JP2010282908A - Lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device capable of preventing contrast unevenness between light sources and an emission line from appearing on a light-emitting surface even though a plurality of point light sources are used. <P>SOLUTION: The lighting device 20 includes a plurality of point light sources 12, a diffusion light guide body 24 for making light incident from the point light source 12, and a light guide plate 28. The diffusion light guide body 24 makes light of the point light source 12 incident from its front face 24a, and emits the light to one side face 28a of the light guide plate 28 from its rear face 24b. The light guide plate 28 emits the light incident from one side face 28a to its front face 28b. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an illuminating device using a point light source, and more particularly to an illuminating device that can improve the uniformity of luminance distribution in a display portion even when a plurality of point light sources are used.

  An illumination device is used as a member for illuminating a display device such as a liquid crystal display device. Conventionally, linear light sources such as cold-cathode tubes have been widely used for such illumination devices, but in recent years, illumination light-emitting devices that use point light sources such as LEDs instead of linear light sources have attracted attention. ing.

  For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2008-171717), a light guide plate, a point light source provided adjacent to a light incident end surface of the light guide plate, and a light emitting surface side of the light guide plate are provided. There is disclosed a planar illuminating device, which is a diffused plate, one end of which is disposed at a position that overlaps the point light source beyond the light incident end surface of the light guide plate.

  In this planar illumination device, by disposing a diffusion plate at a specific position, leakage light from the point light source is guided to the diffusion plate, and as a result, the luminance of the illumination device can be improved. Further, when a notch is formed at a specific position of the diffuser plate, it is possible to avoid the occurrence of a “hot spot” in which the luminance in front of the point light source is particularly noticeable on the light emitting surface of the lighting device. .

JP2008-171717 (Claims)

  However, the illumination device described in Patent Document 1 cannot avoid a hot spot generated on the light emitting surface near the point light source unless a notch is provided. Moreover, even if a notch is provided, it is not possible to suppress the bright lines generated when the image of the point light source is reflected on the light guide plate. Further, when such a notch is formed, it is difficult to adjust the position of the point light source and the notch, and the production cost increases.

Accordingly, an object of the present invention is to provide an illuminating device that can reduce a hot spot region generated in the front direction of the illuminating device with a simple configuration even when a point light source is used.
Another object of the present invention is to provide an illuminating device that can eliminate uneven brightness of the illuminating device even if the outer shape is reduced.
Still another object of the present invention is to provide an illuminating device that can suppress bright lines generated when an image of a point light source is reflected on a light guide plate.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have arranged the light incident surface of the light guide plate and the light incident surface relative to each other even in the conventionally used light guide plate. When a specific diffused light guide is inserted between the point light sources, the hot spot area can be reduced by suppressing uneven brightness between the point light sources, and the bright lines caused by the reflection of the point light sources can be reduced. The present invention has been completed.

That is, the present invention is an illuminating device including a plurality of point light sources, a diffusion light guide that makes light incident from these point light sources, and a light guide plate disposed adjacent to the diffusion light guide. There,
The diffusion light guide is made of a transparent resin containing scattering particles, makes light from the point light source incident from the front surface thereof, and emits light from the rear surface to one side surface of the light guide plate,
The said light guide plate is an illuminating device which makes the light from the said diffusion light guide inject from the said 1 side, and radiate | emits light from the front.

In the illumination device, the width (W _D ) of the diffused light guide and the distance (I) between the point light sources satisfy the relationship of (W _D ) / (I) = 1/5 to 5/1. may, also, the diffusion light guide member having a width _{(W D)} and the light guide plate width _{(W L),} and meet the relation _{(W D) / (W L} ) = 1 / 200~1 / 1 Also good.

  In addition, in such an illumination device, a plurality of parallel groove portions may be disposed on at least one of the front and rear surfaces of the diffusion light guide, and the cross-sectional shape of the groove portions may be an arc shape or a V shape. And at least one selected from the group consisting of trapezoids.

  In particular, it is preferable that the diffusion light guide has prism-shaped grooves on the front and rear surfaces.

  On the other hand, the light guide plate may be provided with a plurality of parallel groove portions on the side surface adjacent to the rear surface of the diffusion light guide, and the cross-sectional shape of the groove portions is an arc shape, a V shape, It may be at least one selected from the group consisting of trapezoids.

In the present invention, since a specific diffusing light guide is inserted between a point light source and a light guide plate to form an illumination device, even if a plurality of point light sources are used, the brightness of the light emitting surface generated between the point light sources Not only can unevenness be effectively suppressed, but also the generation of bright lines due to the reflection of a point light source can be prevented.
Moreover, when the width | variety of such a diffused light guide has a specific relationship, even if it makes an external shape small, the hot spot area | region which generate | occur | produces in the front direction of an illuminating device can be reduced.

It is a schematic plan view for demonstrating the illuminating device of the 1st Embodiment of this invention. It is a schematic exploded perspective view of the illuminating device of the 1st Embodiment of this invention. It is a schematic exploded perspective view of the illuminating device of the 2nd Embodiment of this invention. It is a schematic plan view for demonstrating the cross-sectional shape of the groove part of this invention. It is the schematic for demonstrating the investigation area | region for simulating the brightness | luminance of the illuminating device created in the Example.

  The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. The drawings are not necessarily drawn to scale, but are exaggerated in illustrating the principles of the invention. In the accompanying drawings, the same part number in the plurality of drawings indicates the same part.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show a first embodiment of a lighting device according to the present invention, FIG. 1 is a schematic plan view showing the configuration of the lighting device, and FIG. 2 is a schematic exploded perspective view of the lighting device. .

  In the first embodiment, as shown in FIGS. 1 and 2, the illuminating device 10 includes a plurality of point light sources 12 arranged in a line, and the arrangement direction of the point light sources 12 (Y direction in FIG. 1). The diffusion light guide 14 is arranged so that its longitudinal direction is parallel to the Y direction, and the light guide plate 18 having one side surface (or light incident surface) 18a adjacent to the diffusion light guide 14. And.

  The light emitted from the point light source 12 first enters the front surface (light incident surface) 14 a of the diffusion light guide 14, is diffused inside the diffusion light guide 14, and then the rear surface of the diffusion light guide 14. The light is incident on the light incident surface 18a of the light guide plate 18 from the (light emitting surface) 14b. At this time, the light emitted from the point light source 12 is incident on the front surface 14a of the diffusion light guide 14 with the nonuniformity of the luminance distribution between the point light sources 12, but the inside of the diffusion light guide 14 Since the light incident on the diffused light guide 14 is diffusely reflected inside the diffused light guide 14, the light emitted from the rear surface 14 b of the diffused light guide 14 is in a state in which the unevenness of the luminance distribution is eliminated. The light enters the side surface 18 (light incident surface) 18a.

  The light incident on the light guide plate 18 is directed from the front surface (or light exit surface) 18b of the light guide plate 18 to the normal direction to the light guide plate (Z direction in FIG. 2) by an optical pattern or the like provided on the bottom surface 19 of the light guide plate. Exit. In this way, on the light emitting surface emitted from the light guide plate 18, the uneven brightness due to the point light source 12 is eliminated, and the luminance of the light emitting surface of the illumination device 10 can be made uniform. Furthermore, since the diffusion light guide 14 is inserted between the light guide plate 18 and the point light source 14, the image of the point light source 12 can be prevented from being reflected directly on the light guide plate 18, and as a result, the light guide plate The generation of bright lines at 18 can be effectively suppressed.

  In addition, although not shown in figure in the illuminating device 10, you may arrange | position a reflective material suitably from a viewpoint of improving the emission efficiency of light as needed. Such a reflective material is disposed, for example, on a portion of the light guide plate 18 excluding the light exit surface 18b and the light incident surface 18a, or on a portion of the diffusion light guide 14 excluding the light entrance surface 14a and the light exit surface 14b. Alternatively, the point light source 12 may be disposed around the point light source 12. The reflective material may be a reflective material having direct reflectivity (for example, a metallic color reflective material), a reflective material having scattering reflectivity (for example, a white reflective material), or the like.

  FIG. 3 is a schematic exploded perspective view for explaining a second embodiment of the liquid crystal display device of the present invention. In the second embodiment, the same reference numerals are given to the same structures as those in the first embodiment. Also in this embodiment, a reflective material may be provided as necessary as described above.

  In the second embodiment, the illuminating device 20 includes a plurality of point light sources 12 arranged in a line, the arrangement direction of the point light sources 12 (Y direction in FIG. 3), and the longitudinal direction thereof parallel to the Y direction. And a light guide plate 28 having one side surface (or light incident surface) 27 adjacent to the diffusion light guide 24.

  As shown in FIG. 3, the front surface (light incident surface) 24 a and the rear surface (light emitting surface) 24 b of the diffusion light guide 24 are V-shaped in a cross section parallel to the surface of the light guide plate (that is, an XY cross section). A plurality of groove portions 25 and 26 may be provided. Such groove portions 25 and 26 can be arbitrarily provided, and not only can the groove portions increase the diffusibility of light from the point light source, but also the groove portions 25 and 26 allow the image of the point light source 12 to be formed. Can be prevented from being directly reflected on the light guide plate 28, and as a result, generation of bright lines on the light guide plate 28 can be effectively suppressed.

  In addition, a plurality of groove portions 27 having a V shape in the XY cross section may be optionally provided on the light incident surface 28a of the light guide plate 28. In such a groove, the light diffused from the diffusion light guide is in a state of being further diffused on the light incident surface 28a of the light guide plate, so that it is only possible to further improve the uniformity of luminance in the light guide plate 28. In addition, such a groove portion 27 can prevent the image of the point light source 12 from being directly reflected on the light guide plate 28, and as a result, the generation of bright lines on the light guide plate 28 can be effectively suppressed.

Hereinafter, details of each component will be described in detail.
(Point light source)
Examples of the plurality of point light sources arranged in the illumination device include white LEDs. The distance between the point light sources can be appropriately set according to the size of the illumination device and the required luminance. For example, the distance between the point light sources (I shown in FIG. 1) and the diffusion light guide The width (W _D shown in FIG. 1) is, for example, (W _D ) / (I) = 1/5 to 5/1, preferably 1/4 to 4/1. In particular, it is possible to improve luminance and eliminate light and dark unevenness.
Here, the distance between the point light sources indicates the distance between the central portions of the point light sources, and the width of the diffusion light guide is the X direction in FIG. 1 (or the arrangement direction of the point light sources). (Longitudinal direction) indicates the longest value.

(Diffusion light guide)
A diffused light guide mixes scattering particles (for example, transparent fine particles such as silicone and glass) having a refractive index different from that of a transparent matrix material (for example, polymethylmethacrylate), and uniformly distributes the particles. It is made of a light scattering material dispersed in. The average diameter of the scattering particles may be selected from a wide range of about 1 μm to 100 μm, for example, but is preferably about 1.5 to 50 μm, more preferably about 2 to 20 μm. The concentration of the scattering particles in the matrix material may be, for example, about 0.01 to 1.0 wt%, preferably about 0.1 to 0.5 wt%.

In the present invention, by providing the diffusing light guide, even if the outer shape of the lighting device is reduced, the region where the hot spot is generated can be narrowed and the so-called run-up distance can be shortened. For example, the width of the diffusion light guide (W _D shown in FIG. 1) and the width of the light guide plate (W _L shown in FIG. 1) are about (W _D ) / (W _L ) = 1/200 to 1/1. , Preferably about 1/150 to 1/5, more preferably about 1/100 to 1/8.
Here, the width of the light guide plate is the longest value in the X direction in FIG. 1 (or the direction orthogonal to the arrangement direction of the point light sources).

A plurality of grooves that are parallel to each other may be provided on the light incident surface and / or the light exit surface of the diffusion light guide in order to increase the light diffusion efficiency. Examples of the cross-sectional shape of the groove portion in the XY plane include an arc shape, a V shape, and a trapezoidal shape. These groove portions are not necessarily in contact with each other, but are preferably provided in contact with each other.
Further, the shape of the groove portion is not necessarily uniform on the surface to be formed, but it is preferable that the uniform groove portion is continuously formed.

  As shown in FIG. 4, the width (or pitch: P) of the groove is not particularly limited as long as the diffusion efficiency can be improved. For example, it is about 0.1 to 1 mm, preferably about 0.2 to 0.8 mm. The depth (D) of the groove may be, for example, about 0.05 to 0.5 mm, preferably about 0.08 to 0.4 mm.

  Moreover, when a groove part is circular arc shape, the radius may be about 0.05-0.5 mm, for example, Preferably it may be about 0.08-0.4 mm. Moreover, when a groove part is V-shaped, the V-shaped angle ((theta)) may be about 30-150 degrees, for example, Preferably it may be about 40-140 degrees.

(Light guide plate)
The light guide plate is made of a transparent material (for example, polymethyl methacrylate), and has a flatness (aspect ratio defined by thickness / length) of 10 or more (for example, about 10 to 50, preferably about 15 to 40). ).

  In addition, a plurality of grooves parallel to each other may be disposed on the light incident surface of the light guide plate in order to increase the light diffusion efficiency. Examples of the cross-sectional shape of the groove portion in the XY plane include an arc shape, a V shape, and a trapezoidal shape. These groove portions are not necessarily in contact with each other, but are preferably provided in contact with each other.

  The width (or pitch: P) of the groove is not particularly limited as long as the diffusion efficiency can be improved. For example, it may be about 0.1 to 1 mm, preferably about 0.2 to 0.8 mm. The thickness (D) may be, for example, about 0.05 to 0.5 mm, preferably about 0.08 to 0.4 mm.

  Moreover, when a groove part is circular arc shape, the radius (r) may be about 0.05-0.5 mm, for example, Preferably it may be about 0.08-0.4 mm. Moreover, when a groove part is V-shaped, the V-shaped angle ((theta)) may be about 30-150 degrees, for example, Preferably it may be about 40-140 degrees.

  The light guide plate guides light incident from the light incident surface (that is, the side surface direction of the light guide plate) and emits light from the light output surface (that is, the front direction of the light guide plate). Therefore, the shape of the light guide plate is not particularly limited as long as light can be emitted in the front direction, and may be a rectangular parallelepiped shape having a constant thickness or a wedge shape. An optical pattern such as a dot shape or a cone shape may be provided in order to emit incident light incident from the front side in the front direction. For example, when the light guide plate has a wedge shape, the bottom surface of the light guide plate may be an inclined surface whose thickness gradually decreases from the light incident surface toward the front.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
As the point light source, 10 lamps were used with an LED light source (manufactured by Nichia Corporation, “NSSW0064”) having a distance (I) between adjacent light sources of 15 mm.

  The diffusion light guide was formed into a size of 5 mm in width, 150 mm in depth, and 3.5 mm in height using a transparent acrylic material (manufactured by Hayashi Telemp Co., Ltd., “scatterer resin Harrier α”). Note that triangular prisms (pitch 0.5 mm, depth 0.25 mm, V-shaped angle 90 °) are processed on both the light incident surface and the light exit surface of the diffusion light guide.

  Moreover, as the light guide plate, a transparent acrylic material was used and formed into a rectangular parallelepiped having a width of 60 mm, a depth of 150 mm, and a height of 5 mm. Arc-shaped grooves (pitch 0.6 mm, depth 0.25 mm, circle radius 0.25 mm) are formed on the light incident surface of the light guide plate.

  A plurality of conical depressions were formed as optical patterns on the bottom surface of the light guide plate (that is, the surface facing the light exit surface). These conical depressions are adjusted so that the illumination device has an arbitrary light emission distribution by appropriately changing the depth at the location of the light guide plate to change the surface density.

  These point light sources, the diffusion light guide, and the light guide plate were arranged in the arrangement as shown in FIG. 1 to produce the illumination device of Example 1.

  When the LED was turned on and the luminance distribution of the lighting device and the presence or absence of bright lines were confirmed by visual observation, the lighting device was able not only to eliminate unevenness in brightness and darkness derived from a point light source, but also to generate no bright lines. It was.

(Comparative Example 1)
Without providing the diffusion light guide, the point light source and the light guide plate were adjacent to each other to create an illumination device. A lighting device was produced in the same manner as in Example 1 except that a light absorption layer composed of a quarter-wave plate and a colored film was not provided.
When the LED was turned on and the luminance distribution of the illuminating device and the presence or absence of bright lines were confirmed by visual observation, not only light and dark unevenness originating from the point light source occurred on the light emitting surface of the illuminating device, but also the bright line due to the point light source Occurred.

(Example 2)
A lighting device was manufactured in the same manner as in Example 1 except that the groove portion was not provided on both the light guide plate and the diffusion light guide.

(Example 3)
Groove portions are not formed in the light guide plate, but arc-shaped groove portions (pitch 0.6 mm, depth 0.25 mm, circular radius 0.25 mm) are formed on both the light incident surface and the light exit surface of the diffusion light guide. Except for the above, a lighting device was produced in the same manner as in Example 1.

Example 4
No groove is formed on the light guide plate, and V-shaped grooves (pitch 0.6 mm, depth 0.25 mm, V-shaped angle 90 °) are formed on both the light incident surface and light output surface of the diffusion light guide. A lighting device was manufactured in the same manner as in Example 1 except that.

(Example 5)
Except that arc-shaped grooves (pitch 0.6 mm, depth 0.25 mm, circular radius 0.25 mm) are formed on both the light incident surface and the light exit surface of the diffusion light guide, the same manner as in Example 1 was performed. A lighting device was produced.

(Example 6)
Except that arc-shaped grooves (pitch: 0.9 mm, depth: 0.4 mm, circular radius: 0.4 mm) are formed on both the light incident surface and the light emitting surface of the diffusion light guide, the same as in Example 1. A lighting device was produced.

(Example 7)
Except that arc-shaped grooves (pitch: 0.22 mm, depth: 0.1 mm, circular radius: 0.1 mm) are formed on both the light incident surface and the light emitting surface of the diffusion light guide, the same as in Example 1. A lighting device was produced.

(Example 8)
Except for forming V-shaped grooves (pitch 0.6 mm, depth 0.25 mm, V-shaped angle 60 °) on both the light incident surface and the light exit surface of the diffusion light guide, the same as in Example 1. The lighting device was manufactured.

Example 9
Except for forming V-shaped grooves (pitch 0.6 mm, depth 0.25 mm, V-shaped angle 120 °) on both the light incident surface and the light exit surface of the diffusion light guide, the same as in Example 1. The lighting device was manufactured.

(Example 10)
A lighting device is produced in the same manner as in Example 1 except that a V-shaped groove (pitch 0.6 mm, depth 0.25 mm, V-shaped angle 90 °) is formed only on the light incident surface of the diffusion light guide. did.

(Example 11)
A lighting device is manufactured in the same manner as in Example 1 except that a V-shaped groove (pitch 0.6 mm, depth 0.25 mm, V-shaped angle 90 °) is formed only on the light exit surface of the diffusion light guide. did.

(Example 12)
A V-shaped groove (pitch 0.6 mm, depth 0.25 mm, V-shaped angle 90 °) is formed on the light incident surface of the diffusion light guide, and an arc-shaped groove (pitch 0.6 mm) is formed on the light output surface. The illumination device was manufactured in the same manner as in Example 1 except that the depth was 0.25 mm and the circular radius was 0.25 mm.

(Brightness evaluation method)
In order to clarify the extent of the occurrence of hot spots by a point light source, it was examined by a brightness simulation experiment using the lighting devices produced in the examples and comparative examples. As shown in FIG. 5, a survey area 50 having a length of 6 mm is set between 4 and 10 mm along the X direction from the light incident end face 18 a of the light guide plate, and further, this survey area 50 is 2 mm wide along the Y direction. Are divided into luminance measurement regions 501 having a ratio of the minimum luminance (L _min ) to the maximum luminance (L _max ) from the luminance in each luminance measurement region 501, that is, the ratio of the dark part to the bright part (L _min / L _max ). Was calculated. The results are shown in Table 1.

As shown in Table 1, in each of Examples 1 to 12, the light / dark ratio (L _min / L _max ) is 0.4 or more in any of the examples, and the generation of bright / dark unevenness and bright lines in the lighting device is suppressed. You can evaluate that you can.

On the other hand, when Comparative Example 1 was evaluated in the same manner, the light / dark ratio (L _min / L _max ) was 0.2, and the difference between the bright part and the dark part was very high. It can be evaluated that the occurrence cannot be suppressed.

  In addition, regarding Example 1 and Comparative Example 1, the visual evaluation and these data results coincided.

  The illuminating device of the present invention can suppress the generation of bright and dark unevenness generated between point light sources and bright lines generated by reflection of the point light source even when a plurality of point light sources are used. It is useful as a backlight for the device.

  As described above, the preferred embodiments of the present invention have been described with reference to the drawings. However, various additions, modifications, or deletions can be made without departing from the spirit of the present invention, and these are also included in the present invention. Is included in the range.

DESCRIPTION OF SYMBOLS 10, 20 ... Illuminating device 12 ... Point light source 14, 24 ... Diffuse light guide 18, 28 ... Light guide plate

Claims (8)

A lighting device comprising a plurality of point light sources, a diffusion light guide that makes light incident from these point light sources, and a light guide plate disposed adjacent to the diffusion light guide,
The diffusion light guide is made of a transparent resin containing scattering particles, makes light from the point light source incident from the front surface thereof, and emits light from the rear surface to one side surface of the light guide plate,
The said light-guide plate is an illuminating device which makes the light from the said diffusion light guide inject from the said 1 side, and radiate | emits light from the front. In claim 1, the diffusion light guide member having a width and _{(W D)} and the distance between the point light source (I) _{but, (W D) / (I} ) = 1 / 5~5 / 1 of satisfying the relationship illumination device . According to claim 1 or 2, and the diffusion light guide member having a width _{(W D)} and the light guide plate width _{(W L),} but satisfy the relation _{(W D) / (W L} ) = 1 / 200~1 / 1 Lighting device.   4. The lighting device according to claim 1, wherein the diffusing light guide has a plurality of parallel grooves disposed on at least one of the front surface and the rear surface. 5.   The lighting device according to claim 4, wherein a cross-sectional shape of the groove formed in the diffusion light guide is at least one selected from the group consisting of an arc shape, a V shape, and a trapezoidal shape.   6. The illuminating device according to claim 5, wherein the diffusion light guide has prism-shaped grooves on the front surface and the rear surface.   The lighting device according to claim 1, wherein the light guide plate has a plurality of grooves parallel to each other on a side surface adjacent to the rear surface of the diffusion light guide.   The lighting device according to claim 7, wherein a cross-sectional shape of the groove formed in the light guide plate is at least one selected from the group consisting of an arc shape, a V shape, and a trapezoidal shape.

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