CN1110425A - Substrate having a carbon rich coating - Google Patents

Abstract

The present invention provides a magnetic recording medium, including polymer flexible substrate and magnetic layer aplied on said substrate, and a layer of adhesiveless carbon-rich coating adhered to said magnetic layer. Said invention also provides a method for making carbon-rich coating plasma deposit on a substrate, and its steps are as follows: a. the substrate is placed in a vacuum chamber; b. the plasma gas suited for providing carbon-rich coating is injected into a slender hollow cathode so as to produce carbon-rich plasma in the vacuum chamber; and then it provides sufficient voltage to produce and retain plasma, and retain sufficient vacuum for plasma in vacuum chamber; and c. at the same time of that the radio-frequency bias electrode acts on the magnetic medium, the substrate is exposed to the plasma so as to make plasma accelerate toward the substrate and deposit carbon-rich coating on the substrate.

Description

Substrate having a carbon rich coating

The present invention relates to have the substrate of rich carbon outer layer, particularly have the magnetic recording medium of rich carbon outer layer and a kind of method of plasma-deposited coating.

Magnetic recording medium is made up of the magnetisable material that is attached on the substrate usually.But the bonding coating of pigment that a kind of common magnetic medium is solidified by magnetic is formed (latter is made by the dispersion of magnetisable granules of pigments in the polymer bonding agent), is coated on the non-magnetic carrier flexible, normally polymkeric substance.

Magnetic medium has various Voice ﹠ Video and video tape of comprising, computer format floppy and stretching surface recording disk (SSR), SSR are usually by a kind of hard round carrier with a kind ofly be made up of a thin polymer film that is suitable for being attached to the circumferential recording layer of this carrier.Referring to for example US patent No.4,623,570.

Be optimum operation, magnetic medium should have the durable recording surface of dead smooth, has minimum friction factor.Present recording medium, friction factor usually change with the variation of ambient humidity.When this operates under various environments for use at medium, caused undesirable variation.

Lubricant is usually used in the magnetic medium to help to reduce the wearing and tearing between medium and write head.Lubricant or before coating, be added to adhesives and a magnetizable particles submeter prose style free from parallelism in or add and be impregnated in the magnetosphere as external coating.

Good property medium really should have enough surface conductivities to avoid in use in producing static.For example be coated in nonconductor magnetosphere such as polyethylene terephthalate (PET) or polyamide on the flexible substrate of nonconductor,, may need to do some special processings for reaching suitable electrical conductance.This can finish in magnetic paint by add a kind of conductor such as carbon black before coating.Another kind method is non magnetic charcoal blacking is coated onto the back side of flexible substrate or is coated under the magnetosphere in medium front.

These every kind of methods that electrical conductance is provided are defectiveness all.When carbon black is added in the magnetosphere, cause the loss of signal, because carbon black has occupied the space that may occupy for magnetic paint.Other is coated with silica aerogel layer needs extra procedure of processing, therefore is expensive and has reduced throughput rate.

Present magnetic medium, water vapour can infiltrate magnetosphere and make its lost of life.Very easily the magnetosphere of water leaking-in steam and oxygen also makes bacterium be easy to growth or makes the magnetic paint oxidation.

Carbon coating has been applied in hard disk and the non-bonding material type magnetic medium, referring to as US patent No.4, and 833,031, but in durability, the perviousness aspect is also unsuccessful, and the stability that the The friction coefficient ambient humidity changes is also very poor.Thereby flexible magnetic medium is usually by using the surface to be coated with lubricant and using carbon black to improve its life-span to improve electrical conductance.

Just had in the past with the plasma-deposited method for preparing carbon coating, but defectiveness.U.S.patent No.4,645,977 disclose a kind of method of using induction plasma to form carbon film.Use high gas flow, high pressure and high-energy cause formation rather than smooth, hard and the carbon film of carbon dust.

Although can obtain the equipment of carbon coating and plasma-deposited carbon coating, but still need the flexible carbon medium of the polymer layer that contains magnetisable pigment, it does not need to be dispersed in the conductive particle in the bonding bed of material or the other conductive layer.Also need very durable and magnetic medium than low-friction coefficient (this coefficient is stable in from 0 to 100% ambient humidity range) is arranged.Also need the impervious substantially magnetic recording medium of a kind of water vapour and oxygen.

The invention provides a kind of magnetic recording medium, scribble magnetospheric substrate above it comprises and be attached to the carbon rich coating that does not contain bonding material on the magnetosphere.This substrate be polymkeric substance also be flexible, enriched carbon layer comprises the carbon of at least 50 atomic percentages, generally includes the carbon of 70-95 atomic percentage, the nitrogen of 0.1-20 atomic percentage, the hydrogen of the oxygen of 0.1-15 atomic percentage and 0.1-40 atomic percentage.

Enriched carbon layer is not water vapor permeable and oxygen preferably, about 5-8 of Molls hardness and surface conductivity about 10 ⁸-10 ¹²Ohm/side (ohms/square).When the ambient humidity that is exposed to from 0 to 100%, the magnetic recording medium that has carbon rich coating preferably has basicly stable kinetic friction coefficient.

The present invention also provides a kind of method at the last plasma-deposited carbon rich coating of substrate (comprising magnetic medium), and it comprises the following steps that (a) places vacuum chamber with substrate; (b) borrow the following step to produce rich carbon plasma in vacuum chamber: (1) will suit to provide the plasma gas of carbon rich coating to be injected in the hollow cathode, (2) provide enough voltage to produce and to keep plasma and (3) keep enough vacuum for described plasma in described vacuum chamber; (4) when the rf bias setting acts on this substrate, substrate is exposed in the plasma, plasma quickens and deposits thereon as carbon rich coating to substrate whereby.Though the present disclosure back relates to magnetic recording medium, described method can be used for the deposit carbon coating to the substrate of any energy with plasma-deposited glow discharge method coating.Such substrate comprises (only as an example) film; Fabric strip; Plate or dish; With molding, mach or other structural detail.Usually, substrate thickness is no more than 1cm.

Plasma gas provides any suitable source of the gas such as the saturated unsaturated hydrocarbon of the required component of carbon rich coating, nitrogenous hydrocarbon, and oxygen-containing hydrocarbon contains halocarbon and siliceous hydrocarbon.Plasma gas can be the liquid of gaseous state or vaporization, also can comprise carrier gas such as argon gas.To some application, may also need to use nitrogenous gas.

Usually, rf bias equipment is radio frequency bias electrode, and the about 25KHz of its frequency is to 400KHz, and bias voltage is made an appointment with-100 to-1500 volts.Might increase frequency range up to and comprise the megahertz scope.Preferred generation voltage method is by means of the pulsed D c-power supply.The voltage that produces and maintain in the coreless armature is generally-30 to-4000 volts; Low pressure for-1000V is modal.The power of supplying with coreless armature is generally 200 to 12000 watts, and more common is 500 to 2000 watts.

Hollow cathode preferably by graphite or refractory metal such as tungsten, make by tantalum or molybdenum, and normal length and diameter ratio are about 15: 1 to 1: 30.When hollow cathode was not horizontal year section of circle, " diameter " meaned maximum cross sections size.When applying the thermal sensitivity substrate, the best water-cooled of hollow cathode.

Preferably substrate contacts with radio frequency bias electrode (for example copper coin) during plasma-deposited.Vacuum values maintains about 1-300 millitorr usually, preferred 5-50 millitorr, and combined feed gas flow rate is about 10-500sccm usually.

The bonding formulation of the preferred above-mentioned pigment of magnetic medium has the enriched carbon layer that is coated on the magnetizable layer.

Also can comprise the one or more additional hollow cathode that produces rich carbon plasma.Additional cathode can provide coating or the raising enriched carbon layer accumulation rate more than a type on magnetic medium.

The term " rich carbon " that is used for herein means that enriched carbon layer has at least about 50 atomic percentage carbon.

Term " flexible " expression that is used for the modified magnetic medium of this paper is compared with the flexible rigidity of magnetic data recording disk (for example Winchester or hard disk), and magnetic recording medium has low flexible rigidity D.D is defined as:

D＝ (Ed3)/(12（1-V）)

D=(recording layer+substrate wherein) thickness (m)

E=(recording layer+substrate) Young modulus (N/m ²)

V=(recording layer+substrate) Poisson ratio

The term relevant with enriched carbon layer " impermeable substantially " that is used for herein means that the thick enriched carbon layer of 200 dusts (A) is the restraining barrier of water vapour and oxygen, and allows to see through the water vapour of this layer less than 2 gram/m ²It and oxygen are less than 2cM ³/ M ²-day-atm. oxygen permeability is pressed ASTM Testmethod D-3985 method and is used Modern Controls, Inc., Minneapolis, the Mocon Permeahility Tseter test of Minnesota preparation.Test cabinet with displacement background oxygen, carries out the oxygen permeability test first time with nitrogen wash.In test cabinet, import oxygen then, carry out the permeability test second time after at the appointed time.Test value difference as permeability with the second time for the first time.

Being used for herein " basicly stable " relevant with magnetic recording medium dynamic friction coefficient expression dynamic friction coefficient changes in the defined terms scope and is no more than 20%.

Fig. 1 is a jet plasma vapor deposition device synoptic diagram of the present invention;

Fig. 2 is a Comparative Examples magnetic medium friction factor (Y) and relative humidity %(X axle) curve map of relation;

Fig. 3 is a magnetic medium friction factor of the present invention (Y-axis) and relative humidity %(X axle) curve map of relation;

Fig. 4 is the curve map of magnetic medium peel force (lb/in) (Y-axis) and peel rate (in/min) (X-axis) relation.

The invention provides a kind of magnetic recording medium with rich carbon outer layer. It is a kind of with the method for jet plasma sedimentation at the excellent carbon rich coating of magnetic medium deposition that the present invention also provides. The magnetic medium that preferably can apply with the inventive method generally includes a kind of polymer dispersion (magnetosphere) of the magnetizable particles in bonding dose, on a flexible non-magnetic carrier as coating. Coating also available new method of the present invention is coated onto on other record medium, for example is coated onto to comprise on the medium that is deposited on the thin magnetic film on the substrate. Thin magnetic film can be magnetizable layer such as the cobalt-nickel of steam deposition or the barium iron layer of cobalt-chromium layer or sputter of bonding dose of no polymerization. Carbon rich coating is deposited and is attached on the magnetosphere. Term " flexible " as mentioned above. The difference of flexible media and hard medium is by common hard disk and 3 flexible disc: the Bernoulli dish of Iomega Cor-poration, the D value comparison of ordinary magnetic disc and stretching surface recording dish (SSR) and illustrating.

Hard disk Bernoulli ordinary magnetic disc SSR

D(N-m)36.4 2.00×10 ^-42.00×10 ^-41.98×10 ^-5

Like this, be used for this specification flexible mean D less than 36 preferably less than 1 * 10^-2。

Other flexible product of the present invention has similarly low deflection rigidity usually.

The jet plasma device

With reference to Fig. 1, show jet plasma device (being designated as 10) here. This device comprises the plasma (orifice) gas body source 20 and 22 of linking inlet tube 26 through flow-control device 24 and 25. Plasma gas enters vacuum chamber 30 through flow-control device 24 and 25, and enters in the hollow cathode 40 through import section 28.

Hollow cathode 40 is arranged, anode 50, radio frequency bias electrode 60 and substrate (for example magnetic recording medium) 70 in vacuum chamber 30. Substrate 70 twines switch from first spool 72 and rewinds to second spool 74.

Plasma gas through flow-control device 24 and 25 enters in vacuum chamber 30 and the hollow cathode 40. DC pulse power supply 80(is Airco Temescal Model CL-2A500maA peak power output power supply for example) directly link hollow cathode 40 and borrow circuit 84 to link anode 50 by means of circuit 82, so that the aura discharge to be provided. AC bias voltage power supply 90(is ENI Power systems for example, Inc., Rochoster, the Plasmaloc3 power supply of New York) borrow circuit 92 to link on the radio frequency bias electrode 60. AC power supplies 90 and DC power supply 80 be ground connection (100) all.

Be the situation in the monitoring vacuum chamber 30, installation mass spectrograph 110, emission spectrometer 120 and electric capacity manometer 130 are also linked in the vacuum chamber 30.

Produce in vacuum chamber 30 and keep vacuum and finished by diffusion pump 140 and mechanical pump 150, they borrow vacuum inlet 142 to link in the chamber 30.

Hollow cathode 40 is one various cross sections for example circle, square, rectangle or octagonal hollow pipe. Negative electrode 40 has a gas import 44 and plasma outlet 46. Cathode length is import 44 and exports distance between 46. Negative electrode ' diameter " be defined as the cross-sectional dimension of this negative electrode, no matter negative electrode is cylindrical cross section or other cross section.

Gas from flow-control device 24 and 25 enters import 44 through import section 28. Usually total air inlet flow of plasma gas and 15-500sccM is injected into hollow cathode 40.

Usually, elongated hollow negative electrode 46 draw ratios are about 15: 1 to 1: 30, and are also available outside this ratio range. When negative electrode 40 was circular cross section, its internal diameter was about 0.5cm to 5cm. Negative electrode is preferably extremely difficult melt material such as graphite, molybdenum, tungsten or tantalum with the anti-temperature that is higher than 20000 ℃. Yet the operating temperature that is lower than 20000 ℃ also is very common, because high temperature, pipe 40 must be fixed in the vacuum chamber with a heat-resisting securing member own.

For large diameter pipe, some add ons can be arranged, for example can be used for introducing plasma gas with the concentric quartzy pipe of negative electrode. It can extend from import 44 parts along cathode length (for example extend to cathode length half). Quartzy pipe most advanced and sophisticated (discharge end) the relatively position of cathode outlet 46 affects the voltage of deposition process and can be used to regulate this voltage. Under higher-wattage, temperature is higher in negative electrode and quartzy pipe, and quartzy pipe may break, and therefore has a stone to deceive guard shield between quartz pipe and hollow cathode inside.

The inner element of sleeve cathode is used for carbon source such as acetylene in the broken plasma feed gas. The plasma feed gas when entering into this device, be limited in managing 40 so that its from The port of export 46 ejections.

Preferably in vacuum, produce and keep voltage with the pulsed D c-power supply. It is one common through 0(that preferred pulsed D c-power supply will provide)-200 times/second voltage. The voltage that produces and maintain in the hollow cathode is made an appointment with-30 to-1000 volts usually, but other voltage is also available. The power of supplying with hollow cathode is generally 12000 watts, and more common is 500 to 2000 watts.

Use the pulsed D c-power supply when keeping stable plasma, high relatively electric current rather than electric arc are arranged in vacuum chamber.Finding in the experiment that embodiments of the invention carried out that for simplifying with normal DC power supply, when the plasma electrically current density surpassed a certain limit value, discharge became electric arc.25 kilowatts of DC power supplys that Hipotronics produces have been installed use 480V, the 0-3000V filtering direct current of 3 phase lines at first.Stable glow discharge withstand approximately under-500 volts up to the power supply of about 400mA.Increase plasma current and will produce a unsettled plasma, because voltage is lower than about 100V.This power supply is improved to use 480V, the phase line operation of no-output filter capacitor.This improvement provides pulse (120Hz) the DC electromotive force of 0-3000V under the 0-8 ampere.By improved pulse, even under low-voltage, can keep stable plasma.

Given correct condition, stable jet plasma 160 form in vacuum chamber and launch with the plasma outlet 46 of conical model from negative electrode 40.Preferred plasma will have the broken speed of high feed gas so that the speed of a carbon rich coating fast deposition on substrate 70 to be provided.

Radio frequency bias electrode 60 is sheet metal such as copper coin normally.The water-cooled metal plate is preferred bias voltage equipment.About 100KHz is to 400KHz for the common frequency of radio frequency bias electrode ,-100 volts to-1500 volts approximately of bias voltages.Preferably during plasma-deposited, substrate 70 contacts with radio frequency bias electrode 60.Use bias-voltage, additional plasma produces near radio-frequency electrode 60, and this electrode provides a negative potential for substrate and impels plasma 160 to deposit effectively apace to substrate 70.

The invention provides a kind of rich carbon external coating, this coating has improved the life-span, has increased electric conductivity and the restraining barrier of impermeable substantially water vapour and oxygen is provided.Carbon rich coating of the present invention generally includes a kind of composition that contains greater than 50atom% agraphitic carbon and other component such as oxygen, nitrogen and hydrogen.This carbon rich coating is wear-resistant durable, even and still can adhere well on the magnetic medium under high humility.This carbon rich coating can two-dimentionally stretch and can obviously not reduce its performance, therefore is easy to be used for the SSR dish-type.

The carbon rich coating component can be controlled by following parameters: the pressure of (1) plasma gas, 2) composition of feeding gas, 3) structure and 4 of hollow cathode) electric power that provided of pulsed D c-power supply and radio-frequency power supply.Feeding gas comprises a kind of carbon source, for example saturated and unsaturated hydrocarbon such as methane, ethane, ethene, acetylene or butadiene, nitrogenous hydrocarbon such as methyl amine or acetonitrile; Oxygen-containing hydrocarbon such as methyl alcohol or acetone; Or contain halocarbon such as methyl iodide or methyl bromide; With siliceous hydrocarbon such as tetramethylsilane, chloro trimethyl silane, or tetramethoxy-silicane.Unsaturated hydrocarbon, nitrogenous is preferred with containing halocarbon.

Carbon source can be gaseous state or liquid carbon source volatile or vaporization under serviceability temperature and pressure.Vector gas also can use with hydrocarbon source gas.Carrier gas can be inert gas and nitrogen, neon, argon gas or nitrogen.Nitrogen is found to be carbon rich coating provides required characteristic as having increased the electric conductivity of carbon rich coating.

The thickness of coating is usually greater than 5 nanometers, preferred about 10 to 100 nanometers, preferred again 10-40 nanometer, preferred again 10-20 nanometer.Thicker coating is possible but does not need usually.Substrate moves so that the coating of a desired thickness to be provided with the speed of setting in plasma.For said flow speed and equipment, 74 transmission speeds are generally 4 to 400mm/s to substrate 70 from spool 12 to spool.

Magnetic medium of the present invention uses any polymer bonding material that magnetisable pigment dispersion can be adhered to substrate 70.The example of suitable bonding material comprises Polyvinylchloride, polyvinyl acetate, polyacrylate, polyester, polyesteramide, thermoplasticity polyurethane resin, cellulose derivative such as cellulose acetate butyric acid, Styrene-Butadiene, phenoxy resin, butadiene and methacrylic acid copolymer, at least 2 multipolymers that are selected from following monomer: vinyl chloride, vinyl acetate, vinyl cyanide, vinyl alcohol, vinyl butyryl and vinylidene chloride.For instance, VAGH that is purchased from Union Carbide and other thermosetting, thermoplasticity or radiation curing resin all are available.

Rich carbon external coating will work to increase the life-span and reduce friction factor, therefore can replace conventional lubricant.But it is found that some lubricant can adhere to the carbon rich coating surface and extra benefit is provided.

U.S.patent No.3,490,946 disclose fluorocarbons can be as the lubricant of magnetic recording medium.U.S.patent No.s3,778,308; 4,267,238; With 4,268,556 disclose use PFPE (PPE) as magnetic medium lubricant protective seam.Have suitable side group or end functional group's lubricant can be on carbon rich coating chemical bonding or crosslinked.The lubricant crosslinkable that for example contains the acrylate PFPE.Referring to as U.S.patent No.4,526,833.Add the life-span that for example poly-perfluor ether lubricant external coating (single face of 3.5 inches (80mm) indicators of general diameter adds 0.5mg) discovery has further improved carbon rich coating.

U.S.patent no.4,526,833 PFPE can be with irradiation such as ultraviolet (UV) cross-linking radiation (referring to U.S.P4,526,833 the 9th hurdles, 46-56 is capable).A spot of initiating agent PPE4.5 part weight of 100 parts of weight (for example based on) can mix use with PPE.The modifier that a kind of this class initiating agent is Darocure2959.The Darocure initiating agent can be by reacting modification with following formula perfluor butoxy diisopropoxy-2-propionyl fluoride.Synthesizing of this propionyl fluoride referring to U.S.latent No.4,749,526 Example10,

The structural formula of the Darocure initiating agent of modification is considered to following formula

In an experiment of preparation modification Darocure initiating agent, 295g perfluor butoxy diisopropoxy-2-propionyl fluoride and 66.55g Darocure2959 reaction.This Darocure2959 initiating agent mixes in 1 liter of three-neck flask of mechanical stirrer, condenser and nitrogen bubble device is housed with the 300ml tetrahydrofuran.Perfluor butoxy diisopropoxy-2-propionyl fluoride lasts adding in 10 minutes.Gained brown potpourri refluxes and spends the night.Get dark amber product.

Material as non-magnetic carrier (the magnetic coating composition is coated on this carrier) comprises polyester such as polyethylene terephthalate or gathers 2,6-phthalic acid glycol ester; Polyolefin such as tygon or polypropylene, cellulose derivative such as cellulose triacetate; Such as polyphenylene sulfide, polycarbonate, polyamide or polyimide.The preferred example of carrier comprises the holder polyethylene terephthalate; Gather 2,6-phthalic acid glycol ester and polyimide film.In other flexible sheet of the present invention, in aforesaid material with a kind of substrate and no magnetizable layer is also included within.In this case, plasma can carry out or not carry out pre-service and directly is deposited on the substrate.

About 5 to 100 microns usually of the thickness of these carriers, but according to the magnetic recording medium difference of using, thickness has quite wide variation in above-mentioned scope.Thereby carrier is flexible making has carrier, and the magnetic medium of magnetizable layer and carbon rich coating is flexible.

Magnetic medium of the present invention can have any required shape such as audio cassette, video tape, computer format floppy or SSR.The present invention is specially adapted to SSR(referring to for example U.S.patent No.4, and 623,570, this patent is as the application's list of references).SSR borrows radial tension to be fixed on the stretching structure.

Borrow following non-limiting examples that the present invention is further described.

Embodiment 1-6

Form with the element that changes the gained coating with the feed preparation of various ratios and type carbon rich coating of the present invention.Graphite-pipe is as hollow cathode 40, its long 10cm, and internal diameter 1.2cm is placed on apart from substrate 70 10cm places.Bias voltage remains on-1275V.

Table 1 shows the typical element of carbon rich coating of the present invention and forms and typical processing conditions.The ratio (in a system) that the chemical modification of coating is formed by the composition and the feed gas of change feed gas is finished.Because the data of embodiment 1-4 are with ESCA(chemical analysis neutron spectrum method) acquisition, these data do not comprise by FTIR(Fourier transform spectroscopic methodology) record the protium in the coating.Embodiment 5 and 6 data obtain with micro-combustion analytic approachs (microcombustion anlysis).

The comparative example A

The SSR dish of carbon-bearing coating not is exposed in the environment of various rh values, measures friction factor simultaneously.This is the influence of test relative humidity to the friction factor of dish.The SSR dish is according to U.S.patent No.4, and 623,570 prepare.The magnetic medium that is used for preparing the SSR dish is made up of a magnetosphere that is coated on the 37.5gm PET.Magnetosphere contains the γ-ferriferous oxide of mixing cobalt and the al oxide granule in the polymerization bonding material.The polymerization bonding material comprises polyurethane (Estane 5703) vinyl (VAGH) (product of Union Carbide) and isocyanates.

Fig. 2 shows the relation that the SSR that handles without carbon coils friction factor and relative humidity (%).In whole test specification, humidity is from being lower than 10% to 90%, and friction factor anxious brush when high humility increases.

Friction testing is placed a glass bead (9.5mm diameter) by 10 gram forces of loading with the nominal normal direction and is shown with the SSR dish cart and contact.This dish acts on normal direction and tangential power on the glass bead with the force transducer measurement simultaneously with very low speed (0.1 to 0.3rpm) rotation.The force transducer signal is digitized and uses computer recording.Friction factor (tangential force is divided by normal force) also stores with COMPUTER CALCULATION.Test is to carry out in the closed chamber that a dried nitrogen and moisture nitrogen flow through.Wet nitrogen obtains nitrogen through heating.Be added in the test cabinet relative quantity of wet nitrogen and dried nitrogen, may command relative humidity (RH) by control.

Relative humidity is monitored with industrial hygrometer.To be illustrated in result among Fig. 2 and to be from relative humidity be 10%, and the dish revolution is 2 beginnings.Relative humidity increases by 10% until 90%RH at 2 revolutions of every increase.The bright The friction coefficient relative humidity of the SSR dish cart of the carbon-free processing among Fig. 2 carry to and increase greatly.

Embodiment 7

Magnetic medium of the present invention is to be coated on comparative example A's the SSR dish by jet plasma to prepare.SSR dish is placed on the water-cooled copper plate bias voltage 60 and is exposed in the jet plasma in 22 seconds.Feed gas is the n-propyl chloride of 63sccm and the potpourri of 150sccm argon gas.Pulsed D c-power supply (60Hz) is located at 450mA, makes that pact-500V voltage is added on the negative electrode 40.The bias voltage of bias electrode 60 is pact-1150V, radio frequency (RF) 100KHz.Vacuum chamber pressure is maintained at about 10 millitorrs.The enriched carbon layer that 20nm is thick is deposited on this dish.Jet plasma carbon is handled magnetic medium and is shown in whole relative temperature scope with the stable friction factor that is described in equipment among the comparative example A and method test constant as shown in Figure 3.

Embodiment 8

The life-span that jet plasma carbon applies and uncoated SSR coils tests with two kinds of methods.The SSR dish is used U.S.Patent No.4, and 623,570 method is used magnetic to be coated with the PET roller and prepared.In first method of testing, with 10 gram load forces one glass bead (9.5mm diameter) is pressed the row panel surface, sample rotates with 600rpm speed.This ball is incorporated into the panel surface of dish radius from 2.8 to 3.6cm from the rotation center of dish.Monitoring friction factor and friction factor increase surpass its initial value 20% and are regarded as losing efficacy, and test stops with time one failure logging (record).In order to make the SSR dish more balanced, before test, under 60%RH, they are stored several days.Test is carried out under environment temperature under 5%RH.

Under these conditions, no carbon coating dish continues about 1 minute.Second group of SSR dish undercoat and fluorocarbons lubricant application that is coated with solvent.Fluorocarbons lubricant (trade mark is called F08) is poly-perfluor ether diacrylate.For these dishes, use ether-ether undercoat in the six polyacrylic acid second.Undercoat and lubricant apply with rotation with the solvent solution form respectively.Second group of dish continues about 10 minutes before inefficacy.

The 3rd group only is coated with fluorocarbons (F08) dish sample and also continues about 10 minutes before inefficacy.

The 4th group of sample scribbles thick jet plasma enriched carbon layer of 20nm and fluorocarbons lubricant F08, continues not lose efficacy above 8 hours.Jet plasma coating condition is: feeding gas: 40sccmC ₂H ₂With the 150sccm argon gas; Pulse (60Hz) DC power supply; 475mA ,-500V, bias voltage :-1275V; Pressure: 10 millitorrs; Rolling wheel speed 24cm/m.Carbon rich coating surface resistance about 6 * 10 ¹⁰Europe/side.

In second method, several SSR dishes with aforesaid jet plasma deposition carbon rich coating have been put into a SSR magnetic head (referring to for example U.S.patert No.4,809,1047 Mini scribe type 8438 hard disk machines are to replace initial hard disk recording magnetic head.Disk drive is put in the chamber of environment control and hotwire.Environmental baseline every day is in following set of environmental conditions circulation primary.

Condition # 123456

Temperature (℃) 21 49 4 21 49 4

RH(%) 30 20 30 80 80 80

Lost efficacy with one of two kinds of methods monitoring SSR durability.In method 1, every day used range estimation once by disk.Under the SSR magnetic head, there is the disk of damage zone to be regarded as losing efficacy.Uncoated disk sample in 1 day, lost efficacy (complete cycle of environmental baseline).The sample that scribbles aforesaid HHA undercoat and fluorocarbons lubricant F08 shows the different life-spans, and 5 disk samples have a sample to lose efficacy within one day.6 samples with the thick enriched carbon layer protective seam of jet plasma deposition 20nm were not seen inefficacy in lasting 13 days.In method 2, the single track of SSR disk with the constant frequency square wave of a record current through SSR magnetic head magnetic recording.Disk drive and disk are placed into environmental control room then and start magnetic disk drive motor.The electronic monitoring tracer signal if be lower than common signal value 20% above 8 microsecond signals, then closed the disk drive motor and is also write down the out-of-service time on computers then.In this way, have the SSR disk that sprays carbon rich coating and fluorcarbon lubricant external coating and do not see inefficacy in lasting 80 days.

Embodiment 19

Under the various conditions of listing in the table II, apply the magnetic medium band with the jet plasma coating.Hollow cathode internal diameter 1.2cm is at 20cm place, magnetic medium dead ahead; 50 seconds exposure durations; Bias voltage is-1275V; Pulsed frequency 60Hz; Take-up speed 24cm/m records sample 180 degree and peels off, and the results are given in Fig. 4.

The jet plasma coating is considered to the condition precedent of durable hard coat to the strong adhesion of magnetic medium.The back side of magnetic medium sample adheres on the hard aluminium strip with epoxy resin.The poly-inferior acyl that 25Am is thick (by the Kaptron polyimide of Dupont preparation) band is used for pressure adhesive and adheres to magnetic medium jet plasma coated side.For improving cementability, test sample was handled 24 hours down and cool to room temperature at 600 ℃.Use the Instron instrument, several times of speed under Model1122 peels off with 180 degree are removed the polyimide band from coating.Separating required power is illustrated among Fig. 4.Line 105 and 113 is control sample test results of no jet plasma coating.Line 101,103 and 105 is to store about 24 hours sample testing result under environment temperature, and line 111,113 and 115 is the sample testing results under storage under 600 ℃ and 100% relative humidity 24 hours.All inefficacies occur between bonding agent/carbon rich coating interface rather than between carbon rich coating/magnetic medium interface.It is stronger to peel off intensity level shown in the adhesion of coating even the ratio like this.

Embodiment 10

Coating of the present invention is on silicon and measure the Molls hardness of coating.Under the high bias voltage of pact-1000V, the Molls hardness of coating of the present invention is about 6-8; (approximately-500V), Molls hardness is 5-6, and during no-bias, Molls hardness is lower than 5 in low pressure.

Embodiment 11

Uncoated magnetic medium sample (as described in the comparative example A) to no conductive substrate is tested, and the table of discovery surface resistivity is between 1011 to 1012ohms/square.The magnetic medium that has the jet plasma coating that the present invention prepares under the condition in embodiment 9 (table II, line 103 and 111) has the surface resistivity that is near or below 109ohms/square.Coating of the present invention like this has good antistatic performance, and does not damage other desirable performance such as hardness, clinging power and to water vapour, the imperviousness of oxygen and other gas.

Claims (21)

1, a kind of on substrate the method for plasma-deposited carbon rich coating, it comprises the following steps:

A. substrate is placed vacuum chamber;

B. borrow the following step in this vacuum chamber, to produce rich carbon plasma;

(i) in hollow cathode, inject the plasma that is suitable for providing carbon rich coating;

(ii) provide enough voltage to produce and to keep rich carbon plasma at this hollow cathode;

(iii) keep enough vacuum for described plasma in this vacuum;

C. described substrate is exposed in the described plasma, simultaneously with described substrate near rf bias equipment, described whereby plasma quickens and is deposited on this substrate as carbon rich coating towards described substrate.

2, the process of claim 1 wherein that substrate is a magnetic recording medium.

3, the process of claim 1 wherein that described plasma gas comprises is selected from following gas: saturated and unsaturated hydrocarbon, and nitrogenous hydrocarbon, oxygen-containing hydrocarbon contains halocarbon and siliceous hydrocarbon.

4, the process of claim 1 wherein the frequency of rf bias equipment be 25KHz to 400KHz, bias voltage is 100 volts to 1500 volts.

5, the process of claim 1 wherein that in described vacuum chamber the voltage that produces and keep finished by the pulsed D c-power supply.

6, the process of claim 1 wherein that hollow cathode comprises is selected from following fire resistive material: graphite, molybdenum, tungsten and tantalum.

7, the process of claim 1 wherein that when plasma-deposited substrate contacts with rf bias equipment and described rf bias equipment is current-carrying plate.

8, the process of claim 1 wherein that the vacuum in the vacuum chamber maintains about 1 to 300 millitorr.

9, the process of claim 1 wherein that plasma gas is injected in the hollow cathode with about 10 to 500sccm combined feed gas flow rate.

10, the method for claim 2, wherein said magnetic medium comprise flexible non magnetic substrate and contain the polymerization adhesives of magnetisable pigment that wherein said enriched carbon layer is coated on the polymerization adhesives that contains magnetisable pigment.

11, the method for claim 2, wherein magnetic medium comprises flexible non magnetic substrate and the thin magnetic film that is deposited on this substrate.

12, the process of claim 1 wherein that substrate comprises flexible polymeric film.

13, the method for claim 1 also comprises the additional hollow cathode of one or more one or more additional plasmas of generation.

14, the method for claim 13 wherein is deposited upon on the described substrate more than one type be coated with.

15, press the product of the method preparation of any claim of claim 1 to 14.

16, a kind of magnetic recording medium, it comprises substrate and is coated on this substrate and is included in the magnetosphere of the magnetizable particles in a kind of adhesives, it is characterized in that:

(ⅰ) enriched carbon layer that does not contain adhesives on described magnetized layer; With

(ⅱ) described substrate is that polymkeric substance and flexible rigidity D are less than about 36 Newton meters.

The carbon of 50 to 95 atomic percentages that 17, the magnetic recording medium of claim 16, wherein said enriched carbon layer comprise.

The carbon of 0.0 to 20 atomic percentage that 18, the magnetic recording medium of claim 16, wherein said enriched carbon layer comprise.

19, the magnetic recording medium of claim 18, wherein said enriched carbon layer also comprise the oxygen of 0.1 to 20 atomic percentage and the hydrogen of 0.1 to 40 atomic percentage.

20, the magnetic recording medium of claim 17, wherein said enriched carbon layer surface conductivity is about 10 ⁸To 10 ¹²Ohm/side.

21, the magnetic recording medium of claim 17 wherein also comprises the fluorocarbon lubricant on enriched carbon layer.

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