JP3160594B2 - Light guide plate and flat lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate and a flat illumination device used for a liquid crystal display device, and more particularly to a light guide plate provided with a fine convex portion or concave portion at about half of the surface of an incident end face of the light guide plate. Or, a fine convex or concave portion is provided in the width of 1.2 to 0.2 times the width of the incident end face on the incident end face side of the back face to prevent emission of bright lines, and uniform and bright emitted light is provided. The present invention relates to a light guide plate and a planar lighting device obtained.

[0002]

2. Description of the Related Art A conventional light guide plate is disclosed in Japanese Patent Application Laid-Open No. 8-240.
No. 720 is known. This light guide plate has a colored dot printed portion for absorbing light at the upper end of the reflection sheet provided below the back surface of the light guide plate, and the colored dot printed portion is closer to the fluorescent tube. The area is gradually reduced toward the far side from the object, and the colored dots are made of gray, dark brown, purple, green, or the like. Further, the colored dots are arranged in a plurality of straight lines substantially parallel to the long axis direction of the fluorescent tube, and each center point of the plurality of dots arranged in an arbitrary straight line is a plurality of dots arranged in an arbitrary straight line. The dots are arranged at substantially the midpoint between the center points of the plurality of dots in the row adjacent to the row of dots.

A conventional light guide plate is disclosed in Japanese Unexamined Patent Publication No.
The one shown in Japanese Patent No. 27828 is also known. This light guide plate is provided with a light shielding wall extending along a plane on which the light incident surface rides. Then, a portion where the incident end surface of the light guide plate is connected to the front surface and the back surface is covered with a shielding material.

[0004]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. 8-24072
The conventional light guide plate disclosed in Japanese Patent Application Publication No. 0-115,115, has a colored dot printing portion for absorbing light at an upper surface end of a reflection sheet provided below the back surface of the light guide plate, and the colored dot The printing area should gradually decrease in size from near to far from the fluorescent tube, and colored dots should be gray, dark brown, purple, green, etc. Are arranged in a plurality of straight lines substantially parallel to each other, and each center point of a plurality of dots arranged in an arbitrary straight line is located in a row adjacent to a row of a plurality of dots arranged in an arbitrary straight line. The reflective sheet, which is arranged almost at the center of each center point of the dots and has colored dots for absorbing light printed on the upper end, is provided at the lower portion of the back surface of the light guide plate, so that it is located at the emission position of a sharp bright line. Print colored dots according to the light guide plate Or different position of the light beam emitted to the back surface by the thickness, there is a further problem that the reflecting sheet must be made as no deviation light guide plate and the colored dots printed on the upper surface end portion.

The conventional light guide plate disclosed in Japanese Patent Application Laid-Open No. 8-327828 is provided with a light shielding wall extending along a plane on which a light incident surface is mounted, so that an incident end face portion and a surface of the light guide plate are provided. The part that connects to the rear and rear parts is covered with a shielding material, which blocks light directly, reducing the amount of light incident on the light guide plate, increasing the number of parts of the shielding material and increasing the number of parts of the shielding material, as well as energy loss from the light source And other issues such as productivity.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to make a bright line appearing in the vicinity of the incident end face or the like less than half of the incident end face of the light guide plate and / or the rear face or the like. A fine convex portion and / or concave portion having a width of 1.2 to 0.2 times the width of the incident end face portion is provided to scatter and prevent the appearance of bright lines, and uniform and bright emitted light can be obtained. An object of the present invention is to provide a light guide plate and a planar lighting device.

[0007]

According to a first aspect of the present invention, there is provided a light guide plate provided with a light control portion which is less than or equal to a half of an incident end face in a direction opposite to a side on which a light control portion is provided. 1.2 of the width of the incident end face from the incident end face side of the surface
It is characterized in that a fine convex or concave portion is provided in a width of about 0.2 times.

The light guide plate according to the first aspect of the present invention is arranged such that the light guide plate has a half or less half of the incident end face in the opposite direction where the light control section is provided and / or from the incident end face side of the face where the light control section is provided. Since a fine convex or concave part is provided in a width of 1.2 to 0.2 times the width, it diffuses light rays to the mirror surface that performs total reflection, breaks the critical angle and moves to the position where taper leak occurs Can change the course of the light beam.

In the light guide plate according to the present invention, the width of the incident end face portion from the upper half of the incident end face portion in the direction of the front surface portion or less and / or from the incident end face portion side of the back surface portion may be 1.2. It is characterized in that a fine convex or concave portion is provided in a width of about 0.2 times.

According to a second aspect of the present invention, the width of the incident end face portion from the upper half or less of the incident end face portion toward the front surface side or / and from the incident end face side of the rear face portion is 1.2 to 0.2 times the width of the incident end face portion. Since a fine convex portion or concave portion is provided in the width of the light guide plate, it is possible to prevent the generation of a bright line due to a taper leak that breaks the critical angle even near the incident end face of the wedge-shaped light guide plate having a tapered back surface.

Further, the flat lighting device according to claim 3 is
A width of 1.2 to 0.2 times the width of the incident end face from the incident end face side of the incident end face that is equal to or less than a half in the opposite direction where the light control section is provided. Characterized in that a fine convex portion or a concave portion is provided on the substrate.

According to a third aspect of the present invention, in the flat lighting device, the incident end face portion is not more than a half part in a direction opposite to the side where the light control section is provided and / or from the incident end face side of the face section where the light control section is provided. Since a fine convex or concave portion is provided in a width of 1.2 to 0.2 times the width of the above, the generation of a bright line can be prevented without using extra parts.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

According to the present invention, fine projections or depressions are provided on the light guide plate at a half or less of the incident end face or on the back face of the light guide plate at a width of 1.2 to 0.2 times the width of the incident end face. Accordingly, it is an object of the present invention to provide a light guide plate and a flat illumination device capable of preventing a bright line from appearing in the vicinity of an incident end face portion by changing a traveling direction of light rays by scattering or the like and obtaining uniform and bright emitted light.

FIG. 1 is a perspective view showing the configuration of a light guide plate and a flat illumination device according to the present invention. FIGS. 2A and 2B are schematic ray trajectory diagrams of the light guide plate according to the present invention.

The flat lighting device 1 shown in FIG. 1 includes a light guide plate 2, a light source 8, a reflector 9, and a reflector 10.

The light guide plate 2 is made of a transparent acrylic resin (PMMA) or polycarbonate (PC) having a refractive index of about 1.4 to 1.7, etc., and has an incident end face portion 3 for guiding light from a light source 8; A reflecting end face 4 located on the opposite side to the incident end face 3; side faces 7 and 7 'connected to the incident end face 3 and the reflecting end face 4; a light emitting surface 5; And a back surface portion 6 located on the opposite side.

The light guide plate 2 has a convex or concave light control portion 62 formed on the back surface 6 or the like, and furthermore, a half portion in the opposite direction where the light control portion 62 is provided on the incident end face portion 3. A convex portion or a concave portion 31 that is minute enough is provided. As shown in FIG. 3, the light incident on the light guide plate 2 has a refraction angle γ.
The light travels into the light guide plate 2 within a range satisfying the expression 0 ≦ | γ | ≦ sin ⁻¹ (1 / n). For example, the refractive index of an acrylic resin which is a resin material used for a general light guide plate 2 is n = 1.49.
Therefore, at the incident end face 3 closest to the light source 8,
At an incident angle of 0 °, the light beam proceeds without being refracted in the direction of the reflecting end surface 4 (the energy value of this light beam is the highest). The incident angle at a place close to the front surface 5 or the back surface 6 is also 0 °. Incident at a close angle.

Further, the maximum incident angle is such that the light reflected and scattered by the reflector 9 and the like is incident on the incident end face 3 from the surface 5 to the back 6 and from the back 6 to the surface 5 in an incident angle 90. And the refraction angle γ refracted at the incident end face 3 is in the range of about γ = ± 42 °.

However, in the vicinity of the front surface 5, only γ = −42 ° in the direction of the back surface 6 only, and in the vicinity of the back surface 6, only γ = + 42 ° in the direction of the front surface 5 only.

The light incident on the light guide plate 2 within the range of the refraction angle γ = ± 42 ° is transmitted to the light guide plate 2 and the air layer (refractive index n =
At the interface with 1), the critical angle can be expressed by the equation sin α = (1 / n). For example, since the refractive index of an acrylic resin which is a resin material used for a general light guide plate 2 is about n = 1.49, the critical angle α is α = 42.
°, and if there are no grooves, protrusions, or depressions that disturb the light rays on the front surface portion 5 or the rear surface portion 6 of the light guide plate 2, the light in the light guide plate 2 is totally reflected by the front surface portion 5 or the rear surface portion 6. It proceeds in the direction of the reflection end face 4.

As described above, a light ray having a refraction angle γ = ± 42 ° exists at any position on the incident end face 3, and particularly, in the direction of the front face 5 and the rear face 6 near the incident end face 3. The light beam heading in the direction or the like is a light beam having a refraction angle near γ = 42 °. For example, a light ray having a refraction angle γ = 42 ° that is close to the incident end face 3 and has a high energy value is located near the front face 5 side and near the rear face 6 side of the incident end face 3, as shown in FIG. As shown in the figure, the light beam L1 incident from a position near the front surface portion 5 of the incident end face portion 3 is totally reflected by the front surface portion 5 and travels as a light beam L2 to the back surface portion 6. Then, the light L3 is reflected or refracted by the light control unit 62 provided on the back surface portion 6 and emitted to the outside of the light guide plate 2, reflected by the reflector 10, and has an emission angle smaller than the incident angle. Then, it breaks the critical angle and emits. In the case of the wedge-shaped light guide plate 2, the back surface 6
However, even with a mirror surface, the light beam has an emission angle smaller than the incident angle, becomes a light beam L3 on the surface portion 5, and breaks the critical angle to be emitted.

On the other hand, in the present embodiment, the light from the light source 8 is scattered by the fine convex or concave portion 31 provided on the incident end face 3 toward the surface 5 where bright lines are generated. The generation of bright lines is prevented.

In the wedge-shaped light guide plate 2 having different thicknesses of the incident end face portion 3 and the reflective end face portion 4 in FIG. 1, the place where the fine convex portion or concave portion 31 is provided on the incident end face portion 3 is as follows. A similar effect can be obtained by applying the method to a portion of about half or less in the direction of the surface portion 5 side.

By the way, one of the light rays from the light source 8 which is incident from a place near the rear face 6 of the incident end face 3 is a light ray whose refraction angle in the direction of the front face 5 is γ = + 42 °. The light is totally reflected by the portion 5 and travels again in the direction of the back surface portion 6, travels a long distance, loses energy, and travels to a position away from the incident end surface portion 3, and is not recognized as a bright line. In contrast, FIG.
As shown in (b), the angle of refraction in the direction of the back surface 6 is γ = −.
The light L2b of 42 ° is transmitted to the light control unit 62 provided on the back surface unit 6.
The light beam L3b reflected or refracted by the light source and emitted out of the light guide plate 2 and reflected by the reflector 10 has an emission angle smaller than the incident angle, travels to the surface portion 5, breaks the critical angle, and is emitted. In the case of the wedge-shaped light guide plate 2, the back surface 6
However, even at the mirror surface, the light beam has an emission angle smaller than the incident angle, becomes a light ray L3b on the surface portion 5, and breaks the critical angle to be emitted.

Therefore, the light guide plate 2 according to the present embodiment has a fine surface on which the light control unit 62 is provided, having a width of 1.2 to 0.2 times the width of the incident end face 3 from the incident end face 3 side. A convex portion or a concave portion 61 is provided. The fine convex portions and concave portions 61 diffuse light rays that generate bright lines, thereby preventing the generation of bright lines.

A light ray L2b having a refraction angle γ = −42 ° from the incident end face 3 toward the back face 6 is represented by cotγ * L =
It proceeds to a position x away from the incident end face portion 3 obtained by the expression of x.

Here, the distance x from the incident end face 3, the distance L from the front surface 5 and the back surface 6 of the maximum refraction angle γ at which the bright line appears, and the refraction angle are γ.

For example, when the refraction angle is γ = 42 ° and the thickness of the incident end face 3 of the light guide plate 2 is 2 mm (here, the maximum distance L from the back face 6), the position of the bright line L2b is cot.
(42 °) * 2 = 2.22125, and the incident end face 3
Appearing at a position of about 2.22 mm from the light source, but by providing a fine convex or concave portion 61 in a width of 1.2 to 0.2 times the width of the incident end face portion 3, the bright line is generated. Is diffused to prevent the generation of bright lines.

Here, X = 2.22125 is about 1.111 times the thickness of the incident end face 3 of 2 mm.

In the wedge-shaped light guide plate 2 having different thicknesses of the incident end face 3 and the reflective end face 4 in FIG. A similar effect can be obtained by applying a width of 1.2 to 0.2 times the width of the incident end face 3 from the end face 3 side.

The light source 8 has a linear shape such as a CFL (cold shadow tube), and direct light enters the light guide plate 2 from the incident end face 3 of the light guide plate 2 while other light is reflected by the reflector 9. Light source 8
The light enters the light guide plate 2 through the space between the light guide plate 2 and the reflector 9.

The reflector 9 is made of a sheet or metal on which a white insulating material or a metal such as aluminum is deposited, surrounds the light source 8, reflects the light from the light source 8, and transmits the reflected light to the light guide plate. The light is again incident on the incident end face portion 2 of the light emitting device.

The reflector 10 may be a sheet in which a white material such as titanium oxide is mixed in a thermoplastic resin, or a sheet of a thermoplastic resin, which is formed by depositing a metal such as aluminum, or a sheet in which a metal foil is laminated or a sheet metal. The light from the light source 8 reflects or diffusely reflects light other than the light emitted from the light source 8 to the surface 5 by the light guide plate 2 and is incident on the light guide plate 2 again. All the light from 8 is emitted from the surface portion 5.

As described above, the light guide plate and the flat illumination device according to the present invention have the fine convex portions and concave portions 31 provided on the incident end surface portion 3 and the fine convex portions provided near the incident end surface portion of the back surface portion 6. The portions and the concave portions 61 prevent the appearance of bright lines appearing near the incident end face and the like, and can obtain uniform and bright emitted light.

[0036]

As described above, in the light guide plate according to the first aspect, the incident end face portion is not more than a half of the opposite side where the light control portion is provided and / or the incident end face portion of the face portion where the light control portion is provided. Since a fine convex portion and / or concave portion is provided at a width of 1.2 to 0.2 times the width of the incident end face portion from the side, the light beam can be diffused to the mirror surface that performs total reflection or the critical angle can be obtained. And the path of the light beam to the position where the taper leak is generated can be changed, and the generation of the bright line can be prevented to obtain a uniform and easy-to-view light guide plate.

Further, the light guide plate according to the second aspect of the present invention is arranged such that the width of the incident end face is 1.2 to 0. 2
The provision of a fine convex portion and / or concave portion at twice the width prevents generation of an emission line due to a taper leak that breaks the critical angle even in the vicinity of the incident end surface of a wedge-shaped light guide plate having a tapered back surface, and is uniform. It is possible to obtain a lightweight light guide plate that is easy to see.

Further, the flat lighting device according to claim 3 is
A width of 1.2 to 0.2 times the width of the incident end face from the incident end face side of the incident end face that is equal to or less than a half in the opposite direction where the light control section is provided. Since a fine convex portion and / or a concave portion are provided in the surface illumination device, it is possible to obtain a flat illuminating device that is uniform and easy to see without luminance unevenness and that can prevent the generation of a bright line without using extra parts.

[Brief description of the drawings]

FIG. 1 is a perspective configuration diagram of a light guide plate and a flat lighting device according to the present invention.

2A and 2B are schematic views of a light guide plate according to the present invention.

FIG. 3 is a schematic view of light rays in a light guide plate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Planar illumination device, 2 ... Light guide plate, 3 ... Incident end face part, 4 ...
Reflecting end face portion, 5 front surface portion, 6 back surface portion, 7, 7 'side surface portion, 8 light source, 9 reflector, 10 reflector, 31,
61: fine convex and concave shapes, 62: convex and concave shapes of reflection and refraction actions, γ: refraction angle, n: refraction index, α: critical angle, L: distance of the incident end face from the front surface and the rear surface , X: distance from the incident end face.

Continuation of front page (56) References JP-A-9-244022 (JP, A) JP-A-7-294745 (JP, A) JP-A-10-172318 (JP, A) JP-A-11-7014 (JP, A) JP-A-11-102609 (JP, A) JP-A-8-136733 (JP, A) JP-A-8-152625 (JP, A) JP-A-10-340611 (JP, A) JP-A-9-113907 (JP, A) JP-A-9-105817 (JP, A) JP-A-9-160035 (JP, A) JP-A-11-64642 (JP, A) A) Patent 2737931 (JP, B2) Utility model registration 2540755 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/00 331 F21V 8/00 601 G02F 1/13357

Claims (3)

(57) [Claims] An incident end face for guiding light from a light source, a reflective end face located on the opposite side of the incident end face, a side face connected to the incident end face and the reflective end face, A surface portion that emits light guided from the incident end surface portion, and a back surface portion opposite to the front surface portion, and a convex or concave shape that refracts or reflects on the surface of the front surface portion or the back surface portion. And the like, and a reflector is provided in the vicinity of the back surface portion.
A light guide plate for preventing the generation of a bright line due to a light ray that breaks the field angle , wherein a half or less of the incident end face in a direction opposite to the side on which the light control unit is provided and / or the light control unit is provided. 1.2 to 0.2 of the width of the incident end face from the incident end face side of the provided face part
A light guide plate characterized in that a fine convex portion or concave portion is provided at twice the width. 2. An incident end face for guiding light from a light source, a reflective end face located on the opposite side thinner than the thickness of the incident end face, and a side face connected to the incident end face and the reflective end face. Portion, a surface portion for emitting light guided from the incident end surface portion, and a back surface portion provided on the surface opposite to the surface portion and provided with a convex or concave shape on the surface, the incident end surface portion and the The thickness differs from that of the reflective end face, and the
A wedge-shaped light guide plate for preventing the generation of bright lines , wherein the width of the incident end face portion from the upper half or less of the incident end face portion in the direction of the front surface portion or / and the width of the incident end face portion from the incident end face side of the back surface portion A light guide plate provided with fine convex portions or concave portions having a width of 0.2 times. 3. A light source, an incident end face for guiding light from the light source, a reflective end face located on the opposite side to the incident end face, and a side face connected to the incident end face and the reflective end face A light guide plate having a portion, a surface portion for emitting light guided from the incident end surface portion, and a back surface portion located on the opposite side to the front surface portion; and on the surface of the front surface portion or the back surface portion of the light guide plate. A convex or concave light control unit provided to perform refraction or reflection, and a reflector for reflecting the light of the light source and causing the light to enter the incident end face again , breaking the critical angle. Emit
In a flat illumination device for preventing generation of a bright line by a light beam, a half or less of an incident end face portion in a direction opposite to a side where the light control portion is provided and / or from the incident end face side of a face portion where the light control portion is provided. 1.2 to 0.2 of the width of the incident end face
A flat lighting device characterized in that a fine convex portion or concave portion is provided in a double width.