LIQUID CRYSTAL DAY/NIGHT MIRROR

• US 3,614,210 A
• Filed: 11/06/1969
• Issued: 10/19/1971
• Est. Priority Date: 11/06/1969
• Status: Expired due to Term

• Current Assignee: Sandor Caplan
• Original Assignee: Sandor Caplan
• Inventors: Caplan, Sandor
• Primary Examiner(s): Corbin, John K.
• Application Number:
  US04/874,524
• Time in Patent Office: 712 Days
• Field of Search: 350/16LC,278,281
• US Class Current: 349/195
• CPC Class Codes: B60R 1/088 using a cell of electrically changeable optical characteristic, e.g. liquid-crystal or electrochromic mirrors
• CPC Class Codes: G02F 1/13 based on liquid crystals, e.g. single liquid crystal display cells
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/13756 the liquid crystal selectively assuming a light-scattering state G02F1/1334, G02F1/13718 take precedence

Abstract

The mirror comprises front and rear substrates sandwiching a liquid crystal material therebetween. The front substrate is transparent and has, on its inner surface, a transparent electrode. The rear substrate has, on its inner surface, a metallic electrode having a specular surface. In use, the mirror is mounted relative to a viewer such that images reflected from both the outer surface of the front substrate and the specular surface will reach the viewer. Terminal means are provided for applying a voltage between the electrodes for selectively switching the liquid crystal material between transparent and light-scattering states. Means are provided for obtaining a mirror having a relatively low diffuse reflectance.

Claims

1. A method of selectively obtaining varied brightness reflected images from a day/night mirror comprising:

providing a liquid crystal cell comprising a front surface of low reflectivity, a rear surface of high reflectivity, and a liquid crystal material between said surfaces, said material being reversibly switchable between light-transparent and light-scattering states;

mounting said cell on a vehicle in a manner such that images reflected from both the front and rear surfaces of said cell are visible to a viewer in said vehicle, and selectively applying a voltage across said liquid crystal material and removing said voltage for selectively switching said material between said light-transparent and lightscattering states.

2. A liquid crystal day/night mirror comprising:

front and rear spaced-apart substrates;

a liQuid crystal material sandwiched between said substrates, said material being reversibly switchable between light transparent and light-scattering states;

said front substrate being transparent and having a transparent electrical conductor on the inside surface thereof, said front substrate including a surface having a first reflectivity;

an electrical conductor on the inside surface of said rear substrate; and

a specular surface providing a second reflectivity higher than said first reflectivity on said rear substrate visible through said front substrate when said liquid crystal material is in its transparent state;

the combination of said specular surface and said liquid crystal material, when said material is in its light scattering state, providing diffuse reflectance of light incident on said mirror, the diffuse reflectance of said mirror being less than 45 percent of standard white.

3. A liquid crystal mirror as in claim 2 wherein said specular surface has a reflectivity less than 75 percent.

4. A liquid crystal mirror as in claim 2 wherein said transparent conductor has a light transparency of less than 80 percent.

5. A liquid crystal mirror as in claim 2 wherein said front substrate has a light transparency of less than 80 percent.

6. A liquid crystal mirror as in claim 2 wherein the specular reflectivity of said mirror is between 50 and 55 percent.