Contact Lens Mould And Methods

Abstract

A mould for the production of a contact lens, the mould comprising a first mould half shaped to provide the front surface of the contact lens; and a second mould half shaped to provide the rear surface of the contact lens, wherein the first and second mould halves form a mould cavity, wherein the first mould half has a first rim and the second mould half has a second rim, and the first and second rims fit together to provide a seal for the mould cavity, wherein the first rim is inclined at an angle of x relative to an axis passing through the centre of the first and second mould halves, wherein x is from 30 to 60, and wherein the second rim is inclined at an angle of x-y relative to the axis passing through the centre of the first and second mould halves, where y is from 0 to 4, and wherein the first and second rims provide a guide for the mould halves, a method of making a contact lens using the mould and a method of making a mould.

Claims

1. A mould for the production of a contact lens, the mould comprising: a first mould half shaped to provide the front surface of the contact lens; and a second mould half shaped to provide the rear surface of the contact lens, wherein the first and second mould halves form a mould cavity, wherein the first mould half has a first rim and the second mould half has a second rim, and the first and second rims fit together to provide a seal for the mould cavity, wherein the first rim is inclined at an angle of x relative to an axis passing through the centre of the first and second mould halves, wherein x is from 30 to 60, and wherein the second rim is inclined at an angle of x-y relative to the axis passing through the centre of the first and second mould halves, where y is from 0 to 4, wherein the angle of the first rim and the second rim is before the first and second mould halves are pushed together, and wherein the first and second rims provide a guide for the mould halves, and wherein the first and second mould halves fit together without an interference fit.

2. A mould as claimed in claim 1, wherein x is from 40 to 50.

3. A mould as claimed in claim 1, wherein y is from 0.25 to 2.

4. A mould as claimed in claim 1, wherein the seal forms a sealing annulus having an annular radius of from 25 to 500 m.

5. A mould as claimed in claim 4, wherein the seal forms a sealing annulus having an annular radius of from 50 to 250 m.

6. A method of making a contact lens comprising: providing a first mould half shaped to provide the front surface of the contact lens and a second mould half shaped to provide the rear surface of the contact lens wherein the first and second mould halves form a mould cavity, wherein the first mould half has a first rim and the second mould half has a second rim, and the first and second rims fit together to provide a seal for the mould cavity, wherein the first rim is inclined at an angle of x relative to an axis passing through the centre of the first and second mould halves, wherein x is from 30 to 60, and wherein the second rim is inclined at an angle of x-y relative to the axis passing through the centre of the first and second mould halves, where y is from 0 to 4, and wherein the first and second rims provide a guide for the mould halves; introducing a contact lens monomer composition into the first mould half; mating the first and second mould halves, wherein the first and second rims guide the mould halves together; curing the monomer composition to form a contact lens.

7. (canceled)

8. A method of making a contact lens mould comprising a first mould half and a second mould half, the method comprising: forming a first moulding insert for a first mould half; fitting the first moulding insert into a first master mould; forming a second moulding insert for a second mould half; fitting the second moulding insert into a second master mould; forming a first mould half in the first master mould; and forming a second mould half in the second master mould, wherein at least one of the first or second moulding inserts is formed using a diamond lathe tool with a tip of radius less than 3 m.

9. The method of claim 8, wherein at least one mould insert formed using the diamond lathe tool has an internal corner between two surfaces wherein the radius of the internal corner is less than or equal to 5 m.

10. The method of claim 9, wherein the radius of the internal corner is less than or equal to 3 m.

11. The method of claim 8, wherein said contact lens mould comprises a first mould half shaped to provide the front surface of the contact lens; and a second mould half shaped to provide the rear surface of the contact lens, wherein the first and second mould halves form a mould cavity, wherein the first mould half has a first rim and the second mould half has a second rim, and the first and second rims fit together to provide a seal for the mould cavity, wherein the first rim is inclined at an angle of x relative to an axis passing through the centre of the first and second mould halves, wherein x is from 30 to 60, and wherein the second rim is inclined at an angle of x-y relative to the axis passing through the centre of the first and second mould halves, where y is from 0 to 4, wherein the angle of the first rim and the second rim is before the first and second mould halves are pushed together, and wherein the first and second rims provide a guide for the mould halves, and wherein the first and second mould halves fit together without an interference fit.

12. A method for forming a moulding insert for a contact lens master mould, comprising utilizing a diamond lathe tool with a tip of radius less than 3 m to produce said moulding insert for a contact lens master mould.

Description

[0076] The invention will now be further described with reference to the following drawings in which:

[0077] FIG. 1 shows a cross-section of a male and female mould half according to the present invention;

[0078] FIG. 2 shows two magnified views of FIG. 1 demonstrating the fit at the rim of the male and female mould halves where the mould halves were produced using a zero point radius tool; and

[0079] FIG. 3 shows a magnified view of a cross section of the mould halves made from a mould insert produced using a single point diamond lathe tool with a given radius.

[0080] FIG. 4 shows a series of cross-sections of mould halves having different shapes for forming different lens edges according to the present invention.

[0081] In FIG. 1, there is provided a moulding set 1 formed of a male mould half 3 and a female mould half 5. The male mould half 3 and the female mould half 5 fit together to form a mould cavity 10.

[0082] The male mould half 3 has a rim 15 which meets with a rim 20 of the female mould half 5 to form a sealing rim 25 having an annular radius of approximately 75 m. A central axis 30 passing through the centre points of each mould half is shown. The angle of the rims 15, 20 relative to this axis is approximately 45.

[0083] The mould halves are formed of a medical grade polypropylene. Each mould half is made by injection moulding into a multi-cavity tool using a standard injection moulding machine such as those produced by Arburg, Battenfeld, B.O.Y., Demag, Engel Husky or Sumitomo. One tool is common for many different male mould halves and a separate tool is common for many different female mould halves. In alternative methods it is possible to use one mould tool to produce both the male and female mould halves. Specific mould halves (and therefore specific lenses) are defined by the optical insert tool which can be varied. Once the male and female mould halves are produced, they are loosely assembled together to protect the optic surfaces. Here it is advantageous that the mould halves do not fit together in an interference fit.

[0084] As can be seen in FIG. 2, the rim 15 of the male mould half 3 has a lower angle than the rim 20 of the female mould half 5 by 2. As the two mould halves 3, 5 fit together, they meet first at the point adjacent the mould cavity 10.

[0085] In use, a contact lens monomer mixture is added to the female mould half 3 and the male mould half 5 positioned on top. The male mould half is directed into position by the guiding nature of the rims 15, 20. The mould cavity 10 is full of the monomer mixture. The two mould halves 3, 5 are pushed together and a slight flexibility in the mould material forms a seal along the whole of the rim 20. The two mould halves are then sealed closed using thermal welding.

[0086] It can be seen that the guiding action of the two rims 15, 20 allows the male mould to fit more accurately into position on the female mould whilst at the same time providing an excellent edge seal.

[0087] The lens mould is then treated using UV light to cure the monomer mixture and the mould opened to provide a lens.

[0088] As can be seen in FIG. 2, where a zero point tool has been used to form the master mould, the resultant female mould has a sharp corner at the point that it meets the male mould. Conversely, in FIG. 3, where a single point tool is used to produce the master mould, there is a curve 30. The curve corresponds to an arc having a radius which is the same as the radius of the single point tool. In this case, the radius, labelled R, is 5 m. This curve allows the monomer ingress and results in the formation of a seal around the rim of the lens. The provision of a rim is less satisfactory. Where a zero point tool is used, there is no curvature where the rims meet, providing a better edge seal.

[0089] For previous contact lens mould inserts, it would not be apparent that there was a problem with the use of a single point radius tool. However, with the new moulds of the first aspect, it can be seen that the zero point radius tool provides an advantageous fit of the mould halves.

[0090] FIG. 4 shows a magnified view of a series of different rims formed from the joining of male and female mould halves 3, 5. The different rims 15, 20, 25 fall within the scope of the first aspect of the present invention. The different shapes of the mould halves 3, 5 result in different edge shapes for the lenses that can be produced. As can be seen, in each of these examples, the point where the male mould half and the female mould half meet has a sharp corner in one of the mould halves. In each case therefore, the resultant mould is superior where a zero point tool is used to form the master mould.

[0091] Whilst the invention has been described with reference to a preferred embodiment, it will be appreciated that various modifications are possible within the scope of the invention.

[0092] In this specification, unless expressly otherwise indicated, the word or is used in the sense of an operator that returns a true value when either or both of the stated conditions is met, as opposed to the operator exclusive or which requires that only one of the conditions is met. The word comprising is used in the sense of including rather than in to mean consisting of. All prior teachings acknowledged above are hereby incorporated by reference. No acknowledgement of any prior published document herein should be taken to be an admission or representation that the teaching thereof was common general knowledge in Australia or elsewhere at the date hereof.