TAC Primer Coating with Improved Adhesion

Abstract

An enhanced primer formulation that may be used in a variety of lens and film laminate applications is disclosed herein. The enhanced primer formulation may be used to enhance adhesion between a film or laminate and a polymerizable or polymerized material.

Claims

1. A method for adhering a TAC film or a TAC laminate to a polymerized or polymerizable material, comprising using a primer, said primer resulting from a primer composition comprising: 10-30% by weight of at least one acrylic methacrylate copolymer; 10-30% by weight of at least one functional urethane acrylic oligomer; 1-25% by weight of at least one crosslinking agent; 1-5% by weight of at least one UV or thermal initiator; 50-90% by weight of a solvent; and the thickness of said primer ranging from about 1 m to about 4 m.

2. The method according to claim 1, wherein the crosslinking agent in the primer composition comprises at least two reactive functional groups independently selected from the group consisting of acrylic, acrylate, allyl, vinyl, propargyl, isocyanate, amine, and epoxy.

3. (canceled)

4. The method according to claim 1, wherein the crosslinking agent in the primer composition is a multifunctional acrylate.

5. The method according to claim 4, wherein the multifunctional acrylate is pentaerythritol triacrylate.

6. The method according to claim 1, wherein the methacrylate copolymer in the primer composition contains an acid number from 10 to 80 in the copolymer.

7. (canceled)

8. The method according to claim 1, wherein the polymerized material is polyether block amide film (Pebax film), polycarbonate film, polymethyl methacrylate film, polyamide film (nylon film), polyester film (PET), cellulose acetate butyrate (CAB) film, or a composite film comprising any combination of the preceding.

9. The method according to claim 1, wherein the polymerized material is either casting resin monomer such as allyl diglycol carbonate; middle index acrylic, amine, or styrene monomers, epithio-urethane monomers or a reactive adhesive to bond to an optical film selected from the group consisting of UV acrylic adhesive, polyurethane adhesive, epoxy adhesive, amine adhesive, and two-component polyurethane and epoxy adhesives.

10. The method according to claim 1, wherein the TAC film is a clear optical film or an optical functional film.

11. The method according to claim 1, wherein the TAC laminate is a TAC-PVA-TAC polarizing laminate.

12. (canceled)

13. The method according to claim 1, wherein the solvent in the primer composition is at least one of a ketone solvent, an acetate solvent, a methylene chloride solvent, or a combination thereof.

14. (canceled)

15. The method according to claim 1, wherein the primer composition has a primer hardness between 9B and 6B by pencil hardness test.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0021] FIG. 1 is a side view of a cast polarizing lens 100, where 110 is a TAC film, 120 is a polarizing PVA film, 130 is a primer containing crosslink agent, 140 is CR-39 resin.

[0022] FIG. 2 is a side view of a polarizing photochromic laminate 200, where 110 is a TAC film, 120 is a polarizing photochromic Pebax film, 130 is a primer containing crosslink agent, 150 is a reactive adhesive.

DETAILED DESCRIPTION

[0023] Various features and advantageous details are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments, are given by way of illustration only, and not by way of limitation. Various substitutions, modifications, additions, and/or rearrangements will be apparent to those of ordinary skill in the art from this disclosure.

[0024] In the following description, numerous specific details are provided to provide a thorough understanding of the disclosed embodiments. One of ordinary skill in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0025] Several primer examples (solutions) and comparative primer examples (solutions) were produced. Example variables include presence and absence of crosslinking monomers and different primer thicknesses. The examples and results are described below.

Surfacing And Edging Test (Set) for Cast Delamination

[0026] In the experiments described below, the surfacing and edging test is employed to induce stress potentially leading to delamination in various lens samples.

[0027] The surfacing and edging test is applicable to all ophthalmic lenses with embedded or surface mounted film. Lenses may be coated or uncoated, and may or may not include at least one of a hard coat, an antireflective component, a finishing vacuum coating, and a top coat. The observed failure rates provide an indication of the risk of failures during lens processing.

[0028] Lenses are generated with a power offset. The lenses are then fined with increased pressure to exert mechanical forces on lens edges, resulting in high stress at the interfaces, potentially weakening the adhesion. Polishing is performed in a typical manner known to one skilled in the art. Edging is performed with the most aggressive setting on a typical edger.

[0029] The test results outlined below were performed on polarized CR39 single vision lenses. The lenses were processed to +0.50 power with target thickness 2.8mm. Lenses were blocked with metal alloy at an offset 0.1 diopter between the generator and the fining back curve. The fining pressure was raised to the safe maximum limits of the equipment (25 PSI, Gerber-Coburn). Polishing was performed according to standard operating procedures. Edging was performed on a fast-cycle edger which is selected to be especially aggressive (Triumph edger).

Inspection

[0030] A visual inspection for any anomalies resulting from any of the preceding steps is performed for each lens. Lenses are visually inspected for delamination. Any delamination is interpreted as a lens failure.

Peel Force Measurement for Laminate Adhesion

[0031] The peel force value between TAC and another functional film is measured by Mark-10 equipment. A film witdth of 25 mm is tested in an anhydrous environment. The TAC film is separated firstly from the TAC-Pebax-TAC laminate interface and then peeled at 180 T-peel with a peeling speed of 1.5 mm/min. The peel force value (Newton) is recored when it reaches a certain stable level, usually after peeled above 20 mm. One of skill in the art would consider that the value of the peel force is sufficient, i.e., the film does not delaminate during further surfacing and edging process when the value is above 10 N/inch.

EXAMPLE 1

Primer Formulations and Casting

Step One: Primer Formulations and Coating on TAC Polar Laminate

[0032] Comparative primer solutions consisted of a base primer or a base primer in combination with a crosslinking agent, with the base primer solution serving as a control. The base primer formulation included a an acrylic polymer resin (MW 10,000 to 100,000), a reactive acrylic oligomer, and a UV or thermal initiator. One exemplary, non-limiting crosslinking agent employed in the examples is pentaerythrityl triacrylate. However, other compounds which function to crosslinking base primer components are also effective. A solvent was used to reduce the solid content of the base and modified primers.

[0033] The adhesive strength of the primer formulations was examined using a TAC polar laminate cast in a polymerizable meterial. The laminate used for the experiments below was a TAC-PVA-TAC polar laminate.

[0034] Base and modified primers were coated on both sides of the TAC laminate by a Meyer Rod coating machine with different rod sizes (numbers) at a coating speed of about 4 mm/second. The coatings were then cured using a Fusion conveyer UV system with an average UV intensity of 600 mJ/cm.sup.2 to give a series of TAC polarizing laminate films. Each TAC polar laminate film included either a cured base primer coating (control) or a cured, modified primer coating (comparative primer examples).

Step Two: Polar Laminate Forming and Casting With Polymerizabk Material

[0035] Primer-coated TAC polar laminates were thermally formed using LEMA forming equipment to achieve a 4 or 6 base curve for polarizing lens casting. The curved TAC polar laminate wafers were then placed into a glass mold assembly for casting with a polymerizable material. The examples below employed allyl diglycol carbonate (CR-39) as the polymerizable material. After casting and mold disassembly, a series of TAC polar CR-39 semi-finished (SF) lenses were obtained.

Step Three: Cast TAC Polarizing CR-39Lens SET Evaluation

[0036] The SET results are summarized in Table 1 below. The base primer control lens (Primer #1, supplied by Onbitt Inc) became delaminated during SET test. Two base primer+crosslinker examples (Primers #3 and #4) also became delaminated. These examples included 30% and 10% crosslinker, respectively. Primer #2 (10% crosslinker) did not become delaminated and was coated using a different rod number from Primer #4. Primers #5 and #6 included 5% and 3% crosslinker, respectively, and did not become delaminated. These results show that the crosslinker improves the adhesive strength of the primer. The high crosslinking concentration (30%) resulted in a rigid primer which reduced the adhesion level between TAC and cast resin. When the primer was applied in a thickness greater than 5 m, the adhesion level was sub-optimal. The results demonstrate that there is an inverse correlation between crosslinker concentration and adhesive strength, as lower crosslinker concentrations resulted in improved adhesion, and that primer thickness should be maintained below a certain value.

TABLE-US-00001 TABLE 1 SET Results Primer Thickness Primary CA After Primer Primer Primer Amount Rod X-Hatch Pencil Casting SET # Formulation Component (%) # Adhesion Hardness in CR-39 Results 1 Base PU Acrylate 0% 3.5 Moderate <<9B 2-3 m Delaminated (control) (2-5) 2 Base + CA PU Acrylate + CA 10% 3.5 Moderate 6B-9B 2-3 m No (2-5) Delamination 3 Base + CA PU Acrylate + CA 30% 3.5 Poor ~HB 2-3 m Delaminated (>5) 4 Base + CA PU Acrylate + CA 10% 6 Moderate 6B-9B 5-6 m Delaminated (2-5) 5 Base + PU Acrylate + CA 5% 3.5 Good 6B-9B 1-2 m No CA + (0-1) Delamination additional solvent 6 Base + PU Acrylate + CA 3% 3.5 Good 6B-9B 1-2 m No CA + (0-1) Delamination additional solvent CA = crosslinking agent (pentaerythritol triacrylate); all examples were subjected to rod coating; additional solvent = ethyl acetate.

EXAMPLE 2

Primer for for Tac Film Laminates

[0037] TAC Laminate with Polyether Block AmideFilm by a Primer-Coated TAC Film

[0038] A clear TAC film (Lofo 916) was coated with the Primer #5 primer formulation. The coated TAC film was then UV cured to obtain a primer-coated TAC film. The coated TAC film was laminated with a polyether block amide (Pebax) photochromic film supplied by Transition Inc. by roll lamination at 15 psi using a two-component polyurethane adhesive (U09 FL, supplied by Loctite Inc.). The laminate was then cured at room temperature for 24 hours. The resulting photochromic lamiante displayed excellent adhesion between the TAC and polyether block amide interface. Peel force was measured by Mark 10 equipment with a value above 18 N/inch. Therefore the TAC film is considered to exhibit very good adhesion to the Pebax film.

[0039] In a comparative control example, the TAC and polyether block amide films above were laminated using the same two-component polyurethane adhesive under the same laminating conditions. No primer was used in this control example. The resulting laminate displayed poor adhesion with a peel force of about 5 N/inch. The adhesive strength was also inconsistent across different TAC film types. This experiment demonstrates that a crosslinking component may be added to a primer for increasing the intra-layer adhesive strength within a film laminate.

[0040] The claims are not to be interpreted as including means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) means for or step for, respectively.