Source: http://www.google.com/patents/US4596747?dq=inventor:%22Arthur+R.+Hair%22&ei=VAy0Tsa4NYTl0QGQiqWiBA
Timestamp: 2017-09-23 23:48:30
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Patent US4596747 - Magnetic recording medium - Google Patents
A magnetic recording medium comprising a transparent plastic film substrate, a primer coating layer formed on the substrate and a magnetic layer for magnetic recording formed on the primer coating layer, wherein said primer coating layer is formed by dispersing carbon black in a radiation curable coating...http://www.google.com/patents/US4596747?utm_source=gb-gplus-sharePatent US4596747 - Magnetic recording medium
Publication number US4596747 A
Application number US 06/631,208
Also published as DE3428943A1, DE3428943C2
Publication number 06631208, 631208, US 4596747 A, US 4596747A, US-A-4596747, US4596747 A, US4596747A
Inventors Masaharu Nishimatsu, Toshiaki Ide, Yuichi Kubota, Yoshiaki Saito, Shigeru Shimada
US 4596747 A
A magnetic recording medium comprising a transparent plastic film substrate, a primer coating layer formed on the substrate and a magnetic layer for magnetic recording formed on the primer coating layer, wherein said primer coating layer is formed by dispersing carbon black in a radiation curable coating material composed essentially of at least one oligomer or polymer containing at least one radiation curable unsaturated double bond per molecule and curing the resulting dispersion by radiation.
1. A magnetic recording medium comprising a transparent plastic film substrate, a primer coating layer formed on the substrate and a magnetic layer for magnetic recording formed on the primer coating layer, wherein said primer coating layer is formed by dispersing carbon black in a radiation curable coating material in an amount of 45-200 parts carbon black per 100 parts coating material composed essentially of at least one oligomer or polymer containing at least one radiation curable unsaturated double bond per molecule and curing the resulting dispersion by radiation, with the proviso that wherein said oligomer or polymer contains at least two acryloyl or methacryloyl groups per molecule, it has a molecular weight of at least 200 per each acryloyl or methacryloyl group.
The present invention relates to a magnetic recording medium having excellent antistatic property and surface smoothness as well as good electric characteristics.
It is an object of the present invention to provide a magnetic recording medium which has a low electrostatic property even without the above-mentioned backing layer and which is capable of minimizing dropouts.
The resin component of the radiation curable coating material to be used in the present invention, includes oligomers or polymers containing at least one radiation curable unsaturated double bond per molecule, such as an acrylic double bond, an allyl-type double bond, a maleic double bond or other radiation curable double bonds. It is preferred to use a compound containing at least two (meth) acryloyl groups per molecule, the molecular weight being at least 200 per each acryloyl group. If the molecular weight per (meth) acryloyl group is less than 200, the resin component tends to undergo a substantial volumetric shrinkage at the time of the crosslinking (curing) reaction, whereby the substrate will be curled, thus leading to poor dimensional stability and deterioration of the adhesion of the magnetic layer.
The radiation curable unsaturated polyester resin may be prepared by adding maleic acid, fumaric acid, etc. to at least one polybasic acid component and at least one polyhydric alcohol component, and subjecting the mixture to a dehydration or alcohol removal reaction by a common method, namely, in a nitrogen atmosphere at a temperature of from 180° to 200° C. in the presence of a catalyst, raising the temperature to 240° to 280° C., and conducting the condensation reaction under reduced pressure of from 0.5 to 1 mmHg to obtain a polyester resin. The content of the maleic acid or fumaric acid is usually from 1 to 40 mol %, preferably from 10 to 30 mol %, in the acid component, in view of the crosslinking during the preparation and the radiation curing property.
Resin Preparation (a)
100 parts of a copolymer having a composition of vinyl chloride/vinyl acetate/vinyl alcohol in a weight ratio of 93/2/5% and having a molecular weight of 18000, is heated and dissolved in 238 parts of toluene and 95 parts of cyclohexanone. The solution was heated to 80° C., and 7.5 parts of the after-mentioned TDI adduct was added. Further, 0.002 part of tin octylate and 0.002 part of hydroquinone were added. The mixture was reacted at 82° C. in a nitrogen gas stream until the conversion of isocyanate (NCO) reached at least 90%. After the reaction, the reaction mixture was cooled and diluted with an addition of 238 parts of methyl ethyl ketone. The resin composition thereby obtained was designated as Resin Composition (a). The molecular weight of this resin was 19200, and the molecular weight per methacryloyl group was about 4400.
Preparation of the TDI Adduct
348 parts of tolylene diisocyanate (TDI) was heated to a temperature of 80° C. in a four-necked flask having a capacity of one liter in a nitrogen stream. Then, 260 parts of 2-hydroxy ethyl methacrylate (2 HEMA), 0.07 part of tin octylate and 0.05 part of hydroquinone were added dropwise into the reaction vessel, while cooling to control the temperature in the reaction vessel to be within a range of from 80° to 85° C. After completion of the dropwise addition, the reaction mixture was stirred at 80° C. for 3 hours to complete the reaction. After the completion of the reaction, the reaction product was taken out and cooled to obtain a 2 HEMA adduct of TDI as a white paste.
Resin Preparation (b)
100 parts of a saturated polyester resin (L-411 manufactured by Dynamit-Nobel Co.) was heated and dissolved in 116 parts of toluene and 116 parts of methyl ethyl ketone. The solution was heated to 80° C., and 2.84 parts of an isophorone diisocyanate adduct prepared in the same manner as in Resin Preparation (a) was added. Further, 0.006 part of tin octylate and 0.006 part of hydroquinone were added thereto, and the mixture was reacted in a nitrogen gas stream at 80° C. until the NCO conversion reached at least 90%.
Resin Preparation (c)
291.2 parts of dimethyl terephthalate, 291.2 parts of dimethylisophthalate, 64.8 parts of dimethyl maleate, 251.2 parts of ethylene glycol, 6.48 parts of 1,4-butane-diol, 81.2 parts of 1,3-butane diol and 4.0 parts of tetra-n-butyl titanate, were fed in a reaction vessel and subjected to a methanol removal reaction in a nitrogen gas stream at 180° C. Then, the reaction mixture was heated to 240° to 260° C. and subjected to a condensation reaction under reduced pressure of from 0.5 to 1 mmHg to obtain a linear unsaturated polyester resin having a moledular weight of 8000.
Resin Preparation (d)
250 parts of NIAX polyol PCP-0200 (a polycaprolactone manufactured by Chisso Corporation), 122.2 parts of 2-hydroxyethyl methacrylate, 0.024 part of hydroquinone and 0.033 part of tin octylate, were fed in a reaction vessel, heated to 80° C. and dissolved. Then, 163.6 parts of TDI was dropwise added, while cooling to control the temperature in the reaction vessel to be within a range of from 80° to 90° C. After the completion of the dropwise addition, the mixture was reacted at 80° C. until the NCO conversion reached at least 95%.
Resin Preparation (e)
148 parts of phthalic anhydride, 65 parts of 1,3-butane diol, 30 parts of ethylene glycol and 2.5 parts of p-toluene sulfonic acid, were fed into a reaction vessel, and subjected to an esterification reaction in a nitrogen gas stream at 150° C. for 1 hour and then at 180° C. for 5 hours. Then, the reaction mixture was cooled to 100° C., and 0.3 part of hydroquinone and 28 parts of acrylic acid were added. The mixture was subjected to an esterification reaction for 15 hours to obtain an oligo ester acrylate having a molecular weight of 2000. The molecular weight per acryloyl group of this resin was about 650.
Resin Preparation (f)
250 parts of Adeka Polyether P-1000 (a polyether manufactured by Asahi Denka Kogyo K.K.), 65 parts of 2-hydroxyethyl methacrylate, 0.013 part of hydroquinone and 0.017 part of tin octylate were fed into a reaction vessel, heated to 80° C. and dissolved. Then, 87.0 parts of TDI was dropwise added, while cooling to control the temperature in the reaction vessel to be within a range of from 80° to 90° C. After completion of the dropwise addition, the reaction mixture was reacted at 80° C. until the NCO conversion reached at least 95%.
40 parts of the above-mentioned resin composition (a), 4 parts of carbon black (20 mμm) and 60 parts of a solvent (toluene/methyl ethyl ketone=1/1) were mixed and dissolved to obtain a radiation curable coating material. This coating material was applied onto a polyester film and dried to obtain a dried layer having a thickness of 0.5 μm. Then, electron beam radiation was applied by means of an electro curtain-type electron beam accelerator manufactured by ESI Co., at a radiation dose of 2 Mrad in a nitrogen atmosphere, whereby a cross-linked, cured primer coating layer was obtained.
Preparation of the Magnetic Coating Material
______________________________________Nitrocellulose (H 1/2" manufactured                     8      partsby Asahi Chemical Industry Co., Ltd.)VAGH (manufactured by Union Carbide Co.)                     10     partsUrethane elastomer (Ester 5703,                     9      partsmanufactured by Goodrich Co.)Methyl isobutyl ketone    150    partsCyclohexane               50     partsTo the resin solution having the above composition;Fe--Ni--Co alloy powder   100    partsα-Al2 O3 (0.5 μm powder)                     2      partsLubricant (Higher fatty acid-modified                     1      partsilicone oil)Dispersant (Soybean oil purified lecitin)                     3      parts______________________________________
______________________________________Carbon black (60 mμm)  20    partsResin Composition (a)     40    partsResin Composition (b)     4     partsSolvent (toluene/methyl ethyl ketone =                     56    parts1/1)______________________________________
______________________________________Carbon black (80 mμm)  10    partsResin Composition (c)     7     partsNK ester-A-4G (manufactured by                     3     partsShin Nakamura Kagaku K.K.)Solvent (toluene/methyl ethyl ketone =                     90    parts1/1)______________________________________
______________________________________Carbon black (30 mμm)  5     partsResin Composition (b)     6     partsResin Composition (e)     3     parts1,6-hexane glycol diacrylate                     1     partSolvent (toluene/methyl ethyl ketone =                     90    parts1/1)______________________________________
______________________________________(Radiation curable magnetic layer)______________________________________Magnetic powder (Co-adsorbed iron oxide;                     100    partslength: 0.3 μm; diameter: 0.04 μm;Hc: 1100 Oe)Dispersant (oleic acid)   2      partsSolvent (methyl ethyl ketone/toluene =                     100    parts50/50)______________________________________
______________________________________Vinyl chloride-vinyl acetate copolymer                      10    parts(VAGH manufactured by Union Carbide Co.)Solvent (toluene/methyl ethyl ketone = 1/1)                      90    parts______________________________________
______________________________________Resin Composition (a)     50    partsSolvent (toluene/methyl ethyl ketone =                     50    parts1/1)______________________________________
TABLE 1__________________________________________________________________________Electric                  Tape winding condi-                                    Percentresistance Dropout Tape wind-                     tion during the                               Adhesion                                    transmis-Ω/cm2      Once         100 times              ing condition                     running operation                               (g)  sion__________________________________________________________________________Example 1 6 × 107      50 80   Good   Good      105  0.3Example 2 2 × 107      40 80   Good   Good      115  0.4Example 3 3 × 107      60 90   Good   Good      115  0.2Example 4 1 × 108      50 80   Good   Good      120  0.1Compara- .sup. 1 × 1011      200         500  Bad    Bad       120  3.8tiveExample 1Compara- .sup. 2 × 1011      250         600  Bad    Bad       140  1.5tiveExample 2__________________________________________________________________________
The dropouts were measured at a temperature of 40° C. under a relative humidity of 60%.
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U.S. Classification 428/840.5, 428/522, 360/136, 360/135, 428/323, 427/128, G9B/5.286, 428/408, 428/425.9, 427/131, 360/134, 428/900
International Classification G11B5/738, G11B5/73, C09D4/00
Cooperative Classification Y10T428/31609, Y10T428/31935, Y10T428/30, Y10T428/25, Y10S428/90, G11B5/738
European Classification G11B5/738
Owner name: TDK CORPORATION 13-1, NIHONBASHI 1-CHOME, CHUO-LKU
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:NISHIMATSU, MASAHARU;IDE, TOSHIAKI;KUBOTA, YUICHI;AND OTHERS;REEL/FRAME:004549/0700
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:NISHIMATSU, MASAHARU;IDE, TOSHIAKI;KUBOTA, YUICHI;AND OTHERS;REEL/FRAME:004549/0700