JP4759114B2 - Surface light source element - Google Patents
Surface light source element Download PDFInfo
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- JP4759114B2 JP4759114B2 JP2000120693A JP2000120693A JP4759114B2 JP 4759114 B2 JP4759114 B2 JP 4759114B2 JP 2000120693 A JP2000120693 A JP 2000120693A JP 2000120693 A JP2000120693 A JP 2000120693A JP 4759114 B2 JP4759114 B2 JP 4759114B2
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- Prior art keywords
- light
- guide plate
- light guide
- light source
- plate
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- Optical Elements Other Than Lenses (AREA)
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Description
【0001】
【発明の属する技術分野】
本発明は、パーソナルコンピュータ、コンピュータ用モニタ、ビデオカメラ、テレビ受信機、カーナビゲーションシステムなどに利用される面光源素子に関する。
【0002】
【従来の技術】
液晶パネルに代表される透過型表示装置は、面状に散乱光を発するバックライトとドット状に画素が配置された表示パネルとで構成され、該表示パネルの各画素の光の透過率がコントロールされることによって文字および映像が表示される。バックライトとしては、ハロゲンランプ、反射板、レンズ等が組み合わされて出射光の輝度の分布が制御されるもの、蛍光管が導光板の端面に設けられ、蛍光管からの光が端面と垂直な面から出射されるもの、蛍光管が導光板の下部に設けられたもの(直下型)などが挙げられる。ハロゲンランプを利用したバックライトは、高輝度を必要とする液晶プロジェクタに主に用いられる。一方、導光板を利用したバックライトは薄型化が可能であるため、直視型の液晶TV、パーソナルコンピュータのディスプレイなどに用いられることが多い。
【0003】
液晶TV、ノートパソコンなどに用いられる導光板を利用したバックライトでは、消費電力を軽減すること、および高輝度であることが要求されている。従来の面光源素子では、一般に、導光板の裏面側に反射シートを設け、または導光板裏面にドットを印刷し、あるいは凹凸パターン成形することによって、光源からの光を散乱させている。このような面光源素子で高輝度化を実現することは、冷陰極管などの光源を増やすことで可能であるが、この方法は消費電力の増加につながるため実用的ではない。そこで、導光板上にマイクロプリズムアレイを配置することにより、高輝度化を図った面光源素子が提案されている(USP5,396,350号等参照)。
【0004】
【発明が解決しようとする課題】
導光板上にマイクロプリズムアレイを配置した構成の面光源素子では、マイクロプリズムアレイおよび導光板での光の全反射を利用して光を伝播しており、光の損失が少なく、高輝度化を実現することができる。しかし、導光板の種類によっては、所期の輝度が得られないことがあった。
【0005】
本発明は、上記の課題に鑑みてなされたもので、マイクロプリズムアレイおよび導光板内部の全反射を利用した面光源素子に好適な導光板を提供し、面光源素子の輝度を向上させることを目的とする。
【0006】
【課題を解決するための手段】
上記の課題を解決する本発明の面光源素子は、光源と、該光源の周囲に配置されたリフレクタと、該リフレクタで反射された光源からの光が少なくとも一つの端面から入射される導光板と、該導光板の出射面側に配置され、導光板と対向する面に頂部が導光板と密着して設けられた複数の凸部によって該導光体内部を全反射によって伝搬する光を該導光板と該凸部との密着部から取り出して導光板の出射面からの光を出射面の正面方向に向かわせる出射光制御板とを備えており、前記導光板は直方体であり、導光板端面の表面粗さが0.5μm以下であり、入射端面と直交する導光板端面が空気と接している。
【0007】
【発明の実施の形態】
図1に本発明の面光源素子の一例の概略構成図を示す。この面光源素子は両端面に冷陰極管などの光源2が設けられた直方体の導光板3と、導光板3から出射された光の角度分布を制御する出射光制御板1とを備えている。出射光制御板1は導光板3の出射面5上に配置されており、出射光制御板1の入射面には頂部が導光板3と密着した多数の凸部(マイクロプリズムアレイ)が形成されている。該凸部の断面形状は、放物線状、三角形状などである。この例における凸部は1次元パターンであり、光源が配置されている側の導光板端面と平行になるように凸部の稜線が配置されている。光源2の周りには、導光板3の端面とは反対方向に進む光を反射し、導光板3の端面方向に進行させるリフレクタ4が設けられている。端面から導光板3に入射した光は導光板内を全反射を繰り返しながら伝搬していく。この伝搬光は出射光制御板1の凸部と導光板3の出射面との密着部から出射光制御板1に取り込まれる。これにより、導光板3内を伝搬する光は密着部から順次、出射光制御板1に取り出され、取り出された光は出射光制御板1の凸部内で全反射されながら集光される。本発明の面光源素子では、この導光板3の端面の表面粗さが0.5μm以下である。この表面粗さは表面形状測定器(日本真空技術株式会社製DEKTAK−3030)により測定幅8mmの平均粗さ(RA)を測定したものである。なお、本発明においては入射端面と直交する導光板端面は空気と接している。
【0008】
出射光制御板表面の凸部は、熱プレス法、紫外線硬化による2P法、熱硬化による2P法、雌金型を用いた射出成形法等によって形成することができる。出射光制御板の作製に用いるスタンパは、例えばガラス基板上にネガ型あるいはポジ型の感光性樹脂をコーティングし、この感光性樹脂をフォトマスクを介して露光し、現像後、電鋳を行うことにより作製することができる。出射光制御板は板状である必要はなく、シート状であってもよい。板状およびシート状の何れでも量産性に富むため、安価で大量に製造することが可能である。また該出射光制御板の凸部のパターンは1次元ばかりでなく、2次元的に配置されていても良い。出射光制御板の光出射面にもマイクロレンズアレイが設けられていても良い。
【0009】
導光板の成形に用いる樹脂としては、アクリル樹脂の外にポリカーボネート樹脂、ポリスチレン樹脂等の透明性に優れるものが挙げられる。導光板は、パネルソーおよびNCフライス盤を用いた切削加工により成形することができる。この場合、例えば、パネルソーを用いて基準寸法より両端で数mm大きく切断した後、NCフライス盤でコンパックス刃を用いて粗切削を行い、さらにNCフライス盤でダイヤモンド刃を用いて精密切削を行えば良い。
【0010】
上記の通り説明した面光源素子をバックライトとして用い、その出射面に透過型表示素子を設けることで、表示装置を構成することができる。この透過型表示素子としては、STN、TFT、MINIなどの液晶パネルが挙げられる。
【0011】
【実施例】
以下、実施例により本発明をより詳細に説明する。導光板として住友化学工業(株)製のアクリル板(E011、厚さ6mm)を使用した。まず、基準寸法より8mm大きいサイズになるようにパネルソーでアクリル板を切断した。これを複数枚を重ね合わせた後、粗切削(NCフライス盤でコンパックス刃を用いた。片面2mm、0.48mmの2回通し。)および精密切削(NCフライス盤でダイヤモンド刃を用いた。片面0.01mmの2回通し。)を4つの端面について行って導光板を得た。この導光板の切削端面を表面形状測定器(日本真空技術株式会社製DEKTAK−3030)で測定したところ、表面粗さは0.5μm以下であった。なお、精密切削時のフライス盤の加工速度の違いによる切削端面の表面粗さの差を測定したが、いずれも0.5μm以下であり、速度による有意差は認められなかった。
【0012】
上記実施例と比較するため、同じアクリル板を使用して、同じようにパネルソーで切断し、複数枚を重ね合わせた後、2つの端面について粗切削(NCフライス盤でコンパックス刃を用いた。片面2mm、0.5mmの2回通し。)のみを行い、光源から光が入射する2つの端面については精密切削(NCフライス盤でダイヤモンド刃を用いた片面0.01mmの2回通し)を行うことによって導光板を得た。この導光板の切削端面の表面粗さは10μmであった。
【0013】
上記の実施例および比較例の導光板を、光源、リフレクタおよび出射光制御板と組合わせて構成した面光源素子の中央輝度を測定した結果を表1に示す。表1に、実施例および比較例の導光板の裏面にそれぞれドット印刷を施した上で、これと光源およびリフレクタとを組合わせて(出射光制御板は用いない。)構成した面光源素子の中央輝度を測定した結果をあわせて示す。
【0014】
【表1】
【0015】
以上の結果から、光源が配置されていない導光板端面の表面粗さが0.5μm以下である本発明の導光板を用いることにより、輝度が向上することが分かる。これに対し、ドット印刷を利用した面光源素子では、光源が配置されていない導光板端面の表面粗さの大小に関わらず、輝度は変わっていない。
【0016】
【発明の効果】
本発明によれば、マイクロプリズムアレイおよび導光板内部の全反射を利用した面光源素子の輝度を向上させることができる。
【図面の簡単な説明】
【図1】本発明の面光源素子の一例の概略構成図。
【符号の説明】
1…出射光制御板
2…光源
3…導光板
4…リフレクタ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface light source element used for a personal computer, a computer monitor, a video camera, a television receiver, a car navigation system, and the like.
[0002]
[Prior art]
A transmissive display device typified by a liquid crystal panel is composed of a backlight that emits scattered light in a planar shape and a display panel in which pixels are arranged in a dot shape, and the light transmittance of each pixel of the display panel is controlled. By doing so, characters and images are displayed. As the backlight, a halogen lamp, a reflector, a lens, etc. are combined to control the luminance distribution of the emitted light. A fluorescent tube is provided on the end face of the light guide plate, and the light from the fluorescent tube is perpendicular to the end face. Examples include those emitted from the surface and those in which a fluorescent tube is provided at the lower part of the light guide plate (directly under type). Backlights using halogen lamps are mainly used for liquid crystal projectors that require high brightness. On the other hand, since a backlight using a light guide plate can be thinned, it is often used for a direct-view liquid crystal TV, a display of a personal computer, and the like.
[0003]
A backlight using a light guide plate used in a liquid crystal TV, a notebook personal computer or the like is required to reduce power consumption and to have high luminance. Conventional surface light source elements generally scatter light from a light source by providing a reflective sheet on the back side of the light guide plate, printing dots on the back side of the light guide plate, or forming an uneven pattern. Realization of high brightness with such a surface light source element is possible by increasing the number of light sources such as cold cathode fluorescent lamps, but this method is not practical because it leads to an increase in power consumption. In view of this, a surface light source element has been proposed in which a microprism array is arranged on the light guide plate to increase the luminance (see US Pat. No. 5,396,350, etc.).
[0004]
[Problems to be solved by the invention]
In a surface light source element with a microprism array arranged on a light guide plate, light is propagated using total reflection of light on the microprism array and the light guide plate, resulting in less loss of light and higher brightness. Can be realized. However, the desired luminance may not be obtained depending on the type of the light guide plate.
[0005]
The present invention has been made in view of the above problems, and provides a light guide plate suitable for a surface light source element using total reflection inside a micro prism array and a light guide plate, and to improve the luminance of the surface light source element. Objective.
[0006]
[Means for Solving the Problems]
A surface light source element of the present invention that solves the above problems includes a light source, a reflector disposed around the light source, and a light guide plate on which light from the light source reflected by the reflector is incident from at least one end surface. The light propagating inside the light guide body by total reflection is provided by a plurality of convex portions arranged on the light exit surface side of the light guide plate and having top portions closely contacting the light guide plate on the surface facing the light guide plate. An exit light control plate that is taken out from a contact portion between the light plate and the convex portion and directs light from the exit surface of the light guide plate toward the front direction of the exit surface, and the light guide plate is a rectangular parallelepiped, and the end surface of the light guide plate surface roughness is not more 0.5μm or less, the light guide plate end surface perpendicular to the incident end face that in contact with the air.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic configuration diagram of an example of a surface light source element of the present invention. This surface light source element includes a rectangular parallelepiped light guide plate 3 provided with light sources 2 such as cold cathode tubes at both end faces, and an emitted light control plate 1 for controlling the angular distribution of light emitted from the light guide plate 3. . The outgoing light control plate 1 is disposed on the outgoing surface 5 of the light guide plate 3, and on the incident surface of the outgoing light control plate 1, a large number of convex portions (micro prism arrays) whose tops are in close contact with the light guide plate 3 are formed. ing. The cross-sectional shape of the convex portion is a parabolic shape, a triangular shape, or the like. The convex part in this example is a one-dimensional pattern, and the ridge line of the convex part is arranged so as to be parallel to the end face of the light guide plate on the side where the light source is arranged. Around the light source 2, there is provided a reflector 4 that reflects light traveling in a direction opposite to the end surface of the light guide plate 3 and proceeds in the direction of the end surface of the light guide plate 3. Light incident on the light guide plate 3 from the end face propagates while repeating total reflection in the light guide plate. The propagating light is taken into the outgoing light control plate 1 from a close contact portion between the convex portion of the outgoing light control plate 1 and the outgoing surface of the light guide plate 3. Thereby, light propagating in the light guide plate 3 is sequentially extracted from the contact portion to the outgoing light control plate 1, and the extracted light is condensed while being totally reflected in the convex portion of the outgoing light control plate 1. In the surface light source element of the present invention, the surface roughness of the end face of the light guide plate 3 is 0.5 μm or less. This surface roughness is obtained by measuring an average roughness (RA) having a measurement width of 8 mm using a surface shape measuring instrument (DEKTAK-3030 manufactured by Nippon Vacuum Technology Co., Ltd.). In the present invention, the end face of the light guide plate orthogonal to the incident end face is in contact with air.
[0008]
The convex portion on the surface of the outgoing light control plate can be formed by a hot press method, a 2P method by ultraviolet curing, a 2P method by thermal curing, an injection molding method using a female mold, or the like. For example, a stamper used for producing an outgoing light control plate is obtained by coating a negative or positive photosensitive resin on a glass substrate, exposing the photosensitive resin through a photomask, and performing electroforming after development. Can be produced. The outgoing light control plate does not have to be plate-shaped and may be sheet-shaped. Since both the plate shape and the sheet shape are rich in mass productivity, they can be manufactured in large quantities at a low cost. Further, the pattern of the convex portion of the emitted light control plate may be arranged not only one-dimensionally but also two-dimensionally. A microlens array may also be provided on the light exit surface of the exit light control plate.
[0009]
Examples of the resin used for forming the light guide plate include those having excellent transparency such as polycarbonate resin and polystyrene resin in addition to the acrylic resin. The light guide plate can be formed by cutting using a panel saw and an NC milling machine. In this case, for example, after cutting a few millimeters at both ends from the reference dimension using a panel saw, rough cutting is performed using a Compaqs blade on an NC milling machine, and further precision cutting is performed using a diamond blade on the NC milling machine. .
[0010]
A display device can be configured by using the surface light source element described above as a backlight and providing a transmissive display element on the emission surface. Examples of the transmissive display element include liquid crystal panels such as STN, TFT, and MINI.
[0011]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. An acrylic plate (E011, thickness 6 mm) manufactured by Sumitomo Chemical Co., Ltd. was used as the light guide plate. First, the acrylic board was cut with a panel saw so as to be 8 mm larger than the standard dimension. After superimposing a plurality of sheets, rough cutting (using a Compaqs blade on an NC milling machine. 2 passes on each side: 2 mm and 0.48 mm) and precision cutting (using a diamond blade on an NC milling machine. Single side 0) .01 mm twice) was performed on four end faces to obtain a light guide plate. When the cutting end face of this light guide plate was measured with a surface shape measuring instrument (DEKTAK-3030 manufactured by Nippon Vacuum Technology Co., Ltd.), the surface roughness was 0.5 μm or less. In addition, although the difference of the surface roughness of the cutting end surface by the difference in the processing speed of the milling machine at the time of precision cutting was measured, all were 0.5 micrometer or less, and the significant difference by speed was not recognized.
[0012]
In order to compare with the said Example, it cut | disconnected with the panel saw similarly using the same acrylic board, and after superposing several sheets, it rough-cuts about two end surfaces (The Compaqs blade was used with the NC milling machine. One side. 2 mm and 0.5 mm twice)), and the two end faces where light is incident from the light source are subjected to precision cutting (twice of 0.01 mm on one side using a diamond blade in an NC milling machine). A light guide plate was obtained. The surface roughness of the cut end face of this light guide plate was 10 μm.
[0013]
Table 1 shows the results of measuring the central luminance of the surface light source elements formed by combining the light guide plates of the above-described examples and comparative examples with the light source, the reflector, and the outgoing light control plate. Table 1 shows the surface light source elements that are configured by combining dot light printing on the back surfaces of the light guide plates of the example and the comparative example, and combining the light source and the reflector (the emission light control plate is not used). The results of measuring the central luminance are also shown.
[0014]
[Table 1]
[0015]
From the above results, it can be seen that the luminance is improved by using the light guide plate of the present invention in which the surface roughness of the end face of the light guide plate where the light source is not disposed is 0.5 μm or less. On the other hand, in the surface light source element using dot printing, the luminance does not change regardless of the surface roughness of the end face of the light guide plate where the light source is not arranged.
[0016]
【The invention's effect】
According to the present invention, it is possible to improve the luminance of the surface light source element using total reflection inside the microprism array and the light guide plate.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an example of a surface light source element of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Output light control board 2 ... Light source 3 ... Light guide plate 4 ... Reflector
Claims (1)
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JP2000120693A JP4759114B2 (en) | 2000-04-21 | 2000-04-21 | Surface light source element |
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JP2000120693A JP4759114B2 (en) | 2000-04-21 | 2000-04-21 | Surface light source element |
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JP2001307524A JP2001307524A (en) | 2001-11-02 |
JP4759114B2 true JP4759114B2 (en) | 2011-08-31 |
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JP4274239B2 (en) | 2006-12-27 | 2009-06-03 | ソニー株式会社 | Planar light source device, display device, and planar illumination method |
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JPH0996814A (en) * | 1995-09-29 | 1997-04-08 | Toshiba Lighting & Technol Corp | Illumination device, back light and liquid crystal display device |
JPH09113907A (en) * | 1995-10-17 | 1997-05-02 | Nippon Chemitec Kk | Light transmission plate and surface type illuminating body using the same |
JP3267847B2 (en) * | 1995-12-28 | 2002-03-25 | オーツタイヤ株式会社 | Light guide plate device |
JP3563521B2 (en) * | 1996-02-02 | 2004-09-08 | 三菱レイヨン株式会社 | Marking device |
JPH10293213A (en) * | 1997-04-22 | 1998-11-04 | Toshiba Corp | Backlight device |
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