JP5110875B2 - Surface lighting device - Google Patents

Description

  The present invention relates to a planar illumination device having a light guide plate that diffuses light emitted from a light source and emits illumination light from a light exit surface, and more particularly, to a planar illumination device that illuminates indoors and outdoors, and a liquid crystal display device. The present invention relates to a planar lighting device used as a backlight for a backlight unit, an advertising panel, an advertising tower, or a signboard that illuminates a liquid crystal display panel.

  In the liquid crystal display device, a backlight unit that irradiates light from the back side of the liquid crystal display panel and illuminates the liquid crystal display panel is used. The backlight unit is configured using a light guide plate that diffuses light emitted from a light source for illumination and irradiates the liquid crystal display panel, or an optical member such as a prism sheet or a diffusion film.

  At present, a backlight unit of a large-sized liquid crystal television is mainly a so-called direct type in which an optical member such as a diffusion plate is disposed immediately above a light source for illumination without a light guide plate. In this system, a plurality of cold-cathode tubes, which are light sources, are arranged on the back surface of the liquid crystal display panel, and a uniform light quantity distribution and necessary luminance are ensured with the inside as a white reflecting surface.

  However, in the direct type backlight unit, in order to make the light quantity distribution uniform, the thickness in the direction perpendicular to the liquid crystal display panel needs to be a predetermined thickness, for example, about 30 mm. In the future, a thinner backlight unit will be desired. However, it is considered that it is difficult to realize a backlight unit having a thickness of 10 mm or less, for example, with a direct type, which is thinner from the viewpoint of uneven light quantity. .

Therefore, a backlight unit using a light guide plate in which scattering particles for scattering light in a transparent resin are mixed has been proposed (see, for example, Patent Documents 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 such a planar illumination device, light emitted from a light source and entering the light-scattering light guide from a light incident surface propagates through the interior at a constant rate once or multiple scattering actions. Receive. 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, in addition to 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. A planar illuminating device having a light guide plate in a shape in which light guide plates in a shape having a tendency are put together is described.

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

Here, in the shape which has the tendency to reduce thickness as it leaves | separates from the incident position of a light source described in patent documents 1-4, or in the flat light guide plate, since there is a limit in the reach | attainment distance of light, it is large sized There is also a problem that there is a limit to the conversion.
Furthermore, 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 reach light to a position farther from the light source in order to increase the size. . That is, there is a problem that the planar illumination device cannot be increased in size, thickness, and weight.

In addition to a fluorescent tube such as a cold-cathode tube, a light-emitting diode (hereinafter also referred to as “LED”) can be used as a light source for causing light to enter the light guide plate of such a planar illumination device.
Since the LED can emit light with high directivity, the light incident on the light guide plate can be delivered to the back of the light guide plate by using the LED as a light source, and the planar lighting device can be enlarged. Can do. Furthermore, the configuration of the power supply can be simplified.

In addition, as an LED for emitting white light, a blue light emitting diode (hereinafter also referred to as “blue LED”) and a YAG (yttrium, aluminum, garnet) phosphor are combined, and blue light emitted from the blue light emitting diode is used. There exists a structure which converts into white light with a YAG fluorescent substance.
Thus, white light can be emitted with a simple configuration by combining a blue LED and a phosphor.
However, there is a problem that light emitted by combining such a blue LED and a phosphor has a low color temperature, and it is difficult to adjust the color temperature without reducing the light utilization efficiency. For this reason, there is a problem that the color temperature of the light emitted from the light exit surface of the planar illumination device is low and adjustment is difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a planar illumination device that solves the above-described problems based on the prior art, is thin, lightweight, can emit illumination light without uneven brightness, and can be increased in size. It is in.
Furthermore, in addition to the above object, another object of the present invention is to make it possible to efficiently use the light emitted from the light source and to further emit light with higher brightness from the light emitting surface. To provide an apparatus.
Another object of the present invention is to provide a planar illumination device that can emit light having a desired color temperature with a simple configuration and can increase the light utilization efficiency, in addition to the above object. is there.

In order to solve the above problems, the present invention includes a first light source and a second light source that are spaced apart from each other by a predetermined distance.
The first light source is disposed between the first light source and the second light source, faces the light exit surface, the first light source, includes a first light incident surface including one side of the light exit surface, and faces the second light source and the one side. A light guide plate having a second incident surface including opposite sides and a back surface formed to face the light exit surface,
The back surface of the light guide plate has a cross-section in a plane perpendicular to the one side, and the distance from the light exit surface increases as the distance from the first light incident surface and the second light incident surface toward the center increases. A surface formed by a curve in which the inclination angle with respect to the light emission surface decreases toward the center from the first light incidence surface or the second light incidence surface, and the inclination angle with respect to the light emission surface becomes 0 degrees at the center. A illuminating device is provided.

また、前記一辺に垂直な面における前記導光板の前記背面の断面を表わす曲線の関数は、導関数が不連続点のない関数であることが好ましい。
また、前記導光板の前記背面は、前記一辺に垂直な面における断面が楕円の一部で表わされることが好ましい。 Here, it is preferable that the back surface of the light guide plate is represented by a part of a curve satisfying a high-order polynomial in a cross section in a plane perpendicular to the one side.
Moreover, it is preferable that the back surface of the light guide plate is represented by a part of a curve in which a cross section in a plane perpendicular to the one side satisfies the following formula (a _i , a _j , a _k , b _i , b _j , B _k are arbitrary real numbers, i, j, k are arbitrary natural numbers, and S _i , S _j , S _k are set to −1 ≦ S _i ≦ 1, −1 ≦ S _j ≦ 1, −1 ≦ S. _A real number satisfying _k ≦ 1 is assumed, and n ₁ , n ₂ , and n ₃ are arbitrary natural numbers.)

Moreover, it is preferable that the function of the curve showing the cross section of the said back surface of the said light-guide plate in the surface perpendicular | vertical to the said side is a function with which a derivative does not have a discontinuity point.
Moreover, it is preferable that the back surface of the light guide plate is represented by a part of an ellipse in a section perpendicular to the one side.

In addition, the back surface of the light guide plate has a cross-section in a plane perpendicular to the one side perpendicular to the light exit surface and a straight line passing through an intermediate point between the first light incident surface and the second light incident surface. Is preferably a symmetrical shape.
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. When the length from the first or second light incident surface to the position where the thickness of the light guide plate is the thickest is L _G , the inequality 1.1 ≦ Φ · N _p · L _G · K _C ≦ 8 .2 and 0.005 ≦ K _C ≦ 0.1 are preferably satisfied.

Further, the light source includes at least one LED chip that emits blue light from the light emitting surface;
A phosphor coating part that is disposed between the light emitting surface of the LED chip and the light guide plate, converts blue light emitted from the light emitting surface into white light, and emits blue light emitted from the light emitting surface. It is preferable to have a fluorescent member provided with a blue light transmitting portion that emits blue light as blue light.

Here, it is preferable that the blue light transmitting portion is formed by a transparent film or an opening.
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.
Moreover, it is preferable that the said fluorescent member has the said several blue light transmissive part for every said light emission surface of the said one LED chip.
Furthermore, it is preferable that the fluorescent member is a single sheet-like member common to the plurality of LED chips. It is also preferable to provide the fluorescent member for each of the plurality of LED chips.
Further, when the entire area of the fluorescent member is Sa and the sum of the areas of all the blue light transmitting portions is Sap, the relationship between Sa and Sap is 0.05 ≦ Sap / Sa ≦ 0.40. It is preferable to satisfy.
The fluorescent member is preferably disposed in contact with the light emitting surface, and is preferably disposed in contact with the light incident surface.

  The light source has a light emitting surface longer than the length of an effective cross section of the light incident surface in a direction substantially orthogonal to the light exit surface on the edge side of the light incident surface on which the light incident surface is formed, and the light emitting surface It is preferable that the light guide plate is disposed so as to be opposed to the light incident surface and inclined at a predetermined angle with respect to a direction substantially orthogonal to the light emitting surface.

Furthermore, it is preferable that the light incident surface of the light guide plate is a plane substantially orthogonal to the light exit surface, and an effective cross section of the light incident surface corresponds to the substantially orthogonal plane, The light incident surface is a flat surface that is inclined so as to face the light emitting surface of the light source in a direction substantially orthogonal to the light emitting surface, and an effective cross section of the light incident surface is the surface of the light incident surface. It is also preferable to correspond to a cross section in a direction substantially perpendicular to the light exit surface at the center.
Moreover, it is preferable that the inclination | tilt angle with respect to the direction substantially orthogonal to the said light-projection surface of the light emission surface of the said light source is 15 to 90 degree | times.

  Further, it is preferable that the light guide plate further includes a guide reflection plate that is disposed on the light exit surface side and the inclined surface side of the light incident surface of the light guide plate and guides the light emitted from the light source to the light incident surface. The guide reflection plate is attached to an end portion of the light guide surface of the light guide plate, and is attached to an end portion of the inclined surface of the light guide plate. It is further preferable to have a second guide reflector having an extended portion that is extended to the first guide reflector.

  Alternatively, the light guide plate is a light exit surface that emits planar light, an angle formed with the light exit surface is inclined at an angle greater than 90 °, and a side surface formed at an edge of the light exit surface, A light incident surface that is formed on the opposite side of the light emission surface and is inclined so as to move away from the light emission surface as the distance from the side surface increases. A shape having a surface is also preferable.

According to the present invention, the light guide plate is shaped so that the thickness in the direction perpendicular to the light exit surface increases as the distance from the light entrance surface increases, so that the light incident from the light entrance surface can be delivered farther and thinner. In addition, the light exit surface can be enlarged.
Further, the shape of the back surface is formed by a curve in which the inclination angle with respect to the light emission surface decreases as it goes from the first light incidence surface or the second light incidence surface to the center, and the inclination angle with respect to the light emission surface becomes 0 degrees at the center. By doing so, the light utilization efficiency can be further increased.
In addition, the luminance distribution of light emitted from the light exit surface can be changed to a bell shape.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a planar illumination device according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a perspective view showing an embodiment of a planar illumination device according to the present invention, FIG. 2 is a cross-sectional view taken along the line II-II of the planar illumination device shown in FIG. 1, and FIG. It is an expanded sectional view which expands and shows a part of planar lighting apparatus shown in FIG.
As shown in each figure, the planar illumination device 10 is disposed between the light source 12, the illumination device body 14 that emits uniform light from the rectangular light exit surface 14a, and the light source 12 and the illumination device body 14. The fluorescent member 17 is provided, and the housing 16 that houses the light source 12, the illumination device main body 14, and the fluorescent member 17 is provided. The casing 16 is composed of a lower casing 16a and an upper casing 16b as will be described later.

First, the light source 12 will be described.
4A is a schematic perspective view showing a schematic configuration of the light source 12 of the planar illumination device 10 shown in FIGS. 1 and 2, and FIG. 4B is a diagram of the light source 12 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 12 shown in FIG.
As shown in FIG. 4A, the light source 12 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 light emitting diode chip that emits blue light, and has a light emitting surface 40a having a predetermined area, and emits blue light from the light emitting surface 40a. Here, examples of the LED chip 40 include a GaN-based light emitting diode and an InGaN-based light emitting diode. Here, in the present invention, the blue light is light having a peak wavelength of emitted light of 420 nm to 500 nm, and the light emitting diode that emits blue light is light having a peak wavelength of emitted light of 450 nm to 480 nm. It is preferable to use an emitting light emitting diode.

  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 a line where the surface 18d intersects or a line where the 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 array substrate 42 supports the LED chip 40 on a side surface that is a 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.
In addition, the heat sink is not limited to the air cooling method, and a cooling member using a refrigerant using heat of vaporization such as a water cooling method or a heat pipe 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 whose length in the direction orthogonal to the arrangement direction is shorter than the length of the LED chip 40 in the arrangement direction, 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.

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

Here, as shown in FIGS. 2 and 3, the LED chip 40 and the array substrate 42 are arranged so as to be inclined at a predetermined angle with respect to a direction perpendicular to a light exit surface 18 a of the light guide plate 18 described later. That is, the LED chip 40 is arranged in a direction in which the light emitting surface 40a is inclined at a predetermined angle with respect to a direction perpendicular to a light emitting surface 18a of the light guide plate 18 described later.
This point will be described in detail later.

Next, the fluorescent member 17 will be described.
5A to 5C are views showing a part of the fluorescent member and the light source of the planar illumination device shown in FIG. 2, respectively. FIG. 5A is a top view, and FIG. 5B is a front view. , (C) is a side view.
As shown in FIGS. 5A to 5C, the fluorescent member 17 is a sheet-like member, and is disposed in contact with the light emitting surface 40 a of the LED chip 40 of the light source 12. That is, the fluorescent member 17 is in contact with the light emitting surface 40a at a portion facing the light emitting surface 40a of the LED chip 40 of the light source 12. Here, the arrangement method of the fluorescent member 17 is not particularly limited. For example, the fluorescent member 17 may be adhered to the light emitting surface 40a with an adhesive or the like, or may be fixed in contact with the light emitting surface 40a with a fixing member or the like.

  The fluorescent member 17 is a sheet-like member having a size that covers the light emitting surfaces 40 a of all the LED chips 40 arranged on the array substrate 42, and includes a fluorescent material applying portion 48 and an opening portion 50. In other words, the fluorescent member 17 is basically formed of the phosphor coating portion 48, and rectangular openings 50 are formed at predetermined intervals. That is, the part other than the opening 50 of the fluorescent member 17 is a phosphor coating part 48 formed of a fluorescent material.

The phosphor coating part 48 is made of a YAG (yttrium / aluminum / garnet) phosphor. When the blue light emitted from the LED chip 40 is transmitted through the phosphor coating unit 48, the YAG-based fluorescent material fluoresces.
In this way, when the blue light emitted from the LED chip 40 is transmitted, the phosphor applying unit 48 is configured to emit blue light emitted from the LED chip 40 and light emitted by the YAG-based fluorescent substance being fluorescent. Generate white light. That is, the light emitted from the LED chip 40 and transmitted through the phosphor coating portion 48 changes from blue light to white light. In other words, the phosphor application unit 48 converts the transmitted blue light into white light.

  The openings 50 are rectangular openings, and as described above, a plurality of openings 50 are formed in a matrix at regular intervals on the sheet-like fluorescent member 17. The opening 50 emits blue light emitted from the LED chip 40 as blue light. That is, the light emitted from the LED chip 40 and transmitted through the opening 50 is emitted as blue light as it is.

  As described above, the fluorescent member 17 includes two regions, a region that converts the blue light configured by the phosphor coating portion 48 into white light and a region that transmits the blue light configured by the opening 50 as blue light. Have.

Here, the fluorescent member 17 having the phosphor application part 48 and the opening 50 is formed by, for example, applying a fluorescent material on the entire surface of the transparent sheet to form the phosphor application part on the entire transparent sheet, It can be created by cutting out the part.
As another example, a phosphor coating portion may be created by cutting out a portion to be an opening of a transparent sheet and forming the opening, and then applying a fluorescent material to the transparent sheet.

Next, the lighting device main body 14 will be described in detail.
As shown in FIG. 2, the illumination device main body 14 basically includes a light guide plate 18, an optical member 22, a reflection plate 24, an upper guide reflection plate 34, and a lower guide reflection plate 36.

First, the light guide plate 18 will be described.
As shown in FIG. 2, the light guide plate 18 has a substantially rectangular flat light emission surface 18a and two light incidents formed on both ends of the light emission surface 18a substantially perpendicular to the light emission surface 18a. The first light incident surface 18d and the second light incident surface 18e are parallel to the first light incident surface 18d and the second light incident surface 18e (the first light incident surface 18d and the second light incident surface 18e). The back surface 18b formed symmetrically with respect to the bisector α (see FIG. 1) that bisects the light exit surface 18a (in parallel with the side in contact with the first or second light incident surface 18d or 18e). And have.
The back surface 18b of the light guide plate 18 has a cross section perpendicular to the bisector α, that is, a cross section perpendicular to the light exit surface and perpendicular to the light entrance surface, in other words, a tangent line between the light exit surface and the light entrance surface. In the vertical cross section, the distance from the light exit surface 18a increases from the first light incident surface 18d or the second light incident surface 18e toward the bisector α (central portion), and the first light incident surface 18d. Alternatively, as it goes from the second light incident surface 18e toward the central portion, the inclination angle with respect to the light exit surface 18a (the inclination angle of the tangent line on the back surface at each position) decreases, and the inclination angle is 0 degree at the central portion. .

That is, the light guide plate 18 is arranged such that the distance from the light exit surface 18a increases (increases) as the distance from the first light incident surface 18d and the second light incident surface 18e increases. The thickness in the direction perpendicular to the light exit surface of the light guide plate increases from the two light incident surfaces 18e toward the center of the light guide plate. That is, the light guide plate 18 has the thinnest thickness at both ends, that is, the first light incident surface 18d and the second light incident surface 18e, and has the maximum thickness at the center, that is, at the position of the bisector α. .
Further, the back surface 18b is convex in a direction away from the light exit surface 18a, and the central portion of the light guide plate becomes the apex, and the inclination becomes gentle as it goes from the end surface to the central portion. Is formed by a curve in which the angle between the tangent line and the light exit surface is small. Further, the tangent line on the back surface in the central portion of the light guide plate is parallel to the light exit surface.
Note that the shape of the cross section perpendicular to the bisector α of the light guide plate 18 is the same at any position of the bisector α.

  Further, the above-described light source 12 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, the planar illumination device 10 is arranged so that the two light sources 12 sandwich the light guide plate 18. In other words, the light guide plate 18 is disposed between the two light sources 12 disposed to face each other with a predetermined distance therebetween.

  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. After passing through the inside of the light plate 18 and reflected directly or by the back surface 18b, the light is emitted from the light exit surface 18a. At this time, some light may leak from the back surface 18 b, but the leaked light is reflected by the reflecting plate 24 covering the back surface 18 b of the light guide plate 18 and enters the light guide plate 18 again. The reflector 24 will be described 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 uniform illumination light with little unevenness in brightness 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 (the length to the position of the bisector L), 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, it is possible to emit illumination light that is uniform and has less unevenness in brightness from the light exit surface 18a.

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) ··· formula (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 this invention, it is estimated that a brightness | luminance and illumination intensity 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 .
Irradiance unevenness [(I _Max −I _Min ) / I when the maximum illuminance of light emitted from the side wall of the light guide plate having the measured illuminance distribution is I _Max , the minimum illuminance is I _Min , and the average illuminance is I _{Ave Ave} ] × 100 [%] was calculated.
FIG. 7 shows the relationship between the calculated illuminance unevenness and the particle density. In FIG. 7, the vertical axis represents illuminance unevenness [%], and the horizontal axis represents particle density [pieces / m ³ ]. FIG. 7 also shows the relationship between the light utilization efficiency and the particle density, where the horizontal axis is similarly the particle density and the vertical axis is the light utilization efficiency [%].

As shown in FIG. 7, when the particle density is increased, that is, Φ · N _p · L _G · K _C is increased, the light use 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 22 will be described.
The optical member unit 22 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, it has three diffusion films (diffusion sheets) 22a, 22b and 22c for diffusing the illumination light emitted from the light exit surface 18a of the light guide plate 18 to reduce uneven brightness. .

  The three diffusion films 22a, 22b, and 22c are laminated on the light emission surface 18a of the light guide plate 18 in this order from the light emission surface 18a side.

Here, since the diffusion films 22a, 22b, and 22c are the same sheet-like members, the diffusion film 22a will be described as a representative.
The diffusion film 22a is formed by imparting light diffusibility to a film-like member. The film-like member is optically transparent, such as PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, or COP (cycloolefin polymer). Can be formed into a material.

Although the manufacturing method of the diffusion film 22a is not particularly limited, for example, the surface of the film-like member is subjected to surface roughening by fine unevenness processing or polishing to impart diffusibility, or silica, titanium oxide that scatters light on the surface, It can be formed by coating a pigment such as zinc oxide or beads such as resin, glass or zirconia together with a binder, or kneading the pigment or beads in the transparent resin. In addition, it is possible to use a material having high reflectance and low light absorption, for example, using a metal such as Ag or Al.
In the present invention, as the diffusion film 22a, a mat type or coating type diffusion film can be used.

  In the present embodiment, the optical member unit is composed of three diffusion films 22a, 22b, and 22c. However, the present invention is not limited thereto. For example, as the optical member, in addition to or in place of the above-described diffusion film, A prism sheet that is formed by arranging a plurality of elongated prisms in parallel with each other on the surface of a transparent sheet, and can improve the brightness by improving the condensing property of light emitted from the light exit surface of the light guide plate 18; 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 also be used.

The configuration of the optical member and the number of each member are not particularly limited, and various optical members can be used 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. For example, a configuration in which a prism sheet is disposed between two diffusion films, a configuration in which a diffusion film, a prism sheet, and a transmittance adjusting member are stacked one by one can be used. Further, the arrangement order is not particularly limited.
In addition, the prism sheet may be disposed such that the apex of each prism of the prism sheet faces the light exit surface 18a of the light guide plate 18 or vice versa. As another aspect, the second prism sheet having the same structure is arranged on the first prism sheet so that the prism of the second prism sheet intersects the prism of the first prism sheet. Also good. Furthermore, another prism sheet having a configuration in which a large number of triangular pyramid (pyramid) prisms are arranged on the transparent sheet surface can be used.

Next, the reflecting plate 24 of the lighting device main body will be described.
The reflection plate 24 has a shape corresponding to the back surface of the light guide plate 18, that is, the back surface 18b of the light guide plate 18, and is formed so as to cover the back surface 18b. That is, the reflection plate 24 is arranged on the back surface 18 b side of the light guide plate 18 in a shape along the back surface 18 b of the light guide plate 18.
The reflection plate 24 is formed of a member that reflects light, reflects light leaking from the back surface 18 b of the light guide plate 18, and makes it incident on the light guide plate 18 again.
As described above, the reflector 24 is disposed so as to face the back surface 18b of the light guide plate 18, and the light leaked from the back surface 18b of the light guide plate 18 is reflected and incident on the light guide plate 18, thereby improving the light utilization efficiency. Can be made.

  The reflection plate 24 may be formed of any material as long as it can reflect light leaking from the back surface 18b of the light guide plate 18, for example, a filler is kneaded into PET or PP (polypropylene) and then stretched. Resin sheet with increased reflectivity by forming voids, a sheet with a mirror surface formed by vapor deposition of aluminum on the surface of a transparent or white resin sheet, a resin sheet carrying a metal foil or metal foil such as aluminum, or sufficient on the surface It can be formed of a thin metal plate having excellent reflectivity.

The upper guide reflection plate 34 is disposed between the light guide plate 18 and the diffusion film 22a, that is, on the light emission surface 18a side of the light guide plate 18, and the end portions (first light incident) of the light source 12 and the light emission surface 18a of the light guide plate 18. The end portion on the surface 18d side and the end portion on the second light incident surface 18e side) are disposed so as to cover each other. In other words, the upper guide reflection plate 34 is disposed so as to cover a part of the light exit surface 18a of the light guide plate 18 to a part of the array substrate 42 of the light source 12 in a direction parallel to the optical axis direction. That is, the two upper guide reflectors 34 are disposed at both ends of the light guide plate 18, respectively.
The lower guide reflection plate 36 is disposed on the opposite side of the light guide plate 18 from the light exit surface 18a side, that is, on the back surface 18b side so as to cover a part of the light source 12. In addition, the end portion of the lower guide reflection plate 36 on the center side of the light guide plate is connected to the reflection plate 24.
Here, as the upper guide reflector 34 and the lower guide reflector 36, various materials used for the reflector 24 described above can be used.

Thus, by arranging the upper guide reflection plate 34, it is possible to prevent the light emitted from the light source 12 from leaking to the light exit surface 18 side without entering the light guide plate 18.
Thereby, the light emitted from the LED chip 40 of the light source 12 can be efficiently incident on the first light incident surface 18d and the second light incident surface 18e of the light guide plate 18, and the light use efficiency can be improved. it can.
Similarly, the lower guide reflection plate 36 can prevent light emitted from the light source 12 from leaking to the back surface 18 b side of the light guide plate 18 without entering the light guide plate 18.
Thereby, the light emitted from the LED chip 40 of the light source 12 can be efficiently incident on the first light incident surface 18d and the second light incident surface 18e of the light guide plate 18, and the light use efficiency can be improved. it can.

  Here, the upper guide reflector 34 and the lower guide reflector 36 reflect the light emitted from the light source 12 toward the first light incident surface 18d or the second light incident surface 18e, and the light emitted from the light source 12. Can be incident on the first light incident surface 18d or the second light incident surface 18e, and the shape and width thereof are not particularly limited as long as the light incident on the light guide plate 18 can be guided to the center side of the light guide plate 18.

Next, the housing 16 will be described.
The housing 16 houses and supports the light source 12 and the lighting device main body 14, and basically includes a lower housing 16a, an upper housing 16b, and a folding member 16c.
The lower housing 16a has a shape having an open top surface and a bottom surface portion and side surfaces provided on four sides of the bottom surface portion and perpendicular to the bottom surface portion. That is, it is a substantially rectangular parallelepiped box shape with one surface open.
As shown in FIG. 2, the lower housing 16 a supports the illumination device main body 14 accommodated from above with a bottom surface portion and a side surface portion, and a surface other than the light emission surface 14 a of the illumination device main body 14, that is, illumination. It covers the surface opposite to the light exit surface 14a of the apparatus body 14, that is, the back surface 18b and the side surface.

The upper housing 16b has a rectangular parallelepiped box shape in which a rectangular opening smaller than the rectangular light emission surface 14a of the lighting device body 14 serving as the opening 28 is formed on the upper surface, and the lower surface is opened.
As shown in FIG. 2, the upper housing 16b includes the lighting device main body 14 and the lower housing 16a in which the lighting device main body 14 is accommodated from above the planar lighting device main body 14 and the lower housing 16a (part 4). It is placed so as to cover the other side.

The folding member 16c has a concave (U-shaped) shape in which the shape of the cross section perpendicular to the predetermined direction is always the same. 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 16 c 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 portion 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 16a and the folding member 16c, and a method for joining the upper housing 16b and the folding member 16c, 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 16c 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 a light guide plate that is likely to warp is used, 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.

In the planar illumination device 10 of the present embodiment, a light guide plate support 30 is further disposed between the lower housing 16a and the reflection plate 24. The light guide plate support 30 is made of a resin such as polycarbonate, and is in contact with the lower housing 16 a and the reflection plate 24.
By providing the light guide plate support portion 30, the light guide plate 18 can be prevented from shifting in the housing 16, and the reflector 24 can be brought into close contact with the back surface 18 b of the light guide plate 18.
A power storage unit 32 (see FIG. 1) that stores a power source (not shown) of the light source 12 is attached to the back side of the lower housing 16a.
The planar illumination device 10 is basically configured as described above.

The planar illumination device 10 emits blue light from the light emitting surface 40 a of the LED chip 40. The blue light emitted from the light emitting surface 40a of the LED chip 40 is transmitted through the fluorescent member 17 to be converted into white light, and then the first light incident surface 18d or the second light incident surface 18e of the light guide plate 18. Is incident on.
The light incident from the first light incident surface 18d or the second light incident surface 18e passes through the light guide plate while being scattered by the scatterer as described above, and is reflected directly or by the back surface 18b, and then the light exit surface. Ejected from 18a. Further, a part of the light leaked from the back surface 1b is reflected by the reflecting plate 24, enters the light guide plate 18 again, and is emitted from the light emitting surface 18a.
In this way, the light emitted from the light exit surface 18a passes through (passes through) the optical member 22 such as the diffusion film 22a and is emitted from the light exit surface 14a.

  In this way, the light guide plate 18 of the planar illumination device 10 is formed into a shape in which the thickness in the direction perpendicular to the light exit surface 18a increases as the distance from the first light incident surface 18d or the second light incident surface 18e increases. Light incident from the light incident surface 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 far position, the light guide plate can be made thin and the light exit surface can be made large. Thereby, a planar illuminating device can be reduced in thickness, size, and weight.

  Furthermore, the back surface has a shape in which the cross-section in the direction perpendicular to the bisector α becomes a curve whose inclination angle becomes smaller as it goes from the end to the center (bisector). The efficiency can be increased, and further, light can be prevented from being excessively emitted at the end of the light exit surface, that is, near the first light incident surface or near the second light incident surface of the light exit surface, The occurrence of uneven brightness can be prevented.

Further, as in the present embodiment, the shape of the back surface is a curve that becomes a curve with a smaller inclination angle as the cross section in the direction perpendicular to the bisector α goes from the end to the center (bisector). In addition, by making the light guide plate symmetrical, the luminance distribution of light emitted from the light exit surface is a bell-shaped, that is, a brightness distribution that gradually increases in brightness toward the center, and the center of the light exit surface The luminance of the part can be maximized.
By making the luminance distribution of the light emitted from the light emitting surface into a bell shape, the difference in luminance between the central portion and the peripheral portion is visually felt, and it appears that uniform light is emitted from the light emitting surface. Thereby, 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, in the present invention, the luminance distribution is a bell-shaped distribution. The average luminance of light emitted from the vicinity of the light incident portion of the light exit surface (excluding the portion where the luminance near the light incident portion pole rapidly rises and falls) When the average illuminance) is 1.0, it means a luminance distribution (illuminance distribution) in which the average luminance (average illuminance) of light emitted at the center of the light exit surface is 1.05 to 1.50. .

Here, it is preferable that the back surface of the light guide plate has a shape in which a cross section in a plane perpendicular to the bisector α is represented by a high-order polynomial, specifically, a part of a curve satisfying the following formula (5). In Expression (5), a ₀ and a _i are arbitrary real numbers, and n is an arbitrary natural number (positive integer).

More specifically, the back surface of the light guide plate is a shape represented by a part of a curve whose cross section perpendicular to the bisector α satisfies the following formula (6), that is, a part of an ellipse or a higher-order ellipse. It is preferable that it is the shape represented by these. In Expression (6), a _n and b _n are arbitrary real numbers, and n is an arbitrary natural number.

Further, the back surface of the light guide plate is represented by a shape in which a cross section in a plane perpendicular to the bisector α is represented by a part of a curve satisfying the following formula (7), that is, a hyperbola or a part of a higher-order hyperbola. It is also preferable that it has a shape. In Expression (7), a _n and b _n are arbitrary real numbers, and n is an arbitrary natural number.

In addition, the back surface of the light guide plate has a shape in which a cross section in a plane perpendicular to the bisector α is represented by a part of a curve satisfying the following formula (8), that is, a quadratic function or a 2 ^nth order function. It is also preferable that the shape is expressed in parts. In Expression (8), a _n is any real number, n is an arbitrary natural number.

In addition, the back surface of the light guide plate has a shape in which a cross section in a plane perpendicular to the bisector α is represented by a part of a curve satisfying the following formula (9), that is, a combination of two or more higher-order elliptic functions. A shape represented by a part of a curve is also preferable. In Equation (9), a _n and b _n are arbitrary real numbers, n is an arbitrary natural number (n ≦ 2), C is an arbitrary constant, and S _i is −1. ≦ S _i ≦ 1 is a real number.

Further, the back surface of the light guide plate has a shape in which a cross section in a plane perpendicular to the bisector α is represented by a part of a curve satisfying the following formula (10), that is, a combination of two or more higher-order hyperbolic functions. A shape represented by a part of a curve is also preferable. In Expression (10), a _n and b _n are arbitrary real numbers, n is an arbitrary natural number (n ≦ 2), C is an arbitrary constant, and S _j is −1. ≦ S _i ≦ 1 is a real number.

In addition, the back surface of the light guide plate has a shape in which a cross section in a plane perpendicular to the bisector α is represented by a part of a curve satisfying the following formula (11), that is, two or more 2 ^i- order functions are combined. That is, it is also preferable to have a shape represented by a part of a curve obtained by combining two or more even functions. In the equation (11), _{a n} is any real number, n is an arbitrary natural number (n ≦ 2), _{S j} is a real number satisfying -1 ≦ _{S i} ≦ 1.

Further, the back surface of the light guide plate has a shape in which a cross section in a plane perpendicular to the bisector α satisfies the following formula (12), that is, an ellipse, a higher-order ellipse, a hyperbola, a higher-order It is also preferable to have a shape represented by a part of a curve obtained by selectively combining a hyperbola and a 2 ⁱ degree function. In Equation (12), a _i , a _j , a _k , b _i , b _j , b _k are arbitrary real numbers, i, j, k are arbitrary natural numbers, and S _i , S _j , S _k Is a real number that satisfies −1 ≦ S _i ≦ 1, −1 ≦ S _j ≦ 1, −1 ≦ S _k ≦ 1, and n ₁ , n ₂ , and n ₃ are arbitrary natural numbers (positive integers).

Thus, by making the cross section of the back surface in the plane perpendicular to the bisector α of the light guide plate into a shape represented by a part of the curve satisfying any one of the expressions (6) to (12), The utilization efficiency can be increased, and the luminance distribution of the emitted light can be easily made into a bell shape.
In particular, the shape of the back surface of the light guide plate that is represented by a part of a curve in which a cross section in a plane perpendicular to the bisector α satisfies the following formula (9), that is, a curve that combines at least one elliptic function In the case of the shape represented by a part, in addition to the above effects, an increase in luminance near the light incident portion can be suppressed. As described above, since the increase in luminance in the vicinity of the light incident portion can be suppressed, the light emitted from the light source can be used more efficiently.
Moreover, the design of the back surface of the light guide plate can be facilitated by adopting a shape that combines one symmetrical function or a plurality of symmetrical functions.

Moreover, it is preferable that the function representing the curve of the cross section of the back surface in the plane perpendicular to the bisector α of the light guide plate is a function whose derivative has no discontinuity. That is, it is preferable that the curve on the back surface of the light guide plate has a smooth curve shape without discontinuities.
In this way, by making the back surface of the light guide plate a curved shape whose derivative is represented by a function without discontinuities, the light reflected from the back surface is concentrated at a predetermined position, or the light does not reach only at a predetermined position. It is possible to prevent the occurrence of luminance unevenness due to bright lines, dark lines, etc. in the light emitted from the light exit surface.

Furthermore, it is preferable that the back surface has a shape connected to the light incident surface (the first light incident surface or the second light incident surface) without any discontinuity. That is, it is preferable that the inclination angle of the back surface at the connection portion with the light incident surface is the same angle as the angle of the light incident surface.
Thereby, it is possible to prevent the incident light from being irregularly reflected at the connection portion. In addition, by increasing the tilt angle on the light incident surface side of the back surface, it is possible to suppress an increase in brightness near the light incident surface, to increase the light at the center of the light guide plate, and to use light efficiently. That is, the ratio of the light emitted from the light exit surface to the light emitted from the light source can be increased.

Hereinafter, the surface illumination device will be described in more detail with specific examples.
FIG. 8 is a cross-sectional view illustrating an example of the light guide plate.
In this embodiment, as shown in FIG. 8, the light guide plate, the optical axial length, i.e. the length L _a from the first light entrance plane 18d to the second light entrance plane 18e and 480 mm, the first light The length in the direction perpendicular to the light exit surface of the entrance surface and the second light entrance surface, that is, the thickness d1 of the thinnest portion is 2 mm, and the light is emitted from the light exit surface to the back surface at the bisector α. The length, that is, the thickness D of the thickest part was 4 mm. Furthermore, the back surface of the light guide plate has a shape represented by a part of an ellipse.
More specifically, the back surface of the light guide plate is on a line passing through the bisector α of the light guide plate and perpendicular to the light exit surface in a cross section perpendicular to the bisector α, and the back surface 18b from the light exit surface 18a. an origin point which is 1.8mm move to the side, a direction parallel to the light exit plane to the X-axis, a direction perpendicular to the Y ^{axis, (x 2/241 2)} + (y 2 /2.2 2) = The ellipse represented by 1 has a negative y coordinate (0 <y) and an x coordinate having a curve of −240 to 240 (−240 ≦ x ≦ 240).
As the optical member, three diffusion sheets were used as shown in FIG.
The luminance distribution of light emitted from the light exit surface of the planar illumination device having such a configuration was measured.

For comparison, the shape of the back surface in the cross section perpendicular to the bisector is inclined at a certain angle from the light incident surface toward the center, that is, the cross section perpendicular to the bisector on the back surface is light. The luminance distribution of the light emitted from the light exit surface of the planar lighting device using the light guide plate formed by two straight lines inclined at a predetermined angle with respect to the exit surface was also measured.
Here, the light guide plate as a comparative example has a length d1 of the first light incident surface and the second light incident surface in the direction perpendicular to the light exit surface of 2 mm, and the light exit surface at the bisector α from the rear surface. In addition, the length D, 4 mm, and the central portion of the back surface, that is, the connecting portion of the two straight lines, had a curved surface shape of R = 15000 [mm], and the two straight lines on the back surface were smoothly connected.

  The measurement results are shown in FIG. Here, in the graph of FIG. 9, the vertical axis represents the normalized luminance [a. u. The horizontal axis is the distance (light guide length) [mm] from one light incident surface of the light guide plate. Here, the normalized luminance is relative luminance with respect to an arbitrary reference value.

As shown in FIG. 9, it is understood that the luminance distribution of light emitted from the light exit surface can be a bell shape by making the back surface of the light guide plate part of an ellipse and the entire back surface curved. .
Moreover, it turns out that the whole brightness | luminance and the brightness | luminance of the center part of a light-projection surface can be made high, and light utilization efficiency can be made high by making the whole surface of a back surface into a curved surface shape.

Next, the surface illumination device (Example 1) using the light guide plate that can represent the shape of the back surface with a curve satisfying the equation (6), that is, a part of an ellipse, and the shape of the back surface with the equation (9) It is emitted from the light exit surface of the planar illumination device (Example 2, Example 3) using the light guide plate that can be represented by a curve satisfying the above, that is, a position part of a curve obtained by combining a plurality of higher-order elliptic functions. The illuminance distribution and average brightness of the light were measured.
In Example 1-3, the both light guide plate, the optical axis direction length, i.e. the length _{L a} from the first light entrance plane 18d to the second light entrance plane 18e and 480 mm, the first light entrance Surface, the length of the second light incident surface in the direction perpendicular to the light exit surface, that is, the thickness d1 of the thinnest portion is 2 mm, and the length from the light exit surface to the back surface at the bisector α That is, the thickness D of the thickest part was 4 mm. The light guide plate was formed by kneading and dispersing 0.05% of scattering particles having a particle diameter of 7 μm inside.

Furthermore, in Example 1, the back surface of the light guide plate is on a line passing through the bisector α of the light guide plate and perpendicular to the light exit surface in a cross section in which the shape of the back surface of the light guide plate is perpendicular to the bisector α, and to a point than the light exit surface 18a and 2mm moved to the back 18b side as the origin, the direction parallel to the light exit plane to the X-axis, a direction perpendicular to the Y ^{axis, (x 2/240 2)} + (y 2 / The shape of the ellipse represented by 2 ² ) = 1 is a curve having a negative y coordinate (0 <y) and an x coordinate of −240 to 240 (−240 ≦ x ≦ 240).

Next, in Example 2, the back surface of the light guide plate is on a line that passes through the bisector α of the light guide plate and is perpendicular to the light exit surface in a cross section in which the shape of the back surface of the light guide plate is perpendicular to the bisector α. and a point than the light exit surface 18a and 2mm moved to the back 18b side as an origin, a direction parallel to the light exit plane to the X-axis, a direction perpendicular to the Y ^{axis, 0.8 × {x 2/240} 2} in ^{+ (y 2/2 2)} } + 0.2 × {x 4/240 4} + (y 4/2 4)} = ellipse y-coordinate represented by 1 is negative (0 <y), and, x It was set as the shape from which a coordinate becomes a curve of -240-240 (-240 <= x <= 240).

Furthermore, in Example 3, the back surface of the light guide plate is on a line passing through the bisector α of the light guide plate and perpendicular to the light exit surface in a cross section in which the shape of the back surface of the light guide plate is perpendicular to the bisector α, and points than the light exit surface 18a and 2mm moved to the back 18b side as an origin, a direction parallel to the light exit plane to the X-axis, a direction perpendicular to the Y ^{axis, 0.9 × {x 2/240} 2} + ^{(y 2/2 2)}} + 0.1 × {x 4/240 4} + (y 4/2 4)} = ellipse y-coordinate represented by 1 negative by (0 <y), and, x-coordinate Is a shape having a curve of −240 to 240 (−240 ≦ x ≦ 240).

For comparison, the shape of the back surface in the cross section perpendicular to the bisector is inclined at a certain angle from the light incident surface toward the center, that is, the cross section perpendicular to the bisector on the back surface is light. The illuminance distribution and average luminance of the light emitted from the light exit surface of the planar illumination device using the light guide plate formed by two straight lines inclined at a predetermined angle with respect to the exit surface were also measured.
Here, in the light guide plate of Comparative Example 1, the length d1 of the first light incident surface and the second light incident surface in the direction perpendicular to the light emitting surface is 2 mm, and the light emitting surface at the bisector α is from the light emitting surface. The length to the back surface, D was 4 mm, and the center portion of the back surface, that is, the connecting portion of the two straight lines, had a curved surface shape of R = 25000 [mm], and the two straight lines on the back surface were smoothly connected. The light guide plate was formed by kneading and dispersing 0.05% of scattering particles having a particle diameter of 7 μm inside.
Further, as Comparative Example 2, the other configuration is the same as that of Comparative Example 1 except that the scattering particles kneaded and dispersed therein are 7 μm and 0.08% as the light guide plate. The illuminance distribution of light emitted from the light exit surface was also measured.
The measurement results are shown in FIG. Here, in the graph of FIG. 9, the vertical axis is the relative illuminance [lx], and the horizontal axis is the position [mm] from the center of the light guide plate (the position where the thickness of the light guide plate is the thickest).

As shown in FIG. 10, it can also be seen from Examples 1 to 3 that the luminance distribution of light emitted from the light exit surface can be a bell shape by making the entire back surface of the light guide plate a curved surface. .
Furthermore, as shown in Examples 2 and 3, by making the shape of the back of the light guide plate a shape that can be represented by a part of a curve combining higher-order elliptic functions, that is, a shape that satisfies Equation (9), It can be seen that the increase in the luminance of the light emitted from the vicinity of the light incident portion of the light exit surface can be suppressed.
In addition, as shown in Table 2, it can be seen that Examples 1 to 3 in which the entire back surface of the light guide plate has a curved shape can increase the light utilization efficiency by 5% or more compared to Comparative Example 1. It can also be seen that the average luminance can be increased.
From the above, the effects of the present invention are clear.

  Next, the planar illumination device 10 is provided with an opening 50 in a part of the fluorescent member 17 formed by the phosphor coating part 48 that converts blue light into white light, and is emitted from the light emitting surface 40 a of the LED chip 40. By emitting a part of the blue light to be emitted as blue light, light having a high color temperature can be emitted from the light emission surface of the light guide plate or the planar illumination device. That is, an opening is provided in a part of the fluorescent member arranged between the light incident surface (first light incident surface or second light incident surface) of the light guide plate and the light emitting surface of the LED, and the light emitted from the LED is Light that has a high color temperature is emitted from the light exit surface by transmitting the light that passes through some of the openings as blue light and converting the light that passes through the other phosphor coating parts into white light. Can do. In addition, the blue light and white light which permeate | transmitted the fluorescent member are mixed color by permeate | transmitting a light-guide plate after that.

  Further, since the ratio of the white light and the blue light transmitted through the fluorescent member 17 can be easily adjusted by changing the ratio of the openings 50 formed in the fluorescent member 17, the color temperature can be easily adjusted. Can be made. Accordingly, light having a desired color temperature can be emitted from the light exit surface of the light guide plate or the planar illumination device with simple adjustment. In addition, the color temperature can be easily adjusted rather than controlling the color temperature based on the thickness of the fluorescent material of the fluorescent member.

Here, the fluorescent member 17 has a relationship between Sa and Sap, where Sa is the total area of the fluorescent member 17 and Sap is the sum of the areas of the openings 50, that is, the sum of the areas of the blue light transmitting portions. It is preferable to satisfy 0.05 ≦ Sap / Sa ≦ 0.40.
By setting Sap / Sa to be 0.05 or more, the color temperature can be set to 7000K or more, and by setting it to 0.40 or less, the color temperature can be set to 35000K or less.

Hereinafter, it demonstrates in detail with a specific example.
In this specific embodiment, the luminance of light emitted from the light emitting surface 14a of the planar illumination device 10 in which the ratio of the sum Sap of the area of the blue light transmitting portion to the entire area Sa of the fluorescent member 17 is various values. Distribution and color temperature were measured.
FIG. 11 shows the ratio of the sum Sap of the area of the blue light transmitting portion to the total area Sa of the fluorescent member 17, that is, Sap / Sa is 0.05, 0.1, 0.15, 0.2, 0.25. It is a graph which shows the result of having measured the wavelength distribution (spectral spectrum) of the light inject | emitted from the light emission surface of a planar illuminating device when setting it as 0.3, 0.35, 0.4. Here, in the graph of FIG. 11, the vertical axis is the relative intensity, and the horizontal axis is the wavelength [nm].
FIG. 12 is a graph showing the relationship between the ratio (Sap / Sa) of the sum Sap of the area of the blue light transmitting portion to the total area Sa of the fluorescent member 17 and the color temperature of the light emitted from the light exit surface. is there. Here, in the graph of FIG. 12, the vertical axis is the color temperature [K], and the horizontal axis is the ratio (Sap / Sa) of the sum Sap of the area of the blue light transmitting portion to the entire area Sa of the fluorescent member 17.

As shown in FIG. 12, it can be seen that the color temperature of the light emitted from the light exit surface can be increased by forming the opening.
Furthermore, as shown in FIG. 12, it can be seen that the color temperature can be set to various values by changing Sap / Sa. Specifically, according to this embodiment, the color temperature is adjusted to about 7000 K or more and about 34000 K or less by adjusting the ratio of the opening to the entire fluorescent member between 0.05 ≦ Sap / Sa ≦ 0.40. It can be seen that any color temperature can be achieved. That is, it can be seen that the color temperature can be adjusted only by adjusting the size of the opening.
In addition, as shown in FIG. 11, it can be seen that the color of light emitted from the light exit surface can be adjusted by adjusting the ratio of the opening to the entire fluorescent member.
From the above, the effects of the present invention are clear.

Here, in this embodiment, although the opening part 50 of the fluorescent member 17 was made into the rectangular shape, it is not limited to this, It can be made into various shapes.
13A to 13C are front views showing other examples of the fluorescent member.
For example, as shown in FIG. 13A, the shape of the opening 62a of the fluorescent member 60a is circular, and the portion excluding the opening 62a of the fluorescent member 60a is very good at the phosphor coating portion 64a. Note that the shape of the opening is not limited to a circle, and may be various shapes such as an ellipse, a polygon, and a star.
Further, as shown in FIG. 13B, the shape of the opening 62b of the fluorescent member 60b is a bar shape parallel to one side of the light emitting surface, and the openings 62b are arranged at regular intervals, thereby opening the fluorescent member 60b. The part excluding the part 62b may be used as the phosphor application part 64b.
Furthermore, as shown in FIG. 13C, the shape of the opening 62c of the fluorescent member 60c may be an X-shape, and the portion excluding the opening 62c of the fluorescent member 60c may be a fluorescent material applying portion 64c.

Thus, the shape of the opening is not particularly limited, but it is preferable to provide a plurality of openings with respect to the light emitting surface of one LED chip. By providing a plurality of openings on the light emitting surface of one LED chip, it is possible to easily mix blue light and white light generated by being emitted from the LED chip and transmitted through the fluorescent member. Thereby, there is no color unevenness or color unevenness can be emitted from the light emitting surface, and light having a high color temperature can be emitted.
The area of one opening is preferably 0.1 mm ² or more and 0.5 mm ² or less. By setting the area of one opening to 0.1 mm ² or more, it is possible to reliably form the opening in the fluorescent member, and to emit blue light from the opening, and to 0.5 mm ² or less. The light transmitted through the fluorescent member can be efficiently and reliably mixed in color, and there is no color unevenness or color unevenness from the light emitting surface, and light with a high color temperature can be emitted.

  In the present embodiment, an opening is formed in a part of the fluorescent member, and this opening is a blue light transmitting portion that transmits blue light in a blue color. However, the present invention is not limited to this and is transparent. A fluorescent material is selectively applied to the sheet, and a fluorescent material coated portion and a transparent portion not coated with the fluorescent material are formed on the transparent sheet. It is good also as a blue light transmission part which permeate | transmits as it is.

Moreover, in the said embodiment, although the fluorescent member was arrange | positioned in the position which contacts the light emission surface 40a of the LED chip 40 of the light source 12, it is not limited to this, The light emission surface of LED and the light-incidence surface (1st of a light-guide plate) As long as it is between the light incident surface and the second light incident surface, it may be disposed at any position.
FIG. 14 is an enlarged cross-sectional view showing another example of the planar illumination device of the present invention.
Here, since the planar illumination device of the present embodiment is symmetrical with respect to the above-mentioned bisector, only one end portion of the light guide plate, that is, the end portion on the first light incident surface 18d side is shown. The description of the end on the second light incident surface 18e side is omitted, but the second light incident surface 18e side has the same configuration. The same applies to other examples of the planar illumination device described later.

As shown in FIG. 14, the fluorescent member 17 a may be disposed in contact with the first light incident surface 18 d of the light guide plate 18. Here, the fluorescent member 17a is preferably a sheet having a larger area or the same area as the first light incident surface 18d. By making the area of the first light incident surface the same as that of the fluorescent member 17a or increasing the area of the fluorescent member 17a, the light emitted from the LED chip 40 does not pass through the fluorescent member 17, and the light guide plate 18 It can prevent entering into the 1st light-incidence surface 18d.
As described above, when the fluorescent member 17a is arranged on the first light incident surface 18d of the light guide plate 18, a fluorescent material is directly applied to the first light incident surface 18d of the light guide plate 18 without using a transparent sheet. Thus, the fluorescent member 17a may be provided by forming the phosphor coating portion and the opening.
In any of the above embodiments, the fluorescent member is attached to the light guide plate or the light source. However, the fluorescent member may be a sheet-like independent member and may be arranged between the light emitting surface and the light emitting surface. .

Moreover, in the said embodiment, although the fluorescent member was made into the sheet | seat shape of 1 sheet, this invention is not limited to this, You may arrange | position a fluorescent member separately for every light emission surface of an LED chip.
FIGS. 15A to 15C are views showing a fluorescent member and a part of a light source, respectively, as another example of the planar illumination device. FIG. 15A is a top view, and FIG. (C) is a side view.
The fluorescent member 70 shown in FIGS. 15A to 15C is provided for each LED chip 40, and each fluorescent member 70 is provided in contact with the light emitting surface 40 a of the LED chip 40. In the present embodiment, the fluorescent member 70 is bonded to the light emitting surface 40a.
The fluorescent member 70 includes a phosphor coating portion 72 and an opening 74, and is provided so as to cover the entire light emitting surface 40a of the LED chip 40. The fluorescent member 70 is composed of a phosphor applying part 72 formed by applying a fluorescent substance, and an opening 74 formed as a circular opening having a predetermined diameter at predetermined intervals. That is, the fluorescent member 70 also has a phosphor coating portion 72 that is a region that converts blue light emitted from the LED chip 40 into white light, and an opening that is a region that emits blue light as blue light, that is, transmission of blue light. It consists of parts.

As described above, even when the fluorescent member 70 is provided for each LED chip 40, the light emitted from the light emitting surface 40 a can be emitted from the light emitting surface 40 a by arranging the fluorescent member 70 on the entire surface of the light emitting surface 40 a of the LED chip 40. It passes (passes) through the phosphor coating part 72 or the opening 74.
Thereby, as described above, part of the light emitted from the LED chip 40 can be incident as blue light, and light with a high color temperature can be emitted from the light emitting surface with a simple configuration.

In addition, when a fluorescent member is provided for each light emitting surface of the LED chip, the shape of the opening is not particularly limited, and the opening 74 may be circular as shown in FIG. ), The opening 78a of the fluorescent member 76a may be rectangular.
Further, since the fluorescent member can efficiently mix the emitted light and can emit light with no color unevenness from the light emitting surface, a plurality of transparent portions are provided on the light emitting surface 40a of one LED chip 40. However, as shown in FIG. 16B, one opening 78b may be provided for one light emitting surface 40a. In other words, one opening 78b may be provided for one fluorescent member 76b. Also in this case, the shape of the transparent portion is not particularly limited. In FIG. 16B, the opening 78b is rectangular, but as shown in FIG. 16C, the opening 78c of the fluorescent member 76c is formed. It is good also as a circle, It is not limited to this, It can be set as various shapes, such as an ellipse, a star shape, a polygon, and X shape.

Here, when the fluorescent member 70 is provided in contact with the light emitting surface of the LED as in the present embodiment, the fluorescent material is directly applied to the light emitting surface to form the phosphor coating portion and the opening. Good.
Thereby, the position shift of the fluorescent member 70 can be prevented, and furthermore, the fluorescent member can be formed without using a transparent sheet. Therefore, the member can be loosened, and the apparatus configuration can be simplified.

Next, as shown in FIGS. 2 and 3, the LED chip 40 and the array substrate 42 of the light source 12 of the planar illumination device 10 of the present embodiment are perpendicular to the light exit surface 18 a of the light guide plate 18 and are first. The light incident surface 18d or the second light incident surface 18e is disposed so as to be inclined at a predetermined angle θ with respect to a surface S (hereinafter also referred to as “reference surface S”) parallel to the side in the long side direction. Specifically, the light emitting surface 40 a of the LED chip 40 is arranged with an angle θ inclined with respect to the reference surface S. That is, the light emitting surface 40a is arranged at a position rotated by an angle θ from the reference surface S toward the light emitting surface 18a.
In this way, by arranging the light source 12 to be inclined, light emitted from the light source having a large light emitting surface can be efficiently incident on the light guide plate. By using the light source having a large light emitting surface, the light is emitted from the light source. The amount of light to be increased can be increased. In other words, high-intensity light can be emitted from the light emission surface of the light guide plate by efficiently making the light emitted from the light source having a large light emitting surface incident on the light guide plate.
In addition, by arranging the upper guide reflection plate and the lower guide reflection plate and reflecting the light emitted from the light source, the light emitted from the light source is reflected even when the light emitting surface is inclined at a predetermined angle. The light emitted from the light source can be efficiently incident on the first light incident surface and the second light incident surface of the light guide plate.

Here, the LED chip 40 of the light source 12 is the length of the light emitting surface 40a in the inclination direction, that is, the length a of the light emitting surface 40a of the LED chip 40 in the direction orthogonal to the arrangement direction of the LED chips 40 in this embodiment ( 4) is the length of the cross section of the first light incident surface in the direction orthogonal to the light exit surface 18a on the edge side of the light exit surface 18a of the first light entrance surface 18d, in this embodiment, the light guide plate 18 The length d1 of 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 light exit surface 18a (hereinafter referred to as “the effective section length d1 of the light incident surface”), that is, It is preferable that the first light incident surface 18d or the second light incident surface 18e is longer than the length of the light guide plate in the thickness direction.
By making the length a of the light emitting surface 40a longer than the length d1 of the effective cross section of the light incident surface, more light can be emitted from the light emitting surface.
Further, by arranging the light emitting surface 40a to be inclined at a predetermined angle θ with respect to the reference surface S, even when the length a of the light emitting surface 40a is larger than the length d1 of the effective cross section of the light incident surface, it is efficiently performed. Light can be incident on the light guide plate, and as described above, light with high luminance can be efficiently emitted from the light exit surface of the light guide plate.

Here, the inclination angle θ of the light emitting surface 40a with respect to the reference surface S is preferably 15 ° or more and 90 ° or less, that is, 15 ° ≦ θ ≦ 90 °, and 15 ° or more and 75 ° or less, that is, 15 ° ≦ More preferably, θ ≦ 75 °. Here, the inclination angle θ is an angle obtained by inclining the light emitting surface 40a toward the light emitting surface 18a with respect to the reference surface S. When θ = 90 °, the light emitting surface 40a is parallel to the light emitting surface 18a. Light is emitted from the light emitting surface 40a in the same direction as the light emitted from the light emitting surface 18a of the light guide plate 18.
By making the inclination angle θ of the light emitting surface 40a 15 ° ≦ θ ≦ 90 °, the light use efficiency can be further increased, and the light emitted from the light emitting surface can be made uniform, By setting 15 ° ≦ θ ≦ 75 °, the light utilization efficiency can be further increased and made more uniform.
The light source 12 is preferably arranged with the light emitting surface 40 facing the light exit surface as in this embodiment, but the present invention is not limited to this, and the light emitting surface 40a of the light source 12 is on the back surface 18b. You may arrange it.

Hereinafter, the planar illumination device 10 will be described in more detail with specific examples. Here, since the planar illumination device of the present embodiment has a symmetrical shape with the bisector α as an axis, the first illumination surface side will be described as a representative.
In the surface illumination device of this embodiment, the length a of the light emitting surface 40a of the LED chip 40 in the direction orthogonal to the arrangement direction of the LED chips 40 is 2.5 mm, the thickness w1 of the LED chip 40 is 0.5 mm, and the LED chip. The length d2 of the array support 42 in the direction orthogonal to the arrangement direction of 40 is 3.0 mm, the thickness w2 of the array support 42 is 0.5 mm, and the length of the effective cross section of the first light incident surface 18d of the light guide plate 18 d1 is 2.0 mm, and the length of the upper guide reflector 34 and the light exit surface 18a of the light guide plate 18 is overlapped, that is, the light incident surface 18d and the end of the upper guide reflector 34 on the center side of the light guide plate 18 The distance L was 5 mm. Further, a reflective film having a thickness of 0.1 mm and a reflectivity of 98% is used for the reflector 24 and the lower guide reflector 36, and a reflection having a thickness of 0.1 mm and a reflectivity of 90% is used for the upper guide reflector 34. A film was used. Here, the reflecting plate 24 and the lower guiding reflecting plate 36 are formed of a single reflecting film. Further, the reflecting plate 24 and the lower guiding reflecting plate 36 are bent at a position corresponding to the connecting portion, that is, the first light incident surface 18 d at the end of the light guide plate 18.
When the inclination angle θ of the light emitting surface 40a of the LED chip 40 of the light source 12 of the planar illumination device having such a shape is θ = 15 °, 30 °, 45 °, 60 °, 75 °, The light use efficiency of the light source, that is, the ratio of the light emitted from the light exit surface to the light emitted from the light source was measured.
Further, as shown in FIG. 17A, the light use efficiency of the light source of the planar lighting device in which θ = 0 °, that is, the light emitting surface 40a is arranged at a position or angle parallel to the reference surface S was measured. Further, as shown in FIG. 17B, the planar illumination is arranged such that the length a of the light emitting surface 40a of the LED chip 40 in the direction orthogonal to the arrangement direction of the LED chips 40 is 1.45 mm and θ = 0 °. The light utilization efficiency of the light source of the apparatus was measured. In FIG. 17, the fluorescent member 17 is not shown in order to clearly show the dimension line, but the fluorescent member 17 is disposed in contact with the light emitting surface 40a of the LED chip 40 as in FIG. .
The measurement results are shown in Table 3 below and FIG.

As shown in Table 3 and FIG. 18, the light use efficiency can be made higher by tilting the light emitting surface of the light source by a predetermined angle than when the light emitting surface 40a is arranged at a position parallel to the reference surface S, that is, at an angle. I understand that I can do it. That is, more light can be incident on the light guide plate, and the luminance or illuminance of the light emitted from the light source can be further increased.
Further, in the present embodiment, by setting the inclination angle θ of the light emitting surface 40a to 15 ° ≦ θ ≦ 45 ° or less, the direction orthogonal to the arrangement direction of the LED chips 40 rather than the length of the effective cross section of the light incident surface. It can be seen that the light utilization efficiency can be made higher than the case where the LED chip 40 in which the length a of the light emitting surface 40a of the LED chip 40 is shortened is disposed.
That is, by adjusting the inclination angle θ of the light emitting surface, light emitted from the light source can be made to enter the light guide plate more efficiently, and light with higher luminance and illuminance can be emitted from the light emitting surface.

Next, another embodiment of the planar lighting device will be described.
FIG. 19 is a schematic cross-sectional view showing another embodiment of the planar lighting device of the present invention, and FIG. 20 is an enlarged cross-sectional view of a part of the planar lighting device shown in FIG.
The planar illumination device 100 shown in FIGS. 19 and 20 has the planar illumination shown in FIGS. 1 to 3 except for the shapes of the first light incident surface 18d ′ and the second light incident surface 18e ′ of the light guide plate 18 ′. The configuration is the same as that of the device 10. Therefore, the same components are denoted by the same reference numerals in both, and the detailed description thereof is omitted, and hereinafter, the points peculiar to the planar illumination device 100 will be mainly described.

  The planar illumination device 100 includes a light source 12, an illumination device body 14 ′ that emits uniform light from a rectangular light exit surface 14 a, and a fluorescent member 17 b that is disposed between the light source 12 and the illumination device body 14. And a housing 16 that houses the light source 12, the illumination device main body 14 ', and the fluorescent member 17b. The illumination device main body 14 ′ includes a light guide plate 18 ′, an optical member 22, a reflection plate 24, an upper guide reflection plate 34, and a lower guide reflection plate 36. Here, the light source 12, the housing 16, the optical member 22, the reflector 24, the upper guide reflector 34, and the lower guide reflector 36 have the same configuration as the above-described planar illumination device 10, and therefore will be described in detail. Omitted.

  As shown in FIGS. 19 and 20, the light guide plate 18 ′ has a substantially rectangular flat light exit surface 18a and both ends of the light exit surface 18a with respect to a reference surface S perpendicular to the light exit surface 18a. Two light incident surfaces (first light incident surface 18d ′ and second light incident surface 18e ′) formed at a predetermined angle θ1 are positioned opposite to the light exit surface 18a, and the first light incident surface 18d. 'And parallel to the second light incident surface 18e' (parallel to the side of the light exit surface 18a in contact with the first or second light incident surface 18d 'or 18e') and bisecting the light exit surface 18a into two equal parts In a cross section that is symmetrical to each other about the dividing line α (see FIG. 1) and is perpendicular to the bisector α, light travels from the first light incident surface 18d or the second light incident surface 18e toward the bisector α. The distance from the exit surface 18a increases, and the first light incident surface 18d or the second light incident Toward the center from 18e, the inclination angle is reduced with respect to the light exit plane, the inclination angle at the center has a rear 18b formed by the curve becomes 0 degrees. That is, the back surface 18b is convex in a direction away from the light exit surface 18a, and the central portion of the light guide plate becomes the apex, and the inclination becomes gentler toward the center portion from the end surface. It is formed by a curve with a small angle formed by. Further, the tangent line on the back surface in the central portion of the light guide plate is parallel to the light exit surface.

Further, the light source 12 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 12 are arranged so as to sandwich the light guide plate 18 ′. In other words, the light guide plate 18 ′ is disposed between the two light sources 12 disposed to face each other with a predetermined distance therebetween.
Here, the planar illumination device 100 also has a symmetrical shape with the bisector α as the central axis in the same manner as the planar illumination device 10 described above, and therefore, the first light incident surface side will be described as a representative.

  As shown in FIG. 20, the planar illumination device 100 according to the present embodiment includes a light source disposed so as to face the inclination angle θ <b> 1 of the first light incident surface 18 d ′ with respect to the reference surface S and the first light incident surface 18 d ′. The inclination angle θ with respect to the reference plane S of the issue surface 40a of the 12 LED chips 40 is arranged at the same angle. That is, the first light incident surface 18d 'and the light emitting surface 40a are arranged in parallel.

  Even when the first light incident surface 18 d ′ of the light guide plate 18 is inclined by a predetermined angle with respect to the reference surface S as in the present embodiment, the fluorescent member 17 b is disposed on the light emitting surface 40 a of the LED 40 of the light source 12. The color temperature of the light emitted from the light emitting surface 14 can be increased, and the light emitted from the light emitting surface 14a can be adjusted by adjusting the shape of the blue light transmitting portion, that is, the opening or the transparent portion. The color temperature can be a desired color temperature. Also in the case of the present embodiment, if the arrangement position of the fluorescent member 17b is between the light emitting surface of the LED and the light emission surface of the light guide plate, for example, the fluorescent member 17b is arranged in contact (contact) with the light incident surface, etc. You may arrange in any position.

In addition, by tilting the first light incident surface 18d ′ of the light guide plate 18 with respect to the reference surface S by a predetermined angle θ1, the surface area of the first light incident surface 18 ′ is reduced to the effective cross section of the first light incident surface 18 ′. The surface area can be increased. Thereby, the light emitted from the light emitting surface 40a of the light source 12 can be efficiently incident on the light guide plate 18 ′.
Here, when the first light incident surface 18d ′ is inclined as in the present embodiment, the edge side of the light exit surface 18a of the first light incident surface 18d ′, that is, the first light incident surface 18d. A cross section in a direction substantially orthogonal to the light exit surface 18a at a contact point (tangent, that is, a connecting position) between the light exit surface 18a is an effective cross section of the light entrance surface.
Further, as in the present embodiment, the first light incident surface 18d ′ of the light guide plate 18 is made parallel to the light emitting surface 40a of the light source 12, that is, the inclination angle of the first light incident surface with respect to the reference surface S is set. The light emitted from the light emitting surface 40 a can be efficiently incident on the first light incident surface 18 d ′ of the light guide plate 18 by setting the same angle as the inclination angle of the light emitting surface of the light source disposed facing each other. .

  Here, the inclination angle θ1 of the first light incident surface 18d ′ is preferably the same as the inclination angle θ of the light emitting surface 40a of the light source as in this embodiment, but the present invention is not limited to this. The inclination angle θ1 and the inclination angle θ may be different from each other. That is, the light emitting surface 40a may be disposed at a predetermined angle with respect to the first light incident surface 18d '.

Hereinafter, the planar illumination device 100 will be described in more detail with specific examples.
In the planar illumination device 100 of this embodiment, the length a of the light emitting surface 40a of the LED chip 40 in the direction orthogonal to the arrangement direction of the LED chips 40 is 2.5 mm, the thickness w1 of the LED chip 40 is 0.5 mm, and the LED The length d2 of the array support 42 in the direction orthogonal to the arrangement direction of the chips 40 is 3.0 mm, the thickness w2 of the array support 42 is 0.5 mm, and the effective cross section of the first light incident surface 18d ′ of the light guide plate 18 ′. The length d1 of the first light exit surface 18d ′ is 2.0 mm, that is, the length d3 of the first light exit surface 18d ′ connecting the light exit surface 18a and the back surface 18b is (2.0 / cos θ1). ), The length in which the upper guide reflection plate 34 and the light exit surface 18a of the light guide plate 18 ′ overlap, that is, the first light incident surface 18d ′ and the end of the upper guide reflection plate 34 on the center side of the light guide plate 18 ′. And the distance L to 5 mm. Further, a reflective film having a thickness of 0.1 mm and a reflectivity of 98% is used for the reflector 24 and the lower guide reflector 36, and a reflection having a thickness of 0.1 mm and a reflectivity of 90% is used for the upper guide reflector 34. A film was used. Here, the reflecting plate 24 and the lower guiding reflecting plate 36 are formed of a single reflecting film. Further, the reflecting plate 24 and the lower guiding reflecting plate 36 are bent at a position corresponding to the connecting portion, that is, the first light incident surface 18d ′ of the light guide plate 18 ′.
The light emitting surface 40a of the light source 12 and the first light incident surface 18d ′ of the light guide plate 18 are parallel to each other, that is, the inclination angle θ of the light emitting surface 40a and the inclination angle θ1 of the first light incident surface 18d ′ are the same. It was an angle.
When the inclination angle θ and the first light incident surface θ1 of the light emitting surface 40a of the planar lighting device having such a shape are θ = θ1, and θ = 15 °, 30 °, 45 °, 60 °, 75 ° The light utilization efficiency of the light source of the planar lighting device was measured.
Similarly to the above embodiment, as shown in FIG. 17A, θ = 0 °, that is, the light source of the planar illumination device in which the light emitting surface 40a is arranged at a position and an angle parallel to the reference plane S. Light utilization efficiency was measured. Further, as shown in FIG. 17B, the planar illumination is arranged such that the length a of the light emitting surface 40a of the LED chip 40 in the direction orthogonal to the arrangement direction of the LED chips 40 is 1.45 mm and θ = 0 °. The light utilization efficiency of the light source of the device was also measured.
The measurement results are shown in Table 4 below and FIG.

As shown in Table 4 and FIG. 21, the light emitting surface of the light source and the light incident surface of the light guide plate are inclined by a predetermined angle, so that the light emitting surface 40a is arranged at a position parallel to the reference surface S, that is, at an angle. Alternatively, it can be seen that the light utilization efficiency can be made higher than when the light emitting surface 40a is arranged at a position parallel to the reference surface S. In the present embodiment, the same light source is used, but the light source can be made larger by arranging the light source at an inclination. That is, more light can be incident on the light guide plate, and the luminance or illuminance of the light emitted from the light source can be further increased.
Further, in the present embodiment, the effective angle of the light incident surface is reduced by setting the inclination angle θ of the light emitting surface 40a and the inclination angle θ1 of the light guide plate to θ = θ1 and 15 ° ≦ θ ≦ 60 ° or less. It can be seen that the light utilization efficiency can be made higher than the case where the LED chip 40 in which the length a of the light emitting surface 40a of the LED chip 40 in the direction orthogonal to the arrangement direction of the LED chips 40 is shortened is arranged.
In other words, by adjusting the inclination angle θ of the light emitting surface and the inclination angle θ1 of the light guide plate, the light emitted from the light source is incident on the light guide plate more efficiently, and light with higher luminance and illuminance is emitted from the light emission surface. Can be made.

Next, another specific embodiment will be described.
In the present embodiment, θ = 45 °, and a specific example of the above-described planar illumination device 10 in which the distance L between the first light incident surface 18d and the end of the upper guide reflection plate 34 on the light guide plate 18 center side is 5 mm. Luminance (cd / m ² ), illuminance (lx), light utilization efficiency (%), and average luminance (%) at each position emitted from the light exit surfaces of two planar illumination devices having substantially the same configuration as the example. cd / m ² ) was measured.
Further, θ = θ1 = 45 °, and the surfaces described above except that the distance L between the first light incident surface 18d ′ and the end of the upper guide reflector 34 on the center side of the light guide plate 18 is 5 mm and 10 mm, respectively. Light utilization efficiency (%) of the light sources of the two planar illumination devices and the average luminance (cd / m ² ) of the light emitted from the light exit surface Was measured. In addition, the light utilization efficiency (%) of the light source of the planar illumination device in which the light incident surface of the light guide plate and the light emitting surface of the light source are parallel to the reference surface without the reflection plate and the light emitted from the light emission surface Average brightness (cd / m ² ) was also measured.
Table 5 shows the measured light utilization efficiency (%) and average luminance (cd / m ² ).

As shown in Table 5, it can be seen that the average luminance and the light utilization efficiency can be further increased by inclining the light incident surface and arranging the upper guide reflection member.
It can also be seen that the average luminance can be increased by setting the length L of the upper guide reflector to 5 mm.
From the above, the effects of the present invention are clear.

Next, still another embodiment of the planar lighting device of the present invention will be described.
22A, 22B, and 23 are enlarged sectional views showing other embodiments of the planar lighting device of the present invention. Here, the planar illumination device 110 shown in FIG. 22A, the planar illumination device 110 ′ shown in FIG. 22B, and the planar illumination device 150 shown in FIG. Since the shape of the illumination device 100 is bilaterally symmetric, only one end portion is shown.

  The planar illumination device 110 shown in FIG. 22A is basically the same as the planar illumination device 10 except that the inclination angle θ of the light emitting surface 40a with respect to the reference plane S is 90 °. It is the composition.

The light source 12 of the planar illumination device 110 is disposed at a position where the inclination angle θ of the light emitting surface 40a of the LED chip 40 is 90 °, that is, the light emitting surface 40a is perpendicular to the first light incident surface 18d. The LED chip 40 is disposed on the back surface 18b side of the first light incident surface 18d. That is, the LED chip 40 is disposed adjacent to the end of the first light incident surface 18d on the back surface 18b side so that the light emitting surface 40a is parallel to the direction perpendicular to the first light incident surface 18d.
The fluorescent member 17c is disposed in contact with the light emitting surface 40a of the LED chip 40. In addition, since the shape and structure of the fluorescent member 17c are the same as the fluorescent member 17 mentioned above, it abbreviate | omits.
The upper guide reflection plate 112 is a plate-like member that is bent at the end of the light emission surface of the light guide plate 18, and the first light emitting surface 40 a of the LED chip 40 is partly formed from a part of the light emission surface 18 a of the light guide plate 18. It is arranged to cover up to the end farther from the light incident surface 18d. As the upper guide reflector 112, the same material as that of the upper guide reflector 34 described above can be used.

  In the planar illumination device 110, the light emitted from the light source 12 and transmitted through the fluorescent member 17c is reflected directly or by the upper guide reflector 112, and then enters the light guide plate 18 from the first light incident surface 18d. . The light that has entered the light guide plate 18 is emitted from the light exit surface in the same manner as the planar illumination device 10 described above.

  Similarly, in the configuration of the present embodiment, by arranging the fluorescent member 17e on the light emitting surface 40a of the LED 40 of the light source 12, the color temperature of light emitted from the light emitting surface 14 can be increased, and blue light is also emitted. The color temperature of the light emitted from the light emission surface 14a can be set to a desired color temperature by adjusting the shape of the transmission part, that is, the opening part or the transparent part.

  Thus, even when the inclination angle θ of the light emitting surface 40a is set to 90 °, light emitted from a light source having a large light emitting surface, for example, a light source having a light emitting surface longer than the length of the effective cross section of the light incident surface can be efficiently obtained. The light can be incident on the light exit surface well, and the light use efficiency can be improved. In addition, since the area of the light emitting surface can be increased by setting the inclination angle θ to 90 °, light with high luminance or illuminance can be emitted from the light emitting surface.

  Also in the present embodiment, the arrangement of the fluorescent member is not particularly limited, and as shown in FIG. 22 (B), the position in contact with the first light incident surface 19d of the light guide plate 18 of the planar illumination device 110 ′. Alternatively, the fluorescent member 17c may be disposed.

A planar lighting device 150 shown in FIG. 23 has the same configuration as the planar lighting device 110 shown in FIG. 22A except for the shape of the light guide plate 152.
The light guide plate 152 has a flat light emission surface 152a having a substantially rectangular shape and two side surfaces (first side surface 152f and first side surface) formed at both ends of the light emission surface 152a with a predetermined angle with respect to the light emission surface 152a. Two side surfaces 152g) are symmetrical to each other about a bisector α (see FIG. 1), which is located on the opposite side of the light emitting surface 152a and parallel to the side surface and bisects the light emitting surface 152a. In a cross section perpendicular to the bisector α, the distance from the light exit surface 152a increases from the end toward the bisector α, and the inclination angle with respect to the light exit surface decreases from the end toward the center. And two light incident surfaces (first light incident surfaces) formed between the back surface 152b formed by a curve having an inclination angle of 0 degree in the center and the respective end portions and side surface end portions of the back surface 152b. 152d and second light incident surface 152e) There. Here, the light guide plate 152 has a shape in which an angle formed by the light exit surface 152a and the first side surface 152d is larger than 90 °, and an angle formed by the first light incident surface 152d and the first side surface 152f is smaller than 90 °. The first light incident surface 152d is formed with an inclination angle θ1 of 90 ° with respect to the reference surface S.
In the present embodiment, the cross section in the direction substantially orthogonal to the light exit surface 152a of the light guide plate 152 at the end of the first light incident surface 152d on the end surface 152b side is the effective cross section of the light incident surface.
Since the planar illumination device 150 is symmetrical, only the end portion on the first side surface 152d side is shown in FIG.

The light source 12 includes a plurality of LED chips 40 and a light source support 41, and is disposed to face a first light incident surface 152d formed between the back surface 152b of the light guide plate 152 and the first side surface 152f. .
The light source 12 is disposed at a position where the inclination angle θ of the light emitting surface 40a with respect to the reference surface S is 90 °. Therefore, the light emitting surface 40a of the light source 12 and the first light incident surface 152d are arranged in parallel.

The upper guide reflection plate 112 is disposed so as to cover the light guide plate 152 along a part of the light emission surface 152a on the first side surface 152f side and the shape of the first side surface 152f. Further, the end of the upper light guide plate 112 on the first side surface 152 f side of the light guide plate 152 is connected to the light source 12.
In addition, the lower guide reflection plate 36 and the reflection plate 24 are disposed on the back surface 152 b side of the light guide plate 152.
That is, in the light guide plate 152, the light emission surface 152a, the first side surface 152f, the first light incident surface 152d, and the back surface 152b on the first side surface 152f side are the upper guide reflection plate 112, the light source 12, the lower guide reflection plate 36, and the reflection. The plate 24 is covered with no gap. Here, in this embodiment, the reflecting plate 24 and the lower guiding reflecting plate 36 are integrally formed.

  The fluorescent member 17e is disposed between the first light incident surface 152d and the light emitting surface 40a of the LED. Since the fluorescent member 17e has the same shape and configuration as the fluorescent member 17 described above, a detailed description thereof will be omitted.

The light emitted from the light emitting surface 40a of the light source 12 passes through the fluorescent member 17e, and then enters from the first light incident surface 152d of the light guide plate 152, and directly on the center side of the light guide plate 152 or the first side surface. The light is reflected by 152 f or the upper guide reflector 112 and proceeds toward the center of the light guide plate 152.
The light traveling toward the center of the light guide plate 152 passes through the light guide plate 152 while being scattered by a scatterer (details will be described later) included in the light guide plate 152, as in the light guide plate 18 described above. The light exits from the light exit surface 152a directly or after being reflected by the back surface 152b.

  Similarly, in the configuration of the present embodiment, by arranging the fluorescent member 17e on the light emitting surface 40a of the LED 40 of the light source 12, the color temperature of the light emitted from the light emitting surface 14a can be increased, and the blue light The color temperature of the light emitted from the light emission surface 14a can be set to a desired color temperature by adjusting the shape of the transmission part, that is, the opening part or the transparent part.

Alternatively, the light emitting surface of the light source is inclined at a predetermined angle with respect to the reference surface, the light incident surface of the light guide plate is also inclined at a predetermined angle, and a side surface is provided between the light incident surface and the light emitting surface of the light guide plate. The light emitted from the light source can be efficiently incident on the light guide plate, and the light utilization efficiency can be increased.
Furthermore, by providing a side surface on the light guide plate and arranging the light emission surface on the back side, the area of the light emission surface of the light source can be increased, and light with high luminance or illuminance can be emitted from the light emission surface. it can. In addition, by reflecting the light incident from the light incident surface on the side surface inclined by a predetermined angle, even when the light is incident from the light incident surface provided on the back side, the light exit surface can emit light without unevenness. it can.

Also, by providing the side surface, the light incident from the light incident surface can be reflected by the side surface, and even when the inclination angle of the light incident surface with respect to the reference surface is increased, the light incident from the light incident surface can be easily guided. It can be guided toward the center of the light plate.
Further, as in the present embodiment, the inclination angle θ1 of the first light incident surface 152d with respect to the reference surface S is set to 90 °, that is, the first light incident surface 152 and the light emitting surface are parallel to each other. The area of the surface can be increased.

In the case of a planar illumination device that allows light to enter from the back end of the light guide plate as described above, the scattering cross section of the scattering particles contained in the light guide plate 152 is Φ, parallel to the light exit surface 152a, and the light exit. In the direction perpendicular to the tangent line between the surface 152a and the side surface (the first side surface 152f or the second side surface 152g), the thickness of the light guide plate 152 (light the distance in the vertical direction of the thickness on the exit surface (length)) to a position of maximum and L _G, the density of the scattering particles contained in the light guide plate 152 (number of particles per unit volume) N _p, a correction coefficient the when the _{K C,} the value of _{Φ · N p · L G ·} K C is not less than 1.1, and is 8.2 or less, further, the value of the correction coefficient _{K C} is 0.005 or more 0 It is preferable that the relationship of .1 or less is satisfied. Since the light guide plate 18 includes scattering particles that satisfy such a relationship, it is possible to emit illumination light that is uniform and has less luminance unevenness from the light exit surface 152a.
Also, when the side surfaces are formed, the preferred mode is the same as that of the above-described embodiment. For example, the inclination angle θ = θ1 is preferably 15 ° ≦ θ ≦ 90 °.

Hereinafter, the surface illumination device of the present invention will be described in more detail with specific examples.
In this embodiment, θ = 90 °, that is, the inclination angle of the light emitting surface 40a of the LED chip of the light source, the shape of the upper guide reflector is set to the shape shown in the planar illumination device 110, and the upper guide reflector Except that the length L is 10 mm, the size and configuration are substantially the same as those of the above-described planar illumination device 10. The light use efficiency (%) of the light source of the planar illumination device 110 was measured. Further, θ = 45 °, the length L of the upper guide reflector is 10 mm, and the light use efficiency of the light source of the planar illumination device in which the light incident surface of the light guide plate and the light exit surface of the light source are parallel to the reference surface ( %) Was also measured.
Table 6 shows the measurement results.

  As shown in Table 6, it can be seen that even when θ = 90 °, the light utilization efficiency can be increased as in the case of θ = 45 °.

Such a planar illumination device can be used as a backlight for a planar illumination device that illuminates indoors and outdoors, a backlight that illuminates a liquid crystal panel of a liquid crystal display device, an advertising panel, an advertising tower, or a signboard.
For example, an electric field is partially applied to liquid crystal molecules arranged in a specific direction in advance to change the arrangement of the molecules, and a change in the refractive index generated in the liquid crystal cell is used to change the liquid crystal display panel 4. A liquid crystal panel that displays characters, figures, images, etc. on the surface is arranged on the light emission surface of the surface illumination device, and the liquid crystal panel is illuminated with light emitted from the surface illumination device, thereby providing a liquid crystal display device can do.

  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-described embodiments, and various improvements and modifications may be made without departing from the gist of the present invention. Of course.

In any of the above-described embodiments, as shown in FIG. 2, the light guide plate support portion 30 formed of a resin or the like is disposed between the lower housing 16 a and the reflection plate 24, and the light guide plate 18 is viewed from the back surface 18 bc side. The light guide plate 18 and the reflection plate 24 are brought into close contact with each other while supporting the reflection plate 24, but the present invention is not limited to this.
Here, it is preferable to dispose a buffer member between the surface of the reflection plate 24 opposite to the light guide plate 18 side, that is, between the lower housing 16a and the reflection plate 24 of the present embodiment. Here, the buffer member is a member having rigidity lower than that of the light guide plate deformed along the shape of the light guide plate, such as a sponge.
By supporting the reflection plate 24 and the back surface 18b side of the light guide plate 18 with the buffer member, the reflection plate 24 can be brought into close contact with the light guide plate 18, and the reflection plate 24 can be prevented from being bent. Further, by using the support as a buffer member, the light guide plate and the reflection plate can be brought into contact with each other without unevenness. As a result, only a part of the reflecting plate comes into contact, diffuses the light, prevents the light from being viewed as a bright portion of the light emitted from the light emitting surface, and allows uniform light to be emitted from the light emitting surface. it can.

Here, FIGS. 24A to 24D are exploded cross-sectional views showing an example of a schematic configuration of a buffer member that supports the light guide plate and the reflection plate, respectively.
For example, as shown in FIG. 24A, a rectangular buffer member 202 may be disposed on the surface of the reflecting plate 24 opposite to the light guide plate 18. Here, as the buffer member 202, the maximum stress that acts on the light guide plate 18 from the buffer member 202 when assembled as a planar lighting device, and in this embodiment, the stress that acts on the connection portion with the back surface is 5 [ N / cm ² ] or less is preferably used.
Further, as shown in FIG. 24B, a buffer member 212 composed of multilayer buffer materials 212 a, 212 b, and 212 c is disposed on the surface of the reflector plate 24 opposite to the light guide plate 18, and the light guide plate 18 The thickness of the buffer member 212 may be different depending on the position depending on the shape. Thus, by changing the thickness of the buffer member 212 according to the position, the compression rate of the buffer member can be reduced, and the maximum stress acting on the light guide plate can be reduced. Thereby, the force which acts on a light guide plate can be made more uniform, and a light guide plate and a reflecting plate can be made to closely_contact | adhere.
In addition, as shown in FIG. 24C, the buffer member 222 may have a shape along the back surface of the light guide plate 18. That is, the buffer member 222 has a shape in which a curved surface 222 a having the same shape as the back surface of the light guide plate 18 is formed on the surface on the light guide plate 18 side.
As described above, the light guide plate and the reflection plate can be evenly adhered to each other by forming the buffer member along the back surface of the light guide plate.
Furthermore, as shown in FIG. 24 (D), the buffer member 232 is shaped along the back surface of the light guide plate 18, and the back surface of the light guide plate 18 on the opposite side of the buffer member 232 from the light guide plate 18 side. It is good also as a structure which provided the sheet-metal member 234 along the shape.
By providing the sheet metal member 234 along the shape of the back surface of the light guide plate 18 on the surface opposite to the light guide plate 18 side of the buffer member 232, the compression rate of the buffer member can be made uniform, and the buffer member By supporting the reflection plate via the light guide plate, the light guide plate and the reflection plate can be brought into close contact with each other.

In the above embodiments, the LED chips are arranged in a single row in one direction as the light source. However, the present invention is not limited to this. Good. Moreover, it is good also as a structure which piled up the unit by which the LED chip was arrange | positioned in single row on a support body, ie, the structure laminated | stacked.
On the other hand, in the present embodiment, a plurality of LED chips are arranged in a row, but the present invention is not limited to this, and only one LED chip may be arranged.

  Further, in the present embodiment, the light emitting surface of the light source is disposed at a predetermined angle with respect to the direction orthogonal to the light emitting surface of the light guide plate from the viewpoint that the light emitted from the light source can be efficiently used. However, the light emitting surface of the light source may be arranged perpendicular to the light exit surface of the light guide plate.

In this embodiment, the configuration is simple and inexpensive, and the LED chip of the light source is configured by applying a YAG fluorescent material to the light emitting surface of the blue LED. However, the present invention is not limited to this. Alternatively, an LED chip having a configuration in which a fluorescent material is disposed on the light emitting surface of another single color LED such as a red LED or a green LED may be used.
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.

In addition, since the luminance distribution can be suitably formed into a bell shape and can be suitably used as a planar lighting device of a liquid crystal display device, the shape of the light guide plate is increased in thickness from the end surface toward the center as shown in FIG. However, the present invention 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 the light is incident. The shape in which the thickness of the light guide plate increases as the distance from the surface increases, in other words, the light incident surface is composed of one light incident surface formed at one end of the light exit surface, and the back surface is from the light incident surface. It is composed of a curved surface (curved in a cross section) that is inclined so as to be farther from the light exit surface as it goes to the other end surface facing this, and becomes smaller with respect to the light exit surface as it is far from the light entrance surface. In Thin, it may be thickest shape at the other end face.
In addition, the light source is disposed on any one of the side surfaces of the light guide plate, the four side surfaces are used as light incident surfaces, and the thickness increases from the four light incident surfaces toward the center. The surface is composed of four light incident surfaces formed on the four end sides of the light emitting surface, respectively, and the back surface is inclined so as to move away from the light emitting surface toward the center from each of the four light incident surfaces. The angle of inclination with respect to the light exit surface decreases from the light incident surface toward the central portion, and is composed of a curved surface (curved in the cross section) with an inclination angle of 0 degrees at the central portion, and the thickness at the light incident surface is the thinnest, It is good also as a shape with the thickest thickness in the center part of a back surface.
Even when the light guide plate has such a shape, it is possible to allow light to reach a position far from the light incident surface while maintaining a thin shape, and to further improve the light utilization efficiency. As a result, the light guide plate can be made thinner and the light exit surface can be enlarged, and the light utilization efficiency can be increased.

Further, even when the light guide plate shaped as described above, 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 is preferably satisfies the 1.1 or 8.2 or less. 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.

The light guide plate may be produced by mixing a plasticizer into a 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 the phthalate ester, dioctyl adipate (DOA), diisononyl adipate (DINA), dinormal 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.

It is a schematic perspective view which shows one Embodiment of the planar illuminating device which concerns on this invention. It is the II-II sectional view taken on the line of the planar illuminating device shown in FIG. It is an expanded sectional view which expands and shows a part of planar illumination apparatus shown in FIG. (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). (A)-(C) are the figures which respectively show the fluorescent member of the planar illuminating device shown in FIG. 2, and a part of light source, (A) is a top view, (B) is a front view, ( C) is a side view. 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 relationship between light use efficiency, illumination intensity nonuniformity, and particle density. It is sectional drawing which shows the shape of an example of a light-guide plate. It is a graph which shows the luminance distribution of the light inject | emitted from the light emission surface of a planar illuminating device. It is a graph which shows the luminance distribution of the light inject | emitted from the light emission surface of a planar illuminating device. It is a graph which shows the result of having measured the wavelength distribution of the light inject | emitted from the light emission surface of the planar illuminating device which made Sap / Sa various values. It is a graph which shows the relationship between the ratio of the sum Sap of the area of the blue light transmission part with respect to the whole area Sa of a fluorescent member, and the color temperature of the light inject | emitted from a light-projection surface. (A)-(C) are front views which show another example of a fluorescent member, respectively. It is sectional drawing which shows schematic structure of other embodiment of the planar illuminating device of this invention. (A)-(C) is a figure which shows a fluorescent member and a part of light source of another example of a planar illuminating device, respectively, (A) is a top view, (B) is a front view, (C ) Is a side view. (A)-(C) are front views which show another example of a fluorescent member, respectively. (A) And (B) is an expanded sectional view which shows schematic structure of an example of the planar illuminating device of this invention, respectively. It is a graph which shows the result of having measured the light utilization efficiency of the planar illuminating device which made the inclination angle (theta) of the light emission surface various values. It is sectional drawing which shows schematic structure of other embodiment of the planar illuminating device of this invention. It is an expanded sectional view which expands and shows a part of planar illumination apparatus shown in FIG. It is a graph which shows the result of having measured the light utilization efficiency of the planar illuminating device which made the inclination angle (theta) of the light emission surface various values. (A) And (B) is an expanded sectional view which shows schematic structure of the other example of the planar illuminating device of this invention, respectively. It is an expanded sectional view which shows schematic structure of the other example of the planar illuminating device of this invention. (A)-(D) are the decomposition | disassembly block diagrams which show an example of the buffer member which each supports a light-guide plate and a reflecting plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Planar illuminating device 12 Light source 12a Light emission surface 14 Illuminating device main body 14a, 18a Light emission surface 16 Housing | casing 16a Lower housing | casing 16b Upper housing | casing 16c Folding member 17, 60, 70, 76 Fluorescent member 18 Light guide plate 18b Back surface 18d, 18d '1st light incident surface 18e 2nd light incident surface 22 Optical member 22a, 22b, 22c Diffusion film 24 Reflector plate 28, 50, 74, 78 Opening part 32 Power supply accommodating part 34 Upper guide reflector 36 Lower guide reflector 40 LED chip 41 Light source support part 42 Array substrate 44 Fin 48, 72, 77 Phosphor coating part

Claims (10)

A first light source and a second light source that are spaced apart by a predetermined distance;
The first light source is disposed between the first light source and the second light source, faces the light exit surface, the first light source, includes a first light incident surface including one side of the light exit surface, and faces the second light source and the one side. A light guide plate having a second incident surface including opposite sides and a back surface formed to face the light exit surface,
The light guide plate scatters light entering the first and second light incident surfaces and propagating through the interior substantially parallel to the light exit surface into the light guide plate in a direction perpendicular to the incident direction. Contains scattering particles directed to the light exit surface,
The back surface of the light guide plate has a cross-section in a plane perpendicular to the one side, and the distance from the light exit surface increases as the distance from the first light incident surface and the second light incident surface toward the center increases. A curve satisfying a high-order polynomial in which the inclination angle with respect to the light emission surface decreases toward the center from the first light incidence surface or the second light incidence surface, and the inclination angle with respect to the light emission surface becomes 0 degrees at the center. A planar illumination device having a shape represented in part and smoothly connected to the light incident surface. A light emitting surface, a first light incident surface including one side of the light emitting surface, a side surface formed to face the first light incident surface, and a back surface formed to face the light emitting surface. A light plate,
A first light source disposed facing the first light incident surface,
The light guide plate has a light exit surface in a direction orthogonal to the incident direction by scattering light propagating through the first light incident surface and propagating through the interior substantially parallel to the light exit surface. Contains scattering particles that point to
The back surface of the light guide plate has a cross section in a plane perpendicular to the one side, and the distance from the light emitting surface increases as the distance from the first light incident surface to the side surface increases, and the first light incident surface. In a shape represented by a part of a curve that satisfies a high-order polynomial in which the inclination angle with respect to the light emission surface decreases from the side to the side surface, and the inclination angle with respect to the light emission surface becomes 0 degrees at the position of the side surface. And a planar illumination device that is smoothly connected to the light incident surface. The back surface of the light guide plate has a _i , a _j , a _k , b _i , b _j , b _k as arbitrary real numbers, i, j, k as arbitrary natural numbers, and S _i , S _j , S _k. Is a real number that satisfies −1 ≦ S _i ≦ 1, −1 ≦ S _j ≦ 1, −1 ≦ S _k ≦ 1, and n ₁ , n ₂ , and n ₃ are arbitrary natural numbers, The planar illumination device according to claim 1 or 2, wherein a cross section in a vertical plane is represented by a part of a curve satisfying the following formula.

  4. The planar illumination device according to claim 2, wherein a function of a curve representing a cross section of the back surface of the light guide plate in a plane perpendicular to the one side is a function in which a derivative has no discontinuity. 5.   The planar illumination device according to any one of claims 1 to 4, wherein the rear surface of the light guide plate is represented by a part of an ellipse in a plane perpendicular to the one side.   The back surface of the light guide plate has a cross-section in a plane perpendicular to the one side symmetrical with respect to a straight line perpendicular to the light exit surface and passing through an intermediate point between the first light incident surface and the second light incident surface. The planar illumination device according to any one of claims 1 and 3 to 5. 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 thickness of the light guide plate from the first or second light incident surface of the light guide plate in the light incident direction is When the length to the thickest position is L _G , the following 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 6, wherein: The light source includes at least one LED chip that emits blue light from a light emitting surface;
A phosphor coating part that is disposed between the light emitting surface of the LED chip and the light guide plate, converts blue light emitted from the light emitting surface into white light, and emits blue light emitted from the light emitting surface. The planar illumination device according to claim 1, further comprising a fluorescent member including a blue light transmitting portion that emits blue light as blue light. The light source has a light emitting surface longer than the length of an effective cross section of the light incident surface in a direction substantially orthogonal to the light exit surface on the edge side of the light incident surface on which the light incident surface is formed, and the light emitting surface The planar illumination device according to any one of claims 1 to 8, wherein the planar illumination device is disposed so as to be opposed to the light incident surface of the light guide plate and inclined at a predetermined angle with respect to a direction substantially orthogonal to the light emitting surface. Of the light guide plate, in the incident direction of light, from the first or second light incident surface, and the length L _G of up thickest position perpendicular thickness in the light exit plane, the light exit plane The planar illumination device according to any one of claims 1 to 9, wherein a ratio L _G / D with respect to the light guide plate thickness D at a position where the thickness in the vertical direction is the largest is 60 or more.

Images