Method of forming thin film

• US 20060014912A1
• Filed: 09/22/2005
• Published: 01/19/2006
• Est. Priority Date: 03/26/2003
• Status: Active Grant

• Current Assignee: Daikin Industries Ltd
• Original Assignee: Daikin Industries Ltd
• Inventors: Araki, Takayuki, Kodani, Tetsuhiro
• Granted Patent: US 7,655,742 B2
• Time in Patent Office: Days
• US Class Current: 526/255
• CPC Class Codes: C07C 21/18 containing fluorine
• CPC Class Codes: C08F 114/22 Vinylidene fluoride
• CPC Class Codes: Y10T 428/3154 Of fluorinated addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31544 Addition polymer is perhalogenated

Abstract

There is provided a method of forming a thin film of vinylidene fluoride homopolymer having crystal form I which is applicable to various substrates in relatively easy way (coating conditions, application method, etc.), a process for preparing a vinylidene fluoride homopolymer having crystal form I efficiently at high purity, and novel vinylidene fluoride homopolymers which can give a thin film being excellent in ferroelectricity. The method of forming a thin film of vinylidene fluoride homopolymer comprises (i) a step for preparing a green powder product of vinylidene fluoride homopolymer comprising crystal form I alone or as main component by subjecting vinylidene fluoride to radical polymerization in the presence of a bromine compound or iodine compound having 1 to 20 carbon atoms which contains at least one moiety represented by —CRf¹Rf²X¹, wherein X¹ is iodine atom or bromine atom; Rf¹ and Rf² are the same or different and each is selected from fluorine atom or perfluoroalkyl groups having 1 to 5 carbon atoms and (ii) a step for forming a thin film on a substrate surface by using vinylidene fluoride homopolymer which comprises crystal form I alone or as main component and is obtained from the green powder product of vinylidene fluoride homopolymer comprising crystal form I alone or as main component.

Claims

1. A method of forming a thin film comprising vinylidene fluoride homopolymer which comprises the following steps (i) and (ii).

(i) A step for preparing a green powder product of vinylidene fluoride homopolymer comprising crystal form I alone or as main component by subjecting vinylidene fluoride to radical polymerization in the presence of a bromine compound or iodine compound having 1 to 20 carbon atoms which contains at least one moiety represented by the formula (1):

wherein X¹ is iodine atom or bromine atom;

Rf¹ and Rf² are the same or different and each is selected from fluorine atom or perfluoroalkyl groups having 1 to 5 carbon atoms.

(ii) A step for forming a thin film on a substrate surface by using vinylidene fluoride homopolymer which comprises crystal form I alone or as main component and is obtained from the green powder product of vinylidene fluoride homopolymer comprising crystal form I alone or as main component.

2. The method of forming a thin film of claim 1 which includes a step (iii) for heat-treating the thin film of vinylidene fluoride homopolymer at a temperature of not less than 50°

C. and lower than a crystalline melting point of the vinylidene fluoride homopolymer.

3. The method of forming a thin film of claim 1 which includes a step (iv) for subjecting the thin film of vinylidene fluoride homopolymer to polarization treatment.

4. The method of forming a thin film of claim 1, wherein the bromine compound or iodine compound which contains the moiety of the formula (1) is a perhalo compound.

5. The method of forming a thin film of claim 1, wherein in said formula (1), X¹ is an iodine atom.

6. The method of forming a thin film of claim 1, wherein in the formula (1), both of Rf¹ and Rf² are fluorine atoms.

7. The method of forming a thin film of claim 1, wherein the compound which contains the moiety of the formula (1) is an iodine compound represented by the formula (2):

X²—

(CF₂)_n—

I 

 

(2)

wherein X² is a fluorine atom or iodine atom, n is an integer of 1 to 20.

8. The method of forming a thin film of claim 1, wherein in the vinylidene fluoride homopolymers comprising crystal form I alone or as main component, when attention is given to proportions of the respective vinylidene fluoride homopolymers having crystal form I, II or III in the green powder product of vinylidene fluoride homopolymer which are calculated by IR analysis, the proportion of vinylidene fluoride homopolymers having crystal form I satisfies both of (Equation 1):

100≧

I-form/(I-form+II-form)≧

50% by weight 

 

(Equation

     1)

and (Equation

     2);

100≧

I-form/(I-form+III-form)≧

50% by weight 

 

(Equation

     2).

9. The method of forming a thin film of claim 8, wherein the proportion of vinylidene fluoride homopolymers having crystal form I satisfies both of (Equation 3):

100≧

I-form/(I-form+II-form)≧

70% by weight 

 

(Equation

     3)

and (Equation

     4);

100≧

I-form/(I-form+III-form)≧

70% by weight 

 

(Equation

     4).

10. The method of forming a thin film of claim 1, wherein a number average degree of polymerization of the green powder product of vinylidene fluoride homopolymer comprising crystal form I alone or as main component is from 4 to 15.

11. The method of forming a thin film of claim 1, wherein the step (ii) for forming a thin film of vinylidene fluoride homopolymer is carried out by applying a liquid composition containing the vinylidene fluoride homopolymer on a substrate surface.

12. The method of forming a thin film of claim 1, wherein the step (ii) for forming a thin film of vinylidene fluoride homopolymer is carried out by vacuum vapor deposition of a composition containing the vinylidene fluoride homopolymer on a substrate surface.

13. The method of forming a thin film of claim 11, wherein the step (ii) for forming a thin film of vinylidene fluoride homopolymer is carried out at a temperature of not less than 10°

C. and lower than a crystalline melting point of the vinylidene fluoride homopolymer.

14. The method of forming a thin film of claim 12, wherein the step (ii) for forming a thin film of vinylidene fluoride homopolymer is carried out at a temperature of not less than 10°

C. and lower than a crystalline melting point of the vinylidene fluoride homopolymer.

15. The method of forming a thin film of claim 1, wherein the thin film of vinylidene fluoride homopolymer is formed on a surface of silicon substrate.

16. The method of forming a thin film of claim 1, wherein the thin film of vinylidene fluoride homopolymer is formed on a surface of metallic substrate.

17. The method of forming a thin film of claim 16, wherein the metallic substrate is at least one selected from the group consisting of aluminum, copper, gold, silver and platinum.

18. The method of forming a thin film of claim 1, wherein the vinylidene fluoride homopolymer comprising crystal form I alone or as main component is formed into a thin film on a substrate surface in a thickness of 0.1 to 1,000 nm.

19. A process for preparing a vinylidene fluoride homopolymer which comprises crystal form I alone or as main component and has a number average degree of polymerization of 4 to 15, in which vinylidene fluoride is subjected to radical polymerization in the presence of a radical polymerization initiator and at least one of perfluoro iodides represented by the formula (2):

X²—

(CF₂)_n—

I 

 

(2)

wherein X² is a fluorine atom or iodine atom, n is an integer of 1 to 20.

20. The preparation process of claim 19, wherein the perfluoro iodide of the formula (2) is CF₃I.

21. The preparation process of claim 19, wherein the perfluoro iodide of the formula (2) is represented by the formula (3):

I—

(CF₂CF₂)_n1—

I 

 

(3)

wherein n1 is 1 to 5.

22. The preparation process of claim 19, wherein the number average degree of polymerization of the obtained vinylidene fluoride homopolymer comprising crystal form I as main component is to 12.

23. The preparation process of claim 19, wherein in the vinylidene fluoride homopolymers comprising crystal form I alone or as main component, when attention is given to proportions of the respective vinylidene fluoride homopolymers having crystal form I, II or III in the green powder product of vinylidene fluoride homopolymer which are calculated by IR analysis, the proportion of vinylidene fluoride homopolymers having crystal form I satisfies both of (Equation 1):

100≧

I-form/(I-form+II-form)≧

50% by weight 

 

(Equation

     1)

and (Equation

     2);

100≧

I-form/(I-form+III-form)≧

50% by weight 

 

(Equation

     2).

24. The preparation process of claim 23, wherein the proportion of vinylidene fluoride homopolymers having crystal form I satisfies both of (Equation 3):

100≧

I-form/(I-form+II-form)≧

70% by weight 

 

(Equation

     3)

and (Equation

     4);

100≧

I-form/(I-form+III-form)≧

70% by weight 

 

(Equation

     4).

25. A vinylidene fluoride homopolymer represented by the formula (4):

CF₃-(A¹)-I 

 

(4)

wherein A¹ represents a structural unit of vinylidene fluoride homopolymer which comprises crystal form I alone or as main component and has a number average degree of polymerization of 5 to 12.

28. The vinylidene fluoride homopolymer of claim 25, wherein the vinylidene fluoride homopolymer comprises crystal form I alone or as main component and when attention is given to proportions of the respective vinylidene fluoride homopolymers having crystal form I, II or III which are calculated by IR analysis, the proportion of vinylidene fluoride homopolymers having crystal form I satisfies both of (Equation 1):

100≧

I-form/(I-form+II-form)≧

50% by weight 

 

(Equation

     1)

and (Equation

     2);

100≧

I-form/(I-form+III-form)≧

50% by weight 

 

(Equation

     2).

30. The vinylidene fluoride homopolymer of claim 28, wherein the proportion of vinylidene fluoride homopolymers having crystal form I satisfies both of (Equation 3):

100≧

I-form/(I-form+II-form)≧

70% by weight 

 

(Equation

     3)

and (Equation

     4);

100≧

I-form/(I-form+III-form)≧

70% by weight 

 

(Equation

     4).

26. A vinylidene fluoride homopolymer represented by the formula (5):

I-(A²)-(CF₂CF₂)_m-(A³)-I 

 

(5)

wherein m is an integer of 1 to 5;

A² and A³ are the same or different and each is a structural unit of vinylidene fluoride homopolymer comprising crystal form I alone or as main component;

the sum of number average degree of polymerization of the structural units A² and A³ is 2 to 20.

27. The vinylidene fluoride homopolymer of claim 26, wherein the sum of number average degree of polymerization of the structural units A² and A³ is 4 to 15.

29. The vinylidene fluoride homopolymer of claim 27, wherein the vinylidene fluoride homopolymer comprises crystal form I alone or as main component and when attention is given to proportions of the respective vinylidene fluoride homopolymers having crystal form I, II or III which are calculated by IR analysis, the proportion of vinylidene fluoride homopolymers having crystal form I satisfies both of (Equation 1):

100≧

I-form/(I-form+II-form)≧

50% by weight 

 

(Equation

     1)

and (Equation

     2);

100≧

I-form/(I-form+III-form)≧

50% by weight 

 

(Equation

     2).

31. The vinylidene fluoride homopolymer of claim 29, wherein the proportion of vinylidene fluoride homopolymers having crystal form I satisfies both of (Equation 3):

100≧

I-form/(I-form+II-form)≧

70% by weight 

 

(Equation

     3)

and (Equation

     4);

100≧

I-form/(I-form+III-form)≧

70% by weight 

 

(Equation

     4).