GB2555463A

GB2555463A - Apparatus and method for applying a coating to gemstones

Info

Publication number: GB2555463A
Application number: GB1618323.8A
Authority: GB
Inventors: Stanley Rose Peter; Anthony Harries Trevor; James Francis Evans David; Daws Christopher
Original assignee: De Beers UK Ltd
Current assignee: De Beers UK Ltd
Priority date: 2016-10-31
Filing date: 2016-10-31
Publication date: 2018-05-02
Also published as: WO2018078380A1; GB201618323D0

Abstract

An apparatus 10 for applying a coating to gemstones comprises a chuck 14 configured to retain a plurality of gemstones laterally displaced from and disposed around a rotation axis. There is a dispense aperture located in a dispense arm 16 configured to dispense a quantity of liquid onto a facet of each gemstone. A motor is configured to selectively spin the chuck about the rotation axis so that the gemstones orbit the rotation axis, such that the dispensed liquid forms a coating on the facet of each gemstone. A method of applying a coating to gemstones is also provided.

Description

(54) Title of the Invention: Apparatus and method for applying a coating to gemstones Abstract Title: Apparatus and method for applying a coating to gemstones (57) An apparatus 10 for applying a coating to gemstones comprises a chuck 14 configured to retain a plurality of gemstones laterally displaced from and disposed around a rotation axis. There is a dispense aperture located in a dispense arm 16 configured to dispense a quantity of liquid onto a facet of each gemstone. A motor is configured to selectively spin the chuck about the rotation axis so that the gemstones orbit the rotation axis, such that the dispensed liquid forms a coating on the facet of each gemstone. A method of applying a coating to gemstones is also provided.

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APPARATUS AND METHOD FOR APPLYING A COATING TO GEMSTONES

Technical Field

The present invention relates to an apparatus and a method for applying a coating to gemstones. Specifically, but not exclusively, the invention relates to an apparatus and a method for applying a coating to diamonds.

Background

Forming a mark, for example a very small “micro mark”, on a gemstone such as a diamond gemstone or an industrial diamond is well known. Such marks may comprise a brand name or logo, a serial number, certification mark and the like. The mark may be visible to the naked eye or may only be visible using a suitable magnifying viewer, such as a loupe.

Marks may be formed in a number of ways. One method, known as microlithography, is to coat a facet of the gemstone to be marked with a layer of photoresist. The selected facet may comprise the table facet of the gemstone. The cleaned and dried stone is typically mounted in a dop or holder, as described in WO02/066262A2 and as illustrated in Figure 1. In this example, the dop 1 comprises a base 4 and inwardly inclined sidewalls 5. The gemstone 7 is mounted within the dop 1 using a holding material 3, such as indium, so that its table facet 7a is coplanar with a reference surface 6.

A layer of resist, such as Microposit S1813 G2, is applied evenly to the facet to be marked, usually by spinning the mounted stone about its own central rotation axis to provide a centrifugal force. The stone, or the coated facet of the stone, is then baked. After baking, the resist is exposed to electromagnetic radiation of a suitable wavelength, typically using a mask which corresponds to the mark to be formed. The mask allows some areas of the resist to be exposed, while other areas remain unexposed. A post-exposure bake may optionally be carried out.

Following selective exposure, the facet of the gemstone is introduced to a developer solution, such as Microposit MF-319. The developer may be applied while spinning the stone. The exposed and unexposed areas of the layer of resist develop at different rates, forming a pattern in the photoresist layer corresponding to the desired mark. After washing the stone, the mark is transferred to the facet of the stone itself, for example by etching. Once the mark has been applied to the facet, the gemstone is released from the dop.

Such a process for forming a mark on a gemstone is described in GB2389340B.

Summary

According to a first aspect, there is provided an apparatus for applying a coating to gemstones, comprising a chuck configured to retain a plurality of gemstones laterally displaced from and disposed around a rotation axis, a dispense aperture configured to dispense a quantity of liquid onto a facet of each gemstone and a motor configured to selectively spin the chuck about the rotation axis so that the gemstones orbit the rotation axis, such that the dispensed liquid forms a coating on the facet of each gemstone.

The dispense aperture may be configured to dispense a sufficient quantity of liquid to cover the facet of each gemstone, and the motor may be configured to spin the chuck such that excess liquid is removed from the facet of each gemstone.

The chuck may be configured to retain a plurality of mounted gemstones equiangularly distributed around an outer circumference of the chuck.

The apparatus may be configured to retain each gemstone mounted in a dop. The chuck may comprise a plurality of equiangularly distributed slots for receiving and retaining a respective plurality of dops.

The chuck may be configured to retain mounted gemstones in a substantially flat configuration during spinning.

The dispense aperture may be located in a dispense arm configured to be selectively locatable in a first position over the chuck. The apparatus may further comprise a stop element, and the dispense arm may be configured to be selectively locatable in a second position, adjacent and in contact with the stop element. The dispense arm may comprise a second aperture, each aperture configured to dispense a different liquid.

The liquid may be one of: a photoresist, a developer solution and a wash solution.

The apparatus may further comprise a circular bowl, and the chuck may be located within said bowl.

The apparatus may further comprise a controller, and the motor may be configured to be programmable using the controller. The controller may be configured to generate an index pulse once per revolution of the motor to allow tracking of the motor’s position. The controller may be configured to spin the motor until the index pulse is located and then to move the motor by a predetermined offset.

The chuck may be configured to retain six dops spaced at sixty degree intervals around an outer circumference of the chuck.

A radius of spinning may be approximately 2.5 cm.

According to a second aspect, there is provided a method of applying a coating to gemstones. The method comprises retaining in a chuck a plurality of gemstones laterally displaced from and disposed around a rotation axis, dispensing a quantity of liquid onto a facet of each gemstone and selectively spinning the chuck about the rotation axis so that the gemstones orbit the rotation axis and the dispensed liquid forms a coating on the facet of each gemstone.

The method may further comprise dispensing a sufficient quantity of liquid to cover the facet of each gemstone; and spinning the chuck such that excess liquid is removed from the facet of each gemstone.

The method may further comprise retaining, in the chuck, a plurality of mounted gemstones equiangularly distributed around an outer circumference of the chuck.

The method may further comprise retaining each gemstone mounted in a dop.

The method may further comprise receiving and retaining, in the chuck, a respective plurality of dops in a plurality of equiangularly distributed slots.

The method may further comprise retaining, in the chuck, mounted gemstones in a substantially flat configuration during spinning.

The dispense aperture may be located in a dispense arm, and the method may further comprise configuring the dispense arm to be selectively locatable in a first position over the chuck. The method may further comprise configuring the dispense arm to be selectively locatable in a second position, adjacent and in contact with a stop element. The dispense arm may comprise a second aperture, and the method may further comprise configuring each aperture to dispense a different liquid.

The method may further comprise locating the chuck within a bowl.

The method may further comprise configuring the motor to be programmable using a controller. The method may further comprise configuring the controller to generate an index pulse once per revolution of the motor to allow tracking of the motor’s position. The method may further comprise configuring the controller to spin the motor until the index pulse is located and then to move the motor by a predetermined offset.

The method may further comprise retaining six dops spaced at sixty degree intervals around an outer circumference of the chuck.

A radius of spinning may be approximately 2.5 cm.

Brief Description of the Drawings

Figure 1 illustrates a known method of mounting a gemstone on a dop;

Figure 2a is a perspective view of a first embodiment of an apparatus for applying a coating to gemstones;

Figure 2b is a cross section of an exemplary dop for use with the apparatus of Figure 2a;

Figure 3 is a top down view of the apparatus of Figure 2a;

Figures 4a and 4b are first and second side views of the apparatus of Figure 2a;

Figure 5 is a front view of the apparatus of Figure 2a;

Figure 6 is a schematic illustration of a section of the apparatus of Figure 2a, during operation;

Figures 7a and 7b are schematic illustrations of a known method of spinning a dop and a method of spinning a dop in the apparatus of Figure 2a;

Figure 8 is a perspective view of a second embodiment of an apparatus for applying a coating to gemstones;

Figure 9 is a top down view of the apparatus of Figure 8;

Figures 10a and 10b are first and second side views of the apparatus of Figure 8;

Figure 11 is a front view of the apparatus of Figure 8; and

Figure 12 is a flow chart illustrating a method of applying a coating to gemstones.

Detailed Description

An apparatus 10, 100 for applying a coating to gemstones, such as diamonds, will now be described with reference to Figures 2 to 11. Embodiments of the apparatus 10 enable a coating of photoresist to be applied to the gemstones, while other embodiments of the apparatus 100 enable a coating of developer to be applied. In further embodiments, the apparatus 100 may alternatively or additionally enable the gemstones to be washed using a wash liquid. For simplicity, all embodiments are shown without dops and gemstones in situ.

As described herein, the term coating may refer to a permanent, semi-permanent or temporary coating. The coating may cover the whole of the object to which it is applied, or one or more regions of the object. For example, a coating may be applied to one or more facets of a gemstone, such as a diamond.

Figures 2 to 7 illustrate a first embodiment of an apparatus 10 for applying a coating to a plurality of gemstones, which in this example comprise diamonds. The diamonds may be gemstone quality or industrial diamonds. The gemstones are cut and polished. In this embodiment, the coating to be applied to the gemstones comprises photoresist, such as Microposit S1813 G2.

In this embodiment, the photoresist is applied to a table facet of each gemstone, as part of a process of forming a mark on the table facet. The process may be microlithography, as described above, and the photoresist may be applied prior to the step of baking and exposure. Each gemstone is therefore mounted on its respective dop table up, by methods which are well-known in the art, for example, as described with reference to Figure 1. However, it will be appreciated that other facets of a gemstone may be coated with photoresist, by mounting the gemstone with the appropriate facet facing up.

The apparatus 10 of Figures 2 to 7 comprises a motor, a housing 12, a dop holder 14, a dispense arm 16, a bowl 18 and a controller (not shown here). The dop holder 14 is configured to spin about its central rotation axis A upon operation of the motor. An upper surface or lid of the housing 12a may be configured to retain the bowl 18 and dop holder 14, whilst allowing insertion and removal of one or more dops. To this end, the upper surface 12a may be lockable.

The dop holder 14 (or chuck) is located within the bowl 18, and on a shaft of the motor, which is located in an interior of the housing 12. The holder comprises a substantially circular platform that is configured to hold a plurality of dops, each dop able to hold a single mounted gemstone. In this example, the dop holder 14 is configured to hold six individual dops, equiangularly distributed around the outer circumference of the dop holder 14. In other words, the dop holder 14 can hold six dops spaced at sixty degree intervals. In this example, the diameter of the dop holder is approximately 5 cm. The dop holder 14 may be removable from the motor shaft in order to facilitate cleaning and maintenance.

Each dop is removably mounted on the dop holder 14 in a substantially flat orientation. A dop is located into a central position of the dop holder 14 and then slid sideways into one of six receiving slots, or dop positions 20, in the dop holder 14. A suitable dop 101 supporting a gemstone 7a is shown in Figure 2b. The dop 101 has external sidewalls 102 incorporating a lip 102 which co-operates with the receiving slot to ensure that each dop 101 is held securely in the correct orientation in the dop holder 14. Two dops 101 are shown in place in the dop holder 14 in Figure 3. Once slotted into position, each dop 101 is held in place during operation of the apparatus 10 by the forces generated by the spinning motion of the dop holder 14, such that each dop 101 spins around a central axis A of the dop holder 14 and does not spin around its own central axis. It will be appreciated that once a dop 101 has been positioned into a respective receiving slot 20 the table facet of the gemstone is substantially horizontal i.e. parallel to an upper surface of the dop holder 14.

The dispense arm 16 is located above an upper rim of the bowl 18, such that a dispensing aperture 22 in the underside of the arm can be selectively located vertically above the position of each dop 101, when mounted in the dop holder 14. In this example, the dispense arm 16 is moveable such that it can be swung out in order to be located over the dops’ 101 positions using control signals sent via a solenoid arm 24, or the like, attached to the housing 12 of the apparatus 10. The dop positions 20 are then located directly underneath the dispensing aperture 22 by selective rotation of the dop holder 14 using the motor. Once application of resist is complete the dispense arm 16 can be swung back again to avoid dripping onto the dop holder 14. Alternatively, the dispense arm 16 may be fixed.

The motor is configured to be controlled by and programmable via the controller and comprises an encoder (not shown here) which enables the motor to use an index pulse. This pulse is generated once per revolution of the motor and allows tracking of the motor’s position, and hence the position of the dop holder 14. Upon activation, the motor spins in order to locate the index pulse and then moves by a predetermined offset to rotate the dop holder 14 so that a first dop position 20 is directly vertically located under the aperture 22 of the dispense arm 16. The motor is configured to wait for a predetermined length of time before moving the dop holder 14 by sixty degrees so that a second dop position 20 is directly vertically located under the aperture 22 of the dispense arm 16. This process is repeated until all six dops 101 have been so located. The motor is then configured to operate continuously in order to spin the dop holder 14 about the central rotation axis A of the dop holder 14.

The bowl 18 in which the dop holder 14 is located is configured to collect excess resist coating. The excess coating may be subsequently poured out of the bowl 18 or may be funnelled into a drain at the base of the bowl 18. In this way, excess photoresist may be collected and disposed of, or recycled and re-used. The dop holder 14 is therefore configured to be located towards a base of the bowl 18, so that excess coating may be deposited on the inner surface of the bowl 18. The bowl 18 may optionally be removable from the housing 12 to facilitate cleaning, and an upper surface of the housing 12a may be hinged in order to enable such removal.

The apparatus 10 may further comprise one or more actuators 26, such as buttons, switches, levers and the like, configured to enable a user to selectively operate the apparatus 10. In the example of Figures 2 to 6, the apparatus 10 is provided with a button 26 to activate and a button 26 to deactivate the apparatus 10.

In use, one or more dops 101, up to a maximum of six, are mounted onto the dop holder 14. Figure 3 illustrates the situation where two dops 101 have been mounted and four slots are still empty. Each dop 101 holds a gemstone, mounted table up. Upon activation of the apparatus 10, the motor locates the index pulse, as described above, and then rotates the dop holder 14 so that each dop 101 and its respective gemstone are located in turn underneath the aperture 22 of the dispense arm 16. As each dop 101 is moved into position, the dispense arm 16 dispenses a pre-determined quantity of photoresist onto the table facet of the stone directly below, via the dispensing aperture 22. The quantity of resist applied is controlled by a third party instrument, such as a Hamilton Dispense System Microlab TM 500 series, which is connected to the aperture 22 of the dispense arm 16 via suitable tubing. The quantity of resist dispensed may be in excess of the quantity required to form a coating on the facet of the gemstone and in practice one drop will completely cover the facet so that the subsequent spinning will cause resist to be forced off the facet, leaving behind an even coating.

The length of time for which the motor remains stationary while the photoresist is dispensed, and the volume of resist which is dispensed, may be varied depending upon the application. For example, larger stones may require a greater volume of resist which may take longer to dispense, and hence the motor and the dop holder 14 will accordingly remain stationary underneath the dispense arm aperture 22 for a longer period of time. However, typically the motor remains stationary for a period of around 3 seconds while resist is dispensed, and in practice the volume of resist should be the same for all stones (since it is always more than enough to cover the whole facet).

Once each dop 101 has been located underneath the dispensing aperture 22 of the dispense arm 16 and the table surface of each gemstone has received a suitable volume or deposit of resist, the motor is configured to operate continuously for a predetermined period of time. For example, the motor may spin at around 4000 rpm for a period of around 5 seconds, during which time the dop holder 14 and mounted dops 101 will be spun continuously around a central, common rotation axis A of the dop holder 14, as illustrated in Figure 6. In this example, the radius of spinning i.e. the distance between the rotation axis A and the edge of the dop holder, is approximately 2.5 cm: in general, a radius of a few cm (for example in a range of about 2 cm to about 5 cm) will usually be appropriate. It will be understood that the speed of the motor and/or the spinning period may be modified to suit the specific application. However, the inventors have determined that a spin speed of around 4000 rpm is appropriate for all of the sizes of stone that may be coated using this apparatus 10. Although the direction of spinning is shown as clockwise in Figure 6 it will be understood that the motor may alternatively or additionally be configured to spin the dop holder 14 in an anticlockwise direction.

During continuous spinning, excess photoresist is removed from the table facet of each gemstone by a combination of the centrifugal force produced by the spinning motion of the dop holder 14 and the linear speed of the dop holder 14, so that a substantially uniform layer or coating of photoresist of between about 800 nm and about 1.2 pm thick remains on the table facet. Typically, the coating may vary in thickness across the table facet by around 0.4 pm. This combination of forces is more efficient at removing excess photoresist than the simple centrifugal force supplied by known spinning apparatus, in which a single stone held on a dop is spun about the stone’s own central axis.

As illustrated in Figure 7a, spinning a single dop 1 about its own rotation axis results in a deposit of coating (for example, photoresist) being spun out in all directions. Where a dop is spun about the central rotation axis A of a dop holder 14, as shown in Figure 7b, the combination of forces on the deposit of coating D causes the excess coating to arc out at an angle. This causes an effect not unlike a windscreen wiper across the facet of the stone, as a result of which a thinner, more accurate coating of, for example, photoresist, may be achieved.

The apparatus 10 described above enables a uniform coating of photoresist to be applied to up to six gemstones, within the same time required to apply a coating to just one gemstone i.e. the period of continuous spinning is the same regardless of the number of gemstones being spun. This provides greater efficiency, particularly in a microlithography process having a number of steps, where slower steps may cause bottlenecks. The cost of coating per stone is also reduced.

Figures 8 to 11 illustrate a second embodiment of an apparatus 100 for applying a coating to a plurality of gemstones, which in this example comprise diamonds. The diamonds may be gemstone quality or industrial diamonds. Typically, the gemstones will be cut and polished. In this embodiment, the coating to be applied to the gemstones comprises a developer solution, such as Microposit MF-319. The developer solution is applied to the table facet of each gemstone, as part of a process of forming a mark on the table facet. The process may be microlithography, as described above, and the developer solution may be applied to develop a mark on the gemstone surface, in a step subsequent to optical exposure and to the application of the photoresist coating described with reference to Figure 2 to 7. Each gemstone is therefore mounted on its respective dop table up.

In this embodiment, the apparatus 100 carries out the additional step of cleaning the table surface of the gemstones to be marked using a wash liquid or solution, such as dimethyl sulphoxide analar. The wash solution may be applied before or after the application of the developer solution, or both. Alternatively or additionally, the wash solution may be applied at the same time as the developer solution. The wash solution may be applied prior to the transfer of the mark onto the facet of the gemstone, which may be carried out by etching, for example. At whatever stage it is applied, the purpose of the wash solution is to remove unwanted debris or coatings (such as resist or developer) from the facet to be marked. In some embodiments water may be used in place of (or as well as) other wash liquids.

The apparatus 100 of Figures 8 to 11 is substantially similar to the apparatus 10 of Figures 2 to 7 above in that it comprises a motor, a housing 112, a dop holder 114, a dispense arm 116, a bowl 118 and a controller. The dop holder 114 is configured to spin about its central rotation axis A upon operation of the motor.

The dop holder 114, or chuck, may be identical to the dop holder 14 of the apparatus 10 of Figures 2 to 7, holding up to six dops (not shown here), each supporting a gemstone. It will be appreciated that the dop holder 14 of Figures 2 to 7 may also be used as the dop holder 114 of Figures 8 to 11, for example, where it is desired to transfer the dops as a group.

In order to apply a wash solution in addition to the developer solution, as shown in Figures 8 to 11, the dispense arm 116 comprises two dispensing apertures 122a, 122b, each of which is connected by suitable tubing to a different peristaltic pump. The pumps are connected in turn to the dispense arm 116 and may be controlled by a solenoid arm 124, or the like. The first dispensing aperture 122a may supply a deposit or a squirt of developer solution, and the second dispensing aperture 122b may supply a deposit or a squirt of wash solution. Each dispensing aperture 122a, 122b is angled towards the other aperture 122a, 122b at an angle of around 45 degrees, such that each of the first and second dispensing apertures 122a, 122b points at the same location when the end of the arm is located vertically above the position of each dop, when mounted in the dop holder 114.

In this example, the dispense arm 116 is configured to swing out over the dop holder 114 until the dispensing apertures 122a, 122b are located over a first dop position 120, and to remain so located until each dop in turn has been located directly underneath the dispensing apertures 122a, 122b, using the motor, in order to receive a deposit of developer and/or wash solution. The dispense arm 116 is then configured to swing back in towards the housing 112 until the dispense arm 116 makes contact with a stop element 128. The stop element 128 is located on an upper surface 112a of the housing 112, adjacent the rim of the bowl 118, as best illustrated in Figures 8 and 9. Contact between the dispense arm 116 and the stop element 128 causes any excess droplets of developer and/or wash solution to be removed from the dispensing apertures 122a, 122b of the dispense arm 116 and to fall into a drip tray 132, located adjacent the stop element 128.

The motor is substantially identical to the motor of the apparatus 10 of Figures 2 to 7, in that each dop may be sequentially located directly vertically underneath the appropriate dispensing aperture 122a, 122b. The motor is also configured to operate continuously in order to spin the dop holder 114 about its central axis A.

The bowl 118 is substantially identical to the bowl 18 of the apparatus 10 of Figures 2 to 7, and is configured to collect excess developer solution and excess wash solution, one or both of which may be collected and disposed of or recycled and re-used. A bottom region of the bowl 118 is provided with a drain 130 through which excess solution may flow. The bowl 118 may be removable and may optionally be replaced after application of the developer solution and before application of the wash solution.

The apparatus 100 may further comprise one or more actuators 126, as described with reference to the apparatus 10 of Figures 2 to 7 above.

In use, one or more dops, up to a maximum of six, are mounted onto the dop holder 114. Each dop holds a gemstone, mounted table up. The dops, once mounted, are in a substantially flat configuration. Upon activation of the apparatus 100, the motor rotates the dop holder 114 so that each dop and its respective gemstone are located in turn underneath the apertures 122a, 122b of the dispense arm 116, which is connected to a pump for dispensing developer and/or wash solution. As each dop is moved into position, the dispense arm 116 dispenses a pre-determined quantity of developer and/or wash solution onto the table facet of the stone directly below, via the relevant dispensing aperture 122a, 122b. Approximately 10 ml of developer solution and a similar amount of wash solution is typically dispensed per gemstone, per application.

It will be appreciated that the motor may also be configured to spin the dop holder 114 continuously during application of the developer solution or the wash solution, or both. In this case, the respective solution may be continuously dispensed by the dispense arm 116 until each dop has been sufficiently coated, or until the pre-determined amount has been dispensed. Developer and/or wash solution may be deposited onto the gemstones as well as in between the gemstones during this process. However, this may result in the overall volume of developer and/or wash solution being reduced.

In one specific example, a deposit of developer solution is applied, followed by a deposit of wash solution. In this example, the apparatus 100 may be configured to proceed as follows:

• Start • Spin up to 400rpm o Apply developer for 4 seconds at 400 rpm o Turn off application of developer • Stop for 4 seconds • Spin up to 400rpm o Apply developer for 4 seconds o Turn off application of developer • Stop for 4 seconds • Spin up to 400 rpm o Spin for 1 second then apply wash solution (or water) for 3 seconds o Turn wash solution off • Spin up to 800 rpm o Spin for 1 second • Spin down to 400 rpm o Spin for 1 second then apply wash solution (or water) for 2 seconds o Turn wash solution off • Spin up to 800rpm for 5 seconds • Stop.

The speeds, durations and stop intervals are experimentally determined to optimise developer contact time and sufficient to remove debris.

During the periods of spinning described above, the wash and/or excess developer solution supplied onto the table of each gemstone is spun off by the combination of forces produced by the spinning motion of the dop holder 114, substantially as described with reference to Figures 7a and 7b above.

The apparatus 100 described above with reference to Figures 8 to 11 enables a coating of wash and/or developer solution to be applied to up to six gemstones, within the same time required to apply a coating to just one gemstone. As previously discussed, this provides greater efficiency in a microlithography process having a number of steps. The cost of coating per stone is also reduced. Similar efficiencies and cost savings are achieved during application of the wash solution.

A method of applying a coating to gemstones, such as diamonds, will now be described with reference to Figure 11. The method comprises the steps of:

Step 1: retaining in a chuck a plurality of gemstones disposed around a common rotation axis, each gemstone being mounted on a respective dop.

Step 2: dispensing, using a dispense arm comprising an aperture, a quantity of solution onto a facet of each gemstone.

Step 3: selectively spinning the chuck about the common rotation axis, such that the dispensed solution forms a coating on the facet of each gemstone.

It will be appreciated by the person skilled in the art that various modifications may be made to the above described embodiment, without departing from the scope of the present invention.

For example, while a group of up to six gemstones may be coated with photoresist simultaneously, each gemstone within the group may be individually and separately baked and exposed. As a result, the group of up to six gemstones which are then coated with developer solution may not comprise the same six stones. Where it is desired to track individual gemstones on their respective dops, the dops may be tagged, for example by using RFID tags. Once mounted on a dop, a gemstone may remain mounted during the entire microlithography process.

Although the above apparatus 10, 100 has been described with particular reference to microlithography, the apparatus 10, 100 may be used as part of an alternative process of marking a facet of a gemstone.

The motor has been described as operated using an indexing pulse, but any motor which enables accurate stopping at particular angles may be used.

Claims

CLAIMS:

1. An apparatus for applying a coating to gemstones, comprising:

a chuck configured to retain a plurality of gemstones laterally displaced from and disposed around a rotation axis;

a dispense aperture configured to dispense a quantity of liquid onto a facet of each gemstone; and a motor configured to selectively spin the chuck about the rotation axis so that the gemstones orbit the rotation axis, such that the dispensed liquid forms a coating on the facet of each gemstone.

2. An apparatus according to claim 1, wherein the dispense aperture is configured to dispense a sufficient quantity of liquid to cover the facet of each gemstone, and the motor is configured to spin the chuck such that excess liquid is removed from the facet of each gemstone.

3. An apparatus according to claims 1 or 2, wherein the chuck is configured to retain a plurality of mounted gemstones equiangularly distributed around an outer circumference of the chuck.

4. An apparatus according to any preceding claim, configured to retain each gemstone mounted in a dop.

5. An apparatus according to claim 5, wherein the chuck comprises a plurality of equiangularly distributed slots for receiving and retaining a respective plurality of dops.

6. An apparatus according to any preceding claim, wherein the chuck is configured to retain mounted gemstones in a substantially flat configuration during spinning.

7. An apparatus according to any preceding claim, wherein the dispense aperture is located in a dispense arm configured to be selectively locatable in a first position over the chuck.

8. An apparatus according to claim 7, further comprising a stop element, wherein the dispense arm is configured to be selectively locatable in a second position, adjacent and in contact with the stop element.

9. An apparatus according to claim 7 or 8, wherein the dispense arm comprises a second aperture, each aperture configured to dispense a different liquid.

10. An apparatus according to any preceding claim, wherein the liquid is one of: a photoresist, a developer solution and awash solution.

11. An apparatus according to any preceding claim, further comprising a circular bowl, and wherein the chuck is located within said bowl.

12. An apparatus according to any preceding claim, further comprising a controller, and wherein the motor is configured to be programmable using the controller.

13. An apparatus according to claim 12, wherein the controller is configured to generate an index pulse once per revolution of the motor to allow tracking of the motor’s position.

14. An apparatus according to claim 13, wherein the controller is configured to spin the motor until the index pulse is located and then to move the motor by a predetermined offset.

15. An apparatus according to any preceding claim, wherein the chuck is configured to retain six dops spaced at sixty degree intervals around an outer circumference of the chuck.

16. An apparatus according to any preceding claim, wherein a radius of spinning is approximately 2.5 cm.

17. A method of applying a coating to gemstones, the method comprising: retaining in a chuck a plurality of gemstones laterally displaced from and disposed around a rotation axis;

dispensing a quantity of liquid onto a facet of each gemstone; and selectively spinning the chuck about the rotation axis so that the gemstones orbit the rotation axis and the dispensed liquid forms a coating on the facet of each gemstone.

18. A method according to claim 17, further comprising:

dispensing a sufficient quantity of liquid to cover the facet of each gemstone; and spinning the chuck such that excess liquid is removed from the facet of each gemstone.

19. A method according to claims 17 or 18, further comprising retaining, in the chuck, a plurality of mounted gemstones equiangularly distributed around an outer circumference of the chuck.

20. A method according to claims 17 to 19, further comprising retaining each gemstone mounted in a dop.

21. A method according to claim 20, further comprising receiving and retaining, in the chuck, a respective plurality of dops in a plurality of equiangularly distributed slots.

22. A method according to claims 17 to 21, further comprising retaining, in the chuck, mounted gemstones in a substantially flat configuration during spinning.

23. A method according to claims 17 to 22, wherein the dispense aperture is located in a dispense arm, and the method further comprises configuring the dispense arm to be selectively locatable in a first position over the chuck.

24. A method according to claim 23, further comprising configuring the dispense arm to be selectively locatable in a second position, adjacent and in contact with a stop element.

25. A method according to claims 23 to 24, wherein the dispense arm comprises a second aperture, and the method further comprises configuring each aperture to dispense a different liquid.

26. A method according to claims 17 to 25, wherein the liquid is one of: a photoresist, a developer solution and awash solution.

27. A method according to claims 17 to 26, further comprising locating the chuck 5 within a bowl.

28. A method according to claims 17 to 27, further comprising configuring the motor to be programmable using a controller.

10

29. A method according to claim 28, further comprising configuring the controller to generate an index pulse once per revolution of the motor to allow tracking of the motor’s position.

30. A method according to claim 29, further comprising configuring the controller to

15 spin the motor until the index pulse is located and then to move the motor by a predetermined offset.

31. A method according to claims 17 to 30, further comprising retaining six dops spaced at sixty degree intervals around an outer circumference of the chuck.

32. A method according to claims 17 to 31, wherein a radius of spinning is approximately 2.5 cm.

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