Development of Photonics Polymers for High-Definition Displays

Utilizing zero-birefringence polymer and highly scattered optical transmission (HSOT) polymer technology, we aim to propose a new LCD system through total design which considers all aspects from the backlight to the LCD panel.

The LCD industry has made great strides after its advent in Japan, but as a result of severe international competition, a large share of the market is now occupied by overseas companies. In particular, shares have been taken over by downstream companies such as for LCD TVs and LCD panels, and parts such as the backlight, polarizing plate, and optical film are subject to intense competition. The superior image quality and performance of the LCD display is achieved by numerous parts. By improving the performance of these parts, the image quality and performance of the LCD display will continue to improve. Achieving this will result in strengthening the international competitiveness of Japan's parts makers and LCD display industry henceforth. In this theme, we will develop a new optical film, backlight, and adhesive utilizing photonics polymers ("highly scattered optical transmission (HSOT) polymers," "zero-birefringence polymers and zero-zero-birefringence polymers"). Furthermore, rather than simply improving the performance of each part, our aim is to implement "total design" which considers the entire LCD display to realize a new LCD display system with the world's best standards of image quality and low power consumption.

New LCD display proposed by sub-theme 2

Commercialized LCD (TN)

Formerly, the birefringence of the light passing at an angle through the liquid crystal layer was compensated with retardation film to produce a wide viewing angle.

Our Proposed LCD

With the new method, applying the HSOT Polymer as the backlight and film will make for an LCD with small color change depending on the viewing direction. 

References: A. Tagaya and Y. Koike, SID Symp. Dig. Tech. Pap., Vol.43, 737(2012).

Development of new plastic film using zero-birefringence

We will realize highly efficient film production through the melt extrusion method using zero-birefringence polymers, and aim to provide low cost and the highest performance film in the world.

+ Birefringence Mechanism

 Orientational Birefringence

Birefringence which occurs when polymer main chains is oriented at above glass transition temperature (Tg).

 

Photoelastic Birefringence

Birefringence which occurs when the polymer is elastically deformed at below Tg. Photoelastic birefringence occurs when stress is added and removed when stress is released.

+ Design of zero-zero-birefringence Polymers

 Zero birefringence is produced by cancelling out the anisotropy within the polymer chain through copolymerization of monomers with different polarizability anisotropy (random co-polymerization).

By solving the simultaneous equations indicated at right under conditions Δn0 = C = 0 , we produced zero-zero-birefringence polymers in which two types of birefringence have been made zero simultaneously. It is expected to be applied to the injection molding process and extrusion molding process which had been difficult until now.

[1] A. Tagaya and Y. Koike, et al. Macromolecules, 39, 3019-3023 (2006)

+ Birefringence of Injection Molded Samples

 Birefringence occurs in generic polymer materials during injection molding. As both birefringences in zero-zero-birefringence polymers are accurately cancelled out, light leakage due to birefringence is not observed.

+ Extrusion Molded Film

 By manufacturing optical film for LCDs using the melt extrusion method which has high production efficiency, we expect to produce LCDs with high image quality at low cost.

Observation of extrusion molded film (at right)
With ordinary polymer film, light leakage and color irregularities due to birefringence is observed. (photo at left)

With zero-zero-birefringence polymers, light leakage does not occur and "black" is observed. (photo at right)

Development of thin, low power consumption backlights using the highly scattered optical transmission (HSOT) polymer

We are developing thin, low power consumption backlights using highly scattered optical transmission (HSOT) polymer which can scatter light with high efficiency and produce high grade irradiated light. In a rapidly changing LCD field, we are aiming to realize a high performance backlight which meets the needs of the marketplace.

+ HSOT Polymer Backlight



HSOT polymer has achieved approx. twice the luminance of conventional transparent backlights .

Latest Research Results

+ Development of Super Birefringence Film

We have created the super birefringence film based on over 20 years of research to produce a zero birefringence polymer, and by changing our mindset and reversing course. This is a completely new, never before seen optical film possessing a very large birefringence (retardation) of 8,400-10,500nm. It resolves the rainbow-colored irregularities which occurred due to the film's birefringence which was considered a problem in LCDs. In addition, by attaching this super birefringence film to the front surface of the LCD panel, the polarization phenomenon where the screen would appear completely dark when wearing polarized sunglasses would be resolved, making the image clearly visible.

【Main journal papers and patents relating to these researches】
[1] D. Kobayashi, A. Tagaya and Y. Koike, "A High-Retardation Polymer Film for Viewing Liquid Crystal Displays through Polarized Sunglasses without Chromaticity Change in the Image", Japanese Journal of Applied Physics, Vol. 50, pp. 042602-1-6 (2011).

For details on "super birefringence film" released by Toyobo Co., Ltd., please refer to the following.
COSMOSHINE Super Retarder Film (SRF) (Toyobo website)

+ Development of Zero-Zero-Birefringence Polymer Film for LCD Through the Melt Extrusion Method

We designed and synthesized a zero-zero-birefringence polymer which does not occur orientational birefringence or photoelastic birefringence. We trial manufactured this polymer at a 100-200kg scale and at a 2t scale, succeeded in melt extrusion film-forming, biaxially-stretched a portion of it for use as a polarization plate protective film, and produced a polarization plate. As a result, we confirmed that a polarization plate with superior polarization properties (no light leakage) was derived.

【Main journal papers and patents relating to these researches】

[1] A. Tagaya and Y. Koike, Polymer Journal, 44, 306 (2012).

[2] S. Iwasaki, Z. Satoh, H. Shafiee, A. Tagaya and Y. Koike, Polymer, 53, 3287 (2012).

* Several patents pending

+ Development of Zero-Birefringence Adhesive

We have been the first in the world to succeed in quantitatively measuring the birefringence of adhesives for LCDs, and based on this, designing and synthesizing an adhesive which does not manifest birefringence (zero-birefringence adhesive). In addition, by utilizing this zero-birefringence adhesive to paste a polarization plate onto a glass substrate, and conducting an acceleration test, we succeeded in suppressing light leakage during a black display.

【Main journal papers and patents relating to these researches】

[1] H. Ito, S. Yanai, S. Oda, A. Tagaya and Y. Koike, AIP Advances, 2, 022142-1 (2012).

* Several patents pending

+ Development of a Highly Scattered Optical Transmission (HSOT) Polymer Backlights

(1) Edge light type:

In pursuing design and trial manufacture of light-guiding plates and prism sheets for backlights, we succeeded in trial manufacturing a backlight possessing the world's highest standard light harvesting properties. We are proceeding with total design incorporating this property to create a backlight for a revolutionary LCD.


 (2) Direct type:
We are proceeding to design a backlight for a large type LCD TV. We are aiming to create thinner backlights by placing highly scattered optical transmission (HSOT) polymer elements on LED elements to control light distribution. We are currently proceeding with design and trial manufacture through simulation, and have succeeded in deriving a superior color mixture performance.

Provided by Enplas Laboratories, Inc.


【Main journal papers and patents relating to these researches】
[1] A. Tagaya and Y. Koike, SID2012, (Boston, USA), presented on June 7, 2012.

+ Development of Polarized Laser Backlights

Utilizing zero-zero-birefringence polymers which do not exhibit orientational birefringence and photoelastic birefringence, we designed and trial manufactured polarized laser backlights, and demonstrated for the first time its superior polarized light output characteristics.



Copyright(2012) The Japan Society of Applied Physics(1)

【Main Journal papers and patents relating to these researches】

[1] T. Kurashima, K. Sakuma, T. Arai, A. Tagaya and Y. Koike, Opt. Rev. (in press).
* Several patents pending