Hologram recording material, hologram recording method, optical recording medium, and dye therefor

A hologram recording method comprises:

• effecting hologram recording with a sensitizing dye represented by formula (1):
• D-L-E-LP
• wherein D represents a group containing a sensitizing dye, L represents a single bond or a connecting group, E represents a site capable of disconnecting the bond between E and LP to discolor the sensitizing dye, and LP represent a group containing a site capable of disconnecting the bond between E and LP upon irradiation;
• and
• irradiating with light other than hologram recording light so that the sensitizing dye represented by formula (1) is self-discolored and fixed, to record interference fringes providing a refractive index modulation,
• wherein a hologram recorded by the hologram recording method can be reproduced by irradiating with the same light as the hologram recording light without extinguishing the interference fringes.

A compound represented by one of the formulae (5-1) to (5-5):

• wherein Za1, Za2, Za3 and Za8 each independently represent an atomic group constituting a 5-membered or 6-membered nitrogen-containing heterocyclic group;
• and Za4 to Za7 each independently represent an atomic group constituting a 5-membered or 6-membered ring,
• Ra1, Ra2, Ra3 and Ra5 each independently represent a hydrogen atom, alkyl group, alkenyl group, aryl group or heterocyclic group;
• and Ra4 and Ra6 each independently represent a substituent,
• Ma1 to Ma21 each independently represent a methine group which may have a substituent and may form a ring with a methine group,
• na1, na2, na3 and na5 each independently represent 0 or 1;
• and na4 and na6 each independently represent an integer of 0 to 5, with the proviso that when na4 is 2 or more, Ra4's are the same or different and may be connected to each other to form a ring, and with the proviso that when na6 is 2 or more, Ra6's are the same or different and may be connected to each other to form a ring,
• ka1 to ka5 each independently represent an integer of 0 to 3, with the proviso that:
• when ka1 is 2 or more, Ma3's are the same or different and Ma4's are the same or different;
• when ka2 is 2 or more, Ma10's are the same or different and Ma11's are the same or different;
• when ka3 is 2 or more, Ma12's are the same or different and Ma13's are the same or different;
• when ka4 is 2 or more, Ma16's are the same or different and Ma17's are the same or different;
• and when ka5 is 2 or more, Ma20's are the same or different and Ma21's are the same or different,
• CI represents an ion that neutralizes electric charge of the compound,
• y represents the number of CI's required to neutralize the electric charge,
• the compound represented by comprises a group represented by one of formulae (6-1) to (6-3) in at least one of Ra1, Ra2 and Ma3 to Ma5,
• the compound represented by formula (5-2) comprises a group represented by one of formulae (6-1) to (6-3) in at least one of Ra3, Ma10 and Ma11,
• the compound represented by formula (5-3) comprises a group represented by one of formulae (6-1) to (6-3) in at last one of Ma12 to Ma14,
• the compound represented by formula (5-4) comprises a group represented by one of formulae (6-1) to (6-3) in at least one of Ra4, Ma16 and Ma17, and
• the compound represented by formula (5-5) comprises a group represented by one of the formulae (6-1) to (6-3) in at least one of 1 Ra5, Ra6, Ma20 and Ma21:
• wherein E1 represents at least one of —O—, —S— and —NR31—, wherein R31 represents a hydrogen atom, alkyl group, alkenyl group, cycloalkyl group, aryl group or heterocyclic group,
• R35 represents a hydrogen atom, alkyl group or aryl group;
• R36 represents a substituent;
• and a2 represents an integer of 0 to 4, with the proviso that when a2 is 2 or more, R36's are the same or different and may be connected to each other to form a ring,
• R37 and R38 each independently represent a hydrogen atom or alkyl group;
• R39 and R40 each independently represent an alkyl group;
• R41 represents a substituent;
• and a3 represents an integer of 0 to 3, with the proviso that when a3 is 2 or more, R41's are the same or different and may be connected to each other to form a ring, and
• R42 and R43 each independently represent a substituent;
• and a4 and a5 each independently represent an linger of 0 to 5, with the proviso that when a4 is 2 or more, R42's are the same or different and may be connected to each other to form a ring, and with the proviso that when a5 is 2 or more, R43's are the same or different and may be connected to each other to form a ring.