Methods of Making Light Diffusing Films and Articles Using the Same
Disclosed herein are light diffusing films, methods of making the same and articles using the same. In one embodiment, a method for producing a film, comprising: combining, to form a combination, a polycarbonate having a yellowness index of about 0.8 to about 1.5 as measured in accordance with ASTM E313-73 (D1925), a phosphite stabilizer, an epoxy stabilizer, and light diffusing; forming the combination into the film; wherein the film comprises a hiding power of 0 to about 0.5.
1 . A method for producing a film, comprising:
combining, to form a combination,
a polycarbonate having a yellowness index of about 0.8 to about 1.5 as measured in accordance with ASTM E313-73 (D1925),
a phosphite stabilizer,
an epoxy stabilizer, and
light diffusing;
forming the combination into the film;
wherein the film comprises a hiding power of 0 to about 0.5 that is mathematically described by the following equation:
Hiding
power
(
%
)
=
1
-
∑
i
=
1
n
-
1
L
i
(
on
)
∑
j
=
1
n
-
1
L
j
(
off
)
×
100
wherein: L i (on) is luminance above i th cold cathode fluorescent lamp, L j (off) is luminance at a midpoint between cold cathode fluorescent lamp j and cold cathode fluorescent lamp j+1, and n equals number of CCFL lamps; and
wherein the light diffusing film has a 13 points average luminance that is greater than a 13 points average luminance of a polycarbonate film, as determined by a 13 points test using a Topcon BM-7 instrument, wherein the polycarbonate film comprises about 3.5 wt % acrylate particles based on a total weight of the polycarbonate film, and the polycarbonate film has a thickness of 2 millimeters and a transmission of 50.4% as determined in accordance with ASTM D1003-00 and as measured with instrument Macbeth 7000A, D65 light source illuminant, 10° observer.
2 . The method of claim 1 , wherein the light diffusing particles have a refractive index of about 1.3 to about 1.7 as measured at the Sodium D line with a wavelength of 589 nanometers (nm).
3 . The method of claim 2 , wherein the refractive index is about 1.50 to about 1.53.
4 . The method of claim 1 , further comprising combining a hindered phenol stabilizer with the polycarbonate, the phosphite stabilizer, the epoxy stabilizer, and the light diffusing particles to form the combination.
5 . The method of claim 1 , wherein forming the combination into the film further comprises extruding the combination from an extruder onto calendaring rolls.
6 . The method of claim 5 , wherein the extruder has an extruder speed of about 65 rpm to about 85 rpm, an average barrel temperature of about 200° C. to about 235° C., and a ratio of flow rate (kg/hr) to the extruder speed (rpm) is about 3.5 to about 6.0.
7 . The method of claim 6 , wherein the extruder speed is about 70 rpm to about 80 rpm, and the average barrel temperature is about 204° C. to about 228° C., and the ratio is about 3.7 to about 5.8.
8 . The method of claim 1 , wherein the combining comprises combining about 0.015 wt % to about 0.04 wt % epoxy stabilizer, about 0.04 wt % to about 0.09 wt % phosphite stabilizer, and about 0.001 wt % to about 7 wt % light diffusing particles, wherein the weight percent is based upon a total weight of the combination.
9 . The method of claim 1 , wherein the combining comprises combining about 0.015 wt % to about 0.03 wt % epoxy stabilizer, about 0.01 wt % to about 0.03 wt % hindered phenol stabilizer, and about 0.04 wt % to about 0.09 wt % phosphite stabilizer, wherein the weight percent is based upon a total weight of the combination.
10 . The method of claim 1 , wherein the light diffusing particles comprise polyorgano silsesquioxane.
11 . The method of claim 1 , wherein the light diffusing particles comprise a material are selected from the group consisting of poly(styrene), poly(acrylic acid), poly(methyl methacrylate), poly(acrylic acid-styrene) copolymers, poly(C 1-8 alkylacrylate-C 1-8 alkylmethacrylate) copolymers, and combinations comprising at least one of the foregoing.
12 . A film formed in accordance with the method of claim 1 .
13 . A method for producing a film, comprising:
combining, to form a combination,
about 90 wt % to about 99.9 wt % virgin polycarbonate powder which has not been heat processed, and which has a yellowness index of about 0.8 to about 1.5 as measured in accordance with ASTM E313-73 (D1925);
about 0.04 wt % to about 0.09 wt % phosphite stabilizer,
about 0.015 wt % to about 0.03 wt % epoxy stabilizer,
about 0.01 wt % to about 0.03 wt % hindered phenol stabilizer, and
about 0.001 wt % to about 10 wt % light diffusing particles having a refractive index of about 1.3 to about 1.7,
wherein the weight percentages are based upon a total weight of ingredients combined prior to any reaction;
forming the combination into the film;
wherein the film comprises a hiding power of 0 to about 0.5 that is mathematically described by the following equation:
Hiding
power
(
%
)
=
1
-
∑
i
=
1
n
-
1
L
i
(
on
)
∑
j
=
1
n
-
1
L
j
(
off
)
×
100
wherein: L i (on) is luminance above i th cold cathode fluorescent lamp, L j (off) is luminance at a midpoint between cold cathode fluorescent lamp j and cold cathode fluorescent lamp j+1, and n equals number of CCFL lamps.
14 . The method of claim 13 , wherein the light diffusing film has a 13 points average luminance that is greater than a 13 points average luminance of a polycarbonate film, as determined by a 13 points test using a Topcon BM-7 instrument, wherein the polycarbonate film comprises about 3.5 wt % acrylate particles based on a total weight of the polycarbonate film, and the polycarbonate film has a thickness of 2 millimeters and a transmission of 50.4% as determined in accordance with ASTM D1003-00 and as measured with instrument Macbeth 7000A, D65 light source illuminant, 10° observer.