JPH06349113A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical information recording medium having high preservability over a long period of time and high reliability. CONSTITUTION:One or plural thin films 2-6 including at least a recording film or a reflecting film are laminated on a transparent substrate 1 and a protective film 7 is formed on the thin films by applying and curing a coating material consisting essentially of branched reactive polysiloxane to obtain the objective optical information recording medium. The branched reactive polysiloxane is a polymer of a compd. represented by a general formula SiRR'3 or a compd. represented by a general formula SiR2R'2 and contains 15-35wt.% nonreactive groups and 10-30wt.% reactive groups. In the formulae, R is a nonreactive group and R' is a hydrolyzable reactive functional group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium such as an optical disk or a magneto-optical disk, and more particularly to a material for a protective film formed on a recording film.

[0002]

2. Description of the Related Art Generally, an optical information recording medium such as an optical disk or a magneto-optical disk is provided with a protective film made of a hard and low moisture-permeable material on the recording film in order to prevent the recording film from being corroded or destroyed. There is. Organic polymer materials are often used as the protective film material. For example, a protective film using trialkoxyalkylsilane or dialkoxyalkylsilane has been conventionally known (JP-A-63-42026). But,
If a protective film is formed by using these alone, there is a problem in terms of adhesion and reaction rate with the metal film, necessary corrosion resistance cannot be obtained, and it is insufficient as a protective film for a magneto-optical recording medium. . Therefore, in general, an ultraviolet curable resin is used from the viewpoint of easy handling.

[0003]

Since the curing rate of the ultraviolet curable resin varies depending on the curing conditions, it must be cured in vacuum or in nitrogen to obtain a high curing rate. In addition, the protective film formed by using the ultraviolet curable resin has high water absorption and water permeability when unreacted components remain, and the recording film is apt to corrode. Therefore, an optical information recording medium having a protective film formed by using an ultraviolet curable resin has a problem of low long-term storage stability. An object of the present invention is to solve such drawbacks of conventional products and provide a highly reliable optical information recording medium.

[0004]

In order to achieve the above-mentioned object, the present invention carries a single-layer or multi-layer thin film containing at least a recording film or a reflective film on a substrate, and the branched reactivity on the thin film. Applying a coating agent consisting mainly of polysiloxane,
In the optical information recording medium having a protective film formed by curing, the branched reactive polysiloxane is represented by the general formula: Si
A compound represented by RR'3 (wherein R is a non-reactive group and R'is a hydrolyzable reactive functional group) and the general formula: SiR2R'2 (R and R'are as described above. Same as the above). The composition is preferably 10 to 30% by weight of reactive functional groups and 15 to 35% by weight of non-reactive groups. A protective film using a polysiloxane having a reactive functional group of 30% by weight or more will be cracked, and if it is 10% by weight or less, the film hardness will be low. Further, the branched reactive polysiloxane has a high number average molecular weight of 3OOO to 100OOO because the viscosity increases as the molecular weight increases and it becomes difficult to uniformly coat it on the recording film.

The coating agent has the general formula: SiRR'3
It is preferable that a silicon compound having a molecular weight of 5OO or less represented by (R and R'is the same as above) is contained in an amount of 20% by weight or less.
When the coating agent contains 20% by weight or more of the silicon compound, the hardness is high, but cracks are likely to occur.

The non-reactive group of the branched reactive polysiloxane and the silicon compound having a molecular weight of 50 or less is preferably a phenyl group or an alkyl group having a carbon number of 5 or less, and particularly preferably a methyl group or an ethyl group. The reactive functional group capable of being hydrolyzed is preferably an alkoxyl group having 5 or less carbon atoms and a propenoxy group, and particularly suitable is a methoxy group which has low hydrolysis energy and is easy to handle.

The branched reactive polysiloxane is not limited to being a polymer of two kinds of compounds, and may be one obtained by condensation polymerization of several kinds of compounds having different functional groups. Similarly, the number of silicon compounds having a molecular weight of 5OO or less is not limited to one type, and even if several types are added, the total amount may be 20% by weight or less.

The coating agent in the present invention is usually diluted to an appropriate concentration for use and storage. Examples of the solvent used at that time include alcohols, ketones, ethers, cellosolves, esters, halides, carboxylic acids, aromatic compounds, aliphatic hydrocarbons, etc. Alternatively, it can be used as a mixture of two or more kinds. Of these solvents, particularly preferred are one or more of lower alcohols such as methanol, ethanol and isopropanol, aromatic compounds such as toluene and xylene, and aliphatic hydrocarbons such as hexane, heptane and ligroin. It is a mixture.
Further, these solvents may be used at the time of producing the polymer.

Further, the coating agent in the present invention may optionally contain a crosslinking accelerator, an adhesion improver, a curing catalyst, a leveling agent, a filler and the like.

Although the spin coating method is generally used as the method for forming the protective film in the present invention, the method is not limited thereto and can be appropriately set depending on the situation.

[0011]

The branched reactive polysiloxane reacts with moisture in the air and cures, so that in the atmosphere, a higher reaction rate is obtained as compared with the ultraviolet curable resin whose reaction is inhibited by oxygen. Further, since it is branched, a dense film close to a network structure is formed by the reaction, and the water permeability and the water absorption are extremely low. Moreover, since the branched reactive polysiloxane is synthesized by mixing the bifunctional and trifunctional silicon compounds, the non-reactive groups are appropriately present, and the generation of cracks due to shrinkage during the reaction is eliminated.

[0012]

Embodiment An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a sectional view of an optical information recording medium according to this example. As shown in the figure, the optical information recording medium of the present example has an inorganic dielectric enhancement film 3, a magneto-optical recording film 4, and an inorganic dielectric enhancement film 3 on the preformat pattern forming surface 2 of the transparent substrate 1. An inorganic protective film 5 and a metallic reflective film 6 are sequentially laminated by sputtering, and these film bodies 3 to
A protective film 7 is formed so as to cover 6.

The transparent substrate 1 is made of, for example, ceramic material such as glass, polycarbonate resin, polymethylmethacrylate resin, polymethylpentene resin, epoxy resin,
A transparent resin material such as a photocurable resin is formed into a desired shape and size. On one side of this transparent substrate 2, recording,
A pre-format pattern 2 such as a guide groove for reproducing light and a pre-pit row is formed in a fine uneven shape. The method of forming the preformat pattern 2, the arrangement, and the like are known techniques and are not the subject matter of the present invention, and thus the description thereof is omitted. Appropriate known techniques can be applied to these depending on the type of the magneto-optical disk. The enhancement film 3 multiple-reflects the reproducing laser beam between the surface of the transparent substrate 1 on which the preformat pattern 2 is formed and the magneto-optical recording film 4, and increases the apparent Kerr rotation angle to increase the reproducing C / N ratio. Is provided to obtain, for example, SiO, SiO2, SiN, S
It is formed of an inorganic dielectric material such as i3N4, AlN, Al2O3, etc., whose refractive index of the reproducing laser beam is slightly larger than that of the transparent substrate 1. The magneto-optical recording film 4 may be made of any known magneto-optical recording material, but a perpendicular magnetization film containing a rare earth element and a transition element as main components is particularly preferable. As this type of recording material, Gd
-Fe, Tb-Fe, Dy-Fe, binary alloys such as Gd-Co, Gd-Tb-Fe, Gd-Fe-Co, Tb-F
ternary alloys such as e-Co and Dy-Fe-Co, Gd-Tb
There are quaternary alloys such as -Fe-Co and Tb-Dy-Fe-Co. The inorganic protective film 5 protects the magneto-optical recording film 4 from an impact and a corrosive atmosphere, and multiplexes the reproducing laser beam transmitted through the magneto-optical recording film 4 between the magneto-optical recording film 4 and the reflective film 6. It is provided to reflect and increase the apparent Kerr rotation angle to obtain a large C / N ratio, and is formed of the same inorganic dielectric material as the enhance film 3. The reflection film 6 is provided in order to return the reproducing laser beam transmitted through the magneto-optical recording film 4 to the transparent substrate 1 side and obtain a large signal intensity, and is made of, for example, aluminum, aluminum alloy, stainless steel or the like. It is formed. The protective film 7 has a branched reactive polysiloxane as a main component, is coated with a coating agent containing a silicon compound having a molecular weight of 5OO or less, and is cured. Specific examples will be described below.

Example 1 First, trimethoxymethylsilane and dimethoxymethylsilane were polymerized at a ratio of 3: 5, and the methoxy group was 15% by weight, the methyl group was 20% by weight, and the number average molecular weight was about 60OO. Branched reactive polysiloxane A
Was synthesized. Branched reactive polysiloxane A 100 parts by weight Trimethoxymethylsilane 5 parts by weight γ-glycidoxypropyltrimethoxysilane 1 part by weight Dibutyltin diularate 0.1 parts by weight Toluene 300 parts by weight An optical disk A was prepared by preparing a coating agent A, forming a protective film 7 using the coating agent on the reflective film 6 by spin coating, and then curing the coating film. The thickness of the cured protective film was about 5 μm.

Example 2 As in Example 1, trimethoxyphenylsilane and dimethoxydiphenylsilane were polymerized at a ratio of 9: 2, 13% by weight of methoxy group, 27% by weight of phenyl group, number average molecular weight. A branched reactive polysiloxane B having a molecular weight of about 7500 was synthesized.

Branched reactive polysiloxane 110 parts by weight methyltriethoxysilane 10 parts by weight γ-aminopropyltriethoxysilane 1 part by weight tetrabutyl titanate 0.3 parts by weight ligroin 100 parts by weight xylene 170 parts by weight An optical disc B was prepared in the same manner as in Example 1 by preparing a coating agent B consisting of

Example 3 In the same manner as in Example 1, tripropenoxymethylsilane, dimethoxydimethylsilane and trimethoxyethylsilane were polymerized at a ratio of 2: 7: 8, and the methoxy group was 12% by weight and the propenoxy group was 12% by weight. Is 4% by weight, methyl group is 10% by weight, ethyl group is 8% by weight, and number average molecular weight is about 5OOO.
Was synthesized.

Branched reactive polysiloxane 100 parts by weight Methyltrimethoxysilane 5 parts by weight Octadecyltrimethoxysilane 1 part by weight Tri-n-butylamine 0.1 parts by weight Methanol 100 parts by weight Toluene 200 parts by weight Next, from the above compound The coating agent C was prepared and an optical disk C was produced in the same manner as in Example 1.

[Comparative Example 1] Using an ultraviolet curable resin,
A protective film was formed on the reflective film by spin coating as in the example. UV light is applied to cure it in the atmosphere,
An optical disc D was produced. The thickness of the cured protective film is 8μ
It was m.

The optical disks obtained in the above-mentioned Examples and Comparative Examples were left in an environment of a temperature of 8 ° C. and a relative humidity of 90% for 3OOO hours, after which the reproduction C / N ratio was measured and the presence or absence of corrosion was inspected. It was As a result, the reproduction C / N ratio of the optical disc D is 30%.
Although it was lowered and corrosion was observed in a part of the recording film, deterioration and corrosion of the reproduction C / N ratio were not observed in the optical discs A to C. It was found that the optical information recording medium according to the present invention has a high protective effect against a corrosive atmosphere.

[0021]

As described above, according to the present invention, since the protective film is formed by using the coating agent containing the branched reactive polysiloxane as the main component, the water permeability and the water absorption of the protective film are improved. It is possible to reduce the corrosion of the recording film and improve the long-term storage stability of the optical information recording medium. Further, since the branched polysiloxane of the present invention and the condensate generated upon curing are not corrosive or toxic, it is possible to provide a safe and highly reliable optical information recording medium.

[Brief description of drawings]

FIG. 1 is a cross section of an optical disc according to an embodiment of the present invention.

[Explanation of symbols]

 1 Transparent Substrate 2 Preform Pattern 3 Enhance Film Made of Inorganic Dielectric 4 Magneto-Optical Recording Film 5 Inorganic Protective Film Made of Inorganic Dielectric 6 Reflective Film Made of Metal 7 Protective Film Formed from Branched Reactive Polysiloxane

Claims (4)

[Claims] 1. A transparent substrate on which one or more thin films containing at least a recording film or a reflective film are supported, and a coating agent containing a branched reactive polysiloxane as a main component is applied and cured on the thin films. In the optical information recording medium provided with a protective film, the branched reactive polysiloxane has the general formula:
A compound represented by SiRR'3 (wherein R is a non-reactive group and R'is a hydrolyzable reactive functional group) and a general formula: SiR2R'2 (R and R'in the formula) Is a polymer of a compound represented by the above) and has a non-reactive group of 15
The optical information recording medium is characterized by containing ˜35% by weight and a reactive group of 1O˜3O% by weight. 2. The optical information recording medium according to claim 1, wherein the branched reactive polysiloxane has a number average molecular weight of 3OOO to 100OOO. 3. The coating composition according to claim 1, wherein the coating agent contains a silicon compound represented by the general formula: SiRR′3 (wherein R and R ′ are the same as above) and having a molecular weight of 5OO or less in an amount of 20% by weight or less. An optical information recording medium characterized by the above. 4. The branched reaction according to claim 1, wherein the non-reactive group is an alkyl group or a phenyl group, and the hydrolyzable reactive functional group is an alkoxyl group such as a methoxy group or an ethoxy group, or a propenoxy group. An optical information recording medium comprising a coating agent comprising a polysiloxane and a silicon compound according to claim 3.