JP3553787B2 - Surface illumination device and display device using the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface illumination device suitable as a backlight of a flat-panel display device such as a liquid crystal display device, and more particularly to a surface illumination device with improved luminance unevenness occurring near a light incident surface of a light guide plate and a display using the same. Equipment related.
[0002]
[Prior art]
A surface illumination device used as a backlight of a flat display device such as a liquid crystal display device has a flat light guide plate as disclosed in, for example, JP-A-9-33898 or the like in order to have a thin structure. A sidelight type in which a linear light source is arranged on the side surface is used.
[0003]
By the way, when the surface illumination device is housed in a frame together with the display device, as shown in FIG. 5, a notch 101 of several mm square may be formed in a corner portion of the light guide plate 100 as shown in FIG. The notch 101 is arranged so as to be located outside the effective display area of the display device. However, as the ratio of the effective display area of the display device increases, the distance between the notch 101 and the effective display area is increased. Is becoming very short. Therefore, the notch 101 is a factor that causes uneven brightness of the surface illumination device. That is, among the minute side surfaces 102 and 103 facing the cutout portion 101 of the light guide plate 100, the vicinity of one minute side surface 102 orthogonal to the light incident surface 104 reduces a part of the light incident from the linear light source 105. Since the side surface 102 is reflected, the brightness increases. Further, in the vicinity of the other minute side surface 103 parallel to the light incident surface 104, the light incident from the linear light source 105 is shielded by the part 106 of the frame arranged in the cutout 101, so that the brightness is reduced. Therefore, as the notch 101 approaches the effective display area of the display device, the brightness of the light illuminating the display device tends to be uneven.
[0004]
As shown in FIG. 6, one end of a reflection sheet 108 covering the linear light source 105 is fixed to the upper surface serving as the light exit surface 107 of the light guide plate 100 with a double-sided adhesive 109 or the like. This was a cause of uneven brightness. That is, since the reflection sheet 108 has a high light reflectivity, if a transparent sheet is used as the double-sided adhesive 109 for fixing the reflection sheet 108, that part becomes a pseudo light source, and this pseudo light source causes luminance unevenness. Therefore, in order to suppress the generation of the pseudo light source, a black sheet-like adhesive was used for the double-sided adhesive 109, but on the contrary, light absorption was increased at that portion, causing uneven brightness. Also, the use of a gray sheet as the double-sided adhesive 109 was examined. However, it is difficult to set the gray sheet to a desired density (brightness). Therefore, it is difficult to set a desired light reflectance.
[0005]
[Problems to be solved by the invention]
Therefore, the present invention has been made in view of the above points, and has as its main object to provide a surface illumination device in which the luminance of a light emitting surface, particularly the light emitting surface on the incident surface side, is uniform. Further, it is another object to provide a display device in which luminance unevenness on a display surface is small and display quality is high.
[0006]
[Means for Solving the Problems]
The surface lighting device of the present invention includes a light incident surface on a side surface, a light guide plate including a notch for positioning on at least one side of the light incident surface, and a light guide plate facing the light incident surface of the light guide plate. In the surface illumination device provided with the linear light source arranged in a position, of the two minute side surfaces facing the notch of the light guide plate, the minute side surface in a direction orthogonal to the light incident surface is covered with a light absorbing member. It is characterized by the following.
[0007]
Further, the surface lighting device of the present invention includes a light guide plate provided with a light incident surface on a side surface, and a notch for positioning on at least one side of the light incident surface, and a light guide plate on the light incident surface of the light guide plate. In a surface illumination device including a linear light source arranged to face each other, of the two minute side surfaces facing the cutout portion of the light guide plate, a minute side surface in a direction orthogonal to the light incident surface is formed of a light absorbing member. A minute side surface in a direction parallel to the light incident surface is covered with a light reflective member.
[0008]
Further, the surface illumination device of the present invention has a light incident surface on a side surface, a light exit surface on an upper surface, and a light guide plate including a notch for positioning on at least one side of the light incident surface; A surface provided with a linear light source arranged to face the light incident surface, and a reflective sheet arranged so as to surround the light incident surface and the linear light source, and at least one end of which is fixed to a light emitting surface of the light guide plate; In the lighting device, a light-absorbing sheet is fixed to one end of the reflection sheet, and the sheet and a light-emitting surface of the light guide plate are fixed with a light-transmitting sheet interposed therebetween, and the notch of the light guide plate is fixed. Wherein the minute side surface in a direction orthogonal to the light incident surface is covered with a light absorbing member among the two minute side surfaces facing the light incident surface.
[0009]
The light-absorbing member that covers the micro side surface can have a light absorption rate in the range of 20 to 90%.
[0011]
The display device of the present invention is characterized in that, in a display device in which a transmission type display device is stacked on a surface illumination device, any one of the surface illumination devices is used as the surface illumination device.
[0012]
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 plan view showing a schematic configuration of a surface illumination device, FIG. 2 is a cross-sectional view taken along line II of FIG. 1, and FIG. 3 is a perspective view of a main part (light guide plate 1) thereof. In these figures, reference numeral 1 denotes a light guide plate having a rectangular flat surface made of a thin and transparent acrylic plate or the like. One of the side surfaces is a light incident surface 2 and the upper surface is a light output surface 3. The four corners of the light guide plate 1 are provided with positioning notches 4, two of which are located on both sides of the light incident surface 2. In order to determine the position, the notches 4 may be provided at least at two corners in the diagonal direction of the light guide plate 1. In this case, one notch 4 is provided on one side of the light incident surface 2. Located on the side.
[0013]
A linear light source 5 composed of a cold cathode tube or the like is disposed at a position facing the light incident surface 2 of the light guide plate 1, and a flexible reflection sheet 6 is disposed so as to surround the linear light source 5 and the light incident surface 2. Have been. The reflection sheet 6 can be formed of a thin film sheet of PET or polycarbonate made white by foaming, for example, and is disposed over substantially the entire width of the light incident surface 2 excluding the cutout 4. One end 61 of the reflection sheet 6 is fixed to the light exit surface 3 of the light guide plate 1 with the light control member 7 interposed therebetween, and the other end 62 of the reflection sheet 6 is movable on the back side of the light guide plate 1 or is easily detachable. It is arranged in the state.
[0014]
An optical sheet 8 such as a lens sheet is laminated and arranged on the light exit surface 3 of the light guide plate 1 as necessary, and light leaking from the light guide plate 1 is provided on the side surface and the lower surface of the light guide plate 1 except for the light incident surface 2. A lower surface reflection material 9 and a side surface reflection material 10 for reflecting inside are arranged. These reflectors 9 and 10 may be formed by printing a white film, or may be made of the same material as the reflective sheet 6.
[0015]
Here, of the minute side surfaces 11, 12 facing the cutout portion 4 of the light guide plate 1, the vicinity of the minute side surface 11 in the direction orthogonal to the light incident surface 2 is the light incident on the minute side surface 11 from the light incident surface 2. , And becomes too bright, which causes uneven brightness of the light exit surface 3. Therefore, as shown in FIG. 3, the minute side surface 11 is covered with a light absorbing member 11a. Here, as the light absorbing member 11a, a black film or the like having a light absorption rate close to 100% may be used. However, if the light absorption is more than necessary, the light absorption member 11a may be too dark to cause luminance unevenness. Therefore, it is preferable to use a gray-based member having a light absorption of 20 to 90%. Therefore, for example, the light absorbing member 11a can be provided in the form of a coating by applying gray printing or coating with a light absorption rate of 20 to 90% on the minute side surface 11. With this light absorbing member 11a, light reflection by the minute side surface 11 is suppressed, and luminance unevenness near the minute side surface 11 is improved.
[0016]
On the other hand, among the minute side surfaces 11 and 12 facing the notch portion 4 of the light guide plate 1, the vicinity of the minute side surface 12 in a direction parallel to the light incident surface 2 is a positioning member (not shown) arranged in the notch portion 4. ) Blocks the light from the light source 5, so that it becomes too dark and causes uneven brightness. Therefore, as shown in FIG. 3, the minute side surface 12 is covered with a light-reflective member 12a. Here, as the light-reflective member 12a, the configuration is simplified by utilizing the side-surface reflector 10. That is, by slightly extending one end of the white side reflector 10 to cover the minute side surface 12, the side reflector 10 is also used as the light reflective member 12a. As described above, by covering the minute side surface 12 with the light-reflective member 12a, the luminance is increased due to an increase in the amount of light reflection in the vicinity of the minute side surface 12, and luminance unevenness is improved.
[0017]
In addition, as a place where the uneven brightness occurs, there is a fixed place between the one end 61 of the reflection sheet 6 and the light emitting surface 3 of the light guide plate 1, and the uneven brightness in this portion is eliminated by the light control member 7. Hereinafter, the light control member 7 will be described in detail.
[0018]
The dimming member 7 includes a black light absorbing sheet 71 attached to one end 61 of the reflection sheet 6 via an adhesive layer, and an adhesive disposed between the light absorbing sheet 71 and the light emitting surface 3. And a transparent light-transmitting sheet 72. Here, a black single-sided adhesive tape may be used for the light-absorbing sheet 71, and a transparent double-sided adhesive tape may be used for the light-transmitting sheet 72, or a black double-sided adhesive tape, the light-transmitting sheet 72 may be used for the light-absorbing sheet 71. Alternatively, a transparent single-sided adhesive tape may be used. As the light-transmitting sheet 72, a sheet having a thickness smaller than that of the light-absorbing sheet 71 (thickness: 50 to 80 μm) can be used. For example, the thickness of a polyester support provided with an acrylic or silicone-based adhesive layer is reduced. A thin film sheet of about 20 to 40 μm can be used.
[0019]
Conventionally, the reflection sheet 6 is fixed using either a black double-sided adhesive tape or a transparent double-sided adhesive tape, so that the light emitted from the light source 5 is excessively reflected or absorbed by the double-sided adhesive tape. As a result, luminance unevenness was likely to occur on the light emitting surface 3. However, as described above, this problem could be solved by combining the light absorbing sheet 71 and the light transmitting sheet 72.
[0020]
That is, the light transmissive sheet 72 does not transmit all of the light emitted from the light emitting surface 3, and a part of the light is reflected toward the light guide plate 1. The amount of this reflection varies depending on the refractive index difference between the members constituting the light guide plate 1 and the light transmitting sheet 72, the thickness of the light transmitting sheet 72, and the like. It has been found that the amount can also be controlled. Therefore, by adjusting the thickness of the light transmitting sheet 72 and controlling the amount of reflection, the amount of light reflected by the light transmitting sheet 72 and the amount of light absorbed by the light absorbing sheet 71 can be controlled simultaneously. By setting the thickness of the light transmitting sheet 72 to an optimum value according to the type and mounting position of the light source 5 and the type of the light guide plate 1 and the reflecting sheet 6, the light emitting surface 3 and the reflecting sheet 6 overlap. Luminance unevenness caused by excessive light reflection or light absorption by a portion could be easily eliminated. The light-transmitting sheet 72 is available in a wide variety of products having different thicknesses, and it is easy to obtain a commercially available product as a double-sided or single-sided adhesive tape. This is useful for light control.
[0021]
As described above, with the extremely simple configuration in which the light transmitting sheet 72 is interposed between the light emitting surface 3 and the light absorbing sheet 71, it is possible to improve luminance unevenness.
[0022]
As described above, the above-described surface illumination device was able to improve the luminance unevenness near the light incident surface 2. Therefore, as shown in FIG. 4, the transmission type display device 22 is stacked on the surface illumination device 21. By using the above-described surface lighting device as the surface lighting device 21 of the display device 20, the display luminance distribution of the display device 20 can be stabilized and the display quality can be improved.
[0023]
【The invention's effect】
As described above, according to the present invention, it is possible to improve the luminance unevenness of the light emitting surface, particularly the light emitting surface on the light incident surface side, and to provide a surface illumination device having a uniform luminance distribution. In addition, by combining this surface illumination device with a transmission type display device to constitute a display device, the luminance distribution on the display surface can be stabilized and the display quality can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of a surface lighting device according to an embodiment of the present invention.
FIG. 2 is a sectional view taken along line II of FIG.
FIG. 3 is a perspective view showing a main part of the light guide plate of the embodiment.
FIG. 4 is a schematic configuration diagram of a display device according to an embodiment of the present invention.
FIG. 5 is a plan view for explaining a conventional structure.
FIG. 6 is a cross-sectional view for explaining a conventional structure.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 light guide plate 11 minute side surface 11 a light absorbing member 12 minute side surface 12 a light reflecting member 2 light incident surface 3 light emitting surface 4 notch 5 linear light source 6 reflecting sheet 7 light adjusting member 71 light absorbing sheet 72 light transmittance Sheet

Claims (5)

A light guide plate having a light incident surface on a side surface and a notch for positioning on at least one side of the light incident surface, and a linear light source disposed opposite to the light incident surface of the light guide plate. In the surface lighting device, the surface of the light guide plate, in which two of the minute side surfaces facing the cutout portion, the minute side surface in a direction orthogonal to the light incident surface is covered with a light absorbing member. . A light guide plate provided with a light incident surface on a side surface and having a notch for positioning on at least one side of the light incident surface, and a linear light source disposed opposite to the light incident surface of the light guide plate. In the surface illumination device, of the two minute side surfaces facing the cutout portion of the light guide plate, a minute side surface in a direction orthogonal to the light incident surface is covered with a light absorbing member, and a direction parallel to the light incident surface. A surface lighting device characterized in that the minute side surface of (1) is covered with a light reflecting member. A light guide plate including a light incident surface on a side surface, a light exit surface on an upper surface, and a notch for positioning on at least one side of the light incident surface, and a light guide plate disposed to face the light incident surface of the light guide plate. A linear light source, and a surface illumination device including a light incident surface and a reflective sheet fixed to the light exit surface of the light guide plate, at least one end of which is disposed so as to wrap the linear light source. A light-absorbing sheet is fixed, and the sheet and the light-emitting surface of the light guide plate are fixed with a light-transmitting sheet interposed therebetween, and among the two minute side surfaces facing the cutout portion of the light guide plate, A surface illuminating device, wherein a minute side surface in a direction perpendicular to a light incident surface is covered with a light absorbing member. The surface illuminating device according to claim 1, wherein the light-absorbing member that covers the minute side surface has a light absorption rate set in a range of 20 to 90%. A display device in which a transmission type display device is stacked on a surface illumination device, wherein the surface illumination device according to any one of claims 1 to 4 is used as the surface illumination device.

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