JP2004241282A - Surface emitting device and method of manufacturing surface emitting device - Google Patents

Abstract

A thin surface light emitting device that can be used as a light source such as a backlight of a liquid crystal display is provided.
A surface light emitting device includes an LED chip and a light guide plate having a light extraction surface and an end surface. A part of the LED chip 11 is embedded in the end face of the light guide plate 12, and another part of the LED chip 11 is exposed from the end face 12 b of the light guide plate 12. The surface of the LED chip 11 exposed from the end surface 12 b of the light guide plate 12 is disposed on the mounting board 17. The mounting board 17 is arranged on at least a part of the inner wall surface of the housing 13. The surface light emitting device 1 is formed by filling a light guide plate forming material for forming the light guide plate 12 into a housing 13 in which a mounting substrate 17 on which the LED chips 11 are disposed is disposed on at least a part of the inner wall surface.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface light emitting device that can be used as a light source such as a backlight of a liquid crystal display, and a method of manufacturing the surface light emitting device. In particular, the present invention relates to a thin surface light emitting device that can be reduced in thickness and a method of manufacturing the surface light emitting device.
[0002]
[Prior art]
In recent years, as a light source such as a backlight of a liquid crystal display, a surface light emitting device which emits light from a light emitting diode arranged on an LED chip lead frame as a light emitting element which is a point light source and sealed with a mold resin in a planar manner has been used. ing. This surface light emitting device is configured so that light from one or more light emitting diodes is incident from one end surface of a light guide plate having an opposing main surface and light is emitted from one entire main surface of the light guide plate. You.
[0003]
FIG. 5 shows a schematic cross section as an example of such a surface light emitting device. The light-emitting diode 502 is optically connected to an end face of the plate-shaped light-transmitting member 504 in order to introduce light from the light-emitting diode into the plate-shaped light-transmitting member 504 serving as a light guide plate. Except for the end surface to which the light emitting diode is connected and the light extraction surface, the light guide and the light emitting diode arranged on the mounting substrate 503 are each a reflection plate made of a resin added with aluminum or a white pigment. A covering surface light emitting device is configured at 505. In particular, using a blue LED chip and a phosphor that absorbs blue light emitted from the blue LED chip and converts it into yellow by using a light emitting diode capable of emitting mixed color light such as white light as a light source. Accordingly, the device can be used as a surface light emitting device capable of emitting various luminescent colors. Such a surface light emitting device is rapidly spreading as a liquid crystal backlight of a mobile phone. Further, in the market, a thinner liquid crystal display is desired, and therefore, a thinner surface emitting device is required. There is also known a surface light emitting device in which a light emitting diode is entirely buried in a light guide plate and a power supply connection terminal is drawn out from a side end surface near a buried light source (Patent Document 1).
[0004]
[Patent Document 1]
JP-A-5-127158 [0005]
[Problems to be solved by the invention]
However, when the above-described light emitting diode is used for the surface light emitting device, there is a problem that it is difficult to make the surface light emitting device thinner than the light emitting diode.
Therefore, an object of the present invention is to provide a thin surface emitting device that can be used as a light source such as a backlight of a liquid crystal display.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a surface light emitting device according to claim 1 of the present invention is a surface light emitting device including a light emitting element and a light guide plate having a light extraction surface and an end surface, and a part of the light emitting element. Is embedded in the end face of the light guide plate, and another portion of the light emitting element is exposed from the end face of the light guide plate.
[0007]
Furthermore, in the surface light emitting device according to claim 2 of the present invention, in addition to the features of claim 1, the light emitting element is disposed on a mounting board, and the mounting board is attached to an end face of the light guide plate. Features. With this configuration, the light emitting element can be reliably positioned with respect to the mounting board attached to the end surface of the light guide plate. Therefore, it is possible to prevent a decrease in luminance or the like due to a poor positioning of the light emitting element. Further, when a plurality of light emitting elements are arranged, positioning between the light emitting elements can be reliably performed, and luminance unevenness of the surface light emitting device can be prevented.
[0008]
Furthermore, in the surface emitting device according to claim 3 of the present invention, in addition to the features of claim 2, the light guide plate is disposed in the housing, and the mounting substrate is disposed on at least a part of the inner wall surface of the housing. It is characterized by having been done. With this configuration, the mounting substrate can be reliably positioned with respect to the housing and the light guide plate. Therefore, it is possible to more reliably prevent a decrease in brightness and uneven brightness of the surface light emitting device due to poor positioning of the light emitting element.
[0009]
In order to achieve the above object, a method for manufacturing a surface light emitting device according to claim 4 of the present invention is a method for manufacturing a surface light emitting device including a light emitting element and a light guide plate having a light extraction surface and an end surface. In addition, a light guide plate forming material for forming a light guide plate is filled in a housing in which a mounting substrate on which a light emitting element is disposed is disposed on at least a part of an inner wall surface.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below exemplify a surface light emitting device and a method for manufacturing the surface light emitting device for embodying the technical idea of the present invention, and the present invention relates to the surface light emitting device and the surface light emitting device. The manufacturing method is not specified as follows.
[0011]
Further, the present specification does not limit the members described in the claims to the members of the embodiments. In addition, the size, positional relationship, and the like of the members illustrated in each drawing may be exaggerated for clarity of description. Further, in the following description, the same names and reference numerals denote the same or similar members, and a detailed description thereof will be omitted as appropriate. Further, each element constituting the present invention may be configured such that a plurality of elements are configured by the same member and one member also serves as the plurality of elements, or conversely, the function of one member may be performed by a plurality of members. It can also be realized by sharing.
[0012]
Surface emitting device, the shape of the light guide plate to be used can be selected according to its use and purpose, for example, when used in a backlight of a liquid crystal such as a personal computer, a substantially rectangular flat light guide plate is used, When used for a backlight of a panel meter of an automobile, a light guide plate having a shape according to the design is used.
[0013]
[Embodiment 1]
FIG. 1 is a schematic cross-sectional view of a surface light-emitting device 1 according to Embodiment 1 of the present invention as viewed from a side. The surface light emitting device 1 includes an LED chip 11 as a light emitting element, and a light guide plate 12 having a light extraction surface 12a and an end surface 12b. A part of the LED chip 11 is embedded in the end face 12b of the light guide plate 12, and another part of the LED chip 11 is exposed from the end face 12b of the light guide plate 12. In the example of FIG. 1, in the drawing, the LED chip 11 is exposed such that the surface at the right end thereof forms the same plane as the right end surface of the light guide plate 12. It is embedded so as to be sealed by the light guide plate 12. The surface of the LED chip 11 exposed from the end surface of the light guide plate 12 is arranged on the mounting board 17. The mounting board 17 is arranged on at least a part of the inner wall surface of the housing 13. In the example of FIG. 1, an example is shown in which the mounting substrate 17 and the housing 13 are formed separately, but the mounting substrate 17 and the housing 13 may be integrally formed.
In this case, a wiring pattern is formed on at least a part of the inner wall surface of the housing 13. Further, on the light guide plate 12, a diffusion sheet 14 for making the light from the light guide plate 12 uniform, a first prism sheet 15 and a second prism sheet 16 for directing the light in a viewing direction are sequentially placed. .
[0014]
(LED chip 11)
Can be used in the present invention, a nitride-based compound semiconductor (formula _In i _Ga j _Al k N, where, 0 ≦ i, 0 ≦ j , 0 ≦ k, i + j + k = 1) as, it InGaN and various impurities There are various things, including doped GaN. The LED chip 11 is formed by growing a semiconductor such as InGaN or GaN as a light emitting layer on a substrate by MOCVD or the like. Examples of the semiconductor structure include a homostructure having a MIS junction, a PI junction, and a PN junction, a heterostructure, and a double heterostructure. The emission wavelength of the nitride semiconductor layer can be variously selected depending on the material and the degree of mixed crystal. In addition, a single quantum well structure or a multiple quantum well structure in which the semiconductor active layer is formed of a thin film that produces a quantum effect can be used.
In the present invention, the LED chip 11 has a semiconductor light-emitting layer capable of emitting ultraviolet to blue light, and efficiently uses a yttrium-aluminum-garnet-based phosphor and / or a nitride-based phosphor activated with cerium described later. It is preferable to use an LED chip that can be excited.
[0015]
Further, the LED chip 11 may have an electrode structure in which a semiconductor layer is formed on an insulating substrate such as a sapphire substrate and a p-electrode and an n-electrode are formed on the same surface, and the LED chip 11 may be formed on a conductive or semi-conductive substrate such as a GaN substrate. Alternatively, a counter electrode structure in which a semiconductor layer is formed and a p-electrode and an n-electrode are formed to face each other with the semiconductor layer interposed therebetween may be used.
[0016]
(Light guide plate 12)
As the material used for the light guide plate 12 in the present invention, it is preferable to use a material having excellent light transmittance and moldability, and examples thereof include an acrylic resin, a polycarbonate resin, an amorphous polyolefin resin, and a polystyrene resin. The light guide plate 12 can be formed in various shapes such as a substantially rectangular flat plate shape, a panel shape of a panel meter of an automobile, and a pointer of a meter needle. The light guide plate 12 contains, for example, light-transmitting fine particles having a mean particle size of 3 to 20 μm made of a benzoguanamine-based resin, PET, or the like as a diffusing material.
[0017]
(Housing 13)
The housing used in the present invention can hold at least the mounting substrate 17 on which the LED chips 11 are arranged and the light guide 12. The housing 13 is preferably made of various materials such as resin and metal. In particular, metals such as nickel, iron, and copper, and various alloys such as stainless steel are more preferably used in consideration of light reflection and heat radiation of the LED chip 11. Further, it is preferable that Ag is deposited on the inner wall surface of the housing 13. The size and shape of the housing 13 can be variously selected according to the light guide plate 12, the LED chip 11, and the space. In addition, by forming irregularities on the bottom surface of the housing 13 and forming a light diffusing portion on the back surface of the light guide plate 12, a uniform light emitting surface without luminance unevenness can be obtained. Such unevenness as a light diffusion portion forms a diffusion pattern (for example, a convex portion) in the vicinity of the LED chip 12 such that the interval is high when the luminance is high and the interval is low when the luminance is low. Preferably. By forming such a diffusion pattern, it is possible to further improve the uneven brightness in the vicinity of the LED chip.
[0018]
(Mounting board 17)
As the mounting substrate 17 used in the present invention, an insulating substrate having a conductive pattern formed on the surface can be used. One or more LED chips 11 are arranged on the mounting board 17, and the electrodes of the LED chips 11 and the conductive patterns are electrically connected directly or via wires or the like. Further, the conductive pattern is electrically connected to a connection terminal (not shown), and power is supplied to the LED chip 11 from the outside via the connection terminal. The connection terminal may be extended from the opening direction of the housing 13 (upward in FIG. 1), or an opening may be provided in a part of the inner wall surface of the housing 13 to provide a rear surface of the mounting board 17 (the right side surface in FIG. 1). ) May be exposed.
[0019]
When the LED chip 11 has a same-surface electrode structure in which a p-electrode and an n-electrode are formed on the same surface, so-called flip-chip bonding in which the electrodes are directly bonded to a conductive pattern may be used. May be fixed to the mounting board 17 and bonded to the conductive pattern via a wire, that is, what is called wire bonding. When flip-chip bonding is used, heat generated in the electrodes and the light-emitting layer of the LED chip can be efficiently dissipated to the mounting substrate 17 side, and since the wire bonding is unnecessary, the LED chips 11 are arranged at high density. Becomes possible. On the other hand, when wire bonding is used, short-circuiting between the electrodes of the LED chip 11 is unlikely to occur, so that mass productivity can be increased. In particular, by arranging the bonding position of the wire to the conductive pattern of the mounting board 17 between the LED chips 11, it is possible to prevent the thickness of the surface light emitting device from increasing. Similarly, in the case where the LED chip 11 has a counter electrode structure in which a p-electrode and an n-electrode are formed to face each other, it is preferable that the bonding position of the wire to the conductive pattern of the mounting board 17 be arranged between the LED chips 11.
[0020]
Further, the mounting board 17 and the housing 13 may be integrally formed by forming a conductive pattern on at least a part of the inner wall surface of the housing 13. When the casing 13 is formed of an insulating member such as a resin, for example, a conductive pattern can be directly formed on at least a part of the inner wall surface. When the housing 13 is formed of a conductive member such as a metal, for example, at least a part of the inner wall surface is subjected to a punching process, and the punched portion is connected to another conductive member of the housing 13 via an insulating member. An electrically insulated conductive member may be embedded to form a conductive pattern.
[0021]
(Phosphor)
In the present invention, the phosphor can be contained in the light guide plate 12, the diffusion sheet 14, and the like. Further, the phosphor sheet in which the phosphor is contained in the translucent resin is arranged between the light guide plate 12 and the diffusion sheet 14 or between the diffusion sheet 14 and the first prism sheet 15. You can also. As an example of the phosphor used in the surface emitting device of the present invention, there is a photoluminescent phosphor that emits light when excited by visible light or ultraviolet light. Specific examples of photoluminescent phosphors include yttrium / aluminum / garnet-based phosphor activated with cerium as a phosphor capable of emitting white light by complementary color with light from a nitride semiconductor LED chip capable of emitting blue light. (YAG-based phosphors) and nitride-based phosphors, such as phosphors such as Mg ₅ Li ₆ Sb ₆ O ₁₃ : Mn and Mg ₂ TiO ₄ : Mn, and phosphors in which a plurality of these phosphors are mixed. Can also be used.
[0022]
Here, a yttrium-aluminum-garnet-based phosphor activated with cerium is shown below as a more preferable phosphor. In the present invention, the yttrium-aluminum-garnet-based phosphor activated with cerium is to be interpreted particularly broadly, and a part or the whole of yttrium is at least one selected from the group consisting of Lu, Sc, La, Gd and Sm. This term is used to include a phosphor that emits a fluorescent effect by substituting one element or a part or all of aluminum with one or both of Ga and In.
[0023]
More specifically, the general formula _{(Y z Gd 1-z)} 3 Al 5 O 12: Ce ( where, 0 <z ≦ 1) photoluminescence phosphor and the general formula represented by _{(Re 1-a Sm a)} 3 Re ' ₅ O ₁₂ : Ce (where 0 ≦ a <1, Re is at least one selected from Y, Gd, La, Sc, and Re' is at least one selected from Al, Ga, In.) ) Is a photoluminescent phosphor.
[0024]
In addition, a nitride-based phosphor can be used in addition to or independently of the YAG-based phosphor. The nitride phosphor used in the present invention contains N, and at least one element selected from Be, Mg, Ca, Sr, Ba, and Zn, and C, Si, Ge, Sn, Ti, Zr. And at least one element selected from Hf and activated by at least one element selected from rare earth elements. The nitride-based phosphor used here is excited and emits light by absorbing visible light, ultraviolet light emitted by the LED chip 11, or light emitted from the YAG-based phosphor. Such nitride-based phosphors include, for example, Sr—Ca—Si—N: Eu, Ca—Si—N: Eu, Sr—Si—N: Eu, Sr—Ca—Si—O to which Mn is added. -N: Eu, Ca-Si-ON: Eu, and Sr-Si-ON: Eu-based silicon nitride. The basic constituent elements of the phosphor is represented by the general formula _{L X Si Y N (2 /} 3X + 4 / 3Y): Eu or _{L X Si Y O Z N (} 2 / 3X + 4 / 3Y-2 / 3Z): Eu (L is Sr, Ca, or any of Sr and Ca). In the general formula, X and Y are preferably X = 2, Y = 5 or X = 1, Y = 7. Specifically, the basic constituent elements, Mn is added _{(Sr X Ca 1-X)} 2 Si 5 N 8: Eu, Sr 2 Si 5 N 8: Eu, Ca 2 Si 5 N 8: Eu, Sr _{X Ca 1-X Si 7 N} 10: Eu, SrSi 7 N 10: Eu, CaSi 7 N 10: it is preferable to use a phosphor represented by Eu. The composition of these phosphors may include at least one selected from the group consisting of Mg, Sr, Ca, Ba, Zn, B, Al, Cu, Mn, Cr and Ni. The mixing ratio of Sr and Ca can be changed as desired.
[0025]
Such a nitride-based phosphor absorbs a part of the blue light emitted by the LED chip 11 and emits light in a yellow to red region. By using the nitride-based phosphor together with the YAG-based phosphor, blue light emitted by the LED chip 11, yellow light by the YAG-based phosphor, and red light by the nitride-based phosphor are mixed, and a warm color A surface emitting device that emits white light is obtained.
[0026]
[Embodiment 2]
FIG. 2 is a schematic cross-sectional view of a surface emitting device 2 according to Embodiment 2 of the present invention as viewed from a side. The members denoted by the same reference numerals in the drawings are the same as the members in the first embodiment, and description thereof will be omitted. The second embodiment is different from the first embodiment in that the light source cover 18 is disposed on the light emitting surface side (upper side in FIG. 2) of the LED chip 11. By arranging the light source cover 18 on the light emitting surface side of the LED chip 11 as a light emitting element in this manner, light emission from the LED chip 11 is not directly observed by an observer, so that the vicinity of the LED chip 11 is particularly bright. It is prevented from being observed.
Therefore, more uniform surface light emission can be obtained.
[0027]
As the light source cover 18, similarly to the case 13, various materials such as resin and metal are preferably used. In particular, metals such as nickel, iron, and copper, and various alloys such as stainless steel are more preferably used in consideration of light reflection and heat radiation of the LED chip 11. Further, it is preferable that Ag is deposited on the inner surface (the lower surface in FIG. 2) of the light source cover 18.
Further, by forming irregularities on the inner surface of the light source cover 18 and forming a light diffusion portion, more uniform surface light emission can be obtained. The light source cover 18 can be formed integrally with the housing 13.
[0028]
[Embodiment 3]
FIG. 3 is a schematic cross-sectional view of a surface emitting device 3 according to Embodiment 3 of the present invention as viewed from a side. The members denoted by the same reference numerals in the drawings are the same as the members in the first and second embodiments, and the description is omitted. In Embodiment 3, the light guide plate is
The difference is that the first light guide plate 121 has a light extraction surface 121a and the second light guide plate 122 has an end surface 122b in which a part of the LED chip 11 is embedded. The first light guide plate 121 contains light-transmitting fine particles having a mean particle size of 3 to 20 μm made of a benzoguanamine-based resin, PET, or the like as a diffusing material. The second light guide plate 122 contains at least the above-described phosphor. In the present embodiment, a part of the LED chip 11 is embedded in the end face 122b of the second light guide plate 122, and the other part of the LED chip 11 is exposed from the end face 12b of the second light guide plate 122. The surface light emitting device preferably includes a light source cover 18. Moreover, it is preferable that the second light guide plate 122 is disposed in a space formed by the housing 13 and the light source cover 18. According to the present embodiment, when performing color conversion using a phosphor, a surface emitting device with less chromaticity unevenness can be obtained.
[0029]
【Example】
FIG. 4 schematically shows a method for manufacturing the above-described surface emitting device according to the first embodiment of the present invention. In this embodiment, a housing 13 composed of four frames (inner wall surfaces) and a bottom surface formed of a 0.15 mm-thick metal on which Ag is deposited is used. First, a mounting board 17 on which five LED chips are arranged is arranged in one of the four frames of the housing 13 (FIG. 4A). Next, a light guide plate forming material such as a resin for forming the light guide plate 12 is filled in the housing 13. Then, a diffusion sheet having a thickness of 65 μm, a first prism sheet having a thickness of 65 μm, and a second prism sheet having a thickness of 65 μm are sequentially placed on the light guide plate 12 (FIG. 4B).
[0030]
Thus, the surface emitting device of the present invention is obtained. In the surface light emitting device according to the present invention, since the LED chip 11 itself is sealed by the light guide plate 12, the thickness of the conventional surface light emitting device is 0.8 to 1.0 mm, .25 to 0.35 mm. The thickness of the light guide plate 12 is preferably three times or less, more preferably two times or less, the width of the LED chip 11 in the thickness direction of the light guide plate 12.
[0031]
Further, after being formed as described above, the light source cover 18 can be disposed.
[0032]
In the method of manufacturing the surface light emitting device including the first light guide plate 121 and the second light guide plate 122, first, a part of the opening of the housing 13 is covered with the light source cover 18, and the housing 13 and the light source cover 18 Is filled with a light guide plate forming material such as a resin for forming the second light guide plate 122 in the space formed by the above. Thereafter, the remaining space in the housing 13 can be manufactured by filling a light guide plate forming material such as a resin for forming the first light guide plate 121.
[0033]
【The invention's effect】
As described above, a thin surface emitting device that can be used as a light source such as a backlight of a liquid crystal display can be provided. In the surface light emitting device of the present invention, since the LED chip is directly molded by the light guide plate, even if the chip size is the same, the light emitting diode made of the LED chip and the mold resin for sealing the LED chip is disposed on the light guide plate. A surface light emitting device that is thinner than the surface light emitting device can be obtained.
[0034]
Further, in the surface light emitting device of the present invention, since the LED chip is directly molded by the light guide plate, a surface light emitting device having less luminance unevenness can be obtained as compared with a surface light emitting device using a light emitting diode having high directivity. Furthermore, in the surface light emitting device of the present invention, since the other part of the light emitting element is exposed from the end face of the light guide plate, the heat dissipation property is lower than that of the surface light emitting device in which the light emitting diode is completely buried in the light guide plate. Is high.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a surface emitting device according to a first embodiment of the present invention as viewed from a side.
FIG. 2 is a schematic cross-sectional view of a surface light-emitting device according to Embodiment 2 of the present invention as viewed from a side.
FIG. 3 is a schematic cross-sectional view of a surface emitting device according to Embodiment 3 of the present invention as viewed from a side.
FIG. 4 is a schematic view illustrating a method for manufacturing a surface emitting device according to the present invention.
FIG. 5 is a schematic cross section showing an example of a conventional surface light emitting device.
[Explanation of symbols]
1, 2, 3 Surface emitting device 11 LED chip 12 Light guide plate 13 Housing 14 Diffusion sheet 15 First prism sheet 16 Second prism Sheet 17 Mounting board 18 Light source cover 121 First light guide plate 122 Second light guide plate

Claims (4)

A light emitting element, and a light guide plate having a light extraction surface and an end surface, a surface light emitting device,
A surface light emitting device, wherein a part of a light emitting element is embedded in an end face of a light guide plate, and another part of the light emitting element is exposed from an end face of the light guide plate. The light emitting element is arranged on the mounting board,
The surface emitting device according to claim 1, wherein the mounting substrate is attached to an end surface of the light guide plate. The light guide plate is arranged in the housing,
The surface emitting device according to claim 2, wherein the mounting substrate is disposed on at least a part of an inner wall surface of the housing. A light emitting element, a light guide plate having a light extraction surface and an end surface, a method for manufacturing a surface light emitting device comprising:
A method for manufacturing a surface light emitting device, comprising: filling a light guide plate forming material for forming a light guide plate in a housing in which a mounting substrate on which a light emitting element is disposed is disposed on at least a part of an inner wall surface.

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