Electrochromic mirror with two thin glass elements and a gelled electrochromic medium

• US 5,940,201 A
• Filed: 04/02/1997
• Issued: 08/17/1999
• Est. Priority Date: 04/02/1997
• Status: Expired due to Term

• Current Assignee: Gentex Corporation
• Original Assignee: Gentex Corporation
• Inventors: Tonar, William L., Bauer, Frederick T., Ash, Kevin L.
• Primary Examiner(s): EPPS, GEORGIA Y
• Assistant Examiner(s): Bey, Dawn-Marie
• Application Number:
  US08/834,783
• Time in Patent Office: 867 Days
• Field of Search: 359/267, 359/270, 359/273
• US Class Current: 359/267
• CPC Class Codes: B60R 1/088 using a cell of electrically changeable optical characteristic, e.g. liquid-crystal or electrochromic mirrors
• CPC Class Codes: C09K 9/02 Organic tenebrescent materials
• CPC Class Codes: G02F 1/1503 caused by oxidation-reduction reactions in organic liquid solutions, e.g. viologen solutions
• CPC Class Codes: G02F 1/15165 Polymers
• CPC Class Codes: G02F 1/161 Gaskets; Spacers; Sealing of cells; Filling or closing of cells
• CPC Class Codes: G02F 2001/1502 complementary cell
• CPC Class Codes: G02F 2001/15145 the electrochromic layer comprises a mixture of anodic and cathodic compounds

Abstract

An improved electrochromic rearview mirror for motor vehicles, the mirror incorporating thin front and rear spaced glass elements having a thickness ranging from about 0.5 to about 1.5. A layer of transparent conductive material is placed onto the mirror'"'"'s second surface, and either another layer of transparent conductive material or a combined reflector/electrode is placed onto the mirror'"'"'s third surface. A chamber, defined by the layers on the interior surfaces of the front and rear glass elements and a peripheral sealing member, contains a free-standing gel comprising a solvent and a crosslinked polymer matrix. The chamber further contains at least one electrochromic material in solution with the solvent and interspersed in the crosslinked polymer matrix. The gel cooperatively interacts with the thin glass elements to form a thick, strong unitary member which is resistant to flexing, warping, bowing and/or shattering and further allows the mirror to exhibit reduced vibrational distortion and double imaging.

Claims

1. An electrochromic variable reflectance mirror for motor vehicles, comprising:

front and rear spaced elements, each having front and rear surfaces and each having a thickness ranging from about 0.5 mm to about 1.5 mm;

a layer of transparent conductive material disposed on said rear surface of said front element;

a reflector disposed on one side of said rear element provided that, if said reflector is on said rear surface of said rear element, then said front surface of said rear element contains a layer of a transparent conductive material; and

a perimeter sealing member bonding together said front and rear spaced elements in a spaced-apart relationship to define a chamber therebetween, where said chamber contains a free-standing gel comprising a solvent and a crosslinked polymer matrix, and where said chamber further contains at least one electrochromic material;

where said polymer matrix cooperatively interacts with said front and rear elements, and where said reflector is effective to reflect light through said chamber and said front element when said light reaches said reflector after passing through said front element and said chamber.

2. The electrochromic mirror of claim 1, where said at least one electrochromic material is in solution with said solvent and, as part of said solution, interspersed in said crosslinked polymer matrix.

3. The electrochromic mirror of claim 1, where said front and rear spaced elements each have a thickness ranging from about 0.8 mm to about 1.2 mm.

4. The electrochromic mirror of claim 1, where said front and rear spaced elements each have a thickness of about 1.0 mm.

5. The electrochromic mirror of claim 1, where said polymer matrix results from crosslinking polymer chains and where said polymer chains are formed by polymerizing at least one monomer selected from the group consisting of:

methyl methacrylate;

methyl acrylate;

2-isocyanatoethyl methacrylate;

2-isocyanatoethyl acrylate;

2-hydroxyethyl methacrylate;

2-hydroxyethyl acrylate;

3-hydroxypropyl methacrylate;

vinyl ether n-butyl methyl methacrylate;

tetraethylene glycol vinyl ether;

glycidyl methacrylate;

4-vinylphenol;

acetoacetoxyethyl methacrylate and acetoacetoxyethyl acrylate.

6. The electrochromic mirror according to claim 5, where said polymer chains are cross-linked by reaction with a compound having a functional group selected from the group consisting of aromatic and aliphatic hydroxyl;

aromatic and aliphatic cyanato;

aromatic and aliphatic isocyanato;

aliphatic and aromatic isothiocyanato, with a functionality of at least 2.

7. The electrochromic mirror according to claim 5 where said polymer chains results from the polymerization of at least two distinct monomers.

8. The electrochromic mirror according to claim 7 where said at least two monomers are selected from the group consisting of:

methyl methacrylate;

methyl acrylate;

2-isocyanatoethyl methacrylate;

2-isocyanatoethyl acrylate;

2-hydroxyethyl methacrylate;

2-hydroxyethyl acrylate;

3-hydroxypropyl methacrylate;

vinyl ether n-butyl methyl methacrylate;

tetraethylene glycol divinyl ether;

glycidyl methacrylate;

4-vinylphenol;

acetoacetoxyethyl methacrylate and acetoacetoxyethyl acrylate.

9. The electrochromic mirror according to claim 8, where said at least two monomers are selected from the group consisting of:

methyl methacrylate;

2-isocyanatoethyl methacrylate;

2-hydroxyethyl methacrylate; and

glycidyl methacrylate.

10. The electrochromic mirror according to claim 9 where said at least two monomers comprise 2-hydroxyethyl methacrylate and methyl methacrylate.

11. The electrochromic mirror according to claim 10 where the ratio of 2-hydroxyethyl methacrylate to methyl methacrylate is about 1:

10.

12. The electrochromic mirror according to claim 10 where said polymer chains formed from at least 2-hydroxyethyl methacrylate and methyl methacrylate are crosslinked by a compound having more than one functional group that will react with an active hydrogen.

13. The electrochromic mirror according to claim 9 where said at least two monomers comprise isocyanatoethyl methacrylate and methyl methacrylate.

14. The electrochromic mirror according to claim 13 where the ratio of isocyanatoethyl methacrylate to methyl methacrylate ranges from about 1:

3 to about 1;

50.

15. The electrochromic mirror according to claim 14 where the ratio of isocyanatoethyl methacrylate to methyl methacrylate is about 1:

20.

16. The electrochromic mirror according to claim 14 where said polymer chains formed from at least isocyanatoethyl methacrylate and methyl methacrylate are crosslinked by a compound having a functional group containing more than one active hydrogen.

17. The electrochromic mirror according to claim 5, where said polymer matrix is formed from at least two distinct polymer chains, each of said at least two distinct polymer chains comprise at least one monomer selected from the group consisting of methyl methacrylate and methyl acrylate polymerized with at least one monomer selected from the group consisting of 2-isocyanatoethyl methacrylate;

2-isocyanatoethyl acrylate;

2-hydroxyethyl methacrylate;

2-hydroxyethyl acrylate;

3-hydroxypropyl methacrylate;

glycidyl methacrylate;

4-vinylphenol;

acetoacetoxyethyl methacrylate;

vinyl ether n-butyl methyl methacrylate and acetoacetoxyethyl acrylate, where said first and second polymer chains may be the same or different.

18. The electrochromic mirror according to claim 17 where said first of said at least two polymer chains comprises a copolymer of isocyanatoethyl methacrylate and methyl methacrylate and where said second of said at least two polymer chains comprises a copolymer of 2-hydroxyethyl methacrylate and methyl methacrylate.

19. The electrochromic mirror according to claim 18 where the ratio of isocyanatoethyl methacrylate and methyl methacrylate ranges from about 1:

3 to about 1;

50 and where the ratio of 2-hydroxyethyl methacrylate and methyl methacrylate ranges from about 1;

3 to about 1;

50.

20. The electrochromic mirror according to claim 1, where said cooperative interaction between said free standing gel and said front and rear elements makes said mirror resistant to bending and breaking.

21. The electrochromic mirror according to claim 1, further comprising polymeric beads disposed within said chamber.

22. The electrochromic mirror according to claim 21, where said beads comprise a material that will dissolve within an electrochromic device at ambient or near-ambient temperatures within about 24 hours.

23. The electrochromic mirror according to claim 22, where said beads comprise a copolymer selected from the group consisting of:

MMA/methacrylic acid, MMA/ethylacrylate, MMA/n-butylacrylate, and poly(propylene carbonate).

24. The electrochromic mirror according to claim 22, where said beads do not impart any refractive imperfections to said mirror.

25. The electrochromic mirror according to claim 1, where said layer of transparent conductive material disposed on said rear surface of said front element is a multi-layer stack having a first layer with a high refractive index, a second layer with a low refractive index and a third layer with a high refractive index.

26. The electrochromic mirror according to claim 25, where said first layer comprises ITO and has a thickness between about 200 angstroms and about 400 angstroms, said second layer comprises SiO₂ and has a thickness of between about 200 angstroms and about 400 angstroms, and said third layer comprises ITO and has a thickness of about 1500 angstroms.

27. An electrochromic variable reflectance mirror for motor vehicles, comprising:

bent front and rear spaced elements, each having front and rear surfaces, a layer of transparent conductive material disposed on said rear surface of said front element, a reflector disposed on said front side of said rear element, and a perimeter sealing member bonding together said front and rear spaced elements in a spaced-apart relationship to define a chamber therebetween, where said chamber contains a free-standing gel comprising a solvent and a crosslinked polymer matrix, and where said chamber further contains at least one electrochromic material in solution with said solvent and, as part of said solution, interspersed in said crosslinked polymer matrix, and where said polymer matrix cooperatively interacts with said front and rear elements, and where said reflector material is effective to reflect light through said chamber and said front element when said light reaches said reflector after passing through said front element and said chamber.

28. The electrochromic mirror of claim 27, where said front and rear spaced elements are bent to a convex shape.

29. The electrochromic mirror of claim 27, where said front and rear spaced elements are bent to an aspheric shape.