JP2008021932A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device capable of emitting visible light with more uniform luminance. <P>SOLUTION: The light emitting device 10 includes a plurality of UV-LEDs 12, a reflector 16 which totally reflects ultraviolet light emitted by the UV-LEDs 12, and a filter member 22 having a fluorescent body emitting visible light by receiving ultraviolet light reflected by the reflector 16. With this configuration, the optical path length of the ultraviolet light emitted by the UV-LEDs 12 becomes longer than when the reflector 16 is not interposed. Luminous flux of the ultraviolet light gradually widens and is diffused as the optical length becomes longer and then has its intensity made uniform. Namely, the filter member can be irradiated with the ultraviolet light with the uniform intensity, and the visible light can be emitted with uniform luminance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light emitting device that emits visible light by irradiating a phosphor with ultraviolet light.

  In recent years, a light-emitting device that combines an ultraviolet LED (hereinafter referred to as “UV-LED”) that irradiates ultraviolet rays and a phosphor has been proposed. This type of light emitting device has a mechanism in which a phosphor is irradiated with ultraviolet light by a UV-LED and visible light emitted from the phosphor excited by the ultraviolet light is extracted to the outside.

  Patent Document 1 discloses a surface-emitting LED light source proposed based on this mechanism. This surface-emitting LED light source has a phosphor on the inner surface, a box-shaped, bowl-shaped or dome-shaped reflector having an opening in at least one direction, a UV-LED that irradiates the reflector, and an opening of the reflector And a translucent body covering the. When the UV-LED reaches the surface of the reflector, the phosphor provided on the reflector emits light. Visible light emitted from the phosphor is reflected and diffused by the reflector, and is emitted from the translucent body to the outside. According to this configuration, since visible light is diffused by the reflector, uniform planar light emission is possible.

JP 2001-243821 A

  However, in the technique described in Patent Document 1, a reflecting surface is provided immediately after the phosphor. Therefore, only a part of the visible light generated from the phosphor reaches the reflecting surface, and the visible light finally radiated from the transparent body is not reflected by the visible light diffused by the reflection. Visible light that has reached the transparent body is mixed. As a result, it was difficult to say that the luminance of visible light emitted from the translucent material was uniform. That is, it is difficult to emit light with uniform brightness in a conventional light emitting device using UV-LEDs.

  Therefore, an object of the present invention is to provide a light emitting device that can emit visible light with more uniform luminance.

  A light-emitting device of the present invention is a light-emitting device that emits visible light by irradiating ultraviolet light onto a phosphor, and a plurality of light sources that emit ultraviolet light and a position of the light source at a position that crosses the optical axis of the light source. A reflector provided to be inclined with respect to the optical axis, the reflector reflecting ultraviolet light emitted from a light source, and a filter member in which a phosphor is arranged according to a desired light emission pattern, And a filter member provided at a position for receiving the ultraviolet light reflected by the reflector.

  In a preferred embodiment, the reflector has a shape that irregularly reflects the ultraviolet light emitted from the light source. In another preferred embodiment, the filter member is arranged so that the phosphor of a specific color has a shape corresponding to the desired light emission pattern. In another preferred embodiment, the filter member is configured by silk-printing a desired image with a phosphor-containing ink on a substrate made of a translucent material.

  According to the present invention, the ultraviolet light irradiated from the light source is reflected and diffused by the reflector in advance, and the phosphor is irradiated with the diffused ultraviolet light. In other words, the phosphor is irradiated with uniform intensity. As a result, it is possible to emit visible light with uniform luminance.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a light emitting device 10 according to an embodiment of the present invention. The light emitting device 10 is a light emitting device 10 that utilizes visible light emission from a phosphor that is excited by irradiation with ultraviolet light. Hereinafter, the light emitting device 10 that emits white light will be described as an example. However, as a matter of course, visible light of other colors and patterns may be emitted by appropriately changing the configuration of the phosphor group 20 described later.

  The light emitting device 10 is provided with a plurality of UV-LEDs 12 serving as light sources. Each UV-LED 12 appropriately irradiates ultraviolet light according to control from a drive circuit (not shown). The plurality of UV-LEDs 12 are arranged in an array on the substrate 14 so that the distribution is uniform. Here, each UV-LED 12 is arranged so that its optical axis is substantially parallel to a filter member 22 described later. In other words, each UV-LED 12 is arranged so as not to irradiate the filter member 22 directly.

  A reflector 16 is provided at a position crossing the optical axis of the UV-LED 12. The reflector 16 is disposed so as to be inclined with respect to the optical axis of the UV-LED 12 and receives ultraviolet light irradiated from the UV-LED 12. The reflector 16 is provided with a reflection surface 16 a that totally reflects ultraviolet light, and guides the ultraviolet light irradiated from the UV-LED 12 to the filter member 22.

  A filter member 22 is provided at a position for receiving the reflected ultraviolet light. The filter member 22 includes a phosphor group 20 composed of a plurality of types of phosphors, and a transparent substrate 18 provided as a substrate for the phosphor group 20.

  FIG. 2 is a partially enlarged view of the filter member 22. The transparent substrate 18 is a material that can transmit visible light, for example, a plate material made of glass, transparent resin, or the like. The surface of the transparent substrate 18 is provided with an ultraviolet cut coat that inhibits the transmission of ultraviolet light, so that ultraviolet light included in ambient light such as sunlight does not reach the inside of the light emitting device 10, Ultraviolet light from the UV-LED 12 that has passed through the phosphor group 20 is prevented from leaking outside. Note that the transparent substrate 18 is not necessarily provided, and the filter member 22 may be configured by only the phosphor group 20 described later.

The phosphor group 20 includes a plurality of types of phosphors 30r, 30g, and 30b (hereinafter referred to as “phosphor 30” when the color is not particularly limited) arranged in a mosaic pattern. More specifically, in the phosphor group 20, a red phosphor 30r that emits red visible light upon excitation, a green phosphor 30g that emits green visible light upon excitation, and a blue phosphor 30b that emits blue visible light upon excitation are mosaicked. It is comprised by arranging in the shape. Each phosphor is a known phosphor, for example, Y ₂ O ₂ S: Eu for the red phosphor 30r, ZnS: Cu for the green phosphor 30g, and BaMgAl ₁₀ O ₁₇ : Eu for the blue phosphor 30b. Etc. can be used.

  The three types of phosphors 30r, 30g, and 30b are equal to each other so as to become white visible light (or recognized by the user as white visible light) when colored visible light emitted from each of them is mixed. Are distributed and arranged. Specifically, the substantially rectangular phosphor 30 in a top view is repeatedly arranged in the order of the red phosphor 30r, the green phosphor 30g, and the blue phosphor 30b in the vertical direction and the horizontal direction, respectively. By arranging the three color phosphors 30 in such a pattern, the three colors of visible light emitted by excitation of the three types of phosphors 30 are mixed and extracted as white visible light.

  The size of each phosphor 30 is determined based on the distance from the light emitting device 10 to the user. That is, when the distance from the installation position of the light emitting device 10 to the user of the light emitting device 10 is long, such as a streetlight or an electric bulletin board, even if the size of each phosphor is increased, the position away from the light emitting device 10 The size of each phosphor 30 appears to be small from the users in the room. As a result, the user cannot individually recognize the three colors of visible light emitted from each phosphor 30, but recognizes it as white light in which the three colors are mixed. On the other hand, when the distance from the installation position of the light emitting device 10 to the user is short, such as indoor lighting, if the size of the phosphor 30 is large, the user can obtain three colors emitted from each phosphor 30. The visible light is individually recognized, and it becomes difficult to recognize it as white light. Therefore, it is desirable to reduce the size of each phosphor 30 as the distance from the light emitting device 10 to the user is smaller.

  Next, the mechanism of visible light emission by the light emitting device 10 will be described. As shown in FIG. 1, in this embodiment, the plurality of UV-LEDs 12 are arranged so that their optical axes are substantially parallel to the filter member 22, and the reflector 16 crosses the optical axis. Is provided. Therefore, the ultraviolet light irradiated from the plurality of UV-LEDs 12 first reaches the reflector 16. The ultraviolet light that has reached the reflector 16 is totally reflected by the reflecting surface 16 a of the reflector 16.

  The totally reflected ultraviolet light reaches the phosphor group 20 provided on the filter member 22 and excites the phosphor 30. Visible light is generated by excitation of the phosphor 30. The visible light is transmitted to the outside as white visible light through the transparent substrate 18 made of a translucent material while being mixed with each other. The ultraviolet light transmitted through the phosphor 30 is prevented from leaking outside by the ultraviolet cut coat provided on the surface of the transparent substrate 18.

  By the way, in this embodiment, the filter member 22 is irradiated with ultraviolet rays through the reflector 16. On the other hand, naturally the structure which irradiates the filter member 22 with ultraviolet rays directly by the UV-LED 12 without using the reflector 16 is also conceivable. That is, as illustrated in FIG. 3, a configuration in which a plurality of UV-LEDs 12 are disposed to face the filter member 22 is also conceivable. However, in this case, there is a problem that the distance from each UV-LED 12 to the filter member 22 becomes short, and the intensity distribution of the ultraviolet light becomes sparse.

  That is, the light flux of ultraviolet light emitted from each UV-LED 12 is gradually spread and diffused as it travels. Of course, the longer the optical path length of the ultraviolet light, the higher the degree of diffusion. However, as shown in FIG. 3, when the UV-LED 12 and the filter member 22 are arranged to face each other, a sufficiently long optical path length cannot be ensured, and as a result, the filter member 22 is reached. Variations in the intensity distribution of the ultraviolet light will occur. Here, the intensity of visible light emitted from each phosphor 30 is proportional to the intensity of the irradiated ultraviolet light. Therefore, the variation in the irradiation intensity of the ultraviolet light causes a variation in the luminance of the visible light to be extracted. That is, when the UV-LED 12 and the filter member 22 are arranged to face each other, there arises a problem that the luminance of visible light varies.

  Of course, even when the UV-LED 12 and the filter member 22 are arranged to face each other, this variation in luminance can be prevented by increasing the distance between the UV-LED 12 and the filter member 22. However, in that case, a new problem of increasing the size of the light emitting device 10 occurs. In addition, it is conceivable to prevent variations in the intensity of ultraviolet light irradiation by reducing the arrangement interval of the UV-LEDs 12. Invite.

  On the other hand, in this embodiment, as described above, the filter member 22 is irradiated with ultraviolet rays via the reflector 16. Therefore, the optical path length of the ultraviolet light from the UV-LED 12 to the filter member 22 is longer than the size of the light emitting device 10 and the arrangement interval of the UV-LEDs 12, and the ultraviolet light reaching the filter member 22 is sufficient. It becomes the state diffused to. As a result, the luminance of visible light emitted from the filter member 22 can be made substantially uniform.

  As described above, according to the present embodiment, the reflector 16 is interposed on the optical path of the ultraviolet light, thereby preventing an excessive increase in size and cost of the light emitting device 10 and substantially uniform luminance. Visible light can be generated.

  Next, another embodiment will be described with reference to FIG. FIG. 4 is a schematic cross-sectional view of a light emitting device 10 according to another embodiment. The light emitting device 10 has the same configuration as that of the above-described embodiment except that the reflection surface 16a of the reflector 16 has a shape that diffusely reflects the irradiated ultraviolet light.

  Specifically, in the present embodiment, the reflecting surface 16a of the reflector 16 has a substantially arc-shaped cross section. The ultraviolet light that reaches the reflecting surface 16a is diffusely reflected, and the ultraviolet light is more diffused than when reflected by a flat reflecting surface. As a result, the luminance of visible light emitted from the filter member 22 is made more uniform.

  Note that the shape of the reflecting surface 16a described here is an example, and other shapes may naturally be used as long as they cause irregular reflection. For example, as illustrated in FIG. 5, the reflective surface 16 a having a large number of irregularities may be used.

  In the above description, the light emitting device that emits white visible light has been described. However, by appropriately changing the type and arrangement pattern of the phosphors 30 constituting the phosphor group 20, other light emission patterns are naturally obtained. You may apply to the light-emitting device 10 which light-emits by.

  For example, in the present embodiment, the surface of the phosphor group 20 is a flat surface, but the surface of the phosphor group 20 is non-flat by changing the thickness of each phosphor 30 constituting the phosphor group 20. It may be a surface. By making the surface of the fluorescent substance group 20 into a non-flat surface, the surface area of the fluorescent substance group 20 can be increased, and the emission luminance of visible light can be increased.

  In the above description, white visible light is emitted from the entire surface of the filter member 22, but naturally other colored visible light is emitted by changing the type and arrangement pattern of the phosphor 30 to be used. You may do it.

  Furthermore, the phosphor 30 having a specific color may be arranged in a shape such as a character string or a figure, and the character string or the figure may be emitted with a fluorescent color. Alternatively, the phosphor group 20 may be configured by silk-printing illustrations and photographs on the surface of the transparent substrate using ink containing the phosphor 30. With this configuration, full color light emission is possible.

It is a schematic sectional drawing of the light-emitting device which is embodiment of this invention. It is the elements on larger scale of a filter member. It is a schematic sectional drawing of the conventional light-emitting device. It is a schematic sectional drawing of the light-emitting device which is other embodiment. It is a schematic sectional drawing of the light-emitting device which is other embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Light-emitting device, 12 UV-LED, 14 board | substrate, 16 reflector, 16a reflective surface, 18 transparent substrate, 20 fluorescent substance group, 22 filter member, 30 fluorescent substance.

Claims (4)

A light emitting device that emits visible light by irradiating ultraviolet light onto a phosphor,
A plurality of light sources that emit ultraviolet light;
A reflector provided at a position crossing the optical axis of the light source and inclined with respect to the optical axis of the light source, and reflecting the ultraviolet light emitted from the light source;
A filter member in which a phosphor is arranged according to a desired light emission pattern, the filter member provided at a position for receiving ultraviolet light reflected by the reflector, and
A light emitting device comprising: The light-emitting device according to claim 1,
The reflector has a shape that diffusely reflects ultraviolet light irradiated from a light source. The light-emitting device according to claim 1 or 2,
The light emitting device, wherein the filter member is arranged so that the phosphor of a specific color has a shape corresponding to a desired light emission pattern. The light-emitting device according to claim 1 or 2,
The filter member is configured by silk-printing a desired image with a phosphor-containing ink on a substrate made of a light-transmitting material.

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