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nano tech 2022/Advanced Printing Technology Exhibition 2022/neo functional material 2022 (Jan 26 - 28, 2022)


nano tech 2022/Advanced Printing Technology Exhibition 2022/neo functional material 2022
Unique products about materials were proposed one after another

January 26-28, 2022, nano tech 2022/Advanced Printing Technology Exhibition 2022/neo functional material 2022 were held in Tokyo Big Sight. Main topics in these exhibitions are picked up.

Toray improves perfection level of an original CNT-TFTs

Concerns as electric devices, Toray Industries demonstrated an original CNT-TFTs in this year, too, and appealed to improve its perfection level.

Conductive assist polymer was entwined with bulk SWCNT respectively, to enhance dispersibility in liquid state, and to enhance area uniformity at film state. CNT semiconductor layer was patterned at 10 μm channel length by original ink-jet printing method, was developed by Toray Engineering. Maximum process temperature was minimized to 150 ℃. For this reason, it's possible to correspond to low heat resistance substrate, such as plastic films.


Picture 1. Flexible CNT-TFT (right) and roll type CNT-TFT (left)
Its carrier mobility was increased to 182 cm2/V･s in this time. In short, career mobility of CNT-TFT is superior to that of organic-TFT and oxide-TFT, and is almost same as that of LTPS-TFT. Furthermore, ON/OFF current ratio was increased to 104-105 by increase of purity (93-94%) of semiconductor type CNT. It became to be corresponded to display device.

In the booth, a flexible CNT-TFT on PET film, and roll type CTN-TFT, which was manufactured by Roll to Roll process mainly. And also, as the latest press release, the company announced to fabricate radio-frequency identifiers (RFIDs) and sensors on general-purpose films and has demonstrated their wireless operations.

By the way, the company produces CNT-TFT device at the moment. If market need is increased in a way, the company will examine to collaborate with other makers about manufacturing framework in near future.

Highly dense Ag film is obtained by use of fine Ag grain as sinter aid

With respect to materials, Osaka Soda proposed an original fine Ag grain as a sinter aid. Its diameter is 50-100nm. In short, it's situated to middle of Nano size Ag and μm size Ag. In this proposal, highly dense Ag film is obtained by use of mixed ink, which is mix of this fine Ag grain and μm size Ag.

Film
μm size Ag film
Fine Ag film
Film density
77％
85％
Specific resistance
4.3μ･cm
2.4μ･cm
Joint strength 39MPa  90MPa
Thermal conductivity  120W/mk 220W/mk 

Table 1. Comparison of film characteristics
For example, if these two type Ag grains are mixed at 1:1 ratio, as table 1, film characteristics after sintering is drastically enhanced. Concretely, void and clack is suppressed by burying fine Ag grain into space of μm Ag grains, as a result, reliability such as joint strength is greatly improved. Furthermore, electric characteristics such as specific resistance is enhanced by melting fine Ag grain completely and acceleration of parted melting of μm Ag grain.

Of course, sintering temperature is lowered from 250℃ to 200℃. However, this effect of lowering temperature is less than that of Nano size Ag grain. In short, it's suitable for not plastic films, but rigid substrate such as glass, partially, use of necessity of highly durable wiring.

Clay based gas barrier material appears


Figure 1. Permeability of H2O
Kunimine Industry appealed a gas barrier material "KUNIPIA-RC series", which was based with natural clay. A gas barrier paste can be prepared easily by mixing this material, resin, and organic solvent, such as acetonitrile, ethanol, and isopropanol.

Figure 1 shows permeability of H2O. If this material is doped into the paste at 10-60% ratio, gas barrier property is drastically enhanced. This is reason why penetration path of gas is blocked by stack of montmorillonite crystal (300-500nm × t=1nm). Its sintering temperature is relatively low same as 100℃ and under. For this reason, it's possible to correspond to low thermal resistance substrate, such as plastic film, paper, and so on.

By the way, its appearance is gray. For this reason, transmittance and gas barrier property is relationship of trade-off.

Mitsubishi Pencil appealed Nano size grain with highly uniform diameter


Figure 2. SEM image and grain size distribution of
Nano size grain


Figure 3. Application sample of surface modification
Mitsubishi Pencil introduced an acrylic emulsion polymerization grain, which was named as Nano size grain with particle size regulation. As figure 2, uniformity of grain diameter is high. And also, it's possible to manufacture various size of grains from a few dozen μm to 1000μm. Of course, added value such as thermal resistance, solvent resistance, and others can be added.

First applications are the following:①spacer for LCD (random dispersal), ②addition agent for film, ③porous film, ④surface modification. In case of ④, anchor effect is formed by wet-etching using this grain as masking. In short, surface is roughly treated.

Fine line same as a several μm is printed by original printing method

As regards manufacturing process, National Institute of Advanced Industrial Science and Technology (AIST) appealed an originally fine printing technology, such as a few μm resolution. It is named as adhesion contrast printing. In this method, difference of adhesion of ink is skillfully applied.

Concretely, first of all, laser beam is irradiated to adhesion contrast mask at pattern shape by the laser direct exposure method and etc. As a result, ink adhesion in irradiated area is increased, that in nonirradiated area keeps initial week adhesion. By contrast, an ink is coated to silicon blanket roll by the slit die coating. The next, mask roll and blanket roll are contacted, so that, unnecessary ink is transferred from blanket roll to mask roll. And then, patterned ink is transferred from blanket roll to the work substrate. As the above, ink adhesion is expressed that irradiated area ＞ blanket ＞ adhesion contrast mask. By making use of this phenomenon, ink is patterned. Tact-time of this machine is 90 sec. And also, alignment accuracy is 1 ％ and under.


Picture 2. Printed sample of Ag line and ITO line (L=2μm)
Printing resolution of this method is minimum 0.5 μm. In case of 2-5 μm line width, uniform pattern can be stably obtained. In the booth, Nano size Ag and Nano size ITO printed samples (2 μm width) were exhibited. Furthermore, printed sample with etching resist pattern was exhibited, too.

REMARK
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Stella's repair system“Repair Vision” is suitable for repair use of electrode and so on. Also, it's possible to directly pattern ITO, metal, CNT (Carbon Nano Tube) films by use of this system, too.