JPS607625A - Application of magnetic medium for disc - 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] The present invention relates to a method of applying magnetic media to a disk.

In the past, magnetic media has typically been applied while the dinuks are rotating at low speeds.

The rotational speed of the disk is then increased during the high speed rotation process to drive excess media from the disk by centrifugal force. See, eg, U.S. Pat. Nos. 4,353,937, 4,133,911 and 3,19 B,657. The disk is then subjected to multiple magnetic orientation and drying steps before being baked and polished. Polishing was performed to improve the surface finish of the disk and to reduce the thickness of the magnetic media attached to the disk.

Because the magnetic medium was applied to the disk at a very low speed, the viscosity of the magnetic medium changes very quickly before the high speed rotation process, resulting in a decrease in the thickness of the film of magnetic medium that ultimately adheres to the disk. It has become relatively thick.

However, in this method, the airborne granules are deposited on the disk, and then the high speed rotation is performed as the magnetic medium tries to flow into the granule wheel as the magnetic medium is radially expelled from the disk. There was a high risk of creating radial runs during the process. In addition, during polishing work,
Scratches occurred in the circumferential direction when the particles adhered to the abrasive tape. Additionally, coating flaws known as "wraparound" have occurred when magnetic media flows from one side of the disk around the edges to the other side of the disk.

The present invention overcomes the problems of the prior art by forming a thin magnetic coating film with a high-grade surface finish that eliminates the post-coating polishing operations currently performed. .

According to a preferred method according to the invention, the disk is rotated at high speed during the coating application process as the magnetic media dispensing nozzle moves from the outer diameter of the disk to its inner diameter and then back again to the outer diameter of the disk. Due to the large centrifugal forces created by the high speed rotation and the high discharge pressure of the nozzle, only a very thin film of media ultimately adheres to the disk. Excess media flows along the thin film as it is ejected from the disk, forming a protective layer on the film to prevent rapid changes in viscosity. The high speed rotation step is eliminated, and immediately after the high speed coating step, the speed of the disk is reduced and exposed to an orienting magnetic field during the orienting step. Because the viscosity change of the magnetic medium is kept to a minimum, the magnetic particles in the magnetic medium are more likely to align properly in the direction of the orienting magnetic field than in conventional methods; Improved recording performance. Moreover, the polishing step can be eliminated because the thickness of the media film is much thinner than before and the surface quality of the film is of higher quality. In addition, there is much less exposure of the media to airborne particulates and other contaminants than with traditional methods, and therefore less contamination of the magnetic media. Become.

As a result, whereas in the past, high rotation speed and high rotation time as well as the viscosity of the magnetic medium primarily determined the coating thickness, in the present invention the high speed rotation step is omitted and the magnetic medium is applied during The speed of the disk, the speed of nozzle travel, and the nozzle discharge pressure can be used to determine the thickness and nature of the coating in order to minimize viscosity changes according to the present invention. Thus, the new method of the present invention provides a complete shift in coating parameters compared to conventional methods.

Accordingly, one object of the present invention is to provide an improved method for applying magnetic media to a disk.

Another object of the present invention is to provide a method by which very thin films of 10-20 microinf (D) magnetic media can be applied to disks without post-coating polishing operations.

Yet another object of the present invention is to provide a method of applying media to a disk that provides a high quality surface finish that does not require post-coating polishing.

Another object of the present invention is to provide a method of applying media to a disk while the disk is being rotated at high speed.

Yet another object of the present invention is to provide a method for applying media to a disk such that the disk is immediately exposed to an orienting magnetic field after application of the medium to the disk.

Yet another object of the present invention is to provide a method of applying a magnetic medium to a disk that can minimize changes in the viscosity of the magnetic medium before the magnetic orientation step.

Another object of the present invention is to provide a method of applying magnetic media to a disk that can substantially eliminate coating flaws such as flow, abrasive scratches and wraparound.

Yet another object of the present invention is to provide a method of applying magnetic media to a disk that requires only dry puff polishing, rather than polishing with methods that require polishing oils and solvents.

These and other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings.

FIG. 1 shows a simplified disk coating apparatus 1 in which the method of the invention can be carried out. The details of the disc coating device 1 are not shown, since only the basic structure itself of the disc coating device 1 is important for the invention. The disk coating device 1 is equipped with a rotating spindle 5. The rotational speed of the rotating spindle 5 is variable, for example, up to at least 3,800 r,p,m.

The rotating spindle 5 is rotated many times by a power source (not shown). The disk 10 to which the magnetic medium is applied has a central opening 12 . Opening 12 is rotatably secured to system spindle 5 by any suitable mechanism. Disc 10 has an inner diameter 14 and an outer diameter 15. Inner diameter 14 and outer diameter 15 define a concentric region 16 of disk 10 to which magnetic media is applied. A magnetic media dispensing nozzle 20 is supported by arm 25 . Arm 25 is also pivoted by a motor 30 which is controlled by a controller (not shown). Arm 25 includes a fluid conduit (not shown) that connects nozzle 20 to a source of pressurized fluid-magnetic medium (not shown). In a preferred embodiment, the discharge opening at the top of nozzle 20 is approximately 0.02 inches. Arm 25
can be pivoted by the motor 30 in the direction of the arrow 27, 28, so that the nozzle 20 can be moved from the outer diameter 15 to the inner diameter 14 and back again from the inner diameter 14 to the outer diameter 15. It has become.

The control device for the motor 30 is the nozzle 2 that traverses the disk 10.
Determine the moving speed of 0. A mechanism for changing the discharge pressure of the nozzle 20 may be provided.

Although the basic structure of the disk coating apparatus 10 has been disclosed above, the method according to the prior art is
The following will discuss FIG. 2, which is a graph illustrating the relationship between time and time.

According to the conventional method of FIG.
During this period, the disk 10 is first rotated at approximately 2300 rpm for 10 seconds, during which time the disk 10 is coated with cotton shavings impregnated with a cleaning solution to remove any airborne fine material or particulates from its surface. Wipe it gently with a clean cloth. The speed of the disk 10 is reduced to 150 to 250 rpm for 16 to 18 seconds in step 42, during which time the magnetic medium moves through the nozzle 20 as the nozzle 20 moves from the outer diameter 15 to the inner diameter 14 and then back to the outer diameter 15. Powered by. The discharge pressure of the nozzle 20 is f's
is 0.14 kg/cm2 (2, Opsig) to 0.21 kg/cm2 (3,0 psig).

Step 44 is a high speed rotation step. In this process, the speed of Dinuk 10 is 3000-54 for approximately 8 seconds to 12 seconds.
00' rpm to expel excess media from the disk 10 thereby regulating the thickness of the magnetic film applied to the disk 10. In the orientation step 46, the speed of the disk 10 is increased to 50-50 for 15 to 25 seconds.
60 rpm while being immersed in a magnetic field to tend to properly orient the magnetic grains of the media layer then applied to disk 10. Drying process 48
In order to facilitate drying of the media film, the speed of the disk 10 is increased to 2600 rpm for 20-25 seconds. Next, the disc 10 is burned as usual.
It is treated through a polishing and polishing process.

Having described the conventional method of FIG. 2, the improved method of the present invention is shown in FIG.

The method of the invention also begins with a solvent wash step 50.

During this cleaning process, the disk 10 is rotated at 2300 rpm for 10 seconds, during which time the disk 10 removes even the smallest airborne particles from its surface. For cleaning purposes, wipe gently with a lint-free cloth impregnated with cleaning solvent. It is hoped that this step can be eliminated in the future by better disk handling techniques before placing the disk 10 on the spindle 5. In a step 52 immediately following the solvent cleaning step 50, the speed of the disk 10 is (approximately) 8
The nozzle 20 is increased to 3000-3800 rpm for a period of 2 to 9 seconds (approx.), during which time the nozzle 20 weighs approximately 0.42 kg.
/am2 (6psig) to 0.56kg/crI
I2 (8psig) (ai's at D/Zul discharge pressure
dispensing the body, starting from the outer diameter 15 and moving to the inner diameter 14, pausing at the inner diameter 14 for about 1 second, then about 3.1
cm (1.2 inches) Return to outer diameter 15 at a movement speed of 7 seconds. FIGS. 4 and 5 show that during step 52 the disk 1
2 illustrates the application of fluid-magnetic media to 0. The fluid magnetic medium includes iron oxide particles suspended in a polymeric binder composition. As shown in FIG. 4, the nozzle 20 has an outer diameter of 1
5 towards the inner diameter 14, the thin film γ0 of the medium adheres to the surface of the disk 1o, while the excess (non-adhered) medium layer 80 moves to the nozzle transfer point 90.
radially outwardly toward the outer diameter 15 and then forced out of the disk 10 due to the centrifugal force generated by the high speed rotation of the disk 10. The high speed of rotation of the disk 10 ensures that only a very thin film 70 of media adheres to the disk 10, and in addition, the protective layer 80 has a concentric ring located radially outward from the point of travel 90 of the nozzle 20. ensuring that the shape extends over the entire surface of the disc. The nozzle 20 has an outer diameter of 15 to an inner diameter of 1
4, the excess media layer 80 acts as a protective layer to prevent evaporation of the underlying film 70 and rapid changes in its viscosity. When the nozzle 20 reaches the inner diameter 14, there is a momentary pause (about 1 second) to ensure that the edge of the media film 70 is well constrained at the inner diameter 14. Return movement radially outward toward diameter 15.

As shown in FIG. 5, as nozzle 20 moves back toward outer diameter 15, protective layer 80 also moves back toward outer diameter 15, exposing thin media layer 70 to the atmosphere. The travel speed of the nozzle 20 is about 3.16 rn (1.2 inches) 7 seconds. As soon as nozzle 20 reaches outer diameter 15, disk 10 is immediately moved to orientation step 54 of FIG.

In this step 54, the speed of disk 10 is reduced to about 52 rpm for 10 to 15 seconds, during which disk 10 is exposed to an orienting magnetic field. Note that after the first portion of the thin film TO is exposed to the atmosphere, the disk 10 is exposed to the orienting magnetic field for a few seconds. As a result, only minimal evaporation and viscosity changes will occur from the time the media is first applied to disk 10 and exposed to the atmosphere until the beginning of orientation step 54. As a result, the magnetic particles in thin film 70 are much more susceptible to complete orientation along the lines of the orienting magnetic field than was possible with conventional methods. The result is improved media quality in the finished product and superior properties of the magnetic recording medium.

The orientation step 54 is followed by a very short drying step 56. In a drying step 54, disk 10 is rotated at (approximately) 2300 rpm for up to 5 seconds in the absence of an orienting magnetic field to facilitate drying.

The media film 70 formed by the method of the present invention is much thinner than the thickness (30 microinches) obtained by conventional methods. (10 microinches - 20 microinches). As a result, the film 70 dries much more quickly than with conventional methods, and the drying step 56 can be significantly shortened and even eliminated.

Having thus disclosed the method of the present invention, various advantages and features of the method of the present invention will now be described.

The entire process time is also shorter than the traditional process. (9
55 seconds compared to 5 seconds), resulting in increased production. More importantly, however, this reduction in cycle time reduces the time interval during which the disc is exposed to atmospheric contaminants, thus reducing contamination of the coating due to airborne particulates. be. This is because the thickness of the coating formed by the present invention is much thinner than that of the coating formed by conventional methods, so the coating film dries much faster and therefore stays tacky for a much shorter time interval. This is especially true if the condition is known. While the disk 10 is in the sticky state, it is most susceptible to contamination by airborne particulates that fall and stick onto the media film. Because the media film of the present invention dries quickly, airborne particulates that fall onto the media film are less likely to stick than in conventional methods.

Contamination by particulates is also reduced due to the self-cleaning effect of the new method. That is, keeping the nozzle discharge pressure higher and increasing the rotational speed of the disk during the media application step tends to wash away any particulates that fall onto the disk. This feature of Nyose "Ran"
It can prevent the occurrence of coating scratches known as scratches. In conventional methods, if granules were present on the disk during the rotation process, the media would tend to flow around the granules as they were radially displaced, resulting in a flow of particles onto the disk. Creates radially oriented "runs". In the new method of the present invention, such particulates are generally washed away from the disk.

Wrap-around coating flaws can also be eliminated by the method of the present invention. Wraparound occurs when the outer edge of the disk flows from one side of the disk to the other side of the disk during the application or rotation process. The elimination of low speed media application and high speed rotation steps in favor of a high speed media application process prevents such wraparound from occurring.

Since the new method eliminates the polishing operation after coating, the occurrence of other coating scratches can be prevented. Because of the thickness of the film formed and the quality of its surface, polishing is unnecessary. In the past, such polishing was performed to improve surface finish and reduce media film thickness. By making the magnetic film thinner, it is possible to record more precisely on the disk.

Polishing was conventionally done with an abrasive nylon tape to which rotational power was transmitted, and an abrasive solvent was applied to the disc while it was being abraded with the tape. Circumferential scratches often occur if the polishing tape captures particles on the disk during the polishing operation. Besides, 1. Polishing solvents often introduce contaminants onto the surface of the disc.
It has always been difficult to completely remove contaminants after the polishing operation because of the amount of water present. By eliminating the need for a polishing step, circumferential scratches on the media and stains caused by polishing solvents and other related problems can also be eliminated. Disks produced by the method of the invention require only light polishing with a dry puff rather than polishing with a solvent.

It was primarily noted that the improved method could be used for thinner magnetic film f y+ disks due to the high rotational speed of the disk and nozzle discharge pressure during coating application. If in the past magnetic media was applied at low speeds, the viscosity of the magnetic media increases quickly when it is applied onto a disk exposed to the atmosphere, and therefore the high speed rotation process begins immediately. However, it was difficult for the magnetic medium to flow freely, and a large amount of the magnetic medium adhered to the disk during the high-speed rotation process. Another factor that influences the thickness of the coating applied to the disc is the speed of movement of the nozzle, particularly as it moves from the inner diameter 14 back to the outer diameter 15.

What is interesting is that the film thickness decreases when the speed of arm movement is reduced. This means that a hole is formed in the film 20 due to the pressure of the medium flow discharged from the nozzle 20 when the nozzle 20 is moving back from the inner diameter 14 to the outer diameter 15, and the nozzle discharge pressure and arm movement speed both influence media film thickness.

It is extremely important that the nozzle 20 can be moved smoothly through the equipment used to carry out the method of the invention. In particular, if the nozzle 20 oscillates when returning from the inner diameter 14 to the outer diameter 15, a corresponding change in thickness occurs, resulting in a thinner area in the circumferential direction of the film. As a result, although the nozzle 20 is shown supported by a pivot arm 25, the present invention is not limited to use in such a structure, and the nozzle 20 is
Other devices that move between the inner diameter 14 and the inner diameter 14 are also suitable or not included.

Having thus disclosed the preferred embodiments of this invention, many variations and modifications thereof will become apparent to those skilled in the art.
The invention is limited only by the scope of the claims that follow.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a simplified magnetic media coating apparatus capable of implementing the improved method of the present invention, and FIG. 2 is a graph of disk rotation speed versus time illustrating the prior art method. , FIG. 6 is a graph showing the relationship between disk rotational speed and time, illustrating the improved method of the present invention. FIG. Moving nozzle 20
FIG. 5 is a cross-sectional elevational view illustrating a nozzle 20 that deposits media onto the disk while moving from the inner diameter of the disk back toward the outer diameter of the disk. It is a diagram. 5...Spindle, 10...Disc, 12...
Central opening, 14...inner diameter, 15...outer diameter, 20.
... Nozzle, 52... Coating application process, 54.
... Magnetic alignment step, 56... Drying step, 70... Medium film, 80... Protective layer. Kasu &'t yesterday y)

Claims (1)

[Scope of Claims] (1) comprising a spindle rotatable by a power source and a disk having an inner diameter, an outer diameter and a central opening, the disk being rotatable by the spindle at the central opening; and a nozzle for dispensing a magnetic medium onto the disk at a nozzle discharge pressure, the nozzle being movably mounted relative to the disk and having a diameter between the outer diameter and the inner diameter. the disk is rotated at a rotational speed of at least 5000 rpm during a high speed coating application step, and the nozzle is moved between the outer diameter and the inner diameter during the coating application step; The magnetic medium may be applied to the disk from the nozzle at a nozzle discharge pressure, and the rotational speed of the disk is reduced during an orientation step immediately after the coating application step, and the disk is subjected to an alignment magnetic field during the orientation step. (2. In the method of applying a magnetic medium to a disk according to claim 1, in which the coating is applied during the coating application step. The magnetic medium is dispensed from the nozzle at a predetermined nozzle discharge pressure, and the nozzle discharge pressure during the coating application step is at least 42 kg/cm2 (6 pcm).
A method of applying a magnetic medium to a disk, characterized in that: sig). (3) A method of applying a magnetic medium to a disk according to claim 1, wherein at the beginning of the coating application step, the nozzle starts dispensing magnetic medium at the outer diameter of the disk. A method of applying a magnetic medium to a disk, the method comprising: moving towards the inner diameter of the disk and returning from the inner diameter of the disk to the outer diameter of the disk at the end of the coating application step. (4) A method of applying a magnetic medium to a disk according to claim 6, wherein during the coating application step, when the nozzle moves from the outer diameter toward the inner diameter, a thin film of magnetic medium is applied to the disk. adheres to the disk, and a protective layer of excess magnetic medium flows over the thin film radially outward from the nozzle due to the centrifugal force of the rotating disk, and the nozzle - Once the inner diameter is reached, the protective layer extends from the inner diameter to the outer diameter, and when the protective layer advances with the nozzle toward the outer diameter and the nozzle moves from the inner diameter to the outer diameter, the protective layer extends from the inner diameter to the outer diameter. A method of applying a magnetic medium to a disk, characterized by exposing a film. (5) Permissible In the method of applying a magnetic medium to a disk according to claim 4, when the nozzle moves from the outer diameter to the inner diameter during the coating application step, the nozzle A method of applying a magnetic medium to a dinuuk, characterized by a pause of about 1 second before returning from the inner diameter to said outer diameter. (6) In the method of applying a magnetic medium to a disk according to claim 4, the nozzle has a predetermined moving speed while moving from the outer diameter to the inner diameter, and the movement of the nozzle The speed during the coating application process is 2.5 C7n (1.0 inch) 7 seconds to 3.8 Cr.
A method of applying a magnetic medium to a disk, characterized in that n (1,5 inches) 7 seconds. (7) The method of applying a magnetic medium to a disk according to claim 1, further comprising a drying step subsequent to the orientation step, for promoting drying of the film during the drying step. A method of applying a magnetic medium to a disk, characterized in that the rotational speed of the disk is increased. (8) A method of applying a magnetic medium to a disk according to claim 1, wherein the coating application step has a duration of 7 seconds to 10 seconds. How to apply. (9)% Permissible The method of applying a magnetic medium to a disk according to claim 1, wherein during the coating application step, the rotation speed is between 30''00 rpm and 5800 rpm.
A method of applying a magnetic medium to a disk characterized in that it is within the rpm range. (10) % tolerance In the method for applying a magnetic medium to a disk according to claim 1, the nozzle pressure during the coating application step is 0.42 kg/cIn2 (
6 psig) or 0.56 kli'/cIn"
(8 psig). 0]) A method of applying a magnetic medium to a disk according to claim 1, wherein the coating application step has a duration in the range of 7 seconds to 10 seconds, and during the coating application step, The rotation speed is 600 O
rpm to 6800 rpm and the nozzle discharge pressure is 0.42 kg7cm2 (6pθig) to 0.56 (8 psig).