Synthetic quartz glass substrate, method for manufacturing the same, and method for manufacturing window material for sealing optical element package

Abstract

SOLUTION: A synthetic quartz glass substrate in which two opposing main surfaces are both mirror surfaces, and at least a part of one main-surface side has a plurality of convex-shaped parts. The convex-shaped parts are each formed one by one in a plurality of sections partitioned in a lattice pattern. The convex-shaped parts include a non-spherical surface, wherein in thickness at vertices of the respective convex-shaped parts, a difference D between a thickest portion and a thinnest portion among all thicknesses at the vertices of the convex-shaped parts is 1 μm or less. The other main surface is a plane.EFFECT: From a synthetic quartz glass substrate of the present invention, a window material for sealing an optical element package can be efficiently manufactured which is suitable for sealing an optical element, particularly an optical element in a UV region and especially an optical element package in a deep ultraviolet region, the window material being capable of favorably controlling a light distribution characteristic with respect to light of the optical element.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a synthetic quartz glass substrate suitable as a material for a window material for sealing optical element packages that are applied to packages of optical elements, such as ultraviolet LEDs, which require control of the light distribution, and a method for manufacturing the same, as well as a method for manufacturing a window material for sealing optical element packages using a synthetic quartz glass substrate. [Background technology]

[0002] In recent years, devices that emit light in the ultraviolet region (hereinafter referred to as the UV region), such as the deep ultraviolet region, have been attracting attention for applications such as sterilization of industrial water and household use, and the curing process of ultraviolet-curable resins. Among these, ultraviolet light-emitting diodes (UV-LEDs) have been attracting attention as alternative materials to mercury lamps and other lamps that are subject to environmental regulations. For example, UVC-LEDs, which emit light in the deep ultraviolet region (wavelength 260 to 285 nm), have been actively developed in recent years.

[0003] Generally, LEDs have the characteristic of emitting light linearly forward, and in the case of LEDs in the visible light range, in order to control the light distribution characteristics, they are sealed by molding resin to create a lens shape. However, in the case of UV-LEDs, due to the characteristics of the element, the element is placed on a package carrier using the flip-chip method, and in surface-mount (SMD) packages, a reflector is often used to extract the light. The light that emerges from the package carrier is emitted with a wide-angle light distribution characteristic.

[0004] If resin is used as an encapsulant for elements that emit light in the UV region, it will cause the resin to deteriorate, gradually decreasing transmittance, etc. For this reason, resin-based encapsulants are not suitable for UV-LEDs, and synthetic quartz glass, which has high transmittance for wavelengths in the UV region and high long-term reliability, is often chosen as the encapsulant.

[0005] International Publication No. 2018-131668 (Patent Document 1) discloses components for ultraviolet light-emitting elements that have wavelength-selective light transmittance suitable for sterilization applications, and the quartz glass used therein. It also describes that such quartz glass can be manufactured by a gel casting method using a mold, and describes a method for applying such quartz glass to window components for ultraviolet light-emitting diodes (UV-LEDs).

[0006] Japanese Patent Application Laid-Open Publication No. 2018-002548 (Patent Document 2) describes a method for manufacturing a quartz glass component for ultraviolet LEDs that does not absorb light due to structural defects in the wavelength range of 200 nm to 400 nm by mixing silica powder and a binder component, molding the mixture, and then heat treating and vitrifying it into a transparent glass. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2018-131668 [Patent Document 2] Japanese Patent Application Publication No. 2018-002548 Summary of the Invention [Problem to be solved by the invention]

[0008] As mentioned above, synthetic quartz glass is the first choice for window materials in UV-LEDs because it allows short-wavelength ultraviolet light to pass through. However, synthetic quartz glass is known to be a difficult material to cut, and it is not easy from both a technical and economic standpoint to individually shape synthetic quartz glass substrates into lenses in order to control the light distribution characteristics using synthetic quartz glass.

[0009] The invention described in International Publication No. 2018-131668 (Patent Document 1) describes controlling light distribution using a quartz glass component obtained by melting the pre-vitrified material and pouring it into a mold, but does not describe the shape of the quartz glass component. This is thought to be because when pouring raw materials into a mold and vitrifying them, disadvantages such as incomplete shape control due to expansion and contraction cannot be overcome, and the shape can only be controlled to a certain extent. Furthermore, the quartz glass of the invention described in International Publication No. 2018-131668 (Patent Document 1) is a material different from pure synthetic quartz because it contains metal impurities, raising concerns about coloration due to solarization and reliability when exposed to ultraviolet light for long periods of time. On the other hand, Japanese Patent Application Laid-Open No. 2018-002548 (Patent Document 2) does not describe the shape of a quartz glass component for UV-LEDs that takes light distribution characteristics into consideration.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a synthetic quartz glass substrate suitable as a material for a window material for sealing optical element packages, which can be used to efficiently produce a window material for sealing optical element packages that provides the favorable light distribution characteristics required for optical elements, particularly optical elements in the UV region, and especially optical elements in the deep ultraviolet region, and a method for producing the same. Another aim of the present invention is to provide a method for producing a window material for sealing optical element packages from a synthetic quartz glass substrate. [Means for solving the problem]

[0011] As a result of intensive research into achieving the above-mentioned object, the inventors have discovered that by polishing one main surface of a synthetic quartz glass raw material substrate, the main surface of which has a mirror-finished surface, into a grid pattern so that a single convex portion is formed in each of a plurality of grid-like sections to produce a synthetic quartz glass substrate having a plurality of convex portions, and by dicing the synthetic quartz glass substrate having a plurality of convex portions formed into individual sections, it is possible to efficiently produce window materials for sealing optical element packages that have the favorable light distribution characteristics required for optical elements and are reliable even when exposed to light of a short wavelength such as deep ultraviolet for long periods of time, thereby completing the present invention.

[0012] Accordingly, the present invention provides the following synthetic quartz glass substrate, method for producing a synthetic quartz glass substrate, and method for producing a window material for sealing an optical element package. 1. Both of the opposing main surfaces are mirror surfaces, a plurality of convex portions on at least a portion of one main surface side; the convex portions are formed one by one in each of a plurality of sections that are divided into a grid pattern, the convex portion includes an aspherical surface, In the thickness at each apex of the convex portion, the difference D between the thickest part and the thinnest part of all the thicknesses at the apex of the convex portion is 1 μm or less, The other main surface is flat A synthetic quartz glass substrate characterized by: 2. The synthetic quartz glass substrate according to 1, wherein the mirror surface has a surface roughness (Ra) of 0.05 to 0.5 nm. 3. The synthetic quartz glass substrate according to 1 or 2, characterized in that it has a thickness of 0.3 to 2 mm. 4. The synthetic quartz glass substrate according to 1 or 2, wherein the aspherical surface is a surface whose curvature R varies within a range of 0.3 to 1 within the aspherical surface. 5. The synthetic quartz glass substrate according to 1 or 2, which is used as a window material for sealing optical element packages. 6. (A) preparing a synthetic quartz glass raw material substrate having a flatness TTV (Total Thickness Variation) of 1 μm or less and two opposing main surfaces that are both mirror-finished; (B) A step of forming a plurality of convex portions on at least a portion of one main surface of the synthetic quartz glass raw material substrate, wherein the polishing portion of the rotary processing tool is rotated by 1 to 500 mm so that one convex portion is formed in each of a plurality of sections divided into a lattice pattern on the one main surface side. 2 and polishing the surface by moving the polishing part of the rotary processing tool along the one main surface while rotating the polishing part. A method for producing a synthetic quartz glass substrate, comprising: 7. In the step (B), the rotation speed of the polishing part of the rotary processing tool is 500 to 12,000 rpm, and the processing pressure of the polishing part of the rotary processing tool is 9.8 × 10 -1 ~2.0×10 2 7. The method according to claim 6, wherein the compound is Pa. 8. In the step (B), the polishing is (B1) A plurality of rows of polishing along one direction, which combines polishing by moving the polishing part of the rotary processing tool along one direction and moving the polishing part of the rotary processing tool at a predetermined pitch along another direction perpendicular to the one direction; (B2) rotating the synthetic quartz glass raw material substrate by 90 degrees along the one main surface; (B3) Polishing along the other direction in a plurality of rows, which is a combination of polishing by movement of the polishing part of the rotary processing tool along the other direction perpendicular to the one direction and movement of the polishing part of the rotary processing tool at a predetermined pitch along the one direction perpendicular to the other direction. 7. The method for producing a semiconductor device according to claim 6, comprising: 9. The manufacturing method according to 6, characterized in that in step (B), polishing is carried out while supplying free abrasive particles to the contact area between the one main surface and the polishing portion of the rotary processing tool. 10. After the step (B), (C) a step of etching the surface portion on which the plurality of convex portions are formed. 7. The method for producing a semiconductor device according to claim 6, comprising: 11. The manufacturing method according to 10, characterized in that in step (C), the surface on which the plurality of convex portions are formed is etched by contacting it with an etching solution consisting of hydrofluoric acid or buffered hydrofluoric acid. 12. A step of obtaining a synthetic quartz glass substrate by the method according to any one of 6 to 11; (D) dicing the synthetic quartz glass substrate into individual sections; 1. A method for producing a window material for sealing an optical element package, comprising: [Effects of the Invention]

[0013] From the synthetic quartz glass substrate of the present invention, it is possible to efficiently produce a window material for sealing optical element packages that is suitable as a window material for sealing optical elements, particularly optical elements in the UV region, and especially optical element packages in the deep ultraviolet region, and that can well control the light distribution characteristics of the optical elements. Furthermore, the method for producing a synthetic quartz glass substrate and the method for producing a window material for sealing optical element packages of the present invention make it possible to efficiently produce a window material for sealing optical element packages that has a convex portion on one main surface. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing an example of an optical element package using a window material for sealing an optical element package of the present invention. [Figure 2] 1 is a cross-sectional view showing an example of a window material for sealing an optical element package of the present invention. [Figure 3] 1 is a perspective view showing an example of a synthetic quartz glass substrate of the present invention. [Figure 4] FIG. 10 is a diagram showing the light distribution characteristics of the light-emitting elements used in the examples and comparative examples. [Figure 5] 1 is a diagram showing the light distribution characteristics of light obtained through a window material for sealing an optical element package of the optical element package obtained in Example 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described in detail below. The optical element package has an optical element housed inside a housing member, and the optical element is sealed inside the housing member by a window material for sealing the optical element package. The window material for sealing the optical element package is provided at a position in the optical element package where light passes through. The window material for sealing the optical element package can be used in conjunction with an optical element, a housing member in which the optical element is placed, and an adhesive layer to form an optical element package comprising these.

[0016] Fig. 1 is a cross-sectional view showing an example of an optical element package using the window material for sealing an optical element package of the present invention. In this optical element package 10, the window material for sealing an optical element package 1 is provided so as to cover the opening of a storage member 2, and the window material for sealing an optical element package 1 and the storage member 2 are joined and sealed via an adhesive layer 3. An optical element 4 is stored inside the storage member 2. A reflective member is usually provided inside the storage member 2 together with the optical element, and the optical element package 10 shown in Fig. 1 also has a reflective member 5 inside the storage member 2.

[0017] The optical element targeted by the present invention may be either a light-emitting element or a light-receiving element, but is preferably a light-emitting element. The window material for sealing optical element packages of the present invention can be suitably used for optical elements capable of emitting or receiving light with a wavelength of 220 nm or more, and is suitably used for ultraviolet LED elements (UV-LEDs) and deep ultraviolet LED elements (UVC-LEDs) with a wavelength of 255 to 300 nm, particularly a central emission wavelength of 260 to 300 nm. The wavelength of deep ultraviolet light is usually 260 to 285 nm. Examples of light-emitting elements include UV-LEDs, particularly UVC-LEDs, using aluminum gallium nitride (AlGaN) or sapphire (Al2O3), and surface-emitting elements are preferred.

[0018] [Window material for sealing optical element packages] The window material for sealing optical element packages of the present invention has one convex portion on one main surface and the other main surface is flat, and is a window material for sealing an opening of a housing member that is open on one side through which light passes, while allowing light to pass through.

[0019] 2 is a cross-sectional view showing an example of the window material for sealing optical element packages of the present invention. This window material for sealing optical element packages 1 has one convex portion 11a on one main surface 11 side, and the other main surface 12 is flat.

[0020] The two opposing main surfaces of the window material for sealing optical element packages are preferably mirror-finished. A mirror-finished surface has a surface roughness that allows light to pass through without scattering. The surface roughness can be measured using an atomic force microscope (AFM). The surface roughness (Ra) is preferably 0.5 nm or less, and more preferably 0.3 nm or less. While a surface roughness (Ra) of 0 nm is ideal, forming such a surface is practically impossible, so the surface roughness (Ra) is usually 0.05 nm or more. The surface roughness (Ra) can be evaluated using a surface roughness (Ra) of 1 μm square, which is the same as commonly applied conditions. Note that a surface with a surface roughness (Ra) of 0.5 nm or less is usually a smooth surface that does not diffuse light and can be visually perceived as a mirror surface.

[0021] In window materials for sealing optical element packages, the shape (three-dimensional shape) of the surface (main surface) through which light passes is a major factor determining the light distribution characteristics. If the convex-shaped portion of the main surface of the window material for sealing optical element packages is a perfect sphere, the light distribution characteristics (directivity of light distribution) will be determined to be unique. Therefore, it is preferable that the convex-shaped portion include an aspherical surface. It is preferable that the curvature R of this aspherical surface is not constant within the aspherical surface. In particular, it is preferable that the curvature R of the aspherical surface varies within the aspherical surface. The range of change in this curvature R is not particularly limited, but is preferably 0.3 or more, more preferably 0.4 or more, and also preferably 1 or less, more preferably 0.8 or less. Within these ranges, light is less likely to be refracted when passing through the aspherical surface of the window material for sealing optical element packages, thereby reducing the possibility of multiple reflections and stray light within the window material for sealing optical element packages. Furthermore, particularly when used with light-emitting elements such as low-output UVC-LEDs, this allows for good light extraction, making it easier to obtain the required output. Furthermore, the light distribution angle can be controlled to a desired angle within a required range.

[0022] When designing an aspherical surface, the profile of the aspherical surface can be determined by determining the amount of sag (Z). The amount of sag (Z), which is the profile of the aspherical shape in a direction parallel to the optical axis, is expressed by the following formula (1).

number

[0023] In formula (1), A iThe higher-order terms contribute more to the shape change of the outer peripheral edge portion farther from the center than the lower-order terms. In order to be used by bonding to an optical element package, a gluing area is usually provided on the outer peripheral edge portion for applying an adhesive or the like. Furthermore, when a synthetic quartz glass substrate, which will be described later, is diced to obtain a window material for sealing an optical element package, the outer peripheral edge portion of each section becomes a cutting margin. Taking these factors into consideration, in the case of the window material for sealing an optical element package of the present invention, A i It is not necessary to consider the higher-order terms of the above, and in this case, the sag amount (Z) can be set to the sag amount (Z1) shown in the following formula (2).

number

[0024] When the amount of sag is determined by equation (2), the distance s from the optical axis is a parameter that is appropriately set depending on the point at which the light is to be measured, and can therefore be treated as a constant. Furthermore, since k is also a constant, the profile of the aspherical surface can be determined by setting the curvature R and determining the amount of sag (Z1). In the window material for sealing optical element packages of the present invention, the curvature R in equation (2) can be the curvature R of the aspherical surface of the convex portion. Therefore, the curvature R in equation (2) is preferably 0.3 or more, more preferably 0.4 or more, and preferably 1 or less, more preferably 0.8 or less.

[0025] Window materials for sealing optical element packages are made of synthetic quartz glass. In the case of window materials for sealing optical element packages used for optical elements in the UV region, particularly optical elements in the deep ultraviolet region, by forming the window material for sealing optical element packages from synthetic quartz glass, it is possible to transmit short wavelength light with high transmittance. Synthetic quartz glass makes it possible to control the light distribution characteristics without reducing the theoretical transmittance of the synthetic quartz glass. Because synthetic quartz glass exhibits high transmittance over a wide wavelength range, it can also be used for optical elements in the visible light region, near-infrared region, infrared region, etc.

[0026] The shape (shape of the main surface) of the window material for sealing optical element packages is usually quadrilateral (rectangle or square), and in this case, the size (size of the main surface) of the window material for sealing optical element packages is preferably 2 mm or more, more preferably 3.5 mm or more, in terms of the length of one side, and preferably 8 mm or less, more preferably 6.5 mm or less. This size is particularly suitable for window materials for sealing optical element packages that are mounted using the flip-chip method.

[0027] The thickness of the window material for sealing an optical element package can be appropriately selected taking into consideration the attenuation of the wave intensity of light, the mechanical strength of the optical element package, and the pressure difference between the outside of the window material for sealing an optical element package, i.e., the outside of the optical element package. The thickness of the window material for sealing an optical element package (the thickness at the portion where the distance between one main surface and the other main surface is longest) is preferably 0.3 mm or more, more preferably 0.5 mm or more, and preferably 2 mm or less, more preferably 1.5 mm or less.

[0028] The light distribution characteristics and light distribution angle of a window material for sealing an optical element package can be evaluated using a device such as a light distribution measuring instrument (e.g., LEDGON, manufactured by Instrument Systems). The window material for sealing an optical element package of the present invention can achieve the desired light distribution characteristics and light distribution angle of light passing through the window material for sealing an optical element package. In particular, light emitted from a surface-mounted package (SMD-PKG) in which an ultraviolet light-emitting diode (UV-LED), such as a deep ultraviolet light-emitting diode (UVC-LED), is mounted using a flip-chip method exhibits a characteristic batwing light distribution, in which the output directly above the light-emitting element is weaker than the output around it. However, the window material for sealing an optical element package of the present invention can be controlled to an orientation characteristic that eliminates the batwing light distribution. Furthermore, the orientation angle of light passing through the window material for sealing an optical element package can be appropriately selected depending on the application of the optical element and is not particularly limited. The orientation angle of light passing through the window material for sealing an optical element package is generally set in the range of 10 degrees to 100 degrees.

[0029] The window material for sealing optical element packages of the present invention may have an adhesive layer formed at the joint with a housing member, which is provided on the outer periphery of the window material for sealing optical element packages that is to be joined to the housing member. The adhesive layer can be formed by applying an adhesive layer to a predetermined position. The adhesive layer is typically provided on the outer periphery of the other main surface, which is flat. The width, thickness, etc. of the adhesive layer are appropriately set depending on the housing member.

[0030] The adhesive constituting the adhesive layer is not particularly limited, but is preferably a resin-based adhesive or a metal-based adhesive. Resin-based adhesives are formed from resin-containing resin pastes, have a network within their structure, and can form a three-dimensional structure, making them capable of adhering to substrates and also capable of adhering to many materials, including ceramics and metals. Examples of resin-based adhesives include ultraviolet-curing and silicone-based adhesives, such as TB3114 (manufactured by ThreeBond Co., Ltd.) and KER-3000-M2 (manufactured by Shin-Etsu Chemical Co., Ltd.). Resin-based adhesives can be applied to substrates by known methods.

[0031] On the other hand, metal-based adhesives include low-temperature solders such as Au-Sn and Zn-Sn, sintered materials using metal nanoparticles such as nanosilver particles, and fusions of low-temperature solders and nanoparticles. Commercially available adhesives made from low-temperature solders or sintered materials using nanoparticles can also be used. Examples of adhesives made from fusions of low-temperature solders and nanoparticles include fusions in which nanosilver particles with an average primary particle diameter of 100 nm or less are mixed with one or more solders selected from Sn-Bi, Sn-Zn-Bi, and Sn-Zn, which are known as low-temperature solder materials, and further containing one or more metals selected from zinc, zirconium, tellurium, antimony, and indium. When using metal-based adhesives as adhesives, they can be applied using application methods such as dispensers, screen printing, and inkjet printing. At the time of application, the adhesive is in a paste state. If necessary, the applied adhesive layer can be brought to a semi-cured state (B-Stage) by undergoing a preheating process.

[0032] [Synthetic quartz glass substrate] The synthetic quartz glass substrate of the present invention is suitable for use as a window material for sealing optical element packages. The window material for sealing optical element packages of the present invention, having a predetermined light distribution characteristic, can be obtained by cutting a synthetic quartz glass substrate having a plurality of convex portions formed thereon into individual pieces by a method such as dicing. Therefore, a synthetic quartz glass substrate having a plurality of convex portions on one main surface, one convex portion formed in each of a plurality of sections divided into a lattice pattern, and a flat other main surface is preferred. The plurality of convex portions need only be formed on at least a portion of one main surface, and may be formed on a portion or the entirety of one main surface.

[0033] 3 is a perspective view showing an example of a synthetic quartz glass substrate of the present invention. This synthetic quartz glass substrate 100 has a plurality of convex portions 11a over the entire surface of one main surface 11, with one convex portion 11a formed in each of a plurality of sections 13 divided into a lattice pattern, and the other main surface 12 is flat.

[0034] The convex portions formed on one main surface may be formed at a predetermined interval, but preferably have a shape in which the convex portions are in contact with each other and connected together. When the convex portions are in contact with each other and connected together, the one main surface has an uneven shape. Note that the portion of the one main surface other than the portion where the convex portions are in contact with each other and connected together, for example, the outer peripheral edge portion of the synthetic quartz glass substrate, may be flat, and when the convex portions are formed at a predetermined interval, the space between adjacent convex portions may be flat, and these planes may be, for example, substantially parallel to the other main surface.

[0035] From the viewpoint of obtaining a window material for sealing optical element packages from the synthetic quartz glass substrate, it is preferable that both of the two opposing main surfaces of the synthetic quartz glass substrate are mirror-finished. These mirror-finished surfaces can be the same as the mirror-finished main surfaces of the window material for sealing optical element packages. In particular, it is preferable that the mirror-finished surfaces of the synthetic quartz glass substrate have a surface roughness (Ra) of 0.05 to 0.5 nm.

[0036] The surface of the convex portion of the synthetic quartz glass substrate can be the same as the surface of the convex portion of the window material for sealing optical element packages. In particular, the convex portion of the synthetic quartz glass substrate preferably includes an aspherical surface. Furthermore, although not particularly limited, this aspherical surface is preferably a surface whose curvature R varies within the range of 0.3 to 1 within the aspherical surface.

[0037] The synthetic quartz glass substrate is made of synthetic quartz glass, similar to the window material for sealing an optical element package.

[0038] The shape (shape of the main surface) of the synthetic quartz glass substrate is preferably quadrangular (rectangular or square) or circular. The size of the synthetic quartz glass substrate can be appropriately selected taking into consideration the productivity of the window material for sealing optical element packages, etc. The size of the synthetic quartz glass substrate (size of the main surface) is not particularly limited, but from the viewpoints of ease of processing and productivity, when the shape of the main surface is quadrangular, the length of one side is preferably 100 mm or more and preferably 200 mm or less, and when the shape of the main surface is circular, the diameter Φ is preferably 100 mm or more and preferably 200 mm or less, for example.

[0039] The thickness of the synthetic quartz glass substrate can be appropriately selected taking into consideration the attenuation of light waves emitted from the optical element package obtained from the synthetic quartz glass substrate, the mechanical strength of the optical element package obtained from the synthetic quartz glass substrate, and the pressure difference with the outside of the window material for sealing the optical element package obtained from the synthetic quartz glass substrate, i.e., the outside of the optical element package. The thickness of the synthetic quartz glass substrate (the thickness at the part with the longest distance between one main surface and the other main surface) is preferably 0.3 mm or more, more preferably 0.5 mm or more, and preferably 2 mm or less, more preferably 1.5 mm or less.

[0040] Furthermore, in the synthetic quartz glass substrate, the difference D between the thickest and thinnest portions of the thickness at the apex of each convex portion formed on one main surface (the thickness of the portion of each convex portion where the distance between one main surface and the other main surface is the longest) at all apexes of the convex portions is preferably 1 μm or less, more preferably 0.7 μm or less, even more preferably 0.5 μm or less, and particularly preferably 0.2 μm or less. This difference D is ideally 0 μm, but the practical lower limit is, although not particularly limited, 0.1 μm or more. This difference D affects the thickness tolerance of window materials for sealing optical element packages. To satisfy this difference D, it is preferable that the apex of a convex portion formed from a synthetic quartz glass raw material substrate having a predetermined flatness TTV (described later) is located on one main surface of the synthetic quartz glass raw material substrate before the convex portions are formed.

[0041] [Method of manufacturing synthetic quartz glass substrates] The synthetic quartz glass substrate of the present invention is (A) preparing a synthetic quartz glass raw material substrate; (B) forming a plurality of convex portions on one main surface of the synthetic quartz glass raw material substrate, by bringing a polishing part of a rotary processing tool into contact with the one main surface and moving the polishing part of the rotary processing tool along the one main surface while rotating, so that one convex portion is formed in each of a plurality of sections divided into a lattice pattern on the one main surface side, and polishing the one main surface; The plurality of convex portions may be formed on at least a part of one of the main surfaces, and may be formed on a part or the entirety of the one of the main surfaces.

[0042] The synthetic quartz glass raw material substrate prepared in step (A) preferably has two opposing main surfaces that are mirror-finished, from the viewpoint of obtaining a synthetic quartz glass substrate from the synthetic quartz glass raw material substrate and obtaining a window material for sealing optical element packages from the synthetic quartz glass substrate. These mirror-finished surfaces may be the same as the mirror-finished main surfaces of the window material for sealing optical element packages or the mirror-finished main surfaces of the synthetic quartz glass substrate. In particular, it is preferable that the mirror-finished surfaces of the synthetic quartz glass raw material substrate have a surface roughness (Ra) of 0.05 to 0.5 nm.

[0043] The synthetic quartz glass raw material substrate prepared in step (A) is preferably in the form of a flat plate that can be easily shaped. The shape (shape of the main surface) of the synthetic quartz glass raw material substrate can be the same as that of the synthetic quartz glass substrate. The size of the synthetic quartz glass raw material substrate can be appropriately selected taking into consideration productivity and the like, from the viewpoint of obtaining window materials for sealing optical element packages by dividing the synthetic quartz glass substrate. The size of the synthetic quartz glass raw material substrate can also be the same as that of the synthetic quartz glass substrate.

[0044] The thickness of the synthetic quartz glass raw material substrate can be appropriately selected taking into consideration the attenuation of the wave intensity of light in the optical element package obtained from the synthetic quartz glass substrate, the mechanical strength of the optical element package obtained from the synthetic quartz glass substrate, and the pressure difference with the outside of the window material for sealing the optical element package obtained from the synthetic quartz glass substrate, i.e., the outside of the optical element package. The thickness of the synthetic quartz glass raw material substrate (the thickness at the part where the distance between one main surface and the other main surface is longest) can be the same as that of the synthetic quartz glass substrate.

[0045] From the viewpoint of obtaining a synthetic quartz glass substrate from the synthetic quartz glass raw material substrate and obtaining a window material for sealing an optical element package from the synthetic quartz glass substrate, it is preferable that the synthetic quartz glass raw material substrate have high flatness in order to suppress variation between the obtained window materials for sealing an optical element package. The flatness of the synthetic quartz glass raw material substrate can be evaluated by flatness TTV (Total Thickness Variation). The flatness TTV of the synthetic quartz glass raw material substrate is preferably 1 μm or less, more preferably 0.7 μm or less, even more preferably 0.5 μm or less, and particularly preferably 0.2 μm or less. The TTV is ideally 0 μm, but the practical lower limit is, although not particularly limited, 0.1 μm or more. It is sufficient that the TTV satisfies the above range in the range excluding the outer peripheral edge of the substrate, for example, in the range excluding the range up to 2 mm from the outer periphery of the substrate. In particular, when the substrate is a circular substrate, it is preferable that the above range is satisfied in the range excluding the outer peripheral edge of the substrate.

[0046] A synthetic quartz glass raw material substrate can be obtained, for example, by subjecting a synthetic quartz glass ingot to slicing, chamfering, lapping, a polishing step for mirror finishing, a flatness measurement step, and a precision polishing step. In the precision polishing step, batch double-sided polishing is common, but single-sided polishing or single-wafer polishing, or a combination of these, may also be used.

[0047] In step (B), a plurality of convex portions are formed on one main surface of the synthetic quartz glass raw material substrate. A partial polishing technique using a rotary tool can be used to form the convex portions. For example, the pitch of the convex portions to be formed can be set so that the final window material for sealing optical element packages has the desired size, and partial polishing can be performed by linearly moving the rotary tool along the main surface of the substrate so that the amount of polishing is constant.

[0048] The rotary processing tool can preferably be a router-type rotary processing tool. The material of the polishing part of the rotary processing tool that comes into contact with the synthetic quartz glass raw material substrate is not limited as long as it can grind the substrate surface, but from the viewpoint of reducing polishing damage, it is preferable to select from polyurethane, felt buffs, rubber, cerium pads, etc., with a hardness of A50 to 75 (JIS K 6253 standard). Examples of the three-dimensional shape of the polishing part of the rotary processing tool include a donut shape (circular ring shape), a cylinder shape, a bullet shape, a truncated cone shape, a disk shape, and a barrel shape.

[0049] The contact area between the polishing part of the rotary processing tool and the synthetic quartz glass raw material substrate is preferably 1 mm 2 More than 10mm, preferably 2 More than 500 mm 2 Less than 300mm, preferably 2 The contact area is 1mm or less. 2 If the contact area is narrower, fine processing is possible, but the processing time may be longer and productivity may be lower. 2 If the width is wider, the convex portion will become larger, making it difficult to form the desired shape. Furthermore, the amount of deformation of the polishing portion of the rotary processing tool due to wear is likely to increase, which may result in variations in the convex portions during the processing sequence. Furthermore, the portions other than the convex portion will become larger, which may increase the width of the dicing street when cutting window materials for sealing optical element packages from the synthetic quartz glass substrate, reducing the number of window materials for sealing optical element packages that can be obtained from a single synthetic quartz glass substrate and potentially reducing productivity.

[0050] In this partial polishing, the shape of the synthetic quartz glass raw material substrate is measured in advance, and the polishing amount is set so that the surface of the convex portion becomes a predetermined aspheric surface. The polishing amount can be controlled by the rotation speed of the polishing part of the rotary processing tool and the processing pressure of the polishing part of the rotary processing tool.

[0051] The rotation speed of the polishing part of the rotary processing tool is preferably 500 rpm or more, more preferably 1000 rpm or more, and preferably 12000 rpm or less, more preferably 8000 rpm or less. If the rotation speed is 500 rpm or more, a sufficient amount of polishing can be obtained, and problems such as unpolished areas resulting in inability to process into the desired shape and problems such as a slow polishing rate and low productivity can be reduced. On the other hand, if the rotation speed is 12000 rpm or less, the strength of the polishing part contacting the main surface becomes appropriate, and the occurrence of scratches and the resulting reduction in the strength of the window material for sealing optical element packages, as well as problems such as excessive polishing that make it impossible to form the desired shape, can be suppressed.

[0052] The processing pressure of the polishing part of the rotary processing tool is preferably 9.8 × 10 -1 Pa (approx. 1g / mm 2 ) or more, more preferably 2.0 × 10 Pa (approximately 20 g / mm 2 ) or more, and 2.0 × 10 2 Pa (about 200g / mm 2 ) or less, more preferably 1.5 × 10 2 Pa (about 150g / mm 2 ) or less. The processing pressure is 9.8 × 10 -1 If the processing pressure is 2.0×10 Pa or more, the problem of not being able to form a desired shape due to insufficient processing can be reduced, and production efficiency is good. 2 If the pressure is less than or equal to Pa, the occurrence of scratches can be suppressed, and the wear of the polished portion can also be suppressed.

[0053] The moving speed of the polishing section (rotary processing tool) is preferably constant in order to reduce variations among window materials for sealing optical element packages obtained from synthetic quartz glass substrates.

[0054] In the step (B), polishing is performed so that one convex portion is formed in each of the plurality of sections divided into a grid pattern, for example. (B1) Polishing along a single direction in a plurality of rows, which is a combination of polishing by moving the polishing part of the rotary processing tool along a single direction and moving the polishing part of the rotary processing tool at a predetermined pitch along another direction perpendicular to the single direction; (B2) rotating the synthetic quartz glass raw material substrate by 90 degrees along one main surface; (B3) Polishing along a plurality of rows of other directions, which is a combination of polishing by moving the polishing part of the rotary processing tool along another direction perpendicular to the one direction and moving the polishing part of the rotary processing tool at a predetermined pitch along the one direction perpendicular to the other direction. In this polishing, it is preferable to polish so that the apex of the convex portion formed from the synthetic quartz glass raw material substrate is positioned on one of the main surfaces of the synthetic quartz glass raw material substrate before the convex portion was formed (so that the apex of the convex portion is not polished).

[0055] In each of (B1) and (B3), the polishing by movement along one direction and the polishing by movement along the other direction may be polishing by unidirectional movement of the polishing part (rotary processing tool) (one-way polishing) or polishing by reciprocating movement of the polishing part (rotary processing tool) (reciprocating polishing). Furthermore, in each of (B1) and (B3), polishing may or may not be performed during movement at a predetermined pitch. Furthermore, in (B2), rotation may involve rotating the synthetic quartz glass raw material substrate or rotating the direction of movement of the rotary processing tool.

[0056] The area where the polishing in one direction by the polishing part of the rotary tool intersects with the polishing in the other direction (the vertices of the grid-like sections) is polished twice as hard and is the area that is polished the most. The area including this area and through which the center of the polishing part of the rotary tool passes is located on the dicing street when cutting the window material for sealing optical element packages from the synthetic quartz glass substrate. The area near the dicing street is the outer periphery of the window material for sealing optical element packages obtained from the synthetic quartz glass substrate. This area is usually the overlap area where an adhesive layer is formed, so it does not directly affect the alignment characteristics. Therefore, the effect of this area on the light distribution characteristics does not usually need to be considered.

[0057] The polishing in step (B) may be dry or wet. Abrasive particles are usually used for polishing, but since it is preferable to constantly supply new abrasive particles to the processing tool while polishing, it is preferable to polish while supplying free abrasive particles to the contact area between one main surface of the synthetic quartz glass raw material substrate and the polishing part of the rotary processing tool. The free abrasive particles may be supplied in the form of a slurry. In this case, examples of the free abrasive particles include silica, cerium oxide, alundum, white alundum (WA), alumina, zirconium oxide, SiC, diamond, titanium oxide, and germania. The average primary particle diameter of the free abrasive particles is preferably 10 nm to 10 μm. The free abrasive particles can be used as a slurry dispersed in water.

[0058] A substrate on which a convex portion has been formed by polishing usually has accumulated processing stress, so it is preferable to release the processing stress. It is also preferable to adjust the surface condition of the polished surface. Therefore, in the method for producing a synthetic quartz glass substrate of the present invention, after step (B), (C) A step of etching the surface portion on which the plurality of convex portions are formed. The etching is preferably chemical etching, and it is preferable to carry out an etching treatment in which the surface on which the plurality of convex portions is formed is brought into contact with an etching solution. The etching treatment can release stress in the substrate and also adjust the surface state of the convex portions.

[0059] The etching solution preferably used is an etching solution made of hydrofluoric acid or buffered hydrofluoric acid. The concentration of hydrogen fluoride in hydrofluoric acid or buffered hydrofluoric acid is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less. If the hydrogen fluoride concentration is 1% by mass or more, a sufficient effect of releasing processing stress can be obtained, improving production efficiency. Furthermore, if the hydrogen fluoride concentration is 20% by mass or less, excessive etching is not performed, and the possibility of the shape of the convex portion being extremely deformed by etching can be reduced.

[0060] The etching treatment may be performed by immersing the surface on which the plurality of convex portions is formed in an etching solution, or by pouring the etching solution onto the surface on which the plurality of convex portions is formed. The etching treatment may be performed in batches or single wafers. The etching time may be appropriately selected within a range of preferably 3 minutes or more, preferably 20 minutes or less, and more preferably 15 minutes or less. When the etching treatment time is 3 minutes or more, an etching solution of an appropriate concentration can be used to release stress and easily adjust the surface condition. On the other hand, when the etching treatment time is 20 minutes or less, the possibility of defects caused by redeposition of glass components dissolved from the surface and a decrease in productivity can be suppressed. After the etching treatment, the substrate can be appropriately washed and dried.

[0061] [Method of manufacturing window material for sealing optical element packages] The obtained synthetic quartz glass substrate is cut into individual pieces (small pieces) by a method such as dicing into each lattice-shaped section from the obtained synthetic quartz glass substrate, whereby a window material for sealing an optical element package can be manufactured. The window material for sealing an optical element package of the present invention can be produced by the steps of: obtaining a synthetic quartz glass substrate by the above-mentioned method; (D) cutting the synthetic quartz glass substrate into individual sections; It can be produced by a method comprising:

[0062] In the step of dividing the substrate into individual pieces by dicing, the dicing conditions are not particularly limited, and the dicing can be performed according to a conventional method. For example, when dicing is performed by a blade method, the dicing conditions are appropriately selected depending on the thickness of the synthetic quartz glass substrate.

[0063] To prevent the blade from breaking during processing due to insufficient blade rigidity caused by a blade that is too thin, and to reduce losses due to the wide dicing street caused by a blade that is too thick, the blade thickness is preferably 0.1 mm or more, more preferably 0.2 mm or more, and preferably 0.8 mm or less, more preferably 0.6 mm or less. Furthermore, if the cutting speed is too slow, the processing time increases, reducing productivity, while if it is too fast, the synthetic quartz glass substrate is more likely to be damaged (breaks or cracks). From these viewpoints, the cutting speed is preferably 1 mm / sec or more, more preferably 3 mm / sec or more, and preferably 50 mm / sec or less, more preferably 40 mm / sec or less. If the synthetic quartz glass substrate is thick, dicing can be performed in multiple stages. The above-mentioned ranges can also be applied to the dicing conditions for each stage in the case of multiple stages, and multiple dicing stages under the same or different conditions can be combined. [Example]

[0064] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0065] [Example 1] A synthetic quartz glass plate with a square main surface (main surface size: 150 mm × 150 mm) sliced ​​from the ingot was lapped using a planetary motion double-sided lapping machine and then roughly polished using a planetary motion double-sided polishing machine. It was then precision-polished using a nonwoven polishing cloth with a slurry of cerium oxide (HL-10, manufactured by Mitsui Mining & Smelting Co., Ltd.) dispersed as free abrasive particles in water. The average primary particle size was smaller than that of the particles used in the rough polishing. A synthetic quartz glass base substrate with a thickness of 1 mm and two mirror-finished main surfaces was obtained. The flatness (TTV) of the resulting synthetic quartz glass base substrate was 0.57 μm. Furthermore, the surface roughness (Ra) was measured using an atomic force microscope (AFM) in a 1 μm × 1 μm measurement area, and Ra was 0.12 nm.

[0066] Next, this synthetic quartz glass raw material substrate was set in a partial polishing machine. The partial polishing machine was configured so that the processing tool was attached to a motor, allowing it to rotate, and so that the rotating processing tool could be pressurized with air. The rotating processing tool was a bullet-shaped felt buff tool (manufactured by Nippon Precision Machinery Works Co., Ltd., F3606) with a polishing part having a diameter of 6 mm and a diameter length of 13 mm. The polishing part and the synthetic quartz glass raw material substrate were separated by 200 mm. 2 The contact area was 5000 rpm and the processing pressure was 1.5 × 10 2 Pa (about 150g / mm 2 In this polishing, a slurry in which colloidal silica was dispersed as free abrasive particles in water was supplied as a polishing liquid to the contact area between the main surface and the polishing part of the rotary processing tool.

[0067] First, one main surface of the synthetic quartz glass raw material substrate, which was the object to be polished, was polished back and forth linearly in one direction. Then, a polishing unit (rotary processing tool) was moved in another direction perpendicular to the first direction at a pitch of 3.6 mm, and the operation of polishing back and forth linearly in one direction on one main surface was repeated. Next, the synthetic quartz glass raw material substrate was rotated 90 degrees along one main surface. After the rotation, first, one main surface of the synthetic quartz glass raw material substrate, which was the object to be polished, was polished back and forth linearly in the other direction. Then, the polishing unit (rotary processing tool) was moved in one direction perpendicular to the other direction at a pitch of 3.6 mm, and the operation of polishing back and forth linearly in the other direction on one main surface was repeated. This resulted in a substrate having an aspherical surface, in which convex portions including a surface with a curvature R varying within the aspherical surface within a range of 0.5 to 0.8 were formed in each of a plurality of lattice-shaped sections. In this case, the apex of the formed convex portion was a portion that was not substantially polished by the polishing process portion.

[0068] The resulting substrate was then etched by immersion in buffered hydrofluoric acid (16BHF, manufactured by Morita Chemical Industry Co., Ltd.) for 10 minutes to obtain a synthetic quartz glass substrate. The difference D in thickness at each apex of the convex portions of the resulting synthetic quartz glass substrate between the thickest and thinnest points of all the thicknesses at the apex of the convex portions was 0.57 μm.

[0069] Next, the synthetic quartz glass substrate was diced into individual sections with a dicing street width of 50 μm to obtain a window material for sealing optical element packages, with a main surface size of 3.5 mm × 3.5 mm and a thickness of approximately 1 mm, and with a convex portion formed on the surface, the surface being aspherical and including a surface with a curvature R that varies within the aspherical surface within a range of 0.5 to 0.8.

[0070] Next, 30 pieces were randomly selected from the obtained window material for sealing optical element packages, and 30 optical element packages were fabricated. First, a UVC-LED (center wavelength 265 nm) with a light distribution angle of 125 degrees was prepared, and its light distribution characteristics were measured using a small light distribution measuring device (LEDGON, manufactured by Instrument System). Figure 4 shows the light distribution characteristics of the light-emitting element.

[0071] Next, a UVC-LED was housed in a surface-mount package (SMD-PKG) carrier, and the opening of the SMD-PKG carrier was bonded to the flat surface side (the other main surface side) of the window material for sealing the optical element package by applying a silicone adhesive, KER-3000-M2 (manufactured by Shin-Etsu Chemical Co., Ltd.), in the shape of a window frame, thereby sealing the optical element and obtaining a UVC-LED SMD-PKG.

[0072] Next, the UVC LEDs in the SMD-PKGs were turned on, and the light distribution characteristics and light distribution angle of 30 UVC-LED SMD-PKGs were measured under simulated far-field conditions using a compact light distribution measuring device (LEDGON, manufactured by Instrument System). Figure 5 shows the light distribution characteristics of the light emitted through the window material for sealing optical element packages. The light distribution characteristics of the light emitted through the window material for sealing optical element packages eliminated the batwing light distribution of the UVC-LEDs and focused the light from the UVC-LEDs. The light distribution angle of the light emitted through the window material for sealing optical element packages was within the range of 50±1° for all 30 UVC-LED SMD-PKGs, which was significantly lower than the light distribution angle of the light from the UVC-LEDs (125°). Furthermore, in this case, the variation in the light distribution angle of the light emitted through the window material for sealing optical element packages was kept to within ±1°, indicating minimal variation.

[0073] [Example 2] A synthetic quartz glass plate with circular main surfaces (200 mm diameter) sliced ​​from an ingot was lapped using a planetary double-sided lapping machine and then roughly polished using a planetary double-sided polishing machine. It was then precision-polished using a nonwoven polishing cloth and a water-based slurry containing cerium oxide (HL-10, manufactured by Mitsui Mining & Smelting Co., Ltd.) with a smaller average primary particle size than the particles used in the rough polishing. A synthetic quartz glass base substrate with a thickness of 0.3 mm and two mirror-finished main surfaces was obtained. The total thickness variation (TTV) of the resulting synthetic quartz glass base substrate, excluding a 2 mm radius from the periphery of the main surfaces, was 0.13 μm. Furthermore, the surface roughness (Ra) was measured using an atomic force microscope (AFM) in a 1 μm × 1 μm measurement area, and was found to be 0.15 nm.

[0074] Next, this synthetic quartz glass raw material substrate was set in a partial polishing machine. The partial polishing machine was configured so that the processing tool was attached to a motor and could rotate, and so that the rotating processing tool could be pressurized with air. The rotating processing tool used was a mounted grindstone (Minitor Co., Ltd., Blue Gritstone CA1035) impregnated with WA (white alundum) abrasive grains, with a grinding part in the shape of a truncated cone with a diameter of 4 mm and a diameter length of 12 mm. The grinding part and the synthetic quartz glass raw material substrate were separated by 50 mm so that the light emitted by the window material for sealing optical element packages for UVC-LEDs, which will be described later, would have a Lambertian light distribution. 2 The contact area was 12,000 rpm and the processing pressure was 4.9 × 10 Pa (approximately 20 g / mm 2 In this polishing, no polishing liquid was used, and pure water was supplied to the contact area between the main surface and the polishing part of the rotary processing tool in order to remove the processing heat generated during the polishing.

[0075] First, one main surface of the synthetic quartz glass raw material substrate, which was the object to be polished, was polished back and forth linearly in one direction. Then, the polishing unit (rotary processing tool) was moved in another direction perpendicular to the first direction at a pitch of 5.9 mm, and the operation of polishing back and forth linearly in one direction on one main surface was repeated. Next, the synthetic quartz glass raw material substrate was rotated 90 degrees along one main surface. After the rotation, first, one main surface of the synthetic quartz glass raw material substrate, which was the object to be polished, was polished back and forth linearly in the other direction. Then, the polishing unit (rotary processing tool) was moved in one direction perpendicular to the other direction at a pitch of 5.9 mm, and the operation of polishing back and forth linearly in the other direction on one main surface was repeated. This resulted in a substrate having an aspherical surface, in which convex portions including a surface with a curvature R varying within the aspherical surface within a range of 0.3 to 0.5 were formed in each of a plurality of lattice-shaped sections. In this case, the apex of the formed convex portion was a portion that was not substantially polished by the polishing process portion.

[0076] The resulting substrate was then etched by immersion in buffered hydrofluoric acid (209BHF, manufactured by Morita Chemical Industry Co., Ltd.) for 15 minutes to obtain a synthetic quartz glass substrate. The difference D in thickness at each apex of the convex portions of the resulting synthetic quartz glass substrate between the thickest and thinnest portions of all the thicknesses at the apex of the convex portions was 0.13 μm.

[0077] Next, the synthetic quartz glass substrate was diced into individual sections with a dicing street width of 50 μm to obtain a window material for sealing optical element packages, with a main surface size of 5.8 mm × 5.8 mm and a thickness of approximately 0.3 mm, and with a convex portion formed on the surface, the surface being aspherical and including a surface whose curvature R varies within the range of 0.3 to 0.5 within the aspherical surface.

[0078] Next, 30 pieces were randomly selected from the obtained window material for sealing optical element packages, and 30 optical element packages were fabricated. First, a UVC-LED (center wavelength 265 nm) with a light distribution angle of 125 degrees was prepared, and its light distribution characteristics were measured using a small light distribution measuring device (LEDGON, manufactured by Instrument System).

[0079] Next, a UVC-LED was housed in a surface-mount package (SMD-PKG) carrier, and the opening of the SMD-PKG carrier was bonded to the flat surface side (the other main surface side) of the window material for sealing the optical element package by applying a silicone adhesive, KER-3000-M2 (manufactured by Shin-Etsu Chemical Co., Ltd.), in the shape of a window frame, thereby sealing the optical element and obtaining a UVC-LED SMD-PKG.

[0080] Next, the UVC LEDs in the SMD-PKGs were turned on, and a compact light distribution measuring device (LEDGON, manufactured by Instrument System) was used to measure the light distribution characteristics and light distribution angle of 30 UVC-LED SMD-PKGs under assumed far-field conditions. The light distribution characteristics of the light emitted through the window material for sealing optical element packages showed that the batwing light distribution of the UVC-LEDs was eliminated and the light from the UVC-LEDs was concentrated. The light distribution characteristics of the light emitted through the window material for sealing optical element packages was a Lambertian light distribution, and the half-power angle was within a ±1 degree range for all 30 UVC-LED SMD-PKGs. Furthermore, in this case, the half-power angle variation in the Lambertian light distribution of the light emitted through the window material for sealing optical element packages was kept small, at ±1 degree.

[0081] [Comparative Example 1] A synthetic quartz glass plate with a square main surface (main surface size: 150 mm × 150 mm) sliced ​​from the ingot was lapped using a planetary motion double-sided lapping machine and then roughly polished using a planetary motion double-sided polishing machine. It was then precision-polished using a nonwoven polishing cloth with a slurry of cerium oxide (HL-10, manufactured by Mitsui Mining & Smelting Co., Ltd.) dispersed as free abrasive particles in water. The average primary particle size was smaller than that of the particles used in the rough polishing. A synthetic quartz glass base substrate with a thickness of 1 mm and two mirror-finished main surfaces was obtained. The flatness (TTV) of the resulting synthetic quartz glass base substrate was 2.3 μm. Furthermore, the surface roughness (Ra) was measured using an atomic force microscope (AFM) in a 1 μm × 1 μm measurement area, and Ra was 0.12 nm.

[0082] Next, this synthetic quartz glass raw material substrate was set in a partial polishing machine. The partial polishing machine was configured so that the processing tool was attached to a motor, allowing it to rotate, and so that the rotating processing tool could be pressurized with air. The rotating processing tool was a bullet-shaped felt buff tool (manufactured by Nippon Precision Machinery Works Co., Ltd., F3606) with a polishing part having a diameter of 6 mm and a diameter length of 13 mm. The polishing part and the synthetic quartz glass raw material substrate were separated by 200 mm. 2 The contact area was 5000 rpm and the processing pressure was 1.5 × 10 2 Pa (about 150g / mm 2 In this polishing, a slurry in which colloidal silica was dispersed as free abrasive particles in water was supplied as a polishing liquid to the contact area between the main surface and the polishing part of the rotary processing tool.

[0083] First, one main surface of the synthetic quartz glass raw material substrate, which was the object to be polished, was polished back and forth linearly in one direction. Then, a polishing unit (rotary processing tool) was moved in another direction perpendicular to the first direction at a pitch of 3.6 mm, and the operation of polishing back and forth linearly in one direction on one main surface was repeated. Next, the synthetic quartz glass raw material substrate was rotated 90 degrees along one main surface. After the rotation, first, one main surface of the synthetic quartz glass raw material substrate, which was the object to be polished, was polished back and forth linearly in the other direction. Then, the polishing unit (rotary processing tool) was moved in one direction perpendicular to the other direction at a pitch of 3.6 mm, and the operation of polishing back and forth linearly in the other direction on one main surface was repeated. This resulted in a substrate having an aspherical surface, in which convex portions including a surface with a curvature R varying within the aspherical surface within a range of 0.5 to 0.8 were formed in each of a plurality of lattice-shaped sections. In this case, the apex of the formed convex portion was a portion that was not substantially polished by the polishing process portion.

[0084] The resulting substrate was then etched by immersion in buffered hydrofluoric acid (16BHF, manufactured by Morita Chemical Industry Co., Ltd.) for 10 minutes to obtain a synthetic quartz glass substrate. The difference D in thickness at each apex of the convex portions of the resulting synthetic quartz glass substrate between the thickest and thinnest points of all the thicknesses at the apex of the convex portions was 2.3 μm.

[0085] Next, the synthetic quartz glass substrate was diced into individual sections with a dicing street width of 50 μm to obtain a window material for sealing optical element packages, with a main surface size of 3.5 mm × 3.5 mm and a thickness of approximately 1 mm, and with a convex portion formed on the surface, the surface being aspherical and including a surface with a curvature R that varies within the aspherical surface within a range of 0.5 to 0.8.

[0086] Next, 30 pieces were randomly selected from the obtained window material for sealing optical element packages, and 30 optical element packages were fabricated. First, a UVC-LED (center wavelength 265 nm) with a light distribution angle of 125 degrees was prepared, and its light distribution characteristics were measured using a small light distribution measuring device (LEDGON, manufactured by Instrument System).

[0087] Next, a UVC-LED was housed in a surface-mount package (SMD-PKG) carrier, and the opening of the SMD-PKG carrier was bonded to the flat surface side (the other main surface side) of the window material for sealing the optical element package by applying a silicone adhesive, KER-3000-M2 (manufactured by Shin-Etsu Chemical Co., Ltd.), in the shape of a window frame, thereby sealing the optical element and obtaining a UVC-LED SMD-PKG.

[0088] Next, the UVC LEDs in the SMD-PKGs were turned on, and the light distribution characteristics and light distribution angles of the 30 UVC-LED SMD-PKGs were measured under assumed far-field conditions using a compact light distribution measuring device (LEDGON, manufactured by Instrument System). The light distribution characteristics of the light emitted through the window material for sealing optical element packages showed that the batwing light distribution of the UVC LEDs was eliminated, and the light from the UVC LEDs was concentrated. The light distribution angle of the light emitted through the window material for sealing optical element packages was within the range of 50±2 degrees for all 30 UVC-LED SMD-PKGs, which was significantly lower than the light distribution angle of the light from the UVC LEDs (125 degrees). Furthermore, in this case, the variation in the light distribution angle of the light emitted through the window material for sealing optical element packages was ±2 degrees, which was larger than that of Example 1. In this example, it is believed that the difference D in the synthetic quartz glass substrate was large, which resulted in large variations in the light distribution angle of the window material for sealing an optical element package. [Explanation of symbols]

[0089] 1. Window material for sealing optical element packages 2. Storage member 3 Adhesive layer 4 Optical Elements 5 Reflective material 10 Optical element package 11 One main surface 11a Convex shape part 12 Other main surface 13 plots 100 Synthetic quartz glass substrate

Claims

1. The two opposing main surfaces are both mirror surfaces, a plurality of convex portions on at least a portion of one main surface side; the convex portions are formed one by one in each of a plurality of sections that are divided into a grid pattern, the convex portion includes an aspherical surface, a difference D between the thickest part and the thinnest part of the thickness at each apex of the convex portion is 1 μm or less; The other main surface is flat A synthetic quartz glass substrate characterized by:

2. 2. The synthetic quartz glass substrate according to claim 1, wherein the mirror surface has a surface roughness (Ra) of 0.05 to 0.5 nm.

3. 3. The synthetic quartz glass substrate according to claim 1, wherein the thickness is 0.3 to 2 mm.

4. 3. The synthetic quartz glass substrate according to claim 1, wherein the aspherical surface has a curvature R that varies within a range of 0.3 to 1 within the aspherical surface.

5. 3. The synthetic quartz glass substrate according to claim 1, which is used as a window material for sealing optical element packages.

6. (A) preparing a synthetic quartz glass raw material substrate having a flatness TTV (Total Thickness Variation) of 1 μm or less and two opposing main surfaces that are both mirror-finished; (B) A step of forming a plurality of convex portions on at least a portion of one main surface of the synthetic quartz glass raw material substrate, wherein the polishing portion of the rotary processing tool is rotated by 1 to 500 mm so that one convex portion is formed in each of a plurality of sections divided into a lattice pattern on the one main surface side. 2 and polishing the surface by moving the polishing part of the rotary processing tool along the one main surface while rotating the polishing part. A method for producing a synthetic quartz glass substrate, comprising:

7. In the step (B), the rotation speed of the polishing part of the rotary processing tool is 500 to 12,000 rpm, and the processing pressure of the polishing part of the rotary processing tool is 9.8 × 10 -1 ~2.0 x 10 2 7. The method according to claim 6, wherein the SiO 2 is SiO 2 .

8. In the step (B), the polishing (B1) A plurality of rows of polishing along one direction, which combines polishing by moving the polishing part of the rotary processing tool along one direction and moving the polishing part of the rotary processing tool at a predetermined pitch along another direction perpendicular to the one direction; (B2) rotating the synthetic quartz glass raw material substrate by 90 degrees along the one main surface; (B3) polishing along the other direction in a plurality of rows, which is a combination of polishing by movement of the polishing part of the rotary processing tool along the other direction perpendicular to the one direction and movement of the polishing part of the rotary processing tool at a predetermined pitch along the one direction perpendicular to the other direction; The method of claim 6, comprising:

9. 7. The manufacturing method according to claim 6, wherein in the step (B), polishing is performed while supplying free abrasive particles to a contact portion between the one main surface and the polishing portion of the rotary machining tool.

10. After the step (B), (C) Etching the surface portion on which the plurality of convex portions are formed. The method of claim 6, comprising:

11. 11. The manufacturing method according to claim 10, wherein in the step (C), the surface on which the plurality of convex portions are formed is etched by contacting it with an etching solution made of hydrofluoric acid or buffered hydrofluoric acid.

12. A step of obtaining a synthetic quartz glass substrate by the method according to any one of claims 6 to 11; (D) dicing the synthetic quartz glass substrate into individual sections; 1. A method for producing a window material for sealing an optical element package, comprising:

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