JP5900571B1 - Absorption-type grid polarizing element for ultraviolet rays and optical alignment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a problem of deterioration in polarization performance due to a photocatalytic action of a grid material itself in an absorption type grid polarization element capable of exhibiting sufficient polarization performance for light in the ultraviolet region. SOLUTION: Each linear portion 3 constituting a striped grid 2 provided on a transparent substrate 1 includes a first layer 31 formed of a first material that absorbs light of a first target wavelength. A second layer 32 formed of a second material that absorbs light of the second target wavelength, and a third layer 33 provided between the first layer 31 and the second layer 32, Is provided. The first material is a photocatalytic material such as titanium oxide, and the second material is an oxidizable material such as silicon. The third layer 33 is a barrier layer formed of silicon oxide. Even when an oxidizing active species such as ozone or atomic oxygen is generated during ultraviolet irradiation, the barrier layer 33 oxidizes the second layer 32. Is prevented. [Selection] Figure 1

Description

  The present invention relates to a polarization technique using a grid polarizing element.

  In addition to familiar products such as polarized sunglasses, various types of polarizing elements that obtain polarized light are known as optical elements such as polarizing filters and polarizing films, and are also widely used in display devices such as liquid crystal displays. . Polarizing elements are classified into several types according to the method of extracting polarized light, and one of them is a wire grid polarizing element.

  The wire grid polarizing element has a structure in which a fine striped grid made of metal (conductor) is provided on a transparent substrate. It functions as a polarizer by making the interval between the linear parts constituting the grid narrower than the wavelength of light to be polarized. Of linearly polarized light, polarized light that has an electric field component in the length direction of each linear part is reflected because it is equivalent to a flat metal, while it is reflected for polarized light that has an electric field component in a direction perpendicular to the length direction. Since it is equivalent to being only, there is a transmission through the transparent substrate. For this reason, linearly polarized light in a direction perpendicular to the length direction of the grating is exclusively emitted from the polarizer. By controlling the orientation of the polarizing element so that the length direction of each linear part of the grid faces in the desired direction, polarized light with the axis of polarized light (direction of the electric field component) oriented in the desired direction is obtained. Will be.

  Hereinafter, for convenience of description, linearly polarized light having an electric field component in the length direction of the grating is referred to as s-polarized light, and linearly polarized light having an electric field component in a direction perpendicular to the length direction is referred to as p-polarized light. Usually, the surface that is perpendicular to the incident surface (the surface that is perpendicular to the reflecting surface and includes the incident light and the reflected light) is called an s wave, and the parallel one is called a p wave. Is assumed to be perpendicular to the incident surface.

The basic indicators for the performance of such a polarizing element are the extinction ratio ER and the transmittance TR. The extinction ratio ER is the ratio (Ip / Is) of the intensity (Ip) of p-polarized light to the intensity (Is) of s-polarized light among the intensity of polarized light transmitted through the polarizing element. The transmittance TR is the ratio of the energy of the outgoing p-polarized light to the total energy Iin of the incident s-polarized light and p-polarized light (TR = Ip / Iin). An ideal polarizing element has an extinction ratio ER = ∞ and a transmittance TR = 50%.
In the polarizing element of the invention of this application, since the grid is not limited to metal (wire), in the following description, it may be simply referred to as a grid polarizing element.

JP 2007-17762 A

  In recent years, the grid polarizing element as described above has been used in the field of optical processing. An example of this is a photo-alignment technique for obtaining a film (alignment film) for controlling the arrangement of molecules by irradiation with polarized light. Photo-alignment is a technology that has been widely adopted in the production of high-performance liquid crystal displays. This technique is a technique for obtaining an alignment film by aligning liquid crystal molecules in a certain direction with respect to a substrate or aligning a pretilt angle to be constant by light treatment. An alignment film is formed on a liquid crystal substrate, and a liquid crystal molecule layer is provided thereon to control the alignment of liquid crystal molecules. Previously, alignment films were obtained by a mechanical process called rubbing. However, in order to improve alignment accuracy, photo-alignment using the fact that materials for alignment films are sensitive to light is often adopted. It has become to.

  In photo-alignment, the wavelength of light to which the alignment film material is sensitive is often in the ultraviolet region, and a polarizing element having sufficient performance is required for light in the ultraviolet region. Since the grid polarizing element can irradiate polarized light relatively uniformly in a relatively wide area, it is suitable for optical processing such as photo-alignment in this respect. However, a general wire grid polarizing element as a grid polarizing element is not suitable for polarization of ultraviolet light.

  The wire grid polarizing element can be said to be a reflective grid polarizing element, and selectively reflects s-polarized light and selectively transmits only p-polarized light on a metal grid. For light in the ultraviolet region, even if it is a metal such as aluminum, absorption occurs and the reflectance decreases. That is, since the frequency of light approaches the plasma frequency of free electrons in the metal, the reflectivity of the light in the ultraviolet region is lowered even though it is a metal. Therefore, even if a reflective grid polarizing element such as an aluminum grid can exhibit excellent polarization performance in the visible range, sufficient polarization performance cannot be obtained for light in the ultraviolet range.

On the other hand, as is well known, ultraviolet light has higher energy than visible and infrared light, so it is often used in the field of light processing where some changes are made in the properties and shape of the object. used. Therefore, if a polarizing element that exhibits sufficient polarization performance in the ultraviolet region can be obtained, its significance is extremely large.
In consideration of the above points, the inventors of this application have come up with a grid polarizing element that can be called an absorption type, which operates with a model different from a conventional reflective grid polarizing element. In the absorption type grid polarizing element, a light absorbing material such as a dielectric is used as a material of the grid, and a polarizing action is generated by utilizing a difference in light absorption between s-polarized light and p-polarized light.

The inventors have found that in the process of studying the practical structure and constituent materials of the absorption-type grid polarizing element, there is an unexpected problem of deterioration in polarization performance over time. This problem has been found that a certain kind of grid material causes a reaction corresponding to a photocatalyst, which can cause a decrease in polarization performance.
The invention of this application is based on the research and knowledge conducted by the above-described inventors, and in the absorption grid polarizing element capable of exhibiting sufficient polarization performance for light in the ultraviolet region, the photocatalyst possessed by the grid material itself The problem to be solved is to prevent the problem of deterioration in polarization performance due to action.

In order to solve the above-mentioned problem, the invention according to claim 1 of the present application is composed of a transparent substrate transparent to ultraviolet rays, and a striped grid provided on the transparent substrate, and the grid has ultraviolet rays of a target wavelength. An absorption grid polarizing element for ultraviolet rays composed of a large number of linear parts formed of a material that absorbs light,
Each linear part constituting the grid absorbs light of the first target wavelength and the first layer, which is a layer formed of the first material that absorbs light of the first target wavelength, and which obtains the polarization action. A second layer that is a layer that is formed of the second material and has a polarization effect, and a third layer provided between the first layer and the second layer,
The first material is a dielectric or semiconductor material that has a photocatalytic action by ultraviolet irradiation ,
The second material is a dielectric or semiconductor and is an oxidizable material,
The third layer is a barrier layer that prevents the second layer from being oxidized by the oxidizing active species when the oxidizing active species is generated by the photocatalytic action of the first material in the first layer. It has the structure of.
In order to solve the above problem, the invention according to claim 2 has a structure in which the first material is titanium oxide and the second material is silicon in the structure of claim 1.
In order to solve the above problem, the invention according to claim 3 has a structure in which the third layer is formed of silicon oxide in the structure of claim 2.
In order to solve the above-mentioned problem, the invention according to claim 4 has a structure in which the thickness of the third layer is 2 nm or more in the structure of claim 3.
In order to solve the above-mentioned problem, according to a fifth aspect of the present invention, in the configuration of the fourth aspect, the thickness of the third layer is 30 nm thinner than the first layer and the second layer. The configuration is as follows.
In order to solve the above-mentioned problem, the invention according to claim 6 is the structure according to any one of claims 1 to 5 , wherein the first layer, the second layer, and the third layer are made of light. It has the structure of being laminated | stacked along the propagation direction.
Moreover, in order to solve the said subject, invention of Claim 7 is equipped with the light source and the absorption grid polarizing element for ultraviolet rays in any one of Claims 1 thru | or 6 , and a grid polarizing element is optical orientation. It has the structure that it is arrange | positioned between the irradiation area | region where the film | membrane material for an arrangement | positioning is arranged, and a light source.

As described below, according to the invention described in claim 1 of the present application, since it is an absorption type grid polarizing element, it can be suitably used when polarizing light in the ultraviolet region. Moreover, since each linear part is formed with the layer of the 1st material and the layer of the 2nd material, a polarization effect will be obtained in a broad wavelength range, and versatility is high. Furthermore, since a barrier layer is provided to prevent the second layer from being oxidized by the oxidative active species generated in the first layer, the initial rapid oxidation does not occur in the second layer. The obtained polarization performance is obtained without being impaired.
According to the invention of claim 2, in addition to the above effect, since the first material is titanium oxide and the second material is silicon, in addition to light in the UVA or UVB region such as 365 nm, This is a grid polarization element suitable for obtaining polarized light for light in the UVC region such as 254 nm.
According to the invention described in claim 3, in addition to the above effect, since the material of the third layer is silicon oxide, the state becomes equivalent to the case where the initial oxidation is pre-generated and generated. For this reason, the oxidation of the second layer due to the oxidative active species hardly occurs, and the barrier layer is more suitable.
According to the invention of claim 4, since the thickness of the third layer made of silicon oxide is 2 nm or more, the barrier layer is formed with a thickness greater than the initial rapid oxidation that can occur. become. For this reason, the loss of the second layer can be prevented more reliably.
According to the invention of claim 6 , in addition to the above effect, the first, second and third layers are laminated along the light propagation direction, so that higher polarization performance is obtained in this respect. be able to.
In addition, according to the invention described in claim 7 , since the film material can be subjected to photo-alignment treatment while obtaining the above-mentioned effects, and the versatility of the grid polarizing element is high, the cost of capital investment can be suppressed. Can do.

It is a perspective schematic diagram of a grid polarization element concerning an embodiment. It is the perspective schematic which showed typically about the operation | movement model of an absorption-type grid polarizing element. It is a figure which shows the result of the simulation experiment which confirmed the wave of the x direction magnetic field component Hx. It is the front section schematic diagram showing typically a mode that electric field Ey was newly generated by the wave (rotation) of x direction magnetic field ingredient Hx. It is the figure which showed typically about the significance of each linear part of a grid being formed with two different light absorptive materials. It is a figure which shows the result of the simulation experiment which confirmed the point by which the polarization performance is broadened by the combination of a titanium oxide and a silicon | silicone. It is the figure shown about the experiment which confirmed that degradation arises in one grid material by the combination of two absorption type grid materials. It is a figure which shows the result of the simulation experiment about deterioration of the polarization performance shown in FIG. It is the figure which showed typically about the photocatalytic action by the material of a 1st layer. It is the figure which showed the light absorption spectrum of the oxygen molecule. It is a figure which shows the result of the experiment investigated about the cause of the extinction ratio fall in a medium-to-long term span. It is the schematic shown about the manufacturing method of the grid polarizing element of embodiment. It is a front sectional schematic diagram of a grid polarizing element of other embodiments. It is an example of use of a grid polarization element of an embodiment, and is a section schematic diagram of an optical orientation device carrying a grid polarization element. It is the figure shown about the broadening by the combination of a titanium oxide and titanium nitride as an example of the combination of another material. It is the figure shown about the broadening by the combination of titanium nitride and silicon as an example of the combination of other materials.

Next, modes (embodiments) for carrying out the invention of this application will be described.
FIG. 1 is a schematic perspective view of a grid polarizing element according to the embodiment. The grid polarizing element shown in FIG. 1 is mainly composed of a transparent substrate 1 and a grid 2 provided on the transparent substrate 1.

The transparent substrate 1 is “transparent” in the sense that it has sufficient transparency with respect to the target wavelength (the wavelength of light polarized using a polarizing element). In this embodiment, since ultraviolet rays are assumed to be used, quartz glass (for example, synthetic quartz) is used as the material of the transparent substrate 1.

As shown in FIG. 1, the grid 2 has a striped shape composed of a large number of linear portions 3 extending in parallel. The grid polarizing element performs a polarizing action by alternately and parallelly arranging regions having different optical constants. The space 4 between each linear part 3 is called a gap, and a polarization action is obtained by each linear part 3 and each gap 4. The width W of each linear portion 3 and the width t of the gap 4 are appropriately determined so that a polarization action can be obtained with respect to light of the target wavelength .

  The grid polarizing element of this embodiment operates with an absorption model. More specifically, each linear part 3 which comprises a grid absorbs the 1st layer 31 formed with the 1st material which absorbs the light of 1st object wavelength, and the light of 2nd object wavelength. And a second layer 32 formed of a second material. That is, the grid changing element of the embodiment performs a polarization action for two different wavelengths.

  First, an absorption type grid polarizing element will be described with reference to FIG. FIG. 2 is a schematic perspective view schematically showing an operation model of the absorption type grid polarizing element. As described above, the grid polarizing element is a polarizing element that transmits p-polarized light but does not transmit s-polarized light. Therefore, what should mainly be examined is the behavior of s-polarized light. In the following description, in order to facilitate understanding, it is assumed that each linear portion 3 of the grid 2 is a single layer formed of a single material.

In FIG. 2, for the sake of convenience, it is assumed that light propagates from the top to the bottom on the paper surface, and this direction is the z direction. Further, the direction in which each linear portion 3 of the grid 2 extends is the y direction, and thus the s-polarized light (indicated by Ls in FIG. 2) has an electric field component Ey. The magnetic field component (not shown) of this s-polarized light is in the x direction (Hx).
When such s-polarized light reaches the grid 2 of the grid polarizing element, the electric field Ey of the s-polarized light is weakened by the dielectric constant of each linear portion 3. On the other hand, the medium of the gap 4 is often air, but generally the dielectric constant is smaller than that of each linear portion 3, so the electric field Ey is not weakened in the gap 4 as much as in the grid 2.

即ち、グリッド２間の中央の電界Ｅｙの最も高いところを境に、一方の側ではＨｚは光の伝搬方向前方に向き、他方の側ではＨｚは後方を向く。ここで、図２では省略されているが、ｘ方向の磁界ＨｘはＥｙと同位相で、ｘ軸負の側を向いて存在している。このｘ方向磁界成分Ｈｘは、生成されたｚ方向成分Ｈｚに引っ張られ、波打つように変形する。 As a result, a rotation component of the electric field Ey is generated in the xy plane. Then, according to the following Maxwell equation (Formula 1) corresponding to Faraday's electromagnetic induction, two mutually opposite magnetic fields Hz are induced in the z direction in accordance with the strength of rotation in the xy plane.

That is, with the highest electric field Ey at the center between the grids 2 as a boundary, Hz is directed forward in the light propagation direction on one side and Hz is directed backward on the other side. Here, although omitted in FIG. 2, the magnetic field Hx in the x direction has the same phase as Ey and exists toward the negative side of the x axis. The x-direction magnetic field component Hx is pulled by the generated z-direction component Hz and deforms so as to wave.

  FIG. 3 is a diagram showing a result of a simulation experiment in which the undulation of the x-direction magnetic field component Hx is confirmed. FIG. 3 shows a simulation performed using titanium oxide as the material of each linear portion 3 of the grid 2 and an optical constant (n = 4.03, k = 3.04) at a wavelength of 365 nm. In FIG. 3, the width of each linear portion 3 is 15 nm, the interval between the linear portions 3 is constant at 90 nm, and the height of each linear portion 3 is 170 nm. The simulation was based on the FDTD (Finite-Difference Time-Domain) method, and the software used was MATLAB (registered trademark) of Mathworks (Massachusetts, USA).

In FIG. 3, the dark black portion on the upper side indicates the negative component of the electric field Ez, and the light gray portion in the middle indicates the positive component of the electric field Ez. The magnetic field is indicated by a vector (arrow).
As shown in FIG. 3, the s-polarized light before reaching the grid 2 has only the Hx component because there is no Hz component. However, the generation of the above-mentioned Hz component reaching the grid 2 causes the magnetic field to be generated in the xz plane. It can be confirmed that it undulates. As shown in FIG. 3, the undulation of the magnetic field is a situation that can be said to be a clockwise rotation of the magnetic field.

この様子を図４において模式的に示す。図４は、ｘ方向磁界成分Ｈｘの波打ち（回転）により新たに電界Ｅｙが発生する様子を模式的に示した正面断面概略図である。 When such undulation (rotation) of the magnetic field component Hx occurs, an electric field is further generated in the y direction in FIG. 2 by the Maxwell equation (Equation 2) corresponding to Ampere-Maxwell's law.

This is schematically shown in FIG. FIG. 4 is a schematic front cross-sectional view schematically showing a state in which an electric field Ey is newly generated by undulation (rotation) of the x-direction magnetic field component Hx.

  As shown in FIG. 4, an electric field Ey directed toward the front side of the paper in FIG. 2 is generated in each linear portion 3 due to the undulation (rotation) of the magnetic field component Hx in the xz plane. An electric field Ey directed to the back side is generated. In this case, since the original electric field Ey of the incident s-polarized light is directed toward the front side of the drawing, the electric field in the gap 4 is canceled by the rotation of the magnetic field and acts to divide the wave. As a result, the electric field Ey is localized in each linear portion 3 of the grid 2, and the energy of the s-polarized light is attenuated while propagating through the grid 2 by absorption according to the material of each linear portion 3.

  On the other hand, for p-polarized light, the electric field component is oriented in the x direction (Ex), but when viewed in the y direction, the dielectric constant distribution is uniform, so the electric field rotation component as described above is substantially Does not occur. Therefore, the localization of the electric field such as s-polarized light in the grid 2 and the division of the wave do not substantially occur in the p-polarized light. For this reason, p-polarized light is emitted exclusively from the transparent substrate 1, and a polarizing action is obtained. The absorptive grid polarizing element of the embodiment is based on the premise that s-polarized light and p-polarized light propagate differently in this way due to the difference in the permittivity distribution of the space. It is confirmed that the s-polarized light and the p-polarized light also propagate differently in the grid 2 composed of the semiconductor linear portions 3 such as amorphous silicon, and a polarization action is obtained.

  In the grid polarizing element of the embodiment that operates in such an absorption model, the first and second two layers 31 and 32 are provided in each linear portion 3 as described above. This point has the significance of making the wavelengths that can be polarized multi-wavelength or broadening the band. This point will be described with reference to FIG. FIG. 5 is a diagram schematically showing the significance of the fact that each linear portion 3 of the grid 2 is formed of two different light absorbing materials.

As described above, the absorption-type operation model uses the fact that the electric field of s-polarized light is localized in the grid and is absorbed and attenuated by each linear portion 3. Accordingly, each linear portion 3 is formed of a material that absorbs light of the target wavelength.
Absorption in ultraviolet light materials occurs in general by the above-mentioned metal model (which occurs because the free electron plasma frequency approaches the light frequency), and generally by electronic transitions, especially interband transitions. . In any case, the absorption characteristic in the ultraviolet region, that is, the spectral absorptance varies depending on the material. The absorptance often peaks at a certain wavelength, but when two materials have the absorptivity at which they peak, the peak wavelength varies depending on the material. When two materials with different spectral absorption characteristics are selected as the material for blocking grid polarization, the spectral absorption characteristics are averaged, and polarization performance corresponding to the averaged spectral absorption characteristics can be obtained. Become.

The effects obtained by averaging the spectral absorption characteristics include the case where the peak wavelength of the two absorptances is obtained and a good polarization action is obtained at two different wavelengths (multi-polarization of polarization), and a wide wavelength. In some cases, polarization performance that is constant to some extent can be obtained (broadening of polarization). That is, in FIG. 5, when the absorption peak wavelength of the first material is λ ₁ and the absorption peak wavelength of the second material is λ ₂ , the absorption-type grid polarization element has λ ₁ and λ ₂ . Both can operate efficiently (multi-wavelength). Since the absorption spectrum gradually decreases before and after the peak wavelength, the entire absorption spectrum is as shown by a broken line in FIG. 5, and has a high absorption rate as a whole in a certain wide wavelength range of λ _{1 to} λ _2. It becomes. In other words, when each linear portion 3 is formed by the first material layer 31 and the second material layer 32, a polarizing action can be obtained in a relatively wide wavelength region of λ _{1 to} λ ₂ (broadening). ). Hereinafter, the term “broad” or “broadening” is used as a concept including the above-described multi-wavelength. FIG. 5 schematically shows the case where the polarization action is obtained by two materials having different absorption peak wavelengths, and does not show the measurement data of the absorption spectrum of a specific material.

  Based on such a technical idea, the inventors diligently studied a combination of materials that can exhibit higher polarization performance in a broad region. As a result, it has been found that in one combination of materials, the action of one material can degrade the other material. The action of one material is a so-called photocatalytic action. Hereinafter, this point will be described.

  The inventors paid attention to a combination of titanium oxide and silicon as a grid material capable of obtaining a polarizing action in a broad wavelength region. Titanium oxide has a high absorptance at 280 nm or less (UVC region, for example, 254 nm), and is suitable for polarizing light in this wavelength region. On the other hand, in the range of 280 to 400 nm (UVA region, UVB region), materials such as silicon and titanium nitride have high absorptance, and are suitable for polarizing light in this wavelength region (for example, 365 nm).

  FIG. 6 is a diagram showing the result of a simulation experiment in which the polarization performance is broadened by the combination of titanium oxide and silicon. In this simulation experiment, the structure of each linear part on a quartz transparent substrate was made of titanium oxide only, silicon only, or a layer of titanium oxide and a layer of silicon. Each polarization characteristic was calculated. Titanium oxide and silicon are assumed to be amorphous. Among these, FIG. 6 shows data of the extinction ratio at each wavelength. In FIG. 6, “Si 200 nm” means that each linear part having a height of 200 nm is formed only from silicon, and “TiO 2 200 nm” is a case where each linear part having a height of 200 nm is formed only from titanium oxide. "TiO2 50nm + Si 150nm" means the case where each linear part is formed by laminating a 50nm layer made of only titanium oxide and a 150nm layer made of only silicon, and the other two are the same. is there. The gap width was 80 nm in any case. In addition, RCWA (Rigorous Coupled-Wave Analysis) method was used for the simulation, and RSOFT series DiffractMod (product name) sold by Nippon Simnopsys Godo Kaisha was used for the software.

  As shown in FIG. 6, when each linear part having a height of 200 nm is formed only with titanium oxide, a high extinction ratio is obtained in a wavelength region of about 250 to 270 nm, but the extinction ratio gradually decreases in a longer wavelength region. In the region longer than 350 nm, only a very low extinction ratio can be obtained. Then, when a layer formed of silicon is assigned to each linear portion having a height of 200 nm and the height thereof is increased, the extinction ratio gradually increases in a wavelength region longer than 270 nm as shown in FIG. . When all are formed of a silicon layer, a polarization performance having a peak extinction ratio around 380 nm can be obtained.

  As can be seen from this result, when a part of each of the linear portions made of titanium oxide is replaced with silicon, the polarizing action can be obtained even in a wavelength region exceeding 350 nm where the polarizing action is not substantially obtained. Thus, a relatively uniform polarization action can be obtained in a wider range. Although the transmittance data of the polarization characteristics is not shown in the figure, it is confirmed that the transmittance becomes more uniform in the wavelength range of about 250 to 400 nm when part of the data is similarly replaced with a silicon layer. ing.

  As described above, the effect of broadening the polarization performance can be obtained by combining layers formed of different materials. However, when an absorption grid polarization element broadened by such a combination of materials is configured, an unexpected deterioration may occur in the polarization performance at one wavelength (the polarization performance expected from one material). found. This point will be described with reference to FIG. FIG. 7 is a diagram showing an experiment in which it is confirmed that one grid material is deteriorated by a combination of two absorption grid materials.

  FIG. 7 (1) shows a schematic structure of the grid polarizing element used in this experiment. As shown in FIG. 7 (1), the grid polarizing element used in this experiment has a structure in which each linear portion 3 of the grid 2 is composed of first and second two layers 31 and 32. Specifically, the first layer 31 is titanium oxide and the second layer 32 is silicon. The width of each linear portion 3 is about 30 nm, the width of the gap 4 is about 80 nm, the height of the first layer 31 (titanium oxide) is about 30 nm, and the height of the second layer (silicon) 32 is about 100 nm. . In this example, the first layer 31 is the upper side and the second layer 32 is the lower side.

In the experiment, the polarization performance was evaluated by irradiating the grid polarizing element shown in FIG. At this time, it was examined how the polarization performance changes with time as well as the performance immediately after the grid polarization element is manufactured. That is, FIG. 7 (2) shows changes in transmittance and extinction ratio in each cumulative irradiation time of light in the ultraviolet region. The change in the transmittance and the extinction ratio is shown as a ratio with the value immediately after production (at the start of ultraviolet light irradiation) being 100. The transmittance and extinction ratio data here are obtained using a detector with a wavelength of 365 nm, and are therefore data at a wavelength of 365 nm.
A high pressure mercury lamp manufactured by Ushio Inc. was used as a light source for irradiating ultraviolet light. This lamp is known as a so-called ozone lamp, and this mercury lamp has a rich emission spectrum even in the UVC region below 280 nm. The radiation spectrum of this lamp is shown in FIG.

  As shown in FIG. 7 (2), the transmittance is slightly improved as the irradiation time is increased to 30 hours, 220 hours, and 550 hours, but does not show a significant change with respect to the initial value. On the other hand, the extinction ratio has decreased to 86.0% after 30 hours. Thereafter, it is 86.8% when 220 hours have elapsed, and 76.2% when 550 hours have elapsed. That is, with regard to the extinction ratio, a significant decrease of 14% was observed until the first 30 hours, and thereafter, the decrease in the extinction ratio was slow, and even after 550 hours (10 times or more) had elapsed. Stayed in decline. Since the transmittance is Ip / Iin, it is actually a specific value of 50% or less, but FIG. 7B is a relative value when the initial value is 100%. The extinction ratio (Ip / Is) is the same, and is actually a specific value without a unit, but is shown as a percentage when the initial value is 100.

The data shown in FIG. 7 (2) is data with a wavelength of 365 nm, and in this grid polarization element, the second layer 32, that is, the silicon layer, is provided with a polarization action for light with a wavelength of 365 nm. That is, the decrease in the extinction ratio shown in FIG. 7 (2) is considered to be the result of some deterioration in silicon.
The inventors diligently investigated the cause of the deterioration, and it was speculated that it might be due to the photocatalytic action of titanium oxide used as the material of the first layer 31. That is, as a result of irradiating the titanium oxide of the first layer 31 with ultraviolet light, ozone or oxygen active species (for example, atomic oxygen) is generated, and silicon is oxidized by these active species. It was guessed.

  If the oxidation of silicon in the second layer 32 is caused by the photocatalytic reaction by the titanium oxide used as the first layer 31, it is assumed that the oxidation of silicon occurs exclusively at the interface with the titanium oxide. The inventors conducted a simulation experiment to verify this assumption. This result will be described with reference to FIG. FIG. 8 is a diagram showing the results of a simulation experiment on the deterioration of the polarization performance shown in FIG.

In the experiment of FIG. 8, in the structure of the grid polarizing element shown in FIG. 7A, how the polarization performance changes when an oxide layer is formed on the second layer 32 was obtained by calculation. That is, when the entire height of each linear portion 3 of the grid 2 is constant and the portion on the interface side with the first layer 31 in the second layer (silicon) 32 is replaced with silicon oxide, the polarization performance is improved. We asked how it would change.
Note that the RCWA method is used for the calculation, and software distributed by the National Institute of Standards and Technology (NIST) (http://physics.nist.gov/Divisions/Div844/facilities/scatmech/html/ grating.htm) was used. The optical constants of silicon were n = 4.03 and k = 3.04, and silicon oxides were n = 2.35 and k = 1.33 (both values at 365 nm).

As shown in FIG. 8, in the simulation, when the thickness of the oxide layer in the second layer (silicon) 32 is increased, the transmittance is approximately constant at 38 to 39%, but the extinction ratio is gradually decreased. . That is, the oxidation in the vicinity of the interface between the second layer 32 and the first layer 31 of silicon appears as a reduction in the extinction ratio. Therefore, the decrease in the extinction ratio shown in FIG. 7 (2) is considered to indicate this state.
In the simulation result shown in FIG. 8, the extinction ratio decreases to about 86% with respect to the initial extinction ratio (2046) when the thickness of the silicon oxide layer is about 2 nm. Therefore, the result shown in FIG. 7 (2) is considered to indicate that the oxidation of the second layer 32 proceeds rapidly to a depth of about 2 nm, and thereafter the oxidation proceeds slowly and slowly.

The rapid oxidation of the second layer (silicon) 32 at the beginning of the ultraviolet light irradiation estimated from the above experimental results and simulation results is presumed to be the result of the photocatalytic action of the first layer 31 by titanium oxide. This point will be described with reference to FIG. FIG. 9 is a diagram schematically showing the photocatalytic action by the material of the first layer 31.
Similarly, the case where the first layer 31 is titanium oxide and the second layer 32 is silicon will be described as an example. When the titanium oxide is irradiated with ultraviolet light UV, positive holes of the titanium oxide are excited, thereby generating active species having an oxidizing action (hereinafter referred to as oxidizing active species) (FIG. 9 (1)). Oxidizing active species are ozone, oxygen active species, OH radicals, and the like. These oxidizing active species oxidize the silicon of the second layer 32 at the interface to generate a silicon oxide layer 321 (FIG. 9B).

  The oxidizing active species originally existed as ground-state water and oxygen, but the gas molecules present in the atmosphere are adsorbed on the surface of the first layer 31 or the first It is presumed that it was contained in the layer 31. It is considered that the adsorbed or contained species are decomposed by titanium oxide excited by irradiation with ultraviolet light UV, and as a result, oxidizing active species are generated.

On the other hand, the slow decrease in the extinction ratio after 30 hours (medium-long span) shown in FIG. 7 (2) is considered to be due to oxygen gas molecules present in the atmosphere directly absorbing ultraviolet light. This point will be described with reference to FIGS. FIG. 10 is a diagram showing a light absorption spectrum of oxygen molecules, and FIG. 11 is a diagram showing a result of an experiment for examining the cause of a decrease in the extinction ratio in a medium to long span.
As is well known, oxygen molecules have a Schumann-Runge absorption band in a short wavelength region of 300 nm or less, and a Schumann-Runge continuous absorption band in a shorter wavelength region than the Schumann-Runge absorption band. And it is known that there is a Herzberg absorption band on the long wavelength side of the Schumann-Runge absorption band, and this absorption band is in a wavelength range of about 200 to 240 nm. These points are illustrated in FIG.

  The inventors have found that the decrease in the extinction ratio in the medium to long-term span (after 30 hours) shown in FIG. 7 (2) is due to oxidation caused by oxygen gas molecules being excited by directly absorbing ultraviolet light. I guessed it was the cause. In order to confirm this point, a verification experiment whose result is shown in FIG. 11 was conducted. In this experiment, an ultraviolet lamp that radiates ultraviolet light in the UVA to UVC region was similarly used for a grid polarizing element similar to that shown in FIG. At this time, a polarization experiment was performed using a cut filter that cuts 220 nm or less for a certain grid polarizing element and a cut filter that cuts 240 nm or less for another grid polarizing element.

  In FIG. 11, the transmittance and extinction ratio after 30 hours are set to 100, and the transmittance and extinction ratio after 220 hours and 550 hours are shown as the ratio. As shown here, when 220 nm or less is cut, the extinction ratio is gradually reduced to 77.9% after 550 hours. On the other hand, when 240 nm or less is cut, the extinction ratio hardly decreases, and is 92.2% even after 550 hours. The extinction ratio decreases when the cut is 220 nm or less, and the extinction ratio does not decrease when the cut is 240 nm or less. Therefore, the extinction ratio is reduced by light in the wavelength range of 220 to 240 nm. It is clear. Then, as shown in FIG. 10, since the light absorption of oxygen molecules starts from around 240 nm, the oxygen gas molecules absorb and excite light in the wavelength range of 220 to 240 nm. As a result, the second layer (silicon) It is thought that 32 was oxidized.

  Oxidation by directly absorbing the energy of ultraviolet light by such oxygen molecules is slow because it does not involve photocatalysis, and for this reason, the decrease in the extinction ratio over the medium to long term is also slow. Seem. On the other hand, the decrease in the extinction ratio at the initial stage (until 30 hours elapses) is attributed to the rapid oxidation due to the photocatalytic action, which is considered to be a rapid decrease.

Note that the point of saturation (stop) when there is abrupt oxidation due to photocatalysis is considered as follows.
A general photocatalytic action occurs on the surface of a member (photocatalytic member) formed of a photocatalytic material. The removal of organic contaminants is typical, and ultraviolet light is irradiated with water and oxygen adsorbed on the surface of the photocatalyst member, which decomposes and excites water and oxygen to generate active species. . The generated active species decomposes and removes organic matter.

  Although the photocatalytic action in the grid polarizing element is basically the same, as described above, each linear portion 3 constituting the grid 2 is very fine in the nano order (about the wavelength of light or less). is there. Therefore, when such a fine grid structure is formed with a photocatalytic material such as titanium oxide, it is considered that the entire cross-sectional area of each linear portion 3 is a surface region where photocatalytic action occurs.

That is, although the photocatalytic action is a surface reaction of the photocatalytic member, it is a phenomenon occurring in the region of the depth of the wavelength order. Therefore, in the fine structure of the wavelength order such as the grid polarizing element, the entire Is presumed to have a photocatalytic action. The photocatalytic action is presumed to work strongly against the silicon of the second layer 32 that is in direct contact with it, causing rapid oxidation.
The oxidizing active species generated by the photocatalytic action seems to be due to water and oxygen contained in the first layer 31 (titanium oxide) (titanium oxide is known as a hydrophilic material). It is considered that the species adsorbed on the surface of the first layer 31 may move through the first layer 31 while being excited and reach the interface with the second layer 32 to cause oxidation.

  In any case, when a broad-type grid polarizing element is formed by combining a photocatalytic material such as titanium oxide and an oxidizable material such as silicon as described above, the layer of the oxidizable material is formed. Rapid oxidation occurs. And since the rapid oxidation by this oxidizing active species passes through the interface, it is saturated when the thickness of the oxide layer reaches a certain level, and this oxidation does not proceed to a depth greater than that. . The above experimental results are considered to indicate such a situation.

  The grid polarizing element of the embodiment is based on the above research and knowledge. As shown in FIG. 1, the third layer 33 is provided between the first layer 31 and the second layer 32. ing. The third layer 33 is a barrier layer that prevents the active species generated in the first layer 31 from reaching the second layer 32. Specifically, similarly, the first layer 31 is formed of titanium oxide, and the second layer 32 is formed of silicon. The barrier layer 33 is formed of silicon oxide in this embodiment.

  The thickness of the barrier layer 33 made of silicon is preferably 2 nm or more. As described above, the rapid oxidation of the second layer 32 by the photocatalytic action is saturated in about 30 hours after the start of ultraviolet irradiation, and the thickness thereof is about 2 nm. That is, when a silicon oxide layer having a thickness of 2 nm or more is formed, it is considered that the deeper region than that is not oxidized by the oxidizing active species. Therefore, if the silicon oxide layer is formed with a thickness of 2 nm or more from the beginning, the silicon layer is not oxidized (decreased) by the photocatalytic action. In other words, without the barrier layer 33, the second layer 32 is reduced by about 2 nm by photocatalytic action, but by providing the barrier layer 33, the second layer 32 remains at the originally formed thickness, The expected polarization performance is not impaired. The barrier layer 33 in the embodiment has such technical significance.

In addition, since the barrier layer 33 is provided as a layer having no polarizing action, if the thickness is too large, the height of each linear portion 3 becomes unnecessarily high, and manufacturing becomes difficult. In consideration of manufacturing problems, the barrier layer 33 is preferably about 30 nm thick.
Further, since the oxidation of the second layer 32 in the medium to long term is slow as described above, there are many cases where there is no problem, and the life of the grid polarizing element is replaced with a new one after a certain period of time. Can take action. In addition, when the target wavelength of polarized light is longer than 240 nm, such as 254 nm, if the 240 nm or less is cut with a filter, it is possible to prevent the deterioration of the extinction ratio over the medium to long term.

Next, the polarization action of the grid polarizing element of such an embodiment will be supplementarily described.
As described above, the grid polarizing element of the embodiment is an absorption type, and polarization is performed by the incident polarized light being absorbed (differently attenuated) by s wave and p wave. At this time, the light having the first wavelength that is largely absorbed in the material of the first layer 31 (titanium oxide) is absorbed as described above when propagating through the upper grid region formed by the first layer 31. Polarization takes place in the model of the mold. Then, when the light passes through the upper grid region and propagates through the lower grid region formed by the second layer 32, the light of the second wavelength that is largely absorbed in the material (silicon) of the second layer 32 Similarly, polarization is performed by an absorption type model. As a result, p-polarized light is emitted exclusively from the transparent substrate at the first wavelength and the second wavelength, and multi-wavelength (broad) polarized light is achieved.

Next, the manufacturing method of the grid polarizing element of embodiment is demonstrated using FIG. FIG. 12 is a schematic view illustrating a method for manufacturing the grid polarizing element of the embodiment.
When manufacturing the grid polarizing element of the embodiment, first, the silicon film 51 for the second layer 32 is formed on the quartz transparent substrate 1 (FIG. 12A). As a forming method, various methods can be adopted. For example, an ALD (atomic layer deposition) method can be adopted.

Next, the surface of the silicon film 51 is thermally oxidized to form a silicon oxide layer 52 on the surface (FIG. 12 (2)). As a thermal oxidation method, a method of arranging the transparent substrate 1 with the silicon film 51 in a heating furnace and introducing oxygen gas or the like as appropriate in the same manner as the insulating layer formation in the semiconductor device manufacturing process can be adopted. .
After the silicon oxide layer 52 is formed by thermal oxidation, a titanium oxide film 53 for the second layer 32 is formed thereon (FIG. 12 (3)). Similarly, the ALD method can be adopted as the creation method.

Next, a resist is applied on the titanium oxide film 53, and exposure, development, and etching are performed to form a resist pattern 54 (FIG. 12 (4)). The resist pattern 54 corresponds to the shape of the grid to be formed, and is striped (line and space).
Etching is then performed using the formed resist pattern 54 as a mask to form each linear portion 3 including the first, second, and third layers 31, 32, and 33 (FIG. 12 (5)). Thereby, the grid polarizing element of the embodiment is completed. Etching is performed using different etchants because the materials in each layer are different. Etching is dry etching, anisotropic etching in the thickness direction of the transparent substrate 1, and a technique such as RIE (reactive ion etching) is appropriately used.

  A more specific example of the grid polarizing element of the embodiment will be described. Similarly, when the first layer 31 is titanium oxide, the second layer 32 is silicon, and the third layer is silicon oxide, the first layer The thickness of 31 is 50 nm, the thickness of the second layer is 150 nm, and the thickness of the third layer is 5 nm. In this case, the total thickness (height) of each linear portion is 205 nm and the width is 30 nm. Further, the width of the gap 4 in this example is 80 nm.

Next, a grid polarizing element according to another embodiment will be described with reference to FIG. FIG. 13 is a schematic front sectional view of a grid polarizing element of another embodiment.
In the above-described embodiment, there are two polarizing layers, but there may be three or more layers. An example of this is shown in FIG. That is, as shown in FIG. 13 (1), first, second, and fourth layers 31, 32, and 34 are provided as polarizing layers, and a third layer (barrier layer) 33 is provided at each interface. May be provided. In this example, the first layer 31 is provided in the middle and is titanium oxide having a photocatalytic action as described above, the lower second layer 32 is silicon, and the upper fourth layer 34 is another layer. It is an oxidizable material (for example, titanium nitride). In addition, the first layer 31 is a photocatalytic material and is provided at the bottom, and the second layer 32 that is an oxidizable layer is provided thereon, and the fourth layer 34 is provided thereon. Sometimes it is. In this case, the third layer 33 (barrier layer) is provided only between the first layer 31 and the middle second layer 32, and between the second layer 32 and the fourth layer 34. May not be provided. The same applies when the first layer 31 is located on the top.

  In addition, the first layer 31 and the second layer 32 are layers stacked along the light propagation direction, but the first layer 31 and the second layer 32 are in the light propagation direction. A vertically arranged structure can also be adopted. An example of this is shown in FIG. In this example, each linear portion 3 is formed by first and second layers 31 and 32 arranged in parallel in a direction perpendicular to the light propagation direction. Each of the first and second layers 31 and 32 is a layer that performs a polarizing action, and a third layer (barrier layer) 33 is provided therebetween. The first layer 31 is made of a photocatalytic material, and the second layer 32 is made of an oxidizable material. Also in such a structure, an oxidizing active species can be generated in the first layer 31 by the photocatalytic action induced by irradiation with ultraviolet light. Therefore, if the third layer (barrier layer) 33 is not provided, there will be a problem of an initial rapid extinction ratio reduction with respect to the polarization action of the second layer 32, and the third layer (barrier layer) 33 is provided. It has great significance.

Compared with the embodiment shown in FIG. 13 (2), the polarization performance is better in the structure in which the polarizing layer is laminated in the light propagation direction as in the embodiment of FIG. 1 and the embodiment of FIG. 13 (1). This is advantageous. That is, in the direction perpendicular to the light propagation direction, a higher polarization performance can be obtained if the contrast of the optical constant is clearer.
In the embodiment shown in FIG. 1, a 365 nm silicon layer (second layer 32) is provided on the upper side, and a 254 nm titanium oxide layer (first layer 31) is provided on the lower side. There is also a possibility.

Next, a usage example of such a grid polarizing element will be described. FIG. 14 shows an example of use of the grid polarizing element of the embodiment, and is a schematic cross-sectional view of a photo-alignment apparatus equipped with the grid polarizing element.
The apparatus shown in FIG. 14 is a photo-alignment apparatus for obtaining the above-described photo-alignment film for a liquid crystal display. By irradiating the object (work) 60 with polarized light, the molecular structure of the work 60 is in a certain direction. It will be in a state of being aligned. Therefore, the work 60 is a film (film material) for the photo-alignment film, and is, for example, a polyimide sheet. When the workpiece 60 has a sheet shape, a roll-to-roll conveyance method is adopted, and polarized light is irradiated during the conveyance. A liquid crystal substrate covered with a film material for photo-alignment may be a workpiece. In this case, a configuration in which the liquid crystal substrate is transported on a stage or transported by a conveyor is employed.

The apparatus shown in FIG. 14 includes a light source 61, a mirror 62 covering the back of the light source 61, and a grid polarizing element 63 disposed between the light source 61 and the workpiece 6. The grid polarizing element 63 is that of the above-described embodiment.
As described above, an ultraviolet lamp such as a high-pressure mercury lamp is used as the light source 61. As the light source 61, a light source 61 that is long in the direction perpendicular to the conveyance direction of the workpiece 60 (here, the direction perpendicular to the paper surface) is used.

The grid polarization element 63 selectively transmits p-polarized light with reference to the length direction of each linear portion as described above. Therefore, the grid polarization element 63 is arranged with high attitude accuracy with respect to the work 60 so that the polarization axis of the p-polarized light is directed in the direction in which the optical alignment is performed.
In addition, since it is difficult to manufacture a large-sized grid polarizing element, when it is necessary to irradiate a large area with polarized light, a configuration in which a plurality of grid polarizing elements are arranged on the same plane is adopted. In this case, the surface on which the plurality of grid polarizing elements are arranged is parallel to the surface of the work 60, and each grid is arranged such that the length direction of each linear portion in each grid polarizing element is a predetermined direction with respect to the work 60. A polarizing element is disposed.

  As described above, since the grid polarization element 63 is an absorption type grid polarization element by the first and second layers 31 and 32 formed of materials having different absorption wavelength ranges, polarized light is obtained in a broad wavelength range. be able to. This point has the significance of increasing the versatility of the photo-alignment device and reducing the equipment investment for the device user. That is, when irradiation with polarized light having a different wavelength is necessary because the types of alignment films are different, the conventional optical alignment apparatus needs to be replaced with the grid polarizing element for the different wavelength. On the other hand, in the grid polarizing element of the embodiment, since the wavelength range is broad, different types of alignment films may be processed using the same grid polarizing element. If different alignment films can be processed with the same grid polarizing element, the equipment investment for the apparatus user can be reduced accordingly.

As described above, since the third layer (barrier layer) 33 is provided in the grid polarizing element, there is no problem of an initial rapid extinction ratio reduction. For this reason, the lifetime of a grid polarizing element becomes long, and also in this respect, capital investment can be suppressed more.
Needless to say, such an effect is generally appropriate in optical processing that requires polarized light in a different wavelength region depending on the object, in addition to the photo-alignment.

In the embodiment described above, the material of the first layer 31 having a photocatalytic action was titanium oxide, but in addition, tin oxide, tungsten oxide, iron oxide, zinc oxide, niobium oxide, strontium titanate, potassium tungstate Zirconium oxide, titanium nitride, or the like may be used as the material for the first layer 31.
In addition to silicon, titanium nitride, gallium nitride, aluminum gallium nitride, germanium, or the like may be used as the material of the second layer 32 that is a non-oxide.
Further, as the material of the third layer (barrier layer) 33, silicon nitride may be used in addition to silicon oxide, and a chemically stable fluoride (for example, MgF 2) may be used. .

  FIG. 15 is a diagram showing broadening by a combination of titanium oxide and titanium nitride as an example of another material combination. Here, it is assumed that titanium oxide is rutile and titanium nitride is amorphous. In the example of FIG. 15, for each linear portion having a height of 100 nm and a width of 30 nm, when each linear portion is formed only from titanium oxide, when each linear portion is formed only from titanium nitride, the height is 50 nm. The result of the experiment which investigated how the polarization characteristic changes by the case where each linear part was formed by laminating | stacking a titanium oxide layer and a 50-nm-thick titanium nitride layer is shown. The gap width was common at 100 nm. Similarly, the RCWA method was used for the simulation, and DiffractMod (product name) was used for the software.

  As shown in FIG. 15, in the case of a grid made only of titanium oxide, there is a high extinction ratio peak at around 320 nm, but a low extinction ratio of 100 or less at 250 nm or less. If this is a grid in which a titanium oxide layer and a titanium nitride layer are laminated, the extinction ratio peak near 320 nm is lowered, but the extinction ratio is improved in the wavelength region of 250 nm or less. The same applies to a wavelength region exceeding 350 nm. Thus, by replacing a part of each linear part made of titanium oxide with titanium nitride, the variation in the extinction ratio due to the difference in the wavelength range is reduced, and a polarizing element having more uniform characteristics can be obtained. Even in this case, by providing the barrier layer as described above between the titanium oxide layer and the titanium nitride layer, the titanium nitride is prevented from being oxidized due to the photocatalytic action of the titanium oxide. Therefore, the expected polarization performance can be obtained without being impaired.

  FIG. 16 is a diagram showing broadening by a combination of titanium nitride and silicon as an example of another combination of materials. Here, titanium nitride and silicon are amorphous. Also in the example of FIG. 16, the height of each linear portion is common to 100 nm and the width is 30 nm. When each linear portion is formed only with titanium nitride, when each linear portion is formed only with silicon, nitriding with a height of 50 nm The result of the experiment which investigated how the polarization characteristic changed by the case where each linear part was formed by laminating | stacking a titanium layer and a 50-nm-thick silicon layer is shown by simulation. Similarly, the gap width was common at 100 nm, and the RCWA method and DiffractMod (product name) were used for the simulation.

  As shown in FIG. 16, in the case of a grid made of only titanium nitride, although there is a peak with a high extinction ratio at around 230 nm, the extinction ratio gradually decreases in a longer wavelength region, and in a long wavelength region of 350 nm or more. The extinction ratio is less than 10. It can be seen that when a part of the titanium nitride layer is replaced with a silicon layer, the extinction ratio peak near 230 nm is slightly lowered, but the extinction ratio is greatly improved in the wavelength region of more than 250 nm. Thus, even in the combination of titanium nitride and silicon, the variation in the extinction ratio due to the difference in wavelength range is reduced, and a polarizing element with more uniform characteristics can be obtained. In this example, even when titanium nitride has a photocatalytic action, silicon is oxidized due to the photocatalytic action of titanium nitride by providing the barrier layer as described above between the titanium nitride layer and the silicon layer. Is prevented. Therefore, the expected polarization performance can be obtained without being impaired.

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Grid 3 Linear part 31 1st layer 32 2nd layer 33 3rd layer (barrier layer)
34 Fourth layer 4 Gap 60 Work 61 Light source 62 Mirror 63 Grid polarization element

Claims (7)

An ultraviolet ray composed of a transparent substrate transparent to ultraviolet rays and a striped grid provided on the transparent substrate, and the grid is composed of a large number of linear portions formed of a material that absorbs light of a target wavelength that is ultraviolet rays. Absorption grid polarizing element for
Each linear part constituting the grid absorbs light of the first target wavelength and the first layer, which is a layer formed of the first material that absorbs light of the first target wavelength, and which obtains the polarization action. A second layer that is a layer that is formed of the second material and has a polarization effect, and a third layer provided between the first layer and the second layer,
The first material is a dielectric or semiconductor material that has a photocatalytic action by ultraviolet irradiation,
The second material is a dielectric or semiconductor and is an oxidizable material,
The third layer is a barrier layer that prevents the second layer from being oxidized by the oxidizing active species when the oxidizing active species is generated by the photocatalytic action of the first material in the first layer. An absorption grid polarizing element for ultraviolet rays characterized by the above. 2. The absorption grid polarizing element for ultraviolet rays according to claim 1, wherein the first material is titanium oxide and the second material is silicon. The absorption grid polarizing element for ultraviolet rays according to claim 2, wherein the third layer is made of silicon oxide. The absorption grid polarizing element for ultraviolet rays according to claim 3, wherein the thickness of the third layer is 2 nm or more.   5. The absorption grid polarizing element for ultraviolet rays according to claim 4, wherein the thickness of the third layer is smaller than that of the first layer and the second layer and is 30 nm or less. 6. The ultraviolet absorbing grid according to claim 1, wherein the first layer, the second layer, and the third layer are laminated along a light propagation direction. 6. Polarizing element.   A light source and an absorption grid polarizing element for ultraviolet rays according to any one of claims 1 to 6, wherein the grid polarizing element is disposed between an irradiation region where a film material for photo-alignment is disposed and the light source. A photo-alignment apparatus characterized by being made.

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