Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1999-03-29
2002-01-15
Resan, Stevan A. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S336000, C428S690000, C428S690000, C428S474700, C428S900000
Reexamination Certificate
active
06338896
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic recording medium, which comprises a magnetic layer having ferromagnetic powder dispersed in a binder and being placed at least on one side of a non-magnetic support member, or which comprises a non-magnetic coating layer having non-magnetic powder dispersed in a binder, and a magnetic layer is further provided on a non-magnetic support member. The magnetic recording medium has high electromagnetic transfer characteristics, high adhesion property and good running durability.
In general, in a magnetic recording medium used for audio, video or computer applications, a magnetic layer with ferromagnetic powder dispersed in a binder is provided on a non-magnetic support member, or a non-magnetic coating layer with non-magnetic powder dispersed in a binder is placed on a non-magnetic support member, and a magnetic layer with ferromagnetic powder dispersed in a binder is further placed on the non-magnetic coating layer.
In recent years, technical development has been made in the field of magnetic recording from conventional analog recording toward application of digital recording with less possibility of recording deterioration. Generally, it is necessary to record more signals in digital recording than in analog recording. Also, higher picture quality and higher tone quality are required for the recording and reproducing apparatus and for the recording medium to be used than in analog recording. Also, there are higher demands on more compact design and space-saving than in analog recording. This means that it is necessary to achieve the recording with higher density.
To attain the high density recording, it is necessary to have recording signals with shorter wavelength or narrower recording tracks. For this purpose, it is necessary to have finer ferromagnetic powder, filling at higher density and ultra-smoothening of medium surface. At the same time, writing speed or reading speed on the recording medium must be increased. For this reason, it is attempted to improve the number of revolutions of cylinder or to improve carrier speed of magnetic tape. Further, there are demands to produce thinner recording medium in order to improve volume density.
In the past, polyethylene terephthalate (PET), poly-ethylene-2,6-naphthalate (PEN), etc. have been used as the non-magnetic support member. With the development of thinner magnetic recording medium, it is now difficult to run magnetic tape at the tape/head relative speed of 20 m/sec. or higher in stable manner on a small diameter head, which is rotated at high speed of 5,400 to 9,000 rpm, and there is a tendency that Rf output is decreased and output fluctuation is increased. In the decrease of Rf output and output fluctuation, there are problems such as moving or drawing of the recording medium toward head chip mounting window of cylinder head. This means that the contact between the recording medium and head becomes uneven and gap is generated between them. This leads to loss during recording and reproducing and causes the output decrease or the output fluctuation.
In the so-called head-hitting as described above, it is known that stiffness of the recording medium in lateral direction contributes more than that of longitudinal direction. The stiffness M is expressed by: M=Ebd
3
/12, where E is Young's modulus, b is width of magnetic tape, and d is thickness of magnetic tape. To increase the stiffness in lateral direction, it is effective to increase Young's modulus in lateral direction of the support member by the increase of the percent of stretch in case the thickness is constant. In case thinner recording medium is used, it is no more possible to maintain the stiffness of the recording medium in optimal range merely by increasing the percent of stretch.
In this respect, aromatic polyamide (aramide) has been proposed. When a magnetic recording medium was prepared using an aromatic polyamide support member, adhesion between the non-magnetic support member and the magnetic layer or the non-magnetic coating layer was not sufficient. During running operation, the magnetic layer was often stripped off or dropped off from edge portion due to sliding or friction with the head-running system and this caused dropout or contamination of the running system.
The present applicants have proposed the use of amorphous linear saturated polyester or polyester elastomer as an undercoating agent for polyamide substrate film in JP-B-82042890 and JP-B-82042891. Also, in U.S. Pat. No. 4,308,311, it has been proposed to use an aromatic polyamide with higher Young's modulus as substrate film and the use of alcohol-soluble polyamide as an undercoating agent. However, this was not satisfactory in the adhesive property, and surface property of the magnetic layer was also not sufficient. Further, in JP-A-0729148, a magnetic recording medium has been proposed, which comprises a polyamide undercoating layer on a support member of polyamide film, and there are demands on a magnetic recording medium with smooth undercoating layer with the polyamide film support member and the magnetic layer with high adhesive property.
It is an object of the present invention to provide a magnetic recording medium, which comprises a non-magnetic coating layer having non-magnetic powder dispersed in a binder and being coated on a non-magnetic support member, and a magnetic layer is further placed on it, whereby the magnetic recording medium provides high adhesion between the non-magnetic layer and the non-magnetic support member, has good running durability and good head contact on a recording and reproducing system even when an aramide support member is used, and further has high volume recording density and magnetic layer with good smoothness and high electromagnetic transfer characteristics.
SUMMARY OF THE INVENTION
To attain the above object, the magnetic recording medium according to the present invention comprises a non-magnetic coating layer having non-magnetic powder dispersed in a binder, the non-magnetic coating layer being placed at least on one side of a non-magnetic support member, there is further provided a magnetic layer having ferromagnetic powder dispersed in a binder and being placed on the non-magnetic coating layer, whereby the non-magnetic support member is made of aromatic polyamide, the binder in the lower non-magnetic layer comprises at least one type selected from —SO
3
M, —OSO
3
M, —PO
3
M
2
, or —OPO
3
M
2
, and an undercoating layer comprising polyamide having tertiary amino group is provided between the non-magnetic support member and the lower non-magnetic layer.
The present invention also provides a magnetic recording medium as described above, wherein the polyamide having the tertiary amino group is not soluble in a solvent which is used in the lower non-magnetic layer to be coated after coating of the undercoating layer.
The present invention provides a magnetic recording medium as described above, wherein the polyamide resin having the tertiary amino group is a copolymerized polyamide containing repeating structural units represented by the following formulae (1) and (2) respectively:
Further, the present invention provides a magnetic recording medium, which comprises a magnetic layer having ferromagnetic powder dispersed in a binder and being placed at least on one side of a non-magnetic support member, or a non-magnetic coating layer having non-magnetic powder dispersed in a binder and a magnetic layer having ferromagnetic powder dispersed in a binder and being placed on the non-magnetic coating layer, whereby the non-magnetic support member is made of aromatic polyamide, an undercoating layer is provided between the non-magnetic support member and the lower non-magnetic layer, or in case the lower non-magnetic layer is not present, between the non-magnetic support member and the magnetic layer, the undercoating layer comprising polyamide resin having tertiary amino group and containing repeated structural units expressed by the following formulae (1) and (
Hashimoto Hiroshi
Ishikawa Tatsuo
Meguro Katsuhiko
Fuji Photo Film Co. , Ltd.
Resan Stevan A.
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Magnetic recording medium does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic recording medium, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic recording medium will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2845900