JP2010118531A - White lighting system and lighting fixture for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting system having large luminance, a small temperature increase, and improved chromaticity uniformity, where a plurality of LED chips are arranged linearly. <P>SOLUTION: The lighting system includes: a plurality of light-emitting elements 2 arranged in a line with a prescribed interval; and a phosphor layer 3 for integrally covering the upper and side faces of the plurality of light-emitting elements 2. The interval (d1) of the light-emitting elements is nearly equal to distance (d2) between the side face of the light-emitting elements and that of the phosphor layer 3, thus preventing a change in chromaticity from appearing periodically in illumination light. Also, a film thickness (d3) of the phosphor layer is reduced as compared with d1 or d2, thus further preferably preventing a phenomenon, where emission light (excitation light) from the light-emitting elements has a strong color taste at edges of illumination light. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an illumination device that uses LEDs (semiconductor light emitting elements) arranged in a line as a light source, and more particularly, to a vehicular lamp such as an automotive headlamp.

  In an illuminating device using LEDs, a plurality of LED chips are generally used in order to increase brightness, and are arranged in a predetermined shape. Patent Documents 1 to 3 describe examples of light sources in which a plurality of LED chips are arranged.

  Among lighting devices using LEDs as light sources, it is important that vehicle lamps have a rectangular light emission shape (Patent Document 1) and that the chromaticity is uniform over the entire irradiated surface (Patent Document 2). is there. Patent Document 1 discloses an LED light source in which the light emission shape is rectangular by designing the ratio of the short side and long side of the light emitting surface of the arranged LED chips to be in the range of 1: 2 to 1: 6. Has been. Patent Document 2 discloses an invention in which the chromaticity in the irradiation surface is made uniform by disposing a translucent resin layer between a plurality of LED chips and a phosphor layer covering the LED chips.

  FIG. 2 of Patent Document 1 discloses that a white light source is manufactured by arranging phosphors around a plurality of arranged LED chips.

JP 2006-048934 A JP 2005-109434 A JP 2007-281473 A

  In an optical system in which a light source in which a plurality of LED chips are arranged and a lens or a reflecting surface is combined, it is preferable to arrange the LED chips with a small space between them so that it can be handled as a point light source. This means that the deviation of the light distribution characteristics of each chip is reduced and the maximum luminance can be increased. This maximum brightness is particularly important for vehicle lamps and the like. However, if the space between the LED chips is reduced, there arises a problem that the heat dissipation characteristics are deteriorated. In particular, since it is necessary to increase the brightness of the vehicle lamp, a large current is supplied to the LED chip. Therefore, if the heat dissipation characteristic is low, the LED chip part generates a large amount of heat, resulting in a decrease in luminous efficiency. Cause problems.

  Moreover, the LED light source used for the vehicle lamp has a configuration in which LED chips are usually arranged in a line in the horizontal direction in order to enhance directivity. For this reason, unlike other general illuminations in which a plurality of LED chip rows are arranged side by side, the light beams emitted from the plurality of LED chip rows cannot be overlapped and made uniform, and the colors from the LED chips arranged in a row cannot be obtained. It is necessary to emit light with excellent uniformity of brightness and brightness.

  An object of the present invention is to provide an illuminating device in which a plurality of LED chips are linearly arranged, which has a large luminance, a small temperature rise, and an excellent chromaticity uniformity.

  In order to achieve the above object, according to the present invention, there is provided a lighting device having a plurality of light emitting elements arranged in a row at a predetermined interval, and a phosphor layer that integrally covers the upper surface and side surfaces of the plurality of light emitting elements. Thus, a white illumination device is provided in which the interval (d1) between adjacent light emitting elements is substantially equal to the distance (d2) between the side surface of the light emitting element and the side surface of the phosphor layer. By designing d1 and d2 to be substantially equal, it is possible to prevent periodic chromaticity changes from appearing in the illumination light.

  The film thickness (d3) of the phosphor layer on the upper surface of the light emitting element is smaller than the distance (d1) between the light emitting elements or the distance (d2) between the side surface of the light emitting element and the side surface of the phosphor layer. Further, it is more preferable because the phenomenon that the light emitted from the light emitting element (excitation light) becomes white light at the edge portion of the illumination light can be prevented.

  As another aspect of the present invention, a vehicle lamp is provided. That is, a vehicle lamp having a lamp housing, a white light source disposed in the lamp housing, and a light projecting lens disposed at a position through which light emitted from the white light source passes, the white light source being a predetermined light source A plurality of light emitting elements arranged in a row with a spacing of and a phosphor layer that integrally covers the top and side surfaces of the plurality of light emitting elements, and the interval (d1) between adjacent light emitting elements is the light emitting element The distance between the side surface and the side surface of the phosphor layer is substantially equal to the distance (d2). Thereby, it is possible to prevent periodic chromaticity changes from appearing in the illumination light of the vehicle lamp.

  Further, in the vehicle lamp, the thickness (d3) of the phosphor layer on the upper surface of the light emitting element is the distance (d1) between the light emitting elements, or the distance (d2) between the side surface of the light emitting element and the side surface of the phosphor layer. Is smaller than that, since it is possible to prevent a phenomenon in which the emitted light (excitation light) of the light emitting element becomes white light at the edge portion of the illumination light, which is further preferable.

  Even in a lighting device in which a plurality of LED chips are arranged in a row, it is possible to prevent a decrease in chromaticity uniformity, a decrease in luminance, an increase in temperature, and the like. In particular, it is possible to obtain a white illumination device (light source) that is most suitable for a vehicular lamp combined with a lens or a reflecting surface.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS.

  FIG. 1 is a perspective view of the white illumination device of this embodiment, and FIG. 2 is a cross-sectional view taken along the line A-A ′. As shown in FIGS. 1 and 2, the white lighting device 1 has a plurality of LED chips 2 (four in this case) arranged in a line on a substrate 4 on which wiring is formed in advance, and the upper surface of the plurality of LED chips 2. And the side surface is integrally covered with the phosphor layer 3. The outer shape of the phosphor layer 3 is rectangular.

  As shown in FIG. 1, the distance between adjacent LED chips 2 is d1, and the distance between the side surface of the LED chip 2 and the side surface of the phosphor layer 3 is d2. As shown in FIG. 2, the thickness of the phosphor layer 3 on the upper surface of the LED chip 2 is d3.

  The LED chip 2 is a flip chip, and has a configuration in which a light emitting layer including an active layer is mounted on an LED substrate, and an electrode layer having a predetermined shape is provided thereon, although not shown. The LED chip 2 is mounted on the substrate 4 with the LED substrate facing upward and the electrode layer facing the substrate 4 side. The electrode layer is bonded to the wiring on the substrate 4. As the LED substrate, a material transparent to the light emitted from the light emitting layer is used.

  The light emitting layer of the LED chip 2 is configured to emit blue light from the upper surface and side surfaces. The phosphor layer 3 contains a phosphor that emits yellow fluorescence using blue light as excitation light (for example, a YAG phosphor).

  Therefore, the blue light emitted from the LED chip 2 enters the phosphor layer 3, and part of the blue light excites the phosphor and is converted into yellow light (fluorescence). The remaining blue light passes through the phosphor layer 3 as blue light. Thereby, yellow light (fluorescence) and blue light are mixed, and white light is emitted.

  In the present embodiment, the arrangement and fluorescence of the plurality of LED chips 2 are set so that the distance (d1) between the adjacent LED chips 2 and the distance (d2) between the side surface of the chip 2 and the side surface of the phosphor layer 3 are substantially equal. The shape of the body layer 3 is defined. Further, in addition to this condition, the thickness (d3) of the phosphor layer 3 on the top surface of the chip 2 is the distance (d1) between the chips 2 or the distance (d2) between the side surface of the chip 2 and the side surface of the phosphor layer 3. It is desirable to arrange a plurality of LED chips 2 and phosphor layers 3 so as to be smaller.

  These distances d1, d2, and d3 are determined as described above for the following reason.

  (1) The distance d1 between adjacent LED chips 2 is preferably as small as possible in order to enable handling as a point light source and increase the maximum luminance. If the distance d1 between the LED chips 2 is small, the light emitting area becomes small and becomes close to a point light source, so that it becomes easy to design a lens and a reflecting surface, and the light emitting area with respect to the amount of light becomes small and the maximum luminance is improved.

  (2) On the other hand, in consideration of heat dissipation, it is advantageous that the distance d1 between the LED chips 2 is larger.

  (3) The distance d2 between the LED chip 2 side surface and the phosphor layer 3 side surface seems to be determined regardless of the distance d1 between the chips 2, but the distance d1 between the chips 2 is equal to the side surface 2 of the chip 2 and the phosphor layer 3 When the distance d2 is larger than the distance d2 from the side surface, a periodic chromaticity change corresponding to the arrangement of the plurality of chips 2 arranged in a row occurs, and the chromaticity uniformity of the white light emitted from the upper surface of the chip 2 is poor. turn into.

  That is, as shown in FIG. 3, when the distance d1 between the chips 2 is larger than the distance d2 between the side surface of the chip 2 and the side surface of the phosphor layer 3, the amount of phosphor existing between the adjacent chips 2 is More than the amount of phosphor existing between the two side surfaces and the phosphor layer 3 side surface, the amount of yellow light (fluorescence) generated in the region 31 between the adjacent chips 2 is reduced. It increases more than the amount of yellow light generated between the sides. For this reason, the yellow color of the white light emitted from the region 31 between the adjacent chips 2 is stronger than the white light of the surrounding region 30, and the yellow color is periodically strong for each gap between the LED chips 2. A degree change occurs.

  When an LED lighting device that generates such a periodic chromaticity change is used as a lamp, a periodic chromaticity change appears in the central portion of the irradiation light, resulting in a very poor quality.

  (4) When the distance d2 between the side surface of the chip 2 and the side surface of the phosphor layer 3 is smaller than the film thickness d3 of the phosphor layer 3 on the top surface of the chip 2, the light emitted from the side surface of the LED chip array is The color of the excitation light (light emitted from the LED chip) becomes stronger than the light emitted from the LED. That is, as shown in FIG. 4, a phenomenon occurs in which the excitation light color is more intense than the peripheral region 40 in the edge portion 41 of the illumination light that forms the cut-off line.

  This phenomenon is caused by the fact that the reflectance of the return light is different between the upper surface and the side surface of the LED chip 2. As shown in FIG. 2, when a part of the light 20 emitted from the LED chip 2 in the upper surface direction is reflected inside the phosphor and becomes return light 21 toward the LED chip 2, the main surface of the LED chip 2 is reflected. Since the light is incident from a substantially vertical direction, the light is reflected by the interface of the active layer and the electrode film on the structure of the LED chip 2 and becomes light 22 toward the upper surface again. Thereby, it passes again through the phosphor layer 3 on the upper surface of the LED chip 2 to emit fluorescence. On the other hand, when a part of the light 23 emitted in the side surface direction of the LED chip 2 is reflected inside the phosphor and becomes return light 24 to the LED chip 2, it is parallel to the main plane of the LED chip 2. Since the light is incident on the LED chip 2 from any direction, most of the light is absorbed by the active layer and the electrode, and the reflected light is very small. For this reason, there is little light which goes to a side surface again, and there is also little light quantity which passes the fluorescent substance layer 3 again and light-emits fluorescence.

  For this reason, in the upper surface direction of the LED chip 2, the phosphor layer 3 on the side surface of the LED chip 2 emits sufficient fluorescence even when the film thickness d3 of the phosphor layer 3 is thin. When the distance d2 between the phosphor layer 3 and the side surface of the phosphor layer 3 is small, sufficient fluorescence cannot be emitted and the color of blue light (excitation light) becomes strong.

  This appears in the edge portion 41 of the irradiation light, so-called cut-off line, and can be easily identified as excitation light color unevenness, and deteriorates the quality of the illumination light.

As a result of intensive studies on each dimension according to these ideas, when the white lighting device satisfies the following relationship (a) or (b), the brightness is large, the temperature rise is small, and the chromaticity uniformity is excellent. It was found that a lighting device can be provided. In particular, an excellent light source can be obtained in a vehicular lamp combined with a lens or a reflecting surface.
(a) The distance d1 between the adjacent LED chips 2 and the distance d2 between the side surface of the LED chip 2 and the side surface of the phosphor layer 3 are substantially equal.
(b) The distance d1 between the adjacent LED chips 2 and the distance d2 between the side surface of the LED chip 2 and the side surface of the phosphor layer 3 are substantially equal, and the film thickness d3 of the phosphor layer 3 on the upper surface of the LED chip 2 is The distance d1 between the LED chips 2 and the distance d2 between the side surface of the LED chip 2 and the side surface of the phosphor layer 3 are smaller.

  In the case of the configuration in which the relationship (a) is satisfied, it is possible to prevent a periodic chromaticity change from occurring in the central portion of the irradiation light. Further, in the case of the configuration in which the relationship (b) is satisfied, the blue light (excitation light) color is prevented at the edge portion of the irradiation light that prevents the periodic chromaticity change of the illumination light and forms the cut-off line. Both strong phenomena can be prevented.

  In the lighting device that satisfies the relationship (a) and (b) above, the distance d1 and the distance d2 are substantially equal, not only when d1 and d2 are completely matched, but also in the period that occurs in the illumination light. The chromaticity change may be within a predetermined allowable range, and the case where d1 and d2 are slightly different is also included.

  The illumination device of the present invention can be used as various white illumination devices using a plurality of LED chips. In particular, in the present invention, even when a plurality of LED chips are arranged in a straight line, a phenomenon in which blue light is intensely emitted at the edge portion of illumination light that forms a periodic chromaticity change or a cut-off line. Therefore, it is possible to provide an illumination device that has high brightness, little temperature rise, and excellent chromaticity uniformity. Therefore, white illumination suitable for a vehicular lamp can be provided. For example, a configuration of a vehicle lamp (for example, a headlamp) in which the white illumination device of the present embodiment is arranged in a lamp housing and a light projecting lens is arranged on the front surface thereof is adopted. The light emitted from the white illumination device passes through the light projecting lens and becomes illumination light, which is irradiated forward of the vehicle.

<Example 1>
As Example 1, an illuminating device in which the distance d1 between adjacent LED chips 2 of the above embodiment and the distance d2 between the side surface of the LED chip 2 and the side surface of the phosphor layer 3 were substantially equal was manufactured.

  First, the LED chip 2 having a length of one side of the upper surface of 1.0 mm was placed on the ceramic substrate 4 and the distance between the chips d1 was set to 100 μm, and the four LED chips 2 were linearly arranged and bonded. The phosphor layer 3 was formed on the side surface and upper surface of the LED chip 2 by using a stencil printing (metal mask printing) technique.

  The phosphor layer 3 is made of a paste obtained by mixing 35 wt% to 52 wt% of phosphor particles and 10 wt% of fumed silica for viscosity adjustment with respect to a silicone-based thermosetting resin, and a stainless steel stencil (metal mask). ) Was used for printing. The thickness of the stencil having a thickness approximately equal to the sum of the thickness of the LED chip 2 including the junction with the substrate 4 and the thickness d3 of the phosphor disposed on the LED chip 2 is used. did. The opening width of the stencil was designed such that the distance d2 between the LED chip 2 side surface and the phosphor layer 3 side surface was 100 μm.

  After the paste of the phosphor layer 3 was printed, it was heated at 150 ° C. for 2 hours to cure the silicone resin.

  As a result, a lighting device was manufactured in which the distance d1 between the LED chips 2 of this example and the distance d2 between the side surface of the chip 2 and the side surface of the phosphor layer 3 were all equal to 100 μm.

  When the irradiation light of the illumination device of this example was observed, the chromaticity was uniform over the entire irradiation surface.

  On the other hand, as Comparative Example 1, an illumination device of Comparative Example 1 was manufactured in the same manner, in which the distance d1 between adjacent LED chips 2 was 300 μm and the distance d2 between the side surface of the chip 2 and the side surface of the phosphor layer 3 was 100 μm. When the illumination light of the illumination device of Comparative Example 1 was observed, as shown in FIG. 3, the chromaticity uniformity of the white light emitted from the upper surface of the chip 2 was deteriorated, corresponding to the arrangement of four LED chips arranged in a row. There was a periodic change in chromaticity. For this reason, it was poor. In addition, the area | region where yellowishness was strong respond | corresponded to the area | region of the gap | interval of LED chip 2. FIG.

<Example 2>
As Example 2, the distance d1 between the adjacent LED chips 2 and the distance d2 between the side surface of the LED chip 2 and the side surface of the phosphor layer 3 are substantially equal, and the film thickness of the phosphor layer 3 on the upper surface of the LED chip 2 An illumination device was manufactured in which d3 is smaller than the distance d1 between the LED chips 2 and the distance d2 between the side surface of the LED chip 2 and the side surface of the phosphor layer 3.

  The manufacturing method was basically the same as in Example 1, and the distance d1 between the chips 2 was 100 μm. The distance d2 between the side surface of the LED chip 2 and the side surface of the phosphor layer 3 was also set to 100 μm.

  In addition, the thickness of the stencil was designed so that the thickness d3 of the phosphor disposed on the LED chip 2 was 75 μm.

  When the illumination light of the illumination device of Example 2 was observed, the chromaticity was uniform over the entire irradiated surface.

  On the other hand, as Comparative Example 2, the thickness d3 of the phosphor layer on the upper surface of the LED chip 2 is 120 μm, the distance d1 between adjacent LED chips 2 is 100 μm, and the distance d2 between the side surface of the LED chip 2 and the side surface of the phosphor layer 3 is 100 μm. The lighting device of Comparative Example 2 was manufactured in the same manner as in Example 2 except for the other conditions.

  When the illumination light of the illumination device of Comparative Example 2 was observed, the light emitted from the side surface of the chip row was more bluish than the light emitted from the upper surface, and this was an edge portion 41 of the irradiated light as shown in FIG. It appeared in a so-called cut-off line and could be easily identified as blue unevenness. For this reason, the quality was very bad.

  In addition, when samples with varying thickness d3 of the phosphor layer were prepared and the uniformity of chromaticity was measured, it was found that the uniformity of chromaticity deteriorates when the thickness d3 is smaller than d2 / 2. . Therefore, d3 is preferably d2 / 2 or more in thickness and smaller than d1 or d2. Furthermore, the range of 0.6 × d2 ≦ d3 ≦ 0.8 × d2 is preferable because chromaticity uniformity is particularly improved.

  In Example 1 and Example 2 described above, the phosphor layer 3 is formed by stencil printing. However, the present invention is not limited to this method, and a general phosphor layer forming method such as a screen printing method or a dispensing method can be used. Applicable.

The perspective view which shows the chip | tip space | interval d1 of the illuminating device of this embodiment, and the distance d2 of a chip | tip side surface and a fluorescent substance layer side surface. FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. 1 for explaining a relationship between a distance d2 between the chip side surface and the phosphor layer side surface and a film thickness d3 of the phosphor disposed on the chip upper surface. The illumination light chromaticity distribution figure which shows that the periodic chromaticity change has arisen in the illumination light of an illuminating device. The illumination light chromaticity distribution map which shows that the blue nonuniformity has arisen in the edge part of the illumination light of an illuminating device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... White illuminating device, 2 ... LED chip, 3 ... Phosphor layer, 4 ... Substrate.

Claims (4)

A plurality of light emitting elements arranged in a row at a predetermined interval, and a phosphor layer that integrally covers the top and side surfaces of the plurality of light emitting elements,
The white illumination device according to claim 1, wherein a distance (d1) between the adjacent light emitting elements is substantially equal to a distance (d2) between a side surface of the light emitting element and a side surface of the phosphor layer.   2. The white illumination device according to claim 1, wherein the thickness (d3) of the phosphor layer on the upper surface of the light emitting element is an interval (d1) between the light emitting elements, or a side surface of the light emitting element and the phosphor layer. A white illumination device characterized by being smaller than a distance (d2) from a side surface. A vehicle lamp having a lamp housing, a white light source disposed in the lamp housing, and a light projecting lens disposed at a position through which light emitted from the white light source passes,
The white light source has a plurality of light emitting elements arranged in a row at a predetermined interval, and a phosphor layer that integrally covers the top and side surfaces of the plurality of light emitting elements,
The vehicle lamp according to claim 1, wherein a distance (d1) between the adjacent light emitting elements is substantially equal to a distance (d2) between a side surface of the light emitting element and a side surface of the phosphor layer.   4. The vehicle lamp according to claim 3, wherein the thickness (d3) of the phosphor layer on the upper surface of the light emitting element is the distance (d1) between the light emitting elements or the side surface of the light emitting element and the phosphor layer. A vehicle lamp characterized by being smaller than a distance (d2) from a side surface.

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