JP2010080107A - Planar lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar lighting system having high light utilization efficiency in spite of a larger size, a lower profile and a lighter weight for emitting uniform light while avoiding a reflecting film from damaging a light guide plate. <P>SOLUTION: The planar lighting system includes the light guide plate, two light sources each arranged opposite to the light incident plane of the light guide plate, a casing storing the light guide plate and the light sources, a plurality of supporting columns arranged on the face of the casing opposite to the back face of the light guide plate to contact the back face of the light guide plate, and the reflecting film arranged at a position opposite to the back face of the light guide plate, and having holes at positions corresponding to the supporting columns, shaped almost the same as the cross sections perpendicular to the axial direction of the supporting columns. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a planar illumination device used for a liquid crystal display device or the like.

  As the liquid crystal display device, a planar illumination device (hereinafter also referred to as “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 backlight unit is also required to be larger and thinner and lighter.
However, in the backlight unit using the light guide plate that is emitted from the light exit surface that is different from the surface on which light such as the reverse wedge type as described above is incident, as the size and thickness become lighter, Since it becomes difficult for light to reach (in the direction opposite to the incident surface), the light use efficiency becomes low, and it becomes difficult to emit uniform light from the light exit surface. Therefore, as described above, in the conventional light guide plate, light is leaked from a surface other than the light exit surface, and a reflection film is arranged to guide the leaked light again into the light guide plate. Increases efficiency. In particular, the back surface, which is the surface opposite to the light exit surface, has a large surface area and a large proportion of light leaking. A reflective film is disposed on the back surface, and the light leaked from the back surface is reflected by the reflective film and guided again to the light guide plate, thereby increasing the amount of light emitted from the light exit surface and emitting uniform light.

  However, since the above-described reflective film is formed of a material harder than the light guide plate, if the reflective film is disposed on the back surface of the light guide plate, the reflective film and the light guide plate are rubbed to damage the light guide plate. There arises a problem that the performance of the optical plate cannot be fully exhibited. Especially for large light guide plates, the amount of expansion and contraction due to heat is large, and the amount of expansion and contraction between the light guide plate and the reflection film is different, so the amount of rubbing between the reflection film and the light guide plate increases, and the light guide plate is easily damaged. turn into.

  An object of the present invention is a planar illumination device that solves the problems of the above-described prior art, has high light utilization efficiency, and can emit uniform light even when the size and thickness are reduced. And it is providing the planar illuminating device in which a reflective film does not damage a light-guide plate.

  In order to solve the above problems, the present invention has a rectangular light exit surface, two opposing light incident surfaces each including one side of the light exit surface, and a back surface that is a surface opposite to the light exit surface. A light guide plate, two light sources arranged to face the light incident surface, a housing for housing the light guide plate and the light source, and a surface of the housing facing the back surface of the light guide plate, A plurality of struts arranged to contact the back surface of the light guide plate, and disposed at positions facing the back surface of the light guide plate, and a cross section perpendicular to the axial direction of the struts at a position corresponding to the pillar. The present invention provides a planar illumination device having a reflective film having holes of the same shape.

Here, it is preferable that the support column includes a support portion that contacts the back surface of the light guide plate, and a screw portion that is screwed into a screw hole provided on a surface of the housing facing the back surface of the light guide plate. .
Moreover, it is preferable that the said screw hole provided in the said housing | casing is provided in the pilot hole which carried out the burring process.

  Furthermore, in order to achieve the above object, the second aspect of the present invention includes a rectangular light emitting surface, two opposing light incident surfaces each including one side of the light emitting surface, and the opposite side of the light emitting surface. A light guide plate having a back surface, two light sources disposed to face the light incident surface, a housing for housing the light guide plate and the light source, and the light guide plate of the housing. A pedestal disposed on a surface facing the back surface, a plurality of support columns disposed on the surface of the pedestal facing the back surface of the light guide plate so as to contact the back surface of the light guide plate, and the light guide plate Provided is a planar lighting device having a reflective film that is disposed at a position facing a back surface and has a hole having substantially the same shape as a cross section perpendicular to the axial direction of the column at a position corresponding to the column. Is.

Here, it is preferable that a surface of the pedestal facing the back surface of the light guide plate has substantially the same shape as the back surface of the light guide plate.
Moreover, it is preferable that the said support | pillar has a support part which contact | connects the said back surface of the said light-guide plate, and a screw part screwed together in the screw hole provided in the surface facing the said back surface of the said light-guide plate of the said base.
Further, it is preferable that the screw hole provided in the pedestal is provided in a burring prepared pilot hole.

Moreover, it is preferable that the cross section perpendicular | vertical to the axial direction of the said support part of the said support | pillar is smaller than the cross section perpendicular | vertical to the axial direction of the said thread part of the said support | pillar.
Furthermore, when the thickness of the reflective film is t, the height h of the support portion of the support column is represented by the following formula:
t <h ≦ t + 0.5
It is preferable to satisfy.
Moreover, it is preferable that the surface which contact | connects the said back surface of the said light-guide plate of the said support | pillar is formed spherically.
Furthermore, it is preferable that the support column is made of a material having a hardness equal to or less than that of the light guide plate.
Moreover, it is preferable that the said support | pillar consists of a white raw material or apply | coated white paint.
Furthermore, a metal plate having a hole having substantially the same shape at a position corresponding to a hole provided in the reflection film is pasted on a surface opposite to the surface facing the back surface of the light guide plate of the reflection film. Is preferred.

  According to the present invention, a planar illumination device that has high light utilization efficiency and can emit uniform light even when the size and thickness are reduced, and the reflective film does not damage the light guide plate. Can be obtained.

The planar lighting device according to the present invention will be described below in detail based on preferred embodiments shown in the accompanying drawings.
FIG. 1 is a perspective view showing an outline of a liquid crystal display device including a planar illumination device according to the present invention, and FIG. 2 is a cross-sectional view taken along line II-II of the liquid crystal display device shown in FIG. 3 is a schematic plan view of the planar illumination device (hereinafter also referred to as “backlight unit”) shown in FIG.
4A is a view taken along the line III-III of the illuminating device main body shown in FIG. 2, and FIG. 4B is a cross-sectional view taken along line BB in FIG.

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

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

  The backlight unit 2 is an illumination device that irradiates light from the back surface of the liquid crystal display panel 4 to the entire surface of the liquid crystal display panel 4, and has a light emission surface that has substantially the same shape as the image display surface of the liquid crystal display panel 4.

As shown in FIGS. 1, 2, 3, 4A and 4B, the backlight unit 2 according to the present embodiment includes two light sources 12, a light mixing unit 14, a light guide plate 16, and an optical unit. It has the member unit 18, the illuminating device main body having the reflective film 20, the lower housing 52, the upper housing 54, the folding member 56, and the housing 22 having the support column 58. Further, as shown in FIG. 1, a power storage unit 59 that stores a plurality of power supplies for supplying power to the light source 12 is attached to the back side of the lower housing 52 of the housing 22. In FIG. 3, the light guide plate 16 and the optical member unit 18 are not shown to show the configuration of the reflective film 20.
Hereinafter, each component constituting the backlight unit 2 will be described.

First, the light source 12 will be described.
As shown in FIGS. 2, 3, and 4, the two light sources 12 are arranged so that the light guide plate 16 is sandwiched between them. The light source 12 includes an LED array 30 and a coupling lens 40. In the LED array 30, a plurality of RGB-LEDs 38 formed by using three types of light-emitting diodes of red, green, and blue (hereinafter referred to as R-LED 32, G-LED 34, and B-LED 36, respectively) are arranged in a line. It is configured. FIG. 5 schematically shows how the plurality of RGB-LEDs 38 are arranged. As shown in FIG. 5, R-LED 32, G-LED 34, and B-LED 36 are regularly arranged.
In addition, as shown in FIG. 6, the RGB-LED 38 has three types of LEDs (R-LED 32, G, so that the light emitted from the R-LED 32, G-LED 34, and B-LED 36 intersects at predetermined positions. -The orientation of the optical axis of the LED 34 and B-LED 36) is adjusted. By adjusting the three types of LEDs in this way, the light from these LEDs is mixed into white light.
The RGB-LED 38 configured using three primary color LEDs (R-LED 32, G-LED 34, and B-LED 36) has a color reproduction region as compared with a cold cathode tube (CCFL) that is conventionally used as a light source for a backlight. Therefore, when this RGB-LED 38 is used as a light source for backlight, color reproducibility is higher than in the prior art and a vivid color image can be displayed.

As shown in FIGS. 5 and 6, three ball lenses 42, 44 and 46 are arranged as coupling lenses on the light emission side of each LED of the RGB-LED 38. The ball lenses 42, 44 and 46 are arranged corresponding to the respective LEDs. That is, three ball lenses 42, 44 and 46 are used in combination for one RGB-LED 38. Light emitted from each LED (R-LED 32, G-LED 34 and B-LED 36) is collimated by ball lenses 42, 44 and 46. Then, after intersecting at a predetermined position to be white light, the light is incident on the light mixing unit 14 provided on the side surface of the light guide plate 16. A coupling lens using a combination of the three ball lenses 42, 44, and 46 is a lens having three axes, and the light of each LED of the RGB-LED can be narrowed down to one point and mixed.
Here, the ball lens is used as the coupling lens. However, the present invention is not limited to this, and the coupling lens is not particularly limited as long as the light emitted from the LED can be converted into parallel light. As the coupling lens, for example, a cylindrical lens, a lenticular, a kamaboko type lens, a Fresnel lens, or the like can be used.

In the above embodiment, the red, green, and blue LEDs 32, 34, and 36 are used, and the light emitted from each LED is mixed by the coupling lens 40 to obtain white light. It is not limited. As the light source, a monochromatic LED configured to convert light emitted from the LED into white light using a fluorescent material may be used. For example, when a GaN blue LED is used as a monochromatic LED, white light can be obtained by using a YAG (yttrium, aluminum, garnet) fluorescent material.
If a light source capable of obtaining such white light is used, it is not necessary to use a lens, and the number of members can be reduced.

Next, the light guide plate 16 of the backlight unit 2 will be described.
As shown in FIG. 4 (A), the light guide plate 16 is positioned on the opposite side of the light emission surface 16a having a substantially rectangular shape and parallel to one side of the light emission surface 16a. Two inclined surfaces (a first inclined surface 16b and a second inclined surface 16c) that are symmetrical with respect to a bisector α that bisects the surface 16a and that are inclined at a predetermined angle with respect to the light exit surface 16a; The light source 12 has two light incident surfaces (first light incident surface 16d and second light incident surface 16e) that face the two light sources 12 and on which light from the light sources 12 is incident. The first inclined surface 16b and the second inclined surface 16c are inclined with respect to the light exit surface 16a with a bisector α as a boundary. The light guide plate 16 is thicker from the first light incident surface 16d and the second light incident surface 16e toward the center, with the center being the thickest and the both ends being the thinnest.
That is, the light guide plate 16 has a substantially rectangular shape, the light exit surface 16a is the front surface (surface having a large area), the first light incident surface 16d and the second light incident surface 16e are side surfaces of the plate (elongated in the thickness direction). Surface), the first inclined surface 16b and the second inclined surface 16c serve as the back surface of the plate.
The angles of the first inclined surface 16b and the second inclined surface 16c with respect to the light exit surface 16a are not particularly limited.

  In the light guide plate 16 shown in FIG. 4, the light incident from the first light incident surface 16 d and the second light incident surface 16 e is guided by being scattered by a scatterer (details will be described later) included in the light guide plate 16. The light passes through the inside of the optical plate 16, and is emitted from the light exit surface 16a directly or after being reflected by the first inclined surface 16b and the second inclined surface 16c. At this time, a part of light may leak from the first inclined surface 16b and the second inclined surface 16c, but the leaked light is arranged to face the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16. Then, the light is reflected by the reflection film (not shown) and enters the light guide plate 16 again.

The light guide plate 16 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 16 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 16, Atsipearl, thin cone, silica, zirconia, dielectric polymer, or the like can be used. By including such scattering particles in the light guide plate 16, it is possible to emit illumination light that is uniform and has less luminance unevenness from the light exit surface.
Such a light guide plate 16 can be manufactured using an extrusion molding method or an injection molding method.

Further, the scattering cross-sectional area of the scattering particles contained in the light guide plate 16 is Φ, the length from the light incident surface of the light guide plate to the position where the thickness perpendicular to the light exit surface is maximum in the light incident direction, In the embodiment, half the length of the light incident direction of the light guide plate (the direction perpendicular to the first light incident surface 16 d of the light guide plate 16, hereinafter also referred to as “optical axis direction”) is L _G , and the light guide plate 16. And the density of scattering particles (number of particles per unit volume) is N _p , and the correction coefficient is K _C , the value of Φ · N _p · L _G · K _C is 1.1 or more, and 8.2 or less, further satisfying the relationship of the value of the correction coefficient _{K C} is 0.005 to 0.1. Since the light guide plate 16 includes scattering particles that satisfy such a relationship, the illumination light can be emitted from the light exit surface with uniform brightness and less unevenness in luminance.

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

The attenuation constant ρ is expressed by the following equation (2) using the scattering cross-sectional area Φ of particles and the number of particles N _p per unit volume contained in the medium.
ρ = Φ · N _p (2)
Therefore, the length of the half of the optical axis direction of the light guide plate when the L _G, the light extraction efficiency E _out is given by the following equation (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 16 in a direction perpendicular to the light incident surface of the light guide plate 16 to the center of the light guide plate 16 .
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 16 shown in FIG. 4 In this case, it is a ratio of light reaching the center of the light guide plate (a position having a half length in the optical axis direction of the light guide plate) with respect to light incident on the end face.
E _out ∝exp (−Φ · N _p · L _G ) (3)

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

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

Therefore, it can be seen that the larger the value of Φ · N _p · L _G · K _C is, the more preferable property is for the light guide plate. In other words, by increasing the value of Φ · N _p · L _G · K _C , it is possible to reduce the light emitted from the surface facing the light incident surface and increase the light emitted from the light emission surface. it can. That is, by increasing the value of _{Φ · N p · L G ·} K C, ( hereinafter also referred to as "light use efficiency".) Ratio of light emitted through the light exit plane to the light incident on the incident surface of the high can do. Specifically, by setting 1.1 or the value of _{Φ · N p · L G ·} K C, the light use efficiency can be 50% or more.
Here, when the value of Φ · N _p · L _G · K _C is increased, the illuminance unevenness of the light emitted from the light exit surface 16a of the light guide plate 16 becomes significant, but Φ · N _p · L _G · K _C By making the value of 8.2 or less, the illuminance unevenness can be suppressed to a certain value (within an allowable range). Note that the illuminance and the luminance can be handled in substantially the same manner. Therefore, in the present invention, it is presumed that luminance and illuminance have the same tendency.
Thus, the value of _{Φ · N p · L G ·} K C of the light guide plate of the present invention preferably satisfies the relationship of 1.1 or more and 8.2 or less, 2.0 or more and 7.0 The following is more preferable. 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.

Hereinafter, the light guide plate 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 below. In the determination of Table 1, the case where the light use efficiency is 50% or more and the illuminance unevenness is 150% or less is indicated by ◯, and the case where the light use efficiency is less than 50% or the illuminance unevenness is more than 150% is indicated by x.
Further, in FIG. 7, was measured the relationship between _{Φ · N p · L G ·} K C values and light use efficiency (ratio of light emitted through the light exit surface for light incident on the light incident surface) Results are shown.

As shown in Table 1 and FIG. 7, by setting Φ · N _p · L _G · K _C to 1.1 or more, the light use efficiency is increased, specifically, the light use efficiency is set to 50% or more. It can be seen that by setting it to 8.2 or less, the illuminance unevenness can be reduced to 150% or less.
In addition, when Kc is set to 0.005 or more, the light use efficiency can be increased, and when it is set to 0.1 or less, the illuminance unevenness of light emitted from the light guide plate can be reduced. Recognize.

Then, the particle density N _p of the particles which kneaded or dispersed in the light guide plate creates various values of the light guide plate was measured illuminance distribution of light emitted from the respective positions of the light emitting surface of each light guide plate . In this exemplary embodiment, other conditions except for the particle density N _p, specifically, the scattering cross section [Phi, half the length of the optical axis direction of the light guide plate L _G, the correction coefficient K _C, the light guide plate The shape and the like were the same value. Accordingly, in the present _{embodiment, Φ · N p · L G} · K C changes in proportion to the particle density _{N p.}
FIG. 8 shows the result of measuring the illuminance distribution of the light emitted from the light exit surface for the light guide plates having various particle densities in this way. In FIG. 8, the vertical axis is illuminance [lx], and the horizontal axis is the distance (light guide length) [mm] from one light incident surface of the light guide plate.

Furthermore, the illuminance unevenness when the maximum illuminance of light emitted from the side wall of the light guide plate of the measured illuminance distribution is I _Max , the minimum illuminance is I _Min , and the average illuminance is I _Ave [(I _Max −I _Min ) / I _Ave ] × 100 [%] was calculated.
FIG. 9 shows the relationship between the calculated illuminance unevenness and the particle density. In FIG. 9, the vertical axis is illuminance unevenness [%], and the horizontal axis is particle density [pieces / m ³ ]. FIG. 9 also shows the relationship between light utilization efficiency and particle density, where the horizontal axis is the particle density and the vertical axis is the light utilization efficiency [%].

As shown in FIGS. 8 and 9, when the particle density is increased, that is, Φ · N _p · L _G · K _C is increased, the light utilization efficiency is increased, but the illuminance unevenness is also increased. Further, it can be seen that when the particle density is lowered, that is, Φ · N _p · L _G · K _C is reduced, the light use 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.

Here, the light guide plate 16 includes a first light incident surface 16d, a second light incident surface 16e, a light exit surface 16a, which are light incident surfaces, a first inclined surface 16b, and a second inclined surface 16c, which are light reflecting surfaces. It is preferable that the surface roughness Ra of at least one of the surfaces is smaller than 380 nm, that is, Ra <380 nm.
By making the surface roughness Ra of the first light incident surface 16d and the second light incident surface 16e to be light incident surfaces smaller than 380 nm, the diffuse reflection on the surface of the light guide plate can be ignored, that is, the surface of the light guide plate Diffuse reflection can be prevented, and the incident efficiency can be improved.
Further, by making the surface roughness Ra of the light exit surface 16a smaller than 380 nm, the diffuse reflection transmission on the light guide plate surface can be ignored, that is, the diffuse reflection transmission on the light guide plate surface can be prevented, Light can be transmitted to the back by total reflection.
Furthermore, by making the surface roughness Ra of the first inclined surface 16b and the second inclined surface 16c to be light reflecting surfaces smaller than 380 nm, diffuse reflection can be ignored, that is, diffuse reflection on the light reflecting surface is reduced. It is possible to prevent the total reflection component from being transmitted further.

Here, in the light guide plate, the thickness of the light guide plate on the light incident surface (light incident portion thickness) is D1, and the thickness of the light guide plate on the surface opposite to the light incident surface (center thickness) is D2. When the length in the incident direction (light guide length) is L,
D1 <D2 and
27/100000 <(D2-D1) / (L / 2) <5/100 (A)
The ratio of the weight of the mixed scattering particles to the weight of the light guide plate: the range of Npa is 0.04 wt% <Npa <0.25 wt%
It is preferable to satisfy the relationship. By making the shape satisfying the above relationship, the emission efficiency can be improved to 30% or more.
The light guide plate
D1 <D2 and
66/100000 <(D2-D1) / (L / 2) <26/1000 (B)
The ratio of the weight of the mixed scattering particles to the weight of the light guide plate: the range of Npa is 0.04 wt% <Npa <0.25 wt%
It is also preferable to improve so as to satisfy this relationship. By making the shape satisfying the above relationship, the emission efficiency can be improved to 40% or more.
Furthermore, the light guide plate
D1 <D2 and
1/1000 <(D2-D1) / (L / 2) <26/1000 (C)
The ratio of the weight of the mixed scattering particles to the weight of the light guide plate: the range of Npa is 0.04 wt% <Npa <0.25 wt%
It is further preferable to improve so as to satisfy the relationship. By making the shape satisfying the above relationship, the emission efficiency can be improved to 50% or more.

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

  Here, in this embodiment, the two inclined surfaces (the first inclined surface 16b and the second inclined surface 16c) of the light guide plate 16 are flat surfaces, but a prism row is formed in order to reflect light efficiently. May be.

  In the present embodiment, the light guide plate has a shape that is an inclined surface in which a surface facing the light emitting surface is inclined at a certain angle with respect to the light emitting surface. Any shape may be used as long as the thickness of the light guide plate on the surface facing the light incident surface is thicker than the thickness of the light guide plate. For example, the surface (the first inclined surface 16b and / or the second inclined surface 16c in FIGS. 2 and 4) facing the light exit surface of the light guide plate may be curved. Moreover, when making an inclined surface into a curved surface, it is good also as a convex shape to the light-projection surface side, or a concave shape to a light-projection surface.

Moreover, you may produce a light-guide plate by mixing a plasticizer in said transparent resin.
Thus, by producing a light guide plate with a material in which a transparent material and a plasticizer are mixed, the light guide plate can be made flexible, that is, a flexible light guide plate. It can be deformed into a shape. Therefore, the surface of the light guide plate can be formed into various curved surfaces.
Accordingly, for example, when a light guide plate or a planar illumination device using the light guide plate is used as a display plate related to illumination (illumination), the light guide plate can be attached to a wall having a curvature. Can be used for more types, lighting of a wider range of use, POP (POP advertising), 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.

  As shown in FIGS. 2 and 4, in the backlight unit 2 of the present embodiment, light mixing portions 14 </ b> A and 14 </ b> B are provided in close contact with both side surfaces of the light guide plate 16. The light mixing units 14 </ b> A and 14 </ b> B are columnar optical components in which light scattering particles are mixed in a transparent resin, and have a function of mixing light incident through the coupling lens 40. As the material of the light mixing portions 14A and 14B, basically, the same material as that of the light guide plate 16 can be used, and similarly to the light guide plate 16, a scatterer for scattering light inside can be included. . The density and the like of the scatterers contained in the light mixing portions 14A and 14B may be the same as or different from those of the light guide plate 16. Moreover, since the light mixing parts 14A and 14B are disposed in the vicinity of the LED array 30 as shown in FIG.

Next, the optical member unit 18 will be described.
The optical member unit 18 changes the illumination light emitted from the light exit surface 16a of the light guide plate 16 to light with no uneven brightness, and emits the illumination light without uneven brightness from the light exit surface 24a of the illumination device body 24. As shown in FIG. 2, the polarized light separating film 26 that selectively transmits a predetermined polarized component of the illumination light emitted from the light emitting surface 16a of the light guide plate 16, and the polarized light separated film 26 is emitted. A diffusion film 28 that diffuses the illumination light to reduce luminance unevenness.

The polarization separation film 26 will be described.
In the present embodiment, as a preferred embodiment, the polarization separation film 26 is formed integrally with the light guide plate 16 on the light exit surface 16 a that is the light exit side surface of the light guide plate 16. The polarization separation film 26 selectively transmits a predetermined polarization component, for example, a p-polarization component, out of the light emitted from the light exit surface of the light guide plate, and most of the other polarization components, for example, the s-polarization component. Can be reflected. Since the polarized light separating film 26 allows the reflected light to enter the light guide plate again and can be reused, the light use efficiency can be improved and the luminance can be remarkably improved.
The polarized light separation film 26 is obtained, for example, by stretching a plate material obtained by kneading and dispersing needle-like particles in a transparent resin and orienting the needle-like particles in a predetermined direction.
The polarized light separating film 26 is preferably integrated by pressure bonding or fusion at the time of manufacturing the light guide plate 16. Accordingly, the light can be brought into close contact with each other without interposing air between the light exit surface 16 a of the light guide plate 16 and the polarization separation film 26.
Here, the polarization separation film 26 is formed integrally with the light guide plate 16, but the present invention is not limited to this, and the polarization separation film 26 and the light guide plate 16 are independently manufactured and formed on the light emission side surface of the light guide plate 16. The polarization separation film 26 may be attached and provided.
In the illustrated example, the polarization separation film 26 is provided immediately above the light exit surface of the light guide plate 16. However, the present invention is not limited to this, and may be provided on the diffusion film. In this case, the polarization separation film may be integrated with the diffusion film.
In addition, the polarization separation film is not particularly limited, and various known polarization separation films can be used.

Next, the diffusion film 28 will be described.
As shown in FIG. 2, the diffusion film 28 is disposed between the polarization separation film 26 and the liquid crystal panel 4. The diffusion film 28 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 28 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, which 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, the diffusion film 28 may be a mat type or coating type diffusion film.

The diffusion film 28 may be disposed at a predetermined distance from the light exit surface of the light guide plate 16, and the distance can be appropriately changed according to the light amount distribution from the light exit surface of the light guide plate 16.
Thus, by separating the diffusion film 28 from the light exit surface of the light guide plate 16 by a predetermined distance, light emitted from the light exit surface of the light guide plate 16 is further mixed (mixed) between the light exit surface and the diffusion film 28. ) Thereby, the brightness | luminance of the light which permeate | transmits the diffusion film 28 and illuminates the liquid crystal display panel 4 can be made further uniform.
As a method of separating the diffusion film 28 from the light exit surface of the light guide plate 16 by a predetermined distance, for example, a method of providing a spacer between the diffusion film 28 and the light guide plate 16 can be used.

In the present embodiment, the optical member unit 18 includes the polarization separation film 26 and the diffusion film 28. However, the arrangement order and the number of the polarization separation film 26 and the diffusion film 28 are not particularly limited, and The separation film and the diffusion film are not particularly limited, and various optical members may be used as long as the luminance unevenness of the illumination light emitted from the light exit surface 16a of the light guide plate 16 can be further reduced. it can.
For example, as an optical member, in addition to or in place of the above-described polarization separation film and diffusion film, 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, or a light incident surface It is also possible to use a prism sheet or the like on which a microprism array parallel to the tangent line to the light exit surface is formed.

Next, the reflective film 20 will be described.
The reflection film 20 is provided to reflect light leaking from the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 so as to be incident on the light guide plate 16 again, thereby improving the light use efficiency. be able to. The reflective film 20 has a shape corresponding to the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16, and is disposed to face the first inclined surface 16b and the second inclined surface 16c. In the present embodiment, as shown in FIG. 2, the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 are formed in a triangular cross section, so that the reflective film 20 is also formed in a shape that complements this. Has been.
Further, the reflective film 20 has round holes 20a corresponding to the number of columns 58 at positions corresponding to columns 58 of the casing 22 to be described later, and support portions 72 of the columns 58 are inserted into the round holes 20a. Is done. The round hole 20a is formed larger than the cross section perpendicular to the axial direction of the support portion 72 of the support column 58 and smaller than the cross section perpendicular to the axial direction of the screw portion 74 of the support column 58. The support portion 72 of 58 is inserted, but the screw portion 74 is not inserted. That is, the reflective film 20 is abutted and held on the end surface 76 (shoulder portion) of the screw portion 74.

The reflective film 20 may be formed of any material as long as it can reflect light leaking from the inclined surface of the light guide plate 16. For example, the reflective film 20 may be 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.
Further, it is preferable that a flexible metal plate that can be elastically deformed is attached to the surface of the reflective film 20 opposite to the surface facing the light guide plate 16. In the metal plate, round holes having substantially the same shape are formed corresponding to the round holes 20a of the reflection film 20, and the support portion 72 is inserted and held. By sticking a metal plate to the reflective film 20 to maintain the rigidity of the reflective film 20, it is possible to prevent wrinkles and kinks, and the reflective film 20 has the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16. It is possible to reflect the light leaked from the light and make it enter the light guide plate 16 again.

Next, the housing 22 will be described.
As shown in FIGS. 2 and 3, the housing 22 houses and supports the illuminating device body 24, and the light emitting surface 24 a side and the first inclined surface 16 b and the second inclined surface 16 c of the light guide plate 16. The lower casing 52, the upper casing 54, the reinforcing member 56, and the support 58 are sandwiched and fixed from the side.

  The lower housing 52 has a shape having an open top surface and a bottom surface portion 62 and side surfaces provided on four sides of the bottom surface portion 62 and perpendicular to the bottom surface portion 62. That is, it is a substantially rectangular parallelepiped box shape with one surface open. In addition, a plurality of screw holes 64 are provided in the bottom surface portion 62 of the lower housing 52 so as to be screwed with a support column 58 described later. As shown in FIGS. 2 and 3, the lower housing 52 supports the lighting device main body 24 accommodated from above by the bottom surface portion 62 and the side surface portion, and also surfaces other than the light emission surface 24 a side of the lighting device main body 24. That is, it covers the surface (rear surface) and the side surface opposite to the light exit surface 24a side of the illumination device main body 24.

The screw hole 64 of the lower housing 52 is formed in a hole subjected to bar link processing. By performing burring, the stroke of the screw can be increased. Here, the burring process is a process in which a hole is formed in a thin plate to form a flange.
The height of the burring process may be changed according to the gap between the first inclined surface 16 b and the second inclined surface 16 c of the light guide plate 16 and the lower housing 52. That is, in this embodiment, the height of the burring process in the vicinity of the light incident surface of the light guide plate 16 is high, and the height of the burring process is low in the vicinity of the bisector α of the light guide plate 16 or the burring process is performed. It does not have to be. In this way, by changing the height of the burring according to the gap between the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 and the lower housing 52, the height of the support column 58 can be set according to the installation position. There is no need to change it, and it can be composed of struts of the same height or a few kinds of struts.

FIG. 11A is a front view of the support column 58, and FIG. 11B is a plan view of the support column 58 shown in FIG. 11A.
As shown in FIGS. 11A and 11B, the support column 58 includes a screw portion 74 in which a male screw that is screwed into the screw hole 64 of the lower housing 52 is formed, and is coaxial with the screw portion 74 and has a screw portion. A rod-shaped member having a truncated cone-shaped support portion 72 provided on one end surface 76 of 74. In the cross section in the axial direction, the cross-sectional area of the screw part 74 is formed larger than the round hole 20a of the reflective film 20, and the cross-sectional area of the support part 72 is formed smaller than the round hole 20a of the reflective film 20. Further, the height of the support portion 72 (the length in the axial direction) is higher than the thickness of the reflective film 20, and the height of the support portion 72 is constant for all the columns 58 regardless of the height of the columns 58.

  The support 58 has the tip of the support portion 72 in contact with the first inclined surface 16 b and the second inclined surface 16 c of the light guide plate 16, and the male screw of the screw portion 74 is screwed into the screw hole 64 of the lower housing 52. Fixed. At this time, the support portion 72 is inserted through the round hole 20a at the corresponding position of the reflective film 20, and the reflective film 20 abuts against the end surface 76 of the screw portion 74 on the support portion 72 side and is bonded with an adhesive. . That is, the end surface 76 of the screw portion 74 functions as a shoulder portion 76 that holds the reflective film 20. In addition, since the height of the support portion 72 is higher than that of the reflection film 20, a gap is formed between the light guide plate 16 in contact with the tip of the support portion 72 and the reflection film 20. At this time, since the height of the support portion 72 of the support column 58 is the same for all the support columns 58, the gap between the light guide plate 16 and the reflection film 20 is uniform over the entire area.

  As described above, the reflective film 20 is provided with the round hole 20a, the support portion 72 of the support column 58 fixed to the lower housing 52 is inserted into the round hole 20a of the reflection film 20, and the reflection film is formed by the shoulder portion 76 of the support column 58. 20, the tip of the support portion 72 of the support 58 is in contact with the light guide plate 16, and a gap is provided between the first inclined surface 16 b and the second inclined surface 16 c of the light guide plate 16 and the reflective film 20. The first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 can be prevented from coming into contact with the reflective film 20, and the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 can be prevented from being damaged. Further, by making the heights of all the support portions 72 constant and making the gaps between the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 and the reflective film 20 uniform, the reflective film 20 When the light leaked from the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 is reflected and incident again into the light guide plate 16, the light can be reflected uniformly. It is possible to prevent uneven brightness from occurring in the light emitted from the light exit surface 16a.

Here, the gap between the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 and the reflective film 20 is preferably 0.5 mm or less. That is, when the thickness of the reflective film is s, the height of the support portion 72 (the distance from the shoulder portion 76 to the tip of the support portion 72) h is expressed by the following formula:
s <h ≦ s + 0.5
It is preferable to satisfy.
By providing a gap between the first inclined surface 16 b and the second inclined surface 16 c of the light guide plate 16 and the reflective film 20, the first inclined surface 16 b and the second inclined surface 16 c of the light guide plate 16 are in contact with the reflective film 20. Thus, the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 can be prevented from being scratched, but there is a gap between the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 and the reflective film 20. If it is larger, even if the light leaked from the first inclined surface 16 b and the second inclined surface 16 c of the light guide plate 16 is reflected by the reflection film 20, a part of the light does not enter the light guide plate 16 and the first light guide plate 16 has the first light. The light leaks from the gaps between the inclined surface 16b and the second inclined surface 16c and the reflective film 20, and the luminance of the light emitted from the light emitting surface 16a of the light guide plate 16 decreases. That is, the light utilization efficiency decreases.
Therefore, by setting the gap between the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 and the reflective film 20 to 0.5 mm or less, the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 are formed. The first inclined surface 16b and the second inclined surface 16c of the light guide plate 16, the reflective film 20 and the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 are prevented from being damaged due to contact with the reflective film 20. Light leaking from the gap can be reduced. That is, as compared with the case where no gap is provided between the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 and the reflective film 20, the same light use efficiency can be maintained.

In addition, as a material used for the support 58, a material having good sliding property such as POM (polyacetal) and softer than the light guide plate 16 can be used. By using a material that is softer and more slidable than the light guide plate 16 as a material for the support 58 that contacts the light guide plate 16, it is possible to prevent the support 58 from scratching the light guide plate 16.
Alternatively, it is possible to prevent the column 58 from damaging the light guide plate 16 by using a soft and good slidable material for the portion of the column 58 that contacts the light guide plate 16, that is, the tip of the support portion 72.

Moreover, it is preferable that the surface of the support | pillar 58 is white. A round hole 20a is formed at a position corresponding to the support column 58 of the reflective film 20, and light reaching the position of the round hole 20a of the reflective film 20 is not reflected by the reflective film 20, so that the light exit surface of the light guide plate 16 In the light emitted from 16 a, uneven brightness occurs at a position corresponding to the round hole 20 a of the reflective film 20.
Then, the light which reached the position of the round hole 20a (support 58) can also be reflected by making the surface of the support | pillar 58 arrange | positioned in the position of the round hole 20a of the reflective film 20 into white with high reflectance. Thereby, it is possible to prevent uneven brightness from occurring in the light emitted from the light exit surface 16 a of the light guide plate 16.
In order to make the surface of the column 58 white, the column 58 may be formed using a white material, or white paint may be applied to the surface of the column 58.

FIG. 12A is a front view showing a schematic configuration of another example of the support, and FIG. 12B is a plan view of the support shown in FIG.
As shown in FIGS. 12A and 12B, the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 may be formed such that the tip of the support portion 252 of the column 250 has a hemispherical shape. By making the tip in contact with the hemisphere, it is possible to prevent the column 250 from scratching the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16.

  In this embodiment, the support 58 is fixed to the lower housing 52 by providing the support 58 with the screw portion 74, but the present invention is not limited to this, and the support 58 is attached to the lower housing 52. Other methods may be used as long as they can be fixed. For example, it may be bonded with an adhesive, or the support column 58 may be formed integrally with the lower housing 52. However, the method of providing the screw portion 74 on the support column 58 and screwing the support column 58 to the lower housing 52 can individually adjust the position of the support column 58 in the axial direction, and the tip of the support portion 72 of the support column 58 can be reliably secured. The light guide plate 16 can be brought into contact with the first inclined surface 16b and the second inclined surface 16c. That is, the method of screwing the support column 58 and the lower housing 52 is preferable in that the gap between the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 and the reflective film 20 can be kept uniform.

  Further, the positions where the columns 58 are arranged and the number of columns 58 are not particularly limited as long as the light guide plate 16 and the reflection film 20 can be held. However, when the number of columns 58 increases, the reflection film 20 has many round holes. 20a is provided, and the area of the reflective film 20 is reduced, so that the amount of light reflected by the reflective film 20 and incident on the light guide plate 16 again is reduced. As a result, the light utilization efficiency is reduced and luminance unevenness is likely to occur.

  Further, the size of the cross section perpendicular to the axial direction of the support portion 72 of the support column 58 is not particularly limited as long as the light guide plate 16 and the reflection film 20 can be held, but when the cross section perpendicular to the axial direction of the support portion 72 becomes large. Since the round hole 20a provided in the reflective film 20 is also enlarged and the area of the reflective film 20 is reduced, the amount of light reflected by the reflective film 20 and incident on the light guide plate 16 again is reduced. As a result, the light use efficiency decreases and uneven brightness tends to occur. Therefore, it is preferable that the cross section perpendicular to the axial direction of the support portion 72 of the support column 58 is small.

Further, in this embodiment, the shape of the support portion 72 of the support column 58 is a truncated cone shape, but the present invention is not limited to this, and the cross section perpendicular to the axial direction is more than the round hole 20a of the reflective film 20. Any small shape may be used.
FIG. 13A is a front view showing a schematic configuration of another example of the support 260, and FIG. 13B is a plan view of the support 260 shown in FIG. 13A. In addition, the support | pillar shown in FIG. 13 differs only in the shape of a support part, and since the other site | part has the same structure as the support | pillar 72 shown in FIG. 11, the same code | symbol is attached | subjected to the same site | part, Do different parts mainly.
13 includes a screw portion 74, a shoulder portion 76 that is an end surface of the screw portion, and a columnar support portion 262 that is coaxial with the screw portion 74 and formed on the shoulder portion 76. The cross section perpendicular to the axial direction of the support portion 262 is smaller than the round hole 20 a of the reflection film 20, and the height of the support portion 262 is higher than the thickness of the reflection film 20. The support portion 262 is inserted into the round hole 20 a of the reflective film 20, and the tip of the support portion 262 is in contact with the first inclined surface 16 b and the second inclined surface 16 c of the light guide plate 16 to support the light guide plate 16. The shoulder 76 holds the reflective film 20. Thus, even if the shape of the support portion 262 is changed to a cylindrical shape, the same effect as described above can be obtained. Further, if the shape of the support portion 262 is a columnar shape, the fixing means for the reflective film 20 can be replaced by adhesion with an adhesive, and the round hole 20a of the reflective film 20 and the support portion 262 can be press-fitted.

In this embodiment, the cross section perpendicular to the axial direction of the column is circular, but the column used in the planar lighting device of the present invention is not limited to this, and two columnar shapes having different cross-sectional sizes are used. The members may be combined to form a columnar member having a step. For example, even if a columnar member having a step formed by combining a triangular column or a quadrangular column is used, if the tip of the columnar member abuts the light guide plate and the reflection film is held by the step (shoulder), the reflection film is the same as in the above embodiment. It can hold | maintain so that it may not contact with a light-guide plate, and it can prevent that a light-guide plate is damaged.
However, if a hole other than a circular shape is formed in the reflective film, cracks are easily formed from the corners. Therefore, the cross section perpendicular to the axial direction of the column and the shape of the hole formed in the reflective film are preferably circular.

The upper housing 54 has a rectangular parallelepiped box shape in which a rectangular opening smaller than the rectangular light exit surface 16a of the light guide plate 16 serving as an opening is formed on the upper surface, and the lower surface is opened.
As shown in FIG. 2, the upper housing 54 includes the lighting device main body 24 and the lower housing 52 in which the lighting device main body 24 and the lower housing 52 are housed in the four directions from above the lighting device main body 24 and the lower housing 52. The side portion is also placed so as to cover the side portion.

The folding member 56 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 56 is inserted between the side surface of the lower housing 52 and the side surface of the upper housing 54, and the outer surface of one of the U-shaped parallel portions is the lower housing 52. 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 54.
Here, as a method for joining the lower casing 52 and the folding member 56, and a method for joining the folding member 56 and the upper casing 54, various known methods such as a method using a bolt and a nut, a method using an adhesive, and the like. Can be used.

Thus, by arranging the folding member 56 between the lower housing 52 and the upper housing 54, the rigidity of the housing 22 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.

  In the above embodiment, by placing a column in the lower housing, forming a round hole at a position corresponding to the column of the reflective film, inserting the column through the round hole, and supporting the light guide plate at the tip of the column The light guide plate and the reflective film are prevented from coming into contact with each other, and the light guide plate is prevented from being damaged. However, the present invention is not limited to this, and a pedestal is disposed in the lower housing, and a support is disposed in the pedestal. It is good also as a structure which inserts a support | pillar in a round hole and supports so that a light-guide plate and a reflective film may not contact.

Hereinafter, another embodiment of the present invention will be described in detail with reference to FIG.
FIG. 14 is a cross-sectional view schematically showing the illuminating device body 24 and the housing 102 of the liquid crystal display device 120 using the backlight unit 100 according to another embodiment of the present invention. The backlight unit 100 has the same configuration and shape as the backlight unit 2 described above except that the pedestal 114 is disposed in the lower housing 110 and the support column 58 is disposed on the pedestal 114. Detailed description thereof is omitted.

Since the lower housing 110 has the same configuration as the lower housing 52 of the backlight unit 2 described above except that the screw holes 64 are not formed in the bottom surface portion 112, detailed description thereof is omitted.
A pedestal 114 is attached to the bottom surface portion 112 of the lower housing 110 in place of the support column 58.

The pedestal 114 has substantially the same shape as the back surface opposite to the light exit surface 16a of the light guide plate 16 and is disposed opposite to the back surface of the light guide plate, and 2 on the light source 12 side of the seat surface 116. The shape is formed by a side surface portion provided on the side and perpendicular to the seating surface 116.
In the present embodiment, the rear surface of the light guide plate 16 is composed of a first inclined surface 16b and a second inclined surface 16c, and is directed from the first light incident surface 16d and the second light incident surface 16e toward the central portion (bisector α). Therefore, since the light guide plate 16 is inclined so that the thickness thereof is increased, the seat surface 116 of the pedestal 114 is similarly inclined toward the center. Therefore, the gap between the seat surface 116 and the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 is uniform over the entire area.
Further, the side of the pedestal 114 is fixed to the bottom surface 62 of the lower housing 52 at the end opposite to the seating surface 116.

The seat surface 116 is provided with a plurality of screw holes 118 that are screwed into the screw portions 74 of the support column 58. The screw hole 118 is formed in a burring hole. By performing burring and increasing the stroke of the screw, the support column 58 and the pedestal 114 are securely screwed together.
In addition, if the screw hole 118 of the base 114 and the screw part 74 of the support column 58 are securely screwed together, the burring process may not be performed.

As described above, by arranging the support column 58 on the pedestal 114 disposed on the bottom surface portion 62 of the lower housing 52, the front end of the support portion 72 of the support column 58 is connected to the first inclined surface 16 b and the second inclined surface of the light guide plate 16. The light guide plate 16 and the reflective film 20 can be supported so that the light guide plate 16 and the reflective film 20 do not come into contact with each other. It is possible to prevent the light guide plate from being damaged due to contact between the optical plate 16 and the reflective film 20.
Further, since the gap between the seat surface 116 of the pedestal 114 and the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 is uniform over the entire area, the column 58 having the same shape can be used. It can be simplified.

  Further, by providing a pedestal 114 having a seat surface 116 having substantially the same shape as the back surface of the light guide plate 16 and having a uniform gap between the back surface and the entire region, and placing the support column 58 on the seat surface 116, the same length is obtained. A length post 58 can be used.

Further, by placing a support on the pedestal 114 having a seating surface 116 with a uniform gap with the back surface of the light guide plate 16, a support having a shape that does not have a shoulder for holding the reflective film 20 can be used. Since the reflective film 20 has a round hole 20a larger than the cross section perpendicular to the axial direction of the support column at a position corresponding to the position of the support column, the support film is inserted into the round hole 20a of the reflective film 20, and the reflective film 20 It is supported by the seat surface 116 of the pedestal 114 instead of the shoulder of the column. By not providing a shoulder on the column, the shape of the column can be simplified. Further, since the reflective film 20 can be held over almost the entire area of the seating surface 116 of the pedestal 114, it is possible to prevent the reflective film 20 from being wrinkled or twisted.
The reflective film 20 and the seating surface 116 may be bonded by an adhesive or the like, or the reflective film 20 may be fixed by press-fitting a support column and the round hole 20a of the reflective film 20.

  In this embodiment, the pedestal 114 and the support column 58 are fixed by screwing. However, the present invention is not limited to this, and other methods may be used as long as the support column 58 can be fixed to the pedestal 114. For example, it may be bonded with an adhesive, or the support column 58 may be formed integrally with the base 114. However, the method of screwing the pedestal 114 and the pedestal 114 can individually adjust the position of the support column 58 in the axial direction, and the tip of the support portion 72 of the support column 58 can be surely connected to the first inclined surface 16b of the light guide plate 16 and This is preferable in that it can be brought into contact with the second inclined surface 16c and the gap between the first inclined surface 16b and the second inclined surface 16c of the light guide plate 16 and the reflective film 20 can be kept uniform.

  In addition, as a method for joining the pedestal 114 and the lower housing 110, various known methods such as a method using bolts and nuts, a method using an adhesive, and the like can be used.

The planar illumination device 2 in which the support column 58 is disposed in the lower housing 52 has an advantage that it can be made thinner than the planar illumination device 100 in which the base 114 is provided in the lower housing 110 and the support column 58 is disposed in the support 114. is there. On the other hand, the planar lighting device 100 in which the pedestal 114 is provided in the lower housing 110 and the support column 58 is disposed on the pedestal 114 does not perform burring as compared with the planar illumination device 2 in which the support column 58 is disposed in the lower housing 52. However, since the struts 58 having the same shape can be used, there is an advantage that the configuration can be simplified and the cost can be reduced. Which configuration is used may be determined according to the performance required for the planar illumination device.
Further, a configuration in which the support column 58 is disposed in the lower housing 52 and a configuration in which the pedestal 114 is provided in the lower housing 110 and the support column 58 is disposed in the pedestal 114 may be used in combination. For example, a structure may be adopted in which a pedestal is provided in the lower housing near the light incident surface and a support column is disposed on the pedestal, and a support column is directly disposed on the lower housing in the central portion. If a pedestal is provided in the vicinity of the light incident surface and a column is arranged on the pedestal, and a column is arranged in the lower housing in the center, the thickness of the planar lighting device can be reduced and the column has the same shape. The configuration can be simplified using

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

It is a schematic perspective view which shows one Embodiment of the liquid crystal display device using the planar illuminating device which concerns on this invention. It is the II-II sectional view taken on the line of the liquid crystal display device shown in FIG. FIG. 3 is a schematic plan view of the liquid crystal display device shown in FIG. 2. (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). It is a figure which shows typically the mode of arrangement | positioning of several RGB-LED comprised using three types of light emitting diodes of red, green, and blue. It is a schematic diagram of RGB-LED and a coupling lens. It is a diagram showing the results of measuring the relationship between _{Φ · N p · L G ·} K C and light use efficiency. It is a figure which shows the result of having measured the illumination intensity of the light inject | emitted from each light guide from which particle density differs, respectively. It is a figure which shows the relationship between light use efficiency, illumination intensity nonuniformity, and particle density. It is a figure which shows the result of having measured the relationship between the shape of a light-guide plate, and light utilization efficiency. (A) is a front view which shows schematic structure of an example of a support | pillar, (B) is a top view of the support | pillar shown to (A). (A) is a front view which shows schematic structure of another example of a support | pillar, (B) is a top view of the support | pillar shown to (A). (A) is a front view which shows schematic structure of another example of a support | pillar, (B) is a top view of the support | pillar shown to (A). It is a schematic sectional drawing which shows another example of the planar illuminating device of this invention.

Explanation of symbols

2,100 Backlight unit (planar lighting device)
4 liquid crystal display panel 6 drive unit 10, 120 liquid crystal display device 12 light source 14A light mixing unit 14B light mixing unit 16 light guide plate 16a, 24a light exit surface 16b first inclined surface 16c second inclined surface 16d first light incident surface 16e first Two light incident surfaces 18 Optical member unit 20 Reflective film 20a Round hole 22, 104 Case 24, 102 Illumination device body 26 Polarization separation film 28 Diffusing film 30 LED array 52, 110 Lower case 54 Upper case 56 Folding member 58, 250, 260 Support 62, 112 Bottom surface 64, 118 Screw hole 72, 252, 262 Support portion 74 Screw portion 76 Shoulder portion (Screw end surface)
114 pedestal 116 bearing surface

Claims (13)

A light guide plate having a rectangular light exit surface, at least one light incident surface each including one side of the light exit surface, and a back surface opposite to the light exit surface;
At least one light source disposed opposite the light incident surface;
A housing for housing the light guide plate and the light source;
A plurality of support columns disposed on the surface of the housing facing the back surface of the light guide plate so as to be in contact with the back surface of the light guide plate;
A planar shape having a reflective film that is disposed at a position facing the back surface of the light guide plate and has a hole having substantially the same shape as a cross section perpendicular to the axial direction of the pillar at a position corresponding to the pillar. Lighting device. The support is in contact with the back surface of the light guide plate;
The planar illumination device according to claim 1, further comprising: a screw portion that is screwed into a screw hole provided on a surface of the housing facing the back surface of the light guide plate.   The planar illumination device according to claim 2, wherein the screw hole provided in the housing is provided in a burring prepared pilot hole. A light guide plate having a rectangular light exit surface, at least one light incident surface each including one side of the light exit surface, and a back surface opposite to the light exit surface;
At least one light source disposed opposite the light incident surface;
A housing for housing the light guide plate and the light source;
A pedestal disposed on a surface of the housing facing the back surface of the light guide plate;
A plurality of support columns disposed on the surface of the pedestal facing the back surface of the light guide plate so as to contact the back surface of the light guide plate;
A planar shape having a reflective film that is disposed at a position facing the back surface of the light guide plate and has a hole having substantially the same shape as a cross section perpendicular to the axial direction of the pillar at a position corresponding to the pillar. Lighting device.   The surface illumination device according to claim 4, wherein a surface of the pedestal facing the back surface of the light guide plate has substantially the same shape as the back surface of the light guide plate. The support is in contact with the back surface of the light guide plate;
The planar illumination device according to claim 4, further comprising: a screw portion that is screwed into a screw hole provided on a surface of the base that faces the back surface of the light guide plate.   The planar illumination device according to claim 6, wherein the screw hole provided in the pedestal is provided in a burring prepared pilot hole.   The planar illumination device according to claim 1, wherein a cross section of the support column perpendicular to the axial direction of the support portion is smaller than a cross section of the support column perpendicular to the axial direction of the screw portion. When the thickness of the reflective film is t, the height h of the support portion of the support column is represented by the following formula:
t <h ≦ t + 0.5
The planar illuminating device of Claim 8 which satisfy | fills.   The surface illumination device according to any one of claims 1 to 9, wherein a surface of the support column in contact with the back surface of the light guide plate is formed in a spherical shape.   The planar illumination device according to claim 1, wherein the support column is made of a material having a hardness equal to or less than that of the light guide plate.   The planar lighting device according to any one of claims 1 to 11, wherein the support column is made of a white material or is coated with a white paint.   The metal plate which has the hole of the substantially same shape in the position corresponding to the hole provided in the said reflective film on the surface on the opposite side to the surface facing the said back surface of the said light guide plate of the said reflective film was affixed. The planar illuminating device in any one of -12.

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