JP4974703B2 - Surface lighting device - Google Patents

Description

  The present invention relates to a planar illumination device used for 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 guide plate is disposed immediately above a light source for illumination (see, for example, Japanese Utility Model Publication No. 5-4133). In this system, a plurality of cold-cathode tubes, which are light sources, are arranged on the back surface of the liquid crystal display panel, and a uniform light quantity distribution and necessary luminance are ensured with the inside as a white reflecting surface.

  However, in the direct type backlight unit, in order to make the light quantity distribution uniform, the thickness in the direction perpendicular to the liquid crystal display panel is required to be about 30 mm. In the future, a thinner backlight unit will be desired. However, it is considered difficult to realize a backlight unit having a thickness of 10 mm or less from the standpoint of unevenness in the amount of light in the direct type.

  Therefore, a tandem system has been proposed as a thin backlight unit (see, for example, JP-A-2-208631, JP-A-11-288611, and JP-A-2001-312916).

Japanese Utility Model Publication No. 5-4133 JP-A-2-208631 JP-A-11-288611 JP 2001-312916 A

  However, a thin tandem backlight unit can be realized, but the light utilization efficiency is inferior to that of the direct type due to the relative dimensions of the cold cathode tube and the reflector. In addition, when using a light guide plate that accommodates a cold cathode tube in a groove formed in the light guide plate, reducing the thickness of the light guide plate increases the luminance directly above the cold cathode tube disposed in the groove, thereby emitting light. The brightness unevenness of the surface becomes remarkable.

Therefore, there is a limit to reducing the thickness of the tandem backlight unit.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a planar illumination device that can emit illumination light that has a thin shape and is uniform and has less luminance unevenness.
Furthermore, another object of the present invention is to provide a planar illumination device that can emit light having high color rendering properties and high brightness from the light exit surface, and can increase the size of the light exit surface.

In order to solve the above problems, a first aspect of the present invention includes a light source, a light incident surface on which light emitted from the light source is incident, and a light emission surface that emits light incident from the light incident surface. And a light source plate, wherein the light source provides a planar illumination device having a plurality of LED chips that emit light having a light emission wavelength having two or more main peak wavelengths.
In order to solve the above-mentioned problem, a second aspect of the present invention is a light source composed of a plurality of LED chips that emit light having different emission wavelengths, and a light incident surface on which light emitted from the light source is incident. And a light guide plate having a light emission surface for emitting light incident from the light incident surface, and the LED provides a planar illumination device that emits light having an emission wavelength having two or more main peak wavelengths To do.

Here, in the planar lighting device of the first and second embodiments, the LED chip is disposed on the LED having a light emitting surface that emits light and the light emitting surface of the LED, and is emitted from the LED chip. It is preferable to have a wavelength conversion member that converts a part of the wavelength of the light.
The LED preferably emits light in any one wavelength region of red, blue, green, purple, ultraviolet, near ultraviolet, infrared, and near infrared.
The wavelength conversion member is preferably a phosphor that emits light when light is transmitted therethrough.
Further, the LED chip emits light having main peaks in all of red, blue, and green.

The LED chips are preferably arranged in a row at a position facing the light incident surface.
The LED chip has a length in a direction perpendicular to the light emitting surface of the light guide plate as a, a length in the arrangement direction of the LEDs as b, and an arrangement interval of the LEDs as p. It is preferable to satisfy the relationship of p>b> a.
Furthermore, the light source has two or more LED arrays in which the LED chips are arranged in a row, and uses at least one of a mechanical bonding method and a chemical bonding method, and the LED chip of the LED array and the other LED array are used. It is preferable to have a configuration in which the LED array is stacked with the LED chip spaced apart by a predetermined distance.

In order to solve the above-described problem, the third aspect of the present invention is directed to a light source, a light incident surface on which light emitted from the light source is incident, and a light emission surface that emits light incident from the light incident surface. The light source provides a planar illumination device having at least one LED that emits monochromatic light.
Furthermore, in order to solve the said subject, the 4th form of this invention is the light source provided with the LED unit comprised by LED which inject | emits the light of the mutually different emission wavelength, and the light inject | emitted from the said light source. The LED has a light incident surface that includes an incident light incident surface and a light guide surface that emits light incident from the light incident surface, and the LED provides a planar illumination device that emits monochromatic light.
Here, in the planar lighting devices of the third and fourth embodiments, it is preferable that the LEDs constituting the LED unit are a red light emitting diode, a green light emitting diode, and a blue light emitting diode.

Moreover, it is preferable that the planar lighting device of the 1st-4th form has a light transmissive part further arrange | positioned between the said light source and the said light-incidence surface, and the light inject | emitted from the said light source permeate | transmits.
Moreover, it is preferable that the said light transmissive part is arrange | positioned non-contacting with the said light source and the said light-guide plate.

Furthermore, the light source includes a first light source and a second light source,
The light guide plate is disposed between the first light source and the second light source, faces the first light source, faces a first light incident surface including one side of the light emission surface, and faces the second light source. It is preferable that it has a second incident surface including the opposite side of the one side, and has a shape in which the thickness increases from the first light incident surface and the second light incident surface toward the center.
Moreover, it is preferable that the said light-guide plate contains the scattering particle which scatters the light which injects from the 1st and 2nd light-incidence surface and propagates an inside.
Further, the light guide plate, the scattering cross section of the scattering particles [Phi, the length of the half of the incident direction of the light L _G, the density of the scattering particles N _p, a correction coefficient is K _C, the K _C 0. When 005 to 0.1, it is preferable to satisfy the _{1.1 ≦ Φ · N p · L} G · K C ≦ 8.2.
Moreover, it is preferable that the said light-projection surface of the said light-guide plate has a rectangular external shape.

The light exit surface of the light guide plate is formed flat, and the light guide plate is divided into two equal parts of the light exit surface parallel to the one side of the light exit surface on the opposite side of the light exit surface. It is preferable to have a first inclined surface and a second inclined surface that are formed so as to be symmetrically inclined with respect to the line.
Moreover, it is preferable that the connection part of the said 1st inclined surface and the said 2nd inclined surface is R shape in the cross-sectional shape where the said light-guide plate is perpendicular | vertical to the said bisector.
Moreover, it is preferable that a polarization separation film that selectively transmits a predetermined polarization component and reflects other polarization components is integrally formed with the light guide plate on the light exit surface of the light guide plate.

  Further, the light emitting surface of the light guide plate is formed by a first inclined surface and a second inclined surface that are symmetrically inclined with respect to a bisector of the light emitting surface parallel to the one side of the light emitting surface. A third inclined surface formed on the opposite side of the light emitting surface and symmetrically inclined with respect to a bisector of the light emitting surface parallel to the one side of the light emitting surface; The fourth inclined surface is preferably formed.

  Further, the light emitting surface of the light guide plate is formed by a first inclined surface and a second inclined surface that are symmetrically inclined with respect to a bisector of the light emitting surface parallel to the one side of the light emitting surface. It is preferable that the surface opposite to the light exit surface is formed flat.

Further, the light guide plate includes two or more light guide plates, a surface including one side of the light exit surface of the light guide plate and one side of the light incident surface, one side of the light exit surface of the other light guide plate, and the incident surface. It is preferable that the surface including one side is adjacently disposed.
In the light guide plate, it is preferable that a plurality of diffuse reflectors are disposed on at least one of the surfaces excluding the first light incident surface and the second light incident surface.
Moreover, it is preferable that the said diffuse reflector is arrange | positioned densely as it leaves | separates from the said 1st light incident surface and the said 2nd light incident surface.
The diffuse reflector is preferably disposed on the first inclined surface and the second inclined surface.
In the light guide plate, a part on the first light incident surface side and a part on the second light incident surface side are formed of a material different from other parts, and the first light incident surface side It is preferable that the relationship of Nm> Ni is satisfied, where Nm is a refractive index of a part of the material and a part of the material on the second light incident surface side and Ni is a refractive index of the material of the other part.
Furthermore, the light emitting surface of the light guide plate in the vicinity of the first light incident surface, the first inclined surface in the vicinity of the first light incident surface, the light emitting surface in the vicinity of the second light incident surface, and the first It is preferable to have reflective materials respectively disposed on the second inclined surface in the vicinity of the two light incident surfaces.
The light incident surface preferably has a surface roughness of 380 nm or less.

According to the present invention, by using an LED as a light source, light having high color rendering properties and high color rendering properties can be emitted from the light emitting surface. Furthermore, light can reach a position further away from the light incident surface of the light guide plate, and the apparatus can be enlarged.
Further, the light guide plate is arranged between the first light source and the second light source that are separated from each other by a predetermined distance, and the light guide plate is made up of the light emitting surface and the first light incident surface facing the first light source. And a second incident surface facing the second light source, and the thickness is increased from the first light incident surface and the second light incident surface toward the center, thereby realizing a reduction in thickness. In addition, it is possible to emit planar illumination light that is uniform and has less unevenness.
Furthermore, by making the light guide plate contain scattering particles that scatter the light propagating inside, the light incident on the light guide plate can be scattered, and uniform and uniform planar illumination light can be emitted. Can be further reduced in thickness.

A liquid crystal display device including a planar illumination device according to the present invention will be described in detail based on an embodiment shown in the accompanying drawings.
FIG. 1A is a perspective view showing an outline of a liquid crystal display device including a planar illumination device according to the first embodiment of the present invention, and FIG. 1B is a schematic cross-sectional view of the liquid crystal display device. . 2A is a schematic plan view of a light guide plate and a light source used in the planar lighting device (hereinafter referred to as a backlight unit) according to the present invention, and FIG. 2B is an outline of the light guide plate. It is sectional drawing.
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. .

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.

  The backlight unit 2 according to the first embodiment of the present invention includes two light sources 12 as shown in FIG. 1 (A), FIG. 1 (B), FIG. 2 (A), and FIG. A diffusion film 14, a polarization separation film 16, a light guide plate 18 as a light guide member, a light mixing unit 20, and a reflection sheet 22 are included. Hereinafter, each component constituting the backlight unit 2 will be described.

First, the light source 12 will be described.
As shown in FIG. 1B, the two light sources 12 are arranged so that the light guide plate 18 is sandwiched between them. The light source 12 includes an LED array 24 and a coupling lens 40. In the LED array 24, a plurality of RGB-LEDs 30 formed 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. 3 schematically shows how the plurality of RGB-LEDs 30 are arranged. As shown in FIG. 3, the R-LED 32, the G-LED 34, and the B-LED 36 are regularly arranged.
Further, as shown in FIG. 4, the RGB-LED 30 includes three types of LEDs (R-LED 32, G-type) so that 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.
In this way, by using the LED as the light source, the light emitted from the light source can reach the back of the light guide plate described later.
The RGB-LED 30 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 fluorescent lamp (CCFL) that is conventionally used as a light source for backlight. Therefore, when this RGB-LED 30 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. 3 and 4, three ball lenses 42, 44, and 46 are arranged as coupling lenses on the light emission side of each LED of the RGB-LED 30. 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 30. 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 crossing at a predetermined position to be white light, it enters the light mixing unit 20 of the light guide plate 18. 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.

Next, the light guide plate 18 of the backlight unit 2 will be described.
As shown in FIG. 2A, the light guide plate 18 is positioned on the opposite side of the light emitting surface 18a having a substantially rectangular shape and parallel to one side of the light emitting surface 18a. Two inclined surfaces (a first inclined surface 18b and a second inclined surface 18c) that are symmetrical to each other with respect to a bisector X that bisects the surface 18a and are inclined at a predetermined angle with respect to the light exit surface 18a; The two LED arrays 24 are opposed to each other, and two light incident surfaces (first light incident surface 18d and second light incident surface 18e) on which light from the LED arrays 24 is incident are provided. The first inclined surface 18b and the second inclined surface 18c are inclined with respect to the light exit surface 18a with the bisector X as a boundary. The light guide plate 18 is thicker from the first light incident surface 18d and the second light incident surface 18e toward the center, with the center being the thickest and the both ends being the thinnest.
That is, the light guide plate 18 has a substantially plate shape, the light emission surface 18a is the front surface (surface having a large area), the first light incident surface 18d and the second light incident surface 18e are side surfaces (thickness direction). (Elongated surface), the first inclined surface 18b and the second inclined surface 18c become the back surface of the plate.
The angles of the first inclined surface 18b and the second inclined surface 18c with respect to the light exit surface 18a are not particularly limited.
In addition, prism rows are formed on the first inclined surface 18b and the second inclined surface 18c in a direction parallel to the light incident surfaces 18d and 18e. Instead of such a prism array, optical elements similar to prisms can be regularly formed. For example, an optical element having a lens effect, such as a lenticular lens, a concave lens, a convex lens, or a pyramid type, can be formed on the inclined surface of the light guide plate.

  In the light guide plate 18 shown in FIG. 2, the light incident from the first light incident surface 18d and the second light incident surface 18e is scattered by a scatterer (details will be described later) included in the light guide plate 18 while being guided. The light passes through the inside of the optical plate 18 and is reflected directly or after being reflected by the first inclined surface 18b and the second inclined surface 18c, and then emitted from the light exit surface 18a. At this time, some light may leak from the first inclined surface 18b and the second inclined surface 18c, but the leaked light covers the first inclined surface 18b and the second inclined surface 18c of the light guide plate 18. Then, the light is reflected by a reflection sheet (not shown) and is incident on the light guide plate 18 again.

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

Further, the scattering cross-sectional area of the scattering particles contained in the light guide plate 18 is Φ, the length from the light incident surface of the light guide plate to the position where the thickness in the direction orthogonal 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 18 d of the light guide plate 18, hereinafter also referred to as “optical axis direction”) is L _G , and the light guide plate 18. 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 18 includes scattering particles satisfying such a relationship, it is possible to emit illumination light that is uniform and has less luminance unevenness from the light exit surface.

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

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

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

Therefore, it can be seen that the larger the value of Φ · N _p · L _G · K _C is, the more preferable property is for the light guide plate. In other words, by increasing the value of Φ · N _p · L _G · K _C , it is possible to reduce the light emitted from the surface facing the light incident surface and increase the light emitted from the light emission surface. it can. That is, by increasing the value of _{Φ · N p · L G ·} K C, ( hereinafter also referred to as "light use efficiency".) Ratio of light emitted through the light exit plane to the light incident on the incident surface of the high can do. Specifically, by setting 1.1 or the value of _{Φ · N p · L G ·} K C, the light use efficiency can be 50% or more.
Here, when the value of Φ · N _p · L _G · K _C is increased, the illuminance unevenness of the light emitted from the light exit surface 18a of the light guide plate 18 becomes remarkable, but Φ · N _p · L _G · K _C By making the value of 8.2 or less, the illuminance unevenness can be suppressed to a certain value (within an allowable range). Note that the illuminance and the luminance can be handled in substantially the same manner. Therefore, in the present invention, it is presumed that luminance and illuminance have the same tendency.
Thus, the value of _{Φ · N p · L G ·} K C of the light guide plate 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. 5, to determine 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. 5, by a _{Φ · N p · L G ·} K C to 1.1 or more, increasing the light use efficiency, specifically 50% or more of light use efficiency and 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. 6 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. 6, the vertical axis represents illuminance [lx], and the horizontal axis represents 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 the 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. 7 shows the relationship between the calculated illuminance unevenness and the particle density. In FIG. 7, the vertical axis represents illuminance unevenness [%], and the horizontal axis represents particle density [pieces / m ³ ]. FIG. 7 also shows the relationship between the light utilization efficiency and the particle density, where the horizontal axis is similarly the particle density and the vertical axis is the light utilization efficiency [%].

As shown in FIGS. 6 and 7, when the particle density is increased, that is, Φ · N _p · L _G · K _C is increased, the light use efficiency is increased, but the illuminance unevenness is also increased. It can also be seen that when the particle density is lowered, that is, when Φ · N _p · L _G · K _C is reduced, the light utilization efficiency is reduced, but the illuminance unevenness is reduced.
Here, by the _{Φ · N p · L G ·} K C less than 1.1 and not greater than 8.2, the light use efficiency of 50% or more, and the illuminance unevenness of 150% or less. By setting the illuminance unevenness to 150% or less, the illuminance unevenness can be made inconspicuous.
_{That, Φ · N p · L G} · K C to be to less than 1.1 and not greater than 8.2 yields light use efficiency above a certain level, and illuminance unevenness also seen that it is possible to reduce.

  In this embodiment, as shown in FIG. 1B and FIG. 2B, the light emission surface 18a is a flat surface. However, in this embodiment, the light emission surface is substantially flat. (That is, a plane) is sufficient. For example, if the light emission surface 18a becomes a slightly concave curved surface on the first inclined surface 18d and second inclined surface 18c side due to manufacturing error or aging after molding, etc. Can be used.

Here, the light guide plate 18 includes a first light incident surface 18d, a second light incident surface 18e, a light exit surface 18a, which are light incident surfaces, a first inclined surface 18b, and a second inclined surface 18c, 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 18d and the second light incident surface 18e, which are the light incident surfaces, smaller than 380 nm, the diffuse reflection on the surface of the light guide plate is ignored, that is, on the surface of the light guide plate. Diffuse reflection can be prevented, and incident efficiency can be improved.
Further, by making the surface roughness Ra of the light exit surface 18a smaller than 380 nm, it is possible to ignore the diffuse reflection / transmission on the surface of the light guide plate, that is, to prevent the diffuse reflection / transmission on the surface of the light guide plate. Can transmit light to the back.
Furthermore, by making the surface roughness Ra of the first inclined surface 18b and the second inclined surface 18c to be light reflecting surfaces smaller than 380 nm, it is possible to ignore diffuse reflection, that is, to prevent diffuse reflection on the light reflecting surface. The total reflection component can be transmitted to the back.

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)
Ratio of mixed scattering particle weight to light guide plate weight: Npa range is 0.04% Wt <Npa <0.25% Wt
It is preferable to satisfy the relationship. By making the shape satisfying the above relationship, the emission efficiency can be improved to 30% or more.
Or the light guide plate
D1 <D2 and
66/100000 <(D2-D1) / (L / 2) <26/1000 (B)
Ratio of mixed scattering particle weight to light guide plate weight: Npa range is 0.04% Wt <Npa <0.25% Wt
It is also preferable to improve so as to satisfy this relationship. By making the shape satisfying the above relationship, the emission efficiency can be improved to 40% or more.
Furthermore, the light guide plate
D1 <D2 and
1/1000 <(D2-D1) / (L / 2) <26/1000 (C)
Ratio of mixed scattering particle weight to light guide plate weight: Npa range is 0.04% Wt <Npa <0.25% Wt
It is further preferable to improve so as to satisfy the relationship. By making the shape satisfying the above relationship, the emission efficiency can be improved to 50% or more.

FIG. 8 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. 8 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. 8, 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 the present embodiment, the prism rows are formed on the two inclined surfaces (the first inclined surface 18b and the second inclined surface 18c) of the light guide plate 18 in order to reflect light efficiently, but it is not always necessary to form them. Alternatively, it may be a flat surface on which fine unevenness is not formed.

  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 18b and / or the second inclined surface 18c in FIGS. 1 and 2) facing the light exit surface of the light guide plate may be a curved surface. In addition, when the inclined surface is a curved surface, it may have a convex shape on the light exit surface side or a concave shape on the light exit surface.

Hereinafter, an example of a more preferable shape of the light guide plate will be described with reference to FIG.
FIG. 9A to FIG. 9D are schematic cross-sectional views illustrating other examples of the light guide plate. 10A is a schematic cross-sectional view showing another example of the light guide plate, and FIG. 10B is an enlarged view of the periphery of the connecting portion between the inclined surfaces of the light guide plate shown in FIG. It is a schematic sectional drawing shown.
In the light guide plate 202 shown in FIG. 9A, the first inclined surface 204 includes a first inclined portion 206 on the light incident surface 18d side and a second inclined portion 208 on the light guide plate center side. The first inclined portion 206 and the second inclined portion 208 are inclined at different angles with respect to the light exit surface, and the inclination angle of the second inclined portion 208 is greater than the inclination angle of the first inclined portion 206. Is small. That is, the first inclined surface is formed by an inclined portion whose inclination angle becomes gentler toward the center of the light guide plate.
Further, the second inclined surface 204 ′ has a shape symmetrical to the first inclined surface 204, and the first inclined portion 206 ′ on the second light incident surface 18e side and the first inclined portion 206 ′ on the light guide plate center side. The second inclined portion 208 ′ has a gentle inclination angle.
In this way, the cross-sectional shape of the inclined surface is configured by a plurality of straight lines having different inclination angles, and the inclination angle of the inclined portion on the light incident surface side is larger than the inclination angle of the inclined portion on the center side. By adopting the shape, it is possible to prevent the luminance of the light emitted from the portion near the light incident surface of the light emitting surface from increasing. Thereby, more uniform light can be emitted from the light exit surface.
In FIG. 9A, the inclined surface is configured by two inclined portions, but the number of inclined portions constituting the inclined surface is not particularly limited, and the inclination angle gradually decreases toward the center of the light guide plate. It can be configured by an arbitrary number of inclined portions arranged to be.
For example, as shown in FIG. 9B, the first inclined surface 212 (second inclined surface 212 ′) of the light guide plate 210 is centered on the light guide plate from the first light incident surface 18d (second light incident surface 18e) side. The first inclined portion 214 (214 ′), the second inclined portion 216 (216 ′) having a gentler inclination angle than the first inclined portion 214 (214 ′), and the second inclined portion 216 (216 ′). Alternatively, the third inclined portion 218 (218 ′) having a gentler inclination angle may be used.

Next, the light guide plate 220 shown in FIG. 9C has an R-shaped curved surface portion 222a on the first light incident surface 18d side of the first inclined surface 222, that is, at the connection portion with the first light incident surface 18d. . Similarly, the second inclined surface 222 ′ has an R-shaped curved surface portion 222a ′ on the second light incident surface 18e side.
As described above, the curved surface portion is provided in the connection portion between the light incident surface and the light incident surface of the light guide plate to form an R shape, and the light incident surface and the inclined surface are smoothly connected to each other. It is possible to prevent the brightness of light emitted from the vicinity of the light incident surface from increasing.

Next, in the light guide plate 230 shown in FIG. 9D, the first inclined surface 232 and the second inclined surface 232 ′ are formed in an aspheric shape that can be expressed by a tenth order polynomial.
By making the inclined surface into an aspherical shape in this way, it is possible to prevent the luminance of light emitted from a portion near the light incident surface of the light emitting surface from increasing.

Further, as shown in FIGS. 10A and 10B, the light guide plate 60 has a connecting portion 60f (a central portion of the inclined surface of the light guide plate) between the first inclined surface 60b and the second inclined surface 60c. It is preferable to have a curved surface shape or an R shape and connect them smoothly. That is, the inclined surface of the light guide plate preferably has a shape in which the bisector side is a curve (more specifically, an arc) and the light incident surface side is a straight line in a cross section perpendicular to the bisector. .
As a result, bright lines, dark lines, and the like can be prevented from being generated at the connecting portion 60f between the first inclined surface 60b and the second inclined surface 60c, and more uniform light can be emitted.

Here, the inclined surface 60b of the light guide plate 60, 60c between the connecting portion 60f, that is, when the central portion of the light guide plate 60 and the R-shaped, when the curvature radius of the R shape as R _1, the curvature radius R ₁ It is preferable that the relationship with the length L of the light guide plate in the light incident direction satisfies 3L ≦ R ₁ ≦ 500L.
In addition, the length of the R-shape of the connection portion 60f from the end to the end in the light incident direction is _LR, and the surface parallel to the light exit surface 60a and the first inclined surface 60b (or the second inclined surface). It is preferable that 2R ₁ · sin (θ) ≦ _LR is satisfied, where θ is an angle formed by 60c).
By setting _LR to be 2R ₁ · sin (θ) or more, it is possible to suppress a decrease in luminance at the central portion and to emit more uniform light from the light exit surface.
_LR is preferably 0.98 or less. Thereby, the effect of the present invention can be obtained more suitably.
Furthermore, it is more preferable that the light guide plate has a shape satisfying 3L ≦ R ₁ ≦ 500L and 2R ₁ · sin (θ) ≦ L _R ≦ 0.98L.

Θ can be expressed as the following equation (D) using the maximum thickness t _max of the light guide plate 60, the minimum thickness t _min and the length L of the light guide plate in the light incident direction.

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 lighting 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 the phthalate ester, dioctyl adipate (DOA), diisononyl adipate (DINA), dinormal alkyl adipate (C6, _{8, 10} ) (610A), dialkyl adipate (C7, ₉ ) ( 79A), dioctyl azelate (DOZ), dibutyl sebacate (DBS), dioctyl sebacate (DOS), tricresyl phosphate (TCP), tributyl acetylcitrate (ATBC), epoxidized soybean oil (ESBO), trimellitic acid Examples include trioctyl (TOTM), polyester, and chlorinated paraffin.

  As shown in FIGS. 1 and 2, in the backlight unit 2 of the present embodiment, light mixing portions 20 </ b> A and 20 </ b> B are provided in close contact with both side surfaces of the light guide plate 18. The light mixing units 20 </ b> A and 20 </ b> B are columnar optical components in which particles that scatter light 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 20A and 20B, basically, the same material as that of the light guide plate 18 can be used, and similarly to the light guide plate 18, a scatterer for scattering light can be included therein. . The density and the like of the scatterers contained in the light mixing portions 20A and 20B may be the same as or different from those of the light guide plate 18. Moreover, since the light mixing parts 20A and 20B are disposed close to the LED array 24 as shown in FIG. 2, it is preferable to form the light mixing parts 20A and 20B using a material having high heat resistance.

Next, the polarization separation film 16 will be described.
In the present embodiment, as a preferred embodiment, the polarization separation film 16 is formed integrally with the light guide plate 18 on the light exit surface 18 a that is the light exit side surface of the light guide plate 18. The polarization separation film 16 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 16 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 greatly improved.
The polarized light separating film 16 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 16 is preferably integrated by pressure bonding or fusion at the time of manufacturing the light guide plate 18. Accordingly, the light can be brought into close contact with each other without interposing air between the light exit surface 18 a of the light guide plate 18 and the polarization separation film 16.
Here, the polarization separation film 16 is formed integrally with the light guide plate 18; however, the present invention is not limited to this, and the polarization separation film 16 and the light guide plate 18 are manufactured independently, and are formed on the light emission side surface of the light guide plate 18. The polarization separation film 16 may be attached and provided.
In the illustrated example, the polarization separation film 16 is provided immediately above the light exit surface of the light guide plate 18. 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.

Moreover, as the polarization separation film 16, a well-known thing can be used.
For example, as described in JP-A-6-331824, for at least one polarization plane, the light exit surface of the light guide plate has a refractive index higher than the refractive index of the light guide plate. A birefringent material having a refractive index lower than the average refractive index of the light guide plate can be used for the plane of polarization orthogonal to.
Moreover, a stretched film as described in JP-A-11-281975 can also be used. Here, when using a stretched film, as described in JP-A-11-281975, it is preferable that the stretched film is attached to one side of the light guide plate via an adhesive layer or an adhesive layer.
Moreover, as described in JP-A-7-49496, a multilayer structure in which transparent media having a relatively high refractive index and transparent media having a relatively low refractive index are alternately laminated, In addition, at least one dielectric film having a thickness of preferably 1000 nm or less is formed on at least one surface of the planar transparent support, or a plurality of types of transparent types having different refractive indexes What laminated | stacked the polymer can also be used.
Further, as described in JP-A-7-72475, a transparent support having a substantially W-shaped cross section is provided with at least one dielectric thin film having a thickness equal to or less than a visible light wavelength, and a predetermined thickness. It is also possible to use a polarization separator that transmits the p-polarized component and reflects at least a part of the s-polarized component with respect to the light rays in the vicinity of the incident direction.
And a structured surface comprising a linear array of essentially right-angled isosceles prisms arranged side by side as described in Japanese Patent Application Laid-Open No. 2004-78234. A first material having a plane of perpendicular modulus forming an angle of approximately 45 ° with respect to the tangent to the opposite smooth surface, a second material essentially the same as the first material, and at least one Comprising at least one optical deposit of alternating layers of a high refractive index material and a low refractive index material of a selected optical thickness on a structured plane of the material, the first and second Are all optically bonded to form a single unit in which the refractive index of the first and second materials and the refractive index and optical properties of the plurality of layers of the optical deposition. Thickness produces selective reflection of polarized light In all of the optical deposits, the mixed polarized incident light is separated into an s-polarized component and a p-polarized component, and the s-polarized component is Reflected by other parts of the typical deposit and reflected parallel to the incident light in that part, but proceeding in the opposite direction to the incident light and the p-polarized component is transmitted parallel to the incident light. A reflective polarizer can also be used.
Further, as described in JP-A-61-262705, a polarizing filter function and a phase difference are formed on a transparent material in which A-shaped ridges and V-shaped grooves are alternately provided to form a triangular waveform surface. A polarizing element provided with a dielectric multilayer film having a plate function can also be used.
In addition, a polarizing film as described in US Pat. No. 3,610,729 can be used by continuously laminating a material having birefringence into a layer having a thickness of ¼ of various wavelengths. it can.
Further, as described in US Pat. No. 5,867,316, an optical film formed of a polymer having a continuous phase having birefringence and a small amount of a dispersed phase inside the continuous phase can also be used.
Further, a polarization separation film having a structure in which a metal thin film using surface plasmon is sandwiched with a low refractive index transparent medium as described in JP-A-2003-295183 can also be used.
Furthermore, in addition to the arrangement of the polarization separation film using surface plasmons that transmit only the P-polarized light component parallel to the incident surface and reflect the S-polarized light component perpendicular to the incident surface, the polarization direction of the light is changed, for example, orthogonal By forming a polarization direction changing film such as a λ / 4 phase film or a diffusion film having a slight birefringence that causes a difference of λ / 4 in the optical thickness between the polarization components with the light guide plate. , The luminance can be further improved.

A scattering type polarizing film using an anisotropic scatterer formed by stretching a composite of a liquid crystal and a polymer as described in JP-A-8-76114 is used instead of the polarizing separation film 16. Or oriented such that the axis of the molecular helix extends across the film as described in JP-A-6-281814, and the pitch of the molecular helix in the film is the maximum pitch and the minimum pitch. A cholesteric polarizing film that has been changed so that the difference between them is at least 100 nm may be used as the polarizing separation film 16.
Also, a haze anisotropic layer having a different haze value depending on the vibration direction of linearly polarized light as described in JP-A-2001-343612 can be used. In this case, it is further preferable to attach a first retardation plate to the surface opposite to the light exit surface of the light guide plate, and to install a second retardation plate between the light guide plate and the reflection plate.
Further, as described in JP-A-9-274108, minute regions made of a different material are uniformly dispersed in a transparent polymer film, and the polymer film and the minute regions are orthogonal to each other. Polarization elements having substantially the same refractive index for one of the linearly polarized light and different refractive indexes for the other of the linearly polarized light can be used.

In the above embodiment, the polarization separation film is provided on the light exit surface side of the light guide plate 18 to improve the brightness. As described in the publication, the luminance of light emitted from the light exit surface can also be improved by forming a fine uneven portion having a polarization separation function on the light exit surface of the light guide plate.
Further, instead of the polarization separation film 16, as described in JP-A-9-134607, a refractive index substantially equal to or higher than the refractive index of the light guide plate is provided between the light guide plate and the reflecting member (reflecting plate). An anisotropic material having a refractive index of 1 and a second refractive index smaller than that of the light guide plate, and separating substantially all of the first polarization state from the second polarization state orthogonal to the first polarization state. The luminance can also be improved by disposing a conductive layer.
In addition, as described in Japanese Patent Application Laid-Open No. 2004-363062, the luminance can also be improved by forming a rough surface pattern that is formed of fine protrusions and has a polarization separation function on the inclined back surface of the light guide plate. .
Further, as described in JP-A-10-508151, a concave portion filled with a material different from the material of the optical waveguide is provided in the optical waveguide (light guide plate), and one of these two materials has a refractive index. Is an isotropic material with np, and the other material is an anisotropic material with refractive indices no and ne. Here, regarding the refractive index, no or ne is equal to or substantially equal to np. As a result, polarized light can be separated at the interface between the isotropic material and the anisotropic material, and most of the light irradiated by the light source is changed to light having the same polarization direction before exiting the optical waveguide. Can do. Thus, the luminance can also be improved by applying the configuration described in JP-T-10-508151 to the present invention.
Further, as described in JP-A-9-292530, the light guide plate is composed of two or more layers having a light guide function, and at least one of the first layer and the second layer is duplicated. The brightness is also improved by using a refractive material, providing an interface between the first layer and the second layer, and emitting light scattered, refracted, or diffracted from the surface of the light guide plate at the interface. be able to.

Next, the reflection sheet 22 of the backlight unit will be described.
The reflection sheet 22 reflects light leaking from the inclined surfaces 18c and 18d of the light guide plate 18 and makes it incident on the light guide plate 18 again, and can improve the light use efficiency. The reflection sheet 22 is formed by being bent at the center so as to cover the inclined surfaces 18c and 18d of the light guide plate 18, respectively.
The reflection sheet 22 may be formed of any material as long as it can reflect light leaking from the inclined surfaces 18c and 18d of the light guide plate 18, such as PET or PP (polypropylene). Resin sheet with increased reflectivity by forming voids by kneading and stretching the filler, sheet with mirror surface formed by aluminum vapor deposition on transparent or white resin sheet surface, metal foil such as aluminum or metal foil supported It can be formed of a resin sheet or a metal thin plate having sufficient reflectivity on the surface.

Next, the diffusion film 14 will be described.
As shown in FIG. 1, the diffusion film 14 is disposed between the polarization separation film 16 and the liquid crystal panel 4. The diffusion film 14 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 14 is not particularly limited, for example, the surface of the film-like member is subjected to surface roughening by fine unevenness processing or polishing to impart diffusibility, or silica, titanium oxide that scatters light on the surface, It can be formed by coating a pigment such as zinc oxide or beads such as resin, glass or zirconia together with a binder, or kneading the pigment or beads in the transparent resin. In addition, it is possible to use a material having high reflectance and low light absorption, for example, using a metal such as Ag or Al.
In the present invention, the diffusion film 14 may be a mat type or coating type diffusion film.

The diffusion film 14 may be disposed at a predetermined distance from the light exit surface of the light guide plate 18, and the distance can be appropriately changed according to the light amount distribution from the light exit surface of the light guide plate 18.
Thus, by separating the diffusion film 14 from the light emission surface of the light guide plate 18 by a predetermined distance, the light emitted from the light emission surface of the light guide plate 18 is further mixed (mixed) between the light emission surface and the diffusion film 14. ) Thereby, the brightness | luminance of the light which permeate | transmits the diffusion film 14 and illuminates the liquid crystal display panel 4 can be made further uniform.
As a method of separating the diffusion film 14 from the light exit surface of the light guide plate 18 by a predetermined distance, for example, a method of providing a spacer between the diffusion film 14 and the light guide plate 18 can be used.

As mentioned above, although each component of the backlight unit 2 of the 1st Embodiment of this invention was demonstrated in detail, this invention is not limited to this.
For example, the light emitted from the LED can be mixed, and therefore, it is preferable to provide a mixing unit, and further, a parallel light generation mechanism such as a ball lens or a cylindrical lens is provided since the emitted light can be converted into parallel light. However, the mixing unit and the parallel light generation mechanism are not necessarily provided.
Moreover, it is preferable to provide a mixing part and / or a parallel light production | generation mechanism in a non-contact with a light source and a light-guide plate. By disposing the mixing unit and / or the parallel light generation mechanism in a non-contact manner with the light source and the light guide plate, heat generated from the light source can be transmitted to the mixing unit, the parallel light generation mechanism and the light guide plate, and can be prevented from being deformed by the heat. . Thereby, it is possible to more surely prevent uneven brightness from occurring in the light emitted from the light exit surface.

In the above embodiment, 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. However, the present invention is not limited to this. . As the light source, an LED chip configured by combining one kind of LED and a fluorescent material (that is, a fluorescent material) and converting light emitted from the LED into white light by the 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.
Further, even when one type of LED is used as the light source, the light emitted from the light source can reach the back of the light guide plate described later by using the LED as the light source. Thereby, the apparatus can be enlarged while maintaining the thinness of the apparatus. In addition, it is possible to emit light having higher color rendering properties than a cold cathode tube.

FIG. 11A is a schematic top view showing an embodiment of a planar illumination device (backlight unit) using an LED chip composed of one type of LED and a phosphor as a light source. (B) is a schematic sectional drawing of a planar illuminating device.
Note that the backlight unit 120 shown in FIGS. 11A and 11B has the same configuration as that of the backlight unit 2 shown in FIG. 1 except for the light source 122. Accordingly, the same components are denoted by the same reference numerals in both, and detailed description thereof is omitted, and points specific to the backlight unit 120 will be described below.
The light source 122 includes an LED array 124 and a coupling lens 126, and is disposed to face the first light incident surface 18d and the second light incident surface 18e of the light guide plate 18, as shown in FIG. Yes.
In the LED array 124, a plurality of LED chips 128 are arranged on the heat sink 130 in a row at a predetermined interval. 12A is a schematic perspective view of the configuration of the LED array 124, FIG. 12B is a schematic top view of the configuration of the LED chip 128, and FIG. 12C is a configuration of the multilayer LED array 132. A schematic top view is shown in FIG. 3D and a schematic side view of one embodiment of the heat sink 25 is shown.
As described above, the LED chip 128 has a configuration in which one kind of LED and a fluorescent material are combined, and light emitted from the LED is converted by the fluorescent material and emitted as white light.

The heat sink 130 is a plate-like member parallel to one side of the light guide plate 18, and is disposed to face the light guide plate 18. The heat sink 130 supports a plurality of LED chips 128 on the surface facing the light guide plate 18. The heat sink 130 is formed of a metal having good thermal conductivity such as copper or aluminum, and absorbs heat generated from the LED chip 128 and dissipates it to the outside.
In addition, the heat sink 130 has a length in a direction perpendicular to the first light incident surface and the second light incident surface of the light guide plate 18 as in the present embodiment, and the first light incident surface of the light guide plate 18 and The shape is preferably longer than the length in the short side direction of the surface facing the second light incident surface. Thereby, the cooling efficiency of LED chip 128 can be improved.
Here, the heat sink preferably has a large surface area. For example, as shown in FIG. 12D, the heat sink 130 may be configured by a base portion 130a that supports the LED chip 128 and a plurality of fins 130b connected to the base portion 130a.
By providing a plurality of fins 130b, the surface area can be increased and the heat dissipation effect can be enhanced. Thereby, the cooling efficiency of LED chip 128 can be improved.
The heat sink is not limited to the air cooling method, and a water cooling method can also be used.
In this embodiment, the heat sink is used as the support portion of the LED chip. However, the present invention is not limited to this, and when cooling of the LED chip is not necessary, a plate-like member having no heat dissipation function is used as the support portion. It may be used.

Here, as shown in FIG. 12B, the LED chip 128 of the present embodiment has a rectangular shape in which the length in the direction orthogonal to the arrangement direction is shorter than the length in the arrangement direction of the LED chip 128, that is, the lead. The optical plate 18 has a rectangular shape having a short side in the thickness direction (a direction perpendicular to the light exit surface 18a). In other words, the LED chip 128 has a shape in which b> a, where a is the length in the direction perpendicular to the light exit surface 18a of the light guide plate 18 and b is the length in the arrangement direction. Further, when the arrangement interval of the LED chips 128 is p, p> b. As described above, the relationship between the length a in the direction perpendicular to the light exit surface 18a of the light guide plate 18 of the LED chip 128, the length b in the arrangement direction, and the arrangement interval p of the LED chips 128 satisfies p>b> a. Is preferred.
By making the LED chip 128 into a rectangular shape, a thin light source can be obtained while maintaining a large light output. By reducing the thickness of the light source, the planar illumination device can be reduced in thickness.

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

  In this embodiment, the LED array is a single layer. However, the present invention is not limited to this, and as shown in FIG. 12C, a multilayer LED array 132 having a configuration in which a plurality of LED arrays 124 are stacked. Can also be used as a light source. Even when LEDs are stacked in this way, more LED arrays can be stacked by making the LED chip rectangular and thinning the LED array. By stacking the multilayer LED arrays, that is, by increasing the filling rate of the LED arrays (LED chips), a larger amount of light can be output. In addition, the LED chip of the LED array in the layer adjacent to the LED chip of the LED array preferably has the arrangement interval satisfying the above formula as described above. In other words, the LED array is preferably laminated with the LED chip and the LED chip of the LED array in the adjacent layer separated by a predetermined distance.

As shown in FIG. 3, a ball lens is disposed as a coupling lens 126 on the light emission side of each LED chip 128 of the LED array 124. The coupling lens 126 is disposed corresponding to each LED chip 128. The light emitted from each LED chip 128 is collimated by the coupling lens 126 and enters the light mixing unit 20 of the light guide plate 18.
Here, the ball lens is used as the coupling lens. However, the present invention is not limited to this, and various members can be used 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.

Further, the LED array 24 is not disposed so as to face the first light incident surface and the second light incident surface of the light guide plate 18, and the light emitted from each LED of the LED array 24 is guided to the light guide plate using the light guide. May be. The light guide can be configured using an optical fiber, a light guide made of a transparent resin, or the like.
When the LED array 24 is used as a light source and the LED array 24 is disposed in the vicinity of the side surface of the light guide plate 18, the light guide plate 18 may be deformed or melted by the heat generated by each LED constituting the LED array 24. . Therefore, the LED array 24 is arranged at a position away from the side surface of the light guide plate 18, and the light emitted from the LED chip is guided to the light guide plate 18 using a light guide. Melting can be prevented.

In the above embodiment, a configuration in which a GaN-based blue LED and a YAG-based fluorescent material are combined is illustrated as an LED chip. However, the present invention is not limited to this, and various LED and fluorescent materials are combined. An LED chip can be used.
For example, red LED, green LED, purple LED. LEDs that emit light in various wavelength regions, such as ultraviolet LEDs, near-ultraviolet LEDs, infrared LEDs, and near-infrared LEDs, can be used. Also, any fluorescent material can be used as the fluorescent material depending on the light emitted from the LED chip.

For example, a light source in which a red LED is combined with a blue LED can also be used. Specifically, a light-emitting element in which an LED and a phosphor described in JP-A-2005-228996 are combined can also be used.
A light source combining an infrared LED with red, green, and blue phosphors can also be used. Examples of such a light source include a light emitting device that combines an LED and a phosphor described in JP-A-2000-347691, and a white light-emitting diode that combines an LED and a phosphor described in JP-A-2002-43633. In addition, a light-emitting device in which an LED and a phosphor described in JP-A-2005-126777 are combined can also be used.
Moreover, this invention is not limited to arrange | positioning a fluorescent substance in the light emission surface of LED, and emitting a white light, Instead of arranging a fluorescent substance in the light emission surface of LED, mixing a fluorescent substance in a light-guide plate. Also, white light can be emitted from the light exit surface.
Moreover, it can replace with or arrange | position in addition to arrange | positioning fluorescent substance on the light emission surface of LED, and the structure which has arrange | positioned the optical sheet which apply | coated or mixed fluorescent substance on the light emission surface of a light-guide plate can also be used. Also with the above configuration, white light can be emitted from the light exit surface.

Here, as the LED chip used for the light source, it is preferable to use an LED chip that emits light having two or more main peak wavelengths.
Specifically, an LED chip that emits light having a main peak in each of a blue wavelength region and a green wavelength region, and an LED chip that emits light having a main peak in each of a red wavelength region and a blue wavelength region LED chip that emits light having main peak in each of green wavelength region and red wavelength region, LED that emits light having main peak in each of red wavelength region, blue wavelength region, and green wavelength region A chip or the like can also be used.
As described above, by using an LED chip that emits light of two or more main peaks as the LED chip, light with high color rendering can be emitted with a simple device configuration. Further, white light with high color rendering properties can also be emitted.
An LED chip that emits light having two or more main peak wavelengths can be manufactured by combining the above-described LED that emits light such as R, G, B, infrared, and ultraviolet and a phosphor. it can. In addition, an LED chip that emits various emission colors with a combination of a plurality of peak wavelengths can be manufactured by combining an LED having a plurality of peak wavelengths and a fluorescent material.

Moreover, as a light source, you may comprise a light source with the LED chip which inject | emits the light which has two or more main peak wavelengths of a different kind, ie, two types of LED chips with which light emission wavelengths differ. In this case, the number of the different types of LED chips may or may not be equal, and two types of LED chips may be regularly or irregularly mixed and arranged in an array. That is, it is preferable that the light emitted from the light emission surface of the light guide plate has a desired color balance. In other words, as long as light with a desired color balance can be emitted, the LED chip can be arranged in an arrangement relationship, but the arrangement position is not particularly limited.
Furthermore, it is also preferable to use an LED unit composed of two types of LED chips having different emission wavelengths. That is, it is also preferable that this LED unit is a repeating unit and a plurality of LED units are arranged in an array.
As an example, an LED chip that emits light having a main peak in each of a blue wavelength region and a green wavelength region, and an LED chip that emits light having a main peak in each of a red wavelength region and a blue wavelength region It is preferable to use an LED unit in combination.
In this way, by combining different types of LED chips having two or more main peak wavelengths, light with high color rendering can be emitted from the light emission surface of the planar illumination device. Thereby, for example, light satisfying a desired NTSC ratio can be emitted. Further, white light with high color rendering properties can also be emitted.

In the above embodiment, an LED chip that combines an LED and a phosphor is used as the LED chip of the light source. However, the present invention is not limited to this, and the LED emits light having two or more main peaks. It is also preferable to use. That is, for example, when the LED itself emits light having a main peak in each of the blue wavelength region and the green wavelength region, it is also preferable to use a single LED as a light source LED chip without providing a phosphor. .
As described above, when the LED itself emits light having two or more main peaks, similarly, it is preferable that the LEDs having different types of two or more main peak wavelengths are combined.
In this case, the same effect as that obtained by combining the LED chips can be obtained.
Further, the same effect can be obtained when an LED chip having two or more main peak wavelengths and an LED that emits light having two or more main peaks are combined.

When white light is emitted from the light emission surface, it is preferable to use a pseudo white LED chip or a pseudo white LED as the light source. Here, the pseudo white is a color that is visually close to white or appears white. Here, as the pseudo white LED chip, a configuration in which the above-described GaN-based blue LED and a YAG-based fluorescent material are combined is exemplified.
The pseudo-white LED chip or the pseudo-white LED has two main peak wavelengths of two-wavelength type, that is, an LED chip or LED that emits light that looks white with two main peak wavelengths, and three main peak wavelengths of three There are LED chips or LEDs that emit light that appears to be white with light of three main peak wavelengths, that is, wavelength type.

  In the above embodiment, white light is emitted from the light emission surface. However, the present invention is not limited to this, and light of various colors can be emitted depending on the configuration of the LED and LED chip used as the light source. .

As the light source, it is preferable to use an LED and / or an LED unit that emits light having two different main peaks from the viewpoint that the color rendering can be improved and the apparatus configuration can be simplified. A monochromatic LED may be used as the light source.
Thus, by using a monochromatic LED as a light source, it is possible to provide a planar illumination device that emits light of blue, red, green, etc. from a light emission surface with a simple configuration.
Further, as described above, white light may be emitted by combining the single color LEDs.
The above-described LED chip that emits light having two or more main peaks and / or an LED that emits light having two or more main peaks may be combined with a monochromatic LED. In addition, when comprising a light source by several LED and / or LED chip, the number of each LED and LED chip and the number of kinds are not specifically limited, A various combination can be used.
Moreover, in the said embodiment, although LED and LED chip which all comprise a light source are arrange | positioned by the fixed pattern, arrangement | positioning feeling and arrangement | positioning order are not specifically limited. For example, only a part of the LEDs may be densely arranged, or a combination of LEDs and LED chips in a repeating unit may be combined depending on the position.

Further, in the above embodiment, the heat sink of the LED array has a flat plate shape and is arranged on the back surface side of the LED chip so as to extend in a direction parallel to the light emission surface. The LED chip may be arranged so as to extend from the back surface of the LED chip to the inclined surface side of the light guide plate, that is, the back surface of the reflecting member. Thereby, the area of the direction parallel to the light-projection surface of a planar illuminating device can be made small.
Note that the thickness and / or length of the heat sink when the heat sink is bent and disposed on the inclined surface side of the light guide plate is preferably such that the thickness of the backlight unit is not impaired. By making the heat sink thinner than the maximum thickness and minimum thickness of the light guide plate and placing it on the back side of the inclined surface, the space between the inclined surface of the light guide plate and the housing can be used effectively, The thickness of the lighting device can be reduced.
In addition, as a material for the heat sink, a material having high thermal conductivity, for example, a metal such as aluminum or copper as described above, or other various materials can be used.

Moreover, it is preferable that the heat sink has a heat conductive connection with a housing that supports the light guide plate, the reflecting member, the LED array, and the like from the outside. That is, it is preferable that the heat sink and the housing have a heat conductive connection. By connecting the heat sink and the housing in a heat conductive manner, heat generated from the LED chip can be dissipated in the entire backlight unit (planar illumination device). Thereby, heat can be efficiently radiated.
Here, the heat sink and the housing are not limited to being in direct contact, and may be in contact via a thermal connection body.

In the above embodiment, the first inclined surface 18b and the second inclined surface 18c of the light guide plate 18 are formed with prism rows. However, the first inclined surface 18b and the second inclined surface 18c of the light guide plate 18 have prisms. The same effect can be obtained by arranging a prism sheet on which a prism row is formed on the light exit surface 18a of the light guide plate 18 without forming a row. FIG. 13 schematically shows the configuration of the backlight unit when the prism sheet 26 is disposed on the light exit surface 18 a of the light guide plate 18. In the illustrated example, the light guide plate 18, the polarization separation film 16, and the prism sheet 26 are integrally configured. Here, the light guide plate 18, the polarization separation film 16 and the prism sheet 26 are integrated, but they can also be arranged as independent members.
The prism sheet 26 is a transparent sheet formed by arranging a plurality of prisms in parallel. The prism sheet 26 can improve the light collecting property of the light emitted from the light exit surface of the light guide plate 18 and improve the luminance.
As a method for integrating the light guide plate 18, the polarization separation film 16, and the prism sheet 26, for example, first, a sheet in which the polarization separation film 16 and the prism sheet 26 are integrated is manufactured. Then, the sheet may be integrated with the light guide plate 18 by fusion or pressure bonding when the light guide plate 18 is manufactured.
As a method of integrating the polarization separation film 16 with the prism sheet 26, the prism sheet 26 and the polarization separation film 16 are individually manufactured and simply bonded, or the polarization separation plate material is put into a mold roll of a continuous extruder. A method of fusing with the extruded prism sheet can be used. However, it is not limited to these methods.
In addition, a prism sheet is provided between the polarization separation film 16 and the diffusion sheet 14 of the backlight unit shown in FIG. It may be arranged.

In the example shown in FIG. 13, the prism sheet is composed of one sheet, but the prism sheet can be composed of two sheets. In this case, in one of the two prism sheets, the extending direction of the prism row is parallel to the light incident surfaces (the first light incident surface 18d and the second light incident surface 18e) of the light guide plate 18. And the other is arranged perpendicular to it. That is, the two prism sheets are arranged such that the extending directions of the prism rows are perpendicular to each other.
Moreover, it is preferable that these prism sheets are arranged so that the apex angle of the prism faces the polarization separation film 16 side.

When two prism sheets are arranged, the order of arrangement of the prism sheets is not particularly limited. That is, a prism sheet having a prism extending in a direction parallel to the light incident surface of the light guide plate 18 is disposed immediately above the polarization separation film 16, and is perpendicular to the light incident surface of the light guide plate 18 on the prism sheet. A prism sheet having a prism extending in any direction may be disposed, or vice versa.
In the illustrated example, the prism sheet 26 is used. However, instead of the prism sheet 26, a sheet in which optical elements similar to prisms are regularly arranged may be used. For example, a sheet in which optical elements having a lens effect are regularly arranged such as a lenticular lens, a concave lens, a convex lens, and a pyramid type can be used instead of the prism sheet.
Further, a plurality of diffusion films may be used without using the prism sheet. The number of diffusion films used is 2 or more, preferably 3 sheets.

Further, as shown in FIG. 14, a plurality of diffuse reflectors 140 are formed in a predetermined pattern on the first inclined surface 18b and the second inclined surface 18c of the light guide plate 18, specifically, the end of the light guide plate 18, that is, The density on the first light incident surface 18d side and the second light incident surface 18e side is low, and the density gradually increases from the first light incident surface 18d and the second light incident surface 18e toward the center of the light guide plate 18. The pattern may be formed by printing, for example. By forming such a diffuse reflector 120 on the inclined surface 18b of the light guide plate 18 in a predetermined pattern, generation of bright lines and unevenness on the light exit surface 18a of the light guide plate 18 can be suppressed.
Further, instead of printing the diffuse reflector 140 on the first inclined surface 18b and the second inclined surface 18c of the light guide plate 18, a thin sheet on which the diffuse reflector 140 is formed in a predetermined pattern is used as the first inclined surface of the light guide plate 18. You may arrange | position between 18b and the 2nd inclined surface 18c, and the reflective sheet 22. FIG. The shape of the diffuse reflector 140 can be any shape such as a rectangle, a polygon, a circle, and an ellipse.
Here, as the diffuse reflector, for example, a pigment such as silica, titanium oxide, or zinc oxide that scatters light, or a material that scatters light, such as beads such as resin, glass, or zirconia, is applied together with a binder. It may be a machined object or a surface roughening pattern by fine unevenness processing or polishing on the surface. In addition, it is a material with high reflectance and low light absorption. For example, metals such as Ag and Al can be used. In addition, a general white ink used in screen printing, offset printing, or the like can also be used as the diffuse reflector. For example, an ink in which titanium oxide, zinc oxide, zinc sulfate, barium sulfate, etc. are dispersed in an acrylic binder, a polyester binder, a vinyl chloride binder, etc., or an ink in which silica is mixed with titanium oxide to impart diffusibility. Can be used.

In the present embodiment, the diffuse reflector is made sparse and dense as the distance from the light incident surface increases. However, the present invention is not limited to this, depending on the intensity and spread of the emission line, the required luminance distribution of the emitted light, and the like. For example, it may be arranged at a uniform density over the entire inclined surface, or may be arranged from dense to sparse as the distance from the light incident surface increases. Further, instead of forming such a diffuse reflector by printing, a portion corresponding to the position where the diffuse reflector is disposed may be roughened as a rubbing surface.
In the light guide plate of FIG. 14, the diffuse reflector is disposed on the inclined surface. However, the present invention is not limited to this, and may be disposed on any surface other than the light incident surface as necessary.

Further, a transmittance adjusting member having a function of reducing luminance unevenness of light emitted from the light exit surface may be disposed on the light exit surface side of the planar illumination device.
FIG. 15 is a schematic cross-sectional view of the planar illumination device 180 in which the transmittance adjusting member 182 is arranged.

The planar illumination device 180 includes a light source 190, a diffusion film 14, a light guide plate 18, a reflection sheet 22, a transmittance adjustment member 182, and a prism sheet 188.
Here, the diffusion film 14, the light guide plate 18, and the reflection sheet 22 have the same functions as the diffusion film, the light guide plate, and the reflection sheet of the planar illumination device shown in FIG.
The light source 190 has the same configuration as the LED array 124 including the LED chip 128 and the heat sink 130 described above. In the present embodiment, the LED array 124 includes the first light incident surface 18d and the second light of the light guide plate 18, respectively. It arrange | positions facing the entrance plane 18e. That is, the coupling lens and the light mixing unit are not arranged between each LED array 124 and the first light incident surface 18d and the second light incident surface 18e. Thereby, the light emitted from the LED array 124 is directly incident on the light guide plate 18.
Further, a transmittance adjusting member 182, a diffusion film 14, and a prism sheet 188 are sequentially laminated on the light exit surface 18 a of the light guide plate 18. Here, the prism sheet 188 has the same functional shape as the prism sheet 26 described above, so that the apex angle of the prism is opposed to the diffusion sheet 14, that is, the base of the prism is the light incident surface of the light guide plate 18. It arrange | positions so that it may be parallel to 18a.

  As described above, the transmittance adjusting member 182 is used to reduce the luminance unevenness of light emitted from the light guide plate, and the transparent film 184 and a large number of transmittance adjusting bodies disposed on the surface of the transparent film 184. 186.

  The transparent film 184 has a film shape and is made of PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, other acrylic resins, or COP. It is formed of an optically transparent member such as (cycloolefin polymer).

The transmittance adjusting body 186 is a dot of various sizes having a predetermined transmittance, and has a shape such as a quadrangle, a circle, or a hexagon, and has a predetermined pattern, for example, a dot size or a dot according to a position. Are formed on the entire surface of the transparent film 184 on the light guide plate 18 side by printing or the like.
The transmittance adjuster 186 may be a diffuse reflector, for example, a material such as silica, titanium oxide, zinc oxide or the like that scatters light or a resin or glass, zirconia or other beads coated with a binder, A surface roughening pattern by fine unevenness processing or polishing may be used on the surface. In addition, it is a material with high reflectance and low light absorption. For example, metals such as Ag and Al can be used.
As the transmittance adjusting body 186, a general white ink used in screen printing, offset printing, or the like can be used. For example, an ink in which titanium oxide, zinc oxide, zinc sulfate, barium sulfate, etc. are dispersed in an acrylic binder, a polyester binder, a vinyl chloride binder, etc., or an ink in which silica is mixed with titanium oxide to impart diffusibility. Can be used.

  The transmittance adjusting member 186 arranges a number of transmittance adjusting bodies 186 in a predetermined pattern on the surface of the transparent film 184 on the light guide plate unit 18 side, so that the pattern density of the transmittance adjusting body 186 depends on the position on the surface. Has changed.

Here, the pattern density at an arbitrary position (x, y) of the transmittance adjusting member 182 is ρ (x, y), and the light emitting surface (liquid crystal display) of the backlight unit 180 when the transmittance adjusting member 182 is not provided. The relative luminance of the light emitted from an arbitrary position (x, y) on the panel 4 side surface is defined as F (x, y). At this time, the relationship between the pattern density ρ (x, y) of the transmittance adjusting member 182 and the relative luminance F (x, y) preferably satisfies the following formula (5).
ρ (x, y) = c {F (x, y) −F _min } / (F _max −F _min ) (5)
In Formula (5), F _max is the maximum luminance of light emitted from the light exit surface of the diffusion film 14 of the backlight unit 180 when the transmittance adjusting member 182 is not provided, and F _min is the minimum luminance. is there. Note that the relative luminance F (x, y) uses the maximum luminance F _max as a reference point (F _max = 1).
Here, c is the maximum density, and is preferably 0.5 ≦ c ≦ 1.
Further, when designing the density of the arrangement of the transmittance adjusting bodies according to the above formula, luminance unevenness may be visually recognized depending on the angle observed from other than the front direction. In order to improve this, it is preferable to add a “uniform density distribution (bias density ρb)” to the calculated density distribution. Thereby, luminance unevenness can be reduced and the angle dependency of the luminance unevenness can be eliminated or reduced.
Here, the bias density ρb is preferably 0.01 to 1.50 (1 to 150%). In addition, when the arrangement density exceeds 1 (100%), the transmittance adjusting body is arranged twice. That is, the transmittance adjusting body having the arrangement density of (ρb-1) is arranged on the entire surface of the transmittance adjusting body.
Here, the pattern density ρ (x, y) is an occupancy rate per unit area (1 mm ² ) of the transmittance adjusting body 186 existing at an arbitrary position (x, y), and ρ (x, y). When = 1, the transmittance adjusting body 186 is disposed on the entire surface within the unit area, and when ρ (x, y) = 0, it is not disposed at all within the unit area.

  By disposing the transmittance adjusting body 186 of the transmittance adjusting body member 182 so as to satisfy the pattern density ρ (x, y) of the above equation (5), the light emitted from the light emitting surface of the backlight unit 180 is reduced. It is possible to suppress a decrease in average luminance and reduce luminance unevenness. In this way, by reducing the luminance unevenness using the transmittance adjusting member 182, the diffusion film 14 does not need to sufficiently diffuse the light. As a result, the diffusion film 14 can be made thinner, the use of the prism sheet can be stopped, or the number of prism sheets used can be reduced, providing a lighter and cheaper backlight unit. can do.

Hereinafter, the planar illumination device including the transmittance adjusting member will be described in more detail with specific examples.
In this example, a backlight unit having the same configuration as the backlight unit shown in FIG. 15 was produced. That is, the backlight unit 180 of this embodiment includes the light source 190, the diffusion film 14, the light guide plate 18, the reflection film 22, the transmittance adjusting member 182, and the prism sheet 188.

In this embodiment, the light guide plate 18 has a thickness of the first light incident surface 18d and the second light incident surface 18e of 2 mm, the thickness of the central portion of the light guide plate 18, that is, the maximum thickness of the light guide plate 18, and the first light. The distance from the incident surface 18d to the second light incident surface is 300 mm, the length of the light guide plate 18 in the depth direction, that is, in the direction parallel to the first light incident surface 18d of the light guide plate 18 and parallel to the light exit surface 18a. The length was 500 mm.
The light guide plate 18 is made of acrylic resin having a refractive index of 1.495 as transparent resin and silicone particles having a refractive index of 1.44 as scattering particles. The scattering particles have a particle diameter of 2000 nm. The scattering particles are kneaded and dispersed in a transparent resin so that the scattering plate area Φ is 2.06 × 10 ⁻¹² m ² and the particle density is 220,000 particles / mm ³ .
The gap between the light source 190 (LED array 124) and the light guide plate 18 was set to 0.1 mm.

  In the backlight unit 180 shown in FIG. 15, in order to calculate the pattern density ρ (x, y) of the transmittance adjusting body 186 that satisfies the above formula (5), except that the transmittance adjusting member 182 is not provided, Using a backlight unit having the same configuration and shape, the relative luminance F (x, y) of light emitted from the light exit surface of the backlight unit without the transmittance adjusting member was measured.

Here, the relative luminance F (x, y) was measured as follows.
First, the backlight unit 180 is fixed to an XY stage, and a luminance meter is fixed so as to be perpendicular to the light emission surface of the backlight unit 180. Then, the luminance at the position of the light emitting surface of the backlight unit 180 is measured by a luminance meter to obtain information on the luminance regarding the specific position of the light emitting surface of the light guide plate 18.
Thereafter, by moving the XY stage, the relationship between the position on the light exit surface of the backlight unit 180 and the luminance is obtained, and the calculated maximum luminance is F _max and the minimum luminance is F _min . The maximum luminance F _max was set to 1, and the ratio of the luminance at each position to the maximum luminance F _max was set as the relative luminance F (x, y) at the position (x, y). The measurement results thus measured are shown in FIG. Here, in the graph of FIG. 16, the vertical axis represents relative luminance, and the horizontal axis represents the distance from the center of the light guide plate.

Next, the pattern density ρ (x, y) corresponding to the relative luminance F (x, y) is calculated from the measured maximum luminance F _max and the minimum luminance F _min using the above formula 1. In this example, the relationship between the relative luminance F (x, y) and the pattern density ρ (x, y) when the maximum density c is c = 0.75 was calculated. The relationship between the relative luminance F (x, y) and the pattern density ρ (x, y) is a proportional relationship, and the pattern density ρ (x, y) when the relative luminance F (x, y) is the minimum luminance F _min. Is 0, and the maximum density c = 0.75 at the pattern density ρ (x, y) when the maximum brightness F _max is reached.

  Next, based on the relationship between the calculated relative luminance F (x, y) and the pattern density ρ (x, y), the relative luminance F (x, y) of the backlight unit of the present embodiment shown in FIG. The distribution of the pattern density ρ (x, y) corresponding to is calculated. FIG. 17 shows the distribution of the pattern density ρ (x, y) calculated for the case where the maximum density c is c = 0.75. In FIG. 17, the vertical axis represents the pattern density ρ (x, y), and the horizontal axis represents the distance from the center (central portion) of the light guide plate.

Next, based on the distribution of the pattern density ρ (x, y) that satisfies the formula (5) when the calculated maximum density c is c = 0.75, the transmittance in which the transmittance adjusting body 186 is disposed. The adjustment member 182 was created.
Here, in the present embodiment, the distribution of the pattern density ρ (x, y) is calculated every 0.5 mm in the width direction, and the size in the width direction depends on the calculated pattern density ρ (x, y). A transmittance adjusting member 182 was created by appropriately arranging a transmittance adjusting body 186 of 0 to 1 mm.
Here, in the present embodiment, when the transmittance adjusting body is disposed on the entire surface, that is, when the pattern density ρ (x, y) is 1, the transmission created by the white ink having a transmittance of 33% at a wavelength of 550 nm. A rate adjuster 182 was placed.

  When the transmittance adjusting member 182 created in this way was arranged in the backlight unit 180, the relative luminance of the light emitted from the light exit surface of the backlight unit 180 was measured. The measurement method was the same as the measurement method for measuring the relative luminance F (x, y) described above. The measurement results are shown in FIG. Here, in FIG. 18, the vertical axis represents relative luminance, and the horizontal axis represents the distance from the center (central portion) of the light guide plate. For comparison, the vertical luminance of the light emitted from the light emitting surface of the backlight unit having the same configuration except that the transmittance adjusting member 182 is not provided is also shown.

  As shown in FIG. 18, by arranging the transmittance adjusting member 182, it is possible to reduce luminance unevenness compared to the case where the transmittance adjusting member 182 is not disposed.

Here, as described above, the maximum density c is preferably 0.5 ≦ c ≦ 1. By setting the maximum density c to 0.5 or more, it is possible to suppress a reduction in average luminance, and it is possible to emit uniform light with high luminance.
Further, the transmittance adjusting body 186 preferably has a pattern density ρ (x, y) = 1, that is, the transmittance when the transmittance adjusting body 186 is disposed on the entire surface is 10% or more and 50% or less, and 20%. More preferably, it is 40% or less.
By setting the transmittance to 10% or more, luminance unevenness can be suitably reduced, and by setting the transmittance to 50% or less, luminance unevenness can be reduced without reducing the average luminance.
Furthermore, the said effect can be acquired more suitably by making the transmittance | permeability into 20% or more and 40% or less.

Further, the shape of the transmittance adjusting body may be any shape such as a quadrangle, a triangle, a hexagon, a circle, and an ellipse.
Further, when the linear light source and the uniaxially extending light guide plate as in the present embodiment are used for the backlight unit, the shape of the transmittance adjusting body is an elongated strip shape parallel to the axis of the linear light source. It is good.

  Here, in the said embodiment, although the transparent film was used as an optical member by which the transmittance | permeability adjustment body is arrange | positioned, this invention is not limited to this, The transmittance | permeability adjustment body is arrange | positioned to a diffusion film or a prism sheet. Also good. For example, a transmittance adjusting body may be formed on the diffusion film 14 or the prism sheet 188 shown in FIG. 15 instead of the transparent film. As a result, the number of parts can be reduced, and the manufacturing cost can be reduced.

In addition, the transmittance adjusting body 186 of the transmittance adjusting member 182 has a pattern density distribution adjusted according to the light incident on the transmittance adjusting member 182, but the pattern density distribution of the transmittance adjusting body 186 is a transmittance adjusting member. It may be adjusted by changing the size of the body 186 or may be adjusted by changing the arrangement interval of the transmittance adjusting bodies 186 having a fixed shape.
As a method for arranging the transmittance adjusting body 186 according to the pattern density, various methods such as an FM screening method and an AM core method can be used, and among these, the FM screening method is preferably used. By using the FM screening method, it is possible to disperse and arrange the transmittance adjusting body 186 as fine and uniform dots, and visually recognize the arrangement pattern of the transmittance adjusting body 186 from the light exit surface of the backlight unit. Can be difficult. That is, the arrangement pattern of the transmittance adjusting body 186 is projected from the light emitting surface of the backlight unit, and uneven light can be prevented from being emitted, and more uniform light can be emitted. Further, it is possible to prevent the dot size from becoming too small and the formation of the transmittance adjusting body 186 from becoming difficult.

The transmittance adjuster 186 has a maximum dimension of 500 μm or less. For example, in the case of a rectangular shape, the length of one side is preferably 500 μm or less, and in the case of an elliptical shape, the major axis is preferably 500 μm or less, and preferably 200 μm or less. More preferred. By making the maximum dimension of the transmittance adjusting body 186 500 μm or less, the shape of the transmittance adjusting body 186 becomes difficult to see, and by making the maximum dimension 200 μm or less, the shape of the transmittance adjusting body 186 becomes invisible. When actually used as a liquid crystal display device, the shape of the transmittance adjusting body 186 is not projected onto the light exit surface of the backlight unit, resulting in uneven brightness, and the uneven brightness can be efficiently reduced.
Further, it is more preferable that the transmittance adjusting body 186 has a maximum dimension of 100 μm or less. By setting the maximum dimension to 100 μm or less, the dimension can be more surely less than the discrimination ability of the naked eye. When actually used as a liquid crystal display device, the shape of the transmittance adjusting body 186 is the light of the backlight unit. Luminance unevenness can be reduced more reliably and efficiently without being unevenly projected onto the exit surface.

Moreover, as a method of printing the transmittance adjusting body on the surface of the transparent film, various printing methods such as screen printing, offset printing, gravure printing, and ink jet printing can be used. Offset printing has the advantage that it is excellent in productivity, and screen printing has the advantage that the ink thickness can be increased and the transmittance of the pattern portion can be lowered without increasing the ink density. . Inkjet printing can be printed on a three-dimensional object, and is optimal as a method for forming a transmittance adjusting body on the surface of a light guide plate.
Moreover, when printing the transmittance adjusting body on the surface of the transparent film, an alignment mark may be printed outside the arrangement area of the halftone dot pattern of the transparent film. By forming the alignment mark on the transparent film, it is possible to easily align the light guide plate and the transmittance adjusting member at the time of manufacture.

In the present embodiment, the transmittance adjusting member is provided between the light guide plate and the diffusion film, but the arrangement position is not limited to this, and may be arranged between the diffusion film and the prism sheet.
Moreover, although the transmittance adjusting member is provided by arranging the transmittance adjusting body on the transparent film, the present invention is not limited to this, and the transmittance adjusting body is provided on the surface of the diffusion film, the prism sheet, or the light guide plate. The arranged one may be used as a transmittance adjusting member. Specifically, the transmittance adjusting body is arranged on at least one of the surface of the diffusion film on the light guide plate side (light incident surface) and the surface of the diffusion film opposite to the light guide plate side (light output surface). May be. Further, the transmittance adjusting body may be disposed on at least one of the surface of the prism sheet on the light guide plate side (light incident surface) and the surface of the prism sheet opposite to the light guide plate side (light emission surface). Good. Furthermore, a transmittance adjusting body may be disposed directly on the light exit surface of the light guide plate.
Thus, by providing the transmittance adjusting body on the surface of the diffusion film, the prism sheet or the light guide plate, the transmittance adjusting member can be formed without using a transparent film, and the layer structure can be simplified. Can do.
Further, by arranging the transmittance adjusting body directly on the light exit surface of the light guide plate, in addition to the above effects, the luminance unevenness of the light emitted from the light guide plate can be obtained without taking alignment when the planar lighting device is assembled. In contrast, the transmittance adjusting body can be arranged at an accurate position.

  Moreover, it is preferable to arrange | position the transmittance | permeability adjustment body in several places, ie, several optical members, for example, the surface of a light-guide plate, a diffusion film back surface, etc., and to form several transmittance | permeability adjustment members. By disposing the transmittance adjusting body on a plurality of optical members in this way, it is possible to widen the allowable amount of positional deviation between the arrangement pattern of the transmittance adjusting body and the incident light at each position, and uneven brightness and color. Uniform and uniform light can be emitted. Here, when the transmittance adjusting bodies are arranged at a plurality of locations, the arrangement patterns of the transmittance adjusting bodies may be the same arrangement pattern or different arrangement patterns.

  Moreover, in the said embodiment, although the transmittance | permeability adjustment body of the transmittance | permeability adjustment member was arrange | positioned so that the pattern density (rho) (x, y) of said Formula (5) may be satisfy | filled as a suitable aspect, this invention is limited to this. However, the transmittance adjusting body can be arranged with various pattern densities for suppressing the occurrence of luminance unevenness. For example, the transmittance adjusting member may be a known transmittance adjusting member in which the transmittance adjusting body is arranged so as to have a density distribution in a direction perpendicular to the axis of the linear light source.

Furthermore, it is preferable that white ink is kneaded with ink of any color (ink other than white) on the surface of the transparent film, and the dispersed chromaticity adjusting film is disposed on the light exit surface of the light guide plate. Here, the mixing ratio of the white ink and the ink of any color is less than 1 for the ink of any color with respect to the white ink 100.
By arranging the chromaticity adjustment film, the color of the emitted light can be finely adjusted, and the color rendering properties and color reproducibility can be improved. Thereby, even when a light source having a low color rendering property is used as the light source, the color rendering property can be improved. Moreover, the color of the emitted light can be finely adjusted.

Hereinafter, it demonstrates in detail with a specific Example.
In this embodiment, the three light sources of the LED element having a color temperature of 9150K and the LED element having a color temperature of 8500K are used, and the various inks shown in Tables 2 and 3 below are not disposed. The chromaticity of the light emitted when a proportion of the chromaticity adjusting film was placed was measured.

The measurement results are shown in FIGS.
Here, FIG. 19 is a graph showing the results of measuring the light emitted from the LED elements having a color temperature of 9150K and transmitted through the various chromaticity adjusting films shown in Tables 2 and 3, respectively. It is a graph which shows the result of having measured each light which inject | emitted from the LED element of temperature 8500K, and permeate | transmitted the various chromaticity adjustment films shown in Table 2 and Table 3. FIG.

As shown in FIGS. 19 and 20, the color temperature of the emitted light can be adjusted by arranging various chromaticity adjusting films. That is, as indicated by arrows in FIGS. 19 and 20, the emitted light is changed from the original light source color to various color directions such as R (red) direction, Y (yellow) direction, and M (magenta) direction. Can be shifted to.
Thereby, a color rendering property and a color temperature reproduction range can be improved. Even when a phosphor is arranged on a blue LED to emit white light, red color reproducibility can be improved by arranging a chromaticity adjusting film.

Here, the arrangement position of the chromaticity adjusting film is not particularly limited, and may be arranged between the light emitting surface of the light guide plate and various optical members, between various optical members, and the like. You may arrange | position between.
In place of disposing the chromaticity adjusting film, an ink obtained by mixing a predetermined amount of various inks with the above-described white ink may be applied to the diffusion film, the prism sheet, the light guide plate surface, or the like.

Moreover, in the said embodiment, as FIG. 1 shows, although the light emission side surface 18a was comprised flat, the light-guide plate by which the surface on the opposite side was formed in the inclined surface was used, but the backlight of this invention The light guide plate used in the unit is not limited to such a shape.
Hereinafter, other structural examples of the light guide plate that can be used in the backlight unit of the present invention will be described.

  FIGS. 21A and 21B show other examples of the structure of the light guide plate that can be used in the backlight unit of the present invention. FIG. 21A is a schematic plan view showing the light guide plate 28, the light mixing unit 20, and the light source 12, and FIG. 21B is a schematic cross-sectional view showing the light guide plate 28. In FIGS. 21A and 21B, the light source 12 and the light mixing unit 20 (20A and 20B) have the same functions as the light source and the light mixing unit shown in FIG.

The light guide plate 28 has a structure in which the light guide plate 18 shown in FIG. 1 is turned upside down, and its light emission surface is composed of a pair of flat first inclined surface 28a and second inclined surface 28b, The opposite surface is constituted by a flat surface 28c. The first inclined surface 28a and the second inclined surface 28b of the light guide plate 28 are inclined with respect to the flat surface 28c so that the thickness decreases from the central portion toward the end portion. In the light guide plate 28 having such a structure, light incident from the first light incident surface 28d and the second light incident surface 28e is emitted from the first inclined surface 28a and the second inclined surface 28b.
Similarly to the light guide plate 18 described above, the light guide plate 28 having such a shape is also formed using a transparent resin containing a scatterer. When the half length of the light guide plate is L _G , the density of scattering particles (number of particles per unit volume) contained in the light guide plate is N _p , and the correction coefficient is K _C , Φ · N _p · L _G · the value of K _C is not less than 1.1, and is 8.2 or less, it satisfies the relationship that the value of _{K C} is 0.005 to 0.1. Thereby, uniform illumination light with little unevenness in luminance can be emitted from the first inclined surface 28a and the second inclined surface 28b, which are a pair of inclined surfaces.

Further, in the backlight unit 2 using the light guide plate 18 having the shape shown in FIG. 1, the shape of the reflection sheet 22 is changed to the first inclined surface 18 b and the second inclined surface located on the opposite side to the light emitting side of the light guide plate 18. In accordance with 18c, the light guide plate 18 is inclined from the central portion toward both end faces (the first light incident surface 18d and the second light incident surface 18e), but as shown in FIGS. 21A and 19B. When the light guide plate 28 having a different shape is used for the backlight unit, the reflection sheet 22 is formed flat so as to cover the flat surface 28 c of the light guide plate 28.
In the light guide plate 28 shown in FIGS. 21A and 21B, no prism row is formed on the first inclined surface 28a and the second inclined surface 28b, but the first inclined surface 28a and the second inclined surface 28b are not formed. It is also possible to form a prism row on the inclined surface 28b. In addition, the prism row can be formed on the flat surface 28c which is the surface opposite to the light exit surface of the light guide plate 28.
When the light guide plate 28 having the shape shown in FIGS. 21A and 21B is used in the backlight unit, the light emission side of the light guide plate, that is, the first inclined surface 28b and the second second surface of the light guide plate 28 are used. A polarization separation film is disposed on the inclined surface 28c. The polarization separation film may be formed in close contact with the first inclined surface 28b and the second inclined surface 28c. For example, the polarization separation film is attached to a flat plate made of a transparent resin to produce a polarization separation plate. In addition, the polarization separation plate may be disposed at a predetermined interval from the first inclined surface 28b and the second inclined surface 28c.

  FIGS. 22A and 22B show still another configuration example of the light guide plate that can be used in the backlight unit of the present invention. 22A is a schematic plan view showing the light guide plate 38, the light mixing unit 20, and the light source 12. FIG. 22B is a schematic cross-sectional view showing the light guide plate 38. As shown in FIG. 22A and 22B, the light source 12 and the light mixing unit 20 (20A and 20B) have the same functions as the light source and the light mixing unit shown in FIG. Is omitted.

  In the light guide plate 38 shown in FIGS. 22A and 22B, the light emitting surface on the light emitting side and the opposite surface are formed in the same shape. The light emission surface of the light guide plate 38 has a rectangular outer shape, and is constituted by a pair of flat first inclined surfaces 38a and second inclined surfaces 38b. It is comprised by the 3 inclined surface 38c and the 4th inclined surface 38d. That is, the light guide plate 38 is composed of a pair of inclined surfaces that gently incline from the center to both ends on the light emission side and the opposite side. The first inclined surface 38a and the second inclined surface 38b are inclined with each other at a predetermined angle. Similarly, the third inclined surface 38c and the fourth inclined surface 38d are inclined with each other at a predetermined angle. The angle of the second inclined surface 38b with respect to the first inclined surface 38a and the angle of the fourth inclined surface 38d with respect to the third inclined surface 38c are the same. The light guide plate 38 has the thinnest thickness at both ends, the plate thickness increases from both ends toward the center, and is thickest at the center.

  In the light guide plate 38 shown in FIG. 22, the light incident from the side surface passes through the light guide plate 20 and is emitted from the first inclined surface 38a and the second inclined surface 38b. At this time, a part of light may leak from the third inclined surface 38c and the fourth inclined surface 38d, but the leaked light is arranged to cover the back surface of the light guide plate 38 (not shown). ) And again enter the light guide plate.

FIG. 23 is a schematic cross-sectional view showing a schematic configuration of another example of a planar illumination device (backlight unit) 141 that can be used in the first embodiment. In the present embodiment, the same components as those of the backlight unit 10 shown in FIGS. 1 and 2 are denoted by the same reference numerals, detailed description thereof is omitted, and different portions are mainly described. To do.
The backlight unit 141 includes a light source 142 and a light guide plate 144. Although not shown, similarly to the backlight unit 10 shown in FIGS. 1 and 2, a diffusion film and a prism sheet are disposed on the light exit surface side of the light guide plate 144 of the backlight unit 141. The reflection film 22 is disposed on the inclined surface side (surface side opposite to the light exit surface) of the light guide plate 144.

The light source 142 is the same as the LED array 124 shown in FIGS.
The light guide plate 144 has a substantially rectangular flat light exit surface 144a and is located on the opposite side of the light exit surface 144a, is parallel to one side of the light exit surface 144a, and bisects the light exit surface 144a into two equal parts. Two inclined surfaces (a first inclined surface 144b and a second inclined surface 144c) that are symmetrical to each other with respect to the line X and inclined at a predetermined angle with respect to the light exit surface 144a, and the two LED arrays 124, There are two light incident surfaces (first light incident surface 144d and second light incident surface 144e) on which the light from these LED arrays 124 is incident. The first inclined surface 144b and the second inclined surface 144c are inclined with respect to the light exit surface 144a with the bisector X as a boundary. The light guide plate 144 is thicker from the first light incident surface 144d and the second light incident surface 144e toward the center, with the center being the thickest and the both ends being the thinnest. The light guide plate 144 is made of a material made of a material different in part from the first light incident surface 144d side and part from the second light incident surface 144e side from other portions of the light guide plate 144 (hereinafter referred to as a base material 146). A refractive index member 148 is used.

The low refractive index member 148 forms a light incident surface 144c together with the base material 146, and is in contact with the base material 146 except for the surface that becomes the light incident surface 144c. That is, the surfaces of the low refractive index member 148 on the light exit surface 144 a side, the first inclined surface 144 b side, the second inclined surface 144 c side, and the central portion side are covered with the base material 146. The low refractive index member 148 has a cross-sectional shape that is convex toward the center.
Such a light guide plate can also be manufactured using an extrusion molding method or an injection molding method. Alternatively, the base material 146 and the low refractive index member 148 may be manufactured separately, and the low refractive index member 148 may be embedded in or adhered to the base material 146.
Here, when the refractive index of the low refractive index member 148 is Ni and the refractive index of the base material 146 is Nm, the base material 146 and the low refractive index member 148 satisfy the relationship of Nm> Ni.

A low refractive index member whose refractive index is lower than the refractive index of the base material is provided in a part including the light incident surface, and the light emitted from the light source is incident on the low refractive index member, so that the light incident surface is emitted from the light source. It is possible to reduce the Fresnel loss of light incident on the light and improve the incidence efficiency.
Further, the low refractive index member 148 has a function of making incident light parallel and mixing, that is, a function of a coupling lens and a mixing unit. The backlight unit of the present embodiment can provide light emitted from the light source to a farther position without providing a coupling lens and a mixing unit by providing a low refractive index member, and is uniform. Illumination light without uneven brightness can be emitted.

  Here, it is preferable that the light exit surface of the light guide plate is substantially entirely formed of a low refractive index member. By making the entire surface of the light exit surface a low refractive index member, the light emitted from the light source and incident on the light guide plate can be incident on the low refractive index member, and the incident efficiency can be further improved.

Here, in FIG. 23, the low refractive index member 148 is formed in a convex kamaboko shape toward the center of the light guide plate 144, but the present invention is not limited to this.
24A to 24C are schematic cross-sectional views of other examples of the light guide plate and the light source that can be used in the backlight unit of the present invention. Here, the cross-sectional shape of the light guide plate shown in FIGS. 24A to 24C has the same shape at any position.
FIG. 24A shows a light guide plate 151 having a low refractive index member 152 having a square cross-sectional shape. In FIG. 24B, the cross-sectional shape is trapezoidal. Specifically, the light guide plate 153 is more than the surface 154a which is parallel to the surface 154a which is the light incident surface and the surface 154b opposite to the light incident surface. This shows a light guide plate 153 having a low refractive index member 154 having a trapezoidal shape with a surface 154b on the center side. FIG. 24C illustrates a light guide plate 155 having a low refractive index member 156 whose cross-sectional shape is a triangle, specifically, a triangle having a bottom surface as a light incident surface and a vertex at the center of the light guide plate 155. Is shown.
Incidence efficiency can be improved even if the low refractive index member is shaped as described above.
In addition, the shape of the low refractive index member is not limited to the above example, and may be various shapes such as a semicircular shape, a hyperbolic shape, and a parabolic shape.

As mentioned above, although each component of the other example of the backlight unit which can be used for the 1st Embodiment of this invention was demonstrated in detail, this invention is not limited to this.
FIG. 25 shows a schematic cross-sectional view of still another example of a backlight unit that can be used in the first embodiment of the present invention. Here, the backlight unit 160 has basically the same configuration as the backlight unit 141 shown in FIG. 23 except that the reflection member 162 is provided in the vicinity of the light incident surface 144c of the light guide plate 144. Accordingly, the same reference numerals are given to the same components in both, and detailed description thereof will be omitted, and hereinafter, the points peculiar to the backlight unit 160 will be mainly described.

The reflection member 162 reflects light leaking from the light exit surface 144a, the first inclined surface 144b, and the second inclined surface 144c in the vicinity of the light incident surface of the light guide plate 144 so as to enter the light guide plate again. A part of the light exit surface 144a on the first light incident surface 144d side, a part of the light exit surface 144a on the second light incident surface 144e side, and one of the first inclined surfaces 144b on the first light incident surface 144d side of the light plate 144. And four portions of the second inclined surface 144c on the second light incident surface 144e side are provided by coating, vapor deposition, adhesion, or the like.
The reflection member 162 may be formed of any material as long as it can reflect light leaking from the light exit surface 144a and the inclined surface 144b in the vicinity of the light incident surface of the light guide plate 144. A resin sheet in which a void is formed by kneading and stretching a filler in PET, PP (polypropylene), etc. to increase the reflectivity, a sheet having a mirror surface formed by aluminum vapor deposition on the surface of a transparent or white resin sheet, aluminum, etc. It can be formed of a metal foil or a resin sheet carrying the metal foil, or a metal thin plate having sufficient reflectivity on the surface.

  By providing the reflecting member 162 on the light emitting surface 144a, the first inclined surface 144b, and the second inclined surface 144c in the vicinity of the first light incident surface 144d and in the vicinity of the second light incident surface 144e, a light source in the vicinity of the light incident surface 144c is provided. Since the distance to 142 is short, leakage of light that is easily emitted can be prevented, and light emitted in the vicinity of the light incident surface can reach a farther position. Thereby, the light incident on the light guide plate can be used efficiently.

  Further, since the light incident efficiency can be improved, it is preferable to provide a low refractive index member in the vicinity of the light incident surface of the light guide plate as in this embodiment, but the present invention is not limited to this, and the low refractive index Even if only the reflecting member is provided without providing the rate member, the light utilization efficiency can be increased.

  Here, in this embodiment, the reflecting member is provided on both the light emitting surface and the inclined surface. However, when the reflecting sheet is disposed on the inclined surface, the reflecting sheet serves as the reflecting member. The reflecting member may be provided only on the light exit surface of the part.

Here, in the above-described first embodiment, the description has been made with one light guide plate. However, the present invention is not limited to this, and a plurality of light guide plates are used to form a single light exit surface. May be.
FIG. 26 shows an example of a planar illumination device using a plurality of light guide plates. In FIG. 26, only the light guide plates 18, 18 ′, 18 ″ and the light source 12 are shown to clearly show the arrangement of the light guide plates.

The plurality of light guide plates are disposed at positions where the light exit surfaces of the light guide plates are the same plane and the light incident surfaces are the same plane. Specifically, the light guide plate 18 and the light guide plate 18 ′ adjacent thereto have the same light output surface 18 a of the light guide plate 18 ′ adjacent to the light output surface 18 a of the light guide plate 18, and the light guide plate 18. The first light incident surface 18d and the first light exit surface 18'd of the adjacent light guide plate 18 'are arranged at the same plane. The light guide plate 18 and the adjacent light guide plate 18 ′ are preferably in close contact with each other. Similarly, in the light guide plate 18 ′ and the light guide plate 18 ″, the light exit surface 18′a and the light exit surface 18 ″ a are the same plane, and the first light incident surface 18′d and the first light entrance surface 18′d The light incident surface 18′d is disposed at the same plane. Further, the second light incident surfaces, the first inclined surfaces, and the second inclined surfaces of the light guide plates are also arranged to form the same plane.
The light source 12 is disposed at a position facing the first light incident surface and the second light incident surface of the light guide plates 18, 18 ′, 18 ″. Thereby, the light emitted from the common light source 12 is incident on the first light incident surface and the second light incident surface of the light guide plates 18, 18 ′, 18 ″.

As described above, by arranging a plurality of light guide plates in parallel to form one light exit surface, a planar illumination device having a larger area can be obtained. Thereby, it can be used also as a planar illumination device of a larger liquid crystal display device.
Further, although not shown in FIG. 26, the diffusion film and the prism sheet may also cover the light emission surface formed by the plurality of light guide plates with one diffusion film and the prism sheet, similarly to the light source. preferable.

In each of the above embodiments, the light emission surface is a flat surface, but the present invention is not limited to this.
27A to 27C are diagrams showing another embodiment of the planar illumination device, and FIG. 27A is a schematic perspective view of the planar illumination device 300, and FIG. B) is a side view of the planar illumination device 300, and FIG. 27C is a schematic cross-sectional view showing the longitudinal illumination device 300 in the longitudinal direction.
The planar illumination device 300 includes a light source 302, a light guide plate 304, a diffusion film 306, an acrylic pipe 308, and a reflection film 310.

As shown in FIG. 27C, the two light sources 302 are arranged so that the light guide plate 304 is sandwiched between them. The light source 302 includes a plurality of LEDs 302a, and the LEDs 302a are arranged in a ring shape along the shape of the light incident surface of the light guide plate 304 as shown in FIG. Here, various LED mentioned above can be used as LED302a.
As shown in FIG. 27B, the light guide plate 304 is a hollow cylinder whose light exit surface is formed in a circle and whose outer periphery is a light exit surface in a cross section perpendicular to the incident direction of the light emitted from the light source 302. Has a shape. In addition, as shown in FIG. 27C, the light guide plate 304 has a thickness that increases from the light incident surface (end in the axial direction of the cylindrical shape) corresponding to the upper and lower surfaces of the cylinder toward the center. The thickness at the center is the thickest, and the thickness at both ends is the thinnest. That is, the cross-sectional shape of the light guide plate 304 in the direction parallel to the incident direction of the light emitted from the light source 302 is the same shape as the light guide plate 18 described above, that is, as the distance from the light incident surface increases in the light incident direction. It is a shape where the thickness increases.

The diffusion film 306 is disposed on the light exit surface of the light guide plate 304. That is, the cylindrical light guide plate 304 is arranged in a cylindrical shape so as to cover the outer peripheral surface.
The acrylic pipe 308 has a hollow cylindrical shape and is disposed on the outer periphery of the diffusion film 306. The acrylic pipe 308 is made of a transparent resin.
The reflective film 310 is disposed on the inclined surface side of the light guide plate 304, that is, on the inner surface side of the cylindrical light guide plate 304.
That is, the planar illumination device 300 is laminated from the inside in the order of the cylindrical reflection film 310, the light guide plate 304, the diffusion film 306, and the acrylic pipe 308.
Here, since the surface illumination device 300 has the same configuration as that of the above-described surface illumination device except that the outer shape is a cylindrical shape, detailed description of the shape, material, and the like is omitted. .

Also in the planar illumination device 300, light incident on the light guide plate 304 from the light source 302 is diffused by internal scattering particles, and is reflected directly or reflected by the reflective film 310 and emitted from the light exit surface. The light is emitted through 308.
In the planar illumination device 300, the outer peripheral surface of the cylinder has a light emission surface, and light is emitted from the entire outer peripheral surface. Thereby, light can be emitted in all directions of 360 degrees and can be used similarly to a fluorescent lamp.
Thus, the planar illumination device of the present invention can be formed into a rod shape similar to the rod-shaped fluorescent lamp used as the illumination device, or can be used for the same application as the fluorescent lamp.
In the present embodiment, only the diffusion film is disposed on the light exit surface of the light guide plate, but the same effects as described above can be obtained by disposing various optical members similar to the above-described planar illumination device. .

Further, the shape of the planar lighting device is not limited to a cylindrical shape.
FIG. 28 is a diagram showing still another embodiment of the planar illumination device, FIG. 28A is a schematic side view of the planar illumination device 320, and FIG. 28B is a planar illumination device. It is a schematic sectional drawing which shows the cross section of 320 for a longitudinal direction.
As shown in FIGS. 28A and 28B, the planar illumination device 320 includes a light source 322, a light guide plate 324, and a reflective film 326. Although not shown, a diffusion film and an acrylic pipe are disposed on the outer peripheral surface of the light guide plate 324 in the same manner as the planar illumination device 300.
In the planar illumination device 320, a cross section perpendicular to the incident direction of the light emitted from the light source 322 is formed in a semi-cylindrical shape that halves the circular planar illumination device 300. That is, the light source 322, the light guide plate 324, and the reflection film 326 are formed in a semicylindrical shape.
Such a semi-cylindrical planar illumination device can also be suitably used. For example, when it is arranged on the ceiling as indoor lighting as in the case of a fluorescent lamp, the interior can be brightened by irradiating the ceiling side with light by using a semi-cylindrical shape. Thereby, the room can be efficiently illuminated.

In the planar lighting device 300 shown in FIG. 27, the cylindrical light guide plate is a straight tube rod, but the cylindrical light guide plate may be a bent tube and the planar lighting device may be ring-shaped.
FIG. 29, FIG. 30 and FIG. 31 are schematic front views each showing an example of a shape of a planar illumination device in a ring shape.
A planar illumination device 330 illustrated in FIG. 29 includes eight light sources 332 and four light guide plates 334.
The light guide plate 332 has a cylindrical shape with an outer peripheral surface serving as a light emission surface, and has a shape that increases in thickness from the end surface toward the center. The light guide plate 334 is a curved tube in which the center line of the cylinder from the end surface to the end surface is an arc of 90 degrees.
The light guide plate 332 is disposed so that the end surface thereof faces the end surface of the adjacent light guide plate 332, and the four light guide plates 332 connected to each other form one ring shape.
A light source 332 is disposed on each end face of the light guide plate 334.

  In this way, by arranging a plurality of light guide plates 332 in a curved tube shape and connecting them, a ring-shaped planar illumination device can be obtained.

Further, in the planar illumination device 330, a ring-shaped planar illumination device is formed by four light guide plates. However, the planar illumination device 330 is not limited to this. For example, as shown in FIG. By forming the line into a circular shape, a ring-shaped surface proving device can be formed by the surface illumination device 340 having one light guide plate 344 and two light sources 342 disposed on the end surfaces thereof.
Further, by setting the angle of the circular arc of the cylindrical center line of the light guide plate, it is possible to form a ring shape with an arbitrary number of light guide plates.
Further, the planar illumination device is not limited to a rod shape or a ring shape, and may be various shapes.

Further, when the light guide plate is formed in a cylindrical shape, it is preferable to form a groove 354a in a part of the cylindrical light guide plate 354 of the planar illumination device 350 as shown in FIG. That is, as shown in FIG. 31B, it is preferable to form a groove 354a in a part of the light guide plate 354 in a cross section perpendicular to the incident direction of the light emitted from the light source 342.
By forming the groove 354 a in the light guide plate 354, the reflective film 346 can be easily arranged on the inner surface side of the light guide plate 354.

Another example of the planar lighting device of the present invention will be described.
FIG. 32A is a schematic plan view of the light guide plate 18 and the light source 412 used in the planar illumination device 400 of another example according to the present invention, and FIG. 32B is shown in FIG. 2 is a schematic cross-sectional view of a light guide plate 18 and a light source 412. FIG.
The planar illumination device 400 shown in FIG. 32 is basically the same as the planar illumination device 10 except for the configuration of the light source 412, and is therefore characteristic of the present embodiment. The light source 412 which is a part will be described. Although not shown, a reflection sheet, a diffusion film, a prism sheet, and the like are also arranged in the planar illumination device 400.

Hereinafter, the light source 412 will be described.
As shown in FIG. 32B, the two light sources 412 are arranged so that the light guide plate 18 is sandwiched between them. As shown in FIG. 33, the light source 412 includes a plurality of pseudo white LED chips 440 arranged in a line (line shape), and a plurality of auxiliary LED units 442 arranged corresponding to the pseudo white LED chips 440. The heat sink 130 supports the pseudo white LED chip 440 and the auxiliary LED unit 442.

The pseudo white LED chip 440 is obtained by applying and attaching a fluorescent material to an LED, or by arranging a phosphor layer on the light emission surface side of the LED chip. The pseudo white LED chip 440 transmits the light emitted from the LED through the fluorescent material and emits white light.
As an example, there is a configuration in which a GaN blue LED is used as the LED and a YAG (yttrium, aluminum, garnet) fluorescent material is used as the fluorescent material. As another example, there is a configuration in which an ultraviolet LED is used as an LED, a BaMgEuMn fluorescent material is used as red, a Zns or SrAlEu fluorescent material is used as green, and an SrBaMg fluorescent material is used as blue. Here, the absorption and excitation wavelengths of the red fluorescent material and the blue fluorescent material used in the present embodiment vary depending on their chemical configurations.
As described above, the plurality of pseudo white LED chips 440 are arranged in a line.

The auxiliary LED unit 442 includes a red LED 442a and a blue LED 42b, and is disposed between the pseudo white LED chip 440 and the adjacent pseudo white LED.
In the present embodiment, the red LED 442a is an LED that emits light having a center wavelength of 630 nm, and the blue LED 442b is an LED that emits light having a center wavelength of 480 nm.
In this embodiment, a red LED and a blue LED are used, but an LED that emits light of a single color such as green may be used.
The auxiliary LED unit can use a configuration in which one type or a plurality of types of LEDs that emit light having a light emission wavelength different from that of the pseudo white LED chip are used.

Since the heat sink 130 has the same configuration as the heat sink 130 of the backlight unit 120 described above, description thereof is omitted.
In this embodiment, the heat sink 130 is used, but a plate-like support may be used.
The auxiliary LED unit 442 may be fixed directly to the heat sink 130 or may be fixed to a peripheral member other than the heat sink 130.

As described above, as the light source 412 of the surface illumination device 400, the auxiliary white LED chip 442 in which one or more kinds of LEDs emitting light having a light emission wavelength different from the pseudo white LED chip 440 are combined. Can be combined to improve the color rendering of the light source.
Moreover, the utilization efficiency of the light inject | emitted from an auxiliary | assistant LED unit can be made high by separating a pseudo white LED chip and an auxiliary | assistant LED unit.
Further, even when the pseudo white LED chip and the auxiliary LED unit are separately provided, the light incident from the light source is mixed with the light guide plate. For this reason, even if the pseudo white LED and the auxiliary LED unit are separately arranged, light having no color unevenness can be emitted from the light emitting surface.

Here, in this embodiment, the auxiliary LED unit of the light source is configured by the red LED and the blue LED. However, the present invention is not limited to this, and as shown in FIG. You may comprise by LED452a, green LED452b, and blue LED452c. In FIG. 34A, the auxiliary LED unit 452 is arranged between the pseudo white LED 450, and the red LED 452a, the green LED 452b, and the blue LED 452c are arranged at the positions of the vertices of the triangle. There is no particular limitation.
FIG. 34B shows another arrangement example in which the auxiliary LED unit 452 is configured by a red LED 452a, a green LED 452b, and a blue LED 452c. As shown in FIG. 34B, a configuration may be adopted in which red LEDs 452a, green LEDs 452b, and blue LEDs 452c are linearly arranged between the pseudo white LED chips 450.

Further, the combination of the auxiliary LED units is not particularly limited, and any combination of LEDs that emit RGB or any color can be used.
Furthermore, the above-mentioned auxiliary LED is a combination of two or more different types of LEDs, but the auxiliary LED is monochromatic, that is, one type of LED, for example, the auxiliary LED unit is red as shown in FIG. Only the LED 462 may be used.
In each of the above embodiments, the auxiliary LED unit is disposed between the pseudo white LED and the adjacent pseudo white LED. However, the present invention is not limited to this. (A) The auxiliary LED unit may be arranged in the vicinity of the pseudo white LED in the middle vertical direction, that is, in the direction perpendicular to the extending direction of the plurality of pseudo white LEDs.

Here, in the planar illumination device, Ra represents the average color rendering index of light emitted from the light exit surface of the light guide plate, and R ₉ , R ₁₁ , and R ₁₂ represent the color rendering indices of red, yellow, and blue, respectively. Ra ′ is the average color rendering index of light emitted from the light exit surface of the light guide plate of the planar lighting device in which only the pseudo white LEDs are arranged in rows, and the color rendering index of red, yellow, and blue is When R ₉ ′, R ₁₁ ′, and R ₁₂ ′ are satisfied, it is preferable that the following formula (6) and formula (7) are satisfied.

Here, the average color rendering index Ra, Ra ′ is calculated by the following method.
First, the relative spectral distribution of the reference light is measured. Here, in the present invention, CIE daylight (D ₆₅ ) having a correlated color temperature of 6500 K is defined as the reference light.
When the relative spectral distribution of the reference light is D ₆₅ (λ) and the reflection spectrum of the test color for calculating the color rendering index is T _i (λ), the tristimulus values of the reference light are expressed by the following equations (8) and (9). ).

ここで、Ｄ₆₅光源を基準光として用いる場合、Ｘｎ＝９５．０４５，Ｙｎ＝１００，Ｚｎ＝１０８．８９２となる。

Here, when the D ₆₅ light source is used as the reference light, Xn = 95.045, Yn = 100, and Zn = 108.892.

Next, the relative spectral distribution of light emitted from the light source to be used is measured.
Assuming that the measured relative spectral distribution is P (λ), the tristimulus values of the light source to be used are expressed by the following equations (10) and (11).

When the obtained tristimulus value is converted into L ^* a ^* b ^* , it is expressed as the following formula (12).

Further, from the obtained L ^* a ^* b ^* , the equation difference dEi between the light using the reference light (D ₆₅ ) and the light using the light source is defined as the following equation (13).

From the color difference dEi between the reference light and the LED light source for each test color obtained, the color rendering index and the average color rendering index for each test color are expressed as in the following formula (14).

  As described above, the light emitting surface of the planar illumination device having the same configuration as that of the planar illumination device 400 except for the fact that only the pseudo white LED is used without using the auxiliary LED unit. The average color rendering index Ra ′ of the light emitted from the light and the average color rendering index Ra of the light emitted from the light emitting surface of the planar illumination device 400 are calculated.

In this way, the other parts are emitted from the light emission surface of the planar illumination device having the same configuration as that of the planar illumination device 400 except that the auxiliary LED unit is not used and the light source includes only the pseudo white LED. The average color rendering index Ra ′ of the emitted light and the color rendering index R ₉ ′, R ₁₁ ′, R ₁₂ ′ of red, yellow, and blue are measured, calculated, and emitted from the light exit surface of the surface illumination device 400 The average color rendering index Ra of the emitted light and the color rendering index R ₉ , R ₁₁ , R ₁₂ of red, yellow, and blue are measured and calculated. Further, based on the measured values, K (R) = (R ₉ ′ / R ₉ ), K (G) = (R ₁₁ ′ / R ₁₁ ), K (B) = (R ₁₂ ′ / R ₁₂ ) Is calculated.
The color rendering properties are evaluated based on K (R), K (G), K (B) and Ra ′ / Ra calculated in this way.
In this way, by evaluating the color rendering properties based on K (R), K (G), K (B), and Ra ′ / Ra, it is possible to accurately evaluate the color rendering properties of light emitted from the light source. And comparison with the pseudo white LED can be easily performed. In addition, by designing a light source using this evaluation method, a planar illumination device having a desired color rendering property can be created.
Further, by evaluating whether K (R), K (G), K (B) and Ra ′ / Ra satisfy the above formulas (6) and (7), the color rendering properties can be further improved. It can be judged accurately.

  The color rendering index and the average color rendering index of the light emitted from the light exit surface of the light guide plate of the planar lighting device 400, and the planar lighting device having the same configuration except that the light source is composed of only a pseudo white LED. When the relationship between the color rendering index and the average color rendering index of the light emitted from the light exit surface of the light plate satisfies the above formulas (6) and (7), the color rendering properties can be further improved.

Moreover, as an auxiliary | assistant LED unit, it is preferable to combine 2 or more types of LED which light-emits the light of a different color, ie, the center wavelength of the light to light-emit is 50 nm or more apart.
Moreover, it is preferable that the relationship between the light intensity α of the pseudo white LED and the light intensity β of the auxiliary LED satisfies 0.05 ≦ (β / α) <0.5. When the relationship between α and β satisfies the above range, the effects of the present invention can be obtained more suitably.
When two or more types of LEDs having different center wavelengths are combined as the auxiliary LED unit, the light intensity β _i (i = 1, 2, 3,...) Of each type of LED of the auxiliary LED unit. ) And the light intensity α of the pseudo white LED preferably satisfy 0.05 ≦ (β _i /α)<0.5.

Furthermore, the relationship between the light intensity α of the pseudo white LED chip and the light intensity β of the auxiliary LED is more preferably 0.1 ≦ (β / α) ≦ 0.3. When the relationship between α and β satisfies 0.1 ≦ (β / α) ≦ 0.3, the occurrence of color unevenness can be more reliably prevented, and the color rendering can be preferably improved.
In this embodiment, the auxiliary LED is made smaller than the pseudo white LED chip. However, the relationship between the size of the pseudo white LED chip and the size of the auxiliary LED unit is not particularly limited. For example, the pseudo white LED chip And the auxiliary LED may be the same size.

Also, color rendering properties are evaluated based on K (R), K (G), K (B), and Ra ′ / Ra, a combination of pseudo white LED chip and auxiliary LED unit, its ratio, and auxiliary LED The combination of the LEDs constituting the unit is adjusted, the pseudo white LED chip and the auxiliary LED unit satisfying the above formulas (6) and (7), that is, the light source is determined, and using the determined light source, The planar lighting device is manufactured based on the determined combination.
Thus, by manufacturing a planar lighting device, a planar lighting device with high color rendering can be manufactured.

Other parts are emitted from the light emission surface of the planar illumination device having the same configuration as the planar illumination device 400 except that the light source is provided with only the pseudo white LED chip without using the auxiliary LED unit. The average color rendering index Ra ′ of the emitted light and the color rendering index R ₉ ′, R ₁₁ ′, R ₁₂ ′ of red, yellow, and blue are calculated in advance, and the average color rendering index Ra of the surface illumination device is calculated. And the combination of auxiliary LED units so as to satisfy the above formulas (6) and (7), and the ratio of the ratios when the red, yellow, and blue color rendering evaluation numbers R ₉ , R ₁₁ , and R ₁₂ are satisfied. It can also be used as a design method for a state lighting device.

Other parts are emitted from the light emission surface of the planar illumination device having the same configuration as that of the planar illumination device 400 except that the auxiliary LED unit is not used and the light source includes only the pseudo white LED. The average color rendering index Ra ′ of light and the color rendering index R ₉ ′, R ₁₁ ′, R ₁₂ ′ of red, yellow, and blue are calculated in advance, and the average color rendering index of the manufactured planar lighting device Ra and the color rendering index R ₉ , R ₁₁ , R ₁₂ of red, yellow, and blue are measured, and the color rendering properties of the planar lighting device are determined by whether or not the above formulas (6) and (7) are satisfied. It can also be used as an inspection method for a planar lighting device to be inspected.

Hereinafter, it demonstrates in detail with the result of having measured about the relationship between a pseudo-light-emitting LED chip and an auxiliary | assistant LED unit.
In this example, a Luxeon Flash manufactured by Lumileds, which is a combination of a blue LED and a fluorescent material of YAG (yttrium, aluminum, garnet), was used as the pseudo white LED chip.
Further, the red LED of the auxiliary LED unit is an LED that emits light having a center wavelength of 630 nm or 650 nm, the green LED is an LED that emits light having a center wavelength of 520 nm, and the blue LED is a center wavelength. LEDs that emit light of 470 nm or 480 nm were combined in various combinations depending on the examples. Further, an LED having a spectral half-value angle of about 30 degrees was used as the LED of the auxiliary LED unit.
FIG. 35 shows spectral characteristics of a pseudo white LED chip, a red LED that emits light having a central wavelength of 630 nm, a green LED that emits light having a central wavelength of 520 nm, and a blue LED that emits light having a central wavelength of 470 nm. Here, the vertical axis of the graph of FIG. u. The horizontal axis is the wavelength [nm].
Tables 4 and 5 below show the results of various combinations of the pseudo white LED and the LED of the auxiliary LED unit.
Here, No. 1 in Tables 4 and 5 is an example in which only the pseudo white LED is used as the light source, and No. 2 to No. 14 use the auxiliary LED unit in combination with various LEDs and the pseudo white LED as the light source. This is an embodiment of the present invention.
Table 4 shows the pseudo-white LED chip used as the light source, the center wavelength and arrangement ratio of the LEDs of the auxiliary LED unit, the measured color rendering index R _{1 to} R _8, and the calculated average color rendering index Ra. Here, the upper row of the auxiliary LED column in Table 4 shows the center wavelength of the LED, and the lower row shows the ratio to the pseudo-light-emitting LED.
Table 5 shows the average color rendering index Ra, K (R), K (G), K (B) and determination results calculated from the measured results.
Also, in Table 5, the determination is Δ when one of K (R), K (G), and K (B) is higher than when only the pseudo white LED used as the light source is used. Ra was high when Ra was high with at least one of K (R), K (G), K (B), and Ra, K (R), K (G), and K (B) were all high. The case where ◎, Ra, K (R), K (G), and K (B) all became high on average was designated as ◎.

As shown in Table 4, when Ra, K (R), K (G), and K (B) use a light source that satisfies the above formula (6), that is, No 2, 3, 6, 9, 10, 11, 12, 13, and 14 can increase the color rendering properties.
In particular, Examples No. 13 in Table 4 and Table 5, that is, pseudo white LED is 1, red LED (center wavelength 630 nm) is 0.1 and green LED (center wavelength 520 nm) is 0 as an auxiliary LED unit. .1 When blue LEDs (center wavelength 470 nm) are arranged at a ratio of 0.1, it can be seen that the color rendering properties for all colors can be increased.

In FIG. 36, the auxiliary LED unit is emitted from a light source (No. 9 in Tables 4 and 5) combining a red LED that emits light with a central wavelength of 630 nm and a blue LED that emits light with a central wavelength of 480 nm. As a supplementary LED unit, a red LED that emits light with a central wavelength of 630 nm, a green LED that emits light with a central wavelength of 520 nm, and a blue LED that emits light with a central wavelength of 480 nm are combined as an auxiliary LED unit. The spectral characteristic of the light inject | emitted from a light source (Table 4, No. 13 in Table 5) is shown. For comparison, the spectral characteristics of light emitted from a light source composed only of pseudo white LEDs are also shown.
Here, the vertical axis of the graph of FIG. u. The horizontal axis is the wavelength [nm].
As shown in the graph of FIG. 36, also from the viewpoint of the relative intensity of the emitted light, the planar illumination device using the light source of the combination of No. 9 and No. 13 is more than the No. 1 planar illumination device with only the pseudo white LED. It can be seen that the emission amounts of wavelengths in the red region and the blue region are large.

  In the above embodiment, the pseudo white LED chip is used as the main LED chip because light with high color rendering property, particularly white light with high color rendering property can be emitted with a simple and inexpensive configuration. Can be used. The present invention is not limited to this, and various LED chips or LEDs can be used as long as they are LED chips that emit light having two or more main peak wavelengths. In other words, the main LED chip is not limited to an LED chip that emits light having a main peak in the blue wavelength region and the green wavelength region as in the above embodiment, for example, the red wavelength region and the blue wavelength region. LED chip that emits light having a main peak in the LED, LED chip that emits light having a main peak in the green wavelength region and the red wavelength region, red wavelength region, blue wavelength region, and green wavelength region, respectively An LED chip or the like that emits light having a main peak can also be used.

  In this way, by configuring the LED unit constituting the light source with the main LED chip (or main LED) and the auxiliary LED (or auxiliary LED unit), it is possible to emit light with higher color rendering properties. .

  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.

Moreover, since the shape of the light guide plate can obtain various effects such as thinning and enlargement, the shape of the light guide plate 18 shown in FIGS. 1 and 2 is preferable, but is not limited thereto. Various shapes of light guide plates can be used.
As described above, the shape of the light guide plate is not particularly limited. However, the light guide plate preferably has a shape that increases in thickness as the distance from the light incident surface increases. As illustrated in FIGS. 1 and 2, both ends of the light guide plate are provided. It is preferable that each has a light incident surface, and the thickness increases as the distance from the light incident surface increases. By making the light guide plate thicker as it moves away from the incident surface, the light incident from the light source can reach farther, and the light exit surface is enlarged while maintaining a thinner light guide plate. can do. Thereby, a planar illuminating device can be reduced in thickness and enlarged.

  As another example of the shape of the light guide plate that increases in thickness as it moves away from the light incident surface, the light guide plate shown in FIG. 2 is cut in half, that is, the light incident surface is only one surface. It is good also as a shape which the thickness of a light-guide plate becomes thick as it leaves | separates from. In addition, the light source is disposed on any one of the side surfaces of the light guide plate, the four side surfaces are light incident surfaces, and the thickness increases from the four light incident surfaces toward the center, that is, the light emission surface. The surface on the opposite side may have a quadrangular pyramid shape.

Even when the light guide plate has the shape as described above, it is preferable to contain scattering particles. Further, in the light incident direction, the thickness in the direction perpendicular to the light exit surface from the light incident surface of the light guide plate (of the light guide plate). the length of the position to the thickness) is maximum and _{L G,} the above-described _{Φ · N p · L G ·} K C is preferably satisfies the 1.1 or 8.2 or less. By containing scattering particles in the light guide plate, light incident on the light guide plate can be efficiently diffused, and light with reduced illuminance unevenness and / or luminance unevenness can be emitted from the light exit surface. By satisfying the above, unevenness in illuminance and / or unevenness in luminance is further reduced, and light with high light utilization efficiency can be emitted from the light exit surface.

(A) is a perspective view which shows the outline of a liquid crystal display device provided with the planar illuminating device which concerns on the 1st Embodiment of this invention, (B) is schematic sectional drawing of the liquid crystal display device shown to (A). It is. (A) is a schematic top view of the light guide plate and light source which are used for the planar illuminating device which concerns on this invention, (B) is a schematic sectional drawing of the light guide plate and light source which are shown to (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)-(D) are schematic sectional drawings which show another example of a light-guide plate, respectively. (A) is a schematic sectional drawing which shows another example of a light-guide plate, (B) is a schematic sectional drawing which expands and shows a part of light-guide plate shown to (A). (A) is a schematic plan view of a light guide plate and a light source used in the planar illumination device according to the present invention, and (B) is a schematic cross-sectional view thereof. (A) is a schematic perspective view which shows one Example of a structure of the LED array used for this invention, (B) is a schematic front view of the LED chip of the LED array shown to (A), (C (A) is a schematic front view which shows the structure of the multilayer LED array using the LED array of (A), (D) is a schematic side view which shows one Embodiment of a heat sink. FIG. 2 is a schematic configuration diagram of a backlight unit when a prism sheet is disposed on the light exit surface of the light guide plate shown in FIG. 1. It is a schematic top view of a planar illuminating device provided with the light-guide plate which printed the diffuse reflector on the inclined surface. It is a schematic sectional drawing which shows an example of the planar illuminating device which has a transmittance | permeability adjustment member. It is a graph of the relative brightness | luminance of the light radiate | emitted from the light-projection surface of a backlight unit which is not provided with the transmittance | permeability adjustment member. It is a graph which shows the calculation result which computed distribution of the pattern density of the transmittance | permeability adjustment member which satisfies this invention when the maximum density c is set to 0.75 based on the relative brightness | luminance calculated based on FIG. It is a graph which shows the relative luminance of the light radiate | emitted from the light-projection surface of the planar illuminating device which has arrange | positioned the transmittance | permeability adjustment member when the maximum density c calculated in FIG. 17 is 0.75. It is a graph which shows the result of having measured the light which inject | emitted from the other light source and permeate | transmitted the chromaticity adjustment film. It is a graph which shows the result of having measured the light which inject | emitted from the other light source and permeate | transmitted the chromaticity adjustment film. (A) is a schematic plan view of the other structural example of the light-guide plate which can be used for the backlight unit of this invention, (B) is the schematic sectional drawing. (A) is a schematic plan view of still another configuration example of the light guide plate that can be used in the backlight unit of the present invention, and (B) is a schematic cross-sectional view thereof. It is a schematic sectional drawing which shows the other example of the planar illuminating device of the 1st Embodiment of this invention. (A)-(C) are schematic sectional drawings which show the other example of the light-guide plate used for the planar illuminating device of the 1st Embodiment of this invention, respectively. It is a schematic sectional drawing which shows the structure of another example of the planar illuminating device of the 1st Embodiment of this invention. It is a schematic block diagram of the planar illuminating device using a some light-guide plate. (A) is a schematic perspective view which shows the other Example of a planar illuminating device, (B) is a schematic side view of the planar illuminating device shown to (A), (C) is (A It is a schematic sectional drawing in the longitudinal direction of the planar illuminating device shown in FIG. (A) is a schematic side view which shows the further another Example of a planar illuminating device, (B) is a schematic sectional drawing in the longitudinal direction of the planar illuminating device shown to (A). It is a schematic front view which shows an example of a ring-shaped planar illumination device. It is a schematic front view which shows another example of a ring-shaped planar illuminating device. (A) is a schematic front view which shows another example of a ring-shaped planar illuminating device, (B) is sectional drawing of the planar illuminating device shown to (A). (A) is a top view which shows the outline of the light-guide plate and light source which are used for the other planar illuminating device of this invention, (B) is the schematic sectional drawing. It is a schematic front view which shows the structure of the light source shown in FIG. (A)-(C) is a schematic front view which shows another example of the light source which can be used for the planar illuminating device shown in FIG. 32, respectively. It is a graph which shows the spectral characteristic of the light inject | emitted from each LED of a pseudo white LED and an auxiliary | assistant LED unit. It is a graph which shows the result of having measured the spectral characteristic of the light inject | emitted from a light source.

Explanation of symbols

2, 120, 141, 180 Backlight unit 4 Liquid crystal display panel 6 Drive unit 10 Liquid crystal display device 12, 122, 142, 190 Light source 14 Diffusion film 16 Polarization separation film 18, 28, 38, 144, 151, 153, 155 Optical plate 18a Light exit surface 18b First inclined surface 18c Second inclined surface 18d First light incident surface 18e Second light incident surface 20A, 20B Light mixing unit 22 Reflecting sheet 24 LED array 26, 188 Prism sheet 28a First inclined surface 28b Second inclined surface 28c Flat surface 28d First light incident surface 38a First inclined surface 38b Second inclined surface 38c Third inclined surface 38d Fourth inclined surface 82 Light source 84 LED array 86 LED
88, 126 Coupling lens 90 Light guide member 90a Light exit surface 92 Optical fiber 94 Case 100 Backlight unit 102 Reflective sheet 104, 106 Prism sheet 108 Diffusion sheet 124 LED array 128 LED chip 130 Heat sink 132 Multi-layer LED array 140 Diffuse reflector 146 Base material 148, 152, 154, 156 Low refractive index member 162 Reflective member 182 Transmittance adjusting member 184 Transparent film 186 Transmittance adjusting body

Claims (26)

A light source having a plurality of LED chips;
A light guide plate including a light incident surface on which light emitted from the light source is incident and a light emission surface that emits light incident from the light incident surface;
The light source emits light having an emission wavelength having two or more main peak wavelengths, and an emission wavelength having two or more main peak wavelengths different from the main peak wavelength of the first LED chip And a second LED chip that emits the light . The LED chip includes an LED including a light emitting surface for emitting light, arranged on the light emitting surface of the LED, to claim 1 and a wavelength conversion member that converts a part of the wavelength of the light emitted from the LED The surface illumination device described. The planar illumination device according to claim 2 , wherein the LED emits light in any one wavelength region of red, blue, green, purple, ultraviolet, near ultraviolet, infrared, and near infrared. The planar illumination device according to claim 2 or 3 , wherein the wavelength conversion member is a phosphor that emits light when light is transmitted therethrough. The planar illumination device according to any one of claims 1 to 4 , wherein the LED chip emits light having main peaks in all of red, blue, and green. The LED chip is at a position opposed to the light incident surface, the planar lighting device according to any one of claims 1 to 5 arranged in rows. The LED chip has a length in a direction perpendicular to the light exit surface of the light guide plate as a, a length in the arrangement direction of the LED chips as b, and an arrangement interval of the LED chips as p, The planar illumination device according to claim 6 , wherein a relation of p>b> a is satisfied. The light source has two or more LED arrays in which the LED chips are arranged in a row,
Claim having a reference to at least one of mechanical joining method and a chemical bonding method, a laminate of a distance between the LED chips of the LED chip and the other of said LED array of the LED array by a predetermined distance constituting 6 Or the planar illumination device according to 7 . Furthermore, the planar illuminating device in any one of Claims 1-8 which are arrange | positioned between the said light source and the said light-incidence surface, and have the light transmissive part which the light inject | emitted from the said light source permeate | transmits. The planar illumination device according to claim 9 , wherein the light transmission part is disposed in a non-contact manner with the light source and the light guide plate. The light source includes a first light source and a second light source,
The light guide plate is disposed between the first light source and the second light source, faces the first light source, faces a first light incident surface including one side of the light emission surface, and faces the second light source. wherein a second light entrance plane containing the opposite side of the one side, according to any one of claims 1 to 10, which is shaped thickness becomes thicker toward the center from the first light entrance plane and the second light entrance plane Planar lighting device. The planar illumination device according to claim 11 , wherein the light guide plate contains scattering particles that scatter light that is incident from the first and second light incident surfaces and propagates inside the light guide plate. The light guide plate has a scattering cross section of the scattering particles of Φ, a half length in the light incident direction of L _G , a density of scattering particles of N _P , a correction coefficient of K _C , and a K _C of 0.005 or more. If 0.1 or less, the planar lighting device according to claim 12 which satisfies _{1.1 ≦ Φ · N P · L} G · K C ≦ 8.2. The planar illumination device according to claim 11 , wherein the light emission surface of the light guide plate has a rectangular outer shape. The light exit surface of the light guide plate is formed flat, and the light guide plate is on the opposite side of the light exit surface and on a bisector of the light exit surface parallel to the one side of the light exit surface. On the other hand, the planar illumination device according to any one of claims 11 to 14 , which has a first inclined surface and a second inclined surface formed so as to be symmetrically inclined with respect to each other. The planar lighting device according to claim 15 , wherein the light guide plate has a R-shaped connecting portion between the first inclined surface and the second inclined surface in a cross-sectional shape perpendicular to the bisector. Is selectively transmitting a predetermined polarization component, polarized light separation film for reflecting the other polarized light component is on the light exit surface of the light guide plate of claim 11 to 16 are formed integrally with the light guide plate The planar illumination device according to any one of the above. The light emitting surface of the light guide plate is formed by a first inclined surface and a second inclined surface that are symmetrically inclined with respect to a bisector of the light emitting surface parallel to the one side of the light emitting surface. Furthermore, the third inclined surface and the fourth inclined surface that are symmetrically inclined with respect to a bisector of the light emitting surface parallel to the one side of the light emitting surface are also opposite to the light emitting surface. The planar lighting device according to claim 11 , wherein the planar lighting device is formed by an inclined surface. The light emitting surface of the light guide plate is formed by a first inclined surface and a second inclined surface that are symmetrically inclined with respect to a bisector of the light emitting surface parallel to the one side of the light emitting surface. The planar illumination device according to claim 11 , wherein a surface opposite to the light exit surface is formed flat. Having two or more light guide plates;
A surface including one side of the light exit surface of the light guide plate and one side of the light incident surface, and a surface including one side of the light exit surface of the other light guide plate and one side of the incident surface are disposed adjacent to each other. The planar illumination device according to any one of claims 11 to 19 . The light guide plate, a planar lighting device according to any one of claims 11 to 20 in which a plurality of diffuse reflectors on at least one surface of the surface excluding the first light entrance plane and the second light entrance plane is located . The planar illuminating device according to claim 21 , wherein the diffuse reflectors are arranged densely with distance from the first light incident surface and the second light incident surface. The planar illumination device according to claim 21 or 22 , wherein the diffuse reflector is disposed on a surface opposite to the light exit surface. In the light guide plate, a part on the first light incident surface side and a part on the second light incident surface side are formed of a material different from other parts, and the parts and refractive index of the second portion of the light incident surface side material and Nm, the refractive index of the other part materials when the Ni, of claim 11 to 23 satisfying the relationship Nm> Ni The planar illumination device according to any one of the above. Furthermore, the light emitting surface of the light guide plate in the vicinity of the first light incident surface, the surface on the opposite side of the light emitting surface in the vicinity of the first light incident surface, and the light emitting surface in the vicinity of the second light incident surface. The planar illumination device according to any one of claims 11 to 24 , further comprising a reflective material disposed on a surface opposite to the light exit surface in the vicinity of the second light incident surface. The surface illumination device according to any one of claims 11 to 25 , wherein the light incident surface has a surface roughness of 380 nm or less.

Images