JP2019536074A - Overcoat wire grid polarizer - Google Patents

Abstract

Wire grid polarizers (WGPs) can be durable and have high performance. The WGP may include an array of wires 13 on a substrate 11. Overcoat layer 32 may be disposed at the distal end of the array of wires 13 and may span channels 15 between wires 13. The conformal coat layer 61 may cover the side surface 13s and the distal end 13d of the wire 13 between the wire 13 and the overcoat layer 32. The overcoat layer can include aluminum oxide. The anti-reflection layer 33 can be disposed on the overcoat layer 32.

Description

  The present application relates generally to wire grid polarizers.

  A wire grid polarizer (WGP) can be used to split the light into two different polarization states. One polarization state can pass through the WGP at a high rate and the other polarization state can be absorbed or reflected at a high rate. The effect or performance of WGP is based on a very high percentage of transmission of one polarization (Tp) and the minimum transmission of opposite polarization (Ts). It may be beneficial to have a high contrast (Tp / Ts). Opposite polarization reflectivity (Rs) can also be an important indicator of polarizer performance.

  WGP wires, particularly for visible or ultraviolet light polarization, may have small and fine wires with nanometer size pitch, wire width and wire height. WGP is used in systems that require high performance (eg, computer projectors, semiconductor inspection instruments, etc.). Small defects in WGP, such as corroded and crushed wires, can significantly degrade system performance (eg, distorted images from computer projectors). Normal handling can cause the wires to be crushed. As such, it can be important to protect the wire from corrosion and mechanical damage.

  Oxidation can degrade performance by adversely affecting contrast and / or Rs. Since the aluminum wire forms a native oxide over time, the underlying substantially pure aluminum is consumed, thus reducing the size of the substantially pure aluminum wire and changing the polarization characteristics of the WGP.

  It has been recognized that it would be advantageous to have high wire grid polarizer (WGP) performance and to protect the wire from corrosion, mechanical damage and oxidation. The present invention relates to various embodiments of WGP and methods for making WGP that meet these needs. Each embodiment or method may meet one, some or all of these needs.

  A WGP may include an array of wires disposed on a surface of a transparent substrate, with a channel between adjacent wires. An overcoat layer can be disposed at the distal end of the array of wires and can span the channels.

  In one embodiment, the moisture barrier may cover the side and distal end of the wire between the wire and the overcoat layer. In another embodiment, an antireflective layer can be disposed over the overcoat layer.

A method of manufacturing a WGP may include the following steps in the following order:
1. Providing an array of wires on a surface of a transparent substrate with a channel between adjacent wires. These channels can be filled with air. Each wire may have a cross-sectional profile with a bottom surface disposed closest to the substrate and a distal end disposed farthest from the substrate. Each wire may have opposing sides that each face a channel on the opposing side of the wire and extend from the bottom to the distal end.
2. Applying a moisture barrier to the side and distal end of the wire while maintaining the channel filled with air.
3. Applying an overcoat layer over the moisture barrier at the distal end of the array of wires to span the channel and keeping the channel filled with air.

  The drawings may not be to scale.

1 is a schematic cross-sectional view of a wire grid polarizer (WGP) 10 according to an embodiment of the invention with an array of wires 13 on a surface 11 _f of a transparent substrate 11 with a channel 15 between adjacent wires 13. FIG. 2 is a schematic perspective view of the WGP 10 of FIG. 1 according to an embodiment of the present invention. Is the same as WGP10 in Figures 1-2, but at the distal end portion 13 _d of the array of wires 13, the overcoat layer 32 over the channel 15, and the antireflection layer 33 disposed on the overcoat layer 32 FIG. 4 is a schematic cross-sectional view of WGPs 30 and 40 according to an embodiment of the present invention further comprising Is the same as WGP10 in Figures 1-2, but at the distal end portion 13 _d of the array of wires 13, the overcoat layer 32 over the channel 15, and the antireflection layer 33 disposed on the overcoat layer 32 FIG. 4 is a schematic cross-sectional view of WGPs 30 and 40 according to an embodiment of the present invention further comprising Is similar to WGP10 in Figures 1-2, further comprising an overcoat layer 32 to the distal end portion 13 _d of the array of wires 13, the overcoat layer 32, over channel 15, and the side surface 13 _s of the wire 13 FIG. 2 is a schematic cross-sectional view of a WGP 50 according to an embodiment of the invention, extending downward from a distal end 13 _d to a bottom surface 13 _b . 1 to 2, but the overcoat layer 32 at the distal end 13 _d of the wire 13, and the side surface 13 _s of the wire 13 and the wire 13 between the wire 13 and the overcoat layer 32. further comprising a conformal coating layer 61 covering the distal end portion 13 _d, is a schematic enlarged cross-sectional view of a portion of WGP60 according to an embodiment of the present invention (showing a single wire 13). FIG. 8 is a schematic diagram of image projectors 70 and 80 each comprising at least one WGP 74, according to an embodiment of the present invention. FIG. 8 is a schematic diagram of image projectors 70 and 80 each comprising at least one WGP 74, in accordance with an embodiment of the present invention.

[Definition]
As used herein, the term “conformal coat layer” means a layer that conforms to the topology of WGP.

  As used herein, the term “decrease Rs” means an increase in Rs for selective absorption WGP or a decrease in Rs for reflection WGP.

As used herein, the term “elongate” means that the length L of the wire ₁₃ is substantially greater than the wire width W or wire thickness Th ₁₃ (see FIGS. 1-2). For example, WGP for ultraviolet light or visible light may have a wire width W of 20-100 nanometers and a wire thickness Th ₁₃ of 50-500 nanometers, and about 1 millimeter to 20 centimeters or more, depending on the application. It may have a wire length L. Thus, the elongated wire 13 has a length L that is many times (eg, at least 10 times, at least 100 times, at least 1000 times, or at least 10,000 times) larger than the wire width W and / or the wire thickness Th _13. Can have. The term “elongate” can also mean that the length L of the wire 13 is longer than any wavelength in the wavelength band of the intended application. For example, the length L can exceed 700 nm, which is the longest wavelength of visible light.

  As used herein, the term “placed on” means placed directly on or placed above with some other solid in between.

  As used herein, the term “Tp” mainly refers to the transmittance of transmitted polarized light (usually p-polarized light), and the term “Ts” refers to the transmittance of oppositely polarized light (usually s-polarized light). And the term “Rs” means the reflectivity of the opposite polarization.

As shown in FIGS. 1-2, a wire grid polarizer (WGP) 10 is shown including an array of wires 13 disposed on a surface 11 _f of a transparent substrate 11. The array of wires 13 can be substantially parallel and elongated, with a channel 15 between adjacent wires 13. The channel 15 can be filled with a gas such as a solid, liquid, vacuum or air. Each wire 13, the bottom surface 13 _b is located closest to the substrate 11, the distal end portion 13 _d is positioned farthest from the substrate 11, and the opposite sides 13 of the side surface 13 _s are opposed wires respectively to _s facing the channel 15, and extends from the bottom surface 13 _b to the distal end 13 _d, it may have a cross-sectional profile. Each wire 13 may be made of or include a material for polarizing, including metals and / or dielectrics typically used in wire grid polarizer wires. See, for example, US Pat. No. 7,961,393 and US Pat. No. 8,755,113, which are hereby incorporated by reference.

As shown in FIGS. 3-6, an overcoat layer 32 may be disposed at the distal end 13 _d of the array of wires 13 and span multiple channels 15. The overcoat layer 32 may provide structural support to the wire 13, avoiding the wire from collapsing, and allowing the WGP 30, 40 or 50 to be handled and cleaned.

As shown in FIGS. 3 to 4 and 6, the overcoat layer 32 may extend over the plurality of channels 15 with the minimum overcoat layer 32 entering the channel 15. Alternatively, the overcoat layer 32 may extend almost or all the way down to the side 13 _s of the wire 13 as shown in FIG.

  The overcoat layer 32 may be a transparent dielectric such as silicon dioxide, for example. Careful selection of the material for the overcoat layer 32 may help to avoid degradation of WGP performance over time. For example, the overcoat layer 32 can include aluminum oxide, which can protect the wire 13 from oxidation. The material composition of the overcoat layer 32 may be at least 99 weight percent aluminum oxide in one embodiment, at least 90 weight percent aluminum oxide in another embodiment, at least 50 weight percent aluminum oxide in another embodiment, or at least 20 in another embodiment. It can be a weight percent aluminum oxide.

Due to the incomplete deposition of the overcoat layer 32, the material of the overcoat layer 32 may not be the exact stoichiometric ratio. For example, the term aluminum oxide (Al ₂ O ₃ ) means about two aluminum atoms per three oxygen atoms, such as Al _x O _y , where 1.9 ≦ x ≦ 2.1 and 2.9 ≦ y ≦ 3.1.

As shown in FIG. 5, by extending a part or all of the overcoat layer 32 from the distal end portion 13 _d to the bottom side 13 _s to the bottom surface 13 _b, the side surface 13 _s of the wire 13 Can protect from oxidation. The overcoat layer 32 may include a thickness Th ₃₂ of 10 to 100 nanometers along the side surface 13 _s . The overcoat layer 32 may have this thickness Th ₃₂ along the side surface 13 _s or at points along both side surfaces 13 _s from the distal end 13 _d to the bottom surface 13 _b . Even with the overcoat layer 32 extending down the side 13 _{s of the} wire 13, the channel 15 can still be filled with air. Alternatively, the overcoat layer 32, because they can adversely affect the performance due to its refractive index, the overcoat layer, until the bottom side 13 _s of the wire from the distal end portion 13 _d to the bottom surface 13 _b It may extend only partially, such as <25% of the journey in one aspect or 10-50% of the journey in another aspect.

  The WGP described herein may have one or more of the following differences between the performance measured before the durability test and the performance measured after the durability test: <0.01% Ts Increase, <0.005% Ts increase, <0.001% Ts increase, <1% Rs decrease, <0.5% Rs decrease and <0.25% Rs decrease. These values can be for a single WGP or an average of 100 WGPs. The durability test is performed at a temperature of 300 ° C. for 168 hours or 500 hours. The durability test is performed immediately after manufacture or within 3 weeks after manufacture if the WGP is maintained in a protective environment (eg, room temperature, protected from ultraviolet light, low humidity, etc.). Without the overcoat layer 32, there was an average increase in Ts of about 0.04% and an average decrease in Rs of about 3% after the same durability test of 168 hours.

Prior to the present invention, the main failure of WGP was the broken wire 13. The wire 13 is high (eg, about 200-400 nm) but not too wide (eg, about 50-70 nm) and the distal end 13 _d of the wire 13 was not fixed, so the wire 13 Easily collapsed. The inventors wanted to create a stronger WGP with the wire 13 that is less likely to collapse. Related U.S. Patent Publications include U.S. Patent Application Publication No. 2003/0224116, U.S. Patent Application Publication No. 2012/0075699, U.S. Patent No. 6,288,840, U.S. Patent No. 6,665. 119 and U.S. Pat. No. 7,026,046, which include several ideas for improving durability, and some of these ideas Durability has not been widely used even though durability is a very important issue because it can also cause significant degradation of WGP performance.

  The inventors predicted a significant decrease in performance caused by the addition of the overcoat layer 32, but added the overcoat layer 32 anyway due to the need to increase the stability of the wire. The inventors have discovered that performance degradation due to the addition of the overcoat layer 32 can be avoided by adding an antireflection layer 33 to be disposed on the overcoat layer 32 (FIGS. 3 to 3). 4). The overcoat layer 32 may provide a base or foundation for applying the antireflection layer 33. Any performance degradation due to the addition of the overcoat layer 32 can be avoided or minimized by adding an anti-reflective layer 33 over the overcoat layer 32. This performance quantification is described in the method section below.

As shown in WGP 30 of FIG. 3, the antireflective layer 33 may include a plurality of thin film layers 31 disposed on the overcoat layer 32 that extend continuously across the overcoat layer 32, and the overcoat. Reflection of incident light at the layer 32 can be reduced. An example of the thin anti-reflective layer 33 is at least two pairs of layers, each pair comprising a layer of silicon dioxide, a layer of 95% ZrO ₂ and 5% TiO ₂ and the thickness of each layer Is 30 to 300 nanometers.

As shown in the WGP 40 of FIG. 4, the antireflection layer 33 may include a plurality of protrusions 41 formed in an array and disposed on the overcoat layer 32. The protrusion 41 can be designed to reduce the reflection of incident light at the overcoat layer 32. For example, each protrusion ₄₁ may have a width W ₄₁ and a height H ₄₁ less than 700 nanometers.

As shown in FIG. 6, the conformal coat layer 61 may be disposed on the wire 13. The conformal coat layer 61 can cover the exposed surface of the wire 13. The conformal coat layer 61 can also be disposed on the exposed surface of the substrate 11 (“exposed surface” means the surface of the substrate not covered with the wire 13). The use of conformal coat layer 61 can be beneficial. Because by following the outer shape of the wire 13 and the exposed surface of the substrate 11, the thickness T61 of the conformal coat layer ₆₁ can be minimized, thus reducing any adverse effects of the conformal coat layer 61 on WGP performance. It is. For example, the maximum thickness of conformal coat layer 61 may be <5 nanometers (nm) in one aspect, <10 nm in another aspect, <25 nm in another aspect, or <50 nm in another aspect.

  The conformal coat layer 61 may include an oxidation barrier layer, a moisture barrier layer, or both. Oxidation of the WGP wire 13 can degrade the performance of the WGP by adversely affecting contrast or Rs. Since the oxidation barrier layer can reduce the oxidation of the wire 13, such degradation of WGP performance can be reduced or avoided. The term “oxidation barrier” refers to a first material that can reduce oxygen intrusion into a second material, which can oxidize the second material. An oxidation barrier may be placed on the wire 13 to protect the wire 13 from oxidation. Non-limiting examples of chemicals that can be used as the oxidation barrier layer include aluminum oxide, silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, or combinations thereof.

  WGP corrosion can degrade WGP performance. For example, moisture can condense on the WGP and be carried to the narrow channel 15 between the wires 13 by capillary action. Thereafter, moisture can corrode the wire 13. Corroded areas can have a reduced contrast and Rs can be altered or not polarized at all. The moisture barrier can resist corrosion. The moisture barrier may protect the wire 13 from moisture or other corrosion. Examples of chemicals that can be used as a moisture barrier include, but are not limited to, hafnium oxide, zirconium oxide, aminophosphonate, or combinations thereof. Examples of corrosion protection chemicals are described in US Pat. No. 6,785,050 and US Patent Publication No. 2016/0291209, both of which are hereby incorporated by reference in their entirety. Incorporated into.

  The conformal coat layer 61 includes rare earth oxides such as oxides of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, cadmium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. obtain. These rare earth oxides can be at least part of an oxidation barrier layer, a moisture barrier layer, or both.

The conformal coat layer 61 may be different from the wire 13, that is, (1) there may be a boundary line or boundary layer between the wire 13 and the conformal coat layer 61, or (2) the material of the conformal coat layer 61. There may be some difference compared to the material of the wire 13. For example, natural aluminum oxide can be formed on the surface of the aluminum wire 13. Thereafter, a layer of aluminum oxide (oxidation barrier layer) can be applied to the ribs (eg, by ALD). This additional layer of aluminum oxide is important because the thickness and / or density of native aluminum oxide may be insufficient to protect the core of wire 13 (eg, substantially pure aluminum) from oxidation. It can be. In this example, the oxidation barrier layer (Al ₂ O ₃ ) has the same material composition as the surface of the wire 13 (Al ₂ O ₃ ), but the oxidation barrier layer is (1) between the oxidation barrier layer and the wire 13. And / or (2) may still differ due to differences in material properties such as increased density of the oxidation barrier layer relative to native aluminum oxide.

[Image projector]
The WGP described herein may be used in an image projector, such as the image projector 70 shown in FIG. 7 or the image projector 80 shown in FIG. The image projector 70 or 80 can be a light source 71 or 81 that can emit a beam 73 or 83 of light, one or more spatial light modulators 77, and one or more according to the WGP embodiments described herein. Multiple WGPs 74 may be included.

  Spatial light modulator 77 may be arranged to receive at least a portion of light beam 73 or 83. The spatial light modulator 77 can have a plurality of pixels, and each pixel can receive a signal. The signal can be an electronic signal. Depending on whether each pixel receives a signal or the strength of the signal, the pixel may rotate the polarization of a portion of the beam of light 73 or 83, or the light without causing a change in polarization. A part of the beam 73 or 83 can be transmitted or reflected. The one or more spatial light modulators 77 can be liquid crystal devices / displays (LCDs) and can be transmissive, reflective or transflective.

  One or more WGPs 74 may be placed in at least a portion of the light beam 73 or 83 before entering the spatial light modulator 77, after leaving the spatial light modulator 77, or both. One or more WGPs 74 provide each polarization to the spatial light modulator 77 and depending on the type and rotation of the WGP 74 and whether each pixel has received a signal, each pixel of the spatial light modulator 77. Helps to form an image by transmitting, reflecting, or absorbing light from it.

  Projection lens system 75 may be arranged to receive at least a portion of light beam 73 or 83 and project an image. Projection lens system 75 is described in US Pat. No. 6,585,378 and US Pat. No. 6,447,120, which are hereby incorporated by reference in their entirety. Alternatively, the light beam 73 or 83 can be emitted directly to the user's eye or to another device in place of the projection lens system 75.

As shown in FIG. 7, the image projector 70 may further include a color division optics 72 and a color synthesis optics 78. The light source 71 may emit a beam 73 of light that may initially be unpolarized. The color splitting optics 72 can be positioned to receive at least a portion of the light beam 73, can be positioned between the light source 71 and the spatial light modulator 77, and the light beam 73 can be of a plurality of different colors. dividing the light beam may define a colored beam 73 _c. Beam 73 _c colored may be primary colors.

Color combining optics 78, positioned to receive at least a portion of the deployed obtained, and colored beams 73 _c between the SLM 77 and the projection lens system 75 (or the user's eye or other device) Can be done. Color combining optics 78 may re-synthesize at least a portion of colored beams 73 _c to the final beam or the combined beam 73 _f. Color synthesis optics 78 is used in computer projectors to combine different colors of light into a single image for projection. The color synthesis optics 78 may be referred to as an X-Cube, X-Cube prism, X-prism, light recombination prism, or cross dichroic prism. X-Cubes are typically made from four right angle prisms with dichroic coatings that are fixed to form a cube.

The projection lens system 75 can be arranged to receive the combined beam 73 _f and can project a colored image 73 _i . The colored image 73 _i can be projected on the screen 76 or onto the human eye.

The spatial light modulator 77 may be arranged to receive at least one of the colored beams 73 _c in the optical path between the color splitting optics 72 and the color synthesis optics 78. Image projector 70 may include a spatial light modulator 77 in each of the colored beams 73 _c. One or more WGP74 is before entering the spatial light modulator 77 may be disposed on at least one of or beam 73 _c with both the color after exiting from the spatial light modulator 77.

As shown by the image projector 80 in FIG. 8, the light source 81 can sequentially emit a plurality of different colored light beams to define a colored beam 83. The colored beam 83 can be a primary color. Projection lens system 75 (or the user's eye or other device) may be arranged to receive colored beam 83 and may project colored image 73 _i . The colored image 73 _i can be projected on the screen 76 or onto the human eye. The spatial light modulator 77 can be arranged to receive the colored beam 83 in the optical path between the light source 81 and the projection lens system 75. The WGP 74 may be placed in the colored beam 83 before entering the spatial light modulator 77, after leaving the spatial light modulator 77, or both.

[Method]
The WGP manufacturing method may include some or all of the following steps that may be performed in the following order. There may be additional steps not described below. These additional steps can be before, between or after the described steps.
1. Providing an array of wires 13 disposed on the surface 11 _f of the transparent substrate 11; The array of wires 13 can be substantially parallel and elongated, with a channel 15 between adjacent wires 13. The channel 15 can be filled with air. Each wire 13 may have a cross-sectional profile in which the bottom surface 13 _b is disposed closest to the substrate 11 and the distal end 13 _d is disposed furthest from the substrate 11. Each wire 13 has opposing side surfaces 13 _s that each face a channel 15 on the opposing side surface 13 _s of the wire and extend from the bottom surface 13 _b to the distal end 13 _d. Can do. Please refer to FIGS.
2. Applying a conformal coat layer 61 to the side 13 _s and distal end 13 _d of the wire 13 while maintaining the channel 15 filled with air. Methods for applying conformal coat layer 61 include sputter deposition and vapor deposition. Application of conformal coat layer 61 may include one of the following: (i) applying a moisture barrier layer after applying an oxidation barrier layer; (ii) applying a moisture barrier layer followed by applying an oxidation barrier layer. Or (iii) applying a moisture barrier or oxidation barrier layer. See FIG. 6 and the description of the oxidation barrier layer, moisture barrier layer and conformal coat layer 61 described above.
3. At the distal end portion 13 _d of the array of wires 13, by applying the overcoat layer 32 over the conformal coating layer 61 to span multiple channels 15, and channel 15 to maintain a state of being filled with air step . Overcoat layer 32 may include the above-described materials in weight percent as described above. The overcoat layer 32 may extend down the side surface 13 _{s of the} wire 13 from the distal end 13 _d to the bottom surface 13 _b . The overcoat layer 32 may include various thicknesses T ₃₂ such as 10-100 nanometers along the side surface 13 _s of the wire 13. The overcoat layer 32 can be applied by sputter deposition. See FIGS. 3-5 and the description of overcoat layer 32 above.
4). Applying an antireflection layer 33 on the overcoat layer 32; Please refer to FIGS. 3 to 4 and the description of the antireflection layer 33.

In the method described above, some or all of the performance lost by applying the overcoat layer 32 can be regained by applying the anti-reflective layer 33. Thus, one or more of the following formulas may be true: Tp ₁ -Tp ₂ <2%, Tp ₁ -Tp ₂ <1.5%, Tp ₁ -Tp ₂ <1% or Tp ₁ -Tp ₂ < 0.5%, where the subscript 1 refers to the performance before applying the overcoat layer 32 and the subscript 2 refers to the performance after applying the antireflective layer 33.

Claims (10)

An array of wires disposed on a surface of a transparent substrate, substantially parallel and elongated, with channels between adjacent wires;
Each wire of the array of wires has a cross-sectional profile in which the bottom surface is disposed closest to the transparent substrate and the distal end is disposed furthest from the transparent substrate, and the opposing side surfaces are An array of wires each facing the channel on the opposite side of the wire and extending from the bottom surface to the distal end;
An overcoat layer disposed at the distal end of the array of wires and spanning the channel; and covering the side of the wire and the distal end of the wire between the wire and the overcoat layer A wire grid polarizer (WGP) comprising a conformal coat layer comprising a moisture barrier layer.   The WGP according to claim 1, wherein the conformal coat layer further includes a layer of aluminum oxide different from the wire, disposed between the moisture-proof layer and the wire.   The WGP according to claim 1 or 2, further comprising an antireflection layer disposed on the overcoat layer.   The WGP according to any one of claims 1 to 3, wherein the overcoat layer includes aluminum oxide.   5. The WGP according to claim 1, further comprising an antireflection layer disposed on the overcoat layer, wherein the overcoat layer includes aluminum oxide. 6.   The WGP according to any one of claims 1 to 5, capable of withstanding a 168 hour durability test at 300 ° C immediately after manufacture with an increase in Ts of less than 0.005%.   The WGP according to any one of claims 1 to 6, capable of withstanding a durability test of 168 hours at 300 ° C immediately after production with a reduction in Rs of less than 0.5%.   8. A WGP according to any one of the preceding claims, capable of withstanding a 168 hour durability test at 300 ° C immediately after manufacture with an increase in Ts of less than 0.005% on average over 100 WGPs. . Forming part of an image projector, the image projector
A light source capable of emitting a beam of light;
A spatial light modulator arranged to receive at least a portion of the beam of light and having a plurality of pixels, each pixel receiving a signal and causing a change in polarization based on the signal A spatial light modulator capable of transmitting at least part of the beam of light without rotating or rotating the polarization of at least part of the beam of light,
Including
9. The WGP according to any one of claims 1 to 8, wherein the WGP is disposed in at least a portion of the beam of light before entering the spatial light modulator, after exiting the spatial light modulator, or both. WGP of description. The overcoat layer extends down the side of the wire from the distal end to the bottom including a thickness of 10 to 100 nanometers;
The WGP according to any one of claims 1 to 9, wherein the channel is filled with air.

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