PATENTS

All the technology in this website is in the public domain except Cloud Gel and Weather Panel.

Among Day Chahroudi’s many international patents, the ones below cover in detail the range of Suntek technologies.  Unlike most patents, these intend to elucidate rather than obscure the technology they protect.

LOW-E, CLOUD GEL, AND WEATHER PANEL:
    U.S. Patent 3,953,110; Filed May 20, 1974

WEATHER PANEL:
    U.S. Patent 5,524,381; Filed March 19, 1991; PCT/US93/05173

CLOUD GEL IN PLASIC FILM: MATERIALS, PRODUCTION PROCESSES AND MACHINERY:
    U.S. Patent 5,377,042; Filed December 20, 1993; PCT/US91/05055

CLOUD GEL IN GLASS: MATERIALS, PRODUCTION PROCESSES AND MACHINERY:
    U.S. Patent 7,800,808; Filed October 11, 2005; PCT/US2004/010979

"Success has many fathers, failure none," but the first patent to describe and claim Low-E is the first patent above:

     "In most conventional insulations, infra-red heat losses are prevented by using an infra-red opaque material and by giving the material a very fine structure so that radiation must be emitted and absorbed many times before it can escape. The use of a material which is transparent to visible light yet reflective to infra-red, however, enables the use of a coarse convection baffle without excessive infra-red losses.
     These materials can be vacuum evaporated or chemically deposited. They are all characterized by a loss of carrier mobility at frequencies above the near infra-red. The most common examples are silver, copper, gold, gadolinum, tin oxide, indium oxide, cupric sulfide, and sodium tungstanate bronze. The transmission of these films to visible light can be increased by the use of anti-reflection coatings such as magnesium fluoride."

Chahroudi had Low-E (missivity) coatings vacuum deposited in 1970, three years before joining the MIT faculty. They included copper antireflected on both sides with aluminum oxide and silver antireflected with cerium oxide. Light transmission was high and emissivity was low, but corrosion resistance was poor. Similar coatings had been made previously, but they were used only to heat glazings with electricity. They had low light transmission and/or high emissivoity (heat transmission) because those who made them had no interest in transparent insulation and no knowledge of emissivity.

The Low-E coatings that transmit the most light and the least heat are made, theoretically, from silver. But to have high light transmission, the silver must be only 100 atoms thick, and must form a continuous layer. At that time, an extensive literature stated that it is impossible to make a continuous silver layer thinner than 2000 atoms, and that even then, it corrodes rapidly.

Chahroudi invented a coating for both sides of the silver that does three jobs at once: it makes a 100 atom thick silver layer that is continuous and of theoretical quality; it protects silver from corrosion; and it antireflects silver to greatly increase its light transmission. Then he invented the machinery necessary to make these multiple layers in the laboratory and in production; even on plastic, which is much harder to coat than glass. These materials and production machinery are still the only commercial transparent insulation. (U.S. Patent 4,204,942, filed October, 1978.)

To view a U.S. patent, go to uspto.gov, click "search patents", click "issued patents", and put patent number in "patent number search" box. To view the figures in these patents or applications, click "images" and then click "drawings".