Electrooptical liquid crystal system

• US 5,476,611 A
• Filed: 03/31/1993
• Issued: 12/19/1995
• Est. Priority Date: 03/31/1992
• Status: Expired due to Fees

• Current Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Original Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Inventors: Nolan, Patrick, Coates, David
• Primary Examiner(s): Lovering, Richard D.
• Assistant Examiner(s): KELLY, CYNTHIA HARRIS
• Application Number:
  US08/041,422
• Time in Patent Office: 993 Days
• Field of Search: 252/299.61, 252/299.63, 252/299.66, 252/299.01, 359/103
• US Class Current: 252/299.01
• CPC Class Codes: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals

Abstract

An electrooptical system containing a PDLC film is disclosed. The precursor of the PDLC film comprises

(a) 30-85 wt. % of a liquid crystal mixture containing one or more compounds of the formula I ##STR1## wherein R, Z¹, Z², A¹, A², X², X², Q, n and Y are as defined herein,

(b) 15-68 wt. % of the precursor of the polymer matrix at least comprising

a component A containing at least 5 wt. % of one or more at least difunctional thiol monomers and/or oligomers,

a component B containing at least 10 wt. % of one or more at least difunctional monomers and/or oligomers of the ene type,

a component C containing at least 3 wt. % of one or more monofunctional monomers and/or oligomers of the ene type with a molar mass of less than 250 g/mol,

optionally a component D containing polymerizable compounds other than ene-type or thiol-type compounds; and

(c) 0.1-5 wt. % of a radical photoinitiator, with the mass ratios given under (a), (b) and (c) being related to the mass of the precursor of the PDLC film and the mass ratios of the components A, B and C relating to the mass of the precursor of the polymer matrix.

Claims

1. An electrooptical system comprising

2 electrode layers having a PDLC film positioned therebetween, said PDLC film Comprising a liquid crystal mixture in the form of microdroplets within an optically isotropic, transparent polymer matrix;

wherein one of the refractive indices of said liquid crystal mixture is matched to the refractive index of said polymer matrix;

wherein one of the two switching states of said system has reduced transmission compared with the other switching state, independent of the polarization of the incident light; and

said PDLC film is formed from a precursor comprising;

(a) 30-85 wt. % of a liquid crystal mixture containing one or more compounds of formula I ##STR15## wherein Z¹ and Z² independently of one another, are each a single bond, --CH₂ CH₂ --, --COO--, --OCO-- or --C.tbd.C--, ##STR16## independently of one another, are each trans-1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, or 3,5-difluoro-1,4-phenylene, and one of ##STR17## can also be pyrimidine-2,5-diyl, pyridine-2,5-diyl- or trans-1,3-dioxane-2,5-diyl,

X¹ and X² independently of one another, are each H or F,

Q is CF₂, OCF₂, C₂ F₄, OC₂ F₄ or a single bond,

Y is H, F, Cl or CN,

n is 0, 1 or 2, and

R is alkyl having up to 13 C atoms, in which one or two non-adjacent CH₂ groups can also be replaced by --O--, --CH═

CH-- or a combination thereof;

(b) 15-68 wt. % of a precursor of the polymer matrix comprising

a component A containing at least 5 wt. % of one or more at least difunctional thiol monomers, one or more at least difunctional oligomers or combinations thereof,

a component B containing at least 10 wt. % of one or more at least difunctional monomers of the ene type, one or more at least difunctional oligomers of the ene type or combinations thereof,

a component C containing at least 3 wt. % of one or more monofunctional monomers of the ene type with a molar mass of less than 250 g/mol, one or more monofunctional oligomers of the ene type with a molar mass of less than 250 g/mol or combinations thereof,

optionally a component D containing polymerizable compounds other than ene-type or thiol-type compounds,

wherein the average overall functionality of the ene type monomers and oligomers in the polymer matrix precursor is less than 2; and

(c) 0.1-5 wt. % of a radical photoinitiator, with the weight percentages given for (a), (b) and (c) being based on the total mass of the PDLC film precursor, and the weight percentages given in components A, B and C being based on the total mass of the polymer matrix precursor.

2. An electrooptical system according to claim 1, wherein said system is non-actively addressed and the liquid crystal mixture is based on carbonitrile compounds of formula I wherein Q--Y is CN.

3. An electrooptical system according to claim 2, wherein the liquid crystal mixture contains at least 6 compounds.

4. An electrooptical system according to claim 2, wherein the ratio of 3- and 4-ring compounds to 2-ring compounds in the liquid crystal mixture is not less than 0.18.

5. An electrooptical system according to claim 3, wherein the ratio of 3- and 4-ring compounds to 2-ring compounds in the liquid crystal mixture is not less than 0.18.

13. An electrooptical system according to claim 1, wherein the average overall functionality of ene type monomers and oligomers in the polymer matrix precursor is ≦

1.85.

15. An electrooptical system according to claim 1, wherein the PDLC film precursor exhibits a saturation voltage of less than 25 V.

18. An electrooptical system according to claim 1, wherein the polymer matrix precursor contains more than 10 wt. % of component A.

6. A PDLC film precursor comprising

(a) 30-85 wt. % of a liquid crystal mixture containing one or more compounds of formula I ##STR18## wherein Z¹ and Z² independently of one another, are each a single bond, --CH₂ CH₂ --, --COO--, --OCO+or --C.tbd.C--, ##STR19## independently of one another, are each trans-1,4-cyclohexylene, 1,4-phenyl ene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, or 3,5-difluoro-1,4-phenylene, and one of ##STR20## can also be pyrimidine-2,5-diyl, pyridine-2,5-diyl or trans-1,3-dioxane-2,5-diyl,

X¹ and X² independently of one another, are each H or F,

Q is CF₂, OCF₂, C₂ F₄, OC₂ F₄ or a single bond,

Y is H, F, Cl or CN,

n is 0, 1 or 2, and

R is alkyl having up to 13 C atoms, in which one or two non-adjacent CH₂ groups can also be replaced by --O--, --CH=CH-- or a combination thereof;

(b) 15-68 wt. % of a precursor of the polymer matrix comprising

a component A containing at least 5 wt. % of one or more at least difunctional thiol monomers, one or more at least difunctional oligomers or combinations thereof,

a component B containing at least 10 wt. % of one or more at least difunctional monomers of the ene type, one or more at least difunctional oligomers of the ene type or combinations thereof,

a component C containing at least 3 wt. % of one or more monofunctional monomers of the ene type with a molar mass of less than 250 g/mol, one or more monofunctional oligomers of the ene type with a molar mass of less than 250 g/mol or combinations thereof,

optionally a component D containing polymerizable compounds other than ene-type or thiol-type compounds,

wherein the average overall functionality of the ene type monomers and oligomers in the polymer matrix precursor is less than 2; and

(c) 0.1-5 wt. % of a radical photoinitiator, with the weight percentages given for (a), (b) and (c) being based on the total mass of the PDLC film precursor, and the weight percentages given in components A, B and C being based on the total mass of the polymer matrix precursor.

7. A PDLC film precursor according to claim 6, wherein said system is non-actively addressed and the liquid crystal mixture is based on carbonitrile compounds of formula I wherein Q--Y is CN.

8. A PDLC film precursor according to claim 7, wherein the liquid crystal mixture contains at least 6 compounds.

9. A PDLC film precursor according to claim 7, wherein the ratio of 3- and 4-ring compounds to 2-ring compounds in the liquid crystal mixture is not less than 0.18.

10. A PDLC film precursor according to claim 8, wherein the ratio of 3- and 4-ring compounds to 2-ring compounds in the liquid crystal mixture is not less than 0.18.

11. An electrooptical system comprising

2 electrode layers having a PDLC film positioned therebetween, said PDLC film comprising a liquid crystal mixture in the form of microdroplets within an optically isotropic, transparent polymer matrix;

wherein one of the refractive indices of said liquid crystal mixture is matched to the refractive index of said polymer matrix;

wherein one of the two switching states of said system has reduced transmission compared with the other switching state, independent of the polarization of the incident light; and

said PDLC film is formed from a precursor comprising;

(a) 30-85 wt. % of a liquid crystal mixture containing one or more compounds of formula I ##STR21## wherein Z¹ and Z² independently of one another, are each a single bond, --CH₂ CH₂ --, --COO--, --OCO-- or --C.tbd.C--, ##STR22## independently of one another, are each trans-1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, or 3,5-difluoro-1,4-phenylene, and one of ##STR23## can also be pyrimidine-2,5-diyl, pyridine-2,5-diyl or trans-1,3-dioxane-2,5-diyl,

X¹ and X² independently of one another, are each H or F,

Q is CF₂, OCF₂, C₂ F₄, OC₂ F₄ or a single bond,

Y is H, F, Cl or CN,

n is 0, 1 or 2, and

R is alkyl having up to 13 C atoms, in which one or two non-adjacent CH₂ groups can also be replaced by --O--, --CH═

CH-- or a combination thereof;

(b) 15-68 wt. % of a precursor of the polymer matrix comprising

a component A containing at least 5 wt. % of one or more at least difunctional thiol monomers, one or more at least difunctional oligomers or combinations thereof,

a component B containing at least 10 wt. % of one or more at least difunctional monomers of the ene type, one or more at least difunctional oligomers of the ene type or combinations thereof,

a component C containing at least 3 wt. % of one or more monofunctional monomers of the ene type with a molar mass of less than 250 g/mol, one or more monofunctional oligomers of the ene type with a molar mass of less than 250 g/mol or combinations thereof,

optionally a component D containing polymerizable compounds other than ene-type or thiol-type compounds,

wherein the average overall functionality of the ene type monomers and oligomers in the polymer matrix precursor is 1.1 to less than 2; and

(c) 0.1-5 wt. % of a radical photoinitiator, with the weight percentages given for (a), (b) and (c) being based on the total mass of the PDLC film precursor, and the weight percentages given in components A, B and C being based on the total mass of the polymer matrix precursor.

14. An electrooptical system according to claim 11, wherein the average overall functionality of ene type monomers and oligomers in the polymer matrix precursor is 1.1 up to or equal to 1.85.

16. An electrooptical system according to claim 11, wherein the PDLC film precursor exhibits a saturation voltage of less than 25 V.

19. An electrooptical system according to claim 11, wherein the polymer matrix precursor contains more than 10 wt. % of component A.

12. An electrooptical system comprising

2 electrode layers having a PDLC film positioned therebetween, said PDLC film comprising a liquid crystal mixture in the form of microdroplets within an optically isotropic, transparent polymer matrix;

wherein one of the refractive indices of said liquid crystal mixture is matched to the refractive index of said polymer matrix;

wherein one of the two switching states of said system has reduced transmission compared with the other switching state, independent of the polarization of the incident light; and

said PDLC film is formed from a precursor comprising;

(a) 30-85 wt. % of a liquid crystal mixture containing one or more compounds of formula I ##STR24## wherein Z¹ and Z² independently of one another, are each a single bond, --CH₂ CH₂ --, --COO--, --OCO-- or --C.tbd.C--, ##STR25## independently of one another, are each trans-1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, or 3,5-difluoro-1,4-phenylene, and one of ##STR26## can also be pyrimidine-2,5-diyl, pyridine-2,5-diyl or trans-1,3-dioxane-2,5-diyl,

X¹ and X² independently of one another, are each H or F,

Q is CF₂, OCF₂, C₂ F₄, OC₂ F₄ or a single bond,

Y is H, F, Cl or CN,

n is 0, 1 or 2, and

R is alkyl having up to 13 C atoms, in which one or two non-adjacent CH₂ groups can also be replaced by --O--, --CH═

CH-- or a combination thereof;

(b) 15-68 wt. % of a precursor of the polymer matrix consisting essentially of

a component A containing at least 5 wt. % of one or more at least difunctional thiol monomers, one or more at least difunctional oligomers or combinations thereof,

a component B containing at least 10 wt. % of one or more difunctional monomers of the ene type, one or more difunctional oligomers of the ene type or combinations thereof,

a component C containing at least 3 wt. % of one or more monofunctional monomers of the ene type with a molar mass of less than 250 g/mol, one or more monofunctional oligomers of the ene type with a molar mass of less than 250 g/mol or combinations thereof,

optionally a component D containing polymerizable compounds other than ene-type or thiol-type compounds,

(c) 0.1-5 wt. % of a radical photoinitiator, with the weight percentages given for (a), (b) and (c) being based on the total mass of the PDLC film precursor, and the weight percentages given in components A, B and C being based on the total mass of the polymer matrix precursor.

17. An electrooptical system according to claim 12, wherein the PDLC film precursor exhibits a saturation voltage of less than 25 V.

20. An electrooptical system according to claim 12, wherein the polymer matrix precursor contains more than 10 wt. % of component A.