JP2510292B2 - Laser printing method for magnetic recording media - Google Patents

Description

The present invention relates to a laser printing method for a magnetic recording medium used in a hard disk device or the like which is an external storage device of a computer.

[Conventional technology]

A method of printing on a metal or the like using laser light is generally known. Laser printing is performed by, for example, irradiating a pulse of YAG laser light to engrave numbers, symbols, etc. at a predetermined pulse frequency and printing speed. A predetermined lamp current is passed through the krypton lamp, the yttrium aluminum garnet crystal is excited by the light of the krypton lamp, and oscillates a laser beam. A 1.06 μm YAG laser beam is applied in a pulsed form and scanned in the XY directions by an XY axis polarization mirror as shown in FIG. The laser light is, for example, Ni-P on the Al substrate.
Printing is performed by irradiating a magnetic recording medium in which a layer, a Cr layer, a Co alloy layer, and a carbon layer are laminated. The medium is polished after forming a Ni-P layer, and the surface of the medium has an average roughness Ra of 0.1 μm and a maximum roughness Rmax of 0.8 μm.

[Problems to be Solved by the Invention]

However, when this laser printing is applied to a magnetic recording medium, there are the following problems. That is, laser printing is performed on the clamping area of the magnetic recording medium, in which case the surface smoothness of the magnetic recording medium and the corrosion resistance of the clamping area are impaired by the heat generated during laser irradiation. For example, burrs are generated from the marking portion in the clamping area, and when the medium is mounted on the hard disk device by the spacer through the clamping area, the substrate of the magnetic recording medium is deformed or surface wobbling occurs when the medium rotates. Further, in the magnetic recording medium, a Ni-P non-magnetic layer is formed on the Al substrate by electroless plating, but this non-magnetic layer is recrystallized by heat generated during laser irradiation, resulting in large crystal grains and reduced corrosion resistance. Corrosion of Ni-P generated in the clamping area progresses to reach the recording layer and damage the input information.

The present invention has been made in view of the above points, and an object thereof is to provide a laser printing method capable of obtaining a magnetic recording medium having excellent reliability by optimizing the condition setting in laser printing.

[Means for solving the problem]

As a result of intensive studies on the laser printing of a magnetic recording medium, the present inventors have found that the surface roughness of the medium has a great influence on the light reflectance, and have completed the present invention based on this finding.

According to the present invention, the above-mentioned object is a method of printing on a magnetic recording medium by applying a lamp current to a krypton lamp and irradiating a YAG laser pulse at a predetermined printing speed, and a pulse frequency of the YAG laser pulse. 16-20k
It is achieved by setting within the range of Hz, the lamp current within the range of 10 to 14 A, and the printing speed within the range of 100 to 200 mm / s.

[Action]

When the optimum conditions for laser printing are satisfied, the surface layer of the magnetic recording medium is melted and the initial surface roughness of the medium is smoothed.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings. First
The figure is a diagram showing the relationship between the laser frequency (kHz) and the surface roughness of the marking portion. This laser prints a 0.3 mm wide straight line on the carbon layer, which is the surface of the clamping area of the magnetic recording medium, and scans 1 mm in the direction perpendicular to the straight line to determine the surface roughness (Rmax, Ra) of that area. It was measured. Rma
x is the maximum value of roughness and Ra is the average value. The printing speed was set to 50 mm / s and the lamp current was set to 10A and 14A. When the lamp current is less than 10A, printing is impossible, so 10A is selected as the minimum value. Curves 11 and 12 are Ra (μ
m) and curves 13 and 14 correspond to Rmax (μm). Curve 11 of curve 11 is lamp current 14A, curve 12 and curve
14 is for a lamp current of 10A. It can be seen that both the average roughness and the maximum roughness decrease from the initial values as the pulse frequency of the YAG laser pulse increases. This means that the surface of the medium was melted by the heat generated during the laser printing and the surface smoothness was increased. Therefore, the light irradiation rate is increased from the smoothed carbon layer, and it is possible to clearly distinguish the imprinted print. In the case of a magnetic recording medium, the carbon layer changes from dark brown to silvery white by laser printing. If the frequency exceeds 20kHz and becomes 30kHz, the amount of heat generated during printing will be too large, and burrs will occur from the marking and the Ni
The P layer becomes corrosive. When the lamp current exceeds 14A, both Rmax and Ra increase, so 10-14A is suitable as the lamp current. The frequency range is 16
~ 20kHz is suitable because Rmax and Ra are small.

FIG. 2 is a diagram showing the relationship between the printing speed and the surface roughness. The lamp current was set to 10 A and the frequency was set to 12 kHz.
Curve 15 corresponds to surface roughness Ra and curve 16 corresponds to surface roughness Rmax
Corresponding to. The surface smoothness increases as the printing speed increases. Surface smoothness is 100 when printing speed is 50 mm / s
The reason why the print speed becomes worse than the print speed of ~ 200 mm / s is considered to be the excessive heat generation and the adverse effect. Printing speed
When it exceeds 200 mm / s, the heat generation is insufficient and the surface of the medium does not melt and the surface roughness tends to increase. Therefore, the optimum printing speed is 100 to 200 mm / s. The problem of corrosion of the Ni-P layer is solved under the condition that the surface roughness is smoothed. When the optimum conditions are satisfied, corrosion does not occur even if the magnetic recording medium is left for 1000 hours in an environment of 80 ° C and 80% relative humidity.

〔The invention's effect〕

According to the present invention, there is provided a method of printing on a magnetic recording medium by passing a lamp current through a krypton lamp and irradiating a YAG laser pulse at a predetermined printing speed, wherein the YA
The pulse frequency of the G laser pulse is set within the range of 16 to 20 kHz, the lamp current is set within the range of 10 to 14 A, and the printing speed is set within the range of 100 to 200 mm / s. The initial surface roughness of the recording medium is smoothed, the light reflectance is increased, and the marking part can be identified by a principle different from the conventional printing. In addition, the problem of Ni-P corrosion and the deformation of the medium substrate It is possible to obtain a magnetic recording medium having excellent reliability by solving the above problems.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between frequency and surface roughness for the laser printing method, FIG. 2 is a diagram showing the relationship between printing speed and surface roughness for the laser printing method, and FIG. 3 is the principle of the laser printing device. It is a figure.

Claims (1)

(57) [Claims] 1. A lamp current is applied to a krypton lamp to YA.
A method of printing on a magnetic recording medium by irradiating a G laser pulse at a predetermined printing speed, wherein the pulse frequency of the YAG laser pulse is set within a range of 16 to 20 kHz,
A laser printing method for a magnetic recording medium, wherein the lamp current is set within a range of 10 to 14 A, and the printing speed is set within a range of 100 to 200 mm / s.