NEW METHOD FOR MANUFACTURING OPTICAL PRODUCTS

BACKGROUND OF THE INVENTION

[0001] The invention relates to a method for coating an optical product made of a viscous material, the method employing an integrated automated apparatus for manufacturing a surface component which is hard, scratch-free and comprises an Anti Reflection function, in which method at least one surface of an optical product is plasma-etched and a layer comprising the antireflection function is produced using Chemical Vapor Deposition.

[0002] Optical products are required to have different special char- acteristics depending on their purpose of use. Commonly required characteristics include antireflection, hereinafter AR (antireflective), scratch-freeness, hereinafter SF ₁ UV (Ultra Violet) light blocking, IR (Infra Red) light blocking, reflective coating, anti-fogging surface quality, etc. Moreover, there are many product segments, such as mobile phone lenses, that require decorative char- acteristics, which are typically prints, such as a frame of the product or metallization, produced on the lens.

[0003] On a genera! level, two methods are applied to eyeglasses, protective eyewear and sunglasses. One of the widest known and applied method is one in which the lens is first fitted into the frame and then transferred to a dip varnishing line, from there to cleaning, chemical etching, varnishing, air-drying, and finally to thermal or UV/IR hardening. Next, the lenses are detached from the jigs on which they were in the furnace and placed into another type of holder suitable for what is known as the calotte in a vacuum evaporation system. The most common evaporation system is e-beam. [0004] The above-described method involves a number of drawbacks, the major one of which is the cost factor arising from the fact that the process in question is almost impossible to automate. Another major drawback is that in dip varnishing the solid matter always flows down on a vertically placed lens surface as the lens is lifted from the basin. In other words, there is a significant difference in surface hardness, because there is always more varnish on the lower part of the lens than on the upper part. Measurements have shown that differences in the thickness of the varnish surface account for 50% of the thickness. In other words, the lens area that leaves the basin last is twice as thick as the area on the opposite edge. Moreover, dip varnishing is subject to many other structural problems, such as the fact that the life cycle

and the quality of the varnish substrate are most challenging to maintain, which in turn causes major quality variations in the end product,

[0005] Another known method is the Plasma Impulse Chemical Vapor Deposition (PICVD) developed by Schott AG. This method is illustrated in Figure 17. The main principle of the method is that all work phases are carried out using the PICVD at one and the same work point, a chamber 160.

[0006] In this method based on the PICVD process ail different surface levels, i.e. adhesion surface E, hard surface or SF surface D, AR surface C and topcoat surface B, are made at one and the same work point using the same process technology, i.e. PICVD.

SUMMARY OF THE INVENTION

[0007] It is an object of the invention to provide a novel and improved method for coating an optical product.

[0008] The method of the invention is characterized by manufactur- ing a hard, scratch-free adhesion layer by piezo spraying varnish onto a plasma-etched surface of an optical product, and producing said layer comprising the antireflection function onto the piezo-sprayed layer.

[0009] An advantage of the invention is that it allows coating expenditure to be cut significantly.

BRIEF DISCLOSURE OF THE FIGURES

[0010] Some embodiments of the invention will be discussed in greater detail with reference to the accompanying drawings, in which

Figure 1 is a schematic view of a method of the invention;

Figure 2 is a schematic view of a device used in the method of the invention;

Figure 3 is a schematic view of a second method of the invention;

Figure 4 is a schematic view of a third method of the invention;

Figure 5 is a schematic view of a fourth method of the invention;

Figure 6 is a schematic side view of an optical product, with its coat- ing layers drawn apart, manufactured using the method of the invention;

Figure 7 is a schematic view of a second device used in the method of the invention;

Figure 8 is a schematic view of an end product manufactured with the method of the invention; Figure 9 is a schematic side view of a fifth method of the invention;

Figure 10 is as schematic top view of the method of Figure 9;

Figure 11 is a schematic view of an end product manufactured with the method of Figure 9;

Figure 12 is a schematic side view of a sixth method of the inven- tion;

Figure 13 is a schematic view of a seventh method of the invention;

Figure 14 is a schematic front view of a lens preform;

Figure 15 is a schematic side view of a lens preform;

Figure 16 is a schematic side view of an eight method of the inven- tion;

Figure 17 is a schematic view of a prior art method;

Figure 18 is a schematic side view of ninth method of the invention; and

Figure 19 is a schematic view of a tenth method of the invention. [0011] For the sake of clarity, some of the embodiments shown in the figures have been simplified.

DETAILED DISCLOSURE OF THE INVENTION

[0012] The new method differs from those mentioned above in that it contains at least two different coating methods applied to the same product. Further, the method may contain not only two different coating methods, such as piezo varnishing, one application of which is inkjet printing, and PICVD, but also other work phases, which are typically significant for the good functioning of the coating methods and in which some other function, such as a decorative coating, is produced. [0013] Figure 1 , for example, illustrates plasma etching. The method applied is preferably one known as the open space plasma method, carried out by equipment manufactured by plasma.de, for example.

[0014] In plasma etching the surface to be coated is acted on in such a way that a surface tension suitable for varnish is achieved. Primarily it is a question of a modification to produce a hydrophilic surface.

[0015] After the plasma etching, the coating may still be acted on chemically, for example by means of an alkali wash, which is preferably carried out by means of inkjet printing.

[0016] Piezo varnishing may be applied to produce other functions as well, for example a hard coating and the method may be carried out using a

Xaar 1001 printing head, for example.

[0017] The piezo varnishing method may be applied to produce the following functional coatings, for example:

A. A photochromatic coating, which may be mono-, bi- or trichro- matic and deposited either onto an optical area or a decorative area, the latter being an eyeglass frame or a mobile phone cover, for example;

B. An electrochromatic coating, which may be mono-, bi- or trichromatic and deposited either onto an optical area or a decorative area, the latter being an eyeglass frame or a mobile phone cover, for example; C A sol-gel coating; and

D. Multi-layer coating compositions of two or more coatings or coating layers one on top of the other. For example, a first coating to be deposited onto the product surface may be a polyurethane varnish, which is photochromatic, and a siloxane-based hard coating may be deposited thereon. Both may be spread using an inkjet printer.

[0018] According to an embodiment of the invention, a decorative metal, oxide, nitride or other similar coating is produced using a laser direct write method. The method allows extremely small and detailed decorative or functional coatings to be prepared both onto the optical and the non-optical area of the product. Laser direct write employs a clear plastic film provided with a substance to be evaporated, such as titanium nitride, cobalt oxide or some other suitable substance to be evaporated. When the laser beam hits the plastic film, the evaporating substance in the film evaporates therefrom.

[0019] Figure 1 illustrates one application of the new method used primarily for coating products such as eyeglasses, sunglasses or protective eyewear, protective windows for mobile phone displays, camera lenses and displays. The first actual work process is plasma cleaning of the lens and its etching 1. Cleaning and surface activation are indispensable in view of the hard varnishing or other functional coating to be carried out in the next work phase. Functional coating 2 is based on piezo spraying, one application of which is inkjet printing. This is an advantageous method for coating a product with an organic coating, such as varnishes, polymers or other substances that can be brought into a flowing form.

[0020] InkJet printing is one of the digitally controllable methods and it allows to control the thickness of the coating and also images, logos, etc. to be produced with the coating. One of the advantages of a digitally controlled

process is that photochromatic and electrochromatic functional coatings, for example, may be spread in a controlled manner on only some parts of the work piece, while part of the work piece surface remains uncoated. In addition, by using electrically conductive coating material, it is possible to produce elec- trically conductive circuits or areas. Masks or other similar structures for covering areas that are to be left uncoated are not needed.

[0021] InkJet printing may be carried out in a normal room atmosphere, although it is often advantageous to do it in a gaseous space with no humidity. The gaseous space may contain any known protective gas, dry air, nitrogen gas, etc.

[0022] The chemistry required by inkjet printing is completely different from dip or cast varnish methods, for example. A reason for the difference is that in inkjet printing the coating is formed of droplets, the volume of which is typically 2 to 100 pi. What is essential is that the surface to be coated is clean and has a suitable surface tension to allow the droplets to join together but not to move. If the droplets move, sagging is formed, the coating becomes uneven and unhomogeneous, etc.

[0023] A preferred coating agent, such as an organic varnish, to be used for the coating preferably contains an extremely rapidly volatile diluent, such as acetone. The varnish thus adheres very quickly to the surface to be coated. When in wet state, a 30 μm thick polyurethane varnish, for example, which has a solid matter content of 33% and in which over 55% of the diluent is based on acetone or a similar extremely volatile diluter or solvent, adheres in less than 10 seconds to the extent that 50%, i.e. half, of the diluent has evapo- rated.

[0024] Prior to the actual hardening it is advantageous to carry out what is known as the airing of the coated, or piezo-varnished, lens typically in a chamber of modest negative pressure to ensure that the product does not contain microscopic air bubbles in any part of the optical coating. This procedure also makes the varnish surface firmer, i.e. a more homogeneous, whereby an extremely hard varnish coating is achieved.

[0025] A varnish coating may be hardened in a number of ways: for example thermally, by means of infra red radiation and ultra violet radiation. In the following, two principles will be disclosed in order to achieve a hardening process as rapid as possible. The first one is based on providing the varnish with a material absorbing IR radiation, known as an IR absorber, which works

on a specific wavelength, such as 1064 nm or 3200 nm, etc. The source of radiation applicable in this case is an IR radiation source functioning on the wavelength in question. The idea is that the IR radiation penetrates the actual plastic product but absorbs into the varnish. Hence the temperature of the plastic product does not rise to the extent as that of the varnish; the varnish may have a temperature of 180 ⁰ C, for example, whereas the temperature of the plastic product may be less than 100 ⁰ C.

[0026] The other principle is based on providing the varnish with material-absorbing microwaves, known as a microwave absorber, which reacts to a microwave radiation of a specific frequency, such as 2.56, 6 or 10 GHz. Varnishes to be hardened by microwaves are not commercially available yet, but the inventor has developed such varnishes. It has been observed that varnishes to be hardened with microwaves may be hardened even in half the time it takes to harden varnishes with infrared radiation. [0027] In some cases it is more advantageous to replace the PICVD method, indicated for example in Figure 1 with reference numeral 12, by some other method. For example, electrically conductive optical coatings, such as electrochromatic coatings, from ITO (indium tin oxide), for example, may be challenging to produce if PICVD is used. One of the embodiments of the new method comprise a third coating method based on vacuum coating methods, such as sputtering, e-beam or laser ablation. However, the vacuum process to be used is not restricted to any specific alternative or work order. These are determined separately on the basis of the product to be prepared and the desired functions to be provided therein. One of the methods that may be used is the one known as the sol-gel method.

[0028] It is advantageous to use a front vacuum chamber 4 and a rear vacuum chamber 5 to allow the level of the vacuum to be kept constant in the actual process vacuum chamber 5.

[0029] According to the operating principle of Figure 1 , one or more products (a lens) are placed to jigs. A jig is denoted in Figure 2 with reference numeral 14 and in Figure 7 with reference numeral 59. The products are arranged so as to allow them to be taken through the system in a controlled manner into separate work process spaces 1, 2, 3, 4, 5, 6 and 12. At the end of the work process the jig 14 leaves 11 the system and the actual products 13 may be removed and placed into their correct packaging. Reference numeral 9 denotes a protected intermediate space between the different work points.

[0030] Figure 2 shows an application of the jig 14 with lenses 15 and 16 arranged thereto. The lenses are eyeglass lenses, for example, this application consisting of two lenses in one jig 14, although it is naturally also possible to have one or more of them. [0031] What is essential is that the jig 14 taken through the whole system. Figure 2 shows a function in which the jig 14 may be rotated about its own central axis 18. This is an essential procedure especially when both surfaces of the product 15 and 16 are to be piezo-printed, because the printing of the product is preferably carried out from above 19 towards the surface of the product.

[0032] A typical rotation/turning angle is 180°, which is extremely simple to achieve by using a mechanical gripping means 17, or a linear manipulator.

[0033] The new method includes three main ways of carrying out the piezo varnishing. Figure 3 shows what is known as the grey-zone coating principle. Figure 4 illustrates a three-axle linear varnish system which has a rotating piezo nozzle 75 and in which the product remains immobile. Figure 18 illustrates an application in which the product rotates about its own central axis 85 and piezo varnishing is carried out by moving the end from the centre of the product to the edge thereof.

[0034] Figure 3 illustrates a grey-zone piezo varnish application, in which either a piezo nozzle 20 or a lens 22, 23, 26 moves in such a way that they overlap. The lens is advantageously in a horizontal position so that a varnish spray 21 is directed downwards from above, gravity providing a natural explanation for why this happens. Otherwise the piezo varnishing could be carried out in any position whatsoever. An advantageous way to use a piezo comb 24 is to hold it in place and take the product 23 underneath 25 the comb. Grey-zone piezo printing means that an extremely precise amount of varnish, for example 3 pi per spray droplet, may be applied with extreme precision. This would be most simple if the lens surface were absolutely even, but that is exactly what it is not. Moreover, different lens strengths have different surface curvature, additional variation being caused by mutual differences between the convex and concave sides. The piezo comb 24 is pre-programmed to place the varnish droplets according to a predetermined geometry onto a specific 3D surface.

[0035] A lens 66 is placed to a jig 77 enabling convenient rotation

thereof, i.e. both sides of the lens 66 are very easy to coat, i.e. the jig 77 may be rotated 180° very rapidly without touching the lens 66.

[0036] A piezo spray head 70 is arranged to a holder 75 that may rotate ±40°, for example, about its central axis. The holder 75 in turn is at- tached to a linear axis 69 and 74 forming a travel path in a Z form, the path being in turn linked to a linear axis 74 of a Y-formed movement via a holder 67. Although the lens is rotated at a constant speed about 84 its own central axis 83, the dispensing rate of the piezo spray head 70 may be changed as the spray head moves towards the outer side 86. [0037] It is evident that one cycle at the centre 79 of the lens 66 is shorter than a cycle at the outer edge 86 of the lens and, therefore, if the speed of rotation of the lens is constant, the dispensing onto the lens surface changes. At its simplest also the dispensing of the varnish from the piezo spray head would be constant, but the piezo spray moves slower as it approaches 86 the outer edge of the lens 66, i.e. the same travel path would take longer to cover the closer the spray is to the outer edge.

[0038] Figure 5 illustrates the operating principle of the new method and shows plasma etching 49, hard coating 50 carried out by means of piezo printing, AR coating by means of CVD, most preferably using precisely PICVD 51 , while finishing may be carried out using an extremely hard coating, such as aluminium oxide or some other functional coating, such as an electromagnetic coating provided by laser ablation 52.

[0039] Schott AG, as well as Satisloh AG and Carl Zeiss AG, disclose a product attached to a jig, and a holder, both being placed into a PICVD vacuum chamber typically by means of a manipulator.

[0040] In the new method, which relates to products such as protective covers or lenses for LCD/plasma displays, mobile phone lenses, etc., for which there is no jig, or a separate holder, the product is not even entirely in the PICVD chamber, as shown in Figures 9, 10 and 11 , but in the form of a film or a plate, a part of the piece being left between the blocking surfaces of the chamber.

[0041] As regards a protective display window comprising an antire- flection function, it is advantageous that the AR function is arranged to the rear surface of the protective window, i.e. to the surface closest to the display. This is particularly essential in applications in which the protective window does not come into contact with the display itself, i.e. in applications, in which a void is

left between the protective window and the display.

[0042] The antireflection function may be produced onto the rear surface of the plastic plate or film in a number of ways, for example: by providing the rear surface with a "moth eye" structured surface function, by vacuum evaporation of the coating containing the antireflection, by providing the rear surface with a coating made of varnish or plastic that is in a flowing form or with a coating made by the sol-gel method. The thickness of the plastic plate or film is typically 30 μm to 4 mm, and it forms part of the end product.

[0043] It is therefore extremely advantageous that a product, typi- cally a plate or a band, has a size that allows it to be placed into the PICVD chamber, as shown in Figure 9, between the blocking surfaces of mould chambers in such a way that two plates or bands are opposite to each other. In addition to providing improved quality, it also allows the rear surface to be kept clean and speeds up the entire process significantly. [0044] A lens for a mobile phone may be manufactured (Figure 5) in such a way that at least plasma treatment 49, piezo printing with varnish 50 and creation of AR surfaces using the PICVD method are included in the production process.

[0045] Mobile phone lenses (Figure 11), which typically are sub- jected not only to the processes shown in Figure 5 but also to decorative printing or metallization, are not separate products; instead, they are joined into a plate form accommodating at least two product items.

[0046] Figure 6 shows the different surfaces 53 to 57 and the technological level used for producing them onto the surface of the lens 52. The first coating is an organic or a non-organic varnish substrate 53, typically 100 nm to 100 urn thick and produced onto the surface of the lens 52 by the piezo spray method.

[0047] Layers 54 and 55 are not indispensable, but an IR and LJV blocking coatings may be included among those that are and they may be pro- duced using for example e-beam, sputtering or laser ablation. The agent used for the coating may be ITO (Indium Tin Oxide), ATO (Aluminium Tin Oxide) or some other oxide or oxide composite.

[0048] On the other hand, the varnish substrate 53 of the piezo varnish process of the first work phase may itself be provided with nanofillers added thereto and having the same functionality, i.e. the IR/UV blocking feature.

[0049] A further essential coating is represented by the AR functional coatings 56 produced by a CVD method, preferably by PICVD, and with Siθ ₂ and TiU2 used as agents. In addition, an anti-fogging coating 57, for example, may be used as the final coating. [0050] Figure 7 shows a lens 60 placed to the jig 59 to a holder provided with a memory 61 , 62 or coding 63, such as a data matrix, RF-id (Radio Frequency ID), i.e. each lens 60 is always identifiable irrespective of where it is located. The product is kept in the same jig throughout the work process. A jig 59 with clear gripping areas 65 shaped in such a way that they are easy to grab mechanically is preferred.

[0051] Figures 8 to 11 relate to each other and illustrate an application of the new method, in which the work process is directed to a band, film or plate (reference numerals 114 and 116 in Figure 11 , reference numerai 126 in Figure 12 and reference numeral 138 in Figure 13). The band, film or plate is taken through the disclosed work processes (Figure 5) in such a way that the end product, such as a mobile phone lens (reference numeral 146 in Figure 13), is cut off from a larger plate, band, film in question to produce the end product, such as a finished mobile phone lens.

[0052] On a general level it may be stated that mobile phones lenses in particular represent one of the product segments not so well suited to previously presented applications that relate to eyeglasses, sunglasses and protective eyewear. Naturally the coating process as such is exactly the same, i.e. for example the one shown in Figure 5, but otherwise there is no need to apply the principle of coating separate lenses separately. [0053] Of course it is also possible to handle a protective windows for a displays or a lenses one by one, i.e. as work pieces separate from other similar products. However, it is evidently often more advantageous to handle work pieces comprising a plural number of optical products, which are not detached from the work piece until after the coatings. [0054] Figures 8, 9, 10 and 11 illustrate how to produce not 1 million but more than 50 million lenses per production unit annually, and this with a manufacturing apparatus that is less expensive than Satisloh PiCoat-8R, for example, the maximum production volume of which is 1 million items/year and the amount of human resources needed is not higher than two persons per work shift.

[0055] Figure 10 shows an end product, such as a mobile phone

lens 111 , in which on top of the basic lens material 105, such as PC, PMMA ₁ PA or other viscous material, there is provided a decorative printing 109, hard printing 106 produced by means of piezo spray varnishing, AR coatings 107 provided using PICVD and possibly some other coating 108 produced by laser ablation, e-beam, sputtering, sol-gel, or some other way.

[0056] Of course it would also be possible to coat both sides 113 of the lens 111 with the coatings 101 to 108 disclosed above, but in the new application it is also possible that the other side, i.e. the one that remains facing inwards the product, is structured so as to produce what is known as an AR function onto the surface 112. This means that only the other side of the piece, i.e. the outer surface of the lens, would need to be coated.

[0057] If the lens 111 is to be coated separately, two lenses are placed against each other 110 in such a way that the structured surfaces 112 remain facing each other when they travel through the different work proc- esses.

[0058] Figures 8 to 11 form a series illustrating a solution to the capacity problem, i.e. they show how to obtain a considerably higher production capacity without having to build more physical capacity. The basic idea of the application is that (Figure 13, reference numeral 138) there is no separate, de- tached lens 146, but a predefined area to which lenses 139 to be detached later may be placed. For example, a single surface area of an A4 size accommodates 20 lenses of 40 x 60 mm. This area is either an independent plastic plate of the A4 size, for example, (reference numeral 138 in Figure 13), or a corresponding area may be arranged onto a larger plastic plate or film (refer- ence numeral 126 in Figure 12). In other words, all the work processes are divided into phases to allow them to be carried out simultaneously. The piezo spray printing 128 in Figure 12 comprises a hard varnishing or a functional coating (reference numeral 106 in Figure 10), and a decorative portion (reference numerals 101 and 129 in Figure 12). Next, CVD coating is carried out in a vacuum chamber (reference numeral 131 in Figure 12), most preferably by means of PICVD onto the same area that was earlier subjected to hard, functional and/or decorative coating 128.

[0059] The plate/film 130 is advanced stepwise to allow any final work phases 137 to be carried out, such as coatings required by touch- sensitive screen functions, soil repellent coating, etc., or a decorative coating, produced by means of laser direct write method, for example, which is one of

the laser ablation applications.

[0060] When the A4 surface area of is completely finished, i.e. coated with all the coatings, as shown in Figure 10, the lenses 139 (Figure 13) are cut off from the A4 surface area by means of laser, high-pressure water jet cutter, grinding, sawing or piercing, after which the product is completed.

[0061] The inventors have carried out tests and experimented by running a film and thereby succeeded in confirming the length of each work phase, which on an area of 2 x A4, i.e. an area for about 50 lenses, is 1 minute. [0062] If only one side is subjected to the coating process, i.e. the other side of the plastic plate or film is structured (reference numeral 112 in Figure 16), it is advantageous to apply the new coating method according to Figure 19. This means that a desired amount of film/plate is advanced from a plate or roll 172 in such a way that first plasma etching, piezo spray coating and decorative coating of Figure 5 are produced, always on the same side of the plate and on the top surface thereof. When two areas 181 of a predetermined size have been coated, the entire area is cut off 175 and moved 176 with the coated side facing up 177. Next, two identical pieces 175 of A4 size, for example, are cut off, one of them being rotated 180 ^c 178 and the pieces being arranged in such a way that the structured surfaces, which are not coated, of both plates 177, 179 face each other. The plate pack 177, 179 is then placed into a CVD vacuum chamber in such a way that the outer surfaces, i.e. the surfaces that were piezo-varnished earlier, become aligned with the vacuum spaces 187 and 188 of the chambers. [0063] If the coating is then carried out using the CVD method, for example, only those plate surfaces that are facing the vacuum space 187, 188 are coated, whereas the area between the plates 177 and 179 does not become coated at all, because it does not relate in any way to the vacuum spaces 187 and 188. [0064] Once the desired coating thickness has been achieved, the chamber walls 180 of the vacuum space 187, 188 are moved 189 and 190 away from each other, thus allowing the lens plate pack with both its plates 177 and 179 to be removed, spread onto the working platform with their front side 184, 185 up and cut off by means of laser, water cutting, grinding, sawing or some other way. As an end result, a lens 111 according to Figure 8 is obtained.

[0065] The new method represents two applications, in the first one of which separate products, such as eyeglass lenses, are handled in the basic form in which they normally appear, i.e. in a standard round shape prior to the adjustment and shaping of the lens. When handling the lens, specific holders, jigs, are used to which one or more eyeglass lenses may be placed.

[0066] As stated, the lenses are attached to jigs, which are then taken through all desired work processes in an automated manufacturing method. The coating is always applied to both sides. The method of coating eyeglasses differs from the coating of protective lenses for mobile phone dis- plays, for example, in that the latter is always subjected to a planar surface that has usually already been subjected to other work processes, such as decorative printing carried out by piezo printing, for example, and typically also vacuum metallization. The first application is meant for the treatment of piece goods, different lenses. [0067] The second application of the new method Is as follows:

1) The method involves a surface area of a predetermined size, such as A4 of 225 x 280 mm to which 24 lens areas of 50 x 60 mm in size may be placed. In other words, there is a surface area, such as the disclosed A4 size, to which all the work processes are subjected. This means that there would be 24 lens areas, from which 24 separate lenses would be produced simultaneously, in one and the same work process. Further, this would mean that a 24-fold number of end products, i.e. production capacity.

2) As regards display covers, whether a display cover lens of 50 x 60 mm for a mobile phone, or a plasma, led, oled or some other display technology of 50 inches, only on one side of the display cover may be touched, i.e. on the side facing outwards. Normally the side of the display cover facing the display itself may not be touched, i.e. it is completely protected from contact.

[0068] Most preferably the plate surface in question (Figure 11) is provided with at least 20 lenses of 50 x 60 mm, at least one side of which {Figure 9) has been subjected to all coating work processes; decorative printing 101 , functional coating and hard coating by means of piezo varnishing 106, AR surfaces by means of the PICVD method and eventually some other coating 108 produced by means of laser ablation or laser direct write method, for ex- ample. In that case the size of the work piece is of an order corresponding to a paper of A4 size, the end products being then cut off from this plate by means

of laser A, water cutting B or grinding C, whereby independent products are obtained.

[0069] In the new method the hard coating D and the adhesion or gripping coating E are not produced using PICVD but by means of piezo var- nishing. The fact that the new method does not employ the PICVD work process for producing adhesion coating E and hard coating D provides a number of advantages.

[0070] Coating thicknesses may vary according to application. A simple varnish coating, such as a siloxane-based hard varnish coating applied directly onto the surface of the plastic piece typically has a thickness of 3 to 30 μm, for example 6 μm.

[0071] Coatings comprising a plural number of layers may have even hundreds of layers one on top of the other, trichromatic graphic and photochromattc coating serving as an example. The thickness of a single coat- ing layer may be in the order of 100 nm, although a layer thickness as high as 3 to 30 μm is naturally also possible. A coating composition comprising a photochromatic function of a polyurethane varnish base may have a total thickness of 5 to 500 μm, for example.

[0072] A basic idea of an embodiment of this new method is that PICVD is used for manufacturing only the antireflective coating onto the optical area and possibly also the IR and UV blocking coatings. Other coatings are made of an organic varnish that may contain functional additives, such as photochromatic molecules. Thus the capacity required of the PICVD equipment is not as great as it would be if all the coatings were produced using the PICVD method.

[0073] The thickness of coatings made by PICVD is typically not more than 50 to 500 nm, whereas the thickness of organic varnish coatings produced by inkjet printing is typically over 5 μm.

[0074] A further point to be noted is that it is extremely difficult to use inorganic materials, such as Siθ ₂ or Tiθ ₂ , to produce all the coatings, i.e. also supporting coatings, which the new method enables to manufacture from organic varnish by means of inkjet printing. After all, the optical product to be coated is made of plastic, such as CR39, PMMA, PC, PA, etc., whose thermal expansion coefficient is many times higher than that of the inorganic materials mentioned. For an inorganic oxide surface to adhere at all to plastic at high temperature variations, it may not be too thick, and even when thin, it is most

preferably arranged onto the organic varnish surface. The reason for this is that an inorganic coating on the surface of an organic plastic does not under any circumstances sustain high temperature variations.

[0075] The CVD method involves some weaknesses, such as the contamination of the walls of the vacuum chamber; in other words, they receive a surface layer. This complicates significantly serial manufacture for a number of reasons. Firstly, the walls with a surface layer substantially slow down the suction of the vacuum, i.e. the cycle length increases considerably. Secondly, the composition and stability of the gas mixture are disturbed. These are the essential reasons for why CVD is, on the whole, rarely used for manufacturing large series.

[0076] The new method allows any known CVD method to be applied, although the PICVD (Plasma Impulse Chemical Vapor Deposition) method of Schott AG would be the simplest one to apply, particularly because of it enables the growth mechanism of the surface thickness to be controlled. Originally the PICVD method of Schott AG has been applied to coating inner surfaces of plastic packages, such as PET bottles, to which the method suits excellently. All processes in the method take place within one and the same closed space and thus the coating chamber is not contaminated at all. [0077] In Figure 12 a product, such as a plastic plate, film, band, of which there are two in the most preferred form, is placed between a moving mould frame 241 , 251 and a fixed chamber body 250. The method differs from the PICVD method of the Schott AG type in that when the microplasma 255 is torched, over 90% of the coating is directed to where it is meant to, i.e. to the surface 258 of the product. The other surface 257 in turn remains completely clean, i.e. it is not coated at all. Thus contamination is not directed to anything else but to the inner surface 256 of the chamber body 250. The new method thus allows problems related to known CVD applications, such as the application of the Schott AG, to be largely eliminated. The product/work piece 259 and 260 is placed in such a way that it forms a part of the blocking surface at the same time as the moving walls 241 and 251 of the chamber body block the plates, the product surfaces 259 and 260 against the static body 250.

[0078] In CVD methods variations in the vacuum space are great, the vacuum level of the methods in the suction phase being typically over 1x10^5 mbar, whereas during gas supply and the actual plasma torching, overpressure (>1000 mbar), i.e. pressure higher than normal atmospheric

pressure, may often occur. In the new method this has been taken into account by providing a process space 255, in which the so-called active gases, i.e. those forming the actual coating onto the inner surface 258 of the product 259 and 260, are plasma-torched, whereas secondary vacuum spaces 261 are pro- vided with supply valves 247 and 245, through which completely pure air or any other gas is supplied in such a way that the pressure level is the same both in the vacuum space 262 for the plasma torching and in the secondary vacuum spaces 261 on both sides thereof.

[0079] Similarly, the suction process of the vacuum is carrier out such that an identical pressure level is provided in the main chamber 262, in the actual process chamber and in the secondary vacuum spaces 261 by means of vacuum suction conduits 243 and 246.

[0080] The front side of the movable secondary chambers 241 and 251 , i.e. the planar surface 248 and 252, from where the microwaves are di- rected to the actual process space 262, is typically made of glass, for example quartz glass or plastic, or generally of a substance that does not prevent the propagation of microwaves. The frequency of the radiation is typically between 500 MHz and 500 GHz, although other frequencies, generally from 2.5 to 13.5 GHz, are also possible. [0081] The embodiment of Figure 13 employs a jig 282, i.e. a holder, to which a lens 277 is placed. However, a holder is not necessary. If no holders and jigs are used, the following problems, for example, are avoided: soiling of the holder, which always takes place during the process; the need to place the product to the holder when the work is started; the need for a large number of holders when large volumes are manufactured; high costs induced by holders in process automation and the complexity they involve, because a holder must also be taken into the vacuum process or processes, and a contaminated holder takes up space, slows down the pumping of the vacuum, slows down gas refill, carries impurities into the process, etc. [0082] The new application provides a method that is significantly less expensive, produces a better result both in terms of quality and quantity, is easier as regards the coating and, moreover, more convenient to automatize. Figures 14 and 15 illustrate a lens preform characterized in that in addition to a conventional lens surface or optical area 290 it has a frame area 291 , which is constant in all parts, whatever the 3D geometry of the lens area. In the current procedure only the outer edge, sidewall of the lens may be used as the contact

area, the rest of product surface being cosmetic and not to be touched at any stage of the work process. This is why jigs/holders of different types in one respect or another are always used in vacuum coating steps.

[0083] In other words, a frame 291 of standard dimensions is dis- closed, the dimensions being always standard irrespective of the geometry of the actual lens area 290. The method provides the following advantages: use of an automated coating system is significantly easier, automation is simpler, jigs/holders can be totally disposed of, the production cycle becomes significantly speedier and thereby production volumes per production unit are greater, and the production equipment required is less complex/less expensive.

[0084] The above is important particularly as regards products such as sunglasses, ski or slalom goggles or other protective eyewear or eyewear, in which cost effectiveness is relevant and which are provided not only with an AR function coating but also with another coating that is most advantageously coated using CVD, preferably precisely PICVD. Examples of this kind of special coatings worth mentioning include IR (Infra Red) and UV (Ultra Violet) blocking coatings, which may be produced in a number of ways, but particularly successfully in the same vacuum space that is used for the AR coating produced by CVD, for example by PICVD. The coating may consist of oxides or oxide composites, such as ITO (Indium Tin Oxide) or ATO (Aluminium Tin Oxide) etc., in the form of reflective or mirror coatings, a coating regulating darkness according to the interference of light and produced around the world by the Eastman-Kodak method. [0085] Hence the problem is that the more complicated the coating, the greater the likelihood that a plural number of different production technologies must be applied and therefore the optical product must be transferred from one manufacturing apparatus to another. It is therefore a major advantage if the product to be coated always has a same size or shape, like the frame 291 in Figure 24, that may be touched during the process and at the same be used as a part of the production process. Because of the frame, no jig is needed in the handling, so the frame may be provided with a number of production control codes, such as an RF-ID, a data matrix, a bar code, a mechanical shape or some other code or identifier. [0086] If the optical work piece 294 of Figure 15 is provided with a standard frame 295, 296, the work processes are significantly facilitated, irre-

spective of the geometrical 3D-shape of the actual lens, because the frame may be used as an active part of different work phases, such as the CVD coating shown in Figure 13, in which both ends of a vacuum chamber 271 of an extremely small volume are provided with work pieces 275 and 276 in such a way that only one coating 277 faces the process space.

[0087] The work piece is thus easy to move and to hold by the lens 297, and the frame may further act as a sealing surface to the edge of the chamber wall, whereby no jig or holder needs to be inserted into the vacuum. [0088] An excellent example of the application of the new method is shown in Figure 16, in which the work piece 308, i.e. the lens 308, provided with a standard frame 309 is placed, unlike in Figure 13, into a vacuum chamber of two parts 301 and 302 in such a way that the product itself, the lens 308 forms an interface, whereby two substantially separate process spaces 306 and 307 are formed. Both sides of the lens 308 are coated simultaneously in the CVD process, although the volumes of the process spaces 306 and 307 as such are only a fraction of a normal CVD vacuum space in which the work piece is attached to a jig or a holder.

[0089] As regards PICVD, the volume of the vacuum space is most relevant for work efficiency. The smaller the volume, the faster the work proc- ess is, and the better is also the quality of the work. Figure 16 discloses a new application, in which the vacuum spaces 306 and 307 are minimal, whereby the supply of different gases 310 and 311 is extremely efficient and rapid and, likewise, residual gases 312 are extremely efficiently and rapidly discharged.

[0090] In principle the PICVD method functions like a two-stroke engine: gas 310 is supplied into the vacuum chambers 306 and 307, the gas is torched to form plasma by means of microwaves 303 and 304, whereby a surface layer of a predetermined thickness is produced onto the surface of the work piece 308. To obtain a sufficient surface thickness, more gas must be fed into the chambers 306 and 307 and, prior to this, the previous gas must be removed, the volume of the vacuum thus being of a great importance as regards the time taken up by the production process.

[0091] When a new work piece, such as a lens 308, is placed into the vacuum chamber, both halves of the chambers 306 and 307 are moved away from one another 313, whereby the product 308 can be easily changed. [0092] Figure 13 illustrates the operating principle of this new application, in which an essential aspect is that only one side of the lens 275 and

276 is placed facing inward 277 into the process chamber 271. In this case it is advantageous that if two lenses 275 and 276 are being coated simultaneously, as shown in Figure 13, the CVD method, such as one of the Schott AG type, produces the best possible efficiency when the surface not associated with the product, such as the lenses 275 and 276, is minimized. The smaller the volume of the CVD vacuum chamber, the more efficient is the gas supply 272 and 273 into the chamber 271 , i.e. its cycle rate is higher, and the faster is the gas discharge 274.

[0093] In addition, the shape of the vacuum chamber 271 is relevant to the end result. A round cylindrical shape is the best, and the lower the vacuum space cylinder is, the better, because tests have shown that a cylinder height between 20 and 200 mm is optimal. If an eyeglass lens 275 and 276 of 070 mm is to be coated and the height of the vacuum chamber 271 is 50 mm, the volume is ~2 dl, which is 1/30 of the chambers used in prior art methods. [0094] Another advantage in the use of a process space, or vacuum, of an extremely small volume is that the amount of process gas used is considerably less, which in turn is a cost factor.

[0095] The operating principle of the new application is very simple, the CVD vacuum coating chamber 271 is cylindrical and its diameter corre- sponds to that of the work piece to be coated, and the vacuum chamber is open at both ends. The work pieces, such as the two lenses 275 and 276, to be coated in the chamber are placed at opposite ends of the chamber. When the coating of one side 277 of the lenses 275 and 276 has been completed, the vacuum level/gas pressure is lowered/raised to correspond to ambient val- ues, the lenses 275 and 276 are reversed 281 180° and placed so that the other side faces the coating chamber. After the other side has also been coated similarly, the product is finished.

[0096] In some cases the features disclosed in this application may be applied as such, irrespective of the other features. However, when neces- sary, the features disclosed here may also be used to provide different combinations.

[0097] The drawings and the related specification are only intended to illustrate the inventive idea. The details of the invention may vary within the scope of the claims.