FINETECH JAPAN 2022/13th FILMTECH JAPAN/11th PLASTIC JAPAN
New technologies about MICRO-LED and mini-LED were proposed

December 7-9, FINETECH JAPAN 2022/13th FILMTECH JAPAN/11th PLASTIC JAPAN were held in Makuhari Messe. Main topics in these exhibitions are picked up.

Sharp exhibited the latest TFT-LCD using mini-LED and QD sheet

As concerns display module, Sharp exhibited the latest IGZO-TFT-LCD using mini-LED backlight (BL) and QD (quantum dot) sheet, and appealed highest ever image quality based on mega contrast effect. In this module, 1920 blue mini-LEDs were used. Turn-ON/OFF of each area is finely controlled by ON/OFF control of each mini-LED (area control method), as a result, 1,000,000 : 1 and over was obtained. Of course, practical power consumption of TFT-LCD can be greatly reduced because of area control mechanism.

Pic.1 TFT-LCD using mini-LED backlight

This module is composed of TFT-LCD panel, QD sheet, and BL unit. Blue emission of mini-LED is converted into white emission by the intermediary of QD sheet, and then, its light is converted into RGB original colors. Thickness of module is thin same as 2.1 �o, which is almost same as that of the conventional panel with side light BL module. For this reason, it's competitive with OLED display with respect to slim design.

As picture 1, 15.6-inch module was exhibited in the booth. It's been mass-produced yet for notebook PC.

Toppan appealed fully flexible IGZO-TFT

Pic.2 Flexible TFT

As regards TFT, Toppan demonstrated fully flexible TFT. It's an amorphous IGZO-TFT on polyimide film. Its carrier mobility is 10 cm²/Vs and over. And also, after bend test of 1,000,000 times at R = 1 �o, TFT characteristics inclusive of Vth are not degraded.

As picture 2, various flexible samples were exhibited. Furthermore, in the video presentation, this TFT was curved at 90°, and it's pressed. Its superior flexibility was emphasized a whole lot.

AIST proposed transparent heater and perovskite solar cell were manufactured by use of a new transparent conductive film

As concerns material, National Institute of Advanced Industrial Science and Technology (AIST) proposed a new transparent conductive film as post-ITO film, and its effectivity for transparent heater, perovskite solar cell, and so on.

Fig.1 Surface state of transparent conductive film and its carrier mobility

It's oxide In with H and Ce, and popular name is ICO:H. Firstly, as depo film is deposited in the vacuum chamber at H and Ce doped environment by sputtering method or ion plating method using the conventional ITO target. As a result, amorphous ITO film is obtained RT process. The next, its film is changed to poly crystal by irradiation of excimer laser beam. In this time, thermal damage does not generated against the substrate.

Figure 1 shows surface state of transparent conductive film and its carrier mobility. Grain size was enlarged in proportion as shot times of laser because of proceeding of poly crystal. At poly crystal state = 100 %, grain size was 2.4 μm, and carrier mobility was 133 cm²/Vs. And also, typical sheet resistance was approximate 14Ω/□, which is lower than that of ITO film.

Fig.2 Comparison of light transmittance

Furthermore, as figure 2, high transmittance is obtained not only visible light range, but also IR light range. For this reason, it's suitable for a transparent heater because of use of IR light. In the pilot produced sample, high heat generation could be obtained.

As above, it's effective for tandem type perovskite solar cell. As you know, the existing perovskite material for example CH3NH3PbX3 absorbs visible light basically, not IR light. Therefore, if a tandem device using this film as another generation unit are manufactured, highly efficient device is expected to be obtained because of high light absorption at wide wavelength range.

Fine pattern with high aspect ratio can be formed by use of new metal mesh wiring

On the other hand, Panasonic exhibited a both plane wiring mesh film "FineX", which was started to be mass-produced for touch sensor recently. It's a transparent conductive film with wiring mesh at both plane of plastic film, such as PET, PC (polycarbonate), and COP (cyclo-olefin polymer). It can be finely patterned and at high aspect ratio (relationship of width and thickness). Concretely, aspect ratio of the conventional etching product is about 0.25, on the other hand, that of FineX is about 0.74. In short, low resistance and high transmittance are obtained easily.

Theis characteristics were realized by originally developed Roll-to-Roll process. Figure 3 shows its process image. First of all, deep ditch patterns are formed on the both plane of plastic film by the nanoimprinting method. As a result, reverse pattern against practical electrode is formed. And then, adhesive layer, Cu film, and protect layer are continuously deposited at pattern-free by wet coating method and dry coating method. As a result, a transparent conductive electrode with high aspect ratio is completed.

Pic.3 Display application using FineX

Fig.3 Manufacturing process of both plane wiring mesh using FineX

Its patterning width, light transmittance, sheet resistance, and flexibility are 2μm, 94.1 %, 2Ω/□, and R = 2�o respectively. These values are superior than their values of the etching product.

In the booth, not only simple film, but also applications were exhibited. As picture 4, it's indicated to be suitable for headup display.

NEG appealed a ultra-thin glass as cover glass of foldable products

Pic.4 Bend demonstration of Dinorex UTG

With respect to flexible products, Nippon Electric Glass (NEG) exhibited a ultra-thin glass "Dinorex UTG" as cover glass of foldable products, such as high-end smartphone, tablet, and so on. It's manufactured by original manufacturing method (overflow method). Its breaking stress is 1500 MPa. For this reason, superior flexibility such as R = 3 �o is obtained. As picture 6, bend test was demonstrated repeatedly in the booth.

New photosentive adhesive is best suited for RGB patterning process of Micro/mini-LED

Related on photosensitive material, NIPPON Chemical & Material proposed a negative type photosensitive adhesive "VPA", and appealed its unique feature. It's exposed at 100 - 500 mJ/cm². After curing, high adhesion strength same as 20 MPa and high transmittance same as 90 % are obtained.

Fig.4 RGB pattering process of μ-LED display using VPA

Furthermore, it can be released by not only the conventional wet strip method using alkali acid, but also dry method using excimer laser beam. In short, it's possible to open hole on the object at will, in a word, to directly pattern. For this reason, it can be adopted to existing use such as insulator and sacrifice layer of MEMS and semiconductor and transfer use.

Specially effective use is RGB emission layer manufacturing process of Micro-LED and mini-LED. As figure 4, fine LED chip is transferred from 1st substrate to 2nd substrate (original substrate) selectively by irradiation of laser beam. In short, RGB emission layers can be speedily patterned by laser patterning of RGB layer each other.

Dispersibility and conductivity of CNT compound are obtained at the same time

Fig.5 Comparison of conductive property

As regards carbon nano tube (CNT), Oosaka Gas Chemicals appealed multi wall CNT dispersion technology. In general, CNT is easy to become massed together because of its Nano size. Therefore, after deposition of CNT film, conductivity and uniformity become to be degraded.

For this reason, the company doped an original additive, in order to form uniform network state of CNT. As a result, in CNT compound with resin, high dispersibility and conductivity were realized. Figure 5 shows comparison of conductive property. If this technology is used, sheet resistance becomes to be low at small content of CNT.

By the way, the company does not license out, but produced CNT compound itself.