EP0123258A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Magnetic recording disk
Assignee: Toray Industries Inc
•
Filing: 1984-04-17
•
Granted: —
•
Expires: 2004-04-17
Abstract
Abstract @ A magnetic recording disk which comprises (1) a three-layered laminate consisting of a core layer of a biaxially oriented polyolefinfilm which has a birefringence of not more than 0.01 and an amorphous-region orientation coefficient of not more than 0.2 and two outer layers of a biaxially oriented polyester film adhered to said core layer, and (2) a magnetic layer formed on at least one side of the laminate. The magnetic recording disk of the invention undergoes only slight dimensional changes with variations in humidity and temperature, and the dimensional changes are isotropic in the plane. The disk therefore has an excellent electromagnetic properties such as output fluctuation and outbreak of dropouts caused by the environmental change.
Inventors
- 👤 Kazuhiro Tanaka
- 👤 Ken-Ichi Kawakami
- 👤 Toshiya Yoshii
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 12:48
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/74; G11B5/82; G11B5/825; G11B5/62; G11B5/73; G11B5/739; G11B5/73923; G11B5/73927; G11B5/73931; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10S428/91; Y10T; Y10T428/00; Y10T428/24; Y10T428/24355; Y10T428/24372; Y10T428/24479; Y10T428/24612; Y10T428/24942; Y10T428/2495; Y10T428/24967; Y10T428/24975; Y10T428/26; Y10T428/263; Y10T428/264; Y10T428/265; Y10T428/31504; Y10T428/31786; Y10T428/31797; Y10T428/31855; Y10T428/31938
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
69 words
A magnetic recording disk which comprises (1). a three-layered laminate consisting of a core layer of a biaxially oriented polyolefin film which has a birefringence of not more than 0.01 and an amorphous-region orientation coefficient of not more than 0.2 and two outer leyers of a biaxially oriented polyester film adhereed to said core layer, and (2) a magnetic layer formed on at least one side of the laminate.
Claim 2
Dependent Claim
69 words
A magnetic recording disk which comprises (1). a three-layered laminate consisting of a core layer of a biaxially oriented polyolefin film which has a birefringence of not more than 0.01 and an amorphous-region orientation coefficient of not more than 0.2 and two outer leyers of a biaxially oriented polyester film adhereed to said core layer, and (2) a magnetic layer formed on at least one side of the laminate.
Claim 3
Dependent Claim
20 words
A magnetic recording disk according-to claim 1, wherein the melting point of the polyolefin film is 150° C or above.
Claim 4
Dependent Claim
16 words
A magnetic recording disk according to claim 1, wherein the polyolefin film is isotactic polypropylene film.
Claim 5
Dependent Claim
32 words
A magnetic recording disk according to claim 1, wherein the biaxially oriented polyolefin film has a birefringence of not more than 0.005 and an amorphous-region orientation coefficient of not more than 0.1.
Claim 6
Dependent Claim
29 words
A magnetic recording disk according to claim 1, wherein the biaxially oriented polyester film is a film of polyethylene terephthalate polymer having a birefringence of not more than 0.02.
Claim 7
Dependent Claim
27 words
A magnetic recording disk according to claim 1, wherein the biaxially oriented polyester film has an average surface roughness in the range of 0.001 t0 0.05 µm.
Claim 8
Dependent Claim
33 words
A magnetic recording disk according to claim 1, wherein the laminate has a thickness ratio [(thickness of the core layer)/(combined thickness of the both surface layeres)] in the range of 0.7 to 5.
Claim 9
Dependent Claim
33 words
A magnetic recording disk according to claim 1, wherein the laminate has a thickness ratio [(thickness of the core layer)/(combined thickness of the both surface layers)] in the range of 1 to 4.
Claim 10
Dependent Claim
37 words
A magnetic recording disk according to claim 1, wherein the core layer of the laminate ranges in thickness from 25 to 60 µm and the both surface layers range in thickness from 6 to 30 µm each.
Claim 11
Dependent Claim
37 words
A magnetic recording disk according to claim 1, wherein the core layer of the laminate ranges in thickness from 30 to 50 µm and the both surface layers range in thickness from 10 to 25 µm each.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.