JP2004055327A - Surface light source device, image display device, and light guide plate assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce electric power consumption without decreasing outgoing brightness. <P>SOLUTION: This surface light source device 2 houses a second light guide plate 6 in a space 15 on the back 5 of a first light guide plate 4, and houses a fluorescent lamp 12 in a light source housing recess 17 on the back 11 of the second light guide plate 6. The first light guide plate 4 has fluorescent lamps 10, 10 on facing both sides 8a, 8b, takes in light of the fluorescent lamp 10, 10 from the both sides 8a, 8b, and emits it as surface-like illumination light from an outgoing surface 13. The second light guide plate 6 takes in the light of the a fluorescent lamp 12 from the back 11 opposite to an outgoing surface 16 from which surface-like illumination light is emitted, and emits it from the outgoing surface 16 to the first light guide plate 4 side. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface light source device used as a backlight or the like for illuminating a liquid crystal display panel (a member to be illuminated) such as a liquid crystal color television or a liquid crystal monitor in a planar manner, and an image display device provided with the surface light source device. The present invention also relates to a light guide plate assembly used for these surface light source devices and image display devices.
[0002]
[Prior art]
(First conventional example)
For example, compared to miniaturized image display devices that require portability, such as mobile phones and portable liquid crystal color televisions, images from liquid crystal color televisions and various liquid crystal monitors with large display screens that are not supposed to be carried around are large. As shown in FIG. 16, in the display device, a plurality of fluorescent lamps 51 are arranged in parallel on the back surface (lower surface in the figure) of the diffusion plate 50, and the light of the fluorescent lamps 51 is transmitted from the emission surface 52 of the diffusion plate 50 A surface light source device 54 is provided to emit light in a shape and illuminate a member 53 such as a liquid crystal display panel. However, in such a surface light source device 54, it is necessary to increase the distance from the fluorescent lamp 51 to the diffuser plate 50 in order to make the emitted light uniform, and the thickness (T1) of the device tends to increase. Yes, the overall weight was heavy. For this reason, the image display device 55 including such a surface light source device 54 is not easy to carry in a relatively limited space such as a room, for example, and is sufficiently compatible with recent diversification of lifestyles. I couldn't do that.
[0003]
(Second conventional example)
As a surface light source device used for such a relatively large image display device, a surface light source device 56 as shown in FIG. 17 is known. In the surface light source device 56, a plurality of fluorescent lamps 10 are arranged on both sides (both incident surfaces) 8a and 8b of the light guide plate 57 facing each other, and light from the plurality of fluorescent lamps 10 is transmitted to both sides of the light guide plate 57. After the light enters the light guide plate 57 from the incident surfaces 8a and 8b, the light propagating inside the light guide plate 57 is emitted from the emission surface 58 of the light guide plate 57 in a planar manner. (T2) is smaller than the thickness (T1) of the device of the first conventional example (T1> T2). As a result, the image display device 60 using the surface light source device 56 of the second conventional example is smaller (thinner) and lighter than the image display device 55 using the surface light source device 54 of the first conventional example. This makes it easier to carry by the user than the image display device 55 of the first conventional example.
[0004]
(Third conventional example)
The surface light source device 61 as shown in FIG. 18 is common to the second conventional example in a configuration in which a plurality of fluorescent lamps 10 are disposed on both sides (both incident surfaces) 8a and 8b of a light guide plate 62, respectively. The thickness of the light guide plate 62 is gradually reduced from both the incident surfaces 8a and 8b toward the substantially central portion so that the plate thickness becomes the thinnest at the substantially central portion on the back surface 63 side. Accordingly, in the surface light source device 61 illustrated in FIG. 18, light propagating inside the light guide plate 62 is more easily emitted than the surface light source device 56 according to the second conventional example, and the surface light source device 56 according to the second conventional example. This makes it possible to increase the luminance of the emitted light. In other words, the image display device 64 using the surface light source device 56 of the third conventional example can be made smaller (thinner) and lighter than the first conventional example, and moreover, has a higher output than the second conventional example. It is possible to increase the emission luminance.
[0005]
[Problems to be solved by the invention]
As described above, the surface light source device 56 of the second conventional example and the surface light source device 61 of the third conventional example can be made smaller (thinner) than the first conventional example. It was not possible to fully meet the demand for reduction.
[0006]
Accordingly, it is an object of the present invention to reduce power consumption without lowering the luminance of emitted light.
[0007]
[Means for Solving the Problems]
The surface light source device according to the first aspect of the present invention includes a first light guide plate and a second light guide plate. Among them, the first light guide plate has first light sources disposed on both sides facing each other, and after taking in the light from these first light sources from the both sides, emits the light as planar illumination light from the emission surface. It has become. In the second light guide plate, a second light source is disposed on the back surface opposite to the emission surface from which the planar illumination light is emitted, and after the light from the second light source is taken in from the back surface, the emission surface is formed. From the first light guide plate. A light guide plate engaging recess is formed on the back surface of the first light guide plate opposite to the emission surface, and the second light guide plate is accommodated in the light guide plate engaging recess. Further, a light source housing recess is formed on the back surface of the second light guide plate, and the second light source is housed in the light source housing recess.
[0008]
An image display device according to a second aspect of the present invention includes the surface light source device according to the first aspect of the present invention, and a member to be illuminated by the surface light source device.
[0009]
A light guide plate assembly according to a third aspect of the present invention includes a first light guide plate and a second light guide plate. Among them, the first light guide plate has first light sources disposed on both sides facing each other, and after taking in the light from these first light sources from the both sides, emits the light as planar illumination light from the emission surface. It has become. In the second light guide plate, a second light source is disposed on the back surface opposite to the emission surface from which the planar illumination light is emitted, and after the light from the second light source is taken in from the back surface, the emission surface is formed. From the first light guide plate. A light guide plate engaging recess is formed on the back surface of the first light guide plate opposite to the emission surface. Further, a light source accommodating recess for accommodating the second light source is formed on a back surface of the second light guide plate. Then, the second light guide plate is accommodated in the light guide plate engaging recess of the first light guide plate to form a light guide plate assembly.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
[First Embodiment]
1 to 5 show an image display device 1 according to an embodiment of the present invention. FIG. 1 is an exploded perspective view of the image display device 1. FIG. 2 is an external perspective view of a surface light source device 2 used in the image display device 1 of FIG. FIG. 3 is a front view of the image display device 1 of FIG. FIG. 4 is a diagram of the surface light source device 2 as viewed from a direction A in FIG. 5 is a rear view of the surface light source device 2 shown in FIG. 3 with the reflection sheet 3 removed (as viewed from the direction B in FIG. 3).
[0012]
(Schematic configuration of image display device)
In these drawings, in the image display device 1, the light guide plate assembly 7 is configured by arranging the second light guide plate 6 on the back surface 5 side of the first light guide plate 4, and the light guide plate assembly 7 is configured. Bar-shaped fluorescent lamps 10, 10 as first light sources are arranged on a pair of opposed side surfaces (incident surfaces) 8 a, 8 b of the first light guide plate 4, respectively, and the back surface 11 side of the second light guide plate 6 (FIG. 1). A rod-shaped fluorescent lamp 12 as a second light source is disposed substantially in parallel with the fluorescent lamps 10 and 10 on the first light guide plate 4 side in the central portion of the lower surface side of FIG. In the image display device 1, a liquid crystal display panel 14 as an illuminated member is disposed so as to be opposed to an emission surface (upper surface in FIG. 1) 13 of the first light guide plate 4. The reflection sheet 3 is arranged so as to face the back surface 11. In addition, a diffusion sheet or a prism sheet as a light control member may be appropriately disposed between the first light guide plate 4 and the liquid crystal display panel 14 as needed. The fluorescent lamps 10, 10, 12, the first light guide plate 4, and the second light guide plate 6 constitute the surface light source device 2 that illuminates the liquid crystal display panel 14 in a planar manner.
[0013]
(Light guide plate assembly)
The light guide plate assembly 7 includes a first light guide plate 4 and a second light guide plate 4 formed using a material having excellent light transmittance, such as PMMA (polymethyl methacrylate), PC (polycarbonate), and a cycloolefin resin material. And a light plate 6. Among them, the first light guide plate 4 gradually decreases in plate thickness from one of the pair of incident surfaces 8a and 8b facing to the other, and substantially the center between the pair of incident surfaces 8a and 8b facing each other. The back surface 5 is formed as a smooth circular arc surface, and the emission surface 13 is formed as a flat surface so that the plate thickness becomes the smallest in the portion. That is, as shown in FIG. 3, the first light guide plate 4 has a symmetrical shape with respect to the center portion CL in the left-right direction, and has a thickness from each of the incident surfaces 8a and 8b toward the center portion CL. Has a gradually decreasing cross-sectional shape, and the back surface 5 side is inclined obliquely upward, so that light from the fluorescent lamps 10, 10 propagating inside is easily reflected by the back surface 5, and light is emitted. The light is efficiently emitted from the surface 13. Further, the first light guide plate 4 is configured such that the back surface 5 has a concave shape on the back surface 5 side by making the back surface 5 have an arcuate shape, and a space (light guide plate engaging recess) 15 for accommodating the second light guide plate 6 on the back surface 5 side. Is formed.
[0014]
The second light guide plate 6 is configured to be superimposed on the back surface 5 side of the first light guide plate 4, and the upper surface (emission surface) 16 has a shape corresponding to the back surface 5 side of the first light guide plate 4. The central portion CL is curved so as to have the largest thickness. Further, when the second light guide plate 6 is superimposed on the first light guide plate 4, the back surface (lower surface) 11 side becomes a flat surface that is substantially parallel to the emission surface 13 of the first light guide plate 4. I have. That is, when the second light guide plate 6 is superimposed on the first light guide plate 4 to form the light guide plate assembly 7, the emission surface 13 of the first light guide plate 4 and the back surface 11 of the second light guide plate 6 become substantially parallel. . A light source accommodating recess 17 for accommodating the fluorescent lamp 12 is formed on the back surface 11 of the second light guide plate 6 and substantially at the center in the left-right direction in FIG. The light source accommodating recess 17 of the second light guide plate 6 extends in a direction along the incident surfaces 8a and 8b of the first light guide plate 4 so that the light of the fluorescent lamp 12 can be efficiently emitted into the second light guide plate 6. Is formed so that the cross-sectional shape becomes substantially semicircular.
[0015]
Here, when the light guide plate assembly 7 of the present embodiment is combined with the light exit surface 16 of the second light guide plate 6 so as to overlap the rear surface 5 side of the first light guide plate 4, the rear surface 5 of the first light guide plate 4 The second light guide plate 6 is accommodated in the space 15 on the side, and the thickness of the first light guide plate 4 on the incident surfaces 8a and 8b side is the thickness dimension of the light guide plate assembly 7. Therefore, the light guide plate assembly 7 of the present embodiment does not cause an increase in the size of the surface light source device 2.
[0016]
(Reflective sheet)
The reflection sheet 3 is formed of a material having excellent light reflectivity such as white PET (polyethylene terephthalate), and is formed in a rectangular shape having substantially the same size as the back surface 11 of the second light guide plate 6. The reflection sheet 3 diffuses and reflects the light emitted from the back surface 11 of the second light guide plate 6 and returns the light to the inside of the second light guide plate 6, thereby enabling the effective use of the light from the fluorescent lamps 10, 10, and 12. I do.
[0017]
(Lamp reflector)
The lamp reflectors 18, 18 are made of a resin material having excellent light reflectivity such as white PET or a metal material having excellent light reflectivity such as a stainless steel plate or an aluminum plate, and the upper edge thereof is formed on the light guide plate assembly 7. And the lower end of the first light guide plate 4 is engaged with the lower surface side edge of the reflection sheet 3, and the light from the fluorescent lamps 10, 10 is transmitted to the first light guide plate 4. The light guide plate 4 is guided to the incident surfaces 8a and 8b.
[0018]
(Operation and effect of the present embodiment)
In the image display device 1 according to the present embodiment configured as described above, the light emitted from the fluorescent lamp 12 enters the inside of the second light guide plate 6 from the surface of the light source housing recess 17 of the second light guide plate 6. After entering, the light propagates through the inside of the second light guide plate 6, and in the process of propagating inside the second light guide plate 6, the light whose incident angle with respect to the upper surface (emission surface) 16 becomes smaller than the critical angle is transmitted to the second light guide plate 6. The light exits from the light exit surface 16 of the first light guide plate 6 and enters the inside of the first light guide plate 4 from the back surface 5 side of the first light guide plate 4. Light emitted from the fluorescent lamps 10, 10 is directly or after being reflected by the lamp reflectors 18, 18 and enters the inside of the first light guide plate 4 from the incident surfaces 8a, 8b of the first light guide plate 4, and The light from the fluorescent lamp 12 incident through the second light guide plate 6 propagates inside the first light guide plate 4. Then, of the light propagating through the inside of the first light guide plate 4, the light whose incident angle with respect to the emission surface 13 of the first light guide plate 4 is equal to or smaller than the critical angle is the first light from the emission surface 13 of the first light guide plate 4. The light exits the light guide plate 4. Then, the light emitted from the emission surface 13 of the first light guide plate 4 illuminates the liquid crystal display panel 14 as a member to be illuminated in a planar manner.
[0019]
Here, since the second light guide plate 6 takes in the light of the fluorescent lamp 12 from the back surface 11 facing the emission surface 16, the second light guide plate 6 takes in the light of the fluorescent lamp 12 compared to the mode of taking in the light from the side surface of the light guide plate. Efficiency (outgoing efficiency) of light from the light source is high. Therefore, the surface light source device using the light guide plate assembly 7 in which the first light guide plate 4 is combined with the second light guide plate 6 is different from the second to third conventional examples with a small number of light sources (fluorescent lamps 10, 10, 12). It is possible to emit uniform illumination light having the same brightness, and power consumption is smaller than in the second and third conventional examples. That is, in the surface light source device 2 used in the image display device 1 of the present embodiment, one fluorescent lamp 10 is disposed so as to face the pair of incident surfaces 8a and 8b of the first light guide plate 4, respectively. Then, one fluorescent lamp 12 is disposed at the width direction central portion CL on the back surface 11 side of the second light guide plate 6, and the light from these three fluorescent lamps 10, 10, 12 is efficiently transmitted to the first light guide plate. The light is emitted from the light exit surface 13 of the light emitting device 4 to enable high-luminance surface illumination. Accordingly, power consumption is reduced as compared with the second and third conventional examples in which a plurality of fluorescent lamps 10 are arranged on a pair of opposed incident surfaces 8a and 8b as shown in FIGS.
[0020]
As described above, in the surface light source device 2 used in the image display device 1 according to the present embodiment, since a plurality of fluorescent lamps 10 are not arranged side by side, there is no light absorbed by the adjacent fluorescent lamps 10, 10. The light use efficiency of the fluorescent lamp 10 can be improved. In addition, the brightness of the emitted light near the central portion of the first light guide plate 4, which is a portion where the light of the pair of fluorescent lamps 10, 10 arranged on the first light guide plate 4 is difficult to reach, is reduced by the second light guide plate 6. Can be supplemented with light from the fluorescent lamp 12 disposed in the width direction central portion CL on the back surface 11 side, and the back surface 5 side of the first light guide plate 4 is directly illuminated with light emitted from the second light guide plate 6. Therefore, the efficiency of light emitted from the first light guide plate 4 is improved as compared with the conventional example shown in FIGS. Therefore, according to the surface light source device 2 of the present embodiment, even if the number of the fluorescent lamps 10 is reduced and the power consumption is reduced, the brightness is not inferior to the conventional example shown in FIGS. It becomes possible to illuminate with the illumination light.
[0021]
Further, in the surface light source device 2 used in the image display device 1 of the present embodiment, the second light guide plate 6 is housed on the back surface 5 side of the first light guide plate 4, so that the light guide plate set is provided. The thickness of the three-dimensional body 7 is the thickness of the first light guide plate 4 on the side of the incident surfaces 8a and 8b, and the size of the surface light source device 2 is not increased. Therefore, the surface light source device 2 of the present embodiment can be made smaller and lighter than the first conventional example shown in FIG.
[0022]
[Second embodiment]
FIG. 6 shows a surface light source device 2 used for an image display device 1 according to a second embodiment of the present invention. That is, in the surface light source device 2 of the present embodiment shown in FIG. 6, the first light guide plate 4 is divided into two parts at the center where the plate thickness is the thinnest (the first divided part 4a and the second divided part 4b). 2 is divided into two parts.
[0023]
According to the present embodiment having such a configuration, since the first light guide plate 4 has a symmetrical shape with respect to the center part, one of the divided pieces (4a or 4b) of the divided first light guide plate 4 is formed. 2), the two divided pieces 4a and 4b of the first light guide plate 4 can be formed only by the injection molding die. Therefore, according to the present embodiment, not only the same effects as in the first embodiment can be obtained, but also the die cost can be reduced and the product price can be reduced. . Note that, in the surface light source device 2 of the present embodiment, a diffusion sheet (not shown) is disposed on the emission surface 13 side of the first light guide plate 4, and the light emitted from the first light guide plate 4 is diffused by the diffusion sheet. It is preferable that the divided portion of the first light guide plate 4 be made less noticeable by transmission.
[0024]
[Third Embodiment]
FIG. 7 shows a surface light source device 2 used for an image display device 1 according to a third embodiment of the present invention. That is, the surface light source device 2 of the present embodiment shown in FIG. 7 transmits the light emitted from the second light guide plate 6 between the back surface 5 of the first light guide plate 4 and the emission surface 16 of the second light guide plate 6. A diffusion sheet 20 that diffuses and transmits to the first light guide plate 4 side is arranged.
[0025]
According to the present embodiment having such a configuration, the same effect as that of the surface light source device 2 of the first embodiment can be obtained, and the light emitted from the second light guide plate 6 can be diffused. The fluorescent lamp 12 diffused at 20 and arranged in the central portion on the back surface 11 side of the second light guide plate 6 can be made difficult to see from the emission surface 13 side of the first light guide plate 4. The brightness of the illumination light emitted from the emission surface 13 is made more uniform, and the illumination quality is further improved.
[0026]
[Fourth Embodiment]
In the present embodiment, in the surface light source device 2 of the third embodiment, a perspective view of the diffusion sheet 20 in FIG. 8A and a plan view of the diffusion sheet 20 developed in a plane in FIG. As shown in the figure, a mode in which a light diffusion pattern 21 is formed on the surface of a diffusion sheet 20 to adjust the distribution of light emitted from the second light guide plate 6 is shown (see FIG. 7). That is, the light diffusion pattern 21 formed by printing on the surface of the diffusion sheet 20 is formed so that the formation density becomes highest immediately above the fluorescent lamp 12 and becomes lower as the distance from the position above the fluorescent lamp 12 becomes lower. ing. In the present embodiment, each component 22 of the light diffusion pattern 21 is circular, and the density of the light diffusion pattern 21 is reduced by gradually changing the area of each component 22 from large to small. The gradation becomes denser and sparser as the distance from the position directly above the lamp 12 increases (see FIG. 7).
[0027]
According to the surface light source device 2 of the present embodiment having such a configuration, it becomes difficult for the fluorescent lamp 12 on the second light guide plate 6 side to be visually recognized from the emission surface 13 side of the first light guide plate 4 and the second light guide plate. By adjusting the distribution of the emitted light from the side 6 to the side of the first light guide plate 4, the distribution of the emitted light from the first light guide plate 4 can be adjusted, and the brightness of the light emitted from the first light guide plate 4 can be increased. It can be made even more uniform (see FIG. 7). Further, according to the surface light source device 2 of the present embodiment, it is needless to say that the same effect as the effect of the first embodiment can be obtained.
[0028]
In this embodiment, the light diffusion pattern 21 is formed on the outer surface of the diffusion sheet 20. However, the light diffusion pattern 21 is formed on the inner surface of the diffusion sheet 20 (the surface opposite to the outer surface). You may make it.
[0029]
[Fifth Embodiment]
In the present embodiment, in the surface light source device 2 according to the first embodiment (see FIGS. 1 to 3), as shown in FIG. The light diffusion pattern 21 shown in ()) is formed, and the diffusion sheet 20 of the fourth embodiment is omitted. That is, as shown in FIG. 9, the light diffusion pattern 21 formed on the emission surface 16 of the second light guide plate 6 is formed such that the formation density decreases from dense to sparse as the distance from directly above the fluorescent lamp 12 increases. As a result, the surface light source device 2 of the present embodiment can obtain the same effects as those of the fourth embodiment. In addition, the surface light source device 2 according to the fourth embodiment does not require the diffusion sheet 20 disposed between the second light guide plate 6 and the first light guide plate 4, so that the surface light source device according to the fourth embodiment is unnecessary. 2, the number of parts can be reduced and the product price can be reduced.
[0030]
Although FIG. 9 illustrates an example in which the light diffusion pattern 21 is formed on the emission surface 16 of the second light guide plate 6, the light diffusion pattern 21 may be formed on the back surface 5 side of the first light guide plate 4. Alternatively, the light diffusion patterns 21 may be formed on both opposing surfaces 5, 16 of the second light guide plate 6 and the first light guide plate 4. Further, the light diffusion pattern 21 may be formed on the inner surface of the light source housing recess 17 of the second light guide plate 6 (see FIGS. 1 to 3).
[0031]
[Sixth Embodiment]
FIG. 10 shows a surface light source device 2 used in an image display device 1 according to a sixth embodiment of the present invention. The surface light source device 2 shown in FIG. 10 has an emission surface 16 of the second light guide plate 6 and a back surface 5 of the first light guide plate 4, that is, both surfaces 16, on which the second light guide plate 6 and the first light guide plate 4 are overlapped, 5 is a rough surface 23 such as a matte surface, and diffuses light emitted from the second light guide plate 6 and light incident on the first light guide plate 4, and the fluorescent lamp 12 on the second light guide plate 6 side Are not visually recognized from the exit surface 13 side, and the luminance of the emitted light from the first light guide plate 4 is made uniform. Here, as a method of roughening the emission surface 16 of the second light guide plate 6 and the back surface 5 of the first light guide plate 4, a conventionally known method is employed, for example, by transferring a roughened mold surface during injection molding. Alternatively, a method of directly roughening the first and second light guide plates 4 and 6 by blasting, etching, or the like is employed.
[0032]
According to the surface light source device 2 of the present embodiment having such a configuration, the same effects as those of the fifth embodiment can be obtained.
[0033]
Note that the surface light source device 2 of the present embodiment exemplifies a mode in which a rough surface 23 such as a matte surface is formed on the both surfaces 16 and 5 of the emission surface 16 of the second light guide plate 6 and the back surface 5 of the first light guide plate 4. However, it may be formed on one of the emission surface 16 of the second light guide plate 6 and the back surface 5 of the first light guide plate 4, and the inner surface of the light source accommodating recess 17 of the second light guide plate 6. Alternatively, a rough surface 23 such as a pear surface may be formed (see FIG. 11).
[0034]
[Seventh Embodiment]
FIG. 12 shows a surface light source device 2 used for an image display device 1 according to a seventh embodiment of the present invention. As shown in FIG. 12, the surface light source device 2 according to the present embodiment is different from the surface light source device 2 according to the first embodiment in that the lamp diffuses inside the light source housing recess 17 of the second light guide plate 6. A sheet 24 is arranged, and the light from the fluorescent lamps 12 is diffused by the lamp diffusion sheet 24, and the diffused light is incident on the second light guide plate 6.
[0035]
The surface light source device 2 according to the present embodiment having such a configuration can provide the same effects as those of the surface light source device 2 according to the first embodiment. After being diffused at 24, the light is incident on the second light guide plate 6, and the fluorescent lamp 12 disposed at the center of the second light guide plate 6 on the back surface 11 side is visually recognized from the emission surface 13 side of the first light guide plate 4. Since the brightness can be reduced, the brightness of the illumination light emitted from the emission surface 13 of the first light guide plate 4 is further uniformed, and the illumination quality is further improved. In addition, the surface light source device 2 of the present embodiment uses the lamp diffusion sheet 24 smaller than the diffusion sheet 20 disposed on the superimposed surfaces 5 and 16 of the first light guide plate 4 and the second light guide plate 6 to form the fluorescent lamp 12. Since the light is diffused, the cost and weight can be reduced compared to the surface light source device 2 according to the third embodiment (see FIGS. 7 and 12).
[0036]
(First Modification of Seventh Embodiment)
Here, as shown in FIG. 13, a reflection member (light reflection sheet, light reflection paint or the like) 25 that reflects light is disposed on the inner surface of the lamp diffusion sheet 24 and immediately above the fluorescent lamp 12. The light from the fluorescent lamp 12 disposed on the side of the second light guide plate 6 is prevented from passing straight upward, and the fluorescent lamp 12 disposed on the side of the second light guide plate 6 is prevented from exiting from the exit surface 13 of the first light guide plate 4. You may make it hard to be visually recognized. With this configuration, it is possible to obtain the same effects as in the seventh embodiment, and the illumination light emitted from the first light guide plate 4 is further homogenized. The reflecting member 25 may be arranged on the outer surface of the lamp diffusion sheet 24 and in the vicinity immediately above the fluorescent lamp 12 (see FIG. 12).
[0037]
(Second Modification of Seventh Embodiment)
Further, as shown in FIG. 14, a light diffusion pattern 26 may be formed on the outer surface of the lamp diffusion sheet 24. Here, similarly to the light diffusion pattern 21 formed on the diffusion sheet 20 of the fourth embodiment (see FIG. 8), the light diffusion pattern 26 has the highest density immediately above the fluorescent lamp 12, and It is formed so that the formation density becomes lower as the distance from the position immediately above the fluorescent lamp 12 increases. With this configuration, it becomes difficult for the fluorescent lamp 12 on the second light guide plate 6 side to be visually recognized from the emission surface 13 side of the first light guide plate 4, and light from the fluorescent lamp 12 incident on the second light guide plate 6 is also reduced. By adjusting the distribution, the distribution of the light emitted from the first light guide plate 4 can be adjusted, and the luminance of the light emitted from the first light guide plate 4 can be further uniformed. In this modification, the light diffusion pattern 26 is formed on the outer surface of the lamp diffusion sheet 24. However, the light diffusion pattern 26 may be formed on the inner surface of the lamp diffusion sheet 24. The light diffusion pattern 26 may be formed on the inner surface of the light source housing recess 17 of the second light guide plate 6.
[0038]
[Eighth Embodiment]
FIG. 15 shows a surface light source device 2 used in an image display device 1 according to an eighth embodiment of the present invention, in which a light absorption pattern 27 is formed on the surface of a reflection sheet 3. I have. That is, the light absorbing pattern 27 is formed on the surface (the upper surface in FIG. 15) 28 of the reflection sheet 3 that faces the back surface 11 of the second light guide plate 6. The light absorption pattern 27 is formed such that the formation density is highest in a portion corresponding to the fluorescent lamp 12 (in the vicinity immediately below the fluorescent lamp 12), and the density decreases as the distance from the fluorescent lamp 12 increases. ing. Here, the light absorbing pattern 27 is composed of a large number of substantially circular light absorbing elements 30 formed using light absorbing ink, and by changing the area thereof, the formation density is made to be gradation. It has become.
[0039]
[Other embodiments]
In each of the above-described embodiments, a transparent electrode is printed with a transparent conductive resin on the emission surface side of the first light guide plate to remove high frequency noise emitted from the fluorescent lamp. The image quality can be prevented from being disturbed due to the above, and the display quality of the liquid crystal display panel can be improved.
[0040]
In each of the above-described embodiments, at least one of the first light guide plate 4 and the second light guide plate 6 is made of a material having a refractive index different from that of the first light guide plate 4 or the second light guide plate 6. Fine particles may be mixed.
[0041]
In the present invention, a plurality of light emitting diodes (LEDs) may be arranged instead of the fluorescent lamps 10 and 12, and the plurality of LEDs may be used as a light source.
[0042]
【The invention's effect】
As described above, according to the present invention, since the second light guide plate is accommodated in the light guide plate engaging recess on the back surface of the first light guide plate, the surface light source device and the image display provided with the surface light source device The device can be reduced in size and weight. Further, the present invention not only takes in the light of the first light source from both opposing side surfaces of the first light guide plate, but also takes in the light from the second light source from the back surface of the second light guide plate, The light emitted from the light exit surface of the first light guide plate is taken in from the back surface side of the first light guide plate, and the light use efficiency of the first light source and the second light source is improved. Surface illumination becomes possible, and power consumption can be reduced.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of an image display device according to a first embodiment of the present invention.
FIG. 2 is an external perspective view of the surface light source device according to the first embodiment of the present invention.
FIG. 3 is a front view of the surface light source device according to the first embodiment of the present invention.
FIG. 4 is a plan view of the surface light source device, as viewed from a direction A in FIG. 3;
FIG. 5 is a view seen from a direction B in FIG. 3, and is a rear view of the surface light source device shown with a reflection sheet removed.
FIG. 6 is an external perspective view of a surface light source device according to a second embodiment of the present invention.
FIG. 7 is a front view of a surface light source device according to a third embodiment of the present invention.
FIG. 8A is an external perspective view of a diffusion sheet of a surface light source device according to a fourth embodiment of the present invention, and FIG. 8B is an expanded plan view of the diffusion sheet. It is.
FIG. 9 is an external perspective view of a second light guide plate used in a surface light source device according to a fifth embodiment of the present invention.
FIG. 10 is a front view of a surface light source device according to a sixth embodiment of the present invention.
FIG. 11 is a front view of a surface light source device showing a modification of the sixth embodiment of the present invention.
FIG. 12 is a front view of a surface light source device according to a seventh embodiment of the present invention.
FIG. 13 is a front view of a lamp diffusion sheet showing a first modification of the seventh embodiment of the present invention.
FIG. 14 is an external perspective view of a lamp diffusion sheet showing a second modification of the seventh embodiment of the present invention.
FIG. 15 is an exploded perspective view partially showing a surface light source device according to an eighth embodiment of the present invention.
FIG. 16 is a front view of a surface light source device according to a first conventional example.
FIG. 17 is a front view of a surface light source device according to a second conventional example.
FIG. 18 is a front view of a surface light source device according to a third conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Image display device, 2 ... Surface light source device, 4 ... 1st light guide plate, 5, 11 ... Back surface, 6 ... 2nd light guide plate, 7 ... Light guide plate assembly, 8a, 8b ... Incident surface (side surface), 10 Fluorescent lamp (first light source), 12 Fluorescent lamp (second light source), 13, 16 Outgoing surface, 14 Liquid crystal display panel (member to be illuminated), 15 ... space (light guide plate housing recess), 17 ... light source housing recess

Claims (3)

A first light source is disposed on each of the opposite side surfaces, and a first light guide plate that emits light from these first light sources from the output surfaces as planar illumination light after taking in light from the both side surfaces,
A second light source is disposed on the back surface side opposite to the emission surface that emits planar illumination light, and after taking in light from the second light source from the back surface, the second light source is directed from the emission surface to the first light guide plate side. A second light guide plate for emitting light,
A light guide plate engaging recess is formed on the back surface opposite to the emission surface of the first light guide plate, and the second light guide plate is housed in the light guide plate engaging recess,
A surface light source device, wherein a light source accommodating recess is formed on the back surface of the second light guide plate, and the second light source is accommodated in the light source accommodating recess. An image display device comprising: the surface light source device according to claim 1; and an illuminated member illuminated by the surface light source device. A first light source is disposed on each of the opposite side surfaces, and a first light guide plate that emits light from these first light sources from the output surfaces as planar illumination light after taking in light from the both side surfaces,
A second light source is disposed on the back surface side opposite to the emission surface that emits planar illumination light, and after taking in light from the second light source from the back surface, the second light source is directed from the emission surface to the first light guide plate side. A second light guide plate for emitting light,
A light guide plate engaging recess is formed on the back surface opposite to the emission surface of the first light guide plate,
A light source accommodating recess for accommodating the second light source is formed on a back surface of the second light guide plate,
A light guide plate assembly, wherein the second light guide plate is accommodated in the light guide plate engaging recess of the first light guide plate.

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