Block copolymer and light emitting device using the same

A block copolymer comprising an end group, a block that binds to the end group, and a block that does not bind to the end group, wherein

• said block that does not bind to the end group contains at least one constitutional unit selected from the group consisting of a non-crosslinkable constitutional unit represented by the following formula (X) and a non-crosslinkable constitutional unit represented by the following formula (Z),
• wherein said block that binds to the end group contains a non-crosslinkable constitutional unit represented by the following the formula (Y):
• wherein ArY1 represents an arylene group optionally having a substituent,
• at least one selected from the group consisting of said end group and said block that binds to the end group contains a crosslinkable group, and
• at least one of the following formulae (i) to (iii) is satisfied when the total number of said non-crosslinkable constitutional unit represented by the formula (X) and the total number of said non-crosslinkable constitutional unit represented by the formula (Z) in said block that does not bind to the end group are represented by XI and ZI, respectively, and the total number of said non-crosslinkable constitutional unit represented by the formula (X) and the total number of said non-crosslinkable constitutional unit represented by the formula (Z) in said block that binds to the end group are represented by XII and ZII, respectively:
• XI>XII (i)
• ZI>ZII (ii)
• XI+ZI>XII+ZII (iii)
• wherein,
• aX1 and aX2 each independently represent an integer of 0 or more and 10 or less,
• ArX1 and ArX3 each independently represent an arylene group or a divalent heterocyclic group, and the foregoing groups optionally have a substituent,
• ArX2 and ArX4 each independently represent an arylene group, a divalent heterocyclic group, or a divalent group in which at least one arylene group and at least one divalent heterocyclic group are bonded directly, and the foregoing groups optionally have a substituent, and when a plurality of ArX2 are present, they may be the same or different and when a plurality of ArX4 are present, they may be the same or different,
• RX1, RX2 and RX3 independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or a monovalent heterocyclic group, and the foregoing groups optionally have a substituent, and when a plurality of RX2 are present, they may be the same or different and when a plurality of RX3 are present, they may be the same or different,
• wherein, ArZ represents a divalent heterocyclic group, or a divalent group in which at least one arylene group and at least one divalent heterocyclic group are bonded directly, and the foregoing groups optionally have a substituent.