Liquid crystal device and liquid crystal apparatus

• US 5,686,019 A
• Filed: 10/09/1996
• Issued: 11/11/1997
• Est. Priority Date: 05/17/1994
• Status: Expired due to Fees

• Current Assignee: Breed Automotive Technology, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Nakamura, Katsutoshi
• Primary Examiner(s): Wu, Shean C.
• Application Number:
  US08/728,558
• Time in Patent Office: 398 Days
• Field of Search: 252/299.01, 349/84, 349/123, 349/126, 349/128, 349/132, 349/133, 349/135, 349/187, 428/1
• US Class Current: 252/299.01
• CPC Class Codes: C09K 2323/027 Polyimide
• CPC Class Codes: C09K 2323/0271 Polyimidfluoride
• CPC Class Codes: G02F 1/133711 by organic films, e.g. polymeric films
• CPC Class Codes: G02F 1/133719 with coupling agent molecules, e.g. silane
• CPC Class Codes: G02F 1/133723 Polyimide, polyamide-imide

Abstract

A liquid crystal device is constituted by a first substrate and a second substrate disposed opposite to each other, and a liquid crystal lacking cholesteric phase disposed between the first and second substrates. The first substrate has a surface contacting the liquid crystal showing a surface energy γ₁ (dyne/cm) and the second substrate has a surface contacting the liquid crystal showing a surface energy γ₂ (dyne/cm) satisfying γ₁ >γ₂. The surface of the first substrate is provided with a film of a polyimide or an aromatic polyamide, and the surface of the first substrate having been selectively subjected to a uniaxial aligning treatment. As a result, the liquid crystal can assume a stable alignment state of a bookshelf structure or one close thereto having a small layer inclination angle. The resultant device can show a high contrast and a good responsiveness.

Claims

1. A liquid crystal device, comprising:

a first substrate and a second substrate disposed opposite to each other, and a liquid crystal lacking cholesteric phase disposed between the first and second substrates;

said first substrate having a surface contacting the liquid crystal showing a surface energy γ

₁ (dyne/cm) and said second substrate having a surface contacting the liquid crystal showing a surface energy γ

₂ (dyne/cm) satisfying γ

₁ >

γ

₂ ;

said first substrate comprising a surface film of a polyimide or an aromatic polyamide, the surface of said first substrate having been selectively subjected to a uniaxial aligning treatment.

2. A liquid crystal device according to claim 1, wherein γ

₁ ≧

40 (dyne/cm).

3. A liquid crystal device according to claim 1, wherein γ

₁ ≧

45 (dyne/cm).

4. A liquid crystal device according to claim 1, wherein said uniaxial aligning treatment comprises rubbing.

5. A liquid crystal device according to claim 4, wherein said rubbing has been effected in both a forward direction and a direction substantially reverse to the forward direction.

6. A liquid crystal device according to claim 1, wherein γ

₁ -γ

₂ >

9 (dyne/cm).

7. A liquid crystal device according to claim 1, wherein γ

₁ -γ

₂ >

17 (dyne/cm).

8. A liquid crystal device according to claim 1, wherein said liquid crystal comprises at least one mesomorphic compound lacking cholesteric phase and a compound (a) having a solubility limit with said at least one mesomorphic compound added in a proportion of at least 20% of and below the solubility limit.

9. A liquid crystal device according to claim 1, wherein said liquid crystal lacking cholesteric phase comprises at least one species of compounds represented by the following formula (I):

space="preserve" listing-type="equation">P--Q--A--W--B--(T--D).sub.n --U--V (I),

wherein A, B and D independently denote an aromatic ring, a heterocyclic ring, an alicyclic ring, or a condensed ring structure thereof, each capable of having a substituent;

Q, W and T independently denote a single bond, --O--, --COO--, --OCO--, --C.tbd.C--, --CONR--, --NRCO--, --NR--, --CH₂ --, --CH═

N--, --N═

CH--, --CH═

CH--, --COS--, --SCO--, --CH₂ CH₂ --, --CH₂ O-- or --OCH₂ --, wherein R denotes an alkyl group;

P denotes an alkyl group capable of having a substituent;

n denotes 0, 1 or 2;

U denotes --CO--C_m H_2m --, --O--C_m H_2m --, --C_m H_2m CO--, --C_m H_2m O--, --C_m H_2m --, --OSO₂ --, --SO₂ O--, --SO₂ --, --SO₂ --C_m H_2m --, --O--C_m H_2m --O--C_m H_2m --, --C_m H_2m SO₂ --, --C_m H_2m --O--C_m H_2m --O--, --C_m H_2m --N(C_m'"'"' H_2m'"'"'+1)--SO₂ --, --C_m H_2m --N(C_m'"'"' H_2m'"'"'+1)--CO--, --SO₂ --N(C_m'"'"' H_2m'"'"'+1)--C_m H_2m -- or --CO--N(C_m'"'"' H_2m'"'"'+1)--C_m H_2m --, wherein m and m'"'"' independently denote an integer of 1 to 20;

V denotes --(C_p F_2p O)_q C_r F_2r+1, wherein q is an integer of 1-6;

p is an integer of 1-10 which can be independently set where q is plural, and r is an integer of 1-10.

10. A liquid crystal device according to claim 9, wherein said liquid crystal further includes a compound (a) having a solubility limit with said at least one species of compounds represented by the formula (I) in a proportion of at least 20% of and below the solubility limit.

11. A liquid crystal device according to claim 8, wherein said compound (a) is an achiral compound having a core part comprising a substituted or unsubstituted aliphatic ring, aromatic ring, a heterocyclic ring or condensed ring structure of these or a combination of these with a bonding group or a single bond;

and an unsubstituted alkyl group or a substituted alkyl group free from perfluoro-substitution connected to one or both ends of the core part via a bonding group or a single bond.

12. A liquid crystal device according to claim 8, wherein said compound (a) has a melting enthalpy of at least 25 J/g.

13. A liquid crystal device according to claim 8, wherein said compound (a) has an isotropic-liquid crystal phase transition temperature or isotropic-crystal phase transition temperature which is higher than an isotropic-smectic A phase transition temperature of said at least one mesomorphic compound lacking cholesteric phase.

14. A liquid crystal device according to claim 8, wherein said compound (a) is added in a proportion of at least 40% of and below the solubility limit.

15. A liquid crystal device according to claim 1, wherein said liquid crystal is a chiral smectic liquid crystal.

16. A liquid crystal device according to claim 1, wherein said liquid crystal is a ferroelectric liquid crystal.

17. A liquid crystal device according to claim 1, wherein the surface of said first substrate comprises a film of a polyimide represented by the following general formula (II):

##STR20## wherein K denotes ##STR21## L₁ and L₂ respectively denote ##STR22## M₁ denotes a single bond or --O--; and

a denotes 0, 1 or 2.

18. A liquid crystal apparatus, comprising a liquid crystal device according to claim 1, and means for driving the liquid crystal device.

19. A liquid crystal device according to claim 1, wherein said liquid crystal is aligned to form a bookshelf structure.

20. A liquid crystal device according to claim 1, wherein said surface film on said first substrate is a polyimide formed from a diamine and a tetracarboxylic acid having an aromatic ring.

21. A liquid crystal device according to claim 9, wherein said liquid crystal is aligned to form a bookshelf structure.

22. A liquid crystal device according to claim 9, wherein said surface film on said first substrate is a polyimide formed from a diamine and a tetracarboxylic acid having an aromatic ring.

23. A process for producing a liquid crystal device of the type comprising a first substrate and a second substrate disposed opposite to each other, and a liquid crystal lacking cholesteric phase disposed between the first and second substrates;

said process including the steps of;

forming a film of a polyimide or an aromatic polyamide on a surface contacting the liquid crystal of at least said first substrate; and

subjecting said film to a uniaxial aligning treatment such that said first surface of said first substrate contacting said liquid crystal has a surface energy γ

₁ (dyne/cm), wherein said second substrate has a surface contacting the liquid crystal has a surface energy γ

₂ (dyne/cm) satisfying γ

₁ >

γ

₂.

24. A process according to claim 23, wherein said uniaxial aligning treatment comprises rubbing.

25. A process according to claim 23, wherein the liquid crystal contacting the surfaces of the first and second substrates is aligned to form a bookshelf structure.