JP2004247267A - Lamp reflector, surface light source device and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lamp reflector for efficiently suppressing generation of a bright line with a simple structure, a surface light source device using the reflector, and a display device using the light source device. <P>SOLUTION: In the light source device, a reflecting light adjusting part 104 with reflectance lower than that of other section is disposed in an inner surface of an opening of a lamp reflector 103, thereby a light incident on an angle part of a light guide plate is reduced and the generation of the bright line is suppressed. The light source device comprises the reflector 103; a light source held inside the reflector 103; a plane-like light guide member of which the one side face is inserted into the opening of the reflector 103; and a light flux control means for emitting the light which is guided from the opening of the reflector 103 by the light guide member in plane form from a surface approximately orthogonal to the one side face of the light guide member. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lamp reflector, a surface light source device using the lamp reflector, and a display device using the surface light source device.
[0002]
[Prior art]
2. Description of the Related Art In recent years, transmissive liquid crystal display devices (LCDs) have been widely used for display monitors of personal computers and display devices such as thin TVs. Since the display element of the liquid crystal display device is a non-light emitting element, a surface light source device called a so-called backlight is provided on the rear surface of the liquid crystal display panel in a transmission type liquid crystal display device, and display is performed by light emitted from the surface light source device. It is carried out.
[0003]
A surface light source device can be generally considered to be a mechanism for converting light emitted from a linear light source such as a cold cathode discharge tube into uniform planar light using an optical element such as a light guide plate. There are various mechanisms depending on the use of the display device, which is the final product using the surface light source device, the size of the display screen, the required performance, and the like.
[0004]
For example, even if only the arrangement of the linear light sources is taken, there is a configuration called a direct type disposed on the back surface of the light guide plate, and a configuration called a sidelight type disposed on the side surface of the light guide plate. At present, a sidelight type is mainly used for notebook computers and monitors in order to take advantage of a thin LCD.
[0005]
FIG. 5A shows a configuration example of a conventional side light type surface light source device. The surface light source device includes a light guide plate 1 formed on a substantially flat plate formed of a translucent material, a linear light source 2 disposed along one side surface 1a of the light guide plate 1, and a light emitted from the linear light source 2. A lamp reflector (hereinafter, also simply referred to as a reflector) 3 for guiding the light to the light guide plate without waste is provided, and the light of the linear light source 2 is incident on the side surface 1 a of the light guide plate 1 directly or reflected by the reflector 3.
[0006]
One surface (upper surface in the figure) of the light guide plate 1 is a light emitting surface 1b, on which a light control sheet 5 having a substantially sawtooth vertical cross section and functioning as a continuous body of triangular prisms is provided. The corner is provided facing the observer. In order to improve the light-collecting property, the light control sheet 5 may be provided with two triangular prisms orthogonal to each other in an overlapping manner.
[0007]
On the surface (lower surface in the figure) 1c of the light guide plate 1 opposite to the light emitting surface 1b, a large number of light scattering inks are printed or directly transferred by injection molding or the like to form a large number of patterns formed in a predetermined pattern. A light extraction mechanism 6 composed of dots 6a is provided. In addition, a reflection sheet 7 for returning light emitted from the light guide plate 1 to the light guide plate 1 to the light guide plate 1 and effectively using the light is provided in the lower portion on the side of the surface 1c in proximity to the surface 1c.
[0008]
In the surface light source device having such a configuration, light incident on the light guide plate 1 repeats reflection and refraction at the light extraction mechanism 6, the reflection sheet 7, and the interfaces 1a and 1b of the light guide plate while propagating through the light guide plate 1. Are taken out from the light emitting surface 1a (8 in the figure). Then, the light is condensed by the light control sheet 5 and irradiates the liquid crystal panel via a diffusion sheet (not shown).
[0009]
However, in this configuration, two expensive light control sheets 5 are used in order to increase the light concentration, and in some cases, an upper diffusion sheet and a lower diffusion sheet are used above and below the light control sheet 5, and further, a polarizing sheet is used. The production cost is increased due to the necessity. Further, it is disadvantageous in terms of effective use of light, such as a large amount of scattered light in the light guide plate, and a light return loss due to the light control sheet. In recent years, there has been a great demand for thinner and higher brightness liquid crystal display devices, and there is an urgent need to reduce the number of parts and the thickness of the surface light source device. Therefore, these problems cannot be ignored.
[0010]
Therefore, as shown in FIG. 5B, the light control sheet 5 is arranged in the opposite direction to that of FIG. 5A, and only the reflection sheet 7 is provided on the lower surface of the light guide plate 1. (For example, see FIG. 16 of Patent Document 1). In this configuration, the light guide plate 1 can be reduced in thickness, and the configuration uses one light control sheet 5 (and may further use one diffusion sheet as needed). An inexpensive surface light source device can be realized.
[0011]
[Patent Document 1]
JP 2001-118417 A [Patent Document 2]
JP-A-9-184926
[Problems to be solved by the invention]
On the other hand, in the sidelight type surface light source device as described above, there is a structurally unavoidable luminance unevenness (bright line). That is, ideally, it is preferable that the light from the linear light source 2 is uniformly incident on the light guide plate 1 via the side surface 1a on which the light source is provided. However, the shape of the corner A (FIG. 6A) of the surface 1a of the light guide plate 1 is more or less strictly viewed, and has a rounded shape as shown in FIG. 6B. I have. This is inevitable in manufacturing the light guide plate 1.
[0013]
When such a roundness exists, the light rays incident from the roundness R are condensed by the lens effect, and the reflected light is emitted from the end of the light guide plate 1 to a bright line (slightly brighter than its surroundings) at a position of several mm to several tens mm. It appears as a visible part (FIG. 6C).
[0014]
Since the bright line is particularly conspicuous in the vicinity of the side surface where the light source is provided, the portion is not used as a display area, or a diffusion sheet or a dimming sheet (prism sheet) is provided in multiple layers so that it is not visually noticeable. Then, even if a bright line is generated, it is not a big problem. However, recently, in order to make maximum use of the installation area of the display device, the so-called liquid crystal display has been narrowed in frame (higher ratio of the display area to the display device area). For this reason, it is required that the surface light source device is also used effectively to the very edge, and even if it is several mm, it cannot be wasted.
[0015]
In addition, increasing the brightness of the liquid crystal display is also an important issue, and members such as a diffusion sheet and a light control sheet are tending to be omitted as much as possible from the necessity of more effective and efficient light control.
[0016]
In view of such a situation, various proposals have been made for suppressing bright lines. For example, in the above-mentioned Patent Document 1 (see FIG. 3), a configuration is proposed in which an end portion of a lamp reflector is bent to block light incident on a corner portion of the light guide plate 1, thereby preventing generation of a bright line. .
[0017]
Patent Document 2 (FIG. 1) proposes a configuration in which a bright line is prevented by adjusting the shape of a corner of a light guide plate.
[0018]
However, the configuration in which the reflector is bent to block the incident light to the corners requires strict requirements for the machining accuracy and assembly accuracy of the reflector, which leads to an increase in cost, a decrease in yield, a hindrance to light input efficiency, and a decrease in luminance. There is a risk of lowering.
[0019]
Further, even if the corner shape of the light guide plate is adjusted, the roundness R present on the light incident surface of the light guide plate cannot be completely eliminated, and the fundamental solution for preventing bright lines cannot be achieved. Further, by adjusting the shape of the light guide plate, the shape of the reflector becomes complicated, and there is a problem that it takes time to assemble.
[0020]
The present invention has been made in view of the problems of the related art, and has as its object to provide a lamp reflector that has a simple configuration and can effectively suppress the generation of bright lines.
[0021]
Another object of the present invention is to provide a surface light source device using the lamp reflector according to the present invention, and a display device using the surface light source device.
[0022]
[Means for Solving the Problems]
That is, the gist of the present invention is a lamp reflector that reflects light emitted from a light source on an inner surface and emits the reflected light from an opening, and the inner surface forming the opening has a lower reflectance than other regions. And a reflected light adjusting means having the following characteristics.
[0023]
Further, another gist of the present invention is to provide a lamp reflector of the present invention, a light source held inside the lamp reflector, a plate-shaped light guide member having one side face inserted into an opening of the lamp reflector, and a lamp reflector opening. And a light flux controlling means for emitting light guided from the portion to the light guide member in a plane from a surface substantially perpendicular to one side surface of the light guide member.
[0024]
Another aspect of the present invention resides in a display device using the surface light source device of the present invention as a backlight.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings. ■ (Configuration of surface light source device)
FIG. 1 is a diagram illustrating a configuration example of a side light type surface light source device using a lamp reflector according to an embodiment of the present invention. FIG. 1A illustrates a direction parallel to the length direction of a linear light source 102. FIG. 1B is a side view as seen from the direction of arrow a in FIG. 1A (the direction facing the linear light source 102).
[0026]
The surface light source device according to the present embodiment is the conventional surface light source device shown in FIG. 5B except for the shape of the lower surface of the light guide plate 101, the shape of the reflector 103, and the fact that the reflector 103 has a reflected light adjusting unit 104. Has the same configuration as
[0027]
The light guide plate 101 is a wedge-shaped light guide plate whose thickness decreases as the distance from the linear light source 102 increases, and is formed of a transparent resin such as PMMA, COP (cycloolefin polymer), and polycarbonate. Further, the light emitting surface 101a is provided with minute projections and depressions formed by, for example, sandblasting as a light extraction mechanism (not shown).
[0028]
As shown in FIG. 1B, a vertical groove or a prism is formed on the lower surface 101b of the light guide plate 101 in a direction substantially perpendicular to the longitudinal direction of the linear light source. Further, a reflection sheet 107 is provided below the lower surface 101b. The surface of the reflection sheet 107 facing the lower surface 101b of the light guide plate 101 is formed by a mirror surface, a minute void, or a minute bead coating. A light control sheet 105 having a triangular prism array formed on the light emitting surface 101a of the light guide plate 101 is disposed with the apex angle of the prism facing downward. A diffusion sheet 106 is provided on the light control sheet 105.
[0029]
The linear light source 102 formed of a cold cathode tube, an LED array, or the like is supported and arranged inside the lamp reflector 103 by a support (not shown) such that the length direction is parallel to one side surface 101c of the light guide plate 101.
[0030]
Light emitted from the linear light source 102 is directly or reflected on the inner surface of the reflector 103 and enters the light guide plate 101 from the side surface 101c. Then, the light propagating through the light guide plate 101 is reflected upward by the interface or the reflection sheet on the lower surface 101b side, and propagates while gradually emitting from the light emitting surface 101a. Then, the light emitted in a predetermined direction by the minute unevenness provided on the light emitting surface 101 a is aligned in a direction perpendicular to the emission surface by the prism of the light control sheet 105, and then diffused by the diffusion sheet 106.
[0031]
■ (Reflector configuration)
As shown in FIG. 1, the reflector 103 in the present embodiment has a configuration in which the light guide plate is sandwiched between the openings, and is provided at least at a portion of the opening that is in contact with the corner of the light emitting surface 101 a of the light guide plate 101. It has a reflected light adjusting unit 104. The reflected light adjusting unit 104 has a function of absorbing and / or scattering light that can enter the corner 101 d of the light guide plate 101 among the light emitted by the linear light source 102. As a result, the light incident on the corner 101d of the light guide plate 101 is reduced. Therefore, even if the corner 101d of the light guide plate 101 has a roundness which is inevitable in manufacturing (within the machining accuracy range), the roundness is not affected. The light intensity of the light beam condensed by the light is also reduced, and as a result, it becomes possible to suppress the bright line.
[0032]
FIG. 2 is a perspective view of the reflector 103. FIG. 2 shows the state of FIG. 1 upside down to make the reflected light adjustment unit 104 provided in the reflector 103 easy to understand.
[0033]
The reflected light adjusting unit 104 is a region where the light reflectance is lower than the light reflecting surface (inner surface) of the reflector 103, and can be provided on the surface of the reflector 103 by painting or bonding, for example.
[0034]
Specifically, a paint or tape preferably having an achromatic color (white, black, and intermediate colors) is provided on the surface of the reflector 103 by painting (printing) or bonding. What kind of color to use may be determined by actually experimenting in some ways, but can be determined to some extent according to the color of the inner surface of the reflector. That is, since it is necessary that the reflectance of light is lower than that of the light reflecting surface of the reflector 103, when the entire reflector 103 is formed of a white PET film, the white reflected light adjusting unit 104 is provided. No effect can be expected. On the other hand, when the reflection surface of the reflector 103 is made mirror-finished irrespective of metal or resin, the effect of preventing bright lines can be expected by providing the white reflected light adjustment unit 104.
[0035]
However, since pure white and pure black may cause bright lines and dark lines, respectively, it is actually preferable to use gray which is an intermediate color between them.
[0036]
Note that a bright line (dark line) can be visually understood as a region where the luminance rises (falls) discontinuously visually as compared with the surroundings. Then, the reflected light adjusting unit 104 adjusts the reflectance of the reflecting surface of the reflector 103 so as not to generate a new bright line or dark line due to a sudden change in the reflectance between the reflected light adjusting unit 104 and the reflecting surface of the reflector 103. More preferably, the configuration is such that the reflectance gradually changes to a predetermined reflectance. When the reflected light adjusting unit 104 is formed by printing, a pattern in which the density changes in the width direction of the reflected light adjusting unit 104 (the left-right direction in FIG. 1) is printed, or the pattern is adjusted so as to reach a predetermined reflectance stepwise. This can be realized by printing while changing the key. Alternatively, a configuration may be adopted in which a tape on which similar printing is performed is attached to the reflector 103.
[0037]
The position where the reflected light adjustment unit 104 is provided and the width thereof will be described with reference to FIG. The reflector 103 according to the present embodiment has a configuration in which the light guide plate 101 is inserted into the opening in a small amount. The reflected light adjustment unit 104 is provided at a position where the light guide plate 101 is to be inserted in the opening.
[0038]
Generally, the distance L1 at which the light guide plate 101 is inserted into the reflector 103 is, for example, about 0.2 mm to 2.0 mm. The start position of the reflected light adjusting unit 104 is further 100 μm to 500 μm (L3) behind the distance L1, and the width (L2) of the reflected light adjusting unit 104 is L3 + L1 (the reflected light adjusting unit 104 extends to the end of the reflector 103). Is provided), which is 0.4 mm to 2.5 mm in the above example. The width (L1 + L3-L2) of the portion where the reflected light adjusting unit 104 is not provided from the end of the reflector 103 may be provided as needed.
[0039]
A portion (L2-L3) of the reflected light adjustment unit 104 that opposes the light guide plate 101 is effective in suppressing bright line prevention due to reflection of this portion on the inner surface of the reflector. Therefore, especially when the reflectance of the inner surface of the reflector is high, it is preferable to provide the reflected light adjusting unit 104 to the end of the reflector 103.
[0040]
If there is a portion where the reflected light adjusting unit 104 is not provided from the end of the reflector 103, the reflectance is gradually reduced from the inner surface of the reflector on the light source side to a predetermined value, and the light is directed toward the end of the reflector 103 again. It is preferable to have such a characteristic that the reflectance is gradually increased (returned).
[0041]
When L3 is increased, the brightness is conversely reduced, and when L3 is decreased, the effect of suppressing bright lines is reduced. Therefore, an appropriate value is specifically determined according to the light guide plate 101 to be used.
[0042]
In addition, since the bright line in question is the largest due to light incident from the light-emitting surface side corner of the light guide plate 101, the reflected light adjusting unit 104 is provided only on the inner surface above the opening of the reflector 103 in FIG. Although the configuration described above is shown, a similar reflected light adjustment unit 104 may be provided also on the inner surface below the opening of the light reflector 103 which enters from the corner on the side where the reflection sheet 7 is provided. In this case, the width of the reflected light adjusting unit 104 may be the same as or different from that of the reflected light adjusting unit 104 provided above. However, as in the case of adding to the upper part, if L3 is lengthened more than necessary, the brightness is reduced. Therefore, the length is preferably as short as possible from 100 μm to 500 μm.
[0043]
Although the drawing shows only the case where the present invention is applied to a reflector having a substantially square cross section, the present invention can be applied to a reflector having a curved reflecting surface. Further, the material of the reflector and the color of the reflection surface are not limited.
[0044]
Further, the reflector according to the present invention can be applied to all side light type surface light source devices, including the conventional configuration shown in FIG. 5, and the light guided from the lamp reflector opening to the light guide plate. Are emitted from the light emitting surface of the light guide plate in a planar manner, and various configurations for performing light flux control for controlling the uniformity of luminance and the directionality of light required for the surface light source device, such as a light extraction mechanism, a reflection sheet, and a There is no particular limitation on the presence, number, type, etc. of the light sheet or the like.
[0045]
【Example】
A surface light source device having the configuration shown in FIG. 1 was prepared using the following members.
-Light guide plate: width 290mm, length 220mm. The thickness is 2.8 mm on the light source side (incident surface), the thickness decreases as the distance from the light source increases, and the wedge shape has a final thickness of 0.7 mm. Acrylic resin (PMMA) manufactured by injection molding.
Lamp reflector: A material obtained by bending a material in which a silver vapor deposition layer is coated on a SUS plate and molding it into the shape shown in FIG.
-Reflection sheet: silver-evaporated sheet-Light source: cold cathode tube with a diameter of 1.8 mm-Light control sheet: downward prism lens sheet (manufactured by Mitsubishi Rayon Co., Ltd.). A lens in which the prism apex angle is arranged downward as shown in FIG.
Diffusion sheet: Milky white PET film The amount of light guide plate inserted into the opening of the lamp reflector (L1 in FIG. 3) is 0.8 mm.
[0046]
(Example 1)
Gray (color sample number DIC No. G-147) ink was printed at a uniform density on the inner surface above the opening of the lamp reflector to provide a reflected light adjusting unit. The width (L2) of the reflected light adjusting portion was 1.3 mm, and the width (L3) provided from the light guide plate end to the light source side, which was provided up to the end of the reflector, was 0.5 mm.
(Comparative Example 1)
The configuration was the same as that of the example except that the reflected light adjusting unit was not provided.
[0047]
(Measurement of luminance change)
With respect to the two surface light source devices thus configured, the distance from the end of the light guide plate and the change in luminance were measured using a color luminance meter BM-7 manufactured by Topcon Corporation. FIG. 4 shows the measurement results.
[0048]
In FIG. 4, in the measurement data of the comparative example, bright lines suddenly (several hundred nits) appear at a position of a distance of about 10 mm, whereas in the surface light source device of the embodiment configuration, the luminance change at the same position is gentle. It can be seen that the occurrence of bright lines is suppressed. The effect of suppressing the luminance by the reflected light adjusting unit can be easily understood from the difference between the luminances near the bright line generating position.
[0049]
【The invention's effect】
As described above, according to the present invention, it is possible to realize a lamp reflector that can effectively suppress the occurrence of bright lines with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a side view showing a configuration example of a surface light source device according to an embodiment of the present invention.
FIG. 2 is a perspective view illustrating a configuration example of a lamp reflector according to the embodiment of the present invention.
FIG. 3 is a diagram illustrating a reflected light adjusting unit provided in the lamp reflector in the embodiment of the present invention.
FIG. 4 is a diagram showing the results of luminance measurement of the surface light source devices of the example and the comparative example.
FIG. 5 is a diagram showing a configuration example of a conventional surface light source device.
FIG. 6 is a diagram illustrating generation of bright lines in a conventional surface light source device.

Claims (5)

A lamp reflector that reflects light emitted from a light source on an inner surface and emits the reflected light from an opening,
A lamp reflector, comprising a reflected light adjusting unit having a lower reflectance than other regions on an inner surface forming the opening. 2. The reflection light adjusting means is provided on an inner surface forming the opening and in a region including a position to be opposed to a corner of a light guide member inserted into the opening. The described lamp reflector. 3. The lamp reflector according to claim 2, wherein the reflected light adjusting unit is formed by coloring the area. A lamp reflector according to any one of claims 1 to 3,
A light source held inside the lamp reflector;
A plate-shaped light guide member having one side face inserted into the opening of the lamp reflector,
A surface light source comprising: a light flux controlling unit configured to emit light guided from the lamp reflector opening to the light guide member in a plane from a surface substantially orthogonal to the one side surface of the light guide member. apparatus. A display device using the surface light source device according to claim 4 as a backlight.

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