Dual prism sheet, backlight assembly having the same and method thereof
View Patent ↗A dual prism sheet includes a base film, upper prisms formed on an upper surface of the base film and lower prisms formed on a lower surface of the base film. A cross-section of the upper and lower prisms is formed as an isosceles triangular shape having a base and a vertex angle, and a phase of the upper prisms is delayed between about 0 and about 0.5 times of a prism pitch with respect to a phase of the lower prisms.
1. A dual prism sheet comprising:
a base film;
upper prisms on an entire upper surface of the base film, a cross-section of each of the upper prisms being formed as an isosceles triangular shape; and
lower prisms on an entire lower surface of the base film, a cross-section of each of the lower prisms having an isosceles triangular shape having the substantially same base vertex angle with the upper prisms, such that two sides of the cross-section, which are extended from the lower surface of the base film, have a substantially same length, a phase of the upper prisms being different from a phase of the lower prisms.
2. The dual prism sheet of claim 1 , wherein the phase of the upper prisms is delayed between 0 and about 0.5 times of the prism pitch with respect to the phase of the lower prisms.
3. The dual prism sheet of claim 1 , wherein the upper prisms extend substantially parallel with the lower prisms.
4. The dual prism sheet of claim 1 , wherein the vertex angle of each of the upper and lower prisms is between about 83 degrees and about 88 degrees.
5. The dual prism sheet of claim 1 , wherein the vertex angle of each of the upper and lower prisms is about 86 degrees.
6. The dual prism sheet of claim 1 , wherein the phase of the upper prisms is delayed between about D and about D+0.5 times of the prism pitch with respect to the phase of the lower prisms, wherein D is expressed as follows
D
=
H
tan
(
180
°
-
3
2
α
+
sin
(
sin
(
α
2
+
θ
-
90
°
)
n
)
)
*
1
P
,
wherein H is a thickness of the base film, α is a vertex angle of each of the upper and lower prisms, n is a refractive index of the dual prism sheet, and θ is a mean angle of an incident light with respect to the base film, and P is a pitch of each of the upper and lower prisms.
7. The dual prism sheet of claim 1 , wherein a sum of a prism height of each of the upper prisms and a thickness of the base film is between about 90 microns (μm) to about 175 microns (μm).