JP4335745B2 - Optical disk device and optical medium - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention can be used as an optical disc apparatus including a recording medium such as an optical disc and an optical flying slider that has an objective lens and the like and can be placed on the recording medium. It relates to optical media that can be used.

  A magneto-optical disk is known as one form of optical media from which information is optically read. A magneto-optical disk is a rewritable recording medium that has a recording film having a predetermined magnetic structure and is recorded thermo-magnetically and reproduced using the magneto-optical effect. In recording information on the magneto-optical disk, a predetermined magnetic field is applied to the recording film while the temperature of the recording film is raised by condensing the recording laser beam on the recording film by the objective lens. As a result, a signal is recorded in the recording film as a change in the magnetization direction. When reproducing information from a magneto-optical disk, the reproducing laser beam is condensed on the recording film by the objective lens, and the recording signal is detected by detecting the change in the optical characteristics of the light reflected from the recording film surface. Is read. Therefore, a recording / reproducing apparatus for a magneto-optical disk requires a predetermined optical system including a light source and an objective lens, and a magnetic coil as a magnetic field applying unit.

  In the field of magneto-optical disks, perpendicular magnetic recording and front illumination (FI) magneto-optical disks are attracting attention as recording media that can achieve high recording density. In a perpendicular magnetic recording type and FI type magneto-optical disk, the magnetic layer (recording layer) in which information is recorded and held in the recording film has perpendicular magnetic anisotropy and is recorded from the side opposite to the substrate. Information recording and information reproduction are performed by irradiating the film with laser light and applying a magnetic field. In such a magneto-optical disk recording / reproducing apparatus, an objective lens for condensing a laser beam on a recording film and a magnetic coil as a magnetic field applying means are disposed close to the magneto-optical disk. A floating slider equipped with the objective lens and the magnetic coil may be used. Such a recording / reproducing apparatus is described, for example, in Patent Document 1 below.

JP 2002-324317 A

  FIG. 8 shows a schematic configuration of a conventional optical disk apparatus X2 which is an example of a magneto-optical disk recording / reproducing apparatus. The optical disk device X2 includes a magneto-optical disk 70, an optical flying slider 80, a spindle motor 91, an actuator 92, a suspension 93, and a guide rail 94, and includes a perpendicular magnetic recording type and FI type magneto-optical recording medium. It is comprised as an apparatus for recording and reproducing | regenerating.

  The magneto-optical disk 70 has a laminated structure including a substrate 71, a recording film 72, and a protective film 73, and is configured as a perpendicular magnetic recording type and FI type magneto-optical recording medium. The recording film 72 has a magnetic structure capable of assuming two functions of thermomagnetic recording and reproduction utilizing the magneto-optical effect, and one or two or more perpendicular magnetization films according to the reproduction method, and It has a recording layer made of a dielectric film (a so-called enhancement layer or the like) provided as necessary, and is composed of one perpendicular magnetization film. Information is recorded on the recording layer as changes in the magnetization direction. The protective film 73 is a part for protecting the recording film 72 from dust and the like, and is made of a light transmissive resin material. Such a magneto-optical disk 70 is supported by a spindle motor 91, and rotates when the spindle motor 91 is rotationally driven at a constant rotational speed. That is, the magneto-optical disk 70 in the optical disk apparatus X2 is rotated by a CAV (constant angular velocity 1) method.

  The optical flying slider 80 includes a slider body 81, an objective lens 82, and a magnetic coil (not shown), and is disposed to face the protective film 73 of the magneto-optical disk 70 when information recording and information reproduction are performed. The The medium facing surface of the slider body 81 has a curved shape for generating a so-called gas lubricating film between the magneto-optical disk 70 or the protective film 73 and the optical flying slider 80 when the magneto-optical disk 70 is rotating. (Not shown). The objective lens 82 is for condensing the recording or reproducing laser light L. The magnetic coil is for applying a predetermined magnetic field to the recording film 72. Such an optical flying slider 80 is connected to an actuator 92 via a suspension 93. The suspension 93 applies an urging force to the optical flying slider 80 toward the magneto-optical disk 70.

  The actuator 92 is provided so as to be capable of translational driving along a guide rail 94 extending in the radial direction R of the magneto-optical disk 70, and the optical flying slider 80 is moved along the radial direction R by moving the optical flying slider 80. 80 position control is performed. A light guide path through which laser light L from a light source (not shown) and reflected light from the magneto-optical disk 70 can pass is secured inside the actuator 92, and a reflection mirror 92a is provided in the light guide path. It is arranged.

  When information is recorded by the optical disk device X2, the magneto-optical disk 70 is rotated at a constant speed by the CAV method. As a result, a gas lubrication film is formed between the magneto-optical disk 70 and the optical flying slider 80, and the optical floating slider 80 is disposed so as to float with respect to the magneto-optical disk 70 while facing the protective film 73. Become. In this state, a predetermined magnetic field is applied to the recording film 72 by the magnetic coil while condensing the recording laser light L emitted from the light source (not shown) onto the recording film 72 by the objective lens 82. In this manner, information recording for writing a predetermined signal as a change in the magnetization direction on the recording layer in the recording film 72 is executed.

  When reproducing information by the optical disk device X2, the magneto-optical disk 70 is rotated at a constant speed by the CAV method. As a result, a gas lubrication film is formed between the magneto-optical disk 70 and the optical flying slider 80, and the optical floating slider 80 is disposed so as to float with respect to the magneto-optical disk 70 while facing the protective film 73. Become. In this state, the reproducing laser light L emitted from the light source (not shown) is condensed on the recording film 72 by the objective lens 82, and the polarization direction of the light reflected on the surface of the recording film 72 is detected. In this way, information reproduction for reading the signal recorded in the recording film 72 as a change in the polarization direction of the reflected light is executed.

  In the optical disc apparatus X2, in order to record favorably on the magneto-optical disc 70, it is necessary to appropriately focus the recording laser beam L on the recording film 72 during information recording. Further, in order to reproduce the magneto-optical disk 70 satisfactorily, it is necessary to appropriately collect the reproducing laser beam L on the recording film 72 during information reproduction. That is, in the optical disc apparatus X2, in order to achieve good recording and reproduction, the laser waist generated in the laser light L by passing through the objective lens 82 or the vicinity thereof when executing information recording and information reproduction. The surface of the recording film 72 needs to be located within the predetermined range. However, in the optical disk device X2, it may be difficult to properly focus the laser light L on the recording film 72 over the entire radial position (one-dimensional position in the radial direction R) of the magneto-optical disk 70. .

  In the magneto-optical disk 70 rotating by the CAV method, the linear velocity in the disk circumferential direction gradually increases from the rotation center axis Ax side to the peripheral end side of the magneto-optical disk 70. Therefore, when information recording or information reproduction is performed, the levitation force received by the optical levitation slider 80 increases as the distance of the optical levitation slider 80 from the rotation center axis Ax increases. Accordingly, as shown in FIG. The farther 80 is from the rotation center axis Ax, the longer the flying distance of the optical flying slider 80 from the surface of the magneto-optical disk 70 or the protective film 73 is. FIG. 9 illustrates the flying aspect of the optical flying slider 80 at three different radial positions as virtually for a single magneto-optical disk 70.

  Thus, since the flying distance of the optical flying slider 80 changes along the radial direction R of the magneto-optical disk 70, the laser beam L is focused on the recording film 72 at any position in the radial direction R. Even if the optical system (including the objective lens 82) in the apparatus is set as described above (that is, the position where the laser waist W is formed coincides with the position of the surface of the recording film 72) The waist W and the surface of the recording film 72 are separated. In addition, the further away from the position, the greater the degree of deviation. If the degree of divergence is above a certain level, unacceptable deterioration occurs in the recording signal and the reproduction signal. From the viewpoint of increasing the recording density, the objective lens 82 is desired to have a high NA (numerical aperture). However, the higher the NA of the objective lens 82, the shallower the focal depth of the objective lens 82, and the laser waist W and the recording film. 72 The degree of tolerance for surface divergence tends to be small.

  In the technical field of optical disc apparatuses, there are cases where a focus correction device for adjusting the formation position of the laser waist W following the change in the flying distance as described above is provided in the apparatus. As such a focus correction device, a beam expander or a liquid crystal element arranged in a light guide between the light source and the objective lens 82 is known. However, the use of such a focus correction device in the optical disc apparatus X2 is not preferable because it increases the size of the apparatus and increases the manufacturing cost.

  The present invention has been conceived under such circumstances, and the laser beam that has passed through the objective lens mounted on the optical flying slider can be appropriately condensed on the recording film. It is an object of the present invention to provide an optical disc device and an optical medium that can be used for the optical disc device.

  According to a first aspect of the present invention, there is provided an optical disc apparatus that includes an optical medium and an optical flying slider and performs information recording and / or information reproduction on the optical medium. The optical medium in this apparatus has a recording film that bears a recording function and a reproducing function, and a protective film that covers the recording film, and is accompanied by a rotation operation when information recording and / or information reproduction is performed. The thickness of the protective film gradually decreases from the rotation center side to the peripheral end side in the rotation operation. In addition, the optical flying slider in this apparatus has an objective lens for condensing light on the recording film, and against the optical medium while facing the protective film when performing information recording and / or information reproduction. Is placed on the surface.

  In the optical disk apparatus having such a configuration, when the CAV method, for example, is adopted as a method for rotating the optical media, the farther the optical floating slider is from the rotation center of the optical media when information recording and / or information reproduction is performed. The levitation force received by the optical levitation slider is large, and the levitation distance of the optical levitation slider from the surface of the optical medium or the protective film is long. On the other hand, the thickness of the protective film of the optical medium in this apparatus gradually decreases from the rotation center side to the peripheral end side in the rotation operation of the optical medium. Therefore, in this apparatus, the thickness of the protective film of the optical medium is gradually decreased in a predetermined manner corresponding to the increase in the slider flying distance from the rotation center side to the peripheral end side in the rotation operation of the optical medium. When performing information recording and / or information reproduction, the optical distance from the optical media facing surface of the objective lens of the optical flying slider to the recording film of the optical media is within a predetermined range regardless of the position of the optical flying slider. Can be configured to remain constant within.

  According to a second aspect of the present invention, there is provided an optical disc apparatus that includes a magneto-optical recording medium and an optical flying slider and performs information recording and information reproduction on the magneto-optical recording medium. The magneto-optical recording medium in this apparatus has a recording film that bears a recording function and a reproducing function, and a protective film that covers the recording film, and is accompanied by a rotation operation when information recording and information reproduction are performed. The thickness of the protective film gradually decreases from the rotation center side to the peripheral end side in the rotation operation. Further, the optical flying slider in this apparatus has a magnetic field applying means for applying a magnetic field to the recording film, and an objective lens for condensing light on the recording film, and information recording and information reproduction During the execution of the above, it is arranged so as to float with respect to the magneto-optical recording medium while facing the protective film.

  In the optical disk apparatus having such a configuration, when the CAV method is adopted as a method of rotating the magneto-optical recording medium, for example, the optical flying slider is moved from the rotational center of the magneto-optical recording medium when information recording and information reproduction are performed. The farther the distance, the greater the levitating force received by the optical levitating slider, and the longer the levitating distance of the optical levitating slider from the surface of the magneto-optical recording medium or protective film. On the other hand, the thickness of the protective film of the magneto-optical recording medium in this apparatus gradually decreases from the rotation center side to the peripheral end side in the rotation operation of the magneto-optical recording medium. Therefore, in this apparatus, the thickness of the protective film of the magneto-optical recording medium is gradually decreased in a predetermined manner corresponding to the increase in the slider flying distance from the rotation center side to the peripheral end side in the rotating operation of the magneto-optical recording medium. Therefore, when performing information recording and information reproduction, the optical distance from the medium facing surface of the objective lens of the optical floating slider to the recording film of the magneto-optical recording medium depends on the position of the optical floating slider. Instead, it can be configured to be kept constant within a predetermined range.

  In the first and second aspects of the present invention, preferably, the rotational speed, that is, the angular speed, of the rotational operation of the optical medium or the magneto-optical recording medium is constant. A rotation method with a constant angular velocity (CAV method) is suitable for speeding up access to information recorded on an optical medium or a magneto-optical recording medium.

  According to a third aspect of the present invention, an optical medium is provided. This optical medium has a recording film and a protective film. The recording film has a recording function and a reproducing function, and is irradiated with light when information recording and / or information reproduction is performed. The protective film covers the recording film. During the execution of information recording and / or information reproduction, the present optical medium is accompanied by a rotation operation, and the thickness of the protective film gradually decreases from the rotation center side to the peripheral end side in the rotation operation. Such an optical medium can be used as the optical medium in the first aspect of the present invention, or can be used as the magneto-optical recording medium in the second aspect of the present invention.

  FIG. 1 shows a schematic configuration of an optical disc apparatus X1 according to the present invention. The optical disk device X1 includes a magneto-optical disk 10, an optical flying slider 20, an actuator 30, a fixed optical unit 40, a control unit 50, a spindle motor 61, a suspension 62, and a guide rail 63.

  As shown in FIG. 2, the magneto-optical disk 10 has a laminated structure including a substrate 11, a recording film 12, a heat radiating layer 13 (not shown in FIG. 1), and a protective film 14, and uses a perpendicular magnetic recording system and an FI system. This is configured as a magneto-optical recording medium.

  The substrate 11 is a part for ensuring the rigidity of the magneto-optical disk 10, and has a disk shape as shown in FIG. The substrate 11 has a spiral or concentric pregroove (not shown) on the surface. In the magneto-optical disk 10, a land groove shape (not shown) is formed based on this pre-groove, and a spiral or concentric track is formed. The substrate 11 is made of, for example, a polycarbonate (PC) resin, a polymethyl methacrylate (PMMA) resin, an epoxy resin, or a polyolefin resin.

  The recording film 12 has a magnetic structure capable of performing two functions of thermomagnetic recording and reproduction utilizing the magneto-optical effect, and includes one or more magnetic layers according to the reproduction method, and necessary It consists of a dielectric layer provided according to the above.

  For example, the recording film 12 is composed of a single recording layer (magnetic layer) having both a recording function and a reproducing function. Alternatively, the recording film 12 includes a recording layer (magnetic layer) having a relatively large coercive force and performing a recording function, and a reproducing layer (magnetic layer) having a relatively large Kerr rotation angle and a reproducing function. A two-layer structure. Alternatively, the recording film 12 includes a recording layer (magnetic layer), a reproducing layer (magnetic layer), and an intermediate layer (magnetic layer) between the recording layer (magnetic layer) and the reproducing layer for realizing reproduction by the MSR method, MAMMOS method, or DWDD method. ) Including three or more layers. Each magnetic layer in each magnetic structure that the recording film 12 can take is a perpendicular magnetization film made of an amorphous alloy of a rare earth element and a transition metal and magnetized in the perpendicular direction with perpendicular magnetic anisotropy. As the rare earth element, Tb, Gd, Dy, Nd, Pr, or the like can be used. As the transition metal, Fe, Co, or the like can be used. More specifically, the recording layer is made of, for example, TbFeCо, DyFeCо, or TbDyFeCо having a predetermined composition. When the reproduction layer is provided, the reproduction layer is made of, for example, GdFeCо, GdDyFeCо, GdTbDyFeCо, NdDyFeCо, NdGdFeCо, or PrDyFeCо having a predetermined composition. In the case of providing the intermediate layer, the intermediate layer is made of, for example, GdFe, TbFe, GdFeCо, GdDyFeCо, GdTbDyFeCо, NdDyFeCо, NdGdFeCо, or PrDyFeCо having a predetermined composition. The thickness of each layer is determined according to the magnetic structure desired for the recording film 12.

  Further, the recording film 12 may have an enhancement layer at the interface with the protective film 14 for obtaining a substantially large Kerr rotation angle for the reflected light on the surface of the recording film 12. The enhancement layer is made of SiN, for example, and has a thickness of 10 to 100 nm, for example.

  Such a recording film 12 constitutes a recording surface 12 ′ of the magneto-optical disk 10. As shown in FIG. 3, the recording surface 12 'has concentric inner edge 12A and outer edge 12B. In the magneto-optical disk 10, predetermined information is recorded along the spiral or concentric tracks on the recording surface 12 '.

  The heat dissipation layer 13 is a part for efficiently transmitting heat generated in the recording film 12 or the like to the substrate 11 during laser irradiation. For example, Ag, Ag alloy (AgPdCuSi, AgPdCu, etc.), Al alloy (AlTi, AlCr, etc.) ), Au, or Pt. The thickness of the heat dissipation layer 13 is, for example, 10 to 50 nm.

  The protective film 14 is made of a resin material that covers the recording film 12 in order to protect the recording film 12 from dust and the like and has sufficient permeability to the laser light L emitted from a light source (not shown). As shown in FIG. 1, the thickness of the protective film 14 gradually decreases from the inner edge 12A to the outer edge 12B of the recording film 12 (recording surface 12 '). That is, the thickness of the protective film 14 gradually decreases from the rotation center axis Ax side to the peripheral end side of the magneto-optical disk 10. A mode of gradually decreasing the thickness of the protective film 14 is determined according to a change in the flying distance of the optical flying slider 20 during the rotating operation of the magneto-optical disk 10, as will be described later. As a resin material for constituting such a protective film 14, for example, a transparent ultraviolet curable resin can be employed.

  The magneto-optical disk 10 is supported by a spindle motor 61, and rotates when the spindle motor 61 is rotationally driven at a constant rotational speed. That is, the magneto-optical disk 10 in the optical disk apparatus X1 is rotated by the CAV method in this embodiment. The rotational drive of the spindle motor 61 is controlled based on a predetermined control signal from the control unit 50.

  As clearly shown in FIG. 4, the optical flying slider 20 has a slider body 21, an objective lens 22, and a magnetic coil 23. When the optical disk device X1 performs information recording and information reproduction, the magneto-optical disk 10 The protective film 14 is disposed opposite to the protective film 14. The medium facing surface of the slider body 21 has a predetermined curved shape. More specifically, the linear velocity of the portion facing the slider body 21 in the rotating magneto-optical disk 10 is different from the slider body 21 in the portion facing the slider body 21 in the rotating magneto-optical disk 10. When the relative speed is equal to or higher than a predetermined value, the medium facing surface of the slider body 21 has a curved shape for generating a so-called gas lubricating film between the magneto-optical disk 10 or the protective film 14 and the optical flying slider 20. Have. The objective lens 22 is for condensing the recording or reproducing laser light L from the light source. The magnetic coil 23 is for applying a predetermined magnetic field to the recording film 12. As shown in FIG. 1, the optical flying slider 20 is connected to the actuator 30 via a leaf spring suspension 62. The suspension 62 applies a biasing force to the optical flying slider 20 toward the magneto-optical disk 10.

  The actuator 30 is provided so as to be capable of translational drive along a guide rail 63 extending in the radial direction R of the magneto-optical disk 10, and by moving the optical flying slider 20 along the radial direction R, the optical flying slider is provided. 20 position control is performed. The translation drive of the actuator 30 is controlled based on a predetermined control signal from the control unit 50. In addition, a light guide path through which laser light L from a light source (not shown) and reflected light from the magneto-optical disk 10 can pass is secured inside the actuator 30. In this light guide path, for example, FIG. As shown in FIG. 2, a reflection mirror 31 is provided.

  The fixed optical unit 40 includes a predetermined optical system necessary for recording and reproduction of the magneto-optical recording medium, such as a light source, a prism, and a signal detector. For example, a laser diode can be used as the light source. The wavelength of the laser light L emitted from the light source can be switched based on a predetermined control signal from the control unit 50. The prism is used to shape the beam shape of the laser light L emitted from the light source or to perform spectroscopy on the signal detector. The signal detector detects reflected light from the magneto-optical disk 10 and converts it into an electrical signal, and reads information recorded on the magneto-optical disk 10 from the electrical signal.

  In the optical disk device X1, when the linear velocity of the portion facing the optical flying slider 20 or the slider body 21 in the rotating magneto-optical disk 10 is equal to or higher than a predetermined value, the magneto-optical disk 10 or the protective film 14 and the optical floating slider. A gas lubricating film is formed between the two. That is, a levitation force acts on the optical levitation slider 20, and as a result, the optical levitation slider 20 protects the magneto-optical disk 10 against the urging force from the suspension 62, for example, as shown in FIG. It floats (separates) from the surface of the film 14 and floats on the magneto-optical disk 10. The higher the linear velocity of the portion facing the optical levitation slider 20 in the rotating magneto-optical disk 10, the greater the levitation force acting on the optical levitation slider 20. The greater the levitation force, the greater the optical levitation slider 20 or The flying distance D1 of the slider body 21 from the surface of the protective film 14 (the distance between the slider body 21 and the protective film 14 at a location where a so-called optical axis C that passes vertically through the vertex of the objective lens 22 passes) is large. Further, the linear velocity of the surface of the magneto-optical disk 10 that rotates at a constant rotation speed gradually increases from the rotation center axis Ax side to the peripheral end side in the rotation operation. Therefore, when the optical flying slider 20 is arranged so as to float with respect to the magneto-optical disk 10 that rotates at a constant rotational speed, the flying distance D1 of the optical flying slider 20 is equal to that of the optical flying slider 20. The higher the flying position is from the rotation center axis Ax of the magneto-optical disk 10, the larger the flying position.

  The thickness of the protective film 14 of the magneto-optical disk 10 is set so as to change in the radial direction R of the disk on the premise of such a change in the flying distance D1. Specifically, at the time of information recording and information reproduction by the optical disk apparatus X1, the objective of the optical flying slider 20 that is floated with respect to the magneto-optical disk 10 that rotates at a predetermined rotational speed by the CAV method is used. The optical distance D between the lens 22 and the recording film 12 (recording surface 12 ') of the magneto-optical disk 10 is within a predetermined range regardless of the flying position (distance from the rotation center axis Ax) of the optical flying slider 20. As shown in FIG. 1, the thickness of the protective film 14 gradually decreases from the inner edge 12A to the outer edge 12B of the recording film 12. The optical distance D is a distance between the objective lens 22 and the recording film 12 at a location where a so-called optical axis C that passes vertically through the vertex of the objective lens 22 passes, and is represented by the following formula (1). In the formula (1), D1 is the predetermined flying distance as described above, N1 is the refractive index of the gas lubricant film (air in this embodiment), D2 is the thickness of the protective film 14 at the location where the optical axis C passes, N2 is the refractive index of the protective film 14. D3 and N3 are the length and refractive index from the medium facing surface of the objective lens 22 to the medium facing surface of the slider body 21 at the location where the optical axis C passes, and in this embodiment, the optical axis C is It is the thickness and refractive index of the slider body 21 in the passage location.

  The thickness D2 of the protective film 14 is such that the flying distance from the inner edge 12A to the outer edge 12B of the recording film 12 (recording surface 12 ′) in the radial direction R is maintained in order to maintain such an optical distance D within a predetermined range. It changes so as to compensate for the change in D1. The predetermined range with respect to the optical distance D means that the laser beam L collected through the objective lens 22 of the optical flying slider 20 is optical when a sufficiently small irradiation spot is formed on the recording surface 12 ′. This is a range required for the target distance D. For example, when the distance from the medium facing surface of the objective lens 22 to the laser waist formation position of the laser light collected through the objective lens 22 is equal to the focal length of the objective lens 22, optical The predetermined range for the distance D is, for example, Df ± d / 2 (d is the depth of focus) when the focal length is Df.

  In the present embodiment, since D3 and N3 are constant, D3 × N3 in the above formula (1) is constant. Therefore, assuming an optical distance D ′ (= D1 × N1 + D2 × N2), the thickness D2 of the protective film 14 is recorded in the radial direction R in order to maintain such an optical distance D ′ within a predetermined range. From the inner edge 12A to the outer edge 12B of the film 12 (recording surface 12 ′), the change is made so as to compensate for the change in the flying distance D1.

  FIG. 5 shows a method of manufacturing the magneto-optical disk 10 including the protective film 14 having such a thickness change. In manufacturing the magneto-optical disk 10, first, a substrate 11 as shown in FIG. The substrate 11 is formed by, for example, a resin injection molding method, and a pregroove (not shown) is formed on a predetermined surface thereof. Next, as shown in FIG. 5B, the heat dissipation layer 13 and the recording film 12 are sequentially formed on the substrate 11. The heat dissipation layer 13 and the recording film 12 can be formed by a sputtering method. Next, as shown in FIG. 5C, a protective film 14 is formed on the recording film 12.

  In forming the protective film 14, first, a predetermined ultraviolet curable resin is applied onto the recording film 12 by spin coating. At this time, the thickness of the coating resin is gradually decreased from the inner edge 12A to the outer edge 12B of the recording film 12 by appropriately adjusting various conditions. Examples of the conditions to be adjusted include the dropping position and dropping amount of the ultraviolet curable resin, the rotation speed and the rotation time of the magneto-optical disk 10, and the like. Thereafter, the coating resin is cured by irradiating with ultraviolet rays.

  In this embodiment, the rate of change in thickness of the protective film 14 is constant as shown in FIG. Instead, the absolute value of the rate of change in thickness of the protective film 14 may gradually increase from the inner edge 12A to the outer edge 12B of the recording film 12, for example, as shown in FIG. Alternatively, it may gradually decrease from the inner edge 12A to the outer edge 12B as shown in FIG. 6B, for example.

  When information is recorded by the optical disk device X1, the magneto-optical disk 10 is rotated at a predetermined speed by the CAV method. As a result, a gas lubrication film is formed between the magneto-optical disk 10 and the optical floating slider 20, and the optical floating slider 20 is disposed so as to float with respect to the magneto-optical disk 10 while facing the protective film 14. Become. In this state, a predetermined magnetic field is applied to the recording film 12 by the magnetic coil 23 while condensing the recording laser light L emitted from the light source (not shown) on the recording film 12 by the objective lens 22. In this manner, information recording for writing a predetermined signal as a change in the magnetization direction on the recording layer in the recording film 12 is executed.

  When reproducing information by the optical disk device X1, the magneto-optical disk 10 is rotated at a predetermined speed by the CAV method. As a result, a gas lubrication film is formed between the magneto-optical disk 10 and the optical floating slider 20, and the optical floating slider 20 is disposed so as to float with respect to the magneto-optical disk 10 while facing the protective film 14. Become. In this state, the polarization direction of the light reflected from the surface of the recording film 12 while condensing the reproducing laser light L emitted from a light source (not shown) on the recording film 12 by the objective lens 22. Is detected. In this way, information reproduction for reading the signal recorded in the recording film 12 as a change in the reflected light polarization direction is executed.

  In the optical disk apparatus X1, when information recording and information reproduction are performed, the levitation force received by the optical levitation slider 20 increases as the optical levitation slider 20 becomes farther from the rotation center axis Ax of the magneto-optical disk 10. The flying distance D1 of the optical flying slider 20 from the surface of 10 to the protective film 14 is large. On the other hand, in the optical disk apparatus X1, the objective lens 22 of the optical flying slider 20 and the recording film 12 of the magneto-optical disk 10 which are arranged so as to float with respect to the magneto-optical disk 10 rotating at a predetermined rotational speed by the CAV method. The protective film 14 is maintained such that the optical distance D between the recording surface 12 ′ and the recording surface 12 ′ is maintained within a predetermined range regardless of the flying position of the optical flying slider 20 (distance from the rotation center axis Ax). The thickness of the recording film 12 gradually decreases from the inner edge 12A to the outer edge 12B of the recording film 12. Therefore, in the optical disc apparatus X1, as shown in FIG. 7, the flying position (from the rotation center axis Ax) of the optical flying slider 20 is not provided without separately providing a device for correcting the laser waist forming position of the laser light L. Regardless of the distance, the laser beam L can be appropriately focused on the recording film 12 (FIG. 7 shows virtually the flying state of the optical flying slider 20 at three different radial positions. It is expressed as for one magneto-optical disk 10). In other words, in the optical disc apparatus X1, the formation position of the laser waist W and the position of the surface of the recording film 12 can be appropriately matched or substantially matched without separately providing a focus correction device. Such an optical disc device X1 is suitable for reducing the weight of the device and reducing the manufacturing cost.

  In the optical disk apparatus X1 according to the present invention, instead of the magneto-optical disk 10, for example, another optical medium of a phase change recording method can be adopted as a recording medium. In the case of employing another optical medium, the fixed optical unit 40 has a configuration for executing information recording and information reproduction for the other optical medium.

1 is a schematic configuration diagram of an optical disc apparatus according to the present invention. 2 shows an example of a laminated configuration of magneto-optical disks in the optical disk apparatus of the present invention. FIG. 2 is a plan view showing a magneto-optical disk and an optical flying slider that is floated and arranged on the optical disk apparatus of the present invention. It is sectional drawing showing the state by which the optical levitation slider is levitation-positioned with respect to the magneto-optical disk in the optical disk apparatus of this invention. 1 represents a magneto-optical disk manufacturing method according to the present invention. The example of the thickness change of a protective film is represented. 3 illustrates a flying aspect of an optical flying slider in the optical disc apparatus of the present invention. It is a schematic block diagram of the conventional optical disk apparatus. FIG. 9 illustrates a flying state of an optical flying slider in the optical disk apparatus of FIG. 8.

Explanation of symbols

X1, X2 Optical disk device 10, 70 Magneto-optical disk 12, 72 Recording film 14, 73 Protective film 20, 80 Optical levitation slider 21, 81 Slider body 22, 82 Objective lens 23 Magnetic coil 30, 92 Actuator 40 Fixed optical unit 50 Control unit 61, 91 Spindle motor 62, 93 Suspension 63, 94 Guide rail

Claims (3)

An optical disk device comprising an optical medium and an optical flying slider for performing information recording and / or information reproduction on the optical medium,
The optical medium has a laminated structure including a substrate, a recording film that bears a recording function and a reproducing function, and a protective film that is located on the opposite side of the recording film from the substrate and covers the recording film, Accompanied by a rotation operation during the execution of information recording and / or information reproduction,
The optical levitation slider has an objective lens for condensing light on the recording film, and faces the optical medium while facing the protective film during execution of the information recording and / or the information reproduction. Against the surface,
When the focal length of the objective lens is Df and the focal depth of the objective lens is d, the recording film of the optical medium that rotates when the information recording and / or the information reproduction is executed, The thickness of the protective film is such that the optical distance between the optical levitation slider and the objective lens that is levitationly arranged opposite to the optical medium is maintained within (Df ± d / 2). Is an optical disc apparatus that gradually decreases from the rotation center side to the peripheral end side in the rotation operation. An optical disk device comprising a magneto-optical recording medium and an optical flying slider for performing information recording and information reproduction on the magneto-optical recording medium,
The magneto-optical recording medium has a laminated structure including a substrate, a recording film that bears a recording function and a reproducing function, and a protective film that is located on the opposite side of the recording film from the substrate and covers the recording film. And accompanied by a rotation operation during execution of the information recording and the information reproduction,
The optical flying slider includes magnetic field applying means for applying a magnetic field to the recording film, and an objective lens for condensing light on the recording film, and the information recording and the information reproduction When performing the above, it is arranged so as to float with respect to the magneto-optical recording medium while facing the protective film,
When the focal length of the objective lens is Df and the focal depth of the objective lens is d, the recording film of the magneto-optical recording medium that rotates when the information recording and the information reproduction are executed, The protective film is arranged such that an optical distance between the optically levitated slider and the objective lens that is levitated and arranged opposite to the magneto-optical recording medium is maintained within (Df ± d / 2). The thickness is gradually reduced from the rotation center side to the peripheral end side in the rotation operation.   The optical disk apparatus according to claim 1, wherein a rotation speed of the rotation operation is constant.

Images