JP2012078820A - Wire grid polarizer having a color filter function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire grid polarizer capable of reducing processes when it is used for manufacturing liquid crystal display panels.SOLUTION: The wire grid polarizer is composed of multiple metal lines to be grid lines on a substrate which are arranged in parallel with a shorter period than light waves. The shape of a cross section when cutting it at a vertical face to the longitudinal direction of the grid lines is a polygon. The polygon has six or more vertices, an angle formed between two adjacent sides is 90° or 270° and at least one of the angles formed by two adjacent sides is 270°among the angles formed by two adjacent sides.

Description

  The present invention relates to a wire grid polarizer. In particular, the present invention relates to a wire grid polarizer suitable for a surface light source illumination device, a display, and a projector.

  The wire grid polarizer is used as a polarizer for polarizing light in a surface light source illumination device, a display, and a projector. In the liquid crystal display panel, the liquid crystal layer of each pixel transmits and blocks the light emitted from the backlight to display as a light shutter, so that the liquid crystal layer can function as a light shutter. Two polarizers having a polarization direction perpendicular to each other are provided with a liquid crystal layer interposed therebetween.

  On the other hand, light transmitted through a liquid crystal layer sandwiched between two polarizers and light of a desired color are transmitted through a color filter provided in each pixel, thereby realizing color display.

  Here, the wire grid polarizer has a number of metal lines (wires) serving as grid lines on a substrate made of glass or the like, and a period shorter than the wavelength of light (the period of the grid lines is the width of the grid lines and the grid lines). It is composed of diffraction gratings arranged in parallel with each other. The wire grid polarizer reflects the light whose electric field oscillates in the direction parallel to the grid lines out of the light emitted from the light source and transmitted through the wire grid polarizer, and the electric field oscillates in the direction perpendicular to the grid lines Then, polarized light is generated from the light emitted from the light source.

  In the liquid crystal display panel, in addition to the polarizer and color filter, in order to ensure high-quality visibility as a display, a large number of layers are laminated, the structure is complicated, and many processes are required for manufacturing. Therefore, it is a manufacturing problem to reduce the number of steps by reducing the number of constituent layers.

  As a wire grid polarizer capable of solving such problems, a wire grid polarizer formed in a color filter substrate having a color filter layer has been proposed. By integrating with the color filter layer, the step of bonding to the liquid crystal layer is reduced (see Patent Document 1). However, a wire grid polarizer that can further reduce the manufacturing process has been demanded.

JP 2009-42319 A

  An object of the present invention is to provide a wire grid polarizer that can reduce the number of steps when used in the manufacture of a liquid crystal display panel.

  Therefore, the present inventor has come up with the idea of adding a function different from polarization to the wire grid polarizer and reducing the number of layers to reduce the manufacturing process of the liquid crystal display panel. As a result of intensive studies, the cross-sectional shape of the grid lines made of the metal lines constituting the wire grid polarizer is made more complicated than the conventional simple rectangle or circle, so that the wire grid polarizer The present inventors have found that such a wire grid polarizer can function as both a polarizer and a color filter, and has completed the present invention.

That is, the present invention provides the following [1] to [7].
[1] A wire grid polarizer in which a large number of metal lines serving as grid lines are arranged in parallel with a period shorter than the wavelength of light on a substrate, and the plane is perpendicular to the longitudinal direction of the grid lines. The shape of the cross section when cut is a polygon, the polygon has six or more vertices, the angle formed by two adjacent sides is 90 ° or 270 °, and the angle formed by the two adjacent sides A wire grid polarizer, at least one of which is 270 °.
[2] The wire grid polarizer according to [1], in which a cross-sectional dimension and a period of a lattice line are adjusted so as to simultaneously generate a polarization effect and a color filter effect for a specific wavelength of visible light.
[3] The wire grid polarizer according to [1] or [2], wherein the period of the lattice line is more than 0 nm and not more than 700 nm.
[4] The wire grid polarization according to any one of [1] to [3], wherein the height of the lattice line (the length in the direction perpendicular to the interface between the lattice line and the substrate) is 10 times or less the period of the lattice line Child.
[5] The wire grid polarizer according to any one of [1] to [4], wherein the fill factor exceeds 0 and is 0.99 or less.
[6] The wire grid polarizer according to any one of [1] to [5], wherein a lattice line on the substrate is covered with a resin.
[7] An element comprising the wire grid polarizer according to any one of [1] to [6], capable of polarizing incident light and acting as a narrow band optical filter.

  Since the wire grid polarizer of the present invention has both functions of a polarizer and a color filter, it is industrially useful when used in the production of a liquid crystal display panel because the number of steps can be reduced compared to the conventional one. . If a color filter is required, the wire grid polarizer of the present invention can be used for the surface light source illumination device, display and projector of the present invention.

The schematic diagram which shows a wire grid polarizer and incident light. Parallel thin metal lines (grid lines) 20 having a cross-section 40 perpendicular to the longitudinal axis of the grid lines are arranged on the substrate 10. The surrounding medium 30 present between the two metal lines and above the metal lines may be air or resin. The figure which shows two examples of the method of comprising the shape of the cross section of the lattice line of the wire grid polarizer of this invention with a combination of three rectangles. a) An example in which rectangles are combined so as to share a side perpendicular to the substrate. b) An example in which rectangles are combined so as to share sides parallel to the substrate. The figure which illustrated the shape of the cross section of the grid line of the wire grid polarizer of this invention at the time of cut | disconnecting with the surface perpendicular | vertical with respect to the longitudinal direction of a grid line, and various complicated shapes (Shape1 to Shape10). Any of the cross-sectional shapes shown can be configured by combining rectangles by the method as shown in FIGS. 2a and 2b. The figure which shows the simulation result of an Example and shows the wavelength dependence of the light transmittance of p mode. It shows that three types of polarizers function as color filters. The figure which shows the simulation result of an Example and shows the wavelength dependence of the light transmittance of s mode. It shows that three types of polarizers function as polarizers and block s-mode light. The simulation result of the comparative example is shown, and a p-mode in the case where a simple wire grid polarizer having a rectangular cross-sectional shape is surrounded by a resin (surrounding medium) having a refractive index of 1.5 on the entire surface The transmission spectrum of FIG.

  The present invention relates to an optical device capable of simultaneously selecting both polarization and spectrum of incident light. In particular, the present invention relates to an optical device that selectively transmits linearly polarized light in a specific wavelength region.

  The wire grid polarizer of the present invention can be used for a liquid crystal display. In a conventional liquid crystal display, a polarizer and a color filter are used separately. Conventionally used polarizers are made of PVA, and as a result of removing light having unnecessary polarization from incident light, half of the incident light is not transmitted and is not used. Moreover, the color filter used conventionally has expressed color with dye, and it cannot be said that the light transmittance is high. In addition, the color filters used in the past may be designed to have a longer distance from the panel in which the liquid crystal is sealed in order to prevent the dye from being decomposed by heat. When looking at the screen, there was a problem that the pixels of the liquid crystal panel and the pixels of the color filter appear to be misaligned (parallax error).

Since the wire grid polarizer of the present invention serves both as a polarizer and a color filter, the light transmittance is higher than when the polarizer and the color filter are separately provided.
Since the grid lines of the wire grid polarizer of the present invention are made of metal such as aluminum, they are more resistant to heat than conventional color filters using dyes. Therefore, the wire grid polarizer of the present invention, which is a member serving both as a polarizer and a color filter, can be installed near the light source, and problems caused by the generation of heat such as parallax error can be reduced.

  The wire grid polarizer of the present invention is a wire grid polarizer in which a large number of metal lines serving as grid lines on a substrate are arranged in parallel with a period shorter than the wavelength of light, and in the longitudinal direction of the grid lines. The cross-sectional shape when cut along a plane perpendicular to the polygon is a polygon, the polygon has six or more vertices, and the inner angle formed by two adjacent sides is 90 ° or 270 °, At least one of the inner angles formed by the two sides is 270 °.

  The cross-sectional shape of the grid line is either the width (the length of the side in the direction parallel to the interface between the substrate and the grid line) and the height (the length of the side in the direction perpendicular to the interface between the substrate and the grid line) or one of them. It can also be said that three different rectangles are combined. In addition, each rectangular material can be made different.

  A vertex whose inner angle between two adjacent sides is 270 ° (hereinafter, a vertex whose inner angle between two adjacent sides is 270 ° is an “inner angle 270 ° vertex”, and a vertex whose inner angle between two adjacent sides is 90 ° is referred to as an “inner angle” Among the cross-sectional shapes having two or more “90 ° vertices”, the most preferable one is that the inner angle 270 ° vertices are adjacent to each other, or an even number between the inner angle 90 ° vertices. It is a shape located in In some cases, the inner angle 270 ° apexes adjacent to each other may be located across the three inner angle 90 ° apexes (for example, in the case of shape 4 and shape 10 in FIG. 3).

  The wire grid is also known as a metal zeroth-order diffraction grating, and is formed by arranging thin metal wires as lattice lines in parallel at a constant period. As shown in the schematic diagram of FIG. 1, light in a direction perpendicular to the longitudinal direction of the metal line (referred to as p-mode) is transmitted and light in a direction parallel to the longitudinal direction of the metal line (referred to as s-mode). Therefore, the wire grid polarizer exhibits a polarizing action.

  According to the inventor's simulation, the transmission spectrum of the p-mode of the wire grid polarizer of the present invention exhibits the characteristics of a narrow band optical filter (a filter that transmits light in a narrow wavelength range), particularly at a specific wavelength. A range of light can be transmitted. That is, the transmission peak wavelength is a specific wavelength, and light having a wavelength outside the wavelength designed as the transmission peak wavelength is not transmitted.

  The wire grid polarizer of the present invention has a function as a polarizer for incident light and a function as a color filter for incident light. The second function is the same function as the color filter of the liquid crystal display. The wire grid polarizer of the present invention has both the function of a polarizer and the function of a color filter in a liquid crystal display.

  Based on the above, it is possible to design a more effective polarizer and color filter that shows a transmission peak in a narrow wavelength range in visible light and near infrared light based on the wire grid polarizer of the present invention. And even those designed in that way are easy to manufacture.

  One way to adjust the optical properties of the polarizer / color filter is to design the structure with variables. A conventional wire grid polarizer in which the cross section of the grating line is rectangular is a zero order diffraction grating. Such conventional wire grid polarizers have three design variables: grid line period, grid line height, and fill factor. In the wire grid polarizer of the present invention, a degree of freedom can be added to the design by adding more design variables. For example, the length, width, and material of the various rectangles that make up the cross section of the grid lines can be changed to match the required properties of the polarizer and color filter.

  The cross-sectional shape of the metal wire has conventionally been a rectangle. Therefore, the only design variables were the period of the metal wire and the width and height of the rectangular cross section. Here, the inventors of the present invention can simulate the function of a color filter in addition to the function of a polarizer by changing the cross-sectional shape of the metal wire. And found it.

  A conventional wire grid polarizer having a rectangular cross-sectional shape also exhibits the color filter function, but the peak of the curve indicating the wavelength dependence of transmittance is wide. In other words, there is a large proportion of transmitting light having a wavelength other than the intended light to be transmitted. For example, if the wavelength of light to be transmitted is 540 nm, the transmittance at 700 nm is 30% according to the simulation conducted by the inventors. In the wire grid polarizer of the present invention, the width of the peak of the curve indicating the wavelength dependence of the transmittance is much narrower than that of the conventional wire grid polarizer.

  The period of the lattice lines can be selected to be as large as the wavelength of the light that is the object of the wire grid polarizer and color filter. For example, if the wire grid polarizer is set to function as a color filter for light having a wavelength of 550 nm, and the half-value width of transmitted light or reflected light is 100 nm, the maximum period of the lattice line is The value may be set to 500 nm. The upper limit of the period of the lattice line is determined so that the wire grid polarizer ensures reflection or transmission of light in the 0th order with respect to normal incident light. If higher diffraction orders are allowed, the diffracted light will travel in an undesirable viewing angle direction. The lower limit of the period of the lattice lines may be as small as possible, that is, as long as processing is possible. In the current nano-processing technology, the lower limit is about 50 nm, and the structure of WGP can be processed.

  In the present invention, the shape of the cross section when cut along a plane perpendicular to the longitudinal direction of the grid lines is a contour of a figure formed by contacting three rectangles, and is a polygon having six or more vertices. The rectangle is a rectangle (including a square). Two of the three rectangles may have the same shape as “a polygon having six or more vertices, which is an outline of a figure generated by contacting three rectangles”.

  FIG. 2 shows two examples of a method of configuring the cross-sectional shape of the lattice line of the wire grid polarizer of the present invention by combining three rectangles. a) is an example in which rectangles are combined so as to share a side perpendicular to the interface between the substrate and the lattice line. b) is an example in which the rectangles are combined so as to share a side parallel to the interface between the substrate and the lattice line. In both construction methods, the three rectangular cross sections do not overlap. In the configuration method, the rectangles may be moved relative to each other in the vertical direction (in the case of (a)) or in the horizontal direction (in the case of (b)) along the sides in contact with each other.

  In the cross-sectional view of FIG. 2, d represents the maximum height in the direction perpendicular to the lattice line substrate-lattice line interface, and w represents the maximum width in the direction parallel to the lattice line substrate-lattice interface. Show. The fill factor is determined from the lattice line period p and the w. Values such as w1, d1, w2, d2, w3, d3 are the widths (w1, w2, w3, etc.) and heights (d1, d2, d3). The number of these widths and heights is the number of vertices that can be produced when actually manufacturing the wire grid polarizer of the present invention (the number of cross sections when cut along a plane perpendicular to the longitudinal direction of the grid lines). Limited by the number of corner vertices). Note that d1, d2, and d3 ≦ d, and w1, w2, and w3 ≦ w.

  In the configuration method of FIG. 2a), the following relationship is maintained: w = w1 + w2 + w3, and d is equal to the largest of d1, d2 and d3. In the configuration method of b) of FIG. 2, the following relationship is maintained: d = d1 + d2 + d3, and w is equal to the largest of w1, w2 and w3.

  In the configuration method of FIG. 2a), the following conditions are maintained. All the heights of d1, d2 and d3 may be different from each other. Further, any two of the three heights d1, d2, and d3 may be equal to each other and may be different from the other. Therefore, preferable conditions are d1 ≠ d2 ≠ d3, d1 ≠ d2 = d3, d1 = d2 ≠ d3, d2 ≠ d1 = d3 regardless of the values of the widths w1, w2, and w3. As long as the centers of the three rectangles are not on the same straight line, all three heights d1, d2 and d3 may be the same. When the centers of the three rectangles are on the same straight line (on the horizontal line in the drawing), d1 = d2 = d3 is outside the scope of the claims of the present application. All the widths of w1, w2 and w3 may be different from each other. Regarding the widths w1, w2, and w3, any two of them may be equal to each other and may be different from the other. Also, all of the three widths w1, w2 and w3 may be equal.

  In the configuration method of b) in FIG. 2, the following conditions are maintained. All the widths of w1, w2 and w3 may be different from each other. Further, any two of the three widths w1, w2, and w3 may be equal to each other and may be different from the other. Therefore, acceptable conditions are w1 ≠ w2 ≠ w3, w1 ≠ w2 = w3, w1 = w2 ≠ w3, and w2 ≠ w1 = w3 regardless of the values of the heights d1, d2, and d3. As long as the centers of the three rectangles are not on the same straight line, the three widths w1, w2, and w3 may all be the same. In the case where the centers of the three rectangles are on the same straight line (on a straight line perpendicular to the paper surface of the drawing) and w1 = w2 = w3, it is outside the scope of the claims of the present application. All the heights of d1, d2 and d3 may be different from each other. Regarding the heights d1, d2 and d3, any two of them may be equal to each other and different from the other. Also, all three heights d1, d2 and d3 may be equal.

  FIG. 3 shows ten cross-sectional figures (Shape 1 to Shape 10), and these figures are constructed using the construction method shown in FIG. Each figure is numbered to distinguish it from other figures. Figures 1 to 5 and figures 8 to 10 can be configured using the configuration method shown in FIG. Figures 6 and 7 can be constructed using the construction method shown in FIG. The figures shown in FIG. 3 are examples, and the present invention is not limited to these figures.

  When the number of vertices of the polygon is too large, the effect as a color filter tends to be insufficient. Therefore, the number of vertices of the polygon is usually 30 or less, preferably 20 or less, 12 More than the number is more preferable.

  When the maximum length of one side of the polygon is too small, the effect as a color filter tends to be insufficient. Therefore, the maximum length of one side of the polygon is usually 10 nm or more. Of the sides of the polygon, the length (for example, w1, w2, w3) of the side parallel to the interface between the substrate and the lattice line is preferably 20 nm or more. A more preferable range of the length is 40 nm or more and 250 nm or less. The total width value w is preferably 20 nm or more and 630 nm or less. More preferably, it is the range of 40 nm or more and 360 nm or less. Of the sides of the polygon, the length of the sides perpendicular to the interface between the substrate and the lattice lines (for example, d1, d2, d3) is preferably 20 nm or more. A more preferable range is 40 nm or more and 1000 nm or less.

  The total height of the lattice lines (the length in the direction perpendicular to the interface between the lattice lines and the substrate, d) is preferably 10 times or less of the period of the lattice lines. d is preferably 20 nm or more and 4000 nm or less. More preferably, it is the range of 40 nm or more and 1000 nm or less.

  The fill factor (f) is defined by the ratio of the grid line width (w) to the grid line period (p). That is, f = w / p. Physically, the upper limit of the fill factor is 0.99, and the lower limit is greater than 0 but can be close to 0. However, since the lower limit of processing is about 50 nm in the current nano-processing technology, the lower limit of processing affects the upper and lower limits of the fill factor, and considering the processable range, the preferred range of the fill factor is It is 0.1 or more and 0.9 or less, and 0.2 or more and 0.9 or less is more preferable. Furthermore, as a wire grid polarizer that can be used for both a color filter and a polarizer, according to the inventor's simulation, the fill factor is more preferably in the range of 0.3 to 0.85, and more preferably 0.4 to 0. A range of .85 or less is even more preferable.

  The period of the lattice lines of the wire grid polarizer of the present invention is changed when the designed transmission peak wavelength changes. In addition, the period of the lattice line needs to be shorter than the wavelength of light that is the object of the wire grid polarizer and the color filter. When visible light is used, the period of the lattice line is usually more than 0 nm and 700 nm or less, preferably 50 nm to 700 nm, more preferably 50 nm to 500 nm, and still more preferably 50 nm to 400 nm. .

  In order for the wire grid polarizer of the present invention to exhibit a polarization effect and a color filter effect for a specific wavelength of visible light, the dimensions of the cross section, that is, the cross section is polygonal. The period of each lattice line along with the length of each side of the square is adjusted so as to simultaneously generate the polarization effect and the color filter effect for a specific wavelength of visible light.

  The reason why the wire grid polarizer of the present invention effectively exhibits the color filter effect is considered that electromagnetic resonance (resonace) occurs in accordance with each polygonal shape in the cross section. It is thought that there is. Simulation results show that the wire grid polarizer of the present invention behaves like a resonant cavity. As is well known in resonance physics, the resonance wavelength and the corresponding bandwidth can be finely adjusted by changing the size, shape, and material of the resonance cavity. Therefore, in the wire grid polarizer of the present invention, the selection of w1, d1, w2, d2, w3, and d3 in FIG. 2 which is a shape variable determines the peak wavelength of the transmitted band and the width of the transmitted band. .

  The FDTD (Finite Difference Time Domain) method (finite difference) is set after setting the refractive index of the substrate, the period and cross-sectional shape of the lattice lines arranged on the substrate, the wavelength of the incident light, the vibration direction and the incident angle of the electric field. If the calculation is performed using the time domain method, the behavior of light (electromagnetic waves) can be accurately simulated.

  The FDTD method is a known method described in, for example, “Electromagnetic field and antenna analysis by the FDTD method”, Corona, 1998. The Maxwell equation is divided spatially and temporally, and the spatial and temporal derivatives are separated. This is a simulation method that approximates by a finite difference and tracks and calculates the time change of the electromagnetic field.

  In general, incident light in an arbitrary polarization state can be divided into two orthogonal polarization states, that is, a p mode and an s mode. In the FDTD method used for demonstrating the effect of the present invention, the calculation can be efficiently performed by using the inductive convolution method. For the s-mode in electromagnetic waves, the first electromagnetic field analysis equation obtained by applying the inductive convolution method to the wave equation derived from the Maxwell equation is solved by a computer using the inductive relational equation, For the p mode, the second electromagnetic field analysis formula obtained by applying the recursive convolution method to the Maxwell equation is solved by a computer using the recursive relational expression, and for the p mode and the s mode, It is preferable that the electromagnetic field in the spatial and temporal divisions of the FDTD method is calculated based on the electromagnetic field obtained in this way (see Japanese Patent Application No. 2008-68139).

In the FDTD method, the following Maxwell equations can be used.

(1)
(2)
Here, μ is the magnetic permeability, E is the strength of the electric field, and H is the strength of the magnetic field.
Is a differential operator,
as well as
as well as
Is a unit vector in the x-axis direction, the y-axis direction, and the z-axis direction,

(3)
Is a differential operator defined by.

D in Formula (2) represents the electric flux density and is given by the following formula.

(4)

In equation (4), ε is the dielectric constant of the object.

Ε in the above equation (4) in each region spatially separated in the FDTD method is the first-order Drude model (KS Kunz, and RJ Luebbers, The Finite difference Time Domain Method for Electromagnetics, Chapter 8, CRC Press, Boca Raton , pp.123-162, 1993).

(5)
In equation (5), ω is the angular frequency of light, ωp is the plasma angular frequency, and νc is the collision frequency.

  The wire grid polarizer of the present invention can be produced by forming metal lines in parallel on a transparent substrate by a method commonly practiced in industry.

  Examples of the transparent substrate include substrates made of glass (including quartz glass and calcium fluoride glass), sapphire, crystal, and resin. Examples of the resin include PMMA, polystyrene, polycarbonate, and polyacrylonitrile.

  Examples of the metal wire material include aluminum, gold, silver, platinum, copper, palladium, nickel, chromium, manganese, and titanium, and alloys such as stainless steel, hastelloy, and duralumin can also be used.

  The lattice lines formed on the substrate may be covered with resin. Examples of the resin include PMMA, polycarbonate, polyester, polyolefin, polyamide, polyimide, epoxy resin, and alkyd resin.

  In order to form metal lines in parallel on a transparent substrate, hot embossing nanoimprint lithography, UV-curable nanoimprint lithography, reactive ion etching, electron beam lithography, vapor deposition, A method such as sputtering can be used.

  Examples will be shown below for illustrating the present invention in more detail, but the present invention is not limited to these examples.

In all examples and comparative examples, the change of the degree of polarization with the wavelength of light was determined by computer simulation. The program used for the calculation is a program for calculation of the FDTD method created by the inventors, and simulation was performed by solving Maxwell's equations. The lattice lines are made of aluminum, and the substrate is made of a transparent material having a refractive index of 1.5. The Drude model was used to calculate the dielectric constant ε of the lattice line portion, and ωp = 2.2637 × 10 ¹⁶ s ⁻¹ and νc = 11.99 × 10 ¹³ s ⁻¹ . It is assumed that the light passes through the air and enters perpendicularly to the plane of the polarizer (the interface of the substrate constituting the lattice line).

The degree of polarization dp of the wire grid polarizer of the present invention was calculated from the p-mode light transmittance T _p and the s-mode light transmittance T _s by the following equation (6).

(6)

Example 1
The cross-sectional shape of the lattice line is the shape 1 of FIG. 3 and w = 186.2 nm, d = 300 nm, d1 = 280 nm, and w1 = 53.9 nm. The period of the lattice line was 245 nm. The calculation result of the p-mode light transmittance is indicated by R1 in FIG. 4 (a line connecting the dots ■). It can be seen that the filter functions as a red filter having a peak around 620 nm and a transmittance curve with a half-value width of 60 nm. The peak value of light transmittance is about 90%. The wavelength dependence of the light transmittance of the s mode is shown in R (marked line in FIG. 5) in FIG. dp was 0.98 or more, indicating high polarization performance.

Example 2
The cross-sectional shape of the lattice line is the shape 2 of FIG. 3 and w = 197.6 nm, d = 220 nm, d1 = 20 nm, w1 = 57.2 nm, and w2 = 57.2 nm. The period of the lattice line was 260 nm. The calculation result of the transmittance of the p-mode light is indicated by G2 in FIG. 4 (a line connecting the dots). It can be seen that the filter functions as a green filter having a peak near 535 nm and a transmittance curve with a half-value width of 45 nm. The peak value of light transmittance is about 90%. The wavelength dependence of the light transmittance of the s mode is shown in G (circled line) in FIG. dp was 0.98 or more, indicating high polarization performance.

Example 3
The cross-sectional shape of the lattice line is the shape of shape 3 in FIG. 3 and w = 197.6 nm, d = 275 nm, d1 = 150 nm, w1 = 46.8 nm, d2 = 50 nm. The period of the lattice line was 260 nm. The calculation result of the transmittance of the p-mode light is shown by B2 in FIG. 4 (a line connecting the asterisk dots). It can be seen that the filter functions as a blue filter having a peak around 450 nm and a transmittance curve with a half width of 30 nm. The peak value of light transmittance is about 70%. The wavelength dependence of the light transmittance of the s mode is shown in FIG. 5B (line connecting triangular points). dp was 0.98 or more, indicating high polarization performance.

  In the simulation examples shown in FIGS. 4 and 5, the refractive index of the substrate is 1.5. The refractive index of the surrounding medium (medium that contacts all surfaces of the metal except the interface with the substrate) was 1.5. In all of the examples shown here, the degree of polarization near the peak of transmittance was about 99.98% or more.

Comparative Example 1
The cross-sectional shape of the lattice line was a rectangle, and the width w was 96 nm and the height d was 100 nm. The period of the lattice line was 120 nm. The calculation result of the transmittance of the p-mode light is shown in Comparative Example 1 in FIG. 6 (line connected with ■). Although it has a peak in the vicinity of 530 nm, it has been found that the light transmission curve is wide and the function as a green filter is not sufficient.

Comparative Example 2
The cross-sectional shape of the lattice line was a rectangle, and the width w was 168 nm and the height d was 200 nm. The period of the lattice line was 240 nm. The calculation result of the transmittance of the p-mode light is shown as Comparative Example 2 in FIG. 6 (line connected with a circle). Although it has a peak at around 460 nm, it has been found that the light transmission curve is wide and the function as a blue filter is not sufficient.

Claims (7)

  A wire grid polarizer in which a large number of metal lines serving as grid lines on a substrate are arranged in parallel with a period shorter than the wavelength of light, and cut along a plane perpendicular to the longitudinal direction of the grid lines The cross-sectional shape is a polygon, the polygon has six or more vertices, and the inner angle formed by two adjacent sides is 90 ° or 270 °, and at least of the inner angles formed by the two adjacent sides Wire grid polarizer, one is 270 °.   The wire grid polarizer according to claim 1, wherein the dimension of the cross-sectional shape and the period of the lattice lines are adjusted so as to simultaneously generate a polarization effect and a color filter effect for a specific wavelength of visible light.   The wire grid polarizer according to claim 1 or 2, wherein a period of the lattice line is more than 0 nm and not more than 700 nm.   The wire grid polarizer according to any one of claims 1 to 3, wherein a height of the lattice line (a length in a direction perpendicular to the interface between the lattice line and the substrate) is 10 times or less of a period of the lattice line.   The wire grid polarizer according to any one of claims 1 to 4, wherein a fill factor exceeds 0 and is 0.99 or less.   The wire grid polarizer according to any one of claims 1 to 5, wherein lattice lines on the substrate are covered with a resin.   An element comprising the wire grid polarizer according to claim 1, capable of polarizing incident light and acting as a narrow band optical filter.