Patent Description:
Some light emitting devices such as LEDs include a light emitting element and a light reflecting member that reflects the light from the light emitting element. For example, <CIT> discloses, as a light reflecting member, reflecting material that contains a white pigment, such as titania, zinc oxide, tantalum oxide, niobium oxide, zirconia, alumina, or the like, in a base material which is a heat-resistant resin such as silicone or an inorganic binder.

<CIT>discloses a light-emitting device that comprises a light-emitting element and a light-reflecting covering member which covers the light-emitting element and which includes plate-form light reflective material, silica, and an alkali metal. A method of producing this light-emitting device is also provided.

<CIT> discloses providing a glass ceramic body, whereby light which transmits through the substrate and leaks (i.e. emits) out of the incident direction is reduced, and the number of voids at the surface of the substrate and in the inside of the substrate is low.

The Present invention is defined by the independent claims.

The recent advancements in achieving a higher luminance and higher output light emitting device have brought about a large increase in the temperature of the light reflecting member during the operation of the device. There is thus a need for a high heat resistance light reflecting member.

One obj ect of the present invention is to provide a light emitting device equipped with a high heat resistance light reflecting member, and a method of manufacturing such a light emitting device.

According to certain exemplary embodiments of the present invention, a light emitting device equipped with a high heat resistance light reflecting member, and a method of manufacturing such a light emitting device can be provided.

In the drawings, members having the same functions may be denoted by the same reference numerals. Focusing on the main points and considering ease of understanding, constituent elements may be described in a certain embodiment or example, but may be partially substituted or combined with those described in different embodiments and examples. The explanation of the features already discussed in a previous embodiment or example may be omitted in later embodiments or examples, and only the differences from the earlier embodiment or example may be explained. Specifically, similar effects achieved by similar constituents will not be repeated for each embodiment. The sizes and the relative positions of the members in the drawings may be exaggerated for clarity of explanation. An end surface view that only shows a cut section might be used as a cross-sectional view.

A light emitting device according to Embodiment <NUM> includes a light emitting element and a light reflecting member that reflects the light emitted from the light emitting element. The light reflecting member contains plate-shaped light reflective particles, silica, and an alkali metal. The average particle size of the light reflective particles is in a range of <NUM> µm to <NUM> µm, and the average aspect ratio of the light reflective particles is <NUM> or higher.

Allowing the light reflective particles to function as an aggregate in the light reflecting member having the constituents described above can reduce the deformation of the light reflecting member <NUM> even if the light reflecting member temperature fluctuates. The heat resistance of such a light reflecting member can be increased. This can enhance the heat resistance and the service life of the light emitting device according to Embodiment <NUM>. Because the light reflecting member constructed as above is composed of inorganic materials, in the case of employing an ultraviolet light emitting element, degradation attributable to ultraviolet light can be reduced.

A light reflecting member according to the present disclosure is applicable to light emitting devices of various structures. Accordingly, specific constituents of a light reflecting member itself will be described in detail with reference to Embodiment <NUM> below, and the forms of or the applicable locations for the light reflecting member in a light emitting device, as well as other constituents of the light emitting device (substrate, light emitting element, or the like) will be explained in detail with reference to other Embodiments and Examples discussed later.

A light reflecting member <NUM> is a member that reflects the light emitted from a light emitting element.

The light reflecting member <NUM> is made up of multiple inorganic materials.

As shown in <FIG>, the light reflecting member <NUM> includes light reflective particles <NUM> and a binder <NUM> that binds the light reflective particles <NUM>. The binder <NUM> contains silica and an alkali metal. The light reflecting member <NUM>, as described later, is formed through the heating step in which the mixture of the light reflective particles <NUM>, powdered silica, and an alkaline solution is heated.

The light reflecting member <NUM> may be composed only of inorganic materials, or primarily of inorganic materials.

The light reflecting member <NUM> has protrusions and indentations on its surface. The surface roughness (Ra) attributable to protrusions and indentations is <NUM> to <NUM> microns. The surface roughness can be measured by using a laser microscope.

Also, the light reflecting member <NUM> may have gaps formed therein due to the evaporation of water contained in the alkaline solution. The void formed in this manner is a space including a portion that serves as a path through which water evaporates, and at least a portion of the gap includes a portion that opens to the surface of the light reflecting member. All the gaps may be one continuous space inside the light reflecting member, or may be a plurality of spaces separated inside the light reflecting member. The size and shape of the gaps are irregular. In addition, it can be said that the gaps communicating with the surface of the light reflecting member <NUM> are part of the irregularities on the surface of the light reflecting member <NUM>.

A light reflective particle <NUM>, as an example shown in <FIG>, is a plate-shaped particle having a principal surface 11a and another principal surface 11b located opposite to the principal surface 11a. The principal surface 11a and the other principal surface 11b can also be referred to as the upper surface and the lower surface of the light reflective particle <NUM>. The light reflective particle <NUM> can also be referred to as a flaky particle. <FIG> is a mere schematic diagram of a light reflective particle <NUM> regarded, for example, as a circular plate-shaped particle in a top view to make the shape of the light reflective particle <NUM> more easily understood.

The light reflective particles <NUM>, for example, comprises, consists essentially of, or consists of boron nitride or alumina. These materials would be able to reflect ultraviolet to visible light.

Light reflective particles <NUM> may be primary particles, secondary particles in which two or more primary particles are clumped together, or a mixture of primary particles and secondary particles.

In the light reflecting member <NUM> of a light emitting device, the average aspect ratio of the light reflective particles <NUM> is <NUM> or higher, preferably <NUM> to <NUM>. Here, the light reflective particles <NUM> are slightly fusion-bonded to silica and slightly eluted by an alkaline solution in the heating process. Accordingly, the shapes of the light reflective particles <NUM> contained in the light reflecting member <NUM> formed as a result of heating practically remains the same as those prior to heating. In other words, the light reflective particles <NUM> contained in the heat processed light reflecting member <NUM>, for example, is a plate-shaped particle having the one particle surface and the other principal surface.

The average aspect ratio of the light reflective particles <NUM> is calculated by the exemplary method described below.

The average aspect ratio of the light reflective particles <NUM> is calculated based on the measurements of the thicknesses and the widths of the light reflective particles <NUM> contained in the light reflecting member <NUM> in a cross section of the light emitting device that includes a cross section of the light reflecting member.

First, the light emitting device is cut to expose a cross section.

Subsequently, the exposed cross section is polished to a mirror finish. An image of the mirror-finish cross section is captured by using a scanning electron microscope (SEM) for extracting cross sections of light reflective particles <NUM>, a region which contains about <NUM> light reflective particle cross sections is selected for measurement purposes. The pixel count of the microscope is set to about <NUM> million pixels, and the magnification to <NUM>× to <NUM>×. In the present disclosure, a cross section of a light reflective particle <NUM> refers to a surface practically perpendicular to the one principal surface and/or the other principal surface of the light reflective particle <NUM>. Because of their shapes, the plate-shaped light reflective particles <NUM> tend to be arranged in the light reflecting member <NUM> to overlap one another, i.e., a principal surface of a particle surfaces a principal surface of another particle. Accordingly, appropriately selecting a cross section of the light emitting device to be exposed allows a SEM to extract the cross sections of the light reflective particles <NUM>.

Subsequently, by using image analysis software, the width (the length of a cross section of a light reflective particle in the long-dimension direction) and the thickness (the length of the cross section of the light reflective particle in the transverse direction) of each light reflective particle <NUM> cross section are measured at a point (e.g., the maximum length in each direction), and the average value of the ratio of the width to the thickness calculated. The average value for <NUM> light reflective particles <NUM> is used as the average aspect ratio.

In the case of using boron nitride for the light reflective particles <NUM>, the average aspect ratio of the light reflective particles <NUM> is, for example, <NUM> to <NUM>. In the case of using alumina for the light reflective particles <NUM>, the average aspect ratio of the light reflective particles <NUM> is, for example, <NUM> to <NUM>.

Furthermore, the average particle size of the light reflective particles <NUM> is <NUM> µm to <NUM> µm.

As described above, the light reflective particles <NUM> are slightly fusion-bonded to silica and slightly eluted by an alkaline solution in the heating process. Accordingly, the shapes and dimensions of the light reflective particles <NUM> prior to the heating process are practically identical as the shapes and dimensions of the light reflective particles <NUM> contained in the light reflecting member <NUM> formed as a result of the heating process. Thus, the average particle size of the light reflective particles <NUM> described above is calculated by measuring the particle sizes of the light reflective particles <NUM> using the method described below.

The particle sizes of the light reflective particles <NUM> are calculated by using a scanning electron microscope, e.g., "TM3030 Plus" manufactured by Hitachi High Technologies, Co.

A surface of a double-sided carbon tape is adhered to the sample stage of the microscope, followed by placing the light reflective particles <NUM> on the other surface of the double-sided tape. An image containing <NUM> light reflective particles <NUM> is captured by setting the pixel count of the microscope to <NUM> million pixels, and the magnification to <NUM>× to <NUM>×. Subsequently, the particle sizes of the individual particles are measured by using image analysis software. In the present disclosure, the particle size of a light reflective particle <NUM> is the largest diameter of the particle when viewing the principal surface 11a or the principal surface 11b of the light reflective particle <NUM>. Subsequently, the median diameter of the measured particles is calculated, and the calculated value is used as the average particle size. The particle sizes of the light reflective particles <NUM> may be calculated by extracting a cross section of the light reflecting member by using a SEM, followed by measuring the diameters using image analysis software.

In the case of using boron nitride for the light reflective particles <NUM>, the average particle size of the light reflective particles <NUM> is, for example, <NUM> µm to <NUM> µm. In the case of using alumina for the light reflective particles <NUM>, the average particle size of the reflective particles <NUM> is, for example, <NUM> µm to <NUM> µm.

The calculation methods for the average aspect ratio and the average particle size described above are in the case of calculating the values using primary particles. In the case of using secondary particles, the calculation methods can be applied to individual single particles extracted from the secondary particles.

The content ratio of silica to the light reflective particles <NUM> in the light reflecting member <NUM> in terms of a weight ratio is, for example, <NUM>:<NUM> to <NUM>:<NUM>. In other words, the weight of the light reflective particles <NUM> in the light reflecting member <NUM> is, for example, <NUM> to <NUM> times the weight of the silica in the light reflecting member <NUM>. A ratio falling within this range can reduce the hardening shrinkage of the mixture. If the light reflective particle content is too large, inadequate hardening might result. On the other hand, if the silica content is too large, hardening shrinkage can increase to cause cracking.

The average particle size of silica is, for example, <NUM> µm to <NUM> µm. An average particle size falling within this range can increase the density of the raw materials (light reflective particles and silica) per unit volume, thereby ensuring the strength of the light reflecting member <NUM>.

The average particle size of silica is preferably smaller than the average particle size of the light reflective particles. This allows silica to be disposed in the gaps among the light reflective particles when mixed together. The average particle size of silica can be calculated by measuring the particle distribution of silica by laser diffraction. An average particle size of silica is a value based on the measurements made prior to being mixed with an alkaline solution. This is because silica dissolves in an alkaline solution, making it difficult to measure the particle sizes using the light reflecting member <NUM>. The content ratio of silica to light reflective particles may be calculated using the light reflecting member <NUM>, for example, by observing a cross section of the light reflecting member <NUM> extracted by a SEM, and calculating the ratio based on the areas occupied by silica and the light reflective particles.

The alkali metal contained in the light reflecting member <NUM> is an alkali metal contained in the alkaline solution described above. The alkali metal is, for example, potassium and/or sodium.

The light reflecting member <NUM> containing the light reflective particles <NUM> and silica described above can reflect the light emitted from a light emitting element by utilizing the refractive index difference between the light reflective particles <NUM> and the binder <NUM> that includes silica.

Furthermore, allowing the light reflective particles <NUM> having the average particle size and the average aspect ratio described above to function as an aggregate can reduce the deformation of the light reflecting member <NUM> even if the temperature of the light reflecting member <NUM> fluctuates. Specifically, the expansion of the light reflecting member is reduced when the temperature of the light reflecting member increases because of a light emitting element, and the contraction of the light reflecting member is reduced when the temperature decreases because of a light emitting element. Such a light reflecting member can have high heat resistance. Here, the temperature fluctuations of the light reflecting member <NUM> are caused primarily by the heat propagated from a light emitting element to the light reflecting member <NUM> and the heat generated in the light reflecting member <NUM> itself by the light emitted from the light emitting element.

Achieving such a light reflecting member <NUM> that is resistant to expansion and contraction attributable to temperature fluctuations of the light reflecting member <NUM> can improve the reliability of a light emitting element even under the conditions where the light emitting element generates a high amount of heat (e.g., when a large amount of electric power is supplied to the light emitting element). When a large amount of electric power can be supplied to a light emitting element, the amount of light per light emitting device can be increased.

Furthermore, the light reflecting member <NUM> preferably includes a scattering material. This can increase the reflectivity of the light reflecting member <NUM>. The scattering material, for example, is primarily zirconia or titania. In the case in which the light emitting element emits ultraviolet light, zirconia which hardly absorbs light in the ultraviolet wavelength range is preferable. In the case of adding a scattering material to the light reflecting member <NUM>, the scattering material is dispersed in silica in the binder <NUM>.

For the scattering material, titania may be used alone, or titania may have a coating composed of one or more of silica, alumina, zirconia, zinc, and an organic material. The coating can be formed by a known technique, such as sputtering, vapor deposition, or the like.

For the scattering material, zirconia may be used alone, or zirconia may have a coating composed of one or more of silica, alumina, zinc, and an organic material. The coating can be formed by a known technique, such as sputtering, vapor deposition, and the like. Alternatively, stabilized or partially stabilized zirconia to which calcium, magnesium, yttrium, aluminum, or the like is added may be used.

The average particle size of the scattering material is preferably smaller than the average particle size of the light reflective particles <NUM>. This facilitates the placement of the scattering material among the light reflective particles <NUM>, thereby reducing the transmission of the light emitted from the light emitting element <NUM> through the gaps among the light reflective particles <NUM> in the light reflecting member <NUM>. In other words, the light emitted from the light emitting element <NUM> is reflected by the scattering material positioned in the gaps among the light reflective particles <NUM>. This can increase the light extraction efficiency of the light emitting device. The average particle size of the scattering material is measured by laser diffraction.

Hereinafter, specific structures of light emitting devices equipped with the light reflecting member <NUM> described above in different forms will be explained.

As shown in <FIG>, each of the light emitting devices <NUM>, <NUM>, <NUM>, and <NUM> includes a base <NUM>, a light emitting element <NUM>, and a light reflecting member <NUM>. The light emitting element <NUM> and the light reflecting member <NUM> are disposed on the base <NUM>. The light emitting element <NUM> includes a semiconductor layer <NUM>. The lateral surfaces of the semiconductor layer <NUM> are distanced from the light reflecting member <NUM> at least in part.

A base <NUM> has a bottom portion <NUM> and a wall portion <NUM> that define a recess <NUM>. The recess <NUM> is a space surrounded by the bottom portion <NUM> and the wall portion <NUM>. The bottom portion <NUM> and the wall portion <NUM> may be composed of the same material or different materials.

For the base material <NUM> of the base <NUM>, an insulating material, such as glass, ceramic, resin, wood, pulp, or the like, or a conductive material, such as a semiconductor, metal (e.g., copper, silver, gold, or aluminum), or the like, by itself or as a composite material can be used. For the base material <NUM>, in particular, a metal, ceramic, or the like is preferable, a ceramic which is an inorganic material is more preferable. Examples of ceramics include alumina, aluminum nitride, silicon nitride, mullite and the like. Particularly, aluminum nitride which has high heat dissipation performance is preferable.

The base <NUM> includes conductive parts <NUM>. The conductive parts <NUM>, as shown in <FIG> and <FIG>, include a wiring layer <NUM> and external electrodes <NUM>. The wiring layer <NUM> is disposed on the upper surface 32a of the bottom portion <NUM>, and is electrically connected to the electrodes <NUM> of the light emitting element <NUM> described later. The external electrodes <NUM> are disposed on the lower surface 32b of the bottom portion <NUM>, and electrically connected to external terminals. The wiring layer <NUM> and the external electrodes <NUM> are electrically connected using vias (through holes) formed in the bottom portion <NUM>. The wiring layer <NUM>, as shown in <FIG> and <FIG>, includes an anode side wiring layer <NUM> and a cathode side wiring layer <NUM>.

As shown in <FIG> and <FIG>, in the cross-sectional views, the wall portion <NUM> of the base <NUM> has a constant thickness. As shown in <FIG> and <FIG>, in the top views, the shapes of the outer boundary and inner boundary of the wall portion <NUM> of the base <NUM> are quadrangular. However, the shape of the wall portion <NUM> is not limited to this, and may be known shapes.

A light emitting element <NUM> is disposed on the bottom portion <NUM> of the base <NUM> in the recess <NUM>. One light emitting element <NUM> may be disposed on the bottom portion <NUM> of the base <NUM>. Two or more light emitting elements <NUM> may be disposed on the bottom portion <NUM> of the base <NUM>.

The light emitting element <NUM> includes a substrate <NUM> and a semiconductor layer <NUM>. The substrate <NUM> is a crystal growth substrate on which a semiconductor crystal making up the semiconductor layer <NUM> can be grown. The substrate <NUM> is, for example, a sapphire substrate. The semiconductor layer <NUM> includes, for example, an n-type semiconductor layer, a p-type semiconductor layer, and an active layer between the n-type semiconductor layer and the p-type semiconductor layer.

The peak wavelength of the light emitted by the semiconductor layer <NUM> is, for example, in the <NUM> to <NUM> range. The light emitting element <NUM> emits, for example, ultraviolet or blue light.

In each of the examples shown in <FIG>, <FIG>, a pair of electrodes <NUM> are disposed on the lower surface of the semiconductor layer <NUM> and electrically connected to the wiring layer <NUM>. The pair of electrodes <NUM> disposed on the lower surface of the semiconductor layer <NUM> are p-electrode and n-electrode. The same applies to the examples shown in <FIG>, <FIG>, <FIG>, <FIG> and <FIG>.

The semiconductor layer <NUM> may have a double hetero junction structure. The emission layer may have a single quantum well structure (SQW) or a structure having multiple well layers such as a multiquantum well structure (MQW). The semiconductor layer <NUM> is constructed to emit visible light or ultraviolet light. The semiconductor layer <NUM> which includes such an active layer can include, for example, InxAlyGa<NUM>-x-yN (<NUM>≤x, <NUM>≤y, x+y≤<NUM>).

The semiconductor layer <NUM> may have one or more emission layers. The structure of the semiconductor layer <NUM> having multiple emission layers may be one in which multiple emission layers are provided between an n-type semiconductor layer and a p-type semiconductor layer, or one in which a structure that successively includes an n-type semiconductor layer, an emission layer, and a p-type semiconductor layer is repeatedly stacked. When the semiconductor layer <NUM> includes multiple emission layers, it may include emission layers emitting light of different peak emission wavelengths or the same peak emission wavelength. The same peak emission wavelength may include a variation of about several nanometers. A combination of peak emission wavelengths of such emission layers can be suitably selected. For example, in the case where the semiconductor layer <NUM> includes two emission layers, emission layers can be selected in combinations, such as blue light and blue light, green light and green light, red light and red light, ultraviolet light and ultraviolet light, blue light and green light, blue light and red light, green light and red light, or the like. Each emission layer may include a plurality of active layers emitting light having different peak emission wavelengths or the same peak emission wavelength.

The shape of the light emitting elements <NUM> shown in the top views, <FIG> and <FIG>, is quadrangular. However, the top view shape of the light emitting element <NUM> may be known shapes.

A light reflecting member <NUM> reflects the light emitted from the light emitting element <NUM> in the extraction direction. The light reflected by the light reflecting member <NUM> is extracted from the light emitting device <NUM> upwards, above the base <NUM>.

The light reflecting member <NUM>, in an example not forming part of the present invention as shown in <FIG>, is disposed on the bottom portion <NUM> of the base <NUM> along the inner lateral surfaces 33a of the wall portion <NUM> of the base <NUM>.

The light reflecting member <NUM>, in the example not forming part of the present invention shown in <FIG>, is continuously disposed to entirely surround the peripheral area around the light emitting element <NUM>. In this example, in the top view, two opposing sides of the quadrangularly outlined light emitting element <NUM> are in parallel to two opposing sides of the quadrangularly outlined base <NUM>. The other two opposing sides of the light emitting element <NUM> are in parallel to the other two opposing sides of the base <NUM>.

The light reflecting member <NUM>, without being limited to continuously entirely surrounding the peripheral area around the light emitting element <NUM>, may be intermittently disposed in the peripheral area around the light emitting element <NUM> such that they are distanced from one another. For example, as shown in <FIG>, the light reflecting members <NUM> may be disposed at the four corners formed by the inner lateral surfaces 33a of the wall portion <NUM> so as to be distanced from one another. Alternatively, the light reflecting member <NUM> may have a first portion and a second portion, the first portion being disposed continuously across two of the four corners formed by the inner lateral surfaces 33a of the wall portion <NUM>, and the second portion being disposed continuously across the other two corners distanced from the first portion.

In the light emitting device 100A, the example not forming part of the present invention shown in <FIG>, the light reflecting member <NUM> disposed at each corner practically has a triangular pyramid shape, in which the vertex is an upper corner of the quadrangular recess <NUM> and the height gradually decreases towards the bottom surface that is practically shaped as an isosceles triangle.

In the example shown in <FIG>, none of the four sides of the quadrangular outline of the light emitting element <NUM> in the top view is in parallel to any side of the quadrangular outline of the base <NUM>. Specifically, the light emitting element <NUM> is disposed to surface its four lateral surfaces to the light reflecting members <NUM> disposed at the four corners. In other words, each lateral surface of the light emitting element <NUM> substantially forms a <NUM> degree angle with the wall portion <NUM> in the top view. This allows the light reflecting members <NUM> to more effectively reflect the light exiting the lateral surfaces of the light emitting element <NUM>.

The example shown in <FIG> may also be structured such that the four sides of the quadrangular outline of the light emitting element <NUM> in the top view is not in parallel to any side of the quadrangular outline of the base <NUM>.

The light reflecting member <NUM>, as shown in <FIG>, includes an oblique portion R1 having oblique surfaces whose height h1 from the upper surface 32a to the bottom portion <NUM> decreases from the wall portion <NUM> towards the light emitting element <NUM>. The oblique portion R1 is continuous with the inner lateral surfaces 33a of the wall portion <NUM> and the upper surface 32a of the bottom portion <NUM>. In other words, the oblique portion R1 is provided to straddle the inner lateral surfaces 33a of the wall portion <NUM> and the upper surface 32a of the bottom portion <NUM>. The end P1 of the oblique portion R1 on the light emitting element <NUM> side may be located anywhere between the wall portion <NUM> and the light emitting element <NUM>, and may be in contact with the electrodes <NUM> of the light emitting element <NUM>. When the end P1 is positioned between the wall portion <NUM> and the light emitting element <NUM>, for example, the end P1 is roughly positioned at the halfway point between the wall portion <NUM> and the light emitting element <NUM> as shown in <FIG>. However, regardless of the position of the end P1, the light reflecting member <NUM> is preferably disposed at a distance from the lateral surfaces 2a of the semiconductor layer <NUM>. This can suppress the light reflecting member <NUM> from blocking the light that exits the lateral surfaces 2a of the semiconductor layer <NUM>. In other words, this makes it difficult for the light emitted from the light emitting element <NUM> that is reflected by the light reflecting member <NUM> to return to the light emitting element <NUM>, thereby allowing the light to exit in the desired direction.

In the light emitting device <NUM>, in the example shown in <FIG>, the oblique surface of the oblique portion R1 of the light reflecting member <NUM> that opposes a lateral surface of the light emitting element <NUM> is straight line shaped in a cross section. Similarly, the oblique surfaces of the oblique portion R1 of the light reflecting member <NUM> that oppose the other lateral surfaces of the light emitting element <NUM> are straight line shaped in a cross section. However, the cross-sectional shapes of the oblique surfaces of the oblique portion R1 of the light reflecting member <NUM> may be suitably formed in accordance with the light extraction direction of the light emitting device. For example, the cross-sectional shape of an oblique surface of the oblique portion R1 may be curved to depress towards the base <NUM> (e.g., in the direction towards the perimeter of the base <NUM>) or project in the opposite direction to the base <NUM> (e.g., in the opposite direction to the perimeter of the base). When the cross-sectional shape is curved to depress towards the base <NUM>, the light extraction efficiency can be made higher than in the case of a straight line shape or a curved shape to project in the opposite direction to the base <NUM>.

In the embodiment according to the present invention shown in <FIG>, the light reflecting member <NUM> includes a flat portion R2 that is located on the upper surface 32a of the bottom portion <NUM> and continuous with the oblique portion R1. The flat portion R2 is the portion in which the height (thickness) from the upper surface 32a of the bottom portion <NUM> is practically constant. Here, the height (thickness) being practically constant means to include, for example, the case in which there is a height (thickness) variation within manufacturing tolerance in forming the flat portion R2, i.e., the height can vary by about a few tens of microns, for example. The flat portion R2 is disposed to cover the upper surface 32a of the bottom portion <NUM> and/or the wiring layer <NUM>. The height of the flat portion R2 is preferably equal to or smaller than the height of the lower surface of the light emitting element <NUM> from the upper surface 32a of the bottom portion <NUM>. The light reflecting member <NUM> in the flat portion R2 is preferably disposed at a distance from the lateral surfaces 2a of the semiconductor layer <NUM>.

In the light emitting device <NUM> shown in <FIG>, the light reflecting member <NUM> is disposed on the bottom portion <NUM> of the base <NUM> while the upper portions of the inner lateral surfaces 33a of the wall portion <NUM> is exposed. However, the light reflecting member <NUM> may be disposed to cover the entire inner lateral surfaces 33a of the wall portion <NUM> from the upper edges to the lower edges. In the example shown in <FIG>, the light extraction efficiency of the light emitting device <NUM> can be increased as the areas of the inner lateral surfaces 33a of the wall portion <NUM> covered by the light reflecting member <NUM> increase. Similarly, in the example shown in <FIG>, the light reflecting member <NUM> may be disposed to entirely cover the inner lateral surfaces 33a of the wall portion <NUM> from the upper edges to the lower edges. The light reflecting member <NUM> may be disposed on the upper surface 33c of the wall portion <NUM> or not. The light reflecting member <NUM> disposed on the upper surface 33c of the wall portion <NUM> may cover the upper surface 33c of the wall portion <NUM> in part or whole in the top view. In the case in which the light reflecting member <NUM> covers the upper surface 33c of the wall portion <NUM> in part, the light reflecting member <NUM> disposed on the upper surface 33c of the wall portion <NUM> may be disposed in multiple regions that are distanced from one another in the top view. The light reflecting member <NUM> covering the inner lateral surfaces 33a of the wall portion <NUM> and the light reflecting member <NUM> covering the upper surface 33c of the wall portion <NUM> may be disposed distanced from or continuously with one another.

In the light emitting device <NUM> according to Embodiment <NUM>, the average aspect ratio of the light reflective particles <NUM> is calculated, for example, by exposing the cross section passing the center of and is substantially perpendicular to the upper surface 4a of the light emitting element <NUM> and measuring the thicknesses and the widths of the light reflective particles <NUM> in the light reflecting member <NUM> in the cross section. The cross section described as an example here can also be utilized as the cross section to be exposed for calculating the average aspect ratio of the light reflective particles <NUM> in Embodiment <NUM> to Embodiment <NUM>.

Here, an ultraviolet light emitting element is occasionally disposed on a base that includes a ceramic base material which is highly resistant to photodegradation because ultraviolet light has a greater energy per photon than visible light to readily cause photodegradation of a resin. In the light emitting device <NUM> according to Embodiment <NUM> constructed as above, however, the portion of the surface of the base <NUM> primarily irradiated by the light emitted from the light emitting element <NUM> can be covered by the light reflecting member <NUM>. Thus a resin can be used for the base material <NUM>. In general, a resin base material can reduce the manufacturing cost as compared to a ceramic base material.

The light emitting device according to Embodiment <NUM>, moreover, may include a first protective film <NUM> and/or a second protective film <NUM>. The light emitting devices <NUM> and <NUM> shown in <FIG> do not include either a first protective film <NUM> or a second protective film <NUM>. The light emitting devices <NUM> and <NUM> shown in <FIG> and <FIG> include a first protective film <NUM> and/or a second protective film <NUM>.

A first protective film <NUM> can be disposed between the base <NUM> and the light reflecting member <NUM>. The first protective film <NUM>, in an example not forming part of the present invention as shown in <FIG>, is disposed on the upper surface 32a of the bottom portion <NUM> of the base <NUM>. Providing a first protective film <NUM> can protect the base <NUM> from external factors, such as dust and humidity. This can improve the reliability of the light emitting device <NUM>.

The protective film <NUM> can be a single layer film made of a single material or a multilayer film made up of two or more different materials. Examples of materials for the first protective film <NUM> include inorganic materials, such as alumina, silica, tantalum oxide, niobium oxide, titania, aluminum nitride, silicon nitride, and the like. In the case of employing a multilayer film for the first protective film <NUM>, for example, a film (dielectric multilayer film) stacking a layer made of alumina as a main component and a layer made of silica as a main component, or repeatedly stacking these layers can be used. The thickness of the first protective film <NUM> is, for example, <NUM> to <NUM>. The thickness of the first protective film <NUM> is preferably <NUM> to <NUM>. In the case in which the first protective film <NUM> is a multilayer film, the total thickness of all layers is set to fall within the above ranges.

In order to protect the base <NUM> from external factors, such as dust and humidity, the first protective film is preferably a denser film than the light reflecting member <NUM> as described later.

Furthermore, the first protective film <NUM> can reflect the portion of the light emitted from the light emitting element <NUM> that passed through the light reflecting member <NUM>. This can increase the light extraction efficiency of the light emitting device <NUM>.

A second protective film <NUM> can be disposed on the surface of the light reflecting member <NUM>. The second protective film <NUM> can be further disposed, for example, on the surface of the base <NUM> exposed from the light reflecting member <NUM> and the surface of the light emitting element as shown in an example not forming part of the present invention in <FIG>.

In the case in which the second protective film <NUM> does not cover the light emitting element <NUM>, the second protective film <NUM> is, for example, a dielectric multilayer film having light reflectivity. In the case in which the second protective film <NUM> covers the light emitting element <NUM>, the second protective film <NUM> is, for example, a dielectric multilayer film having light transmissivity with respect to the light from the light emitting element <NUM>.

The second protective film <NUM> suppresses the light reflecting member <NUM>, the wiring layer <NUM>, and/or the light emitting element <NUM> from being damaged by the moisture in the air, corrosive gases, and the like. In other words, providing the second protective film <NUM> increases the moisture resistance and the gas barrier performance of the light reflecting member <NUM>, the wiring layer <NUM>, and/or the light emitting element <NUM>. Furthermore, allowing the second protective film <NUM> to continuously cover the surface of the base <NUM> exposed from the light reflecting member <NUM> and the surface of the light reflecting member <NUM> can enhance the adhesion of the light reflecting member <NUM> to the base <NUM>.

The thickness of and the material for the second protective film <NUM> can be suitably selected depending on whether the second protective film <NUM> reflects or transmits light (i.e., whether or not the second protective film <NUM> covers the light emitting element <NUM>).

In the case in which the second protective film <NUM> reflects light, the material for the second protective film <NUM> can be selected from the same material as that for the first protective film <NUM>, and the thickness can be selected from the same thickness range as that for the first protective film <NUM>.

In the case in which the second protective film <NUM> transmits light, for example, similar to the first protective film <NUM>, a highly light transmissive material is selected from inorganic materials, such as alumina, silica, tantalum oxide, niobium oxide, titania, aluminum nitride, silicon nitride, or the like, and the film thickness is set to increase the light transmissivity. Furthermore, in the case in which the second protective film <NUM> is a light transmissive dielectric multilayer film, the thickness of each dielectric layer making up the dielectric multilayer film is set to have light transmissivity with respect to the light from the light emitting element <NUM>.

A light emitting device <NUM> may include either one or both of first protective film <NUM> and second protective film <NUM>. In the case in which the light emitting device <NUM> includes only a first protective film <NUM> (or only a second protective film <NUM>), the first protective film <NUM> (or the second protective film <NUM>) can be disposed on the outer lateral surfaces 33b of the wall portion <NUM> and the lower surface 32b of the bottom portion <NUM> of the base <NUM>. In the case in which the light emitting device <NUM> includes both first protective film <NUM> and second protective film <NUM>, a layer made by stacking the first protective film <NUM> and the second protective film <NUM> can be disposed on the outer lateral surfaces 33b of the wall portion <NUM> and the lower surface 32b of the bottom portion <NUM> of the base <NUM> and/or the surface of the light emitting element <NUM>.

An example of a method of manufacturing a light emitting device <NUM> according to Embodiment <NUM> (Manufacturing Method <NUM>) will be explained below.

A base <NUM> having a bottom portion <NUM> and a wall portion <NUM> that define a recess is provided. In the case of employing a resin material for the base material <NUM> of the base <NUM>, the bottom portion <NUM> and the wall portion <NUM> can be integrally formed, for example, by injection molding. In the case of employing a ceramic material for the base material <NUM> of the base <NUM>, the base can be manufactured by a so-called post firing or co-firing technique. Regardless of a resin material or ceramic material used for the base material <NUM> of the base <NUM>, the bottom portion <NUM> and the wall portion <NUM> may be formed separately and subsequently bonded using an adhesive or the like.

In the description of Manufacturing Method <NUM> and that of Manufacturing Method <NUM> discussed later, provision of a member is not limited to manufacturing a member, but includes acquiring of a member through a purchase, transfer, or otherwise.

A light emitting element <NUM> which includes a substrate <NUM> and a semiconductor layer <NUM> is disposed on the bottom portion <NUM> of the base <NUM> in the recess <NUM>. The light emitting element <NUM> in any of the examples shown in <FIG> is mounted by connecting the electrodes <NUM> to the wiring layer <NUM> with solder or the like.

A mixture is provided by combining a powder mix, which is composed of light reflective particles <NUM> and silica, with an alkaline solution. At this time, a substance that vaporizes during hardening of the mixture such as water (hereinafter also referred to as a vaporizable substance) is preferably added during mixing. The mixture of the powder mix and the alkaline solution (and a vaporizable substance, if added) can be obtained, for example, by mixing them until uniformly viscous and subsequently agitating and deforming under reduced pressure by using agitation deformation apparatus. In forming the mixture, mixing may be performed at room temperature or while heating. If heated, mixing is preferably performed at <NUM> at most to suppress the mixture from solidifying. The pH of the resultant mixture is, for example, about <NUM>.

The average particle size of the light reflective particles <NUM> is <NUM> µm to <NUM> µm, and the average aspect ratio is <NUM> or higher, preferably <NUM> to <NUM>. The light reflective particles <NUM> comprises, consists essentially of, or consists of, for example, boron nitride or alumina.

The average particle size of silica is, for example, <NUM> µm to <NUM> µm.

The alkaline solution concentration is, for example, <NUM> mol/L to <NUM> mol/L. Setting the alkaline solution concentration too low would deter hardening of the mixture which potentially reduces the strength of or decompose the light reflecting member <NUM>. On the other hand, setting the alkaline solution concentration too high would allow excess alkali metal to precipitate subsequent to hardening the mixture. If the environment allows for condensation, the precipitated metal reacts with condensed moisture, and the products of the reaction can come into contact with and reduce the reliability of the light emitting element <NUM>. The alkaline solution, for example, is a potassium hydroxide solution or sodium hydroxide solution.

Silica and the light reflective particles <NUM> are mixed at a weight ratio falling within the range of <NUM>:<NUM> to <NUM>:<NUM>, for example. In other words, in mixing silica and the light reflective particles <NUM>, the weight of the light reflective particles <NUM> is, for example, <NUM> to <NUM> times the weight of silica.

In the case of providing a mixture without adding any vaporizable substance to the powder mix and the alkaline solution, they are mixed, for example, at a weight ratio of the alkaline solution to the power mixture of <NUM>:<NUM> to <NUM>:<NUM>. In other words, in mixing the alkaline solution and the powder mix, the weight of the powder mix is, for example, <NUM> to <NUM> times the weight of the alkaline solution. Setting the amount of the alkaline solution too small would allow a number of fine lumps to form when mixing the alkaline solution and the powder mix, making forming difficult. On the other hand, if the amount of alkaline solution is too large when mixing the alkaline solution and the powder mix, cracking might occur during hardening, or the strength of the light reflecting member obtained after hardening might be reduced.

In the case of providing a mixture with a vaporizable substance added to the powder mix and the alkaline solution, the alkaline solution and the powder mix are mixed, for example, at a weight ratio of the alkaline solution to the power mixture of <NUM>:<NUM> to <NUM>:<NUM>. In other words, in mixing the powder mix and the alkaline solution, the weight of the powder mix is, for example, <NUM> to <NUM> times the weight of the alkaline solution. The weight ratio of the alkaline solution to the vaporizable substance is, for example, <NUM>:<NUM> to <NUM>:<NUM>. In other words, the weight of the vaporizable substance is, for example, <NUM> to <NUM> times the weight of the alkaline solution.

As described above, in the case of providing a mixture by adding a vaporizable substance, the amount of the alkaline solution can be reduced as compared to the case of not mixing a vaporizable substance. This provides the benefits described below.

In the case in which the light reflecting member <NUM> of a light emitting device <NUM> contains a scattering material, the scattering material is mixed into the mixture. The average particle size of the scattering material, for example, is smaller than the average particle size of the light reflective particles <NUM>. The scattering material primarily includes, for example, zirconia or titania.

In the recess <NUM>, the mixture is disposed on the bottom portion <NUM> of the base <NUM>. The mixture is disposed at a distance from the lateral surfaces 2a of the semiconductor layer <NUM>. The mixture is disposed so as to include a portion in which the height decreases from the wall portion <NUM> towards the light emitting element <NUM>.

The mixture is disposed, for example, by using a dispenser. In accordance with the present invention, the mixture is simultaneously applied to the bottom portion <NUM> and the inner lateral surfaces 33a of the wall portion <NUM>. This can form an oblique portion. The oblique portion becomes the oblique portion R1 after the heating step described later. Furthermore, utilizing wetting and spreading of the applied mixture towards the light emitting element <NUM> can form the portion that practically has a constant height. The portion having a practically constant height becomes the flat portion R2 after the heating step described later. Moreover, simultaneously applying the mixture to the wall portion <NUM> and the bottom portion <NUM> or applying the mixture to the inner lateral surfaces 33a of the wall portion <NUM> can dispose the mixture at a position distanced from the light emitting element <NUM>, thereby suppressing the mixture from covering the lateral surfaces 2a of the semiconductor layer <NUM>.

A light reflecting member <NUM> is formed by hardening the mixture by heating. This can be achieved by heating the base <NUM> on which the mixture and the light emitting element <NUM> are disposed.

This step may include a preliminary hardening step or not. If a preliminary hardening step is included, the heating step includes a preliminary hardening step which hardens the mixture at a first temperature T1, and a full hardening step which hardens the mixture at a second temperature T2 higher than the first temperature T1. The preliminary hardening step is performed at a first temperature T1, for example, <NUM> to <NUM> for <NUM> minutes for <NUM> hours. The full hardening step is performed at a second temperature T2, for example, <NUM> to <NUM> for <NUM> minutes to <NUM> hours.

Preliminarily hardening the mixture prior to the full hardening step at a lower temperature than that of full hardening can make the resultant light reflecting member <NUM> less likely to generate a crack.

Furthermore, preliminary hardening and/or full hardening can be performed at atmospheric pressure, or while applying pressure. Hardening the mixture while applying pressure can increase the reflectance of the formed light reflecting member <NUM> with respect to the light from the light emitting element. This is believed to result because the light reflective particles are more densely populated when the mixture is hardened under pressure. In the case of applying pressure, the pressure applied is, for example, <NUM> MPa.

By following the steps described above, a light emitting device <NUM> according to Embodiment <NUM> can be produced. The step of disposing a light emitting element may be performed before the step of disposing a mixture, or after the step of forming a light reflecting member by heating the mixture. The light emitting device <NUM> may be manufactured piece by piece, or as an integrally formed block of multiple devices which is subsequently divided into individual devices. Specifically, after providing a substrate block which includes a bottom surface and multiple walls, a light emitting element and a mixture are disposed in the individual recesses formed by the bottom surface and the walls. This is followed by hardening the mixture by heating, and dividing the block into individual light emitting devices.

Subsequent to the heating step, a cleaning step can be performed to clean the mixture, i.e., the light reflecting member <NUM>. Performing the cleaning step after the heating step can remove residual alkali components which could not react in the neutralizing reaction between the alkaline solution and silica contained in the mixture. This can reduce the decline of the reliability of the light emitting element. For cleaning the light reflecting member <NUM>, water (preferably pure water) may be used. Besides water, alcohols such as IPA, acids such as diluted hydrochloric acid, salts of weak bases such as ammonium chloride, crown ether, cryptand, or a mixture of these may be used. The light reflecting member <NUM> is cleaned, for example, by dipping the light emitting device <NUM> equipped with the light reflecting member <NUM> in water or a mixture of those described above. This can remove any residual alkali components.

For the step of forming a first protective film, for example, atomic layer deposition (ALD) can be employed. By employing atomic layer deposition, a dense thin first protective film <NUM> can be formed on the surface of the base <NUM> (in the case of <FIG>, on the upper surface 32a of the bottom portion <NUM> of the base <NUM>, the inner lateral surfaces 33a, the upper surface 33c, and the outer lateral surfaces 33b of the wall portion <NUM> of the base <NUM>, and the lower surface 32b of the bottom portion <NUM> of the base). Without being limited to atomic layer deposition, the first protective film may be formed by a known technique, such as sputtering, vapor deposition, or the like.

In the case of manufacturing a light emitting device in the order of providing a base, disposing a light emitting element, and disposing a mixture, the step of forming a first protective film is performed, for example, subsequent to providing a base, but before disposing a light emitting element. In this case, a step of exposing a region of the surface of the wiring layer <NUM> to be connected to the light emitting element <NUM> is included subsequent to forming the first protective film <NUM>. As a method of exposing the region, for example, the first protective film <NUM> located on the region can be removed by grinding. As another example, the protective film <NUM> located on the region can be removed by laser irradiation. As another method, the region can be masked before forming a first protective film <NUM>, followed by removing the mask subsequent to forming the first protective film <NUM>.

The step of forming a first protective film may be performed subsequent to disposing a light emitting element, but before disposing a mixture. In this case, the surface of the light emitting element <NUM> may also be covered by the first protective film <NUM>.

For the step of forming a second protective film, for example, atomic layer deposition can also be used. In the case of manufacturing a light emitting device in the order of providing a base, disposing a light emitting element, and disposing a mixture, the step of forming a second protective film is performed, for example, subsequent to disposing a mixture.

In <FIG>, the second protective film <NUM> is formed on the surface of the light reflecting member <NUM>, the surface of the light emitting element <NUM>, and the upper surface 32a of the bottom portion <NUM> of the base <NUM>. Furthermore, the second protective film <NUM> is formed on the outer lateral surfaces 33b of the wall portion <NUM> of the base <NUM> and the lower surface 32b of the bottom portion <NUM> of the base <NUM>.

With respect to forming a first protective film and forming a second protective film, only one or both of the steps may be performed. In the case of performing both steps, they are performed, for example, in the order of forming a first protective film, disposing a light emitting element, disposing a mixture, and forming a second protective film.

The base material <NUM> of the base <NUM> is not limited to a material different from that for the light reflecting member <NUM>, i.e., it may be made of the same material as that for the light reflecting member <NUM>. This can achieve a higher reflectance than a base material composed of a ceramic, metal, or the like, thereby increasing the light extraction efficiency of the light emitting device. The method of manufacturing this light emitting device according to an example not forming part of the present invention,.

The light emitting devices can be mass produced by using a known method of integrally producing multiple light emitting devices as a block and subsequently dividing the block into individual devices.

In the light emitting element <NUM> disposed in the light emitting device <NUM>, <NUM>, <NUM>, or <NUM> in <FIG>, the semiconductor layer <NUM> is positioned closer to the base <NUM> than the substrate <NUM> is, and the light emitting element is flip-chip mounted on the base <NUM> by electrically connecting the electrodes <NUM> provided on the lower surface of the semiconductor layer <NUM> to the conductive parts <NUM> of the base <NUM>.

The light emitting element of the light emitting devices <NUM>, <NUM>, <NUM>, or <NUM> may be face-up mounted. In this case, the substrate <NUM> of the light emitting element is positioned closer to the base <NUM> than the semiconductor layer <NUM> is, and the electrodes are disposed on the surface of the semiconductor layer <NUM> located opposite to the substrate <NUM>. The electrodes of the light emitting element are electrically connected to the conductive parts <NUM> of the base <NUM> via wires.

Furthermore, the light emitting element may be of the type that includes a support substrate, a semiconductor layer which successively includes from the support substrate side a p-side semiconductor layer, an emission layer, and an n-side semiconductor layer, a p-side electrode, and an n-side electrode. Such a light emitting element obtained by bonding the support substrate and the semiconductor layer is disposed so as to face the support substrate to the base <NUM>. For the support substrate, for example, a silicon substrate can be used.

Such a light emitting element can be manufactured, for example, by the method described below. First, a semiconductor layer is grown on a growth substrate, and a p-side electrode and an n-side electrode electrically connected to the p-side semiconductor layer and the n-side semiconductor layer, respectively, are arranged. Then a support substrate is bonded on the semiconductor layer via a bonding material, and the growth substrate is removed. Then a portion of the semiconductor layer is removed from the semiconductor layer side until the p-side electrode and the n-side electrode are exposed.

The light emitting devices <NUM>, <NUM>, <NUM>, and <NUM> may include a protective device <NUM> such as that shown in <FIG>. The protective device <NUM> is, for example, a Zener diode. In the case of disposing a protective device <NUM> on the bottom portion <NUM> of the base <NUM>, the protective device <NUM> is preferably covered by the light reflecting member <NUM> in part or whole. Covering the protective device <NUM> with the light reflecting member <NUM> can reduce the decline in the light extraction efficiency attributable to the absorption of light by the protective device <NUM>.

The light emitting devices <NUM>, <NUM>, <NUM>, and <NUM> can further include a lid that covers the recess <NUM> of the base <NUM>. The lid, for example, is a light transmissive member including a resin or inorganic material. The lid may contain or may not a wavelength conversion material such as a phosphor. In the case of a lid formed of an inorganic base material that contains a phosphor, YAG (yttrium aluminum garnet) for the phosphor, and alumina or silica for the base material, for example, can be used.

The lid is bonded to the base material <NUM> of the base <NUM> by using a bonding material, for example, solder (Au-Sn, Au-In, or the like), low melting point glass, or a resin (silicone resin, epoxy resin, or the like). In the case in which the light reflecting member <NUM> is disposed on the upper surface 33c of the wall portion <NUM> of the base <NUM>, the light reflecting member <NUM> disposed on the upper surface 33c can concurrently function as a bonding material that bonds the lid and the base. As such, the light reflecting member <NUM> can be used as a bonding material in addition to light reflecting purposes. Using the light reflecting member <NUM> as a bonding material can increase the light extraction efficiency of the light emitting device <NUM>.

The lid may be disposed to achieve a hermetic or non-hermetic construction for the recess <NUM> of the base <NUM>. In the case in which the lid achieves a hermetic construction for the recess <NUM>, the light emitting element <NUM>, the light reflecting member <NUM>, and the like that are disposed on the bottom portion <NUM> of the base <NUM> are less likely to be exposed to the ambient air.

The step of disposing a lid is performed, for example, subsequent to disposing a mixture, and prior or subsequent to forming a light reflecting member (heating step).

In the recess <NUM> of the base <NUM>, a encapsulating member can be disposed to encapsulate the light emitting element <NUM>. The encapsulating member is, for example, a resin containing a phosphor. For the phosphor, for example, YAG (yttrium aluminum garnet), and for the base material for the encapsulating member, alumina or silica can be used. The encapsulating member disposed in the recess <NUM> can encapsulate any member disposed on the bottom portion <NUM> of the base <NUM>, such as the light reflecting member <NUM>, the first protective film <NUM>, the second protective film <NUM>, the protective device <NUM>, and the like.

When the light-emitting element emits ultraviolet light, as the material of the encapsulating member, it is preferable to use a material having resistance to ultraviolet light, such as fluororesin or low-melting glass. When the light-emitting element emits ultraviolet light, the encapsulating member may or may not contain a phosphor in the material of the encapsulating member described above.

When the light reflecting member has gaps inside, the encapsulating member and/or the protective film can be disposed by impregnating the gap opening on the surface of the light reflecting member <NUM>. This can improve the adhesion between the light reflecting member <NUM> and the encapsulating member. When the encapsulating member contains a phosphor, the phosphor may also be disposed inside the gap of the light reflecting member.

The encapsulating member may be disposed via the second protective film <NUM> disposed on the surface of the light reflecting member <NUM> or may be disposed directly on the surface of the light reflecting member <NUM>.

The upper surface of the encapsulating member may be flat or may have unevenness in a cross-sectional view. Alternatively, the upper surface of the encapsulating member may be depressed at the center or may be raised at the center. For example, by forming the upper surface of the encapsulating member into a shape having a lens effect such as a concave lens shape, a convex lens shape, or a Fresnel lens shape, the light from the light emitting element is spread or condensed, thereby increasing the light distribution properties of the light emitting device can be controlled.

A light emitting device <NUM> according to Example <NUM>, not forming part of the present invention, as shown in <FIG> and <FIG>, differs from a light emitting device <NUM> according to Embodiment <NUM> such that the base <NUM> is a plate, and the light reflecting member <NUM> is a frame member that surrounds the light emitting element <NUM>.

The frame-shaped light reflecting member <NUM> can also be considered as a member that defines, together with the base <NUM>, the recess <NUM> in which the light emitting element <NUM> is disposed.

In the light emitting device <NUM> shown in <FIG>, the light reflecting member <NUM> includes an upper surface, inner lateral surfaces, and outer lateral surfaces. The inner lateral surfaces and the outer lateral surfaces of the light reflecting member <NUM> are straight line shaped in the cross section, and are perpendicular to the upper surface 235a of the base <NUM>. However, the inner lateral surfaces and/or the outer lateral surfaces of the light reflecting member <NUM> may be oblique to the upper surface 235a of the base <NUM>. For example, the outer lateral surfaces of the light reflecting member <NUM> may be perpendicular to the upper surface of the base <NUM>, but the inner lateral surfaces of the light reflecting member <NUM> may be oblique such that the width of the light reflecting member <NUM> becomes smaller from the lower edges towards the upper edges of the light reflecting member <NUM>.

In the light emitting device <NUM> shown in <FIG>, the light reflecting member <NUM> includes inner lateral surfaces and outer lateral surfaces in which the upper edges of the inner lateral surfaces are in contact with the upper edges of the outer lateral surfaces. The inner lateral surfaces and the outer lateral surfaces of the light reflecting member <NUM> are curved so as to form a mound on the base <NUM>.

As described above, the inner lateral surfaces and/or the outer lateral surfaces of the light reflecting member may be straight line shaped or curved in a cross section. Without being limited to this, the shapes of the inner lateral surfaces and/or the outer lateral surfaces of the light reflecting member may have a staircase shape in a cross section. The light reflecting member may be such that the upper edges of the inner lateral surfaces and the upper edges of the outer lateral surfaces may be connected via an upper surface or connected directly with one another.

The light emitting device <NUM>, as shown in <FIG>, includes a light transmissive member <NUM> that covers the light emitting elements <NUM> in the space surrounded by the light reflecting member <NUM>, i.e., the recess <NUM>.

As shown in <FIG>, furthermore, a plurality of light emitting elements <NUM> are disposed in the recess <NUM>. In this case, wavelength conversion members containing different fluorescent materials from one another may be individually disposed on the upper surfaces 4a of the light emitting elements <NUM>. The fluorescent materials contained in the individual wavelength conversion members are selected such that the light emitted from the wavelength conversion members disposed on the light emitting elements <NUM> individually produce desired colors. For example, the fluorescent materials contained in the individual wavelength conversion members are suitably selected such that white light exits the wavelength conversion member disposed on a certain light emitting element <NUM>, and incandescent light exits the wavelength conversion member disposed on another light emitting element <NUM>. When structured in this manner, a color tunable light emitting device <NUM>, <NUM> can be produced. The light transmissive member <NUM> may contain or not contain a fluorescent material. Furthermore, such a color tunable structure is also applicable to light emitting devices <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> according to Embodiment <NUM>, Embodiment <NUM>, and Embodiment <NUM>.

Alternatively, a light reflecting white encapsulating member (i.e., a resin containing titania or the same material as that for the light reflecting member <NUM>) may be disposed in the recess <NUM> while exposing the wavelength conversion member disposed on the upper surface 4a of a light emitting element <NUM>.

The shape of the light reflecting member <NUM>, <NUM> in a top view may be annular, and the outer boundary and/or the inner boundary thereof may have various shapes, such as a quadrangle, circle, octagon, and the like. In the case in which the light reflecting member <NUM>, <NUM> is polygonal in the top view, the shape may be substantially polygonal with curved corners.

The light emitting device <NUM>, <NUM> may further include a flat portion, which is made of the same light reflective material as that for the frame member, between the frame-shaped light reflecting member <NUM>, <NUM> and the light emitting element <NUM>. The flat portion is similar to the flat portion R2 in Embodiment <NUM> described earlier. The flat portion may be continuous with or distanced from the light reflecting member <NUM> or <NUM>.

Any of the base which is a light reflecting member, the types of light emitting elements, the protective device, the lid, the encapsulating member, and the member disposed on the light emitting element described with reference to the variations of Embodiment <NUM> is applicable to a light emitting device <NUM> or <NUM> according to Example <NUM>.

A method of manufacturing a light emitting device <NUM> according to Example <NUM> (Manufacturing Method <NUM>, not forming part of the present invention) differs from Manufacturing Method <NUM> in terms of the step of disposing a mixture.

In the step of disposing a mixture in Manufacturing Method <NUM>, for example, a mold having a desired frame shape is placed on the base <NUM> on which a light emitting element <NUM> is disposed, followed by disposing a mixture in the mold. The mixture is allowed to flow into the mold through an inlet port of the mold. Subsequently, the base <NUM> on which the light emitting element <NUM> and the mixture are disposed is heated with the mold still in place to form a light reflecting member <NUM> (forming light reflecting member by heating mixture/heating step). After heating step, the mold is removed. A light reflecting member <NUM> having a desired shape can be produced by utilizing a mold in this manner.

A light emitting device <NUM> according to Example <NUM>, not forming part of the present invention, as shown in <FIG>, differs from a light emitting device <NUM> according to Embodiment <NUM> in that the base <NUM> is a plate, and the light reflecting member <NUM> is disposed to cover the upper surface 335a of the base <NUM>.

In the light emitting device <NUM> shown in <FIG>, the light reflecting member <NUM> is disposed to cover the upper surface 335a of the base <NUM>.

The height of the light reflecting member <NUM> from the upper surface 335a of the base <NUM> is practically constant with a variation of a few tens of microns at most, for example. The height of the light reflecting member <NUM> is preferably equal to or smaller than the height of the light emitting elements <NUM> from the upper surface of the base material <NUM> of the base <NUM> to the lower surfaces of the light emitting elements <NUM>. The light reflecting member <NUM> is preferably disposed at a distance from the lateral surfaces 2a of the semiconductor layer <NUM> of the light emitting elements <NUM>.

Covering the upper surface 335a of the base <NUM> with the light reflecting member <NUM> in this manner can reduce the absorption of the light emitted from the light emitting elements <NUM> by the base <NUM>.

The light reflecting member <NUM> is not limited to that disposed to cover the upper surface of the wiring layer <NUM> as shown in <FIG>, and may be disposed between the base material <NUM> and the wiring layer <NUM>. In other words, the light reflecting member <NUM> may be disposed on the upper surface of the base material <NUM>, and the wiring layer <NUM> disposed on the upper surface of the light reflecting member.

Any of the types of light emitting elements, the protective device, and the member disposed on the light emitting element described with reference to the variations of Embodiment <NUM> is applicable to a light emitting device <NUM> according to Example <NUM>.

A light emitting device <NUM> according to Example <NUM>, not forming part of the present invention, as shown in <FIG>, differs from a light emitting device <NUM> according to Embodiment <NUM> in that the base material <NUM> of the base <NUM> is a plate that is a light reflecting member <NUM>. The light emitting device <NUM> according to Embodiment <NUM> further includes a light guide plate <NUM> having one or more through holes <NUM>. The through holes <NUM>, for example, are two-dimensionally arranged.

The base <NUM>, which is a light reflecting member <NUM>, is preferably provided to expose the lateral surfaces 2a of the semiconductor layer <NUM> of the light emitting element <NUM>.

The base <NUM> which is a light reflecting member <NUM>, together with a light guide plate <NUM> and a plurality of light emitting elements <NUM> individually arranged in the through holes <NUM> of the light guide plate <NUM>, can be utilized as a planar light source.

Any of the types of light emitting elements, the protective device, and the member disposed on the light emitting element described with reference to the variations of Embodiment <NUM> is applicable to a light emitting device <NUM> according to Example <NUM>. Furthermore, the lid and the encapsulating member described with reference to the variations of Embodiment <NUM> are applicable to a light emitting device <NUM> according to Example <NUM>.

Examples <NUM> to <NUM> and Reference Examples <NUM> and <NUM> will be explained.

For each of Reference Examples <NUM> and <NUM>, and Examples <NUM> to <NUM>, a light reflecting member was produced and the light reflecting member was measured to obtain the retention rate of contraction subsequent to heating the light reflecting member at <NUM> for one hour. The amount of the alkaline solution added was appropriately adjusted to achieve the viscosity suited for forming.

The light reflecting member <NUM> of Reference Example <NUM> was provided as described below.

First, a powder mix was provided by mixing light reflective particles <NUM> having the average particle size of <NUM> µm and the average aspect ratio of <NUM> and powdered silica having an average particle size of <NUM> µm in terms of median diameter. The light reflective particles <NUM> used were boron nitride. Silica and boron nitride were mixed at a weight ratio of <NUM>:<NUM>.

A mixture was provided by mixing the powder mix and a <NUM> mol/L alkaline solution. The alkaline solution used was a potassium hydroxide solution. The alkaline solution and the powder mix were mixed at a weight ratio of <NUM>:<NUM>.

Subsequently, the mixture was preliminarily hardened by heating at a <NUM> first temperature under <NUM> MPa pressure for one hour.

Then the mixture was fully hardened by heating at a <NUM> second temperature under <NUM> MPa pressure for two hours to produce a light reflecting member <NUM>.

The light reflecting members <NUM> of the Reference Example <NUM> and Examples <NUM> to <NUM> were provided by a similar method as in Reference Example <NUM> while changing the materials for the light reflective particles, the average particle size of the light reflective particles, the aspect ratio of the light reflective particles, and the weight ratio of silica to light reflective particles as shown in Table <NUM>.

For each of Reference Examples <NUM> and <NUM> and Examples <NUM> to <NUM>, the light reflecting member <NUM>, which was a disk having a diameter of about <NUM> and a thickness of about <NUM>, was divided into two equal parts, and one of the two parts was heated at <NUM> for one hour. Subsequently, the length percentage of a side of the cross section of the heated light reflecting member part compared to the length of the corresponding side of the cross section of the unheated light reflecting member part was calculated (retention rate of contraction). Table <NUM> shows the results.

The results of Reference Examples <NUM> and <NUM> and Examples <NUM> to <NUM> show that the retention rates of contraction of Examples <NUM> to <NUM> were <NUM>% or higher, which were higher than those of Reference Examples <NUM> and <NUM>. As is made clear from the results, the light reflecting members <NUM> in Examples <NUM> to <NUM> which included silica, an alkali metal, and light reflective particles having an average particle size of <NUM> µm to <NUM> µm and an aspect ratio of <NUM> or higher have high heat resistance.

In Example <NUM>, a light emitting device according to Embodiment <NUM> was produced, and the amount of light was evaluated.

The light emitting device of Example <NUM> was produced as described below.

First, a base <NUM> which included conductive parts <NUM> and a base material <NUM> having a recess <NUM> was provided. The recess <NUM> was a rectangular cuboid space having a <NUM> × <NUM> quadrangular base and a <NUM> height. The material used for the bottom portion <NUM> and the wall portion <NUM> of the base <NUM> was AlN. The material used for the conductive parts <NUM> was Au.

Subsequently, a light emitting element <NUM> was disposed on the bottom portion <NUM> of the base <NUM>. The wavelength of the light emitted by the light emitting element <NUM> was <NUM>. The top view shape of the light emitting element <NUM> was quadrangular each side being <NUM>.

Subsequently, a powder mix was provided by combining boron nitride having an average particle size of <NUM> µm and an average aspect ratio of about <NUM> and silica having an average particle size of <NUM> µm at a weight ratio of <NUM>:<NUM>. Subsequently, <NUM> of a <NUM> mol/L potassium hydroxide solution was added to <NUM> of the powder mix (the ratio by weight of the alkaline solution to the powder mix is <NUM>:<NUM>), <NUM> of water was added and mixed using a stirring bar. By subsequently defoaming and agitating the mixture by using a defoaming agitator operable under reduced pressure, a white uniformly viscous mixture was obtained. Furthermore, yttria-stabilized zirconia was added as a scattering material to the resultant mixture.

The mixture produced in the manner described above was disposed in the recess <NUM> by using a nozzle. The mixture was disposed to form an oblique portion R1 whose height decreased from the wall portion <NUM> towards the light emitting element <NUM>.

Subsequently, the base <NUM> on which the light emitting element <NUM> and the mixture were disposed was heated on a hot plate for preliminary hardening the mixture for <NUM> minutes at <NUM> atm pressure. The preliminary hardening was performed at <NUM>. Subsequent to preliminary hardening, the mixture was fully hardened in a pressurized nitrogen atmosphere oven at <NUM> MPa for <NUM> minutes. The full curing was performed at <NUM>.

The light emitting device of Comparative Example <NUM> was the same as the light emitting device of Example <NUM> except for not including a light reflecting member <NUM>.

The amounts of light emitted from the light emitting device <NUM> of Example <NUM> and the light emitting device of Comparative Example <NUM> were compared and evaluated by applying a <NUM> mA forward current.

The amount of light emitted from each of the light emitting devices of Example <NUM> and Comparative Example <NUM> was measured by using an integrating sphere. The measurement results show that the amount of light emitted from the light emitting device of Example <NUM> had a <NUM>% increase from that of the light emitting device of Comparative Example <NUM>.

Claim 1:
A light emitting device (<NUM>) comprising:
a light emitting element (<NUM>), and
a light reflecting member (<NUM>) that reflects light emitted from the light emitting element (<NUM>),
the light reflecting member (<NUM>) comprising plate-shaped light reflective particles (<NUM>), silica, and an alkali metal, wherein
an average particle size of the light reflective particles (<NUM>) is <NUM> µm to <NUM> µm, and
an average aspect ratio of the light reflective particles (<NUM>) is <NUM> or higher; the light emitting device (<NUM>) further comprising a base (<NUM>), wherein
the light emitting element (<NUM>) and the light reflecting member (<NUM>) are disposed on the base (<NUM>),
the light emitting element (<NUM>) comprises a semiconductor layer (<NUM>), and
a lateral surface (2a) of the semiconductor layer (<NUM>) is distanced from the light reflecting member (<NUM>) at least in part, wherein further
the base (<NUM>) has a bottom portion (<NUM>) and a wall portion (<NUM>) that define a recess (<NUM>),
the light emitting element (<NUM>) is disposed in the recess (<NUM>), and
the light reflecting member (<NUM>) is continuously disposed on an inner lateral surface (33a) of the wall portion (<NUM>) and an upper surface (32a) of the bottom portion (<NUM>).