JPH0460935A - Optical imformation recording medium - Google Patents

Abstract

PURPOSE:To suppress warping of a medium due to changes in temp. or humidity by applying and hardening an org. silicon compd. only on the opposite side to the recording film side of the substrate so as to form a first film, and then forming a silicon dioxide film thereon. CONSTITUTION:The first film is formed by applying and hardening an org. silicon compd. only on the opposite side to the groove side of a transparent substrate. Then a silicon dioxide film is formed on th;e first film comprising the org. silicon compd. by bringing the substrate into contact with a hydrosilicofluoric acid aq. soln. in a supersaturated state of silicon dioxide to cause precipitation. By this method, the silicon dioxide film can be formed into almost same thickness as that of the total film thickness of the recording film side. Thereby, warping of the medium due to changes in temp. or humidity can be suppressed.

Description

[Detailed Description of the Invention] The present invention relates to an optical information recording medium such as a magneto-optical disk, and more particularly, to an optical information recording medium such as a magneto-optical disk, which suppresses warping caused by changes in temperature and humidity, and has long-term reliability. Related to optical information recording media.

Optical information recording media such as magneto-optical disks and video disks generally have a structure in which a recording film is provided on a transparent synthetic resin substrate such as polycarbonate or polymethyl methacrylate.

Since all recording medium materials used for recording films are easily oxidized and hydrolyzed, development of protective layers to prevent deterioration of recording films is underway. In addition, in optical information recording media that use synthetic resin substrates, warping occurs due to water absorption and swelling of the substrate, which may cause the recording film to peel off, signal reading to become impossible, or the amount of water that permeates. This causes problems such as deterioration of the recording film. Therefore, how to solve these problems and ensure the long-term reliability of optical information recording media has become an important issue.

Incidentally, in recent years, in order to modify the surface of a synthetic resin molded article, a technique has been developed in which the surface of a synthetic resin molded article is coated with a thin film of an oxide such as silicon dioxide. Methods for coating the oxide film include vacuum evaporation, sputtering, ion blasting, and plasma C.
Various methods such as VD are known, but these film forming methods require special equipment and are difficult to uniformly coat a molded object with a complex shape. Adhesion is insufficient.

Therefore, instead of directly coating the surface of the synthetic resin molded body with a silicon dioxide film, the entire surface of the synthetic resin molded body is coated with an organosilicon compound and cured to form a primary coating, and then the supersaturated state of silicon dioxide is coated and cured. A method (precipitation method) has been proposed in which a silicon dioxide film is formed on the primary film by contacting it with a hydrofluorosilicic acid solution (Japanese Unexamined Patent Publication No. 61-12).
No. 734, JP-A-1-132640, JP-A-1-21
7044 etc.). If this deposition method is applied to a substrate such as a magneto-optical disk, an optical information recording medium with improved moisture resistance, scratch resistance, etc. can be obtained.

However, if the conventional method of forming a primary film and a silicon dioxide film on the entire surface of a molded body is applied to a magneto-optical disk substrate, the groups (microscopic (Irregularities) This may cause the groove to become sluggish, uneven distribution of groove depth may occur, or in severe cases, groups may disappear. This becomes an important problem, especially for substrates containing preformats.

Furthermore, if a recording film is provided on one side (group side) after forming a primary coating and a silicon dioxide coating on the entire surface of the substrate, the thickness of each layer in the cross-sectional structure will not be symmetrical with respect to the substrate. This creates an imbalance in thermal expansion/contraction and swelling due to moisture absorption on the front and back sides of the optical information recording medium, and it is not possible to completely suppress warping that occurs due to changes in temperature and humidity, which is a problem with single-layer discs.

These problems cause a decrease in sensitivity, scattering of laser light, etc., and impair the long-term reliability of the optical information recording medium.

An object of the present invention is to provide an optical information recording medium that is suppressed from warping due to changes in temperature and humidity, has excellent moisture resistance, corrosion resistance, and scratch resistance, and has long-term reliability. .

As a result of intensive research in order to overcome the problems of the prior art, the present inventors have discovered that a transparent synthetic resin substrate is coated and cured with an organosilicon compound only on the surface opposite to the group surface. After forming the primary film, contact with a supersaturated hydrofluorosilicic acid solution of silicon dioxide to form a silicon dioxide film on the primary film, and provide a recording film on the group surface of the thus obtained substrate. The inventors have discovered that the above object can be achieved, and have completed the present invention based on this knowledge.

Since the substrate surface of this optical information recording medium is coated with a silicon dioxide film, its moisture resistance, corrosion resistance, and scratch resistance are significantly improved, and its water absorption is extremely low. In addition, by adjusting the thickness of the primary coating and the silicon dioxide coating, if the thickness of the entire layer is the same as that of the recording film, the symmetry between the front and back sides can be maintained, and an optical information recording medium without warping can be created. can be created.

The present invention has been completed based on these findings.

According to the present invention, in an optical information recording medium having a recording film formed on a substrate, the substrate is coated with an organosilicon compound only on the surface opposite to the recording film. A transparent synthetic resin substrate having a coated and cured primary coating, and a silicon dioxide coating formed on the primary coating by contacting with a supersaturated hydrofluorosilicic acid solution of silicon dioxide. An optical information recording medium is provided.

Each component of the present invention will be explained below.

(Optical information recording medium) The optical information recording medium used in the present invention has a recording film on a transparent substrate made of synthetic resin, and the layer structure of the recording film is usually a magneto-optical material layer and a dielectric layer. It has a multilayer structure including a protective layer and/or a protective layer.

As long as the optical information recording medium in the present invention has the above-mentioned multilayer structure, such as a single-plate specification or a laminated specification, etc.
This includes conventionally known structures, but is particularly effective for single-plate structures.

The synthetic resin used as the material for the substrate may be any synthetic resin with excellent transparency, such as polycarbonate resin, acrylic resin, epoxy resin, etc., which is used for optical information recording media (although not particularly limited). Among these, polycarbonate resins that form strong chemical bonds with organosilicon compounds are preferred.

These substrates are provided with a primary film coated and cured with an organosilicon compound only on the surface (mirror surface) opposite to the surface on which the groups are provided, and on top of that is a supersaturated state of silicon dioxide. A silicon dioxide film is formed by contacting with a hydrofluorosilicic acid solution.

As the recording layer, TbFeCo, GdFe, TbCo,
DyFe, NdDyFeCo, TbFe, GdFeB1
．． Any conventionally known recording film such as a recording film made of GdTbFe or the like, or a film made of a phase change type recording material or a dye-based recording material can be used.

The material for the dielectric layer and/or protective film is 5in.
2. A dielectric material that forms a Si-based transparent layer, such as SiN, 5iAI2ON, and SiAβN, can be preferably used.

(Substrate) <Primary Coating> In the present invention, first, an organosilicon compound is coated and cured only on the surface of the transparent synthetic resin substrate opposite to the group surface side (the surface on which the recording film is provided). Form a primary film.

Examples of organosilicon compounds include general-purpose silane coupling agents containing a vinyl group, a methacryloxy group, an epoxy group, an amino group, an isocyanate group, or the like. Specifically, organosilicon compounds represented by the following general formulas CI] and [II] can be exemplified.

Xn S I Y4-n [I
[However, X is a hydrocarbon group having 1 to 6 carbon atoms, a vinyl group, a methacryloxy group, an epoxy group, an amino group, or a hydrocarbon group having 1 to 10 carbon atoms having an isocyanate group,
Y is an alkoxy group, an alkoxyalkoxy group, an acetoxy group, or a hydrocarbon group having 1 to 10 carbon atoms and having a hydroxyl group, and n is an integer of 0 to 4. ] Specifically, tetramethylsilane, trimethylmethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, phenylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriethoxysilane, Methoxysilane, γ-Incyanatopropyltrimethoxysilane, γ-Isocyanatepropyltriethoxysilane, γ-Isocyanatepropylmethyldimethoxysilane, Glycidoxypropyltrimethoxysilane,
Glycidoxypropyl triethoxysilane, glycidoxypropyltripropoxysilane, glycidoxypropylmethyldimethoxysilane, glycidoxypropylmethyljethoxysilane, glycidoxypropyl ethyldimethoxysilane, glycidoxypropyl ethyl Jetoxysilane, glycidoxypropylbutyldimethoxysilane, glycidoxypropylbutyljethoxysilane, 2-
(2,3-epoxycyclohexyl)ethyltrimethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-anilinopropyltrimethoxysilane, N-phenylaminomethyltrimethoxysilane, N-(triethoxysilylpropyl)
Urea, aminomethyltriethoxysilane, N(β-aminoethyl)aminomethyltrimethoxysilane, aminomethyljethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, vinylacetoxysilane, γ-methacryloxypropyl Examples include trimethoxysilane, γ-mercaptopropyltrimethoxysilane, and the like.

R',-,S i (OOR2). [I
I]C In the formula, R1 is a hydrocarbon group having 1 to 6 carbon atoms, a vinyl group, a methacryloxy group, an epoxy group, an amino group, a mercapto group, an organic group having fluorine or chlorine,
R2 is one or more bonding groups selected from an alkyl group, an acyl group, and an arylalkyl group, and n is 1 to
It is an integer of 4. ] Specifically, for example, vinyltris(t-butylperoxy)silane, vinyltris(cumemberoxy)silane, vinyltris(acedelperoxy)silane, vinyltris(benzoylperoxy)silane, vinyltris(lauroylperoxy)silane , γ-glycidoxypropyltris(t-butylperoxy)silane, γ-glycidoxypropyltris(cumemberoxy)silane, γ-glycidoxypropyltris(acetylperoxy)silane, γ-glycid Xyprobil tris(benzoylperoxy)silane, γ
-glycidoxypropyltris(lauroylperoxy)silane, γ-methacryloxypropyltris(t-butylperoxy)silane, γ-methacryloxypropyltris(cumememberoxy)silane, γ-methacryloxypropyltris(acetyl peroxy)silane, γ
-methacryloxypropyltris(benzoylperoxy)silane, γ-methacryloxypropyltris(lauroylperoxy)silane, and the like.

Furthermore, hydrolysates of these, colloidal silica, etc. can also be used. The hydrolyzate can be obtained, for example, by hydrolysis in water or a mixed solvent of water and alcohol in the presence of an acid.

These organosilicon compounds can be used alone or in combination.

To form a film made of an organosilicon compound on the surface of a synthetic resin substrate (mirror side; opposite side to the side with groups), the organosilicon compound is mixed with an alcohol such as methanol, ethanol, isopropanol, or isobutanol. kind,
Cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve are dissolved in solvents such as toluene, hexane, methyl ethyl ketone, methyl isobutyl ketone, heptane, ethyl acetate, butyl acetate, acetone, and cyclohexanone. After coating by a method or the like, the solvent may be removed by drying. Note that a curing catalyst, a flow control agent, and the like may be added.

Examples of curing methods include heating, ultraviolet ray irradiation, and electron beam irradiation.

The thickness of the primary coating is not particularly limited as long as it can ensure adhesion to the silicon dioxide coating formed thereon, but is usually about 50 to 300.

Silicon dioxide film> Next, the first film coated with an organosilicon compound and cured is brought into contact with a supersaturated hydrofluorosilicic acid solution of silicon dioxide by a precipitation method to form a silicon dioxide film. As a method for forming a silicon dioxide film, a known method disclosed in detail in the above-mentioned Japanese Patent Application Laid-Open No. 12734/1983 can be applied.

A supersaturated hydrofluorosilicic acid solution of silicon dioxide is a solution of silicon dioxide (silica gel,
Aerosil, silica glass, other silicon dioxide-containing substances, etc.) are dissolved, and then water or a reagent (boric acid, aluminum chloride, etc.) is added to create a supersaturated state of silicon dioxide. The substrate on which the primary film has been formed may be brought into contact with this treatment liquid. The contact may be carried out by immersing the substrate in the processing solution or by allowing the processing solution to flow down onto the surface of the substrate, but the immersion method is preferred in order to form a uniform film.

The concentration of hydrofluorosilicic acid in the treatment solution is 1 to 2 mol/β
It is preferable to saturate silicon dioxide in an aqueous solution of hydrofluorosilicic acid with a concentration of more than 2 mol/β, and then dilute it with water to obtain 1
The film formation rate was faster when the concentration was ~2 mol/β (
, is desirable because coating can be carried out efficiently. When adding boric acid to create a supersaturated state, the amount added is 1X10-" to 40% per mole of hydrofluorosilicic acid in the treatment solution.
×10-”mol, preferably 1.2X10-2 to 10X
A range of 10-2 moles is desirable for forming a uniform coating quickly.

In order to efficiently obtain a homogeneous film, it is preferable to continuously add and mix the boric acid aqueous solution while the substrate is immersed in the treatment liquid, and to circulate the treatment liquid and filter it with a filter. When silica gel is used as a source of silicon dioxide, a filter with a pore size of 1.5 μm or less is preferable, and when silica glass or the like is used, a filter with a pore size of 10 μm or less is preferable. In addition, when putting the processing liquid in a dipping tank and bringing it into contact with the substrate, on the surface of the substrate during dipping,
It is preferable for the treatment liquid to flow in a laminar flow in order to form an even and homogeneous film.

Since no primary coating is formed on the group surface side of the substrate, no silicon dioxide coating is deposited, and a coating layer in which silicon dioxide is deposited is formed only on the mirror surface side on which the primary coating is formed.

After forming the silicon dioxide film, the substrate to be treated is washed with ultrapure water, and then heat treatment is performed using high frequency or the like in order to remove adsorbed water and silanol groups in the silicon dioxide film.

The thickness of the silicon monoxide film is not particularly limited and can be determined as appropriate, but usually 100 to several 1,000 people, preferably 500 to 3,000 people can achieve the purpose of surface modification. I can do it.

In addition, the total film thickness of the primary film and silicon dioxide film on the mirror surface side of the substrate is the total film thickness of the recording film surface side (including the dielectric layer, recording layer, and protective layer) formed on the group surface side. If the film thicknesses are made substantially equal, the cross section of the disk will have a symmetrical structure thermally, and warping due to changes in temperature and humidity will be reduced (this is preferable).

For example, by sputtering, a SiN-based dielectric, TbFe, etc.
An optical information recording medium is produced by sequentially laminating a Co-based recording layer and a SiN-based protective layer.

According to the present invention, the silicon dioxide film is provided only on the side opposite to the group surface by the precipitation method, so the group is not filled with the primary film and the silicon dioxide film, and the allowable width of the film thickness can be increased. This allows for a wide range of settings. therefore,
By increasing the film thickness, the effect of blocking water vapor etc. can be increased.

In addition, the film thickness can be made approximately equal to the total film thickness on the recording film side, and as a result, the occurrence of warping due to changes in temperature and humidity can be suppressed, so it is particularly suitable for single-plate discs. .

Furthermore, the silicon dioxide film produced by the precipitation method has excellent adhesion to the substrate, so it does not peel or crack, and has excellent long-term reliability.

(Margin below) [Example] The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited only to these Examples. In addition, the method of the accelerated deterioration test in Examples and Comparative Examples is as follows.

Moisture Permeability Coefficient A sample was prepared on a polycarbonate sheet measuring 10 cm x 10 cm and 18.0 μm thick, coated with a silicon dioxide film on only one side by a precipitation method, and tested at 40° C. with a ridge method permeability tester. Moisture permeability was measured at RH90%.

Amount of warping (radial tilt angle)〉 After setting the disc in a constant temperature machine, 20℃, RH 30%
After being left for 1 hour, the sample was heated to 60° C. and RH 80% over 30 minutes and humidified, and the amount of change in the radial tilt angle was measured after 2 hours. + indicates a concavity on the recording film side.

Accelerated deterioration test〉 In a constant temperature machine at 80℃ and 90%RH,
After 00 hours, the presence or absence of cracks and peeling of the coating on the mirror side was observed.

<Groove Depth of Group> The groove depth of the middle circumference (r=45 mm) was measured using a scanning microscope.

[Example 11] On the mirror side of a magneto-optical disk substrate (diameter 130 mm, thickness 1.2 mm) made of polycarbonate resin (PC),
A primary coating and a silicon dioxide coating were formed in the following manner.

First, γ-clidoxybrobyltrimethoxysilane 35
0 parts by weight, 14 parts by weight of water-dispersed colloidal silica, 9 parts by weight of distilled water, and 3 parts by weight of a 1.2N hydrochloric acid aqueous solution, and after refluxing at 80°C for 4 hours, 57 parts by weight of the solvent was distilled off at a distillation temperature of 80~ Distilled at 90°C. To 66 parts by weight of the hydrolyzate solution of γ-glydoxypropyltrimethoxysilane containing colloidal silica thus obtained, 100 parts by weight of ethyl cellosolve, a curing catalyst, and a flow control agent were added to prepare a paint.

This paint was applied only to the mirror side of the PC board by a spin code method, and heat treated in a hot air drying oven at 120°C for 30 minutes.

P with the obtained primary film (thickness: 20 mm) on the mirror side
A silicon dioxide film manufacturing apparatus similar to that shown in JP-A No. 61-12734 was used to coat the first silicon dioxide film on the c substrate.
A silicon dioxide coating was then deposited over the coating.

That is, the silicon dioxide coating manufacturing apparatus has a dipping tank consisting of an outer tank and an inner tank, and the space between the inner tank and the outer tank is filled with water. This water is heated with a heater to a temperature of 35° C., and is stirred with a stirrer to make the temperature distribution uniform. The inner tank consists of a front part, a middle part, and a rear part, and each part is filled with an aqueous solution of hydrofluorosilicic acid at a concentration of 2.0 mol/ρ, in which silicon dioxide is dissolved and saturated, using industrial silica gel powder as a source of silicon dioxide. 3I2. The reaction solution is full. At this point, the circulation pump was activated to discharge a certain amount of the reaction liquid from the rear of the inner tank, filter it with a filter, and start circulating the treated liquid back to the front of the inner tank.

Thereafter, a 0.5 mol/C boric acid aqueous solution was continuously poured into the rear part of the inner tank and maintained for 10 hours. In this state, the reaction solution became a treatment solution having an appropriate degree of silicon dioxide supersaturation.

Here, the absolute removal rate of the filter was adjusted to 1.5 μm, and the circulation rate of the treatment liquid was adjusted to 240 mβ/min (since the total amount of treatment liquid was about 312, the circulation rate was 8%/min).

Then, a PC board having a primary coating on the mirror side was immersed vertically into the middle of the inner tank, and the conditions were as described above (0.5 mol/β boric acid aqueous solution was added at 0.2 mj2/min, 8%/min). The mixture was circulated for 5 hours and filtered through a 1.5 μm filter.

As a result, a magneto-optical disk substrate was obtained in which only the mirror side was coated with silicon dioxide having a thickness of approximately 2,500 nm.

Next, the treated substrate was scrubbed with ultrapure water and further subjected to high frequency heating.

The substrate thus obtained was introduced into a vacuum chamber of a sputtering apparatus, and the vacuum chamber was evacuated to I x 1'O-' Torr, and then Ar gas was introduced at I x 10-' Torr.

S i A I2. as a dielectric layer on the group surface side. O
N at 900, then Ar gas pressure at 5 x 10-”T.
A magneto-optical disk was obtained by sequentially stacking 1,000 layers of TbFeCo as a recording layer and 900 layers of 5iAI2ON as a protective layer.

[Example 2] Except that the thickness of silicon dioxide was 1,500,
A magneto-optical disk was created in the same manner as in Example 1.

[Example 3] A magneto-optical disk was produced in the same manner as in Example 1, except that the thickness of the silicon dioxide film was 500 mm.

[Comparative Example 1] A magneto-optical disk was produced in the same manner as in Example 1 except that an untreated PC board was used.

[Comparative Example 2] After creating a primary coating with a thickness of 100 mm over the entire surface of the PC board (including the group surface) by dipping, a silicon dioxide coating with a thickness of 2,500 mm was formed over the entire surface using a precipitation method. A magneto-optical disk was produced in the same manner as in Example 1, except that a magneto-optical disk was formed.

[Comparative Example 3] Only on the mirror side of the PC board, a thickness of 2.5 mm was applied by sputtering.
A magneto-optical disk was prepared in the same manner as in Comparative Example 1, except that a silicon dioxide film of 0.000000000000 was provided.

Table 1 summarizes the results of evaluating the magneto-optical disks obtained in Examples and Comparative Examples.

(Leaving space below) From the results of Examples 1 to 3, it was found that by providing a silicon dioxide coating by a precipitation method only on the mirror side of the substrate, warpage caused by the bimetallic effect caused by temperature changes can be suppressed, and high water vapor permeation barrier properties can be achieved. It can be seen that this suppresses moisture permeation of the substrate due to humidity and suppresses warpage.

Furthermore, since the silicon dioxide coating is provided only on the mirror surface side, it is understood that the problem of filling the group grooves that would occur when the entire surface is coated does not occur.

Furthermore, it can be seen that since the silicon dioxide coating formed by the precipitation method has better adhesion to the substrate than the coating formed by the sputtering method, no peeling or cracking occurs even after the accelerated deterioration test.

Patent applicant Sekisui Chemical Co., Ltd. Representative Hiro 1) Kaoru

Claims (1)

[Claims] (1) In an optical information recording medium having a recording film formed on a substrate, the substrate has only the surface opposite to the recording film.
a primary coating coated and cured with an organosilicon compound;
An optical information recording medium characterized in that it is a transparent synthetic resin substrate having a silicon dioxide coating formed on the primary coating by contacting with a supersaturated hydrofluorosilicic acid solution of silicon dioxide.