Japan is using to make printing technology has made big progress of electronic components. Industrial technology research institute, university of Tokyo, Japan in hotan yamagata university announced in April 2016, the precious metals industry developed on the basis of the principle of the new wiring Printing technology "SuPR - NaP method" (Surface PhotoReactive Nanometal Printing, light is nanometer metal Printing method). Using this technique, can realize wiring width ultra-micronization model.the at the same time, large area and high speed manufacturing.

Compared with the common ink jet printing, screen printing, the wiring width of SuPR - NaP method can be narrowed to a few points a, can in the large flexible circuit boards for high-speed printing. Processing temperature as long as 50 ~ 80 ℃, can use PET (polyethylene terephthalate oxalic ester) with lower heat temperature, such as resin as base material.

Tanaka precious metals will be to use the technology to make production of touch panel sensor on the basis of the transparent conductive film, plan from January 2017 to supply samples.

Transparent conductive film beyond the past

To adopt new methods of transparent conductive film on light transmittance and film resistance both over traditional technology (figure 1). This is because the wiring and close to the wavelength of visible light, so the reflectivity, and wiring of ink wiring electrical conductivity is higher than ever before.

Figure 1: at the same time realize the specular transmittance, low membrane resistance of homogeneous wiring

(a) SuPR - NaP and now the light transmittance of transparent conductive film, film resistance. Closer to the top left, the higher the performance of the transparent conductive film. SuPR - NaP method in the film resistivity as 20 Ω / /, the light transmittance as high as 93%. (b) using the previous coating method, there will be a wiring and so on the edge of the thicker "coffee". (c) the SuPR - NaP method processing any wiring width, the thickness of the wiring is basic fixed. (click to enlarge)

Wiring electrical conductivity uniform thickness is very high because the length direction, and the thickness of the section, wiring under the condition of the same width, wiring of sectional area is bigger than when using the previous technology.

Thanks to the SuPR - NaP method to solve the problem of "coffee" in coated wiring. This is a problem of uneven coating, because can't control the thickness of the wiring, when want to increase the thickness, wider wiring phenomenon. The new technology can be in the range of 30 ~ 100 nm control the thickness of the wiring.

Both ultra-micronization model.the and large area

The wiring ultra-micronization model.the have previously achieved. Production of research in 2002 to develop "Super inkjet method (SIJ)" can be printed wiring width is about 1 microns. But this approach is the use of ultramicro droplets, each drawing fine wiring, production speed is very slow, large areas devices were not suitable for mass production.

SuPR - NaP method, by contrast, is through the wavelength of 172 nm ultraviolet (UV) exposure, unified drawing wiring design, by simply using coated ink scraper swept surface and ultra-micronization model.the with large area is not a contradiction, when making large area devices quickly (figure 2). The researchers the trial-manufacture 8 inches (200 mm) of the touch panel sensor. Wavelength of 172 nm UV exposure devices on the market can be used to remove organic matter the surface of the LCD panel "UV processor", make the purchase of equipment and low cost.

Figure 2: use a scraper swept surface can complete printing

A summary of SuPR - NaP coating process. First of all, on the base material such as PET and PEN coating containing fluorine polymer. From the top of the photomask irradiate UV, fire wiring pattern. Then use the scraper coating nano silver ink, only the wiring pattern on the nano silver ink, form a wiring. (click to enlarge)

The difference between using protection adhesion

New technology to achieve a breakthrough, because in the past when printing the feeling control, on the basis of the chemical adsorption selectivity silver ink technology, make good ink on the drawing wiring pattern on the base of (figure 3).

Figure 3: by chemical method, the nano silver ink is fixed on the base material

SuPR - NaP method makes the principle of nano silver ink adhesion on the substrate. To irradiate UV, containing fluorine polymer surface will form a large number of carboxyl. With alkyl amine to protect the base of the silver nanoparticles with here after contact, with the silver binding force more carboxyl will replace alkyl amine, adsorption of silver. (click to enlarge)

Hen control part is letting a wiring pattern on the substrate surface hydrophilicity is high, no design part of the hydrophobic high control technology. The past methods are mostly only parts of the ink "in the" high hydrophilicity, exists in the control wiring thickness and width of narrow wiring restrictions. Moreover, silver and base material, the viscosity difference between when bending and tensile base material, wiring may be peeling off from the base material.

The new method is first thin layer on the substrate coating containing fluorine polymer, and then by UV exposure scale design. On the surface after exposure of fluoropolymer, there will be a lot of carboxyl. No exposure of the high surface hydrophobicity, after exposure, hydrophobic will fell slightly.

Using silver ink by yamagata university professor kurihara are people development, tanaka precious metals is to promote the transition, the ink is about 13 nm in diameter of silver nanoparticles coated with alkyl amine to protect the base. Protect the base is to prevent the silver nanoparticles aggregation, in the past most of the silver ink using carboxyl with silver binding force strong. But because of strong bonding force, after coating silver ink, the need to improve the annealing temperature to remove protection base.

Alkyl amine and the adhesion strength of the silver nanoparticles is weak, after coating can be carboxyl of fluorinated polymer displacement, the silver nanoparticles is fixed on the base material. Leading the technology development of flexible electronics, research director at the centre for the study of the total production of research, graduate school of engineering at the university of Tokyo, department of physical engineering professor hasegawa said duff researchment department: "fixed adhesion is 50 times atmospheric pressure, that is more than 5 mpa, even by 1 mm radius of curvature of the curved 100 times also won't flake."

After adopting new technologies, "coffee" no longer produces. Silver nanoparticles between alkyl amine will fall off when heated to about 50 ~ 80 ℃, and the original annealing temperature above 100 ℃.