JP2009038292A - Light emitting device, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device capable of preventing polarized light emitted by a light emitting element from being disordered, and to provide a manufacturing method thereof. <P>SOLUTION: The light emitting device 1 includes a mounting base 3, the light emitting element 2 which is mounted on the mounting base 3 and emits the polarized light 20, and a light-transmissive resin portion 4 which covers the light emitting element 2 to transmit the polarized light 20 emitted by the light emitting element, and has resin molecules having a non-oriented structure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light emitting device and a method for manufacturing the same, and more particularly to a light emitting device in which a light emitting element that emits polarized light is mounted and a method for manufacturing the same.

  For example, an optical element (light guide plate) that changes the propagation direction of light incident from a light emitting element and outputs the light is used for a backlight of a liquid crystal display or the like. The light output from the light guide plate is input to the liquid crystal panel via the polarizing plate, and an image can be displayed on the liquid crystal display. Light incident on the light guide plate (hereinafter simply referred to as “incident light”) is scattered inside the light guide plate, and then the scattered light can be uniformly emitted over the entire light emitting surface from which the light is extracted. That is, a reflection pattern is formed on the surface of the reflection surface that reflects incident light inside the light guide plate. The incident light is directed by the reflection pattern and propagates inside the light guide plate, and propagates inside the light guide plate. Light is output from the light emitting surface.

In recent years, there is a tendency to employ light emitting elements that use output light as deflected light. If this type of light-emitting element is used as a light source for a liquid crystal backlight or projector, the light component cut by the polarizing plate is reduced, and the luminous efficiency can be improved. Expectations are made as described.
T. Takeuchi et al., “Japanese Journal of Applied Physics vol.39”, 2000, pages 413-416.

  A light-emitting element that emits deflected light is mounted on a base substrate or a package substrate by die bonding, and the mounted light-emitting element is molded with a light-transmitting resin such as silicone resin or epoxy resin. That is, a light emitting device in which the light emitting element is molded with a light transmissive resin can be manufactured. An injection molding method or an extrusion molding method is used for molding the light-transmitting resin. However, in such a light-emitting device, orientation occurs in the resin molecules during thermosetting of the light-transmitting resin. Further, residual stress is generated inside the light-transmitting resin during thermosetting. The occurrence of orientation of the resin molecules and the occurrence of residual stress cause birefringence to appear inside the light-transmitting resin, and the occurrence of this birefringence disturbs the deflected light emitted from the light emitting element.

  The present invention has been made to solve the above problems. Accordingly, an object of the present invention is to provide a light emitting device and a method for manufacturing the same that can prevent the disturbance of the deflected light emitted from the light emitting element.

  In order to solve the above problems, a first feature of the present invention is that a light emitting device includes a mounting base, a light emitting element that is mounted on the mounting base and emits polarized light, covers the light emitting element, and is emitted from the light emitting element. A light-transmitting resin portion that transmits the polarized light and has a non-aligned structure in the resin molecule. Furthermore, in the light emitting device according to the first feature, it is preferable that the light transmissive resin portion has resin molecules randomly present. In the light emitting device according to the first feature, it is preferable that the light transmissive resin portion does not exhibit birefringence. Furthermore, in the light-emitting device according to the first feature, the light-emitting element is formed of a group III nitride semiconductor having a nonpolar plane or a semipolar plane as a main surface, the first conductivity type first semiconductor layer, A light emitting layer on the semiconductor layer and a second semiconductor layer of the second conductivity type on the light emitting layer are preferably provided.

  According to a second feature of the present invention, in a method for manufacturing a light emitting device, a step of mounting a light emitting element that emits deflected light on a mounting base, and a light-transmitting resin that transmits the deflected light emitted from the light emitting element are used as the light emitting element. And a step of forming a light-transmitting resin portion covering the light-emitting element.

  According to a third aspect of the present invention, in a method for manufacturing a light emitting device, a step of mounting a light emitting element that emits deflected light on a mounting base, and a light-transmitting resin that transmits the deflected light emitted from the light emitting element are used as the light emitting element. A step of dropping, and a step of gradually raising the temperature of the light-transmitting resin, curing the light-transmitting resin, and forming a light-transmitting resin portion that covers the light emitting element. In the method for manufacturing a light emitting device according to the second feature or the third feature, a step of dropping and applying a resin from a syringe can be considered as a step of dropping and applying a light transmitting resin.

  ADVANTAGE OF THE INVENTION According to this invention, the light-emitting device which can prevent disorder of the deflection | deviation light emitted from the light emitting element, and its manufacturing method can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic and different from actual ones. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings is contained. Further, the following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is to arrange the components and the like as follows. Not specific. The technical idea of the present invention can be variously modified within the scope of the claims.

(First embodiment)
In the first embodiment of the present invention, an example in which an LED (light emitting diode) is used as a light emitting element and the present invention is applied to a light emitting device having a surface mounting structure will be described.

[Configuration of light emitting device]
As shown in FIG. 1, the light emitting device 1 according to the first embodiment includes a mounting base 3, a light emitting element 2 that is mounted on the mounting base 3 and emits polarized light 20, covers the light emitting element 2, and emits light. A light transmissive resin portion 4 that transmits the polarized light 20 emitted from the element 2 and has a non-aligned structure in the resin molecules (4 m) is provided.

  The mounting base 3 is a package substrate having a real surface structure in the first embodiment, and includes a mounting surface 30 having a concave cross-sectional shape that also serves as the reflector 30R. The light emitting element 2 is mounted on the bottom surface of the mounting surface 30 of the mounting base 3, and a reflector 30 </ b> R having a tapered surface is formed on the mounting base 3 around the side surface of the mounted light emitting element 2. The mounting surface 30 and the reflector 30R are integrally formed.

[Configuration of Light Emitting Element]
The light emitting element 2 is an LED that emits the deflected light 20 in the first embodiment. Here, “polarized light” means that the linearly polarized light component is not uniform (random) but biased, but in the first embodiment, it is not necessary to be 100% linearly polarized light. Therefore, the polarization direction of the deflected light 20 is the direction with the largest linearly polarized light component.

  For example, as illustrated in FIG. 2, the light emitting element 2 according to the first embodiment includes a light emitting unit 220 that generates the deflected light 20 and a deflected light 20 that is mounted on the light emitting unit 220 and is emitted from the light emitting unit 20. And an output unit (substrate) 210 for outputting.

The light emitting unit 220 uses a non-polar plane or semi-polar plane of a GaN crystal as a crystal growth surface, and includes a first semiconductor layer 221 of the first conductivity type, an active layer 222, and Each of the second conductivity type second semiconductor layers 223 is sequentially stacked in the normal direction of the crystal growth surface. For example, if the crystal growth surface is an m-plane that is a nonpolar plane, the light-emitting element 2 is composed of a group III nitride semiconductor having the m-plane as a main surface. Examples of the group III nitride semiconductor include aluminum nitride (AlN), gallium nitride (GaN), and indium nitride (InN). A typical group III nitride semiconductor is represented by Al _x In _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). The GaN semiconductor is a group III-V compound semiconductor well known among hexagonal compound semiconductors containing nitrogen.

  The active layer 222 is supplied with carriers of the first conductivity type from the first semiconductor layer 221 and supplied with carriers of the second conductivity type from the second semiconductor layer 223. When the first conductivity type is n-type and the second conductivity type is p-type, the electrons supplied from the first semiconductor layer 221 and the holes supplied from the second semiconductor layer 223 in the active layer 222 are regenerated. Coupling is performed, and the polarized light 20 is emitted from the active layer 222. The active layer 222 may employ, for example, a quantum well structure in which a well layer (well layer) is sandwiched between barrier layers (layer barrier layers) having a larger band gap than the well layer. it can. The quantum well structure includes not only one well layer but a multiplexed quantum well structure, and further includes a quantum well structure in which the active layer 222 has a multiple quantum well (MQW) structure.

  Usually, light extracted from an active layer made of a group III nitride semiconductor having a c-plane which is a polar plane of a GaN crystal as a crystal growth surface is in a randomly polarized (non-polarized) state. On the other hand, a strong polarization state is realized in the light extracted from the active layer 222 formed by using a group III nitride semiconductor whose crystal growth surface is a non-polar surface or semipolar surface such as a-plane, m-plane other than c-plane can do. For example, when the active layer 222 is configured with the m-plane as the main surface, the polarized light 20 containing a large amount of polarized light components parallel to the m-plane, more specifically, the polarized light components in the a-axis direction, is generated from the active layer 222. Can do. Detailed descriptions of the nonpolar plane and the semipolar plane will be described later.

  The light emitting unit 220 is formed by growing on the crystal growth surface of the output unit 210 by crystal growth. That is, as shown in FIG. 2, the light emitting element 2 includes an output unit 210, the output unit 210, the first semiconductor layer 221 on the output unit 210, and the active layer 222 on the first semiconductor layer 221. And a second semiconductor layer 223 on the active layer 222. In the first embodiment, the output unit 210 is composed of, for example, a GaN single crystal substrate. In the case where the main surface that is a non-polar surface is the main surface serving as the crystal growth surface of the output unit 10, the light emitting unit 220 can be formed on this main surface by crystal growth. That is, the light emitting section 220 is composed of GaN having the m plane as the crystal growth principal surface, and the light emitting element 2 is composed of a group III nitride semiconductor grown with the m plane as the crystal growth principal surface. The main surface of the output unit 210 is the same as the crystal growth surface of the light emitting unit 220.

  The light emitting element 2 further includes a first electrode 211 that supplies an operating voltage to the first semiconductor layer 221 and a second electrode 212 that supplies an operating voltage to the second semiconductor layer 223. As shown in FIG. 2, the first electrode 211 is formed on the surface where the second semiconductor layer 223, the active layer 222, and a part of the first semiconductor layer 221 are partially removed by mesa etching and the first semiconductor layer 221 is exposed. Is disposed. The first semiconductor layer 221 and the first electrode 211 are electrically connected. The second electrode 212 is disposed on the second semiconductor layer 223. The second semiconductor layer 223 and the second electrode 212 are electrically connected.

  For example, aluminum (Al) is used for the first electrode 211, and palladium (Pd) -gold (Au) alloy is used for the second electrode 212, for example. The first electrode 211 is ohmically connected to the first semiconductor layer 211, and the second electrode 212 is ohmically connected to the second semiconductor layer 233. A first conductivity type contact layer may be interposed between the first semiconductor layer 221 and the first electrode 211. In addition, a second conductivity type contact layer may be interposed between the second semiconductor layer 223 and the second electrode 212.

  In the light emitting element 2, the surface (back surface) facing the crystal growth surface (main surface or surface) in contact with the first semiconductor layer 221 of the output unit 210 is an output surface 210A. The deflected light 20 emitted from the active layer 222 is output from the output surface 210A to the outside of the light emitting element 2 as output light. Note that the light-emitting element 2 can extract light from the second semiconductor layer 223 side. Although not shown, the light emitting element 2 according to the first embodiment is electrically connected to the mounting surface 30 of the mounting base 3 via the bump electrodes, and is mounted by a flip chip method.

[Crystal structure of light-emitting element]
The crystal structure of the group cell of III nitride semiconductor constituting the light emitting element 2 can be approximated by a hexagonal crystal structure as shown in FIGS. In the hexagonal crystal structure, the c-axis is a crystal axis along the axial direction of the hexagonal column. The surface (the top surface of the hexagonal column) having the c-axis as a normal line is a c-plane {0001}. When a group III nitride semiconductor crystal is cleaved in two planes parallel to the c-plane, the + c-axis side plane (+ c plane) becomes a crystal plane in which group III atoms are arranged. The plane on the −c axis side (−c plane) is a crystal plane in which nitrogen atoms are arranged. For this reason, the c-plane is called a polar plane because it exhibits different properties on the + c-axis side and the −c-axis side.

  As shown in FIG. 4, four nitrogen atoms are bonded to one group III atom. The four nitrogen atoms are located at the four vertices of a regular tetrahedron with a group III atom arranged in the center. Of these four nitrogen atoms, one nitrogen atom is located in the + c axis direction with respect to the group III atom, and the other three nitrogen atoms are located on the −c axis side with respect to the group III atom. Since it has such a crystal structure, the polarization direction is along the c-axis in the group III nitride semiconductor.

  In the hexagonal crystal structure, each side surface of the hexagonal column is an m-plane {1-100}. A plane passing through a pair of ridge lines that are not adjacent to each other is a-plane {11-20}. The m-plane and the a-plane are crystal planes perpendicular to the c-plane and are orthogonal to the polarization direction, and thus are nonpolar planes, that is, nonpolar planes. Furthermore, since the crystal plane that is inclined with respect to the c-plane (not parallel to the c-plane or perpendicular to it) crosses the polarization direction obliquely, it is a slightly polar plane, that is, a semipolar plane (Semi-polar plane). Specific examples of the semipolar plane include a {10-11} plane shown in FIG. 5A and a {10-13} plane shown in FIG. 5B.

[Molecular structure of light-transmitting resin part]
In the light emitting device 1 according to the first embodiment, the light transmissive resin portion 4 has a non-arranged structure in the resin molecule (4m) as described above, and the light transmissive resin portion 4 having this non-aligned structure has a plurality of structures. Does not develop refraction. Here, as shown in the following formula, the birefringence Δn is a refractive index n _┴ perpendicular to the molecular axis of the resin molecule 4m and a refractive index parallel to the molecular axis of the resin molecule 4m shown in FIG. It is defined by the difference from n _// .

Δn = n _┴ -n _//
If the refractive index n _存在 and the refractive index n _// are equal, there is no birefringence in the light transmissive resin portion 4. In the manufacturing process of the light transmissive resin part, when stress, heat, etc. are applied suddenly, as shown in FIG. 7, the resin molecules 4m of the light transmissive resin part are oriented. That is, the molecular axes of the resin molecules 4m are regularly aligned in one direction. In the light-transmitting resin part in which the resin molecules 4m are oriented, macroscopic birefringence appears. On the other hand, in the light emitting device 1 according to the first embodiment, at least the generation of stress or the rapid heating is reduced in the manufacturing process of the light transmissive resin portion 4, and the resin molecules 4 m are reduced. The arrangement, that is, the direction of the molecular axis of the resin molecule 4m is randomly controlled. In the light transmissive resin part 4 having a non-aligned structure in the resin molecule 4m, since the birefringence does not appear macroscopically, the deflected light 20 emitted from the light emitting element 2 is not disturbed during transmission.

  As described above, in the first embodiment, since the resin molecule 4m includes the light transmissive resin portion 4 having a non-arrayed structure, it is possible to prevent disturbance of the deflected light emitted from the light emitting element 2. The light emitting device 1 can be realized.

[Method for Manufacturing Light Emitting Device]
Next, a method for manufacturing the light emitting device 1 according to the first embodiment will be described with reference to FIGS. First, as shown in FIG. 9, the light emitting element 2 is mounted on the mounting surface 30 of the mounting base 3 by a die bonding method. Here, although not shown in the figure, the electrode in which the first electrode 211 and the second electrode 212 of the light emitting element 2 are disposed on the mounting surface 30 of the mounting base 3 at or after the light emitting element 2 is mounted on the mounting base 3. Is electrically connected.

  As shown in FIG. 10, a syringe dropping application method is used, and a light-transmitting resin 41 is dropped and applied from the syringe 6 to the light emitting element 2 mounted on the mounting surface 30 of the mounting base 3. As shown in FIG. 11, the light emitting element 2 is covered with a light transmissive resin 41, and the light emitting element 2 is resin-sealed with the light transmissive resin 41. In the light transmissive resin 41 using the syringe dropping application method, the internal stress generated in the light transmissive resin 41 can be reduced as compared with a molding resin molding method such as injection molding or extrusion molding.

  Subsequently, as shown in FIG. 12, the light-transmitting resin 41 applied dropwise is heated in a stepwise manner, and the light-transmitting resin 41 is cured to form the light-transmitting resin portion 4. Here, FIG. 12 is data actually performed by the inventor of the present application using a general sealing resin. In the figure, the horizontal axis represents the temperature raising time (hour), and the vertical axis represents the heating temperature (° C.). It is. In this stepwise temperature raising method, first, heating for curing the light transmissive resin 41 is started, and the heating temperature is linearly increased from room temperature to 80 ° C. in 0.5 hours. Next, the heating temperature is kept constant at 80 ° C. for 1.0 hour. Subsequently, the heating temperature is linearly increased from 80 ° C. to a maximum heating temperature of 150 ° C. in 0.5 hours. Subsequently, the heating temperature is kept constant at 150 ° C. for 1.0 hour. Thereafter, in 1.0 hour, it is cooled linearly from the maximum heating temperature of 150 ° C. to room temperature. According to the inventor of the present application, as a result of actually using such a stepwise temperature raising method, birefringence did not appear in the light-transmitting resin part 4 after curing.

  In the method of manufacturing the light emitting device 1 according to the first embodiment, the light transmissive resin portion 4 that covers the light emitting element 2 is formed by the drop coating method, and the light transmissive resin portion 4 is formed stepwise. Since it is cured and formed by the temperature raising method, the disturbance of the deflected light 20 emitted from the light emitting element 2 can be prevented.

(Second Embodiment)
In the second embodiment of the present invention, an example in which the present invention is applied to a light emitting device having a shell-type package structure instead of the light emitting device 1 having the surface mounting structure according to the first embodiment described above will be described. To do. As shown in FIG. 13, the light emitting device 1 according to the second embodiment includes a mounting base 3, a light emitting element 2 that is mounted on the mounting base 3 and emits deflected light 20, covers the light emitting element 2, and emits light. A light transmissive resin portion 4 that transmits the polarized light 20 emitted from the element 2 and has a non-aligned structure in the resin molecules (4 m) is provided.

  In the second embodiment, the mounting base 3 is disposed at one end of the lead 31 and is configured integrally with the lead 31. The lead 31 is used as a cathode electrode in the second embodiment. The basic configuration of the mounting base 3 is the same as that of the mounting base 3 of the light emitting device 1 according to the first embodiment described above, and includes a mounting surface 30 having a concave cross-sectional shape that also serves as the reflector 30R. The light emitting element 2 is mounted on the bottom surface of the mounting surface 30 of the mounting base 3, and a reflector 30 </ b> R having a tapered surface is formed on the mounting base 3 around the side surface of the mounted light emitting element 2. A lead 32 is disposed in a region close to the lead 31. The lead 32 is used as an anode electrode, and one end of the lead 32 is not connected with a symbol but is electrically connected to the light emitting element 2 through a wire.

  The light transmissive resin portion 4 covers the mounting base 3 at one end of the lead 31 and one end of the lead 32, and a hemispherical lens portion 42 on the light emitting element 20, that is, a portion that emits the deflected light 20 from the light emitting element 2. Have Similar to the light transmissive resin portion 4 of the light emitting device 1 according to the first embodiment, the light transmissive resin portion 4 has a non-aligned structure in the resin molecules 4m, thereby reducing the expression of birefringence. Is configured to do.

  In the light emitting device 1 according to the second embodiment configured as described above, the same effect as that obtained by the light emitting device 1 according to the above-described first embodiment can be obtained.

(Other embodiments)
As described above, the present invention has been described according to the first embodiment and the second embodiment described above. However, the description and the drawings constituting a part of this disclosure do not limit the present invention. For example, in the light emitting device 1 according to the first embodiment and the second embodiment, the description has been made on the assumption that the transparent light transmissive resin portion 4 is used. However, the light transmissive resin portion 4 is not necessarily transparent. In the present invention, the light-transmitting resin portion 4 may be formed by mixing any dye such as blue, green, red, or orange into the light-transmitting resin.

  As described above, the present invention includes various embodiments and the like not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

It is a block diagram of the light-emitting device which concerns on the 1st Embodiment of this invention. It is principal part sectional drawing which shows the structure of the light emitting element of the light-emitting device shown in FIG. FIG. 3 is a crystal structure diagram for explaining a nonpolar plane of a group III nitride semiconductor of the light emitting device shown in FIG. 2. FIG. 3 is a crystal structure diagram illustrating an atomic arrangement of a group III nitride semiconductor of the light emitting device shown in FIG. 2. (A) And (B) is a crystal structure figure explaining the semipolar surface of the group III nitride semiconductor of the light emitting element shown in FIG. FIG. 2 is a model diagram of resin molecules in a light transmissive resin portion in the light emitting device shown in FIG. 1. It is a figure which shows the orientation state of the resin molecule | numerator of light transmissive resin. FIG. 2 is a model diagram illustrating a case where resin molecules in a light transmissive resin portion are present randomly in the light emitting device illustrated in FIG. 1. It is 1st process sectional drawing explaining the manufacturing method of the light-emitting device which concerns on 1st Embodiment. It is 2nd process sectional drawing. It is 3rd process sectional drawing. It is a chart explaining the temperature rising method of the light transmissive resin part of the light-emitting device which concerns on 1st Embodiment. It is a block diagram of the light-emitting device which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light-emitting device 2 ... Light emitting element 20 ... Deflection light 210 ... Output part 210A ... Output surface 211 ... 1st electrode 212 ... 2nd electrode 220 ... Light emission part 221 ... 1st semiconductor layer 222 ... Active layer 223 ... 2nd semiconductor layer DESCRIPTION OF SYMBOLS 3 ... Mounting base 30 ... Mounting surface 4 ... Light-transmitting resin part 41 ... Light-transmitting resin 4m ... Resin molecule 6 ... Syringe

Claims (6)

Implementation base,
A light emitting element mounted on the mounting base and emitting polarized light;
A light-transmitting resin portion that covers the light-emitting element, transmits polarized light emitted from the light-emitting element, and has a non-aligned structure in resin molecules;
A light-emitting device comprising:   The light-emitting device according to claim 1, wherein the light-transmitting resin portion has the resin molecules randomly present.   The refractive index in the direction perpendicular to the molecular axis of the resin molecule and the refractive index in the direction parallel to the molecular axis are set to be equal to each other in the light transmissive resin portion. Light-emitting device.   The light emitting element is formed of a group III nitride semiconductor having a nonpolar plane or a semipolar plane as a main surface, and includes a first semiconductor layer of a first conductivity type, a light emitting layer on the first semiconductor layer, and the light emitting layer. The light-emitting device according to claim 1, further comprising a second semiconductor layer of the second conductivity type. Mounting a light emitting element that emits polarized light on a mounting base;
A step of dropping and applying a light-transmitting resin that transmits polarized light emitted from the light-emitting element to the light-emitting element, and forming a light-transmitting resin portion that covers the light-emitting element;
A method for manufacturing a light emitting device, comprising: Mounting a light emitting element that emits polarized light on a mounting base;
A step of dropping and applying a light-transmitting resin that transmits polarized light emitted from the light emitting element to the light emitting element;
A step of gradually raising the temperature of the light transmissive resin, curing the light transmissive resin, and forming a light transmissive resin portion covering the light emitting element;
A method for manufacturing a light emitting device, comprising:

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