JP2010067568A - Light guide plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate having a flat shape, yielding a high light use efficiency, emitting light with minimized unevenness in brightness and achieving a high-in-the-middle or bell-curve brightness distribution required for a large-screen flat screen liquid crystal television, such that a central area of a screen is brighter than a periphery thereof. <P>SOLUTION: Protrusion parts, which have top parts and are formed of curved surfaces on a surface of a light emission surface by extending in parallel to a light incident surface, are arranged in a wave form in a direction orthogonal to the light incident surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light guide plate used in a liquid crystal display device or the like.

  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 by using components such as a light guide plate that diffuses light emitted from a light source for illumination and irradiates the liquid crystal display panel, a prism sheet that diffuses light emitted from the light guide plate, and a diffusion sheet. .

At present, a backlight unit of a large-sized liquid crystal television is mainly used in a so-called direct type in which a light source for illumination is arranged on the back surface of a liquid crystal display panel. 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 order to make the light amount distribution uniform, the direct type backlight unit needs a thickness of about 30 mm in the vertical direction with respect to the liquid crystal display panel, and it is difficult to make it thinner.

On the other hand, as a backlight unit that can be thinned, it is emitted from a light emitting surface that is emitted from a light source for illumination, guides incident light in a predetermined direction, and is different from the surface on which the light is incident. There is a backlight unit using a light guide plate.
As such a backlight unit using a light guide plate, a backlight unit using a light guide plate in which scattering particles for scattering light in a transparent resin are mixed has been proposed.

For example, Patent Document 1 includes a light scattering light guide having at least one light incident surface 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-guiding light source device is characterized in that the light-scattering light-guiding body has a region having a tendency 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. Further, Patent Document 3 includes a light emission direction correcting element made of a plate-like optical material having a light incident surface having repetitive undulations in a prism row and a light emission surface provided with light diffusibility. A liquid crystal display is described, and Patent Document 4 discloses 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. Is described.

  Further, as the light guide plate, in addition to the above, the thickness of the intermediate portion is larger than the thickness of the end portion on the incident side and the end portion on the opposite side, and the thickness increases as the distance from the light incident portion increases. A light guide plate having a reflective surface inclined in the direction, and having a shape such that the distance between the front surface portion and the back surface portion is minimum at the incident portion, and the thickness is maximum at the maximum separation distance from the incident portion. Various inverted wedge type light guide plates such as an optical plate have been proposed (see, for example, cited references 5 to 8).

Japanese Patent Laid-Open No. 7-36037 JP-A-8-248233 JP-A-8-271739 JP-A-11-153963 JP 2003-90919 A JP 2004-171948 A JP 2005-108676 A JP 2005-302322 A

With the increase in size of liquid crystal display devices, the light guide plate is also required to be larger and thinner and lighter.
Here, when the light guide plate is enlarged, it is conceivable that the number of light sources such as LEDs increases in order to emit uniform light from the light exit surface. However, liquid crystal display devices such as liquid crystal televisions are required to reduce power consumption and the number of parts, and the increase in the number of light sources accompanying an increase in size is against this requirement.
That is, the light guide plate is required to be able to emit uniform light from the light exit surface with high light utilization efficiency while realizing an increase in size and reduction in thickness and weight.

In order to satisfy such a demand, as described above, in the conventional light guide plate, various devices are made in the thickness and shape.
However, in these methods, it cannot be said that the demands for size increase and reduction in thickness and weight are particularly satisfied.

Also, in order to emit uniform light from the light exit surface according to such requirements, an emboss pattern, a screen print pattern, and a light guide plate are formed on the reflective surface (opposite surface to the light exit surface) side. It is also known to form V-shaped grooves and prism-like minute patterns.
However, in such a method, when the thickness of the light guide plate is reduced, minute luminance unevenness due to the pattern formed on the reflecting surface occurs. In addition, it is preferable that the light guide plate has a bell-shaped luminance distribution in which the luminance of the central portion is higher than that of the end portion. However, it is difficult to realize the bell-shaped luminance distribution by these methods.

On the other hand, a light scatterer is usually dispersed in the light guide plate in order to emit uniform light.
Here, it is needless to say that the light guide plate is preferably low-cost, but the light scatterer is expensive, and this light scatterer contributes to the cost increase of the light guide plate. . In particular, when the size of the light guide plate is increased, the amount of the light scatterer used is increased, and the cost is improved accordingly.

  Furthermore, as disclosed in the above-mentioned patent document, a reverse wedge-type light guide plate such as a light guide plate in which the thickness of the intermediate portion is formed larger than the thickness of the end portion on the incident side and the end portion on the opposite side, etc. In a light guide plate that is devised in shape, it is necessary to disperse the light scatterers uniformly throughout the entire area of the light guide plate regardless of the shape. For this reason, it is difficult to knead and disperse the light scatterer prior to molding and to control the concentration of the light scatterer, which further increases the cost.

  The object of the present invention is to solve the above-mentioned problems of the prior art, and even when the size and thickness are reduced, light utilization efficiency is high and light with less unevenness in brightness can be emitted, and A light guide plate that can obtain a light distribution near the center of the light exit surface as compared with the periphery, that is, a so-called medium-high or bell-shaped brightness distribution, and satisfies the above characteristics without using a light scatterer. Is to provide.

  In order to solve the above-described problem, the present invention provides a light guide plate having a rectangular light exit surface and a light incident surface including one side of the light exit surface, and the light exit surface has a surface on which the light exits. Provided is a light guide plate characterized in that convex portions extending in parallel with an incident surface and having a top portion and having a curved surface are arranged in a wave shape in a direction perpendicular to the light incident surface. It is.

Here, it is preferable that the light incident surface is provided on two opposing sides of the rectangular light emitting surface.
In addition, when compared between a position far from the light incident surface and a position close to the light incident surface, the formation interval of the protrusions at the far position may be equal to or less than the formation interval of the protrusions at a position near the light incident surface. preferable.
Further, it is preferable that the formation interval of the convex portion gradually becomes narrower as the distance from the vicinity of the light incident surface increases.

Further, since the size of the convex portion in the direction orthogonal to the light incident surface is different, the formation interval of the convex portion at the far position is equal to or less than the formation interval of the convex portion at a position close to the light incident surface. It is preferable to become.
Or it is preferable that the formation interval of the said wavy convex part in the said distant position becomes below the formation interval of the said convex part in the position close | similar to the said light-incidence surface because the formation interval of the said convex part differs.
Here, the height of the convex portion is preferably 25 to 1000 μm.
Moreover, it is preferable that the space | interval of the said convex part is 25-10000 micrometers.

Moreover, it is preferable that the thickness of the light guide plate gradually increases as the distance from the light incident surface increases.
Furthermore, it is preferable that the light guide plate is rectangular, the light incident surfaces are set to both long sides, and the thickness of the light guide plate gradually increases toward the center in the short side direction.
Further, it is preferable that the light scatterer is not dispersed.

According to the light guide plate of the present invention, it is possible to emit light with high light use efficiency and little unevenness in brightness even when the size is increased or the weight is reduced. A bright distribution compared to the portion, that is, a so-called medium-high or bell-shaped brightness distribution can be obtained.
Furthermore, according to the present invention, it is possible to realize a light guide plate that can obtain the above-described effect without using scattering particles.

A planar illumination device using a light guide plate according to the present invention will be described below in detail based on a preferred embodiment shown in the accompanying drawings.
FIG. 1 is a perspective view schematically showing a liquid crystal display device including a planar illumination device using a light guide plate according to the present invention, and FIG. 2 is a cross-sectional view taken along the line II-II of the liquid crystal display device shown in FIG. is there.
3A is a view taken along the line III-III of the planar illumination device (hereinafter also referred to as “backlight unit”) shown in FIG. 2, and FIG. 3B is a diagram of FIG. It is a BB sectional view.

  The liquid crystal display device 10 includes a backlight unit 20, a liquid crystal display panel 12 disposed on the light emission surface side of the backlight unit 20, and a drive unit 14 that drives the liquid crystal display panel 12. In FIG. 1, a part of the liquid crystal display panel 12 is not shown in order to show the configuration of the planar lighting device.

The liquid crystal display panel 12 applies a partial electric field to liquid crystal molecules arranged in a specific direction in advance to change the arrangement of the molecules, and uses the change in the refractive index generated in the liquid crystal cell to make a liquid crystal display. Characters, figures, images, etc. are displayed on the surface of the display panel 12.
The drive unit 14 applies a voltage to the transparent electrode in the liquid crystal display panel 12, changes the direction of the liquid crystal molecules, and controls the transmittance of light transmitted through the liquid crystal display panel 12.

  The backlight unit 20 is an illuminating device that irradiates light from the back surface of the liquid crystal display panel 12 to the entire surface of the liquid crystal display panel 12, and has a light emission surface 24 a having substantially the same shape as the image display surface of the liquid crystal display panel 12.

The backlight unit 20 according to the present embodiment includes an illumination device main body having two light sources 28, a light guide plate 30, and an optical member unit 32 as shown in FIGS. 1, 2, 3A, and 3B. 24, and a casing 26 having a lower casing 42, an upper casing 44, a folding member 46, and a support member 48. As shown in FIG. 1, a power storage unit 49 that stores a plurality of power supplies for supplying power to the light source 28 is attached to the back side of the lower housing 42 of the housing 26.
Hereinafter, each component which comprises the backlight unit 20 is demonstrated.

  The illuminating device body 24 includes a light source 28 that emits light, a light guide plate 30 that emits light emitted from the light source 28 as planar light, and a light that is emitted from the light guide plate 30 by scattering or diffusing the light. And an optical member unit 32 having light without unevenness.

First, the light source 28 will be described.
4A is a schematic perspective view showing a schematic configuration of the light source 28 of the planar illumination device 20 shown in FIGS. 1 and 2, and FIG. 4B is a diagram of the light source 28 shown in FIG. It is a schematic perspective view which expands and shows only one LED chip.
As shown in FIG. 4A, the light source 28 includes a plurality of light emitting diode chips (hereinafter referred to as “LED chips”) 50 and a light source support portion 52.

The LED chip 50 is a chip in which a fluorescent material is coated on the surface of a light emitting diode that emits blue light. The LED chip 50 has a light emitting surface 58 having a predetermined area, and emits white light from the light emitting surface 58.
That is, when the blue light emitted from the surface of the light emitting diode of the LED chip 50 passes through the fluorescent material, the fluorescent material fluoresces. As a result, white light is generated and emitted from the LED chip 50 by the blue light emitted from the light emitting diode and the light emitted from the fluorescent substance after fluorescence.
Here, the LED chip 50 is exemplified by a chip in which a YAG (yttrium / aluminum / garnet) fluorescent material is applied to the surface of a GaN-based light-emitting diode, InGaN-based light-emitting diode, or the like.

The light source support 52 has an array substrate 54 as shown in FIG. The plurality of LED chips 50 described above are arranged on the array substrate 54 in a row at a predetermined interval according to the arranged positions. Specifically, the plurality of LED chips 50 constituting the light source 28 are arranged along the longitudinal direction of the first light incident surface 30d or the second light incident surface 30e of the light guide plate 30 described later, in other words, the first light incident. The surface 30d or the second light incident surface 30e and the light exit surface 30a are arranged in an array parallel to the line where the light exit surface 30a intersects and are fixed on the array substrate 54.
In addition, the light source support part 52 may have a fin for heat dissipation.

  The array substrate 54 is a plate-like member whose one surface is disposed to face the thinnest end surface of the light guide plate 30, and the first light incident surface 30 d or the second light incident surface 30 e that is the side end surface of the light guide plate 30. It is arranged to face. The side surface of the array substrate 54 that is the surface facing the light incident surface 30d or 30e of the light guide plate 30 supports the LED chip 50.

Here, as shown in FIG. 4B, the LED chip 50 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 50 in the arrangement direction, that is, described later. The light guide plate 30 has a rectangular shape with a short side in the thickness direction (direction perpendicular to the light exit surface 30a). In other words, the LED chip 50 has a shape in which b> a when the length in the direction perpendicular to the light exit surface 30a of the light guide plate 30 is a and the length in the arrangement direction is b. Further, q> b, where q is the arrangement interval of the LED chips 50. Thus, the relationship between the length a in the direction perpendicular to the light exit surface 30a of the light guide plate 30 of the LED chip 50, the length b in the arrangement direction, and the arrangement interval q of the LED chips 50 satisfies q>b> a. It is preferable.
By making the LED chip 50 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 28, the planar illumination device can be reduced in thickness. In addition, the number of LED chips can be reduced.

  In addition, since the LED chip 50 can make the light source 28 thinner, it is preferable that the LED chip 50 has a rectangular shape having a short side in the thickness direction of the light guide plate 30. However, the present invention is not limited to this, and the square shape and the circular shape are not limited thereto. LED chips having various shapes such as a shape, a polygonal shape, and an elliptical shape can be used.

Next, the light guide plate 30 will be described.
FIG. 5 is a schematic perspective view showing the shape of the light guide plate 30.
As shown in FIGS. 2, 3 and 5, the light guide plate 30 is substantially perpendicular to the light emission surface 30a on the light emission surface 30a having a rectangular shape and on both end surfaces on the long side of the light emission surface 30a. The two light incident surfaces (the first light incident surface 30d and the second light incident surface 30e) formed on the opposite side of the light emitting surface 30a, that is, on the back side of the light guide plate, Two inclined surfaces (first inclined surface 30b) that are symmetrical with each other about the bisector α (see FIGS. 1 and 3) connecting the centers of the short sides and are inclined at a predetermined angle with respect to the light exit surface 30a. And a second inclined surface 30c).
Hereinafter, the long side direction of the light emitting surface 30a is simply referred to as “long side direction”, and the short side direction of the light emitting surface 30a is simply referred to as “short side direction”.

As shown in FIGS. 2 and 3B, the light exit surface 30a of the light guide plate 30 has a top portion extending in a direction parallel to the long side of the light guide plate 30, and is formed as a curved surface. The convex portions 70 (smooth convex portions 70) are formed in a wavy pattern in the short side direction. In other words, the light emitting surface 30a of the light guide plate 30 has a convex portion 70 formed of a curved surface having apexes parallel to the first light incident surface 30d and the second light incident surface 30e. Arranged in a direction orthogonal to the second light incident surface 30e, the light exit surface 30a has a wave shape.
In the illustrated example, as a preferable example, the pitch P (formation interval) of the convex portions 70 is changed by changing the size of the convex portions (the width in the short side direction of the light emitting surface 30a). The convex portion 70 is formed so as to gradually become smaller from the two-light incident surface 30e toward the center. That is, the pitch P of the convex portions 70 gradually decreases from the first light incident surface 30d toward the second light incident surface 30e, and is minimized at the position of the bisector α that is the center in the short side direction. Gradually increases from the bisector α toward the second light incident surface 30e.
In the illustrated example, the pitch P is changed by changing the size of the convex portion 70 (the width in the short side direction of the light exit surface 30a).

As described above, the light emitting surface 30a of the light guide plate 30 has a top portion extending in parallel to the long side direction (light incident surface) and the convex portion 70 formed of a curved surface is formed in the short side direction (light incident). By forming them in a wavy pattern in a direction (perpendicular to the surface), it is possible to emit medium-high illumination light with little luminance unevenness from the light exit surface 30a while improving the light utilization efficiency.
Furthermore, the light use efficiency is further improved by forming the convex portions 70 so that the pitch P of the convex portions 70 gradually decreases from the first light incident surface 30d and the second light incident surface 30e toward the center. While increasing, it is possible to emit the illumination light with a small degree of unevenness in brightness while increasing the height from the light exit surface 30a.
In addition, according to the present invention, a light guide plate having such excellent characteristics can be realized without dispersing a light scatterer in the light guide plate, which is very advantageous in terms of cost. is there.
Here, in the light guide plate of the present invention, the luminance distribution and the illuminance distribution, and the luminance unevenness and the illuminance unevenness basically have the same tendency. That is, the same illuminance unevenness occurs in the portion where the luminance unevenness occurs, and the luminance distribution and the illuminance distribution tend to have the same tendency.

  The pitch P of the convex portions 70 is gradually decreased from the first light incident surface 30d and the second light incident surface 30e toward the center. However, the present invention is not limited to this, and the pitch P It is only necessary that the pitch P decreases from the first light incident surface 30d and the second light incident surface 30e toward the center.

FIG. 6 is a schematic sectional view showing another example of the light guide plate of the present invention.
The light guide plate 100 shown in FIG. 6 has the light emission surface 100a in which the convex portions 102 are formed instead of the light emission surface 30a in which the convex portions 70 are formed in the light guide plate 30 shown in FIG. Since it has the same configuration as that of the light guide plate 30, the same portions are denoted by the same reference numerals, and the following description will mainly be performed on different portions.
In the embodiment shown in FIGS. 2 and 3, the pitch P is changed so as to gradually decrease toward the center, but the pitch of the convex portions 102 formed on the light exit surface 100a of the light guide plate 100 shown in FIG. P is the size of the convex portion (of the light exit surface 100a) so as to decrease stepwise from the first light incident surface 30d and the second light incident surface 30e toward the bisector α which is the center in the short side direction. The width in the short side direction is changed. That is, the pitch P of the convex portion 102 changes to a smaller pitch P _n for each region L _{n in the} short side direction toward the center of the first light incident surface 30d and the second light incident surface 30e. Here, the n-th pitch from the light incident surface side is P _n, to the area where the pitch P _n are formed with L _n.
At this time, in the region L1 in the short side direction closest to the light incident surface, the convex portions 102 are formed with a pitch P1 over the entire region. In the adjacent region L2 (the bisector α side), the convex portions 102 are formed at a pitch P2 smaller than the pitch P1 over the entire region. In this way, the convex portion 102 is formed so that the formation pitch P gradually decreases for each predetermined region in the short side direction, and the most central region (center in the short side) Ln extends over the entire region. Thus, the convex portions 102 are formed with the smallest pitch Pn. In other words, the pitch of the wavy patterns _are changed stepwise _{P n} satisfying P n _{<P n-1.} At this time, the joints between the pitches _Pn and _Pn-1 are connected so as to change smoothly.
It is not particularly limited to the number n of the pitch P _n, which is the region L _n, and formed to form the pitch P _n, The region L _n to form a pitch P _n, as a different value for each pitch P _n Alternatively, a constant value may be used regardless of the pitch _Pn .
As described above, the light use efficiency is also improved by changing the pitch P of the convex portion so as to decrease stepwise from the first light incident surface and the second light incident surface toward the bisector α. On the other hand, it is possible to emit the illumination light with a small degree of unevenness in brightness with a high degree of medium height from the light exit surface.
In addition, the light guide plate having such excellent characteristics can be realized without dispersing the light scatterer in the light guide plate, which is very advantageous in terms of cost.

Further, the pitch P of the convex portions preferably satisfies 25 μm ≦ P ≦ 10000 μm.
It is preferable that the pitch P of the convex portions formed on the light exit surface of the light guide plate satisfy the above range, so that the illuminance distribution can be made to be medium-high at a suitable ratio while further improving the light utilization efficiency. .

  Moreover, although the height H of the convex part 70 of a present Example is constant, this invention is not limited to this, You may change the height H with the position of the convex part 70. FIG. For example, like the pitch P of the convex portions 70, the height H is maximized in the vicinity of the first light incident surface 30d and the second light incident surface 30e and is minimized at the center, that is, in accordance with the change in the pitch P. The height H may also be changed.

The height H of the convex portion preferably satisfies 25 μm ≦ H ≦ 1000 μm.
The height H of the convex portion formed on the light exit surface of the light guide plate 30 satisfies the above range, so that the illuminance distribution can be set to a medium-high ratio at a suitable ratio while increasing the light utilization efficiency. Is preferred.

Moreover, in the said Example, although the said pitch P is changed by changing the size (width of the short side direction of the light-projection surface 30a) of a convex part, this invention is not limited to this.
FIG. 7 is a schematic cross-sectional view showing another example of the light guide plate of the present invention.

The light guide plate 110 shown in FIG. 7 has the light emission surface 110a in which the convex portions 112 are formed instead of the light emission surface 30a in which the convex portions 70 are formed in the light guide plate 30 shown in FIG. Since it has the same configuration as that of the light guide plate 30, the same portions are denoted by the same reference numerals, and the following description will mainly be performed on different portions.
The light exit surface 110a has a top portion extending in parallel to the long side direction of the light guide plate 110, has a constant width in the short side direction, and is formed with a curved surface, and a flat flat portion 114. Are formed in such a manner that the formation interval of the convex portions 110 decreases from the first light incident surface 30d and the second light incident surface 30e toward the center. That is, convex portions 112 are discretely formed on the light exit surface 110a, and the number of convex portions 112 per unit length is directed from the first light incident surface 30d and the second light incident surface 30e to the center. And increases at the position of the bisector α.
That is, the convex portions 112 closest to the light incident surface are formed with a pitch Pd1. The adjacent convex portions 112 (on the bisector α side) are formed with a pitch Pd2 shorter than the pitch Pd1. In this way, as the bisector α is approached, the pitch Pd is formed to be smaller by shortening the formation interval of the convex portions 112, and at the center (the center in the short side direction) and at the smallest pitch Pdn, A convex portion 112 is formed.
Moreover, the convex part 112 and the flat part 114 are smoothly joined by the curve.

In this way, the light emitted from the light exit surface can also be formed by discretely forming the convex portions 112 so that the density of the convex portions 112 increases as the distance from the light incident surface increases on the light exit surface 110a of the light guide plate 110. The illuminance distribution can be made higher and higher. Further, the light utilization efficiency can be further increased. Moreover, since the convex part 112 and the flat part 114 are joined smoothly, generation | occurrence | production of brightness irregularity can be suppressed. Thereby, thickness reduction of a light-guide plate and enlargement of a light-projection surface can be performed.
That is, according to the present embodiment, the illuminance distribution can be made higher and higher than that of the conventional light guide plate while maintaining a higher light utilization efficiency than that of the conventional light guide plate.
In addition, according to the present embodiment, a light guide plate having such excellent characteristics can be realized without dispersing a light scatterer in the light guide plate, which is very advantageous in terms of cost. is there.

  Note that the lengths for forming the convex portions 112 and the flat portions 114 may be set so that the density of the convex portions 112 increases as the distance from the light incident surface increases. What is necessary is just to form so that the length of the part 112 may become long and the length of the flat part 114 may become short. Alternatively, the length of the flat portion 114 may be constant, and the length of the convex portion 112 may increase as the distance from the light incident surface increases, or the length of the convex portion 112 may be constant and the length of the flat portion 114 may be longer. However, the distance may be shortened as the distance from the light incident surface increases.

The first inclined surface 30b and the second inclined surface 30c are axisymmetric with respect to the bisector α, and the distance from the light emitting surface 30a increases as the distance from the first light incident surface 30d or the second light incident surface 30e increases. The thickness in the direction perpendicular to the light exit surface 30a of the light guide plate 30 is gradually increased from the first light incident surface 30d or the second light incident surface 30e toward the center of the light guide plate 30 so as to move away (become longer). It is inclined to become.
In other words, the light guide plate 30 is thicker from the first light incident surface 30d or the second light incident surface 30e toward the center, and is thickest at the portion corresponding to the bisector α in the center. The two light incident surfaces (the first light incident surface 30d and the second light incident surface 30e) are the thinnest.
That is, the cross-sectional shape of the light guide plate 30 is line symmetric with respect to the central axis passing through the bisector α. In addition, the inclination angle of the first inclined surface 30b and the second inclined surface 30c with respect to the light emitting surface 30a is not particularly limited.

  As described above, the first light incident surface 30d and the second light are formed by increasing the thickness in the direction perpendicular to the light emitting surface 30a as the distance from the first light incident surface 30d and the second light incident surface 30e increases. Light incident from the incident surface 30e can be delivered to a position farther from the first light incident surface 30d and the second light incident surface 30e. Thereby, the light guide plate can be reduced in thickness and weight, and the light emission surface can be increased in size.

Here, in this embodiment, the inclined surface of the light guide plate has a shape with a straight section, but the shape of the first inclined surface and the second inclined surface (that is, the back surface) is not particularly limited, and may be a curved surface. The first inclined surface and the second inclined surface may each be composed of a plurality of inclined surfaces. That is, the inclined surface may have a shape with a different inclination angle depending on the position. Further, the inclined surface may be a convex shape on the light exit surface side, a concave shape, or a shape in which the concave and convex portions are combined.
Here, it is preferable that the inclined surface has a shape in which the inclination angle of the inclined surface with respect to the light exit surface becomes gentler from the light incident surface toward the center of the light guide plate (or the position where the thickness of the light guide plate is the thickest). . By gradually reducing the inclination angle of the inclined surface, it is possible to emit light with no uneven brightness from the light emitting surface.
Furthermore, the inclined surface is more preferably an aspherical shape whose cross-sectional shape can be expressed by a tenth order polynomial. By setting the inclined surface to the above-described shape, it is possible to emit light without uneven brightness regardless of the thickness of the light guide plate.

In the above embodiment, the thickness increases as the distance from the light incident surface increases. However, the present invention is not limited to this, and the back surface 120i is a flat rectangle like the light guide plate 120 shown in FIG. It can also be a shape. Even if the back surface of the light guide plate has a flat rectangular shape, the light emitting surface 30a has a top portion extending in parallel in the long side direction, and the convex portions 70 formed in a curved surface are arranged in a wave shape in the short side direction. In this way, it is possible to emit medium-high illumination light with little unevenness of brightness from the light exit surface 30a while improving the light utilization efficiency, and further, the back surface of the light guide plate has a flat rectangular shape. The light guide plate can be easily manufactured and the cost can be reduced.
In addition, the light guide plate having such excellent characteristics can be realized without dispersing the light scatterer in the light guide plate, which is very advantageous in terms of cost.

Here, the two light sources 28 described above are respectively disposed to face the first light incident surface 30d or the second light incident surface 30e of the light guide plate 30. Specifically, the light source 28 configured by the plurality of LED chips 50a and the light source support portion 52a is disposed to face the first light incident surface 30d, and the light source configured by the plurality of LED chips 50b and the light source support portion 52b. 28 is arranged to face the second light incident surface 30e. Here, in the present embodiment, the length of the light emitting surface 58 of the LED chip 50 of the light source 28 and the length of the first light incident surface 30d and the second light incident surface 30e are substantially the same in the direction perpendicular to the light emitting surface 30a. Length.
As described above, in the planar lighting device 20, the two light sources 28 are arranged so as to sandwich the light guide plate 30. That is, the light guide plate 30 is disposed between the two light sources 28 that face each other at a predetermined interval.

  The light guide plate 30 is made of a transparent resin. Examples of the transparent resin used for the light guide plate 30 include PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, or COP (cycloolefin polymer). Such an optically transparent resin is mentioned.

  In the light guide plate 30 shown in FIG. 2, the light emitted from the light source 28 and incident from the first light incident surface 30d or the second light incident surface 30e passes through the light guide plate 30 and directly or first inclined surface 30b. Or after reflecting on the 2nd inclined surface 30c, it passes the convex part 70 and radiate | emits from the light-projection surface 30a. At this time, some light may leak from the first inclined surface 30b and the second inclined surface 30c, but the leaked light is arranged on the first inclined surface 30b and the second inclined surface 30c side of the light guide plate 30. The light is reflected by the reflecting plate 34 and enters the light guide plate 30 again. The reflector 34 will be described in detail later.

As described above, the light emitting surface 30a of the light guide plate 30 has the top portion extending in parallel with the long side direction and the convex portion 70 formed with a curved surface is formed in a wavy pattern in the short side direction. As a result, it is possible to emit illumination light from the light exit surface 30a with high and low luminance unevenness while improving the light utilization efficiency.
Furthermore, the light use efficiency is further improved by forming the convex portions 70 so that the pitch P of the convex portions 70 gradually decreases from the first light incident surface 30d and the second light incident surface 30e toward the center. While increasing, it is possible to emit the illumination light with a small degree of unevenness in brightness while increasing the height from the light exit surface 30a.
Moreover, since the convex part 70 is changing smoothly, generation | occurrence | production of brightness irregularity can be suppressed.
Furthermore, the first light incident surface 30d and the second light incident surface are formed by increasing the thickness in the direction perpendicular to the light exit surface 30a as the distance from the first light incident surface 30d and the second light incident surface 30e increases. Since the light incident from 30e can be delivered to a position farther from the first light incident surface 30d and the second light incident surface 30e, it is possible to increase the medium-high degree while improving the light utilization efficiency.
In addition, according to the present invention, a light guide plate having such excellent characteristics can be realized without dispersing a light scatterer in the light guide plate, which is very advantageous in terms of cost. is there.
That is, according to the present invention, the illuminance distribution can be made higher than that of the conventional light guide plate without using the light scatterer and maintaining higher light utilization efficiency than that of the conventional light guide plate.

  In the present embodiment, light with higher luminance can be efficiently emitted from the light emission surface, and therefore, the side where the light incident surface 30a of the light guide plate 30 intersects the light incident surface is a long side, and the side where the light incident surface 30a intersects the side surface However, the present invention is not limited to this, and the light incident surface side may be a short side, the side surface side may be a long side, and the light emission surface may be a square shape.

Moreover, although the light guide plate of the above-described embodiment is formed of an optically transparent resin, in addition to this, scattering particles for scattering light propagating inside may be kneaded and dispersed. If scattering particles are kneaded and dispersed in the light guide plate, it leads to an increase in cost, but the illuminance distribution can be made medium to high at a suitable ratio while improving the light utilization efficiency.
As the scattering particles kneaded and dispersed in the light guide plate, Tospearl, silicone, silica, zirconia, dielectric polymer, or the like can be used.

Next, the optical member unit 32 will be described.
The optical member unit 32 converts the illumination light emitted from the light exit surface 30a of the light guide plate 30 into light with no uneven brightness, and emits illumination light with more uniform brightness from the light exit surface 24a of the illumination device body 24. As shown in FIG. 2, a diffusion sheet 32a that diffuses illumination light emitted from the light exit surface 30a of the light guide plate 30 to reduce luminance unevenness, and a tangent line between the light incident surface and the light exit surface It has a prism sheet 32b on which parallel microprism arrays are formed, and a diffusion sheet 32c that diffuses illumination light emitted from the prism sheet 32b to reduce luminance unevenness.

  The diffusion sheets 32a and 32c and the prism sheet 32b are not particularly limited, and a known diffusion sheet or prism sheet can be used. For example, Japanese Patent Application Laid-Open No. 2005-23497 related to the application of the present applicant [ The ones disclosed in [0028] to [0033] can be applied.

In this embodiment, the optical member unit is composed of the two diffusion sheets 32a and 32c and the prism sheet 32b disposed between the two diffusion sheets. However, the arrangement order and arrangement of the prism sheets and the diffusion sheets are not limited. The number is not particularly limited, and is not particularly limited as a prism sheet or a diffusion sheet, and the brightness unevenness of the illumination light emitted from the light exit surface 30a of the light guide plate 30 can be further reduced. For example, various optical members can be used.
For example, as the optical member, a transmittance adjusting member in which a large number of transmittance adjusting bodies made of a diffuse reflector are arranged in accordance with the luminance unevenness can be used in addition to or instead of the above-described diffusion sheet and prism sheet.
In addition, since the light guide plate of the present invention can increase the light use efficiency and secure sufficient luminance, the prism sheet of the optical member unit used to increase the luminance is removed, and the optical member unit is configured only by the diffusion sheet. You can also If it is not necessary to use a prism sheet, the cost can be reduced easily. At this time, the optical member unit may use one diffusion sheet or two diffusion sheets, and may have a two-layer structure, and the number of diffusion sheets is not particularly limited.

Next, the reflecting plate 34 will be described.
The reflection plate 34 is provided to reflect light leaking from the first inclined surface 30b and the second inclined surface 30c of the light guide plate 30 and to make it incident on the light guide plate 30 again, thereby improving the light use efficiency. be able to. The reflecting plate 34 has a shape corresponding to the first inclined surface 30b and the second inclined surface 30c of the light guide plate 30, and is formed so as to cover the first inclined surface 30b and the second inclined surface 30c. In the present embodiment, in FIG. 2, the first inclined surface 30b and the second inclined surface 30c of the light guide plate 30 are formed in a triangular cross section, and the reflecting plate 34 is also formed in a shape that complements this. .

  The reflecting plate 34 may be formed of any material as long as it can reflect light leaking from the inclined surface of the light guide plate 30. For example, the reflecting plate 34 is stretched after kneading a filler in PET, PP (polypropylene), or the like. 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 36 is disposed between the light guide plate 30 and the diffusion sheet 32a, that is, on the light emission surface 30a side of the light guide plate 30, and at the end of the light emission surface 30a of the light source 28 and the light guide plate 30 (first light incident). It is arranged so as to cover the end on the surface 30d side and the end on the second light incident surface 30e side). In other words, the upper guide reflection plate 36 is disposed so as to cover from a part of the light exit surface 30a of the light guide plate 30 to a part of the array substrate 54 of the light source 28 in a direction parallel to the optical axis direction. That is, the two upper guide reflectors 36 are disposed at both ends of the light guide plate 30, respectively.
Thus, by arranging the upper guide reflection plate 36, it is possible to prevent the light emitted from the light source 28 from entering the light guide plate 30 and leaking to the light exit surface 30a side.
Thereby, the light emitted from the LED chip 50 of the light source 28 can be efficiently incident on the first light incident surface 30d and the second light incident surface 30e of the light guide plate 30, and the light utilization efficiency can be improved. .

The lower guide reflection plate 38 is disposed on the side opposite to the light exit surface 30a side of the light guide plate 30, that is, on the first inclined surface 30b and the second inclined surface 30c so as to cover a part of the light source 28. . The end of the lower guide reflector 38 on the center side of the light guide plate is connected to the reflector 34.
By providing the lower guide reflection plate 38, the light emitted from the light source 28 can be prevented from leaking to the first inclined surface 30b and the second inclined surface 30c side of the light guide plate 30 without entering the light guide plate 30. .
Thereby, the light emitted from the LED chip 50 of the light source 28 can be efficiently incident on the first light incident surface 30d and the second light incident surface 30e of the light guide plate 30, and the light utilization efficiency can be improved. .
Here, as the upper guide reflector 36 and the lower guide reflector 38, various materials used for the reflector 34 described above can be used.
In the present embodiment, the reflecting plate 34 and the lower guiding reflecting plate 38 are connected. However, the present invention is not limited to this, and each may be a separate member.

Here, the upper guide reflector 36 and the lower guide reflector 38 reflect the light emitted from the light source 28 toward the first light incident surface 30d or the second light incident surface 30e, and the light emitted from the light source 28 is the first. The shape and width are not particularly limited as long as the light can be incident on the light incident surface 30d or the second light incident surface 30e and the light incident on the light guide plate 30 can be guided to the center side of the light guide plate 30.
In the present embodiment, the upper guide reflector 36 is disposed between the light guide plate 30 and the diffusion sheet 32a. However, the position of the upper guide reflector 36 is not limited to this, and the optical member unit 32 is configured. It may be arranged between the sheet-like members to be arranged, or may be arranged between the optical member unit 32 and the upper housing 44.

Next, the housing 26 will be described.
As shown in FIG. 2, the housing 26 accommodates and supports the lighting device main body 24, and is sandwiched between the light emission surface 24a side and the first inclined surface 30b and second inclined surface 30c side of the light guide plate 30. And a lower casing 42, an upper casing 44, a reinforcing member 46, and a supporting member 48.

  The lower housing 42 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 42 supports the illuminating device main body 24 accommodated from above by the bottom surface portion and the side surface portion, and also a surface other than the light emission surface 24 a of the illuminating device main body 24, that is, the illuminating device. The main body 24 covers the surface (back surface) and the side surface opposite to the light exit surface 24a.

The upper housing 44 has a rectangular parallelepiped box shape in which a rectangular opening smaller than the rectangular light emission surface 24a of the lighting device body 24 serving as an opening is formed on the upper surface, and the lower surface is opened.
As shown in FIG. 2, the upper housing 44 includes the lighting device main body 24 and the lower housing 42 in which the lighting device main body 24 and the lower housing 42 are housed in the four directions from above (the light emission surface side) of the lighting device main body 24 and the lower housing 42. The side portion is also placed so as to cover the side portion.

The folding member 46 has a concave (U-shaped) shape whose cross-sectional shape 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 46 is inserted between the side surface of the lower housing 42 and the side surface of the upper housing 44, and the outer surface of one U-shaped parallel part is the bottom surface of the lower housing 42. It is connected to the side surface portion, and the outer side surface of the other parallel portion is connected to the side surface of the upper housing 44.
Here, as a method for joining the lower housing 42 and the folding member 46, and a method for joining the folding member 46 and the upper housing 44, various known methods such as a method using bolts and nuts, a method using an adhesive, and the like. Can be used.

Thus, by arranging the folding member 46 between the lower housing 42 and the upper housing 44, the rigidity of the housing 26 can be increased, and the light guide plate can be prevented from warping. Thereby, for example, although there is no luminance unevenness or less light can be efficiently emitted, 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. Can be more reliably prevented, and light with no unevenness in brightness or with reduced light can be emitted from the light exit surface.
In addition, various materials, such as a metal and resin, can be used for the upper housing | casing of a housing | casing, a lower housing | casing, and a folding member. In addition, as a material, it is preferable to use a lightweight and high-strength material.
In the present embodiment, the folding member is a separate member, but it may be formed integrally with the upper housing or the lower housing. Moreover, it is good also as a structure which does not provide a folding | turning member.

The support member 48 has a shape with the same cross-sectional shape perpendicular to the extending direction. That is, it is a rod-like member having the same cross-sectional shape perpendicular to the extending direction.
As shown in FIG. 2, the support member 48 is between the reflection plate 34 and the lower housing 42, more specifically, the end of the first inclined surface 30 b of the light guide plate 30 on the first light incident surface 30 d side. The second inclined surface 30c is disposed between the reflecting plate 34 and the lower housing 42 at a position corresponding to the end on the second light incident surface 30e side, and the light guide plate 30 and the reflecting plate 34 are arranged in the lower housing 42. Secure and support.
The light guide plate 30 and the reflection plate 34 can be brought into close contact with each other by supporting the reflection plate 34 with the support member 48. Further, the light guide plate 30 and the reflection plate 34 can be fixed at predetermined positions of the lower housing 42.

In this embodiment, the support member is provided as an independent member. However, the present invention is not limited to this, and the support member may be formed integrally with the lower housing 42 or the reflection plate 34. In other words, a protrusion may be formed on a part of the lower casing 42 and used as a support member, or a protrusion may be formed on a part of the reflector and the protrusion may be used as a support member. .
Also, the arrangement position is not particularly limited, and can be arranged at any position between the reflector and the lower housing, but in order to stably hold the light guide plate, the end side of the light guide plate, In other words, in the present embodiment, it is preferable to dispose near the first light incident surface 30d and near the second light incident surface 30e.

The shape of the support member 48 is not particularly limited, and can be various shapes, and can be made of various materials. For example, a plurality of support members may be provided and arranged at predetermined intervals.
In addition, the support member has a shape that fills the entire space formed by the reflector and the lower housing, that is, the surface on the reflector side is shaped along the reflector, and the surface on the lower housing side is the lower housing. It is good also as a shape along. As described above, when the entire surface of the reflection plate is supported by the support member, it is possible to reliably prevent the light guide plate and the reflection plate from separating, and to prevent uneven brightness from being generated by the light reflected from the reflection plate. be able to.

  As described above, the light guide plate and the planar lighting device according to the present invention have been described in detail. However, the present invention is not limited to the above embodiment, and various improvements and modifications can be made without departing from the gist of the present invention. Changes may be made.

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

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

It is a schematic perspective view which shows one Embodiment of the liquid crystal display device using the planar illuminating device of this invention using the light-guide plate which concerns on this invention. It is the II-II sectional view taken on the line of the liquid crystal display device shown in FIG. (A) is the III-III arrow directional view of an example of the planar illuminating device shown in FIG. 2, (B) is BB sectional drawing of (A). (A) is a perspective view which shows schematic structure of the light source of the planar illuminating device shown to FIG.1 and FIG.2, (B) is a schematic perspective view which expands and shows one LED of the light source shown to (A). FIG. It is a schematic perspective view which shows the shape of a light-guide plate. It is a schematic sectional drawing which shows another example of the light-guide plate of this invention. It is a schematic sectional drawing which shows another example of the light-guide plate of this invention. It is a schematic sectional drawing which shows another example of the light-guide plate of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 12 Liquid crystal display panel 14 Drive unit 20 Planar illuminating device 24 Illuminating device main body 24a, 30a, 100a, 110a Light emission surface 26 Case 28 Light source 30, 100, 110, 120 Light guide plate 30b 1st inclined surface 30c Second inclined surface 30d First light incident surface 30e Second light incident surface 32 Optical member units 32a and 32c Diffusion sheet 32b Prism sheet 34 Reflector plate 36 Upper guide reflector 38 Lower guide reflector 42 Lower housing 44 Upper housing 46 Folding member 48 Support member 50 LED chip 52 Light source support portion 54 Array substrate 58 Light emitting surface 70, 102, 112, convex portion 114 Flat portion 120i Back surface

Claims (11)

A light guide plate having a rectangular light exit surface and a light incident surface including one side of the light exit surface,
On the surface of the light exit surface, convex portions extending in parallel with the light incident surface and having curved surfaces are arranged in a wave shape in a direction perpendicular to the light incident surface. A light guide plate characterized by   The light guide plate according to claim 1, wherein the light incident surfaces are provided on two opposing sides of the rectangular light exit surface.   2. When the distance between the position far from the light incident surface and the position near the light incident surface are compared, the formation interval of the protrusions at the far position is equal to or less than the formation interval of the protrusions at a position close to the light incident surface. 2. The light guide plate according to 2.   The light guide plate according to claim 3, wherein the formation interval of the convex portions gradually decreases as the distance from the vicinity of the light incident surface increases.   The distance between the projections at the far position is equal to or less than the distance between the projections at a position close to the light incidence surface because the size of the projections in the direction orthogonal to the light incident surface is different. Item 5. The light guide plate according to Item 3 or 4.   6. The formation interval of the wavy projections at the distant position is equal to or less than the formation interval of the projections at a position close to the light incident surface due to the difference in the formation interval of the projections. The light guide plate described in 1.   The light guide plate according to claim 1, wherein a height of the convex portion is 25 to 1000 μm.   The light guide plate according to claim 1, wherein an interval between the convex portions is 25 to 10,000 μm.   The light guide plate according to claim 2, wherein the thickness of the light guide plate gradually increases as the distance from the light incident surface increases.   The light guide plate according to claim 9, wherein the light guide plate is rectangular, the light incident surfaces are set to both long sides, and the thickness of the light guide plate gradually increases toward the center in the short side direction. .   The light guide plate according to claim 1, wherein the light scatterer is not dispersed.

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