KR20070092368A - Nano wire grid polarizer and fabrication method thereof - Google Patents

Abstract

A nano wire grid polarizer and a fabrication method thereof are provided to increase an area thereof by performing a simple manufacturing process with a low cost. A resin layer(902) is formed on a base material(901). A nano-sized grid pattern is formed on the resin layer. A conductive metal layer(903) is formed on the resin layer on which the nano-sized grid pattern is formed on. The conductive metal layer is selectively removed from a convex part of the pattern. The base material includes a single resin or a mixed resin of one or more elements selected from glass, quartz, polyester, poly vinyl chloride, poly carbonate, poly-methyl-meta-acrylate, polystyrene, polyester-sulfone, and polyester-ketone. A protective layer(904) is formed on the polarizer.

Description

Nano Wire Grid Polarizer and Fabrication Method Thereof

1 is a schematic view showing the principle of operation of a conventional wire grid polarizer;

2 is a schematic diagram showing in more detail the principle of operation of a wire grid polarizer as a conventional reflective polarizer;

3 is a schematic diagram showing a schematic shape of a conventional wire grid polarizer;

4 is a schematic diagram showing a manufacturing process of a wire grid polarizer using a photomask exposure and etching method according to the prior art;

5 is a schematic diagram showing a manufacturing process of a wire grid polarizer using a nanoimprinting method and an etching method according to the prior art;

6 is a schematic diagram of a process for fabricating a stamper using an interference lithography method;

7 is a schematic diagram illustrating a manufacturing process of a nanowire grid polarizer according to an embodiment of the present invention;

8 is a schematic diagram showing a manufacturing process of a nanowire grid polarizer according to another embodiment of the present invention; And

9 is a cross-sectional view illustrating a structure of a nanowire grid polarizer according to an embodiment of the present invention.

<Explanation of symbols for main parts of the drawings>

801, 901

701, 802, 902: resin layer

702, 803, 903: conductive metal layer

703: adhesive film

710, 810: Stamper

904: protective layer

The present invention relates to a nano wire grid polarizer and a method of manufacturing the same. In particular, the present invention relates to a nano-sized wire grid polarizer having a good polarization separation performance in the visible light region and a manufacturing method thereof.

The polarizer or the polarizer refers to an optical device that derives linearly polarized light having a specific vibration direction among unpolarized light such as natural light. One type of optical device, the wire grid polarizer, is an optical device that generates polarized light using a conductive wire grid as illustrated in FIG . 1 . Since it has higher polarization separation performance than other polarizers, it has been used as a reflective polarizer useful in the wavelength range of the infrared region for more than 110 years.

That is, as shown in FIG. 2 , the wire grid polarizer has a component having a vector orthogonal to the conductive wire grid when light in an unpolarized state is incident when the distance between the wire grids, that is, the pitch is smaller than the wavelength of the incident light, that is, P-polarized light (or Transverse Magnetic polarized light) transmits and reflects a component having a vector parallel to the wire grid, that is, S-polarized light (or Trans-electric Electric (TE) polarized light). However, when the pitch between the wire grids is not small enough, the incident light is not polarized and diffracted, making it difficult to expect a desired effect.

The most important factor that determines the performance of the wire grid polarizer is the relationship between the gap pitch between the wire grids and the incident light wavelength.

As known from U.S. Patent No. 6,122,103 and the like, in the wire grid polarizer as shown in FIG. 3 , the pitch p of the wire grid is in the range of 1/2 to twice the incident light wavelength, that is, in the transition region. When present, it is known that polarization separation performance is greatly reduced for light of a specific wavelength. In other words, in this phenomenon known as Rayleigh resonance, the longest wavelength at which polarization separation performance can occur is expressed by the following equation.

Where p is the wire grid pitch

        n: refractive index of the substrate

θ: incident angle of light

That is, in order for the wire grid polarizer to exhibit sufficient polarization separation performance in the visible light region, the maximum wavelength λ _max that Rayleigh resonance can occur must be shorter than the wavelength of the visible light region. For example, when the angle of incidence of light is within a range of 75 degrees, the wire grid pitch that may exhibit good polarization separation performance is theoretically known to have a maximum value of about 150 nm to 200 nm depending on the refractive index of the substrate.

However, in order to manufacture a nanowire grid having such a pitch, it is necessary to manufacture expensive masks, and complex manufacturing methods such as electron beams and X-ray lithography are complicated, low efficiency, and complicated processes that are difficult to manufacture in large areas. Therefore, it could not be used for a liquid crystal display device for a display and its application has been limited only to an optical element of a small size.

Specifically, conventional wire grid polarizers are typically manufactured by the following two methods.

One method is illustrated in FIG. 4 . According to this method, a conductive metal film is formed on an inorganic substrate such as glass or quartz, a photoresist layer is formed thereon, and the photoresist layer is selectively exposed, developed and patterned by a photomask. Subsequently, the conductive metal film stacked below the photoresist layer is etched using the patterned photoresist layer to pattern the conductive metal film layer. Next, the photoresist layer is removed.

Another method is illustrated in FIG. 5 . According to this method, after forming a conductive metal film on an inorganic substrate and forming a photoresist layer thereon, the photoresist layer is deformed by pressing with a stamper and patterned by exposure and development. Subsequently, the conductive metal film layer laminated under the photoresist layer is etched using the patterned photoresist layer to pattern the conductive metal film layer, and the photoresist layer is removed.

As described above, the wire grid polarizer manufacturing method according to the related art requires a photoresist layer formed on the conductive metal film layer, a patterned photoresist layer, and a photoresist layer removed to pattern the conductive metal film layer. The process is complex and expensive. In addition, since the photomask or stamper used in the conventional method is manufactured by using an electron beam or X-ray, etc., it has to be manufactured with a small area. Therefore, the wire grid polarizer cannot be manufactured in a large area by the prior art.

Accordingly, an object of the present invention is to provide a nanowire grid polarizer having a good polarization separation performance in the visible light region and realizing a large area at low cost and a method of manufacturing the same.

In order to achieve the above technical problem, the present invention comprises the steps of forming a grid pattern with a nano-sized resin layer, forming a conductive metal layer on the upper surface of the resin layer formed with the pattern, the conductivity formed in the convex portion of the pattern It provides a method of manufacturing a nano-wire grid polarizer comprising the step of selectively removing only the metal layer.

The present invention also provides a nanowire grid polarizer comprising the conductive metal layer formed in the recess between the grid patterned resin layer and the nano-scale patterned resin layer prepared by the method.

In another aspect, the present invention provides a nanowire grid polarizer comprising a substrate, a nano-scale grid patterned conductive metal layer prepared on the substrate, by the method.

Hereinafter, the present invention will be described in detail.

The nanowire grid polarizer according to the first exemplary embodiment of the present invention may include a substrate functioning as a support, a conductive metal layer formed on a concave portion between the grid patterned resin layer and the grid patterned resin layer having a nano size on an upper surface of the substrate. It is configured to include.

In the present invention, the substrate and the resin layer may be integrally formed or separately formed.

When the resin layer is integrally formed with the substrate, it is preferable that the resin layer uses an optically transparent organic material such as plastic, which can both serve as a support and also serve as a molding resin in which a pattern can be formed. Do. Non-limiting examples of the resin layer is a polyester, polyether sulfone, polycarbonate, polyester naphthenate-based or polyacrylate-based resin including urethane acrylate, epoxy acrylate, ester acrylate, etc. Etc. can be mentioned. When using a resin layer made of such a material, a separate substrate may not be used.

When the resin layer is formed separately from the substrate, the nanowire grid polarizer according to the present invention is configured to include a substrate and a resin pattern grid-patterned to a nano size on an upper surface of the substrate.

Herein, the substrate serves as a support of the polarizer, and is preferably an optically transparent organic or inorganic material. In particular, an inorganic material such as glass or quartz, or an organic resin selected from polyester, polyvinyl chloride, polycarbonate, polymethyl methacrylate, polystyrene, polyester sulfone, and polyether ketone, etc. It may be used in the form of a film or sheet prepared by mixing.

In addition, the resin layer formed on the upper surface of the substrate may be easily formed nano-scale fine pattern, excellent adhesion with the substrate, when forming a fine pattern by the stamper, easy from the stamper which is a mold after curing It is preferable that it is a transparent liquid photocurable resin having a low viscosity so that it can be separated easily. The preferable viscosity is 300 cps or less, More preferably, it is 100-200 cps.

Non-limiting examples of the photocurable resins include urethane acrylate, epoxy acrylate, ester acrylate, and the like, and these may be used alone or in combination of two or more thereof. In this case, for efficient and rapid photocuring, a radical generating monomer, a photoinitiator, or the like may be further mixed and used.

In the present invention, the nano grid pattern of the resin layer may be formed by pressing, thermosetting or photocuring by a stamper which is a mold finely patterned to a nano grid shape. Here, the nano grid pattern means that the interval of the wire grid, that is, the pitch is 1000 nm or less. The nano grid pattern of the stamper is formed by interference lithography, which does not require a mask and can easily make a large area pattern, and thus can be preferably used for nanogrid patterning of polarizers. Non-limiting examples of the mold material of the stamper may be a metal such as nickel, chromium, rhodium, or an organic material such as epoxy, silicon, or the like.

In the present invention, the conductive metal layer formed on the concave portion of the resin layer surface is used to provide electrical conductivity to the grid portion of the polarizing device of the present invention to exhibit polarization separation performance using a metal material excellent in electrical conductivity and optical performance It is desirable to. Non-limiting examples of the conductive metal layer may include silver, copper, chromium, platinum, gold, nickel, aluminum, and the like, but silver, gold, or aluminum may be particularly preferably used because of excellent electrical conductivity and optical performance. have.

In the present invention, the method of forming the conductive metal layer is not particularly limited, but may be formed using a method such as sputtering, heat evaporation, or electron beam evaporation. have. In particular, in the case of the thermal deposition or electron beam deposition method, the nanopattern resin layer and the evaporation deposition source may be deposited using an oblique deposition method that is deposited at a predetermined angle, not vertical. The thickness of the conductive metal layer formed at this time is determined by the pitch of the grid pattern or the like, but the thickness of the transmittance is preferably 1% or less, specifically, about 30 nm to 300 nm, more preferably about 50 nm to 300 nm. It is because the polarization separation performance with respect to the incident light of a polarizer in the said range is excellent.

In the first embodiment of the present invention, the polarizer can be manufactured by removing the conductive metal layer of the convex portion of the conductive metal layer formed on the entire surface of the resin layer by the method described below.

In addition, the polarizer according to the second exemplary embodiment of the present invention is configured to include a substrate and a metal layer, and may be manufactured by removing the resin layer from the polarizer according to the first exemplary embodiment.

It is preferable that a protective layer is additionally formed on the upper surface of the polarizer according to the present invention, and the protective layer may serve to prevent physical property degradation due to direct external exposure of the polarizer. Non-limiting examples of the material from which the protective layer can be formed include epoxy acrylate and the like. The protective layer may be formed by a coating method or the like. If necessary, the protective layer may further include an additive that can additionally provide functions such as adhesion, antistatic, and abrasion resistance.

In addition, the method of manufacturing a nanowire grid polarizer of the present invention comprises the steps of (a) forming a grid pattern on the resin layer in nano size, (b) forming a conductive metal layer on the upper surface of the resin layer on which the pattern is formed and (c) And selectively removing only the conductive metal layer formed on the convex portion of the pattern.

In the step (c), selectively removing the conductive metal layer may include selectively removing only the conductive metal layer formed on the convex portion of the convex portion through a mechanical or chemical wet etching method. It includes the system.

In this step, the mechanical removal method is a step of plywood the pressure-sensitive adhesive coated film on the conductive metal layer and peeled off the laminated adhesive film in parallel with the width direction of the nano-grid pattern formed on the convex portion of the pattern Removing only the conductive metal layer. Accordingly, only the conductive metal layer formed on the convex portion of the grid pattern may be selectively removed.

In this step, the chemical wet etching method includes removing only the conductive metal layer formed on the convex portion of the pattern by immersing the resultant obtained in the step (b) in the etching solution for removing the conductive metal layer for a predetermined time. Accordingly, only the conductive metal layer formed on the convex portion of the grid pattern can be selectively removed.

In particular, in the case where the depth-to-width aspect ratio of the recess is large, that is, in a narrow and deep pattern, the contact angle between the etching liquid used and the surface of the conductive metal layer is large, the pattern portion is simply subjected to a predetermined time in a pre-optimized etching solution. Only by dipping and removing, only the metal layer formed on the convex portion of the pattern can be more effectively removed. Accordingly, the aspect ratio is 2: 1 or more, preferably 3: 1 to 10: 1, the etching solution used may vary depending on the type of the conductive metal layer, those skilled in the art The etching solution can be easily selected according to the type of the conductive metal layer. For example, when aluminum is used as the conductive metal layer, a polarizer is immersed in an etching solution in which CH ₃ COOH: HNO ₃ : H ₃ PO ₄ is mixed at a volume ratio of 20: 3: 77, and taken out of DI water. in By washing, the conductive metal layer of the convex portion can be removed.

In the present invention, by selectively removing only the conductive metal layer formed on the convex portion of the grid pattern through the mechanical or chemical wet etching, it is possible to obtain a conductive metal layer having a unique shape that cannot be obtained by other methods.

Hereinafter, preferred embodiments of the nanowire grid polarizer and the manufacturing method thereof according to the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 6 is a schematic diagram illustrating a process of fabricating a nano-patterned patterned stamper using interference lithography. FIG.

The mold material of the stamper may be a metal such as nickel, chromium, rhodium, or an organic material such as epoxy or silicon, but is not limited thereto.

It is preferable to use a stamper manufactured in a large area by interference lithography as the stamper, but is not limited thereto. "Interference lithography" is the process of generating standing waves using two or more interference lights to form patterns with periodic intervals in the photoresist. It refers to a pattern formation method having the advantage of making a pattern easily.

The above-mentioned interference lithography can be used to fabricate a stamper used for patterning the resin layer according to the present invention, whereby a stamper having a nano-sized mold can be produced in a large area. As a result, a large-area patterned resin layer can be efficiently produced, and a nano-wire grid polarizer can be produced in large-area using such a method.

In addition, the pattern of the stamper formed by the interference lithography is preferably a grid shape with a constant interval. However, the same shape is not particularly limited as long as it is formed at regular intervals. However, the larger the shape of the depth-to-width aspect ratio is, the easier it is to fabricate the polarizer according to the present invention. In particular, the pattern is preferably in the depth and width of several tens to several hundred nanometers, specifically 150nm to 200nm to form a nano-grid shape that can exhibit a good polarization separation performance in the visible light region.

7 is a schematic diagram schematically illustrating a method of patterning a conductive metal layer, in particular, in accordance with one embodiment of the present invention.

In step S1, a transparent plastic organic resin layer 701, such as polyester, polyethersulfone, polycarbonate, polyester naphthenate, polyacrylate, which can serve as a support and can be formed with a pattern, is prepared.

In step S2, after pressing the resin layer using a stamper 710 patterned to a nano size and thermosetting or photocuring, the stamper 710 is separated from the resin layer 701 to form a fine pattern. Form.

In step S3, the conductive metal layer 702 is formed over the entire surface of the resin layer 701. As the conductive metal layer 702, silver, copper, chromium, platinum, gold, nickel, aluminum, or the like may be used. Preferably, silver, gold, aluminum, or the like having excellent electrical conductivity and optical performance may be used. In an exemplary embodiment of the present invention, aluminum was used as a deposition material, and the initial vacuum degree was 1.8 to 2.4 × 10 ^-6 Torr, RF 200 to 300W, Ar 25sccm, and the working vacuum degree was 60 to 180 using sputtering. Aluminum may be deposited on the upper surface of the resin layer for a second. The thickness of the deposited conductive metal layer 702 is adjusted in the range of 30 nm to 300 nm, preferably 50 nm to 300 nm, and more preferably 50 nm to 100 nm. This is because the polarization separation performance of the visible light is excellent in the above range.

In step S4, the pressure sensitive adhesive (PSA) -coated adhesive film 703 is laminated on the surface of the resin layer 701 on which the conductive metal layer 702 is formed using a laminator or the like. At this time, the adhesive film 703 is brought into contact with the convex portion c of the uneven portions of the grid pattern having an aspect ratio, that is, a depth-to-width ratio (a: b), and is subjected to a constant pressure during plywood. On the other hand, the concave portion (d) of the uneven portion of the grid pattern is maintained in that state without contact with the adhesive film (703).

In step S5, when the adhesive film 703 is peeled off in parallel with the width direction of the grid pattern, the conductive metal layer 702 of the convex portion c of the uneven portion that is subjected to a constant pressure during plywood may be destroyed by plastic deformation and adhesive force. The adhesive film 703 is removed together. At this time, the adhesive film 703 must be removed in a direction parallel to the width direction of the grid pattern so that only the conductive metal layer 702 deposited on the convex portion c can be selectively removed. At this time, the adhesive peeling strength of the adhesive film 703 used is 1,000 kgf / 25mm or less, the PSA thickness is preferably 10㎛ or less, which is the aspect ratio of the resin layer 701 pattern and the pressure at the plywood, the conductive metal layer 702 And the adhesion between the resin layer 701 and the like.

8 is a schematic diagram schematically illustrating a method of patterning a conductive metal layer, in particular, in accordance with another embodiment of the present invention.

In step S1, an inorganic substrate such as glass or quartz or an optically transparent organic material, such as polyester, polyvinyl chloride, polycarbonate, polymethylmethacrylate, polystyrene, polyestersulfone, polyetherketone, which serve as a support A transparent substrate 801 in the form of a film or a sheet prepared by mixing one or more resins alone or two or more, and a stamper 810 having a nano-scale fine pattern formed by using interference lithography were prepared, and the substrate ( The photocurable resin layer 802 is poured into the pattern portion of the stamper 810 between the 801 and the stamper 810, and then the transparent substrate is pressed . Non-limiting examples of the photocurable resin include a single resin such as urethane acrylate, epoxy acrylate, ester acrylate, or two or more kinds of mixed resins, including radical generating monomers such as isobornyl acrylate and benzoin Photoinitiators, such as methyl ether, benzophenone, and (alpha)-hydroxy cyclophenyl ketone, can be mixed and used further.

In step S2, the resin layer 802 is cured by photocuring reaction with the resin layer 802 through UV exposure from the substrate 801 side, and the stamper 810 is removed in step S3. As a result, a resin layer 802 having a nano-scale fine pattern is formed on the substrate 801.

In step S4, the conductive metal layer 803 is formed over the entire surface of the resin layer 802 by sputtering or thermal evaporation. As the conductive metal layer 803, silver, copper, chromium, platinum, gold, nickel, aluminum, or the like may be used, and preferably silver, gold, aluminum, or the like, which is excellent in electrical conductivity and optical performance, may be used. In an exemplary embodiment of the present invention, aluminum is used as the deposition material, and the electron beam evaporation method is used for 300 to 500 seconds at an initial vacuum of 3.3 × 10 ^-7 Torr and a working vacuum of 5 × 10 ^-7 Torr. Aluminum may be deposited on the upper surface of the resin layer 802. At this time, the thickness of the deposited conductive metal layer 803 is controlled in the range of 30nm to 300nm, preferably 50nm to 100nm.

In step S5, the conductive metal layer 803 is removed using a chemical wet etching method. In this case, the etching solution capable of removing the used conductive metal layer 803 may vary depending on the type of the conductive metal layer 803. In an exemplary embodiment of the present invention, aluminum, which is a conductive metal layer 803, may be etched, and an etching solution mixed in a volume ratio of CH ₃ COOH: HNO ₃ : H ₃ PO ₄ = 20: 3: 77 may be used. . The polarizing element in which the conductive metal layer 803 is formed in the etching solution is immersed for 30 to 60 seconds and then taken out and washed with deionized water (DIwater). At this time, when the aspect ratio is large and the contact angle between the used etching solution and the surface of the conductive metal layer 803 is large, the metal layer 803 formed on the convex portion of the pattern is removed after being immersed in the etching solution for a predetermined time, preferably 30 seconds. ) Is selectively removed.

As described above, after the stamper is made using interference lithography, the pattern is transferred, and the conductive metal layer is formed on the entire surface of the pattern, and then selectively removed to remove the polarization as shown in FIG. 9 at a lower cost than the conventional process. A large-area nanowire grid polarizer 900 having excellent performance can be manufactured. In this case, the protective layer 904 may be formed on the conductive metal layer 903 as shown in FIG. 9B . In addition, the protective layer 904 may be formed after removing the resin layer 902 remaining as shown in (c) . Here, the protective layer 904 may be made of a material such as epoxy acrylate, the protective layer may be formed by a coating method or the like. If necessary, the protective layer may be provided with additional functions such as adhesion, antistatic, and abrasion resistance. In addition, the shape of the conductive metal layer 903 formed in the concave portion of the concave-convex portion of the resin layer 902 of the present invention is not particularly limited as long as it can impart excellent polarization separation performance to the polarizer. It can be variously formed in polygonal shape, semi-ellipse shape, arc shape, etc.

As described above, according to the method of manufacturing the nanowire grid polarizer of the present invention, it has a good polarization separation performance in the visible light region and a large area nanowire grid polarizer can be obtained by a simple process of low cost. Accordingly, the nanowire grid polarizer of the present invention may be usefully used in optical devices such as liquid crystal display devices, optical pickup devices, microscope polarizing films, and liquid crystal projectors.

Claims (19)

(a) forming a grid pattern in a nano size on the resin layer; (b) forming a conductive metal layer on an upper surface of the resin layer on which the pattern is formed; And (c) selectively removing only the conductive metal layer formed on the convex portion of the pattern Nanowire grid polarizer manufacturing method comprising a. The method of claim 1, further comprising forming a resin layer on the substrate before step (a). 3. The method of claim 2, wherein the substrate comprises at least one homo or mixed resin selected from glass, quartz, polyester, polyvinyl chloride, polycarbonate, polymethylmethacrylate, polystyrene, polyestersulfone, and polyetherketone. Nanowire grid polarizer manufacturing method. The method of claim 1, further comprising forming a protective layer on an upper surface of the polarizer after the step (c). The nanowire grid polarizer of claim 1, wherein the resin layer comprises a transparent organic material selected from at least one selected from polyester, polyethersulfone, polycarbonate, polyester naphthenate, and polyacrylate. Manufacturing method. The nanowire grid polarizer of claim 1, wherein the step (a) is performed by pressurizing the resin layer with a nano-patterned patterned stamper by means of interference lithography, followed by thermosetting or photocuring. Way. The method of claim 6, wherein the stamper comprises a metal selected from nickel, chromium, and rhodium, or an organic material selected from epoxy and silicon. The method of claim 1, wherein the conductive metal layer comprises at least one selected from Ag, Cu, Cr, Pt, Au, Ni, and Al. The method of claim 1, wherein the conductive metal layer has a thickness of 30 nm to 300 nm. The method of claim 1, wherein the forming of the conductive metal layer in step (b) is performed by sputtering, thermal evaporation, or electron beam deposition.  The method of claim 1, wherein the forming of the conductive metal layer in step (b) is performed by a gradient deposition method. The method of claim 1, wherein (c) selectively removing only the conductive metal layer formed on the convex portion of the pattern comprises: (c1) plywood an adhesive film coated with an adhesive on an upper surface of the conductive metal layer, and (c2) Removing the adhesive film in parallel with the width direction of the nanowire grid pattern to remove only the conductive metal layer formed on the convex portion of the pattern. The method of claim 12, wherein step (c2) is performed by detaching the laminated adhesive film in parallel with the width direction of the nanowire grid pattern. The method of claim 1, wherein the step (c1) of selectively removing only the conductive metal layer formed on the convex portion of the pattern is performed by immersing the resultant of the step (b) in the etching solution for removing the conductive metal layer. And removing only the metal layer. The method of manufacturing a nanowire grid polarizer according to claim 12 or 14, wherein an aspect ratio of the depth to width of the concave portion of the grid patterned resin layer is 2: 1 or more. The method of claim 1, further comprising removing the resin layer after the step (c). The method of claim 16, further comprising forming a protective layer on an upper surface of the polarizer after the step (c). 15. A nanowire grid polarizer comprising a nanoscale grid patterned resin layer prepared by the method of any one of claims 1-14 and a conductive metal layer formed in a recess between the grid patterned resin layer. A nanowire grid polarizer comprising a substrate prepared by the method of claim 16 or 17 and comprising a conductive metal layer nanoscaled on the top surface of the substrate.

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