DEVICE FOR APPLYING A LIQUID LAYER TO A DISK-SHAPED RECORD CARRIER

Abstract: A device for applying a liquid layer to a disk-shaped record carrier (26), which device is provided with a holder (25) rotatable about a center line, for operatively supporting the record carrier, a first annular discharge channel (28) extending around the center line, and a second discharge channel (33) extending around the first annular discharge channel. The annular discharge channels situated under the holder are provided with a first and a second axially extending outer wall, respectively (31, 34), which outer walls extend axially beyond the holder. At least the second outer wall (35) is provided with a deflecting wall directed towards the center line, while the deflecting wall connected with the second outer wall extends radially over the first outer wall, with an annular gap situated between the first outer wall and the deflecting wall.

Description: Title: Device for applying a liquid layer to a disk-shaped record carrier. This invention relates to a device for applying a liquid layer to a disk-shaped recor carrier, which device is provided with a holder rotatable about a center line, for operatively supporting the record carrier, a first annular discharge channel extending around the center line, and a second discharge channel extending around the first annular discharge channel, which annular discharge channels situated under the holder are provided with a first and a second axially extending outer wall, respectively, which outer walls extend axially beyond the holder, while at least the second outer wall is provided with a deflecting wall directed towards the center line. Such a device is used, for instance, for applying a liquid dye to an optical record carrier. The dye is provided adjacent the center line or in a spiral on the record carrier, whereafter the record carrier is rotated about the center line at a relatively high speed, as a result of which the dye spreads over the record carrier. This method, also referred to as spin coating, is known per se and leads to a relatively good distribution of the dye across the record carrier. In the device known per se, the first outer wall of the first annular discharge channel serves to catch the liquid substance that is slung from the record carrier during rotation. Due to the rotation of the record carrier, at least at the top of the record carrier an air flow is created, which is directed from the center fine towards the outer edge of the record carrier. This air flow entrains relatively small droplets of liquid substance. This air flow is largely removed through the second discharge channel. In the known device, it is moreover possible that at the underside of the record carrier, under excess pressure, a gas such as, for instance, compressed air, is supplied to avoid the possibility of liquid substance ending up on the underside of the record carrier and to prevent the edge of the record carrier from being bent down as a result of rotation. This compressed air, too, is largely carried off via the second annular discharge channel. In the known device, adjacent the edges of the record carrier, an undefined turbulent air stream is created in which droplets can be trapped and be spread. These droplets can end up on the record carrier and thus cause errors in the liquid layer to be cured. Moreover, the droplets may fly out of the device and foul the surroundings. The invention contemplates a device whereby the liquid layer can be spread over the record carrier in a controlled manner. In the device according to the invention, this object is achieved in that the deflecting wall connected with the second outer wall extends radially over the first outer wall, with an annular gap situated between the first outer wall and the deflecting wall. By virtue of the deflecting wall extending over the first outer wall, an improved air flow is obtained, whereby air flowing away from the record carrier is received in the annular gap and is discharged. In this way, there is substantially no uncontrolled air flow with droplets present therein towards the record carrier and towards surroundings outside the device, so that contamination of the record carrier or the surroundings and loss of the liquid substance are avoided. One embodiment of the device according to the invention is characterized in that the deflecting wall, on a side remote from the second outer wall, is deflected in the direction of the holder. By virtue of the deflecting wall deflected in the direction of the holder, a relatively small opening is obtained between the deflecting wall and the record carrier, through which a controlled air flow will take place. Another embodiment of the device according to the invention is characterized in that the deflecting wall is located in radial direction at 0-50 mm, preferably 3-10 mm from the edge of the record carrier operatively disposed on the holder. It has been found that given such a radial distance, a desired air flow with a resultant desired distribution of the Hquid layer is obtained. A further embodiment of the device according to the invention is characterized in that the second outer wall is detachably positionable over the holder, while the deflecting wall extends in radial direction over the record carrier operatively disposed on the holder. If the second outer wall extends over the record carrier, the second outer wall must be detachable to enable the record carrier to be taken into and out of the holder. A still further embodiment of the device according to the invention is characterized in that in axial direction, an end of the deflecting wall remote from the second outer wall is located closer to the holder than an end of the first outer wall. Thus, air is first guided in the direction of the first outer wall, and only after passing the deflecting wall is it guided into the gap between the first outer wall and the deflecting wall. This results in a uniform, substantially radial air flow at the edge of the record carrier. Yet a further embodiment of the device according to the invention is characterized in that at least one of the outer walls is provided, on a side proximal to the holder, with a lining which is anti-adhesive to the Hquid layer to be operatively applied to the record carrier. By providing the walls with an anti-adhesive lining, no adhesion of the liquid substance to these walls occurs. Such adhesion would adversely affect the air flow present in the discharge channels. Moreover, it involves the risk that relatively old, liquid substance adhered to the walls comes off as a result of the air flow and would undesirably end up on the record carrier. As no adhesion occurs in the device according to the invention, this risk is avoided in a relatively simple manner. A still further embodiment of the device according to the invention is characterized in that at least the first annular discharge channel includes an obtuse angle with the center Hne. As the annular discharge channel includes an obtuse angle with the center Hne, a sloping discharge channel is obtained, so that the Hquid substance present in the discharge channel can flow relatively fast to the lowest portion of the discharge channel. What is prevented in this way is that the liquid substance might dry out, harden or crystallize in the discharge channel. The invention will be further elucidated with reference to the drawing, wherein: Fig. 1 shows a cross section of a device according to the prior art, and Fig. 2 shows a cross section of a device according to the invention. In the figures, corresponding parts are provided with a corresponding reference numeral. Fig. 1 shows a device 1 according to the prior art which is provided with a frame 2 in which a shaft 4 rotatable about a center line 3 is bearing-mounted. The shaft 4 is provided with a holder (not shown) on which a record carrier 5 is disposed. The frame 2 is provided with a number of air supply ducts 6 which terminate in a s ace 7 located between the record carrier 5 and the frame 2. The frame 2 is provided with a first annular discharge channel 8 and a second annular discharge channel 9 extending around channel 8. The first discharge channel 8 is bounded by a first outer wall 10. The second discharge channel 9 is bounded by the outer wall 10 as well as by a second outer wall 11. Between the wall 10 and the holder 5, a gap 12 is located, while between the walls 10 and 11 a gap 13 is located. The device 1 is further provided with a supply device with which a liquid substance for forming the Hquid layer can be appHed in a narrow strip adjacent the shaft 4 onto the record carrier. Such a supply device is known, for instance, from European patent EP-Bl-0,594,252 and will therefore not be elucidated further. After the liquid substance has been provided on the record carrier, the shaft 4 is rotated about the center line 3, as a result of which the Hquid substance will spread over the rotating record carrier 5. During rotation, via the opening 6 a gas under excess pressure, such as, for instance, compressed air, is passed into the space 7, which will flow out of the space 7 in the direction indicated by arrow PI. This air flow prevents the possibility of liquid substance ending up on the underside of the record carrier 5 and/or holder. Also, through rotation, an air suction action is created adjacent the center Hne 3, such air being subsequently guided over the surface of the record carrier in the direction indicated by arrow P2. Adjacent the edges of the record carrier and/or holder, a turbulent air flow P3 is created due to the air flows Pi and P2, the shape of the gaps 12, 13 and possibly the Hquid substance already adhering to the walls 10, 11. Through this turbulent air flow P3, droplets of liquid substance are led back to the record carrier, so that an uneven distribution of the Hquid substance on the record carrier is obtained. Moreover, due to the turbulent air flow P3, droplets are also slung out of the device 1, which leads to fouling of the surroundings. Also, there is a risk that despite the air flow PI, droplets of the liquid substance nonetheless end up against the underside of the record carrier, which is also undesired. Fig. 2 shows a device 21 according to the invention which is provided with a frame 22 in which a shaft 24 rotating about a center line 23 is bearing-mounted. Mounted on the shaft 24 is a holder 25 for a record carrier 26. The frame 22 is provided with an annular discharge channel 28 which includes an obtuse angle with the center Hne 23, as a result of which the portion of the discharge channel 28 located near the left-hand side of Fig. 2 is located higher than the portion located adjacent the right-hand side in Fig. 2. Thus, a sloping discharge channel is obtained. Adjacent the lowermost portion of the discharge channel 28, an outflow channel 29 is provided, via which liquid substance present in the discharge channel 28 can be discharged. The bottom 30 of the discharge channel 28 tapers, so that the Hquid substance simply flows to the lowest point of the discharge channel 28 and then through the sloping discharge channel ends up in the discharge opening 29. The discharge channel 28 is bounded on an outer side by an outer waH 31 which, adjacent a side remote from the frame 22, is provided with an edge 32 bent towards the center line 23. Situated around the first annular discharge channel 28 is a second annular discharge channel 33 which, on a side proximal to the center line 23, is bounded by the wall 31, while on a side remote from the center line 23 it is bounded by an outer wall 34. The outer wall 34, on a side remote from the frame 22, is provided with a deflecting wall 35 extending towards the center line 23. The deflecting wall 35, on a side remote from the second outer wall 34, is provided with a wall part 36 deflected in the direction of the frame 22. Situated between the wall parts 32 and 36 is an annular gap 37. The wall part 36 includes an angle with the horizontal plane. The angle α is preferably between 45 and 90°. Situated between the waU part 36 and the frame 22 is an annular gap 38. In operation, the wall part 36 is situated a distance d from the record carrier 26. The distance d is preferably between 0 and 50 mm and in particular between 3 and 10 mm. The distance h in axial direction between the record carrier 26 and the wall 36 is preferably between —10 mm and 10 mm. The dimensions d, α and h depend on the diameter and thickness of the record carrier. The operation of the device 21 is as foUows. In a manner already described above, liquid substance is provided adjacent the center line 23 in a ring or in a spiral on the record carrier 26, after which the record carrier 26, with the aid of the holder 25, is rotated about the center line 23 in the direction indicated by arrow P4. During rotation, via openings 39 in the frame 22, compressed air is passed into the space 40 situated between the record carrier 26 and the frame 22, which air will flow out of the space 40 in the direction indicated by arrow P5. Through the rotation, at the same time an air suction action in the direction indicated by arrow P6 is created. This air is subsequently guided over the surface of the record carrier 26 in radial direction away from the center line 23. Through the shape of the wall part 36 and the distance thereof to the record carrier 26, there arises adjacent the edges of the record carrier 26 a controlled air flow which extends virtually completely in radial direction. This air flow, together with the air flow P5, is guided through the gap 37 in the direction indicated by arrow P7 to the second annular discharge channel 33. The liquid substance flowing off the record carrier 26 will, under the influence of gravity and due to the velocity resulting from rotation, will end up substantially completely in the first annular discharge channel 28, whenee it is discharged via the discharge opening 29. Due to the controlled air flow adjacent the edges of the record carrier 26, no droplets of the Hquid substance will end up on the upper side or underside of the record carrier 26 or be slung out of the device 21. Moreover, in this manner, the amount of required air is relatively small, so that the air to be discharged from the second annular discharge channel 33 is relatively hmited. Since the air is led directly to the second discharge channel 33, substantially no air flow arises in the first discharge channel 28, so that the liquid present therein substantially does not dry out. As a result, the liquid can be discharged via the discharge opening 29 relatively well and be reused. Also, through the controlled air flow, a stable positioning of the record carrier on the holder is obtained, which has a positive effect on the spread of the Hquid substance over the record carrier as weU as on the removal of the record carrier from the holder. It is also possible to make the deflecting wall 35 of detachable design, such that the deflecting wall 35 is not fitted over the record carrier 26 until after the record carrier 26 has been placed on the holder 25, and is removed before the record carrier 26 is removed from the holder 25. In such a case, the deflecting wall can also extend over the record carrier 26 (d<0, for instance d = -50 mm). The device can be rendered suitable for record carriers having various diameters in the order of from 3 to 30 cm.

Claims: CLAIMS 1. A device for applying a Hquid layer to a disk-shaped record carrier, which device is provided with a holder rotatable about a center line, for operatively supporting the record carrier, a first annular discharge channel extending around the center line, and a second discharge channel extending around the first annular discharge channel, which annular discharge channels situated under the holder are provided with a first and a second axially extending outer wall, respectively, which outer walls extend axially beyond the holder, while at least the second outer wall is provided with a deflecting wall directed towards the center line, characterized in that the deflecting waH connected with the second outer wall extends radially over the first outer wall, with an annular gap situated between the first outer wall and the deflecting wall. 2. A device according to claim 1, characterized in that the deflecting wall, on a side remote from the second outer wall, is deflected in the direction of the holder. 3. A device according to claim 1 or 2, characterized in that the deflecting wall is located in radial direction at 0-50 mm, preferably 3-10 mm, from the edge of the record carrier operatively disposed on the holder. 4. A device according to any one of the preceding claims, characterized in that the deflecting wall is located, in axial direction, at -10 to 10 mm from the edge of the record carrier operatively disposed on the holder. 5. A device according to claim 1 or 2, characterized in that the second outer wall is detachably positionable over the holder, while the deflecting wall extends in radial direction over the record carrier operatively disposed on the holder. 6. A device according to any one of the preceding claims, characterized in that, in axial direction, an end of the deflecting wall remote from the second outer wall is located closer to the holder than an end of the first outer waU. 7. A device according to any one of the preceding claims, characterized in that at least one of the outer walls is provided, on a side proximal to the holder, with a lining which is anti-adhesive to the liquid layer to be operatively applied to the record carrier. 8. A device according to any one of the preceding claims, characterized in that at least the first annular discharge channel includes an obtuse angle with the center line. 9. A device according to claim 8, characterized in that the annular discharge channel is provided with a gutter-shaped bottom.

Inventors: TEN THIJE JORIS JOHAN, TEN THIJE, JORIS, JOHAN
Applicants: OTB GROUP BV, TEN THIJE JORIS JOHAN, OTB GROUP B.V., TEN THIJE, JORIS, JOHAN
Application year: 2001
Main classification: G11B7
IPC codes: B05C11, G11B7