阅读说明：本技术 制备基于液晶的切换元件的方法 (Method for producing a liquid crystal-based switching element ) 是由 R·梵拉克 P·沃伯恩特 于 2020-05-12 设计创作，主要内容包括：本发明涉及一种用于制备在光学澄清状态及散射状态下可操作且在其间可电切换的切换元件的方法,其中使提供于含有包含一种或多种介晶化合物、一种或多种手性化合物及一种或多种可聚合介晶化合物的液晶介质的层中的该一种或多种可聚合介晶化合物在直流(DC)电场的存在下在该层中经受聚合。本发明进一步涉及一种通过进行该方法获得或可由其获得的切换元件且涉及该切换元件在窗中的用途。(The invention relates to a method for preparing a switching element operable in an optically clear state and a scattering state and electrically switchable therebetween, wherein a layer provided in a liquid crystalline medium containing one or more mesogenic compounds, one or more chiral compounds and one or more polymerizable mesogenic compounds is subjected to polymerization in the presence of a Direct Current (DC) electric field in the layer. The invention further relates to a switching element obtained or obtainable by carrying out the method and to the use of the switching element in a window.)

1. A method for making a switching element operable in an optically clear state and a scattering state and electrically switchable therebetween, comprising

(i) Providing a liquid-crystalline medium comprising one or more mesogenic compounds, one or more chiral compounds and one or more polymerizable mesogenic compounds, which is inserted as a layer between two opposite transparent substrates each provided with electrodes,

wherein the liquid crystal medium has a clearing point of 70 ℃ or higher, and

wherein the one or more polymerizable mesogenic compounds are present in the medium in an amount of 4% by weight or less, based on the total content of the medium, and

(ii) polymerizing the one or more polymerizable mesogenic compounds in the layer in the presence of a direct current electric field.

2. Method according to claim 1, wherein the applied direct current electric field induces homeotropic alignment in the layer comprising the liquid crystalline medium, wherein the layer preferably has a thickness in the range of 4 μ ι η to 40 μ ι η, more preferably 10 μ ι η to 25 μ ι η.

3. The method according to claim 1 or 2, wherein the polymerization as set forth in step (ii) is carried out by photo-polymerization, preferably using UV light.

4. A process according to one or more of claims 1 to 3, wherein the liquid-crystalline medium as set forth in claim 1 further comprises one or more photoinitiators.

5. Method according to one or more of claims 1 to 4, wherein one or more of the one or more polymerisable mesogenic compounds comprises one, two or more acrylate and/or methacrylate groups.

6. The process according to one or more of claims 1 to 5, wherein the polymerization as set forth in step (ii) uses a monomer having a molecular weight ranging between 0.1mW/cm²To 100mW/cm²Preferably the UV light is carried out for a period of 1 minute to 240 minutes.

7. The process according to one or more of claims 1 to 6, wherein after step (ii), the heat treatment is preferably carried out in the presence of an electric field, in particular in the presence of a direct current electric field.

8. A method according to one or more of claims 1 to 7, wherein the electrode is arranged as a transparent electrically conductive layer supported on the substrate and facing the liquid-crystalline medium,

wherein preferably, the transparent conductive layers are respectively embedded between two transparent dielectric layers,

and wherein optionally further an alignment layer is provided in direct contact with the liquid crystalline medium.

9. Method according to one or more of claims 1 to 8, wherein the liquid-crystalline medium as set forth in claim 1 contains at least 15% by weight, based on the total content of the medium, of one or more mesogenic compounds of the formula I

Wherein

R¹And R²Independently of one another, represent a group selected from: F. cl, CF₃、OCF₃And a linear or branched alkyl or alkoxy group having 1 to 15 carbon atoms or a linear or branched alkenyl group having 2 to 15 carbon atoms, said alkyl or said alkoxy or said alkenyl group being unsubstituted, CN or CF₃Mono-or polysubstituted with halogen and wherein one or more CH₂The radicals may in each case, independently of one another, be replaced by-O-, -S-, -CO-, -COO-, -OCO-, -OCOO-or-C.ident.C-in such a way that the oxygen atoms are not linked directly to one another,

A¹¹to represent

n represents 0 or 1, and

A²¹、A³¹and A⁴¹Independently of each other represent

Wherein L, identically or differently at each occurrence, is a halogen selected from F, Cl and Br.

10. The process according to one or more of claims 1 to 9, wherein the liquid-crystalline medium further comprises one or more mesogenic compounds selected from the group of compounds of formulae II and III

Wherein

R³、R⁴、R⁵And R⁶Independently of one another, represent a group selected from: F. CF (compact flash)₃、OCF₃CN and a linear or branched alkyl or alkoxy group having 1 to 15 carbon atoms or a linear or branched alkenyl group having 2 to 15 carbon atoms, the alkyl or alkoxy group or the alkenyl group being unsubstituted, CN or CF₃Mono-or polysubstituted with halogen and wherein one or more CH₂The radicals may in each case be replaced, independently of one another, by-O-, -S-, -CO-, -COO-, -OCO-, -OCOO-or-C.ident.C-in such a way that the oxygen atoms are not linked directly to one another, and

L¹、L²、L³、L⁴and L⁵Independently of one another, H or F.

11. The process according to one or more of claims 1 to 10, wherein the liquid-crystalline medium exhibits a positive dielectric anisotropy Δ ∈ and an optical anisotropy Δ n of 0.13 or more, measured at 20 ℃ and 589nm, and

wherein the one or more chiral compounds contained in the liquid-crystalline medium have a size of 5 μm^-1Or greater absolute helical twisting forceThe value is obtained.

12. A switching element operable in an optically clear state and a scattering state and electrically switchable therebetween, wherein the switching element is obtained or obtainable by performing a method according to one or more of claims 1 to 11.

13. A switching element operable in an optically clear state and a scattering state and electrically switchable therebetween, comprising a switching layer comprising a material comprising

-a liquid-crystalline medium comprising one or more mesogenic compounds and one or more chiral compounds, wherein the liquid-crystalline medium has a clearing point of 70 ℃ or more, and

a polymeric component comprising one or more polymeric structures obtained or obtainable by polymerizing one or more polymerizable mesogenic compounds, wherein the polymeric component is contained in the material in an amount of 4 wt.% or less based on the total content of the material,

wherein the switching element has a haze in the optically clear state of less than 6%, preferably determined according to ASTM D1003.

14. A switching element according to claim 12 or 13, wherein the liquid crystalline medium exhibits a helical pitch of 0.55 μm or more in the scattering state.

15. A window comprising a switching element according to one or more of claims 12 to 14.

Examples

The liquid crystal mixture and the composite system are realized by the compositions and characteristics as given below. The properties and optical properties were investigated.

Reference example 1

Liquid-crystalline base mixture B-1 was prepared and characterized by its general physical properties, having the compositions and characteristics indicated in the following table.

Reference example 2

A liquid-crystalline base mixture B-2 was prepared and characterized by its general physical properties, having the compositions and characteristics indicated in the following table.

Reference example 3

A liquid-crystalline base mixture B-3 was prepared and characterized by its general physical properties, having the compositions and characteristics indicated in the following table.

Reference example 4

A liquid-crystalline base mixture B-4 was prepared and was characterized by its general physical properties, having the compositions and characteristics indicated in the following table.

Reference example 5

A liquid-crystalline base mixture B-5 was prepared and characterized by its general physical properties, having the compositions and characteristics indicated in the following table.

Reference example 6

A liquid-crystalline base mixture B-6 was prepared and characterized by its general physical properties, having the compositions and characteristics indicated in the following table.

Reference example 7

A liquid-crystalline base mixture B-7 was prepared and characterized by its general physical properties, having the compositions and characteristics indicated in the following table.

Reference example 8

A liquid-crystalline base mixture B-8 was prepared and characterized by its general physical properties, having the compositions and characteristics indicated in the following table.

Example 1

Cholesteric mixture C-1 was prepared by mixing: 98.78% of mixture B-1 as described above with reference to example 1 and 0.44% of chiral dopant R-5011 from Merck KGaA, Darmstadt, Germany, 0.75% of a compound of the formula RM-A,

and 0.03% of a compound of formula A-1

The mixture C-1 was filled into an electro-optical cell with a glass substrate (405 mm. times.400 mm) with ITO electrodes and a polyimide alignment layer (AL-1254, rubbed with TN), with a cell gap of 25 μm.

The box was preheated at 40 ℃ for 15 minutes.

Subsequently, when a DC voltage (70V) was applied, a voltage of 4mW/cm was applied by irradiating with UV light (Philips iSOLde CLEO Performance 80W with cut-off filter²Light intensity) the irradiation box was subjected to polymerization at 40 ℃ for 60 minutes.

After photopolymerization, the cell was subjected to a heat treatment at 150 ℃ for 30 minutes, with no voltage applied.

Haze of the obtained cell was measured using a haze meter i (haze-gard i) from BYK-Gardner.

The resulting box had a clear state with 4.2% haze and a private (scattering) state with 95.8% haze.

The cell exhibits favorable homogeneous clear and scattering states and favorable switching and electro-optical properties. In addition, the cartridge exhibits advantageous low pressure sensitivity.

Comparative example 1

Cholesteric mixture C-1 was prepared as described in example 1 above. The mixture C-1 was filled into an electro-optical cell with a glass substrate (405 mm. times.400 mm) with ITO electrodes and a polyimide alignment layer (AL-1254, rubbed with TN), with a cell gap of 25 μm.

The box was preheated at 40 ℃ for 15 minutes.

Subsequently, when a square wave voltage (70V (peak to peak), 20Hz) was applied, a UV light (Philips iSolde CLEO Performance 80W with cut-off filter, 4 mW/cm) was passed through²Light intensity) the irradiation box was subjected to polymerization at 40 ℃ for 30 minutes.

After photopolymerization, the cell was subjected to a heat treatment at 150 ℃ for 30 minutes, with no voltage applied.

Haze of the obtained cell was measured using a haze meter i from BYK-Gardner.

The resulting cassette had a clear state with 8.9% haze and a private (scattering) state with 96.9% haze.

The box in the clear state exhibited a relatively large residual haze, discernible as a white turbid appearance.

Example 2

Cholesteric mixture C-1 was prepared as described in example 1 above. The mixture C-1 was filled into an electro-optical cell with a glass substrate with ITO electrodes and a polyimide alignment layer (AL-1254, rubbed with TN), with a cell gap of 25 μm.

The box was preheated at 40 ℃ for 15 minutes.

Subsequently, when a DC voltage (70V) was applied, a voltage of 4mW/cm was applied by irradiating with UV light (Philips iSOLde CLEO Performance 80W with cut-off filter²Light intensity) the irradiation box was subjected to polymerization at 40 ℃ for 30 minutes.

After photopolymerization, the cell was subjected to a heat treatment at 150 ℃ for 30 minutes, with a DC voltage (70V) applied.

Haze of the obtained cell was measured using a haze meter i from BYK-Gardner.

The resulting box had a clear state with 2.2% haze and a private (scattering) state with 95.8% haze.

The cell exhibits favorable homogeneous clear and scattering states and favorable switching and electro-optical properties. In addition, the cartridge exhibits advantageous low pressure sensitivity.

Comparative example 2

Cholesteric mixture C-1 was prepared as described in example 1 above. The mixture C-1 was filled into an electro-optical cell with a glass substrate (405 mm. times.400 mm) with ITO electrodes and a polyimide alignment layer (AL-1254, rubbed with TN), with a cell gap of 25 μm.

The box was preheated at 40 ℃ for 15 minutes.

Subsequently, when a square wave voltage (70V, 20Hz) was applied, a UV light (Philips iSolde CLEO Performance 80W with cut-off filter, 4 mW/cm) was passed through²Light intensity) the irradiation box was subjected to polymerization at 40 ℃ for 30 minutes.

After photopolymerization, the cell was subjected to a heat treatment at 150 ℃ for 30 minutes, with a square wave voltage (70V, 20Hz) applied.

Haze of the obtained cell was measured using a haze meter i from BYK-Gardner.

The resulting cassette had a clear state with 6.2% haze and a private (scattering) state with 96.0% haze.

The box in the clear state exhibited a relatively large residual haze, discernible as a white turbid appearance.

Example 3

Cholesteric mixture C-2 was prepared by mixing: 98.89% of mixture B-1 as described above with reference to example 1 and 0.33% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 0.75% of the compound of the formula RM-A as shown above in example 1 and 0.03% of the compound of the formula A-1 as shown above in example 1.

The mixture C-2 was filled into an electro-optical cell with a glass substrate with ITO electrodes (triangular shape, side length 1200mm) and a polyimide alignment layer (AL-1254, rubbed with TN), with a cell gap of 25 μm.

The box was preheated at 40 ℃ for 15 minutes.

Subsequently, when a DC voltage (70V) was applied, a voltage of 4mW/cm was applied by irradiating with UV light (Philips iSOLde CLEO Performance 80W with cut-off filter²Light intensity) the irradiation box was subjected to polymerization at 40 ℃ for 60 minutes.

After photopolymerization, the cell was subjected to a heat treatment at 150 ℃ for 30 minutes, with no voltage applied.

The box exhibits a uniform privacy and clear state in which no undesirable residual haze is discernable. In addition, the cartridge exhibits advantageous low pressure sensitivity.

Comparative example 3

Cholesteric mixture C-1 was prepared as described in example 1 above. The mixture C-1 was filled into an electro-optical cell with a glass substrate (405 mm. times.400 mm) with ITO electrodes and a polyimide alignment layer (AL-1254, rubbed with TN), with a cell gap of 25 μm.

The box was preheated at 40 ℃ for 15 minutes.

Subsequently, when a square wave voltage (70V, 0.2Hz) was applied, UV light (Phi with cut-off filter) was passed throughlips iSOLde CLEO Performance 80W，4mW/cm²Light intensity) the irradiation box was subjected to polymerization at 40 ℃ for 30 minutes.

After photopolymerization, the cell was subjected to a heat treatment at 150 ℃ for 30 minutes, with no voltage applied.

The obtained box exhibits a non-uniform appearance in both the clear state and the private state.

Comparative example 4

Cholesteric mixture C-1 was prepared as described in example 1 above. The mixture C-1 was filled into an electro-optical cell with a glass substrate (405 mm. times.400 mm) with ITO electrodes and a polyimide alignment layer (AL-1254, rubbed with TN), with a cell gap of 25 μm.

The box was preheated at 40 ℃ for 15 minutes.

Subsequently, when a square wave voltage (70V, dynamic frequency: nonlinear logarithmic shape, starting at 0.1Hz and ramping up to 40Hz over 5 minutes, followed by a restart) was applied, by passing with UV light (Philips iSOLde CLEO Performance 80W with cut-off filter, 4 mW/cm)²Light intensity) the irradiation box was subjected to polymerization at 40 ℃ for 30 minutes.

After photopolymerization, the cell was subjected to a heat treatment at 150 ℃ for 30 minutes, with no voltage applied.

The obtained box exhibits a non-uniform appearance in both the clear state and the private state.

Example 4

Cholesteric mixture C-3 was prepared by mixing: 98.89% of mixture B-2 as described above with reference to example 2 and 0.33% of chiral dopant R-5011, commercially available from Merck KGaA, Darmstadt, Germany, 0.75% of the compound of formula RM-A as shown above in example 1 and 0.03% of the compound of formula A-1 as shown above in example 1.

Mixture C-3 was processed according to example 1 to obtain an electro-optical cell.

The cell exhibits favorable homogeneous clear and scattering states and favorable switching and electro-optical properties. In addition, the cartridge exhibits advantageous low pressure sensitivity.

Example 5

Cholesteric mixture C-4 was prepared by mixing: 98.64% of the mixture B-1 as described above with reference to example 1 and 0.42% of a chiral dopant R-5011 from Merck KGaA, Darmstadt, Germany, 0.45% of a compound of the formula RM-B

0.45% of a compound of formula RM-C

And 0.04% of a photoinitiator available from Ciba, Switzerland651 (hereinafter abbreviated as IRG-651)

Mixture C-4 was processed according to example 1 to obtain an electro-optical cell.

The cell exhibits favorable homogeneous clear and scattering states and favorable switching and electro-optical properties. In addition, the cartridge exhibits advantageous low pressure sensitivity.

Example 6

Cholesteric mixture C-5 was prepared by mixing mixture B-3 as described above with reference to example 3 with chiral dopant S-1011 available from Merck KGaA, Darmstadt, Germany so that a pitch of 2 μm was obtained, wherein 99.25% of this mixture was further mixed with 0.75% of a compound of formula RM-a as shown in example 1 above to obtain mixture C-5.

Mixture C-5 was further processed as described in example 1.

The cell exhibits favorable clarifying and scattering states and favorable switching and electro-optical properties. In addition, the cartridge exhibits advantageous low pressure sensitivity.

Example 7

Cholesteric mixture C-6 was prepared by mixing: 98.28% of mixture B-4 as described in reference example 4 and 0.42% of chiral dopant R-5011, commercially available from Merck KGaA, Darmstadt, Germany, 0.63% of the compound of the formula RM-B as shown in example 5 above, 0.63% of the compound of the formula RM-C as shown in example 5 above and 0.04% of IRG-651.

Mixture C-6 was further processed as described in example 1.

The cell exhibits favorable clarifying and scattering states and favorable switching and electro-optical properties. In addition, the cartridge exhibits advantageous low pressure sensitivity.

Examples 8 to 11

Cholesteric mixtures C-7, C-8, C-9 and C-10 were prepared as described for C-1 in example 1 above, using mixtures B-5, B-6, B-7 and B-8 instead of B-1 as described in reference examples 5, 6, 7 and 8, respectively.

The mixtures C-7, C-8, C-9 and C-10 were further processed as described in example 2.

The cell exhibits favorable clarifying and scattering states and favorable switching and electro-optical properties. In addition, the cartridge exhibits advantageous low pressure sensitivity.

Example 12

Cholesteric mixture C-11 was prepared by mixing: 98.60% of mixture B-2 as described above with reference to example 2 and 0.65% of chiral dopant R-5011, commercially available from Merck KGaA, Darmstadt, Germany and 0.75% of a compound of the formula RM-A as shown above in example 1.

Mixture C-11 was processed according to example 1 to obtain an electro-optical cell.

The cell exhibits favorable homogeneous clear and scattering states and favorable switching and electro-optical properties. In addition, the cartridge exhibits advantageous low pressure sensitivity.