JP2828196B2 - Composite disc - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite disk obtained by forming a magnetic layer capable of writing / reading a small amount of data on an optical disk having an optical recording layer.
The present invention relates to a composite disk suitable for forming an optimum protective layer between an optical recording layer and a magnetic layer and causing a magnetic head to contact and run to perform good magnetic recording and reproduction.

[0002]

2. Description of the Related Art A read-only optical disk, which reads out information signals recorded on an optical recording layer formed on a transparent substrate by using laser light, duplicates the same information in a large amount and in a short time. Is now widely spread. This read-only optical disc is classified into a CD, a CD-ROM, a CD-V, a CD-I, and the like, depending on the information content recorded.

[0003] Since these optical disks are dedicated to reproduction, a small amount of additional information cannot be newly recorded in the same optical disk. to solve this problem,
An optical disk has been developed in which an optical recording area is provided in a part of the optical disk. However, since this optical disc records information by light, the optical disc and its reproducing apparatus have been expensive.

Therefore, in order to solve such a disadvantage, for example, Japanese Patent Application Laid-Open No. 62-75956,
As disclosed in JP-A-138462 or JP-A-4-337546, there has been proposed a composite disc in which a magnetic layer area in which a small amount of information can be written / read by a magnetic recording method is provided on the optical disc.

[0005] The prior art will be described below with reference to the accompanying drawings. FIG. 9 is a partial sectional view showing a conventional composite disc. 9, 1 is a substrate, 2 is an optical recording layer, 5 is a magnetic layer, 6 is a magnetic layer protective film, 7 is a magnetic head, 8 is a signal pit, 13 is a protective layer, and 12 is a protective layer. Reference numeral 22 denotes a composite disk, and 22 denotes an optical disk.

Signal pits 8 corresponding to information are formed on one surface of a substrate 1 made of a transparent polycarbonate resin by an injection molding method, and an optical recording layer 2 made of aluminum is formed thereon. Have been. This optical recording layer 2
From the substrate side where the signal pits 8 are not formed, the laser
Light is incident thereon, reflected by the optical recording layer 2, and used to read the shape of the signal pit 8. A protective layer 13 made of a resin is formed on the optical recording layer 2 to form an optical disk 22. Further, on the protective layer 13, a magnetic layer 5 for writing a small amount of rewritable information by a magnetic recording method is provided. A magnetic layer protective film 6 made of resin is formed on the magnetic layer 5 to prevent the magnetic layer 5 from being damaged by sliding of the magnetic head 7.
A composite disk 12 is configured. The magnetic recording / reproducing on / from the magnetic layer 5 is performed by the magnetic head 7.

[0007]

By the way, when a magnetic layer is provided on an optical disk to form a composite disk and rewritable information is recorded and reproduced, the rotation speed of the composite disk is usually low. It is necessary to use a contact recording method that makes contact with the magnetic disk. On the other hand, since the surface deflection of the composite disk is large because the optical disk has a basic configuration, the contact load between the magnetic head and the composite disk is required for stable magnetic recording and reproduction. Must be set to a predetermined value.

The applicant of the present application has manufactured various composite disks by forming a magnetic layer on a conventional optical disk. The composite disks are manufactured by a magnetic head contact method.
Research on magnetic recording / reproducing for the magnetic layer was performed. According to this, when the characteristics of the protective layer of the optical recording layer made of urethane acrylate constituting the conventional optical disk affect the running characteristics of the magnetic head and the contact load between the magnetic head and the composite disk is made relatively small, The modulation characteristic cannot be set to a value in the specified range.
When the contact load between the magnetic head and the composite disk is increased to improve the running characteristics of the magnetic head in order to bring the performance characteristics into the specified range, the running of the magnetic head
It has been found that the optical information signal (optical recording layer or signal pit) may be destroyed, and often exceeds the error correction capability of the optical disk.

In view of the above, the present invention has been made in view of the above points. In a composite disc, the amount of warpage is kept within a predetermined range, and the corrosion of the optical recording layer occurs even in a high-temperature and high-humidity environment. To prevent the destruction of the optical information signal due to the running of the magnetic head and to improve the stability of the running of the magnetic head, thereby providing a composite disk having excellent magnetic recording / reproducing characteristics and high reliability. It is intended for.

[0010]

According to the present invention, there is provided a composite disk comprising: a disc-shaped transparent substrate made of polycarbonate resin; an optical recording layer made of aluminum on which optical information is to be recorded; A protective layer made of an ultraviolet curable resin for protecting the recording layer, a magnetic layer of a predetermined shape mainly made of an ultraviolet curable resin and magnetic powder on which additional information is magnetically recorded, and the magnetic layer in contact running of a magnetic head In a composite disc in which a magnetic layer protective film for protecting the magnetic disk is sequentially laminated, the protective layer has a thickness of 5 to 100 μm, and the Young's modulus of the protective layer is ² to 100 kg / mm ² . The above object is achieved.

The composite disk of the present invention is a
An optical recording layer made of aluminum on which optical information is to be recorded on a disk-shaped transparent substrate made of a carbonate resin, a protective layer made of an ultraviolet curable resin for protecting the optical recording layer, and additional information A composite disk in which a magnetic layer of a predetermined shape mainly composed of an ultraviolet curing resin and magnetic powder on which magnetic recording is performed, and a magnetic layer protective film for protecting the magnetic layer during contact running of a magnetic head are sequentially laminated. In the above, the protective layer may be a first protective layer made of an ultraviolet curable resin in contact with the optical recording layer, and an ultraviolet ray formed on the first protective layer and having a Young's modulus smaller than that of the first protective layer. The above-mentioned object is achieved by comprising the second protective layer made of a cured resin.

Further, in the composite disk of the present invention, the protective layer comprises the first protective layer made of an ultraviolet curable resin in contact with the optical recording layer, and the ultraviolet curable resin formed on the first protective layer. The composite disk comprising the second protective layer, wherein the first protective layer has a Young's modulus of 10
And 0~200kg / mm ^2, by which the Young's modulus of the second protective layer was 2~100kg / mm ^2, is to achieve the above object.

[0013]

An embodiment of the present invention will be described below with reference to the accompanying drawings. <Embodiment 1> FIG. 1 is a partial sectional view showing an embodiment of a composite disc according to the present invention, which shows a composite disc in which a protective layer is composed of two layers. In FIG. 1, 1 is a substrate, 2 is an optical recording layer, 3a is a first protective layer, 3b is a second protective layer, 5 is a magnetic layer, 6 is a magnetic layer protective film, and 7 is a magnetic head. 8 is a signal pit, 10 is a composite disc, 20
Denotes optical disks, respectively.

Signal pits 8 are formed on a transparent polycarbonate resin substrate 1 having a diameter of 120 mm by an injection molding method using a stamper. An aluminum film having a thickness of 100 nm is formed as an optical recording layer 2 on the entire surface of the signal pit 8 by a sputtering method. On the entire surface of the optical recording layer 2, an ultraviolet curable resin A type having a Young's modulus of 100 kg / mm ² (hereinafter, abbreviated as A type resin).
The contents will be described later. ) Is applied by a spin coating method, and then cured by ultraviolet rays to form a first protective layer 3a having a thickness of 5 μm. Further, an ultraviolet curable resin having a predetermined Young's modulus (a plurality of types) is applied on the first protective layer 3a by a spin coat method, and then cured by ultraviolet rays to form a second protective film having a thickness of 50 μm. 3b is formed, and the optical disk 20 is obtained.

Next, a magnetic paint mainly containing an ultraviolet curable resin is applied on the second protective layer 3b (that is, the optical disk 20) by, for example, screen printing, and cured by ultraviolet rays to form a magnetic material having a predetermined shape. The layer 5 is formed. Next, on the magnetic layer 5, for example, dimethylpolysiloxane
After applying trimethylpropane triacrylate containing wt% by a spin coat method, it is cured by ultraviolet rays to form a magnetic layer protective film 6 having a predetermined thickness. For example, dimethylsiloxane was applied on the magnetic layer protective film 6 to improve the slidability with the magnetic head 7, and a lubricating layer (not shown) was formed. In addition,
In the composite disk 10, the second protective layer 3b has a Young's modulus of 0.5.
A plurality of types were manufactured in a range of 1 to 210 kg / mm ² . Here, the Young's modulus is 0.1-100k
Those having a range of less than g / mm ² use an ultraviolet curable resin type B (hereinafter, abbreviated as “B type resin”, the content of which will be described later), and have a Young's modulus of 100 to 210 kg / m.
In the range of m ² , A type resin was used.

A magnetic head 7 is brought into contact with the plurality of types of composite disks 10 to perform magnetic recording and reproduction, and the modulation and the second waveform are obtained from the reproduced output waveform.
The relationship with the Young's modulus of the protective layer 3b was obtained. The result is shown in FIG. FIG. 4 is a diagram showing a modular disk having two protective layers according to an embodiment of the present invention.
FIG. 6 is a graph showing a relationship between the elasticity of the second protective layer and the Young's modulus of the second protective layer. The vertical axis in FIG. 4 is (A−B) × 100 / (A +
B) (%), as shown in FIG. 3 (FIG. 3 is a conceptual diagram for explaining the modulation), the maximum value of the envelope 8 of the reproduced waveform is The minimum value is determined as A, and the minimum value is determined as B, and represents the degree of modulation. If this value exceeds 20%, the reliability of magnetic recording and reproduction is reduced, and digital signal processing becomes difficult.

According to FIG. 4, as the Young's modulus of the second protective layer 3b increases from 10 to 210 kg / mm ² , the modulation value increases from 3 to 43%. If the Young's modulus of the second protective layer 3b is 100 kg / mm ² or less, the modulation value in magnetic recording / reproducing is 20%.
The following good values are shown, and it can be seen that the contact running between the magnetic head 7 and the composite disk 10 at this time is stable. Note that the ^second modulus of the Young's modulus is in the range of 0.1 to 10 kg / mm 2.
Although the composite disk 10 having the protective layer 3b formed thereon can be expected to have a low modulation value, in practice, a magnetic paint is screen-printed to form the magnetic layer 5 on the second protective layer 3b. When applied, the Young's modulus is 0.1 ~
In the case of the second protective layer 3b in the range of ² kg / mm ^2, a phenomenon that the second protective layer 3b sticks to the screen occurs, and it has been confirmed that there is a problem in manufacturing.

Hereinafter, the A type resin, the B type resin, the magnetic paint, the magnetic recording / reproducing conditions and the like will be described. First,
The A-type resin is a mixture of trimethylolpropane triacrylate (TMPTA) and CL-50 (trade name, manufactured by Nippon Kayaku Co., Ltd.). The mixing ratio is 1:
The Young's modulus is 1 corresponding to the range of 2 to 2: 1 (wt%).
A type resin in the range of 00 to 300 kg / mm ² is obtained. On the other hand, the B-type resin is a mixture of neopentyl glycol diacrylate hydroxypivalate (which may be isobornyl acrylate) and CL-50. The mixing ratio is 1: 5 to 3: 2 (wt%)
The Young's modulus is 0.1 to 100 kg / m corresponding to the range of
A B-type resin in the range of m ² is obtained. A and B
For both type resins, 5 wt.
A photoinitiator consisting of wt% of 2-hydroxy-2-methyl-1-phenylpropan-1-one (manufactured by Merck Japan Ltd.) is added.

The measurement of the Young's modulus of the resin was performed as follows. Resin is 4mm wide, 30mm long, 50μ thick
m to form a measurement sample. A tensile stress of 15 ± 5 g was applied to this sample using a thermal stress strain measuring device (model TMA / SS10, manufactured by Seiko-Electronic Industries Co., Ltd.), and Young's modulus was determined from the relationship between the stress and strain at that time. I asked.

Next, the magnetic paint will be described. The main component of the magnetic paint is an ultraviolet-curing resin, such as acrylic acid ester-based trimethylpropane triacrylate (TMPTA) manufactured by Nippon Kayaku Co., Ltd. CMX-473, a higher fatty acid ester (glycerin monofatty acid ester) as a dispersant, and Darocure-4265 manufactured by Merck Co., Ltd. as a photo-curing agent. A three-roll mill is charged with predetermined amounts of an ultraviolet curable resin, a magnetic powder having a magnetic powder content of 15 wt%, a dispersant, and a photocuring agent, and the mixed liquid is sufficiently kneaded to disperse the magnetic powder. A magnetic paint was prepared.

Next, conditions for magnetic recording and reproduction will be described. The magnetic head 7 has a track width of 200 μm and a gap length of 7
A μm ferrite head was used. The recording track is
It is concentric and the track pitch is 600 μm. The rotation speed of the composite disc 10 during recording and reproduction was 360 rpm, and a rectangular wave signal of 62.5 kHz was recorded and reproduced. The recording voltage at this time was a voltage that was 10% higher than the saturation recording voltage. The reproduction output waveform is an oscilloscope waveform of the output from the head amplifier that has performed the predetermined amplification. C ₁ error of the optical information unit - is to secure the magnetic head 7 to a predetermined track position, is slid in a still state, after 100,000-pass, was determined by reproducing the signal of the optical information section.

Example 2 A first protective layer 3a having a thickness of 5 μm and a Young's modulus were formed on the optical recording layer 2 by using an A type resin or a B type resin having a predetermined Young's modulus (a plurality of types are provided). Is 50 kg / mm ² using a B-type resin,
A composite disk 10 was manufactured in the same manner as in Example 1 except that the second protective layer 3b having a thickness of 50 μm was formed. The composite disk 10 was prepared by changing the Young's modulus of the first protective layer 3a in the range of ²⁰ to 200 kg / mm ² .
Made several types. Here, the Young's modulus is 20-100k
Those having a range of less than g / mm ² used a B-type resin, and those having a Young's modulus in a range of 100 to 200 kg / mm ² used an A-type resin. These composite disc 10, is slid by the magnetic head 7, after 100,000-pass, by reproducing the signal of the optical information section, C ₁ error - was measured.

FIG. 5 shows the results of these measurements. FIG.
FIG. 4 is a graph showing the relationship between C ₁ error and Young's modulus of the first protective layer when the protective layer is composed of two layers in one embodiment of the composite disk of the present invention. According to FIG. 5, the first protective layer 3a has a Young's modulus of 20 to 200 kg /.
As it increases to mm ² , the C ₁ error decreases from 4.7 to 0.5. Optical disk 2 of composite disk 10
C ₁ error 0 parts - standard value of 3% or less. When the Young's modulus of the first protective layer 3a is 90 kg / mm ² or more, the C ₁ error is 3% or less. The Young's modulus of the first protective layer 3a is 90
At kg / mm ² or less, the C ₁ error sharply increases and deviates from the standard value. This indicates that the optical information section (optical recording film and signal pits) is partially destroyed by causing the magnetic head 7 to contact and travel with a predetermined contact load.

<Embodiment 3> FIG. 2 is a partial cross-sectional view showing an embodiment of a composite disk according to the present invention, in which the protective layer is composed of one layer. In FIG. 2, 1 is a substrate, 2 is an optical recording layer, 3c is a protective layer, 5 is a magnetic layer, 6 is a magnetic layer protective film, 7 is a magnetic head, 8 is a signal pit, and 11 is a signal pit. Reference numeral 21 denotes a composite disk, and 21 denotes an optical disk. 120mm diameter transparent polycarbonate
Signal pits 8 are formed on a resin substrate 1 by an injection molding method using a stamper. An aluminum film having a thickness of 100 nm is formed as an optical recording layer 2 on the entire surface of the signal pit 8 by a sputtering method. An A-type resin having a Young's modulus of 100 kg / mm ² is applied to the entire surface of the optical recording layer 2 by a spin coating method, and then cured by ultraviolet rays to form a protective layer 3 c having a predetermined thickness (a plurality of types exist).
Is formed, and the optical disk 21 is obtained.

Next, the protective layer 3c (that is, the optical disk 21) is coated with the magnetic paint mainly containing the ultraviolet curable resin used in the first embodiment by, for example, screen printing, and cured by ultraviolet rays. A magnetic layer 5 having a predetermined shape is formed. Next, trimethylpropane triacrylate containing, for example, 3% by weight of dimethylpolysiloxane is applied on the magnetic layer 5 by a spin coat method, and then cured by ultraviolet rays to form a magnetic layer protective film 6 having a predetermined thickness. To form For example, dimethylsiloxane was applied on the magnetic layer protective film 6 to improve the slidability with the magnetic head 7, and a lubricating layer (not shown) was formed. In the composite disk 11, the protective layer 3c has a thickness of 2
A plurality of types changed in the range of 10 to 10 μm were manufactured.

[0026] These composite disk 11 is slid by the magnetic head 7, after 100,000-pass, by reproducing the signal of the optical information section, C ₁ error - was measured. FIG. 6 shows the results of these measurements. FIG. 6 shows C _{1 in the} case where the protective layer is composed of one layer in one embodiment of the composite disc of the present invention.
FIG. 4 is a graph showing the relationship between an error and the thickness of a protective layer.
According to FIG. 6, as the thickness of the protective layer 3c increases from 2 to 10 μm, the C ₁ error increases from 4.8 to 0.5%.
To decrease. When the film thickness becomes 4.5 μm or more, the C ₁ error becomes 3% or less of the standard value, and when the film thickness becomes 8 μm or more, the change substantially stops and the film becomes stable.

Example 4 An A type resin having a predetermined Young's modulus (a plurality of types) is applied on the optical recording layer 2 by a spin coat method, and then cured by ultraviolet rays to form a protective layer having a thickness of 5 μm. A composite disk 11 was obtained in the same manner as in Example 3, except that 3c was formed. Note that the composite disk 11
Means that the Young's modulus of A-type resin is 100 to 300 kg / m
m ² , and the protective layer 3 c was formed.
Made several types. These composite discs 11 were allowed to stand for 96 hours in an environment of a temperature of 55 ° C. and a relative humidity of 95%, and a radial warp angle at a radius of 55 mm before and after the composite disc 11 was measured. I asked. The measurement of the warp angle is based on ISO / IEC 1008
The measurement was performed using a dedicated measuring device capable of measuring the level of the warp angle specified in the paragraph No. 9.

FIG. 7 shows the results of these measurements. FIG.
In one embodiment of the composite disc of the present invention,
FIG. 4 is a graph showing a relationship between an increase in a warp angle and a Young's modulus of a protective layer in a case where the protective layer is composed of layers. As shown in FIG.
Young's modulus of the protective layer 3c is 100 to 300 kg / mm ²
The increase in the warp angle increases from 0.1 to 0.4 as
Increases linearly to 8 °. The standard value of the warp angle of the optical disk 21 portion of the composite disk 11 is ± 0.6 °, and in order to stay within this standard value, the amount of change in the warp angle before and after the environmental test is 0.3 ° or less. There is a need. If the Young's modulus of the protective layer is 210 kg / mm ² or less, it can be understood that it is good.

[0029] On <Example 5> The optical recording layer 2, a Young's modulus using an A type resin is 100 kg / mm ^2, a first protective layer 3a with a thickness of 5 [mu] m, the Young's modulus is 5 kg / mm ²
The composite disk 10 was manufactured in the same manner as in Example 1 except that the second protective layer 3b having a predetermined thickness (there were a plurality of types) was formed using the B type resin. In the composite disk 10, the second protective layer 3b has a thickness of 10 to 115.
A plurality of types were manufactured by changing the range up to μm. These composite disks 10 were subjected to a temperature of 55 ° C. and a relative humidity of 95%.
Was left in the above environment for 96 hours, the radial warp angle of the composite disk 10 before and after at a position of a radius of 55 mm was measured, and the change amount of the warp angle was obtained.

FIG. 8 shows the results of these measurements. FIG.
In one embodiment of the composite disc of the present invention, the protective layer has two layers.
FIG. 4 is a graph showing a relationship between an increase in a warp angle and a film thickness of a second protective layer in the case of being constituted by layers. As shown in FIG.
As the thickness of the second protective layer 3c increases from 10 to 115 μm, the amount of increase in the warpage angle increases linearly from 0 to 0.43 °. In order to reduce the warpage angle increase to 0.3 ° or less, the thickness of the second protective layer may be set to 105 μm or less.

In the above-described composite disk, the Young's modulus and the thickness of the protective layer formed between the optical recording film and the magnetic layer depend on the damage of the optical information portion due to the running of the magnetic head and the magnetic recording characteristics of the magnetic head. The effect of this is explained.
To prevent damage to the optical information area due to contact running of the magnetic head, either form a relatively thin protective layer with a resin having a large Young's modulus and a small thickness, or use a resin with a small Young's modulus to protect a thick film. What is necessary is just to form a layer. on the other hand,
In order to stably maintain the running property of the magnetic head and ensure the modulation characteristics, a resin having a large Young's modulus is not preferable, and a thick protective layer may be formed of a resin having a small Young's modulus.

However, a resin having a small Young's modulus has a long molecular chain and a small number of functional groups, so that the gaps in the network structure become large. This may cause corrosion of the optical recording film.
Therefore, the protective layer has a two-layer structure, the optical recording film side is formed of a resin having a large Young's modulus, and the magnetic layer side is formed of a resin having a small Young's modulus. It is possible to obtain a composite disc with high performance.

As described above, trimethylolpropane triacrylate (TMPTA) and a CL-50 (trade name, manufactured by Nippon Kayaku Co., Ltd.) in a predetermined mixing ratio to which a photoinitiator has been added as the A-type resin. ) Was described.
However, the present invention is not limited thereto, and TMPTA and caprolactone-modified neopentyl hydroxypivalate glyco-
A mixture with ludia acrylate (HX620: trade name, manufactured by Nippon Kayaku Co., Ltd.) at a mixing ratio of 4: 5 to 2: 1 (wt%) may be used, or butanediol-diacrylate and C may be used.
A mixture with L-50 in a mixing ratio of 1: 1 to 2: 1 (wt%) may be used, or neopentyl glycol diacrylate may be used.
Mixing ratio of CL-50 to CL-50 2: 3 to 3: 2 (wt
%) Or butanediol-diacrylic acid
And HX620 in a mixing ratio of 3: 2 to 5: 2 (wt.
%), Or a mixture ratio of neopentyl glycol diol acrylate and HX620 of 1: 1 to 2: 1.
(Wt%) mixture, each having a Young's modulus of 1
It is possible to obtain an A-type resin of 100 to 200 kg / mm ² (naturally, it contains a predetermined amount of photoinitiator).

On the other hand, as a B-type resin, neopentyl glycol diacrylate hydroxypivalate (which may be isobornyl acrylate) in a predetermined mixing ratio, to which a photoinitiator is added, and CL-50 are used. The mixture has been described, but is not limited to this.
A and HX620 in a mixing ratio of 1: 7 to 4: 5 (wt.
%) Or butanediol-diacrylic acid
And HX620 in a mixing ratio of 1: 5 to 3: 2 (wt.
%) Or a mixture ratio of neopentyl glycol diacrylate and HX620 of 1: 6 to 1: 1.
(Wt%) mixture, each having a Young's modulus of 2
A B-type resin of タ イ プ 100 kg / mm ² can be obtained (naturally containing a predetermined amount of photoinitiator).

The case where the protective layer or the second protective layer is formed of an ultraviolet curable resin has been described above. However, the present invention is not limited to this case. For example, polyvinyl alcohol which does not attack polycarbonate can be used. Butyral resin or vinyl acetate may be used.

There are the following methods for forming a magnetic layer. A magnetic paint is applied on a polyethylene terephthalate (PET) film to form a magnetic layer having a predetermined shape, and a heat-sealing agent having a predetermined film thickness (for example, a trigger adhesive) is formed on the magnetic layer. : Trade name, Toyo Ink Manufacturing Co., Ltd.) Then, the heat-fusing agent side of this PET film is arranged at a predetermined position on the protective layer or the second protective layer of the optical disk, and after heating and bonding, the PET is peeled off. This allows
A magnetic layer is formed on the protective layer or the second protective layer of the optical disc via a heat-sealing agent. As described above, even if the magnetic layer is formed on the protective layer or the second protective layer of the optical disk via the heat sealing layer, good modulation characteristics and protection of the optical information section can be achieved. Needless to say.

[0037]

As described above, the composite disk according to the present invention according to the first aspect of the present invention comprises an optical recording layer on which optical information is to be recorded, a protective layer, In a composite disk in which a magnetic layer and a magnetic layer are sequentially laminated, by setting the thickness of the protective layer to 5 to 100 μm and setting the Young's modulus of the protective layer to 5 to 100 kg / mm ² , the amount of warpage is a predetermined value. In the high temperature and high humidity environment, the optical recording layer does not corrode, prevents the destruction of the optical information signal due to the magnetic head running, and improves the stability of the magnetic head running. Thus, a composite disk having improved magnetic recording / reproducing characteristics and high reliability can be provided.

In the composite disk according to the present invention, an optical recording layer for recording optical information, a protective layer, and a magnetic layer having a predetermined shape are sequentially laminated on a disk-shaped transparent substrate. In the composite disc described above, the protective layer comprises a first protective layer in contact with an optical recording layer, and a second protective layer formed on the first protective layer and having a Young's modulus smaller than the Young's modulus of the first protective layer. By comprising the protective layer, the amount of warpage is maintained within a predetermined value range, the optical recording layer does not corrode even in a high-temperature and high-humidity environment, and the destruction of the optical information signal due to running of the magnetic head is prevented. Thus, it is possible to improve the stability of the magnetic head running, thereby providing a composite disk having excellent magnetic recording / reproducing characteristics and high reliability.

The composite disk according to the present invention according to claim 3 is the composite disk according to claim 2, wherein the first protective layer has a Young's modulus of 100 to 200 kg / mm ² and the second protective layer has a Young's modulus of 100 to 200 kg / mm ^2. Young's modulus of 2 to 100 kg / mm
By setting it to ² , the amount of warpage is kept within a predetermined value range,
Corrosion of the optical recording layer does not occur even in a high-temperature and high-humidity environment, preventing the destruction of optical information signals due to running of the magnetic head, and improving the stability of running of the magnetic head. And a composite disk having high reliability can be provided.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an embodiment of a composite disc according to the present invention, showing a composite disc in which a protective layer is composed of two layers.

FIG. 2 is a partial cross-sectional view showing one embodiment of the composite disc of the present invention, showing a composite disc in which a protective layer is composed of one layer.

FIG. 3 is a conceptual diagram for explaining modulation.

FIG. 4 is a graph showing the relationship between the modulation and the Young's modulus of the second protective layer when the protective layer is composed of two layers in one embodiment of the composite disc of the present invention.

FIG. 5 is a graph showing the relationship between the C ₁ error and the Young's modulus of the first protective layer when the protective layer is composed of two layers in one embodiment of the composite disk of the present invention.

FIG. 6 is a graph showing the relationship between the C ₁ error and the thickness of the protective layer when the protective layer is composed of one layer in one embodiment of the composite disk of the present invention.

FIG. 7 is a graph showing the relationship between the increase in the warp angle and the Young's modulus of the protective layer when the protective layer is composed of one layer in one embodiment of the composite disc of the present invention.

FIG. 8 is a graph showing the relationship between the amount of increase in the warp angle and the thickness of the second protective layer when the protective layer is composed of two layers in one embodiment of the composite disk of the present invention.

FIG. 9 is a partial sectional view showing a conventional composite disc.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 optical recording layer 3a first protective layer 3b second protective layer 3c protective layer 5 magnetic layer 6 magnetic layer protective film 7 magnetic head 8 signal pit 10 composite disk 11 composite disk 12 composite disk 13 protective layer 20 optical disk 21 optical disk 22 optical disk

Claims (3)

(57) [Claims] 1. A composite disc in which an optical recording layer on which optical information is to be recorded, a protective layer, and a magnetic layer having a predetermined shape are sequentially laminated on a disk-shaped transparent substrate, A composite disc having a thickness of 5 to 100 μm and a Young's modulus of the protective layer of ² to 100 kg / mm ² . 2. A composite disc in which an optical recording layer on which optical information is to be recorded, a protective layer, and a magnetic layer having a predetermined shape are sequentially laminated on a disk-shaped transparent substrate. A first protective layer in contact with the optical recording layer, and a second protective layer formed on the first protective layer and having a Young's modulus smaller than that of the first protective layer. Composite disc. 3. The composite disk according to claim 2, wherein the first protective layer has a Young's modulus of 100 to 200 kg / mm.
^2, and the Young's modulus of the second protective layer is 2 to 100 kg /
composite disc, characterized in that was mm ^2.