JP2001076389A - Method for sticking together optical disk, and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk with high quality by restraining the formation of a void between those optical disk substrates when the optical disk substrates are stuck together. SOLUTION: In this method, two optical disk substrates A, B respectively having one or two information recording layers and electrically conductive thin films A', B' formed thereon are stuck together via an adhesive to manufacture one optical disk. In such a case, a voltage is directly applied between the thin films A', B' facing each other via the adhesive for at least a part of period of time until two optical disk substrates A, B are mutually superposed via the adhesive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding apparatus for forming one optical disk by bonding an optical disk substrate having a conductive thin film as a reflective layer and an information recording layer with an adhesive.

[0002]

2. Description of the Related Art As a conventional example, a description will be given of an optical disk bonding apparatus. In an optical disk bonding apparatus using a liquid adhesive, it is necessary to prevent voids (bubbles) in the adhesive layer after bonding. Is important, and various methods have been considered for this purpose.Either method has a void or diameter of about 0.1 mm or more.
Small voids of about 0.05 mm to 0.1 mm or less, or a mixture of these voids are formed between the disk substrates.

As a method capable of considerably improving such a conventional method, the present applicant has filed a patent application (Japanese Patent Application No. 10-257530) as described below. This invention will be described with reference to FIG.

[0006] Among the two disk substrates A and B, the adhesive surface of the lower disk substrate A is turned upward, and an annular adhesive liquid film a is formed thereon. On the bonding surface of the upper disk substrate B, a plurality of dot-like adhesive liquid films b are formed on an imaginary circle having a diameter slightly larger than or approximately equal to the diameter of the annular adhesive liquid film a. Thereafter, the two disk substrates A and B are brought close to each other with the bonding surfaces thereof facing each other, and the annular adhesive liquid film a and the dot-like adhesive liquid film b are brought into contact with each other, whereby the two disk substrates A and B are brought into contact with each other. , Stack B. Next, two disk substrates A,
By spinning B, the adhesive liquid film a and the adhesive liquid film b are stretched, and the excess adhesive is shaken off to form an adhesive layer having a uniform thickness between the disk substrates A and B.

That is, the upper disk substrate B is disposed outside the annular adhesive liquid film a on the lower disk substrate A surface.
By appropriately contacting the tops of the dot-like adhesive liquid films b on the virtual circle on the surface, voids generated at the moment when these liquid films come into contact with each other, so as not to generate minute voids, and When the contact portion spreads over the entire liquid film, air between the liquid films can be eliminated, so that the occurrence of voids at this time is reduced.

However, even with such a method, it is extremely difficult to sufficiently reduce the contact area at the moment when the liquid film a of the adhesive and the liquid film b of the adhesive come into contact with each other. I can't. Therefore, the present inventors have disclosed Japanese Patent Application Nos. 11-23408 and 1-1990.
In the application inventions such as Japanese Patent Application No. 1-234197 and Japanese Patent Application No. 11-237935, the generation of voids is remarkably reduced by sandwiching two disk substrates to be bonded between electrodes and applying a predetermined voltage between the electrodes. We propose a bonding method to reduce it.

[0007]

This bonding method is extremely effective in terms of suppressing the generation of voids. However, two disk substrates to be bonded are sandwiched between electrodes, and a predetermined voltage is applied between the electrodes. Since a voltage is applied, in order to apply a predetermined voltage between the conductive thin films acting as a reflective film where the effect of this voltage application is most expected, a voltage several times as large as that must be applied between the electrodes. . This means that discharge generally occurs easily, and since the two disc substrates bonded to each other are charged, it may be difficult to peel off due to electrostatic attraction when they are stacked. May be necessary.

Therefore, the present invention provides a method and an apparatus for directly applying a voltage between the conductive thin films of two disk substrates to be bonded in order to eliminate such an obstacle.

Means for Solving the Problems In order to solve the above problems, the invention according to claim 1 is directed to two optical disks each having one or two information recording layers and a conductive thin film formed thereon. In an optical disk laminating method for manufacturing one optical disk by bonding substrates together with an adhesive, when the two optical disk substrates are overlapped with each other via an adhesive, at least when the adhesive is in contact with the liquid, at least the conductive material is used. It is intended to provide an optical disk laminating method characterized in that a voltage is applied directly between conductive thin films.

In order to solve the above-mentioned problem, the invention according to claim 2 is the invention according to claim 1, wherein the adhesive is supplied to the bonding surface of the one optical disk substrate in an annular or dotted line to form an annular or dotted line. Forming a liquid film in the shape of a dotted line, and supplying the adhesive in a plurality of dots on an imaginary circle on the bonding surface of the other optical disk substrate to form a liquid film in the form of a dotted line. It provides a matching method.

In order to solve the above-mentioned problem, the invention according to claim 3 is the invention according to claim 2, wherein the voltage application to the conductive thin film is performed by changing the dotted-line liquid film to the annular or dotted-line liquid film. It is an object of the present invention to provide an optical disk laminating method, which is started before the contact and ends after the dotted liquid film has completely contacted the annular or dotted liquid film.

[0011] In order to solve the above-mentioned problems, the invention according to claim 4 is a method in which two or more optical disk substrates each having one or two information recording layers and a conductive thin film formed thereon are bonded with an adhesive. In an optical disk bonding apparatus for manufacturing one optical disk by bonding together, a DC power supply for generating a desired DC voltage and one of the conductive thin films facing each other via the adhesive are selectively connected to one conductive member. And a low voltage connection mechanism for selectively contacting the other conductive member to the other of the conductive thin films facing each other via the adhesive, at least when the adhesive is in contact with the liquid. An object of the present invention is to provide an optical disc bonding apparatus characterized in that a voltage is applied between conductive thin films.

In order to solve the above-mentioned problem, the invention of claim 5 provides an optical disk bonding apparatus according to claim 4, wherein a resistance means is connected in series with the DC power supply.

In order to solve the above problem, according to a sixth aspect of the present invention, in the fifth aspect, after the conductive member to which a positive or negative voltage is applied is set to a predetermined low voltage, the conductive member is connected to the conductive member. An optical disk laminating apparatus characterized by being separated from a conductive thin film.

[0014] In order to solve the above-mentioned problems, the invention according to claim 7 is based on any one of claims 4 to 6,
The one conductive member of the voltage application mechanism or the other conductive member of the low-voltage connection mechanism is composed of three or more conductive members, and these three or more conductive members are arranged at substantially equal intervals around an optical disc substrate. A virtual circle drawn by each tip of the conductive member is arranged so as to be concentric with the information recording layer, and the diameter of the virtual circle is larger than the diameter of the information recording layer and larger than the diameter of the conductive thin film. An object of the present invention is to provide an optical disc bonding apparatus characterized by being set to be within a small range.

[0015]

First, the principle of the present invention will be described. The present invention is based on the finding that when the liquid film of the adhesive formed on the upper and lower optical disk substrates comes into contact for the first time, the smaller the contact area is, the more difficult it is to form a small void. By applying a voltage directly between the conductive thin films acting as a reflection film of the optical disk substrate, the top of the liquid film of the adhesive is tapered by the action of a voltage, so that the initial contact area is sufficiently reduced. In addition, by applying positive and negative charges having different polarities to the liquid film of the adhesive on the conductive thin film of the upper and lower disk substrates by applying a voltage, the bonding of the positive and negative charges when the liquid films come into contact is performed. It is intended to improve the spreadability by increasing the wetting between the upper and lower liquid films and between the liquid films and the optical disk substrate, thereby further suppressing the generation of voids.

As a generally known digital versatile disk (DVD), a single-sided single-layer optical disk having a recording layer including a pit row and a reflective layer only on one optical disk substrate to be bonded, Single-sided optical disc having a recording layer on an optical disc substrate, or one side 2 in which one reflective layer is made of a translucent film
There is a layered optical disk or a double-sided double-layered optical disk in which two single-sided double-layered optical disks are bonded to each other. The present invention can be applied to the production of these various types of DVDs.

An embodiment according to the present invention will be described below with reference to the drawings. This embodiment is characterized in that a small applied voltage is required by directly applying the voltage between the reflection films of the optical disk substrates via the conductor.

In FIG. 1, the lower optical disc substrate A
Is sucked and held by a lower suction stage 1 having a normal vacuum suction function, and the upper optical disc substrate B is sucked and held by an upper suction stage 2 similar to the lower suction stage 1. Each of the optical disc substrates A and B has a normal recording layer (not shown) on one surface, and reflection films A ′ and B ′ formed thereon.
Having. As shown in FIG. 9, liquid films a and b of an adhesive are provided on the reflection films A ′ and B ′, respectively. A continuous annular liquid film a is formed on the lower optical disk substrate A, and discontinuous liquid films b are formed on the upper optical disk substrate B at substantially constant intervals in a virtual circle indicated by a chain line b ′. Here, the continuous annular liquid film a of the lower optical disc substrate A
The diameter of the center circle is D and the upper optical disc substrate
The diameter of the virtual circle indicated by the chain line b 'of B is also D, which is substantially equal to each other.

This device further includes a DC power supply 3 capable of varying the output voltage, a switch 4 capable of switching between a contact 4a on the ground side and a contact 4b on the power supply side, and a reflective film A ′ on the lower optical disc substrate A. A short circuit with a voltage application mechanism 5 for selectively applying a predetermined voltage, a low voltage connection mechanism 6 for selectively coupling the reflection film B of the upper optical disc substrate B to a low voltage such as a ground voltage; It has resistance means 7 for prevention. Since the voltage application mechanism 5 and the low voltage connection mechanism 6 have substantially the same configuration, the voltage application mechanism 5 and the like will be described with reference to FIG.

The lower suction stage 1, which functions as a receiving table, has its lower center surface fixed to an elevating shaft 1A that moves up and down by a driving device (not shown), and the upper portion of the elevating shaft 1A has a lower suction stage. A center axis 1A protruding upward from the center of the stage 1 is formed. The center axis 1A has a diameter suitable for the center hole X of the lower optical disk substrate A, and aligns the lower optical disk substrate A. . A reflective film A 'is formed on a recording layer (not shown) of the lower optical disk substrate A, and a liquid film a of an adhesive is formed on the reflective film A' in an annular shape as described above.

A voltage applying mechanism 5 is provided on the lower optical disk substrate A side. The voltage applying mechanism 5 includes a conductive member 5 that can directly contact the reflective film A ′ of the lower optical disc substrate A.
A, a vertical drive cylinder 5C having a cylinder rod 5C 'coupled to the conductive member 5A via an insulating member 5B, and a cylinder rod having a tip fixed to the vertical drive cylinder 5C
5D '. For example, the conductive member 5A is made of a metal material having elasticity and has a relatively thin plate shape, one end of which is connected to a power source, and the vertical drive cylinder 5C and the horizontal drive cylinder 5D operate. As a result, the other end comes into contact with or separates from the reflection film A ′.

Next, the bonding method will be described while explaining the operation of this apparatus. As shown in FIG.
The lower suction stage 1 and the upper suction stage 2 respectively include a lower optical disc substrate A and an upper optical disc substrate B provided on the reflective films A ′ and B ′, respectively, on the adhesive liquid films a and b. It is held by suction so as to face each other at a certain interval. At this time, the conductive member 5A of the voltage applying mechanism 5
Is not in contact with the reflection film A 'of the lower optical disk substrate A, and the switch 4 is closed to the contact 4a on the ground side. Similarly, the conductive member 6A of the low-voltage connection mechanism 6, which is always connected to the ground side, does not contact the reflective film B 'of the upper optical disc substrate B. Therefore, in this period, the reflection films A ′ and B ′
No voltage is applied between them.

Next, as shown in FIG. 2, the elevating shaft 1A
Rise, and the lower optical disc substrate A rises accordingly. When the optical disk substrate A reaches a certain position, the reflection film A 'of the optical disk substrate A comes into contact with the conductive member 5A of the voltage applying mechanism 5, and the voltage applying mechanism 5 is operated accordingly, and the cylinder rod of the vertical driving cylinder 5C is moved. 5C 'is extended and conductive member 5A
Is raised at substantially the same speed as the rising speed of the optical disk substrate A. On the other hand, the low-voltage connection mechanism 6 also operates to similarly raise the conductive member 6A, and before and after the conductive member 5A contacts the optical disc substrate A, the conductive member 6A lightly contacts the reflective film B of the upper optical disc substrate B, Stop.

Further, the optical disk substrate A is moved to a predetermined position (for example, the reflection films A ′ and B ′) by the ascending movement of the elevating shaft 1A.
When the distance increases to about 20 mm), the switch 4 is closed by the contact 4b on the power supply side as shown in FIG.
, A voltage is applied between the reflection films A ′ and B ′ by the power supply 3. Immediately before the liquid films a and b of the adhesive are in contact with each other, the magnitude of the voltage is such that the tip portions thereof are deformed into a tapered shape, and at the same time, the liquid film a and the liquid film b of the adhesive are wetted. Is set to a value not less than the voltage at which the electric field is improved and spread easily, and not more than the voltage at which the discharge does not occur between the reflection films A ′ and B ′, for example, about 100 to 500V. Therefore,
This voltage forms an electric field in the space between the reflection films A ′ and B ′. At this time, the resistance means 7 erroneously sets the reflection film A 'or B'
Even if the conductive member 5A and the conductive member 6A are directly connected to each other, short-circuit prevention is performed so that a large current does not flow from the power supply 3 to the reflection films A 'and B'. At this time, although the resistance means 7 has, for example, several MΩ to several tens of MΩ, almost no current flows, so that the voltage drop of the resistance means 7 does not matter.

By applying the voltage, a liquid film a of the adhesive
The liquid film b and the liquid film b have charges opposite to each other, and when they attract each other, the top of the liquid film a and the tip of the liquid film b tend to taper. Then, as the space between the optical disk substrates A and B narrows, the electric field in that space increases, and the liquid film a
When the liquid and the liquid film b come into contact with each other, the attraction force of the electric field becomes maximum, and the top of the liquid film a and the tip of the liquid film b further taper,
Since the top of the tapered liquid film a and the tip of the liquid film b contact first, the area at the moment when the liquid film a and the liquid film b come into contact is much smaller than in the past.

Here, the voltage application between the conductive thin films starts before the dotted liquid film comes into contact with the annular or dotted liquid film, and the dotted liquid film is applied to the circular liquid film. It is preferable to end the process after all of the liquid films have come into contact with the annular or dotted line liquid film.

FIG. 4 shows the state after the liquid contact. When the top of the liquid film a and the tip of the liquid film b come into contact with each other, the negative and positive charges of the liquid film a and the liquid film b are neutralized, so that wetting property is improved and the optical disk substrate A is raised When the distance between the optical disk substrates A and B becomes narrower, the discontinuous liquid film b rapidly expands into an oval shape along the annular continuous liquid film a, and spreads. Together form an annular liquid film, which spreads inward and outward between the optical disk substrates A and B, having positive and negative charges remaining on the surface.

Next, as shown in FIG. 5, the switch 4 is closed to the contact 4a on the ground side. As a result, the reflection film A 'of the optical disk substrate A is connected to the ground through the conductive member 5A of the voltage applying mechanism 5, the switch 4 and the resistance means 7. Therefore, the conductive member 5A has a low voltage close to zero voltage.

Thereafter, as shown in FIGS. 6 and 7, both the voltage applying mechanism 5 and the low-voltage connecting mechanism 6 are operated.
First, the respective vertical drive cylinders 5C and 6C are operated for a short time to float the conductive members 5A and 6A from the reflective films A ′ and B ′, and then the horizontal drive cylinders 5D and 6D are operated to thereby perform the conductive members 5A and 5A.
6A is pulled out from between the optical disk substrates A and B, and returns to the original position. Thereafter, the distance between the optical disk substrates A and B is further reduced at a very low speed. This speed is, for example, about the descending speed due to the gravity acting on the optical disc substrate B and the negative pressure due to the wetting of the upper and lower adhesives. Thus, the conductive members 5A and 6A
Since the voltage between the conductive member 5A and the reflective film A 'is separated after the voltage between them is reduced to almost zero, no discharge occurs between the conductive member 5A and the reflective film A' so that the optical disk substrates A and B are damaged. There is nothing.

Actually, in this state, the optical disk substrates A and B
The liquid film of the adhesive between them spreads inward and outward as compared with the drawing, and microscopic voids and voids larger than that were not visible when visually observed through the optical disk substrates A and B.

Thereafter, the lower suction stage 1 performs a downward movement by a driving device (not shown) and stops at a set position. At this time, the optical disk substrates A and B are suction-held on the upper suction stage 2. Thereafter, the upper suction stage 2 makes a revolving motion together with the optical disc substrates A and B by a revolving means (not shown), and the optical disc substrates A and B
Is transferred to a spinner device (not shown), the centrifugal force causes the film to have a uniform film thickness, and unnecessary adhesive is shaken off. Note that, of course, the spin treatment may be performed at the contact position.

According to this embodiment, the top of the liquid film a and the tip of the dot-like liquid film b are tapered by the application of voltage, and the tips come into contact with the adhesive. Generation of minute voids that are easily formed during bonding is suppressed. In order to improve the wettability, the discontinuous liquid film b rapidly expands into an oval shape without voids along the annular continuous liquid film a, and the liquid film a and the liquid film b Spreads outward between the optical disk substrates A and B, whose surfaces bear positive and negative charges, so that air is not entrained in this process, and therefore, spin processing is performed between the optical disk substrates A and B. It was confirmed that the generation of minute voids and large voids having a diameter larger than that can be significantly suppressed in the adhesive layer spread uniformly and thinly.

In this embodiment, it is assumed that the diameter of the center of the continuous annular liquid film a of the lower optical disc substrate A is equal to the diameter of the virtual circle indicated by the chain line b ′ of the upper optical disc substrate B. As described above, the effect of the present invention can be obtained even if one of the diameters is somewhat larger and the liquid film is formed only on one of the optical disk substrates. Furthermore, even if the adhesive is discontinuously formed on both optical disk substrates in a dotted line, the effect of the present invention can be similarly obtained if the distance between the liquid films adjacent to each other is relatively small.

As is clear from the above description, in the direct voltage application method, a conductive member acting as an electrode is brought into direct contact with each conductive thin film as a reflection film. At this time, it cannot be said that there is no case where the conductive thin film is damaged such as scratches. As a countermeasure, a conductive member may be brought into contact with the outer peripheral portion of the conductive thin film having no information recording layer below. But,
Although the information recording layer is manufactured so as to be exactly concentric with the optical disk substrate, in general, the conductive thin film often deviates to any one due to manufacturing variations, and the edge of the conductive thin film and the optical disk substrate The distance from the edge of the conductive thin film is narrow and non-uniform, and the outer peripheral portion of the conductive thin film without the information recording layer below is 2 mm or less even when they are formed at the concentric position. Is 60mm, and the radius of the information recording layer is 58mm), so it is extremely difficult to make a single conductive member contact the conductive member exactly to the outer periphery of the conductive thin film where no information recording layer exists. Technique.

To remove such difficulties,
Three or more conductive members are arranged around the optical disk substrate at substantially equal intervals, and a virtual circle drawn so as to include each end of the conductive member is arranged concentrically with the information recording layer. The position of each conductive member is set so that the diameter is larger than the diameter of the information recording layer and smaller than the diameter of the conductive thin film. By setting the position of the conductive member in this manner, even if the conductive thin film is displaced due to variations in the manufacturing process, one end of the conductive member contacts the conductive thin film, and any end of the conductive member has information. It does not contact the conductive thin film portion where the recording layer exists.

In the above embodiment, the switch 4 is used for easy understanding of the description.
And a controllable power supply 3 capable of supplying a DC output voltage having a desired pulse width as a power supply 3 without using the power supply 3. Conductive members via capacitors and resistors
A circuit configuration in which 5A is connected to the ground potential may be used.

Furthermore, a DC power supply and a switch for selectively applying a negative voltage to the low-voltage connection mechanism 6 may be connected between the ground and the low-voltage connection mechanism 6 as needed. Therefore, in this case, a positive voltage is applied to the conductive thin film A ′ of one optical disk substrate A, and the other optical disk substrate B
A negative voltage is applied to the conductive thin film B ′. Further, it is convenient that these power supplies can adjust the magnitude of the output voltage and the duty cycle. The power supply 3 generally comprises a commercial AC power supply and a rectifier for rectifying the AC power. A DC voltage having a frequency higher than the commercial frequency is connected by connecting a chopper circuit to the output side of the rectifier. The same or more effect can be obtained by the method of intermittently applying.

[0038]

As described above, in the present invention, at the time of laminating optical disk substrates, a voltage is directly applied between the reflective films before they are laminated, and a voltage is applied until the opposing adhesives come into contact with each other. Therefore, liquid contact is performed at a low applied voltage in a state in which the adhesive is very preferable, and not only can the formation of voids between bonded objects be significantly suppressed, but also the danger of discharge And a high quality optical disc can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an optical disc bonding according to the present invention.

FIG. 2 is a diagram for explaining optical disc bonding according to the present invention.

FIG. 3 is a diagram for explaining optical disc bonding according to the present invention.

FIG. 4 is a diagram for explaining optical disc bonding according to the present invention.

FIG. 5 is a diagram for explaining optical disc bonding according to the present invention.

FIG. 6 is a diagram for explaining optical disc bonding according to the present invention.

FIG. 7 is a diagram for explaining optical disc bonding according to the present invention.

FIG. 8 is a diagram for explaining an embodiment of the optical disc bonding apparatus according to the present invention.

FIG. 9 is a diagram for explaining the optical disc bonding according to the present invention.

FIG. 10 is a diagram for explaining a conventional optical disc bonding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Upper suction stage 2 ... Lower suction stage 3 ... DC power supply 4 ... Switch 5 ... Voltage application mechanism 6 ... Low voltage connection mechanism 7 ... Resistance means A and B ... Optical disk substrates A ', B' ... Conductive thin films a, b of optical disk substrates A, B ... Liquid film of adhesive

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masahiro Nakamura 1-1-18 Takada, Toshima-ku, Tokyo Origin Electric Co., Ltd. (72) Inventor Hideo Kobayashi 1-1-18-1 Takada, Toshima-ku, Tokyo Origin Electric Co., Ltd. F term (reference) 4J040 JB07 LA09 LA11 MB03 MB05 MB14 NA17 NA21 PA25 PA32 PA35 PB01 5D121 AA07 FF01 FF18

Claims (7)

[Claims] 1. An optical disk sticker for manufacturing one optical disk by bonding one or two information recording layers and two optical disk substrates each having a conductive thin film formed thereon on an adhesive. In the bonding method, when the two optical disk substrates are overlapped via an adhesive, a voltage is directly applied at least between the conductive thin films when the adhesives are in contact with each other. 2. The optical disk according to claim 1, wherein the adhesive is supplied in an annular or dotted line on the adhesive surface of the one optical disk substrate to form an annular or dotted liquid film and the other optical disk. An optical disc bonding method, characterized in that the adhesive is supplied in a plurality of dots on a virtual circle on a bonding surface of a substrate to form a dotted liquid film. 3. The method according to claim 2, wherein the voltage application to the conductive thin film is started before the dotted liquid film comes into contact with the annular or dotted liquid film, and the dotted liquid is applied. An optical disc laminating method, which is completed after the film has completely contacted the annular or dotted liquid film. 4. An optical disk sticker for manufacturing one optical disk by bonding one or two information recording layers and two optical disk substrates each having a conductive thin film formed thereon on an adhesive. In the matching device, a DC power supply for generating a desired DC voltage, a voltage application mechanism for selectively contacting one conductive member with one of the conductive thin films facing each other via the adhesive, and A low-voltage connection mechanism for selectively contacting the other conductive member with the other of the conductive thin films facing each other, and applying a voltage between at least the conductive thin films when the adhesive is in contact with the liquid. Optical disk bonding device. 5. The optical disk bonding apparatus according to claim 4, wherein a resistance means is connected in series with the DC power supply. 6. The optical disk bonding apparatus according to claim 5, wherein the conductive member to which the positive or negative voltage is applied is set to a predetermined low voltage, and then the conductive member is separated from the conductive thin film. . 7. The voltage applying mechanism according to claim 4, wherein the one conductive member of the voltage applying mechanism or the other conductive member of the low voltage connecting mechanism comprises three or more conductive members. The plurality of conductive members are arranged at substantially equal intervals around the optical disk substrate, and a virtual circle drawn so as to include each tip of the conductive member is arranged concentrically with the information recording layer, and the virtual circle is formed. An optical disc bonding apparatus, wherein the diameter of the optical disc is set to be larger than the diameter of the information recording layer and smaller than the diameter of the conductive thin film.