JP5353666B2 - Wire grid polarizer and optical head device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wire grid polarizer configured to increase the polarization transmittance of one of two orthogonal linear polarization components of incident light, and reduce that of the other linear polarization component, and an optical head device using the wire grid polarizer. <P>SOLUTION: The wire grid polarizer has a metal layer on one side face of a translucent substrate that extends so as to be arranged periodically at predetermined intervals in one direction, and has a grid structure layer formed of a lattice structure having a triangular or trapezoidal cross sectional shape, and satisfies Tp(1-Ts)&ge;0.94 for the light of 660 nm/785 nm and/or Tp(1-Ts)&ge;0.85 for the light of 405 nm, where Tp and Ts are polarization transmittances of the two orthogonal linear polarization components of the incident light. The optical head device achieves stable recording and reproduction using the wire grid polarizer. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a wire grid type polarizer as a polarizer that transmits only light of a specific polarization direction among incident light, and “Blu-ray” (registered trademark) as an optical system that handles optical storage. Information recording and / or reproduction (hereinafter referred to as “recording / reproduction”) on a high-density optical recording medium such as BD) and an optical recording medium (hereinafter referred to as “optical disk”) such as a CD, DVD, or magneto-optical disk. ).

  In optical systems that handle optical discs and optical systems that have image display functions such as liquid crystal displays, polarizers that transmit only light of a specific linearly polarized light out of light emitted from a light source such as a semiconductor laser are used. ing. For example, in an optical head device that performs recording / reproduction of an optical disc, stable recording / reproduction can be performed when the intensity of light condensed on the information recording surface of the optical disc is stabilized. However, when the polarization state of the light emitted from the semiconductor laser fluctuates during operation due to a change in temperature or the like, the transmitted light is transmitted by the optical component having polarization dependency arranged in the optical path from the semiconductor laser to the optical disk. Since it changes from the desired polarization state, the intensity of the light condensed on the information recording surface of the optical disc fluctuates, and stable recording / reproduction cannot be performed. For this reason, a polarizer (polarizing plate) is disposed in the vicinity of the light emitting side of the semiconductor laser, and for example, only the light of a specific linearly polarized light is transmitted straight, thereby stabilizing the intensity of the light condensed on the optical disk. An optical head device is realized.

  As this polarizer, for example, there is an absorptive polarizer that absorbs light in a specific polarization direction, and it is known to be produced by stretching a dichroic dye such as iodine between resin films. Yes. In addition, there is a polarizing diffraction grating as a diffractive polarizer that diffracts light in a specific polarization direction. For example, in a polarizing diffraction grating, when light reflected by an optical disk returns in the direction of a semiconductor laser in an optical head device, oscillation noise is generated between the light emitted from the semiconductor laser and the return light. Although there is a possibility, an example of reducing this oscillation noise by combining a polarizing diffraction grating and a quarter wave plate is also shown ("Diffraction" supervised by the Optical Design Research Group of the Japan Optical Society, Japan Society of Applied Physics) Introduction to optical elements, augmented revised edition "pp. 216-217).

  However, the conventional absorption polarizer transmits light of a specific polarization direction (for example, the first polarization direction) and absorbs light of the second linearly polarized light orthogonal to the first polarization direction. Also, a certain percentage of absorption occurs for the first linearly polarized light, and the transmittance of the first linearly polarized light to be transmitted (the transmittance in a specific polarization direction is referred to as “polarized transmittance”). ") Was not able to be high enough. The polarizing diffraction grating, which is a diffractive polarizer, can obtain a high polarization transmittance in the first linearly polarized light, but the second linearly polarized light is diffracted and optical such as an optical head device is obtained. There was a problem of noise in the apparatus.

  A reflective polarizer that reflects light in a specific polarization direction is a polarizer that is less likely to cause the above problems. Among the reflective polarizers, those that reflect specific linearly polarized light include, for example, a polarizer made of a laminate of a birefringent resin and a wire grid polarizer. In addition, there is a polarizer made of a cholesteric phase liquid crystal that reflects specific circularly polarized light instead of linearly polarized light. Among them, a high polarization transmittance can be obtained for light having a desired polarization direction, and a low polarization transmittance (high polarization reflectance) can be obtained for light having a polarization direction orthogonal to the desired polarization direction. For example, a wire grid polarizer having a structure in which a plurality of metal portions (metal thin wires) are arranged in parallel on a transparent substrate has been attracting attention. Note that the ratio between the polarization transmittances of two polarization directions orthogonal to each other is also referred to as an extinction ratio or polarization separation ability.

  In general, a wire grid polarizer has an electric field vector orthogonal to the longitudinal direction of the fine metal wires in the incident light when the pitch of the fine metal wires is sufficiently shorter than the wavelength of the incident light (the first vector) The component of (linearly polarized light) has a function of transmitting and reflecting the component (second linearly polarized light) having the electric field vector in the longitudinal direction of the metal conductor (thin wire). In addition, unlike the above characteristics, there is a function of absorbing or reflecting the first linearly polarized light component and transmitting the second linearly polarized light component. As an example of the latter function, there is an optical pickup device using a metal one-dimensional grating, and the pitch of the metal conductor to be the metal one-dimensional grating is set particularly for light having a wavelength of 780 nm for CD. It has been reported that desired optical characteristics can be obtained even if it is relatively wide (Patent Document 1).

Further, a wire grid in which, for example, a structure in which metal wires made of Al and dielectric layers made of MgF ₂ are alternately laminated in parallel with the flat substrate on the flat substrate is arranged at periodic intervals. A type polarizer has been reported (Patent Document 2). This wire grid polarizer is incident on the first linear polarization direction (p-polarized light) of light in the visible light region shorter than the wavelength of 780 nm, which is incident obliquely from the normal of the substrate surface. While exhibiting high transmittance, it exhibits low transmittance (high reflectance) with respect to light of the second linearly polarized light (s-polarized light).

Japanese Patent No. 3519618 Japanese Patent No. 4152645

  The metal one-dimensional grating used in the optical head device according to Patent Document 1 uses a resonance region from the vicinity of the ratio h / d = 0.1 between the grating thickness (h) and the grating period (d). The value can be increased. However, in the case of a metal one-dimensional grating using this resonance region, if the wavelength of the incident light is λ and d is set so that λ / d is about 1.4, diffracted light is actually generated. It becomes noise (stray light). In addition, in order to obtain desired characteristics without generating unnecessary diffracted light, the value of d must be reduced, and the polarization transmittance is likely to fluctuate greatly due to fluctuations in the peak wavelength of incident light. . Therefore, the metal one-dimensional grating of Patent Document 1 has a problem that it is difficult to obtain a stable polarization transmittance without generating diffracted light with respect to incident light. Furthermore, when the incident light is in the ultraviolet region (450 nm or less), the value of d has to be made smaller, and there is a problem that high accuracy is required in manufacturing.

  In addition, the wire grid polarizer according to Patent Document 2 has p-polarized light with high transmittance, although the transmitted beam contrast of p-polarized light and s-polarized light is uniform in the visible light region. The polarization transmittance is about 83%. However, the polarization transmittance of 83% for p-polarized light is not particularly high. Furthermore, it has a shorter wavelength than the visible light region. For example, the transmittance of p-polarized light tends to be lower with respect to light having a wavelength of 400 nm included in the BD wavelength band of the optical head device. Therefore, among the light having the wavelength in the visible light region and the light having the wavelength shorter than the visible light region, the second linear light has a higher polarization transmittance than the first linearly polarized light (p-polarized light). A wire grid polarizer having low polarization transmittance (high polarization reflection / absorption) for polarized light (s-polarized light) has been desired.

  In addition, for example, in order to obtain a high polarization transmittance with respect to light having a wavelength of around 400 nm, a conventional wire grid polarizer must be processed so that the pitch of a diffraction grating having a thin metal wire is shorter than 80 nm. I must. Here, as an example, consider the polarization transmittance of a wire grid polarizer having a configuration in which a metal part (metal fine wire) is formed on a transparent substrate. FIG. 19 is a schematic cross-sectional view of a conventional wire grid polarizer 200, which is referred to as a simple wire grid in which rectangular metal parts 202 are formed on a transparent substrate 201 with a periodic pitch p. It has a configuration. The metal part 202 has a width w and a height h.

  It is known that the optical characteristics of a wire grid polarizer are obtained by simulation based on a rigorous coupled wave analysis (RCWA) method. Here, when using the software G-solver of US G-solver, for example, the material of the metal part 202 is Al, and the pitch p, width w, and height h of the wire grid polarizer 200 are changed. The polarization transmittance was calculated. Specifically, FIG. 20A shows the polarization transmittance Tp of the first linearly polarized light (P-polarized light) that is transmitted when light having a wavelength of 405 nm is incident from the normal direction of the surface of the transparent substrate 201. FIG. 20B shows the characteristics of the polarization transmittance Ts of the second linearly polarized light (S-polarized light) to be blocked (reflected). At this time, the duty (w / p) was set to 0.5.

  As a polarizer, what has the characteristic that Tp is high and Ts is low is preferable. Here, from FIG. 20A, in order to increase Tp, it is preferable to shorten the pitch p of the metal part 202, and from FIG. 20B, to decrease Ts, the height of the metal part 202 is high. It can be seen that it is preferable to increase the length h. 21A shows the polarization transmittance Tp of S-polarized light when light having a wavelength of 650 nm is incident from the normal direction of the surface of the transparent substrate 201. FIG. 21B shows the same conditions. The characteristics of the polarization transmittance Ts of S-polarized light are shown. Further, FIG. 21C shows the polarization transmittance Tp of S-polarized light when light having a wavelength of 785 nm is incident from the normal direction of the surface of the transparent substrate 201, and FIG. The characteristics of the polarization transmittance Ts of S-polarized light are shown. Also in FIGS. 21A to 21D, the pitch p of the metal part 202 is shortened to increase Tp, and the height h of the metal part 202 is increased to decrease Ts. preferable.

  Further, as an index indicating the characteristics of the polarizer, there is an extinction ratio (or contrast) CR, which is expressed by CR = Tp / Ts. The CR varies depending on the use of the polarizer. For example, in a display device such as a liquid crystal display or a liquid crystal projector, the Ts value can be preferentially lowered rather than the Tp value being increased in order to increase the extinction ratio. A high CR is obtained by using a polarizer.

  Further, in order to obtain a polarizer having a high Tp value preferentially as compared with the polarizer characteristic in which CR is increased by preferentially lowering the Ts value as described above, FIG. A shorter pitch p is preferable to a). However, in order to obtain a high Tp, the pitch p of the metal part 202 must be 100 nm or less, which makes it difficult to manufacture with high accuracy and a stable optical characteristic cannot be obtained. . Further, even if manufacturing can be performed with high accuracy, from FIGS. 21 (a) to 21 (d), Tp is about 0.9 when the pitch p is 100 nm or less with respect to light of 650 nm and 785 nm. Although shown, there was still a problem that a sufficiently large Tp value could not be obtained.

  The present invention has been made to solve such a problem of the prior art. A wire grid polarizer having a high polarization transmittance and polarization resolution for incident light and a high extinction ratio for polarization components orthogonal to each other is provided. provide. It is another object of the present invention to provide an optical head device capable of performing stable recording / reproduction with high light utilization efficiency by using this wire grid type polarizer.

The present invention has been made to solve the above problems, and is stretched so as to be periodically arranged in one direction at a constant interval on one plane, and has a triangular or trapezoidal lattice shape. and the transparent substrate having the grid structure layer made of, anda metal part comprising a metal on one side of the grid side of the grid structure layer, the convex portions in the lattice shape of the grid structure layer A metal portion containing a metal on one side surface of the side surfaces, the width of the top of the convex portion in the lattice shape of the grid structure layer is 30 nm or less, and the convex portion in the lattice shape of the grid structure layer The ratio of the film-forming range of the metal part to the height of 0.75 is not less than 0.75, and the light incident on the translucent substrate is converted into the first linearly polarized light orthogonal to the longitudinal direction of the grid of the grid structure layer. Light and the grid structure Are divided into light components of the second linearly polarized light parallel to the longitudinal direction of the grating, Tp is the polarization transmittance of the first linearly polarized light, and Ts is the polarization transmittance of the second linearly polarized light. A wire grid polarizer that reflects the second linearly polarized light and has a Tp (1-Ts) of 0.94 or more for long wavelength light including the visible light region. To do.

  Moreover, when the light of 660 nm and the light of 785 nm enter into the said translucent board | substrate, Tp (1-Ts) provides said wire grid type polarizer which becomes 0.94 or more.

The width of the top of the convex portion in the grid shape of the grid structure layer is 10 nm or less, and the ratio of the film forming range of the metal portion to the height of the convex portion in the grid shape of the grid structure layer is 0.8. or more, the light-transmissive substrate, when the 405nm light is incident, Tp (1-Ts) to provide the wire grid polarizer to be 0.85 or more.

  The metal part provides the wire grid polarizer described above, which is made of a material mainly composed of Al.

  In addition, the translucent substrate has the configuration in which the first optical material portion and the second optical material portion having the grid structure layer are stacked on the first optical material portion. Offer a child.

  The translucent substrate provides the wire grid polarizer described above, wherein a protective film is laminated on the grid structure layer of the second optical material portion.

Further, the light transmitting substrate having a grid structure layer that is stretched so as to be periodically arranged in one direction at a constant interval on one plane and has a grid structure layer having a triangular or trapezoidal lattice shape, and the grid anda metal part comprising a metal on one side of the side surface of the protrusion in the lattice shape of the structural layer, the width of the top of the convex portions in the lattice shape of the grid structure layer has a 30nm or less, the The ratio of the film forming range of the metal part to the height of the convex part in the grid shape of the grid structure layer is 0.75 or more, and the light incident on the translucent substrate is transmitted in the longitudinal direction of the grid of the grid structure layer The first linearly polarized light orthogonal to the first linearly polarized light and the second linearly polarized light parallel to the longitudinal direction of the grid of the grid structure layer are divided into components, and the polarization transmittance of the first linearly polarized light is expressed as Tp. , Of the second linearly polarized light When the light transmittance is Ts, a wire grid type in which the second linearly polarized light is absorbed and Tp (1-Ts) is 0.85 or more for light having a wavelength shorter than the visible light region. A polarizer is provided.

The width of the top of the convex portion in the grid shape of the grid structure layer is 10 nm or less, and the ratio of the film forming range of the metal portion to the height of the convex portion in the grid shape of the grid structure layer is 0.8. or more, the light-transmissive substrate, when the 405nm light is incident, Tp (1-Ts), provides the wire-grid polarizer to be 0.85 or more.

  Moreover, the said metal part provides said wire grid type polarizer which consists of any material among Ge, a-Si, Mo, Os, PbS, SiGe, and W.

  The translucent substrate provides the wire grid polarizer described above, wherein a protective film is laminated on the grid structure layer of the second optical material portion.

  A light source, an objective lens for condensing the light emitted from the light source onto the optical disc, and a direction of a photodetector for guiding the light emitted from the light source toward the optical disc and receiving the light reflected by the optical disc. An optical head device comprising: a beam splitter that deflects the light grid; wherein the wire grid polarizer is disposed in an optical path between the light source and the beam splitter.

  Furthermore, a light source, an objective lens for condensing the light emitted from the light source onto the optical disc, a beam splitter for branching the light emitted from the light source into the direction of the optical disc and the direction of the monitoring photodetector, and the optical disc An optical head device comprising: a photodetector that receives light reflected from the light source; and a light amount control unit that controls the amount of light emitted from the light source in accordance with the amount of light detected by the monitoring photodetector. The optical head device is provided with the wire grid polarizer disposed in the optical path between the light source and the beam splitter and / or in the optical path of the beam splitter and the monitoring photodetector.

  The present invention relates to a wire grid polarizer having a high polarization transmittance and polarization resolution for incident light and a high extinction ratio to polarization components orthogonal to each other, and an optical head device for recording / reproducing an optical disc. It is possible to provide an optical head device having a high effect and capable of realizing stable recording / reproduction by stabilizing the amount of light collected on the optical disk.

1 is a schematic perspective view of a wire grid polarizer (first embodiment). FIG. Manufacturing process figure of wire grid type polarizer (1st Embodiment). The perspective schematic diagram of a wire grid type polarizer (second embodiment). The manufacturing process figure of a wire grid type polarizer (2nd Embodiment). The perspective schematic diagram of a wire grid type polarizer (3rd Embodiment). Manufacturing process figure of wire grid type polarizer (3rd Embodiment). (A) An optical head device using one light source (semiconductor laser element) and a wire grid polarizer. (B) An optical head device using two light sources (semiconductor laser elements) and a wire grid polarizer. Another optical head device using two light sources (semiconductor laser elements) and a wire grid polarizer. (A) The graph which shows the characteristic of the polarization transmittance with respect to the wavelength of the light which injects into the wire grid type polarizer which concerns on Example 1. FIG. (B) The graph which shows the characteristic of polarization separation power with respect to the wavelength of the light which injects into the wire grid type polarizer which concerns on Example 1. FIG. (A) The graph (405 nm) which shows the characteristic of the polarization transmittance with respect to the vapor deposition angle (theta) of Al of the wire grid type polarizer which concerns on Example 8. FIG. (B) The graph (405 nm) which shows the characteristic of polarization separation power with respect to Al vapor deposition angle (theta) of the wire grid type polarizer which concerns on Example 8. FIG. (A) The graph which shows the characteristic of the polarization | polarized-light transmittance with respect to the wavelength of the light which injects into the wire grid type polarizer which concerns on Example 9. FIG. (B) The graph which shows the characteristic of polarization separation power with respect to the wavelength of the light which injects into the wire grid type polarizer which concerns on Example 9. FIG. 10 is a graph showing the characteristics of polarization transmittance with respect to the wavelength of light incident on a wire grid polarizer according to Example 10. (B) The graph which shows the characteristic of polarization separation power with respect to the wavelength of the light which injects into the wire grid type polarizer which concerns on Example 10. FIG. 10 is a graph showing the characteristics of polarization transmittance with respect to the wavelength of light incident on a wire grid polarizer according to Example 11. (B) The graph which shows the characteristic of the polarization separation ability with respect to the wavelength of the light which injects into the wire grid type polarizer which concerns on Example 11. FIG. 10 is a graph showing the characteristics of polarization transmittance with respect to the wavelength of light incident on a wire grid polarizer according to Example 12; (B) The graph which shows the characteristic of polarization separation power with respect to the wavelength of the light which injects into the wire grid type polarizer which concerns on Example 12. FIG. 14 is a graph showing the characteristics of polarization transmittance with respect to the wavelength of light incident on a wire grid polarizer according to Example 13; (B) The graph which shows the characteristic of the polarization separation power with respect to the wavelength of the light which injects into the wire grid type polarizer which concerns on Example 13. FIG. 18 is a graph showing the characteristics of polarization transmittance with respect to the wavelength of light incident on a wire grid polarizer according to Example 14; (B) The graph which shows the characteristic of polarization separation power with respect to the wavelength of the light which injects into the wire grid type polarizer which concerns on Example 14. FIG. 18 is a graph showing the characteristics of polarization transmittance with respect to the wavelength of light incident on a wire grid polarizer according to Example 15. (B) The graph which shows the characteristic of polarization separation power with respect to the wavelength of the light which injects into the wire grid type polarizer which concerns on Example 15. FIG. 18 is a graph showing the characteristics of polarization transmittance with respect to the wavelength of light incident on a wire grid polarizer according to Example 17; (B) The graph which shows the characteristic of polarization separation ability with respect to the wavelength of the light which injects into the wire grid type polarizer which concerns on Example 17. FIG. The cross-sectional schematic diagram of the conventional wire grid type polarizer. (A) The characteristic (405 nm) of the polarization transmittance Tp in the P polarization direction with respect to the pitch (p) and the height (h) in the conventional wire grid polarizer. (B) The characteristic (405 nm) of the polarization transmittance Ts in the S polarization direction with respect to the pitch (p) and the height (h) in the conventional wire grid polarizer. (A) The characteristic (650 nm) of the polarization transmittance Tp in the P polarization direction with respect to the pitch (p) and the height (h) in a conventional wire grid polarizer. (B) The characteristic (650 nm) of the polarization transmittance Ts in the S polarization direction with respect to the pitch (p) and the height (h) in a conventional wire grid polarizer. (C) The characteristic (785 nm) of the polarization transmittance Tp in the P polarization direction with respect to the pitch (p) and the height (h) in the conventional wire grid type polarizer. (D) The characteristic (785 nm) of the polarization transmittance Ts in the S polarization direction with respect to the pitch (p) and the height (h) in the conventional wire grid polarizer.

(First embodiment of wire grid polarizer)
FIG. 1 is a schematic perspective view illustrating a configuration of a wire grid polarizer according to the present embodiment. The wire grid polarizer 10 has a translucent substrate 11 having a lattice shape in which a triangular or trapezoidal pattern is periodically formed on one surface, and the triangular or trapezoidal lattice pattern. Among them, the metal part 12 formed on one side surface. In addition, it is preferable to provide the antireflection film 13 on the surface of the translucent substrate 11 opposite to the lattice pattern shape, because interface reflection is suppressed and the utilization efficiency of incident light is improved.

  If a portion of the translucent substrate 11 constituting the lattice pattern shape, that is, a layer having a height of H in FIG. 1 is a grid structure layer 11a, the grid structure layer 11a has a plane whose top is 30 nm or less. The trapezoidal shape is more preferable, the trapezoidal shape with the top of the head being a plane of 10 nm or less is more preferable, and the triangular shape (the width of the top of the top is 0) is more preferable. For example, in the case of a trapezoidal shape, when the width of the plane of the top of the head is larger than 30 nm, the metal part 12 is also formed on the top of the head, and a desired polarization transmittance described later may not be obtained.

  In FIG. 1, the cross section of the grid structure layer 11a is triangular, the pitch corresponding to one period of the periodic lattice is P, and the triangular height and width are H and W, respectively. The duty is expressed as W / P. Further, when the cross section of the grid layer 11a is trapezoidal, the width of the top of the grid layer 11a is Wt, and the relationship of Wt <W is established. Hereinafter, the case where the grid layer 11a has a triangular shape, that is, Wt = 0 will be described. Here, first, by setting the pitch P to a distance shorter than the wavelength shorter than the visible light region, desired optical characteristics described later can be obtained with respect to incident light.

  Further, if the pitch P is to be shortened, a high accuracy is required for the shape of the mold for producing the grid structure layer 11a, and difficulty in producing the grid structure layer 11a arises. It may not be stable. On the other hand, when the pitch P is increased, it becomes difficult to obtain a high polarization transmittance for desired linearly polarized light. Therefore, for example, when λ is a wavelength shorter than the visible light region, the pitch P is preferably in the range of 0.2λ to 0.5λ, and more preferably in the range of 0.3λ to 0.4λ. Here, linearly polarized light that obtains a high polarization transmittance is linearly polarized light in a direction (X-axis direction) orthogonal to the longitudinal direction of the grating.

  In this way, by giving the above-mentioned pitch P to the wavelength λ in the visible light region and adjusting and setting H, W, and Wt accordingly, the wire grid polarizer 10 in FIG. When light is incident, a high polarization transmittance Tp is obtained for linearly polarized light (= P-polarized light) that becomes an electromagnetic wave component in the X-axis direction, and linearly-polarized light that becomes an electromagnetic wave component in the Y-axis direction. A low polarization transmittance Ts (high polarization reflectance / polarization absorption rate) is obtained for (= S-polarized light). The higher the value of the height H, the higher Tp and the lower Ts. The smaller the value of the width W, the higher Tp and the lower Ts. That is, as the aspect ratio H / W is larger, desired characteristics can be obtained. Further, in the production of a wire grid type polarizer, the relationship of H ≧ 2W and W ≦ 0.5P (Duty ≦ 0.5) are preferable. Further, it is more preferable that 3W ≧ H ≧ 2W and 0.25 ≦ W / P ≦ 0.5.

  For example, when λ = 405 nm as light having a shorter wavelength than the visible light region, the pitch P is preferably in the range of 80 to 200 nm, and more preferably in the range of 120 to 160 nm. At this time, the wavelength of the incident light is, for example, high Tp and low for light of wavelength 405 nm, light of wavelength 660 nm, and light of wavelength 785 nm as light of the wavelength of the blue laser used in the optical head device. Ts is obtained.

  As the translucent substrate 11, various materials such as a resin plate and a resin film can be used as long as they are transparent to incident light. However, when an optically isotropic material such as glass or quartz glass is used. This is preferable because it does not affect the birefringence of the transmitted light. Although various metal materials can be used for the metal part 12 depending on the surrounding medium, it is generally preferable that the refractive index is low. Further, as shown in FIG. 1, by forming the metal part 12 on one side surface of the grid structure layer 11a, the medium on the side facing the grid structure layer 11a in the metal part 12 is air (refractive index = 1). Therefore, for example, as compared with a structure in which metal is embedded in a glass substrate or a resin substrate (refractive index≈1.5), desired optical characteristics can be easily obtained as a polarizer.

  For example, when the wire grid polarizer 10 is a light reflection type that generates a polarization reflection function, Al or an Al alloy is preferably used. For example, when Al has a refractive index (n) of 0.50932 and an extinction coefficient (k) of 4.9534 with respect to light having a wavelength of 405 nm, and the metal part 12 of the wire grid polarizer 10 is, It exhibits a very high polarization separation ability, that is, a high transmittance with respect to one linearly polarized light and a low transmittance (high reflectance) with respect to the other orthogonally polarized light. Moreover, the surface part of Al is oxidized by itself, and that part functions as a protective film. Moreover, in order to raise the degree of hardness which is one of the mechanical properties of Al as the metal part 12, you may use Al alloy.

  The light-reflecting wire grid polarizer 10 transmits P-polarized light with high transmittance when light is incident from an oblique direction with respect to the normal direction of the surface of the translucent substrate 11. It can also function as a polarization beam splitter that regularly reflects S-polarized light with high reflectivity. The wire grid polarizer 10 is not limited to functioning as a polarization beam splitter, and when light is incident from an oblique direction with respect to the normal direction of the surface of the translucent substrate 11, of the incident light, The light component parallel to the longitudinal direction of the grating is S-polarized light, and the light orthogonal to it is defined as P-polarized light.

  Further, when the wire grid polarizer 10 is a light absorption type that generates a polarization absorption function, the metal part 12 that generates the polarization absorption function has a high refraction with respect to light of a target wavelength (for example, 405 nm). A material having a rate (n) and a high extinction coefficient (k) is preferred. Examples of the material of the metal part 12 include Mo, W, Ta, Os, a-Si (amorphous silicon), GaAs, InP, PbS, Ge, Si alloy, and Ge alloy. Among these, Ge and SiGe alloys are particularly preferably used from the viewpoints of availability and workability.

About the structure of the wire grid type polarizer 10, when the grid structure layer 11a is a triangular pattern, it is preferable to form the metal part 12 by vapor-depositing on almost the entire surface of one side of the triangular pattern. Here, when an angle θ in the thickness direction (evaporation direction) of the metal part 12 is given with reference to the plane of the translucent substrate 11 on the side having no lattice pattern, one side of the triangular pattern is given. When θt is a threshold value of the angle of vapor deposition on almost the entire surface, θt is
θt = Tan ⁻¹ (H / (P (1−0.5 W / P))) (1)
It is preferable to form the metal portion 12 so as to substantially satisfy the above formula (1).

  Further, in the above formula (1), when this θ becomes larger than the threshold value θt, the polarization with respect to the P-polarized light that proceeds in the normal direction (Z-axis direction) of the plane of the translucent substrate 11 in FIG. As the transmittance Tp decreases, the polarization transmittance Ts for S-polarized light also decreases. On the other hand, when θ is smaller than the threshold θt, the polarization transmittance Tp for P-polarized light is not significantly reduced, but the polarization transmittance Ts for S-polarized light is increased, so that desired characteristics cannot be obtained. Accordingly, when the unit of θt and θ is [°], it is preferably in the range of θt−8 ≦ θ ≦ θt + 8, and more preferably in the range of θt−5 ≦ θ ≦ θt + 5.

  Further, when θ = θt, desired optical characteristics as a polarizer can be obtained by setting the thickness T of the metal portion 12 formed in the vapor deposition direction to an optimum value. Desirable optical characteristics include a high Tp value, particularly for light in the visible light region and light having a shorter wavelength, and a low Ts value for light having the same wavelength. It is preferable that the value of 1-Ts) is large. Specifically, the value of Tp (1-Ts) is preferably 0.85 or more, more preferably 0.9 or more, and further preferably 0.94 or more. For example, light incident on the wire grid polarizer 10 has a wavelength of λ = 405 nm, a wavelength of λ = 660 nm that is red, and a wavelength of λ = 785 nm that is near infrared as light having a wavelength used in the optical head device. When the material of the metal part 12 is Al, when the thickness T is about 30 nm, Tp (1-Ts) can be set to a value close to the maximum.

  Further, for example, when Al is used as the metal part 12 to generate a function of reflecting S-polarized light, Tp (1-Ts) ≧ 0 with respect to light of λ = 660 nm and / or light of λ = 785 nm. .94 and a structure of a wire grid polarizer that can handle light with λ = 405 nm, Tp (1−Ts) ≧ 0 for light with λ = 405 nm. A characteristic satisfying 85 can be obtained. As the metal portion 12, a material having a low refractive index (n) and a high extinction coefficient (k) is preferable, and Ag and the like are also targets, but Al is particularly preferably used because of its high extinction coefficient.

  Further, when the metal part 12 is made of, for example, Ge and has a function of absorbing S-polarized light, a wire grid polarizer structure that can handle λ = 405 nm light is used. In contrast, characteristics satisfying Tp (1-Ts) ≧ 0.85 can be obtained.

  Next, an example of a method for manufacturing the wire grid polarizer 10 will be described. FIG. 2 is a schematic view showing a manufacturing process for obtaining the wire grid polarizer 10, and proceeds in the order of FIGS. 2 (a) to 2 (f). FIG. 2A shows a translucent substrate 21 before processing the translucent substrate 11 of FIG. Although not shown, first, there may be a step of forming an optical multilayer film or the like corresponding to an antireflection film on one plane of the translucent substrate 11. FIG. 2B shows a case in which a curable resin 22 is formed on a translucent substrate 21, and the curable resin 22 is applied to the translucent substrate 21 to obtain a uniform film thickness using a spin coater or the like. . FIG. 2C shows a process (photoimprint process) in which the mold 23 is pressed against the curable resin 22 and the UV light 24 is irradiated in this state. As a material of the mold die 23, a resin mold formed on a resin film such as Si, quartz, or PET is used. In addition, as the curable resin, a UV light curable resin that is cured by UV light, a thermosetting resin that is cured by heat, or a sol-gel material may be used to press the mold 23 and thermally cure. Good.

  FIG. 2 (d) shows a step of releasing the mold 23, and a resin 22 a having a triangular lattice pattern formed on the translucent substrate 21 is obtained. FIG. 2E shows a process of performing etching processing such as dry etching from the resin 22a side along the normal direction of the plane of the translucent substrate 21, and the translucent substrate is etched with an etching gas 25 or the like. The surface 21 is etched to obtain a translucent substrate 11 having a grid structure layer 11a having a triangular lattice pattern. FIG. 2 (f) shows a step of forming the metal portion 12 on the surface on one side of the grid structure layer 11 a, and the plane on the side facing the grid structure layer 11 a in the translucent substrate 11 is shown. The wire grid polarizer 10 can be obtained by forming the metal portion 12 having a thickness T by vacuum deposition or the like from the direction of the angle θt as a reference. Note that the metal part 12 is not limited to oblique vapor deposition, and may be a method of selectively forming a film using a sputtering vapor deposition or a mask in which an angle emitted from a plasma source is adjusted.

(Second embodiment of wire grid polarizer)
FIG. 3 is a schematic perspective view showing the configuration of the wire grid polarizer according to the present embodiment. The wire grid polarizer 30 has a translucent substrate 31 having a lattice shape in which a triangular or trapezoidal pattern is periodically formed on one surface, and the triangular or trapezoidal lattice pattern. Among them, the metal part 32 formed on one side surface. In addition, it is preferable to provide the antireflection film 33 on the surface opposite to the lattice pattern shape in the translucent substrate 31 because the interface reflection is suppressed and the utilization efficiency of incident light is improved. The translucent substrate 31 includes a first optical material portion 31a and a second optical material portion 31b. For example, the first optical material portion 31a has a planar substrate shape, and the second optical material portion. 31b includes a grid structure layer 31c serving as a lattice pattern. A combination of materials in which the refractive index of the first optical material portion 31a and the refractive index of the second optical material portion 31b are substantially equal is preferable because the interface reflection between them is suppressed. In the present embodiment, as will be described later, since etching is not performed in the manufacturing process, the shape of the lattice pattern hardly changes, and more stable optical characteristics can be obtained.

  Further, in FIG. 3, when the grating pitch is P, the height of the triangular shape, and the width are H and W, respectively, these preferable value ranges given to obtain desired optical characteristics are as follows. This is the same as the wire grid polarizer 10 according to the embodiment. As the first optical material portion 31a, various materials such as a resin plate and a resin film can be used as long as the first optical material portion 31a is transparent to incident light, but an optically isotropic material such as glass or quartz glass is used. When used, it is preferable because it does not affect the birefringence of the transmitted light. The second optical material portion 31b is preferably made of a resin material that is transparent to incident light from the viewpoint of ease of processing. As the metal part 32, Al, Ge, etc. are used like the metal part 12 of the wire grid type polarizer 10 which concerns on 1st Embodiment.

  Next, a method for manufacturing the wire grid polarizer 30 will be described. FIG. 4 is a schematic view showing a manufacturing process for obtaining the wire grid polarizer 40, and proceeds in the order of FIG. 4 (a) to FIG. 4 (e). FIG. 4A is a transparent substrate corresponding to the first optical material portion 31a of FIG. 3, and although not shown, first, it corresponds to an antireflection film on one plane of the first optical material portion 31a. There may be a step of forming an optical multilayer film or the like. FIG. 4B shows a case in which a curable resin 41 is formed on the first optical material portion 31a. The curable resin 41 is applied to the first optical material portion 31a and is uniformly applied by a spin coater or the like. Get film thickness. FIG. 4C shows a process (photoimprint process) in which the mold die 42 is pressed against the curable resin 41 and the UV light 43 is irradiated in this state. As a material of the mold die 42, a mold formed on a resin film such as Si, quartz, or PET is used. Alternatively, a thermosetting resin or a sol-gel material may be used instead of the UV light curable resin, and the mold die 42 may be pressed and thermally cured.

  FIG. 4D shows a step of releasing the mold die 42. From the resin in which a grid structure layer 31c having a triangular lattice pattern is formed on the first optical material portion 31a. A second optical material portion 31b is obtained. FIG. 4E shows a step of forming the metal part 32 on the surface on one side of the grid structure layer 31c, and the thickness from the direction of the angle θt with reference to the plane of the first optical material part 31a. The wire grid polarizer 30 can be obtained by forming the metal portion 32 of T by vacuum deposition or the like. The metal portion 32 is not limited to oblique vapor deposition, and may be a method of selectively forming a film using a sputtering vapor deposition or a mask in which an angle emitted from a plasma source is adjusted.

(Third embodiment of wire grid polarizer)
FIG. 5 is a schematic perspective view showing the configuration of the wire grid polarizer according to the present embodiment. The wire grid type polarizer 50 has a structure having a protective film 51a with respect to the configuration of the wire grid type polarizer 30. Avoid. Specifically, in the wire grid type polarizer 50, a protective film 51a is formed so that the translucent substrate 51 covers the surface on the grid structure layer 31c side, and the metal part 52 is provided on one side surface on the protective film 51a. Have. When the second optical material portion 31b is made of a resin material, the protective film 51a can suppress mechanical damage or optical damage of the resin material and can obtain stable optical characteristics. As the protective layer 51a, for example, a material such as SiO ₂ , ZrO ₂ , Ta ₂ O ₅ is used.

  Next, a method for manufacturing the wire grid polarizer 50 will be described. FIG. 6 is a schematic view showing a manufacturing process for obtaining the wire grid polarizer 50, and proceeds in the order of FIG. 6 (a) to FIG. 6 (f). First, since FIG. 6A to FIG. 6D are the same steps as FIG. 4A to FIG. 4D, the manufacturing method in the wire grid polarizer 30 according to the second embodiment. Based on the above description, the description is omitted here. FIG. 6E shows a step of forming the protective film 51a on the grid structure layer 31c side of the second optical material portion 31b made of resin so as to cover the second optical material portion 31b. The protective film 51a is formed by a method such as vacuum deposition or sputter deposition. FIG. 6F shows a step of forming the metal part 52 on the surface corresponding to one side of the grid structure layer 31c in the protective film 51a, and the plane of the first optical material part 31a is used as a reference. The wire grid polarizer 50 can be obtained by forming the metal portion 52 having a thickness T from the direction of the angle θt by vacuum deposition or the like. The metal portion 52 is not limited to oblique vapor deposition, and may be a method of selectively forming a film using a sputtering vapor deposition or a mask in which an angle emitted from a plasma source is adjusted.

(Embodiment of optical head device)
FIG. 7A and FIG. 7B are schematic views showing the configuration of an optical head device using the wire grid polarizer 10, 30 or 50 according to the present embodiment. The optical head device 60a shown in FIG. 7A is a semiconductor that emits at least one of light in the 405 nm wavelength band for BD, light in the 660 nm wavelength band for DVD, and light in the 785 nm wavelength band for CD. Light emitted from a light source 61 such as a laser element passes through the wire grid polarizer 55, and light having a specific polarization direction enters the polarization beam splitter 63. Here, the light source 61 may be, for example, a one-wavelength laser that emits only light in the 660 nm wavelength band, a two-wavelength laser that emits light in the 660 nm wavelength band, light in the 785 nm wavelength band, and further in the 405 nm wavelength band. A three-wavelength laser that also emits light may be used. Further, the light source 61 and the wire grid polarizer 55 may be integrated, and may be mounted in a CAN package, for example.

  Here, it is assumed that P-polarized light is emitted from the light source 61. However, an S-polarized light component is also generated due to a change in operating temperature or the like, and actually elliptically polarized light may be emitted. Including. At this time, the wire grid polarizer 55 will be described as transmitting P-polarized light and blocking S-polarized light orthogonal to the P-polarized light. As a result, a part of the S-polarized light generated by the light source 61 is blocked by the wire grid polarizer 55, and only the P-polarized light is transmitted. The wire grid polarizer 55 may be the wire grid polarizer 10, 30 or 50 described above. The wire grid polarizer 55 is not limited to the arrangement in which light is incident from the normal direction of the substrate surface, and may be inclined from the normal direction of the substrate surface as long as large astigmatism is not generated. Good. In this case, the amount of light that returns to the light source 61 out of S-polarized light that is regularly reflected is reduced, so that oscillation of light from the light source 61 can be stabilized.

When the P-polarized light that has passed through the wire grid polarizer 55 enters the polarization beam splitter 63, it is reflected toward the optical disk 67 with a specific reflectance R _BP [%] of the polarization beam splitter 63. The P-polarized light reflected by the polarizing beam splitter 63 passes through the quarter-wave plate 65 and becomes circularly-polarized light (here, clockwise circularly polarized light). Condensed on the recording surface. Depending on the arrangement of the objective lens 66, a rising mirror (not shown) that deflects the traveling direction by 90 ° may be arranged in the optical path between the polarizing beam splitter 63 and the quarter-wave plate 65.

Then, the return light reflected by the optical disk 67 becomes counterclockwise circularly polarized light, passes through the objective lens 66 and the quarter-wave plate 65 again, and becomes S-polarized light. The light travels straight at the transmittance T _BS [%] and is collected on the photodetector 68. In this case, it is preferable that the transmittance _TBS is a characteristic close to 100 [%] as the characteristic of the polarizing beam splitter 63, because the amount of light detected by the photodetector 68 increases and the light use efficiency increases. Even if a part of the S-polarized light is reflected by the polarizing beam splitter 63 to the wire grid polarizer 55 side, the S-polarized light can be sufficiently reflected or absorbed, so that the light does not travel to the light source 61 side. Therefore, stabilization of the light emitted from the light source 61 can also be realized.

Further, part of the P-polarized light that has passed through the wire grid polarizer 55 passes straight through the polarizing beam splitter 63 with a transmittance T _BP (≠ 0) [%], and reaches the monitoring photodetector 64. To do. At this time, most of the light incident on the polarization beam splitter 63 is a component of P-polarized light, and therefore the ratio of R _BP to T _BP is the optical disk with respect to the total light amount incident on the polarization beam splitter 63. It is equal to the ratio of the amounts of light branched to the 67 side and the monitor photodetector 64 side. Therefore, the amount of light emitted from the light source 61 is controlled by a light amount control means (not shown) so as to keep the amount of light received by the monitor photodetector 64 constant, so that the light is collected on the information recording surface of the optical disc 57. The amount of light to be emitted can be kept constant.

  Further, instead of arranging the wire grid polarizer 55 in the optical path between the light source 61 and the polarizing beam splitter 63, the same function is provided in the optical path between the polarizing beam splitter 63 and the monitoring photodetector 64. A wire grid polarizer 56 may be disposed. Further, a wire grid polarizer 55 is disposed in the optical path between the light source 61 and the polarization beam splitter 63, and the wire grid polarizer is disposed in the optical path between the polarization beam splitter 63 and the monitoring photodetector 64. 56 may be arranged. In this way, it is possible to reduce the light component that becomes noise superimposed on the light detected by the monitor photodetector 64, and to realize an optical head device capable of more stable recording and reproduction.

  The configuration of the optical head device is not limited to FIG. 7A, and may be the configuration of the optical head device 60b shown in FIG. 7B. The optical head device 60b has the same configuration as that of the optical head device 60a except that the optical path from the light source to the wire grid polarizer is different. , Avoid duplicate descriptions. In the optical head device 60b, light sources 61a and 61b that emit light in a specific wavelength band are arranged independently. For example, light in a 405 nm wavelength band emitted from the light source 61a is emitted by, for example, the dichroic prism 62. Light in the 660 nm wavelength band that is transmitted straight through and emitted from the light source 61b is reflected and adjusted so that the optical axes of these wavelengths of light are substantially aligned. Therefore, the light of a plurality of wavelength bands incident on the wire grid polarizer 55 follows the same optical path as that of the optical head device 60 a and reaches the monitoring photodetector 64 and the photodetector 68.

  In addition, there is a light source that emits light in another wavelength band, for example, light in the 785 nm wavelength band for CD, and the wire grid polarizer 55 is placed in an optical path common to light in three different wavelength bands. It may be arranged to obtain desired characteristics for light of each wavelength. For example, the light source 61 of the optical head device 60a may be a semiconductor laser that emits light of three wavelength bands, or the light source 61b of the optical head device 60b may be a semiconductor laser that emits light of two wavelength bands. May be. Note that the wavelength band of 405 nm is 385 nm to 430 nm, the wavelength band of 660 nm is 630 nm to 690 nm, and the wavelength band of 785 nm is 760 nm to 810 nm.

  FIG. 8 is a schematic diagram showing a configuration of another optical head device 70 using the wire grid polarizer 10, 30, or 50 according to the present embodiment. In FIG. 8, in particular, a wire grid polarizer 55 corresponding to the wire grid polarizer 10, 30 or 50 is disposed in an optical path common to light of three different wavelength bands for BD / DVD / CD. Is done. The optical head device 70 includes a light source 71a that emits light in the 405 nm wavelength band, a light source 71b that emits light in the 660 nm wavelength band and light in the 785 nm wavelength band, transmits light in the 405 nm wavelength band, and 660 nm. The dichroic prism 72 that reflects the light in the wavelength band and the light in the 785 nm wavelength band enters the wire grid polarizer 55 with the optical axes of these three wavelength bands substantially aligned. At this time, it is preferable to adjust the light sources 71a and 71b so that the light component in a specific polarization direction (for example, P-polarized light) becomes most of the incident light.

Here, the wire grid polarizer 55 transmits the P-polarized light and blocks the S-polarized light orthogonal to the P-polarized light, so that the P-polarized light passes through the polarization beam splitter 73 and is collimated by the collimator lens 74. It becomes parallel light and enters the dichroic prism 75. Note that the collimator lens 74 can easily change the optical path length of light in a plurality of wavelength bands by making divergent (convergent) light into parallel light. For example, the dichroic prism 75 has a function of reflecting light in the 405 nm wavelength band and transmitting light in the 660 nm wavelength band and the 785 nm wavelength band in a straight line. That is, in this case, the optical disk 79a corresponds to BD, and the optical disk 79b corresponds to DVD / CD. The light in the 405 nm wavelength band reflected by the dichroic prism 75 passes through the quarter-wave plate 77a and the objective lens 78a and is condensed on the information recording layer of the optical disk 79a. The light in the 660 nm wavelength band and the light in the 785 nm wavelength band that have been transmitted straight through the dichroic prism 75 are reflected by the reflection mirror 76 and transmitted through the quarter wavelength plate 77b and the objective lens 78b to the information recording layer of the optical disk 79b. Condensate.

  The light of each wavelength band reflected from the optical disks 79a and 79b is transmitted through the objective lenses 78a and 78b, and is transmitted through the quarter-wave plates 77a and 77b to become S-polarized light. Then, the S-polarized light in each wavelength band follows an optical path in the opposite direction to the forward path, is reflected by the polarization beam splitter 73, and is condensed on the photodetector 80. Although not shown, in the optical head device 70, for example, a monitoring photodetector may be provided on an extended optical path in which the photodetector 80 and the polarization beam splitter 73 are arranged. In this case, a wire grid polarizer having the same function as that of the wire grid polarizer 55 may be provided in the optical path between the polarization beam splitter 73 and the monitoring photodetector.

  As described above, in the illustrated optical head devices 60a, 60b, and 70, not only light in the 405 nm wavelength band but also light in the 660 nm wavelength band and / or light in the 785 nm wavelength band is incident on the wire grid polarizer 55. The wire grid polarizers 55 and 56 preferably have sufficient polarization transmittance and polarization separation ability for light in these wavelength bands. The sufficient polarization transmittance means that when the light in the polarization direction that transmits the P-polarized light as described above, Tp (1-Ts) ≧ 0.94 in the 660 nm wavelength band and the 785 nm wavelength band. It is preferable to satisfy this, and it is more preferable to satisfy the relationship of Tp (1-Ts) ≧ 0.85 in the 405 nm wavelength band.

  In the optical head devices 60a, 60b, and 70, the example in which the wire grid polarizers 55 and 56 are disposed has been described, but the present invention is not limited thereto. For example, in an optical head device using light in three wavelength bands, a plurality of optical head devices may be used in the optical head device for the purpose of using light of different polarization components in BD optical paths and DVD / CD optical paths which are different optical paths. Alternatively, a wire grid polarizer may be used. Further, a wire grid type polarizer that generates an absorption function is arranged in an optical path common to light of a plurality of wavelength bands, for example, to generate a function as a polarizer for light of 405 nm wavelength band, and 660 nm A wavelength-selective function of transmitting light in the wavelength band and / or light in the 785 nm wavelength band without a large polarization transmittance difference depending on the polarization direction may be generated.

(Examples of the reflective wire grid polarizer according to the first embodiment: Examples 1 to 8)
(Example 1 to Example 7)
In this example, with respect to the wire grid polarizer 10 according to the first embodiment, among the incident light, high polarization transmittance is obtained for P-polarized light and low polarization for S-polarized light. It is designed to obtain transmittance. First, an antireflection film 13 in which Ta ₂ O ₅ and SiO ₂ are alternately laminated is formed on one surface of a quartz glass substrate corresponding to the light-transmitting substrate 11 in the wire grid polarizer 10 shown in FIG. . Thereafter, a UV photocurable resin is applied to the surface facing the antireflection film 13, and the film is made uniform by a spin coater.

  Next, a mold die made of Si having a lattice shape having a groove depth of 120 nm, a groove width of 36 nm, and a triangular or trapezoidal pitch of 120 nm is formed with UV light. Press against the curable resin. Then, with the mold die pressed, UV light having a wavelength of about 365 nm is exposed to cure the UV light curable resin. Then, the UV light curable resin is etched to transfer the same shape as the mold to the quartz glass substrate, thereby obtaining the grid structure layer 11a having a height H = 120 nm, a width W = 36 nm, and a pitch P = 120 nm. At this time, a plurality of mold dies having different widths only at the bottoms of the grooves are prepared, and a plurality of translucent substrates 11 having different top widths Wt [nm] of the grid structure layer 11a corresponding to the widths of the bottoms of the grooves are prepared. obtain. Then, the conditions of Examples 1 to 7 shown in Table 1 are given by changing the deposition angle θ [°] of Al and the deposition thickness T [nm] of Al. When Wt = 0 (Example 1), the cross-sectional shape of the grid structure layer 11a is triangular.

For the wire grid polarizer 10 having the structure of Examples 1 to 7, light having a wavelength λ = 405 nm, light having a wavelength λ = 660 nm , and light having a wavelength λ = 785 nm from the normal direction of the plane of the light-transmitting substrate 11 Table 2 shows the results of calculating the polarization transmittance Tp of P-polarized light and the polarization transmittance Ts of S-polarized light at each wavelength.

  From this result, Tp (1-Ts) is about 0.94 or more for 660 nm light and 785 nm light, and high polarization separation ability is obtained. Further, for light of 405 nm, Tp (1-Ts) has a high polarization separation ability of about 0.85 or more under the conditions of Examples 1 to 3, that is, the condition that the width Wt of the crown is 10 nm or less. can get. Thus, when the cross section of the grid structure layer 11a has a trapezoidal shape, a desired high polarization separation performance is obtained for light of 660 nm and light of 785 nm when the top is 30 nm or less, and is 10 nm or less. Furthermore, the desired high polarization separation ability can be obtained even for light of 405 nm.

  FIG. 9A shows a graph in which Tp and Ts are given to the vertical axis when the horizontal axis is in the range of 300 to 900 nm with the wavelength λ as the wavelength for the wire grid polarizer of Example 1. FIG. Further, FIG. 9B shows a graph of the wire grid polarizer of Example 1 in which the horizontal axis is in the range of 300 to 900 nm with the wavelength λ, and the vertical axis is given by Tp (1-Ts). As a result, high Tp and low Ts can be obtained over a wide wavelength range, and a higher Tp (1-Ts) value can be obtained. Specifically, Tp (1-Ts) is 0.94 or more for light having a wavelength of 545 nm or more. In addition, Tp (1-Ts) is 0.85 or more for light having a wavelength of 370 nm or more.

(Example 8)
Next, as Example 8, in the same manner as in Example 1, on the quartz glass surface, height H = 120 nm, width W = 36 nm, pitch P = 120 nm (duty: W / P = 0.3). The grid structure layer 11a having a triangular cross section is obtained. Then, when the film thickness of Al is T = 30 nm and the deposition angle θ is changed in the range of 30 to 60 [°], the polarized light transmission when light having a wavelength of 405 nm is incident on the obtained wire grid type polarizer. The simulation results of the rate (Tp, Ts) and the polarization separation ability are shown in FIG. 10 (a) and FIG. 10 (b), respectively.

  FIG. 10A is a graph showing the characteristics of the polarization transmittances Ts and Tp with respect to the vapor deposition angle θ, and FIG. 10B is a graph showing the characteristics of the polarization separation ability Tp (1-Ts) with respect to the vapor deposition angle θ. It is. From this result, it was confirmed that in this example, the highest polarization separation ability was exhibited when the vapor deposition angle θ was 49.6 °. When this optimum vapor deposition angle θt [°] is given, Tp (1−Ts) is 0.85 or more if the amount of change Δθ in angle is within 8 [°] with reference to θt. Therefore, it is preferably within 5 [°].

(Examples of the absorption-type wire grid polarizer according to the first embodiment: Examples 9 to 15)
Example 9
In this example, as Example 9, with respect to the wire grid polarizer 10 according to the first embodiment, among the incident light, a high polarization transmittance Tp is obtained for P-polarized light, and S-polarized light is also obtained. It is designed so that a low polarization transmittance Ts can be obtained by absorbing light. The absorption-type wire grid polarizer 10 that absorbs incident S-polarized light is different from the first to eighth embodiments in that Ge is deposited on the grid structure layer 11a as the metal portion 12, but other basics. The general configuration and manufacturing method are the same.

  Next, as Example 9, in the same manner as in Example 1, the height H = 120 nm, the width W = 36 nm, and the pitch P = 120 nm (duty: W / P = 0.3) on the quartz glass surface. The grid structure layer 11a having a triangular cross section is obtained. Then, the metal portion 12 is formed by setting the Ge film thickness T = 20 nm and the vapor deposition angle θ to 44 ° to obtain a wire grid polarizer. Then, with respect to the obtained wire grid type polarizer, when 405 nm light, 660 nm light, and 785 nm light are incident, polarization transmittance (Tp, Ts), and Tp (1− The simulation results of Ts) are shown in Table 3. FIG. 11A shows a graph in which Tp and Ts are given to the vertical axis when the horizontal axis of the wire grid polarizer of Example 9 is in the range of 300 to 900 nm, where the horizontal axis is the wavelength λ. Further, FIG. 11B shows a graph of the wire grid polarizer of Example 9 in which the horizontal axis is in the range of 300 to 900 nm with the wavelength λ, and the vertical axis is given by Tp (1-Ts).

  From this result, in this embodiment, high polarization separation ability is exhibited when the wavelength of incident light is 600 nm or less. In particular, it can be confirmed that Tp (1-Ts) shows a high value of 0.915 for 405 nm light. It can also be confirmed that Tp (1-Ts) is 0.85 or more for light having a wavelength in the range of 310 to 590 nm.

(Example 10)
The present embodiment is different from the ninth embodiment in that a-Si is vapor-deposited on the grid structure layer 11a instead of Ge as the metal portion 12 of the absorption wire grid polarizer 10 that absorbs incident S-polarized light. However, other basic configurations and manufacturing methods are the same. Specifically, as Example 10, in the same manner as in Example 1, the height H = 120 nm, the width W = 36 nm, and the pitch P = 120 nm (duty: W / P = 0.3) on the quartz glass surface. The grid structure layer 11a having a triangular cross section is obtained. Then, the metal portion 12 is formed by setting the a-Si film thickness T = 25 nm and the vapor deposition angle θ to 44 ° to obtain a wire grid polarizer.

  FIG. 12A shows a graph in which Tp and Ts are given to the vertical axis when the horizontal axis is in the range of 300 to 900 nm with the wavelength λ as the wavelength for the wire grid polarizer of Example 10. Further, FIG. 12B shows a graph of the wire grid polarizer of Example 10 in which the horizontal axis is the wavelength λ and is in the range of 300 to 900 nm, and the vertical axis is Tp (1-Ts). From this result, in this example, it can be confirmed that Tp (1-Ts) is 0.85 or more for light having a wavelength in the range of 370 to 490 nm.

(Example 11)
In this embodiment, the metal portion 12 of the absorption type wire grid polarizer 10 that absorbs incident S-polarized light is vapor-deposited on the grid structure layer 11a instead of Ge. Other basic configurations and manufacturing methods are the same. Specifically, as Example 11, in the same manner as in Example 1, on the quartz glass surface, height H = 120 nm, width W = 36 nm, pitch P = 120 nm (duty: W / P = 0.3) The grid structure layer 11a having a triangular cross section is obtained. Then, the metal part 12 is formed by setting the Mo film thickness T = 25 nm and the vapor deposition angle θ to 44 ° to obtain a wire grid polarizer.

  FIG. 13A shows a graph in which Tp and Ts are given to the vertical axis when the horizontal axis is in the range of 300 to 900 nm with the wavelength λ as the wavelength for the wire grid polarizer of Example 11. FIG. 13B shows a graph of the wire grid polarizer of Example 11 in which the horizontal axis is the wavelength λ and the range is 300 to 900 nm, and the vertical axis is Tp (1-Ts). From this result, in this example, it can be confirmed that Tp (1-Ts) is 0.85 or more for light having a wavelength in the range of 360 to 790 nm.

(Example 12)
This embodiment differs from the ninth embodiment in that Os is vapor-deposited on the grid structure layer 11a instead of Ge as the metal portion 12 of the absorption-type wire grid polarizer 10 that absorbs incident S-polarized light. Other basic configurations and manufacturing methods are the same. Specifically, as Example 12, the height H = 120 nm, the width W = 36 nm, and the pitch P = 120 nm (duty: W / P = 0.3) on the quartz glass surface in the same manner as in Example 1. The grid structure layer 11a having a triangular cross section is obtained. Then, the metal part 12 is formed by setting the film thickness T of Os = 25 nm and the vapor deposition angle θ to 44 ° to obtain a wire grid polarizer.

  FIG. 14A shows a graph in which Tp and Ts are given to the vertical axis when the horizontal axis is in the range of 300 to 900 nm with the wavelength λ being the horizontal axis for the wire grid polarizer of Example 12. Further, FIG. 14B shows a graph of the wire grid polarizer of Example 12 in which the horizontal axis is in the range of 300 to 900 nm with the wavelength λ, and the vertical axis is given Tp (1-Ts). From this result, it can be confirmed that in this example, Tp (1-Ts) is 0.85 or more for light having a wavelength in the range of 360 to 560 nm.

(Example 13)
In the present embodiment, PbS is vapor deposited on the grid structure layer 11a instead of Ge as the metal portion 12 of the absorption type wire grid polarizer 10 that absorbs incident S-polarized light. Other basic configurations and manufacturing methods are the same. Specifically, as Example 13, in the same manner as in Example 1, the height H = 120 nm, the width W = 36 nm, and the pitch P = 120 nm (duty: W / P = 0.3) on the quartz glass surface. The grid structure layer 11a having a triangular cross section is obtained. And the metal part 12 is formed by setting the film thickness T of PbS T = 25 nm and the vapor deposition angle θ to 44 ° to obtain a wire grid polarizer.

  FIG. 15A shows a graph in which Tp and Ts are given on the vertical axis when the horizontal axis is in the range of 300 to 900 nm with the wavelength λ as the wavelength for the wire grid polarizer of Example 13. Further, FIG. 15B shows a graph of the wire grid polarizer of Example 13 in which the horizontal axis is in the range of 300 to 900 nm with the wavelength λ, and the vertical axis is given by Tp (1-Ts). From this result, in this example, it can be confirmed that Tp (1-Ts) is 0.85 or more with respect to light having a wavelength in the range of 360 to 540 nm.

(Example 14)
This embodiment differs from the ninth embodiment in that SiGe is deposited on the grid structure layer 11a instead of Ge as the metal portion 12 of the absorption-type wire grid polarizer 10 that absorbs incident S-polarized light. Other basic configurations and manufacturing methods are the same. SiGe having a composition ratio of Si and Ge of 65:35 is used. Specifically, as Example 14, in the same manner as in Example 1, on the quartz glass surface, height H = 120 nm, width W = 36 nm, pitch P = 120 nm (duty: W / P = 0.3) The grid structure layer 11a having a triangular cross section is obtained. And the metal part 12 is formed by setting the film thickness T = 25 nm of SiGe and the vapor deposition angle θ to 44 ° to obtain a wire grid polarizer.

  FIG. 16A shows a graph in which the vertical axis indicates Tp and Ts when the horizontal axis is in the range of 300 to 900 nm with the wavelength λ as the wavelength for the wire grid polarizer of Example 14. Further, FIG. 16B shows a graph in which the horizontal axis of the wire grid polarizer of Example 14 is in the range of 300 to 900 nm with the wavelength λ, and Tp (1-Ts) is given on the vertical axis. From this result, in this example, it can be confirmed that Tp (1-Ts) is 0.85 or more with respect to light in the wavelength range of 360 to 440 nm.

(Example 15)
In this embodiment, the metal portion 12 of the absorption type wire grid polarizer 10 that absorbs incident S-polarized light is vapor-deposited on the grid structure layer 11a instead of Ge. Other basic configurations and manufacturing methods are the same. Specifically, as Example 15, in the same manner as in Example 1, on the quartz glass surface, height H = 120 nm, width W = 36 nm, pitch P = 120 nm (duty: W / P = 0.3) The grid structure layer 11a having a triangular cross section is obtained. Then, the metal part 12 is formed with a W film thickness T = 25 nm and a vapor deposition angle θ of 44 ° to obtain a wire grid polarizer.

  FIG. 17A shows a graph in which Tp and Ts are given on the vertical axis when the horizontal axis is in the range of 300 to 900 nm with the wavelength λ as the wavelength for the wire grid polarizer of Example 15. Further, FIG. 17B shows a graph in which the horizontal axis of the wire grid polarizer of Example 15 is in the range of 300 to 900 nm with the wavelength λ, and Tp (1-Ts) is given on the vertical axis. From this result, in this example, it can be confirmed that Tp (1-Ts) is 0.85 or more with respect to light having a wavelength in the range of 360 to 720 nm.

(Example of wire grid polarizer according to the second embodiment: Example 16)
In this example, as Example 16, for the wire grid polarizer 30 according to the second embodiment, among the incident light, a high polarization transmittance Tp is obtained for P-polarized light, and S-polarized light is obtained. It is designed to obtain a low polarization transmittance Ts for light. The reflective wire grid polarizer 30 that reflects incident S-polarized light has a quartz glass substrate as the first optical material part that constitutes the translucent substrate 31, and the second optical material part. A transparent resin having a refractive index after curing of 1.5 is used.

First, Ta ₂ O ₅ and SiO ₂ are alternately formed on one surface of a quartz glass substrate having a refractive index of about 1.5 corresponding to the first optical material portion 31a in the wire grid polarizer 30 shown in FIG. A laminated antireflection film 33 is formed. Thereafter, a UV photocurable resin is applied to the surface facing the antireflection film 33, and the film thickness is made uniform by a spin coater.

  Next, a mold mold made of Si having a lattice shape with a groove having a triangular cross section of 120 nm, a groove width of 36 nm, and a triangular pitch of 120 nm is pressed against the UV photocurable resin. . Then, with the mold die pressed, UV light having a wavelength of about 365 nm is exposed to cure the UV light curable resin, thereby obtaining the second optical material portion 31b having the grid structure layer 31c. At this time, the refractive index of the UV light curable resin is about 1.5. Next, Al is deposited on the grid structure layer 31c as the metal portion 32 at a deposition angle θ = 44 ° and a thickness T = 36 nm to obtain a wire grid polarizer 30 having the same optical characteristics as in the first embodiment. it can.

(Example of wire grid polarizer according to third embodiment: Example 17)
In this example, as Example 17, for the wire grid polarizer 50 according to the third embodiment, among the incident light, a high polarization transmittance Tp is obtained for P-polarized light, and S-polarized light is also obtained. It is designed to obtain a low polarization transmittance Ts for light. The reflective wire grid polarizer 50 that reflects incident S-polarized light has a quartz glass substrate as the first optical material part 31a, and a refractive index after curing as the second optical material part 32b. A transparent resin having a ratio of 1.5 is used.

First, Ta ₂ O ₅ and SiO ₂ are alternately formed on one surface of a quartz glass substrate having a refractive index of about 1.5 corresponding to the first optical material portion 31a in the wire grid polarizer 50 shown in FIG. A laminated antireflection film 33 is formed. Thereafter, a UV photocurable resin is applied to the surface facing the antireflection film 33, and the film thickness is made uniform by a spin coater.

Next, a mold made of Si having a lattice shape in which a groove having a triangular cross section has a depth of 120 nm, a groove width of 36 nm, and a triangular pitch of 120 nm (duty: W / P = 0.3) The mold is pressed against the UV light curable resin. Then, with the mold die pressed, UV light having a wavelength of about 365 nm is exposed to cure the UV light curable resin, thereby obtaining the second optical material portion 31b having the grid structure layer 31c. At this time, the refractive index of the UV light curable resin is about 1.5. Next, SiO _{2 serving} as the protective film 51a is formed on the grid structure layer 31c side of the second optical material portion 31b so that the thickness D is about 10 nm, thereby obtaining the translucent substrate 51. Then, Al is deposited on the SiO ₂ as the metal part 52 at a deposition angle θ = 50 ° and a thickness T = 27 nm, whereby the wire grid polarizer 50 can be obtained.

  And it is a parameter | index of polarization | polarized-light transmittance (Tp, Ts) when 405 nm light, 660 nm light, and 785 nm light inject with respect to the wire grid type | mold polarizer obtained in the present Example, and polarization separation ability. Table 4 shows the simulation result of Tp (1-Ts). FIG. 18A shows a graph in which Tp and Ts are given to the vertical axis when the horizontal axis is in the range of 300 to 900 nm with the wavelength λ as the wavelength for the wire grid polarizer of Example 17. FIG. Further, FIG. 18B shows a graph in which the horizontal axis of the wire grid polarizer of Example 17 is in the range of 300 to 900 nm with the wavelength λ, and Tp (1-Ts) is given on the vertical axis.

  From this result, it was confirmed that the present example shows high polarization separation ability when the wavelength of incident light is 300 to 900 nm. Specifically, Tp (1-Ts) is 0.94 or more for light having a wavelength of 490 nm or more. In addition, Tp (1-Ts) is 0.85 or more for light having a wavelength of 360 nm or more. Further, mechanical damage of the (UV light curable) resin material that becomes the second optical material portion 31b can be reduced.

  As described above, the wire grid polarizer according to the present invention has a component that transmits light out of the first linearly polarized light and the second linearly polarized light that are orthogonal to each other. The polarization transmittance of the first linearly polarized light is high, and the polarization transmittance of the second linearly polarized light can be lowered. In particular, by using a wire grid polarizer that has the desired polarization transmission characteristics for light of the wavelength used in the optical head device, an optical head device that achieves stable recording and reproduction with high light utilization efficiency is realized. Can and is useful.

10, 30, 50, 55, 56, 200 Wire grid polarizers 11, 31, 51 Translucent substrates 11a, 31c Grid structure layers 12, 32, 52, 202 Metal parts 13, 33 Antireflection film 21 Before processing Translucent substrates 22, 22a, 41, 41a (curable) resin 23, 42 Mold 24 UV light 25 Etching gas 31a First optical material part 31b Second optical material part 51a Protective films 60a, 60b, 70 Optical head devices 61, 61a, 61b, 71a, 71b Light sources 62, 72, 75 Dichroic prism 63, 73 Polarizing beam splitter 64 Monitor photodetectors 65, 77a, 77b 1/4 wavelength plates 66, 78a, 78b Objective lens 67 79a, 79b Optical disks 68, 80 Photo detector 74 Collimator lens 76 Reflective mirror 201 Transparent substrate

Claims (13)

A translucent substrate having a grid structure layer that is stretched so as to be periodically arranged in one direction at regular intervals on one plane, and has a grid structure layer having a triangular or trapezoidal lattice shape;
A metal part including a metal on one side surface among the side surfaces of the convex portion in the grid shape of the grid structure layer,
The width of the top of the convex portion in the grid shape of the grid structure layer is 30 nm or less,
The ratio of the film forming range of the metal part to the height of the convex part in the grid shape of the grid structure layer is 0.75 or more,
The light incident on the translucent substrate is converted into a first linearly polarized light orthogonal to the longitudinal direction of the grid of the grid structure layer and a second linearly polarized light parallel to the longitudinal direction of the grid of the grid structure layer. The light component is divided into light components, and when the polarization transmittance of the first linearly polarized light is Tp and the polarization transmittance of the second linearly polarized light is Ts, the second linearly polarized light is reflected. ,
A wire grid polarizer in which Tp (1-Ts) is 0.94 or more with respect to light on the long wavelength side including the visible light region.   The wire grid polarizer according to claim 1, wherein Tp (1-Ts) is 0.94 or more when 660 nm light and 785 nm light are incident on the translucent substrate. The width of the top of the convex portion in the grid shape of the grid structure layer is 10 nm or less,
The ratio of the film forming range of the metal part to the height of the convex part in the grid shape of the grid structure layer is 0.8 or more,
The wire grid polarizer according to claim 1 or 2, wherein Tp (1-Ts) is 0.85 or more when 405 nm light is incident on the translucent substrate.   The wire grid polarizer according to claim 1, wherein the metal part is made of a material mainly composed of Al.   The said translucent board | substrate has a structure by which the 1st optical material part and the 2nd optical material part which has the said grid structure layer on the said 1st optical material part are laminated | stacked. The wire grid type polarizer described in the item.   6. The wire grid polarizer according to claim 5, wherein the translucent substrate has a configuration in which a protective film is laminated on the grid structure layer of the second optical material portion. A translucent substrate having a grid structure layer that is stretched so as to be periodically arranged in one direction at regular intervals on one plane, and has a grid structure layer having a triangular or trapezoidal lattice shape;
A metal part including a metal on one side surface among the side surfaces of the convex portion in the grid shape of the grid structure layer,
The width of the top of the convex portion in the grid shape of the grid structure layer is 30 nm or less,
The ratio of the film forming range of the metal part to the height of the convex part in the grid shape of the grid structure layer is 0.75 or more,
The light incident on the translucent substrate is converted into a first linearly polarized light orthogonal to the longitudinal direction of the grid of the grid structure layer and a second linearly polarized light parallel to the longitudinal direction of the grid of the grid structure layer. It is divided into light components, and when the polarization transmittance of the first linearly polarized light is Tp and the polarization transmittance of the second linearly polarized light is Ts, the second linearly polarized light is absorbed. ,
A wire grid polarizer in which Tp (1-Ts) is 0.85 or more for light having a shorter wavelength than the visible light region. The width of the top of the convex portion in the grid shape of the grid structure layer is 10 nm or less,
The ratio of the film forming range of the metal part to the height of the convex part in the grid shape of the grid structure layer is 0.8 or more,
The wire grid polarizer according to claim 7, wherein Tp (1-Ts) is 0.85 or more when 405 nm light is incident on the translucent substrate.   9. The wire grid polarizer according to claim 7, wherein the metal portion is made of any one of Ge, a-Si, Mo, Os, PbS, SiGe, and W. 10.   The said translucent board | substrate has a structure by which the 1st optical material part and the 2nd optical material part which has the said grid structure layer on the said 1st optical material part are laminated | stacked. The wire grid type polarizer described in the item.   11. The wire grid polarizer according to claim 10, wherein the translucent substrate has a configuration in which a protective film is laminated on the grid structure layer of the second optical material portion. A light source;
An objective lens for condensing the light emitted from the light source onto the optical disc;
In an optical head device comprising: a beam splitter that guides light emitted from the light source in the direction of the optical disc and deflects it in the direction of a photodetector that receives the light reflected by the optical disc.
An optical head device in which the wire grid polarizer according to any one of claims 1 to 11 is disposed in an optical path between the light source and the beam splitter. A light source;
An objective lens for condensing the light emitted from the light source onto the optical disc;
A beam splitter that branches light emitted from the light source into the direction of the optical disc and the direction of the photodetector for monitoring;
A photodetector for receiving light reflected from the optical disc;
In an optical head device comprising: a light amount control unit that controls a light amount of light emitted from the light source in accordance with a light amount of light detected by the monitor photodetector.
The wire grid type polarizer according to any one of claims 1 to 11 is disposed in an optical path between the light source and the beam splitter and / or in an optical path of the beam splitter and the monitoring photodetector. Optical head device.

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