EP0060300A1 - Electron beam curing of magnetic media - Google Patents

Electron beam curing of magnetic media

Info

Publication number
EP0060300A1
EP0060300A1 EP19810902865 EP81902865A EP0060300A1 EP 0060300 A1 EP0060300 A1 EP 0060300A1 EP 19810902865 EP19810902865 EP 19810902865 EP 81902865 A EP81902865 A EP 81902865A EP 0060300 A1 EP0060300 A1 EP 0060300A1
Authority
EP
European Patent Office
Prior art keywords
radiation
acrylated
molecular weight
acrylate prepolymer
magnetic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19810902865
Other languages
German (de)
English (en)
French (fr)
Inventor
Hao-Jan Chang
Akihira A. Nishimura
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ampex Corp
Original Assignee
Ampex Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ampex Corp filed Critical Ampex Corp
Publication of EP0060300A1 publication Critical patent/EP0060300A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F299/00—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers
    • C08F299/02—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates
    • C08F299/022—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates from polycondensates with side or terminal unsaturations
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/702—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the bonding agent
    • G11B5/7021—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the bonding agent containing a polyurethane or a polyisocyanate
    • G11B5/7022—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the bonding agent containing a polyurethane or a polyisocyanate containing mixtures of polyurethanes or polyisocyanates with other polymers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/702—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the bonding agent
    • G11B5/7023—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the bonding agent containing polyesters, polyethers, silicones, polyvinyl resins, polyacrylresins or epoxy resins
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/702—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the bonding agent
    • G11B5/7026—Radiation curable polymers

Definitions

  • the invention relates to electron beam (EB) cured magnetic recording media and to a process for making such media.
  • EB electron beam
  • Magnetic media are composed of a nonmagnetic substrate or support coated with a cured resin binder containing dispersed finely divided magnetic particles. Normally the backing is made of plastic although other materials such as paper, glass, or metal can be used. Such magnetic media are ordinarily in the form of a tape, belt, disc or the like. In this regard the word "tape” is frequently used hereinafter to generically denote such media since tape is the most common form of magnetic recording media. It will be understood, however, that all forms of magnetic media are included within the scope of this invention.
  • the binders used in tape are typically curable high molecular weight thermoplastic polymers. These binders are usually cured in the fluid state with a chemical curing agent such as a diisocyanate. The curing process causes crosslinking of the thermoplastic polymer chains as well as other reactions involving the diisocyanate. Chemical curing of tape binders has disadvantages and drawbacks. The curing reaction is generally unpredictable and is highly sensitive to temperature variations, moisture, and stoichiometry. More importantly it generally provides a cured binder having a lower than desired crosslink density. It also results in the curing agent being incorporated into the binder, which agent does not directly contribute to the magnetic or mechanical properties of the tape.
  • a prime object of the present invention is to provide an EB-cured magnetic recording media having improved magnetic and mechanical properties as compared to the prior chemically cured or radiation-cured magnetic media. Another object is to provide a process for making such media that involves no chemical curing agents such as diisocyanates.
  • One aspect of the invention is a magnetic medium comprising a nonmagnetic substrate coated with a radiation-cured polymeric binder having magnetic particles dispersed therein characterized in that the binder comprises a radiation-cured mixture of a high molecular weight thermoplastic polymer and a radiation- curable acrylate prepolymer.
  • a second aspect of the invention is a process for making the above described magnetic medium comprising the steps of preparing a fluid mixture of a solution of a radiation-curable polymeric binder and magnetic particles, coating a nonmagnetic substrate with the fluid mixture, evaporating the solvent from the coating to solidify the coating, calendering the dried coated substrate, and exposing the dried coared substrate to sufficient radiation to cure the coating characterized in that the polymeric binder comprises a mixture of a high molecular weight thermoplastic polymer and a radiation-curable acrylate prepolymer.
  • Figure 1 is a block diagram showing the manufacture of a magnetic tape according to the process of the present invention.
  • Figure 2 is a side view of a coating and curing line wherein the curing is done by means of an electron beam.
  • the principal polymeric component of the magnetic binder composition in terms of quanitity is a high molecular weight thermoplastic polymer. This component is essential to obtaining a magnetic medium having appropriate mechanical properties.
  • These polymers are typically linear fully polymerized homopolymers or copolymers having a weight average molecular weight of at least about 50,000, usually in the range 100,000 to 800,000 and more usually 100,000 to 300,000.
  • polystyrene-butadiene copolymers examples include styrene-butadiene copolymers, acrylonitrile-butadiene-copolymers, vinylacetate-vinylchloride copolymers, polyesters, polyamides, polycarbonates, polysulfones, polyacrylates, polyacrylic acid, polyvinylacetal, polyvinylbutyral, polyurethanes, and epoxy and phenoxy resins.
  • Polyurethanes both polyesterurethanes and polyetherurethanes, are a preferred class of high molecular weight thermoplastic polymers.
  • the other essential polymeric component of the magnetic binder is a radiation-curable acrylic prepolymer.
  • prepolymer denotes low molecular weight partially polymerized molecules, including molecules commonly called oligomers. These prepolymers are preferably polyfunctional, that is, they contain more than one reactive acrylate group. Difunctional and trifunctional acrylate prepolymers are particularly preferred. Their weight average molecular weight will usually be less than about 10,000, more usually less than 5,000. They are susceptible to rapid radiation-induced crosslinking using either nonparticulate (ultraviolet. X-ray, or gamma) radiation or particulate ( ⁇ -particles, electrons, ⁇ -particles, protons) radiation.
  • Electron beam radiation is preferred because its generation, focussing, and shielding are simple relative to other forms of radiation.
  • Examples of EB-curable acrylate prepolymers that may be used in the mixture are acrylated epoxy resins, acrylated urethanes, acrylated alkyd urethanes, acrylated polycaprolactams, acrylated polyethers, acrylated unsaturated acid modified drying oils, and acrylated polyesters. Specific examples of such prepolymers are
  • the ratio of the high molecular weight thermoplastic polymer to the acrylate prepolymer in the mixture can vary from 50:50 to 90:10 and is preferably in the range of 60:40 to 80:20 on a resin solids basis by weight.
  • the acrylate prepolymer can be from as little as 10% to as much as 50% of the total polymer in the binder.
  • Minor amounts of other conventional additives may be included in the magnetic binder composition if desired.
  • additives are: dispersants such as lecithin, organic esters of phosphoric acid, quaternary ammonium compounds, and other surfactants to aid in the deagglomeration and dispersal of the magnetic particles; conductive pigments, such as conductive carbon black, to reduce the electrical resistivity of the tape; and lubricants to minimize head-tape friction.
  • dispersants such as lecithin, organic esters of phosphoric acid, quaternary ammonium compounds, and other surfactants to aid in the deagglomeration and dispersal of the magnetic particles
  • conductive pigments such as conductive carbon black
  • lubricants to minimize head-tape friction.
  • the inclusion of materials, such as methacrylate polymers, that are preferentially degraded by radiation should be avoided.
  • the binder contains no chemical curing agent.
  • the third essential ingredient in the magnetic binder is finely divided magnetic particles.
  • magnétique particles examples include ⁇ ferric oxides, doped iron oxides, chromium dioxide, and elemental iron, cobalt and/or nickel.
  • Acicular ⁇ ferric oxide is most commonly used. Particle size should be such as to obtain a good dispersion of the magnetic component in the mixture.
  • the particle length of the ⁇ ferric oxide will usually be in the range of 0.2 to 1 ⁇ m and it will usually have an aspect ratio of 5:1 to 10:1. It will normally constitute about 60% to about 90% by weight of the magnetic binder composition after drying.
  • the polymeric components are dissolved in a common solvent such as tetrahydrofuran, cylcohexanone, methyl ethyl ketone, toluene, and methyl isobutyl ketone that will evaporate rapidly.
  • a common solvent such as tetrahydrofuran, cylcohexanone, methyl ethyl ketone, toluene, and methyl isobutyl ketone that will evaporate rapidly.
  • the polymer concentration in the solution will typically be in the range of 0.05 to 0.20 mg/ml.
  • This solution, containing the homogeneously dispersed magnetic particles is applied to the magnetic substrate using conventional coating machinery at a thickness in the range of about 2.5 to 15 ⁇ m. After the coating is applied, the coated substrate is dried to evaporate off the solvent leaving a solid coating that is dry to the touch.
  • the coated substrate is calendered and then exposed to radiation of sufficient energy and dose to cure the magnetic binder composition.
  • the strength of the radiation will depend upon a number of factors such as the percentage of the acrylate prepolymer in the coating, the activity or crosslinkability of the acrylate prepolymer, the thickness of the coating and the duration of exposure.
  • electron beam radiation is preferred. UV radiation is the least desirable since its use will normally require inclusion of photoinitiators in the binder and it is highly absorbed by additives such as pigments.
  • an electron beam energy of no more than 300 KeV is employed since higher energies do not result in a better cure of the binder and may cause damage to many magnetic tape substrate materials.
  • the dose can vary from 1 to 15 Mrad.
  • FIG. 1 shows the general plan for manufacturing a magnetic tape utilizing the present invention. Although this particular figure shows the manufacture of a tape, it is obvious that the same technique could be used to manufacture other magnetic media by making suitable modifications as are well-known to those skilled in the art.
  • a coating mixture is prepared as is later described in the examples.
  • This mixture is then coated at 5 on a tape utilizing well-known tape coating tech niques.
  • the tape Before the tape has dried, it is ordinarily oriented as at 7 by passing it through a strong magnetic field.
  • the tape is passed through a conventional drying oven which may be followed by burnishing or similar operations.
  • the tape is then calendered at 11 and at this point the tape is dry, i.e. the binder is in a solid, thermoplastic state.
  • the tape is now passed through an electron beam curing apparatus at 13 wherein the crosslinking reaction(s) take place.
  • the tape may then be slit at 15, burnished at 17 and then spooled at 19. All of these operations are conventional in the tape making field and are well- known to those skilled in the art except step 13 which consists of passing a tape through a device wherein it is exposed to an electron beam.
  • Figure 2 shows a typical election beam curing process wherein an electron beam generator 21 is provided with suitable shielding 23 and 25.
  • the tape is passed under the generator 21 and between the shields 23 and 25 so that .the electron beam 29 impinges on the tape.
  • This polyurethane is a member of a family of polyurethane resins which are made by reacting P,P'-diphenylmethane diisocyanate, adipic acid and butanediol-1,4 in such proportions that all of the isocyanate groups have reacted to give a substantially unreactive polymer. It is sold by B.F. Goodrich and has the following characteristics:
  • the final mix was then milled for an additional six hours, followed by separations, filtration, coating, drying, calendering and electron beam curing at a dose of 10 Mrad.
  • Example 2 Utilizing the same general procedures as outlined in Example 2 and the standard procedure of sandmilling, additional magnetic media were made and tested as follows:
  • a solvent-free epoxyacrylate resin which contains active acrylic unsaturation in the polymer molecule. It is sold by Freeman Company and has the following properties:
  • UV Photoinitiator % by weight
  • the reference tape was Memorex 716 tape.
  • Chroma SNR signal to noise ratio
  • Video SNR was measured by Rhode & Schwaz meter. 0 means reference, +1.0 means 1.0 dB better than reference.
  • 1st Number represents the time length of measurement, e.g. 2'; measured for 2 minutes 2' 30" measured for 2-1/2 minutes
  • 4th Number represents general rating 1-10, lower the number, the better.
  • Activity Detector was measured by home-made, instrument using electrical reading to test the physical flaw of the tape. Using a scale of 0 to 10, lower the number, the better.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Paints Or Removers (AREA)
  • Magnetic Record Carriers (AREA)
  • Polymerisation Methods In General (AREA)
EP19810902865 1980-09-22 1981-09-22 Electron beam curing of magnetic media Withdrawn EP0060300A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US18997980A 1980-09-22 1980-09-22
US189979 1980-09-22

Publications (1)

Publication Number Publication Date
EP0060300A1 true EP0060300A1 (en) 1982-09-22

Family

ID=22699560

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19810902865 Withdrawn EP0060300A1 (en) 1980-09-22 1981-09-22 Electron beam curing of magnetic media

Country Status (11)

Country Link
EP (1) EP0060300A1 (cs)
JP (1) JPS5786131A (cs)
AU (1) AU546317B2 (cs)
BR (1) BR8106017A (cs)
CA (1) CA1167408A (cs)
DE (1) DE3137691C2 (cs)
FR (1) FR2491246A1 (cs)
GB (1) GB2084589B (cs)
IE (1) IE51908B1 (cs)
MX (1) MX158193A (cs)
WO (1) WO1982001099A1 (cs)

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4408020A (en) * 1982-06-28 1983-10-04 The B. F. Goodrich Company Curable polyurethanes
JPS5979431A (ja) * 1982-10-29 1984-05-08 Konishiroku Photo Ind Co Ltd 磁気記録媒体
EP0123081A3 (en) * 1983-03-09 1986-11-26 DeSOTO, INC. Coatings for magnetic recording structures and production thereof
US4507458A (en) * 1983-04-14 1985-03-26 Takeda Chemical Industries, Ltd. Urethane acrylate compositions
JPS6057531A (ja) * 1983-09-07 1985-04-03 Kao Corp 磁気記録媒体
DE3332564A1 (de) * 1983-09-09 1985-03-28 Basf Ag, 6700 Ludwigshafen Magnetische aufzeichnungstraeger
DE3418482A1 (de) * 1984-05-18 1985-11-21 Basf Ag, 6700 Ludwigshafen Magnetische aufzeichnungstraeger
US4594262A (en) * 1984-07-05 1986-06-10 Minnesota Mining And Manufacturing Company Electron beam adhesion-promoting treatment of polyester film base
US4543268A (en) * 1984-07-05 1985-09-24 Minnesota Mining And Manufacturing Company Electron-beam adhesion-promoting treatment of polyester film base for magnetic recording media
JPH0610856B2 (ja) * 1984-08-04 1994-02-09 ティーディーケイ株式会社 磁気記録媒体
US5281482A (en) * 1988-04-22 1994-01-25 Minnesota Mining And Manufacturing Company Magnetic recording medium comprising magnetic particles and an electron beam curable polyurethane binder having segments derived from a specified unsaturated diol
US5028683A (en) * 1988-04-22 1991-07-02 Minnesota Mining And Manufacturing Company Electron-beam curable polyurethane compositions; and method

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GB829512A (en) * 1957-01-31 1960-03-02 Dow Chemical Co Method for cross-linking vinyl chloride polymers
US3104983A (en) * 1959-08-26 1963-09-24 Ibm Method of curing magnetic tape binder comprising butadiene-acrylonitrile and phenolicresin with subatomic radiation
DE1240934B (de) * 1965-09-15 1967-05-24 Basf Ag Bindemittel fuer ferromagnetische Pulver bei der Herstellung von Magnetogrammtraegern
DE2100037C3 (de) * 1971-01-02 1980-06-19 Hartmann, Job-Werner, Dr., 6700 Ludwigshafen Verfahren zur Herstellung von magnetischen Aufzeichnungsträgern
GB1431854A (en) * 1972-04-07 1976-04-14 Sony Corp Magnetic recording media and methods of making them
US4072592A (en) * 1974-05-20 1978-02-07 Mobil Oil Corporation Radiation curable coating
JPS5845474B2 (ja) * 1974-05-20 1983-10-11 モビル オイル コ−ポレ−シヨン 放射硬化性塗料
JPS5921909B2 (ja) * 1974-10-31 1984-05-23 東レ株式会社 放射線硬化性塗料組成物
US4152485A (en) * 1977-08-05 1979-05-01 Toyo Boseki Kabushiki Kaisha Magnetic recording medium
FR2425094B1 (fr) * 1978-05-01 1985-07-19 Minnesota Mining & Mfg Compositions photopolymerisables
FR2456963A1 (fr) * 1979-05-18 1980-12-12 Eastman Kodak Co Produit photographique muni d'une piste d'enregistrement magnetique et procede pour sa fabrication
US4273633A (en) * 1979-06-11 1981-06-16 Union Carbide Corporation Radiation curable dispersions containing high molecular weight essentially nonpolymerizable vinyl resins
JPS5625230A (en) * 1979-08-06 1981-03-11 Sony Corp Magnetic recording medium
FR2463478B1 (fr) * 1979-08-06 1986-07-18 Sony Corp Element d'enregistrement magnetique
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Non-Patent Citations (1)

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Title
See references of WO8201099A1 *

Also Published As

Publication number Publication date
WO1982001099A1 (en) 1982-04-01
AU546317B2 (en) 1985-08-29
MX158193A (es) 1989-01-16
GB2084589A (en) 1982-04-15
CA1167408A (en) 1984-05-15
JPS5786131A (en) 1982-05-29
AU7554681A (en) 1982-04-01
DE3137691C2 (de) 1984-05-17
DE3137691A1 (de) 1982-05-27
GB2084589B (en) 1984-08-22
BR8106017A (pt) 1982-06-08
FR2491246A1 (fr) 1982-04-02
IE51908B1 (en) 1987-04-29
IE812187L (en) 1982-03-22
FR2491246B1 (cs) 1984-12-28

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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Effective date: 19821122

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Inventor name: CHANG, HAO-JAN

Inventor name: NISHIMURA, AKIHIRA A.