Light-emitting module, method for manufacturing the same, and liquid-crystal display device

A light-emitting module includes a light-guiding plate having a light-extracting surface, a plurality of first light-emitting elements and a plurality of second light-emitting elements having a light-emission characteristic different from a light-emission characteristic of the first light-emitting elements, the first light-emitting elements and the second light-emitting elements being alternately mounted on a surface of the light-guiding plate opposite to the light-extracting surface, with electrodes facing a direction opposite to the light-extracting surface of the light-guiding plate, a light-reflective member covering each of the first light-emitting elements and each of the second light-emitting elements to expose electrodes of each of the first light-emitting elements and electrodes of each of the second light-emitting elements from a first surface, first wiring formed on the first surface to connect the electrodes of the first light-emitting elements, and second wiring formed on the first surface to connect the electrodes of the second light-emitting elements.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

The present application claims priority under 35 U. S. C. § 119 to Japanese Patent Application No. 2019-141764, filed Jul. 31, 2019. The disclosure of Japanese Patent Application No. 2019-141764 is incorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates to a light-emitting module, a method for manufacturing the same, and a liquid-crystal display device.

A light-emitting device in which a plurality of first LED elements and a plurality of second LED elements having light-emission characteristics different from light-emission characteristics of the first LED elements are flip-chip mounted on a board having wiring electrodes is known (See, for example, Japanese Patent Publication No. 2014-229676). In this light-emitting device, the wiring electrodes connect the first LED elements in series and connect the second LED elements in series, and a portion of the wiring electrodes connecting the first LED elements to one another passes through between an anode electrode and a cathode electrode of the second LED element mounted on the board.

SUMMARY

However, high accuracy in mounting is required in the light-emitting device described above because the first LED elements and the second LED elements are flip-chip mounted on the board having the wiring electrodes.

Accordingly, an object of the present disclosure is to provide a light-emitting module having a structure that can relax the requirement to mount light-emitting elements accurately.

A light-emitting module according to an embodiment of the present disclosure includes a light-guiding plate having a light-extracting surface, a plurality of first light-emitting elements and a plurality of second light-emitting elements having a light-emission characteristic different from a light-emission characteristic of the first light-emitting elements, the first light-emitting elements and the second light-emitting elements being alternately mounted on a surface of the light-guiding plate opposite to the light-extracting surface, with electrodes facing opposite to the light-extracting surface of the light-guiding plate, a light-reflective member covering each of the first light-emitting elements and each of the second light-emitting elements to expose electrodes of each of the first light-emitting elements and electrodes of each of the second light-emitting elements from a first surface, first wiring formed on the first surface to connect the electrodes of the first light-emitting elements, and second wiring formed on the first surface to connect the electrodes of the second light-emitting elements.

Certain embodiments of the present disclosure can provide a light-emitting module having a structure that can relax the requirement to mount light-emitting elements accurately.

DETAILED DESCRIPTION OF EMBODIMENTS

Certain embodiments of the invention will be described below referring to the accompanying drawings. The description below includes terms indicating specific directions or positions (such as “up”, “down”, and other terms containing these terms) as appropriate. These terms are used to facilitate understanding of the invention referring to the drawings, and the meanings of these terms do not limit the technical scope of the present invention. A portion with the same reference numeral in a plurality of drawings represents the same or equivalent portion or member.

In the embodiments described below, examples of light-emitting modules are described to give a concrete form to the technical idea of the present invention, and the present invention is not limited to the description below. Unless otherwise specified, sizes, materials, shapes, and relative positions of constituent components described below are not intended to limit the scope of the present invention thereto, but rather are described as examples. Constitutions described in one embodiment may be applicable to other embodiments and modified examples. Sizes or positional relationships of components illustrated in the drawings may be exaggerated in order to clarify the descriptions.

First Embodiment

FIG. 1is a schematic plan view of an illustrative light-emitting module according to a first embodiment of the present disclosure.FIG. 2is a schematic bottom view of the illustrative light-emitting module according to the first embodiment.FIGS. 3A and 3Bare schematic cross-sectional views of the illustrative light-emitting module according to the first embodiment viewed upside down with a light-guiding plate facing downward.FIG. 3Aschematically shows a cross section along the line A-A ofFIG. 2, andFIG. 3Bis a schematic enlarged view of the portion B ofFIG. 3A.

As shown inFIG. 1toFIG. 3B, a light-emitting module100includes a light-guiding plate1, light-emitting element units3(1) and3(2), bonding members14, a second light-reflective member16, first wiring5(1), and second wiring5(2). In the light-emitting module100, a single light-guiding plate1has a plurality of recesses1b, in each of which a respective one of the light-emitting element units3(1) or3(2) is disposed.

In the description below, “a plan view” refers to a view in which an object of interest is viewed in the normal direction of a first main surface1cof the light-guiding plate1, and “a shape in a plan view” refers to the shape of the object of interest viewed in the normal direction of the first main surface1cof the light-guiding plate1.

The light-emitting element unit3(1) includes a light-emitting element11(1), a light-transmissive member10covering a main light-emitting surface11cof the light-emitting element11(1), and a first light-reflective member15covering lateral surfaces of the light-emitting element11(1).

The light-emitting element unit3(2) includes a light-emitting element11(2), the light-transmissive member10covering the main light-emitting surface11cof the light-emitting element11(2), and the first light-reflective member15covering lateral surfaces of the light-emitting element11(2).

The light-emitting element11(1) differs from the light-emitting element11(2) in light-emission characteristic. The statement “differ in light-emission characteristic” as used herein indicates, for example, that the light-emitting element11(1) differs from the light-emitting element11(2) in emission wavelength, and alternatively, that the light-emitting element11(1) and the light-emitting element11(2) are the same in emission wavelength and different in luminance.

The light-emitting element unit3(1) and the light-emitting element unit3(2) share the same structure except that light-emitting elements of the light-emitting element unit3(1) have light-emission characteristics different from light-emission characteristics of light-emitting elements of the light-emitting element unit3(2). In the description below, the light-emitting element unit3(1) and the light-emitting element unit3(2) are simply referred to as light-emitting element units3unless they need to be distinguished from each other. Similarly, the light-emitting element11(1) and the light-emitting element11(2) are simply referred to as light-emitting elements11unless they need to be distinguished from each other.

The light-emitting elements11each have the main light-emitting surface11c, an electrode formation surface11dopposite to the main light-emitting surface11c, and lateral surfaces between the main light-emitting surface11cand the electrode formation surface11d.

The light-emitting element11is disposed such that, for example, the main light-emitting surface11cfaces the light-guiding plate1. A pair of electrodes11bare formed on the electrode formation surface11dof the light-emitting element11. One of the pair of electrodes11bis an anode electrode111, and the other one is a cathode electrode112.

The light-emitting element11includes, for example, a light-transmissive substrate such as a sapphire substrate and a semiconductor layered structure layered on the light-transmissive substrate. The semiconductor layered structure includes a light-emitting layer and p-type and n-type semiconductor layers disposed such that the light-emitting layer is disposed between the p-type semiconductor layer and the n-type semiconductor layer. The p-type and n-type semiconductor layers are electrically connected to the anode electrode111, which is the p-side electrode, and the cathode electrode112, which is the n-side electrode, respectively.

There is no particular limitation on the length, width, and height of the light-emitting element11. A semiconductor light-emitting element of preferably 1,000 μm or less, more preferably 500 μm or less, further preferably 200 μm or less, in length and width in a plan view is used for the light-emitting element11.

With a light-emitting element11having a length and width within the above ranges, high-definition images can be provided through local dimming of a liquid-crystal display device. In particular, a light-emitting element11having the length and width of 500 μm or less is available at a low price, so that the cost of the light-emitting module100can be reduced.

A light-emitting element having a length and a width that are both 250 μm or less has a small area of the upper surface, and the amount of light emitted from the lateral surfaces of the light-emitting element is relatively increased. In other words, light emitted from such a light-emitting element is likely to have a batwing distribution, and such a light-emitting element is therefore preferably used in the light-emitting module100according to the first embodiment in which the light-emitting element is bonded to the light-guiding plate and in which the distance between the light-emitting element and the light-guiding plate is very short.

The height of the light-emitting element11is preferably in a range of 0.10 mm to 0.25 mm. The light-emitting element11preferably has such a height that the electrode formation surface11dof the light-emitting element11protrudes from the recess1bwhen the light-emitting element unit3is mounted in the recess1b.

The light-emitting element11may have any appropriate shape, such as a square or elongated rectangular shape, in a plan view.

For a high-definition liquid-crystal display device, several thousand or more light-emitting elements are used, and mounting of the light-emitting elements is therefore important. With light-emitting elements each having an elongated rectangular shape in a plan view, even if rotational misalignment (such as misalignment in ±90° directions) of some of the light-emitting elements occur in the step of mounting the light-emitting elements, such rotational misalignment can be easily detected by visual observation. Further, formation of the first wiring5(1) and the second wiring5(2) is facilitated because the anode electrode111and the cathode electrode112can be formed apart from each other.

On the other hand, in the case in which light-emitting elements each having a square shape in a plan view are used, small light-emitting elements can be mass-produced. The density (intervals) of the light-emitting elements11, in other words, distances between the light-emitting elements11, can be, for example, in a range of about 0.05 mm to 20 mm, preferably about 1 mm to 10 mm. Intervals between the light-emitting elements11are distances between the centers of adjacent light-emitting elements11(1) and11(2). Each of the light-emitting elements11is designed to be disposed substantially at the center of a respective one of light-emitting element units3, so that the intervals between the light-emitting element units3are also in a range of about 0.05 mm to 20 mm, preferably about 1 mm to 10 mm.

A known semiconductor light-emitting element can be used for each light-emitting element11. In the first embodiment, a light-emitting diode mounted such that its electrodes face a direction opposite to the light-extracting surface of the light-guiding plate is illustrated for the light-emitting element11. The light-emitting element11emits, for example, blue light. An element that emits light other than blue light can be used for the light-emitting element11. For example, a color (such as blue) of light emitted from the light-emitting element11and a color (such as yellow) of light that has been subjected to wavelength conversion by the light-transmissive member10, which is a wavelength conversion member, are mixed to generate white light, which is radiated from the light-emitting element unit3.

An element that emits light with any appropriate wavelength can be selected for the light-emitting element11. Examples of elements that emit blue and green light include a light-emitting element employing a nitride semiconductor (InXAlYGa1-X-YN, where 0≤X, 0≤Y, and X+Y≤1) or GaP. A light-emitting element containing a semiconductor such as GaAlAs and AlInGaP can be used for an element that emits red light. Alternatively, semiconductor light-emitting elements made of materials other than the materials described above can be used. The emission wavelengths can be changed by changing the materials for the semiconductor layers and their mixing ratios. The compositions, emission colors, sizes, and number of the light-emitting elements to be used may be appropriately selected according to the purpose.

The light-transmissive member10is, for example, a wavelength conversion member and adjusts the wavelengths of light emitted from the light-emitting element11to emit the light toward the light-guiding plate1. The case in which the light-transmissive member10is a wavelength conversion member is described below.

The light-transmissive member10covers the main light-emitting surface11cof the light-emitting element11and transmits light emitted from the main light-emitting surface11c. The light-transmissive member10may contain a substance that excites light emitted by the light-emitting element11or may contain a substance that diffuses and/or reflects the light.

The light-transmissive member10preferably has a thickness in a range of 0.05 mm to 0.30 mm. If the light-transmissive member10is too small, the effectiveness of wavelength conversion is reduced. If the thickness of the light-transmissive member10is too large, absorption of wavelength-converted light may occur. Accordingly, the thickness of the light-transmissive member10preferably is in the range described above.

The light-transmissive member10receives light emitted from the light-emitting element11and converts the light into light with different wavelengths. In the light-transmissive member10, a wavelength conversion substance is dispersed in a base material. The light-transmissive member10may include a plurality of layers. For example, the light-transmissive member10can have a two-layer structure including a first layer in which a wavelength conversion substance is added to a base material and a second layer, which serves as a light-diffusing member, in which a diffusing material is added to a base material.

The base material may be a light-transmissive material such as an epoxy resin, a silicone resin, a mixture of these resins, and glass. It is effective to select a silicone resin as the base material in view of resistance to light and ease of formation of the light-transmissive member10. For the base material of the light-transmissive member10, a material having a refractive index higher than a refractive index of the material of the light-guiding plate1is preferably used.

An example of the wavelength conversion substance contained in the light-transmissive member10is a phosphor. Examples of the phosphor include YAG phosphors, β-SiAlON phosphors, and fluoride phosphors such as KSF phosphors. The light-transmissive member10may contain a single wavelength conversion substance or a plurality of wavelength conversion substances.

In the case in which the wavelength conversion member contains a plurality of wavelength conversion substances, for example, the wavelength conversion member can contain a β-SiAlON phosphor that emits light having a color in the green range and a fluoride phosphor, such as a KSF phosphor, that emits light having a color in the red range. This structure expands the color reproduction range of the light-emitting module100. In this case, the light-emitting element11preferably contains a nitride semiconductor (InXAlYGa1-X-YN, where 0≤X, 0≤Y, and X+Y≤1), which can emit light with short wavelengths that can efficiently excite the light-transmissive member10.

In the case of using, for example, a light-emitting element11configured to emit light having a color in the blue range to obtain a light-emitting module100that emits light having a color in the red range, the light-transmissive member10may contain 60 wt % or more, preferably 90 wt % or more, of a KSF phosphor (red phosphor). That is, the light-transmissive member10may contain a wavelength conversion member that emits light having a predetermined color to provide light having a predetermined color. For the wavelength conversion substance, quantum dots may be used. The wavelength conversion substance may be disposed in any appropriate arrangement inside the light-transmissive member10. For example, the wavelength conversion substance may be substantially uniformly distributed or disposed predominantly in some portion. Also, a plurality of layers each containing a wavelength conversion substance may be layered in the light-transmissive member10.

The phosphor contained in the light-transmissive member10of the light-emitting element unit3(1) may be different from the phosphor contained in the light-transmissive member10of the light-emitting element unit3(2) in order to make the emission color of the light-emitting element unit3(1) different from the emission color of the light-emitting element unit3(2).

A light-transmissive adhesive member19covers a portion of the lateral surfaces of the light-emitting element11and a portion of the light-transmissive member10. An outer lateral surface of the light-transmissive adhesive member19is preferably an inclined surface spreading from a lateral surface of the light-emitting element11toward the light-transmissive member10, more preferably a convex curved surface protruding toward the light-emitting element11. With this structure, a larger amount of light emitted from the lateral surface of the light-emitting element11can be guided to the light-transmissive member10, so that the light extraction efficiency can be enhanced.

The light-transmissive adhesive member19may be disposed between the main light-emitting surface11cof the light-emitting element11and the light-transmissive member10. For example, with the light-transmissive adhesive member19containing a diffusing agent or the like, light emitted from the main light-emitting surface11cof the light-emitting element11is diffused in the light-transmissive adhesive member19before entering the light-transmissive member10, so that unevenness in luminance can be reduced. The same member as the bonding member14described below can be used for the light-transmissive adhesive member19.

The first light-reflective member15covers the electrode formation surface11dand the lateral surfaces of the light-emitting element11. Specifically, the first light-reflective member15covers the electrode formation surface11dof the light-emitting element11, the lateral surfaces of the light-emitting element11not covered with the light-transmissive adhesive member19, and the outer lateral surfaces of the light-transmissive adhesive member19. In the light-emitting element unit3, the first light-reflective member15is in contact with the light-transmissive member10, and each of the outer lateral surfaces of the first light-reflective member15and a corresponding one of outer lateral surfaces of the light-transmissive member10are substantially in the same plane.

The first light-reflective member15is made of a material having good light reflectivity, preferably a white resin in which a light-reflective additive such as white powder is added to a transparent resin. In the light-emitting element unit3, the first light-reflective member15covers the surfaces of the light-emitting element11other than the main light-emitting surface11cto reduce leakage of light in the directions other than the direction toward the main light-emitting surface11c. That is, the first light-reflective member15reflects light emitted from the lateral surfaces and the electrode formation surface11dof the light-emitting element11to allow light emitted from the light-emitting element11to be effectively radiated to the outside through the first main surface1cof the light-guiding plate1, so that the light extraction efficiency of the light-emitting module100can be enhanced.

The first light-reflective member15is preferably made of a white resin having a reflectance of 60% or more, preferably 90% or more, of light emitted from the light-emitting element11. The first light-reflective member15is preferably a resin containing a white pigment such as white powder. A silicone resin containing white inorganic powder such as titanium oxide is particularly preferable.

The first light-reflective member15is in contact with at least a portion of each of the lateral surfaces of the light-emitting element11and surrounds the light-emitting element11to embed the light-emitting element11such that the electrodes11bof the light-emitting element11are exposed on a surface of the first light-reflective member15.

The light-guiding plate1is a light-transmissive member from which light incident from the light source is surface-emitted to the outside. The light-guiding plate1has the first main surface1cserving as the light-emitting surface and a second main surface1dopposite to the first main surface1c. The second main surface1dof the light-guiding plate1has a plurality of recesses1b. In the first embodiment, grooves1eare formed between adjacent recesses1b.

Each light-emitting element unit3is disposed in a respective one of the recesses1b. Specifically, a portion of the light-emitting element unit3is disposed in the recess1bof the light-guiding plate1such that the light-transmissive member10faces the bottom surface of the recess1b. This structure allows for reducing the thickness of an entirety of the light-emitting module. The light-guiding plate1can have a plurality of recesses1b, and each of the light-emitting element units3can be disposed in a respective one of the recesses1bto constitute the light-emitting module100.

The second light-reflective member16, which will be described below in detail, disposed in the grooves1eis preferably a white resin that reflects light emitted from the light-emitting element units3. The second light-reflective member16that is a white resin prevents light emitted from a light-emitting element11from being incident on an adjacent section of the light-guiding plate1divided by the grooves1e, so that leakage of light emitted from each light-emitting element11to an adjacent section can be reduced.

The size of the light-guiding plate1is appropriately selected according to the size of the liquid-crystal display device in the case in which the light-emitting module100is used for a backlight source for a liquid-crystal display device. The size of the light-guiding plate1is such that each side of the light-guiding plate1is, for example, in a range of about 1 cm to 200 cm, preferably about 3 cm to 30 cm, in the case of the light-guiding plate1having a plurality of recesses1b. The light-guiding plate1can have a thickness in a range of about 0.1 mm to 5 mm, preferably 0.1 mm to 3 mm. The light-guiding plate1can have a shape such as a substantially rectangular or substantially circular shape in a plan view.

For the material of the light-guiding plate1, a resin material such as thermoplastic resins including acrylic resins, polycarbonates, cyclic polyolefins, poly(ethylene terephthalate), and polyesters and thermosetting resins including epoxies and silicones or an optically transparent material such as glass can be used. A thermoplastic resin material is particularly preferable because efficient manufacture by injection molding is possible. Among these materials, polycarbonates, which are highly transparent and inexpensive, are preferable. In the manufacturing process, even a thermoplastic material with a low thermal resistance such as polycarbonates can be used for the light-guiding plate1of the light-emitting module100manufactured without being exposed to a high-temperature environment as with solder reflow.

The light-guiding plate1may be a single layer or may have a layered structure of a plurality of light-transmissive layers. In the case in which a plurality of light-transmissive layers are layered, a layer with a refractive index different from a reflective index of the plurality of light-transmissive layers, such as an air layer, is preferably disposed between any layers of the plurality of light-transmissive layers. With this structure, diffusion of light is facilitated, and the light-emitting module with reduced unevenness in luminance may be obtained. Such a structure may be obtained by, for example, disposing a spacer between any light-transmissive layers of the plurality of light-transmissive layers to separate the corresponding light-transmissive layers such that an air layer is provided the corresponding light-transmissive layers.

Alternatively, a light-transmissive layer may be disposed on the first main surface1cof the light-guiding plate1, and a layer with a different refractive index, such as an air layer, may be disposed between the first main surface1cof the light-guiding plate1and the light-transmissive layer. With this structure, diffusion of light is facilitated, and the liquid-crystal display device with reduced unevenness in luminance may be obtained. Such a structure can be achieved by, for example, disposing a spacer between a light-guiding plate1and the light-transmissive layer to separate from each other such that an air layer is provided.

The light-guiding plate1has the recesses1bon the second main surface1d. Each light-emitting element unit3is disposed in a respective one of the recesses1bsuch that the light-transmissive member10faces the bottom surface of the recess1b.

The inner lateral surfaces of the recess1bare larger than the outer lateral surfaces of the light-emitting element unit3in a plan view. Specifically, the inner lateral surfaces of the recess1bare located outside the outer lateral surfaces of the light-emitting element unit3as shown inFIGS. 3A and 3B.

In a plan view of the light-guiding plate1, the recess1bhas a quadrangular inner shape, and the light-emitting element unit3to be disposed in the recess1balso has a quadrangular outer shape. Each outer lateral surface of the quadrangular light-emitting element unit3disposed in the quadrangular recess1bcan be parallel to a corresponding inner lateral surface of the recess1bfacing the outer lateral surface, but this structure is not limiting as described below.

The size of the recess1bin a plan view can be appropriately changed according to the outer shape of a corresponding light-emitting element unit3. The size of the recess1bin a plan view can be such that, for example, its diameter in the case of a circular shape, its major axis in the case of an elliptic shape, or the length of its diagonal in the case of a quadrangular shape is in a range of 0.05 mm to 10 mm, preferably 0.1 mm to 2 mm. The depth of the recess1bcan be in a range of 0.05 mm to 4 mm, preferably 0.1 mm to 1 mm.

The recess1bmay have, for example, a substantially rectangular or substantially circular shape in a plan view, and the shape can be selected according to the intervals between the recesses1band the like. In the case in which the intervals (distance between the centers of two closest recesses1b) of the recesses1bare substantially equal, it is preferable that each of the recesses1bhave a substantially circular or substantially square shape. Among these shapes, with a substantially circular shape, spread of light emitted from the light-emitting element unit3can be increased.

The recess1bmay more preferably have such a height from the bottom surface of the recess1bto the second main surface1dthat the main light-emitting surface11cof the light-emitting element11and the second main surface1dare substantially in the same plane in a cross-sectional view as shown inFIGS. 3A and 3B. The recess1bmay have a height that allows the upper surface of the light-emitting element11to be located at a position higher than the second main surface1dwhen the light-emitting element11is mounted in the recess1b. In this structure, the light-emitting element11is protruded from the recess1b, so that the wiring operation of the electrodes11band the like can be facilitated. The height of the recess1bis preferably adjusted according to the height of the light-emitting element11as described above.

Each bonding member14is a light-transmissive member and is in contact with the inner lateral surfaces of the recess1band the outer lateral surfaces of the light-emitting element unit3. Each bonding member14is disposed in contact with a portion of the first light-reflective member15located outside the recess1b, in other words, disposed so as to cover a region covering the outer lateral surfaces of the light-transmissive member10and the outer lateral surfaces of the first light-reflective member15.

Further, the outer lateral surfaces of the bonding member14are inclined surfaces14a. The inclined surfaces14aeach make an acute inclination angle α with the outer lateral surface of the first light-reflective member15. With the bonding member14having the inclined surfaces14a, light transmitted through the bonding member14and incident on the inclined surfaces14acan be uniformly reflected toward the light-emitting surface. Each bonding member14may also be disposed between the corresponding light-transmissive member10and the bottom surface of the corresponding recess1b.

Further, the bonding member14is in contact with the second main surface1dof the light-guiding plate1. This structure increases the region in which the inclined surfaces14aare formed and the amount of light to be reflected, so that unevenness in luminance can be reduced. The inclination angle α formed by the inclined surface14aof the bonding member14and the outer lateral surface of the first light-reflective member15can be in a range of 5° to 85°, preferably 5° to 50°, more preferably 100 to 45°.

Each bonding member14fills the gap between the inner lateral surfaces of the recess1band the outer lateral surfaces of the light-emitting element unit3inside the recess1band is widened toward the second main surface1dof the light-guiding plate1such that a bottom portion of the bonding member14is in contact with the second main surface1dof the light-guiding plate1. A width dl between each outer lateral surface of the light-emitting element unit3and a corresponding inner lateral surface of the recess1bvaries according to the inner diameter of the recess Tb, the outer diameter of the light-emitting element unit3, their shapes, the orientation of the light-emitting element unit3when mounted in the recess Tb, the tolerances of the mounting position of the light-emitting element unit3, and the like. Further, the inclination angle α also varies according to the height of the bonding member14, that is, the height of the light-emitting element unit3(the height of the light-emitting element11and the thickness of the light-transmissive member10) and the depth (height) of the recess1b. Hence, the inclination angle α, which is formed by the inclined surface14aof the bonding member14and the outer lateral surface of the first light-reflective member15and be widened toward the second main surface1d, is selected according to these conditions.

A light-transmissive thermosetting resin material such as epoxy resins and silicone resins can be used for the bonding member14. The light transmittance of the bonding member14is 60% or more, preferably 90% or more. The bonding member14may contain a diffusing material or the like or may contain white powder or the like, which is a light-reflective additive. Alternatively, the bonding member14may be made of only a light-transmissive resin material containing no diffusing material or white powder.

Optical Functional Portion1a

The light-guiding plate1can have, on the first main surface1c, optical functional portions1athat have the functions of reflecting and diffusing light emitted from the light-emitting element units3. The light-guiding plate1allows light emitted from the light-emitting element units3to spread out in the lateral direction, so that the emission intensity in the plane of the light-guiding plate1can be uniform. The optical functional portions1acan have the function of, for example, allowing light to spread out in the plane of the light-guiding plate1.

For example, each optical functional portion1ais a conical recess (seeFIGS. 3A and 3BandFIG. 13), a pyramidal recess such as a quadrangular pyramidal recess and a hexagonal pyramidal recess, a truncated conical recess (seeFIG. 14), or a truncated pyramidal recess formed on the first main surface1c. This structure allows incident light to be reflected at the interface between the inclined surface of the recess and a material with a refractive index different from a refractive index of the light-guiding plate1(such as air) inside the optical functional portion1a, in a lateral direction of the light-emitting element unit3.

For example, the optical functional portion1amay have a recess that is defined by the inclined surface and provided with a light-reflective material (such as a white resin and a reflective film made of metal).

Further, the depth of the recess, which is the optical functional portion1a, is selected in consideration of the depth of the recess1bdescribed above. That is, the optical functional portion1aand the recess1bcan have any appropriate depth such that the optical functional portion1aand the recess1bcan be separated from each other.

As described below, the optical functional portion1ais preferably disposed at a position corresponding to each light-emitting element unit3, in other words, at a position opposite to the light-emitting element unit3disposed on the second main surface1d. In particular, it is preferable that the optical axis of the light-emitting element unit3substantially coincide with the central axis of the optical functional portion1a.

This allows the center of the optical functional portion1aformed on the first main surface1cto coincide with the center of the bottom surface of the recess1bformed on the second main surface1d. In this structure, disposing the light-emitting element unit3at the center of the recess1ballows the optical axis of the light-emitting element unit3to easily coincide with the central axis of the optical functional portion1a. The size of the optical functional portion1acan be appropriately selected.

With the structure in which the light-guiding plate1has a plurality of recesses1band a plurality of optical functional portions1aand each of the light-emitting element units3is disposed in a respective one of the recesses1b, both of the light-emitting element units3and the optical functional portions1acan be arranged with high positional accuracy. Accordingly, with the optical functional portions1a, light emitted from the light-emitting elements11is uniform with accuracy, so that a high-quality backlight source with small unevenness in luminance and color can be obtained.

In the light-guiding plate1, disposing the optical functional portions1aat positions of the recesses1bin which the light-emitting element units3are disposed facilitates alignment of the light-emitting elements11with the optical functional portions1aand prevents misalignment.

In the light-emitting module100in which a plurality of light-emitting element units3are disposed on the light-guiding plate1having a plurality of recesses b, the light-emitting element units3are two-dimensionally arranged in a plan view of the light-guiding plate1. The light-emitting element units3are preferably disposed in the recesses1btwo-dimensionally arranged along two perpendicular directions, or the x direction and the y direction, as shown inFIG. 1.

Intervals px in the x direction and intervals py in the y direction between the recesses1bin which the light-emitting element units3are disposed may be same as in the example shown inFIG. 1or may be different from each other. The two directions of the arrangement do not necessarily have to be perpendicular to each other.

The intervals in the x and y directions are not limited to regular intervals but may be irregular intervals. For example, the recesses1b, in each of which a respective one of the light-emitting element units3is disposed, may be arranged such that the intervals increase from the center of the light-guiding plate1toward its periphery. The statement “intervals between the light-emitting element units3disposed in the recesses b” refers to distances between the optical axes of the light-emitting element units3, that is, the distances between the centers of the light-emitting element units3.

The second light-reflective member16covers a portion of the second main surface1dof the light-guiding plate1and a portion of the light-emitting element units3. Specifically, the second light-reflective member16covers the second main surface1dof the light-guiding plate1, the inclined surfaces14aof the light-transmissive bonding members14, and a portion of the outer lateral surfaces of the first light-reflective members15not covered with the bonding members14.

The second light-reflective member16reflects light emitted from the light-emitting elements11and light entering the light-guiding plate1to guide the light toward the first main surface1eserving as the light-emitting surface for radiating light to the outside, so that the light extraction efficiency can be enhanced. Layering the second light-reflective member16on the light-guiding plate1reinforces the light-guiding plate1. Further, with the second light-reflective member16serving as both of a member that protects the light-emitting elements11and a layer for reflecting light incident on the surface of the second main surface of the light guide plate1, the thickness of the light-emitting module100can be reduced.

A material same as a material used for the first light-reflective member15described above, that is, a white resin in which a light-reflective additive such as white powder is added to a transparent resin, can be suitably used for the second light-reflective member16. The second light-reflective member16effectively radiates light emitted from the light-emitting elements11to the outside through the first main surface1cof the light-guiding plate1.

As in the first light-reflective member15, a white resin having a reflectance of 60% or more, preferably 90% or more, of light emitted from the light-emitting elements11is suitably used for the second light-reflective member16. The white resin is preferably a resin containing a white pigment such as white powder. A silicone resin containing white inorganic powder such as titanium oxide is particularly preferable. A relatively large amount of a material is used for a member covering a surface of the light-guiding plate1, so that using an inexpensive material such as titanium oxide at a high content for the member allows for reducing a price of the light-emitting module100.

The first light-reflective member15and the second light-reflective member16may be collectively referred to as a light-reflective member17.

Arrangement of Light-Emitting Element Units3(1) and3(2) and Wiring of Electrodes

As shown inFIG. 2andFIG. 3A, the light-emitting element units3(1) and the light-emitting element units3(2) are alternately arranged in the light-emitting module100.

Specifically, the light-emitting elements11(1) and the light-emitting elements11(2) having light-emission characteristics different from the light-emission characteristics of the light-emitting elements11(1) are alternately mounted such that the electrodes11bface a direction opposite to the first main surface1c(light-extracting surface) of the light-guiding plate1. This arrangement can reduce unevenness in luminance of the light-emitting module100. To further reduce unevenness in luminance of the light-emitting module100, a diffusion layer may be disposed on the first main surface1c, which serves as the light-emitting surface, of the light-guiding plate1. Examples of the diffusion layer include a diffusion sheet made of a poly(methyl methacrylate) (PMMA) resin.

There is no particular limitation on the arrangement of the light-emitting elements11(1) and the light-emitting elements11(2), and a checkered pattern may be employed. The checkered pattern is particularly suitable in terms of reduction in unevenness in luminance of the light-emitting module100.

Eight light-emitting elements11(1) and eight light-emitting elements11(2) are arranged in a four-by-four matrix inFIG. 2, but this arrangement is not limiting. The number of the light-emitting elements11(1) and11(2), the number of rows, and the number of columns can be appropriately selected according to the purpose.

The first light-reflective member15covers each of the light-emitting elements11(1) and11(2) such that the electrodes11bof each light-emitting element11(1) and the electrodes11bof each light-emitting element11(2) are exposed on a wiring formation surface15a. A wiring formation surface16aof the second light-reflective member16is continuous with the wiring formation surface15a, the wiring formation surface16aand the wiring formation surface15aare substantially in the same plane.

The first wiring5(1) connecting the electrodes11bof the light-emitting elements11(1) of the light-emitting element units3(1) to each other and the second wiring5(2) connecting the electrodes11bof the light-emitting elements11(2) of the light-emitting element units3(2) to each other are formed on the wiring formation surfaces15aand16a.

Each of the first wiring5(1) and the second wiring5(2) is, for example, a layered film of Ni/Ru/Au layered in this order. In this case, for example, the Ni layer can have a thickness of about 2 to 8 nm, the Ru layer can have a thickness of about 9 to 15 nm, and the Au layer can have a thickness of about 22 to 28 nm. The materials and thicknesses of the first wiring5(1) and the second wiring5(2) described above are illustrative examples.

InFIG. 2, the first wiring5(1) is indicated by dot patterns different from dot patterns of the second wiring5(2) for convenience. The first wiring5(1) is indicated by a dense dot pattern, while the second wiring5(2) is indicated by a sparse dot pattern. That is, the light-emitting elements11(1) of the light-emitting element units3(1) are disposed in the portions indicated by the dense dot pattern, while the light-emitting elements11(2) of the light-emitting element units3(2) are disposed in the portions indicated by the sparse dot pattern.

Only the first wiring5(1) shown inFIG. 2is indicated by the dot pattern inFIG. 4A, andFIG. 4Bschematically shows the connection of the light-emitting elements11(1) by the first wiring5(1).

As shown inFIG. 4A, for example, a portion6(1) of the first wiring5(1) serves as an anode-side external connecting terminal, and a portion6(2) of the first wiring5(1) serves as a cathode-side external connecting terminal. In this case, four series circuits each containing two light-emitting elements11(1) are connected in parallel as shown inFIG. 4B. When a predetermined voltage is applied between the anode-side external connecting terminal6(1) and the cathode-side external connecting terminal6(2), a current flows through each light-emitting element11(1), and each light-emitting element11(1) emits light.

Only the second wiring5(2) shown inFIG. 2is indicated by the dot pattern inFIG. 5A, andFIG. 5Bschematically shows the connection of the light-emitting elements11(2) by the second wiring5(2).

As shown inFIG. 5A, for example, a portion6(3) of the second wiring5(2) serves as an anode-side external connecting terminal, and a portion6(4) of the second wiring5(2) serves as a cathode-side external connecting terminal. In this case, four parallel circuits each containing two light-emitting elements11(2) are connected in series as shown inFIG. 5B. When a predetermined voltage is applied between the anode-side external connecting terminal6(3) and the cathode-side external connecting terminal6(4), a current flows through each light-emitting element11(2), and each light-emitting element11(2) emits light.

In the light-emitting module100, the light-emitting elements11(1) and the light-emitting elements11(2) may be turned on independently or at the same time.

For example, in the case in which the emission wavelengths of the light-emitting elements11(1) are different from the emission wavelengths of the light-emitting elements11(2), three emission colors can be provided by switching between three patterns composed of lighting of only the light-emitting elements11(1), lighting of only the light-emitting elements11(2), and lighting of the light-emitting elements11(1) and the light-emitting elements11(2) at the same time.

Alternatively, light control can be achieved by mixing daylight white and warm white instead of switching between the emission colors.

Alternatively, in the case in which the light-emitting elements11(1) have the same emission wavelengths as the same emission wavelengths of the light-emitting elements11(2), and the light-emitting elements11(1) are low-luminance products while the light-emitting elements11(2) are high-luminance products, a higher current may be allowed to flow through the light-emitting elements11(1) than a current allowed to flow through the light-emitting elements11(2). This allows for reducing unevenness in luminance.

FIG. 6is a schematic, partial, enlarged plan view ofFIG. 2. As shown inFIG. 2andFIG. 6, the first wiring5(1) includes an interelectrode trace passing through an interelectrode region11mbetween the anode electrode111and the cathode electrode112of the light-emitting element11(2). While, the second wiring5(2) does not include a trace passing through an interelectrode region In between the anode electrode111and the cathode electrode112of the light-emitting element11(1).

FIG. 6is a schematic enlarged view of a portion containing upper two light-emitting elements of the leftmost column inFIG. 2. The wiring is patterned in substantially the same way in the portion containing lower two light-emitting elements of the leftmost column inFIG. 2. The wiring is patterned in substantially the same way in the other columns.

With the first wiring5(1) and the second wiring5(2) patterned in this way, the electrodes11bof the light-emitting elements11(1) and11(2) alternately arranged can be wired without using jumpers or through holes.

Fixed-width separation grooves7(1) and7(2) are formed on both sides of the interelectrode trace passing through the interelectrode region11m. The separation groove7(1) is parallel to the separation groove7(2). There is no particular limitation on the widths of the separation grooves7(1) and7(2), and the widths are, for example, 10 μm or more and 30 μm or less.

The term “fixed-width” as used herein is not limited to the case in which the widths are completely uniform but includes the case in which the difference between the minimum width and the maximum width is 5 μm or less. The term “parallel” is not limited to the case of complete parallelism but includes the case in which the difference between the minimum interval and the maximum interval is 5 μm or less.

The separation groove7(1) separates the second wiring5(2) connected to the anode electrode111of the light-emitting element11(2) from the interelectrode trace of the first wiring5(1) passing through the interelectrode region11m. The separation groove7(2) separates the second wiring5(2) connected to the cathode electrode112of the light-emitting element11(2) from the interelectrode trace of the first wiring5(1) passing through the interelectrode region11m. There is no particular limitation on the width of the interelectrode trace of the first wiring5(1) passing through the interelectrode region11m, and the width is, for example, 30 μm or more and 100 μm or less.

The interelectrode trace passing through the interelectrode region11mand the separation grooves7(1) and7(2) extend from the interelectrode region11mof the light-emitting element11(2) in a direction toward the adjacent light-emitting element11(1) below the light-emitting element11(2) inFIG. 6.

The separation groove7(2) branches into two separation grooves7(3) and7(4) before the light-emitting element11(1). The separation groove7(3) passes through the interelectrode region11nof the light-emitting element11(1) and separates the first wiring5(1) connected to the anode electrode111of the light-emitting element11(1) from the first wiring5(1) connected to the cathode electrode112of the light-emitting element11(1).

The separation groove7(1) passes outside the anode electrode111of the light-emitting element11(1) and merges with the separation groove7(3) passing through the interelectrode region11nof the light-emitting element11(1). The separation groove7(4) passes outside the cathode electrode112of the light-emitting element11(1).

This structure in which the first wiring5(1) and the second wiring5(2) are separated and insulated by a plurality of fixed-width separation grooves can be easily obtained by a processing method employing a laser described below referring toFIG. 10Cand other drawings.

Manufacturing Process of Light-Emitting Module100

FIGS. 7A to 7C and 8A to 8Care schematic diagrams illustrating a manufacturing process of light-emitting element units according to the first embodiment. Through steps shown in7(a) to7(c) and8(a) to8(c), the light-emitting element units3are provided.

First, in a step shown inFIG. 7A, the light-transmissive member10having a uniform thickness is disposed on the upper surface of a base sheet30. Specifically, for example, the light-transmissive member10is releasably attached on the upper surface of the base sheet30with an adhesive layer therebetween.

Next, in a step shown inFIG. 7B, the structure shown inFIG. 7Ais disposed on the upper surface of a plate33such that the lower surface of the base sheet30is brought into contact with the upper surface of the plate33.

Next, in a step shown inFIG. 7C, a plurality of light-emitting elements11(1) and a plurality of light-emitting elements11(2) are alternately mounted on the light-transmissive member10such that the electrodes11bface a direction opposite to the light-transmissive member10. For example, the light-emitting elements11(1) and the light-emitting elements11(2) can be arranged in a checkered pattern. The main light-emitting surface11cof the light-emitting elements11is bonded to the light-transmissive member10.

The light-emitting elements11(1) and11(2) are bonded to the light-transmissive member10using the light-transmissive adhesive members19. The light-transmissive adhesive members19are applied on the light-transmissive member10and/or on the main light-emitting surfaces11cof the light-emitting elements11(1) and11(2) to bond the light-emitting elements11(1) and11(2) to the light-transmissive member10. At this time, the applied light-transmissive adhesive members19creep up the lateral surfaces of the light-emitting elements11(1) and11(2) to cover a portion of the lateral surfaces of the light-emitting elements11(1) and11(2) as shown inFIG. 7C. The light-transmissive adhesive members19may also be disposed between the light-transmissive member10and the main light-emitting surfaces11cof the light-emitting elements11(1) and11(2).

The gaps between the light-emitting elements11(1) and the light-emitting elements11(2) have dimensions that allow light-transmissive members10having an outer shape of a predetermined size to be obtained by performing cutting between the light-emitting elements11(1) and the light-emitting elements11(2), as shown inFIG. 8C. The gaps between the light-emitting elements11(1) and the light-emitting elements11(2) determine the outer shapes of the light-transmissive members10.

Next, in a step shown inFIG. 8A, the first light-reflective member15is formed to embed the light-emitting elements11(1) and11(2). The first light-reflective member15is preferably a white resin. The first light-reflective member15is disposed on the light-transmissive member10and hardened in a state where the first light-reflective member15embeds the light-emitting elements11(1) and11(2). The first light-reflective member15has such a thickness as to allow each of light-emitting elements11(1) and11(2) to be entirely embedded, that is, a thickness as to allow the electrodes11bof each of the light-emitting elements11(1) and11(2) to be embedded in first light-reflective member15inFIG. 8A. The first light-reflective member15can be formed using a technique such as compression molding, transfer molding, and application.

Next, in a step shown inFIG. 8B, a portion of the hardened first light-reflective member15is removed to expose the electrodes11bof the light-emitting elements11(1) and11(2). Further, electrode protective terminals, which are not shown in the drawings, may be formed using an electrically-conductive film on the electrodes11bexposed from the first light-reflective member15. In this case, the electrically-conductive film made of a material such as copper, nickel, and gold is disposed on the surface of the first light-reflective member15by sputtering or the like to be connected to the electrodes11b, and then a portion of the electrically-conductive film is removed, so that the electrically-conductive film is layered on the electrodes11bto serve as the electrode protective terminals for the light-emitting element units3. Removal of the electrically-conductive film can be performed by, for example, dry etching, wet etching, or laser ablation.

Next, in a step shown inFIG. 8C, the first light-reflective member15and the light-transmissive member10are cut to perform singulation into the light-emitting element units3(1) and3(2). In the singulated light-emitting element units3(1) and3(2), the light-emitting elements11(1) and11(2) are bonded to the light-transmissive members10. The first light-reflective members15are disposed around the light-emitting elements11(1) and11(2), and the electrodes11bare exposed on the surface of the first light-reflective members15.

To provide the light-emitting element units, all or some of the steps described above may be performed. Alternatively, the light-emitting element units may be purchased.

FIGS. 9A to 9C and 10A to 10Care schematic diagrams illustrating a manufacturing process of the light-emitting module according to the first embodiment. Each of the light-emitting element units3manufactured through the steps described above is bonded to a respective one of the recesses1bof the light-guiding plate1in steps shown inFIG. 9AtoFIG. 10C.

The light-guiding plate1having the recesses1bon the second main surface1dis first provided. For example, the light-guiding plate1is made of a thermoplastic resin such as a polycarbonate and has the recesses1bon the second main surface1das shown inFIG. 9AandFIG. 9B.

The light-guiding plate1can be molded by, for example, injection molding, transfer molding, or compression molding. The light-guiding plate1can be mass-produced at a low cost while reducing misalignment of the recesses1bby forming a material into a shape having the recesses1bwith a mold. The recesses may be formed by performing cutting with an NC processing machine or the like after the light-guiding plate1is formed into a plate. For example, the conical optical functional portions1amay also be formed on the first main surface1c.

Each of the light-emitting element units3is bonded to a respective one of the recesses1bof the light-guiding plate1. A portion of the light-emitting element unit3is disposed in the recess1bin which the light-transmissive bonding member14in a liquid state has been applied. Specifically, the light-transmissive member10of the light-emitting element unit3faces the bottom surface of the recess1b. The first light-reflective member15is located outside the recess1b.

The light-emitting element unit3is disposed such that the center of the light-transmissive member10coincides with the center of the recess1bin a plan view and is bonded to the light-guiding plate1by hardening the bonding member14. The inner lateral surfaces of the recess1bare larger than the outer lateral surfaces of the light-emitting element unit3in a plan view, which allows a clearance18between the inner lateral surfaces of the recess1band the outer lateral surfaces of the light-emitting element unit3to be formed when the light-emitting element unit3is disposed in the recess1b. The clearance18is filled with the unhardened bonding member14applied in the recess1b.

The amount of the bonding member14to be applied in the recess1bis adjusted such that the bonding member14is squeezed out of the clearance18between the inner lateral surfaces of the recess1band the outer lateral surfaces of the light-emitting element unit3to the outside of the recess1b. The bonding member14squeezed out of the recess1bcreeps up to have contact with a portion of the first light-reflective member15and to cover the portion of the first light-reflective member15. Further, the bonding member14spreads to have contact with the second main surface1dand covers a portion of the second main surface1d, so that the upper surfaces of the bonding member14are the inclined surfaces14ainclined outward from the upper end portion of the light-emitting element unit3in a vertical cross-sectional view. Each of the inclined surfaces14aof the bonding member14make an acute angle with a corresponding outer lateral surface of the first light-reflective member15. The inclination angle α is preferably in a range of 5° to 50°.

The amount of the bonding member14to be applied in the recess1bcan be such that the bonding member14covering the outer lateral surface of the light-emitting element unit3reaches a position higher than a position of the second main surface1dof the light-guiding plate1, that is, such that the bonding member14overflows the recess1boutward, when the light-emitting element unit3is bonded to the recess1b. The amount of the bonding member14to be applied is adjusted such that the position at which the inclined surface14aof the bonding member14has contact with the outer lateral surface of the first light-reflective member15is below the edge of the outer lateral surface of the light-emitting element unit3on the electrode side.

Alternatively, after the light-emitting element unit3is bonded to the light-guiding plate1, the unhardened bonding member14may be applied in the clearance18to cover a portion of the first light-reflective member15. In other words, the bonding member14is applied so that the bonding member14is accommodated in the recess1bwhen the light-emitting element unit3is disposed in the recess1b. After that, the bonding member14is further applied to cover the outer lateral surfaces of the light-emitting element unit3, specifically the outer lateral surfaces of the first light-reflective member15. At this time, the amount of the bonding member14to be applied is adjusted such that the outer lateral surfaces of the light-emitting element unit3are not entirely covered. It is more preferable that the bonding member14be applied such that the bonding member14covers a portion of the second main surface1dof the light-guiding plate1.

After the light-emitting element unit3is disposed in the light-guiding plate1, the second light-reflective member16is formed on the second main surface1dof the light-guiding plate1in a step shown inFIG. 9C. The second light-reflective member16has such a thickness as to allow the light-emitting element unit3to be embedded in the second light-reflective member16.

Next, in a step shown inFIG. 10A, a portion of the hardened second light-reflective member16is removed to expose the electrodes11bon the surface of the second light-reflective member16. The wiring formation surface16aof the second light-reflective member16is continuous with the wiring formation surface15a, and the wiring formation surface16aand the wiring formation surface15aare substantially in the same plane.

The second light-reflective member16is formed to have such a thickness as to allow the light-emitting element unit3to be embedded in the second light-reflective member16in a step shown inFIG. 9C, but the second light-reflective member16may be formed to have such a thickness that the surface of the second light-reflective member16and the surfaces of the electrodes11bare in the same plane or the surface of the second light-reflective member16is located below the surfaces of the electrodes11bto eliminate the removal step described above.

Next, in a step shown inFIG. 10B, a metal layer24is formed on the entire surface of the light-reflective member17(the wiring formation surface15aof the first light-reflective member15and the wiring formation surface16aof the second light-reflective member16) including the surfaces of the electrodes11bof the light-emitting element11. For example, the metal layer24is formed by layering Ni/Ru/Au in this order by sputtering. In this case, for example, the Ni layer can have a thickness of about 2 to 8 nm, the Ru layer can have a thickness of about 9 to 15 nm, and the Au layer can have a thickness of about 22 to 28 nm. The materials and thickness of the metal layer24described above are illustrative examples.

Instead of sputtering, the metal layer24may be formed by vapor deposition, atomic layer deposition (ALD), metal organic chemical vapor deposition (MOCVD), plasma-enhanced chemical vapor deposition (PECVD), atmospheric-pressure plasma-enhanced chemical vapor deposition, or the like.

Next, in a step shown inFIG. 10C, a portion of the metal layer24is removed using a laser to form the first wiring5(1) connecting the electrodes11bof the light-emitting elements11(1) and the second wiring5(2) connecting the electrodes11bof the light-emitting elements11(2).

Irradiating the metal layer24with laser light causes, for example, laser ablation, so that a portion of the metal layer24is removed. Laser ablation is a phenomenon that the surface of a solid is removed when the radiation intensity of laser light applied on the surface of the solid reaches or exceeds a certain magnitude (threshold). The metal layer24can be patterned by laser ablation without a mask or the like.

The laser light can be applied to the metal layer24by continuously or successively moving its irradiation spot on the metal layer24. Continuous or pulsed laser light may be applied. The intensity, the diameter of the irradiation spot, and the moving speed of the irradiation spot of the laser light can be selected in consideration of thermal conductivities of the light-reflective member17and the metal layer24and the difference in their thermal conductivities so that laser ablation of the metal layer24on the light-reflective member17takes place. The diameter of the irradiation spot is preferably about 20 μm.

The wavelength of the laser light is preferably a wavelength at which the reflectance of the metal layer24is low. For example, a wavelength at which the reflectance is 90% or less is preferably selected. For example, in the case in which Au constitutes the outermost surface of the metal layer24, a laser with an emission wavelength in the green range (such as 532 nm) or a laser with an emission wavelength in the ultraviolet range (such as 355 nm) shorter than the green range is preferred to a laser with an emission wavelength in the red range (such as 640 nm). This constitution can improve the efficiency of ablation and enhance mass production.

The angle of the laser that scans the portion between the electrodes11bis preferably corrected according to the rotation at the time of mounting of the light-emitting element11.

The step shown inFIG. 10Cincludes a step of forming, in the interelectrode region between the anode electrode111and the cathode electrode112, the interelectrode trace included in the first wiring5(1) and separating the second wiring5(2) connected to the anode electrode111from the second wiring5(2) connected to the cathode electrode112by forming two fixed-width separation grooves in the interelectrode region.

Through this step, the second wiring5(2) connected to the anode electrode111is spaced apart from the second wiring5(2) connected to the cathode electrode112, and the first wiring5(1) of another path is formed in the interelectrode region between the anode electrode111and the cathode electrode112. The efficiency of the manufacturing process can thus be enhanced.

The light-emitting module100in which a plurality of light-emitting element units3are disposed on a single light-guiding plate1is manufactured through the above steps.

As described above, the light-emitting module100has the structure in which each of the first wiring5(1) and the second wiring5(2) is directly connected to a corresponding one of the electrodes11bof the light-emitting elements11(1) and11(2) that have been mounted on the light-guiding plate1. Accordingly, the requirement to mount the light-emitting elements11(1) and11(2) accurately can be relaxed compared with the structure disclosed in Japanese Unexamined Patent Application Publication No. 2014-229676 and the like in which electrodes of light-emitting elements are connected to wiring by flip-chip bonding.

In the light-emitting module100, the light-emitting elements11(1) and the light-emitting elements11(2) that have light-emission characteristics different from light-emission characteristics of the light-emitting elements11(1) are alternately mounted, so that unevenness in luminance can be reduced. In the light-emitting module100, the light-emitting elements11(1) and the light-emitting elements11(2) having different light-emission characteristics are alternately mounted, which allows for switching between the emission colors and light control by mixing daylight white and warm white.

In the light-emitting module100, the light-guiding plate1has the recesses b, and each of the light-emitting element units3is disposed in a respective one of the recesses b, so that the thickness of an entirety of the light-emitting module can be reduced. Further, with the light-guiding plate1having the recesses1bin each of which a respective one of the light-emitting element units3is disposed, the accuracy in mounting of the light-emitting element units3on the light-guiding plate1is improved.

In particular, each of the light-emitting element units3, in which the light-emitting element11is bonded to the light-transmissive member10to be an integrated structure, is disposed in a respective one of the recesses1bof the light-guiding plate1, so that the accuracy in mounting of the light-transmissive members10and the light-emitting elements11on the light-guiding plate1is improved. This allows for improving light-emission characteristics.

In the light-emitting module100in which light emitted from the light-emitting elements11is transmitted through the light-transmissive members10, guided to the light-guiding plate1, and radiated to the outside, the light-emitting elements11, the light-transmissive members10, and the light-guiding plate1can be accurately arranged. Accordingly, light-emission characteristics such as unevenness in emission color and unevenness in luminance of light radiated from the light-guiding plate1to the outside can be reduced, so that good light-emission characteristics can be obtained.

With the bonding member14in contact with the outer lateral surfaces of the light-transmissive member10, the inner lateral surfaces of the light-guiding plate1, and the first light-reflective member15located outside the recess Tb, light emitted from the light-transmissive member10toward the second light-reflective member16can be guided more laterally outward from the light-emitting element unit3. The unevenness in luminance is thus is reduced. A larger amount of light emitted from the light-transmissive member10can be incident on the light-guiding plate1, so that the light extraction efficiency can be enhanced.

First Modified Example of First Embodiment

In a first modified example of the first embodiment, a plurality of light-guiding plates each having a single recess in which a single light-emitting element unit is disposed are arranged in a planar manner. In the first modified example of the first embodiment, description of the same components as in the embodiment described above may be omitted.

FIG. 11is a first schematic bottom view of a light-emitting module according to the first modified example of the first embodiment.FIG. 12is a second schematic bottom view of the light-emitting module according to the first modified example of the first embodiment.

As in a light-emitting module100A shown inFIG. 11, a plurality of light-guiding plates1A each having a single recess1bin which a single light-emitting element unit3is disposed may be arranged in a planar manner. In this case, the light-guiding plate TA may have inclined surfaces if inclined toward the peripheral edges on the periphery of the second main surface1d.

The second light-reflective member16is disposed on the surfaces of the inclined surfaces1f. The second light-reflective member16bonded to the inclined surfaces if prevents leakage of light to the surroundings of the light-guiding plate TA, so that reduction in the intensity of light emitted from the first main surface1cof the light-guiding plate TA can be prevented.

In the light-guiding plate TA, for example, the recess1bhas a quadrangular inner shape, and the light-emitting element unit3to be disposed in the recess1balso has a quadrangular outer shape in a plan view. In this case, for example, each outer lateral surface of the light-emitting element unit3can be parallel to a corresponding inner lateral surface of the recess1bfacing the outer lateral surface as shown inFIG. 11.

It is preferable that each outer lateral surface of the light-emitting element unit3be rotated 45° relative to a corresponding inner lateral surface of the recess Tb, as in a light-emitting module100B shown inFIG. 12. In the light-emitting modules100A and100B, it is preferable that the center of the bottom surface of the recess Tb substantially coincide with the center of the light-emitting element unit3in a plan view. This structure allows the distances from the lateral surfaces of the light-emitting element unit3to corresponding inner lateral surfaces of the recess Tb to be uniform, so that unevenness in emission color of the light-emitting modules100A and100B can be reduced.

As described above, the light-emitting element unit3having a quadrangular outer shape may be disposed such that each side intersects with the corresponding side of the quadrangular recess Tb, in other words, such that the light-emitting element unit3is rotated relative to the quadrangular recess1b. In the example shown inFIG. 12, the light-emitting element unit3is rotated 45° relative to the quadrangular recess1babout the center of the light-emitting element unit3.

Second Modified Example of First Embodiment

A second modified example of the first embodiment relates to the inclined surfaces14aof the bonding member14. In the second modified example of the first embodiment, description of the same components as in the embodiment described above may be omitted.

FIG. 13is a first schematic enlarged cross-sectional view of the vicinity of a light-emitting element unit3in a light-emitting module according to the second modified example of the first embodiment.FIG. 14is a second schematic enlarged cross-sectional view of the vicinity of a light-emitting element unit3A in the light-emitting module according to the second modified example of the first embodiment.FIG. 15is a first schematic enlarged cross-sectional view of the vicinity of an inclined surface14aof the light-emitting module shown inFIG. 13.FIG. 16is a second schematic enlarged cross-sectional view of the vicinity of the inclined surface14aof the light-emitting module shown inFIG. 13.

As in a light-emitting module100C shown inFIG. 13and a light-emitting module100D shown inFIG. 14, the inclined surface14aof the light-transmissive bonding member14can be a curved surface in a cross-sectional view. The light-emitting element unit3A shown inFIG. 14differs from the light-emitting element unit3shown inFIG. 13in that a light-transmissive resin member20is further included on the outer lateral surfaces of the light-transmissive member10.

In the case in which the inclined surface14ais a curved surface, the inclination angle α is defined as the angle between the outer lateral surface of the first light-reflective member15and the straight line (indicated by a dashed line inFIG. 15) connecting the upper end of the inclined surface14aof the bonding member14covering the outer lateral surface of the first light-reflective member15and the periphery of a portion of the second main surface1dof the light-guiding plate1covered with the inclined surface14a, as shown inFIG. 15.

In the light-emitting module100C shown inFIG. 13and the light-emitting module100D shown inFIG. 14, the inclined surface14aof the bonding member14is a convex curved surface protruding toward the recess1b. The directions of travel of light reflected at the inclined surface14acan thus vary, and unevenness in luminance can be reduced.

Further, the inclined surface14aof the bonding member14in the light-emitting module100D shown inFIG. 14covers a portion of the second main surface1dof the light-guiding plate1such that an outer periphery of the inclined surface14ais located at a position outer than an outer periphery of the inclined surface14ashown inFIG. 13. It is preferable that the bonding member14cover a greater area of the second main surface1din a cross-sectional view. This structure allows for increasing the area of the inclined surface14a, so that reflection of light may be increased. In the case in which a single light-guiding plate1is provided with a plurality of light-emitting element units3, it is preferable that each bonding member14do not have contact with the bonding member14covering an adjacent light-emitting element unit3.

In the light-emitting module100C shown inFIG. 13and the light-emitting module100D shown inFIG. 14, the inclined surfaces14amay cover the entire outer lateral surfaces of the first light-reflective member15as shown inFIG. 16. That is, in the examples shown inFIG. 13andFIG. 14, the inclined surface14acovers a portion of the outer lateral surface of the first light-reflective member15other than the upper portion of the outer lateral surface, but the upper end of the inclined surface14amay be located at the upper end of the first light-reflective member15as shown inFIG. 16.

The structure shown inFIG. 16allows light traveling in the lateral direction of the light-emitting element unit to be also reflected at the inclined surface14aand the most of the light to be used, so that light can be further spread out. There may be leakage of light from the upper portion of the first light-reflective member15covered with the bonding member14that has crept up the first light-reflective member15. However, the present light-emitting module includes the first wiring5(1) or the second wiring5(2) disposed above the first light-reflective member15, and leakage of light can therefore be reduced using reflection at the first wiring5(1) or the second wiring5(2).

Also in the case in which the inclined surface14ais not a curved surface in a cross-sectional view as shown inFIGS. 3A and 3Band other drawings, covering the entire outer lateral surfaces of the first light-reflective member15with the inclined surfaces14ain substantially the same manner as in the case shown inFIG. 16has substantially the same effects as described above.

The light-emitting module10D shown inFIG. 14further includes the light-transmissive resin member20on the outer lateral surfaces of the light-transmissive member10of the light-emitting element unit3A, so that the outer lateral surfaces of the light-transmissive member10can be protected in a step of singulation into the light-emitting units3A. For example, a light-transmissive resin with a light transmittance of 60% or more, preferably 90% or more, can be used for the light-transmissive resin member20. The first light-reflective member15of the light-emitting element unit3A is in contact with the light-transmissive member10and the light-transmissive resin member20.

For example, the light-emitting element unit3A of the light-emitting module100D shown inFIG. 14is manufactured below.FIGS. 17A to 17D and 18A to 18Care schematic diagrams illustrating a manufacturing process of the light-emitting element units according to the second modified example of the first embodiment.

First, in a step shown inFIG. 17A, the light-transmissive members10having a uniform thickness are disposed on the upper surface of the base sheet30. Specifically, for example, the light-transmissive members10are releasably attached on the upper surface of the base sheet30with an adhesive layer therebetween.

Next, in a step shown inFIG. 17B, the light-transmissive resin member20is formed on the upper surface of the base sheet30to embed the light-transmissive members10. The light-transmissive resin member20covers and protects the outer lateral surfaces of the light-transmissive members10.

Next, in a step shown inFIG. 17C, a portion of the hardened light-transmissive resin member20is removed to expose the light-transmissive members10on the upper surface of the light-transmissive resin member20.

Next, in a step shown inFIG. 17D, the structure shown inFIG. 17Cis disposed on the upper surface of the plate33such that the lower surface of the base sheet30is brought into contact with the upper surface of the plate33. After that, each of a plurality of light-emitting elements11(1) and each of a plurality of light-emitting elements11(2) are alternately mounted on a respective one of the light-transmissive members10such that the electrodes11bface a direction opposite to the light-transmissive members10. For example, the light-emitting elements11(1) and the light-emitting elements11(2) can be arranged in a checkered pattern.

Specifically, the light-transmissive adhesive members19are applied on the light-transmissive members10and/or on the main light-emitting surfaces11cof the light-emitting elements11(1) and11(2), and the main light-emitting surfaces11care bonded to the light-transmissive members10. Each of the light-emitting elements11(1) and11(2) is bonded to a respective one of the light-transmissive member10such that the center of the main light-emitting surface11cof the light-emitting element11(1) or11(2) substantially coincides with the center of the light-transmissive member10in a plan view.

Next, in a step shown inFIG. 18A, the first light-reflective member15is formed to embed the light-emitting elements11(1) and11(2). The first light-reflective member15is disposed on the light-transmissive members10and the light-transmissive resin member20and hardened such that the first light-reflective member15embeds the light-emitting elements11(1) and11(2).

Next, in a step shown inFIG. 18B, a portion of the hardened first light-reflective member15is removed to expose the electrodes11bof the light-emitting elements11(1) and11(2).

Next, in a step shown inFIG. 18C, the first light-reflective member15and the light-transmissive resin member20are cut to perform singulation into the light-emitting element units3A(1) and3A(2). In each of the singulated light-emitting element units3A(1) and3A(2), the light-transmissive member10that has the outer circumferential surface covered with the light-transmissive resin member20is bonded to the light-emitting element11(1) or11(2). Further, the first light-reflective member15is disposed around the light-emitting element11(1) or11(2), and the electrodes11bare exposed on the surface of the first light-reflective member15.

Each of the light-emitting element units3A(1) and3A(2) manufactured through the above steps is bonded to a respective one of the recesses1bof the light-guiding plate1in substantially the same manner as in the above steps shown inFIG. 9AtoFIG. 10C, and the second light-reflective member16covering the second main surface1dof the light-guiding plate1and the light-emitting element units3A(1) and3A(2) is formed. The light-emitting module100D is thus manufactured.

Third to Fifth Modified Examples of First Embodiment

Third to fifth modified examples of the first embodiment are modified examples of wiring connecting the electrodes of the light-emitting elements. In the third to fifth modified examples of the first embodiment, description of the same components as in the embodiment described above may be omitted.

FIG. 19is a schematic bottom view of an illustrative light-emitting module according to the third modified example of the first embodiment. Only the first wiring5(1) shown inFIG. 19is indicated by the dot pattern inFIG. 20A, andFIG. 20Bschematically shows the connection of the light-emitting elements11(1) by the first wiring5(1). Only the second wiring5(2) shown inFIG. 19is indicated by the dot pattern inFIG. 21A, andFIG. 21Bschematically shows the connection of the light-emitting elements11(2) by the second wiring5(2).

In a light-emitting module100E shown inFIG. 19, separation grooves enclosed by dashed lines are added to the light-emitting module100shown inFIG. 2. The circuit connection shown inFIG. 20AtoFIG. 21Bis thus provided.

As shown inFIG. 20A, for example, the portion6(1) of the first wiring5(1) serves as the anode-side external connecting terminal, and the portion6(2) of the first wiring5(1) serves as the cathode-side external connecting terminal. In this case, eight light-emitting elements11(1) are connected in series as shown inFIG. 20B. When a predetermined voltage is applied between the anode-side external connecting terminal6(1) and the cathode-side external connecting terminal6(2), a current flows through each light-emitting element11(1), and each light-emitting element11(1) emits light.

As shown inFIG. 21A, for example, the portion6(3) of the second wiring5(2) serves as the anode-side external connecting terminal, and the portion6(4) of the second wiring5(2) serves as the cathode-side external connecting terminal. In this case, eight light-emitting elements11(2) are connected in series as shown inFIG. 21A. When a predetermined voltage is applied between the anode-side external connecting terminal6(3) and the cathode-side external connecting terminal6(4), a current flows through each light-emitting element11(2), and each light-emitting element11(2) emits light.

FIG. 22is a schematic bottom view of an illustrative light-emitting module according to the fourth modified example of the first embodiment. Only the first wiring5(1) shown inFIG. 22is indicated by the dot pattern inFIG. 23A, andFIG. 23Bschematically shows the connection of the light-emitting elements11(1) by the first wiring5(1). Only the second wiring5(2) shown inFIG. 22is indicated by the dot pattern inFIG. 24A, andFIG. 24Bschematically shows the connection of the light-emitting elements11(2) by the second wiring5(2).

In a light-emitting module100F shown inFIG. 22, separation grooves enclosed by dashed lines are added to the light-emitting module100shown inFIG. 2. The circuit connection shown inFIG. 23AtoFIG. 24Bis thus provided.

As shown inFIG. 23A, for example, the portion6(1) of the first wiring5(1) serves as the anode-side external connecting terminal, and the portion6(2) of the first wiring5(1) serves as the cathode-side external connecting terminal. In this case, two series circuits each containing four light-emitting elements11(1) are connected in parallel as shown inFIG. 23B. When a predetermined voltage is applied between the anode-side external connecting terminal6(1) and the cathode-side external connecting terminal6(2), a current flows through each light-emitting element11(1), and each light-emitting element11(1) emits light.

As shown inFIG. 24A, for example, the portion6(3) of the second wiring5(2) serves as the anode-side external connecting terminal, and the portion6(4) of the second wiring5(2) serves as the cathode-side external connecting terminal. In this case, two series circuits each containing four light-emitting elements11(2) are connected in parallel as shown inFIG. 24B. When a predetermined voltage is applied between the anode-side external connecting terminal6(3) and the cathode-side external connecting terminal6(4), a current flows through each light-emitting element11(2), and each light-emitting element11(2) emits light.

FIG. 25is a schematic bottom view of an illustrative light-emitting module according to the fifth modified example of the first embodiment. Only the first wiring5(1) shown inFIG. 25is indicated by the dot pattern inFIG. 26A, andFIG. 26Bschematically shows the connection of the light-emitting elements11(1) by the first wiring5(1). Only the second wiring5(2) shown inFIG. 25is indicated by the dot pattern inFIG. 27A, andFIG. 27Bschematically shows the connection of the light-emitting elements11(2) by the second wiring5(2).

In a light-emitting module100G shown inFIG. 25, separation grooves enclosed by dashed lines are added to the light-emitting module100shown inFIG. 2, and the separation grooves otherwise provided in the regions enclosed by dot-dash lines are eliminated. The circuit connection shown inFIG. 26AtoFIG. 27Bis thus provided.

As shown inFIG. 26A, for example, the portion6(1) of the first wiring5(1) serves as the anode-side external connecting terminal, and the portion6(2) of the first wiring5(1) serves as the cathode-side external connecting terminal. In this case, four series circuits each containing two light-emitting elements11(1) are connected in parallel as shown inFIG. 26B. When a predetermined voltage is applied between the anode-side external connecting terminal6(1) and the cathode-side external connecting terminal6(2), a current flows through each light-emitting element11(1), and each light-emitting element11(1) emits light.

As shown inFIG. 27A, for example, the portion6(3) of the second wiring5(2) serves as the anode-side external connecting terminal, and the portion6(4) of the second wiring5(2) serves as the cathode-side external connecting terminal. In this case, four series circuits each containing two light-emitting elements11(2) are connected in parallel as shown inFIG. 27B. When a predetermined voltage is applied between the anode-side external connecting terminal6(3) and the cathode-side external connecting terminal6(4), a current flows through each light-emitting element11(2), and each light-emitting element11(2) emits light.

As described above, the separation grooves can be easily added or eliminated on the basis of the light-emitting module100shown inFIG. 2. Light-emitting modules including various wiring patterns in each of which a plurality of light-emitting elements11(1) include light-emitting elements connected in parallel and light-emitting elements connected in series and in each of which a plurality of light-emitting elements11(2) include light-emitting elements connected in parallel and light-emitting elements connected in series can thus be provided. The additional separation grooves can be formed with a laser, similarly to the other separation grooves.

Second Embodiment

In a second embodiment, in illustrative liquid-crystal display device employing the light-emitting module according to the first embodiment as a backlight source is described. In the second embodiment, description of the same components as in the embodiment described above may be omitted.

FIG. 28is a schematic diagram showing the structure of the illustrative liquid-crystal display device according to the second embodiment. As shown inFIG. 28, a liquid-crystal display device1000includes a liquid-crystal panel120, two lens sheets110aand110b, a diffusion sheet110c, and the light-emitting module100according to the first embodiment in this order from the top.

The liquid-crystal display device1000is what is called a direct-lit liquid-crystal display device in which the light-emitting module100is disposed below the liquid-crystal panel120. In the liquid-crystal display device1000, the liquid-crystal panel120is irradiated with light emitted from the light-emitting module100. Other members such as a polarizing film and a color filter may be included in addition to the components described above.

Generally, because the distance between a liquid-crystal panel and the light-emitting module is reduced in a direct-lit liquid-crystal display device, unevenness in emission color and unevenness in luminance of the light-emitting module may affect unevenness in emission color and unevenness in luminance of the liquid-crystal display device. Accordingly, a light-emitting module with reduced unevenness in emission color and unevenness in luminance is desired as a light-emitting module for a direct-lit liquid-crystal display device. By using the light-emitting module100for the liquid-crystal display device1000, unevenness in luminance and unevenness in emission color can be reduced, while maintaining a reduced thickness of the light-emitting module100, such as 5 mm or less, 3 mm or less, and 1 mm or less.

The case in which a single light-emitting module100is used as a backlight for the single liquid-crystal display device1000is not limiting. A plurality of light-emitting modules100may be arranged to constitute a backlight for the single liquid-crystal display device1000. For example, producing a plurality of small light-emitting modules100and inspecting each of the small light-emitting modules100allows for improving the yield compared with the case of producing a large light-emitting module100in which many light-emitting elements11are mounted.

The light-emitting module100is preferably used as a backlight for the liquid-crystal display device1000because light with uniform intensity is emitted from the light-guiding plate1as described above.

The use described above is not limiting, and the light-emitting module100can be suitably used as a backlight for a television, a tablet, a smartphone, a smartwatch, a head-up display, digital signage, or a bulletin board. The light-emitting module100can also be used as a light source for lighting for an emergency light, a linear lighting, various illuminations, or vehicle installation. Any of the light-emitting modules100A to100G may be used instead of the light-emitting module100.

Preferable embodiments and the like have been described above in detail, but the embodiments and the like described above are not limiting. Various modified examples and replacement can be performed on the embodiments and the like described above within the scope of the claims.

For example, a light-transmissive member having a function such as diffusing may be further layered on the light-guiding plate1. In the case in which the optical functional portion1ais a recess, the light-transmissive member is preferably disposed such that the light-transmissive member blocks the opening (in other words, a portion close to the first main surface1cof the light-guiding plate1) of the recess but does not fill up the recess. This structure allows an air layer to be present in the recess of the optical functional portion1aand allows light emitted from the light-emitting element11to spread out well.