JPH0426935A - Optical disk - Google Patents

Abstract

PURPOSE:To obtain the optical disk which does not warp in spite of the generation of a change in temp. and humidity of an abrupt grade and is highly resistant to dust pickup and flawing by forming an SiO2 layer to a specific film thickness. CONSTITUTION:Large warpage arises in the event of a change in the temp. and humidity with veneers which are not stuck to each other in the case of use of a plastic substrate 1 consisting of polycarbonate, etc. The veneers in this state is not suitable for practicable use. The SiO2 layer 2 which has a moistureproof effect and is formed by a liquid phase thin film forming method is, thereupon, formed in at least the exposed part of the substrate 1. The effect of preventing the warpage is not sufficiently obtd. if the thickness of the SiO2 layer 2 is smaller than 500Angstrom . The film thickness of the SiO2 layer 2 is, thereupon, increased to >=500Angstrom . The optical disk which does not warp in spite of the generation of the abrupt change in the temp. and humidity and is highly resistant to the flawing and dust pickup is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc for recording and reproducing information using light.

[Prior art] Substrate materials for optical disks include transparent plastic substrates,
It is easy to reproduce and is low cost, especially on polycarbonate substrates.

However, when a plastic substrate with a relatively high moisture permeability coefficient, such as a polycarbonate substrate, is used, the substrate warps due to water absorption only on the surface that does not form the recording surface. Especially when used in environments with significant changes in temperature and humidity,
A large warpage occurs, and as a result, the actuator's force tracking surfer cannot follow it stably, resulting in malfunctions and errors, which poses a serious problem in practice.

A known method for preventing warping is to form a moisture-proof film on the surface of the substrate opposite to the surface on which the recording film is formed. FIG. 12 is a sectional view of an optical disc showing a conventional method disclosed in, for example, Japanese Patent Application Laid-Open No. 292639. In the figure, 1 is a plastic substrate, 4 is a recording film, and 8
9 is an ultraviolet curable resin layer, and 9 is a moisture-proof film.

The moisture-proof film may be either organic or inorganic, and if it is an organic film, coating, etc. may be used, and if it is an inorganic film, a sputtering method, vacuum evaporation method, CVD method, etc. may be used.

However, when a moisture-proof film is formed on a portion of the tissue, warping that occurs when temperature and humidity change with a gentle gradient can be prevented, but warping that occurs when temperature and humidity change with a steep gradient cannot be prevented.

This is because moisture is rapidly absorbed from the parts of the substrate on which the moisture-proof film is not formed, and the moisture distribution inside the substrate becomes temporarily uneven, causing warping due to local expansion.

[Problems to be Solved by the Invention] Therefore, it is necessary to form a light-transmitting moisture-proof film over the entire surface of the disk so that the material of the substrate is not exposed to the atmosphere. However, as shown in the above-mentioned Japanese Patent Application Laid-Open No. 1-292639, it is known that it is extremely difficult to form a uniform film over the entire surface. In other words, conventional spin code, sputtering, and evaporation methods do not use masks during the manufacturing process, which can result in film boundaries or small holes (holes, pinholes) in the film. Therefore, there have been problems in that the moisture-proofing effect cannot be improved or the protective film may peel off or deteriorate due to these boundaries and holes.

Furthermore, in the case of an optical disc, since the laser light is incident from the substrate side, the light also passes through the moisture-proof film formed on the substrate. Therefore, it is necessary to form a moisture-proof film without compromising the needs of optical technology, such as the enhancement effect of magneto-optical disks and the reduction of incident light intensity and noise. Conventional film forming methods, which require control of constants, thickness, surface roughness, etc., require sophisticated technology and increase manufacturing costs.

In addition, the optical disc may get dusty or get scratched when it is wiped. Therefore, to prevent this, it is known to form a heart coat film or an antistatic film on the surface of the substrate, or if an antistatic function is added to the conventional heart coat material, it will function as an initial hard coat material. will be halved. For example, in the case of a polycarbonate board, it is 3H on the board and 7H after heart coating.
There was a problem that there was no film that had both the heart coat function and the antistatic function at the same time, such as a film with an antistatic function resulting in 4H.

Furthermore, since conventional Bart coat materials and antistatic materials are UV-curable or thermosetting resins, spin cords are the main method of forming films on the surface of the substrate, so the entire exposed surface of the substrate It was difficult to form a film. In other words, if the innermost slope of the board and the end surface are made of the same board material, for example, when Tisfu is used in a cartridge, the parts that have not been coated after the heart coating will hit the protrusions of the cartridge and wear out, causing further damage. The problem was that wear debris or dust got on the surface and wiping it off caused another scratch.

Therefore, silicon dioxide (Si) is coated on a substrate using a liquid phase thin film forming method as shown in Japanese Patent Application Laid-Open No. 63-112632.
02) A method of forming a film has been proposed. In this method, the entire tissue is immersed in the treatment liquid, so a film can be uniformly formed over the entire surface except for the part where the tissue is held in the solution.

However, if the film is thin, the film is not dense enough, or the film forms islands, even if the film is formed, it will not be able to prevent moisture from permeating, and the moisture resistance of the film will deteriorate. It is not possible to prevent the tisf from warping.

Also, when forming a film on a base material with low hardness such as a polycarbonate substrate, the hardness of the base material is more affected than the hardness of the film itself. However, the effect as a hard coat material cannot be obtained.

Furthermore, the antistatic function is obtained because the film is conductive, which prevents the accumulation of charges and makes it difficult for static electricity to occur. In this case, there is no way for the charges to escape and the charges tend to accumulate, resulting in extremely low conductivity and no antistatic function.

In addition, when forming a recording film after forming a SiO2 layer through PD processing in the substrate state, if the thickness of the SiO2 layer is thick, the shape of the grooves and pre-pits formed on the substrate will change. It is possible to make a slight correction by adjusting the settings of the standber that molds the board, but
If the groove formed on the unadjusted substrate is thick enough to be filled, calculations can be made to optimize the standber settings, but it may not be possible to obtain a good groove and the signal cannot be read. cause trouble.

The present invention was made to solve the above-mentioned problems, and its purpose is to obtain an optical tissue that does not warp even when a steep temperature and humidity change occurs and is resistant to dust and scratches. It is said that

[Means for Solving the Problems] The optical disk according to the present invention is an optical recording medium consisting of a substrate and an optical recording layer having a memory function, in which an optical recording layer and a protective layer covering the optical recording layer are formed. This is an optical disk in which a SiO2 layer is formed on the entire surface by a liquid phase thin film formation method, and the thickness of the SiO2 layer is 500 Å or more.Secondly, the substrate and the memory function are In an optical disc in which two optical recording media consisting of an optical recording layer and an optical recording layer are bonded together so that the recording layers face each other, and then a SiO2 layer is formed on the entire surface by a liquid phase thin film formation method, the film thickness of the SiO2 layer is 500
Thirdly, it is an optical recording medium consisting of a substrate and an optical recording layer having a memory function, and before forming the optical recording layer, the entire surface of the substrate is coated.
This optical disc is characterized in that the thickness of the SiO2 layer is 500 Å or more in an optical disc in which an optical recording layer is formed after forming an SiO2 layer by a liquid phase thin film forming method.

"Function" By having the optical disc of the present invention configured as described above, it is possible to obtain an optical disc that does not warp even if a steep temperature/humidity change occurs and is resistant to dust and scratches.

[Example] The optical recording film forming the optical disc of the example of this invention is
It may be formed by a conventional known method. For example, after forming a dielectric film such as SiNx, an amorphous recording film having perpendicular magnetic anisotropy such as TbFeCo is formed, and a protective film such as SiNx is formed on top of the amorphous recording film having perpendicular magnetic anisotropy. Obtained by forming a film.

When using a plastic substrate such as polycarbonate,
If the veneer is not laminated, it will warp significantly when the temperature and humidity change, making it unsuitable for practical use.

Therefore, SiO2 using a liquid phase thin film formation method with moisture-proofing effect
forming a layer on at least the exposed portion of the substrate;
It has been found through experiments that if the thickness of the SiO2 layer is less than 500, a sufficient warpage prevention effect cannot be obtained.

Figure 7 shows a 130mm groove and pre-pit formed.
An optical disc in which a SiO2 layer of various thicknesses is formed on a polycarbonate substrate of φ by the liquid phase thin film forming method shown in JP-A No. 63-112632, and then an optical recording film as shown in the example above is formed. , the environment is 60℃50
%RH to 60° C.90% old] are summarized in Table 7.

The moisture-proofing effect of the SiO2 layer formed on the substrate appears when
It is 500 Å or more.

Furthermore, when the hardness of the substrate side surface of these optical disks was measured, the hardness was as shown in FIG. 8, and it was almost saturated at 400 people, and stably exceeded 7H at 500 Å or more.

Furthermore, when these photonices were charged to 60 mV and then discharged, and the change in the charged potential was measured as shown in Figure 9, the time for the charged potential to be halved and the half-life were as shown in Figure 10. It rapidly becomes smaller than that of a human being, and becomes stable at 500 Å or more, and then shortens to about 10 seconds.

As described above, when a SiO2 layer is formed on a substrate by the liquid phase thin film formation method, the film needs to have a thickness of 500 Å or more in order to obtain warpage, hardness, and antistatic effects.

However, when the groove shapes of these optical discs were observed and determined using an electron microscope, it was found that the groove shape was 200 mm as shown in Figure 11.
If the number exceeds 0, the groove will be completely filled with the SiO2 layer, making it impossible to calculate the correction design for the change due to the SiO2 layer. That is, if a SiO2 layer is previously formed on the surface where the groove is formed, the thickness needs to be 2000 Å or less.

The present invention will be specifically explained below using examples.

In Figure 1, 1 is a polycarbonate substrate, 2 is an S
iO2 layer, 3 is SiNx dielectric layer, 4 is TbFeC.

The magnetic layer 5 is a SiNx dielectric layer. 1, which was molded using an optimally designed standber to compensate for the change in groove shape caused by the SiO□ layer shown in FIG.
After forming 1000 SiO2 layers of No. 2 by the liquid phase thin film forming method shown in No. 112632, No. 3, 4 and 5 were laminated in this order by sputtering.

This optical disc was heated to 50"C90 at 60℃ and 50%RH.
The warping angle (tilt) that occurred when the environment was changed to %RH was as small as 0.3 mrad, and the surface hardness of the substrate side was 7H1, with a half-life of 10 seconds, which resulted in high surface hardness and good properties. It has both antistatic effect. Furthermore, since the groove shape was optimized in advance at the standby stage, good signal recording and reproducing characteristics were obtained, equivalent to those obtained when a disk was prepared without forming an SiO2 layer. In the optical disc of this invention, before forming the optical recording film,
Since it forms an iO2 layer, the substrate is less likely to be scratched or dusted during film formation by sputtering, making handling easier and dust removal easier, improving work efficiency and helping to improve yield. .

Next, another embodiment will be described.

In Figure 2, 1 is a polycarbonate substrate and 2 is an S
iO2 layer, 3 is SiNx dielectric layer, 4 is TbFeC.

Magnetic layer 55 is a SiNx dielectric layer. After masking the area where groove 1 is formed to prevent contact with the liquid,
1000 SiO2 layers of No. 2 were formed by the liquid phase thin film forming method disclosed in JP-A No. 63-], No. 2632, and layers No. 3, 4, and 5 were laminated thereon in this order by sputtering.

This optical disc was heated from 60℃50%RH to 60℃90%RH.
Warpage angle (tilt) that occurs when changing the environment to RH
is very small at 0.3 mrad, and the surface hardness on the substrate side is 7H1. The half-life of the charged potential is 10 seconds, and it has both high surface hardness and good antistatic effect. Furthermore, even though the region where the grooves were formed was masked, there was no change in the shape of the grooves, and the signal recording and reproducing characteristics were good. Since the optical disk of this invention forms a SiO2 layer before forming an optical recording film, the substrate is less likely to be scratched or dusted during film formation by sputtering, making it easy to handle and remove dust. This improves work efficiency and improves yield.

Next, another embodiment will be described.

In Figure 3, 1 is a polycarbonate substrate and 2 is an S
iO2 layer, 3 is SiNx dielectric layer, 4 is TbFeC.

5 is a magnetic layer, 5 is a SiNx dielectric layer, and 6 is a protective layer made of resin. After laminating 3, 4, and 5 on 1 by sputtering in this order, 6 was formed to cover 3, 4, and 5, and the liquid phase thin film forming method shown in JP-A-63-112632 was applied to the entire surface. 1000 SiO2 layers of 2 were formed using the same method.

Change this optical disc from 60℃ 50% old 1 to 60℃ 90%
Warpage angle (tilt) that occurs when changing the environment to RH
is very small at 0.3 mrad, and the half-life of the 7H1 charge potential on the substrate side is 10 seconds, which provides both high surface hardness and good antistatic effect. Also, SiO
Since the recording film was formed before forming the □ layer, the signal recording and reproducing characteristics were good. Since the optical disc of this invention forms a SiO2 layer on the entire surface after forming an optical recording film,
Since the SiO2 layer is formed not only on the substrate side but also on the recording film side, an optical disk that is resistant to scratches and dust over the entire disk can be obtained.

Next, another embodiment will be described.

In Figure 4, 1.1' is a polycarbonate substrate,
2 is SiO2 layer, 3.3' is SiNx dielectric layer, 4.4
' is a TbFeCo magnetic layer, 5.5° is a SiNx dielectric layer, and 7 is an adhesive layer. 1 and 3.4.5 were laminated in this order by sputtering, and the two sheets were bonded together using epoxy adhesive resin so that the recording layers faced each other. By the liquid phase thin film forming method shown, 1000 people formed 2 Sin2 layers.

The surface hardness of this optical disk is as high as 7H throughout, the half-life of the charged potential is 10 seconds, and it has both high surface hardness and good antistatic effect.

Furthermore, since it is bonded together, there is no warping and deformation, and since it has twice the recording area, a high-density recording medium can be obtained.

Next, another embodiment will be described.

In Figure 5, 1.1° is the polycarbonate substrate,
2.2′ is a Sin□ layer, 3.3′ is a SiNx dielectric layer,
4.4'' is a TbFeCo magnetic layer, 5.5'' is a SiNx dielectric layer, and 7 is an adhesive layer. Si shown in FIG.
1, which was molded using an optimally designed stubber to compensate for the change in groove shape caused by the O2 layer,
By the liquid phase thin film formation method shown in No. 32, SiO□ of 2
After 1000 layers were formed, two sheets of 3.4.5 were laminated in this order by sputtering and bonded together using an epoxy adhesive resin so that the recording films faced each other.

The surface hardness of this optical disk is as high as 7H throughout, the half-life of the charged potential is 10 seconds, and it has both high surface hardness and good antistatic effect.

Furthermore, since it is bonded together, there is no warping and deformation, and since it has twice the recording area, a high-density recording medium can be obtained. In addition, since a two-Si layer is formed before forming the optical recording film, the substrate is less likely to be scratched or dusted during film formation by sputtering or bonding, making handling easier and removing dust. It is easy to use, improves work efficiency, and helps improve yield.

Next, another embodiment will be described.

In Figure 6, 1.1' is a polycarbonate substrate;
2.2' is the 5102 layer, 3.3' is the SiNx dielectric layer,
4.4' is TbFeCo magnetic layer, 5.5' is SiN
x dielectric layer. After masking the area where the grooves of No. 1 are formed to prevent contact with the liquid,
By the liquid phase thin film formation method shown in No. 832, 2 SiO
1000 □ layers were formed, and 3, 4, and 5 were laminated in this order by sputtering, and two sheets were bonded together using an epoxy adhesive resin so that the recording films faced each other.

The surface hardness of this optical disk is as high as 7H throughout, the half-life of the charged potential is 10 seconds, and it has both high surface hardness and good antistatic effect.

Furthermore, since it is bonded together, there is no warpage and deformation, and since it has twice the recording area, a high-density recording medium can be obtained. In addition, since the region where the groove is formed is masked, good recording and reproducing characteristics can be obtained without any change in the groove shape, and since the SiO□ layer is formed before the recording film is formed, sputtering is possible. Since the substrate is less likely to be scratched or dusted during film formation or bonding using the method, it is easy to handle and remove dust, which improves work efficiency and helps improve yield.

The optical disc according to the present invention is not limited to the above embodiments, and the substrate may be a plastic substrate or glass substrate other than a polycarbonate substrate, and the adhesive layer is not limited to epoxy resin, but may be made of other resins. It doesn't matter.

However, when forming the Sin2 layer by a liquid phase thin film formation method after adhesion, it is preferable to use a material with good sealing properties so that liquid does not enter from the interface.

[Effects of the Invention] As explained above, in the optical disc according to the present invention, when a Sin layer is formed by a liquid phase thin film forming method on at least the exposed portion of the substrate material, the film thickness of the 8102 layer is By setting the thickness to 500 Å or more, it is possible to obtain an optical disc that does not warp even when sudden changes in temperature and humidity occur, and is resistant to scratches and dust.

[Brief explanation of drawings]

Figures 1 to 6 are cross-sectional views of optical tissues showing examples of the present invention, and Figure 7 shows the film thickness of the 8102 layer and the warping when the environment changes from 50% RH to 60°C and 90% old 1 at bO. A graph showing the relationship between the angle change amount, Figure 8 shows the relationship between the film thickness of the Sin2 layer and the surface hardness, Figure 9 is an example of the measurement of the chargeability characteristics, and Figure 10 shows the 5102 layer. Figure 11 shows the relationship between the film thickness and the half-life of the charged potential for SiO2.
This graph shows the relationship between the layer thickness and the groove shape of the substrate.
FIG. 11(a) shows the relationship between film thickness and groove depth, and FIG. 11(b) shows the relationship between film thickness and groove width. FIG. 12 is a block diagram of a conventional optical disc. In the figure, 2 is a SiO2 layer. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Masuo Oiwa Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 SiO2 layer film P4 (A) Figure 9 Figure 10 Figure 11 (b) Procedure amendment i (voluntary) 1. Incident Relation to the case of the person making the amendment Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Moriya Shiki, representative of Mitsubishi Electric Corporation 4. Address of the agent: Mitsubishi Electric Corporation, 2-2-3 Marunouchi, Chiyoda-ku, Tokyo, -6 5. Detailed description of the invention and drawings in the specification to be amended 6. Contents of the amendment (1) Details Book page 10, line 14, page 12, line 4, 1st
On page 3, line 6, page 14, line 8, page 15, line 8, and page 16, line 6, ``7H'' will be corrected to ``5H.'' (2) In the drawings, Figure 8 will be corrected as shown in the attached sheet. Above Figure 8 Procedural Amendment - (Voluntary) April 2, 1991 3, Representative of the person making the amendment Moriya Shiki (Contact information: 03 (3213) 3421 Patent Department) & Subject of amendment (1) Description of the specification Claims column (2> Detailed description of the invention in the specification & Contents of amendment (1) The scope of claims in the specification is corrected as shown in the attached sheet. (2) Section 12 in the specification On the 19th line of the page, the phrase "Mask the area covered" is corrected to "Mask the ml covered". 7. Attached animals (1) One document showing the corrected scope of claims. Claims (1) In an optical recording medium consisting of a substrate and an optical recording layer having a memory function, after forming an optical recording layer and a protective layer covering the optical recording layer, a liquid phase thin film is formed on the entire surface. From this, in the optical disk forming the layer 5io, the film thickness of the SiO2 layer is 5io.
An optical disc characterized by having a diameter of 00 Å or more. (2) After bonding two optical recording media consisting of a substrate and an optical recording layer with a memory function so that the recording layers face each other, a Si02 layer is formed on the entire surface using a liquid phase thin film formation method. In the optical disc, the thickness of the 5iO1 layer is 5
An optical disc characterized by having a diameter of 00 Å or more. (3) In an optical recording medium consisting of a substrate and an optical recording layer having a memory function, before forming the optical recording layer, an Si02 layer is formed on the substrate by a liquid phase thin film formation method, and then the optical recording layer is formed. In the optical disc to be formed, the thickness of the SiO2 layer is 5
An optical disc characterized by having a diameter of 00 Å or more.

Claims (3)

[Claims] (1) In an optical recording medium consisting of a substrate and an optical recording layer having a memory function, after forming an optical recording layer and a protective layer covering it, a SiO_2 layer is formed on the entire surface by a liquid phase thin film formation method. An optical disc characterized in that the thickness of the SiO_2 layer is 500 Å or more. (2) An optical disc in which two optical recording media consisting of a substrate and an optical recording layer with a memory function are bonded together so that the recording layers face each other, and then a SiO_2 layer is formed on the entire surface using a liquid phase thin film formation method. , the thickness of the SiO_2 layer is 5
An optical disc characterized by having a diameter of 00 Å or more. (3) In an optical recording medium consisting of a substrate and an optical recording layer having a memory function, before forming the optical recording layer,
An optical disc in which an optical recording layer is formed after forming an SiO_2 layer by a liquid phase thin film forming method, wherein the SiO_2 layer has a film thickness of 500 Å or more.