What is claimed is:
1. A vinylpyrrolidone polymer, which contains at least one antioxidant in a ratio of 0.0000130 weight % to the vinylpyrrolidone polymer.
2. A vinylpyrrolidone polymer according to claim 1, wherein the antioxidant is a compound having a phenolic hydroxyl group.
3. A vinylpyrrolidone polymer according to claim 1, wherein the antioxidant is a compound of general formula (1) andor (2) below:
4
wherein each of R1, R2, R3, R4, and R5 is, independently of each other, at least one member selected from the group consisting of a hydrogen atom, alkyl groups, substituted alkyl groups, aryl groups, and substituted aryl groups, wherein R1 and R2, or R3 and R4, may be bonded to each other to form a cyclic structure.
4. A vinylpyrrolidone polymer according to claim 1, wherein the antioxidant includes the joint use of a radical scavenger with a peroxide decomposer.
5. A vinylpyrrolidone polymer according to claim 1, which further contains a radical formation inhibitor.
6. A vinylpyrrolidone polymer, which is adjusted such that the reduction ratio of the K value defined by Fikentscher’s equation will be within 5% when the vinylpyrrolidone polymer is subjected to a forcible test in which the vinylpyrrolidone polymer is kept heated at 120 C. under normal pressure in air for 2 hours.
7. A vinylpyrrolidone polymer, which is adjusted such that the reduction ratio of the K value defined by Fikentscher’s equation will be within 5% when the vinylpyrrolidone polymer is subjected to a promotion test in which the vinylpyrrolidone polymer is kept heated at 50 C. in a solution state for 14 days.
8. A vinylpyrrolidone polymer according to claim 1, pH of the aqueous solution of which with a concentration of 5 weight % is in the range of 4 to 12.
9. A vinylpyrrolidone polymer according to claim 3, pH of the aqueous solution of which with a concentration of 5 weight % is in the range of 4 to 12.
10. A resin composition, which comprises a vinylpyrrolidone polymer as a resin component, and further comprises at least one antioxidant in a ratio of 0.0000130 weight % to the vinylpyrrolidone polymer.
11. A stabilization process for a vinylpyrrolidone polymer, which comprises the step of mixing the vinylpyrrolidone polymer with at least one antioxidant in a ratio of 0.0000130 weight % to the vinylpyrrolidone polymer.
12. A preservation process for a vinylpyrrolidone polymer, which comprises the step of suppressing the oxygen concentration to not higher than 50,000 ppm in a gas phase that contacts with the vinylpyrrolidone polymer.
13. A preservation process for a vinylpyrrolidone polymer according to claim 12, which further comprises the steps of putting the vinylpyrrolidone polymer into an airtight container and evacuating the container.
14. A preservation process for a vinylpyrrolidone polymer according to claim 12, which further comprises the steps of putting the vinylpyrrolidone polymer into an airtight container and displacing air in the container with an inert gas andor carbonic acid gas.
15. A preservation process for a vinylpyrrolidone polymer according to claim 13, which further comprises the steps of putting the vinylpyrrolidone polymer into an airtight container and displacing air in the container with an inert gas andor carbonic acid gas.
16. A preservation process for a vinylpyrrolidone polymer according to claim 12, which further comprises the steps of putting the vinylpyrrolidone polymer into an airtight container and enclosing at least one deoxidizing agent together with the vinylpyrrolidone polymer in the container.
17. A preservation process for a vinylpyrrolidone polymer according to claim 15, which further comprises the steps of putting the vinylpyrrolidone polymer into an airtight container and enclosing at least one deoxidizing agent together with the vinylpyrrolidone polymer in the container.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A method of manufacture of ferroelectric memory comprising a ferroelectric film, said method comprising:
assembling a chip of said ferroelectric memory;
writing data to said ferroelectric memory, after the chip assembly process; and,
subjecting said ferroelectric memory, after the data writing process, to heat treatment at a heat treatment temperature T1 ( C.) below the phase transition temperature Tc ( C.) of the ferroelectric film, causing imprinting in said ferroelectric film.
2. The method of manufacture of ferroelectric memory according to claim 1, wherein subjecting said ferroelectric memory to heat treatment is performed at said heat treatment temperature T1 ( C.) such that (Tc150) ( C.)T1 ( C.)(Tc50) ( C.) is satisfied.
3. The method of manufacture of ferroelectric memory according to claim 1, wherein said ferroelectric film is an SrBi2Ta2O9 film and subjecting said ferroelectric memory to heat treatment is performed substantially for one hour, and said heat treatment temperature T1 ( C.) is substantially 220 C.
4. The method of manufacture of ferroelectric memory according to claim 1, wherein read-only memory is manufactured as said ferroelectric memory.
5. The method of manufacture of ferroelectric memory according to claim 1, wherein heat treatment of said ferroelectric memory is performed in said chip assembly process.
6. The method of manufacture of ferroelectric memory according to claim 1, wherein subjecting said ferroelectric film to heat treatment is performed at a heat treatment temperature t1 ( C.) for stabilizing the polarization state of said ferroelectric film in the polarization direction corresponding to said data.
7. A method of manufacture of ferroelectric memory comprising:
assembling a chip of said ferroelectric memory which has a ferroelectric film;
writing data to said ferroelectric memory, after the chip assembly process;
providing a read-only memory through subjecting said ferroelectric memory, after the data writing process, to a first heat treatment at a heat treatment temperature T1 ( C.) below the phase transition temperature Tc ( C.) of the ferroelectric film; and
selecting said ferroelectric film comprised by said read-only memory, after the first treatment process, to a second heat treatment at a heat treatment temperature T2 ( C.) equal to or higher than the phase transition temperature Tc ( C.) of the ferroelectric film.
8. The method of manufacture of ferroelectric memory according to claim 7, wherein subjecting said ferroelectric memory to heat treatment is performed at said heat treatment temperature T1 ( C.) such that (Tc150) ( C.)T1 ( C.)(Tc50)( C.) is satisfied.
9. The method of manufacture of ferroelectric memory according to claim 7, wherein said ferroelectric film is an SrBi2Ta2O9 film, said first heat treatment process is performed substantially for one hour and said heat treatment temperature T1 ( C.) is substantially 220 C., and said second heat treatment process is performed at said heat treatment temperature T2 ( C.) of substantially 350 C. or higher.
10. The method of manufacture of ferroelectric memory according to claim 7, wherein random-access memory is manufactured as said ferroelectric memory after said second heat treatment process.
11. The method of manufacture of ferroelectric memory according to claim 7, wherein said ferroelectric memory is subjected to heat treatment in said chip assembly process.
12. The method of manufacture of ferroelectric memory according to claim 7, wherein said second heat treatment temperature T2 ( C.) is approximately the phase transition temperature Tc ( C.) of said ferroelectric film.
13. The method of manufacture of ferroelectric memory according to claim 7, wherein said second heat treatment process causes the remanent polarization of said ferroelectric film to be zero.