JP2005228718A - Light guide plate - Google Patents

Light guide plate Download PDF

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JP2005228718A
JP2005228718A JP2004039086A JP2004039086A JP2005228718A JP 2005228718 A JP2005228718 A JP 2005228718A JP 2004039086 A JP2004039086 A JP 2004039086A JP 2004039086 A JP2004039086 A JP 2004039086A JP 2005228718 A JP2005228718 A JP 2005228718A
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light
guide plate
light guide
light source
incident surface
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JP4386750B2 (en
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Junji Miyashita
純司 宮下
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Citizen Electronics Co Ltd
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Citizen Electronics Co Ltd
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Priority to JP2004039086A priority Critical patent/JP4386750B2/en
Priority to CNB2005100082623A priority patent/CN100434988C/en
Priority to DE102005006585.6A priority patent/DE102005006585B4/en
Priority to KR1020050012192A priority patent/KR101013532B1/en
Priority to US11/058,411 priority patent/US7357557B2/en
Publication of JP2005228718A publication Critical patent/JP2005228718A/en
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  • Light Guides In General And Applications Therefor (AREA)
  • Liquid Crystal (AREA)
  • Planar Illumination Modules (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate of a surface light source preventing emission lines and bright spots near the light source, and uniformalizing intensity distribution of light after incidence into the light guide plate. <P>SOLUTION: The light guide plate is made of a platy translucent material with its side faces as light-incident faces and changing optical paths of light from the light source arranged in opposition to the light-incident faces, and irradiates surface illumination light on an illumination object from its top face. The plate has concavities and convexities formed on the light-incident faces consisting of a smoothly continuing curved surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は例えば液晶パネルを背面より照射する面状光源に用いられる導光板に関し、特に携帯電話等の小型の液晶パネルに適する面状光源用の導光板に関する。   The present invention relates to a light guide plate used for a planar light source that irradiates a liquid crystal panel from the back, for example, and more particularly to a light guide plate for a planar light source suitable for a small liquid crystal panel such as a mobile phone.

近年、ブック型のワードプロセッサやコンピュータ、又は携帯電話機、携帯TVのような小型、薄型の情報機器の表示装置として、薄型でしかも見易いバックライト機構を有する液晶表示装置が用いられている。このようなバックライト機構としては、液晶パネルを背後から全面にわたり照射する面状光源が用いられており、この面状光源としては蛍光ランプ又はＬＥＤ（発光ダイオード）よりなる光源と、その光束を液晶パネルに照射する面状の光束に変換する導光板よりなるものが一般的である。この中で、特に近年は、更なる小型、薄型化と長寿命化を目的として光源としてＬＥＤ等を用いた面状光源が多く使用されるようになってきている。また、これらの面状光源は光源を導光板の真下に配置する直下型と、光源を導光板の側方に配置するサイドライト型とに大別されるが、携帯電話機などの小型化・薄型化が重視される機器には、もっぱらサイドライト型が採用されている。   2. Description of the Related Art In recent years, a liquid crystal display device having a thin and easy-to-see backlight mechanism has been used as a display device for small and thin information devices such as book-type word processors, computers, mobile phones, and portable TVs. As such a backlight mechanism, a planar light source that irradiates the entire surface of the liquid crystal panel from behind is used. As this planar light source, a light source composed of a fluorescent lamp or an LED (light emitting diode) and a light flux of the liquid crystal are used. In general, a light guide plate that converts a planar light beam to be irradiated on the panel is used. Among these, particularly in recent years, a planar light source using an LED or the like as a light source has been increasingly used for the purpose of further miniaturization, thinning and long life. In addition, these planar light sources are roughly classified into a direct type in which the light source is disposed directly under the light guide plate and a side light type in which the light source is disposed on the side of the light guide plate. The sidelight type is adopted exclusively for the equipment where emphasis is placed on manufacturing.

以下、図を用いて従来技術におけるサイドライト型面状光源について説明する。図５は、従来技術におけるサイドライト型面状光源の要部を示す斜視図、図６は導光板の光入射面付近を示す部分拡大平面図である。図５に示すように、サイドライト型面状光源はその基本的な構成として、透明材料からなる略直方体の導光板１と、この導光板１の側方に配置される光源２として３個の発光ダイオード（ＬＥＤ）を備えている。   Hereinafter, the side light type planar light source in the prior art will be described with reference to the drawings. FIG. 5 is a perspective view showing a main part of a sidelight type planar light source in the prior art, and FIG. 6 is a partially enlarged plan view showing the vicinity of a light incident surface of a light guide plate. As shown in FIG. 5, the basic structure of the side light type planar light source is as follows. The light guide plate 1 is a substantially rectangular parallelepiped made of a transparent material, and three light sources 2 are arranged on the side of the light guide plate 1. A light emitting diode (LED) is provided.

導光板１は、液晶パネル７の裏面側に配置され、多くの場合、導光板１の下面側には光源２からの光を液晶パネル側に向かわせるための光反射シート（図示せず）が設けられている。さらに、導光板１の上面側には光源２からの光を均一に分散させるための拡散シート（図示せず）や光を集光させるためのプリズムシート（図示せず）が設けられている場合が多い。   The light guide plate 1 is disposed on the back side of the liquid crystal panel 7, and in many cases, a light reflecting sheet (not shown) for directing light from the light source 2 toward the liquid crystal panel is provided on the lower surface side of the light guide plate 1. Is provided. Furthermore, when the light guide plate 1 is provided with a diffusion sheet (not shown) for uniformly dispersing light from the light source 2 and a prism sheet (not shown) for condensing light on the upper surface side of the light guide plate 1. There are many.

導光板１は無色透明なプラスチック材等の透光部材よりなる板状で略直方体の形状をしており、その上面を光出射面１ｂとし、導光板１の１つの側面を光入射面１ａとし、この光入射面１ａと対向する位置に光源２が配置されている。光源２から照射された照射光３は光入射面１ａから入射した後、光出射面１ｂに向かって導光板内部で反射を繰り返しながら伝搬し、臨界角以下の成分を導光板１の光出射面１ｂから照明光４として外部に出射する。外部に出射した照明光４は液晶パネル７を背後から照明する。   The light guide plate 1 is a plate-like shape made of a transparent member such as a colorless and transparent plastic material and has a substantially rectangular parallelepiped shape. The upper surface of the light guide plate 1 is a light emitting surface 1b, and one side surface of the light guide plate 1 is a light incident surface 1a. The light source 2 is disposed at a position facing the light incident surface 1a. Irradiation light 3 emitted from the light source 2 is incident from the light incident surface 1a, and then propagates while repeating reflection inside the light guide plate toward the light output surface 1b, and a component having a critical angle or less is transmitted to the light output surface of the light guide plate 1. The light is emitted from 1b as illumination light 4. The illumination light 4 emitted to the outside illuminates the liquid crystal panel 7 from behind.

このようなサイドライト型面状光源においては、図６に示すように光源２からの照射光３が入射角ａで導光板１に入射する際、光の屈折が生じ、導光板１の内部に入射した後の光５となって法線となす角ｂで入射する。導光板１の材料であるアクリル樹脂やポリカーボネイト樹脂等は空気より屈折率が大きいため、法線となす角ｂは入射角ａよりも小さくなる。この時、光源２より照射される照射光３は発光ダイオード（ＬＥＤ）自身の指向性をもっており、この指向性を持った照射光３が光入射面１ａで屈折して入射するため導光板１の内部に入射した後の光５の指向性は光源２の照射光の指向性より狭くなる。   In such a sidelight type planar light source, as shown in FIG. 6, when the irradiation light 3 from the light source 2 enters the light guide plate 1 at an incident angle a, light is refracted, and the light is generated inside the light guide plate 1. The incident light 5 is incident at an angle b formed with the normal. Since the acrylic resin, polycarbonate resin, or the like, which is the material of the light guide plate 1, has a refractive index larger than that of air, the angle b formed with the normal line is smaller than the incident angle a. At this time, the irradiation light 3 irradiated from the light source 2 has the directivity of the light emitting diode (LED) itself, and the irradiation light 3 having this directivity is refracted and incident on the light incident surface 1a. The directivity of the light 5 after entering the inside becomes narrower than the directivity of the irradiation light of the light source 2.

図７は、光源２からの照射光３と導光板１の内部に入射した後の光５の指向性を示したものである。図７（ａ）は光源２としての発光ダイオード（ＬＥＤ）自身の照射光３の指向性を示し、図７（ｂ）は光源２の照射光３が導光板１の光入射面1ａから入射し、導光板１の内部に入射した後の光５の指向性を示している。光源２としての点光源である発光ダイオード（ＬＥＤ）自身の照射光３は図７（ａ）の曲線１０１に示すような指向性を有する。この指向性を有する照射光３を導光板１の内部に入射した後の光５の指向性は図７（ｂ）の曲線１０２に示すような指向性を示し、前述したように、導光板１に入射した後の光５の指向性の方がＬＥＤ自身の照射光３の指向性より狭くなる。このため光入射面を平坦な面により形成した従来技術の導光板１においては、導光板１に入射した後の光５の強度分布が不均一になるという問題があった。   FIG. 7 shows the directivity of the irradiation light 3 from the light source 2 and the light 5 after entering the light guide plate 1. FIG. 7A shows the directivity of the irradiation light 3 of the light emitting diode (LED) itself as the light source 2, and FIG. 7B shows the irradiation light 3 of the light source 2 incident from the light incident surface 1 a of the light guide plate 1. The directivity of the light 5 after entering the inside of the light guide plate 1 is shown. The irradiation light 3 of the light-emitting diode (LED) itself that is a point light source as the light source 2 has directivity as shown by a curve 101 in FIG. The directivity of the light 5 after the irradiation light 3 having directivity is incident on the inside of the light guide plate 1 shows the directivity as shown by the curve 102 in FIG. 7B. As described above, the light guide plate 1 The directivity of the light 5 after entering the LED becomes narrower than the directivity of the irradiation light 3 of the LED itself. For this reason, the conventional light guide plate 1 in which the light incident surface is formed as a flat surface has a problem that the intensity distribution of the light 5 after entering the light guide plate 1 becomes non-uniform.

このような問題を解決するために側面を光入射面とし、この光入射面に複数の均一なプリズムよりなる凹凸を設けた導光板の例が開示されている。（例えば、特許文献１参照。）。この導光板は光入射面の形状が前述の導光板１と異なっており、その他の基本的な構成は前述の導光板１と同様であるため、この光入射面について説明し、その他の説明は省略する。図８は導光板を示し、図８（ａ）は導光板の平面図、図８（ｂ）は図８（ａ）のＡ部における光入射面を示す部分拡大斜視図である。また、図９は、図８（ａ）のＡ部における光入射面を示す部分拡大平面図である。以下、この導光板について図に基づいて説明する。   In order to solve such a problem, an example of a light guide plate is disclosed in which a side surface is a light incident surface and the light incident surface is provided with irregularities made of a plurality of uniform prisms. (For example, refer to Patent Document 1). This light guide plate is different from the light guide plate 1 in the shape of the light incident surface, and the other basic configuration is the same as that of the light guide plate 1 described above. Omitted. 8 shows a light guide plate, FIG. 8 (a) is a plan view of the light guide plate, and FIG. 8 (b) is a partially enlarged perspective view showing a light incident surface in part A of FIG. 8 (a). FIG. 9 is a partially enlarged plan view showing a light incident surface in a portion A of FIG. Hereinafter, the light guide plate will be described with reference to the drawings.

図８に示すように、導光板１１の側面の光入射面１１ａには導光板１１の厚み方向に走る複数のプリズム状の凸部１２が均一に分布して凹凸が形成されている。ここで、凸部１２と凸部１２の間は導光板１１の厚み方向に略並行な複数の尺状の平面部１３となっている。また、プリズム状の凸部１２は１対の斜面１２ａ、１２ｂを接続して断面が略三角形形状に形成されている。   As shown in FIG. 8, the light incident surface 11 a on the side surface of the light guide plate 11 has a plurality of prism-like convex portions 12 that run in the thickness direction of the light guide plate 11 and are unevenly formed. Here, between the convex part 12 and the convex part 12, there are a plurality of scale-like plane parts 13 substantially parallel to the thickness direction of the light guide plate 11. The prism-shaped convex portion 12 has a substantially triangular cross section by connecting a pair of inclined surfaces 12a and 12b.

この導光板１１においては図９に示すように光入射面１１ａに設けたプリズム状の凸部１２における１対の斜面１２ａ、１２ｂの効果により、光入射面１１ａを擬似的平面と見なした時、光入射面１１ａに入射する入射角が大きい光に対しても導光板１１の内部に入射した後の光１５、１７の法線となす角を前述の導光板１よりも増大させ、結果として光入射面１１ａ全体に関し、導光板１１内部への入射した後の光の角度範囲を増大させることができる。また、平面部１３については前述の導光板１における平面状の光入射面１ａの場合と同様、導光板１１の内部に入射した後の光１６となって導光板１１の内部に入射される。   In the light guide plate 11, as shown in FIG. 9, when the light incident surface 11a is regarded as a pseudo plane due to the effect of the pair of inclined surfaces 12a and 12b in the prism-shaped convex portion 12 provided on the light incident surface 11a. The angle formed by the normal lines of the light 15 and 17 after entering the light guide plate 11 even for light having a large incident angle incident on the light incident surface 11a is larger than that of the light guide plate 1 as a result. With respect to the entire light incident surface 11a, the angular range of light after entering the light guide plate 11 can be increased. Further, the planar portion 13 is incident on the light guide plate 11 as light 16 after entering the light guide plate 11 as in the case of the planar light incident surface 1 a of the light guide plate 1 described above.

特開平２００２−１９６１５１号公報（第３−５頁、図２）Japanese Patent Laid-Open No. 2002-196151 (page 3-5, FIG. 2)

しかしながら、前述の導光板１１においては図９に示すようにプリズム状の凸部１２と平面部１３とによって形成される光入射面１１ａの形状が不連続な形状であるため光入射面１１ａから導光板１１の内部に入射した後の光１５、１６、１７の指向性は図１０に示すような歪んだ形状となる。図９において導光板１１の平面部１３から導光板１１の内部に入射した後の光１６は、図１０における曲線１０４に示す指向性を示す。また、図９において凸部１２の一方の斜面１２ａから導光板１１の内部に入射した後の光１７は、図１０における曲線１０５に示す指向性を示す。また、図９において凸部１２の他方の斜面１２ｂから導光板１１の内部に入射した後の光１５は、図１０における曲線１０３に示す指向性を示す。このように光入射面１１ａから導光板１１の内部に入射した後の光１５、１６、１７の指向性が歪んだ形状となり、この指向性に対応して光の強度分布が不均一化するという問題があった。また、このように光の強度分布が不均一な導光板を用いたサイドライト型面状光源による液晶表示装置においては、光源からの輝線や、光源からの照射光が干渉し合って輝点が生じ表示画面に輝度ムラが発生し表示画面の品位が著しく低下するという問題があった。   However, in the light guide plate 11 described above, the light incident surface 11a formed by the prism-shaped convex portion 12 and the flat portion 13 is discontinuous as shown in FIG. The directivity of the light 15, 16, 17 after entering the inside of the optical plate 11 has a distorted shape as shown in FIG. 10. 9, the light 16 after entering the light guide plate 11 from the flat portion 13 of the light guide plate 11 exhibits the directivity indicated by the curve 104 in FIG. 9, the light 17 after entering the light guide plate 11 from one inclined surface 12a of the convex portion 12 exhibits the directivity indicated by the curve 105 in FIG. In addition, the light 15 after entering the light guide plate 11 from the other inclined surface 12b of the convex portion 12 in FIG. 9 exhibits the directivity indicated by the curve 103 in FIG. Thus, the directivity of the light 15, 16, 17 after entering the light guide plate 11 from the light incident surface 11 a is distorted, and the light intensity distribution becomes non-uniform corresponding to this directivity. There was a problem. In addition, in such a liquid crystal display device using a side-light type planar light source using a light guide plate with a non-uniform light intensity distribution, bright lines from the light source and light emitted from the light source interfere with each other to create a bright spot. As a result, there is a problem that luminance unevenness occurs on the display screen and the quality of the display screen is remarkably lowered.

（発明の目的）
本発明の目的は、上記従来技術における課題を解決して光源付近での輝線や輝点を防止し、光の強度分布を均一化することができる面状光源の導光板を提供することにある。 (Object of invention)
An object of the present invention is to provide a light guide plate for a planar light source that solves the problems in the prior art described above, prevents bright lines and bright spots near the light source, and makes the light intensity distribution uniform. .

上記目的を達成するために本発明の導光板は、板状の透光材よりなり、その側面を光入射面とし該光入射面に対向して配置された光源からの光を光路変換してその上面から照明対象物に対し面状の照明光を出射する導光板において、導光板の光入射面に滑らかに連続した曲面からなる凹凸が形成されていることを特徴とする。   In order to achieve the above object, the light guide plate of the present invention is made of a plate-shaped light-transmitting material, and its side surface is used as a light incident surface, and light from a light source disposed opposite to the light incident surface is converted into an optical path. In the light guide plate that emits planar illumination light from the upper surface to the illumination object, the light incident surface of the light guide plate is formed with unevenness formed of a smoothly continuous curved surface.

また、凹凸は滑らかな曲面からなる凹部と滑らかな曲面からなる凸部とが導光板の光入射面の長手方向に交互に繰り返し形成されていることを特徴とする。
また、曲面は２次曲面からなることを特徴とする。
また、曲面を粗面にしたことを特徴とする。
また、導光板は略直方体の形状をなすことを特徴とする。 Further, the concave and convex portions are characterized in that concave portions made of smooth curved surfaces and convex portions made of smooth curved surfaces are alternately and repeatedly formed in the longitudinal direction of the light incident surface of the light guide plate.
In addition, the curved surface is a quadratic curved surface.
Further, the curved surface is roughened.
The light guide plate has a substantially rectangular parallelepiped shape.

以上のように本発明の導光板は、その側面を光入射面とし、光入射面の形状を連続した凹凸の滑らかな曲面とすることにより導光板内部に入射した後の光の指向性を滑らかに補正することができる。これにより、導光板に入射した後の光の強度分布が均一化され光源付近での輝線や輝点を防止することができる。この結果、本発明の導光板と発光ダイオードとにより高品位のサイドライト型面状光源を構成することができる。さらに本発明の導光板を用いたサイドライト型面状光源により液晶表示パネルを照明すれば、液晶表示装置の表示画面における輝度ムラを低減して高品位の表示画面を表示することができる。   As described above, the light guide plate of the present invention has a light incident surface as its side surface, and the light incident surface has a smooth curved surface with continuous irregularities, thereby smoothing the directivity of light after entering the light guide plate. Can be corrected. Thereby, the intensity distribution of the light after entering the light guide plate is made uniform, and bright lines and bright spots in the vicinity of the light source can be prevented. As a result, a high-quality side light type planar light source can be configured by the light guide plate and the light emitting diode of the present invention. Further, if the liquid crystal display panel is illuminated by a sidelight type planar light source using the light guide plate of the present invention, it is possible to reduce the luminance unevenness on the display screen of the liquid crystal display device and display a high quality display screen.

以下、本発明の実施形態について図１から図４を参照して詳細に説明する。図１は本実施の形態の導光板を用いたサイドライト型面状光源の示す図であり、図１（ａ）は平面図、図１（ｂ）は図１（ａ）のＡ−Ａ断面図である。本実施形態における導光板は光入射面に特徴があり、その基本的な構成は前述の従来技術と類似している。したがって、従来例同様な構成要素については同一番号を付与し説明を省略する。   Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 4. 1A and 1B are diagrams showing a sidelight type planar light source using the light guide plate of the present embodiment. FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along line AA in FIG. FIG. The light guide plate in the present embodiment is characterized by a light incident surface, and its basic configuration is similar to the above-described prior art. Therefore, the same components as those in the conventional example are given the same reference numerals and the description thereof is omitted.

図１に示すように本実施形態における面状光源は導光板２１と光源２として３個のＬＥＤを備えている。導光板２１は透光性を有するプラスチック材、例えばアクリル樹脂等を射出成形して板状で略直方体形状に形成され、その上面は光出射面２１ｂとなっている。光出射面２１ｂと対向する下面２１ｃには、光源２からの照射光が導光板２１内に入射した後の光２６を光出射面２１ｂに向けて反射させるための手段として、その表面に複数の微小なシボ又は複数個の半球状ドット等が設けられ下面２１ｃは光反射面となっている。   As shown in FIG. 1, the planar light source in this embodiment includes a light guide plate 21 and three LEDs as the light source 2. The light guide plate 21 is formed into a substantially rectangular parallelepiped shape by injection molding of a light-transmitting plastic material such as acrylic resin, and the upper surface thereof is a light emitting surface 21b. The lower surface 21c facing the light exit surface 21b has a plurality of surfaces on the surface as means for reflecting the light 26 after the irradiation light from the light source 2 enters the light guide plate 21 toward the light exit surface 21b. A small grain or a plurality of hemispherical dots are provided, and the lower surface 21c is a light reflecting surface.

また、導光板２１は、その１つの側面を光入射面２１ａとし、この光入射面２１ａと対向する位置に光源２が配置されている。光源２の照射光は図１（ｂ）に示すように光入射面２１ａから入射した後、光出射面２１ｂに向かって導光板２１内部で反射を繰り返しながら伝搬し、臨界角以下の成分を導光板２１の光出射面２１ｂから照明光２５として外部に出射する。外部に出射した照明光２５は液晶パネル７を背後から照明する。これにより本実施形態におけるサイドライト型面状光源は、この導光板２１の光出射面２１ｂに発光面を形成して、光源２より照射された照射光により面状光源を形成するようになされている。   The light guide plate 21 has one side surface as a light incident surface 21a, and the light source 2 is disposed at a position facing the light incident surface 21a. The light emitted from the light source 2 is incident from the light incident surface 21a as shown in FIG. 1 (b), and then propagates while being repeatedly reflected inside the light guide plate 21 toward the light emitting surface 21b, and guides components below the critical angle. The light is emitted to the outside as illumination light 25 from the light emitting surface 21 b of the light plate 21. The illumination light 25 emitted to the outside illuminates the liquid crystal panel 7 from behind. As a result, the side light type planar light source in the present embodiment forms a light emitting surface on the light emitting surface 21b of the light guide plate 21, and forms a planar light source by the irradiation light emitted from the light source 2. Yes.

図２は図１のＢ部の拡大図であり、図２（ａ）は導光板２１の光入射面２１ａを示す部分拡大平面図、図２（ｂ）は光入射面２１ａの部分拡大斜視図である。図２に示すように、導光板２１の光入射面２１ａには導光板２１の厚み方向に延長される滑らかな曲面からなる凸部２２と、同じく厚み方向に延長される滑らかな曲面からなる凹部２３とが導光板２１の光入射面２１ａの長手方向に交互に繰り返し形成され、滑らかに連続した曲面からなる凹凸が形成されている。ここでこの凹凸は、凸部２２と凹部２３とが直接接続して形成される。さらに凸部２２と凹部２３とは滑らかな２次曲面で形成されており、導光板２１の厚み方向に一定の断面形状により形成されている。したがって凸部２２と凹部２３との横断面形状は２次曲線となる。   2 is an enlarged view of part B of FIG. 1, FIG. 2 (a) is a partially enlarged plan view showing a light incident surface 21a of the light guide plate 21, and FIG. 2 (b) is a partially enlarged perspective view of the light incident surface 21a. It is. As shown in FIG. 2, the light incident surface 21 a of the light guide plate 21 has a convex portion 22 made of a smooth curved surface extending in the thickness direction of the light guide plate 21 and a concave portion made of a smooth curved surface similarly extended in the thickness direction. 23 are alternately and repeatedly formed in the longitudinal direction of the light incident surface 21 a of the light guide plate 21, thereby forming unevenness including a smoothly continuous curved surface. Here, the unevenness is formed by directly connecting the convex portion 22 and the concave portion 23. Further, the convex portion 22 and the concave portion 23 are formed with smooth secondary curved surfaces, and are formed with a constant cross-sectional shape in the thickness direction of the light guide plate 21. Therefore, the cross-sectional shape of the convex portion 22 and the concave portion 23 is a quadratic curve.

この２次曲線については特に限定されるものではないが、本実施形態においては、図３に示すように、ｘ軸とｙ軸の交点２４を中心とし、ｘ軸方向の半径Ｃ、ｙ軸方向の半径Ｄでｘ２／Ｃ２＋ｙ２／Ｄ２＝１の式で表される楕円２７の楕円弧からなる２次曲線で凸部２２と凹部２３との横断面形状を形成した。即ち、楕円２７の中心２４を通るｙ軸で楕円２７を分断し、一方の楕円弧からなる２次曲線を凸部２２の横断面形状とし、他方の楕円弧からなる２次曲線を凹部２３の横断面形状としたものである。また、この時の楕円２７のｙ軸方向が光入射面２１ａを巨視的に平面と見なした場合、この平面と平行となるように凸部２２と凹部２３との形状が形成される。さらに、この楕円２７の半径Ｃ、Ｄは３０〜５００μｍの範囲で所定の値に設定されることが好ましい。 The quadratic curve is not particularly limited. In the present embodiment, as shown in FIG. 3, the radius C in the x-axis direction and the y-axis direction are centered on the intersection 24 of the x-axis and the y-axis. The cross-sectional shape of the convex part 22 and the concave part 23 was formed by a quadratic curve composed of an elliptical arc of an ellipse 27 represented by an equation of x 2 / C 2 + y 2 / D 2 = 1 with a radius D of. That is, the ellipse 27 is divided by the y-axis passing through the center 24 of the ellipse 27, a quadratic curve made of one elliptical arc is used as the cross-sectional shape of the convex portion 22, and a quadratic curve made of the other elliptical arc is taken as the cross-sectional shape of the concave portion 23. It is a shape. Further, when the y-axis direction of the ellipse 27 at this time regards the light incident surface 21 a as a macroscopic plane, the shapes of the convex portions 22 and the concave portions 23 are formed so as to be parallel to the plane. Further, the radii C and D of the ellipse 27 are preferably set to predetermined values in the range of 30 to 500 μm.

以上のように本実施形態における導光板２１は、図２（ａ）に示すように連続した凹凸の滑らかな２次曲線からなる光入射面２１ａより光源２の照射光を入射することによって、導光板２１の内部に入射した後の光２６の強度分布が均一化され、その指向性が図４（ａ）の曲線１０６に示すような滑らかな指向性に補正される。これによって光源２付近での輝線や輝点を防止することができる。尚、図４（ｂ）、図４（ｃ）に示す曲線１０７、１０８は、楕円２７の半径Ｃ、Ｄの比であるＤ／Ｃの値を変え、光入射面２１ａを形成する凸部２２と凹部２３の形状を変化させた時の導光板２１の内部に入射した後の光２６の指向性を示したものである。このように、凸部２２と凹部２３との形状を変化させることにより導光板２１の内部に入射した後の光２６の指向性を制御することができる。したがって導光板２１と光源２との位置関係等に合わせて楕円２７の半径Ｃ、Ｄの比であるＤ／Ｃの値を変えることによって光入射面２１ａの形状を最適化し、光入射面２１ａから導光板２１の内部に入射した後の光２６の指向性を滑らかに補正することができる。   As described above, the light guide plate 21 in the present embodiment is guided by the incident light of the light source 2 from the light incident surface 21a formed of a continuous quadratic smooth quadratic curve as shown in FIG. The intensity distribution of the light 26 after entering the inside of the optical plate 21 is made uniform, and the directivity is corrected to a smooth directivity as shown by the curve 106 in FIG. Thereby, bright lines and bright spots near the light source 2 can be prevented. Note that the curves 107 and 108 shown in FIGS. 4B and 4C change the value of D / C, which is the ratio of the radii C and D of the ellipse 27, and the convex portions 22 forming the light incident surface 21a. The directivity of the light 26 after entering the light guide plate 21 when the shape of the recess 23 is changed is shown. Thus, the directivity of the light 26 after entering the light guide plate 21 can be controlled by changing the shapes of the convex portions 22 and the concave portions 23. Therefore, the shape of the light incident surface 21a is optimized by changing the value of D / C which is the ratio of the radii C and D of the ellipse 27 in accordance with the positional relationship between the light guide plate 21 and the light source 2, and the like. The directivity of the light 26 after entering the light guide plate 21 can be corrected smoothly.

また、図１（ｂ）に示すように導光板２１の内部に入射した後の光２６は、光出射面２１ｂと下面２１ｃとの間で反射を繰り返しながら伝搬し、臨界角以下の成分からなる照明光２５を光出射面２１ｂより出射して液晶表示パネル７の背後から照明する。この結果、液晶表示パネル７の表示画面における輝度ムラを低減して高品位の表示画面を表示することができる。   Further, as shown in FIG. 1B, the light 26 after entering the inside of the light guide plate 21 propagates while being repeatedly reflected between the light emitting surface 21b and the lower surface 21c, and consists of a component having a critical angle or less. Illumination light 25 is emitted from the light exit surface 21 b and illuminated from behind the liquid crystal display panel 7. As a result, luminance unevenness on the display screen of the liquid crystal display panel 7 can be reduced and a high-quality display screen can be displayed.

尚、本実施形態においては、断面が２次曲線からなる凸部と凹部とが交互に繰り返し形成する場合について述べたが、本発明はこれに限らず、例えば断面が３次、４次等の多次曲線からなる凸部と凹部とが交互に繰り返し形成しても良い。
また、凸部と凹部とを直接接続する例で説明したが、これに限定されるものではなく、凸部と凹部との間を滑らかな曲面で接続しても良い。
また、凸部または凹部を一種類の曲面で形成する例で説明したが、複数の曲面を組み合わせて凸部または凹部を形成しても良い。 In the present embodiment, the case where the convex portion and the concave portion having a quadratic cross section are alternately and repeatedly formed has been described. However, the present invention is not limited to this, and the cross section is, for example, tertiary or quartic. Convex parts and concave parts made of a multi-order curve may be alternately and repeatedly formed.
Moreover, although the example which directly connects a convex part and a recessed part was demonstrated, it is not limited to this, You may connect between a convex part and a recessed part with a smooth curved surface.
Moreover, although the example which forms a convex part or a recessed part with one type of curved surface demonstrated, you may form a convex part or a recessed part combining several curved surfaces.

また本実施形態においては、導光板の光入射面に表面処理を施さない例で説明したが、これに限らず、この光入射面を粗面により形成して光拡散面としてもよい。これによって、さらに輝度ムラを低減することができる。
また、光入射面に一種類の凸部と凹部とを交互に繰り返し形成する場合について説明したが、これに限らず、光源から照射する照射光の指向性等に応じて光源より遠ざかるに従って凸部及び凹部の形状を徐々に変化させてもよい。これによって、指向性をより滑らかにすることができる。 In this embodiment, the example in which the light incident surface of the light guide plate is not subjected to the surface treatment has been described. However, the present invention is not limited to this, and the light incident surface may be formed as a rough surface to be a light diffusion surface. Thereby, luminance unevenness can be further reduced.
In addition, the case where one type of convex portion and concave portion are alternately and repeatedly formed on the light incident surface has been described. However, the present invention is not limited thereto, and the convex portion is further away from the light source according to the directivity of irradiation light emitted from the light source. In addition, the shape of the recess may be gradually changed. Thereby, directivity can be made smoother.

さらに本実施形態では液晶表示装置の面状光源に本発明の導光板を適用する場合について説明したが、これに限らず、種々の照明機器、表示装置等のサイドライト型面状光源に広く適用することができる。   Further, in the present embodiment, the case where the light guide plate of the present invention is applied to the planar light source of the liquid crystal display device has been described. However, the present invention is not limited to this, and is widely applied to sidelight type planar light sources such as various illumination devices and display devices. can do.

本発明の実施形態における導光板を用いたサイドライト型面状光源を示す図であり、図１（ａ）は平面図、図１（ｂ）は図１（ａ）のＡ−Ａ断面図である。It is a figure which shows the sidelight type planar light source using the light-guide plate in embodiment of this invention, Fig.1 (a) is a top view, FIG.1 (b) is AA sectional drawing of Fig.1 (a). is there. 図１のＢ部の拡大図であり、図２（ａ）は光入射面を示す部分拡大平面図、図２（ｂ）は光入射面の部分拡大斜視図である。FIG. 2B is an enlarged view of a portion B in FIG. 1, FIG. 2A is a partially enlarged plan view showing a light incident surface, and FIG. 2B is a partially enlarged perspective view of the light incident surface. 本発明の実施形態における導光板の光入射面を示す部分拡大平面図である。It is a partial enlarged plan view which shows the light-incidence surface of the light-guide plate in embodiment of this invention. 本発明の実施形態における導光板の内部に入射した後の光の指向性を示す図である。It is a figure which shows the directivity of the light after injecting into the inside of the light-guide plate in embodiment of this invention. 従来技術におけるサイドライト型面状光源の要部を示す斜視図である。It is a perspective view which shows the principal part of the sidelight type planar light source in a prior art. 従来技術における導光板の光入射面付近を示す部分拡大平面図である。It is the elements on larger scale which show the light-incidence surface vicinity of the light-guide plate in a prior art. 従来技術における光の指向性を示し、図７（ａ）は光源自身の照射光の指向性を示す図、図７（ｂ）は導光板の内部に入射した後の光の指向性を示す図である。FIG. 7A shows the directivity of the light in the prior art, FIG. 7A shows the directivity of the irradiation light of the light source itself, and FIG. 7B shows the directivity of the light after entering the light guide plate. It is. 従来技術における導光板を示し、図８（ａ）は導光板の平面図、図８（ｂ）は図８（ａ）のＡ部を示す部分拡大斜視図である。FIG. 8A is a plan view of the light guide plate, and FIG. 8B is a partially enlarged perspective view showing a portion A of FIG. 8A. 従来技術における導光板の光入射面付近を示す部分拡大平面図である。It is the elements on larger scale which show the light-incidence surface vicinity of the light-guide plate in a prior art. 従来技術における導光板の内部に入射した後の光の指向性を示す図である。It is a figure which shows the directivity of the light after injecting into the inside of the light-guide plate in a prior art.

符号の説明Explanation of symbols

１、１１
導光板
１ａ、１１ａ 光入射面
１ｂ、１１ｂ 光出射面
２ 光源（ＬＥＤ）
３ 光源からの照射光
４ 導光板から出射する照明光
５ 導光板の内部に入射した後の光
７ 液晶パネル
１２ 凸部
１２ａ、１２ｂ 斜面
１３ 平面部
１５、１６、１７ 導光板の内部に入射した後の光
２１
導光板
２１ａ 光入射面
２１ｂ 光出射面
２１ｃ 導光板の下面
２２ 凸部
２３ 凹部
２４ 楕円の中心
２５ 照明光
２６ 導光板の内部に入射した後の光
２７ 楕円
1, 11
Light guide plate 1a, 11a Light incident surface 1b, 11b Light exit surface 2 Light source (LED)
3 Light emitted from the light source 4 Illumination light emitted from the light guide plate 5 Light after entering the inside of the light guide plate 7 Liquid crystal panel 12 Protrusions 12 a and 12 b Slope 13 Plane portions 15, 16 and 17 Entered inside the light guide plate Rear light 21
Light guide plate 21a Light incident surface 21b Light exit surface 21c Lower surface 22 of light guide plate Convex portion 23 Concave portion 24 Ellipse center 25 Illumination light 26 Light 27 after entering light guide plate 27 Ellipse

Claims (5)

板状の透光材よりなり、その側面を光入射面とし該光入射面に対向して配置された光源からの光を光路変換してその上面から照明対象物に対し面状の照明光を出射する導光板において、前記導光板の光入射面に滑らかに連続した曲面からなる凹凸が形成されていることを特徴とする導光板。   It is made of a plate-shaped translucent material, and its side surface is used as a light incident surface, and light from a light source arranged opposite to the light incident surface is converted into an optical path. In the light guide plate to be emitted, the light guide plate is characterized in that irregularities made of a smoothly continuous curved surface are formed on the light incident surface of the light guide plate. 前記凹凸は滑らかな曲面からなる凹部と滑らかな曲面からなる凸部とが前記導光板の光入射面の長手方向に交互に繰り返し形成されていることを特徴とする請求項１記載の導光板。   2. The light guide plate according to claim 1, wherein the concave and convex portions are formed by alternately and repeatedly forming concave portions made of a smooth curved surface and convex portions made of a smooth curved surface in the longitudinal direction of the light incident surface of the light guide plate. 前記曲面は２次曲面からなることを特徴とする請求項１または請求項２記載の導光板。   The light guide plate according to claim 1, wherein the curved surface is a quadratic curved surface. 前記曲面を粗面にしたことを特徴とする請求項１から請求項３のいずれか１項に記載の導光板。   The light guide plate according to any one of claims 1 to 3, wherein the curved surface is a rough surface. 前記導光板は略直方体の形状をなすことを特徴とする請求項１記載の導光板。
The light guide plate according to claim 1, wherein the light guide plate has a substantially rectangular parallelepiped shape.
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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20070071295A (en) * 2005-12-29 2007-07-04 엘지.필립스 엘시디 주식회사 Back-light unit and liquid crystal display device using thereof
JP2008026889A (en) * 2006-06-22 2008-02-07 Tohoku Univ Front light for reflective liquid crystal display, and reflective display apparatus
CN100426087C (en) * 2006-01-06 2008-10-15 清华大学 Light guide plate and backlight module using same
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CN100426087C (en) * 2006-01-06 2008-10-15 清华大学 Light guide plate and backlight module using same
JP2008026889A (en) * 2006-06-22 2008-02-07 Tohoku Univ Front light for reflective liquid crystal display, and reflective display apparatus
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KR100875491B1 (en) 2006-09-19 2008-12-22 주식회사 나모텍 Light guide plate, backlight unit and liquid crystal display device using the same
US8749729B2 (en) 2008-02-07 2014-06-10 Sony Corporation Light guide plate, surface-emitting apparatus, liquid crystal display apparatus, and method of producing a light guide plate
WO2009099219A1 (en) 2008-02-07 2009-08-13 Sony Corporation Light guide plate, surface illumination device, liquid crystal display device, and manufacturing method for the light guide plate
DE102009022662A1 (en) 2008-05-26 2010-01-14 Citizen Electronics Co., Ltd., Fujiyoshida-shi Planar light emitting device and liquid crystal display device
US8154688B2 (en) 2008-05-26 2012-04-10 Citizen Electronics Co., Ltd. Planar light-emitting device and liquid crystal display apparatus
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JP2013502043A (en) * 2009-08-12 2013-01-17 スリーエム イノベイティブ プロパティズ カンパニー Light guide
JP5460893B2 (en) * 2011-02-15 2014-04-02 三菱電機株式会社 Angular intensity distribution shaping member and surface light source device
US9103950B2 (en) 2011-02-15 2015-08-11 Mitsubishi Electric Corporation Surface light source device and liquid crystal display device

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