JP6770037B2 - LCD projector - Google Patents

Description

The present invention relates to a polarizing element typified by a polarizing plate, a polarizing filter, or the like, and more specifically, inorganic polarized light utilizing a difference in light absorption rate due to light interference in the used band and optical anisotropy in the in-plane axial direction. It relates to a liquid crystal projector using an element.

In a liquid crystal display device (particularly a transmissive liquid crystal display device), it is indispensable to arrange a polarizing plate on the surface of the liquid crystal panel because of its image forming principle. The polarizing plate has a function of absorbing one of orthogonal polarized light components (so-called P-polarized wave and S-polarized wave) and transmitting the other. Conventionally, as such a polarizing plate, a dichroic polarizing plate in which an iodine-based or dye-based polymer organic substance is contained in a film is often used.

As a general method for producing a dichroic polarizing plate, a method of dyeing with a polyvinyl alcohol-based film and a dichroic material such as iodine, cross-linking with a cross-linking agent, and uniaxially stretching is used. Since it is produced by stretching in this way, this type of polarizing plate generally tends to shrink. Further, since the polyvinyl alcohol-based film uses a hydrophilic polymer, it is very easily deformed especially under humidifying conditions. And since the film is basically used, the mechanical strength as a device is weak.

In recent years, the applications of liquid crystal display devices have expanded and their functions have become more sophisticated. Along with this, high reliability and durability are required for each device constituting the liquid crystal display device. For example, in the case of a liquid crystal display device that uses a light source having a large amount of light, such as a transmissive liquid crystal projector, the polarizing plate receives strong radiation. Therefore, the polarizing plates used for these need to have excellent heat resistance. However, since the film-based polarizing plate as described above is composed of an organic substance, there is naturally a limit to improving these characteristics.

On the other hand, there is an inorganic polarizing plate as a polarizing plate having high heat resistance. For example, an inorganic polarizing plate (trade name "Polarcor") manufactured by Corning Inc. of the United States has a structure in which silver fine particles are diffused in glass, and no organic substance such as a film is used. Plasma resonance of island-shaped fine particles is used for the polarization principle of the inorganic polarizing plate. When the shape of the metal fine particles is elliptical, the resonance wavelength differs between the major axis direction and the minor axis direction. That is, optical anisotropy occurs. As a result, a predetermined polarization characteristic of absorbing a polarization component parallel to the long axis and transmitting a polarization component parallel to the short axis can be obtained (selective light absorption of polarized waves due to optical anisotropy).

The absorption wavelength due to the resonance of the metal fine particles depends on the characteristics of the metal, the shape anisotropy of the fine particles, the peripheral dielectric constant, and the like. And so far, a wide range of research has been conducted. In particular, there are many studies on Au (gold), Ag (silver), Cu (copper) and the like. For example, for Au fine particles, there is a method of obtaining shape anisotropy by forming gold fine particles on glass by sputtering and stretching them (see Non-Patent Document 1). For Ag fine particles, a method of precipitating silver fine particles in glass by thermal reduction of silver halide (see Patent Documents 1 and 2), and oblique deposition of fine columnar structures made of substances transparent and opaque with respect to the wavelength of the band used. There is a method of obtaining polarization characteristics (see Patent Document 3). For Cu fine particles, there is a method using silver halide (see Patent Document 4).

Further, Patent Document 5 below discloses a wire grid type polarizing plate. The wire grid type polarizing plate is formed by forming a plurality of thin metal wires on a substrate in a grid pattern at a pitch smaller than the wavelength of light in the band of use. It reflects polarized light components parallel to the fine metal wires and is orthogonal to the fine metal wires. A predetermined polarization characteristic is made to appear by transmitting the polarization component.

Since the resonance wavelength of Au fine particles, Ag fine particles and Cu fine particles is on the long wavelength side, it is difficult to obtain good polarization characteristics in the visible light region. On the other hand, it is known that Al (aluminum) fine particles have a resonance wavelength about 200 nm shorter than that of Ag fine particles, so that good polarization characteristics can be obtained in the visible light region (see Non-Patent Document 2). However, since aluminum is very easily oxidized, a method of precipitating Al metal fine particles on glass by a heat reduction method like other metal fine particles cannot be adopted.

Therefore, Patent Document 6 below discloses some methods for producing a polarizing plate using Al fine particles as metal fine particles. As an example, after depositing an Al film on a glass substrate, pattern etching is performed in an island shape using photolithography technology, and the glass substrate is further heated to about 750 ° C. and stretched to form Al particles into an elliptical shape. The method is disclosed. Further, as another example, a method of removing the resist pattern after forming an Al film on one side surface portion of the resist pattern formed on the glass substrate is disclosed.

Further, Non-Patent Document 3 described below states that a high quenching ratio can be realized at a wavelength of 1 μm or less by using Ge (germanium) instead of Al.

U.S. Pat. No. 6,772,608 Japanese Unexamined Patent Publication No. 56-169140 JP-A-2002-372620 JP-A-8-50205 Special Table 2003-508813 Gazette Japanese Unexamined Patent Publication No. 2000-147253

Optical Review Vol.4 No.3 1997 411-416 J.Opt Soc. Am.A Vol.8 No.4 619-624 J.Lightwave Tec. Vol.15 No.6 19971042-1050 J. Microelectromechanical Systems Vol. 10 No. 1 2001 33-40

The polarizing element using Al particles described in Patent Document 6 is used as a substrate in order to prevent the reaction between the Al particles and the glass during the drawing step of the substrate under a temperature condition higher than the melting point of Al (660 ° C.). Calcium aminoborate glass that does not react with is used. However, this type of glass has a problem that the production cost is high because it is more expensive and difficult to obtain than general silicate glass.

Further, in the method for manufacturing a polarizing element using Al particles described in Patent Document 6, island-shaped particles are formed by pattern etching of an Al film using a resist pattern as a mask. On the other hand, the polarizing plate used in the projector usually requires a large area and a high quenching ratio. Therefore, when the purpose is a polarizing plate for visible light, the resist pattern size needs to be sufficiently shorter than the visible light wavelength, for example, a size of several tens of nm. Further, in order to obtain a high quenching ratio, it is necessary to form a pattern at a high density.

Therefore, in the method of forming a high-density fine pattern by using the lithography technique as described in Patent Document 6, it is necessary to use a fine pattern forming method such as an electron beam drawing method. Since electron beam drawing is a method of drawing individual patterns with an electron beam, productivity is poor and it is not practical.

Further, when the Al film is etched and removed by chlorine plasma, chloride adheres to the side wall of the Al pattern, so that a separate step for removing the chloride is required. Further, although the removal of Al chloride can be performed by wet etching, it is difficult to realize a desired fine pattern shape because the chemical solution that reacts with Al chloride reacts not a little with Al.

Further, the wire grid type polarizing element has a drawback that an undesired polarizing component is reflected. This is an obstacle for many purposes, especially when used in displays, and can cause image quality degradation due to reflected light.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal projector using a polarizing element capable of obtaining a desired polarization characteristic in a use band.

In solving the above problems, in the polarizing element of the present invention, a substrate transparent to light in the used band and a strip-shaped thin film extending in one direction on the substrate are primary at a pitch smaller than the wavelength of light in the used band. The reflective layers arranged in the original lattice pattern, the dielectric layer formed on the reflective layer, and the inorganic fine particles arranged in a primary lattice pattern on the dielectric layer at positions corresponding to the strip-shaped thin film. It is provided with an inorganic fine particle layer having a light absorbing action. Inorganic fine particles are substances such as metals and semiconductors in which the extinction constant of the optical constant is not zero, that is, they have a light absorbing action.

The polarizing element having the above configuration utilizes four actions of transmission, reflection, interference, and selective light absorption of polarized waves due to optical anisotropy, thereby having a polarized wave (TE) having an electric field component parallel to the lattice of the reflecting layer. Wave (S wave)) is attenuated, and polarized wave (TM wave (P wave)) having an electric field component perpendicular to the lattice is transmitted.

That is, the TE wave is attenuated by the selective light absorption action of the polarized wave due to the optical anisotropy of the inorganic fine particle layer composed of the inorganic fine particles having shape anisotropy. The one-dimensional lattice-shaped reflection layer functions as a wire grid and reflects TE waves transmitted through the inorganic fine particle layer and the dielectric layer. By appropriately adjusting the thickness and refractive index of the dielectric layer, the TE wave reflected by the reflective layer is partially absorbed when it passes through the inorganic fine particle layer, is partially reflected, and returns to the reflective layer. .. In addition, the light that has passed through the inorganic fine particle layer interferes and is attenuated. By selectively attenuating the TE wave as described above, a desired polarization characteristic can be obtained.
If low reflection is required on the exit side, light may be incident from the reflection layer side. In this case as well, the same transmission contrast as described above can be obtained due to the selective absorption effect of the inorganic fine particle layer.

The inorganic fine particle layer is set by the wavelength range of light applied. That is, by using an aluminum-based material (metal fine particles made of aluminum or an alloy thereof) and a semiconductor material (semiconductor fine particles containing silicon, beta iron silicide, germanium, and tellurium) for the inorganic fine particle layer, high extinction in the visible light region is achieved. A polarizing element having a ratio can be obtained. For example, the inorganic fine particles are made of a simple substance of Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, Si, Ge, Te, Sn, an alloy containing these, or a silicide-based semiconductor material. It would be nice to have it.

The substrate is not particularly limited as long as it is transparent to light in the band used, and a general-purpose glass material can be preferably used. It is also possible to construct the substrate with sapphire, crystal, or the like. Further, the reflective layer is not particularly limited as long as it is a material having reflectivity to light in the use band, and a metal film such as aluminum is preferable.

The inorganic fine particles in the inorganic fine particle layer are preferably formed in an oblong shape having a major axis in a direction parallel to the lattice direction of the reflection layer and a minor axis in a direction perpendicular to the lattice direction. This is because the optical anisotropy is strengthened when the shape is such a shape. The inorganic fine particle layer having such shape anisotropy is preferably formed obliquely from a direction perpendicular to the lattice direction of the reflective layer, particularly vapor deposition or ion beam sputtering. Further, it is desirable that the inorganic fine particles have a size equal to or smaller than the wavelength of the band used and the individual particles are completely isolated.

Further, the dielectric layer has a concavo-convex shape in which a convex portion is formed immediately above the strip-shaped thin film and a concave portion is formed between the strip-shaped thin films, and the inorganic fine particle layer is the top of the convex portion of the dielectric layer or at least one side surface thereof. It is preferable that the portion is formed.

Further, on the other surface of the substrate, a one-dimensional lattice-shaped uneven portion formed parallel to the direction in which the strip-shaped thin film of the reflective layer extends, and an inorganic fine particle primary lattice on the top or at least one side surface of the uneven portion. It is preferable that a light absorption layer composed of a second inorganic fine particle layer arranged in a shape is provided.

Further, it is preferable that an antireflection layer is formed between the reflection layer and the substrate.
Further, the antireflection layer is rubbed so that the surface of the substrate corresponds to the arrangement direction of the inorganic fine particles, and the surface after the rubbing treatment has shape anisotropy so as to correspond to the arrangement direction of the inorganic fine particles. It is preferable that the inorganic fine particles having the above are attached.

Further, it is preferable that one or a plurality of laminated structures of the dielectric layer / the inorganic fine particle layer are stacked on the inorganic fine particle layer.

Further, in solving the above problems, the polarizing element of the present invention is inorganic on the top or at least one side surface of the one-dimensional lattice-shaped uneven portion formed on the surface of the substrate different from the polarizing element according to claim 1. The polarizing element having the second inorganic fine film layer in which the fine particles are arranged in a one-dimensional lattice pattern is formed on each substrate so that the direction in which the strip-shaped thin film of the reflective layer extends and the lattice longitudinal direction of the uneven portion are aligned. It is characterized in that the back surfaces are bonded to each other.

Further, it is preferable that a protective layer transparent to light in the band used is formed on the outermost surface of the polarizing element.

In solving the above problems, the liquid crystal projector of the present invention is characterized by including a lamp, a liquid crystal panel, and the above-mentioned polarizing element.

As described above, according to the present invention, it is possible to improve the polarization characteristics, and in particular, the desired polarization characteristics (contrast obtained from the extinction ratio or the transmission axis transmittance / absorption axis transmittance) in the visible light region. It is possible to provide an inorganic polarizing element having higher durability than a conventional polarizing element. Furthermore, by stacking the laminated structure of the dielectric layer / the inorganic fine particle layer, it is possible to realize high contrast and low reflection with a thinner film thickness than in the case of a single layer, so that the manufacturing process can be shortened and the material cost can be reduced. There is also a great advantage in the production of polarizing elements.
Further, according to the liquid crystal projector of the present invention, since a polarizing element having excellent light resistance characteristics against strong light is provided, a highly reliable liquid crystal projector can be realized.

It is a figure which shows the schematic structure of the polarizing element by 1st Embodiment of this invention, A is a side sectional view, B is a plan view. It is the schematic which shows the structure of the oblique sputtering film formation. A diagram illustrating a method of forming a germanium particle film by injecting germanium sputtered particles onto a stationary substrate from an oblique (10 °) direction, measurement results of optical constants of the formed germanium particle film, and germanium particles. It is a figure which shows the surface structure of a membrane. The figure explaining the method of forming a germanium particle film by injecting germanium sputtered particles into a rotating substrate from a vertical (90 °) direction, and the figure showing the measurement result of the optical constant of the formed germanium particle film. is there. It is a figure explaining the operation of the polarizing element shown in FIG. It is a figure which shows one polarization characteristic of the polarizing element of the structure shown in FIG. It is a figure which shows one polarization characteristic of a wire grid type polarizing element. It is a schematic side sectional view which shows the modification of the structure of the polarizing element shown in FIG. It is a schematic side sectional view of the polarizing element according to 2nd Embodiment of this invention. It is a schematic side sectional view of the polarizing element according to the 3rd Embodiment of this invention. It is a figure which shows the schematic structure of the polarizing element according to 4th Embodiment of this invention. It is a figure which shows the polarization characteristic of the polarizing element of the structure shown in FIG. 1 and the polarizing element of the structure shown in FIG. It is a figure which shows the contrast characteristic of the polarizing element of the structure shown in FIG. 1 and the polarizing element of the structure shown in FIG. It is a figure which shows the exit surface stray light countermeasure example (1) in the polarizing element of the structure shown in FIG. It is a figure which shows the exit surface stray light countermeasure example (2) in the polarizing element of the structure shown in FIG. It is sectional drawing which shows the structure of the optical engine part of the liquid crystal projector which concerns on this invention. It is explanatory drawing which shows the state of adhering inorganic fine particles to each of a flat substrate and a substrate having a one-dimensional lattice-shaped convex portion. It is external perspective view of the crystal substrate which has the convex part of one-dimensional lattice shape. It is a figure which shows the relationship between the major axis and the film thickness of an inorganic fine particle in an oblique film formation. It is a figure which shows the precondition of the polarizing element in the optical characteristic simulation. It is a figure which shows the optical property of the polarizing element when the constituent material of an inorganic fine particle layer is Ge fine particle, Ge thin film. It is a relationship diagram of the height of aluminum as a reflection layer in the polarizing element of this invention, and contrast. It is a figure which shows the polarization characteristic of the polarization element sample of Example 2. It is a figure which shows the uneven state of the texture structure formed by a rubbing process. It is a figure which shows the transmittance characteristic of a substrate before and after a rubbing process. It is a figure which shows the surface structure of the Ge fine particle film (antireflection film) provided on the rubbing processed substrate. It is a figure which shows the improvement of the polarization characteristic of the antireflection film by rubbing processing.

Hereinafter, each embodiment of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and various modifications can be made based on the technical idea of the present invention.

(First Embodiment)
FIG. 1 is a schematic configuration diagram of a polarizing element 10 according to the first embodiment of the present invention, where A is a side sectional view and B is a plan view.

The polarizing element 10 of the present embodiment includes a substrate 11, a reflective layer 12 in which a strip-shaped thin film 12a extending in one direction parallel to the main surface of the substrate 11 is formed in a one-dimensional lattice shape on one surface of the substrate 11. It includes a dielectric layer 13 formed on the reflective layer 12 and an inorganic fine particle layer 14 formed on the dielectric layer.

The substrate 11 is made of a material that is transparent to light in the band used (visible light region in this embodiment), for example, glass, sapphire, or crystal. In this embodiment, glass, particularly quartz (refractive index 1.46) or soda-lime glass (refractive index 1.51), is used. The component composition of the glass material is not particularly limited, and an inexpensive glass material such as silicate glass, which is widely distributed as optical glass, can be used, and the manufacturing cost can be reduced.

By using a crystal or sapphire substrate having high thermal conductivity as a constituent material of the substrate 11, it can be advantageously used as a polarizing element for an optical engine of a projector having a large amount of heat generation.

As the constituent material of the reflective layer 12, a lattice material of a normal wire grid type polarizer can be used, and aluminum is used in this example, but in addition to this, silver, gold, copper, molybdenum, and chromium are used. , Titanium, nickel, tungsten, iron, silicon, germanium, tellurium and other metals or semiconductor materials can be used. In addition to the metal material, it may be composed of an inorganic film or a resin film other than the metal formed with high surface reflectance by, for example, coloring.

The strip-shaped thin film 12a in the reflective layer 12 is arranged in a one-dimensional lattice pattern on the surface of the substrate 11 at a pitch smaller than the wavelength in the visible light region, and is formed by, for example, pattern processing of the metal film using a photolithography technique. .. The reflective layer 12 has a function as a wire grid polarizer, and among the light incident on the surface of the substrate 11, a polarized wave (TE) having an electric field component in a direction parallel to the lattice (lattice axis direction, Y axis direction). The wave (S wave)) is attenuated, and a polarized wave (TM wave (P wave)) having an electric field component is transmitted in a direction perpendicular to the lattice (a direction perpendicular to the lattice, an X-axis direction).

The pitch, line width / pitch, lattice depth, and lattice length of the metal lattice (one-dimensional lattice pattern of the strip-shaped thin film 12a) constituting the reflective layer 12 are preferably in the following ranges.
0.05 μm <pitch <0.8 μm
0.1 <(line width / pitch) <0.9
0.01 μm <lattice depth <1 μm
0.05 μm <lattice length

Further, in order to reduce the reflection of the substrate surface in the non-formed region of the reflective layer 12, the surface of the substrate 11 is preliminarily coated with a non-reflective coating, and then the reflective film 12, the dielectric layer 13, and the inorganic fine particle layer 14 are formed. You may do it. The non-reflective coating can be composed of a general laminated film having a high refractive index film and a low refractive index film. By applying the same non-reflective coating to the back surface of the substrate 11, the reflection on the substrate surface can be reduced.

The dielectric layer 13 is optically transparent to visible light such as SiO2 formed on the surface of the substrate 11 by a sputtering method or a sol-gel method (for example, a method of coating a sol by a spin coating method and gelling by heat curing). It is made of material. The dielectric layer 13 forms a base layer of the inorganic fine particle layer 14, and as will be described later, the polarized light transmitted through the inorganic fine particle layer 14 and reflected by the reflective layer 12 with respect to the polarized light reflected by the inorganic fine particle layer 14. It is desirable that the film is formed for the purpose of adjusting the phase of the light and enhancing the interference effect, and the film thickness is deviated by half a wavelength. However, since the inorganic fine particle layer has an absorption effect, the reflected light can be absorbed and the film thickness is not optimized. However, the improvement of the contrast can be realized, and in practical use, it may be determined by the balance between the desired polarization characteristics and the actual manufacturing process. The practical film thickness range is 1 to 500 nm, more preferably 300 nm or less.

As the material constituting the dielectric layer 13, general materials such as SiO2, Al2O3, and MgF2 can be used. These can be thinned by general vacuum film formation such as sputtering, vapor deposition method, and thin film deposition method, or by coating a sol-like substance on a substrate and thermosetting it. Further, the refractive index of the dielectric layer 13 is preferably larger than 1 and preferably 2.5 or less. Further, since the optical characteristics of the inorganic fine particle layer 14 are also affected by the refractive index of the surroundings, it is possible to control the characteristics of the polarizing element by the dielectric layer material.

As shown in FIG. 1B, the inorganic fine particle layer 14 has a major axis direction parallel to the one-dimensional lattice direction (Y-axis direction) of the reflection layer 12 and a minor axis direction perpendicular to the lattice direction (X-axis direction). The oblong island-shaped inorganic fine particles 14a are linearly arranged in one direction (one-dimensional lattice direction) parallel to the main surface of the substrate 11. Further, the inorganic fine particle layer 14 is provided above the metal lattice (belt-shaped thin film 12a) constituting the reflective layer 12 and on the dielectric layer 13, respectively. Therefore, the inorganic fine particle layer 14 has a wire grid structure on the substrate 11 having a pattern similar to that of the one-dimensional lattice of the reflective layer 12.

When the inorganic fine particles 14a constituting the inorganic fine particle layer 14 have a shape anisotropy between the X-axis direction and the Y-axis direction, the optical constants can be made different in the major axis direction and the minor axis direction. .. As a result, a predetermined polarization characteristic of absorbing the polarization component parallel to the long axis and transmitting the polarization component parallel to the short axis can be obtained. If the inorganic fine particles 14a do not have shape anisotropy (for example, circular shape), TM wave absorption also occurs in the TE wave absorption band, which is not preferable.

In order to control the shape anisotropy of the inorganic fine particle layer 14, the inorganic fine particle 14a is deposited only on the top of the dielectric layer 13 by reducing the arrangement pitch of the metal lattice (belt-shaped thin film 12a) constituting the reflective layer 12. It is effective to do so. As a result, the metal fine particles 14a can be isolated. Further, as a method for forming the metal fine particles 14a, oblique sputtering film formation, for example, an ion beam sputtering method for forming a film from the surface of the substrate 11 from an oblique direction is effective. The metal fine particles 14a do not have to be formed in a perfect island shape, as long as grain boundaries are formed.

FIG. 2 shows a state of oblique sputtering film formation for forming the inorganic fine particle layer 14 of the present invention. Although an example of ion beam sputtering is shown here, the present invention is not limited to this, and any sputtering method may be used.

In FIG. 2, 1 is a stage supporting the substrate 11, 2 is a target, 3 is a beam source (ion source), and 4 is a control board. The stage 1 is inclined by a predetermined angle θ with respect to the normal direction of the target 2, and the substrate 11 has a direction in which the longitudinal direction of the convex portion 14a of the uneven portion 14 is orthogonal to the incident direction of the inorganic fine particles from the target 2. Is located in. The angle θ is, for example, 0 ° to 20 °. The ions extracted from the beam source 3 irradiate the target 2. The inorganic fine particles ejected from the target 2 by the irradiation of the ion beam are incident on the surface of the substrate 11 from an oblique direction and adhere to the surface of the substrate 11. At this time, if the flat plate-shaped control plates 4 are arranged on the substrate 11 at regular intervals (for example, 50 mm), the direction of the incident particles on the surface of the substrate 11 is controlled, and the particles are deposited only on the side wall portion of the uneven portion 14. Can be done. The film thickness of the inorganic fine particle layer 14 at this time is preferably 200 nm or less.

Further, the inorganic fine particle layer 14 has optical anisotropy in the arrangement direction of the inorganic fine particles 14a and in the direction orthogonal to the arrangement direction of the inorganic fine particles 14a. Even if the inorganic fine particle layer 14 does not form an oblong aggregate as described above and is in a uniform film state, when the film is formed by a method such as ion beam sputtering from an oblique direction, the film is formed. Since the optical anisotropy as a layer can be strengthened, it is effective as the inorganic fine particle layer of the present invention.

FIG. 3 shows the experimental results of the optical anisotropy enhancing effect by such oblique ion beam sputtering. As shown in FIG. 3A, a germanium particle film 44 was prepared by incident and depositing germanium sputtered particles with the substrate 41 stationary at a direction of 10 ° with respect to the surface of the glass substrate 41 by an ion beam sputtering method. FIG. 3B shows the measurement results of the optical constants (refractive index, extinction constant) of the produced germanium particle film 44. The measurement was performed by a spectroscopic ellipsometer. The film thickness at this time is 10 nm. Due to the occurrence of optical anisotropy, there is a difference in the refractive index n and the extinction constant k in the plane. This means that the light absorption characteristics differ in the axial direction depending on the wavelength, and by using this film as the inorganic fine particle layer of the polarizing element of the present invention, high polarization contrast can be obtained.

FIG. 3C shows the result of observing the surface shape of this particle film with an electron microscope. In order to avoid the influence of the roughness of the glass surface, a single crystal Si substrate was used as the substrate, and oblique sputtering film formation was performed under the same conditions as in FIG. 3A. The germanium fine particles have grain boundaries and have a vertically long shape in the y-axis direction, and the size thereof is smaller than the measurement wavelength. In principle, such isolation and anisotropy of particles occur due to the steering effect in the oblique film formation. As a result, when viewed as a film, optical anisotropy is generated. As described above, the surface state of the inorganic fine particle layer in the present invention is different from that of a general thin film.

For comparison, as shown in FIG. 4A, germanium sputtered particles were formed while rotating the substrate 41 from the vertical direction of the substrate 41, and the measured values of the optical constants of the obtained germanium particle film 44 are shown in FIG. 4B. Shown. The optical anisotropy of the refractive index n and the extinction constant k did not occur, and each optical constant was a value close to the literature value. That is, in this case, it is a normal thin film state. The surface condition was measured by the same method as in FIG. 3C, but no grain boundary was visible at the same magnification. This suggests that this film is in a homogeneous thin film state.

The absorption wavelength of the inorganic fine particles 14a due to the optical anisotropy depends on the characteristics of the material, the shape anisotropy of the fine particles, the permittivity of the surroundings, and the like. In the present embodiment, the inorganic fine particle layer 14 is formed so that the polarization characteristic can be obtained with respect to the visible light region. Here, as the material constituting the inorganic fine particles 14a, it is necessary to select an appropriate material for the polarizing element 10 according to the band used. That is, a metal material or a semiconductor material is a material satisfying this, and specifically, as a metal material, Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, Si, Ge, Te, Sn. Examples thereof include simple substances or alloys containing these. Further, examples of the semiconductor material include Si, Ge, and Te. Further, silicide-based materials such as FeSi2 (particularly β-FeSi2), MgSi2, NiSi2, BaSi2, CrSi2, and CoSi2 are suitable. In particular, by using aluminum-based metal fine particles made of aluminum or an alloy thereof, or semiconductor fine particles containing beta-iron silicide, germanium, and tellurium as the material of the inorganic fine particles 14a, high contrast (high extinction ratio) is achieved in the visible light region. Can be obtained.

In addition, in order to give polarization characteristics to a wavelength band other than visible light, for example, an infrared region, fine particles of Ag (silver), Cu (copper), Au (gold), etc. are used as the inorganic fine particles constituting the inorganic fine particle layer. Is preferable. This is because the resonance wavelength in the long axis direction of these metals is in the vicinity of the infrared region. In addition to this, materials such as molybdenum, chromium, titanium, tungsten, nickel, iron, and silicon can be used according to the band used.

The lattice arrangement of the reflection layer 12 is not limited to the one-dimensional periodic arrangement in the X-axis direction as shown in the drawing, but may be a two-dimensional periodic arrangement in the X- and Y-axis directions. In this case, the shape anisotropy of the inorganic fine particle layer 14 can be expressed by the two-dimensional periodic structure of the reflective layer.

In the polarizing element 10 of the present embodiment configured as described above, the surface side of the substrate 11, that is, the formation surface side of the lattice-shaped reflection layer 12, the dielectric layer 13 and the inorganic fine particle layer 14 is the light incident surface. .. The polarizing element 10 utilizes the four actions of light transmission, reflection, interference, and selective light absorption of polarized waves due to optical anisotropy, so that the electric field component (lattice axis) parallel to the lattice of the reflective layer 12 is used. A polarized wave (TE wave (S wave)) having a direction (Y-axis direction) is attenuated, and a polarized wave (TM wave (P wave)) having an electric field component (perpendicular to the lattice, X-axis direction) perpendicular to the lattice is attenuated. To be transparent.

That is, as shown in FIG. 5A, the TE wave is attenuated by the selective light absorption action of the polarized wave due to the optical anisotropy of the inorganic fine particle layer 14 having shape anisotropy. The lattice-shaped reflective layer 12 functions as a wire grid and reflects TE waves transmitted through the inorganic fine particle layer 14 and the dielectric layer 13 as shown in FIG. 5B. At this time, by forming the dielectric layer 13 so that the phase of the TE wave transmitted through the inorganic fine particle layer 14 and reflected by the reflective layer 12 is shifted by half a wavelength, the TE wave reflected by the reflective layer 12 is generated by the inorganic fine particle layer 14. It is attenuated by canceling out due to interference with the reflected TE wave. As described above, the TE wave can be selectively attenuated. As described above, a film thickness that deviates by half a wavelength is desirable, but since the inorganic fine particle layer has an absorption effect, improvement in contrast can be realized even if the film thickness of the dielectric layer is not optimized, and practically, desired polarization is achieved. It may be decided based on the balance between the characteristics and the actual manufacturing process.

Further, when low reflection is required on the exit side, light may be incident from the reflection layer side. In this case as well, the same transmission contrast as described above can be obtained due to the selective absorption effect of the inorganic fine particle layer. This is because, as described later, the magnitude of the transmission contrast depends on the thickness of the reflective layer. Applying this to actual use, for example, in the optical engine portion (FIG. 16) of the liquid crystal projector of the present invention described later, the polarizing plate of the present invention is applied to the incident polarizing plate 10A for the purpose of avoiding unwanted reflected light to the liquid crystal panel. When used, the film surface of the polarizing plate (the inorganic fine particle layer 14 side in FIG. 5) is arranged so as to face the liquid crystal panel side. By doing so, the unwanted reflections will return to the light source side. Similarly, when the polarizing plate of the present invention is used as the emitting polarizing plate 10B or 10C, the film surface of the present polarizing plate (the inorganic fine particle layer 14 side in FIG. 5) may be directed toward the liquid crystal panel side. Although the direction of light incident on this polarizing plate is opposite when used for an incident polarizing plate and an outgoing polarizing plate, it is practical because the same transmission contrast can be obtained regardless of which side the light is incident on. There is no problem.

In FIG. 6, an aluminum lattice having a pitch of about 160 nm (line width of about 55 nm) and a lattice depth of 160 nm is formed as a reflective layer 12 on a substrate 11 made of glass (corning 1737), and SiO2 is formed on the aluminum lattice as a dielectric layer 13. It shows the polarization characteristics of a polarizing element formed by laminating a germanium fine particle layer at 30 nm and 10 nm by oblique film formation by ion beam sputtering. The transmittance of the absorption shaft is almost zero, and the reflectance is also low. The contrast in this case is about 500 at a wavelength of 550 nm, and the polarizing plate has good characteristics. By optimizing parameters such as pitch and film thickness, the contrast can be further improved.

Further, if necessary, by coating the front surface and the back surface of the substrate with antireflection films, it is possible to prevent reflection from air and the substrate surface and improve the transmittance of the transmission shaft. The antireflection film may be a generally used low refractive index film such as MgF2, or a multilayer film composed of a low refractive index film and a high refractive index film. Furthermore, coating the outermost surface of this polarizing element with a transparent substance such as SiO2 as a protective film with a film thickness within a range that does not affect the polarization characteristics is effective in improving reliability such as improving moisture resistance. is there. However, since the optical characteristics of the inorganic fine particles are also affected by the refractive index of the surroundings, the formation of the protective film may cause changes in the polarization characteristics. In addition, the reflectance for incident light also changes depending on the optical thickness of the protective film (refractive index x film thickness of the protective film), so the protective film material and its film thickness should be selected in consideration of these factors. As the material, a substance having a refractive index of 2 or less and an extinction coefficient close to zero is desirable. Such substances include SiO2 and Al2O3. These can be formed by general vacuum film formation methods (gas phase film formation method, sputtering method, vapor deposition method, etc.) and sol in which these are dispersed in a liquid by spin coating method, dipping method, etc. is there. Further, a self-assembled monolayer as described in Non-Patent Document 4 can also be used. A water-repellent self-assembled film is preferable for the purpose of improving moisture resistance. Perfluorodecyltrichlorosilane (FDTS), Octadecanetrichlorosilane (OTS), etc. are examples, and since they have water repellency, they are also effective in terms of antifouling measures. Further, in the case of a silane-based self-assembled monolayer, the self-assembled monolayer may be deposited after coating SiO2 as an adhesion layer on the polarizing element by the above method for the purpose of improving the adhesion.

FIG. 7 shows an example of the polarization characteristics of a polarizing element having a wire grid structure in which only a reflective layer is formed on a substrate. It can be seen that the reflectance of the absorption axis (TE wave, S wave) is extremely high at around 80%. The contrast in the transmission direction was about 200. Comparing FIGS. 6 and 7, it is clear that the reflectance of the absorption shaft can be significantly reduced according to the present embodiment, the transmission and reflection of the TE wave or the S wave are suppressed, and the light is extinguished in the transmission direction. The ratio can be greatly improved.

The polarizing element 10 can be manufactured, for example, as follows. That is, a metal film and a dielectric film are laminated on the substrate 11, a lattice pattern of the metal film and the dielectric film is formed by photolithography or the like, and then an inorganic fine particle layer 14 is formed by an oblique sputtering film formation method. By adjusting the incident angle at the time of oblique sputtering film formation, fine particles can be concentratedly deposited near the apex of the convex portion composed of the strip-shaped thin film 12a and the dielectric layer 13.

In addition to the above, it is also possible to apply a method in which a transparent material is formed on a transparent substrate in a one-dimensional lattice pattern, and a metal layer, a dielectric layer, and an inorganic fine particle layer are sequentially laminated on the convex portion of the lattice by oblique film formation. is there. Further, a method may be used in which a metal film, a dielectric film, and a fine particle film are sequentially laminated on the substrate, and then these are collectively etched in a one-dimensional lattice pattern.

Further, as shown in FIG. 8, after the reflective layer 12 is formed on the substrate 11 in a one-dimensional lattice pattern, the dielectric layer 13 is formed on the entire surface of the substrate 11. As a result, the dielectric layer 13 has a concavo-convex shape in which a convex portion is formed immediately above the strip-shaped thin film 12a of the reflective layer 12 and a concave portion is formed between the strip-shaped thin films 12a. After that, a polarizing element having the same effect as that of the example of FIG. 1 can be produced by forming the inorganic fine particle layer 14 on the side surface of the top of the convex portion of the dielectric layer 13 by the oblique sputtering film formation method. it can. The formation region of the inorganic fine particle layer 14 is not limited to one side surface portion of the top portion of the dielectric layer 13 shown, but may be both side surface portions.

(Second Embodiment)
FIG. 9 is a side sectional view showing a schematic configuration of the polarizing element 20 according to the second embodiment of the present invention. In the figure, the parts corresponding to the first embodiment described above are designated by the same reference numerals, and detailed description thereof will be omitted.

In the polarizing element 20 of the present embodiment, a one-dimensional lattice-shaped reflective layer 12 is formed on the surface (one surface) of the substrate 11, and the dielectric layer 13 and the inorganic fine particle layer 14 are formed on the reflective layer 12. Are formed in sequence. Then, on the back surface (the other surface) of the substrate 11, a concavo-convex portion 15 made of a dielectric material and a second second inorganic fine particle layer 16 formed on the top or at least one side surface of the concavo-convex portion 15 are formed. A selective light absorption layer 17 for polarized waves due to optical anisotropy is provided.

In the polarizing element 10 of the first embodiment in which the selective light absorbing layer 17 for polarized waves due to optical anisotropy is not provided, the back surface side of the substrate 11 exhibits a mirror surface due to the reflecting layer 12, so that the polarizing element is transmitted. Then, the light reflected and returned by another optical element such as a lens arranged in the next stage of the polarizing element is reflected again by the mirror surface. Such stray light causes deterioration of image quality such as ghosts in the liquid crystal projector.

In the present embodiment, by providing the selective light absorption layer 17 of the polarized wave due to the optical anisotropy of the above configuration on the back surface side of the substrate 11, the stray light is absorbed and the reflection in the reflection layer 12 is prevented. The concavo-convex portion 15 constituting the selective light absorption layer 17 for polarized waves due to optical anisotropy is made of the same material as the dielectric layer 13 and is formed parallel to the direction in which the strip-shaped thin film 12a of the reflection layer 12 extends. It is formed in a one-dimensional grid pattern. The second inorganic fine particle layer 16 is formed by linearly arranging inorganic fine particles on the top or side surface of the convex portion of the uneven portion 15, and is made of the same material as the inorganic fine particle layer 14 on the surface side of the substrate 11. By doing so, the optical anisotropy is exhibited and the absorption effect on the incident light from the back surface of the substrate 11 appears.

The uneven portion 15 is formed by a sputtering method, a sol-gel method, or the like in the same manner as the method for forming the dielectric layer 13. For imparting the uneven shape, pattern processing using photolithography technology or press formation by nanoimprint method is preferable. As a method for forming the second inorganic fine particle layer 16, an oblique film formation similar to the method for forming the inorganic fine particle layer 14 on the surface side of the substrate 11 is preferable. The second inorganic fine particle layer 16 is formed on the top, one side surface portion, or both side surface portions of the uneven portion 15.

Alternatively, as another method for manufacturing the polarizing element 20, the polarizing element 10 shown in FIG. 1, the uneven portion 15 made of a dielectric material on another substrate, and the top or at least one side surface portion of the uneven portion 15 are formed. Using a polarizing element provided with a selective light absorption layer 17 for polarized waves due to optical anisotropy composed of a second second inorganic fine particle layer 16, the back surfaces of each substrate are bonded to each other with a transparent adhesive. The polarizing element 20 may be used. In this case, it is preferable that the arrangement directions of the inorganic fine particles of the inorganic fine particle layers 15 and 25 are aligned.

(Third Embodiment)
FIG. 10 is a side sectional view showing a schematic configuration of the polarizing element 30 according to the third embodiment of the present invention. In the figure, the parts corresponding to the first embodiment described above are designated by the same reference numerals, and detailed description thereof will be omitted.

The polarizing element 30 of this embodiment is configured for the same purpose as that of the second embodiment described above. That is, in the polarizing element 30 of the present embodiment, the antireflection layer 18 is formed between the substrate 11 and the reflection layer 12. By providing the antireflection layer 18 directly under the one-dimensional lattice-shaped reflection layer 12 in this way, the reflection of the incident light from the back surface of the substrate 11 is prevented.

The antireflection layer 18 is preferably a black layer such as a carbon black film. As a result, the incident light from the back surface of the substrate 11 can be efficiently absorbed. Further, in addition to carbon, an oxygen-deficient silicon oxide layer and a low-reflection material having a reflectance lower than that of the reflection layer 12 can be applied. Alternatively, the same material as the inorganic fine particle layer 14 may be used as the antireflection layer 18. In the illustrated example, the dielectric layer 19 is provided for the purpose of reducing the reflectance by obtaining an interference effect between the reflective layer 12 and the antireflection layer 18. The processing of the dielectric layer 19 and the antireflection layer 18 into a lattice shape can be performed at the same time by, for example, pattern processing of the reflection layer 12.

As a modification of this embodiment, there is the following method. That is, the surface of the substrate 11 is subjected to a rubbing treatment, and the substrate 11 is composed of irregularities in a state in which fine streaks are aligned in one direction so as to correspond to the arrangement direction of the inorganic fine particles 14a of the inorganic fine particle layer 14 subsequently formed on the surface. A texture structure is formed, and then a thin film (antireflection layer) composed of inorganic fine particles having shape anisotropy is formed on the surface after the rubbing treatment by the above-mentioned oblique sputtering method so as to correspond to the arrangement direction of the inorganic fine particles 14a. It is good to do. Due to the texture structure, the arrangement of the inorganic fine particles is improved so that the long axis direction of the inorganic fine particles is the longitudinal direction of the streaks, the polarization characteristics of the thin film are improved, and the ghost countermeasure effect can be enhanced. At the same time, an increase in transmission contrast characteristics as a polarizing element can be expected.

(Fourth Embodiment)
FIG. 11 is a side sectional view showing a schematic configuration of the polarizing element 40 according to the fourth embodiment of the present invention. In the figure, the parts corresponding to the first embodiment described above are designated by the same reference numerals, and detailed description thereof will be omitted.

The polarizing element 40 of the present embodiment is characterized in that one or a plurality of laminated structures of the dielectric layer 13 / the inorganic fine particle layer 14 are stacked on the inorganic fine particle layer 14 of the polarizing element 10 of the first embodiment. There is. That is, in FIG. 11, in the polarizing element 40, the strip-shaped thin film 12a forming the reflective layer 12, the dielectric layer 13, and the inorganic fine particle layer 14 are laminated in this order on the substrate 11, and the inorganic fine particle layer 14 is laminated. The laminated structure 1a of the dielectric layer 13 / the inorganic fine particle layer 14 is further stacked to form a wire grid structure. Further, the laminated structure 1a may be further stacked on the laminated structure 1a. As a result, the interference effect between the layers can be enhanced to increase the contrast in the transmission axis direction at a desired wavelength, and at the same time, the reflection component from the polarizing element, which is not preferable in the transmission type liquid crystal display device, can be reduced over a wide range.

In order to confirm the effect of stacking the laminated structures 1a in the present embodiment, the polarizing element 10 having no laminated structure 1a shown in FIG. 1 and the polarizing element 40 having one laminated structure 1a shown in FIG. 11 The polarization optical characteristics with respect to the wavelength were simulated and calculated by wavelength exact coupling wave analysis (RCWA). Here, the reflective layer 12 is a layer made of Al (notation Al), the dielectric layer 13 is a layer made of SiO2 (notation SiO2), and the inorganic fine particle layer 14 is made of Ge formed by oblique sputter film formation (notation Ge). In the green light region (around 550 nm of the wavelength), which is practically important for liquid crystal display devices, the contrast required as the ratio of the transmittances in the transmission axis X direction and the absorption axis Y direction is about 4000 to 5000, and the reflectance is the lowest. Therefore, the optimization calculation was performed using the thickness of the reflective layer 12, the thickness of the dielectric layer 13, and the thickness of the inorganic fine particle layer 14 as parameters. The one-dimensional lattice pitch of the reflective layer 12 was 150 nm, and the lattice width (width of the band-shaped thin film 12a): space (interval between the band-shaped thin films 12a) = 0.275: 0.725. Further, in order to suppress the influence of stray light due to the rereflection of the return light to the polarizing element emitting surface, a Ge layer having a thickness of 15 nm is added to the polarizing element emitting surface (between the reflecting layer 12 and the substrate 11). ..

As a result of the above condition setting, the layer structure optimized at the contrast of 4000 to 5000 is as follows. The number in parentheses is the film thickness of each layer, and the total film thickness of the polarizing element 40 is thinner than that of the polarizing element 10. This contributes to the reduction of the thin film deposition time and the etching time, which is advantageous in manufacturing.
Polarizing element 10; Ge (15 nm) / Al (240 nm) / SiO2 (205 nm) / Ge (90 nm) from the 11th surface of the substrate
Polarizing element 40; Ge (15 nm) / Al (220 nm) / SiO2 (90 nm) / Ge (45 nm) / SiO2 (90 nm) / Ge (45 nm) from the 11th surface of the substrate.

As a result of the above, FIG. 12 shows the obtained polarized optical characteristics. Further, FIG. 13 shows the contrast result in that case.
In FIG. 12, the absorption axis reflectance in the vicinity of the wavelength of 550 nm is smaller in the polarizing element 40 (data in the solid line described as two layers) than in the polarizing element 10 (data in the dotted line described as a single layer). Correspondingly, in FIG. 13, the contrast in the vicinity of the wavelength of 550 nm is larger in the polarizing element 40 (two layers) than in the polarizing element 10 (single layer).

In this case, the calculation was performed on the assumption that the structure is for the green light region (wavelength 550 nm) and one laminated structure 1a is stacked (two layers), but the film thickness of each layer is also optimized in other wavelength regions. By doing so, the same effect can be obtained. Further, the same effect can be obtained in a configuration in which a plurality of laminated structures 1a are stacked (two or more layers).

As a method for manufacturing the polarizing element 40 of the present invention, for example, there are the following three methods. That is, as the first method, a reflective layer material (metal lattice material) and a dielectric film are laminated on the substrate 11, a one-dimensional lattice pattern is formed or etched by a method such as nanoimprint or photolithography, and then oblique sputtering is performed. Fine particles are formed by the film method. According to this, by adjusting the incident angle at the time of oblique sputtering film formation, it is possible to intensively deposit inorganic fine particles near the apex of the dielectric layer 13 which is a convex portion. As a second method, a transparent material is used to form a one-dimensional lattice-shaped uneven portion on a transparent substrate, and a reflective layer material, a dielectric film, and an inorganic fine particle material are sequentially laminated by diagonal film formation for several times. It is a thing. The third method is to sequentially laminate the laminated structure of (dielectric film / inorganic fine particle thin film) on the thin film (metal lattice film) of the reflective layer for the number of layers and then etch. The inorganic fine particle material does not have to be completely island-shaped, as long as grain boundaries are formed. Further, the dielectric layer 13 and the inorganic fine particle layer 14 may be manufactured by combining a forming method by sputtering film formation and etching and a forming method by oblique sputtering film formation. Although the type of substrate material is not limited in executing the above manufacturing process, a crystal or sapphire substrate having high thermal conductivity is suitable for application to a projector having a large amount of heat generation.

Further, as in the first embodiment, a protective film made of SiO2 or the like is deposited on the uppermost portion of the polarizing element 40 for the purpose of improving reliability such as moisture resistance within a range in which changes in optical characteristics do not affect the application. You may. Further, for the purpose of reducing the reflection of the substrate 11, a non-reflective coating (a general laminated film of a high refraction film and a low refraction film, etc.) is applied in advance, and then the polarizing element 40 is manufactured by the manufacturing process to achieve black and white contrast. Can be improved.

By the way, with the polarizing element 40 having the structure described so far, since the light emitting surface (reflection layer 12) is made of metal, the reflectance becomes high when there is return light. Therefore, also in the present embodiment, it is advisable to take measures against stray light on the exit surface as shown in the second embodiment and the second embodiment.
14 and 15 show an example of measures against stray light on the exit surface according to the present embodiment.

FIG. 14 is an example in which the configuration of FIG. 9 is applied to the present embodiment.
The polarizing element 40A is formed in the polarizing element 40 on a surface (back surface) opposite to the surface on which the reflective layer 12 is formed on the substrate 11 and an uneven portion 15 made of a dielectric material, and on the top or at least one side surface of the uneven portion 15. A selective light absorption layer 17 for polarized waves due to optical anisotropy composed of a second second inorganic fine particle layer 16 is provided.

FIG. 15 is an example in which the configuration of FIG. 10 is applied to the present embodiment.
The polarizing element 40B is a polarizing element 40 in which an antireflection layer 18 is provided directly under the one-dimensional lattice-shaped reflection layer 12, and a dielectric material is provided for the purpose of obtaining an interference effect between the reflection layer 12 and the antireflection layer 18. Layer 19 is provided. In FIG. 15, the dielectric layer 19 under the reflective layer 12 may not be provided, and the antireflection layer 18 may be simply formed under the reflective layer 12. Further, when the antireflection layer 18 is the same as the inorganic fine particle layer 14, it also contributes to the improvement of the contrast, but for the purpose of simply preventing the reflection of the return light, the antireflection under the reflection layer 12. It is preferable to provide a layer (low reflection layer) having a reflectance lower than that of the reflection layer 12 as the layer 18. As the low-reflection material, it is effective if the reflectance is lower than that of the reflective layer 12, and it is also possible to use an oxide film such as carbon or oxygen-deficient SiOx, or to use metal or semiconductor fine particles.

When the antireflection layer 18 and the dielectric layer 19 are added under the reflection layer 12, or when the antireflection layer 18 is formed directly under the reflection layer 12, these films are formed before the film for the reflection layer is formed. If the film is etched at the same time as the etching for forming the reflective layer 12, these layers can be formed only directly under the strip-shaped thin film 12a of the reflective layer 12, so that the transmission characteristics can not be affected.

Next, the liquid crystal projector according to the present invention will be described.
The liquid crystal projector of the present invention includes a lamp serving as a light source, a liquid crystal panel, and the above-mentioned polarizing elements 10, 20, 30, and 40 of the present invention.

FIG. 16 shows a configuration example of an optical engine portion of the liquid crystal projector according to the present invention. Here, the description will be made on the premise that the polarizing element 10 is used.
The optical engine portion of the liquid crystal projector 100 includes an incident side polarizing element 10A for red light LR, a liquid crystal panel 50, an outgoing pre-polarizing element 10B, an outgoing main polarizing element 10C, an incident side polarizing element 10A for green light LG, and a liquid crystal panel 50. Exit pre-polarizing element 10B, exit main polarizing element 10C, incident side polarizing element 10A for blue light LB, liquid crystal panel 50, exit pre-polarizing element 10B, exit main polarizing element 10C, and each exit main polarizing element 10C. It is equipped with a cross-polarized prism 60 that synthesizes incoming light and emits it to a projection lens. Here, the polarizing elements 10, 20 and 30 of the present invention are applied to the incident side polarizing element 10A, the outgoing pre-polarizing element 10B, and the outgoing main polarizing element 10C, respectively.

In the liquid crystal projector 100 of the present invention, the light emitted from the light source lamp (not shown) is separated into red light LR, green light LG, and blue light LB by a dichroic mirror (not shown), and the incident side corresponding to each light. The light LR, LG, and LB incident on the polarizing element 10A and then polarized by the respective incident side polarizing elements 10A are spatially modulated by the liquid crystal panel 50 and emitted, and the exit pre-polarizing element 10B and the exit main polarizing element 10C are emitted. After passing through, it is synthesized by the cross dichroic prism 60 and projected from a projection lens (not shown). Even if the light source lamp has a high output, it uses the polarizing element 10 (20, 30, 40) of the present invention, which has excellent light resistance to strong light, so that a highly reliable liquid crystal projector can be realized. can do.

The polarizing element of the present invention is not limited to the application to the liquid crystal projector, and is suitable as a polarizing element that receives heat as a usage environment. For example, it can be applied as a polarizing element of a liquid crystal display of a car navigation system or an instrument panel of an automobile.

The results of verifying the polarization characteristics of the polarizing element according to the present invention are shown below.
(Example 1)
In the polarizing element 10 of FIG. 1, the method of forming the inorganic fine particle layer 14 by the oblique sputtering film formation method is also advantageous from the viewpoint of improving the polarization characteristics. The reason for this will be described with reference to FIG. That is, as shown in FIG. 3C, the inorganic fine particles have a vertically long shape in the direction orthogonal to the particle incident direction of the oblique film formation in the substrate surface. However, in the case of forming a film on a flat surface such as Si or glass (FIG. 17A), the isolation and shape of the particles depend on the distribution in the direction of the incident particles and the self-organizing action due to the steering effect. , The major axis direction of each particle cannot be completely matched with the y axis direction of FIG. 3A. This causes disturbance of the polarization axis. On the other hand, if the convex portion of the substrate surface is formed into a one-dimensional lattice by forming the reflective layer (metal lattice) and the dielectric layer, the film is formed diagonally from the direction orthogonal to the longitudinal direction of the one-dimensional lattice (Fig.). 17 (b)), the fine particles inevitably follow the lattice direction, and the disturbance of the polarization axis of the fine particle layer is largely eliminated. Therefore, it is considered that the inorganic fine particles formed on the lattice have a larger optical anisotropy than when the inorganic fine particles are formed on a flat substrate. When an inorganic fine particle layer made of Ge is formed on a substrate in which a reflective layer made of Al is provided in a one-dimensional lattice pattern, it is difficult to measure the optical constant of the Ge fine particles independently, but it is better than FIG. 3A. It is considered to have large optical characteristics.

Therefore, as a lattice substrate imitating a substrate in which a reflective layer made of Al is provided in a one-dimensional lattice pattern, a crystal substrate having a lattice pitch of 150 nm and one-dimensional lattice-like irregularities formed on the surface as shown in FIG. The characteristics were evaluated. In addition, a flat substrate using Corning 1737 glass as a flat substrate for comparison was also evaluated. Here, when Ge was obliquely deposited on each substrate by the method of oblique sputtering deposition shown in FIG. 3A by ion beam sputtering, the transmission axis contrast at a wavelength of 550 nm was 1.3 (flat substrate). ), 2.7 (lattice substrate), and the contrast was about twice as high when the film was formed on the lattice shape. This supports the above effect.

In the oblique film formation, as shown in FIG. 19, the shape of the film-formed particles changes with the film thickness (thickness in the growth direction of the inorganic fine particles), which affects the optical anisotropy. That is, when the film thickness b of the inorganic fine particles is smaller than the major axis a of the particles (FIG. 19A), the inorganic fine particles have optical anisotropy in two directions (X and Y directions) on the substrate surface, and the direction of the major axis a of the particles is the absorption axis. It becomes. On the other hand, when the film thickness b of the inorganic fine particles is larger than the major axis a of the particles (FIG. 19B), the inorganic fine particles have optical anisotropy in the thickness direction and the in-plane axial direction, and the direction of the particle film thickness b. Is the absorption axis, so that the directions of optical anisotropy are substantially reversed in FIGS. 19A and 19B. In the present invention, since the lattice direction is used as the absorption axis, it means that the polarization characteristic deteriorates when the film thickness is thick. Therefore, it is desirable to use it in a region where (particle major axis a)> (particle film thickness b) as shown in FIG. 19A.

By the way, even if a thin film having no optical anisotropy (for example, a germanium thin film) is formed on the dielectric layer 13 instead of the inorganic fine particle layer 14, the reflectance in the absorption axis direction can be increased by optimizing the film thickness. Suppression is possible. However, in this case, since the interference effect is dominant in the suppression, there is a problem that the wavelength band is narrow and the transmittance in the transmission axis direction is reduced due to the absorption in the transmission axis direction. Further, since the interference effect is sensitive to the film thickness, it is necessary to strictly control the film thickness of the dielectric layer 13 and the film thickness of the germanium thin film in order to obtain desired characteristics. On the other hand, in the present invention, since germanium fine particles having optical anisotropy are used, the design range is wide and the production is easy.

Therefore, the difference in optical characteristics between the case where the inorganic fine particle layer 14 in the polarizing element 10 is a thin film and the case where the inorganic fine particle layer 14 is a fine particle is simulated by the wavelength exact coupling wave analysis (RCWA) method. Here, the film thickness (aluminum thickness) of the reflective layer 12 is 200 nm, the lattice pitch is 150 nm, the aluminum width is 45 nm, and the film thickness (SiO2) of the dielectric layer 13 is 30 nm with respect to the film thickness of the Ge thin film and the Ge fine particles. The dependence of absorption axis reflectance, transmission axis transmittance, and transmission contrast at a wavelength of 450 nm was calculated. Further, the optical constant of the Ge thin film uses the value of FIG. 4B, and the optical constant of the Ge fine particles is the incident light in the model shown in FIG. 20 in consideration of the increase in anisotropy when the film is formed on the lattice. The calculation was performed on the assumption that fine particles sufficiently smaller than the wavelength are distributed in the dielectric layer in the same axial direction. Further, the volume fraction of Ge in the dielectric layer 13 was calculated as 0.4, and the aspect ratio was calculated as 20.
The result is shown in FIG. 21 (a) is the result of absorption shaft reflectance, FIG. 21 (b) is the result of transmission shaft transmittance, and FIG. 21 (c) is the result of transmission contrast. It can be seen that in the case of Ge fine particles, the contrast is about the same, the transmittance is higher, and the film thickness range in which the reflectance can be reduced is wider than in the case of the Ge thin film.

(Example 2)
In the polarizing element 10 having the configuration shown in FIG. 1, the transmission contrast thereof can be easily controlled by changing the height (film thickness) of the reflective layer 12. As an example, in FIG. 22, the wavelength strict coupling wave of the reflection layer film thickness (aluminum height) and the transmission contrast at a wavelength of 550 nm when the pitch is 150 nm and the aluminum width is 37.5 nm as the primary lattice-shaped reflection layer 12 made of Al. The calculation result by the analysis (RCWA) is shown.

Further, in the polarizing element 10 having the configuration shown in FIG. 1, the optical characteristics thereof can be easily controlled by changing the height (film thickness) of the dielectric layer 13. Here, RF sputtering is performed on a glass (corning 1737) substrate 11 as a primary lattice-shaped reflective layer 12 made of Al, the film thickness (aluminum height) of which is 200 nm, the pitch of which is 150 nm, and the lattice width of 50 nm. The polarizing element 10 of the present invention has a dielectric layer 13 made of SiO2 formed by film formation and whose film thickness is changed to 0, 19, 37, 56, 74 nm, and an inorganic fine particle layer 14 made of Ge fine particles having a thickness of 30 nm. The relationship between the dielectric layer film thickness at wavelengths of 450, 550, and 650 nm, the transmission axis transmittance, the contrast, and the absorption axis reflectance of the obtained sample was determined. The results are shown in Table 1.

From the obtained results, for example, when it is desired to reduce the absorption shaft reflectance, the film thickness of the dielectric layer 13 may be in the range of 19 to 37 nm. Further, when it is used in an application where the influence of reflection is small, the film thickness of the dielectric layer 13 can be set to 0. This means a reduction in the manufacturing process, which leads to an improvement in productivity. In addition, it achieves high contrast at wavelengths of 450 to 650 nm and is suitable for projector applications with a wide wavelength range.
On the other hand, regarding the transmittance, it shows a high transmittance of 70% or more at a wavelength of 450 nm and 80% or more at wavelengths of 550 and 650 nm. It is possible to further improve the transmittance by narrowing the grid pitch.
Further, the contrast can be adjusted by adjusting the height of the metal lattice. If you need higher contrast, you can raise the aluminum grid, and if you want to lower it, you can lower it.

Next, a sample of the polarizing element having the configuration shown in FIG. 1 was prepared. Here, an aluminum lattice having a pitch of 150 nm and a lattice depth of 30 nm is formed as a reflective layer 12 on a substrate 11 made of glass (corning 1737), and SiO2 of 30 nm is formed as a dielectric layer 13 on the aluminum lattice, and then, Using the ion beam sputtering apparatus shown in FIG. 2, oblique sputtering deposition was performed on the substrate 11 at room temperature at a substrate inclination angle θ = 5 °, and a Ge fine particle layer was laminated as an inorganic fine particle layer 14 by 30 nm, and a film thickness was formed on the outermost layer as a protective film. A 30 nm SiO2 was formed to prepare a polarizing element sample shown in FIG.
FIG. 23 shows the polarization characteristics of the polarizing element sample. In this case, since the film thickness of the reflective layer is thin (the height of aluminum is low), the contrast is about 3 in the blue region, but the reflectance is suppressed to 2% or less by the effect of Ge fine particles. In the case of a polarizing element having such performance, Ge fine particles are deposited on the side wall of the convex portion composed of the reflective layer / dielectric layer, and have a good shape as an anisotropic optical absorbing element.

In the polarizing element 10 of the present invention, the lattice shape (shape and height of the reflective layer 12 / dielectric layer 13 in FIG. 1, the pitch of the primary lattice, etc.) and the steering effect (size, aspect ratio, arrangement, etc. of the inorganic fine particles 14a) ), It is possible to realize a fine particle shape suitable as an absorption type polarizing element.

(Example 3)
In the polarizing element 10 shown in FIG. 1, as a countermeasure against stray light on the exit surface (ghost countermeasure), fine streaks are aligned in one direction so as to correspond to the arrangement direction of the inorganic fine particles 14a formed later on the surface of the substrate 11. A thin film made of inorganic fine particles having shape anisotropy corresponding to the arrangement direction of the inorganic fine particles 14a on the surface after the rubbing treatment so as to have a certain texture structure (thin film to be the antireflection layer 18 (hereinafter referred to as “thin film”). , Anti-reflection film)). Specifically, a texture structure is mechanically formed on the surface of the substrate 11 with an abrasive material such as an abrasive tape, and then an antireflection film composed of inorganic fine particles is formed on a lattice by an oblique sputtering film formation method. Since the inorganic fine particles having shape anisotropy due to the steering effect can be formed like the inorganic fine particle layer 14 to be filmed, the polarization effect of the inorganic fine particles is enhanced, and as a result, the ghost suppressing effect can be enhanced. Hereinafter, a concrete example will be described.

Here, the effect was verified using D20000 manufactured by Nippon Microcoating as an abrasive. Corning 1737 glass was used for the substrate, and the surface was rubbed in one direction with D20000 to form a texture. FIG. 24 shows the results of measuring the substrate surface after texture formation by an AFM (atomic force microscope). The horizontal axis is the position on the substrate, and the vertical axis is the height of unevenness on the surface. The average pitch of the irregularities on the surface of the substrate was 160 nm. Moreover, when the transmittance of the substrate before and after the texture formation was examined, it was found that the transmittance did not change before and after the texture formation (before and after polishing) as shown in FIG. That is, according to this method, it is possible to easily perform nano-level precision processing without deteriorating the transmission characteristics of the substrate.

Next, an antireflection film having a film thickness of 10 nm made of Ge fine particles was formed on the substrate after the texture formation by performing oblique sputtering film formation with the substrate inclination angle θ = 5 ° by the ion beam sputtering apparatus shown in FIG. At this time, regarding the relationship between the Ge incident direction and the substrate, the substrate was arranged so that the y direction was the texture longitudinal direction in FIG. 3A, and a sputtering film thickness was formed. When the shape of the Ge fine particles in the antireflection film was observed with an AFM (atomic force microscope) of the obtained sample, a state in which the Ge fine particles were aligned along the texture was observed as shown in FIG. 26. It was.

FIG. 27 shows the transmission characteristics of this sample. For comparison, the transmission characteristics of a sample in which the 1737 glass substrate that had not been rubbed was left as it was and the antireflection layer was formed under the same conditions other than that were also examined. In FIG. 27, the sample of this example is referred to as “texture substrate”, and the comparative sample is referred to as “as is”. As a result, the polarization characteristics were observed due to the steering effect in both cases, but the one with the texture had a higher transmittance in the x direction and a large difference from the transmittance in the y direction, and showed good polarization characteristics. ..
In the present invention, the sample of the present embodiment (an antireflection film formed on a substrate having a texture structure) is used to form the layer structure of the polarizing element 10 in FIG. 1 on the antireflection layer 12, but the reflection layer 12 or the dielectric. At the same time that the body layer 13 is patterned, the antireflection film is also processed into a lattice shape to form the antireflection layer 18. As a result, the effect of preventing ghosts can be enhanced, and at the same time, the transmission contrast characteristics of the polarizing element can be expected to increase.

1 ... Stage, 2 ... Target, 3 ... Beam source, 4 ... Control plate, 10, 10A, 10B, 10C, 20, 30, 40, 40A, 40B ... Polarizing element, 11 ... Substrate , 12 ... Reflective layer, 12a ... Band-shaped thin film, 13, 19 ... Dielectric layer, 14 ... Inorganic fine particle layer, 14a ... Inorganic fine particles, l5 ... Concavo-convex portion (selective light absorption layer of polarized waves due to optical anisotropy), 16 ... Inorganic fine particle layer (selective light absorption layer of polarized waves due to optical anisotropy), 17 ... Selective light absorption layer of polarized waves due to optical anisotropy, 18 ... Antireflection layer, 1a ... Laminated structure, 50 ... LCD panel, 60 ... Cross-polarized light prism, 100 ... LCD projector

Claims (18)

A light source, a liquid crystal panel, an incident side polarizing plate, an outgoing side polarizing plate,
With
The incident side polarizing plate and the outgoing side polarizing plate are
A light-transparent substrate and
A reflective layer in which strip-shaped thin films extending in one direction on the substrate are arranged in a one-dimensional lattice pattern at a pitch smaller than the wavelength of the light.
The dielectric layer and the inorganic fine particle layer formed on the reflective layer,
A transmissive liquid crystal projector, which is a polarizing element in which the inorganic fine particle layer is arranged on the liquid crystal panel side of the substrate. The transmissive liquid crystal projector according to claim 1, wherein the emitting side polarizing plate is arranged parallel to the liquid crystal panel. The transmissive liquid crystal projector according to claim 1 or 2, wherein no other optical member is interposed between the liquid crystal panel and the emitting side polarizing plate. The transmissive liquid crystal projector according to claim 1, wherein one or a plurality of laminated structures of the dielectric layer / the inorganic fine particle layer are stacked on the inorganic fine particle layer. The dielectric layer has a concavo-convex shape in which a convex portion is formed immediately above the strip-shaped thin film and a concave portion is formed between the strip-shaped thin films.
The transmissive liquid crystal projector according to claim 1, wherein the inorganic fine particle layer is formed on the top of a convex portion of the dielectric layer or at least one side surface portion thereof. The transmissive liquid crystal projector according to claim 5, wherein the dielectric layer is formed on the entire surface of the reflective layer. The transmissive liquid crystal projector according to claim 5 or 6, wherein the inorganic fine particle layer is formed on both side surfaces of a convex portion of the dielectric layer. The transmissive liquid crystal projector according to claim 1, wherein the reflective layer is a metal layer. The transmissive liquid crystal projector according to claim 1, wherein the substrate is made of glass, sapphire, or quartz. The inorganic fine particles contained in the inorganic fine particle layer are a simple substance of Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, Si, Ge, Te, Sn, an alloy containing these, or a silicide-based semiconductor. The transmissive liquid crystal projector according to claim 1, which is made of a material. The transmissive liquid crystal projector according to claim 1, wherein the aggregate of the inorganic fine particles contained in the inorganic fine particle layer has shape anisotropy. The first aspect of claim 1, wherein the inorganic fine particle layer has optical anisotropy in the arrangement direction of the aggregates of the inorganic fine particles contained in the inorganic fine particle layer and the direction orthogonal to the arrangement direction of the aggregates of the inorganic fine particles. Transmissive LCD projector. The polarizing element has a one-dimensional lattice-shaped uneven portion formed on the other surface of the substrate parallel to the direction in which the strip-shaped thin film of the reflective layer extends, and inorganic fine particles arranged on at least one side surface portion of the uneven portion. The transmissive liquid crystal projector according to claim 1, further comprising a second layer of inorganic fine particles. The transmissive liquid crystal projector according to claim 1, wherein an antireflection layer is formed between the reflection layer and the substrate. The antireflection layer is rubbed so that the surface of the substrate corresponds to the arrangement direction of the inorganic fine particles contained in the inorganic fine particle layer, and the surface after the rubbing treatment corresponds to the arrangement direction of the inorganic fine particles. The transmissive liquid crystal projector according to claim 14, wherein inorganic fine particles having shape anisotropy are attached. On the other surface of the substrate, a one-dimensional lattice-shaped uneven portion formed parallel to the direction in which the strip-shaped thin film of the reflective layer extends, and an inorganic fine particle in a primary lattice shape on the top or at least one side surface of the uneven portion. The transmissive liquid crystal projector according to claim 1, wherein a light absorbing layer composed of a second inorganic fine particle layer arranged in is provided. A polarizing element having the polarizing element and a second inorganic fine particle layer in which inorganic fine particles are arranged in a one-dimensional lattice pattern on the top or at least one side surface of a one-dimensional lattice-shaped uneven portion formed on the surface of another substrate. The transmission type according to claim 1, further comprising a polarizing element in which the back surfaces of the substrates are bonded to each other so that the direction in which the strip-shaped thin film of the reflection layer extends and the direction in which the grid of the uneven portion extends are aligned. LCD projector. The transmissive liquid crystal projector according to claim 1, wherein the incident side polarizing plate and the outgoing side polarizing plate have polarization characteristics corresponding to the wavelength of the light.

Images