JP4527986B2 - Wire grid polarizer - Google Patents

Description

  The present invention relates to a wire grid polarizer.

  There are several types of reflective polarizers used for light, such as linear polarizers composed of a laminate of resins having birefringence, and circular polarizers typified by cholesteric liquid crystals. The reflective polarizer of the birefringent resin laminate that is currently used as a brightness enhancement film for liquid crystal displays transmits one of the P-polarized component and S-polarized component of the light from the liquid crystal backlight, and the other as the backlight. Reflect to the side. The light that has returned to the backlight side returns to the reflective polarizer again in a state where the polarization state has been eliminated by birefringence of the members of the backlight part and scattering / reflection at the backlight part. The part is transmitted through the polarizer. By repeating this cycle, the light utilization efficiency can be increased. However, at present, the polarization separation performance of these reflective polarizers is low, and the contrast of a liquid crystal display is insufficient with a reflective polarizer alone, so it is necessary to use it together with an absorption polarizing plate with high polarization separation performance It becomes. For this reason, there are problems such as an increase in the number of parts constituting the liquid crystal display and an increase in the manufacturing cost of the display and an increase in the thickness of the product.

  On the other hand, as another type of reflective polarizer, there is a wire grid polarizer. FIG. 1 shows a schematic diagram of a general wire grid polarizer. The wire grid polarizer 100 has a structure in which fine metal wires 110 are arranged in parallel on a substrate 120 transparent to incident light 130 in a non-polarized state. In FIG. 1, the light incident surface is orthogonal to the wire grid polarizer and is a surface whose normal is the longitudinal direction of the fine metal wire. When the pitch p, which is the interval between the straight metal thin wires, is sufficiently shorter than the wavelength of the incident light 130, the component (that is, P-polarized light) 150 having an electric field vector orthogonal to the metal thin wire 110 of the incident light 130 is transmitted. A component (ie, S-polarized light) 140 having an electric field vector parallel to the thin line is reflected. Since the wire grid polarizer has high polarization separation performance, it has been used for a long time as a useful polarizer in the infrared region (Non-Patent Document 1).

  Although it is known that the wire grid type polarizer is a reflection type polarizer having high polarization separation performance, in order to show good polarization separation performance in the visible range, the metal fine wire has a dimensional accuracy of about 100 nm or less. There is a problem that it is necessary to arrange them regularly and technically difficult to manufacture. However, in recent years, wire grid polarizers for visible light have been produced and sold due to advances in microfabrication technology (Non-Patent Document 2).

One of the factors that determine the performance of the wire grid polarizer is the relationship between the pitch p [nm] and the wavelength λ [nm] of incident light. When the pitch p of the fine metal wires is in the range of about one half to twice the wavelength, the polarization separation performance is remarkably deteriorated with respect to light of a specific wavelength. Such a phenomenon is generally called “Rayleigh resonance”, and the longest wavelength (maximum resonance wavelength) λ _{res-max at which} this resonance occurs is known to be expressed by the following formula 1 (non-patent document). Reference 3).
λ _res-max = p (n + sin θ) Equation 1
(In Formula 1, n and θ mean the refractive index of the substrate and the incident angle of light, respectively.)

Before and after the wavelength at which Rayleigh resonance occurs, the performance of the wire grid polarizer drops sharply. Therefore, in order to show sufficient polarization separation performance for visible light, the maximum resonance wavelength λ _res-max is larger than the wavelength of visible light. Should also be shorter.

FIG. 2 and FIG. 3 show the relationship between the transmission efficiency of P-polarized light and S-polarized light and the incident light wavelength of a general wire grid polarizer calculated by electromagnetic field simulation software “MW-Studio” manufactured by CST GmbH in Germany. The relationship between the degree of polarization of transmitted light and the wavelength is shown. The calculation is performed under the condition that light enters the wire grid polarizer from the metal thin wire side, the incident angle θ = 0 °, the pitch p = 200 nm, the wire width w = 100 nm, the wire thickness t = 100 nm, and the substrate refractive index n is 1. .4 and 1.6. As a material for the metal wire, silver having high electrical conductivity and high visible light reflectance was selected. The degree of polarization was calculated based on Equation 2 below. Here, Tp represents the transmittance of P-polarized light, and Ts represents the transmittance of S-polarized light.
Polarization degree = ((Tp−Ts) / (Tp + Ts)) ^0.5 Equation 2

As shown in FIG. 2, P-polarized light that is transmitted light is greatly affected by the refractive index of the substrate as compared to S-polarized light. When the substrate refractive index n is 1.4 and 1.6, the maximum resonance wavelength λ _res-max exists in a sufficiently ultraviolet region of 289 nm and 331 nm, respectively, and any substrate refraction occurs at an incident angle θ = 0 °. Even at the rate n, the degree of polarization of transmitted light with respect to visible light exceeds 95%, and it can be seen that it has good polarization separation performance.

However, increasing the angle of incidence, the maximum resonance wavelength lambda _res-max according to equation 1 is shifted to the long wavelength side. From the simulation result and Equation 1, λ _res-max at various _θs is calculated, and the result is shown in FIG. As the incident angle increases, the value of λ _res-max increases. At the incident angle θ = 30 °, the substrate refractive indexes n = 1.4 and 1.6 are 392 nm and 449 nm, respectively. It can be said that sufficient polarization separation performance is not exhibited for visible light.

FIG. 4 shows the relationship between the incident angle θ and the maximum resonance wavelength λ _res-max when the substrate refractive index n is 1.5. The maximum resonance wavelength λ _res-max is θ = 0 °, 30 °. When the incident angle θ is 30 °, the polarization separation performance is abruptly lowered for short-wavelength visible light.

In order to shift the maximum resonance wavelength λ _res-max to the short wavelength side, there are three methods from Equation 1. First, it is possible to reduce the pitch p. However, it is technically difficult to reduce only the pitch p while maintaining the thickness t of the thin metal wire that does not transmit light. Second, there is a method in which incident light is incident perpendicularly to the wire grid polarizer. However, if the incident angle is limited, the use as a polarizer is significantly limited. The third is to reduce the refractive index n of the substrate, but there are few low-refractive-index materials that are transparent to visible light and inexpensive, and particularly resin materials.

In order to solve these problems, in Patent Document 1, in order to reduce the effective refractive index of the medium surrounding the fine metal wire, the substrate is covered with a low-refractive material magnesium fluoride that covers the interface between the fine metal wire and the substrate. A technique has been proposed in which a fine metal wire is formed on a rib, and the maximum resonance wavelength λ _res-max has been successfully reduced from about 450 nm to about 400 nm under certain conditions.

  Patent Document 2 discloses a technique that uses a physical phenomenon called resonance enhancement tunneling. Here, the fine metal wires in the general wire grid polarizer shown in FIG. 1 are replaced with wires in which thin metal wires having a thickness of 66 nm and dielectric fine wires having a thickness of 33 nm are alternately laminated, and the pitch is changed. p and wire width w are 130 nm and 52 nm, respectively.

  However, both the method of providing a magnesium fluoride layer described in Patent Document 1 and the method of providing a rib on a substrate and arranging a thin metal wire on the substrate make the process complicated and increase the manufacturing cost. There is a problem. Further, the technique of Patent Document 2 is not a versatile technique because it requires a more advanced technique than that of Patent Document 1 and requires a large amount of cost.

  In the prior art as described above, an optically homogeneous material having no birefringence such as glass is used for the substrate of the wire grid type polarizer.

  A general method for obtaining circularly polarized light from light in a non-polarized state having no polarization characteristic is to convert the light in the non-polarized state into linearly polarized light with a linear polarizer, and further pass this linearly polarized light through a quarter-wave plate. Two types of optical elements, a linear polarizer and a quarter-wave plate, are required. A circular polarizer that converts light in a non-polarized state into circularly polarized light is used as a liquid crystal display provided with a touch panel, an optical element for measuring polarization, or the like.

J. et al. P. Auton, Applied Optics. Vol. 6.1023 (1967) F. J. et al. Kahn, Private Line Report on Projection Display. Vol. 7). No. 10.3 (2001) Philosophy Magazine, Vol. 14 No. 79.60 (1907) Special table 2003-502708 Special table 2002-328234 JP 2001-74935 A JP-A-9-90122

  An object of the present invention is to improve the polarization separation performance of a wire grid polarizer without using expensive materials or complicated processes. Another object of the present invention is to provide a novel wire grid polarizer capable of obtaining arbitrary polarized light.

  The present invention uses a material that easily generates birefringence, such as a resin, for a transparent substrate in a wire grid type polarizer, expands the refractive index anisotropy by using birefringence by a stretching process, and transmits the polarizer. The polarization separation performance is enhanced by reducing the refractive index of the substrate with respect to the light to be emitted.

That is, the present invention relates to a wire grid polarizer in which straight metal thin wires are arranged in parallel to each other on a transparent resin substrate having birefringence and at the same interval, and refracted within the substrate surface. The present invention relates to a wire grid polarizer characterized in that the direction in which the rate is the lowest and the longitudinal direction of the fine metal wires are orthogonal. Furthermore, the present invention relates to a wire grid polarizer, characterized in that the direction in which the refractive index is lowest in the plane and the longitudinal direction of the fine metal wires intersect with an inclination of 45 °.

  According to an embodiment of the present invention, the wire grid polarizer substrate has birefringence, and the direction in which the refractive index is the lowest in the plane of the substrate and the longitudinal direction of the metal wire are substantially orthogonal to each other. The highest polarization separation performance can be obtained when the is arranged.

  According to another embodiment of the present invention, the substrate of the wire grid polarizer has birefringence, the direction in which the refractive index is lowest in the plane of the substrate, and the longitudinal direction of the thin metal wire is approximately 45 °. By arranging the fine metal wires so as to have an inclination and setting the substrate thickness to an appropriate value, the light transmitted through the wire grid can be made into a circularly polarized state or an S-polarized state. A circularly polarizing plate that can convert light in a non-polarized state into circularly polarized light and a polarizer in which both transmitted light and reflected light are in the S-polarized state are obtained.

  A birefringent material that can be used as a substrate for a wire grid polarizer is a visible material typified by calcite when a wire grid polarizer is used in applications that require heat resistance, such as liquid crystal projectors. An inorganic birefringent crystal that is highly transparent to light can be used. It is also possible to impart an external field-induced birefringence by applying an external field such as an electric field or a magnetic field to a high heat resistant inorganic material such as glass having no in-plane birefringence.

  On the other hand, if the heat resistance is not so required, a resin can be used as a transparent body having in-plane birefringence. Preferred resins include polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene (PS), and polyethylene. Terephthalate (PET), polyethylene naphthalate (PEN), diethylene glycol biscarbonate (CR-39), styrene / acrylonitrile copolymer (SAN), styrene / methacrylic acid copolymer (MS), alicyclic acrylic resin, alicyclic And highly transparent resins such as polyolefin resin, which are usually used as a plate or film for a substrate.

In general, when a plate or film is produced with a resin, a stretching step is included, but birefringence occurs when the resin is stressed or stretched. Birefringence generated by stretching is called orientation birefringence, and polymer molecules are oriented in a specific direction by the shearing force at the time of stretching, so that anisotropy occurs in the refractive index. Is done.
Δn = f · Δn ⁰ Formula 3
(Where Δn is the orientation birefringence, Δn ⁰ is the intrinsic birefringence, and f is the orientation distribution function.)

[Delta] n ⁰ is of intrinsic material, for example, a typical a highly transparent resin PMMA, PC, PS, PET Δn 0 each, -0.0043,0.106, -0.10,0.105 It is a town. When a material with positive Δn ^0, that is, a material having positive orientation birefringence, is uniaxially stretched, the refractive index in the stretching direction within the substrate surface is higher than the refractive index before stretching, and the refractive index in the non-stretching direction is low. Become. In contrast, a material having orientation birefringence having a negative Δn ⁰ has a low refractive index in the stretching direction and a high refractive index in the non-stretching direction in the substrate plane.

That is, when a material having a positive orientation birefringence with a refractive index n is stretched in a certain direction (the stretching direction is defined as the X axis, and the axis perpendicular to the X axis in the substrate plane is defined as the Y axis), each refractive index n _X in the X-axis direction after stretching, the refractive index n _Y in the Y-axis _{direction, n + Δn X, n-} Δn Y , and becomes to have a plane birefringence. Here, Δn _X and Δn _Y are the amounts of change in the refractive index in the X-axis direction and Y-axis direction (respectively positive values), and Δn _X + Δn _Y = Δn. Similarly, when a material having a negative orientation birefringence is stretched in the X-axis direction, n _X and n _Y are n−Δn _X and n + Δn _Y , respectively.

As will be apparent from the results of electromagnetic field simulation described later, the polarization separation performance of the wire grid polarizer is improved if the refractive index in the P-polarization direction is low. When forming a wire grid on a stretched resin film having positive orientation birefringence, the substrate viewed from the P-polarized light is arranged by arranging the metal fine wires so that the stretching direction and the longitudinal direction of the metal fine wires are orthogonal to each other. the refractive index of the reduced only [Delta] n _Y than before stretching, conversely, if the material having a negative orientation birefringence, when the thin metal wire is arranged such that the longitudinal direction of the stretching direction and the metal thin wire are parallel, P The refractive index of the substrate viewed from the polarization becomes smaller by Δn _X than before stretching. Therefore, it is possible to improve the polarization separation performance of the wire grid type polarizer as compared with the case where the thin metal wires are arranged on the same material that is not stretched. In particular, the greater the intrinsic birefringence Δn ⁰ , the greater the effect of improving the polarization separation performance by stretching.

  For example, by stretching a resin having positive orientation birefringence with a refractive index of 1.5 before stretching, the refractive index in the in-plane X-axis direction is 1.6 and the refractive index in the Y-axis direction is 1.4. As a result, a polarization separation performance equivalent to that when a substrate having a refractive index of 1.4 is used is exhibited.

  In the above description, uniaxial stretching has been described. In the case of biaxial stretching, the direction in which the degree of orientation is highest in the substrate plane is the X axis or the Y axis.

  The fine metal wires of the wire grid polarizer are very thin in both thickness and width, and the performance deteriorates due to slight scratches. To prevent the damage, the fine metal wires can be covered with a protective layer such as resin or glass. preferable. In addition, the coating is effective in preventing rust on the surface of the fine metal wire. Especially when using a rust-resistant metal such as silver for the fine metal wire, the coating is also used to prevent the performance degradation due to the decrease in the conductivity of the fine metal wire. It is preferable to do.

  In order to reduce the reflection of P-polarized light at the interface between the substrate and the protective layer, it is preferable that the refractive indexes in the direction perpendicular to the metal thin wires of the protective layer and the substrate are substantially matched.

  In addition, it is preferable to provide an antireflection structure on the substrate or the protective layer in order to increase the light use efficiency.

  The material of the fine metal wire is not particularly limited, but it is preferable to use a metal material such as silver or aluminum that exhibits high reflectivity with respect to visible light and has high conductivity.

  The height t (metal thickness) of the fine metal wire is determined based on the polarization separation performance of the wire grid polarizer. Specifically, the light transmittance may be 1% or less, and the thickness is 30 nm or more. If it is, good performance can be obtained. If the metal is too thin, the transmission of light cannot be ignored, and the polarization separation performance is degraded. On the other hand, if the metal is too thick, the light utilization efficiency decreases, so the upper limit of the thickness is about 300 nm. When forming a metal fine wire with aluminum, it is desirable that metal thickness is about 40-200 nm.

Pitch p of the thin metal wire, 0 ° incidence, may if below the wavelength of light used is maximum resonance wavelength lambda _res-max derived from the Formula 1 in the refractive index n = 1 of the vacuum, for the visible light Since there is no problem if it is 400 nm, the pitch p may be 380 nm or less.

  Regarding the wire width w, the polarization separation performance of the wire grid polarizer is improved when w is about half of the pitch p, and it is preferable that the range is 0.3p <w <0.7p.

  The cross-sectional shape of the thin metal wire is not particularly limited, and may have a square, rectangular, trapezoidal, circular, elliptical, or other various shapes.

  There are various methods for manufacturing a wire grid polarizer, and methods for manufacturing a wire grid polarizer for visible light include an interference exposure method using an extreme ultraviolet laser, and a manufacturing method using electron beam lithography. This is a general method. These are methods for producing a fine metal wire having a desired pitch, wire width and thickness by lithography.

  In addition, as another technique, in Patent Document 3, by forming a metal film on a transparent flexible substrate and stretching the substrate and the metal film, an anisotropic shape can be given to the metal film, It is described as having a function as a wire grid polarizer. When this method is used in the present invention, it is preferable to use a material having a negative orientation birefringence in which the refractive index is as low as possible and the birefringence in the stretching direction is lowered.

Patent Document 4 pitches 1μm on a SiO ₂ substrate, in a line width 0.1 [mu] m, after having formed a gold thin metal wire grid, a SiO ₂ film is formed on the surface of the grating, the more lattice direction parallel It is described that a wire grid polarizer having a pitch of 0.1 μm and a line width of 0.01 μm can be produced by heating and stretching the whole.

  The result of electromagnetic field simulation is described with a substrate having in-plane birefringence. The simulation conditions are the same as those described in the prior art, except that the substrate has in-plane birefringence. In the future, for simplicity, when the direction of the lowest refractive index of the substrate having in-plane birefringence is the x axis and the direction of the highest refractive index is the y axis, the substrate has a birefringence of (nx, ny). It will be described as having. Here, the X-axis (and the Y-axis meaning the non-stretching direction) and the x-axis (and y-axis) that mean the stretching direction do not necessarily match.

Parallel to the case where the longitudinal direction of the fine metal wires is perpendicular to the x-axis with respect to the substrate having a substrate birefringence of (1.4, 1.6) (hereinafter, this arrangement will be described as “x⊥ arrangement”). Calculations were made for certain cases (hereinafter described as “x _|| configuration”). Each arrangement is shown in FIG. FIG. 5A shows the x⊥ arrangement, and FIG. 5B shows the x _|| arrangement.

The pitch, line width, and thickness of the fine metal wires are the same as in the previous calculation. The simulation result of the polarization degree of transmitted light is shown in FIG. It can be seen that Rayleigh resonance occurs at 289 nm and 331 nm in the case where the birefringence of the substrate is in the x 、 arrangement and in the x _|| arrangement, but the effect of Rayleigh resonance at 331 nm is smaller and better in the case of x⊥. Performance.

This is because a substrate that influences P-polarized light that is transmitted light when incident light is polarized and separated by a wire grid type polarizer having a substrate birefringence of (nx, ny) and the fine metal wires are arranged in x⊥. It is qualitatively explained that this is because the refractive index of nx is nx whereas the x _|| configuration is ny. The same is true when the incident angle θ is increased, but the transmitted light has a higher degree of polarization in the x⊥ arrangement.

As a simulation result of the reflected light, FIG. 7 shows a case where the substrate refractive index is uniform and n = 1.4 and 1.6, and the substrate birefringence (1.4, 1.6) is x⊥ arrangement. The degree of polarization of reflected light calculated under four conditions in the case of x _|| configuration with birefringence (1.4, 1.6) is shown. Comparing FIG. 7 and FIG. 6, it can be seen that the reflected light is more greatly affected by birefringence than the transmitted light. That is, of the birefringence (nx, ny), the refractive index in the direction orthogonal to the wire grid almost determines the polarization characteristics, and the x⊥ arrangement has a higher degree of polarization in the visible light wavelength range. Recognize.

From FIG. 7, in the case of the substrate refractive index n = 1.6 and the birefringence (1.4, 1.6) x _|| arrangement, there is a wavelength region where the degree of polarization exceeds 99% in the vicinity of 310 nm. However, it is raised as a remarkable point. This result shows that the polarization degree of reflected light can be increased in a specific wavelength range by appropriately setting the pitch, wire width, height, and substrate refractive index (or birefringence) of the wire grid polarizer. Show.

Next, the light use efficiency by recycling the reflected light described in the background section will be compared. The light utilization efficiency is defined as in the following equation 4.
Light utilization efficiency = Tp × (Rs + Rp) Equation 4
(In Equation 4, Rs and Rp are the reflectances of S-polarized light and P-polarized light, respectively.)

FIG. 8 shows the relationship between the wavelength and the light utilization efficiency. The x⊥ arrangement is superior to the x _|| arrangement in terms of light utilization efficiency.

  As described above, when the substrate birefringence is (nx, ny), 1) the transmittance of P-polarized light, 2) the degree of polarization of transmitted light, 3) the degree of polarization of reflected light, and 4) the use of light. It can be seen that the x⊥ arrangement is superior in any of the indexes representing the performance of the four wire grid polarizers, ie, efficiency.

  Note that the accuracy of orthogonality between the longitudinal direction of the metal wire grating and the direction of the lowest refractive index of the substrate having in-plane birefringence is determined by the polarization separation performance required for the wire grid polarizer, and high polarization separation. When the wire grid polarizer of the present invention is used for applications where performance is not required, some errors are allowed.

  Up to this point, the linearly polarized light separation performance under the condition where the longitudinal direction of the fine metal wires is arranged perpendicularly or parallel to the x direction of the birefringent substrate has been described. In the case where the thin metal wires are arranged, the thin metal wire serves as a linear polarizer and the substrate serves as a wave plate. Therefore, by controlling the substrate thickness (d), the polarization performance of transmitted light can be variously controlled.

  In particular, when φ = 45 °, the substrate is so-called when (nx−ny) · d = λ / 4 + N · λ / 2 (λ: wavelength of incident light, N = 0, 1, 2,...) Is satisfied. Since it functions as a λ / 4 wavelength plate, the transmitted light is circularly polarized. Further, when the condition of (nx−ny) · d = λ / 2 + N · λ / 2 is satisfied, the substrate functions as a λ / 2 wavelength plate, and the transmitted light is S-state linearly polarized light. FIG. 9 shows a schematic diagram thereof.

  Usually, when obtaining circularly polarized light from light in a non-polarized state, an optical element that produces linearly polarized light and a λ / 4 plate are used in combination. Metal fine wires are arranged at 45 ° on a substrate having birefringence, and By controlling the in-plane birefringence and the thickness of the substrate to appropriate values so as to be a λ / 4 plate, substantially one optical element can obtain circularly polarized light. Further, when the in-plane birefringence and the thickness are controlled so that the birefringent substrate is a λ / 2 plate, a unique optical element capable of obtaining S-polarized light for both transmitted light and reflected light is obtained.

<Example 1>
In-plane birefringence was imparted to the PET film by stretching in the following procedure, and the aluminum thin wires were arranged in an x⊥ arrangement.

  A PET film having a thickness of 80 μm and a refractive index of 1.58 was uniaxially stretched at 110 ° C. and 3.5 times in width. The refractive index in the stretching direction after stretching was 1.60, and the refractive index in the non-stretching direction was 1.52.

  Next, an aluminum layer having a thickness of 120 nm was formed on the stretched PET film by resistance heating vapor deposition, and a photoresist layer was provided by spin coating.

  Subsequently, a stripe pattern (pitch 180 nm, line: space≈1: 1) is formed in a direction parallel to the stretching direction of the PET film by two-beam interference exposure with an ArF laser (wavelength 193 nm), and after development, dry etching is performed. Aluminum was removed to obtain a wire grid polarizer.

  A solid laser beam having a wavelength of 405 nm and a semiconductor laser beam having a wavelength of 635 nm were incident perpendicularly to the wire grid polarizer from the thin aluminum metal surface of the wire grid polarizer, and the polarization separation performance was measured. The polarization degrees of transmitted light at 405 nm and 635 nm were 98.2% and 99.6%, respectively.

<Comparative Example 1>
An aluminum wire was arranged in a direction orthogonal to the stretching direction of the film (x _|| arrangement) on a PET film having in-plane birefringence in the same manner as in Example 1, and the degree of polarization was measured. As a result, 405 nm and 635 nm were measured. The polarization degrees of were 94.0% and 99.1%, respectively, and the polarization separation performance was inferior to that of Example 1.

  From the results of Example 1 and Comparative Example 1, when producing a wire grid polarizer by arranging metal thin wires on a substrate having in-plane birefringence, the direction in which the refractive index of the substrate decreases and the longitudinal direction of the wire are orthogonal to each other. It was shown that the polarization separation performance is improved.

  According to the present invention, it is possible to improve the performance of a wire grid polarizer without going through a complicated process. If the wire grid polarizer according to the present invention is used in a liquid crystal display, the light use efficiency can be greatly improved, and the battery life of a mobile information terminal can be greatly extended or the weight can be reduced. In addition, the cost can be reduced by reducing the number of parts, and the product can be made thinner. Thus, it can be said that the present invention has a high utility value in a wide range of industrial fields using polarized light.

It is a schematic diagram of the wire grid type polarizer in a prior art. It is a figure which shows the wavelength dependence of the transmission efficiency of P polarization | polarized-light and S polarization | polarized-light of a wire grid type polarizer in a prior art. It is a figure which shows the wavelength dependence of the polarization degree of the wire grid type polarizer in a prior art. It is a figure which shows the incident angle dependence of the maximum resonance wavelength in a prior art. (A) represents the x⊥ placement of the wire grid polarizer on a birefringent substrate, (b) is a schematic view showing an x _|| placement of the wire grid polarizer on a birefringent substrate. It is a figure which shows the wavelength dependence of the polarization degree of the transmitted light of the wire grid type polarizer on the birefringent substrate in this invention. It is a figure which shows the wavelength dependence of the polarization degree of the reflected light of the wire grid type polarizer on the birefringent substrate in this invention. It is a figure which shows the wavelength dependence of the utilization efficiency of the light of the wire grid type polarizer on the birefringent substrate in this invention. It is a schematic diagram which shows the characteristics of the polarizer which arranged the wire at an angle of 45 degrees with respect to the x-axis on the birefringent substrate in the present invention.

Claims (3)

  The direction in which the refractive index is the lowest in the plane of the substrate in a wire grid polarizer in which straight metal thin wires are arranged on a transparent resin substrate having birefringence in parallel and at the same interval. And a wire grid polarizer in which the longitudinal directions of the fine metal wires are orthogonal to each other. In a wire grid polarizer in which straight metal fine wires are arranged on a transparent resin substrate having birefringence in parallel with each other and at the same interval, the substrate is a half-wave plate, A wire grid polarizer, characterized in that the direction in which the refractive index is lowest in the plane of the substrate and the longitudinal direction of the fine metal wires intersect with an inclination of 45 °. 3. The wire grid polarizer according to claim 1, wherein birefringence of a transparent resin substrate is introduced by stretching.

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