CA2286839C

CA2286839C - Method and device for gluing two substrates

Info

Publication number: CA2286839C
Application number: CA002286839A
Authority: CA
Inventors: Klaus Weber; Ulrich Speer
Original assignee: Steag Hamatech AG
Current assignee: Steag Hamatech AG
Priority date: 1997-04-30
Filing date: 1998-04-02
Publication date: 2005-01-25
Anticipated expiration: 2018-04-02
Also published as: HK1040668B; JP2001052383A; DK0992341T3; DK0979169T3; ES2169514T3; JP2000513654A; WO1998049010A2; CN1087223C; CN1316330A; DE59802343D1; EP0992341A3; WO1998049010A3; HK1040668A1; EP0979169B1; EP0992341B1; HK1027532A1; EP0992341A2; DE59806283D1; ATE210017T1; ATE227646T1

Abstract

The invention relates to a method for gluing two substrates (3, 6) to a substrate disk (23), wherein an adhesive is applied to the surface of the first substrate (3, 6) which is to be glued and the surface o f a second substrate (6, 3) which is to be glued is placed on top of the first substrate (3, 6). The inventive method provides for particularl y good, homogenous and rapid gluing of the substrates without inclusion of air and requires only simple means since the substrates (3, 6) are rotated around their centre axis so that the adhesive can be ejected. The invention also relates to devices for carrying out the above method.

Description

METHOD AND DEVICE FOR GLUING TWO SUBSTRATES
The invention relates to a method and a device for gluing two substrates to a substrate disc wherein an adhesive is applied to the surface of a first substrate to be glued and a second substrate is placed with its surface to be glued onto the first substrate wherein the substrates are spun about their center axis for removing excess adhesive.
Methods and devices of this kind are known from DE 40 41 199 A1, Derwent abstract 94-246139/30, and EP 0 744 739 A1. In order to manufacture, for example, so-called digital video discs (also known as DVD). Digital video discs are comprised of two substrates or partial substrates on which the digital video information is stored on one surface and which are then glued together with their faces that have no information stored thereon. For connecting the two substrates to a substrate disc, for example, a digital video disc, very precisely operating devices are required because the substrates not only must be precisely stacked above on another, but the adhesive action must be uniform over the entire disc surface, without air inclusions and without having different adhesive layer thickness.
Only in this way an error-free substrate disc will be produced.
Furthermore, the conventional devices for gluing two substrates are modified page very complex with regard to their construction and require a large space.
From US 4,990,208 a method and a device are.known for producing optical storage media of two substrates, in which during the curing process by UV radiation a quartz glass plate is placed onto the substrate for exerting a pressure. A curing process employed for the manufacture of optical storage media is furthermore known from US 5,779,855. In this method, the optical storage medium is placed during curing between two plates transparent for UV radiation. Patent Abstracts of Japan Vol. 018, No. 502 (M-1676), 20 September 1994, and JP 06170855A (Ricoh Co. Ltd), 21 June 1994,. a device for curing a plastic film by ultraviolet radiation is known, in which for heat dissipation nitrogen is supplied laterally and removed through a central opening in the upward direction.
The printed document Patent Abstracts of Japan Vol. 012, No. 267 (M-722), 26 July 1988 and JP 63 049424 A (Sony Corp), 2 March 1988, and JP 63 049424 A (Sony Corp), 2 March 1988, discloses a method in which discs to be glued together are bent relative to straight lines staggered by 90° to one another so that initially contact is made only at one location.

modified page It is an object of the invention to provide a method and a device for gluing two substrates which allows for a reliable, uniform gluing of the substrates, results in good substrates discs with minimal reject rate and is still simple to execute and simple in its construction while allowing for high productivity.
According to the present invention, there is provided a method for gluing two substrates (3,6) to form a substrate disc (23), said method comprising the steps of:
- applying an adhesive onto a surface of a first substrate (3) to be glued;
- placing a second substrate (6) with its surface to be glued onto the first substrate, whereby, during placing said second substrate (6) onto said first substrate, at least one of the substrates (3, 6) is bent in its edge area away from the other substrate (6,3) by controllably moving an inner gripper (41) and an outer gripper (42) in an axial direction of the substrates and relative to one another;
wherein the inner gripper (41) and/or the outer gripper (42) engages the substrate (3,6) via circumferential distributed suction cups (46,48) and wherein the substrate will first contact at an inner area and will be rolled form said inner area outwardly, and rotating the substrates (3,6) about their central axes for centrifugally removing the adhesive.
According to another aspect of the present invention, there is also provided a device for gluing two substrates (3,6) to a substrate disc (23), said device comprising:
at least one gluing station (10) having at least one adhesive application device (15,16) and at least one adhesive centrifugal device (11,12);
a bending device (40) for bending at least one of the substrates (3,6) to be glued at its edge area away from the other substrate (6,3);
said bending device (40) comprising an inner gripper (41) engaging the inner area of the substrates (3,6) to be bent and an outer gripper (42) engaging the outer area of the substrate (3,6) to be bent, the inner and outer grippers (41,42) being movable relative to each other.
The aforementioned object is inventively solved by a method of the aforementioned kind in which at least one of the surfaces of the substrate to be glued, preferably the surface of the substrate to be glued onto which the actual adhesive is applied, is preferably provided with a precoating. In this manner, the gliding action for the primary adhesive, respectively, the primary lacquer is substantially improved so that the adhesive distribution over the entire surface is not only faster but also more uniform. The precoating allows to very uniformly distribute the adhesive between the substrates to be glued in a simple manner over the entire surface to be glued and to prevent inclusions such as air bubbles etc. The substrates accordingly adhere over the entire substrate surface fixedly to one another, and the substrate discs have a uniform thickness over the entire surface area.
3a The adhesive is preferably as so-called ultraviolet synthetic lacquer which can be rapidly cured by 3b radiation treatment with ultraviolet light and which allows for excellent adhesion between the two substrates. Preferably, the adhesive is applied as an annular strip onto the surface of a substrate to be glued which is then distributed by spinning over the entire substrate surface.
Preferably, an adjustable, precise pressure is exerted onto the second substrate after having been placed onto the first substrate which improves the uniform distribution of the adhesive between the substrates. The upper substrate to be placed onto the lower one is preferably placed by a single arm handling device with precision drive in a finely adjusted movement precisely centrally onto the first substrate, and the required pressure is applied.
The aforementioned object is inventively also solved in that at least one of the substrates, upon placement onto the other substrate, is bent in the edge area away from the other substrate by having an inner gripper and an outer gripper move relative to one another for bending at.least one of the substrates. By doing so, air bubbles or other inclusions in the adhesive layer or in the adhesive can be reliably and safely removed. When bending the substrate to be stacked on top, it will first contact at the center, and only after being released completely will be "rolled" from the central inner area outwardly, so that the adhesive ring is forced and rolled from the modified page inner area to the outer area toward the substrate edges so that air inclusions and bubbles are removed.
A further embodiment of the invention resided in that the edges of the substrates to be glued are cleaned after removal of the adhesive by spinning force. Due to the cleaning process a reliable sealing of the substrate disc edge is, additionally, provided which contributes to an increased quality of the finished product. For cleaning the substrate disc edges it is suggested to provide an adhesive suction device which is pressed spring-elastically onto the edge of the substrate disc. For increasing the productivity, this cleaning of the substrate edge is carried out -directly after the centrifugal removal of the adhesive without requiring an additional position change of the substrate disc or the separate cleaning station for the edge cleaning process.
The glued substrate discs are preferably dried in an adhesive drier, and, when using UV lacquer, in a UV
drier, so that the manufacturing process is substantially shortened. Such an adhesive drier can, for example, be embodied as a device, as known in the art. The substrate discs can be guided, for example, with rotating movement underneath a UV lamp.

One solution of the aforementioned object is especially advantageous when a quartz or glass plate is placed onto the substrate disc during the drying process so that with its own weight during drying it presses onto the substrate disc and keeps it planar.
1 o Preferably, afterthe drying process during which it has been heated, the quartz or glass plate is cooled before it is placed onto the next substrate disc. Cooling of the quartz or glass plate takes place according to one embodiment with ionized air whereby the glass plates are moved by a changing system respectively-between the cooling process and the placement step onto the substrate disc. It is also advantageous to perform drying in a nitrogen atmosphere which contributes to a faster and final drying of the substrate discs.
2 o After the gluing and drying process, the substrate discs are tested in an inspection station, for example, by a scanner with regard to flaws and, depending on the measured results, are released or separated as rejects.
The inventive method is controlled and/or visually represented by a data processing program which is run, for example, on a personal computer.

The aforementioned object is furthermore solved by a device of the aforementioned kind which comprises a coating or predispensing device which, in the direction of movement of the manufacturing process, is arranged upstream of the gluing station, respectively, upstream of the adhesive application device. The precoating device provides at least one of the surfaces of the substrates to be glued, preferably the surface onto which the other substrate is to be placed, with a prelacquering which improves the gliding action of the adhesive or of the primary lacquer and thus results in a more uniform and faster distribution of the primary lacquer during the spinning process. With the corresponding substrate manipulation device, especially when provided with a precision drive, a substrate is precisely centrally positioned and is subjected to a precisely adjustable pressure applied to the substrate to be placed onto the first one so that a precise adjustable pressure is applied to the two substrates to thereby improve or increase the distribution and the speed during the adhesive process. The advantages to be derived from the afore disclosed method can also be achieved with the inventive device, i.e., to apply the adhesive quickly, reliably, and uniformly onto the surfaces of the substrates to be glued without having to content with inclusions, for example, modified page air bubbles, between the substrates which would result in non-uniform thickness of the substrate discs and in to substrate discs with reduced quality, respectively, in high reject rates.
According to a further inventive principle for solving the object, a bending device is suggested for bending at least one of the substrates to be glued at its edges away from the other substrate., wherein an inner gripper engaging the inner area of the substrate to be bent and an outer gripper engaging the outer area of the substrate to be bent are movable relative to one another in the axial direction. In this manner, an even more improved prevention of air bubbles or other inclusions in the adhesive layer. is achieved because the two substrates to be glued will contact one another beginning at the inner portion and continuing outwardly so that bubbles or air inclusions will be pressed outwardly and removed during this rolling process, and they especially provide for bending of the lower substrate relative to the upper substrate. For the engagement of the inner andlor outer grippers suction cups or suction cup groups are advantageously provided. The outer gripper can have them arranged also over the entire circumference.
A further embodiment of the invention is a device provided with a cleaning device for cleaning the substrate disc edges. The s modified page cleaning device effects at the same time a sealing of the substrate disc edge and thus a quality improvement of the resulting product.
The cleaning device has preferably an adhesive suction device which, according to a further embodiment of the invention, can be pressed spring-elastically onto the substrate disc edge. The cleaning device is preferably part of an adhesive centrifugation device so that the substrate discs must not be transported to a corresponding station for the cleaning process but instead can be cleaned at their edges directly after completion of the spinning process in a respectively determined position.
The adhesive centrifugation device, respectively, the substrate disc edge cleaning device is preferably provided downstream thereof with a drying station which, upon use of adhesives or lacquer that by UV
embodied as an ultraviolet drier.
For improving the quality of the glued discs and the productivity, the drying station preferably has a quartz or glass plate placement device. The quartz or glass plate can be moved back and forth by a sliding or changing system between the substrate disc 8a modified page area and a cooling area.
The drying station has preferably UV lamps wherein advantageously reflective surfaces for the lamp radiation are provided in the area of the substrate edges. Accordingly, a drying and curing of the adhesive at the edge and rim area of the substrate disc is possibly quickly and reliably. The drying station has arranged downstream thereof, according to a further embodiment of the inventive device, an inspection station in which, as a function of the measured results of the testing process, the finished substrates are released or rejected.
The inventive device is especially very. inexpensive and ,because of its compact construction, can be realized with minimal dimensions and preferably with a protective cabin with doors and windows. With a corresponding so-called flow box a substantially laminar flow and a clean room-similar environment for the manufacture of the substrate discs can be produced in the cabin.
The inventive device can be used as an individual machine or can be integrated into a manufacturing line.
Substrate discs in the context of the present invention are not only digital video discs but also, in general, discs which are formed by gluing at least two partial discs.

The invention will be disclosed in the following with the aid of preferred embodiments in reference to the figures.
It is shown in:
Fig. 1 a schematic representation of the inventive device in a plan view, and Fig. 2 a schematic representation of an embodiment for the bending device.
In the embodiment of Fig. 1 for an inventive device, the method sequence is carried out in method steps from the right to the left. In a first supply station 1 the first substrates 3 are provided by a supply table 2. In similar manner, a second supply station 4 with a second supply table 5 delivers second substrates 6 which are to be glued with their surface free of information onto the corresponding surface of the first substrate 3. With an overhead handling device 7 the first substrates 3 are removed from the supply station 1, are rotated by 180°, so that the side to be glued free of information faces upwardly and is placed onto a preset location at the receiving turntable 8. The handling device 9 transports the second substrate 6 with the side to be glued facing downwardly, i.e., without rotation of the substrate 6, onto a respective location of the turntable 8. The receiving turntable 8 has a special division, i.e., a two position ~

division by which confusion in regard to the two substrates 3 and 6 to be glued can be avoided even after power failure.
The turntable 8 supplies the first and second substrates 3 or 6 to a gluing station 10 which comprises to adhesive centrifugal devices or process pots 11 and 12 and a respective adhesive applicator or a dispenser 13, 14, a respective substrate disc edge cleaning device 15, 16, as well as a precoating device or predispensing unit 17 and respective handling devices 18, 19.
The method at the adhesive station 10 is carried out as follows. Firstly, the first substrates 3 resting on the receiving turntable 8 and having surfaces to be glued facing upwardly, thus representing the lower substrates during the gluing process, are positioned on a table 20 of the precoating device 17 by the handling device 19 in a certain turntable position and are there precoated by the coating device 21 in order to provide the optimal gliding properties for the actual adhesive or the primary lacquer to be applied in a subsequent method step. The precoated first substrates 3 are then returned onto the receiving turntable 8.
The single arm handling device 18 with precision drive then places the first substrates 3 taken from the receiving turntable 8 into the two adhesive spinning devices 11 or 12. In a subsequent method step, an adhesive is applied with the adhesive application device or the main dispensing unit 13, 14, for example, in the form of a UV synthetic lacquer approximately in the shape of a ring.
Subsequently, the second upper substrate 6 is removed from the turntable 8 and is placed precisely centrally onto the first lower substrate 3. The plates of the adhesive centrifugal devices 11, 12 are then rotated so that the adhesive between the substrates 3 and 6 is centrifugally removed.
In the following it will be explained in more detail with the aid of Fig. 2 how the upper or lower substrate 3 or 6 can be slightly bent so that the removal of air inclusions or air bubbles occurring during application of the adhesive or adhesive ring is facilitated and the adhesive distribution is additionally improved and accelerated. Via the precision drive .of the single arm handling device 18 not only the velocity with which the second upper substrate 6 is placed but also a precise pressure with which the substrate 6 is placed onto the adhesive ring can be controlled as well as the deceleration with which the substrate edge of the bent substrate is released.
After centrifugally removing the adhesive, the substrate edge cleaning device 15 or 16 will be operated by which in the represented embodiment an adhesive suction device is spring ' CA 02286839 1999-10-15 elastically pressed onto the edge of the substrate disc to be glued.
The edge cleaning action that is achieved therewith also achieves additionally a sealing action of the substrate disc edge so that the product quality is improved.
The glued substrate discs 23 are then removed by a single arm handling device 24 from the adhesive station 10 and are placed onto a further turntable 25 of a drying station 26 in which the substrate discs 23 are guided underneath a UV drier 27 in a cycled manner and are irradiated with UV lamps so as to be dried. The UV
drier 27 is preferably provided with two to four 4 HPA lamps in one or two stations.
The drying station 26 has furthermore a glass plate handling device 28 in the form of a pusher or changing device with which the quartz or glass plates 29 are placed onto the substrate discs 23 to be dried. The plates 29 rest with their own weight on the substrate discs 23. The glass plates 29 are cooled, after removal from the substrate discs 23 by the glass plate handling device 28, with ionized air in order to be subsequently placed onto further substrate discs 23.
The dried substrate discs 23 are supplied by a three-arm handling device 30 from the turntable 25 of the drying station 26 to ~

a receiving station 31 in which an inspection station 34 is positioned which inspects the finished substrates 23 for quality assurance and, as a function of the result of this control, respectively, of its measured values, will control the three-arm handling device 30 such that the flawless substrate discs 23 are placed onto a further turntable 35 and the flawed substrate discs 23 are placed onto a reject spindle 36.
Due to its compact construction, the inventive device has small dimensions with a length of 2,900 millimeter, a width of 1,250 mm, and a height of 1,900 millimeter, which allow for flexible use of the device even in smallest spaces as individual_machines as well as integrated in manufacturing lines.
Fig. 2 shows in a schematic and partially cross-sectional representation an embodiment for a bending device 40 for bending one of the substrates to be glued or both of the substrates to be glued at the respective edge areas away from the respective other _ substrate. The bending device 40 has an inner gripper 41 and an outer gripper 42 which are movable relative to one another by a hydraulic cylinder 43. The inner gripper 41 has a suction cup 43 which is connected by a respective vacuum connector 44 to a vacuum source and engages the substrate 3 or 6 in order to w14 ~

transport it by a lifting and lowering cylinder 45.
The outer gripper 42 has multiple suction cups 4fi distributed about the outer gripper circumference which engage the substrates 3 or 6 at their outer areas for bending them.
The bending occurs when the oufier gripper 42 with the cylinder 43 is lifted relative to the inner gripper 41.
The invention has been explained with the aid of preferred embodiments. However, to a person skilled in the art further numerous designs and developments are known without deviating from the gist of the invention. The inventive device was described in connection with the manufacture of digital .video discs. The principles of the invention however can also be applied to methods and devices for producing other products in which two substrates are to be glued to one another.

Claims

WHAT IS CLAIMED IS:

1. A method for gluing two substrates (3,6) to form a substrate disc (23), said method comprising the steps of:
- applying an adhesive onto a surface of a first substrate (3) to be glued;
- placing a second substrate (6) with its surface to be glued onto the first substrate, whereby, during placing said second substrate (6) onto said first substrate, at least one of the substrates (3, 6) is bent in its edge area away from the other substrate (6,3) by controllably moving an inner gripper (41) and an outer gripper (42) in an axial direction of the substrates and relative to one another;
wherein the inner gripper (41) and/or the outer gripper (42) engages the substrate (3,6) via circumferential distributed suction cups (46,48) and wherein the substrate will first contact at an inner area and will be rolled form said inner area outwardly, and rotating the substrates (3,6) about their central axes for centrifugally removing the adhesive.

2. A method according to claim 1, further comprising the steps of:
- placing a quartz or glass plate (29) onto the substrate disc and drying the substrate disc; and - cooling the quartz or glass plate (29) after the drying process before placing the quartz or glass plate onto the next substrate disc (23).

3. A method according to claim 2, wherein the quartz or glass plate is cooled with ionized air.

4. A method according to claim 2, wherein drying is carried out in a nitrogen atmosphere.

5. A method according to claim 1, further comprising the step of cleaning the edge of the glued substrate discs (23) after centrifugal removal of the adhesive.

6. A method according to claim 5, wherein edge cleaning is carried out in a station (10) in which gluing of the substrates (3,6) is performed.

7. A method according to claim 5, wherein a suction device for removing an adhesive is pressed elastically onto the edges of the glued substrate disc (23).

8. A method according to claim 1, further comprising the step of inspecting the glued and dried substrate discs (23) for flaws.

9. A method according to claim 1, said method comprising the step of:
- providing a surface of a first substrate (3) to be glued with a pre-coating prior to the application of the adhesive.

10. A method according to claim 9, wherein the adhesive is an ultraviolet synthetic lacquer.

11. A method according to claim 9, wherein the adhesive is applied as an adhesive ring onto the precoated surface of the first substrate (3).

12. A method according to claim 1, further comprising the step of exerting an adjustable pressure onto the second substrate (6).

13. A device for gluing two substrates (3,6) to a substrate disc (23), said device comprising:
at least one gluing station (10) having at least one adhesive application device (15,16) and at least one adhesive centrifugal device (11,12);
a bending device (40) for bending at least one of the substrates (3,6) to be glued at its edge area away from the other substrate (6,3);
said bending device (40) comprising an inner gripper (41) engaging the inner area of the substrates (3,6) to be bent and an outer gripper (42) engaging the outer area of the substrate (3,6) to be bent, the inner and outer grippers (41,42) being movable relative to each other.

14. A device according to claim 13, wherein said inner gripper (41) and said outer gripper (42) are moveable relative to one another in an axial direction of the substrates (3,6).

15. A device according to claim 13, wherein said inner gripper (41) and said outer gripper (42) have suction cups (43,46).

16. A device according to claim 13, said device comprising:
a drying device (26) with a quartz or glass plate placing device (28), wherein said drying device (26) has a quartz or a glass plate cooling device.

17. A device according to claim 16, wherein a cooling medium used in said cooling device is ionized air.

18. A device according to claim 16, wherein said drying station (26) comprises ultraviolet lamps and reflective areas for the lamp radiation provided in area of the substrate edges.

19. A device according to claim 13, further comprising an inspection station (34) arranged downstream of said drying station (26).

20. A device according to claim 13, further comprising a substrate disc edge cleaning device (15,16).

21. A device according to claim 20, wherein said substrate disc edge cleaning device (15,16) comprises a suction device for removing the adhesive from the edges.

22. A device according to claim 20, wherein said substrate disc edge cleaning device (15,16) is pressed spring-elastically onto the substrate disc edge.