Information writable film and a sample storage body

An information writable film applicable to the surface of a target, the color of the area of the target where the information to be written by a laser marking is not limited and a mark written in the information writable film in white, comprising;

• a writable film layer made of light-transmissive material formed in a film shape, wherein a color former including a photo-sensitive composition or a heat-sensitive composition, which can be changeable from a black color with light transmission ratio at 0% to 95% to a white color state by shifting a physical characteristic or a chemical characteristic by irradiating a particular wavelength laser beam, is mixed with a transparent plastic resin having a desired chemical resistance and structural strength;
• a reading assistance layer under the writable film layer, whose color is darker black having lower light transmission ratio than that of the writable film layer, and having adhesiveness to the surface of the target;
• the writable film layer with the reading assistance layer as two layers having enhanced chemical resistance and structural strength by mixing with the transparent plastic resin, and the deterioration of the contrast ratio due to mixing with the transparent plastic resin is avoided by superimposing the black color of the reading assistance layer,
• wherein an anti-heat contraction black layer having black color or dark color and having higher rigidity than that of the writable film layer is applied under the writable film layer as the reading assistance layer, which serves both as the component for absorbing heat generated in the writing process of the identification code by the laser beam to the writable film layer and as the component for prevention of heat contraction due to its rigidity and as the component for enhancing the contrast ratio by its black or dark color.