To developers of display manufacturers
Make a strong black
How to make an excellent
blackening performance required
for the next generation display with
high definition and fine pitch?
The answer from Mitsubishi Materials is…
DIABLA【 Sputtering target 】
The black matrix is no longer needed.
Solving the issues by blackening
on surface TFT wiring surface.
In recent years, 4K and 8K high-definition displays have appeared on the market.
However, one of the problems with high definition is the low brightness.
Therefore, the black matrix deposited on the color filter in order to hide the wiring is eliminated and instead,
the surface blackening treatment on TFT wiring started to become adopted.
The DIABLA sputtering target shows unprecedented performance in the deposition of blackened layers on TFT wiring.
DIABLATARGETExample of use
Black MatrixConventional display
Blackening the TFT wiringDisplay with DIABLA
A new material for
blackening film that
conventional materials!Maintains high blackening
performance even after array
Lineup of DIABLA that can flexibly respond
to various processes!
DIABLA is composed of elements that do not contaminate semiconductors.
Metal mesh(Touch sensor)
Moire patter less
Thinner than organic BM
Cr free material
TFT array/top side(LCD, OLED)
Black matrix less
Screen door less
Wide aperture area
TFT array/back side(LCD, OLED)
DC sputtering is available and
no reactive gas is required!Stable deposition with highly uniform films
DIABLATARGETR&D engineer interview
Mitsubishi Materials Corporation
Advanced Products Company Sanda plant R&D Department
Thin Film Material Group
Mr.Keita Umemoto / Mr.Shin Okano /
Extensive knowledge of
materials and wiring
opens the door to solutions.
From the left, Mr.Okano, Mr.Umemoto and Mr. Kaneko
From the left, Mr.Okano, Mr.Umemoto and Mr. Kaneko
Calls for “a new strong black” have always reached Mitsubishi Materials. In response,
we launched a new material development project. A variety of challenges faced the product development process.
The opened doors to the solutions close by unexpected reasons repeatedly.
But the three engineers never gave up and moved forward.
then, finally a goal with joy was waited for them.
Display manufacturing challenges of search for
“The next black matrix”
Umemoto: With the recent trend toward larger TVs with 4K and 8K resolution, it has become clear that the high-definition panels used in displays have major challenges. Conventionally, as a method of shielding light reflection on the surface of TFT wiring, a black matrix has been adopted for the color filter substrate, in which black is placed at the parts where the wiring is located. However, the higher the definition, the more black areas occupy on the screen, and as a result, the luminance become lower. They can make the black part smaller, but it is technically difficult. Our company clients also wanted a next-generation method that was not a black matrix. To solve this problem, we have been studying a “blackening wiring” method in which a thin film is formed on the surface of the TFT wiring to make it appear black. This eliminates the need for a black matrix. However, on the process of blackening the TFT wiring, a new problem was found in that the thin film material lacked stability and durability.
“blackness” “strength” “processability”
“without reactive gas”
Set requirements for ideal new materials
Umemoto: Initially, molybdenum oxide, copper oxide, and copper nitride, which have been used in metal mesh wiring for touch sensors, were considered as materials for the blackening film. However, it can be said that these materials are weak against alkali and water, which are essential in the wiring process, and have low heat resistance and durability. When our company launched a project to find a new material for blackening film, the following 4 conditions were mentioned as the target material conditions: “Sufficient blackness (low reflectivity)” “durability” “processability” and “without for reactive gas”. Not only is it necessary to use the low reflectivity to make it look black, but it is also highly desirable to have durability that does not follow the harsh TFT wiring manufacturing process where alkali, water and high temperature are common. We also considered that it is an important condition that it has excellent processability and is easy to wire, and that no reactive gas is used during film formation. This is because reactive sputtering, which uses reactive gas, has a problem that it is difficult to obtain uniform film quality in a large substrate such as a display.
“Conventional materials cannot solve the problem.”
Days of searching for prototypes based on the
Umemoto: It was good to set targets, but we knew that conventional materials could not achieve them, so we had to consider materials from a new perspective, without being bound by existing knowledge and stereotypes. Every day, while looking at the periodic table, we examined the material properties, screened them, and picked up candidates for trial manufacture. Dozens of samples were immediately procured as candidates, and a blackening film was produced on a trial basis, but some of them did not turn black very much. The most important thing was durability, so even if it was a passing mark in terms of strength, if it wasn’t black enough, we would have to choose again. Optical simulation played an important role in the next issue of how to reduce reflectance while maintaining durability. Through repeated examinations of materials with the lowest reflectivity in theory, we were finally able to reach the ideal solution of the current DIABLA film.
Solutions of two new challenges
One is making the composition to satisfy customer’s
The other is establish the mass-production system.
Kaneko: I was incharge of “Customization” of the DIABLA film for each customer. There are some etching by chemical or gas to dissolve unnecessary thin film on the manufacturing process but the etching methods are different from customer to customer. We repeatedly examined the composition according to their requests and optimized it based on the evaluation results. Several hundred compositions were examined.
Umemoto: By creating a database of trial production and evaluation results, rational and efficient composition design has become possible.
Okano: I was in charge of developing mass-production technology for DIABLA targets in parallel with the material development carried out by Umemoto and Kaneko. I selected the manufacturing process with consideration of the product size and productivity applied to the actual display from the the conceptual stage. The DIABLA target is a ceramic material with low reflectivity and excellent durability. However, there were some difficulties which we can not overcome with our knowledge and experiences of sintering in terms of its densification and enlargement. The most difficult point was to establish mass production technology quickly while adopting a new sintering method.
DIABLA target is available in various applications other than TFT for display
Umemoto: We presented the results of our DIABLA target at IDW(International Display Workshops), which achieved the 4 goals of “blackness”, “strength”, “Ease of processing”, and “without for reactive gas”. As a result, we received high praise from the display industry. DIABLA will be available in a variety of applications because of its high performance. So if you contact us, we can propose the best solution, in particular concerning TFT various displays such as liquid crystal displays and organic EL displays, because we have accumulated a wide range of knowledge. In addition, it is possible to improve the resolution and yield of black matrices by taking advantage of the fact that the film thickness can be reduced from several μm to 100 nm, which is less than 1/10 of conventional thickness. High durability is also attractive in the field of touch sensors. It is also expected to be applied to optical devices such as image sensors and TOF sensors.
We face many troubles and have to work hard as R&D, but when we obtain expected results, we get the impression that cannot be replaced by anything else. If our products are highly evaluated and our customers feels happy, the days we have struggled will be rewarded. We believe that responding to customers’ requests will lead to pioneering the future of display industry with our customers together.