JP2001155384A - Information recording disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information recording disk of single plate structure which has small tilt value, is excellent in environment resistant operating property, can stably execute recording and reproducing without increasing tilt when rapid temperature change is caused and can obtain stable tracking characteristic even in the case of rapid rotation to enable high transmit rate. SOLUTION: Substrate thickness at an information recording surface is 0.3 mm<= and <=0.7 mm, an annular recessed part is provided between an information recording region and the recessed part on the same axis as a base body. An annular projected part is formed on a rear surface of the annular recessed part so that base body thickness at the annular recessed part is about equal to the substrate thickness at the information recording surface. Further the annular recessed part and the annular projected part are formed so that recessed quantity of the annular recessed part and projected quantity of the annular projected part from the information recording surface are respectively <=0.2 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin type substrate capable of achieving a high recording density among optical disks for information recording such as an optical disk, a phase change disk, and a magneto-optical disk manufactured by injection molding. The present invention relates to a structure of an information recording disk which is small in size, has excellent environmental resistance, and can perform stable recording and reproduction even in an outdoor environment.

[0002]

2. Description of the Related Art In information recording disks typified by DVDs (digital versatile disks) and ASMOs (advanced storage magnetic optical) that have been proposed in recent years, a laser beam has a shorter wavelength and a lens aperture has to be reduced. By increasing the numerical aperture (NA) (Numerical Aperture) to 0.6 or more and narrowing the laser beam, high recording density is achieved. In this case, the thickness of the substrate is reduced from 1.2 mm, which is the mainstream of conventional optical disks, to 0.6 mm, in order to suppress coma caused by the inclination of the disk. In terms of material mechanics, the elastic modulus of the substrate is 3
Since it is proportional to the power, a thickness of 0.6 mm causes mechanical deformation in the manufacturing process, especially in the injection molding step of the substrate, that is, deterioration of the tilt characteristics, so that various improvement efforts have been made.

On the other hand, in the case of a relatively small-diameter and inexpensive information recording disk represented by a mini disk, the plastic itself forming the base of the information recording disk is vibrated and thermally deformed by using ultrasonic waves to form a magnetic hub. Is locked to the disk in a loosely fitted state. Since this method can be obtained only by stamping and pressing a metal hub, an expensive insert molding die is not required, and the means for mounting to the information recording disk is also improved by using an ultrasonic welding machine to form the disk base. Since plastics can be locked in an extremely short time by being heated and deformed by vibration, they are often used as an advantageous means in terms of manufacturing cost.
By the way, in an information recording disk of an optical pulse magnetic field modulation system represented by an ASMO, a recording film is laminated on a recording surface provided with a spiral guide groove, and about 0.01 mm of an ultraviolet curable resin is formed on the recording film. A magnetic field is applied to the magnetic head by using a magnetic head and the magnetic head is floated by sliding contact or head spacing of 0.1 mm or less, so that the product form must be a single-plate structure. This point is greatly different from the point that DVDs, which are currently popular in the market, are bonded to each other to form a 1.2 mm thick structure. In this case, not only the disc manufacturing process such as stress due to injection pressure during injection molding and thermal stress during film formation, but also low temperature in the market environment after shipment as a product,
Even when the disk is left at a high temperature or when a sudden temperature change is involved, it is necessary to take measures to prevent the disk from being deformed.
The deformation of the disk is called an optical tilt, and may cause a reduction in the effective laser power value or an offset in tracking. In particular, conventional information recording discs were mostly used in office environments for the purpose of storing data for personal computers and workstations, but recently developed, for example, moving images and still images for digital cameras. If it is used for recording video, it must be used in ski resorts below freezing and in summer beaches to guarantee recording and playback characteristics in extremely harsh environments.

On the other hand, in order to increase the data transfer rate as an information storage system, high-speed rotation of a disk is essential. Even at this high-speed rotation, resonance is liable to occur in a single-plate structure, so-called non-reproducibility. There was a problem of running out of surface. Since the recording surface vibrates at a high frequency due to the non-reproducible surface runout, focus and tracking cannot be followed due to an amplitude exceeding the servo band of the pickup, so that recording and reproduction cannot be performed.

Further, in order to lock the disk with the rotating mechanism and drive the disk without idling with respect to the rotating shaft even when the disk is rotated at a high speed, a clamping force of at least 5 Nf is required. Even in this case, the rigidity of the substrate must be ensured at the inner peripheral portion so that the disk is not deformed by the clamping force.

As described above, in the information recording system, the aperture ratio NA of the lens is increased along with the shortening of the wavelength of the laser beam in order to further increase the storage capacity, and the thickness of the substrate is made thinner in response to this. On the other hand, for the purpose of high-speed rotation to increase the data transfer rate and operation guarantee in various environments,
The tilt characteristics of the substrate tend to become more and more severe. There is a trade-off between substrate thickness and mechanical properties, and securing mechanical properties with a thin substrate is the most important issue.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an information recording disk having a single-plate structure, which has a small tilt value, has excellent environmental resistance, and does not increase the tilt when a sudden temperature change is involved. And an information recording disk capable of stably recording / reproducing and obtaining stable tracking characteristics even at a high rotation speed capable of a high transfer rate.

[0008]

The present inventors have conducted intensive studies to solve various problems, and as a result, according to the first aspect of the present invention, as a means for increasing the rigidity of the veneer structure, An annular concave portion is provided coaxially with the base between the recording area and the concave portion, and an annular convex portion is formed on the back surface of the annular concave portion so that the thickness of the substrate is substantially equal to the thickness of the substrate on the information recording surface. The concave and convex amounts of the annular convex portion from the recording surface were set to be 0.2 mm or less. If the thickness of the substrate in the annular uneven portion is smaller than the thickness of the substrate on the recording surface, the rigidity of the portion is insufficient, and the disk is warped starting from this portion. When the thickness of the base in the annular uneven portion is larger than the thickness of the substrate, the warp occurs at the vicinity of the boundary between the uneven portion and the flat portion. In this case, the rigidity is determined by the thickness of the substrate, and even if the thickness of the uneven portion is made larger than the thickness of the substrate, no further effect can be obtained.

On the other hand, it is possible to propose a method of securing rigidity by increasing the thickness of the substrate on the inner peripheral side from the recording area. However, in this case, the thickness of the base is not uniform, and shrinkage occurs in the thick portion. Or the birefringence near the inner circumference may be deteriorated. Further, in a flat shape having no unevenness, warpage is generated as a whole including the inner peripheral portion, and an effect higher than the substrate rigidity determined by the plate thickness cannot be expected.

Further, according to the present invention, as a means for increasing the rigidity of the substrate, a portion connecting a back surface located on the opposite side of the information recording surface of the substrate to a step for forming the concave portion is provided with C
Good mechanical properties can be obtained by chamfering 0.1 or more and C 0.3 or less, or rounding R 0.1 or more and R 0.3 or less. This avoids stress concentrations at the corners and increases stiffness. 0.3m for chamfering and rounding
By setting m or less, the occurrence of shrinkage due to thickening is prevented.

Next, the shape of the substrate will be described. First, the substrate thickness of the recording surface is preferably thinner in order to increase the NA and suppress coma aberration. However, in order to secure the flow length during injection molding, that is, L / D, a plate having a thickness of 0.3 mm or more is required. Thickness is required, and from the viewpoint of substrate rigidity, the thickness is selected in the range of 0.3 mm or more and 0.7 mm or less. Next, the outer diameter of the substrate is 65 mm in order to reduce the size of the recording / reproducing apparatus itself.
(2.5 inches) or less, especially 51 mm (2.0 inches).
Inches) or less is particularly preferred. Further, the thickness of the inner bottom surface of the recess for accommodating the hub is preferably 0.5 mm or more, and 0.5 mm or more.
mm, the strength of the disk reference surface is insufficient,
There is a possibility that the disc may be damaged when the mold is released from the mold, or the disc may be warped due to the clamping force.

Although it is advantageous to use a material having higher rigidity as a molding material, there are few options for satisfying optical characteristics and transferability.
0 ° C, polycarbonate at about 1000 poise at a shear rate of 1/1000 second, polymethyl methacrylate,
A molding material for an optical disc such as a norbornene-based amorphous polyolefin is used, and the present invention can be applied to any material.

Here, the problems caused by the single-plate structure will be specifically described.

For example, recording is performed by magneto-optical recording using an optical pulse magnetic field modulation method, and reproduction is performed by a CAD type (Center Aperture Detection;
When manufacturing an information recording disk of the magnetic super-resolution reproducing type (center opening detection type), the formed substrate is subjected to a first dielectric layer, a reproducing layer, an auxiliary magnetic layer, a second dielectric layer, After the recording layer, the magnetic capping layer, the third dielectric layer, and the reflective layer are sequentially sputtered, an acrylic UV curable resin is applied by a spin coater and cured by an UV exposure device. Next, a metal hub is placed in a columnar recess at the center of the substrate, and the base is vibrated and deformed using an ultrasonic welding machine to complete the information recording disk with the hub. When the information recording disk thus completed is used in an environment of, for example, -20 ° C or 50 ° C,
The substrate is warped due to the difference in linear expansion coefficient between the sputtered film or the ultraviolet curable resin and the substrate material. In order to prevent this warpage, it is conceivable to make the linear expansion coefficients uniform. However, if importance is placed on the characteristics of the recording film, there are no options, and increasing the substrate rigidity is the most effective means.

Next, means for forming the annular concave portion and the annular convex portion can be achieved by forming an insertion piece on the inner peripheral portion of the cavity of the injection molding die and providing the convex portion and the concave portion on the die.
In addition, although the shapes of the annular concave portion and the annular convex portion are to be provided from the viewpoint of injection molding, it is desirable to form a substantially trapezoidal approximation on the mold side, and the width of the molded substrate is also required. 1m to avoid local decrease in strength
m or less is desirable.

As described above, in order to form a conventional loosely-fitted hub, a concave portion is formed in the inner peripheral portion of the disk, and the thickness of the substrate is set to 0.3 mm or more and 0.7 mm or less in response to an increase in NA. Information recording disks with a single-plate structure not only have problems with manufacturing processes such as stress due to injection pressure during injection molding and thermal stress during film formation, but also have low temperatures, high temperatures left in a market environment, or rapid temperature changes. In some cases, there is a problem that the disk is deformed. According to the present invention, it is possible to provide an information recording disk having excellent tilt characteristics regardless of the thickness of the thin substrate. Also, even when the disk is rotated at high speed to increase the data transfer rate, the resonance speed can be increased, making it ideal for disks with high recording density and high transfer rate, especially when used outdoors. It is most suitable as a compact camera, a sound recording / reproducing device, and a vehicle-mounted reproducing device.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the information recording disk according to the present invention will be specifically described below, but the present invention is not limited thereto.

(Embodiment 1) First, a first embodiment of an information recording disk according to the present invention will be described with reference to FIGS. 1, 2, 8, and 9, respectively. As shown in FIG. 1, the information recording disk 1 of the first embodiment has a substrate outer diameter of 50 mm and an inner diameter of 1 mm.
It is formed in a disk shape of 1 mm and is manufactured by an injection molding method using a molded substrate 2 made of polycarbonate resin as a base. An information recording surface 6 is formed on the information recording disk 1, and a laser beam is irradiated from the objective lens 24, passes through the molded substrate 2 made of polycarbonate resin, and transmits a signal to the information recording surface 6 formed on the upper surface. Record and play back. The substrate thickness of the information recording surface 6 is 0.6 mm, and the information recording surface 6 is formed with a plurality of grooves and a plurality of uneven marks on which address information is recorded. A center hole 9 into which the rotating shaft 21 is inserted is formed in the inner periphery, and a recess 4 on which the hub 3 is mounted is formed in the inner periphery of the information recording disk 1 around the center hole 9. On the opposite surface of the concave portion 4, a disk reference surface 8 which forms a reference surface perpendicular to the information recording surface 6 is formed in a convex shape, and the thickness of the disk reference surface 8 is 0.7 mm. A rotating shaft 21 provided on the side of a driving device (not shown) has a turntable 20 for forming a horizontal reference plane of the information recording surface 6 with respect to the rotating shaft, and a hub 3 attached to the information recording disk 1. Is attached to the drive unit, and when the information recording disk 1 is mounted on the drive device, the turntable 2 is turned on.
Numeral 0 positions the information recording disk 1 in the radial direction in the center hole 9 and positions the information recording disk in the horizontal direction with respect to the recording surface on the disk reference surface 8.

At this time, the hub 3 is attracted by the magnet 22 provided on the turntable 20, and the information recording disk 1 does not come off the turntable 20 even if the rotating shaft 21 rotates at high speed. A welding swaging protrusion 10 for preventing the hub 3 from coming off is formed on the inner surface of the information recording disk 1 on the upper surface of the concave portion 4 by ultrasonic welding, and the hub 3 is engaged with the concave portion 4 in a loosely fitted state. When the information recording disk 1 is removed from the drive device, the hub 3 does not fall out of the recess 4.

FIG. 2 is a sectional view showing the inner peripheral portion of the information recording disk 1 in detail. The inner peripheral portion of the information recording disk 1 is formed with a concave portion 4 on which the hub 3 is placed. The inner peripheral step 7a in the thickness direction of the substrate is formed. An annular recess 5 having a recess amount of 0.2 mm from the recording surface is formed between the inner peripheral step portion 7a and the information recording surface 6, and further, on the back surface thereof, the thickness of the base of the recording surface and the thickness of this portion. Are formed so as to be substantially equal to each other. The cross-sectional shapes of the annular concave portion and the convex portion are substantially trapezoidal, are approximately 1 mm in width, and are arranged concentrically with the center hole 9.

FIGS. 8 and 9 show the sectional structure of the injection mold 30 of the present invention. The injection mold 30 is configured by combining a fixed mold 31 and a movable mold 41 coaxially (X axis). The fixed die 31 includes a fixed die set 32 and a spool bush 3 sequentially inserted on the center axis X thereof.
6, a fixed bush 37, a stamper suction bush 35, a fixed mirror 33, and a stamper 34 forming a signal surface of the information recording disk 1. The spool bush 36 is connected to a molding machine nozzle (not shown) for flowing molten resin into a mold during injection molding. Fixed bush 37
Is a cylindrical insertion piece inserted into the outer periphery of the spool bush 36. The recess 4 is formed on the board, into which the hub 3 is inserted. It plays the role of a female mold when punching the center hole 9. The stamper 34 is formed with a plurality of grooves serving as an inverted pattern corresponding to the information recording surface 6 of the information recording disk 1 and a plurality of concave / convex marks recording address information. The outer periphery is vacuum-sucked through a stamper vacuum suction hole 33 a provided on the fixed mirror in the groove 35 a, and is attached to the fixed mirror 33 in close contact. Stamper suction bush 3
5 is formed with an annular convex portion 35b, which forms an annular concave portion 5 on the disk. The surface of the fixed mirror 33 is mirror-finished for the purpose of mounting the stamper 34 in close contact with the fixed mirror 33. Since expansion and contraction due to heat during molding are repeated between the fixed mirror 33 and the stamper, DLC, Ti
A hard film such as N, TiC, TiCN is deposited by PVD, CVD or the like.

On the other hand, the movable mold 41 is
And ejector pins 4 sequentially inserted on the central axis X
8, gate cutter 44, ejector sleeve 46,
It includes a movable bush 45, a movable mirror 43, and a cavity ring 47 that forms the outer diameter of the molded substrate 2. The ejector pins 48 serve to release a spool (not shown) which is an unnecessary part as a molded substrate cooled in the mold. The ejector sleeve 46 is inserted movably in the central axis direction into a cylindrical cylinder 46a formed in the movable die set 42, and is for releasing the molded substrate 2 from the cavity similarly to the ejector pins. is there. The movable mirror 43 is for forming a surface on which laser light is incident on the substrate, and is finished to a mirror surface at a level at which light is not diffracted and transmittance is impaired. Gate cutter 4
After filling the cavity into the cavity, the resin 4 advances to the fixed mold side and plays the role of a male mold when punching the center hole 9 of the molded substrate 2. The thickness of the gate 44a is smaller than the cavity interval and is 0.3 within a range that does not hinder the flow of the resin.
mm. Here, air passages for mold release on the fixed mold side and on the movable mold side are formed in gaps forming the fixed bush 37 and the stamper suction bush 35 and the movable piece 43 and the movable bush 45 on the cavity. Is formed, and serves to uniformly release the substrate molded at a high temperature from the cavity. Further, on the movable bush 45, a concave portion 45 for forming the annular convex portion 5a on the disk is provided.
a is formed.

When the fixed mold 31 and the movable mold 41 are mounted on the molding machine, they are supported by four rods (not shown) parallel to the central axis X, and the movable mold 41 is moved in the central axis X direction. It is slidable on the rod for movement. When the movable mold 41 is combined with the fixed mold 31 as shown in FIG. 8, the fixed bush 37, the stamper 34, the stamper suction bush 35, the movable mirror 43, the cavity ring 47, the movable bush 45, and the ejector sleeve 46. A cavity 30a is defined.

The injection mold 30 shown in FIG. 8 was mounted on an injection molding machine DISK3 (not shown) manufactured by Sumitomo Heavy Industries, Ltd. using bolts (not shown), and injection molding of the molding substrate 2 was performed. . First, the mold temperature of the fixed mold 31 and the movable mold 41 was adjusted to 125 ° C, and the cylinder temperature was adjusted to 380 ° C. Next, the molding machine nozzle is connected to the spool bush 36.
, And the fixed mold 31 and the movable mold 41 are clamped by a mold clamping mechanism (not shown) of the injection molding machine (not shown) at a force of 10 ton.
The molten polycarbonate resin (Teijin Kasei Panlite AD5503) was injected into the cavity 30a of the injection mold 30. After the cavity 30a was filled with the resin, the pressure was maintained for a certain period of time to replenish the volume contraction of the resin due to cooling. Next, the mold clamping force is increased
The resin in the cavity was compressed while increasing the pressure to ON, and the gate cutter 44 was protruded toward the fixed bush 37 on the fixed mold 31 side to cut the gate 44a and start cooling. After the cooling time of 8 seconds passed while maintaining the mold clamping force at 15 tons, first, the mold was opened while blowing the mold release air from the fixed mold side to uniformly peel the molded substrate 2 from the stamper. Next, mold release air is blown from the movable mold side to uniformly peel the molded substrate 2 from the movable mirror 43, and the ejector sleeve 46 and the ejector pin 48
The molded substrate 2 and the spool, which were protruded and solidified, were released from the cavity. Thus, a molded substrate 2 made of a transparent polycarbonate resin having a diameter of 50 mm was obtained.

Next, as shown in FIG. 10, a first dielectric layer 51 was first sputtered on the obtained molded substrate 2 using a sputtering apparatus. The first dielectric layer 51 is the recording layer 5
5 is provided to cause multiple interference of light beams between the molded substrate 2 and the apparent Kerr rotation angle, and is made of SiN and has a film thickness of 60 nm. Next, the reproducing layer 52 was laminated. The reproducing layer 52 is made of a rare earth-transition metal amorphous film GdFeCo exhibiting in-plane magnetization at room temperature,
The film thickness was 30 nm. The reproducing layer 52 was adjusted so that it was in an in-plane magnetization state near room temperature and changed to a perpendicular magnetization state at a certain critical temperature or higher. On this reproducing layer 52, an auxiliary magnetic layer 53 having a function as a mask layer was added. The auxiliary magnetic layer 53 is made of a rare earth-transition metal amorphous film GdFe exhibiting in-plane magnetization at room temperature, and has a thickness of 15 nm. The auxiliary magnetic layer 53 plays a role of improving the reproduction resolution by making the change of the magnetization direction of the reproduction layer 52 from in-plane to perpendicular to a temperature gradient caused by the reproduction laser beam. Auxiliary magnetic layer 53
A second dielectric layer 54 was laminated thereon. Second dielectric layer 54
Is made of SiN, has a thickness of 5 nm, and magnetostatically couples the reproducing layer 52 and the recording layer 55. Next, the recording layer 55 was laminated via the second dielectric layer 54. The recording layer 55 is made of a rare earth-transition metal amorphous film TbFeCo exhibiting perpendicular magnetization, and has a thickness of 50 nm. On the recording layer 55, a magnetic capping layer 56 was laminated. Magnetic capping layer 56
Is a rare earth-transition metal amorphous film G showing in-plane magnetization at room temperature.
It was made of dFeCo and had a thickness of 5 nm. The magnetic properties of the magnetic capping layer were adjusted so that the perpendicular magnetic anisotropic energy and the demagnetizing magnetic field energy were equal so that the magnetization was easily rotated in the direction of the external magnetic field. A third dielectric layer 57 was laminated on the magnetic capping layer. Third dielectric layer 57
Is made of SiN and has a thickness of 20 nm. On the third dielectric layer 57, a reflective layer 58 was laminated. The reflection layer 58 is made of Al
It is made of 97Ti3, has a thickness of 40 nm, and plays a role of reflecting laser light together with the third dielectric layer 57 and controlling heat distribution.

Next, in order to protect the entire film from the first dielectric layer 51 to the reflective layer 58 from chemical corrosion such as oxidation and contact with a magnetic head, an acrylic ultraviolet curing resin ( (UV resin) was spin-coated and cured using an ultraviolet exposure device. Finally, the metal hub 3 made of SUS430 is placed in the column-shaped concave portion 4 at the center of the substrate, and the base is vibrated and deformed using an ultrasonic welding machine to form the welded caulked projections 10, thereby forming the hub. The information recording disk 1 with the tag was completed.

(Example 2) In Example 1, the thickness of the substrate on the recording surface of the molded substrate 2 was 0.6 mm, but in Example 2, the thickness of the substrate on the recording surface was changed to 0.4 mm. An information recording disk was completed in the same manner as in Example 1.

(Example 3, Comparative Examples 1 to 4) In Example 1, the amount of concavity and convexity of the annular concavo-convex portion of the molded substrate 2 from the base recording surface was 0.2 mm. The information recording disk was completed in the same manner as in the first embodiment. Comparative Example 1 FIG. 3, Comparative Example 2 FIG. 4, Comparative Example 3
FIG. 5 shows the relationship between the irregularities on the inner peripheral portion of the disk.

[0029]

[Table 1]

(Examples 4 to 7, Comparative Examples 5 and 6) Example 1
In the figure, the amount of unevenness of the annular uneven portion of the molded substrate 2 from the substrate is set to be 0.
In this embodiment and the comparative example, as a means for further increasing the substrate rigidity, as shown in FIGS. 6 and 7, the respective surfaces are vertically arranged between the information recording surface 6 and the concave portion 4 in which the hub is accommodated. A rising portion 7 to be connected is formed, and a C chamfer shown in Table 2 is formed on an outer peripheral surface of the rising portion 7, that is, a right angle portion 7c where the outer peripheral step portion 7b and the information recording surface intersect.
An information recording disk was completed in the same manner as in Example 1 except that corner rounding was added.

[0031]

[Table 2]

(Evaluation of Disk) (Evaluation of Shrinkage of Inner Peripheral Part of Disk) First, with respect to the molded substrate before film formation, the result of visual observation of shrinkage at the inner peripheral part is shown in Table 3. From Table 3, Comparative Examples 3, 5 and 6 were good except that shrinkage was observed. Example 5
In Example 7, a slight shrinkage was confirmed. These are the results reflecting the thickness of the inner peripheral step, and it can be said that shrinkage is more likely to occur as the thickness increases. This close not only impairs the appearance,
There is a possibility that the birefringence of the inner peripheral portion of the substrate may be deteriorated.

[0033]

[Table 3]

(Change of Tilt with Ambient Temperature) Next, as an environmental operability test on the formed disk, the tilt characteristics of the disk in each temperature environment were determined by a triangulation method. The triangulation method is a so-called tilt sensor method using a semiconductor laser light source and a light position detecting element (PSD), and a method utilizing the linear movement of the return light of the reflected beam due to the inclination of the object to be measured. It is. For evaluation of environmental operability, the obtained disk was placed in a thermostat, and was stored at -20 ° C, -10 ° C, -5 ° C, 23 ° C, 50 ° C, and 50 ° C.
After the temperature was adjusted for 12 hours at each temperature in the order of ° C. and 70 ° C., the disk was rotated at 2400 r / min, and the respective tilt values, that is, the tilt angles at the radii of 14 mm and 24 mm were obtained. Samples are intractable Examples 1 to 7,
And Comparative Examples 1, 2, and 4 were used. The evaluation results are shown in FIGS.
As shown in FIG. From the figure, it was confirmed that the change of the tilt value due to the temperature change was small in all the examples except the example 2 having the different substrate thickness. Also, in Example 2, the tilt value was the same level as that of the comparative example, even though the substrate thickness was 0.4 mm, indicating that the present invention is effective.

(Tracking Error at High Speed Rotation) Next, regarding the resonance when the disk is rotated at high speed, the disk is tracked using a pickup, and the number of rotations is changed to 1800, 2400 and 3000 r / min, respectively. Then, the amplitude of the optical head was detected by a capacitance sensor attached to the pickup. The apparatus used was a commercially available LM1200 mechanical property evaluation device manufactured by Ono Sokki Co., Ltd. This device uses an air spindle to rotate the disc with high precision, and the optical system uses a laser wavelength of 650 nm, N
A0.6. In addition, the servo followability is the focus f
₀ 2.0 kHz, tracking f ₀ 2.4 kHz, the focusing method is an astigmatism method, and the tracking method is a push-pull method. The samples used were Examples 1 to 7 and Comparative Examples 1, 2, and 4, which had no contraction on the inner peripheral portion of the disk, as in the measurement of the change in tilt with respect to the environmental temperature. Table 4 shows the evaluation results.
From the table, it was confirmed that the amplitude value at the time of high speed rotation of 3000 r / min was small in all the examples except for the example 2 having a different substrate thickness. Also, in Example 2, although the substrate thickness was 0.4 mm, the amplitude value was the same level as that of the comparative example, which indicates that the present invention is effective.

[0036]

[Table 4] Unit: mm (Change in tilt with respect to clamping force) Next, the relationship between the clamping force when the disk was clamped and the amount of warpage generated in the disk was determined by triangulation. The clamping force was determined by the product of the suction area and the vacuum pressure by adjusting the vacuum pressure while keeping the suction area constant using vacuum suction. Examples 1, 5, and 7 and Comparative Examples 1, 2, and 4 were used as samples. The evaluation results are shown in FIGS. From the figure, it can be confirmed that in Examples 1, 5, and 7, the change in the tilt value when the clamping force was increased was small.

[0037]

According to the present invention, in an information recording disk having a single-plate structure having a substrate thickness of 0.3 mm or more and 0.7 mm or less in response to an increase in NA, information recording is performed as a means for increasing substrate rigidity. An annular concave portion is provided coaxially with the base between the region and the concave portion, and an annular convex portion is formed on the back surface of the annular concave portion so that the thickness of the base is substantially equal to the substrate thickness on the information recording surface. By making the concave amount and convex amount from the information recording surface of the convex portion 0.2 mm or less, it is possible to obtain a disk with no shrinkage in the inner peripheral portion, and a small tilt value, excellent environmental preservability, and rapid It is possible to provide an information recording disk capable of recording and reproducing information stably without increasing the tilt when the temperature changes. In addition, stable tracking characteristics can be obtained even at a high rotation speed at which a high transfer rate is possible. As a means for further increasing the rigidity of the substrate, a rising portion is formed between the information recording surface and the concave portion in which the hub is accommodated, connecting the respective surfaces in a vertical direction, and a right angle at which the outer peripheral surface at the rising portion intersects the information recording surface. Good mechanical properties can be obtained by chamfering C0.1 or more and C0.3 or less or rounding R0.1 or more and R0.3 or less. An information recording disk obtained by depositing this substrate has few reading errors, and is particularly suitable as a small camera used outdoors, a sound recording / reproducing device, and a vehicle-mounted reproducing device.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an information recording disk according to a first embodiment of the present invention inserted into a driving rotary shaft.

FIG. 2 is a detailed sectional view showing an inner peripheral portion of the disk according to the first embodiment of the present invention.

FIG. 3 is a detailed sectional view showing an inner peripheral portion of a disk according to a first comparative example of the present invention.

FIG. 4 is a detailed sectional view showing an inner peripheral portion of a disk according to a second comparative example of the present invention.

FIG. 5 is a detailed sectional view showing an inner peripheral portion of a disk according to a third comparative example of the present invention.

FIG. 6 is a detailed sectional view showing an inner peripheral portion of a disk according to fourth and fifth embodiments of the present invention.

FIG. 7 is a detailed sectional view showing an inner peripheral portion of a disk according to sixth and seventh embodiments of the present invention.

FIG. 8 is a sectional view showing an injection mold for molding the information recording disk of the first embodiment according to the present invention.

FIG. 9 is a detailed sectional view of an injection mold for molding the information recording disk of the first embodiment according to the present invention.

FIG. 10 is a cross-sectional view illustrating a film structure of various examples according to the present invention and a comparative example.

FIG. 11 shows Examples 1 to 3 and Comparative Examples 1 and 2 according to the present invention.
FIG. 4 is an experimental result diagram showing a relationship between an ambient temperature of an information recording disk and a tilt value at a radius of 14 mm shown in FIG.

FIG. 12 shows Examples 1 to 3 and Comparative Examples 1, 2 and 2 according to the present invention.
FIG. 4 is an experimental result diagram showing a relationship between an ambient temperature of an information recording disk and a tilt value at a radius of 24 mm shown in FIG.

FIG. 13 shows a radius 1 according to the first and fourth to seventh embodiments of the present invention.
FIG. 4 is an experimental result diagram showing a relationship between an ambient temperature of an information recording disk and a tilt value at 4 mm.

FIG. 14 shows a radius 2 shown in the first and fourth to seventh embodiments according to the present invention.
FIG. 4 is an experimental result diagram showing a relationship between an ambient temperature of an information recording disk and a tilt value at 4 mm.

FIG. 15 shows Examples 1, 5, 7 and Comparative Examples 1 and 2 according to the present invention.
FIG. 8 is an experimental result diagram showing a relationship between a clamping force and a tilt value of the information recording disk at a radius of 14 mm shown in FIGS.

FIG. 16 shows Examples 1, 5, 7 and Comparative Example 1 according to the present invention.
FIG. 9 is an experimental result diagram showing a relationship between a clamping force and a tilt value of the information recording disk at a radius of 24 mm shown in FIGS.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 information recording disk 2 molded substrate 3 hub 4 concave portion 5 annular concave portion 5a annular convex portion 6 information recording surface 7 step portion 7a inner peripheral step portion 7b outer peripheral step portion 7c right angle portion 8 disk reference surface 9 center hole 10 welding swaging protrusion 20 turn Table 21 Rotation axis 22 Magnet 23 Rotation axis reference plane 24 Objective lens 30 Injection mold 30a Cavity 31 Fixed mold 32 Fixed die set 33 Fixed mirror 34 Stamper 35 Stamper suction bush 35a Stamper vacuum suction groove 35b Stamper suction bush convex part 36 Spool bush 37 Fixed bush 41 Movable mold 42 Movable die set 43 Movable mirror 44 Gate cutter 44a Gate 45 Movable bush 45a Movable bush recess 46 Ejector sleeve 46a Cylindrical cylinder 47 Cavity Ring 48 Ejector pin 33a Stamper vacuum suction hole 51 First dielectric layer 52 Reproducing layer 53 Auxiliary magnetic layer 54 Second dielectric layer 55 Recording layer 56 Magnetic capping layer 57 Third dielectric layer 58 Reflective layer 59 Protective layer

Claims (6)

[Claims] 1. An information recording optical disk having a columnar recess for accommodating a hub in the center of the surface of a disc-shaped base, and a hole for inserting a spindle formed on the bottom of the recess coaxially with the base. In the above, the substrate thickness on the information recording surface is 0.
3 mm or more and 0.7 mm or less, an annular recess is provided coaxially with the base between the information recording area and the recess, and the annular recess is formed so that the thickness of the base in the annular recess is substantially equal to the thickness of the substrate on the information recording surface. An information recording disk, wherein an annular convex portion is formed on the back surface of the concave portion, and the concave amount and convex amount of the annular concave portion and the annular convex portion from the information recording surface are each 0.2 mm or less. 2. A chamfer of C0.1 or more, C0.3 or less, or R, at a position connecting a back surface of the substrate opposite to the information recording surface and a step for forming the concave portion.
2. The information recording disk according to claim 1, wherein corner rounding of not less than 0.1 and not more than R 0.3 is performed. 3. The information recording disk according to claim 1, wherein a thickness of an inner bottom surface of the concave portion in which the hub is accommodated is 0.5 mm or more. 4. The information recording disk according to claim 1, wherein the outer diameter of the substrate is 65 mm or less. 5. The information recording disk according to claim 1, wherein the recording method is magneto-optical recording of light pulse magnetic field modulation. 6. The information recording disk according to claim 1, wherein recording / reproduction is performed at a rotation speed of 2400 r / min or more.