JP2015103571A - Light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting device arranged to introduce excitation light from a light guide member into a wavelength conversion member and to take out, from a side face thereof, light emitted by the wavelength conversion member in response to the excitation light, by which the loss of light energy can be prevented, and a higher brightness can be achieved.SOLUTION: A light-emitting device comprises: a light-emitting part 50 including a wavelength conversion member 20, and a reflection member 43 covering an upper surface of the wavelength conversion member; and a light guide member 10 fixed to a backside of the light-emitting part and serving to supply light for exciting a fluorescent material included in the wavelength conversion member. The light-emitting part 50 has a total reflection layer 41 formed on each sides of the wavelength conversion member; the total reflection layer is formed from a material smaller than the wavelength conversion member in refraction index. The light-emitting device preferably comprises means for directing light introduced from the light guide member into the wavelength conversion member toward a side face of the light-emitting part.

Description

  The present invention relates to a light emitting device in which a light guide and a wavelength conversion member such as a phosphor plate are combined. In particular, a reflection member is disposed on both surfaces of the wavelength conversion member, and light is extracted from a side surface on which the reflection member is not disposed. The present invention relates to a light emitting device.

  Conventionally, a light-emitting device using a wavelength conversion member that absorbs excitation light transmitted by a light guide such as an optical fiber and converts the wavelength to emit light in a predetermined wavelength range has been proposed (Patent Document 1). In this type of light emitting device, a light guide is connected to the bottom surface of the disk-shaped wavelength conversion member, and a reflection film is disposed on the bottom surface and the top surface excluding the light guide so as to extract light from the side surface. This light-emitting device serves as a light source having semi-bidirectional characteristics suitable for a vehicle lamp.

JP 2013-131335 A

  In the light emitting device described above, a loss occurs when the light converted by the wavelength conversion member is repeatedly reflected by the reflection films provided on both surfaces of the wavelength conversion member before propagating through the wavelength conversion member and being extracted from the side surface. For example, even when the reflective member is a metal (Ag) having the highest reflection efficiency, the reflectance is 98%, and the loss increases by repeating the reflection. Also, when using a dielectric with an increased reflection function in combination with a metal film, it is necessary to increase the number of layers in order for the dielectric to have an increased reflection function, which causes the reflection characteristics on the high incident angle side to deteriorate rapidly. It is known to be. In the light emitting device that extracts light from the side surface as described in Patent Document 1, the characteristics on the high incident angle side of the reflecting member are important in order to extract light from the side surface. It becomes.

As described above, the loss of light energy due to the characteristics of the reflecting member is an obstacle to high brightness, but there is also a problem of quenching due to heat converted from light.
An object of the present invention is to achieve high brightness in a light-emitting device that extracts light from a side surface.

  In order to solve the above problems, the present invention provides the following light-emitting device. That is, the light-emitting device of the present invention excites the phosphor included in the wavelength conversion member, which is fixed to the back surface of the light-emitting unit, and the light-emitting unit that includes the wavelength conversion member and the reflection member that covers the top surface of the wavelength conversion member. A light guide device that supplies light to be emitted, wherein a side surface of the light emitting unit is a light emitting surface, and the light emitting unit is refracted by the wavelength converting member on both sides of the wavelength converting member. A total reflection layer made of a material having a refractive index lower than the refractive index is formed.

  A light emitting device that reduces energy loss of light propagating in the wavelength conversion material by providing layers that totally reflect light in both sides of the wavelength conversion material within a predetermined light incident angle range (an angle greater than the critical angle) The brightness can be increased. Further, since heat generation due to energy loss is reduced, reliability is improved.

The figure which shows the whole light-emitting device outline | summary of 1st Embodiment. The figure which shows the example of a change of the light-emitting device of 1st Embodiment. The figure which shows another modification of the light-emitting device of 1st Embodiment. The figure explaining the course of light in a 1st embodiment The figure which shows the whole outline | summary of the light-emitting device of 2nd Embodiment. (A)-(c) is a figure which shows the principal part of the light-emitting device of 2nd Embodiment, and its modification. The figure which shows the one aspect | mode of the light-emitting device of 3rd Embodiment. The figure which shows another aspect of the light-emitting device of 3rd Embodiment. The figure which shows the whole light-emitting device outline | summary of 4th Embodiment.

  Hereinafter, an embodiment of a light emitting device of the present invention will be described with reference to the drawings.

<First Embodiment>
As shown in FIG. 1, the light emitting device of the present embodiment includes a light guide member 10 that guides excitation light, and a light emitting unit that includes a wavelength conversion member 20 that absorbs excitation light and emits light having a wavelength different from that of the excitation light. In order to efficiently emit light from the side surface of the wavelength conversion member 20, a specific light reflection structure is formed on both surfaces of the wavelength conversion member 20. The wavelength conversion member 20 and the light reflecting structure are referred to as a light emitting part.

First, the structure constituting the light emitting device of this embodiment will be described with reference to FIG.
A light emitting device 100 shown in FIG. 1 includes a light guide member 10 held by a holding member 12 and a light emitting unit 50 fixed to the upper surface of the holding member 12. The light guide member 10 is supported by the holding member 12 such that one end thereof is substantially flush with the upper surface of the holding member 12. The other end of the light guide member 10 is connected to the light source 30.

  The light emitting unit 50 includes the wavelength conversion member 20, total reflection layers 41 a and 41 b (referred to collectively as a total reflection layer 41) formed on both surfaces thereof, and a reflection disposed on the total reflection layer 41 a on the upper surface side. The lower surface side is fixed to the upper surface of the holding member 12 where the tip of the light guide member 10 is exposed through the bonding material 60. The wavelength conversion member 20 absorbs excitation light introduced from the light source 30 through the light guide member 10 into the light emitting unit 50 and emits light having different wavelengths. The excitation light and the light emitted from the wavelength conversion member 20 propagate through the wavelength conversion member 20 and are emitted from the side surface of the light emitting unit 50.

Next, details of each element of the light emitting device 100 will be described.
The light source 30 used in the light emitting device 100 of the present embodiment may be any light source that emits light having a wavelength that excites the phosphor contained in the wavelength conversion member 20, such as a light emitting diode having an emission wavelength from the ultraviolet light to the blue light region. A solid light source such as a laser diode can be used. For example, a laser diode that emits ultraviolet light of about 405 nm using a GaN-based material or a laser diode that emits blue light of about 450 nm can be used.

  The light guide member 10 guides the excitation light from the excitation light source 30, is an optical fiber composed of a core at the center and a clad covering the periphery thereof, and is made of a known material such as quartz glass or plastic. Can do. Although a core diameter is not specifically limited, For example, a thing about 0.2 mm can be used. In order to increase the angle of light emitted from the light exit surface of the light guide member 10, it is preferable to use an optical fiber having a large numerical aperture NA. The numerical aperture NA is determined by the refractive index of the core and the refractive index of the cladding. In general, the refractive index of the core is higher than that of the cladding, so that the excitation light introduced into the light guide member 10 from the light incident surface of the light guide member 10 (the end portion on the light source 30 side) is entirely at the boundary between the core and the cladding. The light exits from the light exit surface (end surface on the wavelength conversion member 20 side) while being confined in the core by reflection. The angle of the emitted light is determined by the numerical aperture (NA = sin θmax), and the larger the numerical aperture, the larger the angle. By using an optical fiber having a large numerical aperture and widening the angle of outgoing light, it is possible to reduce the return of light to the optical fiber and increase the incident light to the wavelength conversion member 20. However, the angle of the light emitted from the optical fiber needs to be smaller than the angle (Brewster angle) where the light is not totally reflected by the total reflection layer 41b described later.

  The optical fiber may be a single wire fiber or a multi-wire fiber. In addition, a single-mode fiber or a multi-mode fiber may be used, but when a multi-mode fiber is used, a laser beam having a Gaussian distribution can generally be made to have a uniform distribution. The light reflected at a large angle within 20 can be increased. The multimode fiber may be either a circular multimode fiber or a rectangular multimode fiber.

  Although not shown in the drawing, a condensing lens or the like is disposed between the excitation light source 30 and the light incident surface of the light guide member 10 in order to efficiently take in the light from the excitation light source 30 into the optical fiber. Also good.

  The light guide member 10 is supported by the holding member 12 in a state of being inserted into a hole penetrating the holding member (ferrule) 12, and one end thereof is located on the same plane as the end surface 12 a of the holding member 12. The material of the holding member 12 is not particularly limited, but a metal such as stainless steel, nickel, zirconia, resin, glass, or the like is used. Moreover, it is preferable that the end surface 12a by which the wavelength conversion member 20 is arrange | positioned of the holding member 12 is a reflective surface. The reflective surface may be formed by mirror polishing the end surface 12a of the holding member 12, or a reflective film 15 such as a metal film or a dielectric film may be formed on the surface of the holding member 12 by vapor deposition or plating. Good. Further, a member having a reflective surface on the surface (reflective member) may be attached to the end surface 12 a of the holding member 12. The reflective film 15 is formed except for the portion of the end face 12a where the optical fiber tip is located.

  As the bonding material 60 for bonding the light guide member 10 and the light emitting unit 50, a high heat-resistant and translucent material such as silicone resin or glass can be used. In particular, those having high translucency in the wavelength range of excitation light and the wavelength range of light emitted from the wavelength conversion member are preferable. Further, the refractive index of the bonding member 60 is preferably approximately the same as that of the core of the light guide member 10. The thickness of the bonding material 60 is not particularly limited, but is preferably about 1 μm to 5 μm.

The wavelength conversion member 20 absorbs excitation light incident from the excitation light source 30 via the light guide member 10 and generates light having a wavelength different from that of the excitation light. A phosphor that absorbs the light and emits light having a longer wavelength is used. Specifically, as the ultraviolet light-excited phosphor, (Ca, Sr) S: Eu ²⁺ , CaAlSiN ₃ : Eu ²⁺ , (Ca, Sr) AlSiN ₃ : Eu ²⁺ , (Sr, Ba) ₂ SiO ₅ : Eu ²⁺ , (Ca, Sr) ₂ Si ₅ N ₈ : Eu ²⁺ , KSiF ₆ : Mn ⁴⁺ , KSiF ₆ : Mn ⁴⁺ , KTiF ₆ : Mn ^{4+ and} other red light emitting phosphors, Y ₃ Al ₅ O ₁₂ : Ce ³⁺ (YAG) , (Sr, Ba) ₂ SiO ₄ : Eu ²⁺ , Ca _x (Si, Al) ₁₂ (O, N) ₁₆ : Eu ²⁺ , (Ba, Sr, Ca) ₂ SiO ₄ : Eu ²⁺ , Tb ₃ Al ₅ O _{^{12: Ce 3+, CaGa 2 S}} 4: Eu 2+, Ca-α-Sialon: yellow-emitting phosphor of ^{Eu 2+} and the _{like, Y 3 (Ga, Al)} 5 O 12: Ce 3+, Lu 3 a _{^{5 O 12: Ce 3+, (}} Ba, Sr) 2 SiO 4: Eu 2+, SrGa 2 S 4: Eu 2+, Ca 3 Sc 2 Si 3 O 12: Ce 3+, CaSc 2 O 4: Eu 2+, CaSc 2 O ₄ : Ce ³⁺ , (Si, Al) ₆ (O, N) ₈ : Eu ²⁺ , β-Sialon: Eu ²⁺ , (Sr, Ba) Si ₂ O ₂ N ₂ : Eu ²⁺ , Ba ₃ Si ₆ O ₁₂ N ₂ : Green light-emitting phosphors such as Eu ²⁺ are listed. These may be used alone or in combination of two or more depending on the desired emission color of the light emitting device.

As a form of the phosphor, a phosphor powder dispersed in glass or resin, a glass phosphor obtained by adding a luminescent center ion to a glass matrix, a phosphor ceramic, or the like can be used. Specifically, the phosphor powder is dispersed in glass or resin. Specifically, the phosphor powder described above is contained in a glass containing components such as P ₂ O ₃ , Si ₂ , B ₂ O ₃ , and Al ₂ O _3. Are dispersed. As the glass phosphor, oxynitride glass such as Ca—Si—Al—O—N or Y—Si—Al—O—N added with Ce ³⁺ or Eu ²⁺ as an activator (emission center ion). Examples include phosphors. Examples of the phosphor ceramic include a sintered body having the phosphor composition described above and substantially free of a resin component.

Among these, phosphor ceramics which are sintered bodies of phosphor powders are preferable, and in particular, highly transparent ones that hardly contain pores or grain boundary impurities that cause light scattering in the sintered body are preferable. . Since phosphor ceramics have high thermal conductivity, it is possible to reduce a phenomenon (temperature quenching) in which light emission of the phosphor is weakened by heat. The pores in the sintered body of the phosphor ceramic can be reduced by selecting a flux used when manufacturing the sintered body and adjusting the pressure and temperature during sintering. In addition, the value of specific gravity of the phosphor ceramic can be used as an index for evaluating the remaining amount of pores, and it is particularly desirable that the value is 95% or more with respect to the theoretical value for calculating the value. By using phosphor ceramics with high translucency as a phosphor plate, it is possible to increase the light extraction efficiency from the phosphor layer without losing excitation light or fluorescence by diffusion. Further, the heat generated in the phosphor plate can be diffused efficiently.
However, the wavelength conversion member 20 may contain a small amount of a light diffusing material as long as the translucency is not impaired.

  The shape of the wavelength conversion member 20 is not particularly limited, but in the present embodiment, it has a cylindrical shape with a low height, that is, a disk shape, and includes two parallel circular surfaces 20a and 20b and a short cylindrical side surface. 20c. The light guide member 10 (optical fiber) is fixed to one of the two parallel surfaces of the wavelength conversion member 20 by a bonding material or the like. The two surfaces 20a and 20b are formed with a plurality of layers 40 for reflecting light except for a portion where the light guide 10 is joined. The excitation light incident on the wavelength conversion member 20 by the light guide member 10 and the light emitted from the wavelength conversion material 20 by the excitation light are repeatedly reflected on the surfaces 20a and 20b of the wavelength conversion member 20 and extracted from the side surface 20c. That is, the side surface 20 c becomes the light emission surface of the wavelength conversion member 20. The surfaces 20a and 20b of the wavelength conversion member 20 are preferably smooth in order to express the function of the total reflection layer in contact with these surfaces, and particularly preferably a mirror surface. Specifically, the average roughness (Ra) is preferably less than 20 nm.

  The total reflection layer 41 is made of a translucent material having a refractive index smaller than that of the material constituting the optical fiber (core) and the wavelength conversion member 20 constituting the light guide member 10.

The difference in refractive index between the material constituting the total reflection layer 41 and the wavelength conversion member 20 is preferably 0.1 or more, more preferably 0.2 or more. Since the refractive index of YAG as a typical phosphor is 1.85, the refractive index is preferably 1.65 or less. As such a low refractive index material, specifically, Na ₅ Al ₃ F ₁₄ (thiolite) (n = 1.33), AlF ₃ (n = 1.36), MgF ₂ (n = 1.38) , CaF ₂ (n = 1.43), SiO ₂ (n = 1.45), Al ₂ O ₃ (n = 1.64), and other dielectric materials can be used. Of these, SiO ₂ is preferable from the viewpoint of film formability. From the viewpoint of performance including total reflectivity, MgF ₂ is preferable.

  The thickness of the total reflection layer 41 is not limited. However, in the case where a multilayer film (dielectric reflection layer 42) of a dielectric layer described later is provided on the total reflection layer 41, it is preferably 300 nm or more, more preferably Is 500 nm or more. Moreover, it is preferably 2 μm or less, more preferably 1 μm or less. By setting the thickness to 300 nm or more, a sufficient total reflection function can be obtained without causing interference with the increased reflection layer 42. The total reflection layer 41 can be formed on the surface of the wavelength conversion member 20 by a method such as sputtering or vacuum deposition.

  By arranging such total reflection layers 41 (41a, 41b) on both surfaces of the wavelength conversion member 20, a predetermined incident angle is obtained when light propagates to the side surface while repeating reflection in the wavelength conversion member 20. Light having a larger incident angle can be totally reflected between the wavelength conversion member 20 and the total reflection layer 41 to prevent light loss due to reflection. The function of the total reflection layer 41 will be described in detail later.

The reflection layer 43 disposed on the total reflection layer 41a reflects light transmitted through the total reflection layer 41a and returns it to the wavelength conversion member 20, and may be a film or a substrate. In the case of a film, use a metal reflective film such as Ag, Ag alloy, Al, Rh, Pt, Au, Cu, Ti, and Si and a dielectric multilayer film such as SiO ₂ , Al ₂ O ₃ , TiO ₂ , and ZnO. Can do. These films can be formed by sputtering, vacuum deposition, plating, or the like. In the case of a substrate, a mirror-surface Al substrate or a substrate on which a metal film or an optical multilayer film is formed can be used, and can be bonded to the total reflection layer 41 with a bonding material. As the bonding material, the same material as the bonding portion where the light emitting portion 50 and the light guide member 10 are bonded can be used.

  FIG. 1 shows a case where the reflective layer 43 is disposed only on the total reflection layer 41a located on the upper surface side of the wavelength conversion member 20, but as shown in FIG. The reflective layer 43 may be formed on the bonding material 60 side of the reflective layer 41b. By providing the reflection layer 43 so as to sandwich the wavelength conversion member 20 and the total reflection layers 41a and 41b on both sides thereof, the light transmitted through the total reflection layer 41b can be reflected and returned to the wavelength conversion member 20. Wave loss can be reduced. Further, since the wavelength conversion member 20 and the holding member 12 or the reflection film 15 formed thereon can be eutectic bonded with solder, AuSn, or the like via the lower reflective layer 43, the wavelength conversion member The heat generated at 20 can be effectively released to the holding member side 12 and temperature quenching can be prevented.

  Furthermore, the light emitting device 100 according to the present embodiment may be provided with an increased reflection layer 42 between the total reflection layer 41 and the reflection layer 43 as shown in FIG. In the case where the increased reflection layer 42 is laminated on the lower total reflection layer 41, in order not to prevent the light from entering the wavelength conversion member 20 from the light guide member 10, other than the portion where the tip of the light guide member 10 is fixed. Formed in the region.

The increased reflection layer 42 is an optical multilayer film in which low-refractive index materials and high-refractive index materials are alternately stacked, and the thickness of each layer is adjusted to ¼ of the wavelength λ of incident light so that the number of layers is sufficient. As a result, incident light is hardly transmitted and reflected light can be obtained. Therefore, the thickness of the layer is adjusted in consideration of the wavelength of the excitation light and the light emitted from the wavelength conversion member 20, and is specifically about 10 nm to 100 nm. The total thickness is preferably about 0.01 μm to 3 μm. As a low refractive index material, for example, Na ₅ Al ₃ F ₁₄ (thiolite) (n = 1.33), AlF ₃ (n = 1.36), CaF ₂ (n = 1.38), SiO ₂ (n = 1.45), Al ₂ O ₃ (n = 1.64), etc. are used. As a high refractive index material, CeO ₂ (n = 2.13), Ta ₂ O ₅ (n = 2.20), Ti ₃ O ₅ (n = 2.31), TiO ₂ (n = 2.35). Nb ₂ O ₅ (n = 2.37) or the like is used. The reflective layer 42 can be formed by sequentially depositing these materials by a method such as sputtering or vacuum deposition.

Next, the function of the total reflection layer 41 in the light emitting device 100 of this embodiment will be described.
The total reflection layer 41 has a function of reflecting light whose incident angle at the interface with the total reflection layer 41 is greater than or equal to a critical angle among light propagating through the wavelength conversion member 20 and confining the light in the wavelength conversion member 20. The critical angle θT is determined by the refractive index of the wavelength conversion member 20 and the total reflection layer 41 according to Snell's law. For example, the wavelength conversion member 20 is a YAG phosphor having a refractive index of 1.85, and the total reflection layer 41 has a refractive index of 1. .45 of SiO ₂ ,
sin (θT) = 1.45 / 1.85
θT = 51.6
It becomes. That is, incident light having an incident angle of 51.6 ° or more is totally reflected at the interface between the wavelength conversion member 20 and the total reflection layer 41, and is incident on the wavelength conversion member 20 in the combination of the total reflection layer and the wavelength conversion material. Theoretically, if the angle is 51.6 ° or more, there is no loss of light energy, and light can propagate through the wavelength conversion member 20 and be extracted from the side surface of the light emitting unit. Incidentally, when a total reflection layer having a refractive index of 1.65 is provided for YAG, total reflection is possible at an incident angle of 63 ° or more.

  When only the reflection layer 43 is provided without providing the total reflection layer, for example, even when the reflection layer 43 is the metal film (Ag) having the highest reflectivity, the reflectivity is not 100% and has a certain absorption in the visible light region. . In general, when a dielectric multilayer film (increased reflection layer 42) having increased reflectivity is arranged in addition to a metal film, the reflectivity is improved, but the increased reflection layer has a high incidence angle, particularly high incidence of 70 degrees or more. It has a characteristic that the reflectivity suddenly decreases with respect to light of an angle. Therefore, even if a light reflection effect is obtained for light having a low incidence angle, a light reflection effect cannot be obtained at a high incidence angle.

  In the present embodiment, by providing the total reflection layer 41, the reflection function of the metal film or the increased reflection layer can be supplemented, and the light extraction efficiency can be greatly improved.

  On the incident side to the wavelength conversion member 20, when a solid light source such as an LED or LD is used as the excitation light source 30, the excitation light from the solid light source has directivity, so that the excitation light is wavelength converted from the light guide member 10. The light enters the total reflection layer 41b located below the member 20 at a low incident angle, and can enter the wavelength conversion member 20 without being totally reflected at the interface between the light guide member 10 and the total reflection layer 41b.

  The reason why the light emitted from the light guide member 10 is not totally reflected will be described in detail with reference to FIG. FIG. 4 is an enlarged view of the connection portion between the light guide member 10 and the light emitting portion 50, and the path of light is indicated by an arrow. In the following description, it is assumed that the thickness of each layer (film) is uniform and the interface is parallel.

  Here, the refractive index of the core 10a of the light guide member (optical fiber) 10 is n1, the refractive index of the cladding 10b is n2, the refractive index of the bonding material 60 is n3, the refractive index of the total reflection layer 41 is n4, and the core 10a The reflection angle with the cladding 10b is θ1, the incident angle from the core 10a to the bonding material 60 is θ2, the refraction angle from the core 10a to the bonding material 60 is θ3, and the refraction angle from the bonding material 60 to the total reflection layer 41 is θ4. To do.

Equation (1) is established from Snell's law, and Equation (2) is obtained from Equation (1).
n1 · sin θ2 = n3 · sin θ3 = n4 · sin θ4 (1)
sin θ4 = (n1 / n4) sin θ2 (2)

On the other hand, the maximum value of the angle of light emitted from the optical fiber (core) 10a is when the reflection angle θ1 between the core and the clad satisfies the critical angle, that is, the expression (3).
n1 · sin θ1 = n2 · sin90 °
sin θ1 = n2 / n1 (3)

In addition, since θ1 + θ2 = 90 ° and the relationship of the formula (4),
sin θ2 = √ (1−sin ² θ1) (4)
Formula (2) can be represented by Formula (5) using Formula (3) and Formula (4).
sin θ4 = (1 / n4) √ (n1 ² −n2 ² ) (5)

Here, “√ (n1 ² −n2 ² )” on the right side of Expression (5) is the numerical aperture NA (NA = √ (n1 ² −n2 ² )) of the optical fiber, and Expression (5) is the numerical aperture NA. And can be represented by equation (6).
sin θ4 = (1 / n4) · NA (6)

Therefore, the refraction angle θ4 from the bonding material 60 to the total reflection layer 41b is determined by the refractive index n4 of the total reflection layer 41 and the numerical aperture NA of the optical fiber 10, as shown in Expression (7).
θ4 = sin ⁻¹ ((1 / n4) · NA) (7)

Assuming that the total reflection layer 41 is SiO ₂ (refractive index 1.45) and the optical fiber has an NA of 0.30, θ4 is about 12 ° and enters the total reflection layer at an angle close to normal incidence. . The light incident on the total reflection layer 41 enters the wavelength conversion member 20 at an angle θ4. However, since the refractive index of the total reflection layer 41 is smaller than the refractive index of the wavelength conversion member 20, the total reflection layer 41b, the wavelength conversion member 20, The total reflection does not occur at the interface, and the light is transmitted through the total reflection layer 41 b and introduced into the wavelength conversion member 20.

Further, in order to prevent light from being totally reflected at the interface between the bonding member 60 and the total reflection layer 41b, the refraction angle θ4 from the bonding material 60 to the total reflection layer 41b may be less than 90 °. The incident angle θ2 from the core when total reflection occurs is obtained by setting θ4 = 90 ° in equation (2) (equation (8)).
sin θ4 = (n1 / n4) sin θ2 = 1
θ2 = sin ⁻¹ (n4 / n1) (8)

  In equation (8), if the refractive index n1 of the core is 1.46 and the refractive index n4 of the total reflection layer 41 is 1.45, the critical value of the angle θ2 at which total reflection occurs is about 83 °, and the angle θ2 is Total reflection occurs when it is greater than 83 °. On the other hand, the maximum value θmax of the angle θ2 of the light emitted from the core 10a to the bonding material 60 is NA = n · sin θmax (n is the refractive index of the bonding material), and the refractive index of the bonding material 60 (silicone resin) is 1.4 When NA is 0.30, it is about 12.3 °, which is smaller than 83 °. Therefore, total reflection does not occur at the interface of the total reflection layer 41b, and light from the light guide member 10 is introduced into the wavelength conversion member 20 through the total reflection layer 41b.

  As described above, according to the light emitting device of this embodiment, the total reflection layers are arranged on both surfaces of the wavelength conversion member, so that the excitation light transmitted from the light guide member 10 enters the wavelength conversion member without loss. In addition, since the light transmitted to the wavelength conversion member can be propagated to the side surface which is the light emitting surface in a confined state, high light emission efficiency can be realized. Further, since the amount of heat generated due to the loss of light energy can be reduced, the reliability is high.

  In the embodiment shown in the drawings, the entire side surface of the light emitting unit 50 is a light extraction surface. However, the light shielding member and the reflecting member are arranged on a part of the side surface, and the directivity characteristics of the light emitting device of the present embodiment. It is also possible to adjust.

Second Embodiment
In the light emitting device according to the present embodiment, the ratio of light that is reflected at a high angle in the wavelength conversion member 20 by directing light incident on the wavelength conversion member 20 from the light guide member 10 to the side on the upper surface side of the wavelength conversion member 20. It is a feature that means for increasing is provided. Hereinafter, the light-emitting device of this embodiment will be described with reference to FIG. In FIG. 5, the same elements as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  Also in the light emitting device shown in FIG. 5, the light emitting unit 50 including the wavelength conversion member 20 is fixed to the light emitting surface of the light guide member 10, and the total reflection layers 41 (41 a 1 and 41 b are formed on both surfaces of the wavelength conversion member 20. ) Is provided as in the first embodiment. In the present embodiment, the concave portion is formed on the upper surface side of the portion of the wavelength conversion member 20 that faces the light guide member 10, and the total reflection layer 41 a of the portion has a convex shape 411 on the wavelength conversion member 20 side. It is a feature.

  The convex portion (convex portion 411) of the total reflection layer 41a refracts light incident at an angle close to perpendicular to the wavelength conversion member 20 (incidence angle close to 0 degrees) and guides it in the side surface direction of the wavelength conversion member 20. It has a function to do. The shape of the convex portion 411 is preferably such that the shape and size of the bottom surface are approximately the same as the cross section of the light guide member 10, and when the cross section of the light guide member 10 is circular, FIGS. As shown in Fig. 4, the shape may be a conical shape or a conical conical surface curved outward or inward.

The inclination of the convex portion 411 is preferably such that the angle (incident angle) of light that enters the wavelength conversion member 20 from the light guide member 10 and strikes the convex portion is not less than the critical angle θT. That is, as shown on the right side of FIG. 5, the path of light incident from the light guide member 10 is 11, the perpendicular of the convex portion is 12, the perpendicular of the main plane of the total reflection layer is 13, and the incident light is approximately in the normal 13. If parallel, the angle θ1 of the inclined surface with respect to the incident light, the incident angle θ2 with respect to the inclined surface of the incident light, and the incident angle θ3 at which the light is reflected by the inclined surface and incident on the main plane are respectively (Equations (9) and (10)).
θ1 + θ2 = 90 ° (9)
2θ2 + θ3 = 180 ° (10)

Here, when θT is a critical angle, the conditions under which light is totally reflected on the inclined surface and the main plane are as follows.
θ2> θT (11)
θ3> θT (12)
From these equations (9) to (12), the angle θ (= 90 ° −θ1) of the inclined surface with respect to the main plane is obtained.
θT <θ <(90 ° −θT / 2) (13)
It becomes. For example, at the critical angle θT (52 °) when the wavelength conversion member 20 is YAG and the total reflection layer 41 is SiO ₂ ,
52 ° <θ <64 °
It becomes. Thereby, the light which hits the convex part 411 is totally reflected, and can go to a side surface direction.

When the light from the optical fiber has a maximum angle (α) spread with respect to the vertical direction, Expression (13) becomes the following Expression (14).
θT−α <θ <{(90 ° −θT / 2) −α / 2} (14)

  As described above, the case where the convex portion 411 has the shape shown in FIG. 6A has been described as an example, but considering that there is a certain distribution (Gaussian distribution) in the incident angle of light incident from the light guide member 10, FIG. 6 (b) and (c) are preferable, and in particular, the shape shown in FIG. 6 (b) is preferable in order to make light having an incident angle having a Gaussian distribution close to a uniform distribution.

  In the light emitting device of this embodiment, as a method of forming the convex portion 411 on the total reflection layer 41a, a concave portion corresponding to the convex portion 411 is formed on the upper surface of the wavelength conversion member 20 by etching, fine processing, etc. A method of forming the total reflection layer 41a thereon can be employed. When the reflecting member disposed on the total reflection layer 41a is the reflection layer 43, the film may be formed on the total reflection layer 41a by vapor deposition, plating, or the like. It is desirable to arrange the reflective layer 41a so that the upper surface thereof is flat, that is, without a recess.

  According to the present embodiment, the light in the wavelength conversion member 20 is formed by forming the shape that reflects the light from the light guide member 10 sideways on the total reflection layer 41a on the upper surface side corresponding to the light guide member 10. Can be reduced, the proportion of light reflected at a high angle in the wavelength conversion member 20 can be increased, and light can be extracted more efficiently.

<Third Embodiment>
The light emitting device according to the present embodiment is characterized in that means for widening the incident angle of light incident on the wavelength conversion member 20 from the light guide member 10 is provided at the junction between the end faces of the wavelength conversion member 20 and the light guide member 10. It is. Hereinafter, the light-emitting device of this embodiment will be described with reference to FIGS. 7 and 8. In FIG.7 and FIG.8, the same element as 1st Embodiment is shown with the same code | symbol, and the overlapping description is abbreviate | omitted.

  The angle of the light that enters the light wavelength conversion member 20 from the light guide member 10 through the total reflection layer 41b is not totally reflected by the total reflection layer 41b. In order to take advantage of the function of the total reflection layer 41b in the wavelength conversion member 20 and efficiently guide light to the side surface, the angle is preferably large within the limit. The light emitted from the optical fiber has a Gaussian distribution, but by changing the shape of the end face of the optical fiber instead of being flat, the Gaussian distribution can be made uniform and the emission angle can be widened.

  In the light emitting device shown in FIG. 7, the angle of light emitted from the light guide member 10 is widened by making the end surface of the light guide member 10 concave with respect to the end surface of the holding member 12. The concave shape may be a spherical shape as shown in the figure, may be a cone shape or a pyramid shape, and can be formed by polishing the end face. In any case, the distribution of the light emitted from the light guide member 10 can be made close to a uniform distribution, and the emission angle can be widened.

  In the light emitting device shown in FIG. 8, the concave portion 21 is provided in the lower surface portion of the wavelength conversion member 20 to which the light guide member 10 is joined. The recess 21 can be formed by wet etching, RIE, or the like, and the total reflection layer 41b is formed to cover the recess 21. Also in this case, the same effect as that of substantially increasing the numerical aperture can be obtained as in the light emitting device shown in FIG.

  Further, as shown in the lower part of FIG. 8, the aspect shown in FIG. 7 may be combined with the aspect shown in FIG. That is, the end surface of the optical fiber is made concave, and the lower surface of the wavelength conversion member 20 corresponding to the end surface is made concave.

  According to this embodiment, the light incident on the wavelength conversion member 20 from the light guide member 10 can be made to have a uniform distribution, and the incident angle can be expanded within the limit of the Brewster angle. Thereby, similarly to 2nd Embodiment, the ratio of the light which carries out high angle reflection within the wavelength conversion member 20 can be increased, and light can be taken out still more efficiently.

<Fourth embodiment>
The light emitting device of the present embodiment is characterized in that a material having a core center shifted from the center of the light guide member is used as the light guide member. FIG. 9 shows a light emitting device of this embodiment. In FIG. 9, the same elements as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  A cross section of the light guide member 10 is shown on the lower side of FIG. The illustrated light guide member 10 is a bundle fiber in which a plurality of cores are bundled. In the figure, a bundle fiber composed of three cores is shown, but the number of cores is not limited to three and may be larger. In this bundle fiber, the core is arranged radially with respect to the center of the fiber, and there is no core at the center. The upper drawing of FIG. 9 shows a cross section of a bundle fiber having a plurality of cores, and its end face is processed into a conical shape as shown.

  In such a bundle fiber, since the light emission surface is inclined, the emission optical axis is inclined with respect to the vertical. Thereby, depending on the refractive index of the substance (bonding material) existing between the core and the total reflection layer 41, the light emission angle changes as compared with the case where the end face is horizontal, and the effect of widening the numerical aperture is substantial. The same effect can be obtained.

  As mentioned above, although each embodiment of the present invention was described, the above-mentioned embodiment can also be combined suitably, and the modification mentioned in explanation of each embodiment is about other embodiments unless there is technical contradiction. Can be applied similarly.

  The light emitting device of the present invention is excellent in light extraction efficiency from the side, and can be used for vehicular lamps and other general lighting. In particular, since it has semi-bidirectionality, it is suitable for a vehicular lamp.

  According to the present invention, a light-emitting device with extremely low light loss and high operation reliability is provided.

DESCRIPTION OF SYMBOLS 10 ... Light guide member, 12 ... Holding member, 15 ... Reflection film, 20 ... Wavelength conversion material, 30 ... Light source, 41 ... Total reflection layer, 42 ... Increase reflection Layer, 43 ... reflective layer, 50 ... light emitting part, 60 ... bonding material, 411 ... convex part.

Claims (6)

A light emitting part including a wavelength converting member and a reflecting member covering the upper surface of the wavelength converting member; and a light guide member that is fixed to the back surface of the light emitting part and supplies light that excites the phosphor contained in the wavelength converting member. A light emitting device in which a side surface of the light emitting unit is a light emitting surface,
The light emitting device is characterized in that a total reflection layer made of a material having a refractive index lower than that of the wavelength conversion member is formed on both sides of the wavelength conversion member. The light-emitting device according to claim 1,
A light-emitting device, wherein a reflection member is disposed on a back surface of the light-emitting portion except for a portion where the light guide member is fixed. The light-emitting device according to claim 1 or 2,
The reflection member includes a metal reflection layer and an increased reflection layer provided between the metal reflection layer and the total reflection layer. The light-emitting device according to claim 1,
A part of the total reflection layer located on the upper surface of the wavelength conversion member is convex toward the wavelength conversion member. The light-emitting device according to claim 1,
The light guide member is characterized in that an end surface fixed to the light emitting portion is concave or convex. The light-emitting device according to claim 1,
The light emitting device according to claim 1, wherein a surface of the light emitting portion on which light from the light guide member is incident is recessed toward the wavelength converting member.

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