Support Guide

Abstract

A support guide (11) for a transporting a flexible elongate substrate (13) is described. The support guide (11) comprises a support surface (17) and a fluid supply means for supplying a fluid between the support surface and the substrate (13). The fluid maintains the substrate spaced from the support surface (17) and the flow of the fluid between the substrate and the support surface causes a net longitudinal force on the substrate.

Description

This invention relates to a support guide for flexible elongate substrates. In particular, this invention relates to a support guide for flexible elongate substrates on which electronic devices are manufactured. In particular, the invention relates to a contact-less support guide for roll-to-roll manufacturing equipment, for example for use in continuous film processing

This invention also provides a transporting apparatus for transporting flexible elongate substrates (films) comprising at least one of the support guides and a manufacturing apparatus for manufacturing electronic devices comprising at least one of the support guides.

A large number of electronic devices are manufactured by sequentially depositing multiple layers of microscopically aligned structures on a substrate. For example, active matrix display devices are manufactured by depositing a plurality of microscopically patterned and aligned layers of conductors, semiconductors and insulators on a transparent substrate. Electronic devices manufactured in this way are susceptible to defects caused by foreign particles becoming deposited on the substrate during the manufacturing processes. The foreign particles become trapped between the layers and cause the electronic devices to malfunction. To minimise the number of defects caused by foreign particles, electronic devices are usually manufactured in a clean air environment known as a clean room.

Currently, most electronic devices manufactured by the above-described method are manufactured on rigid substrates such as glass panels or silicon wafers. However, there has recently been increased interest in manufacturing electronic devices on flexible substrates such as thin plastic films.

Flexible substrates enable the use of reel-to-reel transporting in which the substrate is unwound from an unprocessed reel, passed through a number of processing stages in which it is transported in different directions, and rewound onto a processed reel. The processing stages may, for example, include coating, printing, exposure, curing and etching stages. Reel-to-reel transporting is known as a low cost, mass production technology that may provide significant productivity and efficiency improvements in the manufacture of electronic devices. However, there are a number of problems associated with the application of conventional reel-to-reel transporting technology to the manufacture of electronic devices.

Firstly, conventional reel-to-reel transporting employs a plurality of rotatable rollers to transport the substrate. Although these rollers usually run on bearings, the rotational movement of the rollers and bearings is a source of foreign particle contamination in the clean air environment, and causes defects in the electronic devices being manufactured.

Secondly, in conventional reel-to-reel transporting, the surface of the substrate being transported comes into frequent contact with the rotatable rollers. The layers of microscopically patterned and aligned structures that are sequentially deposited on the substrate during manufacture of the electronic devices are highly sensitive to such contact, which may cause contamination or damage.

Thirdly, in conventional reel-to-reel transporting, most of the rollers are not driven. Instead, only the processed reel, onto which the processed substrate is wound, is driven. The tension in the substrate then pulls the substrate over the rollers in the processing stages, and unwinds the substrate from the unprocessed reel. Each of the processing stages and the unprocessed reel provide a resistance load on the substrate due to friction. The tension in the substrate consequently varies along its length, being greatest at the processed reel end and least at the unprocessed reel end. A certain amount of tension is also required to bend the substrate around each roller. The different tensions at each processing stage cause a different amount of stretch and creep in the substrate, and this limits the dimensional accuracy and resolution of the structures that are deposited on the substrate. Correct alignment of structures that are deposited in different processing stages is also complicated by the varying tension in the substrate. Air rollers are known, but they use a lot of air which in itself is highly disadvantageous in a clean room, invoke turbulence and are energy inefficient.

According to a first aspect of the invention, there is provided a support guide for a transporting a flexible elongate substrate, the support guide comprising a support surface and a fluid supply means for supplying a fluid between the support surface and the substrate, wherein the fluid maintains the substrate spaced from the support surface and the flow of the fluid between the substrate and the support surface causes a net longitudinal force on the substrate.

According to a second aspect of the invention, there is provided a support guide for a transporting a flexible elongate substrate, the support guide comprising a support surface and a fluid supply means for supplying a fluid between the support surface and the substrate, wherein an envelope of the support surface is substantially cylindrical, wherein a portion of the support surface around which the substrate passes is curved with a first constant radius of curvature, and a portion of the support surface at which the substrate enters or exits has radius of curvature which increases from the first constant radius of curvature to a second radius of curvature at which the support surface is substantially straight.

The support guide thus supports the substrate without touching it, with the substrate being supported by a cushion of fluid. The substrate may be supported by the kinetic energy of the fluid or by the static pressure of the fluid. By supporting the substrate in this way, the risk of contamination or damage caused by direct contact between the support guide and the substrate can be eliminated.

The support guide of the invention does not rotate and has no moving parts. Consequently, when used in reel-to-reel processing applied to the manufacture of electronic devices, it does not cause any particle contamination in the clean air environment, and defect rates may be minimised.

By providing a net longitudinal force on the substrate in accordance with the first aspect of the invention at each support guide in a reel-to-reel transporting system, the system may be arranged so that tension in the substrate is substantially constant throughout the system. This allows for improved dimensional accuracy and resolution of structures that are deposited on the substrate, and improved alignment of structures that are deposited in different processing stages. The net longitudinal force on the film is provided by shear stresses from the fluid flows.

By modified entry and exit regions in accordance with the second aspect of the invention, increased resistance to fluid flow can be provided, thereby reducing flow loss, and reducing contamination. In addition, by providing a support region which extend until the substrate is straight, laminar flow can be obtained at the entry and exit regions, which also reduces turbulence.

In a preferred embodiment, the support guide is further for changing the direction of travel of the substrate, and the support surface defines a substantially cylindrical surface around which the substrate travels. The substrate is held in mechanical equilibrium by the tension in the substrate, which provides a net force towards the support surface, and which is opposed to a force of the fluid from the fluid supply means.

The fluid supply means may comprise at least one fluid supply channel, or jet, formed in the support surface to be covered by the substrate. In this case, the axis of at least one of the fluid supply channels may be at an angle to the normal of the support surface. Fluid may then be directed towards the substrate at an angle to the normal of the support surface, thereby providing the net longitudinal force on the substrate.

The fluid supply means may alternatively or additionally comprise at least one opening formed in the support surface to be covered by the substrate. In this case, the support surface may define the wall of a chamber through which fluid is supplied, the fluid passing through the at least one opening. In embodiments, the area of the at least one opening formed in the support surface may be at least 67%, preferably at least 75%, and most preferably at least 80% of the area of the support surface that is to be covered by the substrate. The at least one opening formed in the support surface is preferably arranged so that it is to be overlapped by the substrate at its edges.

In a preferred embodiment, the support surface has a varying radius at substrate entry and exit regions. In particular, the radius may gradually increase in a direction away from a central region of the support surface. In this way, fluid flow at the substrate entry and exit regions, and thus fluid loss, may be minimised. Reducing fluid loss improves system efficiency and may help to maintain a clean air environment, particularly if the fluid is gaseous.

The substrate entry and exit regions of the support surface are preferably adapted to provide differential fluid flow (fluid loss) between the support surface and the substrate, thereby providing the net longitudinal force on the substrate. This may be achieved by providing differential spacing between the support surface and the substrate at the substrate entry and exit regions.

For example, there may be greater spacing between the support surface and the substrate at the substrate exit region than at the substrate entry region, thereby providing the net longitudinal force on the substrate in the forward direction. Alternatively, there may be greater spacing between the support surface and the substrate at the substrate entry region than at the substrate exit region, thereby providing the net longitudinal force on the substrate in the backwards direction.

The fluid supply means may be a pressurised gas supply means, such as a pressurised ionised air supply means, or alternatively a pressurised liquid supply means.

The invention also provides a transporting apparatus for transporting flexible elongate substrates and a manufacturing apparatus for manufacturing electronic devices, each comprising at least one of the support guides of the invention.

The invention also provided a method for transporting a flexible elongate substrate, the method comprising: passing the substrate over a support surface; and supplying a fluid between the support surface and the substrate, wherein the fluid maintains the substrate spaced from the support surface and the flow of the fluid between the substrate and the support surface causes a net longitudinal force on the substrate.

Throughout this description the terms “length” and “longitudinal” are used to refer to the direction of travel of the elongate substrate. The direction of travel of the substrate may change, for example, as it travels around the support guide. Consequently, the longitudinal direction may also vary.

Preferred embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

FIG. 1 is a diagram of a manufacturing apparatus that employs reel-to-reel technology to transport a substrate;

FIG. 2 is a diagram of a support guide according to the invention;

FIG. 3 is a diagram showing the geometry at the substrate entry and exit regions of the support guide;

FIG. 4 shows one example of support guide of the invention;

FIG. 5 is a diagram showing the longitudinal force on the substrate; and

FIGS. 6(a) and 6(b) are diagrams showing alternative support guides according to the invention.

The present invention relates to a support guide for use in reel-to-reel transporting. An apparatus for manufacturing electronic devices may employ reel-to-reel transporting, and such an apparatus 1 is schematically shown in FIG. 1. The apparatus comprises an unprocessed reel 3 from which an unprocessed flexible elongate substrate is unwound, and a processed reel 5 on which the processed substrate is wound. Between the reels 3, 5 are a number of processing stages 7. The processing stages each comprise a number of support guides over which the substrate is passed, and processing equipment (not shown) for processing the substrate. The processing equipment may, for example, include equipment for printing, exposure, curing or etching the substrate.

FIG. 2 shows a support guide 11 according to the invention. The processing stages 7 shown in FIG. 1 may comprise several of the support guides shown in FIG. 2. FIG. 2 also shows a flexible elongate substrate 13 to be supported by the support guide 11. The substrate may be a PET film having a width of approximately 1 meter, a thickness of approximately 200 microns, and a Young's modulus of approximately 5 GPa.

Referring to FIG. 2, the support guide 11 comprises a thin walled cylindrical vessel 15. The cylindrical vessel has a length of approximately 1 meter and a radius of approximately 5 centimeters. The outer surface of the cylindrical vessel 15 forms a support surface 17. In use, the substrate 13 travels around the support surface through an angle of approximately 180°.

FIG. 2 shows schematically a fluid supply means 18, which will comprise a pumped fluid source.

It can be shown that the tension required in the substrate to bend it around the support guide may be calculated according to the following equation: $\begin{array}{cc}F=\frac{wE{d}^3}{12R^2}& \mathrm{Equation}1\end{array}$ where w is the width of the substrate, E is the Young's modulus of the film, d is the thickness of the film and R is the radius of curvature of the substrate/support guide.

For the substrate and support guide described above, a tension of 1.3 N is required to bend the substrate around the support guide. For a processing stage comprising a large number of support guides, the total tension may be considerable.

The cylindrical vessel 15 of the support guide is supported at its ends by brackets (not shown). The supporting brackets prevent any rotational movement of the cylindrical vessel.

The cylindrical vessel 13 has an opening 19 formed in the support surface 17. The opening 19 is substantially rectangular in shape (although it could of course be different in shape) and is completely covered by the substrate 13 traveling around the support surface 17. The width of the opening 19 is smaller than the width of the substrate 11, so that the substrate 13 overlaps the edges of the opening 19. Similarly, the length of the opening 19 is smaller than the length of the portion of the substrate 13 around the support surface 17 (i.e. it extends around less than 180 degrees in this example), so that an entry and an exit region are defined at the lengthwise ends of the opening 19.

The cylindrical vessel 15 has a pressurized air inlet manifold (not shown) at one end. Pressurized air is supplied to the cylindrical chamber through the pressurized air inlet manifold. In use, the pressurized air flows through the opening 19 in the support surface 17 to provide a cushion of air between the support surface 17 and the substrate 13, thereby supporting the substrate 13.

The support surface 17 comprises a substrate entry region 21 and a substrate exit region 23. The substrate entry region 21 is the region of the support surface 17 at which the substrate 13 begins to travel around the support guide 11. The substrate exit region 23 is the region of the support surface 17 at which the substrate 13 begins to travel away from the support guide 11.

The outer envelope of the support surface 17 is substantially circular in cross section. However, according to the invention, the substrate entry and exit regions 21, 23 of the support surface 17 have adapted geometry, as shown in FIG. 3.

In particular, the substrate entry and exit regions 21, 23 of the support surface are extended in order to minimize the flow (loss) of pressurized air from the cylindrical vessel 15 between the support surface 17 and the substrate 13. This is achieved by providing a support surface 17 that closely follows the shape of the bent substrate at the substrate entry and exit regions 21, 23.

FIG. 3 shows a cross section of the substrate exit region 23 of the support surface 17 in detail. The arrow 29 indicates the direction of travel of the substrate 13. The solid line 25 represents the adapted geometry of the substrate exit region 23. It can be seen that the geometry of the support surface in this region diverges from the circular geometry 27 on which the central region of the support surface is based. Essentially, the radius R of the support surface increases at the exit region 23.

The adapted geometry 25 provides a narrow gap between the support surface and the substrate. Compared to an arrangement in which the support surface has wholly circular geometry, the length (in the substrate movement direction) of the gap, i.e. the longitudinal distance L from the edge 30 of opening 19 in the support surface to the point where the support surface and substrate diverge, is elongated, thereby minimizing airflow (air loss). The gap is preferably of a substantially constant height.

The entry and exit portions of the support surface start with the same curvature R as the main envelope of the support surface, but the curvature then increases to infinity so that the support surface is locally straight at the entry and exit region. The elongated entry and exit regions give increased resistance to fluid flow and also provide laminar flow.

As well as minimizing airflow, the geometry of the support surface 17 at the substrate entry and exit regions is preferably adapted to provide a net longitudinal force on the substrate 13 traveling around the support guide, thereby propelling the substrate around the support guide. This is achieved by adapting the geometry of the support surface 17 to provide differential airflow (air loss) at the substrate entry and exit regions 21, 23, with the result that a differential force is exerted on the substrate. In particular, the geometry at the substrate entry and exit regions 21, 23 is adapted so that, in use, the spacing between the support surface 17 and the substrate 13 is larger at the substrate exit region than at the substrate entry region.

It is possible to provide different spacing at the entry and exit regions by taking advantage of the fact that the substrate seeks a mechanical equilibrium. This mechanical equilibrium will correspond to the air pressure decreasing linearly over the length of the gaps at the entry and exit regions. This defines the local curvature and shape of the substrate.

FIG. 4 shows an example of the cross sectional shape of one example of support. As shown, the entry region 21 is relatively thin and short, and the exit region 23 is relatively wide and long. The entry and exit regions are both sufficiently long to provide laminar flow.

FIG. 5 shows a diagram of the space, or gap, defined by the support surface 17 and the substrate 13 at the substrate entry or exit region 21, 23. Air flows from an area of high pressure 33 adjacent the opening 19 to an area of ambient pressure 35 where the substrate diverges from the support surface. The shear force supplied to the support surface or the substrate is given by the following equation: 2F_w=ph   Equation 2 where F_w is the shear force, p is the pressure difference and h is the height of the gap.

It can be seen from equation 2 that the shear force is proportional to the height of the gap. Consequently, by providing gaps of different height at the substrate entry and exit regions, 21, 23, a net longitudinal force on the substrate 13 can be provided. This force may be in the direction of travel, thereby reducing tension in the substrate, or alternatively against the direction of travel, thereby increasing tension. The latter arrangement may be advantageous for processing stages where a high substrate tension is required.

The shear force supplied to the support surface or the substrate is not dependent on the length of the gap between the support surface and the substrate. Accordingly, the geometry of the support surface may be adapted further so that the gap having the greater height is also longer. The greater length reduces airflow (air loss), and goes some way to compensating for the increased air loss caused by the gap having a greater height.

FIG. 6(a) shows an alternative support guide according to the invention. This support guide is similar to that shown in FIG. 2. However, instead of the fluid supply means comprising an opening formed in the support surface, the fluid supply means comprises a plurality of pressurized air channels, or jets 31, formed into the support surface 17. The jets 31 supply pressurized air between the support surface 17 and the substrate 13. This pressurized air maintains the substrate 13 spaced from the support surface 17, either through the kinetic energy of the air or through its static pressure. The jets are also positioned in the support surface so that their axis is at an angle to the normal of the support surface. The pressurized air from the jets travels towards the substrate 13 and impacts the substrate at an angle to its normal, thereby causing a net longitudinal force on the substrate. This longitudinal force may either be in the direction of travel of the substrate or against the direction of travel of the substrate. The geometry of the support surface 17 at the substrate entry and exit regions may also be adapted as described above with reference to the support guide shown in FIG. 2.

Other support guides according to the invention may provide a flat support surface, with the substrate traveling across the support surface in a straight line. In this case, it is not possible to use tension in the substrate to maintain the substrate in mechanical equilibrium. Accordingly, support surfaces 17 may be provided on either side of the substrate 13, as shown in FIG. 6(b). In this case, the fluid from the fluid supply means of each support surface 17 provides an equal and opposite force on the substrate 17 in a direction normal to the substrate surface, although additional measures may be required to ensure stability of the substrate. Various modifications may be made to the support guides according to the invention. For example, the support guides may be adapted for use with pressurized liquids, such as solvents, instead of pressurized air. Such support guides may be used in, for example, etching process equipment. Also, the fluid supply means may comprise a combination of openings and channels, or jets.

A small number of specific examples have been given above, but it will be apparent to those skilled in the art that the invention can be adapted in numerous ways. For example, the roller of the invention can be designed for redirecting a web through any desired angle for example as shown schematically in FIG. 1, not just 180 degrees as in the example above. The various features described above may be used in different combinations to those shown.

Claims

1. A support guide (11) for a transporting a flexible elongate substrate (13), the support guide comprising a support surface (17) and a fluid supply means (18) for supplying a fluid between the support surface and the substrate, wherein the fluid maintains the substrate spaced from the support surface and the flow of the fluid between the substrate and the support surface causes a net longitudinal force on the substrate.

2. A support guide (11) for a transporting a flexible elongate substrate (13), the support guide comprising a support surface (17) and a fluid supply means (18) for supplying a fluid between the support surface and the substrate, wherein an envelope of the support surface is substantially cylindrical, wherein a portion of the support surface around which the substrate passes is curved with a first constant radius of curvature (R), and a portion (21,23) of the support surface at which the substrate enters or exits has radius of curvature which increases from the first constant radius of curvature (R) to a second radius of curvature at which the support surface is substantially straight.

3. The support guide as claimed in claim 2, wherein the portions (21,23) of the support surface at which the substrate enters and exits each have the radius of curvature which increases from the first constant radius of curvature to the second radius of curvature.

4. The support guide as claimed in claim 3, wherein the lengths of the portions (21,23) of the support surface of varying curvature at which the substrate enters and exits are different.

5. The support guide as claimed in claim 1, wherein the fluid maintains the substrate spaced from the support surface (17) and the flow of the fluid between the substrate and the support surface causes a net longitudinal force on the substrate.

6. The support guide of claim 5, further for changing the direction of travel of the substrate, wherein part of the support surface (17) defines a substantially cylindrical surface around which the substrate travels.

7. The support guide of claim 6, wherein the fluid supply means comprises at least one fluid supply channel (31) formed in the support surface to be covered by the substrate.

8. The support guide of claim 7, wherein the axis of at least one of the fluid supply channels is at an angle to the normal of the support surface, thereby providing the net longitudinal force on the substrate.

9. The support guide of claim 6, wherein the fluid supply means comprises at least one opening (19) formed in the support surface to be covered by the substrate, the support surface (17) defining the wall of a chamber through which fluid is supplied.

10. The support guide of claim 9, wherein the area of the at least one opening (19) formed in the support surface is at least 75% of the area of the support surface to be covered by the substrate (13).

11. The support guide of claim 9, wherein the at least one opening (19) formed in the support surface is arranged to be overlapped by the substrate at its edges.

12. The support guide of claim 6, wherein the support surface (17) is adapted to provide differential fluid flow between the support surface and the substrate at the substrate entry and exit regions (21,23), thereby providing a net longitudinal force on the substrate.

13. The support guide of claim 12, wherein the support surface is adapted to provide the differential fluid flow by providing differential spacing between the support surface (17) and the substrate (13) at the substrate entry and exit regions (21,23).

14. The support guide of claim 13, wherein the support surface is adapted to provide greater spacing between the support surface and the substrate at the substrate exit region (23) than at the substrate entry region (21), thereby providing a net longitudinal force on the substrate in the forward direction.

15. The support guide of claim 13, wherein the support surface is adapted to provide greater spacing between the support surface and the substrate at the substrate entry region (21) than at the substrate exit region (23), thereby providing the net longitudinal force on the substrate in the backwards direction.

16. The support guide of claim 12, wherein the support entry or exit region that is adapted to provide the greater spacing is longer.

17. The support guide of claim 1, wherein the fluid supply means (18) is a pressurised gas supply means.

18. The support guide of claim 1, wherein the fluid supply means (18) is a pressurised liquid supply means.

19. The support guide of claim 1, for transporting a flexible elongate substrate (13) on which electronic devices are manufactured.

20. A transporting apparatus (1) for transporting flexible elongate substrates, the transporting apparatus comprising at least one of the support guides (11) of claim 1.

21. A manufacturing apparatus for manufacturing electronic devices, the manufacturing apparatus comprising the transporting apparatus (1) of claim 20.

22. A method for transporting a flexible elongate substrate, the method comprising: passing the substrate (13) over a support surface (17); and supplying a fluid between the support surface (17) and the substrate (13), wherein the fluid maintains the substrate (13) spaced from the support surface (17) and the flow of the fluid between the substrate and the support surface causes a net longitudinal force on the substrate.

23. The method of claim 22, further for changing the direction of travel of the substrate, wherein the support surface (17) defines a substantially cylindrical surface around which the substrate travels.

24. The method of claim 23, wherein the fluid is supplied through at least one fluid supply channel (31) formed in the support surface and covered by the substrate.

25. The method of claim 24, wherein the axis of at least one of the fluid supply channels (31) is at an angle to the normal of the support surface, thereby providing the net longitudinal force on the substrate.

26. The method of claim 23, wherein the fluid is supplied through at least one opening (19) formed in the support surface and covered by the substrate, the support surface defining the wall of a chamber through which fluid is supplied.

27. The method of claim 23, further comprising providing differential fluid flow between the support surface and the substrate at substrate entry and exit regions (21,23), thereby providing the net longitudinal force on the substrate.

28. The method of claim 22, wherein the fluid is a pressurised gas.

29. The method of claim 22, wherein the fluid is a pressurised liquid.

30. The method of claim 22, for transporting a flexible elongate substrate on which electronic devices are manufactured.