JP2008300194A - Hollow type surface lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hollow type surface lighting device capable of high luminance and high uniformity of illumination light without making the device large in size. <P>SOLUTION: The hollow type surface lighting device has a light reflection surface member 2 arranged on the bottom side of a unit case 1, a light-emitting surface member 3 arranged on the front side of the unit case, a hollow light guide region 10 in the space interposed between the light reflection surface member and the light-emitting surface member, LED light sources 5 mounting many LEDs on a wiring board arranged adjacent to the hollow light guide region, and an LED collimator 9 which condenses the light from the LED light source so that its optical axis may be in parallel to the face of the light-emitting surface member of the unit case arranged at the emitting part of the LED light source. The light reflection surface member 2 is made a mountain shape with the central part rising and has a narrow dispersion part 21 with lower dispersion characteristics than the other portion installed respectively on the lower part on both sides of the ridge line coming out of the LED collimator. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hollow 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.

  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 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. The backlight unit having an LED as a light source has been mainly used for small devices such as mobile phones and mobile terminals so far, but recently, a large-sized liquid crystal display such as a 20-inch-type liquid crystal monitor or a liquid crystal television is used. 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. For this reason, a plurality of point light sources (LEDs) are arranged on the side portion of the light guide plate, which is generally employed in a small backlight unit, and light is emitted. The light guide plate side light system that emits light from the surface light emitting portion on the front side of the light plate is not adopted as a backlight of a large liquid crystal display device.

  As a backlight unit for a large-sized liquid crystal display device, as described in Japanese Patent Application Laid-Open No. 2005-316337 (Patent Document 1), a direct-type backlight unit in which an LED light source is disposed directly under a surface light emitting unit is used. It has become common.

  In such a direct type backlight unit, since the light source is an LED, if the distance between a large number of arranged LEDs and the surface light emitting part is too close, it is recognized as uneven brightness and uneven color, and the liquid crystal display illuminated by it Deteriorating quality. This phenomenon appears more prominently 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 part (diffusion plate) in order to reduce luminance unevenness and color unevenness leads to an increase in the thickness of the entire device, which is preferable against the recent trend of thinning. Absent.

  As a hollow sidelight type backlight unit that is thin and can be increased in size, a backlight unit described in JP-A-8-171806 (Patent Document 2) is known. The one described in Patent Document 2 is an irregular light source in which a long light source having a light emitting part on one side and a bottom part on the front side in the light emission direction of this light source are inclined upwardly at a part away from the light source. A layer, an air layer that guides light irregularly reflected by the irregular reflection layer toward the upper surface, a light diffusion layer provided on the upper surface of the housing, and a long convex lens body that is disposed close to the light emitting portion of the light source. . In this conventional backlight unit, the light from the long light source tends to be collected linearly at one place of the irregular reflection layer due to the light condensing characteristic of the long convex lens body, and uniform luminance is obtained over the entire light emitting surface. There are problems that are difficult to obtain, especially with large-area backlight units.

On the other hand, what was described in Unexamined-Japanese-Patent No. 2006-106212 (patent document 3) is also known as a backlight unit of a hollow sidelight system. However, the device described in Patent Document 3 has a problem that the number of LEDs of the light source is small and it is difficult to emit white light necessary for the backlight unit over a large area.
JP 2005-316337 A JP-A-8-171806 JP 2006-106212 A

  The present invention has been made in view of the above-described conventional technical problems, and is a side-light type hollow surface illumination device that increases the brightness of illumination light without increasing the size of the device, and An object of the present invention is to provide a hollow surface illumination device capable of achieving high uniformity.

  In the present application, the “side light system” means that light is emitted from a light source on the back side of the light emitting surface in a direction parallel to the light emitting surface, and the light is refracted, reflected, diffused and guided to the light emitting surface. Refers to the lighting system.

  One feature of the present invention is that a light reflecting surface member is disposed on the bottom surface side of a hollow unit case, a light emitting surface member is disposed on the front side of the unit case facing the light reflecting surface member, The space between the light reflecting surface member and the light emitting surface member is a hollow light guide region, and LED light sources formed by mounting a large number of LEDs on a wiring board are arranged adjacent to both sides of the hollow light guide region, An LED collimator arranged so as to be emitted to the hollow light guide region and condensing the light from the LED light source so that the optical axis thereof is parallel to the surface of the light emitting surface member of the unit case. A hollow surface illuminating device having a configuration in which the LED is arranged in parallel with the LED array on the emitting portion, wherein the light reflecting surface member swells along a line parallel to the LED row at the center of the bottom surface of the unit case. , The ridge line is gradually lowered toward the both sides of the ridge line, and a narrow angle scattering part having a scattering characteristic lower than the other part is provided on the upper surface of the lower part on both sides of the ridge line. This is a hollow surface illumination device.

  Another feature of the present invention is that a light reflecting surface member is disposed on a bottom surface side of a hollow unit case, a light emitting surface member is disposed on a front side of the unit case facing the light reflecting surface member, A space sandwiched between the light reflecting surface member and the light emitting surface member is defined as a hollow light guide region, and an LED light source formed by mounting a large number of LEDs on a wiring board is arranged adjacent to one side of the hollow light guide region. An LED collimator disposed so as to be emitted to the hollow light guide region and condensing the light from the LED light source so that the optical axis thereof is parallel to the surface of the light emitting surface member of the unit case. The light reflecting surface member is low on the LED collimator side and gradually increases as the distance from the LED collimator increases. None flop type, scattering properties than other portions on the lower part the upper surface out of the LED collimator low upper surface of the LED collimator side is hollow planar lighting device provided with low narrow angle scattering portion.

  According to the present invention, the LED collimator is disposed on the emission side of the LED light source to efficiently introduce the light from the LED light source into the hollow light guide region in the unit case as light having a high degree of parallelism. The light can be emitted uniformly from the whole, and illumination light with high brightness and high uniformity can be emitted.

  Further, according to the present invention, the light reflecting surface member is formed in a mountain shape, and the narrow angle scattering portion having a scattering characteristic lower than that of the other portion is emitted from the LED collimator on each of the lower upper surfaces on both sides of the ridge line. Because it is provided, it is possible to reflect the light incident directly under the emitting part of the LED collimator to the farther side of the light reflecting surface member, and as a result, illumination light with high brightness and high uniformity from the entire surface light emitting part. Can be emitted and can be used as a backlight unit of a large-sized liquid crystal display device.

  Further, according to the present invention, the light reflecting surface member has a one-slope shape, and comes out of the LED collimator on the upper surface of the lower part, exits the LED collimator on the upper surface of the lower part, and has a scattering characteristic on the upper surface of the lower part than other parts. Is provided with a low-angle scattering part, so that the light incident directly under the emitting part of the LED collimator can be reflected further to the far side of the light reflecting surface member. In addition, it is possible to realize a one-side incident type side light type hollow surface illumination device that can emit illumination light with high uniformity.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  (First Embodiment) FIGS. 1 and 2 show a backlight unit for a liquid crystal display device as a hollow surface illumination device according to one embodiment of the present invention. This backlight unit is a double-sided incident type, and is a mountain-shaped light reflecting surface that rises in a mountain shape along a line parallel to one side at the center of the bottom of the rectangular unit case 1 and gradually decreases as it goes away from both sides of the ridgeline. A member 2 is arranged. A light emitting surface member 3 is disposed on the front opening surface which is the light emitting surface of the unit case 1. The unit case 1 is covered with the front frame 4 from the light emitting surface member 3 side, and is integrated with the unit kit 1 to assemble the backlight unit of the present embodiment. A space portion sandwiched between the light reflecting surface member 2 and the light emitting surface member 3 in the unit case 1 is a hollow light guide region 10.

  The light reflecting surface member 2 is made by laminating a metal or resin material with a highly reflective and diffuse reflecting material such as a white PET film or white ink, and the luminance distribution on the light emitting surface member 3 becomes uniform. In this way, the distance from the light emitting surface member 3 is changed. In addition to the above, the light diffusive reflective material may be a highly reflective aluminum having a specular reflectivity coated with a light transmissive diffusing material. A narrow-angle scattering member 21 having narrow-angle scattering characteristics is attached to each of the lower portions on both sides of the mountain-shaped light reflecting surface member 2 or provided as a part of the light reflecting surface member 2.

  The narrow-angle scattering member 21 has an optical characteristic that has a lower scattering characteristic than other parts and a high reflection characteristic, so that the scattering distribution characteristic of the reflection component becomes narrower than that of the other parts. Of the light emitted from the collimator 9 to be described later into the space that becomes the hollow light guide region 10, the light in the vicinity of the collimator 9 is close to the distance from the light source. The ratio of the amount of reflected light that is reflected closer to the distance is greater than the amount of reflected light that reaches the target. If there is a lot of light that is reflected nearby, that part will become too bright. Therefore, the reflectance of only this part is lowered or the ratio of the light reflected in the vicinity of the collimator 9 is lowered by narrowing the light so that the light hitting the surface is not diffused or scattered. The distribution of reflected light can be made uniform. In general, light that hits the reflecting surface at some angle (incident angle) will be emitted in the opposite direction at the same angle as the incident angle if the reflecting surface is a perfect mirror. If there is a surface structure or a fine reflecting member that diffusely reflects light on the surface or inside the transparent layer, the light is scattered or diffused on the reflecting surface regardless of the incident angle. A narrow-angle scattering member eliminates this phenomenon and increases the ratio of light radiated to the opposite side at an angle substantially equal to the incident angle as much as possible.

  In order to obtain a narrow angle distribution characteristic, when the light reflecting surface member 2 is formed of a white PET sheet or white ink, an aluminum foil having a specular reflection characteristic on its upper surface as shown in FIGS. This is realized by laminating a silver vapor deposition sheet or a highly reflective multilayer film 21. In addition, when the reflecting surface member 2 is made of a highly reflective aluminum having a specular reflectivity coated with a light transmissive diffusing material, the coating layer of the light transmissive diffusing material is deleted only in the corresponding part. Realize with.

  The light emitting surface member 3 is formed by overlapping optical sheets such as diffusion sheets 3B and 3C and a lens sheet 3D on at least the light transmission diffusion plate 3A. By uniformly diffusing and emitting the light reflected by the reflecting member 2, the luminance unevenness on the light emitting surface is eliminated and the uniformity is increased.

  The unit case 1 is formed of a metal having a high thermal conductivity such as an aluminum alloy. The LED light sources 5 are disposed on both side surfaces parallel to the ridge line of the light reflecting surface member 2 in the unit case 1.

  The LED light source 5 has a large number of LEDs 7 arranged in a row or a plurality of rows on a long and narrow wiring board 6 having a width that can be accommodated on the corresponding side surface of the unit case 1. 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 1 by screwing, bonding or other means. Yes. 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 1. For the LED 7 mounted on the LED light source 5, three-color LEDs of red (R), green (G), and blue (B) arranged at a quantity ratio for combining with a desired white chromaticity are used. Alternatively, a white LED package in which a blue LED and a yellow phosphor are combined is used.

  An elongate LED collimator 9 in which concave grooves 8 having a shape covering the rows of LEDs 7 are formed on the emission side of the LED light source 5, that is, the side facing the hollow light guide region 10. The LED collimator 9 is a member for condensing light from the LED 7 of the LED light source 5 in the thickness direction of the hollow light guide region 10 and entering the hollow light guide region 10, for example, acrylic or polycarbonate It is formed with transparent resin like this, or glass.

  As shown in detail in FIGS. 3 and 4, a concave groove 8 is formed on the incident portion side facing the row of LEDs 7 of the LED collimator 9. The groove wall surface of the concave groove 8 guides the incident light InA having a convex shape for guiding the emitted light having an angle close to the optical axis of the LED 7 into the body and the emitted light having an angle away from the optical axis of the LED 7 into the body. It is a plane-shaped incident surface InB1, InB2. In the figure of the LED collimator 9, the side surfaces located on the lower side and the upper side are total reflection surfaces TIR1 and TIR2 that totally reflect the light in the body. The exit part of the LED collimator 9 corresponds to the convex exit surface ExA corresponding to the incident light from the entrance surface InA and the light totally incident on the entrance surfaces InB1 and InB2 and then totally reflected by the total reflection surfaces TIR1 and TIR2. The exit surfaces ExB1 and ExB2 are concave curved surfaces.

  Lights RYA, RYB1, and RYB2 that enter the LED collimator 9 from the row of LEDs 7 and are emitted from the LED collimator 9 to the hollow light guide region 10 are directed toward the light emitting surface member 3 on the reflecting surface of the reflecting surface member 2 having an optimized shape. The light is reflected and emitted from the light emitting surface of the light emitting surface member 3 with high luminance and no luminance unevenness. The presence of the LED collimator 9 condenses light emitted from the LED 7 at a wide angle at a high efficiency and a narrow angle with a light utilization efficiency of 80% or more, and suppresses reflection loss in the hollow light guide region 10 to a minimum.

  Further, as shown in FIG. 5, the narrow angle scattering member 21 provided at a position near the LED collimator 9 in the lower part of the reflecting surface member 2 enters the hollow light guide region 10 from the LED light source 5 through the LED collimator 9. Of the light, the light incident on this portion is effectively reflected to the far side, so that the light can be widely dispersed in the hollow light guide region 10 and the luminance can be made uniform throughout the light emitting surface member 3. .

  FIG. 6A shows a direction perpendicular to the light source line by the pair of LED light sources 5 provided on the two opposite side surfaces of the light emitting surface in the backlight unit 30 of the present embodiment (perpendicular to the LED arrangement direction or the LED direction). A luminance distribution measurement line 31 is defined as a direction parallel to the optical axis direction, and FIG. 6C shows the luminance distribution A between the light source lines by the pair of LED light sources 5 on the luminance distribution measurement line 31. FIG. 6B shows the luminance distribution characteristic B in the surface light emitting member 3 when the narrow angle scattering member 21 is not disposed. In this case, the LED light source 5 is installed so as to face the positions of the upper and lower long sides in the backlight unit 30 of FIG. As is apparent from the luminance distribution characteristics A and B, the luminance of the peripheral portion of the light emitting surface member 3 that tends to increase the luminance without the narrow-angle scattering member 21 can be suppressed. The degree of uniformity can be improved.

  (Second Embodiment) A one-side incident type backlight unit according to a second embodiment of the present invention will be described with reference to FIG. In the first embodiment shown in FIGS. 1 and 2, the light reflecting surface member 2 has a mountain shape with a ridge line at the center, and the LED light source 5 is adjacent to the lower portions on both sides of the light reflecting surface member 2 in the unit case 1. Although the backlight unit installed on each of the side surfaces is shown, the backlight unit of the present embodiment uses a one-slope reflective surface member 2A, and one LED light source 5 is connected to the reflective surface member 2A in the unit case 11. It is the structure installed in the side part adjacent to a low part. In FIG. 7, the same elements as those in FIGS. 1 and 2 indicate the same elements.

  Even in the present embodiment, the narrow-angle scattering member 21 is installed in the lower part of the one-slope shaped light reflecting member 21 near the LED collimator 9. Thereby, the light L1 incident on this portion of the light incident on the hollow light guide region 10 via the LED collimator 9 from the LED light source 5 is effectively reflected farther in the hollow light guide region 10, As a result, the luminance uniformity of the light emitting surface member 3 can be improved.

  (Third Embodiment) A backlight unit according to a third embodiment of the present invention will be described with reference to FIGS. The backlight unit of the present embodiment is characterized in that the light emitting surface member 3 ′ is composed of a transparent plate 3 </ b> A ′ and optical sheet groups 3 </ b> B to 3 </ b> D. In addition, the other structure in this Embodiment is common in 1st Embodiment shown in FIG. 1, FIG. 2, Therefore Therefore, below, it demonstrates using a common code | symbol for a common element.

  This backlight unit is provided with a mountain-shaped light reflecting surface member 2 that rises along a line parallel to one side at the center of the bottom surface of the rectangular unit case 1 and gradually decreases toward the both sides of the ridgeline. . A light emitting surface member 3 is disposed on the front opening surface which is the light emitting surface of the unit case 1. The unit case 1 is covered with the front frame 4 from the light emitting surface member 3 side, and is integrated with the unit kit 1 to assemble the backlight unit of the present embodiment. A space portion between the light reflecting surface member 2 and the light emitting surface member 3 ′ in the unit case 1 is a hollow light guide region 10. Also in this embodiment, the light reflection surface member 2 is provided with the narrow angle diffusing member 21 as in the first embodiment, but this narrow angle diffusing member 21 is not provided when not necessary. Also good.

  The light emitting surface member 3 ′, which is a feature of the present embodiment, is an optical element such as diffusion sheets 3B and 3C for uniformly diffusing outgoing light with respect to the transparent plate 3A ′, and a lens sheet 3D for condensing light. It is configured by stacking sheets, and by uniformly diffusing and emitting the light reflected through the hollow light guide region 10 and hitting the mountain-shaped light reflecting member 2, uneven brightness on the light emitting surface is eliminated, It works to increase the degree of uniformity.

  The transparent plate 3A 'in the light emitting surface member 3' is a transparent plate that is formed of a transparent resin such as acrylic or polycarbonate, glass, or the like, has a light transmittance of 90% or more, and has a smooth surface.

  According to the present embodiment, by using such a transparent plate 3A ′, even when the light emitted from the LED light source 5 reaches the surface light emitting portion in the vicinity of the light source, the surface reflection of the light transmission diffusion plate 3A is achieved. Due to the effect, it can be led away from the LED light source 5 side, and the amount of light in the region away from the LED light source 5 is insufficient even when the size of the surface light emitting unit is increased or the entire apparatus is thinned. As a result, the luminance uniformity of the surface light emitting portion can be increased.

  The configuration of the light emitting surface member 3 ′, which is a feature of the present embodiment, can also be adopted as the light emitting surface member 3 in the one-side incident type backlight unit as in the second embodiment.

The disassembled perspective view of the backlight unit of the 1st Embodiment of this invention. Sectional drawing of the backlight unit of the said embodiment. The partially broken perspective view of the LED collimator employ | adopted in the said embodiment. Sectional drawing which shows the condensing characteristic of the LED collimator in the said embodiment. Sectional drawing which shows the light reflection scattering behavior in the hollow light guide area | region in the backlight unit of the said embodiment. The graph which shows the luminance distribution characteristic of the backlight unit of the said embodiment and the comparative example which does not use a narrow angle scattering member. Sectional drawing of the backlight unit of the 2nd Embodiment of this invention. The disassembled perspective view of the backlight unit of the 3rd Embodiment of this invention. Sectional drawing of the backlight unit of the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Unit case 2 Reflecting surface member 3,3 'Light emitting surface member 3A Light transmission diffusing plate 3A' Transparent plate 4 Front frame 5 LED light source 6 Wiring board 7 LED
9 LED collimator 10 Hollow light guide area

Claims (3)

A light reflecting surface member is disposed on the bottom side of the hollow unit case,
A light emitting surface member is disposed on the front side of the unit case facing the light reflecting surface member,
A space sandwiched between the light reflecting surface member and the light emitting surface member in the unit case is a hollow light guide region,
An LED light source formed by arranging and mounting a large number of LEDs on a wiring board is arranged adjacent to both sides of the hollow light guide region so as to be emitted to the hollow light guide region,
An LED collimator that condenses the light from the LED light source so that the optical axis thereof is parallel to the surface of the light emitting surface member of the unit case, and is arranged in parallel to the array of the LEDs at the emission portion of each LED light source A hollow surface illumination device of
The light reflecting surface member has a mountain shape that rises along a line parallel to the LED row at the center of the bottom surface of the unit case, and gradually decreases toward the both sides of the ridge line, and lower upper surfaces on both sides of the ridge line, respectively. A hollow surface illumination device characterized in that a narrow-angle scattering part having a scattering characteristic lower than that of the other part is provided on the upper surface of the lower part from the LED collimator. A light reflecting surface member is disposed on the bottom side of the hollow unit case,
A light emitting surface member is disposed on the front side of the unit case facing the light reflecting surface member,
A space sandwiched between the light reflecting surface member and the light emitting surface member in the unit case is a hollow light guide region,
An LED light source formed by arranging and mounting a large number of LEDs on a wiring board is arranged adjacent to one side of the hollow light guide region and emitted to the hollow light guide region,
An LED collimator for condensing the light from the LED light source so that the optical axis thereof is parallel to the surface of the light emitting surface member of the unit case is arranged at the emitting portion of the LED light source in parallel with the array of the LEDs. A hollow surface illumination device,
The light reflecting surface member has a one-slope shape in which the LED collimator side is low and gradually increases as the distance from the LED collimator increases. The light reflecting surface member exits from the LED collimator on the lower upper surface on the LED collimator side and has another surface on the lower upper surface. A hollow surface illumination device provided with a narrow angle scattering portion having a scattering characteristic lower than that of the portion.   The hollow surface illumination device according to claim 1, wherein the light emitting surface member has a smooth surface on the back surface facing the light reflecting surface member.

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