JP2016038537A - Wire grid polarizer, light source module and projection display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire grid polarizer achieving high polarization separation performance to visible light.SOLUTION: The wire grid polarizer comprises: a transparent substrate; an antireflection layer formed on one surface of the transparent substrate by using a material with a refractive index lower than that of the transparent substrate; and a wire grid formed on the antireflection layer. The wire grid has a pitch of equal to or less than 1/2 of a wavelength of incident light in a visible wavelength region. The antireflection layer is formed using a porous material which is a porous structured optical material composed of a composite including a structure formed using a transparent material and holes with particle sizes of 100 nm or less. A refractive index n of the antireflection layer falls within a range of n=n-0.1nto n+0.1n, where nrepresents the refractive index of a gap part which is an atmosphere around the wire grid, nrepresents the refractive index of the transparent substrate, and n=(n*n).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wire grid polarizer, a light source module using the same, and a projection display device.

  As an optical component used in various optical devices, a reflective polarizer that transmits one of linearly polarized light orthogonal to each other and reflects the other of incident light is known. One of the reflective polarizers A wire grid type polarizer may be mentioned. FIG. 19 is a configuration diagram of a general wire grid polarizer. In the wire grid polarizer 900 shown in FIG. 19, a wire grid 910 having a structure in which fine metal wires 911 are arranged in parallel to each other is formed on one main surface of a transparent substrate 940. The atmosphere around the wire grid 910, that is, the gap 920 between the thin metal wires 911 is filled with air.

  FIG. 20 is an explanatory diagram showing an example of incident light, reflected light, and transmitted light in the wire grid polarizer 900 shown in FIG. In FIG. 20, the light incident surface is orthogonal to the surface on which the wire grid 910 is formed, that is, the main surface of the transparent substrate 940, and the normal direction is the longitudinal direction of the fine metal wires 911 (see FIG. XZ plane in FIG. When the pitch Pi of the wire grid 910, which is the distance between the straight metal wires 911, is sufficiently shorter than the wavelength of the incident light 801, the incident light 801 is a component having an electric field vector orthogonal to the longitudinal direction of the metal wires 911. P-polarized light is transmitted (see transmitted light 802 in FIG. 20), and S-polarized light, which is a component having an electric field vector parallel to the longitudinal direction of the thin metal wire 911, is reflected (see reflected light 803 in FIG. 20). . Since such a wire grid polarizer 900 has high polarization separation performance, it has long been used as a useful polarizer, for example, when handling light in the infrared wavelength region (for example, Non-Patent Document 1). .

One of the factors that determine the performance of the wire grid polarizer 900 is the relationship between the pitch Pi of the wire grid 910 and the wavelength λ of incident light. For example, when the pitch Pi is in the range of approximately ½ to 2 times the wavelength λ, the polarization separation performance is significantly reduced with respect to light of a specific wavelength. Such a phenomenon is generally called “Rayleigh resonance”, and the maximum resonance wavelength λ _res-max that is the longest wavelength at which this resonance occurs is expressed by the following equation (1). In addition, the relationship as shown by Formula (1) is described also in patent document 1, for example. In the formula (1), n _s represents a refractive index of the transparent substrate 940, theta represents the angle of incidence of the light with respect to the wire grid 910.

λ _res−max = Pi (n _s + sin θ) (1)

At the wavelength at which Rayleigh resonance occurs and in the vicinity of the wavelength, the performance of the wire grid polarizer sharply decreases. Therefore, in order to obtain sufficient polarization separation performance for visible light, the maximum resonance wavelength λ _res-max must be shorter than the wavelength of visible light.

As a method of moving the maximum resonance wavelength λ _res-max to the short wavelength side, there are three methods based on the above formula (1). In the first method, the pitch Pi of the wire grid 910 is shortened. However, only the pitch Pi has to be shortened while maintaining the thickness t of the fine metal wires 911 so as not to transmit S-polarized light, and there is a problem that such ultrafine processing is technically difficult. In the second method, the incident angle θ to the wire grid 910 is set to zero, that is, the light is incident vertically so that the incident light to the wire grid polarizer 900 is not obliquely incident. However, if the incident angle θ is limited, there is a problem that the use as a polarizer is significantly limited. The third method reduces the refractive index (n _s ) of the transparent substrate 940 that forms the wire grid 910. However, there are few optical materials that are transparent to visible light and have a sufficiently small refractive index, and there is a problem that options are particularly limited in the case of resin materials that are easy to process.

As a technique for solving the problem in the third method among the methods described above, Non-Patent Document 1 includes a “blooming layer” between the transparent substrate 940 and the wire grid 910. It is described that it is effective to form a single-layer antireflection film. Incidentally, Non-Patent Document 1, a simple impedance matching formula, completely based on the parameters of the thin metal strips having conductivity, blooming layer is equal to the square root of the refractive index n _s of the transparent substrate 940 refraction It is stated that it must have a rate n and an optical film thickness of ¼ of the target wavelength λ. Here, the optical film thickness means refractive index n × film thickness d.

Patent Document 1 describes a wire grid polarizer having a magnesium fluoride layer corresponding to the blooming layer described in Non-Patent Document 1. Further, FIG. 8 of Patent Document 1 shows, as an effect of the magnesium fluoride layer, calculation of transmittance wavelength dependency for P-polarized light having an incident angle of 45 ° in a wire grid polarizer having a magnesium fluoride layer. Results are shown. In the wire grid polarizer, a magnesium fluoride layer having a refractive index n = 1.38 is formed as a blooming layer on a glass substrate having a refractive index n _s = 1.525, and silver or aluminum is further formed thereon. Are formed so that the pitch Pi = 200 nm, the wire width w = 100 nm, and the thickness t = 100 nm.

Japanese Patent No. 48004337

J. P. Auton, "Infrared Transmission Polarizers by Photolithography," APPLIED OPTICS. Vol.6 No.6, 1967, p.1023-1027.

  However, in the method of providing a magnesium fluoride layer having a refractive index of about 1.38 between the transparent substrate 940 and the wire grid 910 as described in Patent Document 1, regardless of the thickness d of the layer. The transmittance for P-polarized light is low, and the polarization separation performance is not sufficient. For example, according to FIG. 8 of Patent Document 1, the maximum transmittance with respect to P-polarized light in the visible wavelength region is only about 84%, and is further lower than 80% in the wavelength region of 450 nm or less. For this reason, when used in an optical device that utilizes P-polarized transmitted light from a polarizer, there is a problem in that the light utilization efficiency is reduced.

  Accordingly, an object of the present invention is to provide a wire grid type polarizer capable of obtaining high polarization separation performance with respect to visible light. More specifically, an object of the present invention is to provide a wire grid polarizer that can obtain a higher P-polarized light transmittance without reducing the S-polarized light reflectance in the visible wavelength region. Another object of the present invention is to provide a light source module that can efficiently emit linearly polarized light. Another object of the present invention is to provide a projection display device with high light utilization efficiency.

The wire grid polarizer according to the present invention includes a transparent substrate, an antireflection layer formed on one surface of the transparent substrate using a material having a lower refractive index than the transparent substrate, and an antireflection layer. The pitch of the wire grid is ½ or less of the wavelength of incident light in the visible wavelength range, and the antireflection layer is made of a transparent material and has a particle size Is formed using a porous material, which is an optical material having a porous structure composed of a composite with pores of 100 nm or less, and the refractive index of the gap, which is the atmosphere around the wire grid, is n ₁ , a transparent substrate the refractive index _n S _of, when the ^{_{n AR = (n 1 · n}} S) 1/2, refractive index n of the antireflection _{layer, n = n AR -0.1n AR ~n} AR + 0.1n AR It is in the range of.

  In the wire grid polarizer, the gap may be filled with a porous structure formed of the same or different porous material as the material of the antireflection layer.

  In addition, the porous material may be a material in which metal oxide fine particles including pores are bonded by a matrix component whose main component is a metal oxide.

  The metal oxide fine particles may be hollow silica particles.

  The fine metal wires of the wire grid may be formed of silver or aluminum and an alloy containing any one or more of palladium, neodymium, iridium, bismuth, gold, copper, platinum, zinc, and tin.

  Further, the wire grid polarizer may have a transmittance of 90% or more of P-polarized light orthogonal to the longitudinal direction of the fine metal wires of the wire grid at a wavelength of 460 nm to 600 nm.

  In addition, a light source module according to the present invention includes a light emitting element provided in a container and a substrate provided above the light emitting element and forming a light emission surface. The wire grid polarizer described is formed.

  Further, the substrate is a phosphor-containing substrate containing a phosphor, and transmits light having a light emission wavelength from the light-emitting element to the surface opposite to the surface on which the wire grid of the phosphor-containing substrate is formed, In addition, a dichroic mirror layer that reflects light having a fluorescence emission wavelength that is the emission wavelength from the phosphor may be formed.

  The projection display device according to the present invention utilizes a light source unit including three light sources that emit light of different wavelengths, a scan mirror that reflects incident light and scans the screen, and a polarization separation function. In the optical path between the polarization beam splitter and the scan mirror, the polarization beam splitter that reflects the light from the light source unit and guides it to the scan mirror and transmits the light reflected by the scan mirror to reach the screen A projection-type display device including a quarter-wave plate to be disposed, wherein the wire-grid polarizer described in any of the above is provided as a polarizing beam splitter.

  Further, the projection display device according to the present invention utilizes a light source unit including three light sources that emit light of different wavelengths, a reflective liquid crystal display element, a projection lens, and a polarization separation function, from the light source unit. A polarizing beam splitter that reflects and guides the reflected light to the reflective liquid crystal display element and transmits the light reflected by the reflective liquid crystal display element to reach the projection lens. It comprises the wire grid type polarizer as described in above.

  Further, the polarization beam splitter may be formed so that the wire grid is limited to the incident region of the light from the light source unit.

  According to the present invention, the P-polarized light transmittance can be improved with a simple configuration without reducing the S-polarized light reflectance in the visible wavelength region. Therefore, a wire grid polarizer having high polarization separation performance for visible light can be obtained. Can be provided. Further, according to the present invention, it is possible to provide a light source module capable of efficiently emitting linearly polarized light. Further, according to the present invention, it is possible to provide a projection display device with high light utilization efficiency.

It is a block diagram which shows the example of the wire grid type polarizer concerning 1st Embodiment. It is explanatory drawing which shows the example of the incident light and outgoing light (reflected light and transmitted light) in the wire grid type polarizer. 4 is a schematic cross-sectional view showing an example of a porous material used for the antireflection layer 130. FIG. 5 is an explanatory diagram showing an example of a method for forming a wire grid 110. FIG. It is explanatory drawing which shows the other example of the formation method of the wire grid. It is a schematic cross section which shows the example of the LED light source concerning 2nd Embodiment. It is a schematic cross section which shows the other example of the LED light source concerning 2nd Embodiment. It is a schematic cross section which shows the other example of the LED light source concerning 2nd Embodiment. It is a schematic cross section which shows the wire grid type polarizer which has the other example of the fluorescent substance containing board | substrate 270. FIG. It is a block diagram which shows the example of the projection type display apparatus of 3rd Embodiment. It is a graph showing a third embodiment (third embodiment) S Examples of the incident angle dependence of polarization reflectance R _s and P-polarized light transmittance T _p of the wire grid polarizer 420 of. It is a block diagram which shows the other example of the projection type display apparatus of 3rd Embodiment. It is a graph which shows the calculation result of the polarization efficiency of the wire grid type polarizer 100 of the 1st example. It is a graph which shows the calculation result of the polarization efficiency of the wire grid type polarizer 100 of the 2nd example. It is a graph which shows the calculation result of the polarization efficiency of the wire grid type polarizer of the 1st comparative example. It is a graph which shows the calculation result of the polarization efficiency of the wire grid type polarizer of the 2nd comparative example. It is a graph which shows the calculation result of the polarization efficiency of the wire grid type polarizer 100 of the 4th example. It is a graph which shows the calculation result of the polarization efficiency of the wire grid type polarizer 100 of the 5th example. It is a block diagram of a general wire grid type polarizer. FIG. 20 is an explanatory diagram showing an example of incident light and outgoing light (reflected light and transmitted light) in the wire grid polarizer shown in FIG. 19.

Embodiment 1. FIG.
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram illustrating an example of a wire grid polarizer according to the first embodiment of the present invention. FIG. 2 is an explanatory diagram showing the relationship between incident light and outgoing light (reflected light and transmitted light) in the wire grid polarizer 100 shown in FIG. In the wire grid polarizer 100 shown in FIG. 1, an antireflection layer 130 formed of an optical member having a refractive index lower than the refractive index of the transparent substrate 140 is laminated on the transparent substrate 140, and the reflection thereof. On the prevention layer 130, there is a wire grid 110 in which a plurality of fine metal wires 111 extending in one direction are arranged in parallel with each other at a predetermined pitch.

  The pitch Pi of the wire grid 110, that is, the interval between the thin metal wires 111 is set sufficiently shorter than the wavelength of incident light. As a result, as shown in FIG. 2, the P-polarized light, which is a component having an electric field vector orthogonal to the longitudinal direction of the thin metal wire 111, is transmitted from the incident light 151 (the transmitted light 152 in FIG. 2). S-polarized light which is a component having an electric field vector parallel to the longitudinal direction of 111 is reflected (reflected light 153 in FIG. 2). In FIG. 2, as an example of the light incident surface with respect to the wire grid polarizer 100, the metal thin wires 111 that are orthogonal to the surface of the transparent substrate 140 on which the wire grid 110 is formed and that constitute the wire grid 110. The plane (XZ plane) having the normal direction as the longitudinal direction is shown.

  Although not shown, an antireflection film may be formed on the other main surface of the transparent substrate 140. The configuration of the antireflection film is not particularly limited, and examples thereof include an optical multilayer film made of a transparent dielectric material.

  The transparent substrate 140 is not particularly limited as long as it is made of a transparent optical material that substantially does not absorb light in the visible wavelength region. Examples of the optical material include glass, optical crystals, resins, sintered bodies, and composite materials thereof. For example, general optical glass or resin material that is inexpensive and has high optical uniformity can be used. For example, even in the case of a transparent substrate having a refractive index of 1.40 to 1.64 with respect to light in the visible wavelength region, the atmosphere around the wire grid 110 and the transparent substrate 140 are separated by the antireflection layer 130 described later. Since reflection by the interface can be suppressed, the P-polarized light transmittance can be improved. Here, the visible wavelength range is a wavelength range of 430 nm to 660 nm with relatively high visibility, but is not limited thereto. In addition, when the P-polarized light transmittance is 90% or more at a wavelength of 460 nm to 600 nm, it can be said that the effect of the present invention is sufficiently obtained.

  The antireflection layer 130 is a transparent optical material that substantially does not absorb light in the visible wavelength range, and is made of an optical material that substantially satisfies the following formula (2).

n = (n ₁ · n _S ) ^1/2 (2)

Here, n ₁ represents the refractive index of the atmosphere around the wire grid 110, that is, the refractive index of the filler in the gaps between the metal thin wires 111 (hereinafter referred to as gap portions 120), and n represents the refraction of the antireflection layer 130. N _S represents the refractive index of the transparent substrate 140.

  Formula (2) is an antireflection condition for the interface between the atmosphere around the wire grid 110 and the transparent substrate 140. The P-polarized light transmittance can be improved by forming the antireflection layer 130 using an optical material that satisfies the antireflection condition represented by the formula (2).

Note that, as a realistic range, if n shown in the above equation (2) is within a range of −10% to + 10%, the antireflection condition is assumed to be satisfied. In addition, it is more preferable if the difference is within a range of −5% to + 5%. That is, based on equation _(2), when given an _{n AR} to ^{_{n AR = (n 1 · n}} S) 1/2, range of _{n = n AR -0.1n AR ~n AR} + 0.1n AR may be any _internal, within the range of _{n = n AR -0.05n AR ~n AR} + 0.05n AR, more preferred.

For example, if the refractive index n _S of the transparent substrate 140 is 1.40 to 1.64, the antireflection layer 130 may be made of an optical material having a refractive index n of 1.18 to 1.28. An optical multilayer film is one of the common anti-reflective film configurations. Such an optical multilayer film, that is, a plurality of layers are laminated to prevent reflection by using interference at the interface of each layer. Such a configuration is not applied to the configuration of the antireflection layer 130. In other words, when the antireflection layer 130 is composed of a plurality of layers, the refractive index of each layer is required to be at least lower than the refractive index n _S of the transparent substrate 140.

Thickness d of the antireflection layer 130, the optical thickness, i.e. refractive index n × thickness d is the wavelength lambda ₀ in the visible wavelength range, is adjusted to be substantially equal to λ _0/4. For example, in the case of incident light having an incident angle θ, the optical path length difference in the antireflection layer 130 is represented by n × d × cos θ, and thus the film thickness d of the antireflection layer 130 is set to λ ₀ / (4 × n × cos θ ) So as to be approximately equal to. Here, the wavelength λ ₀ is preferably set in a range of 510 nm to 590 nm with high visibility. In addition, the above “substantially” may be any difference within a range of −10% to + 10%.

By the way, it is a transparent optical material having substantially no light absorption in the visible wavelength region, and the refractive index satisfies the formula (2) with respect to the refractive index (n _S ) of general optical glass or resin. A low refractive index material having a value, i.e., n = 1.18 to 1.28, does not exist at a level that can be commercialized. Therefore, in the present invention, an optical material having a porous structure (hereinafter referred to as a porous material) is used as the optical material constituting the antireflection layer 130. More specifically, a porous material composed of a composite of a structure 131 formed using a transparent material having a refractive index of 1.33 or more and air or vacuum holes 132 having a refractive index of 1.0. Is used. Here, the transparent material used as the material of the structure 131 may be a single refractive index material or a mixture of a plurality of refractive index materials.

  FIG. 3 is a schematic cross-sectional view showing an example of a porous material used for the antireflection layer 130. A porous material 130a shown in FIG. 3A has a hole 132a (for example, a bubble) made of air or a vacuum having a refractive index of 1.0 in a structure 131a made of a transparent material having a refractive index of 1.33 or more. Is an example of an optical member having a porous structure as a whole.

  Also, the porous material 130b shown in FIG. 3B includes an outer shell 131b which is a structure made of a transparent material having a refractive index of 1.33 or more, and air having a refractive index of 1.0 inside the outer shell 131b. Alternatively, this is an example of an optical member having a porous structure as a whole, in which a plurality of hollow particles 133 having a hollow portion 132b made of a vacuum are bonded. In addition, the void | hole 132 in the porous material 130b includes not only the hollow portion 132b of each hollow particle 133 but also the void portion 132c formed between the hollow particle 133 and the hollow particle 133.

The refractive index n of the antireflection layer 130 in the case of a porous material made of a composite may be obtained from the refractive index and volume ratio of each medium included in the porous material constituting the antireflection layer 130. For example, in the entire volume of the antireflection layer 130, the volume ratio of the structure 131 formed of _a transparent material having _a refractive index na is V _a , and the volume ratio of the holes 132 having _a refractive index n ₀ is V _o (however, _{Assuming that} V _o + V _a = 1), it can be approximated by n = n ₀ × V _o + n _a × V _a .

For example, when silicon oxide (SiO ₂ : silica) is used as the material of the structure 131, the refractive index is about 1.45. Therefore, when n _a = 1.45, the volume ratio V _a is set to 0.40. By adjusting between 0.62, it can be set as the optical material of refractive index n = 1.18-1.28. The material of the structure 131 is not particularly limited as long as the (effective) refractive index n of the antireflection layer 130 made of a porous material finally obtained satisfies the antireflection condition, but is not limited to silicon oxide. For example, aluminum oxide (Al ₂ O ₃ : alumina), titanium oxide (TiO ₂ : titania), zirconium oxide (ZrO ₂ : zirconia), tantalum pentoxide (Ta ₂ O ₅ ), tin oxide (SnO), etc. Examples thereof include metal oxides and organic materials. Hereinafter, fine particles formed using a metal oxide may be referred to as metal oxide fine particles.

  In addition, in order to reduce or prevent scattering of incident light in the visible wavelength region due to the holes 132, the maximum diameter R of the holes 132 included in the porous material is approximately 100 nm or less of the shortest visible wavelength. The following is preferable, and 50 nm or less which is approximately 1/8 or less is more preferable. In the case of a structure in which particles are bonded as shown in FIG. 3B, the average primary particle diameter only needs to satisfy the above condition instead of the maximum diameter R. When particles having such an average primary particle diameter are used, the maximum diameter R of the pores 132 in the porous material tends to be 100 nm or less or 50 nm or less, and the transparency is also improved.

  Moreover, in the porous material 130b, a matrix component (binder component) may be used as a method for bonding particles. If the method of bonding particles using a matrix component is used, the antireflection layer 130 made of the porous material can be formed by a wet method. Therefore, a dry method such as a physical vapor deposition method such as a vacuum vapor deposition method or a thermal CVD method is used. It can be formed at a lower cost than chemical vapor deposition.

The matrix component is preferably a metal oxide as described above. The metal oxide used for the particle material and the metal oxide used for the matrix component may be the same or different. The matrix component is preferably composed only of a metal oxide. For example, a component such as a resin may be contained in an amount of 30% by mass or less, preferably 10% by mass or less, and more preferably 2% by mass or less. In the case where the matrix component is used, the refractive index n of the antireflection layer 130 calculated including the volume ratio of the matrix component may satisfy the antireflection condition described above. That is, the total volume of the anti-reflection layer 130, the volume ratio V _a of the structure 131 in which the refractive index is formed by a transparent material n _a, the volume ratio of matrix components V _m of the refractive index n _m, the refractive index If the volume ratio of the holes 132 having n ₀ is V ₀ (where V ₀ + V _m + V _a = 1), it can be approximated by n = n ₀ × V ₀ + n _m × V _m + n _a × V _a .

  Also, the particles on the side to be bonded are not necessarily limited to those made of one type or material, and those made of two or more types or materials can be used in combination. For example, two or more types of particles having different shapes may be used, or two or more types of particles having different materials may be used. Further, particles made of a plurality of materials may be used. The shape of the particle is not particularly limited, and examples thereof include a spherical shape, a cylindrical shape, and a rectangular parallelepiped shape.

  Moreover, the hollow particles having voids inside (hollow particles) are preferred as the particles, and in particular, the (effective) refractive index n of the finally formed porous material can be lowered, Moreover, hollow silica particles that are easy to produce are preferred examples. The hollow silica particles are hollow particles 133 in which the main component of the outer shell 131b is silicon oxide. The outer shell 131b is not necessarily formed so as to cover the entire hollow portion 132b, and a part of the hollow portion 132b may be exposed from the outer shell 131b. The hollow particles are preferable because the average refractive index of the porous material, and thus the refractive index n of the antireflection layer 130, can be easily adjusted by adjusting the thickness of the outer shell 131b. Further, in the case of hollow silica particles, the average refractive index of the porous material and thus the refractive index n of the antireflection layer 130 can be easily set to 1.1 to 1.4 at a wavelength of 550 nm, for example.

  When hollow silica particles are used, the thickness of the outer shell 131b of each hollow silica particle is not particularly limited and varies depending on the particle diameter, but is preferably 0.5 nm to 50 nm, and more preferably 1 nm to 20 nm, as an example. Also in other particles, as a reference, the thickness of the outer shell 131b is preferably about 1/50 to 1/3, more preferably about 1/5 to 1/3 of the particle size. .

  Further, the hollow silica particles may be aggregated in the matrix component. For example, about 2 to 10 aggregates may be dispersed in the matrix component. In this case, the strength and wear resistance of the metal oxide film constituting the antireflection layer 130 tend to increase. In this case, the particle size (hereinafter also referred to as the average aggregate particle size) as the aggregate is preferably 60 nm to 400 nm, and more preferably 100 nm to 200 nm. Also in other particles, as a reference, the average aggregate particle diameter is preferably 1.5 times or more the average particle diameter (average primary particle diameter) in a non-aggregated state. In addition, the average particle diameter of the particle | grains in this invention points out the value measured by observation using a transmission electron microscope (TEM).

  In addition to the method of bonding a plurality of particles as described above, the porous material, for example, a part of itself (for example, a part of contained substances) disappears by firing, and finally pores are formed. Such a pore-forming substance can also be used (see FIG. 3A). Even when such a pore-forming substance is used, the antireflection layer 130 made of a porous material can be formed by a wet method, and can be formed at a lower cost than the dry method. The material that does not disappear among the pore-forming substances, which is also a material of the structure 131, is preferably made of a metal oxide. For example, a component such as an organic resin is 30% by mass or less, preferably 10% by mass or less, and Preferably you may contain 2 mass% or less. Further, the metal oxide is not particularly limited as long as the refractive index n of the finally obtained antireflection layer 130 satisfies the above-described antireflection conditions, but silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, Preferable examples include tantalum pentoxide and tin oxide.

  Further, as described above, the antireflection layer 130 is not necessarily limited to a single layer structure. For example, the antireflection layer 130 may be configured by laminating two or more porous materials. As an example of the antireflection layer 130 having a multilayer structure, porous structures made of different kinds of porous materials may be alternately laminated, or porous materials of the same kind and having different compositions may be used. A porous structure made of a porous material may be alternately laminated. In any case, there is no particular limitation as long as the average refractive index n of the entire antireflection layer 130 satisfies the above-described antireflection condition.

  Next, a method for forming the antireflection layer 130 will be described. Hereinafter, a method of forming a metal oxide film using metal oxide particles (hollow silica particles) as the antireflection layer 130 will be described. In addition, although a hollow silica particle can be manufactured by removing the core of a core-shell type fine particle as shown below, it is not restricted to it.

  The core-shell type fine particles are produced, for example, by dispersing core fine particles as a core in a dispersion medium and then reacting a precursor as an outer shell. Examples of the core fine particles include those that dissolve, decompose, or sublime by heat, acid, or light, depending on the production method of the hollow silica particles. For example, thermally decomposable organic polymer particles such as surfactant micelles, water-soluble organic polymers, styrene resins, acrylic resins, and acid-soluble inorganic particles such as sodium aluminate, calcium carbonate, basic zinc carbonate, and zinc oxide Alternatively, metal chalcogenide semiconductors such as zinc sulfide and cadmium sulfide, and photodissolvable inorganic fine particles such as zinc oxide can be used. In addition, the mixture of 2 or more types chosen from these may be sufficient. Among these, workability and productivity when removing the core are good, and rapid aggregation of the hollow silica particles can be suppressed during the core removal, and a highly transparent metal oxide film can be obtained. Zinc oxide is preferred.

  The core fine particles may be synthesized by either a dry method such as a gas phase method or a wet method such as a liquid phase method, and may be a monodisperse or an aggregate. The size and shape of the core fine particles are not particularly limited, and are appropriately selected in consideration of the dissolution rate of the core fine particles, the size of the pores (hollow portion 132b) in the hollow silica particles, and the like.

  The dispersion medium is not particularly limited, and examples thereof include water, alcohols, ketones, esters, ethers, glycol ethers, nitrogen-containing compounds, and sulfur-containing compounds. The dispersion medium does not necessarily contain water, but considering that it can be used as it is in the case of hydrolysis / polycondensation of the precursor as the outer shell, the dispersion medium is water alone or a mixed solvent of water and an organic solvent. Is preferred.

  The dispersion of the core fine particles in the dispersion medium is preferably performed by adding a dispersant and peptizing with a dispersing machine such as a ball mill, a bead mill, a sand mill, a homomixer, or a paint shaker. A hydrolysis catalyst such as acid or alkali is added to the dispersion of the core fine particles, and a precursor which becomes an outer shell is reacted at a pH of 8 or higher, for example. Thereby, an outer shell is formed on the surface of the core fine particles, and core-shell type fine particles are obtained. Examples of the precursor serving as the outer shell include one or a mixture of two or more selected from silicic acid, silicate, and alkoxide silicate, and may be a hydrolyzate or polymer thereof.

  In order to shorten the formation time of the outer shell, the pH during mixing of the core fine particle dispersion is preferably 9 to 11, and the temperature is preferably 20 ° C to 100 ° C. In order to increase the ionic strength and facilitate the formation of the outer shell, the core fine particle dispersion may be added with an electrolyte such as magnesium hydroxide, and the pH may be adjusted with these electrolytes.

Thereafter, for example, the core fine particles in the core-shell type fine particles are dissolved to form hollow silica particles. The core fine particles dissolve as ions, for example, at pH 8 or lower. When the core fine particles are ZnO fine particles, they are dissolved as Zn ²⁺ ions. The core fine particles can be dissolved by adding an acid or using an acidic cation exchange resin. According to the acidic cation exchange resin, since the dissolution of the core fine particles proceeds slowly, it is possible to suppress a rapid increase in ion concentration and to suppress rapid aggregation of the hollow silica particles. When agglomeration occurs rapidly, the aggregated particle diameter becomes too large, and the transparency of the metal oxide film may be reduced.

The acidic cation exchange resin preferably dissolves at least the core fine particles, and the dispersion has a pH of 8 or less, preferably 6 or less. Here, the acidity of the acidic cation exchange resin is determined by the functional group, and includes —SO ₃ H group for strong acidity and —COOH group for weak acidity. The addition amount of the acidic cation exchange resin is preferably in a range where the total exchange capacity is larger than at least the amount of ions such as Zn ²⁺ generated. The resin amount is preferably in the range of 1.1 to 5 times the required amount. There is a tendency that the dissolution rate of the core fine particles increases as the amount of the acidic cation exchange resin added increases.

  The dissolution temperature is not particularly limited, and the dissolution reaction basically proceeds even at room temperature. A higher temperature is preferable for increasing the diffusion rate of dissolution reaction and dissolved ions, for example, preferably 10 ° C to 100 ° C, more preferably 20 ° C to 80 ° C. After dissolution of the core fine particles, the dispersion of the hollow silica particles can be obtained by separating the cation exchange resin by solid-liquid separation operation such as filtration.

  Thereafter, a dispersion of hollow silica particles and a precursor as a matrix component are mixed to prepare a coating liquid that is applied to the surface of the transparent substrate 140. As for the solid content conversion amount of the precursor used as a matrix component, 0.05-15 times is preferable with respect to the mass of a hollow silica particle. By setting such a ratio, a metal oxide film (antireflection layer 130) having a good porous structure and high hardness can be formed.

  Examples of the precursor used as the matrix component include metal alkoxides of metals contained in the matrix component and / or hydrolyzed polycondensates thereof. As the metal alkoxide, silicate silicate is preferable, and is selected from, for example, silicate alkoxide having a fluorine-containing functional group such as perfluoropolyether group and / or perfluoroalkyl group, vinyl group and epoxy group in addition to ethyl silicate. Silicate alkoxides containing one or more functional groups may be used.

  Examples of the silicate alkoxide containing a perfluoropolyether group include perfluoropolyether triethoxysilane, and examples of the silicate alkoxide containing a perfluoroalkyl group include perfluoroethyltriethoxysilane, vinyl Examples of the silicate alkoxide containing a group include vinyltrimethoxysilane and vinyltriethoxysilane. Examples of the silicate alkoxide containing an epoxy group include 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3 -Glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, etc. are mentioned.

  Further, when an organic resin is used as a part of the matrix component, an ultraviolet curable organic resin is preferable, and examples thereof include an acrylic resin, a urethane acrylate resin, an epoxy acrylate resin, a polyester acrylate, a polyether acrylate, an epoxy resin, and a silicone resin. It is done.

The coating liquid can contain a surfactant for improving the wettability to the coating surface in addition to the hollow silica particles and the precursor of the matrix component. As the surfactant, any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant can be used. As the surfactant, —CH ₂ CH ₂ O—, —SO ₂ —, —NR— (R is a hydrogen atom or an organic group), —NH ₂ —, —SO ₃ Y, —COOY (Y is a hydrogen atom, Nonionic surfactants having a structural unit of sodium atom, potassium atom or ammonium ion are preferred.

  Nonionic surfactants include, for example, alkyl polyoxyethylene ether, alkyl polyoxyethylene-polypropylene ether, fatty acid polyoxyethylene ester, fatty acid polyoxyethylene sorbitan ester, fatty acid polyoxyethylene sorbitol ester, alkyl polyoxyethylene amine , Alkyl polyoxyethylene amide, polyether-modified silicone surfactants, and the like.

  The coating liquid can contain various additives as required in addition to the surfactant. For example, one selected from coloring, conductivity, polarization, ultraviolet shielding, infrared shielding, antifouling, antifogging, photocatalyst, antibacterial, phosphorescent, battery, refractive index control, water repellency, oil repellency, fingerprint removal, slipperiness, etc. What gives 2 or more types of functions may be included.

  Application of the coating liquid is, for example, roller coating, hand coating, brush coating, dipping, spin coating, dip coating, coating by various printing methods, curtain flow, bar coating, die coating, gravure coating, micro gravure coating, reverse coating, Roll coating, flow coating, spray coating, ink jet, dip coating or the like can be used.

  After coating, the antireflection layer 130 made of a metal oxide film having a porous structure can be formed by drying the coating film. Drying only needs to be able to remove the solvent and convert the precursor into a matrix component. For example, it may be held at room temperature to about 200 ° C., but in order to make it stronger, 500 ° C. to 700 ° C. for 1 minute to Heat treatment for about 60 minutes is preferable.

  Moreover, you may perform irradiation by an ultraviolet-ray, an electron beam, etc. as needed, for example, in order to raise mechanical strength. Furthermore, in order to improve adhesion, discharge treatment such as plasma treatment, corona treatment, UV treatment, ozone treatment, chemical treatment such as water, acid or alkali, or physical treatment using an abrasive can be performed.

  In addition, in the above-described production method, except for a portion using water alone or a mixed solvent of water and an organic solvent as a dispersion medium for core-shell type fine particles, it can be applied to metal oxide fine particles in general other than hollow silica particles. is there. The method for producing core-shell type fine particles can be applied to all hollow particles. Further, examples of matrix components, imparting functions to the coating liquid, and drying methods of the coating liquid are applicable to all porous materials having a structure in which particles are bonded.

  Next, a method for forming the antireflection layer 130 (metal oxide film) having a porous structure using a pore-forming substance will be described. In the example shown below, a metal alkoxide and / or hydrolyzed polycondensate thereof contained in a matrix component (in this example, the structure 131a) is used as a solvent to form pores in a porous structure. A particulate organic material is added to obtain a coating solution. Examples of the organic substance include acrylic resin, urethane acrylate resin, epoxy acrylate resin, polyester acrylate, polyether acrylate, epoxy resin, silicone resin, cellulose resin, and styrene resin. The coating liquid may contain various additives such as the above-described surfactants as necessary.

  Then, after apply | coating a coating liquid to the surface of the transparent base material 140 and making it dry, it bakes at the temperature of 200 to 700 degreeC. By this firing, particulate organic substances can be vaporized and removed. Thereby, the void | hole 132a is formed in the position of particulate organic substance, and the antireflection layer 130 which consists of a metal oxide film which has a porous structure can be formed.

  Further, as another method, a dispersion liquid in which hollow particles such as hollow silica particles produced by the above production method or a production method different from the above is dispersed in an organic solvent is applied to the surface of the transparent substrate 140 and applied. The antireflection layer 130 having a porous structure can be formed by drying the dispersion. After preparing a coating liquid in which hollow particles are dispersed in a transparent resin binder instead of an organic solvent and applying it to the surface of the transparent substrate 140, the transparent resin of the binder is cured by ultraviolet rays or heat to obtain a porous structure The antireflection layer 130 may be obtained. Examples of hollow silica particles having a primary particle size of 100 nm or less include, for example, Suriria (registered trademark) manufactured by JGC Catalysts and Chemicals, Silinax (registered trademark) manufactured by Nittetsu Mining Co., Ltd., and Nanoballoon (registered trademark) manufactured by Grandex Corporation. Etc. may be used. When a transparent resin binder is used, the transparent resin used for the binder is preferably as low as possible in order to reduce the amount of hollow particles used and realize the antireflective layer 130 having a low refractive index. For example, an amorphous fluororesin having a refractive index of 1.34 (for example, Cytop (registered trademark) manufactured by Asahi Glass Co., Ltd.) is preferable.

Next, the wire grid 110 will be described. Although the material of each metal fine wire 111 which comprises the wire grid 110 is not specifically limited, Silver (Ag), aluminum (Al), etc. which show a high reflectance with respect to the light of a visible wavelength range and have high electrical conductivity are preferable. That is, the optical constants of the wire grid 110 (n _w: refractive index, k _w: extinction coefficient) at a value smaller than the refractive index n _w is 1 is the extinction coefficient k _w Gayori larger such metal materials are preferred . For example, since the use of the silver is a metal material having a refractive index relatively small in the visible wavelength range, high P-polarized light transmittance (hereinafter, represented by T _P) is obtained, preferably. Further, the use of aluminum as the metal material extinction coefficient is relatively large in the visible wavelength range, S-polarized light transmittance (hereinafter, represented by T _S) to reduce the high extinction ratio T _{P /} T _S is obtained Therefore, it is preferable.

  When using silver, adding about 1% of a metal such as palladium (Pd) and alloying (for example, APC) improves heat resistance and deterioration over time in a high-temperature and high-humidity environment. preferable. Regarding the effect of alloying element addition on the corrosion resistance of silver thin films, see, for example, the document “Takashi Onishi et al.,“ Effect of alloying element addition on the corrosion resistance of silver thin films ”, Kobe Steel Technical Report Vol.52 No.2, September 2002”. It is described in. In order to improve the oxidation resistance without reducing the reflectivity with respect to silver, 0.3 to 1.5 atomic weight of copper (Cu), gold (Au), iridium (Ir), palladium (Pd), etc. % Added alloy is effective. An alloy to which zinc (Zn), tin (Sn) or the like is added in an amount of about 2 atomic% is effective for improving the sulfidation resistance. An alloy to which gold (Au), platinum (Pt), or palladium (Pd) is added is effective for improving NaCl resistance. Further, silver-neodymium-copper (Ag-Nd-Cu) -based, silver-gold-copper (Ag-Au-Cu) -based, silver-bismuth (Ag-Bi) -based alloys, and the like can also be used.

The height of the wire grid 110, that is, the thickness t of each thin metal wire 111, a required value is determined from the desired polarization separation performance. For example, when the transmittance T _s of incident light of S-polarized light is 1% or less, good polarization separation performance can be obtained if the thickness t of the thin metal wire 111 is 30 nm or more. If the fine metal wire 111 is too thin, light transmission through the fine metal wire 111 cannot be ignored, and the polarization separation performance is degraded. On the other hand, if the thin metal wire 111 is too thick, the P-polarized light transmittance _TP and the S-polarized light reflectance R _s are lowered.

  When the metal thin wire 111 is formed of silver or an alloy thereof, the thickness t is preferably about 100 nm to 250 nm. In addition, when the adhesive strength at the interface between the fine metal wire 111 and the antireflection layer 130 is low, in order to improve the adhesion to the antireflection layer 130, chromium is used as an adhesion layer between the fine metal wire 111 and the antireflection layer 130. A metal film such as Cr or a metal oxide film may be formed with a thickness of 10 nm or less that does not affect the optical characteristics.

For example, the pitch Pi of the wire grid 110 may be a value such that the maximum resonance wavelength λ _res-max when incident at 0 ° is equal to or less than the wavelength of incident light. For example, if the filler 120 in the gap 120, that is, the atmosphere around the wire grid 110 is air (refractive index n ₁ = 1), the visibility is high if the shortest wavelength of incident light is estimated to be about 430 nm in the visible wavelength range. Since the visible wavelength range can be covered and there is no problem as an optical element for visible light, the pitch Pi may be 400 nm or less. Furthermore, the pitch Pi is more preferably 200 nm or less in order to maintain high P-polarized light transmittance and S-polarized light reflectance without generating diffracted light even for obliquely incident light other than 0 °. As the pitch Pi decreases, it becomes technically difficult to perform fine processing on a metal material. Therefore, in order to obtain stable polarization separation performance, Pi = 150 nm to 200 nm is more preferable.

  Since the wire width w of the wire grid 110, that is, the width of each metal thin wire 111 (length in the short direction) is about half of the pitch Pi (w = 0.5 Pi), the polarization separation performance is good. A value satisfying 0.3 Pi ≦ w ≦ 0.7 Pi is preferable.

  The cross-sectional shape of the fine metal wire 111 is not particularly limited, and may be a square, a rectangle, a trapezoid, a triangle, an ellipse, or other various shapes. Here, when the cross-sectional shape is a cross-sectional shape other than a square or a rectangle, the wire width w corresponds to the average value of the widths of the fine metal wires 110 in the height direction of the wire cross-sectional shape.

  The wire grid 110 can be formed by various manufacturing methods. In the case of a wire grid type polarizer in which light in the visible wavelength range is incident, for example, as shown in FIG. 4, a metal (including an alloy) that is a material of the metal thin wire 111 is formed on the antireflection layer 130. The thin metal film 601 may be formed with a predetermined thickness (FIG. 4A), and then finely processed to obtain each thin metal wire 111. Note that the thickness of the metal film is set to a thickness that satisfies at least the height t of the thin metal wire 111.

  Specifically, a resin resist 602 processed into a concavo-convex shape with a pitch corresponding to the pitch Pi of the wire grid 110 is formed as a mask on the metal film 601 (FIG. 4B), and then the metal film 601 is etched. What is necessary is just to process (FIG.4 (c)). For the patterning of the resin resist 602, an interference exposure method using an extreme ultraviolet laser and a manufacturing method using electron beam lithography can be generally used. As another technique for producing a resin resist, an ultraviolet curable resin or a thermosetting resin is formed by using a mold having a concave cross section formed by inverting the convex shape of the cross section formed by each thin metal wire 111 of the wire grid. And a method of patterning. Next, using the patterned resin resist 602 as a mask, the metal film 601 is etched to form a wire grid 110 composed of a plurality of fine metal wires 111. Here, dry etching conditions suitable for resin and metal microfabrication, or metal film solution and wet etching conditions are appropriately adjusted. Dry etching, metal film dissolution, and wet etching are all methods for producing a wire grid 110 having a desired pitch Pi, wire width w, and thickness t by etching.

  Further, another manufacturing method of the wire grid 110 will be described below. On the antireflection layer 130, as shown in FIG. 5A, the wire grid 110 has a concave cross-sectional shape that matches the shape of the fine metal wire 111 at a position where the fine metal wire 111 is formed. The patterned resin resist 603 is formed so that the depth of each concave shape is equal to or greater than the thickness t of the thin metal wire 111. For patterning the resin resist 603, a method similar to that for the resin resist 602 may be used. Here, when the resin resist remains also at the concave position of the resin resist 603 on the antireflection layer 130, reactive dry etching using a gas in which oxygen gas is mixed with argon is performed, and the remaining resin resist is removed. Exclude. As a result, an opening 6031 corresponding to the shape (in particular, the width and height) of the thin metal wire 111 is provided on the surface of the antireflection layer 130. Next, a metal film 604 serving as a material for the fine metal wires 111 of the wire grid 110 is formed on the entire surface including the concave position of the patterned resin resist so as to have a predetermined film thickness t (FIG. 5B). ). Finally, the resin resist 603 is peeled off (lifted off) with an organic solvent to produce a wire grid 110 made of a plurality of fine metal wires 111 having a desired pitch Pi, wire width w, and thickness t on the antireflection layer 130. (FIG. 5C).

In the above embodiment, the case where the filler in the gap 120 of the wire grid 110 is air (refractive index n ₁ = 1.0) has been described as an example. However, the filler in the gap 120 is other than air. Also good. Even in such a case, the antireflection layer 130 only needs to be configured to satisfy the above-described antireflection condition with respect to the interface of the gap 120 with the filler. For example, the gap 120 may be filled with a porous material used for the material of the antireflection layer 130. In that case, let n _{1 be} the refractive index of air, which is a medium located in the upper layer of the filler, and use the filler as a porous material having a refractive index n defined by equation (2) or lower. That's fine.

  The filler in the gap 120 of the wire grid 110 is preferably a low refractive index material so that the antireflection conditions can be easily satisfied at the interface of each medium. In addition, a filler is not limited to the porous material used for the material of the antireflection layer 130, For example, another porous material may be sufficient. If the gap 120 of the wire grid 110 is filled with a solid material such as a porous material layer, it is useful for preventing deformation and damage of the fine metal wires 111 and reducing the area where the fine metal wires 111 are in contact with the outside air. Durability can be improved.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described. Hereinafter, a light source module using the wire grid polarizer according to the present invention will be described. FIG. 6 is a schematic cross-sectional view showing an example of the light source module of the present embodiment. An LED light source 200a shown in FIG. 6 is an example in which the wire grid polarizer 100 of the first embodiment is combined with a surface-mounted LED light source. In an LED light source 200a shown in FIG. 6, an LED chip 220, which is a light emitting element, is mounted on a substrate 210 on which a lead frame or the like is mounted. Moreover, in this example, the base material 210 and the side wall part 230 form a container for filling a phosphor that converts the wavelength of light emitted from the LED chip 220. The container is filled with the phosphor 240, and at least a portion in contact with the phosphor 240 among the inner surfaces of the base material 210 and the side wall portion 230 constituting the container is covered with the reflecting member 250. ing. And the wire grid type polarizer 100 is being fixed to the upper end of the side wall part 230 so that the light emission surface of the fluorescent substance 240 with which the container was filled may be sealed. In FIG. 6, the electrode wiring of the LED chip 220 and the lead frame on the substrate 210 are not shown.

  For example, the phosphor 240 may be obtained by dispersing inorganic phosphor fine particle powder having a size of about 1 μm to 30 μm in a sealing resin such as a silicone resin or an epoxy resin.

For example, when a blue light emitting LED chip 220 (for example, an LED chip using GaInN) is used, a yellow LED is used as the phosphor 240 to form a white LED. For example, Y ₃ Al ₅ O ₁₂ : Ce (YAG: Ce for simple description) can be used as the yellow fluorescence. When an LED chip 220 that emits ultraviolet to violet light (for example, an LED chip using GaInN) is used, the phosphor 240 is a mixture of blue fluorescence and yellow fluorescence or a mixture of blue fluorescence, green fluorescence, and red phosphor. It becomes white LED by using. For example, (Sr, Ca, Ba) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu or Sr ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu can be used as the blue fluorescence (ultraviolet excitation phosphor). The green fluorescence is, for example, (Ba, Sr, Mg) ₂ SiO ₄ : Eu, Mn, Sr ₃ Si ₁₃ Al ₃ O ₂ N ₂₁ : Eu or 3 (Ba, Mg) O · 8Al ₂ O ₃ : Eu. , Mn, etc. can be used. The red fluorescence, for _{example, Sr 2 Si 7 Al 3 ON} 13: Eu and the composition _La 2 _O 2 S: Eu and the like can be used. There are other combinations of various LED chips and phosphors.

  For the container (base 210 and side wall 230), a resin molded product is advantageous in terms of cost. However, when the light output of the LED chip 220 is high, a material having high heat resistance and heat dissipation such as glass and ceramics is used. It is preferable to use it. In the example shown in FIG. 6, the base material 210 that is also the bottom surface portion of the container and the side wall portion 230 are separate members, but these may be an integrated container.

  When alumina ceramics is used as the material for the container, the reflectance in the visible wavelength region remains at about 75%. In such a case, a configuration including the above-described reflecting member 250 in order to obtain a higher reflectance is preferable.

  Since the light emission 301 of the LED chip 220 and the fluorescent light emission 302 of the phosphor 240 are diffused light, the portion that contacts the phosphor 240 (such as the base material 210 (including the lead frame) and the inner surface of the side wall portion 230) has high reflectance. By covering with the member which has, light can be efficiently radiate | emitted ahead (-Z direction of FIG. 6). For example, the reflecting member 250 may be a resin mixed with fine particles such as titanium oxide, alumina, and zinc oxide as a solid scattering material. If such a member is used, a reflectance of 80 to 90% with respect to visible wavelength light can be obtained. Further, when a silver-based member (a silver reflective film or the like) is used, a high reflectance of 90% or more can be obtained. It is also possible to form the container itself with a member having a high reflectance as described above.

  Further, for example, a glass frit (glass fine powder) having a large refractive index difference and a ceramic filler may be used as raw materials, and the container may be made of glass ceramics which is a composite of glass and ceramics by low-temperature firing. A specific example is GCHP (Glass-Ceramics Substrate for High-Power LED Lighting) manufactured by Asahi Glass. GCHP has a high reflectivity of about 95% in the visible wavelength region. If such a member is used, an LED light source with high light extraction efficiency can be realized without providing a separate reflecting member 250. Further, since there is no decrease in light extraction efficiency due to the deterioration of reflectance with time of the silver reflection film, there is also an effect that a stable emitted light amount can be obtained.

  For example, the surface of the lead frame is preferably subjected to silver or nickel plating having a high reflectance as the reflecting member 250.

  In the example shown in FIG. 6, the single LED chip 220 is mounted on the base 210, but a plurality of LED chips 220 may be mounted on the base 210 in order to increase the amount of emitted light.

  Moreover, you may apply | coat only to the front flat surface of the LED chip 220, without filling the fluorescent substance 240 into the whole container like the LED light source 200b shown in FIG. In the case of using the LED chip 220 that suppresses light emitted from the side surface of the chip and mainly emits light forward from the chip surface, the structure in which the phosphor 240 is provided only on the front flat surface of the LED chip 220 has a high light emission density. This is preferable because it can be maintained.

  In the case where the light emission 301 of the LED chip 220 and the fluorescence emission 302 of the phosphor 240 are randomly polarized, of the light incident on the wire grid polarizer 100, the P-polarized component having an electric field vector orthogonal to the longitudinal direction of the thin metal wire 111. The light becomes P-polarized light 303 that passes through the wire grid 110 and exits forward. On the other hand, of the light incident on the wire grid polarizer 100, the S-polarized light having the electric field vector in the longitudinal direction of the thin metal wire 111 is reflected by the wire grid 110 and re-enters the phosphor 240. It becomes light 304. Thereafter, the S-polarized light 304 is depolarized from the S-polarized light by light scattering due to the interaction with the phosphor fine particles in the phosphor 240, reflection from the base material 210, the side wall 230, or the reflecting member 250. Thus, the light is again converted into P-polarized light 305 incident on the wire grid polarizer 100. The P-polarized light 305 passes through the wire grid 110 and is emitted as it is. Note that some of the light 304 reflected by the wire grid 110 maintains S-polarized light. When the light 304 enters the wire grid polarizer 100 again while maintaining the S-polarized light, the light 304 is reflected by the wire grid 110 and re-enters the phosphor 240.

  That is, regardless of whether the light is the light emission 301 from the LED chip 220, the fluorescent light emission 302 from the phosphor 240, or the light 304 reflected by the wire grid 110 in the past, the wire grid type Of the light incident on the polarizer 100, the P-polarized light component is transmitted through the wire grid 110 and emitted to the outside. On the other hand, the light of the S polarization component is confined in the container until converted to P polarization. If the light of the S-polarized component becomes P-polarized light after being reflected and scattered in the container and is incident on the wire grid polarizer 100 again, it passes through the wire grid 110 and is emitted to the outside. Is done. Therefore, P-polarized light (light 303 and light 305) is efficiently obtained by using the phosphor 240 that absorbs little light in the visible wavelength region and the wire grid polarizer 100 having high P-polarized light transmittance and high S-polarized light reflectance. ) Is obtained.

For example, when the extraction efficiency I _{p_out} of P-polarized light emitted from the LED light source 200a is expressed as a light amount ratio with respect to the extraction efficiency I _{p_nowg} of P-polarized light of a conventional LED light source that does not use the wire grid polarizer 100, (3). In Expression (3), I _{p_in} represents the P-polarized component ratio in the light emission 301 of the LED chip 220 and the fluorescence emission 302 of the phosphor 240. Further, T _{p_wg} and R _{s_wg} represent the P-polarized light transmittance and the S-polarized light reflectance of the wire grid polarizer 100, respectively. _{R_pkg} represents the reflectance at the interface between the phosphor 240 and the container. _{R_pkg} corresponds to the reflectance in consideration of the area of the reflecting member 250 and the LED chip 220 and the reflectance thereof. _{T_ph} represents the transmittance of the phosphor. _{T_ph} may be 100% minus the light absorption rate of the phosphor 240. Further, η _p represents the probability that the reflected light 304 (substantially S-polarized component light) is converted to P-polarized light due to the light scattering of the phosphor fine particles and the light scattering of the reflecting member 250.

_{Ip_out} = [ _{Ip_in} * _{Tp_wg} / {1- _{Rs_wg} * _{R_pkg} * _{T_ph} * (eta) _p }] / _{Ip_nowg}
... Formula (3)

Specific examples are shown below. I _{p_in} and I _{p_nowg} may be set to 0.5 (50%), for example, when the light emission 301 from the LED chip 220 and the fluorescent light emission 302 from the phosphor 240 are completely random polarized light. In addition, η _p is used when the light re-entering the wire grid polarizer is depolarized and becomes completely random polarized light due to, for example, reflection at the container interface and light scattering at the phosphor fine particles and the reflecting member. Is 0.5 (50%). Under these assumptions, for example, I _{p_in} = 0.5 (50%), T _{p_wg} = 0.95 (95%), R _{s_wg} = 0.98 (98%), _{R_pkg} = 0.85 (85 _{%), T _ph = 0.98 (} 98%), when to be _{η p = 0.5 (50%)} , the I p_out = 1.61.

  That is, in the case of a conventional LED light source equipped with an LED chip 220 that emits randomly polarized light, the emitted light of the P-polarized component obtained from the LED light source is 50% of the emitted light, but according to the LED light source 200a, the wire By providing the grid-type polarizer 100, about 80% of the P-polarized light component that is about 1.61 times that of the conventional LED light source can be obtained.

Furthermore, as a comparison object, when a conventional wire grid polarizer is used instead of the wire grid polarizer 100, T _{p_wg} = 0.9 (90%) and R _{s_wg} = 0.98 (98%) are estimated. Even so, I _{p_out} = 1.52, and only 76% of P-polarized component outgoing light is obtained, which is even lower in the blue wavelength region of 480 nm or less. As described above, if the wire grid polarizer of the present invention, which is provided with the antireflection layer 130 and has not only high S-polarized reflectance but also high P-polarized transmittance, is used for light extraction of an LED light source, P An LED light source that can efficiently extract the light of the polarization component is obtained.

  Next, some usage examples of the LED light source of this embodiment will be shown. The LED light source of the present embodiment is suitable for a backlight of a liquid crystal display device that converts light from a backlight into linearly polarized light using a polarizing plate and enters the liquid crystal layer, for example. Since most of the light emitted from the LED light source can be converted to P-polarized component light, the absorbed polarized component by the polarizing plate can be reduced. Therefore, it is possible to reduce the power consumption of the LED light source necessary for obtaining the same display luminance, to reduce the heat generated by the light absorption of the polarizing plate, and to reduce the cost for cooling the liquid crystal display device.

  Further, even when the LED light source of the present embodiment is used as a light source of a projection display device using a small transmissive liquid crystal display element or a reflective liquid crystal display element, for example, the same effect can be obtained.

  Further, for example, the LED light source of the present embodiment is also suitable as a light source for a projector or a light source for indoor lighting. In such a case, when the light emitted from the LED light source of the present embodiment is obliquely incident on a transparent member interface such as a screen or a window glass, it becomes P-polarized incident light having a low reflectance at the interface. It is preferable to arrange an LED light source. Thereby, the intensity | strength of the S-polarized interface reflected light used as stray light, such as a reflection, can be reduced, and visibility improves.

  FIG. 8 is a schematic cross-sectional view showing another example of the LED light source of the present embodiment. An LED light source 200c illustrated in FIG. 8 is an example of an LED light source having a configuration called a “remote phosphor” in which an LED chip 220, which is a light emitting element serving as a light source, and a phosphor are arranged apart from each other. More specifically, in the LED light source 200c, the hollow portion 260 of the container is not filled with the phosphor to form an atmospheric layer, and the transparent substrate of the wire grid polarizer 100c for light extraction is formed with the phosphor. After forming the phosphor-containing substrate 270 as a substrate, the wire grid type polarizer 100c is arranged apart from the LED chip 220. In the LED light source 200c shown in FIG. 8, a dichroic mirror layer 280 is further formed on the surface of the phosphor-containing substrate 270 on the LED chip 220 side.

  By disposing the phosphor (more specifically, the phosphor-containing substrate 270) at a position away from the LED chip 220, the heat generated by the LED chip 220 does not directly affect the phosphor, and the fluorescence of the phosphor as the temperature rises. A decrease in luminous efficiency can be suppressed. Moreover, since the structure which reduces the fluorescence light emission from the fluorescent substance which injects into LED chip 220 is possible so that it may mention later, the heat_generation | fever of LED chip 220 accompanying fluorescence absorption can also be suppressed.

  The phosphor-containing substrate 270 is, for example, a form in which the phosphor is uniformly dispersed in a transparent substrate such as glass or resin, a form in which the phosphor is applied to the surface of the transparent substrate on the LED chip 220 side, or a phosphor Various configurations are possible, such as a configuration in which is held between two transparent substrates. FIGS. 9A and 9B are schematic configuration diagrams of a wire grid polarizer 100c showing an example of the phosphor-containing substrate 270. FIG. FIG. 9A shows an example of a wire grid polarizer 100c having a phosphor-containing substrate 270 configured to sandwich the phosphor 240 by two transparent substrates 271a and 271b. For example, the phosphor-containing substrate 270 includes a transparent substrate 271a such as glass on which one side is formed with the antireflection layer 130 and the wire grid 110, and a transparent substrate 271b such as glass on which one side is formed with the dichroic mirror layer 280. Further, the phosphor 240 may be configured to be sandwiched with a uniform thickness. FIG. 9B shows an example of a wire grid polarizer 100c having a phosphor-containing substrate 270 configured such that the phosphor 240 is coated on the surface of the transparent substrate 271 on the LED chip 220 side. For example, in the phosphor-containing substrate 270, the phosphor 240 is uniformly coated on the other surface of the transparent substrate 271 such as glass having the antireflection layer 130 and the wire grid 110 formed on one side thereof. A configuration in which a dichroic mirror layer 280 is formed on the surface may be employed.

  Here, materials other than the phosphor used for the phosphor-containing substrate 270 (for example, the materials of the transparent substrates 271, 271 a and 271 b) absorb light with respect to the emission wavelength of the LED chip 220 and the fluorescence emission wavelength of the phosphor. Those with less are preferred. In addition, the phosphor-containing substrate 270 preferably has a structure in which light scattering occurs inside and the polarization state changes. Further, in the optical path between the antireflection layer 130 and the dichroic mirror layer 280 in the wire grid polarizer 100c, a quarter wavelength plate for the visible wavelength region is disposed to actively change the polarization state. May be.

  The dichroic mirror layer 280 is an optical functional layer formed on the outermost surface of the phosphor-containing substrate 270 on the LED chip 220 side, that is, the surface in contact with the hollow portion 260, and includes the phosphor-containing substrate 270 and the hollow portion 260. At the interface, it has a back reflection preventing function for preventing the reflection of the light emission 301 of the LED chip 220 and a front reflection function for reflecting the fluorescent light emission 302 of the phosphor contained in the phosphor-containing substrate 270 at the same interface. . For example, the dichroic mirror layer 280 exhibits high transmission performance with respect to the emission wavelength of the LED chip 220 and also exhibits high reflection performance with respect to the fluorescence emission wavelength of the phosphor included in the phosphor-containing substrate 270. An optical multilayer film configured as described above is preferable.

  For example, an LED chip 220 whose emission wavelength range is 430 nm to 510 nm (blue) and a phosphor 240 such as YAG: Ce whose wavelength range of fluorescence emission is 510 nm to 670 nm (yellow) by a semiconductor material such as GaInN. Is used, the dichroic mirror layer 280 may be an optical multilayer film having a transmittance of 95% or more at a wavelength of 430 nm to 500 nm and a reflectance of 95% or more at a wavelength of 520 nm to 670 nm. Further, for example, an LED chip 220 having a light emission wavelength range of 350 nm to 400 nm (ultraviolet to purple) using a semiconductor material such as GaInN and a mixture of blue fluorescence and yellow fluorescence, or blue fluorescence, green fluorescence, and red phosphor. When using a phosphor 240 that generates fluorescence emission in the visible wavelength range of 430 nm to 670 nm by a mixture or the like, the dichroic mirror layer 280 has a transmittance of 95% or more at a wavelength of 350 nm to 410 nm and a reflectance of a wavelength of 430 nm to 670 nm. May be an optical multilayer film of 95% or more. The dichroic mirror layer 280 satisfying these conditions includes, for example, a high refractive index dielectric thin film and a low refractive index dielectric thin film, each having an optical film thickness of 20 to 60 layers alternately with the wavelength of incident light or less. It can be obtained by laminating to a degree. Since such an optical multilayer film is a design and manufacturing technique known to those skilled in the art, description thereof is omitted.

  In addition, since the phosphor-containing substrate 270 reduces light emitted from the side surface to the outside, the reflecting member that reflects the light emission 301 of the LED chip 220 and the fluorescent light emission 302 of the phosphor contained in the phosphor-containing substrate 270 also on the side surface. (Not shown) is preferably formed.

  The gas filling the hollow portion 260 in the container is preferably a gas that can efficiently dissipate heat generated from the LED chip 220 to the outside, such as air. It is more preferable that other members including the dichroic mirror layer 280 and the phosphor-containing substrate 270 also have high heat dissipation. In addition, you may fill the hollow part 260 in a container with transparent resin. In this case, since the heat generated by the LED chip 220 is directly transmitted to the phosphors in the phosphor-containing substrate 270, the cooling effect is reduced. However, the light emitted from the LED chip 220 is emitted from the LED chip 220 due to total reflection at the interface with the gas. Since the light that has not been emitted can be used, the light utilization efficiency is improved. In other words, the hollow portion 260 in the container may be optimally designed from the viewpoint of improving the light extraction efficiency of the LED chip and heat dissipation that suppresses the decrease in the fluorescence emission efficiency associated with the heat generation of the phosphor.

  In the LED light source 200c shown in FIG. 8, the light emission 301 of the LED chip 220 passes through the dichroic mirror layer 280 and enters the phosphor-containing substrate 270. At least a part of the light incident on the phosphor-containing substrate 270 is converted into light (fluorescence emission 302) having a fluorescence emission wavelength of the phosphor by exciting the phosphor in the phosphor-containing substrate 270. At this time, a part of the light emission 301 of the LED chip 220 and a part of the fluorescent light emission 302 of the phosphor incident on the phosphor-containing substrate 270 become light traveling forward in the phosphor-containing substrate 270. The light passes through the antireflection layer 130 and enters the wire grid 110. Of the light incident on the wire grid 110, a P-polarized component having an electric field vector orthogonal to the longitudinal direction of the thin metal wire 111 passes through the wire grid 110 and is emitted as P-polarized light 303. On the other hand, of the light incident on the wire grid 110, the S-polarized component having the electric field vector in the longitudinal direction of the thin metal wire 111 is reflected by the wire grid 110 and re-enters the phosphor-containing substrate 270. Become. The light 304 that is the reflected light from the wire grid 110 is then depolarized from the S-polarized light by light scattering due to interaction with the phosphor fine particles in the phosphor-containing substrate 270, reflection by the dichroic mirror layer 280, and the like. The P-polarized light 305 incident on the antireflection layer 130 and the wire grid 110 again is transmitted through the wire grid 110 and emitted forward.

  In the case of this example, the light of the P-polarized component of the light emission 301 and fluorescent light emission 302 traveling forward is transmitted through the wire grid 110 and emitted to the outside as viewed from the wire grid polarizer 100. On the other hand, most of the light of the S polarization component (for example, 98% or more) is confined in the phosphor-containing substrate 270 until it is converted to P polarization. Note that the light of the S-polarized component becomes light of the P-polarized component that travels forward through reflection in the phosphor-containing substrate 270, passes through the wire grid 110, and is emitted to the outside. Therefore, like the wire grid polarizer 100c, it has a phosphor that absorbs little light in the visible wavelength range, and has high P-polarized light transmittance and S-polarized light reflectance at the interface between the wire grid 110 and the phosphor-containing substrate 270. By using a wire grid polarizer, an LED light source that efficiently emits P-polarized light (light 303 and light 305) can be obtained.

Embodiment 3. FIG.
Next, a third embodiment of the present invention will be described. Below, a projection type display apparatus provided with the polarization beam splitter using the wire grid type polarizer mentioned above is explained. FIG. 10 is a configuration diagram illustrating an example of a projection display device according to the present embodiment. A projection display device 400 shown in FIG. 10 includes an RGB light source unit 410, a wire grid polarizer 420 that functions as a polarization beam splitter, an RGB-compatible quarter-wave plate 430, and a MEMS scanner 440.

  The RGB light source unit 410 is a light source unit that multiplexes and emits linearly polarized light of three colors of blue (B), green (G), and red (R) on the same optical axis. The RGB light source unit 410 includes, for example, three laser light sources corresponding to each of blue (B), green (G), and red (R), and linearly polarized light emitted from these laser light sources on a predetermined optical path. And a light source optical system for guiding. Here, blue (B) has a wavelength in the range of 450 nm ± 10 nm, that is, 440 nm to 460 nm, green (G) has a wavelength in the range of 520 nm ± 15 nm, that is, 505 nm to 535 nm, and red (R) has a wavelength in the range of 638 nm ± 15 nm, that is, 623 nm to 653 nm.

  The wire grid polarizer 420 of this embodiment is basically the same as the wire grid polarizer 100 of the first embodiment. Note that the wire grid polarizer 420 functions as a polarization beam splitter in the projection display device 400 as described above. That is, it has a function of branching incident RGB light by its polarization component. More specifically, it reflects the S-polarized light component of the incident RGB light and transmits the P-polarized light component.

  The quarter-wave plate 430 is reflected after the S-polarized RGB light reflected by the wire grid polarizer 420 is incident on the MEMS scanner 440 and passes through the quarter-wave plate 430 in a reciprocating manner. What is necessary is just to produce the phase difference of 1/4 wavelength so that it may convert into RGB light.

  The MEMS scanner 440 is a micromechanical mirror or the like formed by MEMS technology, and is used for scanning light on the display surface of the screen 450. Instead of the MEMS scanner 440, a configuration may be provided that includes a first scan mirror that scans light in the horizontal direction and a second scan mirror that scans light in the vertical direction. Moreover, a galvanometer mirror may be used for the first scan mirror and the second scan mirror, and one mirror may be a galvanometer mirror and the other mirror may be a micromechanical mirror.

  There are various configurations of a projection type display device using a general polarization beam splitter, and some examples are described in, for example, Japanese Patent No. 4856758. The projection display device 400 of the present embodiment is not particularly limited with respect to the components other than the polarization beam splitter.

  In the projection display apparatus 400, RGB linearly polarized light (light 501 in FIG. 10) emitted from the RGB light source unit 410 is S-polarized with respect to the wire grid polarizer 420 (the electric field vector is in the Y-axis direction in FIG. 10). The RGB light source unit 410 and the wire grid type polarizer 420 are arranged so that the light becomes the following light. As a result, most of the light 501 emitted from the RGB light source unit 410 (for example, 98% or more) is reflected by the wire grid 110 of the wire grid polarizer 420 and enters the quarter-wave plate 430 ( Light 502 in FIG. The linearly polarized light 502 incident on the quarter-wave plate 430 is converted into circularly polarized light and then incident on the MEMS scanner 440. The MEMS scanner 440 performs two-axis rotational vibration centering on an axis (Y ′ axis) perpendicular to the paper surface and an axis (X ′ axis) in the paper surface in response to an electric signal of a drive power source (not shown). , Reflect the incident light. The light reflected by the MEMS scanner 440 (circularly polarized light corresponding to RGB) is again converted to linearly polarized light by passing through the quarter-wave plate 430, and P-polarized light 503 in the wire grid 110. And enters the wire grid polarizer 420. The P-polarized light incident on the wire grid polarizer 420 passes through the wire grid 110 and scans on the screen 450 in the horizontal and vertical directions (light 503 in FIG. 10).

  The light 503 is driven to be lit at high speed in accordance with a video signal input from the outside in synchronization with the scanning signal of the MEMS scanner 440. As a result, a scanned color image of ± Φh ° in the horizontal direction on the screen 450 and ± Φv ° in the vertical direction is generated. Note that the wire grid polarizer 420 and the quarter wavelength plate 430 may be element sizes having at least an effective area in the region irradiated with the light 503 of the scanning color image.

  By the way, most of the polarization beam splitters used in the projection display device utilize P-polarized light transmission and S-polarized light reflection by the optical multilayer film. For example, when the polarizing beam splitter is of a flat plate type, that is, when an optical multilayer film having an S-polarized reflection function and a P-polarized light transmission function is formed on a flat plate such as glass, it has a wide wavelength band of RGB. It was difficult to realize high S-polarized reflection and P-polarized light transmission characteristics (Problem 1). For example, when the polarizing beam splitter has a structure in which an optical multilayer film is formed on one inclined surface of two right-angled isosceles triangular prism glasses and the inclined surfaces are bonded together, air parallel to the reflecting surface of the MEMS scanner 440 is used. There is a problem that stray light noise is generated due to residual reflection due to the interface between glass and glass remaining as fixed bright spots on the screen (Problem 2).

  The projection display apparatus 400 of the present embodiment solves such a conventional problem by using a wire grid polarizer 420 as a polarization beam splitter. In the present embodiment, the wire grid polarizer 420 has a region (hereinafter referred to as a light beam area) in which the light 501 from the RGB light source unit 410 (light flux diameter of about 1 mm) is incident on the wire grid polarizer 420. The wire grid 110 is formed limited to a range to be covered (for example, in an area of 1 to 1.5 times the beam diameter). Note that the wire grid 110 is not formed in a region where the light 501 is not incident (for example, a peripheral region). The antireflection layer 130 is preferably formed on the entire surface.

  For example, the wire grid polarizer 420 has a diameter of 1.5 mm centered on the optical axis of the light 501 emitted from the RGB light source unit 410 on the antireflection layer 130 formed on the entire surface of the transparent substrate 140. Only the wire grid 110 may be formed. Further, for example, the wire grid 110 is within a range of 1.5 mm in width around the optical axis in the X-axis direction corresponding to the horizontal direction of scanning on the screen 450, and in the Y-axis direction corresponding to the vertical direction of scanning on the screen 450. You may form only in the range equivalent to the light beam width scanned with the MEMS scanner 440. FIG.

  By limiting the formation range of the wire grid 110 in this way, it is also possible for the S-polarized light 501 in the wide wavelength band from the RGB light source unit 410 and the P-polarized light 503 in the wide incident angle range from the MEMS scanner 440. It can be used as a highly efficient polarizing beam splitter.

  Hereinafter, a specific example will be described with reference to FIG. For example, it is assumed that light emitted from the RGB light source unit 410 is RGB laser light having a light beam diameter of about 1 mm. Further, the light is linearly polarized light in a direction perpendicular to the paper surface (Y-axis direction in FIG. 10) and travels in a plane parallel to the paper surface (in the XZ plane in FIG. 10) to prevent reflection. It is assumed that the incident light is incident on the wire grid 110 formed only in a partial region on the surface of the layer 130 as an S-polarized light with an incident angle θ = 35 ° (see the light 501 in FIG. 10).

  In the above example, most of the light 501 incident on the region where the wire grid 110 is formed is reflected according to the S-polarized reflectance of the wire grid 110 (for example, 98% or more), and the quarter-wave plate 430 is reflected. (Light 502 in FIG. 10). Thereafter, the light 502 is converted into circularly polarized light by the quarter wavelength plate 430 and is incident on the MEMS scanner 440. Thereafter, the circularly polarized light is reflected by the MEMS scanner 440 and converted into linearly polarized light by the quarter-wave plate 430 to become P-polarized light 503 in the wire grid 110, and a wire grid polarizer. Re-enters 420.

  At this time, the incident angle and the incident position of the P-polarized light 503 incident on the wire grid polarizer 420 change according to the mirror rotation angle of the MEMS scanner 440. Here, for example, the incident angle θ of the light 503 to the wire grid polarizer 420 is 35 ° ± in the direction parallel to the paper surface (X-axis direction in FIG. 10) according to the mirror rotation angle of the MEMS scanner 440. 10 changes in the range of 24 ° (for example, θ = 35 ° + 24 ° = 59 ° for the light 503a, θ = 35 ° −24 ° = 11 ° for the light 503c, and the like) Direction) in a range of 0 ° ± 16 °. Even in such a case, if the region where the wire grid 110 is formed is limited to a diameter of 1.5 mm from the position where the light 501 is incident, for example, the light 503 incident on the wire grid 110 is incident. The change in angle falls within 35 ° ± 5 ° in the direction parallel to the paper surface and within 0 ° ± 5 ° in the direction perpendicular to the paper surface. Thus, since the incident angle θ of the light 503b incident on the wire grid 110 can be reduced and the angle range of θ can be narrowed, most of the P-polarized light incident on the wire grid 110 (for example, 90% or more) is transmitted. it can.

  On the other hand, among the light 503 incident on the wire grid polarizer 420, the light that enters the region where the wire grid 110 is not formed (for example, the light 503 a, 503 c, etc.) Since it functions as an antireflection film that suppresses interface reflection with the material 140, most (for example, 95% or more) can pass through the wire grid polarizer 420.

  Moreover, the projection type display apparatus 400 of this embodiment has also solved the above-described problem 2. That is, according to the projection display apparatus 400 of the present embodiment, the fixed bright spot that becomes the stray light noise does not occur for the following reason.

  In the projection display device 400 of the present embodiment, the reflection surface of the MEMS scanner 440 is inclined by driving, and the inclination angle is 0 ± 12 ° in the direction parallel to the paper surface (X′-axis direction in FIG. 10), and on the paper surface. It is about 0 ° ± 8 ° in the vertical direction (Y′-axis direction in FIG. 10). For this reason, the inclination angle at the interface between the wire grid polarizer 420 and air is not equal. That is, since the reflection surface of the MEMS scanner 440 and the surface of the transparent base material 140 of the wire grid polarizer 420 are not in a parallel relationship, the residual reflected light at the interface is projected as a fixed bright spot on the screen. There is no.

  In addition, as a more preferable form, the quarter wave plate 430 is formed so that the reflected light from the air interface does not become a fixed bright spot on the screen. It is inclined with respect to a plane perpendicular to the plane (X′Y ′ plane in FIG. 10) so as not to coincide with the range of 0 ° ± 8 ° which is the scanning angle in the vertical direction. More specifically, the quarter-wave plate is disposed so that the surface of the quarter-wave plate 430 is inclined with respect to the Y ′ axis. For example, the tilt angle is greater than 8 ° with respect to the Y axis ′ with the X ′ axis as the rotation center. By doing so, it is possible to prevent light reflected by the air interface of the quarter-wave plate 430 from being projected on the screen.

  As described above, according to the present embodiment, a projection image free from unnecessary stray light noise can be obtained, and a small projection display device with high light utilization efficiency can be provided.

  In the above description, the case where the wire grid polarizer 420 is designed so as to have the best characteristics at an incident angle θ = 35 ° has been described as an example. There may be. For example, it may be 45 °. In order to maintain the characteristics even at an incident angle of 45 °, the fabrication becomes difficult in terms of microfabrication, but the pitch Pi of the wire grid 110 may be narrowed.

FIG. 11 shows the incident angle dependence of the S-polarized light reflectance R _s and the P-polarized light transmittance T _p of the wire grid polarizer 420 when the optimum incident angle of the wire grid polarizer 420 with respect to the visible wavelength region is 35 °. It is a graph which shows sex. More specifically, the incident angle in the XZ plane of FIG. 10, that is, the plane defined by the normal direction of the transparent substrate 140 and the short direction of the fine metal wires 111 of the wire grid 110 is θ _xz. A wire grid polarizer 420 obtained by optimizing the antireflection layer 130 and the wire grid 110 so as to obtain a high P-polarized light transmittance T _p with _{respect to} incident light in the visible wavelength region where the _plane = 35 °. _Shows an example of calculation results of spectral reflectance (R _s ) and spectral transmittance (T _p ) for incident light in the visible wavelength range of θ _{xz plane} = 25 °, 30 °, 35 °, 40 °, 45 °. It is a graph.

According to FIG. 11, the wavelength dependence of the polarization efficiency varies depending on the incident angle, but if the incident light is in the visible wavelength region and the incident angle θ _{xz plane} is within the range of 35 ° ± 10 °, the high polarization efficiency. That is, it has high spectral reflectance (R _s ) and high spectral transmittance (T _p ). For example, according to FIG. 11, the wire grid polarizer 420 of this example is incident light having a wavelength of 445 nm to 660 nm, and incident light in the range of incident angle θ _{xz plane} = 35 ° ± 10 °. For example, it can be seen that it has an S-polarized light reflectance R _{s of} 98% or more and a P-polarized light transmittance T _{p of} about 85% or more (wavelength average of about 95%). Further, if the incident angle θ _{xz plane} is within the range of 35 ° ± 5 °, the P-polarized light transmittance T _{p of} about 90% or more (wavelength average of about 95%) with respect to incident light with a wavelength of 440 nm to 660 nm. It becomes.

In addition to the use of wire grid polarizer 420 is also predetermined incident angle (e.g., 35 °) to the incident light of RGB wavelength band of both high S-polarized light reflectance R _s and P-polarized light transmittance T _p The same effect can be obtained if the polarizing beam splitter has a functional surface that is formed in a specific area of a flat substrate.

  FIG. 10 shows an example of a projection display device 400 using a MEMS scanner 440 that functions as an image generation unit, a quarter-wave plate 430, and a wire grid polarizer 420 that functions as a polarization beam splitter. Although shown, the configuration of the projection display device of the present embodiment is not limited to this. For example, the projection display device uses a reflective liquid crystal display element that generates a two-dimensional image as an image generation unit instead of the MEMS scanner 440 and the quarter-wave plate 430, and additionally transmits through the wire grid polarizer 420. A configuration may be adopted in which a projection lens for enlarging and forming a two-dimensional image generated by the reflective liquid crystal display element on the screen 450 is disposed on the light emission side.

  As the reflective liquid crystal display element, for example, an active matrix silicon semiconductor substrate with a reflective pixel electrode in which an electrode made of a metal reflective film is formed for each pixel, and a CMOS transistor that applies a voltage according to an image signal is connected to each electrode Alternatively, LCoS (Liquid Crystal on Silicon) in which a liquid crystal layer is sandwiched by a glass substrate having a transparent electrode formed on the entire display surface may be used. LCoS functions as a voltage variable phase difference plate because the retardation value of the liquid crystal layer changes according to the voltage applied to the pixel electrode with reference to the voltage applied to the transparent electrode.

An example of a projection display device 400a having such an LCoS is shown in FIG. A projection display device 400a shown in FIG. 12 includes LCoS 460 as a reflective liquid crystal display element. Reference numeral 470 denotes a projection lens. In the projection type display device 400a shown in FIG. 12, the S-polarized light (light flux 502 ′ in FIG. 12) reflected by the wire grid polarizer 420 after being emitted from the RGB light source unit 410 is set in the voltage in the LCoS 460. Is incident on a pixel having a V _off value, that is, a pixel to which a voltage at which the retardation value of the liquid crystal layer is zero with respect to the wavelength λ of incident light is applied, the light is reflected by a reflective pixel electrode formed in the pixel. Although it is reflected and reciprocates through the liquid crystal layer, the polarization state of light does not change before and after the incidence of LCos 460. Therefore, the light exits the LCoS 460 as S-polarized light and enters the wire grid polarizer 420 again. As a result, the light is reflected by the wire grid 110 and does not reach the screen 450. Therefore, the V _off pixel is a dark display pixel. In FIG. 12, light 504 ′ is shown as an example of the light.

On the other hand, S-polarized light (light flux 502 ′ in FIG. 12) emitted from the RGB light source unit 410 and reflected by the wire grid polarizer 420 is a pixel having a voltage setting of V _on in the LCoS 460, that is, the wavelength of incident light. When incident on a pixel to which a voltage having a retardation value of λ / 4 is applied to λ with respect to λ, the light is reflected by a reflective pixel electrode formed in the pixel and reciprocates through the liquid crystal layer. The polarization state of light changes before and after the incidence. In the case of this example, light incident as S-polarized light is converted into P-polarized light and emitted. Therefore, the S-polarized light is converted to P-polarized light, exits LCoS 460, and enters the wire grid polarizer 420 again. As a result, the light passes through the wire grid 110 and reaches the screen 450. Therefore, the V _on pixel is a bright display pixel. FIG. 12 shows light 503 ′ as an example of the light.

If the voltage applied to LCoS 460 is an intermediate voltage between V _off and V _on , the retardation value of the liquid crystal layer becomes an intermediate value in the range of 0 to λ / 4. In this case, the light incident on the pixel is emitted from the LCoS 460 as light having a ratio of the S-polarized component and the P-polarized component corresponding to the applied voltage, and reenters the wire grid polarizer 420. Then, the P-polarized component of the light is transmitted through the wire grid 110, and the S-polarized component is reflected from the wire grid 110. As described above, the ratio of the S-polarized component and the P-polarized component of the light emitted from the LCoS 460 re-entering the wire grid polarizer 420 can be adjusted according to the voltage applied to the liquid crystal layer in the LCoS 460. This makes it possible to display a gradation.

  As shown in FIG. 12, when LCoS is used, the wire grid polarizer 420 functioning as a polarization beam splitter forms the wire grid 110 in an area corresponding to at least the light beam irradiated on the entire display pixel of the LCoS 460. . That is, as shown in FIG. 12, when LCoS is used, a light beam 501 ′ having a cross-sectional area covering the entire display pixel of LCoS 460 is emitted from the RGB light source unit 410. For this reason, the light beam 503 ′ reflected by the wire grid polarizer 420 and reciprocatingly transmitted through the LCoS 460 is also a light beam having a cross-sectional area covering the entire display pixel of the LCoS 460, and the wire of the wire grid polarizer 420. Re-enters the grid 110. When the light beam is incident on the wire grid 110 of the wire grid polarizer 420, it is transmitted through the wire grid 110 and emitted as a P-polarized light beam 503 'in accordance with the ratio of the P-polarized component contained in each light. The luminous flux 503 ′ is enlarged and projected on the screen 450 by the projection lens 470.

Further, for example, when three RGB laser light sources are used for the RGB light source unit 410, the emitted light can be made to be a light close to a parallel light by the collimating lens, so that the RGB incident on the wire grid type polarizer 420 as a polarization beam splitter The light emitted from the light source unit 410 (for example, the light beam 501 ′) and the light emitted from the LCoS 460 (for example, the light beam 503 ′) are near the incident angle θ = 45 ° with respect to the wire grid polarizer 420. In such a case, the polarization efficiency is maximized for incident light in the visible wavelength region with an incident angle θ = 45 °, that is, both the S-polarized reflectance R _s and the P-polarized transmittance T _p are high. It is preferable to adjust the design so that Specifically, the pitch Pi and the wire width w of the wire grid 110 may be processed more finely than 200 nm and 100 nm, respectively.

  Also, as shown in FIG. 12, the LED light source unit 410 may use the LED light sources 200R, 200G, and 200B of the second embodiment corresponding to three RGB instead of the three RGB laser light sources. . When the LED light sources 200R, 200G, and 200B according to the second embodiment corresponding to RGB are used, the RGB light source unit 410 emits linearly polarized light that becomes S-polarized light with respect to the wire grid polarizer 420 serving as a polarizing beam splitter. A light source configuration that allows efficient incidence is preferable. Since the conventional LED light source emits randomly polarized light, among the light incident on the wire grid polarizer 420, the P-polarized light corresponding to half of the amount of light emitted from the LED light source passes through the wire grid 110 and becomes projection light. Does not contribute. Therefore, by using the LED light sources 200R, 200G, and 200B of the second embodiment, P-polarized light as viewed from the wire grid polarizer 420 out of the light emitted from the LED chip 220 or the fluorescent light converted in wavelength by the phosphor 240. It is effective for improving the light utilization efficiency to convert the S light into S-polarized light and increase the outgoing light of the S-polarized component.

  In the example shown in FIG. 12, the emitted light from the three LED light sources 200B, 200G, and 200R that emit blue (B), green (G), and red (R), respectively, is condensed into condensing lenses 411B, 411G, 411R, and The RGB light source unit 410 is configured to be light that is close to parallel light by the collimator lens 414 and the RGB three colors are combined on the same optical axis using the RGB combining dichroic mirrors 412 and 413.

  The LED light source 200B may directly use blue (B) light emission with a wavelength of 430 nm to 460 nm from a GaInN LED chip without using a phosphor, or irradiate the blue phosphor with ultraviolet light from the ultraviolet of the LED chip. Blue fluorescence that is generated may be used. The LED light sources 200G and 200R may use green fluorescence and red fluorescence generated by irradiating the green phosphor and red phosphor with ultraviolet to violet emission of the LED chip.

  The RGB combining dichroic mirror 412 is, for example, a transparent optical multilayer film designed to reflect blue (B) and transmit green (G) and red (R) with respect to divergent light having a central incident angle of 45 °. The film may be formed on one side of the glass substrate.

  The RGB combining dichroic mirror 413 is an optical multilayer film designed to reflect red (R) and transmit green (G) and blue (B) with respect to diverging light having a central incident angle of 45 °, for example. May be formed on one side of the transparent glass substrate.

  As shown in the second embodiment, a wire grid type polarizer is formed on the light emission surface of the LED light sources 200B, 200G, and 200R, and the longitudinal direction of the fine metal wires 111 of the wire grid 110 is the paper surface. By setting the parallel direction (in the X′-Z ′ plane in FIG. 12), light having a polarization component perpendicular to the paper surface, which is a P polarization component for the wire grid polarizer in the LED light source, is efficiently emitted. However, when used as an RGB light source in the present embodiment, the wire grid polarizers of the LED light sources 200B, 200G, and 200R are designed and adjusted so that the polarization efficiency is maximized in the respective RGB wavelength ranges, thereby further increasing the polarization. Output light is obtained.

  The wire grid polarizer 420 used as a polarization beam splitter emits from the RGB light source unit 410 by setting the longitudinal direction of the fine metal wires 111 of the wire grid to the direction perpendicular to the paper surface (Y′-axis direction in FIG. 12). Linearly polarized light that efficiently reflects linearly polarized light (in this example, light having a polarization component perpendicular to the paper surface and light having an S polarization component for the wire grid polarizer 420), and makes a large amount of light incident on the LCoS 460. Of light.

  In addition, in order to obtain a high-contrast projection display image, an optical path between the RGB light source unit 410 and the wire grid polarizer 420 (hereinafter referred to as “light extinction ratio”) is used to complement the extinction ratio of the wire grid polarizer 420 used as a polarization beam splitter. , Or an optical path between the wire grid polarizer 420 and the projection lens 470 (hereinafter referred to as an optical path B), an absorption type polarizer (not shown) having a high extinction ratio may be disposed. . In the optical path A, light of a polarization component perpendicular to the paper surface (light of S polarization component for the wire grid polarizer 420) is transmitted and light of a polarization component parallel to the paper surface (P polarization component for the wire grid polarizer 420). A polarizer that absorbs light of a polarization component perpendicular to the paper surface and transmits light of a polarization component parallel to the paper surface may be disposed in the optical path B.

  As described above, according to the present embodiment, it is possible to provide a projection display device that does not generate stray light and has high light utilization efficiency.

  Hereinafter, examples of the wire grid polarizer of each embodiment described above and an optical device using the same will be described in detail.

Example 1.
The first example is an example of the wire grid polarizer 100 according to the first embodiment shown in FIG.

In this embodiment, borosilicate glass having a refractive index n _S = 1.52 in the visible wavelength region is used as the transparent substrate 140, and the reflectance of incident light having an incident angle of 0 ° in the visible wavelength region is applied to one surface thereof. An antireflection film (not shown) of 0.5% or less is formed. Next, an antireflection layer 130 having a film thickness d = 202 nm is formed on the other surface of the transparent substrate 140 using a porous material having an average refractive index n = 1.25.

  In this embodiment, the antireflection layer 130 is formed by the following procedure using a hollow silica membrane bonded with hollow silica particles as the porous material.

  First, a hollow silica sol is obtained by the following procedures (1) to (2).

(1) In a glass reaction vessel having a capacity of 200 ml, ethanol 60 g, ZnO fine particle water dispersion sol (product of Sakai Chemical Industry Co., Ltd., product name: NANOFINE-50, average primary particle size 20 nm, average aggregated particle size 100 nm, solid content conversion) After adding 30 g of 10% by mass) and 10 g of tetraethoxysilane (SiO ₂ solid content of 29% by mass), an aqueous ammonia solution was added to adjust the pH to 10, and the mixture was stirred at 20 ° C. for 6 hours. 100 g of a fine particle dispersion (solid content concentration 6 mass%) is obtained.

(2) 100 g of a strongly acidic cation exchange resin (manufactured by Mitsubishi Chemical Corporation, trade name: Diaion (registered trademark), total exchange capacity of 2.0 meq / ml or more) is added to the obtained core-shell type fine particle dispersion. After stirring for a time to reach pH = 4, the strongly acidic cation exchange resin is removed by filtration to obtain 100 g of a hollow SiO ₂ fine particle dispersion. The thickness of the outer shell of the SiO ₂ hollow particles is about 10 nm, and the pore diameter is about 20 nm. The SiO ₂ fine particles are aggregate particles, and the average aggregate particle size is 100 nm.

Hollow silica sol obtained by the above procedure (0.7 g, solid content concentration: 15% by mass), nitric acid partial hydrolyzate of tetraethoxysilane (2 g, solid content concentration: 2.25% by mass), isopropanol (7.3 g) ) At room temperature to prepare a coating solution. The ratio between the hollow silica particles and the matrix component contained in the coating liquid is 7: 3 (mass ratio) in terms of SiO ₂ .

  Then, the said coating liquid is apply | coated to one surface (surface on the side in which the antireflection film is not formed) of the transparent base material 140 by a spin coat method. Thereafter, a heat treatment is performed at 200 ° C. for 45 minutes to perform a dehydration reaction of the precursor, thereby forming a hollow silica film that is a metal oxide film. As a result, an antireflection layer 130 made of a hollow silica membrane having a porous structure in which hollow silica particles are dispersed in a matrix component is obtained.

  Next, an APC film to be the metal fine wires 111 of the wire grid 110 is formed on the surface of the obtained antireflection layer 130 by a sputtering method so as to have a film thickness t = 156 nm. Here, APC is a silver alloy in which palladium (Pd) and copper (Cu) are added to silver (Ag), and has a feature of improving environmental resistance while maintaining low resistance and high reflection of pure silver, and is made of APC. An APC film can be obtained by using a sputtering target.

  Next, an ultraviolet curable resin is applied onto the obtained APC film, and a nanoimprint mold in which the uneven shape of the wire grid 110 corresponding to the pitch Pi = 200 nm prepared in advance is engraved in the quartz substrate is pressure-bonded. The resin is cured by irradiating with ultraviolet rays, and the nanoimprint mold is pulled away. Thereby, the resist resin 602 to which the uneven shape of the wire grid 110 is transferred is obtained.

  Next, the residue remaining on the bottom surface of the concave portion of the resist resin 602 is removed by reactive ion etching using a mixed gas of oxygen and argon to form an opening. As a result, the APC film is exposed with a width of about Pi / 2 = 100 nm in each opening. Further, the APC film exposed at the opening of the resist resin 602 is removed by reactive ion etching using a mixed gas of nitrogen compound and argon. Finally, the remaining resist resin 602 is removed with an organic solvent to form a thin metal wire 111 made of an APC film having a pitch Pi = 200 nm, a wire width w = 100 nm, and a thickness t = 156 nm, thereby obtaining a wire grid 110. . In this way, the wire grid polarizer 100 is manufactured.

FIG. 13 is a graph showing the calculation result of the polarization efficiency of the wire grid polarizer 100 of this example. In FIG. 13, a straight line in the longitudinal direction of the wire grid 110 (Y-axis direction in FIG. 1) when light in the visible wavelength region is incident on the wire grid polarizer 100 of the present embodiment at an incident angle θ = 0 °. Spectral reflectance (S-polarized reflectance R _s ) for S-polarized light that is polarized light and spectral transmittance (P-polarized transmittance T for P-polarized light that is linearly polarized (X-axis direction in FIG. 1) orthogonal thereto. The calculation result of _p ) is shown. For the calculation of the polarization efficiency, the value of silver (Ag) (n _w = 0.00006λ−0.015, k _w =) is used as the optical constant (n _w : refractive index, k _w : extinction coefficient) of the APC film. 0.0072λ; λ is the wavelength in nm). Also, the calculation is based on the literature “MGMoharam, DAPommet, EBGrann, and TKGayload,“ Stable implementation of the rigorous coupled-wave analysis for surface relief gratings: enhanced transmittance matrix approach ”, Journal of the Optical Society of America A, vol.12, no .5, May 1995, p.1077-1086 ”was performed by electromagnetic field simulation using the exact coupled wave theory (RCWA).

As shown in FIG. 13, in the visible wavelength region of 420 nm to 640 nm, high P-polarized light transmittance and S-polarized light reflectance with T _p of 90% or more and R _s of about 98% are obtained. Here, in the wavelength region of 440 nm to 580 nm, the P-polarized light transmittance is as high as 95% or more. Therefore, a wire grid polarizer having a high efficiency and a high polarization separation function can be obtained.

  In this embodiment, an example in which the antireflection layer 130 is formed using a hollow silica film is shown. However, as a material of the antireflection layer 130, particles that do not cause scattering and diffraction in a transparent medium in the visible wavelength region. A material other than the hollow silica film may be used as long as it has a porous structure in which air with a diameter or vacuum bubbles are dispersed and the average refractive index n = 1.25.

Example 2
The second embodiment is an example in which the material of the wire grid 110 of the first embodiment is aluminum (Al). In this embodiment, in the step of forming the APC film that becomes the fine metal wires 111 of the wire grid 110 in the first embodiment, an aluminum film is formed with a film thickness t = 175 nm. Others are the same as in the first embodiment.

FIG. 14 is a graph showing the calculation results of the polarization efficiency of the wire grid polarizer 100 of this example. FIG. 14 also shows the calculation results of the S-polarized reflectance R _s and the P-polarized light transmittance T _p when light in the visible wavelength region is incident on the target wire grid polarizer 100 at an incident angle θ = 0 °. ing. Note that n _w = 0.0004λ−0.109 and k _w = 0.0119λ + 0.006 are used as the optical constants of the aluminum film.

As shown in FIG. 14, in this example, T _p is lower than that in the first example. However, in the visible wavelength range of 430 nm to 620 nm, T _p is approximately 90% or more and R _s is about 97%. It has high P-polarized light transmittance and S-polarized light reflectance. Therefore, a wire grid polarizer having a high efficiency and a high polarization separation function can be obtained.

Comparative Example 1
Next, a comparative example with respect to the first embodiment will be shown. In the first comparative example, the same material as that of the wire grid polarizer 100 of the first embodiment is used, but the antireflection layer 130 is not formed and the wire grid 110 is formed on the transparent substrate 140. FIG. 15 is a graph showing the calculation results of the polarization efficiency of the wire grid polarizer of this comparative example. FIG. 15 also shows the S-polarized light reflectance R _s and the P-polarized light transmittance T _p when light in the visible wavelength region is incident on the target wire grid polarizer at an incident angle θ = 0 °.

Comparative Example 2
Further, another comparative example with respect to the first embodiment will be shown. In the second comparative example, a magnesium fluoride MgF ₂ film having a refractive index n = 1.38 is formed as an equivalent to the antireflection layer 130, and the other points are the wire grid polarizer 100 of the first embodiment. In the same manner as described above, a wire grid polarizer is manufactured. In this comparative example, the film thickness d of the magnesium fluoride MgF ₂ film is set to 190 nm so that the average of the P-polarized light transmittance T _p is maximized in the visible wavelength region. FIG. 16 is a graph showing the calculation results of the polarization efficiency of the wire grid polarizer of this comparative example. FIG. 16 also shows the S-polarized light reflectance R _s and the P-polarized light transmittance T _p when light in the visible wavelength region is incident on the target wire grid polarizer at an incident angle θ = 0 °.

In the first comparative example and the second comparative example, the T _p sharply decreases in the visible short wavelength region of 500 nm or less as compared with the first and second examples. Further, since T _p is narrower wavelength range of 90% or more, it is not suitable for a wire grid polarizer for the visible wavelength range.

Example 3
The third example is an example of a wire grid polarizer 420 used as a polarization beam splitter in the third embodiment. In this embodiment, the incident angle in the XZ plane of FIG. 10, that is, in the plane defined by the normal direction of the transparent substrate 140 and the short direction of the thin metal wires 111 of the wire grid 110 is θ _{xz plane.} = of 35 ° to the incident light in the visible wavelength range, so that high P-polarized light transmittance T _p is obtained, was optimal design of the anti-reflection layer 130 and the wire grid 110.

  First, an antireflection film and an antireflection layer 130 are formed on the surface of the transparent substrate 140 by the same method as in the first embodiment. In this example, the same hollow silica film as that of the first example is used as the material of the antireflection layer 130, and the antireflection layer 130 having an average refractive index n = 1.25 and a film thickness d = 250 nm is formed. Next, by the same method as in the first embodiment, a fine metal wire 111 made of an APC film having a pitch Pi = 200 nm, a wire width w = 100 nm, and a thickness t = 135 nm is formed, and a wire grid 110 is obtained.

FIG. 11 described above shows the S-polarized reflectance R _s for the incident light in the visible wavelength range of the incident angles θ = 25 °, 30 °, 35 °, 40 °, and 45 ° of the wire grid polarizer 420 of the present embodiment. and is a graph showing the calculation results of the P-polarized light transmittance T _p. As shown in FIG. 11, the wire grid polarizer 420 of the present embodiment, a tendency that T _p is reduced by the larger angles of incidence the shorter wavelength side is observed. However, for example, T _p tends to decrease with respect to a short wavelength region of 450 nm or less at 45 ° incidence, but in a visible wavelength region, T _p is 90% or more and a high P-polarized light transmittance and R _s Is high S-polarized reflectance of about 98% or more. Therefore, it becomes a wire grid type polarizer having a high polarization separation function with high efficiency with respect to visible light having an incident angle θ = 35 ° ± 10 °. Further, since a higher P-polarized light transmittance can be obtained for visible light having an incident angle θ = 35 ° ± 5 °, the wire grid polarizer has a higher efficiency and a higher polarization separation function. That is, it is possible to obtain a highly efficient polarization beam splitter that splits incident light into P-polarized transmitted light and S-polarized reflected light at a separation angle of 110 °.

Example 4
In the fourth example, in the configuration of the wire grid polarizer 100 of the first embodiment, holes having a diameter of 100 nm or less are dispersed in a transparent material in the atmosphere around the wire grid 110, that is, in the gap portion 120. This is an example in which a porous material made of a composite is filled. It is to be noted that the second embodiment is the same as the first embodiment except that the gap portion 120 of the wire grid 110 is filled with a porous material and the average refractive index n and film thickness d of the antireflection layer 130 are different.

  In this embodiment, first, an antireflection layer 130 made of a hollow silica film having an average refractive index n = 1.18 and a film thickness d = 210 nm is formed on the surface of the transparent substrate 140. Next, a thin metal wire 111 made of an APC film having a pitch Pi = 200 nm, a wire width w = 100 nm, and a thickness t = 142 nm is formed on the antireflection layer 130 in the same manner as in the first embodiment, and the wire A grid 110 is obtained. Further, a hollow silica film that is the same porous material as that used for the antireflection layer 130 is formed in the gap 120 of the produced wire grid 110 so that the average refractive index n is 1.18.

In the first to third examples, a hollow silica film having an average refractive index n = 1.25 is formed as the antireflection layer 130. However, in this example, the average refractive index n = 1.18. The configuration of the porous material, that is, various parameters of the hollow silica membrane are adjusted. Since the hollow silica film is formed by mixing hollow silica particles and a precursor material as a matrix component, for example, by adjusting the mass ratio of the hollow silica particles and the matrix component or selecting the matrix component material, the refractive index n Can be adjusted. Specifically, hollow silica particles having a hollow volume ratio of about 70% are mixed with a matrix component having a refractive index of 1.45 equivalent to silica (SiO ₂ ) so that the volume ratio of the hollow silica particles is about 85%. Thus, a hollow silica membrane having a porous structure with an average refractive index n = 1.18 can be obtained.

  Here, as described above, when a hollow silica film is formed in the gap 120 after the production of the wire grid 110, a metal fine wire is formed so as to fill the gap 120 with a dispersion liquid in which hollow silica particles are dispersed in an organic solvent. Apply onto 111 and dry the dispersion. Alternatively, a coating liquid in which hollow silica particles are dispersed in an amorphous fluororesin binder is applied on the metal thin wire 111 so as to fill the gap 120, and the resin is cured and solidified. At this time, a hollow silica film may remain on the thin metal wires 111 of the wire grid 110. However, the thinner the hollow silica film, the higher the P-polarized light transmittance in the visible wavelength range, which is preferable. Specifically, 100 nm or less is preferable.

  As another method for manufacturing the wire grid 110, after forming a hollow silica film having an average refractive index n = 1.18 and a film thickness (d + t) = 352 nm on the surface of the transparent substrate 140, the surface of the formed hollow silica film is dried. By etching, a linear lattice having concave portions with a pitch Pi = 200 nm, a width of 100 nm, and a depth t = 142 nm is formed, and an APC film that becomes the metal thin wires 111 of the wire grid 110 is formed so as to fill the concave portions of the formed linear lattice. May be. That is, in this method, a hollow silica film that fills the gap 120 around the wire grid 110 is formed together with the antireflection layer 130, and then an APC film that becomes the metal thin wire 111 of the wire grid 110 is formed. In addition, in the step of forming the APC film in the concave part of the linear lattice made of the hollow silica film, the APC film is covered with a resin such as a resist in advance so that the APC film does not remain on the hollow silica film surface other than the concave part. The resist is removed later. Alternatively, the APC film other than the concave portion of the hollow silica film may be removed by polishing the surface.

FIG. 17 is a graph showing the calculation results of the polarization efficiency of the wire grid polarizer 100 of this example. FIG. 17 also shows the S-polarized light reflectance R _s and the P-polarized light transmittance T _p when light in the visible wavelength region is incident on the target wire grid polarizer at an incident angle θ = 0 °.

As shown in FIG. 17, also in the wire grid polarizer 100 of this example, high P-polarized light having a high visibility of 90% or more in the wavelength region of 460 nm to 600 nm and 80% or more in the wavelength region of 440 nm to 650 nm. A transmittance T _p is obtained.

Example 5 FIG.
In this embodiment, in the configuration of the above-described fourth embodiment, the material of the fine metal wires 111 of the wire grid 110 is aluminum (Al). In this embodiment, in the step of forming the APC film to be the metal thin wires 111 of the wire grid 110 of the fourth embodiment, an aluminum film is formed with a film thickness t = 162 nm. The antireflection layer 130 is formed of a hollow silica film having a refractive index n = 1.20. That is, a hollow silica film having a refractive index n = 1.20 and a film thickness d = 210 nm is used as the antireflection layer 130. A hollow silica film having the same refractive index has a pitch Pi = 200 nm, a wire width w = 100 nm, and a thickness t = The gap 120 between the fine metal wires 111 made of 162 nm aluminum is filled.

FIG. 18 is a graph showing the calculation results of the polarization efficiency of the wire grid polarizer 100 of this example. 18 also shows the S-polarized light reflectance R _s and the P-polarized light transmittance T _p when light in the visible wavelength region is incident on the target wire grid polarizer at an incident angle θ = 0 °. As shown in FIG. 18, also in the wire grid polarizer 100 of the present embodiment, 90% or more of P-polarized light is transmitted in the wavelength range of 460 nm to 610 nm with high visibility and 80% or more in the wavelength range of 440 nm to 660 nm. The rate T _p is obtained.

Since the wire grid polarizer of the present invention is a polarizer having high P-polarized light transmittance and S-polarized light reflectance in the visible wavelength region, it can be used as a polarization conversion element or polarizing beam splitter that reuses one of the polarized light. In particular, it can be used as a polarization conversion element provided on a window member of a light source module that efficiently emits specific linearly polarized light, or as a polarization beam splitter of a projection display device using a MEMS scanner.

DESCRIPTION OF SYMBOLS 100, 100c Wire grid type polarizer 110 Wire grid 111 Metal fine wire 120 Gap part 130 Antireflection layer 130a, 130b Porous material 131, 131a Structure 132, 132a Hole 133 Hollow particle 131b Outer shell 132b Hollow part 132c Cavity part 140 Transparent base material 151 Incident light 152 Transmitted light 153 Reflected light 200, 200a, 200b, 200c, 200R, 200G, 200B LED light source 210 Base material 220 LED chip 230 Side wall part 240 Phosphor 250 Reflective member 260 Hollow part 270 Phosphor-containing substrate 271, 271 a, 271 b Transparent substrate 280 Dichroic mirror layer 400, 400 a Projection display device 410 RGB light source unit 411 R, 411 G, 411 B Condensing lens 412, 413 RGB multiplexing Lee black dichroic mirror 414 collimating lens 420 wire grid polarizer 430 quarter wave plate 440 MEMS scanner 450 screen 460 the reflection type liquid crystal display device (LCoS)
470 Projection lens 601, 604 Metal film 602, 603 Resin resist 6031 Opening 900 Wire grid polarizer 940 Transparent substrate 910 Wire grid 911 Metal wire 920 Gap 801 Incident light 802 Transmitted light 803 Reflected light

Claims (11)

A transparent substrate;
An antireflection layer formed on one surface of the transparent substrate using a material having a refractive index lower than that of the transparent substrate;
A wire grid formed on the antireflection layer,
The pitch of the wire grid is ½ or less of the wavelength of incident light in the visible wavelength range,
The antireflection layer is formed using a porous material which is an optical material having a porous structure composed of a composite of a structure formed using a transparent material and pores having a particle size of 100 nm or less, When the refractive index of the gap, which is the atmosphere around the wire grid, is n ₁ , and the refractive index of the transparent base material is n _S , n _AR = (n ₁ · n _S ) ^1/2 , refractive index _{n, n = n AR -0.1n AR ~n} AR + 0.1n wire-grid polarizer being in the range of _AR. The wire grid polarizer according to claim 1, wherein the gap is filled with a porous structure formed of a porous material that is the same as or different from the material of the antireflection layer. 3. The wire grid polarizer according to claim 1, wherein the porous material includes metal oxide fine particles including pores bonded together by a matrix component whose main component is a metal oxide. The wire grid polarizer according to claim 3, wherein the metal oxide fine particles are hollow silica particles. Each thin metal wire of the wire grid is formed of silver, aluminum, or an alloy containing one or more of palladium, neodymium, iridium, bismuth, gold, copper, platinum, zinc, and tin. The wire grid type polarizer of any one of -4. The wire grid polarizer according to any one of claims 1 to 5, wherein, at a wavelength of 460 nm to 600 nm, the transmittance of P-polarized light orthogonal to the longitudinal direction of the fine metal wires of the wire grid is 90% or more. A light emitting element provided in a container, and a substrate provided above the light emitting element and forming a light emitting surface,
The wire grid type polarizer of any one of Claims 1-6 is formed by using the said board | substrate as a transparent base material. The light source module characterized by the above-mentioned. The substrate is a phosphor-containing substrate containing a phosphor,
Light of the emission wavelength from the phosphor is transmitted to the surface opposite to the surface on which the wire grid of the phosphor-containing substrate is formed, and the light of the fluorescence emission wavelength that is the emission wavelength from the phosphor is transmitted. The light source module according to claim 7, wherein a reflecting dichroic mirror layer is formed. A light source unit including three light sources each emitting light of a different wavelength;
A scan mirror that reflects incident light and scans the screen;
A quarter wave plate,
Light disposed between the light source unit and the quarter-wave plate and utilizing a polarization separation function, reflects light from the light source unit and guides it to the scan mirror and reflects light reflected by the scan mirror. A polarizing beam splitter that passes through and reaches the screen;
A quarter wave plate disposed in an optical path between the polarizing beam splitter and the scan mirror;
A projection display apparatus comprising the wire grid polarizer according to any one of claims 1 to 6 as the polarization beam splitter. A light source unit including three light sources each emitting light of a different wavelength;
A reflective liquid crystal display element;
A projection lens;
A polarized beam that reflects the light from the light source unit and guides it to the reflective liquid crystal display element and transmits the light reflected by the reflective liquid crystal display element to reach the projection lens by using a polarization separation function. With a splitter,
A projection display apparatus comprising the wire grid polarizer according to any one of claims 1 to 6 as the polarization beam splitter. The projection type display device according to claim 9 or 10, wherein in the wire grid polarizer provided as the polarization beam splitter, the wire grid is formed only in an incident region of light from the light source unit.

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