Polarized light splitting element

Abstract

Provided are a polarized light splitting element, a method of manufacturing the same, a light radiating device, a method of radiating light, and a method of manufacturing an ordered photo-alignment film. The polarized light splitting element has excellent durability with respect to UV rays and heat, and low pitch dependence of polarization characteristics, so that it is easily manufactured. In addition, the polarized light splitting element may realize a high polarization degree and extinction ratio even in a short wavelength region.

Claims

1. An ultraviolet (UV) polarized light splitting element, comprising: a substrate; and an unevenness having a convex part including a light absorbing material having a refractive index of 3.2 to 10 and an extinction coefficient of 0.5 to 10 with respect to light having a wavelength of 300 nm, and a concave part including a dielectric material, the unevenness being formed on the substrate, wherein the convex part has a pitch of 100 to 180 nm, a width of 50 to 80 nm, and a ratio (W/P) of a width (W) of the convex part to a pitch (P) of the convex part is 0.2 to 0.8, wherein in the following Equation 1, a is 0.74 to 10, and b is 0.05 to 10, and in the following Equation 2, c is 1.3 to 10 and d is 0.013 to 0.1:
(a+bi).sup.2=n.sub.1.sup.2(1W/P)+n.sub.2.sup.2W/P[Equation 1]
(c+di).sup.2=n.sub.1.sup.2n.sub.2.sup.2/((1W/P)n.sub.2.sup.2+Wn.sub.1.sup.2/P)[Equation 2] where i is an imaginary number, n.sub.1 represents a refractive index of the dielectric material with respect to light having a wavelength of 300 nm, n.sub.2 represents a refractive index of the convex part with respect to light having a wavelength of 300 nm.

2. The element according to claim 1, wherein the refractive index of the dielectric material with respect to light having a wavelength from 250 to 350 nm is 1 to 3.

3. The element according to claim 1, wherein the refractive index of the convex part with respect to light having a wavelength from 250 to 350 nm is 3.2 to 10.

4. The element according to claim 1, wherein the convex part has an extinction coefficient of 0.5 to 10 with respect to light having a wavelength in a UV region.

5. The element according to claim 1, wherein the light absorbing material is at least one selected from the group consisting of silicon, titanium oxide, zinc oxide, zirconium oxide, tungsten, tungsten oxide, gallium arsenide, gallium antimonide, aluminum gallium arsenide, cadmium telluride, chromium, molybdenum, nickel, gallium phosphide, indium gallium arsenide, indium phosphide, indium antimonide, cadmium zinc telluride, tin oxide, cesium oxide, strontium titanium oxide, silicon carbide, iridium, iridium oxide, or zinc selenium telluride.

6. The element according to claim 1, D calculated by Equation 3 is 0.67 to 0.98:
D=(TcTp)/(Tc+Tp),[Equation 3] where Tc represents a transmission rate of light having a wavelength of 250 to 350 nm polarized in a direction perpendicular to the convex part with respect to the polarized light splitting element, and Tp represents a transmission rate of light having a wavelength of 250 to 350 nm polarized in a direction parallel to the convex part with respect to the polarized light splitting element.

7. The element according to claim 1, wherein the convex part has a height of 20 to 300 nm.

8. The element according to claim 1, wherein R calculated by Equation 4 is 2 to 2000:
R=Tc/Tp,[Equation 4] where Tc represents a transmission rate of light having a wavelength of 250 to 350 nm polarized in a direction perpendicular to the convex part with respect to the polarized light splitting element, and Tp represents a transmission rate of light having a wavelength of 250 to 350 nm polarized in a direction parallel to the convex part with respect to the polarized light splitting element.

9. A method of manufacturing the UV polarized light splitting element of claim 1, comprising: forming the convex part on the substrate using the light absorbing material; and forming the unevenness by introducing the dielectric material into the concave part formed by the convex part.

10. A light radiating device, comprising: an apparatus onto which a target is loaded; and the polarized light splitting element of claim 1.

11. The device according to claim 10, further comprising: a photo-alignment mask between the apparatus onto which the target is loaded and the polarized light splitting element.

12. The device according to claim 11, further comprising: a light source capable of radiating linearly polarized light toward a mask.

13. A method of radiating light, comprising: loading a target onto the apparatus onto which the target is loaded of the device of claim 11; and radiating light onto the target by means of a polarized light splitting element and a mask.

14. A method of forming an arranged photo-alignment film, comprising: loading a target onto the apparatus onto which the target is loaded of the device of claim 11; and radiating linearly polarized light onto the photo-alignment film by means of a polarized light splitting element and a mask.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a cross-sectional view of an exemplary polarized light splitting element;

(2) FIG. 2 is a schematic top view of the exemplary polarized light splitting element;

(3) FIG. 3 is an image of the exemplary polarized light splitting element taken from above;

(4) FIG. 4 is a diagram of arrangement of an exemplary light radiating means;

(5) FIG. 5 is a diagram of an exemplary light radiating device;

(6) FIG. 6 is a graph showing Tc values of a polarized light splitting element including unevenness formed of silicon of Example 3 according to an increase in refractive index in a UV region, when an extinction coefficient of the polarized light splitting element is fixed;

(7) FIG. 7 a graph showing Tp values of the polarized light splitting element including unevenness formed of silicon of Example 3 according to an increase in refractive index in a UV region, when the extinction coefficient of the polarized light splitting element is fixed; and

(8) FIG. 8 is a graph showing Tc and Tp of polarized light splitting elements manufactured in Example 3 and a Comparative Example.

MODES FOR INVENTION

(9) Though the present application will be described in more detail with reference to Examples and Comparative Example below, the scope of a polarized light splitting element of the present application is not limited to the following Examples.

Manufacture of Polarized Light Splitting Element

Example 1

(10) Impurities on a surface of quarts glass were removed by ultrasonic cleaning in acetone and isopropyl alcohol (IPA) each at 60 C. for 20 minutes. Subsequently, a GaAs thin film (refractive index with respect to light having a wavelength of 300 nm: 3.69, extinction coefficient: 1.97) was deposited to a thickness of 50 nm on the quartz glass through E-beam evaporation at a speed of 1 /sec. Mr-8010r produced by Micro Resist was spin-coated on the deposited GaAs thin film to have a thickness of 100 nm and then baked at 95 C. for 1 minute. Afterward, imprinting was performed using an imprinting master with a pitch of 150 nm. In the imprinting, a press was set to 160 C., maintained at 40 Bar for 3 minutes, cooled for 2 minutes, and demolded at 100 C. Then, the GaAs was dry-etched using an ICP RIE apparatus. After that, the resist for imprinting was removed using acetone as an organic solvent, thereby manufacturing a polarized light splitting element having a width (W) of a convex part of 75 nm and a pitch (P) of 150 nm.

Example 2

(11) An InP polarized light splitting element having a width (W) of a convex part of 75 nm and a pitch (P) of 150 nm was manufactured by the same method as described in Example 1, except that an InP thin film (refractive index with respect to light having a wavelength of 300 nm: 3.2, extinction coefficient: 1.74) was deposited on quartz glass to have a thickness of 50 nm through e-beam evaporation.

Example 3

(12) A silicon polarized light splitting element having a width (W) of a convex part of 75 nm and a pitch (P) of 150 nm was manufactured by the same method as described in Example 1, except that a silicon thin film (refractive index with respect to light having a wavelength of 300 nm: 5, extinction coefficient: 4.09) was deposited on quartz glass to have a thickness of 50 nm through e-beam evaporation.

Comparative Example

(13) Impurities on a surface of quarts glass were removed by ultrasonic cleaning in acetone and isopropyl alcohol (IPA) each at 60 C. for 20 minutes. Subsequently, an aluminum thin film (refractive index with respect to light having a wavelength of 300 nm: 0.28, extinction coefficient: 3.64) was deposited to a thickness of 200 nm on the quartz glass through e-beam evaporation at a speed of 1 /sec. Mr-8010r produced by Micro Resist was spin-coated on the deposited aluminum thin film to have a thickness of 100 nm and then baked at 95 C. for 1 minute. Afterward, imprinting was performed using an imprinting master with a pitch of 150 nm. In the imprinting, a press was set to 160 C., maintained at 40 Bar for 3 minutes, cooled for 2 minutes, and demolded at 100 C. Then, the aluminum was dry-etched using an ICP RIE apparatus. After that, the resist for imprinting was removed using acetone as an organic solvent, thereby manufacturing an aluminum polarized light splitting element having a width (W) of a convex part of 75 nm and a pitch (P) of 150 nm.

Experimental Example

(14) Physical properties of the polarized light splitting elements manufactured in Examples 1 to 3 and the Comparative Example were evaluated by the following methods:

(15) Measurement Method 1: Measurement of Transmittance

(16) After a polarized light source was formed by inserting two sheets of unused aluminum polarized light splitting elements into a transmittance measuring apparatus, the manufactured polarized light splitting element was placed perpendicular to a polarization direction and Tp and Tc were measured. Here, Tp represents a transmittance of polarization parallel to a convex part, and Tc represents a transmittance of polarization perpendicular to a convex part.

(17) Measurement Method 2: Measurement of Refractive Index and Extinction Coefficient

(18) A refractive index and an extinction coefficient of a convex part of the polarized light splitting element manufactured in each of the Examples and Comparative Example were measured by radiating light having a wavelength of 300 nm onto the polarized light splitting element using a spectroscopic ellipsometer and oscillation modeling.

(19) TABLE-US-00001 TABLE 1 Real optical constant Material of Extinction Wavelength (nm) convex part Refractive index coefficient 250 GaAs 2.89 4.05 InP 2.55 3.51 Si 1.7 3.68 Al 0.20 3.0 275 GaAs 3.92 2.90 InP 3.65 2.06 Si 1.87 5.00 Al 0.23 3.3 300 GaAs 3.69 1.97 InP 3.20 1.74 Si 5.0 4.09 Al 0.28 3.64 325 GaAs 3.50 1.91 InP 3.10 1.78 Si 5.13 3.18 Al 0.33 3.95 350 GaAs 3.52 2.00 InP 3.19 1.95 Si 5.5 2.90 Al 0.39 4.3

(20) Calculation of Effective Refractive Index of the Polarized Light Splitting Element

(21) W and P values of each of the polarized light splitting elements of Examples 1 to 3 and Comparative Example, a refractive index (n.sub.1) of a dielectric material (air), and an optical coefficient (n.sub.2) of a convex part of the polarized light splitting element measured above were assigned to Equations 1 and 2, and the results are shown in Table 2.

(22) TABLE-US-00002 TABLE 2 Real optical Wavelength Material of constant Effective refractive index (nm) convex part n.sub.2 N.sub.//(a + bi) N.sub.(c + di) 250 GaAs 2.89 + 4.05i 2.09 + 2.81i 1.42 + 0.028i InP 2.55 + 3.51i 1.85 + 2.42i 1.42 + 0.037i Si 1.7 + 3.68i 1.24 + 2.52i 1.44 + 0.035i Al 0.20 + 3.0i 0.15 + 2.0i 1.50 + 0.012i 275 GaAs 3.92 + 2.90i 2.13 + 1.99i 1.41 + 0.042i InP 3.65 + 2.06i 2.65 + 1.42i 1.39 + 0.033i Si 1.87 + 5.00i 1.87 + 3.48i 1.44 + 0.040i Al 0.23 + 3.3i 0.17 + 2.22i 1.48 + 0.010i 300 GaAs 3.69 + 1.97i 2.68 + 1.35i 1.39 + 0.032i InP 3.20 + 1.74i 2.35 + 1.19i 1.38 + 0.042i Si 5.0 + 4.09i 3.58 + 2.86i 1.41 + 0.017i Al 0.28 + 3.64i 0.21 + 2.48i 1.47 + 0.009i 325 GaAs 3.50 + 1.91i 2.55 + 1.31i 1.39 + 0.036i InP 3.10 + 1.78i 1.58 + 1.18i 1.39 + 0.088i Si 5.13 + 3.18i 3.67 + 2.22i 1.41 + 0.017i Al 0.33 + 3.95i 0.24 + 2.70i 1.46 + 0.008i 350 GaAs 3.52 + 2.00i 2.56 + 1.37i 1.39 + 0.035i InP 3.19 + 1.95i 2.34 + 1.33i 1.39 + 0.043i Si 5.5 + 2.90i 3.94 + 2.02i 1.40 + 0.017i Al 0.39 + 4.3i 0.28 + 2.96i 1.45 + 0.0074i

(23) Calculation of Extinction Ratio

(24) Based on the transmittance measured according to each wavelength band, an extinction ratio (Tc/Tp) was calculated. Extinction ratios by wavelength bands of Examples 1 to 3 and Comparative Example are shown in Table 3.

(25) TABLE-US-00003 TABLE 3 Extinction ratios by materials of polarized light splitting elements composed of Al and light absorbing material Extinction ratio in each wavelength band 250 nm 275 nm 300 nm 325 nm 350 nm Example 1 51.50074 291.3341 234.8004 294.8964 532.1686 Example 2 13.4354 166.7665 73.3974 1064.73 1711.022 Example 3 34.71716 204.9879 207.9338 683.9417 1762.759 Com- 0.233146 6.649053 38.55189 89.0692 134.102 parative Example

(26) As shown in Table 1, in the cases of GaAs, InP, and Si included in a convex part, the refractive index with respect to light having a wavelength of 300 nm was 1 to 10, and the extinction coefficient with respect to light having a wavelength of 300 nm was 0.5 to 10. In the case of Al, since the extinction coefficient with respect to light having a wavelength of 300 nm was 3.64, and the refractive index with respect to light having a wavelength of 300 nm was 0.28, Al was not included in the light absorbing material of the present application.

(27) As seen from Table 2, like Examples 1 to 3, when a convex part was formed using GaAs, InP or silicon, in n.sub.//, a in the case of Al, which is Comparative Example, was less than 0.74, and a in the case of Si, which is an Example, was 0.74 or more, which was higher than in the case of Al, and b was higher in the case of Si than the case of Al.

(28) In addition, as shown in Table 3, in a UV wavelength band, compared to the polarized light splitting element manufactured in Comparative Example, the polarized light splitting elements manufactured in Examples 1 to 3 had considerably higher extinction ratios, even though they were manufactured to have the same pitch of 150 nm as in Comparative Example.

(29) In addition, referring to FIG. 6, when the polarized light splitting element having a convex part formed of silicon in Example 1 had a certain extinction coefficient in a UV region, particularly, in a wavelength band from 250 to 310 nm, as the refractive index increased, the value of Tc generally increased. In this case, a width of the transmittance increased toward a short wavelength region, and as shown in FIG. 7, as the refractive index in the UV region increased, the value of Tp decreased. That is, the polarized light splitting element in which a convex part was formed of silicon had a high extinction ratio in a short wavelength range.

(30) In addition, Tc and Tp of the polarized light splitting elements manufactured to have the same pitch of 150 nm according to Example 3 and Comparative Example were measured using a spectrometer produced by N & K, and the results are shown in FIG. 8. As shown in FIG. 8, the polarized light splitting element in which a convex was formed of silicon had a very excellent polarization separating property, and in a short wavelength range (approximately 250 to 270 nm) compared to that in which the convex part was formed of aluminum, and a height (50 nm) of the convex part of the polarized light splitting element having the convex part formed of silicon was smaller than that (150 nm) of the convex part of the polarized light splitting element having the convex part formed of aluminum, and thus the polarized light splitting element was easily manufactured.

(31) While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.