Radiation-transmitting suppression film, and radiation-transmitting suppression filter and imaging device using the same

Abstract

The present invention provides a radiation-transmitting suppressing film that can protect a photographing device from radiation without adversely affecting the photographing performance of the photographing device. The radiation-transmitting suppressing film of the present invention includes a polyvinyl alcohol-based resin film containing boric acid, and the product of the boric acid content (wt%) in the polyvinyl alcohol-based resin film and the thickness (μm) of the polyvinyl alcohol-based resin film is 500 or greater.

Description

Technical Field

[0001] This invention relates to: a radiation transmission suppression film, a radiation transmission suppression filter using the radiation transmission suppression film, and an imaging device. Background Technology

[0002] With the development of imaging and remote control technologies, filming and video recording in high-radiation environments has become practical. For example, there is an increasing demand for such filming and video recording in nuclear power facilities, outer space, or medical settings. However, in such high-radiation environments, the lifespan of the imaging device is shortened due to the effects of radiation. Furthermore, since lead and other materials commonly used for radiation shielding are opaque, they are unsuitable as protective components for imaging devices.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-000006 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] The present invention was made to solve the above-mentioned problems, and its main objective is to provide a radiation transmission inhibition film that can protect the shooting device from radiation without adversely affecting the shooting performance of the shooting device.

[0008] Solution for solving the problem

[0009] According to one aspect of the present invention, a radiation transmission suppression film is provided, comprising a polyvinyl alcohol-based resin film containing boric acid, wherein the product of the boric acid content (wt%) in the polyvinyl alcohol-based resin film and the thickness (μm) of the polyvinyl alcohol-based resin film is 500 or more.

[0010] In one embodiment, the transmittance of the radiation through the suppression film is 80% or more.

[0011] In one embodiment, a protective film is further included, which is laminated on one or both sides of the polyvinyl alcohol-based resin film.

[0012] In one embodiment, the protective film comprises at least one resin selected from cellulose resins, cyclic olefin resins, and acrylic resins.

[0013] According to another aspect of the present invention, a radiation transmission suppression filter is provided, comprising: the aforementioned radiation transmission suppression film, and a support for holding the radiation transmission suppression film.

[0014] In one embodiment, the radiation transmission suppression filter comprises two or more of the aforementioned radiation transmission suppression films.

[0015] According to another aspect of the present invention, an imaging apparatus is provided which is detachably equipped with the aforementioned radiation transmission suppression filter.

[0016] The effects of the invention

[0017] According to the radiation transmission suppression film based on embodiments of the present invention, it is possible to absorb neutron rays due to the boron atoms present in boric acid. Furthermore, boric acid can generate tetrahydroxyborate anions in aqueous solution, forming hydrogen bonds with polyvinyl alcohol (PVA)-based resins. Therefore, the radiation transmission suppression film based on embodiments of the present invention can stably perform this function while having a simple structure. Moreover, by employing a laminated structure with a protective film capable of absorbing β-rays, a film with the desired radiation transmission suppression function can be achieved. As a result, the radiation transmission suppression film based on embodiments of the present invention can be suitably used as a protective component for imaging devices used in high-radiation environments. Attached Figure Description

[0018] Figure 1 This is a cross-sectional schematic diagram of a radiation transmission suppression film based on one embodiment of the present invention.

[0019] Figure 2 This is a schematic exploded perspective view illustrating a radiation transmission suppression filter mounted on an imaging device according to one embodiment of the present invention.

[0020] Figure 3 This is a graph showing the relationship between the product of the thickness of the PVA-based resin film and the boric acid content in the radiation transmission suppression film of the embodiments and comparative examples, and the neutron ray transmittance (relative value). Detailed Implementation

[0021] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

[0022] A. Radiation transmission suppression film

[0023] The radiation transmission suppression film according to embodiments of the present invention comprises a polyvinyl alcohol-based resin film containing boric acid. The product of the boric acid content (wt%) in the polyvinyl alcohol-based resin film and the thickness (μm) of the polyvinyl alcohol-based resin film is typically 500 or more. In one embodiment, the light transmittance of the radiation transmission suppression film is 80% or more.

[0024] A-1. Overall Structure of Radiation Transmission Suppression Film

[0025] Figure 1 This is a cross-sectional schematic diagram of a radiation transmission suppression film according to one embodiment of the present invention. The radiation transmission suppression film 100 illustrated in the figure includes: a PVA-based resin film 10 containing boric acid, a first protective film 20 laminated on one side of the boric acid-containing PVA-based resin film 10, and a second protective film 30 laminated on the other side. The first protective film 20 and / or the second protective film 30 may be omitted depending on the purpose, etc.

[0026] The first protective film 20 and the second protective film 30 can be laminated onto the PVA-based resin film 10 through adhesive layers (e.g., adhesive layer, bonding agent layer), or they can be laminated onto the PVA-based resin film 10 tightly without adhesive layers.

[0027] The aforementioned PVA-based resin film 10 can be a single layer (single-layer film) as shown in the example, or it can be a stacked structure of multiple PVA-based resin films. There is no particular limitation on the number of stacked PVA-based resin films, as long as the boric acid content and thickness of the PVA-based resin film have a desired relationship.

[0028] The transmittance of the aforementioned radiation transmission suppression film is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The radiation transmission suppression film based on the embodiments of the present invention can balance such high transmittance with the desired radiation transmission suppression function, and therefore can be suitable as a protective component for imaging devices used in high-radiation environments. The transmittance can be measured, for example, using a UV-Vis spectrophotometer (such as the V-7100 manufactured by Nippon Spectrophotometer Co., Ltd., or the LPF-200 manufactured by Otsuka Electronics Co., Ltd.).

[0029] A-2. PVA-based resin films containing boric acid

[0030] Any suitable resin can be used as the PVA-based resin for forming the aforementioned PVA-based resin film. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymers can be obtained by saponifying ethylene-vinyl acetate copolymers. The degree of saponification of the PVA-based resin is typically 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be determined according to JIS K 6726-1994. Using a PVA-based resin with this degree of saponification results in excellent durability. Excessive saponification may lead to gelation.

[0031] The average degree of polymerization of PVA-based resins can be appropriately selected according to the purpose. The average degree of polymerization is typically 1000–10000, preferably 1200–5000, and more preferably 1500–4500. It should be noted that the average degree of polymerization can be determined according to JIS K 6726-1994.

[0032] The boric acid content in the aforementioned PVA-based resin film is preferably 10% by weight or more, more preferably 12% to 35% by weight, and even more preferably 15% to 30% by weight. When the boric acid content is within this range, the desired radiation (especially neutron radiation) transmission suppression function can be achieved. The boric acid content (by weight%) can be determined using the boric acid index calculated by attenuated total reflectance spectroscopy (ATR).

[0033] (Borate content index) = (Borate peak 665cm) -1 (Intensity) / (Reference peak 2941cm) -1 (intensity)

[0034] (Borate content) = (Borate index) × a + b

[0035] Here, "a" and "b" are constants that can be obtained by measuring known samples, and these values ​​vary depending on the measuring device.

[0036] The thickness of the aforementioned PVA-based resin film is preferably 5 μm or more, more preferably 10 μm to 100 μm, and even more preferably 20 μm to 70 μm. If this thickness is too thin, the radiation transmission suppression function (especially neutron rays) may be insufficient. If the thickness is within this range, the non-uniformity of boric acid content in the thickness direction can be suppressed, and as a result, the desired radiation transmission suppression function can be easily achieved. It should be noted that when the PVA-based resin film has a stacked structure of multiple PVA-based resin films, the aforementioned thickness refers to the thickness of each individual PVA-based resin film.

[0037] The product of the boric acid content [in weight %] in the aforementioned PVA-based resin film and the thickness of the PVA-based resin film (the total thickness of all films when multiple PVA-based resin films are stacked) [in μm] is typically 500 or more, preferably 3000 or more, more preferably 5000 or more, and even more preferably 7000 or more. When the PVA-based resin film satisfies such a relationship between boric acid content and film thickness, the desired radiation transmittance suppression function can be appropriately obtained.

[0038] The light transmittance of the aforementioned PVA-based resin film is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. If the light transmittance of the PVA-based resin film is within the above range, a radiation transmission suppression film that balances high light transmittance with the desired radiation transmission suppression function can be obtained.

[0039] The aforementioned PVA-based resin film may or may not contain iodine. With a PVA-based resin film that does not contain iodine, the desired light transmittance can be easily obtained.

[0040] A-3. Method for manufacturing PVA-based resin films containing boric acid

[0041] The aforementioned PVA-based resin film can be manufactured, for example, by introducing boric acid into the PVA-based resin film, or by forming a resin solution containing PVA-based resin and boric acid into a film. From the viewpoint of preventing PVA-based resin from clumping and obtaining a resin film with high uniformity, the method of introducing boric acid into the PVA-based resin film is preferred. The PVA-based resin film used for introducing boric acid can be a single-layer film, a laminate of multiple films, or a laminate of a resin substrate and a PVA-based resin layer coated on its surface.

[0042] The method for introducing boric acid into the aforementioned PVA-based resin film typically includes a boric acid introduction step of contacting the PVA-based resin film with an aqueous boric acid solution. Depending on the purpose, this may further include a cleaning step and / or a drying step. Contact with the aqueous boric acid solution is preferably performed by immersing the PVA-based resin film in the solution. Boric acid generates a tetrahydroxyborate anion in the aqueous solution, thus forming hydrogen bonds with the PVA-based resin through the aforementioned contact (typically immersion), allowing for easy introduction into the PVA-based resin film.

[0043] The boric acid content in the above-mentioned boric acid aqueous solution is, for example, 1% by weight or more, preferably 3% to 10% by weight. The temperature of the boric acid aqueous solution is, for example, 20°C to 45°C. In addition, the immersion time is, for example, 10 seconds to 300 seconds.

[0044] In one embodiment, the PVA-based resin film can be stretched while being immersed in an aqueous boric acid solution. By stretching, defects such as wrinkles caused by swelling of the PVA-based resin film can be prevented, and poor appearance when bonded to a protective film can be prevented.

[0045] The stretching described above is representative of uniaxial stretching. The stretching direction can be the length direction (MD direction) or the width direction (TD direction) of the film. The stretching method can be dry stretching, wet stretching, or a combination of both.

[0046] The stretching ratio can be, for example, 1.5 to 7.0 times, preferably 2.0 to 6.0 times.

[0047] A typical cleaning process involves immersing a PVA-based resin film infused with boric acid in a cleaning solution. Pure water is a representative example of such a cleaning solution.

[0048] The temperature of the cleaning solution is, for example, 5°C to 50°C. The immersion time is, for example, 1 second to 300 seconds.

[0049] The drying process can be carried out using any suitable method. Examples of drying methods include natural drying, air drying, vacuum drying, and heat drying. Heat drying is preferred. When performing heat drying, the heating temperature is, for example, 30°C to 100°C. The drying time is, for example, 20 seconds to 10 minutes.

[0050] A-4. First protective film

[0051] The first protective film can be composed of any suitable resin film. Specific examples of materials that are the main components of this film include thermoplastic resins such as cellulose-based resins, cyclic olefin-based resins, acrylic resins, polyester-based resins, polyvinyl alcohol-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyethersulfone-based resins, polysulfone-based resins, polystyrene-based resins, polyolefin-based resins, and acetate-based resins. These resins are preferably transparent. These resins can be used alone or in combination. Cellulose-based resins, cyclic olefin-based resins, and acrylic resins are preferred. This is because these resin films function well as the first protective film and can maintain a high degree of adhesion between the aforementioned PVA-based resin film and the first protective film, thus improving the resistance to damp heat of the radiation transmission suppression film. Furthermore, the desired radiation (especially beta rays) transmission suppression function can be achieved.

[0052] As a cellulose-based resin, any suitable cellulose-based resin can be used. Specific examples include cellulose-based resins with triacetyl cellulose (TAC) and lower fatty acid esters as main components. Cellulose-based resins with lower fatty acid esters as main components are described, for example, in paragraphs 0106 to 0112 of Japanese Patent Application Publication No. 2002-82225.

[0053] As a cellulose-based resin, cellulose-based resins substituted with acetyl and propionyl groups can also be used. The degree of acetyl substitution can be expressed as "degree of acetyl substitution (DSac)," which indicates the average number of the three hydroxyl groups present in the repeating unit of cellulose that are substituted by acetyl groups. The degree of propionyl substitution can be expressed as "degree of propionyl substitution (DSpr)," which indicates the average number of the three hydroxyl groups present in the repeating unit of cellulose that are substituted by propionyl groups. The degree of acetyl substitution (DSac) and the degree of propionyl substitution (DSpr) can be determined using the method described in paragraphs 0016 to 0019 of Japanese Patent Application Publication No. 2003-315538 (A. Blumstein, J. Asrar, R.B. Blumstein, Liq. Cryst. Ordered Fluids 4.311 (1984), which applies a method based on... 1 The degree of substitution of cellulose acetate by H-NMR is determined by the method of determination.

[0054] The degree of acetyl substitution (DSac) and degree of propionyl substitution (DSpr) of the above-mentioned cellulose resin film are preferably 2.0 ≤ DSac + DSpr ≤ 3.0. The lower limit of DSac + DSpr is preferably 2.3 or more, more preferably 2.6 or more. The upper limit of DSac + DSpr is preferably 2.9 or less, more preferably 2.8 or less.

[0055] The degree of propionyl substitution (DSpr) of the aforementioned cellulose-based resin film is preferably 1.0 ≤ DSpr ≤ 3.0. The lower limit of DSpr is preferably 2.0 or more, more preferably 2.5 or more. The upper limit of DSpr is preferably 2.9 or less, more preferably 2.8 or less.

[0056] The cellulose-based resin film is more preferably provided that the degree of acetyl substitution (DSac) and the degree of propionyl substitution (DSpr) are 2.0 ≤ DSac + DSpr ≤ 3.0 and 1.0 ≤ DSpr ≤ 3.0.

[0057] The cellulose resins substituted with acetyl and propionyl groups described above may have other substituents besides acetyl and propionyl groups. Examples of other substituents include ester groups such as butyrate groups; ether groups such as alkyl ether groups and aralkyl ether groups; etc.

[0058] As a method of substitution with the aforementioned acetyl and propionyl groups, any suitable method can be employed. For example, basic cellulose is prepared by treating cellulose with a strong caustic soda solution, and then acylated by passing a mixture of acetic anhydride and propionic anhydride in a specified amount. The degree of substitution, “DSac+DSpr”, is adjusted by partially hydrolyzing the acyl group.

[0059] As a cyclic olefin resin, any suitable cyclic olefin resin can be used. A representative example of a cyclic olefin resin is that it can be polymerized using norbornene monomers as polymerization units. Examples of such norbornene monomers include norbornene, and its alkyl and / or alkylene-substituted derivatives, such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, etc., and their halogenated or other polar group-substituted derivatives; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc.; dimethyl octahydronaphthalene, etc. Its alkyl and / or alkylene substituents, and polar group substituents such as halogens, for example, 6-methyl-1,4:5,8-dimethylbridged-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethylbridged-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethylene-1,4:5,8-dimethylbridged-1,4,4a,5,6,7,8,8a- Octahydronaphthalene, 6-chloro-1,4:5,8-dimethylbridged-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4:5,8-dimethylbridged-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4:5,8-dimethylbridged-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:5,8-dimethylbridged- 1,4,4a,5,6,7,8,8a-octahydronaphthalene, etc.; 3- to 4-mers of cyclopentadiene, such as 4,9:5,8-dimethylbridged-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzo[a]indene, 4,11:5,10:6,9-trimethylbridged-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecylhydro-1H-cyclopentane, etc. Cycloolefin resins can also be copolymers of norbornene monomers and other monomers.

[0060] As an acrylic resin, any suitable (meth)acrylic resin can be used. Examples include poly(meth)acrylates such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymers, methyl methacrylate-(meth)acrylate copolymers, methyl methacrylate-acrylate-(meth)acrylic acid copolymers, methyl methacrylate-styrene copolymers (MS resin, etc.), and polymers having alicyclic hydrocarbon groups (e.g., methyl methacrylate-cyclohexyl methacrylate copolymers, methyl methacrylate-norborneol ester copolymers, etc.). Poly(meth)acrylic acid C, such as poly(methyl methacrylate), is preferably listed. 1-6Alkyl esters. More preferably, methyl methacrylate-based resins are listed as having methyl methacrylate as the main component (50-100% by weight, preferably 70-100% by weight). It should be noted that in this specification, "(meth)acrylic acid" refers to acrylic acid and / or methacrylic acid.

[0061] Specific examples of (meth)acrylic resins include ACRYPET VH and ACRYPET VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and high Tg (meth)acrylic resins obtained through intramolecular crosslinking and intramolecular cyclization reactions (e.g., (meth)acrylic resins with glutaric anhydride structures and (meth)acrylic resins with lactone ring structures).

[0062] Examples of (meth)acrylic resins with a glutaric anhydride structure include those described in Japanese Patent Application Publication Nos. 2006-283013, 2006-335902, and 2006-274118.

[0063] Examples of (meth)acrylic resins with a lactone ring structure include those described in Japanese Patent Application Publication Nos. 2000-230016, 2001-151814, 2002-120326, 2002-254544, and 2005-146084.

[0064] The thickness of the first protective film is preferably 15 μm or more, more preferably 20 μm to 80 μm, and even more preferably 30 μm to 60 μm. If the thickness of the first protective film is within such a range, the desired radiation (especially beta rays) transmission suppression function can be achieved, and it can be used in small imaging devices.

[0065] A-5. Second protective film

[0066] The specific composition of the second protective film is as described in item A-4 above regarding the first protective film. The second protective film may have the same composition as the first protective film, or it may have a different composition.

[0067] B. Radiation transmission suppression filter

[0068] The radiation transmission suppression film described in item A above can be used by incorporating it into a radiation transmission suppression filter. Therefore, embodiments of the present invention also include radiation transmission suppression filters. Figure 2This is a schematic exploded perspective view illustrating a radiation transmission suppression filter based on one embodiment of the present invention mounted on an imaging device. The radiation transmission suppression filter 200 illustrated in the figure includes a radiation transmission suppression film 100 and a support 110 for holding the radiation transmission suppression film 100. The radiation transmission suppression film is as described in item A above. The support can adopt any suitable configuration. In one embodiment, the radiation transmission suppression filter may include two or more radiation transmission suppression films. In this case, the radiation transmission suppression filter can hold two or more radiation transmission suppression films with one support, or it can be configured as a combination of multiple supports each holding one or more radiation transmission suppression films.

[0069] C. Filming equipment

[0070] A radiation transmission suppression filter, including the radiation transmission suppression film described in item A above, can be installed in an imaging device for use. Therefore, embodiments of the present invention also include imaging devices. A representative example of an imaging device is a camera device. For example... Figure 2 As shown, the radiation transmission suppression filter 200 is detachably mounted on the imaging device (typically, the top of the lens of a camera device) 300. The radiation transmission suppression film included in the radiation transmission suppression filter has the specified transmittance as described above, therefore, imaging can be performed even when the radiation transmission suppression filter is mounted on the imaging device. Multiple radiation transmission suppression filters can also be mounted on the imaging device.

[0071] Example

[0072] The present invention will be specifically described below through examples, but the present invention is not limited to these examples.

[0073] [Example 1]

[0074] A 75 μm thick PVA film (manufactured by Kuraray Co., Ltd., product name: VF-PS750, degree of polymerization: approximately 2400, degree of saponification: 99.9%) was immersed in a bath containing 3% boric acid at 40°C for 60 seconds, while being stretched at a stretch ratio of 2.3 times to obtain a boric acid-containing PVA film. The thickness of the obtained PVA film was 47 μm. A triacetyl cellulose (TAC) film (40 μm thick) was then bonded to both sides of the obtained PVA film using a PVA aqueous solution to fabricate a radiation transmission suppression film 1.

[0075] The obtained radiation transmission suppression film 1 is used for the following evaluation. The results are shown in Table 1.

[0076] Boric acid content

[0077] For the radiation transmission suppression film 1 obtained in Example 1, the boric acid peak (665 cm⁻¹) was determined by attenuated total reflectance spectroscopy (ATR) using a Fourier transform infrared spectrometer (FT-IR) (Perkin Elmer, trade name "SPECTRUM2000"). -1 The intensity and reference peak (2941 cm⁻¹) -1 The intensity of the boric acid peak is determined by the following formula: The boric acid content index is calculated from the obtained boric acid peak intensity and the reference peak intensity. Then, the boric acid content is determined from the calculated boric acid content index using the following formula.

[0078] (Borate content index) = (Borate peak 665cm) -1 (Intensity) / (Reference peak 2941cm) -1 (intensity)

[0079] (Boric acid content) = (Boric acid index) × 6.6 + 0.5

[0080] Here, "6.6" and "0.5" are constants obtained based on standard curves obtained by measuring known samples using the aforementioned Fourier transform infrared spectrometer (FT-IR) (Perkin Elmer, trade name "SPECTRUM2000").

[0081] Light transmittance

[0082] The total transmittance of the radiation transmission suppression film 1 was measured using Otsuka Electronics Co., Ltd. under the product name "LPF-200".

[0083] Neutron beam transmittance

[0084] Neutron irradiation was performed using the nuclear reactor (UTR-KINKI) owned by the Institute of Atomic Energy, Kindai University. First, radiation transmission suppression film 1 of the sample to be evaluated was attached to an imaging plate (manufactured by FUJIFILM Corporation, BAS-IP-ND-2025), which served as the photosensitive material, and the sample was irradiated with neutron rays. Then, the neutron irradiation dose to the photosensitive material was scanned and quantified using an image analysis device (manufactured by GE Healthcare, Amersham Typhoon scanner). The irradiation dose of each sample's attached portion was expressed as a relative value when the irradiation dose of the unattached portion of the sample (reference example) was set to 100.

[0085] [Example 2]

[0086] Five radiation transmission suppression films prepared in Example 1 were stacked using an acrylic adhesive (thickness: 20 μm) to create radiation transmission suppression film 2. For the obtained radiation transmission suppression film 2, the transmittance and neutron transmittance were measured in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0087] [Example 3]

[0088] Ten layers of the radiation transmission suppression film prepared in Example 1 were stacked using an acrylic adhesive (thickness: 20 μm) to prepare radiation transmission suppression film 3. For the obtained radiation transmission suppression film 3, the transmittance and neutron transmittance were measured in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0089] [Comparative Example 1]

[0090] A TAC laminate was obtained by laminating two TAC films (40 μm thick) using a PVA aqueous solution. Five of these TAC laminates were then laminated using an acrylic adhesive (20 μm thick) to fabricate a radiation transmission suppression film C1. For the obtained radiation transmission suppression film C1, the transmittance and neutron transmittance were measured in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0091] [Table 1]

[0092]

[0093] Figure 3 The following is shown: the relationship between the product of the thickness of the PVA-based resin film for radiation transmission suppression film obtained in the examples and comparative examples and the neutron transmittance (relative value).

[0094] As shown in Table 1 and Figure 3 As shown, it was confirmed that when the product of the thickness of the PVA-based resin film and the boric acid content is greater than 500, the transmission of neutron rays is suppressed.

[0095] Industrial availability

[0096] The radiation transmission suppression film of the present invention can be suitably used as a protective component for imaging devices used in high radiation environments such as nuclear power facilities, outer space, or medical sites.

[0097] Explanation of reference numerals in the attached figures

[0098] 10 PVA-based resin films

[0099] 20 First protective film

[0100] 30 Second protective film

[0101] 100% radiation transmission suppression film

[0102] 110 bracket

[0103] 200 radiated line transmission suppression filter

[0104] 300 camera device

Claims

1. A neutron radiation transmission suppressing film comprising a polyvinyl alcohol-based resin film containing boric acid. The product of the boric acid content (in weight %) in the polyvinyl alcohol resin film and the thickness (in μm) of the polyvinyl alcohol resin film is 500 or more. The transmittance of neutron rays through the suppression film is over 80%.

2. The neutron radiation transmission suppression film according to claim 1, further comprising a protective film laminated on one or both sides of the polyvinyl alcohol-based resin film.

3. The neutron radiation transmission suppression film according to claim 2, wherein, The protective film comprises at least one resin selected from cellulose resins, cyclic olefin resins, and acrylic resins.

4. A neutron radiation transmission suppression filter comprising: a neutron radiation transmission suppression film according to any one of claims 1 to 3, and a support for holding the neutron radiation transmission suppression film.

5. The neutron radiation transmission suppression filter according to claim 4, comprising two or more of the neutron radiation transmission suppression films.

6. An imaging device having a detachably mounted neutron ray transmission suppression filter as claimed in claim 4 or 5.

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