JP2009205968A - Plane lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device without making it large-sized, and also, with high luminance, high proportion, and little color unevenness, as well as with high display quality. <P>SOLUTION: With a backlight unit 1, light is emitted from a blue-color LED 5B, a green-color LED 5G, and red-color LED 5R. Here, the red-color LED 5R is a light-emitting element of an inverted pyramid shape, with excellent emission efficiency. For that, there is a fear of stray light generated as the light is reflected at a wiring board 6 and a wall face of the magazine 15 of a collimator lens 9. Such stray light is absorbed by a light-absorbing part 16 formed at each wall face forming the magazine 15 of the collimator lens 9 to have red-color stray light prevented from getting intense, and moreover, emitted light from the blue-color LED 5B and the green-color LED 5G is increased by the collimator lens 9 at a light-emitting face member 4 in the vicinity of the light source part where emitted light from the red-color LED 5R has been relatively prevalent, so that color unevenness is surely restrained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface illumination device that emits illumination light having a uniform luminance distribution from a light emitting surface, such as a backlight unit of a liquid crystal display device using an LED as a light source.

  In recent years, as a light source of a backlight unit for a liquid crystal display device, there has been a movement to replace a cold cathode discharge lamp with an LED. This is largely because the LED does not contain mercury, which is a harmful substance, and is suitable as an environmentally conscious light source, and the power consumption can be greatly reduced by recent significant improvement in luminous efficiency. Backlight units equipped with LEDs as light sources have been mainly used for small devices such as mobile phones and mobile terminals, but recently, large-sized liquid crystal displays such as 20-inch-type liquid crystal monitors and liquid crystal televisions. The movement of adopting the equipment is also progressing.

  In the case of a large liquid crystal display device, the backlight unit is required to have high luminance. Therefore, it is not a structure in which surface light is emitted from a light guide plate generally employed in a small backlight unit, but a structure in which LED light sources are arranged directly under a surface light emitting portion as shown in JP-A-2005-316337. Has become commonplace.

  However, since the LED is a point light source, if the distance between the arranged LED and the surface light emitting unit is too close, it is recognized as luminance unevenness and color unevenness, which deteriorates the quality of the liquid crystal display. This phenomenon appears more conspicuously when a high-power LED having a power of 1 W class or more is used as a light source in order to realize high luminance. On the other hand, increasing the distance between the LED and the surface light emitting portion in order to reduce luminance unevenness and color unevenness leads to an increase in the thickness of the entire device, which is not preferable against the recent trend of thinning. Further, in order to improve the color reproducibility on the liquid crystal panel (for example, 100% or more of the NTSC standard ratio), it is necessary to ensure color mixing when the light source is composed of blue, green and red single-color LEDs. Therefore, it is necessary to further increase the thickness.

Therefore, for example, in Japanese Patent Application Laid-Open No. 2006-106212, an LED light source in which a large number of LEDs are arranged and mounted on a wiring board is arranged on the side portion of the apparatus to emit light, and the light guided to the hollow light guide region. A backlight unit technology that reflects light and emits light from a surface light emitting portion on the front side has been proposed.
JP 2005-316337 A JP 2006-106212 A

  In the technology of the backlight unit disclosed in Patent Document 2, a reflector is formed in the LED light source unit so that LED emitted light in the apparatus thickness direction is condensed and emitted to the hollow light guide region. . At that time, if the light condensing property is insufficient, the luminance is high in the area near the light source of the surface light emitting unit, and the luminance is low in the area far from the light source. For this reason, it is necessary to increase the size of the reflector in order to improve the light condensing performance. This is because the size of the device other than the effective light emitting region (so-called frame portion) becomes larger, and the entire device becomes larger. It is not preferable.

  On the other hand, when blue, green, and red single-color LEDs are arranged and mounted on the wiring board as the light source, the red LED has a larger temperature dependency of the light emission output than the blue LED and the green LED ( It is necessary to suppress heat generation as much as possible, that is, to improve luminous efficiency. There is an example of a red LED with improved luminous efficiency, in which the shape of the light emitting element is changed from the normal shape to improve the light extraction efficiency from the light emitting element. In such a red LED, the luminous efficiency is improved. However, part of the light is emitted toward the mounting substrate. This is recognized as a reddish color unevenness in the vicinity of the light source unit in the surface illumination device, and when used as a liquid crystal backlight, it leads to a decrease in display quality.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a surface illumination device that does not increase in size and has high luminance, high uniformity, low color unevenness, and high display quality.

  The present invention includes a hollow unit case, a light reflecting surface member disposed on the bottom surface side of the unit case, a light emitting surface member disposed on the front side of the unit case facing the light reflecting surface member, A plurality of LEDs including a first LED having one light distribution and a second LED having a second light distribution different from the first light distribution are arranged and mounted on a wiring board, An LED light source disposed adjacent to the hollow light guide region so as to emit light to the hollow light guide region, which is a space formed between the light reflecting surface member and the light emitting surface member, and emission of the LED light source A sectional shape in the thickness direction of the unit case including the optical axis of the first LED and a sectional shape in the thickness direction of the unit case including the optical axis of the second LED. From the LED light source formed in different shapes It is characterized by comprising a condensing component to parallel to the light emitting surface of the light-emitting surface member.

  According to the surface illumination device of the present invention, there is an excellent effect that the size of the device is not increased, and the display quality is high with high luminance, high uniformity, little color unevenness.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 17 show an embodiment of the present invention, FIG. 1 is an exploded perspective view of a backlight unit, FIG. 2 is a cross-sectional view of the backlight unit, and FIG. 3 is a structural explanatory diagram of a light emitting element of a red LED. FIG. 4 is an explanatory diagram of light emission of a light emitting element of a red LED, FIG. 5 is an explanatory diagram of light emitted from an LED light source, and FIG. 7 is a partially broken perspective view seen from the exit side of the collimator lens, FIG. 8 is a cross-sectional view showing the condensing characteristic of the collimator lens, FIG. 9 is an explanatory view showing the luminance distribution characteristic of the backlight unit, and FIG. FIG. 11 is an explanatory diagram of a collimator lens as an example different from FIG. 10, FIG. 12 is an explanatory diagram of a collimator lens as an example different from FIG. 10, and FIG. As an example different from 14 is an explanatory view of a collimator lens as an example different from FIGS. 10 to 13, FIG. 15 is an explanatory view of a collimator lens as an example different from FIGS. 10 to 14, and FIG. 16 is a collimator. FIG. 17 is an explanatory diagram for comparing the difference in chromaticity distribution of the light emitting surface due to the improvement of the collimator lens.

  1 and 2, reference numeral 1 denotes a backlight unit for a liquid crystal display device as an example of a surface illumination device. The backlight unit 1 includes a rectangular and hollow unit case 2 and a bottom surface of the unit case 2. The light reflecting surface member 3 disposed on the side, the light emitting surface member 4 disposed on the front side facing the light reflecting surface member 3 of the unit case 2, and a large number of LEDs 5 are arranged and mounted on the wiring board 6. In the hollow light guide region 7, the light is emitted from the pair of opposed end portions of the unit case 2 to the hollow light guide region 7 which is a space formed between the light reflecting surface member 3 and the light emitting surface member 4. A pair of LED light sources 8 disposed adjacent to each other, and a condensing component that is disposed in the vicinity of the emitting portion of each LED light source 8 and makes the light from the LED light source 8 parallel to the light emitting surface of the light emitting surface member 4 A pair of collimator lenses 9 and a unit Case 2 and a front frame 10 that covers the light-emitting surface member 4 side are the main constructed.

  The unit case 2 is formed of a metal having a high thermal conductivity such as an aluminum alloy.

  The light reflecting surface member 3 is formed by laminating a highly reflective and diffuse reflecting material such as a white PET (polyethylene terephthalate) film or white ink on a metal or resin base material, and the luminance distribution on the light emitting surface member 4 is It is formed in a shape in which the distance from the light emitting surface member 4 is changed so as to be uniform. For this reason, it forms so that the distance from the light emission surface member 4 becomes short, so that the distance from the LED light source 8 becomes far (the center of the unit case 2). In addition to the above, the light diffusive reflective material may be a material in which a light transmissive diffusing material is coated on highly reflective aluminum or the like having specular reflectivity.

  The light-emitting surface member 4 is configured by further stacking optical sheets such as diffusion sheets 4b and 4c and a lens sheet 4d on the light transmission diffusion plate 4a. The light-emitting surface member 4 passes through the hollow light guide region 7 and passes through the light reflection member 2. By uniformly diffusing and emitting the reflected light, the luminance unevenness on the light emitting surface is eliminated and the uniformity is increased.

  The LED light source 8 is formed by mounting a large number of LEDs 5 in a row or a plurality of rows on a long and narrow wiring board 6 formed in a width that can be accommodated on the side surface of the unit case 2. The wiring board 6 is made of a photothermally conductive metal such as aluminum or a similar alloy, or a ceramic such as aluminum nitride, and is fixed to the side wall of the high thermal conductivity unit case 2 by screwing, bonding or other means. ing. In addition, it is preferable to interpose a highly heat conductive double-sided tape, sheet or grease between the wiring board 6 and the side wall of the unit case 2.

  The LEDs 5 are a plurality of LEDs that are colored in blue, green, red, etc., arranged in a quantity ratio for combining with a desired white chromaticity. The red LED is the first LED, and the blue LED and the green LED are the second. LED is provided.

  The blue LED 5B and the green LED 5G use an InGaN (indium gallium nitride) based semiconductor as a light emitting element.

  On the other hand, the red LED 5R uses an AlInGaP (aluminum indium gallium phosphide) semiconductor as a light emitting element. As shown in FIG. 3, the light emitting element 5RA of the red LED 5R according to the present embodiment includes, in order from the lower layer (wiring substrate 6) side, an n-type GaP (gallium phosphide) substrate 5RAa, an n-type AlInGaP cladding layer 5RAb, a light emitting layer 5RAc, A p-type AlInGaP cladding layer 5RAd and a p-type GaP layer 5RAe are formed. Although illustration is omitted, an Al bonding pad (anode) is formed on the p-type GaP layer 5RAe via a contact for ohmic contact. Further, an Au alloy electrode (cathode) is formed under the n-type GaP substrate 5RAa. The n-type GaP substrate 5RAa is cut into an inverted pyramid after the formation of the epitaxial layer.

  FIG. 4 shows an example of light rays generated from the light-emitting layer 5RAc of the red LED 5R employed in the present embodiment in which the light-emitting element is an inverted pyramid, and light rays generated from the light-emitting layer 5RBc in the normal cuboid light-emitting element 5RB.

  As shown in FIG. 4A, in the case of the inverted pyramid type light emitting element 5RA, the light is emitted from the light emitting element 5RA beyond the critical angle to the outside as compared with the rectangular parallelepiped light emitting element 5RB shown in FIG. 4B. The amount of light to be increased can be increased.

  In other words, the red LED 5R employed in the present embodiment employs a light emitting efficiency that suppresses heat generation compared to a normal red LED. However, a certain amount of emitted light traveling toward the wiring board 6 as in the light ray R2 is also generated. As shown in FIG. 5, such a light ray R <b> 2 is reflected as stray light on the wiring substrate 6 of the LED light source 8 and the wall surface of the storage unit 15 of the collimator lens 9 and enters the collimator lens 9. Such light (light illustrated by RYL1 and RYL2 in FIG. 5) travels to the hollow light guide region 7 without being collected by the collimator lens 9, and is thus emitted from the light emitting surface member 4 in the vicinity of the LED light source 8. There is a risk of being recognized as reddish color unevenness in the vicinity of the light source unit.

  For this reason, in the present embodiment, the light absorbing portion is formed on each wall surface forming the storage portion 15 of the collimator lens 9, that is, on the surface 6 a, 2 a, 10 a of the LED light source 8 of the wiring substrate 6, unit case 2, front frame 10. 16 is formed.

  The light absorbing portion 16 directly reflects the light reflectance in the emission wavelength region of the red LED 5R on the wiring board 6, the unit case 2, and the LED light source 8 side surfaces 6a, 2a, and 10a of the front frame 10 with the blue LED 5B and the green LED 5G. The color which is lower than the light reflectance in the emission wavelength region is formed by silk printing or resist printing. Specifically, in the present embodiment, red stray light may become strong as described above. Therefore, in order to prevent this, the light absorbing unit 16 is printed by silk printing or resist printing a blue-green color. Is formed.

  In this embodiment, in order to prevent red stray light, the light absorbing portion 16 is formed by silk-printing or resist printing a blue-green color, but depending on the specifications, stray light from the blue LED 5B is formed. In order to prevent this blue stray light, the light absorbing portion 16 may be formed by silk printing or resist printing of a yellow color. Similarly, the stray light of the green LED 5G is strong, and in order to prevent this green stray light, the light absorbing portion 16 may be formed by silk-printing or resist printing a purple color.

  Moreover, in this Embodiment, the light absorption part 16 is formed by silk-printing or resist printing on the LED light source 8 side surface 6a, 2a, 10a of the wiring board 6, the unit case 2, and the front frame 10. However, if a sufficient stray light prevention effect can be obtained with only one of the wall surfaces, the light absorbing portion 16 does not have to be formed on all of these surfaces.

  Further, in the present embodiment, the light absorbing portion 16 is formed by silk printing or resist printing. However, a separate member whose color itself is intended can be provided as a light absorbing portion, or wiring. You may make it employ | adopt the member in which the color itself of materials itself, such as the board | substrate 6, the unit case 2, and the front frame 10, is intended.

  FIG. 6 shows the chromaticity distribution (Cx) in the case of the conventional resist color (white) and the resist color of the present invention (blue-green). That is, as shown in FIG. 6A, in the backlight unit 1 of the present embodiment, the direction perpendicular to the light source line by the pair of LED light sources 8 provided on each of the two opposite side surfaces of the light emitting surface (LED array) The measurement line is perpendicular to the direction or the optical axis direction of the LED 5, and FIG. 6B shows the chromaticity distribution (Cx) between the light source lines by the pair of LED light sources 8 on the measurement line. . Since the Cx value mainly depends on the amount of light in the red wavelength region, color unevenness due to redness can be compared. In the resist color (blue-green: solid line) of the present embodiment, an increase in the Cx value at the light emitting surface end (near the light source) is reduced as compared with the conventional resist color (white: broken line). This indicates that the color unevenness in the vicinity of the light source portion has been reduced.

  As described above, according to the present embodiment, even when a red LED equipped with an inverted pyramid light emitting element with high luminous efficiency is used, stray light generated as a harmful effect is cut off, and the luminance from the entire surface light emitting unit is reduced. The light can be emitted without unevenness and color unevenness.

  On the other hand, an elongated collimator lens 9 in which concave grooves 11 are formed so as to cover the rows of LEDs 5 is disposed on the emission side of the LED light source 8, that is, the side facing the hollow light guide region 7. The collimator lens 9 is a member for condensing light from the LED 5 of the LED light source 8 in the thickness direction of the hollow light guide region 7 and entering the hollow light guide region 7. For example, acrylic or polycarbonate These are made of transparent resin or glass.

  As shown in FIGS. 7 and 8, the concave grooves 11 facing the rows of the collimator lenses 9 basically have a convex incident surface InA that guides radiated light having an angle close to the optical axis of the LED 5 into the lens. And a plane-shaped incident surface InB1 and InB2 for guiding an angle (wide angle side) away from the optical axis of the LED 5 into the lens.

  On the side surfaces adjacent to the incident surfaces InB1 and InB2 of the collimator lens 9, total reflection surfaces TIR1 and TIR2 that totally reflect the light in the lens are formed.

  The exit portion of the collimator lens 9 corresponds to the convex exit surface ExA corresponding to the incident light from the entrance surface InA, and the light totally reflected by the total reflection surfaces TIR1 and TIR2 after entering from the entrance surfaces InB1 and InB2. Concave-curved exit surfaces ExB1 and ExB2 are formed.

  In the backlight unit 1 of the present embodiment, as shown in FIG. 8, the light from the LED 5 of the LED light source 8 is condensed in the thickness direction of the hollow light guide region 7 by the collimator lens 9, The light can be incident on the light region 7.

  That is, in the collimator lens 9, the light RYA incident on the incident surface InA from the LED 5 is refracted by the incident surface InA and the exit surface ExA having a convex cross section and is condensed in the thickness direction of the hollow light guide region 7. The light RYB1 and RYB2 incident on the incident surfaces InB1 and InB2 are condensed in the thickness direction of the hollow light guide region 7 by total reflection on the total reflection surfaces TIR1 and TIR2 and refraction on the output surfaces ExB1 and ExB2. .

  Thus, the light RYA, RYB1, RYB2 emitted from the collimator lens 9 to the hollow light guide region 7 is reflected in the direction of the light emitting surface member 4 by the reflecting surface of the light reflecting surface member 3 whose shape is optimized. The light is emitted from the light emitting surface of the member 4 with high luminance and no luminance unevenness.

  According to the backlight unit 1 of the present embodiment, the light emitted from the LED 5 that is the light source at a wide angle due to the presence of the collimator lens 9 is condensed at a high efficiency and a narrow angle with a light utilization efficiency of 80% or more. The reflection loss in the hollow light guide region 7 can be minimized, and the luminance can be improved as compared to the conventional hollow type backlight unit. Further, in the conventional hollow type backlight unit, the reflection surface of the hollow light guide region is made to have a specular reflection characteristic or a reflection characteristic close to it in order to make the light reach as far as possible from the light source, and locally on the light emitting surface. In the case of the backlight unit 1 of the present embodiment, the light source has a high light condensing property. Therefore, even if the reflecting surface is made diffusely reflective, the luminance uniformity as shown in FIG. In addition, it is possible to prevent the occurrence of local bright lines. Here, FIG. 9 shows the luminance distribution between the light source lines by the pair of LED light sources 8 on the same measurement line as in FIG.

  In addition, as an optical component which condenses the light from LED5 of the LED light source 8 in the thickness direction of the hollow light guide region 7 and enters the hollow light guide region 7, it is a collection by total reflection and refraction as in this embodiment. A convex cylindrical lens or the like may be used in addition to the collimator lens combined with light.

  10 is a diagram for explaining the collimator lens 9 according to the present embodiment in detail. FIG. 10A is a perspective view of the collimator lens 9 viewed from the LED light source 8 side (incident side). (B) is a longitudinal sectional view parallel to the light emitting surface including the optical axis of the LED of the collimator lens 9, FIG. 10 (c) is a B0-B0 section, an R1-R1 section, G1 in FIG. 10 (b). It is a figure which shows -G1 cross section and B1-B1 cross section.

  In the embodiment of the present invention, since the reverse pyramid type light emitting element 5RA with good luminous efficiency is used for the red LED 5R, as shown in FIG. 5, the light is emitted from the light emitting surface member 4 in the vicinity of the LED light source 8, There is a risk of being recognized as reddish color unevenness in the vicinity of the light source unit. This can be expected to be prevented by the light absorbing portion 16, but the shape of the collimator lens 9 is changed as follows in order to further improve color unevenness.

  That is, when the shape of the collimator lens 9 in the portion facing the red LED 5R is a reference shape, the thickness of the unit case 2 including the optical axis of each LED in the portion facing the blue LED 5B and the portion facing the green LED 5G. In the wide-angle region away from the vicinity of the optical axis of the cross-sectional shape in the vertical direction, the light distribution in the thickness direction of the unit case 2 of the light emitted from the collimator lens 9 is increased as compared with the reference shape. The shape is changed.

  Specifically, as shown in FIG. 10, the incident surfaces InAB1 and InAG1 of the collimator lens 9 corresponding to the positions of the blue LED 5B and the green LED 5G are used as the incident surfaces of the collimator lens 9 corresponding to the position of the red LED 5R. It is formed farther from the LEDs 5B and 5G than the InAR1. That is, in FIGS. 10B and 10C, LB1 = LG1> LR1.

  As a result, the amount of light emitted from the collimator lens 9 of the blue LED 5B and the green LED 5G increases in light intensity compared to the original reference design in the wide-angle region. FIG. 16A shows an example of a light distribution of outgoing light from the conventional collimator lens 9.

  From this example, it can be seen that increasing the light distribution of blue and green in a wide-angle region from ± 15 ° is suitable for approximating the light distribution of each color. Accordingly, based on this result, FIG. 16B shows a comparative example of the light distribution in the case where the cross-sectional shape of the portion corresponding to the position of the blue LED 5B and the green LED 5G is changed and in the case of the reference design. In this way, the collimator lens 9 with the changed light distribution is adopted as an example.

  Specifically, as an example of applying the change in the cross-sectional shape of the collimator lens 9, it is desirable to carry out as follows.

  When the light intensity in the optical axis direction is 1, the light intensity in the portion of the collimator lens 9 at the portion facing the red LED 5R whose light intensity in the 90 ° direction is 0.1 or more with respect to the optical axis is used as a reference. Light distribution in the thickness direction of the unit case 2 of the emitted light of the collimator lens 9 in the portion of the collimator lens 9 facing the blue LED 5B or the green LED 5G whose luminous intensity in the 90 ° direction is less than 0.1 The light distribution in the wide-angle region is increased from ± 15 ° of.

  Thus, in the light emitting surface member 4 in the vicinity of the light source portion where the emitted light from the red LED 5R is relatively large, the emitted light from the blue LED 5B and the green LED 5G can be increased, and the inverted pyramid type with good luminous efficiency can be obtained. The color unevenness of the light emitting surface member 4 in the vicinity of the light source part due to the adoption of the red LED 5R including the light emitting element 5RA can be surely suppressed together with the light absorbing part 16.

  FIG. 17 shows a comparison of the chromaticity distribution (Cx) between the conventional collimator lens and the collimator lens according to the present embodiment on the same measurement line as that of FIG. Since the Cx value mainly depends on the amount of light in the red wavelength region, color unevenness due to redness can be compared. In the case where the collimator lens according to the present embodiment is used, an increase in Cx at the light emitting surface end portion (near the light source portion) is reduced as compared with the conventional collimator lens. This indicates that the color unevenness in the vicinity of the light source portion has been reduced.

  In the present embodiment, the incident surfaces InAB1 and InAG1 of the portion of the collimator lens 9 corresponding to the positions of the blue LED 5B and the green LED 5G are respectively set to be greater than the incident surface InAR1 of the portion of the collimator lens 9 corresponding to the position of the red LED 5R. The LEDs 5B and 5G are stepped away from the LEDs 5B and 5G. However, as shown in the collimator lens 9A in FIG. That is, the incident surfaces InAB2 and InAG2 of the collimator lens 9A corresponding to the positions of the blue LED 5B and the green LED 5G are further away from the respective LEDs 5B and 5G than the incident surface InAR2 of the collimator lens 9A corresponding to the position of the red LED 5R. (In FIG. 11B and FIG. 11C, LB2 = LG2> LR2), each of the incident surfaces InAB2, InAG2, and InAR2 is formed of a continuous curved surface. As a result, the amount of light emitted from the collimator lens 9A of the blue LED 5B and the green LED 5G increases in light intensity compared to the original reference design in the wide-angle region.

  Further, as shown in the collimator lens 9B of FIG. 12, in consideration of the difference in the light distribution characteristics of the blue LED 5B, the green LED 5G, and the red LED 5R, the incident surface InAB3 of the collimator lens 9B of the portion facing the position of the blue LED 5B is The part of the collimator lens 9B facing the position of the red LED 5R is formed farther from the blue LED 5B than the part of the collimator lens 9B facing the incident surface InAR3, and the part of the collimator lens 9B facing the position of the green LED 5G is relative to the position of the blue LED 5B. It may be formed away from the green LED 5G than the incident surface InAB3 of the collimator lens 9B. That is, in FIGS. 12B and 12C, LG3> LB3> LR3. As a result, the amount of light emitted from the collimator lens 9B of the blue LED 5B and the green LED 5G increases in light quantity more accurately than the original reference design in the wide-angle region. Even in this case, it may be formed by a continuous curved surface as described in FIG.

  Furthermore, in the present embodiment, the shapes of the incident surfaces InAB1 and InAG1 of the collimator lens 9 corresponding to the positions of the blue LED 5B and the green LED 5G are changed. As shown in the collimator lens 9C of FIG. In addition, the shape on the exit surface ExAB1, ExAG1 side may be changed. In other words, the exit surfaces ExAB1 and ExAG1 of the collimator lens 9C corresponding to the positions of the blue LED 5B and the green LED 5G are closer to the respective LEDs 5B and 5G than the exit surface ExAR1 of the collimator lens 9C corresponding to the position of the red LED 5R. (In FIG. 13B and FIG. 13C, LB4 = LG4 <LR4). As a result, the amount of light emitted from the collimator lens 9C of the blue LED 5B and the green LED 5G increases in light intensity compared to the original reference design in the wide angle region.

  Further, the exit surfaces ExAB1, ExAG1, and ExAR1 of the collimator lens 9 corresponding to the positions of the blue LED 5B, the green LED 5G, and the red LED 5G are not formed in a step shape but may be formed in a continuous curved surface. good. That is, as shown in the collimator lens 9D of FIG. 14, the exit surfaces ExAB2 and ExAG2 of the portion of the collimator lens 9D opposite to the positions of the blue LED 5B and the green LED 5G are emitted from the portion of the collimator lens 9D opposite to the position of the red LED 5R. It is formed so as to be closer to the respective LEDs 5B and 5G than the surface ExAR2 (FIG. 14 (b) and FIG. 14 (c), LB5 = LG5 <LR5), and each of these emission surfaces ExAB2, ExAG2, and ExAR2 are It is formed with a continuous curved surface. As a result, the amount of light emitted from the collimator lens 9D of the blue LED 5B and the green LED 5G increases in light intensity compared to the original reference design in the wide-angle region.

  Further, as shown in the collimator lens 9E of FIG. 15, in consideration of the difference in the light distribution characteristics of the blue LED 5B, the green LED 5G, and the red LED 5R, the exit surface ExAB3 of the collimator lens 9E corresponding to the position of the blue LED 5B is The portion of the collimator lens 9E facing the position of the red LED 5R is formed closer to the blue LED 5B than the surface of the collimator lens 9E, and the portion of the collimator lens 9E facing the position of the green LED 5G is positioned at the position of the blue LED 5B. Alternatively, it may be formed so as to be closer to the green LED 5G than the exit surface ExAB3 of the collimator lens 9E in a portion opposite to. That is, in FIGS. 15B and 15C, LG6 <LB6 <LR6. As a result, the amount of light emitted from the collimator lens 9E of the blue LED 5B and the green LED 5G increases more accurately than the original reference design in the wide-angle region. Even in this case, it may be formed by a continuous curved surface as described in FIG.

  Further, the examples shown in FIGS. 10 to 15 may be combined. For example, both the incident surface side and the exit surface side of the collimator lens 9 may be changed stepwise or in a continuous curved surface.

  In the backlight unit 1 according to the embodiment of the present application configured as described above, light is emitted from the LED light source 8 (from the blue LED 5B, the green LED 5G, and the red LED 5R) as shown in FIG. At this time, the red LED 5R is an inverted pyramid-type light emitting element 5RA, and has a light emission efficiency with reduced heat generation compared to a normal red LED.

  Therefore, stray light that is reflected by the wiring substrate 6 of the LED light source 8 and the wall surface of the storage portion 15 of the collimator lens 9 as shown by RYL1 and RYL2 in FIG.

  Such stray light is a light absorbing portion 16 formed on each wall surface forming the storage portion 15 of the collimator lens 9, that is, on the wiring substrate 6, the unit case 2, and the LED light source 8 side surfaces 6a, 2a, and 10a of the front frame 10. Therefore, red stray light is prevented from becoming strong.

  Further, even if there is red stray light that is not absorbed by the light absorbing portion 16, the blue LED 5B and the light emitting surface member 4 near the light source portion where the emitted light from the red LED 5R is relatively large by the collimator lens 9 Since the emitted light from the green LED 5G is increased, color unevenness is reliably suppressed.

  As described above, according to the embodiment of the present invention, since the red LED having the inverted pyramid type light emitting element is used, the luminous efficiency is good, and the hollow light guide region is condensed by using the collimator lens. Therefore, the reflection loss in the hollow light guide region 7 can be minimized, and the luminance can be improved as compared with the conventional hollow type backlight unit. Furthermore, the light absorption part 16 is formed in each wall surface which forms the storage part 15 of the collimator lens 9, Moreover, the cross-sectional shape of the collimator lens 9 is made into the light emission distribution from the collimator lens 9 of blue LED and green LED, and a wide angle area | region. Since the light quantity is formed to be larger than that of the original reference design, the red stray light is surely prevented from being strengthened.

  In the present embodiment, the cross-sectional shape of the collimator lens 9 is changed and the light absorbing portion 16 is formed so as to surely eliminate the color unevenness due to the red color. Depending on the specifications, it may be possible to cope with this by merely providing a change in the cross-sectional shape of the collimator lens 9.

  In this embodiment, an example in which an inverted pyramid type light emitting element is used for a red LED has been described. However, when the light emitting element emitting light in other colors (blue, green, etc.) is an inverted pyramid type, Needless to say, the present invention can be applied by replacing the portions corresponding to the red LED and the corresponding color LED of the embodiment.

Disassembled perspective view of backlight unit Cross section of the backlight unit Structure diagram of light emitting element of red LED Explanatory drawing of light emission of light emitting element of red LED Illustration of light emitted from LED light source Explanatory drawing which compares the difference in light emission surface chromaticity distribution by having provided the light absorption part Partially broken perspective view seen from the exit side of the collimator lens Sectional view showing the condensing characteristics of the collimator lens Explanatory diagram showing the luminance distribution characteristics of the backlight unit Illustration of collimator lens Explanatory drawing of the collimator lens as an example different from FIG. Explanatory drawing of the collimator lens as an example different from FIG. 10, FIG. Explanatory drawing of the collimator lens as an example different from FIGS. Explanatory drawing of the collimator lens as an example different from FIGS. Explanatory drawing of the collimator lens as an example different from FIGS. Illustration of light distribution of collimator lens Explanatory drawing comparing the difference in chromaticity distribution of light emitting surface due to improved collimator lens

Explanation of symbols

1 Backlight unit (surface lighting device)
2 Unit case 3 Light reflecting surface member 4 Light emitting surface member 5 LED
5B Blue LED (second LED)
5G green LED (second LED)
5R red LED (first LED)
5RA Light Emitting Element 6 Wiring Board 7 Hollow Light Guide Area 8 LED Light Source 9 Collimator Lens (Condensing Component)
15 Storage 16 Light absorber

Claims (5)

A hollow unit case,
A light reflecting surface member disposed on the bottom side of the unit case;
A light emitting surface member disposed on the front side of the unit case facing the light reflecting surface member;
A plurality of LEDs including at least a first LED having a first light distribution and a second LED having a second light distribution different from the first light distribution are arranged and mounted on a wiring board. An LED light source disposed adjacent to the hollow light guide region so as to emit light to the hollow light guide region which is a space formed between the light reflecting surface member and the light emitting surface member;
A cross-sectional shape in the thickness direction of the unit case including the optical axis of the first LED, disposed in the vicinity of the emitting portion of the LED light source, and a thickness direction of the unit case including the optical axis of the second LED A light-collecting component that makes the light from the LED light source parallel to the light emitting surface of the light emitting surface member,
A surface illumination device comprising:   The light absorption part which absorbs the light from the light emitting element of the said LED going to directions other than the said condensing component was provided in at least one of the said wiring board and the storage part of the said condensing component, The said 1st aspect is characterized by the above-mentioned. Surface lighting device.   3. The surface illumination device according to claim 1, wherein the first LED is an inverted pyramid type LED. The second LED is at least an LED other than the emission color of the first LED,
The unit case in which a light distribution in a wide-angle region set in advance in a cross-sectional shape in the thickness direction of the unit case including the optical axis of the second LED of the light collecting component includes the optical axis of the first LED The surface illumination device according to claim 3, wherein the cross-sectional shape of the light-collecting component is formed so as to be larger than a preset light distribution in a wide-angle region in the cross-sectional shape in the thickness direction.   A shape in which the cross-sectional shape of the condensing component is different depending on at least one of providing a difference in the distance from the LED to the incident surface of the light and providing a difference in the distance to the exit surface from which the light incident from the LED exits The surface illumination device according to any one of claims 1 to 4, wherein:

Images