Process for producing fluorinated crosslinked product and use thereof

1. A process for producing a fluorinated crosslinked product, the process comprising:

irradiating a fluorinated polymer with active energy rays having a wavelength of from 150 to 300 nm,

wherein the fluorinated polymer is at least one member selected from the group consisting of:

a polymer consisting of a unit (1) and a unit (2),

wherein the unit (1) is represented by the following formula (1):

wherein X 1 and X 2 are each independently a hydrogen atom or a fluorine atom, R f1 is a fluoroalkylene group or a fluoroalkylene group having at least two carbon atoms and an etheric oxygen atom between carbon-carbon atoms, Q 1 is a single bond or an etheric oxygen atom, and Z 1 is OH, OR 1 or NR 2 R 3 , wherein R 1 is an alkyl group, and R 2 and R 3 are each independently a hydrogen atom or an alkyl group,

wherein the unit (2) is at least one member selected from the group consisting of units represented by the following formulas (2-1) to (2-4):

wherein Q2 is a Cl-5 perfluoroalkylene group which optionally contains an etheric oxygen atom and in which some of fluorine atoms are optionally substituted by halogen atoms other than fluorine atoms;

a polymer consisting of the unit (1), the unit (2), and a unit (3), wherein the unit (3) is at least one unit derived from a fluoroethylene:

a polymer consisting of the unit (1), the unit (2), and a unit (4), wherein the unit (4) is at least one unit represented by the following formula (4):

—[CX3X4.CY1Y2]-  (4),

wherein X3 and X4 are each independently a hydrogen atom, a fluorine atom, or a chlorine atom, Y1 is a hydrogen atom, a fluorine atom, or a chlorine atom, Y2 is a hydrogen atom, a fluoroalkvl group which optionally contains an etheric oxygen atom between carbon-carbon atoms, a fluoroalkoxygroup which optionally contains an etheric oxygen atom between carbon-carbon atoms;

a polymer consisting of the unit (1), the unit (2), the unit (3), and the unit (4);

a polymer consisting of the unit (1), the unit (3), and the unit (4); and

a polymer consisting of the unit (1) and the unit (4),

wherein a proportion of the unit (1) is from 3 mol % to 50 mol % based on the total units in the fluorinated polymer.

2. The process according to claim 1 , wherein the unit (1) is —[CF 2 —CF(O(CF 2 ) 3 COOCH 3 )]— or —[CF 2 —CF(OCF 2 CF(CF 3 )O(CF 2 ) 3 COOCH 3 )]—.

3. The process according to claim 1 , wherein the fluoroethylene is at least one of tetrafluoroethylene, trifluoroethylene, and chlorofluoroethylene.

4. The process according to Claim 1 , wherein the unit (4) is a unit derived from a perfluoromethyl vinyl ether, a unit derived from a perfluoropropyl vinyl ether, a unit derived from a hexafluoropropene or a unit derived from ethylene.

5. The process according to claim 1 , wherein the fluorinated polymer has a mass average molecular weight of from 3,000 to 20,000.

6. The process according to claim 1 , wherein the fluorinated polymer has a mass average molecular weight of from 20,000 to 200,000.

7. The process according to claim 1 , wherein the fluorinated polymer has —COZ 1 in the formula (1) in an amount of from 0.1 to 4 mmol/g.

8. The process according to claim 1 , wherein the fluorinated crosslinked product has a transmittance at a wavelength of 365 nm of at least 70% in a film having a thickness of 0.5 mm.

9. A light emitting device encapsulated in a light-transmitting manner with a fluorinated crosslinked product obtained by the process of claim 1 .

10. The light emitting device according to claim 9 , which is UV-LED.

11. The process according to claim 1 , wherein the fluorinated polymer has —COZ 1 in the formula (1) in an amount of from 0.1 to 1 mmol/g.