Laser_Marker_Methodes

Transparent conductive film

The industry's first*1 “unique roll-to-roll construction method” used in double-sided full wiring metal mesh.

Characteristics of transparent conductive films

electronic materials and transparent conductive film metal showing mesh structure

Transparent conductive films have the function of transmitting both electricity and visible light.  ITO (Indium Tin Oxide) has been widely used as a transparent electrode for various applications, such as touch displays or solar battery cells.

ITO generally having a resistance of 10s or 100s Ω/sq., in order to meet the demand for lower resistance required in recent years ITO has to be applied thickly, however that causes problems like transmissivity loss or color change (yellowing).

To solve these problems, metal mesh has been developed as an alternative of ITO.

Indium Tin Oxide Metal Mesh
(shown on the right side)
Rare metal ⇒ Expensive Low cost material
Ceramic material ⇒ Fragile Flexible / Bendable
High resistance Low resistance
Colored when resistance lowered  

Conventional etching type metal mesh

transparent conductive film with Wiring line width and thickness relations

Etching method is generally used to produce metal meshes, but there is a trade-off between lower resistance and finer wiring lines. When large size is required, transmissivity is sacrificed by the increased line width in order to lower the resistance.

In addition, metal remainder at the cross point, which tends to happen in the metal mesh produced by etching process, causes deterioration of appearance.

transparent conductive film showing problems with Etching

Problems with the etching method

  • Trade-off between lower resistance and finer wiring lines
  • Metal remainder at cross point

Industry’s first unique roll to roll process

Panasonic has developed a double-sided full wiring metal mesh using industry’s first unique roll-to-roll process to achieve high wiring aspect ratio, realizing low resistance and high transmissivity at the same time.

electronic materials: transparent conductive film and roll-to-roll

Wiring with High Aspect Ratio

transparent conductive film wiring with high aspect ratio

As shown in the graphic, resistance value is inversely proportional to the cross-sectional area of the wire.

Therefore the cross-sectional area must be increased to keep the resistance value low.

R = ρ * (L / A) R: Resistance
ρ: Resistivity
L: Wire length
A: Wire cross-sectional area

Panasonic can make surface of film by flat

Panasonic’s metal mesh produced by its unique process has high aspect ratio wiring lines by gaining a cross-sectional area to depth direction while keeping the fine line width, achiving low resistance and excellent transmissivity at the same time.

Aspect ratio = Line depth (thickness) / Line width

electronic-materials: transparent conductive film - etching process comparison

Wire thinning and aperture ratio​

Wire thinning greatly contributes to the aperture ratio.

Since a metal blocks light, the narrower the metal wiring line width is, the greater the aperture ratio becomes. Aperture ratio is proportional to the transmissivity, therefore Panasonic’s metal mesh films can achieve high transmissivity.​

AR = (P - W)2 / p2

AR: Aperture ratio
P: Mesh pitch
W: Wire width

electronic materials: transparent conductive film - Wire thinning and Aperture Ratio

Visibility of wiring lines​

Metal wiring lines are visible due to metal reflection if the line width is not thin enough. In Panasonic’s metal mesh, wiring line width is 2um or less so mesh pattern is invisible to human eyes.​

Panasonic’s metal mesh​

  • Invisible due to fine wiring of 2um or less​
  • Blackening treatment on metal surface to reduce reflection​
electronic materials, transparent conductive film showing line width and visibility relation

Application: High frequency tele-communication​

High speed, large capacity, multi-connection and low latency 5G/6G tele-communication uses high frequency bands.  In general, higher frequencies cause issues such as deterioration of radio wave signals due to the influence of various substances, or waves not reaching far enough especially in a city area dense with buildings due to its straight propagation characteristics.​

Panasonic will apply its transparent conductive film technology to provide new solutions to these issues.​

Transparent Antenna

Since 5G/6G tele-communication uses high frequency bands, it is strongly affected by various substances and devices nearby.​ Therefore, the placement of 5G/6G antennas is less flexible, and ideally they should be placed on the top surface of devices.​

Transparent antennas, utilizing Panasonic’s transparent conductive film technology, can be placed anywhere without disturbing the design and function of displays, windows etc.​

electronic materials: transparent conductive film showing application transparent antenna

Meta-surface​

High frequency radio waves propagates in a straight line, so radio waves cannot reach in long distance, especially in the areas where buildings are densely concentrated.  For this reason, there is a need for metasurface devices, such as reflectors that propagate radio waves in far distance, and lenses that draw radio waves into the room.​

Panasonic contributes to 5G/6G world by applying its transparent conductive film to metasurface technology.​

electronic materials: transparent conductive film application meta-surface

Application: Transparent display​

In current highly advanced information society, AR (Augmented Reality) has been adopted in various scenes including in-vehicles.​ For further penetration of AR, transparent displays are expected to be commercialized that can show sufficient amount of information without obstructing the viewing area.

Applying Panasonic‘s transparent conductive film technology to the backplane of transparent display enables clear display of information while keeping high transmissivity.​

electronic materials: transparent conductive film application of a transparent display

Application: Transparent Heater​

Along with the practical application of autonomous driving, various cameras and sensors are newly equipped on the exterior of vehicles.  In order to prevent false detection caused by fogging or freezing, transparent heaters that do not interfere with the sensing function are required.​

Panasonic applies transparent conductive film technology to a transparent heater to realize a highly stable sensing environment.​ Transparent film heater can be also placed on the lens of surveillance cameras, which have been rapidly installed in recent years, to ensure stable function.​

electronic materials: transparent conductive film application for transparent heater

Touch sensor application

Panasonic’s metal mesh based transparent conductive film has both low resistance and high transmissivity at the same time.

When used for touch sensors, it will realize customer’s various needs / wants, which could not be realized by conventional transparent conductive films.​

electronic materials: transparent conductive film with the touch sensor application

Items​

Conventional etching process​
Metal mesh*​

Panasonic’s unique process​
Metal mesh*​

Visibility​ - Wiring Line Width​

×​

4 um​

◎​

≦2 um​

Transmissivity​

○​

90.3%​

◎​

94.1%​

Sheet Resistance​

◎​

2 ohms/sq.​

◎​

2 ohms/sq.​

Frame Wiring (L/S)​

△​

15/15 um​

◎​

8/8 um​

Base material​

◎​

PET and COP​

◎​

PET, PC and COP​

Bendability​

◎​

≧ R2 mm​

◎​

≧ R2 mm​

*Comparison between our own prototypes​