JP2552345B2 - Method for manufacturing magneto-optical recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a magneto-optical recording medium, and more particularly to a technique for improving the adhesion between a substrate and a recording layer.

(Prior Art) A magneto-optical recording medium (hereinafter, also simply referred to as a recording medium) is actively researched and developed as a high density recording medium having a rewritable magnetic film.

Among the magneto-optical recording materials forming the magnetic film of such a recording medium, an amorphous alloy of a rare earth metal and a transition metal (hereinafter sometimes simply referred to as RE-TM alloy) has a magnetization direction. A perpendicular magnetic film oriented perpendicular to the film formation surface, a large coercive force (KOe), and relatively easy film formation by sputtering, vacuum evaporation or other deposition techniques. In terms of the above, research has advanced most and practical application has advanced.

However, the magnetic film made of the RE-TM alloy has low corrosion resistance (see, for example, Reference |: "Opto-Magnetic Disk" (edited by Shutake Imamura, published by Trikeps Co., Ltd., p. 427)) and has a magneto-optical effect. There is a drawback that (Kerr effect) is small.

Therefore, a recording layer composed of a protective film made of various materials sandwiching a magnetic film made of a RE-TM alloy is formed on the surface of the substrate to prevent corrosion of the magnetic film and to utilize multiple reflections of light. A structure for increasing the rotation angle of the upper Kerr is known (the above document: page 119).

First, prior to the description of the present invention, the conventional magneto-optical recording medium described above will be described.

FIG. 3 is an explanatory diagram showing a schematic cross section for explaining one configuration example of a conventional recording medium. In the figure, some hatching and the like showing the cross section are omitted.

As can be understood from FIG. 3, the recording layer 17 is formed by sequentially depositing the protective film 13a, the magnetic film 15 and the protective film 13b on the surface of the substrate 11 to form the recording medium 19. .

Of these, the substrate 11 is made of, for example, polycarbonate resin, glass, epoxy resin, or any other suitable material and has a disc shape.

Further, the protective films 13a and 13b are formed of, for example, SiO, SiO ₂ , AlN,
It was formed by depositing Si ₃ N ₄ , AlSiN, AlSiON or other protective film material. As already mentioned, this protective film can be deposited by, for example, a sputtering method, a vacuum evaporation method, or another method.
This is performed by a deposition technique depending on the material forming the protective film.

Furthermore, the magnetic film 15 is composed of the above-mentioned RE-TM alloy, and as such an alloy, for example, a Tb-Fe alloy, a Tb-Co alloy, a Tb-Fe-Co alloy or others, a combination of a rare earth metal and a transition metal is used. , Various are known.

In the recording medium 19 having such a structure, the protective film 13a disposed on the reading side of the medium 19 has a C / N ratio (Carrier / Nois).
Since it is a factor that affects the e Ratio (carrier to noise ratio), it is necessary to satisfy the following conditions.

Material with high refractive index to increase apparent Kerr rotation angle Wavelength of light used for writing and reading (usually 750-9
A material having a light-transmitting property at about 00 (nm)) A corrosion-resistant material capable of protecting the magnetic film from moisture, for example, in an environment where a medium is used. The protective film 13b is shown at least as described above. As long as the material satisfies the corrosion resistance, it may be composed of another material that does not satisfy the conditions that bring about the Kerr effect enhancement.

Further, as another structure of a conventionally known recording medium, there is also known a structure in which a reflective film is added to the above-described magnetic film 15 and protective films 13a and 13b to form a recording layer. This reflective film may be made of aluminum (Al), gold (Au), copper (C
Various reflective film materials including u) and titanium (Ti) are used.

As a structure including such a reflective film, first, as shown in FIG. 4A, a protective film 13a, a magnetic film 15, and a protective film 13b are provided.
Also known is a recording medium 25 having a structure in which a recording layer 23 is formed on the surface of the substrate 11 by sequentially depositing a reflection film 21 on the substrate 11.

In addition, usually, the above-mentioned reflective film is provided so as to sandwich the magnetic film between it and the substrate, and as another structure including the reflective film, as shown in FIG. 4 (B), on the surface of the substrate 11, Protective film 13
a, the magnetic film 15, the reflective film 21, and the protective film 13b are sequentially deposited,
A recording medium 29 having a structure in which the recording layer 27 is formed on the surface of the substrate 11 is also known.

In such a conventional recording medium, information is written by a thermomagnetic writing method using a laser beam focused to a spot diameter of about 1 (μm) and an external magnetic field, and is a perpendicular magnetic film as described above. Very high density recording of ⁸ (bit / cm ² ) is possible. Also, in principle,
It has an excellent feature that the erase and rewrite can be repeated almost infinitely.

(Problems to be Solved by the Invention) As described above, in the conventional magneto-optical recording medium, the substrate is made of synthetic resin such as polycarbonate resin or epoxy resin, or glass, and the surface of the substrate is recorded with various configurations. It is manufactured by forming layers. As we all know,
Among the above-mentioned substrate materials, the magneto-optical recording medium tends to be formed by using a synthetic resin which is superior in mechanical strength and cheaper than glass.

However, in the conventionally known magneto-optical recording medium manufacturing technology, cracks and peeling occur at the interface between the substrate made of synthetic resin and the recording layer, and stable characteristics of the magneto-optical recording medium over a long period of time can be obtained. There was a problem that it was difficult to maintain.

In view of the above-mentioned conventional problems, an object of the present invention is to improve the adhesion between a substrate made of a synthetic resin and a recording layer, thereby providing excellent characteristics for a long time. Therefore, it is to provide a manufacturing technique of a magneto-optical recording medium which can be stably exhibited.

(Means for Solving the Problem) In order to achieve this object, according to the method of manufacturing a magneto-optical recording medium of the present invention, after the surface of a substrate made of synthetic resin is reverse-sputtered, the surface of the substrate is formed. A method of manufacturing a magneto-optical recording medium for forming a recording layer is characterized in that reverse sputtering is performed in a mixed gas atmosphere of argon gas and nitrogen gas. In this case, the content of nitrogen gas in the mixed gas is 3 mol% or more (however, 100 mol% is not included)
Is.

Further, in carrying out the present invention, it is preferable that the recording layer is formed by contacting the surface of the substrate and depositing a protective film containing nitrogen.

(Operation) According to the method of manufacturing the magneto-optical recording medium of the present invention,
After reverse sputtering the surface of a substrate made of synthetic resin in a mixed gas atmosphere of argon gas and nitrogen gas with a nitrogen gas content of 3 mol% or more (however, not including 100 mol%), the surface of this substrate The recording layer is formed on the.

In this case, since the mixed gas contains the argon gas, the reverse sputtering gives a physical change to the surface of the substrate (for example, the formation of irregularities or sputter cleaning), and the mixed gas also contains the nitrogen gas, which causes the physical change. In addition to such changes, it is considered that chemical changes derived from nitrogen gas can be applied to the surface of the substrate. Therefore, it is considered that the above-mentioned improvement in adhesion can be achieved.

Further, as a conventionally known protective film, one containing nitrogen is excellent in terms of corrosion resistance, but a protective film containing nitrogen is formed by contacting the surface of the substrate which has undergone the above-described physical change and chemical change. It is considered that the adhesion can be synergistically improved by forming the recording layer by depositing.

(Example) An example of a method for manufacturing a magneto-optical recording medium according to the present invention will be described below with reference to the drawings. In addition, the examples described below will be described with preferred numerical examples within the scope of the present invention and other conditions, but these are merely examples,
It is to be understood that this invention is not limited to only these particular conditions.

In this embodiment, the case where the above-mentioned reverse sputtering is carried out in a mixed gas atmosphere of an inert gas such as argon gas and nitrogen gas will be specifically described. Further, in this embodiment, as an example of the structure of the recording medium, the above-mentioned third
The recording media according to the examples and comparative examples will be described with the structures shown in FIG.

In this example, in the total of the number of mols of argon gas and the number of mols of nitrogen gas, the ratio of the number of mols of nitrogen gas is expressed as the content in the unit of “mol%”, and the content is varied. A plurality of samples were prepared by changing the values.

<Description of Manufacturing Conditions> First, the manufacturing conditions of the recording medium as the sample according to the example will be described. In order to facilitate understanding of the description, refer to FIG. 3 described above for the stacking relationship of the recording media.

First, reverse sputtering is performed on the surface of the substrate 11 made of polycarbonate resin for 30 minutes under the conditions of the mixed gas pressure of 3 (mTorr) and the input power of 100 (W).

Then, a protective film 13a made of AlSiN is deposited on the surface of the substrate 11 subjected to the above-described reverse sputtering to a thickness of about 800 (Å). The film deposition conditions at this time are:
(W), the gas pressure of argon was 3 (mTorr).

Next, the composition ratio of terbium: iron: cobalt is 22: 70: 8.
Prepare the target for the magnetic film (the ratio of the number of atoms),
Under the same sputtering conditions as above, the magnetic film 15 is deposited on the surface of the protective film 13a with a thickness of about 800 (Å).

Then, under the same conditions as the protective film 13a described above,
A protective film with a thickness of about 1500 (Å) on the surface of the magnetic film 15 described above.
Put on 13b.

In this way, after the surface of the substrate is reverse-sputtered in the mixed gas atmosphere described above, the protective film 13a, on the surface of the substrate 11,
A magnetic layer 15 and a protective film 13b were sequentially deposited to form a recording layer 17, and a recording medium as a sample according to the example was obtained.

<Explanation of Adhesion Test> Next, the procedure of the adhesion test performed on the recording medium according to the above-described embodiment and the test results will be described.

Conventionally, various adhesion tests are known, but in this example, the measurement was performed according to the "Z / AD cycle test" defined in "JIS C5024". Hereinafter, the procedure of the adhesion test will be described with reference to the drawings.

The procedure of the adhesion test of this example will be described. A sample was held under two conditions of a temperature condition shown in FIG. 2A and a humidity condition shown in FIG. )But
The 40-hour test was conducted multiple times. Incidentally, FIG. 2 (A) is an explanatory diagram showing temperature (° C.) on the vertical axis and holding time (hours) on the horizontal axis, and FIG. 2 (B) shows relative humidity (%) on the vertical axis. FIG. 3 is an explanatory diagram showing the holding time (hours) on the horizontal axis.

With reference to these figures, regarding the adhesion test of 1 (cycle), the temperature condition and the humidity condition will be explained in correspondence with each time section. Holding time 0 to 2 (hour) Temperature 25 (° C) and relative humidity Maintain 90 (%) Hold time 2-5 (hours) Maintain relative humidity 90 (%) and raise temperature from 25 (° C) to 65 (° C) over 3 hours Hold time 5-8 ( Time) Temperature 65 (℃) and relative humidity 90 (%) are maintained Hold time 8 to 10 (hours) Relative humidity 90 (%) is maintained and 65 (℃) to 25 (℃) is maintained for 2 hours. Decrease temperature Hold time 10 to 12 (hours) Maintain relative humidity 90 (%) and raise temperature from 25 (℃) to 65 (℃) over 2 hours Hold time 12 to 15 (hours) Temperature Maintains 65 (℃) and relative humidity of 90 (%) Hold time 15 to 18 (hours) Maintains relative humidity of 90 (%) and cools from 65 (℃) to 25 (℃) over 3 hours Protection Time from 18 to 19.5 (time) Temperature 25 (° C.) and relative humidity of 90% to maintain the retention time from 19.5 to 20 (hours) Relative humidity 90% to 0%, and temperature 25
From (℃) to -10 (℃) over 0.5 hours, holding time 20 to 22 (hours) Temperature -10 (℃) and relative humidity 0 (%) holding time 22 to 22.5 (hours) Relative humidity from 0 (%) to 90 (%) and temperature -10
Increases from (℃) to 25 (℃) over 0.5 hours Holding time 22.5 to 24 (hours) Temperature 25 (℃) and relative humidity 90 (%) Holding time 24 to 27 (hours) Relative humidity Maintain 90 (%) and increase temperature from 25 (℃) to 65 (℃) over 3 hours Hold time 27 to 30 (hours) Maintain temperature 65 (℃) and relative humidity 90 (%) Hold time 30 to 32 (hours) Relative humidity 90 (%) is maintained, and temperature is lowered from 65 (℃) to 25 (℃) over 2 hours Hold time 32 to 34 (hours) Relative humidity 90 (%) ) Is maintained and the temperature is raised from 25 (℃) to 65 (℃) over 2 hours. Holding time 34 to 37 (hours) Maintaining temperature 65 (℃) and relative humidity 90 (%) Holding time 37 ~ 39 (hours) Relative humidity 90 (%) is maintained, and temperature is lowered from 65 (℃) to 25 (℃) over 2 hours Hold time 39 to 40 (hours) Temperature 25 (℃) and relative humidity 90 (%) was maintained.

Moreover, in the evaluation of this adhesion test, 1
Each time the (cycle) holding operation was performed, the sample surface was observed with the naked eye, and the presence or absence of cracks on the sample surface was examined.

FIG. 1 shows the number of trials (cycles) of the Z / AD cycle test performed until cracks were observed for a plurality of samples according to the example on the vertical axis, and the above-mentioned nitrogen gas content (cycle) on the horizontal axis. It is a characteristic curve figure which takes and shows.
In this example, the above-mentioned adhesion test was conducted up to 10 (cycles). Therefore, in the figure, when the crack occurrence was not observed even at the maximum number of trials of 10 (cycles), the measurement results are plotted with "●", and the crack occurrence is confirmed corresponding to each trial number. Is "○"
Is plotted at.

As can be understood from FIG. 1, when the content of nitrogen gas was 2 (mol%), cracking was observed at 3 (cycles). On the other hand, the nitrogen gas content should be 2
Gradually increase from (mol%), 3 (mol%), 4 (mol
%) And 5 (mol%) for the samples according to the examples, 5 (cycle), 7 (cycle) or 9 respectively.
Depending on the (cycle) and the content, the degree of improvement in adhesiveness became large. Furthermore, the nitrogen gas content is set to 10
In the case of (mol%) to 60 (mol%), no crack was observed even when the above-mentioned adhesion test was repeated 10 (cycles).

For comparison, a sample according to Comparative Example 1 was prepared under the same conditions as the sample according to the example except that the reverse sputtering was not performed in the manufacturing procedure described above, and the Z / AD cycle test was done.

In addition, for further comparison, among the manufacturing procedures described above,
A sample according to Comparative Example 2 was prepared under the same conditions as the sample according to the example except that reverse sputtering was performed in an argon gas atmosphere, and a Z / AD cycle test was performed in the same manner as described above.

As a result, in the sample according to Comparative Example 1, 1 (cycle)
After performing the exposure operation of No. 3, cracking was observed. Further, in the sample according to Comparative Example 2, crack generation was observed after 3 (cycle) holding scans.

As can be understood from the test results and comparative results according to this example, in a mixed gas of argon gas and nitrogen gas (the content of nitrogen gas is 3 mol% or more (however, 100 mol% is not included)) atmosphere. In the method of the present invention, in which the surface of the substrate made of synthetic resin is reverse-sputtered and then the recording layer is formed, the adhesion can be improved as compared with the conventional technique. That is, when the reverse sputtering is performed in the mixed gas atmosphere described above, the adhesion can be further improved as compared with the case where the reverse sputtering is performed using only the inert gas. Further, since the protective film 13a described above is made of a material containing nitrogen, it is considered that the adhesion is further improved.

Although the embodiments of the present invention have been described in detail above, it is clear that the method of the present invention is not limited to the conditions of the above-described embodiments.

For example, in the above-described embodiments, a polycarbonate substrate is exemplified as the substrate made of synthetic resin, and a protective film made of AlSiN is illustrated as an example of a constituent component which is in contact with the substrate and constitutes the recording layer.

However, in producing a recording medium by performing reverse sputtering in the above-mentioned mixed gas atmosphere, the same effects as those of the above-described embodiment can be expected without being limited to the materials of the constituent components in contact with the substrate. .

Further, in the present invention, it is preferable to use a mixed gas of an inert gas and a nitrogen gas in reverse sputtering the surface of the substrate, and to make the material in contact with the substrate contain nitrogen. This is also effective when the material in contact with the substrate is a material containing no nitrogen.

When reverse sputtering is performed using this mixed gas, AlN, Si ₃ N ₄ or A instead of AlSiN described above is used as a protective film.
A material containing nitrogen such as lSiON may be used.

Further, the method of the present invention is not limited to the recording medium having the structure shown in FIG. 3, and the effect can be obtained, and a recording medium having a recording layer including a reflective film, or other various lamination relationships can be used. Even when applied to a recording medium that has
The same effect as that of the above-described embodiment can be expected.

It is obvious that these materials, arrangement relations, numerical conditions and other specific conditions described above can be changed and modified in any suitable design within the scope of the object of the present invention.

(Effect of the Invention) As is clear from the above description, according to the method for manufacturing a magneto-optical recording medium of the present invention, a mixed gas of argon gas and nitrogen gas (content of nitrogen gas is 3 mol% or more (however, , 100 mol% are not included.)) In the atmosphere, the surface of the substrate made of synthetic resin is reverse-sputtered, and then the recording layer is formed on this surface. For this reason, by causing a physical change or a chemical change by the above-mentioned gas, it is possible to improve the adhesion between the substrate and the recording layer.

Therefore, by applying the method of the present invention, it is possible to improve the adhesiveness between the recording layer and the substrate made of a synthetic resin which is excellent in mechanical strength and is inexpensive, and in turn, has excellent characteristics. It can be expected to provide a magneto-optical recording medium capable of stably exhibiting the above characteristics over a long period of time.

[Brief description of drawings]

FIG. 1 is a characteristic curve diagram showing the measurement results of the adhesion test for explaining the embodiments of the present invention, and FIGS. 2 (A) and 2 (B) show the conditions of the adhesion test performed in the examples. For the purpose of explanation, an explanatory view showing the temperature condition or the humidity condition in 1 (cycle) in correspondence with the holding time, and FIG. 3 shows the structure of the sample prepared in the example of the present invention
In order to explain the prior art, an explanatory view shown by a schematic substrate cross section, and FIGS. 4 (A) and 4 (B) are for explaining the prior art.
It is explanatory drawing shown similarly to FIG. 11 ... Substrate, 13a, 13b ... Protective film, 15 ... Magnetic film, 17,23, 27 ... Recording layer 19, 25, 29 ... Magneto-optical recording medium, 21 ... Reflective film.

Continuation of the front page (56) Reference JP 63-229642 (JP, A) JP 63-217546 (JP, A) JP 60-191451 (JP, A) JP 63-306553 (JP , A) JP 63-70946 (JP, A) JP 1-107340 (JP, A)

Claims (2)

(57) [Claims] 1. A method of manufacturing a magneto-optical recording medium, comprising forming a recording layer on the surface of a substrate after the surface of the substrate made of synthetic resin is reverse-sputtered, wherein the reverse sputtering is performed with a nitrogen gas content of 3 mol%. A method for manufacturing a magneto-optical recording medium, which is performed in a mixed gas atmosphere of argon gas and nitrogen gas as described above (however, not including 100 mol%). 2. The method for manufacturing a magneto-optical recording medium according to claim 1, wherein the recording layer is formed by contacting the surface of the substrate with a protective film containing nitrogen. Manufacturing method of magneto-optical recording medium.