TWI416519B - Method of manufacturing optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an optical recording medium for achieving reduction of acceleration in a shaft direction (FE: focusing error), and acceleration in a track direction (TE: tracking error). <P>SOLUTION: When producing an optical recording medium having a constitution made by laminating a first substrate 11 and a second substrate 12 with an ultraviolet curing resin 30, at a first stage in an ultraviolet exposure process, ultraviolet is radiated toward a periphery from the center and the ultraviolet curing resin 30 in an area inside the periphery is tentatively cured while leaving at least the periphery, and in a second stage, ultraviolet radiation is performed for whole area exposure curing in the state where a clamp area 14 of the substrate is held still by a center pin 22 which contacts. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

Optical recording medium manufacturing method

The present invention relates to a method of manufacturing an optical recording medium having a structure of a bonded optical disk substrate.

Disc-shaped optical recording media for recording, playing, and erasing information by illumination of light have been developed and have been put to practical use. For example, a disc having a structure in which a two-substrate has a resin adhesive layer formed therebetween has been manufactured and is commercially available. Specific examples of these discs include DVDs and laser discs.

A typical optical recording medium has various structures in accordance with its function. A variety of media are known, for example, optical recording media having minute recesses and projections (pits and grooves) formed on an optically transparent substrate, and a metal reflective layer, an adhesive layer, and a printing bond between the substrates. An optical recording medium such as a layer.

Optically transparent substrates include glass, polycarbonate (PC) or acrylic resins (eg, polymethyl methacrylate (PMMA)). The metal reflective layer comprises an alloy of gold, silver and aluminum. The adhesive layer is formed of an ultraviolet curable resin.

In the following, any optically transparent substrate on which pits or grooves are formed, an optically transparent substrate on which a functional layer is formed, and optically only as a cover substrate The substrates that are transparent are referred to as substrates.

In this method, a substrate-bonding type optical recording medium is manufactured by dropping a UV-curable resin liquid onto a substrate on which a recording layer and/or a reflective layer are formed in a concentric manner by a dispenser. Covering another substrate (for example, an optically transparent substrate whose function is used as a cover layer) on the substrate; rotating at an appropriate rotation speed for a suitable length of time to rotate and discharge excess ultraviolet curable resin; The substrate is irradiated for photohardening.

Next, the substrate bonding process will be specifically described.

In the case of a system in which a laser beam enters from one side to perform recording and playback, for convenience of explanation, when the incident side of the laser beam is disposed on the bottom side, the base substrate is referred to as La, and the top substrate. It is called Lb.

In the process of joining the two discs with the ultraviolet resin interposed between the two discs, the ultraviolet resin type adhesive between the two substrates is irradiated with ultraviolet rays from above. In this process, the disc is transported with the surface on the layer forming side of the La substrate facing upward.

The Lb substrate is provided on the cap (rotary table) of the rotation applying device, and the side having the barrier layer (reflecting layer and/or recording layer) faces upward. While the rotary table was rotated at a rate of about 10 rpm, an ultraviolet curable resin liquid having a viscosity of about 500 cp was dropped on the substrate by a dispenser to be applied concentrically toward the periphery of the disk with a radius of about 30 mm. Next, La is turned over so that the front side faces downward (that is, the formation side of the layer faces downward, and light is incident from above), and overlaps with the Lb substrate. This rotary table is rotated at a rate of several hundred to several thousand rpm to expand the ultraviolet curable resin to the peripheral end of the substrate.

Thereafter, the overlapped substrates are transported to the irradiation table, and then subjected to ultraviolet curing treatment to obtain a bonded type of optical disk.

However, in the above bonding process, the deformation of the substrate was not corrected. Therefore, the radial tilt (RD) value and the circumferential tilt (TD) value of the substrate increase, so that a defective product is often manufactured.

In order to improve or correct the RD and TD values, for example, when the substrate is irradiated with ultraviolet rays, the shape of the substrate (deformation) is fixed or corrected by using a cap having a vacuum suction function or a cap having a substrate receiver. , RD and TD).

These methods are effective for improving RD and TD values. However, this will cause an increase in the values of axial acceleration (focus error (FE)) and rail direction acceleration (tracking error (TE)). In this regard, we have found that the causes of this deterioration are: (1) since the disc substrate is attached to the cap, so that minute dust including adhesive dust is fixed between the disc substrate and the cap; (2) due to the dish There are adsorbed contact portions and non-contact portions in the surface of the sheet, so that the micro-scale concave and convex surfaces are formed thereon, the adhesive is hardened into a wave shape; and (3) the vacuum suction holes on the cap are on the disc substrate. The pore marks are left, and the ultraviolet curable resin is hardened as it is.

In recent years, there has been a strong demand for increasing the recording rate, especially in the field of DVDs. The level of improvement in axial acceleration and rail direction acceleration is emphasized.

For example, the axial acceleration (focus error) and rail-direction acceleration (tracking error) of single-layer DVD+/-R/RW, DVD+RW, and dual-layer discs are based on the Orange Book's Residual focus and tracking. The error is to be regulated. The axial acceleration at the outermost circumference is now required to be no more than 1.0 m/s ² and the rail direction acceleration is not more than 0.4 m/s ² .

The above axial acceleration is when the number of revolutions is 30 Hz (1800 rpm), and the acceleration of the recording layer perpendicular to the reference plane is measured in a frequency band from 30 Hz to 1.5 kHz. When the deterioration of the acceleration is caused by the concave portion and the convex portion on the surface of the disc substrate, such a substrate has a large acceleration value for initial responsiveness, subsequent characteristics, focus stability, and tracking servo. There are adverse effects.

The focus error (FE) and tracking error (TE) were measured using the FE/TE test function of a driver (PX-716A manufactured by Plextor Corporation). When the substrate is rotated at a high speed, the amplitude of each of the FE/TE can be measured.

Typically, a DVD+/-R/RW disc drive has two optical servo functions, namely a focus survo function and a tracking survo function. During playback, even when the distance between the pickup device and the optical disk varies due to the bending of the optical disk, the focus of the pickup device can be maintained by the focus servo. During playback, even when the center hole of the optical disc is eccentric and/or the rail is partially tortuous, the tracking of the pickup device can be maintained by the tracking servo.

When the two servos are active, the control signal for adjusting the objective lens is calculated to accurately read the pits.

These control signals are referred to as focus error signals and tracking error signals, which are typically represented by FE/TE, which has the following meanings.

The FE system uses a digital to analog converter (DAC) to obtain the amplitude level of the control signal (focus actuator control signal) for the pickup device to adjust the focus of the laser on the surface of the optical disc. Therefore, it is possible to detect a defective optical disc and a disc having poor physical properties, such as a curved optical disc, before recording. The narrower the change in the FE value, the smaller the curvature of the optical disc.

The TE system uses the DAC as a pickup device to obtain the value of the amplitude level of the control signal (tracking actuator control signal) to follow the oscillation of the optical disc.

With FE/TE, the acceleration of the media at high speeds can be checked.

It has been confirmed that the axial acceleration described above is remarkably deteriorated when the substrate is placed on the surface of the irradiation table having dust and/or an adhesive of several micrometers on the surface thereof by ultraviolet irradiation and hardening. An optical recording medium having an axial acceleration of not more than 1.0 m/s ² is produced, and the yield constant and the equipment operation ratio can be improved to a practical level.

The reason why the dust is attracted to the surface of the stage where the ultraviolet ray is irradiated is, for example, the dust originally attached to the substrate is transferred to the pedestal. The ultimate goal would be the optical recording medium of the quality of the actual dust adversely affect the size of the order of ¹⁰⁰ microns. Adhesion or transfer of dust from the human body, or dust adhesion or transfer occurring during the transport of the optical disc and/or the R tilt between the application of the protective layer and the bonding of the substrate (ie, at least one day), is awaiting solved problem.

Further, a special reason why the resin is attached to the surface of the cap is that when the two substrates are bonded to each other, the resin dripped from the peripheral portion of the substrate, and when a mechanical problem causes the disc to remain, the resin flows into the inner circular hole or the peripheral portion.

Various studies on the substrate bonding method for improving the quality of the final object (i.e., optical recording medium) have been made (for example, Japanese Patent No. 363493). Based on the expectation of increasing the recording rate in the field of optical recording media, it is required to improve the corresponding method of manufacturing an optical recording medium to further reduce FE/TE.

For these reasons, the inventors have confirmed that there is a need for a method of manufacturing an optical recording medium in which, when optically hardened to bond a substrate to manufacture a optical disk, the focus error associated with axial acceleration and the axial acceleration are related by the method. Tracking errors can be reduced.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method of manufacturing an optical recording medium in which a focus error related to axial acceleration and a tracking error related to a rail acceleration are obtained by bonding the substrate to form a disc via optical hardening. Can be reduced.

Briefly, this and other objects of the present invention will be more readily apparent from the following description, and may be accomplished by a method of manufacturing an optical recording medium, either separately or in combination, comprising first having a central illumination with ultraviolet light. And the first substrate and the second substrate bonded to each other by the ultraviolet curing resin, and at least not irradiating the outer circumferential portion of the bonded substrate so that the ultraviolet rays in the inner region of the outer circumferential portion The hardened resin is hardened, and secondly, the two bonded substrates are statically fixed by a central pin that contacts only the sandwiched regions of the bonded substrates, and the bonded substrates are irradiated with ultraviolet rays.

Preferably, in the above method for manufacturing an optical recording medium, the first illumination is performed from the center toward the outer circumferential portion by spot illumination, and the bonded substrate is rotated to the first During the irradiation.

More preferably, in the above method of manufacturing an optical recording medium, the first irradiation is performed by area irradiation.

More preferably, in the above method of manufacturing an optical recording medium, the outer circumferential portion is a region surrounded by the periphery of the two-bonded substrate and at least 5 mm therebetween.

These and other objects, features and advantages of the present invention will become apparent from

The optical recording medium manufactured by the method of the present invention has a laminated structure of two disk-shaped substrates (a first substrate and a second substrate) having a central hole with an adhesive layer of an ultraviolet curing resin therebetween.

Any known material can be used for the substrate. In the present invention, since the ultraviolet curable resin existing between the two substrates is to be optically cured, the substrate on the ultraviolet irradiation side is made of a material transparent to ultraviolet rays.

Depending on the optical recording medium (ie, the final target), the first and second substrates may have respective different types of structures. Specific examples of these substrates are optically transparent substrates such as glass, polycarbonate (PC) or acrylic resin (polymethyl methacrylate). On such an optically transparent substrate, for example, minute concave portions and convex portions (pits and grooves) are formed, or a metal reflective layer, a magneto-optical recording layer, and a phase change recording layer are stacked.

The recording layer may be formed on both the first substrate and the second substrate, or when one of the substrates functions to cover the substrate, then the recording layer is on the other substrate.

Next, a method of manufacturing the optical recording medium of the present invention will be described in detail using a specific example and with reference to the accompanying drawings, but the invention is not limited thereto.

example 1

In Example 1, as exemplified in Fig. 1, the recording layer was formed by sputtering on a dish substrate having a center hole to obtain the first substrate 11.

The first substrate 11 is vacuum-adsorbed on the turntable 20, and the recording layer side of the first substrate 11 faces upward.

Next, when the rotary table 20 is rotated at about 10 rpm, the ultraviolet curable resin 30 having a viscosity of 500 cp is dripped onto the substrate in a concentric manner toward the circumference of the disk by a dispenser (not shown). It is approximately 30 mm with respect to the center of the first substrate 11.

Next, another disk-shaped substrate (ie, the second substrate 12) is overlapped and bonded to the first substrate 11. Next, the rotary table 20 is rotated at a rate of several hundreds to several thousands of rpm to expand the ultraviolet curable resin 30 to the periphery of the dish substrate.

Next, the ultraviolet curable resin 30 is irradiated to be hardened.

The treatment of ultraviolet radiation is carried out in two separate steps. As illustrated in Fig. 2, in Fig. 2, the irradiation head 50 is moved from the center to the peripheral portion of the substrate in the direction indicated by the arrow A to perform ultraviolet irradiation of the spot. In this hardening step, at least the outer circumferential portion of the first substrate 11 is not irradiated, and the ultraviolet curable resin 30 existing inside the outer circumferential portion is temporarily hardened.

The outer circumferential portion represents, for example, an area surrounded by the surroundings and at least 5 to 10 mm from there. In the first hardening step, the ultraviolet curable resin 30 present in the annular region including the center hole having a radius of 20 to 50 mm is temporarily hardened. By controlling the rotational speed of the rotary table 20, the thickness of the ultraviolet curable resin 30 can be adjusted to form a uniform resin layer. In this step, as shown in FIG. 3, the ultraviolet curable resin 30 existing at the outer circumferential portion between the substrates 11 and 12 is not hardened.

As described above, the resin is soft enough when the ultraviolet curable resin 30 located at the outer circumferential portion between the substrates 11 and 12 remains unhardened, even when the first substrate 11 is in contact with the turntable 20, Margin. This makes it possible to correct the shape deformation of the substrate which causes the focus error and the tracking error before the optical recording medium is manufactured.

In addition, by temporarily hardening the inner circumferential portion before the outer circumferential portion is hardened in the first hardening step, the substrates are not changed in RD (radial inclination or R-tilt), oscillation, and thickness of the resin layer. In this case, it is transferred to the next process, that is, the second irradiation stage.

The bonded substrate 13 is removed from the rotary table 20 by the transporting tip 40 and placed on the light irradiation table 21 for the second stage of ultraviolet irradiation, as exemplified in Figs.

The light irradiation stage 21 has a center pin 22 projecting from the center hole of the bonded substrate 13 while being in contact with the bonded substrate 13 only by the clamping region 14, as exemplified in FIG. In this state, the bonded substrate 13 is placed on the light irradiation stage 21 in a static manner, and there is no physical contact load on the area formed by the grooves.

Ultraviolet rays are irradiated from above the bonded substrate 13 to optically harden the ultraviolet curable resin between the substrates 11 and 12, and to obtain a bonded type of optical disc.

The TE (tracking error) / EF (focus error) of the obtained optical disk is measured by using a driver (PX-716A). As a result, as exemplified in FIG. 7, the values of FE/TE of the first substrate 11 and the second substrate 12 are varied within a narrow range with respect to the surface, and it is confirmed that it is stable at an appropriate level. Level.

Example 2

In Example 2, in the above-described first irradiation step, the irradiation head 51 having the structure illustrated in Fig. 8 and capable of irradiating the range to be irradiated with ultraviolet rays is used instead of the spot irradiation illustrated in Fig. 2. The area of the bonded substrate 13 to be irradiated with ultraviolet rays is from the center to the outer circumferential direction. That is, the irradiation of the fixed-width range is performed, leaving the outer circumferential portion of the bonded substrate 13 not to be irradiated, and further, the ultraviolet-curable resin in the inner region of the circumferential portion is temporarily hardened.

Other conditions and structures for manufacturing a bonded optical disc are the same as those in the first embodiment.

When the TE/EF of the obtained optical disk is measured using a driver (PX-716A), the values of FE/TE of the first substrate 11 and the second substrate 12, as in the case of Example 1, are related to the surface and are narrow Within the scope of the change, and confirmed that it is stable at an appropriate level.

Example 3

Example 3 is described below. As exemplified in Fig. 9, an ultraviolet curable resin is applied to the first substrate 11 and the second substrate 12, and the ultraviolet curable resin is diffused by rotating the two substrates. The first substrate 11 overlaps with the second substrate 12 and is bonded to each other in a vacuum while preventing the incorporation of air bubbles.

Other conditions and structures for manufacturing a bonded optical disc are the same as those in the second embodiment.

When the TE/EF of the obtained optical disk is measured using a driver (PX-716A), the values of FE/TE of the first substrate 11 and the second substrate 12, as in the case of Example 1, are related to the surface and are narrow Within the scope of the change, and confirmed that it is stable at an appropriate level.

Comparative example 1

As exemplified in Fig. 1, a dish-shaped substrate having a center hole is prepared, and a recording layer is sputtered thereon to obtain a first substrate 11. The first substrate 11 is vacuum-adsorbed on the turntable 20, and the recording layer side of the first substrate 11 faces upward.

Next, when the rotary table 20 is rotated at about 10 rpm, the ultraviolet curable resin 30 having a viscosity of 500 cp is dropped onto the substrate by a dispenser (not shown), and the radius is toward the periphery of the disk in a concentric manner. It is approximately 30 mm with respect to the center of the first substrate 11.

Next, it is bonded to another dish substrate (ie, the second substrate 12) in an overlapping manner. Next, the rotary table 20 is rotated at a rate of several hundreds to several thousands of rpm to expand the ultraviolet curable resin 30 to the periphery of the dish substrate.

Next, ultraviolet irradiation treatment is performed.

The bonded substrate is removed from the turntable 20 without the ultraviolet curable resin between the substrates being cured. The bonded substrate is placed on the light irradiation table 60 as exemplified in Fig. 10, and has a receiving portion at the outer circumferential portion and the inner circumferential portion of the light irradiation table, respectively. Next, the entire bonded substrate is irradiated with ultraviolet rays from above to harden the ultraviolet resin and obtain the optical disk. In this example, the receiving portions 61 and 62 of the light irradiation stage 60 are not in contact with the groove forming region of the optical disk, and thus there is no load on the region.

The TE/EF of the manufactured disc was measured using a driver (PX-716A). As exemplified in Fig. 11, as a result, in particular, the inner circumferential portion and the outer circumferential portion were largely deformed, and deterioration of TE and FE was confirmed.

Comparative example 2

The first substrate 11 (the substrate on which the recording layer is sputtered) is vacuum-adsorbed on the turntable 20, and the recording layer side of the first substrate 11 faces upward.

Next, when the rotary table 20 is rotated at about 10 rpm, the ultraviolet curable resin 30 having a viscosity of 500 cp is dripped onto the substrate by a dispenser (not shown), and is concentrically oriented toward the periphery of the disk, the radius of which is relative to The center of the first substrate 11 is approximately 30 mm.

Next, it is bonded to another dish substrate (ie, the second substrate 12) in an overlapping manner. Next, the rotary table 20 is rotated at a rate of several hundreds to several thousands of rpm to expand the ultraviolet curable resin 30 to the periphery of the dish substrate. Next, the number of revolutions of the rotary table 20 is controlled so that the layers between the two substrates have a uniform thickness.

As shown in FIG. 12, the bonded substrate 13 is placed on the light irradiation stage 70, and the bonded substrate 13 is in overall contact with the substrate receiving portion 65. The ultraviolet irradiation head is moved from the inner circumferential portion of the bonded substrate 13 to the outer circumferential portion, and is irradiated toward the outer circumferential portion by the light spot to optically harden the ultraviolet resin, and thus the optical disk is obtained.

Therefore, the groove forming portion of the obtained optical disk is affected by the contact between the groove forming portion and the substrate receiving portion 65 before the ultraviolet curable resin is cured. The fine dust and the resin adhering to the surface of the light irradiation stage 70 cause the concave portion and the convex portion of the resin layer between the substrates 11 and 12. When the TE/EF of the manufactured optical disc is measured using a driver (PX-716A), as shown in Fig. 13, as a whole, since the bonded substrate 13 has a large deformation, the result is actually unsatisfactory.

In each of the above examples, it is described that a disc of a type of a laminated substrate is manufactured, and light is received from the inside of the disc. The method of the present invention is not limited thereto and can be applied to a single-layer optical disc, or other types or processes that wish to reduce the acceleration of the adhesive type to a high level of accuracy.

This document claims priority and contains the subject matter of the Japanese Patent Application No. 2o06-201787 filed on Jul. 25, 2006, which is incorporated herein by reference.

The present invention has been fully described, and it will be apparent to those skilled in the art that the present invention may be modified and modified without departing from the spirit and scope of the invention as described herein.

11. . . First substrate

12. . . Second substrate

13. . . Bonded substrate

14. . . Clamp zone

20. . . Rotary table

twenty one. . . Light irradiation station

twenty two. . . Center pin

30. . . UV curing resin

40. . . Shipping tip

50. . . Illuminating head

51. . . Illuminating head

60. . . Light irradiation station

61, 62. . . Undertaking department

70. . . Light irradiation station

65. . . Substrate receiving part

The other objects, features and advantages of the present invention will become more apparent from the aspects of the accompanying drawings in which 1 is a graph of the process of the optical recording medium; FIG. 2 is a graph illustrating the processing of the first ultraviolet irradiation of Example 1; FIG. 3 is a graph illustrating the process of the optical recording medium of Example 1; A diagram for transferring the bonded substrate to the light-illuminating stage; FIG. 5 is a view illustrating a state in which the bonded substrate is placed on the light-illuminating stage; FIG. 6 is an example of ultraviolet irradiation in the second step. Figure 7 is a graph illustrating the results of tracking error (TE) and focus error (FE); Figure 8 is a graph illustrating the process of the optical recording medium of Example 2; and Figure 9 is an optical recording medium illustrating Example 3. FIG. 10 is a view illustrating a process of ultraviolet irradiation of the optical recording medium of Comparative Example 1; FIG. 11 is an example of tracking error (TE) and focus error (FE) of Comparative Example 1. Graphical results; Figure 12 illustrates the optical system of Comparative Example 2 graphics recording medium of the ultraviolet irradiation; graphical results of the tracking error (TE) of Comparative Example 2 and a focus error (FE) of the system 13 illustrated in FIG.

11. . . First substrate

12. . . Second substrate

20. . . Rotary table

30. . . UV curing resin

Claims (5)

A method of manufacturing an optical recording medium, comprising: first, irradiating a first substrate and a second substrate with ultraviolet rays, wherein the first substrate and the second substrate have central holes and are bonded to each other by ultraviolet curing resin, but At least not irradiating the outer circumferential portion of the bonded substrate to harden the ultraviolet curable resin in a region inside the outer circumferential portion; and secondly, the pliers contacting only the bonded substrate with the center pin After the nip is fixed to hold the two bonded substrates, the two bonded substrates are irradiated with ultraviolet rays, wherein the outer circumferential portion and the inner side of the outer circumferential portion during the first irradiation Both are placed at the receiving portion at the same height, and during the second irradiation, only the region inside the outer circumferential portion is placed at the receiving portion, so that the optical recording medium The disc shape is fixed. The method of manufacturing an optical recording medium according to claim 1, wherein the first irradiation is performed from the center toward the outer circumferential portion by spot irradiation, and the bonding is performed during the first irradiation. The substrate is rotated. The method of manufacturing an optical recording medium according to claim 1, wherein the first irradiation is performed by area irradiation. The method of manufacturing an optical recording medium according to claim 1, wherein the outer circumferential portion is a region surrounding the two bonded substrates and at least 5 mm from the inside. The method of producing an optical recording medium according to claim 1, further comprising temporarily curing the ultraviolet curable resin which is present in an annular region having a radius of 20 nm to 50 nm including the central opening.