JP2015106596A - Light extraction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light extraction device capable of efficiently extracting ultraviolet light as a surface light source, the ultraviolet light being produced from an LED having an emission wavelength of 200-350 nm.SOLUTION: A light extraction device includes: an LED; and a translucent member that has a first surface provided with an incident port through which light emitted from the LED enters, a second surface from which incident light is emitted, and surfaces other than the first and second surfaces, and is made of an inorganic material allowing the light to be transmitted therethrough. The LED has an emission wavelength of 200-350 nm, and the translucent member has a reflective layer made of aluminum, on the whole surface of the first surface other than the incident port and on the whole surface other than the first and second surfaces.

Description

  The present invention relates to a novel light extraction device. Specifically, a novel light extraction device that extracts light emitted from an LED having an emission wavelength of 200 to 350 nm (an LED (Light Emitting Diode) having an emission wavelength peak in the range of 200 to 350 nm) About.

  Since the LED is a point light source, there is a drawback in that unevenness of light tends to occur when a large area is irradiated by the LED. For this reason, various studies have been made to use light emitted from LEDs as a surface light source. For example, a point light source can be converted into a surface light source and light can be extracted by forming irregularities on a surface other than light emitted from a transparent light guide plate (translucent member) or providing a reflective layer. Has been done.

  Usually, as these LEDs, those in the visible light region having a practical emission wavelength of 400 nm or more are specified. When taking out the light of the surface light source from the LED in the visible light region, a transparent resin such as an acrylic resin or a polycarbonate resin is used for the light guide plate (transparent member), and an opaque white synthetic resin is also used as the reflective layer. A sheet is used by being laminated on the light guide plate with an adhesive or the like (for example, see Patent Document 1).

  On the other hand, in recent years, development of an ultraviolet LED (deep ultraviolet LED) that emits light having an emission wavelength peak in the ultraviolet region, particularly in the deep ultraviolet region, has been progressing due to environmental problems. For example, many studies have been made on ultraviolet LEDs made of a laminate in which a group III nitride semiconductor crystal layer is laminated on a heterogeneous material substrate such as a sapphire substrate or a silicon carbide substrate, or a group III nitride homogenous substrate ( Non-patent documents 1 to 3).

  Since such an ultraviolet LED is also a point light source, a light extraction device using a surface light source is required in the same way as an LED in the visible light region in order to broaden the application of the ultraviolet LED.

JP 2003-45214 A

Applied Physics Letters 3 (2010) 041001 Applied Physics Express 3 (2010) 072103 Applied Physics Express 5 (2012) 122101

  However, when the light extraction device used in the conventional visible light region is used, a product having sufficient light extraction performance and durability cannot be obtained. In other words, since organic synthetic resins are decomposed and deteriorated by ultraviolet light, the conventional light extraction device used in the visible light region cannot be used as it is. Therefore, development of a light extraction device for ultraviolet LEDs has been desired. In particular, when the light emission wavelength is a short wavelength, for example, 200 to 300 nm, the light emission efficiency is extremely lowered. Therefore, it has been desired to develop an apparatus that can efficiently extract light in this region.

  Accordingly, an object of the present invention is to provide a light extraction device that can efficiently extract the light of a point light source emitted from an LED having an ultraviolet region, that is, an emission wavelength of 200 to 350 nm, as a surface light source. .

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. And as a result of examining the structure, material, etc. of the device that can take out the point light source of the ultraviolet LED as a surface light source, by combining a reflective layer made of aluminum and a translucent member that transmits ultraviolet light made of an inorganic material, As a result, the present invention has been completed.

That is, the present invention
LED, and a first surface provided with an entrance through which light emitted from the LED is incident, a second surface from which incident light is emitted, and a surface other than the first and second surfaces In the light extraction device provided with the translucent member having,
The emission wavelength of the LED is 200 to 350 nm,
The translucent member is made of an inorganic material that transmits the light of the LED, and is made of aluminum on the entire surface other than the entrance of the first surface and on the entire surface other than the first and second surfaces. A light extraction device having a layer.

  Among these, the translucent member is preferably formed of an inorganic material made of quartz and a reflective layer made of aluminum through an adhesion layer made of an active metal.

  Further, in the apparatus of the present invention, the translucent member is made of aluminum on a second surface at a position where the first surface and the second surface face each other and the entrance is opposed. It is preferable to have a first reflecting member. By adopting such a correspondence, uniform ultraviolet light can be extracted. Furthermore, the apparatus of the present invention further includes at least one second reflecting member made of aluminum on the second surface of the translucent member, and the first reflecting member and the second reflecting member are respectively provided. It is preferable that they are arranged at intervals.

  According to the light extraction device of the present invention, since a translucent member (light guide plate) using an inorganic material that is not deteriorated by ultraviolet light and a reflective layer made of aluminum having a high reflectance of ultraviolet light are used, ultraviolet light is used. Light can be used as a surface light source efficiently and for a long time. In particular, the translucent member is a first reflection made of aluminum on the second surface at a position where the first surface and the second surface are opposed to each other and the entrance is facing. By adopting a form having a member, ultraviolet light absorption in the light-transmitting member (light guide plate) can be further suppressed, and light can be extracted uniformly. As a result, it can be particularly suitably used as a surface light source device for an LED having an emission wavelength of 200 to 300 nm, which is difficult to produce an LED having high emission intensity.

It is a top view of the optical extraction apparatus which concerns on the example of 1 aspect (1st embodiment) of this invention. It is sectional drawing in the (i)-(i) line | wire of FIG. It is the front view seen from the light extraction surface (2nd surface) of the light extraction apparatus which concerns on the example of an aspect (2nd embodiment) of this invention. It is sectional drawing in the (ii)-(ii) line | wire of FIG.

  The present invention converts light (point light source) emitted from an ultraviolet LED having an emission wavelength of 200 to 350 nm into a surface light source. Hereinafter, each component will be described.

(LED)
An LED having an emission wavelength of 200 to 350 nm can be manufactured by a known method, for example, by the method described in Non-Patent Documents 1 to 3 described in the background art.
The light extraction device of the present invention will be described in detail with reference to the drawings.

(First embodiment)
1 and 2 show a diagram of a light extraction device according to an example of the present invention (first embodiment). Although this figure shows an embodiment having one ultraviolet LED, a plurality of ultraviolet LEDs may be arranged. The light extraction device of the present invention includes an ultraviolet LED 1, a translucent member 2, and a reflective layer 3. In the first embodiment, the second surface 23 and the first surface of the translucent member 2 are perpendicular to each other. Therefore, in the first embodiment, the second surface 23 exists in a substantially parallel direction with respect to the light generated from the ultraviolet LED 1 (light incident from the incident port 22 of the first surface 21). The light is reflected by the reflective layer 3 or the like existing on the surface 24 other than the first and second surfaces, and the light is extracted from the second surface 23. In this case, the second surface from which light is extracted is preferably the main surface having the largest area.

  The ultraviolet light radiated from the ultraviolet LED 1 is incident from the entrance 22 in the first surface 21 of the translucent member 2. The translucent member 2 has a second surface 23 from which ultraviolet light is emitted as a surface light source, and a surface 24 other than the first and second surfaces. In this translucent member 2, aluminum is formed on the entire surface other than the entrance of the first surface and on the entire surface other than the first and second surfaces (on the entire surface 24 other than the first and second surfaces). A reflective layer 3 made of is disposed. With this arrangement, light can be efficiently extracted from the second surface 21.

(Translucent member)
The translucent member 2 must be formed of an inorganic material that transmits ultraviolet light. By using an inorganic material, durability can be improved even for ultraviolet LEDs. Examples of specific materials include quartz, aluminum nitride, calcium fluoride, magnesium fluoride, and sapphire. Among these, quartz is preferable in consideration of moldability and cost. The thickness of the translucent member is not particularly limited, and may be determined as appropriate according to the intended use.

  In the case of the first embodiment, the reflecting member in the second embodiment described in detail below may be provided on the second surface 23. However, in order to extract light efficiently, It is better not to provide it. In order to extract light efficiently, it is preferable to provide fine irregularities on the second surface 23. Further, a convex portion for diffusing light can be provided on the other surface facing the second surface 23.

(Reflective layer)
The reflective layer 3 is disposed on the entire surface other than the entrance of the first surface and on the entire surface other than the first and second surfaces in order to extract light efficiently. The reflective layer 3 is made of aluminum. By using aluminum, ultraviolet light can be taken out efficiently. For example, silver or the like often used for a reflection layer of a light extraction device in the visible light region has a reflectance of about 30% at a wavelength of 250 nm, whereas aluminum has 90%. From this, it can be seen that in the case of ultraviolet light, it is necessary to form the reflective layer 3 made of aluminum.

  The reflective layer 3 is disposed on the surface where the translucent member 2 is required. The method of arrange | positioning on each surface of the translucent member 2 is not restrict | limited in particular, It is preferable to arrange | position so that the translucent member 2 may contact | adhere. Therefore, it is most preferable to deposit aluminum on the necessary surface of the translucent member 2 to form the reflective layer 3. Further, after depositing an adhesion layer made of an active metal such as Ti, Cr, V, etc. on the translucent member 2, aluminum can also be deposited thereon (FIGS. 1 and 2 show this adhesion). Layers are not shown.) By pre-depositing an adhesion layer made of an active metal, adhesion between the translucent member and aluminum can be improved. However, when the adhesion layer is deposited in advance, it is preferable to make the adhesion layer as thin as possible. That is, the adhesion layer preferably absorbs ultraviolet light and is, for example, a thin film with a thickness of 0.1 nm to 5 nm. The thickness of the reflective layer 3 made of aluminum is not particularly limited, but is preferably 100 nm or more, and more preferably 100 μm or more and 1 μm or less.

  By setting it as the above aspects, ultraviolet light can be taken out efficiently.

  Next, a second embodiment in the case where the first surface 21 and the second surface 22 of the translucent member 2 are arranged to face each other will be described.

(Second embodiment)
3 and 4 show a second embodiment. 3 and 4 show an embodiment having one ultraviolet LED, a plurality of ultraviolet LEDs may be arranged. Moreover, although the cylindrical example was shown, it does not restrict | limit in particular, A polygonal cylindrical form may be sufficient. In this second embodiment example, the first surface 21 'and the second surface 23' are opposed to each other, and the aluminum is formed on the second surface 23 'at the position where the entrance 22 faces. It has at least the 1st reflective member 31 which consists of. Except for the point that the first surface 21 'and the second surface 23' face each other and the point that the first reflecting member 31 is provided on the second surface 23 ', the same configuration and material as in the first embodiment. Etc. can be adopted. Specifically, it is formed on the material of the translucent member 2, the entire surface of the first surface 21 'other than the entrance 22', and the entire surface other than the first and second surfaces (the other surface 24 '). The reflective layer 3 made of aluminum can have the same thickness, configuration, arrangement, thickness, etc. as in the first embodiment. Further, when an adhesion layer is used, it is preferable to use the same method as in the first embodiment (the adhesion layer is not shown in FIGS. 3 and 4). Also in this case, the second surface 23 ′ becomes the main surface.

  The second embodiment is characterized in that the first surface 21 ′ and the second surface 23 ′ are opposed to each other and that the first reflecting member 31 is provided on the second surface 23 ′. That is, the first surface 21 ′ and the second surface 23 ′ are opposed to each other so that the light extraction surface (second surface 23 ′) and the light incident surface (first surface 21 ′) Will face each other. In this case, by providing the first reflecting member 31, the reflecting layer 3 on the first surface 21 ', preferably the second reflecting member 32 on the second surface 23', the light emitted from the ultraviolet LED 1 is , Reflected and scattered into the translucent member 2. As a result, ultraviolet light can be extracted from the second surface 23 'in a more uniform state. In this embodiment, by using a translucent member having high transparency to ultraviolet light and aluminum having a high reflectance (reflective layer, first and second reflective members), each member is arranged as described above. Even when an ultraviolet LED having an emission wavelength of 200 to 300 nm is used, a decrease in emission intensity can be suppressed. Therefore, it can be suitably used for the light extraction device of such a short wavelength ultraviolet LED.

  In order to reflect the ultraviolet light from the first surface 21 ′, it is necessary to provide at least the first reflecting member 31 made of aluminum on the second surface 23 ′ at the position where the entrance 22 ′ faces. . The size (area) of the first reflecting member 31 is not particularly limited, and is based on the state of light generated from the ultraviolet LED, the distance between the first surface 21 ′ and the second surface 23 ′, and the like. Although it may be determined accordingly, it is preferable that it is equal to or larger than the opening area of the entrance port 23 '. Specifically, it may be about 1 to 2 times the opening area. As a matter of course, since the light cannot be extracted when the first reflecting member 31 covers the entire second surface 23 ′, the area of the first reflecting member 31 is larger than that of the second surface 23 ′. Need to be smaller.

  In the second embodiment, in order to extract light more uniformly, at least one second reflecting member 32 made of aluminum is further provided on the second surface 23 ′ of the translucent member 2. And it is preferable that the 1st reflection member 31 and the 2nd reflection member 32 are arrange | positioned at intervals, respectively. There may be a plurality of the second reflecting members 32. In this case, as a matter of course, the first reflecting member 31 and each of the second reflecting members 32 must be arranged at intervals. The shape of the second reflecting member 32 is not particularly limited. However, as shown in FIG. 4, the second reflecting member 32 may be formed in a circular shape as long as each has an interval. Moreover, it is not limited to a circular shape and may be a polygonal continuous shape. Further, the second reflecting members 32 can be arranged so as to be scattered.

  When arranging the second reflecting member 32, the total area of the total area of the second reflecting member 32 and the area of the first reflecting member 31 must be smaller than the area of the second surface 23 ′. It is preferable to set it as about 5 to 50% of the area of surface 23 'of this, and also about 5 to 30%.

  The first reflecting member 31 and the second reflecting member 32 are made of aluminum, like the reflecting layer 3. The reason for having to be aluminum is the same reason as that of the reflective layer 3 of the first embodiment. Moreover, the 1st reflective member 31 and the 2nd reflective member 32 can also be formed on 2nd surface 23 'through the contact | adherence member 4 which consists of active metals. The thickness or the like of the adhesion member 4 is preferably a thin film, and the specific thickness is also the same as the reason described in the adhesion layer of the reflective layer 3 of the first embodiment (that is, the adhesion member 4 has the same thickness). The thickness is preferably 0.1 to 5 nm.) Moreover, it is preferable that the thickness of the 1st reflective member 31 and the 2nd reflective member 32 is also the same thickness as the said reflective layer 3 for the same reason (that is, the 1st reflective member 31 and the 2nd reflective member 32). The thickness is preferably 100 nm or more, and more preferably 100 μm or more and 1 μm or less.

  Further, in the second embodiment, in order to extract ultraviolet light more efficiently, the surface on which the first reflecting member 31 and the second reflecting member 32 are not arranged on the second surface 23 ′ is illustrated. Although it is not, it can also be made into a fine uneven shape.

  By setting it as the above aspects, ultraviolet light can be taken out more uniformly. Therefore, the light extraction device of the present invention can be used in a water cleaning device or the like in which a conventional mercury lamp is used. It can also be used in general household appliances such as refrigerators, washing machines, vacuum cleaners, and air conditioners.

1 UV LED
2 Translucent member 21, 21 ′ First surface 22 Entrance 23, 23 ′ Second surface 24, 24 ′ Surface other than first and second surfaces 3 Reflective layer 31 First reflective member 32 Second reflection Member 4 Adhering member

Claims (5)

LED, and a first surface provided with an entrance through which light emitted from the LED is incident, a second surface from which incident light is emitted, and a surface other than the first and second surfaces In the light extraction device provided with the translucent member having,
The emission wavelength of the LED is 200 to 350 nm,
The translucent member is made of an inorganic material that transmits the light of the LED, and is made of aluminum on the entire surface other than the entrance of the first surface and on the entire surface other than the first and second surfaces. A light extraction device comprising a layer.   2. The light extraction device according to claim 1, wherein the translucent member is formed of an inorganic material made of quartz and a reflective layer made of aluminum through an adhesion layer made of an active metal.   The translucent member has a first reflecting member made of aluminum on the second surface at a position where the first surface and the second surface face each other and the entrance is opposed to each other. The light extraction device according to claim 1, wherein:   On the second surface of the translucent member, at least one second reflecting member made of aluminum is further provided, and the first reflecting member and the second reflecting member are arranged at intervals. The light extraction device according to claim 3.   The light extraction device according to claim 4, wherein the first reflection member and the second reflection member are formed through an adhesion member made of an active metal.

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