JP2003338093A - Disk type information recording medium and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the long-term traveling property of a head by uniformizing and flattening the thickness of an overcoating protective film for protecting the recording layer and dielectric layer of a disk type information recording medium, such as a magneto-optical disk. <P>SOLUTION: In forming the overcoating protective film on the disk formed with the recording layer and dielectric layer on the surface of a substrate, a process step of discharging a protective film material in the form of liquid from a discharge nozzle while moving the discharge nozzle inward across the inner peripheral surface of the disk from the central part in the radial direction of the disk and a process step of developing the discharged protective film material by rotating the disk at three stages of successively greater angular speeds are performed. The material shear resistance and rotational centrifugal force based on surface tension or the like are matched by the multi-mode to rotate the disk at three stages of the angular speeds, by which the thickness of the protective film is uniformized. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc type information recording medium and a method for manufacturing the same, and more particularly to a disc type information recording medium for recording an information signal in the fields of video and audio and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the rapid development of information networks in recent years, DVDs, C
As seen in D, HD, etc., the demand for higher density has become stronger than ever before. Under such circumstances, the magneto-optical disk has attracted attention as a personal small-sized general-purpose information recording medium, and a part thereof has already been commercialized.

In a magneto-optical disk, a recording layer and a dielectric layer whose magnetization is reversed are formed on a substrate, and contact stability, running property, and contact stability are provided on the magnetic layer for magnetic field modulation.
It is configured by sequentially stacking a protective film for ensuring moisture resistance and a sliding film. Optically transparent glass or plastic is used for the substrate, the recording layer is made of an amorphous alloy film such as TbFeCo, the dielectric layer is made of silane nitride, etc., the protective film and the sliding film are made of various resins, It is made of ceramic, inorganic material, etc.

Among them, the above-mentioned protective film and sliding film have the following properties: adhesion, flatness, smoothness, abrasion / wear resistance, mechanical strength,
Not only physical properties important for practical use such as moisture resistance are required, but also thinning and homogenization are required so as not to obstruct the magnetization reversal of the recording layer. An approach for thinning and uniformizing is, for example, (1) Japanese Patent Laid-Open No. 06-3020.
No. 20 discloses that the finish of the disk outer peripheral portion is improved by improving the tension of the resin, and (2) Japanese Patent Laid-Open No. 09-204697 discloses a wind flow by installing a suction jig on the outer peripheral portion of the disk. It is disclosed that the homogenization is promoted by (3) Japanese Patent Application Laid-Open No. 11-102544 discloses that the film thickness is related to the viscosity of the material (a considerably high viscosity range) and is controlled by a calculation formula. .

[0005]

Since the magneto-optical disk is a system in which recording pits for magnetic field reversal are formed by a magnetic head while rotating at high speed during recording / reproducing, extremely constant relative running property is required. Moreover, since the magnetic head moves up and down during recording, the flatness of the protective film is critically important in order to make the entire area of the disk an effective range.

However, the above-mentioned conventional techniques have not been sufficiently studied from such a point of view, and it is unavoidable that the thickness accuracy is lowered, the protrusions are generated, and the area margin is lost. Therefore, it is still a challenge to realize stable long-term running property and flatness of the protective film.

[0007]

In order to solve the above problems, the present invention has the following features. 1) The film thickness is made uniform by optimizing the rotational angular velocity of the disk when forming the protective film.

2) The formation of protrusions is suppressed by optimizing the total number of rotations of the disk when forming the protective film. 3) The film thickness is stabilized by controlling the atmospheric humidity within a certain range when forming the sliding film.

Regarding the above 1), if the viscosity range of the protective film material generally used is within the following range:
Equation (1) is established, and the film thickness D is inversely proportional to the angular velocity ω. Since the protective film material exhibits shear resistance due to surface tension when developed, it is necessary to devise the setting of the angular velocity ω in order to control the shear resistance value. Therefore, in the present invention, by rotating the disk at three stages of angular velocities, the material shear resistance and the rotational centrifugal force are matched, and the thickness of the protective film is made uniform. If the angular velocity is set to 2 steps,
In terms of matching between material shear resistance and rotational centrifugal force, no remarkable effect was obtained compared with the case of 1 step, and if 4 steps or more, it is advantageous from the aspect of tact surface and actual control system capacity. Less is. At that time, continuously discharging the protective film material while moving the discharge nozzle inward from the center part in the radial direction of the disc to the inner peripheral part of the disc is more advantageous for uniformizing the film than discharging at a fixed point. Is.

[0010]

[Equation 1] Regarding the above 2), the protrusions when forming the film are due to the fluctuation phenomenon of volatilization / scattering in the micro portion of the film material. If too much time is taken for developing the material, minute protrusions such as material traces may occur. Protrusions are generated on the entire surface of the film. Therefore, in the present invention, in order to prevent this, by controlling the total number of revolutions of the disk,
The time is suppressed while the protective film material is sufficiently developed.

Regarding the above 3), in the low-viscosity liquid generally used as the material of the sliding film,
The above equation (1) is related as in the following equation (2), and the film thickness D is related to the humidity RH.

[0012]

[Equation 2] The temperature factor also affects evaporation, but since a solvent with a high boiling point is generally used for the sliding film material, it does not so much during coating, and rather the humidity factor becomes dominant. Therefore, in the present invention, by controlling the atmospheric humidity, the volatility of the solvent is stabilized, the film thickness of the film material as a solute is stabilized, and its homogenization is realized by controlling the angular velocity and time of the disk. To do.

With these features, the accuracy of the film thickness uniformity is improved, the generation of protrusions is prevented, and the information recording medium having a wide recording area margin and having the continuous sliding resistance and running resistance is realized. It is a thing.

That is, the invention of claim 1 provides a disc type information recording medium in which an overcoat protective film and a sliding film are sequentially formed on a disc having a recording layer and a dielectric layer formed on the surface of a substrate. During manufacturing, the overcoat protective film is formed by sequentially ejecting a liquid protective film material between the radial center of the disc and the inner peripheral portion of the disc, and ejecting the ejected protective film material over the disc. It is characterized in that it is formed by performing a step of expanding by rotating at three angular velocities.

According to a second aspect of the present invention, in the method of manufacturing the disc-type information recording medium according to the first aspect, the liquid is protected while the discharge nozzle is moved inward from the central portion in the radial direction of the disc to the inner peripheral portion of the disc. A feature is that the film material is discharged. According to a third aspect of the present invention, in the method for manufacturing the disc-type information recording medium according to the first or second aspect, when the disc is a 2-inch disc, the protective film material is ejected in a radial direction of the disc. The central portion is at a position 19 to 21 mm from the center of the disc, the inner peripheral portion is at a position 10 to 12 mm from the center of the disc, the discharge amount of the protective film material is 450 to 850 μl, and the rotation of the disc is set to 3000 to It is characterized in that it is set to a predetermined low speed, medium speed, and high speed within a range of 8000 rpm, and is sequentially controlled so that the slope time between the respective speeds is 0.2 sec or less.

By combining these conditions, a uniform film can be formed on the entire surface of the disk. For a 2-inch disc, if the ejection position is out of the above range, uncoating may occur at the inner peripheral edge, swelling of the thickness may occur at the outer peripheral edge, and uniformity may not be achieved. When the position can be controlled with high accuracy, it is preferable that the ejection position is from 20 mm to 11 mm from the center of the disc. If the slope time is longer than 0.2 sec, the material may be diffused. Therefore, the slope time is set to 0.2 sec or less according to the capability of the control system.

According to a fourth aspect of the present invention, in the method for manufacturing the disc type information recording medium according to the third aspect, the discharge amount of the protective film material is 550 to 650 μl, and the rotation of the disc is within the range of 3000 to 6000 rpm. The predetermined low speed, medium speed, and high speed, and sequential control is performed so that the rotation time at each speed is 1 to 2 seconds.

According to a fifth aspect of the invention, in the method of manufacturing the disc-type information recording medium according to any one of the first to fourth aspects, the total number of rotations of the disc when forming the overcoat protective film is 350. It is characterized by being within rotation.

According to a sixth aspect of the present invention, in the method of manufacturing a disc-type information recording medium according to the fifth aspect, the total number of rotations of the disc is 150 to 250. According to a seventh aspect of the present invention, in the method for manufacturing the disc-type information recording medium according to any one of the first to sixth aspects, the protective film material has a viscosity at 25 ° C. of 100 mPa · s.
It is characterized by being the following ultraviolet-curable acrylic ester resin.

According to an eighth aspect of the invention, in the method of manufacturing the disc-type information recording medium according to the first aspect, the sliding film is
The discharge position of the liquid sliding film material is the inner circumference of the disc, the discharging amount of the sliding film material is 400 to 500 μl, and the disc is rotated at a predetermined angular velocity within the range of 5000 to 7000 rpm for 1 to 2 seconds. It is characterized in that it is formed by single-step control as described above.

According to a ninth aspect of the present invention, in the method for manufacturing a disc-type information recording medium according to the eighth aspect, the atmospheric humidity when forming the sliding film is set to 35 to 55% RH.

According to a tenth aspect of the present invention, in the method of manufacturing the disc type information recording medium according to the ninth aspect, the atmospheric humidity is set to 40 to 50% RH. The invention described in claim 11 is the method for manufacturing a disc-type information recording medium according to any one of claims 1, 8, 9, or 10, wherein the sliding film material has a kinematic viscosity of 300.
It is characterized in that it is a polydimethyl silicone of about 800 mm ² / s.

According to a twelfth aspect of the present invention, in the method of manufacturing the disc-type information recording medium according to any one of the first to eleventh aspects, the disc-type information recording medium is a magneto-optical disc. .

According to a thirteenth aspect of the present invention, there is provided a disc type information recording medium in which an overcoat protective film and a sliding film are sequentially formed on a disc having a recording layer and a dielectric layer formed on a substrate surface. The overcoat protective film is uniformly discharged by sequentially ejecting the liquid protective film material from the central portion in the radial direction of the disc to the inner peripheral portion of the disc, while rotating the disc at three sequentially increasing angular velocities within a predetermined range. The sliding film is formed by discharging a liquid sliding film material to the inner peripheral portion of the disk and rotating the disk at an angular velocity within a predetermined range.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG. FIG. 1 is a sectional view of a magneto-optical disk according to an embodiment of the present invention. In the figure, 1 is a substrate, which is an optically transparent material such as glass or plastic and is formed in an annular shape with a thickness of about 1 mm.
Reference numeral 2 is a dielectric film, and a silane nitride film or the like is formed with a thickness of about 0.2 μm by sputtering or the like. 3 is a magneto-optical film (recording layer), which is a material exhibiting magnetization reversal, such as Tb.
It is composed of alloys such as FeCo. Reference numeral 4 is a reflective film, and an aluminum film or the like is formed by sputtering or the like. Reference numeral 5 is a protective film, and 6 is a sliding film, which are laminated in this order in order to secure contact stability, running property, and moisture resistance.

The protective film 5 corresponds to the contact surface with the magnetic head for reversing the magnetization, and is made of a light / thermosetting resin such as acrylic or epoxy having a thickness of 2 to 10 μm from the viewpoint of moisture resistance, mechanical strength and adhesiveness. Formed to a degree. In the present invention, an acrylic resin such as a photopolymerizable acrylic ester compound can be preferably used.

The sliding film 6 is made of a material exhibiting lubricity. A polydimethyl silicone compound is desirable in combination with the acrylic resin used for the protective film 5. Sliding film 6 made of polydimethyl silicone compound
Since the affinity and the bonding relationship with the acrylic resin are likely to be strong, the repetitive running characteristics are dramatically improved as compared with the case where the sliding film 6 is made of another material. (Embodiment 1) A magneto-optical disk (hereinafter, simply referred to as a disk) as shown in FIG. 1 is formed by forming a dielectric layer, a magneto-optical layer and a reflective layer on a substrate by a commonly used thickness and film forming method. (Hereinafter, the substrate at this stage is referred to as a disk material), and a protective film and a sliding film are further formed thereon to prepare a plurality of types.

The substrate is made of polycarbonate material (diameter 5
0.8 mm (2 inches), thickness 0.6 mm) is used, and as the protective film material, a UV-curable acrylic ester resin (450 G, Nippon Kayaku Co., Ltd.) having a viscosity of 80 mPa · s at 25 ° C. is used. , The sliding film material has a kinematic viscosity of 500 mm ²
/ S of polydimethyl silicone (TSF456, Toshiba Silicone Co., Ltd.) was used in a solution of 0.35 wt% dissolved in n-heptane.

At the time of forming the protective film, the discharge nozzle is fixed at a distance of 12 mm from the center of the disc in the radial direction, and the disc material is rotated at a low speed while dropping 425 microliters of the above-mentioned protective film material. The protective film material was started and then rotated under the coating conditions (angular velocity ω, time sec) shown in Table 1 to spread the protective film material on the disk material, and then cured. The slope time between each angular velocity is 0.2 sec, and the curing condition is 0.65 J / c.
m ² .

In forming the sliding film, the discharge nozzle was fixed at a position of a distance of 12 mm from the center of the disk in the radial direction, and the above-mentioned sliding film material was dropped at 396 microliters while the disk material was spun at a low speed. Then, rotation was started, and then rotation was carried out at 5,500 rpm for 3.2 seconds, whereby the sliding film material was spread on the disk material, and then cured.

With respect to the formed protective film, the reflectance was measured with an optical instrument while making a stroke in the disk radial direction, and the thickness of the protective film (thickness ratio: sample No. 1) was measured.
The absolute value of the thickness obtained in 1. was set to 1, and the relative ratio) was calculated to evaluate the uniformity. The results are shown in Figure 2. As a comparative example, a commercially available 2 inch disk manufactured in the same manner as above was used except for the protective film and the sliding film.

[0032]

[Table 1] As can be seen from Table 1 and FIG. 2, in the disk of the comparative example,
The thickness (thickness ratio) of the protective film tends to increase from the inner peripheral portion to the outer peripheral portion of the disc, which is an undesirable surface for recording characteristics.

Among the disks produced in the first embodiment, sample No. 1 formed in a single mode with a constant angular velocity ω. 1 and No. 2 is the thickness of the protective film (thickness ratio)
Although the sloping rate at which is increased is improved, the essential tendency is almost the same as that of the comparative example.

On the other hand, the sample No. formed in the multi-mode (sequential control) in which the angular velocity is 3 steps.
In Nos. 3 to 6, the thickness (thickness ratio) of the protective film was substantially constant from the inner peripheral portion to the outer peripheral portion of the disc. This indicates that by forming the film in multi-mode (sequential control), the shear resistance of the liquid and the flow characteristics can be optimized, and a protective film having a uniform thickness can be obtained.

As described above, by adopting the multi-mode film forming conditions in which the three different angular velocities are mixed, it becomes possible to flatten the protective film from the inner peripheral portion to the outer peripheral portion of the disc, and to make the recording area It is possible to realize a disc-type information recording medium having excellent recording / reproducing characteristics, in which a margin can be effectively utilized. (Embodiment 2) A magneto-optical disk was manufactured by using the same disk material, protective film material, and sliding film material as in Embodiment 1 described above, except that the coating conditions for the protective film were changed.

As shown in Table 2, sample No. 7-8
Then, the discharge nozzle is fixed at a position of a distance of 12 mm from the center of the disc in the radial direction, and the disc material is rotated at a low speed while dropping the protective film material (referred to as a fixed point).
Then, it was rotated by a sequence control with an angular velocity of 3 steps. Sample No. In Nos. 9 to 12, the discharge nozzle was moved inward from the position 20 mm from the center of the disc to the position 11 mm, while the protective film material was continuously dropped (referred to as multiple points) while the disc material was moved at a low speed. At that time, the rotation was started, and then the rotation was performed by a sequence control in which the angular velocity was 3 steps. The produced disc was evaluated by counting the number of protrusions generated on its surface. The results are shown in Fig. 3.

[0037]

[Table 2] As can be seen from Table 2 and Fig. 3, the total number of revolutions is almost the same,
Sample No. different in discharge method. 7 (fixed point) and No. 9
When compared with (multipoint), there was a significant difference in the number of protrusions. This is considered to be because in the case of multi-point discharge, volatilization and scattering of the protective film material are suppressed in a micro area.

Even in the case of multi-point discharge, the sample No. 3 in which the rotation states of the respective steps are almost the same and the total number of rotations is different. 1
0 and No. 12 and Sample No. 12 having a large total number of rotations. In Sample No. 12, the protrusions were generated in the vicinity of the outer circumference and the inner circumference, but the total number of rotations was small. In No. 10, almost no protrusion was generated. This result shows that it is not desirable to spend too much time on the development of the protective film material, and it seems that the total number of revolutions of 350 revolutions or less is effective. Sample No. in which the discharge method and the total number of rotations (140 rotations) matched well. In No. 11, no protrusion was generated and a very smooth surface was obtained. On the other hand, even if the total number of rotations is within 350, the sample N of fixed point discharge is
o. In No. 8, the number of protrusions was relatively large and finely generated near the inner peripheral edge.

As described above, in the multi-mode in which the three different angular velocities are mixed, the total number of revolutions is set within 350 revolutions, and the film forming conditions for multipoint ejection are adopted,
A protective film with a smooth surface can be obtained, and it becomes possible to improve wear resistance against head crashes,
It is possible to realize a durable disc-type information recording medium. (Embodiment 3) A magneto-optical disk was manufactured by using the same disc material, protective film material, and sliding film material as in the above-mentioned Embodiment 1, and changing the coating conditions of the sliding film in various ways.

As the protective film, the multi-mode sample No. which gave the best result in the second embodiment was used. It was formed under the condition of 11. At the time of forming the sliding film, as in the first embodiment, the discharge nozzle is fixed at a position of a distance of 12 mm from the center of the disk in the radial direction, and the sliding film material is 396 microliters. While dripping, the disc material started to rotate at a low speed, and then 3.2 sec at 5500 rpm.
c rotated.

However, the atmospheric humidity in the vicinity of the spinner holding the disk material was set to various values within the range of 10 to 80% RH. For that purpose, the whole spinner was installed in a small room, humidified with a humidifier, and conditioned while monitoring with a thermo-hygrometer near the spinner. Also, in sample 12, 0.6w
A t% polydimethylsilicone solution was used and the temperature at the time of film formation was set to 20 ° C. In Sample 13, a 0.6 wt% polydimethylsilicone solution was used and the film formation temperature was set to 25 ° C.
C., and in Sample 14, a 0.4 wt% polydimethylsilicone solution was used, and the temperature during film formation was 20.degree.

With respect to the sliding film formed under each coating condition, the absorbance was measured from the difference spectrum using FT-IR (JASCO 8900) to determine the thickness (relative ratio) of the sliding film. The results are shown in Fig. 3.

The sample No. of FIG. 12 (diamond), sample No. 13 (square), sample No. 14 (triangle)
In Fig. 2, the thickness (relative ratio) of the sliding film is significantly different between the low-humidity atmosphere and the high-humidity atmosphere. This is based on the difference in the volatilization rate of the solvent in the polydimethylsilicone solution, which is the material for the sliding film. Seem. That is, the film quality is bulky (thick) because the solvent evaporates rapidly when dried at 10% RH.
On the contrary, the film quality is low (thin) under high humidity of 80% RH, and the film thickness is relatively constant around 50% RH. From this result, it can be seen that in order to control the variation of the film thickness within 5%, it is desirable to coat in a humidity-controlled atmosphere of around 50% ± 5 RH.

Although the effect of temperature on the film thickness is also observed (see Sample No. 12 and No. 13), it was found that it can be eliminated by changing the set value of the concentration (see Sample No. 13 and No. 14). ).

Further, the sliding characteristics of the disk provided with the sliding film formed under each coating condition were tested using a rotary tester equipped with a magnetic head. A disc with a sliding film formed under high humidity conditions produces squeaking noises, etc.
It was determined to be defective. The disc having the sliding film formed under the low humidity condition was judged to be defective because a film such as an adhesive film was observed on the head surface after the test. On the other hand, 50
The disk provided with the sliding film formed inside and outside the% RH did not show any phenomenon such as squeaking and surface adhesion even after 10 million passes of the magnetic head, and showed only good back-and-back running performance. .

As can be seen from the above, the thickness of the sliding film was stabilized by controlling the humidity atmosphere at the time of forming the sliding film to preferably 40 to 50% RH, generally ± 5% RH. It is possible to realize a disc-type information recording medium having excellent sliding characteristics such as abrasion resistance and running resistance.

The disk-type information recording medium provided with the protective film and the sliding film formed as described above not only has stable running properties, but also has no characteristic deterioration due to changes in temperature and humidity, and has a flatness. Also, recording and writing by the magnetic head becomes smooth, and the magnetic head arm is not damaged. Therefore, traveling performance, high durability (low friction and low damage), and high quality can be secured. Such an effect is particularly desired for the magneto-optical disk, but it goes without saying that it is also suitable for other optical disk type information recording media.

The above-mentioned materials for the substrate and the film are merely examples, and any material can be used as long as it has a function suitable for the purpose.
It is not limited to the above and can be used. It will be understood that, depending on the disc size, it is necessary to change the discharge rate of the film material, the angular velocity of the disc material, and the number of stages of the angular velocity.

[0049]

As described above, according to the present invention, 1) flattening of the protective film can be realized by the multi-mode film forming method in which the angular velocity of the disk is three stages.

2) By discharging the protective film material at multiple points and controlling the angular velocity and the total number of revolutions of the disk, the protective film can be smoothed and the crash running property can be prevented. 3) By controlling the atmospheric humidity during the formation of the sliding film within a certain range, the film thickness of the sliding film can be stabilized, good sliding characteristics and running resistance can be secured, and long life can be achieved. it can.

Therefore, it is possible to secure running property, high durability and high quality.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of an optical disc type information recording medium according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the thickness of a protective film formed by the method of the present invention and the disk radial position.

FIG. 3 is a diagram showing the relationship between the thickness of a sliding film formed by the method of the present invention and the atmospheric humidity during film formation.

[Explanation of symbols]

1 substrate 2 Dielectric film 3 Magneto-optical film (recording layer) 4 Reflective film 5 protective film 6 Sliding film

Claims (13)

[Claims] 1. When manufacturing a disc type information recording medium by sequentially forming an overcoat protective film and a sliding film on a disc having a recording layer and a dielectric layer formed on a substrate surface, the overcoat is formed. For the protective film, a step of ejecting a liquid protective film material between the central portion in the radial direction of the disc and the inner peripheral portion of the disc, and the ejected protective film material is rotated sequentially at three large angular velocities of the disc. A method of manufacturing a disc-type information recording medium, which is characterized in that it is formed by performing a step of developing it. 2. The disc-type information recording medium according to claim 1, wherein the liquid protective film material is ejected while the ejection nozzle is moved inward from the center of the disc in the radial direction to the inner periphery of the disc. Production method. 3. The disc is a 2-inch disc, the radial center of the disc for ejecting the protective film material is located at a position of 19 to 21 mm from the center of the disc, and the inner circumference of the disc is located at a position of 10 to 12 mm from the center of the disc. The discharge amount of the protective film material is 450 to 850 μl, the rotation of the disk is set to a predetermined low speed, medium speed, or high speed within the range of 3000 to 8000 rpm, and the slope time between the speeds is 0. The sequential control is performed so that the time is not more than 0.2 sec.
A method for manufacturing a disc-type information recording medium according to any one of 1. 4. The discharge amount of the protective film material is 550 to 650 μm.
and the rotation of the disk is 3000 to 6000 rp
4. The disc-type information recording according to claim 3, wherein predetermined low speed, medium speed and high speed within a range of m and sequential control are performed so that the rotation time at each speed is 1 to 2 seconds. Medium manufacturing method. 5. The disk-type information recording medium according to claim 1, wherein the total number of rotations of the disk when forming the overcoat protective film is within 350 rotations. Method. 6. The method for producing a disc-type information recording medium according to claim 5, wherein the total number of revolutions of the disc is 150 to 250. 7. The protective film material has a viscosity of 100 at 25 ° C.
7. The method for producing a disc-type information recording medium according to claim 1, wherein the method is an ultraviolet-curable acrylic ester resin having a mPa · s or less. 8. The sliding film has a discharge position of a liquid sliding film material as an inner peripheral portion of the disc, and a discharging amount of the sliding film material is 400 to 400.
Rotate the disc to 5000-700 with 500 μl.
2. The method for manufacturing a disc-type information recording medium according to claim 1, wherein the disk-type information recording medium is formed by single step control so as to rotate at a predetermined angular velocity within a range of 0 rpm for 1 to 2 seconds. 9. An atmospheric humidity of 35 when forming the sliding film.
9. The method for manufacturing a disc-type information recording medium according to claim 8, wherein the RH is about 55%. 10. The method for producing a disc-type information recording medium according to claim 9, wherein the atmospheric humidity is 40 to 50% RH. 11. The kinematic viscosity of the sliding film material is 300 to 800 m.
A polydimethyl silicone of m ² / s, Claim 1, Claim 8, Claim 9, or Claim 10.
A method for manufacturing a disc-type information recording medium according to any one of 1. 12. The method for manufacturing a disc-type information recording medium according to claim 1, wherein the disc-type information recording medium is a magneto-optical disc. 13. A disc type information recording medium comprising a disc having a recording layer and a dielectric layer formed on the surface of a substrate, and an overcoat protective film and a sliding film sequentially formed on the disc. While the liquid protective film material is sequentially dropped from the central portion in the radial direction of the disc to the inner peripheral portion of the disc, the disc is rotated uniformly at three large angular velocities within a predetermined range to be uniformly formed. The moving film is a liquid sliding film material dropped on the inner circumference of the disk.
A disc-type information recording medium, which is formed by rotating a disc at an angular velocity within a predetermined range.