JP7506328B2 - Light source and light emitting device including the light source - Google Patents

Description

The present invention relates to a light-emitting device.

In recent years, various electronic components have been proposed and put into practical use, and the performance required for these components is also increasing. In particular, electronic components are required to maintain their performance for a long time even under harsh operating environments. Such requirements are no exception for light-emitting devices using semiconductor light-emitting elements such as light-emitting diodes (LEDs). That is, in the general lighting field and the in-vehicle lighting field, the performance required for light-emitting devices is increasing day by day, and even higher output (higher brightness) and higher reliability are required. Furthermore, there is a demand to supply them at low prices while maintaining these high performances.
In particular, in the case of backlights used in LCD TVs and general lighting fixtures, design is important and there is a strong demand for thinner products.

For example, Patent Document 1 discloses that by combining a secondary optical lens with an LED, a batwing-type light distribution characteristic can be achieved, and light can be diffused uniformly over a short irradiation distance, resulting in a thinner fixture.
Moreover, Patent Document 2 discloses that a batwing light distribution is realized by devising a mold shape.

JP 2006-114863 A JP 2012-231036 A

However, in the method of combining with a secondary lens described in Patent Document 1, Fresnel loss occurs due to surface reflection when light enters the secondary lens and when it exits from the secondary lens, reducing the light utilization efficiency. In addition, costs for the lens and lens mounting are incurred, increasing costs.
In the method described in Patent Document 2, the thickness of the phosphor-containing layer varies depending on the angle, causing unevenness in the light distribution color, and therefore there has been a demand for improving the color unevenness.

The embodiment of the present invention has been made in consideration of the above circumstances, and provides a light-emitting device that enables batwing light distribution with improved light distribution color unevenness without using a secondary lens.

The light-emitting device according to this embodiment includes a base having conductor wiring, a light-emitting element placed on the base and electrically connected to the conductor wiring, and a light-transmitting sealing member that covers the light-emitting element, the sealing member having a convex shape, a height in the optical axis direction that is greater than the width of the bottom surface of the sealing member, and containing a light diffusing material.

According to an embodiment of the present invention, it is possible to provide a light emitting device that enables batwing light distribution with improved light distribution color uniformity without using a secondary lens.

1A and 1B are a top view and a cross-sectional view illustrating an example of a light emitting device according to an embodiment of the present invention. FIG. 4 is a diagram showing the light distribution characteristics of the light emitting device of the present embodiment. 1 is a cross-sectional view showing an example of a light emitting device according to an embodiment of the present invention. 1 is a cross-sectional view showing an example of a light emitting device according to an embodiment of the present invention. 1 is a cross-sectional view showing an example of a light emitting device according to an embodiment of the present invention. FIG. 2 is a top view showing an example of the light emitting device of the present embodiment. 11A to 11C are diagrams showing examples of the shape of the sealing member of the light emitting device according to Examples 3 to 5. FIG. 13 is a diagram showing the light distribution characteristics of the light emitting devices of Examples 3 to 5. FIG. 13 is a diagram showing the luminance distribution of the light-emitting devices of Examples 3 to 5. FIG. 11 is a luminance distribution diagram of Examples 3 to 5.

Hereinafter, the embodiments of the present invention will be described with reference to the drawings as appropriate. However, the light emitting device described below is intended to embody the technical idea, and unless otherwise specified, the present invention is not limited to the following. Furthermore, the contents described in one embodiment or example can be applied to other embodiments or examples.
Furthermore, in the following description, the same names and symbols indicate the same or similar components, and detailed descriptions will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured in such a manner that a single component serves multiple elements by configuring multiple elements with the same component, or conversely, the function of a single component may be shared by multiple components.

[First embodiment]
1(A) and 1(B) are schematic structural diagrams showing an example of a light emitting device of the first embodiment, where FIG. 1(A) is a top view and FIG. 1(B) is a cross-sectional view taken along line II of FIG. 1(A).
1, in this embodiment, a base 101 has a light emitting element 105 mounted by flip-chip mounting via a connection member 103 so as to straddle a pair of conductor wirings 102 provided on the surface of the base. A region of the upper surface of the conductor wiring 102 that is electrically connected to the light emitting element 105 is exposed from the insulating member 104.

An underfill 106 is formed on the lower part of the light-emitting element 105 (i.e., between the lower surface of the light-emitting element 105 and the base 101) and on the side surface of the light-emitting element 105, and a sealing member 108 containing a light diffusing material is formed on top of the underfill 106.

The sealing member 108 has a convex shape (e.g., approximately hemispherical, approximately conical, approximately cylindrical, mushroom-shaped, etc.), and is formed so that its height A in the optical axis (L) direction is longer than the width C of the bottom surface of the sealing member 108. In the description of this specification, the normal line passing through the center of the light-emitting element 105 is called the optical axis L. With this configuration, the light emitted from the light-emitting element 105 is scattered by the light diffusing material, and the light intensity emitted from the light-emitting device 100 is approximately proportional to the apparent area ratio of the sealing member 108. As a result, a batwing-type light distribution characteristic as shown in FIG. 2 can be realized. In other words, the light-emitting device 100 of this embodiment exhibits light distribution characteristics in which the center is darker than the outer periphery when the light-emitting element 105 is turned on and observed from the optical axis direction.

The sealing member 108 is formed so that its outer shape is circular or elliptical when viewed from above. In the case of an ellipse, the radius B of the base has a major radius and a minor radius, but in this specification, the minor radius is defined as radius B.

Fig. 2 is a diagram showing the light distribution characteristic of the light emitting device according to this embodiment. As shown in Fig. 2, the light emitting device according to this embodiment has a so-called batwing-type light distribution characteristic in which the relative luminous intensity is stronger at a light distribution angle of around 50 to 60 degrees than when the light distribution angle is 0 degrees, and the light distribution is wider.
2 shows the cases where the aspect ratio (A/B) obtained by dividing the height A of the sealing member in the optical axis direction by the radius B of the bottom surface of the sealing member is 2.8, 3.2, and 3.5. It can be seen that the larger the aspect ratio, the lower the relative luminous intensity near 0° and the wider the light distribution. In order to diffuse light uniformly, it is preferable that the aspect ratio is 2.0 or more.

Since the light emitting element 105 is directly covered with the sealing member 108, Fresnel loss can be reduced and light extraction efficiency can be improved compared to the case where a secondary lens is used.
Moreover, the light emitting element 105 is preferably disposed at a height of 0.5 mm or less from the upper surface of the base.

Furthermore, when the concentration of the light diffusing material is increased, the light emitting device 100 of this embodiment exhibits a luminance distribution in which the center is darker than the outer periphery when the light emitting element 105 is turned on and observed along the optical axis.
This is because the optical path length in the optical axis direction as viewed from the light emitting element 105 is longer than the optical path length in the direction perpendicular to the optical axis, so that the light from the light emitting element 105 is scattered and attenuated.
Therefore, by adjusting the concentration of the light diffusing material, it is possible to reduce the amount of light in the optical axis direction and achieve batwing light distribution without significantly increasing the aspect ratio, and less resin is required, improving productivity.

A preferred embodiment of the light emitting device 100 according to the present embodiment will now be described.
(Base 101)
The base 101 is a member for mounting the light emitting element 105. The base 101 has, on its surface, conductor wiring 102 for supplying power to the light emitting element 105.
Examples of materials for the base 101 include ceramics, phenolic resin, epoxy resin, polyimide resin, BT resin, polyphthalamide (PPA), polyethylene terephthalate (PET), and other resins. Among these, it is preferable to select resin as the insulating material from the viewpoints of low cost and ease of molding. Alternatively, it is preferable to select ceramics as the material for the base 101 in order to obtain a light-emitting device with excellent heat resistance and light resistance.

Examples of ceramics include alumina, mullite, forsterite, glass ceramics, nitrides (e.g., AlN), carbides (e.g., SiC), etc. Among these, ceramics made of alumina or containing alumina as a main component are preferable.
Furthermore, when resin is used as the material constituting the base 101, glass fiber or inorganic filler such as SiO ₂ , TiO ₂ , or Al ₂ O ₃ may be mixed into the resin to improve mechanical strength, reduce the thermal expansion coefficient, improve light reflectance, etc. Furthermore, the base 101 may be any material that can insulate and separate the pair of conductor wirings 102, and may be a so-called metal substrate in which an insulating layer is formed on a metal member.

(Conductor wiring 102)
The conductor wiring 102 is a member electrically connected to the electrodes of the light-emitting element 105 and serves to supply current (electric power) from the outside. In other words, it serves as an electrode or a part thereof for passing electricity from the outside. Usually, at least two conductor wirings, one positive and one negative, are formed separately.

The conductor wiring 102 is formed on at least the upper surface of the base, which is the mounting surface for the light-emitting element 105. The material of the conductor wiring 102 can be appropriately selected depending on the material used for the base 101, the manufacturing method, etc. For example, when ceramic is used as the material for the base 101, the material of the conductor wiring 102 is preferably a material with a high melting point that can withstand the firing temperature of the ceramic sheet, and it is preferable to use a high melting point metal such as tungsten or molybdenum. Furthermore, it may be coated with other metal materials such as nickel, gold, silver, etc. by plating, sputtering, vapor deposition, etc.

When glass epoxy resin is used as the material of the base 101, the material of the conductor wiring 102 is preferably a material that is easy to process. When injection-molded epoxy resin is used, the material of the conductor wiring 102 is preferably a material that is easy to process, such as punching, etching, and bending, and has relatively high mechanical strength. Specific examples include metals such as copper, aluminum, gold, silver, tungsten, iron, and nickel, or metal layers and lead frames of iron-nickel alloys, phosphor bronze, copper containing iron, and molybdenum. The surface may be further coated with a metal material. This material is not particularly limited, but may be, for example, silver alone, or an alloy of silver and copper, gold, aluminum, rhodium, or a multilayer film using these silver and each alloy. In addition, the method of disposing the metal material may be a sputtering method or a vapor deposition method in addition to a plating method.

(Connection member 103)
The connecting member 103 is a member for fixing the light emitting element 105 to the base 101 or the conductor wiring 102. Examples of the connecting member 103 include insulating resins and conductive members, and in the case of flip chip mounting as shown in Fig. 1B, a conductive member is used. Specific examples of the connecting member 103 include 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, an Sn-containing alloy, an Sn-Cu-containing alloy, an Sn-Cu-Ag-containing alloy, an Au-Ge-containing alloy, an Au-Si-containing alloy, an Al-containing alloy, a Cu-In-containing alloy, a mixture of a metal and a flux, and the like.

The connecting member 103 may be in a liquid, paste, or solid form (sheet, block, powder, or wire), and may be appropriately selected depending on the composition and shape of the substrate. The connecting member 103 may be formed of a single member, or a combination of several types may be used.

(Insulating member 104)
The conductor wiring 102 is preferably covered with an insulating member 104 except for the portion electrically connected to the light emitting element 105 or other materials. That is, as shown in each drawing, a resist for insulatingly covering the conductor wiring 102 may be disposed on the base, and the insulating member 104 can function as the resist.

When the insulating member 104 is disposed, it is not only for the purpose of insulating the conductor wiring 102, but also by containing a white filler similar to the underfill material described below, it is possible to prevent light leakage and absorption and increase the light extraction efficiency of the light emitting device 100.
The material of the insulating member 104 is not particularly limited as long as it is an insulating material that absorbs little light from the light emitting element, and examples of the material that can be used include epoxy, silicone, modified silicone, urethane resin, oxetane resin, acrylic, polycarbonate, polyimide, and the like.

(Light-emitting element 105)
The light emitting element 105 mounted on the base body is not particularly limited, and any known element can be used. In this embodiment, however, it is preferable to use a light emitting diode as the light emitting element 105.
The light emitting element 105 can be selected from those with any wavelength. For example, as blue and green light emitting elements, those using ZnSe, nitride semiconductors (In _x Al _y Ga _1-x-y N, 0≦X, 0≦Y, X+Y≦1), and GaP can be used. As red light emitting elements, GaAlAs, AlInGaP, etc. can be used. Furthermore, semiconductor light emitting elements made of other materials can also be used. The composition, emission color, size, number, etc. of the light emitting elements used can be appropriately selected depending on the purpose.

Various emission wavelengths can be selected depending on the material of the semiconductor layer and its degree of crystal mixing. The positive and negative electrodes may be on the same side, or on different sides.

The light-emitting element 105 of this embodiment has a light-transmitting substrate and a semiconductor layer laminated on the substrate. In this semiconductor layer, an n-type semiconductor layer, an active layer, and a p-type semiconductor layer are formed in that order, with an n-type electrode formed on the n-type semiconductor layer and a p-type electrode formed on the p-type semiconductor layer.

As shown in FIG. 1, the electrodes of the light-emitting element 105 are flip-chip mounted on the conductor wiring 102 on the surface of the base 101 via the connection member 103, and the surface opposite to the surface on which the electrodes are formed, i.e., the main surface of the translucent substrate, is used as the light extraction surface. The light-emitting element 105 is arranged to straddle two conductor wirings 102 that are insulated and separated into positive and negative, and is electrically connected and mechanically fixed by the conductive connection member 103. The mounting method of this light-emitting element 105 can be a mounting method using solder paste, or a mounting method using bumps, for example. In addition, it is also possible to use a small packaged product in which the light-emitting element is sealed with resin or the like as the light-emitting element 105, and there are no particular limitations on the shape or structure.

As described later, in the case of a light emitting device including a wavelength conversion member, a nitride semiconductor (In _x Al _y Ga _1-x-y N, 0≦X, 0≦Y, X+Y≦1) capable of emitting short wavelength light capable of efficiently exciting the wavelength conversion member 109 is preferably used.

(Underfill 106)
When the light emitting element 105 is flip-chip mounted, it is preferable that an underfill 106 is formed between the light emitting element 105 and the base 101. The underfill 106 contains a filler for the purposes of enabling efficient reflection of light from the light emitting element 105 and bringing the thermal expansion coefficient closer to that of the light emitting element 105.
The material of the underfill 106 is not particularly limited as long as it is a material that absorbs little light from the light emitting element, and examples of the material that can be used include epoxy, silicone, modified silicone, urethane resin, oxetane resin, acrylic, polycarbonate, polyimide, and the like.

If the filler contained in the underfill 106 is a white-based filler, it will be easier for light to be reflected, and the light extraction efficiency can be improved. In addition, it is preferable to use an inorganic compound as the filler. Here, white includes a filler that appears white due to scattering when there is a difference in refractive index between the filler and the material around it, even if the filler itself is transparent.

Here, the reflectance of the filler is preferably 50% or more for light of the emission wavelength, and more preferably 70% or more. In this way, the light extraction efficiency of the light emitting device 100 can be improved. The particle size of the filler is preferably 1 nm or more and 10 μm or less. By setting the particle size of the filler in this range, the resin fluidity as an underfill is improved, and even narrow gaps can be covered without problems. The particle size of the filler is preferably 100 nm or more and 5 μm or less, and more preferably 200 nm or more and 2 μm or less. The shape of the filler may be spherical or scaly.

It is preferable to appropriately select and adjust the particle size of the filler and the material of the underfill so that the side surface of the light-emitting element is not covered by the underfill. This is to ensure that the side surface of the light-emitting element can be used as a light extraction surface.

(Sealing member 108)
The sealing member 108 is a member disposed on the base so as to cover the light emitting element 105 in order to protect the light emitting element 105 from the external environment and to optically control the light output from the light emitting element. In this embodiment, the light emitting element 105 is directly covered with the sealing member 108.

The material for the sealing member 108 may be a light-transmitting material such as epoxy resin, silicone resin, or a mixture of these, or glass. Of these, it is preferable to select silicone resin, taking into consideration its light resistance and ease of molding.

The sealing member 108 contains a light diffusing material for diffusing the light from the light emitting element 105. By having the light diffusing material, the light emitted from the light emitting element 105 in the direction of the optical axis L is diffused to the entire surroundings by the light diffusing material.

In addition to the light diffusing material, the sealing member 108 may also contain a wavelength conversion material such as a phosphor that absorbs the light from the light emitting element 105 and emits light of a different wavelength from the output light from the light emitting element, or a colorant that corresponds to the light emission color of the light emitting element.

The sealing member 108 can be formed by compression molding or injection molding so as to cover the light-emitting element 105. Alternatively, the viscosity of the material of the sealing member 108 can be optimized, and the material can be dripped or drawn onto the light-emitting element 105, allowing the surface tension of the material itself to form the shapes shown in the figures.

In the case of the latter forming method, a sealing member can be formed in a simpler manner without the need for a mold. In addition, as a means for adjusting the viscosity of the material of the sealing member formed by this forming method, in addition to the inherent viscosity of the material, the viscosity can also be adjusted to the desired level by using the light diffusing material, wavelength conversion material, and coloring agent as described above.

(Light Diffusion Material)
Specific examples of the light diffusing material include oxides such as _SiO2 , _{Al2O3 , Al} (OH) ₃ , MgCO3, _TiO2 , _ZrO2 , ZnO, _Nb2O5 , MgO, _Mg (OH) ₂ , _SrO , _In2O3 , _TaO2 , HfO, SeO, _Y2O3 , _CaO , _Na2O , and _B2O3 , nitrides such as SiN, AlN, and AlON, and fluorides such as _MgF2 . These may be used alone _or in combination. Alternatively, they may be divided into a plurality of layers and laminated.

Organic fillers may also be used as light diffusing materials. For example, various resins in particulate form may be used. In this case, examples of various resins include silicone resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, polytetrafluoroethylene resin, epoxy resin, cyanate resin, phenol resin, acrylic resin, polyimide resin, polystyrene resin, polypropylene resin, polyvinyl acetal resin, polymethyl methacrylate resin, urethane resin, and polyester resin.

It is preferable that the light diffusing material is a material that does not substantially convert the wavelength of the light from the light emitting element. This makes it possible to suppress unevenness in the light distribution color caused by the thickness of the wavelength conversion material-containing layer varying with the angle.

The content of the light diffusing material may be sufficient to diffuse light, for example, about 0.01 to 30 wt%, preferably about 2 to 20 wt%. Similarly, the size of the light diffusing material may be sufficient to diffuse light, for example, about 0.01 to 30 μm, preferably about 0.5 to 10 μm. The shape may be spherical or scaly, but spherical is preferable to diffuse light uniformly. However, the concentration of the light diffusing material changes relatively depending on the refractive index difference with the sealing material and the thickness, and the above figures are merely a guide.
For example, the light emitting element itself usually has the strongest light intensity in the direction of the optical axis. Therefore, if the concentration of the diffusing material is too low, when the light emitting element is turned on and observed along the optical axis, the central part may not have a darker luminance distribution than the peripheral part. Therefore, it is preferable to adjust the concentration of the diffusing material so that the central part has a darker luminance distribution than the peripheral part.

In addition, by controlling the concentration of the light diffusing material in the sealing member 108, it is possible to observe the light emitting device 100 from the optical axis, making the center dark and the periphery bright. With this configuration, it is possible to further suppress the amount of light in the optical axis direction and obtain batwing-type light distribution characteristics.

The light emitting device of this embodiment can achieve a wide light distribution without using a secondary lens, so when multiple light emitting elements 105 are mounted on the base 101, the light can be diffused uniformly over a short irradiation distance even if the distance between adjacent light emitting elements is 20 mm or more. This makes it possible to achieve a surface light source with reduced luminance unevenness using multiple light emitting elements. Here, the distance between adjacent light emitting elements refers to the shortest distance between two adjacent light emitting elements 105, as shown by distance F in Figure 6.

[Second embodiment]
FIG. 3 is a cross-sectional view showing an example of a light emitting device according to the second embodiment.
In this embodiment, the wavelength conversion member 109 is disposed in contact with the light emitting element 105, and the sealing member 108 containing a light diffusing material is formed so as to cover the wavelength conversion member 109.

As described above, if the entire sealing member 108 contains a wavelength conversion material, the thickness of the wavelength conversion material-containing layer varies depending on the angle, resulting in uneven light distribution color. For this reason, in this embodiment, the wavelength conversion member 109 is formed around the light emitting element 105, and the sealing member 108 with optical performance is formed on top of it. This makes it possible to form separately the area where wavelength conversion is performed (wavelength conversion member 109) and the area where optical performance is imparted (sealing member 108), thereby suppressing uneven light distribution color while realizing the desired light distribution characteristics.

(Wavelength conversion member 109)
The wavelength conversion member may be, for example, a member that absorbs light from a light-emitting element having a nitride-based semiconductor as a light-emitting layer and converts the wavelength into light of a different wavelength. The fluorescent material may be, for example, a nitride-based fluorescent material or an oxynitride-based fluorescent material that is mainly activated with a lanthanoid element such as Eu or Ce. More specifically, it is preferable that the fluorescent material is at least one of the fluorescent materials selected from those broadly classified as (D1) to (D3) below.
(D1) Phosphors such as alkaline earth halo apatite, alkaline earth metal borate halogen, alkaline earth metal aluminate, alkaline earth metal sulfide, alkaline earth metal thiogallate, alkaline earth metal silicon nitride, germanate, etc., which are mainly activated by a lanthanoid element such as Eu or a transition metal element such as Mn. (D2) Phosphors such as rare earth aluminate, rare earth silicate, alkaline earth metal rare earth silicate, etc., which are mainly activated by a lanthanoid element such as Ce. (D3) Phosphors such as organic or organic complexes, which are mainly activated by a lanthanoid element such as Eu.

Among them, the YAG (Yttrium Aluminum Garnet) phosphor, which is a rare earth aluminate phosphor mainly activated with a lanthanoid element such as Ce, is preferable. The YAG phosphor is represented by the following composition formulas (D21) to (D24), etc.
( _{D21) Y3Al5O12 : Ce}
( _D22 ) ( _Y0.8Gd0.2 ) _{3Al5O12 : Ce}
( _D23 ) _{Y3 ( Al0.8Ga0.2} ) _5O12 :Ce
(D24) (Y,Gd) ₃ (Al,Ga) _{5O12 :} Ce

Also, for example, a part or all of Y may be replaced with Tb, Lu _{, etc. Specifically, Tb3Al5O12:Ce, Lu3Al5O12 : Ce , etc.} may be used. Furthermore, phosphors other than the above-mentioned phosphors that have _similar performance, action, and effect may also be used.

The particle size of such a phosphor is preferably about 2.5 to 30 μm, for example.
In this specification, the term "particle size" refers to an average particle size, and the value is determined by an air permeability method or F.S.S.S. No. (Fisher-SubSieve-Sizer-No.) (a value represented by a so-called D bar (a bar above D)).

The wavelength conversion member may be, for example, a light-emitting material called a nanocrystal or quantum dot. Such materials include semiconductor materials, for example, semiconductors of the II-VI, III-V, IV-VI, and I-III-VI groups, specifically, nano-sized highly dispersed particles such as CdSe, core-shell type CdS _x Se _1-x /ZnS, GaP, InAs, InP, GaN, PbS, PbSe, Cu(In,Ga)S ₂ , and Ag(In,Ga)S ₂ . Such quantum dots can have a particle size of, for example, 1 to 100 nm, preferably about 1 to 20 nm (about 10 to 50 atoms). By using quantum dots with such a particle size, internal scattering can be suppressed, and scattering of light in the wavelength conversion region can be suppressed.

The light emitting device 200 shown in FIG. 3 may have the same configuration as the light emitting device 100 of the first embodiment, except that it has a wavelength conversion member 109 around the light emitting element 105 .
In this embodiment, the wavelength conversion member 109 has a convex shape in the optical axis L direction, similar to the sealing member 108. The wavelength conversion member 109 is disposed so as to be in contact with a portion where the surface of the light emitting element 105 is exposed, so that wavelength conversion takes place between the light emitting element and the sealing member 108. In the example shown in FIG. 3, the wavelength conversion member 109 is formed in a substantially hemispherical shape that covers the light emitting element 105.

It is preferable that the wavelength conversion member 109 is formed so that its outer shape is circular or elliptical when viewed from above.

It is preferable that the height (D) of the wavelength conversion member 109 in the optical axis (L) direction is 1/2 or less of the height (A) of the sealing member 108 in the optical axis (L) direction. This ensures the thickness of the sealing member 108 and reduces color unevenness.

Furthermore, it is preferable that the width (E) of the wavelength conversion member 109 is 4/5 or less of the width (C) of the sealing member 108. This ensures the thickness of the sealing member 108 and reduces color unevenness.

The sealing member 108 of the light emitting device of the second embodiment may further contain a wavelength conversion member such as a phosphor. In this case, it is preferable that the emission wavelength of the wavelength conversion member 109 is longer than the emission wavelength of the wavelength conversion member such as a phosphor contained in the sealing member 108. This makes it possible to prevent the light that has been wavelength converted by the wavelength conversion member 109 from being wavelength converted again by the wavelength conversion member contained in the sealing member.

[Modification of the second embodiment]
4 is a cross-sectional view showing a modified example of the light emitting device 200 of the second embodiment. The light emitting device 300 of this modified example uses a small LED package product as the light emitting element 105, which is provided with a wavelength conversion member and a reflective member 203. Specifically, the side and bottom surfaces of the light emitting element 105 are covered with the reflective member 203, and an LED package 201 provided with a wavelength conversion member 109 on the top surface of the light emitting element 105 is placed on the base 101. The terminal 204 of the LED package 201 and the conductor wiring 102 are electrically connected by the connecting member 103.

As with the second embodiment, this modified example also allows the area where wavelength conversion is performed and the area where optical performance is imparted to be formed separately, thereby suppressing unevenness in the light distribution color. This configuration allows the use of light sources whose chromaticity has been selected in advance, thereby improving the chromaticity yield of the product.

[Third embodiment]
FIG. 5 is a cross-sectional view showing an example of a light emitting device 400 according to the third embodiment.
In this embodiment, the radius of the region (bottom surface of the sealing member 108) where the sealing member 108 and the base 101 contact is formed to be smaller than the maximum radius of the sealing member 108 in the width direction. In this way, the sealing member 108 has an inverse tapered portion 205 in the vicinity of the base 101, so that the light emitted from the light emitting element in a direction directly to the side of the optical axis (L) is refracted to change direction toward the upper surface of the base, thereby increasing the amount of light that illuminates the entire surface without hitting the base. The sealing member 108 may have the same configuration as the light emitting device 100 of the first embodiment or the light emitting device 200 of the second embodiment, except that it is inversely tapered in the vicinity of the base 101.

The present invention will be explained in more detail below with reference to examples, but it should be understood that the present invention is not limited to these examples.
[Example 1]
In this embodiment, as shown in FIGS. 1A and 1B, a glass epoxy base material is used as the substrate 101, and a Cu material of 35 μm is used as the conductor wiring.
The light emitting element is a nitride-based blue LED having a square shape with sides of 600 μm in plan view and a thickness of 150 μm, and an epoxy-based white solder resist is used for the insulating member 104. Silicone resin containing 30 wt% titanium oxide as a filler is used as the underfill 106, and the lower surface and side surface of the light emitting element 105 are covered with the underfill 106. The sealing member 108 is made of silicone resin containing 30 wt% SiO ₂ filler as a light diffusing material, and is approximately semi-spherical with a circular outer shape as viewed from above, as shown in FIGS. 1A and 1B. The height A in the optical axis direction is 5.5 mm, the radius B of the bottom surface of the sealing member 108 is 1.7 mm, and the aspect ratio (A/B) is 3.2.

With this configuration, the light emitted from the light emitting element 105 is scattered by the _SiO2 filler, which is a light diffusing material, and the light intensity emitted from the light emitting device 100 is approximately proportional to the apparent area ratio of the sealing member 108. As a result, it is possible to realize a light distribution characteristic as shown in Fig. 2 with an aspect ratio of 3.2. This light distribution has a higher relative luminous intensity around 50° to 60° than around 0°, and can be controlled as a batwing light distribution.

[Example 2]
As shown in FIG. 3, this embodiment is similar to the first embodiment, except that a sealing member 108 containing a wavelength conversion member 109 is formed around the light emitting element 105 .
In this embodiment, the wavelength conversion member 109 uses a silicone resin containing a YAG-based phosphor, and the sealing member 108 uses a silicone resin containing a SiO ₂ filler as a light diffusing material.
With this configuration, the blue light from the light-emitting element 105 and the yellow light whose wavelength has been converted by the wavelength conversion member 109 are combined to produce white light, which is further diffused within the sealing member 108, thereby obtaining a batwing light distribution with little color unevenness in all directions.

In Examples 3 to 5, the shape of the sealing member 108 was changed and the light distribution characteristics and luminance distribution were confirmed. The light-emitting device of Example 3 is shown in Figure 7 (A), the light-emitting device of Example 4 in Figure 7 (B), and the light-emitting device of Example 5 in Figure 7 (C).

The light emitting devices of Examples 3 to 5 have in common that the sealing member 108 has a convex shape, the height in the optical axis direction is longer than the width of the bottom surface of the sealing member 108, the sealing member 108 contains a light diffusing material, and the upper surface of the sealing member 108 has a curvature.
The substrate is a glass epoxy base material, the conductor wiring is a 35 μm Cu material, the light emitting element is a 150 μm thick nitride blue LED with a square shape of 600 μm on a plan view, and the insulating material is an epoxy white solder resist.

[Example 3]
As shown in Fig. 7A, the sealing member 108 of the third embodiment has a larger curvature in the vicinity of the optical axis than in other portions, and is shaped like a cone. The side surface of the sealing member also has a curvature. In the third embodiment, as shown in Fig. 3, the phosphor layer is formed by applying phosphor onto the light-emitting element. A YAG-based phosphor is used as the phosphor, and a white light-emitting device is formed.

[Example 4]
7B, the curvature of the sealing member 108 in Example 4 is smaller in the vicinity of the optical axis than in the other portions, and the surface in the vicinity of the optical axis is nearly flat. In addition, the side surface of the sealing member has a surface that is nearly perpendicular to the upper surface of the base (the upper surface of the light-emitting element), and the sealing member is nearly cylindrical.

Such a shape can be formed as follows.
First, a resin is prepared by dispersing a diffusion material in a resin that has been made highly thixotropic by adding a nanofiller, and the resin is applied while being pulled up by controlling the vertical direction (z direction) of the dispenser. When the resin is pulled up to the required height, the pulling is stopped and the resin is supplied until the vertical cross section is close to a rectangle. When the desired shape is obtained, the supply of the resin is stopped and the resin is cut by scraping the upper surface. Note that, although an example in which the upper surface of the sealing member has a curvature is shown here, the upper surface may be flat.
In the fourth embodiment, a phosphor layer is formed by coating a phosphor on a light emitting element in the same manner as in the third embodiment, and a white light emitting device is obtained.

[Example 5]
7C, the sealing member 108 of the fifth embodiment has an upper portion 10 and a lower portion 20, and the upper portion 10 is mushroom-shaped with a diameter G larger than a diameter H of the lower portion 20. In the upper portion 10, the curvature in the vicinity of the optical axis is smaller than the curvature of the other portions, as in the fourth embodiment, and the surface in the vicinity of the optical axis is nearly flat. The side surface of the lower portion 20 has a surface that is substantially perpendicular to the upper surface of the base (the upper surface of the light-emitting element) and is formed into a substantially cylindrical shape, and the upper portion 10 is formed into a substantially spherical shape.
Moreover, the diameter of the side surface of the sealing member increases from bottom to top, and after reaching a maximum at the point of diameter G, gradually decreases further upward. In this manner, when the light emitting device is viewed from above, the upper portion 10 overlaps the lower portion 20 so as to encompass it, so that the periphery of the bottom of the sealing member, where the luminance is high, cannot be seen directly when viewed from above, and therefore, as described later, uniformity can be improved.
In the fifth embodiment, a white light emitting device is formed by forming a phosphor layer using an LED package 201 as shown in FIG.

(Orientation characteristics and brightness distribution)
As shown in Fig. 8, the light distribution characteristics of all the light emitting devices are batwing light distributions. The light emitting device of Example 5 shows substantially the same light distribution characteristics as the light emitting devices of Examples 3 and 4, except that the brightness near the optical axis is flatter.
On the other hand, Fig. 9 is a graph showing the luminance distribution of the sealing member 108 and its surroundings in the light emitting devices of Examples 3 to 5 as viewed from above, and Fig. 10 shows the in-plane luminance distribution as viewed from above. Fig. 10(A) shows the luminance distribution of Example 3, Fig. 10(B) shows the luminance distribution of Example 4, and Fig. 10(C) shows the luminance distribution of Example 5.
Looking at the luminance distributions in Figures 9 and 10, the light emitting device of Example 5 has the best uniformity. Here, uniformity refers to the brightness ratio (dark area/bright area) between the brightness of the darkest area (dark area) near the optical axis and the brightness of the brightest area (bright area). The larger this value is, the smaller the difference between the bright area and the dark area is, and the better the uniformity is. The brightness ratio of Example 3 is 0.157, the brightness ratio of Example 4 is 0.557, and the brightness ratio of Example 5 is 0.717.
When the light diffusing plate or the like, which is the irradiated surface, is very close to the light emitting device, the influence of the luminance distribution of the light emitting device itself, which is not shown in the light distribution characteristic shown in Fig. 8, appears, and therefore, in the light emitting device of Example 3, a donut-shaped light and dark shape appears on the irradiated surface, with the optical axis being dark and the periphery being bright. In contrast, in Examples 4 and 5, the light emitting devices have good luminance uniformity, and therefore it is possible to suppress the occurrence of a light and dark shape near the optical axis of the irradiated surface.

From the results of Examples 3 and 4, when the curvature of the sealing member 108 near the optical axis is smaller than the curvature of the other parts, the difference in the optical path length within the sealing member between on the optical axis and its surrounding area becomes small, so that the difference in the amount of light passing through in the optical axis direction becomes small, and uniformity is improved.
In addition, the reason why the light emitting device of Example 5 has the best uniformity is believed to be that the reflected light from the white solder resist around the bottom of the sealing member, which was the brightest in Example 4, is blocked and scattered by the sealing member itself.
In this case, the difference in diameter between the upper portion 10 and the lower portion 20 is, for example, about 1.1 to 2.0 times, and preferably about 1.2 to 1.5 times, the diameter of the upper portion 10 relative to the diameter of the lower portion 20. Note that this diameter ratio varies depending on the aspect ratio and light distribution characteristics of the sealing member, and is therefore not limited to the above-mentioned range.

The light-emitting device of the present invention can be used as a backlight source for liquid crystal displays, various lighting fixtures, etc.

REFERENCE SIGNS LIST 100, 200, 300, 400 Light emitting device 101 Base 102 Conductor wiring 103 Connection member 104 Insulation member 105 Light emitting element 106 Underfill 108 Sealing member 109 Wavelength conversion member L Optical axis 201 LED package 203 Reflection member 204 Terminal 205 Reverse tapered portion

Claims (12)

A light-emitting element;
A light source having a sealing member that covers the light emitting element,
The sealing member contains a light diffusing material having a content of 0.01 to 30 wt %,
The shape of the sealing member has a bottom surface, and when a normal line passing through the center of the light emitting element is defined as an optical axis (L) , the height of the sealing member in the optical axis (L) direction is longer than the width of the bottom surface at a maximum width position when viewed from the optical axis (L) direction ,
A wavelength conversion member is provided around the light emitting element,
the wavelength conversion member is disposed in contact with an exposed surface of the light emitting element so that wavelength conversion is performed on the light emitted from the light emitting element before the light reaches the sealing member;
A light source having a batwing-type light distribution characteristic. The light source according to claim 1, wherein the height of the wavelength conversion member in the optical axis (L) direction is equal to or less than 1/2 the height of the sealing member in the optical axis (L) direction. The light source according to claim 1, wherein the underfill contains a filler on the underside of the light-emitting element. The light source according to claim 3, wherein the reflectance of the filler is 50% or more for light having an emission wavelength of the light emitting element. A substrate is provided.
A light emitting device comprising a plurality of light sources according to claim 1 on the base. A substrate is provided.
A light emitting device comprising a plurality of light sources according to claim 2 on the base. A substrate is provided.
A light emitting device comprising a plurality of light sources according to claim 3 on the base. A substrate is provided.
A light emitting device comprising a plurality of light sources according to claim 4 on the base. The light-emitting device according to claim 5, wherein the distance between adjacent light-emitting elements of each of the light sources is 20 mm or more. The light-emitting device according to claim 6, wherein the distance between adjacent light-emitting elements of each of the light sources is 20 mm or more. The light-emitting device according to claim 7, wherein the distance between adjacent light-emitting elements of each of the light sources is 20 mm or more. The light-emitting device according to claim 8, wherein the distance between adjacent light-emitting elements of each of the light sources is 20 mm or more.

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