Claims
- 1. A magnetic tape cartridge for recording and reproducing digital signals having a wavelength of 1 .mu.m or less, comprising:
- a magnetic tape including:
- a base film which has a glass transition temperature Tg of 70.degree. C., which has a pre-heat-treatment coefficient of thermal shrinkage exceeding 0.6% in its longitudinal direction as measured in an unloaded state after being kept at 105.degree. C. for 30 minutes in a pre-heat-treated and unloaded state, and which subsequently is heat treated at a temperature of 80.degree. to 100.degree. C. for at least one hour to produce a coefficient of thermal shrinkage of 0.6% or less in a longitudinal direction of the tape as measured in an unloaded state after being kept at 105.degree. C. for 30 minutes in an unloaded state; and
- a magnetic layer formed on said base film;
- wherein said magnetic tape has a total thickness of 14 .mu.m or less; and
- wherein said magnetic tape has a coefficient of thermal shrinkage of 0.6% or less in a longitudinal direction of the tape as measured in an unloaded state after being kept at 105.degree. C. for 30 minutes in an unloaded state, said magnetic tape being wound around a hub at least 300 turns.
- 2. The magnetic tape cartridge as in claim 1, wherein said base film is polyethylene terephthalate film.
- 3. A magnetic tape cartridge for recording and reproducing digital signals having a wavelength of 1 .mu.m or less, comprising:
- a magnetic tape including:
- a base film of polyethylene terephthalate film, which has a pre-heat-treatment coefficient of thermal shrinkage exceeding 0.6% in its longitudinal direction as measured in an unloaded state after being kept at 105.degree. C. for 30 minutes in a pre-heat-treated and unloaded state, and which subsequently is heat treated at a temperature of 80.degree. to 100.degree. C. for at least one hour to produce a coefficient of thermal shrinkage of 0.6% or less in a longitudinal direction of the tape as measured in an unloaded state after being kept at 105.degree. C. for 30 minutes in an unloaded state; and
- a magnetic layer formed on said base film;
- wherein said magnetic tape has a total thickness of 14 .mu.m or less; and
- wherein said magnetic tape has a coefficient of thermal shrinkage of 0.6% or less in a longitudinal direction of the tape as measured in an unloaded state after being kept an 105.degree. C. for 30 minutes in an unloaded state, said magnetic tape being wound around a hub at least 300 turns.
- 4. A method for producing a magnetic tape cartridge for recording and reproducing digital signals having a wavelength of 1 .mu.m or less, comprising the steps of:
- heat treating a base film, which has a glass transition temperature Tg of 70.degree. C., which has a pre-heat-treating coefficient of thermal shrinkage exceeding 0.6% in its longitudinal direction as measured in an unloaded state after being kept at 105.degree. C. for 30 minutes in an unloaded state, at a temperature of 80.degree. to 100.degree. C. for at least one hour to produce a coefficient of thermal shrinkage of 0.6% or less in a longitudinal direction of the tape as measured in an unloaded state after being kept at 105.degree. C. for 30 minutes in an unloaded state;
- forming a magnetic layer on said base film to form a magnetic tape which has a total thickness of 14 .mu.m or less and which has a coefficient of thermal shrinkage of 0.6% or less in a longitudinal direction of the tape as measured in an unloaded state after being kept at 105.degree. C. for 30 minutes in an unloaded state; and
- winding said magnetic tape at least 300 turns around a hub.
- 5. The magnetic tape cartridge as in claim 4, wherein said base film is polyethylene terephthalate film.
Priority Claims (1)
Number |
Date |
Country |
Kind |
3-225067 |
Aug 1991 |
JPX |
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Parent Case Info
This application is a continuation of application Ser. No. 07/925,251 filed on Aug. 6, 1992, now abandoned.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
5055349 |
Yasafuku et al. |
Oct 1991 |
|
5093064 |
Utsumi et al. |
Mar 1992 |
|
5340636 |
Kamada |
Aug 1994 |
|
Foreign Referenced Citations (1)
Number |
Date |
Country |
59-132421 |
Jul 1984 |
JPX |
Non-Patent Literature Citations (2)
Entry |
Digital Video Recording Technique, p. 158, Japan, Aug. 1990. |
"The Composite Digital Format and Its Applications," Engberg et al., SMPTE Journal, Oct. 1987, pp. 934-942. |
Continuations (1)
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Number |
Date |
Country |
Parent |
925251 |
Aug 1992 |
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