Light emitting device and wavelength conversion member

A light emitting device includes a laser light, a wavelength conversion member, a base member and a lid. The wavelength conversion member includes a plurality of projected portions each extending along a first direction on an upper surface side thereof and arranged side by side in a second direction. Each of the plurality of projected portions has a first surface extending along the first direction. The first surface is inclined with respect to a reference surface. The laser light source and the wavelength conversion member are arranged so that an optical axis of first light from the laser light source extends along the second direction when viewed from above and is inclined with respect to the reference surface, and light directly incident to the first surface along a direction parallel to the optical axis of the first light is regularly reflected toward an upward direction.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Japanese Patent Application No. 2016-120912, filed on Jun. 17, 2016, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

The present invention relates to a light emitting device and a wavelength conversion member.

A light source device including a semiconductor laser element, and a fluorescent material layer disposed separately from the semiconductor laser element is known (see Japanese Patent Application Laid-open No. 2011-129354). In such a light source device, the upper surface of a fluorescent material layer is irradiated with first light from a laser element, and the first light, and fluorescent light from the fluorescent material layer are extracted to the upper surface side. The laser element is disposed while avoiding an area directly above the fluorescent material layer so as not to obstruct the paths of the first light and fluorescent light from the fluorescent material layer.

SUMMARY

However, in such a light source device, first light reflected at the upper surface of a fluorescent material layer hardly travels in an upward direction. Specifically, since a part of the first light from a laser element may be approximately regularly reflected to the upper surface of the fluorescent material layer, the first light reflected at the upper surface of the fluorescent material layer travels principally to a side opposite to a side on which the laser element is disposed. On the other hand, fluorescent light from the fluorescent material layer tends to show a light distribution characteristic like a normal distribution having a maximum intensity in the upper part. Thus, for example, where an upward direction from the fluorescent material layer is a light extraction direction in the light source device, the first light regularly reflected at the upper surface of the fluorescent material layer is difficult to efficiently extract to the outside. Thus, a conventional light source device does not have sufficient light extraction efficiency.

The present application includes the following aspects. A light emitting device includes a laser light, a wavelength conversion member, a base member and a lid. The laser light source is configured to emit first light. The wavelength conversion member contains one kind of fluorescent material or a mixture of two or more kinds of fluorescent material, and configured to emit second light. The wavelength conversion member includes an upper surface arranged to be irradiated with the first light, and a plurality of projected portions each extending along a first direction on an upper surface side of the wavelength conversion member and arranged side by side in a second direction perpendicular to the first direction. Each of the plurality of projected portions has a first surface extending along the first direction. The first surface is inclined with respect to a reference surface on which bottoms of a plurality of grooves defined by the plurality of projected portions are arranged. The lid is bonded to the base member. The base member and the lid enclose the laser light source and the wavelength conversion member. The laser light source and the wavelength conversion member are arranged so that the first light and the second light are extracted from the upper surface side of the wavelength conversion member, an optical axis of the first light extends along the second direction when viewed from above and is inclined with respect to the reference surface, and light directly incident to the first surface along a direction parallel to the optical axis of the first light is regularly reflected toward an upward direction.

A wavelength conversion member includes an upper surface, one kind of fluorescent material or a mixture of two or more kinds of fluorescent material, and a plurality of projected portions. The plurality of projected portions each extending along a first direction on an upper surface side of the wavelength conversion member and arranged side by side in a second direction perpendicular to the first direction. Each of the plurality of projected portions has a first surface and a second surface. The first surface extends along the first direction and inclined with respect to a reference surface on which bottoms of a plurality of grooves defined by the plurality of projected portions are arranged. The second surface extends along the first direction when viewed from above and inclined with respect to the reference surface. The first surface is arranged so that light along the second direction when viewed from above and inclined with respect to the reference surface is regularly reflected toward an upward direction. The first surface and the second surface of each of the plurality of projected portions are arranged so that light regularly reflected at the second surface of one of the plurality of projected portions is regularly reflected toward the upward direction at the first surface of an adjacent one of the plurality of projected portions.

With the light emitting device, the first light can be reflected in the upward direction at the upper surface of the wavelength conversion member, and therefore light extraction efficiency can be improved. With the wavelength conversion member, a light emitting device having improved light extraction efficiency can be provided.

DETAILED DESCRIPTION

Hereinafter, an embodiment will be described with reference to the drawings as appropriate. It is to be noted that a light emitting device and a wavelength conversion member as described below are intended to implement the technical concept of the present invention, and the present invention is not limited to the following embodiment unless otherwise specified. The sizes, positional relations and so on of members shown in drawings may be exaggerated for clarification of explanation.

FIG. 1Ais a schematic top view showing a light emitting device10according to one embodiment, andFIG. 1Bis a schematic sectional view taken along line1B-1B inFIG. 1A. The light emitting device10includes a laser light source11which emits first light and a wavelength conversion member12which has an upper surface12A and emits second light. In the light emitting device10, the upper surface12A of the wavelength conversion member12is irradiated with the first light, and the first light and the second light are extracted from a side of the upper surface12A of the wavelength conversion member12. InFIGS. 1A and 1B, the optical axis of the first light is denoted by an arrow of symbol L. With the light emitting device10, the first light can be easily reflected in an upward direction at the upper surface12A of the wavelength conversion member12, and therefore light extraction efficiency can be improved. Hereinafter, the wavelength conversion member12, and the light emitting device10including the wavelength conversion member12will be described in detail.

The wavelength conversion member12has the upper surface12A. The upper surface12A is irradiated with the first light emitted from the laser light source11, and the first light and the second light are extracted from the upper surface12A side. The wavelength conversion member12contains one kind of fluorescent material and a mixture of two or more kinds of fluorescent material.

As shown inFIGS. 1A and 1B, the wavelength conversion member12has on the upper surface12A side thereof a plurality of projected portions12c. The plurality of projected portions12ceach extend in a first direction A1, and are arranged side by side in a second direction A2perpendicular to the first direction A1when viewed from above. In the wavelength conversion member12, the plurality of projected portions12cis arranged so as to be connected in the second direction A2.

A partial enlarged view ofFIG. 1Bis shown inFIG. 2.FIG. 2is a schematic view of the wavelength conversion member12at a cross-section extending perpendicularly to the first direction A1. As shown inFIG. 2, the wavelength conversion member12is disposed in such a manner that the optical axis L of the first light extends along the second direction A2, and is inclined with respect to a reference surface B when viewed from above provided that the reference surface B is a surface including the bottoms of the plurality of grooves12ddefined by the plurality of projected portions12c. Each of the plurality of projected portions12chas a first surface121extending in the first direction A1when viewed from above, the first surface121being inclined with respect to the reference surface B so that light directly incident to the first surface121along the optical axis L of the first light is regularly reflected in an upward direction. In this specification, the term “directly incident” means that light which is not reflected at the upper surface12A of the wavelength conversion member is incident to a surface of the wavelength conversion member, and the term “directly incident” does not exclude a situation in which light passes through a lens etc. to be incident to a surface of the wavelength conversion member.

In the wavelength conversion member12, the first light applied in a direction inclined with respect to the reference surface B is easily reflected in an upward direction owing to the first surface121. The fluorescent material contained in the wavelength conversion member12is excited by the first light to emit fluorescent light (the second light) principally in an upward direction. Thus, the direction of the maximum intensity of the first light reflected by the wavelength conversion member12can be made close to the direction of the maximum intensity of the fluorescent light, and therefore the light emitting device10having improved light extraction efficiency can be provided. Further, the plurality of projected portions12ceach extend in the first direction A1when viewed from above. Accordingly, the first light can be reflected in an upward direction at a relatively wide flat surface as compared to a case where the upper surface12A of the wavelength conversion member is merely roughened, and therefore a light source device having excellent light extraction efficiency can be obtained.

The first surface121of the projected portion12cmay be a surface having the following relationships with a straight line (line LAinFIG. 2) parallel to the optical axis L of the first light. First, the first surface121is a surface that is non-perpendicular to the line LAparallel to the optical axis L of the first light. Next, the line LAdirectly crosses the first surface121of one projected portion12c. These relationships allow the first light to be directly incident on at least a part of the first surface121. Further, as shown inFIG. 2, a straight line (line LBinFIG. 2) that is line-symmetric to the line LAwith respect to a straight line normal to the first surface121is a line showing light travelling in an upward direction from the wavelength conversion member12. When the first surface121has these relationships with the line LA, the first light applied to the first surface121can be reflected in an upward direction.

The upward direction can also be referred to as a light extraction direction. For example, a range of approximately −30° to +30° with respect to a direction perpendicular to the reference surface B can be set to the upward direction. As described later, for example in the specific example of the light emitting device10shown inFIG. 4, a direction in which an opening of a lid22extends may be the upward direction. The upper surface12A of the wavelength conversion member12is a surface which is irradiated with the first light.

Another example of projected portions12cis shown inFIGS. 3A to 3C.FIGS. 3A to 3Care schematic views of the wavelength conversion member12at a cross-section extending perpendicularly to the first direction A1. As shown inFIGS. 3A to 3C, each of the plurality of projected portions12cmay further have a second surface122. The second surface122is a surface which extends in the first direction A1when viewed from above, and to which light along the optical axis L of the first light is directly incident. The second surface122is inclined with respect to the reference surface B so that the first light regularly reflected at the second surface122of one projected portion (first projected portion12c1) among the plurality of projected portions12cis regularly reflected in an upward direction at the first surface121of other projected portion (second projected portion12c2) adjacent to the first projected portion12c1. As shown inFIGS. 3A to 3C, the first projected portion12c1and the second projected portion12c2are arranged side by side in this order from the side closest to a first light emitting port of the laser light source11.

It is considered that by using the wavelength conversion member12having the second surface122, the intensity distribution of light traveling in an upward direction from the wavelength conversion member12can be improved. In the case of the projected portion12cshown inFIG. 2, the bottom of a groove12dand an area in the vicinity thereof are hardly irradiated directly with the first light from the laser light source11. Accordingly, the amount of fluorescent light from the fluorescent material is small at the bottom of the groove12dand an area in the vicinity thereof. Thus, the light emission intensity distribution of mixed light of the first light and the second light becomes uneven. On the other hand, in the case of the wavelength conversion member12provided with projected portions12ceach having the second surface122as shown inFIGS. 3A to 3C, almost the whole of a region including the bottom of the groove12dand an area in the vicinity thereof, i.e. a region extending from the second surface122of the first projected portion12c1to the first surface121of the second projected portion12c2can be irradiated directly with the first light from the laser light source11. Accordingly, the fluorescent material can be excited in almost the whole of the region including the bottom of the groove12dand an area in the vicinity thereof.

More specifically, the projected portions12cshown inFIGS. 3A to 3Cmay have the first surface121and the second surface122which have the following relationships with the line LAparallel to the optical axis L of the first light. First, as shown inFIG. 3A, the first surface121is a surface that is non-perpendicular to the line LAparallel to the optical axis L, and the line LBthat is line-symmetric to the line LAwith respect to a straight line normal to the first surface121is a line showing light travelling in an upward direction from the wavelength conversion member12. These projected portions are the same as the projected portions12cshown inFIG. 2, but they are different in the following respects from the projected portions12cshown inFIG. 2and the projected portions12cshown inFIGS. 3A to 3C. First, the line LAdirectly crosses the second surface122of the first projected portion12c1as shown inFIG. 3B. The first surface121of the second projected portion12c2is disposed at a position at which the line LAcrosses a line LCthat is line-symmetric to the line LAwith respect to a straight line normal to the second surface122of the first projected portion12c1. Further, a line LDthat is line-symmetric to the line LCwith respect to a straight line normal to the first surface121of the second projected portion12c2is a line showing light travelling in an upward direction from the wavelength conversion member12. The projected portions12cshown inFIGS. 3A to 3Care formed in such a manner that the first surface121and the line LAdirectly cross each other over the whole of the first surface121, and therefore the second light can be extracted from almost the whole of a region extending from the lower end to the upper end of the first surface121.

Preferably, the area of the second surface122is larger than the first surface121in each of the plurality of projected portions12cas shown inFIGS. 3A to 3C. In other words, the width of the second surface122in the second direction A2is preferably larger than the width of the first surface121in the second direction A2when the lengths of the first surface121and the second surface122in the first direction A1are substantially equal to each other. Preferably, the first surface121of the second projected portion12c2is disposed at a position at which the line LAcrosses the line LCthat is line-symmetric to the line LAwith respect to a straight line normal to the second surface122of the first projected portion12c1in the vicinity of the upper end of the second surface122as illustrated inFIG. 3C. Accordingly, most of the first light reflected at the second surface122can be re-reflected at the adjacent first surface121to travel in an upward direction.

Preferably, the wavelength conversion member12has the plurality of projected portions12cwithin an area which is irradiated with the first light from the laser light source11at a time. Accordingly, deviation of the light emission intensity distribution of the first light in the top view can be reduced. Specifically, the width W1of each of the plurality of projected portions12cmay be in a range of 5 μm or more to 80 μm or less. The height H of each of the plurality of projected portions12cmay be in a range of 3 μm or more to 35 μm or less. When like the projected portion12cshown inFIG. 2, the projected portion12chas such a shape that the bottom of the groove12dand an area in the vicinity thereof are not irradiated directly with the first light from the laser light source11, it is preferred to reduce the width W1. Accordingly, the distance between regions irradiated directly with the first light can be reduced, and therefore the luminance distribution can be made more uniform. Specifically, the width W1of each of the plurality of projected portions12cis preferably in a range of 5 μm or more to 20 μm or less. Here, for example, the height H of each of the plurality of projected portions12cis preferably in a range of 3 μm or more to 10 μm or less. The width W1of the projected portion12cis the shortest distance between one end and the other end of the projected portion12cin the second direction A2in top view. The height H of the projected portion12cis the shortest distance between the reference surface B and the upper end of the projected portion12c.

In top view, the length of the projected portion12cin the first direction A1is preferably large enough for the first surface121to function as a reflecting surface. Specifically, the length of the projected portion12cin the first direction A1can be made larger than the width W1. For example, the length of the projected portion12cin the first direction A1is made equal to the length of the wavelength conversion member12in the first direction A1.

As shown inFIG. 1B, all projected portions12ccan be made to have the same size. On the other hand, since the incidence angle of the first light to the wavelength conversion member12slightly varies within the upper surface12A, the size and the inclined angle of the projected portion12ccan be accordingly varied within the upper surface12A.

The number of projected portions12cdisposed within an area which is irradiated with the first light from the laser light source11at a time is, for example, 3 or more. As shown inFIG. 1B, an outer edge portion of the wavelength conversion member12along the first direction A1is not required to be provided with projected portions12c. For example, a flat surface substantially parallel to the reference surface B can be disposed on the outer edge portion of the wavelength conversion member12along the first direction A1, and the plurality of projected portions12ccan be disposed inside the outer edge portion. The reference surface B is, for example, a surface parallel to a lower surface12B which is a surface opposite to the upper surface12A.

The upper surface12A of the wavelength conversion member12can be constituted by only the plurality of projected portions12cwithin an area which is irradiated with the first light from the laser light source11at a time. That is, adjacent projected portions12ccan be continuously disposed. For example, the plurality of projected portions can be formed in such a manner that one projected portion12cincludes only one first surface121and one second surface122, and the first surface121and the second surface122are continuous with each other over two adjacent projected portions. The first surface121and the second surface122are typically flat surfaces, but may have projected portions and recessed portions in the surface as long as the first light can be reflected in an intended direction. For example, a height difference smaller than the height H of the projected portion12cmay exist on the first surface121or the second surface122.

The wavelength conversion member12contains one kind of fluorescent material or a mixture of two or more kinds of fluorescent material. The fluorescent material contained in the wavelength conversion member12is excited by the first light to emit the second light as fluorescent light. The first light and the second light are mixed to obtain, for example, white light. In this specification, when there are two or more kinds of fluorescent material, all the light emitted by these fluorescent materials is included in the second light. When the first light is blue light, white light can be obtained as mixed light of the first light and the second light by selecting yellow light, or yellow light and red light as the second light. Examples of the fluorescent material which emits yellow light include YAG and LAG. Examples of the fluorescent material which emits red light include CASN and BSESN. The fluorescent material can be included in the projected portion12c. In other words, the fluorescent material can be included in a portion of the wavelength conversion member12above the reference surface B. However, when only the projected portion12ccontains the fluorescent material, wavelength conversion may be insufficient. Thus, it is preferred that in the wavelength conversion member12, a portion below the reference surface B also contains the fluorescent material. A light-transmissive material (e.g. alumina) having a refractive index different from that of the fluorescent material can be mixed with the wavelength conversion member12. Accordingly, light can be scattered in the wavelength conversion member12, and extracted from the upper surface12A.

The laser light source11emits the first light that excites the fluorescent material contained in the wavelength conversion member12. The wavelength conversion member12is irradiated with the first light in a direction different from an upward direction from the wavelength conversion member12(i.e. light extraction direction). In this arrangement, light from the wavelength conversion member12travels principally in a direction different from a direction toward the laser light source11, and therefore the necessity of a member that blocks light traveling toward the laser light source11from the wavelength conversion member12can be eliminated. Further, in this arrangement, the safety of the light emitting device10can be improved. If the light emitting device has the laser light source11disposed above the wavelength conversion member12, the light extraction direction to the outside of the light emitting device and the optical path of laser light emitted by the laser light source11may be almost coincident with each other in case where the wavelength conversion member12is dislocated from a laser light irradiation position due to, for example, detachment of the wavelength conversion member12. In this case, laser light is directly extracted to the outside of the light emitting device. However, when the light emitting device10has the laser light source11disposed in a direction different from an upward direction from the wavelength conversion member12, it can be ensured that the light extraction direction to the outside of the light emitting device and the optical path of laser light emitted by the laser light source11are not coincident with each other even if the wavelength conversion member12is dislocated. Accordingly, laser light is hardly extracted directly to the outside of the light emitting device10even if the wavelength conversion member12is dislocated. Thus, the light emitting device10with high safety can be obtained.

As the laser light source11, for example, a semiconductor laser element can be used. The semiconductor laser element, and at least one member such as an optical member such as a lens, a fiber and a reflecting mirror may be combined, and collectively designated as the laser light source11. The laser light source11is disposed in such a manner that the optical axis L of the first light emitted from the laser light source11is situated at the surface of any one of the plurality of projected portions12c. A first light irradiation region of the wavelength conversion member12is smaller than, for example, the upper surface12A. The first light irradiation region can be specified as, for example, a region that is irradiated with a part of the first light which has an intensity ranging from a peak intensity value downward to a certain intensity of, for example, 1/e2.

The first light emitted from the laser light source11is laser light (coherence light) until it arrives at the wavelength conversion member12after being emitted from the laser light11, but the first light after it is reflected at the upper surface12A of the wavelength conversion member12, and the first light extracted to the outside after entering the wavelength conversion member12may be non-laser light (incoherence light). Light which originates from the laser light source11and which is not subjected to wavelength conversion (e.g. blue light) is defined as the first light irrespective of whether it is laser light or not.

The first light may be, for example, light having a peak wavelength in a range of 350 nm to 600 nm. When the first light is combined with a yellow fluorescent material such as YAG to obtain white light, the first light having a peak wavelength in a range of 430 nm to 460 nm is preferred. Examples of the light source which emits laser light having such a peak wavelength include GaN-based semiconductor laser elements. The GaN-based semiconductor laser element has a quantum well structure including a well layer of, for example, InGaN.

As shown inFIG. 1B, the lower surface12B of the wavelength conversion member12may be provided with a light reflecting member13. When the first light and/or the second light is reflected in an upward direction by the light reflecting member13, the light extraction efficiency of the light emitting device10can be further improved. For example, the light reflecting member13includes a dielectric multilayer film and/or a metal film which reflects both the first light and the second light.

A laser package as a light emitting device20is shown inFIG. 4.FIG. 4is a schematic sectional view of the light emitting device20. As shown inFIG. 4, the light emitting device20includes a base member23, and a lid22bonded to the base member23, and the base member23and the lid22form an enclosed space. The enclosed space is, for example, a hermetically enclosed space. In this enclosed space, a laser element as a laser light source21which emits the first light, and the wavelength conversion member12including a fluorescent material which is excited by the first light to emit the second light are disposed. The lid22includes a light shielding portion22amade of metal etc., and a light-transmissive portion22bmade of glass etc., and the light-transmissive portion22bis disposed so as to close an opening provided in the light shielding portion22a.

In the light emitting device20, a light extraction direction, i.e. “upward direction” can be determined according to a positional relation between the opening in the light shielding portion22aand the wavelength conversion member12. For extracting light to the outside from the enclosed space of the light emitting device20, it is necessary to cause the light to pass through the opening in the light shielding portion22a. Thus, here, the upward direction is a direction connecting the upper surface of the wavelength conversion member12and the opening in the light shielding portion22a.

The “upward direction” can also be defined by a straight line connecting the outer edge of the first light irradiation region on the upper surface of the wavelength conversion member12and the outer edge of the opening in the light shielding portion22a(line LEinFIG. 4). Here, the inclined angle of the line LBwith respect to the reference surface B may be made larger than the inclined angle of the line LEwith respect to the reference surface B of the wavelength conversion member12. The inclined angle is an angle which is formed with respect to the reference surface B and which is 90° or less. Accordingly, the first light can be reflected in an upward direction, i.e. a light extraction direction by the projected portion12cof the wavelength conversion member12. For example, the inclined angle of the line LBshown inFIG. 2is about 80°, and is thus larger than the inclined angle of the line LE(about 60°) shown inFIG. 4. In the case of the projected portion12chaving the second surface122, similarly the inclined angle of the line LDwith respect to the reference surface B may be made larger than the inclined angle LEwith respect to the reference surface B. For example, the inclined angle of the line LDshown inFIG. 3Ais about 80°, and is thus larger than the inclined angle of the line LE(about 60°) shown inFIG. 4.

The laser light source21(laser element) is mounted on the base member23directly or with a sub-mount24interposed therebetween in such a manner that for example, the emission direction of the first light is substantially parallel to the bottom surface in the enclosed space. Here, a transparent body25such as a prism is disposed in the enclosed space, and the first light is refracted downward by means of a difference in refractive index between the transparent body25and a gas filled into the enclosed space. Accordingly, the upper surface of the wavelength conversion member12can be irradiated with the first light. With consideration given to a spread angle of laser light, a lens26may be provided on an optical path for the first light and between the laser light source21and the transparent body25. As the lens26, a converging lens or a collimating lens is selected.

In the light emitting device20, the optical axis of the first light for defining the projected portion12cis the optical axis of the first light in a region just before the light is incident to the wavelength conversion member12. InFIG. 4, the projected portion12cis defined by the optical axis of the first light in a region after the first light passes through the transparent body25and before the wavelength conversion member12is irradiated with the first light.

A laser module as a light emitting device30is shown inFIG. 5. As shown inFIG. 5, the light emitting device30includes a solid light source as a laser light source31which emits first light; the wavelength conversion member12which is irradiated with the first light; and an optical system32such as a lens to which the first light and the second light are incident from the wavelength conversion member12. The first light and the second light pass through the optical system32, and are then extracted to the outside from, for example, a window33.

In the light emitting device30, the “upward direction” is a direction connecting the upper surface of the wavelength conversion member12and the light incidence surface of the optical system32. As in the case of the light emitting device20, the “upward direction” can also be defined by a straight line connecting the outer edge of the first light irradiation region on the upper surface of the wavelength conversion member12and the outer edge of the light incidence surface of the optical system32(line LFinFIG. 5). Here, the inclined angle of the line LBwith respect to the reference surface B is made larger than the inclined angle of the line LFwith respect to the reference surface B of the wavelength conversion member12. Accordingly, the first light can be reflected in an upward direction, i.e. a light extraction direction by the projected portion12cof the wavelength conversion member12. In the case of the projected portion12chaving the second surface122, similarly the inclined angle of the line LDwith respect to the reference surface B is made larger than the inclined angle LFwith respect to the reference surface B.

The light emitting device30may include a reflection mechanism34which reflects the first light emitted by the laser light source31toward the wavelength conversion member12. The reflection mechanism34includes, for example, a microelectromechanical systems (MEMS) device such as a digital micromirror device having a large number of mirror surfaces. Accordingly, the first light irradiation position in the wavelength conversion member12can be made variable. The laser light source31is, for example, a laser package obtained by hermetically enclosing a semiconductor laser element. The light emitting device30may include a heat dissipater35thermally connected to the lower surface of the wavelength conversion member12. When the first light irradiation position is made variable by the reflection mechanism34etc., accordingly the direction of the first light applied to the wavelength conversion member12, i.e. the inclination of the optical axis with respect to the reference surface B may also be variable. Here, for example, the projected portion12cis formed using as a reference the optical axis of a part of the applied first light which travels to the central part. Alternatively, using as a reference the optical axis of the first light which is actually applied to each part of the wavelength conversion member12, the projected portion12cof each part may be formed.

(Modification of Wavelength Conversion Member12)

The wavelength conversion member12may include a notched portion12e. An example thereof is shown inFIGS. 6A to 6C.FIG. 6Ais a schematic top view showing the wavelength conversion member12, andFIG. 6Bis a schematic sectional view taken along line6B-6B inFIG. 6A.FIG. 6Cis a partial enlarged view ofFIG. 6B.

The notched portion12eis provided in a grid shape when viewed from above. A plurality of projected portions12cis provided in at least a part of a region surrounded by the grid-shaped notched portion12e. Accordingly, spread of light in the wavelength conversion member12can be limited by the notched portion12ein application of the first light to regions surrounded by the notched portion12e. Thus, the wavelength conversion member12having the notched portion12eis particularly suitable for the light emitting device30in which the first light irradiation position in the wavelength conversion member12is variable.

Further, a light shielding member may be embedded in the notched portion12e. For example, the first light irradiation region is sized to fit within a region surrounded by the notched portion12e. The width W2of the notched portion12emay be in a range of 3 μm or more to 10 μm or less. The width W2of the notched portion12ecan be made smaller than the width W1of the projected portion12cas shown inFIG. 6C. The depth D of the notched portion12eis preferably smaller than the height H of the projected portion12cfor limiting spread of light in the wavelength conversion member12. The depth D of the notched portion12eis, for example, 30 μm or more, or 50 μm or more. The depth D of the notched portion12emay be such a depth that the wavelength conversion member12is fully divided. The notched portion12emay be formed by mechanical cutting, or formed by chemical etching or molding.

EXAMPLES

A wavelength conversion member having a shape as shown inFIG. 2was prepared as the wavelength conversion member12of Example 1. The wavelength conversion member12of Example 1 has the plurality of projected portions12ceach extending in the first direction A1and arranged side by side in the second direction A2. The plurality of projected portions12cis each shaped to have the first surface121. The shape of the wavelength conversion member12in plan view is substantially a square having a size of about 1 mm×1 mm, and the thickness of the wavelength conversion member12is about 100 μm. The upper surface of the wavelength conversion member12is provided with16projected portions12chaving the same shape. The projected portions12ceach have a width of about 60 μm and a height of about 30 μm. The projected portion12cincludes two surfaces including the first surface121. The first surface121is positioned so as to be irradiated directly with laser light, and the other surface is positioned so as not to be irradiated directly with laser light. The angle formed by the first surface121and the other surface is about 70°. The wavelength conversion member12contains YAG as a fluorescent material. A photograph of a cross-section of the prepared wavelength conversion member12is shown inFIG. 7A.FIG. 7Ais an optical microscope photograph, and the straight line at the lower right inFIG. 7is a line corresponding to a length of 20 μm. The same wavelength conversion member as the wavelength conversion member12was used to prepare a measurement sample having the same structure as that of the light emitting device20(laser package) shown inFIG. 4except that the lid22was not provided. As the laser light source21(laser element), a GaN-based semiconductor laser element which emits laser light (first light) having a peak wavelength of about 450 nm was used. The angle of the first surface121of the projected portion12cwith respect to a direction L parallel to the optical axis of laser light applied to the wavelength conversion member12was about 55°.

For the measurement sample, a light distribution characteristic was measured. The results are shown inFIG. 7B. The results shown inFIG. 7Bare measurement results in the second direction. InFIG. 7B, the abscissa represents a position in the second direction with the upward direction set to 0°, and the ordinate represents a relative luminous intensity with the maximum luminous intensity set to 1. InFIG. 7B, the solid line represents blue light (first light), and the broken line represents yellow light (second light). The first light from the laser light source11was applied to the wavelength conversion member12in a direction of about −70°.

Comparative Example

A wavelength conversion member of a comparative example is the same as the wavelength conversion member12of Example 1 except that projected portions are not provided. The wavelength conversion member of the comparative example was used to prepare a measurement sample including the same members as in Example 1, and a light distribution characteristic was measured. The results are shown inFIG. 8. The results shown inFIG. 8are measurement results in the second direction. InFIG. 8, the abscissa represents a position in the second direction with the upward direction set to 0°, and the ordinate represents a relative luminous intensity with the maximum luminous intensity set to 1. InFIG. 8, the solid line represents blue light (first light), and the broken line represents yellow light (second light). The first light from the laser light source11was applied to the wavelength conversion member in a direction of about −70°.

Evaluation of Example 1

By using the wavelength conversion member12of Example 1, the light distribution characteristic for blue light (the first light) was improved as compared to the case where the wavelength conversion member of the comparative example was used as shown inFIGS. 7B and 8. Specifically, inFIG. 8, the luminous intensity of blue light was the maximum around +50°, and inFIG. 7B, the luminous intensity of blue light was the maximum around −30° and around +30°, and these positions were closer to the position at which the luminous intensity of yellow light (the second light) was the maximum. The luminous intensity of yellow light is the maximum around −12° in bothFIGS. 7B and 8. Thus, by providing the wavelength conversion member12with projected portions12ceach having the first surface121, the position of the maximum luminous intensity of the first light can be made closer to the position of the maximum luminous intensity of the second light. Accordingly, when the lid22is provided, a part having the maximum luminous intensity can be extracted to the outside for each of the first light and the second light, so that the light extraction efficiency of the light emitting device20can be improved.