JP2000215513A - Optical recording medium and optical recorder therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical recording medium which is not damaged by collision with an optical head, does not contaminate the optical system of the optical head and can well perform recording and reproduction, even when the medium is used in a recording and reproducing device, using a film surface incidence system by which recording density can be increased. SOLUTION: An optical recording layer, a transparent intermediate layer and a transparent lubricating layer are successively formed on a resin substrate with pits and/or grooves to obtain the objective optical recording medium. The transparent lubricating layer is formed using a fluorocarbon and the ratio of the number of fluorine atoms to that of carbon atoms with respect to 1 set for carbon in the layer as measured by ESCA method is in the range of 0.8-1.8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium and an optical recording apparatus, and more particularly, to an optical recording medium and an optical recording apparatus capable of increasing a recording density and reducing reproduction errors.

[0002]

2. Description of the Related Art With the development of computer technology, the capacity of recording devices has been steadily increasing. Conventional optical disks include a read-only type (ROM) and a rewritable type (R
AM), write-once type, and the like. In these media, an optical head is provided on the side opposite to the recording surface of the optical disk substrate.
A so-called substrate surface incidence system is adopted in which read light or recording light emitted from an optical head passes through a substrate and reaches a recording surface. In this case, since the optical head is provided with an objective lens controlled in the optical axis direction by an actuator in order to focus light on the recording surface, the distance between the optical head and the disc is usually about 1 mm. Are provided.

On the other hand, in recent years, as a recording / reproducing device having a large capacity and a high-speed access, a device using an existing various optical disk as a magnetic recording hard disk has been proposed. That is, a so-called film surface in which one or two or more optical disks fixed coaxially are built in, an optical head is provided to face each recording surface, and light is irradiated from the recording surface side without passing through the substrate. Attention has been paid to a method of performing recording and reproduction by incidence. In the conventional substrate incidence method, the numerical aperture of the objective lens could not be increased because the aberration of the light spot increased due to the inclination of the substrate and the variation in the thickness of the substrate. It is possible to increase the numerical aperture of the lens and reduce the light spot, thereby increasing the capacity of the optical disk and enabling high-speed access like a hard disk.

FIG. 1 shows an example. In the apparatus shown in FIG. 1, a plurality of optical disks 1a, 1b, and 1c are mounted coaxially on a rotating shaft 2, and optical disks 3a, 4a, 3b, and 4b are provided on both surfaces of each disk 1 so as to sandwich the disks. You. These optical heads 3, 4 are provided with support arms 5a, 6a, 5b, 6
b and is coaxially mounted on the shaft 7 and moves in conjunction therewith. The moving direction of the optical head is configured to move in the radial direction of the optical recording medium 1 or to rotate around the shaft 7 on which the heads 3 and 4 are supported.

However, according to the study of the present inventors, it has been found that there are the following problems when an optical disc is used for the recording / reproducing apparatus. That is, while the distance between the optical head and the substrate is usually 1 mm or more in the conventional optical disk, the distance between the optical head and the substrate is extremely large when the optical disk is used in the above-mentioned recording / reproducing apparatus of the film surface incidence type. Since the optical head is close and usually within 5 μm, there is a possibility that the optical head collides with the optical disk to damage the medium or damage the head. In particular, collisions are likely to occur during dynamic loading. Therefore, a structure is required in which an intermediate layer having high hardness and high lubricity is provided on the optical recording layer, and a lubricant is applied to provide a lubricating layer.

As the lubricating layer, for example, the use of a hard disk lubricant can be considered. As a lubricant for the hard disk, FOMBLIN manufactured by Ausimont is used.
Z derivative (main chain:-[(OCF ₂ CF ₂ ) _p- (OC
F ₂ ) _q ]-) is generally widely used. Among them, DOL having a hydroxyl group as a functional group at both terminals (-(OCF ₂ CH ₂ OH) bonded to both ends of the main chain) is preferred. Used at a high rate. As the application method,
For example, a fluorine-based inert liquid (eg, 3M HFE)
_{7200: C 4 F 9 OC 2} H 5) dipping method using a solution of a concentration of about 1 to 3 g / l of the lubricant as a solvent have been widely adopted.

[0007] However, the above-mentioned lubricant for hard disks is usually a high molecular compound and a substance having a low vapor pressure and hardly evaporating at about room temperature. Since the laser power is adjusted so that the layer reaches the Curie temperature or higher, the temperature of the outermost lubricating layer also rises, and some lubricant molecules evaporate and adhere to the optical system of the optical head, that is, the nearest lens. , Causing contamination. As the contamination of the lens progresses, effective laser power attenuation and light scattering occur,
This will hinder recording and reproduction. In other words, there is a possibility that a fatal problem such as an increase in noise or a failure in recording may occur, which may shorten the life of the drive.

[0008]

According to the present invention, even when used in a recording / reproducing apparatus of a film surface incident type capable of increasing the recording density, there is no possibility of damage due to collision with an optical head. It is another object of the present invention to provide an optical recording medium capable of performing good recording and reproduction without contaminating an optical system of an optical head.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and found that the above object can be achieved by improving the constituent material of the lubricating layer of the optical recording medium. The present invention has been completed. In an optical recording medium in which an optical recording layer, a transparent intermediate layer, and a transparent lubricating layer are sequentially formed on a resin substrate on which pits and / or grooves are formed, the transparent lubricating layer is Is formed using a fluorocarbon, and the atomic ratio of fluorine to carbon measured by the ESCA method is such that the ratio of fluorine to carbon is 0.8 to 0.8.
The present invention provides an optical recording medium having a range of 1.8.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A resin substrate provided with pits and grooves, a metal substrate such as an aluminum substrate or a glass substrate is used for the optical recording medium of the present invention. Examples of the resin used include an acrylic resin, a polyolefin resin such as a norbornene-based resin, a liquid crystal polymer, and a polycarbonate. Specifically, for example, polymethyl methacrylate (PMM
A), ARTON (Nippon Synthetic Rubber Co., Ltd., norbornene-based ester-substituted cyclic olefin ring-opening polymer hydrogenated product), ZEO
NEX (Nippon Zeon Co., Ltd., hydrogenated norbornene-based cyclic olefin polymer), aromatic polyester-based liquid crystal polymer, polycarbonate, and the like.

Based on a stamper provided with pits / grooves,
Using these resins, pits / grooves are transferred and formed by injection molding, injection compression molding, radiation curing, or the like to form a resin substrate. Unlike glass, metal, ceramic, etc., the width or length is 2 μm or less and the depth is 100 n by using resin.
Fine pits and grooves of m or less can be formed accurately and efficiently. In the case of a metal substrate, it is difficult to form pits and grooves directly on the substrate surface. For example, a thin resin sheet is once adhered to a metal substrate, and then a pit / groove stamper is used. This is performed by compression molding. In the case of a glass substrate, pits and grooves can be formed by etching or the like. The thickness of the substrate is generally about 0.5 to 3 mm. If the thickness is smaller than this, it is particularly noticeable in the case of a resin substrate, but the substrate is sagged by its own weight, making it difficult to obtain flatness.
If it exceeds 3 mm, there is almost no difference in strength.

As the optical recording layer formed on the substrate, various types can be adopted. For example, a magneto-optical recording layer, a phase change recording layer and a dye recording layer are used. The layer configuration is not particularly limited, and various layer configurations can be adopted. As the magneto-optical recording layer, for example, TbFe,
TbFeCo, TbCo, GdFeCo, DyTbFe
Amorphous magnetic film of rare earth such as Co and transition metal, MnB
i, a polycrystalline perpendicular magnetization film such as MnCuBi, a Pt / Co multilayer film or the like is used. The magneto-optical recording layer may be a single layer, or Gd for enabling overwriting and MSR.
Two or more magnetic layers such as TbFe / TbFe may be stacked and used.

As the phase change type recording layer, for example, GeSb
Te, InSbTe, AgSbTe, AgInSbTe
Can be used. Preferably, ｛(Sb_Two
Te _Three)_1-x(GeTe)_x｝_1-ySb_y(0.2 <x
<0.9, 0 ≦ y <0.1) alloy, and 1 for the ternary alloy
In, Ga, Zn, Sn, Si, C up to about 0 atomic%
u, Au, Ag, Pd, Pt, Pb, Cr, Co, O,
Including at least one of S, Se, Ta, Nb, and V
Alloy thin films. Or high speed overlay
Sb₇₀Te₃₀Sb near the eutectic point
MSbTe (M = In, G
a, Zn, Ge, Sn, Si, Cu, Au, Ag, P
d, Pt, Pb, Cr, Co, O, S, Se, Ta, N
(At least one of b and V) alloy thin film is preferable.

On the optical recording layer, a transparent intermediate layer having properties such as weather resistance, high hardness and high lubricity is provided. The material of the intermediate layer is selected in consideration of these properties. A dielectric is preferable in terms of weather resistance and high hardness. As the dielectric, an oxide, a nitride, a chalcogenide, a carbide, a fluoride, a mixture thereof, or the like is used. Al ₂ O ₃ or Ta as an oxide
₂ O ₅ , metal oxides such as TiO ₂ alone or a mixture thereof, or a composite oxide of Al-Ta-O, and the like,
Examples of the nonmetal oxide include SiO ₂ and SiO. Examples of the nitride include silicon nitride and aluminum nitride. As chalcogenides, AnS, Zn
Zinc chalcogenides such as Se, II- such as CdS and CdSe
Group V compounds, rare earth sulfides such as La ₂ S ₃ and Ce ₂ S ₃ , TaS ₂ , MgS, CaS and the like can be mentioned. Zinc chalcogenides are chemically stable, especially ZnS
Is most preferred because of its low toxicity. Examples of a method for forming these dielectric layers include vapor deposition and sputtering, and sputtering is more preferred.

Materials having excellent lubricity include a carbon film, a hydrogenated carbon film, a nitrogenated carbon film, a carbonized film such as TiC and SiC, a nitrided film such as SiN and TiN, SiO ₂ and Al ₂ O.
₃ , composed of an oxide film such as ZrO _2, etc.
It is formed by a sputtering method or the like. More preferred are a carbon film, a hydrogenated carbon film and a nitrogenated carbon film. The hydrogenated carbon film is not particularly limited as long as it contains hydrogen and carbon, and is not particularly limited. For example, a carbon target is used, and a sputtering gas (usually, an inert gas such as argon is used). It can be formed by a method of sputtering in a plasma containing hydrogen gas.

The nitrogenated carbon film is not particularly limited as long as it is a film containing nitrogen and carbon. For example, using a carbon target, a sputter gas, a nitrogen gas, a nitrogen monoxide gas, a nitrogen dioxide gas may be used. Alternatively, it can be formed by sputtering in a plasma containing a nitrogen-containing gas such as ammonia gas or a nitrogen-containing gas such as air. For example, when air is used, the content of air in the sputtering atmosphere is usually 2 to 20% by volume.
It is. Further, for example, a hydrogenated and nitrogenated carbon film can be formed by simultaneously mixing a hydrogen gas and a nitrogen (containing) gas into a sputtering gas.

The intermediate layer has a role as a protective layer and a lubricating layer, but may have a plurality of layers. For example, when a protective layer having high weather resistance and high hardness is provided on the side in contact with the recording layer, and a lubricating layer having excellent lubricity is provided on the side in contact with the lubricating layer, both excellent properties can be obtained as a whole, which is preferable. . Of these, hydrogenated carbon is particularly preferred, and it is desirable that at least the outermost surface of the intermediate layer be a hydrogenated carbon layer.

As a layer in contact with the magneto-optical recording layer, silicon nitride, SiO ₂ , Ta ₂ O ₅ or the like is preferably used. As a layer in contact with the phase-change recording layer, a mixture of ZnS and a metal oxide is preferably used. Preferably, a reflective layer is provided between the substrate and the recording layer. As the reflective layer, a metal or alloy having a high reflectivity is used.
l, Ag, Au, Cu and alloys containing these as main components. Furthermore, between the substrate or the reflective layer and the recording layer,
A transparent intermediate layer may be provided for the purpose of amplifying by interfering light or for the purpose of protecting the recording layer. As the material, the above-described dielectric or the like is preferably used.

In the present invention, the transparent lubricating layer is
Use orocarbon. Fluorocarbon is plasma heavy
Alternatively, it is formed by a sputtering method. Plastic
As a fluorocarbon monomer in Zuma polymerization
Is a par of ethylene tetrafluoride, propylene hexafluoride, etc.
Fluoroalkene or perfluorocyclohexane, par
Even if it is a gas or liquid at normal temperature, such as fluorobenzene
The vapor pressure is high enough and the vapor
10 minds^-3Torr or more, and glow discharge is possible
If the degree of substitution of fluorine is high
No. In particular, ethylene tetrafluoride and propylene hexafluoride are steam
High pressure, high polymerization rate, low cost and easy handling
This is an advantageous monomer gas in this respect. Plasma polymerization conditions
5 × 10 5 monomer gas between parallel plate electrodes^-3To
From rr, 5 × 10 ^-2Torr introduced and high frequency power applied
It is done by doing.

In the sputtering method, a polyfluorocarbon such as polytetrafluoroethylene, which is a fluororesin, is used as a target material, and the sputtering conditions are also 5 × 10 ⁻³ T between parallel plate electrodes.
5 × 10 ⁻² Torr of Ar gas was introduced from orr,
This is performed by applying high frequency power. The structure of the fluorocarbon sputtered film or plasma polymerized film can be controlled by the discharge conditions (discharge power, discharge gas flow rate, gas pressure, etc.) or the shape of the device. For example, for plasma-polymerized films, the lower the discharge power, the higher the gas pressure, and the lower the gas flow rate, the higher the ratio of the number of fluorine atoms to the number of carbon atoms relative to the carbon atom. be able to.

The atomic ratio (F / C) of fluorine and carbon constituting the fluorocarbon in the present invention is a value measured by the ESCA method, and is 0.8 to 1.8 with respect to 1 carbon.
, Preferably in the range of 1.0 to 1.5.
The ESCA method referred to in the present invention is an abbreviation of soft X-ray excitation photoelectron spectroscopy, and is based on the energy spectrum of photoelectrons struck out from atoms in a sample compound by irradiation with soft X-rays, and the type of element near the surface of the sample And a method for analyzing the state of chemical bonding.

In the present invention, the fluorine 1S orbital (F1S) spectrum on the surface of the fluorocarbon film and the carbon 1S (C
1S) The orbital spectrum was measured. The ratio of the number of carbon atoms to the number of fluorine atoms is determined by the integrated intensity of the F1S peak and the C1S
It is derived from the ratio of the spectrum to the integrated intensity. This F /
When C exceeds 1.8, the film structure has a low degree of cross-linking between carbon atoms due to the large number of fluorine atoms, and therefore, the adhesion to the hydrogenated carbon film tends to decrease. May be peeled or scratched.

On the other hand, when the F / C is less than 0.8, a film structure having a small number of fluorine atoms and a high degree of cross-linking between carbon atoms is obtained, but at the same time, a large amount of residual radicals, so that oxygen tends to be easily taken in. As a result, the lubricity is reduced, and there is a possibility that the head may be damaged due to contact with the head or the head itself may be damaged. That is, as a condition for forming the film having a small F / C, the discharge power at the time of plasma polymerization is set to be high. Then, a large amount of CF ions and radicals are adsorbed on the growth surface of the film to form a large number of adsorption sites. Fluorine atoms may be released by the impact of high energy electrons. With this high discharge power, a high film formation rate is obtained, and as a result, the film grows without compensating for the above-mentioned adsorption sites, and a polymer film having a large amount of residual radicals (dangling pounds) is formed. Then, after film formation, residual radicals and oxygen in the atmosphere are combined.

The thickness of the lubricating layer is preferably from 0.5 to 20 nm, more preferably from 0.5 to 10 nm.
If the film thickness is less than 0.5 nm, the lubricity is insufficient and the possibility of damage when the head comes into contact with the disk is high, which is not preferable. On the other hand, if the film thickness exceeds 20 nm, peeling may occur when the head comes into contact with the disk, which is not preferable.

The optical recording medium 1 of the present invention can be recorded and reproduced by using a conventional film-surface incident type optical recording apparatus.
That is, as shown in FIG. 1, a plurality of optical recording media 1a,
1b and 1c are coaxially mounted on the rotating shaft 2, and the optical heads 3a, 4
a, 3b and 4b are provided. These optical heads 3, 4
Are mounted on the support arms 5a, 6a, 5b, 6b, are coaxially mounted on the shaft 7, and move in conjunction therewith. The moving direction of the optical head may be in the radial direction of the optical recording medium 1 or may be turned around the shaft 7 on which the heads 3 and 4 are supported.

The distance between the optical disk 1 and the heads 3 and 4 differs depending on each head, but is usually set to 5 μm or less. In the case of a floating type head in which a lens, a reflecting mirror, or an optical fiber is installed on a floating type slider, in order to maintain this distance, a slider is used to obtain the spring pressure of the arm that presses the slider against the disk and the buoyancy required for floating. The area and shape of the part are set. Further, a contact type head or the like in which the slider portion and the disk surface are partially in contact can be used. When recording information sent from outside, each head detects address (physical position on the substrate) information based on pre-recorded preformats such as pits and grooves. Information is recorded on the recording layer of the optical disc to be recorded. Regarding the method of recording information, either one head or both heads may be used at the same time.

When reading the information recorded on the disk, the position of the recorded information is searched by a head and read. At this time, each head performs its own servo adjustment on the recorded information so that the reproduced signal intensity is maximized. When the rotation of the disk is stopped, the position of the head is set in a state of contact with the disk as in the so-called CSS method, or close to or in contact with the disk only during rotation of the disk as in the dynamic loading method, They are far enough apart.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. However, the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 A polycarbonate substrate having a diameter of 130 mm and a thickness of 1.2 mm was produced by an injection molding method. About 5 depth on the surface
A pit row having a thickness of 0 nm, a width of about 1 μm, and a length of about 1 μm was formed. On top of this, an AlTa reflective layer (thickness 350 °) / Si
Nx dielectric layer (thickness 100 °) / TbFeCo (thickness 3)
00Å) / SiNx dielectric layer (thickness 800Å) / hydrogenated carbon layer (100Å thickness) by sputtering. Next, a fluorocarbon film was formed as a lubricating layer under the following conditions. That is, a monomer gas of propylene hexafluoride was introduced into a vacuum vessel at 300 SCCM, the pressure was set to 1 × 10 ^-2, and 13.5 mm was placed between a stainless steel circular cathode having a diameter of 130 mm and an anode equipped with the disk.
A high frequency voltage of 6 MHz was applied to generate glow discharge. The discharge power was 150 W, and the interval between the parallel plate electrodes was 50 mm.

The optical disk thus provided with a lubricating layer is
Fourier transform infrared spectrophotometer (FT-IR, trade name JI
When the thickness of the lubricating layer was measured using R-5300 (manufactured by JEOL Ltd.), it was a plasma polymerized film having a thickness of about 15 nm. Next, after performing initialization five times using a laser initialization device (optical disk bulk eraser LK101A, manufactured by Shibasoku), the thickness of the lubricating layer was measured in the same manner.
Initialization conditions were as follows: laser power: 150 mW, laser wavelength: 810 nm, disk rotation speed: 6 m / s, laser head feed speed: 50 μm / rotation. The residual ratio of the film thickness due to the laser initialization was almost 100%. Next, a drug test was performed. That is, when the glide head for a hard disk is in contact with the disk, the speed is 1 rpm.
For one minute, ie, one revolution. Microscopic observation of the circular portion contacted by the head was performed, but no damage was observed. F / of the lubricating layer of the disk used at this time
The C value was 1.23.

Example 2 A test was performed in the same manner as in Example 1 except that a tetrafluoroethylene resin was formed as a lubricating layer by a sputtering method (sputtering conditions: an argon gas of 1 × 10 ⁻² Torr was introduced, and 13. High frequency power of 56 MHz / 200 W is supplied). The thickness was about 15 nm. The residual ratio of the film thickness after laser irradiation was almost 100%. No scratches were observed in the drag test. The F / C value of the lubrication layer is 1.5
Met.

Comparative Example 1 A similar test was performed as in Example 1, except that the lubricating layer was formed by a dipping method. The lubricating layer was formed by the following method. Audimont FO as a lubricant
MBLIN Z DOL2000 is dissolved in HFE7200 which is a chlorofluorocarbon-based solvent, and 1.
After adjusting the concentration to 0 g / l and then immersing the disk for 3 minutes, the disk was pulled up at a speed of 3 mm per second. The thickness of the lubricating layer was about 2 nm. The residual ratio of the film thickness due to laser evaporation was approximately 80%. No scratches were observed in the drag test. The F / C value of the lubricating layer was 2.0.

Comparative Example 2 A test was conducted in the same manner as in Example 1 except that the plasma polymerization discharge power was changed to 800 W.
It was 5 nm. The residual ratio of the film thickness due to laser evaporation was almost 100%. Dragging scratches with the head were observed in the drag test. Scratches due to the head were observed in the drag test. The F / C value of the lubricating layer was 0.7.

From the above Examples and Comparative Examples, it is shown that the amount of evaporation of the lubricating layer can be almost completely suppressed in the present invention. That is, according to the present invention, the thermal evaporation of the polyfluorocarbon coating film in the case of the dipping method is eliminated, and an optical recording medium provided with a dense and excellent heat-resistant lubricating film can be obtained. In addition, the lubrication and durability of the film are satisfactory, and there is no fear that scratches or damage to the head will occur unless there is a great deal of trouble.

[0035]

The optical recording medium of the present invention exhibits good lubrication characteristics even when used for a long period of time, so that recording and reproduction with a proximity optical head such as a flying head can be performed well.

[Brief description of the drawings]

FIG. 1 is a side view showing an optical recording apparatus.

[Explanation of symbols]

 1a, 1b, 1c Optical recording medium 2 Rotation axis 3a, 4a, 3b, 4b Optical head 5a, 6a, 5b, 6b Support arm 7 axis

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 11/10 521 G11B 11/10 521E // C10N 40:18 F term (Reference) 4H104 CD02A EA21A PA16 5D029 LA05 LA07 LA13 LA14 LA16 LB07 LC18 LC21 5D075 EE03 FF11 FG04 FG10

Claims (5)

[Claims] 1. An optical recording medium in which an optical recording layer, a transparent intermediate layer and a transparent lubricating layer are sequentially formed on a resin substrate having pits and / or grooves formed thereon, wherein the transparent lubricating layer is formed using fluorocarbon. An optical recording medium characterized in that the atomic ratio of fluorine to carbon measured by the ESCA method is in the range of 0.8 to 1.8 with respect to 1 carbon. 2. The optical recording medium according to claim 1, wherein the transparent lubricating layer is formed by a plasma polymerization method or a sputtering method. 3. The optical recording medium according to claim 1, wherein the transparent intermediate layer has at least one outermost layer comprising one or more layers containing hydrogenated carbon. 4. The transparent lubricating layer has a thickness of 0.5 to 20 nm.
The optical recording medium according to claim 1, wherein 5. An optical recording apparatus using the optical recording medium according to claim 1 to perform recording and / or reproduction with a floating or contact type head.