背景技术：
[0005]When operating the operation buttons or key buttons of mobile phones, PDAs, and personal computers and the like in dark places, these buttons or keys are illuminated in order to make the positions of the operation buttons and key buttons easily viewable.
[0006]Conventionally, in order to brightly illuminate the key buttons of a mobile phone and the like, a planar light emitting device is used, and as one aspect of this planar light emitting device, a side surface light emitting type planar light emitting device is widely employed.
[0007]That is to say, this side surface light emitting type planar light emitting device is constituted from a light guiding plate (light guiding film) that is arranged on the back surface side of the display panel such as a liquid crystal panel, and a light source that is arranged at a side end face of this light guiding film. Also, examples of the light source that is applied to this planar light emitting device include a light emitting diode (LED), a cold-cathode tube, and the like.
[0008]As one example of this illumination device, for example, Patent Document 1 discloses a push button switch-type illumination device. As shown in FIG. 11, in this push button switch-type illumination device, a substrate 103 is arranged inside of a case that consists of an upper case 101 and a lower case 102. A keypad 105 that is provided with a plurality of operation keys 104 is provided above this substrate 103. A light guiding plate 106 is arranged between this keypad 105 and the substrate 103, and switching elements 107 corresponding to the operation keys 104 are arranged on the upper surface side of the substrate 103. The operation keys 104 of the keypad 105 are exposed to the outside via a plurality of operation holes 101a that are formed in the upper case 101. Along with that, a display device 109 such as a liquid display panel is provided at an end portion of the substrate 103. This display device 109 can be viewed from outside via a display window 101b that is formed in the upper case 101.
[0009]Then, the light guiding plate 106 provided between the substrate 103 and the keypad 105 illuminates the operation keys 104 from the rear-face side (inner side). A light source 108 is provided at one end portion of the light guiding plate 106. The light guiding plate 106 projects the light that is made incident from the light source 108 onto the light guiding plate 106 to the rear-face side of the keypad 105, and thereby illuminates the operation keys 104 from the rear-face side.
[0010]Also, as another structure example of a planar light emitting device that is provided with this light guiding plate, a plurality of the light sources 111 are arranged at the end portion side of the light guide 110, as shown in FIG. 12 and FIG. 13. A switch sheet 112 is arranged on the rear-face side (the lower-surface side in the drawing) of the light guide 110. A key mat 113 is arranged on the front-surface side (the upper-surface side in the drawing) of the light guide 110. A light extracting portion 110a that consists of a plurality of concave-convex portions (concave-convex portions) is provided at required positions of the light guide 110, and illumination light is guided to the surface side (upper-face side) of the light guide 110 via the light extracting portion 110a.
[0011]In recent years, in this kind of planar light emitting device, it has been desired to illuminate the operation keys so as to selectively cause only specified operation keys to emit light, or so as to selectively cause only specified operation keys not to emit light.
[0012]As a method of achieving this issue, for example Patent Document 2 discloses a structure that provides a light-blocking portion that consists of a non-light-transmissive resin at the light guide. That is to say, in this structure, by dividing the aforementioned light guide into a plurality of regions, providing a slit at the portion that becomes the boundary of each region, and filling the non-light-transmissive resin in the interior of the slit, the light-blocking portion that consists of the non-light-transmissive resin is provided at the boundary of each region of the light guide. In order to realize this structure, in the structure disclosed in Patent Document 2, as shown in FIG. 14A to FIG. 14D, a UV curable resin film 151 is formed by spin coat method on a carrier base 150, and after curing the resin film, a slit 152 is formed at the required position by selective etching. Thereafter, using a resin dispenser 153, a black resin 155 is filled in the slit 152, and by curing this resin 155, the light-blocking portion 156 is formed.
[0013]Also, for example Patent Document 3 discloses an illumination device that can respectively illuminate the upper portion and lower portion of a push button using only one light guide. This illumination device is provided with a light-blocking rib that has a notched portion, and a light guide body that is attached to this light-blocking rib. This light guide body is provided with a first light guide portion and a second light guide portion that illuminate the upper portion and lower portion of the push button respectively. These first and second light guide portions are integrated via a crank-shaped connection portion. By fitting the crank-shaped connection portion in the notched portion of the light-blocking rib, the light guide body is attached to the light-blocking rib. In this way, by using only one light guide body, it is possible to perform separate illumination.
[0014]Furthermore, for example Patent Document 4 (Japanese Unexamined Patent Application, First Publication No. 2008-152951) discloses a switch sheet module that can cause a plurality of key switches to emit light with fewer light emitting elements at every group. This switch sheet module is provided with a light guide sheet portion that covers the upper surface of the key switch, and the light guide sheet portion is constituted by a plurality of light conductive sheet materials of which at least one portion is overlapped, and an LED is arranged at each light conductive sheet material.
[0015]The method that is disclosed in paragraph 0034 to paragraph 0035 of Patent Document 2 (Japanese Unexamined Patent Application, First Publication No. 2008-41431) manufactures the UV-curable resin film 151 that becomes a light guide by spin coat method (as shown in FIG. 14A to FIG. 14C), and after subjecting this resin film 151 to UV curing, forms the slit 152 by selective etching. Thereafter, resin is injected into this slit 152, and by curing this resin, a hard light-blocking portion 156 is formed. Accordingly, the method according to Patent Document 2 has the problem that the manufacture requires excessive time and effort.
[0016]Also, as shown in paragraph 0036 to paragraph 0037 of Patent Document 2, even in the case of adopting a method that applies an insert formation technique, since a step that sandwiches a black, hard resin in a metal mold and flows a light guide material from both sides is required, it has the problem of requiring excessive time and effort for manufacture.
[0017]The method that is disclosed in Patent Document 2 is a method that provides the light-blocking portion 156 in the resin film 151 that is formed with the spin coat method and has a thickness of about 0.3 mm to 2 mm, and the thickness of the light-blocking portion 156 that is filled and formed in the slit 152 of the resin film 151 is 0.3 mm to 2 mm, and thus extremely thick. As shown in FIG. 5 and FIG. 6 of Patent Document 2, the light-blocking portion 156 and the resin film 151 that are integrally molded are completely bonded. Accordingly, in the case of the material that constitutes the light-blocking portion 156 differing from the material that constitutes the resin film 151, there is a possibility of the light-blocking portion 156 exfoliating by a change in the environmental temperature, due to the difference of the linear expansion coefficients of these materials. Also, by having a structure that fills in the entirety of the slit 152 with the light-blocking portion 156, the heat dissipation around the slit formation portion of the resin film 151 worsens, and so there is the possibility of discoloration occurring in the resin material that constitutes the light guide due to the working temperature environment.
[0018]Furthermore, it is conceivable to apply the technique disclosed in Patent Document 3 (Japanese Unexamined Utility Model Application, First Publication No. H05-53070) to provide a light-blocking member in a push button switch-type illumination device disclosed in Patent Document 1 (Japanese Unexamined Patent Application, First Publication No. 2001-167655). However, the field of application of the technique given in Patent Document 3 is car audio, and the structure of Patent Document 3 is therefore can be applied when there is ample space. On the other hand, in the field of mobile telephones, there is a desire to make the overall thickness as thin as possible, and so applying the technique that is disclosed in Patent Document 3 is not easily done.
具体实施方式：
[0078]Herein below, the planar light emitting device according to the embodiments of the present invention shall be described.
[0079]The following embodiments shall be described in detail in order to allow better understanding of the gist of the present invention, and unless otherwise specified, will not serve to limit the present invention.
First Embodiment
[0080]FIG. 1A to FIG. 2B are outline drawings that show the planar light emitting device according to the first embodiment of the present invention. Among them, FIG. 1A is a plan view, FIG. 1B is a cross-sectional view along line A-A′ of FIG. 1A, FIG. 2A is a partial enlarged view of the planar light emitting device shown in FIG. 1B, and FIG. 2B is a partial cross-sectional view of a switch sheet that is incorporated in the same planar light emitting device.
[0081]As shown in FIG. 1A and FIG. 1B, the planar light emitting device 10 of the present embodiment is provided with two first light sources 11 and 11, one second light source 12, a sheet-like light guide 13 that is arranged in the vicinity of the exit face 11a of the first light source 11, and a switch sheet 20 that is arranged on one surface (rear surface, lower surface) 13a side of the light guide 13. This light guide 13 has a rectangular shape in the plan view of FIG. 1A. Note that in the present embodiment, two first light sources and one second light source are provided, but it is not limited thereto, and for example one first light source can be provided as necessary.
[0082]As shown in FIG. 1B, the switch sheet 20 is bonded to the light guide 13 via a first adhesive material (a first spacer) 15 that is provided in a frame shape at the periphery of the one surface (rear surface, lower surface) 13a of the light guide 13. Due to this structure, a gap 18 is provided between the light guide 13 and the switch sheet 20. That is to say, the light guide 13 and the switch sheet 20 are not in contact, but rather the light guide 13 and the switch sheet 20 are oppositely arranged spaced apart by the gap 18 in accordance with the thickness of the first adhesive material 15. This first adhesive material 15 is provided in a rectangular shape along the outer periphery of the light guide 13, as shown by the dotted line in FIG. 1A.
[0083]An adhesive that retains its own shape is used as the first adhesive material 15. Examples of such an adhesive include acrylic resin, polyurethane resin, epoxy resin, urethane resin, natural rubber adhesive, synthetic rubber adhesive, or a double-sided adhesive tape in which these resins or adhesives are coated on both sides of a backing material that consists of resin or paper.
[0084]The thickness of the gap 18 that is provided between the light guide 13 and the switch sheet 20, that is, the distance between the light guide 13 and the switch sheet 20 (in other words, the thickness of the first adhesive material 15) is not particularly limited, and it is sufficient for the light guide 13 and the switch sheet 20 not to make contact in the situation of the planar light emitting device 10 being used. In order to make the overall planar light emitting device 10 thinner, the distance between the light guide 13 and the switch sheet 20 is approximately 0.01 mm to 0.05 mm, and for example more than or equal to 0.03 mm and less than or equal to 0.05 mm is preferred.
[0085]The light guide 13 according to the present embodiment is partitioned into two regions. That is to say, as shown in FIG. 1A and FIG. 1B, the light guide 13 is partitioned into a first region 13A and a second region 13B. A through slit 13C having a U-shape in plan view that penetrates the light guide 13 in the thickness direction is provided at the boundary portion between the first region 13A and the second region 13B. That is to say, as shown in FIG. 1A, the through slit 13C forms a U-shape in plan view. Moreover, as shown in FIG. 1B, this through slit 13C penetrates in the thickness direction of the light guide 13.
[0086]In the planar light emitting device 10 of this first embodiment, as shown in FIG. 1A, in the case of the end portion of the light guide 13 of the side adjacent to the first light sources 11 being a first end portion, and the end portion of the light guide 13 on the opposite side of this first end portion being a second end portion, both ends 13g of the U-shaped through slit 13C are arranged near the edge of the light guide 13 in the middle of the second end portion.
[0087]In the light guide 13, the first region 13A and the second region 13B are connected by a bridge portion 13h that is adjacent to both ends 13g of the U-shaped through slit 13C. The width of the bridge portion 13h is about the same as the width of the first adhesive material 15. Thereby, the wrapping around of light between the first region 13A and the second region 13B via this portion is restricted to a minimum. In FIG. 1A and FIG. 1B, the first adhesive material 15 is provided in a rectangular shape along the outer periphery of the light guide 13 as shown by the dotted line in FIG. 1A, but it is not limited thereto. Moreover, the first adhesive material 15 may also be provided along the U-shape at the outer periphery of the second region 13B of the light guide 13. Furthermore, the first adhesive material 15 may also be provided along the U-shape at the inner periphery of the first region 13A of the light guide 13 corresponding to the second region 13B. These first adhesive materials 15 are preferably the same thickness.
[0088]The structure of the present embodiment is a structure that provides the bridge portion 13h at both end sides of the through slit 13C. However, it is also acceptable to adopt a constitution that omits the bridge portion 13h and brings the through slit 13C all the way to the end portion of the light guide 13. That is to say, in the present embodiment, the first region 13A and the second region 13B are connected by the bridge portion 13h so as not to be completely independent. However, the present embodiment is not limited thereto, and it is possible for the first region 13A and the second region 13B to be two completely independent pieces that are not connected.
[0089]In the case of the first region 13A and the second region 13B being independent, it is possible to make a structure that provides the first adhesive material 15 to be extended to the periphery of the through slit 13C, and individually fixes and bonds the first region 13A and the second region 13B of the light guide 13 onto the switch sheet 20 using the first adhesive material 15. That is to say, it is possible to provide the first adhesive material 15 along the U-shape of the through slit 13C at the outer periphery of the second region 13B and the inner periphery of the first region 13A.
[0090]Also, as shown in FIG. 1A, one end portion (free end) 13f of the second region 13B of the light guide 13 is formed so as to be diagonally cut away in the case of viewing the light guide 13 in plan view. The second light source 12 such as an LED is arranged on the switch sheet 20 at the outside of the one end portion 13f and within the through slit 13C so as to face the one end portion 13f. This second light source 12 can individually make light incident on the second region 13B via the one end portion 13f of the light guide 13.
[0091]Note that in the U-shaped through slit 13C seen in plan view in FIG. 1A, a light-blocking adhesive layer 14 described below is omitted at the one end portion 13f for making light incident from the second light source 12 to the second region 13B. That is to say, it is possible to introduce light from the second light source 12 to the second region 13B of the light guide 13 via the one end portion 13f at which the light-blocking adhesive layer 14 is not formed.
[0092]The light guide 13 according to the present embodiment consists of a sheet-shaped resin, and for example has a rectangular shape in plan view.
[0093]The resin that constitutes the light guide 13 it is not particularly limited, provided it is a light transmissive resin and an elastically deformable resin, and any one chosen from the group consisting of polyurethane resin, polycarbonate resin, silicone resin, polystyrene resin, polyimide resin, an elastomer of polymethyl methacrylate (PMMA), and urethane acrylate is used.
[0094]Among these resins, a resin that has a moderate rigidity is preferred in order to maintain a constant width of the gap 18 that is provided between the light guide 13 and the switch sheet 20, that is, so that the light guide 13 and the switch sheet 20 do not make contact. Specifically, polyurethane resin, silicone resin, or polycarbonate resin is preferable.
[0095]Moreover, since polyurethane resin and silicone resin have elasticity, the upper surface of the light guide 13 that consists of these resins is difficult to damage, and has a nice feel when pressing the switch element 30, described later, that is provided on the switch sheet 20. Also, a polycarbonate resin has a characteristic of having high light transmission even when the thickness is thin.
[0096]The thickness of the light guide 13 is not particularly limited, and the thickness of the light guide 13 can be set such that the transmission of the outgoing light from the first light sources 11 and the second light source 12 is high, and in the case of the operator pressing a necessary position of the light guide 13 with an operating device such as a fingertip or a pen, the operating device can perform input to the switch element 30 of the switch sheet 20, and on the other hand in the case of not pressing the switch element 30 of the switch sheet 20, can constantly maintain the width of the gap 18 that is provided between the light guide 13 and the switch sheet 20 (that is to say, can ensure that the light guide 13 and the switch sheet 20 do not make contact). The thickness of the light guide 13 is 0.05 mm to 0.3 mm and preferably for example more than or equal to 0.1 mm and less than or equal to 0.2 mm in order to make the planar light emitting device 10 thinner.
[0097]Then, a light-blocking adhesive layer 14 that is formed by a hot press process is provided on the inner surface side of the through slit 13C of the light guide 13. As shown in FIG. 1B, the light-blocking adhesive layer 14 is formed along the inner wall surface of the through slit 13C having a U-shape in plan view so as to cover the entire inner wall surface thereof, except for the one end portion 13f that faces the second light source 12 as shown in FIG. 1A. That is to say, this light-blocking adhesive layer 14 consists of a main body portion 14a, a flange portion 14b, and a bottom portion (base portion) 14c, and is formed in an approximate U-shape in transverse section. The main body portion 14a is continued to the flange portion 14b, and the bottom portion 14c is provided in an extended manner from the lower portion of the main body portion 14a. Among these, the main body portion 14a adheres to the inner wall surface of the through slit 13C, and covers the through slit 13C. The flange portion 14b is formed extending to the upper portion side of the main body portion 14a, and covers the upper surface opening edge portion of the through slit 13C by a predetermined width. The bottom portion (base portion) 14c is formed to project from the bottom surface of the light guide 13 at the lower portion side (switch sheet 20 side) of the main body portion 14a, adhere to the upper surface (one surface) of the switch sheet 20, and fill the gap between the bottom portion of the through lit 13C and the light guide 13. That is to say, the bottom portion 14c covers the space of the bottom portion of the through slit 13C until the switch sheet 20.
[0098]Since the light-blocking layer 14 is formed to be thinner than the width of the through slit 13C, and is formed so as to cover the entire inner wall surface of the through slit 13C, a groove-type recess portion (concave portion) 16 is formed between the mutually facing main body portions 14a, 14a at the inner side of the through slit 13C. That is to say, the light-blocking adhesive layer 14 is formed in a state of a space (recess portion) being left on the interior side (inner side) of the through slit 13C.
[0099]As shown in FIG. 2A, the light-blocking adhesive layer 14 of the present embodiment has a two-layer structure that consists of a hot melt layer 14A that is arranged on the inner wall surface side of the through slit 13C and on the upper surface side of the switch sheet 20, and a light-blocking layer 14B that is laminated to the hot melt layer 14A. As shown in FIG. 2A, the light-blocking layer 14B is provided with a flange portion that covers the opening edge portion of the through slit 13C, a main body portion that is connected to this flange portion and that covers the inner wall surface of the through slit 13C, and a bottom portion that is provided in an extended manner from the lower portion of the main body portion. In the present embodiment, unless particularly limited, the light-blocking layer 14B and the light-blocking adhesive layer 14 have the same structure.
[0100]The hot melt layer 14A is a layer that consists of a hot melt adhesive that has a solid form in its initial state, but softens by heating to become flowable, and then hardens to have an adhering performance by subsequent cooling.
[0101]As a hot melt adhesive that can be applied as the hot melt layer 14A, it is possible to use an ethylene-vinyl acetate resin hot melt adhesive, a polyamide resin hot melt adhesive, a polyurethane resin hot melt adhesive, a polyolefin resin hot melt adhesive, a styrene resin hot melt adhesive, and the like.
[0102]The hot melt layer 14A is formed by using a layer that consists of the aforementioned hot melt adhesive, causing the layer to thermally deform along the through slit 13C by a hot press process that will be described later to expand into a shape conforming to the through slit 13C, and then cooling to bond and harden the layer.
[0103]Note that the hot melt adhesive generally has a slightly viscous tackiness at room temperature, which is advantageous for temporarily installation on the surface of the light guide 13 at room temperature, and thus has the characteristic of temporary positioning of a light-blocking adhesive material for forming the light-blocking adhesive layer 14 being easy when using the hot press process described later.
[0104]The light-blocking layer 14B consists of a resin with a softening point that is near that of the hot melt layer 14A, and consists of a light-blocking resin material with a black color or a dark color having a high light blocking effect, such as black PET (black inorganic particles, such as carbon black, blended with polyethylene terephthalate resin), black urethane, polyethylene naphthalate (PEN), and polymethyl methacrylate resin (PMMA).
[0105]Note that in the present invention, since the light-blocking resin material that constitutes the light-blocking layer 14B should block light, in addition to a black resin or a dark resin having a high light-blocking performance as mentioned above, a structure that includes a material with light reflectivity is one type of resin with a light blocking effect of the present embodiment. For example, the light-blocking layer 14B made of resin having light reflectivity that includes a filler that has light reflecting properties may be applied as a light-blocking layer.
[0106]Here, examples of the respective dimensions such as the thickness and width of the through slit 13C and the light-blocking adhesive layer 14 shall be described.
[0107]Given the object of applying the through slit 13C to a planar light emitting device that is provided with a switch sheet compatible with a thin electronic device, the width of the through slit 13C that is applied to the planar light emitting device 10 of the present embodiment is preferably less than or equal to 1 mm, and more preferably more than or equal to 0.1 mm and less than or equal to 1 mm or less, and for example can be formed in a range of 0.3 mm to 0.4 mm. When the width of the through slit 13C exceeds 1 mm, the through slit width with respect to the totality becomes too large, which is not preferable.
[0108]Also, in the light-blocking adhesive layer 14, the length (the length along the width direction of the through slit 13C) of the flange portion 14b that covers the upper surface opening edge portion of the through slit 13C by a predetermined width can be formed to be 0.05 mm to 0.5 mm, for example, around 0.1 mm. When the length of the flange portion 14b is less than 0.05 mm, the adhesiveness is not sufficient, and when it is greater than 0.5 mm, it becomes too long and there is the possibility of it having an adverse effect on other members.
[0109]Furthermore, the thickness of the light-blocking adhesive layer 14 may be suitably changed in accordance with the width of the through slit 13C, but in any case it is necessary to leave a space on the inner side of the through slit 13C equivalent to a thickness that does not entirely fill the through slit 13C over the width direction thereof. Accordingly, the hot melt layer 14A and the light-blocking layer 14B that constitute the light-blocking adhesive layer 14 are formed with a thickness of 10 μm to 250 μm, for example, approximately 25 μm. When the thickness is less than 10 μm, the adhesiveness and light blocking performance are not sufficient, and when the thickness exceeds 250 μm, the through slit 13C ends up being filled in, and there is a possibility of the space on the inner side of the through slit 13C being eliminated.
[0110]Accordingly, the light-blocking adhesive layer 14 forms the recess portion 16 so as to leave a space at the inner side of the through slit 13C without covering the entire through slit 13C, and is formed so as to cover the opening edge portion and the inner wall surface of the through slit 13C, and cover the gap between the bottom portion of the through slit 13C and the upper surface of the switch sheet 20. That is to say, the light-blocking adhesive layer 14 is formed in a U-shape that has the recess portion 16, with the bottom portion of the U-shape inserted in the through slit 13C from the bottom portion of the U-shape until making contact with the upper surface of the switch sheet 20.
[0111]Next, the light-extracting portion 19 that is formed on one surface (the surface on the switch sheet 20 side) 13a of the light guide 13 adopts a structure such as forming a concave-convex portion 19A at the necessary region of the one surface 13a of a resin sheet that constitutes the light guide 13. At the region where the concave-convex portion 19A is formed, light leaks out from the interior of the light guide 13 to the one surface 13a of the light guide 13.
[0112]The plurality of light-extracting portions 19 that are formed on the one surface 13a side of the light guide 13 are aligned in plan view with a plurality of pressure-sensitive switch elements 30 that are incorporated in the switch sheet 20. That is to say, as shown in FIG. 1B, the light-extracting portions 19 are respectively arranged so as to be vertically opposite a metal plate 23 of the switch element 30, however, these installation positions need not be in complete agreement in the vertical orientation, and may be at a position that is slightly shifted in plan view.
[0113]As shown in FIG. 1A and FIG. 2B, in the switch sheet 20 that is applied in the present embodiment, a plurality of contact members 22 are provided at a predetermined interval on the one surface (hereinbelow referred to as the upper surface) 21a of the substrate 21 that faces the light guide 13. The metal plate 23 with a dome shape is provided so as to cover each contact member 22 that is positioned nearly at the center. Furthermore, a pressing sheet 25 is provided via an adhesive layer 24 so as to cover these dome shape metal plates 23.
[0114]In greater detail, as shown in FIG. 2B, the plurality of contact members 22, which consist of an electrically conductive material, are provided at a predetermined interval on the upper surface 21a of the substrate 21 that consists of a printed wiring substrate such as a PCB (printed circuit board) or an FPC (flexible printed circuit), and this predetermined interval can be set in accordance with the arrangement positions and dimensions of the key buttons that are to be illuminated. An annular contact member 26 that consists of an electrically conductive material is provided at the surrounding area of each contact member 22. The dome shaped metal plate 23 for switching between conduction and non-conduction of the contact member 22 and the contact member 26 is provided so as to cover the contact member 22 and the contact member 26.
[0115]This metal plate 23 is provided with flexibility that enables it to connect and disconnect with the contact member 22, and constitutes a bowl-shaped metal dome that has a convex shape on the opposite side of the upper surface 21a of the substrate 21. That is to say, the metal plate 23 is an arch-shaped flexible plate that projects upward in the cross-sectional view of FIG. 2B, and curves downward when an external force is applied, and recovers to the original shape via its flexibility when the external force is removed. More specifically, when for example an operator pushes the center of the upper surface 23a of the metal plate 23 by an operating device such as a fingertip, the center of the upper surface 23a of the metal plate 23 deforms so as to bend toward the upper surface 21a side of the substrate 21. Thereby, the metal plate 23 abuts the contact member 22, and the contact member 22 and the contact member 26 conduct.
[0116]Accordingly, a single pressure-sensitive switch element 30 is constituted on the switch sheet 20 by the contact member 22 that is provided on the upper surface 21a of the substrate 21, the contact member 26 that is provided around the contact member 22, the metal plate 23 that is provided so as to cover the contact member 22 and the contact member 26, and the pressing sheet 25 that covers these metal plates 23. A plurality of such switch elements 30 is provided on the substrate 21.
[0117]Also, the position of the metal plate 23 is held by the adhesive layer 24 that is formed on the rear surface side (substrate 21 side) of the pressing sheet 25.
[0118]As the first light source 11 and the second light source 12, one that consists of a light emitting element such as a light emitting diode (LED) or a luminous body such as a cold-cathode tube is used. In the case of the first light source 11 and the second light source 12 consisting of an LED, the light emitting element chip is housed in a box-shaped case, and it is constituted so as to be able to emit the light that this light emitting element chip has emitted from an exit face 11a on the case side surface of the first light source 11, or from an exit face 12a on the case side surface of the second light source 12.
[0119]Also, the first light source 11 is connected to an electrical circuit, not illustrated, on the substrate 21 by solder 29. Similarly, the second light source 12 is connected to another electrical circuit on the substrate 21 by solder (not illustrated).
[0120]In the first region 13A of the light guide 13, when the outgoing light from the first light sources 11 and 11 is made incident on the one end surface 13e that is adjacent to the first light sources, the incident light propagates through the interior of the light guide 13 while repeatedly reflecting between the one surface (rear surface) 13a and the other surface (front surface) 13b of the light guide 13. When the concave-convex portions and the like are formed at the required regions of the one surface 13a of the light guide 13, the light that propagates through the interior leaks out from the concave-convex portions. Thereby, it is possible to emit light from the light extracting portion 19 of the light guide 13 to the outside, and it is possible to visually confirm this light from the outside of the light guide 13 through the light guide 13. That is, it is possible to emit light from the light extracting portion 19 and visually confirm this light from the outside via the light guide 13 by light that propagates through the interior of the light guide 13.
[0121]Similarly, in the second region 13B of the light guide 13, when the outgoing light from the second light source 12 is made incident on the one end portion 13f thereof, the incident light propagates through the interior of the light guide 13 while repeatedly reflecting between the one surface (rear surface) 13a and the other surface (front surface) 13b of the light guide 13. It is possible to emit the light from the light extracting portion 19 that is provided at the one surface 13a of the light guide 13 to the outside, and visually confirm the light from the outside via the light guide 13.
[0122]The concave-convex portion 19A that constitutes the light extracting portion 19 can be constituted from micro dots that are formed on the one surface 13a of the light guide 13 by for example a printing method such as a screen printing method, a gravure printing method, a pad printing method, or the like. However, the concave-convex portion 19A is not limited only to the micro dots, and may also be a structure that forms the concave-convex portion by a method such as etching on the one surface 13a of the light guide 13.
[0123]In the planar light emitting device 10 of the present embodiment, when the position of the light extracting portion 19 of the light guide 13 is pressed by an operating device such as a fingertip or a pen by an operator, since the operating device causes the metal plate 23 to bend downward and deform, the center of the metal plate 23 abuts the contact member 22, and it is possible to cause the contact member 22 to conduct with the contact member 26.
[0124]Accordingly, according to the planar light emitting device 10 of the present embodiment, it is possible to perform position display of the switch portion where the metal plate 23 is provided by the leak light from each light extracting portion 19. In addition, by pressing the light extracting portion 19 with an operating device such as a pen or a fingertip to cause the metal plate 23 to deform, and switching the conduction of the contact member 22 and the contact member 26, it is possible to perform an ON/OFF (conduction and non-conduction) operation of each switch element 30.
[0125]The light guide 13 of the planar light emitting device 10 of the present embodiment is segmented into the first region 13A and the second region 13B, and the through slit 13C is provided between these two regions, with the light-blocking adhesive layer 14 being arranged within the through slit 13C. Accordingly, in the first region 13A of the light guide 13, when the outgoing light from the first light sources 11 and 11 is made incident on the one end face 13e of the light guide 13, it is possible to cause light to be emitted only through the light-extracting portions 19 that are provided at the first region 13A with that incident light, and there is no light emission through the light-extracting portion 19 that is provided at the second region 13B by that incident light. Also, in the second region 13B of the light guide 13, when the outgoing light from the second light source 12 is made incident on the one end portion 13f thereof, it is possible to cause only the light-extracting portion 19 that is provided at the second region 13B to emit light by that incident light, and there is no light emission through the light-extracting portions 19 that are provided at the first region 13A by that incident light.
[0126]That is to say, according to the structure of the present embodiment, since the opening edge portion of the through slit 13C of the light guide 13 is covered by the flange portion 14b of the light-blocking adhesive layer 14 (flange portion of the light-blocking layer), the inner wall surface of the through slit 13C is covered by the main body portion 14a of the light-blocking adhesive layer 14 (main body portion of the light-blocking layer), and the portion of the gap between the bottom portion of the through slit 13C and the switch sheet 20 is covered by the bottom portion 14c of the light-blocking adhesive layer 14 (bottom portion of the light-blocking layer), there is no leakage of light to the sides of other regions via the through slit 13C of the light guide 13.
[0127]Also, since the light-blocking adhesive layer 14 adheres to the opening edge portion of the through slit 13C and the upper surface of the switch sheet 20 (upper surface of the pressing sheet 25) by the hot melt layer 14A, it is possible to firmly bond the light-blocking adhesive layer 14 to both the light guide 13 and the switch sheet 20, and even if thermal stress is repeatedly received due to the installation environment, and even if a repeated pressing force is received due to the switch operation on the switch sheet 20, there is little risk of the light-blocking adhesive layer 14 exfoliating from the light guide 13 or the switch sheet 20. In addition, since the hot melt layer 14A can be readily press fitted and bonded to the through slit 13C portion by a hot press process using a heating and pressing jig such as a hot press jig described later, it is possible to carry out the structure of the present embodiment extremely easily.
[0128]Next, since the light-blocking adhesive layer 14 is provided with at least the two layers of the hot melt layer 14A and the light-blocking layer 14B, the hot melt layer 14A is furnished with a strong adhesive force, and the light-blocking layer 14B has an excellent light-blocking performance, and thus it is possible to divide functions between the layers. Accordingly, using the light-blocking adhesive layer 14 that satisfies both the adhesive force and light-blocking performance at a sufficiently high level, it is possible to achieve a structure that covers the through slit 13C. However, the present embodiment is not limited only to this, and for example by blending a black filler or additive with the hot melt layer, it is possible to provide a light-blocking performance to the hot melt layer itself. In the case of such a structure, it is preferable to ensure that the adhesive force of the hot melt layer itself does not drop excessively.
[0129]Furthermore, when the bottom portion 14c of the light-blocking adhesive layer 14 (bottom portion of the light-blocking layer) is provided so as to fill the gap between the bottom portion of the through slit 13C of the light guide 13 and the switch sheet 20, since the light-blocking adhesive layer 14 closes the gap between the bottom portion of the through slit and the switch sheet 20, it is possible to inhibit the entry of dust to the switch sheet 20 side via the through slit 13C. Accordingly, it is possible to prevent the mixing of foreign matter to the switch sheet 20 side, and it is possible to provide the planar light emitting device 10 with excellent dust control and waterproof performance. Thereby, even in the case of the planar light emitting device 10 of the present embodiment being used over a long period, it is possible to prevent the infiltration of dust to the switch sheet 20 side, and it is possible to prevent malfunctioning of the switch sheet.
[0130]Accordingly, it is possible to provide the planar light emitting device 10 with high dust control and waterproof performance that has a simple structure and is provided with a light-blocking structure that has a superior effect of preventing the leakage of light to adjacent regions by segmenting the light guide 13 into regions, has excellent adhesive strength, and can endure thermal stress due to changes in the environmental temperature and repeated pressing force.
[0131]Next, a structure is made in which the light-blocking adhesive layer 14 is formed over the facing inner wall surfaces of the through slit 13C of the light guide 13 and the upper surface of the switch sheet 20 that is close to them (the upper surface of the pressing sheet 25), and the recess portion 16 is formed on the inside of the through slit 13C. By such a structure, even if the light guide 13 undergoes repeated thermal contraction and thermal expansion so as to narrow or widen the width of the through slit 13C by repetition of thermal expansion of the light guide 13, and as a result repeated thermal stress is made to act on the light-blocking adhesive layer 14, since it is possible for the light-blocking adhesive layer 14 to easily deform i