JPH04125873A - Hub of disk and its manufacture - Google Patents

Abstract

PURPOSE:To improve abrasion resistance by forming metal nitride coat whose N/metal is within a prescribed range on a surface. CONSTITUTION:A hub is arranged in a vacuum, the surface is cleaned, a metal is ionized by arc discharge and the metal nitride coat is adhered under a condition that the N/metal ratio becomes 0.8-1.2 in a nitrogen gas atmosphere. It is desirable that the thickness of the coat is 0.5-1.5mum and hardness is 2000-3500Kg/mm<2>.

Description

[Detailed description of the invention] 【Technical field】

The present invention relates to a hub for an optical disk or a magnetic disk and a method for manufacturing the same.

[Prior art]

In optical discs and magnetic discs, the recording medium is formed into an annular shape, and a rotating hub made of metal such as stainless steel is fitted and fixed in the central hole of the annular recording medium to support and drive it. The rotating hub has a central hole for receiving the spindle bin from the device side and an off-axis hole for receiving the drive bin at an eccentric position,
When a disk is loaded into a recording/reproducing device, the drive bin automatically slides on the surface of the hub and fits into the off-axis hole. At this time, abrasion, scratches, and powder particles occur on the surface of the hub, which adhere to the surface of the recording medium and cause dropouts and reduced output. FIG. 1 shows an outline of the exploded structure of a floppy magnetic disk device. Between an upper case 1 and a lower case 2, there is a magnetic disk 4 with a rotating hub 3 fitted and fixed in a central hole, and liner sheets 5 on both sides of the magnetic disk 4. The 0-rotation hub 3 has a square center hole 7 for receiving a central spindle bin (not shown) on the playback device side, and a drive bin (not shown) located at an eccentric position.
The receptacle (not shown) has an off-axis square hole 8 for receiving it. When the disk drive is installed in the recording/reproducing device, the spindle bin and the drive bin will automatically try to enter these holes, but since these bins are not necessarily aligned correctly with the holes 7.8, the drive bin will It rotates while sliding on the surface of the hub 3 to find the hole position and fit into it.

[Problems to be solved by the invention]

The rotating hub 3 is usually made of stainless steel (SUS430) or plated (for example, hard chrome plating), but the parts that come into contact with the metal drive bottle and spindle pin are used many times. During this time, the disc gradually wears out and causes powder to fall off, and when this adheres to the disk surface, it causes original recording, dropouts, and a decrease in output, resulting in malfunctions when recording and reading information. By the way, in order to solve these problems, it has been proposed to form a metal nitride film on the surface of a friction sliding member (for example, a tape guide) by ion blasting (Japanese Utility Model Publication No. 87691/1983). However, the adhesion of the ion blating film to the base metal is not sufficient, and the particles fall off and adhere to the surface of the magnetic tape, causing problems such as dropouts, reduced output, and back coat scraping. It cannot be avoided sufficiently. One reason for this is that the surface oxide layer, oil, dirt, etc. of the base metal cannot be removed sufficiently, but even if the surface is cleaned, it is not always possible to obtain sufficiently satisfactory wear resistance, and friction Problems such as the inability to achieve a sufficiently low level remain. In other words, it is desirable to improve the physical properties of the metal nitride itself. Therefore, the purpose of the present invention is to improve the wear resistance of the rotating hub of media such as optical disks or magnetic disks. [Means for solving the problem] The present invention provides a method of forming a metal nitride coating having an N/metal ratio of 0.8 to 1.2 on the surface of the hub of an optical disk or magnetic disk. The above-mentioned problems are solved by a disk hub characterized by: Preferably, the thickness of the metal nitride coating is 0.5 to 1.5 μm, and the hardness is 2000 to 35 μm.
00kg/mm8. Such a metal nitride coating is prepared by placing the hub in a vacuum, preferably applying plasma gas to the surface to clean the surface, and then ionizing the metal by arc discharge to reduce the N/metal ratio in a nitrogen gas atmosphere. It is formed by an ion blasting method which consists of depositing a metal nitride coating under conditions of 0.8 to 1.2. Preferably, the deposition rate of the metal nitride coating is 0.5-2.0 μm/hr. The ion blating method is a method in which raw materials are evaporated and ionized and then deposited on a substrate.
Radio frequency excitation method in which metal vapor is ionized by inert gas or reactive gas of about 0-4 and high frequency RF excitation, electrons from multiple hot cathodes collide with metal vapor in the presence of inert gas or reactive gas. Multi-cathode method for ionization by introducing an inert gas into a cathode gun to generate a plasma electron beam, which collides with the metal to evaporate and ionize it, using an inert or reactive gas atmosphere if necessary HCD method (hollow cathode gun method), bias probe method in which a bias probe with positive voltage is installed between the metal evaporation source and the substrate in a reactive gas or inert gas, There are low-pressure plasma methods that apply an electric potential, and cluster ion methods that form cluster ions by squeezing metal vapor from a metal evaporation source using a thin nozzle, but the method suitable for the purpose of the present invention uses arc discharge to generate metal vapor. This is an arc discharge method that ionizes. Among the arc discharge methods, ion brating, which is performed under high vacuum conditions, imparts strong kinetic energy to ions, and it has been found that it is possible to produce metal nitrides with high film forming efficiency and high quality. In the present invention, metals that can be used to form a metal nitride film on the surface of the metal base of the sliding member include Cr, Hf, Ti, Zr, and Mo.
%W%Si%B, etc., especially Ti, S
L and B are preferred, and the metal nitride has an N/metal ratio of 0.8
The ratio must be controlled to be ~1.2; if the ratio is smaller than this range, friction will increase due to sliding between metals. If the ratio is larger than this range, the abrasion resistance will be reduced and powder will fall off. Ion blating by arc discharge reduces the film forming speed to 0.
．． It was found that it was necessary to control it within the range of 5 to 2.0 μm/hr. If it is slower than this range, there is a drawback that productivity will be poor. On the other hand, if the film forming speed is too high, the metal nitride will form a columnar structure, resulting in poor surface properties, increased friction, and poor adhesion to the medium. The thickness of the metal nitride coating is preferably 0.5 to 1.5 μm.
It is. If the film thickness is larger than this range, the metal nitride coating will easily peel off from the substrate due to internal stress, causing malfunctions due to dropouts or decreased output. If the film thickness is thinner than this range, the metal nitride coating will peel off from the substrate. They form islands on the (hub), reducing wear resistance, and substances deposited on the substrate surface transfer to the recording medium, causing adverse effects. The hardness of the metal nitride coating is preferably 2000 to 3500.
kg/mm", and the hardness roughly corresponds to the N/metal ratio, so if it is lower than this range, the metal content will increase and the friction between the drive bottle and the drive bottle will approach metal friction (and the friction will increase. If it is too large, the drive bottle will be worn out, causing malfunctions. Preferably, the surface of the metal hub is activated by plasma treatment to increase the bonding force of the ion plating film to the substrate, which will be deposited in the next step. Plasma treatment includes Ar, He,
Rare gases such as Ne, H2°Nt, Co, C(L, Hz
This is carried out by introducing gases such as 01NO, NO, NH, etc. into a vacuum chamber, turning them into plasma, and bringing the plasma into contact with the substrate. Conventional conditions are used for the plasma treatment. Direct current or alternating current can be used as a power source at a gas pressure of 0.01 to 10 Torr, and the frequency of alternating current can be used from 50 Hz to 5 GHz. Processing conditions vary depending on the shape and amount of sample, but power consumption: 10W-10KW Processing time: 0.5 seconds to 1
Can be set to 0 minutes. By performing this pretreatment, the problem of powder falling off mentioned above can be avoided. The reason for this is that the surface oxide layer is removed by plasma impact, and furthermore, oil, dirt, etc. are sufficiently removed, resulting in a surface cleaning effect and surface activation, which improves adhesion. In addition, by reducing the contact angle, wetting is improved (and adhesion is improved).The effect can be further improved by applying a bias potential to the substrate side during plasma pretreatment. Alternatively, or before that, ultrasonic cleaning may be performed using alcohol, acetone, chlorofluorocarbon, etc. The film forming method will be explained in detail using the arc discharge apparatus shown in Figure 2. 'T o r r, then the metal evaporation source (target) 23 such as Ti, SL, etc. is heated and melted with an electron gun 30. After sufficient melting and a predetermined metal evaporation rate is obtained, the ionization electrode A voltage is applied to ionize the evaporated metal.To control the current flowing through the ionization electrode, thermionic emission is performed to obtain a predetermined current value.Then, the gas supply passage 2
Operate valve 1 to introduce nitrogen gas at a predetermined flow rate. While adjusting the exhaust system 22, for example, 10-' Torr.
Adjust to. Once stabilized, the shutter is opened and the film is deposited. Stable film formation can be achieved by feeding back the current flowing through the substrate using the electron gun control system. Thermionic emission electrode 28
The ionized particles traveling due to the electric field distribution formed by the ionization electrode 31 collide with other evaporated particles and further propagate the ionized particles.The ionized particles with strong kinetic energy are accelerated by the bias voltage 25 and
2 (hub) at a high speed and efficiency. At this time, nitrogen gas reacts while adhering and growing to form a film. Conditions such as potential, current, temperature, etc. of each part can be easily set by experiment. Further, the substrate may be heated in advance to improve adhesion. Next, the present invention will be explained in detail. [Explanation of Examples] Using the apparatus shown in FIG. First, a disc hub-shaped base was manufactured from stainless steel, and this base was loaded into the film forming apparatus shown in Fig. 2 and explained above, using Ti, Si, etc. as the metal. ,
A titanium nitride film was formed on the surface of the substrate under the conditions of N2'' gas pressure of 10' Torr, 300 SCCM, and arc current of 100 A. First, the hub was subjected to plasma treatment, and gas Ar, 50 SCCM,
The test was carried out under the conditions of a pressure of 0.5 Torr, an RF frequency of 13°56 GHz, a power of 500 W, and a reaction time of 1 minute. Next, N/T of titanium nitride is formed into a film by using Ti as the target and adjusting the film forming pressure as the film forming conditions.
The i ratio (atomic ratio) was adjusted to obtain a titanium nitride coating with a thickness of 1.0 μm. The measurement results are shown in Table 1. Various measurements were carried out by the following methods. The determination was made using the following method. 1) Using a measurement bottle made of friction SUS with hard Cr plating, the surface of the hub was slid and the force applied to the measurement bottle was measured with a strain gauge. 2) Abrasion resistance When a measurement bottle with a tip of R = 5 mm and hard chrome plating was slid over the sample surface 1000 times, the wear depth was measured using a surface roughness meter and the following results were obtained. Expressed based on standards. 0.05 μm or less 0 0.05 ~ O, I μm O o, 1 ~ 1.9 μm × 1.0 or more It was measured using 4) Number of trucks whose output has decreased by 50% during one round after inputting an output reduction signal and applying the deck again after a wear test. 5) Chucking mistake. Check if the drive bin is chucked in the normal position.
Number of mistakes after chucking 00 times. 6) Number of tracks whose output decreased by 50% or less when a signal was input to 10 discs and played back after a wear test. 7) Film thickness and film forming speed Measured using a quartz crystal film thickness monitor. The N/metal ratio was measured by ESCA. Table 1 From this table, it can be seen that the N/Ti ratio is preferably 0.8 to 1.2. If the ratio is smaller than this range, friction will increase due to sliding between metals. If the ratio is larger than this range, the abrasion resistance will be reduced and powder will fall off. Hardness is preferably 2000-3500 kg/m
It is m2. Hardness roughly corresponds to the N/metal ratio, so if it is lower than this range, the metal content will increase and the friction between it and the drive bottle will approach metal friction, increasing the friction. If it is larger than this range, the drive bin will be worn out, causing malfunction. Example 2 Next, the N/Ti ratio was set to 1.0, the film forming speed was adjusted, and a film was formed to a thickness of 1.0 μm. Table 2 shows the results.
The measurement was performed using the following method. 1) Adhesiveness to the medium The hub and the shoe key were attached using double-sided tape cut out to the size of the adhesive surface of the hub, peeled off 180 degrees, and the adhesive strength was expressed as the load applied to the load cell. 2) The warpage of the hub was scanned over 20 mm using a stylus type surface roughness meter, and the height was determined from the profile. The value shown is the value obtained by subtracting the measured value of the untreated product from the measured value. 3) Surface roughness The surface roughness was scanned over 3 mm with a stylus-type surface roughness stylus and expressed as Ra. Table 2 From this table, it can be seen that when the film forming rate is slower than 0.5 μm/hr, the adhesion is good and the friction is low, but it takes time. On the other hand, if it is thicker than 2.0 μm/hr, the friction will become thicker and the adhesive strength will decrease.
0 μm/hr is suitable. In addition, it was confirmed by microscopic observation that a columnar structure developed when the rate exceeded 2.0 μm/hr. Example 3 Next, the film thickness was changed at a film forming rate of 1.0 μ/hr. The results are shown in Table 3. Table 3 From Table 3, a thickness of 0.5 to 1.5 μm is suitable; if the film thickness is larger than this range, the metal nitride is likely to peel off from the substrate due to internal stress, resulting in dropouts and output power. If it is thinner than this range, the metal nitride coating will form islands on the base (hub), reducing wear resistance, and deposits on the base surface may transfer to the recording medium, causing adverse effects. It can be seen that this occurs. Example 4 In this example, a film of 5isN4 was formed as a metal nitride in the same manner as in Example 1, using SL instead of Ti. The results are shown in Table 4. Table 4 As is clear from Table 4, in this example, the thickness is 1° to 2. It turns out that Oum is suitable.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a magnetic disk case equipped with a conventional disk hub, and FIG. 2 shows an example of the ion blating thin film manufacturing apparatus of the present invention.

Claims (6)

[Claims] (1) A metal hub for an optical disk or a magnetic disk, characterized in that the surface of the hub is coated with a metal nitride having an N/metal ratio of 0.8 to 1.2. (2) The disk hub according to item 1 above, wherein the metal nitride coating has a thickness of 0.5 to 1.5 μm. (3) Hardness of metal nitride coating is 2000 to 3500 kg
/mm^2. (4) Place a hub for an optical disk or magnetic disk in a vacuum, ionize the metal to form a nitride by arc discharge, and place the metal in a nitrogen gas atmosphere to form the N/metal of the metal nitride coating. A method for manufacturing a disk hub having a metal nitride coating, characterized in that the ions are deposited on the substrate under conditions such that the ratio is 0.8 to 1.2 to form a wear-resistant coating. (5) Film forming speed of metal nitride coating is 0.5 to 2.0 μm
/hr. (6) The method for manufacturing a disk hub according to the above item 4 or 5, wherein the surface of the hub is cleaned by applying plasma gas to the surface of the hub before ionizing the metal to form a nitride by arc discharge. .