JPH0760531B2 - Optical recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium such as a magneto-optical recording medium that records and reproduces information using heat and light such as laser light.

Prior Art and its Problems One of optical recording media is a magneto-optical memory medium.

Recording media for magneto-optical memory include MnBi, MnAlGe, MnSb, MnCuBi, GdFe, TbFe, GdCo and PtC.
o, TbCo, TbFeCo, GdFeCo, TbFeO ₃ , GdIG, GdTbFe, GdT
Materials such as bFeCoBi and CoFe ₂ O ₄ are known. They are,
It is formed as a thin film on a transparent substrate such as plastic or glass by a method such as a vacuum vapor deposition method or a sputtering method. The characteristics common to these magneto-optical recording media are that the easy axis of magnetization is perpendicular to the film surface and that the Kerr effect and the Faraday effect are large.

As a recording method of a magneto-optical recording medium utilizing this property, there is, for example, the following method.

First, the entire film is magnetized to "0", that is, uniformly magnetized (this is called erase method). Next, a laser beam is applied to the portion where "1" is to be recorded. When the laser beam is emitted, the temperature rises, and when the Curie point is approached and when the Curie point is exceeded, the holding power is maintained.
Approach Hc. Then, when the laser beam is turned off and returned to room temperature, the magnetization is reversed by the energy of the demagnetizing field, and when the laser beam is irradiated, an external magnetic field is applied in the direction opposite to the initial direction to return to room temperature. It is inverted and the signal "1" is recorded.

In addition, since the initial state of recording is "0", "0" remains as it is in the portion not irradiated with the laser beam.

Similarly, the reading of the recorded magneto-optical memory is performed by using a laser beam and rotating the polarization plane of the reflected light depending on the direction of magnetization of the laser beam irradiation light, that is, the magneto-optical effect.

The first requirement for such a medium is that the Curie point is about 100 to 200 ° C and the compensation point is near room temperature.

Second, there are relatively few defects such as grain boundaries that cause noise.

Thirdly, it is possible to obtain a magnetically and mechanically uniform film over a relatively large area without using a method such as high temperature film formation or long time film formation.

In response to such demands, in recent years, rare earth-transition metal amorphous perpendicular magnetic thin films have attracted much attention among the above materials.

However, when a magneto-optical recording medium made of such a rare earth-transition metal amorphous thin film is stored while being in contact with the atmosphere, the rare earth is selectively corroded by oxygen and water in the atmosphere penetrating through the substrate. Alternatively, it will be oxidized and it will be impossible to record or reproduce information.

Therefore, in general, much research has been conducted on a structure having a protective intermediate layer provided between the magnetic thin film layer and the substrate.

Examples of the intermediate layer include an inorganic vacuum-deposited film such as SiO and SiO ₂ or a coating film intermediate layer of a room temperature curable resin.

However, in these intermediate layers, sufficient moisture resistance cannot be obtained, and there are problems such as storage deterioration.

In order to deal with such a problem, JP-A-60-177449 discloses a proposal to improve weather resistance by using glass as an intermediate layer.

On the other hand, the present inventors formed a plasma polymerized film on the substrate,
A proposal has been made to improve adhesion and weather resistance (Japanese Patent Application No. 60-180729).

Further, in order to improve the characteristics and durability of the medium, in particular, the adhesion between the substrate and the magnetic thin film layer, a plasma polymerized film is formed on the substrate that has been subjected to the plasma treatment, and the magnetic thin film is formed on this. We are proposing to provide layers (Japanese Patent Application Sho
60-181327).

Further, for the purpose of preventing deterioration of the medium due to moisture from the surface of the magnetic thin film layer, a plasma polymerized film is formed on the surface of the magnetic thin film layer and used as a protective layer, or on the plasma polymerized film, a radiation is further applied. A proposal has been made to provide a protective layer containing a curable compound (Japanese Patent Application No. 60-182).
No. 767, No. 61-183285).

Further, for the purpose of improving the characteristics of the medium, particularly durability and storability in a high-humidity atmosphere, a plasma polymerized film underlayer is provided on the substrate. It has been proposed that an amorphous magnetic thin film layer of a rare earth-transition metal is formed through the formation of a plasma polymerized film protective layer on the magnetic thin film layer (Japanese Patent Application No. 60-184799).
issue).

Further, in JP-A-60-260628, a thermoplastic resin molded body is formed of a plasma polymerized film containing one or more monomers selected from tetrafluoroethylene, acrylonitol, acrylic acid, metal methacrylate, vinyl chloride and vinylidene chloride. Is proposed to improve weather resistance.

However, even with these proposals, there is a demand for a magneto-optical recording medium which is not sufficient in terms of adhesiveness to an intermediate layer or a protective layer and weather resistance, does not necessarily satisfy required characteristics, and has further excellent characteristics. .

Incidentally, such a problem also applies to an optical recording medium having a so-called phase transition type recording layer.

II Object of the Invention An object of the present invention is to provide an optical recording medium having excellent weather resistance and adhesiveness.

III DISCLOSURE OF THE INVENTION Such an object is achieved by the present invention described below.

That is, the first aspect of the present invention is an optical recording having a plasma-polymerized film underlayer on a substrate, an intermediate layer on the plasma-polymerized film underlayer, and a recording layer on the intermediate layer. A medium, wherein the plasma-polymerized film is obtained by polymerizing a monomer of an organic compound having a carbonyl group,
And the refractive index of this plasma polymerized film at 6328Å is 1.3.
It is an optical recording medium characterized by being ~ 1.7.

A second invention has a plasma-polymerized film underlayer on the substrate, and an intermediate layer on the plasma-polymerized film underlayer.
An optical recording medium having a recording layer on the intermediate layer, and a plasma-polymerized film protective layer formed on the recording layer directly or through a protective layer, wherein the plasma-polymerized film has a carbonyl group. It is obtained by polymerizing the monomer of the compound, and the refractive index at 6328Å of this plasma polymerized film is
The optical recording medium is 1.3 to 1.7.

IV Specific Structure of the Invention Hereinafter, the specific structure of the present invention will be described in detail.

1 and 2 are cross-sectional views showing one embodiment of a magneto-optical recording medium of the optical recording media of the present invention.

In the embodiment shown in FIG. 1, the magneto-optical recording medium 1 of the present invention
Has a plasma-polymerized film underlayer 12 on a substrate 11, an intermediate layer 15 on the plasma-polymerized film underlayer 12, and a rare earth-transition metal non-layer as a recording layer on the intermediate layer 15. It has a crystalline magnetic thin film layer 14.

Further, a protective layer 16 and a protective film 19 are further provided on the amorphous magnetic thin film layer 14.

In addition, in the embodiment shown in FIG. 2, a rare earth-transition metal amorphous magnetic thin film layer 14 is further provided directly or on a protective layer.
A plasma-polymerized film protective layer 17 is formed via 16. Further, a protective film 19 is further provided on the plasma polymerized film protective layer 17.

In the present invention, the plasma-polymerized film underlayer 12 (the embodiment shown in FIGS. 1 and 2) and the plasma-polymerized film protective layer 17 (the embodiment shown in FIG. 2) contain a monomer of an organic compound having a carbonyl group. It is polymerized.

As the monomer of the organic compound having a carbonyl group,
Aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, caproaldehyde, heptaaldehyde, acrylaldehyde, benzaldehyde, crotonaldehyde, etc .; Ketones such as acetone, methyl ethyl ketone, diethyl ketone, isobutyl methyl ketone, Acetophenone, propiophenone, benzophenone, cyclobutanone, cyclohexanone, 4-pyrone, anthrone, pyridone, pyrrolidone, methyl vinyl ketone, etc .; ketene, such as phenylketene, dimethylketene, etc .; carboxylic acids, such as formic acid, acetic acid, propionic acid, butyric acid , Isobutyric acid, valeric acid, isovaleric acid, acrylic acid, propiolic acid, methacrylic acid, crotonic acid, isocrotonic acid, etc .; Carvone Acid esters, for example, methyl acrylate, methyl methacrylate, phenyl acetate, diethyl malonate,
Ethylene diacetate, diethyl succinate, etc .; Lactones and lactams such as γ-butyrolactone, (γ-, δ-) valerolactone, 2-pyrrolidone,
2-piperidone, etc .; peracids of carboxylic acids, carboxylic acid anhydrides, hydroxy acids having a carboxyl group as a main group, alkoxy acids, oxo acids, amino acids, amic acids, etc., among which acetone, acrylic acid, methacryl Acid, methyl acrylate and the like are preferable.

These may be used alone or in combination of two or more.

In the present invention, the plasma polymerized film has a refractive index n of 6328Å of 1.3 to 1.7, preferably 1.4 to 1.6.

The reason why such a refractive index is set is that if n is less than 1.3, the denseness of the film cannot be obtained, moisture or the like from the substrate 11 or the like cannot be cut off, and the adhesiveness is not sufficient. , 1.
If it exceeds 7, the hardness of the polymer film increases, and a sputtered film, a vapor deposition film, etc. installed in contact with the polymer film, such as an intermediate layer described later.
This is because the adhesion with 15, the protective layer 16 and the like becomes poor.

The glass (described later) preferably used as the material for the intermediate layer 15 and the protective layer 16 in the present invention has a n of 6328Å of about 1.5, and should be a plasma polymerized film having a similar value of n. Is preferred.

In order to obtain such n, a low film formation rate and low pressure plasma polymerization conditions may be selected as described later.

In the present invention, the plasma polymerized film underlayer 12 (the embodiment shown in FIGS. 1 and 2) and the plasma polymerized film protective layer 17 (the embodiment shown in FIG. 2) each have a thickness of 10 to 1000Å, preferably 50 to
A good value is 600Å.

The reason why such a thickness is set is that if the thickness is less than 10 Å, the effect of the present invention cannot be obtained, and even if the thickness exceeds 1000 Å, there is no difference in the effect of the present invention, and it is not necessary to make the thickness more than this value.

An ellipsometer or the like may be used to measure the film thickness.

The film thickness can be controlled by controlling the reaction time at the time of forming the plasma polymerized film, the flow rate of the raw material gas, and the like.

The plasma polymerized film underlayer 12 forms a polymerized film by bringing the above-mentioned discharge plasma of the source gas into contact with the substrate.

Further, the plasma-polymerized film protective layer 17 (the embodiment shown in FIG. 2) forms a plasma-polymerized film on the magnetic thin film layer 14 similarly to the underlayer 12.

By forming such a protective layer 17, the moisture resistance is further improved.

The plasma-polymerized film protective layer 17 may be formed on the magnetic thin film layer 14 with a protective layer 16 made of the same material as the intermediate layer 15 described later interposed therebetween.

When the principle of plasma polymerization is outlined, when a gas is kept at a low pressure and an electric field is applied, free electrons, which are present in a small amount in the gas, have a very large intermolecular distance as compared with atmospheric pressure, and thus are subjected to electric field acceleration to generate 5 to 10 eV. Acquires the kinetic energy (electron temperature) of.

When the accelerated electrons collide with atoms or molecules, the orbits or molecular orbits are separated, and these are dissociated into electrons, ions, neutral radicals, and other normally unstable chemical species.

The dissociated electrons are again accelerated by the electric field to dissociate another atom or molecule, and the chain action immediately turns the gas into a highly ionized state. And this is called plasma gas.

Since gas molecules have few opportunities to collide with electrons, they do not absorb much energy and are kept at a temperature close to room temperature.

Such a system in which the kinetic energy of electrons (electron temperature) and the thermal motion of molecules (gas temperature) are separated is called constant temperature plasma. The present invention aims to form a plasma polymerized film on a substrate by utilizing this situation. Since the low temperature plasma is used, there is no thermal effect on the substrate.

An example of an apparatus for forming a plasma polymerized film on the surface of a substrate is shown in FIG. FIG. 3 shows a plasma polymerization apparatus using a frequency variable power source.

In FIG. 3, in the reaction vessel R, the source gas from the source gas source 511 or 512 is supplied to the mass flow controller 5 respectively.
Supplied via 21 and 522. When separate gases are supplied from the gas source 511 or 512, they are mixed and supplied in the mixer 53.

The raw material gas may have a flow rate range of 1 to 250 ml / min.

In the reaction container R, the substrate 111 to be processed is provided with one rotary electrode 5
Supported by 22.

Then, an electrode 551 facing the rotary electrode 552 is provided so as to sandwich the substrate 111 to be processed.

One electrode 551 is connected to, for example, a variable frequency power source 54, and the other rotary electrode 552 is grounded at 8.

Further, in the reaction vessel R, a vacuum system for exhausting the inside of the vessel is provided, and this includes an oil rotary pump 56, a liquid nitrogen trap 57, an oil diffusion pump 58 and a vacuum controller 59. These vacuum systems use 0.1 Torr inside the reaction vessel.
Maintained in the vacuum range of less than 0.005 to 0.08 Torr.

In the operation, first, the inside of the reaction vessel R is evacuated until it becomes 10 ⁻⁵ Torr or less, and then, it is supplied in a mixed state into the vessel at a processing gas or at a predetermined flow rate.

The film forming rate is preferably 50 to 200Å / nim.

At this time, the vacuum in the reaction vessel is less than 0.1, preferably 0.0
It is managed in the range of 05 to 0.08 Torr.

When the flow rate of the raw material gas becomes stable, the power is turned on. In this way, the polymerized film is formed on the plasma on the substrate.

When a liquid monomer is used as the raw material in the present invention, a container containing the liquid monomer at the gas sources 511 and 512 in FIG. 3 may be installed in a constant temperature bath before use.

Note that Ar, N ₂ , He, H ₂ or the like may be used as the carrier gas.

Further, the applied current, the processing time, etc. may be set under normal conditions.

As the plasma generation source, any of microwave discharge, direct current discharge, alternating current discharge and the like can be used in addition to high frequency discharge.
In the present invention, since the operating pressure is particularly low, it is preferable to use the magnetron system which also uses a magnetic field.

When a liquid monomer is used as a raw material in the present invention, a container containing the liquid monomer at the gas sources 511 and 512 in FIG. 3 may be installed in a constant temperature bath before use.

The C content of the plasma polymerized film thus formed is 30.
It is preferably ˜90 at%.

Further, H is generally contained in the plasma polymerized film in an amount of about 5 to 40 at%.

The content of C, H and other elements in the plasma polymerized film may be analyzed according to SIMS (double ion mass spectrometry) or the like. When using SIMS, on the plasma polymerized film surface,
It may be calculated by counting C, H and other elements.

Alternatively, while performing ion etching with Ar or the like, C,
It may be calculated by measuring the profiles of H and other elements.

For the measurement of SIMS, Surface Science Basic Course Vol. 3 (198
4) Basics and applications of surface analysis (p70) Follow the description in "SIMS and LAMMA".

Furthermore, the C = O group present in the plasma polymerized film was confirmed by FTIR or the like.

The substrate 11 used in the optical recording medium of the present invention is made of resin.

Preferred resins include acrylic resins, polycarbonate resins, epoxy resins, polymethylpentene resins and the like.

Among these resins, a polycarbonate resin is preferable in terms of durability, particularly resistance to warping and the like.

In this case, the polycarbonate resin may be any of an aliphatic polycarbonate, an aromatic-aliphatic polycarbonate and an aromatic polycarbonate, but an aromatic polycarbonate resin is particularly preferable. Of these, a polycarbonate resin made of bisphenol is preferable in terms of melting point, crystallinity, handling, and the like. Among them, the bisphenol A type polycarbonate resin is most preferably used. The number average molecular weight of the polycarbonate resin is preferably about 10,000 to 15,000.

The refractive index at 830 nm of such a substrate 11 is usually about 1.55 to 1.59.

Since recording is performed through the substrate 11, the transmittance for writing light or reading light is 86% or more.

Since recording is performed through the substrate 11, the transmittance for writing light or reading light is 86% or more.

The substrate 11 is usually disc-shaped and has a thickness of about 1.2 to 1.5 mm.

A tracking groove may be formed on the surface of the disk-shaped substrate on which the magnetic thin film layer is formed.

The depth of the groove is about λ / 8n, especially λ / 6n to λ / 12n (here,
n is the refractive index of the substrate). The width of the groove is
It is about the track width.

Then, it is usually preferable to irradiate the writing light and the reading light from the back surface side of the substrate with the magnetic thin film layer located in the concave portion of the groove as a recording track portion.

With this configuration, the write sensitivity and the read C / N ratio are improved, and the tracking control signal is increased.

Further, the other substrate shape may be a tape, a drum, or the like.

In the present invention, the plasma polymerized film underlayer 12 may be formed on the plasma-treated substrate 11.

By plasma-treating the surface of the substrate 11, the adhesive force between the substrate 11 and the plasma polymerized film underlayer 12 is improved.

The principle, method, formation conditions, etc. of the plasma treatment method for the surface of the substrate 11 are basically the same as those of the plasma polymerization method described above.

However, as a general rule, the plasma treatment uses an inorganic gas as the treatment gas, and on the other hand, as a general rule, the formation of the plasma-polymerized film underlayer 12 by the above-mentioned plasma polymerization method makes it possible to use an organic gas (in some cases, an inorganic gas may be mixed. Is used as a source gas.

The plasma processing gas of the present invention is not particularly limited.

That is, H ₂ , Ar, He, O ₂ , N ₂ , air, HN ₃ , O ₃ , H ₂ O, N
Any one selected from NOx and the like such as O, H ₂ O, NO ₂ and the like, or a mixture of these may be used.

Further, the frequency of the plasma processing power source is not particularly limited, and may be any of direct current, alternating current, microwave, and the like.

A plasma polymerized film may be further formed on the back surface of the substrate 11 (on the side where the magnetic thin film layer 14 as a recording layer is not formed).

The intermediate layer 15 in the present invention is a compound containing oxygen, carbon, nitrogen, sulfur, etc., for example, SiO ₂ , SiO, AlN, Al ₂ O ₃ , Si.
Various derivative substances such as ₃ N ₄ , ZnS, BN, TiO ₂ , TiN, etc. or mixtures thereof; glass, for example, borosilicate glass,
Materials such as barium borosilicate glass, aluminum borosilicate glass, etc., or those containing Si ₃ N ₄ etc. may be used. Of these, borosilicate glass having 40 to 80 wt% SiO ₂ , barium borosilicate glass, aluminum borosilicate glass, and those obtained by substituting a part of SiO ₂ with Si ₃ N ₄ or the like are preferable.

Among these, the following are particularly preferable.

(1) 40-60 wt% of silicon oxide, 50 wt% or less of divalent metal oxide such as BaO, CaO, SrO, MgO, ZnO, PbO and / or 10 wt% of alkali metal oxide, boron oxide and / or oxidation Those containing aluminum.

(2) Ba, Ca, S as Si and other metal or metalloid elements
At least one of r, Mg, Zn, Pb, etc., at least one of Al, B, and at least one of alkali metal elements, and the Si atomic ratio in the total metal or semimetal is 0.3 to 0.9, further including O and N, O / (O + N) 0.4-0.8
What is.

Such an intermediate layer 15 has a thickness of 500 to 3000Å, preferably 800 to
A thickness of 2500Å is recommended.

If it is less than 500Å, the weather resistance is not sufficient, and 1
This is because if it exceeds 500Å, the sensitivity is reduced when the medium is too thick.

As these intermediate layers 15, the above-mentioned glass layer is formed as a protective layer underlayer in a thickness of about 300 to 1000 Å, and Si is formed on top of this.
_{O 2, SiO, Si 3 N} 4, AlN, Al 2 O 3, ZnS , etc., or a mixture thereof dielectric material as the dielectric layer 500 to 1,500
It is preferable to have a layer of about Å.

In this case, the dielectric layer preferably has a refractive index of 1.8 to 3.0 at 800 nm, and preferably contains Si and a rare earth metal and / or Al and contains O and N.

In the present invention, the magnetic thin film layer 14 as a recording layer is for magnetically recording information by a modulated heat beam or a modulated magnetic field, and the recorded information is magnetic-optically converted and reproduced. is there.

As a material of such a magnetic thin film layer 14, an alloy of a rare earth metal such as Gd and Tb and a transition metal such as Fe and Co is formed as an amorphous film by sputtering, vapor deposition, etc. And Co are essential components.

In this case, the total content of Fe and Co is preferably 65 to 85 at%.

And the balance is substantially rare earth metals, especially Gd and / or Tb.

And, as a preferable example thereof, TbFeCo, GdFeCo, GdTbFe
There are Co etc.

In these magnetic thin film layers, Cr in the range of 10 at% or less,
Al, Ti, Pt, Si, Mo, Mn, V, Ni, Cu, Zn, Ge, Au, etc. may be contained.

In addition, as a rare earth element, Sc, Y, L in the range of 10 at% or less
a, Ce, Pr, Nd, Pm, Sm, Eu, Dy, Ho, Er, Tm, Yb, Lu
Etc. may be contained.

The thickness of such a magnetic thin film layer is preferably 0.01 to 1 μm.

Other materials for the recording layer include so-called phase transition type materials such as Te-Se, Te-Se-Sn, Te-Ge, Te-In, Te-Sn, Te-Ge-Sb-S, Te -Ge-As-Si, Te-Si, Te-Ge-Si-Sb, Te-Ge-Bi, Te-Ge-In-Ga, Te-Si-Bi-Tl, Te-Ge-Bi-In-S , Te-As-Ge-Sb, Te-Ge-Se-S, Te-Ge-Se, Te-As-Ge-Ga, Te-Ge-S-In, Se-Ge-Tl, Se-Te-As , Se-Ge-Tl-Sb, Se-Ge-Bi, Se-S (above, Japanese Patent Publication No. 54-41902, Patent No. 1004
No. 835) TeO _x (Te dispersed in the Te oxide described in JP-A-58-54338 and JP 974257), TeO _x + PbO _x (JP 974258), TeO _x + VO _x (JP 974257), others, Te-Tl, Te-Tl-
Si, Se-Zn-Sb, Te-Se-Ga, TeN _x , etc.Te, chalcogen-based Ge-Sn mainly composed of Se, Si-Sn, etc. amorphous-crystalline alloy Ag-Zn that causes a crystalline transition, There are alloys such as Ag-Al-Cu and Cu-Al that cause a color change due to a change in crystal structure, and alloys such as In-Sb that cause a change in crystal grain size.

A protective layer 16 is preferably provided on such a magnetic thin film layer 14.

As the material of the protective layer 16, glass and dielectric substances such as various oxides and nitrides are preferable as in the case of the intermediate layer 15, but the above-mentioned glass is particularly preferable.

The thickness of the protective layer 16 is generally about 300 to 1500Å.

The protective layer 16 may be formed by vacuum vapor deposition, sputtering or the like.

In the optical recording medium of the present invention, as the material of the protective film 19, generally known various organic materials may be used.

More preferably, a radiation-curable compound cured with radiation such as electron beam or ultraviolet ray is used.

Examples of the radiation-curable compound to be used include acrylic double bonds such as acrylic acid, methacrylic acid, or their ester compounds having an unsaturated double bond that is sensitive to ionization energy and exhibits radical polymerizability, such as diallyl phthalate. Examples thereof include monomers, oligomers and polymers having or introduced in the molecule a group capable of being crosslinked or polymerized by radiation such as an allyl double bond, an unsaturated double bond such as maleic acid and a maleic acid derivative.

A compound having a molecular weight of less than 2000 is used as the radiation-curable monomer, and a compound having a molecular weight of 2000 to 10,000 is used as the oligomer.

These include styrene, ethyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol methacrylate, 1,6-hexane glycol diacrylate, 1,6-hexane glycol dimethacrylate, etc., but particularly preferred ones As, pentaerythritol tetraacrylate (methacrylate), pentaerythritol acrylate (methacrylate), trimethylolpropane triacrylate (methacrylate), trimethylolpropane diacrylate (methacrylate), polyfunctional oligoester acrylate (Aronix M-7100, M-5400 , M-5500, M-
5700, M-6250, M-6500, M-8030, M-8060, M-8100 etc., Toa Gosei), acrylic modified urethane elastomer (Nipporan 4040), or functional groups such as COOH introduced into these Acrylate (methacrylate) of a phenol ethylene oxide adduct, a compound having an acryl group (methacryl group) or ε-caprolactone-acryl group on the pentaerythritol condensed ring represented by the following general formula, 1) (CH ₂ = CHCOOCH ₂ ) ₃ -CCH ₂ OH (special acrylate A) 2) (CH ₂ = CHCOOCH ₂ ) ₃ -CCH ₂ OH ₃ (special acrylate B) 3) [CH ₂ = CHCO (OC ₃ H ₆ ) _n- OCH ₂ ] _3- CCH ₂ CH ₃ (Special acrylate C) In the formula, a compound of m = 1, a = 2, b = 4 (hereinafter referred to as a special pentaerythritol condensate A), a compound of m = 1, a = 3, b = 3 (hereinafter referred to as a special pentaerythritol) Tol condensate B), m = 1, a = 6, b = 0 compound (hereinafter referred to as special pentaerythritol condensate C), m = 2, a = 6, b = 0 compound (hereinafter, Special pentaerythritol condensate D), and special acrylates represented by the following general formula.

8) CH ₂ = CHCOO- (CH ₂ CH ₂ O) ₄ -COCH = CH ₂ (special acrylate H) 12) AM-N _n -MA A: acrylic acid, M: dihydric alcohol N: dibasic acid (special acrylate L) Further, the radiation-curable oligomer is a polyfunctional oligoester acrylate represented by the following general formula. And acrylic modified urethane elastomers, or those into which a functional group such as COOH is introduced.

Further, a radiation-curable compound obtained by subjecting a thermoplastic resin to radiation-sensitive modification may be used.

Specific examples of such a radiation curable resin include acrylic double bonds such as acrylic acid, methacrylic acid, or their ester compounds showing an unsaturated double bond having radical polymerizability, such as diallyl phthalate. It is a resin in which a group such as an allyl double bond, an unsaturated bond such as maleic acid or a maleic acid derivative, which is crosslinked or polymerized by irradiation with radiation is contained or introduced in the molecule of the thermoplastic resin.

Examples of the thermoplastic resin that can be modified into a radiation curable resin include vinyl chloride copolymers, saturated polyester resins, polyvinyl alcohol resins, epoxy resins, phenoxy resins, and fibrin derivatives.

Other resins that can be used for radiation-sensitive modification include polyfunctional polyester resins, polyetherester resins, polyvinylpyrrolidone resins and derivatives (PVP olefin copolymers), polyamide resins, polyimide resins, phenolic resins, spiroacetal resins, An acrylic resin containing at least one of a hydroxyl group-containing acrylic ester and methacrylic ester as a polymerization component is also effective.

The thickness of the protective film 6 of such a radiation-curable compound is 0.1
-30 μm, more preferably 1-10 μm.

If the film thickness is less than 0.1 μm, a uniform film cannot be formed, the moisture-proof effect in an atmosphere with high humidity is not sufficient, and the durability of the magnetic thin film layer 4 is not improved. If it exceeds 30 μm, warpage of the recording medium or cracks in the protective film may occur due to shrinkage during curing of the resin film, which is not practical.

Such a coating film may be usually formed by combining various known methods such as spinner coating, gravure coating, spray coating and dipping. The layer forming conditions of the coating film at this time may be appropriately determined in consideration of the viscosity of the mixture of the coating film composition, the target coating film thickness, and the like.

In order to cure such a coating film to form a protective layer, the coating film may be irradiated with a radiation such as an electron beam or an ultraviolet ray.

When using an electron beam, the radiation characteristics are as follows: acceleration voltage 10
It is expedient to use a radiation accelerator of 0 to 750 KV, preferably 150 to 300 KV, and to irradiate it with an absorbed dose of 0.5 to 20 megarads.

On the other hand, when ultraviolet rays are used, a photopolymerization sensitizer is usually added to the above-mentioned radiation-curable compounds.

The photopolymerization sensitizer may be any conventionally known one, for example, benzoin methyl ether, benzoin ethyl ether, α-methylbenzoin, benzoin series such as α-chlordeoxybenzoin, benzophenone, acetophenone, bisdialkylaminobenzophenone, etc. Examples thereof include ketones, quinones such as acetoraquinone and phenanthraquinone, and sulfides such as benzyl disulfide and tetramethylthiuram monosulfide.
The photopolymerization sensitizer is preferably in the range of 0.1 to 10% by weight based on the resin solid content.

Then, in order to cure the coating film containing such a photopolymerization sensitizer and the radiation-curable compound by ultraviolet rays, various known methods may be used.

For example, a UV bulb such as a xenon discharge tube or a hydrogen discharge tube may be used.

A protective plate is usually provided on the protective film 19 via an adhesive layer.

That is, this protective plate is used only in the case of so-called single-sided recording in which recording / reproducing is performed only from the back surface (surface on the side where the magnetic thin film layer 14 is not provided) of the substrate 11.

The resin material of such a protective plate is not particularly required to have transparency or the like, and various resins such as polyethylene, polyvinyl chloride, polystyrene, polypropylene, polyvinyl alcohol, methacrylic resin, polyamide, polyvinylidene chloride, and polycarbonate. Various thermoplastic resins such as polyacetal, fluororesin, phenol resin, urea resin, unsaturated polyester resin, polyurethane, alkyd resin, melamine resin, epoxy resin, silicon resin and the like can be used.

Note that various inorganic materials such as glass and ceramic may be used as the protective plate.

The shape, dimensions, etc. of this product are substantially the same as those of the substrate 11 described above.

Such a protective plate is bonded via the adhesive layer as described above. The adhesive layer is usually an adhesive such as a hot melt resin and has a film thickness of about 1 to 100 μm.

On the other hand, instead of using the above protective plate, the above magnetic thin film layer
14, using another set of substrates having the protective layer 16, the protective film 19 and the like, both magnetic thin film layers are opposed to each other with the magnetic thin film layers facing inside, and bonded using an adhesive layer, and writing is performed from the back surface side of both substrates. It may be a so-called double-sided recording type.

Furthermore, the back surface of the substrate 11 and the protective plate (magnetic thin film layer 14
It is preferable to provide a hard coat layer as various protective films on the surface (on the side not provided).

The material of the hard coat layer may be the same as the material of the protective film 19 described above.

According to the present invention, a plasma polymerized film underlayer is provided on a substrate, an intermediate layer is provided on the plasma polymerized film underlayer, and a recording layer is provided on the intermediate layer. Or a structure having a plasma-polymerized film protective layer directly on the recording layer or through a protective layer, wherein the plasma-polymerized film is obtained by polymerizing a monomer of an organic compound having a carbonyl group. Since the plasma polymerized film has a refractive index of 1.3 to 1.7 at 6328Å, an optical recording medium excellent in weather resistance and adhesiveness can be obtained.

In particular, when an intermediate layer made of a material such as glass, a protective layer or the like is provided in contact with this, the adhesion becomes strong.

VI Specific Examples of the Invention Hereinafter, the present invention will be described in more detail by showing specific examples of the invention.

Example 1 A substrate 11 made of a bisphenol A-based polycarbonate resin (molecular weight: 15000) having a diameter of 13 cm and a thickness of 1.2 mm was placed in a vacuum chamber, and a vacuum of 10 ⁻⁵ Torr was once drawn, and then Ar was used as a processing gas. , Flow rate: 50 ml / min, gas pressure 0.1 Torr
While maintaining the above, a high-frequency voltage of 13.56 MHz was applied to generate plasma, and the surface of the substrate 11 was plasma-treated.

After that, the plasma polymerized film underlayer 12 is further subjected to the following conditions.
Was formed on the substrate 11.

The abbreviations in the table indicate the following.

MMA… Methyl methacrylate, MA… Methyl acrylate, AA… Acrylic acid, MEK… Methyl ethyl ketone, TFE… Tetrafluoroethylene, VC… Vinyl chloride, VDC… Vinylidene chloride The refractive index n of these plasma polymerized films is measured at 6328Å did.

Also measured by elemental analysis SIMS of these plasma polymerized film,
The film thickness was measured by an ellipsometer.

Furthermore, the presence of C = O groups in the plasma polymerized film was confirmed by FTIR measurement.

Glass (SiO ₂ 48 wt%, Al ₂ O ₃ 15 wt%, B ₂ O ₃ 14 wt%, Na ₂ O 3 wt
%, K ₂ O 2wt%, BaO 5wt%, CaO 9wt%, MgO 4wt%) intermediate layer 15 by high frequency magnetron sputtering
Layered in Å.

21at% Tb, 68at% Fe, 7at% Co, 4at on this intermediate layer 15
A% Cr alloy thin film was deposited by sputtering to a thickness of 800 Å to form a magnetic thin film layer 14.

The target used was an Fe target on which Tb, Co, and Cr chips were placed.

A protective layer 16 made of glass (the same as the case of the intermediate layer) is formed on the magnetic thin film layer 14 by sputtering to a film thickness of 1000Å, and a coating composition containing the following radiation-curable compound is formed on the protective layer 16. The protective film 19 was formed by spinner coating.

(Coating composition) Polyfunctional oligoester acrylate 100 parts by weight Photosensitizer 5 parts by weight After applying such a coating composition, it was irradiated with ultraviolet rays for 15 seconds to be crosslinked and cured to obtain a cured film.

The film thickness at this time was 5 μm.

Note that the same processing as this was performed on the back surface of the substrate 11 described above. Further, a protective plate made of a polycarbonate resin having a diameter of 13 cm was adhered onto the protective layer film 19 with an adhesive.

Various magneto-optical disks shown in Table 1 were produced in this manner, and the following characteristic values of these samples were measured.

(1) C / N ratio (storage deterioration) C / N ratio at the initial stage and C / N after storage at 60 ° C, 90% RH for 1000 hours
The ratio change (deterioration) amount was measured under the following conditions.

Rotation speed 4m / sec Carrier frequency 500KHz Resolution 30KHz Recording power (830nm) 3 to 4mW Playback power (830nm) 1mW (2) Bit error rate Initial and bit of EFM signal after 1000 hours storage at 60 ℃ and 90% RH The error rate was measured.

(3) Adhesive strength An adhesive tape was adhered to the surface of the protective film 19 of the manufactured magneto-optical disk at a constant pressure, and this adhesive tape was separated at a constant speed in the angular direction of 180 °, and the substrate and the sputter laminate (intermediate Layer, magnetic thin film layer, protective layer, protective film) was measured.

Then, the value Wo of the adhesive strength of sample No. 11 (blank)
The value W of the adhesive strength of each sample was expressed as an improvement rate (%) shown below. This is the initial improvement rate.

The improvement rate after storage for 1000 hours at 60 ° C and 90% RH (5)
Was similarly calculated.

Example 2 In the sample 1 of Example 1, a plasma-polymerized film protective layer 17 was further provided on the protective layer 16 and a protective film 19 was provided thereon, and a magneto-optical disk was prepared in the same manner as in Sample 1.
In this case, the polymerized film used as the protective layer 17 is the plasma polymerized film 1 like the underlayer 12. This is sample A.

For this sample A, the C / N ratio and bit error rate were measured in the same manner as in Example 1. However, the storage time is 2000
It was time. The results are shown below.

It should be noted that such an effect is caused by phase transition type Te-Ge, TeO _x , Te-
The same was realized in the recording layer such as Se.

The effects of the present invention are clear from the above examples.

[Brief description of drawings]

1 and 2 are sectional views showing one embodiment of a magneto-optical recording medium showing an example of the present invention. FIG. 3 is a schematic diagram of a plasma polymerization apparatus. Explanation of symbols 1 ... Magneto-optical recording medium, 11 ... Substrate, 12 ... Plasma polymerized film underlayer, 14 ... Magnetic thin film layer, 15 ... Intermediate layer, 16 ...
Protective layer, 17 …… Plasma polymer protective layer 19 …… Protective film, 53 …… Mixer, 54 …… DC, AC and variable frequency power supply, 56 …… Oil rotary pump, 57 …… Liquid nitrogen trap, 58 …… Oil diffusion pump, 59 …… Vacuum controller, 111 …… Processed substrate, 511, 512 …… Source gas source, 5
21,522 …… Mass flow controller, 551,552 …… Electrodes

Claims (4)

[Claims] 1. An optical recording medium having a plasma polymerized film underlayer on a substrate, an intermediate layer on the plasma polymerized film underlayer, and a recording layer on the intermediate layer. The plasma-polymerized film is obtained by polymerizing a monomer of an organic compound having a carbonyl group, and
An optical recording medium having a refractive index at 28Å of 1.3 to 1.7. 2. The thickness of the underlayer of the plasma polymerized film is 10 to 1000Å
The optical recording medium according to claim 1, wherein 3. A plasma-polymerized film underlayer on a substrate, an intermediate layer on the plasma-polymerized film underlayer, a recording layer on the intermediate layer, and a recording layer on the intermediate layer. An optical recording medium having a plasma-polymerized film protective layer formed directly or through a protective layer, wherein the plasma-polymerized film is obtained by polymerizing a monomer of an organic compound having a carbonyl group, and the plasma-polymerized film at 6328Å An optical recording medium having a refractive index of 1.3 to 1.7. 4. The optical recording medium according to claim 3, wherein the plasma polymerized film underlayer and the plasma polymerized film protective layer each have a thickness of 10 to 1000 Å.