JP2004319364A - Lighting system and liquid crystal display device - Google Patents

Lighting system and liquid crystal display device Download PDF

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Publication number
JP2004319364A
JP2004319364A JP2003114087A JP2003114087A JP2004319364A JP 2004319364 A JP2004319364 A JP 2004319364A JP 2003114087 A JP2003114087 A JP 2003114087A JP 2003114087 A JP2003114087 A JP 2003114087A JP 2004319364 A JP2004319364 A JP 2004319364A
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JP
Japan
Prior art keywords
surface
light
fresnel lens
guide plate
light guide
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
JP2003114087A
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Japanese (ja)
Inventor
Yuzo Hayashi
Mitsuo Oizumi
満夫 大泉
祐三 林
Original Assignee
Alps Electric Co Ltd
アルプス電気株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alps Electric Co Ltd, アルプス電気株式会社 filed Critical Alps Electric Co Ltd
Priority to JP2003114087A priority Critical patent/JP2004319364A/en
Publication of JP2004319364A publication Critical patent/JP2004319364A/en
Application status is Withdrawn legal-status Critical

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Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting system and a liquid crystal display device capable of performing a surface emission of uniform luminance with a simple structure. <P>SOLUTION: The light emitted from a light source 13 that is substantially a spot light source is gradually extended in width toward a Fresnel lens surface 12c. The Fresnel lens surface 12c reflects the light extended in substantially a triangular shape toward an incident surface 12a so as to form uniform parallel lights over the whole width of a light guide plate. The light emitted from the substantially spot-like light source 13 can be extended at an uniform luminance over the whole surface of the light guide plate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lighting device for realizing surface light emission and a liquid crystal display device using the same.
[0002]
[Prior art]
For example, an illumination device that illuminates a liquid crystal display panel from the back needs to uniformly illuminate a wide irradiation surface without luminance unevenness in order to maintain good visibility of the entire liquid crystal display panel. As an illumination device that realizes such surface emission, for example, an illumination device that emits surface light with uniform illuminance on one surface of this light guide plate by using a substantially flat light guide plate having a large number of grooves and protrusions formed on the surface. It has been known. (For example, refer to Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2001-243822
[Problems to be solved by the invention]
In the lighting device provided with the light guide plate as described in Patent Document 1, it is necessary to make the light from the light source uniformly enter the entire light incident surface of the light guide plate so that the entire light exit surface of the light guide plate emits light with uniform luminance. is there. For this reason, a lighting device having a conventional light guide plate is provided with a rod-shaped light guide or the like that faces the incident surface of the light guide plate and spreads the light of the LED element, which is a point light source, uniformly to the width of the incident surface of the light guide plate. Needed.
[0005]
However, the conventional lighting device in which another light guide for expanding the light of the light source is provided between the point light source and the light guide plate has a large number of components and is complicated, so that the manufacturing cost is high, and the low cost of the lighting device is low. Had been hindered. Further, this has been an obstacle to downsizing and reducing the size of the lighting device provided with the light guide plate.
[0006]
The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a lighting device and a liquid crystal display device capable of emitting a surface light with uniform luminance with a simple configuration.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, one or more light sources and one side end surface form an incident surface for introducing the light of the light source into the inside, and emit the light to the upper surface or the lower surface. A light guide plate having a substantially flat plate shape having an uneven surface on which a number of fine projections to be reflected are arranged, and a Fresnel lens surface provided on the other side end surface of the light guide plate facing the incident surface. An apparatus is provided.
[0008]
In such a lighting device, even if a point light source is used as the light source, the light from the point light source can be spread over the entire light guide plate with uniform luminance by the Fresnel lens surface. Accordingly, light with uniform brightness and no unevenness can be emitted from the lighting device. In such a lighting device, there is no need to provide another intermediate light guide between the light guide plate and the light source, which spreads the light of the light source, which is a point light source, and then enters the light guide plate. And greatly contributes to reduction in size and weight.
[0009]
The Fresnel lens surface may be integrally molded with the other side end surface of the light guide plate, and the Fresnel lens surface may be formed by attaching a lens sheet having a Fresnel lens shape to the other side end surface of the light guide plate. It may be formed by attaching. The Fresnel lens surface can be easily formed on the light guide plate by integrally molding such a Fresnel lens shape on the other side end surface of the light guide plate, or by pasting the Fresnel lens shape on the other side end surface of the light guide plate. become.
[0010]
The light guide plate may further include a diffuse reflection plate facing the upper surface or the lower surface, and the light guide plate and the diffusion reflection plate may be housed in a diffusely reflective casing. The diffuse reflection plate may be formed of fine irregularities formed on the surface. Such a diffuse reflection plate or a casing whose inner surface is diffusely reflective can reduce leakage light that does not contribute as illumination light and increase luminance.
[0011]
The light guide plate may further include an anti-reflection layer on the surface of the light-exiting surface.The anti-reflection layer may prevent light incident on the light guide plate or light from the light guide plate from being irregularly reflected. Can improve the efficiency of use.
[0012]
The focal length of the Fresnel lens forming the Fresnel lens surface may be set to be substantially the same as the distance between the light source and the Fresnel lens surface. By setting the focal length of the Fresnel lens and the distance between the light source and the Fresnel lens surface to be substantially the same, the light of the substantially point light source emitted from the light source can be transmitted most efficiently over the entire light guide plate. It is possible to spread with uniform brightness.
[0013]
A reflection layer may be further formed to face the Fresnel lens surface. At this time, it is preferable that the distance between the light source and the Fresnel lens surface is set to approximately twice the focal length of the Fresnel lens constituting the Fresnel lens surface. By further providing a reflection layer on the Fresnel lens surface, the light use efficiency of the light guide plate is further improved, and the distance between the light source and the Fresnel lens surface is determined by the focal length of the Fresnel lens constituting the Fresnel lens surface. By setting it to approximately twice, when a reflective layer is further formed facing the Fresnel lens surface, the light of the substantially point light source emitted from the light source can be distributed most efficiently over the entire light guide plate. It becomes possible to widen with brightness.
[0014]
According to the liquid crystal display device including the above-described lighting device and the liquid crystal display panel, it is possible to provide a liquid crystal display device having uniform luminance and excellent visibility without unevenness.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a liquid crystal display device provided with the lighting device of the present invention, and FIG. 2 is an external perspective view showing the lighting device. The liquid crystal display device 9 houses a backlight (illumination device) 10, a liquid crystal display panel 20 disposed on the upper surface side (observation side), a diffuse reflection plate 30 disposed on the lower surface side, and these components. And a housing 40 to be provided.
[0016]
As shown in FIGS. 1 and 2, the backlight (illumination device) 10 is in contact with a substantially flat transparent light guide plate 12 and a central portion of one side end surface (hereinafter, referred to as an incident surface) 12a. And a point light source 13 provided. The surface of the light guide plate 12 on the side of the diffuse reflection plate 30 is an uneven surface 19 having a substantially saw-tooth cross section in which a plurality of ridges 14 extending substantially in parallel with the incident surface 12a of the light guide plate 12 are formed. I have. The other side end surface (hereinafter, referred to as a Fresnel lens surface) 12c of the light guide plate 12 is a Fresnel lens surface 12c having a Fresnel lens formed on the surface. The surface of the light guide plate 12 on the side of the liquid crystal display panel 20 is an emission surface 12b formed in a plane.
[0017]
The liquid crystal display panel 20 is a transmissive or transflective liquid crystal display panel in which pixels (not shown) are formed in a matrix in a display area. The liquid crystal display panel 20 is illuminated from the back side 20a by the backlight (illumination device) 10, so that the liquid crystal display panel 20 can be clearly observed even in a dark place where external light cannot be obtained.
[0018]
The diffuse reflection plate 30 includes a reflection film made of a high-reflectance metal thin film such as aluminum or silver for reflecting light emitted from the uneven surface 19 of the light guide plate 12 toward the light guide plate 12 again. . The diffuse reflection plate 30 has a large number of fine irregularities 30a serving as light scattering means for preventing the reflected light from becoming strong in a specific direction and preventing the visibility of the liquid crystal display device from being lowered. In addition, as the light scattering means, in addition to the reflection film having a concave and convex shape, a scattering film or the like in which resin beads having a different refractive index from the material forming the resin film in the resin film may be used. it can. The housing 40 is formed of, for example, a metal plate, and the entire inner surface thereof is finished to a reflective surface having diffuse reflection properties.
[0019]
The light guide plate 12 constituting the backlight (illumination device) 10 is a flat plate that is disposed on the back surface side 20 a of the liquid crystal display panel 20 and emits light emitted from the light source 13 toward the liquid crystal display panel 20 from the emission surface 12 b side. And is made of, for example, a transparent acrylic resin. On the lower surface side of the light guide plate 12, a plurality of ridges 14 are formed in a stripe shape in a plan view in parallel with each other to form a prism shape.
[0020]
FIG. 3 is a partially enlarged view of the ridge 14. As shown in FIG. 3, the ridges 14 forming the uneven surface 19 are wedge-shaped in longitudinal section formed by a pair of slopes formed to be inclined with respect to the horizontal reference plane z of the uneven surface 19. One of these slope portions is a gentle slope portion 14a, and the other is a steep slope portion (slope portion) 14b formed at a steeper inclination angle than the gentle slope portion 14a.
[0021]
The gentle slope portion 14a is formed to have an inclination angle θ1 with respect to the horizontal reference plane z, and the steep slope portion 14b is formed to have an inclination angle θ2. The direction is the same as the normal. In FIG. 3, the light propagating from the left side (the light source 13 side) to the right side in the light guide plate 12 is reflected to the outside of the uneven surface 19 by the steep slope portion 14 b of the uneven surface 19.
[0022]
Here, the reflection of the propagating light by the steep slope 14b will be described with reference to FIGS. FIG. 4 is a partial cross-sectional configuration diagram showing the steep slope portion 14b shown in FIG. 3 in an enlarged manner. In the backlight (illumination device) 10 according to the present embodiment, as shown in FIG. 4, the propagation light Lin that enters the steep slope 14 b from the inside of the light guide plate 12 and the reflected light Lout of the propagation light Lin by the steep slope 14 b. The steep slope portion 14b is formed so as to have an inclination angle θ2 such that the angle θ4 formed by the above becomes an obtuse angle. That is, at the position where the steep slope 14b (the ridge 14) is formed, the propagation light Lin is incident on the steep slope 14b at an incident angle exceeding 45 °. Accordingly, it is possible to prevent the propagation light Lin that has entered the steep slope portion 14b from being transmitted to the maximum, and as a result, the amount of light reflected by the steep slope portion 14b increases, and the brightness of the backlight 10 improves. .
[0023]
In the backlight 10, the inclination angle θ1 of the gentle slope portion 14a shown in FIG. 3 is in the range of 0.5 ° to 5 ° with respect to the horizontal reference plane z, and the inclination angle θ2 of the steep slope portion 14b is 40 ° or more. It is preferable that the angle be in the range of 60 ° or less. Within such a range, light propagating in the plane of the light guide plate 12 can be efficiently emitted toward the diffuse reflection plate 30.
[0024]
If the range of the inclination angle θ1 of the gentle slope portion 14a is less than 0.5 °, the average brightness of the backlight 10 decreases, and if it exceeds 5 °, the amount of light emitted from the light guide plate 12 is made uniform. You can't do that. When the inclination angle θ2 of the steep slope portion 14b is less than 40 ° or more than 45 °, the amount of light passing through the steep slope portion 14b and leaking increases, and the amount of light emitted from the emission surface 12b (ie, the backlight) 10) is not preferred.
[0025]
Further, in the backlight 10 of the present embodiment, the pitch P of the protrusions 14 (the interval between the apexes of the protrusions 14 or the interval between the bottoms of the protrusions 14) is constant within the uneven surface 19 of the light guide plate 12, and Assuming that the pixel pitch of the liquid crystal display panel 20 is p, it is preferable that P = 0.6p to 0.8p. Further, in the case of the backlight 10 of the present embodiment, the height h (the distance between the horizontal reference plane z and the bottom top of the ridge 14) of the ridge 14 is also constant in the plane of the emission surface 12b. Note that the pitch P and the height h of the ridges 14 do not necessarily need to be constant in the surface of the uneven surface 19, and even if these are changed to form the ridges 14, they exceed the technical scope of the present invention. is not. For example, the pitch P may be coarse on the light source side, and may be finer as the distance from the light source increases. Further, even if the ridges 14 are formed by changing the inclination angles θ1 and θ2 of the respective ridges 14, they do not exceed the technical scope of the present invention.
[0026]
In the present embodiment, since the uneven surface 19 of the backlight 10 is formed so as to face the lower surface side facing the diffuse reflection plate 30, there is no possibility that the ridge 14 will be damaged during the mounting operation. Further, since the upper surface on the liquid crystal display panel 20 side is a flat surface, there is an advantage that the liquid crystal display panel 20 can be stably installed. By forming an anti-reflection layer on such a surface, light loss can be prevented. For example, a multi-layer anti-reflection layer may be formed.
[0027]
In addition, an antireflection layer may be further formed on the surface of the protrusions 14 that form the uneven surface 19. In this case, it is necessary to select a material having a smaller refractive index than that of the light guide plate material as the material of the antireflection layer.
[0028]
The light source 13 provided at the center of the light incident surface 12a of the light guide plate 12 is formed of an LED element which is a substantially point light source. The light source 13 may include one or more LED elements. For example, white light may be obtained from three colors of R, G, and B LEDs.
[0029]
The Fresnel lens surface 12 c of the light guide plate 12 has a Fresnel lens formed integrally with the surface of the light guide plate 12. The Fresnel lens is a substantially planar lens in which small lenses are arranged in an annular shape, and has fine annular annular grooves formed at a predetermined angle according to the focal length set on the other side end surface of the light guide plate 12. And the entire Fresnel lens surface 12c constitutes one lens.
[0030]
It is preferable that such a focal length F1 of the Fresnel lens surface 12c and a distance L1 between the light emitting surface of the light source 13 and the Fresnel lens surface 12c be set to be substantially the same, and within a range of about ± 15% at the maximum. Is good.
[0031]
As shown in FIG. 5, light emitted from the light source 13, which is a substantially point light source, illuminates only the substantially central portion of the light guide plate 12 near the incident surface 12a. The light incident from the central portion of the incident surface 12a gradually widens toward the Fresnel lens surface 12c. The Fresnel lens surface 12c reflects the light spread from the light source 13 in a substantially triangular shape toward the incident surface 12a so as to be uniform parallel light over the entire width of the light guide plate 12. As a result, the light emitted from the light source 13, which is a substantially point light source, can be spread with uniform brightness over the entire light guide plate 12 as shown in FIG. At this time, by setting the focal length F1 and the distance L1 to be substantially the same, the light of the substantially point light source emitted from the light source 13 is spread most efficiently with uniform brightness over the entire light guide plate 12. be able to.
[0032]
In this manner, the light spread with uniform brightness over the entire light guide plate 12 by the Fresnel lens surface 12c is emitted toward the diffuse reflection plate 30 by the ridges 14 forming the uneven surface 19 as shown in FIG. . Then, the light reflected by the diffuse reflection plate 30 again toward the light guide plate 12 passes through the light guide plate 12 and exits with uniform brightness from the entire exit surface 12b. The light emitted from the light guide plate 12 illuminates the entire display surface of the liquid crystal display panel 20 from the rear surface 20a with uniform brightness without unevenness. Thus, the liquid crystal display device 9 of the present invention can observe the liquid crystal display panel 20 illuminated with uniform luminance even in a dark place where external light cannot be obtained.
[0033]
As described above, in the lighting device 10 of the present invention, by forming the Fresnel lens surface 12c on the side end surface of the light guide plate 12, a point light source is used as the light source 13 as light incident on the incident surface 12a of the light guide plate 12. Also, the light of the point light source is spread with uniform brightness over the entire area of the light guide plate 12 by the Fresnel lens surface 12c. Therefore, since it is not necessary to spread the light incident on the incident surface 12a uniformly over the entire incident surface 12a in advance, a rod-shaped light source for uniformly spreading light from an LED element or the like, which is a point light source, to the width of the incident surface of the light guide plate. A light guide different from the light guide plate 12, such as the light guide of the above, becomes unnecessary. Therefore, a substantially point light source such as an LED element can be directly attached to the incident surface of the light guide plate 12, and the number of constituent members is reduced, which greatly contributes to the low cost of the lighting device. In addition, since a light guide different from the light guide plate 12 is not required, it is also useful for reducing the size and weight of the lighting device.
[0034]
FIG. 6 is a sectional view showing another embodiment of the liquid crystal display device of the present invention. In this embodiment, the light guide plate 52 constituting the backlight (illumination device) 50 has an uneven surface 54 on the upper surface side facing the liquid crystal display panel 53. The uneven surface 54 has a substantially triangular longitudinal cross section in which a number of ridges 55 are arranged. One of these slopes is a gentle slope 55a, and the other is a steeper slope than the gentle slope 55a. It is a steep slope portion (slope portion) 55b formed at an angle.
[0035]
The gentle slope portion 55a has an inclination angle θ7 with respect to the horizontal reference plane z, and the steep slope portion 55b has an inclination angle θ8. Are inclined in opposite directions to each other. Of these, the gentle slope portion 55a contributes to the propagation of light in the light guide plate 52, and the steep slope portion 55b serves as a reflection surface that contributes to light reflection. The inclination angle θ7 of such a gentle slope portion 55a is in the range of 1.0 ° or more and 2.5 ° or less, preferably 1.0 ° or more and 2.0 ° or less with respect to the horizontal reference plane z. The inclination angle θ8 of 55b is in the range of 41 ° to 46 °, preferably 42 ° to 45 °.
[0036]
When the range of the inclination angle θ7 of the gentle slope portion 55a is less than 1.0 °, the average luminance of the backlight (illumination device) 50 decreases, and when it exceeds 2.5 °, the average brightness in the plane of the light guide plate 52 is reduced. The amount of emitted light cannot be made uniform. Further, when the inclination angle θ2 of the steep slope portion 55b is less than 41 ° or more than 46 °, the amount of light that leaks through the steep slope portion 55b increases, which is not preferable because it causes brightness unevenness.
[0037]
FIG. 7 is a perspective view showing a backlight (illumination device) 50 included in the liquid crystal display device of FIG. One side end (hereinafter, referred to as an incident surface) 52a of the light guide plate 52 in this embodiment is an incident surface, and a light source 59 having an LED element, which is a substantially point light source, is attached to a central portion. A Fresnel lens sheet 56 on which a Fresnel lens surface 56a is formed is attached to the other side end 52b of the light guide plate 52. Further, a reflection sheet 57 having a reflection layer 57a is attached to the surface of the Fresnel lens sheet 56.
[0038]
Thus, by attaching the Fresnel lens sheet 56 to one side end 52a of the light guide plate 52, the Fresnel lens surface 56a can be easily formed at the side end of the light guide plate 52. Like the first embodiment, the Fresnel lens surface 56a has an incident surface such that the light emitted from the light source 59, which is a substantially point light source, becomes uniform parallel light over the entire width of the light guide plate 52. The light is reflected toward 52a. Thus, light emitted from the light source 59, which is a substantially point light source, can spread with uniform luminance over the entire light guide plate 52.
[0039]
In the second embodiment, the reflectance of the light emitted from the light source 59 on the Fresnel lens surface 56a is further increased by further providing the reflection sheet 57 on the back surface side of the Fresnel lens surface 56a. This makes it possible to minimize the amount of light leaking from the Fresnel lens surface 56a, and further increase the luminance of the backlight (illumination device) 50. The reflection sheet 57 may be formed of a mirror-like metal film such as an aluminum sheet.
[0040]
When the reflection sheet 57 is provided on the back surface side of the Fresnel lens surface 56a as in the second embodiment, the distance L2 between the light emitting surface of the light source 59 and the Fresnel lens surface 56a is set to the focal length F2 of the Fresnel lens surface 56a. It is preferable to set about twice. By setting the distance L2 to be approximately twice the focal length F2, the light of the substantially point light source emitted from the light source 59 can be spread most efficiently with uniform luminance over the entire light guide plate 52. By providing the reflection sheet 57, the depth of the groove constituting the Fresnel lens surface 56a can be reduced, and the molding of the Fresnel lens sheet 56 is facilitated.
[0041]
Referring again to FIG. 6, on lower surface 52 c of light guide plate 52, diffuse reflection plate 61 having a large number of fine irregularities 61 a formed on the surface is formed to diffuse light emitted from lower surface 52 c of light guide plate 52. The light is reflected again toward the light guide plate 52. Then, the light transmitted through the light guide plate 52 illuminates the liquid crystal display panel 53 from the back side with uniform luminance and without unevenness. Note that a low-diffusion sheet 62 is adhered to the back surface of the liquid crystal display panel 53. Such a low diffusion sheet 62 plays a role in efficiently introducing the light emitted from the uneven surface 54 of the light guide plate 52 into the liquid crystal display panel 53.
[0042]
In the liquid crystal display device 65 according to the second embodiment, the backlight (illumination device) 50 and the liquid crystal display panel 53 also have a case 64 in which the entire inner surface is finished as a reflective surface having diffuse reflection properties. It should just be stored in. Accordingly, it is possible to prevent light leaking from a portion other than the liquid crystal display panel 53, and to enhance the visibility of the liquid crystal display device 65. In the present embodiment, the example in which the Fresnel lens surface 56a is formed by a sheet is described, but the end surface of the light guide plate 52 may be formed into a Fresnel lens surface by a molding method.
[0043]
The fine irregularities 30a and 61a constituting the diffuse reflection plates 30 and 61 in the first and second embodiments have, for example, a shape as shown in FIG. Is also good. The recess 72 constituting the diffuse reflection plate 71 has an inner surface shape in the longitudinal section X that is asymmetric with respect to the center O of the recess 72. On the other hand, the inner surface shape of the concave section 72 in the longitudinal section Y is substantially equal to the center O of the concave section 72.
[0044]
According to the diffuse reflection plate 71 having the concave portion 72 having the above-described shape, as shown in FIG. 8, as a total reflection characteristic in the longitudinal section X, a specific reflectance while sufficiently securing the reflectance in the regular reflection direction is obtained. Reflection characteristics in which reflected light is appropriately concentrated in the direction can be obtained. FIG. 9 shows that the diffuse reflection plate 71 in which a plurality of the concave portions 72 are formed is irradiated with light at an incident angle of 30 ° from the direction closer to the x direction than the normal direction of the surface of the base material, and based on the visual angle. Relationship between viewing angle (θ °) and brightness (reflectance height) when continuously changing from perpendicular position (0 °) to 60 ° centering on 30 ° which is the direction of regular reflection on the material surface It is shown. In the reflection characteristic represented by this graph, the integral value of the reflectance in the reflection angle range smaller than the regular reflection angle of 30 ° is larger than the integral value of the reflectance in the reflection angle range larger than the regular reflection angle. The reflection direction tends to shift to the normal side from the regular reflection direction.
[0045]
When the diffuse reflection plate 71 having the concave portion 72 having the above-described shape is employed in the liquid crystal display devices 9 and 65, the light reflected by the diffusion reflection plate 71 has a directivity of increasing the reflectance in a specific direction. As a result, the emission efficiency can be increased at a specific emission angle. In addition, since the directivity of high reflectance in a specific direction is obtained as described above, the liquid crystal display surface can be adjusted in a specific viewing angle range, for example, by adjusting the liquid crystal display surface to the normal viewing angle direction. It is possible to control the brightness to be higher.
[0046]
In each of the above embodiments, the case where the lighting device according to the present invention is used as a backlight has been described. However, the lighting device according to the present invention is preferably used as a front light that is disposed on the upper surface of a liquid crystal display panel. Can be used. In that case, the light guide plate surface on which the ridges are formed may be disposed on the upper surface (observation surface) of the liquid crystal display panel, and the configuration may be such that the diffuse reflection surface placed below is removed. it can. According to this configuration, illumination light having higher luminance than that of the conventional front light can be obtained, and a liquid crystal display device having a bright display can be provided.
[0047]
【The invention's effect】
As described above in detail, according to the lighting device of the present invention, even if a point light source is used as the light source, the light from the point light source can be spread over the entire light guide plate with uniform luminance by the Fresnel lens surface. Become. Accordingly, light with uniform brightness and no unevenness can be emitted from the lighting device. In such a lighting device, there is no need to provide an intermediate light guide between the light guide plate and the light source to spread the light of the light source, which is a point light source, and then enter the light guide plate. It greatly contributes to miniaturization and reduction in size and weight.
[0048]
The Fresnel lens surface may be integrally molded with the other side end surface of the light guide plate, and the Fresnel lens surface may be formed by attaching a lens sheet having a Fresnel lens shape to the other side end surface of the light guide plate. It may be formed by attaching. The Fresnel lens surface can be easily formed on the light guide plate by integrally molding such a Fresnel lens shape on the other side end surface of the light guide plate, or by pasting the Fresnel lens shape on the other side end surface of the light guide plate. become.
[0049]
The light guide plate may further include a diffuse reflection plate facing the upper surface or the lower surface, and the light guide plate and the diffusion reflection plate may be housed in a diffusely reflective casing. The diffuse reflection plate may be formed of fine irregularities formed on the surface. Such a diffuse reflection plate or a casing whose inner surface is diffusely reflective can reduce leakage light that does not contribute as illumination light and increase luminance. The surface of the uneven surface may further include an anti-reflection layer.
[0050]
The focal length of the Fresnel lens forming the Fresnel lens surface may be set to be substantially the same as the distance between the light source and the Fresnel lens surface. By setting the focal length of the Fresnel lens and the distance between the light source and the Fresnel lens surface to be substantially the same, the light of the substantially point light source emitted from the light source can be transmitted most efficiently over the entire light guide plate. It is possible to spread with uniform brightness.
[0051]
A reflection layer may be further formed to face the Fresnel lens surface. At this time, it is preferable that the distance between the light source and the Fresnel lens surface is set to approximately twice the focal length of the Fresnel lens constituting the Fresnel lens surface. By further providing a reflection layer on the Fresnel lens surface, the light use efficiency of the light guide plate is further improved, and the distance between the light source and the Fresnel lens surface is determined by the focal length of the Fresnel lens constituting the Fresnel lens surface. By setting it to approximately twice, when a reflective layer is further formed facing the Fresnel lens surface, the light of the substantially point light source emitted from the light source can be distributed most efficiently over the entire light guide plate. It becomes possible to widen with brightness.
[0052]
According to the liquid crystal display device including the lighting device and the liquid crystal display panel as described above, a liquid crystal display device having uniform luminance, excellent uniformity, and excellent visibility can be used at a low level.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a liquid crystal display device provided with the lighting device of the present invention.
FIG. 2 is an external perspective view of the lighting device shown in FIG. 1;
FIG. 3 is a partial perspective view showing an enlarged view of a ridge of a light guide plate.
FIG. 4 is a partial cross-sectional view for explaining a light guiding state of the light guide plate.
FIG. 5 is an explanatory diagram for explaining an operation of a Fresnel lens surface.
FIG. 6 is a cross-sectional view illustrating a liquid crystal display device including a lighting device according to a second embodiment.
FIG. 7 is an exploded perspective view of the lighting device shown in FIG. 6;
FIG. 8 is an enlarged perspective view showing another embodiment of the diffuse reflection plate.
FIG. 9 is a graph showing reflection characteristics of the diffuse reflection plate shown in FIG.
[Explanation of symbols]
9 Liquid crystal display device 10 Backlight (illumination device)
12 Light guide plate 12a Incident surface (one side end surface)
12b Outgoing surface 12c Fresnel lens surface (the other side end surface)
13 Bar light guide (light source)
14 ridge 14a 1st slope (slow slope)
14b 2nd slope (steep slope)
19 Uneven Surface 20 Liquid Crystal Display Panel 30 Diffuse Reflecting Plate 30a Uneven Surface 40 Case 57a Reflective Layer

Claims (11)

  1. One or more light sources, and one side end surface forms an incident surface for introducing the light of the light source into the inside, and has an uneven surface on which a large number of fine protrusions for emitting and reflecting the light are arranged on an upper surface or a lower surface. With a substantially flat light guide plate,
    A lighting device, comprising a Fresnel lens surface on the other end surface of the light guide plate facing the incident surface.
  2. The lighting device according to claim 1, wherein the Fresnel lens surface is formed integrally with the other side end surface of the light guide plate.
  3. The lighting device according to claim 1, wherein the Fresnel lens surface is formed by attaching a lens sheet having a Fresnel lens shape to the other side end surface of the light guide plate.
  4. The lighting device according to claim 1, further comprising a diffuse reflection plate facing the upper surface or the lower surface of the light guide plate.
  5. The lighting device according to claim 4, wherein the light guide plate and the diffuse reflection plate are housed in a casing having a diffuse reflection inner surface.
  6. The lighting device according to claim 4, wherein the diffuse reflection plate has fine irregularities formed on a surface thereof.
  7. The lighting device according to claim 1, further comprising an anti-reflection layer on a surface of an emission surface of the light guide plate.
  8. The illumination according to any one of claims 1 to 7, wherein a focal length of a Fresnel lens constituting the Fresnel lens surface is set substantially equal to a distance between the light source and the Fresnel lens surface. apparatus.
  9. The lighting device according to any one of claims 1 to 8, wherein a reflection layer is further formed to face the Fresnel lens surface.
  10. The lighting device according to claim 9, wherein a distance between the light source and the Fresnel lens surface is set to be approximately twice a focal length of a Fresnel lens forming the Fresnel lens surface.
  11. A liquid crystal display device comprising: the lighting device according to claim 1; and a liquid crystal display panel.
JP2003114087A 2003-04-18 2003-04-18 Lighting system and liquid crystal display device Withdrawn JP2004319364A (en)

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US7911444B2 (en) 2005-08-31 2011-03-22 Microsoft Corporation Input method for surface of interactive display
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US20100231491A1 (en) * 2006-02-16 2010-09-16 Kiminori Mizuuchi Light source device and liquid crystal display device using such light source device
US8451398B2 (en) 2006-02-16 2013-05-28 Panasonic Corporation Light source device and liquid crystal display device using such light source device
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US8651726B2 (en) 2010-11-19 2014-02-18 Reald Inc. Efficient polarized directional backlight
US9519153B2 (en) 2010-11-19 2016-12-13 Reald Inc. Directional flat illuminators
US9482874B2 (en) 2010-11-19 2016-11-01 Reald Inc. Energy efficient directional flat illuminators
US9250448B2 (en) 2010-11-19 2016-02-02 Reald Inc. Segmented directional backlight and related methods of backlight illumination
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US10062357B2 (en) 2012-05-18 2018-08-28 Reald Spark, Llc Controlling light sources of a directional backlight
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US9678267B2 (en) 2012-05-18 2017-06-13 Reald Spark, Llc Wide angle imaging directional backlights
US10365426B2 (en) 2012-05-18 2019-07-30 Reald Spark, Llc Directional backlight
US9709723B2 (en) 2012-05-18 2017-07-18 Reald Spark, Llc Directional backlight
US9350980B2 (en) 2012-05-18 2016-05-24 Reald Inc. Crosstalk suppression in a directional backlight
US10175418B2 (en) 2012-05-18 2019-01-08 Reald Spark, Llc Wide angle imaging directional backlights
US8917441B2 (en) 2012-07-23 2014-12-23 Reald Inc. Observe tracking autostereoscopic display
US9420266B2 (en) 2012-10-02 2016-08-16 Reald Inc. Stepped waveguide autostereoscopic display apparatus with a reflective directional element
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US10054732B2 (en) 2013-02-22 2018-08-21 Reald Spark, Llc Directional backlight having a rear reflector
US9872007B2 (en) 2013-06-17 2018-01-16 Reald Spark, Llc Controlling light sources of a directional backlight
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