Differentially cured materials and process for forming same
A structure includes a layer which includes a first cured portion and a second cured portion which are formed from a same light curable material. The first cured portion is cured to a first amount, and the second cured portion is cured to a second amount. The first amount is sufficiently different than the second amount to result in a visible discontinuity on the surface of the structure. A method for forming a pattern in a radiation curable material includes providing between a radiation source and the radiation curable material, a pattern that can block a portion of the radiation from the radiation source. The material is cured with radiation from the radiation source to form a pattern in the radiation curable material.
1. A method for continuously forming an optical film from a radiation curable liquid material comprising:
providing a mold that defines a shape for optical structures to be formed in the optical film;
placing the radiation curable liquid material in the mold;
positioning a radiation transparent base film adjacent to the radiation curable liquid material in the mold;
positioning a radiation source such that it can irradiate the curable liquid material while the radiation curable material is in the mold;
overlapping a mask film on a base film, the mask film being disposed between the radiation source and the base film, wherein the mask film comprises a pattern that further defines areas of the optical film where curved portions are to be made in the shape of the optical structures as would otherwise be defined by the mold alone; and
simultaneously curing and patterning the liquid material by exposing it to the radiation source, wherein radiation passes through both the mask film and through the transparent base film at the same time, to reach the liquid material in the mold, and to thereby cure the liquid material and at the same time to pattern cured optical structures and further patterning the optical structures with the curved portions in their shape as a single step, the resulting curved optical structures thus being formed via differential exposure to radiation during the curing step, as caused by the mask film.
2. The method of claim 1 wherein the optical structure is formed in a surface of the optical film, opposite the base film.
3. The method of claim 1 wherein the radiation source emits ultraviolet light.
4. The method of claim 1 wherein the radiation curable liquid material is a monomer is selected from polyester, urethane, epoxy acrylates or methacrylates.
5. The method of claim 1 wherein the pattern is configured in the form of a logo, geometric form, or alphanumerics.
6. The method of claim 1 wherein the pattern is formed on the mask film.
7. The method of claim 1 wherein the radiation curable liquid is deposited between the base film and the mold.
8. The method of claim 7 wherein the pattern is removably placed on the base film.
9. The method of claim 1 , wherein the optical structures comprise linear prisms, lenticular structures, cube-corner prisms, lens structures, and/or sub-wavelength structures.
10. The method of claim 1 , wherein the optical structures are used in a display.
11. The method of claim 10 , wherein the optical structures include a liquid crystal display.
12. The method of claim 1 , wherein the pattern is used to mark the optical film.
13. A method for making a continuous optical film having parallel prism structures, the method comprising:
providing a rotating cylinder mold having linear grooves formed on an outer surface thereof, the linear grooves used as a mold for defining the parallel prism structures with aligned peaks;
dispensing a radiation curable liquid material onto the rotating cylinder mold at a dispensing location;
continuously feeding a radiation transparent optical base film and a mask film, the mask film having a pattern used in further defining features of the optical base film, near the dispenser location;
positioning the continuous mask film adjacent to the continuously fed optical base film near the dispensing location such that the optical base film and mask film are placed against the rotating mold, wherein the optical film is positioned nearest the rotating mold and the mask film is positioned outside of the optical base film;
providing a radiation source for simultaneously curing and patterning the liquid material by irradiating the liquid material through the adjacent mask film and optical base film, such that the radiation travels first through the mask film and then through the transparent optical base film before curing the liquid material, and such that the radiation source causes simultaneous patterning of the liquid material while the liquid material is being cured, to thereby define the optical base film including the prism structures having deformed peaks in an area of the liquid material blocked from the irradiation by the pattern;
separating the adjacent mask film and optical base film; and
thereafter, individually collecting the optical base film and the mask film.