export1 on 四月 5th, 2012

EL发光技术85问

1、  发光线不亮问题如何判定与解决

A、 去认定电源、驱动器连接及良好否

B、 检查发光线接头处,判定接头是否被不恰当弯折,需要重新连接。

C、 快速剪去发光线尾端1CM,防止尾端两电极相连

2、  户外可否使用?颜色是否牢固?

A、 可以在户外使用,注意防止驱动器潮湿

B、 长期户外使用红色和橙色发光线易褪色,一般是一年以上,原因是有机荧光燃料耐紫外线不好,虽然已添加抗紫外线剂。红色燃料的褪色是染料界的难题

3、  发光线材料成分是否有环境污染?

A、 污染和环境污染

B、 主体成分:铜丝、KPT电致发光荧光粉(硫化锌)、塑料PVC\PU\PE\TPU

4、  安装使用时不恰当的拉扯及弯折的后果

A、 发光线发光层断裂,有黑点,易发生短路打火

B、 发光时有可移动黑斑

C、 发光线与电线连接处断裂

D、 一般地说,直径细的线抗拉性差

5、  发光线独立工作条件

交流工作,电压:90V-150V  频率:1000-4000HZ

6、  驱动器独立工作条件

DC3V, 6V, 9V, 12V18V24V.AC110V, 220

7、  驱动器不工作问题判定与解决

A、 检测电源接头与发光线连接

B、 检查驱动器有无鸣叫,通常驱动器工作有微小声音

C、 如驱动器使用以后发生不亮,应放置3-5分钟,或重复与发光线连接,再尝试使用。因为驱动器有断电后延时保护,其再次工作时需先释放电容储藏的电荷

D、 发光线与驱动器连接不好时,有时工作会使驱动器发热,这时应断电。因为驱动发热后工作会不正常

8、  驱动器为何有声音

发光线亮度与频率成正比增长,变压器高频工作会有轻微叫声

9、  驱动器功率与发光线的对应关系

A、 驱动器额定条件应与规定长度发光线匹配,否则易损坏发光线及驱动器

B、 大功率驱动器驱动短发光线,会增加发光线亮度,降低发光线使用寿命

C、 大功率驱动器驱动短发光线有时闪动开关会无效

10、发光线与驱动器的使用注意

A、 驱动器不要空载

B、 与发光线连接处勿弯折

11、发光线越粗越亮吗?

A、粗发光线增加视觉宽度面积,是人感觉发光强度增加

B、因塑料加厚,实际仪器测试是亮度下降

12、发光线颜色与亮度关系

发光线透明剂黄色较亮

13、发光线的寿命与使用方式的关系

发光线户内使用标准3000小时,户外1000小时以内(或长期超市或高温高频高压工作),在气候干燥时户内可以使用到5000小时或更长。

14、发光线与其他产品的技术及效果区别

  霓虹灯/冷阴极灯 串灯 半导体二极管 EL线 光纤
发光形式 连续线性 电光源 电光源 连续线性 电光源
发光颜色 红蓝绿 红黄 全色组合 全色 全色组合
热辐射程度 较强 较弱
工作电压范围 AC 10000V DC 110-220V DC 3V DC 3V-AC220V DC 3V
每米耗电量 15-40W/M 15W/M(15点) 2W/M(33点) 0.3W/M _________
发光亮度 较强 较强
使用寿命 3000H 1000H 20000H 1000-3000H 10000H
直径范围 2-8mm 8mm 8mm 1-8mm 0.5-10mm
连续长度范围 0.1-2m 1-20m 1-20m 0.01-100m 0.01-5m
工作外配电源 需要 不需要 需要 需要 需要
遗弃有害物质 汞、玻璃 玻璃、塑料 塑料 塑料 塑料
弯曲角度 不可 大于90度 大于90度 大于15度 大于120度
视觉效果 鲜艳夺目,动感刺激,使人高度兴奋 动感夺目,使人兴奋 鲜艳夺目,动感刺激,使人兴奋 鲜艳协调,柔和安静 鲜艳绚丽,柔和安静
应用领域 户外高层建筑广告 户外低层建筑装饰 户外高层建筑,户内装饰 户内外低层建筑及绿化装饰广告 户内装饰
安装/维护 复杂 简单 极复杂 极简单 较简单

15、发光线为何省电

发光线每米耗电0.2-0.3瓦,所以它很节省电力,加驱动器每米耗电约为0.4瓦。它的工作主要依靠频率。

16、发光线使用安全

发光线工作电流6mA/m,并且不会发热。其材料无毒无害,可以安全使用。如果人体接触会有轻微电麻感觉,应及时用绝缘材料封闭。

17、发光线是否防水

发光线是防水的,可以在水中使用。注意线体的连接及截断处应用防水胶密封。驱动器不能在水中工作。

18、发光线可否变色

发光线变色时依赖于多芯颜色与多闪驱动器组合实现

19、发光线可否滚动亮

发光线可以滚动发光,连接方法是多段单独连接,使用多闪驱动器控制,类似霓虹灯。

20、发光线可否直接与城市照明电联

普通发光线不能与城市照明电连接,必须经过驱动器,否则会有危险

21、发光线为何可以发光

电场激发荧光粉发光

22、驱动器与变压器的区别

A、变压器室连接电源与驱动器(指DC12V,3V),变压器不可使发光线发光

B、驱动器是连接发光线,驱动器是专用产品

23、不同颜色不同直径的发光线可否连接

可以连接。因为发光芯线部分是一样的直径。

24、发光线有多少种颜色

可以配出各种颜色。

25、电池可以使用驱动多长时间

使用高能新电池AA两节,3V驱动1米发光线连续常亮30小时

使用12V(8节5号电池)。工作10米线可以发光50小时,工作60米线可以发光5小时

26、评价发光线技术指标是什么

亮度(CM/㎡),寿命(小时),工作条件(电压、频率)

标准测试:90V,200HZ,使用寿命,5000小时,亮度10-2CM/㎡

110V,400HZ,使用寿命,3000小时,亮度60-2CD/㎡

130V,1000HZ,使用寿命,1000小时,亮度130-2CD/㎡

180V,4000HZ,使用寿命,1000小时,亮度130-5CD/㎡

27、发光线研究起源于什么时候

1965年在美国开始研究。1995年以色列ELAM开始产业化。

中国1975年中科院长春物理所快开始研究

28、电致发光技术起源于什么时候

1930年在美国开始相关技术研究,1958年中科院物理研究所开始研究。

29、发光器件常用的单位

A、光通量    流明/瓦 Lm    流明

B、照度      流明/米 Lux    勒克司(意思那个距离物体反射,多用于电光源)

C、亮度      坎特拉/平方米 Cd/㎡  坎特拉(单位面积强度,多用于面光源)

30、常见照度对比

日光    3-10万Lux

办公室照明    400Lux

星光    0.00005Lux

31、常见光通量对比

节能灯  70Lm

LED灯  40Lm

发光线  28Lm

32、常见亮度对比

电视屏幕       300 Cd/㎡

高亮发光线     200 Cd/㎡

普通发光片     90 Cd/㎡

33、发光线可否制成超薄平面发光

经过合理设计可以制成双面超薄发光板

34、DC3V电池带外接电源插孔使用要求

电池与外接变压器不可以同时使用,同时使用时非充电电池会发生爆炸

35、不同直径的发光线颜色为什么有变化

发光线的直径不同其颜色会有一定范围的变化,主要是塑料燃料透光与塑料薄厚反射作用导致。另外不同驱动器工作条件不同,也会引起发光颜色的变化。

36、发光线使用场合建议

室内,服装,玩具,广告,建议使用0.8-2.0MM线

室外矮建筑装饰(3层楼一下),建议使用2.0-5.0MM线

室外高建筑装饰(8层楼一下),建议使用霓虹网灯,从而增加发光面积提高可视距离

37、EL冷光片及EL发光线工作时是否出现发热

EL工作时不应该有发热现象,如果发现请立即关闭切断电源

38、EL发光片与EL线有何区别

两者原理是一样的,前者需要订制,成本高,团不可更改,自己无法实施;后者成本低,使用者可以自己制作图案。

39、EL线价格计算方法

EL线半成品价格是按米计算,驱动器是单独按个体计算。EL线成品是按套计算,已经包含驱动器。

40、EL发光片尺寸可以多大?

单片EL发光片的尺寸决定丝网印刷机,通常80*80cm,最大100*100cm(1平方米)。但EL发光片可以相互拼接,所以其面积可以大于10平方米以上。

41、EL发光片颜色有多少种?

EL发光自身颜色常见主要有:绿、蓝绿;通过添加染料、颜料可以产生白色。其他颜色都是通过发光片外表面印刷或灯片的颜色转化而来。

42、EL片是否可以户外使用

不建议用户在户外使用,尤其是长期使用。其颜色会发生变化,使用寿命大大缩短

43、EL片发光亮度下降原因

EL片发光亮度下降主要原因是空气中的潮气导致发光材料老化

44、老化后的EL片特征

不发光时表面变灰或黑,发光时有褐色斑点(块)出现

45、EL不发光时是否会老化

EL不工作时不会产生老化,包括EL片、EL线等器件

46、EL发光电子检测标准

国际及国内组织规定EL检测标准AC115V,400HZ

47、EL冷光发光使用寿命达到是否会突然不亮

EL老化时,亮度是逐渐衰弱,不会发生突然不亮

48、EL冷光发光寿命指标

EL寿命分为半寿命及全寿命概念。初始亮度下降一半的时间为半寿命,通常为3000小时。全寿命约为8000小时。

49、EL冷光发光片闪动是由什么控制

EL闪动控制使用驱动器的芯片完成,其控制时间与多路多段也是有电路芯片决定的

50、驱动电源电压

大面积大尺寸可以是DC12V加变压器完成,服装可以是DC3V,4.5V等

51、是否可以剪裁

在设计范围内可以剪裁切割,但不可以理解为“随意”

52、EL冷光发光厚度

在加封保护膜后,厚度多是小雨0.5毫米

53、EL冷光发光是否可以AC220V/110V使用

特殊加工的EL片可以在AC220V/110V(市电)下直接使用

54、EL冷光发光所使用的发光粉有几种颜色

EL发光材料有红色(有毒)、橙(亮度相对低)、蓝(寿命短)、绿。其中绿色及蓝绿色是经常使用的。

55、EL冷光发光片功率是多少

不同材料生产、不同工厂生产是不一样的,但通常是小于60W/平方米

56、EL冷光发光有多亮

通常EL在标准测试条件115V\400HZ时,发光为70-90Cd/平方米

57、EL冷光发光器件很亮是否好

亮度高于100Cd/平方米会大幅度降低使用寿命

58、EL冷光发光生产为何时间很长

EL制造大多数是使用丝网印刷技术,团制版需要时间

59、EL冷光发光片样品价格为何很贵

丝网印刷技术、图案制版需要消耗大量材料,只有批量生产成本可以下降

60、荧光-磷光-发光的区别

现在从发光物理学上讲,意义基本是一样的。原有定义上区别是:

A、 发光:字面含义范围更为广泛,泛指所有明亮现象

B、 荧光:多是指有特定材料自身被动所导致的发光

C、 磷光:发光时间长于荧光的材料。具体可分为:光致发光、电致发光

D、 化学发光、X射线发光等等

61、三基色发光粉是什么

红蓝绿三色发光材料简单称三基色粉。其可以是灯用发光材料,显示发光材料等。其主要目标是配比实现白色发光。

62、EL有紫外发光?紫外发光材料分类?

多数发光材料在紫外线下都有发光。其实光致发光材料的基本特点。具体为:有机物类/无机物类,长波类/短波类等

63、EL发光片有几种形式

四种:EL塑料片屏,EL抽瓷屏,EL玻璃屏,EL发光布

64、EL冷光可以像电视一样变化图案吗?

理论上可以实现矩阵式显示,实现文字图案显示。通过电路控制辉度,可以实现图像显示。

65、EL冷光白色发光可以像纸一样白吗?

EL白色发光使用染料实现,其染料在温度、稀释剂配比等方面有不同,都会影响颜色

66、EL冷光可以弯曲吗?

可以,但只能是圆角度弯曲

67、EL冷光片是否可以自己连接

不可以自行连接于改装控制器

68、EL冷光片坏了可否自己修复

不可以

68、EL片价格计算方法

EL价格是按平方厘米计算的,包含驱动器否需要单独明确

69、EL是否可以有辉度变化

普通EL无法实现辉度变化

70、EL驱动器分类

EL驱动器分通用类及专用类(特制),通用类适合于检测或实验性使用。

71、EL驱动器与发光片主要对应关系指标

驱动面积与闪动状态(多路及时间),每种发光片应配置专署驱动器。

72、EL发光片可视距离

0.1平方米夜晚可视距离在200米以上

73、EL驱动形式有几种?

主要有3种:1)变压器式驱动(重用,面积可以打,主要用在广告);2)芯片式驱动(驱动面积小,主要应用在电子配套产品中);3)无驱动(不常用,亮度低,主要用在简易暗照明中)。

74、订制EL片加工前需要提供的数据

尺寸、图案、闪动时间、控制器使用及电线长度

75、EL冷光片及EL线使用时会发热吗?

正常工作的EL器件是不会发热的,但当驱动器与发光片线不匹配时就会发热。长时间使用会损坏驱动器或发光器件,甚至导致燃烧。

76、EL器件工作时是否有声音

EL器件工作时大都会有声音,但芯片式驱动除外。

77、EL广告片为何会逐渐变色?

EL背光主要是白色产生,白色是用荧光染料配色,荧光染料在一定时间或紫外线下回逐渐褪色。

78、电致发光的种类

有机发光器件(大分子/小分子),无机薄膜器件,无机薄膜器件,无机粉末器件。

79、塑料EL片的柔软性决定因素是什么

柔软性决定于PET薄膜的厚度有关,其小于0.1毫米时就会很柔软

80、服装可以使用吗?

可以使用,但EL片不可以水洗。

81、EL最亮的颜色是?

蓝绿色或绿色

82、EL器件是否可以有变色效果

EL器件通过工艺实施控制,外表面经过遮掩,可以视觉上实现变色。

83、EL器件闪动东发光形成细腻的流水效果是什么原理

通过细腻的线条印刷及电路逐一控制器实现

84、EL器件纽扣电池可否使用

小面积的EL片,纽扣电池可以使用

85、提高EL发光片亮度有方法?

提高电压,增加频率可以提高亮度,但是有限度的,亮度可以在150Cd/平方米以上。

export1 on 四月 5th, 2012

电致发光材料详细介绍

一、电致发光(electroluminescence,EL)是某些物质受到外界电场的作用而发出光,也就是电能转换为光能的现象。具有这种性能的物质可作为一种电控发光器件。一般它们是固体元件,具有相应速度快、亮度高、视角广的特点,同时又具有易加工的特点,可制成薄型的、平面的、甚至是柔性的发光器件。

二、无机电致发光元件

致发光元件,使用的是由无机半导体材料制成的发光二极管。发光二极管是一种通过电流能发光的二极体,简称为LED(light emit diode).然而,LED真正作为全彩色的室内外影像显示系统,还是近几年的事,因为一直找不到性能足够好的发蓝光的LED无机材料。

发红光的LED无机材料其分子组成是Ga-Al-As

发绿的LED无机材料其分子组成是GaP

发绿的LED无机材料以GaN为主成分

缺点:

生产成本太高——高温、高真空、不易大规模成产

对环境有的影像大——无机物不易降解

无机EL是在高电场下发光的

三、有机电致发光材料(OLED)

OLED用于平板显示,具有:视野角度宽、轻薄、便于携带;高亮度、对比度高、色彩丰富、响应速度快;可实现软屏。

OLED还有工作温度范围宽、低驱动、工艺简单、成本低等优点。

在制造商,由于采用有机材料,可以通过有机合成方法获得,与无机材料相比较,不仅不耗费自然资源,而且还可以通过合成新的更好性能的有机材料,使OLED的性能不断地向前发展。

四、有机电致发光的机理

有机处理的电致发光属于注入式的复合发光。一般认为,聚合物和小分子电致发光的机理是:在外界电压的驱动下,有电极注入的电子和空穴在有机物中复合,释放出能量,传递给有机发光物质的分子,使其从基态跃迁到激发态,当受激分子从激发态回到基态时,由辐射跃迁而产生发光现象。

五、5个阶段

有机电致发光过程通常包括以下5个阶段

1)              载流子的注入:在外加电场的作用下,电子和空穴分别从阴极和阳极注入到夹

2)              在电极之间的有机功能薄膜层。

2)载流子的迁移:注入的电子和空穴分别从电子传输层和空穴传输层像发光层迁移。

3)载流子的复合:电子和空穴结合产生激子。

4)激子的迁移:激子在电场作用下迁移,将能量传递给发光分子,并激发电子从基态跃迁到激发态。

5)电致发光:激发态能量通过辐射失活,产生光子,释放能量。

六、评价OLED的一些主要参数

一般来讲,有机EL发光材料及器件的性能可以从发光性能和电学性能两方面来评价。发光性能主要包括发射光谱、发光亮度、发光效率、发光色度和寿命;电学性能主要包括电流与电压的关系、发光亮度与电压的关系等。这些都是衡量有机EL材料和器件性能的重要参数,对于发光的基础理论研究和技术应用极为重要。

1)  发射光谱

发射光谱又称荧光光谱,是发射的荧光相对强度随波长的分布,一般用荧光测量仪测得。发光光谱通常有光致发光(PL)光谱和电致发光(EL)光谱两种。PL光谱需要光能激发,并使激发光的波长和强度保持不变;EL光谱需要电能激发,可以测量在不同电压或电流密度下的EL光谱。通过比较器件的EL光谱和不同载流子传输材料和发光材料的PL光谱,可以得出复合区的位置以及实际发光物质的有用信息。

2)  发光强度

发光强度的单位是cd/m-2,表示没平方米的发光强度,通过测量被测表面的像在光电池表面所产生的照度即可获得,因为这个像面照度正比于物体亮度,且不随物体距离的变化而变化。

3)  发光效率

有机EL的发光效率可以用量子效率、功率效率和流明效率三种方法表示。量子效率是指输出的光子数与注入的电子空穴对数之比。

由于人眼之恩能够感觉到可见光,而且对可见光的敏感程度随波长而变,因此用人眼来衡量发光器件的功能时,多用流明效率这个参量。流明效率也叫光度效率,是发射的光通量L(一流明为单位)与输入的电功率Px之比。

4)  发光色度

由于人眼对不同颜色的感觉不同,不能用来测量颜色,仅能判断颜色相等的程度。为了客观地描述和测量颜色,1931年国际照明委员会(CIE)建立了标准色度系统,推荐了标准照明无和标准观察者。通过测量物体颜色的三刺激值(X,Y,Z)来确定颜色。试验中,一般用色度计来测量颜色。

5)  发光寿命

寿命定义为亮度降低到初始亮度的50%时所需的时间。应用市场要求OLED在连续操作下的使用寿命达到10000小时以上,储存寿命达到5年。目前,绿色OLED在恒电流和100cd/m-2的初始亮度下,已经达到了实用化要求。研究中发现,影响OLED寿命的因素之一是水分子和氧气,特别是水分子对有机EL材料的光氧化作用,因此需要将器件封装,以隔绝水和氧。

6)  电流密度和电压的关系

电流密度随电压变化的曲线反应了器件的点穴性质。OLED的电流密度和电压的关系类似于发光二极管,具有整流效应,即只在正向偏压下才有电流通过。在低电压时,电流密度随电压的增加而缓慢增加,超过一定电压,电流密度会急剧上升。

7)  亮度和电压的关系

亮度和电压的关系曲线反应OLED器件的光电特性,与器件的电流和电压的关系相似,

即在低电压下,电流密度缓慢增加,亮度也缓慢增加,在高电压驱动时,可以得到启动电压信息。启动电压定义为亮度等于1cd/m-2的电压。

七、OLED分类

1、根据采用有机材料的不同分为两种技术:一种是采用小分子材料,简称OLED;另一种是采用高分子材料,简称:PLED;

2、按照驱动方式又分为被动式矩阵PM-OLED和主动式矩阵AM-OLED,前者采用ITO玻璃基板,后者采用TFT基板。

对于聚合物电致发光过程则解释为:在电场的作用下,将看农学和电子分别注入到共轭高分子的最高战友轨道(HOMO)和最低空轨道(LUMO),于是就会产生正、负极子,极子在聚合物链段上转移,最后复合形成单重激子,单重态激子辐射跃迁而发光。

export1 on 四月 5th, 2012

A History of Electroluminescent Displays

 

By

Jeffrey A. Hart

Indiana University

Stefanie Ann Lenway

University of Minnesota

and

Thomas Murtha

University of Minnesota

Second Draft

September 1999

We are grateful for the comments provided by Christopher King, Sey Shing Sun, Richard Tuenge, T. Peter Brody, and Runar Tornqvist.  Research assistance was provided by Craig Ortsey.  This research was supported by a grant from the Alfred P. Sloan Foundation.  Please do not cite or quote without the written permission of the authors.

 

 

Introduction

Electroluminescent displays (ELDs) have their origins in scientific discoveries in the first decade of the twentieth century, but they did not become commercially viable products until the1980s.  ELDs are particularly useful in applications where full color is not required but where ruggedness, speed, brightness, high contrast, and a wide angle of vision is needed.  Color ELD technology has advanced significantly in recent years, especially for microdisplays.  The two main firms that have developed and commercialized ELDs are Sharp in Japan and Planar Systems in the United States.

What Is Electroluminescence?

There are two main ways of producing light: incandescence and luminescence.  In incandescence, electric current is passed through a conductor (filament) whose resistance to the passage of current produces heat.  The greater the heat of the filament, the more light it produces.  Luminescence, in contrast, is the name given to “all forms of visible radiant energy due to causes other than temperature.”[1][1]

There are a number of different types of luminescence, including (among others): electroluminescence, chemiluminescence, cathodoluminescence, triboluminescence, and photoluminescence.  Most “glow in the dark” toys take advantage of photoluminescence: light that is produced after exposing a photoluminescent material to intense light.   Chemiluminescence is the name given to light that is produced as a result of chemical reactions, such as those that occur in the body of a firefly.  Cathodoluminescence is the light given off by a material being bombarded by electrons (as in the phosphors on the faceplate of a cathode ray tube).  Electroluminescence is the production of visible light by a substance exposed to an electric field without thermal energy generation.[2][2]

An electroluminescent (EL) device is similar to a laser in that photons are produced by the return of an excited substance to its ground state, but unlike lasers EL devices require much less energy to operate and do not produce coherent light.  EL devices include light emitting diodes, which are discrete devices that produce light when a current is applied to a doped p-n junction of a semiconductor, as well as EL displays (ELDs) which are matrix-addressed devices that can be used to display text, graphics, and other computer images.  EL is also used in lamps and backlights.

There are four steps necessary to produce electroluminescence in ELDs:

  1. 1.      Electrons tunnel from electronic states at the insulator/phosphor interface;
  2. 2.      Electrons are accelerated to ballistic energies by high fields in the phosphor;
  3. 3.      The energetic electrons impact-ionize the luminescent center or create electron-hole pairs that lead to the activation of the luminescent center; and
  4. 4.      The luminescent center relaxes toward the ground state and emits a photon.

All ELDs have the same basic structure.  There are at least six layers to the device.  The first layer is a baseplate (usually a rigid insulator like glass), the second is a conductor, the third is an insulator, the fourth is a layer of phosphors, and the fifth is an insulator, and the sixth is another conductor.

ELDs are quite similar to capacitors except for the phosphor layer.   You can think of an ELD as a “lossy capacitor” in that it becomes electrically charged and then loses its energy in the form of light.[3][3]  The insulator layers are necessary to prevent arcing between the two conductive layers.

An alternating current (AC) is generally used to drive an ELD because the light generated by the current decays when a constant voltage is applied.  There are, however, EL devices that are DC driven (see below).

Scientific Origins

Electroluminescence was first observed in silicon carbide (SiC) by Captain Henry Joseph Round in 1907.[4][4]  Round reported that a yellow light was produced when a current was passed through a silicon carbide detector.[5][5]  Round was an employee of the Marconi Company and a personal assistant to Guglielmo Marconi.  He was an inventor in his own right with 117 patents to his name by the end of his life.[6][6]

The second reported observation of electroluminescence did not occur until 1923, when O.V. Lossev of the Nijni-Novgorod Radio Laboratory in Russia again reported electroluminescence in silicon carbide crystals.[7][7]

B. Gudden and R.W. Pohl conducted experiments in Germany in the late 1920s with phosphors made from zinc sulfide doped with copper (ZnS:Cu).  Gudden and Pohl were solid state physicists at the Physikalisches Institut at the University of G`ttingen.[8][8]  They reported that the application of an electrical field to the phosphors changed the rate of photoluminescent decay.[9][9]

The next recorded observation of electroluminescence was by Georges Destriau in 1936, who published a report on the emission of light from zinc sulfide (ZnS) powders after applying an electrical current.[10][10]  Destriau worked in the laboratories of Madame Marie Curie in Paris.  The Curies had been early pioneers in the field of luminescence because of their research on radium.  According to Gooch, Destriau first coined the word “electroluminescence” to refer to the phenomenon he observed.

Gooch also argues that one should keep in mind the differences between the “Lossev effect” and the “Destriau effect:”

The Lossev effect should be distinguished from the Destriau effect.  Destriau’s work involved zinc sulphide phosphors, and he observed that those phosphors could emit light when excited by an electric field…[The Lossev effect, in contrast, involves electroluminescence] in p-n junctions.[11][11]

During World War II, a considerable amount of research was done on phosphors in connection with work on radar displays (which was later to benefit the television industry in the form of better cathode ray tubes).  Wartime research also included work on the deposition of transparent conductive films for deicing the windshields of airplanes.  That work was later to make possible a whole generation of new electronic devices.

In the 1950s, GTE Sylvania fired various coatings, including EL phosphors onto heavy steel plates to create ceramic EL lamps.[12][12]  During this period, most research focused on powder EL phosphors to get bright lamps requiring minimal power and with a potentially long lifetime.  Research funding was cut back when it was determined that product lifetimes were too short (approximately 500 hours).[13][13]

The first thin-film EL structures were fabricated in the late 1950s by Vlasenko and Popkov.[14][14]  These two scientists observed that luminance increased markedly in EL devices when they used a thin film of Zinc Sulfide doped with Manganese (ZnS:Mn).  Luminance was much higher in thin film EL (TFEL) devices than in those using powdered substances.  Such devices however were still too unreliable for commercial use.

Russ and Kennedy introduced the idea of depositing insulating layers under and above the phosphor layer on a TFEL device.[15][15]  The implications for reliability of TFEL devices was not appreciated at the time, however.

Soxman and Ketchpel conducted research between1964 and 1970 that demonstrated the possibility of matrix addressing a TFEL display with high luminance, but again unreliability of the devices remained a problem.[16][16]

In the mid-1960s, there was a revival of EL research in the United States focused on display applications.  Sigmatron Corporation first demonstrated a thin-film EL (TFEL) dot-matrix display in 1965.  Unfortunately, Sigmatron was unable to successfully commercialize these displays and it folded in 1973.[17][17]

In 1968, Aron Vecht first demonstrated a direct current (DC) powered EL panel using powdered phosphors.[18][18]  Research on powdered phosphor DC-EL devices continued, especially for use in watch dials, nightlights and backlights, but most subsequent research on ELDs focused on thin-film AC driven devices.  An early example was the work of  Peter Brody and his associates at Westinghouse Research Laboratories on EL and AM-EL devices between 1968 and 1974.[19][19]

In 1974, Toshio Inoguchi and his colleagues at Sharp Corporation introduced an alternating current (AC) TFEL approach to ELDs at the annual meeting of the Society for Information Display (SID).  The Sharp device used zinc sulfide doped with manganese (ZnS:Mn) as the phosphor layer and yttrium oxide (Y2O3) for the sandwiching insulators.  This was the first high-brightness long-lifetime ELD ever made.   Sharp introduced a monochrome ELD television in 1978.  The paper Inoguchi published on his group’s research helped to reinvigorate EL research in the rest of the world, including at Tektronix, a U.S. electronics firm based in Portland, Oregon.[20][20]

Tektronix’ research on EL began in 1976.  The management at Tektronix were familiar with the work reported by Inoguchi’s team.  They decided to start a new program on ELDs at Tektronix Applied Research Laboratories.  The work begun there was continued when the Tektronix researcher left to create a spinoff firm called Planar Systems.  Several other large U.S. companies also were conducting research on ELDs in the 1970s, including: IBM, GTE, Westinghouse, Aerojet General, and Rockwell.   All these companies realized that ELDs had potential advantages over existing LCD technology in the following areas:

  1. 1.      Contrast
  2. 2.      Multiplexing, and
  3. 3.      3.      Viewing angle.

The most important problem that had to be solved before mass production of ELDs could begin was increasing the reliability of the EL thin film stack.  Since the devices operated at very high field levels — about 1.5 MV/cm — there was a high probability that they would break down, especially if there was insufficient uniformity in the stack.  Sharp, Tektronix, and Lohja  Corporation in Finland were able to solve this problem between 1976 and 1983 using slightly different approaches.

The second major problem was to get access to high-voltage drivers for the displays.  Sharp ended up developing their own; Tom Engibous developed drivers for EL displays at Texas Instruments by modifying the design his group had done for plasma displays.[21][21]   Planar used the TI drivers in its products until it could find additional suppliers.

The introduction to the market in 1985 of Grid and Data General laptops with EL displays from Sharp and Planar respectively helped to build the foundations for the nascent laptop computer industry at a time when LCDs did not have sufficient brightness or contrast to be used in commercial products.  Both Planar and Sharp monochrome ELDs used a phosphor layer made from zinc sulfide doped with manganese (ZnS:Mn).  These displays gave off an amber (orange-yellow) color that was bright but also pleasing to the eye.

Research on Color ELDs

One of the key disadvantages of ELDs relative to liquid crystal displays (LCDs) was that until 1981 ELDs were not capable of displaying more than one color.   Even after 1981, color ELDs were limited to a limited range of colors (red, green, and yellow) until 1993 when a blue phosphor was discovered.

In 1981, Okamoto reported that a rare-earth doped ZnS could be used in the phosphor layer of a TFEL device.[22][22]

In 1984, William Barrow of Planar and his colleagues announced that they were able to get blue-green emissions from strontium sulfide doped with cerium (SrS:Ce).

In 1985, Shosaku Tanaka at Tottori University and his colleagues reported that they had duplicated the work done at Planar on SrS:Ce phosphors but added that they had gotten calcium sulfide (CaS) to emit a deep red color.  In 1988, Tanaka’s group announced that they had gotten white light from a TFEL display using a combination of SrS:Ce and SrS doped with Europium (SrS:Eu).  The idea here was to use the white light in connection with a color filter to produce a full color display analogously to the way that it is done in liquid crystal displays.  The advantage of doing this with ELDs was that such a display would not require a backlight.  The main disadvantage was the added cost and difficulty of introducing a color filter.

In 1994, Soininen and coworkers at Planar International in Finland announced that a SrS:Ce/ZnS:Mn white phosphor deposited by atomic layer epitaxy achieves sufficient luminance and stability for use in color EL display products.[23][23]

Further work on blue phosphors was done by Reiner Mach and his colleagues at the Heinrich Hertz Institute in Berlin.  Additional work on SrS:Ce blue phosphors was done at Westaim Corporation.

A SrS:Cu blue phosphor showing improved blue color and efficiency was reported by Sey-Shing Sun of Planar in 1997. Planar demonstrated true white color EL prototype displays using this blue phosphor in a SrS:Cu/ZnS:Mn multi-layer structure.  The SrS:Cu phosphor will enable color EL displays to be produced with a wider color gamut.[24][24]

Barrow and his team at Planar announced a prototype of a multi-color EL display using ZnS:Mn and ZnS:Tb phosphor layers in 1986.  By 1988, they had a prototype full-color display using a patterned phosphor structure.  Commercial production of multicolor ELDs did not occur until 1993 at Planar, however, and full color ELDs have been produced only in the form of microdisplays (see section below on AMEL microdisplays).[25][25]  These color AMEL microdisplays used the ALE SrS:Ce/ZnS:Mn white phosphor with either sequential or spatial color filtering.

Planar Systems

Planar Systems, Inc., was formed in 1983 as a spinoff from Tektronix.  It was founded by three senior managers from Tektronix’ Solid State Research and Development Group:  John Laney, James Hurd, and Christopher King.[26][26]  Hurd became the President and CEO, Laney worked on manufacturing issues, and King became the firm’s chief technical officer.  Tektronix gave Planar its rights to certain technologies in exchange for an equity stake (in 1994 its share was still 7.5 percent).[27][27]  Planar remained privately held until it went public in 1993.

In 1984, Planar opened its first manufacturing facility in Beaverton, Oregon.  It shipped its first bulk order in 1985 to Nippon Data General for an early laptop computer with a CGA (640×200) EL panel.

Once volume manufacturing of ELDs began, a number of additional problems had to be solved in order to improve prospects for sales in the competitive markets for flat panel displays:

  1. 1.      Luminous efficiency had to be increased;
  2. 2.      Better driving methods were needed; and
  3. 3.      Gray scale capability of ELDs had to be enhanced.

The initial ELD prototypes had brightness levels of only about 20 foot lamberts (fLs).  Commercial products in the 1990s were to have brightness levels of 100 fLs.

The initial drive scheme for ELDs at Planar was to apply a single polarity voltage pulse to each line of the display and then an opposite polarity pulse to the entire panel.  This was called “the refresh method.”  In 1984/85, it was determined that this drive method led to “burn in” — some pixels would become unusable over time.  A new drive scheme invented by Tim Flegal called symmetric drive replaced the refresh method.  In symmetric drive, pulses of alternate polarities were applied to each line so that a net zero dc voltage was developed.  This prevented “burn in.”

Tim Flegal was also responsible for pioneering a variety of gray scale driving methods, including pulse width, analog voltage, and frame rate modulation.  High performance analog drivers at reasonable prices were difficult to obtain, and Planar had difficulty getting Texas Instruments to supply them because of the relatively low volumes involved (from TI’s perspective), but eventually Planar found a new supplier for these circuits: Supertex.[28][28]

One of Planar’s key markets after the decline in demand for monochrome displays for laptop computers was military displays.  Planar provided EL displays to defense contractors like Norden Systems and Computing Devices Canada, Ltd. (CDC).  These displays were monochrome with limited gray scaling.  Planar diversified its sales out of military applications toward industrial and medical equipment. By the mid 1990s, over a third of Planar’s sales were to medical equipment firms.

Because of Planar’s willingness to work with customers to adapt products for specific applications, it was able to command a price premium over the products of its main competitor, Sharp.  By the late 1980s, Planar controlled over 90 percent of the world market for ELDs.

Planar purchased the Finlux Display Electronics unit of Lohja Oy (Finland) in December 1990.  Finlux was renamed Planar International, Ltd.  Its headquarters remained in Espoo, Finland. The main reason for the purchase of Finlux was to obtain a marketing and production base in Europe but an important secondary reason was to get access to Finlux’s atomic layer epitaxy (ALE) technology (see the section on Finlux below).[29][29]

EL displays were not well suited to military applications by the early 1990s.  By that time, the military wanted color displays that were bright enough to be seen in airplane cockpits and tanks under a variety of environmental lighting conditions.  In August 1994, Planar purchased the avionics display operations of Tektronix and formed a wholly owned subsidiary called Planar Advance to manage this business.[30][30]  Planar Advance initially invested about $10 million in CRT-based displays for cockpits, but was blindsided by the DoD’s policy of switching to ruggedized TFT LCDs.  In response to this shift, Planar Advance purchased TFT LCD glass from dpiX and assembled them into “mil spec” units for the DoD.  This move permitted Planar to diversify its display offerings out of ELDs but it also necessitated a redefinition of the core competence of the firm.

In 1992, Planar helped to organized a consortium to develop color ELDs called the American Display Consortium.  This consortium was funded by the Department of Commerce under the Advanced Technology Program (ATP) created by the Clinton administration.  The total funding for the consortium was to be $30 million; half funded by the government and half by the consortium’s private firms.  The National Institute for Standards and Technology (NIST) supervised the consortium on behalf of the Department of Commerce.  Other members of this consortium were: Candescent Technologies, dpiX, Electro Plasma, FED Corporation, Kent Display Systems, Lucent Technologies, OIS, Photonics Imaging, SI Diamond, Standish Industries, Three-Five Systems, and Versatile Information Products.

In Spring 1995 Planar organized a consortium to develop the next generation of High Resolution and Color TFEL Displays. This consortium was funded by the Department of Defense under the DARPA managed Technology Reinvestment Program (TRP). The total funding for the consortium was to be $30 million; half funded by the government and half by the consortium’s private firms.  Other members of the consortium were: AlliedSignal Aerospace, Computing Devices of Canada, Ltd., Advanced Technology Materials, Boeing, CVC Products, Georgia Tech Research Institute, Hewlett Packard, Honeywell, Lawrence Livermore National Laboratory, Los Alamos National Laboratory, Oregon State University, Positive Technologies and the University of Florida.[31][31]

In 1989, the Defense Advanced Research Projects Agency (DARPA) began to fund work on advanced displays as part of its High Definition Systems program.  DARPA issued a Broad Area Announcement in that year and in subsequent years asking for proposals.

Planar won one of the first grants from DARPA in 1990 and used the funds to set up a laboratory to develop color ELDs.

Planar participated in a variety of DARPA programs, but perhaps the most significant was its work with Kopin and the David Sarnoff Research Center on active matrix EL (AMEL) microdisplays beginning in 1993.

The AMEL device is processed on a silicon wafer substrate using the inverted EL structure with a transparent ITO top electrode.  The lower EL electrode is the top metallization layer of the silicon IC.

ALE was used to make the device because of its excellent “conformal coating” characteristics.  ALE resulted in very few pinhole defects, a key requirement for reliable EL devices with top electrodes.

The pixel size of the first generation of AMEL displays was 24 microns.  The second generation of displays used pixels of 12 microns.  Smaller pixels meant higher resolution, lower power consumption and lower cost of production for a given display format.[32][32]

In October 1995, Planar announced an arrangement to supply AMEL displays to Virtual I-O, a Seattle-based manufacturer of consumer head mounted displays for virtual reality entertainment systems.[33][33]  Unfortunately, Virtual I-O went bankrupt in 1997 before any of these displays could be sold to the public.

 In March 1996, Planar was a awarded a DoD contract to supply an AMEL-based head mounted display (HMD) for the military’s Land Warrior Program.[34][34]  On May 16, 1996, Planar announced that it had developed an AMEL microdisplay that was one-inch square, 3mm thick, and weighed only 4 grams. In 1997 Planar announced that it had developed a 0.75 inch diagonal full-color VGA AMEL microdisplay using an LC sequential color shutter.[35][35](ref: R. Tuenge, et al., SID 97 Digest (1997), p.862 ).  Planar now has a brighter full-color microdisplay capable of displaying 32k colors that does not require the LC shutter.

Its profits also steadily increased in both absolute terms and per share but with a decline in 1998.  Planar went public with an IPO in 1993.

 A Brief History of Sharp’s EL Operations

The head of research at Sharp, Sanai Mita, was convinced that ELDs could be used eventually to make flat TVs.  Mito was formerly a professor at Osaka Municipal University.  He and his team mounted a major effort in the mid 1970s to develop TFELs.[36][36]

The key research at Sharp was done by Toshio Inoguchi and his colleagues.  The successful demonstration of a working TFEL display in September 1978 at the Consumer Electronics  Show in Chicago was the “finest hour” of Inoguchi’s group.  This display was only a few inches in diagonal, but it was also only 3 cm thick.

Sharp began mass production of ELDs in 1983.  One of its earliest displays was used in the U.S. Space Shuttle’s obital navigation system in that same year.[37][37]   Another early application of a Sharp ELD was in a Grid laptop computer.  This display provided resolution equivalent to a quarter VGA (320×240).

1983 was also the year that Shinji Morozumi at Seiko announced that his group was able to build a TFT LCD television.   That announcement took Sharp by surprise and they redirected their efforts toward catching up with Seiko in LCDs.  By 1987, Sharp was able to market their own TFT LCD television.[38][38]  They were able to capitalize on their lead in mass production of STN LCDs for calculators to quickly develop production technologies for high-volume TFT manufacturing.  After 1987, TFT LCD production was far more important to Sharp’s corporate strategy than EL production.  Nevertheless, the firm remained active in both research and production of ELDs, providing strong competition to Planar and Lohja.  Sharp continues to market EL displays for niche markets.

A Brief History of the Finlux Display Division of Lohja Oy[39][39]

In 1975, a research group headed by Dr. Tuomo Suntola recognized that thin film electroluminescence would be an ideal flat panel display technology provided that luminance stability and reliability problems could be overcome. To solve these problems a new thin-film deposition method called atomic layer epitaxy (ALE) was developed (see Figure 6). The basic idea was to build thin films layer by layer using surface-controlled chemical exchange reactions. The result is a dense, pinhole film with very good step coverage properties.  This research activity started in a small company called Intrumentarium that was acquired in 1977 by Lohja Oy, a Finnish conglomerate which was primarily a manufacturer of construction material.  Lohja was the second largest Finnish electronics company after Nokia, and the new ELD technology was considered a good fit for its strategy of diversification into electronics.

Figure 6. ALE  sequences for a binary compound   (courtesy of  Tuomo Suntola)


A. First precursor reacts with the surface. Chemi­sorption occurs through ligand exchange between the precursor molecules and the bonding sites.

B. When all bonding sites are filled the surface reaction is saturated. Bonding sites for the second precursor have been created.

C. Second precursor reacts with the surface created in steps A and B. Chemi­sorption occurs as long as bonding sites are available, until saturation …

D. and the formation of bonding sites for the first precursor  begins  again. The cycle of sequences A to D are repeated the necessary number of times for the desired layer thickness.

 Excellent ELD results based on its proprietary ALE technology were for the first time presented at the annual meeting of the Society for Information Display (SID) in 1980, where they received a lot of attention.  In 1983, three large information boards were delivered to the Helsinki Vantaa airport. Each of these was comprised of more than 700 character modules. They proved that ALE technology could meet reliability requirements necessary for commercial use. That technology was licensed to Sintra Alcatel in France in 1983.  However, the driver costs of the ELD character modules were too high to make them commercially viable, and as a result Finlux began development of a 9-inch 512×256 matrix display for computer and industrial applications.  A large manufacturing plant was constructed in a new science park set up in Espoo close to Helsinki.  Core manufacturing technologies, including ALE deposition equipment, were developed in-house, which delayed the start of mass production until 1986.  Half-page ELD matrix displays with resolutions of 640×200, 650×350 and 640×400 were subsequently manufactured at this plant.

The investments and development costs for ELDs were essentially funded internally by Lohja Oy because little public or customer-paid funding was available. This situation changed when color ELD development was started in 1988 as part of an EU-supported international consortium. The first color EL display based on an innovative device structure was brought to market in 1993.

Lohja Corporation was never able to make the Finlux Display Division profitable because of a lack of experience in managing microelectronics businesses.  The Finnish economy benefited from rapid economic growth from the late 1970s until the late 1980s.  But when the Soviet Union broke apart in 1991, the Finnish economy suffered because of its dependence upon the Soviet Union as a customer for exports.  In 1991, the Finlux Display Division was sold to Planar Systems and was renamed Planar International.

The two ELD operations were of approximately the same size at the time of the merger.  The merger permitted savings in marketing costs and materials purchases.  Planar Systems succeeded in making Planar International profitable in just a few years by using more experienced management, but without changing manufacturing technology and with only minor changes in staffing. The ALE manufacturing technology still forms the basis for the production of high volume ELDs at both Planar Systems and Planar International.  Much of the color development results that were achieved in Finland were also of direct benefit to the work on color ELDs at Planar Systems in the United States, and in particular the AMEL microdisplays discussed above.

In addition, in 1996, Planar Systems began to market a new generation of monochrome ELDs called ICEBrite displays.  The ICEBrites combined ALE grown phosphors and insulators with high contrast layers developed by Eric Dickey in the late 1980s.[40][40]

Organic Light Emitting Diodes (OLEDs)

In the late 1990s, several research laboratories announced that they had made breakthroughs in getting thin films of organic materials to emit light analogously to EL devices.  Because organic materials offered a number of process advantages over inorganic phosphors, these announcements were taken very seriously by potential investors.  This is not the place to go into the details of these developments.  Suffice it to say that the emergence of OLEDs led to a relative decline in interest in further work on color ELDs.  Planar Systems set up its own OLED program in collaboration with ___ as did several other display manufacturers.  It is possible that inability to solve the technological problems that have to be solved in order to manufacture OLEDs in high volumes will result in a return to research on color ELDs and other alternatives to TFT LCDs.  For the moment, however, the momentum is with the OLED research groups.

 

Conclusions

Electroluminescent displays (ELDs) have a venerable history starting with the experiments of Captain Henry J. Round in 1907, O.V. Lossev in the Soviet Union, and Georges Destriau in France.  Electroluminescence was mostly a scientific curiosity until the invention of thin film deposition techniques and the discovery that a sandwich of conductors, insulators and phosphors could result in a very efficent  and long-lasting form of emissive display.  ELDs were very important in the early days of the laptop computer industry and remained important in niche markets for military, medical and industrial equipment where high brightness, speed, contrast, and ruggedness are necessary.  The rise of the color TFT LCD display forced the ELD producers to engage in research on color ELDs with the result that there are now multicolor ELDs on the market and full-color AMELs in development for microdisplays.  The ELD industry is currently limited to two major players: Planar and Sharp.  Planar acquired its only European competitor, the Finlux Display Division of Lohja Oy, in 1990.  Sharp remains committed to competing in ELDs but its main focus is on liquid crystal displays.  Most of the important research on ELDs remains within the corporate laboratories of Planar and Sharp, but several publicly funded research laboratories and consortia have also made important contributions to ELD technology.

 [1][1] “Solid State Lamp Theory,” Technical Information provided by Lumex Opto/Components, Inc. at http://lumex.com/tech_notes/thery_1.html, access on July 13, 1999.

[2][2] P.D. Rock, A. Naman, P.H. Holloway, Sey Shing Sun, and R.T. Tuenge, “Materials Used in Electroluminescent Displays,” http://www.distec.com/Electro.htm, accessed on July 13, 1999.

[3][3] Ken Burrows, “Screen Printing EL Lamps for Membrane Switches,”  http://www.screenweb.com/main/newstand/99/el_lamps990128.html accessed on July 13, 1999.

[4][4] Http://nina.ecse.rpi.edu/shur/SiC/tsld011.htm accessed on July 13, 1999.  The publication of his observations was in Henry J. Round, “A Note on Carborundum,” Electrical World, v. 19 (February 9, 1907), p. 309.

[5][5] C.H. Gooch, Injection Electroluminescent Devices (New York: Wiley, 1973), p. 2.

[6][6] W.J. Baker, A History of the Marconi Company (New York: St. Martin’s Press, 1972), pp. 281-285; http://members.xoom.com/_XOOM/jon_uk/biography.html accessed on July 13, 1999.

[7][7]O.V. Lossev, “Wireless Telegraphy and Telephony,” Telegrafia i Telefonia bez provodor, no. 18 (1923), p. 61 and no. 26 (1924), p. 403; and O.V. Lossev, “Luminous Carborundum Detector and Detection Effect and Oscillations with Crystals,” Philosophical Magazine, v. 6, no. 39 (1928), 1024-1044.  See also http://www.lumex.com/tech_notes/thery_1.html accessed on July 13, 1999; and Gooch, p. 2.

[8][8] http://gwdu19.gwdg.de/~ugmk/his_eng.html accessed on July 15, 1999.

[9][9] B. Gudden and R.W. Pohl, “gber Ausleuchteung der Phosphoreszenz durch elektrische Felder,”  Zeitschrift fhr Physik, vol. 2 (1929), 192-196; B. Gudden and R.W. Pohl, “Lichtelektrische Beobachtungen an Zinksulfiden,” Zeitschrift fhr Physik, vol. 2 (1930), 181-191.

[10][10] Georges Destriau, “Recherches sur les scintillations des sulfures de zinc aux rayons “,” Journal de Chemie Physique, v. 33 (1936), 587-625.

[11][11] Gooch, p. 2.

[12][12] Burrows.

[13][13] Rack, et al., p. 2.

[14][14] N.A. Vlasenko and Iuri A. Popkov, “Study of the Electroluminescence of a Sublimed ZnS-Mn Phosphor,” Optics & Spectroscopy, v. 8 (1960), 39-42.

[15][15] M.J. Russ and D.I. Kennedy, “The Effects of Double Insulating Layers on the Electroluminescence of Evaporated ZnS:Mn Films,” Journal of the Electrochemical Society, v. 114 (1967), 1066- 1071.

[16][16] Edwin J. Soxman and Richard D. Ketchpel, “Electroluminescence Thin Film Research Reports” JANAIR Final Report 720903 (July 15, 1972). JANAIR is the Joint Army-Navy Aircraft Instrumentation Project.  Soxman and Ketchpel were employed by Sigmatron, Inc.  See also, Yoshimasa A. Ono, Electroluminescent Displays (Singapore: World Scientific, 1995), pp. 3-4.

[17][17] Bob Johnstone, We Were Burning: Japanese Entrepreneurs and the Forging of the Electronic Age (New York: Basic Books, 1999), p. 139.

[18][18] Aron Vecht, “High Efficiency D.C. Electroluminescence in ZnS (Mn,Cu),” British Journal of Applied Physics, vol. 1, Ser. 2 (January 1968), 134-136.

[19][19] Peter Brody, et al., “A 6×6 inch 20-lpi Electroluminescent Display Panel,” IEEE Transactions, Electron Devices (September 1975), 22,739.

[20][20] Toshio Inoguchi, M. Takeda, Y. Kakihara, Y. Nakata, and M. Yoshida, Digest of the 1974 SID International Symposium (1974), 84-  .

[21][21] Email correspondence from Chistopher King on July 15, 1999.

[22][22] K. Okamoto, Ph.D. Dissertation, Osaka University (1981).

[23][23] Email correspondence from Richard Tuenge, August 18, 1999.

[24][24] Ibid.

[25][25] Ono, pp. 4-5.

[26][26] http://www.planar.com/profile.htm accessed on May 8, 1997; and email correspondence from Christopher King on July 15, 1999.  Also coming to Planar from Tektronix were: Richard Coovert, Brian Dolinar, Donald Cramer, William Barrow, and Hal Merritt.

[27][27] Hoover’s Online profile, accessed at http://www.hoovers.com on May 8, 1997.

[28][28] Email correspondence from Christopher King on July 15, 1999.

[29][29] Interview with James Hurd, CEO of Planar, on June 10, 1996.

[30][30] Annual Report (1994), p. 14.

[31][31] “Planar and ARPA Sign TRP Agreement,” Business Wire, March 22, 1995.

[32][32] Christopher N. King, “Electroluminescent Displays…,” accessed at http://planar.com/download/tech/mrsnf98.pdf, p. 6.

[33][33] “Planar Systems  announces the world’s first full-color active matrix electroluminescent (AMEL) miniature headmount display,” Business Wire, May 15, 1996.

[34][34] Andrew MacLellan, “Smaller Displays Gain,” Electronic News, May 20, 1996, p. 1.

[35][35] Richard T. Tuenge, et al., SID 97 Digest (1997), p.862.

[36][36] Johnstone, p. 139.

[37][37] Electronic Industries Association of Japan (EIAJ), Research Report on the Visions of the Electronic Display Industry in the Year 2000, translated from Japanese by InterLingua (Tokyo: EIAJ, 1993), p. 58; and Johnstone, p. 140.

[38][38] Johnstone, p. 141.

[39][39] Information for this section was provided by Runar Tornqvist of Planar International.

[40][40] Eric Dickey, U.S. Patent No. 5,404,389 (1996).

export1 on 四月 5th, 2012

    冷光(E.L, Electro Luminesence)电机发光(EL)早在1936年首度由Destria博士发现,是一项已有六十年历史的技术,直到近年由于固态化学与薄膜半导体技术的发展,EL平面显示器才逐渐受到重视。EL可依发光材料分为有机和无机两种,过去多以无机的研究为主。目前,有机电激发光材料在操作寿命达到突破后,已经达工业化价值。EL可应用致文字处理机、个人计算机、等各种OA机器,以及车辆用导航终端机等各种用途。此外,EL显示器的全彩化已达实用水准,在不久的将来,渴望提升高精细的全彩EL显示器。由于信息科技的发展,平面显示器(Flat Panel Display;FPD)逐渐成为电子应用产品中的主流,举凡日常生活中的各种电器用品,包括;电视、汽车仪表板、手表、广告看板…..等。

EL冷光源特点

        1、高效节能、发光率高、功耗低,比普通白炽灯节电70%-80%;不产生热量、不含紫外线、无电磁辐射,对人体无伤害,为绿色环保型光源;

    2、超薄平整。EL发光体厚度仅为0.2-0.4MM,是目前市场上其它类型光源所不能达到的;

  3、面发光。EL发光体不需要借助导光板、散射剂就可以达到表面亮度一致,且亮度均匀、柔和;

  4、无散射。EL发光体作为指示牌等指示类发光体时,因无散射而大大提高了分辨率,降低了能耗;

  5、重量轻、随意性强。EL发光体可任意弯曲、粘贴或悬挂,可制做各种不同规格的图形和文字,由于重量极轻,非常便于安装和更换,大大节约了用工成本,降低了劳动强度;

  6、无光污染。EL发光体光线柔和,光色纯正,色彩艳丽丰富,对人的视觉不会造成任何刺激;

  7、穿透力强、能见度高。尤其适用于雨、雾天等视线条件极差的情况下;

  8、防水、防震,使用寿命长。EL发光体在常温下使用寿命可达8000-12000小时;

  9、抗高温(80°C),耐低温(﹣40°C)电源配备均能适合(交、直流)。