JP2019083217A - Light emitting device - Google Patents

Abstract

To provide a light emitting device in which luminance unevenness is restrained.SOLUTION: A light emitting device comprises a board 11, a plurality of light sources 20 located on the board 11, a light diffusion plate 33, a half mirror 31 located between the light diffusion plate 33 and the plurality of light sources 20 on the board 11, and a scattering reflection part 32 located between the board 11 and the light diffusion plate 33 and above at least a portion of emitting surfaces of the plurality of light sources 20. The scattering reflection part 32 is located on a surface of the light diffusion plate 33 on the side of the half mirror 31, or an upper surface 31a or a lower surface 31b of the half mirror 31, and includes a resin and particles dispersed in the resin.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a light emitting device.

  In recent years, a direct light emitting device using a semiconductor light emitting element has been proposed as a backlight used for a display device such as a liquid crystal display device. For example, Patent Documents 1 and 2 disclose a light emitting device in which a plurality of light emitting diodes (LEDs: Light Emitting Diodes) are arranged, and a reflecting plate and a half mirror whose reflectance is partially controlled are combined.

JP 2012-174371 A JP 2012-212509 A

  In the direct type light emitting device, it is required to reduce the luminance unevenness of the light emitted from the light source. One exemplary embodiment of the present application provides a light emitting device in which uneven brightness is suppressed.

  A light emitting device according to an embodiment of the present disclosure includes a substrate, a plurality of light sources located on the substrate, a light diffusion plate, a half mirror located between the light diffusion plate and the plurality of light sources of the substrate, A scattering and reflecting unit is provided between the substrate and the light diffusion plate, and located above at least a part of the emission surface of the plurality of light sources.

  According to the embodiment of the present invention, it is possible to provide a light emitting device in which uneven brightness is suppressed.

It is sectional drawing which shows an example of embodiment of a light-emitting device. It is a top view of a light source unit. It is a figure which shows the light distribution characteristic of the light radiate | emitted from a light source. It is a figure which shows an example of the angle dependence characteristic of the reflectance of the half mirror of embodiment, and the transmittance | permeability. It is a figure which shows the relationship of the reflective wavelength zone | band of the half mirror of embodiment, and the light emission wavelength of a light emitting element. It is a top view which shows arrangement | positioning of the scattering and reflecting part of embodiment. It is a top view which shows the other arrangement | positioning of the scattering and reflecting part of embodiment. It is a top view which shows the structure of the scattering and reflecting part of embodiment. It is sectional drawing which shows the other structure of the scattering and reflecting part of embodiment. It is sectional drawing which shows another example of embodiment of a light-emitting device. It is sectional drawing which shows another example of embodiment of a light-emitting device. It is sectional drawing which shows another example of embodiment of a light-emitting device. It is sectional drawing which shows another example of embodiment of a light-emitting device. It is a figure which shows the luminance distribution of an Example and a reference example.

  According to the study of the inventor of the present application, in the half mirror used in the light emitting device disclosed in Patent Documents 1 and 2, it is necessary to control the reflectance partially depending on the size and the specification of the display panel. For this reason, the half mirror to be used must be prepared as a special exclusive member, and as a result, it is thought that the half mirror used for the light emitting device for a large screen liquid crystal television will be a very expensive part. Be

  Further, in the light emitting device disclosed in Patent Document 2, the half mirror is configured using aluminum as a reflector. However, since aluminum absorbs a part of visible light, the light emitted from the light source is repeatedly reflected between the half mirror and the reflection plate, and is absorbed by the half mirror, and the extraction efficiency to the outside decreases. It will In addition, when the reflectances of the half mirrors are partially different, uneven brightness may occur at boundaries where the reflectances are different. In view of such problems, the inventor of the present application has conceived a light emitting device having a novel structure.

  Hereinafter, embodiments of the light emitting device of the present disclosure will be described in detail with reference to the drawings. The following embodiments are exemplifications, and the light emitting device of the present disclosure is not limited to the following embodiments. In the following description, terms indicating a specific direction or position (for example, "upper", "lower", "right", "left" and other terms including those terms) may be used. These terms only use relative orientations and positions in the referenced drawings for the sake of clarity. As long as the relative directions and positions in terms of terms such as “upper” and “lower” in the referred drawings are the same, the drawings other than the present disclosure, actual products, etc. do not have the same arrangement as the referred drawings. May be Further, the sizes and positional relationships of the components shown in the drawings may be exaggerated for the sake of easy understanding, and the size in an actual surface light emitting device or the size between components in an actual surface light emitting device It may not reflect the relationship. Further, in the present disclosure, “parallel” and “vertical” or “orthogonal” mean that two straight lines, sides or faces, etc. are about 0 ° to ± 5 ° and 90 ° to ± 5 unless otherwise specified. Including the case in the range of ° degree.

(Structure of light emitting device 101)
FIG. 1 is a cross-sectional view showing an example of the light emitting device 101 of the first embodiment. The light emitting device 101 includes a light source unit 10 including a substrate 11 and a plurality of light sources 20 disposed on the substrate 11, a half mirror 31, a light diffusion plate 33 and a scattering reflector 32 and emits light from the light source 20 of the light source unit 10. And a light transmitting laminate 30 through which light is transmitted. Each component will be described in detail below.

[Substrate 11]
The substrate 11 has an upper surface 11a and a lower surface 11b, and a plurality of light sources 20 are disposed and supported on the upper surface 11a side. The conductor wiring layer 13 and the metal layer 12 described in detail below are provided on the upper surface 11 a and the lower surface 11 b of the substrate 11. Moreover, the division member 15 which respectively encloses the some light source 20 is provided in the upper surface 11a.

  As a material of the substrate 11, for example, ceramics and resin can be used. A resin may be selected as the material of the substrate 11 in terms of low cost and ease of molding. Examples of the resin include phenol resin, epoxy resin, polyimide resin, BT resin, polyphthalamide (PPA), polyethylene terephthalate (PET) and the like. The thickness of the substrate can be appropriately selected, and the substrate 11 may be either a flexible substrate that can be manufactured by a roll-to-roll method, or a rigid substrate. The rigid substrate may be a bendable thin rigid substrate.

Moreover, you may select ceramics as a material of the board | substrate 11 from a viewpoint of being excellent in heat resistance and light resistance. Examples of the ceramic include alumina, muraite, forsterite, glass ceramics, nitrides (eg, AlN), carbides (eg, SiC), LTCC and the like.

The substrate 11 may be formed of a composite material. Specifically, an inorganic filler such as glass fiber, SiO ₂ , TiO ₂ or Al ₂ O ₃ may be mixed with the above-mentioned resin. For example, glass fiber reinforced resin (glass epoxy resin) etc. are mentioned. Thereby, the mechanical strength of the substrate 11 can be improved, the thermal expansion coefficient can be reduced, and the light reflectance can be improved.

  The substrate 11 may have a laminated structure as long as at least the upper surface 11 a has electrical insulation. For example, the substrate 11 may use a metal plate provided with an insulating layer on the surface.

[Conductive wiring layer 13]
The conductor wiring layer 13 is provided on the upper surface 11 a of the substrate 11. The conductor wiring layer 13 has a wiring pattern for supplying power to the plurality of light sources 20 from the outside. The material of the conductor wiring layer 13 can be appropriately selected depending on the material used as the substrate 11, the manufacturing method, and the like. For example, when a ceramic is used as the material of the substrate 11, the material of the conductor wiring layer 13 is formed of, for example, a high melting point metal that can be co-fired with the ceramic of the substrate 11. For example, the conductor wiring layer 13 is formed of a high melting point metal such as tungsten or molybdenum. The conductor wiring layer 13 may have a multilayer structure. For example, the conductor wiring layer 13 may be a high melting point metal pattern formed by the above-described method, and a metal layer containing another metal such as nickel, gold, silver or the like formed on the pattern by plating, sputtering, vapor deposition or the like. May be provided.

  When using glass epoxy resin as a material of the board | substrate 11, it is preferable to select the material which is easy to process as a material of the conductor wiring layer 13. As shown in FIG. For example, a metal layer such as copper or nickel formed by plating, sputtering, vapor deposition, or attachment by a press can be used. The metal layer can be processed into a predetermined wiring pattern by masking and etching by printing, photolithography or the like.

[Metal layer 12]
The light source unit 10 may further include a metal layer 12 on the lower surface 11 b of the substrate 11. The metal layer 12 may be provided on the entire lower surface 11 b for heat radiation, or may have a wiring pattern. For example, the metal layer 12 may have a circuit pattern of a drive circuit for driving the light source 20. Furthermore, components constituting the drive circuit may be mounted on the circuit pattern of the metal layer 12.

[Light source 20]
The plurality of light sources 20 are disposed on the upper surface 11 a side of the substrate 11. FIG. 2 is a top view of the light source unit 10. The plurality of light sources 20 are arranged in one or two dimensions on the upper surface 11 a of the substrate 11. In the present embodiment, the plurality of light sources 20 are two-dimensionally arranged along two orthogonal directions, that is, the x direction and the y direction, and the arrangement pitch px in the x direction is equal to the arrangement pitch py in the y direction. However, the arrangement direction is not limited to this. The pitches in the x direction and the y direction may be different, and the two directions in the array may not be orthogonal. Further, the arrangement pitch is not limited to equal intervals, and may be uneven intervals. For example, the light sources 20 may be arranged so that the distance from the center to the periphery of the substrate 11 becomes wider.

Each light source 20 at least includes a light emitting element 21 having an emitting surface 21 a. The light source 20 may include a covering member 22 that covers the exit surface 21 a. When the light source 20 includes the covering member 22, the surface 22 a of the covering member 22 is an exit surface of the light source 20. The light source 20 is a covering member 22
When the light emitting element 21 does not include the light emitting element 21, the light emitting surface 21 a of the light emitting element 21 is also the light emitting surface of the light source 20. Each light source 20 may include one or more light emitting elements 21. In this case, the light emitting element 21 may emit white light, or the light emitted from the light emitting element 21 may emit white light as a whole of the light source 20 by transmitting through the covering member 22. Further, the light source 20 includes, for example, a light emitting element including three light emitting portions emitting red, blue and green light, or three light emitting elements emitting red, blue and green light, respectively. , And blue and green lights may be mixed to emit white light. Alternatively, in order to enhance the color rendering of light emitted from the light source 20, the light source 20 may include a light emitting element that emits white light and a light emitting element that emits another color.

The light emitting element 21 is a semiconductor light emitting element, and a known light emitting element such as a semiconductor laser or a light emitting diode can be used. In the present embodiment, a light emitting diode is illustrated as the light emitting element 21. The light emitting element 21 can select an element that emits light of an arbitrary wavelength. For example, as a blue or green light emitting element, an element using ZnSe, a nitride-based semiconductor (In _x Al _y Ga _{1 -xy} N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1), or GaP may be used. it can. In addition, as a red light emitting element, an element including a semiconductor such as GaAlAs or AlInGaP can be used. Furthermore, semiconductor light emitting devices made of materials other than these can also be used. The composition, emission color, size, number, and the like of the light-emitting elements to be used can be appropriately selected depending on the purpose. When the covering member 22 includes the wavelength conversion member, the light emitting element 21 is a nitride semiconductor (In _x ) capable of emitting light of a short wavelength that can efficiently excite the wavelength conversion member.
It is preferable to contain Al _y Ga _1-xy N, 0 ≦ X, 0 ≦ Y, and X + Y ≦ 1).

  Various emission wavelengths can be selected depending on the material of the semiconductor layer and the mixed crystal ratio thereof. It may have positive and negative electrodes on the same side, or may have positive and negative electrodes on different sides.

  The light emitting element 21 has, for example, a light transmitting substrate and a semiconductor laminated structure stacked on the substrate. The semiconductor laminated structure includes an active layer and an n-type semiconductor layer and a p-type semiconductor layer sandwiching the active layer, and an n-side electrode and a p-side electrode are electrically connected to the n-type semiconductor layer and the p-type semiconductor layer, respectively. There is. In the present embodiment, the n-side electrode and the p-side electrode are located on the surface opposite to the emission surface.

  The n-side electrode and the p-side electrode of the light emitting element 21 are electrically connected and fixed to the conductor wiring layer 13 provided on the upper surface 11 a of the substrate 11 by a bonding member 23 described later. That is, the light emitting element 21 is mounted on the substrate 11 by flip chip bonding.

  The light emitting element 21 may be a bare chip or may include a package having a reflector on the side surface. In addition, a lens or the like may be provided to widen the emission angle of light emitted from the emission surface 21a.

  The covering member 22 covers at least the emission surface 21 a of the light emitting element 21 and is supported by the upper surface 11 a of the substrate 11. The covering member 22 prevents the emission surface 21 a from being exposed to the external environment and being damaged. As a material of the covering member 22, a translucent material such as an epoxy resin, a silicone resin, a resin in which these are mixed, and glass can be used. From the viewpoint of light resistance and ease of molding of the covering member 22, it is preferable to select a silicone resin as the covering member 22.

The covering member 22 may contain a diffusion member, a wavelength conversion member, a coloring agent, and the like. For example, the light source 20 may include a light emitting element 21 for emitting blue light and a wavelength conversion member for converting blue light into yellow light, and may emit white light by a combination of blue light and yellow light. Alternatively, it includes a light emitting element 21 for emitting blue light, a wavelength conversion member for converting blue light to green light, and a wavelength conversion member for converting blue light to red light, wherein blue light, green light and red light White light may be emitted by combination. For example, a β-sialon phosphor is mentioned as a wavelength conversion member which converts blue light to green light, and a fluoride-based phosphor such as a KSF-based phosphor is mentioned as a wavelength conversion member which converts blue light to red light. The color reproduction range of the light emitting device can be expanded by including a β-sialon phosphor and a fluoride-based phosphor such as a KSF-based phosphor as the wavelength conversion member. Alternatively, a light source may be used that includes a semiconductor light emitting element that emits blue light, a semiconductor light emitting element that emits green light, and a wavelength conversion member that converts blue light or green light to red light.

  The covering member 22 can be formed by compression molding or injection molding so as to cover the light emitting surface 21 a of the light emitting element 21. In addition, it is also possible to optimize the viscosity of the material of the covering member 22 and drop or draw it on the light emitting element 21 to control the shape by the surface tension of the material itself. According to the latter formation method, the covering member can be formed by a simpler method without the need for a mold. Further, as means for adjusting the viscosity of the material of the covering member 22 by such a forming method, in addition to the inherent viscosity of the material, the desired viscosity using the light diffusing material, the wavelength conversion member, and the coloring agent as described above It can also be adjusted to

  FIG. 3 is a view showing an example of light distribution characteristics of light emitted from the light source 20. As shown in FIG. The light source 20 preferably has a bat wing type light distribution characteristic. Thus, by suppressing the amount of light emitted in the direction immediately above the light source 20 and widening the light distribution of each light source, it is possible to further improve the uneven brightness. The bat wing type light distribution characteristic is defined in a broad sense by the light emission intensity distribution in which the light emission intensity is strong at an angle where the absolute value of the light distribution angle is larger than 0 °, with the optical axis L of the light source 20 being 0 °. . In particular, in a narrow sense, it is defined as a light emission intensity distribution in which the light emission intensity is strongest around 45 ° to 90 °. That is, in the bat wing type light distribution characteristic, the central portion is darker than the outer peripheral portion.

  The light source 20 may have a light reflection layer 24 on the emission surface 21 a of the light emitting element 21 in order to realize a bat wing type light distribution characteristic. The light reflecting layer 24 may be a metal film or a dielectric multilayer film. Thereby, light in the upper direction of the light emitting element 21 is reflected by the light reflecting layer, the light quantity immediately above the light emitting element 21 is suppressed, and it is possible to realize a bat wing type light distribution characteristic. Alternatively, the outer shape of the covering member 22 may be adjusted to provide a light source having a bat wing type light distribution characteristic.

[Bonding member 23]
The bonding member 23 electrically connects and fixes the light emitting element 21 to the conductor wiring layer 13. For example, the bonding member 23 may be an Au-containing alloy, an Ag-containing alloy, a Pd-containing alloy, an In-containing alloy, a Pb-Pd-containing alloy, an Au-Ga-containing alloy, an Au-Sn-containing alloy, a Sn-containing alloy, or a Sn-Cu-containing alloy Sn—Cu—Ag containing alloy, Au—Ge containing alloy, Au—Si containing alloy, Al containing alloy, Cu—In containing alloy, mixture of metal and flux, etc.

  As the bonding member 23, liquid, paste, solid (sheet, block, powder, wire) can be used, and can be appropriately selected according to the composition, the shape of the substrate, etc. . Moreover, these joining members 23 may be formed by a single member, or may be used in combination of several kinds.

  The bonding member 23 may not electrically connect the light emitting element 21 and the conductor wiring layer 13. In this case, the bonding member 23 connects the region other than the p-side electrode and the n-side electrode of the light emitting element 21 to the top surface 11 a of the substrate 11, and the p-side electrode and the n-side electrode and the conductor wiring layer 13 It is electrically connected by a wire or the like.

[Insulating member 14]
The light source unit 10 may further include an insulating member 14 that covers areas other than the area electrically connected to the light emitting element 21 of the conductor wiring layer 13 and other elements and the like. As shown in FIG. 1, an insulating member 14 is provided on a part of the conductor wiring layer 13 on the upper surface 11 a side of the substrate 11. The insulating member 14 functions as a resist for imparting insulation to a region other than the region electrically connected to the light emitting element 21 of the conductor wiring layer 13 and other elements and the like. The insulating member 14 includes, for example, a resin, and a reflecting material made of an oxide particle such as titanium oxide, aluminum oxide, silicon oxide or the like dispersed in the resin in order to be able to reflect light from the light emitting element 21. It is also good. The insulating member 14 having light reflectivity reflects the light emitted from the light emitting element 21 on the side of the upper surface 11a of the substrate 11 to prevent light leakage and absorption on the side of the substrate 11, thereby improving the light extraction efficiency of the light emitting device. Let

[Classification member 15]
The dividing member 15 includes wall portions 15ax, 15ay and a bottom portion 15b. As shown in FIG. 2, a wall 15 ay extending in the y direction is disposed between two light sources 20 adjacent in the x direction, and a wall 15 ax extending in the x direction between two light sources 20 adjacent in the y direction. It is arranged. Therefore, each light source 20 is surrounded by two wall portions 15ax extending in the x direction and two wall portions 15ay extending in the y direction. The bottom 15b is located in a region 15r surrounded by the two walls 15ax and the two walls 15ay. In the present embodiment, since the arrangement pitch of the light source 20 in the x direction and the y direction is equal, the outer shape of the bottom portion 15 b is square.
A through hole 15e is provided at the center of the bottom 15b, and the bottom 15b is positioned on the insulating member 14 so that the light source 20 is positioned in the through hole 15e. The shape and size of the through hole 15 e are not particularly limited, as long as the light source 20 can be located inside. The outer edge of the through hole 15e is located near the light source 20 so that the light from the light source 20 can be reflected also by the bottom 15b, that is, it occurs between the through hole 15e and the light source 20 in top view It is preferable that the gap be narrow.

  As shown in FIG. 1, in the yz cross section, the wall portion 15ax includes a pair of inclined surfaces 15s extending in the x direction. Each of the pair of inclined surfaces 15s is connected to each other at one of two sides extending in the x direction, and constitutes a top 15c. The other is connected to the bottom 15 b located in two adjacent areas 15 r respectively. Similarly, the wall portion 15ay extending in the y direction includes a pair of inclined surfaces 15t extending in the y direction. Each of the pair of inclined surfaces 15t is connected to each other at one of two sides extending in the y direction, and constitutes a top 15c. The other is connected to the bottom 15 b located in two adjacent areas 15 r respectively.

  The bottom 15b, the two walls 15ax, and the two walls 15ay form a light emitting space 17 having an opening 17a. In FIG. 2, light emitting spaces 17 arranged in 3 rows and 3 columns are shown. The pair of inclined surfaces 15 s and the pair of inclined surfaces 15 t face the opening 17 a of the light emission space 17.

  The partitioning member 15 has light reflectivity, and reflects light emitted from the light source 20 toward the opening 17 a of the light emission space 17 by the inclined surfaces 15 s and 15 t of the wall portions 15 ax and 15 ay. Further, light incident on the bottom portion 15 b is also reflected to the opening 17 a side of the light emission space 17. Thereby, the light emitted from the light source 20 can be efficiently incident on the light transmitting laminate 30.

The light emission space 17 divided by the dividing member 15 is the minimum unit of the light emission space when the plurality of light sources 20 are driven independently. In addition, when the light emitting device 101 is viewed as the surface light source from the top surface 30 a of the light transmitting laminate 30, it is the minimum unit area of local dimming. When a plurality of light sources 20 are driven independently, a light emitting device capable of driving by local dimming in the smallest light emission space unit is realized. If the adjacent light sources 20 are driven simultaneously and driven so as to synchronize the ON / OFF timing, driving by local dimming becomes possible in larger units.

  For example, the dividing member 15 may be molded using a resin containing a reflective material made of metal oxide particles such as titanium oxide, aluminum oxide, silicon oxide or the like, or molded using a resin not containing a reflective material After that, a reflective material may be provided on the surface. It is preferable that the reflectance with respect to the emitted light from the light source 20 of the division member 15 is 70% or more, for example.

  The dividing member 15 can be formed by molding using a mold or optical molding. As a molding method using a mold, molding methods such as injection molding, extrusion molding, compression molding, vacuum molding, pressure molding, press molding and the like can be used. For example, by vacuum forming using a reflective sheet formed of PET or the like, it is possible to obtain the sorting member 15 in which the bottom portion 15b and the wall portions 15ax and 15ay are integrally formed. The thickness of the reflective sheet is, for example, 100 to 500 μm.

  The lower surface of the bottom portion 15b of the dividing member 15 and the upper surface of the insulating member 14 are fixed by an adhesive member or the like. The insulating member 14 exposed from the through holes 15 e preferably has light reflectivity. It is preferable to dispose an adhesive member around the through hole 15 e so that the light emitted from the light source 20 does not enter between the insulating member 14 and the dividing member 15. For example, it is preferable to arrange the adhesive member in a ring shape along the outer edge of the through hole 15e. The adhesive member may be a double-sided tape, an adhesive sheet of a hot melt type, or an adhesive liquid of a thermosetting resin or a thermoplastic resin. These adhesive members preferably have high flame retardancy. Moreover, it may be fixed not with an adhesion member but with another coupling member such as a screw or a pin.

Half mirror 31
The half mirror 31 of the light transmitting laminate 30 is disposed above the light source 20 so as to cover the opening 17 a of the light emitting space 17 located in the light source unit 10.

  The half mirror 31 has a transmission characteristic and a reflection characteristic which reflect a part of incident light and transmit the remaining light. The half mirror 31 has a reflectance of about 30% to about 75% with respect to the light emission wavelength band of the light source at the time of vertical incidence. The reflectance of the half mirror 31 is substantially equal over the entire area of the half mirror 31. Here, “substantially equal” means that, for example, the reflectance of light incident perpendicularly to the main surface (upper surface 31 a and lower surface 31 b) is a value within an average value ± 5% at any measurement point. Say.

  The half mirror 31 preferably has a dielectric multilayer film structure in which two or more dielectric films having different refractive indexes are laminated on a translucent substrate. Specific materials of the dielectric film include metal oxide film, metal nitride film, metal fluoride film, resin such as polyethylene terephthalate (PET), etc., for the light emitted from the light source 20 and the wavelength conversion layer 34 described later It is preferable that the material be less absorbed. The dielectric multilayer film reflects part of incident light at the interface due to the difference in refractive index of the laminated dielectric films. The reflectance can be adjusted by changing the phase of the incident light and the reflected light and adjusting the degree of interference between the two lights depending on the thickness of the dielectric film. The adjustment of the phase by the thickness of the dielectric film depends on the wavelength of light to be transmitted. Therefore, if multiple dielectric films are laminated and the wavelength of light to be reflected is made different for each dielectric film, the wavelength dependence of reflectance Sex can also be adjusted. Therefore, by using the dielectric multilayer film, it is possible to realize the half mirror 31 which has less absorption of light and can arbitrarily adjust the reflectance characteristic.

Further, if a dielectric multilayer film structure is used, the optical path length differs between light incident perpendicularly and light incident obliquely, even in the case of a dielectric film having a uniform thickness. For this reason, it is also possible to control the reflectance by the incident angle of light incident on the half mirror 31. In particular, by setting the reflectance to be lower at oblique incidence than at normal incidence, as described later, the direction of the optical axis L of the light source 20, that is, the direction perpendicular to the main surface of the half mirror 31. The reflectivity can be increased, and the reflectivity for light incident at a large angle φ with respect to the optical axis L can be reduced. That is, when the light emitting device is observed from the outside, the luminance unevenness on the surface can be further reduced by increasing the transmittance when the angle to the optical axis is large.

  FIG. 4 shows an example of the angle dependency of reflectance and transmittance of the half mirror 31. When the optical axis L is 0 ° and the absolute value of the light distribution angle (φ in FIG. 1) is about 40 ° or less, the reflectance is 60%, and the light reflection angle is 40 ° or more. The rate is reduced and the transmittance is increased. By having such a reflectance characteristic, the above-mentioned uneven brightness can be suppressed more effectively.

  FIG. 5 is a view showing an example of the emission spectrum of light emitted from the light source 20 and the reflectance characteristic of the half mirror 31. As shown in FIG. The horizontal axis indicates the wavelength, and the vertical axis indicates the reflectance or the relative emission intensity. The reflectance indicates a value in the direction perpendicular to the main surface of the half mirror 31. In the reflectance characteristic in the vertical direction of the half mirror 31, it is preferable that the band on the longer wavelength side than the emission peak wavelength of the light source 20 is wider than the band on the short wavelength side. In the example shown in FIG. 5, the emission peak wavelength of the light source 20 is about 450 nm. For example, a band having a reflectance of 40% or more of the half mirror 31 is a 50 nm band of 400 to 450 nm on the shorter wavelength side than 450 nm, while 450 to 570 nm on the longer wavelength side than 450 nm The band of 120 nm.

  In general, the reflection wavelength band of the half mirror is shifted to the short wavelength side due to the increase in the optical path length when light is obliquely incident as compared with the case where light is perpendicularly incident. For example, when light of a certain wavelength λ is incident on the half mirror from the vertical direction, even if it has the characteristic of reflecting light with a predetermined reflectance, if it is obliquely incident on the half mirror, the reflected wavelength band Shifts by δ towards the short wavelength side. Therefore, light of a wavelength shorter than the wavelength λ is reflected at the same reflectance by an amount corresponding to the shift amount δ of the reflection wavelength band, but the reflectance for light of the wavelength λ is lowered.

  In such a case, as described above, in the reflectance characteristic of the half mirror 31 in the vertical direction, the reflection is performed so that the band on the longer wavelength side than the emission peak wavelength of the light source 20 becomes wider than the band on the short wavelength side. By designing the rate characteristics, even if the reflection wavelength band is shifted to the short wavelength side by δ by obliquely incident light, the same reflectance can be maintained because the band on the long wavelength side is wide. For example, even if light is obliquely incident on the half mirror 31 within the range where the absolute value of the light distribution angle (φ in FIG. 1) described above is about 40 ° or less, the reflectance decreases and the optical axis L of the light source 20 By transmitting a large amount of light that is slightly obliquely incident on the light source, it is possible to suppress that the uneven brightness is emphasized.

[Light diffuser 33]
The light diffusion plate 33 is located on the upper surface 31 a side of the half mirror 31. The light diffusion plate 33 diffuses and transmits incident light. The light diffusion plate 33 is made of, for example, a material such as polycarbonate resin, polystyrene resin, acrylic resin, polyethylene resin, or the like, which absorbs little light with respect to visible light. The light diffusion structure is provided on the light diffusion plate 33 by providing unevenness on the surface of the light diffusion plate 33 or dispersing materials having different refractive indexes in the light diffusion plate 33. As the light diffusion plate, one commercially available under the name of a light diffusion sheet, a diffuser film or the like may be used.

[Scatter Reflector 32]
The scattering / reflecting portion 32 is located between the half mirror 31 and the light diffusing plate 33 or on the lower surface 31 b of the half mirror 31. In the present embodiment, the scattering and reflecting portion 32 is provided on the lower surface 33 b of the light diffusing plate 33. In the case where the light diffusion plate 33 to be described later is made of a polystyrene resin, the scattering and reflecting portion 32 is preferably provided to the half mirror 31. Since the material forming the half mirror 31 has a linear expansion coefficient smaller than that of polystyrene resin, it is possible to suppress the occurrence of positional deviation between the light source 20 and the scattering and reflecting portion 32 due to thermal expansion.

  FIG. 6 shows the positional relationship between the scattering / reflecting portion 32 and the exit surface of the light source 20 (the surface 22 a of the covering member 22 or the exit surface 21 a) in the top view of the light emitting device 101. As shown in FIGS. 1 and 6, the scattering / reflecting portion 32 is located at least above the emission surface of each light source 20, that is, on the optical axis of the light source 20. The scattering and reflecting unit 32 scatters and reflects incident light. Since the light emitted from the light sources 20 has a high light emission intensity on the optical axis L, the provision of the scattering / reflecting portion 32 suppresses uneven brightness in the light from each light source 20. Assuming that the optical axis L of each light source 20 is 0 °, the light emission intensity becomes relatively weak at an angle where the absolute value of the light distribution angle is larger than 0 °. For this reason, since it is not necessary to scatter light above the top 15 c of the dividing member 15 which is the boundary of the light emission space 17, the scattering and reflecting portion 32 may not be provided.

  In FIG. 6, the scattering and reflecting part 32 has a circular shape centered on the optical axis of each light source 20 in top view, but the shape of the scattering and reflecting part 32 is not limited to a circle. Depending on the light distribution characteristic of the light source 20, the shape of the ellipse, the rectangular isotropy, and the irregular reflection portion 32 can be determined so that light can be scattered more uniformly. When the light emission intensity on the optical axis of the light source 20 is weaker than that around the optical axis due to the light source 20 having a bat wing type light distribution characteristic, for example, the scattering and reflecting portion 32 is In a top view, it may have a ring shape. That is, the scattering and reflecting portion 32 may be located above at least a part of the light emitting surface of each light source 20.

  When the top 15 c is in contact with the light diffusion plate 33 or the half mirror 31, the light reflected by the light diffusion plate 33 or the half mirror 31 increases the amount of light emitted to the wall portions 15 ax and 15 ay. Since the region in the vicinity of 15c becomes bright, it is preferable that the scattering / reflecting portion 32 be provided immediately above the wall portions 15ax, 15ay. As a result, it is possible to suppress the occurrence of uneven brightness due to the region in the vicinity of the top 15 c becoming bright.

  The scattering / reflecting portion 32 includes a resin and particles of an oxide such as titanium oxide, aluminum oxide or silicon oxide, which are particles of a reflective material dispersed in the resin. The average particle size of the oxide particles is, for example, about 0.05 μm or more and 30 μm or less. The scattering and reflecting portion 32 may further include a pigment, a light absorbing material, a phosphor and the like. When a photocurable resin mainly composed of acrylate, epoxy or the like is used as the resin, the lower surface 33b of the light diffusion plate 33 is coated with a resin before curing including a reflective material, and then, for example, it is scattered and reflected by irradiating ultraviolet light. The portion 32 can be formed. The resin may be photocured by the light emitted from the light source 20. The uncured resin in which the reflective material is dispersed can be disposed, for example, by a printing method using a plate or an inkjet method.

  The particles of the reflective material for scattering light in the scattering / reflecting portion 32 may be uniformly distributed, or in a region where the absolute value of the light distribution angle of the light source 20 is smaller than in a region where the absolute value of the light distribution angle is larger It may be arranged at high density. The scatter reflector 32 'shown in FIG. 7A includes a first portion 32a and a second portion 32b. The first portion 32a is located immediately above the emission surface 21a, and the second portion 32b is located around the first portion.

  The density of reflective particles in the second portion 32b is less than the density of reflective particles in the first portion 32a. Here, the density of particles is represented by, for example, a plane in top view, that is, a number density represented by the number of particles per unit area in the xy plane.

For example, as shown in FIG. 7B, the scattering / reflecting portion 32 ′ densely arranges, in the first portion 32a, the minute regions 32c of the uncured resin in which the particles of the reflective material are dispersed by the printing method or the inkjet method. The second portion 32 b can be formed by arranging at a lower density than the first portion 32 a. Further, as shown in FIG. 7C, a first layer 32d of an uncured resin in which particles of a reflective material are dispersed is formed in the first portion 32a and the second portion 32b, and the first layer 32a is formed with the first layer 32d only. A second layer 32e may be formed on the layer 32d. In the scattering and reflecting portion 32 ′ having the structure shown in FIG. 7B or 7C, the density of the particles of the reflector in the scattering and reflecting portion 32 ′ in the xy plane satisfies the above-described relationship.

  The scattering / reflecting portion 32 may be provided on the upper surface 31 a or the lower surface 31 b of the half mirror 31 as shown in FIGS. 8 and 9. Further, as shown in FIG. 10, the scattering and reflecting portion 32 may be provided on the upper surface 33 a of the light diffusing plate 33.

[Wavelength conversion layer 34]
The light emitting device 101 may further include the wavelength conversion layer 34 in the light transmitting laminate 30. The wavelength conversion layer 34 is located on the side of the light diffusion plate 33 opposite to the side on which the half mirror 31 is located, that is, on the upper surface 33 a side. The wavelength conversion layer 34 absorbs a part of the light emitted from the light source 20, and emits light of a wavelength different from the wavelength of the light emitted from the light source 20.

  Since the wavelength conversion layer 34 is separated from the light emitting element 21 of the light source 20, it is possible to use a light converting substance which is difficult to use in the vicinity of the light emitting element 21 and has poor resistance to heat and light intensity. . As a result, the performance of the light emitting device 101 as a backlight can be improved. The wavelength conversion layer 34 has a sheet shape or a layer shape, and includes the wavelength conversion material described above.

  When the wavelength conversion layer 34 is used, as shown in FIG. 11, the reflectance at the wavelength of light emitted by the wavelength conversion layer 34 is smaller than the emission wavelength of the light source 20 located between the wavelength conversion layer 34 and the half mirror 31. A further high dichroic layer 38 may be provided.

[Prism array layers 35 and 36, reflective polarizing layer 37]
The light emitting device 101 may further include prism array layers 35 and 36 and a reflective polarizing layer 37 in the light transmitting laminate 30. The prism array layers 35, 36 have a shape in which a plurality of prisms extending in a predetermined direction are arranged. For example, in FIG. 1, the prism array layer 35 has a plurality of prisms extending in the y direction, and the prism array layer 36 has a plurality of prisms extending in the x direction. The prism array layers 35 and 36 refract light incident from various directions in the direction (z direction) toward the display panel facing the light emitting device. As a result, the light emitted from the upper surface 30a of the light transmitting laminate 30 which is the light emitting surface of the light emitting device 101 mainly has many components perpendicular (parallel to the z axis) to the upper surface 30a, and the light emitting device 101 is viewed from the front (z axis direction) The brightness when viewed from) can be increased.

  The reflective polarization layer 37 selectively transmits light in a polarization direction that matches the polarization direction of a polarizing plate disposed on the back light side of a display panel, for example, a liquid crystal display panel, and polarizes light in a direction perpendicular to the polarization direction. Are reflected to the prism array layers 35 and 36 side. When part of the polarized light returned from the reflective polarizing layer 37 is reflected again by the prism array layers 35 and 36, the wavelength conversion layer 34, and the light diffusing plate 33, the polarization direction changes and the polarization of the polarizing plate of the liquid crystal display panel The light is converted into polarized light having a direction, and enters the reflective polarization layer 37 again to be emitted to the display panel. Thereby, the polarization directions of the light emitted from the light emitting device 101 are aligned, and the light of the polarization direction effective for improving the luminance of the display panel is emitted with high efficiency.

  As the prism array layers 35 and 36 and the reflective polarizing layer 37, those commercially available as optical members for backlight can be used.

[Transparent laminate 30]
The light transmitting laminate 30 is configured by laminating the half mirror 31, the scattering and reflecting portion 32, the light diffusing plate 33, the wavelength conversion layer 34, the prism array layers 35 and 36, and the reflective polarizing layer 37 described above. . At least one interface of these layers may not be in contact with each other and a space may be formed. However, in order to make the thickness of the light emitting device 101 as small as possible, it is preferable that two layers adjacent to each other be stacked without providing a space.

  The light transmitting laminate 30 is supported by a support at a predetermined distance from the light source unit 10, for example. It is preferable that the lower surface 30 b of the light transmitting laminate 30 be in contact with the top 15 c of the dividing member 15. For example, the top 15 c may be joined to the lower surface 31 b of the half mirror 31 by a connecting member, or may be joined to the half mirror 31 or the like by a pin, a screw or the like. Since the top 15 c is in contact with the lower surface 30 b of the light transmitting laminate 30, light emitted from the light source 20 in one light emitting space 17 can be prevented from entering the adjacent light emitting space 17.

  The distance OD between the half mirror 31 and the substrate 11 is preferably set to 0.2 times or less of the arrangement pitch P of the light sources 20 (OD / P ≦ 0.2). More preferably, the interval OD is not less than 0.05 times and not more than 0.2 times the arrangement pitch P of the light sources 20 (0.05 ≦ OD / P ≦ 0.2). According to the conventional configuration, when the distance between the light transmitting laminate 30 and the substrate on which the light source 20 is mounted is set to be short as described above, the luminance unevenness of the light emitting device is largely generated. However, according to the light emitting device 101 of the present disclosure, it is possible to make the luminance distribution uniform by using the half mirror 31 and the scattering and reflecting portion 32.

  The light emitting device 101 can be assembled by respectively producing the light source unit 10 and the light transmitting laminate 30 and supporting the light transmitting laminate 30 with respect to the light source unit 10 by the above-described support.

(Operation of light emitting device 101, effect)
The operation of the light emitting device 101, in particular, the reason why the luminance unevenness of the light emitted from the light source 20 is suppressed will be described. When the light emitting device 101 is used as a surface light emitting device like a backlight, it is preferable that the uneven brightness on the upper surface 30 a of the light transmitting laminate 30 which is the light emitting surface from the light emitting device 101 be as small as possible.

  However, the light source 20 is a point light source, and the illuminance of the surface illuminated by the light emitted from the light source 20 is inversely proportional to the square of the distance. For this reason, the illuminance of light incident on the lower surface 30b of the light transmitting laminate 30 is higher in the region R1 in the vicinity immediately above the light source 20 in the top view than in the region R2 located around R1. This is because the distance between the light source 20 and the upper surface 30a in the region R1 is shorter than the distance between the light source 20 and the upper surface 30a in the region R2.

  On the other hand, when the light emitting device 101 is used as a backlight, it is required that the thickness of the display device is small from the viewpoint of the design, appearance or function of the display device, and the thickness (height) of the light emitting device 101 is also It is required to be small. Therefore, it is preferable that the interval OD between the light source unit 10 and the light transmitting laminate 30 be smaller. When the OD decreases, the amount of light directly incident on the light transmitting laminate 30 from the light source 20 increases. Therefore, unless the distance OD between the light sources 20 is shortened as much as possible, the above-described uneven brightness on the upper surface 30a becomes large.

The light emitting device 101 of the present embodiment includes the half mirror 31 and the scattering and reflecting unit 32. The half mirror 31 is closer to the light source 20 than the scattering and reflecting unit 32, and reflects a part of the light emitted from the light source 20. The light reflected by the half mirror 31 is incident on the substrate 11 supporting the light source 20, and is reflected on the substrate 11 side to be incident on the half mirror 31 again. The light incident again is diffused more than the light directly incident on the half mirror 31 from the light source 20 due to the reflection on the half mirror 31 and the substrate 11 side. For this reason, a part of the light emitted from the light source 20 is reflected once or more between the half mirror 31 and the substrate 11 to make the light from the light source 20 as a surface larger than the light emitting surface of the light source 20 It can be emitted from the half mirror 31.

  The light emitted from the half mirror 31 is incident on the scattering / reflecting portion 32 located above at least the emission surface 21 a of the light source 20 and is scattered. For this reason, light having a high luminous flux density in the vicinity of the optical axis L of the light source 20 can be selectively diffused, and luminance unevenness can be reduced.

  In particular, when the half mirror 31 is formed of a dielectric multilayer film, the absorption of light in the half mirror 31 can be suppressed, and the utilization efficiency of light can be enhanced. The half mirror 31 has a substantially uniform reflectance in the vertical direction. This characteristic can be realized by laminating dielectric films. For example, if a display panel manufacturing technique is used, the half mirror 31 having a large area can be manufactured relatively easily and inexpensively. Therefore, it is possible to inexpensively manufacture the half mirror 31 having excellent characteristics, and it is possible to reduce the manufacturing cost of the light emitting device.

  Further, by setting the reflectance in the half mirror 31 to be lower in reflectance at oblique incidence than in vertical incidence, a large amount of light directly incident on the half mirror in the direction of the optical axis L of the light source 20 is reflected. Thus, the reflection of light directly incident on the half mirror 31 at a large angle with respect to the optical axis L can be reduced. Therefore, the present invention is particularly effective in reducing the uneven brightness due to the direct light of the light source 20.

  In addition, the scattering / reflecting portion 32 includes a resin and particles dispersed in the resin, and the density of the particle in top view is a second portion 32 b located closer to the periphery than the first portion 32 a immediately above the emission surface of each light source The scattering / reflecting portion 32 may be arranged such that As a result, the degree of scattering can be made different in the scattering / reflecting portion 32, and the unevenness in brightness can be further reduced by increasing the scattering in the region where the luminous flux density is high.

  The scattering and reflecting portion 32 may be provided on any of the upper surface 31 a of the half mirror 31 and the lower surface 33 b of the light diffusion plate 33. The linear expansion coefficient of the half mirror 31 is smaller than the linear expansion coefficient of the light diffusion plate 33, and the linear expansion coefficient difference between the substrate 11 and the half mirror 31 is smaller than the linear expansion coefficient difference between the substrate 11 and the light diffusion plate 33. In the case, the scattering and reflecting unit 32 may be provided to the half mirror 31. In this case, positional deviation of the scattering and reflecting portion 32 with respect to the light source 20 due to expansion and contraction due to heat can be reduced. Therefore, it is possible to realize the light emitting device 101 in which a change in optical characteristics due to heat during operation is small.

  Also, in general, the reflection wavelength band of the half mirror is shifted to the short wavelength side with respect to the obliquely incident light as compared with the light perpendicularly incident on the half mirror. Therefore, in the reflectance characteristics in the vertical direction of the half mirror 31, by designing the reflectance characteristics so that the band on the longer wavelength side than the emission peak wavelength of the light source 20 becomes wider than the band on the short wavelength side, Even if the reflection wavelength band is shifted to the short wavelength side with respect to light incident slightly obliquely from the optical axis, it is possible to suppress the reduction of the reflectance and the enhancement of the luminance unevenness.

Furthermore, since the light source 20 has a bat-wing type light distribution characteristic, the illuminance in the region R1 of FIG. 1 can be reduced, so that the light emitting device 101 emits light from the top surface 30a of the light transmitting laminate 30 which is the emitting surface. Uneven luminance can be suppressed. In particular, by having a light distribution characteristic in which the light amount with an elevation angle of less than 20 ° with respect to the horizontal direction of the light source 20 is 30% or more of the total light amount, it is possible to further suppress uneven brightness. Thus, the light emitting device 1 of the present disclosure
According to 01, it is possible to effectively suppress the uneven brightness on the upper surface 30 a of the light transmitting laminate 30 which is the light emitting surface from the light emitting device 101.

(Example)
The light emitting device 101 is manufactured, and the result of examining the luminance distribution of the light emitting device 101 will be described. The light source 20 includes a nitride-based blue light emitting element 21 and a covering member 22 and is a light source having a bat wing type light distribution characteristic.

  For the half mirror 31, Toraya's Picasas 100 GH10 having a transmittance of 50% was used. A light diffusion sheet was used for the light diffusion plate 33. For the wavelength conversion layer 34, a phosphor sheet containing a green phosphor and a red phosphor was used. A prism sheet is used as the prism array layers 35 and 36, and the extending directions of the prisms are orthogonal to each other. A reflective polarizing film was used as the reflective polarizing layer 37. In the scattering and reflecting portion 32, a white ink in which titanium oxide particles are dispersed in a resin was printed on the lower surface 33b of the light diffusion plate 33 by an ink jet printer. The light sources 20 were arranged in 5 rows and 5 columns at a pitch P of 18.8 mm. The distance OD between the substrate 11 and the half mirror 31 was set to 1.8 mm. It was OD / P = 0.096.

  For comparison, a light emitting device (hereinafter referred to as a light emitting device according to a reference example) in which the distance OD between the substrate 11 and the half mirror 31 was set to 3.8 mm without using the half mirror 31 was manufactured. It was OD / P = 0.20.

  The light emitting devices of the example and the reference example were turned on, and the result of photographing the light emitting surface is shown in FIG. As can be seen from FIG. 12, using the half mirror 31 and the scattering / reflecting portion 32, the luminance distribution characteristic in which the luminance unevenness is suppressed equal to or more than the reference example set to OD = 3.8 mm without using the half mirror 31 Was found to be obtained. That is, it has been found that a light emitting device can be realized in which the luminance distribution is equal to or more than the reference example even if the distance OD between the substrate 11 and the half mirror 31 is 1⁄2 or less.

  When the relative luminance was measured, the luminance of the light emitting device of the example was about 85% of that of the reference example. This is considered to be because the light extraction efficiency is slightly reduced by inserting the half mirror 31.

  From these results, according to the light emitting device of the present disclosure, even if the distance between the half mirror and the substrate is 0.2 times or less of the distance between two adjacent light sources, the luminance distribution is uniform, and uneven luminance is obtained. It turned out that a small number of light emitting devices can be realized.

  The light emitting device of the present disclosure can be used as a backlight source of a liquid crystal display, various lighting devices, and the like.

DESCRIPTION OF SYMBOLS 10 light source unit 11 substrate 11a upper surface 11b lower surface 12 metal layer 13 conductor wiring layer 14 insulation member 15 division member 15ax, 15ay wall 15b bottom 15c top 15e through hole 15r area 15s area 15s, inclined surface 17 light emitting space 17a opening 20 light source 21 light emission Element 21a Emitting surface 22 Covering member 23 Bonding member 30 Light transmitting laminates 30a, 31a, 33a Upper surfaces 30b, 31b, 33b Lower surface 31 Half mirrors 32, 32 'Scattering reflection part 32a First part 32b Second part 32b Micro area 32d First layer 32e Second layer 33 Light diffusing plate 34 Wavelength conversion layer 35, 36 Prism array layer 37 Reflection type polarizing layer 101 Light emitting device

Claims (1)

A substrate,
A plurality of light sources located on the substrate;
A light diffuser,
A half mirror positioned between the light diffusion plate and the plurality of light sources of the substrate;
A scattering / reflecting portion located between the substrate and the light diffusing plate, and located above at least a part of the emission surface of the plurality of light sources;
, A light emitting device.

Images