An anti-forgery color conversion film includes a photonic crystal structure whose color is converted by an external stimulus such as a breath. The photonic crystal structure includes a first refractive index layer including a first polymer exhibiting a first refractive index; and a second refractive index layer which is alternately laminated with the first refractive index layer and includes a second polymer exhibiting a second refractive index. A consumer who purchases an article including the color conversion film may easily distinguish the authenticity of the article.

An anti-forgery color conversion film includes a photonic crystal structure whose color is converted by an external stimulus such as a breath. The photonic crystal structure includes a first refractive index layer including a first polymer exhibiting a first refractive index; and a second refractive index layer which is alternately laminated with the first refractive index layer and includes a second polymer exhibiting a second refractive index. A consumer who purchases an article including the color conversion film may easily distinguish the authenticity of the article.

A method can include milling a plurality of silicon particles to form a plurality of milled silicon particles. The milled silicon particles can optionally include collecting the milled silicon particles, powdering the milled silicon particles, and milling the milled silicon particles a second time.

A silicon material can include a silicon aggregate comprising a plurality of porous silicon nanoparticles welded together. The silicon aggregate can optionally have a polyhedral morphology. A method can include: receiving a plurality of porous silicon nanoparticles and cold welding the plurality of porous silicon nanoparticles into an aggregated silicon particle.

A silicon material can include a silicon aggregate comprising a plurality of porous silicon nanoparticles welded together. The silicon aggregate can optionally have a polyhedral morphology. A method can include: receiving a plurality of porous silicon nanoparticles and cold welding the plurality of porous silicon nanoparticles into an aggregated silicon particle.

A separator for a rechargeable battery includes a porous substrate and a heat resistance layer on at least one surface of the porous substrate. The heat resistance layer includes an acryl-based copolymer, an alkali metal, and a filler. The acryl-based copolymer includes a unit derived from (meth)acrylate or (meth)acrylic acid, a cyano group-containing unit, and a sulfonate group-containing unit.

A separator for a rechargeable battery includes a porous substrate and a heat resistance layer on at least one surface of the porous substrate. The heat resistance layer includes an acryl-based copolymer, an alkali metal, and a filler. The acryl-based copolymer includes a unit derived from (meth)acrylate or (meth)acrylic acid, a cyano group-containing unit, and a sulfonate group-containing unit.

Provided is a paint-protective coating material formed from an acrylic coating composition comprising an acrylic polymer as base polymer. The acrylic polymer-forming monomers includes a monomer (m.sub.T) having a homopolymer Tg of 90° C. or higher and a monomer (m.sub.L) having a homopolymer Tg of −30° C. or lower. The monomer (m.sub.T) includes at least acrylonitrile. In the monomers, the monomers (m.sub.T) and (m.sub.L) have a molar ratio (m.sub.T/m.sub.L) of 0.8 or higher and 1.5 or lower. The paint-protective coating material has storage moduli of 150 MPa or higher and 1000 MPa or lower at 23° C., and 0.40 MPa or higher at 70° C.

Provided is a paint-protective coating material formed from an acrylic coating composition comprising an acrylic polymer as base polymer. The acrylic polymer-forming monomers includes a monomer (m.sub.T) having a homopolymer Tg of 90° C. or higher and a monomer (m.sub.L) having a homopolymer Tg of −30° C. or lower. The monomer (m.sub.T) includes at least acrylonitrile. In the monomers, the monomers (m.sub.T) and (m.sub.L) have a molar ratio (m.sub.T/m.sub.L) of 0.8 or higher and 1.5 or lower. The paint-protective coating material has storage moduli of 150 MPa or higher and 1000 MPa or lower at 23° C., and 0.40 MPa or higher at 70° C.

Provided is a paint-protective coating material formed from an acrylic coating composition comprising an acrylic polymer as base polymer. The acrylic polymer-forming monomers includes a monomer (m.sub.T) having a homopolymer Tg of 90° C. or higher and a monomer (m.sub.L) having a homopolymer Tg of −30° C. or lower. The monomer (m.sub.T) includes at least acrylonitrile. In the monomers, the monomers (m.sub.T) and (m.sub.L) have a molar ratio (m.sub.T/m.sub.L) of 0.8 or higher and 1.5 or lower. The paint-protective coating material has storage moduli of 150 MPa or higher and 1000 MPa or lower at 23° C., and 0.40 MPa or higher at 70° C.