Inorganic plate with film and package

Abstract

To provide an inorganic plate with a film, which is excellent in ultraviolet transmissivity, and which can enhance airtightness within a package when used for the package on which an optical element is mounted.SOLUTION: An inorganic plate 1 with a film includes: an inorganic plate 2 having a first principal surface 2a and a second principal surface 2b having ultraviolet transmissivity and facing each other; and an antireflection film 3 provided on the first principal surface 2a of the inorganic plate 2. The antireflection film 3 includes: a magnesium fluoride layer 5 provided on the first principal surface 2a of the inorganic plate 2; and a silicon oxide layer 6 provided on an outermost layer on the opposite side from the inorganic plate 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an inorganic board with a film having ultraviolet light transmittance and a package using the inorganic board with a film. [Background technology]

[0002] It has been known that ultraviolet light, such as deep ultraviolet light, has a sterilizing effect and an organic matter decomposition effect, and light-emitting elements that emit ultraviolet light, such as LEDs, are widely used in medical facilities and food factories. In recent years, UV cameras have been attracting attention, and the demand for imaging elements, such as image sensors, that are compatible with ultraviolet wavelength ranges, including the deep ultraviolet range, is also increasing.

[0003] Optical elements such as light-emitting elements and imaging elements are mounted in a package and sealed before use (for example, Patent Document 1). The package is composed of a case body in which the optical element is mounted, and a cover member that seals the inside of the housing. As the cover member, a film-coated inorganic plate having an anti-reflection film provided on the surface of an inorganic plate is used. By providing such a film-coated inorganic plate in front of the optical element, the optical element is protected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-000188 Summary of the Invention [Problem to be solved by the invention]

[0005] The anti-reflection film of the inorganic plate with a film that transmits ultraviolet light is desirably made of a material that does not absorb ultraviolet light. However, the material that does not absorb ultraviolet light may not have sufficient wettability with the bonding material used to bond the inorganic plate with a film and the case body in the manufacturing process of the package as described above, and may not be able to sufficiently increase the airtightness when sealing the inside of the package.

[0006] The object of the present invention is to provide a film-coated inorganic plate and a package using the film-coated inorganic plate, which has excellent ultraviolet transmittance and can increase the airtightness within the package when used in a package mounting an element such as an imaging element or a light-emitting element (hereinafter referred to as an optical element). [Means for solving the problem]

[0007] Various embodiments of a film-coated inorganic board that solves the above problems and a package using the film-coated inorganic board will be described below.

[0008] The film-coated inorganic plate according to aspect 1 of the present invention comprises an inorganic plate having ultraviolet light transparency and having opposing first and second main surfaces, and an antireflection film provided on the first main surface of the inorganic plate, the antireflection film including a magnesium fluoride layer provided on the first main surface of the inorganic plate, and a silicon oxide layer provided as an outermost layer on the side opposite the inorganic plate.

[0009] In the inorganic plate with a film according to the first aspect, since a magnesium fluoride layer is provided on the first main surface of the inorganic plate, the ultraviolet transmittance can be increased, and in particular, the ultraviolet transmittance in the deep ultraviolet region can be increased. In addition, since a silicon oxide layer is provided on the outermost layer of the antireflection film, when the inorganic plate with a film and another member are bonded together via a bonding material such as a resin adhesive, the wettability to the bonding material can be increased compared to when the magnesium fluoride layer is the outermost layer, and the adhesion when the inorganic plate with a film is bonded to another member can be increased. Therefore, when such an inorganic plate with a film is used as a cover member of a package that mounts an optical element, the adhesion between the inorganic plate with a film and the case body can be increased in the manufacturing process, and the airtightness inside the package can be increased. In this specification, the ultraviolet region refers to a wavelength of 100 nm or more and 380 nm or less, and the deep ultraviolet region refers to a wavelength of 100 nm or more and 280 nm or less. However, when judging ultraviolet transmittance, it shall be confirmed by measuring the light transmittance at a wavelength of 190 nm or more and 380 nm or less, and when judging ultraviolet transmittance in the deep ultraviolet range, it shall be confirmed by measuring the light transmittance at a wavelength of 200 nm.

[0010] The film-attached inorganic plate of aspect 2 is preferably such that in aspect 1, the thickness ratio of the magnesium fluoride layer to the silicon oxide layer (magnesium fluoride layer / silicon oxide layer) is 1.5 or more and 5 or less. In this case, it is possible to make it even more difficult for cracks to occur in the antireflection coating due to stresses inherent in the magnesium fluoride layer and the silicon oxide layer.

[0011] The film-attached inorganic plate of aspect 3 is preferably configured such that the inorganic plate is made of quartz glass in aspect 1 or aspect 2. In this case, the ultraviolet transmittance of the film-attached inorganic plate in the deep ultraviolet region can be further increased.

[0012] The film-attached inorganic plate of aspect 4, when the antireflection film is a first antireflection film in any one of aspects 1 to 3, preferably further comprises a second antireflection film provided on the second main surface of the inorganic plate, and the second antireflection film preferably includes a magnesium fluoride layer provided on the second main surface of the inorganic plate. In this case, the ultraviolet transmittance in the deep ultraviolet region of the film-attached inorganic plate can be further increased.

[0013] The film-attached inorganic plate of aspect 5 is preferably the same as that of aspect 4, in which the second antireflection film includes a silicon oxide layer provided as the outermost layer on the side opposite to the inorganic plate. In this case, it is possible to avoid erroneously using the surface of the film-attached inorganic plate, on which no silicon oxide layer is provided, for bonding.

[0014] In the film-attached inorganic plate of aspect 6, in any one of aspects 1 to 5, the number of magnesium fluoride layers included in the antireflection film is preferably 1. In this case, it is possible to make it even more difficult for the ultraviolet transmittance of the film-attached inorganic plate in the deep ultraviolet region to decrease.

[0015] In the film-attached inorganic plate of aspect 7, in any one of aspects 1 to 6, the number of the silicon oxide layers included in the antireflection film is preferably 1. In this case, it is possible to further prevent the decrease in ultraviolet transmittance in the deep ultraviolet region of the film-attached inorganic plate from occurring.

[0016] In the film-coated inorganic plate of aspect 8, in any one of aspects 1 to 7, the contact angle of pure water with respect to the surface of the film-coated inorganic plate on the antireflection film side is preferably 7° or less. In this case, the adhesiveness when the film-coated inorganic plate is bonded to another member with a bonding material can be further improved, and the airtightness inside the package in which an optical element is mounted can be further improved.

[0017] The film-attached inorganic plate of aspect 9, in any one of aspects 1 to 8, preferably has a light transmittance of 80% or more at a thickness of 0.5 mm and a wavelength of 200 nm. In this case, for example, when the film-attached inorganic plate is used as a cover member of a package mounting an imaging element, ultraviolet light in the deep ultraviolet region can be more reliably incident on the imaging element. Also, in this case, for example, when the film-attached inorganic plate is used as a cover member of a package mounting a light-emitting element, ultraviolet light in the deep ultraviolet region emitted from the light-emitting element can be more reliably transmitted.

[0018] The package of aspect 10 of the present invention comprises a case body having a bottom and a side wall, an optical element provided on the bottom of the case body, and a cover member provided on the side wall of the case body, wherein the cover member is a film-coated inorganic plate of any of aspects 1 to 9, and the anti-reflection film of the film-coated inorganic plate and an upper surface of the side wall of the case body are bonded via a bonding material to seal the inside of the package containing the optical element. Effect of the Invention

[0019] According to the present invention, it is possible to provide a film-coated inorganic plate which has excellent ultraviolet transmittance and which, when used in a package mounting an optical element, can increase the airtightness within the package, and a package using the film-coated inorganic plate. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a film-attached inorganic plate according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a film-attached inorganic board of a first modified example. [Diagram 3] FIG. 3 is a schematic cross-sectional view showing a film-attached inorganic board according to a second modified example. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a package including a film-attached inorganic board according to one embodiment of the present invention. [Diagram 5] FIG. 5 shows the light transmission spectra of the film-attached inorganic plates of Examples 1 to 4 and Comparative Example 1, and the inorganic plate of Reference Example 1 in the wavelength range of 190 nm to 400 nm. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Preferred embodiments will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[0022] [Inorganic board with film] FIG. 1 is a schematic cross-sectional view showing a film-attached inorganic plate according to one embodiment of the present invention.

[0023] As shown in Fig. 1, the film-coated inorganic plate 1 includes an inorganic plate 2, a first anti-reflection film 3, and a second anti-reflection film 4. The inorganic plate 2 is UV-transmissive. The inorganic plate 2 has a substantially rectangular plate shape. However, the inorganic plate 2 may have a substantially circular plate shape, and the shape of the inorganic plate 2 is not particularly limited.

[0024] The inorganic plate 2 has a first main surface 2a and a second main surface 2b facing each other. A first antireflection film 3 is provided on the first main surface 2a of the inorganic plate 2. In addition, a second antireflection film 4 is provided on the second main surface 2b of the inorganic plate 2.

[0025] The first antireflection coating 3 has a magnesium fluoride layer 5 and a silicon oxide layer 6. The magnesium fluoride layer 5 is provided on the first main surface 2a of the inorganic plate 2. The silicon oxide layer 6 is provided on the magnesium fluoride layer 5. The silicon oxide layer 6 is provided as the outermost layer on the side opposite to the inorganic plate 2.

[0026] The second antireflection coating 4 has a magnesium fluoride layer 5 and a silicon oxide layer 6. The magnesium fluoride layer 5 and the silicon oxide layer 6 are made of the same material and have the same thickness as the first antireflection coating 3. In the second antireflection coating 4, the magnesium fluoride layer 5 is provided on the second main surface 2b of the inorganic plate 2. The silicon oxide layer 6 is provided on the magnesium fluoride layer 5. The silicon oxide layer 6 is provided as the outermost layer on the side opposite to the inorganic plate 2.

[0027] The magnesium fluoride layer 5 is a film containing magnesium fluoride (MgF2) as a main component. The silicon oxide layer 6 is a film containing silicon oxide (SiO2) as a main component. In this specification, a film containing a material as a main component refers to a film containing 90 mass % or more of the material, and it is preferable that the film containing a material as a main component is a film composed only of the material excluding impurities.

[0028] Since magnesium fluoride does not have an absorbing effect in the ultraviolet region, a film-attached inorganic plate formed by providing a magnesium fluoride film on an inorganic plate can provide an anti-reflection function in the ultraviolet region. However, since the magnesium fluoride film has poor wettability with a bonding material such as a resin adhesive, when the surface of the film-attached inorganic plate on which the magnesium fluoride film is provided is bonded to another member by a bonding material, the adhesion may not be sufficiently improved. For example, when the film-attached inorganic plate is used as a cover member of a package that mounts an optical element, when the film-attached inorganic plate is bonded to a case body by a bonding material in the manufacturing process, if the magnesium fluoride film side is bonded, the adhesion between the film-attached inorganic plate and the case body may not be sufficiently improved because the wettability between the magnesium fluoride film and the bonding material is poor. Therefore, a film-attached inorganic plate formed by providing a magnesium fluoride film on an inorganic plate has a problem that the airtightness inside the package in which the optical element is mounted cannot be sufficiently improved.

[0029] In contrast, in the film-coated inorganic plate 1 of the present embodiment, a magnesium fluoride layer 5 is provided on the first main surface 2a and the second main surface 2b of the inorganic plate 2. Therefore, in the film-coated inorganic plate 1, the ultraviolet ray transmittance can be increased, and in particular, the ultraviolet ray transmittance in the deep ultraviolet region can be increased.

[0030] Furthermore, in the film-coated inorganic plate 1 of this embodiment, a silicon oxide layer 6 is provided on the outermost layer of the first antireflection film 3 and the second antireflection film 4. Therefore, when the film-coated inorganic plate 1 is bonded to another member via a bonding material such as a resin adhesive, the wettability to the bonding material can be increased compared to when the magnesium fluoride layer 5 is the outermost layer, and the adhesion when the film-coated inorganic plate 1 is bonded to another member can be increased. Therefore, when the film-coated inorganic plate 1 of this embodiment is used as a cover member of a package mounting an optical element, the adhesion between the film-coated inorganic plate 1 and the case body can be increased in the manufacturing process, and the airtightness inside the package can be increased.

[0031] Furthermore, since the magnesium fluoride film does not have high weather resistance, there is a problem that the magnesium fluoride film deteriorates when exposed to the atmosphere for a long period of time. In the film-coated inorganic plate 1 of the present embodiment, the weather resistance of the first antireflection film 3 and the second antireflection film 4 can be improved by providing the silicon oxide layer 6, which has extremely high weather resistance, on the outermost layer of the first antireflection film 3 and the second antireflection film 4.

[0032] In this embodiment, the total light transmittance of the film-coated inorganic plate 1 at a thickness of 0.5 mm and a wavelength of 190 nm to 380 nm is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. In this case, the ultraviolet transmittance of the film-coated inorganic plate 1 can be further increased. The upper limit of the total light transmittance of the film-coated inorganic plate 1 at a thickness of 0.5 mm and a wavelength of 190 nm to 380 nm is preferably as high as possible, but in practice, it can be set to, for example, 95%.

[0033] In this embodiment, the light transmittance of the film-coated inorganic plate 1 at a thickness of 0.5 mm and a wavelength of 200 nm is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. In this case, the ultraviolet transmittance in the deep ultraviolet range of the film-coated inorganic plate 1 can be further increased. The upper limit of the light transmittance of the film-coated inorganic plate 1 at a thickness of 0.5 mm and a wavelength of 200 nm is preferably as high as possible, but can be set to 95% in practice.

[0034] In this embodiment, the contact angle of pure water with respect to the surface 3a of the film-coated inorganic plate 1 on the side of the first antireflection film 3 is preferably 7° or less, more preferably 5° or less. In this case, the adhesiveness when the film-coated inorganic plate 1 is bonded to another member with a bonding material can be further improved, and the airtightness inside the package in which the optical element is mounted can be further improved. In addition, the lower limit of the contact angle of pure water with respect to the surface 3a of the film-coated inorganic plate 1 on the side of the first antireflection film 3 is preferably as small as possible, but in reality, it can be set to, for example, 4°.

[0035] The contact angle (θ) of pure water with respect to the surface 3a of the film-coated inorganic plate 1 on the side of the first antireflection film 3 can be measured based on the sessile drop method (θ / 2 approximation method) of JIS R 3257:1999.

[0036] In this embodiment, an anti-reflection film is provided on each of the first main surface 2a and the second main surface 2b, which are the main surfaces on both sides of the inorganic plate 2. However, in the present invention, as in the film-attached inorganic plate 1A of the first modified example shown in FIG. 2, an anti-reflection film (first anti-reflection film 3) may be provided only on the first main surface 2a of the inorganic plate 2. That is, an anti-reflection film (second anti-reflection film 4) may not be provided on the second main surface 2b of the inorganic plate 2. However, in this case, when the film-attached inorganic plate 1A is attached to another member by a bonding material, it is attached to the other member from the first anti-reflection film 3 side via the bonding material. However, in the present invention, as in the film-attached inorganic plate 1 shown in FIG. 1, it is preferable that an anti-reflection film is provided on each of the first main surface 2a and the second main surface 2b, which are the main surfaces on both sides of the inorganic plate 2.

[0037] Also, as in the film-coated inorganic plate 1B of the second modification shown in FIG. 3, the second antireflection film 4B may be composed only of the magnesium fluoride layer 5. That is, in the second antireflection film 4B, the silicon oxide layer 6 may not be provided on the magnesium fluoride layer 5. Even in this case, when the film-coated inorganic plate 1B is bonded to another member with a bonding material, it is bonded to the other member from the first antireflection film 3 side via the bonding material. Note that, when the second antireflection film 4B is composed only of the magnesium fluoride layer 5 as in the second modification, the ultraviolet transmittance of the film-coated inorganic plate 1B in the deep ultraviolet region can be further improved.

[0038] In this embodiment, the magnesium fluoride layer 5 and the silicon oxide layer 6 are provided on the entire surface of the inorganic plate 2. However, in the present invention, the magnesium fluoride layer 5 may be provided partially only in an area where ultraviolet light transmission is required. Also, the silicon oxide layer 6 may be provided partially only in an area that is to be bonded to another member.

[0039] In this embodiment, in consideration of the transmittance in the ultraviolet region, it is preferable that the first antireflection film 3 and the second antireflection film 4 each have one magnesium fluoride layer 5 and one silicon oxide layer 6. However, in the present invention, the first antireflection film 3 and the second antireflection film 4 may have multiple magnesium fluoride layers 5 or multiple silicon oxide layers 6 within a range that does not deteriorate the transmittance in the ultraviolet region, as long as the silicon oxide layer 6 is provided on the outermost layer that is bonded to other members, and further, all or part of the multiple silicon oxide layers 6 may be replaced with aluminum oxide (Al2O3) layers. In this case, it is preferable that the magnesium fluoride layers 5 and the silicon oxide layers 6 (aluminum oxide layers) are alternately laminated.

[0040] Hereinafter, each member constituting the film-coated inorganic board 1 will be described in detail.

[0041] (Inorganic board) The total light transmittance of the inorganic plate 2 at a thickness of 0.5 mm and a wavelength of 190 nm to 380 nm is preferably 90% or more, more preferably 93% or more, and even more preferably 94% or more. In this case, the UV transmittance of the film-coated inorganic plate 1 can be further increased. The upper limit of the total light transmittance of the inorganic plate 2 at a thickness of 0.5 mm and a wavelength of 190 nm to 380 nm is preferably as high as possible, but can be set to 95% in practice.

[0042] In this embodiment, the light transmittance of the inorganic plate 2 at a thickness of 0.5 mm and a wavelength of 200 nm is preferably 90% or more, more preferably 93% or more, and even more preferably 94% or more. In this case, the ultraviolet transmittance in the deep ultraviolet region of the film-coated inorganic plate 1 can be further increased. The upper limit of the light transmittance of the inorganic plate 2 at a thickness of 0.5 mm and a wavelength of 200 nm is preferably as high as possible, but in reality, it can be set to 95%.

[0043] Examples of materials that can be used for the inorganic plate 2 include ultraviolet-transmitting glass, sapphire, and diamond. Examples of ultraviolet-transmitting glass include quartz glass and borosilicate glass. Of these, it is preferable that the inorganic plate 2 is a quartz glass plate. In this case, the ultraviolet transmittance of the film-coated inorganic plate 1 in the deep ultraviolet region can be further increased.

[0044] The inorganic plate 2 may have a thickness of, for example, 0.1 mm to 1.5 mm.

[0045] (Anti-reflective film) The first antireflection film 3 and the second antireflection film 4 are preferably made of the same material and have the same thickness. However, the first antireflection film 3 and the second antireflection film 4 may be made of different materials and may have different thicknesses. The antireflection films used for the first antireflection film 3 and the second antireflection film 4 will be described below.

[0046] The total thickness of the antireflection film is preferably 15 nm or more, more preferably 20 nm or more, and even more preferably 25 nm or more, and is preferably 60 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less.

[0047] In particular, in the antireflective film, the thickness ratio of the magnesium fluoride layer 5 to the silicon oxide layer 6 (magnesium fluoride layer 5 / silicon oxide layer 6) is preferably 1.5 or more, more preferably 2 or more, even more preferably 2.5 or more, and is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less.

[0048] Large tensile stress is likely to occur in the magnesium fluoride layer 5 provided on the inorganic plate 2. Meanwhile, large compressive stress is likely to occur in the silicon oxide layer 6 provided on the inorganic plate 2. Therefore, when both the magnesium fluoride layer 5 and the silicon oxide layer 6 are provided on the inorganic plate 2, cracks may occur throughout the antireflective film. Here, when the above-mentioned thickness ratio (magnesium fluoride layer 5 / silicon oxide layer 6) is within the above range, the stresses in the magnesium fluoride layer 5 and the silicon oxide layer 6 are more likely to be balanced, making it even more difficult for cracks to occur in the antireflective film.

[0049] The thickness of the magnesium fluoride layer 5 is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 18 nm or more, and is preferably 50 nm or less, more preferably 30 nm or less, and even more preferably 25 nm or less. By specifying the thickness of the magnesium fluoride layer 5 within the above range, it is possible to improve the antireflection function of the film-coated inorganic plate 1 in the deep ultraviolet region while avoiding a decrease in ultraviolet transmittance due to an increase in film thickness. As a result, it is possible to further increase the ultraviolet transmittance of the film-coated inorganic plate 1, and further prevent cracks from occurring in the antireflection film.

[0050] The number of magnesium fluoride layers 5 in the antireflection film is preferably one. In this case, it is possible to further prevent a decrease in the ultraviolet transmittance in the deep ultraviolet region of the film-coated inorganic plate 1. However, the number of magnesium fluoride layers 5 in the antireflection film may be, for example, one or more and three or less, and is not particularly limited.

[0051] The thickness of the silicon oxide layer 6 is preferably 2 nm or more, more preferably 4 nm or more, and even more preferably 6 nm or more, and is preferably 15 nm or less, more preferably 10 nm or less, and even more preferably 8 nm or less. By setting the thickness of the silicon oxide layer 6 to the above upper limit or less, the ultraviolet transmittance of the film-coated inorganic plate 1 can be increased, and the anti-reflection film can be made even less susceptible to cracks. In addition, by setting the thickness of the silicon oxide layer 6 to the above lower limit or more, the weather resistance of the film-coated inorganic plate 1 can be further improved.

[0052] The number of silicon oxide layers 6 in the antireflection film is preferably one. In this case, it is possible to further prevent a decrease in the ultraviolet transmittance in the deep ultraviolet region of the film-coated inorganic plate 1. However, the number of silicon oxide layers 6 in the antireflection film may be, for example, one or more and three or less, and is not particularly limited.

[0053] The method for forming the magnesium fluoride layer 5 and the silicon oxide layer 6 is not particularly limited, and the magnesium fluoride layer 5 and the silicon oxide layer 6 can be formed, for example, by forming the magnesium fluoride layer 5 and the silicon oxide layer 6 on the inorganic plate 2 using a deposition method such as a sputtering method or a vacuum deposition method.

[0054] Incidentally, the sputtering method and the vapor deposition method may be any conventionally known method, but the substrate temperature during film formation is preferably 250° C. or higher, more preferably 270° C. or higher, and preferably 350° C. or lower. In particular, when the substrate temperature during film formation of the silicon oxide layer 6 is within the above range, the contact angle of pure water with the surface of the film-coated inorganic plate 1 on the anti-reflection film side can be further reduced, and the adhesion when the film-coated inorganic plate 1 is bonded to another member with a bonding material can be further improved.

[0055] [package] FIG. 4 is a schematic cross-sectional view showing a package including a film-attached inorganic board according to one embodiment of the present invention.

[0056] As shown in FIG. 4, the package 11 includes a film-coated inorganic plate 1 serving as a cover member, a case body 12, and an image sensor 13 serving as an imaging element.

[0057] The case body 12 has a bottom 12a and a frame-shaped side wall 12b. The side wall 12b is provided on the bottom 12a. The case body 12 may be made of a material such as ceramics, such as aluminum nitride, or glass ceramics.

[0058] A film-attached inorganic plate 1 is provided as a cover member on an upper surface 12c of a side wall portion 12b of a case body 12. The upper surface 12c of the side wall portion 12b and the film-attached inorganic plate 1 are bonded with a bonding material 14, thereby sealing the inside of a package 11 on which an image sensor 13 is mounted. In this embodiment, the film-attached inorganic plate 1 is bonded to the upper surface 12c of the side wall portion 12b via the bonding material 14 from the first antireflection film 3 side. In the first antireflection film 3, a silicon oxide layer 6 is provided on the entire surface of the inorganic plate 2, but the silicon oxide layer 6 may be provided partially at a location where the bonding material 14 is provided.

[0059] There is no particular limitation on the bonding material 14, and for example, a resin adhesive or a solder film can be used. As the resin adhesive, a resin such as an ultraviolet curing adhesive can be used.

[0060] The image sensor 13 is disposed on the bottom 12a of the case body 12. In this embodiment, the package 11 is equipped with the image sensor 13 as an imaging element, but the package 11 may be equipped with other optical elements such as light-emitting elements such as deep ultraviolet LEDs, and is not particularly limited.

[0061] In the package 11 of the present embodiment, the above-mentioned film-coated inorganic plate 1 is used as a cover member. This can improve the airtightness inside the package 11. In addition, since the film-coated inorganic plate 1 has excellent ultraviolet transmittance, the package 11 of the present embodiment can allow ultraviolet light to be efficiently incident on the image sensor 13.

[0062] In this embodiment, the film-coated inorganic plate 1 is used as a cover member for the package 11, but the film-coated inorganic plate 1 may be directly bonded to the image sensor 13 via the bonding material 14. Even in this case, the film-coated inorganic plate 1 and the image sensor 13 can be reliably bonded by bonding the first antireflection film 3 side of the film-coated inorganic plate 1 to the image sensor 13 via the bonding material 14. In addition, ultraviolet light can be efficiently incident on the image sensor 13 through the film-coated inorganic plate 1.

[0063] The present invention will be described in more detail below with reference to specific examples. The present invention is not limited to the following examples, and can be modified as appropriate within the scope of the present invention.

[0064] Example 1 First, a quartz glass plate (manufactured by Hubei Feilihua Quartz Glass Co., Ltd., product number "JGS-1", thickness: 0.5 mm) was prepared as an inorganic plate. Next, a magnesium fluoride (MgF2) layer and a silicon oxide (SiO2) layer were formed on a first main surface of the inorganic plate by a vacuum deposition method. More specifically, the substrate temperature was set to 300°C, no carrier gas was introduced, and the MgF2 film material placed in the hearth liner was irradiated with thermoelectrons to heat it, and the film formation rate was set to 0.5 nm / sec, and the MgF2 layer was formed on one main surface of the inorganic plate. Next, O2 gas was used as a carrier gas, and the SiO2 film material placed in the hearth liner was irradiated with thermoelectrons to heat it, and the film formation rate was set to 0.5 nm / sec, and the SiO2 layer was formed on the MgF2 layer. The thickness of the MgF2 layer was 20 nm, and the thickness of the SiO2 was 5 nm. Similarly, an MgF2 layer was formed on the second main surface of the inorganic plate in the same thickness by the same method as on the first main surface, and an SiO2 layer was formed thereon in the same thickness by the same method as on the first main surface, thereby obtaining a film-coated inorganic plate.

[0065] Example 2 A film-coated inorganic substrate was obtained in the same manner as in Example 1, except that the thickness of the SiO2 layer was 10 nm.

[0066] Example 3 A film-coated inorganic substrate was obtained in the same manner as in Example 1, except that the thickness of the SiO2 layer was 15 nm.

[0067] Example 4 A film-coated inorganic substrate was obtained in the same manner as in Example 1, except that the thickness of the SiO2 layer was 20 nm.

[0068] Comparative Example 1 A film-coated inorganic substrate was obtained in the same manner as in Example 1, except that the SiO2 layer was not provided.

[0069] (Reference example 1) The quartz glass plate was used as it was as an inorganic plate without being subjected to any film forming treatment.

[0070] [evaluation] (Contact angle evaluation) The contact angle θ of pure water with respect to the surface on the antireflection film side of each of the film-coated inorganic plates of Examples 1 to 4 and Comparative Example 1 was measured.

[0071] The contact angle θ was measured based on the sessile drop method (θ / 2 approximation method) of JIS R 3257: 1999. Specifically, 5 mg of pure water was dropped onto each of the film-attached inorganic plates placed horizontally, and then the water droplet was photographed from directly above using a measuring microscope (Nikon Corporation), and the contact angle θ was calculated from the outer diameter of the water droplet.

[0072] The contact angle θ of pure water with respect to the surface on the antireflection film side of the film-coated inorganic plate in Example 1 was 3.7°, and similarly, the contact angle θ was 3.7° to 4.1° in Examples 2 to 4. Meanwhile, in Comparative Example 1, the contact angle θ was 7.5°.

[0073] (Evaluation of light transmittance) The light transmittance of the film-attached inorganic plates of Examples 1 to 4 and Comparative Example 1, and the inorganic plate of Reference Example 1 was measured using a spectrophotometer (Hitachi High-Tech Corporation, product number "U-4150") Fig. 5 shows the light transmission spectra of the film-attached inorganic plates of Examples 1 to 4 and Comparative Example 1, and the inorganic plate of Reference Example 1 in the wavelength range of 190 nm to 400 nm.

[0074] 5, it was confirmed that the film-coated inorganic plates of Examples 1 to 4 have high ultraviolet transmittance in the deep ultraviolet region. In particular, it was confirmed that the film-coated inorganic plates of Examples 1 and 2 have significantly improved ultraviolet transmittance in the deep ultraviolet region.

[0075] From the above, it was confirmed that the film-coated inorganic plates of Examples 1 to 4 have high UV transmittance in the deep ultraviolet range, while having a smaller contact angle with pure water than the film-coated inorganic plate of Comparative Example 1, and can improve the airtightness within a package containing an optical element.

[0076] (Reference examples 2~5) In Reference Examples 2 to 5, a film-coated inorganic board was obtained in the same manner as in Example 2, except that the thickness of the SiO2 layer was set as shown in Table 1 below.

[0077] [evaluation] (Highly Accelerated Life Test (HAST Test)) A highly accelerated life test (HAST test) was performed on the inorganic plates with the film of Example 2 and Reference Examples 2 to 5, and the presence or absence of cracks in the entire anti-reflective film after the HAST test was evaluated according to the following evaluation criteria. The HAST test was performed using a HAST CHAMBER (manufactured by ESPEC, product number "EHS-211M") at a temperature of 134°C and a humidity of 95% for 24 hours. In this evaluation, the cracks in the entire anti-reflective film were confirmed to be peeling at the interface between the MgF2 film and the SiO2 film.

[0078] <Evaluation criteria> A: No cracks in the anti-reflective coating after HAST test B: After the HAST test, less than 50% of the anti-reflective coating had cracks. C: After the HAST test, more than 50% of the anti-reflective coatings had cracks.

[0079] The results are shown in Table 1 below.

[0080] [Table 1] [Explanation of symbols]

[0081] 1, 1A, 1B...Inorganic plate with membrane 2…Inorganic board 2a…First main surface 2b…Second main surface 3a…Surface 3...First anti-reflection coating 4, 4B…Second anti-reflection coating 5…Magnesium fluoride layer 6...Silicon oxide layer 11. Package 12…Case body 12a...Bottom 12b...Side wall part 12c…Top surface 13...Image sensor 14...Joining material

Claims

1. an inorganic plate having ultraviolet light transmissibility and having a first main surface and a second main surface opposed to each other; an anti-reflection film provided on the first main surface of the inorganic plate; Equipped with The anti-reflection film is a magnesium fluoride layer provided on the first main surface of the inorganic plate; A silicon oxide layer provided on the outermost layer opposite to the inorganic plate; The inorganic plate with a film comprising:

2. 2. The film-coated inorganic board according to claim 1, wherein a thickness ratio of the magnesium fluoride layer to the silicon oxide layer (magnesium fluoride layer / silicon oxide layer) is 1.5 or more and 5 or less.

3. The film-coated inorganic substrate according to claim 1 or 2, wherein the inorganic substrate is made of quartz glass.

4. When the antireflection film is a first antireflection film, The optical fiber further includes a second anti-reflection film provided on the second main surface of the inorganic plate, The film-coated inorganic plate according to claim 1 , wherein the second anti-reflection film comprises a magnesium fluoride layer provided on the second main surface of the inorganic plate.

5. The film-coated inorganic plate according to claim 4 , wherein the second anti-reflection film includes a silicon oxide layer provided as an outermost layer on the side opposite to the inorganic plate.

6. The film-coated inorganic plate according to claim 1 , wherein the number of the magnesium fluoride layers included in the antireflection film is one.

7. The film-coated inorganic plate according to claim 1 , wherein the number of the silicon oxide layers included in the anti-reflection film is one.

8. 3. The film-coated inorganic plate according to claim 1, wherein a contact angle of pure water with respect to the surface of the film-coated inorganic plate on the anti-reflection film side is 7[deg.] or less.

9. 3. The film-coated inorganic plate according to claim 1, wherein the film-coated inorganic plate has a thickness of 0.5 mm and a light transmittance at a wavelength of 200 nm of 80% or more.

10. a case body having a bottom and a side wall; an optical element provided on the bottom of the case body; a cover member provided on the side wall portion of the case body; A package comprising: The cover member is the film-attached inorganic plate according to claim 1 or 2, the anti-reflection film of the film-coated inorganic plate and an upper surface of the side wall portion of the case body are bonded via a bonding material, thereby sealing the inside of the package containing the optical element.

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