Light-emitting module and surface-emitting light source including a plurality of wiring formations between two terminals

A light-emitting module according to an embodiment includes a plurality of light-emitting elements, light-guiding plates each having a light-exiting surface, and a wiring layer connected to electrodes of the plurality of light-emitting elements on a surface opposite to the light-exiting surface. The wiring layer includes a first terminal, a second terminal, a first wiring pattern connecting the first terminal and the second terminal, a second wiring pattern connecting the first terminal and the second terminal, a third wiring pattern disposed between the first wiring pattern and the second wiring pattern to connect the first terminal and the second terminal, a fourth wiring pattern connecting the first to third wiring patterns in parallel, the fourth wiring pattern being connected to the first terminal, and a fifth wiring pattern connecting the first to third wiring patterns in parallel, the fifth wiring pattern being connected to the second terminal.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2019-103227 filed on May 31, 2019, and Japanese Patent Application No. 2020-017838 filed on Feb. 5, 2020, the disclosures of which are hereby incorporated by reference in their entireties.

BACKGROUND

Embodiments of the present disclosure relate to a light-emitting module and a surface-emitting light source.

There is a backlight module or a lighting module employing a surface-emitting light source in which a plurality of light-emitting elements such as small LEDs are two dimensionally arranged on a plane (See, for example, Japanese Patent Application No. 2011-129646).

In such a surface-emitting light source, variances in luminance between light-emitting elements cause luminance unevenness, which may affect the quality of images or illumination.

SUMMARY

According to certain embodiments, a light-emitting module and a surface-emitting light source with reduced variations in luminance can be provided.

A light-emitting module according to an embodiment of the present disclosure includes a plurality of light-emitting elements arranged in a plan, a light-guiding plate, and a wiring layer. The light-guiding plate has a light-exiting surface and provided for the plurality of light-emitting elements. The wiring layer is disposed on a wiring formation surface opposite to the light-exiting surface of the light-guide plate. The wiring formation surface is constituted of electrodes of the plurality of light-emitting elements exposed at the wiring formation surface, and connected to the electrodes of the plurality of light-emitting elements. The wiring layer comprises a first terminal, a second terminal capable of receiving a lower voltage than a voltage applied to the first terminal, and a plurality of wiring patterns. The wiring patterns include: a first wiring pattern connecting the first terminal and the second terminal; a second wiring pattern connecting the first terminal and the second terminal; a third wiring pattern disposed between the first wiring pattern and the second wiring pattern to connect the first terminal and the second terminal; a fourth wiring pattern connecting the first wiring pattern, the second wiring pattern, and the third wiring pattern in parallel, the fourth wiring pattern being connected to the first terminal; and a fifth wiring pattern connecting the first wiring pattern, the second wiring pattern, and the third wiring pattern in parallel, the fifth wiring pattern being connected to the second terminal. A wiring length from the first terminal through the first wiring pattern to the second terminal, a wiring length from the first terminal through the second wiring pattern to the second terminal, and a wiring length from the first terminal through the third wiring pattern to the second terminal are the same. A resistance of the third wiring pattern is lower than a resistance of the first wiring pattern and lower than a resistance of the second wiring pattern.

According to the certain embodiments of the present disclosure, a light-emitting module and a surface-emitting light source with reduced variances in luminance can be provided.

DESCRIPTION

The following describes embodiments of the present invention referring to the accompanying drawings.

The drawings are schematic or conceptual, and the relationship between the thickness and the width of each unit, the ratio between the sizes of units, and other relationships are not necessarily the same as the actual relationships. Also, the dimensions and ratios of the same unit may be different between drawings.

In the specification and the drawings of the present application, substantially the same element as an element described referring to a drawing previously described is indicated by the same reference numeral, and its detailed description is omitted as appropriate.

First Embodiment

FIG. 1is a schematic plan view showing an example of a portion of a light-emitting module according to the present embodiment.

FIG. 1schematically shows the layout of wiring patterns of a wiring layer40in a light-emitting module20of the present embodiment. As described below, the wiring layer40is disposed on a wiring formation surface34e(FIG. 6BandFIG. 7) of the light-emitting module20.

Three-dimensional coordinates can be used in the following description. The wiring layer40and the wiring formation surface are parallel to the XY plane. The three-dimensional coordinates are in a right-handed coordinate system, and the Z-axis extends in a facing direction from the plane of the drawing. Light-emitting elements32are mounted on the wiring patterns of the wiring layer40, and the light-exiting surfaces of the light-emitting elements32face the negative direction of the Z-axis.

The light-emitting module20includes a plurality of light-emitting elements32and the wiring layer40as shown inFIG. 1. The light-emitting elements32are disposed on the wiring layer40and are therefore arranged substantially in the XY plane. As described below, the light-exiting surfaces of the light-emitting elements32face the negative direction of the Z-axis, and the light-exiting surfaces of the light-emitting elements32facing the same direction constitute the surface-emitting light source.

The wiring layer40includes a plurality of wiring patterns that are substantially parallel to the XY plane, and are each used for electrical connection of the corresponding light-emitting elements32.

The wiring layer40includes terminals41pand41nand wiring-pattern groups40aand40b. The wiring-pattern groups40aand40bare connected in parallel between the terminals41pand41n. A DC or pulse voltage lower than the voltage applied to the terminal (first terminal)41pcan be applied to the terminal (second terminal)41n.

The wiring-pattern groups40aand40bare geometrically equivalent circuits. In other words, the wiring-pattern groups40aand40bare constituted of the same components and are symmetric about a point C1. The point C1is the center of the wiring layer40. More specifically, the wiring layer40has a rectangular shape having a length (width) Ws in the X-axis direction and a length Ls in the Y-axis direction in a top view of the XY plane, and the point C1, which is the center of the wiring layer40, is located at the point of (½)×Ws and (½)×Ls, in other words, located in the middle of Ws and middle of Ls. As the wiring-pattern groups40aand40bare equivalent as described above, the constitution of the wiring-pattern group40awill be mainly described below.

The terminal41pis located at a position including the point at which the straight line parallel to the X-axis passing through the point C1intersects with the center in the width direction of a Y wiring pattern42a. The terminal41nis located at a position including the point at which the straight line parallel to the X-axis passing through the point C1intersects with the center in the width direction of a Y wiring pattern43a.

The wiring-pattern group40aincludes wiring patterns (hereinafter referred to as Y wiring patterns)42ato45a(i.e.,42a,43a,44aand45a) extending in the Y-axis direction, and wiring patterns (hereinafter referred to as X wiring patterns)46aand47aextending in the X-axis direction. The wiring-pattern group40bincludes Y wiring patterns42bto45band X wiring patterns46band47b.

The Y wiring patterns44aand45a(hereinafter referred to as third wiring patterns) are disposed between the Y wiring patterns42a(hereinafter referred to as first wiring pattern) and43a(hereinafter referred to as second wiring pattern). The Y wiring patterns42ato45ahave substantially the same wiring lengths and are disposed at substantially regular intervals. The wiring lengths of the Y wiring patterns42ato45aeach refer to the length from the point, at which the center line in the width direction of corresponding one of the Y wiring patterns42ato45aintersects with the center line in the width direction of the X wiring pattern46a, to the point, at which the center line in the width direction of corresponding one of the Y wiring patterns42ato45aintersects with the center line in the width direction of the X wiring pattern47a. In this example, the wiring lengths of the Y wiring patterns42ato45aare respectively a wiring length L1in the Y-axis direction. The Y wiring patterns42a,44a,45a, and43aare aligned substantially parallel to each other in this order in the positive direction of the X-axis at substantially regular intervals L2. The wiring length L1refers to the distance between the centers of the widths of the X wiring patterns46aand47a. The intervals L2are respectively the distances between adjacent Y wiring patterns, that is, the distances between the centers of the widths of the Y wiring patterns42ato45a.

The X wiring pattern46a(hereinafter referred to as fourth wiring pattern) is connected to one end of each of the Y wiring patterns42ato45a. The X wiring pattern47a(hereinafter referred to as fifth wiring pattern) is connected to the other end of each of the Y wiring patterns42ato45a. That is, the Y wiring patterns42ato45aconnect the X wiring patterns46aand47a. In other words, the X wiring patterns46aand47aconnect the Y wiring patterns42ato45ain parallel. The X wiring patterns46aand47aare disposed substantially parallel to each other at the interval L1.

The X wiring pattern46ais connected to a wiring pattern49aat a joint49a1between the X wiring pattern46aand the Y wiring pattern42a, and is connected to the terminal41pvia the wiring pattern49a. The wiring pattern49ais elongated in the Y-axis direction. The position of the joint49a1is the point of intersection of the center line in the width direction of the Y wiring pattern42aand the center line in the width direction of the X wiring pattern46a.

The X wiring pattern47ais connected to a wiring pattern48aat a joint48a1between the X wiring pattern47aand the Y wiring pattern43a, and is connected to the terminal41nvia the wiring pattern48a. The wiring pattern48ais elongated in the Y-axis direction. The position of the joint48a1is the point of intersection of the center line in the width direction of the Y wiring pattern43aand the center line in the width direction of the X wiring pattern47a.

The length of the wiring pattern48afrom the joint48a1to the terminal41nis a length L3. The length of the wiring pattern49afrom the joint49a1to the terminal41pis a length L4. The same applies to the wiring-pattern group40b. That is, a wiring pattern48bhas the length L3, and a wiring pattern49bhas the length L4. The wiring-pattern groups40aand40bare connected in parallel by the terminals41pand41n, and therefore the path length from the terminal41pto the terminal41nthrough the wiring-pattern group40ais substantially equal to the path length from the terminal41pto the terminal41nthrough the wiring-pattern group40b. The following describes the above feature more specifically.

In the wiring-pattern group40a, the wiring length from the terminal41pthrough the Y wiring pattern42ato the terminal41nis L4+L1+3×L2+L3=L4+L1+3×L2+L3.

As for the Y wiring pattern44a, the wiring length from the terminal41pthrough the Y wiring pattern44ato the terminal41nis L4+L2+L1+2×L2+L3=L4+L1+3×L2+L3.

As for the Y wiring pattern45a, the wiring length from the terminal41pthrough the Y wiring pattern45ato the terminal41nis L4+2×L2+L1+L2+L3=L4+L1+3×L2+L3.

As for the Y wiring pattern43a, the wiring length from the terminal41pthrough the Y wiring pattern43ato the terminal41nis L4+3×L2+L1+L3=L4+L1+3×L2+L3.

As described above, as for the Y wiring patterns42ato45aseparated from each other and connected in parallel by the X wiring patterns46aand47a, the wiring length from the terminal41pto the terminal41ndoes not substantially vary whichever one of the Y wiring patterns42ato45ais selected. That is, the wiring layer40is a wiring pattern constituted by substantially equal-length wiring.

In this example, the thicknesses of the terminals41pand41nand the X and Y wiring patterns42ato49a(i.e.,42a,43a,44a,45a,46a,47a,48aand49a) and42bto49b(i.e.,42b,43b,44b,45b,46b,47b,48band49b) are the same.

The terminals41pand41nand the X and Y wiring patterns42ato49aand42bto49bof the wiring layer40are formed of, for example, sintered bodies of electrically conductive particles or paste containing electrically conductive particles. The electrically conductive particles are, for example, particles of Ag or Cu.

FIG. 2AandFIG. 2Bare schematic plan views showing an example of a portion of the light-emitting module of the first embodiment.

FIG. 2Ais a schematic enlarged view of the Y wiring pattern42a. The Y wiring patterns43a,42b, and43bhave substantially the same structure.

As shown inFIG. 2A, the Y wiring pattern42aincludes a plurality of wiring patterns42a1,42a2, and42a3. The wiring pattern42a1is connected to the X wiring pattern47a. The wiring pattern42a3is connected to the X wiring pattern46a. A gap42a4exposed from the wiring formation surface34eis formed between the wiring patterns42a1and42a2. A gap42a5is formed between the wiring patterns42a2and42a3. That is, the wiring42a2is disposed between the wiring patterns42a1and42a3with the gaps42a4and42a5on both sides therebetween.

A width Wp1of the wirings42a1to42a3(i.e.,42a1,42a4,42a2,42a5and42a3) is constant throughout the wiring length L1.

The light-emitting elements32(FIG. 1) are mounted astride the gaps42a4and42a5. That is, in this example, the anode terminal of the light-emitting element32mounted astride the gap42a4is connected to the wiring pattern42a2, and its cathode terminal is connected to the wiring pattern42a1. The anode terminal of the light-emitting element mounted astride the gap42a5is connected to the wiring pattern42a3, and its cathode terminal is connected to the wiring pattern42a2.

The two light-emitting elements32disposed on the Y wiring pattern42aare connected in series by the wirings42a1to42a3.

FIG. 2Bis a schematic enlarged view of the Y wiring pattern44a. The Y wiring patterns45a,44b, and45bhave substantially the same structure.

As shown inFIG. 2B, the Y wiring pattern44aincludes a plurality of wiring patterns44a1,44a2, and44a3. The wiring pattern44a1is connected to the X wiring pattern47a. The wiring pattern44a3is connected to the X wiring pattern46a. A gap44a4is formed between the wiring patterns44a1and44a2. A gap44a5is formed between the wiring patterns44a2and44a3. That is, the wiring44a2is disposed between the wiring patterns44a1and44a3with the gaps44a4and44a5on both sides therebetween.

Similarly to the case of the Y wiring pattern42a, the light-emitting elements32are mounted astride the gaps44a4and44a5. The two light-emitting elements32are connected in series by the wirings44a1to44a3(i.e.,44a1,44a4,44a2,44a5and44a3).

In this example, the wiring44a2has a different shape from the shapes of other wirings44a1and44a3. The central portion of the wiring44a2is a rectangular portion having a width Wp2and a length Lp2. The width Wp2is wider than the width Wp1of other portions or wirings44a1and44a3. The length Lp2is shorter than the wiring length L1of the Y wiring pattern44a. In this example, the width of the wiring44a1near the joint between the wiring44a1and the X wiring pattern47ais greater than the width Wp1of other portions.

As described below, in the case in which the clearance between the electrodes of the light-emitting element32is narrow, the wiring layer can be formed such that the electrodes of the light-emitting element32are short-circuited, and then the wiring between the electrodes can be cut by, for example, laser light. In the case in which the wiring is thicker, the portion to be cut at which the wiring is partially removed by laser light is long, and the cutting may be incomplete. The width of the portion of the wiring on which the light-emitting element32is to be mounted is therefore often limited. Accordingly, it is preferable to adjust the resistance by changing the widths and thicknesses of the portions of the wiring44a2except for the portions on which the light-emitting elements32are to be mounted.

As for the Y wiring patterns42ato45a(i.e.,42a,43a,44aand45a), the widths and lengths of the wirings44a1to44a3are appropriately determined to adjust the resistances of the Y wiring patterns44aand45adisposed between the Y wiring patterns42aand43asubstantially parallel to each other.

As described above, in the present embodiment, the Y wiring patterns42ato45aand42bto45bconnected in parallel are connected to the terminals41pand41nto constitute equal-length wiring. In this case, electric currents that flow through the Y wiring patterns42ato45aand42bto45bcan be substantially equalized by adjusting the resistance of each of the Y wiring patterns42ato45aand42bto45b.

The light-emitting elements32are disposed at regular intervals in the X direction and regular intervals in the Y direction as described below, so that the luminances of the light-emitting elements32can be made substantially uniform by making the electric currents that flow through the light-emitting elements32substantially equal. The light-emitting elements32are disposed at regular intervals in the XY plane, and emit light with substantially uniform luminance, so that the light-emitting module20functions as a surface-emitting light source that emits light with uniform luminance.

FIG. 3is a schematic bottom view showing an example of a portion of the light-emitting module according to the embodiment.

As shown inFIG. 3, a plurality of light-emitting elements32of the light-emitting module20are disposed at substantially regular intervals in the X-axis direction and disposed at substantially regular intervals in the Y-axis direction. The intervals between the light-emitting elements32are indicated by P2in the X-axis direction and P1in the Y-axis direction.

A structure in which the light-guiding plate34is combined with the light-emitting elements32is referred to as a cell30. The light-emitting elements32are disposed substantially at the center of each cell of a light-guiding plate34. Each cell of the light-guiding plate34has a substantially rectangular shape with a width We in the X-axis direction and a length Lc in the Y-axis direction in a plan view of the XY plane. The light-guiding plate34guides light emitted from the light-emitting elements32(which are disposed substantially at the center of each cell) to the negative direction of the Z-axis. That is, the surface of the light-guiding plate34shown inFIG. 3serves as the light-exiting surface.

In this example, the light-emitting module20includes a plurality of cells30two-dimensionally arranged in a four-by-four array. The light-emitting module20has a width Ws of 4×Wc in the X-axis direction and a length Ls of 4×Lc in the Y-axis direction.

In this example, the light-emitting elements32are light-emitting diodes, such as white light-emitting diodes. Colored light-emitting diodes are also applicable. The colored light-emitting diodes can be of the same color or different colors. White diodes can be mixed with colored light-emitting diodes. The light-emitting elements32do not have to be light-emitting diodes but can be laser diodes or the like.

The cells are two-dimensionally arranged in a four-by-four array in the light-emitting module20of this example, but the arrangement of the cells is not limited to this arrangement. The arrangement may be, for example, a two-by-eight array. The number of the cells included in the light-emitting module20is also not limited to 16, and a desired number is applicable.

The circuit is constituted of two series connections by eight parallel connections in the above description, but this constitution is not limited thereto. For example, a constitution of four series connections by four parallel connections can be employed. The arrangement of the light-emitting elements32included in the light-emitting module20is not limited to four by four but can be, for example, two by eight. The number of the light-emitting elements32included in the light-emitting module20is also not limited to 16, and a desired number can be selected.

The operation of the light-emitting module of the embodiment will be described.

In this example, two light-emitting elements are connected in series by the wiring layer40, and four sets of the two light-emitting elements each connected in series are connected in parallel to constitute the two of the wiring-pattern groups40aand40bas described above. The two of the wiring-pattern groups40aand40bare connected in parallel. That is, the light-emitting module20in this example includes 16 light-emitting elements of 2 series connections by 8 parallel connections.

FIG. 4is an equivalent circuit diagram simplified to illustrate the operation of the light-emitting module20of the embodiment.

As shown inFIG. 4, an equivalent circuit140of the circuit constituted in the wiring layer40includes terminals141pand141n, a first equivalent circuit140a, and a second equivalent circuit140b, which are connected in parallel between the terminals141pand141n. The first equivalent circuit140acorresponds to the wiring-pattern group40a, and the second equivalent circuit140bcorresponds to the wiring-pattern group40b. As described above, the equivalent circuits140aand140bare equivalent and have the same pattern. The description of the equivalent circuit140bis omitted as appropriate.

The equivalent circuit140aincludes a plurality of light-emitting elements132and a plurality of wirings142ato149a(i.e.,142a,143a,144a,145a,146a,147a,148aand149a). Two light-emitting elements132are connected in series on each of the wirings142ato145a. The series circuits each including two light-emitting elements132are connected in parallel by the wirings146aand147a.

The above parallel circuit is connected to the terminal141pvia the wiring149aand to the terminal141nvia the wiring148a.

The same applies to the equivalent circuit140b, which includes a plurality of light-emitting elements132and a plurality of wirings142bto149b(i.e.,142b,143b,144b,145b,146b,147b,148band149b).

The circuit configuration of the light-emitting module20is not limited to two series connections by eight parallel connections. A desired configuration can be employed as long as the Y wiring patterns constitute equal-length wiring with respect to the terminals as described above. For example, a circuit configuration of four series connections by four parallel connections or a circuit configuration of eight series connections by two parallel connections can be employed. In the case in which the number of the cells30is different, appropriate numbers of series and parallel connections can be selected.

An equivalent circuit using the resistance of each of the wirings142ato149a(i.e.,142a,143,a,144aand145a) can be derived on the assumption that the light-emitting elements132in the equivalent circuit140described above are constant-voltage circuits with a voltage of 0 V or a sufficiently low voltage.

FIG. 5is an equivalent circuit diagram simplified to illustrate the operation of the light-emitting module of the embodiment.

FIG. 5shows a resistor network based on the first equivalent circuit140a. The second equivalent circuit140bcan be regarded as the same resistor network.

An equivalent circuit240for the wiring layer40includes portions242ato245a(i.e.,242a,243a,244aand245a) respectively corresponding to the Y wiring patterns42ato45a, and portions246aand247arespectively corresponding to the X wiring patterns46aand47aas shown inFIG. 5. The equivalent circuit240also includes portions248aand249arespectively corresponding to the wiring patterns48aand49a. Each of the portions242ato249a(i.e.,242242a,243a,244a,245a,246a,247a,248a,249a) has a resistance based on the material constituting the wiring pattern and its width, length, and thickness.

The portion242ahas a resistance R1. The portion243ahas a resistance R2. The portions244aand245apositioned between the portions242aand243arespectively have resistances R3and R4.

As for the portion247a, the resistance between the portions242aand244ais r13, the resistance between the portions244aand245ais r34, and the resistance between the portions245aand243ais r42.

As for the portion246a, the resistance between the portions242aand244ais r31, the resistance between the portions244aand245ais r43, and the resistance between the portions245aand243ais r24.

If equal-length wiring is constituted between the terminals241pand241nsuch that the path lengths through the portions242ato245aare substantially equal as described above, for example, the resistances r13, r34, r42, r31, r43, and r24are equal, and the resistances R1, R2, R3, and R4are equal.

A current source is connected between the terminals241pand241nunder the above conditions, and the electric currents of the portions242ato245aare simulated while sweeping the current. The result shows that these electric currents are not equal.

More specifically, it is observed that electric currents I1and I2that flow through the outside portions242aand243aare higher than electric currents I3and I4that flow through the portions244aand245apositioned between the portions242aand243a.

To equalize all the electric currents that flow through the portions242ato245a, the resistances of the portions242ato245aare required to be adjusted. The portions242ato245aare connected in parallel by the portions246aand247a. Hence, the resistances R1and R2of the portions242aand243apositioned at outside are lower than the resistances R3and R4of the portions244aand245apositioned between the portions242aand243a.

Accordingly, adjusting the resistances R3and R4can make the electric currents I1and I2that flow through the portions242aand243asubstantially equal to the electric currents I3and I4that flow through the portions244aand245a. In this case, the resistances R3and R4are lower than the resistances R1and R2.

In the case in which the thickness of the wiring patterns is constant throughout the wiring layer40, the wiring patterns44aand45aare formed in greater widths than the widths of the wiring patterns42aand43a.

In the case in which the wiring patterns in the wiring layer40are formed in variable thicknesses, the wiring patterns44aand45acan be formed in greater thicknesses than the thicknesses of the wiring patterns42aand43a.

The effects of the light-emitting module of the present embodiment will be described.

In the light-emitting module20of the present embodiment, the resistance of each of the Y wiring patterns connected in parallel and provided with the light-emitting elements32is appropriately adjusted, so that the electric currents that flow through the light-emitting elements mounted on the Y wiring patterns can be substantially equalized. Substantially equalizing the electric currents that flow through the light-emitting elements arranged in a plane can reduce luminance variances in the plane, to thereby providing a surface-emitting light source that emits light with uniform luminance.

The light-emitting module20of the present embodiment can have a structure in which the light-emitting elements32are densely arranged because the light-emitting elements32are disposed at regular intervals in the XY plane. Employing such a structure in the light-emitting module20of the present embodiment is particularly effective because the differences of the electric currents that flow through the light-emitting elements greatly affect the luminance variances in the plane.

The Y wiring patterns do not have to be arranged parallel to each other, and the wiring lengths of the Y wiring patterns do not have to be equal, as long as the resistances of the wiring patterns are set so as to substantially equalize the electric currents that flow through the Y wiring patterns separated from each other and connected in parallel by the X wiring patterns as described above.

The case in which two Y wiring patterns are connected between two Y wiring patterns has been described above, but five or more Y wiring patterns can be included as long as three or more Y wiring patterns are included. In the case in which five Y wiring patterns are included, for example, three Y wiring patterns positioned between outside Y wiring patterns respectively have resistances lower than the resistances of the outside Y wiring patterns. For example, the three Y wiring patterns positioned between the outside Y wiring patterns respectively have widths greater than the widths of the outside Y wiring patterns.

Second Embodiment

FIG. 6Ais an illustrative schematic plan view of a surface-emitting light source of the present embodiment.

FIG. 6Bis a schematic cross-sectional view taken along the line AA′ and viewed in a direction of the arrows ofFIG. 6A.

As shown inFIG. 6A, a surface-emitting light source10includes a plurality of light-emitting modules20. The light-emitting modules20are arranged in the XY plane. In this example, four light-emitting modules20are arranged in the X-axis direction, and two light-emitting modules20are arranged in the Y-axis direction, to be arranged in two dimensions as a whole.

The surface-emitting light source10includes connectors70pand70n. A lower DC or pulse voltage than the voltage applied to the connector70pis applied to the connector70n.

The light-emitting modules20constituting the surface-emitting light source10are connected to a board60with an insulating connecting member50interposed therebetween as shown inFIG. 6B. The insulating connecting member50is, for example, a bonding sheet in which an adhesive has been applied over the both surfaces of a resin sheet. The board60is, for example, a flexible printed circuit board formed of an insulating base material such as a polyimide.

The board60includes a wiring pattern62. In this example, the wiring pattern62is formed on the surface opposite to the surface on which the connecting member50is disposed. The board60further includes an insulating layer66covering the wiring pattern62. The insulating layer66can secure insulation of the wiring pattern62. The insulating layer66is, for example, a resist.

The board60is provided with the connector70n(and the connector70pnot shown in this drawing) to enable the surface-emitting light source10to be electrically connected to an external circuit via the connectors70pand70n.

Vias70run through the connecting member50and the board60. Via holes64for the vias70reach the wiring layer40of the light-emitting module20, and the vias70electrically connect the light-emitting module20to the wiring pattern62of the board60. The vias70are respectively connected to the terminals41pand41nin the wiring layer40of the light-emitting module20.

For example, the wiring pattern62on the board60connects the light-emitting modules20in parallel. The connection is not limited thereto, and the wiring pattern62is appropriately formed to constitute a desired circuit. For example, different operating power sources can be connected to a plurality of light-emitting modules20electrically separated from each other to adjust the luminance and to set the chromaticity by screen division.

FIG. 7is a schematic enlarged cross-sectional view of the portion B ofFIG. 6B.

As shown inFIG. 6B, the light-emitting module20includes a plurality of cells30. The cells30are each has a structure in which the light-emitting element32is supported by the light-guiding plate34as described referring to the first embodiment above.

The cell30includes the light-emitting element32and a portion of the light-guiding plate34. The light-guiding plate34has a light-exiting surface34afacing the negative direction of the Z-axis. The light-guiding plate34has a surface34bopposite to the light-exiting surface34a. The surface34bof the light-guiding plate34has a recess34c.

The light-emitting element32is inserted into the recess34cand fixed to the light-guiding plate34by an insulating fixing member33.

On the surface34b, an insulating member34dis provided with such a thickness that the electrodes of the light-emitting element32are exposed. In this example, the insulating member34dhas a wiring formation surface34eopposite to the surface connected to the surface34bof the light-guiding plate34.

The wiring layer40is disposed on the wiring formation surface34e. The wiring layer40is the same as in the first embodiment described above. The two electrodes of the light-emitting element32constitute a circuit with the wiring pattern of the wiring layer40.

In the case in which the light-emitting element32is in small size, the distance between the electrodes is small, and the gap of the wiring pattern is short. Hence, in this example, an insulating resin35is applied at a position on the wiring layer40corresponding to the gap between the electrodes of the light-emitting element32. The insulating resin35is, for example, an acrylic resin, epoxy-based resin, or a resist.

The light-exiting surface34aof the light-guiding plate34preferably has at least one depressed portion34f. The depressed portion34fis a depression, preferably having, for example, the shape of a cone, a truncated cone, a polygonal pyramid, or a truncated polygonal pyramid.

FIG. 8is an illustrative schematic cross-sectional view of the light-emitting element.

As shown inFIG. 8A, the light-emitting element32includes a semiconductor chip32e, two electrodes32b1and32b2, and a phosphor layer32c. The surface provided with the phosphor layer32cis the main light-exiting surface of the semiconductor chip32e. The semiconductor chip32eincludes the electrodes32b1and32b2on the side of the surface opposite to the surface provided with the phosphor layer32c. The electrodes32b1and32b2are an anode electrode and a cathode electrode.

The semiconductor chip32esupports the phosphor layer32cusing an insulating supporting member32d. The supporting member32dis formed of, for example, a transparent resin. An insulating member32fcovers the semiconductor chip32eand the supporting member32d. The insulating member32fis formed of, for example, a white resin.

As shown also in this drawing, the electrodes32b1and32b2of the light-emitting element32are exposed from the insulating member34d. The surface of the insulating member34don which the electrodes32b1and32b2are exposed is the wiring formation surface34e. The wiring layer40indicated by dashed lines is disposed on the wiring formation surface34e.

FIG. 8Bis a schematic cross-sectional view of another example of the light-emitting element. The upper surface and the lateral surfaces of the semiconductor chip32eare covered with the phosphor layer32c. The lower surface of a semiconductor chip32eand the lower surface of the phosphor layer32care covered with the insulating member32f. The insulating member32fis, for example, an insulating white resin member containing titanium oxide as a light-diffusing material.

A method of manufacturing the surface-emitting light source10of the present embodiment will be described.

FIG. 9AtoFIG. 10Bschematically illustrate the method of manufacturing the surface-emitting light source of the present embodiment.

InFIG. 9AtoFIG. 9D, upper drawings are schematic perspective views of a structure for producing the light-emitting module20, and lower drawings are schematic cross-sectional views of a portion corresponding to a cell in the structure.

FIG. 10Ais a schematic perspective view of the structure, andFIG. 10Bis a schematic cross-sectional view that shows the assembly process of the finished light-emitting module20.

A structure134is provided as shown inFIG. 9A. The structure134is formed by, for example, injection molding of a synthetic resin such as a polycarbonate. The structure134has the light-exiting surface34aand the surface opposite to the light-exiting surface34a. The single structure134shown inFIG. 9Aincludes a plurality of cells shown inFIG. 6Band other drawings, and the cells are each indicated by thin lines in the schematic perspective view. The same applies toFIG. 9BtoFIG. 9D.

The light-emitting element32is mounted at the surface34bside of the structure134as shown inFIG. 9B. The light-emitting element32is disposed into the recess34cof the structure134.

An insulating member134dis formed at the surface34bside of the structure134as shown inFIG. 9C. When or after the insulating member134dis formed, the thickness (the length in the Z-axis direction) thereof is adjusted such that the electrodes of the light-emitting element32are exposed. For example, the material of the insulating member134dis formed to cover the electrodes of the light-emitting element32, and the insulating member134dcan be removed from the surface opposite to the light-exiting surface34ato expose the electrodes of the light-emitting element32. The insulating member134dconstitutes the wiring formation surface34e.

The wiring layer40is formed on the wiring formation surface34eas shown inFIG. 9D. The wiring layer40is formed by, for example, printing. In the case in which the clearance between the electrodes of the light-emitting element32is narrow, the wiring layer can be formed such that the electrodes of the light-emitting element32are short-circuited, and then the wiring between the electrodes can be cut with, for example, a processing machine. Examples of the processing machine include a laser processing machine.

Scribe lines S are formed in the structure134as shown inFIG. 10A. After forming the scribe line, the structure134is divided along the scribe lines S. The light-emitting modules20can be obtained by the division along the scribe lines S.

The required number of the divided light-emitting modules20is aligned and connected to the board60as shown inFIG. 10B. The connecting member50is adhered on the surface of the board60intended to be connected to the light-emitting modules20. The wiring pattern62is disposed on the surface opposite to the surface of the board60on which the connecting member50is adhered. The via holes64is formed at corresponding positions to electrically connect the wiring pattern62to the terminals of the light-emitting modules20. The via holes64are filled with electrically conductive members. The electrically conductive members are, for example, electrically conductive metal paste.

The surface-emitting light source10is produced in this manner.

The effects of the surface-emitting light source10of the present embodiment will be described.

The surface-emitting light source10of the present embodiment includes a plurality of light-emitting modules20. The light-emitting modules20are arranged in the same XY plane such that their light-exiting surfaces are flush with one another. In each light-emitting module20, as described above, the light-emitting elements32are arranged in the XY plane, and the electric currents that flow through the Y wiring patterns are substantially equal. The light-emitting module20can therefore achieve surface emission with substantially uniform luminance. A plurality of such light-emitting modules20are arranged in the surface-emitting light source10and connected to one another by the wiring pattern62preliminarily disposed on the board, so that the luminance variances of the surface-emitting light source can be reduced.

A required size of the light source can be easily achieved because the surface-emitting light source10can be constituted by arranging a plurality of light-emitting modules20.

Third Embodiment

As described above, the wiring patterns can have any shapes. In the present embodiment, luminance variances of the light-emitting elements are reduced by changing the shapes of the X wiring patterns and the Y wiring patterns in a top view of the XY plane to more strictly match the resistances.

FIG. 11is a schematic top view showing an example of a portion of a light-emitting module according to the present embodiment.

FIG. 11shows the layout of wiring patterns of a wiring layer340in a light-emitting module320of the present embodiment. Similarly to the case of the first embodiment described above, the wiring layer340is disposed on the wiring formation surface34e(FIG. 6BandFIG. 7). The proportion of the area of the wiring layer340to the area of the wiring formation surface34eis larger than in the case of the first embodiment. Hence, the light extraction efficiency can be improved by reflecting light traveling toward the surface34bof the light-guiding plate34to guide the light to the light-exiting surface. The insulating resin35(FIG. 7) is applied over the entire wiring layer340in this example.

The wiring layer340includes terminals341pand341nand wiring-pattern groups340aand340b. The terminals341pand341nare portions of the X wiring patterns exposed from the insulating resin35(FIG. 7) so as to be connected to the vias70(FIG. 6B) in the case of employing the second embodiment described above. A positive voltage with reference to the voltage applied to the terminal341nis applied to the terminal341p. Similarly to the case of the first embodiment, the wiring-pattern groups340aand340bare connected in parallel between the terminals341pand341n. The wiring-pattern groups340aand340bare geometrically equivalent circuits and are symmetric about the point C1. The shapes of the terminals341pand341nand the wiring patterns constituting the wiring-pattern groups340aand340bin the present embodiment differ from the shapes of the corresponding terminals and the wiring patterns constituting the wiring-pattern groups in the first embodiment, and the dimensions of the wiring layer340and the light-emitting elements32to be mounted are the same as the dimensions of the corresponding wiring layer and the corresponding light-emitting elements to be mounted in the first embodiment. The same components in the first embodiment are indicated by the same reference numerals, and their detailed description is omitted as appropriate.

The wiring-pattern group340aincludes Y wiring patterns342ato345a(i.e.,342a,343a,344aand345a) and X wiring patterns346aand347a. The wiring-pattern group340bincludes Y wiring patterns342bto345b(i.e.,342b,343b,344band345b) and X wiring patterns346band347b. As the wiring-pattern group340bhas geometrically the same shape as the wiring-pattern group340a, the group340aof wiring patterns will be described.

The Y wiring patterns342ato345aare disposed substantially parallel to each other between the X wiring pattern346aand the X wiring pattern347a. The Y wiring patterns344aand345aare disposed between the Y wiring pattern342aand the Y wiring pattern343a. A gap342a4is formed between the Y wiring pattern342aand the X wiring pattern347a. A gap342a5is formed between the Y wiring pattern342aand the X wiring pattern346a. The light-emitting elements32are respectively disposed astride the gaps342a4and342a5. A plurality of gaps are formed between the Y wiring patterns343ato345aand the X wiring patterns346aand347a, and the light-emitting elements32are disposed astride the gaps.

The Y wiring patterns342ato345ahave substantially the same wiring lengths. The Y wiring patterns344aand345ahave substantially the same widths. The widths of the Y wiring patterns344aand345aare respectively greater than the widths of the Y wiring patterns342aand343a. The light-emitting elements32are disposed on both ends of each of the Y wiring patterns342ato345ain the Y-axis direction, and the resistances of the Y wiring patterns344aand345aare lower than the resistances of the Y wiring patterns342aand343a. In this example, the width of the Y wiring pattern342ais greater than the width of the Y wiring pattern343a, to thereby reduce the luminance variances of the light-emitting elements32at both ends in the X-axis direction.

In this manner, the luminance variances of the light-emitting module320in the two-dimensional plane can be effectively reduced by appropriately selecting the shapes of the Y wiring patterns and the X wiring patterns.

According to the embodiments described above, a light-emitting module and a surface-emitting light source with reduced luminance variances can be provided.

A few embodiments of the present invention have been described above, but these embodiments are not intended to limit the scope of the invention but provide examples. These novel embodiments can be worked in other various forms, and omission, replacement, or change in a wide range can be carried out as long as the gist of the present invention is not changed. These embodiments and their modifications are included in the scope or gist of the invention and in the range of the claimed invention and its equivalents. In addition, the above embodiments can be combined with each other.