TWI872763B - Method for manufacturing a wire-grid polarizer - Google Patents

Abstract

A method for manufacturing a wire-grid polarizer, comprising forming a thin metal layer on a transparent substrate, followed by the electroforming process to form a plurality of metal wires on the thin metal layer, and finally performing a chemical reaction to convert the thin metal layer exposed between the plurality of metal wires into a transparent dielectric layer to form the metal wire polarizer.

Description

Method for manufacturing metal wire polarizer

The present invention relates to a wire-grid polarizer (WGP), and more particularly to a method for manufacturing a low-cost wire-grid polarizer with good transmittance and extinction ratio.

FIG1 shows a conventional metal wire polarizer 10 to illustrate the operating principle of the metal wire polarizer 10. FIG2 shows a cross-sectional view of the metal wire polarizer 10 of FIG1. The metal wire polarizer 10 includes a transparent substrate 12 and a plurality of metal wires 14. The plurality of metal wires 14 are arranged in parallel on the transparent substrate 12 to form a metal wire grid. Assuming that the incident light Li is unpolarized light, the incident light Li includes P polarized light Ip and S polarized light Is, wherein the intensities of the P polarized light Ip and the S polarized light Is are equal. The electric field of the P polarized light Ip is perpendicular to the plurality of metal wires 14, while the electric field of the S polarized light Is is parallel to the plurality of metal wires 14. When the incident light Li irradiates the metal wire polarizer 10, the S polarized light Is interacts with the plurality of metal wires 14 to form an electric dipole, so that most of the S polarized light Is is reflected by the metal wire polarizer 10 and becomes the S polarized light Rs of the reflected light Lr, and only a small part of the S polarized light Is passes through the metal wire polarizer 10 and becomes the S polarized light Ts of the transmitted light Lt. Since the electric field of the P polarized light Ip is perpendicular to the plurality of metal wires 14, it does not interact with the plurality of metal wires 14 to generate an electric dipole, and the P polarized light Ip almost completely passes through the metal wire polarizer 10, that is, the P polarized light Ip of the incident light Li is almost equal to the P polarized light Tp of the transmitted light Lt.

The quality of the metal wire polarizer 10 can be judged by the transmittance Tr and extinction ratio Er of the metal wire polarizer 10, where Tr=Tp/Ip and Er=Tp/Ts. The greater the transmittance Tr and extinction ratio Er, the better the effect of the metal wire polarizer 10. Generally speaking, the smaller the line width W of the metal wire 14 and the higher the height H, the greater the transmittance Tr and extinction ratio Er.

In order to obtain good transmittance Tr and extinction ratio Er, the metal wire polarizer 10 is manufactured using process technologies such as nano-imprint lithography and dry etching. However, the production cost of nano-scale lithography and dry etching is relatively high, resulting in the unit price of the metal wire polarizer 10 being too high, making it difficult to promote the application scope of the metal wire polarizer 10 and expand the scale of its application market.

FIG3 shows a cross-sectional view of a metal wire polarizer 20 made using an electrocasting process. The metal wire polarizer 20 of FIG3 includes a transparent substrate 22, a transparent conductive layer 24, and a plurality of metal wires 26. Since the metal wires 26 cannot be directly electrocasted on the transparent substrate 22, a transparent conductive layer 24 must be first covered on the transparent substrate 22, and then a plurality of metal wires 26 are formed on the transparent conductive layer 24 by electrocasting. The plurality of metal wires 26 are arranged in parallel on the transparent conductive layer 24 to form a metal wire grid. The cost of the electrocasting process is relatively low, about 1/10 of the process such as nanoimprint lithography and dry etching. In order to have good electrocasting properties, the thickness of the transparent conductive layer 24 needs to be increased to reduce the resistance of the transparent conductive layer 24, thereby increasing the electrocasting rate and improving the uniformity of the electrocasting. However, the transparent conductive layer 24 has optical absorption rate and conductivity, so as the thickness of the transparent conductive layer 24 increases, the transmittance Tr and extinction ratio Er of the metal linear polarizer 20 will decrease.

Therefore, a method for manufacturing a metal wire polarizer with low cost and good transmittance and extinction ratio is desired.

The purpose of the present invention is to provide a method for manufacturing a metal wire polarizer with low cost and good transmittance and extinction ratio.

According to the present invention, a method for manufacturing a metal wire polarizer includes forming a thin metal layer on a transparent substrate, then forming a plurality of metal wires on the thin metal layer by an electrocasting process, and finally performing a chemical reaction to convert the portion of the thin metal layer exposed between the plurality of metal wires into a transparent dielectric layer to form the metal wire polarizer. The metal wire of the present invention is formed by an electrocasting process, so the cost of the metal wire polarizer of the present invention is relatively low, and the thin metal layer between the plurality of metal wires is converted into a transparent dielectric layer by a chemical reaction, so the metal wire polarizer of the present invention has good transmittance and extinction ratio.

Figure 4 is a first embodiment of the method for manufacturing a metal linear polarizer of the present invention. FIGS. 5 to 10 are used to illustrate the manufacturing method of FIG. 4 . As shown in step S10 of FIG. 4 and FIG. 5 , the manufacturing method of the metal linear polarizer 30 of the present invention includes forming a thin metal layer 34 on a transparent substrate 32 , where the material of the thin metal layer 34 can be but is not limited to aluminum, nickel, copper or iron. One of the functions of the thin metal layer 34 is to form metal lines through an electroforming process in the following step S12.

After the thin metal layer 34 is formed, step S12 is then performed. In step S12, a photoresist pattern 40 is first formed on the thin metal layer 34, as shown in FIG6 . The photoresist pattern 40 can be a hard photoresist or a soft photoresist. The photoresist pattern 40 can be formed using, but is not limited to, an embossing adhesive. After the photoresist pattern 40 is formed, a plurality of parallel metal wires 36 are then formed on the area of the thin metal layer 34 not covered by the photoresist pattern 40 using an electroplating process, as shown in FIG7 . The materials of the thin metal layer 34 and the metal wires 36 can be the same or different. After the plurality of metal wires 36 are formed, the photoresist pattern 40 is removed, as shown in FIG8 . In FIG. 8 , the cross-sectional shape of the metal wire 36 is a rectangle, but the present invention is not limited thereto. The shape of the metal wire 36 may be various regular or irregular shapes, for example, the cross-sectional shape of the metal wire 36 may be a trapezoid that is wide at the top and narrow at the bottom or narrow at the top and wide at the bottom.

After forming a plurality of metal lines 36 and removing the photoresist pattern, step S14 is performed. Step S14 is to chemically react the portion of the thin metal layer 34 exposed between the plurality of metal lines 36 to convert the portion into a transparent dielectric layer 38, so that incident light can pass through. The chemical reaction of step S14 includes but is not limited to oxidation, nitridation, fluorination or sulfidation. After the chemical reaction of step S14, the thin metal layer 34 and the metal lines 36 form a metal wire grid to form the metal wire polarizer 30 of the present invention.

In one embodiment, if the thin metal layer 34 and the metal wire 36 are made of the same material, or the thin metal layer 34 and the metal wire 36 are made of different materials but both can undergo chemical reactions, the thin metal layer 34 exposed between the plurality of metal wires 36 and the surface layer of the plurality of metal wires 36 will be converted into a transparent dielectric layer 38 in the chemical reaction of step S14, as shown in FIG. 9 .

In one embodiment, if the thin metal layer 34 and the metal wires 36 are made of different materials and the metal wires 36 do not undergo chemical reactions, only the thin metal layer 34 exposed between the plurality of metal wires 36 is converted into a transparent dielectric layer 38 during the chemical reaction in step S14, as shown in FIG. 10 .

In one embodiment, when the thin metal layer 34 and the metal wire 36 are made of different materials and the activity of the thin metal layer 34 is greater than that of the metal wire 36, after the chemical reaction in step S14, a larger portion of the thin metal layer 34 is converted into the dielectric layer 38, so the metal wire grid will present a shape that is wider at the top and narrower at the bottom, as shown in FIG. 11 .

In one embodiment, the metal line 36 may be composed of multiple layers of different materials. As shown in FIG12 , each metal line 36 includes a first metal layer 362 and a second metal layer 364. When the activity of the first metal layer 362 is greater than that of the second metal layer 364, after the chemical reaction in step S14, a larger portion of the first metal layer 362 is converted into the dielectric layer 38, so the metal line 36 will present a shape that is narrow at the top and wide at the bottom, as shown in FIG12 . On the contrary, when the activity of the first metal layer 362 is less than that of the second metal layer 364, after the chemical reaction in step S14, a larger portion of the second metal layer 364 is converted into the dielectric layer 38, so the metal line 36 will present a shape that is wide at the top and narrow at the bottom.

Figure 13 is a second embodiment of the manufacturing method of the metal linear polarizer of the present invention. Figures 14 to 19 are used to illustrate the manufacturing method of Figure 13. As shown in step S20 of FIG. 13 and FIG. 14 , the manufacturing method of the metal linear polarizer 50 of the present invention includes forming an optical film layer 52 on a transparent substrate 32 , where the optical film layer 52 may be but is not limited to an anti-reflective layer. After the optical film layer 52 is formed, step S22 is performed. A thin metal layer 34 is formed on the optical film layer 52, as shown in FIG. 15 .

After the thin metal layer 34 is formed, step S24 is performed. In step S24, a photoresist pattern 40 is first formed on the thin metal layer 34, as shown in FIG16. After the photoresist pattern 40 is formed, a plurality of parallel metal lines 36 are formed on the area of the thin metal layer 34 not covered by the photoresist pattern 40 by an electroplating process, as shown in FIG17. The materials of the thin metal layer 34 and the metal lines 36 can be the same or different. After the plurality of metal lines 36 are formed, the photoresist pattern 40 is removed, as shown in FIG18.

After forming the plurality of metal lines 36 and removing the photoresist pattern, step S26 is performed. Step S26 is to chemically react the portion of the thin metal layer 34 exposed between the plurality of metal lines 36 to convert the portion into a transparent dielectric layer 38, so that incident light can pass through. If the thin metal layer 34 and the metal lines 36 are made of the same material, or the thin metal layer 34 and the metal lines 36 are made of different materials but both can undergo a chemical reaction, the thin metal layer 34 exposed between the plurality of metal lines 36 and the surface layer of the plurality of metal lines 36 will be converted into a transparent dielectric layer 38 in the chemical reaction of step S26, as shown in FIG. 19 . After the chemical reaction in step S26, the thin metal layer 34 and the metal wire 36 form a metal wire grid to form the metal wire polarizer 50 of the present invention. The chemical reaction in step S26 includes but is not limited to oxidation, nitridation, fluorination or sulfidation.

The manufacturing method of the present invention is to form the metal wire 36 by an electrocasting process, so the cost of the metal wire polarizer 30 and 50 of the present invention is relatively low, and the thin metal layer 34 between the plurality of metal wires 36 is converted into a transparent dielectric layer 38 through a chemical reaction, so the metal wire polarizer of the present invention has good transmittance and extinction ratio. On the other hand, the metal wire grid of the metal wire polarizer 10 and 20 of FIG. 2 and FIG. 3 only includes the metal wire 14 or 26, while the metal wire grid of the metal wire polarizer 30 of FIG. 10 includes the thin metal layer 34 and the metal wire 36, so the height of the metal wire grid of the metal wire polarizer 30 of the present invention is greater than the height of the metal wire grid of the metal wire polarizer 10 and 20, and thus has better transmittance and extinction ratio. In FIGS. 9 and 19 , the chemical reaction causes the surface layer of the metal wire 36 to be converted into a dielectric layer 38. Generally speaking, the thickness of the converted surface layer will not be greater than the thickness of the thin metal layer 34. Therefore, compared with the metal wire grids of the metal wire polarizers 10 and 20 of FIGS. 2 and 3 , the metal wire grids of the metal wire polarizers 30 and 50 of FIGS. 9 and 19 have a smaller width and a higher height, and thus have better transmittance and extinction ratio.

The above is only an embodiment of the present invention and does not constitute any form of limitation on the present invention. Although the present invention has been disclosed as above by the embodiments, it is not intended to limit the present invention. Any person with ordinary knowledge in the relevant technical field can make some changes or modifications to the technical contents disclosed above into equivalent embodiments within the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

10: Metal wire polarizer 12: Transparent substrate 14: Metal wire 20: Metal wire polarizer 22: Transparent substrate 24: Transparent conductive layer 26: Metal wire 30: Metal wire polarizer 32: Transparent substrate 34: Thin metal layer 36: Metal wire 38: Dielectric layer 40: Photoresist pattern 50: Metal wire polarizer 52: Optical thin film layer Er: Extinction ratio H: Height Ip: P polarized light Is: S polarized light Li: Incident light Lr: Reflected light Lt: Transmitted light Rs: S polarized light S10: Step S12: Step S14: Step S20: Step S22: Step S24: Step S26: Step Tp: P polarized light Tr: Transmittance Ts: S polarized light W: Line width

FIG. 1 shows a conventional metal wire polarizer. FIG. 2 shows a cross-sectional view of the metal wire polarizer of FIG. 1. FIG. 3 shows a cross-sectional view of a metal wire polarizer made using an electrocasting process. FIG. 4 shows a first embodiment of a method for making a metal wire polarizer of the present invention. FIG. 5 to FIG. 10 are used to illustrate the method for making FIG. 4. FIG. 11 shows an embodiment in which the activity of a thin metal layer is greater than that of a metal wire. FIG. 12 shows an embodiment in which a metal wire is composed of multiple layers of different materials. FIG. 13 shows a second embodiment of a method for making a metal wire polarizer of the present invention. FIG. 14 to FIG. 19 are used to illustrate the method for making FIG. 13.

S10: Step

S12: Step

S14: Step

Claims (7)

A method for manufacturing a metal line polarizer comprises the following steps: forming a thin metal layer on a transparent substrate; forming a plurality of metal lines on the thin metal layer by an electrocasting process, wherein the plurality of metal lines are arranged in parallel and a portion of the thin metal layer is exposed between the plurality of metal lines; and performing a chemical reaction to convert the portion of the thin metal layer into a transparent dielectric layer to form the metal line polarizer. A production method as described in claim 1, wherein the chemical reaction includes oxidation, nitridation, fluorination or sulfidation. The manufacturing method as described in claim 1, wherein the surface layer of the plurality of metal wires is converted into the dielectric layer through the chemical reaction. A manufacturing method as described in claim 1, wherein the plurality of metal wires and the thin metal layer are made of the same material. A manufacturing method as described in claim 1, wherein the plurality of metal wires and the thin metal layer are made of different materials. The manufacturing method as described in claim 1, wherein each of the metal lines includes multiple layers of different materials. The manufacturing method as described in claim 1 further includes forming an optical thin film layer between the transparent substrate and the thin metal layer.