Surface emitting device and liquid crystal display

The present invention relates to a surface light emitting device and a liquid crystal display device.

[0002] Conventionally, in a reflective liquid crystal display device that displays by using ambient light as a light source, the brightness thereof depends on the amount of ambient light, so that the surroundings are sufficient such as when used in a dark place. In an environment where light cannot be obtained, there is a problem that the visibility of the display is extremely lowered. Therefore, a liquid crystal display device of a type in which a front light (surface emitting device) is arranged on the front side of a reflective liquid crystal display unit (liquid crystal display element) and used as an auxiliary light source has been proposed. The liquid crystal display device equipped with this front light operates as a normal reflective liquid crystal display device in an environment where sufficient ambient light can be obtained, such as outdoors in the daytime, and turns on the front light as a light source as needed. Is. FIG. 10 shows an example of a liquid crystal display device in which a front light is arranged on the front surface of the liquid crystal display unit. The liquid crystal display device 100 shown in FIG. 10 includes a liquid crystal display unit 120 and a front light 110, and the front surface of the liquid crystal display unit 120 (so that the light guide plate 112 is arranged in the display area of the liquid crystal display unit 120). The front light 110 is arranged on the upper surface of FIG. 10).

[0003] The front light 110 includes a flat plate-shaped light guide plate 112 produced by injection molding a transparent acrylic resin or the like, and a rod-shaped bar light source 113 arranged on the side end surface side of the light guide plate 112. A light source cover 115 made of a U-shaped metal plate in a side view is attached from the bar light source 113 side. That is, the light source cover 115 accommodates the bar light source 113 inside, and grips the side end portion of the upper and lower surfaces of the light guide plate 112 on the bar light source side on the inner surface of the opening side tip portion of the light source cover 115. The light guide plate 112 and the bar light source 113 are supported in close contact with each other at a predetermined position. Further, on the inner surface side of the light source cover 115, reflection made of a silver thin film or the like for returning the light emitted toward the inner surface of the light source cover 115 to the light guide body 113a without incident on the light guide plate 112 is used. A membrane (not shown) is provided. The lower surface of the light guide plate 112 (on the liquid crystal display unit 120 side) is an exit surface from which light is emitted, and the surface opposite to the exit surface (upper surface of the light guide plate 112) is light propagating inside the light guide plate 112. Wedge-shaped grooves 114 are alternately arranged periodically to form a prism surface 112c in order to change the direction of the prism surface 112c.

[0004] The bar light source 113 includes a rod-shaped light guide 113a and light emitting diodes (LEDs) 113b as light emitting elements arranged at both ends thereof, and the light emitted from the LED 113b is provided. Is guided to the side end surface of the light guide plate 112 by the light guide body 113a, and light is introduced into the light guide plate 112.

[0005] The liquid crystal display unit 120 is a reflective liquid crystal display unit, and displays by reflecting the light incident from the front light 110 by a built-in or external reflector. The liquid crystal display device 100 having the above configuration reflects this external light to perform normal reflection display in an environment where sufficient external light can be obtained, and in a dark place where external light cannot be obtained, the front light 110 is used. It is designed to be used as a light source and reflect this light for display.

[0006] However, in the liquid crystal display device 100 having the above configuration, the brightness of the front light 110 is partially increased when an acceleration test is performed in which heating and cooling are periodically repeated. In some cases, the phenomenon of a decrease in liquid crystal occurred. When the present inventors investigated this problem, it was clarified that the decrease in brightness was caused by the displacement between the light guide plate 112 and the light guide 113a.

[0007] FIG. 11 is a plan view showing an optical path of the front light 110 shown in FIG. As shown in FIG. 11, the light guide body 113a of the bar light source 113 has a surface opposite to the light guide plate 112 as a prism surface 118, and the light incident on the light guide body 113a from the LED 113b is the prism surface. It is reflected by 118 and emitted to the light guide plate 112 side. In the front light 110 having such a structure, the propagation direction of the light reflected by the prism surface 118 is limited to a narrow range. Therefore, in order to uniformly introduce the light into the light guide plate 112, the bar light source 113 It is necessary to precisely adjust the position of the light guide plate 112 with respect to the light guide plate 113a, and in particular, it is necessary to precisely position the light guide plate 112 in the width direction of the light guide plate 112. For example, as shown by the broken line in FIG. 11, when the light guide plate 112 is displaced to the right of the paper surface indicated by the arrow, the amount of light at the right end 116 of the light guide plate 112 is partially reduced and the amount of emitted light is in-plane. It tends to be non-uniform, and the visibility of the liquid crystal display device is partially reduced.

[0008] As described above, in the liquid crystal display device 100, the bar light source 113 and the light guide plate 112 are formed by attaching a side view U-shaped light source cover 115 to the side end portion on the bar light source 113 side. Since it is fixed, the light guide plate 112 is gripped on the inner surface side of the light source cover 115. In such a structure, since the light guide plate 112 is sandwiched between the wide inner surface of the light source cover 115, the expansion and contraction of the reflective film provided on the inner surface side of the light source cover 115 can be affected by the wide inner surface of the light source cover 115. The position of the light guide plate 112 is likely to shift.

[0009] Therefore, one of the objects of the present invention is to arrange the bar light source and the light guide plate at an accurate position, and improve the light source cover so that the arrangement can be maintained, so that the light source cover is excellent in reliability. The purpose is to provide a surface light emitting device. Another object of the present invention is to provide a highly reliable liquid crystal display device by making it possible to hold the surface light emitting device using the improved light source cover and the liquid crystal display element at an accurate position. To provide.

[Means for Solving the Problems] In order to achieve the above object, the present invention has adopted the following configuration. The surface light emitting device of the present invention has a rod-shaped light source, a light guide plate having a structure in which the light of the light source is incident from a side end surface and emitted from an exit surface, and a cover member that supports the rod-shaped light source and the light guide plate. In the surface light emitting device provided with the above, the cover member is made of a metal plate having spring characteristics and has a substantially U-shaped cross section, and the width of the cover member on the U-shaped opening side is not. The width of the cover member is smaller than the width of the opening side, and the cover member is placed on the rod-shaped light source and the light guide plate, and the light guide plate is gripped by the U-shaped opening side of the cover member to form the rod shape. It is configured so that the light source and the light guide plate are in close contact with each other and supported.<u style="single">Therefore, projecting portions projecting in the width direction of the light guide plate are formed at both ends of the cover member, and the length of the light guide plate extends from each projecting portion in a direction orthogonal to the length direction of each projecting portion. The protrusions along the direction are extended, the distance between the two protrusions is formed to be substantially the same as the width of the light guide plate, and the protrusions are fitted to fix the surface light emitting device to the housing. It is characterized by forming a joint.</u>[0011] With such a configuration, it is possible to firmly support the light guide plate by the strong spring force of the cover member, maintain the adhesion between the light guide plate and the bar light source, and prevent the two from slipping. Therefore, it is possible to realize a surface light emitting device having excellent reliability.<u style="single">Further, by providing such a structure as a support structure for the light guide plate by the light source cover member and a positioning structure for the light guide plate by projecting pieces extending at both ends of the bar light source, the light guide plate for heating and cooling is provided. Due to the expansion and contraction of the bar light source and the cover member, the positions of the light guide plate and the bar light source do not shift, and the light of the bar light source can be reliably transmitted to the light guide plate without loss, so that the LED light emission is efficient. Since it can be often used in a light guide plate, a more reliable surface light emitting device can be obtained.</u><u style="single">Further, in the surface light emitting device of the present invention, the projecting piece is configured as a fitting portion for fixing the surface light emitting device to the housing, so that the surface light emitting device is mounted on an electronic device. In addition, it becomes easy to fix the surface light emitting device at an accurate position, and the work efficiency at the time of manufacturing can be improved.</u>[0012] Next, in the surface light emitting device of the present invention, a protrusion is provided at a position above the rod-shaped light source on the U-shaped upper surface of the cover member, and the protrusion is the rod-shaped. A surface light emitting device configured to hold the light source and to support the rod-shaped light source and the light guide plate in close contact with each other by gripping the light guide plate on the U-shaped opening side of the cover member. did. With such a configuration, both the bar light source and the light guide plate can be firmly gripped by the strong spring force of the cover member, and the light guide plate and the bar light source are maintained in close contact with each other and are displaced from each other. It is possible to realize a more reliable surface light emitting device by making it difficult.

Next, in the surface light emitting device of the present invention, the width of the most advanced portion of the cover member on the U-shaped opening side is configured to be larger than the width of the narrowest portion of the cover member. Is preferable. This is to facilitate insertion of the bar light source and the light guide plate into the cover member when assembling the cover member, the bar light source, and the light guide plate into the surface light emitting device.

[0014] In the surface light emitting device having the present configuration, it is possible to use an apparatus having a reflective film for reflecting light from a light source on the inner surface of a metal plate having a spring characteristic constituting the cover member. This is to efficiently guide the light from the light source to the light guide plate. Alternatively, the metal plate having spring characteristics that constitutes the cover member can also be made of a stainless steel plate that has undergone mirror surface electropolishing. Since there is no adhesive film and the material itself, there is an advantage that obstacles such as thermal expansion difference and peeling can be eliminated. Further, the metal plate having spring characteristics constituting the cover member may be made of chrome-plated low alloy steel. This is because the material cost is low and the effect of contributing to cost reduction can be expected.

【0015】<u style="single"> Further, the surface light emitting device of the present invention is</u>The projecting pieces have a base portion extending from both ends of the cover member along the thickness direction of the light guide plate, and a plate shape extending from the tip of the base along the length direction of the light guide plate. The fitting plate was formed by projecting from the outer side edge of the fitting plate and bending upward at the connecting portion with the fitting plate and bending upward from the tip end portion of the fitting plate. It shall be equipped with a hooking protrusion.<u style="single">Is preferable.</u>【0017】<u style="single"></u>As described above, the surface light emitting device of the present invention can accurately position the light source and the light guide plate by the projecting pieces, and has a structure in which these are extremely difficult to shift. By fixing to the body, for example, the positions of the display device and the light guide plate arranged on the back side of the light guide plate can be accurately positioned.

Next, the liquid crystal display device of the present invention is a liquid crystal display device provided with the surface light emitting device according to any one of the above on the front side of the liquid crystal display element. That is, by providing the surface light emitting device of the present invention having the above-mentioned excellent reliability, it is possible to realize a liquid crystal display device that exhibits excellent visibility for a long period of time without causing a decrease in brightness due to heating or cooling. Can be done.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments.

(Surface light emitting device) (First embodiment) FIG. 1 is a perspective view of a front light (surface emitting device) according to an embodiment of the present invention, and FIG. 2 is shown in FIG. It is a partial plan view of a front light. The front light 10 shown in these figures is arranged on a flat plate-shaped light guide plate 12 made of a transparent resin material and one end of a side end surface of the light guide plate 12 (one end on the short side side of the rectangular light guide plate 12). It is configured to include a rod-shaped bar light source 13. Further, a light source cover 15 having a substantially U-shaped cross section is attached from the bar light source 13 side, and the upper and lower surfaces of the light guide plate 12 are sandwiched between the tip side of the light source cover 15 to sandwich the light source plate 12 and the bar light source 13. And are fixed.

[0021] The light guide plate 12 is a transparent flat plate-shaped member, and has a side end surface 12a facing the bar light source 13 as an incoming light surface, and light introduced into the inside from the side end surface 12a is substantially equal to the side end surface 12a. The parallel wedge-shaped grooves 14 are reflected by the reflecting surface 12c formed in an intermittent stripe shape, so that the light is emitted from the opposite surface (lower surface in the drawing) of the reflecting surface 12c. The light guide plate 12 can be manufactured by a method of injection molding a resin material such as a transparent acrylic resin into a flat plate. Further, as the material constituting the light guide plate 12, in addition to the acrylic resin, a transparent resin material such as a polycarbonate resin or an epoxy resin, glass or the like can be used.

As shown in FIG. 2, the bar light source 13 is arranged in a square columnar rod-shaped light guide portion 13a made of an acrylic resin, a polycarbonate resin, or the like, and at both ends of the light guide portion 13a in the longitudinal direction. It is composed of light emitting elements 13b and 13b consisting of light emitting diodes (LEDs). Of the side surfaces of the light guide portion 13a, the surface opposite to the light guide plate 12 has a prism surface 18 in which a prism shape is formed, and the light introduced into the light guide portion 13a from the light emitting elements 13b and 13b is emitted. By reflecting the light on this surface, the light propagation direction is changed to the light guide plate 12 side, and the light emitted from the light emitting elements 13b and 13b is irradiated to the side end surface side of the light guide plate 12.

[0023] In the present embodiment, the bar light source 13 is configured to include a light emitting element 13b made of an LED, but this light emitting element uses a cold cathode tube, an organic EL element, or the like. Any of them may be preferably used as long as the side end surface 12a of the light guide plate 12 can be uniformly irradiated with light.

[0024] The light source cover 15 is attached from the bar light source 13 side in order to support and fix the bar light source 13 and the light guide plate 12, and the light source cover 15 is, for example, low alloy steel, stainless steel, or phosphor bronze. , Beryllium copper and other metal plates with excellent spring characteristics can be processed to form a structure. Among these, those having high light reflectance are preferable, and stainless steel subjected to bright electropolishing treatment, low alloy steel coated with a thin film such as silver or aluminum, or chrome plated, or copper alloy is preferably used. .. In the present embodiment, the light source cover 15 has a substantially U-shaped shape when viewed from the side, and is configured so that the width of the U-shaped opening is narrowed to strengthen the spring force when the light guide plate is gripped. It shall be. Further, side plates covering the outside of the light emitting elements 13b and 13b may be provided on both side ends of the light source cover 15.

FIG. 3 is a partial cross-sectional view of the front light 10 shown in FIG. 2 along the AA line. As shown in FIGS. 2 and 3, the cross-sectional shape of the light source cover 15 of this embodiment is substantially U-shaped, and the opening side of the substantially U-shaped cross section is narrowed to form an opening. The upper surface (reflection surface 12c) of the light guide plate 12 is pressed and fixed at the narrowest tangent line 15a on the side. In the front light 10 of the present embodiment, the light source cover 15 attached from the bar light source 13 side is supported by the tangent line 15a on the upper surface side of the light guide plate 12, while the light source is supported on the lower surface side of the light guide plate 12. The structure is supported by the inner surface of the lower part of the cover 15. With this structure, the light guide plate can be firmly gripped by the spring force of the light source cover, so that the adhesion between the light guide plate and the bar light source can be maintained. Further, the stress due to the expansion and contraction of the light source cover is less likely to be applied to the wide surface of the light guide plate 12, and the front light 10 in which the positions of the light guide plate 12 and the bar light source 13 are not easily displaced is realized. Further, if the light reflectance on the inner surface side of the light source cover 15 is set high, the light incident on the inner surface side of the light source cover 15 is reflected by this reflecting surface, so that the structure can improve the light utilization efficiency. it can.

[0026] FIG. 4 is a perspective view showing a liquid crystal display device 200 configured by arranging the front light 10 of the present embodiment on the front surface of the liquid crystal display unit 20 and supporting both of them by a housing 30. In the liquid crystal display device 200 of the present embodiment, the liquid crystal display unit 20 is housed inside the box-shaped housing 30, the front light 10 is arranged on the front surface (upper surface) of the liquid crystal display unit 20, and the housing 30 has a front light 10. The hook-shaped hooking member 30a provided is engaged with the projecting piece 16 of the cover member 15, and the front light 10, the liquid crystal display unit 20, and the housing 30 are integrally fixed.

[0027] FIG. 5 is a diagram illustrating the dimensional relationship of the cross section of the light source cover 15 in the first embodiment. As shown in the figure, the light source cover 15 in the first embodiment has a substantially U-shaped cross section (inverted U-shaped in the figure), and has the widest width on the U-shaped opening side. The width F of the narrow tangent 15a is smaller than the width A of the innermost part of the U-shape on the opposite side. That is, F &lt;A in Fig. 5. Since the light source cover 15 is made of a metal having excellent spring characteristics, a strong spring force is generated at the tangent line 15a portion, and the light guide plate can be strongly pressed and firmly gripped. Further, the width D of the tip 15c portion on the U-shaped opening side of the light source cover 15 is slightly larger than the width F of the tangent 15a portion. That is, F &lt;D in Fig. 5. This is to facilitate inserting the bar light source 13 and the light guide plate 12 into the light source cover 15 when assembling the surface light emitting device.

[0028] FIG. 6 is a diagram illustrating a dimensional relationship when the bar light source 13 and the light guide plate 12 are inserted into the light source cover 15 of the first embodiment. As shown in the figure, the width A of the innermost portion 15b of the light source cover 15 is slightly larger than the thickness B of the light guide plate 12 and the bar light source 13. That is, B &lt;A in Fig. 6. The width F of the tangent line 15a of the light source cover 15 is slightly smaller than the thickness B (= C) of the light guide plate 12 and the bar light source 13. That is, F &lt;B (= C) in FIGS. 5 and 6. Therefore, the light guide plate 12 can be strongly sandwiched and gripped by the spring force of the light source cover 15 at the portion of the tangent line 15a. When the light guide plate 12 and the bar light source 13 are inserted, the width F'of the tangent line 15a becomes the thickness B of the light guide plate 12 and the bar light source 13, and a spring force is generated. That is, in FIG. 6, F &lt;F'= B (= C).

[0029] FIG. 7 is a perspective view showing an enlarged engagement portion between the housing 30 of the liquid crystal display device shown in FIG. 4 and the front light 10, as shown in FIG. 1 on both upper sides of the light source cover 15. The projecting pieces 16 and 16 are formed so as to extend in the thickness direction of the light guide plate 12 (only one side thereof is shown in FIG. 7), and each projecting piece 16 is formed at both ends on the upper side of the light source cover 15. It is provided with a base portion 16d extending along the thickness direction of the light guide plate 12 from the light source plate 12 and a fitting plate 16a extending along the length direction of the light guide plate 12 from the tip end portion of the base portion 16d, and has two protrusions. The distance between the pieces 16 and 16 is almost the same as the width of the light guide plate 12. In other words, in the front light 10 of the present embodiment, the light guide plate 12 is inserted between the projecting pieces 16 and 16 of the light source cover 15 and is positioned and fixed in the width direction thereof. Therefore, even if the stress of moving the light guide plate 12 in the width direction acts on the light guide plate 12, the protrusions 16 and 16 limit the movement of the light guide plate 12 in the width direction, so that the position of the light guide plate 12 The structure is such that the deviation is extremely unlikely to occur.

[0030] The distance between the projecting piece 16 and the light guide plate 12 is preferably 0.1 mm or less. When the distance between the projecting piece 16 and the light guide plate 12 exceeds 0.1 mm, the positional deviation between the light guide portion 13a of the bar light source 13 and the light guide plate 12 exceeds 0.1 mm, and the exit surface of the light guide plate 12 This is not preferable because the brightness in the above is partially reduced and the uniformity of the brightness is lowered.

Further, the projecting piece 16 includes a base portion 16d extending in the thickness direction of the light guide plate 12, a plate-shaped fitting plate 16a extending from the base portion 16d and formed in parallel with the light guide plate 12. A hooking portion 16b that protrudes outward from the fitting plate 16a and is slightly bent upward (perpendicular to the fitting plate 16a) at its base end and extends from the tip of the fitting plate 16a. It is composed of a hooking protrusion 16c that is bent upward (perpendicular to the fitting plate 16a) at the base end. The projecting piece 16 is provided to fix the front light 10 to the front surface of the display device or to an electronic device. By adopting the above structure, positioning when fixing the front light 10 and mounting thereof can be facilitated, and misalignment of the front light 10 can be prevented.

As shown in FIG. 7, in the liquid crystal display device of this example, the hook-shaped hooking member 30a provided on the housing 30 is engaged with the hooking portion 16b of the projecting piece 16 to engage the front light 10 Is fixed. The width of the hooking member 30a is substantially the same as the length of the fitting plate 16a of the projecting piece 16 (the length from the tip end of the base portion 16d to the base end portion of the hooking protrusion 16c). As a result, the hooking member 30a engaged with the protrusion 16 is in a state of being substantially in contact with the base portion 16d and the hooking protrusion 16c arranged on the side surface thereof. Therefore, the movement of the light guide plate 12 of the front light 10 fixed to the housing 30 in the length direction is restricted by the hooking member 30a sandwiched between the base portion 16d and the hooking protrusion 16c, and the front light 10 and the front light 10 are restricted. , The position with the liquid crystal display unit 20 is hard to shift. Further, with this structure, the front light 10 can be accurately positioned with respect to the housing 30 and the position can be maintained. Further, according to the above configuration, when the front light 10 is fixed to the housing 30, it is only necessary to engage the hooking member 30a with the projecting piece 16, and the liquid crystal display device can be configured extremely easily.

(Second Embodiment) (Surface Light Emitting Device) Next, FIG. 8 shows a cross-sectional view of a cover member used in the surface light emitting device according to another embodiment. The difference between the cover member of the present embodiment and the cover member of the first embodiment shown in FIGS. 5 and 6 is that the U-shaped upper surface of the cover member 15 is the rod-shaped bar light source 13. A protrusion 15e is provided at the upper position, the bar light source 13 is gripped by the protrusion 15e, and the light guide plate 12 is gripped by the tangent line 15a on the U-shaped opening side of the cover member 15. The point is that the light guide plate 12 and the bar light source 13 are configured to be more securely adhered and supported.

[0034] FIG. 9 is an external perspective view showing a state in which the light guide plate 12 and the bar light source 13 are gripped by using the cover member 15 shown in FIG. 8 and assembled into a surface light emitting device. The light guide plate 12 and the bar light source 13 are gripped by the tangential portion 15a and the protrusion portion 15e of the cover member 15, respectively. The protrusion 15e is seen as a depression from the outside. With such a configuration, both the bar light source and the light guide plate can be gripped by the strong spring force of the cover member, and the light guide plate and the bar light source can be maintained in close contact with each other and displaced from each other. It is possible to realize a more reliable surface light emitting device by making it difficult.

(Liquid Crystal Display Device) The liquid crystal display device according to the second embodiment uses a surface light emitting device whose cover member has been redesigned as described above, and is a method of assembling the surface light emitting device and the liquid crystal display panel. Is the same as in the case of the first embodiment, and thus the description thereof will be omitted.

[Effects of the Invention] As described in detail above, the surface light emitting device of the present invention has a rod-shaped light source and a guide having a structure in which the light of the light source is incident from the side end surface and emitted from the exit surface. In a surface light emitting device including a light plate, a rod-shaped light source, and a cover member that supports the light guide plate, the cover member is made of a metal plate having spring characteristics and has a substantially U-shaped cross section. .. Further, the width of the cover member on the U-shaped opening side is smaller than the width on the non-opening side, and the cover member is placed over the rod-shaped light source and the light guide plate, and the U-shape of the cover member is formed. The surface light emitting device is configured so that the rod-shaped light source and the light guide plate are brought into close contact with each other and supported by gripping the light guide plate on the opening side of the mold. With such a configuration, the light guide plate can be firmly supported by the strong spring force of the cover member, the adhesion between the light guide plate and the bar light source is maintained, the two are hard to shift, and the reliability is excellent. A surface light emitting device can be realized.<u style="single">Further, the surface light emitting device of the present invention has a structure in which the projecting piece is a fitting portion for fixing the surface light emitting device to the housing, so that the surface light emitting device can be mounted on an electronic device. The surface light emitting device can be easily fixed at an accurate position, and the work efficiency at the time of manufacturing can be improved. Further, in the surface light emitting device of the present invention, as described above, the light source and the light guide plate can be accurately positioned by the projecting pieces, and the structure is such that these are extremely hard to shift, so that the cover member can be reliably secured by the fitting portion. By fixing the light guide plate to the housing, for example, the positions of the display device and the light guide plate arranged on the back side of the light guide plate can be accurately positioned.</u>[0037] Further, in the surface light emitting device of the present invention, a protrusion is provided on the U-shaped upper surface of the cover member at a position above the rod-shaped light source, and the rod-shaped light source is formed by the protrusion. The surface light emitting device is configured so that the rod-shaped light source and the light guide plate are brought into close contact with each other by gripping the light guide plate on the U-shaped opening side of the cover member. With such a configuration, both the bar light source and the light guide plate can be firmly gripped by the strong spring force of the cover member, and the light guide plate and the bar light source are maintained in close contact with each other and are displaced from each other. It becomes possible to realize a more reliable surface light emitting device by making it difficult.

[0038] Next, in the surface light emitting device of the present invention, a device having a reflective film for reflecting light from a light source on the inner surface of a metal plate having spring characteristics constituting the cover member can be used. .. Alternatively, it can also be made of a stainless steel plate that has been subjected to mirror surface electropolishing. Furthermore, it can be composed of chrome-plated low alloy steel. By appropriately selecting the material of the cover member in this way, the light from the 15 light sources can be efficiently guided to the light guide plate, and a surface light emitting device having good performance can be obtained at low cost.

[0039] Further, in the surface light emitting device of the present invention, projecting pieces are provided at both ends of the cover member to sandwich the light guide plate, so that the light guide plate is prevented from being displaced in the width direction between the light guide plate and the bar power supply. Therefore, it is possible to obtain a highly reliable surface light emitting device while maintaining the adhesion between the bar light source and the light guide plate.

Next, the liquid crystal display device of the present invention includes a surface light emitting device having a protrusion on a cover member, a liquid crystal display element arranged on the exit surface side of the surface light emitting device, and the surface light emitting device and the liquid crystal. A housing for supporting the display element is provided, and a hook-shaped hooking member provided on the housing is engaged with a projecting piece of a cover member of the surface light emitting device, so that the surface light emitting device and the liquid crystal are displayed. Since the display element and the housing are integrally fixed, the surface light emitting device can be easily and accurately fixed to the housing via the fitting portion (projection piece). In particular, if the length of the fitting plate of the projecting piece and the width of the hooking member are substantially the same, it is possible to make the misalignment of the surface light emitting device with respect to the housing extremely unlikely, and it is reliable. It is possible to realize a liquid crystal display device having excellent properties.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an embodiment of a front light of the present invention.

FIG. 2 is a partial plan view showing a light passage of the front light shown in FIG.

FIG. 3 is a cross-sectional view taken along line AA of the front light shown in FIG.

FIG. 4 is a perspective view showing an example of a liquid crystal display device provided with a front light according to the present invention.

FIG. 5 is a cross-sectional view showing an embodiment of a cover member used for the front light according to the present invention.

FIG. 6 is a cross-sectional view illustrating a state in which the cover member shown in FIG. 5 is incorporated in a front light.

FIG. 7 is an enlarged perspective view showing an engaged portion between a housing and a front light of the liquid crystal display device shown in FIG. 4.

FIG. 8 is a cross-sectional view showing another embodiment of a cover member used for the front light according to the present invention.

FIG. 9 is a perspective view illustrating a state in which the cover member shown in FIG. 8 is incorporated in the front light.

FIG. 10 is a perspective view showing an example of a conventional front light.

11 is a partial plan view showing a light passage of the front light shown in FIG. 10. FIG.

[Explanation of symbols] 10 ... Front light, 12 ... Light guide plate, 13 ... Bar light source, 15 ... Cover member, 16 ... Projection piece, 20 Liquid crystal display unit, 30 Housing, 200 Liquid crystal display device, 110 Front light, 112 Light guide plate, 113 Bar light source, 115 Cover member, 120 Liquid crystal display unit