sub.3 are in a state aligned in polydomains.

[0300] The corresponding investigations were also carried out for versions a) and b) of the switching layer. With small deviations, the same values for the diffusive transmission in the scattering state were measured as for version c) explicitly described above.

Example 4

[0301] A switching element 4 according to the invention comprises a switching layer S.sub.4 according to the invention having a thickness of 24.5 m in the layer sequence depicted below.

TABLE-US-00019 Glass substrate layer 11 Electrically conductive ITO layer 12 Polyimide orientation layer 13 Switching layer S.sub.4 consisting of 98.95% by weight of base mixture #3, 0.78% by weight of dichroic dyes D1, D2 and D3, i.e. 0.154% by weight of D1, 0.292% by weight of D2 and 0.336% by weight of D3 0.27% by weight of chiral dopant S-5011 Polyimide orientation layer 15 Electrically conductive ITO layer 16 Glass substrate layer 17

[0302] Switching element 4 has [0303] a transmission intensity in the light-clear switching state of 74% (voltage=25 V), [0304] a transmission intensity I.sub.observer in the dark-opaque switching state of 15% (voltage=5 V) and [0305] a transmission intensity I.sub.tot in the dark-opaque switching state of 21%.

[0306] Switching element 4 is irradiated here with parallel light rays on substrate layer 11.

[0307] Thus, in switching element 4 in the switched state of the scattering switching layer, {1(15/21)}.Math.100=29% of the light rays are deflected out of their originally parallel direction by scattering of more than 2.5.

[0308] In the dark-opaque switching state, the molecules of switching layer S4 are in a state aligned in polydomains.

Example 4b

[0309] A switching element 4b according to the invention comprises a switching layer S.sub.4b according to the invention having a thickness of 24.5 m in the layer sequence depicted below.

TABLE-US-00020 Glass substrate layer 11 Electrically conductive ITO layer 12 Polyimide orientation layer 13 Switching layer S.sub.4b consisting of 99.73% by weight of base mixture #3, 0.27% by weight of chiral dopant S-5011 Polyimide orientation layer 15 Electrically conductive ITO layer 16 Glass substrate layer 17

[0310] Switching element 4b has [0311] a transmission intensity in the clear switching state of 90% (voltage=25 V), [0312] a transmission intensity I.sub.observer in the opaque switching state of 42% (voltage=5 V) and [0313] a transmission intensity I.sub.tot in the opaque switching state of 90%.

[0314] Switching element 4b is irradiated here with parallel light rays on substrate layer 11.

[0315] Thus, in switching element 4b in the switched state of the scattering switching layer, {1(42/90)}.Math.100=53% of the light rays are deflected out of their originally parallel direction by scattering of more than 2.5.

[0316] In the opaque switching state, the molecules of switching layer S.sub.4b are in a state aligned in polydomains.

Example 5

[0317] A switching element 5 according to the invention comprises a switching layer S.sub.5 according to the invention in the following layer sequence:

TABLE-US-00021 Glass substrate layer 11 Electrically conductive ITO layer 12 Rubbed planar-orienting polyimide orientation layer 13 having a pre-tilt angle of 5 Switching layer 14 consisting of 95.23% by weight of base mixture #3, 3.91% by weight of dichroic dyes D1, D2 and D3, i.e. 0.77% by weight of D1, 1.46% by weight of D2 and 1.68% by weight of D3, 0.86% by weight of chiral dopant S-811 Rubbed planar-orienting polyimide orientation layer 15 having a pre-tilt angle of 5, where the rubbing direction runs at an angle of 240 to the rubbing direction of orientation layer 13 Electrically conductive ITO layer 16 Glass substrate layer 17 Glass substrate layer 24 Electrically conductive ITO layer Polyimide orientation layer 25 (rubbed antiparallel, planar) having a small tilt angle Switching layer S.sub.5 consisting of 99.73% by weight of base mixture #3 and 0.27% by weight of chiral dopant S-5011 Polyimide orientation layer 26 (rubbed antiparallel, planar) having a small tilt angle Electrically conductive ITO layer Glass substrate layer 27

[0318] Switching layer 14 here has a layer thickness of 5 m.

[0319] The following switching states are switched:

TABLE-US-00022 Switching Voltage Switching Voltage state in S14 in S14 state in S.sub.5 in S.sub.5 1 light 12 V clear 25 V 2 dark 0 V clear 25 V 3 light 12 V opaque 5 V 4 dark 0 V opaque 5 V

[0320] Switching element 5 has [0321] a transmission intensity in switching state 1 of 74%, [0322] a transmission intensity I.sub.observer in switching state 4 of 14% and [0323] a transmission intensity I.sub.tot in switching state 4 of 23%.

[0324] Switching element 5 is irradiated here with parallel light rays on substrate layer 11.

[0325] Thus, in switching element 5 in the switched state of the scattering switching layer, {1(14/23)}.Math.100=39% of the light rays are deflected out of their originally parallel direction by scattering of more than 2.5.

[0326] In the opaque switching state, the molecules of switching layer S.sub.5 are in a state aligned in polydomains.

Example 6

[0327] A switching element 6 according to the invention comprises a switching layer S.sub.6 according to the invention having a thickness of 25 m in the layer sequence depicted diagrammatically below.

TABLE-US-00023 Glass substrate layer 28 Electrically conductive ITO layer 29 Homeotropically orienting polyimide orientation layer 30 Switching layer S.sub.6 consisting of nematically arranged molecules (component a)) and a polymer component (components b) and c)) with the proportions by weight a) 83.93% by weight of base mixture #1 ( = 5.7) b) 15.99% by weight of reactive mesogen RM82 and c) 0.08% by weight of the photoinitiator Irgacure 651 Homeotropically orienting polyimide orientation layer 31 Electrically conductive ITO layer 32 Glass substrate layer 33

[0328] For the production of switching layer S6, base mixture #1, reactive mesogen RM82 and the photoinitiator Irgacure 651 are mixed in the above-mentioned weight ratio and photopolymerised for 3 minutes.

[0329] Switching element 6 has [0330] a transmission intensity in the clear switching state of 90%, [0331] a transmission intensity I.sub.observer in the opaque switching state of 45% and [0332] a transmission intensity I.sub.tot in the opaque switching state of 87%.

[0333] The switching voltage for the opaque switching state is 150 V.

[0334] Switching element 6 is irradiated here with parallel light rays on substrate layer 28.

[0335] In switching element 6 in the switched state of the scattering switching layer, {1(45/87)}.Math.100=48% of the light rays are deflected out of their originally parallel direction by scattering of more than 2.5.

Example 7

[0336] A switching element 7 according to the invention comprises a switching layer S.sub.7 according to the invention in the layer sequence depicted diagrammatically below.

TABLE-US-00024 Glass substrate layer 28 Electrically conductive ITO layer 29 Homeotropically orienting polyimide orientation layer 30 Switching layer S.sub.7 consisting of nematically arranged molecules (component a)) and a polymer component (components b) and c)) with the proportions by weight a) 89.70% by weight of base mixture #4 b) 10.00% by weight of reactive mesogen R#1 and c) 0.30% by weight of the photoinitiator Irgacure 651 Homeotropically orienting polyimide orientation layer 31 Electrically conductive ITO layer 32 Glass substrate layer 33

[0337] For the production of switching layer S.sub.7, base mixture #4 (clearing point: 81 C., optical anisotropy: 0.1531, dielectric anisotropy: 5.0), reactive mesogen R#1 (available from Merck under the name RM82) and the photoinitiator Irgacure 651 are mixed in the above-mentioned weight ratio and photopolymerised for 3 minutes.

[0338] Switching element 7 exhibits [0339] a diffusive transmission of 0.3% and backwards scattering of 13% at a voltage of 0 volts and [0340] a diffusive transmission of 75.5% and backwards scattering of 13% at a voltage of 60 volts.

Example 8

[0341] A switching element 8 according to the invention comprises a switching layer S.sub.8 according to the invention in the layer sequence depicted diagrammatically below.

TABLE-US-00025 Glass substrate layer 28 Electrically conductive ITO layer 29 Homeotropically orienting polyimide orientation layer 30 Switching layer S.sub.8 consisting of nematically arranged molecules (component a)) and a polymer component (components b) and c)) with the proportions by weight a) 89.70% by weight of base mixture #4 b) 5.0% by weight of reactive mesogen R#1 (diacrylate) and c) 3.00% by weight of reactive mesogen R#2 (monoacrylate) and d) 2.00% by weight of reactive mesogen R#3 (monoacrylate) and e) 0.30% by weight of the photoinitiator Irgacure 651 Polyimide orientation layer 31 Electrically conductive ITO layer 32 Glass substrate layer 33

[0342] For the production of switching layer S.sub.8, base mixture #4 (clearing point: 81 C., optical anisotropy: 0.1531, dielectric anisotropy: 5.0), reactive mesogens R#1, R#2 and R#3 and the photoinitiator Irgacure 651 are mixed in the above-mentioned weight ratio and photopolymerised for 3 minutes.

[0343] Switching element 8 exhibits [0344] a diffusive transmission of 1.1% and backwards scattering of 14% at a voltage of 0 volts and [0345] a diffusive transmission of 82.5% and backwards scattering of 13% at a voltage of 50 volts.