Fluid light controlling medium for a vehicle rearview mirror

• US 4,917,824 A
• Filed: 01/22/1988
• Issued: 04/17/1990
• Est. Priority Date: 06/09/1986
• Status: Expired due to Fees

• Current Assignee: Donnelly Mirrors Limited
• Original Assignee: Donnelly Mirrors Limited
• Inventors: Lynam, Niall, Molyneux, Keith W.
• Primary Examiner(s): Lee, Mary C.
• Assistant Examiner(s): SCALZO, CATHERINE KILBY
• Application Number:
  US07/146,838
• Time in Patent Office: 816 Days
• Field of Search: 350/266, 350/267, 350/268, 350/277, 350/312, 350/642, 252/582 A, 252/582 P, 252/582 S
• US Class Current: 252/582
• CPC Class Codes: B60R 1/089 using a liquid filtering layer of variable thickness
• CPC Class Codes: G02B 1/06 made of fluids in transparent cells
• CPC Class Codes: G02B 3/12 Fluid-filled or evacuated lenses
• CPC Class Codes: G02B 5/08 Mirrors vehicle mirrors involving special optical features B60R1/08
• CPC Class Codes: G02B 5/24 Liquid filters G02B5/23 takes precedence

Abstract

A fluid composition for use in a rearview mirror of the type which contains a U.V. stable fluid light controlling medium, the composition consisting of a solvent, e.g., propylene carbonate, with a freezing point less than -30° C. and a boiling point greater than 80° C., a dye or mixture of dyes, e.g., a 1,2-chrome dye and a phthalocyanine dye, which is soluble in the solvent and optionally a U.V. stabilizing agent, e.g., a benzophenone, benzotriazole or organo-nickel complex, which is also soluble in the solvent. The dye or mixture of dyes has specifically defined light absorbance characteristics and in use is a fluid which is nontoxic, easy to handle, has a relatively high flash point, and is relatively inert to glass, rubbers and plastics.

Claims

1. A fluid composition for use as a light attenuating medium in a rearview mirror consisting essentially of:

(a) a carrier fluid, the major component of which is propylene carbonate, such that said carrier fluid has a freezing point ≦

-30°

C., a boiling point ≧

80°

C., and a viscosity within 5°

C. of the freezing point thereof of up to 50 centipoise;

(b) a light absorbing dye in solution, rather than in dispersion, in said carrier fluid consisting of an azo, anthraquinoid, phthalocyanine or 1,2-chrome dye or a mixture of two or more thereof, said dye or mixture of dyes remaining in solution at a temperature below -30°

C. and having an absorbance characteristic when combined with the other fluid components according to Beer-Lambert'"'"'s Law;

space="preserve" listing-type="equation">Ix=Ioe.sup.-acx

wherein

Ix=intensity of illumination after-traveling through the fluid;

Io=initial intensity of illumination;

α

=average absorbance coefficient of the dye or dye mixture in the visible range of radiation;

c=concentration of the dye or dye mixture; and

x=light pathlength through the light absorbing medium such that

space="preserve" listing-type="equation">α

cx=A

where A has a value in the range 0.05 to 11.0 and where the maximum value of A for the day position of the mirror is 0.28 and where the minimum value of A for the night position of the mirror is 2.00; and

(c) a U.V. stabilizing agent in solution in said carrier fluid which is a benzophenone, benzotriazole or organo-nickel complex.

2. A fluid composition as claimed in claim 1 wherein the solvent or solvent mixture has a freezing point ≦

-40°

C. and a boiling point ≧

120°

C.

3. A fluid composition as claimed in claim 1 wherein the dye comprises a mixture of Lampronol Black BF and Savinyl Blue GLS in a ratio of 0.6:

1 by weight.

4. A fluid composition as claimed in claim 1 wherein the U.V. stabilizing agent comprises Cyasorb U.V. 5411.

5. A fluid composition as claimed in claim 1 wherein the carrier fluid additionally includes a minor amount of one or more of the following solvents:

methanol, ethanol, isopropanol, 1-butanol, 2-pentanol, n-amyl alcohol, isoamyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, gamma butyrolactone, anisole, p-cymene, dimethyl formamide and amyl acetate.

6. The fluid composition of claim 1 in which said dye is a mixture of a 1,2-chrome complex and a phthalocyanine dye in a ratio of 0.6:

1 by weight.