Polarization device, method of manufacturing the same, liquid crystal device, and electronic apparatus

The wire grid type polarization device includes a substrate, and a metal layer formed on one face of the substrate in a substantially stripe shape in a plan view, a first dielectric layer provided on two side faces opposite to each other among a plurality of side faces of the metal layer and in a top part of the metal layer, and a second dielectric layer provided on the first dielectric layer. A substrate side end portion of the second dielectric layer is located between the one surface of the substrate and the top part of the first metal layer and a plurality of metal layers that includes a first metal layer having a first side face, a second side face opposed to the first side face, and a top part. First and second dielectric layers are provided in the first side face, the second side face, and the top part of the first metal layer. The first dielectric layer is provided between the first metal layer and the second dielectric layer. The optical absorption rate of the first dielectric layer is less than that of the second dielectric layer.

This application is a Reissue application of U.S. patent application Ser. No. 13/159,274, filed Jun. 13, 2011, now U.S. Pat. No. 8,416,371, which issued on Apr. 9, 2013 and claims priority to Japanese Patent Application No. 2010-136851, filed on Jun. 16, 2010.

BACKGROUND

1. Technical Field

The present invention relates to a polarization device, a method of manufacturing the polarization device, a liquid crystal device, and an electronic apparatus.

2. Related Art

As a light modulating device in various electro-optical apparatuses, a liquid crystal device has been used. As a structure of the liquid crystal device, a structure in which a liquid crystal layer is interposed between a pair of substrates oppositely disposed has been widely known. In addition, a configuration, which includes a polarization device that allows a predetermined polarized light to be incident to the liquid crystal layer, and an alignment film that controls an arrangement of liquid crystal molecules at the time of not applying a voltage, is typical.

As the polarization device, a film-type polarization device manufactured by extending a resin film including iodine or a dichroic dye in one direction and aligning the iodine or dichroic dye in this extension direction, and a wire grid type polarization device formed by lining a nano-scaled metal fine wire on a transparent substrate are known.

The wire grid type polarization device is made from an inorganic material, such that the polarization device has the merit of superior heat resistance, and is used in a field where heat resistance is especially necessary. For example, the polarization device is used as a polarization device for a light valve of a liquid crystal projector. As such a wire grid type polarization device, for example, there is disclosed a technique described in JP-A-10-73722. In addition, as a wire grid type polarization device in which a reflectance is suppressed, for example, there is disclosed a technique described in JP-A-2010-72591.

In JP-A-10-73722, a metal lattice on a substrate is oxidized by a heat treatment and thereby an oxide film is formed on the metal lattice surface, such that it is possible to provide a polarization device having superior environment resistance. However, in a method disclosed in JP-A-10-73722, a substrate is processed at a temperature of 500° C. or higher, such that cracking or deformation of the substrate is apt to occur. In addition, the metal lattice itself is damaged by heat expansion, and thereby dimension of the metal lattice, such as height and width, which determines a characteristic of the polarization device is changed. Therefore, there is a problem that a polarization characteristic of the polarization device, which is entirely uniform, cannot be shown. Furthermore, there is a problem that when the temperature is raised at the time of operating the liquid crystal device, the property of the metal lattice is changed, such that the polarization characteristic is lowered.

In JP-A-2010-72591, a method of manufacturing a wire grid type polarization device in which a light absorbing layer is provided on a light reflecting layer is disclosed, but there is not disclosed a method of manufacturing a wire grid type polarization device, in which an oxidized film is provided on a top face and side faces of the light reflecting layer, and a light absorbing layer is provided on the oxidized film.

SUMMARY

An advantage of some aspects of the invention is to solve at least a part of the above-described problems.

According to an aspect of the invention, there is provided a polarization device including a substrate, and a plurality of metal layers that is provided on one face of the substrate in a stripe shape and includes a first dielectric layer and a second dielectric layer. An optical absorption rate of the second dielectric layer is higher than that of the first dielectric layer. In two side faces opposite to each other in a plurality of side faces of a first metal layer and a top part of the first metal layer among the plurality of metal layers, the first dielectric layer included in the first metal layer is provided between the second dielectric layer included in the first metal layer and the first metal layer, and a substrate side end portion of the second dielectric layer included in the first metal layer is located between the one face of the substrate and the top part of the first metal layer.

According to this aspect of the invention, it is possible to transmit a TM wave that is linearly polarized light vibrating in a direction orthogonal to an extension direction of the metal layer, and to absorb a TE wave that is linearly polarized light vibrating in the extension direction of the metal layer.

That is to say, the TE wave incident from the second dielectric layer side of the substrate is attenuated by an optical absorption effect of the second dielectric layer, and a part of the TE wave passes through the second dielectric layer and the first dielectric layer without being absorbed and is reflected from the metal layer (functions as a wire grid). When the reflected TE wave passes through the first dielectric layer, a phase difference is applied thereto, and the reflected TE wave is attenuated by an interference effect and the remainder thereof is absorbed by the second dielectric layer. Therefore, due to the above-described attenuation effect of the TE wave, it is possible to obtain an absorption type polarization device having a desired polarization characteristic. In addition, both side faces and a top part of the metal layer are covered by the first dielectric layer, such that it is possible to prevent the deterioration of the metal layer, which is caused by oxidation or the like and thereby it is possible to suppress the decrease in a polarization separation function.

In addition, it is preferable that the second dielectric layer includes a first member and a second member, and the first and second members provided to the first metal layer overlap each other over the top part of the first metal layer.

According to this configuration, it is possible to more effectively absorb the TE wave incident from a second dielectric layer side of the substrate.

In addition, it is preferable that the first metal layer is provided at one end side of the substrate, a second metal layer among the plurality of metal layers is provided at the other end side of the substrate, a volume per unit length of the first member provided to the first metal layer is larger than a volume per unit length of the first member provided to the second metal layer, and a volume per unit length of the second member provided to the first metal layer is smaller than a volume per unit length of the second member provided to the second metal layer.

According to this configuration, it is possible to make variance in a sum of the volume of the first and second members, that is, in the volume of the second dielectric layer, small. As a result, in-plane variation in an absorbance rate of the TE wave can be reduced and thereby an optical characteristic uniform over entire surfaces of the polarization device can be realized.

In addition, it is preferable that the plurality of metal layers is formed of a material selected from aluminum, silver, copper, chrome, titanium, nickel, tungsten, and iron, the first dielectric layer is formed of an oxide of the plurality of metal layers, and the second dielectric layer is formed of a material selected from silicon, germanium, molybdenum, and tellurium.

According to this configuration, when the polarization device is used under a high temperature environment, it is possible to suppress oxidation of the metal layer, and thereby it is possible to suppress the deterioration of the polarization characteristic of the polarization device. In addition, it is possible to increase the absorption rate of the TE wave of the absorption type polarization device.

In addition, it is preferable that the first and second members are formed of the same material as each other. According to this configuration, it is possible to increase in-plane uniformity of the substrate in the TE wave attenuation effect. As a result, it is possible to increase in-plane uniformity of the polarization characteristic of the absorption type polarization device.

In addition, it is preferable that in a region between the plurality of metal layers, a groove is formed in the substrate.

According to this configuration, it is possible to reduce an effective refraction index of a boundary region between the substrate and the metal layer, such that the reflection of the TM wave at the boundary region can be suppressed. As a result thereof, the transmittance of the TM wave is increased, and thereby it is possible to obtain a bright polarization device.

According to another aspect of the invention, there is provided a method of manufacturing a polarization device including a substrate, a plurality of metal layers provided on one face of the substrate in a stripe shape, a first dielectric layer provided on a surface of one metal layer among the plurality of metal layers, and a second dielectric layer that is provided on the first dielectric layer and includes a first member and a second member. The method includes forming the first dielectric layer by oxidizing a surface of the plurality of metal layers provided on one surface of the substrate in an oxide gas atmosphere; forming the first member by depositing a material of the first member on the first dielectric layer from a first direction opposite to one side face among a plurality of side faces of the one metal layer; and forming the second member by depositing a material of the second member as an upper layer of the first dielectric layer from a second direction opposite to the other side face opposite to the one side face among the plurality of side faces of the one metal layer.

According to this aspect of the invention, it is possible to make a variance in the sum of the volume of the first and second members, that is, the volume of the second dielectric layer, small. As a result, it is possible to easily manufacture a absorption type polarization device in which in-plane variation in an absorbance rate of the TE wave can be reduced and thereby an optical characteristic uniform over all the surfaces of the polarization device can be realized.

In addition, in this method, the surface of the metal layer is covered by a metal oxide layer having a high density, such that even when the temperature is raised at the time of operating a liquid crystal device or the like in which the polarization device is included, deterioration of the metal layer owing to oxidation or the like does not easily occur. As a result thereof, it is possible to manufacture at relatively low temperatures a polarization device whose polarization characteristic is not easily diminished.

In addition, it is preferable that in the forming of the first member, the material of the first member is deposited on the first dielectric layer so that a substrate side end portion of the first member is located between the one face of the substrate and the top part of the one metal layer, and in the forming of the second member, the material of the second member is deposited as the upper layer of the first dielectric layer so that a substrate side end portion of the second member is located between the one face of the substrate and the top part of the one metal layer.

According to this method, transmittance of the TM wave is increased and thereby it is possible to obtain a bright polarization device.

In addition, it is preferable that in the forming of the second member, the second member is formed so that the second member overlaps the first member over the top part of the one metal layer.

According to this method, it is possible to more effectively absorb the TE wave incident from a second dielectric layer side of the substrate.

In addition, it is preferable that a first metal layer among the plurality of metal layers is provided at one end side of the substrate, a second metal layer among the plurality of metal layers is provided at the other end side of the substrate, a volume per unit length of the first member provided to the first metal layer is larger than a volume per unit length of the first member provided to the second metal layer, and a volume per unit length of the second member provided to the first metal layer is smaller than a volume per unit length of the second member provided to the second metal layer.

According to this method, it is possible to make variance in the sum of the volume of the first and second members, that is, in the volume of the second dielectric layer, small. As a result, in-plane variation in an absorbance rate of the TE wave can be reduced and thereby an optical characteristic uniform over all the surfaces of the polarization device can be realized.

In addition, it is preferable that the plurality of metal layers is formed of a material selected from aluminum, silver, copper, chrome, titanium, nickel, tungsten, and iron, the first dielectric layer is formed of an oxide of the material selected for the plurality of metal layers, and the second dielectric layer is formed of a material selected from silicon, germanium, molybdenum, and tellurium.

According to this method, when the polarization device is used under a high temperature environment, it is possible to suppress oxidation of the metal layer, and thereby it is possible to suppress the deterioration of the polarization characteristic of the polarization device. In addition, it is possible to increase the absorption rate of the TE wave of the absorption type polarization device.

In addition, it is preferable that the first and second members are formed of the same material as each other.

According to this method, it is possible to increase in-plane uniformity of the substrate in the TE wave attenuation effect. As a result thereof, it is possible to increase in-plane uniformity of the polarization characteristic of the absorption type polarization device.

In addition, it is preferable that the oxide gas is ozone gas.

According to this method, it is possible to increase the oxidation rate of the metal layer and thereby it is possible to provide a manufacturing method with a high productivity. In addition, it is possible to increase the density of the metal oxide layer and thereby it is possible to further improve oxidation resistance and abrasion resistance.

In addition, it is preferable that in the forming of the dielectric layer, the metal layer is irradiated with ultraviolet light.

According to this method, decomposition reaction of ozone is promoted, and thereby it is possible to form an oxide film at a low temperature. In addition, the density of the metal oxide layer can be increased, and thereby it is possible to further improve the oxidation resistance and abrasion resistance.

In addition, it is preferable that the method further includes forming a groove in the substrate, in a region between the plurality of metal layers.

According to this method, it is possible to reduce an effective refraction index of a boundary face between the substrate and the metal layer, such that the reflection of the TM wave at the boundary face can be suppressed. As a result thereof, the transmittance of the TM wave is increased, and thereby it is possible to obtain a bright polarization device.

According to still another aspect of the invention, there is provided a projection type display apparatus including a light source; a liquid crystal electro-optical device to which light emitted from the light source is incident; a projective optical system that allows the light passed through the liquid crystal electro-optical device to be incident to a surface to be projected; and the above-described polarization device provided at least one of between the light source and the liquid crystal electro-optical device on an optical path of the light emitted from the light source and between the liquid crystal electro-optical device and the projective optical system on an optical path of the light passed through the liquid crystal electro-optical device.

According to this configuration, the projection type display apparatus includes the polarization device having a high heat resistance, such that it is possible to suppress the deterioration of the polarization device, which is caused by oxidation or the like, even when the high-output light source is used. Therefore, it is possible to provide the projection type display apparatus that has a high reliability and a superior display characteristic.

According to yet another aspect of the invention, there is provided a liquid crystal device including a liquid crystal layer interposed between a pair of substrates; and the above-described polarization device, which is interposed between at least one substrate among the pair of substrates and the liquid crystal layer.

According to this configuration, it is possible to provide a liquid crystal device including the polarization device that has a superior optical characteristic and reliability.

According to still yet another aspect of the invention, there is provided an electronic apparatus including the above-described liquid crystal device.

According to this configuration, it is possible to provide an electronic apparatus that has a superior display quality and reliability.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

First Embodiment

Hereinafter, a polarization device and a method of manufacturing the polarization device according to an embodiment of the invention will be described with reference to the drawings.FIGS. 1A and 1Bare schematic diagrams of a polarization device1A of this embodiment, in whichFIG. 1Ais a partial perspective view andFIG. 1Bis a partial cross-sectional view, in which the polarization device1A is cut out at the YZ plane.

In addition, in the following description, the orthogonal XYZ coordinate system is set and a positional relationship of each member will be described with reference to the XYZ coordinate system. At this time, a plane, which is parallel to a plane11c of a substrate11provided with a metal layer12, is set as the XY plane, and an extending direction of the metal layer12is set as the X-axis direction. An arrangement axis of the metal layer12is the Y-axis. In addition, in all of the following drawings, the scale and thickness of each component is appropriately made to be different for easy understanding of the drawings.

Polarization Device

As shown inFIGS. 1A and 1B, the polarization device1A includes a substrate11, a plurality of metal layers12formed on the substrate11in a stripe shape in a plan view, first dielectric layers13, each covering one of the metal layers12, and second dielectric layers14, each being provided on each of the first dielectric layers13. The first dielectric layer13covers a first side face12a extending in an X-axis direction of the metal layer12, a second side face12b opposite to the first side face12a, and a top part12c.

As the substrate11, a glass substrate is used. However, the substrate11may be formed of a translucent material. For example, quartz, plastic, or the like may be used for the substrate. In addition, since the polarization device1A may accumulate heat and gain a high temperature depending on a usage of the polarization device1A, as the material of the substrate11, glass or quartz having high heat resistance is preferable.

As a material of the metal layer12, a material having a high reflectance with respect to light in a visible range is used. In this embodiment, as the material of the metal layer12, aluminum is used. A metallic material such as silver, copper, chrome, titanium, nickel, tungsten, and iron may be used other than aluminum.

The first dielectric layer13is formed on the first side face12a, the second side face12b, and the top part12c of the metal layer12. As a material of the first dielectric layer13, a material having a high translucency in a visible range, for example, a dielectric material such as aluminum oxide is used. In this example, as the first dielectric layer13, an oxide of the metal layer12is used. As described later, the first dielectric layer13may be formed by oxidizing the metal layer12.

A groove portion15is provided between two adjacent metal layers12. The groove portion15is provided with a substantially equal distance in the Y-axis direction at a cycle shorter than a wavelength of visible light. The metal layer12and the first dielectric layer13are arranged in the Y-axis direction with the same cycle as each other.

For example, a height H1of the metal layer12is 50 to 200 nm, and a width L1of the metal layer12in the Y-axis direction is 40 nm. A height H2of the first dielectric layer13is 10 to 100 nm, and a width L2of the first dielectric layer13in the Y-axis direction is 5 to 30 nm. The width L2of the first dielectric layer13may be called a thickness of the first dielectric layer13at a side face of the metal layer12.

In addition, a distance S between two adjacent first dielectric layers13(width of the groove portion15in the Y-axis direction) is 70 nm, and a cycle P (pitch) is 140 nm.

The second dielectric layer14is provided on the first dielectric layer13in regard to the first side face12a, the second side face12b, and the top part12c of the metal layer12. That is, the first dielectric layer13is provided between the second dielectric layer14and the metal layer12. In addition, the second dielectric layer14extends in the X-axis direction similar to the metal layer12. As a material of the second dielectric layer14, a material having an optical absorption rate higher than that of the first dielectric layer13in a visible range is used.

In this embodiment, germanium is used. Other than germanium, for example, silicon, molybdenum, tellurium, or the like may be used. In addition, in the YZ cross-section shown inFIG. 1B, a width L3of the second dielectric layer14in the Y-axis direction has a value that is larger than double the sum of the width L1of the metal layer12and the width L2of the first dielectric layer13and that is smaller than the cycle P (pitch) of the first dielectric layer13(or the metal layer12).

The second dielectric layer14includes a first member14a formed at the side of the first side face12a of the metal layer12, that is, on a first side face13a of the first dielectric layer13and a second member14b formed at the side of the second side face12b of the metal layer12, that is, on a second side face13b of the first dielectric layer13, and the first and second members14a and14b overlap each other at the top part12c (upper end) of the metal layer12.

Suppose that a second dielectric layer14K which is provided to a metal layer12K and a second dielectric layer14M which is provided to a metal layer12other than the metal layer12K are selected. If a cross-sectional area of a first member14aK making up the second dielectric layer14K in a YZ cross-section and a cross-sectional area of a first member14aM making up the second dielectric layer14M in the YZ cross-section are compared to each other, the cross-sectional area of the first member14aK is different from the cross-sectional area of the first member14aM. Similarly, a cross-sectional area of a second member14bK making up the second dielectric layer14K is different from a cross-sectional area of a second member14bM making up the second dielectric layer14M.

The above-described difference in the cross-sectional area corresponds to the difference in a volume per unit length. Here, a definition of the volume per unit length of the first member14a will be described by using a metal layer12K. In the first members14aK provided corresponding to the metal layer12K, a value obtained by dividing a volume of the first member14aK in a region where the metal layer12K and the first member14aK are commonly provided in the X-axis direction by a length of the region in the X-axis direction is defined as the volume per unit length of the first member14aK. A volume per unit length of the second member14b and a volume per unit length of the second dielectric layer14are also defined in a similar way. Hereinafter, in this specification, the volume per unit length is referred to as a volume for simplicity.

Specifically, the volume of the first member14a and the volume of the second member14b depend on a distance from a first end11a of the substrate11in the Y-axis direction. More specifically, the volume of the first member14a becomes large as it approaches the first end11a, and the volume of the second member14b becomes large as it approaches a second end11b opposite to the first end11a. In addition, in the metal layer12that is closest to the first end11a, the volume of the first member14a making up the second dielectric layer14is larger than the volume of the second member14b making up the second dielectric layer14, and in the metal layer12that is the most distant from the first end11a, the volume of the first member14a making up the second dielectric layer14is smaller than the volume of the second member14b making up the second dielectric layer14.

However, the volume of the second dielectric layer14represented by the sum of the volume of the first member14a and the volume of the second member14b has approximately a constant value in any second dielectric layer14.

That is, as shown inFIG. 1B, the volume of the first member14aK is different from the volume of the second member14bK, the volume of the first member14aL is different from the volume of the second member14bL, and the volume of the first member14aM is different from the volume of the second member14bM, but the volume of the second dielectric layer14K, the volume of the second dielectric layer14L, and the volume of the second dielectric layer14M are approximately the same as each other.

A relationship between the volume of the first member14a, the volume of the second member14b, and the volume of the second dielectric layer14is also true of a relationship of a cross-sectional area of the first member14a, a cross-sectional area of the second member14b, and the cross-sectional area of the second dielectric layer14represented by the sum of the cross-sectional area of the first member14a and the cross-sectional area of the second member14b, in the YZ cross-section.

In addition, in regard toFIG. 1A, the dependency on the distance from the first end11a in the volume of the first member14a and the volume of the second member14b, is drawn exaggeratedly.

As described above, the polarization device1A including the metal layer12, the first dielectric layer13, and the second dielectric layer14is configured to transmit a transverse magnetic (TM) wave21that is linearly polarized light vibrating in a direction (Y-axis direction) orthogonal to the extension direction of the metal layer12and to absorb a transverse electric (TE) wave22that is linearly polarized light vibrating in the extension direction (X-axis direction) of the metal layer12.

Method of Manufacturing Polarization Device

Hereinafter, a method of manufacturing the polarization device1A of this embodiment will be described.FIGS. 2A to 2Dshow process diagrams illustrating a method of manufacturing the polarization device in the first embodiment.

The method of manufacturing the polarization device1A according to this embodiment includes a metal layer forming process of forming the plurality of metal layers12with a stripe shape in a plan view on the substrate11, a first dielectric layer forming process of forming the first dielectric layer13on the first side face12a, the second side face12b, and the top part12c of the metal layer12, and a second dielectric layer forming process of forming the second dielectric layer14(the first and second members14a and14b) on the first side face13a, the second side face13b, and the top part13c (upper end) of the first dielectric layer13, that is, a side of the first dielectric layer13, which is opposite to the metal layer12.

Furthermore, the process of forming the second dielectric layer includes a first member forming process of obliquely forming a film from a direction from one of two first dielectric layers13adjacent to each other to form a first member14a on the top part and a side face of the first dielectric layer13, and a second member forming process of obliquely forming a film from a direction from the other of the first dielectric layers13to form the second member14b as an upper layer of the first dielectric layer13. Hereinafter, description will be given with reference to the drawings.

In the process of forming the metal layer ofFIG. 2A, the metal layer12is formed on a plane11c of the substrate11. Specifically, an aluminum film is formed on the substrate and a resist film is formed on the aluminum film. Subsequently, the resist film is exposed and then is developed, and thereby a stripe-shaped pattern is formed in the resist film. Subsequently, the aluminum film is etched until the plane11c of the substrate11comes to appear by using the resist film as an etching mask. Subsequently, the resist film is removed, and thereby a plurality of metal layers12disposed in a stripe shape is formed on the substrate11.

In the first dielectric layer forming process ofFIG. 2B, the first dielectric layer13is formed on the first side face12a, the second side face12b, and the top part12c of each of the metal layers12. Specifically, the substrate11on which the metal layers12are formed is disposed in a vacuum vessel that is formed of quartz or the like and ozone gas is controlled within a range of 50 Pa to 100 Pa therein.

Subsequently, the metal layers12are irradiated by ultra-violet light (wavelength<310 nm) from the plane11c side of the substrate11. The ultraviolet light is emitted by a Deep-UV lamp. For example, an intensity of the ultraviolet light is 120 mW/cm2. The ozone gas has a high absorption coefficient within a wavelength of 220 nm to 300 nm, such that as a result of optical absorption reaction, oxygen atoms in an excited state, which has high energy, may be generated efficiently.

The excited oxygen atoms have a diffusion coefficient (activity) greater than that of normal oxygen atoms have, and show a high oxidation rate. In addition, an oxidized film may be formed at a low temperature lower than that in thermal oxidation. In this process, a side, which is opposite to the plane11c of the substrate11, is irradiated by a halogen lamp and thereby a temperature of the substrate is increased to 150° C. Accordingly, the oxidation reaction is further promoted. Under this environment, ozone oxidation is performed for 20 minutes, and thereby an aluminum oxidized film (first dielectric layer13) with a thickness L2of 30 nm is formed on a surface of the metal layer12. The thickness of the first dielectric layer may be appropriately selected depending on a magnitude of a phase difference applied to visible light.

According to the manufacturing method of this embodiment, it is possible to form the oxidized film (first dielectric layer13) of the metal layer12at a temperature lower than that in the related art. Therefore, it is possible to decrease cracking or deformation of the substrate, and it is possible to decrease variation before and after the heat treatment in the dimensions of the metal layer12such as the height and the width that determine the characteristics of the polarization device. Therefore, it is possible to increase an in-plane uniformity of the polarization characteristics of the polarization device1A.

In addition, according to the manufacturing method of this embodiment, it is possible to cover the first side face12a, the second side face12b, and the top part12c of the metal layer12with the first dielectric layer13a density higher than that in the related art. Therefore, even when the temperature is raised in use, it is possible to prevent the deterioration of the metal layer12, which may be caused by oxidation or the like, and thereby it is possible to lower a decrease in the polarization characteristic.

In the first member forming process ofFIG. 2C, germanium is obliquely deposited to form the first member14a on the first side face13a and the top part13c (upper end) of the first dielectric layer13. Specifically, a sputtered particle20is deposited on the first side face13a and the top part13c (upper end) of the first dielectric layer13in a first direction D1that is oblique with respect to a surface normal line (Z-axis direction) of the plane11c of the surface11on which the metal layer12and the first dielectric layer13are formed and that is opposite to the first side face12a of the metal layer12, for example, by using a sputtering apparatus, to form the first member14a. In addition, inFIGS. 2C and 2D, a main incident direction of the sputtered particle20is indicated by an arrow. An angle between the surface normal line of the plane11c of the substrate11and the incident direction of the sputtered particle20may be appropriately set within a range of 40° to 85°.

In the second member forming process ofFIG. 2D, germanium is obliquely deposited to form the second member14b as an upper layer of the first dielectric layer13. Specifically, a sputtered particle20is deposited on the second side face13b and the first member14a of the first dielectric layer13from a second direction D2that is oblique with respect to the surface normal line of the plane11c of the substrate11and that is opposite to the second side face12b of the metal layer12, for example, by using a sputtering apparatus, to form the second member14b as an upper layer of the first dielectric layer13. An angle between the surface normal line of the plane11c of the substrate11and the incident direction of the sputtered particle20may be appropriately set within a range of 40° to 85°.

As described above, the first and second members14a and14b are formed, whereby it is possible to form the second dielectric layer14. Through the above-described processes, the polarization device1A can be manufactured. In addition, in this embodiment, as the material of the first and second members, germanium is used, but the material of the first member may be different from that of the second member. In this case, it is preferable that the difference in the optical absorption rate between the material of the first member and the second member is small.

Here, in the first member forming process, due to a so-called shadowing effect where a part of the metal layer12and a part of the first dielectric layer13are shadowed at the time of obliquely forming a film, the first member is hardly formed at the groove portion15formed between two adjacent metal layers12. Similarly, in the second member forming process, due to the shadowing effect at the time of obliquely forming a film, the second member is hardly formed at the groove portion15.

As a method of forming the second dielectric layer on the first dielectric layer, a method in which the material of the second dielectric layer is deposited on the first dielectric layer from a direction (Z-axis direction) that is parallel with the surface normal line of the substrate11may be considered. In this case, the material of the second dielectric layer is also deposited at a region (groove portion15) between the two adjacent metal layers12on the substrate11.

However, when the second dielectric layer is formed at the groove portion15, the characteristics of the polarization device1A as a polarization plate is deteriorated, such that it is necessary to remove the second dielectric layer formed at the groove portion15. On the other hand, according to the manufacturing method of this embodiment, it is possible to prevent the second dielectric layer from being formed at the groove portion15, such that a process of removing the second dielectric layer formed at the groove portion15is not necessary.

The first member14a is provided on the first side face13a of the first dielectric layer13, but a substrate11side end portion14az of the first member14a is located between the plane11c of the substrate11and the top part13c (upper end) of the first dielectric layer13. That is, the end portion14az of the first member14a is terminated on the face of the first side face13a.

Similarly, the second member14b is provided on the second side face13b of the first dielectric layer13, but a substrate11side end portion14bz of the second member14b is located between the plane11c of the substrate11and the top part13c (upper end) of the first dielectric layer13. That is, the end portion14bz of the second member14b is terminated on the face of the second side face13b.

As described above, neither the first member14a nor the second member14b are provided at the groove portion15. As shown inFIG. 1B, a cross-section of the second dielectric layer14in a YZ cross-section has a shape where a portion having the greatest width L3in the second dielectric layer14is located at the top part side of the second dielectric layer14rather than the substrate11side end portion14az of the first member14a and the substrate11side end portion14bz of the second member14b.

In addition, at the time of obliquely forming a film in the above-described first member forming process and the second member forming process, there is a tendency that an amount of the sputtered particles to be deposited between a region close to a target of the sputtering apparatus and a region far away from the target is different in the plane11c of the substrate11. Specifically, as it is close to the target, the amount of the sputtered particles to be deposited becomes large.

Therefore, in the first member forming process ofFIG. 2C, a volume of the first member14a becomes large as it approaches the target of the sputtering apparatus (a positive direction side of the Y-axis) and becomes small as it moves away from the target (a negative direction side of the Y-axis). On the other hand, in the second member forming process ofFIG. 2D, a volume of the second member14b becomes large as it approaches the target of the sputtering apparatus (the negative direction side of the Y-axis) and becomes small as it moves away from the target (the positive direction side of the Y-axis).

Therefore, as described above with reference toFIG. 1B, the volume of the first member14aK is different from that of the second member14bK, the volume of the first member14aL is different from that of the second member14bL, and the volume of the first member14aM is different from that of the second member14bM, but the volumes of the second dielectric layer14K, the second dielectric layer14L, and the second dielectric layer14M are approximately equal each other. That is, the second dielectric layer14having approximately the same volume is formed on the metal layers12, respectively.

Hereinafter, an operation of the polarization device1A of this embodiment will be described.

As described above, in regard to the polarization device1A, the metal layer12is formed of a material such as aluminum that has a high optical reflectance within a visible region. In addition, the first dielectric layer13is formed of a material such as aluminum oxide that has a high optical transmittance in a visible region. Furthermore, the second dielectric layer14(the first and second members14a and14b) is formed of a material such as germanium that has an optical absorption rate higher than that of the first dielectric layer13in a visible region.

As described above, the polarization device1A has a structure where the metal layer12and the first and second dielectric layers13and14are laminated, such that it is possible to transmit the TM wave21that is linearly polarized light vibrating in a direction orthogonal to the extension direction of the metal layer and to absorb the TE wave22that is linearly polarized light vibrating in the extension direction of the metal layer.

That is to say, the TE wave22incident from the second dielectric layer14side of the substrate11is attenuated by an optical absorption effect of the second dielectric layer14, and when apart of the TE wave22passes through the second dielectric layer14and the first dielectric layer13without being absorbed, a phase difference is applied thereto. The TE wave22passed through the first dielectric layer13is reflected from the metal layer12(functions as a wire grid). When the reflected TE wave22passes through the first dielectric layer13, a phase difference is applied thereto, and the reflected TE wave22is attenuated by an interference effect and a remainder thereof is absorbed again by the second dielectric layer14.

Therefore, due to the above-described attenuation effect of the TE wave22, it is possible to obtain a desired absorption type polarization characteristic.

In a case where the material of the second dielectric layer14is deposited on the first dielectric layer13from a direction oblique with respect to the Z-axis direction for preventing the second dielectric layer14from being formed in the groove portion15, an amount of deposition of the material of the second dielectric layer14becomes different depending on the distance from a target. Therefore, the attenuation effect of the TE wave22may become non-uniform in a plane of the substrate11, but according to the manufacturing method of this embodiment, it is possible to form the first and second members14a and14b formed of the same material on the metal layers12, respectively, in a manner that the volume of the second dielectric layer14provided to each of the metal layer12is approximately the same with each other, such that it is possible to increase in-plane uniformity of the substrate11in the attenuation effect of the TE wave22. As a result thereof, it is possible to increase in-plane uniformity of the polarization characteristic in the absorption type polarization device.

In addition, the entirety of both side faces and top face of the metal layer12is covered by the first dielectric layer13with a density higher than that in the related art, such that the deterioration of the metal layer, which may be caused by oxidation or the like, is prevented, and thereby it is possible to prevent the decrease in a polarization separation function. Since an area of remaining side face of the metal layer12is extremely small compared to the total surface area of the metal layer12, the remaining side face of the metal layer12is not necessary to be covered by the first dielectric layer13, but it may be covered.

As described above, according to this embodiment, it is possible to obtain the polarization device1A in which the in-plane uniformity of the polarization characteristic is high, and the polarization characteristic is not easily decreased even when a temperature is raised in use.

Modified Example of First Embodiment

FIG. 3shows an explanatory diagram of a polarization device1B according to a modified example of the first embodiment. The polarization device1B is partially common to the polarization device1A of the first embodiment. There is a difference in that a region16, which has a refraction index lower than that of the substrate11, is formed between the metal layers12.

As shown inFIG. 3, the polarization device1B has a region16having a refraction index lower than that of the substrate11between two adjacent metal layers12, in addition to the configuration of the polarization device1A.

The region16is formed by removing the substrate11exposed between the two adjacent metal layers12through dry etching or the like. A digging depth H3is substantially the same as a height H1of the metal layer12.

According to this configuration, it is possible to reduce an effective refraction index of a boundary region between the substrate and the metal layer, such that the reflection of the TM wave21at the boundary region is suppressed and as a result, it is possible to increase the transmittance of the TM wave21.

Projection Type Display Apparatus

Hereinafter, embodiments of an electronic apparatus according to the invention will be described. A projector800, which is shown inFIG. 4, includes a light source810, dichroic mirrors813and814, reflective mirrors815,816, and817, an incident lens818, a relay lens819, an emission lens820, light modulating units822,823, and824, a cross dichroic prism825, and a projective lens826.

The light source810includes a lamp811such as a metal halide, and a reflector812that reflects light of the lamp. In addition, as the light source810, an ultrahigh pressure mercury lamp, a flash mercury lamp, a high pressure mercury lamp, a Deep UV lamp, a xenon lamp, a xenon flash lamp or the like may be used other than the metal halide.

The dichroic mirror813transmits red light included in white light emitted from the light source810and reflects blue light and green light. The transmitted red light is reflected from the reflective mirror817and is incident to the light modulating unit822for red light. In addition, among the blue light and the green light reflected from the dichroic mirror813, the green light is reflected from the dichroic mirror814and is incident to the light modulating unit823for green light. The blue light passes through the dichroic mirror814and is incident to the light modulating unit824via a relay optical system821including the incident lens818that is provided to prevent light loss caused by a long optical path, the relay lens819, and the emission lens820.

In the light modulating units822to824, an incident side polarization device840and an emission side polarization device section850are disposed with a liquid crystal light valve830interposed therebetween. The incident side polarization device840is provided on a light path of light emitted from the light source810and between the light source810and the liquid crystal light valve830. In addition, the emission side polarization device section850is provided on a light path of light passed through the liquid crystal light valve830and between the liquid crystal light valve830and the projection lens826. The incident side polarization device840and the emission side polarization device section850are disposed in a manner that transmission axes thereof are orthogonal to each other (cross-Nicole arrangement).

The incident side polarization device840is a reflection type polarization device described in the first embodiment and reflects light in a vibration direction orthogonal to the transmission axis.

On the other hand, the emission side polarization device section850includes a first polarization device (pre-polarization plate, synonymous with a pre-polarizer)852, and a second polarization device854. As the first polarization device852, the above-described polarization device of the second embodiment of the invention, which is provided with a protective film and has a high heat resistance, is used. In addition, the second polarization device854is a polarization device formed of an organic material as a formation material. The first and second polarization devices852and854are absorption type polarization devices, respectively, and the first and second polarization devices852and854absorb light in cooperation with each other. In addition, as the first polarization device852, the polarization device according to the first embodiment of the invention may be used. In addition, as the incident side polarization device840, the polarization device according to the invention may be used.

In general, an absorption type polarization device, which is formed of an organic material, is apt to be deteriorated due to heat, such that it is difficult to be used as a polarization device of a large output projector in which high brightness is necessary. However, in the projector800according to the invention, the first polarization device852, which is formed of an inorganic material having high heat resistance, is disposed between the second polarization device854and the liquid crystal light valve830, and the first and second polarization devices852and854absorb light in cooperation with each other. Therefore, it is possible to suppress the deterioration of the second polarization device854formed of an organic material.

Three colored light beams modulated by respective light modulating units822to824are incident to a cross dichroic prism825. The cross dichroic prism825includes four right angle prisms bonded to each other, and at a boundary face thereof, a dielectric multi-layered film reflecting red light and a dielectric multi-layered film reflecting blue light are formed in an X-shape. The three colored light beams are synthesized by these dielectric multi-layered films and light representing a color image is formed. The synthesized light is projected on a screen827by a projection lens826that is a projective optical system and the image is enlarged and displayed.

The projector800with the above-described configuration uses the polarization device according to the invention is utilized as the emission side polarization device section850, whereby it is possible to suppress the deterioration of the polarization device even when the high-output light source is used. Therefore, it is possible to provide the projector800that has a high reliability and a superior display characteristic.

Liquid Crystal Device

FIG. 5shows a cross-sectional schematic diagram illustrating an example of a liquid crystal device300including the polarization device according to the invention. The liquid crystal device300of this embodiment has a configuration where a liquid crystal layer350is interposed between an element substrate310and a counter substrate320.

The element substrate310includes a polarization device330, and the counter substrate320includes a polarization device340. The polarization device330and the polarization device340are the above-described polarization devices of the first embodiment.

The polarization device330includes a substrate main body331, a metal layer332, and a protective film333, and the polarization device340includes a substrate main body341, a metal layer342, and a protective film343. However, the first and second dielectric layers13and14, which include the metal layers332and342, respectively, are not shown inFIG. 5. In this embodiment, the substrate main bodies331and341are substrates of the polarization device and also serve as substrates for the liquid crystal device. In addition, the metal layers332and342are disposed to intersect each other. In any of the polarization devices, the metal layer is disposed at an inner face side (liquid crystal layer350side).

At the liquid crystal layer350side of the polarization device330, a pixel electrode314, an interconnection and a TFT device (not shown), and an alignment film316are provided. Similarly, at an inner face side of the polarization device340, a common electrode324and an alignment film326are provided.

In the liquid crystal device configured as described above, the substrate main bodies331and341combine the functions of the substrate for the liquid crystal device and the substrate for the polarization device, whereby it is possible to reduce the number of parts. Therefore, the entirety of the apparatus can be made to be slim, and thereby the function of the liquid crystal device300can be improved. Furthermore, the apparatus structure is simple, such that the manufacturing thereof is easy and thereby a reduction in cost may be realized.

Electronic Apparatus

Hereinafter, another embodiment related to an electronic apparatus according to the invention will be described.FIG. 6shows a perspective view illustrating an example of the electronic apparatus using the liquid crystal device shown inFIG. 5. A mobile phone (electronic apparatus)1300shown inFIG. 6includes the liquid crystal device as a small-sized display section1301, a plurality of operation buttons1302, an earpiece1303, and a mouthpiece1304. Therefore, it is possible to provide the mobile phone1300including a display section that has superior reliability and can display in high quality.

In addition, the liquid crystal device may be suitably used as an image display section of an electronic book, a personal computer, a digital still camera, a liquid crystal television, a projector, a view finder type or monitor direct vision type video tape recorder, a car navigation apparatus, a pager, an electronic pocket book, a calculator, a word processor, a work station, a television phone, a POS terminal, an apparatus having a touch panel, or the like, other than the mobile phone.

The invention is not limited to the above-described embodiment and various changes may be made without departing from the scope of the invention.

Test Production Verification of Polarization Device and Evaluation of Reliability

For confirming the effect of the invention, first, a polarization device not including the second dielectric layer was manufactured and characteristics thereof were evaluated.

In the evaluation, it was assumed that the polarization device according to the invention was applied as a polarization device for a light valve of a liquid crystal projector. The polarization device according to the invention is formed of an inorganic material and has a high heat resistance, and thereby can be applied as an incident side polarization device of a liquid crystal projector having the high output light source described above.

In the incident side polarization device as described above, it is necessary to have high transmittance with respect to TM light, and to have a high reflectance and a low transmittance with respect to TE light. Specifically, when the transmittance I(TM) of TM light is greater than 80%, and the transmittance I(TE) of the TE light is less than 1%, there is no problem in use, and it is more preferable that the contrast defined by I(TM)/I(TE) is 100 or more. In addition, a time where the transmittance of the TE light is changed by 10% from an initial value is defined as a product lifespan.

Test production levels are shown in Table 1. A width L2of the first dielectric layer13is controlled by a processing time of the above-described ozone oxidation. In each sample, the following are common. The height H1of aluminum (metal layer12): 160 nm, the width S of the groove portion15: 70 nm, and the cycle P of the first dielectric layer13(or metal layer12): 140 nm. Sample No. 1 is a comparative example where the ozone processing is not performed, and a naturally oxidized film is formed on a surface of the metal layer12. The naturally oxidized film is different from the first dielectric layer13according to the invention, but in Table 1, a thickness of the naturally oxidized film of Sample No. 1 is shown as a width L2of a first dielectric layer for convenience.FIG. 7shows SEM observation results of Nos. 2, 3, and 4. In the observation, in order to measure a width of the dielectric layer, the aluminum was dissolved to expose the first dielectric layer13.

With respect to the sample manufactured as described, a reliability test was performed at 300° C. under the atmosphere environment. Next, a lifespan where transmittance of the TE light was changed by 10% from an initial value and a magnification of extended lifespan with No. 1 given as a reference were shown in Table 2. In the measurement, a spectral photometer U-4100 (trade name; manufactured by Hitachi High-Technologies Corporation) was used.

From the results, the lifespan is significantly increased by the formation of the dielectric layer, and No. 3 (width of the dielectric layer is 20 nm) shows the highest value in the magnification of the extended lifespan. Here, the formed first dielectric layer13(aluminum oxide) has a lattice constant greater than that of the metal layer12(aluminum) by substantially 20%. Therefore, like the case of No. 4, it is considered that when the metal layer is converted into the first dielectric layer13by 40% or more with respect to the width (60 nm) of the metal layer12before the ozone processing, crystal defects occur according to the change in volume, and as a result thereof, oxygen is introduced by using the crystal defects as an introduction path and thereby the oxidation is progressed. From the above description, it could be seen that in the case of the test-produced polarization device, when the width L2of the first dielectric layer13was controlled in a range of 25% to 40% inclusive with respect to the width of the metal layer12before the ozone processing, it was possible to manufacture the polarization device having the longest product lifespan.

From the results, it was confirmed that the reflection type polarization device having the configuration of the invention had superior optical characteristics and the configuration of the invention was effective for solving the problems.

Optical Characteristic Evaluation by Simulation Analysis

Next, a simulation analysis result of the absorption type polarization device including the second dielectric layer14according to the first embodiment will be described.

In the analysis, an evaluation was performed under an assumption that the polarization device according to the invention was applied to a polarization device for a light valve of a liquid crystal projector. The polarization device according to the invention is formed of an inorganic material and the heat resistance is high, such that it is possible to apply the polarization device as a pre-polarization plate of the liquid crystal projector including a high output light source.

In the above-described pre-polarization plate, it is important to have high optical transmittance with respect to TM light and to transmit the TM light well. On the other hand, as described above, two sheets of polarization devices absorb the TE light in cooperation with each other, such that the absorption rate of the TE light is not necessary to be so high. Specifically, when the transmittance of the TM light is greater than 80%, and the absorption rate of the TE light is greater than 40%, there is no problem in use. In regard to the absorption rate of the TE light, it is more preferable to be greater than 50% so as to reduce the burden to two sheets of polarization devices. In addition, to prevent the TE light from being reflected from the pre-polarization plate and returning to the light valve, it is preferable that the reflectance of the TE light is small, and more preferably, 20% or less.

Here, in the analysis described below, the evaluation was performed with a reference that the transmittance of the TM light was greater than 80%, the reflectance of the TE light was less than 20%, and the absorption rate of the TE light was greater than 40%.

In the simulation analysis, the shape of the polarization device and a refraction index of a constituent material or the like were set as parameters by using GSolver that is an analysis software manufactured by Grating Solver Development Company.

A numerical calculation was performed by using a model where the metal layer12(aluminum), the first dielectric layer13(aluminum oxide), and the second dielectric layer14(germanium) were formed in this order from the substrate. In the first embodiment (FIGS. 1A and 1B), the entire surface of the metal layer12was covered by the first dielectric layer13, and the top part13c of the first dielectric layer13was covered by the second dielectric layer14.

In the calculation, the setting was as follows. The height H1of the aluminum (metal layer12): 80 nm, the width L1: 20 nm, the height of H2of the aluminum oxide (first dielectric layer13): 20 nm, the width L2: 20 nm, the height of germanium (second dielectric layer14): 0 to 30 nm, the width L3: 60 nm, the width S of the groove portion15in the Y-axis direction: 80 nm, and the cycle P of the first dielectric layer13(or the metal layer12) was 140 nm. In addition, as the refraction index and an extinction coefficient of the constituent material of the above-described polarization device, each parameter stored in the GSolver was used.

In the above-described model, a change in characteristics in a case of changing the thickness of the germanium was obtained.FIGS. 8A to 8Cshow a graph illustrating a simulation result in each characteristic of the transmission, the reflection, and the absorption with respect to the TM light and the TE light.FIGS. 8A to 8Cshow the transmission characteristic, the reflection characteristic, and the absorption characteristic, respectively, in which the thickness of the germanium is shown in a horizontal axis and the value (unit: %) in each optical characteristic at a wavelength of 532 nm (green color) is shown in a vertical axis. Here, the height of the germanium was changed from 0 to 30 nm.

From the analysis result, it could be seen that as the height of the germanium increased, the transmittance and reflectance of the TE light decreased and the absorption rate of the TE light increased, and it was obvious that the optical characteristic of the TE light was seriously affected by the height of the germanium. In a case of being used as the above-described absorption type polarization device, it is preferable that a region where the absorption rate of the TE light is 40% or more and the reflectance is 20% or less is selected, and specifically, the height of the germanium is set to a value between 3 nm and 15 nm. In addition, since the absorption rate of the TE light is reduced when the height of the germanium becomes 10 nm or more, it is preferable that the height of the germanium is set to a value between 3 nm and 8 nm.

From these results, it was confirmed that the absorption type polarization device having the configuration of the invention had superior optical characteristics and the configuration of the invention was effective for solving the problems.

The entire disclosure of Japanese Patent Application No. 2010-136851, filed on Jun. 16, 2010 is expressly incorporated by reference herein.