JPH02101651A - Optical recording medium and production thereof - Google Patents

Abstract

PURPOSE:To improve the hardness over the entire part of protective layers of the recording medium and to obtain the high effect of protecting the recording layer or reflecting layer of the medium by forming a part of the protective layers of the recording medium of an enhancement layer mixed with <=20vol.% reinforcing fillers. CONSTITUTION:The optical recording medium is constituted by forming two layers of the protective layers 5A, 5B on the recording layer or reflecting layer 4, and providing a transparent substrate 1, signal patterns 2, an enhancement layer 3 as an underlying layer or the recording layer or reflecting layer 4. The 1st protective layer 5a laminated on this recording layer or reflecting layer 4 is formed of the dielectrics of the inorg. compd. similar to the compd. used to form the enhancement layer 3 and the 2nd protective layer 5B to be formed thereon is formed of the high-polymer film mixed with <=20vol.% reinforcing fillers like with the protective layer 5. The hardness over the entire part of the protective layers is improved and the high effect of protecting the recording layer or reflecting layer 4 is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a single-layer optical recording medium and a method for manufacturing the same, and in particular, the structure of a protective layer provided on a recording layer or a reflective layer and a method for manufacturing the same. Regarding.

[Conventional technology]

A single-plate optical recording medium has a structure in which a recording layer or a reflective layer formed on a signal surface of a transparent substrate is covered with a protective layer. In this way, since the protective layer in an optical recording medium with a single-layer structure is exposed to the outside, it has higher mechanical and physical strength than the protective layer in an optical recording medium with a laminated structure. It is required to have high stability and a high sealing effect of the recording layer or reflective layer.

Conventionally, the protective layer material has been 5iOz.

Zr0z, 5iaN4. Dielectric materials made of inorganic compounds such as TiN have been proposed (see JP-A-61-258353 and JP-A-60-131659).

In addition, it has been conventionally known to form a protective layer made of an ultraviolet curable resin on the recording layer (see Japanese Unexamined Patent Publication No. 57-27494) or to form a rust preventive layer on the recording layer (
(See Japanese Patent Laid-Open No. 61-54058) has been proposed.

Furthermore, it has been proposed to form a protective layer made of a metal film on the recording layer (see Japanese Patent Laid-Open No. 58-60441).

[Problem to be solved by the invention]

However, among the above-mentioned protective layers, only one of the protective layers is formed of an inorganic dielectric material. When the protective layer is formed by sputtering, defects such as pinholes are likely to occur, and since air and moisture enter through these defects, there is a problem that the recording layer or reflective layer is likely to be corroded. In particular, since it is easily affected by the surface condition of the underlying layer, if the recording layer or reflective layer and protective layer are sequentially formed by sputtering, the influence of defects such as pinholes and gaps between columnar particles in the recording layer As a result, more defects occur in the protective layer.

In addition, a protective layer formed of an ultraviolet curable resin or a rust preventive agent is less effective in preventing corrosion of the recording layer or reflective layer because the ultraviolet curable resin and antirust agent themselves have moisture permeability.
The function as a protective layer cannot be fully demonstrated.

On the other hand, when the protective layer is formed of a metal film, the above-mentioned intrusion of air and moisture does not pose a problem, but on the other hand, there is a problem that the thermal conductivity increases and the recording sensitivity deteriorates.

Furthermore, among the above-mentioned protective layers, the protective layer formed of an inorganic compound dielectric, an ultraviolet curable resin, and a rust preventive agent is
Mechanical and physical strength such as abrasion resistance and impact resistance are insufficient, and it is easily worn out after short-term use or damaged by collision with foreign objects, so it cannot be applied to optical recording media with a single-plate structure. do not have.

The purpose of the present invention is to eliminate such drawbacks of the prior art,
To provide an optical recording medium with high recording sensitivity and excellent durability.

[Means to solve the problem]

In order to achieve the above object, the present invention is characterized in that the protective layer is formed of a polymer film mixed with 20% by volume or less of a reinforcing filler.

Further, when laminating a protective layer on the recording layer or reflective layer, drop a liquid material of a polymer compound in which 20% by volume or less of reinforcing filler is uniformly dispersed on the recording layer or reflective layer,
The manufacturing feature is that the protective layer is formed by spin coating.

[Effect]

When a predetermined reinforcing filler is mixed into a polymer film, mechanical and physical strengths such as abrasion resistance and impact resistance are improved.

Moreover, when the mixing rate of the reinforcing filler is set to 20% by volume or less, there is almost no dropout of the filler from the polymer membrane. Therefore, the desired durability can be maintained even when applied to an optical recording medium with a single-layer structure in which the protective layer may come into direct or indirect contact with other members such as a magnetic head or a cartridge case. Problems such as dust generation are also less likely to occur.

Furthermore, since a polymer film is used as the base material for the protective layer, pinholes and increased thermal conductivity do not become a problem, and the inclusion of reinforcing fillers improves moisture permeability, which is a drawback of polymer films. Since this decreases, the sealing effect of the recording layer or reflective layer is also improved.

In addition, when a spin coating method is used as a means of forming a protective layer, it is possible to simplify production equipment and improve mass production compared to vacuum film formation methods such as sputtering, and it is possible to manufacture optical recording media. You can lower the cost by 1~.

〔Example〕

First, embodiments of the present invention will be generally described using the optical disk medium shown in FIGS. 1 to 3 as an example.

FIG. 1 is a sectional view showing the basic structure of an optical recording medium according to the present invention, in which a base layer 3, a recording layer or reflective layer 4, and a protective layer 5 are provided on a signal pattern forming surface 2 of a transparent substrate 1. Laminated in sequence.

The transparent substrate 1 is formed into a circular shape using a transparent material such as glass, polymethyl methacrylate (PMMA), polycarbonate (PC), or epoxy resin, and has a center hole 1b formed in its center. On one side of the transparent substrate 1, a pre-group 2a corresponding to a tracking signal and a pre-pit 2 corresponding to an address signal etc.
b is formed and constitutes the signal pattern forming surface 2.

The method for forming the pre-groups 2a and pre-pits 2b can be appropriately selected depending on the substrate material. That is, in the case of the transparent substrate 1 made of glass, the so-called 2P method in which a replica is formed using a photocurable resin is suitable. Furthermore, in the case of the transparent substrate 1 made of thermoplastic resin such as PMMA or PC, injection molding is suitable. Furthermore, in the case of the transparent substrate 1 made of thermosetting resin such as epoxy resin, a casting method is suitable.

The underlayer 3 is formed mainly to improve the recording sensitivity of the recording layer 4, which will be described in detail later, and to prevent moisture from permeating from the transparent substrate 1 to the recording layer or the reflective layer. It is formed as necessary, and can be omitted if it is not necessary.

The underlayer 3 for improving the recording sensitivity of the recording layer 4 is formed of an appropriate material depending on the type of heat mode recording material constituting the recording layer.

For example, for a recording layer made of a magneto-optical recording material, for example, SiN, Si○+AIN, 5tiN4°T i O
, A l z O=, or the like is formed. The enhancement layer is intended to increase the apparent Kerr rotation angle by reflecting the reproduction laser beam multiple times between the magneto-optical recording layer and the signal pattern forming surface of the transparent substrate 1. 800~ for 2
It is formed to a thickness of 1200 angstroms. Also,
For recording layers made of perforated heat mode recording materials, for example, polytetrafluoroethylene, guanine,
melts below the melting, decomposition, or sublimation temperature of the heat mode recording material, such as nitrocellulose;
Formed by organic compounds that decompose or sublimate.

On the other hand, as the base layer 3 for preventing the transmission of moisture from the transparent substrate 1 to the recording layer or the reflective layer 4, a dielectric material made of the same inorganic compound as that used to form the enhancement layer can be used.

The recording layer 4 can be formed using any known heat mode recording material, such as a low melting point alloy, an organic dye, a magneto-optical recording material, or a phase change type recording material.

In addition, if the optical recording medium is read-only,
A reflective layer is formed in place of the recording layer.

The base M3 and the recording layer or reflective layer 4 are formed by, for example, a vacuum film forming method such as sputtering.

The protective layer 5 is formed of a polymer film in which 20% by volume of reinforcing filler is uniformly dispersed. This protective layer 5 is
A ring shape is formed on the signal pattern forming surface 2 of the transparent substrate 1, and its outer peripheral end 5a and inner peripheral end 5b are formed on the transparent substrate 1 so that the base layer 3 and the recording layer or reflective layer 4 are not exposed to the outside. is coated on. Further, a region 1a where the protective layer 5 is not covered is provided between the inner circumferential end 5b of the protective layer and the center hole 1b.

Examples of the reinforcing filler include α-Fe303,
Ti0z, Al2O:I, 5iOz, SiC.

Cr: Fine particles of an inorganic compound such as l O3, - Fine particles of an organometallic compound represented by the formula RCOOM (wherein R is a hydrocarbon having 10 to 20 carbon atoms, and M is a metal other than an alkali metal), carbon Conductive fine particles such as a blank, and a lubricant such as a fatty acid organic compound, a fluorine organic compound, or a silicon organic compound can be used.

Here, the fine particles of the inorganic compound and the fine particles of the organometallic compound have higher hardness than the polymer membrane that is the base material of the protective layer, and have the function of directly improving the mechanical and physical strength of the protective layer. Further, the conductive fine particles have the function of preventing static electricity from accumulating, and preventing damage to the protective layer due to attachment of highly hard foreign matter, head crashes in magneto-optical recording media, and the like.

Furthermore, the lubricant has the function of preventing the adhesion of foreign matter and of alleviating the WI impact force acting on the protective layer when a head crash or the like occurs.

Examples of the fatty acid organic compound used include fatty acids, metal salts of fatty acids, fatty acid esters, and fatty acid amides.

Specific examples of the fatty acids include myristic acid, palmitic acid, oleic acid, and stearic acid.

Examples include behenic acid.

Specific examples of the metal salts of the fatty acids include calcium salts, magnesium salts, aluminum salts, iron salts, cobalt salts, zinc salts, barium salts, and lead salts of the aforementioned fatty acids.

Examples of the fatty acid ester include butyl stearate, monoglyceride stearate, monoglyceride palmitate, monoglyceride oleate, and pentaerythritol tetrastearate.

Examples of the fatty acid amide include caproic acid amide,
These include capric acid amide, lauric acid amide, palmimic acid amide, behenic acid amide, oleic acid amide, linoleic acid amide, and methylene bisstearic acid amide.

Examples of the fluorine-based organic compound include trichlorofluoroethylene, perfluoropolyether, and perfluoroalkyl polyether.

Examples of the silicon-based organic compound include silicone oil.

Note that as the reinforcing filler dispersed in the protective layer 5, one type of substance selected from the above-mentioned substances can be used alone, or a plurality of types of substances can be used in any combination. . When the reinforcing filler is in the form of powder or granules, the particle size is preferably adjusted to 1 μm or less in order to ensure the smoothness of the surface of the protective layer 5.

As the polymeric material that is the base material of the protective layer 5, it is preferable to use a substance selected from the group of radiation-curable resins and thermosetting resins. The radiation curable resin referred to herein includes ultraviolet ray curable resin, electron beam curable resin, and the like.

As a means for forming the protective layer 5, a so-called spin coating method is suitable because it can be manufactured using inexpensive and small-sized manufacturing equipment and has high mass productivity. In this case, a protective layer 5 that facilitates handling of the polymer compound and has a highly uniform thickness is used.
In order to form this, it is more preferable to drop an unpolymerized polymer compound onto the inner periphery of the recording layer or reflective layer 4, form a thin film by spin coating, and then polymerize the polymer compound. .

In this optical recording medium, a predetermined reinforcing filler is mixed into the protective layer 5, so that the mechanical and physical strength of the protective layer 5, such as abrasion resistance and impact resistance, is improved, and the reinforcing filler is Since the mixing rate is set to 20% by volume or less, there is almost no dropout of the filler from the polymer membrane. Therefore, the protective layer may be exposed to the outside and come into direct or indirect contact with the magnetic head or other components such as the cartridge case. Optical recording media can be put into practical use.

In addition, since a polymer film is used as the base material for the protective layer, there are no problems with pinholes or increased thermal conductivity, and the addition of a reinforcing filler reduces moisture permeability, which is a drawback of polymer films. Since this decreases, the sealing effect of the magneto-optical recording layer 4 is improved, and from this point of view as well, the service life of the optical recording medium can be extended.

Further, since the spin coating method is used as a means for forming the protective layer 5, production equipment can be simplified and mass productivity can be improved, and the production cost of the optical recording medium can be reduced.

Next, another example of the optical recording medium according to the present invention will be explained based on FIG.

As shown in this figure, in the optical recording medium of this example, two protective layers 5at5b are formed on the recording layer or reflective layer 4. The transparent substrate 1, the signal pattern 2, the enhancement layer 3, and the recording layer or reflective layer 4 are the same as those in the previous embodiment, so the same members are denoted by the same reference numerals and the explanation thereof will be omitted.

First protective layer 5a laminated on the recording layer or reflective layer 4
For example, S iN, S io, AIN.

The dielectric material is made of the same inorganic compound as the enhancement layer and underlayer, such as 5i3Ns, TiC, Al2O3, etc.

Further, the second protective layer 5b laminated on the first Wi-retention layer 5a is similar to the protective layer 5 in the embodiment described above.
It is formed using a polymer film mixed with 0% by volume or less of a reinforcing filler.

In the optical recording medium shown in FIG. 2, a protective layer made of an inorganic compound is interposed below the filler-containing protective layer, so that the hardness of the entire protective layer is improved and a higher protective effect of the recording layer or reflective layer 4 can be obtained. can.

Next, still another example of the optical recording medium according to the present invention will be explained based on FIG. 3.

As shown in this figure, in the optical recording medium of this example, a lubricant layer 6 is coated on a protective layer 5.

The transparent substrate 1, signal pattern 2, enhancement layer 3, recording layer or reflective layer 4, and protective layer 5 are the same as in the embodiment shown in FIG. do.

The lubricant layer 6 is a lubricant of the same type as the lubricant mixed into the protective layer 5 as a reinforcing filler, that is, for example, a fatty acid-based organic compound or a fluorine-based organic compound.

The optical recording medium shown in FIG. 3, which is formed using at least one organic compound selected from the group of silicon-based organic compounds or a solid lubricant, has a lubricant layer 6 coated on the protective layer 5. The abrasion resistance and water retention or oil repellency of the layer 5 are further improved, and a higher protective effect of the recording layer or reflective layer 4 can be obtained.

Hereinafter, more specific examples of the composition of the protective layer containing reinforcing filler will be shown, and the effects of the present invention will be discussed.

First composition example> Fine particles of inorganic compound (particle size: 1 μm or less) 15 parts by weight Carbon black 3 parts by weight Oilel oleate 0.7 parts by weight Ultraviolet curable resin (including reactive diluent) 100 parts by weight The layer formation procedure is as follows.

First, a solution of an ultraviolet curable resin having the above-mentioned composition and having a viscosity adjusted to several tens to hundreds of voices is prepared.

Next, this solution was filtered through a 2 μm filter, and the
It is coated on the transparent substrate (more precisely, on the recording layer or other protective layer formed on the transparent substrate) which is rotationally driven at an arbitrary rotational speed between 5000 rpm and has a film thickness of 5 to 2.
Forms a coating film of 0 μm.

Finally, an integrated light amount of 1000 to 2000 mJ is applied to the coating film.
/cm” of ultraviolet rays to harden the ultraviolet curable resin,
crosslink.

Second composition example> Fine particles of inorganic compound (particle size: 1 μm or less) 15 parts by weight Carbon black 7 parts by weight Polyurethane resin 100 parts by weight Bifunctional or trifunctional isocyanate 10% by weight However, on the protective layer of the above composition overcoat with lubricant.

The procedure for forming the protective layer in this example is as follows.

First, a solution of a polyurethane resin having the following composition and having a viscosity adjusted to several tens to hundreds of poise is prepared.

Fine particles of inorganic compound (particle size: 1 μm or less) 15 parts by weight Carbon black 7 parts by weight Polyurethane resin 100 parts Next, to this solution, 10% by weight of bifunctional or trifunctional incyanate based on the polyurethane resin was added. After redispersion, 2 μm
Filter with a filter.

Next, this solution is applied onto the first protective layer of the transparent substrate which is rotated at an arbitrary rotational speed between 500 and 5000 rpm to form a coating film having a thickness of 5 to 20 μm.

Next, the transparent substrate on which the coating film was formed was heated to 80°C to 120°C.
The product is placed in a baking oven at 10° C. for about 10 minutes to perform a solvent removal treatment and a reaction treatment of the polyurethane resin and isocyanate.

Furthermore, on the second protective layer mixed with this reinforcing filler, 0.00% of a fatty acid ester or a silane coupling agent containing fluorocarbon such as CFa or CzFs at the end is applied.
Overcoat the 5-5% solution.

Finally, the transparent substrate on which the lubricant layer was formed was heated to 80°C
After being stored in a baking oven at 120° C. for about 10 minutes to perform a solvent removal treatment, it is cured at a temperature of 60° C. for about 1 hour to promote crosslinking by incyanate.

The table below shows the difference in surface hardness and the abrasion resistance test results between the protective layer of each of the composition examples described above and a conventionally known protective layer of an ultraviolet curable resin containing no filler. However, the wear resistance test is performed by sliding a magnetic head on the protective layer of an optical recording medium that is rotated at 1800 rpm, and evaluated by the number of passes of the magnetic head until the protective layer is damaged. did.

As shown in the above table, all of the protective layers according to the present invention have higher surface hardness than a protective layer made of an ultraviolet curable resin alone, and also have excellent abrasion resistance. Note that not only the protective layers of the first and second composition examples, but also all of the protective layers listed in the examples above have similar effects.

The present invention applies not only to disc-shaped optical recording media.

For example, the invention can be applied to optical recording media of any shape, such as card-shaped optical recording media.

〔Effect of the invention〕

As explained above, the optical recording medium of the present invention has improved mechanical and physical strength such as abrasion resistance and impact resistance because the protective layer is formed with a polymer film mixed with a predetermined reinforcing filler. be done. Moreover, since the mixing rate of the reinforcing filler is set to 20% by volume or less, there is almost no dropout of the filler from the polymer membrane. Therefore, the present invention can be applied to optical recording media having a single-layer structure in which the protective layer is in direct contact with other members such as a magnetic head or a cartridge case.

In addition, since a polymer film is used as the base material for the protective layer,
Pinholes and increased thermal conductivity do not become a problem,
Furthermore, the inclusion of the reinforcing filler reduces the moisture permeability, which is a drawback of polymer films, and thus improves the sealing effect of the recording layer or reflective layer.

Furthermore, since the spin coating method is used as a means for forming the third layer, production equipment can be simplified and mass productivity can be improved, and the production cost of the optical recording medium can be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the basic structure of the optical recording medium according to the present invention, FIG. 2 is a sectional view showing another example of the optical recording medium according to the present invention, and FIG. 3 is a sectional view showing the basic structure of the optical recording medium according to the present invention. FIG. 7 is a cross-sectional view showing still another example of a recording medium. 1: Transparent substrate, 2: Signal pattern forming surface, 3: Base layer,
4: Recording layer, 5: Protective layer, 6: Lubricating layer, X-X: Disc center. Figure 1 Figure 3 Figure 2 Figure 2 7:1 Akira Translation 2: I official title/l"kuno 3, lower counterfeit 4, i this 4 criminal layer yo no 1 return πbW 5' 47 ili /1 x- x: ゛4゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゜゜゜゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛1

Claims (16)

[Claims] (1) In an optical recording medium having a single-plate structure in which at least a recording layer or a reflective layer and a protective layer are laminated on the signal pattern forming surface of a transparent substrate, at least a part of the protective layer is
An optical recording medium characterized in that it is formed of a polymer film mixed with a reinforcing filler of 0% by volume or less. (2) An optical recording medium characterized in that fine particles of an inorganic compound are mixed as the reinforcing filler according to claim (1). (3) An optical recording medium characterized in that fine particles of an organometallic compound are mixed as the reinforcing filler according to claim (1). (4) An optical recording medium characterized in that conductive fine particles are mixed as the reinforcing filler according to claim (1). (5) An optical recording medium characterized in that a lubricant is mixed as the reinforcing filler according to claim (1). (6) As the reinforcing filler according to claim (1), a mixture of at least two or more substances selected from fine particles of an inorganic compound, fine particles of an organic metal compound, conductive fine particles, and a lubricant is mixed. Characteristic optical recording media. (7) The inorganic compound according to claim (2) or claim (6) is α-Fe_2O_3, Al_2O_3, TiO_
2. An optical recording medium characterized by being at least one inorganic compound selected from the group of SiO_2, Cr_2O_3, and SiC. (8) An optical recording medium characterized in that the organometallic compound according to claim (3) or claim (6) has the following general formula. General formula RCOOM However, R in the formula is a hydrocarbon having 10 to 20 carbon atoms M is a metal other than an alkali metal (9) An optical recording medium, wherein the conductive fine particles according to claim (4) or (6) are carbon black. (10) The lubricant according to claim (5) or claim (6) contains at least one compound selected from the group of fatty acid-based organic compounds, fluorine-based organic compounds, and silicon-based organic compounds.
An optical recording medium characterized in that it is a type of organic compound. (11) An optical recording medium, wherein the polymer film according to claim (1) is formed of a polymer material selected from the group of radiation-curable resins and thermosetting resins. (12) The protective layer according to claim (1) comprises a first protective layer made of an inorganic compound and laminated on the recording layer or reflective layer, and a polymer film mixed with 20% by volume or less of a reinforcing filler. and a second protective layer laminated on the first protective layer. (13) The optical recording medium according to claim (1), wherein the surface of the protective layer is coated with a lubricant layer. (14) The lubricant layer according to claim (13) is formed of at least one type of organic compound selected from the group of fatty acid-based organic compounds, fluorine-based organic compounds, and silicon-based organic compounds. optical recording medium. (15) A method for producing an optical recording medium, which includes a step of forming at least a recording layer or a reflective layer and a protective layer on the signal pattern forming surface of a transparent substrate, when laminating the protective layer on the recording layer or the reflective layer. , a protective layer is formed by dropping a liquid material of a polymer compound in which 20% by volume or less of a reinforcing filler is uniformly dispersed onto the recording layer or reflective layer, and using a spin coating method. A method for manufacturing an optical recording medium. (16) In the method for producing an optical recording medium according to claim (15), an unpolymerized polymer compound is dropped onto the recording layer or the reflective layer, a thin film is formed by spin coating, and then the polymer A method for producing an optical recording medium, comprising polymerizing a compound.