Light-emitting device and luminaire

A light-emitting device includes a substrate, a reflecting layer formed on the substrate, a light-emitting element placed on the reflecting layer, and a sealing resin layer that covers the reflecting layer and the light-emitting element. The oxygen permeability of the sealing resin layer is equal to or lower than 1200 cm3/(m2·day·atm), and the ratio of the area of the reflecting layer covered by the sealing resin layer to the entire area on the resin substrate covered by the sealing resin layer is between 30% and 75% inclusive.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2011-125234, filed Jun. 3, 2011; and No. 2011-167518, filed Jul. 29, 2011; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a light-emitting device including light-emitting elements and a luminaire.

BACKGROUND

A luminaire including a light-emitting device in which plural light-emitting elements such as light-emitting diodes (LEDs) are disposed on a substrate as a light source is widely known. As the luminaire of this type, for example, a base light of a so-called ceiling mounting type directly attached to the ceiling is known.

The light-emitting device is configured by, for example, directly mounting the plural light-emitting elements on the surface of a resin substrate formed of a resin material. In such a light-emitting device, the respective light-emitting elements are covered and sealed by sealing resin layers including phosphors and thermosetting resin.

However, in the light-emitting device of such a type, it is known that an organic gas emitted from the resin substrate and the gas in the atmosphere permeate through sealing resin layers. Therefore, it is likely that the performance of the light-emitting device deteriorates and the life of the light-emitting device is reduced.

Specifically, when the organic gas or the gas such as oxygen and water vapor in the atmosphere permeates through the sealing resin layers and reaches a reflecting layer, it causes the discoloration of the reflecting layer, the deterioration of the reflection performance, and the reduction in the luminous flux maintenance factor. Further, it is likely that bonding wires connecting the light-emitting elements and electrodes are corroded by the gas permeated through the sealing resin layers, the possibility of rupture of the wires is increased, and the life of the light-emitting device is reduced.

Therefore, there is a demand for development of a light-emitting device that can extend the life and improve the performance and a luminaire including such a light-emitting device.

DETAILED DESCRIPTION

According to one embodiment, a light-emitting device includes a resin substrate, a reflecting layer formed on the resin substrate, a protection layer formed around the reflecting layer, a light-emitting element placed on the reflecting layer, and a sealing resin layer that covers the reflecting layer, the protection layer, and the light-emitting element. The oxygen permeability of the sealing resin layer is equal to or lower than 1200 cm3/(m2·day·atm). A ratio of the area of the reflecting layer to the area of a sealing region on the resin substrate covered by the sealing resin layer is within a range of a ratio equal to or higher than 30% and equal to or lower than 75%.

Various embodiments will be described hereinafter with reference to the accompanying drawings.FIGS. 1 to 7are diagrams of a light-emitting device1according to an embodiment.FIG. 8is a diagram of a luminaire20including the light-emitting device1. The same components in the figures are denoted by the same reference numerals and signs and redundant explanation of the components is omitted.

As shown inFIG. 1, the light-emitting device1includes a resin substrate10, plural light-emitting elements11, and sealing resin layers12that cover the light-emitting elements11. As shown inFIG. 6, reflecting layers18are formed on the front surface of the resin substrate10. A resist layer45, which is a protection layer, is formed around the reflecting layers18. The light-emitting elements11are placed on the reflecting layers18. The sealing resin layers12are formed on the reflecting layers18and a part of the resist layer45around the reflecting layers18.

The resin substrate10may be formed of glass epoxy resin or other synthetic resin materials. For example, a glass epoxy printed board (FR-4, CEM-3, etc.) can be used.

The resin substrate10is formed in an elongated rectangular shape. For example, the length of the resin substrate10can be set to 230 mm and the width of the resin substrate10can be set to 35 mm. The thickness of the resin substrate10is desirably equal to or larger than 0.5 mm and equal to or smaller than 1.8 mm and can be set to, for example, 1 mm. The shape of the resin substrate10is not limited to the rectangular shape and may be a square shape or a circular shape.

Alternatively, in order to improve thermal radiation properties of the light-emitting elements11, a resin substrate including a base plate of metal can also be used. Specifically, as shown inFIGS. 5 and 6, the resin substrate10is formed by sticking a copper foil46or the like to the surface of the glass epoxy resin and providing an insulating layer47on the copper foil46except a portion of the copper foil46. This is a structure equivalent to a printed board generally used in an electric product.

In the light-emitting device1according to this embodiment, the plural light-emitting elements11are mounted side by side on the surface of the resin substrate to form rows and individually covered by the sealing resin layers12. Ends of the sealing resin layers12are formed as spherical surfaces having a substantially fixed radius centered on the light-emitting elements11at the ends of the rows.

Further, the resist layer45, which is the protection layer, is formed on the front surface of the resin substrate10to cover the periphery of the reflecting layers18. The resist layer45is provided over substantially the entire front surface of the resin substrate10. A white resist having high reflectance is suitably used for the resist layer45. For convenience of explanation, inFIGS. 2 to 4, a wiring pattern15and the like are shown. However, when the white resist layer45is actually formed, the wiring pattern15and the like are less easily seen visually.

The long side of the resin substrate10includes plural perforated sections40prepared for fixing the resin substrate10. The perforated sections40are arcuate cutout sections connected to the outer periphery of the resin substrate10. The perforated sections40are used when the light-emitting device1is fixed to a luminaire main body21of the luminaire20shown inFIG. 8. In this embodiment, shaft sections of attachment screws41functioning as fixing means are screwed into the luminaire main body21of the luminaire20piercing through the cutout sections. The heads of the attachment screws41are caught by the cutout sections and fixed. Consequently, the light-emitting device1is fixed to the luminaire main body21.

As shown inFIG. 3, the resin substrate10includes a groove141on the front surface side of the resin substrate10. As shown inFIG. 1, a power-supply connector42, a connection connector43, and a capacitor C are mounted on the front surface of the resin substrate10.

The groove141is a mark formed for removing a connection pattern14explained later. The power-supply connector42is connected to a power-supply. The connection connector43is used when the plural light-emitting elements11are coupled to one another. The capacitor C is provided to prevent the light-emitting elements11from being turned on by mistake because noise is accumulated in a lighting circuit.

As shown inFIGS. 2 to 4andFIG. 6, the resin substrate10includes, on the front surface side of the resin substrate10, the wiring pattern15embedded in the resist layer45. The wiring pattern15includes mounting pads15a, power-supply conductors15b, and power-supply terminals15c.

As shown inFIG. 2, one mounting pad15ais basically formed in a substantially rectangular shape extending along the longitudinal direction of the resin substrate10. The mounting pad15aincludes two slender power-supply conductors15b1extending in the longitudinal direction of the resin substrate10from the short sides. The power-supply conductor15b1includes plural, in this embodiment, six power feeders15b2projecting in a direction orthogonal to the extending direction of the power-supply conductors15b1.

The power-supply conductors15belectrically connect the mounting pads15a. The power-supply terminals15care prepared at ends of the power-supply conductors15b. The power-supply connector42is connected to the power-supply terminals15c.

As shown inFIG. 2, the mounting pad15aconnects with the power-supply conductors15b1of an adjacent mounting pad in the longitudinal direction of the resin substrate10along one of the long sides and the center of the adjacent mounting pad while leaving insulation space therebetween. Inlet sections15b3that fit with the power feeders15b2are also formed in the mounting pads15a. Among the mounting pads15ahaving such a shape, the mounting pads15aadjacent to each other are combined in a form reversed about an axis along the longitudinal direction of the resin substrate10. The plural mounting pads15aare arranged in the longitudinal direction to form the wiring pattern15.

As shown inFIG. 6, the wiring pattern15has a three-layer structure. The wiring pattern15is formed by electrolytically plating, on the front surface of the resin substrate10, in order from below, copper (Cu) as a first layer151, nickel (Ni) as a second layer152, and silver (Ag) having high reflectance as a third layer153.

The surfaces of a part of the mounting pads15aand the power feeders15b2are used as the reflecting layers18. The resist layer45is formed around the reflecting layers18. The reflecting layers18exposed from the resist layer45have high reflectance because the reflecting layers18are silver-plated. In the case of this embodiment, the total beam reflectance of the reflecting layers18is 90%. Nickel (Ni) forming the second layer152is formed by electrolytic plating to have film thickness equal to or larger than 5 μm. Silver (Ag) forming the reflecting layers18is formed by electrolytic plating to have film thickness equal to or larger than 1 μm. By setting the dimensions of the film thicknesses as explained above, the reflecting layers18are formed in uniform thickness and have uniform reflectance.

The light-emitting elements11are placed on the reflecting layers18in which the mounting pads15aare exposed. Each of the light-emitting elements11is a solid-state light-emitting element such as an LED. The number of light-emitting elements11mounted on the resin substrate10is not specifically limited. When the light-emitting elements are LEDs, LEDs of a face-up type or a flip-chip type are used.

In order to cause a light-emitting section of the light-emitting device1to output white light, bare chips of the LEDs that emit blue light are used. The light-emitting elements11are bonded on the reflecting layers18by a silicone resin insulative adhesive16having translucency.

In this embodiment, the light-emitting elements11are Indium-Gallium-Nitride (InGaN) bare chips and have a structure in which a light-emitting layer is laminated on a translucent sapphire element resin substrate. The light-emitting layer is formed by sequentially laminating an n-type nitride semiconductor layer, an InGan layer, and a p-type nitride semiconductor layer.

Electrodes for feeding an electric current to the light-emitting layer include plus electrodes formed by p-type electrode pads on p-type nitride semiconductor layers and minus electrodes formed by n-type electrode pads on n-type nitride semiconductor layers. As shown inFIGS. 3 and 6, these electrodes are electrically connected on the wiring pattern15by bonding wires17. More specifically, the upper surfaces of the light-emitting elements11and the reflecting layers18in which the mounting pads15are exposed are connected. The upper surfaces of the light-emitting elements11and the reflecting layers18in which the power feeders15b2are exposed are connected.

The bonding wires17are thin lines of gold (Au). The bonding wires17are connected via a bump containing gold (Au) as a main component in order to improve mounting strength and reduce damage to the light-emitting elements11. The bonding wires17are not limited to gold (Au) and other metal thin lines may be used.

As representatively shown inFIG. 3, the plural light-emitting elements11are arranged on the mounting pad15ato correspond to the power feeders15b2. In the first embodiment, six light-emitting elements11are mounted on one mounting pad15ato correspond to each of the power feeders15b2in the center and the power feeders15b2along the long sides, i.e., twelve light-emitting elements11are mounted in total. The light-emitting elements11are provided in the same manner in each of the plural mounting pads15aarranged in the longitudinal direction of the resin substrate10. The light-emitting elements11of the mounting pads15aare arranged to form plural rows. In this embodiment, the light-emitting elements11form two rows in the longitudinal direction.

Since the power feeders15b2of the mounting pad15aenter the inlet sections15b3of the mounting pad15aadjacent to the mounting pad15a, the light-emitting elements11are arranged in the center of the mounting pad15a. Therefore, heat generated from the light-emitting elements11is effectively radiated through the mounting pad15a.

The light-emitting elements11disposed in this way receive the supply of power by being sequentially connected from an anode of the power-supply to the plus electrodes of the light-emitting elements11via the mounting pad15aand the bonding wires17(one ends are connected to the reflecting layers.18, which are exposed surfaces of the mounting pad15a) and connected from the minus electrodes of the light-emitting elements11to the power feeders15b2adjacent thereto via the bonding wires17(one ends are connected to the reflecting layers18, which are exposed surfaces of the power feeders15b2). In this embodiment, the bonding wires17are connected in a direction orthogonal to a direction in which the light-emitting elements11form the rows.

In the light-emitting device1in which the light-emitting elements11are connected as explained above, the twelve light-emitting elements11on one mounting pad15aare connected in parallel, and the nine mounting pads15aare connected in series. The capacitors C inserted to prevent a lighting error include first capacitors, each of which is connected between electrodes of mounting pads15aand a second capacitor connected to a series circuit formed of all the mounting pads15a.

As shown inFIG. 6, the light-emitting elements11and the bonding wires17are covered by the sealing resin layers12. The sealing resin layers12are provided to cover the reflecting layers18and a part of the resist layer45.

The sealing resin layers12are formed of sealing resin containing an appropriate amount of phosphors in transparent thermosetting resin. The phosphors are excited by light emitted by the light-emitting elements11and emits light having color different from a color of light emitted by the light-emitting elements11. In this embodiment, since the light-emitting elements11emit blue light, in order to emit white light as output light of the light-emitting device1, a yellow phosphor that radiates yellow light having a complementary color relation with the blue light is used. As the phosphors, for example, Yttrium Aluminum Garnet (YAG):Cerium (Ce) can be used.

With the light-emitting device1having the structure according to this embodiment, a phenomenon occurs in which an organic gas generated from the resin substrate10permeates through the sealing resin and reaches the reflecting layers18formed of silver or the like. When a general aluminum substrate or ceramic substrate is used, an organic gas is not generated from the substrate. In a package LED in which an LED chip is not directly mounted on a substrate, organic gas does not permeate through the sealing resin and reach the reflecting layers18. However, in the light-emitting device1having the structure in this embodiment, the reflecting layers18are discolored by the organic gas generated from the resin substrate10and the reflectivity of the reflecting layers18is degraded. As a result, a luminous flux maintenance factor falls.

Therefore, in this embodiment, thermoplastic resin having oxygen permeability equal to or smaller than 1200 cm3/(m2·day·atm) is used as a sealing resin material. It is possible to suppress permeation of the organic gas and suppress degradation of the reflecting layers by using the thermoplastic resin having oxygen permeability equal to or smaller than 1200 cm3/(m2·day·atm). A reason for this is explained later with reference to a specific example.

Examples of the thermoplastic resin having oxygen permeability equal to or smaller than 1200 cm3/(m2·day·atm) include a silicon resin haying a phenyl group.

In this embodiment, as shown inFIGS. 1,4and6, the sealing resin layers12cover the respective light-emitting elements11one by one. As shown inFIG. 6, the respective sealing resin layers12are formed in a dome-shape convexity. In the bases of the sealing resin layers12adjacent to each other, continuous sections12s are formed to extend to each other. As a result, as shown inFIGS. 1 and 4, the sealing resin layers12of the light-emitting elements11forming one light-emitting element row are tied in a row. In the case of this embodiment, the sealing resin layers12are formed in two rows in the longitudinal direction of the resin substrate10and cover and seal the light-emitting elements11and the bonding wires17.

The sealing resin layers12are formed by dripping the thermoplastic resin in an unhardened state, which contains the phosphors and the viscosity and the amount of which are adjusted, onto the light-emitting elements11and thereafter curing the thermoplastic resin through heating treatment or by leaving the thermoplastic resin untouched for a specified time. For example, a dispenser can be used for dripping the thermoplastic resin.

The dripped thermoplastic resin is formed in a dome shape as shown inFIG. 6. The base of the dome shape expands in the outer circumferential direction according to the fluidity of the resin material. As explained above, the bases of the adjacent sealing resin layers12extend to each other to form the continuous sections12s. Therefore, the adjacent sealing resin layers12are fused by the continuous sections12s and integrally harden.

The respective sealing resin layers12are not limited to the embodiment and may be independent from one another. The bases of the adjacent sealing resin layers12do not have to be continuous. Alternatively, each of the sealing resin layers12may be formed to cover the plural light-emitting elements11. A method of forming the sealing resin layers12is not limited to the forming method explained above.

FIG. 7is a schematic diagram of the sealing resin layer12applied to one light-emitting element11viewed from above. For convenience, components covered by the sealing resin layer12are indicated by dotted lines. In a covering region of the sealing resin layer12, the reflecting layer18is exposed from the resist layer45. In other words, the edge of the reflecting layer18exposed to the front surface side is present in the covering region of the sealing resin layer12.

The light-emitting element11is placed on the reflecting layer18. The light-emitting element11is connected by the bonding wire17to each of the reflecting layers18and the adjacent reflecting layer18, on which the light-emitting element11is placed.

In this embodiment, when the area of a region on a substrate covered by the sealing resin layer12, i.e., the reflecting layer18and the resist layer45covered by the sealing resin layer12(an area of a substantially circular region surrounded by a solid line inFIG. 7) is assumed to be 100%, the area of the reflecting layer18is set within a range of a ratio equal to or larger than 30% and equal to or smaller than 75%.

Since the reflectance of the reflecting layer18is higher than the reflectance of the resist layer45around the reflecting layer18, the light-emitting efficiency of the light-emitting device1is higher when the area of the reflecting layer18is larger. For example, a difference between the light reflectance of the reflecting layer18and the light reflectance of the resist layer45at the time when light having wavelength of 450 nm is irradiated on the reflecting layer18and the resist layer45is equal to or larger than 3.5%.

However, since the resist layer45has higher adhesion to the sealing resin than the reflecting layer18, if the area of the resist layer45covered by the sealing resin layer12is too small, the adhesion of the sealing resin layer12weakens. Therefore, an area ratio of the reflecting layer18and the resist layer45in the sealing region is desirably set in the range explained above.

Specifically, the area of the reflecting layer18covered by the sealing resin layer12is set to 30% to 75% of the area of the covering region. This makes it possible to increase the reflectance and improve the light-emitting efficiency and strengthens the adhesion of the sealing resin layer12. If the area of the reflecting layer18is smaller than 30%, the light-emitting efficiency is deteriorated. On the other hand, if the area of the reflecting layer18exceeds 75%, peeling and the like of the sealing resin layer12are more likely to occur and reliability is deteriorated. A reason for this is explained later with reference to a specific example.

The thermoplastic resin having oxygen permeability equal to or smaller than 1200 cm3/(m2·day·atm) is used as the sealing resin material and the area of the reflecting layer18covered by the sealing resin layer12is set in the range of 30% to 75% of the area of the entire covering region according to this embodiment. This makes it possible to suppress degradation of the reflecting layer18and improve the light-emitting efficiency and the luminous flux maintenance factor of the light-emitting device1. Consequently, it is possible to extend the life of the light-emitting device1. For example, according to this embodiment, it is possible to increase a luminous flux maintenance factor to 90% or more when the light-emitting device1is lit at a rated value for 1000 hours at temperature of 85° and humidity of 85%.

Further, thermosetting resin having hardness measured by a durometer (type A) in a range of hardness equal to or higher than 45 and equal to or lower than 89 is desirably used for the sealing resin layer12used in this embodiment. Since the hardness is equal to or higher than 45, the strength of the sealing resin layer12can be increased. Consequently, for example, even if an object comes into contact with the sealing resin layer12when the light-emitting device1is handled, it is possible to prevent the sealing resin layer12from being destroyed. On the other hand, since the hardness is equal to or lower than 89, even if the sealing resin repeatedly expands and contracts due to temperature changes caused by switching the light-emitting device1on and off, it is possible to prevent the bonding wires17on the inside of the sealing resin layer from being ruptured.

A more desirable range of the hardness of the thermosetting resin fluctuates according to the use of the light-emitting device1. However, the hardness of the thermosetting resin is desirably set in a range of, for example, 62 to 78. In the case of the light-emitting device1with which an object is highly likely to come into contact with the sealing resin layer12during handling, it is desirable to use relatively hard thermoplastic resin. On the other hand, in the case of the light-emitting device1with which an object is less likely to come into contact during handling, it is possible to further reduce the likelihood of rupture of the bonding wires17using relatively soft thermoplastic resin.

Furthermore, the thermosetting resin used in this embodiment is desirably thermosetting resin that causes interfacial peeling of the sealing resin layer12from the resin substrate10when forcible stress is applied to the surface of the resin substrate10in a surface direction. By using the resin that causes the interfacial peeling of the sealing resin layer12, it is possible to prevent internal fracture of the sealing resin layer12from occurring when stress is applied to the resin substrate10.

If the internal fracture of the sealing layer12occurs, a long period of time from the internal fracture event may pass before the light-emitting elements11stop lighting. Therefore, it is not easy to find a failure. On the other hand, if the resin that causes the interfacial peeling is used, the luminance of only the light-emitting element11in which peeling occurs falls. Therefore, it is easy to find a failure.

Such thermoplastic resin is desirably thermoplastic resin that does not cause the interfacial peeling from the resin substrate10and does not cause the resin internal fracture when stress of 800 g is applied in a JIS pencil scratch test (1 kg load). By using the resin that causes neither the interfacial peeling nor the resin internal fracture when the stress of 800 g is applied, it is possible to secure the strength of the sealing resin layer12and improve the durability of the light-emitting device1.

Examples of the thermosetting resin include a silicon resin having a phenyl group. In this case, examples of the resist layer45to which the thermosetting resin bonds include white paint containing white pigment such as titania.

Furthermore, the thermosetting resin used in this embodiment desirably has a refractive index equal to or higher than 1.50 and equal to or lower than 1.66. Since the refractive index of the sapphire element resin substrate of the light-emitting elements11is about 1.76, if resin having a refractive index equal to or higher than 1.50 is used, extraction efficiency of light from the sapphire element resin substrate to the sealing resin layer12is improved. As a result, an amount of light reaching the phosphors increases. Consequently, it is possible to improve the light-emitting efficiency of the light-emitting device1. On the other hand, by using resin having a refractive index equal to or lower than 1.66, it is possible to suppress deterioration in extraction efficiency of light from the sealing resin layer12to the external air.

As shown inFIGS. 5 and 6, the resin substrate10includes a pattern of a copper foil46for thermal radiation formed over substantially the entire surface on the rear side. This pattern includes eighteen blocks divided into a matrix shape of two blocks in the width direction of the resin substrate10and nine blocks in the longitudinal direction of the resin substrate10to correspond to the mounting pads15aon the front surface side.

Since the resin substrate10includes the copper foil46having a relatively large area in this way, heat generated by the light-emitting elements11is equally diffused over the entire resin substrate10. Therefore, the thermal radiation performance of the resin substrate10is stabilized. As shown inFIG. 5, a discontinuous zone46awhere the copper foil46is not formed is present orthogonal to the longitudinal direction of the resin substrate10. Therefore, a warp and deformation caused in the resin substrate10by heat are suppressed. As shown inFIG. 6, the copper foil46is covered by the insulating layer47.

An outline of a manufacturing process for the light-emitting device1configured as explained above is explained with reference toFIGS. 2 to 4.

First, as shown inFIG. 2, the wiring pattern15and the connection pattern14are formed on the front surface side of the resin substrate10. The wiring pattern15has the three-layer structure explained above. The connection pattern14has a three-layer structure same as the three-layer structure of the wiring pattern15. The wiring pattern15functions as a power-supply path for supplying electric power to the light-emitting elements11. The connection pattern14functions as a connection path for setting the mounting pads15ato equal potential when nickel (Ni) of the second layer and silver (Ag) of the third layer are electrolytically plated on the pattern of copper (Cu) of the first layer.

In a formation process for the wiring pattern15and the connection pattern14, a copper (Cu) pattern is formed as the first layer on the front surface of the resin substrate10. Subsequently, nickel (Ni) and silver (Ag) are electrolytically plated in order respectively as the second layer and the third layer.

As shown inFIG. 3, the connection pattern14is scraped off by a router, a trimmer, or the like from the front surface side of the resin substrate10on which the wiring pattern15and the connection pattern14are formed. As a result, the electrical connection among the mounting pads15ais cut off. Since the connection pattern14is scraped off, the groove141linearly recessed in a rectangular shape in the longitudinal direction is formed on the front surface side of the resin substrate10as a trace excluding a portion that bypasses the perforated sections40.

When the wiring pattern15is formed, the plural light-emitting elements11are mounted to form a light-emitting element row. As shown inFIG. 4, the mounted light-emitting elements11are respectively covered and sealed by the sealing resin layers12. The sealing resin layers12are continuously arranged to cover the row of the light-emitting elements11arranged in the longitudinal direction of the resin substrate10.

The luminaire20including the light-emitting device1is explained with reference toFIG. 8. In the luminaire20shown inFIG. 8, the light-emitting device1is built in to face downward. The luminaire20is a luminaire of a ceiling mounting type set on the ceiling and used.

The luminaire20includes the luminaire main body21having an elongated substantially rectangular parallel piped shape. The luminaire main body21includes plural light-emitting devices1, in this embodiment, two linearly-connected light-emitting devices1. A power-supply unit including a power-supply circuit is incorporated in the luminaire main body21. A front cover22having light diffusibility is attached to the luminaire main body21and covers an opening of the luminaire main body21opened downward.

The light-emitting device1having the configuration explained above is further explained. When the light-emitting device1is energized by the power-supply circuit, the light-emitting elements11are turned on all together. When lights emitted from the light-emitting elements11are transmitted through the sealing resin layers12, the lights excite the phosphors in the sealing resin layers12to emit light. When the emitted lights of the light-emitting elements11and the excitation light of the sealing resin layers12are combined, white light is obtained. Therefore, the light-emitting device1functions as a surface light source that emits white light.

In this case, the sealing resin layers12have a dome shape and the light-emitting elements11are arranged in the centers of the domes. Therefore, the lights emitted from the light-emitting elements11are suppressed from being totally reflected on the inner side of boundary surfaces of the sealing resin layers12. As a result, degradation in light-emitting efficiency due to a reflection loss is suppressed.

The adjacent sealing resin layers12extend to each other in the bases of the sealing resin layers12. Until the sealing resin layers12are hardened, the sealing resin layers12are mutually mixed by the continuous sections12s. Therefore, fluctuations in the volumes of the sealing resin layers12are averaged. Since the external shapes of the sealing resin layers12are averaged, fluctuations in light outputs, light emission colors, and the like of the lights emitted from the respective light-emitting elements11are reduced. Therefore, light irradiated by the light-emitting device1is homogenized. Consequently, the luminaire20including the light-emitting device1stably emits light.

In the embodiment, while the light-emitting elements11are emitting light, the mounting pads15afunction as heat spreaders that diffuse heat generated by the light-emitting elements11. When the light-emitting device1is emitting light, most light traveling to the resin substrate10among the light emitted from the light-emitting elements11is reflected on the reflecting layers18, which are formed on the surface layers of the mounting pads15a. Light traveling in a direction along the resin substrate10among the light emitted by the light-emitting elements11is reflected on the surface of the white resist layer45having high reflectance in a direction.

According to the embodiment explained above, it is possible to provide the light-emitting device1having the suppressed degradation of the reflecting layers18covered by the sealing resin, improved light-emitting efficiency and luminous flux maintenance factor, and an extended life. Further, it is possible to provide the luminaire20including such a light-emitting device and having the extended life.

The light-emitting device1and the luminaire20including the light-emitting device1can be applied as light sources mounted on a luminaire, a display apparatus, and the like used indoor or outdoor.

EXAMPLES

A relation between the oxygen permeability and a luminous flux maintenance factor of the thermosetting resin forming the sealing resin layer was examined.

The light-emitting device1was manufactured using the FR-4 substrate10having width of 27 mm and length of 200 mm. Four light-emitting elements11were arranged in a row at an interval of 3 mm in the same sealing resin layer12. The width of the sealing resin layers12having the dome shape was set to 2.9 mm. An electric current of about 30 mA at a voltage of about 3 V was used as the power source for the light-emitting elements11. A silicon resin having a phenyl group and having oxygen permeability equal to or lower than 1200 cm3/(m2·day·atm) was used as the material for the sealing resin layer12. A ratio of the area of the reflecting layers18to the area of the regions covered by the sealing resin layers12was set to 50%.

Example 2 and Comparative Examples 1 to 2

The light-emitting devices1were manufactured in the same manner as the example 1 except that thermosetting resin having oxygen permeability shown in Table 1 was used as the material of the sealing resin layers12.

Lighting Test

The light-emitting devices1of the examples 1 and 2 and the comparative examples 1 and 2 were lit for 100 hours at 120° and luminous flux maintenance factors were measured. A result of the measurement is shown in Table 1 andFIG. 9.

As it is seen from Table 1, in the examples 1 and 2 in which the thermosetting resin having the oxygen permeability of 1200 cm3/(m2·day·atm) or lower was used, the luminous flux maintenance factor was conspicuously higher than that luminous flux maintenance factor in the comparative examples 1 and 2.

Examples 3 and 4 and Comparative Examples 3 to 5

The light-emitting devices1were manufactured in the same manner as the example 1 except that a ratio of the area of the reflecting layers18to the area of the regions covered by the sealing resin layers12was set as shown in Table 2.

Light Emission Test and Cycle Test

The light-emitting devices1of the examples 3 and 4 and the comparative examples 3 to 5 were lit immediately after product manufacturing and light-emitting efficiency was measured. A result of the measurement is shown in Table 2 as relative values to light-emitting efficiency of 100% obtained when the area of the reflecting layers18is 100%. A heat cycle test was performed using alternately repeating heating and cooling conditions with a temperature difference of 160° C. The number of cycles at a point when peeling of the sealing resin layers12occurred was observed. A result of the observation is shown in Table 2 andFIG. 10.

As it is seen from Table 2, as the ratio of the area of the reflecting layers18decreased, although the light-emitting efficiency was decreased, the number of cycles at which peeling occurred increased. As indicated by the examples 3 and 4, by setting the area of the reflecting layers18in a range of 30% to 75%, it is possible to realize the light-emitting device1having high light-emitting efficiency and long life.

Examples 5 to 8

The light-emitting devices1were manufactured in the same manner as the example 1 except that, as the material of the sealing resin layers12, phenylic silicone resin, the hardness measured by the durometer (type A) of which was as shown in Table 3 and the oxygen permeability of which was 1200 cm3/(m2·day·atm), was used.

Rupture Test

The light-emitting devices1, of the examples 5 to 8, were the subject of a heat cycle test using repeating heating and cooling conditions with a temperature difference of 160° C. The number of cycles at a point when rupture of the bonding wires17occurred was observed. External stress was applied to the sealing resin layers12of the light-emitting devices1and stress at the time when rupture of the bonding wires17occurred was measured. A result of the observation and the measurement is shown in Table 3 andFIG. 11.

As it is seen from Table 3, the result indicates that, in the examples 5 to 7 in which the hardness was equal to or higher than 45, the external force at which rupture occurred was large and durability was high. The result indicates that, in the examples 6 to 8 in which the hardness was equal to or lower than 89, the number of cycles at which rupture occurred in a heat cycle test was large and durability was high. Consequently, as indicated by the examples 6 and 7, by using the thermoplastic resin having hardness of 45 to 89, it is possible to realize the light-emitting device1having high durability against external stress and a heat cycle and extended life.

Examples 9 and 10

The light-emitting devices1were manufactured in the same manner as the example 1 except that, as the material of the sealing resin layers12, phenylic silicone resin, the oxygen permeability of which was 1200 cm3/(m2·day·atm), was used.

Light-Emitting Efficiency Test

The light-emitting devices1of the examples 9 and 10 were lit immediately after product manufacturing and light-emitting efficiency was measured. A result of the measurement is shown in Table 4.

The result indicates that, in the example 10 in which the refractive index was 1.59, the light-emitting efficiency was higher than the light-emitting efficiency in the example 9 in which the refractive index was 1.41. Therefore, the result indicates that, by using the thermoplastic resin having a high refractive index as the sealing resin material, it is possible to improve the light-emitting efficiency.

The light-emitting device1and the luminaire20including the light-emitting device1according to another embodiment are explained. This embodiment is the same as the first embodiment except that the sealing resin layers12that seal the light-emitting elements11of the light-emitting device1are different as explained below. Therefore, in the following explanation,FIGS. 1 to 8are referred to when necessary.

In this embodiment, as in the first embodiment, the sealing resin layers12include phosphors and transparent thermosetting resin. However, as this thermosetting resin, resin having oxygen permeability and water vapor permeability is used.

The oxygen permeability of the resin is equal to or lower than 1200 cm3/(m2·day·atm). The water vapor permeability of the resin is equal to or lower than 35 g/m2-day. As the thermosetting resin having the oxygen permeability and the water vapor permeability, for example, resin-based silicone resin can be used.

As explained above, the sealing resin layers12that have the oxygen permeability and seal the light-emitting elements11have low permeability of oxygen and an organic gas. Therefore, these gases are suppressed from reaching the reflecting layers18made of silver on which the light-emitting elements11are mounted. Moreover, in addition to the low gas permeability, the sealing resin layers12have the water vapor permeability equal to or lower than g/m2-day. Therefore, permeability of water vapor in the atmosphere is also low. Consequently, water vapor included in the outdoor air is also suppressed from permeating through the sealing resin layers12and reaching the reflecting layers18.

Therefore, the reflecting layers18are suppressed from being discolored by gas and water vapor that permeate through the sealing resin layers12. The degradation in the reflectivity of the reflecting layers18is suppressed. As a result, it is possible to the improve luminous flux maintenance factor.

At the same time, rupture of the bonding wires17caused by gas and water vapor that permeate through the sealing resin layers12less easily occurs. Specifically, since the sealing resin layers12that less easily allow an organic gas and water vapor to permeate therethrough is adopted, it is possible to increase the hardness of the sealing resin layers12and reduce stress acting on the bonding wires17. As a result, it is possible to extend the life of the light-emitting device1.

The water vapor permeability of the thermosetting resin included in the sealing resin layers12is suitably equal to or lower than 25 g/m2-day. If such a range of permeability is set, deterioration of the reflecting layers18rarely occurs and the luminous flux maintenance factor can be further improved. If the water vapor permeability of the thermosetting resin is set closer to “0”, the hardness of the sealing resin layers12tends to increase. Therefore, a lower limit of the water vapor permeability of the thermosetting resin does not have to be set to “0”.

According to the light-emitting device and the luminaire of at least one of the embodiments described above, by setting the oxygen permeability of the sealing resin layer to be equal to or lower than 1200 cm3/(m2·day·atm) and setting the area of the reflecting layer included in the sealing region by the sealing resin layer in the range of an area equal to or higher than 30% and equal to or lower than 75%, it is possible to extend the life and improve the performance of the light-emitting device and the luminaire including the light-emitting device.