１． Use as a thermal acid generator (TAG)

The TA-100 series is a sulfonium salt-type thermal acid generator (TAG), and the IK-1 series is an iodonium salt-type TAG.
The basic thermal properties of TA-100 are shown in Table 1. When heated alone, the thermal decomposition temperature of TAG is 156°C for TA-100, compared to 247°C for IK-1.

Table 1 List of Thermal Properties

The heat flow when combined with jER® 828, a bisphenol A-type glycidyl ether, is shown in the figure below. As shown in Table 1, IK-1 begins to polymerize at 210°C, while TA-100 begins to polymerize at 100°C.
The heat flow when combined with the alicyclic epoxy, Celoxide P2021, is also shown in the figure below.
With this monomer, IK-1 begins to polymerize at 125℃, while TA-100 begins to polymerize at 70℃.

Figure 1, 2: Cationic polymerization exothermic behavior (left: Bisphenol A type epoxy, right: Alicyclic epoxy)

2. Restraining the coloring of cured materials

The TA-100 series includes two types: TA-100, which has a PF3(C2F5)3 counter anion, and TA-100FG, which has a FG anion counter anion. Although TA-100 and TA-100FG are equivalent in terms of acid generation temperature and acid strength, there is a significant difference in terms of the coloring of cured materials.
As shown in Figure 3, TA-100FG, which uses FG anions, is able to suppress the discoloration of cured materials even at high temperatures.
We have also developed IK-1FG, which uses FG anions, as part of the IK-1 series.
Like TA-100FG, IK-1FG is also able to greatly suppress the discoloration of cured materials.

【Figure 3: Appearance of cured resin before and after heat treatment】

3. Solubility in various solvents and monomers

Both TA-100 and IK-1 show excellent solubility in various organic solvents and monomers.

Table 2: Solubility in Various Solvents

Table 3: Solubility in Various Monomers

4. Storage stability

Table 4 shows the storage stability (the period during which the viscosity coefficient is 2.0 or less) of resins containing TA-100.
As shown in the table, when it is combined with jER 828, a bisphenol A-type glycidyl ether, it shows particularly excellent storage stability.

Table 4: Storage stability in monomer

5. Use as a photoacid generator (PAG) (IK-1 series only)

The TA-100 series does not have sufficient photo-responsiveness, so it can only be used as a thermal acid generator (TAG).
In contrast, the IK-1 series has a strong light absorption spectrum in the wavelength range below 300nm, making it possible to use it not only as a thermal acid generator (TAG) but also as a photo acid generator (PAG).
When using the IK-1 series as a photo acid generator (PAG), a sensitizer is required, especially when using i-line (365nm) as a light source.
Sensitizers that can be obtained commercially include anthracene-based sensitizers such as dibutoxy anthracene (DBA) and thioxanthene-based sensitizers such as isopropyl thioxanthone (IPTX), which can be expected to have a significant sensitizing effect.
The UV absorption spectra of IK-1 and sensitizers in acetonitrile are shown in Figure 4.

Figure 4: UV absorption spectrum in acetonitrile

Because the generated acid of IK-1 is HPF3(C2F5)3, it shows high activity in deprotection reactions and cationic polymerization reactions.
Therefore, it is possible to photopolymerize it with less light irradiation than conventional iodonium salt-type PAGs that use B(C6F5)4 anions.
Figure 5 shows the results of a photopolymerization reaction experiment when it was blended with alicyclic epoxy resin.

Figure 5 UV curability (pencil hardness test)