Patent Description:
An ultraviolet LED configured to emit light in a deep ultraviolet wavelength band is expected to be applied in a wide range of fields, such as virus sterilization, drinking water, air purification, resin curing, decomposition of environmental pollutants, a food field, and various kinds of medical equipment.

A gas light source, such as a mercury lamp, has been used as an existing deep ultraviolet light source. However, a range of use of the gas light source is limited because of its short lifetime, its emission wavelength, which is limited only to an emission line of a gas, a substance contained therein that is harmful to a human body/environment, such as mercury, and an extremely large size and power consumption of the light source. Therefore, there has been an increasing demand for realization of an alternative technology. Under such circumstances, it is strongly desired to develop a mercury-free, low environmental-load, downsized, high-output ultraviolet LED, and an ultraviolet LED using a nitride-based semiconductor (AlGaN) has been actively developed.

The ultraviolet LED emits light having a wavelength of from <NUM> to <NUM>, and has a problem in that a lens made of a silicone resin, which has hitherto been used for a visible light LED, undergoes deterioration of the resin or does not transmit the light.

In addition, there is also a problem in that light extraction efficiency from an ultraviolet LED element is extremely low. Accordingly, a material that absorbs as little light as possible is required also for a window material or a lens material, and use of an optical member made of quartz glass has been considered (Patent Documents <NUM> and <NUM>).

However, there are problems in that, with a window plate made of quartz glass, light is diffused, and hence a desired light intensity is not obtained, and a hemispherical lens is difficult to mount on a package.

Meanwhile, an injection molding method is known as a method of manufacturing a quartz glass member with high accuracy in dimensions and shape (Patent Documents <NUM> and <NUM>).

This method can provide a transparent quartz glass body by degreasing and purifying a molded body, followed by firing, but has a problem in that purification treatment with chlorine or hydrogen chloride generates an optical absorption band at a wavelength of about <NUM> (<NUM> eV) due to an oxygen-deficient defect (Non Patent Document <NUM>).

In addition, there is a proposal of a method involving, after vitrification, repairing the oxygen-deficient defect with an atmosphere containing oxygen or an atmosphere containing water vapor. However, the method is limited in its effect to a quartz glass surface and requires treatment at high temperature. Accordingly, there is a risk of a reduction in transmittance due to an influence of contamination with an impurity (Patent Documents <NUM> and <NUM>).

In addition, in recent years, rapid progress has been made in shortening wavelengths of semiconductor light-emitting elements (LEDs). Of those, an ultraviolet LED having, as its emission region, ultraviolet light having a relatively long wavelength (commonly called UVA, and falling within a wavelength range of from <NUM> to <NUM>) has already been put into practical use for curing a UV-curable resin.

UVB (falling within a wavelength range of from <NUM> to <NUM>) and UVC (falling within a wavelength range of from <NUM> to <NUM>) each having a shorter wavelength than UVA are currently being intensively developed. In particular, UV light having a wavelength of around <NUM>, which is called a germicidal ray, has an intense germicidal action, and hence there is a demand that its practical use be soon achieved as inexpensive means for sterilizing water or sterilizing air.

It is said that there are significant technical obstacles between UVA and UVB or UVC. One of the obstacles is a substrate material, and another is a transmitting material. UVA is formed on a sapphire substrate (AI<NUM>O<NUM>), but UVB and UVC each require an AIN substrate due to lattice constant matching.

Meanwhile, for ultraviolet light of UVA, a window or a lens can be formed using an organic resin having a high UV transmission property, such as a silicone or Teflon (trademark). However, for ultraviolet light of UVB or UVC, such organic material is insufficient in terms of light transmission property, and is also insufficient in terms of durability against UV light. In addition, a borosilicate-based glass material having a satisfactory UV transmission property, which is often used for a UVA-LED also cannot be used due to problems with the light transmission property (even borosilicate glass hardly transmits ultraviolet light having a wavelength of <NUM> or less) and the durability.

For this reason, silica glass has been exclusively used as a window material or lens material for a UVB-LED or a UVC-LED (Patent Documents <NUM> and <NUM>). The silica glass has a high transmission property for UV light and also has high durability, and hence has sufficient characteristics as the window material or lens material for a UVB-LED or a UVC-LED. However, the silica glass needs polishing in order to constitute a smooth surface having a high light transmission property suitable as the window material or the lens material, and hence cannot integrally constitute a smooth surface in a member in which a plain surface and a spherical surface coexist. For example, when, as proposed in the present invention, an outer peripheral portion has a plain surface and a structure having a convex spherical surface shape is formed inside a central side, a planar silica glass plate material and a hemispherical lens need to be each independently produced, polished, and bonded to each other.

However, from the viewpoint of serving as a member for a UVB-LED or a UVC-LED, there is hardly any adhesive having a sufficient transmission property and sufficient durability in such wavelength region.

In addition, mounting of LEDs, not limited to ultraviolet LEDs, is classified into a shell-type package and an SMD-type package. An LED element is an extremely fragile semiconductor element, and hence needs to be kept in a sealed environment for the purpose of preventing deterioration due to moisture or the like in the atmosphere. The shell-type package is a package in which a surrounding space of an LED is sealed with a resin, and is widely used as an inexpensive LED package.

Meanwhile, the SMD-type package has a structure in which an LED element is mounted on a concave recessed portion, a bottom surface and a side wall surface are each constituted of a reflector, and an upper surface is tightly sealed with a window material for hermetic sealing (Patent Document <NUM>).

Further, when output is insufficient with one LED element, a multi-type package in which a plurality of elements are arranged in one package is also beginning to be widely used.

Document <CIT> is directed to an ultraviolet light emitting device. An ultraviolet light emitting element is placed on a sub-mount. A lens part formed of quartz glass, that allows the ultraviolet light emitted from the ultraviolet light emitting element to pass, is fixed on an upper surface of a side wall portion. The ultraviolet light emitted from the ultraviolet light emitting element has a peak wavelength of about <NUM> or less, and may be classified into a UV-A wavelength range, a UV-B wavelength range, and a UV-C wavelength range.

Document <CIT> describes an optical member of synthetic quartz glass for excimer lasers and a method for producing the same. A synthetic quartz glass molded article for optical window has an outer diameter of <NUM> and a thickness of <NUM>. The OH group-content of the resulting synthetic quartz glass molded article for the optical window of excimer lasers was determined by infrared spectrophotometric analysis and was found to be <NUM> ppm. The ultraviolet transmittance of the synthetic quartz glass molded article for optical window was determined by ultraviolet spectrophotometry and as a result, any absorption at <NUM> was not observed and the internal transmittance of the synthetic quartz glass molded article for optical window was found to be not less than <NUM>%.

A first object of the present invention is to provide a silica glass member to be used for hermetic sealing of an ultraviolet LED configured to emit ultraviolet light in a wavelength range of from <NUM> or more to <NUM> or less, in particular, a silica glass member for hermetic sealing of an ultraviolet surface mount device (SMD) LED element to be suitably used for hermetic sealing of, and as a transmission window material for, a surface mount-type package (commonly called an SMD) having an ultraviolet LED mounted thereon and configured to emit ultraviolet light in a wavelength range of from <NUM> or more to <NUM> or less. A second object of the present invention is to provide a method of manufacturing a quartz glass member for hermetic sealing of an ultraviolet LED, which involves repairing an oxygen-deficient defect so that there can be obtained a quartz glass member for an ultraviolet LED improved in light absorption at a wavelength of about <NUM> and free of absorption due to a structural defect at a wavelength of from <NUM> to <NUM>.

The invention provides an ultraviolet SMD LED element package according to independent claim <NUM>. Independent claim <NUM> is the corresponding method claim. Preferred embodiments of the present invention are described in the dependent claims. The embodiments which do not fall within the scope of the claims are to be interpreted as examples not forming part of the present invention but useful for a better understanding of the invention.

The transmittance measurement with the integrating sphere is described. In the transmittance measurement of silica glass in which internal scattering due to a bubble or a granular structure exists, a transmittance measurement apparatus based on a general optical system cannot distinguish between internal absorption and a scattering loss, and hence allows the scattering loss to be measured as absorption. Meanwhile, a transmittance measurement apparatus including the integrating sphere, which is applicable to UV light, enables also scattered light to be introduced into a photodetector, and hence enables an absorption amount excluding the scattering loss to be measured. In other words, an internal transmittance obtained by the transmittance measurement using the integrating sphere is considered not to include the scattering loss, and hence enables the scattering loss to be estimated through a comparison to an internal transmittance obtained by the general transmittance measurement. Specifically, the following equation holds- internal transmittance obtained by general transmittance measurement (=internal absorption+scattering loss)-internal transmittance obtained by integrating sphere measurement (internal absorption)=scattering loss. In actuality, even the integrating sphere measurement cannot pick up all the scattering loss, and hence it is reasonable to consider that part of the scattering loss is measured. However, the intensity of the scattering loss can be specified through this comparison.

The silica glass member for hermetic sealing of the present invention is silica glass suitable for a transparent window material and/or a lens material for an LED configured to emit ultraviolet light of UVB or UVC, in which the window material and the lens material, which have originally been separately cut out and subjected to polishing processing, are integrally formed, thereby having an advantage of being able to be inexpensively supplied. In addition, in this case, when a plurality of lens portions are simultaneously formed in one silica glass member for sealing, there is an advantage in that a further cost effect is obtained.

As specific means, powder of synthetic silica glass is mixed and kneaded with a binder, and the mixture is subjected to press molding in a mold for molding a required shape to provide a green body, which is subjected to heat treatment to be made transparent. Thus, a silica glass molded body for hermetic sealing of the present invention having a complicated shape integrally and homogeneously formed into a predetermined shape can be obtained.

Originally, some requirements need to be satisfied in order to constitute a window material or a lens material for ultraviolet light having a short wavelength, such as UVB or UVC, by mold molding using silica glass powder as a starting material. That is, the following are required in order to obtain the required transmittance, light durability, and moldability: the purity and particle size of the silica glass powder serving as the starting material be appropriately controlled; the inner surface finish of the molding mold be sufficiently smooth so as not to require post-polishing; structural defects of silica glass generated in the degreasing and molding steps be sufficiently suppressed/cured; and gaps between particles of the powder or a dissolved gas be sufficiently removed, to thereby reduce bubbles to prevent unnecessary scattered light from being emitted.

The integral molding of the silica glass member by the mold molding has a great advantage in terms of manufacturing method in that a plurality of lens portions can be simultaneously formed. Particularly among LED packages in recent years, there have been an increasing number of packages each having placed therein a plurality of LEDs for the purpose of increasing the output. In this case, it is important that the positional relationship between individual LEDs and lens portions be accurately adjusted.

In the present invention, a window material and lens-like convex portions are manufactured in a state of being integrally formed, and as a result, the position of each of the lens portions is determined as a transfer of a position designed as a mold. Accordingly, there is an advantage in that the position can be extremely accurately determined. As the mold molding of a silica glass member, besides the press molding, there are known injection molding, transfer molding, a slip casting method, and the like (Patent Documents <NUM> to <NUM>).

First, the present invention exhibits the remarkable effect capable of providing the silica glass member to be used for hermetic sealing of an ultraviolet LED configured to emit ultraviolet light in a wavelength range of from <NUM> to <NUM>, in particular, the silica glass member for hermetic sealing of an ultraviolet SMD LED element to be suitably used for hermetic sealing of, and as a transmission window material for, a surface mount-type package (SMD) having an ultraviolet LED mounted thereon and configured to emit ultraviolet light in a wavelength range of from <NUM> or more to <NUM> or less.

Secondly, the present invention exhibits the remarkable effect capable of providing the method of manufacturing a quartz glass member for hermetic sealing of an ultraviolet LED, which involves repairing an oxygen-deficient defect so that there can be obtained a quartz glass member for an ultraviolet LED improved in light absorption at a wavelength of about <NUM> and free of absorption due to a structural defect at a wavelength of from <NUM> to <NUM>.

Embodiments of the present invention are described below with reference to the attached drawings. However, these embodiments are described as examples, and it is understood that various modifications may be made thereto.

One embodiment of a silica glass member for hermetic sealing of an ultraviolet LED according to the present invention is described below. <FIG> are explanatory diagrams for illustrating a case in which ultraviolet SMD LED elements <NUM> are sealed with one embodiment of a silica glass member <NUM> for hermetic sealing according to the present invention forming part of the claimed invention.

<FIG> is a cross-sectional explanatory diagram, <FIG> is a planar explanatory diagram, and <FIG> is a schematic perspective explanatory diagram. In <FIG>, reference numeral <NUM> denotes a hermetic sealing container, which has a bottom wall <NUM> and a side wall <NUM>, and is configured to open upward through an opening <NUM>. The upper surface of an upper end outer peripheral portion <NUM> of the side wall <NUM> of the hermetic sealing container <NUM> is formed to be a plain surface to serve as a container outer periphery joining plain surface 22a. The ultraviolet SMD LED elements <NUM> are placed on the upper surface of the bottom wall <NUM>. In the example illustrated in <FIG>, there is illustrated an example in which two ultraviolet SMD LED elements <NUM> are placed. However, two or more ultraviolet SMD LED elements <NUM> may be arranged, and for example, four or six ultraviolet SMD LED elements <NUM> may be arranged.

The silica glass member <NUM> for hermetic sealing of the present invention is not particularly limited in terms of dimensions as long as the opening <NUM> of the hermetic sealing container <NUM> can be sealed therewith. For example, in the case of the example illustrated in <FIG>, the dimensions are set as follows: a width W of the silica glass member <NUM> for hermetic sealing illustrated in <FIG>: <FIG> mm, a length L of the silica glass member <NUM> for hermetic sealing illustrated in <FIG>: <FIG> mm, a diameter d of each of lens-like convex portions <NUM> illustrated in <FIG>: <FIG> mm, and a thickness t of a portion at a substrate joining plain surface 24a illustrated in <FIG> mm.

The silica glass member <NUM> for hermetic sealing includes a silica glass substrate 10A, which is homogeneously and integrally formed without an internal boundary, and is configured to emit light in a wavelength range of from <NUM> to <NUM>. The silica glass substrate 10A has a first surface <NUM> on an inside opposed to the ultraviolet SMD LED element <NUM> and a second surface <NUM> on an outside corresponding to the first surface <NUM>. The outer peripheral portion of the first surface <NUM> has formed therein the substrate joining plain surface 24a for joining to the container outer periphery joining plain surface 22a. Meanwhile, the second surface <NUM> on the outside corresponding to the first surface <NUM> has formed therein the lens-like convex portions <NUM> configured to process emitted light from the ultraviolet SMD LED elements <NUM>. In the example illustrated in <FIG>, there is illustrated an example in which two lens-like convex portions <NUM> are formed in a parallel state with a connecting flat portion <NUM> interposed therebetween, corresponding to the two ultraviolet SMD LED elements <NUM> being placed in the hermetic sealing container <NUM>.

With, reference to the configuration described above, its action is described. Under a state in which the container outer periphery joining plain surface 22a of the hermetic sealing container <NUM>, in which the two ultraviolet SMD LED elements <NUM> are placed on the bottom wall <NUM>, and the substrate joining plain surface 24a are joined to each other, the hermetic sealing container <NUM> is covered with the silica glass member <NUM> for hermetic sealing, to thereby bring the inside of the hermetic sealing container <NUM> into a hermetically sealed state. Thus, emitted light from the ultraviolet SMD LED elements <NUM> is processed with satisfactory light extraction efficiency.

The shape of the silica glass substrate 10A may be as illustrated in <FIG>, in which the entirety of the first surface <NUM> is formed to be a plain surface and the second surface <NUM> has formed therein the lens-like convex portions <NUM> each having a hemispherical shape. However, the shape of the silica glass substrate 10A is not limited thereto, and any other shape may also be adopted as long as the shape can process emitted light from the ultraviolet SMD LED elements <NUM>.

Examples of other shapes of the silica glass substrate 10A are illustrated in <FIG>. In the example illustrated in <FIG>, the two lens-like convex portions <NUM> are each formed in a hemispherical shape having formed therein a hollow portion <NUM>. In the example illustrated in <FIG>, as the two lens-like convex portions <NUM>, the lens-like convex portions <NUM> each having a hemispherical shape are formed in the second surface <NUM> as in <FIG>, while hanging enlarged portions <NUM> each having an ellipsoidal shape are formed in the first surface, corresponding to the two lens-like convex portions <NUM> each having a hemispherical shape. Also when the hermetic sealing container <NUM> in which the ultraviolet SMD LED elements <NUM> are placed is brought into a hermetically sealed state using the silica glass member <NUM> for hermetic sealing with the silica glass substrate 10A having the shape of each of <FIG>, emitted light from the ultraviolet SMD LED elements <NUM> can be processed with satisfactory light extraction efficiency, as with the example of <FIG>.

One embodiment of a method of manufacturing a quartz glass member for hermetic sealing of an ultraviolet LED according to the present invention, forming part of the claimed invention, is described below. In the manufacturing method of the present invention, an oxygen-deficient defect is generated by a chlorine-based gas to be used in purification treatment intended to remove a metal impurity, but heat treatment with an oxidizing atmosphere for repairing the oxygen-deficient defect is performed to repair the oxygen-deficient defect. Thus, there can be obtained a quartz glass member for hermetic sealing of an ultraviolet LED improved in light absorption at a wavelength of about <NUM> and free of absorption due to a structural defect at a wavelength of from <NUM> to <NUM>. An atmosphere containing oxygen and/or water vapor is suitably used as the oxidizing atmosphere.

In addition, in terms of transmittance, bubbles, surface shape, and the like, which are required characteristics for use as an optical member for an ultraviolet LED, characteristics equal to or higher than those of quartz glass produced by subjecting bulk quartz glass to grinding processing are required, and quartz glass to be suitably used for an optical member for an ultraviolet LED can be obtained by the following method.

In a molding step, after mixing of silica powder and binder component, the raw materials subjected to kneading involving degassing treatment may be molded with a metal mold. In a heat treatment step, the following steps are performed: a degreasing step at <NUM>,<NUM> or less with an atmosphere containing oxygen; a purification step for a metal impurity at <NUM>,<NUM> or less with an atmosphere containing hydrogen chloride; and a step of repairing an oxygen-deficient defect at a wavelength of about <NUM> at <NUM>,<NUM>'C or less with an oxidizing atmosphere. A vitrification step after the heat treatment step is suitably performed at <NUM>,<NUM> or less. An Al concentration in the silica powder serving as a main raw material is suitably <NUM> ppm or less. It is more preferred that heating treatment with a hydrogen atmosphere be performed after the vitrification step. With this, quartz glass to be suitably used for an optical member for an ultraviolet LED can be obtained.

The degassing treatment of the raw material has an effect of suppressing the generation of bubbles during the vitrification step.

Examples of the binder component include cellulose-based components (methyl cellulose, carboxymethyl cellulose, and hydroxyethyl alcohol), agar, vinyl-based components (polyvinyl alcohol and polyvinyl pyrrolidone), starch-based components (dialdehyde starch, dextrin, and polylactic acid), acrylic components (sodium polyacrylate and methyl methacrylate), and a plant viscous substance. Of those, polyvinyl alcohol or methyl cellulose is suitable.

When the temperature of the degreasing step exceeds <NUM>,<NUM>, crystallization proceeds during this step to make it difficult to perform vitrification into transparent glass again through the subsequent steps. Therefore, the degreasing step is suitably performed at <NUM>,<NUM> to <NUM>, more preferably <NUM>,<NUM> to <NUM>.

The purification step becomes more effective as its temperature increases. However, when the temperature exceeds <NUM>,<NUM>, shrinkage of a molded body proceeds to make it difficult for a gas to penetrate the inside of the molded body in the treatment with an atmosphere containing oxygen and/or water vapor in the next step, to thereby reduce the effect of repairing an oxygen-deficient defect. Therefore, the purification step is suitably performed at <NUM>,<NUM> to <NUM>, more preferably <NUM>,<NUM> to <NUM>,<NUM>.

When the temperature of the step of promoting repairing of an oxygen-deficient defect exceeds <NUM>,<NUM>, likewise, crystallization becomes liable to proceed to make it difficult to perform vitrification into transparent glass. Therefore, the step of promoting repairing of an oxygen-deficient defect is suitably performed at <NUM>,<NUM> to <NUM>, more preferably <NUM>,<NUM> to <NUM>.

It is known that, when the silica powder serving as a main raw material or any of various additives contains a metallic element as an impurity, crystallization is accelerated in various heat treatments, and in particular, as a heat treatment temperature increases, the rate of the crystallization increases. In the present invention, when Al is present in the silica powder at a concentration of more than <NUM> ppm, a transparent glass body cannot be obtained, and a white and opaque crystallized product is obtained. Therefore, the Al concentration of the silica powder is preferably <NUM> ppm or less.

When the molding step is performed with a metal mold, the glass member can be produced in a larger quantity and more inexpensively than by prior art grinding and polishing processing, and hence a great contribution can be made to the widespread use of ultraviolet LEDs. Injection molding, press molding, transfer molding, or the like may be suitably used as a molding method.

In addition, when the glass member is subjected to the heat treatment with a hydrogen atmosphere, hydrogen molecules can be incorporated into the glass, and hence the following effect can be expected: even when a structural defect is generated in the glass by light emitted by an ultraviolet LED, the structural defect is repaired.

Through the use of the method of manufacturing a quartz glass member for hermetic sealing of an ultraviolet LED of the present invention, the silica glass member for hermetic sealing of an ultraviolet LED of the present invention can be suitably manufactured.

Now, the present invention is more specifically described by way of Examples. Needless to say, however, the present invention is not limited to these Examples.

<NUM> Parts by weight of mixed powder obtained by mixing spherical synthetic silica powder having a diameter of <NUM> (product name: ADMAFINE SO-E3) and spherical synthetic silica powder having a diameter of <NUM> (product name: ADMAFINE SO-E5) at a weight ratio of <NUM>:<NUM>, <NUM> parts by weight of an aqueous solution of <NUM> wt% METOLOSE (product name: SM-<NUM>), and <NUM> part by weight of a lubricant (product name: UNILUBE 50MB-<NUM>) were mixed and then kneaded with a triple roll mill to form plastic matter. The term "plastic matter" as used herein refers to a kneaded product of silica glass powder, in a state of having higher viscosity than a slurry, and having hardness and plasticity comparable to those of a clay.

The formed plastic matter is degassed by being further kneaded under reduced pressure. Specifically, for example, kneading extrusion is performed using a kneading extrusion molding machine manufactured by Miyazaki Iron Works Co. under a reduced pressure of <NUM> MPa, with the result that the generation of bubbles after sintering can be reduced to a required degree.

The plastic matter subjected to the degassing treatment was injection-molded into a metal mold at an increased pressure of <NUM> MPa to provide a molded body having a predetermined shape. Here, with regard to the metal mold, the surface roughness of a sealing portion of a plain surface portion needs to be finished to <NUM> or less, preferably <NUM> or less in terms of Ra value. Similarly, the surface roughness of a lens-like projecting portion also needs to be finished to <NUM> or less, preferably <NUM> or less in terms of Ra value. Further, as a mold shape, a plain surface part for sealing needs to satisfy very high flatness in order to realize hermetic sealing, but in the case of a metal mold, sufficient flatness can be realized even with general processing accuracy.

The removed molded body (hereinafter green body) was air-dried in a clean atmosphere having a cleanliness level of about <NUM>,<NUM> at room temperature for about <NUM> hours.

The green body after the drying was put in a silica glass container having a flat bottom portion, and together with the container, was subjected to heat treatment in a horizontal tubular furnace having a furnace core tube made of silica glass under various atmospheres and temperatures.

The temperature in the furnace was increased from room temperature at a temperature increase rate of <NUM>/min to <NUM> and kept thereat. The atmosphere at the time of the temperature increase is <NUM>% nitrogen. After the temperature in the furnace had stabilized at <NUM>, nitrogen was stopped, and the temperature was kept for <NUM> hour while oxygen was flowed at a concentration of <NUM>%. Thus, organic matter, such as METOLOSE, contained in the green body was completely oxidized and removed.

After the completion of the degreasing treatment with an oxygen atmosphere, the oxygen was switched to <NUM>% nitrogen, and the temperature in the furnace was again increased at a temperature increase rate of <NUM>/min to <NUM>,<NUM> and kept thereat. The nitrogen was switched to <NUM>% hydrogen chloride, and purification treatment with hydrogen chloride was performed for <NUM> hour. The purification treatment reduces the concentrations of metal impurities, such as an alkali metal, iron, and copper, in silica glass. Meanwhile, hydrogen chloride gas reacts with Si-OH in the silica glass to form a Si-Cl bond, and hence, when the green body after the purification treatment is sintered as it is, the following reaction occurs: 2Si-Cl—>Si=Si+C1<NUM>. The Si=Si bond is a structural defect called an oxygen-deficient defect. The Si=Si bond has absorption at a wavelength of <NUM>, and at the same time, has extremely weak resistance to ultraviolet light. Accordingly, the defect is not suited for the purpose of the present invention, and hence needs to be cured.

After the purification treatment, the hydrogen chloride serving as the atmosphere gas was switched to <NUM>% nitrogen, and the furnace temperature was decreased at a temperature decrease rate of <NUM>/min to <NUM>,<NUM> and kept at <NUM>,<NUM>. In addition, after it was confirmed that the furnace temperature had reached <NUM>,<NUM>, the nitrogen was switched to <NUM>% oxygen, and the temperature was kept for <NUM> hour. After the treatment, the oxygen was replaced with nitrogen, followed by cooling to room temperature, and the resultant was removed.

The removed green bodies were arranged on a smooth carbon plate with their convex portions facing up, and were placed in a vacuum furnace. The inside of a vacuum chamber was evacuated to a vacuum (<NUM>×<NUM>-<NUM> Pa), and then the temperature was increased at a temperature increase rate of <NUM>/min to <NUM>,<NUM>, and kept at <NUM>,<NUM> for <NUM> minutes while a vacuum break (normal pressure <NUM> MPa) was performed with nitrogen. After that, electricity was turned off to cool the furnace. After <NUM> hours, the resultant was removed. Thus, a silica glass member for LED hermetic sealing of interest was obtained.

The surface roughness of a sealing portion (substrate joining plain surface) and a convex portion were measured with a Mitutoyo surface <NUM> roughness meter. The results are shown in Table <NUM>. It was confirmed that the surface roughness of each of the portions fell within a predetermined range. In Table <NUM>, measurement results at three measurement points (n) are shown.

Transmittance measurement cannot be performed for a lens shape. Therefore, a transparent flat plate measuring <NUM> mmx20 mmx2 mm was produced using exactly the same materials and manufacturing method as those of Example <NUM> and subjected to general transmittance measurement (measurement apparatus-UVATIS/NIR SPECTROMETER LAMBDA <NUM> manufactured by PerkinElmer, Inc. The results are shown in Table <NUM> and <FIG> (graphical representation of an apparent transmittance and a theoretical transmittance). An internal transmittance for ultraviolet light having a wavelength of <NUM> to <NUM> and an internal transmittance for ultraviolet light having a wavelength of <NUM> or more and less than <NUM> were determined from the apparent transmittance by the calculation expression shown below. The internal transmittances are shown in Table <NUM>. It was confirmed that each of the internal transmittances fell within a predetermined range.

Internal Transmittance- determined from (AT/TT)x100 for an apparent transmittance AT% at a thickness of <NUM> using a theoretical transmittance TT% (value obtained by subtracting reflection losses at a front surface and a back surface from <NUM>%) of quartz glass at each wavelength shown in Table <NUM>.

Transmittance Measurement with Integrating Sphere: measured using measurement apparatus: UVA/IS/NIR SPECTROMETER LAMBDA <NUM> manufactured by PerkinElmer, Inc. , integrating sphere- MODEL#<NUM> RSA ASSY. The results are shown in Table <NUM> and <FIG> together with the results of the general transmittance measurement, and calculated differences therebetween are shown in Table <NUM>. As apparent from Table <NUM>, it was confirmed that the differences each fell within a predetermined range.

(<NUM>) Measurement of Diameters and Numbers of Bubbles: Transmittance measurement cannot be performed for a lens shape. Therefore, a transparent flat plate measuring <NUM> mmx20 mmx2 mm was produced using exactly the same materials and manufacturing method as those of Example <NUM>, and was further divided and polished to produce three transparent flat plates (volume: <NUM><NUM>) each measuring <NUM>×<NUM> mmxl mm. The diameters and numbers of bubbles were measured for those transparent flat plates with a microscope at a magnification of <NUM> times. Finally, the cross-sectional areas of the bubbles were converted to values per <NUM><NUM> of volume. The measurement results are shown in Table <NUM>. No bubble having a bubble diameter of <NUM> or more was observed. As a method of calculating an area, the maximum value of a bubble class was taken as a diameter (for example, calculation was performed assuming <NUM> to <NUM> as a diameter of <NUM>). It was confirmed that the use of silica glass having such cross-sectional area of bubbles enabled use as a silica glass member for hermetic sealing of a surface mount-type package with a sufficiently suppressed scattering intensity.

(<NUM>) OH Group Concentration: The OH group concentration of a silica <NUM> glass sample measuring <NUM> mmx20 mmx2 mm produced using the same materials and manufacturing method as those of Example <NUM> was measured with an infrared spectrophotometer, and as a result, the contained OH group concentration was found to be <NUM> ppm. Further, in the oxygen treatment of Example <NUM>, the oxygen was humidified by bubbling with water, and as a result, a silica glass body having OH group concentration of <NUM> ppm was obtained. When each of those samples was irradiated with ultraviolet light having a wavelength of <NUM>, fluorescence was not observed. Thus, the samples were each found to be suited as a silica glass member for hermetic sealing of a surface mount-type package for a UV-LED.

A planar silica glass plate material and a hemispherical lens were each independently produced, polished, and bonded to each other using any of adhesives A to E described below to produce a silica glass member having a shape similar to that of Example <NUM>, which was subjected to transmittance measurement. The results are shown in <FIG>. In <FIG>, for comparison, the transmittance of the silica glass member of Example <NUM> is also shown. As apparent from <FIG>, all the silica glass members joined with the adhesives were found not to have sufficient transmission properties for UVB (falling within a wavelength range of from <NUM> to <NUM>) and UVC (falling within a wavelength range of from <NUM> to <NUM>).

The adhesives A to E are as described below.

<NUM> Parts by weight of mixed powder obtained by mixing spherical synthetic silica powder having an average particle diameter of <NUM> (ADMAFINE SO-E3 manufactured by Admatechs Company Limited) and spherical synthetic silica powder having an average particle diameter of <NUM> (ADMAFINE SO-E5 manufactured by Admatechs Company Limited) at a weight ratio of <NUM>:<NUM>, <NUM> parts by weight of an aqueous solution of <NUM>% methylcellulose (METOLOSE SM-<NUM> manufactured by Shin-Etsu Chemical Co. ), and <NUM> part by weight of a lubricant (UNILUBE 50MB-<NUM> manufactured by NOF Corporation) were mixed and then kneaded with a triple roll mill. Through the use of a vacuum extrusion molding machine, the mixture was degassed, and subjected to kneading extrusion under a reduced pressure of <NUM> MPa.

The mixture of the silica powder and the binder subjected to the degassing treatment was injection-molded into a metal mold at an increased pressure of <NUM> MPa to provide a molded body having a predetermined shape. Here, with regard to the metal mold, an in-plane surface roughness needs to be finished to <NUM> or less, preferably <NUM> or less in terms of Ra value.

The thus produced molded body was air-dried in a clean atmosphere having a cleanliness level of about <NUM>,<NUM> at room temperature for about <NUM> hours.

The molded body after the drying was put in a quartz glass container having a flat bottom portion, and together with the container, was subjected to heat treatment in a horizontal tubular furnace having a furnace core tube made of quartz glass under various atmospheres and temperatures. In the heat treatment step, the following steps (a) to (c) were performed.

The temperature in the furnace was increased from room temperature at a temperature increase rate of <NUM>/min to <NUM> and kept thereat. The atmosphere at the time of the temperature increase is <NUM>% nitrogen. After the temperature in the furnace had stabilized at <NUM>, nitrogen was stopped, and the temperature was kept for <NUM> hour while oxygen was flowed at a concentration of <NUM>%. Thus, organic matter, such as METOLOSE, contained in the molded body was completely oxidized and removed.

After the completion of the degreasing treatment with an oxygen atmosphere, the oxygen was switched to <NUM>% nitrogen, and the temperature in the furnace was again increased at a temperature increase rate of <NUM>/min to <NUM>,<NUM> and kept thereat. The nitrogen was switched to <NUM>% hydrogen chloride, and purification treatment with hydrogen chloride was performed for <NUM> hour. The purification treatment reduces the concentrations of metal impurities, such as an alkali metal, copper, and iron, in quartz glass. Meanwhile, hydrogen chloride reacts with Si-OH in the quartz glass to form a Si-Cl bond, and hence, when the molded body after the purification treatment is vitrified as it is, the following reaction occurs- 2Si-Cl→Si=SiH-Cl<NUM>. The Si=Si bond is a structural defect called an oxygen-deficient defect. The Si=Si bond has absorption at a wavelength of about <NUM>, and at the same time, has extremely weak resistance to ultraviolet light. Accordingly, the defect is not suited for the purpose of the present invention, and hence needs to be cured.

After the purification treatment, the hydrogen chloride serving as the atmosphere gas was switched to <NUM>% nitrogen, and the temperature was decreased at a temperature decrease rate of <NUM>/min to <NUM>,<NUM> and kept thereat. The nitrogen was switched to oxygen <NUM>%, and treatment for repairing an oxygen-deficient defect in quartz glass with oxygen was performed for <NUM> hour. After the treatment, the oxygen was switched to <NUM>% nitrogen, followed by cooling to room temperature, and the resultant was removed.

The removed molded bodies were arranged on a smooth carbon plate, and placed in a vacuum furnace. The inside of a vacuum chamber was evacuated to a degree of vacuum of <NUM>×<NUM>-<NUM> Pa, and then the temperature was increased at a temperature increase rate of <NUM>/min to <NUM>,<NUM>. After having reached <NUM>,<NUM>, the temperature was kept for <NUM> minutes while a vacuum break was performed with nitrogen to increase the pressure to <NUM> MPa. After that, electricity was turned off to cool the furnace. After <NUM> hours, the resultant was removed. Thus, a quartz glass member for hermetic sealing of an ultraviolet LED of interest was obtained.

Physical property values were evaluated in accordance with the following measurement methods.

The obtained quartz glass member was decomposed with hydrofluoric acid, and subjected to measurement by ICP emission spectrometry.

The obtained quartz glass member was visually observed. A case of transparent quartz glass was evaluated as "Satisfactory", a case of being opaque due to crystallization (devitrification) was evaluated as "Crystallization", and a case of containing visually recognizable bubbles was evaluated as "Bubbles".

A flat plate measuring <NUM> mmx20 mmx2 mm was produced, and subjected to measurement with a UV'VIS spectrophotometer in the wavelength range of from <NUM> to <NUM> to confirm the presence or absence of absorption at a wavelength of <NUM>. A case in which absorption at a wavelength of <NUM> was absent was evaluated as "Absent", a case in which the absorption was present was evaluated as "Present", and a case in which crystallization made measurement impossible was evaluated as "Unmeasurable".

Various conditions and measurement results are collectively shown in Table <NUM>. The transmittance measurement results of the quartz glass member for hermetic sealing of an ultraviolet LED obtained in Example <NUM> at wavelengths of from <NUM> to <NUM> are shown in <FIG>.

A quartz glass member for hermetic sealing of an ultraviolet LED was obtained in the same manner as in Example <NUM> except that the treatment for repairing an oxygen-deficient defect was performed at a temperature ofl,<NUM>, and under an atmosphere containing water vapor produced by a method involving bubbling pure water kept at <NUM> with oxygen serving as a carrier.

The quartz glass member for hermetic sealing of an ultraviolet LED obtained in Example <NUM> was subjected to hydrogen treatment in a hydrogen atmosphere at <NUM> and <NUM> MPa (heating treatment with a hydrogen atmosphere) to introduce hydrogen molecules into the glass. Thus, a quartz glass member for hermetic sealing of an ultraviolet LED was obtained.

A quartz glass member for hermetic sealing of an ultraviolet LED was obtained by performing the same treatments as in Example <NUM> except that mixed powder obtained by mixing spherical synthetic silica powder having an average particle diameter of <NUM> (ADMAFINE SO-El manufactured by Admatechs Company Limited), spherical synthetic silica powder having an average particle diameter of <NUM> (ADMAFINE SO-E3 manufactured by Admatechs Company Limited), and spherical synthetic silica powder having an average particle diameter of <NUM> (ADMAFINE SO-E5 manufactured by Admatechs Company Limited) at a weight ratio of <NUM>:<NUM>:<NUM> was used as a raw material.

A quartz glass member was obtained in the same manner as in Example <NUM> except that the step of promoting repairing of an oxygen-deficient defect was not performed. The transmittance measurement results of the quartz glass member obtained in Comparative Example <NUM> at wavelengths of from <NUM> to <NUM> are shown in <FIG>.

Treatments were performed in the same manner as in Example <NUM> except that the degreasing temperature of the degreasing step in the heat treatment step was set to <NUM>,<NUM>. The state after the heat treatment step was not particularly different from that of the sample of Example <NUM>, and hence the sample of Comparative Example <NUM> was subjected to vitrification, but became opaque due to crystallization.

Treatments were performed in the same manner as in Example <NUM> except that the purification temperature of the purification step in the heat treatment step was set to <NUM>,<NUM>. Although the volume of the sintered body after the heat treatment step was slightly shrunk, the sintered body was subjected to vitrification as it was. As a result, a large number of extremely fine bubbles were mixed therein.

Treatments were performed in the same manner as in Example <NUM> except that the oxygen-deficient defect repairing temperature of the step of promoting repairing of an oxygen-deficient defect in the heat treatment step was set to <NUM>,<NUM>. The state after the heat treatment was not particularly different from that of the sample of Example <NUM>, and hence the sample of Comparative Example <NUM> was subjected to vitrification, but became opaque due to crystallization.

The glass member obtained in Comparative Example <NUM> was kept in an oxygen atmosphere at <NUM>,<NUM> for <NUM> hours. The transmittance of the resultant sample was measured. As a result, it was found that, although absorption at a wavelength of <NUM> was slightly improved, the transmittance in the entire region of from <NUM> to <NUM> was reduced due to the influence of contamination caused by the heat treatment.

Claim 1:
An ultraviolet surface mount device, SMD, LED element (<NUM>) surface mount-type package comprising a silica glass member (<NUM>) for hermetic sealing of an ultraviolet SMD LED element (<NUM>) that is configured to emit light in a wavelength range of from <NUM> to <NUM>, in particular from <NUM> to <NUM>, and is placed in a hermetic sealing container (<NUM>) having a container outer periphery joining plain surface (22a) formed in an outer peripheral portion thereof, the silica glass member (<NUM>) for hermetic sealing comprising a silica glass substrate (10A), which is homogeneously and integrally formed without an internal boundary, wherein the silica glass substrate (10A) has:
a first surface (<NUM>) on an inside opposed to the ultraviolet SMD LED element (<NUM>); and
a second surface (<NUM>) on an outside corresponding to the first surface (<NUM>),
wherein an outer peripheral portion of the first surface (<NUM>) has formed therein a substrate joining plain surface (24a) for joining to the container outer periphery joining plain surface (22a), and
wherein the second surface (<NUM>) on the outside corresponding to the first surface (<NUM>) has formed therein a lens-like convex portion (<NUM>) configured to process emitted light from the ultraviolet SMD LED element (<NUM>),
characterized in that
the silica glass member (<NUM>) for hermetic sealing has an internal transmittance at a thickness of <NUM> of <NUM>% to <NUM>% for ultraviolet light having a wavelength of <NUM> to <NUM> and an internal transmittance at a thickness of <NUM> of <NUM>% to <NUM>% for ultraviolet light having a wavelength of <NUM> or more and less than <NUM>,
wherein the silica glass member (<NUM>) for hermetic sealing contains OH groups at a concentration of <NUM> ppm to <NUM> ppm.