JPH03116459A - Production of optical disk - Google Patents

Abstract

PURPOSE:To adhere two substrates without causing squeezing of an adhesive from the center hole of the substrates by irradiating a light-transmissive part of the substrates to cure the inner circumferential part of the adhesive on the transparent area, and then curing the other part of the adhesive not cured yet. CONSTITUTION:First, one of two transparent substrates 2, 8 having center hole 1 is covered with a recording film 4 in a manner that the inner circumferential area of the substrate remains as a light-transmissive part 3. For example, on the recording film side 4 of the substrate 2, light-curing type adhesive 7 is applied, on which the substrate 8 is stuck to spread the adhesive. At the same time, the light-transmissive part 3 is irradiated with light to immediately cure the adhesive 7 on the transparent area to adhere the two transparent substrates 2, 8. Namely, the adhesive 7 is cured with light while spread in the light-transmissive part 13, the adhesive is prevented from squeezing out to the inner circumferential area from the light-transmissive part 3. Thereby, two substrates can be adhered without squeezing of the adhesive from the center hole of the substrates.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing an optical disc on which information is recorded optically.

[Prior Art] [Prior Art] Optical disks are high-density, high-capacity information recording media, and are used for document files, image files, computer memory, etc., and therefore require extremely high reliability. expensive.

The structure of the optical disc includes the following types.

■Single-plate structure with a recording film attached to a substrate made of transparent material■Air sandwich structure in which two single-plate optical discs are bonded together with adhesive on the inner and outer peripheries via spacers■Two disks Full-adhesive structure in which single-plate optical disks are glued together with adhesive so that the entire surface is in close contact.The most reliable optical disk among these is the two-layer laminated structure with a large bonding area. This is because it has excellent mechanical strength (impact resistance, peeling resistance), weather resistance (humidity resistance, temperature resistance), and warpage resistance.

By the way, conventional optical discs have been manufactured by the process shown in FIGS. 3(a) to 3(e). That is, Fig. 3(a)
In this step, a recording film 4 is formed on a disk-shaped transparent substrate 2 by vacuum evaporation, sputtering, or the like.

Next, as shown in FIG. 3(b), this is placed on the turntable 6 through the centering shaft 5, and while being rotated, a light curing adhesive or a two-component curing adhesive 7 is applied.
The adhesive 7 is applied using the coating nozzle 13 to thinly spread the adhesive 7 on the recording film 4 on the surface layer of the substrate 2.

Next, as shown in FIGS. 3(C) and 3(d), the protective substrate 8 and the substrate 2 are overlapped, and the adhesive 4 is spread by pressing with a pressure plate 10 or by centrifugal force due to spin. Pasting is being done.

[Problem to be solved by the invention] However, in the optical disc manufacturing method using the conventional technology,
Highly accurate center hole diameter formed during substrate manufacturing, and eccentricity between the center hole and a spiral or concentric recording/reproducing guide groove with a width of 1.0 to 2°0 pm provided on the recording surface. However, when the substrate 2 and the protective substrate 8 are bonded together, a protruding portion 15 of the adhesive is generated from the end surface of the substrate center hole 1 and hardens, which deteriorates the accuracy of the inner diameter of the center hole 1 and causes damage to the recording/reproducing device. There have been problems in that mounting is difficult, and furthermore, the amount of eccentricity between the center hole 1 and the recording and reproducing guide groove increases, making recording and reproducing impossible.

In other words, it is difficult to adjust the amount of adhesive applied down to a minute amount, and if the amount of adhesive applied is small, the adhesive will not spread evenly in spin cords, etc., and voids may occur, making it difficult to fill uniformly. 11 adhesive may need to be applied in somewhat excess. The average thickness of the adhesive after curing is about 100 μm, but there is a tolerance range of 20 to 30 μm, and even within this tolerance range, there may be subtle changes in the pressing force and time. According to
The adhesive easily overflowed from the center hole 1.

For this reason, there was a serious problem in that the adhesive protruding from the center hole 1 adhered to the center ring shaft 5 and hardened. This issue can be summarized as follows.

■ When the adhesive adheres to the center ring shaft 5 and hardens,
First, it becomes difficult to remove the substrate 2 from the centering shaft 5, and if it is removed forcibly, the optical disk will be destroyed. Therefore, the yield is poor.

(2) Even if the centering shaft 5 is removed, the cured adhesive 15 protruding into the center hole 1 must be removed by cutting or the like. This post-processing such as cutting increases the cost due to the increased number of man-hours.

■ In addition, each time the centering shaft 5 is used, it must be cleaned to remove the hardened adhesive that has adhered to the centering shaft 5, and for this reason, many centering shafts are It is necessary to use it while preparing and replacing it, which deteriorates productivity.

Furthermore, even if you try to prevent the adhesive 4 from protruding or adhering to the centering shaft 15 by adjusting the amount of the adhesive 4,
Another problem was that sufficient adhesion could not be achieved because it was difficult to spread the adhesive 4 uniformly over the entire surface.

An object of the present invention is to eliminate the above-mentioned problems, and to control the spread of adhesive toward the center hole of the inner circumference during bonding, and to bond two sheets without causing the adhesive to protrude from the center hole of the substrate. An object of the present invention is to provide a highly productive method for manufacturing an optical disk in which substrates can be bonded together.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration.

That is, in the present invention, a recording film is formed to have a light-transmitting part on the inner peripheral part of at least one of two transparent substrates having a central hole in the center, and a photocuring property is applied to the recording film side of the substrate. After applying an adhesive having a certain amount, the substrates are overlapped and light is irradiated to the light-transmitting part to harden the adhesive on the inner peripheral part corresponding to the light-transmitting part, and then other uncured parts are coated. This is a method for manufacturing an optical disc, characterized by curing an adhesive.

In the present invention, it is preferable to use a combination of light and heat curing resin as the liquid adhesive having photocurable properties. Further, in the present invention, it is particularly preferable to use an ultraviolet curable resin or an ultraviolet and heat curable resin as the adhesive.

[Function] As described above, in the first stage of the optical disc manufacturing method of the present invention, of the two transparent substrates having a central hole in the center,
A recording film is configured to have a light-transmitting part on at least one inner circumference, and an adhesive having photocuring properties is applied to the recording film side of the substrate, and then the substrates are stacked and the adhesive is spread. At this time, at the same time, by irradiating the light-transmitting portion with light, the adhesive that is spreading in the portion corresponding to the light-transmitting portion is immediately photocured, and the two transparent substrates are first superimposed. That is, since the adhesive that is spreading in the portion corresponding to the light-transmitting portion is simultaneously photocured, it is possible to prevent the adhesive from spreading in the inner circumferential direction from the light-transmitting portion. The reason for this is that the photocuring reaction generally occurs instantaneously as a radical reaction, and the flow of the adhesive is stopped in an extremely short period of time.

The second step of the present invention is to then cure the adhesive throughout the other uncured portions.

As explained above, the adhesive hardens in the transparent area around the center and does not spread further toward the center hole, so the two substrates can be bonded together without the adhesive protruding from the edge of the center hole of the substrate. can be bonded together, making it possible to significantly improve productivity.

[Example] Embodiments of the present invention will be described below based on the drawings.

Note that parts corresponding to those in the conventional example are given the same reference numerals.

FIGS. 1(a) to 1(e) show a first embodiment of the method for manufacturing an optical disc of the present invention, and are process diagrams for laminating an optical disc having a full-surface adhesive structure and capable of recording and reproducing information on only one side.

In FIG. 1(a), on the signal surface of a disk-shaped transparent substrate 2 having a center hole 1, an annular light-transmitting portion 3 and a recording film 4 are formed on the inner circumference by vapor deposition, sputtering, or the like.

Next, as shown in FIG. 1(b), the substrate 2 is placed on a highly flat turntable 6 with the recording film 4 facing upward, with the centering shaft 5 passing through the center hole 1. Thereafter, while rotating the turntable 6, the liquid photocurable adhesive 7 is applied concentrically with the application nozzle 13.

Next, as shown in FIG. 1(C), a transparent protective substrate 8 is placed on top of the substrate 2, and a high plate having a transparent hole 9 on the inner periphery of the transparent portion 3 of the substrate 2 is placed on top of the substrate 2. Flatness pressure plate 1
0, apply pressure from above the protective substrate 8 to spread the adhesive 7, and at the same time turn on the light emitting lamp 11 installed on the top of the pressure plate 10, and apply pressure from the transparent hole 9 of the pressure plate 10. The protection substrate 8 is irradiated with light.

Therefore, the adhesive spread in the area corresponding to the transparent hole 9 under pressure is hit by the light that has passed through the protective substrate 8, and is instantly cured, causing the adhesive to spread in the direction of the center hole 1. Regulated.

Also, since the adhesive cures with light instantaneously, you can irradiate it with light while checking visually or with a sensor to see if the adhesive has spread to the center. Alternatively, pressure may be applied with a constant stroke length and light may be irradiated.

The distance between the two substrates is determined at the stage of light irradiation at the center.

Next, as shown in FIG. 1(d), the adhesive 7 is applied to the center hole 1.
Although the spread in the direction is restricted, since it spreads over the entire surface of the other parts of the substrate 2, in this state, the pressure plate 1
0 is removed, and the entire surface of the protective substrate 8 is irradiated with light to cure the uncured portions of the adhesive 7.

If the optical disk is manufactured as described above, it is possible to bond the substrate 2 together without the adhesive 7 protruding from the center hole 1 of the substrate 2.

In the present invention, the viscosity of the adhesive is preferably about 1200 cps. The thickness of the adhesive layer after curing is preferably about 100 μm, with an average thickness of 20 to 30 μm.
It has a permissible width of .

Next, other embodiments of the present invention will be described.

FIGS. 2(a) to 2(e) show a second embodiment of the optical disc manufacturing method of the present invention, and are process diagrams for laminating a double-sided recordable and reproducible optical disc having a fully adhesive structure.

In this embodiment, the two substrates 2.2' both have a recording film 4.4.
This embodiment differs from the first embodiment in that a light and heat curing adhesive 7 is used as the adhesive used for bonding since the recording film 4.4' does not transmit light.

That is, as shown in FIGS. 2(a) to 2(C), the substrate 2 and the substrate 2' are bonded together in the same manner as in the first embodiment, and the adhesive 7 on the inner circumference is first cured by light. After curing and controlling the spread of the adhesive toward the center hole,
As shown in FIG. 2(d), the adhesive 7 is heated in an oven 14 set at a temperature suitable for thermosetting, for a necessary period of time, and the uncured portion of the adhesive is cured by thermosetting.

In this way, by using the light and heat curing adhesive 7, it is possible to easily manufacture an optical disc capable of double-sided recording and playback without the adhesive 7 protruding from the center hole 1 of the substrate 2. becomes.

In the first and second embodiments, a case was described in which an optical disk with a full-surface contact structure was manufactured. However, two substrates each having a recording film are placed inside each other so that the recording films face each other with a certain space between them. A similar effect can be obtained with an optical disc having an air sandwich structure in which the periphery and the outer periphery are bonded together with a spacer interposed therebetween.

The substrate used in the present invention is an acrylic resin with excellent light transmission properties, which has been commonly used in the past.
Polycarbonate resin, hard tempered glass, etc. can be used. The adhesive may be a commonly used acrylic resin adhesive, as long as it does not attack the recording film 4.
Epoxy resin type, UV curing adhesive or UV curable adhesive
Although a thermosetting adhesive can be used, it is necessary to consider the light absorption characteristics of the material that will become the substrate.

The reason for considering the light absorption characteristics of the substrate material is that when using acrylic resin, polycarbonate resin, hard reinforced glass, etc. for the substrate, these materials absorb most of the ultraviolet rays with a wavelength of 300 nm or less and do not transmit them. The adhesive used for lamination has a photocuring reaction wavelength range of 300~
It is desirable to use one having a wavelength of 400 nm.

The recording film 4 may be of any type, such as TeOx, TbFeCo, etc., as long as it can be recorded and reproduced with light such as a laser beam.

[Effects of the Invention] As described above, according to the present invention, it is possible to restrict the spread of the adhesive toward the center hole in the inner circumference during bonding, and prevent the adhesive from protruding from the center large end face of the substrate. Two boards can be bonded together without any problems. That is, since the adhesive is irradiated with light and cured instantly while the adhesive is spreading, it is possible to prevent the adhesive from protruding from the central large end surface of the substrate.

Optical discs can be manufactured without deteriorating the highly accurate center hole diameter formed during substrate manufacturing and the eccentricity between the center hole and the recording/playback guide groove, and the center hole can be cut after bonding. There is no need for correction through post-processing, and man-hours and costs can be reduced. In addition, it is possible to prevent the adhesive protruding from the center hole from adhering to the centering shaft for preventing positional shift and hardening, making it easy to remove the substrate from the centering shaft after bonding. There is no need to clean or replace the centering shaft every time it is used, and productivity can be improved.

[Brief explanation of drawings]

Fig. 1 shows a first embodiment of the present invention, and is a process diagram of bonding an optical disc that has a full-surface adhesive structure and is capable of recording and reproducing information on only one side. FIG. 3 is a process diagram for laminating an optical disk capable of recording and reproducing on both sides, which is constructed of a structure that allows for double-sided recording and playback; FIG. 3 is a bonding process diagram in a conventional optical disc manufacturing method. 1: Center hole 2 3: Transparent part 4 5: Center ring shaft 6 7: Adhesive 8 9: Transparent hole 10 11: Light emitting lamp 12 13: Coating nozzle 14 Substrate recording film Turntable protection substrate Pressure plate Reflector plate Oven 15: Adhesive protrusion part

Claims (2)

[Claims] (1) Of the two transparent substrates with a center hole in the center,
A recording film is formed so as to have a light-transmitting part on at least one inner periphery, and an adhesive having photocuring properties is applied to the recording film side of the substrate, and then the substrates are stacked and the light-transmitting part is formed. A method for manufacturing an optical disc, which comprises irradiating light to cure an adhesive on an inner peripheral portion corresponding to the light-transmitting portion, and then curing adhesive on other uncured portions. (2) The method for manufacturing an optical disc according to claim 1, wherein the adhesive having photocurable properties is a combined photocurable and thermosetting resin.