JP2019120925A - Polarizing plate and method for manufacturing the same, and optical instrument - Google Patents

Abstract

To provide a polarizing plate excellent in control of reflectance characteristics and a method for manufacturing the same, and an optical instrument having the polarizing plate.SOLUTION: A polarizing plate 10 having a wire grid structure comprises a transparent substrate 1, and grid-like projections 6 arranged with a pitch smaller than a wavelength of light in a use band on the transparent substrate and extending in a predetermined direction. Each of the grid-like projections 6 has, in order from the transparent substrate 1 side, a reflection layer 2, a first dielectric layer 3 and an absorption layer 4. When viewed from the predetermined direction, the reflection layer and the first dielectric layer have substantially the same width. The minimum width of the absorption layer is smaller than the minimum width of the first dielectric layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarizing plate, a method of manufacturing the same, and an optical apparatus.

  Conventionally, a metal grating having a pitch smaller than the wavelength of light in the working band is formed on a substrate as a polarizing element, and a dielectric layer and an inorganic fine particle layer are formed on the metal grating to interfere with light reflected from the metal grating. An absorption type wire grid type polarization element has been proposed which cancels out the effect and transmits the other polarization component. With respect to such a polarizing element, in recent years, along with the increase in luminance of liquid crystal projectors, control requirements for reflectance characteristics under strong light environment as well as high transmittance characteristics are increasing.

  Here, the reflectance characteristic is determined by the interference between layers constituting the lattice structure and the absorption in the layer. And the method of controlling a reflectance is proposed by using the material according to a request | requirement for a dielectric layer etc. (refer patent document 1). However, in Patent Document 1, since each layer is designed as a rectangular shape, it is difficult to form a complete rectangle at the nano level, so material design in consideration of the shape becomes a very difficult situation.

  In addition, a method is proposed to control the reflectance characteristics of the obtained polarizing element by forming a fine pattern on the resin base material and controlling the reflectance and wavelength of the base material before forming the metal layer. (See Patent Document 2). However, since the base material used in Patent Document 2 is made of resin, it is inferior in heat resistance and light resistance as compared to a wire grid polarization element made of an inorganic material, and it is used for long-term use under strong light environment I am anxious.

JP-A-2010-530994 Unexamined-Japanese-Patent No. 2015-212741

  The present invention has been made in view of the above background art, and an object thereof is to provide a polarizing plate excellent in control of reflectance characteristics, a method of manufacturing the same, and an optical apparatus including the polarizing plate.

  The inventor of the present invention is a polarizing plate having a wire grid structure including: a transparent substrate; and a grid-like convex portion arranged on the transparent substrate at a pitch shorter than the wavelength of light in the working band and extending in a predetermined direction. The reflection layer, the first dielectric layer, and the absorption layer are provided on the lattice-like convex portion sequentially from the transparent substrate side, and the reflection layer when viewed from the predetermined direction, the first dielectric If the relationship between the minimum width of the layer and the absorption layer is specified, the effect of shifting the wavelength range of the light absorption action can be expressed, and as a result, it is found that a polarizing plate excellent in control of reflectance characteristics can be obtained. We came to complete the invention.

That is, the present invention is a polarizing plate having a wire grid structure, and is arranged on the transparent substrate (for example, the transparent substrate 1 described later) and the transparent substrate at a pitch shorter than the wavelength of light in the use band And a grid-like convex part (for example, grid-like convex part 6 described later) extending to the bottom, and the grid-like convex part and the reflective layer (for example, reflective layer 2 , A first dielectric layer (for example, a first dielectric layer 3 described later), an absorption layer (for example, an absorption layer 4 described below), and a second dielectric layer (for example, a first dielectric described later) Body layer 5), and when viewed from the predetermined direction, the reflective layer and the first dielectric layer have substantially the same width, and the minimum width of the absorption layer is Smaller than the minimum width of the reflective layer and the first dielectric layer, and the maximum width of the absorption layer is smaller at the absorption layer And also a polarizing plate is the width of one of the outermost surface.

  The outermost surface may be the outermost surface on the first dielectric layer side.

  The outermost surface may be the outermost surface on the second dielectric layer side.

  The reflective layer may be substantially rectangular when viewed from the predetermined direction.

  The first dielectric layer may be substantially rectangular when viewed from the predetermined direction.

  The transparent substrate may be transparent to the wavelength of light in the working band, and may be made of glass, quartz or sapphire.

  The reflective layer may be made of aluminum or an aluminum alloy.

  The first dielectric layer may be made of Si oxide.

  The second dielectric layer may be made of Si oxide.

  The absorption layer may contain Fe or Ta and may contain Si.

  The surface of the polarizing plate on which light is incident may be covered by a protective film made of a dielectric.

  The surface of the polarizing plate on which light is incident may be covered with an organic water repellent film.

Yet another aspect of the present invention is a method of manufacturing a polarizing plate having a wire grid structure, comprising a reflective layer forming step of forming a reflective layer on one side of a transparent substrate, and a second surface of the reflective layer opposite to the transparent substrate. A first dielectric layer forming step of forming the first dielectric layer; an absorption layer forming step of forming an absorption layer on the surface of the first dielectric layer opposite to the reflection layer; The second dielectric layer forming step of forming a second dielectric layer on the surface opposite to the first dielectric layer, and selectively etching the formed laminated body, the wavelength of the light in the working band is exceeded. And an etching step of forming grid-like convex portions arranged in a short pitch on the transparent substrate and extending in a predetermined direction, wherein in the etching step, isotropic etching and anisotropic etching are combined, And the reflective layer when viewed from the predetermined direction The first dielectric layer has substantially the same width, and the minimum width of the absorption layer is smaller than the minimum widths of the reflective layer and the first dielectric layer, and the maximum width of the absorption layer is It is a manufacturing method of the polarizing plate made into the width | variety of at least one outermost surface in the said absorption layer.

  The outermost surface may be the outermost surface on the first dielectric layer side.

  The outermost surface may be the outermost surface on the second dielectric layer side.

  Another present invention is an optical device provided with the above-mentioned polarizing plate.

  ADVANTAGE OF THE INVENTION According to this invention, the polarizing plate excellent in control of a reflectance characteristic, its manufacturing method, and an optical instrument provided with the polarizing plate can be provided.

It is a cross section showing the polarizing plate concerning one embodiment of the present invention. It is a cross section showing the polarizing plate concerning one embodiment of conventional structure. Graph showing the results of simulation verification of the relationship between the wavelength and the absorption axis reflectance for the polarizing plate shown in FIG. 1 and the polarizing plate shown in FIG. 2 optimized for the green band (wavelength λ = 520 to 590 nm) It is. Graph showing the results of simulation for verifying the relationship between the wavelength and the absorption axis reflectance for the polarizing plate shown in FIG. 1 and the polarizing plate shown in FIG. 2 optimized for the blue band (wavelength λ = 430 to 510 nm) It is. Graph showing the result of simulation verification of the relationship between the wavelength and the absorption axis reflectance for the polarizing plate shown in FIG. 1 and the polarizing plate shown in FIG. 2 optimized for the red band (wavelength λ = 600 to 680 nm) It is. For the polarizing plate shown in FIG. 1 and the polarizing plate shown in FIG. 2 optimized for the green band (wavelength λ = 520 to 590 nm), the volume and absorption axis of the absorbing layer in the green band (wavelength λ = 520 to 590 nm) It is a graph which shows the result of having verified the relation with reflectance by simulation. For the polarizing plate shown in FIG. 1 and the polarizing plate shown in FIG. 2 optimized for the blue band (wavelength λ = 430-510 nm), the volume and absorption axis of the absorbing layer in the blue band (wavelength λ = 430-510 nm) It is a graph which shows the result of having verified the relation with reflectance by simulation. For the polarizing plate shown in FIG. 1 and the polarizing plate shown in FIG. 2 optimized for the red band (wavelength λ = 600 to 680 nm), the volume and absorption axis of the absorbing layer in the red band (wavelength λ = 600 to 680 nm) It is a graph which shows the result of having verified the relation with reflectance by simulation. It is a cross section showing the polarizing plate concerning one embodiment of the present invention. It is a cross section showing the polarizing plate concerning one embodiment of conventional structure. A graph showing the result of simulation verification of the relationship between the wavelength and the absorption axis reflectance for the polarizing plate shown in FIG. 9 and the polarizing plate shown in FIG. 10 optimized for the green band (wavelength λ = 520 to 590 nm) It is. A graph showing the result of simulation verification of the relationship between the wavelength and the absorption axis reflectance for the polarizing plate shown in FIG. 9 and the polarizing plate shown in FIG. 10 optimized for the blue band (wavelength λ = 430 to 510 nm) It is. A graph showing the result of simulation verification of the relationship between the wavelength and the absorption axis reflectance for the polarizing plate shown in FIG. 9 and the polarizing plate shown in FIG. 10 optimized for the red band (wavelength λ = 600 to 680 nm) It is. About the polarizing plate shown in FIG. 9 and the polarizing plate shown in FIG. 10 optimized for the green band (wavelength λ = 520 to 590 nm), the volume and absorption axis of the absorbing layer in the green band (wavelength λ = 520 to 590 nm) It is a graph which shows the result of having verified the relation with reflectance by simulation. About the polarizing plate shown in FIG. 9 and the polarizing plate shown in FIG. 10 optimized for the blue band (wavelength λ = 430-510 nm), the volume and absorption axis of the absorbing layer in the blue band (wavelength λ = 430-510 nm) It is a graph which shows the result of having verified the relation with reflectance by simulation. For the polarizing plate shown in FIG. 9 and the polarizing plate shown in FIG. 10 optimized for the red band (wavelength λ = 600 to 680 nm), the volume and absorption axis of the absorbing layer in the red band (wavelength λ = 600 to 680 nm) It is a graph which shows the result of having verified the relation with reflectance by simulation. It is a cross section showing the polarizing plate concerning one embodiment of the present invention. It is a cross section showing the polarizing plate concerning one embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Polarizer]
The polarizing plate of the present invention is a polarizing plate having a wire grid structure, and is a transparent substrate and a grating arranged on the transparent substrate at a pitch (period) shorter than the wavelength of light in the working band and extending in a predetermined direction And a convex portion. Further, the lattice-like convex portion has at least a reflection layer, a first dielectric layer, and an absorption layer in order from the transparent substrate side. In the polarizing plate of the present invention, layers other than the transparent substrate, the reflective layer, the first dielectric layer, and the absorbing layer may be present as long as the effects of the present invention are exhibited.

  FIG. 1 is a schematic cross-sectional view showing a polarizing plate 10 according to an embodiment of the present invention. As shown in FIG. 1, the polarizing plate 10 has a transparent substrate 1 transparent to light in the use band and a lattice-like convex arranged at a pitch shorter than the wavelength of the light in the use band on one surface of the transparent substrate 1. And 6. The lattice-like convex portion 6 has a reflective layer 2, a first dielectric layer 3, and an absorption layer 4 in order from the transparent substrate 1 side. That is, in the polarizing plate 10, the grid-like convex portion 6 formed by laminating the reflective layer 2, the first dielectric layer 3, and the absorption layer 4 in this order from the transparent substrate 1 side is formed on the transparent substrate 1. It has a wire grid structure arranged in a one-dimensional grid.

  Here, as shown in FIG. 1, the extending direction (predetermined direction) of the grid-like convex portion 6 is referred to as a Y-axis direction. Further, a direction orthogonal to the Y-axis direction and in which the grid-like convex portions 6 are arranged along the main surface of the transparent substrate 1 is referred to as an X-axis direction. In this case, light incident on the polarizing plate 10 is preferably incident from the direction orthogonal to the X-axis direction and the Y-axis direction on the side of the transparent substrate 1 on which the lattice-shaped convex portion 6 is formed.

  A polarizing plate having a wire grid structure utilizes polarized light having an electric field component parallel to the Y-axis direction by utilizing the four effects of transmission, reflection, interference, and selective light absorption of polarized light by optical anisotropy. TE waves (S waves) are attenuated, and polarized waves (TM waves (P waves)) having electric field components parallel to the X-axis direction are transmitted. Therefore, in FIG. 1, the Y-axis direction is the direction of the absorption axis of the polarizing plate, and the X-axis direction is the direction of the transmission axis of the polarizing plate.

  The light incident from the side of the polarizing plate 10 shown in FIG. 1 on which the lattice convex portion 6 is formed is partially absorbed and attenuated when passing through the absorbing layer 4 and the first dielectric layer 3. Among the light transmitted through the absorbing layer 4 and the first dielectric layer 3, the polarized wave (TM wave (P wave)) is transmitted through the reflecting layer 2 with high transmittance. On the other hand, of the light transmitted through the absorption layer 4 and the first dielectric layer 3, a polarized wave (TE wave (S wave)) is reflected by the reflective layer 2. The TE wave reflected by the reflective layer 2 is partially absorbed when passing through the absorbing layer 4 and the first dielectric layer 3, and partially reflected back to the reflective layer 2. Further, the TE wave reflected by the reflective layer 2 interferes and attenuates when passing through the absorbing layer 4 and the first dielectric layer 3. As described above, by selectively attenuating TE waves, the polarizing plate 10 can obtain desired polarization characteristics.

  The grid-like convex portions in the polarizing plate of the present invention, when viewed from the extending direction (predetermined direction) of each one-dimensional grating as shown in FIG. 1, that is, in the cross-sectional view orthogonal to the predetermined direction , And the first dielectric layer 3 and the absorption layer 4.

  Here, dimensions in the present specification will be described with reference to FIG. The height means the dimension in the direction perpendicular to the main surface of the transparent substrate 1 in FIG. The width W means a dimension in the X-axis direction orthogonal to the height direction when viewed from the Y-axis direction along the extending direction of the grid-like convex portion 6. Further, when the polarizing plate 10 is viewed from the Y-axis direction along the extending direction of the grid-like convex portions 6, the repetition interval in the X-axis direction of the grid-like convex portions 6 is referred to as a pitch P.

  In the polarizing plate of the present invention, the pitch P of the grid-like convex portions is not particularly limited as long as it is shorter than the wavelength of the light of the working band. The pitch P of the grid-like convex portions is preferably, for example, 100 nm to 200 nm from the viewpoint of ease of preparation and stability. The pitch P of the grid-like convex portions can be measured by observing with a scanning electron microscope or a transmission electron microscope. For example, the pitch P can be measured at any four places using a scanning electron microscope or a transmission electron microscope, and the arithmetic mean value thereof can be used as the pitch P of the grid-like convex portions. Hereinafter, this measurement method is referred to as electron microscopy.

  In the polarizing plate of the present invention, the reflective layer and the first dielectric layer have substantially the same width when viewed from the extending direction of the grid-like convex portion (predetermined direction: Y-axis direction), And, the minimum width of the absorption layer is characterized by being smaller than the minimum widths of the reflective layer and the first dielectric layer. Thereby, a polarizing plate excellent in control of reflectance characteristics can be realized.

(Transparent substrate)
The transparent substrate (the transparent substrate 1 in FIG. 1) is not particularly limited as long as it is a substrate showing translucency to light in the use band, and can be appropriately selected according to the purpose. The term "shows translucency to light in the use band" does not mean that the transmittance of light in the use band is 100%, and means that the light transmissivity capable of maintaining the function as a polarizing plate Just show it. Examples of light in the use band include visible light having a wavelength of about 380 nm to 810 nm.

  The main surface shape of the transparent substrate is not particularly limited, and a shape (for example, a rectangular shape) according to the purpose is appropriately selected. The average thickness of the transparent substrate is preferably 0.3 mm to 1 mm, for example.

  As a constituent material of the transparent substrate, a material having a refractive index of 1.1 to 2.2 is preferable, and glass, quartz, sapphire and the like can be mentioned. From the viewpoint of cost and light transmittance, it is preferable to use glass, particularly quartz glass (refractive index 1.46) or soda lime glass (refractive index 1.51). The component composition of the glass material is not particularly limited. For example, inexpensive glass materials such as silicate glass widely distributed as optical glass can be used.

  Further, from the viewpoint of thermal conductivity, it is preferable to use quartz or sapphire having high thermal conductivity. As a result, high light resistance to strong light is obtained, and it is preferably used as a polarizing plate for an optical engine of a projector having a large amount of heat generation.

  In the case of using a transparent substrate made of an optically active crystal such as quartz, it is preferable to dispose the grid-like convex portion 6 in the parallel direction or the vertical direction with respect to the optical axis of the crystal. Thereby, excellent optical characteristics can be obtained. Here, the optical axis is a direction axis in which the difference in refractive index between O (ordinary ray) and E (abnormal ray) of light traveling in the direction is minimized.

(Reflective layer)
The reflective layer (the reflective layer 2 in FIG. 1) is formed on one side surface of the transparent substrate, and a metal film extending in a band shape is arranged in the Y axis direction which is an absorption axis. In the present invention, another layer may be present between the transparent substrate and the reflective layer.

  The reflective layer 2 of the polarizing plate 10 according to the embodiment of the present invention shown in FIG. 1 extends perpendicularly to the surface direction of the transparent substrate 1 and extends in a direction in which the grid convexes extend (predetermined direction: When viewed from the Y-axis direction, that is, in a cross-sectional view orthogonal to the predetermined direction, it has a rectangular shape. The reflective layer has a function as a wire grid type polarizer, and attenuates a polarized wave (TE wave (S wave)) having an electric field component in a direction parallel to the longitudinal direction of the reflective layer, in the longitudinal direction of the reflective layer. A polarized wave (TM wave (P wave)) having an electric field component in the orthogonal direction is transmitted.

  The constituent material of the reflective layer is not particularly limited as long as it is a material having reflectivity to light in the use band, and, for example, Al, Ag, Cu, Mo, Cr, Ti, Ni, W, Fe, Si, Examples include elemental elements such as Ge and Te, and alloys containing one or more of these elements. Among them, the reflective layer is preferably made of aluminum or an aluminum alloy. In addition to these metal materials, for example, an inorganic film or resin film other than a metal having a high surface reflectance due to coloring or the like may be used.

  The film thickness of the reflective layer is not particularly limited, and is preferably, for example, 100 nm to 300 nm. The film thickness of the reflective layer can be measured, for example, by the above-mentioned electron microscopy.

  In the polarizing plate of the present invention, the width of the reflective layer is substantially the same as that of the first dielectric layer described later, and the minimum width thereof needs to be larger than the minimum width of the absorption layer described later. In the present invention, this makes it possible to realize a polarizing plate excellent in control of reflectance characteristics. The width of the reflective layer is, for example, preferably in the range of 35 nm to 45 nm, although it depends on the relationship with the pitch P of the grid-like convex portions. In addition, these widths can be measured, for example by the above-mentioned electron microscopy.

  As a method of making the minimum width of the reflection layer larger than the minimum width of the absorption layer, for example, there is a method of changing the balance by using isotropic etching and anisotropic etching in combination.

(First dielectric layer)
The first dielectric layer (the first dielectric layer 3 in FIG. 1) is formed on the reflective layer, in which dielectric films extending in a band shape in the Y axis direction, which is the absorption axis, are arranged. In the present invention, another layer may be present between the reflective layer and the first dielectric layer.

  The first dielectric layer 3 of the polarizing plate 10 according to the embodiment of the present invention shown in FIG. 1 is stacked on the reflective layer perpendicularly to the surface direction of the transparent substrate 1 and has a grid-like convex shape. When viewed from the extending direction of the part (predetermined direction: Y-axis direction), that is, in a cross-sectional view orthogonal to the predetermined direction, it has a rectangular shape.

  The film thickness of the first dielectric layer is formed in a range in which the phase of the polarized light transmitted through the absorbing layer and reflected by the reflective layer is shifted by a half wavelength with respect to the polarized light reflected by the absorbing layer. Specifically, the film thickness of the first dielectric layer is appropriately set in the range of 1 to 500 nm in which the interference effect can be enhanced by adjusting the phase of polarization. The film thickness of this first dielectric layer can be measured, for example, by the above-mentioned electron microscopy.

Examples of the material constituting the first dielectric layer include Si oxides such as SiO ₂ , metal oxides such as Al ₂ O ₃ , beryllium oxide and bismuth oxide, MgF ₂ , cryolite, germanium, titanium dioxide, Common materials such as silicon, magnesium fluoride, boron nitride, boron oxide, tantalum oxide, carbon, or a combination thereof can be mentioned. Among them, the first dielectric layer 3 is preferably made of Si oxide.

  The refractive index of the first dielectric layer is preferably greater than 1.0 and 2.5 or less. Since the optical properties of the reflective layer are also influenced by the refractive index of the surrounding, the polarization properties can be controlled by selecting the material of the first dielectric layer.

  In addition, by appropriately adjusting the film thickness and the refractive index of the first dielectric layer, it is possible to reflect a portion of the TE wave reflected by the reflective layer back to the reflective layer when transmitting through the absorbing layer. The light passing through the absorption layer can be attenuated by interference. By selectively attenuating TE waves in this manner, desired polarization characteristics can be obtained.

  In the polarizing plate of the present invention, the width of the first dielectric layer needs to be substantially the same as that of the above-described reflective layer, and the minimum width thereof needs to be larger than the minimum width of the absorption layer described later. In the present invention, this makes it possible to realize a polarizing plate excellent in control of reflectance characteristics. The width of the first dielectric layer is, for example, preferably in the range of 35 nm to 45 nm, although it depends on the relationship with the pitch P of the grid-like convex portions. In addition, these widths can be measured, for example by the above-mentioned electron microscopy.

(Absorbent layer)
The absorption layer (the absorption layer 4 in FIG. 1) is formed on the first dielectric layer, and extends in a band shape in the Y axis direction which is the absorption axis and is arranged. The present invention is characterized in that the minimum width of the absorption layer is smaller than the above-mentioned minimum widths of the reflective layer and the first dielectric layer when viewed from the Y axis direction (predetermined direction) which is the absorption axis. In the present invention, by setting the shape of the absorption layer as described above, the effect of shifting the wavelength range of the light absorption action can be expressed, and as a result, a polarizing plate excellent in control of reflectance characteristics can be realized. it can.

  The absorption layer 4 of the polarizing plate 10 according to the embodiment of the present invention shown in FIG. 1 is orthogonal to the predetermined direction when viewed from the extending direction (the predetermined direction: the Y-axis direction) of the grid-like convex portion. It has a substantially isosceles trapezoidal shape in a sectional view, and has a tapered shape whose side surface is inclined in a direction in which the width becomes narrower toward the tip end side (the side opposite to the transparent substrate 1).

  In the present embodiment, the maximum width of the absorption layer 4 is the width of the outermost surface of the absorption layer 4 on the transparent substrate 1 side, which is the direction in which the grid-like convex portions 6 extend (predetermined direction: Y-axis direction) When viewed from a cross section perpendicular to the predetermined direction, that is, substantially the same as the maximum widths of the reflection layer 2 and the first dielectric layer 3 which are rectangular.

  Further, the minimum width of the absorption layer 4 is the width of the outermost surface of the absorption layer 4 on the opposite side to the transparent substrate 1, and this is from the direction in which the grid convex portion 6 extends (predetermined direction: Y-axis direction) When viewed, that is, smaller than the minimum width of the reflective layer 2 and the first dielectric layer 3 which is rectangular in a cross-sectional view orthogonal to the predetermined direction.

As a constituent material of the absorption layer, one or more kinds of substances having a light absorbing action, such as metal materials and semiconductor materials, having a non-zero extinction constant of optical constants, may be mentioned. Ru. Examples of the metal material include elemental elements such as Ta, Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, Sn, etc., or an alloy containing one or more of these elements. As the semiconductor material, Si, Ge, Te, ZnO, suicide material _{(β-FeSi 2, MgSi 2} , NiSi 2, BaSi 2, CrSi 2, CoSi 2, TaSi , etc.). By using these materials, the polarizing plate 10 can obtain a high extinction ratio to the applied visible light region. Among them, the absorption layer preferably contains Fe or Ta and is configured to contain Si.

  When a semiconductor material is used as the absorption layer, the band gap energy of the semiconductor needs to be equal to or less than the use band because the band gap energy of the semiconductor is involved in the absorption function. For example, in the case of use in visible light, it is necessary to use a material having an absorption at a wavelength of 400 nm or more, that is, a band gap of 3.1 ev or less.

  The film thickness of the absorption layer is not particularly limited, and for example, 10 nm to 100 nm is preferable. The film thickness of the absorption layer 4 can be measured, for example, by the above-mentioned electron microscopy.

  Note that the absorption layer can be formed as a high density film by a vapor deposition method or a sputtering method. Moreover, the absorption layer may be comprised from two or more layers from which a constituent material differs.

  The maximum width of the absorption layer is preferably in the range of 35 nm to 45 nm, for example, although it depends on the relationship with the pitch P of the grid-like convex portions. In addition, the maximum width of the absorption layer may be, for example, substantially the same as the width of the first dielectric layer located under the absorption layer. In addition, these widths can be measured, for example by the above-mentioned electron microscopy.

  As described above, in the present invention, the minimum width of the absorption layer needs to be smaller than the above-mentioned minimum width of the reflective layer and the first dielectric layer when viewed from the Y axis direction (predetermined direction) which is the absorption axis. is there. In the present invention, this makes it possible to realize a polarizing plate excellent in control of reflectance characteristics. The minimum width of the absorbing layer is, for example, preferably less than 100% and preferably in the range of 60 to 90% with respect to the maximum width of the absorbing layer. In addition, these widths can be measured, for example by the above-mentioned electron microscopy.

(Diffusion barrier layer)
The polarizing plate of the present invention may have a diffusion barrier layer between the first dielectric layer and the absorption layer. That is, in the polarizing plate shown in FIG. 1, the lattice-like convex portion 6 sequentially includes the reflective layer 2, the first dielectric layer 3, the diffusion barrier layer, and the absorbing layer 4 from the transparent substrate 1 side. Have. By having the diffusion barrier layer, diffusion of light in the absorption layer is prevented. This diffusion barrier layer can be made of a metal film such as Ta, W, Nb, Ti or the like.

(Protective film)
Further, in the polarizing plate of the present invention, the surface on the light incident side may be covered with a protective film made of a dielectric, as long as the change in optical characteristics is not affected. The protective film is made of a dielectric film, and can be formed, for example, by using chemical vapor deposition (CVD) or atomic layer deposition (ALD) on the surface of the polarizing plate (the surface on which the wire grid is formed). . Thereby, it is possible to suppress the oxidation reaction more than necessary to the metal film.

(Organic water repellent film)
Furthermore, in the polarizing plate of the present invention, the surface on the light incident side may be covered with an organic water repellent film. The organic water repellent film is made of, for example, a fluorine-based silane compound such as perfluorodecyltriethoxysilane (FDTS), and can be formed by using, for example, the above-mentioned CVD or ALD. Thereby, the reliability such as the moisture resistance of the polarizing plate can be improved.

  The present invention is not limited to the above-described embodiment shown in FIG. 1, and modifications and improvements as long as the object of the present invention can be achieved are included in the present invention.

  FIG. 9 is a schematic cross-sectional view showing a polarizing plate 30 according to another embodiment of the present invention. The polarizing plate 30 shown in FIG. 9 is the same as the polarizing plate 30 shown in FIG. 1 except that the second dielectric layer 5 is formed on the absorption layer 4 of the polarizing plate 10 shown in FIG. The same configuration as the polarizing plate 10 shown in FIG.

(Second dielectric layer)
The second dielectric layer 5 of the polarizing plate 30 shown in FIG. 9 is stacked on the absorption layer in a direction perpendicular to the surface direction of the transparent substrate 1, and the extending direction of the grid-like convex portion Direction: when viewed from the Y-axis direction, that is, in a cross-sectional view orthogonal to the predetermined direction, has a rectangular shape. Further, in the polarizing plate 30 shown in FIG. 9, the width of the second dielectric layer 5 is the same as the width of the first dielectric layer 3.

  The film thickness, material, refractive index, shape, and the like of the second dielectric layer are the same as those of the first dielectric layer described above.

  In the embodiment shown in FIG. 9, the maximum width of the absorption layer 4 is the width of the outermost surface of the absorption layer 4 on the transparent substrate 1 side, which corresponds to the extending direction of the grid-like convex portion 6 (predetermined direction: When viewed from the Y-axis direction, that is, substantially the same as the maximum widths of the reflective layer 2 and the first dielectric layer 3 which are rectangular in a cross-sectional view orthogonal to the predetermined direction.

  Further, the minimum width of the absorption layer 4 is the width of the outermost surface of the absorption layer 4 on the opposite side to the transparent substrate 1, and this is from the direction in which the grid convex portion 6 extends (predetermined direction: Y-axis direction) When viewed, that is, smaller than the minimum width of the reflective layer 2 and the first dielectric layer 3 which is rectangular in a cross-sectional view orthogonal to the predetermined direction.

  FIG. 17 is a schematic cross-sectional view showing a polarizing plate 50 according to another embodiment of the present invention. The polarizing plate 50 shown in FIG. 17 is obtained by forming the second dielectric layer 5 on the absorption layer 4 in the grid-like convex portion 6, and the configuration of FIG. 9 is the same except that the shape of the absorption layer 4 is different. It has the same configuration as the polarizing plate 30 shown.

  The absorption layer 4 of the polarizing plate 50 shown in FIG. 17 is substantially isosceles when viewed from the extending direction of the grid-like convex portion (predetermined direction: Y-axis direction), that is, in a cross-sectional view orthogonal to the predetermined direction. It has a tapered shape in which the side surface is inclined in a direction in which the width increases toward the tip end side (the opposite side of the transparent substrate 1).

  In the embodiment shown in FIG. 17, the maximum width of the absorption layer 4 is the width of the outermost surface of the absorption layer 4 opposite to the transparent substrate 1, which corresponds to the extending direction of the grid-like convex portion 6 ( When viewed from the predetermined direction: Y-axis direction, that is, substantially the same as the maximum widths of the reflective layer 2 and the first dielectric layer 3 which are rectangular in a cross-sectional view orthogonal to the predetermined direction.

  Further, the minimum width of the absorption layer 4 is the width of the outermost surface of the absorption layer 4 on the transparent substrate 1 side, which is as viewed from the direction in which the grid convex portion 6 extends (predetermined direction: Y-axis direction) That is, it is smaller than the minimum width of the reflective layer 2 and the first dielectric layer 3 which is rectangular in cross section orthogonal to the predetermined direction.

  FIG. 18 is a schematic cross-sectional view showing a polarizing plate 60 according to another embodiment of the present invention. The polarizing plate 60 shown in FIG. 18 is obtained by forming the second dielectric layer 5 on the absorption layer 4 in the grid-like convex portion 6, and the configuration of FIG. 9 is the same except that the shape of the absorption layer 4 is different. It has the same configuration as the polarizing plate 30 shown.

  The absorption layer 4 of the polarizing plate 60 shown in FIG. 18 has a thickness direction as viewed from the extending direction of the grid-like convex portion (predetermined direction: Y-axis direction), that is, in a cross-sectional view orthogonal to the predetermined direction. The shape has a minimum width substantially at the center and a maximum width on the side in contact with the first dielectric layer and the second dielectric layer.

  In the embodiment shown in FIG. 18, the maximum width of the absorption layer 4 is the length of the side in contact with the first dielectric layer and the second dielectric layer. When viewed from the direction (predetermined direction: Y-axis direction), that is, substantially the same as the maximum widths of the reflective layer 2 and the first dielectric layer 3 which are rectangular in a cross-sectional view orthogonal to the predetermined direction.

  Further, the minimum width of the absorption layer 4 is a width substantially at the center of the absorption layer 4 in the film thickness direction, which is as viewed from the direction in which the grid convex portion 6 extends (predetermined direction: Y-axis direction) That is, it is smaller than the minimum width of the reflective layer 2 and the first dielectric layer 3 which is rectangular in a cross sectional view orthogonal to the predetermined direction.

[Method of manufacturing polarizing plate]
The manufacturing method of the polarizing plate of the present invention includes a reflection layer forming step, a first dielectric layer forming step, an absorption layer forming step, and an etching step.

  In the reflective layer forming step, the reflective layer is formed on one side of the transparent substrate. In the first dielectric layer forming step, the first dielectric layer is formed on the reflective layer formed in the reflective layer forming step. In the absorbing layer forming step, an absorbing layer is formed on the first dielectric layer formed in the first dielectric layer forming step. In each of these layer forming steps, each layer can be formed by, for example, a sputtering method or a vapor deposition method.

  In the etching step, by selectively etching the laminate formed through the above-described respective layer forming steps, grid-like convex portions arranged on the transparent substrate at a pitch shorter than the wavelength of the light of the used band are formed. . Specifically, a one-dimensional grid-like mask pattern is formed by, for example, photolithography or nanoimprinting. Then, the laminated body is selectively etched to form lattice-like convex portions arranged on the transparent substrate at a pitch shorter than the wavelength of the light of the working band. As an etching method, for example, a dry etching method using an etching gas corresponding to an etching target can be mentioned.

  In the present invention, in particular, by changing the balance by combining isotropic etching and anisotropic etching, the reflection layer and the first dielectric layer have substantially the same width, and the minimum width of the absorption layer is the reflection. Smaller than the minimum width of the layer and the first dielectric layer.

  In addition, the manufacturing method of the polarizing plate of this invention may have the process of coat | covering the surface with the protective film which consists of dielectrics. Moreover, the manufacturing method of the polarizing plate of this invention may have the process of coat | covering the surface with an organic type water repellent film.

[Optical equipment]
An optical apparatus according to the present invention includes the polarizing plate according to the present invention described above. The polarizing plate according to the present invention can be used for various applications. As an applicable optical apparatus, a liquid crystal projector, a head-up display, a digital camera etc. are mentioned, for example. In particular, since the polarizing plate according to the present invention is an inorganic polarizing plate having excellent heat resistance, it is suitably used for applications such as liquid crystal projectors and head-up displays which require heat resistance compared to organic polarizing plates made of organic materials. be able to.

  When the optical device according to the present invention includes a plurality of polarizing plates, at least one of the plurality of polarizing plates may be the polarizing plate according to the present invention. For example, when the optical device according to the present embodiment is a liquid crystal projector, at least one of the polarizing plates disposed on the incident side and the output side of the liquid crystal panel may be the polarizing plate according to the present invention.

  According to the polarizing plate of the present invention described above, the method for manufacturing the same, and the optical device, the following effects can be obtained.

  The polarizing plate according to the present invention has a wire grid structure including a transparent substrate, and grid-like convex portions arranged on the transparent substrate at a pitch shorter than the wavelength of light in the working band and extending in a predetermined direction. A reflective layer, a first dielectric layer, and an absorption layer are provided on the lattice-like convex portion sequentially from the transparent substrate side, and the reflective layer when viewed from the predetermined direction, the first dielectric, By specifying the relationship between the minimum width of the body layer and the absorption layer, the effect of shifting the wavelength range of the light absorption action can be exhibited, and as a result, the control of the reflectance characteristic becomes excellent. Therefore, according to the present invention, it is possible to provide a polarizing plate excellent in control of reflectance characteristics, a method of manufacturing the same, and an optical apparatus including the polarizing plate 1.

  Next, examples of the present invention will be described, but the present invention is not limited to these examples.

Example 1 and Comparative Example 1
[Creating a polarizing plate]
In Example 1, it is the polarizing plate 10 which has a structure shown in FIG. 1, Comprising: A green zone (wavelength λ = 520-590 nm), a blue zone (wavelength λ = 430-510 nm), and a red zone (wavelength λ = 600 ̃ What was optimized for each of 680 nm) was created, and each was subjected to simulation.
In addition, as Comparative Example 1, polarizing plates 20 different from the polarizing plate 10 of Example 1 only in the structure of the absorption layer 3 were respectively prepared and provided for simulation. The polarizing plate 20 serving as Comparative Example 1 has a structure shown in FIG. 2, and when viewed from the direction in which the grid convex portion 6 extends (predetermined direction: Y-axis direction), that is, a cross sectional view orthogonal to the predetermined direction Thus, the shape of the absorption layer 4 is rectangular, and has substantially the same width as the reflective layer 2 and the first dielectric layer 3.

[Simulation method]
The optical characteristics of the polarizing plate 10 and the polarizing plate 20 were verified by electromagnetic field simulation by RCWA (Rigorous Coupled Wave Analysis) method. For the simulation, a grating simulator Gsolver from Grating Solver Development was used.

[simulation result]
FIG. 3 is a graph showing the results of verification of the relationship between the wavelength and the absorption axis reflectance for the polarizing plate 10 and the polarizing plate 20 optimized for the green band (wavelength λ = 520 to 590 nm).
FIG. 4 is a graph showing the results of verification of the relationship between the wavelength and the absorption axis reflectance for the polarizing plate 10 and the polarizing plate 20 optimized for the blue band (wavelength λ = 430 to 510 nm).
FIG. 5 is a graph showing the results of verification of the relationship between the wavelength and the absorption axis reflectance for the polarizing plate 10 and the polarizing plate 20 optimized for the red band (wavelength λ = 600 to 680 nm).

  In FIGS. 3 to 5, the horizontal axis indicates the wavelength λ (nm), and the vertical axis indicates the absorption axis reflectance (%). Here, the absorption axis reflectance means the reflectance of polarized light (TE wave) in the absorption axis direction (Y-axis direction) incident on the polarizing plate. Further, in FIGS. 3 to 5, the graph indicated by the broken line represents the result of the polarizing plate 10 of the present invention as Example 1, and the graph indicated by the solid line is the polarizing plate 20 as Comparative Example 1. Represents the result of

  As shown in FIGS. 3 to 5, the waveform position of the polarizing plate 10 of Example 1 is shifted as compared to the polarizing plate 20 of Comparative Example 1, and the green band (wavelength λ = 520 to 590 nm), blue band In all of (wavelength λ = 430 to 510 nm) and red band (wavelength λ = 600 to 680 nm), the absorption axis reflectance can be suppressed low.

FIG. 6 shows the volume and absorption axis reflectivity of the absorbing layer in the green band (wavelength λ = 520 to 590 nm) for the polarizing plate 10 and the polarizing plate 20 optimized for the green band (wavelength λ = 520 to 590 nm) It is a graph which shows the result of having verified the relation between and by simulation.
FIG. 7 shows the volume and absorption axis reflectivity of the absorbing layer in the blue band (wavelength λ = 430 to 510 nm) for the polarizing plate 10 and the polarizing plate 20 optimized to the blue band (wavelength λ = 430 to 510 nm) It is a graph which shows the result of having verified the relation between and by simulation.
FIG. 8 shows the volume and absorption axis reflectivity of the absorbing layer in the red band (wavelength λ = 600 to 680 nm) for the polarizing plate 10 and the polarizing plate 20 optimized for the red band (wavelength λ = 600 to 680 nm) It is a graph which shows the result of having verified the relation between and by simulation.

  6-8, the horizontal axis shows the volume of the absorption layer, and the vertical axis shows the absorption axis reflectance (%). Here, the absorption axis reflectance means the reflectance of polarized light (TE wave) in the absorption axis direction (Y-axis direction) incident on the polarizing plate, as described above. In FIGS. 6 to 8, the point where the volume of the absorbing layer is 100% represents the result of the polarizing plate 20 serving as Comparative Example 1, and the range where the volume is smaller than 100% is Example 1 The result of the polarizing plate 10 of the present invention is shown.

  As shown in FIG. 6 to FIG. 8, in the polarizing plate 10 of Example 1, the waveform position shifts with the volume change of the absorption layer, whereby the green band (wavelength λ = 520 to 590 nm), blue band ( It can be seen that control of the reflectance characteristics is possible and can be optimized in all of the wavelength λ = 430 to 510 nm) and the red band (wavelength λ = 600 to 680 nm).

Example 2 and Comparative Example 2
[Creating a polarizing plate]
In the second embodiment, the polarizing plate 30 having the structure shown in FIG. 9 is a green band (wavelength λ = 520 to 590 nm), a blue band (wavelength λ = 430 to 510 nm), and a red band (wavelength λ = 600 to What was optimized for each of 680 nm) was created, and each was subjected to simulation.
In addition, as Comparative Example 2, polarizing plates 40 different from the polarizing plate 30 of Example 2 only in the structure of the absorption layer 3 were respectively prepared and provided for simulation. The polarizing plate 40 serving as Comparative Example 2 has a structure shown in FIG. 10, and when viewed from the direction in which the grid-like convex portion 6 extends (predetermined direction: Y-axis direction), that is, a cross-sectional view orthogonal to the predetermined direction Thus, the shape of the absorption layer 4 is rectangular, and has substantially the same width as the reflective layer 2 and the first dielectric layer 3.

[Simulation method]
The optical properties of the polarizing plate 30 and the polarizing plate 40 were verified by electromagnetic field simulation by RCWA (Rigorous Coupled Wave Analysis) method. For the simulation, a grating simulator Gsolver from Grating Solver Development was used.

[simulation result]
FIG. 11 is a graph showing the results of verification of the relationship between the wavelength and the absorption axis reflectance for the polarizing plate 30 and the polarizing plate 40 optimized for the green band (wavelength λ = 520 to 590 nm).
FIG. 12 is a graph showing the results of verification of the relationship between the wavelength and the absorption axis reflectance for the polarizing plate 30 and the polarizing plate 40 optimized for the blue band (wavelength λ = 430 to 510 nm).
FIG. 13 is a graph showing the results of verification of the relationship between the wavelength and the absorption axis reflectance for the polarizing plate 30 and the polarizing plate 40 optimized for the red band (wavelength λ = 600 to 680 nm).

  In FIGS. 11 to 13, the horizontal axis indicates the wavelength λ (nm), and the vertical axis indicates the absorption axis reflectance (%). Here, the absorption axis reflectance means the reflectance of polarized light (TE wave) in the absorption axis direction (Y-axis direction) incident on the polarizing plate. Moreover, in FIG. 11 to FIG. 13, the graph shown by the broken line represents the result of the polarizing plate 30 of the present invention as Example 2, and the graph shown by the solid line is the polarizing plate 40 as Comparative Example 2. Represents the result of

  As shown in FIGS. 11 to 13, the waveform position of the polarizing plate 30 of Example 2 is shifted as compared to the polarizing plate 40 of Comparative Example 2, and the green band (wavelength λ = 520 to 590 nm), blue band In all of (wavelength λ = 430 to 510 nm) and red band (wavelength λ = 600 to 680 nm), the absorption axis reflectance can be suppressed low.

FIG. 14 shows the volume and absorption axis reflectivity of the absorbing layer in the green band (wavelength λ = 520 to 590 nm) for the polarizing plate 30 and the polarizing plate 40 optimized for the green band (wavelength λ = 520 to 590 nm) It is a graph which shows the result of having verified the relation between and by simulation.
FIG. 15 shows the volume and absorption axis reflectivity of the absorbing layer in the blue band (wavelength λ = 430 to 510 nm) for the polarizing plate 30 and the polarizing plate 40 optimized for the blue band (wavelength λ = 430 to 510 nm) It is a graph which shows the result of having verified the relation between and by simulation.
FIG. 16 shows the volume and absorption axis reflectivity of the absorbing layer in the red band (wavelength λ = 600 to 680 nm) for the polarizing plate 30 and the polarizing plate 40 optimized to the red band (wavelength λ = 600 to 680 nm) It is a graph which shows the result of having verified the relation between and by simulation.

  In FIG. 14 to FIG. 16, the horizontal axis indicates the volume of the absorbing layer, and the vertical axis indicates the absorption axis reflectance (%). Here, the absorption axis reflectance means the reflectance of polarized light (TE wave) in the absorption axis direction (Y-axis direction) incident on the polarizing plate, as described above. In FIG. 14 to FIG. 16, the point where the volume of the absorbing layer is 100% represents the result of the polarizing plate 40 serving as Comparative Example 2, and the range where the volume is smaller than 100% is Example 2. The result of the polarizing plate 30 of the present invention is shown.

  As shown in FIGS. 14 to 16, in the polarizing plate 30 of Example 2, the waveform position is shifted along with the volume change of the absorption layer, whereby a green band (wavelength λ = 520 to 590 nm) and a blue band ( It can be seen that control of the reflectance characteristics is possible and can be optimized in all of the wavelength λ = 430 to 510 nm) and the red band (wavelength λ = 600 to 680 nm).

10, 20, 30, 40, 50, 60 Polarizer 1 Transparent substrate 2 Reflective layer 3 First dielectric layer 4 Absorbing layer 5 Second dielectric layer 6 Lattice-like convex part P Lattice-like convex part pitch W width L light

Claims (16)

  A polarizing plate having a wire grid structure,
  A transparent substrate,
  And a grid-like convex portion arranged on the transparent substrate at a pitch shorter than the wavelength of light in the working band and extending in a predetermined direction,
  The lattice-like convex portion includes, in order from the transparent substrate side, a reflective layer, a first dielectric layer, an absorption layer, and a second dielectric layer.
  When viewed from the predetermined direction, the reflective layer and the first dielectric layer have substantially the same width, and the minimum width of the absorption layer is the reflective layer and the first dielectric. A polarizing plate, which is smaller than the minimum width of the body layer, and the maximum width of the absorption layer is the width of at least one outermost surface of the absorption layer.   The polarizing plate according to claim 1, wherein the outermost surface is the outermost surface on the first dielectric layer side.   The polarizing plate according to claim 1, wherein the outermost surface is the outermost surface on the second dielectric layer side.   The polarizing plate according to any one of claims 1 to 3, wherein the reflective layer is substantially rectangular when viewed from the predetermined direction.   The polarizing plate according to any one of claims 1 to 4, wherein the first dielectric layer is substantially rectangular when viewed from the predetermined direction.   The polarizing plate according to any one of claims 1 to 5, wherein the transparent substrate is transparent to the wavelength of light in a working band, and is made of glass, quartz or sapphire.   The polarizing plate according to any one of claims 1 to 6, wherein the reflective layer is made of aluminum or an aluminum alloy.   The polarizing plate according to any one of claims 1 to 7, wherein the first dielectric layer is made of Si oxide.   The polarizer according to any one of claims 1 to 8, wherein the second dielectric layer is made of Si oxide.   The polarizing plate according to any one of claims 1 to 9, wherein the absorbing layer contains Fe or Ta and contains Si.   The polarizing plate according to any one of claims 1 to 10, wherein a surface of the polarizing plate on which light is incident is covered with a protective film made of a dielectric.   The polarizing plate according to any one of claims 1 to 11, wherein the surface of the polarizing plate on which light is incident is covered with an organic water repellent film.   A method of manufacturing a polarizing plate having a wire grid structure, comprising:
  A reflective layer forming step of forming a reflective layer on one side of the transparent substrate;
  Forming a first dielectric layer on a surface of the reflective layer opposite to the transparent substrate;
  An absorbing layer forming step of forming an absorbing layer on the surface of the first dielectric layer opposite to the reflecting layer;
  Forming a second dielectric layer on a surface of the absorbing layer opposite to the first dielectric layer;
  Etching on the transparent substrate at a pitch shorter than the wavelength of light in the working band by selectively etching the formed laminate, and forming a grid-like convex portion extending in a predetermined direction; Have
  In the etching step, by combining isotropic etching and anisotropic etching, the reflective layer and the first dielectric layer have substantially the same width when viewed from the predetermined direction, and the absorption layer A method of manufacturing a polarizing plate, wherein the minimum width is smaller than the minimum width of the reflective layer and the first dielectric layer, and the maximum width of the absorption layer is the width of at least one outermost surface of the absorption layer. .   The method for manufacturing a polarizing plate according to claim 13, wherein the outermost surface is the outermost surface on the side of the first dielectric layer.   The method for manufacturing a polarizing plate according to claim 13, wherein the outermost surface is the outermost surface on the second dielectric layer side.   An optical apparatus comprising the polarizing plate according to any one of claims 1 to 12.

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