JPH09167860A - Planar light source - Google Patents
Planar light sourceInfo
- Publication number
- JPH09167860A JPH09167860A JP32553795A JP32553795A JPH09167860A JP H09167860 A JPH09167860 A JP H09167860A JP 32553795 A JP32553795 A JP 32553795A JP 32553795 A JP32553795 A JP 32553795A JP H09167860 A JPH09167860 A JP H09167860A
- Authority
- JP
- Japan
- Prior art keywords
- guide plate
- light
- light guide
- light source
- light emitting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Liquid Crystal (AREA)
- Led Device Packages (AREA)
- Led Devices (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は液晶ディスプレイのバッ
クライト、照光式操作スイッチ等に使用される面状の光
源に係り、特に低電力で高輝度に発光し長寿命な発光光
源である面状光源に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar light source used for a backlight of a liquid crystal display, an illuminated operation switch, etc., and more particularly to a planar light source which emits light with high brightness at low power and has a long life. Regarding the light source.
【０００２】[0002]
【従来の技術】今日、ノート型パソコン、携帯電話、ワ
ープロ、液晶モニター等が急速に普及している。これに
伴って電子機器の動作状態を表示する表示画面に対する
社会の要求がますます高まりを見せている。表示画面は
光のない環境化でも使用できるようにバックライト用の
面状光源により発光させてある。この様なバックライト
等として使用する面状光源には、Ｅｌｅｃｔｒｏ Ｌｕ
ｍｉｎｅｓｃｅｎｃｅ（以下、ＥＬと呼ぶ。）、サイド
ライト方式を利用した冷陰極管等が挙げられる。しか
し、面状光源としてＥＬを使用した場合、それ自体が面
状発光光源であり薄型化には向いているものの発光輝度
が暗く、寿命が短いという問題点を有する。特に、発光
面側に複数の膜が介在するカラー液晶等のバックライト
として使用する場合においては更なる高輝度化、均一性
が求められる上に発光色の選択幅が広いことが要求され
るため問題となる。2. Description of the Related Art Today, notebook personal computers, mobile phones, word processors, liquid crystal monitors and the like are rapidly spreading. Along with this, society's demand for a display screen that displays the operating state of electronic devices is increasing. The display screen is illuminated by a planar light source for backlight so that it can be used even in a light-free environment. The surface light source used as such a backlight is an Electro Lu
There are a minence (hereinafter referred to as EL), a cold cathode tube using a side light system, and the like. However, when an EL is used as a planar light source, it is a planar light emitting light source by itself, and although it is suitable for thinning, it has a problem that the emission brightness is dark and the life is short. Especially when used as a backlight for color liquid crystal or the like in which multiple films are interposed on the light emitting surface side, further high brightness and uniformity are required, and a wide selection range of emission colors is required. It becomes a problem.
【０００３】また、サイドライト方式を利用した冷陰極
管は拡散板と蛍光管を用いて面状光源とすることができ
るものである。この面状光源は、発光輝度自体ＥＬに比
べ明るくすることが可能であるが蛍光管の外形が小さい
もので４〜８ｍｍと大きく装置構造が大型化する。ま
た、寿命が短く、昇圧回路や安定化回路等を必要とし駆
動回路が複雑化、大型化するという問題点を有する。し
かしながら、高輝度、低電力、長寿命及び小型化が可能
な面状光源が開発されていないために液晶モニター等に
使用する面状光源として、大型では冷陰極管、小型〜中
型にはＥＬと使い分けられているのが現状である。Further, a cold cathode tube using the sidelight system can be used as a planar light source by using a diffusion plate and a fluorescent tube. This planar light source can be brighter than the emission brightness itself EL, but the external shape of the fluorescent tube is small, which is as large as 4 to 8 mm, and the device structure becomes large. In addition, there is a problem that the life is short, a booster circuit, a stabilizing circuit, etc. are required, and the driving circuit becomes complicated and large. However, since a planar light source capable of high brightness, low power consumption, long life and miniaturization has not been developed, as a planar light source used for a liquid crystal monitor or the like, a large-sized cold cathode tube and a small to medium-sized EL are The current situation is that they are used properly.
【０００４】従って、高輝度、低電力、小型化及び長寿
命化が可能な新規な面状光源の開発が要望されている。Therefore, there is a demand for the development of a novel planar light source capable of high brightness, low power consumption, miniaturization and long life.
【０００５】一方、寿命が長く小型化が可能な発光光源
として固体発光素子である発光素子（以下、ＬＥＤと呼
ぶ。）を利用した面発光素子として実開昭６３−４３１
７７号が挙げられる。このようなＬＥＤを用いた発光光
源の一例を図３及び図４に示す。図３の様に青と緑と赤
の波長を有するＬＥＤをそれぞれ複数個平面上に配置
し、出力光を拡散板で拡散させて面発光体としている。
これにより赤、青、緑の３波長を発光させフィルターを
通して液晶カラーテレビに利用できる。On the other hand, as a surface emitting device utilizing a light emitting device (hereinafter referred to as an LED) which is a solid state light emitting device as a light emitting light source having a long life and capable of being miniaturized, it is practically used as a surface emitting device.
No. 77 is mentioned. An example of a light emitting light source using such an LED is shown in FIGS. 3 and 4. As shown in FIG. 3, a plurality of LEDs having wavelengths of blue, green, and red are arranged on a plane, and output light is diffused by a diffusion plate to form a surface light emitter.
As a result, three wavelengths of red, blue and green are emitted and can be used for liquid crystal color television through filters.
【０００６】しかしながら、上記構成は自然光に近づけ
るためには青、緑、赤の各ＬＥＤの最小単位を近づけざ
るを得ない。一方、各ＬＥＤの最小単位を小さくすると
自然光に近づけることはできるが発光部が集中してしま
うため色むらを生じ均一に面発光できないという問題点
があった。However, in the above-mentioned structure, the minimum unit of each of the blue, green, and red LEDs has to be close in order to approach the natural light. On the other hand, if the minimum unit of each LED is reduced, it is possible to make it closer to natural light, but since the light emitting portions are concentrated, there is a problem that color unevenness occurs and uniform surface emission is not possible.
【０００７】[0007]
【発明が解決しようとする課題】本発明は上述の問題点
を解決し、ＬＣＤや各種スイッチのバックライト等に利
用できる面状光源を実現すると共に、高輝度、高信頼性
及び均一性の優れた白色発光可能な面状光源を提供する
ことにある。さらには白色以外の任意色の発光が可能な
面状光源を提供することにある。SUMMARY OF THE INVENTION The present invention solves the above problems and realizes a planar light source that can be used as a backlight for LCDs and various switches, and is excellent in high brightness, high reliability and uniformity. Another object is to provide a planar light source capable of emitting white light. Another object is to provide a planar light source capable of emitting light of any color other than white.
【０００８】[0008]
【課題を解決するための手段】本願発明は、導光板の端
面の少なくとも一箇所に光学的に接続された多色発光素
子と、前記導光板の第１の主面上に設けられた反射材
と、前記導光板の第２の主面上の少なくとも一部に設け
られた拡散膜と、を有し前記拡散膜を介して発光させる
面状光源であって、前記第１の主面上に設けられた反射
材と、前記多色発光素子と光学的に接続された導光板端
面を介して設けられた前記第２の主面上に反射層を有す
る面状光源である。また、反射層の反射率が９５％以上
である面状光源である。さらに、前記多色発光素子が同
一反射基板上に少なくとも４５０〜４９０ｎｍの発光波
長を有する半導体と４９５ｎｍ〜５６０ｎｍの発光波長
を有する半導体及び６１０ｎｍ〜７００ｎｍの発光波長
を有する半導体とを設けられた面状光源である。さらに
また、前記反射層の導光板と接する表面に微細な凹凸が
施されている面状光源である。According to the present invention, there is provided a multicolor light emitting element optically connected to at least one position of an end surface of a light guide plate, and a reflector provided on the first main surface of the light guide plate. And a diffusion film provided on at least a part of the second main surface of the light guide plate to emit light through the diffusion film, the flat light source being provided on the first main surface. It is a planar light source having a reflection layer provided on the second main surface provided via an end surface of a light guide plate optically connected to the provided reflective material and the multicolor light emitting element. In addition, the surface light source has a reflectance of 95% or more. Further, the multi-color light emitting device is a planar surface provided with a semiconductor having an emission wavelength of at least 450 to 490 nm, a semiconductor having an emission wavelength of 495 nm to 560 nm, and a semiconductor having an emission wavelength of 610 nm to 700 nm on the same reflective substrate. It is a light source. Furthermore, it is a planar light source in which the surface of the reflective layer in contact with the light guide plate is provided with fine irregularities.
【０００９】[0009]
【効果】請求項１の構成とすることによって、多色発光
素子を用いた面状光源においても高輝度で均一性及び混
色性の優れた面状光源とすることができる。請求項２の
構成とすることによって、さらに混色性が向上する。請
求項３の構成とすることによって、カラー表示可能なバ
ックライトとすることができる。さらに、カラー液晶等
のバックライトとして利用することができる。請求項４
の構成とすることによってさらに面均一性及び導光板と
の密着性が向上する。According to the structure of claim 1, even in a planar light source using a multicolor light emitting element, a planar light source with high brightness and excellent uniformity and color mixing can be obtained. With the configuration of claim 2, the color mixing property is further improved. With the structure of claim 3, it is possible to provide a backlight capable of color display. Further, it can be used as a backlight for a color liquid crystal or the like. Claim 4
With this structure, the surface uniformity and the adhesion with the light guide plate are further improved.
【００１０】[0010]
【実施態様例】本願発明者らは種種の実験の結果、多色
発光素子を利用した面状光源において導光板上に配され
る反射部材と多色発光素子の特定の配置によって混色
性、均一性が大きく変化することを見いだし本願発明を
成すに至った。白色発光可能な面状光源として、平面的
に配置したＲ（赤）Ｇ（緑）Ｂ（青）のＬＥＤの代わり
に導光板の端面にＲＧＢのＬＥＤを配置することで発光
面全体が白色に発光した。[Examples] As a result of various experiments, the inventors of the present invention have shown that in a planar light source using a multicolor light emitting element, a color mixing property and a uniform color mixing property can be obtained depending on a specific arrangement of the reflecting member arranged on the light guide plate and the multicolor light emitting element. The inventors have found that the characteristics significantly change and have completed the present invention. As a planar light source capable of emitting white light, instead of the planarly arranged R (red) G (green) B (blue) LEDs, RGB LEDs are arranged on the end surface of the light guide plate to make the entire light emitting surface white. It fired.
【００１１】しかしながら、導光板端部にＲＧＢのＬＥ
Ｄを設け発光させた場合、面状光源全体としては混色性
良く白色に発光できるにもかかわらず多色発光素子が設
けられた導光板端部においては部分的にＲＧＢ個々の発
光色がバラバラに発光してリング状にみえる。However, RGB LEs are attached to the end of the light guide plate.
When D is provided and light is emitted, the surface light source as a whole can emit white light with good color mixture, but at the end of the light guide plate provided with the multicolor light emitting elements, the individual RGB emission colors are partially dispersed. It emits light and looks like a ring.
【００１２】即ち、導光板端面では部分的に白色に見え
ず混色性が崩れる場合があった。本願発明者らは、この
部分的な混色性低下を導光板端面上に設けられた反射部
材によって解消できることを見いだした。この理由は定
かではないが、平面的にＬＥＤを直接見るものと異なり
導光板を介して見るものはＲＧＢのＬＥＤの最小単位を
できるだけ近づけて配置しても導光板端面では各発光素
子に用いられる半導体のバンドギャップの違いに伴う光
の吸収、各発光素子の視野角の違い、ＬＥＤの配置、さ
らにはＬＥＤから発光された光が導光板の光放出面に接
触する角度の違い等により導光板端面での混色性が崩れ
ると考えられる。導光板上に設けられた反射部材は上述
の拡散したＲＧＢ個々の発光を反射させて混合させるこ
とにより導光板端部の混色性を向上させることができる
と考えられる。また、ＬＥＤを近づけたことにともなう
蛍現象の低下、さらには面状光源全体としての輝度向上
が図られる。That is, in some cases, the end surface of the light guide plate did not appear white and the color mixing property was broken. The inventors of the present application have found that this partial decrease in color mixing can be eliminated by a reflecting member provided on the end surface of the light guide plate. The reason for this is not clear, but what is viewed through the light guide plate is different from that where the LED is viewed directly in a plane, and even if the minimum unit of RGB LEDs is arranged as close as possible, it is used for each light emitting element at the end surface of the light guide plate. Light guide plate due to absorption of light due to difference in semiconductor band gap, difference in viewing angle of each light emitting element, arrangement of LEDs, and difference in angle at which light emitted from the LED contacts the light emitting surface of the light guide plate. It is considered that the color mixing property at the end face is lost. It is considered that the reflection member provided on the light guide plate can improve the color mixing property of the end portion of the light guide plate by reflecting and mixing the above-mentioned diffused RGB individual light emission. In addition, the firefly phenomenon due to the approach of the LEDs can be reduced, and the brightness of the planar light source as a whole can be improved.
【００１３】以下図面を用いて本願発明を詳述する。図
１は本願発明の面状光源の平面図を表し、図２は図１の
ａ−ａ断面図である。図１において反射機能を有する基
板上にＲＧＢがそれぞれ発光可能な半導体発光素子が配
置され導光板と光学的に接続できるように配置されてい
る。導光板の裏面には発光素子からの光を導光板の一方
の面である所望の方向に反射させるために裏面反射材が
配置され、導光板の表面側には裏面から反射された光を
均一にさせるための拡散膜が設けられている。The present invention will be described in detail below with reference to the drawings. 1 is a plan view of a planar light source of the present invention, and FIG. 2 is a sectional view taken along the line aa of FIG. In FIG. 1, semiconductor light emitting elements capable of emitting RGB light are respectively arranged on a substrate having a reflection function, and arranged so as to be optically connected to a light guide plate. A back surface reflector is arranged on the back surface of the light guide plate to reflect the light from the light emitting element in a desired direction, which is one surface of the light guide plate, and the light reflected from the back surface is uniform on the front surface side of the light guide plate. A diffusion film is provided for the purpose.
【００１４】（導光板）本願発明に用いられる導光板と
しては、多色発光素子からの光を効率よく導き面状にさ
せるものであり透過率、耐熱性に優れ均一に形成できる
ことが求められる。また、導光板の形状は所望に応じて
長方形や多角形等種種の形状とすることができる。具体
的な構成材料としては、アクリル樹脂、ポリカーボネイ
ト樹脂、硝子等が挙げられる。導光板の厚みは、板厚が
厚いほど光の利用効率が高くなるが多色発光素子の配置
や種類等から１０ｍｍ以下が好ましい。導光板の端面に
多色発光素子が埋設されることにより、導光板と多色発
光素子とが光学的に接続されている。また、導光板が四
角形であれば四方の端面全てに発光素子を接続してもよ
いことはいうまでもなく、ＬＥＤの個数も限定するもの
ではない。(Light Guide Plate) The light guide plate used in the present invention is one that efficiently guides the light from the multicolor light emitting element into a planar shape and is required to have excellent transmittance and heat resistance and to be uniformly formed. Further, the shape of the light guide plate may be various shapes such as a rectangle and a polygon as desired. Specific examples of the constituent material include acrylic resin, polycarbonate resin, glass and the like. As the thickness of the light guide plate increases, the light utilization efficiency increases, but it is preferable that the thickness of the light guide plate is 10 mm or less in view of the arrangement and type of the multicolor light emitting elements. By embedding the multicolor light emitting element in the end face of the light guide plate, the light guide plate and the multicolor light emitting element are optically connected. Further, it goes without saying that if the light guide plate is a quadrangle, the light emitting elements may be connected to all four end faces, and the number of LEDs is not limited.
【００１５】さらに、反射材や反射層と接する導光板面
に凹凸を形成させることで発光素子からの光を散乱させ
ることができる。また、拡散膜と接する導光板面に凹凸
を形成させることで拡散膜が導光板に張り付いてできる
干渉縞を防ぐことができる。Further, light from the light emitting element can be scattered by forming irregularities on the surface of the light guide plate which is in contact with the reflecting material or the reflecting layer. Further, by forming irregularities on the surface of the light guide plate that is in contact with the diffusion film, it is possible to prevent interference fringes that are formed by the diffusion film sticking to the light guide plate.
【００１６】なお本発明において、多色発光素子と導光
板の端面とが光学的に接続されているとは、導光板の端
部から多色発光素子が発光する光を導入することをい
う。具体的には多色発光素子を導光板に埋設することは
もちろんのこと、多色発光素子を光透過性樹脂などによ
り接着したり、光ファイバー等を用いて導光板の端面に
多色発光素子の発光を導くことである。In the present invention, the fact that the multicolor light emitting element and the end face of the light guide plate are optically connected means that light emitted from the multicolor light emitting element is introduced from the end portion of the light guide plate. Specifically, it is not only necessary to embed the multicolor light emitting element in the light guide plate, but also to bond the multicolor light emitting element with a light-transmissive resin or the like, or use an optical fiber or the like to attach the multicolor light emitting element to the end surface of the light guide plate. It is to guide the light emission.
【００１７】（多色発光素子）半導体発光素子である多
色発光素子は、液相成長法やＭＯＣＶＤ法等により基板
上にＧａＡｌＮ、ＺｎＳ、ＺｎＳｅ、ＳｉＣ、ＧａＰ、
ＧａＡｌＡｓ、ＡｌＩｎＧａＰ、ＩｎＧａＮ、ＧａＮ、
ＡｌＩｎＧａＮ等の半導体を発光層として形成させた物
が用いられる。半導体の構造としては、ＭＩＳ接合やＰ
Ｎ接合を有したホモ構造、ヘテロ構造あるいはダブルへ
テロ構成のものが挙げられる。半導体層の材料やその混
晶度によって発光波長を紫外光から赤外光まで種種選択
することができる。(Multicolor Light Emitting Element) A multicolor light emitting element which is a semiconductor light emitting element is formed on a substrate by GaAlN, ZnS, ZnSe, SiC, GaP, by a liquid phase growth method, a MOCVD method or the like.
GaAlAs, AlInGaP, InGaN, GaN,
A material in which a semiconductor such as AlInGaN is formed as a light emitting layer is used. Semiconductor structures include MIS junction and P
Examples thereof include a homo structure having an N junction, a hetero structure, and a double hetero structure. The emission wavelength can be selected from ultraviolet light to infrared light depending on the material of the semiconductor layer and its degree of mixed crystal.
【００１８】本発明では一つのＬＥＤの発光波長の発光
出力は２００μＷ以上、更に好ましくは３００μＷ以上
の出力が好ましい。ＬＥＤの発光出力が２００μＷより
も少ないと、たとえ導光板の端面に光学的に接続するＬ
ＥＤの数を増やしても、充分な明るさの均一な面状発光
の光源が得られにくい傾向にあるからである。In the present invention, the emission output of one LED at the emission wavelength is preferably 200 μW or more, more preferably 300 μW or more. If the light output of the LED is less than 200 μW, even if L is optically connected to the end face of the light guide plate.
This is because even if the number of EDs is increased, it tends to be difficult to obtain a light source of uniform surface emission with sufficient brightness.
【００１９】面状光源の輝度を向上させるための具体的
な材料として緑色及び青色を発光する半導体は窒化ガリ
ウム系化合物半導体を用いることが好ましく、また、赤
色ではガリウム、アルミニュウム、砒素系の半導体やア
ルミニュウム、インジュウム、ガリウム、燐系の半導体
を用いることが好ましい。また、波長の異なるＬＥＤチ
ップは、所望によって複数用いることができ、例えば青
色を２個、緑色及び赤色をそれぞれ１個ずつとすること
が出来る。また、発光波長は必ずしも青色、緑色、赤色
に限られる物ではなく、所望に応じて黄色などが発光で
きるように半導体のバンドギャプを調節すれば良い。ま
た、ＬＥＤチップの配置としては、混色性向上のために
発光波長の長いＬＥＤチップほど中央側に配置させ１つ
の多色発光素子として用いてもよい。光学的には、それ
ぞれの発光素子を直線状に配置することが好ましい。具
体的な例としては、青緑色ＬＥＤチップに挟まれた黄色
ＬＥＤチップを用いて白色光を発光させることが出来
る。なお、白色バックライト用の多色発光素子として利
用するためには赤色の発光波長が６１０ｎｍから７００
ｎｍ、緑色が４９５ｎｍから５６５ｎｍ、青色の発光波
長が４３０ｎｍから４９０ｎｍであることが好ましい。As a concrete material for improving the brightness of the planar light source, it is preferable to use a gallium nitride-based compound semiconductor as a semiconductor that emits green and blue, and for red, a gallium, aluminum, or arsenic-based semiconductor, It is preferable to use an aluminum, indium, gallium, or phosphorus-based semiconductor. If desired, a plurality of LED chips having different wavelengths can be used. For example, two blue chips and one green and one red can be used. Further, the emission wavelength is not necessarily limited to blue, green, and red, and the band gap of the semiconductor may be adjusted so that yellow or the like can be emitted as desired. As for the arrangement of the LED chips, in order to improve the color mixing property, the LED chips having longer emission wavelengths may be arranged closer to the center and used as one multicolor light emitting element. Optically, it is preferable to arrange the respective light emitting elements linearly. As a specific example, white light can be emitted using a yellow LED chip sandwiched between blue-green LED chips. In addition, in order to use as a multicolor light emitting element for a white backlight, a red light emission wavelength is from 610 nm to 700 nm.
nm, green is 495 nm to 565 nm, and blue emission wavelength is preferably 430 nm to 490 nm.
【００２０】（支持体）支持体としては、導光板端面と
隙間なく配すことができ多色発光素子の各ＬＥＤチップ
を嵌入しうる溝が形成されるものが好ましい。具体的に
は加熱溶着で形成できる材料であるとして、ポリカーボ
ネート、ポリエチレン、アクリル、ウレタン、塩化ビニ
ル、ナイロン、ポリエチレンテレフタレートが好まし
い。さらに、支持体は導光板の端面支持体に向かう光を
効率よく反射して、導光板に入射させるために白色に着
色していることが好ましい。また、多色発光素子ではＬ
ＥＤからの発熱量が多くなるため熱伝導部材を介して共
通基板上に多色発光素子を配しても良い。熱伝導部材と
しては熱伝導度がよいことが求められる。具体的には、
０．０１ｃａｌ／ｃｍ2／ｃｍ／℃以上が好ましくより
好ましくは ０．５ｃａｌ／ｃｍ2／ｃｍ／℃以上であ
る。これらの条件を満たす材料としては、鉄、銅、アル
ミニュウム、鉄入り銅、錫入り銅、メタライズパターン
付きセラミック等が挙げられる。(Support) As the support, it is preferable that the support be provided with a groove which can be arranged without a gap from the end face of the light guide plate and into which each LED chip of the multicolor light emitting element can be fitted. Specifically, polycarbonate, polyethylene, acrylic, urethane, vinyl chloride, nylon, and polyethylene terephthalate are preferable as the material that can be formed by heat welding. Further, it is preferable that the support is colored white so as to efficiently reflect the light traveling toward the end face support of the light guide plate and make it enter the light guide plate. Also, in a multicolor light emitting element, L
Since the amount of heat generated from the ED increases, the multicolor light emitting element may be arranged on the common substrate via the heat conducting member. The heat conducting member is required to have good heat conductivity. In particular,
0.01cal / cm 2 / cm / ℃ or more preferably preferably 0.5cal / cm 2 / cm / ℃ above. Materials satisfying these conditions include iron, copper, aluminum, iron-containing copper, tin-containing copper, metallized patterned ceramics, and the like.
【００２１】（反射材）本願発明に用いられる反射材
は、導光板下側（即ち、第１の主面）と側面等に配置し
導光板内部を反射しながら進んできた光を無駄なく発光
面方向に反射させる働きをする。従って、発光素子から
の光を導光板内に散乱させるものであればよく形状や大
きさは特定されず、導光板を保持するケース状部材と兼
用することや導光板の面上に加工することもできる。ま
た、面状光源を均一に発光させるためには反射材をスト
ライプ状とし、表面輝度が一定となるように、発光素子
に接近するにつれて、単位面積あたりの反射材の面積を
減じるようなパターンとすることができる。さらに、発
光素子の配置により、発光を面状均一とするように反射
材の形状を適宜変更することができる。(Reflecting Material) The reflecting material used in the present invention is disposed on the lower side of the light guide plate (that is, the first main surface) and the side surface, and emits the light that has proceeded while reflecting inside the light guide plate without waste. It works to reflect in the plane direction. Therefore, as long as it scatters the light from the light emitting element into the light guide plate, its shape and size are not specified, and it can also be used as a case-shaped member that holds the light guide plate or can be processed on the surface of the light guide plate. You can also Further, in order to make the planar light source emit light uniformly, the reflecting material is formed into a stripe shape, and the pattern is such that the area of the reflecting material per unit area is reduced as the light emitting element is approached so that the surface luminance becomes constant. can do. Further, by arranging the light emitting elements, the shape of the reflecting material can be appropriately changed so that the light emission can be made uniform in a planar shape.
【００２２】この様な反射材として白色顔料が含有され
た発砲ポリエステル等をフィルム状に加工したものが挙
げられる。これら反射材はシリコン樹脂やエポキシ樹脂
等によって導光板に装着される。An example of such a reflecting material is a foamed polyester containing a white pigment, which is processed into a film. These reflective materials are attached to the light guide plate by using silicone resin, epoxy resin, or the like.
【００２３】（拡散膜）導光板の上面（即ち、第２の主
面）に配置し、導光板からの光を散乱させて輝度を均一
化する働きをする。従って、光透過率が高く効率よく拡
散させることが必要である。本願発明に用いられる拡散
膜としては、光透過率として、７０％以上の透過率を有
することが好ましい。この様な材質として透明で耐熱性
が高いポリカーボネートフィルムやポリエステルフィル
ムに屈折性微粒子樹脂ビーズや透光性無機微粒子をコー
ティングしたものさらにはエンボス加工したものが挙げ
られる。本願発明の拡散膜は導光板の第２の主面及び反
射膜上をも覆ってもまた、反射膜を除く導光板の第２の
主面のみを覆っても良い。(Diffusion film) It is arranged on the upper surface (that is, the second main surface) of the light guide plate, and functions to scatter the light from the light guide plate to make the brightness uniform. Therefore, it is necessary to have a high light transmittance and diffuse the light efficiently. The diffusion film used in the present invention preferably has a light transmittance of 70% or more. Examples of such a material include a transparent polycarbonate film or polyester film having high heat resistance, coated with refractive fine resin beads or translucent inorganic fine particles, and further embossed. The diffusion film of the present invention may cover the second main surface of the light guide plate and the reflecting film, or may cover only the second main surface of the light guide plate excluding the reflecting film.
【００２４】また、２色を発光する多色発光素子と、２
色が混合しあった発光色と補色関係にある顔料を添加さ
せた拡散膜と、を用いて白色表示可能な多色面状光源と
することもできる。A multicolor light emitting element which emits two colors and two
It is also possible to make a multicolor planar light source capable of displaying white by using a diffusion film to which a pigment having a complementary color relationship with the colors of mixed colors is added.
【００２５】さらに、ＲＧＢの３色を発光する多色発光
素子の場合は、白色顔料を含有させて白色表示可能な多
色面状光源とする。なお、白色顔料を多色発光素子から
の距離に反比例させて含有させ濃淡をつけた拡散膜とし
て用い均一な輝度を有する白色表示可能な多色面状光源
とすることもできる。Furthermore, in the case of a multicolor light emitting element which emits the three colors of RGB, a white pigment is included to provide a multicolor planar light source capable of displaying white. It is also possible to use a white pigment as a multi-color planar light source capable of displaying white with uniform brightness by using a diffusing film that contains a white pigment in inverse proportion to the distance from the multi-color light emitting element and is provided with shading.
【００２６】（反射層）本願発明に用いられる反射層と
は、多色発光素子からの発光や反射材からの反射光を導
光板を介して再び反射材側等に反射させて多色発光素子
から放出された個々の発光色を混合せしめ混色性を高め
るものであり、多色発光素子から放出される発光に対し
て９５％以上の反射率を有するものが好ましく、より好
ましくは９８％以上のものである。また、導光板上に設
けられることからその上に設けられる液晶などとの配置
を考慮して好ましくは３ｍｍ以下、より好ましくは１ｍ
ｍ以下の膜厚が好ましい。(Reflective Layer) The reflective layer used in the present invention is a multicolor light emitting element in which light emitted from the multicolor light emitting element or reflected light from the reflective material is reflected again to the reflective material side through the light guide plate. In order to enhance the color mixing property by mixing the individual luminescent colors emitted from the light emitting element, it is preferable that the reflectance is 95% or more, and more preferably 98% or more with respect to the light emitted from the multicolor light emitting element. It is a thing. Further, since it is provided on the light guide plate, it is preferably 3 mm or less, more preferably 1 m in consideration of the arrangement with the liquid crystal and the like provided thereon.
A film thickness of m or less is preferable.
【００２７】反射層は混色性を向上させる一方、導光板
の発光面側に設けられるものであることから大きくさせ
すぎると面発光光源の面積率が低下する。したがって、
多色発光素子や導光板等によって種種異なるが好ましく
は多色発光素子と光学的に接続された導光板端面から１
５ｍｍ以下が好ましい。While the reflective layer improves the color mixing property, it is provided on the light emitting surface side of the light guide plate. Therefore, if the reflective layer is made too large, the area ratio of the surface emitting light source decreases. Therefore,
It depends on the multicolor light emitting element, the light guide plate, etc., but is preferably 1 from the end surface of the light guide plate optically connected to the multicolor light emitting element.
It is preferably 5 mm or less.
【００２８】上記反射率を満たす反射層の材料としてポ
リエチレンテレフタレート樹脂、ポリカーボネート樹
脂、ポリプロピレン樹脂等の樹脂中に反射材としてチタ
ン酸バリウム、酸化アルミニュウム、酸化チタン、酸化
珪素、燐酸カルシュウム等を含有させて形成させたフィ
ルム状部材が挙げられる。また、Ａｌ、Ａｇ、Ｃｕ等の
金属膜を導光板上にメッキ、スパッタリングにより形成
させても良い。また、反射層の表面は更なる混色性向上
のために凹凸を設けて多色発光素子からの発光を散乱さ
せる構成としても良く、反射性と散乱性向上のために多
層構成とすることも可能である。具体的には散乱性向上
のためのガラス不織布上に金属コートしたものなどが挙
げられる。これら反射層はシリコン樹脂やエポキシ樹脂
等によって導光板に装着される。A material such as polyethylene terephthalate resin, polycarbonate resin, polypropylene resin, etc. as a material of the reflection layer satisfying the above reflectance is made to contain barium titanate, aluminum oxide, titanium oxide, silicon oxide, calcium phosphate etc. as a reflection material. An example of the film-shaped member is formed. Alternatively, a metal film of Al, Ag, Cu or the like may be formed on the light guide plate by plating or sputtering. Further, the surface of the reflective layer may be provided with irregularities for further improving the color mixing property so as to scatter the light emitted from the multicolor light emitting element, or a multilayer structure may be provided for improving the reflectivity and the scattering property. Is. Specifically, a nonwoven fabric coated with a metal on a glass nonwoven fabric for improving the scattering property is exemplified. These reflective layers are attached to the light guide plate with silicone resin or epoxy resin.
【００２９】以下、本願発明の具体的実施例を説明する
が本願発明はこれら実施例のみに限定されるものでない
ことは言うまでもない。Specific examples of the present invention will be described below, but it goes without saying that the present invention is not limited to these examples.
【００３０】[0030]
［実施例１］白色反射部材であるチタン酸バリウムをア
クリル系バインダー中に分散したものを厚さ２ｍｍのア
クリル板の片面にスクリーン印刷し硬化させることによ
って裏面反射材を形成した。[Example 1] A back reflector was formed by screen-printing a white reflective member containing barium titanate dispersed in an acrylic binder on one surface of an acrylic plate having a thickness of 2 mm and curing it.
【００３１】次に、裏面反射材が形成されたアクリル板
を１０×３ｃｍの長方形に切断し、アクリル板の端面
（切断面）を全て研磨した後、多色発光素子が光学的に
接続される端面を除いて研磨面にＡｌの側面反射材を形
成することにより、反射材が形成された導光板を得た。Next, the acrylic plate on which the back surface reflecting material is formed is cut into a rectangle of 10 × 3 cm, all the end faces (cut faces) of the acrylic plate are polished, and then the multicolor light emitting elements are optically connected. By forming a side surface reflective material of Al on the polished surface except the end surface, a light guide plate on which the reflective material was formed was obtained.
【００３２】一方、面状光源に用いられる多色発光素子
の各ＬＥＤチップは、緑色、青色及び赤色の発光層の半
導体としてそれぞれＩｎＧａＮ（発光波長５２５ｎ
ｍ）、ＩｎＧａＮ（発光波長４７０ｎｍ）、ＧａＡｌＡ
ｓ（発光波長６６０ｎｍ）を使用して構成させた。On the other hand, each LED chip of the multicolor light emitting element used for the planar light source is made of InGaN (emission wavelength 525n) as a semiconductor of the green, blue and red light emitting layers.
m), InGaN (emission wavelength 470 nm), GaAlA
s (emission wavelength 660 nm).
【００３３】具体的には、赤色を発光するＬＥＤチップ
用の半導体ウエハーは、温度差液晶成長法で連続的にＰ
型ガリウム・砒素基板上にＰ型ＧａＡｌＡｓを成長し、
その上にＮ型ＧａＡｌＡｓを成長し、発光領域であるＰ
型ＧａＡｌＡｓを形成させる。青色及び緑色を発光する
半導体ウエハーは、厚さ４００μｍのサファイヤ基板上
にＮ型及びＰ型窒化ガリウム化合物半導体をＭＯＣＶＤ
成長法でそれぞれ５μｍ、１μｍ堆積させヘテロ構造の
ＰーＮ接合を形成したものである。Specifically, a semiconductor wafer for an LED chip that emits red light is continuously exposed to P by a temperature difference liquid crystal growth method.
P-type GaAlAs is grown on a type gallium arsenide substrate,
N-type GaAlAs is grown on top of this to form the P
A type GaAlAs is formed. For semiconductor wafers emitting blue and green light, MOCVD of N-type and P-type gallium nitride compound semiconductors is performed on a sapphire substrate having a thickness of 400 μm.
The heterostructure PN junction is formed by depositing 5 μm and 1 μm respectively by a growth method.
【００３４】なお、Ｐ型窒化ガリウム半導体は、Ｐ型ド
ーパントであるＭｇをドープした後アニールして形成さ
せる。The P-type gallium nitride semiconductor is formed by doping P-type dopant Mg and then annealing.
【００３５】こうしてできたウエハーをそれぞれ３５０
μ角にしＲＧＢのＬＥＤチップを１画素の多色発光素子
として共通支持体上にＡｇペーストを用いて固定させた
後、電気的接続を行った。共通の支持体はポリカーボネ
ート樹脂１００ｇ中に酸化珪素６０ｇ含有させたものを
熱硬化により一体形成した。一体形成された支持体に
は、導光板の端面の大きさに合わせて直方体に形成され
多色発光素子がそれぞれ配置できるよう３箇所穴が設け
られてある。Each of the thus-formed wafers is 350
After making a μ-square RGB LED chip as a multi-color light emitting element of one pixel on a common support by using Ag paste, electrical connection was performed. The common support was integrally formed by thermosetting a material in which 60 g of silicon oxide was contained in 100 g of polycarbonate resin. The integrally formed support body is formed in a rectangular parallelepiped in accordance with the size of the end surface of the light guide plate and is provided with three holes so that the multicolor light emitting elements can be arranged respectively.
【００３６】導光板と支持体とを透光性樹脂を用いて光
学的に接続させた後、多色発光素子が設けられた導光板
端面上に発光面を一部覆う形で反射層を配置した。反射
層の大きさは導光板の端面の長さに等しく導光板上に設
けられた反射層の幅は多色発光素子と光学的に接続され
た導光板端面から５ｍｍ幅である。反射層は、ポリカー
ボネート樹脂１００ｇ中にチタン酸バリウム７０ｇ含有
させ熱硬化させることによって反射率９９％が得られて
いる。After the light guide plate and the support are optically connected by using a light-transmissive resin, a reflection layer is arranged on the end surface of the light guide plate provided with the multicolor light emitting element so as to partially cover the light emitting surface. did. The size of the reflection layer is equal to the length of the end surface of the light guide plate, and the width of the reflection layer provided on the light guide plate is 5 mm from the end surface of the light guide plate optically connected to the multicolor light emitting element. The reflection layer has a reflectance of 99% by containing 70 g of barium titanate in 100 g of a polycarbonate resin and thermally curing it.
【００３７】最後に導光板の発光面上にはポリカーボネ
ートのエンボスフィルムである白色拡散層を全面に渡っ
て配置した。こうしてできた面状光源に電源を接続した
ところ主面側から完全に面状均一な白色発光が得られ
た。また、多色発光素子近傍の導光板端面においても混
色が崩れることはなかった。輝度は８４ｃｄ／ｍ2であ
った。Finally, a white diffusion layer, which is an embossed film of polycarbonate, was arranged over the entire light emitting surface of the light guide plate. When a power source was connected to the thus-formed planar light source, a planar uniform white light emission was obtained from the main surface side. Further, the color mixture was not broken even at the end surface of the light guide plate near the multicolor light emitting element. The brightness was 84 cd / m 2 .
【００３８】［比較例１］反射層を用いない以外は実施
例１と全く同様にして面状光源を形成させた。面状光源
からは均一な白色発光が得られているものの多色発光素
子が設けられている導光板端面近傍では赤、青、緑の発
光色がそれぞれリング状に見られた。面状光源としての
輝度は７８ｃｄ／ｍ2であった。Comparative Example 1 A planar light source was formed in exactly the same manner as in Example 1 except that the reflective layer was not used. Although uniform white light emission was obtained from the planar light source, red, blue, and green emission colors were seen in a ring shape near the end surface of the light guide plate provided with the multicolor light emitting element. The brightness as a planar light source was 78 cd / m 2 .
【００３９】［実施例２］反射材及び反射層を同一材料
とし、ポリカーボネート樹脂１００ｇ中に酸化チタン５
０ｇ含有させることによって形成させた反射率９９％の
フィルムをエポキシ樹脂を用いて導光板に張り合わせた
以外は実施例１と同様にして面状光源を形成させた。こ
うしてできた面状光源に電源を接続しバックライト用光
源としたところ、多色発光素子近傍においても混色性が
崩れることなくほぼ面状均一に白色発光が得られた。輝
度は８６ｃｄ／ｍ2であった。Example 2 The same material was used for the reflecting material and the reflecting layer, and titanium oxide 5 was added to 100 g of polycarbonate resin.
A planar light source was formed in the same manner as in Example 1 except that a film having a reflectance of 99% formed by containing 0 g thereof was attached to a light guide plate using an epoxy resin. When a power source was connected to the thus-produced planar light source to provide a light source for a backlight, white light emission was obtained almost uniformly in a planar manner even in the vicinity of the multicolor light emitting element without degrading the color mixing property. The brightness was 86 cd / m 2 .
【００４０】［実施例３］反射層の導光板端面に接触す
る面側に凹凸を設けた以外は実施例２と同様にして形成
させた。こうしてできた面状光源に電源を接続しバック
ライト用光源としたところ、多色発光素子近傍において
も混色性が崩れることなくほぼ面状均一に白色発光が得
られた。輝度は８５ｃｄ／ｍ2であった。なお、反射層
と導光板の密着性が実施例２と比較して向上していると
考えられる。[Example 3] A film was formed in the same manner as in Example 2 except that unevenness was provided on the surface side of the reflecting layer that contacts the end surface of the light guide plate. When a power source was connected to the thus-produced planar light source to provide a light source for a backlight, white light emission was obtained almost uniformly in a planar manner even in the vicinity of the multicolor light emitting element without degrading the color mixing property. The brightness was 85 cd / m 2 . It is considered that the adhesion between the reflective layer and the light guide plate is improved as compared with Example 2.
【００４１】[0041]
【発明の効果】以上説明したように、本発明の面状光源
は、多色発光素子を用いた面状光源においても高輝度で
均一性及び混色性の優れた面状光源とすることができ
る。また、カラー表示可能なバックライトとすることが
できる。さらに面均一性及び導光板との密着性が向上し
信頼性の優れた面状光源とすることができる。蛍現象を
緩和すると共に面均一性を向上させることができる。As described above, the surface light source of the present invention can be used as a surface light source having high brightness and excellent uniformity and color mixing even in a surface light source using a multicolor light emitting element. . In addition, a backlight capable of color display can be used. Further, the surface uniformity and the adhesion to the light guide plate are improved, and the surface light source having excellent reliability can be obtained. It is possible to alleviate the firefly phenomenon and improve the surface uniformity.
【００４２】更にフィルムに微細な凹凸を形成すること
により、光を散乱させる作用を高め、フィルムが導光板
に張り付いて干渉縞ができるのを防ぐことができる。こ
のように、本発明の面状光源は、バックライト用光源と
してだけでなく、蛍光物質を利用した照光式操作スイッ
チ等に利用することもできる。Further, by forming fine irregularities on the film, it is possible to enhance the action of scattering light and prevent the film from sticking to the light guide plate to form interference fringes. As described above, the planar light source of the present invention can be used not only as a light source for a backlight but also as an illuminated operation switch using a fluorescent substance.
【図１】 本発明の面状光源の模式的平面図である。FIG. 1 is a schematic plan view of a planar light source of the present invention.
【図２】 図１の面状光源のａ−ａにおける模式的断面
図である。2 is a schematic cross-sectional view taken along line aa of the planar light source of FIG.
【図３】 本願発明と比較のために示した面状光源の模
式的平面図である。FIG. 3 is a schematic plan view of a planar light source shown for comparison with the present invention.
【図４】 図２の面状光源のｂ−ｂにおける模式的断面
図である。4 is a schematic cross-sectional view taken along the line bb of the planar light source of FIG.
１０１・・・・・多色発光素子 １０２・・・・・導光板 １０３・・・・・反射材 １０４・・・・・反射層 １０５・・・・・拡散膜 １０６・・・・・支持体 ２０１・・・・・ＬＥＤ ２０２・・・・・導光板 ２０３・・・・・反射材 ２０４・・・・・拡散膜 101 ... Multicolor light emitting element 102 ... Light guide plate 103 ... Reflecting material 104 ... Reflecting layer 105 ... Diffusing film 106 ... Support 201 ... LED 202 ... Light guide plate 203 ... Reflecting material 204 ... Diffusion film
Claims (4)
に接続された多色発光素子と、前記導光板の第１の主面
上に設けられた反射材と、前記導光板の第２の主面上の
少なくとも一部に設けられた拡散膜と、を有し前記拡散
膜を介して発光させる面状光源であって、 前記第１の主面上に設けられた反射材と、前記多色発光
素子と光学的に接続された導光板端面を介して設けられ
た前記第２の主面上に反射層を有することを特徴とする
面状光源。1. A multicolor light emitting element optically connected to at least one location of an end surface of a light guide plate, a reflector provided on a first main surface of the light guide plate, and a second member of the light guide plate. A surface light source that has a diffusion film provided on at least a part of the main surface thereof and emits light through the diffusion film, and a reflector provided on the first main surface; A planar light source having a reflection layer on the second main surface provided via an end surface of a light guide plate optically connected to a multicolor light emitting element.
求項１記載の面状光源。2. The planar light source according to claim 1, wherein the reflectance of the reflective layer is 95% or more.
４９０ｎｍの発光波長を有する半導体と４９５ｎｍ〜５
６０ｎｍの発光波長を有する半導体及び６１０ｎｍ〜７
００ｎｍの発光波長を有する半導体とを同一支持体上に
設けた請求項１記載の面状光源。3. The multicolor light emitting device has at least 450 to
Semiconductor having an emission wavelength of 490 nm and 495 nm to 5
Semiconductor having an emission wavelength of 60 nm and 610 nm to 7
The planar light source according to claim 1, wherein a semiconductor having an emission wavelength of 00 nm is provided on the same support.
造である請求項１に記載の面状光源。4. The planar light source according to claim 1, wherein the surface of the reflective layer that is in contact with the light guide plate has an uneven structure.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32553795A JP3624503B2 (en) | 1995-12-14 | 1995-12-14 | Planar light source |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32553795A JP3624503B2 (en) | 1995-12-14 | 1995-12-14 | Planar light source |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09167860A true JPH09167860A (en) | 1997-06-24 |
| JP3624503B2 JP3624503B2 (en) | 2005-03-02 |
Family
ID=18177994
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP32553795A Expired - Fee Related JP3624503B2 (en) | 1995-12-14 | 1995-12-14 | Planar light source |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3624503B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000275636A (en) * | 1999-03-25 | 2000-10-06 | Seiko Epson Corp | Light source and illumination device as well as liquid crystal device using the illumination device |
| WO2002050607A1 (en) * | 2000-12-18 | 2002-06-27 | Zeon Corporation | Lighting unit for liquid crystal display device |
| JP2003298120A (en) * | 2002-04-03 | 2003-10-17 | Idec Izumi Corp | Light source device and fluorescent pattern sheet, method of manufacturing them, liquid crystal display device using them, lighting device, bulletin light, display light, and push button switch |
| JP2004134804A (en) * | 2002-10-14 | 2004-04-30 | Lumileds Lighting Us Llc | Circuit device |
| JP2007235085A (en) * | 2006-02-03 | 2007-09-13 | Hitachi Chem Co Ltd | Method of manufacturing package substrate for packaging optical semiconductor element and method of manufacturing optical semiconductor device using the same |
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| US9658380B2 (en) | 2014-09-10 | 2017-05-23 | Citizen Electronics Co., Ltd. | Planar lighting device |
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Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000275636A (en) * | 1999-03-25 | 2000-10-06 | Seiko Epson Corp | Light source and illumination device as well as liquid crystal device using the illumination device |
| WO2002050607A1 (en) * | 2000-12-18 | 2002-06-27 | Zeon Corporation | Lighting unit for liquid crystal display device |
| US7036972B2 (en) | 2000-12-18 | 2006-05-02 | Zeon Corporation | Lighting unit for liquid crystal display device |
| JP2003298120A (en) * | 2002-04-03 | 2003-10-17 | Idec Izumi Corp | Light source device and fluorescent pattern sheet, method of manufacturing them, liquid crystal display device using them, lighting device, bulletin light, display light, and push button switch |
| JP4707315B2 (en) * | 2002-10-14 | 2011-06-22 | フィリップス ルミレッズ ライティング カンパニー リミテッド ライアビリティ カンパニー | Circuit equipment |
| JP2004134804A (en) * | 2002-10-14 | 2004-04-30 | Lumileds Lighting Us Llc | Circuit device |
| US7786493B2 (en) | 2006-01-06 | 2010-08-31 | Sony Corporation | Light emitting diode, method for manufacturing light emitting diode, integrated light emitting diode, method for manufacturing integrated light emitting diode, light emitting diode backlight, light emitting diode illumination device, light emitting diode display, electronic apparatus, electronic device, and method for manufacturing electronic device |
| JP2007235085A (en) * | 2006-02-03 | 2007-09-13 | Hitachi Chem Co Ltd | Method of manufacturing package substrate for packaging optical semiconductor element and method of manufacturing optical semiconductor device using the same |
| JP2008050573A (en) * | 2006-07-25 | 2008-03-06 | Hitachi Chem Co Ltd | Thermosetting resin composition for reflecting light, substrate for loading optical semiconductor element using the same, method for producing the same and optical semiconductor device |
| US9387608B2 (en) | 2006-11-15 | 2016-07-12 | Hitachi Chemical Company, Ltd. | Thermosetting resin composition for light reflection, method for manufacturing the resin composition and optical semiconductor element mounting substrate and optical semiconductor device using the resin composition |
| US10381533B2 (en) | 2006-11-15 | 2019-08-13 | Hitachi Chemical Company, Ltd. | Optical semiconductor element mounting substrate and optical semiconductor device using thermosetting resin composition for light reflection |
| US9658380B2 (en) | 2014-09-10 | 2017-05-23 | Citizen Electronics Co., Ltd. | Planar lighting device |
| GB2593927A (en) * | 2020-04-09 | 2021-10-13 | Design Led Products Ltd | Homogeneous colour lighting device |
| US11947151B2 (en) | 2020-04-09 | 2024-04-02 | Design Led Products Limited | Homogeneous color LED lighting device with wavelength dependent modifier on output surface of lightguide |
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|---|---|
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