JP2003338084A - Recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording medium wherein warpage due to a change in temperature and humidity is prevented and reduction of manufacturing time, reduction of manufacturing costs and enhancement of productivity can be realized. <P>SOLUTION: In the recording medium (for example, a magneto-optical disk), a recording layer 2 is formed on one surface of a substrate 1 made of polycarbonate, for example, and a moisture non-permeable film 3 and a temperature deformation preventing film 4 are successively formed on the other surface of the substrate 1. The recording layer 2 is formed by film-depositing and successively laminating a lower base layer 2d, a magnetic recording layer 2c, a reflection layer 2b and an upper base layer 2a by a sputtering method. The upper and the lower base layers 2a and 2d are made of SiN, for example, the magnetic recording layer 2c is made of TbFeCo, for example, and the reflection layer 2b is made of aluminum, for example. The moisture non-permeable film 3 is formed by film-depositing SiN, for example, by a sputtering method. SiN has light transmissivity and moisture non-permeability. The temperature deformation preventing film 4 is formed by applying a modacrylic UV curing resin, for example, by a spin coating method and then curing the resin by UV irradiation. <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 recording medium using a resin substrate, and more specifically, it prevents warpage due to changes in temperature and humidity of the environment, shortens film formation time, and reduces manufacturing cost. Recording media that improve productivity (for example, disks such as magnetic disks, magneto-optical disks, and optical disks)
Regarding

[0002]

2. Description of the Related Art Resin substrates are used for optical disks and magnetic disks. As an example thereof, FIG. 9 shows a schematic sectional view of a conventional magneto-optical recording medium. In a conventional magneto-optical recording medium (hereinafter, also simply referred to as a medium), a recording layer 2 and a protective coating layer 5 are formed in this order on one surface of a substrate 1 made of a synthetic resin such as polycarbonate or polyacrylate. A hard coat layer 6 is formed on the other surface to prevent damage to the substrate 1. Recording layer 2 is base layer 2
d, the magnetic recording layer 2c, the upper layer 2a, and the reflective layer 2b. The upper layer 2a and the base layer 2d are each made of a moisture impermeable inorganic substance, and the hard coat layer 6 is made of a synthetic resin.

In the conventional medium, the medium warps due to changes in temperature and humidity of the storage environment or the use environment. When the temperature changes, the medium warps like a bowl due to the bimetal effect due to the difference in the thermal expansion coefficients of the upper layer 2a or the underlayer 2d and the substrate 1. When the humidity changes, moisture does not flow in and out on the lower surface of the substrate 1 that is in contact with the underlying layer 2d, but moisture does flow in and out of the substrate 1 and the hard coat layer 6.
This is because the substrate 1 and the hard coat layer 6 are made of synthetic resin, and the synthetic resin material generally has water absorbability and moisture permeability. Therefore, if the humidity changes,
Due to this phenomenon difference, the water distribution inside the medium becomes temporarily non-uniform, and the higher the water content expands, the more the medium warps.

When the medium is extremely warped, there is a problem that recording / reproducing cannot be performed. Therefore, Japanese Patent Laid-Open No.
Japanese Patent Application Laid-Open No. 001-216685 discloses a magneto-optical recording medium that prevents a warp due to humidity and a change in humidity by providing a moisture-impermeable warp prevention film on a surface of a substrate opposite to a recording layer formed of a plurality of layers. ing. The warp prevention film is made of a moisture impermeable inorganic material such as silicon nitride, silicon oxide, or silicon carbide. The thickness of the warpage prevention film required to prevent the warpage of the medium due to both temperature and humidity is
The product of the thickness of each layer of the recording layer and the Young's modulus of each layer of the recording layer is determined so as to be equal to the product of the thickness of the warp prevention film and the Young's modulus of the warp prevention film.

[0005]

The warp prevention film of the disclosed medium requires a thickness of 150 to 200 nm. In addition, since the warp prevention film is formed by sputtering an inorganic substance, it takes a long time to form the film, which causes a problem that the manufacturing cost is high and the productivity is very poor.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a moisture-impermeable film made of an inorganic material and a temperature deformation preventing film made of an organic material so that the storage environment or A recording medium capable of preventing warpage even when the temperature and humidity change in the use environment, shortening the film formation time, reducing the manufacturing cost, and improving the productivity (for example, a magnetic disk, It is to provide a disc such as a magneto-optical disc and an optical disc.

Another object of the present invention is to combine an inorganic moisture-impermeable film having a minimum necessary thickness with an organic temperature-deformation-preventing film that is easy to form, so that it can be used in a storage environment or a use environment. A recording medium (for example, a magnetic disk, a magneto-optical disk) capable of preventing warpage even when the temperature and humidity change, shortening the film formation time, reducing the manufacturing cost, and improving the productivity. , Optical discs and the like).

[0008]

A recording medium according to a first invention is a recording medium having a recording layer on one surface of a substrate,
A moisture impermeable film made of an inorganic material provided on the other surface of the substrate, and a temperature deformation preventing film made of an organic material provided on the surface of the recording layer and / or the moisture impermeable film. And

A recording medium according to a second aspect of the present invention is a recording medium having a recording layer on one surface of a substrate, wherein two moisture-impermeable membranes made of an inorganic material are provided on the other surface of the substrate, and the two layers. And a temperature deformation prevention film made of an organic substance interposed between the moisture impermeable films.

A recording medium according to the third invention is the first or second recording medium.
In the recording medium according to the invention, the film thickness of the moisture impermeable film is 1
It is characterized by being 0 nm or more and 80 nm or less.

The recording medium according to the fourth aspect of the present invention is the first to third aspects.
In the recording medium according to any one of the inventions, the temperature deformation prevention film has a film thickness of 2 μm or more and 8 μm or less.

In the case of the first invention, moisture does not flow into and out of the substrate from the moisture impermeable film side. Therefore, the recording medium does not warp when the humidity changes. Further, due to the presence of the temperature deformation prevention film, the recording medium does not warp even when the temperature changes. Moreover, since the temperature deformation prevention film is made of an organic material that can be easily formed, it is possible to shorten the film forming time, reduce the manufacturing cost, and improve the productivity.

According to the second aspect of the invention, moisture does not flow into and out of the substrate from the two layers of the moisture impermeable film. Therefore, the recording medium does not warp when the humidity changes. Furthermore,
Since the temperature deformation prevention film is interposed between the two moisture impermeable films, the recording medium does not warp even when the temperature changes. Moreover, since the temperature deformation prevention film is made of an organic material that can be easily formed, it is possible to shorten the film forming time, reduce the manufacturing cost, and improve the productivity.

In the case of the third invention, the lower limit of the thickness of the moisture impermeable film is set to 10 nm. If it is less than 10 nm,
Impervious effect cannot be obtained. On the other hand, the upper limit of the thickness of the moisture impermeable film is 80 nm. If it exceeds 80 nm, the effect is the same, but it takes a long time to form the film to the extent of impairing the practicality.

As a result, the thickness of the moisture impermeable film made of the same inorganic material as that of the conventional magneto-optical recording medium (see Japanese Patent Laid-Open No. 2001-216685) is 1/20 to 2 / thickness as compared with the warp prevention film made of the same inorganic material. Since it is possible to make the thickness as thin as about 5, the time required for film formation can be significantly reduced. Therefore, the manufacturing cost is reduced and the productivity is improved.

In the case of the fourth invention, the lower limit of the thickness of the temperature deformation preventing film is 2 μm. If it is less than 2 μm, the effect of preventing temperature deformation cannot be obtained. On the other hand, the upper limit of the thickness of the temperature deformation prevention film is 8 μm. If the thickness exceeds 8 μm, not only the effect of preventing temperature deformation is not obtained, but also the temperature deformation preventing film is made of an organic material having water absorbability and hygroscopicity, and therefore there is a risk of water absorption and expansion.

Since a temperature deformation prevention film made of an organic material that is easy to form is provided, a warp prevention film made of an inorganic material of a conventional magneto-optical recording medium that requires a thick film to prevent warpage due to temperature change can be formed. In comparison, the time required for film formation can be significantly reduced. Therefore, the manufacturing cost is reduced,
Productivity is also improved.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. (Embodiment 1) FIG. 1 shows a schematic cross-sectional view of a magneto-optical recording medium (for example, a magneto-optical disk) according to Embodiment 1 of the present invention. In the figure, 1 is a substrate, 2 is a recording layer, 3 is a moisture impermeable film, and 4 is a temperature deformation preventing film. The recording layer 2 is formed on one surface of the substrate 1 The moisture impermeable film 3 and the temperature deformation preventing film 4 are sequentially formed on the surface.

The substrate 1 is made of polycarbonate, for example. As the recording layer 2, a base layer 2d, a magnetic recording layer 2c, a reflective layer 2b, and an upper layer 2a are formed by a sputtering method and are sequentially laminated. The upper layer 2a and the base layer 2d are made of, for example, Si.
The magnetic recording layer 2c is made of, for example, TbFeCo, and the reflective layer 2b is made of, for example, aluminum.
The moisture impermeable film 3 is also formed of, for example, SiN by a sputtering method. SiN has optical transparency and moisture impermeability. The temperature deformation prevention film 4 is formed by applying, for example, a modified acrylic ultraviolet curable resin by a spin coating method and then curing it by irradiating with ultraviolet rays. The composition of the acrylic ultraviolet curable resin is the same as the composition of the hard coat layer formed for the purpose of preventing damage to the substrate of the conventional magneto-optical recording medium.

In the recording medium according to the present invention (for example, a disk such as a magnetic disk, a magneto-optical disk, an optical disk, etc.), the moisture impermeable film and the temperature deformation preventing film preferably have thicknesses of 10 to 80 nm and 2 to 8 μm, respectively. Within the range.
The reason will be described below.

FIG. 2 is a schematic cross-sectional view showing how the warp of a magneto-optical recording medium (for example, a magneto-optical disk) is measured. In the figure, 10 is a magneto-optical recording medium (for example, a magneto-optical disk), 20 is a displacement measurement sensor for measuring the displacement of the warp of the magneto-optical recording medium 10, and 30 is a holding portion for holding the magneto-optical recording medium 10. Show. A-A indicates the center of the magneto-optical recording medium 10, and r1 indicates the magneto-optical recording medium 1.
0 radius (43 mm), r2 is the measurement radius (about 38 mm) from AA to the center of the displacement measuring sensor 20,
3 shows the pressing radius (15 mm) from AA to the outer diameter of the pressing part 30. With respect to the warp of the magneto-optical recording medium 10, the displacement sensor 20 measures the displacement generated at the measurement radius r2 when the central portions of both surfaces of the magneto-optical recording medium 10 are sandwiched between the pressing portions 30 and the temperature or humidity is changed. taking measurement. The warp of the magneto-optical recording medium 10 is a positive warp when the magneto-optical recording medium 10 warps upward.

FIG. 3 is a schematic cross-sectional view of a magneto-optical recording medium (for example, a magneto-optical disk) used for measuring the moisture impermeable effect without forming a temperature deformation preventing film. For the moisture impermeable film 3, two types of samples of SiN and SiO ₂ are used, and the substrate 1 and the upper layer 2 are used.
The constituent materials of a, the reflection layer 2b, the magnetic recording layer 2c, and the underlayer 2d were the same as those of the magneto-optical recording medium (hereinafter, also simply referred to as medium) of FIG. FIG. 4 is a graph showing the correlation between the film thickness of the moisture impermeable film of FIG. 3 and the humidity deformation coefficient. The humidity deformation coefficient in the figure is obtained by changing the film thickness of the moisture impermeable film 3 variously and changing the relative humidity by 10% (hereinafter referred to as 10% RH).
The displacement of the warp generated in the medium is shown and calculated by the equation (1).

Humidity deformation coefficient = tan ⁻¹ (x / (r2-r3)) × (180 / 3.14) / 10 ³ (1) where x is the displacement of the warp of the medium per 10% RH (μ
m). That is, the humidity deformation coefficient in FIG. 4 converts the displacement x (μm) generated in the measurement radius r2 into the warp of the entire medium.

The thickness of each layer at the time of this measurement is the substrate 1
Is 0.6 mm, the upper layer 2a is 15 nm, and the reflective layer 2b is 4
0 nm, the magnetic recording layer 2c is 100 nm, and the underlayer 2
d is 65 nm. The recording layer 2 is made of impermeable Si.
Since it has a sandwich structure of the N upper layer 2a and the underlayer 2d, moisture does not penetrate from the recording layer 2 to the substrate 1.

As shown in FIG. 4, when the film thickness of the moisture impermeable film 3 is 20 nm or more, the humidity deformation coefficient surely becomes zero. It can be seen that the warp can be prevented. Therefore, the impermeable membrane 3
The lower limit of the film thickness of can be determined to be 10 nm.

Next, the upper limit of the film thickness of the moisture impermeable film 3 will be described. FIG. 5 is a graph showing the correlation between the film thickness of the moisture impermeable film of FIG. 3 and the reflectance. The vertical axis in the figure represents the reflectance at the interface between the substrate 1 (polycarbonate) and the impermeable film 3 when the film thickness of the impermeable film 3 is changed and laser light is irradiated from the impermeable film 3 side. Is calculated. However, non-moisture permeable membrane 3, when the SiN refractive index of SiN and 2.0, in the case of SiO ₂ is calculated reflectivity refractive index of SiO ₂ as 1.5.

As is apparent from FIG. 5, the reflectances of the substrate 1 and the moisture impermeable film 3 are periodically sinusoidal as the thickness of the moisture impermeable film 3 changes. This is because the reflectivity is large in the mountain portion of the sine curve, and therefore the magnetic recording layer 2
It means that the laser light reaching c is reduced. Therefore, the film thickness of the portion where the reflectance is small, that is, where the sine curve has a valley may be appropriately selected. However, since the moisture-impermeable film 3 is formed by sputtering an inorganic substance, when the moisture-impermeable film 3 is a thick film, it takes a very long time to form the film, and the manufacturing cost and the productivity are significantly deteriorated. For this reason, the moisture impermeable film 3 that is as thin as possible is desired. Therefore, the thinnest film thickness where the sine curve shows a valley is determined as the upper limit of the film thickness of the moisture impermeable film 3. Then, in the case of SiN, the film thickness is 0n.
In the case of SiO ₂ , the film thickness is about 60 nm. However, as described above, the moisture-impermeable film 3 needs to have a thickness of 10 nm or more in order to obtain the moisture-impermeable effect, and in this case, the latter of about 60 nm can be selected. However, 20 nm
The upper limit of the film thickness of the moisture impermeable film 3 can be determined to be 80 nm in consideration of the manufacturing error.

From the above, the film thickness of the impermeable film of the recording medium (for example, a disk such as a magnetic disk, a magneto-optical disk, an optical disk) according to the present invention can be preferably 10 nm or more and 80 nm or less. Preferably 20
It is 60 nm or more and 60 nm or less.

Since the moisture-impermeable film 3 is made of an inorganic material having a slow film formation rate as compared with the magnetic metal material, the thickness of the moisture-impermeable film 3 which obtains the moisture-impermeable effect is changed from that of the inorganic material of the conventional medium as described above. The film formation time can be greatly reduced by making the film thickness as much as 1/20 to 2/5 thinner than the warp prevention film. Therefore, the manufacturing cost is reduced and the productivity is improved. However, if the moisture-impermeable film 3 is made thin, the medium warps when the temperature changes. Therefore, it is necessary to prevent the warp of the medium due to the temperature change by further providing the temperature deformation preventing film 4 on the surface of the moisture impermeable film 3 as shown in FIG. The description will be given below.

FIG. 6 is a graph showing the correlation between the film thickness of the temperature deformation preventing film and the temperature deformation coefficient. The temperature deformation coefficient in the figure is 0, 3, 5, 6, 9 and 15 μ for the temperature deformation prevention film 4.
The displacement of the warp generated in the magneto-optical recording medium (FIG. 1) of the first embodiment when the temperature is changed by 10 ° C. by changing m to m is shown.

The thickness of each layer at the time of this measurement is the substrate 1
Is 0.6 mm, the upper layer 2a is 15 nm, and the reflective layer 2b is 4
0 nm, the magnetic recording layer 2c is 100 nm, and the underlayer 2d is 6 nm.
5 nm, and the moisture impermeable film 3 is 60 nm. In the measurement of FIG. 6, only moisture impermeable film 3 is made of SiN.

The warp of the medium generated when the film thickness of the temperature deformation preventing film 4 is 0 μm causes the recording layer 2, the substrate 1 and the moisture impermeable film 3 to expand as the temperature rises, but the substrate 1 expands. Is the largest, followed by the recording layer 2 and the moisture impermeable film 3.

First, considering expansion in the case of only the substrate 1 and the recording layer 2, the expansion of the recording layer 2 does not follow the expansion of the substrate 1. Therefore, since the substrate 1 expands more, the medium warps positively. Next, considering the expansion in the case of only the impermeable membrane 3 and the substrate 1, the substrate 1
Also, the same phenomenon as in the case of only the recording layer 2 occurs, and in this case, the medium warps in a negative direction.

From the above, when the structure of the substrate 1, the recording layer 2 and the moisture impermeable film 3 is considered, the expansion of the recording layer 2 is the expansion of the moisture impermeable film 3 with respect to the expansion of the substrate 1. Therefore, the difference in expansion between the recording layer 2 and the moisture impermeable film 3 is equivalent to the fact that only the recording layer 2 side of the substrate 1 works. That is,
As described above, the same phenomenon occurs when the expansion of the recording layer 2 does not follow the expansion of the substrate 1, and the substrate 1 expands to a greater extent, so that the medium warps positively.

When the film thickness of the temperature deformation preventing film 4 is 5 μm, each of the recording layer 2, the substrate 1, the moisture impermeable film 3 and the temperature deformation preventing film 4 expands as the temperature rises.
And the expansion of (the moisture impermeable film 3 + the temperature deformation prevention film 4) are equal. That is, the expansion is balanced on both sides of the substrate 1. Therefore, since the expansion difference does not occur on one side of the substrate 1 due to the expansion of the substrate 1, the medium does not warp with respect to the temperature change.

When the thickness of the temperature deformation preventing film 4 is t (μm) larger than 5 μm, the expansion coefficient is balanced on both surfaces of the substrate 1 as described above, and further (t-5) μ.
The system is the same as that of the case where the m temperature-preventing film is provided. Therefore, it is considered that the temperature deformation prevention film 4 expands more than the recording layer 2, and the medium warps positively.

From the above, it can be seen in FIG. 6 that the maximum temperature deformation prevention effect is obtained when the film thickness of the temperature deformation prevention film 4 is 5 μm. Therefore, it can be determined that the optimum film thickness of the temperature deformation prevention film 4 is 5 μm. Further, from the figure, it is considered that the film thickness of the temperature deformation prevention film 4 that can obtain a sufficient temperature deformation prevention effect is 5 ± 3 μm, that is, 2 to 8 μm. Therefore, the lower limit value of the film thickness of the temperature deformation preventing film 4 can be determined to be 2 μm, but regarding the upper limit value of 8 μm, it is necessary to further consider the following.

That is, since the temperature deformation prevention film 4 is made of a modified acrylic UV-curable resin of an organic substance, it has water absorbency and hygroscopicity. Therefore, the thicker the temperature deformation preventing film 4 is, the more the water absorption and expansion occur, so that the medium may be warped.

FIG. 7 is a graph showing the correlation between the film thickness of the temperature deformation prevention film and the humidity deformation coefficient. The humidity deformation coefficient in the figure is 0, 3, 5, 6, 9 and 15μ for the temperature deformation prevention film 4.
The displacement of the warp generated in the magneto-optical recording medium of the first embodiment (FIG. 1) when changed to m and changed by 10% RH is shown.

When the thickness of the temperature deformation prevention film 4 is up to 6 μm,
Warpage of medium against humidity is small. However, when the film thickness of the temperature deformation prevention film 4 is 9 μm and 15 μm, the medium warps positively because the temperature deformation prevention film 4 causes water absorption expansion. From this result, as the temperature deformation prevention film 4 becomes thicker,
It can be understood that moisture absorption rapidly increases.

When the film thickness of the temperature deformation preventing film 4 is 8 μm, the deformation of the medium is 10 μm when the humidity changes by 10% RH, and the deformation occurs in the operating environment defined by the ISO 90 mm cartridge magneto-optical disk standard. Humidity change width 3% RH ~
Even at 85% RH, the maximum change is only 82 μm. When the film thickness of the temperature deformation preventing film 4 is 9 μm, the medium deformation occurs by 20 μm due to the change of 10% RH, and the humidity change width in the ISO operating environment also changes by 164 μm, which greatly exceeds the standard of 100 μm. Therefore, the upper limit of the film thickness of the temperature deformation prevention film 4 is preferably 8 μm as described above.

From the above, the film thickness of the temperature deformation preventing film of the recording medium (for example, a disk such as a magnetic disk, a magneto-optical disk, an optical disk) according to the present invention is preferably 2 μm.
It can be 8 μm or less and more preferably 5 μm or less.
It is about μm.

Compared with the conventional anti-warp film made of an inorganic material of a medium, which requires a thick film to prevent warpage due to temperature change, the temperature-deformation prevention film 4 is made of an organic material which can be easily formed. This time can be significantly reduced. Therefore, the manufacturing cost is reduced and the productivity is improved.

In the magneto-optical recording medium (for example, magneto-optical disk) according to the first embodiment, the temperature deformation preventing film is provided on the surface of the moisture impermeable film, but the present invention is not limited to this, and the recording layer and / or Alternatively, it may be provided on the surface of the impermeable membrane.

(Embodiment 2) FIG. 8 shows a schematic sectional view of a magneto-optical recording medium (eg, a magneto-optical disk) according to Embodiment 2 of the present invention. A magneto-optical recording medium (for example, a magneto-optical disk) has a recording layer 2 including an underlayer 2d, a magnetic recording layer 2c, a reflective layer 2b and an upper layer 2a formed on one surface of a substrate 1. On the other hand, on the other surface of the substrate 1, a moisture impermeable film 31, a temperature deformation preventing film 4, and a moisture impermeable film 32 are formed in this order. Here, both the moisture impermeable films 31 and 32 are made of Si.
The constituent materials of the other layers and the film forming method of each layer are the same as those in the first embodiment, and thus the description thereof will be omitted. However, regarding the thickness of each layer, the substrate 1 has a thickness of 0.6 mm, the upper layer 2a has a thickness of 15 nm, and the reflective layer 2b has a thickness of 40 mm.
nm, the magnetic recording layer 2c is 100 nm, and the underlayer 2d is 65 nm.
nm, the moisture impermeable films 31 and 32 are each 40 nm, and the temperature deformation preventing film 4 is 3 μm.

Also in the magneto-optical recording medium (for example, magneto-optical disk) according to the second embodiment, the recording layer 2 formed on one surface of the substrate 1 includes the moisture impermeable upper layer 2a of SiN and the underlying layer 2d. Since it has a sandwich structure, no moisture penetrates from the recording layer 2 to the substrate 1. On the other hand, since the moisture impermeable layers 31 and 32 having moisture impermeable property with the temperature deformation prevention film 4 made of an organic material interposed are formed on the other surface of the substrate 1, the light according to the first embodiment Similar to a magnetic recording medium (for example, a magneto-optical disk), it is possible to prevent the medium from warping due to both temperature and humidity changes. Further, by combining a thin moisture impermeable film made of an inorganic material and a temperature deformation preventing film made of an organic material, which can be easily formed, the time required for the film formation can be greatly reduced. Therefore, the manufacturing cost is reduced and the productivity is improved.

Although polycarbonate is used as the substrate in the first and second embodiments, the present invention is not limited to this, and polyacrylate or other synthetic resin may be used.

The upper layer 2a and the base layer 2d are made of Si.
Although N is used for the description, it is not limited to this, and silicon oxide,
Silicon carbide or mixtures thereof may be used.

The magnetic recording layer is made of an amorphous material of TbF.
Although description has been made using eCo, the present invention is not limited to this, and Co, F
Metals such as e, Ni, Co-Fe, and Ni-Co or oxides thereof may be used.

Further, although SiN or SiO ₂ is used for the moisture impermeable film, the moisture impermeable film is not limited to this, and silicon carbide or a mixture thereof may be used.

Furthermore, although the organic modified acrylic UV-curable resin is used for the temperature deformation preventing film, the invention is not limited to this, and other acrylic resin or urethane resin may be used.

In the first and second embodiments described above, the magneto-optical recording medium (eg, magneto-optical disk) is taken as an example, but the present invention can be applied to optical disks such as CD-R and CD-RW and magnetic disks. .

[0053]

As described above, according to the present invention, by providing a moisture impermeable film made of an inorganic substance and a temperature deformation preventing film made of an organic substance, in a storage environment or a use environment,
A recording medium capable of preventing warpage even when a change in temperature and humidity occurs, shortening the film formation time, reducing the manufacturing cost, and improving the productivity (for example, a magnetic disk, a magneto-optical disk, Discs such as optical discs)
Can be provided.

Further, according to the present invention, by combining a moisture impermeable film of an inorganic substance having a minimum necessary thickness and a temperature deformation preventing film of an organic substance which can be easily formed, in a storage environment or a use environment, A recording medium capable of preventing warpage even when a change in temperature and humidity occurs, shortening the film formation time, reducing the manufacturing cost, and improving the productivity (for example, a magnetic disk, a magneto-optical disk, Discs such as optical discs) can be provided.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a magneto-optical recording medium according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a measurement state of warpage of a magneto-optical recording medium.

FIG. 3 is a schematic cross-sectional view of a magneto-optical recording medium used for measuring a moisture impermeable effect without forming a temperature deformation preventing film.

FIG. 4 is a graph showing the correlation between the film thickness of the moisture impermeable film of FIG. 3 and the humidity deformation coefficient.

5 is a graph showing the correlation between the film thickness of the moisture impermeable film of FIG. 3 and the reflectance.

FIG. 6 is a graph showing the correlation between the film thickness of the temperature deformation prevention film and the temperature deformation coefficient.

FIG. 7 is a graph showing the correlation between the film thickness of the temperature deformation prevention film and the humidity deformation coefficient.

FIG. 8 is a schematic sectional view of a magneto-optical recording medium according to a second embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view of a conventional magneto-optical recording medium.

[Explanation of symbols]

1 substrate 2 recording layers 2a Upper stratum 2b reflective layer 2c magnetic recording layer 2d underlayer 3, 31, 32 Impermeable membrane 4 Temperature deformation prevention film 5 Protective coat layer 6 hard coat layer 10 Magneto-optical recording medium (magneto-optical disk) 20 Displacement measuring sensor 30 Holding part

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 11/105 G11B 11/105 526J F term (reference) 5D006 CC03 CC04 DA03 FA03 FA04 5D029 LB02 LB07 LB12 LC19 LC21 NA17 NA18 NA20 5D075 EE03 FG04

Claims (4)

[Claims] 1. A recording medium having a recording layer on one surface of a substrate, wherein a moisture impermeable film made of an inorganic material is provided on the other surface of the substrate, and a surface of the recording layer and / or the moisture impermeable film. A recording medium, comprising: a temperature deformation preventing film made of an organic material provided on the recording medium. 2. A recording medium having a recording layer on one surface of a substrate, comprising: a two-layer moisture impermeable film made of an inorganic material, which is provided on the other surface of the substrate; A recording medium, comprising: a temperature deformation preventing film made of an organic material interposed between the recording medium and the recording medium. 3. The moisture-impermeable film has a thickness of 10 nm or more and 80 or more.
The recording medium according to claim 1 or 2, wherein the recording medium has a thickness of not more than nm. 4. The recording medium according to claim 1, wherein the film thickness of the temperature deformation prevention film is 2 μm or more and 8 μm or less.