Method of and apparatus for laminating disc-shaped substrates

A method of and an apparatus for laminating disc-shaped substrates capable of automatically bonding an adhesive agent to disc-shaped substrates effectively and continuously. The method includes providing an adhesive sheet body comprising a plurality of adhesive agents each covered with a release paper, peeling off the release paper from the adhesive sheet body, positioning the adhesive sheet body from which the release paper has been peeled over a lower disc-shaped substrate, pressing the adhesive sheet body to allow the adhesive agent adhered to the lower surface thereof to bond or transfer onto a surface of the lower disc-shaped substrate, peeling off the adhesive sheet body from the adhesive agent bond onto the surface of the lower disc-shaped substrate, placing an upper disc-shaped substrate on the lower disc-shaped substrate, and pressing the upper disc-shaped substrate against the lower disc-shaped substrate, to bond the substrates to one another. The apparatus includes a holding table which supports a disc-shaped substrate thereon, supporting members (i.e. tension rollers) between which an adhesive sheet body extends over the holding table, a centering shaft for positioning the adhesive sheet body, a laminating roller for pressing the adhesive sheet body against the lower disc-shaped substrate, and a peeling member for peeling off the adhesive sheet body bonded onto the lower disc-shaped substrate.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a method of and an apparatus for
 laminating disc-shaped substrates, particularly to a method of integrally
 laminating two disc-shaped substrates using an adhesive sheet and an
 apparatus for carrying out the method, namely, an apparatus for bonding
 the adhesive sheet body onto two disc-shaped substrates.
 2. Prior Art
 Computers, especially personal computers have recently become popular, and
 the types of storage media for use therewith have increased. These types
 include magnetic discs, optical discs (e.g., CD-ROM), optical magnetic
 discs (e.g., MO), etc. The demand for optical discs has increases
 recently.
 A DVD is one type of optical disc, and a disc-shaped substrate that is a
 single plate constituting the DVD is standardized to have a thickness of
 0.6 mm, an outer diameter of 120 mm, an inner diameter of its central hole
 of 15 mm. Since such a thin disc-shaped substrate formed of a single plate
 is low in mechanical strength and is easily deformable, and in view of
 storage capacity, two disc-shaped substrates each having the same
 thickness (0.6 mm) are bonded onto each other to form an integrated
 substrate in a practical use thereof.
 Such a high density storage disc (i.e. a DVD) is generally used as a
 laminated structure as set forth above, but is not used as a single plate.
 In such a case, it is necessary that both the upper and lower disc-shaped
 substrates be bonded onto each other.
 A series of steps have been taken to manufacture an integrated storage disc
 (e.g. an optical disc) by bonding two disc-shaped substrates (see FIG.
 22), as in the following.
 (1) a step of placing a lower disc-shaped substrate D1 on a holding table
 2A;
 (2) a step of coating an adhesive agent R made of UV cured resin to the
 lower disc-shaped substrate D1;
 (3) a step of placing an upper disc-shaped substrate D2 on the lower
 disc-shaped substrate D1 to overlay the former on the latter;
 (4) a step of rotating the holding table 2A to develop the adhesive agent R
 interposed between the disc-shaped substrates D1 and D2 on the entire
 surfaces thereof; and
 (5) a step of irradiating the developed adhesive agent made of UV cured
 resin with UV to cure the adhesive agent.
 The storage disc is manufactured by the aforementioned steps, namely, the
 two disc-shaped substrates D1 and D2 are bonded onto each other to form a
 single integrated optical disc.
 However in such a bonding method, since the adhesive agent is developed in
 a wider range by rotating the holding table, the adhesive agent is
 scattered outwardly due to centrifugal force. The periphery of the storage
 disc is made dirty or contaminated by the spray of the adhesive agent, or
 the adhesive agent is scattered and lost and hence the using efficiency of
 the adhesive agent is lowered.
 Further, there is a problem that the thickness of the adhesive layer is not
 at all uniform. Still further, there is another problem that the number of
 manufacturing steps increases to increase the manufacturing cost because
 of the necessity of the step of irradiating adhesive agent with UV to cure
 the adhesive agent.
 Accordingly, a method of bonding two disc-shaped substrates using an
 adhesive agent without requiring the developing step of the adhesive agent
 as set forth above has been studied. In the bonding method using an
 adhesive agent, the adhesive agent is bonded onto one of two disc-shaped
 substrates to be bonded, thereafter the other disc-shaped substrate is
 overlaid on the disc-shaped substrate onto which the adhesive agent is
 bonded.
 An adhesive agent is generally used in a state where it is bonded onto a
 sheeting, i.e. an adhesive sheet body forming a base member, that is, a
 plurality of adhesive sheets or the adhesive agents are adhered to the
 adhesive sheet body. Accordingly, it is very ineffective to peel off the
 adhesive agent adhered to the adhesive sheet body one by one manually to
 bond or transfer it onto the lower disc-shaped substrate when two
 disc-shaped substrates are bonded onto each other. Further, fine air
 bubbles are liable to enter between the adhesive and the lower disc-shaped
 substrate when manually peeling off the adhesive agent. Still further, the
 bonding operation of an adhesive agent needs to be automated to
 incorporate the bonding operation of the adhesive agent to the disc-shaped
 substrates into the laminating lines of the disc-shaped substrates so as
 to produce a series of laminating lines which are sequentially controlled
 as a whole. That is, it is necessary to automatically bond the adhesive
 agent to the disc-shaped substrate to produce continuous laminating lines.
 SUMMARY OF THE INVENTION
 The present invention has been developed to solve the aforementioned
 problems. That is, it is an object of the invention to provide a method of
 laminating disc-shaped substrates capable of automatically bonding an
 adhesive agent to the disc-shaped substrate very effectively and
 continuously, and an apparatus for carrying out this method.
 It is another object of the invention to provide a method of laminating
 disc-shaped substrates capable of preventing air from entering between the
 adhesive and one substrate when bonding the disc-shaped substrates by the
 adhesive agent, and an apparatus for carrying out this method.
 The inventors of the present application endeavored themselves to study the
 aforementioned problems and have found that release paper can be peeled
 off from an adhesive agent bonded onto an adhesive sheet body, and the
 exposed adhesive agent can be bonded onto the lower disc-shaped substrate
 so as to sequentially bond the adhesive agent to the lower disc-shaped
 substrate, and thereafter has completed the invention.
 A first aspect of the invention resides in a method of laminating
 disc-shaped substrates comprising preparing an adhesive sheet body S
 comprising a plurality of adhesive agents S2 each covered with a release
 paper S3, peeling off the release paper S3 from the adhesive sheet body S,
 positioning the adhesive sheet body S from which the release paper S3 is
 peeled off over a lower disc-shaped substrate D1, pressing the adhesive
 sheet body S to allow the adhesive agent S2 adhered to the lower surface
 of the adhesive sheet body S to bond or transfer onto a surface of the
 lower disc-shaped substrate D1, peeling off the adhesive sheet body S from
 the adhesive agent S2 bonded onto the surface of the lower disc-shaped
 substrate D1, placing an upper disc-shaped substrate D2 on the lower
 disc-shaped substrate D1, pressing the upper disc-shaped substrate D2
 against the lower disc-shaped substrate D1, thereby bonding the lower
 disc-shaped substrate D1 and the upper disc-shaped substrate D2.
 A second aspect of the invention resides in the method of laminating
 disc-shaped substrates comprising the steps of:
 (1) preparing an adhesive sheet body S comprising a plurality of adhesive
 agents S2 each covered with a release paper S3;
 (2) peeling off the release paper S3 from the adhesive sheet body S;
 (3) positioning each adhesive agent S2 of the adhesive sheet body S over a
 lower disc-shaped substrate D1 using a positioning member;
 (4) pressing the adhesive sheet body S from which the release paper S3 is
 peeled off against the lower disc-shaped substrate D1 to allow the
 adhesive agent S2 adhered to the lower surface of the adhesive sheet body
 S to bond onto a surface of the lower substrate D1 by moving a laminating
 member from one end of the lower disc-shaped substrate D1 to the other end
 thereof;
 (5) peeling off the adhesive sheet body S from the adhesive agent S2 bonded
 onto the lower disc-shaped substrate D1 using a peeling member;
 (6) placing an upper disc-shaped substrate D2 on the lower disc-shaped
 substrate D1; and
 (7) pressing the upper disc-shaped substrate D2 against the lower
 disc-shaped substrate D1 to integrally laminate the disc-shaped substrates
 D1 and D2.
 A third aspect of the invention resides in the method of further including
 a step of collecting the release paper S3 in the second aspect of the
 invention.
 A fourth aspect of the invention resides in the method wherein the step of
 collecting the release paper S3 in the second aspect of the invention is
 performed using an adhesive tape having an adhesion relative to the
 release paper S3 which is greater than that of the adhesive agent S2
 relative to the release paper S3.
 A fifth aspect of the invention resides in the method wherein the step of
 (3) in the second aspect of the invention is performed in a state where a
 weak tension is applied to the adhesive sheet body S.
 A sixth aspect of the invention resides in the method of laminating
 disc-shaped substrates of the second aspect of the invention, wherein the
 step of (3) is performed by inserting the tip end of a centering shaft 3
 serving as the positioning member into a hole P of the adhesive sheet.
 A seventh aspect of the invention resides in the method wherein the
 adhesive sheet body S used in the step of (3) in the second aspect of the
 invention is slightly inclined relative to the lower disc-shaped substrate
 D1.
 An eighth aspect of the invention resides in the method wherein the
 laminating member used in the step of (4) in the second aspect of the
 invention is a rolling laminating roller.
 A ninth aspect of the invention resides in the method wherein the peeling
 in the step of (5) in the second aspect of the invention is performed by
 the peeling member that traverses over the lower disc-shaped substrate D1.
 A tenth aspect of the invention resides in the method wherein the peeling
 member in the ninth aspect of the invention peels off the adhesive sheet
 body S from the adhesive agent S2 while supporting the adhesive sheet body
 S in a state where the adhesive sheet body S and the lower disc-shaped
 substrate D1 do not contact each other to keep a slight gap therebetween.
 An eleventh aspect of the invention resides in the method wherein the
 peeling member in the ninth aspect of the invention has two support rods
 and the adhesive sheet body S is extended between these two support rods.
 A twelfth aspect of the invention resides in the method wherein the peeling
 member in the ninth aspect of the invention peels off the adhesive sheet
 body S at an acute angle between the adhesive sheet body S and the lower
 disc-shaped substrate D1.
 A thirteenth aspect of the invention resides in a method of laminating
 disc-shaped substrates comprising the steps of:
 (1) preparing an adhesive sheet body S comprising a plurality of adhesive
 agents S2 each covered with a release paper S3;
 (2) peeling off the release paper S3 from the adhesive sheet body S;
 (3) positioning each adhesive agent S2 of the adhesive sheet body S over a
 lower disc-shaped substrate D1 by inserting the tip end of the positioning
 member into the hole P of the adhesive sheet body S;
 (4) pressing the adhesive sheet body S from which the release paper S3 is
 peeled off to allow the adhesive agent S2 adhered to the lower surface of
 the adhesive sheet body S to bond or transfer onto a surface of the lower
 disc-shaped substrate D1 by moving a rolling laminating roller from one
 end of the lower disc-shaped substrate D1 to the other end thereof;
 (5) peeling off the adhesive sheet body S from the adhesive agent S2 bonded
 onto the surface of the lower disc-shaped substrate D1 in the manner that
 the peeling member traverses while supporting the adhesive sheet body S in
 a state where the adhesive sheet body S and the lower disc-shaped
 substrate D1 do not contact each other to keep a slight gap therebetween.
 (6) placing an upper disc-shaped substrate D2 on the lower disc-shaped
 substrate D1; and
 (7) pressing the upper disc-shaped substrate D2 against the lower
 disc-shaped substrate D1 to bond the lower disc-shaped substrate D1 and
 the upper disc-shaped substrate D2.
 A fourteenth aspect of the invention resides in a laminating apparatus for
 laminating disc-shaped substrates comprising a holding table (2) to place
 a lower disc-shaped substrate D1 thereon, supporting members (tension
 rollers 5A, 5B) for extending an adhesive sheet body S therebetween at a
 given interval over the holding table (2), a centering shaft (3) for
 positioning the adhesive sheet body S, a laminating roller 1 for pressing
 the adhesive sheet body S against the lower disc-shaped substrate D1 to
 bond the adhesive sheet body S onto the lower disc-shaped substrate D1
 while moving on the lower disc-shaped substrate D1 from one end thereof to
 the other thereof, and a peeling member 4 for peeling off the adhesive
 sheet body S bonded onto the lower disc-shaped substrate D1 from the lower
 disc-shaped substrate D1.
 A fifteenth aspect of the invention resides in the laminating apparatus
 wherein the centering shaft 3 in the fourteenth aspect of the invention
 comprises a second small diameter portion 32 that is inserted into a boss
 hole 21 of the holding table 2, a first small diameter portion 31 that is
 inserted into the hole P of the adhesive sheet body S, and a large
 diameter portion 33 that contacts the back surface of the adhesive sheet
 body S.
 A sixteenth aspect of the invention resides in the laminating apparatus
 wherein the peeling member 4 in the fourteenth aspect of the invention
 comprises a base 41 that traverses and rolls, a leading support rod 43 and
 an angle restriction support rod 42 respectively provided at positions
 remote from the center of the base 41 by given intervals.
 A seventeenth aspect of the invention resides in the laminating apparatus
 wherein the angle restriction support rod 42 of the peeling member 4 in
 the sixteenth aspect of the invention has an acute angle portion 42A by
 which the adhesive sheet body S is peeled off from the lower disc-shaped
 substrate D1 at an acute guiding angle .alpha..
 With the employment of the methods of laminating disc-shaped substrates
 according to the first to the twelfth aspects of the invention, the
 adhesive agent can be continuously and automatically bonded onto the lower
 disc-shaped substrate thereby making it possible to effectively bond the
 disc-shaped substrates.

PREFERRED EMBODIMENT OF THE INVENTION
 A method of laminating disc-shaped substrates according to the present
 invention will be now described with reference to FIGS. 1 to 9 showing the
 steps for bonding an adhesive agent S2 to a lower disc-shaped substrate
 D1.
 Before explaining the present invention with reference to FIGS. 1 to 9, an
 adhesive sheet body S, which is prepared for performing the present
 invention, is explained. The adhesive sheet body S comprises a carrier S1
 formed of a long base or sheet, adhesive agent S2 which is bonded onto the
 carrier S1 and formed of synthetic resin tape such as thin polyethylene
 and a release paper S3 temporarily bonded onto the surface of the adhesive
 agent S2 (See FIG. 1).
 FIG. 20(A) is a front view of the adhesive sheet body S, FIG. 20(B) is a
 side view of the adhesive sheet body S and FIG. 20(C) is a side view
 showing a state where the release paper S3 is removed or peeled off from
 the adhesive sheet body S.
 The adhesive agent S2 forms a fixed medium for integrally laminating the
 disc-shaped substrates D1 and D2 described later, and comprises a
 plurality of LP (long-playing record)-shaped sheets (or doughnut shape)
 (See FIG. 21(A)) each bonded onto the surface of the carrier S1 at regular
 intervals. There is employed a pressure sensitive adhesive agent as the
 adhesive agent S2 such as rubber-based adhesive agent, acrylic adhesive
 agent, silicon adhesive agent, and a vinyl adhesive agent. It is possible
 to select the optimum thickness of the adhesive agent S2 depending on the
 kind of optical disc to be designed.
 The release paper S3 is temporarily adhered to the adhesive agent S2 to
 cover the adhesive agent S2 and has the same shape as that of the adhesive
 agent S2 (See FIG. 21(B)).
 The adhesive sheet body S has many holes P each penetrating the carrier S1,
 adhesive agent S2 and the release paper S3 at the same time when it is
 manufactured. Each hole P is utilized for positioning the adhesive agent
 S2 relative to the holding table 2 using a centering shaft serving as a
 positioning member, described later. The release paper S3 is peeled off
 from the adhesive sheet body S when the adhesive sheet body S is supplied
 between a pressing body 1 and the holding table 2.
 Described next is a flow or series of steps of bonding the adhesive agent
 S2 onto the lower disc-shaped substrate D1.
 FIG. 1 shows a method of bonding the adhesive agent S2 and an apparatus for
 laminating the adhesive sheet body S wherein the adhesive sheet body S is
 released and unwound from a first supply roller 8. Bonded matter such as
 dust is removed from the adhesive sheet body S by a cleaning roller 7
 after the adhesive sheet body S unwound from the first supply roller 8.
 Thereafter, the adhesive sheet body S passes through a pitch feed roller
 6, then it is supplied to a tension roller 5A provided upstream relative
 to the holding table 2 (hereinafter referred to as upstream tension roller
 5A). The adhesive sheet body S that passed through the upstream tension
 roller 5A then passes through a space between the holding table 2 and a
 laminating roller 1 serving as a laminating member, and delivered to a
 tension roller 5B provided downstream relative to the holding table 2
 (hereinafter referred to as downstream tension roller 5B).
 The holding table 2 is installed on a rotary table T and it is moved right
 under the centering shaft 3 by the rotary motion of the rotary table T.
 The lower disc-shaped substrate D1 has been already placed on the holding
 table 2. The adhesive sheet body S receives a pressing force between the
 holding table 2 and pressing body 1 so as to allow the adhesive agent S2
 to be bonded onto the surface of the lower disc-shaped substrate D1 which
 is placed on the holding table 2 in a state where the adhesive sheet body
 S is extended between the upstream tension roller 5A and the downstream
 tension roller 5B. After the adhesive agent S2 is bonded onto the surface
 of the lower disc-shaped substrate D1, the adhesive sheet body S passes
 through the downstream tension roller 5B, then it is supplied to a feed
 roller 11.
 The feed roller 11 is positively driven so as to move the adhesive sheet
 body S when necessary.
 The adhesive sheet body S fed from the feed roller 11 is wound by a winding
 roller 13 through a hanging roller 12. Since the hanging roller 12 is hung
 from the adhesive sheet body S the roller 12 lowers when the adhesive
 sheet body S is fed from the feed roller 11. A detector 12A detects the
 lowering position of the hanging roller 12, and issues a detection signal.
 The winding roller 13 is rotated upon detection of the detection signal
 from the detector 12A so as to wind the adhesive sheet body S by a given
 amount. In the flow of steps as set forth above, the adhesive agent S2 is
 bonded onto the lower disc-shaped substrate D1.
 Meanwhile, the adhesive sheet body S is supplied between the holding table
 2 and laminating roller 1 in a state where the release paper S3 is removed
 from the adhesive agent S2 while the adhesive agent S2 is exposed on the
 lower surface of the adhesive sheet body S.
 An adhesive tape L is used as means for removing or peeling off the release
 paper S3 from the adhesive sheet body S. Referring to the function of the
 adhesive tape L, as illustrated in FIG. 1, the adhesive sheet body S first
 unwound from the supply roller 8 has the adhesive agent S2 adhered to the
 lower surface thereof, and the release paper S3 is applied to the adhesive
 face of the adhesive agent S2.
 The adhesive tape L that is supplied from a supply roller 9 has an adhesive
 face confronting the adhesive sheet body S (namely, it is provided on the
 front side thereof), and the adhesive face of the adhesive tape L opposes
 the release paper S3 of the adhesive sheet body S and they contact each
 other at a guide roller 81. The adhesive tape L and the adhesive sheet
 body S respectively pass through the guide roller 81, cleaning roller 7,
 pitch feed roller 6, upstream tension roller 5A, then they are pressed
 against each other. As a result, the adhesive face of the adhesive tape L
 is bonded onto the release paper S3 of the adhesive sheet body S.
 After the adhesive sheet body S passes through the upstream tension roller
 5A, the release paper S3 is peeled off from the adhesive sheet body S
 owing to adhesion of the adhesive tape L. When the adhesive tape L
 receives the release paper S3, it is wound by a winding roller 10 so that
 the release paper S3 is collected. The reason why the release paper S3 is
 collected when it is separated from the adhesive sheet body S using the
 adhesive tape L is caused by the difference of adhesion, namely, the
 adhesion of the adhesive tape L relative to the release paper S3 is
 greater than that of the adhesive agent S2 relative to the release paper
 S3. That, the adhesive tape L is must have adhesion relative to the
 release paper S3 which is greater than the peeling strength of the release
 paper S3 relative to the adhesive agent S2.
 In such a manner, the release paper S3 is removed from the adhesive sheet
 body S that passes through the tension roller 5A and supplied between the
 holding table 2 and the laminating roller 1, and the adhesive agent S2 is
 exposed on the lower surface of the adhesive sheet body S.
 Briefly referring to the laminating roller 1 serving as a laminating member
 having an important function according to the invention, it has a function
 to press the adhesive sheet body S to the lower disc-shaped substrate D1
 so as to bond the adhesive sheet body S to the lower disc-shaped substrate
 D1.
 Accordingly, it is preferable that the laminating roller 1 be provided with
 a layer made of a flexible material at the outer periphery thereof, and a
 heater built therein so that the entire laminating roller 1 can be heated
 and the heating can be adjusted. The width of the laminating roller 1 is
 designed to be slightly wider than that of the lower disc-shaped substrate
 D1. The laminating roller 1 can roll and move, by a driving apparatus (not
 shown), in parallel with the adhesive sheet body S while it presses the
 lower disc-shaped substrate D1. When the bonding of the adhesive sheet
 body S on the entire surface of the lower disc-shaped substrate D1 is
 completed, the laminating roller 1 is moved away from the lower
 disc-shaped substrate D1 and returns to the original position.
 Meanwhile, the adhesive sheet body S is supported between the upstream
 tension roller 5A and the downstream tension roller 5B while the adhesive
 agent S2 formed of an LP (long-playing record)-shaped (doughnut shaped)
 sheet is provided at the lower surface thereof.
 At this time if the lower end of the upstream tension roller 5A is slightly
 higher than that of the downstream tension roller 5B, the laminating can
 be performed in an excellent condition, described later. This is also
 important from a technical point of view.
 If the adhesive sheet body S is moved, the adhesive sheet body S that is
 supported by the tension rollers 5A and 5B is fed in a state where a given
 tension is applied to the adhesive sheet body S by the driving of the feed
 roller 11, as shown in FIG. 1.
 Then, when the adhesive sheet body S is stopped, the downstream tension
 roller 5B is slightly moved so that the tension is scarcely applied to the
 adhesive sheet body S (initial state).
 Subsequently, as shown in FIG. 3, the centering shaft 3 serving as a
 positioning member is lowered so that the adhesive sheet body S
 (specifically, adhesive agent 52) is positioned relative to the lower
 disc-shaped substrate D1 by the projection (composed a first small
 diameter portion 31 and a second small diameter portion 32) provided on
 the tip end of the centering shaft 3.
 Meanwhile, at the instant when the projection of the centering shaft 3
 enters the hole P of the adhesive sheet body S when the centering shaft 3
 is lowered, the upstream tension roller 5A is slightly retracted so as to
 apply the tension to the adhesive sheet body S. At this time, the
 downstream tension roller 5B is positioned as it is.
 As mentioned above, when a slight tension is applied to the adhesive sheet
 body S, the adhesive sheet body S is placed in a stable state without
 being vibrated so that the first small diameter portion 31 of the
 centering shaft 3 can be accurately inserted into the hole P of the
 adhesive sheet body S.
 Further referring to the positioning of the adhesive sheet bodys by the
 centering shaft 3, when the centering shaft 3 is lowered, the projection
 (first small diameter portion 31) provided at the lower end of a large
 diameter portion 33 is inserted into the hole P of the adhesive sheet body
 S, and the second small diameter portion 32 that is a part of the
 projection is engaged in a hole 21 defined in the boss (hereinafter
 referred to as a boss hole) of the holding table 2 (see FIG. 10A). At this
 time, the adhesive sheet body S and the lower disc-shaped substrate Dl are
 positioned concentrically.
 That is, the first small diameter portion 31 provided at the tip end of the
 centering shaft 3 is inserted into the hole P of the adhesive sheet body
 S, and the second small diameter portion 32 of the centering shaft 3 that
 is smaller than the first small diameter portion 31 in diameter is
 inserted into the central hole H of the lower disc-shaped substrate D1 so
 that the centering shaft 3 is engaged in the boss hole 21.
 Accordingly, the adhesive sheet body S and the lower disc-shaped substrate
 D1 are positioned concentrically.
 At this time, since the adhesive sheet body S is tightened, it is
 positioned over the upper end of the small diameter portion 31 and
 contacts the lower surface of the large diameter portion 33. Accordingly,
 the adhesive sheet body S does not contact the surface of the lower
 disc-shaped substrate D1 so that the adhesive agent of the adhesive sheet
 body S is accurately positioned right over the lower disc-shaped substrate
 D1.
 The adhesive agent is drawn through a small hole, not shown, provided on
 the holding table 2 and the lower disc-shaped substrate D1 is sucked and
 held by the holding table 2 without moving but remains positioned on the
 holding table 2.
 When the adhesive sheet body S is disposed slightly inclined owing to the
 vertical relation between the upstream tension roller 5A and the
 downstream tension roller 5B, the adhesive sheet body S is tightened in an
 inclined state so that the first small diameter portion 31 provided at the
 tip end of the centering shaft 3 easily enters the hole P of the adhesive
 sheet body S.
 Explaining the boss hole 21 provided on the holding table, a boss body, not
 shown, is installed slightly vertically in the boss hole 21.
 Accordingly, when the lower disc-shaped substrate D1 is placed on the
 holding table 2 in the previous step, not shown, the boss body protrudes
 from the boss hole 21 so that the lower disc-shaped substrate D1 is
 positioned in advance relative to the holding table 2.
 After the lower disc-shaped substrate D1 is placed on the holding table 2,
 the boss body stands by while it is retracted at the innermost of the boss
 hole 21, so as to avoid obstruction of the laminating operation of the
 adhesive sheet body S on the holding table 2.
 Then, the laminating roller 1 that stands by at the upper portion of the
 lower disc-shaped substrate D1 is lowered to contact one end of the lower
 disc-shaped substrate D1 that has been already positioned (see FIG. 4).
 At this time, the centering shaft 3 completes its function, and hence it
 rises immediately to return to the original position (see FIG. 5)
 Subsequently as shown in FIG. 6, the laminating roller 1 rolls on the lower
 disc-shaped substrate D1 (precisely on the adhesive sheet body S on the
 lower disc-shaped substrate D1) in the direction denoted by the arrow.
 With the rolling operation of the laminating roller 1, the adhesive sheet
 body S is pressed against the lower disc-shaped substrate D1, and hence
 the contacting surface between the adhesive sheet body S and lower
 disc-shaped substrate D1 gradually enlarges.
 Finally, when the laminating roller 1 passes the other end of the lower
 disc-shaped substrate D1, the adhesive sheet body S is completely bonded
 onto the entire surface of the lower disc-shaped substrate D1.
 In such a special pressing manner, the adhesive agent S2 adhered to the
 lower surface of the adhesive sheet body S is bonded (transferred) to the
 surface of the lower disc-shaped substrate D1 without the interposition of
 air bubbles or the like, and puckering of the adhesive sheet body S is
 avoided.
 The operations of the centering shaft 3 and the laminating roller 1 are now
 described more in detail.
 FIGS. 10(A), 10(B) and 10(C) are views showing the operations of the
 centering shaft 3 and laminating roller 1.
 As shown in FIG. 10(A), the projection (second small diameter portion 32)
 of the centering shaft 3 is engaged in the holding table 2 and the
 adhesive sheet body S is positioned over the upper end of the first small
 diameter portion 31 of the projection in a state where the adhesive sheet
 body S is positioned in contact with the large diameter portion 33 of the
 centering shaft 3.
 Further, since a slight tension is applied onto the adhesive sheet body S,
 the adhesive sheet body S does not contact the surface of the lower
 disc-shaped substrate D1, as mentioned above.
 Then, as shown in FIG. 10(B), the laminating roller 1 is lowered to contact
 one end of the lower disc-shaped substrate D1. At this time, although a
 part of the adhesive sheet body S is pressed against the end of the lower
 disc-shaped substrate D1, the centering shaft 3 completes its function and
 moves away from the lower disc-shaped substrate D1 since the positioning
 of the adhesive sheet body S relative to the lower disc-shaped substrate
 D1 is completed.
 As shown in FIG. 10(C), the laminating roller 1 rolls on the lower
 disc-shaped substrate D1 while pressing the adhesive sheet body S relative
 to the lower disc-shaped substrate D1. The adhesive agent S2 formed of the
 LP-shaped (doughnut shaped) sheet is applied from one end of the lower
 disc-shaped substrate D1 to the other end thereof in the manner that the
 bonded area between the adhesive sheet body S and the lower disc-shaped
 substrate D1 gradually enlarges in the direction from one end to the other
 end of the lower disc-shaped substrate D1.
 At this time, since the adhesive sheet body S is subsequently pressed
 against the lower disc-shaped substrate D1 so as to remove the air
 therebetween in an inclined state, air bubbles or the like do not enter
 between the adhesive agent S2 and the lower disc-shaped substrate D1 and
 puckering is not generated therebetween. As a result, the adhesive agent
 S2 is uniformly bonded onto the surface of the lower disc-shaped substrate
 D1.
 Referring now back to FIG. 7, the laminating roller 1 rises and returns to
 the original position as shown in dotted lines upon completion of the
 bonding of the adhesive sheet body S relative to the lower disc-shaped
 substrate D1. At this time, the adhesive agent S2 is in a state where it
 is bonded onto both the adhesive sheet body S and the lower disc-shaped
 substrate D1, namely, in a state where the adhesive agent S2 is bonded
 onto both the carrier S1 of the adhesive sheet body S and the surface of
 the lower disc-shaped substrate D1.
 Then, as shown in FIG. 8, a peeling member 4 that is positioned downstream
 relative to the holding table 2 traverses over the lower disc-shaped
 substrate D1 placed on the holding table 2. Since the viscosity of the
 adhesive agent S2 relative to the surface of the lower disc-shaped
 substrate D1 is greater than that relative to the carrier S1, the adhesive
 sheet body S and the adhesive agent S2 (precisely, the carrier S1 and the
 adhesive agent S2) are separated or peeled from one another when the
 peeling member 4 traverses. Since the lower disc-shaped substrate D1 is
 sucked and held by the holding table 2 as mentioned above, the peeling
 operation can be accurately performed.
 The adhesive sheet body S is peeled off from the lower disc-shaped
 substrate D1 (precisely, the adhesive agent S2 on the lower disc-shaped
 substrate) and becomes free upon completion of the traverse of the peeling
 member 4.
 The function of the peeling member 4 is now explained. The peeling member 4
 comprises a rotating base or member 41 (rotating on its own axis) and two
 support rods respectively fixed to the base 41, and it is reciprocally
 movable so as to move across (traverse) over the holding table 2.
 The two support rods comprise an angle restriction support rod 42 that is a
 fan-shaped rod body in cross section, and a leading support rod 43 that is
 a circular rod body having a small diameter. An arc of the fan-shaped rod
 body does not always conform to the shape formed in accordance with the
 length of the radius. The leading support rod 43 and the angle restriction
 support rod 42 are provided at positions remote from the center of the
 base 41 by given intervals.
 The angle restriction support rod 42 supports the adhesive sheet body S in
 a state where the adhesive sheet body S and the lower disc-shaped
 substrate D1 do not contact each other to keep a slight gap therebetween.
 The angle restriction support rod 42 has an acute angle portion 42A for
 peeling off the adhesive sheet body S while keeping an acute guiding angle
 .alpha., that is acute (90.degree. or less) relative to the lower
 disc-shaped substrate D1. The shape of the angle restriction support rod
 42 is not limited to that set forth above, if it has the acute angle
 portion 42A.
 To peel off the adhesive sheet body S from the lower disc-shaped substrate
 D1, the peeling member 4 is first rotated about 180.degree. in a state
 where the adhesive sheet body S is interposed between the angle
 restriction support rod 42 and the leading support rod 43 (see FIG.
 11(A)), thereby forming the adhesive sheet body S in an inverse Z-shape
 (see FIG. 11(B)). Preferably, the leading support rod 43 may be rotated to
 an extent to assume a position where the acute angle portion 42A of the
 angle restriction support 42 affords the guide angle .alpha.. At this
 time, the adhesive sheet body S is extended between the angle restriction
 support rod 42 and the leading support rod 43.
 Then, when the peeling member 4 is moved in parallel with the holding table
 or the lower disc-shaped substrate D1 so as to traverse over the holding
 table 2, the angle restriction support rod 42 of the peeling member 4
 traverses in the manner that it supports the adhesive sheet body S in a
 state where the adhesive sheet body S and the lower disc-shaped substrate
 D1 do not contact each other to keep a slight gap therebetween, and it is
 pulled up by the leading support rod 43. In this case, the adhesive sheet
 body S is peeled off from the surface of the lower disc-shaped substrate
 D1 at an acute angle relative to the lower disc-shaped substrate D1,
 namely, in a state where the former is positioned at an acute angle
 relative to the latter owing to an oblique plane 42U of the angle
 restriction support rod 42 (see FIG. 11(C)).
 The shape of the angle restriction support rod 42 is not limited to that
 set forth above, if it has the acute angle portion 42A, for example, FIG.
 12 shows a modified example of the angle restriction support rod 42.
 FIGS. 12(A) and 12(B) are views showing a state where the adhesive sheet
 body S is interposed between the angle restriction support rod 42 and the
 leading support rod 43, wherein FIG. 12(A) is a simplified front view and
 FIG. 12(B) is a simplified side view.
 FIGS. 13(A) and 13(B) are views showing a state where the peeling member 4
 is rotated so as to form the adhesive sheet body S in an inverse Z-shape
 wherein FIG. 13(A) is a simplified front view and FIG. 13(B) is a
 simplified side view.
 In this modified example, the angle restriction support rod 42 is
 triangular in cross section and has the acute angle portion 42A.
 If the guiding angle a of the adhesive sheet body S is acute, the adhesive
 agent S2 of the adhesive sheet body S is uniformly peeled off without
 adhering to the carrier S1 of the adhesive sheet body S.
 For example, if the guiding angle .alpha. is obtuse (90.degree. or more), a
 part of the adhesive agent S2 is frequently adhered to the carrier Si of
 the adhesive sheet body S.
 The inventor of the application experimentally confirmed that the peeling
 operation is smoothly performed.
 After the adhesive sheet body S is peeled off from the lower disc-shaped
 substrate D1, the holding table 2 installed on a rotary table T at the
 station X is quickly moved to the next station Y. That is, the holding
 table 2 at the first station X on which the adhesive agent S2 is bonded
 onto the lower disc-shaped substrate D1 is moved to the next station Y
 (see FIG. 14). Thereafter, the peeling member 4 returns to the original
 position shown in FIG. 2.
 The adhesive agent S2 is bonded onto the lower disc-shaped substrate D1 as
 described above, and hence the adhesive agent S2 is uniformly bonded onto
 the lower disc-shaped substrate D1 as shown in FIG. 15.
 In the next station Y, another upper disc-shaped substrate D2 is overlaid
 and placed on the lower disc-shaped substrate D1 onto which the adhesive
 agent S2 is bonded (see FIG. 16). Since the lower and upper disc-shaped
 substrates D1 and D2 that are overlaid on each other are not subjected to
 press application, they are not firmly laminated with each other.
 Accordingly, the holding table 2 is moved to a third station Z (see FIG.
 14) where two disc-shaped substrates D1 and D2 are subjected to press
 application so to be completely bonded onto each other.
 FIG. 17 shows a state where the lower disc-shaped substrate D1 and upper
 disc-shaped substrate D2 that are placed on the holding table 2 are
 pressed against each other by a pressing body 100 (in this case, the
 holding table 2 rises). The pressing body 100 used here is hemispherical
 and formed of a flexible material. When the thus overlaid two disc-shaped
 substrates D1 and D2 receive the pressing force between the pressing body
 100 and holding table 2, they are bonded strongly to each other.
 Accordingly, the laminating roller 1 can press the upper disc-shaped
 substrate D2 in the manner so that the contact portion (pressing portion)
 between itself and the lower disc-shaped substrate D1 increases gradually
 from the central portion to the outer portion (radially). As a result, air
 bubbles or the like are not contained between the lower disc-shaped
 substrate D1 and upper disc-shaped substrate D2. In the manner set forth
 above, the lower disc-shaped substrate D1 and upper disc-shaped substrate
 D2 are completely bonded onto each other, thereby forming a high quality
 optical disc (See FIG. 18).
 FIG. 19 is a block diagram showing main laminating steps 1 to 6 of the
 disc-shaped substrates.
 Although the present invention has been described with reference to the
 preferred embodiment, it is not limited to this embodiment but can be
 modified variously without departing from the spirit of the invention.
 Concrete means used to carry out the method of laminating disc-shaped
 substrates is not limited to those in the preferred embodiment as
 illustrated in the accompanying drawings.
 For example, the construction of the laminating roller used in the present
 invention may be of any type having no heating means therein. The moving
 direction of the laminating roller for pressing the adhesive sheet body
 onto the disc-shaped substrate may be left to right in addition to right
 to left shown in FIG. 6.
 Further, the peeling member may be of any means for holding and stretching
 the release paper in addition to the peeling member as disclosed in the
 preferred embodiment.
 With the arrangement of the method of laminating the disc-shaped substrates
 according to the present invention, the adhesive agent separated from the
 adhesive sheet body can be uniformly bonded onto the surface of the lower
 disc-shaped substrate without containing air bubbles or the like and
 puckering is not generated therebetween. Different from the conventional
 method using UV cured resin, the developing step of the adhesive agent and
 the irradiating step of UV are respectively dispensed with, thereby
 reducing the manufacturing steps of the storage disc.
 When two disc-shaped substrates are bonded to complete the optical disc,
 the thickness of the intermediate layer (adhesive agent layer) between two
 disc-shaped substrates can be easily changed by merely changing the
 thickness of the adhesive agent bonded onto the adhesive sheet body. It is
 possible to automate the bonding of the adhesive agent on one of
 disc-shaped substrates, thereby enabling very effective sequential
 laminating steps.
 Although a particular preferred embodiment of the invention has been
 disclosed in detail for illustrative purposes, it will be recognized that
 variations or modifications of the disclosed apparatus, including the
 rearrangement of parts, lie within the scope of the present invention.