JP2017142386A - Ultraviolet rays filter layer, method for forming ultraviolet rays filter layer, ultraviolet rays filter, grid polarization element, and polarized light irradiation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filtering technique that allows a sufficient blocking of lights with such wavelengths that generate ozone while reducing loss of lights with a used wavelength, can response to oblique incidence, and can be practically used for taking measures against ozone.SOLUTION: A filter layer 2 formed on a transparent base plate 1 has a structure in which zirconium oxide or tantalum oxide as an absorbent material 22 is dispersed in an ultraviolet rays transmitting material 21, and the thickness of the layer is 100 μm or less. When the volume mixing ratio of the absorbent material 22 to the entire layer is x and the thickness of the layer is y, the relation of 24.319x≤y≤3040.1xis established in the case of zirconium oxide and the relation of 6.2213x≤y≤24.187xis established in the case of tantalum oxide. The volume mixing ratio of the absorbent material 22 to the whole is 0.9 or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a filter technology for ultraviolet rays.

  Optical processing, that is, processing of an object using optical energy is actively performed in the manufacture of various products. In light processing, light (photon energy) as energy is inversely proportional to wavelength, and therefore, ultraviolet rays having high energy are often used. A typical example is exposure processing in photolithography, which is a microfabrication technique. In addition, ultraviolet rays are used in applications such as curing, cleaning, and sterilization of ultraviolet curable resins.

  Recently, treatments for obtaining alignment films necessary for the production of liquid crystal displays have also been performed using ultraviolet rays. That is, when ultraviolet-polarized light is irradiated onto a resin film such as polyimide, the molecules in the film are aligned in the direction of the polarized light, and an alignment film is obtained. Compared to a mechanical alignment process called rubbing, a high-performance alignment film can be obtained, so that it has been widely adopted as a manufacturing process for high-quality liquid crystal displays. This technique is called photo-alignment.

JP 2014-174286 A

What should be noted in the use of such ultraviolet rays is the generation of ozone. FIG. 13 is a diagram showing a light absorption spectrum of oxygen molecules. As shown in FIG. 13, absorption of oxygen molecules starts around 240 nm, and stronger absorption occurs at wavelengths shorter than 200 nm. In general, a wavelength shorter than 200 nm is an ozone generation wavelength. However, even in a wavelength region of about 200 to 240 nm, there is a certain amount of absorption, and ozone is generated not a little.
As is well known, ozone is harmful to the human body and has a strong oxidizing action. Active oxygen (atomic oxygen) generated by decomposing ozone also has a strong oxidizing action. In applications such as cleaning and sterilization, the oxidizing action of ozone may be used positively, but problems such as deterioration due to oxidation of the object often occur due to the oxidizing action of ozone.

  It should be noted in this respect that light having a shorter wavelength is used in the ultraviolet region in order to use higher energy. In the emission line spectrum of a mercury lamp, which is a typical ultraviolet light source, conventionally, wavelengths such as 436 nm and 365 nm were often used, but recently, shorter wavelengths such as 254 nm have been used more often. It is coming. As can be seen from FIG. 13, 254 nm is very close to the ozone generation wavelength region. That is, the processing is performed in a situation where the problem of ozone generation is adjacent to each other.

  In consideration of the problem of ozone, a technique for irradiating ultraviolet rays without generating ozone has been developed in the field of light source technology. It is a light source called a so-called ozone-less lamp. The ozone-less lamp is a lamp having a structure in which a trace amount of impurities is mixed in the envelope. The impurity absorbs light having an ozone generation wavelength, and prevents light having an ozone generation wavelength from being emitted from the envelope. In addition, what kind of impurities are used is the know-how of the lamp manufacturer or the envelope glass manufacturer, and is not disclosed to the public.

However, there are some problems in the prior art that avoids the problem of ozone generation by the ozoneless lamp.
One is related to the recent trend to use shorter wavelength light. This point will be described with reference to FIG. FIG. 14 is a diagram showing the light blocking characteristic of ozone generation wavelength by a publicly disclosed ozone-less lamp envelope (ozone-less envelope), comparing spectral transmission characteristics of an ozone-less envelope and a normal envelope FIG.

  As shown in FIG. 14, in the conventional ozone-less envelope, the light blocking characteristic of the ozone generation wavelength is not so steep. That is, as shown in FIG. 14, although light having a wavelength of about 215 nm or less is completely blocked, there is a considerable transmittance in the range of 220 to 240 nm, and light in this range is transmitted. It is estimated that a considerable amount of ozone has been generated. If an attempt is made to cut off the wavelength in this range, light in the range of about 250 to 260 nm is also cut off considerably. When the object is processed using light in this range (for example, 254 nm) (for example, its In the case where the material is exposed to light in such a wavelength range), it is estimated that the processing efficiency is reduced.

  Another problem, which is not generally known, is the temperature characteristics of the ozone-less envelope. Ultraviolet absorption by impurities has temperature characteristics, and the absorption characteristics change as the temperature changes. According to the inventor's research, the envelope used in the conventional ozone-less lamp absorbs a lot of light having a longer wavelength as the temperature rises. As is well known, the lamp is hot when lit. Therefore, in practice, more absorption than that shown in FIG. 14 occurs on the long wavelength side, and when processing is performed using this wavelength band, it is presumed that the processing efficiency is greatly reduced. Although it is conceivable to suppress the temperature rise by cooling the lamp, it is necessary to keep the envelope of the lamp at a certain high temperature for stable light emission, and if cooling is performed to suppress the characteristic change of the ultraviolet absorbing material Cooling becomes excessive and light emission becomes unstable.

As a structure that avoids the problem of ozone generation without using an ozone-less lamp, a structure in which a filter is disposed between the light source and the object and the light having the ozone generation wavelength is blocked by the filter is conceivable. However, this structure also has some problems.
A filter that transmits and blocks light at a certain wavelength is known as a so-called sharp cut filter. This type of filter has a filter layer made of a dielectric multilayer film, and transmits and blocks a selected wavelength by utilizing reflection and interference of light in the multilayer film.

  One problem of using such a multilayer interference filter is the incident angle characteristic of light. Multi-layer interference filters use light interference in the multi-layer film, so that desired transmission and blocking characteristics can be obtained for vertically incident light, but transmission and blocking characteristics for obliquely incident light are reduced. To do. Therefore, there is no problem when it is used under the condition where only vertical light is incident, but there is also light incident obliquely, and the ozonization wavelength is not sufficiently blocked for such light. Unless a light source with high linearity such as a laser is used, in most cases there is light incident obliquely, and the ozone generation wavelength is not sufficiently cut off.

  As another problem, in the case of a multilayer interference filter, it tends to have a characteristic that the transmittance for each wavelength changes periodically so as to wave. This is peculiar because it uses the interference of light. Spattering of spectral transmission characteristics is eliminated when the number of layers of the multilayer film is increased. However, in order to sufficiently eliminate the undulation, there is a problem that the number of layers must be increased and the manufacturing cost is increased. .

  As a configuration not using the multilayer interference filter, it is conceivable to manufacture a plate-like optical member using the same material as the envelope glass used in the ozone-less lamp and use it as a filter. However, this type of glass product is manufactured by melting a glass material in a furnace, introducing impurities therein, mixing, cooling, and solidifying. Therefore, it is practically impossible to manufacture a filter product having slightly different characteristics on the premise of mass production. In the field of light processing, in order to investigate the effective wavelength, processing is carried out little by little, and since the effective wavelength differs for each product type, processing is often performed with light of a different wavelength depending on the lot. In this case, filters having different ozone generation wavelength blocking characteristics are required depending on various applications and purposes. However, the diversion of the envelope glass for the ozone-less lamp is not realistic considering the field of light processing. .

  The invention of the present application was made to solve such problems of the prior art, and sufficiently blocks light having a wavelength close to the ozone generation wavelength range while effectively blocking light having the ozone generation wavelength. Providing highly practical light control technology for ozone countermeasures that prevents the transmission and blocking characteristics from being impaired even in the case of oblique incidence, and that can be finely adjusted according to the application and purpose. The purpose is to do.

In order to solve the above problems, the invention according to claim 1 of the present application is an ultraviolet filter layer in which zirconium oxide is dispersed in an ultraviolet transmitting material,
The layer thickness is 100 μm or less,
When the volume mixing ratio of zirconium oxide to the entire layer is x and the thickness of the layer is y,
24.319x ^-1.996 ≤ y ≤ 3040.1x ^-1.953
It has the structure of becoming the relationship of.
In order to solve the above problem, the invention according to claim 2 is an ultraviolet filter layer in which tantalum oxide is dispersed in an ultraviolet transmitting material,
The layer thickness is 100 μm or less,
When the volume mixing ratio of tantalum oxide to the entire layer is x and the thickness of the layer is y,
6.2213x- ^1.926 ≤ y ≤ 24.187x ^-2.068
It has the structure of becoming the relationship of.
In order to solve the above-mentioned problem, the invention according to claim 3 has a structure in which the ultraviolet ray transmitting material is silicon oxide or alumina in the structure of claim 1 or 2.
In order to solve the above problem, the invention according to claim 4 has a structure in which the volume mixing ratio is 0.9 or less in the structure according to any one of claims 1 to 3.
Moreover, in order to solve the said subject, invention of Claim 5 is a formation method of the filter layer for ultraviolet rays of the said Claim 1, Comprising:
A thin film is formed by multi-source sputtering using a first cathode having a target formed of the ultraviolet transmissive material and a second cathode having a target formed of the zirconium oxide. A filter layer.
Moreover, in order to solve the said subject, invention of Claim 6 is a formation method of the filter layer for ultraviolet rays of the said Claim 2, Comprising:
A thin film is formed by multi-source sputtering using a first cathode provided with a target formed of the ultraviolet transmissive material and a second cathode provided with the target formed of the tantalum oxide, and the formed thin film is converted into an ultraviolet ray. A filter layer.
In order to solve the above-mentioned problem, an invention according to claim 7 is an ultraviolet ray comprising a transparent substrate transparent to ultraviolet rays and the filter layer according to any one of claims 1 to 4 formed on the transparent substrate. It is a filter for use.
In order to solve the above problem, the invention according to claim 8 is the structure according to claim 7, wherein the volume mixing ratio is gradually or stepwise increased as the distance from the transparent substrate is increased. Have.
In order to solve the above problems, the invention according to claim 9 is a transparent substrate transparent to ultraviolet rays, a striped grid formed on the transparent substrate, and a light incident side with respect to the grid. It has the structure of the grid polarizing element which consists of a filter layer in any one of Claims 1 thru | or 4 formed in the position.
In order to solve the above problem, the invention according to claim 10 is the configuration according to claim 9, wherein the filter layer is arranged on the incident side of the grid with a layer transparent to ultraviolet rays interposed. Has been
The volume mixing ratio is configured to increase gradually or stepwise as the distance from the transparent layer increases.
In order to solve the above-mentioned problem, the invention according to claim 11 is arranged between the ultraviolet light source and the irradiation position where the object irradiated with the polarized light which is ultraviolet is located and the ultraviolet light source. Or it has the structure that it is a polarized light irradiation apparatus provided with the grid polarizing element of 10.

As described below, according to the invention described in claim 1 or 2 of the present application, it is possible to block light of 200 nm ozone generation wavelength by 50% or more while setting the transmittance of ultraviolet light of 250 nm or more to 50% or more. Further, since the thickness of the layer is 100 μm or less, productivity is not a problem. Furthermore, there is no dependence on the incident angle because interference in the multilayer film is not used. For this reason, it can be suitably used in applications where obliquely incident light exists.
According to the invention of claim 4, in addition to the above effect, since the volume mixing ratio is 0.9 or less, the thermal stability is poor, or the influence of internal interference appears in the transmission / cutoff characteristics. Problems do not occur.
Further, according to the invention of claim 5 or 6, in addition to the above effect, the ultraviolet filter layer is formed by multi-source sputtering, so that there is an effect that the blocking / transmission characteristics can be finely adjusted according to the use and purpose. can get.
Further, according to the seventh aspect of the invention, in addition to the above effect, the ozone generation wavelength can be blocked by being arranged at an arbitrary position in the light irradiation path from the light source to the object. For this reason, it can be used while being appropriately cooled, and it is easy to prevent characteristic changes due to temperature rise.
According to the eighth aspect of the invention, in addition to the above effect, the volume mixing ratio increases as the distance from the transparent substrate increases, so that the effect of being thermally stable or suppressing interference inside becomes higher. .
According to the ninth aspect of the invention, the object can be irradiated with polarized light while obtaining the above effect. In addition, it is possible to easily prevent the characteristic change of the filter layer by cooling the grid polarizing element.
According to the invention of claim 10, in addition to the above effect, the volume mixing ratio increases as the distance from the transparent layer increases, so the effect of being thermally stable or suppressing interference inside is higher. Become.
According to the eleventh aspect of the present invention, the object can be irradiated with polarized light while obtaining the above effect.

It is the cross-sectional schematic which showed each embodiment of the filter layer for ultraviolet rays of this invention, and the filter for ultraviolet rays of this invention. It is the schematic which showed the spectral transmittance of the filter layer of embodiment. It is the schematic which showed the spectral transmittance of the filter layer of embodiment. It is the schematic which showed the spectral transmittance of the filter layer of embodiment. It is the schematic which showed the spectral transmittance of the filter layer of embodiment. It is the graph which showed the relationship between the layer thickness and volume mixing ratio when the transmittance | permeability will be 50% about each of a zirconium oxide and a tantalum oxide. It is the figure shown about the more preferable range of the combination of the thickness and volume mixing ratio in the filter layer of embodiment, and shows the case of zirconium oxide. It is the figure shown about the more preferable range of the combination of the thickness and volume mixing ratio in the filter layer of embodiment, and shows the case of a tantalum oxide. It is the schematic of the filter layer of 2nd embodiment. It is the figure which showed an example of the manufacturing method of the filter layer of embodiment, and is the schematic shown about formation of the filter layer by multi-source sputtering method. It is a perspective schematic diagram of a grid polarization element of an embodiment. It is the cross-sectional schematic of the polarized light irradiation apparatus carrying a grid polarizing element. It is the figure which showed the light absorption spectrum of the oxygen molecule. It is the figure which showed the cutoff characteristic of the ozone generation wavelength by the envelope (ozone-less envelope) of an ozone-less lamp, and is the figure which compared and showed the spectral transmission characteristics of an ozone-less envelope and a normal envelope.

Next, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described.
FIG. 1 is a schematic cross-sectional view showing each embodiment of the ultraviolet filter layer of the present invention and the ultraviolet filter of the present invention.
The ultraviolet filter according to the embodiment includes a transparent substrate 1 that transmits ultraviolet rays and an ultraviolet filter layer 2 according to the embodiment provided on the transparent substrate 1. The ultraviolet filter layer (hereinafter simply referred to as the filter layer) 2 is a layer in which zirconium oxide or tantalum oxide as the absorbing material 21 is dispersed in the ultraviolet transmitting material 21.

The transparent substrate 1 is made of quartz glass in this embodiment. The thickness of the transparent substrate 1 is sufficient as long as the filter layer 2 can be stably held, and may be, for example, about 0.1 to 10 mm.
The ultraviolet transmissive material 21 is silicon oxide in this embodiment. Zirconium oxide or tantalum oxide as the absorbent material 21 is uniformly dispersed in the silicon oxide. Although silicon oxide and zirconium oxide are both in an amorphous state, they may be partially bonded to form a network or a microcrystal may be formed.

In the filter layer 2, zirconium oxide or tantalum oxide has a role of absorbing light having an ozone generation wavelength. The volume mixing ratio of zirconium oxide or tantalum oxide is set to 0.9 or less in volume ratio, assuming that the entire layer is 1. The thickness of the filter layer 2 is 100 μm or less.
When the thickness of the layer is y and the volume mixing ratio is x, in the case of zirconium oxide, 24.319x- ^1.996 ≦ y ≦ 3040.1x- ^1.953 . In the case of tantalum oxide, it is set to 6.2213x- ^1.926 ≦ y ≦ 24.187x− ^2.068 .

The blocking of light having an ozone generation wavelength by such a filter layer is based on the results of research by the inventors of the present application. Hereinafter, this point will be described.
The inventor intended to develop an optical means other than the multilayer interference filter having a problem such as having an angular characteristic in order to solve the problem of ozone generation when an ultraviolet light source is used. At this time, it was assumed that light having a wavelength longer than 250 nm is sufficiently transmitted so that light having a wavelength of 254 nm, which is the emission line spectrum of mercury, can be used effectively.

As a filter other than the multilayer interference filter, a filter in which an absorbing material is dispersed in a transmission layer is well known. This type of filter is for visible light and is known as a colored glass filter. In addition, an absorption type filter without wavelength selectivity is known as an ND filter.
The absorption type filter in which these absorbing materials are dispersed is for visible light or has no wavelength selectivity (all wavelength absorption), and is not known for ultraviolet rays. The inventor of the present application diligently studied whether it is possible to obtain a filter layer that is an absorption-type ultraviolet filter layer and is effective for preventing ozone.

In order to block light of 250 nm or less by absorption and sufficiently transmit light having a wavelength longer than 250 nm, a material that starts absorption from around 250 nm, that is, light having a wavelength longer than 250 nm is not absorbed. A material that absorbs shorter wavelengths is an effective material. The inventor diligently studied and evaluated various materials from this viewpoint, and it has been found that two materials, zirconium oxide and tantalum oxide, are effective materials.
However, according to the inventor's research, a structure in which a 100% zirconium oxide layer or a 100% tantalum oxide layer is provided on a certain transparent substrate does not work. This is because zirconium oxide and tantalum oxide have some absorption for light having a wavelength of 250 nm or slightly longer (including 254 nm), and the transmittance of these wavelengths is low in a layer of 100%. Because it will end up. Accordingly, it is necessary to have a structure in which zirconium oxide or tantalum oxide is dispersed in a material transparent to these wavelengths to reduce the concentration.

  In this case, the thickness of the layer in which zirconium oxide or tantalum oxide is dispersed becomes a problem. This is because light is absorbed and absorbed by the absorbing material (zirconium oxide or tantalum oxide) when propagating in the layer, so that the total amount of absorption (blocking amount) depends on the length in the propagation direction, that is, the layer thickness. It is because it is decided. Even if the concentration is reduced, if the layer is thickened, the total amount of absorption increases, and even if the concentration is increased, the total amount of absorption decreases if the layer is thin.

From such a point of view, the inventor is effective in the amount of mixing (volume mixing ratio) for measures against ozone in a layer in which zirconium oxide or tantalum oxide is dispersed in a material transparent to ultraviolet rays. We have intensively studied how to determine the thickness of the layer at that time.
The inventor examined in this research using the effective medium approximation method (EMA). EMA is an approximate theory for analyzing a composite material as if it were a homogeneous medium with an effective dielectric constant. In the study, the Maxwell-Garnet approximation was used and the optimal volume mixing ratio and layer thickness were determined by optical fitting. Optical fitting is a method for obtaining the composition (volume mixing ratio) of a material from the refractive index measured for the composite material, but the inventor conversely refracts from the relative dielectric constant obtained at various volume mixing ratios. A technique was adopted in which the refractive index (complex refractive index) was obtained and the necessary layer thickness was determined based on the imaginary part (extinction coefficient). This will be specifically described below.

In the filter layer of the embodiment shown in FIG. 1, the relative permittivity ε _t of the ultraviolet light transmitting material is set to be the relative permittivity ε _a of zirconium oxide or tantalum oxide as the absorbing material. Then, _let ε _eff be the relative dielectric constant of the entire layer by the effective medium approximation method. In this case, according to the Maxwell-Garnet approximate expression, ε _eff is obtained by the following expression 1.

次に、消衰係数ｋに基づき、以下の式３により吸収係数αが求められる。式３において、λは波長である。

図２〜図５は、このようにして計算により求められた実施形態のフィルタ層の分光透過率を示した概略図である。図２及び図３が酸化ジルコニウムの場合、図４及び図５が酸化タンタルの場合を示す。尚、計算において、酸化ジルコニウムの比誘電率は５．２９（波長２５４ｎｍ）、酸化タンタルの比誘電率は８．９６（波長２５４ｎｍ）とした。 Next, from the obtained ε _eff , the extinction coefficient k of this layer is obtained by the following equation 2. In Equation 2, ε ₁ is the real part of ε _eff , and ε ₂ is the imaginary part of ε _eff . Since light is handled, the relative permeability is set to 1.

Next, based on the extinction coefficient k, the absorption coefficient α is obtained by the following expression 3. In Equation 3, λ is a wavelength.

2-5 is the schematic which showed the spectral transmittance of the filter layer of embodiment calculated | required by calculation in this way. 2 and 3 show the case of zirconium oxide, and FIGS. 4 and 5 show the case of tantalum oxide. In the calculation, the relative dielectric constant of zirconium oxide was 5.29 (wavelength 254 nm), and the relative dielectric constant of tantalum oxide was 8.96 (wavelength 254 nm).

  As described above, even if the absorption coefficient is the same, if the thickness of the layer is different, the absorption rate of the entire layer is different. It is the figure which showed the spectral transmittance. 2 (1) shows a case where the thickness of the filter layer containing zirconium oxide is 100 nm, (2) shows a case of 1 μm, FIG. 3 (2) shows a case where the thickness of the layer is 3 μm, and (4) becomes 10 μm. Each case is shown. In each figure, fa is the volume mixing ratio of zirconium oxide to the whole. 4 (1) shows the case where the thickness of the filter layer containing tantalum oxide is 1 nm, (2) shows the case of 1 μm, and FIG. 5 (2) shows the case where the thickness of the layer is 3 μm (4 ) Is 10 μm. Similarly, fa is the volume mixing ratio of tantalum oxide.

As shown in FIGS. 2 and 3, in the case of a filter layer containing zirconium oxide, when the wavelength of light is shortened, the spectral characteristics drop from the wavelength around 250 to 260 nm. As a matter of course, the transmittance decreases as the thickness of the layer increases.
In the case of tantalum oxide, although the wavelength at which absorption starts is slightly longer at 280 to 300 nm, a similar tendency is shown.

The inventor set the condition of 50% transmission (50% cutoff) in order to determine the necessary cutoff / transmission characteristics as the filter layer, and reorganized these calculation results. This result is shown in FIG. FIG. 6 is a graph showing the relationship between the layer thickness and the volume mixing ratio when the transmittance is 50% for each of zirconium oxide and tantalum oxide. FIG. 6 (1) is a case of zirconium oxide, and (2) is a case of tantalum oxide.
In each graph of FIG. 6, the horizontal axis represents the volume mixing ratio with respect to the whole of zirconium oxide or tantalum oxide. The vertical axis indicates the thickness (nm) of the layer when the transmittance is 50% on a logarithmic scale. Since the thickness of the layer at which the transmittance is 50% varies depending on the wavelength, (1) and (2) in FIG. 6 show 50% transmission for 200 nm, 210 nm, 220 nm, 230 nm, 235 nm, 240 nm, 245 nm, 250 nm, and 254 nm. The relationship of thickness to volume mixing ratio is shown.

As shown in FIGS. 6A and 6B, as the volume mixing ratio is increased, the 50% transmission thickness decreases exponentially. For each value obtained by calculation, formulas of curves obtained by the least square method (power approximation) are shown in FIGS. 6 (1) and 6 (2).
Referring to zirconium oxide in more detail, in the case of zirconium oxide, as shown in FIG. 6 (1), when the thickness of a layer that provides 50% transmittance at 250 nm is y and the volume mixing ratio is x, y = 3040.1x- ^1.953 . In the region above this graph, y> 3040.1x- ^1.953 , the transmittance at 250 nm is less than 50%. In other words, any combination of layer thickness and volume mixing ratio in this region is inappropriate because the transmittance at 250 nm is less than 50%. For example, even when the volume mixing ratio is as low as 0.3 (thin zirconium oxide concentration), if the layer is as thick as about 100 μm, a transmittance of 50% at 250 nm cannot be achieved. Further, when the volume mixing ratio is 0.8, for example, a transmittance of 50% cannot be achieved unless the volume mixing ratio is reduced to about 5 μm. Therefore, first, in order to ensure a minimum 50% transmission at 250 nm to use 254 nm light, in the case of zirconium oxide, the layer thickness y is y with respect to the volume mixing ratio x. It is necessary to have a relationship of ≦ 3040.1x ^−1.953 .

Next, conditions necessary for blocking light having an ozone generation wavelength will be described.
As shown in FIG. 13, although the absorption of oxygen molecules starts around 240 nm, the absorption coefficient increases rapidly around 200 nm. Therefore, as one idea, it is possible to determine the characteristics of the filter layer so as to block at least 50% of light of 200 nm or less. When this is applied to the result of FIG. ^6A , the 50% transmission thickness y at a wavelength of 200 nm has a relationship of y = 24.319x- ^1.996 with respect to the volume mixing ratio x. Therefore, in the region above this graph (a combination of layer thickness and volume mixing ratio), the transmittance at a wavelength of 200 nm is less than 50, which satisfies the condition. That is, if the layer thickness y has a relationship of y ≧ 24.319x− ^1.996 with respect to the volume mixing ratio x, light of 50% or more can be blocked at 200 nm.
To summarize these results, in the case of a filter layer in which zirconium oxide is dispersed in silicon oxide, the relationship of the layer thickness y to the volume mixing ratio x of zirconium oxide is 24.319x- ^1.996 ≦ y ≦ 3040. If it is set to .1x- ^1.953 , a filter layer that blocks 50% or more of light at 200 nm while securing a transmittance of 50% or more at 250 nm can be obtained.

In the above, necessary conditions were examined on the assumption that 200 nm or less was cut off. However, in order to obtain a cutoff of 50% or more (transmittance of less than 50%) in a wavelength range of 220 nm or less, 240 nm or less, which is closer to 250 nm. You can also For example, in order to block light of 50% or more at a wavelength of 220 nm or less while ensuring a transmittance of 50% or more at a wavelength of 250 nm, as shown in FIG. 6, 97.494x- ^1.971 ≦ y ≦ 3040. ^What is ^necessary is ^just 1x- ^1.953 . For example, in order to block light of 50% or more at a wavelength of 240 nm or less while securing a transmittance of 50% or more at a wavelength of 250 nm, 586.28x- ^1.958 ≦ y ≦ 3040.1x- ^1.953 What should I do? The same applies to other wavelengths.

In the case of tantalum oxide shown in FIG. 6B, the thickness of the layer that transmits 50% at 250 nm is expressed by y = 24.187x− ^2.068 . The thickness of the layer that is 50% blocked at 200 nm is represented by y = 6.2213x- ^1.926 . Therefore, using tantalum oxide, to obtain a transmittance of 50% or more at 250 nm or more while blocking 50% or more of light at 200 nm or less, the layer thickness y is 6.2213x with respect to the volume mixing ratio x. ^{It is sufficient to set −1.926} ≦ y ≦ 24.187x− ^2.068 .
For example, in order to transmit 50% or more at 250 nm or more while blocking 50% or more at 240 nm or less, 15.671x− ^2.069 ≦ y ≦ 24.187x− ^2.068 may be set.

  The above has considered only the necessary transmittance and blocking rate, but considering the practicality of the filter layer, conditions from other viewpoints are also necessary. One is the upper limit of the layer thickness. Regardless of whether it is zirconium oxide or tantalum oxide, if the concentration is low (volume mixing ratio is small), it is only necessary to make the layer thicker, but there is actually an upper limit in the manufacturing process. Can do. As will be described later, the filter layer of the embodiment is formed by a film forming method such as sputtering or a baking method. In any of the manufacturing methods, there is a problem that it takes a very long time to form a thick layer, and it is difficult to form a uniform layer in terms of thickness and quality. Considering manufacturing problems, the layer thickness should be up to about 100 μm.

For example, when zirconium oxide is used as the absorbing material, as shown in FIG. 6A, the 50% thickness at 240 nm when the volume mixing ratio is 0.1 is about 100 μm. Therefore, when zirconium oxide is used, the volume mixing ratio is preferably 0.1 or more. However, when the cutoff wavelength is a lower wavelength such as 220 nm or 200 nm, even if the layer is formed with a thickness of less than 100 μm at a volume mixing ratio of less than 0.1, a cutoff rate of 50% or more may be obtained. .
In the case of tantalum oxide, the 50% transmission thickness when the volume mixing ratio is 0.1 is 100 μm or less and the volume mixing ratio is 0.1 or more, regardless of which is the cutoff wavelength in the range of 200 to 250 nm. There is no problem.

  Further, when the volume mixing ratio increases, the layer approaches 100% zirconium oxide and 100% tantalum oxide. In this case, several other problems may occur. That is, since the filter layer is a transmission type layer, the filter layer is provided for a member transparent to ultraviolet rays, such as the transparent substrate in the embodiment, and is held by the member. In this case, when the volume mixing ratio of the absorbent material in the filter layer is close to 100%, a large difference in coefficient of thermal expansion between the holding member and the holding member occurs. In this case, deformation such as peeling or cracking of the layer is likely to occur due to the difference in thermal expansion coefficient.

As another problem, when the volume mixing ratio of the absorbent material is close to 100%, the difference in refractive index with respect to the member to be held becomes large. As a result, light is likely to interfere in the filter layer due to reflection at the interface, and the influence of interference is likely to occur. The influence of interference appears as a wave of spectral transmittance, which causes a problem that it becomes difficult to evaluate and predict performance.
Therefore, the volume mixing ratio of zirconium oxide or tantalum oxide is preferably not so high and should be up to about 0.9.

When the relationship between the layer thickness and the volume mixing ratio as described above is shown more easily, the relationship is as shown in FIGS. 7 and 8 are diagrams showing a more preferable range of combinations of thickness and volume mixing ratio in the filter layer of the embodiment. FIG. 7 shows the case of zirconium oxide, and FIG. 8 shows the case of tantalum oxide.
In the case of zirconium oxide, when 50% or more of 200 nm or less is cut off, the range is indicated by a thick line in FIG. In addition, when 50% or more of 240 nm or less is cut off, the range is indicated by a thick line in 7 (2). Although the lower limit range of the volume mixing ratio is not shown in FIG. 7 (1), the volume mixing ratio when the thickness of the layer for blocking 50% or more of 200 nm exceeds 100 μm is the lower limit. . Although illustration is omitted, the same applies to the case of 220 nm, 230 nm, and 235 nm, and the lower limit is the volume mixing ratio when the thickness of the layer for blocking 50% or more exceeds 100 μm.

The same applies to tantalum oxide, and the range indicated by the thick line in FIG. 8A is a combination range in which 50% or more of 200 nm or less is blocked while achieving a transmittance of 50% or more at 250 nm or more, FIG. The range indicated by the thick line in 2) is a combination range in the case where 50% or more is blocked at 240 nm or less while achieving a transmittance of 50% or more at 250 nm or more.
Since the ultraviolet filter of the above-described embodiment is not a specific part of the light source, it can be arranged at an arbitrary position between the light source and the object. For this reason, it can be used while cooling as will be described later, and it is easy to prevent characteristic changes due to temperature rise.

Next, the filter layer of the second embodiment will be described.
FIG. 9 is a schematic view of the filter layer of the second embodiment. The filter layer 2 of this embodiment is also a layer formed on the transparent substrate 1 and is a layer in which zirconium oxide or tantalum oxide as the absorbing material 22 is mixed and dispersed in the ultraviolet transmitting material 21.
In this embodiment, the volume mixing ratio of zirconium oxide or tantalum oxide is not uniform in the thickness direction of the layer but has a gradient. This is a feature point. More specifically, as schematically illustrated in FIG. 9, the concentration (volume mixing ratio) of zirconium oxide or tantalum oxide is low on the transparent substrate 1 side, and gradually or stepwise as the distance from the transparent substrate 1 increases. It is getting higher.

  The filter layer of the second embodiment having such a structure is superior in thermal stability and has an advantage that internal interference of light is suppressed. As described above, in the structure in which the filter layer 2, which is a different material, is formed on the transparent substrate 1, if the difference in thermal expansion coefficient at the interface is large, problems such as peeling or cracking of the layer are likely to occur during heating. Also, if the refractive index is greatly different on both sides of the interface, light interference is likely to occur inside due to reflection at the interface.

As in the second embodiment, the volume mixing ratio of zirconium oxide or tantalum oxide in the filter layer has a gradient, and the volume mixing ratio increases gradually or stepwise in the direction away from the transparent substrate 1. Changes in the coefficient of thermal expansion in the thickness direction are also slow, and changes in the refractive index are also slow. For this reason, deformation at the time of heating hardly occurs and internal reflection is also suppressed. For this reason, it is possible to obtain an excellent filter layer 2 having excellent thermal stability and less undulation of transmission characteristics.
In the case of the second embodiment, the selection of the combination of the layer thickness and the volume mixing ratio is performed so as to satisfy the above condition in the volume mixing ratio averaged in the layer thickness direction.

Next, a method for manufacturing a filter layer according to an embodiment in which the layer thickness and the volume mixing ratio are selected in this manner will be described.
The filter layer of the embodiment can be formed by a film forming method or a firing method.
First, the film forming method will be described. The filter layer of the embodiment can be suitably formed by a multi-source sputtering method. FIG. 10 is a diagram illustrating an example of the filter layer manufacturing method according to the embodiment, and is a schematic diagram illustrating the formation of the filter layer by multi-source sputtering.

When forming the filter layer of the embodiment, the transparent substrate 1 is put into a multi-source sputtering apparatus. The multi-source sputtering apparatus includes two cathodes 72 and 73 in a film forming chamber 71, and the target materials of the two cathodes 72 and 73 are different.
When forming the filter layer 2 of the embodiment in which the absorbing material is, for example, zirconium oxide, the target material in the first cathode 72 is silicon oxide, and the target material is zirconium oxide in the second cathode 73. High frequency power is applied to each of the cathodes 72 and 73, and inductively coupled or capacitively coupled plasma is formed by sputtering discharge to sputter each target. As a result, a film in which silicon oxide and zirconium oxide are mixed is formed on the transparent substrate 1, and this film becomes the filter layer 2. The transparent substrate 1 is placed on the rotation stage 74, and the rotation stage 74 rotates during film formation, so that silicon oxide and zirconium oxide are uniformly mixed, and the filter layer 2 is formed. In some cases, the transparent substrate 1 is stationary and the cathodes 72 and 73 rotate. Further, there may be a case where the mixing is performed uniformly by, for example, linear movement other than rotation.

In the multi-source sputtering, the ratio of input power to the cathodes 72 and 73 is determined according to the volume mixing ratio described above. At this time, since the sputtering yield varies depending on the material, the charging ratio to each of the cathodes 72 and 73 is determined in consideration thereof.
When the filter layer 2 of the second embodiment is formed, the input power to the second cathode (zirconium oxide target) 73 with respect to the first cathode (silicon oxide target) 72 is initially reduced, and thereafter The input power ratio to the second cathode 73 is increased gradually or stepwise. Thereby, the volume mixing ratio of zirconium oxide increases as the deposited film moves away from the transparent substrate 1, and the filter layer 2 of the second embodiment is obtained.

In the case where the absorbing material 22 is tantalum oxide, the target material of the second cathode 73 is merely changed to tantalum oxide, and the rest is the same as above.
In addition, although argon is usually used as a gas for sputtering discharge, reactive sputtering may be performed using a gas to which oxygen gas is added. In this case, it is possible to form a film while oxidizing silicon using a silicon target and to oxidize zirconium or tantalum using a zirconium or tantalum target.

According to the above-described method for forming the filter layer 2 by multi-source sputtering, the volume ratio of the layers can be adjusted by adjusting the deposition time by adjusting the ratio of the input power to each cathode. You can also adjust. For this reason, it is possible to easily obtain the filter layer 2 having different blocking / transmitting characteristics depending on the application and purpose, and the practicality is high.
As the sputtering method, another method such as ion beam sputtering may be employed.

Next, the sol-gel method will be described as an example of the firing method.
Metalloxane-based inorganic polymer materials are known as sol-gel materials for synthesizing metal oxides. This includes synthesis of silicon oxide by sol-gel using polysiloxane, synthesis of zirconium oxide by sol-gel using polyzirconoxane, and synthesis of tantalum oxide by sol-gel using polytantaloxane (for example, , Www.artkagaku.co.jp/pdf/ART-2.pdf). Therefore, for example, when zirconium oxide is used as an absorbent material, a polysiloxane such as TEOS and polyzirconia are mixed to form a gel solution, which is hydrolyzed and condensed while appropriately using a catalyst and adjusting ph. Make it. In this case, the volume mixing ratio of polysiloxane and polyzircoxane is determined according to the volume mixing ratio in the filter layer described above. And a transparent substrate is immersed in this gel, and a gel film is made to adhere by dip coating. Then, the filter layer of the embodiment is formed by exposing to a high temperature for a predetermined time in an air or oxygen atmosphere and baking. Firing is performed, for example, by heating at 600 ° C. for 10 minutes. Depending on the required filter layer thickness, dip coating and firing may be repeated multiple times. When tantalum oxide is used as the absorbing material, polytantaloxane is used instead of polyzirconium, but the filter layer can be formed basically in the same manner.

  When the filter layer of the second embodiment is formed by the sol-gel method, the dip coating and baking of the gel material are repeated a plurality of times, and the sol having a small ratio of polyzirconia (or polytantaloxane) is initially used. A gelled solution is used. Then, each time the repetition is performed, the ratio is increased little by little to perform dip coating and firing.

Next, a grid polarizing element will be described as one application of the filter layer of the embodiment. The following description is also a description of an embodiment of the grid polarizing element invention. FIG. 11 is a schematic perspective view of the grid polarizing element of the embodiment.
The grid polarizing element 3 shown in FIG. 11 is structurally the same as the wire grid polarizing element, and has a structure in which a striped (line and space) grid 30 is provided on a transparent substrate 31. In the wire grid polarization element, each linear part of the grid is made of metal. However, since the grid polarization element 3 of the embodiment polarizes ultraviolet rays, each linear part 32 of the grid 30 is made of dielectric or semiconductor. It has become. Specifically, each linear portion 32 is made of titanium oxide or silicon.

  The wire grid polarization element selectively reflects linearly polarized light (s-polarized light) whose electric field is directed in the longitudinal direction of each linear part of the grid, and the electric field is directed in a direction perpendicular to the longitudinal direction of each linear part. Polarized light is obtained by selectively transmitting the linearly polarized light (p-polarized light). The grid polarization element 3 is an absorption-type grid polarization that obtains polarized light by selectively absorbing s-polarized light. It is an element. The width of the space (gap) between the linear portions 32 of the grid 30 is about the wavelength of light to be polarized or less. The operation principle of the absorption grid polarizing element is disclosed in Japanese Patent Application Laid-Open No. 2014-199362 and Japanese Patent Application Laid-Open No. 2015-18016, and detailed description thereof is omitted.

In FIG. 11, light (ultraviolet rays) enters the grid 30 from the side opposite to the transparent substrate 31. Most of the light that has passed through the grid 30 and transmitted through the transparent substrate 31 becomes p-polarized light whose electric field is oriented in a direction perpendicular to the longitudinal direction of each linear portion 32 of the grid 30.
As shown in FIG. 11, the grid polarizing element of the embodiment has a structure in which a protective film 33 is provided on the opposite side of the grid 30 from the transparent substrate 31, and the filter layer 2 of the embodiment is formed thereon. It has become. The protective film 33 is a structure that protects each linear portion 32 of the grid 30 from collapse or the like, and is formed of a material that transmits ultraviolet rays, for example, silicon oxide.

  As described above, the filter layer 2 is provided for the purpose of blocking light having an ozone generation wavelength. In particular, the grid polarizing element has a problem that each linear portion 32 of the grid 30 is oxidized by the oxidizing action of ozone or atomic oxygen. This point is remarkable when silicon is used as the grid material, and there is a problem that silicon becomes silicon oxide by oxidation and does not function as the grid material. The grid polarizing element is used with an ultraviolet light source such as a mercury lamp or an ultraviolet LED. Oxidation of the grid 30 due to ozone is easily promoted by heating with light from a light source.

On the other hand, as shown in FIG. 11, in the grid polarizing element of the embodiment, the filter layer 2 is provided so as to cover the grid 30, and the filter layer 2 effectively emits light having an ozone generation wavelength as described above. Shut off. For this reason, the oxidation of each linear part 32 of the grid 30 is suppressed, and a grid polarizing element having a stable performance over a long period of time is provided.
The filter layer 2 is disposed on the light incident side with respect to the grid 30. Therefore, in the structure in which the filter layer 2 is provided on the side opposite to the transparent substrate 31 with the grid 30 interposed therebetween, the grid polarizing element is disposed in a posture with the filter layer 2 side facing the light source. In some cases, the grid polarizing element may be arranged with the transparent substrate 31 side as the light source side. In this case, the filter layer 2 is provided on the back surface of the transparent substrate 31 (the side on which the grid 30 is formed). The surface on the opposite side of the surface).

The method for forming the filter layer 2 will be described supplementarily. In the case of the multi-source sputtering method described above, the grid 30 formed on the transparent substrate 31 and the protective film 33 formed thereon are put into a film forming chamber. As described above, the filter layer 2 is formed by multi-source sputtering.
In the case of the sol-gel method, a polysiloxane-polyzircoxane mixed sol liquid (or polysiloxane-polytantaloxane mixed sol) is obtained by forming the grid 30 on the transparent substrate 31 and forming the protective film 33 thereon. The filter layer 2 is formed by immersing it in a gelled liquid and baking it. At this time, masking may be performed so that the solution does not enter between the linear portions 32 of the grid 30.

  Next, as a usage example of an optical component including a filter layer, a polarized light irradiation apparatus equipped with the grid polarizing element will be described. The following description is also an explanation of the embodiment of the invention of the ultraviolet irradiation device. FIG. 12 is a schematic cross-sectional view of a polarized light irradiation apparatus equipped with a grid polarizing element. In this example, the polarized light irradiation device is a device that irradiates polarized light for photo-alignment (photo-alignment device).

The polarized light irradiation device shown in FIG. 12 includes a light source 41, a mirror 42 that covers the back of the light source 41, a grid polarizing element 3 disposed between the light source 41 and the irradiation position R, a light source 41, a mirror 42, A lamp house 43 or the like that houses the grid polarizing element 3 or the like is provided. The grid polarizing element 3 is that of the above embodiment.
As the light source 41, an ultraviolet lamp such as a high-pressure mercury lamp is used. The light source 41 has a rod shape, and the mirror 42 has a bowl shape that is long in the length direction of the light source 41. The cross-sectional shape perpendicular to the length direction of the mirror 42 is a parabola or an elliptical arc.

Light from the light source 41 and the mirror 42 passes through the grid polarization element 3 to become polarized light, and is irradiated to the set irradiation position R. And the conveyance mechanism 50 which conveys the workpiece | work 5 so that it may pass through the irradiation position R is provided, and polarized light is irradiated to the workpiece | work 5 by passing through the irradiation position R. FIG.
The workpiece 5 has a rectangular plate shape, and the transport mechanism 50 is a mechanism that transports the workpiece 5 by moving a stage 51 on which the workpiece 5 is placed. The irradiation position R is long (for example, rectangular) in a certain direction, and the transport mechanism 50 is a mechanism for transporting the workpiece 5 in a direction orthogonal to or intersecting with this direction.

  As described above, the grid polarizing element 3 selectively transmits p-polarized light with reference to the length direction of each linear portion 21. Therefore, the grid polarization element 3 is arranged with high posture accuracy with respect to the posture of the work 5 when passing through the irradiation position R 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 3, when a large area needs to be irradiated with polarized light, a configuration in which a plurality of grid polarizing elements 3 are arranged on the same plane is adopted. . As the light source, a configuration in which a plurality of light sources are arranged in a row to be equivalent to a long light source, or a plurality of light sources are arranged in parallel to cover a wide area may be employed.

  A cooling mechanism is provided to cool the inside of the lamp house 43. In this example, the cooling mechanism performs air cooling, and is provided in the exhaust duct 45 connected to the upper portion of the lamp house 43, the wind tunnel plate 44 that forms an air passage for cooling air in the lamp house 43, and the exhaust duct 45. And a cooling fan (not shown). When the cooling fan operates, cooling air flows in the lamp house 43 as indicated by broken line arrows in FIG. The cooling air enters the lamp house 43 from the opening (light emission port) on the lower surface of the lamp house 43 and rises while cooling the grid polarizing element 3. The cooling air flows along the inner surface of the lamp house 43, cools the light source 41 and the mirror 42, and is discharged through the exhaust duct 45. A structure may be employed in which cooling air is circulated in the lamp house 43 and a radiator is disposed on the circulation path to cool the lamp house 43.

In the apparatus shown in FIG. 11, the light from the light source 41 is polarized by the grid polarization element 3, and the polarized light is applied to the workpiece 5. Since the grid polarization element 3 includes the filter layer 2 and exhibits stable polarization performance over a long period of time, the work 5 is always irradiated with high-quality polarized light stably and photo-alignment is performed.
Further, the grid 3 is cooled by the cooling mechanism. This means that the filter layer 2 included in the grid 3 is also cooled. Therefore, even when the filter layer 2 has temperature characteristics and the characteristics change due to the temperature rise, in this embodiment, there is no problem of a decrease in the ozone generation wavelength blocking performance due to the characteristics change. This is a major difference from ozoneless lamps.

  In the apparatus shown in FIG. 11, the filter layer is provided in another optical member arranged on the incident side of the grid polarizing element 3 in addition to the case where the filter layer is provided on the incident side of the grid polarizing element 3. Also good. Specifically, an ultraviolet filter including the transparent substrate 1 and the filter layer 2 described above may be provided between the light source 41 and the grid polarizing element 3. Even in this case, oxidation of the grid polarizing element 3 can be prevented.

  However, irregularly reflected light and stray light are present in the lamp house 43. If the filter layer is located away from the grid polarizing element 3, the diffused reflected light and stray light do not pass through the filter layer, and the grid polarizing element 3 May be incident on the That is, there may be light having an ozone generation wavelength that enters from the side of the space between the ultraviolet filter and the grid polarizing element 3 and reaches the grid polarizing element. Considering this, the configuration in which the grid polarizing element 3 includes a filter layer is preferable.

Although the polarized light irradiation device was a photo-alignment device, it may be processed by irradiating with polarized light when manufacturing a viewing angle compensation film. It can be set as the apparatus carrying the provided grid polarizing element.
In addition, in an ultraviolet irradiation device that irradiates non-polarized ultraviolet rays, the ultraviolet optical member including the filter layer according to the embodiment may be mounted. Applications such as an exposure apparatus for photolithography and an ultraviolet irradiation apparatus for curing an ultraviolet curable resin are conceivable. For example, a structure in which a filter layer is provided on the surface of an ultraviolet lens that refracts light for a certain purpose and has an ozone generation wavelength blocking effect in addition to refraction can be considered.

In each of the above embodiments, the transparent substrate 1 is quartz glass, but a sapphire substrate may be used as the transparent substrate. In this case, alumina may be employed as the ultraviolet transmitting material 21 in the filter layer 2.
In addition to the transmission type filter using the transparent substrate 1, the ultraviolet filter may include a reflection type ultraviolet filter using a substrate that reflects ultraviolet rays (for example, aluminum). In this case, the light enters the filter layer, passes through the filter layer, is reflected by the substrate, passes through the filter layer again, and is emitted. However, in the case of a reflection type filter, the refractive index and thermal expansion coefficient of the substrate and the filter layer are often greatly different, and the transmission type is more suitable for problems such as internal interference and peeling due to the difference in thermal expansion. Are better.
Note that the Maxwell-Garnet approximation is used in the EMA analysis described above, but the Bruggeman approximation and the Lorentz-Lorenz approximation are also known. The inventors have confirmed that similar analysis results can be obtained even when these approximate expressions are used.

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Filter layer 21 Ultraviolet transparent material 22 Absorbing material 3 Grid polarizing element 30 Grid 31 Transparent substrate 32 Linear part 33 Protective layer 41 Light source 42 Mirror 5 Workpiece 50 Transport mechanism 71 Film formation chamber 72 First cathode 73 Second Cathode

Claims (11)

An ultraviolet filter layer in which zirconium oxide is dispersed in an ultraviolet transmitting material,
The layer thickness is 100 μm or less,
When the volume mixing ratio of zirconium oxide to the entire layer is x and the thickness of the layer is y,
24.319x ^-1.996 ≤ y ≤ 3040.1x ^-1.953
A filter layer for ultraviolet rays characterized by the following relationship. An ultraviolet filter layer in which tantalum oxide is dispersed in an ultraviolet transmitting material,
The layer thickness is 100 μm or less,
When the volume mixing ratio of tantalum oxide to the entire layer is x and the thickness of the layer is y,
6.2213x- ^1.926 ≤ y ≤ 24.187x ^-2.068
A filter layer for ultraviolet rays characterized by the following relationship.   The ultraviolet filter layer according to claim 1, wherein the ultraviolet transmissive material is silicon oxide or alumina.   The ultraviolet filter layer according to claim 1, wherein the volume mixing ratio is 0.9 or less. A method for forming an ultraviolet filter layer according to claim 1,
A thin film is formed by multi-source sputtering using a first cathode having a target formed of the ultraviolet transmissive material and a second cathode having a target formed of the zirconium oxide. A method for forming a filter layer for ultraviolet rays, characterized by comprising a filter layer for use. It is a formation method of the filter layer for ultraviolet rays according to claim 2,
A thin film is formed by multi-source sputtering using a first cathode having a target formed of the ultraviolet transmissive material and a second cathode having a target formed of the tantalum oxide. A method for forming a filter layer for ultraviolet rays, characterized by comprising a filter layer for use.   An ultraviolet filter comprising: a transparent substrate transparent to ultraviolet rays; and the filter layer according to any one of claims 1 to 4 formed on the transparent substrate.   The ultraviolet filter according to claim 7, wherein the volume mixing ratio increases gradually or stepwise as the distance from the transparent substrate increases.   The transparent substrate transparent to ultraviolet rays, the striped grid formed on the transparent substrate, and the filter layer according to any one of claims 1 to 4, formed at a position on the light incident side with respect to the grid. A grid polarizing element comprising: The filter layer is arranged on the incident side of the grid with a layer transparent to ultraviolet rays interposed therebetween,
The grid polarization element according to claim 9, wherein the volume mixing ratio is gradually or stepwise increased as the distance from the transparent layer is increased.   An ultraviolet light source, and the grid polarizing element according to claim 9 or 10 disposed between an irradiation position where an object irradiated with polarized light that is ultraviolet light is located and the ultraviolet light source. Polarized light irradiation device.

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