DE3338854C2 - Magnetic recording material - Google Patents

Description

The invention relates to a magnetic recording medium rial according to the preamble of claim 1.

There is already a method of stabilizing poly ester films by heat treatment in US-A-4,275,107 wrote. In addition, have non-magnetic support as Principles for use in conventional magnetic recording materials in general a heat shrink in the machines in the range of 0.2 to 0.25% in a balanced manner foils and in the range of 0.25 to 0.4% in tensioned Fo lien. Furthermore, some previous references describe Improvements in the skewing property of magne recording materials, for example JP-A-50- 156403, 50-156404 and 56-11624, however, is known in these References do not denote the relationship between the heat shrink in the machine direction of non-magnetic carriers as Basics for magnetic recording materials and the Skew characteristic of the obtained magnetic recording specified materials.

US-A-4 042 569 describes a method of treatment a polyester film in which the polyester film at a Tempe Heat in the range of 100 to 190 ° C under tension warmth delt is. The percent heat shrinkage of the polyester film in the machine direction is not more than 2%. Indeed the disclosed polyester film is by no means suitable as a carrier for a magnetic recording material because of heat Treatment temperature of over 140 ° C none for a magnetic Recording material absolutely necessary smooth surface can be obtained.

The invention is therefore based on the object, a magne table material with improved skew to create  

This object is achieved by that specified in claim 1 or 2 solved magnetic recording material.

The dependent claims give advantageous embodiments of a such magnetic recording material.

The term "heat shrinkage" is used here for the value used by shrinkage of a wearer at a tempe temperature of 70 ° C for 48 hours without any application Tension on the carrier was determined.

Materials not suitable for use in the invention Magnetic supports include polyesters such as polyethylene tereph thalate or polyethylene-2,6-naphthalate, cellulose, such as Cellulo seacetate, cellulose triacetate, cellulose acetate butyrate or Cellu loose propionate, ionomers, polyimides, polyamides, polyamide-imides, Polyvinyl chlorides, polyvinyl chloride copolymers, polysulfones and Polycarbonates. In particular, polyester materials are for the Carrier preferred, especially polyethylene terephthalate.

If the amount of heat shrinkage is 0.15% over The skew increases as the heat increases shrinkage increases, with a distortion of the wiedergege Benen pictures are strikingly observed. If otherwise the amount of heat shrinkage is 0.15% or less, can visually distort the reproduced pictures hardly observed. Therefore, the percentage Heat shrinkage 0.15% or less as a rule, before preferably 0.11% or less.  

An effective method of reducing heat shrinkage For example, the carrier is 0.15% or less the previous heat treatment of a carrier, the Trä through a heat zone under the conditions: 0 to 18 kg / 1 m Width of the support, a thickness of the support of 15 microns, corre sp a tensile stress of 0 to 1.18 · 10⁷ N / m², a tempera from 100 to 140 ° C and a treatment time of 2 to 20 s, whereby the percentage of heat shrinkage of the non- magnetic carrier in the machine direction 0.15% or less is. Preferably, a tensile stress of 0 to 9.12 x 10⁶ N / m² at a temperature of 110 to 130 ° C and a treat time from 3 to 10 s. In the continuous heat mebehandlung, the applied tension can be proportional to Width of the carrier to be treated are regulated.

Another method is the heat treatment of a Carrier in roll condition. The heat treatment in the roll condition can at a winding tension of 3.92 · 10⁶ to 1.31 · 10⁷ N / m² for a support of 4 000 m in length at a temperature of 40 to 100 ° C and a treatment time of 20 to 80 h carried out become. Preferably, a roll of the carrier, with a Winding tension of 3.26 × 10⁶ to 1.11 × 10⁷ N / m² is wound, heat treated at 60 to 80 ° C for 20 to 48 hours. At this Heat treatment can increase the applied voltage proportional to Width of the carrier can be adjusted and the treatment time can be proportional to the length of the wound carrier be presented.

The heat treatment is carried out according to the invention, to remove the residual stress of the carrier caused when the carrier is made.  

The method of forming the invention used The magnetic recording layer can be a common method and is, for example, in US-A-3,630,771 corresponding JP-B-47-22073, 52-8807, 53-9841, 45-46011, 55-20291, and the US A-4 135 016, corresponding to JP-B-56-26890.

The following example serves to further explain the Invention, without the invention being limited thereto. In the case of play all parts are based on the weight.

example 1

Co-modified γ-Fe₂O₃ (Hc: 5.01 × 10⁴ A / m average particle size: 0.33 μm) 300 parts Nitrocellulose (average degree of polymerization, 80, degree of nitration: 12.2) 52 parts Polyurethane resin (made from neopentyl adipate and diphenylmethane diisocyanate, molecular weight: 60,000) 29 parts Carbon black (electrically conductive carbon black, average particle diameter: 40 nm) 18 parts Cr₂O₃ (average particle diameter: 0.2 μm) 4.5 parts stearic acid 6 parts oleic acid 3.5 parts Methyl ethyl ketone / butyl acetate (3: 7) 770 parts

The above mass was in a ball mill and a sand mill mixed and dispersed to the  produce magnetic coating composition. The obtained magnetic coating composition was applied in different ways raised by straps to the magnetic record to obtain tapes. The results are from Table 1 can be seen.

The carriers used in this example were Biaxially stretched polyethylene terephthalate with a thickness of 15 microns. The continuous heat action and the heat treatment in the wound up stood were among those listed in the table Conditions performed. The out on the carrier formed magnetic recording layer contains one usual binder, which nitrocellulose and polyurethane contains. The skew value was measured after the magnetic recording tape through 300 times Video recorder ("NV-8300") at 40 ° C and 80% re had run lati moisture.

The heat shrinkage of the carrier was determined by placing a gap of about 10 inches exactly on the test sample of the support at 23 ° C and 65% relative humidity Measured the sample in an oven 70 ° C was hung for 48 hours, then at 23 ° C and 65% relative humidity during was allowed to stand for more than 30 min and the mar kierte distance was measured again exactly. The processes Heat shrinkage was measured from the distance before and calculated after the heat treatment. The heat treatment the carrier in the condition of a whale was destined for a carrier of 4000 m in length, which is around a core with a Diameter of 15.2 cm was wound.  

Since the skew value is 17 μS or less in order to obtain normal reproduced images, visually determined using a video recording device, it results from the test results, that the heat shrinkage of the carrier 0.15% or has to be less.  

Table I

Claims (7)

1. A magnetic recording material having a non-magnetic carrier and a magnetic recording layer applied thereon, characterized in that the non-magnetic carrier is subjected to a heat treatment at a temperature of 100 to 140 ° C, a tensile stress of 0 to 1.18 x 10⁷ N / m² and a treatment time in the range of 2 to 20 s and that the percentage heat shrinkage of the non-magnetic carrier in the machine direction is 0.15% or less. 2. Magnetic recording material with a non-magneti carrier and a magnetic applied thereto Recording layer, characterized in that the non-magnetic carrier in the roll condition of a heat at a temperature of 40 to 100 ° C, a Winding tension of 3.92 · 10⁶ to 1.31 · 10⁷N / m² and a Treatment time is in the range of 20 to 80 h and that the percentage heat shrinkage of the non-magne machine direction supports 0.15% or less is. 3. A magnetic recording material according to any one of claims 1 or 2, characterized in that the percentage Heat shrinkage is 0.11% or less.   4. Method for treating a carrier for a magnetic Recording material, characterized in that a non-magnetic carrier at a temperature in the range from 100 to 140 ° C while the carrier is being heat treated under a tensile stress in the range of 0 to 1.18 x 10⁷ N / m² is held, wherein the heat treatment during a Period of 2 to 20 s, for a carrier with a thickness of 15 microns, is performed. 5. The method according to claim 4, characterized in that a Temperature in the range of 110 to 130 ° C, a tensile stress in the range of 0 to 9.12 · 10⁶ N / m² and a period of 3 to 10 s are applied. 6. Method for treating a carrier for a magnetic Recording material, characterized in that a non-magnetic carrier in roll condition at a temperature temperature in the range of 40 to 100 ° C, while the carrier is under a winding tension in the range of 3.92 · 10⁶ to 1.31 · 10⁷ N / m² is kept for a period of 20 to Heat treated for 80 h, calculated for a carrier with a length of about 4000 m. 7. A method for treating a carrier according to claim 6, characterized in that a winding tension in the range from 3.26 x 10⁶ to 1.11 x 10⁷ N / m² and a temperature of 60 to 80 ° C and a period of about 20 to 48 hours applied become.