JP2008147043A - Planar lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin and lightweight planar lighting system capable of emitting illumination light without luminance irregularity or reduced in luminance irregularity, and allowing increase of its size. <P>SOLUTION: The above problem is solved by forming this planar lighting system into a structure including: a light guide plate having a flat light emitting surface emitting planar light, a light entering surface formed at an edge of the light emitting surface for entering light advancing in a direction parallel to the light emitting surface, and a back surface formed on a surface on the side opposite to the light emitting surface, and having a shape increasing the thickness in a direction vertical to the light emitting surface as it separates from the light entering surface; a light source arranged oppositely to the light entering surface for entering light into the light entering surface; and a reflecting member of a flat shape arranged on the back surface side of the light guide plate, and reflecting the light emitted from the back surface; and a support member arranged between the light guide plate and the reflecting member, and supporting the light guide plate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a planar illumination device that illuminates an interior or exterior having a light source and a light guide plate that receives light emitted from the light source and exits from a light exit surface, or a backlight that illuminates a liquid crystal panel of a liquid crystal display device, The present invention relates to a planar lighting device used as a backlight for advertising panels, advertising towers, billboards and the like.

A liquid crystal display device uses a backlight unit that irradiates light from the back side of a liquid crystal panel (LCD) to illuminate the liquid crystal panel.
At present, the so-called direct type is the mainstream for backlight units of large-sized liquid crystal televisions (see, for example, Patent Document 1). The direct type backlight unit has a configuration in which a plurality of cold cathode tubes, which are light sources, are arranged on the back surface of the liquid crystal panel, and the inside of the casing in which the cold cathode tubes are arranged has a white reflecting surface as a liquid crystal panel Lighting up. However, in order to make the light amount distribution uniform in this method, in principle, the liquid crystal panel needs to have a thickness of about 30 mm in the vertical direction.

  In recent years, thinning, low power consumption, and large size of liquid crystal display devices have been demanded. However, in the direct backlight unit described above, when the thickness is 10 mm or less, unevenness in the amount of light occurs. There was a limit to reducing the thickness.

Here, as a backlight unit that can be reduced in thickness, light emitted from a light source for illumination and guided incident light is guided in a predetermined direction and emitted from a light emitting surface that is different from the surface on which the light is incident. There is a backlight unit using a light guide plate.
As such a backlight unit using a light guide plate, a backlight unit using a light guide plate in which scattering particles for scattering light in a transparent resin are mixed has been proposed (for example, Patent Document 1). To 4).

For example, Patent Document 1 includes a light-scattering light guide having at least one light incident region and at least one light extraction surface region, and light source means for performing light incidence from the light incident surface region. The light-scattering light-guide light source device is characterized in that the light-scattering light guide has a region that tends to decrease in thickness as the distance from the light incident surface increases.
Patent Document 2 includes a light scattering light guide, a prism sheet disposed on the light extraction surface side of the light scattering light guide, and a reflector disposed on the back side of the light scattering light guide. A surface light source device is described. Patent Document 3 discloses a liquid crystal including a light emitting direction correcting element made of a plate-like optical material having a light incident surface having repetitive undulations in a prism array and a light emitting surface provided with light diffusibility. A display is described, and Patent Document 4 describes a light source device that includes a light scattering light guide provided with scattering ability therein, and a light supply unit that supplies light from an end surface of the light scattering light guide. Has been.

In the planar illumination device including the light scatterer light guide plate mixed with the light scatterers described in Patent Documents 1 to 4, the light emitted from the light source and entering the light scatter light guide from the light incident surface In the process of propagating the light, it undergoes a single or multiple scattering action at a certain rate. In addition, a substantial part of the light reaching the both surfaces of the light scattering light guide or the surface of the reflector is reflected and returned to the light scattering light guide.
Through such a complex process, a light beam emitted with high efficiency from the light extraction surface is generated with directivity in the obliquely forward direction when viewed from the direction of the light source. That is, the light emitted from the light source is emitted from the light extraction surface of the light scattering light guide.
Thus, it is described that uniform light can be emitted with high emission efficiency by using a light guide plate mixed with scattering particles.

  As the light guide plate, besides the light guide plate having a shape having a tendency to reduce the thickness as the distance from the light incident surface increases, the thickness decreases as the distance from the light incident surface increases. There is described a planar illumination device having a light guide plate in a shape in which light guide plates having a shape having a tendency are attached.

JP 07-36037 A JP 08-248233 A Japanese Patent Application Laid-Open No. 08-271739 JP-A-11-153963

However, in the planar illumination device using the light guide plate described in Patent Documents 1 to 4, it is necessary to increase the thickness of the light guide plate itself in order to make the light reach a position farther from the light source in order to increase the size. . That is, there is a problem that the planar lighting device cannot be reduced in thickness and weight.
In addition, the shape described in Patent Documents 1 to 4 that has a tendency to reduce the thickness as it moves away from the incident position of the light source, or the flat plate shape has a limit on the reach of light, so there is a limit to the increase in size. There is also a problem.

  In addition, by using a light source with a large light emitting surface and making more light incident on the light guide plate, light with higher luminance or higher illuminance can be emitted from the light exit surface, but depending on the shape of the light guide plate There is also a problem that there is a limit to the size of the light emitting surface of the light source that can be used.

An object of the present invention is to solve the above-described problems based on the prior art, and to emit illumination light that is thin, lightweight, has no brightness unevenness, or has reduced brightness unevenness, and can be increased in size. It is to provide a state lighting device.
In addition to the above object, another object of the present invention is to provide a planar illumination device that can use a light source having a large light emitting surface area and can emit light with higher luminance.

In order to solve the above-mentioned problems, a first aspect of the present invention is a flat light emitting surface for emitting planar light, formed at an edge of the light emitting surface, and in a direction parallel to the light emitting surface. A light incident surface for allowing the traveling light to enter, and a back surface formed on a surface opposite to the light exit surface; the thickness in a direction perpendicular to the light exit surface increases as the distance from the light entrance surface increases. A light guide plate that is thicker;
A light source disposed opposite to the light incident surface and causing light to enter the light incident surface;
A flat reflection member that is disposed on the back side of the light guide plate and reflects light emitted from the back surface;
The planar illumination device is provided between the light guide plate and the reflection member and includes a support member that supports the light guide plate.

Here, it is preferable that the reflection member is arranged with a parallelism with respect to the light exit surface of the light guide plate of 0.3 mm or less.
Moreover, it is preferable that the said reflection member is arrange | positioned so that the surface of the said light-guide plate may be substantially parallel to the said light emission surface of the said light-guide plate.

Further, the support member preferably has a transmittance of 80% or more.
Moreover, it is preferable that the said supporting member is arrange | positioned in the said light-incidence surface vicinity of the said light-guide plate.
Moreover, it is preferable that the said supporting member is a shape which condenses the light which injected from the said light source side.

The planar lighting device further includes a housing formed in a box shape that covers the light guide plate and has an opening formed on the light exit surface side of the light guide plate. The surface of the light guide plate that faces the back surface is preferably the reflecting member.
Here, it is preferable that the casing is further formed with a reflecting member on a surface perpendicular to the light emitting surface.

The light guide plate includes a large number of scattering particles therein, the scattering cross-sectional area of the scattering particles is Φ, the density of the scattering particles is N _p , the correction coefficient is K _C , and the light guide plate has a light incident direction. the length from the light incident surface to the thickest position the thickness of the light guide plate is taken as L _G, the inequality _{1.1 ≦ Φ · N p · L} G · K C ≦ 8.2
0.005 ≦ K _C ≦ 0.1
Is preferably satisfied.

In the light guide plate, the light exit surface has a rectangular shape, and the light incident surface is formed at two opposite sides of the light exit surface, respectively, a first light incident surface and a second light incident surface. And the back surface is closest to the light exit surface in the first light incident surface and the second light incident surface, and is the midpoint of the line connecting the first light incident surface and the second light incident surface In this case, it is preferable that the light exit surface is an inclined surface farthest from the light exit surface.
Further, the light guide plate includes a plurality of scattering particles therein, the density of the scattering particles and N _p, the distance from the first light entrance plane to the second light entrance plane is L, the first light entrance plane Where D1 is the thickness of the light guide plate and D2 is the thickness at the midpoint of the light guide plate, the following inequality 27/100000 <(D2-D1) / (L / 2) <26/1000
0.04% wt <Np <0.25% wt
Is preferably satisfied.

The light source includes a plurality of the LED chips and a support that supports the LED chips, and the LED chips are arranged in a row on a surface of the support that faces the light incident surface. Preferably it is.
In the light source, it is preferable that a length of a light emitting surface in a direction perpendicular to the light emitting surface is longer than that of the light incident surface.

In order to solve the above-described problem, the second aspect of the present invention is a flat light emitting surface for emitting planar light, formed on an edge of the light emitting surface, and in a direction parallel to the light emitting surface. A light incident surface for allowing traveling light to enter, and a back surface formed on a surface opposite to the light exit surface, and a thickness in a direction perpendicular to the light exit surface increases as the distance from the light entrance surface increases. An illuminating device main body including a light guide plate having a shape and a light source that is disposed to face the light incident surface and makes light incident on the light incident surface;
Covering the outer periphery of the illuminating device main body, and having a shape in which an opening is formed on the light exit surface side of the light guide plate, and is configured with a housing that supports the illuminating device main body,
The housing provides a planar lighting device in which a surface facing the back surface is formed of a flat reflecting member that reflects light emitted from the back surface.

  According to the above configuration, the present invention can efficiently use the light emitted from the light source, and can emit light having no unevenness in brightness or reduced from the light emitting surface. Further, the apparatus can be made lighter and thinner, and the size can be increased, that is, the light emission surface can be increased.

Furthermore, by setting the parallelism between the reflecting member and the light exit surface to be 0.3 mm or less, it is possible to more surely prevent unevenness in luminance from being emitted from the light exit surface, and to make it substantially parallel. As a result, it is possible to more reliably prevent the occurrence of luminance unevenness.
Moreover, light utilization efficiency can be made higher by making the transmittance | permeability of a supporting member 80% or more.

DESCRIPTION OF EMBODIMENTS A planar illumination device according to the present invention will be described in detail based on an embodiment shown in the accompanying drawings.
FIG. 1 is a perspective view showing an outline of a liquid crystal display device including a planar illumination device according to the present invention, and FIG. 2 is a cross-sectional view taken along line II-II of the liquid crystal display device shown in FIG.
3A is a view taken along the line III-III of the planar illumination device (hereinafter also referred to as “backlight unit”) shown in FIG. 2, and FIG. It is a BB line sectional view of).

  The liquid crystal display device 2 includes a backlight unit 10, a liquid crystal display panel 4 disposed on the light emission surface side of the backlight unit 10, and a drive unit 6 that drives the liquid crystal display panel 4. In FIG. 1, a part of the liquid crystal display panel 4 is not shown in order to show the configuration of the planar lighting device.

The liquid crystal display panel 4 applies a partial electric field to liquid crystal molecules arranged in a specific direction in advance to change the arrangement of the molecules, and uses the change in the refractive index generated in the liquid crystal cell to make a liquid crystal display. Characters, figures, images, etc. are displayed on the surface of the display panel 4.
The drive unit 6 applies a voltage to the transparent electrode in the liquid crystal display panel 4 to change the direction of the liquid crystal molecules to control the transmittance of light transmitted through the liquid crystal display panel 4.

  The backlight unit 10 is an illuminating device that irradiates light from the back surface of the liquid crystal display panel 4 to the entire surface of the liquid crystal display panel 4, and has a light emission surface that has substantially the same shape as the image display surface of the liquid crystal display panel 4.

The backlight unit 10 according to the present invention includes an illuminating device body having two light sources 17, a light guide plate 18, and an optical member unit 20, as shown in FIGS. 1, 2, 3A, and 3B. 14, and a casing 16 having a lower casing 22, an upper casing 24, a folding member 26, and a support member 28. As shown in FIG. 1, a power storage unit 32 that stores a plurality of power supplies for supplying power to the light source 17 is attached to the back side of the lower housing 22 of the housing 16.
Hereinafter, each component which comprises the backlight unit 10 is demonstrated.

  The illuminating device main body 14 has a light source 17 that emits light, a light guide plate 18 that emits light emitted from the light source 17 as planar light, and light emitted from the light guide plate 18 by scattering or diffusing the light. The optical member unit 20 has no light.

First, the light source 17 will be described.
4A is a schematic perspective view showing a schematic configuration of the light source 17 of the planar illumination device 10 shown in FIGS. 1 and 2, and FIG. 4B is a diagram of the light source 17 shown in FIG. FIG. 4C is a cross-sectional view, and FIG. 4C is a schematic perspective view showing only one LED chip of the light source 17 shown in FIG.
As shown in FIG. 4A, the light source 17 includes a plurality of light emitting diode chips (hereinafter referred to as “LED chips”) 40 and a light source support portion 41.

The LED chip 40 is a chip in which a fluorescent material is applied to the surface of a light emitting diode that emits blue light. The LED chip 40 has a light emitting surface 40a having a predetermined area, and emits white light from the light emitting surface 40a.
That is, when the blue light emitted from the surface of the light emitting diode of the LED chip 40 passes through the fluorescent material, the fluorescent material fluoresces. Accordingly, when the blue light emitted from the LED chip 40 is transmitted, white light is generated and emitted by the blue light emitted from the light emitting diode and the light emitted by the fluorescent substance being fluorescent.
Here, examples of the LED chip 40 include a chip in which a YAG (yttrium, aluminum, garnet) fluorescent material is applied to the surface of a GaN-based light-emitting diode, an InGaN-based light-emitting diode, or the like.

  As shown in FIG. 4B, the light source support portion 41 includes an array substrate 42 and a plurality of fins 44. The plurality of LED chips 40 described above are arranged on the array substrate 42 in a row at a predetermined interval. Specifically, the plurality of LED chips 40 are arranged along the longitudinal direction of the first light incident surface 18d or the second light incident surface 18e of the light guide plate 18 to be described later, in other words, the light emitting surface 18a and the first light incident. They are arranged in an array parallel to the line where the surface 18d intersects or the line where the first light exit surface 18a and the second light incident surface 18e intersect.

The array substrate 42 is a plate-like member whose one surface is disposed to face the thinnest side end surface of the light guide plate 18, and the first light incident surface 18 d or the second light incident surface 18 e that is the side end surface of the light guide plate 18. It is arranged to face. The LED chip 40 is supported on the side surface of the array substrate 42 which is the surface facing the light incident surface 18 b of the light guide plate 18.
Here, the array substrate 42 of the present embodiment is formed of a metal having good thermal conductivity such as copper or aluminum, and also has a function as a heat sink that absorbs heat generated from the LED chip 40 and dissipates it to the outside. .

Each of the plurality of fins 44 is a plate-like member made of a metal having good thermal conductivity such as copper or aluminum, and is adjacent to the surface of the array substrate 42 opposite to the surface on which the LED chip 40 is disposed. The fins 44 are connected with a predetermined distance.
By providing a plurality of fins 44 on the light source support portion 41, the surface area can be increased and the heat dissipation effect can be enhanced. Thereby, the cooling efficiency of LED chip 40 can be improved.
The heat sink is not limited to the air cooling method, and a water cooling method can also be used.
In this embodiment, the array substrate 42 of the light source support portion 41 is used as a heat sink. However, when cooling of the LED chip is not necessary, a plate-like member having no heat dissipation function is used as the array substrate instead of the heat sink. Also good.

Here, as shown in FIG. 4C, the LED chip 40 of the present embodiment has a rectangular shape in which the length in the direction orthogonal to the arrangement direction is shorter than the length in the arrangement direction of the LED chip 40, that is, described later. The light guide plate 18 has a rectangular shape with a short side in the thickness direction (direction perpendicular to the light exit surface 18a). In other words, the LED chip 40 has a shape in which b> a, where a is a length in the direction perpendicular to the light exit surface 18a of the light guide plate 18 and b is a length in the arrangement direction. Further, q> b, where q is the arrangement interval of the LED chips 40. Thus, the relationship between the length a in the direction perpendicular to the light exit surface 18a of the light guide plate 18 of the LED chip 40, the length b in the arrangement direction, and the arrangement interval q of the LED chips 40 satisfies q>b> a. It is preferable.
By making the LED chip 40 into a rectangular shape, a thin light source can be obtained while maintaining a large light output. By reducing the thickness of the light source, the planar illumination device can be reduced in thickness. In addition, the number of LED chips can be reduced.

  In addition, since the LED chip 40 can make the light source thinner, it is preferable that the LED chip 40 has a rectangular shape with a short side in the thickness direction of the light guide plate 18, but the present invention is not limited to this, and a square shape, a circular shape, LED chips having various shapes such as a polygonal shape and an elliptical shape can be used.

  In this embodiment, the LED chips are arranged in a single row to form a single layer structure. However, the present invention is not limited to this, and a plurality of LED chips are provided on the array support 41 as shown in FIG. A multi-layer LED array having a configuration in which a plurality of LED arrays 46 each having a configuration 40 are stacked may be used as the light source 17 ′. Thus, even when the LED arrays 46 are stacked, more LED arrays 46 can be stacked by making the LED chip 40 rectangular and making the LED array 46 thin. As described above, by stacking the multilayer LED arrays 46, that is, by increasing the filling rate of the LED arrays (LED chips), a larger amount of light can be output. In addition, the LED chip of the LED array in the layer adjacent to the LED chip of the LED array preferably has the arrangement interval satisfying the above formula as described above. In other words, the LED array is preferably laminated with the LED chip and the LED chip of the LED array in the adjacent layer separated by a predetermined distance.

Next, the light guide plate 18 will be described.
FIG. 5 is a schematic perspective view showing the shape of the light guide plate 18.
As shown in FIGS. 2, 3 and 5, the light guide plate 18 is formed in a substantially rectangular flat light emission surface 18a and at both ends of the light emission surface 18a substantially perpendicular to the light emission surface 18a. The two light incident surfaces (the first light incident surface 18d and the second light incident surface 18e) and the opposite side of the light exit surface 18a, that is, on the back side of the light guide plate, the first light incident surface 18d and Parallel to the second light incident surface 18e, symmetrical with respect to a bisector α (see FIGS. 1 and 3) that bisects the light exit surface 18a, and a predetermined angle with respect to the light exit surface 18a It has two inclined surfaces (the 1st inclined surface 18b and the 2nd inclined surface 18c) inclined by. The first inclined surface 18b and the second inclined surface 18c are arranged such that the distance from the light emitting surface 18a increases (becomes larger) as the distance from the first light incident surface 18d and the second light incident surface 18e increases. As the distance from the light incident surface 18d and the second light incident surface 18e toward the center of the light guide plate is increased, the thickness in the direction perpendicular to the light exit surface of the light guide plate is increased. Further, the back surface, which is the surface opposite to the light exit surface 18a of the light guide plate 18, is composed of a first inclined surface 18b and a second inclined surface 18c.
That is, the light guide plate 18 has the thinnest thickness at both end portions, that is, the first light incident surface 18d and the second light incident surface 18e, and the central portion, that is, the first inclined surface 18b and the second inclined surface 18c intersect. The thickness is maximum at the position corresponding to the equipartition line α. In other words, the light guide plate 18 has a shape in which the thickness in the direction perpendicular to the light exit surface 18a of the light guide plate increases as the distance from the first light incident surface 18d or the second light incident surface 18e increases. The inclination angles of the first inclined surface 18b and the second inclined surface 18c with respect to the light exit surface 18a are not particularly limited.

Further, the above-described light source 17 is disposed to face the first light incident surface 18d and the second light incident surface 18e of the light guide plate 18, respectively. That is, in the planar lighting device 10, the two light sources 17 are arranged so as to sandwich the light guide plate 18. In other words, the light guide plate 18 is disposed between two light sources 17 that are disposed to face each other with a predetermined distance therebetween. In the present embodiment, the length of the light emitting surface 40a of the LED chip 40 of the light source 17 is substantially the same as the length of the first light incident surface 18d and the second light incident surface 18e in the direction perpendicular to the light emitting surface 18a. That's it.
Thus, the light incident from the light incident surface is formed by increasing the thickness in the direction perpendicular to the light exit surface 18a as the light guide plate 18 is separated from the first light incident surface 18d or the second light incident surface 18e. Can be delivered to a position farther from the light incident surface, and the light exit surface can be enlarged. Moreover, since the light incident from the light incident surface can be suitably delivered to a distant position, the light guide plate can be thinned.

  In the light guide plate 18 shown in FIG. 2, the light incident from the first light incident surface 18d and the second light incident surface 18e is scattered by a scatterer (details will be described later) included in the light guide plate 18 while being guided. The light passes through the inside of the optical plate 18 and is reflected from the first inclined surface 18b and the second inclined surface 18c, and then emitted from the light exit surface 18a. At this time, some light may leak from the first inclined surface 18b and the second inclined surface 18c, but the leaked light is disposed on the first inclined surface 18b and the second inclined surface 18c side of the light guide plate 18. The light is reflected by the lower housing 22 and enters the light guide plate 18 again. The lower housing 22 will be described in detail later.

  The light guide plate 18 is formed by kneading and dispersing scattering particles for scattering light in a transparent resin. Examples of the transparent resin material used for the light guide plate 18 include PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, or COP (cycloolefin polymer). An optically transparent resin such as As scattering particles kneaded and dispersed in the light guide plate 18, Atsipearl, thin cone, silica, zirconia, dielectric polymer, or the like can be used. By including such scattering particles in the light guide plate 18, it is possible to emit illumination light that is uniform and has less luminance unevenness from the light exit surface. Such a light guide plate 18 can be manufactured using an extrusion molding method or an injection molding method.

Further, the scattering cross section of the scattering particles contained in the light guide plate 18 is Φ, the light incident direction (the direction parallel to the traveling direction of the light incident on the light guide plate, parallel to the light exit surface, the light exit surface and the light entrance Perpendicular to the light exit surface 18a from the first light incident surface 18d or the second light incident surface 18e of the light guide plate 18 in the direction perpendicular to the tangent to the surface (the first light incident surface or the second light incident surface). The length up to the position where the thickness of the direction becomes the maximum, in this embodiment, the light incident direction of the light guide plate (in this embodiment, the direction perpendicular to the first light incident surface 18d of the light guide plate 18, hereinafter "light L _{G is} the half length (length to the position of the bisector α), and the density of scattering particles (number of particles per unit volume) contained in the light guide plate 18 is N _p. , when the correction coefficient and _{K C,} the value of _{Φ · N p · L G ·} K C is 1.1 or more, One 8.2 or less, further, the value of the correction coefficient _{K C} is better to satisfy the relationship of 0.005 to 0.1. Since the light guide plate 18 includes scattering particles that satisfy such a relationship, the illumination light can be emitted from the light exit surface 18a with uniform brightness and less unevenness in luminance.

In general, the transmittance T when a parallel light beam is incident on an isotropic medium is expressed by the following formula (1) according to the Lambert-Beer rule.
T = I / I ₀ = exp (−ρ · x) (1)
Here, x is a distance, I ₀ is incident light intensity, I is outgoing light intensity, and ρ is an attenuation constant.

The attenuation constant ρ is expressed by the following equation (2) using the scattering cross-sectional area Φ of particles and the number of particles N _p per unit volume contained in the medium.
ρ = Φ · N _p (2)
Therefore, from the incident surface of the light guide plate in a direction parallel to the traveling direction of light of the light guide plate to the thickest position thickness length, the length of the half of the optical axis direction of the light guide plate when the L _G, light extraction The efficiency E _out is given by the following formula (3). Here, half the length L _G of the optical axis of the light guide plate, the length from one of the light incident surface of the light guide plate 18 in the direction perpendicular to the light incident surface of the light guide plate 18 to the center of the light guide plate 18 .

Furthermore, the light extraction efficiency and are, with respect to the incident light, the fraction of light reaching the position spaced the length L _G in the optical axis direction from the light incident surface of the light guide plate, for example, the light guide plate 18 shown in FIG. 2 In this case, it is a ratio of light reaching the center of the light guide plate (a position having a half length in the optical axis direction of the light guide plate) with respect to light incident on the end face.
E _out ∝exp (−Φ · N _p · L _G ) (3)

Here the formula (3) applies to a space of limited size, to introduce a correction coefficient K _C for correcting the relationship between the expression (1). The compensation coefficient K _C is a dimensionless compensation coefficient empirically obtained where light optical medium of limited dimensions propagates. Then, the light extraction efficiency E _out is expressed by the following formula (4).
_{E out = exp (-Φ · N} p · L G · K C) ··· (4)

According to the equation (4), when the value of Φ · N _p · L _G · K _C is 3.5, the light extraction efficiency E _out is 3%, and Φ · N _p · L _G · K _C When the value of is 4.7, the light extraction efficiency E _out is 1%.
From this result, it is understood that the light extraction efficiency E _out decreases as the value of Φ · N _p · L _G · K _C increases. Since light is scattered as it travels in the direction of the optical axis of the light guide plate, the light extraction efficiency E _out is considered to be low.

Therefore, it can be seen that the larger the value of Φ · N _p · L _G · K _C is, the more preferable property is for the light guide plate. In other words, by increasing the value of Φ · N _p · L _G · K _C , it is possible to reduce the light emitted from the surface facing the light incident surface and increase the light emitted from the light emission surface. it can. That is, by increasing the value of _{Φ · N p · L G ·} K C, ( hereinafter also referred to as "light use efficiency".) Ratio of light emitted through the light exit plane to the light incident on the incident surface of the high can do. Specifically, by setting 1.1 or the value of _{Φ · N p · L G ·} K C, the light use efficiency can be 50% or more.

Here, when the value of Φ · N _p · L _G · K _C is increased, the illuminance unevenness of the light emitted from the light exit surface 18a of the light guide plate 18 becomes remarkable, but Φ · N _p · L _G · K _C By making the value of 8.2 or less, the illuminance unevenness can be suppressed to a certain value (within an allowable range). Note that the illuminance and the luminance can be handled in substantially the same manner. Therefore, in the present invention, it is presumed that luminance and illuminance have the same tendency.

Thus, the value of _{Φ · N p · L G ·} K C of the light guide plate 18 of the present invention preferably satisfies the relationship of 1.1 or more and 8.2 or less, 2.0 or more and 8. More preferably, it is 0 or less. The value of _{Φ · N p · L G ·} K C is more preferably as long as 3.0 or more, most preferably, not less than 4.7.
The correction coefficient K _C is preferably 0.005 or more and 0.1 or less (0.005 ≦ K _C ≦ 0.1).

Hereinafter, the light guide plate 18 will be described in more detail with specific examples.
First, the scattering cross section Φ, particle density N _p , half length L _G of the light guide plate in the optical axis direction, and correction coefficient K _C are set to various values, and the values of Φ · N _p · L _G · K _C are different. About each light-guide plate, the light use efficiency was calculated | required by computer simulation, and also illumination intensity nonuniformity was evaluated. Here, the illuminance unevenness [%] is the maximum illuminance of light emitted through the light exit plane of the light guide plate and I _Max, a minimum illuminance and I _Min, Average illuminance when the I _Ave [(I _Max - I _Min ) / I _Ave ] × 100.
The measured results are shown in Table 1. The determination in Table 1 is indicated by ◯ when the light use efficiency is 50% or more and the illuminance unevenness is 150% or less, and when the light use efficiency is less than 50% or the illuminance unevenness is more than 150%.

Further, in FIG. 6, measuring the relationship between _{Φ · N p · L G ·} K C values and light use efficiency (ratio of light emitted through the light exit plane 18a to light incident on the light incident surface) The results are shown.
As shown in Table 1 and FIG. 6, by making Φ · N _p · L _G · K _C be 1.1 or more, the light use efficiency is increased, specifically, the light use efficiency is 50% or more. It can be seen that by setting it to 8.2 or less, the illuminance unevenness can be reduced to 150% or less.
In addition, when Kc is set to 0.005 or more, the light use efficiency can be increased, and when it is set to 0.1 or less, the illuminance unevenness of light emitted from the light guide plate can be reduced. Recognize.

Then, the particle density N _p of the particles which kneaded or dispersed in the light guide plate creates various values of the light guide plate was measured illuminance distribution of light emitted from the respective positions of the light emitting surface of each light guide plate . In this exemplary embodiment, other conditions except for the particle density N _p, specifically, the scattering cross section [Phi, half the length of the optical axis direction of the light guide plate L _G, the correction coefficient K _C, the light guide plate The shape and the like were the same value. Accordingly, in the present _{embodiment, Φ · N p · L G} · K C changes in proportion to the particle density _{N p.}
FIG. 7 shows the results of measuring the illuminance distribution of the light emitted from the light exit surface of the light guide plates having various particle densities in this way. In FIG. 7, the vertical axis is illuminance [lx], and the horizontal axis is the distance (light guide length) [mm] from one light incident surface of the light guide plate.

Furthermore, the illuminance unevenness when the maximum illuminance of light emitted from the side wall of the light guide plate of the measured illuminance distribution is I _Max , the minimum illuminance is I _Min , and the average illuminance is I _Ave [(I _Max −I _Min ) / I _Ave ] × 100 [%] was calculated.
FIG. 8 shows the relationship between the calculated illuminance unevenness and the particle density. In FIG. 8, the vertical axis is illuminance unevenness [%], and the horizontal axis is particle density [pieces / m ³ ]. FIG. 8 also shows the relationship between light utilization efficiency and particle density, where the horizontal axis is the particle density and the vertical axis is the light utilization efficiency [%].

As shown in FIGS. 7 and 8, when the particle density is increased, that is, Φ · N _p · L _G · K _C is increased, the light utilization efficiency is increased, but the illuminance unevenness is also increased. It can also be seen that when the particle density is lowered, that is, when Φ · N _p · L _G · K _C is reduced, the light utilization efficiency is reduced, but the illuminance unevenness is reduced.
Here, by the _{Φ · N p · L G ·} K C less than 1.1 and not greater than 8.2, the light use efficiency of 50% or more, and the illuminance unevenness of 150% or less. By setting the illuminance unevenness to 150% or less, the illuminance unevenness can be made inconspicuous.
_{That, Φ · N p · L G} · K C to be to less than 1.1 and not greater than 8.2 yields light use efficiency above a certain level, and illuminance unevenness also seen that it is possible to reduce.

Next, the optical member unit 20 will be described.
The optical member unit 20 converts the illumination light emitted from the light exit surface 18a of the light guide plate 18 into light with no uneven brightness, and emits illumination light with more uniform brightness from the light exit surface 14a of the illumination device body 14. As shown in FIG. 2, a diffusion sheet 20a that diffuses illumination light emitted from the light exit surface 18a of the light guide plate 18 to reduce unevenness of brightness, and a tangent line between the light incident surface and the light exit surface It has a prism sheet 20b on which parallel microprism arrays are formed, and a diffusion sheet 20c that diffuses illumination light emitted from the prism sheet 20b to reduce luminance unevenness.

  As the diffusion sheets 20a and 20c and the prism sheet 20b, those disclosed in [0028] to [0033] of Japanese Patent Application Laid-Open No. 2005-23497 related to the applicant's application can be applied.

In this embodiment, the optical member unit is composed of the two diffusion sheets 20a and 20c and the prism sheet 20b disposed between the two diffusion sheets. However, the arrangement order and arrangement of the prism sheets and the diffusion sheets are not limited. The number is not particularly limited, and is also not particularly limited as a prism sheet or a diffusion sheet, as long as the luminance unevenness of the illumination light emitted from the light exit surface 18a of the light guide plate 18 can be further reduced, Various optical members can be used.
For example, as the optical member, a transmittance adjusting member in which a large number of transmittance adjusting bodies made of a diffuse reflector are arranged in accordance with the luminance unevenness can be used in addition to or instead of the above-described diffusion sheet and prism sheet.

Next, the housing 16 will be described.
As shown in FIG. 2, the housing 16 accommodates and supports the illuminating device main body 14 and is sandwiched between the light emitting surface 14 a side and the first inclined surface 18 b and the second inclined surface 18 c side of the light guide plate 18. The lower casing 22, the upper casing 24, the folding member 26, and the support member 28 are included.

  9A is a schematic perspective view showing the shape of the lower housing, FIG. 9B is a schematic perspective view showing the shape of the upper housing, and FIG. 9C is the folding member. It is a schematic perspective view which shows a shape.

As shown in FIG. 9A, the lower housing 22 has a shape in which an upper surface is opened and a bottom surface portion 22a and side surface portions 22b provided on four sides of the bottom surface portion 22a and perpendicular to the bottom surface portion 22a. It is. That is, it is a substantially rectangular parallelepiped box shape with one surface open. The bottom surface portion 22a is flat, and the inner surface is formed of a reflecting member.
The reflecting member may be formed of any material as long as it can reflect light leaking from the back surface (first inclined surface and second inclined surface) of the light guide plate, for example, PET or PP (polypropylene). A resin sheet in which voids have been formed by stretching after filler is kneaded and stretched, etc., a sheet with a mirror surface formed by aluminum vapor deposition or the like on the surface of a transparent or white resin sheet, a metal foil such as aluminum or a metal foil It can be formed of a supported resin sheet or a thin metal plate having sufficient reflectivity on the surface.

  As shown in FIG. 2, the lower housing 22 supports the illuminating device main body 14 accommodated from above by the bottom surface portion 22a and the side surface portion 22b, and is a surface other than the light emitting surface 14a of the illuminating device main body 14, that is, The surface (rear surface) and the side surface opposite to the light exit surface 14a of the lighting device body 14 are covered.

As shown in FIG. 9B, the upper casing 24 has a rectangular opening smaller than the rectangular light emitting surface 14a of the illuminating device body 14 serving as the opening 24a on the upper surface, and the lower surface is opened. It is a rectangular parallelepiped box shape.
As shown in FIG. 2, the upper housing 24 includes the illumination device main body 14 and the lower housing 22 in which the illumination device main body 14 is accommodated from above the planar illumination device main body 14 and the lower housing 22 (on the light emission surface side). The other side surface portion 22b is also placed so as to cover it.

Further, as shown in FIG. 9C, the folding member 26 has a shape in which the shape of the cross section perpendicular to the predetermined direction is always the same concave (U-shaped) shape. That is, it is a rod-like member having a U-shaped cross section perpendicular to the extending direction.
As shown in FIG. 2, the folding member 26 is inserted between the side surface of the lower housing 22 and the side surface of the upper housing 24, and the outer surface of one U-shaped parallel part is the bottom surface of the lower housing 22. The side surface 22 b is connected, and the outer side surface of the other parallel portion is connected to the side surface of the upper housing 24.
Here, as a method for joining the lower housing 22 and the folding member 26, and a method for joining the folding member 26 and the upper housing 24, various known methods such as a method using bolts and nuts, a method using an adhesive, and the like. Can be used.

By arranging the folding member 26 in this manner, the rigidity of the housing 16 can be increased, and the light guide plate can be prevented from warping. Thus, for example, light can be emitted efficiently with little or no luminance unevenness, but even when using a light guide plate that is likely to warp, the warp can be corrected more reliably, or the light guide plate can be warped. It is possible to more reliably prevent the occurrence of light, and to emit light from the light exit surface with no or reduced brightness unevenness.
In addition, various materials, such as a metal and resin, can be used for the upper housing | casing of a housing | casing, a lower housing | casing, and a folding member. In addition, as a material, it is preferable to use a lightweight and high-strength material.
In the present embodiment, the folding member is a separate member, but it may be formed integrally with the upper housing or the lower housing. Moreover, it is good also as a structure which does not provide a folding | turning member.

The support member 28 has a shape having the same cross-sectional shape perpendicular to the predetermined direction. That is, it is a rod-like member having the same cross-sectional shape perpendicular to the extending direction.
As shown in FIG. 2, the support member 28 is between the light guide plate 18 and the lower housing 22, more specifically, an end portion of the first inclined surface 18 b of the light guide plate 18 on the first light incident surface 18 d side. The light guide plate 18 is fixed to and supported by the lower housing 22.
The light guide plate 18 is fixed to a predetermined position of the lower housing 22 by the support member 28.

The shape of the support member 28 is not particularly limited, and can be made of various materials.
In the present embodiment, the support member is provided as an independent member. However, the present invention is not limited to this, and the support member may be formed integrally with the lower housing 22 or the light guide plate 18. That is, even if a protrusion is formed on a part of the lower housing 22 and this protrusion is used as a support member, a protrusion is formed on a part of the light guide plate 18 and this protrusion is used as a support member. Good.
In addition, the arrangement position is not particularly limited and can be arranged at a predetermined position between the light guide plate and the lower housing, but in order to stably hold the light guide plate, the end side of the light guide plate, that is, In the present embodiment, it is preferable to dispose near the first light incident surface 18d and near the second light incident surface 18e.

The planar illumination device 10 is basically configured as described above.
In the planar lighting device 10, light emitted from the light sources 17 disposed at both ends of the light guide plate 18 is incident on the light incident surfaces (the first light incident surface 18 d and the second light incident surface 18 e) of the light guide plate 18. The light passes through the light guide plate 18 while being scattered by the scatterer included in the light guide plate 18 and is reflected directly or after being reflected by the first inclined surface 18b and the second inclined surface 18c, and then emitted from the light exit surface 18a. . At this time, part of the light leaking from the first inclined surface 18 b and the second inclined surface 18 c is reflected by the reflecting member of the bottom surface portion 22 a of the lower housing 22 and enters the light guide plate 18 again.
In this way, the light emitted from the light emission surface 18 a of the light guide plate 18 passes through the optical member 20 and is emitted from the light emission surface 14 a of the illumination device body 14 to illuminate the liquid crystal display panel 4.
The liquid crystal display panel 4 displays characters, figures, images, etc. on the surface of the liquid crystal display panel 4 by controlling the light transmittance according to the position by the drive unit 6.

The bottom surface portion 22a of the casing 16 of the planar lighting device 10 on which the reflecting member of the lower casing 22 is formed has a flat shape, that is, the light guide plate side surface (reflecting surface) of the lower casing 22 is formed. By flattening, a space is formed between the first inclined surface 18b and the second inclined surface 18c of the light guide plate 18 and the bottom surface portion 22a of the housing 16, and light leaking from the light guide plate 18 and the light guide plate 18 is reflected. A space can be formed between the reflecting member and the reflecting member.
As a result, light leaking from the first inclined surface 18b and the second inclined surface 18c of the light guide plate 18, reflected, and then re-entered the light guide plate can cause uneven brightness in the light emitted from the light exit surface 18a. Can be prevented. In other words, in the case of a configuration in which the back surface of the light guide plate, that is, the first inclined surface 18b and the second inclined surface 18c and the reflecting member are arranged in close contact with each other, there is uneven adhesion on the bonding surface between the light guide plate and the reflecting member. If this occurs or part of the reflecting member peels over time, uneven brightness may occur. However, as in the present embodiment, the bottom surface portion 22a of the lower housing 22 serving as the reflecting member is made flat, and the light guide plate By forming a space with the back surface of the light, it is possible to prevent uneven brightness.
Moreover, a structure and an assembly can also be simplified by not sticking the back surface of a light-guide plate and a reflection member closely.
Furthermore, as in the present embodiment, by integrally forming the lower housing and the reflecting member, the apparatus configuration can be simplified and the assembly can also be simplified.
Furthermore, it is possible to increase the light emission surface while keeping the light guide plate thin, and the device can be reduced in weight, thickness, and size.

Further, as in the present embodiment, the light guide plate has the thickest shape at the center and the thinnest at both ends, and the reflecting member has a flat shape, so that the luminance distribution of light emitted from the light exit surface is a bell shape. It can be.
Luminance distribution of light emitted from the light exit surface is bell-shaped, that is, a brightness distribution that gradually increases in brightness toward the center, and by visually increasing the brightness at the center of the light exit surface, The difference in brightness between the central part and the peripheral part is felt to be small, and uniform light appears to be emitted from the light exit surface. Accordingly, light having a luminance distribution that can be suitably used for a liquid crystal television or the like can be emitted from the planar lighting device.

Here, it is preferable that the bottom surface portion 22a of the lower housing 22 of the present embodiment, that is, the flat reflecting member, is arranged so that the parallelism with respect to the light exit surface 18a of the light guide plate is 0.3 mm or less. It is more preferable that they are arranged in parallel with each other. In other words, the parallelism between the reflecting member and the light exit surface 18a is preferably 0.3 mm or less, and more preferably substantially parallel. That is, it is preferable to arrange the casing (reflecting member) and the light guide plate at a position where the parallelism between the reflecting member and the light exit surface is 0.3 mm or less, and the casing (reflecting member) at a position that is substantially parallel. And a light guide plate are more preferable.
By disposing the reflecting member at a position where the parallelism with respect to the light exit surface of the light guide plate is 0.3 mm or less, and setting the distance between the reflecting member and the light exit surface within a certain range, uneven brightness occurs in the emitted light. This can be prevented more reliably, and by arranging at substantially parallel positions, it is possible to more reliably prevent uneven brightness from occurring. Further, when a symmetrical light guide plate is used as in the present embodiment, the luminance distribution can be made symmetrical with no deviation.

  Moreover, in this embodiment, since the apparatus configuration can be further simplified, the bottom surface portion 22a of the lower housing 22 is formed of a reflective member. However, the present invention is not limited to this, and is a separate member from the lower housing. As another example, a flat reflecting member that reflects light that has leaked from the first inclined surface 18b and the second inclined surface 18c of the light guide plate 18 and enters the light guide plate 18 may be provided.

  Moreover, it is preferable that the lower housing | casing 22 also forms the inner surface of the side part 22b, ie, the surface at the side of the light-guide plate 18 of the side part 22b, with a reflecting member. In this way, the side surface portion 22b is used as a reflecting member, and the light leaking from the surface between the light exit surface 18a and the back surface (the first inclined surface 18b and the second inclined surface 18c) of the light guide plate 18 is reflected, and again the light guide plate. Can be made incident. As a result, the light utilization efficiency can be increased, and the luminance at the end of the light exit surface can be reduced, thereby preventing unevenness in luminance.

In the light guide plate of the present embodiment, the thickness of the light guide plate (light incident portion thickness) on the light incident surface is D1, and the light guide plate is at the maximum thickness, that is, in the bisector α in the present embodiment. The thickness (center thickness) of the light guide plate is D2, and the length of the light guide plate in the light incident direction (light guide length), that is, the length from the first incident surface to the second incident surface is L (in this embodiment, L = 2L _G ))
D1 <D2 and
27/100000 <(D2-D1) / (L / 2) <5/100 (A)
Ratio of mixed scattering particle weight to light guide plate weight: Npa range is 0.04% Wt <Npa <0.25% Wt
It is preferable to satisfy the relationship. By making the shape satisfying the above relationship, the emission efficiency can be improved to 30% or more.

Or the light guide plate
D1 <D2 and
66/100000 <(D2-D1) / (L / 2) <26/1000 (B)
Ratio of mixed scattering particle weight to light guide plate weight: Npa range is 0.04% Wt <Npa <0.25% Wt
It is also preferable to improve so as to satisfy this relationship. By making the shape satisfying the above relationship, the emission efficiency can be improved to 40% or more.

Furthermore, the light guide plate
D1 <D2 and
1/1000 <(D2-D1) / (L / 2) <26/1000 (C)
Ratio of mixed scattering particle weight to light guide plate weight: Npa range is 0.04% Wt <Npa <0.25% Wt
It is further preferable to improve so as to satisfy the relationship. By making the shape satisfying the above relationship, the emission efficiency can be improved to 50% or more.

FIG. 10 shows the results of measuring the light utilization efficiency for light guide plates having different inclination angles of the inclined surfaces, that is, light guide plates having various shapes with different (D2-D1) / (L / 2). Here, the horizontal axis in FIG. 10 is (D2-D1) / (L / 2) of the light guide plate, and the vertical axis is the light utilization efficiency [%].
From the measurement results shown in FIG. 10, the light utilization efficiency can be increased to 30% or more by setting the shape of the light guide plate to 27/100000 <(D2-D1) / (L / 2) <5/100. By using 66/100000 <(D2-D1) / (L / 2) <26/1000, the light utilization efficiency can be increased to 40% or more, and 1/1000 <(D2-D1) / ( It can be seen that the light utilization efficiency can be 50% or more by setting L / 2) <26/1000.

In addition, the light guide plate is not limited to the above shape, and may have various shapes as long as the thickness of the light guide plate increases as the distance from the light incident surface increases.
For example, prism rows may be formed on the first inclined surface 18b and the second inclined surface 18c in a direction parallel to the first light incident surface 18d and the second light incident surface 18e. Further, instead of such a prism array, an optical element similar to a prism can be regularly formed. For example, an optical element having a lens effect, such as a lenticular lens, a concave lens, a convex lens, or a pyramid type, can be formed on the inclined surface of the light guide plate.

In addition, the shape of the light guide plate is not limited to the shape of the present embodiment. For example, the light guide plate shown in FIG. 2 is cut in half, that is, the light incident surface is only one surface, and is separated from the light incident surface. In accordance with the above, the shape of the light guide plate is increased, in other words, the light incident surface is composed of one light incident surface formed on one edge of the light exit surface, and the inclined surface is changed from the light incident surface to this. It may be composed of one inclined surface that is inclined so as to be farther from the light exit surface toward the other opposite end surface, and may have the thinnest shape on the light incident surface and the thickest shape on the other end surface. In addition, the light source is arranged on any one of the side surfaces of the light guide plate, the four side surfaces are light incident surfaces, and the thickness increases from the four light incident surfaces toward the center, that is, the light emission of the light guide plate The surface opposite to the surface has a quadrangular pyramid shape, in other words, the light incident surface is composed of four light incident surfaces respectively formed on the four end sides of the light exit surface, and the inclined surface is Each of the four light incident surfaces is composed of four inclined surfaces that are inclined so as to move away from the light exit surface toward the center. The thickness of the light incident surface is the thinnest, and the thickness at the position where the four inclined surfaces intersect is the thickest. It is good also as a shape.
Even if the light guide plate has such a shape, light can reach a position far from the light incident surface while maintaining a thin shape. Thereby, the light guide plate can be thinned and the light emission surface can be enlarged.
Again, with the light guide plate having the above shape, the length of the direction of incidence of light from the light incident surface of the light guide plate to a position where the direction of thickness perpendicular to the light exit surface is maximum and L _G, above Φ · N _p · L _G · K _C preferably satisfies 1.1 or more and 8.2 or less and satisfies 0.005 ≦ K _C ≦ 0.1. By satisfying the above range, illuminance unevenness can be reduced and light with high light utilization efficiency can be emitted from the light exit surface.

Moreover, you may produce a light-guide plate by mixing a plasticizer in said transparent resin.
Thus, by producing a light guide plate with a material in which a transparent material and a plasticizer are mixed, the light guide plate can be made flexible, that is, a flexible light guide plate. It can be deformed into a shape. Therefore, the surface of the light guide plate can be formed into various curved surfaces.
By making the light guide plate flexible in this way, for example, when using a light guide plate or a planar lighting device using the light guide plate as a display plate for illumination, the wall having a curvature is also used. It becomes possible to mount the light guide plate, and the light guide plate can be used for more types, a wider range of electric decoration, POP (POP advertisement), and the like.

Here, as the plasticizer, phthalate ester, specifically, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), di-2-ethylhexyl phthalate (DOP (DEHP)) ), Di-normal octyl phthalate (DnOP), diisononyl phthalate (DINP), dinonyl phthalate (DNP), diisodecyl phthalate (DIDP), phthalic acid mixed ester (C _{6 to} C ₁₁ ) (610P, 711P, etc.) And butylbenzyl phthalate (BBP). In addition to phthalate esters, dioctyl adipate (DOA), diisononyl adipate (DINA), di-normal alkyl adipate (C6, _{8, 10} ) (610A), dialkyl adipate (C7, ₉ ) ( 79A), dioctyl azelate (DOZ), dibutyl sebacate (DBS), dioctyl sebacate (DOS), tricresyl phosphate (TCP), tributyl acetylcitrate (ATBC), epoxidized soybean oil (ESBO), trimellitic acid Examples include trioctyl (TOTM), polyester, and chlorinated paraffin.

Further, the support member preferably has a transmittance of 80% or more.
By setting the transmittance of the support member to 80% or more, light emitted from the light source and not incident on the light incident surface of the light guide plate is transmitted, and the light guide plate 18 is transmitted from the first inclined surface 18b and the second inclined surface 18c side. Light can be incident. Thereby, the light emitted from the light source can be used more efficiently.
Here, the support member can be made of a material used for the above-described light guide plate, for example, so that the transparency can be 80% or more.

Furthermore, it is preferable that the support member has a shape for condensing incident light, that is, a shape having a lens effect for condensing transmitted light. In other words, it is preferable that the support member has a shape in which light incident from the light source side is collected and emitted to the central portion side of the light guide plate.
By condensing the light transmitted through the support member and emitting it to the central portion side of the light guide plate, the light can reach the central portion of the light guide plate.

  FIGS. 11 to 13 are views showing examples of support members each having a lens effect. Specifically, FIG. 11A is a schematic perspective view illustrating an example of the shape of the support member, and FIG. 11B is a cross-sectional view of FIG. FIG. 12A is a schematic perspective view illustrating another example of the shape of the support member, and FIG. 12B is a cross-sectional view of FIG. FIG. 13A is a schematic perspective view illustrating another example of the shape of the support member, and FIG. 13B is a cross-sectional view of FIG.

A support member 52 shown in FIGS. 11A and 11B has a shape that has the same cross-sectional shape perpendicular to a predetermined direction, and the cross-sectional shape of the support member 52 has a rectangular shape (rectangular shape) with one side as a curve 52a. It is. That is, the support member 52 has a cross-sectional shape formed by a curved line 52a that is concave with respect to the opposite side of one of the four sides of the rectangle, that is, curved away from the opposite side. The support member 52 is arranged such that one of two surfaces each constituted by two straight lines not facing the curve 52a is in contact with the light guide plate and the other is in contact with the reflection member (housing) in the cross section. Is fixed to the reflecting member.
The support member 52 is arranged such that the surface formed by the curve 52a faces the center of the light guide plate and the surface formed by the straight line 52b facing the curve 52a faces the light source, and is emitted from the light source. The light incident from the line segment side is emitted from the curve 52a side.
In this way, the support member is formed in a shape having a semi-cylindrical cross section, and light is emitted from the curve side, whereby the light incident on the support member can be condensed and emitted.

Next, the supporting member 54 shown in FIGS. 12A and 12B has a shape in which the cross-sectional shape perpendicular to the predetermined direction is the same, and the cross-sectional shape has a predetermined thickness at the apex other than the apex angle 54a. It has a substantially triangular shape. In other words, the support member 54 has a shape in which the shape of the cross section is a convex portion formed by two straight lines that are separated from a side facing a part of one of the four sides of the rectangle.
The support member 54 is arranged in such a direction that the surface formed by the triangular base 52b in the cross section faces the light source, and the two surfaces formed by the two sides forming the apex angle 54a face the center of the light guide plate. The light emitted from the light source and incident from the surface formed by the base 54b is emitted from two surfaces formed by the two sides forming the apex angle 54a. In addition, the support member 54 has an end corresponding to two apexes other than the apex angle 54a having a predetermined thickness, one end of which is in contact with the light guide plate, and the other end is a reflection member (housing). The light guide plate is fixed to the reflecting member.
As described above, the light incident on the support member can be condensed and emitted by making the support member have a substantially triangular cross section and emitting light from the apex side.

The support member 56 shown in FIGS. 13A and 13B has a shape in which a cross section perpendicular to a predetermined direction has the same shape, a cross section has a rectangular shape, and a prism is formed on one of the four sides. The shape 56a is formed.
The support member 56 is disposed such that the surface on which the prism 56a is formed is opposed to the center side of the light guide plate, and the surface opposite to the surface on which the prism 56a is formed is emitted from the light source. The light incident on the support member 56 is emitted from the surface on which the prism 56a is formed. Further, the support member 56 has two surfaces that are not opposed to the surface on which the prism 56a is formed, that is, one surface of the two surfaces that are in contact with the surface on which the prism 56a is formed is in contact with the light guide plate, The other surface is disposed in contact with the reflecting member (housing) and fixes the light guide plate to the reflecting member.
Thus, the light incident on the support member can be condensed and emitted also by forming the prism on the surface opposite to the surface facing the light source of the support member.

As described above, the support member is formed into a semi-cylindrical shape, a substantially triangular shape, and a shape in which a prism is formed on the surface, so that the light transmitted through the support member can be collected, emitted from the light source, and incident on the light incident surface. The light that was not incident on the can be delivered further. As a result, luminance unevenness can be generated, and the luminance at the central portion of the light guide plate can be prevented from decreasing.
Note that the shape of the support member having the lens effect is not limited to the above shape, and may be various shapes such as a collimator lens shape, a concave lens, and a convex lens.

In FIGS. 11 to 13, the surface of the support member in contact with the light guide plate and the surface of the support member in contact with the reflection member are parallel, but the surface of the support member in contact with the light guide plate is the same as that of the light guide plate. The shape is preferably the same as the shape of the inclined surface. Specifically, in the case of this embodiment, it is preferable to incline the surface of the support member that contacts the light guide plate at the same angle as the inclined surface.
That is, it is preferable that the support member has a shape that matches the light guide plate and the support member in contact with the light guide plate and the support member.
Thus, the light guide plate can be reliably supported by setting the surface of the support member on the side in contact with the light guide plate to have the same shape as the inclined surface (back surface) of the light guide plate.

Next, FIG. 14 is a schematic cross-sectional view showing another example of the planar illumination device.
The planar illumination device 80 shown in FIG. 14 has the same configuration as the planar illumination device 10 shown in FIG. 2 except for the shape of the light source 84. Therefore, the same reference numerals are given to the same constituent elements in both, and detailed description thereof will be omitted. Hereinafter, points peculiar to the planar illumination device 80 will be described mainly.

The planar lighting device 80 includes a lighting device body 82 including a light source 84, a light guide plate 18, and an optical member 20, and a housing 16 including a lower housing 22, an upper housing 24, a folding member 26, and a support member 28. .
Since each member of the housing | casing 16, the light-guide plate 18, and the optical member 20 are the same as each member of the planar illuminating device 10 mentioned above, description is abbreviate | omitted.

  The light source 84 includes a plurality of LED chips 86 and a light source support portion 88. The light source 84 has the same configuration as the light source 12 described above except for the size of the LED chip 86 and the light source support 41.

The LED chip 86 has a length in the direction perpendicular to the light emitting surface of the light emitting surface, that is, the length in the vertical direction in FIG. 14, the length in the short side direction of the first light incident surface 18d and the second light incident surface 18e. That is, the shape is longer than the length in the vertical direction in FIG.
Moreover, the light source support part 88 is a shape whose length in the direction perpendicular | vertical to a light-projection surface is longer than an LED chip.
As described above, the length of the light emitting surface of the LED chip in the direction perpendicular to the light emitting surface is longer than the length of the first light incident surface 18d and the second light incident surface 18e in the short side direction, and the light source emits light. By enlarging the surface, the amount of light emitted from the light source can be increased, and the luminance of the light emitted from the light emission surface can be further increased.

Here, when the LED chip of the light source is enlarged as in this embodiment, the transmittance of the support member is preferably 80% or more.
In this way, by setting the transmittance of the support member to 80% or more, even when the light emitting surface of the light source is made larger than the light incident surface of the light guide plate, the light that has not entered the light incident surface is removed from the support member. The light can be transmitted and incident on the light guide plate from the first inclined surface side and the second inclined surface side of the light guide plate.

  In this way, the LED chip of the light source is enlarged, that is, the length of the light emitting surface in the direction perpendicular to the light emitting surface is longer than the length of the first light incident surface 18d and the second light incident surface 18e in the short side direction. By making it long and further making the transparency of the support member 80% or more, the amount of light emitted from the light source can be increased, the light emitted from the light source can be used efficiently, and Light with high luminance can be emitted from the light emission surface.

  In this embodiment, the LED chips are arranged in a single row in the longitudinal direction of the light incident surface. However, as shown in FIG. 4D, the light emitting surface such as a configuration in which a plurality of LED arrays are stacked. When a plurality of LED chips are arranged in a direction perpendicular to the light emitting surface, the lengths of the LEDs at both ends in the direction perpendicular to the light emitting surface are longer than the lengths in the short side direction of the first light incident surface 18d and the second light incident surface 18e. The same effect can be obtained by using a long shape. That is, the length from the end to the end of the light emitting surface of the LED chips arranged on the light emitting surface is the length in the direction perpendicular to the light emitting surface of the light emitting surface of the light source.

  The planar lighting device according to the present invention has been described in detail above. However, the present invention is not limited to the above embodiment, and various improvements and modifications are made without departing from the gist of the present invention. May be.

For example, as a light source LED chip, a YAG fluorescent material is applied to the light emitting surface of a blue LED. However, the present invention is not limited to this, and a fluorescent material is arranged on the light emitting surface of another single color LED such as a red LED or a green LED. You may use the LED chip of the structure which carried out.
Moreover, the LED unit of the structure which combined three types of LED of red LED, green LED, and blue LED as a light source can also be used. In this case, white light can be obtained by mixing light emitted from the three types of LEDs.
Further, a semiconductor laser (LD) can be used instead of the LED.

It is a schematic perspective view which shows one Embodiment of the liquid crystal display device using the planar illuminating device which concerns on this invention. It is the II-II sectional view taken on the line of the liquid crystal display device shown in FIG. (A) is the III-III arrow directional view of the planar illuminating device shown in FIG. 2, (B) is BB sectional drawing of (A). (A) is a perspective view which shows schematic structure of the light source of the planar illuminating device shown in FIG.1 and FIG.2, (B) is sectional drawing of the light source shown to (A), (C) is It is a schematic perspective view which expands and shows one LED of the light source shown to (A), (D) is a front view which shows schematic structure of another example of a light source. It is a schematic perspective view which shows the shape of a light-guide plate. It is a diagram showing the results of measuring the relationship between _{Φ · N p · L G ·} K C and light use efficiency. It is a figure which shows the result of having measured the illumination intensity of the light inject | emitted from each light guide from which particle density differs, respectively. It is a figure which shows the relationship between light use efficiency, illumination intensity nonuniformity, and particle density. (A) is a schematic perspective view which shows the shape of a lower housing | casing, (B) is a schematic perspective view which shows the shape of an upper housing | casing, (C) is a schematic perspective view which shows the shape of a folding | turning member. It is. It is a graph which shows the result of having measured light utilization efficiency about the light guide plate of various different shapes, respectively. (A) is a schematic perspective view which shows an example of the shape of a supporting member, (B) is sectional drawing of (A). (A) is a schematic perspective view which shows another example of the shape of a supporting member, (B) is sectional drawing of (A). (A) is a schematic perspective view which shows another example of the shape of a supporting member, (B) is sectional drawing of (A). It is sectional drawing which shows schematic structure of another example of the planar illuminating device of this invention.

Explanation of symbols

2 Liquid crystal display device 4 Liquid crystal display panel 6 Drive unit 10, 80 Planar illumination device 14, 82 Illumination device body 14a Light exit surface 16 Case 17, 84 Light source 18 Light guide plate 18a Light exit surface 18b First inclined surface 18c Second Inclined surface 18d First light incident surface 18e Second light incident surface 20 Optical member unit 20a, 20c Diffusion sheet 20b Prism sheet 22 Lower housing 22a Bottom surface portion 22b Side surface portion 24 Upper housing 24a Opening portion 26 Folding members 28, 52, 54, 56 Support member 32 Power supply storage section 40, 86 LED chip 40a Light emitting surface 41, 88 Light source support section 42 Array support body 44 Fan

Claims (14)

A flat light exit surface that emits planar light, a light incident surface that is formed at an edge of the light exit surface, and enters light traveling in a direction parallel to the light exit surface; the light exit surface; Has a back surface formed on the opposite surface, and as the distance from the light incident surface increases, the light guide plate has a shape in which the thickness in the direction perpendicular to the light exit surface increases.
A light source disposed opposite to the light incident surface and causing light to enter the light incident surface;
A flat reflection member that is disposed on the back side of the light guide plate and reflects light emitted from the back surface;
A planar illumination device having a support member disposed between the light guide plate and the reflection member and supporting the light guide plate.   The planar illumination device according to claim 1, wherein the reflection member is arranged with a parallelism of the light guide plate with respect to the light exit surface of 0.3 mm or less.   The planar illumination device according to claim 1, wherein the reflecting member is arranged such that a surface of the light guide plate is substantially parallel to the light exit surface of the light guide plate.   The planar illumination device according to claim 1, wherein the support member has a transmittance of 80% or more.   The planar illumination device according to claim 1, wherein the support member is disposed in the vicinity of the light incident surface of the light guide plate.   The planar illumination device according to any one of claims 1 to 5, wherein the support member has a shape for condensing light incident from the light source side. Further, the housing has a box shape that covers the light guide plate and has an opening formed on the light exit surface side of the light guide plate.
The surface illumination device according to any one of claims 1 to 6, wherein a surface of the housing facing the back surface of the light guide plate is the reflective member.   The planar lighting device according to claim 7, wherein the casing further includes a reflecting member formed on a surface perpendicular to the light exit surface. The light guide plate is
It includes a large number of scattering particles inside, the scattering cross section of the scattering particles is Φ, the density of the scattering particles is N _p , the correction coefficient is K _C , and the light guide surface from the light incident surface of the light guide plate in the light incident direction. when the length of the position to the thickness of the optical plate becomes thickest was _{L G,} the inequality _{1.1 ≦ Φ · N p · L} G · K C ≦ 8.2
0.005 ≦ K _C ≦ 0.1
The planar illumination device according to any one of claims 1 to 8, wherein: The light guide plate is
The light exit surface is rectangular;
The light incident surface is composed of a first light incident surface and a second light incident surface that are respectively formed on two opposite sides of the light exit surface;
The back surface is closest to the light emitting surface at the first light incident surface and the second light incident surface, and the light emitting surface at a midpoint of a line connecting the first light incident surface and the second light incident surface. The planar illumination device according to any one of claims 1 to 9, wherein the planar illumination device is configured by a farthest inclined surface. The light guide plate includes a plurality of scattering particles therein, the density of the scattering particles and N _p,
When the distance from the first light incident surface to the second light incident surface is L, the thickness at the first light incident surface is D1, and the thickness at the midpoint of the light guide plate is D2, the following inequality 27/100000 <( D2-D1) / (L / 2) <26/1000
0.04% wt <Np <0.25% wt
The planar illuminating device of Claim 10 which satisfies these. The light source includes a plurality of the LED chips and a support that supports the LED chips,
The planar lighting device according to claim 1, wherein the LED chips are arranged in a line on a surface of the support that faces the light incident surface.   The planar illumination device according to claim 12, wherein the light source has a length of a light emitting surface in a direction perpendicular to the light emitting surface longer than the light incident surface. A flat light exit surface that emits planar light, a light incident surface that is formed at an edge of the light exit surface, and enters light traveling in a direction parallel to the light exit surface; the light exit surface; Is provided with a back surface formed on the opposite surface, and is disposed to face the light incident surface and the light incident surface in a shape in which the thickness in the direction perpendicular to the light exit surface increases as the distance from the light incident surface increases. An illuminating device main body including a light source that makes light incident on the light incident surface;
Covering the outer periphery of the illuminating device main body, and having a shape in which an opening is formed on the light exit surface side of the light guide plate, and is configured with a housing that supports the illuminating device main body,
The planar lighting device, wherein a surface of the housing that faces the back surface is formed by a flat reflecting member that reflects light emitted from the back surface.

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