JPH09292531A - Light transmission plate, optical deflecting plate and surface illuminator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce loss caused by diffusion and reflection and to emit light having high luminance in uniform distribution by forming plural projecting parts for totally reflecting light made incident from an incident end face part to a surface part side on a rear surface part. SOLUTION: This light transmission plate 12 is provided with the surface part 15 from which the light is emitted, the rear surface part 21 positioned on an opposite side to the part 15, and the incident end face part 13 which is positioned on one end side of the parts 15 and 21 and connected to the parts 15 and 21, and also to which the light from a light source lamp 14 is introduced. In the plate 12, the light made incident from the part 13 is emitted from the part 15. A recessed surface and a projecting surface deflecting the light emitted from the part 15 in a specified direction are wavily formed on the part 15, and plural projecting parts 23 respectively having an inclined surface for totally reflecting the light made incident from the part 13 toward the part 15 side are formed on the part 21.

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 for radiating light introduced from a side end face from a surface, a light deflector plate superposed on the light guide plate and for controlling the direction of light emitted from the surface of the light guide plate, and these. The present invention relates to a flat lighting device using a light guide plate and a light deflection plate, and is particularly suitable for use in illuminating a liquid crystal display surface.

[0002]

2. Description of the Related Art A flat illuminating device used as a so-called backlight light source of a liquid crystal display is a device which guides light from a light source lamp into a transparent light guide plate from a side end face of the light guide plate and reflects the light in the light guide plate. This light is uniformly emitted from the entire surface of the light guide plate.
In consideration of the characteristics of the liquid crystal display in which the flat illuminator is used, the functions required of the flat illuminator include that the flat illuminator has a thin plate shape as a whole and that the power consumption of the light source lamp is minimized. In addition, it is particularly important to emit uniform light throughout.

For such a purpose, the conventional flat lighting device is provided with a light reflecting sheet on the back surface side of the light guide plate and a prism sheet in which prism surfaces of isosceles triangular prisms are arranged in parallel on the front surface side of the light guide plate. A structure in which two prisms are superposed on each other is adopted so that the longitudinal directions of the prism surfaces are orthogonal to each other. That is, the light emitted from the back side of the light guide plate is made to enter the light guide plate again by the light reflection sheet, and the light emitted from the surface of the light guide plate is converged by the pair of prism sheets, so that high-luminance illumination light can be obtained. We are careful about.

There is also known a number of dots of hundreds of μm in size printed with white ink or the like on the back surface of the light guide plate for the purpose of uniformly dispersing the light incident on the light guide plate. In this case, a light diffusing sheet is interposed between the light guide plate and the prism sheet so that the dots do not obstruct the eyes, and the light emitted from the surface of the light guide plate is dispersed by the light diffusing sheet.

[0005]

The light emitted from the surface of the light guide plate has a directivity which is usually uncontrollable and depends on the structure of the light guide plate. In most cases, the viewing direction does not match. For this reason, if the prism sheet is simply superimposed on the surface of the light guide plate, light from the light guide plate is emitted only from one slope side of the prism surface, and a uniform distribution of light intensity cannot be obtained.

Therefore, in the case where dots of white ink are printed on the back surface of the light guide plate to diffuse the light propagating in the light guide plate, there is a drawback that light absorption loss occurs. Moreover, to make these dots inconspicuous,
Since it is necessary to use a light diffusion sheet together, most of the light that passes through this light diffusion sheet becomes diffused light,
As a result of the significant reduction in brightness, a bright light source with a large amount of light must be used. In addition, it is impossible to control the traveling direction of light at all.

Although the conventional prism sheet can converge the diffused light from the light guide plate, the light emitted from the light guide plate is not perpendicular to the surface of the light guide plate,
Generally, there are many components inclined in a direction away from the light source. Therefore, the conventional prism sheet cannot deflect light emitted from the surface of the light guide plate in a desired direction, that is, in a direction perpendicular to the surface of the light guide plate.

Further, since the conventional flat lighting device uses two prism sheets in addition to the diffusion sheet, which are superposed on the light guide plate, the number of parts is large and the thickness can be reduced as a whole. could not. In addition, the light loss due to the interface reflection between the diffusion sheet and the two prism sheets is large, and it is necessary to use a bright light source with a large amount of light, which becomes a factor that hinders downsizing of the entire device and reduction of power consumption. .

[0009]

OBJECTS OF THE INVENTION The first object of the present invention is to reduce loss,
Moreover, it is to provide a light guide plate capable of emitting high-luminance light with a uniform distribution.

A second object of the present invention is to provide a light deflection plate capable of optimally controlling the emission direction of light from the surface of the light guide plate.

A third object of the present invention is to provide a flat lighting device which has a small number of parts as well as a loss of light and is compact and capable of reducing power consumption.

[0012]

According to a first aspect of the present invention, a front surface portion from which light is emitted, a rear surface portion opposite to the front surface portion, and one surface side of the front surface portion and the rear surface portion are located. And a light-incident end face portion for introducing light from a light source and being connected to the front surface portion and the rear surface portion, and a light guide plate for emitting light incident from the light incident end surface portion from the front surface portion. In the light guide plate, a plurality of convex portions for totally reflecting the light incident from the incident end surface portion toward the front surface portion are formed on the back surface portion.

According to the present invention, a part of the light from the light source that enters the light guide plate from the incident end face portion is totally reflected by the convex portion provided on the back surface of the light guide plate, and the surface of the light guide plate is not lost. The light is emitted from the section to the outside of the light guide plate.

In a second aspect of the present invention, a front surface part from which light is emitted, a back surface part opposite to the front surface part, and one surface side of the front surface part and the back surface part are located. A light guide plate having an incident end face portion for introducing light from a light source while being connected to the front and back portions, and for causing light incident from the incident end face portion to be emitted from the front surface portion, the front surface The portion is provided with a light deflecting means for deflecting the light emitted from the surface portion in a predetermined direction,
In the light guide plate, a plurality of convex portions for totally reflecting the light incident from the incident end face portion to the front surface side are formed on the back surface portion.

According to the present invention, a part of the light from the light source that enters the light guide plate from the incident end face portion is totally reflected by the convex portion provided on the back surface of the light guide plate, and the surface of the light guide plate is not lost. The light is emitted from the portion to the outside of the light guide plate, but is emitted to the outside of the light guide plate in a state of being deflected in a predetermined direction by the light deflecting means formed on the surface portion of the light guide plate.

Further, a third mode according to the present invention is a light deflection plate which is used by being superposed on a surface portion of a light guide plate from which light is emitted, the light guide plate being located on the opposite side of the surface portion. A back surface portion, and an incident end surface portion for introducing light from a light source, which is located on one end side of the front surface portion and the back surface portion, is connected to the front surface portion and the back surface portion,
The light deflection plate is a flat surface portion along the surface portion,
And a prism surface having a triangular prism shape that extends in a direction parallel to the incident end surface portion and is arranged in a direction orthogonal to the incident end surface portion, and the prism surface has a distance from the flat surface portion toward the incident end surface portion side. The first inclined surface that expands and the second inclined surface that follows the first inclined surface are alternately provided, and the angle formed by the plane portion and the first inclined surface is the plane portion and the first inclined surface. Two
The angle is smaller than the angle formed by the inclined surface of the optical deflector.

According to the present invention, since the angle formed by the flat surface portion and the first inclined surface is smaller than the angle formed by the flat surface portion and the second inclined surface, the first inclined surface is formed more than the second inclined surface. The refraction of the light by the surface works largely, and the deflection of the light in the direction in which the distance between the first inclined surface and the flat surface portion widens is generated as a whole.

On the other hand, according to a fourth aspect of the present invention, a front surface part from which light is emitted, a back surface part opposite to the front surface part, and one surface side of the front surface part and the back surface part are located. And a light guide plate having an incident end face connected to the back face, a light source for projecting light toward the incident end face of the light guide plate, and a flat flat portion along the front face of the light guide plate. Light having a triangular prism shape that extends in a direction parallel to the incident end face portion of the light guide plate and is arranged in a direction orthogonal to the incident end face portion, and is superimposed on the surface portion of the light guide plate. A light-reflecting sheet that covers a portion of the light guide plate other than the surface portion and the incident end surface portion, and the light incident from the incident end surface portion on the back surface portion of the light guide plate. Shaped with multiple protrusions for total internal reflection In flat illumination apparatus characterized by being.

According to the present invention, a part of the light from the light source that enters the light guide plate from the incident end face portion is totally reflected by the convex portion provided on the back surface of the light guide plate, and the surface of the light guide plate is not lost. The light is emitted from the section to the outside of the light guide plate. Light emitted to the outside of the light guide plate from portions other than the surface portion and the incident end face portion of the light guide plate is re-introduced into the light guide plate by the light reflecting sheet, and finally emitted from the surface portion of the light guide plate. The light emitted from the surface portion of the light guide plate is deflected in a predetermined direction by the light deflection plate.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION In the light guide plate according to the first aspect and the second aspect of the present invention, the convex portion may have an inclined surface whose distance from the surface portion increases toward the incident end face portion side. , The refractive index of the material forming the light guide plate is n ₁ , and α = sin
⁻¹ (1 / n ₁ ), and the pi is π, the angle θ ₁ between the inclined surface and the surface portion is {(2π / 9)-(α / 2)} to {(11π / 36) − (α / 2)} is desirable. The convex portion may have an arc surface having a predetermined curvature in a plane orthogonal to the incident end face portion, and the refractive index of the material forming the light guide plate is n ₁ , α = sin ^−1.
(1 / n ₁ ), the circular constant is π, and the radius of the convex portion is r,
The relationship between the radius of curvature R of the arc surface and the protrusion amount h of the arc surface from the back surface is h = R (1-cos θ ₂ ) and R = r / sin
θ ₂ and θ ₂ is preferably in the range of {(2π / 9)-(α / 2)} to {(11π / 36)-(α / 2)}. Further, it is desirable that the convex portion is set so that the ratio of the back surface portion per unit area increases as the distance from the incident end face portion increases, and the size of the convex portion is 1
It is effective to be in the range of 0 μm to 150 μm.

In the light guide plate according to the second aspect of the present invention, the light deflecting means has concave and convex surfaces extending in a direction orthogonal to the incident end face portion and arranged alternately along the width direction of the light guide plate. The prism surface may have a triangular prism shape that extends in a direction orthogonal to the incident end face portion and is arranged along the width direction of the light guide plate.

On the other hand, in the flat illumination device according to the fourth aspect of the present invention, the light deflecting means for deflecting the light emitted from this surface portion in a predetermined direction is formed on the surface portion of the light guide plate. Is also good. In this case, the light deflector may have an uneven surface having a predetermined radius of curvature that extends in a direction orthogonal to the incident end surface portion and is arranged alternately along the width direction of the light guide plate. It may have prism faces in the form of triangular prisms that extend in the orthogonal direction and are arranged along the width direction of the light guide plate. In addition, the convex part is
It may have an inclined surface with a larger distance from the surface on the incident end face side, or may have an arc surface with a predetermined curvature in a plane orthogonal to the incident end face part. Further, it is desirable that the convex portion is set such that the ratio of the back surface portion per unit area increases as the distance from the incident end surface portion increases, and the prism surface of the light deflection plate is
The first inclined surface and the second inclined surface following the first inclined surface are alternately arranged, and the first inclined surface and the second inclined surface, which are spaced apart from each other by the distance from the incident end surface portion side, are alternately formed. The corner is flat and the second
It is effective that the angle is smaller than the angle formed with the inclined surface.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the flat lighting device according to the present invention will be described in detail with reference to FIGS.

As shown in FIG. 1 showing the sectional structure of the flat lighting device according to the present embodiment and FIG. 2 showing the external appearance of the flat lighting device, the flat lighting device 11 of the present embodiment is a rectangular plate-shaped conductor. The light plate 12, the linear light source lamp 14 arranged along the incident end face portion 13 of the light guide plate 12, and the light deflection plate 16 superposed on the surface portion 15 of the light guide plate 12.
And a light reflection sheet 17 that covers the portion of the light guide plate 12 other than the incident end face portion 13 and the surface portion 15. In addition, the light source lamp 14 including a cold cathode tube and a plurality of LEDs,
It is surrounded by a reflector 18 having a parabolic cross section, and the reflected light from the reflector 18 enters the light guide plate 12 from the incident end face portion 13 of the light guide plate 12 substantially in parallel with the surface portion 15.

The light guide plate 12 in this embodiment is formed of a transparent acrylic resin (PMMA) having a refractive index of 1.49, and an incident end face portion 13 for introducing light from the light source lamp 14 and this incident light. The reflecting end face portion 19 located on the opposite side of the end face portion 13, a pair of side end face portions 20 connected to both side ends of the incident end face portion 13 and the reflecting end face portion 19, and the incident end face portion 13 and the reflecting end face portion 19, Side end face part 2
It is surrounded by 0 and has a front surface portion 15 and a back surface portion 21 for emitting the light incident from the incident end face portion 13. The back surface portion 21 located on the opposite side of the front surface portion 15 is arranged with respect to the front surface portion 15 so that the distance between the front surface portion 15 and the back surface portion 21 becomes narrower on the reflection end surface portion 19 side than on the incident end surface portion 13 side. The taper shape is inclined from 0.5 degrees to 1 degree.

FIG. 3 schematically showing the back surface portion 21 of the light guide plate 12 and FIG. 4 showing the extracted enlarged shape along the IV-IV arrow cross section thereof and FIG. 4 and its extracted enlarged shape along the VV arrow cross section. As shown in FIG. 5 and FIG. 6 which is an enlarged view VI of the arrow, the triangular prism having the inclined surface 22 on the back surface 21 of the light guide plate 12 is such that the distance from the front surface 15 increases toward the incident end surface 13 side. The rectangular convex portions 23 forming the are arranged at random so that moire fringes and the like are not generated between the convex portions 23 and the uneven surface 24 (described later) formed on the surface portion 15 and the light deflection plate 16. There is. The convex portion 23 is for efficiently totally reflecting the light that is incident from the incident end face portion 13 and propagates in the light guide plate 12 and guides it to the surface portion 15 side, and each convex portion 23 is visible to the naked eye. Each side is set to a size of 150 μm or less so that it cannot be identified, but it is preferably 10 μm or more in consideration of the problem of light diffusion due to being too small and the ease of manufacturing.

In this way, the size of the convex portion 23 is 10 to 1
By setting the thickness in the range of 50 μm, it is not necessary to use a conventional light diffusion sheet, and it becomes possible to control the traveling direction of light relatively easily.

By the way, the light rays incident on the light guide plate 12 are
Depending on the refractive index n of the light guide plate 12,

[0029]

## EQU1 ## It proceeds in the range of the incident angle α satisfying 0 ≦ | α | ≦ sin ⁻¹ (l / n). In addition, the light guide plate 12
An incident ray L _I propagating in the inside of the object at an incident angle α with respect to the direction parallel to the surface portion 15 causes total reflection on the inclined surface 22 having an inclination angle θ with respect to the direction parallel to the surface portion 15. In order to do so, if the refractive index of the light guide plate 12 is n (= 1.49), its critical angle is φ, and the circular constant is π,

[0030]

## EQU00002 ## .theta..ltoreq. (. Pi./2)-.alpha.-.phi. However, sin φ = 1 / n, and in the case of the light guide plate 12 using an acrylic resin as in this embodiment,
The critical angle φ is about 42 °.

Further, in order that the reflected light beam L _O totally reflected by the back surface portion 21 is emitted from the front surface portion 15 of the light guide plate 12 to the outside,

[0032]

It is necessary to satisfy θ ≧ {(π / 2) −α−φ} / 2. That is, in order to effectively extract the light propagating in the light guide plate 12 to the outside, the inclination angle θ of the inclined surface 22 of the convex portion 23 is

[0033]

## EQU4 ## It is necessary to satisfy −π / 36 ≦ θ− (π / 4) + (α / 2) ≦ π / 18.

The energy of the reflected light emitted to the outside of the light guide plate 12 is the energy when the light reflection sheet 17 does not exist.
As shown in FIG. 7, it becomes maximum when the incident angle α is 0 degree, becomes gradually smaller as the incident angle α becomes larger, and becomes almost 0 at about 42 degrees or more. However, due to the presence of the light reflection sheet 17, the light guide sheet 12 is finally removed from the surface portion 15 by the presence of the light reflection sheet 17.
Goes out all outside.

As described above, the incident light beam L _I is totally reflected on the inclined surface 22 of the convex portion 23, and the reflected light beam L _O is not totally reflected on the surface portion 15 to the outside of the light guide plate 12. In order to emit, the incident angle α and the inclination angle θ need to exist within the shaded area shown in FIG. 7. Refractive index n is 1.
The inclination angle θ satisfying such a condition in this embodiment using 49 acrylic resins is in the range of about 24 degrees to about 48 degrees, and the incident angle α in this case is 0 degrees to about 24 degrees.
Degree.

That is, all incident light rays having an incident angle α of 24 degrees or less are totally reflected by the inclined surface 22 of the convex portion 23 and propagate to the surface portion 15 side. Most of the incident light rays L _I having an incident angle α of more than 24 degrees are emitted from the convex portion 23 to the outside of the light guide plate 12, but the light reflection sheet 17 again causes the light guide plate 1 to pass through.
2, and finally exits from the surface portion 15 to the outside of the light guide plate 12. Further, a part of the incident light ray with the incident angle α exceeding 24 degrees causes interface reflection on the inclined surface 22 of the convex portion 23, propagates to the surface portion 15 side, and is emitted to the outside of the light guide plate 12.

The light incident on the light guide plate 12 is generated by the light guide plate 1.
As its energy decreases as it progresses through 2,
It is necessary to gradually change the occupancy rate of the convex portion 23 provided on the back surface portion 21 of the light guide plate 12. Specifically, the area ratio of the convex portions 23 per unit area of the rear surface portion 21 (hereinafter, referred to as “the reflected light beam emitted from the front surface portion 15” has uniform luminance over the entire surface portion 15). The occupancy rate is the traveling direction of the light from the light source lamp 14 (in FIG. 1,
As shown in FIG. 8, which shows the relationship between the position of the back surface portion 21 along the right direction) and the occupancy rate of the convex portion 23, the occupancy rate is set to be larger toward the reflection end surface portion 19 side.

In this case, the front surface portion 15 of the light guide plate 12 which is close to the incident end surface portion 13 has a tendency that the light from the light source lamp 14 is directly transmitted to increase the brightness, and thus the rear surface close to the incident end surface portion 13 is formed. The occupancy of the convex portion 23 in the portion 21 is set to be smaller than that of the portion that follows it. Similarly,
The surface portion 15 near the reflection end surface portion 19 of the light guide plate 12 is
Since the reflected light from the reflection end face portion 19 tends to be transmitted to increase the brightness, the back surface portion 2 close to the reflection end face portion 19
The occupancy rate of the convex portion 23 in 1 is set to be smaller than that of the subsequent portion.

In this embodiment, the maximum value of the occupation ratio of the convex portion 23 is set to about 70%, but this is set to about 10%.
Of course, it is also possible to set it to 0%.

The surface portion 15 of the light guide plate 12 extends in a direction orthogonal to the incident end face portion 13 (left and right direction in FIG. 1) and is arranged along the width direction of the light guide plate 12 so as to have a predetermined radius of curvature. Uneven surfaces 24 and 25 are formed. Concave 2
The reference numeral 4 diffuses the light emitted from the surface portion 15, while the convex surface 25 focuses the light emitted from the surface portion 15 so that a more uniform luminance distribution can be obtained. It is desirable that the interval between each of the concave surface 24 and the convex surface 25 adjacent to each other is set to about 30 to 100 μm,
The difference in height between the concave surface 24 and the convex surface 25 is preferably about 10 to 45 μm.

As shown in FIG. 9 showing the side surface shape of the light deflector plate 16, the light deflector plate 16 in this embodiment is made of a transparent acrylic resin and is smooth to face the surface portion 15 of the light guide plate 12. The flat surface portion 26 and the triangular prism-shaped prism surface 27 extending in the direction parallel to the incident end surface portion 13 of the light guide plate 12 and arranged in the direction orthogonal to the incident end surface portion 13. The prism surface 27 is the incident end face portion 1 of the light guide plate 12.
The first inclined surface 28 in which the distance from the flat surface portion 26 increases toward the 3rd side
And the second inclined surface 29 following the first inclined surface 28 are alternately provided, and the angle δ ₁ between the flat surface portion 26 and the first inclined surface 28 is equal to the flat surface portion 26 and the second inclined surface 28. Angle formed with surface 29 δ ₂
Smaller than, for example, set δ ₁ to (28 ± 3) degrees,
δ ₂ is set to (62 ± 3) degrees.

The light reflection sheet 17 described above is used as the light guide plate 12.
Is for covering the reflection end surface portion 19, the pair of side end surface portions 20 and the back surface portion 21 and reflecting the light emitted from them to the inside of the light guide plate 12 again to be emitted from the front surface portion 15 of the light guide plate 12. The inner surface is mirror-finished by aluminum deposition.

In the above-mentioned embodiment, the corrugated surfaces 24 and 25 having a predetermined radius of curvature are formed on the surface portion 15 of the light guide plate 12 in a corrugated form. However, a prism surface having an isosceles triangular prism shape having an apex angle of about 95 to 105 degrees is formed. It may be formed continuously. Also,
Although the triangular column shape is adopted as the convex portion 23, it is also possible to adopt a shape having an arc surface having a predetermined radius of curvature.

A schematic structure of another embodiment of the light guide plate 12 according to the present invention is shown in FIG. 10. The portions having the same functions as those of the previous embodiment are designated by the same reference numerals and will not be duplicated. The description will be omitted. That is, the light guide plate 1
The convex portions 31 formed by the arcuate surface 30 having a predetermined radius of curvature are randomly arranged on the back surface portion 21 of No. 2, and the convex portions 31 are formed.
And the uneven surface 24 and the light deflection plate 1 formed on the surface portion 15.
Care is taken to prevent moire fringes and the like from occurring between 6 and 6. The convex portion 31 efficiently totally reflects the light that is incident from the incident end face portion 13 and propagates in the light guide plate 12 to efficiently reflect the light.
The diameter of each convex portion 31 is set to 150 μm or less so that the individual convex portions 31 cannot be discerned with the naked eye, but this is too small to cause a problem of light diffusion and easy manufacturing. In consideration of the property, it is desirable that the thickness is 10 μm or more.

In this way, the size of the convex portion 23 is 10 to 1
By setting the thickness in the range of 50 μm, it is not necessary to use a conventional light diffusion sheet, and it becomes possible to control the traveling direction of light relatively easily.

Here, the refractive index of the material forming the light guide plate 12 is n, α = sin ⁻¹ (1 / n), the circular constant is π, and the convex portion 31.
When the radius of the arc surface is represented by r, the relationship between the radius of curvature R of the arc surface 30 and the protrusion amount h of the arc surface 30 from the back surface portion 21 is h.
= R (1-cos θ ₂ ) and R = r / sin θ ₂ ,
₂ from {(2π / 9)-(α / 2)} to {(11π / 3
6)-(α / 2)} is designed so that an efficient light guide plate 12 utilizing total reflection due to the same effect as the convex portion 23 having the inclined surface 22 can be obtained. it can.

[0047]

According to the light guide plate and the flat lighting device of the present invention, a plurality of convex portions for totally reflecting the light incident from the incident end face portion of the light guide plate to the front surface side are formed on the back surface portion of the light guide plate. Therefore, a part of the light from the light source that has entered the light guide plate from the incident end face portion is totally reflected by the convex portion projecting on the back face portion of the light guide plate, and the surface portion of the light guide plate from the light guide plate without loss. It can be emitted to the outside.

Further, since the light deflecting means for deflecting the light emitted from the surface portion of the light guide plate in the predetermined direction is formed on the surface portion of the light guide plate, it is emitted from the surface portion of the light guide plate to the outside of the light guide plate. The light can be deflected in a predetermined direction by the light deflector formed on the surface of the light guide plate.

Further, according to the light guide plate of the present invention, the angle formed by the flat surface portion of the light guide plate and the first inclined surface is set smaller than the angle formed by the flat surface portion and the second inclined surface. Two
The refraction action of light by the first inclined surface is larger than that of the inclined surface, and as a whole, the deflecting action of light in the direction in which the distance between the first inclined surface and the flat surface portion is widened can be further strengthened.

On the other hand, the convex portion protruding from the back surface of the light guide plate is
Since the ratio of the back surface to the unit area per unit area increases as the distance from the incident end surface increases, the luminance distribution of the outgoing light can be made uniform, and the size of the protrusion is reduced to 1
By setting the thickness to 0 to 150 μm, a good light guide plate with no conspicuous convex portion can be obtained, and it is not necessary to use a light diffusion sheet together.

Further, when the light deflecting means is integrally formed on the surface of the light guide plate, it is possible to further omit the conventionally used prism sheet, resulting in less light loss and power consumption, and A thinner flat illumination device can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic structure of an embodiment of a flat lighting device according to the present invention.

FIG. 2 is an exploded perspective view of the embodiment shown in FIG.

FIG. 3 is a bottom view showing the appearance of the back surface of the light guide plate in the embodiment shown in FIG.

FIG. 4 is an enlarged sectional view taken along the line IV-IV in FIG.

FIG. 5 is a sectional view taken along the line VV in FIG. 4;

FIG. 6 is an enlarged view of an arrow VI portion in FIG.

FIG. 7 is a graph showing a relationship between an incident angle α of an incident light ray incident on a convex portion, an inclination angle θ of an inclined surface of the convex portion, and light energy.

FIG. 8 is a graph showing the relationship between the back surface portion of the light guide plate from the incident end surface portion to the reflective end surface portion and the occupancy rate of the convex portion per unit area thereof.

9 is an extracted enlarged view showing a side surface shape of the light deflecting plate in the embodiment shown in FIG. 1. FIG.

FIG. 10 is a sectional view of a main portion of another embodiment of the light guide plate according to the present invention.

[Explanation of symbols]

11 Planar Illumination Device 12 Light Guide Plate 13 Incident End Facet 14 Light Source Lamp 15 Surface Part 16 Light Deflection Plate 17 Light Reflecting Sheet 18 Reflector 19 Reflection End Facet 20 Side End Facet 21 Backside 22 Slope 23 Convex 24 Concave 25 Convex 26 Plane Part 27 Prism surface 28 First inclined surface 29 Second inclined surface 30 Arc surface 31 Convex portion L _I Incident ray L _O Reflected ray α Incident angle of incident ray θ Inclined angle of inclined surface

Claims (19)

[Claims] 1. A front surface portion from which light is emitted, a back surface portion opposite to the front surface portion, and one end side of the front surface portion and the back surface portion connected to the front surface portion and the back surface portion and a light source. And an incident end face portion for introducing light from the light guide plate for emitting light incident from the incident end face portion from the front surface portion, the back surface portion from the incident end face portion. A light guide plate having a plurality of convex portions for totally reflecting incident light to the surface portion side. 2. A front surface part from which light is emitted, a back surface part opposite to the front surface part, and one end side of the front surface part and the back surface part connected to the front surface part and the back surface part and a light source. A light guide plate having an incident end face portion for introducing light from the surface, and letting the light incident from the incident end face portion emerge from the surface portion, wherein the surface portion emerges from the surface portion. Light deflecting means for deflecting the light in a predetermined direction is formed, and a plurality of convex portions for totally reflecting the light incident from the incident end face portion to the front surface side are formed on the back surface portion. The light guide plate characterized by having. 3. The light guide plate according to claim 1, wherein the convex portion has an inclined surface in which a distance between the convex portion and the surface portion increases toward the incident end surface portion side. 4. The refractive index of the material forming the light guide plate is n.
₁ , α = sin ⁻¹ (1 / n ₁ ), and the circular constant is represented by π, the angle θ ₁ formed between the inclined surface and the surface portion is {(2π /
9)-(α / 2)} to {(11π / 36)-(α /
The light guide plate according to claim 3, wherein the light guide plate is in the range of 2)}. 5. The light guide plate according to claim 1, wherein the convex portion has an arc surface having a predetermined curvature in a plane orthogonal to the incident end surface portion. 6. The refractive index of the material forming the light guide plate is n.
₁ , α = sin ⁻¹ (1 / n ₁ ), the circular constant is π, and the radius of the convex portion is r, the radius of curvature R of the arc surface and the protrusion of the arc surface from the back surface portion. The relationship with the quantity h is h = R (1-
cos θ ₂ ) and R = r / sin θ ₂ , and θ ₂ is {(2
π / 9)-(α / 2)} to {(11π / 36)-(α
/ 2)}. The light guide plate according to claim 5, wherein 7. The method according to claim 1, wherein the convex portion is set such that the ratio of the back surface portion per unit area increases as the distance from the incident end surface portion increases. The light guide plate of Crab. 8. The size of the convex portion is 10 μm to 15 μm.
It exists in the range of 0 micrometer, The light-guide plate in any one of Claim 1 to 7 characterized by the above-mentioned. 9. The light deflecting means has concavo-convex surfaces having a predetermined radius of curvature which extend in a direction orthogonal to the incident end surface portion and are arranged alternately along the width direction of the light guide plate. The light guide plate according to any one of claims 2 to 8. 10. The light deflecting means has a triangular prism-shaped prism surface extending in a direction orthogonal to the incident end face portion and arranged along the width direction of the light guide plate. Item 9. The light guide plate according to any one of items 8. 11. A light deflection plate, which is used by being superposed on a surface portion of a light guide plate from which light is emitted, wherein the light guide plate has a back surface portion located on the opposite side of the front surface portion, the front surface portion and the light guide plate. The light deflection plate is located on one end side of the back surface portion and connected to the front surface portion and the back surface portion, and an incident end surface portion for introducing light from a light source, and the light deflection plate is smooth along the front surface portion. A flat part,
And a prism surface having a triangular prism shape that extends in a direction parallel to the incident end surface portion and is arranged in a direction orthogonal to the incident end surface portion, and the prism surface has a distance from the flat surface portion toward the incident end surface portion side. The first inclined surface that expands and the second inclined surface that follows the first inclined surface are alternately provided, and the angle formed by the plane portion and the first inclined surface is the plane portion and the first inclined surface. 2. An optical deflector which is smaller than the angle formed by the inclined surface of 2. 12. A front surface part from which light is emitted, a back surface part opposite to the front surface part, and an incident end surface located on one end side of the front surface part and the back surface part and connected to the front surface part and the back surface part. A light guide plate having a portion, a light source that projects light toward the incident end face portion of the light guide plate, a smooth flat portion along the surface portion of the light guide plate, and the incident end face portion of the light guide plate. A prismatic surface having a triangular prism shape that extends in a direction parallel to and arranged in a direction orthogonal to the incident end surface portion, and that is overlapped with the surface portion of the light guide plate; A light reflection sheet that covers a portion other than the front surface portion and the incident end surface portion, and the back surface portion of the light guide plate is provided with a plurality of light beams for totally reflecting the light incident from the incident end surface portion toward the front surface portion. Characterized in that a convex portion is formed Flat lighting device. 13. The light deflection means for deflecting light emitted from the surface portion in a predetermined direction is formed on the surface portion of the light guide plate.
The flat lighting device according to. 14. The light deflecting means has concavo-convex surfaces having a predetermined radius of curvature that extend in a direction orthogonal to the incident end surface portion and are arranged alternately along the width direction of the light guide plate. The flat lighting device according to item 13. 15. The light deflecting means has a triangular prism-shaped prism surface extending in a direction orthogonal to the incident end face portion and arranged along the width direction of the light guide plate. Flat lighting system. 16. The flat lighting device according to claim 12, wherein the convex portion has an inclined surface in which a distance between the convex portion and the surface portion increases toward the incident end surface portion side. 17. The flat lighting device according to claim 12, wherein the convex portion has an arc surface having a predetermined curvature in a plane orthogonal to the incident end face portion. 18. The projection is set so that the proportion of the back surface portion per unit area increases as the projection portion is farther from the incident end surface portion.
The flat lighting device according to any one of claims 2 to 17. 19. The prism surface of the light deflecting plate includes a first inclined surface whose distance from the flat surface portion increases toward the incident end surface portion, and a second inclined surface which follows the first inclined surface. And the angle formed by the plane portion and the first inclined surface is smaller than the angle formed by the plane portion and the second inclined surface. 19. The flat lighting device according to any one of 18.