Magnetic recording medium and method for producing the same

• US 5,474,814 A
• Filed: 10/12/1993
• Issued: 12/12/1995
• Est. Priority Date: 03/13/1992
• Status: Expired due to Term

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Komatsu, Kazunori, Tomaru, Mikio
• Primary Examiner(s): Beck, Shrive
• Assistant Examiner(s): Bareford, Katherine A.
• Application Number:
  US08/134,617
• Time in Patent Office: 791 Days
• Field of Search: 427/599, 427/548, 427/549, 427/130
• US Class Current: 427/549
• CPC Class Codes: G11B 5/733 characterised by the addition of non-magnetic particles base layers having a non-magnetic layer under a soft magnetic layer G11B5/736; magnetic recording media substrates G11B5/739
• CPC Class Codes: G11B 5/7368 Non-polymeric layer under the lowermost magnetic recording layer base layers having a non-magnetic layer under a soft magnetic layer G11B5/736; magnetic recording media substrates G11B5/739
• CPC Class Codes: G11B 5/845 in a magnetic field

Abstract

A magnetic recording medium which is optimum for high-density recording in which not only orientation of magnetic particles to the direction of thickness of a magnetic layer can be performed effectively but the orientation is maintained, and a method for producing such a magnetic recording medium. The method includes the steps of multiply applying a lower layer containing inorganic powder and resin, an intermediate layer containing resin and an upper layer as a magnetic layer containing needle-shaped ferromagnetic powder onto a non-magnetic support in the condition where all the layers are wet, and drying and solidifying the layers while the ferromagnetic powder contained in the upper layer is oriented at a predetermined angle with respect to the direction of thickness of the intermediate layer. In an another embodiment, only two layers are applied to the support including a non-magnetic layer and a magnetic layer.

Claims

1. A method for producing a magnetic recording medium, comprising the following steps:

applying a lower non-magnetic layer and an upper magnetic layer onto a non-magnetic support, said upper magnetic layer including elongate ferromagnetic particles which are elongate along a major axis thereof, each of said layers being at least partially wet, wherein said lower layer has a viscosity which is greater than a viscosity of said upper layer absent said ferromagnetic particles;

generating a magnetic field which extends across said support at an angle selected from a range of 10 degrees to 90 degrees, inclusive, with respect to a surface of said support onto which said lower non-magnetic layer is applied so that each of said ferromagnetic particles is oriented with said major axis extending at said selected angle and each of said ferromagnetic particles is attracted into said lower non-magnetic layer, so that said ferromagnetic particles have lower end portions embedded in said lower non-magnetic layer, wherein the viscosity of said lower layer during said generating is not lower than 10 poise; and

drying each of said layers.

2. The method of claim 1, wherein said generating step is conducted prior to said drying step.

3. The method of claim 1, wherein said generating step includes the step of generating said magnetic field with a magnet provided only on a support side of said magnetic medium.

4. A method for producing a magnetic recording medium comprising the steps of:

applying a lower non-magnetic layer, an intermediate non-magnetic layer and an upper magnetic layer onto a non-magnetic support, said intermediate layer being applied between said lower and upper layers after applying said lower layer and before applying said upper layer, said upper magnetic layer including ferromagnetic particles which are elongate along a major axis thereof, each of said layers being partially wet, wherein said intermediate layer has a viscosity which is greater than a viscosity of said upper layer absent said ferromagnetic particles;

generating a magnetic field which extends across said support at an angle selected from a range of 10 degrees to 90 degrees with respect to a surface of said support onto which said lower non-magnetic layer is applied so that each of said ferromagnetic particles is oriented with said major axis extending at said selected angle and each of said ferromagnetic particles is attracted into said intermediate non-magnetic layer, so that said ferromagnetic particles have lower end portions embedded in said intermediate non-magnetic layer, wherein the viscosity of said intermediate layer is not less than 20 poise during said generating; and

drying each of said layers.

5. The method of claim 4, wherein said generating step includes the step of providing magnets on opposite sides of said support, said magnets in combination generating said magnetic field.

6. The method of claim 4, wherein said generating step is conducted during said drying step.

7. The method of claim 4, wherein said lower layer includes inorganic powder and resin and said intermediate layer includes resin.