Release liner for protecting optical wafers

Abstract

A protective release liner for an optical wafer or a multi-layer film cuttable to the optical wafer, the liner having a melting point (T m and one or more liner layers B each comprising a polymer B independently selected from polymers having a melting point of 140°C to 170°C, wherein film A has a first surface configured to directly contact an optical wafer when the liner is adhered to the optical wafer and a second surface opposite the first surface, and film B is disposed on the second surface of film A, wherein the combined thickness of the one or more liner layers A is at least 5 μm and the combined thickness of the one or more liner layers B is at least 30 μm.

Description

[Technical Field]

[0001] The present disclosure relates to an improved release liner for protecting optical wafers. It also relates to optical wafers protected by the improved release liner. It also relates to the use of the improved release liner for protecting optical wafers to avoid defect formation on wafers during wafer formation. [Background technology]

[0002] Optical wafers (hereafter simply referred to as "wafers") can be included in ophthalmic lenses to provide a function to the ophthalmic lens. Wafers are generally composed of a functional film or layer protected by one or two protective films or layers. The function provided by the wafer can be, for example, a light absorbing function (e.g., for UV, visible, and / or IR light absorption), a photochromic function, a polarizing function, or a color enhancing function.

[0003] Thus, the wafer is a film that has optical and thermomechanical properties that make it suitable for inclusion in an ophthalmic lens, and includes a functional film (or layer) that provides the lens with the desired function or functions. In some cases, the wafer can be used directly as an ophthalmic lens.

[0004] The wafer may be included in an ophthalmic lens by injection molding the wafer into a lens mold (in the case of a thermoplastic lens substrate) or by casting the lens substrate into the lens mold against the wafer (in the case of a thermoset lens substrate). The wafer may thus be included on the front surface of the lens substrate, on the back surface of the lens substrate, or embedded in the lens substrate.

[0005] The wafers may also be included in ophthalmic lenses by laminating the wafer onto a lens substrate, in which case an adhesive may be used to ensure strong adhesion of the wafer onto the lens substrate.

[0006] Generally, a wafer is made by cutting it to a desired size from a film having the same layer structure as the wafer. Furthermore, before the wafer is included in an ophthalmic lens, it is necessary to form the wafer, that is, to give the wafer a desired curvature. This step of forming the wafer is carried out using a former, which heats and presses the wafer to give it the desired curvature.

[0007] When manufacturing an ophthalmic lens comprising a wafer, the wafer or the film used to make the wafer is subjected to various process steps (e.g., cutting the wafer to a desired dimension, forming the wafer to a desired curvature, etc.). During this process, it is important to protect the wafer or the film used to make the wafer to avoid cosmetic defects in the final lens. For example, it is necessary to protect the wafer or the film used to make the wafer from possible contamination or scratches. For this purpose, the wafer or the film used to make the wafer is covered on one or both of its major surfaces with a release liner. The liner is removed (by peeling) if necessary in the final step of the process (e.g., before the injection molding or casting step, or before laminating the wafer onto a lens substrate).

[0008] The use of a protective release liner is currently essential for consumer acceptance of lenses obtained through processes involving the use of wafers.

[0009] However, to be acceptable for mass production, the liner must, in addition to effectively protecting the wafer, also: - Easy to cut without leaving residue on the edges, - To prevent unnecessary peeling of the wafer edge when handling the protective wafer; - not leaving any melt residue on the former used to give the wafer the desired curvature; - Does not stick to the operator's gloves, - have excellent peelability, including easy peel initiation, no tearing of the liner during peeling, and no residue left behind after peeling; Several requirements must be met, including:

[0010] Moreover, the inventors behind the present disclosure have discovered that the wavy patterns observed on ophthalmic lenses obtained through processes involving the use of wafers are caused by the use of an improper liner. In fact, they have discovered that such wavy patterns are initially present on the liner (often when the liner includes a polypropylene layer) and are transferred to the wafer during the step of forming the wafer with the desired curvature (it is necessary to keep the liner on the wafer during this step to avoid other issues related to melting and contamination of the wafer and / or former). The wavy patterns thus transferred to the wafer are retained in the final ophthalmic lens. Summary of the Invention [Means for solving the problem]

[0011] In order to solve these problems, the present invention provides: Melting point (T m a film A comprising one or more liner layers A each comprising a polymer A independently selected from the group consisting of polymers having A film B including one or more liner layers B each including a polymer B independently selected from polymers having a melting point of 140°C to 170°C; 1. A protective release liner for an optical wafer or a multi-layer film cuttable to an optical wafer, comprising: the film A includes a first surface configured to directly contact the optical wafer when the liner is adhered to the optical wafer, and a second surface opposite the first surface; and The film B is disposed on the second surface of the film A; A protective release liner is provided, wherein the combined thickness of the one or more liner layers A is at least 5 μm and the combined thickness of the one or more liner layers B is at least 30 μm. [Brief explanation of the drawings]

[0012] [Figure 1] Two commercial polarizing wafers are shown with a protective layer made of triacetyl cellulose. DETAILED DESCRIPTION OF THE INVENTION

[0013] As defined herein, an ophthalmic lens is a lens designed for use in a monocle or eyeglasses (including sunglasses, goggles, and safety glasses). As defined herein, contact lenses are not ophthalmic lenses. Ophthalmic lenses are typically used to protect the eye and / or correct vision. Ophthalmic lenses can be uncorrected ophthalmic lenses (also called plano lenses or afocal lenses) or corrective ophthalmic lenses. Corrective lenses can be single vision lenses, bifocal lenses, trifocal lenses, or progressive lenses. As defined herein, an ophthalmic lens can be a finished lens or a semi-finished lens. Semi-finished lenses are subjected to various processing steps such as surfacing, tinting, coating, edging, etc. before being finally included in eyeglasses or a monocle. Finished lenses can be included directly in eyeglasses or monocles.

[0014] As defined herein, a film is a stack of one or more layers.

[0015] A layer corresponds to the thickness of a given material between two interfaces. As defined herein, a stack of two or more layers is not a layer.

[0016] Generally, it is possible to observe the interface between two successive layers microscopically.

[0017] The layers may be assembled by coextrusion or by pressing one layer onto the other. In some cases, inserting an adhesive layer between two layers and then pressing them together helps assemble the two layers. In some cases, the electrostatic forces between the layers are sufficient to assemble them with only minimal pressure. For purposes of this definition, an adhesive layer counts as a layer.

[0018] As defined herein, a film or layer "disposed on" a surface is defined as a film or layer that (a) is positioned over the surface, (b) need not be in direct contact with the surface, i.e., one or more intervening layers may be disposed between the surface and the film or layer, and (c) need not completely cover the surface. Preferably, however, a film or layer "on" a surface completely covers the surface.

[0019] As defined herein, the outer surface of a membrane or layer is the surface of said membrane or layer that does not have any other layers disposed thereon. As defined herein, a membrane or layer may have zero, one, or two outer surfaces.

[0020] The protective release liner of the optical wafer or multi-layer film cuttable to optical wafers of the present disclosure comprises: Melting point (T m a film A comprising one or more liner layers A each comprising a polymer A independently selected from the group consisting of polymers having A film B including one or more liner layers B each including a polymer B independently selected from polymers having a melting point of 140°C to 170°C; Including, the film A includes a first surface configured to directly contact the optical wafer when the liner is adhered to the optical wafer, and a second surface opposite the first surface; and The film B is disposed on the second surface of the film A; The total thickness of the one or more liner layers A is at least 5 μm, and the total thickness of the one or more liner layers B is at least 30 μm.

[0021] For example, polymer A has a melting point (T m ) can be selected from polymers having the following structure.

[0022] For example, polymer B may be selected from polymers having a melting point of 150°C to 170°C.

[0023] For example, the protective release liner of the optical wafer or multi-layer film cuttable to optical wafers of the present disclosure may be: Melting point (T) of 115℃ to 135℃ m a film A comprising one or more liner layers A each comprising a polymer A independently selected from the group consisting of polymers having a film B including one or more liner layers B each including a polymer B independently selected from polymers having a melting point of 150°C to 170°C; and the film A includes a first surface configured to directly contact the optical wafer when the liner is adhered to the optical wafer, and a second surface opposite the first surface; and The film B is disposed on the second surface of the film A; The total thickness of the one or more liner layers A is at least 5 μm, and the total thickness of the one or more liner layers B is at least 30 μm.

[0024] In the present disclosure, the melting point of a polymer is determined by the following parameters: - first equilibration step at -90.00 °C, - + / - 0.80°C modulation applied every 60 seconds, - First ramp to 250.00°C at 5.00°C / min, - Second ramp to -90.00°C at 10.00°C / min, - Third ramp to 250.00°C at 5.00°C / min, can be measured by modulated differential scanning calorimetry in accordance with the ISO11357-3 standard using

[0025] It is believed that liner layer B protects the underlying liner layers (including liner layer A) from heat and improves the strippability of the liner. If the total thickness of liner layer B is insufficient, residues or dimple-like defects will remain on the wafer after stripping of the liner.

[0026] It is believed that liner layer A simultaneously provides good adhesion and release properties, while providing a cushion that helps avoid imprinting unwanted patterns (that may be present on liner layer B) onto the wafer during formation. Moreover, liner layer A also reduces the amount of residue or defects remaining on the wafer after stripping of the liner, compared to other types of liner layers that provide good adhesion.

[0027] The liner of the present disclosure can be used with various types of wafers and strongly reduces the appearance of ripple patterns when forming wafers compared to prior art liners. Moreover, it generally has excellent properties that make it suitable for use in mass production.

[0028] In the liners disclosed herein, each liner layer A can be devoid of a polymer with a melting point below 100° C. For example, in the liners disclosed herein, each liner layer A can be devoid of a polymer with a melting point below 115° C.

[0029] In the liners disclosed herein, each liner layer A may comprise at least 90% by weight of polymer A, based on the weight of liner layer A.

[0030] In the liners disclosed herein, each liner layer A may comprise polymer A as the only polymer present in said liner layer A. In this case, non-polymeric additives may be present in liner layer A.

[0031] In the liners disclosed herein, each liner layer B may comprise at least 90% by weight of polymer B, based on the weight of liner layer B.

[0032] In the liners disclosed herein, each liner layer B may comprise polymer B as the only polymer present in said liner layer B. In this case, non-polymeric additives may be present in liner layer B.

[0033] In the liners disclosed herein, polymer A can be a polymer that contains at least 80 mol% ethylene monomers relative to the total amount of monomers in the polymer. For example, polymer A can be polyethylene (defined as a polymer that contains 100 mol% ethylene monomers relative to the total amount of monomers in the polymer) or a copolymer of ethylene and methacrylic acid that contains at least 90 mol% ethylene monomers relative to the total amount of monomers in the polymer.

[0034] In the liners disclosed herein, polymer B can be polypropylene.

[0035] In the liners disclosed herein, the first side of Film A may provide static adhesion onto the optical wafer, or the liner may adhere to the optical wafer via an adhesive layer.

[0036] For example, the first side of film A may be the side of the adhesive layer that is in direct contact with liner layer A, or it may be the side of liner layer A. In particular, the liner layer A to which the first side of film A belongs or the liner layer A that is in direct contact with the adhesive layer to which the first side of film A belongs may have a thickness comprised between 10 μm and 150 μm, such as between 10 μm and 130 μm, for example between 10 μm and 70 μm, for example between 15 μm and 50 μm.

[0037] In the liners disclosed herein, Film A may lack a layer having a melting point above 135°C.

[0038] In the liners disclosed herein, Film A may lack a polypropylene layer.

[0039] In the liners disclosed herein, film A may include only one or more liner layers A, or may include only one or more liner layers A and one or more adhesive layers.

[0040] In the liners disclosed herein, Film B may lack a layer having a melting point below 140°C.

[0041] In the liners disclosed herein, film B may include only one or more liner layers B, or may include only one or more liner layers B and one or more adhesive layers.

[0042] In the liners disclosed herein, the thickness of each layer A or B can be from 1 μm to 150 μm, for example from 1 μm to 100 μm or from 10 μm to 150 μm.

[0043] In the liners disclosed herein, the total thickness of the one or more liner layers A may be at least 10 μm, such as from 10 μm to 150 μm, such as from 10 μm to 130 μm, such as from 10 μm to 70 μm, such as from 10 μm to 50 μm.

[0044] In the liner disclosed herein, film A may have a thickness of at least 10 μm, such as comprised between 10 μm and 150 μm, such as between 10 μm and 130 μm, such as between 10 μm and 70 μm, such as between 10 μm and 50 μm.

[0045] In the liners disclosed herein, the total thickness of the one or more liner layers B can be at least 35 μm, such as from 35 μm to 100 μm, or at least 40 μm, such as from 40 μm to 60 μm.

[0046] In the liner disclosed herein, film B may have a thickness of at least 35 μm, for example comprised between 35 μm and 100 μm, or at least 40 μm, for example comprised between 40 μm and 60 μm.

[0047] In the liners disclosed herein, film A can be in direct contact with film B.

[0048] In the liners disclosed herein, liner layer A may be coextruded with liner layer B.

[0049] In the liners disclosed herein, film B may comprise only two liner layers B separated by an adhesive layer. Specifically, film B may consist of only two liner layers B separated by an adhesive layer.

[0050] The present disclosure also provides the following sequence: A first release liner according to any one of the preceding claims; optionally a front primer layer; A front layer that is in direct contact with the front primer layer, functional layer, Back layer, Optionally, a back primer layer in direct contact with the back layer; Optionally, a second release liner according to any one of the preceding claims, 1. A multi-layer film suitable for stacking together to make an optical wafer comprising the same, The outer surface of the first liner is the outer surface of the multi-layer film, and the first surface of film A of the first liner is Front layer, or When applied, a front primer layer, Direct contact with Further, when applicable, the outer surface of the second liner is the outer surface of the multi-layer film, and the first surface of film A of the first liner is Back layer, or When applicable, a back primer layer, This relates to a multi-layer film that is in direct contact with the substrate.

[0051] In the multi-layer films disclosed herein, the front and back layers can be considered the outermost layers of a protective film that protects the functional layer or protective layers that protect the functional layer.

[0052] A primer layer can be used when casting a lens' polymeric material onto a wafer to increase adhesion of the polymeric material to one or both of the wafer's protective films or layers. For example, Korean Patent No. 993596B1, International Publication No. 2018 / 052454, and International Publication No. 2019175354A1 describe primer coatings for improving adhesion between a triacetyl cellulose (TAC) protective layer of a wafer and a cast CR-39 plastic lens in which the wafer is embedded. International Publication No. 2021 / 170702 describes a primer coating for improving adhesion of a polarizing wafer with a cast TAC protective film or layer positioned on top of a poly(thio)urethane lens (TAC-on-TOP), such as an ultra-high refractive index UHI Mitsui 7® lens. In a TAC-on-TOP lens, there is only one adhesive interface between the TAC film or layer and the lens.

[0053] The primer composition can be applied to either surface of the wafer or to both surfaces of the wafer.

[0054] The primer composition may be applied to the wafer by any method, including but not limited to spraying or roll coating. The primer composition may be air-dried or air-oven dried and cured by exposure to UV radiation or heat.

[0055] In the multi-layer films disclosed herein, the front and back layers can each comprise a thermoplastic polymer.

[0056] In the multi-layer films disclosed herein, the thermoplastic polymer included in the front layer and the thermoplastic polymer included in the back layer may be independently selected from the list including polycarbonate, poly(methyl methacrylate), polyethylene terephthalate, cyclic olefin copolymer, polyamide, and cellulose acetate butyrate.

[0057] In the multi-layer films disclosed herein, both the front and back layers may comprise at least 90% by weight of thermoplastic polymer, based on the weight of the front and back layers, respectively.

[0058] In the multilayer films disclosed herein, the thermoplastic polymer in the front layer and the thermoplastic polymer in the back layer can both be polycarbonate, poly(methyl methacrylate), polyethylene terephthalate, cyclic olefin copolymer, polyamide, or cellulose acetate butyrate.

[0059] The multi-layer films disclosed herein may further include an adhesive layer between the functional layer and the front layer, said adhesive layer being in direct contact with the functional layer and the front layer.

[0060] The multi-layer films disclosed herein may further include an adhesive layer between the functional layer and the backing layer, said adhesive layer being in direct contact with the functional layer and the backing layer.

[0061] The present disclosure also relates to optical wafers made with the multi-layer films of the present disclosure.

[0062] Optical wafers can be made using the multi-layer films of the present disclosure by cutting the film to the appropriate dimensions.

[0063] The present disclosure also relates to the use of the liners disclosed herein to protect optical wafers during their formation while avoiding or limiting imprinting of patterns onto the optical wafers during formation.

[0064] In the uses disclosed herein, the optical wafer can be an optical wafer disclosed herein. [Example]

[0065] In an embodiment, a liner according to the present disclosure, Liner 1, is as follows: a polyethylene layer having a melting point of 120°C and a thickness of 25 μm, coextruded with a polypropylene layer having a melting point of 160°C and a thickness of 5 μm; - an adhesive layer having a thickness of about 5 μm, and - a polypropylene layer having a melting point of 160 ° C and a thickness of 40 μm, Stacked on top of each other.

[0066] Figure 1 shows two commercial polarizing wafers with a protective layer made of triacetyl cellulose. On the left, the liner used (not according to the invention) was a single layer of polypropylene with a melting point of 163°C and a thickness of 45 μm, glued directly onto the wafer. On the left, liner 1 is used. The texture visible on the left is absent on the right.

[0067] [Table 1]

[0068] Table 1 reports the patterns observed when forming various types of wafers with protective layers made of polycarbonate. The liner of the present invention significantly reduces the appearance of wavy patterns and the number of defects compared to the original liner. The original liner is made of a layer containing a copolymer of ethylene and methacrylic acid with a melting point of 96°C and a thickness of 5.5 μm, coextruded with a polypropylene layer with a melting point of 161°C and a thickness of 45 μm.

Claims

1. 1. A protective release liner for an optical wafer or a multi-layer film cuttable to said optical wafer, said liner comprising: Melting point (T ｍ a film A comprising one or more liner layers A each comprising a polymer A independently selected from the group consisting of polymers having the formula a film B comprising one or more liner layers B each comprising a polymer B independently selected from polymers having a melting point of 140°C to 170°C; Including, the film A includes a first surface configured to directly contact the optical wafer when the liner is adhered to the optical wafer, and a second surface opposite the first surface; and the film B is disposed on the second surface of the film A; A protective release liner, wherein the total thickness of said one or more liner layers A is at least 5 μm, and the total thickness of said one or more liner layers B is at least 30 μm.

2. 10. The liner of claim 1, wherein each liner layer A comprises at least 90% by weight of said polymer A, based on the weight of said liner layer A.

3. 3. The liner of claim 1 or 2, wherein each liner layer B comprises at least 90% by weight of said polymer B, based on the weight of said liner layer B.

4. The liner according to any one of claims 1 to 3, wherein polymer A is a polymer comprising at least 80 mol % of ethylene monomers compared to the total amount of monomers in the polymer.

5. The liner according to any one of claims 1 to 4, wherein polymer B is polypropylene.

6. The liner according to any one of claims 1 to 5, wherein the first surface of the film A is the surface of an adhesive layer that is in direct contact with the liner layer A, or is the surface of the liner layer A.

7. The liner according to any one of claims 1 to 6, wherein the one or more liner layers A have a total thickness of at least 10 µm.

8. The liner according to any one of claims 1 to 7, wherein the one or more liner layers B have a total thickness of at least 35 µm.

9. The following order: A first release liner according to any one of claims 1 to 8. optionally a front primer layer; a front layer in direct contact with the front primer layer; functional layer, Back layer, Optionally, a back primer layer in direct contact with said back layer; Optionally, a second release liner according to any one of claims 1 to 8, 1. A multi-layer film suitable for stacking together to make an optical wafer comprising the same, The outer surface of the first liner is the outer surface of the multi-layer film, and the first surface of the film A of the first liner is the front layer, or When applicable, said front primer layer, Direct contact with Further, when applicable, the outer surface of the second liner is the outer surface of the multi-layer film, and the first surface of the film A of the first liner is the back layer, or When applicable, said back primer layer, Multi-layer film that comes into direct contact with the skin.

10. 10. The multi-layer film of claim 9, wherein the front layer and the back layer each comprise a thermoplastic polymer.

11. 11. The multilayer film of claim 10, wherein the thermoplastic polymer in the front layer and the thermoplastic polymer in the back layer are independently selected from the list including polycarbonate, poly(methyl methacrylate), polyethylene terephthalate, cyclic olefin copolymer, polyamide, and cellulose acetate butyrate.

12. 12. The multi-layer film of claim 10 or 11, wherein the front layer and the back layer both comprise at least 90% by weight of a thermoplastic polymer, based on the weight of the front layer and the back layer, respectively.

13. 13. The multilayer film of claim 10, wherein the thermoplastic polymer in the front layer and the thermoplastic polymer in the back layer are both polycarbonate, poly(methyl methacrylate), polyethylene terephthalate, cyclic olefin copolymer, polyamide, or cellulose acetate butyrate.

14. An optical wafer made from the multilayer film of any one of claims 9 to 13.

15. 9. Use of a liner according to any one of claims 1 to 8 to protect an optical wafer when forming said optical wafer while avoiding or limiting imprinting of a pattern onto said optical wafer during formation.

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