Functional film laminate

Abstract

This invention relates to the development of a multi-layer PC polar laminate and its cut and form process. The laminate displays increased adhesion between a PC film layer and an adjacent film layer. As a result of the increased adhesion, less adhesive may be applied between laminate layers, which positively affects PC cracking and mold cavity contamination.

Claims

1. A method for producing an ophthalmic lens comprising a laminate with at least one polycarbonate layer adhered to at least one polyvinyl alcohol (PVOH) layer, the method comprising: treating a polycarbonate (PC) film with an aminosilane primer in a concentration range of from 0.5 to 15%; applying a PVOH-based resin adhesive to a PVOH film; laminating the treated PC film to the PVOH film to produce a laminate; heat curing the laminate; and cutting the laminate into a laminate wafer; wherein the laminate may further comprise one or more additional layers or sublayers, each layer or sublayer being independently selected from the group consisting of PC, PVOH, polymethyl methacrylate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate, cyclic olefin copolymer, norbornene-containing olefin polymer, polyurethane, polystyrene, polyethylene terephthalate, and other clear or colored film layers.

2. The method of claim 1, wherein the PVOH film comprises a boron content less than 5%.

3. The method of claim 2, wherein the PVOH film comprises a boron content less than 2%.

4. The method of claim 1, wherein the PVOH-based resin adhesive further comprises a crosslinker.

5. The method of claim 4, wherein the crosslinker is an amine, acrylate, isocyanate, melamine, aldehyde, or a metal.

6. The method of claim 1, wherein the post-curing PVOH-based resin adhesive layer thickness is less than 10 m.

7. The method of claim 6, wherein the post-curing PVOH-based resin adhesive layer thickness is less than 5 m.

8. The method of claim 1, wherein the heat curing further comprises passing the laminate through a multipass oven at a temperature of at least 60 C., for at least 5 minutes.

9. The method of claim 1, further comprising thermoforming the laminate wafer, the thermoforming comprising: maintaining the laminate wafer above a critical relative humidity, drying the laminate wafer to a pre-determined moisture content, and pre-heating the laminate wafer to prevent PVOH layer microcracking; and thermoforming the laminate wafer in a thermoforming device.

10. The method of claim 9, further comprising incorporating the laminate wafer into an ophthalmic lens by a lens-production method selected from the group consisting of injection molding, casting, and lamination.

11. The method of claim 1, wherein the aminosilane primer is selected from the group consisting of 3-aminopropyl-triethoxysilane, 3-aminopropyl-trimethoxysilane, 3-aminopropyldimethylethoxysilane, 3-aminopropyl-methyldiethoxysilane, 3-aminoethyl-triethoxysilane, bis(3-triethoxysilyl-propyl) amine, bis(3-trimethoxysilyl-propyl) amine, N-(n-butyl)-3-aminopropyl-trimethoxysilane, N-(n-butyl)-3-aminopropyl-methyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane, N-(2-aminoethyl)-3-aminopropyl-methyldimethoxysilane, 2-aminoethyl-3-aminopropyl-methyldimethoxysilane, 2-aminoethyl-3-aminopropyl-trimethoxysilane, (3-trimethoxysilylpropyl) diethylenetriamine, N,N-di(2-aminoethyl)-3-aminopropyl-trimethoxysilane, N,N-di(2-aminoethyl)-3-aminopropyl-triethoxysilane, N,N-di(2-aminoethyl)-3-aminopropyl-methyldimethoxysilane, N,N-di(2-aminoethyl)-3-aminopropyl-methyldiethoxysilane, N[N-(2-aminoethyl)-2-aminoethyl)]-3-aminopropyl-trimethoxysilane, N-methyl-3-aminopropyl-trimethoxysilane, N-methyl-3-aminopropyl-methyldimethoxysilane,N-methyl-3-aminopropyl-triethoxysilane, N-methyl-3-aminopropyl-methyldiethoxysilane, N-cyclohexyl-3-aminopropyl-trimethoxysilane, N-cyclohexyl-3-aminopropyl-triethoxysilane, and N-phenyl-3-aminopropyl-trimethoxysilane.

12. The method of claim 1, wherein the ophthalmic lens further comprises a hard coat layer on a substrate side opposite to the laminate.

13. A method for increasing the adhesion between a PC film layer and a PVOH film layer of an optical article, comprising: treating the PC film with an aminosilane primer in a concentration range of from 0.5 to 15%; applying a layer of a PVOH-based resin adhesive to the PVOH film; laminating the primer-treated PC film to the PVOH film to produce a laminate; heat curing the laminate; thermoforming the laminate; and subjecting the laminate to heat and pressure; wherein the laminate may further comprise one or more additional layers or sublayers, each layer or sublayer being independently selected from the group consisting of PC, PVOH, polymethyl methacrylate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate, cyclic olefin copolymer, norbornene-containing olefin polymer, polyurethane, polystyrene, and polyethylene terephthalate, and other clear or colored film layers.

14. The method of claim 13, wherein the aminosilane primer is selected from the group consisting of 3-aminopropyl-triethoxysilane, 3-aminopropyl-trimethoxysilane, 3-aminopropyl-dimethylethoxysilane, 3-aminopropyl-methyldiethoxysilane, 3-aminoethyl-triethoxysilane, bis(3-triethoxysilyl-propyl) amine, bis(3-trimethoxysilyl-propyl) amine, N-(n-butyl)-3-aminopropyl-trimethoxysilane, N-(n-butyl)-3-aminopropyl-methyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane, N-(2-aminoethyl)-3-aminopropyl-methyldimethoxysilane, 2-aminoethyl-3-aminopropyl-methyldimethoxysilane, 2-aminoethyl-3-aminopropyl-trimethoxysilane, (3-trimethoxysilylpropyl) diethylenetriamine, N,N-di(2-aminoethyl)-3-aminopropyl-trimethoxysilane, N,N-di(2-aminoethyl)-3 aminopropyl-triethoxysilane, N,N-di(2-aminoethyl)-3-aminopropyl-methyldimethoxysilane, N,N-di(2-aminoethyl)-3 aminopropyl-methyldiethoxysilane, N[N-(2-aminoethyl)-2-aminoethyl)]-3-aminopropyl-trimethoxysilane, N-methyl-3-aminopropyl-trimethoxysilane, N-methyl-3-aminopropyl-methyldimethoxysilane,N-methyl-3-aminopropyl-triethoxysilane, N-methyl-3-aminopropyl-methyldiethoxysilane, N-cyclohexyl-3-aminopropyl-trimethoxysilane, N-cyclohexyl-3-aminopropyl-triethoxysilane, and N-phenyl-3-aminopropyl-trimethoxysilane.

15. The method of claim 13, wherein the PVOH film comprises a boron content lower than 5%.

16. The method of claim 15, wherein the PVOH film comprises a boron content less than 2%.

17. The method of claim 13, wherein the PVOH-based resin further comprises a crosslinker.

18. The method of claim 17, wherein the crosslinker is an amine, acrylate, isocyanate, melamine, aldehyde, or a metal.

19. The method of claim 13, wherein the post-curing PVOH-based resin adhesive layer thickness is less than 10 m.

20. The method of claim 1, wherein during the treating, the concentration range of the aminosilane primer is between 4 and 6%.

21. The method of claim 13, wherein during the treating, the concentration range of the aminosilane primer is between 4 and 6%.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a depiction of one embodiment of the invention. The exemplary tri-layer laminate comprises a PVOH film laminated between PC films. A PVOH-based adhesive adheres the PVOH film to the PC films. The tri-layer laminate includes protective film layers on the exterior surfaces.

(2) FIGS. 2A and 2B illustrate PVOH crazing for different conditions. FIG. 2A includes 100 microscopy images of PVOH layers that compares crazing for films of different boron content after a drying step at 82 C. At low relative humidity (10%), the high boron content film displays crazing. At higher relative humidity, neither of the films display crazing, suggesting that high relative humidity can overcome the crazing tendency of a high boron content film. FIG. 2B includes 100 microscopy images of PVOH layers that compares crazing for thermoformed films after pre-heating and no pre-heating. Base=8.0, Storage=28 C. at 60% relative humidity. The no pre-heat, high boron content film displays the highest level of crazing. Preheating the high boron film decreased the level of crazing. Under no pre-heating conditions, the low boron content film displayes significantly less crazing than the high boron film. Crazing is not visible in the low boron, pre-heated film. This demonstrates that both low boron content and pre-heating prior to thermoforming reduce or prevent crazing.

(3) FIG. 3 includes 100 microscopy images of PVOH layers that compares crazing for thermoformed films after pre-heating and no pre-heating. The conditions model indoor, room-temperature conditions, with storage temperature and relative humidity that are lower than the conditions of FIG. 2B (22 C. vs 28 C. and Rh 10% vs 60%, respectively). The respective films (boron content and preheat) display higher crazing levels than the films in 2B, demonstrating that high relative humidity and high storage temperature reduce crazing. Additionally, the crazing trend mirrors the trend in FIG. 2B which demonstrates that both low boron content and pre-heating prior to thermoforming reduce or prevent crazing.

(4) FIG. 4 illustrates an example of PC cracks after the hard coating process.

DETAILED DESCRIPTION

(5) 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.

(6) 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.

(7) Disclosed herein is a method for increasing adhesion of PVOH films to adjacent films in a laminate. As a result of the increased adhesion, less adhesive may be applied between laminate layers, which positively affects PC cracking and mold cavity contamination. While investigating the laminate cut and form processes, factors that affect PVOH crazing were identified.

(8) A. PC Film Adhesion

(9) It is known that PVOH-based adhesives adhere to PVOH films. PVOH-based adhesives, however, do not adhere very well to PC films. It was found that treating the PC layers with an aqueous solution of an aminosilane primer promotes adhesion of the PVOH-based adhesive to the PC film. It was also found that the primer-treated PC displayed significantly improved adhesion to PVOH films after thermoforming and molding of the lens.

(10) B. PVOH Crazing During the Wafer Forming Step

(11) During ophthalmic lens production, laminate sheets are cut into wafers for incorporation into a lens. During the wafer-forming step, PVOH layers often develop networks of fine, cracks, which is known as crazing. It was found that PVOH crazing could be controlled by (a) optimizing the boric acid level in the stretched PVOH layer; (b) incorporate a pre-heating step during thermoforming, and/or (c) control the storage humidity above a critical humidity level.

(12) C. PC Cracking after Hard Coating

(13) During the ophthalmic lens thermoforming and lens production, e.g., injection molding, casting, or UV lamination, excessive stress is placed on the front PC layer which can lead to the formation of cracks. During the hard coating process, lenses are heated, blasted with utrasonic waves, and subjected to aggressive caustic treatment. PC films are not compatible with hydroxide solutions, and the harsh hard conditions can cause propagation of cracks in the PC layer. The PC crack issue has presented a problem for established lens production processes. It is believed that the PC cracking is caused by internal stresses that are created at the interface of the PC stretched film and the glue/other layer during the wafer forming process and lens molding process. Testing has indicated that the layers adjacent to a PC layer can have a significant impact on PC cracks because adjacent layers can induce extra stress on the neighboring PC layer during processing. The PVOH-based adhesive of the present invention has a minimal impact on transmitting stress to PC layers, in part due to the low requisite adhesive layer thickness. Some laminates incorporate layers adjacent to the PC layer which are greater than or equal to 80 m. Such a layer may have inadequate thermal mechanical properties which is exacerbated by the excessive thickness to have an impact on stress transmitted to the neighboring PC layer. In some embodiments, the PVOH-based adhesive layer is less than 5 m thick and thermo-mechanically suitable, thereby minimizing stress on the adjacent PC layer. It was found that laminates disclosed herein with PVOH-based adhesive and aminosilane primer presented no PC cracking when processed through hard coating.

(14) D. Insert Contamination

(15) The PVOH-based adhesive and primer thickness is on the order of a few microns. The post-curing PVOH-based resin adhesive layer thickness is less than 10 m, preferably less than 5 m. This adhesive layer thickness is significantly less than other known solutions, including polyurethane and UV acrylic adhesives. The minimized adhesive layer thickness presents an advantage during injection molding where the adhesive could be squeezed out of the polarizing structure due to the high pressures involved in the process. The ejected adhesive accumulates at the edges of mold cavities, and may be incorporated into and cause defects in subsequently-produced lenses. The ejected adhesive accumulation, or insert contamination, is identified as white speck/gummy speck and requires extensive and repetitive cleaning of the mold. This ejected adhesive contamination problem may be ameliorated by the inventive PVOH-based resin adhesive, which may be applied in relatively thin layers.

(16) E. Edging:

(17) Edging is an additional criteria for qualitatively evaluating the adhesive properties on the lens. For this method, lenses are subjected to an edging test using edgers thought to be more aggressive in the cutting action to obtain the shape of a standard frame. The edged lenses are carefully inspected for delaminations after edging that could occur between the PC and PVOH films. After submission of 20 lenses each for base 1.50 to a power of 4 and 8.50 to a power of +4, it was found that none of the lenses had delamination after being edged to the shape of frame mount.

(18) F. Exemplary Laminate Production Steps

(19) 1: Treat a PC film with a primer solution of 3-aminopropyl-triethoxysilane diluted to 5% in water. The primer solution may be be at a temperature ranging from ambient temperature to 80 C., preferably between 50 and 60 C. Rinse the treated PC film at 60 C. for 90 seconds in heated DI water. The film is then dried using a drying step.

(20) 2: Laminate two treated PC films to either side of a PVOH film using a PVOH-based adhesive to give a tri-layer laminate. Adhesive=5% Z-320; 5% Glyoxal; 0.1% HCl and the remainder water. Z320 is an acetoacetyl modified PVOH resin. Glyoxal is the two-carbon dialdehyde, ethanedial.

(21) 3: Heat cure the adhesive by passing the tri-layer laminate through a multipass oven at a temperature of at least 90 C. for 5 minutes and wind to a roll.

(22) 4: Cut laminate into flat sections for transport.

(23) G. Exemplary Thermoforming Steps

(24) 1: Die-cut laminate to appropriate circular shape.

(25) 2: Maintain storage conditions for die-cuts above a critical relative humidity. This reduces/prevents PVOH crazing, especially for laminate using high boric acid PVOH film and/or older laminate.

(26) 3: Immediately prior to thermoforming, dry the circles to an appropriate moisture content to preserve color and polarization efficiency. Drying conditions include heating to 82 C. for 12 hrs.

(27) 4: Pre-heat the circles at 140 C. for 5 minutes.

(28) 5: Immediately load the wafers from pre-heat to a thermoforming device which performs the thermoforming operation to produce a wafer of desired base. Thermoforming conditions are set at 152 C. for 2 to 10 minutes.

(29) H. Adhesion

(30) The PC-aminosilane treatment is important for enhanced PC to PVOH adhesion. The PVOH-based adhesive layer is approximately 1 m thick. Application of heat and pressure, by thermoforming, for example, to a laminate comprising an aminosilane-treated PC layer increases adhesion as the heat and pressure reinforce the interfacial and cohesive strength of the glue. The pressure and heat during molding is approximately 1200 psi and 130 C. The inventive method comprising PC-aminosilane treatment, a PVOH-based adhesive, and subsequently-applied heat and pressure provides exceptional adhesion for such a thin layer of adhesive. The adhesion from laminate to lens increased from approximately 12 N/in to over 60 N/in (Table 1).

(31) Adhesion was measured using a tensile testing device from Instron to measure the force as the PC to PVOH interface is peeled apart at a set speed in the laminate's machine direction. The test was arranged so that the peel was 180 degrees on the laminate and 90 degrees on the lens. The results produced are given as Newtons per extension length. This force is then converted to peel strength by dividing the force (Newtons) by the sample width. The steady-state peel strength values obtained are reported in Table 1 below for both Wintec and Examples of this invention on the laminate and after injection molding to a 1.50 base lens.

(32) The lamination equipment used for Examples 1 and 2 is a bench-top laboratory laminator from ChemInstruments. It consists of a 3 ply wet lamination where the PVOH-based resin adhesive is dispensed to each side of the middle PVOH polarizing layer film and between the outer PC layers to produce a tri-layer laminate. The roller nip speed/pressure and film tension are precisely controlled to produce a consistent spreading of the adhesive between the layers. For example 3, the laminate was produced on a similar but a larger, industrialized 3 ply wet laminator.

(33) TABLE-US-00001 TABLE 1 Laminate (180 deg) 1.50 Base Lens (90 deg) MGC/Wintec PC/PVOH/PC 20 to 25 N/in 63 N/in (1 sample) laminate with polyurethane adhesive Example 1 12 N/in (1 sample) 98 N/in (1 sample) PC/PVOH/PC laminate Example 2 15 N/in (1 sample) 32 N/in (1 sample) PC/PVOH/PC laminate Example 3 6 N/in (1 sample) 30 N/in (1 sample) PC/PVOH/PC laminate

Example 1

(34) The 3-layer laminate for Example 1 of this invention used the following specific steps:

(35) PC film: Non-stretched polycarbonate film (250 micrometers thick)

(36) PVOH film: stretched and polarized film from Onbitt (color grey category 3, 1700 dp, 2.5% Boron)

(37) Adhesive formulation: 5% Z320+5% Glyoxal+0.05 w/w 1N HCl/Z320+90% DI water

(38) Aminosilane treatment steps for PC film:

(39) 1. 5.7% A1100 (aminosilane) at 60 C. for 90 s (withdraw rate=2.6 m/min)

(40) 2. DI rinse 1 at 60 C. for 30 s

(41) 3. DI rinse 2 at 60 C. for 1 minute (withdraw rate=2.6 m/min)

(42) 4. Dry at room temperature

(43) Lamination (from Chemtura Instruments)

(44) Gap=0.018 inches

(45) Pressure=30 psi

(46) Speed=2 m/min

(47) Post-lamination cure=60 C./10 min, 20 C./1 day, 90 C./3 hrs.

Example 2

(48) The 3-layer laminate for Example 2 of this invention used the following specific steps:

(49) PC film=Stretched polycarbonate film (300 micrometers thick; 4400-4800 nm retardation value)

(50) PVOH film=stretched and polarized film from Onbitt (color grey category 3, 1700 dp, 2.5% Boron)

(51) Adhesive formulation=5% Z320+5% Glyoxal+0.05 w/w 1N HCl/Z320+90% DI water

(52) Aminosilane treatment steps for PC film:

(53) 5.7% A1100 at 60 C. for 90 s (withdraw rate=not controlled)

(54) DI rinse at room temperature under facet for 30 seconds

(55) Dry at room temperature

(56) Lamination (benchtop laboratory laminator from Chemm Instruments)

(57) Gap=0.018 inches

(58) Pressure=30 psi

(59) Speed=2 m/min

(60) Post-lamination cure=60 C./10 min, 20 C./7 day, 90 C./10 min

Example 3

(61) The 3-layer laminate for Example 3 of this invention used the following specific steps: PC film=Stretched polycarbonate film (300 micrometers thick; 4400-4800 nm retardation value) PVOH film=stretched and polarized film from Onbitt (color grey category 3, 2400 dp, 1.8% Boron) Adhesive formulation=5% Z320+5% Glyoxal+0.05 w/w 1N HCl/Z320+90% DI water

(62) Aminosilane treatment steps for PC film:

(63) 5.7% A1100 at 60 C. for 82 seconds (withdraw rate=4 m/min)

(64) DI rinse at 50 C. for 70 seconds

(65) Dry at 40 C. for 130 seconds

(66) Lamination

(67) Gap=none (touching rollers)

(68) Pressure=unknown

(69) Speed=3.3 m/min

(70) Post-lamination cure=90 C./5 min

(71) 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.