JP2008268294A - Wire grid polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wire grid polarizing plate with which metal wires are prevented from being in contact with one another and high optical performance is exercised. <P>SOLUTION: The wire grid polarizing plate includes: a substrate 1 having grid-shaped protruding parts 1a on its surface; dielectric layers 2 mounted on regions including the grid-shaped protruding parts 1a; and metal wires 3 mounted on the dielectric layers 2, wherein the metal wires 3 are constructed with an alloy including impurities, and the alloy is characterized by including the impurities with the content to reduce their average particle diameter to a distance between the grid-shaped protruding parts at a height imparting the half height full width of the grid-shaped protruding parts or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wire grid polarizing plate having a grid-like convex portion.

  With the recent development of photolithography technology, it has become possible to form a fine structure pattern having a pitch at the wavelength level of light. Such a member or product having a pattern with a very narrow pitch is useful not only in the semiconductor field but also in the optical field.

For example, a wire grid in which conductor wires such as metal are arranged in a lattice pattern at a specific pitch on a substrate has a considerably smaller pitch than incident light (for example, a visible light wavelength of 400 nm to 800 nm) (for example, If it is less than half), it reflects almost all electric field vector components that oscillate in parallel to the conductor line and almost transmits perpendicular electric field vector components. it can. Such a wire grid polarizing plate is desirable from the viewpoint of effective use of light because it can reflect and reuse light that does not pass through. An example of such a wire grid polarizer is disclosed in Patent Document 1.
JP 2006-201782 A

  In the wire grid polarizing plate disclosed in Patent Document 1, the metal wire is formed by depositing a metal such as aluminum by a method such as vacuum deposition. When forming a metal wire by such a method, if the pitch of the grid comprised with a metal wire becomes narrow, possibility that metal wires will contact in a manufacturing process becomes high. Since a wire grid polarizing plate in which metal wires are in contact with each other cannot exhibit high optical performance, it is desired to suppress contact between metal wires as much as possible.

  This invention is made | formed in view of this point, and it aims at providing the wire grid polarizing plate which can suppress the contact between metal wires and can exhibit high optical performance.

  The wire grid polarizing plate of the present invention comprises a substrate having a grid-like convex portion on a surface thereof, and a metal wire provided on a region including the grid-like convex portion, and the metal wire contains impurities. The alloy includes an impurity having a content such that the average particle diameter is equal to or less than the interval between the lattice-shaped protrusions at a height that gives a half-value width of the lattice-shaped protrusions. It is characterized by that.

  In the wire grid polarizer of the present invention, the alloy is preferably an aluminum alloy, and the impurity is preferably at least one element selected from the group consisting of silicon, magnesium, manganese, and iron.

  In the wire grid polarizing plate of the present invention, the content of the impurities in the alloy is preferably 0.05% by weight or more.

  In the wire grid polarizing plate of the present invention, it is preferable that the pitch of the grid-like convex portions is 150 nm or less, and the average particle diameter of the alloy is not more than the pitch.

  In the wire grid polarizing plate of the present invention, it is preferable that the interval between the lattice-shaped convex portions at a height that gives the half-value width of the lattice-shaped convex portions is 80 nm or less.

  According to the wire grid polarizing plate of the present invention, the substrate includes a base material having a lattice-like convex portion on the surface, and a metal wire provided on a region including the lattice-like convex portion, and the metal wire is an impurity. The alloy contains an impurity having a content such that the average particle diameter is equal to or less than the interval of the lattice-shaped protrusions at a height that gives a half-value width of the lattice-shaped protrusions. Since it contains, the contact between metal wires can be suppressed and a high optical performance can be exhibited.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing a part of a wire grid polarizer according to an embodiment of the present invention. This wire grid polarizing plate is composed of a base material 1 having a lattice-like convex portion 1a on the surface, a dielectric layer 2 provided on the base material 1, and a metal wire 3 erected on the dielectric layer 2. It is mainly composed. The dielectric layer 2 is not necessarily provided.

  The material used for the substrate 1 may be a resin that is substantially transparent in the visible light region, and is preferably a resin with excellent processability. For example, polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, cycloolefin resin (COP), cross-linked polyethylene resin, polyvinyl chloride resin, polyarylate resin, polyphenylene ether resin, modified polyphenylene ether resin, polyetherimide resin, polyether Amorphous thermoplastic resins such as sulfone resin, polysulfone resin, polyether ketone resin, polyethylene terephthalate resin (PET), polyethylene naphthalate resin, polyethylene resin, polypropylene resin, polybutylene terephthalate resin, aromatic polyester resin, polyacetal Examples thereof include crystalline thermoplastic resins such as resins and polyamide resins, and ultraviolet curable resins and thermosetting resins such as acrylics, epoxies, and urethanes. Moreover, you may use the composite base material which combined the ultraviolet curable resin and the thermosetting resin, inorganic substrates, such as glass, the said thermoplastic resin, and a triacetate resin as the base material 1. FIG.

  The pitch p of the lattice-like convex portions 1a of the substrate 1 is 150 nm or less, preferably 80 nm to 120 nm in consideration of polarization characteristics over a wide band in the visible light region. The smaller the pitch p, the better the polarization characteristics. However, for visible light, sufficient polarization characteristics can be obtained at a pitch p of 80 to 120 nm. If the polarization characteristics of the short wavelength light in the vicinity of 400 nm are not important, the pitch p may be increased to about 150 nm.

  When the thermoplastic resin is used for the base material 1, the pitch p of the grid-like convex parts 1 a can be controlled by adjusting the conditions of the stretching process that is performed after the base-like shape is given to the base material 1. . In the present invention, the pitch p of the grid-like convex portions 1a of the substrate 1, the pitch of the dielectric layer 2, and the pitch of the metal wires 3 are substantially equal to the pitch of the wire grid of the present invention, and the same pitch is used. Can take.

  There is no restriction | limiting in the cross-sectional shape of the grid-like convex part 1a of the base material 1. FIG. Examples of the cross-sectional shape include a trapezoidal shape, a rectangular shape, a square shape, a prism shape, and a sine wave shape such as a semicircular shape. Here, the sinusoidal shape means that it has a curved portion formed by repetition of a concave portion and a convex portion. In addition, the curved part should just be a curved curve, for example, the shape which has a constriction in a convex part is also included in a sine wave form. Further, from the viewpoint of facilitating covering of the lattice-like convex portion 1a of the substrate 1 and at least a part of its side surface with the dielectric, it is preferable that the end portion, vertex, or valley of the shape is curved with a gentle curvature. Further, from the viewpoint of increasing the adhesion strength between the substrate 1 and the dielectric layer 2, it is more preferable that these cross-sectional shapes are sinusoidal.

  As a method of providing a grid-like convex part on the substrate 1, for example, a stretched member having a concave-convex grid with a pitch of 100 nm to 100 μm on the surface is used as a longitudinal direction of the concave-convex grid (a direction parallel to the grid of the grid-like convex part). And a free end uniaxial stretching process in a direction substantially parallel to the longitudinal direction with the width of the stretched member in a direction substantially perpendicular to the longitudinal direction being made free. As a result, the pitch of the convex portions of the concavo-convex lattice of the stretched member is reduced, and a base material (stretched member) having a lattice-like convex portion with a pitch of about 120 nm or less is obtained. The pitch of the lattice-shaped convex portions is set in a range of 100 nm to 100 μm, but can be appropriately changed according to the required pitch of the lattice-shaped convex portions and the draw ratio.

  In addition, in order to obtain a stretched member having a concavo-convex grid with a pitch of 100 nm to 100 μm on the surface, a mold having a concavo-convex grid with a pitch of 100 nm to 100 μm formed by an interference exposure method using a laser beam or a cutting method is used. The concavo-convex lattice shape may be transferred to the stretched member by a method such as hot pressing. The interference exposure method is an exposure method using interference fringes formed by irradiating laser light of a specific wavelength from two directions of angle θ ′, and is a laser used by changing angle θ ′. It is possible to obtain a concavo-convex lattice structure having various pitches within a range limited by the wavelength of. Lasers that can be used for interference exposure are limited to TEM00 mode lasers, and ultraviolet lasers that can oscillate TEM00 mode lasers are argon lasers (wavelengths 364 nm, 351 nm, and 333 nm) and fourth harmonics of YAG lasers (wavelength 266 nm). ) And the like.

  Alternatively, as a method of providing the grid-like convex portions on the substrate 1, a method of transferring and molding the grid-like convex portions on the surface of the base material using a mold having a grid-like convex portion having a pitch of 120 nm or less on the surface. Is mentioned. Here, the mold having a grid-like convex part having a pitch of 120 nm or less on the surface is obtained by conducting the conductive treatment, the plating process, and the base material in the order obtained by the above method. It can produce by performing the removal process.

  The dielectric constituting the dielectric layer 2 may be a dielectric that is substantially transparent in the visible light region. A dielectric material having strong adhesion between the material constituting the substrate 1 and the metal constituting the metal wire 3 can be suitably used. For example, silicon (Si) oxide, nitride, halide, carbide alone or a composite thereof, aluminum (Al), chromium (Cr), yttrium (Y), zirconia (Zr), tantalum (Ta), Metal oxides such as titanium (Ti), barium (Ba), indium (In), tin (Sn), zinc (Zn), magnesium (Mg), calcium (Ca), cerium (Ce), copper (Cu) , Nitrides, halides, carbides or composites thereof (dielectrics in which other elements, simple substances, or compounds are mixed in a dielectric substance) can be used.

  The method for forming the dielectric layer 2 on the region including the lattice-shaped protrusions of the substrate 1 having the lattice-shaped protrusions 1 a is appropriately selected depending on the material constituting the dielectric layer 2. For example, a physical vapor deposition method such as a sputtering method or a vacuum vapor deposition method can be suitably used. The sputtering method is preferable from the viewpoint of adhesion strength.

  The metal constituting the metal wire 3 is preferably a metal having high light reflectance in the visible light region and good adhesion to the material constituting the dielectric layer 2. For example, it is preferably made of an alloy of aluminum (Al) or silver (Ag). More preferably, it is made of an Al alloy from the viewpoint of cost.

  In a wire grid polarizing plate having a pitch of 100 nm level, there is a problem of contact and bonding between metal wires in the metal wire forming step. Therefore, the present inventors pay attention to the fact that it is necessary to suppress the increase in particle diameter in order to prevent contact and bonding between metal wires in a wire grid having a fine pitch, It has been found that the inclusion of impurities in the constituent metal can suppress the growth of the particle diameter and prevent contact and bonding between the metal wires.

  As described above, the alloy constituting the metal wire 3 includes a predetermined impurity. By including such an impurity, when the metal wire 3 is formed, the particle growth is hindered by the impurity when deposited on the dielectric layer 2, and the particle diameter can be suppressed from becoming larger than necessary. For this reason, particle growth in the width direction (horizontal direction) of the metal wire 3 can be suppressed. As a result, contact and bonding between metal wires can be prevented.

  The content of impurities contained in the alloy constituting the metal wire 3 is equal to or less than the interval (space s) between the lattice-shaped protrusions 1a at a height at which the average particle diameter of the alloy gives the half-value width of the lattice-shaped protrusions 1a. Set as follows. By setting in this way, the growth of alloy particles is suppressed when depositing the alloy, and contact and bonding between metal wires can be prevented. Therefore, the content of impurities in the alloy is appropriately set according to the pitch of the metal wires of the wire grid polarizer. The content of impurities in the alloy is preferably 0.05% by weight or more. Moreover, it is preferable that the space | interval of the grid-like convex part 1a in the height which gives the half value width of the grid-like convex part 1a is 80 nm or less.

  In order to prevent contact and bonding between metal wires, it is desirable to appropriately control the relationship between the pitch of the grid-like convex portions and the average particle diameter of the alloy. For example, when the pitch of the grid-like convex portions is 150 nm or less, the average particle diameter of the alloy is preferably not more than the pitch. Therefore, the content of impurities in the alloy is adjusted so as to satisfy such a relationship, that is, to realize the average particle diameter.

  The impurity contained in the alloy is preferably at least one element selected from the group consisting of silicon, magnesium, manganese, and iron.

  As a method of depositing metal on the substrate 1 or the dielectric layer 2 to form the metal wire 3, the material constituting the substrate 1 or the dielectric layer 2 and the metal constituting the metal wire 3 are used. The method is not particularly limited as long as sufficient adhesion can be obtained. For example, a physical vapor deposition method such as a vacuum vapor deposition method, a sputtering method, or an ion plating method can be suitably used. Among them, a method is preferable in which the metal can be selectively stacked on the convex portion of the dielectric layer 2 selectively or biased to one side surface of the convex portion of the dielectric layer 2. An example of such a method is a vacuum deposition method.

Next, examples performed for clarifying the effects of the present invention will be described.
(Preparation of a substrate having a grid-like convex part)
-Preparation of COP plate with concavo-convex lattice shape transferred A nickel stamper having a concavo-convex lattice with a pitch of 230 nm and a height of the concavo-convex lattice of 230 nm was prepared. The concavo-convex grating was produced by patterning using a laser interference exposure method, and the cross-sectional shape was a sine wave shape, and the shape from the top surface was a striped lattice shape. Moreover, the plane dimension was 500 mm in both length and width. Using this nickel stamper, the uneven grid shape was transferred to the surface of a cycloolefin resin (hereinafter abbreviated as COP) plate having a thickness of 0.5 mm and a width and width of 520 mm by hot pressing, and the uneven grid shape was transferred to the COP. A plate was made.

-Reduction of pitch by stretching Next, the COP plate to which the concavo-convex lattice shape was transferred was cut into a rectangle of 520 mm x 460 mm to obtain a stretching COP plate as a stretched member. At this time, it was cut out so that the longitudinal direction (520 mm) of 520 mm × 460 mm and the longitudinal direction of the concavo-convex lattice were substantially parallel to each other.

  Next, silicone oil was applied to the surface of the stretching COP plate by spraying and left in a circulating air oven at about 80 ° C. for 30 minutes. Next, both ends 10 mm in the longitudinal direction of the stretching COP plate were fixed with a chuck of a stretching machine, and in that state, the stretching COP plate was left in a circulating air oven adjusted to 113 ± 1 ° C. for 10 minutes. After that, when the distance between the chucks was stretched 5 times at a speed of 250 mm / min, the stretching was finished, and after 20 seconds, the stretched COP plate (stretched COP plate) was taken out in a room temperature atmosphere, and the distance between the chucks was maintained. Cooled down. About 40% of the center portion of the stretched COP plate was substantially uniformly constricted, and the portion with the smallest width was 200 mm.

  When the surface and cross section of this stretched COP plate were observed with a field emission scanning electron microscope (FE-SEM), the pitch and height of the fine concavo-convex grating were 100 nm / 95 nm (pitch / height), respectively. It was found that the cross-sectional shape was sinusoidal, the shape from the top surface was a striped lattice shape, and was substantially reduced in size similar to the uneven lattice shape before stretching.

-Nickel stamper preparation The surface of the obtained COP plate with a pitch of 100 nm was coated with 30 nm of gold as a conductive treatment by sputtering, and then electroplated with nickel, and each 0.3 mm thick, 300 mm long, 180 mm wide A nickel stamper having a fine concavo-convex lattice on the surface was prepared.

Production of lattice convex transfer film using ultraviolet curable resin About 0.1 mm thick polyethylene terephthalate resin film (hereinafter referred to as PET film), UV curable resin (TB3078D manufactured by ThreeBond Co., Ltd., refractive index 1.41) is approximately Apply 0.03 mm, and place it on the nickel stamper with the coated surface facing down on the surface with a fine unevenness grid of 100 nm pitch so that air does not enter between the nickel stamper and the PET film from each end. Ultraviolet rays were irradiated at 1000 mJ / cm ² from the film side using an ultraviolet lamp with a central wavelength of 365 nm, and the fine uneven lattice of the nickel stamper was transferred. Subsequently, after peeling the PET film from the nickel stamper, the PET film was further irradiated with UV light at 500 mJ / cm ^{2 in a} nitrogen atmosphere to cure the uncured component of the UV curable resin, and a 300 mm long by 180 mm wide grid. A convex-shaped convex transfer film was produced. The obtained lattice-like convex transfer film was observed by FE-SEM, and it was confirmed that the cross-sectional shape was sinusoidal and the shape from the upper surface was a striped lattice.

(Production of wire grid polarizer: Examples 1 to 3)
Formation of Dielectric Layer Using Sputtering Method A lattice-shaped convex transfer film produced using an ultraviolet curable resin as described above was coated with a dielectric using a sputtering method. In this embodiment, a case where silicon nitride is used as a dielectric will be described. The dielectric was coated at an Ar gas pressure of 0.67 Pa, a sputtering power of 4 W / cm ² , and a coating speed of 0.22 nm / s. As a layer thickness comparison sample, a glass substrate having a smooth surface was inserted into the apparatus simultaneously with the lattice-shaped convex transfer film, and film formation was performed so that the dielectric laminate thickness on the smooth glass substrate was 20 nm.

-Metal deposition using vacuum deposition method After forming a dielectric layer on the lattice-shaped convex transfer film, a metal wire was formed using an electron beam vacuum deposition method (EB deposition method). In this example, an aluminum alloy (Al alloy) having a different composition was used as the metal (Examples 1 to 3). Deposition was performed with a degree of vacuum of 2.5 × 10 ⁻³ Pa, a deposition rate of 4 nm / s, and a substrate temperature of room temperature. As a layer thickness comparison sample, a glass substrate having a smooth surface was inserted into the apparatus at the same time as the dielectric laminated lattice-shaped convex transfer film, and vapor deposition was performed so that the Al deposition thickness on the smooth substrate was 200 nm. Note that the angle θ formed by the normal of the substrate surface and the evaporation source in a plane perpendicular to the longitudinal direction of the lattice was 20 °. Further, an Fe substrate having a purity of 99.999% or more was also inserted into the apparatus simultaneously with the dielectric laminated grid-like convex transfer film as a sample for composition analysis. For comparison, vapor deposition was performed using 99.999% high-purity aluminum as a metal (comparative example). The weight ratio of the Al alloy used is shown in Table 1 below.

-Removal of unnecessary metal by etching After laminating dielectric and Al on the lattice-shaped convex transfer film, the film is treated in a 0.1 wt% sodium hydroxide aqueous solution at room temperature for a treatment time of 30 seconds to 90 seconds. In FIG. 1, the substrate was washed (etched) while changing at intervals of 10 seconds, and immediately washed with water to stop the etching. The film was dried to obtain a wire grid polarizer. The size of the wire grid polarizing plate was 300 mm long and 180 mm wide. The cross sections of the three types of wire grid polarizers were observed with an FE-SEM, and the interval (space) between the lattice-shaped protrusions at a height that gives the half-value width of the lattice-shaped protrusions was examined. The results are also shown in Table 1 below. Moreover, the SEM image of the typical surface of the wire grid polarizing plate (Example 1- Example 3) obtained using Al alloy for a metal is shown to Fig.2 (a). As can be seen from FIG. 2 (a), there was no contact or bonding between the metal wires. On the other hand, a typical SEM image of the surface of a wire grid polarizer (comparative example) obtained using pure aluminum as the metal is shown in FIG. As can be seen from FIG. 2 (b), there was contact and bonding between the metal wires.

-Composition analysis by fluorescent X-ray The composition of the Al alloy film on the Fe substrate was quantified by fluorescent X-ray. As a result, in the Al / Si alloy (Example 1), Al / Si = 99.5 wt% / 0.5 wt%, and in the Al / Mg alloy (Example 2), Al / Mg = 93.7. In the Al / Mn alloy (Example 3), Al / Mn = 97.4% by weight / 2.6% by weight. In Al (comparative example), no other metal was detected.

Measurement of average particle diameter by X-ray diffraction X-ray diffraction of the obtained wire grid polarizer was measured, and the average particle diameter of the aluminum alloy constituting the metal wire was estimated by Scherrer's equation. The results are also shown in Table 1 below.
As can be seen from Table 1, in the wire grid polarizing plates of Examples 1 to 3, the average particle diameter of the alloy constituting the metal wire is between the lattice-shaped convex portions at a height that gives the half-value width of the lattice-shaped convex portions. In the wire grid polarizing plate of the comparative example, the average particle diameter of the alloy constituting the metal wire exceeds the interval between the lattice-shaped protrusions at a height that gives the half-value width of the lattice-shaped protrusion. It was.

(Evaluation of polarization performance by spectrophotometer)
About the obtained wire grid polarizing plate of the Example and the comparative example, the degree of polarization and the light transmittance were measured using the spectrophotometer. Here, the transmitted light intensity in a parallel Nicols state and a crossed Nicols state with respect to linearly polarized light was measured, and the degree of polarization and the light transmittance were calculated from the following equations. The measurement wavelength range was 400 nm to 700 nm as visible light. FIG. 3 is a characteristic diagram showing a change in polarization degree over a wavelength range of 400 nm to 700 nm, and FIG. 4 is a characteristic diagram showing a change in light transmittance over a wavelength range of 400 nm to 700 nm.
Polarization degree = [(Imax−Imin) / (Imax + Imin)] × 100%
Light transmittance = [(Imax + Imin) / 2] × 100%
Here, Imax is the transmitted light intensity at the time of parallel Nicols, and Imin is the transmitted light intensity at the time of crossed Nicols.

  As can be seen from FIG. 3, the wire grid polarizers (Examples 1 to 3) according to the present invention exhibited an excellent degree of polarization over almost the entire visible light region. Further, as can be seen from FIG. 4, the wire grid polarizers (Examples 1 to 3) according to the present invention showed excellent light transmittance over almost the entire visible light region. On the other hand, since the wire grid polarizing plate of the comparative example has contact and bonding between the metal wires, the degree of polarization and light transmittance are inferior over almost the entire visible light region as compared with the example.

  The present invention is not limited to the embodiment described above, and can be implemented with various modifications. For example, the dimensions, materials, and the like in the above-described embodiment are illustrative, and can be changed as appropriate. Moreover, the polarizing plate in the said embodiment does not need to be a plate-shaped member, and may be a sheet form and a film form as needed. In addition, various modifications can be made without departing from the scope of the present invention.

It is sectional drawing which shows a part of wire grid polarizing plate which concerns on embodiment of this invention. (A) is a microscope picture which shows the SEM image of the typical surface of the wire grid polarizing plate which concerns on this invention, and is a microscope picture which shows the SEM image of the typical surface of the wire grid polarizing plate which concerns on a comparative example. . It is a characteristic view which shows the change of the polarization degree over wavelength 400nm -700nm. It is a characteristic view which shows the change of the light transmittance over wavelength 400nm -700nm.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material 1a Lattice-like convex part 2 Dielectric layer 3 Metal wire

Claims (5)

  A substrate having a grid-like convex portion on a surface thereof, and a metal wire provided on a region including the grid-like convex portion, and the metal wire is made of an alloy containing impurities. The wire alloy polarizing plate is characterized in that the alloy contains impurities having a content such that an average particle diameter thereof is equal to or less than a distance between the lattice-shaped convex portions at a height that gives a half-value width of the lattice-shaped convex portions. .   2. The wire grid polarizer according to claim 1, wherein the alloy is an aluminum alloy, and the impurity is at least one element selected from the group consisting of silicon, magnesium, manganese, and iron.   The wire grid polarizer according to claim 1 or 2, wherein a content of the impurities in the alloy is 0.05% by weight or more.   The wire grid polarizing plate according to any one of claims 1 to 3, wherein the pitch of the lattice-shaped convex portions is 150 nm or less, and the average particle diameter of the alloy is the pitch or less.   The wire grid polarizing plate according to any one of claims 1 to 4, wherein an interval between the lattice-shaped protrusions at a height that gives a half-value width of the lattice-shaped protrusions is 80 nm or less.