JP3813187B2

JP3813187B2 - LCD module

Info

Publication number: JP3813187B2
Application number: JP14333094A
Authority: JP
Inventors: 克徳竹内; 直人福田; 秀光手島
Original assignee: Tottori Sanyo Electric Co Ltd; Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 1994-06-24
Filing date: 1994-06-24
Publication date: 2006-08-23
Anticipated expiration: 2021-08-23
Also published as: JPH086019A

Description

【０００１】
【産業上の利用分野】
本発明は背面の照明手段を内蔵したいわゆる液晶モジュールに関する。
【０００２】
【従来の技術】
従来よりいわゆる液晶モジュールにおいては、特開平４−７５１９号公報に示される様に、液晶セルを周辺の駆動回路や背面の照明手段とともに金属のフレーム枠に収納して、取扱い易くしていた。このような液晶モジュールにおいては、背面の照明手段としては液晶セルの真下に光源を配置するのではなく、液晶セルの背面に導光板を配置し、その導光板の側面に線状光源を配置する側面照明型の照明手段を用いる方が液晶モジュールを薄く構成できるので好まれ、その場合、導光板や線状光源は樹脂製などの枠体によって支持される。
【０００３】
【発明が解決しようとする課題】
係る液晶モジュールにおいては、線状光源の光量を多くしようとするために温度上昇を招き、また線状光源の光を導光板で拡散して用いるため、光量の変化や光量の分布の変化によって照明条件が著しく影響を受けることになる。これに対して、線状光源は螢光管や冷陰極管からなり、いずれもガス体励起輻射などを利用するので温度の変化に伴って光量や寿命が影響を受けるが、とりわけ１本の管の場所によって温度変化が生じるとその影響が大きい。そしてこの様な影響としては、具体的には表示面の端部や隅において照度が低下して表示品位が劣化するばかりか見かけ状のコントラストが低下して表示が判読し難く、さらには線状光源の寿命が例えば完全露出の状態に比べて半分程度に短くなり、不都合であった。この様な症状の原因を検討した結果、線状光源の管の端部が管の中央部に比較して温度が低くなっており、これは線状光源の支持の仕方によって影響を受けていることが判明した。
【０００４】
【課題を解決するための手段】
本発明は上述の点を考慮して成されたもので、側面照明型の背面照明手段を持つ液晶モジュールの線状光源両端に、枠体と接触して係止する突起を有したホルダーを設け、枠体とホルダーとの間には空間が形成されているものである。
【０００５】
【作用】
これによって少なくとも線状光源の両端だけが著しく温度低下することはなくなり、線状光源全体が一定の空気層により包囲され温度分布の著しい不均等は生じなくなる。
【０００６】
【実施例】
図１ａ、ｂは本発明実施例の液晶モジュールの線状光源部分を含む断面図で、１は液晶を２枚の基板１１で挾持した液晶セルで、ツイストネマティック、スーパーツイストネマティックなどのモードの透過型のもので、基板の前後には偏光板１２を有している。又液晶セル１の基板の周辺部には駆動回路１３等が接続配置されているが、駆動素子１３は例えば箔状電極を有する樹脂フィルムに支持されたいわゆるＴＡＢと呼ばれるものを例示しているが、ベアチップを液晶セル基板若しくは駆動回路基板に直接接続固着してもよく、いずれも液晶を駆動するために液晶セル１の周辺部の端子に接続され、共通端子や電源などは駆動素子を支持する駆動回路基板に接続すればよい。
【０００７】
２は液晶セル１の背面に配置された導光板で、アクリル樹脂平板若しくはそのような平板の積層体からなり、裏面に拡散効果を持たせる白色印刷などが適宜設けられ、背面には反射シート２１、表面には光拡散シート２２が貼付されているが、この様な構成に限られるものではなく、例えば透明な平板とレンズシートが組み合わせて設けられていてもよい。３は導光板２の側面に配置された線状光源で、螢光管とか冷陰極管などからなる。
【０００８】
４は導光板２と線状光源３を支持する枠体で、図の例では上枠４１と下枠４２の組合せにより導光板２や線状光源３を挾持する樹脂成形品からなり、その枠体４の上に緩衝剤４５を介して液晶セル１が載置されている。５はこれらの構成部品を相互に固定収納する金属製のフレーム枠である。このフレーム枠５には略中央に液晶セル１の表示面を露出させる透孔５１が設けてあり、液晶セル１を収納して枠体４等に、側面に設けた爪でカシメるか若しくはビスなどで相互に固定する。尚これらの構成要件の説明に限定されるものではなく、例えば枠体４は単一の樹脂成形品からなり、導光板等はその単一枠体に設けられた透孔に嵌合させてもよく、また必要に応じて、モジュールを構成する裏面の全面若しくは部分的に底板を設けてもよい。
【０００９】
この様な構造の液晶モジュールにおいて、線状光源３は、その管３１の両端に、枠体４に係止する突起６１を有したホルダー６を有し、これにより、その両端は熱伝導性の低いホルダー６により空間７を介して枠体４に支持されている。さらにこの線状光源３の少なくとも中央部、より好ましくは支持用両端部を除く光放出部において、空間７と連通する線状光源を被う空間７７が形成される様に非接触に反射シート８で被われている。この様な反射シート８は、空間７７を確保すると共に線状光源３の光を効率よく導光板２の中に導くもので、白色シート、アルミニウムシート等を略円筒状に形成し、一端を導光板２の端部の裏面側に接着し、他端をその導光板２の表面側に接着すれば容易に非接触、高反射効率を得るように配置できるが、枠体４に設けた曲面４３を利用してもよい。
【００１０】
従来も線状光源の両端にホルダーを用いることは行っていたが、それは線状光源の管を固定することが目的で、例えばシリコン樹脂のような軟質ホルダーを用いており、この場合熱伝導率が０．５〜３×１０^-3ｃａｌ／ｓｅｃ／ｃｍ／度Ｃと大きいため、線状光源の熱がそれを支えている両端部からのみ枠体４を通じて放熱され温度が低下し、線状光源の中央部と端部で著しい温度差を生じていた。
【００１１】
これに対して本発明は、枠体４に対する固定は実質的にホルダー６の突起６１で行っているので、つまり支持は点接触であり面接触ではないから熱伝搬路の制限を受けるので、線状光源３の熱がそれを支持することによって伝達しにくい。またホルダー６として例えばポリカーボネート樹脂のような熱伝導率４〜８×１０^-4ｃａｌ／ｓｅｃ／ｃｍ／度Ｃという熱伝導率の低い材料で支持されると共に、線状光源３の全体を空気層７、７７で被うことによって、線状光源３を全体的に均一な熱分布に保ちやすくなっている。
【００１２】
上述の効果を、画面の有効面積２０ｃｍ×２５ｃｍ、線状光源として直径３ｍｍ、長さ２３ｃｍの冷陰極管を用い、最も照度の高くなるインバータ電源を用いコントラストが高く観察される電圧で点灯表示させ、点灯初期のコントラスト１：１０のグラフィック表示において比較した。その結果、従来例として、まずシリコン樹脂ホルダーを用い反射シートを線状光源に巻き付けたものでは、２０分経過後に画面の上下でコントラスト変化が現れ３０分経過後、画面全体が暗くなり始め、次いでシリコン樹脂ホルダーを用い反射シートを線状光源に非接触に巻き付けたものでは、１５分経過後に画面の上下でコントラスト変化が現れ３０分経過後、画面の隅の表示が判読困難な状態となった。それに対して本発明の突起のあるポリカーボネート樹脂ホルダーを用いたものでは、２０分経過後にも画面上で目視のコントラスト変化は生じず、１時間経過後でも画面の表示は明確に判読できた。現実にはこの様な強い照明をすると使用者の眼の疲労が著しくなるためもっと光量を低下させるので、本発明実施例では判読不能などの実用上の問題は発生しないものである。
【００１３】
【発明の効果】
以上の様な構成にすることによって、少なくとも線状光源の両端だけが著しく温度低下することはなくなり、あるいは線状光源全体が一定の空気層により包囲され温度分布の著しい不均衡は生じなくなるので、導光板で拡散して用いる場合であっても片寄った照明条件の著しい影響は受けない。これによって、表示面の端部や隅において照度が低下して表示品位が劣化するとか表示が判読し難くなることは極めて稀となり、さらには線状光源の寿命が著しく短くなることもなくなった。
【図面の簡単な説明】
【図１】本発明実施例の液晶モジュールの線状光源を含む部分の断面図ａ，ｂである。
【符号の説明】
１液晶セル
２導光板
３線状光源
４枠体
６ホルダー
７空間
８反射シート[0001]
[Industrial application fields]
The present invention relates to a so-called liquid crystal module incorporating a backside illumination means.
[0002]
[Prior art]
Conventionally, in a so-called liquid crystal module, a liquid crystal cell is housed in a metal frame frame together with a peripheral drive circuit and a back illumination means as shown in Japanese Patent Laid-Open No. 4-7519 to facilitate handling. In such a liquid crystal module, a light source plate is not disposed directly under the liquid crystal cell as the illumination means on the back surface, but a light guide plate is disposed on the back surface of the liquid crystal cell, and a linear light source is disposed on the side surface of the light guide plate. It is preferable to use a side illumination type illumination means because the liquid crystal module can be made thin. In this case, the light guide plate and the linear light source are supported by a frame made of resin or the like.
[0003]
[Problems to be solved by the invention]
In such a liquid crystal module, the temperature rises in order to increase the amount of light from the linear light source, and the light from the linear light source is diffused and used by the light guide plate. Conditions will be significantly affected. On the other hand, the linear light source is composed of a fluorescent tube or a cold cathode tube, both of which utilize gas body excitation radiation and the like, and therefore the light quantity and life are affected by the temperature change. If the temperature changes depending on the location, the effect will be great. Such effects include, specifically, the illuminance at the edges and corners of the display surface, which deteriorates the display quality as well as the apparent contrast. For example, the lifetime of the light source is shortened to about half that of a fully exposed state, which is inconvenient. As a result of examining the cause of such a symptom, the temperature of the end of the tube of the linear light source is lower than that of the central portion of the tube, which is influenced by the way the linear light source is supported. It has been found.
[0004]
[Means for Solving the Problems]
The present invention has been made in consideration of the above points, and holders having protrusions that come into contact with and lock the frame body are provided at both ends of a linear light source of a liquid crystal module having a side illumination type backlighting means. A space is formed between the frame and the holder.
[0005]
[Action]
As a result, the temperature at least at both ends of the linear light source is not significantly lowered, and the entire linear light source is surrounded by a certain air layer, so that the temperature distribution is not significantly uneven.
[0006]
【Example】
1A and 1B are cross-sectional views including a linear light source portion of a liquid crystal module according to an embodiment of the present invention. Reference numeral 1 denotes a liquid crystal cell in which a liquid crystal is held by two substrates 11, and transmission of modes such as twist nematic and super twist nematic. It has a polarizing plate 12 before and after the substrate. Further, a drive circuit 13 and the like are connected and arranged on the periphery of the substrate of the liquid crystal cell 1, and the drive element 13 is exemplified by a so-called TAB supported by a resin film having a foil-like electrode, for example. The bare chip may be directly connected and fixed to the liquid crystal cell substrate or the driving circuit substrate, both of which are connected to the peripheral terminals of the liquid crystal cell 1 for driving the liquid crystal, and the common terminal and the power source support the driving element. What is necessary is just to connect to a drive circuit board.
[0007]
Reference numeral 2 denotes a light guide plate disposed on the back surface of the liquid crystal cell 1, which is made of an acrylic resin flat plate or a laminate of such flat plates, and is appropriately provided with white printing or the like for giving a diffusion effect on the back surface. The light diffusion sheet 22 is affixed to the surface, but is not limited to such a configuration. For example, a transparent flat plate and a lens sheet may be provided in combination. Reference numeral 3 denotes a linear light source disposed on the side surface of the light guide plate 2 and includes a fluorescent tube or a cold cathode tube.
[0008]
Reference numeral 4 denotes a frame that supports the light guide plate 2 and the linear light source 3, and in the example shown in the figure, the frame is made of a resin molded product that holds the light guide plate 2 and the linear light source 3 by a combination of the upper frame 41 and the lower frame 42. The liquid crystal cell 1 is placed on the body 4 via a buffer 45. Reference numeral 5 denotes a metal frame that fixes and stores these components. The frame frame 5 is provided with a through-hole 51 that exposes the display surface of the liquid crystal cell 1 at substantially the center. The liquid crystal cell 1 is accommodated in the frame body 4 or the like by caulking or screwing with a claw provided on the side surface. Fix each other together. However, the present invention is not limited to the description of these constituent elements. For example, the frame 4 is made of a single resin molded product, and the light guide plate or the like may be fitted in a through hole provided in the single frame. In addition, if necessary, a bottom plate may be provided on the entire back surface of the module or partially.
[0009]
In the liquid crystal module having such a structure, the linear light source 3 has holders 6 having projections 61 that are engaged with the frame body 4 at both ends of the tube 31, so that both ends are thermally conductive. The lower holder 6 supports the frame body 4 through the space 7. Further, at least the central portion of the linear light source 3, more preferably the light emitting portion excluding the support end portions, the reflection sheet 8 is contactlessly formed so that a space 77 covering the linear light source communicating with the space 7 is formed. It is covered with. Such a reflection sheet 8 secures the space 77 and efficiently guides the light from the linear light source 3 into the light guide plate 2. A white sheet, an aluminum sheet, or the like is formed in a substantially cylindrical shape, and one end thereof is guided. If it adheres to the back surface side of the edge part of the optical plate 2 and the other end adheres to the surface side of the light guide plate 2, it can be arranged so as to easily obtain non-contact and high reflection efficiency, but the curved surface 43 provided on the frame 4 May be used.
[0010]
Conventionally, holders were used at both ends of the linear light source, but the purpose was to fix the tube of the linear light source. For this purpose, a soft holder such as silicon resin was used. Is as large as 0.5 to 3 × 10 ⁻³ cal / sec / cm / degree C. Therefore, the heat of the linear light source is dissipated through the frame 4 only from both ends supporting the linear light source, and the temperature decreases. There was a significant temperature difference between the center and end of the light source.
[0011]
On the other hand, in the present invention, the fixing to the frame body 4 is substantially performed by the protrusion 61 of the holder 6, that is, the support is a point contact and not a surface contact, and therefore the heat propagation path is limited. The heat of the light source 3 is difficult to transfer by supporting it. The holder 6 is supported by a material having a low thermal conductivity of 4 to 8 × 10 ⁻⁴ cal / sec / cm / degree C, such as polycarbonate resin, and the entire linear light source 3 is an air layer. 7 and 77 makes it easy to keep the linear light source 3 in a uniform heat distribution as a whole.
[0012]
The above-mentioned effects are lit and displayed at a voltage with a high contrast using an inverter power source with the highest illuminance, using a cold cathode tube with an effective area of 20 cm x 25 cm, a linear light source of 3 mm in diameter and 23 cm in length. Comparison was made in a graphic display with a contrast of 1:10 at the beginning of lighting. As a result, as a conventional example, in the case where a reflection sheet is wound around a linear light source using a silicon resin holder, a contrast change appears at the top and bottom of the screen after 20 minutes, and the entire screen starts to darken after 30 minutes. When a reflective sheet is wrapped around a linear light source using a silicone resin holder, a contrast change appears on the top and bottom of the screen after 15 minutes, and the display at the corners of the screen becomes difficult to read after 30 minutes. . On the other hand, in the case of using the polycarbonate resin holder having the projections of the present invention, the visual contrast change did not occur on the screen even after 20 minutes, and the display on the screen was clearly readable even after 1 hour. In reality, when such strong illumination is applied, the user's eyes become extremely tired and the light quantity is further reduced. Therefore, in the embodiment of the present invention, practical problems such as incomprehension do not occur.
[0013]
【The invention's effect】
By adopting the above-described configuration, at least only the both ends of the linear light source do not significantly decrease in temperature, or the entire linear light source is surrounded by a certain air layer and no significant imbalance in temperature distribution occurs. Even when the light is diffused by the light guide plate, it is not significantly affected by the biased illumination conditions. As a result, the illuminance is reduced at the edges and corners of the display surface and the display quality is deteriorated or the display becomes difficult to read, and the life of the linear light source is not significantly shortened.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view a and b of a portion including a linear light source of a liquid crystal module according to an embodiment of the present invention.
[Explanation of symbols]
1 Liquid Crystal Cell 2 Light Guide Plate 3 Linear Light Source 4 Frame 6 Holder 7 Space 8 Reflective Sheet

Claims

In the liquid crystal module comprising: a liquid crystal cell; a light guide plate disposed on a back surface of the liquid crystal cell; a linear light source disposed on a side surface of the light guide plate; and a frame that supports the light guide plate and the linear light source. The light source has a holder made of polycarbonate resin only at both ends,
The liquid crystal module according to claim 1, wherein the holder is provided with a protrusion that contacts and locks the frame body, and a space is formed between the frame body and the holder .

In the liquid crystal module comprising: a liquid crystal cell; a light guide plate disposed on a back surface of the liquid crystal cell; a linear light source disposed on a side surface of the light guide plate; and a frame that supports the light guide plate and the linear light source. The light source has a holder with a thermal conductivity of 4-8 × 10 ⁻⁴ cal / sec / cm / degree C only at both ends,
The liquid crystal module according to claim 1, wherein the holder is provided with a protrusion that contacts and locks the frame body, and a space is formed between the frame body and the holder .