JP2018029031A - Led illumination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an LED illumination device that uniformly emits light with strong directivity from a wide area.SOLUTION: An LED illumination device 100 has a plurality of LED chips 10 arrayed in one-dimensionally. So as to cover all the LED chips 10, provided is a light scattering layer 30. The light scattering layer 30 is provided so that a gap to the LED chips 10 in vertical direction is X. Over the light scattering layer 30, provided is a light collection layer 40 so as to cover the light scattering layer 30 from above. The light collection layer 40 is provided so that a gap to the light scattering layer 30 in vertical direction is Y. The light collection layer 40 has multiple structures (light collection structures) that collect scattered light incident from the lower side to improve directivity to the upper side.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a structure of an LED lighting device in which a plurality of light emitting diodes (LEDs) are used as a light source.

  Instead of fluorescent lamps and incandescent lamps, light-emitting diodes (LEDs) with lower power consumption and higher durability are used in various light sources. In principle, LEDs can only emit monochromatic (constant wavelength) light, such as blue or red light. In addition, an LED is composed of a semiconductor layer composed of, for example, a single crystal of a nitride semiconductor, and since the size of the single body can be substantially manufactured only as small as several millimeters, the LED is actually a point light source. Form.

  On the other hand, as a light source for illumination, for example, a light source that emits light uniformly from a wide area rather than a point shape is preferable. The uniformity required here is uniformity regarding the light intensity and the spectrum of light. In addition, for illumination, white light (light having a broad emission spectrum) is preferable instead of monochromatic light as described above. For this reason, when an LED is used for illumination, a phosphor that absorbs light emitted from the LED and emits light (fluorescence) having a wavelength different from that of the LED emits light. The light and the light emitted by the fluorescence are mixed. Specifically, an LED that emits blue light and a phosphor that emits yellow fluorescence are used, and white light (pseudo white light) in which blue light emitted from the LED and fluorescent light emitted from the phosphor are mixed is used. Be emitted.

  Moreover, in order to ensure the breadth of a light source, several LED is arranged and used. At this time, the actual light source is an individual small LED, but the apparent light source has a large spread by connecting a plurality of LEDs, that is, emits light uniformly over a wide range. It looks like this. Here, in general, it is preferable to increase the directivity of the emitted light so that the traveling direction is concentrated in a specific direction, that is, to collect light, thereby increasing the illuminance.

  The structure of such an illumination device (LED illumination device) using an LED as a light source is described in Patent Document 1, for example. In this structure, a plurality of small LEDs are arranged, and a large phosphor (color temperature conversion layer) and an internal roughening prism sheet are sequentially provided so as to cover them. The monochromatic light emitted from each LED becomes pseudo white light mixed with the light emitted from the phosphor on the upper side, is emitted to the upper side, and is incident on the internal roughened prism sheet. The internal prism sheet is made of an organic material, and on the lower side (side closer to the LED), a large number of granular materials are dispersed, and functions as a light scattering layer that scatters incident light in various directions. As a result, the apparent light source appears to have a large spread as described above. Since light is dispersed and emitted in various directions by the light scattering layer, a large number of convex shapes (prism elements) are arranged on the upper surface of the internal roughened sheet in order to improve the directivity of light. . By means of the individual prism elements, the direction in which light is emitted can be concentrated in particular on the upper side.

  Further, in the LED lighting device described in Patent Document 2, a plurality of LED chips each formed by integrating a phosphor with an LED are arranged, and a prism sheet is provided on the upper side thereof apart from the LED chip. The prism sheet is a sheet on which a prism element as described above is formed. By providing the prism element on the LED chip side (lower side), light emitted from the LED chip can be diffused. Is provided on the opposite side (upper side) of the LED chip, so that light can be condensed. For this reason, if prism sheets are provided on both the upper and lower sides, light diffusion can be performed on the side closer to the LED chip and light can be condensed on the side far from the LED chip, as in the technique described in Patent Document 1.

  In this way, an illumination device that is preferably used for general illumination, such as an indoor ceiling lamp, can be obtained using the LED.

JP 2011-1224023 A WO2012 / 063759A1

  The LED lighting device as described above is used for various purposes in addition to general indoor lighting. For example, for lighting in an inspection device for inspecting a surface scratch such as a metal or a resin material. Is also used. In such a case, in order to make it easy to recognize fine scratches with high contrast, it is particularly preferable to increase the directivity of light, that is, to increase the degree of light collection. At this time, uniform light emission over a wide range is required as described above.

  In the configuration described in Patent Document 1, light is diffused (scattered) below the internal roughened prism sheet, and condensed on the upper side. In this case, since the distance from when the light is scattered to when it is collected is short, the effect of light diffusion becomes insufficient, and each LED as a light source is apparently separated to cause unevenness in light emission, resulting in a wide range. It was difficult to make uniform light emission.

  In the technique described in Patent Document 2, the light source can be spread and condensed. However, when light is scattered by the prism element on the lower surface of the prism sheet, the component that does not pass through the prism sheet and totally reflects to the LED side (lower side) cannot be ignored, thereby reducing the substantial emission intensity. did. Further, a part of the light of the totally reflected component is again incident on the phosphor on the LED side, is reflected again, and is emitted to the upper side again. At this time, since fluorescence is emitted again, the spectrum of the finally emitted light changes from the desired one. For this reason, unevenness may occur in the intensity and color (spectrum) of the emitted light.

  For this reason, when using LED as a light source, it was difficult to emit light with strong directivity from a wide area.

  The present invention has been made in view of such problems, and an object thereof is to provide an invention that solves the above problems.

In order to solve the above problems, the present invention has the following configurations.
The LED lighting device according to the present invention includes a light scattering layer that scatters light by covering the light emitting diode from above so that a gap is formed between the light emitting diode (LED) and the light emitting diode, and the light scattering layer. A light condensing layer that covers the light scattering layer from above so as to form a gap between the light scattering layer and the light emitted from the light scattering layer.
The LED lighting device according to the present invention includes a fluorescent layer that absorbs light emitted from the light emitting diode and emits fluorescence having a wavelength different from that of the light emitted from the light emitting diode, below the light scattering layer. To do.
The LED lighting device of the present invention is characterized in that a plurality of the light emitting diodes are arranged, and a light emitting diode chip having a configuration in which the fluorescent layer is integrated with the light emitting diode for each light emitting diode is used.
In the LED lighting device of the present invention, the vertical distance between the light emitting diode chip and the light scattering layer is at least five times the distance between the light emitting diode chips adjacent in the horizontal direction. .
The LED lighting device according to the present invention includes a protective layer that covers the light collecting layer from above so that a gap is formed between the LED lighting device and the light collecting layer.
In the LED lighting device of the present invention, the light scattering layer has a structure in which granular materials are dispersed in a transparent organic material.
In the LED lighting device according to the present invention, the material constituting the granular material is transparent and has a refractive index different from that of the organic material.
In the LED lighting device according to the present invention, the light condensing layer includes irregularities formed on the upper surface side.

  Since this invention is comprised as mentioned above, the LED illuminating device which emits light with a strong directivity uniformly from the area | region which spreads can be obtained.

It is sectional drawing along two mutually perpendicular directions of the LED lighting apparatus which concerns on embodiment of this invention. It is sectional drawing of the LED chip used for the LED lighting apparatus which concerns on embodiment of this invention. It is the result of having measured the angle dependence of the light intensity in the LED lighting apparatus used as the Example of this invention, and the comparative example which does not comprise a condensing layer.

  Hereinafter, an LED lighting apparatus according to an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view of the LED lighting device 100. In this LED lighting device 100, for example, light emitting diode chips (LED chips) 10 as described in Japanese Patent Application Laid-Open No. 2012-69885 are arranged one-dimensionally on the upper surface of a substrate 20 constituting a horizontal plane. Fig.1 (a) is sectional drawing perpendicular | vertical to the arrangement direction in the location with a LED chip, FIG.1 (b) is sectional drawing along the arrangement direction. In FIG. 1B, the horizontal interval between the LED chips is L. Here, the light is condensed in a direction perpendicular to the arrangement direction, that is, in FIG. 1A, the light is set to have a particularly high upward directivity. On the other hand, in FIG. 1B, each LED chip 10 is a light emitting source, but when viewed from above, each LED 10 that is a light emitting source cannot be separately recognized, and FIG. ) In the left-right direction over a wide range.

  FIG. 2 is a cross-sectional view schematically showing the structure of the LED chip 10. Here, for example, the structure described in JP 2012-69885 A is simplified and shown. Here, a semiconductor layer (light emitting diode) 11 made of a nitride semiconductor and emitting light of a short wavelength (blue) is mounted on a metal lead frame 12, and the reflection layer 13 is a semiconductor on the lead frame 12. Surrounding the layer 11 is provided. The reflection layer 13 is provided so as to reflect the light emitted from the semiconductor layer 11 upward in the surroundings. For this reason, the light emitted from the semiconductor layer 11 is emitted upward in FIG. However, since only the reflective layer 13 and the lead frame 12 limit the traveling direction of the light, the directivity is not high.

  In addition, a fluorescent layer 14 in which a fluorescent material is added to a resin material is formed in the interior surrounded by the reflective layer 13 on the upper side of the lead frame 12 by sealing the semiconductor layer 11 therein. This fluorescent material absorbs blue light emitted from the semiconductor layer 11 and emits yellow light having a longer wavelength and a wider spectral band. Therefore, the light emitted from the light emitting diode (semiconductor layer 11) and the light emitted from the fluorescent layer 14 are mixed and emitted upward from the LED chip 10, and this light has a long spectrum from the blue side. It becomes white light (pseudo white light) having a spread over the wavelength side. Actually, various wirings are connected to the semiconductor layer 11 and the lead frame 12 in order to flow current to the semiconductor layer 11, but the description thereof is omitted in FIG.

  The width D of the LED chip 10 in FIG. 2 is about 5 mm, for example, and is smaller than the entire width of the LED lighting device 100 in FIG. In the structure of FIG. 2, no light is emitted downward, and the semiconductor layer 11 serving as a light emission source is smaller than the width D. Further, the thickness T of the semiconductor layer 11 is smaller than D. For this reason, light is actually emitted radially upward with the small semiconductor layer 11 as the center.

  In FIG. 1B, the LED chips 10 are one-dimensionally arranged on the substrate 20 with an interval L, and L is about the same as D. 1A and 1B, light is emitted radially from each LED chip 10 individually as indicated by arrows A1 and B1 above each LED chip 10, respectively.

  A light scattering layer 30 is provided on the upper side of the LED chip 10 so as to cover all the LED chips 10. The light scattering layer 30 is provided so that the distance in the vertical direction from the LED chip 10 is X by sandwiching the spacer 21 between the light scattering layer 30 and the substrate 20 at the end. Here, X >> T. The light scattering layer 30 is configured by dispersing a large number of transparent and small granular materials (scattering structures) in a transparent organic material, similarly to the lower portion of the internally roughened prism sheet described in Patent Document 1, Due to the difference in refractive index between the organic material and the granular material, light incident on the interface between the organic material and the granular material is scattered. At this time, since the particles are randomly dispersed, the light emitted from the LED chip 10 is diffused by the light scattering layer 30, and this diffusion occurs at each point in the in-plane direction of the light scattering layer 30. . For this reason, after passing through the light scattering layer 30, light is emitted from each point in the plane of the light scattering layer 30 as indicated by arrows A2 and B2 in FIGS. . When this state is viewed from above, the upper surface of the light scattering layer 30 appears to emit light uniformly, making it difficult to recognize individual LED chips 10. That is, particularly in FIG. 1B, it appears that light is emitted uniformly over the entire surface of the light scattering layer 30 even though a plurality of small LED chips 10 provided in a divided manner are used. .

  On the upper side of the light scattering layer 30, a light collecting layer 40 is provided so as to cover the light scattering layer 30 from above. The condensing layer 40 is provided so that the vertical distance between the light-scattering layer 30 and the light-scattering layer 30 is Y by sandwiching the spacer 22 between the light-scattering layer 30 at the end. The condensing layer 40 is the same as the upper side of the internally roughened prism sheet described in Patent Document 1 or the prism sheet provided with the prism element on the upper side in Patent Document 2, and collects scattered light incident from the lower side. A large number of structures (light condensing structures) that emit light and increase the directivity toward the upper side are provided in the light condensing layer 40. In order to collect light in a direction perpendicular to the arrangement direction of the LED chips 10, the condensing layer 40 is provided with irregularities serving as prism elements (condensing structures) along the arrangement direction. For this reason, the uneven | corrugated shape used as this condensing structure is shown only in Fig.1 (a) perpendicular | vertical to the arrangement direction of LED chip 10. FIG. Thereby, in FIG. 1A, the light is focused so that the direction of the light after passing through the condensing layer 40 is mainly on the upper side as indicated by an arrow A3. On the other hand, since the light is not condensed in the arrangement direction, in FIG. 1B along this arrangement direction, this light is divergent light whose direction is the same as that of the arrow B2, as indicated by the arrow B3. Become.

  On the upper side of the light collecting layer 40, a uniformly formed transparent protective layer 50 is provided so as to be separated from the light collecting layer 40 so as to cover the light collecting layer 40. The protective layer 50 does not scatter or condense light, and the protective layer 50 serves as a window for protecting the condensing layer 40, the light scattering layer 30, the LED chip 10 and the like below and for extracting light. The protective layer 50 functions. The protective layer 50 corresponds to the protective cover in Patent Document 2. For this reason, the arrow A4 indicating the direction of light after passing through the protective layer 50 in FIG. 1A is the same direction as the arrow A3 in the lower layer, and after passing through the protective layer 50 in FIG. The arrow B4 indicating the direction of light is also the same direction as the arrow B3 below it. The protective layer 50 is made of, for example, a transparent, uniform, and flat organic material.

  In the above configuration, light (arrows A1 and B1) emitted radially upward from the LED chip 10 is incident on the flat light scattering layer 30. At this time, it is preferable that the individual LED chips 10 do not emit light separately from each other when viewed from the upper side of the light scattering layer 30, but the light scattering layer 30 seems to emit light as a whole. For this purpose, it is preferable that X is made sufficiently large so that light emitted from each LED chip 10 is incident on the light scattering layer 30 from the lower side in a sufficiently diffused state. At this time, if the distance L between the LED chips 10 is large, X must be increased accordingly. For this reason, it is preferable that X is 5 times or more of L. As described above, X can be set by the spacer 21. In addition, since X >> T, the distance between the substrate 20 and the light scattering layer 30 can be actually set to X. In FIGS. 1 and 2, for convenience, the relationship between D, T, X, Y, and L is shown differently from the actual one.

  At this time, unlike the case where light is scattered using a prism sheet as described in Patent Document 2, there are few components that totally reflect downward. Furthermore, when X is small, there is a high possibility that the totally reflected component will re-enter the fluorescent layer 14 in the LED chip 10, but even if there is a component that totally reflects by increasing X, The possibility that the light of this component will re-enter the fluorescent layer 14 is low, and this light is reflected on the substrate 20 side and enters the light scattering layer 30 again, or this light does not pass through the light scattering layer 30. It is emitted to the outside as it is. For this reason, it is unlikely that the spectrum of light traveling from the light scattering layer 30 toward the light collecting layer 40 is adversely affected by the totally reflected light. However, since the LED lighting device 100 increases in size when X increases, X is set in consideration of the overall size of the LED lighting device 100.

  In the condensing layer 40, in order to make apparent light emission uniform over a wide area in the entire condensing layer 40, it is preferable that the light is incident on the condensing layer 40 from the lower side in a sufficiently divergent state. For this purpose, it is preferable to provide a gap between the light scattering layer 30 and the light collecting layer 40, that is, to increase the interval Y. Specifically, the interval Y is preferably optically thick enough to be at least 10 times the wavelength of blue light (approximately 460 nm) that becomes the short wavelength side end in the spectrum of emitted light. For this reason, the light-scattering layer 30 and the condensing layer 40 are comprised separately.

  Further, since the protective layer 50 has only a function of transmitting light, the interval between the protective layer 50 and the light collecting layer 40 can protect the upper surface of the light collecting layer 40 adjacent to the protective layer 50. Set as appropriate. In particular, since the prism shape (condensing structure) as described above is formed on the upper surface of the condensing layer 40, the prism-shaped portion and the protective layer 50 are not in direct contact with each other, and the prism structure These intervals are set so that is covered with the protective layer 50 when viewed from above.

  Or when the surface of the condensing layer is protected by another structure, the protective layer 50 is unnecessary. Conversely, the protective layer may have a function of scattering light in the same manner as the light scattering layer 30. However, in order to maintain the light collecting effect by the light collecting layer 40, it is preferable to make the light scattering effect weaker than that of the lower light scattering layer 30.

  FIG. 3 shows an example in which L = 4 mm, X = 20 mm, and Y = 0.75 mm in the above structure, and a protective layer in a direction perpendicular to the arrangement direction when the condensing layer 40 is not provided in the same structure. Is the result of measuring the angular distribution of the light intensity after passing through (based on the upward direction in FIG. 1A). Here, it is standardized with reference to the intensity of light emitted upward (when the angle is 0 °). As the light condensing layer 40, a light condensing structure using a prism structure having a period of 50 μm and a depth of 25 μm in FIG. From this result, it can be confirmed that the embodiment can emit light with improved upward directivity.

  In the above configuration, the fluorescent layer is provided in each LED chip. However, the fluorescent layer is not used in each LED chip, and the light emitting element in the LED chip may be only the semiconductor layer. In such a case, similarly to the structure described in Patent Document 1, for example, a large fluorescent layer can be provided so as to cover the entire arrayed LED chips, and a light scattering layer and a condensing layer are formed thereon as in the above. Can be provided. At this time, if the distance between the fluorescent layer and the light scattering layer is X, and the distance between adjacent semiconductor layers (light emitting diodes) is L, the same effect can be obtained.

  Alternatively, even in the case of emitting monochromatic light without using a fluorescent layer, it is clear that the above configuration is effective when the light source spread and the light directivity are required as described above. In this case, the same effect can be obtained if the distance between the semiconductor layer (light emitting diode) emitting monochromatic light and the light scattering layer is X and the distance between adjacent semiconductor layers is L. In this case, the light emission wavelength of the light emitting diode is arbitrary, and the dimensions of the scattering structure and the light collecting structure can be set according to this.

  In addition, as long as it is possible to function in the same manner, the structure of the light scattering layer or the individual scattering structure that scatters light, and the structure of the condensing layer or the individual light condensing structure that collects light thereafter, as described above. Different structures can be used. At this time, in the above structure, the LEDs are arranged along one direction and are condensed in a direction perpendicular to the arrangement direction. For example, the LEDs may be arranged two-dimensionally. Even in this case, the condensing layer or the condensing structure can be appropriately set according to the condensing direction.

10 Light emitting diode chip (LED chip)
11 Semiconductor layer (light emitting diode)
12 Lead frame 13 Reflective layer 14 Fluorescent layer 20 Substrate 21, 22 Spacer 30 Light scattering layer 40 Condensing layer 50 Protective layer 100 LED lighting device

Claims (8)

A light emitting diode (LED);
A light scattering layer that covers the light emitting diode from above so that a gap is formed between the light emitting diode and scatters light;
A light condensing layer that covers the light scattering layer from above so that a gap is formed between the light scattering layer and collects light emitted from the light scattering layer;
LED lighting device characterized by comprising.   The LED according to claim 1, further comprising a fluorescent layer that absorbs light emitted from the light emitting diode and emits fluorescence having a wavelength different from that of the light emitted from the light emitting diode, below the light scattering layer. Lighting device.   The LED lighting device according to claim 2, wherein a plurality of the light emitting diodes are arranged, and a light emitting diode chip having a configuration in which the fluorescent layer is integrated with the light emitting diode for each of the light emitting diodes. .   4. The LED illumination according to claim 3, wherein a distance in the vertical direction between the light emitting diode chip and the light scattering layer is not less than 5 times a distance between the light emitting diode chips adjacent in the horizontal direction. apparatus.   5. The LED according to claim 1, further comprising a protective layer that covers the light collecting layer from above so that a gap is formed between the light collecting layer and the light collecting layer. Lighting device.   The LED light device according to any one of claims 1 to 5, wherein the light scattering layer has a structure in which particles are dispersed in a transparent organic material.   The LED illuminating device according to claim 6, wherein the material constituting the granular material is transparent and has a refractive index different from that of the organic material.   8. The LED lighting device according to claim 1, wherein the condensing layer includes irregularities formed on an upper surface side. 9.

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