Composite infrared windows using silicon and plastic

• US 5,851,631 A
• Filed: 12/08/1995
• Issued: 12/22/1998
• Est. Priority Date: 12/08/1995
• Status: Expired due to Fees

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Lurier, Jeanette, Bitting, Herbert C., Borden, Michael R., Taylor, Christopher D.
• Primary Examiner(s): Thibodeau, Paul J.
• Assistant Examiner(s): Rickman, Holly C.
• Application Number:
  US08/569,536
• Time in Patent Office: 1,110 Days
• Field of Search: 428/34, 428/446, 428/451, 428/337, 428/339, 428/428, 428/911, 428/156, 428/172, 359/585, 359/586, 257/436, 257/437, 257/680, 52/204.7, 52/786.1, 52/788.1, 52/796.1, 52/800.1, 52/800.14, 244/3.16
• US Class Current: 428/156
• CPC Class Codes: B32B 2037/243 Coating
• CPC Class Codes: B32B 2307/558 Impact strength, toughness
• CPC Class Codes: B32B 2605/006 Transparent parts other than made from inorganic glass, e.g. polycarbonate glazings
• CPC Class Codes: B32B 27/06 as the main or only constituent of a layer, which is next to another layer of the same or of a different material next to a layer of a particular substance B32B9/045; next to a bituminous or tarry layer B32B11/046; next to a water setting substance layer B32B13/12; next to a metal layer B32B15/08; next to a glass layer B32B17/10; next to a layer formed of natural mineral fibres or particles B32B19/045; next to a wood layer B32B21/08; next to a cellulosic plastic layer B32B23/08; next to a natural or synthetic rubber layer B32B25/08
• CPC Class Codes: B32B 27/32 comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: B32B 3/30 characterised by a layer formed with recesses or projections, e.g. hollows, grooves, protuberances, ribs apertured layer B32B3/266; layer with cavities or internal voids B32B3/26
• CPC Class Codes: B32B 7/12 using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: B32B 9/045 of synthetic resin
• CPC Class Codes: G02B 5/208 for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation
• CPC Class Codes: Y10T 428/24479 including variation in thickness
• CPC Class Codes: Y10T 428/24612 Composite web or sheet
• CPC Class Codes: Y10T 428/266 of base or substrate
• CPC Class Codes: Y10T 428/269 including synthetic resin or polymer layer or component

Abstract

Low-cost composite infrared windows that are transparent to long wave infrared radiation (8-12 microns) that provide sufficient strength and impact resistance for automotive-type environments, and the like. The windows may be used with night vision systems for automobiles, surveillance imaging systems, and other applications requiring low cost, long wave infrared windows. In one embodiment, the composite infrared window is a sandwich comprised of a polyethylene plastic film bonded with an acrylic adhesive to a relatively thin (0.015-0.040 inch) silicon substrate. The thin silicon substrate is mechanically stiff and low cost, and transmits in the 8-12 micron bandpass. The thin (0.001-0.007 inch) plastic film provides an exterior particle impact absorbing layer sufficient to enable the use of the window in automotive applications. In another embodiment, the infrared window is a dual pane, long wave infrared transmitting window comprising a thin, antireflection coated, silicon window and a plain or reinforced, embossed, plastic window that may be mounted in a frame.

Claims

1. A composite infrared window comprising:

a silicon substrate having a first surface and a second surface;

a first antireflection coating on the first surface of the silicon substrate;

a second antireflection coating on the second surface of the silicon substrate;

an infrared-transmissive plastic film having a surface embossed to reduce reflection therefrom; and

an adhesive disposed between the first antireflection coating and the plastic film and bonding them together.

2. The window of claim 1 wherein the plastic film comprises a polyethylene film.

3. The window of claim 1 wherein the silicon substrate has a thickness between 0.015 and 0.040 inches.

4. The window of claim 3 wherein the adhesive comprises an acrylic adhesive.

5. The window of claim 1 wherein at least one of the antireflection coatings is used to grade the refractive index between the silicon window and the plastic film.

6. The window of claim 1 wherein the silicon substrate comprises float zone silicon.

7. A composite infrared window comprising:

a first window segment comprising a polished silicon wafer;

a first antireflection coating disposed on a first surface of the first window segment;

a second antireflection coating disposed on a second surface of the first window segment;

a second window segment comprising an infrared-transmissive plastic film said second window segment being embossed on both sides; and

a frame for holding the first window segment and the second window segment such that the second window segment overlies but does not contact the first window segment.

8. The window of claim 7 wherein the silicon substrate comprises optical grade silicon.

9. The window of claim 7 wherein the silicon substrate comprises float zone silicon.

10. The window of claim 7 wherein the second window segment is approximately 0.002-0.010 inches thick.

11. The window of claim 7 wherein the polished wafer of silicon is between 0.015 and 0.040 inches thick.