Detalled Exotanatton of the Invention (0001) INDUSTRIAL FIELD OF UTILISATION This inventio relates to machines for the polishing and grinding of surfaces of boards and other items for hard disks, and the tape used in these machines, and in particular relates to polishing nd texturing machines which are able to perform electrolytic polishing of the surface of boards and the like while simultaneously polishing and grinding, and the tape for use in these machines.

(0002) PRIOR ART Hard disks, that is metalilc, thin-film magnetic disks, are generally magnetic memory media with a magnetic layer on the surface of an aluminium disk board: but with constant hopes for further imdrovement in the memory density there is the impending necessity for a reduction in tille distance between the magnetic head and magnetic disk. Bringing both of these surface$ to a smooth, mirror-like finish, however, creates excessive contact areas in both, obstructjng smooth running, and giving rise to problems upon start-up in particular.

To deal with is problem, polishing and texturing is generally conducted in which filament print of ridges and grooves is created through grinding after the surface of the disk board has been poli hed smooth. The polishing process is performed by supplying a polishing cloth with a lishing solution that contains grains to bring the surface of the disk board to a mirror-like sßrFace. The texturing process uses items such as tape which has polishing grains fixed in lits surface, or buffs impregnated with slurries which contain polishing grains to form concentrically circular filament print on the surface of the disk board.

To achieve en ured smooth running of the disk and high memory density, polishing and texturing must ae performed so as there are no anormal protrusions on the surface, and the ridges and grooves are accurate and even. In normal polishing and grinding with polishing grain, however, deep ridges and large protn sions are frequently formed, leading to rea-write errors and problems with the floating stability of heads in these areas.

(0003) PROBLEMS THE INVENTION SEEKS TO SOLVE The task for this invention is to create disk boards with surface properties whereby the surface has no protrusions, the surface roughness Ra (average roughness of concentric lines) is no more than 50 A and the maximum surface roughness Rmax (the maximum height of surface protrusions) is no more than 50 A. To achieve this, it is necessary to both process the surface of the disk board to a high-precision mirror finish, and create grooves of uniform depth in that surface. Boards are generally polished to a superior mirror finish by using finer polishing agents, but this leads to reduced processing efficiency and poor productivity. Furthermore, once a large processing mark, or scratch is made, its removal reduces processing efficiency and requires significant amounts of processing time. As far as texturing is concemed, it is difficult to improve surface properties through mechanical means. Other issues that this invention seeks to address is the improvement of processing efficiency and the expediting of the production of uniform surface properties.

(0004) MEASURES FOR SOLVING THE PROBLEMS In addressing the aforementioned problems, the inventors of this invention have removed the minute protrusions that occur when polishing with filings and when forming process marks, and burring that occurs when processing, by utilising the action of electrolytic polishing in concurrence with polishing and grinding under the concept of producing a smooth processed board with no anormal protrusions; that is to create superior texture patterns on highly polished, mirror-finish boards. This invention is the result of repeated experiments, evaluations and investigations. In other words, the substance of this invention is: 1) a device with which electrolytic polishing and polishing and texturing can be conducted simultaneously, whereby in the polishing and texturing process by tape with a metallic surface, the object being processed functions as an anode, a cathode is positioned near the surface being processed to conduct electrolytic polishing, and solution of combined electrolytic solution and processing solution is present between, and in contact with, the surface being processed and the cathode, and; 2) the polishing and texturing tape used in the said device. Furthermore, the cathode may be positioned on the processing side of the tape or on the reverse side of the surface being processed. The tape's backing may be synthetic resin film, woven material or non-woven cloth, and has a surface on one side of flocked fibres or a porous, synthetic resin foam which is capable of holding polishing grains. In devices in which the cathode is positioned on the reverse side of the surface being processed, non-conductive liquid-permeable is used. Confirmation was made that through the use of this invention's device processes were simplified, surface properties superior to the two-stage processing method were obtained, and processing efficiency was boosted approximately ten-fold.

(0005) The most significant feature of this invention is that the addition of electrodes to the polishing and grinding device allows for the simultaneous and parallel conducting of mechanical polishing and grinding, and electro-chemical polishing by combining electrolytic solution with polishing or grinding solution and passing a current between the solution and the object being processed. The electrode (cathode) is formed by placing a cathode roller or cathode rod (Diagram 3) on the processing side of the tape in proximity to the surface being processed. Altematively, the pressure roller on the reverse side of the tape may act as an electrode. It is also possible to have the tape itself act as an electrode by using a conductive backing for the polishing and texturing tape and ensuring the tape's structure allows the passage of liquid. Another way of forming an electrode is to place a metallic tape on the reverse side of a liquid-permeable tape and moving them along together. In all cases, it is essential that the object being processed and the electrode (cathode) be joined together by the electrolytic solution.

(0006) Synthetic resin film is useful as the tape-shaped backing for this invention's combination electrolytic polishing and polishing and texturing tape. A typical example of this is 100- 200 lim thick polyethylene terphthalate (PET) film, in which holes may be punched in a specific pattern as necessary. Film to be used may be selected from materials which have the necessary mechanical strength, and which can withstand environmental conditions including electrolytic solution.

(0007) All types of woven material and non-woven cloth may also be used as the tape-shaped backing. Some of the liquid-permeable textiles include loose-weave woven material, knitted material, non-woven cloth, materials that have intemal space, or comparatively densely-woven material and non-woven cloth in which holes have been punched. Textiles may be chosen at discretion as long as they have sufficient mechanical strength and chemical resistance, with polyester textiles being particularly suited. The width of the texturing tape is generally 35-89 mm, but it may be cut to fit the size of the disk.

(0008) Either the entire surface, or most of the surface, of one side of this invention's texturing tape is covered with a layer which is capable of holding polishing grains. Diamond, alumina or other granules of an average diameter of no more than 3 m are used as the polishing grains, with these being disperse in an mulsion liquid, combined with electrolytic solution, and supplied to the space between the rotating disk board that is being polished and this invention's texturing tape which runs in contact with this. Surface structures which will temporarily hold polishing grains in the texturing tape surface to allow effective polishing of the disk surface at this time include porous synthetic polymer foams or flocked surfaces.

(0009) The flocking process involves pre-coating the surface into which fibres will be flocked with a binder resin, flocking extremely short fibres in this surface through the use of static electricity, and fixing them in place with the binder resin. Fibres for flocking include polyamide, polyester, acrylic and other fibres which do not readily conduct electricity and are not affected by electrolytic solution, with fibres of no more than 1 denier and no longer than 1 mm being well suited. A base resin of acrylic ester emulsion blended with epoxy resin and a catalyst as a cross-linking agent can be used as an appropriate binder, but this is not the only possibility. When flocking is done to a specific pattern, methods such as the rotary screen method are used to print the binder resin in the pattern. The entire surface may simply be coated when the tape-shaped backing has already had a pattern of holes punched in it.

(0010) For the porous synthetic resin foam, create a porous resin layer with a known foaming agent, such as synthetic resins such as polyurethane, polyvinyl chloride, polyethylene, polystyrene and polyvinyl formal, and foaming conditions, to make the surface porous apart from the outermost layer. Use such methods as the rotary screen method mentioned above for specific patterns.

(0011) When using conductive tape-shaped backing or an electrode on the reverse side of the tape, it is preferable that the electrical resistance in the direction of the thickness of the texturing tape, which is formed from this layer and the tape-shaped backing, is at least 1 x 101° Q, in the flocking or in the porous resin. This is because when this layer has good conductivity, a short circuit is formed between the electrode and the disk board, current ceases to flow in the electrolytic solution, and electrolytic polishing is interrupted.

(0012) To ensure that there is no unevenness in the surface which is being polished or textured, for the pattern of the surface which is capable of holding polishing grains, it is necessary to use a position in which a mostly uniform contact area can be obtained in the width direction of the surface of the object being polished vis-à-vis the running of the texturing tape.

(0013) ACTION In the polishing and texturing processes by tape with a metallic surface in this invention, the object being processed acts as the anode, a cathode is positioned close to the surface being processed to conduct electrolytic polishing, and a solution of combined electrolytic solution and processing solution is present between, and in contact with, the surface being processed and the cathode; in doing so it is possible to conduct electrolytic polishing simultaneously with polishing and texturing, resulting in dramatic improvement in surface performance, such as smoother processed surfaces and greater uniformity of texturing, and also a significant boost to processing efficiency.

(0014) EMBODIMENTS Embodiment 1 of this invention will be explained with a texturing process example. After passing a 300 mm wide, 150 lim thick piece of polyethylene terphthalate (PET) film through a static electricity flocking device and coating it with an acrylic ester emulsion-type binder in the coating part, it was flocked with a pile of 0.5 denier, 0.2 mm long nylon fibres, and heat-cured to fix the pile. Ten holes of 2.4 mm in diameter per 20 mm x 20 mm square were created in the flocked film, and the film cut down to 37 mm in width to make texturing tape.

(0015) Diagram 4 explains the simultaneous processes of texturing using this texture tape and electrolytic polishing. Texture tape (1) runs along in contact with rotating disk board (7), with metallic pressure roller (8) pressing the tape against the surface of the disk from behind. Whilst electrolytic solution (10), into which polishing grains (9) have been dispersed, is supplied to the space between rotating disk board (7) and running texture tape (1), a voltage is applied between disk board (7) and pressure roller (8) for simultaneous texturing and electrolytic polishing.

(0016) Diagram 3 shows a different simultaneous process. In this example, an electrode referred to as cathode rod (11) is set in a position close to the front side of the texturing tape, with the cathode rod and the surface being processed being connected by electrolytic solution (10). Results of processing with this composition were similar to those in the previous item.

(0017) Measurement of surface properties of disk boards processed in the aforementioned manner gave surface roughness, Ra, as 7 A, and maximum surface roughness, Rp, as<BR> 10 A, which are naturally far superior in comparison to the values of 20 A and 100 A, respectively, obtained when only mechanical texturing was conducted, and markedly better results were able to be obtained in a short period of time than when normally conducting texturing and polishing over two stages.

(0018) EFFECT This invention's texturing tape enables simultaneous mechanical texturing and electrolytic polishing, resulting in at least comparable, if not superior, surface properties with one- stage processing than conventional two-stage processing methods; that is grooves and ridges are even, and there are no anormal protrusions. The efficient supply of hard disks without the occurrence of read-write (R/W) errors has, therefore, become possible.

SIMPLE EXPLANATION OF DIAGRAMS Dtagram 1 Cross-sectional, explanatory diagram of the embodiment of this invention's texturing tape.

Diagram 2 Cross-sectional, explanatory diagram of other embodiments of this invention's texturing tape.

Diaaram 3 Explanatory diagram for this invention's process of simultaneous texturing (using texturing tape) and electrolytic polishing.

Dtagram 4 Explanatory diagram of another composition for this invention's simultaneous texturing (using texturing tape), and electrolytic polishing.

EXPLANATION OF SYMBOLS 1 Texturing tape 2 Porous tape backing (film) 3 Binder resin layer 4 Flocked fibres 5 Porous tape backing (non-woven cloth) 6 Porous synthetic resin foam 7 Disk board 8 Pressure roller 9 Polishing grains 10 Electrolytic solution 11 Cathode rod Control No. KC9708-1