JP2009210672A - Wire grid type polarizing element, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wire grid type polarizing element enhancing tightness of a metal wire to a film base material, and to provide a method of manufacturing the same. <P>SOLUTION: The wire grid type polarizing element includes: a base material 1 having grating-like protrusions 1a juxtaposed with a prescribed space; and the metal wires 2 to cover each of the grating-like protrusions 1a of the base material 1 and at least one part of a side face thereof. Each metal wire 2 is constituted of a spattering film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wire grid type polarizing element and a manufacturing method thereof.

  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 small pitch is useful in a wide range of applications not only in the semiconductor field but also in the optical field.

  For example, a wire grid in which conductor wires made of metal or the like are arranged in a lattice pattern at a specific pitch has a pitch that is considerably smaller than incident light (for example, visible light wavelength 400 nm to 800 nm). For example, if it is less than half, most of the electric field vector component light that oscillates in parallel to the conductor line is reflected, and almost no electric field vector component light perpendicular to the electric conductor line is transmitted. It can be used as a polarizing plate that produces a single polarized light. The wire grid type polarizing element 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 type polarizing element is disclosed in Patent Document 1. The wire grid polarizer includes metal wires spaced at a grid period smaller than the wavelength of incident light.
JP 2002-328234 A

  In the wire grid type polarizing element, metal wires are provided at a very narrow pitch, and this metal wire exerts a polarizing action. Therefore, the metal wires are arranged on the substrate in a state where a predetermined pitch is maintained. Must be. For this reason, it is desirable that the adhesion of the metal wire to the substrate is high. In particular, when forming a metal wire on a film, there is a problem that the adhesion of the metal wire is poor.

  This invention is made | formed in view of this point, and it aims at providing the wire grid type polarizing element with the high adhesiveness of the metal wire with respect to a film base material, and its manufacturing method.

  The wire grid type polarizing element of the present invention is provided so as to cover a base material having lattice-like convex portions arranged in parallel at a predetermined interval, and at least a part of the lattice-like convex portions and side surfaces of the base material. A metal wire, and the metal wire is formed of a sputtering film.

  In the wire grid type polarizing element of the present invention, the metal of the metal wire is preferably selected from the group consisting of aluminum, aluminum alloy, silver and silver alloy.

  The method of manufacturing a wire grid type polarizing element of the present invention includes a step of preparing a base material having lattice-like convex portions arranged in parallel at a predetermined interval, and at least one of the lattice-like convex portions and the side surfaces of the base material. And a step of forming a metal wire by sputtering so as to cover the portion.

  In the manufacturing method of the wire grid type polarizing element of the present invention, it is preferable to form the metal wire by forming a film from above at an angle of 90 ° or less with respect to the vertical direction in the cross section of the metal wire.

  The wire grid type polarizing element of the present invention is provided so as to cover a base material having lattice-like convex portions arranged in parallel at a predetermined interval, and at least a part of the lattice-like convex portions and side surfaces of the base material. Since the metal wire is formed of a sputtering film containing a plasma gas component, the adhesion of the metal wire to the film substrate can be increased.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic view showing a part of a wire grid type polarizing element according to an embodiment of the present invention. The wire grid type polarizing element shown in FIG. 1 includes a base material 1 in which grid-like convex portions 1a are arranged in parallel at predetermined intervals, a metal wire 2 provided on the grid-like convex portions 1a of the base material 1, It consists mainly of. In addition, the metal wire 2 provided on the grid | lattice-like convex part 1a may be provided so that at least one part of the side surface of the grid | lattice-like convex part 1a may be covered. The form of the wire grid type polarizing element may be a film-like body or a plate-like body.

  The material constituting the substrate 1 may be a resin that is substantially transparent in the visible light region. 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 (PET) resin, polyethylene naphthalate resin, polyethylene resin, polypropylene resin, polybutylene terephthalate resin, aromatic polyester resin, polyacetal Examples include crystalline thermoplastic resins such as resins and polyamide resins, and ultraviolet (UV) curable resins and thermosetting resins such as acrylic, epoxy, and urethane types. That. Moreover, it can also be set as the structure which combined the ultraviolet curable resin and thermosetting resin which are the resin base materials 1 as a base material, inorganic board | substrates, such as glass, the said thermoplastic resin, and a triacetate resin.

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

  There is no limitation on the cross-sectional shape of the concave portions of the fine concavo-convex lattice formed by the lattice-like convex portions 1a and the plurality of lattice-like convex portions. For example, these cross-sectional shapes may be a sine wave shape such as a trapezoidal shape, a rectangular shape, a square shape, a prism shape, or 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.

  Although there is no particular limitation on the method for obtaining the substrate having the lattice-shaped convex portions of the present invention, it is preferable to use the method described in Japanese Patent Application Laid-Open No. 2006-224659 by the present applicant.

  Specifically, in the present invention, as a method I for obtaining a substrate having a lattice-shaped convex portion, a stretched member having a concave-convex lattice with a pitch of 100 nm to 100 μm on the surface is used as a longitudinal direction of the concave-convex lattice (lattice-shaped convex portion). It is preferable to fabricate the stretched member by free end uniaxial stretching in a direction substantially parallel to the longitudinal direction in a state in which the width of the stretched member in a direction substantially orthogonal to the lattice is free. As a result, the pitch of the convex portions of the concavo-convex grid of the stretched member is reduced, and a substrate (stretched member) having a fine concavo-convex grid is obtained. The pitch of the concavo-convex grid is set in the range of 100 nm to 100 μm, but can be appropriately changed according to the required pitch of the fine concavo-convex grid and the draw ratio.

  Here, the stretched member refers to a transparent substrate such as a plate-like body, a film-like body, or a sheet-like body composed of an amorphous thermoplastic resin or a crystalline thermoplastic resin as a base material used in the present invention. Can be mentioned. The thickness and size of the stretched member are not particularly limited as long as the uniaxial stretching process is possible.

In addition, in order to obtain a stretched member having a concavo-convex lattice with a pitch of 100 nm to 100 μm on the surface, a mold having a concavo-convex lattice with a pitch of 100 nm to 100 μm formed by an interference exposure method using laser light 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 used by changing the angle θ ′. It is possible to obtain an uneven grating structure having various pitches within the laser wavelength range. As the laser that can be used for the interference exposure, limited to laser _{TEM 00} mode, as the ultraviolet light laser capable lasing of _{TEM 00} mode, an argon laser (wavelength 364 nm, 351 nm, 333 nm) and, of YAG laser fourth harmonic ( Wavelength 266 nm).

  In the present invention, in the uniaxial stretching treatment, first, the width direction of the stretched member (direction perpendicular to the longitudinal direction of the concavo-convex grid) is set free, and the longitudinal direction of the concavo-convex grid of the stretched member is uniaxially stretched. Secure to. Subsequently, after heating to an appropriate temperature at which the stretched member softens and holding it for an appropriate period of time, the pitch of the target fine concavo-convex lattice is set at an appropriate drawing speed in one direction substantially parallel to the longitudinal direction. Stretching is performed up to a stretching ratio corresponding to. Finally, it is a method of obtaining a base material having a lattice-shaped convex part by cooling the member to be stretched to a temperature at which the material is cured while maintaining the stretched state. As an apparatus for performing this uniaxial stretching process, an apparatus for performing a normal uniaxial stretching process can be used. Further, the heating condition and the cooling condition are appropriately determined according to the material constituting the stretched member.

  Further, in the present invention, the method II for obtaining a substrate having a lattice-like convex portion is a method of transferring a fine concavo-convex lattice onto the surface of the substrate used in the present invention using a mold having a fine concavo-convex lattice on the surface, and molding It is a method to do. Here, a mold having a fine concavo-convex lattice on the surface is prepared by sequentially performing a conductive treatment, a plating treatment, and a resin base material removal treatment on a base material having a lattice-like convex portion obtained by Method I. Can do.

  According to this method, since the mold having the lattice-shaped convex portions is used, it is possible to mass-produce the substrate having the lattice-shaped convex portions used in the present invention without going through a complicated stretching process. Furthermore, by appropriately combining and repeatedly using Method I and Method II, it becomes possible to produce a finer concavo-convex grid from a concavo-convex grid having a relatively large pitch.

  The metal constituting the metal wire 2 preferably has a high light reflectivity in the visible light region and has high adhesion with the material constituting the substrate 1. For example, it is preferably made of aluminum, silver or an alloy thereof. From the viewpoint of cost, it is more preferable that it is made of aluminum or an alloy thereof.

  The metal wire 2 is composed of a sputtering film containing a plasma gas component. That is, in the manufacturing method of the wire grid type polarizing element of the present invention, a base material 1 having lattice-like convex portions 1a arranged in parallel at a predetermined interval by the above-described method is prepared. A metal wire 2 is formed by sputtering so as to cover at least a part of the lattice-shaped convex portion 1a and its side surface.

  Thus, the metal wire 2 formed by sputtering has improved adhesion to the substrate 1. In particular, adhesion is improved as compared with a metal wire formed on a film substrate by vapor deposition.

  The reason why the adhesion of the metal wire 2 of the present invention to the base material 1 is thus presumed as follows. Sputtering ionizes a plasma gas component (for example, argon) and ejects desired target particles to form a film on a substrate. Therefore, the kinetic energy is very high as several tens of times compared to a vapor deposition film. It is presumed that the adhesion to the substrate 1 will be high. In addition, it is speculated that the substrate is bombarded by electrons in the plasma and the surface is cleaned.

  As described above, the wire grid type polarizing element having the metal wire composed of the sputtering film of the present invention is characterized in that the adhesion to the substrate 1 is higher than that of the conventional metal wire composed of the vapor deposition film. In addition, there are limited materials that can be formed by vapor deposition films, and there is a problem that the composition ratio is not stabilized before and after vapor deposition when an alloy is vapor deposited. Another characteristic is that such problems do not occur. Furthermore, according to the sputtering method, the film formation rate can be kept constant, which is excellent from the viewpoint of film thickness management.

  FIG. 2 is a diagram showing the amount of Ar in the film obtained by fluorescent X-ray. FIGS. 2A and 2B show the amount of Ar in the sputtering film, and FIG. The amount of Ar in the film is shown. As can be seen from FIGS. 2A and 2B, it can be seen that the sputtering film contains Ar. In particular, a larger amount of Ar is detected in the lower sputtering pressure (FIG. 2A). This is thought to be because molecular collisions decreased due to low pressure, kinetic energy increased, and Ar was easily incorporated into the film. On the other hand, Ar is not detected in the deposited film as shown in FIG.

  In sputtering, the number of atoms of the discharge gas is much larger than the number of sputtered particles that collide with the substrate, and the energy of the sputtered particles is also large, so that gas can be easily taken in during film formation. This can be verified from the fact that the composition of the metal wire constituting the polarizing element of the present invention contains a plasma gas component (for example, argon) which is an atom of the discharge gas.

  The value of the plasma gas component contained in the metal wire of the present invention is 0.01 atomic% to 30 atomic%, preferably 0.02 atomic% to 10 atomic%, when measured by the fluorescent X-ray method. . Thus, when it is a metal wire comprised by the sputtering film | membrane and contains said amount of a plasma gas component, it can be said that the adhesiveness of the base material 1 and a metal wire is high.

  On the other hand, if there is a lot of gas other than the plasma gas component, such as oxygen or nitrogen in a vacuum atmosphere, or water that comes out of the absorbed resin substrate, oxides and nitrides that are not originally intended to combine with the sputtered particles Is not preferable because a film is formed. Therefore, in the present invention, it is desirable to sufficiently dry and exhaust before film formation so as to reduce the influence of gas taken in during film formation as much as possible so as to reduce the influence of back pressure.

  In addition, since the degree of vacuum at the time of film formation is lower in sputtering than in vapor deposition, the mean free path to the base material of flying particles is shorter than in vapor deposition. When the free path of the flying target particles is shortened, the angular distribution of the flying particles on the substrate surface is widened. As a result, a large number of particles fly into the concave portions of the substrate to form a film. If the film is formed thick in the concave portion of the substrate in this manner, the metal is not formed in a wire shape but on the entire surface, and the light transmittance is drastically reduced, which is not preferable in practice. Therefore, in order to lengthen the mean free path of flying target particles, it is desirable to reduce the pressure during film formation by controlling the flow rate of plasma gas (Ar gas) for discharge and reducing it to the limit at which discharge is possible. .

From the above viewpoint, in sputtering, the degree of vacuum before film formation is preferably 1.0 × 10 ⁻³ Pa or less, and the degree of vacuum during film formation is preferably 2.0 Pa or less. In particular, the degree of vacuum before film formation is preferably 1.0 × 10 ⁻⁴ Pa or less, and the degree of vacuum during film formation is preferably 0.5 Pa or less. Moreover, it is preferable that the electric power in sputtering is 2.2 W / cm ² or more.

  Here, in the apparatus shown in FIG. 3, the metal wire film formation when the degree of vacuum during film formation is changed will be described. FIG. 3 is a diagram showing a schematic configuration of the sputtering apparatus. In FIG. 3, a substrate mounting table 12 is provided at the bottom of the vacuum chamber 11, and a substrate 13 is mounted on the substrate mounting table 12. A target mounting table 14 is provided on the upper surface in the vacuum chamber 11, and a sputtering target 15 is mounted on the target mounting table 14. A gas supply pipe 16 and a gas exhaust pipe 17 are attached to the side surface of the vacuum chamber 11, and a high frequency power source 18 is connected to the substrate mounting table 12. In the apparatus shown in FIG. 3, the substrate mounting table 12 is formed so that the substrate 13 is inclined by θ with respect to the normal direction (vertical direction), and film formation is performed at an angle θ. ing. As a result, a sufficient shielding effect can be obtained for the lattice-shaped convex portions 1a, and anisotropic film formation can be realized.

Using the sputtering apparatus shown in FIG. 3, the degree of vacuum during film formation was changed to 0.2 Pa, 0.6 Pa, and 2.0 Pa, and a plasma gas was used as Ar gas to form aluminum on the substrate. Other conditions in sputtering are as follows.
Base material-target distance: 105 mm
Inclination angle (θ): 60 °
Electric power: 200W (target size: 3 inches φ)
Degree of vacuum before film formation: 4.0 × 10 ⁻⁴ Pa

The wire grid type polarizing element thus obtained is shown in FIGS. Further, the resistivity and degree of polarization of these wire grid type polarizing elements were examined. The resistivity was measured with a resistivity meter, and the degree of polarization was measured using a 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 was calculated from the following equation. These results are shown in Table 1 below.
Polarization degree = (Imax−Imin) / (Imax + Imin) × 100%

  Moreover, the higher the degree of vacuum during film formation, the smaller the proportion of particles that diffused during sputtering, and the shielding effect against the lattice-shaped convex portions was exhibited. That is, as can be seen from FIG. 4, the higher the degree of vacuum during film formation, the more aluminum was deposited without the film formation in the recesses.

  In addition, the distance from the target to the base material is preferably set to a distance with less particle diffusion. Specifically, the distance from the sputtering target is preferably 10 mm or more and 200 mm or less. Further, it is preferable to form a metal wire by forming a film from above at an angle (θ) of 90 ° or less with respect to the vertical direction in the cross section of the metal wire. In sputtering, by doing so, a sufficient shielding effect can be obtained with respect to the lattice-like convex portions of the substrate, and anisotropic film formation can be performed.

Next, examples performed for clarifying the effects of the present invention will be described.
(Example)
By the above-described method, a mold having a fine concavo-convex grid provided on one side of a TAC (Triacetylcellulose) base material by UV transfer is prepared, and aluminum is deposited on the grid-shaped convex part of the fine concavo-convex grid by a DC magnetron sputtering method to a thickness of 120 nm. About a film was formed to form a metal wire. The degree of vacuum before film formation at this time was 4.0 × 10 ⁻⁴ Pa, the degree of vacuum during film formation was 0.2 Pa, and the sputtering power was 200 W. After the film formation, the aluminum between the lattice-shaped protrusions was etched using an aqueous sodium hydroxide solution. Thus, the wire grid polarizing element of the Example was produced.

  In the wire grid type polarizing element of the obtained example, the metal wire was not peeled off from the substrate even by the etching process. Further, when the degree of polarization of the wire grid type polarizing element of the example was measured using a spectrophotometer as described above, it was 99.9% and had a high degree of polarization.

  The present invention is not limited to the embodiment described above, and can be implemented with various modifications. For example, in the above-described embodiment, the case where the metal wire is formed on the lattice-like convex portion of the base material in which the lattice-like convex portions are arranged in parallel at a predetermined interval has been described. The present invention is not limited, and the present invention can be similarly applied to the case where metal wires are formed at predetermined intervals on a base material that does not have a grid-like convex portion. In addition, the dimensions, materials, and the like in the above embodiment are illustrative, and can be implemented with appropriate changes. In addition, various modifications can be made without departing from the scope of the present invention.

It is a figure which shows the wire grid type polarizing element which concerns on embodiment of this invention. It is a figure which shows the amount of Ar in the film | membrane calculated | required by the fluorescent X-ray, FIG. 2 (a), (b) shows the amount of Ar in a sputtering film, FIG.2 (c) shows Ar in a vapor deposition film. Indicates the amount. It is a figure which shows an example of a sputtering device. (A)-(c) is a figure which shows the film-forming state of a metal wire

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,13 Base material 1a Grid-shaped convex part 2 Metal wire 11 Vacuum chamber 12 Base material mounting table 14 Target mounting table 15 Sputtering target 16 Gas supply pipe 17 Gas exhaust pipe 18 High frequency power supply

Claims (4)

  A substrate having grid-like convex portions arranged in parallel at a predetermined interval; and a metal wire provided so as to cover at least a part of the grid-like convex portions and the side surfaces of the base material, The wire grid type polarizing element, wherein the metal wire is formed of a sputtering film.   2. The wire grid type polarizing element according to claim 1, wherein the metal of the metal wire is selected from the group consisting of aluminum, an aluminum alloy, silver and a silver alloy.   A step of preparing a base material having lattice-like convex portions arranged in parallel at a predetermined interval, and a step of forming a metal wire by sputtering so as to cover at least a part of the lattice-like convex portions and the side surfaces of the base material And a method of manufacturing a wire grid type polarizing element. 2. The method of manufacturing a wire grid type polarizing element according to claim 1, wherein the metal wire is formed by forming a film from above at an angle of 90 [deg.] Or less with respect to a vertical direction in a cross section of the metal wire. .