JP2005183030A - Light guide plate and lighting system - Google Patents

Light guide plate and lighting system Download PDF

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JP2005183030A
JP2005183030A JP2003418008A JP2003418008A JP2005183030A JP 2005183030 A JP2005183030 A JP 2005183030A JP 2003418008 A JP2003418008 A JP 2003418008A JP 2003418008 A JP2003418008 A JP 2003418008A JP 2005183030 A JP2005183030 A JP 2005183030A
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light
guide plate
light guide
end surface
angle
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Taketoshi Masamoto
武寿 政本
Yasunori Onishi
康憲 大西
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Seiko Epson Corp
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Seiko Epson Corp
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<P>PROBLEM TO BE SOLVED: To provide a light guide plate and a lighting system capable of manufacturing at low cost and in a short time, and having high light utilization efficiency. <P>SOLUTION: The light guide plate can suitably be used in the lighting system as a backlight unit or the like of a liquid crystal device for example, and has a light outgoing surface emitting out light, a reflecting surface, and a light incoming end surface to which light from a light source is incident. The light guide plate has a wedge-shaped cross section, and has the thickness gradually decreasing with being apart from the light incoming end surface on the light source side. The reflecting surface reflecting light incoming to the inside of the light guide plate from the light incoming end surface and the light outgoing surface emitting light are formed in a plane and mirror surface. Since reflecting surface has an inclined angle larger than 0 degree to the light outgoing surface, incident light into the light guide plate from the light incoming end surface changes direction only the angle according to the inclined angle in every reflection on the reflecting surface, and when the angle between the light outgoing surface and light exceeds a critical angle, light comes out from the light outgoing surface. Since a specific pattern shape for reflecting light incident in the inside of the light guide plate from the light incoming end surface is not installed on the reflecting surface according to the incline angle, a mold used in the manufacture of the light guide plate can be manufactured easily and in a short time, cost is reduced and time requiring the manufacture is shortened. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は照明装置に関し、特に液晶装置などのバックライトユニットとして好適な面発光型の照明装置に関する。   The present invention relates to a lighting device, and more particularly to a surface-emitting type lighting device suitable as a backlight unit such as a liquid crystal device.

液晶装置においては、透過表示を行うために液晶パネルの背面側にバックライトユニットが設けられる。一般的には、バックライトユニットは、光源と、光源からの光を平面状の光として液晶パネルの背面に照射する導光板と、導光板から出射した光を拡散するシートとを備えて構成される。光源から導光板に入射した光は、導光板の出光面と反射面との間で反射を繰り返した後、出光面から外部へ出光する。近年では、照明装置の軽量化や発光効率の向上などの観点から、導光板の形状は、光源側から遠ざかるにつれてその板厚が減少していく、いわゆる「楔形」の断面形状を有するものが多く使用されている。楔形の導光板を使用した照明装置の例が、例えば特許文献1乃至3に記載されている。   In the liquid crystal device, a backlight unit is provided on the back side of the liquid crystal panel in order to perform transmissive display. In general, a backlight unit includes a light source, a light guide plate that irradiates the back surface of the liquid crystal panel with light from the light source as planar light, and a sheet that diffuses light emitted from the light guide plate. The The light incident on the light guide plate from the light source is repeatedly reflected between the light exit surface and the reflection surface of the light guide plate, and then exits from the light exit surface to the outside. In recent years, from the viewpoint of reducing the weight of the lighting device and improving the light emission efficiency, the shape of the light guide plate often has a so-called “wedge” cross-sectional shape in which the thickness decreases as the distance from the light source increases. in use. Examples of illumination devices using a wedge-shaped light guide plate are described in Patent Documents 1 to 3, for example.

導光板の厚みが一定の平板形状で、その表面が鏡面の場合、光は導光板出光面から出射しない。上記のような照明装置では、光を出射させるために、導光板の出光面、反射面の一方、または両方に光の反射方向を変えるための細かなパターンや形状が設けられる。導導光板に入射した光は出光面、反射面に形成されたパターンで反射されるたびに徐々に角度が変化し、導光板表面と光との間の角度が臨界角を超えた光が導光板から外部へ出光する。   When the light guide plate is a flat plate having a constant thickness and its surface is a mirror surface, light is not emitted from the light guide plate exit surface. In the illumination device as described above, in order to emit light, a fine pattern or shape for changing the light reflection direction is provided on one or both of the light exit surface and the reflection surface of the light guide plate. The angle of light incident on the light guide plate changes gradually each time it is reflected by the pattern formed on the light exit surface and reflection surface, and light whose angle between the light guide plate surface and the light exceeds the critical angle is guided. Light exits from the light plate.

しかし、導光板の反射面にそのようなパターンを設けたり、特殊な形状としたりする加工にはコスト及び製作時間を要する。通常、導光板は金型を使用して樹脂などを成形して製作するので、反射面にパターンなどを形成するためには金型にそのような加工を施す必要がある。よって、対応する微細なパターンや形状を金型側に形成する必要があり、その形状が微細、複雑であるほど金型の製作コスト及び製作時間が増大してしまう。   However, the process of providing such a pattern on the reflecting surface of the light guide plate or making it a special shape requires cost and production time. Usually, since the light guide plate is manufactured by molding a resin or the like using a mold, it is necessary to perform such processing on the mold in order to form a pattern or the like on the reflecting surface. Therefore, it is necessary to form a corresponding fine pattern or shape on the mold side, and as the shape becomes finer and more complicated, the production cost and production time of the mold increase.

特開平8−313732号公報JP-A-8-313732 特開平11−287993号公報Japanese Patent Laid-Open No. 11-287993 特開平10−73820号公報Japanese Patent Laid-Open No. 10-73820

本発明は上記の点に鑑みてなされたものであり、低コスト及び短時間で製作可能な光利用効率の高い導光板を提供すること、およびその導光板を使用した照明装置を提供することを課題とする。   The present invention has been made in view of the above points, and provides a light guide plate with high light utilization efficiency that can be manufactured at low cost and in a short time, and an illumination device using the light guide plate. Let it be an issue.

本発明の1つの観点では、光を出射する出光面と、前記出光面と対向する反射面と、光源からの光が入射する入光端面とを備え、前記出光面と前記反射面との距離が前記入光端面から遠ざかるにつれて減少する楔形状の断面を有する導光板において、前記出光面及び前記反射面は少なくとも一方が平面かつ鏡面であり、前記出光面に対する前記反射面の傾斜角が0度より大きい。   In one aspect of the present invention, a light exit surface that emits light, a reflective surface that faces the light exit surface, and a light incident end surface on which light from a light source enters, a distance between the light exit surface and the reflective surface In the light guide plate having a wedge-shaped cross section that decreases with increasing distance from the light incident end surface, at least one of the light exit surface and the reflective surface is a plane and a mirror surface, and the inclination angle of the reflective surface with respect to the light exit surface is 0 degree. Greater than.

上記の導光板は、例えば液晶装置のバックライトユニットなどとして使用される照明装置に好適に使用することができ、光を出射する出光面と、前記出光面と対向する反射面と、光源からの光が入射する入光端面とを備える。導光板の断面形状は楔形であり、光源側の入光端面から遠ざかるにつれて板厚が減少する形状となっている。また、入光端面から導光板内部に入射した光を反射する反射面、及び、光が出射する出光面の双方が平面かつ鏡面となっている。反射面を出光面に対して0度より大きい傾斜角で形成するので、入光端面から導光板内に入射した光は反射面で反射される度に傾斜角に応じた角度だけ方向を変えられ、出光面と光との角度が臨界角を超えると光は出光面から出光する。このように、傾斜角に応じた反射面には、入光端面から導光板内部に入射した光を反射するための特別なパターン形状を設けないので、導光板の製造に使用する金型を容易かつ短時間で製作でき、低コスト化及び製作に要する時間の短縮が可能となる。好適な実施例では、前記傾斜角は5度以下であることが好ましく、特に2度が好ましい。   The light guide plate can be suitably used for an illumination device used as a backlight unit of a liquid crystal device, for example, and includes a light exit surface that emits light, a reflective surface that faces the light exit surface, and a light source. A light incident end face on which light is incident. The cross-sectional shape of the light guide plate is a wedge shape, and the plate thickness decreases as the distance from the light incident end surface on the light source side increases. Moreover, both the reflective surface which reflects the light which injected into the inside of the light-guide plate from the light-incidence end surface, and the light emission surface from which light radiate | emits become a plane and a mirror surface. Since the reflecting surface is formed with an inclination angle larger than 0 degree with respect to the light exit surface, the light incident on the light guide plate from the light incident end face can be redirected by an angle corresponding to the inclination angle every time it is reflected by the reflecting surface. When the angle between the light exit surface and the light exceeds the critical angle, the light exits from the light exit surface. In this way, the reflective surface according to the inclination angle is not provided with a special pattern shape for reflecting the light incident on the inside of the light guide plate from the light incident end surface, so that the mold used for manufacturing the light guide plate is easy. Moreover, it can be manufactured in a short time, and the cost can be reduced and the time required for the manufacturing can be shortened. In a preferred embodiment, the inclination angle is preferably 5 degrees or less, particularly 2 degrees.

上記の導光板の一態様では、前記反射面及び前記出光面の少なくとも一方は、前記入光端面と略直交する方向に延びる複数の凹部が、前記入光端面の長さ方向に複数繰り返し形成されている。導光板の出光面及び反射面を平面かつ鏡面とするので、導光板に対して光源からの光が入射する方向と垂直な方向、即ち入光端面の長さ方向には光の拡散性が不足する傾向が生じる。特に光源として複数のLEDなどの点光源を使用する場合には、LEDの近傍に明暗の部分ができ、輝度ムラなどが生じやすい。そこで、入光端面と垂直な方向に複数の凹部をストライプ状に形成することにより、その凹部の長さと垂直な方向、即ち入光端面と平行な方向に光の拡散性を向上させることができ、輝度ムラなどを低減することができる。上記の複数の凹部は、前記入光端面と平行な方向における断面形状が異なることが好ましい。複数の凹部の断面形状が異なる方が、より光をランダムに拡散させやすくなり、輝度ムラが生じにくくなる。   In one aspect of the light guide plate, at least one of the reflection surface and the light exit surface is formed with a plurality of recesses extending in a direction substantially perpendicular to the light entrance end surface, and a plurality of recesses are formed in the length direction of the light entrance end surface. ing. Since the light exit surface and reflection surface of the light guide plate are flat and mirror surfaces, the light diffusibility is insufficient in the direction perpendicular to the direction in which light from the light source enters the light guide plate, that is, in the length direction of the light incident end surface. Tend to occur. In particular, when a point light source such as a plurality of LEDs is used as the light source, a bright and dark portion is formed in the vicinity of the LED, and uneven brightness tends to occur. Therefore, by forming a plurality of recesses in a stripe shape in a direction perpendicular to the light incident end face, light diffusibility can be improved in a direction perpendicular to the length of the recess, that is, in a direction parallel to the light incident end face. In addition, luminance unevenness can be reduced. The plurality of recesses preferably have different cross-sectional shapes in a direction parallel to the light incident end face. Different cross-sectional shapes of the plurality of recesses make it easier to diffuse light randomly, and luminance unevenness is less likely to occur.

本発明の他の観点では、照明装置は、上記の導光板と、凹凸面が前記出光面と対向するように前記導光板と対向配置されたプリズムシートと、を備え、前記プリズムシートの突部の頂角が60度〜70度の範囲内である。   In another aspect of the present invention, an illuminating device includes the light guide plate described above, and a prism sheet that is disposed to face the light guide plate so that a concavo-convex surface faces the light output surface, and the protrusion of the prism sheet Is within the range of 60 to 70 degrees.

上記の導光板では、出光面と反射面との間の傾斜角を適切に設定することにより、出光面から出射する光に指向性を与え、その角度を一定の範囲内に集中させることができる。よって、出光面から多くの光が出射する角度に対してプリズムシートの頂角を適切な範囲に設定すれば、導光板から出射した光のより多くの部分をプリズムシートを介して照明装置外部へ出射することが可能となり、光源からの光の使用効率を向上させることが可能となる。   In the above light guide plate, by appropriately setting the inclination angle between the light exit surface and the reflection surface, directivity can be given to the light emitted from the light exit surface, and the angle can be concentrated within a certain range. . Therefore, if the apex angle of the prism sheet is set to an appropriate range with respect to the angle at which a lot of light is emitted from the light exit surface, a larger part of the light emitted from the light guide plate is transferred to the outside of the illumination device via the prism sheet. The light can be emitted, and the use efficiency of light from the light source can be improved.

本発明の他の観点では、電気光学装置において、基板に電気光学物質を配置してなる電気光学基板と、上記の照明装置とを備え、前記電気光学基板は前記プリズムシートに対して前記導光板の反対側に配置されてなる。これにより、低コストで輝度ムラの少ない電気光学装置を提供することができる。   In another aspect of the present invention, the electro-optical device includes an electro-optical substrate in which an electro-optical material is disposed on the substrate, and the illumination device, and the electro-optical substrate has the light guide plate with respect to the prism sheet. It is arranged on the opposite side. As a result, an electro-optical device with low luminance and less luminance unevenness can be provided.

以下、図面を参照して本発明の好適な実施形態について説明する。   Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[第1実施形態]
図1に本発明の第1実施形態に係る照明装置の概略構成を示す。図1において、照明装置10は、液晶装置2などのバックライトユニットとして使用される面発光型の照明装置であり、導光板11と、光源12と、反射シート13と、プリズムシート14とを備える。導光板11から出射した光Lは、図示のようにプリズムシート14を通過して液晶装置2を背面から照明する。これにより、液晶装置2の透過表示が可能となる。
[First Embodiment]
FIG. 1 shows a schematic configuration of a lighting apparatus according to the first embodiment of the present invention. In FIG. 1, an illuminating device 10 is a surface-emitting illuminating device used as a backlight unit such as a liquid crystal device 2, and includes a light guide plate 11, a light source 12, a reflective sheet 13, and a prism sheet 14. . The light L emitted from the light guide plate 11 passes through the prism sheet 14 as illustrated to illuminate the liquid crystal device 2 from the back side. Thereby, the transmissive display of the liquid crystal device 2 becomes possible.

図2(a)に照明装置10の側面図を示す。なお、説明の便宜上、反射シート13は図示を省略している。光源12は例えば光源として複数のLED(図示せず)を備え、光源と対向する導光板11の端面(以下、「入光端面」と呼ぶ。)11cに光を出射する。導光板11は平面形状が矩形であり、アクリル樹脂などの透明樹脂から構成される。図1及び2における上側の面11aは光を出射する面(以下、「出光面」と呼ぶ。)であり、下側の面11bは光を反射する面(以下、「反射面」と呼ぶ。)である。   FIG. 2A shows a side view of the illumination device 10. For convenience of explanation, the reflection sheet 13 is not shown. The light source 12 includes, for example, a plurality of LEDs (not shown) as a light source, and emits light to an end surface (hereinafter referred to as “light incident end surface”) 11 c of the light guide plate 11 facing the light source. The light guide plate 11 has a rectangular planar shape and is made of a transparent resin such as an acrylic resin. The upper surface 11a in FIGS. 1 and 2 is a surface that emits light (hereinafter referred to as “light-emitting surface”), and the lower surface 11b is a surface that reflects light (hereinafter referred to as “reflecting surface”). ).

導光板11は、図示のようにいわゆる楔形の断面形状を有しており、入光端面11cから遠ざかるにつれて板厚が減少していく。即ち、入光端面11cから遠ざかるにつれて、出光面11aと反射面11bとの距離が減少していく断面形状を有している。光源12から出射した光Lは、入光端面11cから導光板11内に入り、反射面11bと出光面11aとの間で反射を繰り返す。そして、出光面11aと光のなす角が臨界角を超えると、出光面11aを透過して外部へ出光する。   As shown in the drawing, the light guide plate 11 has a so-called wedge-shaped cross-sectional shape, and the plate thickness decreases as the distance from the light incident end surface 11c increases. That is, it has a cross-sectional shape in which the distance between the light exit surface 11a and the reflection surface 11b decreases as the distance from the light incident end surface 11c increases. The light L emitted from the light source 12 enters the light guide plate 11 from the light incident end surface 11c, and is repeatedly reflected between the reflecting surface 11b and the light emitting surface 11a. When the angle between the light exit surface 11a and the light exceeds the critical angle, the light exits the light exit surface 11a and exits to the outside.

光源12から出射した光は導光板11内を遠くへ伝搬するほどエネルギーが低下するので、入光端面と反対側の端面11dに近づくほど光は暗くなる。そこで、導光板11の断面形状を楔形として、入光端面と反対側の端面11d側へ近づくほど板厚を薄くすることにより反対側の光出射効率を上げることで、導光板の面内における明るさを均一化することができる。また、楔形状化は、導光板11の軽量化にも有効である。   The light emitted from the light source 12 decreases in energy as it travels farther through the light guide plate 11, so that the light becomes darker as it approaches the end surface 11d opposite to the light incident end surface. Therefore, the cross-sectional shape of the light guide plate 11 is a wedge shape, and the light emission efficiency on the opposite side is increased by decreasing the plate thickness toward the end surface 11d opposite to the light incident end surface, thereby increasing the brightness within the surface of the light guide plate. The thickness can be made uniform. The wedge shape is also effective for reducing the weight of the light guide plate 11.

プリズムシート14は、その片面に断面が略三角形の凹凸を形成したシートであり、導光板11の出光面1aから出光した光を効率的に液晶装置2側へ向ける役割を有する。本実施例のプリズムシート14は、「逆プリズム型」とも呼ばれ、凹凸形状が導光板11と対向するように配置されるものである。図2に示すように、導光板11の出光面11aから出射した光Lはプリズムシート14により略垂直方向へ向けられる。   The prism sheet 14 is a sheet having a substantially triangular cross section formed on one side thereof, and has a role of efficiently directing light emitted from the light exit surface 1 a of the light guide plate 11 toward the liquid crystal device 2. The prism sheet 14 of this embodiment is also called an “inverted prism type”, and is arranged so that the concavo-convex shape faces the light guide plate 11. As shown in FIG. 2, the light L emitted from the light exit surface 11 a of the light guide plate 11 is directed in a substantially vertical direction by the prism sheet 14.

本実施例では、導光板11の出光面11a及び反射面11bはいずれも平面かつ鏡面となっている。導光板11の出光面11aに光拡散のための凹凸形状などを設ける手法が知られているが、本実施例では鏡面とすることにより光の利用効率を高めている。   In the present embodiment, the light exit surface 11a and the reflection surface 11b of the light guide plate 11 are both flat and mirror surfaces. A technique is known in which a light emitting surface 11a of the light guide plate 11 is provided with a concavo-convex shape for light diffusion. In this embodiment, the use efficiency of light is enhanced by using a mirror surface.

通常、導光板11の反射面11bには、一般的には光の角度を変えるために所定のパターンが形成される。そのようなパターンの一例を図2(b)に示す。図2(b)に示す導光板18は、その反射面19をステップ状(段差状)に形成している。このステップ形状により、反射面19に入射する光の方向を変更する。導光板11内に入った光は、反射面19により何度か方向を変えられ、出光面との角度が臨界角を超えたときに導光板18から外部へ出射する。しかしながら、前述のように、導光板にこのような形状を設けるにはコスト及び時間を要する。   Usually, a predetermined pattern is generally formed on the reflecting surface 11b of the light guide plate 11 in order to change the angle of light. An example of such a pattern is shown in FIG. The light guide plate 18 shown in FIG. 2B has a reflective surface 19 formed in a step shape (step shape). The direction of light incident on the reflecting surface 19 is changed by this step shape. The light that has entered the light guide plate 11 is changed in direction several times by the reflection surface 19 and is emitted to the outside from the light guide plate 18 when the angle with the light output surface exceeds a critical angle. However, as described above, providing such a shape on the light guide plate requires cost and time.

本発明では、そのような形状を設けず、導光板11の反射面11bを鏡面とする。いま、図2(a)に示すように、導光板11の反射面11bが出光面11aに対してなす傾斜角を「α」とする。図2(c)は導光板11の出光面11a、反射面11bの一部で光が反射する様子を模式的に示す。   In the present invention, such a shape is not provided, and the reflection surface 11b of the light guide plate 11 is a mirror surface. Now, as shown in FIG. 2A, the inclination angle formed by the reflecting surface 11b of the light guide plate 11 with respect to the light exit surface 11a is “α”. FIG. 2C schematically shows how light is reflected by a part of the light exit surface 11 a and the reflection surface 11 b of the light guide plate 11.

図示のように、ある光Lが出光面11aに対して角度Xで入射し、全反射したとすると、反射面11bは出光面11aに対して傾斜角αを有するので、反射面11bに対しては、(X+α)の角度を有する。この光が反射面11bにより再度全反射したとすると、11aに入射する角度は(x+2α)となる。このように出光面、反射面による反射を繰り返すことで、2αだけ増加することになる。よって、光Lは導光板11内の反射面11bで複数回反射されることにより方向が徐々に変化し、やがて出光面11aに対する角度が臨界角を超えると出光面11aから出射することになる。従って、傾斜角αを適切に定めることにより、反射面11bを鏡面(即ち、特殊なパターン形状を設けない)としても、導光板11から光を出射させることができる。   As shown in the figure, when a certain light L is incident on the light exit surface 11a at an angle X and totally reflected, the reflection surface 11b has an inclination angle α with respect to the light exit surface 11a. Has an angle of (X + α). If this light is totally reflected again by the reflecting surface 11b, the angle of incidence on 11a is (x + 2α). Thus, by repeating the reflection by the light emitting surface and the reflecting surface, the number increases by 2α. Therefore, the light L is reflected a plurality of times by the reflecting surface 11b in the light guide plate 11, and the direction gradually changes. When the angle with respect to the light emitting surface 11a eventually exceeds the critical angle, the light L is emitted from the light emitting surface 11a. Therefore, by appropriately determining the inclination angle α, light can be emitted from the light guide plate 11 even if the reflecting surface 11b is a mirror surface (that is, no special pattern shape is provided).

上述のように、導光板11内の光は反射を繰り返すことにより角度2αずつ方向が変化するので、導光板11から光を出射させるためには傾斜角α>0でなければならない。一方、傾斜角αが大きすぎると導光板11の楔形状が急峻すぎて好ましくない。経験的には、傾斜角は0<α<5度程度が好適であり、特に傾斜角α=2程度が最適である。   As described above, the direction of the light in the light guide plate 11 is changed by the angle 2α by repeating the reflection. Therefore, in order to emit the light from the light guide plate 11, the inclination angle α> 0 must be satisfied. On the other hand, if the inclination angle α is too large, the wedge shape of the light guide plate 11 is too steep, which is not preferable. Empirically, the inclination angle is preferably about 0 <α <5 degrees, and the inclination angle α = 2 is particularly optimal.

上記の説明から理解されるように、反射面11bによる1回の反射によって光は2αずつ角度を変えていくのであるから、傾斜角を小さく設定すれば、導光板11内で反射を繰り返す光の角度は少しずつ変化していくことになる。よって、出光面11aと光の角度が臨界角を超えたときでも臨界角を大きく超えることなくなり、多くの光が臨界角を少し超えた程度の角度で出光していくことになる。よって、出光面11aから出光した光の方向は、出光面11aに対して平行に近い所定の角度範囲内に集中する。即ち導光板11から出射する光に意図的に指向性をもたせることができる。逆にいえば、傾斜角αを適切に決定すれば、出光面11aから出ていく光の方向をかなり効率的に制御し、特定の方向に集中させることができる。よって、その方向の光を、出光面11aに対して垂直な方向に向けるようにプリズムシート14の凹凸形状を設定すれば、導光板11から出光した光を高い効率で垂直方向、即ち液晶装置2などの被照明物の方向に向けることができる。経験的には、前述のように傾斜角を0<α<5度の範囲に設定した場合、導光板11の出光面11aから出射する光が出光面11aとなす角(図2(a)における角度「γ」)のピークは15〜20度程度となる。この場合、プリズムシート14を通過する光の方向を導光板11の出光面11aに対して略垂直とするためには、プリズムシート14の凹凸形状を構成する三角形の頂角「β」は、60<β<70の範囲内が好ましく、特にβ=65程度が最適である。   As understood from the above description, the light changes its angle by 2α by one reflection by the reflection surface 11b. Therefore, if the inclination angle is set to be small, the light that repeats reflection in the light guide plate 11 will be described. The angle will change little by little. Therefore, even when the angle between the light exit surface 11a and the light exceeds the critical angle, the critical angle is not greatly exceeded, and a lot of light is emitted at an angle slightly exceeding the critical angle. Therefore, the direction of the light emitted from the light exit surface 11a is concentrated within a predetermined angle range that is nearly parallel to the light exit surface 11a. That is, the directivity can be intentionally given to the light emitted from the light guide plate 11. In other words, if the inclination angle α is appropriately determined, the direction of light exiting from the light exit surface 11a can be controlled fairly efficiently and concentrated in a specific direction. Therefore, if the concave / convex shape of the prism sheet 14 is set so that the light in that direction is directed in a direction perpendicular to the light exit surface 11a, the light emitted from the light guide plate 11 can be efficiently emitted in the vertical direction, that is, the liquid crystal device 2. Can be directed toward the object to be illuminated. Empirically, when the inclination angle is set in the range of 0 <α <5 degrees as described above, the angle formed by the light exiting surface 11a of the light guide plate 11 and the light exiting surface 11a (in FIG. 2A). The peak of the angle “γ” is about 15 to 20 degrees. In this case, in order to make the direction of light passing through the prism sheet 14 substantially perpendicular to the light exit surface 11 a of the light guide plate 11, the apex angle “β” of the triangle that forms the concavo-convex shape of the prism sheet 14 is 60 The range of <β <70 is preferable, and in particular, β = 65 is optimal.

以上説明したように、本発明では、導光板11の反射面11bを平面かつ鏡面とし、特殊な形状加工を施さないので、導光板11を製作するための金型の製作が単純化され、コスト及び時間の両方を改善することができる。また、導光板11の出光面11aと反射面11bのなす傾斜角α、さらにはプリズムシート14の凹凸形状を規定する三角形の頂角βの値を適切に決定することにより、光源からの光を高い効率で利用することができる。
[第2実施形態]
次に、本発明の第2実施形態について説明する。第2実施形態は、上述の第1実施形態において、導光板11の出光面11a又は反射面11bに光拡散のための加工を施すことを特徴とする。上述のように、第1実施例では導光板11の出光面11a及び反射面11bの両方を鏡面とするので、光の拡散性、特に入光端面11cに平行な方向における光の拡散性が不足しやすくなる。このため、光源12として複数のLEDなどの点光源を使用すると、LEDの前が明るくなるとともにLEDの間が暗くなり、明るさのムラが生じる(「ホットスポット現象」などと呼ばれる。)。図3に複数のLEDを備える光源12を使用した場合の導光板11の明るさの状態を模式的に示す。図3において、光源12は4個のLED12aをその長さ方向に併設してなる。各LED12aは導光板11の入光端面11cの方向に光を出射するので、導光板11の入光端面11c近傍には図示のように明るい領域(ホットスポット)16が生じ、その間は暗い領域となる。各LED12aからの光は導光板11の長さ方向、即ち入光端面11cから反対側の端面11dへ向かう方向に進むので、導光板11の長さ方向(方向B)には輝度ムラは比較的生じにくい。しかし、導光板11の出光面11a及び反射面11bはいずれも鏡面であるので、導光板11の横方向(方向A)、即ち入光端面11cに平行な方向には光の拡散性が低くなり、輝度ムラが生じやすい。
As described above, in the present invention, since the reflecting surface 11b of the light guide plate 11 is a flat and mirror surface and is not subjected to special shape processing, the manufacture of the mold for manufacturing the light guide plate 11 is simplified and the cost is reduced. Both time and time can be improved. Further, by appropriately determining the inclination angle α formed by the light exit surface 11a and the reflection surface 11b of the light guide plate 11 and the apex angle β of the triangle that defines the uneven shape of the prism sheet 14, the light from the light source can be determined. It can be used with high efficiency.
[Second Embodiment]
Next, a second embodiment of the present invention will be described. The second embodiment is characterized in that in the first embodiment described above, the light exit surface 11a or the reflection surface 11b of the light guide plate 11 is processed for light diffusion. As described above, in the first embodiment, since both the light exit surface 11a and the reflection surface 11b of the light guide plate 11 are mirror surfaces, the light diffusibility, particularly the light diffusivity in the direction parallel to the light incident end surface 11c is insufficient. It becomes easy to do. For this reason, when a point light source such as a plurality of LEDs is used as the light source 12, the front of the LED becomes bright and the space between the LEDs becomes dark, resulting in uneven brightness (referred to as “hot spot phenomenon” or the like). FIG. 3 schematically shows the brightness state of the light guide plate 11 when the light source 12 including a plurality of LEDs is used. In FIG. 3, the light source 12 includes four LEDs 12a in the length direction. Since each LED 12a emits light in the direction of the light incident end surface 11c of the light guide plate 11, a bright region (hot spot) 16 is generated in the vicinity of the light incident end surface 11c of the light guide plate 11, and a dark region is formed between them. Become. Since the light from each LED 12a travels in the length direction of the light guide plate 11, that is, the direction from the light incident end surface 11c toward the opposite end surface 11d, the luminance unevenness is relatively small in the length direction of the light guide plate 11 (direction B). Hard to occur. However, since both the light exit surface 11a and the reflection surface 11b of the light guide plate 11 are mirror surfaces, the light diffusibility is low in the lateral direction (direction A) of the light guide plate 11, that is, in the direction parallel to the light incident end surface 11c. , Uneven brightness tends to occur.

そこで、本実施形態では導光板11の出光面11a及び反射面11bの少なくとも一方に光拡散のための凹凸形状を形成する。第2実施例に係る照明装置の構成を図4に模式的に示す。図4(a)は、照明装置の光源12及び導光板11の平面図である。図示のように導光板11には、その出光面11a及び反射面11bの少なくとも一方にストライプ状の微少な凹部17を複数形成する。各凹部17は、導光板11の長さ方向B、即ち入光端面11cと略垂直な方向に略平行に設けられている。また、複数の凹部17は導光板11の幅方向Aのほぼ全体にわたって設けられている。   Therefore, in this embodiment, an uneven shape for light diffusion is formed on at least one of the light exit surface 11a and the reflection surface 11b of the light guide plate 11. FIG. 4 schematically shows the configuration of the illumination device according to the second example. FIG. 4A is a plan view of the light source 12 and the light guide plate 11 of the illumination device. As shown in the figure, the light guide plate 11 is formed with a plurality of fine stripe-shaped concave portions 17 on at least one of the light exit surface 11a and the reflection surface 11b. Each concave portion 17 is provided substantially parallel to the length direction B of the light guide plate 11, that is, the direction substantially perpendicular to the light incident end face 11c. The plurality of recesses 17 are provided over substantially the entire width direction A of the light guide plate 11.

図4(b)に、図4(a)における導光板11の切断面X1−X2における断面図を示す。図示のように、各凹部17は全てが同一形状である必要はなく、光の拡散性を高めるためにはむしろランダムな形状又はそれぞれ異なる形状であることが好ましい。このように導光板11の長さ方向にストライプ状の複数の凹部17を形成することにより、導光板11に対して光源12から入射した光を、入光端面11cと平行な方向Aに拡散することができる(図4(b)を参照)。よって、導光板11の出光面11a及び反射面11bをともに平面かつ鏡面とした場合でも、それらの一方に上記の微細なストライプ状の凹部17を複数形成することにより、導光板11の幅方向の拡散性を向上し、輝度ムラなどを防止することができる。なお、この微細な凹部17は実際には導光板11の表面をざらつかせる加工を施すものであり、これにより導光板の出光面11a及び反射面11bに特殊なパターン形状を形成するものではないのでコストや製造時間への影響は少なく、また導光板の平坦性を損なうこともない。   FIG. 4B is a cross-sectional view taken along the cutting plane X1-X2 of the light guide plate 11 in FIG. As shown in the figure, it is not necessary for all the concave portions 17 to have the same shape, and it is preferable that the concave portions 17 have a random shape or a different shape in order to improve the light diffusibility. By forming the plurality of stripe-shaped recesses 17 in the length direction of the light guide plate 11 in this way, the light incident from the light source 12 on the light guide plate 11 is diffused in the direction A parallel to the light incident end face 11c. (See FIG. 4 (b)). Therefore, even when the light exit surface 11a and the reflection surface 11b of the light guide plate 11 are both flat and mirror surfaces, by forming a plurality of the fine stripe-shaped concave portions 17 on one of them, the width direction of the light guide plate 11 can be increased. Diffusivity can be improved and uneven brightness can be prevented. The fine recesses 17 are actually processed to roughen the surface of the light guide plate 11, and thus do not form special pattern shapes on the light output surface 11a and the reflection surface 11b of the light guide plate. Therefore, there is little influence on cost and manufacturing time, and the flatness of the light guide plate is not impaired.

なお、第2実施形態による照明装置は、上述のように導光板に拡散のための凹部を形成した点以外は第1実施形態による照明装置と基本的に同様である。   The illumination device according to the second embodiment is basically the same as the illumination device according to the first embodiment, except that the light guide plate is provided with a recess for diffusion as described above.

次に、上述したストライプ状の凹部の形成方法について説明する。上述の凹部17は、導光板の射出成形や金型成形を行う際に、使用する金型を研削加工などによって加工して微細な凹凸を形成し、それを用いて射出成形などを行うことにより形成される。研削加工はストライプ状の凹部を形成するのに適しており、グラインダ(砥石)を用いて容易に高精度で形成することができる。具体的には、図5に示すように、円形のグラインダ31を回転させ、グラインダ31に接するように載置した金型30を移動させて金型の表面を研削加工する。こうして、金型30自体にストライプ状の凹凸が形成される。   Next, a method for forming the above-described stripe-shaped recess will be described. The above-mentioned concave portion 17 is formed by processing the mold to be used by grinding or the like to form fine irregularities when performing injection molding or mold molding of the light guide plate, and performing injection molding or the like using the mold. It is formed. Grinding is suitable for forming striped recesses, and can be easily formed with high accuracy using a grinder. Specifically, as shown in FIG. 5, the circular grinder 31 is rotated, the mold 30 placed so as to be in contact with the grinder 31 is moved, and the surface of the mold is ground. Thus, striped irregularities are formed on the mold 30 itself.

図6に、そうして製作された金型30を用いた導光板11の製造方法を模式的に示す。図6(a)のように、研削加工によりストライプ状の凹凸を形成した金型30と、相手側の金型32との間に射出などにより樹脂を封入する。そして樹脂が硬化した後で、金型30及び32を分離し、内部の樹脂により構成される導光板11を取り出す。こうして、ストライプ状の複数の凹部17が形成された導光板11が得られる。   In FIG. 6, the manufacturing method of the light-guide plate 11 using the metal mold | die 30 manufactured in that way is shown typically. As shown in FIG. 6A, a resin is sealed between a mold 30 in which stripe-shaped irregularities are formed by grinding and a mating mold 32 by injection or the like. And after resin hardens | cures, metal mold | die 30 and 32 are isolate | separated and the light-guide plate 11 comprised with internal resin is taken out. In this way, the light guide plate 11 having a plurality of stripe-shaped recesses 17 is obtained.

以上説明したように、第2実施形態では、導光板11の出光面11a及び反射面11bの少なくとも一方にストライプ状の複数の凹部17を設けたので、入光端面11cに平行な方向における光の拡散性を向上させることができる。よって、光源12のLED近傍に生じる明暗を除去することができ、また、導光板11の全体において入光端面11cに平行な方向における輝度ムラを低減することができる。これにより、当該照明装置を使用する液晶装置などの表示品質が向上するとともに、工数の削減、低コスト化などが図られる。また、LEDからの光の使用効率を改善することができるので、必要に応じて光源12に使用するLEDの数を削減することも可能となる。   As described above, in the second embodiment, since the plurality of stripe-shaped recesses 17 are provided on at least one of the light exit surface 11a and the reflection surface 11b of the light guide plate 11, light in a direction parallel to the light incident end surface 11c is provided. Diffusibility can be improved. Therefore, it is possible to remove the brightness and darkness generated in the vicinity of the LED of the light source 12, and to reduce luminance unevenness in the direction parallel to the light incident end face 11c in the entire light guide plate 11. As a result, the display quality of a liquid crystal device or the like that uses the lighting device is improved, and the number of steps and the cost can be reduced. Moreover, since the use efficiency of the light from LED can be improved, it becomes possible to reduce the number of LED used for the light source 12 as needed.

なお、上記の説明では、ストライプ状の凹部17を出光面11又は反射面11bに形成するとしたが、その代わりに又はそれに加えて、導光板11の入光端面11cに同様の凹部17を形成してもよい。また、凹部17は必ずしも導光板11の対象となる面全体に形成する必要はなく、部分的に形成しても構わない。   In the above description, the striped recesses 17 are formed on the light exit surface 11 or the reflection surface 11b. Instead of or in addition to this, the same recesses 17 are formed on the light incident end surface 11c of the light guide plate 11. May be. Further, the concave portion 17 is not necessarily formed on the entire target surface of the light guide plate 11 and may be formed partially.

本発明の第1実施形態に係る照明装置の概略構成を示す斜視図である。It is a perspective view which shows schematic structure of the illuminating device which concerns on 1st Embodiment of this invention. 照明装置の出光原理を示す図である。It is a figure which shows the light emission principle of an illuminating device. 点光源を用いた場合の導光板内の輝度分布を模式的に示す。The luminance distribution in the light-guide plate at the time of using a point light source is shown typically. 第2実施形態に係る導光板の構成を模式的に示す。The structure of the light-guide plate which concerns on 2nd Embodiment is shown typically. 導光板を作成する金型の研削加工の例を説明する図である。It is a figure explaining the example of the grinding process of the metal mold | die which produces a light-guide plate. 導光板の製作方法を示す図である。It is a figure which shows the manufacturing method of a light-guide plate.

符号の説明Explanation of symbols

2 液晶装置、 10 照明装置、 11 導光板、 12 光源、
13 反射シート、 14 プリズムシート、 17 凹部、 30 金型

2 liquid crystal device, 10 lighting device, 11 light guide plate, 12 light source,
13 reflection sheet, 14 prism sheet, 17 recess, 30 mold

Claims (7)

光を出射する出光面と、前記出光面と対向する反射面と、光源からの光が入射する入光端面とを備え、前記出光面と前記反射面との距離が前記入光端面から遠ざかるにつれて減少する楔形状の断面を有する導光板であって、
前記出光面及び前記反射面は少なくとも一方が平面かつ鏡面であり、前記出光面に対する前記反射面の傾斜角が0度より大きいことを特徴とする導光板。
A light exit surface that emits light, a reflective surface that faces the light exit surface, and a light incident end surface on which light from a light source is incident, and the distance between the light exit surface and the reflective surface becomes farther from the light incident end surface A light guide plate having a wedge-shaped cross section that decreases,
At least one of the light exit surface and the reflection surface is a plane and a mirror surface, and an inclination angle of the reflection surface with respect to the light exit surface is greater than 0 degree.
前記傾斜角が5度以下であることを特徴とする請求項1に記載の導光板。   The light guide plate according to claim 1, wherein the inclination angle is 5 degrees or less. 前記傾斜角が2度であることを特徴とする請求項1に記載の導光板。   The light guide plate according to claim 1, wherein the inclination angle is 2 degrees. 前記反射面及び前記出光面の少なくとも一方は、前記入光端面と略直交する方向に延びる複数の凹部が、前記入光端面の長さ方向に複数繰り返し形成されていることを特徴とする請求項1乃至3のいずれか一項に記載の導光板。   The at least one of the reflection surface and the light exit surface has a plurality of concave portions extending in a direction substantially orthogonal to the light entrance end surface, and a plurality of recesses are repeatedly formed in a length direction of the light entrance end surface. The light guide plate according to any one of 1 to 3. 前記複数の凹部は、前記入光端面と平行な方向における断面形状が異なることを特徴とする請求項4に記載の導光板。   The light guide plate according to claim 4, wherein the plurality of recesses have different cross-sectional shapes in a direction parallel to the light incident end surface. 請求項1乃至5のいずれか一項に記載の導光板と、
凹凸面が前記出光面と対向するように前記導光板と対向配置されたプリズムシートと、を備え、
前記プリズムシートの突部の頂角が60度〜70度の範囲内であることを特徴とする照明装置。
The light guide plate according to any one of claims 1 to 5,
A prism sheet disposed so as to face the light guide plate so that an uneven surface faces the light exit surface,
An illuminating device, wherein an apex angle of a projection of the prism sheet is in a range of 60 degrees to 70 degrees.
基板に電気光学物質を配置してなる電気光学基板と、
請求項6に記載の照明装置とを備え、
前記電気光学基板は、前記プリズムシートに対して前記導光板の反対側に配置されてなることを特徴とする記載の電気光学装置。
An electro-optic substrate formed by arranging an electro-optic material on the substrate;
A lighting device according to claim 6,
The electro-optical device according to claim 1, wherein the electro-optical substrate is disposed on the opposite side of the light guide plate with respect to the prism sheet.
JP2003418008A 2003-12-16 2003-12-16 Light guide plate and lighting system Withdrawn JP2005183030A (en)

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