GB2543130A

GB2543130A - Improved coatings and method of applying the same

Info

Publication number: GB2543130A
Application number: GB1613450.4A
Authority: GB
Inventors: Navabpour Parnia; Ernest Cooke Kevin; Sun Haifin
Original assignee: Teer Coatings Ltd
Current assignee: Teer Coatings Ltd
Priority date: 2015-08-04
Filing date: 2016-08-04
Publication date: 2017-04-12
Anticipated expiration: 2036-08-04
Also published as: GB201513760D0; GB2543130B

Abstract

A coating is formed by depositing silicon (Si) or a Si compound onto a surface using chemical vapour deposition (CVD). At least part of the same (unitary) layer or another layer (of a plurality of layers) is applied using physical vapour deposition (PVD). The coating is preferably a demoulding film formed on the surface of a mould. The preferred silicon compound is hexamethyldisiloxane (HMDSO) and some of the coating is preferably applied by plasma assisted chemical vapour deposition (PECVD) in which radio frequency (RF) or pulsed direct current (DC) potential is applied to the surface to be coated. The preferred PVD uses magnetron sputtering from a Si containing target. Preferred pre-treatments include removal of oxidation and roughening.

Description

Improved Coatings and Method of Applying the same

The invention to which this application relates is the provision of a form of coating to assist in the release of materials from moulds.

The use of polymer coatings as release films for moulds is known. In order to be effective, moulds must be easily separated or demoulded from the moulded materials and without causing damage thereto and the release films which are formed on the surface of the mould with which the moulded material contacts aim to assist in this process step. However, such films are susceptible to wear and have a relatively short lifetime and so over time the separation can be increasingly problematic and the risk of damage to the moulded materials.

In addition, spray films and coatings, such as PTFE release coatings, have to be reapplied frequently and there are safety concerns with such coating methods particularly with regard to respiratory health of the operators which apply the coatings or are in the vicinity thereof.

It is therefore an aim of the present invention to provide a coating and a method for applying the same that addresses the abovementioned problems. A further aim is to provide a mould with a coating which improves the ability for the material which is moulded in the mould to be subsequently removed therefrom.

In a first aspect of the invention there is provided a method of applying a coating to at least part of a surface for assisting in the release of one or more materials subsequently applied to the coated surface, said coating including silicon and/or one or more compounds containing silicon and wherein at least a layer of the coating is applied using Chemical Vapour Deposition and at least part of the same layer or a further layer of the coating is applied using Physical Vapour Deposition.

In one embodiment the surface is the surface of a mould and the coated surface aids the removal of one or more materials which enter the mould in a moulding process from the mould once the moulding process is completed.

Typically the coating acts as a release coating or demoulding film and the coating created is an organosilicon coating.

Preferably the silicon compounds include organosilicon or organosilane compounds. Further preferably the compounds include hexamethyldisiloxane (HMDSO).

In one embodiment at least one layer or at least a part of the same is applied using Plasma Assisted Chemical Vapour Deposition (PACVD).

In one embodiment the coating is applied in a chamber in which there is provided a vacuum or atmospheric pressure environment and one or more deposition means are provided within said environment to deposit one or more coatings or layers of the selected compound and/or a combination of compounds onto the surface or surfaces of the article which is to be coated.

In one embodiment the coating is applied as a unitary layer. In an alternative embodiment the coating is applied as a series of layers, with successive layers having compositions and/or structures.

In one embodiment the thickness of the coating which is applied is selected with respect to the particular usage of the surface to which the coating is to be applied, the materials to which the surface is to be exposed, and/or the number of mould usages for which the coating is required to be effective.

In one embodiment in the coating method, respective selected gases flow into a chamber in which the mould surface to be coated is exposed, and the gases are at least partially broken down and the substances deposited to form the coating are derived from the breaking down of the gases.

In one embodiment an RF or pulsed DC potential is applied to the surface of the mould which is to be coated.

In one embodiment an electrode can also be present helping in breaking down the gases.

In one embodiment precursor chemical gases are used with as low a toxicity value as possible. By-products which are potentially either corrosive or toxic are separated and trapped before the opening of the chamber to atmosphere following the application of the coating.

Typically the coating which is applied has low surface energy . and the surface morphology is suited to resist attachment of the moulded material thereto.

In one embodiment of the invention the physical vapour deposition is magnetron sputtering from at least one silicon target or silicon containing composite target.

In one embodiment the coating is applied to the surface of moulds which are mounted on a rotary holder within a vacuum chamber in which a number of magnetrons are located to allow material to be deposited from the magnetrons onto the mould surfaces to form the coating thereon.

In one embodiment the magnetrons are unbalanced and provided with respective magnet arrays incorporated therein or located adjacent thereto so as to create a substantially closed field configuration. In an alternative embodiment the coating is applied using a substantially linear coating application.

In one embodiment the method includes the initial step of removing oxidation which may have occurred on the surface of the mould which is to be coated with the removal performed, in one embodiment, by the use of sputter cleaning and /or chemical etching.

In one embodiment, following the removal of oxidation the surface of the mould onto which the coating is to be applied is pre-treated so as to create a roughening effect on the same.

In one embodiment the method includes a final step of creating a high surface area external surface effect to the coating.

In one embodiment the external surface of the coating is provided with a hydrophobic or hydrophilic characteristic.

Preferably the magnetron sputtering of material and the Plasma deposition occurs simultaneously to form the coating.

In a second aspect of the invention there is provided a coating or film suitable for assisting in the release of one or more materials from a mould surface to which the coating is applied, said coating including silicon and/or one or more compounds containing silicon.

In one embodiment a layer or part of a layer has been applied using chemical vapour deposition and at least part of the same layer or a further layer is applied using physical vapour deposition.

In a third aspect of the invention there is provided a mould including a coating suitable for assisting in the release of one or more materials from said mould in use, said coating including silicon and/or one or more compounds containing silicon.

In one embodiment the coating has been applied with a layer or part of the same applied using chemical vapour deposition and at least part of the layer or a further layer applied using a physical vapour deposition.

Specific embodiments of the invention are now described with reference to the accompanying drawings, wherein:-

Figure 1 illustrates a PACYD chamber in one embodiment;

Figure 2 illustrates a HMDSO molecule;

Figure 3 illustrates a chamber in which the coating is applied in accordance with one embodiment of the invention;

Figure 4 illustrates a coating in accordance with one embodiment of the invention;

Figure 5 illustrates a coating chamber of a type which can be used to apply the coating in accordance with one embodiment of the invention; and

Figure 6 illustrates the formation of a coating in accordance with one embodiment of the invention.

The present invention, in one example, uses apparatus including a chamber 2 in which is provided apparatus to allow PACVD -Plasma Assisted Chemical Vapour Deposition to be performed. At the top wall of the chamber there is provided an RF antenna 4 on a quartz plate 6 and a base electrode 8 receives thereon the moulds 10 with the surfaces 15 of the same which are to be coated exposed. The base electrode 8 is connected to an RF or pulsed DC-biased via RF or pulsed DC supply, 12. In this example, the RF power supplies are matched at 13.56MHz.

Magnetrons 16, 18 are provided and are used to increase the plasma density in the chamber.

In one example the coating which is applied using the PACVD apparatus is a SiOx-like coating and which is created using SiH4 + Oxygen.

In one embodiment a precursor such as Hexadimethylsiloxane or HMDSO such as [(CH3)3Si]20 is used and is shown in Figure 2.This precursor can be used selectively in order to modify the contact angle and/or surface energy of the coating which is applied is the Hexadimethylsiloxane or HMDSO.

The HMDSO is decomposed in the chamber such as by using Oxygen and Argon plasma which is generated in the chamber and the "unused" CHx groups coming from the decomposition of the monomer are transformed into C02, CO, H20, H2 compounds.

As a function of the ratios of the gases used in the coating chamber and hence the process, a SiOxCyHz coating can be developed with controlled CyHz/SiOx content.

Figure 3 illustrates a schematic view of the process within the chamber in which Plasma polymers SiOxCyHz are applied onto the moulds 10 surfaces to create a coating of the type shown in Figure 4 with multiple layers 17,19 on the mould 10 surface 15.

Figure 5 illustrates a plan view of a controlled environment in the form of a plasma chamber 2 with the top wall removed for ease of illustration and in which the coatings can be applied in accordance with the invention.

In this example the moulds 10 with the respective surfaces 15 to be coated are placed in a holder 20 which rotates in the chamber 2 as indicated by arrow 21 and is RF or pulsed-DC biased. Preferably the chamber and apparatus provided is in the form of a closed field magnetron sputtering system. In the illustrated embodiment of the system, four magnetrons 26 are provided with magnet polarities which act to retain a strong plasma within the coating chamber. The material from the targets 24 of the respective magnetrons, e.g. silicon, is deposited using a closed-field unbalanced magnetron sputtering method. At the same time as the sputtering of the silicon material, the plasma within the chamber assists in the dissociation of the gases which are introduced into the chamber, e.g. PIMDO + oxygen, and these are present in the chamber so that the material used to form the coating in accordance with the invention is deposited simultaneously from both the magnetron targets 24 and the gases onto the surface of the moulds so as to form the coating.

One form of the coating is shown in Figure 6 and the coating is shown in cross section. The coating in this example is a multi layered coating 34 formed with an initial layer 28 which is applied to the surface 15 of the mould and the surface 15 is the surface to which the moulded material will contact and has to be removed and released from once the material has been moulded.

In this example the coating includes an initial layer 28 of Silicon and to form this the apparatus is operated such that only the magnetrons are operated for a period of time such that Silicon material from the targets 24 is deposited onto the surface 15. Subsequent to that, the layer 30 is applied to the layer 28 and is formed of Si + 02 in which case the material from targets 24 continues to be sputtered along with the creation of Oxygen in the chamber so that the required layer composition is formed.

The final and external layer 32 of the coating is formed and comprises Si + 02 +HMDSO and this is formed by the simultaneous deposition of material from the targets 24 and the gases within the chamber.

The current invention therefore provides a mould with a surface for contact with the product moulded therein which is coated in a manner so as to allow the improved release of the moulded product from the said coated surface, and hence the mould, whilst at the same time, as the coating is provided in a form which is relatively long lasting and resilient to damage, increasing the life of the mould in comparison to conventional systems.

Claims

1. A method of applying a coating to at least part of a surface for assisting in the release of one or more materials subsequently applied to the coated surface, said coating including silicon and/or one or more compounds containing silicon and wherein at least a layer of the coating is applied using Chemical Vapour Deposition and at least part of the same layer or a further layer of the coating is applied using Physical Vapour Deposition.

2. A method according to claim 1 wherein the surface is the surface of a mould and the coated surface aids the removal of one or more materials which enter the mould in a moulding process from the mould once the moulding process is completed.

3. A method according to claim 1 wherein the coating acts as a release coating or demoulding film.

4. A method according to any of the preceding claims wherein the coating is an organosilicon coating.

5. A method according to claim 1 wherein compounds containing silicon include organosilicon or organosilane compounds.

6. A method according to claim 1 wherein the compounds containing silicon include Hexadimethysiloxane (HMDSO).

7. A method according to claim 1 where at least part of a layer or at least one layer of the coating is applied using Plasma Assisted Chemical Vapour Deposition (PACVD).

8. A method according to claim 1 wherein the coating is applied in a chamber in which there is provided a vacuum or an atmospheric pressure environment.

9. A method according to claim 8 wherein one or more material deposition means are provided within said chamber vacuum or said environment to deposit one or more coatings or layers of the selected compound and/or a combination of compounds onto the surface or surfaces of the article which is to be coated.

10. A method according to claim 1 wherein the coating is applied as a unitary layer.

11. A method according to claim 1 wherein the coating is applied as a plurality of layers.

12 A method according to claim 8 wherein respective selected gases flow into the chamber in which the surface to be coated is exposed and the gases are at least partially broken down and substances derived from the breaking down of the gases form the coating.

13 A method according to claim 12 wherein an RF or pulsed DC potential is applied to the surface which is to be coated.

14 A method according to claim 12 wherein an electrode assists in breaking down the gases.

15 A method according to claim 8 wherein precursor chemical gases are used in the chamber in the coating method and any by-products which are potentially corrosive or toxic are separated and trapped before the opening of the chamber to atmosphere following the application of the coating.

16 A method according to claim 8 wherein the Physical Vapour Deposition uses magnetron sputtering from at least one silicon target or silicon containing composite target which is provided as part of a magnetron located in the chamber.

17. A method according to claim 16 wherein the sputtering of material from the magnetron and plasma deposition of material occurs simultaneously to form at least part of the coating.

18. A method according to claim 8 wherein the coating is applied to a surface of each of a plurality of moulds which are mounted on a holder within the chamber in which a number of magnetrons are located to allow material to be deposited from the magnetron targets onto the surface of the moulds to form the coating thereon.

19. A method according to claim 18 wherein the magnetrons are unbalanced and provided with respective magnets or magnet arrays incorporated therein or located adjacent thereto so as to create a substantially closed field deposition configuration within the chamber and within which closed filed the moulds are located.

20. A method according to claim 1 wherein the method includes the initial step of removing oxidation from the surface which is to be coated.

21. A method according to claim 20 wherein following the removal of oxidation the surface is treated so as to create a roughening effect on the same.

22. A method according to claim 1 wherein the method includes a final step of creating a high surface area outer surface of the coating.

23 A method according to any of the preceding claims wherein the external surface of the coating is hydrophobic or hydrophilic.

24. A coating of film suitable for assisting in the release of one or more materials from a mould surface to which the coating is applied using the method defined in claims 1-23, said coating including silicon or one or more compounds containing silicon. 25 A mould including a coating suitable for assisting in the release of one or more moulded materials from said mould, said coating including silicon and/or one or more compounds containing silicon. 26 A mould according to claim 25 wherein the coating is applied to the mould applied using the method as defined in claims 1-23.