# US 7,608,349 B2 · Polyester film for recording medium and magnetic recording tape

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- Number: US 7,608,349 B2
- Document ID: US7608349B2
- Status: Granted
- Kind: B2
- Application number: 10/544,446
- Filed: 2004-02-04
- Published: 2006-07-06
- Granted: 2009-10-27
- Earliest claimed: 2003-02-07
- Assignees: Toray Industries, Inc.
- Inventors: Masaaki Ono; Kazuyoshi Fukata; Masahiro Yagi
- Web page: https://patentgrep.com/patent/US7608349B2

## CPC

- B32B 27/36: comprising polyesters
- B32B 15/09: comprising polyesters
- C08J 7/0427: {with only one layer of a composition containing a polymer binder (with more layers C08J7/042)}
- C08J 7/043: Improving the adhesiveness of the coatings per se, e.g. forming primers (adhesives in the form of films or foils characterised by the primer layers between the polymer carriers and the adhesives C09J7/50)
- C08J 7/046: Forming abrasion-resistant coatings; Forming surface-hardening coatings
- G11B 5/73927: {Polyester substrates, e.g. polyethylene terephthalate}
- G11B 5/73929: {comprising naphthalene ring compounds, e.g. polyethylene naphthalate substrates}
- G11B 5/73931: {Two or more layers, at least one layer being polyester}
- B32B 2307/208: Magnetic, paramagnetic
- B32B 2367/00: Polyesters, e.g. PET, i.e. polyethylene terephthalate
- B32B 2429/02: Records or discs
- C08J 2367/02: Polyesters derived from dicarboxylic acids and dihydroxy compounds; (C08J2367/06 takes precedence)
- Y10T 428/24405: Polymer or resin [e.g., natural or synthetic rubber, etc.]
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A polyester film for recording medium, having one major surface thereof provided with a coating layer containing fine particles of 5 to 60 nm diameter and an organic compound, wherein the number of fine surface projections existing on the surface of the coating layer is in the range of 3 million to 100 million/mm2, and the number of surface defects of 120 nm or greater height attributed to foreign matter contained in the film is 30/100 cm2 or less, and wherein the polyester contains a titanium compound substantially not having any particle diameter. Thus, there are provided a magnetic recording tape for digital data recording that can reduce dropouts and excels in durability, and further provided a polyester film that is suitable as a base film thereof.

## Claims

### Claim 1

A polyester film for recording medium, having one major surface thereof provided with a coating layer containing fine particles with a particle diameter of 5 to 50 nm and an organic compound, wherein a number of fine surface projections existing on a surface of said coating layer is in a range of 3 million to 7 million/mm2, and a number of surface defects with a height of 120 nm or greater attributed to foreign matter attributed to a catalyst, contained in said film is 15/100 cm2 to 30/100 cm2, and wherein a polyester of said polyester film contains 1) a titanium compound at a content of 2 to 6 ppm as a titanium atom equivalent relative to polyester and a phosphorus compound at a content of 0.2 to 9 ppm as a phosphorus atom equivalent relative to polyester, and a ratio of a content of said titanium compound to a content of said phosphorus compound is in a range of 0.7 to 10 at a molar ratio (Ti/P) of titanium atom to phosphorus atom, and not having a particle shape of titanium dioxide, and 2) 0 ppm of antimony and 0 ppm of germanium.

### Claim 2 (depends on 1)

The polyester film for recording medium according to claim 1, wherein a thickness of said film is less than 9.0 μm.

### Claim 3 (depends on 1)

The polyester film for recording medium according to claim 1, wherein said polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate.

### Claim 4 (depends on 1)

The polyester film for recording medium according to claim 1, wherein said film is used for a magnetic tape of a digital recording system.

### Claim 5 (depends on 1)

A magnetic recording tape wherein a ferromagnetic metal thin layer is provided on a surface of said coating layer of said polyester film according to claim 1.

### Claim 6 (depends on 1)

The polyester film of claim 1, wherein a surface roughness, Ra, of the coating layer is 0.5-4.0 nm.

### Claim 7 (depends on 1)

The polyester film of claim 1, wherein the phosphorous compound is at a content of 2 to 6 ppm.