JP3881684B2 - optical disk - Google Patents

Description

  The present invention relates to an optical disc and a manufacturing method thereof, and more particularly to an optical disc having a thin substrate on which laser light is incident and a manufacturing method thereof.

  In recent years, research on various optical information recording has been advanced in the field of information recording. This optical information recording can be densified, can be recorded / reproduced in a non-contact manner, and is being realized in a wide range of applications as a method that can be realized at low cost. As an optical disk at present, an information layer is provided on a transparent resin substrate having a thickness of 1.2 mm, and the information layer is protected by an overcoat, or an information layer is provided on one or both of a 0.6 mm transparent resin substrate. A structure in which sheets are bonded together is used.

  In recent years, methods for increasing the numerical aperture (NA) of an objective lens and methods for shortening the wavelength of a laser to be used have been studied as methods for increasing the recording density of an optical disk. At this time, if the thickness of the recording / reproducing side substrate (the substrate on which the laser beam is incident) is thinner, the influence of the aberration received by the laser spot can be reduced, and the allowable value of the tilt angle (tilt) of the disc can be increased. For this reason, it has been proposed that the thickness of the recording / reproducing side substrate is about 0.1 mm, the NA is about 0.85, and the laser wavelength is about 400 nm.

  In the current DVD (Digital Versatile Disc), a method is mainly used in which two transparent resin substrates having a thickness of 0.6 mm subjected to processing such as film formation are bonded with a radiation curable resin. Even when the thickness of the recording / reproducing side substrate becomes about 0.1 mm due to high density, it is desirable to use the same equipment as in the present method to bond them together.

However, in an optical disc having a structure in which two substrates are bonded together , there is a problem that if the recording / reproducing side substrate becomes thin for high density recording, the recording / reproducing side substrate is likely to be peeled off or cracked. In addition, it is necessary to suppress eccentricity (center shift) when bonding two substrates. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disc having excellent substrate durability and small eccentricity of bonded substrates.

In order to achieve the above object, an optical disc of the present invention includes a first substrate having a signal region on one principal surface and having a center hole A, and the first substrate bonded to the one principal surface side of the first substrate . an optical disk and a thin light-transmissive second substrate than the first substrate, the second substrate has the center hole a central hole B is also larger in diameter than the previous SL first substrate And the second substrate are bonded together by an adhesive member disposed between the first substrate and the second substrate, and the first substrate is disposed on the one main surface side, A convex portion formed in an annular shape so as to surround the first central hole A and having an outer diameter equal to or smaller than the diameter of the central hole B; and the height of the convex portion from the one main surface is the second substrate It is characterized by being larger than the sum of the thickness of the adhesive member and the thickness of the adhesive member.

According to the present invention, it is possible to suppress eccentricity when two substrates are bonded together, and it is possible to cope with a decrease in strength of the substrate due to thinning of the recording / reproducing side substrate. Therefore, an optical disc having excellent substrate durability and capable of high density recording can be obtained.

  In the optical disc, the height of the convex portion may be 0.05 mm or more and 0.5 mm or less.

In the above optical disc, the upper SL adhesive member may be disposed to the outer edge from the inner peripheral end of the at least a second substrate.

  In the optical disc, the thickness of the second substrate may be in the range of 0.03 mm to 0.3 mm. According to this configuration, an optical disc capable of recording information at a particularly high density can be obtained.

  In the optical disc, a plurality of signal recording layers may be formed in the signal area of the first substrate.

  In the optical disc, the adhesive member may be a radiation curable resin. According to the said structure, manufacture becomes easy.

In the above optical disc, the first substrate, said has a clamping area in the region between the signal area of the one main surface and the center hole A, the central hole B may be greater than the clamp region. According to this configuration, the optical disk can be stably fixed. Further, it is possible to prevent the second substrate from being peeled off when the optical disk is clamped.

  In the optical disc, the thickness of the clamp region of the first substrate may be 1.1 mm or greater and 1.3 mm or less.

  In the optical disc, an average thickness of the adhesive member may be in a range of 0.5 μm to 30 μm.

  In the optical disc, the wavelength of the laser irradiated for information reproduction may be 450 nm or less. According to this configuration, information can be recorded particularly at high density.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, about the same part, the same code | symbol may be attached | subjected and the overlapping description may be abbreviate | omitted.

( Reference example )
First, an example of an optical disc that does not have a convex portion will be described . FIG. 1A is a plan view and FIG. 1B is a cross-sectional view.

  Referring to FIG. 1, an optical disc 10 is bonded to a first substrate 11 (hatching is omitted. Hereinafter, hatching of the first substrate may be omitted in the same manner) and the first substrate 11. And a second substrate 12. Then, the first substrate 11 and the second substrate 12 are bonded together by a radiation curable resin (adhesive member) 13 disposed between the first substrate 11 and the second substrate 12.

  The first substrate 11 includes a signal area SA on one main surface 11a. A signal recording layer 14 is formed in the signal area SA. The structure of the signal area SA differs depending on the use of the optical disk. When the optical disk 10 is a read-only disk, for example, a pit having an uneven shape is formed in the signal area SA of the main surface 11a, and a film made of Al or the like is formed on the pit as a signal recording layer. It is formed. When the optical disk 10 is a recording / reproducing disk, a recording film made of a phase change material, a dye, or the like is formed in the signal area SA so as to enable recording / reproducing.

  The first substrate 11 includes a circular center hole A having a diameter of dA (for example, 15 mm) at the center thereof. Although the thickness of the 1st board | substrate 11 does not have limitation in particular, The sum total with the thickness of the 2nd board | substrate 12 may be in the range of 0.5 mm-0.7 mm or 1.1 mm-1.3 mm. preferable. There is no limitation in particular about the outer diameter of the 1st board | substrate 11, For example, it is 120 mm. The first substrate 11 is made of, for example, a thermoplastic resin such as polycarbonate resin or acrylic resin, or a thermosetting resin such as vinyl ester resin or polyester resin.

  The second substrate 12 is a substrate thinner than the first substrate 11 and is translucent. The thickness of the second substrate 12 is in the range of 0.03 mm to 0.3 mm, and more preferably in the range of 0.03 mm to 0.12 mm. Specifically, the thickness of the second substrate 12 is, for example, 0.05 mm or 0.1 mm. By making the sum of the thickness of the first substrate 11 and the thickness of the second substrate 12 within a range of 1.1 mm to 1.3 mm, compatibility with an existing optical disc can be ensured. Moreover, the conventional manufacturing apparatus of an optical disk can be utilized by making the total thickness into the range of 0.5 mm-0.7 mm or 1.1 mm-1.3 mm.

  The second substrate 12 is a substrate irradiated with laser light (preferably having a wavelength of 450 nm or less) irradiated for recording / reproducing signals, and is made of a light-transmitting material. Specifically, the second substrate 12 is made of, for example, a thermoplastic resin such as a polycarbonate resin or an acrylic resin, or a thermosetting resin such as a vinyl ester resin or a polyester resin. The second substrate 12 includes a circular center hole B having a diameter of dB at the center thereof. As shown in FIG. 1A, the center hole B is preferably larger than the clamp region C.

  Here, the clamp area C is an area held when the optical disk 10 is transported or rotated for recording / reproduction. The thickness of the clamp region C of the first substrate 11 is preferably 1.1 mm or greater and 1.3 mm or less.

  The radiation curable resin 13 as an adhesive member is disposed at least from the inner peripheral end 12s to the outer peripheral end 12t of the second substrate. That is, the radiation curable resin 13 is disposed at least on the entire main surface of the second substrate 12 on the first substrate 11 side. The radiation curable resin 13 may be disposed up to the inner peripheral end 11s of the first substrate. The radiation curable resin 13 is a resin that is cured by radiation. As the radiation curable resin 13, for example, an ultraviolet curable resin that is cured by ultraviolet irradiation, a resin that is cured by electron beam irradiation, or the like can be used. As shown in FIG. 1A, it is preferable that the radiation curable resin 13 is disposed on the outer peripheral side of the clamp region C or is disposed so as to cover the entire clamp region C. The average thickness of the radiation curable resin 13 is preferably in the range of 0.5 μm to 30 μm. In place of the radiation curable resin 13, an adhesive member such as a double-sided tape may be used.

In the optical disc 10 of this, since the second substrate 12 on the light incident side is thin, it is capable of high density recording. In addition, since the diameter of the center hole B of the second substrate 12 is larger than the diameter of the center hole A of the first substrate 11, the second substrate 12 is not easily peeled or cracked, and handling is easy. Furthermore, since the radiation curable resin is disposed up to the inner peripheral end 12s of the second substrate 12, the second substrate 12 is not easily peeled or cracked, and handling is easy.

  The first substrate 11 is formed in an annular shape so as to surround the center hole A on the one main surface 11a side, and surrounds the center hole A and the convex portion whose outer diameter is equal to or smaller than the diameter of the center hole B. Thus, it is preferable to include at least one selected from concave portions formed in an annular shape and having a diameter equal to or smaller than the diameter of the center hole B.

(Embodiment 1)
FIG. 2A shows a plan view and FIG. 2B shows a cross-sectional view of the optical disc 20 in the case where the first substrate has the above-described annular convex portion. FIG. 3A shows a plan view and FIG. 3B shows a cross-sectional view of the optical disc 30 in the case where the first substrate has convex portions of other shapes . Also, the first substrate, the first substrate 51 and 56 in the case and a recess of the projecting portion and the annular toric, shown in Figure 4 a cross-sectional view, respectively, (A) and (B). The first substrates 21 , 31 , 51 , and 56 are the same as the first substrate 11 except for the convex portions and the concave portions. That is, the one principal surface 21a, 31a , 51a, and 56a correspond to the one principal surface 11a. The optical disk 2 0 Contact and 3 0, respectively, is the same as the optical disc 10, except the first substrate 2 1 Contact and 3 1, a repetition of the same explanation is avoided.

As shown in FIGS. 2A and 2B, the first substrate 21 of the optical disc 20 is formed in an annular shape so as to surround the center hole A on the one main surface 21a side where the signal area SA is formed. And the outer diameter L1 is provided with the convex part 22 equal to the diameter dB of the center hole B. By the convex portion 22, manufacture of the optical disk can be easily as described below. Moreover, it is preferable that the height (height from one main surface 21a) of the convex part 22 is 0.05 mm or more and 0.5 mm or less. Further, as shown in FIG. 2B, the height of the convex portion 22 is preferably larger than the sum of the thickness of the second substrate and the radiation curable resin 13 (even in the following convex portions). The same). As a result, when the optical disk 20 is superposed and held and stored, the reproduction surface does not directly touch another optical disk, and the reproduction surface is not damaged. Further, as shown in FIG. 2B, the convex portion 22 is formed so as to be in contact with the inner peripheral end of the second substrate 12 (the outer diameter L1 of the convex portion 22 is equal to the diameter dB of the center hole B). (It is the same for the following convex portions). Thereby, the eccentricity between the first substrate 11 and the second substrate 12 can be suppressed. Furthermore, since the center cone of the clamp and the motor turntable do not come into contact with the second substrate 12 during recording / reproduction, it is possible to cope with a decrease in strength due to the thinning of the second substrate 12, and the tilt increases. This can be suppressed.

  As shown in FIGS. 3A and 3B, the first substrate 31 of the optical disc 30 is formed in an annular shape so as to surround the center hole A on the one principal surface 31a side where the signal area SA is formed. In addition, a protrusion (step) 32 having an outer diameter L1 equal to the diameter dB of the center hole B is provided. The convex portion 32 in this case is formed up to the inner peripheral end of the first substrate 31.

Figure 4 (A), the first substrate 51, on one main surface 51a side of the signal area SA is formed, the central hole is formed in an annular shape to surround the A and outer diameter of the central hole B A convex portion 22 having a diameter equal to or smaller than the diameter of the convex portion 22 and a concave portion 42 arranged in an annular shape so as to surround the convex portion 22. Thereby , the effect of a convex part and a recessed part is acquired.

Figure 4 (B), the first substrate 56, on one main surface 56a side of the signal area SA is formed, the central hole is formed in an annular shape to surround the A and outer diameter of the central hole B The convex part 32 which is below this diameter, and the recessed part 42 arrange | positioned annularly so that the convex part 32 may be enclosed. Thereby , the effect of a convex part and a recessed part is acquired.

It should be noted that the optical disc 2 0 Contact and 3 0 the materials given above, it is needless to say that the same effects as the optical disc 10.

In the present exemplary type condition it has been described an optical disk signal recording layer only on the first substrate is formed. However, in the optical disc of the present invention and the manufacturing method thereof, a signal recording layer may be formed on the second substrate ( the same applies hereinafter). For example, in the optical disk of the present invention and the manufacturing method thereof, a semitransparent signal recording layer may be formed on the second substrate, and both the first substrate and the second substrate may be provided with the signal recording layer. Further, a plurality of signal recording layers may be formed on the first substrate ( the same applies hereinafter). With these configurations, an optical disk having a two-layer structure can be obtained. In this case, the information recorded in both signal recording layers can be reproduced by the laser light incident from the second substrate side.

( Optical disk manufacturing method )
Here , an example of the manufacturing method of the optical disk of the present invention will be described . Shows a manufacturing process in the case of producing an optical disk 10 described in Reference Example 5, the same applies to the case of manufacturing the optical disc 20 and 30 described above.

The manufacturing method described here, FIG. 5 (A), the first and the first substrate 11 having a center hole A includes a signal area SA on the main surface 11a, the center is larger in diameter than the center hole A A light-transmitting second substrate 12 that has a hole B and is thinner than the first substrate 11 is brought into close contact with the radiation curable resin 13a before curing so that the one principal surface 11a is on the inside (step). (A)). At this time, the radiation curable resin 13a is disposed from at least the inner peripheral end 12s to the outer peripheral end 12t of the second substrate 12. Incidentally, the radiation-curable resin 13a is the inner peripheral end 11s to may be located in the first substrate 11, as described in Reference Example, it may be arranged so as not to clamp area C.

The signal area SA of the first substrate 11 is formed by, for example, molding a resin by an injection molding method or a photopolymer method to form concave and convex pits, and then forming a reflective film (signal recording layer) made of Al having a film thickness of, for example, 50 nm. 14) can be formed by sputtering. Further, when the signal region SA is formed of a phase change film or a dye film, it can be formed by a sputtering method or a vapor deposition method. The first substrate 11 is, for example, a polycarbonate substrate having a thickness of 1.1 mm, a diameter of 120 mm, and a center hole diameter of 15 mm.

The second substrate 12, For example other, is 90 [mu] m, an outer diameter of 120 mm, a center hole diameter is polycarbonate or acrylic substrates of 40mm thickness. The second substrate 12 can be formed by an injection molding method or a casting method. The thickness of the second substrate 12 is in the range of 0.03 mm to 0.3 mm.

Thereafter, as shown in FIG. 5 (B), the radiation curable resin 13a is cured by irradiating the radiation curable resin 13a with radiation (such as ultraviolet rays and electron beams) to form a radiation curable resin 13 after curing. Then, the first substrate 11 and the second substrate 12 are bonded together (step (b)). Radiation may be irradiated continuously or in pulses (the same applies to the following manufacturing method ). In this way, the optical disk 10 can be manufactured.

  Hereinafter, in the first step, two methods will be described with respect to the method of bringing the first substrate 11 and the second substrate 12 into close contact with each other with the radiation curable resin 13a interposed therebetween.

In the first method, the first substrate 11 and the second substrate 12 are integrated with the radiation curable resin 13a interposed therebetween, and then the integrated first substrate 11 and second substrate 12 are rotated. This is a method of stretching the radiation curable resin 13a. This method, an example of a step in FIG. In the step of FIG. 6, first, as shown in FIG. 6 (A), applying a radiation-curable resin 13a in an annular shape by the nozzle 71 on the first substrate 11. At this time, the first substrate 11 or the nozzle 71 is rotated at a low speed (20 rpm to 120 rpm). Further, in order to firmly adhere to the inner peripheral end 12s of the second substrate 12, the radiation curable resin 13a is placed on the first substrate 11 and the inner peripheral end 12s is disposed (for example, a radius of 20 mm to 20 mm). Apply to 25mm position).

Next, as shown in FIG. 6 (B), the first substrate 11 and second substrate 12 is superimposed are opposed so as to concentrically. However, since the radiation-curable resin 13a in the clamping area C adheres influence on the tilt increases, as shown in FIG. 6 (C), the radiation 72, such as ultraviolet annularly on the outer peripheral side of the clamping area C irradiation Then, it is preferable to prevent the radiation curable resin 13a from entering the inner periphery any more. That is, the step (a) may include a step of curing at least a part of the radiation curable resin 13a disposed on the inner side of the signal area SA before rotating the first substrate 11 (the following first step). The same applies to the method 2). The radiation curable resin 13a may be applied on the second substrate 12.

Thereafter, as shown in FIG. 6 (D), the two substrates are rotated at a high speed (1000 rpm to 10000 rpm) while the first substrate 11 and the second substrate 12 are overlapped, and the outer peripheral portion. The radiation curable resin 13a is diffused up to. As a result, it is difficult for bubbles to enter the bonded portion, and excess radiation curable resin 13 a is shaken off and discharged from between the first substrate 11 and the second substrate 12. In this way, step (a) can be performed.

  In the above process, in order to make the thickness of the radiation curable resin 13a uniform, the radiation curable resin depends on the number of rotations / rotation time of the substrate for resin diffusion and the thickness of the radiation curable resin 13a. It is preferred to select a viscosity of 13a. Generally, in the above method, the thickness of the radiation curable resin 13a tends to be thin on the inner peripheral side and thick on the outer peripheral side. In order to perform recording / reproduction under conditions such as a laser with a wavelength of 400 nm and an objective lens having an NA of 0.85, which are being studied for increasing the density of optical disks, the variation in film thickness of the radiation curable resin 13 is The central value (the sum of the thickness of the second substrate 12 and the thickness of the radiation curable resin 13, for example, 0.1 mm) is required to be within a range of about ± 3 μm.

In the first method, Table 1 shows the relationship between the in-plane variation of the radiation curable resin 13 after curing and the viscosity of the radiation-curable resin 13a.

As apparent from Table 1, the viscosity of the radiation curable resin 13a by less 10 mPa · s or more 1500 mPa · s, 6 [mu] m or less variation in the thickness of the radiation curable resin 13 after curing, i.e. ± 3 [mu] m or less It can be.

  Table 2 shows the relationship between the viscosity of the radiation curable resin 13a and the tact time in the first method.

  As is apparent from Table 2, in order to shorten the tact time, it is preferable that the viscosity of the radiation curable resin 13a is in the range of 10 mPa · s to 600 mPa · s.

Next, the 2nd method for performing a 1st process is demonstrated. In the second method, after the radiation curable resin 13a is dropped onto the first substrate 11, the first substrate 11 is rotated to apply the radiation curable resin 13a onto the first substrate 11, and then In this method, the first substrate 11 and the second substrate 12 are adhered to each other with the radiation curable resin 13a interposed therebetween. This method, an example of a step in FIG. In the second method, first, as shown in FIG. 7 (A), applying a radiation-curable resin 13a in an annular shape by the nozzle 71 on the first substrate 11. This process is similar to the process described in FIG. 6 (A).

Next, as shown in FIG. 7 (B), the first substrate 11 is rotated at a high speed (1000 rpm to 10000 rpm) to extend the radiation curable resin 13a to the outer periphery. At this time, as explained in the step of FIG. 6 (C), the laser light may be irradiated to the annular radiation curable resin 13a of the outer circumference side of the clamping area C.

Thereafter, as shown in FIG. 7 (C), the first substrate 11 and second substrate 12 overlapped such that the concentric circles, brought into close contact. Thus, the said process (a) can be performed. In addition, the distribution of the radiation curable resin 13a can be made more uniform by applying an appropriate pressure uniformly at the time of superposition. At this time, care must be taken so that bubbles do not enter. To ensure that no air bubbles, as shown in FIG. 8, it is preferable to perform the step of adhering the substrate vacuum chamber 90 within, i.e. in a vacuum atmosphere.

Table 3 shows the relationship between the viscosity of the radiation curable resin 13a and the in-plane variation of the radiation curable resin 13 after curing in the second method.

As is apparent from Table 3, by setting the viscosity of the radiation curable resin 13a to 10 mPa · s or more and 15000 mPa · s or less, variation in the film thickness of the radiation curable resin 13 after curing is 6 μm or less (± 3 μm or less). It can be.

  Table 4 shows the relationship between the viscosity of the radiation curable resin 13a and the tact time in the first method.

  As is apparent from Table 4, in order to shorten the tact time, it is preferable that the viscosity of the radiation curable resin 13a is in the range of 10 mPa · s to 1000 mPa · s.

As described above, according to the method of manufacturing the above SL of the optical disc, the optical disc can be easily manufactured. In the second method, a radiation curable resin may be applied to the second substrate and then adhered to the first substrate.

In the above manufacturing method, instead of the first substrate 11, the first substrate 21 and 31 described in Embodiment 1 may be used 5 1 or 56. By using such a substrate, it is possible to prevent the radiation-curable resin 13a is applied to the O protrusion of annular remote peripheral side. In this case, since it is not necessary to perform the step of irradiating radiation in an annular shape, production is facilitated. Further, by making the outer diameter L1 of the convex portion the same as the diameter dB of the second substrate 12, it is possible to prevent eccentricity from occurring when the first substrate and the second substrate are bonded together.

  Although the embodiments of the present invention have been described above by way of examples, the present invention is not limited to the above-described embodiments, and can be applied to other embodiments based on the technical idea of the present invention.

  According to the optical disk of the present invention, an optical disk in which the reproduction surface is not damaged can be obtained.

It is (A) top view and (B) sectional drawing which show an example about the optical disk of a reference example . Shows an example with the optical disk of the present invention (A) a plan view and (B) is a cross-sectional view. It is (A) top view and (B) sectional drawing which show another example about the optical disk of this invention. It is sectional drawing which shows (A) an example and (B) another example about the board | substrate used for the optical disk of this invention. It is process sectional drawing which shows an example about the manufacturing method of the optical disk of this invention . It is process sectional drawing which shows a one part process about the manufacturing method of the optical disk of this invention . It is process sectional drawing which shows a one part process about the manufacturing method of the optical disk of this invention. It is shown to cross-sectional view a part of a process for optical disc manufacturing method of the present invention.

Explanation of symbols

10,20,3 0 optical disc 11, 21, 31, 5 1,5 6 first substrate 11a, 12a, 21a, 31a, 5 1a, 56a one main surface 1 2 a second substrate 12s peripheral end 12t outer peripheral end 13, 13 a Radiation curable resin (adhesive member)
14 signal recording layers 22 and 32 convex portion 42 concave portion
71 nozzles
A , B Center hole C Clamp area SA Signal area dA, dB, L 1 diameter

Claims (10)

A first substrate having a signal region on one main surface and having a central hole A, and a light-transmitting second thin film bonded to the one main surface side of the first substrate and thinner than the first substrate An optical disc comprising a substrate,
The second substrate has a central hole B having a diameter larger than that of the central hole A,
The previous SL first substrate and the second substrate, are bonded by arranged adhesive member between the first substrate and the second substrate,
The first substrate includes, on the one main surface side, a convex portion that is formed in an annular shape so as to surround the center hole A and whose outer diameter is equal to or less than the diameter of the center hole B ,
An optical disc, wherein a height of the convex portion from the one main surface is larger than a sum of a thickness of the second substrate and a thickness of the adhesive member.   The optical disc according to claim 1, wherein a height of the convex portion from the one principal surface is 0.05 mm or more and 0.5 mm or less. Before SL adhesive member, an optical disk according to 請 Motomeko 1 or 2, characterized in that it is arranged to the outer edge of at least the inner peripheral edge of the second substrate. The optical disk according to any one of claims 1 to 3 , wherein the thickness of the second substrate is in a range of 0.03 mm to 0.3 mm. Wherein the signal area of the first substrate, an optical disk according to any one of claims 1 to 4, a plurality of signal recording layers are formed. The optical disk according to any one of claims 1 to 5, wherein the adhesive member is a radiation curable resin. The first substrate has a clamp region in a region between the signal region of the one main surface and the central hole A,
The optical disk according to claim 1, wherein the center hole B is larger than the clamp region. The optical disc according to any one of claims 1 to 7, wherein a thickness of the clamp region of the first substrate is 1.1 mm or more and 1.3 mm or less. The average thickness of the adhesive member is an optical disk according to any one of claims 1-8 is in the range of 0.5Myuemu～30myuemu. The optical disk according to any one of claims 1 to 9 , wherein a wavelength of a laser irradiated for reproducing information is 450 nm or less.

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