JPH03225626A - Optical recording method - Google Patents

Abstract

PURPOSE:To avoid disadvantages on recording/reproducing when waving of an optical recording medium is caused by using a protective film of specified film thickness. CONSTITUTION:The medium consists of a synthesized resin substrate 1 UV- curing resin layer 2 for sticking, Si3N4 base film 3 to give corrosion resistance and to prevent deterioration in recording/reproducing characteristics, recording film 4, Si3N4 transparent dielectric film 5 to enhance the Kerr rotation angle, and a protective film comprising a glass sheet. On recording, the film 4 is irradi ated with laser beam from a floating type optical head through the film 6 while a perpendicular magnetic field of about 200 - 300 Oe is applied on the the surface of the optical disk where the laser light is focused. The beam reflected from the disk is made to enter a photodiode for reproducing. The film 6 is made 100mum thick with allowance within + or -10mum considering that the error of film formation is regarded + or -10%. Variation of distance between the film 6 and the objective lense which focuses the beam on the film 4 is specified within + or -10mum so that the beam is surely forcused on the medium to make the illuminance distribution within about + or -10mum from the optimum focus point.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a recording film whose optical properties can be changed by means of light, heat, etc. on a substrate of an optical recording medium, and a suitable surface of the recording film. It relates to an optical recording method in which information is recorded, reproduced, or erased by converging a laser beam from a light source, and in particular, recording and reproduction are not hindered even if the optical recording medium causes surface wobbling, etc. This invention relates to improvements in optical recording methods.

[Conventional technology]

In this optical recording method, for example, as shown in FIG. 9, the main part of an optical recording medium (c) is composed of a transparent substrate (a) of about 1.2 thickness and a recording film (b), A laser beam (2) focused to a diameter of about 1 μm using an objective lens (not shown) is irradiated onto the surface of the recording film (b) of the optical recording medium (C) to change the optical properties of the recording film (b). This is a method of recording and reproducing information.

By the way, in this optical recording method, it is necessary to always focus the laser beam passing through the objective lens on the appropriate surface of the recording film (b), so a focusing servo that controls the position of the objective lens is usually applied. It is being

In this case, if the numerical aperture of the objective lens is (NA) and the wavelength of the laser beam is (λ), then the depth of focus is ±2・λ
/(2・NA)', and is given by, for example, a typical value of a semiconductor laser and an objective lens applied to a conventional optical recording device (λ=780 nm, NA=0.
48) and find the depth of focus, the value is at most about ±2 μm.

Therefore, as shown in FIG. 10, the surface of the transparent substrate (a) on the opposite side to the recording film (b) is far away from the focal position of the laser beam, and there may be scratches, dust, etc. on this surface. In this optical recording method, a laser beam is irradiated from the transparent substrate (a) side to the recording film (b) side, as shown in FIG. method is adopted.

As a focusing control method for the objective lens, for example, as shown in FIG.
) is equipped with a focus control coil (Fc), and a method is known in which the movement of the objective lens (d) in the focus direction is controlled by applying an energization signal to the focus control coil (Fc).

However, in this method, the weight of the optical head (He) increases due to the inclusion of the focus control coil (Fc). There is a drawback that it takes a long time, so-called access time.

Therefore, in recent years, as shown in FIG. 12, the optical head (He) is mounted in a floating manner by an appropriate spring-like suspension (e), and the optical head (He) is mounted using an airflow caused by the rotation of the optical recording medium (C). A simple method for controlling the movement of He) in the focus direction has been devised.

That is, according to this method, the optical head (He) floats following the surface runout of the optical recording medium (c), so for example, when the floating amount of the optical head (He) is 5 μm, It is possible to suppress the variation in the distance between c) and the objective lens (d) to less than ±0.5 μm, and the optical head (He) is lightweight since it is not equipped with the focus control coil. This method has the advantage of shortening access time.

However, in this method, the focus of the optical head (He) is controlled using the air flow accompanying the rotation of the optical recording medium (c), so the general optical recording medium (c) that rotates at a constant speed is ), there is a drawback that the amount of floating changes between the inner circumferential side and the outer circumferential side, which have different rotational speeds, making it impossible to perform sufficient focus control.

In addition, considering this change in floating amount, the above optical recording medium (c)
It is also possible to variably control the rotational speed of Even if the control can be made constant, the thickness of the transparent substrate (a) may vary due to the fact that the laser beam is irradiated from the transparent substrate (a) side of the optical recording medium (c) to the recording film (b) side. The objective lens (d) and the recording film (
b) Since the distance between the two lenses always fluctuates, there is still a drawback that the focus cannot be controlled sufficiently.

Against this technical background, the applicant has already proposed an optical recording method incorporating a new focus control means.

That is, as shown in FIG. 13, this method uses a diffusion lens (g) that is composed of a convex or concave lens and that diffuses the laser beam from the light source (f), and an air flow that accompanies the rotation of the optical recording medium (c). an objective lens (d) that is mounted on the optical head (He) floating by the lens and converges the laser beam diffused by the diffusion lens (g) onto the recording surface of the optical recording medium (c);

A collimating lens (h) is provided on the optical axis between the diffusing lens (g) and the objective lens (d), and converts the laser beam diffused by the diffusing lens (g) into a parallel beam.
), and perturbs at least one of the diffusing lens (g) or the collimating lens (h) in the optical axis direction in response to the surface deflection of the optical recording medium (c), the floating amount of the optical head (He), etc. By doing so, as shown in FIGS. 14(A) to (C), the objective lens (d)
The angle of incidence of the laser beam on the recording film (b) is changed, and the convergence position of the laser beam changes with this change, so that the laser beam can be reliably focused on the appropriate surface of the recording film (b). This method dramatically improves focus accuracy regardless of surface runout of the recording medium (c) or changes in the floating amount of the optical head (He).

[Problem to be solved by the invention]

By the way, by adopting this optical recording method, it has become possible to always focus the laser beam from the light source on the appropriate surface of the recording film, but on the other hand, the laser spot that is focused on the appropriate surface of the recording film is A new problem has emerged: the illuminance distribution within the spot deteriorates depending on the convergence position, causing an insufficient amount of light.

That is, when there is no surface wobbling of the optical recording medium and therefore no perturbation of the diffusing lens, collimating lens, etc., a parallel beam as shown in FIG. 14(B) is incident on the objective lens (d), The laser beam with the highest illuminance distribution is converged on the appropriate surface of the recording film (b) (hereinafter, the convergence position of the laser beam at this time is referred to as the "optimum convergence position"), but optical recording The collimating lens etc. are perturbed due to surface runout of the medium, and the convergence position of the laser beam is shifted from this "optimum convergence position" to the objective lens (d
) side (see FIG. 14C) or the opposite side (see FIG. 14C), the problem is that the illuminance distribution within the laser spot decreases.

In addition, FIGS. 15(A) and 15(B) show this phenomenon, where the above-mentioned "optimum light focusing position" is indicated as 0 on the horizontal axis, and the peak of the laser beam corresponding to the amount of deviation from this position is shown. When the intensity changes are plotted sequentially, the result is as shown in Figure 15 (A). On the other hand, when the amount of change in the half-width of the laser beam corresponding to the amount of deviation from the above-mentioned "optimum light collection position" is plotted, the result is shown in Figure 15 (A). It is as shown in (B).

The permissible change range of peak intensity and half-width for focusing is usually about 10%, so
From FIGS. 15(A) and 15(B), the variable range of the convergence position of the laser beam is approximately ±20 μm at most, and therefore,
To perform proper focus control without causing insufficient light intensity, move the laser beam from the light source ± from the above “optimum focus position”.
It was necessary to converge to a position of about 20 μm.

By the way, the main parts of the optical recording medium applied to this type of optical recording method are composed of a transparent substrate and a recording film because the laser beam is irradiated from the substrate side as described above. This transparent substrate is generally manufactured by injection molding of PMMA (polymethyl methacrylate), PC (polycarbonate), or the like. In the case of a transparent substrate with a thickness of about 1 mm, in normal production,
Thickness unevenness and variation of up to about ±100 μm occur within a lot and between lots. However, even if such variations occur, focus control is possible when this optical recording medium is applied to an optical head system equipped with a focus control coil, and therefore there is a significant difference in recording and playback. Conventionally, standard restrictions on the thickness of optical recording media have been set relatively loosely so as not to cause any problems.

However, when an optical recording medium with such variations is applied to the above-mentioned floating head recording method,
The range of change in the distance between the recording film and the objective lens is ±100 μm or more, which corresponds to the variation in the thickness of the transparent substrate, and therefore,
Adjust the laser beam from the light source ± from the above “optimum focusing position”
It becomes impossible to converge to a position of about 20 μm,
There was a problem that caused malfunctions due to a decrease in the amount of light during recording and playback.

Although it is possible to improve the accuracy of the thickness by using a glass material as the transparent substrate, there is a problem in that the cost increases due to the necessity of precision polishing.

In addition, if the thickness of the transparent substrate is large, since the recording film surface is irradiated with a laser beam through the transparent substrate, the recording/reproducing characteristics may be affected by refractive index unevenness, birefringence, or optical recording within the transparent substrate. Another problem is that it is easily affected by media skew, etc.

[Means to solve the problem]

The present invention has been made in view of the above-mentioned problems, and its object is to develop a new optical recording method that does not interfere with recording and reproduction even if the optical recording medium suffers from surface wobbling or the like. It is about providing.

That is, the present invention includes a diffusion lens that is composed of a convex lens or a concave lens and that diffuses a laser beam from a light source, and a laser beam that is mounted on an optical head that floats due to the air flow accompanying the rotation of an optical recording medium and that is diffused by the diffusion lens. an objective lens that converges the laser beam onto the recording film surface of the optical recording medium; and a collimating lens that is provided on the optical axis between the diffusion lens and the objective lens and converts the laser beam diffused by the diffusion lens into a parallel beam. perturbing at least one of the diffusing lens or the collimating lens in the optical axis direction in response to surface wobbling of the optical recording medium, and converging the laser beam from the light source onto the appropriate surface of the recording film. Based on the premise of an optical recording method that records, reproduces, or erases information optically, the main parts of the optical recording medium are a substrate, a recording film provided on at least one surface of this substrate, and a recording film provided on at least one surface of the substrate. and a light-transmitting protective film to cover the optical recording medium, and the laser beam from the light source is irradiated from the protective plate side of the optical recording medium, and the film thickness formation error when forming the protective film is ±t%. In some cases, the thickness of the protective film is set to (2000/t) μm or less.

In such technical means, the substrate may be made of a transparent single material such as glass, polycarbonate, polyacrylonitrile, polymethyl methacrylate, epoxy resin, polythene pen, etc., or a laminated material of these materials, as in the past. Alternatively, it may be constructed of a light-opaque material such as aluminum. When a resin material such as polycarbonate is used, a base material such as SiO□ or ZrO2 may be provided on the substrate in order to prevent thermal damage to the resin material.

Furthermore, as the recording material provided on the above substrate, conventionally,
In addition to the non-rewritable recording materials that are widely used in Method 1 and R-bubble method J, etc., the r-hole drilling can also be applied to the following rewritable recording materials.

That is, Tea, , In-5e, In-3b-
Phase change recording materials such as Te, Ge-3b-Te and Te
Magneto-optical recording materials such as FeCo, Cd-Co, Mn-B1, and Co/Pt are applicable.

It goes without saying that the recording film made of these recording materials may be provided only on one side of the substrate, or may be provided on both sides.

Next, as the protective film covering the recording film, any material can be used as long as it has light transmittance, can be formed into a thin film, and has appropriate strength, such as glass, Stow, etc.
, ZnS, 5ihNa, Ta205, AIN
, ZnS-SiO□, etc., and as for the method of forming it, a protective film material previously processed into a sheet may be laminated to the substrate side to form a protective film, or the above materials may be used by sputtering method or vapor deposition method. A method of direct formation using an appropriate film deposition method such as the like may be adopted, and the formation method is arbitrary. Note that by forming a light-transmitting carbon thin film on the surface of this protective film, there is an advantage that sufficient lubricity can be imparted between the optical head and the optical recording medium.

In addition, in this technical method, unlike the conventional method in which the laser beam is irradiated from the transparent substrate side, the laser beam is irradiated from the protective film side toward the recording film, so the film thickness of the protective film is important. It has significant technical meaning.

In other words, if this protective film is too thick, as with the conventional method of irradiating a laser beam from the transparent substrate side, the above-mentioned "optimal light collection position" will be affected due to variations in the thickness due to errors in film thickness formation.
It becomes difficult to converge the laser beam to a position within ±20 μm from This is because there is a risk that recording/playback may be affected due to such factors.

Therefore, when determining the upper limit value of the film thickness of the above-mentioned protective film, the laser beam from the light source should be
It is possible to converge to a position of about ±20 μm from
In addition, it is necessary to set the recording/reproducing characteristics within a range where the recording/reproducing characteristics are not affected by refractive index unevenness within the protective film or skew of the optical recording medium.

Taking as an example a case in which a thin glass plate is used as a protective film material, the thickness of the glass plate according to normal production is 50~
The film thickness formation error (1) for a 1000 μm glass plate is about ±10% of the thickness dimension, so the film thickness of the glass plate is
By setting 000-, lO = 200 μm or less, the thickness unevenness can be kept within ±20 μm, and therefore the laser beam from the light source can be reliably placed at a position of about ±20 μm from the “optimal light collection position”. It becomes possible to converge.

On the other hand, when determining the lower limit of the film thickness of the above-mentioned protective film, in addition to considering the effects of scratches, dust, etc. during recording and playback, the abrasion resistance of the protective film and the possibility of forming a thin film during manufacturing are considered. It is necessary to set it taking into account gender, etc.

The following documents are known regarding the effects of scratches, dust, etc. during recording and reproduction.

That is, this [EEE TRANSACTION C
ONSUMERELECTRC0N5U,NOVEMB
ER1976 “SYSTEM CODING PARAM
ETER3, MECHANIC3AND ELECTR
O-MECHANIC3OF THE REFLECT
IVE VIDEODisc PLAYER" i: If dust, fingerprints, etc. with a particle size of 20 μm, which are thought to exist in a normal closed space, adhere to the surface of the protective cover, the amount of reflected light will decrease rapidly if the thickness of the protective cover is reduced to 300 μm or less. It is stated that the degree of modulation (α) of the data decreases, and that when the particle size of the dust is 5 μm or less, the recording/reproducing characteristics are not affected if the thickness of the protective cover is set to 100 μm or more.

Here, the "degree of modulation (α) of the amount of reflected light" refers to a value determined by α=(maximum value of amount of reflected light−minimum value of amount of reflected light)=(maximum value of amount of reflected light−minimum value of amount of reflected light).

Figure 5 is a graph showing the relationship between the thickness of the protective layer (μm) and the degree of modulation (%) of the amount of reflected light. It can be confirmed that by setting the thickness of the protective film to 100 μm or more, it does not affect the recording/reproducing characteristics.

In addition, (β) in the figure indicates that the particle size of fingerprints and attached dust is 20μ.
In the case of m, (γ) indicates the case where the particle diameter of the attached dust is 5 μm or less.

Such conditions can be easily achieved by handling the optical recording medium in a cartridge with a shutter and by blowing clean air over the surface of the optical recording medium during use.

Therefore, when determining the lower limit of the film thickness of the above-mentioned protective film, the above-mentioned conditions are satisfied, and appropriate consideration is given to the abrasion resistance of the protective film, the possibility of forming a thin film during manufacturing, etc. Can be set to a value. Of course, by further improving the cleanliness conditions, the lower limit of the thickness of the protective film can be set to 100 μm or less.

In addition, in this technical means, conventional methods can be applied as is for detecting the surface deflection of the optical recording medium and the amount of surface deflection, such as the astigmatism method, the beam decentering method, the knife-edge method, etc. method, wobbling method, etc. can be applied.

Furthermore, the above-mentioned means for detecting surface wobbling of the optical recording medium may be placed anywhere on the optical axis between the light source and the diffusion lens, or on the optical axis between the diffusion lens and the objective lens. It may be provided.

In addition, perturbation (movement) is performed in response to surface runout of the optical recording medium, etc.
The lens to be used is a collimating lens or a diffusing lens composed of a convex lens or a concave lens, and depending on the case, both the collimating lens and the diffusing lens may be perturbed (moved).

[Effect]

According to the above-mentioned technical means, the main part of the optical recording medium is composed of a substrate, a recording film provided on at least one surface of the substrate, and a light-transmissive protective film covering the recording film. In addition, when the laser beam from the light source is irradiated from the protective film side of the optical recording medium, and the film thickness formation error when forming the protective film is ±t%, the film thickness of the protective film is Since it is set to less than (2000/t) μm, the film thickness error of the above protective film is (2000/t) x (±t/100) = ±20
μm, and the variation in the distance between the recording film and the objective lens that converges the laser beam onto the recording film surface is within ±20 μm, and the laser beam from the light source is adjusted to the above-mentioned “optimum focusing position”.
It is possible to reliably converge the laser beam to a position within ±20 μm from It becomes possible to make the distance between the recording film and the recording film closer than that in the past.

〔Example〕

Hereinafter, embodiments in which the present invention is applied to a magneto-optical recording method will be described in detail with reference to the drawings.

◎First Example The equipment used in this example is as shown in Figures 12 to 13.
The conventional magneto-optical recording device shown in the figure is applied as is, but the structure of the magneto-optical disk incorporated in this device and the direction of laser beam irradiation are different from the conventional one.

That is, as shown in FIGS. 1 and 2, this magneto-optical disk has a substrate (1) with a thickness of about 1.2 cm made of synthetic resin such as polycarbonate or polymetal methacrylate.
, an ultraviolet curable resin layer (2) for bonding formed on this substrate (1), and an ultraviolet curable resin layer (2) provided on this ultraviolet curable resin layer (2), which is effective for corrosion resistance and prevention of deterioration of recording/reproducing characteristics. A base film (3) made of 5tJt, and a recording film (3) having a magneto-optic effect formed of a rare earth-transition metal alloy such as TeFeCo, which is provided on the base film (3).
4), and a transparent dielectric film (5) made of 5isNt provided on the recording film (4) to increase the Kerr rotation angle;
A thickness of 100 μm provided on this transparent dielectric layer (5)
The main part is composed of a protective film (6) made of a glass sheet, and a laser beam is irradiated from the protective film (6) side to the surface of the recording film (4) via a floating optical head (not shown). On the other hand, a perpendicular magnetic field of 200 to 3000 e is applied toward the light collecting surface of the magneto-optical disk (7) to perform a recording operation, and the laser beam reflected from the surface of the magneto-optical disk (7) is directed to the same optical path. The light is incident on a photodiode (not shown) through the light source, and a reproduction operation is performed.

In the recording method according to this embodiment, the thickness of the glass sheet protective film (6) of the magneto-optical disk (7) is 100 μm, and even if the film thickness formation error is estimated to be ±10%, the protective film cannot be protected. The film thickness error of the film (6) is within ±10 μm.

Therefore, the variation in the distance between the recording film (4) and the objective lens for converging the laser beam onto the recording film (4) surface is ±10.
Since it is within μm, it is possible to reliably converge the laser beam from the light source at a position approximately ±10 μm from the above-mentioned "optimal light collection position" where the illuminance distribution is maximum, and the protective film is as thin as 100 μm. Since the laser beam is irradiated from the (6) side, the recording film (4)
The distance between the optical head and the optical head on which the objective lens is mounted can be made closer than that in the past.

Therefore, focus control is possible without causing insufficient light intensity, and since the film is thin, the influence of refractive index unevenness, birefringence, etc. in the protective film (6) is small, which has the advantage of preventing malfunctions during recording and playback. have.

In addition, because the distance between the recording film (4) and the optical head on which the objective lens is mounted becomes closer, it becomes possible to use a light source with a smaller beam diameter than before, and the optical system becomes smaller, allowing for smaller devices. In addition, as the optical head approaches the optical head, the efficiency of magnetic field generation by the magnetic field generating coil (not shown) mounted on this head increases. It has the advantage of increasing the strength and speeding up the recording or rewriting speed. On the other hand, it is possible to produce the same magnetic field strength as the conventional one even if the coil is made smaller, so the optical head can be made lighter and smaller. This has the advantage of speeding up access time.

Furthermore, when the magnetic field generating coil is small and has a sufficiently low inductance, high-speed polarity reversal is possible, which has the advantage of enabling overwriting using the magnetic field modulation method.

In addition, Fig. 4 shows the magnetic field strength (Oe) in the coil axis direction at a point on the coil axis at a distance r (μm) away from the coil when a magnetomotive force NI is applied to a soft magnetic core with a radius of 500 μm and a relative magnetic permeability of 1000. FIG.

From this graph, it can be seen that by setting the thickness of the protective film on the magneto-optical disk thin and keeping the distance between the optical head and the recording film small, a sufficient perpendicular magnetic field can be obtained with a small magnetomotive force NI. It can be understood. Incidentally, when the distance r is 100 μm or less, the magnetomotive force N I =0.02
200 Oe required for magneto-optical recording at AT
It is possible to provide a sufficient magnetic field as described above.

r.Manufacture of Magneto-Optical Disk" Hereinafter, a method for manufacturing the magneto-optical disk used in the first embodiment will be described.

First, as shown in FIG. 3(A), a transparent dielectric film (5) made of 5iJz and a TeFe
Co recording film (4) and 5iIN4 base film (3)
and are sequentially deposited.

On the other hand, as shown in FIG. 3(B), an ultraviolet curable adhesive is placed on a substrate (1) made of synthetic resin such as polycarbonate or polymetal methacrylate and having a thickness of 1.2 iun molded by injection molding. (20) is applied to a thickness of about 20 μm, and the base film (3) of the protective film (6) made of the glass sheet is laminated on the surface of the adhesive (20), facing the adhesive (20).
0) was cured to obtain a magneto-optical disk as shown in FIG.

In this manufacturing method, a transparent dielectric film (5) and a recording film (4) are preliminarily formed on the surface of the protective film (6) made of a glass sheet.
, and after depositing the base film (3), it is adhered to the substrate (1) side.
Base film (3), recording film (4), and transparent dielectric film (
5) is deposited by sputtering, an ultraviolet curable adhesive is applied to the transparent dielectric film (5) to a thickness of about 20 μm, and a 100 μm thick glass sheet protective film (5) is applied on this surface. 6) may be laminated to obtain a magneto-optical disk as shown in FIG.

However, in this manufacturing method, when laminating the 100 μm glass sheet protective film (6) on the substrate (1) side, uniform pressure is applied to the entire protective film (6) to prevent uneven thickness of the adhesive. It is important to suppress the thickness to 5 μm or less.

In other words, this thickness unevenness is also caused by the optical head and the recording film (4).
This is because it is related to the variation in the distance between the two, and by performing such processing, it becomes possible to suppress the variation in the distance to ±15 μm or less.

◎Second Embodiment In this embodiment, recording films (41) (42) and protective films (61) (6) are provided on both sides of the substrate (1) as shown in FIG.
2) The recording method according to the first embodiment is different from that of the first embodiment except that a magneto-optical disk (7) on which is formed is used and a double-sided type magneto-optical recording device as shown in FIG. It's Roma-.

This magneto-optical disk (7) was manufactured using the latter manufacturing method in the first embodiment, that is, a base film (1) was formed on the substrate (1).
3) A recording film (4) and a transparent dielectric film (5) are sequentially deposited by sputtering, and an ultraviolet curing adhesive is applied to a thickness of about 20 μm on this transparent dielectric film (5). After coating, a protective film made of glass sheet with a thickness of 100 μm (6)
It is manufactured by a method of laminating layers.

The method according to this embodiment also has the same advantages as the first embodiment, and particularly has a remarkable advantage in reducing the size of the device.

In addition, in the recording apparatus shown in FIG.
Although the structure is such that a single magneto-optical disk (7) can be attached, it goes without saying that this method may also be applied to an apparatus that can accommodate a plurality of magneto-optical disks.

〔Effect of the invention〕

According to the present invention, since the variation in the distance between the recording film and the objective lens that converges the laser beam onto the recording film surface is within ±20 μm, the laser beam from the light source can be adjusted by ±2 from the “optimal convergence position”.
It is possible to reliably converge the laser beam to a position of approximately 0 μm, and since the laser beam is irradiated from the side of the thin protective film with a film thickness of (2000/t) μm or less, the optical head on which the objective lens is mounted and the recording It becomes possible to make the distance between the films closer than in the past.

Therefore, focus control is possible without causing insufficient light intensity, and since the film is thin, the effects of refractive index unevenness, birefringence, etc. within the protective film are small, so it has the effect of preventing malfunctions during recording and playback. There is.

In addition, because the distance between the objective lens and the recording film is shortened, it is possible to use a light source with a smaller beam diameter than before, which has the effect of making the separation chamber smaller because the optical system is smaller. .

Furthermore, when this technical means is applied to a magneto-optical recording method, the magnetic field formation efficiency is increased compared to the conventional method as the distance between the recording film and the optical head becomes closer, resulting in the effect of increasing the recording or rewriting speed. In addition, the optical head on which the coil is mounted can be made lighter and smaller, which has the effect of speeding up access time.

[Brief explanation of drawings]

1 to 8 show embodiments of the present invention, FIG. 1 is an explanatory perspective view of the optical recording method according to the first embodiment, and FIG.
The figure is a sectional view of a magneto-optical disk applied to this method, FIGS. 3(A) and 3(B) are explanatory sectional views showing the manufacturing process of this magneto-optical disk, and FIG. A graph showing the relationship between the distance and the magnetic field strength in the coil axis direction at this distant point, Figure 5 is a graph showing the relationship between the thickness of the protective layer and the degree of modulation of the amount of reflected light, and Figure 6 is a graph showing the relationship between the thickness of the protective layer and the degree of modulation of the amount of reflected light. FIG. 7 is a sectional view of a modified example of the magneto-optical disk in the first embodiment, FIG. 7 is a sectional view of a double-sided magneto-optical disk applied in the second embodiment, and FIG. 9 to 15 show conventional examples, and FIG. 9 is an explanatory perspective view of a conventional optical recording method, and FIG.
The figure is a schematic sectional view of an optical recording medium applied to the method, FIGS. 11 and 12 are schematic perspective views of a recording device applied to the conventional optical recording method, and FIG. 13 is a conventional optical recording method. A configuration explanatory diagram illustrating focus control in the device, FIGS. 14A to 14C are partially enlarged views, and FIG.
) is a diagram showing the relationship between the amount of deviation from the optimum focusing position of the laser spot and the peak intensity of the spot, and FIG. 15(B) is a diagram showing the relationship between the amount of deviation from the optimum focusing position and the half-width of the laser spot. are shown respectively. [Explanation of symbols] (1)...Substrate (4)...Recording film (6)...Protective film (7)...Magneto-optical disk patent Applicant: Fuji Zero-Nx Co., Ltd. Agent Patent attorney Tomohiro Nakamura (2 others) Figure 2 Figure Figure 00 200 300 r (μm) 00 00 200 300 Ri0 Protective layer thickness (μm) 00 Figure Figure 9 Figure 10 Figure 11 12 Figure 15

Claims (1)

[Claims] A diffusing lens configured with a convex lens or a concave lens and diffusing a laser beam from a light source; and a diffusing lens mounted on an optical head that floats due to air flow accompanying the rotation of an optical recording medium, and the laser beam is diffused by the diffusing lens. an objective lens that converges the laser beam onto the recording film surface of the optical recording medium; and a collimating lens that is provided on the optical axis between the diffusion lens and the objective lens and converts the laser beam diffused by the diffusion lens into a parallel beam. perturbing at least one of the diffusing lens or the collimating lens in the optical axis direction in response to surface wobbling of the optical recording medium, and converging the laser beam from the light source onto the appropriate surface of the recording film. In an optical recording method for optically recording, reproducing, or erasing information, the main parts of the optical recording medium include a substrate, a recording film provided on at least one surface of the substrate, and a light beam covering the recording film. and a transparent protective film, and the laser beam from the light source is irradiated from the protective film side of the optical recording medium, and the film thickness formation error when forming the protective film is ±t%. An optical recording method characterized in that the thickness of the protective film is set to (2000/t) μm or less.