TransparentOLEDCurrent Status and Technical Analysis of Display Development
Introduction
Since1987the year Professor Deng Qingyun achieved low-voltage driving of double-layer organic electro
luminescent devices,
OLED(Organic Light Emitting Diodes) has made significant
progress, showing a rapid development trend in the display panel field. Compared with traditional
liquid crystal displays,
OLEDit is a self-emissive display technology that does not require
a backlight, thus featuring thinness, wide viewing angle, and high contrast.
In addition,
OLEDusing solid-state organic materials as the light-emitting layer, its reflective positive
electrode and semi-transparent cathode form an optical microcavity. Using the microcavity effect, the
full width at half maximum of the emitted light can be controlled within35nmtherefore,OLEDpanel color purity
is high and the color gamut is wide. EachOLED
characteristic is favored by panel manufacturers and consumers, quickly occupying wearable, hand
held, television, and automotive display markets. Its panel shipments have been increasing year by year, and the market
penetration rate is expected to increase to2025in the year73%。
In recent years, led by Samsung, there has been a revolution in the appearance of the panel industry. The emergence of
flexible screens has made consumers realize for the first time that screens can change from straight to curved,
and from curved to rolled. Flexible displays usePI(polyimide) film as a substrate,
withTFTdrive circuits and depositedOLEDmaterials, and finally using
TFEthin film encapsulation technology to achieve the purpose of isolating water and oxygen. The application fields of flexible screens are
very wide, and with the breakthrough of technical bottlenecks, the yield will be further
improved.
It is worth mentioning that
OLEDdevice structure is very suitable for making
transparent displays. Research in this area has always been a hot topic in the industry.
OLEDTransparent screens have broad application prospects and can be used for window displays, outdoor advertising
signs, flat panel displays, and even as glass windows, which has a science fiction feel. At present, related products have been launched on the market, with small sizes represented by
Kairos's transparentdisplay smartwatches, and large sizes represented by Samsung's
inch transparent55TV.
OLEDSouth Korea'sLG Displayhas mastered the technology for mass production of large
Size transparentOLEDdisplays, and it is believed that more products will be
launched into the market in the future.Facingincreasinglyfiercecompetitionin the displaypanelmarket市场curvedpanelscreenfullscreen、folding screenetcnew conceptsareemerging endlessly,showingthatpanelmanufacturerswanttostandoutmust，achieve productdifferentiation.实现产Displaycan beregarded asTransparentanewtechnologicalbreakthroughpoint. Currently,的技术standit seemsthat,，目前来Compared to，相对于LCD、MicroLEDetcItsHeTechnology，OLED
In terms of the feasibility of producing transparent screen products, this technology is the most mature and suitable.
。
1Classification of Transparent Display Technology
A transparent panel is transparent like ordinary glass when it is turned off, while
when working, it not only allows us to see the image displayed on the panel, but also allows us to see
the object behind the display screen. In the currently reported cases,
PDP、
LCD、
Micro-LED、OLEDand other technologies can achieve transparent display. Below we
will give a brief introduction:
1.1 PDPTransparent Display
NowadaysPDPdisplay screen products are very rare. Its working principle is similar to
Abstract：
OLEDThe emergence of display technology has broken people's inherent understanding of display screens. Display products made using this technology can be light, thin, easy to carry, and have vibrant colors. The
productsOLEDcan be made not only in the conventional planar shape but also as curved surfaces or even foldable, giving an unparalleled sense of visual immersion. Combined with
technology, we can make the display panelLCDtransparent, unlikeOLEDtransparent technology that relies on external light for display, transparent40%display is a self-luminous technology with high transparency, generally overOLED
%. Transparent
OLEDdisplay technology provides us with different presentation forms and visual impact. Combined with the prevalence of modern IoT, it is expected to propel the development of a ubiquitous screen display era. This article is based on transparent
Keywords：
OLED
; transparent
display; transparent
cathode
Library of Congress Classification
yuanTN
873
wen
Document Identification CodeyuanA
Article Numberyuan2095-2945yuan2020yuan08-0135-03
Abstract': The emergence of OLED display technology has broken people's inherent understanding of the display screen. The
display products made by this technology can be light, easy to carry and colorful. Besides the conventional plane shape, the products
can also be made into curved surfaces or even folded, giving people an unparalleled sense of visual immersion. Combined with OLED
technology, we can make the display panel transparent. Different from the transparent technology that LCD relies on external light for
display, transparent OLED display belongs to self-luminous technology, and the transparency is generally more than 40%. Transparent
OLED display technology gives us different presentation forms and visual impact, combined with the popularity of the modern Internet
of things, it is believed that it will promote the development of the "ubiquitous screen" display era. This paper describes the origin
of its deve
lop
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and
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Key
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Science and Technology Innovation and Application
Technology Innovation and Application
Similar to common fluorescent lamps, it is a display technology that utilizes gas to generate plasma discharge,
then excites the phosphor to emit visible light. BecausePDPit does not require
TFTa driving circuit, as long as the opaque electrodes, phosphors,
and barrier layers in the panel are replaced, transparent display can be achieved.2011Year, Korea Daejeon Science
Institute of Technology used a highly transparent silica sol-gel as insulation
layer,
SU-8photoresist as a barrier layer, resulting in
transmittance close to63%of
PDPdisplay screen, achieving good visual effects
。
1.2Liquid crystal transparent display
LCDbelongs to a non-self-luminous display technology, which relies on the
light emitted by the backlight to display different colors through red, green and blue color films. To useLCD
technology
to realize transparent display, there are generally two methods. The first is to
remove the backlight
，
using external light as a light source to achieve a transparent effect. The second is to rearrange the backlight
module and place the backlight on the side of the display screen. The former is suitable for
making large-size panels, while the latter is suitable for small-size products.
2012Year, JD
side showed the first domestic32inch transparent LCD screen using the first
method. This display has full HD, low power consumption, wide viewing angle, and high contrast
features, becoming the focus of the exhibition at that time.
1.3 Micro-LEDTransparent Display
Micro-LEDis a micro light-emitting diode display, which is a self-luminous display
technology, composed of10microns or lessLEDgrains to form light-emitting pixels.
Due to the extremely small size of the light-emitting pixels, it has an innate
advantage in making transparent displays.2019Year, Tianma atSIDconference showed the cooperation withPlayNitrideto complete
inch transparency7.56display product,60%ofMicro-LEDthe prototype has a resolution of
，the bezel is less than114PPI，and can be used for in-vehicle0.8mmdisplays. However,
the technology is still immature, and there is still a period of time needed for technical accumulation in terms of mass transfer, chipMicro-LEDyield, and trichromatic display.
良率、三基色显示化等方面仍需要一段时间的技术沉淀。
1.4 OLEDTransparent Display
OLEDCommon microstructures include bottom-emission and top-emission devices. Their
electrode designs all use one side for total reflection and the other side for light transmission
method, which is the so-called single-sided displayOLED. Among them, the light emitted by the top-emission device does not pass through
layer, so it has a higher apertureTFTratio than the bottom-emission device. If we use a transparent anode and a semi-transparent cathode to make
deviceOLED器
then we will get a double-sided displayOLED，but the drawback is that this will reduce
OLEDdevice efficiency to25%，and the color saturation is less than50%，which is difficult to meet
user needs.OLEDTransparent displays utilize their self-luminous and thin
properties, with a thickness that can be controlled to around1mm，and products such as watches, televisions, and shop windows made using this technology have a unique charm. Samsung,
，Panasonic, etc.
LG Display、松下等
companies have already exhibited related prototypes. AlthoughOLEDthe thickness is very thin, it uses
用的LTPS(low-temperature polycrystalline silicon) driver circuits and some functional layers have
very low transmittance, so to achieve transparent display, the circuit needs to be rearranged or
the opaque functional layers need to be replaced with transparent materials to obtain higher transmittance,
which will be discussed in detail below.
2TransparentOLEDDisplay Technology Analysis
Currently common transparentOLEDpanel transmittance is around45%，using
OLEDthin and self-luminous characteristics, it is not difficult to achieve transparent display. Combining our production experience, the technology can be introduced in the following three aspects:
合我们的生产经验可分为以下三个方面进行技术介绍：
2.1Transparent Substrate Technology
Commonly used in the marketOLEDpanel products mostly useLTPSas a drive
circuit. The higher the resolution, the denser the circuit arrangement. The light transmission of the circuit part is
not good, especially usingITO/Ag/ITOas the anode, the total reflection layer is completely
opaque. Therefore, the first thing we consider isTFTThe circuit is redesigned
by arranging the light-emitting pixels and circuits compactly to create light-transmitting areas
(Figure1). In addition, we tried to retain only
breakthrough
one
pixel as a light-emitting display area in a group of four pixels, with the remaining three pixels being non-display areas
removing
non
-
display
of
area
anode,
planar layer
and
pixel
definition
layer
，
Through
this
method
the
resulting
base
market
transparency
rate
reached
56%
(Figure
2).
From
the
material
perspective
the
deeper
the
color
the
stronger
its light absorption capacity. Currently, the materials used for the planar layer and pixel definition layer have a transmittance of approximately
透过率约为70%Therefore, using transparent materials to replace them can further
improve the substrate transmittance.
Figure1TransparentOLEDshows a schematic diagram of the transparent area setting
Figure2Top-emission transparentOLEDdisplay pixel arrangement schematic diagram
2.2Transparent cathode technology
Top-emissionOLEDdevices generally useCMM(conventional metal mask)
evaporation15nmof a magnesium-silver alloy as a semi-transparent cathode; however, the reflection of light by the metal means that the product transmittance can only reach
反射导致产品透过率只能达到28%To address this issue,
we useFMM(fine metal mask) to evaporate
the cathode in the pixel area of the display area, without evaporating the cathode material in the non-display area. Then, connecting the cathode in the display area can increase the product transmittance to
行搭接，可使产品透过率提升至42%Due toFMMhigh
Price
which brings significant cost pressure to actual production, we attempted to selecttransparent materials as the cathode.ITO90%(indium tin oxide) is a good conductor with a transparency of
above
It is deposited on the surface of the organic film by magnetron sputtering to act as the cathode, which can obtain good transparency while weakening the microcavity effect
leading to color shift. Considering thePlasmagenerated during the sputtering process may
OLEDadversely affectthedevice performance, researchers used
PLDtransparent materials as the cathode.(pulsed laser deposition) technology to achieve damage-free depositiontransparent materials as the cathode.
of thin films. Besides
this, nanosilver wires, graphene, and metal meshes are materials that exhibit excellent transparency and conductivity. Their existence has driven the development of transparent panels.
展。
2.3Other improvement technologies
In light loss mechanisms, we refer to the reflection loss at the interface between materials with different refractive indices as Fresnel loss. To improve transparency, we must find ways to reduce light loss as light passes through the display panel. For example, there is an air gap between the packaging glass and
the
Cover glass, and the optical mismatch between glass and air causes light loss. If a transparent degassing agent is used to fill the gap,
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Technology Innovation and Application
Technical Innovation
then not only can the transparency of the panel be improved, but also the compressive strength of the panel can be enhanced
那么不仅可以提高面板的透明度，还可以增强面板的抗压
Strength. In addition, the common glass transmittance is generally91%，research shows that in
Applying an anti-reflective coating to the glass surface to reduce the reflection of external light can make
The transmittance of glass increased to98%，for improving transparency is a simple
Easy method.
3Conclusion
OLEDDisplays have advantages unmatched by other traditional display technologies,
Benefiting from the maturity of upstream technology and the growth of downstream demand, with the gradual reduction of production costs
LaterOLEDThe market penetration rate of panels will further expand. Currently,
Display panel manufacturers in various countries have actively deployed and put into production.OLED器
Pieces are very suitable for making transparent panels, while transparentOLEDIs a visual
Impactful product, and its appearance will surely make waves in the consumer market
。
Of course, transparentOLEDPanels currently have problems such as insufficient brightness and low contrast
Problems that have been criticized, but with the improvement of transparent substrate technology and transparent cathode technology,
Further improvement, coupled with the emergence of more transparent materials, these technical
Difficulties will be solved one by one.
Referencesyuan
[1]Ma Dongge.OLEDDisplay and Illumination——
—From basic research to future applications[J].Liquid
Crystal
And
a
，20
16，31
（
3
）：
22
9-2
41.
[
2]
Hu
Kai, Chen
Yuxiang
，Li
Qing
.
Transparent
a
Technological advances[J].Electronic devices,2012
（06）：21-28.
[3]Chen Xiao.TransparentLCDDisplay technology research[J].Optoelectronic technology,
2019，39（02）：
137-
14
2.
[
4]
Lü Fang, Gu Jiannan, Bian Mengying, etc..Organic light-emitting diode (OLED) top-emission device
of
Transparent
Electric
Pole
[J].
Science
Technology
Communication
Report
，
20
18
（12
)
：
11
11
-
1
122.
[
5]
Park
S.
K.
，
Ry
u
M.
，
Y
and
g
S.
，
e
t
a
l.O
x
id
e
TFT Driving Trans
parent AMOLED[J]. Journal of the SID，
2010，18（
1）：
245-248.
Spectrum analysis, by extracting the power spectral density at the corresponding position, the signal-to-interference ratio is obtained
Value; on the other hand, for signals with non-linear modulation methods, by measuring the baseband signal
The degree of phase ambiguity can also determine the quality of the frequency point. For this purpose, it is necessary to introduce
The mechanism of non-equal time division duplex, within the time unit of a frame, the vast
Most of the time is used for downlink communication, leaving a small amount of time as an uplink report,
Allows the called user to allow the calling party to know the frequency quality and establish the corresponding link
Correction frequency table.
For unintentional interference from the enemy, idle channel scanning can be performed irregularly
Scan, analyze and record the frequency, period and other information of the intercepted signal, and in the subsequent
Communication, notch filtering is performed on the repeated bands to reduce the unintentional interference of the enemy station to me
The harm caused by the party.
3.4Frequency-hopping power adaptation
Frequency-hopping power adaptive technology is used in frequency-hopping communication when facing enemy tracking
In the case of interference such as style or blocking interference, a method similar to fixed-frequency communication is used
Increase the transmission power to resist aiming interference, and fight against the double
The two sides are competing in the power domain.
3.5Hybrid anti-interference
Frequency-hopping technology cannot effectively counteract various interferences. By using frequency-hopping technology and
The combination of other anti-jamming technologies can more effectively improve the anti-jamming performance of ultra-shortwave frequency-hopping radios.
The anti-jamming performance of ultra-shortwave frequency-hopping radio stations can be improved more effectively by combining other anti-jamming technologies.
（
1)FHAndMDS(Multi-level Direct Sequence Integration).MDSNarrow
band direct-sequence spread spectrum function,MDScombined with frequency hopping, through multi-level processing, makes direct-sequence
retain anti-jamming tolerance while occupying a narrowband spectrum. It has
higher practical value in the ultra-shortwave band.
（
2)FHAndFCS(Free Channel Scanning).FCSThis method can better deal with
partial blocking interference, excluding the jamming signals of enemy stations. While frequency hopping
can better counteract tracking interference, the combination of the two takes advantage of each other's strengths and has
comprehensive anti-jamming capabilities.
3.6Network-level anti-jamming
Adhocnetworks are a special type of peer-to-peer network used for radio communication,
formed by implementing multiple hops, forming a wireless self-organizing network architecture, belonging to the network
level anti-jamming communication method. The network structure can adopt a hierarchical structure,
and the media access control can consider combining collision avoidance multiple access protocols with synchronous
orthogonal frequency-hopping networking methods.
4Conclusion
Frequency-hopping communication systems, due to their strong anti-jamming capabilities, strong confidentiality, high communication frequency
band utilization, good anti-destruction capability, and fast access, are very suitable for modern information
warfare conditions of electronic warfare requirements, so it has been widely used in ship communication
applications, especially in frequency-hopping radio stations.
This paper analyzes the key factors affecting the anti-jamming performance of frequency-hopping communication systems
and the methods and means of jamming frequency-hopping communication systems. From the perspective of anti-jamming,
technical approaches and basic implementation methods for enhancing the anti-jamming capability of ship ultra-shortwave frequency-hopping communication are given.
However, in order to further improve the anti-jamming capability of frequency-hopping communication, and in order to make communication more secure and reliable,
the combination of multiple methods can more effectively improve the comprehensive anti-jamming capability.
The combination of multiple methods is more effective in improving the overall anti-jamming capability.
Referencesyuan
[1]Zhang Aimin, Liang Shujian, Ma Zhiqiang, etc..Overview of Anti-jamming Technology in Military Communication[J].
Communication Technology,2011，44（
8）：15-17.
[2]Yao Fuqiang.Communication Anti-jamming Engineering and Practice[M].Beijing: Electronics Industry Press,
2008：
1-25.
[3]Wei Bingchao, Xiang Wei.Research on Anti-jamming Technology for Military Satellite Communication[J].Radio Communication Technology,
15-18.2008，34（
1）：[4]
Zhang Zhijian, Guan Jianxin, Zhang QinResearch on Anti-jamming of Military Communication Based on Cognitive Radio.J
[
Ship
].
Ship
Ship
Electric
Son
Engineering
，
2009
，29
（
1
）：
1-
4.
[
5]
Ma
Zhong
Gui
，
Zhou Xian
Wei
.
Based on Self
Adapting
Intelligent
Intelligent
Energy
Anti-jamming Method of Cognitive Radio Based on Adaptive Intelligent Antenna
[J].Journal of Radio Science,2010，25（
4）：767-771.
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