JP7204611B2 - Polarizing plate and manufacturing method thereof - Google Patents

Description

The present invention relates to a polarizing plate and a manufacturing method thereof.

Conventionally, as a polarizing element, a metal grating with a pitch smaller than the wavelength of light in the operating band is formed on a substrate, and a dielectric layer and an inorganic fine particle layer are formed on the metal grating to interfere the light reflected from the metal grating. An absorptive wire-grid polarizing element has been proposed that cancels out the other polarized component and transmits the other polarized component.

With the recent increase in brightness and definition of liquid crystal projectors, there is a growing demand for such polarizing elements to further reduce the reflectance. If the reflectance is high, it causes malfunction of the liquid crystal panel, and stray light causes deterioration of image quality.

Here, the reflectance characteristics of the wire grid type polarizing element are determined by the interference between layers and the absorption within the layers that constitute the grating structure. A method has been proposed for controlling the reflectance by using a material that meets the requirements for the absorption layer or the like in the grating structure (see Patent Document 1).

As described in Patent Literature 1, the grid-like protrusions may be made of various materials. If a polarizing element with a low reflectance can be obtained with inexpensive materials and low manufacturing costs, the recent demands of the industry can be more satisfied.

Japanese Patent Publication No. 2010-530994

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described background art, and an object thereof is to provide a polarizing plate having sufficient reflectance characteristics using inexpensive raw materials and inexpensive manufacturing equipment.

The present inventors have proposed a polarizing plate having a wire grid structure, which includes a transparent substrate and grid-shaped protrusions arranged on the transparent substrate at a pitch shorter than the wavelength of light in the operating band and extending in a predetermined direction. If an impurity semiconductor obtained by adding a trace amount of a specific element to an intrinsic semiconductor is contained in the absorption layer constituting the lattice-shaped convex portions, a polarizing plate having sufficient reflectance characteristics can be manufactured using inexpensive raw materials and inexpensive manufacturing equipment. The present inventors have found that it can be obtained, and have completed the present invention.

That is, the present invention provides a polarizing plate having a wire grid structure, comprising: a transparent substrate; and grid-shaped projections arranged on the transparent substrate at a pitch shorter than the wavelength of light in the working band and extending in a predetermined direction. , wherein the grid-shaped convex portion includes at least a reflective layer and an absorbing layer, and the absorbing layer is a polarizing plate containing an impurity semiconductor.

The impurity semiconductor may be a p-type semiconductor.

The impurity semiconductor may contain a pentavalent element.

The impurity semiconductor may be an n-type semiconductor.

The impurity semiconductor may contain a trivalent element.

The end surfaces of the transparent substrate and the grid-like protrusions may be exposed surfaces where the constituent materials of the transparent substrate and the grid-like protrusions are exposed.

An electrode may be provided on the exposed surface.

Another aspect of the present invention is an optical device comprising any one of the polarizing plates described above.

Still 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 an absorbing layer forming step of forming a layer, wherein the absorbing layer forming step is a method of manufacturing a polarizing plate in which the absorbing layer is formed by sputtering a target made of an impurity semiconductor.

The impurity semiconductor may be a p-type semiconductor.

The impurity semiconductor may contain a trivalent element.

The impurity semiconductor may be an n-type semiconductor.

The impurity semiconductor may contain a pentavalent element.

According to the present invention, a polarizing plate having sufficient reflectance characteristics can be provided using inexpensive raw materials and inexpensive manufacturing equipment.

It is a cross-sectional schematic diagram which shows a polarizing plate. It is a top view of a polarizing plate concerning one embodiment of the present invention. 4 is a graph showing the polarization optical properties of the polarizing plate of Example 1. FIG. 5 is a graph showing the polarization optical properties of the polarizing plate of Comparative Example 1. FIG.

BEST MODE FOR CARRYING OUT THE 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, comprising a transparent substrate and gratings arranged on the transparent substrate at a pitch (period) shorter than the wavelength of light in the operating band and extending in a predetermined direction. and a convex portion. Further, the grid-like projections include at least a reflective layer and an absorbing layer, and the absorbing layer includes an impurity semiconductor. The polarizing plate of the present invention may have layers other than the transparent substrate, the reflective layer, and the absorbing layer 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 one embodiment of the invention. As shown in FIG. 1, the polarizing plate 10 includes a transparent substrate 1 and grid-like protrusions 5 arranged on one surface of the transparent substrate 1 at a pitch shorter than the wavelength of light in the working band. The lattice-shaped convex portion 5 has a reflective layer 2, a gap layer 3, and an absorbing layer 4 in order from the transparent substrate 1 side. That is, the polarizing plate 10 has a one-dimensional lattice pattern of the lattice-like projections 5 formed by laminating the reflective layer 2 , the gap layer 3 , and the absorbing layer 4 in this order from the transparent substrate 1 side on the transparent substrate 1 . It has a wire grid structure arranged in

Here, as shown in FIG. 1, the direction (predetermined direction) in which the grid-like projections 5 extend is referred to as the Y-axis direction. Further, the direction orthogonal to the Y-axis direction and in which the grid-like protrusions 5 are arranged along the main surface of the transparent substrate 1 is referred to as the X-axis direction. In this case, the light incident on the polarizing plate 10 is preferably incident on the side of the transparent substrate 1 on which the grid-like projections 5 are formed, from a direction orthogonal to the X-axis direction and the Y-axis direction.

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

Light incident from the side of the polarizing plate 10 shown in FIG. Of the light that has passed through the absorption layer 4 and the gap layer 3, the polarized wave (TM wave (P wave)) passes through the reflection layer 2 with high transmittance. On the other hand, among the light transmitted through the absorption layer 4 and the gap layer 3 , the polarized wave (TE wave (S wave)) is reflected by the reflective layer 2 . A portion of the TE wave reflected by the reflective layer 2 is absorbed while passing through the absorption layer 4 and the gap layer 3 , and a portion of the TE wave is reflected back to the reflective layer 2 . Also, the TE wave reflected by the reflective layer 2 interferes and attenuates when passing through the absorbing layer 4 and the gap layer 3 . By selectively attenuating the TE wave as described above, the polarizing plate 10 can exhibit desired polarization characteristics.

The grid-like projections in the polarizing plate of the present invention are, as shown in FIG. , a gap layer 3 and an absorption layer 4 .

Here, the dimensions in this specification will be explained with reference to FIG. The height H means the dimension in the direction perpendicular to the main surface of the transparent substrate 1 in FIG. The width W means the 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 5 . Further, when the polarizing plate 10 is viewed from the Y-axis direction along the direction in which the grid-like protrusions 5 extend, the repetition interval of the grid-like protrusions 5 in the X-axis direction is referred to as a pitch P.

In the polarizing plate of the present invention, the pitch P of the lattice-like projections is not particularly limited as long as it is shorter than the wavelength of light in the working band. From the standpoint of ease of fabrication and stability, the pitch P of the grid-like projections is preferably 100 nm to 200 nm, for example. The pitch P of the grid-like projections can be measured by observing with a scanning electron microscope or a transmission electron microscope. For example, using a scanning electron microscope or a transmission electron microscope, the pitch P can be measured at any four locations, and the arithmetic mean value can be used as the pitch P of the grid-shaped convex portions. This measuring method is hereinafter referred to as electron microscopy.

The polarizing plate of the present invention is characterized in that the absorption layer included in the grid-like projections contains an impurity semiconductor. As a result, a polarizing plate having sufficient reflectance characteristics can be realized using inexpensive raw materials and inexpensive manufacturing equipment.

(Transparent substrate)
The transparent substrate (transparent substrate 1 in FIG. 1) is not particularly limited as long as it is transparent to light in the operating band, and can be appropriately selected according to the purpose. "Exhibiting translucency with respect to light in the operating band" does not mean that the transmittance of light in the operating band is 100%. just show it. The light in the usable band includes, for example, visible light with a wavelength of about 380 nm to 810 nm.

The shape of the main surface of the transparent substrate is not particularly limited, and a shape (for example, a rectangular shape) is appropriately selected according to the purpose. 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 examples thereof include glass, crystal, sapphire, and the like. From the viewpoint of cost and light transmittance, it is preferable to use glass, particularly silica glass (refractive index: 1.46) or soda lime glass (refractive index: 1.51). The composition of the glass material is not particularly limited, and an inexpensive glass material such as silicate glass, which is widely distributed as optical glass, can be used.

From the viewpoint of thermal conductivity, it is preferable to use crystal or sapphire, which have high thermal conductivity. As a result, high light resistance against strong light is obtained, and it is preferably used as a polarizing plate for an optical engine of a projector that generates a large amount of heat.

When a transparent substrate made of an optically active crystal such as quartz is used, it is preferable to dispose the lattice-like projections parallel or perpendicular to the optical axis of the crystal. This provides excellent optical properties. Here, the optical axis is a direction axis that minimizes the difference in refractive index between O (ordinary ray) and E (extraordinary ray) of light traveling in that direction.

(reflective layer)
The reflective layer (reflective layer 2 in FIG. 1) is formed on one side surface of the transparent substrate, and is formed by arranging a strip of metal film extending in the Y-axis direction, which is the absorption axis. In addition, in the present invention, another layer may exist between the transparent substrate and the reflective layer.

The reflective layer 2 of the polarizing plate 10 according to one embodiment of the present invention shown in FIG. It has a rectangular shape when viewed from the Y-axis direction), that is, in a cross-sectional view perpendicular to a predetermined direction. The reflective layer has a function as a wire grid polarizing element, 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, and A polarized wave (TM wave (P wave)) having an electric field component in an orthogonal direction is transmitted.

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

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

The width of the reflective layer is preferably in the range of 30 nm to 40 nm, for example, although it depends on the relationship with the pitch P of the lattice-shaped convex portions. These widths can be measured, for example, by the electron microscopy method described above. Moreover, it is preferable that the width of the reflective layer is substantially the same as that of the absorption layer and the like, which will be described later. When the width of the reflective layer is made different from that of the other layers forming the lattice-shaped convex portions, for example, isotropic etching and anisotropic etching are used in combination to change the balance. be done.

(gap layer)
The gap layer (gap layer 3 in FIG. 1) is an arbitrary layer in the present invention. It is formed on the reflective layer, and is formed by arranging dielectric films extending in strips in the Y-axis direction, which is the absorption axis. It is. In addition, in the present invention, another layer may exist between the reflective layer and the gap layer.

The gap layer 3 of the polarizing plate 10 according to one embodiment of the present invention shown in FIG. It has a rectangular shape when viewed from the extending direction (predetermined direction: Y-axis direction), that is, in a cross-sectional view perpendicular to the predetermined direction.

The thickness of the gap layer is such that the phase of the polarized light transmitted through the absorption layer and reflected by the reflection layer shifts by half a wavelength from the polarized light reflected by the absorption layer. Specifically, the film thickness of the gap layer is appropriately set within a range of 1 to 500 nm in which the phase of polarized light can be adjusted to enhance the interference effect. The thickness of the gap layer can be measured, for example, by the electron microscopy method described above.

_The material _constituting the _gap layer is a material _transparent to visible light. Quartzite, germanium, titanium dioxide, silicon, magnesium fluoride, boron nitride, boron oxide, tantalum oxide, carbon, or combinations thereof. Among these, the gap layer is preferably made of Si oxide.

The refractive index of the gap layer is preferably greater than 1.0 and less than or equal to 2.5. Since the optical properties of the reflective layer are also affected by the refractive index of the surroundings, the polarization properties can be controlled by selecting the material of the gap layer.

Further, by appropriately adjusting the film thickness and refractive index of the gap layer, the TE wave reflected by the reflective layer can be partially reflected and returned to the reflective layer when passing through the absorbing layer. Light that has passed through can be attenuated by interference. By selectively attenuating the TE wave in this manner, desired polarization characteristics can be obtained.

The width of the gap layer is preferably in the range of 30 nm to 40 nm, for example, although it depends on the relationship with the pitch P of the lattice-like protrusions. These widths can be measured, for example, by the electron microscopy method described above. Also, the width of the gap layer is preferably substantially the same as that of the reflective layer described above.

(absorbent layer)
The absorbing layer (absorbing layer 4 in FIG. 1) is an essential layer in the present invention, is provided on the opposite side of the reflective layer to the transparent substrate, and constitutes a part of the grid-like projections. That is, the absorption layers are arranged in a belt-like manner extending in the Y-axis direction, which is the absorption axis. In the present invention, another layer such as the above-described gap layer may exist between the reflective layer and the absorbing layer.

The absorbing layer 4 of the polarizing plate 10 according to one embodiment of the present invention shown in FIG. It has a rectangular shape when viewed from the extending direction (predetermined direction: Y-axis direction), that is, in a cross-sectional view perpendicular to the predetermined direction.

The width of the absorption layer is preferably in the range of 30 nm to 40 nm, for example, although it depends on the relationship with the pitch P of the grid-like projections. These widths can be measured, for example, by the electron microscopy method described above. Also, the width of the absorption layer is preferably substantially the same as that of the reflective layer described above. When the width of the absorption layer is made different from that of the other layers forming the grid-like projections, for example, isotropic etching and anisotropic etching are combined to change the balance. be done.

The polarizing plate of the present invention is characterized in that the absorption layer contains an impurity semiconductor. As a result, a polarizing plate having sufficient reflectance characteristics can be realized using inexpensive raw materials and inexpensive manufacturing equipment.

Impurity semiconductors contained in the absorption layer include impurity semiconductors obtained by adding impurities to intrinsic semiconductors such as Si and Ge. As the intrinsic semiconductor, Si is preferable from the viewpoint of availability and price.

It is known that an intrinsic semiconductor such as silicon becomes an n-type semiconductor or a p-type semiconductor by adding a small amount of impurities. For example, when silicon is doped with boron, it becomes a p-type semiconductor, and it is known that as the amount of doping increases, the resistivity decreases sharply.

Since the resistivity of silicon as an intrinsic semiconductor is about 10 ³ Ωcm, it is necessary to use a high-frequency method when forming a silicon film by sputtering. Here, high-frequency sputtering requires a high-frequency power supply, matching, etc., and generally requires a complicated device configuration. becomes expensive.

However, as described above, an impurity semiconductor obtained by adding a small amount of impurities to an intrinsic semiconductor has a sharply reduced resistivity. For this reason, it is possible to carry out the sputtering with a direct-current system, which is a simple configuration device. Therefore, in the polarizing plate of the present invention, since the absorption layer contains an impurity semiconductor, it is possible to reduce both the cost of the manufacturing apparatus itself due to the simplification of the film forming apparatus and the cost required for production.

In the present invention, since a semiconductor material is used as the absorption layer, the bandgap energy of the semiconductor is involved in the absorption action, and it is necessary to keep the bandgap energy below the operating band. For example, when using visible light, it is necessary to use a material that absorbs at a wavelength of 400 nm or more, that is, has a bandgap of 3.1 ev or less.

The impurity semiconductor contained in the absorption layer is not particularly limited as long as the bandgap energy is equal to or lower than the use band, and may be either a p-type semiconductor or an n-type semiconductor. As impurities to be added to the intrinsic semiconductor, in the case of a p-type semiconductor, it is preferable to contain a trivalent element such as B and Al. Addition examples include: In the case of an n-type semiconductor, it is preferable to contain a pentavalent element such as P, As or Sb. are mentioned.

The film thickness of the absorption layer is not particularly limited, and is preferably 10 nm to 100 nm, for example. The thickness of the absorbing layer can be measured, for example, by electron microscopy as described above. Also, the absorption layer may be composed of two or more layers of different constituent materials.

(diffusion barrier layer)
The polarizing plate of the present invention may have a diffusion barrier layer between the gap layer and the absorption layer. That is, in the polarizing plate shown in FIG. 1, the lattice-shaped convex portion 5 has the reflective layer 2, the gap layer 3, the diffusion barrier layer, and the absorbing layer 4 in order from the transparent substrate 1 side. Having a diffusion barrier layer prevents diffusion of light in the absorption layer. This diffusion barrier layer can be composed of a metal film such as Ta, W, Nb, or Ti.

(Protective film)
In the polarizing plate of the present invention, the surface on the light incident side may be covered with a dielectric protective film as long as the change in optical characteristics is not affected. The protective film is composed of a dielectric film, and can be formed, for example, by using CVD (Chemical Vapor Deposition) or ALD (Atomic Layer Deposition) on the surface of the polarizing plate (the surface on which the wire grid is formed). . As a result, it is possible to suppress an excessive oxidation reaction to the metal film.

(Organic water-repellent film)
Furthermore, the polarizing plate of the present invention may be covered with an organic water-repellent film on the light incident side surface. The organic water-repellent film is composed of, for example, a fluorine-based silane compound such as perfluorodecyltriethoxysilane (FDTS), and can be formed by using the above-described CVD or ALD, for example. Thereby, reliability such as 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 includes modifications and improvements within the scope of achieving the object of the present invention.

[End face of polarizing plate]
In the polarizing plate of the present invention, it is preferable that the end surfaces of the transparent substrate and the grid-like projections are exposed surfaces where the constituent materials of the transparent substrate and the grid-like projections are exposed. That is, as shown in FIG. 2(a), when the direction of the arrow is the direction in which the grid-like protrusions extend, the grid-like protrusions and the end surface 11 of the transparent substrate form the structure of the transparent substrate and the grid-like protrusions. It is an exposed surface where the material is exposed.

Since the end face of the polarizing plate is an exposed face where the constituent material of the lattice-like projections is exposed, that is, the absorption layer containing the impurity semiconductor is exposed, a conductive contact can be made from the end as needed. It becomes possible to For example, as shown in FIG. 2(b), by directly providing a contact electrode on the end face 11 of the lattice-like projections and the transparent substrate, which is an exposed surface where the constituent material of the lattice-like projections is exposed, static electricity can be eliminated. As a result, for example, even if dust enters an optical device such as a liquid crystal projector, deterioration of light transmittance due to adhesion of dust to the polarizing plate and corrosion from the dust part can be prevented. can be suppressed.

[Method for producing polarizing plate]
The manufacturing method of the polarizing plate of the present invention has at least a reflective layer forming step and an absorbing layer forming step.

(Reflection layer forming step)
In the reflective layer forming step, a reflective layer is formed on one side of the transparent substrate. Examples of methods for forming the reflective layer include sputtering and vapor deposition.

(Absorptive layer forming step)
In the absorption layer forming step, an absorption layer is formed on the reflective layer formed in the reflective layer forming step, or on any layer such as a gap layer, if any.

The present invention is characterized in that, in the absorption layer forming step, the absorption layer is formed by sputtering the target made of the impurity semiconductor described above.

(Etching process)
In the etching step, by selectively etching the laminate formed through the above-described layer forming steps, lattice-like projections arranged on the transparent substrate at a pitch shorter than the wavelength of light in the operating band are formed. . Specifically, a one-dimensional lattice mask pattern is formed by, for example, photolithography or nanoimprinting. Then, by selectively etching the laminate, grid-like projections arranged on the transparent substrate at a pitch shorter than the wavelength of light in the working band are formed. As an etching method, for example, there is a dry etching method using an etching gas corresponding to an etching target.

In particular, in the present invention, the width of the layer forming the lattice-like projections can be arbitrarily adjusted by changing the balance by combining isotropic etching and anisotropic etching.

The method of manufacturing the polarizing plate of the present invention may include a step of covering the surface with a dielectric protective film. Moreover, the method for producing the polarizing plate of the present invention may have a step of coating the surface with an organic water-repellent film.

[Optical equipment]
An optical device of the present invention includes the above-described polarizing plate of the present invention. The polarizing plate according to the present invention can be used for various purposes. Examples of applicable optical equipment include liquid crystal projectors, head-up displays, digital cameras, and the like. 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 that 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 this embodiment is a liquid crystal projector, at least one of the polarizing plates arranged on the incident side and the exit side of the liquid crystal panel may be the polarizing plate according to the present invention.

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

<Example 1>
[Preparation of polarizing plate]
A wire grid polarizing plate having the configuration shown in FIG. 1 was produced. That is, on one surface of a transparent substrate, lattice-shaped projections are arranged in a one-dimensional lattice pattern, and the lattice-shaped projections include, in order from the transparent substrate, a reflective layer, a gap layer, and an absorption layer. A polarizing plate having a structure was produced.

Glass was used as the substrate, aluminum was used as the material of the reflective layer, and the thickness of the reflective layer was 200 nm. The material of the gap layer was silica, and the thickness was 20 nm.

An absorption layer was formed on the gap layer by a sputtering method. Silicon containing 100 ppm of boron was used as the target material. The volume resistivity of the target was 0.01 Ω·cm, and the thickness of the absorption layer was 20 nm.

Subsequently, etching was performed to obtain a wire grid polarizing plate having the structure shown in FIG.

[Measurement of polarization characteristics]
The optical properties of the obtained polarizing plate were measured using a spectrophotometer (manufactured by JASCO Corporation, V-570) under the following conditions.
(Measurement condition)
Transmittance of P-polarized light and S-polarized light: Measured at an incident angle of 0° and within a wavelength range of 400 to 700 nm Reflectance of P-polarized light and S-polarized light: Measured at an incident angle of 5° and within a wavelength range of 400 to 700 nm

FIG. 3 shows the verification results of the polarization characteristics. In the graph of FIG. 3, the X axis indicates wavelength (nm), the Y1 axis indicates transmittance or reflectance (%), and the Y2 axis indicates contrast. In addition, the simulation results are plotted for the following items.
Tp: P-polarized transmittance Ts: S-polarized transmittance Rp: P-polarized reflectance Rs: S-polarized reflectance CR: Contrast (Tp/Ts)

Here, the P-polarized light transmittance (Tp) means the transmittance of polarized light (TM wave) incident on the polarizing plate in the transmission axis direction (X-axis direction). The S-polarized light transmittance (Ts) means the transmittance of polarized light (TE wave) incident on the polarizing plate in the absorption axis direction (Y-axis direction). The P-polarized light reflectance (Rp) means the reflectance of polarized light (TM wave) incident on the polarizing plate in the transmission axis direction (X-axis direction). The S-polarization reflectance (Rs) means the reflectance of polarized light (TE wave) incident on the polarizing plate in the absorption axis direction (Y-axis direction).

<Comparative Example 1>
A polarizing plate was produced in the same manner as in Example 1 except that Ta (volume resistivity: 131 nΩ·cm) was used as the absorption layer, and the same simulation as in Example 1 was performed. FIG. 4 shows the verification results of the polarization characteristics.

The polarizing plate in Example 1 has a low S-polarized reflectance (Rs) in the green band (around 550 nm), which is an important wavelength when used as a visible polarizing plate, compared to the polarizing plate in Comparative Example 1. I know.

REFERENCE SIGNS LIST 10 polarizing plate 1 transparent substrate 2 reflective layer 3 gap layer 4 absorbing layer 5 grid-like projections 11 end face of transparent substrate and grid-like projections 12 contact electrode H height of grid-like projections W width of grid-like projections P grating Pitch of convex part

Claims (13)

A polarizing plate having a wire grid structure,
a transparent substrate;
grid-shaped projections arranged on the transparent substrate at a pitch shorter than the wavelength of light in the operating band and extending in a predetermined direction;
the grid-shaped convex portion has a reflective layer, a gap layer, and an absorbing layer in order from the transparent substrate side ;
_The gap layer is selected from the group consisting of SiO2 , _Al2O3 , _beryllium oxide, bismuth oxide, MgF2 _, cryolite, germanium, titanium dioxide, magnesium fluoride, boron nitride, boron oxide, tantalum oxide and carbon. including one or more of the
The absorption layer is a polarizing plate containing an impurity semiconductor. The polarizing plate according to claim 1, wherein the impurity semiconductor is a p-type semiconductor. 3. The polarizing plate according to claim 2, wherein the impurity semiconductor contains a trivalent element. The polarizing plate according to claim 1, wherein the impurity semiconductor is an n-type semiconductor. 5. The polarizing plate according to claim 4, wherein the impurity semiconductor contains a pentavalent element. 6. The polarizing plate according to any one of claims 1 to 5, wherein end surfaces of the transparent substrate and the grid-like projections are exposed surfaces where constituent materials of the transparent substrate and the grid-like projections are exposed. 7. The polarizing plate according to claim 6, wherein the exposed surface is provided with an electrode. An optical device comprising the polarizing plate according to any one of claims 1 to 7. A method for 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;
a gap layer forming step of forming a gap layer on the reflective layer;
an absorption layer forming step of forming an absorption layer on the gap layer ;
_The gap layer is selected from the group consisting of SiO2 , _Al2O3 , _beryllium oxide, bismuth oxide, MgF2 _, cryolite, germanium, titanium dioxide, magnesium fluoride, boron nitride, boron oxide, tantalum oxide and carbon. including one or more of the
The absorption layer forming step is a method of manufacturing a polarizing plate, in which an absorption layer is formed by sputtering a target made of an impurity semiconductor. 10. The method of manufacturing a polarizing plate according to claim 9, wherein the impurity semiconductor is a p-type semiconductor. 11. The method of manufacturing a polarizing plate according to claim 10, wherein the impurity semiconductor contains a trivalent element. 10. The method of manufacturing a polarizing plate according to claim 9, wherein the impurity semiconductor is an n-type semiconductor. 13. The method of manufacturing a polarizing plate according to claim 12, wherein the impurity semiconductor contains a pentavalent element.

Images