Method for applying a colorant and a functional colorant to one side of a substrate

Abstract

Method for one-sided application of a coloring and a functional coloring to a substrate, comprising the following steps (a) to (d): (a) Providing a substrate to be provided on one side with a coloring and a functional coloring, wherein the substrate is a half-part made of plastic glass with a first main side and a second main side opposite the first main side, which has a convex shape, (b) Applying a colorant to both main sides of the substrate provided in step (a), (c) Applying a functional coloration to the second main surface of the substrate which in step (b) has been colored on both main surfaces, wherein the functional coloration is caused by at least one photochromic dye and the at least one photochromic dye is contained in a photoresist which forms a polymeric layer on the substrate, and (d) Post-processing the substrate provided with a functional stain on the second main surface in step (c) such that the staining on the first main surface is removed, resulting in a substrate provided with a staining and a functional staining only on the second main surface.

Description

[0001] The present invention relates to a method for providing a substrate on one side with a coloration and a functional coloration.

[0002] Self-tinting lenses, also called photochromic lenses, can react to UV light. Depending on the intensity of the UV light hitting the lens, it becomes dark or light. The darkening or lightening of the lens is made possible by a functional tint applied to the lens. The functional tint is caused by a photochromic dye, which reacts to UV light irradiation with a reversible change in its molecular structure and thus also in its absorption behavior. When the UV light irradiation subsides, the photochromic dye returns to its original molecular structure and thus also its original absorption behavior. A photochromic dye thus enables a reversible switching back and forth between a dark and a light tint.

[0003] Typically, the functional tint is only applied to one of the two main concave and convex sides of the lens. Therefore, functional tinting on both main sides is generally problematic, as it makes the associated effect of the functional tint, such as darkening or lightening of the lens, difficult to control. This is due to the different intensity of the UV light hitting the two main concave and convex sides. The UV light hitting the main convex side is primarily crucial for eye protection, as this is directed directly at the wearer. Therefore, the functional tint is normally applied to the front convex side of the lens.

[0004] The above statements also apply equally to the provision of the spectacle lens with a tint, which serves to impart a specific color tone to the spectacle lens in addition to the functional tint, which is particularly desirable for sunglasses. In contrast to functional tinting, dyes are used for tinting which - apart from their absorption properties - have no functional properties whatsoever and are therefore referred to as non-functional dyes. Like functional tinting, tinting is typically only applied to one side of the spectacle lens, with the tinting and the functional tint then being on the same main side of the spectacle lens. As a rule, the tint is first applied to one side of the convex main side of the spectacle lens. The functional tint is then applied on top of this.

[0005] Various methods are known in the prior art for providing spectacle lenses with a tint and a functional tint on one side.

[0006] In this context, for example, the method for colouring a plastic lens described in EP 1 122 355 A1 can be mentioned.This comprises a step of setting up the lens in a predetermined position in a vapor deposition apparatus, a step of setting up a base body for use in a dyeing operation in the vapor deposition apparatus, wherein a dyeing medium containing a dissolved or finely dispersed, sublimable non-functional dye is applied to the base body to form a dye application surface and the base body is arranged such that the dye application surface faces the convex main surface of the lens without being in contact with it, and a step of heating the base body by a heating source under vacuum conditions in the vapor deposition apparatus, whereby the non-functional dye of the dye application surface is sublimated and vapor deposition of the sublimated non-functional dye takes place onto the convex main surface of the lens.

[0007] The functional coloring, which is in the form of a photoresist, is then applied to the convex main surface of the lens, which has previously been colored. The photoresist forms a polymer layer on the substrate. The polymer layer with the functional coloring is unaffected by the underlying coloring.

[0008] The procedure described above is suitable for providing a spectacle lens with a coloring and a functional coloring on one side. However, the process known from EP 1 122 355 A1 requires very complex equipment, which is why spectacle lenses obtained using it are correspondingly expensive. As mentioned above, the said process requires a special vapor deposition device with a specially designed base body on which a dye application surface is formed. However, such a device cannot be used for other process steps in spectacle lens production. Since the non-functional dye of the dye application surface must also be sublimable, not just any non-functional dye can be used in the said process. All of these disadvantages stand in the way of series production of spectacle lenses.

[0009] Furthermore, DE 35 16 568 A1 discloses a method for coloring plastic ophthalmic lenses with organic dyes. Furthermore, EP 3 561 581 A1 discloses an ophthalmic lens with a photochromic coating and a method for producing the same.

[0010] The present invention is therefore based on the object of providing a method which is capable of providing a substrate on one side with a coloring and a functional coloring, wherein the method to be provided is intended to enable this in a simple and thus cost-effective manner.

[0011] The above object is achieved by the embodiments of the present invention characterized in the claims.

[0012] In particular, the invention provides a method for providing a substrate with a coloring and a functional coloring on one side, wherein the method according to the invention comprises the following steps (a) to (d): (a) Providing a substrate to be provided with a coloring and a functional coloring on one side, wherein the substrate is a half-part made of plastic glass with a first main side and a second main side opposite the first main side, which has a convex shape, (b) applying a coloring to both main sides of the substrate provided in step (a), (c) applying a functional coloring to the second main side of the substrate provided with a coloring on both main sides in step (b), wherein the functional coloring is caused by at least one photochromic dye and the at least one photochromic dye is contained in a photoresist which forms a polymeric layer on the substrate, and (d) post-processing the substrate provided with a functional coloring on the second main side in step (c) in such a way that the coloring on the first main side is removed, whereby a substrate provided with a coloring and a functional coloring only on the second main side is obtained.

[0013] The method according to the invention enables the single-sided application of a coloring and a functional coloring to a substrate in a simple and thus cost-effective manner. Since both main sides of the substrate are initially provided with a coloring, no specially adapted device is required, such as a vapor deposition device, which allows only one of the two main sides of the substrate to be provided with a coloring. Thus, in the method according to the invention, the substrate can be colored in a conventional coloring system. At the same time, this lowers the requirements for the non-functional dye used for the coloring, since it does not have to be sublimable. All this favors series production of ophthalmic lenses based on the method according to the invention.

[0014] In the following, the method according to the invention for providing a substrate with a coloring and a functional coloring on one side, which is Fig. 1 is shown schematically, described in more detail: In step (a) of the method according to the invention, a substrate is provided to be provided on one side with a coloring and a functional coloring. According to the present invention, the substrate is a half-part made of plastic glass. A half-part, sometimes also referred to as a "blank," is understood here to be a semi-finished product that differs from a finished product in that it is not yet immediately usable for a predetermined purpose, such as as a lens for an eyeglass lens.

[0015] The substrate has a first main side and a second main side opposite the first main side. The first main side of the substrate corresponds to the back of the future spectacle lens, which faces the wearer, while the second main side of the substrate corresponds to the front of the future spectacle lens, which faces away from the wearer. According to the present invention, the second main side of the substrate has a convex shape. As far as the shape of the first main side of the substrate is concerned, the method according to the invention is not further restricted. For example, the first main side of the substrate can have a concave or planar shape. In contrast to a blank, which still has plane-parallel main sides, the half-part serving as the substrate already reveals a spectacle lens due to the shape of the second main side. The second main side of the substrate therefore already corresponds to the final optically effective surface.Compared to a blank, the semi-finished part is already given a basic geometric shape that roughly corresponds to that of the finished product.

[0016] The half-part serving as the substrate is made of plastic glass. Compared to mineral glass, plastic glass has the advantage of being lower in density and thus lighter for the same substrate size. Furthermore, plastic glass offers greater shatter resistance than mineral glass. Suitable plastic materials for the production of plastic glasses are known to those skilled in the art. For example, the half-part serving as the substrate can be made of polythiourethane, polymethyl methacrylate, polycarbonate, polyacrylate, polydiethylene glycol bisallyl carbonate, or combinations thereof, although other transparent plastic materials can also be used in principle.

[0017] In step (b) of the process according to the invention, a coloring is applied to both main sides of the substrate prepared in step (a). The coloring serves solely to impart a specific color tone to the substrate. As mentioned at the beginning, dyes are used which – apart from their absorption properties – have no functional properties whatsoever and therefore do not allow reversible switching between a dark and a light tint. Accordingly, non-functional dyes, such as those used in the process according to the invention, are non-photochromic. Various classes of non-functional dyes are described in the prior art. These are often azo dyes, cyanine dyes, anthraquinone dyes, or the like, which are frequently used in the conventional coloring of spectacle lenses.The skilled person routinely selects a suitable non-functional dye or a mixture of suitable non-functional dyes.

[0018] With regard to the application of the coloring in step (b), the method according to the invention is not further restricted. In a preferred embodiment, the application of the coloring in step (b) is carried out by immersing the substrate in a dyeing bath containing at least one non-functional dye dissolved or dispersed in a liquid medium. As a result of the immersion in the dyeing bath, the substrate is completely provided with a coloring. In addition to the second main side, the first main side of the substrate is also provided with the coloring. The dyeing bath is not subject to any particular restriction as long as it can provide the substrate with a coloring.

[0019] The dyeing bath, which can be part of a conventional dyeing system suitable for a wide variety of applications, is filled with a liquid medium. The at least one non-functional dye is dissolved or dispersed in this liquid medium. The liquid medium can be a water bath, but is not limited to this. To promote the application of the dye to the substrate, the liquid medium is typically heated to a temperature in the range of 60 to 100°C, for example to a temperature in the range of 75 to 95°C. The adjustable heating temperature of the liquid medium depends not least on its boiling point. At elevated temperatures, the absorption of the non-functional dye by the surface of the substrate is promoted. Further details regarding the dyeing process in a dyeing bath are known to those skilled in the art.

[0020] The extent of dye uptake can ultimately be specifically controlled based on the duration of immersion. The extent of dye uptake increases with the duration of immersion. As the extent of dye uptake increases, the transmittance of the substrate colored on both main sides in step (b) decreases. When selecting the duration of immersion, it is important to note that the desired transmittance, also referred to as target transmittance, is only achieved after post-processing in step (d). For example, the removal of the dye on the first main side, possibly together with part of the underlying substrate material, as described in more detail below in connection with step (d), increases the transmittance. The transmittance before ablation is therefore lower than the transmittance after ablation, i.e. lower than the target transmittance.

[0021] In step (c) of the process according to the invention, a functional dye is applied to the second main side of the substrate provided with a dye on both main sides in step (b). The functional dye serves to impart a specific functional property to the substrate. According to the present invention, the functional property is based on a reversible change in the absorption behavior caused by an external stimulus such as UV light. Accordingly, the functional dye is induced by at least one photochromic dye. Various classes of photochromic dyes are described in the prior art. These are often chromenes, viologens, fulgides, and fulgimides, and in particular also spiro compounds such as spirooxazines or spiropyrans, but are not limited to these. The skilled person routinely selects a suitable photochromic dye or a mixture of suitable photochromic dyes.

[0022] According to the present invention, the at least one photochromic dye is contained in a photoresist, wherein the photoresist, as mentioned above, forms a polymeric layer on the substrate.

[0023] In a preferred embodiment, the functional dyeing is applied in step (c) by spin coating. If the functional dyeing is applied by spin coating in step (c), this is expediently only done on the second main side of the substrate. A functional dyeing applied to the first main side of the substrate would, together with the underlying dyeing, be removed in step (d) anyway. Instead of spin coating, the functional dyeing can also be applied in step (c) by dipping. Naturally, the substrate is completely provided with a functional dye. In addition to the second main side, the first main side of the substrate is also provided with the functional dye.

[0024] In step (d) of the method according to the invention, the substrate provided with a functional coloring on the second main side in step (c) is post-processed. The post-processing in step (d) is carried out in such a way that the coloring on the first main side is removed. If there is a functional coloring above the coloring on the first main side, which results, for example, from the application of the dipping process in step (c), this is removed simultaneously. The post-processing in step (d) ultimately produces a substrate which is provided with a coloring and a functional coloring only on the second main side and thus on one side.

[0025] With regard to the post-processing in step (d), the method according to the invention is not further restricted. In a preferred embodiment, the post-processing in step (d) is carried out by at least one form of surface processing selected from the group consisting of milling, grinding, and polishing. In principle, however, any other form of surface processing is conceivable, as long as it ensures residue-free removal of the coloring.

[0026] If necessary, in step (d), in addition to the coloring on the first main side, a portion of the underlying substrate material is also removed. This makes it possible to adjust the geometric shape of the substrate to later requirements, for example with regard to the desired optical effect, for example with regard to the desired refractive power as resulting from an ophthalmic prescription. It should be noted that the removal of the substrate material also influences the transmission. This must be taken into account when applying the coloring in step (b). If a comparatively large amount of substrate material has to be removed in step (d) to achieve the desired optical effect, a longer immersion time in the dye bath must be provided in step (b) in order to achieve the target transmission.

[0027] In addition to steps (a) to (d), the method according to the invention can further comprise a step of applying one or more coating layers to at least one of the two main sides of the substrate, which is provided with a coloring and a functional coloring only on the second main side, hereinafter also referred to as step (e). Typically, in step (e), in addition to the second main side of the substrate, which is provided with a coloring and a functional coloring, the first main side of the substrate is also coated. Typical coating layers include hard coatings, which serve to protect against scratches, interference / anti-reflective coatings, which serve to reduce reflections, and easy-care coatings, sometimes also referred to as "topcoat" or "cleancoat", which serve to repel water and dirt, but are not limited thereto. Appropriate measures for applying such coating layers are known to those skilled in the art.Insofar as, according to the present invention, a photoresist is used when applying the functional coloring in step (c), it may be necessary to remove excess residues of the photoresist at the edges of the substrate before annealing in step (e).

[0028] According to the present invention, the substrate is provided with a coloring and a functional coloring only on the second main side, which has a convex shape. However, the method according to the invention can be easily modified such that, instead of the second main side, the first main side of the substrate, which has, for example, a concave or planar shape, is provided with a coloring and a functional coloring. Accordingly, in step (c), the functional coloring is applied to the first main side of the substrate, and in step (d), the coloring is then removed from the second main side, optionally together with a portion of the underlying substrate material.

[0029] The substrate obtained using the process according to the invention, which is provided with a single-sided coloring and a functional coloring, is versatile and can be used, for example, as a lens for an eyeglass lens. The substrate is then edge-machined for fitting into an eyeglass frame. Description of the figure: Fig. 1 shows a schematic representation of the method according to the invention. Fig. 1 Step (e) also shown is optional. List of reference symbols: 1 substrate (half part made of plastic glass) 11 first main page of the substrate 12 second main page of the substrate 2 Coloring 3 Functional staining Example

[0030] The following embodiment serves to further explain the present invention, but is not limited to it.

[0031] In accordance with the process of the invention, substrates were coated on one side with a dye and a functional dye. Different non-functional dyes, such as anthraquinone dyes or azo dyes, were used for the dyeing. However, the same photochromic dye was always used for the functional dyeing.

[0032] As substrates, half-sections made of plastic glass with a first main surface, which had a planar shape, and a second main surface, which had a convex shape, were initially prepared. The substrates were then immersed in a dyeing bath. This contained the respective non-functional dye for coloring in an aqueous solution. By immersing them in the dyeing bath, the substrates were completely dyed. The immersion time was chosen so that the target transmittance was achieved after post-processing. The dyeing process took place at a temperature range of 60 to 100°C.

[0033] Subsequently, the transmittance of the substrates was measured at a wavelength of 380 to 780 nm, with the transmittance being weighted by the relative spectral luminosity (V-lambda curve). A "Lens Colour Analyser TFM-1" transmission measuring device from "tec5 AG" was used for this purpose. The measured values ​​are listed in Table 1 and are referred to therein as the transmittance before ablation. Due to the fact that both main sides of the substrates were initially colored, and due to the fact that the half-sections serving as substrates were still relatively thick, the transmittance before ablation was comparatively low.

[0034] The functional dye was then applied to the second main surface of the fully dyed substrates. This was done either by spin coating or by dipping using a photoresist containing the photochromic dye for the functional dye.

[0035] After the functional coloring had been applied, the substrates were temporarily stored in a warehouse for semi-finished products before they were finally post-processed. This was achieved by a suitable form of surface processing, whereby in addition to the coloring on the first main side, a portion of the underlying substrate material was also removed, so that the desired optical effect was achieved. The transmittance of the substrates was measured again under the previously mentioned conditions, resulting in the measured values ​​referred to in Table 1 as transmittance after removal. These corresponded to the target transmittance. By removing the coloring on the first main side together with a portion of the underlying substrate material, the transmittance of the substrates increased accordingly, as can be seen from a comparison of the transmittance after removal with the transmittance before removal. Table 1 Color tone of the substrate after coloring Transmission before ablation [%] Transmission after ablation [%] brown 11,5 55,0 green 22,2 50,0 gray 18,0 50,0

[0036] A hard coating was then applied to both main surfaces of the substrates, which had been coated on one side with a color and a functional color on the other, using a dipping process. An interference / anti-reflective coating was then applied to this. The resulting substrates possessed all the required properties and thus represented raw, round lenses that could then be edge-machined for fitting into a frame.

[0037] As can be seen from the exemplary embodiment, the method according to the invention enables the one-sided provision of a substrate with a coloring and a functional coloring in a simple and thus cost-effective manner.

Claims

[1] A method for providing a substrate with a coloring and a functional coloring on one side, comprising the following steps (a) to (d): (a) Providing a substrate to be provided with a coloring and a functional coloring on one side, wherein the substrate is a half-part made of plastic glass with a first main side and a second main side opposite the first main side, which has a convex shape, (b) applying a coloring to both main sides of the substrate provided in step (a), (c) applying a functional coloring to the second main side of the substrate provided with a coloring on both main sides in step (b), wherein the functional coloring is caused by at least one photochromic dye and the at least one photochromic dye is contained in a photoresist which forms a polymeric layer on the substrate, and (d) post-processing the substrate provided with a functional coloring on the second main side in step (c) in such a way that the coloring on the first main side is removed, whereby a substrate provided with a coloring and a functional coloring only on the second main side is obtained. [2] The method of claim 1, wherein the first main side of the substrate has a concave or planar shape. [3] The method according to claim 1 or 2, wherein the half-part serving as a substrate is made of polythiourethane, polymethyl methacrylate, polycarbonate, polyacrylate, polydiethylene glycol bisallyl carbonate or combinations thereof. [4] A method according to any one of claims 1 to 3, wherein the application of the coloring in step (b) is carried out by immersing the substrate in a dyeing bath containing at least one non-functional dye dissolved or dispersed in a liquid medium. [5] Method according to one of claims 1 to 4, wherein the application of the functional dye in step (c) is carried out by spin coating or by means of a dipping process. [6] Method according to one of claims 1 to 5, wherein the post-processing in step (d) is carried out by at least one form of surface processing selected from the group consisting of milling, grinding and polishing. [7] Method according to one of claims 1 to 6, wherein in step (d) in addition to the inking on the first main side, a part of the underlying substrate material is also removed. [8] A method according to any one of claims 1 to 7, further comprising the following step (e): Applying one or more coating layers to at least one of the two main sides of the substrate which is provided with a coloring and a functional coloring only on the second main side.

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