We extend the theorem by Hong et al. which gives the upper bounds of the maximum average differential and linear hull probabilities (MADP and MALHP) for SPN block cipher with optimal or quasi-optimal diffusion layers, to the case of nested SPN (NSPN) cipher. Applying the extended theorem to two NSPN ciphers, Hierocrypt-3 of 128-bit block and Hierocrypt-L1 of 64-bit block, we estimated that MADP and MALHP for 2-round Hierocrypt-3 are bounded by 2-96, and that those for 2-round Hierocrypt-L1 are bounded by 2-48. The extended theorem is also applied to AES, and found that MADP and MALHP are bounded by 2-96 for its 4-round reduced model. The last result outperforms the best previous result 2-92 for 10-round by Keliher et al.

We developed material and process technologies concerned to DDF, which is formed on MgO surface around the inter-pixel gap to prevent vertical crosstalk discharge in stripe rib structure. First we tried with thin film deposition and lift-off patterning to find Al2O3 and TiO2 are both available for DDF material. Next we tried with thick film printing in favor of mass productivity for large size PDPs. In case DDF included PbO glass, we met serious hardship in generating discharge. The problem was perfectly solved by having thick film DDF composed of 100 nm sized Al2O3 grains without glass component. Its γi was about 1/5 that of MgO, suggesting that the thick film DDF is almost compatible with thin film Al2O3 in electron emission characteristics. Such very small grain size contributes to DDF transparency, which is excellently high. In addition to it, such DDF is equipped with cushioning effect to prevent dot defects caused by rib breakage. Furthermore the DDF functions as getter during panel exhaustion to bring deep blue color by promoting deoxidization of blue phosphor provided that its volume is small enough. Transparent DDF may be rather better than black one with respect to bright room contrast ratio, not to mention to avoiding terrible sparking discharge. Thus material and process technologies for DDF have been almost fixed in success.

We developed a new method to improve the efficiency of the PDP (plasma display panel) by the use of a novel protecting film or Gd doped MgO film. In the cells of the PDP, the VUV (vacuum ultraviolet ray) is generated by Xe discharge. The VUV is simply absorbed by the protecting film or MgO film. Therefore, normally the absorbed VUV doesn't contribute to the light conversion efficiency. However, the novel protecting film or MgO:Gd film radiates the ultraviolet ray of which 317 nm wavelength, by the irradiation of the shorter wavelength VUV, and it excites the blue phosphor. Consequently the efficiency of blue emission is improved.