Method of preparing volume type hologram film

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of the present invention will be described hereafter.
First, a sensitive material layer comprised of a vinylcarbazole polymer as a principal component is formed on a light-transmissive substrate.
Utilizable as the light-transmissive substrate are substrates having sufficient rigidity such that no vibration occurs owing to the irradiation of a laser beam, and having no remarkable absorption at the visible light region.
Particularly with regard to the light transmission properties, it is preferable to use a substrate having a light transmittance of 30% or more, preferably 50% or more, at 400 nm and also a light transmittance of 40% or more, preferably 80% or more, at 450 to 800 nm when the light transmittance is measured according to the method described in ASTM D-1003.
To exemplify the light-transmissive substrates used in the present invention, there are included: glass, poly(methyl) pentene, polyvinyl chloride or the like, and, if necessary, a substrate having been made transparent by effecting drawing in the biaxial direction at the time of forming to cause orientation crystallization; and a substrate comprising an amorphous polymer such as polymethyl methacrylate, polycarbonate, polyallylate polyether ether ketone, polysulfone, a styrene/methyl methacrylate copolymer or acrylic acid polyhydric alcohol esters (CR-39).
It is also possible to use water soluble substrates in the event that the substrate is dissolved and removed in a solvent as described later.
For example, water soluble substrates are formed from water soluble alkali halides as exemplified by sodium chloride, sodium bromide, potassium chloride, potassium bromide, etc.
There is no particular limitation in the shape of the substrate comprised of these alkali halides, but it may preferably be in the shape of a flat sheet of approximately from 2 mm to 10 mm in thickness.
The surface of the substrate on which the sensitive material layer is formed may be smooth or of any form including curved or uneven form, where a sensitive material layer of the form corresponding to its surface is formed