AIST has Developed the “Ultimate Dark Sheet” that does not Reflect Light

“Ultimate dark sheet” that does not reflect light, developed by AIST. Absorbs 99.5% of visible light, can be mass-produced with rubber.

Black is a color that absorbs light, but it still reflects some light when it strikes a black object. However, the National Institute of Advanced Industrial Science and Technology (AIST) has developed the “ultimate dark sheet” that absorbs almost all of the light but does not reflect light. The seat is made of rubber and is said to be excellent in mass productivity. How does it work?

The “dark” hitch is in the surface structure of the sheet. The surface of a normal rubber sheet is flat, but the surface of the dark sheet is covered with a fine conical “jagged” height of several tens of micrometers. . When light enters the jagged structure, part of the light is absorbed by the rubber and the rest of the light is reflected back into the jagged structure. The reflected light hits and gets jagged further, and when it is absorbed, it repeats reflection and absorption, so that most of the light is finally absorbed by the rubber.
When the light enters the jagged edge, the light travels deeper while repeating absorption and reflection, so that the light hardly comes out.

This system has absorbed about 99.5% of light in the ultraviolet to visible light range. Furthermore, “thermal infrared” with a long wavelength among infrared rays is said to have achieved an absorption rate of about 99.9%.

The jagged structure is realized by applying an ion beam launched from a particle accelerator (cyclotron) to a resin substrate. When ions collide with the substrate, a minute conical “crater” is formed on the substrate.

Use the resin substrate as a “mold” and place rubber on it to transfer the structure to the rubber surface. As a result, a structure in which a large number of cones stand on the rubber surface is completed. The dark sheet can be replicated many times from the mold resin substrate, which means that it is excellent in mass production.

The “dark material” with such a high light absorptivity is “Venta Black” by UK Surrey Nanosystems. Venta Black is known as the “black substance in the world” and can absorb more than 99.9% of visible light.

“The (Venta Black) is difficult to use in normal environments because it breaks or peels off when touched,” said Amemiya Kunihisa Research Group Director of AIST, who developed the dark sheet.

“The dark sheet is made of rubber and has excellent durability and flexibility” (same as above), explaining the advantages that Venta Black does not have.

Because the dark sheet is made of rubber, it is durable and flexible.

The research results were announced in April this year, and it is said that we have already received many inquiries. On the other hand, due to the limitations of the particle accelerator device, the maximum size of the mold is 10 cm square, and there are still practical issues such as whether the oil stains on the surface can be sufficiently cleaned.

The company intends to further research toward practical application, such as improving the absorption rate in the visible light region and solving the problem of mold size.

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