A conventional polymerization inhibitor is for example an agent to scavenge radicals generated during storage of a radical polymerizable compound and used to stably handle the radical polymerizable compound, but is unnecessary when the radical polymerizable compound is to be subjected to radical polymerization reaction, and is preferably removed at the time of the radical polymerization reaction. The object of the present invention is to obviate inconvenience of removing the polymerization inhibitor at the time of radical polymerization. The radical polymerization control agent contained in a radical polymerizable composition of the present invention functions as a radical polymerization inhibitor for example stored in a dark place, but loses its radical polymerization inhibiting effect when polymerization is initiated while being irradiated with light at a certain specific wavelength at the time of polymerization. Thus, radical polymerization of the radical polymerizable compound is easily initiated without increasing the amount of a radical polymerization initiator. That is, the radical polymerization control agent of the present invention is a radical polymerization control agent which is a corn pound having an effect to inhibit radical polymerization of a radical polymerizable compound and which loses the radical polymerization inhibiting effect under irradiation with light rays containing light within a wavelength range of from 300 nm to 500 nm.

A conventional polymerization inhibitor is for example an agent to scavenge radicals generated during storage of a radical polymerizable compound and used to stably handle the radical polymerizable compound, but is unnecessary when the radical polymerizable compound is to be subjected to radical polymerization reaction, and is preferably removed at the time of the radical polymerization reaction. The object of the present invention is to obviate inconvenience of removing the polymerization inhibitor at the time of radical polymerization. The radical polymerization control agent contained in a radical polymerizable composition of the present invention functions as a radical polymerization inhibitor for example stored in a dark place, but loses its radical polymerization inhibiting effect when polymerization is initiated while being irradiated with light at a certain specific wavelength at the time of polymerization. Thus, radical polymerization of the radical polymerizable compound is easily initiated without increasing the amount of a radical polymerization initiator. That is, the radical polymerization control agent of the present invention is a radical polymerization control agent which is a corn pound having an effect to inhibit radical polymerization of a radical polymerizable compound and which loses the radical polymerization inhibiting effect under irradiation with light rays containing light within a wavelength range of from 300 nm to 500 nm.

A process for synthesizing an azo compound by oxidation of a hydrogen compound in the presence of a catalyst and a compound of formula (I) is described in which R.sub.1, R.sub.2 and R.sub.3
(R.sub.1)(R.sub.2)C(PO.sub.3(R.sub.3).sub.2).sub.2  (I)
are as defined. The use of a compound of formula (I) as complexing agent for a catalyst is also described.

A process for synthesizing an azo compound by oxidation of a hydrogen compound in the presence of a catalyst and a compound of formula (I) is described in which R.sub.1, R.sub.2 and R.sub.3
(R.sub.1)(R.sub.2)C(PO.sub.3(R.sub.3).sub.2).sub.2  (I)
are as defined. The use of a compound of formula (I) as complexing agent for a catalyst is also described.

A process for synthesizing an azo compound by oxidation of a hydrogen compound in the presence of a catalyst and a compound of formula (I) is described in which R.sub.1, R.sub.2 and R.sub.3
(R.sub.1)(R.sub.2)C(PO.sub.3(R.sub.3).sub.2).sub.2  (I)
are as defined. The use of a compound of formula (I) as complexing agent for a catalyst is also described.

An azo compound excellent in solubility in solvent and having a high absorbance coefficient is disclosed, as well as an ink containing the azo compound. Such an ink contains a solvent having a relative permittivity at 22° C. and at a measurement frequency of 1 kHz of 3 or less and having a solubility in water at 25° C. of 20 mg/L or less, and an azo compound.

An azo compound excellent in solubility in solvent and having a high absorbance coefficient is disclosed, as well as an ink containing the azo compound. Such an ink contains a solvent having a relative permittivity at 22° C. and at a measurement frequency of 1 kHz of 3 or less and having a solubility in water at 25° C. of 20 mg/L or less, and an azo compound.

A conventional polymerization inhibitor is for example an agent to scavenge radicals generated during storage of a radical polymerizable compound and used to stably handle the radical polymerizable compound, but is unnecessary when the radical polymerizable compound is to be subjected to radical polymerization reaction, and is preferably removed at the time of the radical polymerization reaction. The object of the present invention is to obviate inconvenience of removing the polymerization inhibitor at the time of radical polymerization.

The radical polymerization control agent contained in a radical polymerizable composition of the present invention functions as a radical polymerization inhibitor for example stored in a dark place, but loses its radical polymerization inhibiting effect when polymerization is initiated while being irradiated with light at a certain specific wavelength at the time of polymerization. Thus, radical polymerization of the radical polymerizable compound is easily initiated without increasing the amount of a radical polymerization initiator. That is, the radical polymerization control agent of the present invention is a radical polymerization control agent which is a corn pound having an effect to inhibit radical polymerization of a radical polymerizable compound and which loses the radical polymerization inhibiting effect under irradiation with light rays containing light within a wavelength range of from 300 nm to 500 nm.

A conventional polymerization inhibitor is for example an agent to scavenge radicals generated during storage of a radical polymerizable compound and used to stably handle the radical polymerizable compound, but is unnecessary when the radical polymerizable compound is to be subjected to radical polymerization reaction, and is preferably removed at the time of the radical polymerization reaction. The object of the present invention is to obviate inconvenience of removing the polymerization inhibitor at the time of radical polymerization.

The radical polymerization control agent contained in a radical polymerizable composition of the present invention functions as a radical polymerization inhibitor for example stored in a dark place, but loses its radical polymerization inhibiting effect when polymerization is initiated while being irradiated with light at a certain specific wavelength at the time of polymerization. Thus, radical polymerization of the radical polymerizable compound is easily initiated without increasing the amount of a radical polymerization initiator. That is, the radical polymerization control agent of the present invention is a radical polymerization control agent which is a corn pound having an effect to inhibit radical polymerization of a radical polymerizable compound and which loses the radical polymerization inhibiting effect under irradiation with light rays containing light within a wavelength range of from 300 nm to 500 nm.

A process for synthesizing an azo compound by oxidation of a hydrogen compound in the presence of a catalyst and a compound of formula (I) is described in which R.sub.1, R.sub.2 and R.sub.3

(R.sub.1)(R.sub.2)C(PO.sub.3(R.sub.3).sub.2).sub.2(I)

are as defined. The use of a compound of formula (I) as complexing agent for a catalyst is also described.