JPH01500703A - Improved method for producing granular recording media and media obtained thereby - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Improved method for producing granular recording media and the resulting medium Background of the invention field of invention The present invention provides a magnetic recording medium using a granular magnetic recording material, ¥! once magnetism increased to f media containing sexual particles.

The present invention and prior art will be described with reference to the drawings.

Figures 1.2.3 and 4 are useful in understanding both the prior art and the present invention. It represents a conceptual concept.

Figures 5 and 6 illustrate a method of electrodeposition of magnetic coatings according to the prior art.

FIG. 7 is a graph useful for understanding the principle of the present invention.

Figures 8a and 8b illustrate particle alignments useful in understanding the present invention.

FIG. 9 is a block diagram of an electrodeposition apparatus according to one embodiment of the present invention.

FIG. 10 is a perspective view of the butter engraved on the anode according to the second embodiment of the present invention. Ru.

FIG. 11 is an enlarged view of FIG. 1O.

FIG. 12 shows a part of an electrodeposition apparatus according to a second embodiment of the present invention.

Digital magnetic recording continues to increase the density of data recorded on magnetic media. It's hot. This requirement requires recording more tracks per senna and recording shorter signal wavelengths, resulting in higher area data. Recording density can be obtained. Furthermore, in modern digital recording, the medium is recorded first. It is necessary to provide the ability to override the data that has been created. i.e. old data New data recorded on the device does not effectively erase previously recorded data. Must be. Override is a complicated phenomenon, & the thinner the air medium, Previously recorded longer wavelengths are more effectively overlaid by newly recorded shorter wavelengths. It is known in the prior art to be ridden. The data recording signal is Individual digital encoding methods typically encode frequency components over several octaves. include.

Therefore, the override (i.e., cancellation) ability is must span the entire range. Improper cancellation of the long absorption length signal will cause the medium to residual long-wavelength magnetism is generated.

This interacts with the newly recorded signal to cause unintended pulse congestion and cause a shift. A solution to this problem is to measure the media thickness using short wavelength signals. For the purpose of limiting the recording medium to the extent that The goal was to reduce the physical thickness of the body. But this solution comes at a cost. It will be done. The amplitude of the signal read from the medium during playback is proportional to the magnetization of the medium, which is proportional to the total volume of material produced. Magnetization by limiting the thickness of the magnetic coating The available material volume is reduced and the signal amplitude is reduced.

A wide variety of methods have been used in the prior art to solve the problem of the volume of magnetizable material. It was. The most common processing method for producing media is suspension with binders and solvents. By coating the granular magnetic material on the support material. Solvent is ejected during drying process The medium is then compressed or calendered to reduce the density of the magnetic layer. It will be done. The final density achieved is highly dependent on two factors. The first is that the coating process involves particles. - Dynamic control of the flow as it involves flowing the mixture of the mixture and the solvent onto the support. The rheological parameters establish the minimum amount of solvent required for stable flow.

When the solvent is driven out during drying, pores remain. The more solvent you use, the more the pores will be The result will be larger. Calendaring reduces the action of stomata; Brushing does not necessarily compress the material enough to completely eliminate the effects of pores. Second However, even if compression is 100% effective in eliminating pores, the number of particles in one particle A limit is placed on the density at which geometric shapes can be obtained. For example, consider the dispersion of isomorphic spherical particles. Then, the maximum backing horn (packing fraction) C The total volume of m bodies divided by the volume of the cube containing them, decimal or % ] has a theoretical maximum value of 0.72. A medium consisting of isomorphic spherical particles is larger. There is no calendering that can compress it to a large density.

Figure 1 shows a spherical particle with a hexagonal close-packed structure and the backing limit value of 7 A typical unavoidable gap 10° 12.14 resulting in 0.72 is shown. generally magnetic recording Particles are not spherical but acicular It is. particles of this type) are generally longitudinally and horizontally oriented (i.e. the length of the particle's principal axis versus the length of the particle's principal axis). Length ratio] 2 to 7 motsu. For clarity, the ideal cross section, i.e. the particle Consider an acicular particle with a uniform rectangular or circular cross section over its entire length. is advantageous. Acicular particles have a rectangular cross section and are aligned as shown in Figure 2. If we consider an ideal example, the resulting tissue would be backing horn 1.0. have.

When particles with cylindrical cross sections are arranged randomly in the coating, pores 13.1 5 [Figure 3] is inevitable, and as a result, the °C backing fraction descend. On the other hand, if this kind of particles are perfectly aligned as shown in Figure 4, They will contain typical slits 16.18.20 created by circular cross-sections . The actual particles have almost the shape described above, but the magnetic particles are actually cigar-shaped; It has an irregular cross section. In fact, the tapes and discs covered by the prior art During processing, a fairly low backing fraction of around 0.4 was obtained. . Reason 7: Presence of pores The fact that one particle is actually deer-shaped, and The problem is that the particles cannot be perfectly aligned.

In addition to the above-mentioned web coating method, it is also a prior art to create a magnetic coating by electrodeposition. For the technique? It is known as This method is widely used in the field of electrocoating. It is an application of the Japanese method of "electrophoresis" phenomenon.Electrocoating is a coating on the inside of a gold maple can. It is applied to a wide variety of painting conditions, from painting to car bodies. [R.L. ・Eetes, @Electric Painting”, Tesington, Niropart Traber, UK, 196 6 years]. Publication No. 52-25321 (@electrodeposition paint for magnetic recording'') , a water-soluble acrylic polycarbonate homogeneously emulsified in water is mixed with magnetic particles in fat. Admixtures have been described for use in the electrodeposition of magnetic coatings.

The method described in the above publication is shown in FIG. Container 42 contains solvent, binder and magnetic It contains a mixture 43 of sexual particles. Cathode 44 and anode 46 in mixture 4 3, and a DC power source 48 is connected between the cathode 44 and the anode 46. each grain 1 due to the interface between the particles and the binder-solvent solution. There is a tendency to obtain L load.

A diffusion layer of charge then surrounds the charged particle, so the combination of charged particle and diffusion layer is Becomes electrically neutral. The particles are placed under an electric force due to the electric field between the cathode and the anode. , and the diffusion layer tends to move with the particles to which it is attached, but at the same time The diffusion layer is electrically attached to the other electrode. As the particles move, new charges are added The particles accumulate in the front picture in the direction of movement, and the diffusion layer dissipates in the opposite direction. [J.M. ・Boxliss and N.K.N. Reddy, “Modern Chemistry”, New York: Plenum Press, 1974, 2 volumes, 833 pages]. ah quoted earlier The publication indicates that the magnitude of the electric field is approximately 17 V/volt. This is magnetic sufficient to move the magnetic particles towards the electrode where they are deposited as a magnetic coating 41. It is an electric field [Figure 6].

Summary of the invention In the method of electrodepositing acicular particles to form a magnetic film, the particles are deposited on a support. Rather than using an electric field strength of sufficient magnitude to cause a single particle to It is taught by the present invention to employ an electric field strength that is also sufficient to align. It will be done.

When the electric field strength is increased, the density of the X-attached medium increases rapidly and significantly. It has been found that a point is reached when it is markedly characterized. The strength of this world is upon us. The resulting medium (precipitated at this electric field strength) ) is a main packing fraction of 0.5 or higher, generally 0.9 It has a lot of things. To explain this point in more detail, this critical electrolysis In the event, the electric field not only drives the particles towards the 1aLh where they are deposited. It is further assumed that the particles are rotated with their major axes pointing in the direction of the electric field. Ru. This rotation occurs because the electric field exerts a torque on the charged particle relative to the angle between the principal axis and the direction of the electric field. Happens to give. This electric field is similar to that associated with a parallel plate capacitor. is essentially uniform between electrodes. The direction of the electric field lines is always perpendicular to the sea turtle electrode plane. Therefore, the particles are oriented at one pole (which is also the support of the medium) with their major axes perpendicular to the electrodes. , are deposited in parallel alignment with each other. The graph in Figure 7 is the needle found here. Dependence of the backing fraction for sized particles as a function of the electric field strength show. to perfectly align one particle against the force couple given by the medium There is a wide range of field strengths for relatively low values where the electric field is insufficient (and these low electric fields It is observed that in the field strength region, the particles reach the cathode with a somewhat random orientation. There will be. As previously assumed, when the particles are perfectly aligned by the electric field, the coating An increase in temperature occurs.

If the particles are only partially aligned, they are still randomly deposited on the cathode. [Figure 8a]. According to the present invention, one particle as shown in the graph of FIG. perfect alignment [Figure 8b].

and the associated increase in bucking fraction when the electric field is approximately 325 V/c It first occurs suddenly at °C when the critical strength of rn(76) is reached.

If the main axis is connected at M, the above-mentioned IC high-density magnetism 1- is obtained. . By controlling the deposition time, a thin but dense layer, which is desirable for magnetic recording, can be obtained. ・A layer with ・barride characteristics can be obtained. Electrical power obtained according to the teachings of the present invention In deposited coatings, the major axes are aligned perpendicular to the support. ℃ known in the art As shown in the figure, the preferred direction of magnetization for anisotropic magnetic particles is generally determined by the particle's active motion. I'm taking a bath. This type of electrodeposition layer using anisotropic particles allows the recording magnetic field to perpendicular to the surface of the medium. It will be appreciated that it is suitable for perpendicular recording. Perpendicular recording is shortwave They are currently of great interest because they are particularly suitable for recording signals.

The numerical values of the present invention can be applied to the production of magnetic films suitable not only for perpendicular recording but also for longitudinal recording. Ru. Even if the main axis of the acicular particle is perpendicular to the longitudinal recording magnetic field lines, the result is that longitudinal recording is not possible. It will be done. To provide this type of coating, cobalt-doped acicular particles Reims Patent No. 2429,841 and French Patent No. 2.199.155 as described in the specification] on a support according to the teachings of the present invention. this species The doped acicular particles not only act on their main axes but also move on their moving axes and become magnetized at °C. It has characteristics that support vertical recording, and therefore it would support vertical recording as well. .

A second form of the invention provides an integrated, unalterable magnetic pattern. this kind of The pattern is always used, for example, to position the magnetic head of a disk drive using this media. One burst of servo information for positioning is stored during "stitching" C. This kind of pata The anode is etched or machined into the surface of the anode used for electrodeposition. suppressed surface packing density (areal paCkin) that replicates the pattern g aensity, ) can also be obtained from the body (r)er output Vc. engraved The pattern has the shape of a servo burst for this period. The resulting electrodeposition medium By magnetizing.

A signal is reproduced from the patterned medium, the amplitude of which is proportional to the variation in packing density; This provides servo information for system control.

To obtain a patterned electrodeposited layer of media, the electrodes are placed in the following conditions. i.e. The distance between anode and cathode is caused by the pattern details engraved on the node surface. It has a value of 2m[. The distance bl is the pattern groove carved from the cathode to the anode. The distance d2 is the distance from the cathode to the land.

E=V/d (in the formula, %E is the strength of the electric field, and ■ is the electric field between the anode and cathode. pressure, and d is the distance between the anode and cathode. Essentially two corresponding electric fields 17) [E1 = V/di and E2 = V/(12 got rel. For these electric field strengths, El is equal to the critical electric field strength, and E2 is the critical electric field strength. It is calculated to be smaller than the strength. Electrodeposition characteristics shown in the plot of Figure 7 Accordingly, a larger charge of particles exists at a position on the cathode where the °C electric field has a value El. Particles are precipitated with a packing density, and particles are precipitated with a lower packing density at positions where the electric field is E2. Ru. In this way, the packing density of the deposited medium describes a pattern inscribed on the anode.

The rest of the anode surface is at a distance di from the cathode, so these The medium in the region is deposited with a higher packing density and is suitable for recording data.

When the resulting medium is then applied with a direct current magnetic field, due to the difference in packing density, essentially two A magnetized region with a certain magnetic field strength is created. These differences in magnetic field strength are similar to standard magnetic fields. It can be read by recording technology. The electrodeposited pattern is integrated with the recording medium However, non-patterned areas on the surface of the electrodeposited media cannot be erased or changed. Recording and reproduction by any magnetic recording and reproduction method known in the art or can be erased.

description of the invention The basic implementation of the invention may be further understood by referring to FIG. cormorant. The electric motor 50 is a sand mill''52 of a type well known in the art, such as an eye. Drives a 1-mini motor mill manufactured by Kerr Machinery Co. (Chicago, Illinois) Ru. Small glass beads are used in a continuously operating sand mill 52 to remove solvents and binders. , the mixture 'a53 of magnetic particles and gunpowder is finely dispersed. These are analogies The following weight percentages are used:

Cyclohexane (solvent) 80.5% Magnetic particles 16,1 Polyurethane (binder) 2.3 Surfactant 1.1 The surfactant has the trade name 1 Gafac R, E, 610”. A complex phosphene of the type manufactured by the Gough Company of ester-free acid. This surfactant is an anionic surfactant and magnetic Not only does it increase the number of charges present on a particle, but it also controls the sign of the charge. . In this form the particles are positively charged. Cationic surfactants have a charge sign change the number, so that it is deposited on the 7 node instead of on the transparent cathode. Probably. The polyurethane binder has the trade name “Nippolan” Available from Nippon Urethane Co., Ltd. (Japan Urethane Co., Ltd.).

The mixture is pumped from the sand mill 52 by a pump 54 into a container 56 where it is electrodeposited. will be held. Inside the vessel 56 there is a disk anode 58 and an equal area disk cathode. The board 60 (the latter is used as a support for the magnetic coating) is a non-conductive standoff. 62 and a non-conductive spacer 64 separates the anode 58 and cathode 60. I'm away. Spacer 64 provides a spacing of 1.33 (7) Located in the central area. This area is not addressed during recording, so a magnetic coating is required. This is an area where it is not possible.

The flow of the mixture is continuous and the mixture 53 is passed through the sand mill by return pipe w&66. 52. A DC power supply 68 of about 432V connects the anode 58 and cathode 60. Electrodeposition is performed at an electric field strength of about 325 V/cm. in the mixture The current of is mainly due to the ionic double layer hII, and the mixture t'j, 10-10 Ohm - High resistance of bacteria. Therefore the current is limited by the resistance of the mixture Ru. The mixture has substantially more resistance than the deposited coating.

Deposition continues with a constant current as the coating is deposited on the cathode.

The deposition time is approximately 5 seconds, resulting in a coating approximately 10 microns thick. coated The cathode is then rinsed and opened to dry to drive out the adhering solvent, resulting in The surface is a magnetic medium in the shape of a disk.

Other examples for carrying out the invention 1. Solvent: Tetrahydrofuran (THE), an easily available organic solvent.

Binder: Desolite 2764-70-130 Acrylic available from DeSoto Inc., DeBrains, IL.

Surfactant: EmCOl CC55, quaternary ammonium acetate , available from Uicco's Chemical Company (New York, NY).

2. Solvent: Acetone, an easily available organic solvent.

Binder 22Vporan, polyurethane, available from Nippon Urethane Co., Ltd. (Japan).

Surfactant: Emcol ccss, quaternary ammonium acetate, Uicco Chemi Available from Cal Corporation (New York, NY).

3. Solvent: Methyl in butyl ketone (MIBK), an easily available organic solvent.

Binder: Desolite 2764-70-130 acrylate, manufactured by De Soto (Iri) Available from Des Plaines, Neu.

Surfactant: Gafac R, E, 610, phos7ate ester-free acid, Gafac It is available from the company, New York, New Jersey.

4. @ Agent: Methyl ethyl ketone (MEK), an easily available organic solvent.

Binder 221 borane, polyurethane, available from Nippon Urethane Co., Ltd. (Japan).

Surfactant: Gafac R,E, 610, phosphate ester-free acid, Gafac Available from the company (Zene, Ney.).

The proportions of each of the above mixtures can be chosen within a wide range of individual combinations; There is a critical voltage associated with this.

In a second embodiment of the invention, the patterning medium is first manufactured using an anode shown in FIG. 1O. This can be understood by considering the structure of the code. The pattern to be replicated is Consists of servo bursts.

To dingru. Typical pattern 32% 34 corresponding to servo burst is the anode 5 It is shown inscribed at 8'. (In each figure.

Different but related elements are designated using the same reference symbol.

However, corresponding elements in the various figures are distinguished by dashes. ] 11th r142'! The properties of the carved burst patterns 32 and 34 are shown in more detail. Before As described above, magnetized servo bursts on the media provide regenerative starvation signals and Bobursts are not recorded and define regions of annularly varying packing density in the electrodeposited media. It is obtained by Referring to FIG. 11, the grooves cut into the anode 58' 92.94°96.90.98.100 and land 93°95.97.99, 101 and 103 provide a mechanism for achieving density changes as previously described. Groove 92.9 4.96.90.98°Zoo is relative to the main surface of the anode 58' (with a depression) It is recognized that the groove pitch is chosen to correspond to the frequency of the servo burst. There will be. For example, the groove 92°94.96 regarding the servo burst pattern 34 ．． 90)! Twice the groove 98.100 regarding the partner's servo burst pattern 32 It has a pitch of Images of these grooves and associated lands reflect the degree of media filling. servo signal frequency 2 read by the disk head when the disk rotates. will give f and f. Here 1/f’t @ grooves 98 and 100 This is the time interval between the occurrences of the corresponding signals.

Referring to FIG. 12, a portion of the anode 58' and cathode 60' 9 shows a state in which the apparatus of FIG. 9 is arranged for depositing a magnetic medium. medium electricity Particles and solvent for adhesion.

The composition of the binder and surfactant mixture 66'' has been previously described. The major surface 78 of the electrode 58'' is essentially parallel to the cathode 60''. cathode 60' to the major surface 78 of the anode 58' and coplanar with the major surface 78 of the anode. Butter 7 land 93', 95', 97', 99', 101', 1 03', the electric field generated on the surface of the cathode 60' is a critical electric field. It is equal to the world. Groove 92' from cathode 60# to anode 58' , 94', 96', 90', 98', 100' The electric field generated on the surface of the sword 60" is smaller than the critical electric field. . When the distance from the main surface of the anode to the cathode is 1.33 cm, the cathode Approximately 432■ applied voltage 1 between the electrode and the anode! Critical electric field of 325 V/cm give. The anode pattern has a small temperature (both deep and 3-way grooves are used) grooves of lower packing density [111] than the critical electric field sufficient to deposit the I image. A small electric field is obtained. Under these conditions, the pattern engraved on the anode cannot be reversed. Finally, a 10 micron thick coating is deposited on the cathode within about 5 seconds.

After removal from the electrodeposition mixture, the medium is syringed and dried.

A direct current induced from a constant current solenoid or stationary magnet then causes the medium to magnetically saturated. This allows patterns with different packing densities to have different magnetizations. pattern, which can be read by ordinary magnetic reproducing means.

FIG. 2 FIG, 5 (Shintake Sentake) FIG, 6 (1 ship) Electric field V/cm FIG.7 FIG, 8a FIG, 8b FIG.9 FIG. 10 FIG, I2 international search report international search report

Claims (1)

[Claims] 1. Magnetic media by electrodeposition of acicular magnetic particles on a support with a conductive surface It is a method of manufacturing the body, a. The particles are dispersed in a liquid, and the particles acquire an electric charge at the interface between the liquid and the particles. preparing a dispersion (53); b. The electrodes (58, 60) are immersed in the dispersion, during which At least one of these electrodes (60) is for electrodepositing the particles thereon. is a support for, and c. By applying a DC voltage (68) to the electrodes (58, 60), the support A direct current electric field is generated at the surface, and the electric field has a critical electric field strength that aligns the particles in the direction of the electric field. (76), and the electric field is located between the electrodes (58, 60) and the The aligned particles are precipitated in cooperation with the dispersion liquid (53), and at least one of the supports is A method comprising forming a magnetic recording medium on an electrode (60). 2. An improved apparatus for electrodepositing magnetic particles on a support to form a magnetic recording medium. The device comprises electrodes (58, 53) immersed in a liquid (53) containing magnetic particles. 60) A DC electric field is formed between the electrodes, which causes the particles to (60) to form a magnetic recording medium by electrodeposition on a. Critical electric field strength (76), which makes the magnetic particles perpendicular to the surface of the magnetic recording medium. Directly aligned DC electric field, and b. Consisting of acicular magnetic particles in a mixture of solvent, binder and surfactant, substantially The liquid constituting the dispersion (53) has a resistivity of 106-109 ohm-cm. and magnetic particles, wherein the electrical resistance of the dispersion is the same as the electrical resistance of the deposited medium during electrodeposition. substantially greater than the electrical resistance, whereby electrodeposition occurs essentially at constant current A device consisting of 3. a. a support (60) having at least one electrically conductive interface; b. at least one layer of gaseous magnetic particles deposited on the surface, the volume filling of the layer being The packing density is area-controlled in a predetermined manner. A magnetic recording medium consisting of 4. 4. The medium of claim 3, wherein the volumetric packing density is essentially constant. 5. the volumetric packing density has a first value or a second value; the first value is 0.5 or more; 4. The medium according to claim 3, wherein the binary value is 0.5 or less. 6. A method of manufacturing a magnetic medium using a granular magnetic material using an electrodeposition apparatus, The field strength (76) is adopted, and the packing density of the magnetic medium is determined in advance. differ according to the pattern (32, 34), a. The patterns (32, 34) are inserted into the grooves (58'') of the electrodeposition device. 90', 92', 94', 96', 98', 100') and lands (93', 95', 97', 99', 101'); b. Second electrode (60'') in the electrodeposition apparatus, facing the first electrode (58''), and placing the first electrode (58'' ), the grooves (90', 9) of the first electrode (58'') 2', 94', 96', 88', 100') and the electric field between the second electrode (60'') has a first magnitude smaller than the critical electric field strength (76) of the electrodeposition device, and The land (93', 95', 97', 99', 101') of the electrode (58'') The electric field between the two electrodes (60'') is essentially equal to the critical electric field strength (76) of the electrodeposition device. has a new second magnitude, and c. the electric field having first and second magnitudes; The medium is electrodeposited on the second electrode (60'') under the control of a method characterized in that images are imaged as corresponding differences in the packing densities of the media; .