Bigger, brighter billboards? Large-surface light-emitting plastic film created

Published Date
Date : March 3, 2015

Source: Technical Research Centre of Finland (VTT)

Summary: Based on OLED technology and implemented by means of a printing machine, a new method allows for patterned and flexible light-emitting surfaces on advertising displays, info signs and lighting fixtures, for instance. The method also enables transparent smart surfaces to be attached to window panels or packaging.

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Organic Light-Emitting Diode (OLED) technology is based on electroluminescence, as it occurs in an organic semiconductor. In OLED, an organic, light-emitting semiconductor is placed between two electrodes, one of which is transparent, letting out the light created in the structure. When conducted through the component, electric current produces light.

Credit: VTT

Based on OLED technology and implemented by means of a printing machine, this method developed by VTT Technical Research Centre of Finland Ltd provides an opportunity to create patterned and flexible light-emitting surfaces on advertising displays, info signs and lighting fixtures, for instance. The method also enables transparent smart surfaces to be attached to window panels or packaging.

OLED technology (Organic Light-Emitting Diode) is commonly used in mobile phone displays and television sets, though until now has only been found in glass surfaces, implemented using traditional microelectronics manufacturing methods. Using VTT's method, OLED elements can now be printed not only onto glass or steel surfaces but also onto flexible plastic films, enabling significantly larger light surfaces and expanding the usage possibilities of the technology.

This type of light-emitting plastic film and processing in ambient atmosphere has not been created before on this scale.

Traditional printing methods such as gravure and screen printing, enabling very large production volumes, are used for manufacturing OLED light surfaces. Production is, therefore, possible in facilities such as traditional printing houses.

Manufactured using the gravure and screen printing methods, OLED light surfaces are around 0.2 mm thick, and include electrodes and polymer layers measuring up to a few hundred nanometres, in which the light emission occurs. This phenomenon is called electroluminescence; it entails an organic semiconductor emitting light in an electric field. The luminosity of OLED (lm/W) amounts up to around one third of an LED's luminosity. It has one advantage: OLED emits light throughout its entire surface, whereas LED is a spotlight technology.

At this point, VTT's plastic OLED film will only emit light for around a year, since light-emitting polymer materials are susceptible to oxygen and moisture. In the future, the film's lifespan will increase as the development of screen protectors continues and the film's application possibilities grow.

"The plastic film is optimally suited to advertising campaigns, in which large light-emitting surfaces can be used to draw significantly more attention than can be gained through mere printed graphics or e-ink-type black-and-white displays that do not emit light," says Head of Research Area Raimo Korhonen from VTT.

It is also possible to use OLED light as a transmitter in wireless data transfer, which opens up new possibilities for utilising printed light surfaces in Internet of Things applications.

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Materials provided by Technical Research Centre of Finland (VTT). Note: Content may be edited for style and length.

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Technical Research Centre of Finland (VTT). "Bigger, brighter billboards? Large-surface light-emitting plastic film created." ScienceDaily. ScienceDaily, 3 March 2015. <www.sciencedaily.com/releases/2015/03/150303074918.htm>.

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https://www.sciencedaily.com/releases/2015/03/150303074918.htm

New flexible films for touch screen applications achieve longer lasting display

Published Date

Date : March 6, 2015

Source: The Optical Society

Summary: Today, touch screens are everywhere, from smart phones and tablets, to computer monitors, to interactive digital signage and displays. Many touch screens are made of layered thin (billionths of a meter thick) films of indium-tin oxide, an inorganic material that is electrically conductive, which allows electrical signals to travel from the "touch" to the edges of the display, where they are sensed by the device--as well as optically transparent. But these and other inorganic materials have a downside, as anyone who has ever dropped their smart phone knows: they are brittle and shatter easily. The solution? Make the screens flexible and durable without sacrificing any of their electrical or optical properties. Researchers have now created thin sheets of hybrid materials that may enable the next generation of consumer electronics.

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This is a plot of the percentage resistance increase of the ITO/SiO 2 /Nb 2 O 5 /PET and ITO/L/H/PET substrates as a function of the number of bending cycles [ 32-35 ] . (b) Photograph of the ITO/L/H/PET substrate during the bending test at minimum width of 40 mm. (c) Plot of the percentage resistance increase of the ITO/L/H/PET substrates prepared with and without acid as a function of the duration in a chamber maintained at 85 °C and 85% relative humidity.

Credit: Soo-Young Park

Today, touch screens are everywhere, from smart phones and tablets, to computer monitors, to interactive digital signage and displays. Many touch screens are made of layered thin (billionths of a meter thick) films of indium-tin oxide, an inorganic material that is electrically conductive, which allows electrical signals to travel from the "touch" to the edges of the display, where they are sensed by the device--as well as optically transparent.

But these and other inorganic materials have a downside, as anyone who has ever dropped their smart phone knows: they are brittle and shatter easily. The solution? Make the screens flexible and durable without sacrificing any of their electrical or optical properties. A paper in the latest issue of The Optical Society (OSA) journal Optical Materials Express describes a new type of thin film that achieves just that.

The paper by polymer scientists Soo-Young Park and A-Ra Cho of Kyungpook National University in Daegu, South Korea, describes a method to create a type of so-called "hybrid" film, composed of both inorganic and organic materials.

A process known as the sol-gel fabrication technique can create hybrid films-- but it, too, is less than ideal, because it requires the use of acids that corrode the metals and metal oxides in the devices' electronic components. "Therefore," said Park, "acid-free methods of synthesizing organic-inorganic hybrid materials are needed for optical thin-film applications."

Park and Cho start with a co-polymer composed of two organic materials, methyl methacrylate and 3-(trimethoxysilyl) propyl methacrylate, which are combined with another chemical called trialkoxysilane. This co-polymer is then reacted with two inorganic chemicals, titanium isopropoxide and tetraethyl orthosilicate, to synthesize hybrid layers with high (1.82) and low (1.44) refractive indexes.

The refractive index is a measure of the extent to which light is bent as it passes through the material. Most transparent materials have indexes that fall between one and two. Inorganic thin-layer and hybrid films alike have layers with different refractive indexes to help tune the wavelengths of light that pass through the film (or touch screen).

Tests of the new hybrid films indicate that both the high and low refractive index layers are highly transparent--with transparencies of 96 percent and 100 percent, respectively, when compared to bare glass.

The new hybrid materials are produced entirely in solution, at low temperatures, and without the need for high-vacuum (i.e., very low-pressure) conditions, which significantly reduces production costs. In addition, the process allows for the creation of multilayered films in which the layers have thicknesses that would allow the films to be used for anti-reflective coatings, opening the door to potential new applications.

The hybrid films showed less depreciation in flexibility after 10,000 bending cycles than the inorganic layered films. Resistance of a material increases because of the formation of minute cracks as it flexes--just as it would when used in a flexible display screen. A film with higher resistance has lower electrical conductivity, meaning that more voltage must be applied to send a signal through it, which further degrades the material.

"The resistance increases less over time in the hybrid thin-layer film, so a display made from this type of film will last longer," Park said.

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Materials provided by The Optical Society. Note: Content may be edited for style and length.

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Journal Reference:

1. A-Ra Cho, Soo-Young Park. Synthesis of titania- and silica-polymer hybrid materials and their application as refractive index-matched layers in touch screens. Optical Materials Express, 2015; 5 (4): 690 DOI: 10.1364/OME.5.000690

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Super-flexible liquid crystal device for bendable and rollable displays

Published Date

Date:

December 9, 2016

Source:

Tohoku University

Summary:

A super flexible liquid crystal (LC) device has been developed, in which two ultra-thin plastic substrates are firmly bonded by polymer wall spacers.

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Wearable information terminals (left) and large rollable-screen TV (right) are made using super-flexible LC technology covering large areas, with high-resolution at low-cost.

Credit: Image courtesy of Tohoku University

Researchers at Tohoku University have developed a super flexible liquid crystal (LC) device, in which two ultra-thin plastic substrates are firmly bonded by polymer wall spacers.

The team, led by Professor Hideo Fujikake and Associate Professor Takahiro Ishinabe of the School of Engineering, hopes the new organic materials will help make electronic displays and devices more flexible, increasing their portability and all round versatility. New usage concepts with flexibility and high quality display could offer endless possibilities in near-future information services.

Previous attempts to create a flexible display using an organic light-emitting diode (OLED) device with a thin plastic substrate were said to be promising, but unstable. The plastic substrates are poor gas-barriers for oxygen and water vapor, and the OLED materials can seriously be damaged by their gasses. As for flexible OLEDs, there has also been no device fabrication technology established so far for large-area, high-resolution and low-cost displays.

To overcome these challenges, Fujikake's research team decided to try making existing LC displays flexible by replacing the conventional thick glass substrates, which are both rigid and heavy, with the plastic substrates, because LC materials do not deteriorate even for poor gas barrier of flexible substrates.

Flexible LC displays have many advantages, such as established production methods for large-area displays. The material itself, which is inexpensive, can be mass produced and shows little quality degradation over time.

However, in conventional flexible LC displays, one important problem remains. The gap of plastic substrates (100 μm thick) sandwiching an LC layer becomes non-uniformed when the LC device is bent, causing the display image to be distorted.

In their study, Fujikake's team developed a super-flexible LC device by bonding two ultra-thin transparent polyimide substrates (10 μm thick approximately) together, using robust polymer wall spacers.

The ultra-thin transparent substrate is made using the coating and debonding processes of a polyimide solution supplied by Mitsui Chemicals. The result is a flexible sheet, similar to food-wrapping cling film.

The substrate has the attractive features of heat resistance, and the ability to form fine pixel structures, including transparent electrodes and colour filters. The refractive index anisotropy is extremely small, making wide viewing angles and high contrast ratio possible.

The polymer wall spacers bonding substrates are formed by irradiating a twisted-alignment LC layer including monomer component with patterned ultra-violet light through single thin substrate. While the substrate gap is more variable as the substrate thickness is decreased, the stabilization of ultra-thin substrates becomes possible by small pitch polymer walls.

The research team also demonstrated that the device uniformity is kept without breaking spacers even after a roll-up test to a curvature radius of 3mm for rollable and foldable applications.

The above research results show that LC displays with large-area, high-resolution and excellent stability can be as flexible as OLED displays. The super-flexible LC technology is applicable to mobile information terminals, wearable devices, in-vehicle displays and large digital signage.

Moving forward, the team plans to form image pixels and soften the peripheral components of polarizing films, and a thin light-guide sheet for backlight.

Part of the results of this research was first announced at the International Symposium on Society for Information Display held in San Francisco, USA, in May, 2016.

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Materials provided by Tohoku University. Note: Content may be edited for style and length.

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Tohoku University. "Super-flexible liquid crystal device for bendable and rollable displays." ScienceDaily. ScienceDaily, 9 December 2016. <www.sciencedaily.com/releases/2016/12/161209111928.htm>.

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Wood & Timber Prices 2013

Forestry&logging, Pulp&paper, Woodworking

We have prepared the summing-up publication covering wood and timber industry prices in 2013 in Russia and its export markets, having collected all data available by year-end in 35 descriptive charts.
In these charts, price data from different sources are compared (Russian Statistic Agency, Russian Customs, Eurostat, Metla institute, Vienna commodity exchange, The Customs of Japan, US and Canada, Bumprom pulp&paper association of Russia etc.)
Full list of charts (.pdf)
WhatWood Weekly subscribers received this publication as a bonus. This review was also included as a free supplement to the Russian Forest Industry Annual Review 2013, which is to be published in March 2014.
If you are registered and logged in, the price will be shown with a 5% discount.
There are two easy ways to purchase this product, choose the one which is the most convenient for you:
1. Send us a request to zakaz@whatwood.ru, and we’ll contact you promptly (within 1-2 working days) to issue an invoice and perform your order.
2. Click on the “Buy now” button below to add the product into the cart, then pay your order in the cart using Visa, MasterCard or any other method available via ROBOKASSA payment service.

price

€150

Read more on http://whatwood.ru/english/tovary/wood-timber-prices-2013/