JP2016024419A - Wire grid polarizer, polarized image pickup device, and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire grid polarizer that can inexpensively prevent enlarging of an area where metal thin wires in the wire grid polarizer are oxidized and that can suppress degradation in optical performances by an oxidized region.SOLUTION: The wire grid polarizer includes a substrate, a plurality of metal thin wires arranged in a grid pattern on the substrate, and a protective film covering the metal thin wires. Each metal thin wire is broken at least at one portion thereof. When a grid direction is referred to the axial direction of the metal thin wire, the metal thin wire is preferably divided into a plurality of pieces in the grid direction.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a wire grid polarizer, a polarization imaging device, and a projector.

As a polarizing element that can be used in a wide wavelength band, a wire grid polarizer having a structure in which thin metal wires are arranged in a grating shape is used. The wire grid polarizer is characterized by being resistant to temperature changes because of the use of an inorganic material, and having a thickness equivalent to the height of a thin metal wire (about 200 nm), so that the function can be expressed and the thickness can be easily reduced.
Since the wavelength range in which the wire grid polarizer can be used is determined by the wire grid period of the wire, the wire grid polarizer has been conventionally used as a polarizing element for infrared rays. In recent years, wire grid elements that can be used in the visible light region have been developed due to the development of nano-processing technology. In particular, wire grids formed on glass substrates are made of inorganic materials. For this reason, application to the use of a projector etc. which have high heat resistance and are exposed to high temperatures is being studied.

  The wire grid polarizer has a problem that the fine metal wires are oxidized (corroded) in response to moisture in the air and the optical performance is deteriorated. Usually, a protective film is formed on the surface of the wire grid to avoid oxidation. However, if there is a defect in the protective film itself, oxidation occurs from that defect, and the oxidation spreads along the grid direction of the fine metal wire. Therefore, even if a small defect originates, the optical characteristics deteriorate over a wide range. End up.

  On the other hand, Patent Document 1 discloses that corrosion resistance can be obtained by forming a monomolecular film such as aminophosphonate on the surface of the wire grid for the purpose of preventing oxidation of the wire grid. Patent Document 2 discloses that the fine metal wires (grid lines) are aluminum and are covered with silicon oxide and aluminum oxide to improve the corrosion resistance.

  However, even with these techniques, when a part of the fine metal wire is oxidized, the oxidized portion spreads from this, and diffusion cannot be suppressed. Moreover, in the production of a wire grid polarizer, it is common to form a wire grid on the entire surface of a relatively large glass substrate and then cut it to a required size with a dicing saw or the like. Has no protective film and is oxidized from the cut surface. Therefore, it is necessary to form a protective film separately or to form the protective film after partially removing the fine metal wires in accordance with the position to be cut in advance.

Patent Document 3 proposes a method in which a portion without a wire grid is formed in advance near the position to be cut for the purpose of preventing oxidation from the cut surface.
However, it is not sufficient in terms of suppressing the spread of the oxidized portion of the fine metal wire. In addition, it is necessary to add a manufacturing process in which a portion without a wire grid is formed in the vicinity of the position to be cut, and there is a problem that the cost cannot be reduced by these methods.
Therefore, in these techniques, when a part of the thin metal wire is oxidized, the expansion of the oxidized region cannot be prevented, and the cost for suppressing the oxidized region is not sufficiently suppressed. There was a problem.

  Accordingly, in view of the above problems, the present invention provides a wire grid polarizer that can prevent the expansion of a region where metal fine wires in a wire grid polarizer are oxidized at a low cost and can suppress deterioration of optical performance due to the oxidized region. The purpose is to provide.

  In order to solve the above problems, a wire grid element of the present invention includes a substrate, a plurality of fine metal wires arranged in a grid shape on the substrate, and a protective film covering the fine metal wires, The metal thin wire is characterized in that at least one portion is broken.

  ADVANTAGE OF THE INVENTION According to this invention, it can prevent the expansion of the area | region where the metal fine wire in a wire grid polarizer is oxidized at low cost, and can provide the wire grid polarizer which can suppress deterioration of the optical performance by an oxidized area | region. it can.

It is a cross-sectional schematic diagram (A) which shows an example of the conventional wire grid polarizer, and a schematic diagram (B) which shows the shape of a metal fine wire. It is a schematic diagram which shows an example of the conventional wire grid polarizer. It is a schematic diagram which shows an example of the state by which the conventional wire grid polarizer was oxidized. It is a schematic diagram which shows the shape of the metal fine wire in an example of the wire grid polarizer which concerns on this invention. It is a schematic diagram which shows an example of the wire grid polarizer which concerns on this invention. It is a schematic diagram which shows an example of the state by which the wire grid polarizer which concerns on this invention was oxidized. It is a schematic diagram which shows the other example of the wire grid polarizer which concerns on this invention. It is a figure which shows an example of the polarized image imaging device which concerns on this invention. It is a figure which shows an example of the projector which concerns on this invention. It is a figure which shows an example of the result of the simulation in the wire grid polarizer which concerns on this invention. It is a figure which shows the other example of the result of the simulation in the wire grid polarizer which concerns on this invention. It is a figure which shows the other example of the result of the simulation in the wire grid polarizer which concerns on this invention.

  Hereinafter, a wire grid polarizer, a polarization imaging device, and a projector according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and other embodiments, additions, modifications, deletions, and the like can be changed within a range that can be conceived by those skilled in the art, and any aspect is possible. As long as the functions and effects of the present invention are exhibited, the scope of the present invention is included.

  The wire grid polarizer of the present invention includes a substrate 1, a plurality of fine metal wires 2 arranged in a grid on the substrate 1, and a protective film 3 covering the fine metal wires 2, and each fine metal wire 2 is , At least one location is disconnected.

  At least one portion of the fine metal wire 2 is broken, and each fine wire or broken surface is covered with a protective film 3. Since the fine metal wire 2 is disconnected, the range in which the fine metal wire 2 is oxidized even if the fine metal wire 2 is oxidized from the defective portion or cut surface of the protective film 3 can be suppressed, so that the influence on the optical characteristics can be suppressed.

<Conventional wire grid polarizer>
Examples of conventional wire grid polarizers are shown in FIGS. FIG. 1A is a schematic cross-sectional view showing an example of a conventional wire grid polarizer, and FIG. 1B is a schematic view showing a grid wire.

  As shown in FIG. 1A, a thin metal wire 2 is formed on a substrate 1, and the substrate 1 and the thin metal wire 2 are covered with a protective film 3. In addition, the protective film 3 should just cover the surface of the metal fine wire 2, may cover the board | substrate 1, and does not need to cover it. In addition, as shown in FIG. 1B, in the conventional wire grid polarizer, the fine metal wires 2 arranged in a grid are basically unbroken and go straight in the grid direction (the axial direction of the fine metal wires 2). The end surface (cut surface 4a) is connected to the opposite end surface (cut surface 4b).

  FIG. 2 shows an example of a conventional wire grid polarizer, and illustrates a use area 5 (corresponding to a display area of a liquid crystal panel) when the wire grid polarizer is used in, for example, a projector. Further, a protective film defect portion 6 corresponding to a defect of the protective film 3 is shown. As described above, in the conventional wire grid polarizer, the fine metal wires 2 arranged in a grid shape are basically unbroken. Therefore, in a high-temperature and high-humidity environment or the like, when the metal thin wire 2 is oxidized from a defect in the protective film 3 or a defect portion of the protective film 3 such as the cut end faces (cut surfaces 4a and 4b), the metal thin wire 2 is continuous Oxidation progresses with respect to the part which is carrying out, and the corrosion part 7 will be formed over a wide range.

  FIG. 3 is a diagram illustrating an example of a state in which a conventional wire grid polarizer is oxidized. As shown in FIG. 3, the fine metal wire 2 is oxidized from the protective film defect portion 6, and the corroded portion 7 is formed extensively. Moreover, in the cut surfaces 4a and 4b, the metal fine wire 2 is oxidized from the end surface of the metal fine wire 2, and the corroded portion 7 is formed extensively. For this reason, the corroded portion 7 is formed extensively inside the use region 5 starting from the protective film defect 6, and the corroded portion 7 extends from the cut surfaces 4 a and 4 b to the inside of the use region 5. This has caused a problem that the optical characteristics deteriorate over a wide range.

<One Embodiment of Wire Grid Polarizer According to the Present Invention>
Examples of the wire grid polarizer according to the present embodiment are shown in FIGS. FIG. 4 is a diagram showing the shape of the fine metal wire in the present embodiment. As shown in FIG. 4, the fine metal wire 2 is disconnected. Although how it is disconnected is not particularly limited, the position of the disconnected portion of the thin metal wire 2 may be different in the direction orthogonal to the grid direction as shown in FIG. In addition, for example, as illustrated in FIG. 7, the position of the broken portion of the fine metal wire 2 may be the same in a direction orthogonal to the grid direction.

  FIG. 5 is a diagram illustrating an example of a wire grid polarizer according to the present embodiment. As shown in FIG. 5, in the wire grid polarizer of the present embodiment, the fine metal wires 2 arranged in a grid shape are disconnected from the cut surface 4 a to the opposite cut surface 4 b in some places. Yes. Therefore, even if the protective film defect portion 6 is present, the corroded portion 7 can be minimized.

  FIG. 6 is a diagram illustrating an example of a state in which the wire grid polarizer according to the present embodiment is oxidized. Since the fine metal wires 2 are divided into a plurality of pieces and the individual fine metal wires 2 are individually covered with the protective film 3, even if a defect occurs in the protective film 3, it is the protective film 3 containing the defects that is oxidized. It is limited to the coated fine metal wire 2. Further, even if a part of the cut surfaces 4a and 4b is oxidized, the corroded portion 7 can be minimized. Therefore, the spread of the corroded portion 7 starting from the protective film defect portion 6 can be suppressed, and the corroded portion 7 is prevented from spreading from the cut surfaces 4a and 4b to the inside of the use region 5. Can do. Thereby, oxidation does not spread over a wide range, and deterioration of optical performance due to oxidation can be suppressed.

  In the present embodiment, each of the thin metal wires 2 is a region where the fine metal wires 2 are oxidized starting from the protective film defect portion 6 and the cut surfaces 4a and 4b (corrosion portions) because at least one portion is broken. 7) can be suppressed. Moreover, when the axial direction of the metal fine wire 2 is made into a grid direction, it is preferable that the metal fine wire 2 is divided | segmented into multiple in the grid direction. At this time, it is preferable that the protective film 3 covers the thin metal wire 2 including the divided surface. As described above, the breakage of the corroded portion 7 can be further suppressed by disconnection at a plurality of locations of the fine metal wires 2.

Next, details of each configuration of the wire grid polarizer according to the present embodiment will be described.
The substrate 1 is not particularly limited as long as it is a transparent substrate. For example, a glass plate, a plastic plate, etc. are mentioned.
Examples of the glass material used as the substrate 1 include borosilicate glass, synthetic quartz, crystallized glass, extremely low expansion glass ceramics, low expansion glass, optical glass, special glass, alkali-free glass, white plate glass, and blue plate glass.
The thickness of the substrate 1 is not particularly limited and can be appropriately changed, but can be 0.3 to 1 mm.

The material of the metal thin wire 2 is not particularly limited, and examples thereof include Al and other metals, and an alloy containing these may be used. Among these, Al is preferable because high polarization characteristics can be obtained in a wide wavelength region.
The height h of the fine metal wire 2 is not particularly limited, but is preferably 50 to 200 nm. The length of the fine metal wire 2 will be described later.

The material of the protective film 3 is not particularly limited, and examples thereof include monomolecular films such as Al oxide, Si oxide, Si nitride, and aminophosphonate.
Although it does not restrict | limit especially as a film thickness of the protective film 3, 5-20 nm is preferable.

  Next, the relationship between the length L of the divided metal wires 2 and the distance G between the divided metal wires 2 in the grid direction will be described. Another example of the wire grid polarizer according to this embodiment is shown in FIG. FIG. 7A is a cross-sectional view of the wire grid polarizer, and FIG. 7B is a diagram showing the shape of the thin metal wire 2. In FIG. 7, the protective film 3 is omitted.

In FIG. 7, the height h of the fine metal wires 2, the length L of the divided metal wires 2, the distance G between the divided metal wires 2 in the grid direction, the line width WL of the metal wires 2, and the division in the periodic direction. The distance WS between the fine metal wires 2 and the WG period P of the fine metal wires 2 divided in the periodic direction are shown. Note that the WG period P indicates the arrangement period of the divided metal wires 2 in the direction (period direction) perpendicular to the grid direction, and the relationship of P = WL + WS is established as shown in FIG.
Here, the extinction ratio will be described. The extinction ratio is also called contrast, and is expressed as TM transmittance / TE transmittance. The TM transmittance indicates the transmittance on the transmission side, and the TE transmittance indicates the transmittance on the blocking side. As shown in FIG. 7, the direction parallel to the grid direction is the TE direction, and the direction parallel to the periodic direction is the TM direction. It is known that the TM transmittance is ideally 1 and the TE transmittance is ideally 0, and the extinction ratio is preferably large.

  In the present embodiment, the ratio L / G between L and G is preferably 300 or more and 2000 or less. Within this range, an extinction ratio comparable to that of a wire grid polarizer in which the fine metal wires 2 are not divided can be obtained. If L / G is less than 300, a sufficient extinction ratio cannot be obtained. If L / G is larger than 2000, the metal fine wire 2 is close to an undivided shape, and expansion of the oxidized region (corroded portion 7) of the metal fine wire 2 cannot be suppressed.

The WG period P of the divided metal wires 2 is preferably 50 nm or more and 150 nm or less, and the length L of the divided metal wires is preferably 30 μm or more and 100 μm or less. When this range is satisfied, an extinction ratio comparable to that of a wire grid polarizer in which the fine metal wires 2 are not divided in the visible light wavelength range can be obtained.
At this time, the distance G between the divided metal wires 2 in the grid direction is preferably 50 nm or more and 300 nm or less. When satisfying this range, an extinction ratio comparable to that of a wire grid polarizer in which the fine metal wires 2 are not divided can be obtained in the visible light region.

Moreover, in this embodiment, it is preferable to have a dielectric between the thin metal wires 2 divided in the grid direction. By having the dielectric, the mechanical reliability of the wire grid polarizer can be increased.
The dielectric, and it is not particularly limited, for example, _SiO 2 transparent in the visible light wavelength, SiN, _Al 2 _{O 3} and the like.

  Although the manufacturing method of the wire grid polarizer which concerns on this embodiment is not restrict | limited in particular, For example, the following method is mentioned. First, for example, Al for forming the metal thin wire 2 is formed on the substrate 1, and the protective film 3 is formed thereon. Subsequently, a resist pattern is formed. Here, a pattern from which a desired shape of the fine metal wire 2 is obtained is formed. Next, Al and the protective film 3 are etched to obtain a wire grid polarizer.

Next, an embodiment of the polarization image capturing apparatus according to the present invention will be described. A polarization image capturing apparatus according to this embodiment is shown in FIG. The polarization image capturing apparatus according to this embodiment includes an image sensor 22 that photoelectrically converts an incident light beam, and the wire grid polarizer of the present invention provided on the light beam incident surface side of the image sensor 22. To do.
In the polarization image pickup device, the image pickup elements 22 (also referred to as light receiving elements) are two-dimensionally arranged at equal intervals in the horizontal direction and the vertical direction as shown in the drawing, and in front of each image pickup element (on the light receiving surface side). Polarizers 21 (wire grid polarizers) having different polarization axes for each region are two-dimensionally arranged.
In addition, among the plurality of regions, four regions of 2 × 2 in length and width, which are regions surrounded by a black dotted line in FIG. 8, each region has a different polarization axis and takes out light of different polarization components. A set of polarizer arrays 23 is formed. Since the polarization component transmitted through the wire grid polarizer array in which a large number of these four regions are arranged is received by the image sensor 22 (for example, CCD) for each region, polarization information can be obtained as an image.

In such a case, the wire grid polarizer functions as a polarizing filter, but the polarization imaging device is also used in harsh environments such as in-vehicle use, and in the wire grid polarizer of the present invention, Even in such a case, it can be fully utilized.
Note that the polarization axis of the image sensor 22, the arrangement thereof, the arrangement of the image sensor, and the like are not limited.
When borosilicate glass is used as the substrate 1 of the wire grid polarizer, a highly reliable wire grid polarizer can be formed on the glass substrate. In the case of stacking with the above devices or the like, since bonding can be performed at the wafer level by anodic bonding, low-cost mounting becomes possible.

  Next, the projector according to the present invention will be described. The embodiment according to the projector is a projector that uses the wire grid polarizer described above as the polarizer 31. The projector is required to project an image clearly, and when the function of the polarization separation element is lowered, the image quality is affected. In the present embodiment, the use of a wire grid polarizer that can prevent expansion of the region where the metal thin wire 2 is oxidized and suppress optical performance deterioration due to the oxidized region, thereby suppressing image deterioration. A projector that can be obtained is obtained.

FIG. 9 shows the configuration at the center of the display unit of the three-plate liquid crystal projector. The light from the light source is divided into three panels, R (red), G (green), and B (blue), through a wavelength separation (dichroic) mirror, and light is emitted from the back side to the liquid crystal panel used for display. Is irradiated. The light transmitted through the panel is collected by the dichroic cross prism 34 into one, and finally the image on the panel is enlarged and projected by the projection lens 35. The condenser lens 33 is a lens made of shelf silicate glass, and is used to efficiently collect light from the light source. The light from the light source is modulated by the LC light valve 32.
Here, the wire grid polarizer in the present invention can be used for a projector using a spatial light modulator such as LCOS.

  Hereinafter, the present invention will be described with reference to examples and comparative examples. In addition, this invention is not limited to the Example illustrated here.

Example 1
On a glass substrate having a diameter of 150 mm and a thickness of 0.525 mm, a thin metal wire 2 of Al, a WG period P of 150 nm, a height h of 200 nm, a width WL of the thin metal wire 2 of 60 nm, and a length of the divided thin metal wire 2 The thickness L was set to 30 μm and formed by EB (Electron Beam) lithography and dry etching. Further, Al ₂ O ₃ having a film thickness of 10 nm was used for the protective film 3 of the thin metal wire 2. After forming the wire grid, it was cut into a rectangle having a width of 13 mm and a length of 9 mm by dicing. The produced wire grid polarizer had a shape as shown in FIG. 5, and the number of thin metal wires 2 was about 87,000 in the periodic direction.

FIG. 5 shows a case where the obtained wire grid polarizer is used in a liquid crystal projector panel (XGA, pixel number 1024 × 768) having a diagonal size of 0.63 inches and a pixel size of about 12 μm in order to estimate the influence of deterioration. Consider a case where a protective film defect 6 as shown is generated.
When the protective film defect portion 6 is a defect having a diameter of 1 μm, the protective film defect portion 6 includes seven (7 in the periodic direction × 1 in the grid direction) divided fine metal wires 2. Since the thin wires 2 are individually covered with the protective film 3, the oxidized region is limited to these seven. In this case, the number of pixels affected by this defect was about 3 pixels ((0.0004)% of the pixel area). In addition, the oxidation generated from the cut surfaces 4a and 4b also stops progressing at the length of the divided thin metal wires 2, and as shown in FIG. 6, the oxidation does not reach the use area 5 and affects the image. I was able to suppress it.

(Comparative Example 1)
An Al metal thin wire 2 was formed on a glass substrate having a diameter of 150 mm and a thickness of 0.525 mm by EB lithography and dry etching with a WG period P of 150 nm, a height h of 200 nm, and a line width WL of the metal thin wire 2 of 60 nm. Further, Al ₂ O ₃ having a film thickness of 10 nm was used for the protective film 3 of the fine metal wire 2. After forming the wire grid, it was cut into a rectangle having a width of 13 mm and a length of 9 mm by dicing. The produced wire grid polarizer had a shape as shown in FIG. 5, and the number of thin metal wires 2 was about 87,000 in the periodic direction.

In order to estimate the influence of deterioration in the same manner as in Example 1, the obtained wire grid polarizer is used for a liquid crystal projector panel (XGA, pixel number 1024 × 768) having a diagonal size of 0.63 inches and a pixel size of about 12 μm. Consider the case where the protective film defect portion 6 as shown in FIG. 5 occurs.
When the protective film defect portion 6 is a defect having a diameter of 1 μm, about 20 fine metal wires are oxidized starting from this defect and oxidized in a vertically long region having a width of 1 μm, and a corroded portion as shown in FIG. 7 was formed. In this case, the number of pixels affected by this defect is about 768 pixels (0.1% of the pixel area), and bright vertical lines are generated in the projected image. Further, the oxidation generated from the cut surfaces 4a and 4b also extends along the grid direction, and thus has the same influence as the defect of the protective film 3. Therefore, compared with the wire grid polarizer obtained in Example 1, the wire grid polarizer obtained in Comparative Example 1 was oxidized over a wide range and the polarization characteristics were inferior.

(L / G evaluation 1)
In order to sufficiently cover the individual fine metal wires 2 with the protective film 3, the length L of the divided fine metal wires 2 should be as short as possible, and the distance G between the fine metal wires 2 in the grid direction should be as wide as possible. Good. However, since the optical characteristics change depending on these values, it is necessary to select dimensions that match the required optical characteristics.

Therefore, the following simulation was performed in order to obtain the relationship between the length L of the divided metal wires 2 and the distance G between the divided metal wires 2 in the grid direction.
First, in order to examine the length L of the divided thin metal wires 2, the thin metal wires 2 are divided with respect to the extinction ratio (TM transmittance / TE transmittance) of the wire grid polarizer in which the thin metal wires 2 are not divided. We examined how the extinction ratio of the wire grid polarizer changed. Therefore, a simulation was performed using the ratio L / G of L and G of the wire grid polarizer obtained by dividing the thin metal wire 2 as a parameter. As a simulator, Diffract mod (manufactured by R soft) was used.
Here, as conditions in the simulation, the material of the metal thin wire 2 was Al, the WG period P of the metal thin wire 2 was 150 nm, the height h was 200 nm, and the line width WL was 75 nm.

The obtained result is shown in FIG. In FIG. 10, G is fixed to 150 nm, incident light with wavelengths of 266 nm, 450 nm, 550 nm, 650 nm, and 800 nm is used, and the extinction ratio in a wire grid polarizer in which the metal thin wire 2 is not divided is compared for each wavelength. In FIG. 10, when the vertical axis is 100%, the extinction ratio in the wire grid polarizer in which the fine metal wires 2 are not divided is the same as the extinction ratio in the wire grid polarizer in which the fine metal wires 2 are divided. It shows that. Therefore, it is preferable that the extinction ratio is larger than 100%.
Hereinafter, a wire grid polarizer in which the fine metal wires 2 are not divided is referred to as an undivided wire grid polarizer, and a wire grid polarizer in which the fine metal wires 2 are divided is referred to as a divided wire grid polarizer.

FIG. 10 shows that when L / G is 300 or more, it exceeds 100% at all wavelengths, and the extinction ratio is better than that of the undivided wire grid polarizer. Further, as L / G increases, the extinction ratio converges and shows a substantially constant value at all wavelengths.
Where L / G is smaller than 300, the extinction ratio decreases from the long wavelength side. The division of the thin metal wire 2 is a structural change in the grid direction, in other words, a structural change in the TE direction. Therefore, even if L / G changes, the TM transmittance, which is a molecule of the extinction ratio, is not affected.
However, in the TE direction, when L / G decreases, in other words, the length L of the divided thin metal wires 2 decreases, and when the distance G between the divided thin metal wires 2 increases, the light inside the thin metal wires 2 is increased. It becomes difficult for the free electrons excited by the TE direction component to move. That is, like the TM direction, no light is reflected or absorbed, and light is transmitted. Therefore, when L / G becomes small, the TE transmittance increases and the extinction ratio as a whole decreases.

  From this result, when used in a visible light region (wavelength of about 400 to 650 nm) of a projector or the like, the length L of the divided metal thin wire 2 is preferably 30 μm or more (L / G is 200 or more). Moreover, in UV applications (wavelength of about 10 to 400 nm) such as a maskless exposure apparatus, the length L of the divided metal thin wire 2 is preferably 6 μm or more (L / G is 40 or more).

(L / G evaluation 2)
Next, in order to obtain the change in the extinction ratio at the distance G between the divided metal wires 2 in the grid direction, the following simulation was performed. Here, simulation was performed under the same conditions as the L / G evaluation 1 except that L was fixed at 60 μm and G was used as a parameter.

  The obtained results are shown in FIG. FIG. 11 shows the same tendency as in FIG. 10, where the extinction ratio becomes saturated as G decreases with respect to the extinction ratio of the undivided wire grid polarizer, that is, as L / G increases. Approaching. That is, the shape of the undivided wire grid polarizer is approached, and an extinction ratio equivalent to that of the undivided wire grid polarizer is obtained.

  From this result, in the split wire grid polarizer, the performance can be designed by L / G regardless of the values of L and G. When used in a visible light region (wavelength of about 400 to 650 nm) of a projector or the like, it is preferable to design performance so that L / G is 200 or more. Further, in UV applications (wavelength of about 10 to 400 nm) such as a maskless exposure apparatus, if L / G is 40 or more, it can be used with the same performance as an undivided wire grid polarizer.

  FIG. 12 shows the relationship between L and G with respect to L / G obtained as described above. In FIG. 12, hatched portions represent design values that can be used in the visible light region (wavelength of about 400 to 650 nm). It should be noted that the design value can be obtained in the same manner for the case where it can be used in a region having a wavelength other than the visible light region.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Metal thin wire 3 Protective film 4a, 4b Cut surface 5 Use area 6 Protective film defect part 7 Corrosion part 21, 31 Polarizer 22 Image sensor (CCD)
23 A set of polarizer arrays 32 Condenser lens 33 LC light valve 34 Dichroic cross prism 35 Projection lens G Distance between fine metal wires in grid direction L Length of fine metal wire P WG period WL Line width of fine metal wire WS Metal in periodic direction Spacing between thin wires

JP 2011-248284 A JP 2013-130598 A JP-T-2006-507517

Claims (8)

A substrate, a plurality of fine metal wires arranged in a grid on the substrate, and a protective film covering the fine metal wires,
Each said metal fine wire is a wire grid polarizer characterized by the disconnection at least one place.   2. The wire grid polarizer according to claim 1, wherein when the axial direction of the fine metal wires is a grid direction, the fine metal wires are divided into a plurality in the grid direction.   The L / G is 300 or more and 2000 or less, where L is the length of the divided metal wires and G is the distance between the divided metal wires in the grid direction. 2. The wire grid polarizer according to 2.   The arrangement period of the divided fine metal wires in a direction perpendicular to the grid direction is 50 nm or more and 150 nm or less, and the length of the divided fine metal wires is 30 μm or more and 100 μm or less. 2. The wire grid polarizer according to 2.   The wire grid polarizer according to claim 4, wherein a distance between the divided thin metal wires in the grid direction is 50 nm or more and 300 nm or less.   The wire grid polarizer according to any one of claims 2 to 5, wherein a dielectric is provided between the divided thin metal wires in the grid direction.   Polarized image imaging comprising: an image sensor that photoelectrically converts an incident light beam; and the wire grid polarizer according to claim 1 provided on a light beam incident surface side of the image sensor. apparatus.   A projector comprising the wire grid polarizer according to claim 1.